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Appl. Sci., Volume 7, Issue 6 (June 2017) – 119 articles

Cover Story (view full-size image): Foamed concrete contains numerous pores which strongly affect the material characteristics and properties. An appropriate investigation is necessary for more detailed understanding of foamed concrete, and the micro-CT imaging and quantitative methods are used to examine the material. Using the methods, the pore characteristics and the relative density of solids are examined, and the material properties of the foamed specimen are numerically computed. The results demonstrate the effects of the pore characteristics on the local and global properties of foamed concrete and can be used for developing the material with lower thermal conductivity by minimizing the strength reduction. Click here
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3675 KiB  
Article
Arginine-Mediated Self-Assembly of Porphyrin on Graphene: A Photocatalyst for Degradation of Dyes
by Duong Duc La, Rahul V. Hangarge, Sidhanath V. Bhosale, Ha Duc Ninh, Lathe A. Jones and Sheshanath V. Bhosale
Appl. Sci. 2017, 7(6), 643; https://doi.org/10.3390/app7060643 - 21 Jun 2017
Cited by 40 | Viewed by 8442
Abstract
Porphyrin nanostructures with well-controlled size, shape and functionality can be used for visible-light photocatalysis. In this work, a graphene@porphyrin nanofibre composite was successfully fabricated via arginine-mediated self-assembly of tetrakis (4-carboxyphenyl) porphyrin (TCPP) on graphene nanoplates (GNPs). The formation and crystallisation of the graphene@porphyrin [...] Read more.
Porphyrin nanostructures with well-controlled size, shape and functionality can be used for visible-light photocatalysis. In this work, a graphene@porphyrin nanofibre composite was successfully fabricated via arginine-mediated self-assembly of tetrakis (4-carboxyphenyl) porphyrin (TCPP) on graphene nanoplates (GNPs). The formation and crystallisation of the graphene@porphyrin nanofibre composite was fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) and fluorescence spectroscopy. The assembled TCPP nanofibers were 50–200 nm in diameter with length in micrometers long, which were densely and uniformly distributed on the surface of graphene. The GNPs@TCPP nanofibers showed enhanced visible-light photocatalytic activity in comparison with free-standing TCPP nanorods for the degradation of Rhodamine B (RhB) and methyl orange (MO). The possible photodegradation mechanism of these dyes by the GNPs@TCPP nanofiber photocatalyst was proposed. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic diagram of arginine-mediated self-assembly of porphyrin nanofibers on graphene surface.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) images of (<b>A</b>) graphene nanoplates, (<b>B</b>) free-standing arginine-induced tetrakis (4-carboxyphenyl) porphyrin (TCPP) aggregates.</p> Full article ">Figure 3
<p>(<b>A</b>) Low and (<b>B</b>) high-resolution SEM images of arginine-induced self-assembly of TCPP on the graphene surface, respectively.</p> Full article ">Figure 4
<p>(<b>A</b>) and inset of (<b>A</b>) UV-vis absorption spectra and (<b>B</b>) photoluminescence (PL) spectra of monomeric TCPP molecules (black line), free-standing TCPP nanobelts (red line) and graphene nanoplates (GNP)s@TCPP fibers (blue line).</p> Full article ">Figure 5
<p>XRD patterns of monomeric TCPP molecule and GNPs@TCPP nanofibers.</p> Full article ">Figure 6
<p>(<b>A</b>,<b>C</b>) Photocatalytic performance and (<b>B</b>,<b>D</b>) kinetic simulation curve for RhB and methyl orange degradation, respectively, of (<b>a</b>) control without catalyst, (<b>b</b>) GNPs, (<b>c</b>) free-standing TCPP nanobelts, (<b>d</b>) GNPs@TCPP nanofibers.</p> Full article ">Figure 7
<p>The possible mechanism of the GNPs@TCPP nanofibers photocatalyst for dye degradation.</p> Full article ">
2800 KiB  
Article
Computational Analysis and Artificial Neural Network Optimization of Dry Turning Parameters—AA2024-T351
by Waqas Saleem, Muhammad Zain-ul-abdein, Hassan Ijaz, Abdullah Salmeen Bin Mahfouz, Anas Ahmed, Muhammad Asad and Tarek Mabrouki
Appl. Sci. 2017, 7(6), 642; https://doi.org/10.3390/app7060642 - 21 Jun 2017
Cited by 21 | Viewed by 5723
Abstract
In dry turning operation, various parameters influence the cutting force and contribute in machining precision. Generally, the numerical cutting models are adopted to establish the optimum cutting parameters and results are substantiated with the experimental findings. In this paper, the optimal turning parameters [...] Read more.
In dry turning operation, various parameters influence the cutting force and contribute in machining precision. Generally, the numerical cutting models are adopted to establish the optimum cutting parameters and results are substantiated with the experimental findings. In this paper, the optimal turning parameters of AA2024-T351 alloy are determined through Abaqus/Explicit numerical cutting simulations by employing the Johnson-Cook thermo-viscoplastic-damage material model. Turning simulations were verified with published experimental data. Considering the constrained and nonlinear optimization problem, the artificial neural networks (ANN) were executed for training, testing, and performance evaluation of the numerical simulations data. Two feedforward backpropagation neural networks were developed with ten hidden neutrons in each hidden layer. The Log-Sigmoid transfer function and the Levenberg-Marquardt algorithm were applied in the model. The ANN models were studied with four input parameters: the cutting speed (200, 400, and 800 m/min), tool rake angle (5°, 10°, 14.8°, and 17.5°), cutting feed (0.3 and 0.4 mm), and the contact friction coefficients (0.1 and 0.15).The two target parameters include the tool-chip interface temperature and the cutting reaction force. The performance of the trained data was evaluated using root-mean-square error and correlation coefficients. The ANN predicted values were compared both with the Abaqus simulations and the published experimental findings. All of the results are found in good approximation to each other. The performance of the ANN models demonstrated the fidelity of solving and predicting the optimum process parameters. Full article
(This article belongs to the Section Mechanical Engineering)
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Figure 1

Figure 1
<p>Basic architecture of an ANN.</p> Full article ">Figure 2
<p>Turning simulations model.</p> Full article ">Figure 3
<p>Parametric sensitivity analysis (cutting reaction force (N), chip stress (MPa), and tool-chip interface temperate (°C)) [<a href="#B53-applsci-07-00642" class="html-bibr">53</a>].</p> Full article ">Figure 4
<p>ANN model for cutting simulations.</p> Full article ">Figure 5
<p>(<b>a</b>) Neural network performance plot for tool-chip interface temperature (<span class="html-italic">T</span>); (<b>b</b>) Neural network regression plots for chip-tool interface temperature (<span class="html-italic">T</span>); (<b>c</b>) Neural network performance and gradient epochs (chip-tool interface temperature); (<b>d</b>) Neural training and the output window for chip-tool interface temperature (<span class="html-italic">T</span>).</p> Full article ">Figure 5 Cont.
<p>(<b>a</b>) Neural network performance plot for tool-chip interface temperature (<span class="html-italic">T</span>); (<b>b</b>) Neural network regression plots for chip-tool interface temperature (<span class="html-italic">T</span>); (<b>c</b>) Neural network performance and gradient epochs (chip-tool interface temperature); (<b>d</b>) Neural training and the output window for chip-tool interface temperature (<span class="html-italic">T</span>).</p> Full article ">Figure 6
<p>(<b>a</b>) Neural network performance plot for cutting reaction force (<span class="html-italic">RF</span>); (<b>b</b>) Neural network regression plots for cutting reaction force (<span class="html-italic">RF</span>); (<b>c</b>) Neural network performance and gradient epochs for cutting reaction force (<span class="html-italic">RF</span>); (<b>d</b>) Neural training and output window for cutting reaction force (<span class="html-italic">RF</span>).</p> Full article ">Figure 6 Cont.
<p>(<b>a</b>) Neural network performance plot for cutting reaction force (<span class="html-italic">RF</span>); (<b>b</b>) Neural network regression plots for cutting reaction force (<span class="html-italic">RF</span>); (<b>c</b>) Neural network performance and gradient epochs for cutting reaction force (<span class="html-italic">RF</span>); (<b>d</b>) Neural training and output window for cutting reaction force (<span class="html-italic">RF</span>).</p> Full article ">Figure 7
<p>Comparison of experimental [<a href="#B42-applsci-07-00642" class="html-bibr">42</a>] and ANN simulated results.</p> Full article ">
6972 KiB  
Article
Design and Implementation of an Interactive Interface for Demand Response and Home Energy Management Applications
by Barış Yener, Akın Taşcıkaraoğlu, Ozan Erdinç, Mustafa Baysal and João P. S. Catalão
Appl. Sci. 2017, 7(6), 641; https://doi.org/10.3390/app7060641 - 21 Jun 2017
Cited by 10 | Viewed by 5772
Abstract
Demand response (DR) implementations have recently found wide application areas in the context of smart grids. The effectiveness of these implementations is primarily based on the willingness of end-users to be involved in such programs. In this paper, an interactive and user-friendly interface [...] Read more.
Demand response (DR) implementations have recently found wide application areas in the context of smart grids. The effectiveness of these implementations is primarily based on the willingness of end-users to be involved in such programs. In this paper, an interactive and user-friendly interface is presented in order to facilitate and accordingly to increase the participation of end-users in DR programs. The proposed interface has the capability of providing the targeted information about the DR events to end-users and system operators, as well as allowing end-users to interactively monitor and control the progress of their appliances. In addition to its benefits to system operators and thus to the improved operation of power systems, the proposed interface particularly aims to exploit the potential energy-related cost savings by providing the required information and resources to end-users via mobile phone. A separate interface apart from the mentioned end-user oriented interface has also been developed for the system operator to more effectively check the status of DR applications in detail. The capabilities of the proposed concept are evaluated in a real smart home in terms of various aspects. Full article
(This article belongs to the Special Issue Smart Home and Energy Management Systems)
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Figure 1

Figure 1
<p>General scheme of the proposed structure.</p> Full article ">Figure 2
<p>Schematic illustration of the proposed interactive interface.</p> Full article ">Figure 3
<p>General flowchart of the proposed concept.</p> Full article ">Figure 4
<p>Detailed flowchart of the block hypertext preprocessor (PHP).</p> Full article ">Figure 5
<p>Detailed flowchart of the block system operator.</p> Full article ">Figure 6
<p>Detailed flowchart of the block home energy management (HEM) device.</p> Full article ">Figure 7
<p>Detailed flowchart of the block Node.JS.</p> Full article ">Figure 8
<p>Detailed flowchart of the block user interface.</p> Full article ">Figure 9
<p>The general overview of the interactions among the system components.</p> Full article ">Figure 10
<p>The system operator interface logging screen.</p> Full article ">Figure 11
<p>The system operator interface screen for creating new demand response (DR) events: general overview.</p> Full article ">Figure 12
<p>The system operator interface screen for the list of present and previous events.</p> Full article ">Figure 13
<p>The notifications on the end-user interface.</p> Full article ">Figure 14
<p>The appliance selection and confirmation screen on the end-user interface.</p> Full article ">Figure 15
<p>The auto-reply menu on the end-user interface.</p> Full article ">Figure 16
<p>Daily consumption values of appliances. (<b>a</b>) A representative day in winter; (<b>b</b>) A representative day in summer.</p> Full article ">Figure 17
<p>Energy costs with and without the proposed management algorithm.</p> Full article ">Figure 18
<p>Price history screen of the HEM module.</p> Full article ">
3206 KiB  
Article
FERMI: Present and Future Challenges
by Luca Giannessi and Claudio Masciovecchio
Appl. Sci. 2017, 7(6), 640; https://doi.org/10.3390/app7060640 - 21 Jun 2017
Cited by 16 | Viewed by 5299
Abstract
We present an overview of the FERMI (acronym of Free Electron laser Radiation for Multidisciplinary Investigations) seeded free electron laser (FEL) facility located at the Elettra laboratory in Trieste. FERMI is now in user operation with both the FEL lines FEL-1 and FEL-2, [...] Read more.
We present an overview of the FERMI (acronym of Free Electron laser Radiation for Multidisciplinary Investigations) seeded free electron laser (FEL) facility located at the Elettra laboratory in Trieste. FERMI is now in user operation with both the FEL lines FEL-1 and FEL-2, covering the wavelength range between 100 nm and 4 nm. The seeding scheme adopted for photon pulse production makes FERMI unique worldwide and allows the extension of table top laser experiments in the extreme ultraviolet/soft X-ray region. In this paper, we discuss how advances in the performance of the FELs, with respect to coherent control and multi-colour pulse production, may push the development of original experimental strategies to study non-equilibrium behaviour of matter at the attosecond-nanometer time-length scales. This will have a tremendous impact as an experimental tool to investigate a large array of phenomena ranging from nano-dynamics in complex materials to phenomena that are at the heart of the conversion of light into other forms of energy. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Figure 1

Figure 1
<p>Sketch of the High Gain Harmonic Generation (HGHG) free electron laser (FEL) configuration. Seed laser pulse and electron beam are superimposed in a first undulator indicated as modulator. The FEL interaction induces an electron energy modulation with the periodicity of the seed wavelength. The dispersive section converts this energy modulation into a density modulation containing higher order Fourier components of the original modulation. One of these components is finally amplified in the radiator.</p> Full article ">Figure 2
<p>Schematic layout of FERMI (acronym of Free Electron laser Radiation for Multidisciplinary Investigations) FEL-2, implementing the HGHG double stage cascade in the fresh-bunch high-gain harmonic generation configuration. The first stage (mod1-disp1-rad1) is analogous to the high-gain harmonic generation scheme of FEL-1 shown in <a href="#applsci-07-00640-f001" class="html-fig">Figure 1</a>. The second stage (mod2-disp2-rad2) is based on the same concept, but the seed is the radiation produced in the first stage. The two stages are separated by a delay line (delay) which lengthens the electron path with respect to the radiation path allowing to shift the seed over a “fresh” portion of the electron beam.</p> Full article ">Figure 3
<p>Spectrum in seeded mode (<b>a</b>) and in Self-Amplified Stimulated Emission (SASE) mode; (<b>b</b>) Wavelengths are dispersed along the horizontal axis. The vertical axis represents the vertical position at the spectrometer detector. The distribution on the vertical axis gives the projection of the beam spatial distribution on the vertical plane.</p> Full article ">Figure 4
<p>Spectrum of FERMI FEL-2 at harmonic 65 of the input seed. As in <a href="#applsci-07-00640-f003" class="html-fig">Figure 3</a>, wavelengths are dispersed along the horizontal axis. As in <a href="#applsci-07-00640-f003" class="html-fig">Figure 3</a> the vertical axis represents the vertical position at the spectrometer detector.</p> Full article ">Figure 5
<p>Histogram of the energy per pulse measured from FEL-1 at harmonic 5 (51 nm). Acquisition of 220 consecutive shots, average 131 µJ, standard deviation 4.8 µJ.</p> Full article ">Figure 6
<p>Various method for the generation of multiple pulses adopted on FERMI FEL-1. (<b>a</b>) Two colors can be generated by tuning the final amplifier to different harmonics of the seed. The output pulse is composed by the superposition of the two harmonic components; (<b>b</b>) A double seed can be injected with a temporal delay between the two seed pulses comprised between 200 and 600–700 fs. The two seed pulses can be separated in frequency to generate two distinguishable colors, by ensuring they are both included in the gain bandwidth of the FEL amplifier (0.7–0.8%); (<b>c</b>) A larger frequency separation between the two pulses is also possible if the amplifier is tuned to different harmonics of the seed.</p> Full article ">Figure 7
<p>Sketch of the four wave mixing (FWM) experimental scheme. After the full stop: The non-linear interaction of the three photon pulses (i.e., coherent electromagnetic fields <span class="html-italic">E</span><sub>1,2,3</sub>) that may have different frequencies and wavevectors (1,2,3) is represented in the figure. The pulses may have as well different polarization, bandwidth and time delays. In the inset is depicted the phase matching condition.</p> Full article ">Figure 8
<p>FEL-based FWM experiment stimulated by transient extreme ultraviolet (XUV) gratings (inset (b) reports the phase matching geometry: <span class="html-italic">k</span><sub>FEL1</sub>, <span class="html-italic">k</span><sub>FEL2</sub>, <span class="html-italic">k</span><sub>opt</sub> and <span class="html-italic">k</span><sub>out</sub> are the wavevectors of the two FEL pulses, the optical pulse and the FWM signal, respectively). The signal (XTG) has been registered on a charged coupled detector (CCD).</p> Full article ">Figure 9
<p>(<b>a</b>) Sketch of the FEL-based X-ray analogue of coherent Raman scattering (XCRS) experiment; (<b>b</b>,<b>c</b>) are the excitation processes and level scheme for a XUV/X-ray CRS experiment involving core transitions in both the excitation and probing process; (<b>d</b>) Phase matching diagram.</p> Full article ">Figure 10
<p>(<b>a</b>) Scheme of the experiment. Left: a 2<span class="html-italic">p</span> electron is excited to 4<span class="html-italic">s</span> by one photon and then emitted as a <span class="html-italic">p</span>-wave by a second photon. Right: a 2<span class="html-italic">p</span> electron process is emitted as an (<span class="html-italic">s + d</span>)-wave by a one-photon process. (<b>b</b>) Asymmetry parameter <span class="html-italic">A<sub>LR</sub></span> as a function of Δ<span class="html-italic">ϕ</span> (black curve), and <span class="html-italic">β</span><sub>1</sub> (green), <span class="html-italic">β</span><sub>3</sub> (blue) and <span class="html-italic">β</span><sub>2</sub> (red) parameters as a function of Δ<span class="html-italic">ϕ</span>. Experimental data are shown as markers with error bars. The lines are sinusoidal or straight line fits for <span class="html-italic">β</span><sub>1</sub>, <span class="html-italic">β</span><sub>3</sub>, and <span class="html-italic">β</span><sub>2</sub> respectively.</p> Full article ">
11695 KiB  
Article
Multidisciplinary Aerodynamic Design of a Rotor Blade for an Optimum Rotor Speed Helicopter
by Jiayi Xie, Zhifeng Xie, Ming Zhou and Jun Qiu
Appl. Sci. 2017, 7(6), 639; https://doi.org/10.3390/app7060639 - 20 Jun 2017
Cited by 14 | Viewed by 10637
Abstract
The aerodynamic design of rotor blades is challenging, and is crucial for the development of helicopter technology. Previous aerodynamic optimizations that focused only on limited design points find it difficult to balance flight performance across the entire flight envelope. This study develops a [...] Read more.
The aerodynamic design of rotor blades is challenging, and is crucial for the development of helicopter technology. Previous aerodynamic optimizations that focused only on limited design points find it difficult to balance flight performance across the entire flight envelope. This study develops a global optimum envelope (GOE) method for determining blade parameters—blade twist, taper ratio, tip sweep—for optimum rotor speed helicopters (ORS-helicopters), balancing performance improvements in hover and various freestream velocities. The GOE method implements aerodynamic blade design by a bi-level optimization, composed of a global optimization step and a secondary optimization step. Power loss as a measure of rotor performance is chosen as the objective function, referred to as direct power loss (DPL) in this study. A rotorcraft comprehensive code for trim simulation with a prescribed wake method is developed. With the application of the GOE method, a DPL reduction of as high as 16.7% can be achieved in hover, and 24% at high freestream velocity. Full article
(This article belongs to the Section Mechanical Engineering)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Framework of GOE method to determine blade parameters.</p> Full article ">Figure 2
<p>Definition of rotor tip wake geometry.</p> Full article ">Figure 3
<p>Induced velocity on TPP for the wake measurement experiment. PWM expresses the present prescribed wake method; FVM expresses the free-vortex method referred to Bhagwat [<a href="#B21-applsci-07-00639" class="html-bibr">21</a>]; EXP is the experimental data [<a href="#B19-applsci-07-00639" class="html-bibr">19</a>].</p> Full article ">Figure 4
<p>Trim results of certain ultra-light helicopter (The superscript U and C express simulation by UMARC and CAMRAD II , and superscript P expresses present simulation.).</p> Full article ">Figure 5
<p>Time history of induced power and profile power for a blade.</p> Full article ">Figure 6
<p>Induced power and profile power with twist variation.</p> Full article ">Figure 7
<p>Section lift with twist variations in hover.</p> Full article ">Figure 8
<p>Section lift with twist variations in <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>0.18</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 9
<p>Section drag with twist variations in <math display="inline"> <semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>0.18</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 10
<p>Induced power loss and profile power loss with blade taper variation.</p> Full article ">Figure 11
<p>Blade planform.</p> Full article ">Figure 12
<p>Power losses with tip sweep variations.</p> Full article ">Figure 13
<p>Induced power and profile power with rotor speed variation.</p> Full article ">Figure 14
<p>DPL improvement and its corresponding design parameters in GOE method. (<b>a</b>) DPL improvement; (<b>b</b>) Optimum rotor speed; (<b>c</b>) Taper ratio; (<b>d</b>) Blade twist; (<b>e</b>) Tip sweep angle; (<b>f</b>) Start position of tip sweep.</p> Full article ">Figure 15
<p>DPL time history by GOE method.</p> Full article ">
5227 KiB  
Article
Levels of Organic Pollution Indicators in Groundwater at the Old Landfill and Waste Management Site
by Eugeniusz Koda, Anna Miszkowska and Anna Sieczka
Appl. Sci. 2017, 7(6), 638; https://doi.org/10.3390/app7060638 - 20 Jun 2017
Cited by 71 | Viewed by 8707
Abstract
The aim of this paper was to assess groundwater quality in a landfill and waste management site, with special regard to levels of organic pollution indicators: chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC). Analysis of specific indicators [...] Read more.
The aim of this paper was to assess groundwater quality in a landfill and waste management site, with special regard to levels of organic pollution indicators: chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC). Analysis of specific indicators was conducted for piezometers located in the area of the Radiowo landfill, the composting plant and the facilities adjacent to the landfill. The article discusses the temporal and spatial changes of selected organic pollution indicators. Based on the results of groundwater monitoring, several maps of COD, BOD and TOC areal distribution were provided. Statistical distribution of monitoring data was presented using box-and-whisker plots. Pearson’s correlation coefficients between selected pollution indicators were measured with a significance level set at p < 0.01 and p < 0.05. The strongest correlation was observed between BOD and COD. The maximum BOD/COD ratio was observed at the level of 1.561 before the closure of the vertical barrier, whereas, at present, average values of this ratio are below 0.18. The results indicate significant improvement of groundwater quality in the landfill site after the closure of the vertical barrier. In particular, this refers to BOD values, which decreased even 160 times in the 1998–2016 monitoring period. Full article
(This article belongs to the Section Chemical and Molecular Sciences)
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Figure 1

Figure 1
<p>Location of the study area in relation to protected areas.</p> Full article ">Figure 2
<p>Location of the groundwater monitoring network in the study area.</p> Full article ">Figure 3
<p>Distribution of the mean values of the biochemical oxygen demand (BOD) in groundwater in 1998, 2004 and 2016.</p> Full article ">Figure 4
<p>Temporal changes of the BOD level in piezometers located in the landfill area.</p> Full article ">Figure 5
<p>Temporal changes of the BOD level in piezometers located in the area of composting plant.</p> Full article ">Figure 6
<p>Temporal changes of the BOD level in piezometers located in the area of adjacent facilities.</p> Full article ">Figure 7
<p>Distribution of the mean values of the chemical oxygen demand (COD) in groundwater in 1998, 2004 and 2016.</p> Full article ">Figure 8
<p>Temporal changes of the COD level in piezometers located in the landfill area.</p> Full article ">Figure 9
<p>Temporal changes of the COD level in piezometers located in the area of composting plant.</p> Full article ">Figure 10
<p>Temporal changes of the COD level in piezometers located in the area of adjacent facilities.</p> Full article ">Figure 11
<p>Distribution of the mean values of the total organic carbon (TOC) in groundwater in 2004 and 2016.</p> Full article ">Figure 12
<p>Temporal changes of the TOC level in piezometers located in the landfill area.</p> Full article ">Figure 13
<p>Temporal changes of the TOC level in piezometers located in the area of composting plant.</p> Full article ">Figure 14
<p>Temporal changes of the TOC level in piezometers located in the area of adjacent facilities.</p> Full article ">Figure 15
<p>Box-and-whisker plots of the BOD level in particular piezometers.</p> Full article ">Figure 16
<p>Box-and-whisker plots of the COD level in particular piezometers.</p> Full article ">Figure 17
<p>Box-and-whisker plots of the TOC level in particular piezometers.</p> Full article ">
7234 KiB  
Article
Functionalization of a Hydrophilic Commercial Membrane Using Inorganic-Organic Polymers Coatings for Membrane Distillation
by Lies Eykens, Klaus Rose, Marjorie Dubreuil, Kristien De Sitter, Chris Dotremont, Luc Pinoy and Bart Van der Bruggen
Appl. Sci. 2017, 7(6), 637; https://doi.org/10.3390/app7060637 - 20 Jun 2017
Cited by 9 | Viewed by 5262
Abstract
Membrane distillation is a thermal separation technique using a microporous hydrophobic membrane. One of the concerns with respect to the industrialization of the technique is the development of novel membranes. In this paper, a commercially available hydrophilic polyethersulfone membrane with a suitable structure [...] Read more.
Membrane distillation is a thermal separation technique using a microporous hydrophobic membrane. One of the concerns with respect to the industrialization of the technique is the development of novel membranes. In this paper, a commercially available hydrophilic polyethersulfone membrane with a suitable structure for membrane distillation was modified using available hydrophobic coatings using ORMOCER® technology to obtain a hydrophobic membrane that can be applied in membrane distillation. The surface modification was performed using a selection of different components, concentrations, and application methods. The resulting membranes can have two hydrophobic surfaces or a hydrophobic and hydrophilic surface depending on the application method. An extensive characterization procedure confirmed the suitability of the coating technique and the obtained membranes for membrane distillation. The surface contact angle of water could be increased from 27° up to 110°, and fluxes comparable to membranes commonly used for membrane distillation were achieved under similar process conditions. A 100 h test demonstrated the stability of the coating and the importance of using sufficiently stable base membranes. Full article
(This article belongs to the Special Issue Wastewater Treatment and Reuse Technologies)
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Figure 1

Figure 1
<p>Coating procedure.</p> Full article ">Figure 2
<p>Mechanism of the hydrolysis and polycondensation reactions.</p> Full article ">Figure 3
<p>Single component system with perfluorodecyl (PFD), <span class="html-fig-inline" id="applsci-07-00637-i001"> <img alt="Applsci 07 00637 i001" src="/applsci/applsci-07-00637/article_deploy/html/images/applsci-07-00637-i001.png"/></span> represents the inorganic network.</p> Full article ">Figure 4
<p>The second system (Ak/T/D/BTFO2N system), <span class="html-fig-inline" id="applsci-07-00637-i001"> <img alt="Applsci 07 00637 i001" src="/applsci/applsci-07-00637/article_deploy/html/images/applsci-07-00637-i001.png"/></span> represents the inorganic network, <span class="html-fig-inline" id="applsci-07-00637-i002"> <img alt="Applsci 07 00637 i002" src="/applsci/applsci-07-00637/article_deploy/html/images/applsci-07-00637-i002.png"/></span> represents the organic network formation.</p> Full article ">Figure 5
<p>The third system (V/Mc/F13 system), <span class="html-fig-inline" id="applsci-07-00637-i001"> <img alt="Applsci 07 00637 i001" src="/applsci/applsci-07-00637/article_deploy/html/images/applsci-07-00637-i001.png"/></span> represents the inorganic network, <span class="html-fig-inline" id="applsci-07-00637-i002"> <img alt="Applsci 07 00637 i002" src="/applsci/applsci-07-00637/article_deploy/html/images/applsci-07-00637-i002.png"/></span> represents the organic network formation.</p> Full article ">Figure 6
<p>Schematic of the membrane distillation setup.</p> Full article ">Figure 7
<p>Pore size distribution untreated PES-membrane, membrane 3, and membrane 4 using porometry.</p> Full article ">Figure 8
<p>EDX (energy-dispersive X-ray spectroscopy) spectra of the cross section for membrane 3.</p> Full article ">Figure 9
<p>Long term experiment of membrane 6, <span class="html-italic">T<sub>f</sub></span> = 45 °C, <span class="html-italic">T<sub>p</sub></span> = 40 °C, <span class="html-italic">v</span> = 0.13 m·s<sup>−1</sup>, NaCl concentration = 35 g·L<sup>−1</sup>.</p> Full article ">
927 KiB  
Article
Random Forest Prediction of IPO Underpricing
by David Quintana, Yago Sáez and Pedro Isasi
Appl. Sci. 2017, 7(6), 636; https://doi.org/10.3390/app7060636 - 20 Jun 2017
Cited by 25 | Viewed by 6344
Abstract
The prediction of initial returns on initial public offerings (IPOs) is a complex matter. The independent variables identified in the literature mix strong and weak predictors, their explanatory power is limited, and samples include a sizable number of outliers. In this context, we [...] Read more.
The prediction of initial returns on initial public offerings (IPOs) is a complex matter. The independent variables identified in the literature mix strong and weak predictors, their explanatory power is limited, and samples include a sizable number of outliers. In this context, we suggest that random forests are a potentially powerful tool. In this paper, we benchmark this algorithm against a set of eight classic machine learning algorithms. The results of this comparison show that random forests outperform the alternatives in terms of mean and median predictive accuracy. The technique also provided the second smallest error variance among the stochastic algorithms. The experimental work also supports the potential of random forests for two practical applications: IPO pricing and IPO trading. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Histogram of the initial returns for the sample of 866 companies taken public between January 1999 and May 2010 on AMEX, NASDAQ, and NYSE exchanges.</p> Full article ">Figure 2
<p>Out-of-bag root mean square error (RMSE) of underpricing prediction vs. the number of grown trees for five different leaf sizes. Experiments were conducted on the training set.</p> Full article ">Figure 3
<p>Out-of-bag independent variable importance measured by the standardized mean decrease in accuracy on the training set. Considered values are: width of price range (RANGE); offering price (PRICE); IPO price adjustment (P_ADJ); dummy variable representing whether the company operates in the technology sector (TECH); the size of the offering (LSIZE); and the proportion of the company retained by insiders (RETAINED).</p> Full article ">Figure 4
<p>Return obtained investing according to the priorities set by the random forests (average over 15 runs on the test set). IPOs are ranked by the forecasted initial returns. Average cumulative return for rank <span class="html-italic">n</span> averages are the actual initial returns of the <span class="html-italic">n</span> highest ranking IPOs.</p> Full article ">
3704 KiB  
Review
Soliton Content of Fiber-Optic Light Pulses
by Fedor Mitschke, Christoph Mahnke and Alexander Hause
Appl. Sci. 2017, 7(6), 635; https://doi.org/10.3390/app7060635 - 19 Jun 2017
Cited by 23 | Viewed by 8536
Abstract
This is a review of fiber-optic soliton propagation and of methods to determine the soliton content in a pulse, group of pulses or a similar structure. Of central importance is the nonlinear Schrödinger equation, an integrable equation that possesses soliton solutions, among others. [...] Read more.
This is a review of fiber-optic soliton propagation and of methods to determine the soliton content in a pulse, group of pulses or a similar structure. Of central importance is the nonlinear Schrödinger equation, an integrable equation that possesses soliton solutions, among others. Several extensions and generalizations of this equation are customary to better approximate real-world systems, but this comes at the expense of losing integrability. Depending on the experimental situation under discussion, a variety of pulse shapes or pulse groups can arise. In each case, the structure will contain one or several solitons plus small amplitude radiation. Direct scattering transform, also known as nonlinear Fourier transform, serves to quantify the soliton content in a given pulse structure, but it relies on integrability. Soliton radiation beat analysis does not suffer from this restriction, but has other limitations. The relative advantages and disadvantages of the methods are compared. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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<p>Evolution of a fundamental nonlinear Schrödinger equation (NLSE) soliton.</p> Full article ">Figure 2
<p>(Left) If a pulse with soliton order <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>1.2</mn> </mrow> </semantics> </math> is launched, a slowly decaying beat with radiation lets the soliton emerge gradually; (right) at <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics> </math>, one generates a higher-order soliton, a structure with periodic shape oscillation.</p> Full article ">Figure 3
<p>Soliton and radiation energies as a function of soliton order <span class="html-italic">N</span>. Energy is normalized to units of fundamental soliton <math display="inline"> <semantics> <msub> <mi>E</mi> <mi>sol</mi> </msub> </semantics> </math> of Equation (<a href="#FD5-applsci-07-00635" class="html-disp-formula">5</a>). The fundamental soliton is at the black dotted markers. Individual soliton energies (grey lines) add up to a cumulative value (piecewise linear blue trace); the latter approximates the total pulse energy (red dashed parabola). The difference between both is shown on an expanded, inverted scale in the lower part (green curve). From [<a href="#B2-applsci-07-00635" class="html-bibr">2</a>].</p> Full article ">Figure 4
<p>Evolution of an Akhmediev breather at <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mn>4</mn> </mrow> </semantics> </math>. <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi>mod</mi> </msub> <mo>=</mo> <mn>2</mn> <mi>π</mi> <mo>/</mo> <msub> <mi>ω</mi> <mi>mod</mi> </msub> </mrow> </semantics> </math>.</p> Full article ">Figure 5
<p>Evolution of a Peregrine soliton (left) and a Kuznetsov–Ma soliton (right). <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi mathvariant="normal">c</mi> </msub> <mo>=</mo> <mn>2</mn> <mi>π</mi> <mo>/</mo> <msub> <mi>ω</mi> <mi mathvariant="normal">c</mi> </msub> </mrow> </semantics> </math>.</p> Full article ">Figure 6
<p>Dispersion-managed fiber consists of alternatingly normally (dispersion compensating fiber (DCF)) and anomalously dispersive fiber (standard single mode fiber (SSMF)) segments. The dispersion parameter <math display="inline"> <semantics> <msub> <mi>β</mi> <mn>2</mn> </msub> </semantics> </math> alternates between values of <math display="inline"> <semantics> <msubsup> <mi>β</mi> <mn>2</mn> <mo>+</mo> </msubsup> </semantics> </math> and <math display="inline"> <semantics> <msubsup> <mi>β</mi> <mn>2</mn> <mo>−</mo> </msubsup> </semantics> </math>; the lengths of segments are <math display="inline"> <semantics> <msup> <mi>L</mi> <mo>+</mo> </msup> </semantics> </math> and <math display="inline"> <semantics> <msup> <mi>L</mi> <mo>−</mo> </msup> </semantics> </math>, respectively. The dispersion map period is <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi>map</mi> </msub> <mo>=</mo> <msup> <mi>L</mi> <mo>+</mo> </msup> <mo>+</mo> <msup> <mi>L</mi> <mo>−</mo> </msup> </mrow> </semantics> </math>.</p> Full article ">Figure 7
<p>Evolution of a dispersion-managed soliton over two dispersion map periods.</p> Full article ">Figure 8
<p>Nonlinear spectrum calculated for a Gaussian pulse shape (Equation (<a href="#FD18-applsci-07-00635" class="html-disp-formula">18</a>)) with <math display="inline"> <semantics> <mrow> <msub> <mi>A</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>3</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <msub> <mi>P</mi> <mn>0</mn> </msub> <mo>,</mo> <msub> <mi>T</mi> <mn>0</mn> </msub> </mrow> </semantics> </math> fulfilling Equation (<a href="#FD4-applsci-07-00635" class="html-disp-formula">4</a>). (Left) The discrete spectrum, consisting of two solitons of the same center frequency. The reference energy here is chosen as <math display="inline"> <semantics> <mrow> <msub> <mi>E</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>2</mn> <msub> <mi>P</mi> <mn>0</mn> </msub> <msub> <mi>T</mi> <mn>0</mn> </msub> </mrow> </semantics> </math>. (Right) The power spectral density (PSD) of the linear radiation part.</p> Full article ">Figure 9
<p>Direct scattering analysis of an <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> soliton with different time window widths <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi mathvariant="normal">W</mi> </msub> <mo>/</mo> <msub> <mi>T</mi> <mn>0</mn> </msub> </mrow> </semantics> </math>. The difference between the soliton energy found by direct scattering transform (DST) and the analytical value is shown. Labels on the right indicate the number of sample points used. Solid curve: expected truncation error, Equation (<a href="#FD28-applsci-07-00635" class="html-disp-formula">28</a>) of the input pulse.</p> Full article ">Figure 10
<p>Energy and frequency eigenvalues of a fundamental soliton obtained using the DST method. The soliton was perturbed by Raman self-frequency shift (blue, solid, Raman response time: <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi mathvariant="normal">R</mi> </msub> <mo>=</mo> <mn>0.03</mn> <mspace width="3.33333pt"/> <msub> <mi>T</mi> <mn>0</mn> </msub> </mrow> </semantics> </math>), third-order dispersion (orange, solid, TODparameter: <math display="inline"> <semantics> <mrow> <msub> <mi>β</mi> <mn>3</mn> </msub> <mo>=</mo> <mn>0.5</mn> <mspace width="3.33333pt"/> <msub> <mi>T</mi> <mn>0</mn> </msub> <msub> <mi>β</mi> <mn>2</mn> </msub> </mrow> </semantics> </math>), and linear loss (green, dashed, loss length: <math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi mathvariant="sans-serif">α</mi> </msub> <mo>=</mo> <mn>200</mn> <mspace width="3.33333pt"/> <msub> <mi>L</mi> <mi mathvariant="normal">D</mi> </msub> </mrow> </semantics> </math>).</p> Full article ">Figure 11
<p>(Left) Soliton radiation beat analysis (SRBA) chart from repeated numerical simulations with increasing soliton number <span class="html-italic">N</span>; (right) corresponding predictions of beat signals and its overtones (from [<a href="#B88-applsci-07-00635" class="html-bibr">88</a>]).</p> Full article ">Figure 12
<p>Full-frequency SRBA chart to determine the soliton content of an <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics> </math> soliton. Grey scale corresponds to the log of the Fourier transform of the spatial evolution of the spectral power density. Arrows labeled <math display="inline"> <semantics> <msub> <mi>S</mi> <mn>1</mn> </msub> </semantics> </math> and <math display="inline"> <semantics> <msub> <mi>S</mi> <mn>2</mn> </msub> </semantics> </math> mark traces pertaining to the first and second soliton; their beat note is also highlighted (from [<a href="#B93-applsci-07-00635" class="html-bibr">93</a>]).</p> Full article ">Figure 13
<p>(Left) SRBA chart for an energy scan of a DM soliton. For an explanation of the procedure, and the apparent white vertical stripes in particular, see the text. (Right) Extract of the left panel, with standardized line types. The fundamentals pertaining to three constituent solitons are labeled <math display="inline"> <semantics> <msub> <mi>S</mi> <mn>1</mn> </msub> </semantics> </math>–<math display="inline"> <semantics> <msub> <mi>S</mi> <mn>3</mn> </msub> </semantics> </math>. The dashed line labeled ‘sol’ is for reference; it represents the spatial frequency for a non-DM soliton in a fiber with <math display="inline"> <semantics> <mrow> <msub> <mi>β</mi> <mn>2</mn> </msub> <mo>=</mo> <msub> <mover> <mi>β</mi> <mo>¯</mo> </mover> <mn>2</mn> </msub> </mrow> </semantics> </math> (from [<a href="#B93-applsci-07-00635" class="html-bibr">93</a>]).</p> Full article ">
5116 KiB  
Article
Optimized Design of Thermoelectric Energy Harvesting Systems for Waste Heat Recovery from Exhaust Pipes
by Marco Nesarajah and Georg Frey
Appl. Sci. 2017, 7(6), 634; https://doi.org/10.3390/app7060634 - 19 Jun 2017
Cited by 19 | Viewed by 7054
Abstract
With the increasing interest in energy efficiency and resource protection, waste heat recovery processes have gained importance. Thereby, one possibility is the conversion of the heat energy into electrical energy by thermoelectric generators. Here, a thermoelectric energy harvesting system is developed to convert [...] Read more.
With the increasing interest in energy efficiency and resource protection, waste heat recovery processes have gained importance. Thereby, one possibility is the conversion of the heat energy into electrical energy by thermoelectric generators. Here, a thermoelectric energy harvesting system is developed to convert the waste heat from exhaust pipes, which are very often used to transport the heat, e.g., in automobiles, in industrial facilities or in heating systems. That is why a mockup of a heating is built-up, and the developed energy harvesting system is attached. To build-up this system, a model-based development process is used. The setup of the developed energy harvesting system is very flexible to test different variants and an optimized system can be found in order to increase the energy yield for concrete application examples. A corresponding simulation model is also presented, based on previously developed libraries in Modelica®/Dymola®. In the end, it can be shown—with measurement and simulation results—that a thermoelectric energy harvesting system on the exhaust pipe of a heating system delivers extra energy and thus delivers a contribution for a more efficient usage of the inserted primary energy carrier. Full article
(This article belongs to the Special Issue Development and Application of Thermoelectric Power Generators, Energy Harvesters and Refrigerators)
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<p>Measured temperatures at an oil-fired heating on the campus, visualized by the web interface.</p> Full article ">Figure 2
<p>Measurement in a private house: (<b>a</b>) Measured temperatures at the heating and the cockle stove; (<b>b</b>) Power consumptions of the pumps in the heating.</p> Full article ">Figure 3
<p>Real system versus mockup: (<b>a</b>) Real oil-fired heating on the campus; (<b>b</b>) Heating mockup in the laboratory.</p> Full article ">Figure 4
<p>Model-based development process for thermoelectric energy harvesting systems [<a href="#B23-applsci-07-00634" class="html-bibr">23</a>].</p> Full article ">Figure 5
<p>Thermal design to collect the heat: (<b>a</b>) segment cooling aggregate to extract heat from flowing medium; (<b>b</b>) Temperature measurement of each section of the segment cooling aggregate for a 20/80 heating load.</p> Full article ">Figure 6
<p>Heating mockup with attached thermoelectric energy harvesting systems (EHS); (<b>a</b>) shows the complete setup; (<b>b</b>) shows an enlargement of a partial excerpt of (<b>a</b>); (<b>c</b>) shows an enlargement of a partial excerpt of (<b>b</b>).</p> Full article ">Figure 7
<p>Switch cabinet of the Heating Mockup: (<b>a</b>) complete switch cabinet; (<b>b</b>) Enlargement of the front panel to realize different wiring structures.</p> Full article ">Figure 8
<p>Simulation model of the thermoelectric EHS at the heating mockup.</p> Full article ">Figure 9
<p>Measurement and simulation data for the heating mockup: heating scenario of the oil-fired heating on campus on 15 November 2016 between 8:42 a.m. and 10:22 a.m., executed on 21 December 2016 at the Heating Mockup. Above: temperature curves of each section as well as the set and real inside pipe temperature at the beginning; below: produced power and energy of the EHS and the corresponding simulation results.</p> Full article ">Figure 10
<p>Schematic system consideration of the heat flow rates for the EHS at the heating mockup.</p> Full article ">
6411 KiB  
Article
Experimental Investigation on the Effects of DBD Plasma on the Film Cooling Effectiveness of a 30-Degree Slot
by Ye Jee Kim, Gi Mun Kim, Youhwan Shin and Jae Su Kwak
Appl. Sci. 2017, 7(6), 633; https://doi.org/10.3390/app7060633 - 19 Jun 2017
Cited by 4 | Viewed by 4449
Abstract
The effects of dielectric barrier discharge (DBD) plasma on the film cooling effectiveness of a 30-degree slot was experimentally investigated in a low-speed wind tunnel. The pressure sensitive paint (PSP) technique was used to measure the film cooling effectiveness, and two blowing ratios [...] Read more.
The effects of dielectric barrier discharge (DBD) plasma on the film cooling effectiveness of a 30-degree slot was experimentally investigated in a low-speed wind tunnel. The pressure sensitive paint (PSP) technique was used to measure the film cooling effectiveness, and two blowing ratios (0.5 and 1.0) were tested. A sinusoidal waveform with a 1-kHz frequency was supplied to the exposed electrode. Two input voltages (6 and 7 kV) and two exposed electrode locations were considered. The results showed that the film cooling effectiveness of the slot was higher for the blowing ratio of the 1.0 case than that for the blowing ratio of the 0.5 case regardless of plasma operation. The higher input voltage case (7 kV) showed higher film cooling effectiveness than the lower input voltage case (6 kV). The improvement in film cooling effectiveness facilitated by the DBD plasma was more significant when the coolant had less momentum. The maximum improvement of the area averaged film cooling effectiveness was 2.3% for the case with the exposed electrode located at the slot exit and a blowing ratio of 0.5. Full article
(This article belongs to the Special Issue Advances in Thermal System Analysis and Optimization)
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<p>Schematic of test setup (not to scale).</p> Full article ">Figure 2
<p>Waveforms of the input voltage and current (6 kV input voltage case).</p> Full article ">Figure 3
<p>Pressure sensitive paint (PSP) calibration curve.</p> Full article ">Figure 4
<p>Distribution of film cooling effectiveness without plasma.</p> Full article ">Figure 5
<p>Distributions of film cooling effectiveness (<math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi mathvariant="normal">e</mi> </msub> </mrow> </semantics> </math> = 0 w).</p> Full article ">Figure 5 Cont.
<p>Distributions of film cooling effectiveness (<math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi mathvariant="normal">e</mi> </msub> </mrow> </semantics> </math> = 0 w).</p> Full article ">Figure 6
<p>Laterally-averaged film cooling effectiveness (<math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi mathvariant="normal">e</mi> </msub> </mrow> </semantics> </math> = 0 w).</p> Full article ">Figure 7
<p>Schematic of the flow with the dielectric barrier discharge (DBD) plasma.</p> Full article ">Figure 8
<p>Distributions of film cooling effectiveness (<math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi mathvariant="normal">e</mi> </msub> </mrow> </semantics> </math> = 10 w).</p> Full article ">Figure 9
<p>Laterally-averaged film cooling effectiveness (<math display="inline"> <semantics> <mrow> <msub> <mi>L</mi> <mi mathvariant="normal">e</mi> </msub> </mrow> </semantics> </math> = 10 w).</p> Full article ">Figure 10
<p>Overall area averaged film cooling effectiveness.</p> Full article ">Figure 11
<p>Test setup to investigate the effect of plasma on the PSP emission.</p> Full article ">Figure 12
<p>Laterally-averaged intensity difference for the cases with and without plasma on the PSP-coated surface.</p> Full article ">
739 KiB  
Article
Supercritical Transesterification of Waste Vegetable Oil: Characteristic Comparison of Ethanol and Methanol as Solvents
by Sujeeta Karki, Nawaraj Sanjel, Jeeban Poudel, Ja Hyung Choi and Sea Cheon Oh
Appl. Sci. 2017, 7(6), 632; https://doi.org/10.3390/app7060632 - 17 Jun 2017
Cited by 18 | Viewed by 6691
Abstract
Transesterification of waste vegetable oil is one of the promising partial substitutes for fossil fuels. The degradation characteristics of waste vegetable oil using supercritical alcohols (ethanol and methanol) have been studied in this research. The elementary target was to conduct comparative analysis of [...] Read more.
Transesterification of waste vegetable oil is one of the promising partial substitutes for fossil fuels. The degradation characteristics of waste vegetable oil using supercritical alcohols (ethanol and methanol) have been studied in this research. The elementary target was to conduct comparative analysis of the effect of supercritical methanol and supercritical ethanol as solvents on the transesterification along with the analysis of product obtained in terms of carbon number. The experiments were carried out at transesterification temperatures of 250, 270 and 290 °C, retention time of 0 to 60 min at an interval of 15 min and oil to alcohol molar ratios of 1:6, 1:12 and 1:18 for both alcohols. The conversion increased with increase in transesterification temperature and retention time. At 290 °C, almost 99% conversion was achieved for 60-min holding time for both alcohols. Increase in conversion of waste vegetable oil was observed as the molar ratio increased. Supercritical transesterification resulted into ester yield higher than 95% with non-ester composition and glycerol collectively less than 5%. Full article
(This article belongs to the Section Energy Science and Technology)
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<p>Schematic diagram of the experimental apparatus.</p> Full article ">Figure 2
<p>(<b>a</b>) SCE (supercritical ethanol); (<b>b</b>) SCM (supercritical methanol) based conversion for 1:6 molar ratios of oil to alcohol at different retention time.</p> Full article ">Figure 3
<p>(<b>a</b>) SCE and (<b>b</b>) SCM based conversion at 290 °C for three different molar ratios of oil to alcohol at different retention time.</p> Full article ">
2276 KiB  
Article
Demonstration of High-Speed Optical Transmission at 2 µm in Titanium Dioxide Waveguides
by Manon Lamy, Christophe Finot, Julien Fatome, Juan Arocas, Jean-Claude Weeber and Kamal Hammani
Appl. Sci. 2017, 7(6), 631; https://doi.org/10.3390/app7060631 - 17 Jun 2017
Cited by 23 | Viewed by 5182
Abstract
We demonstrate the transmission of a 10-Gbit/s optical data signal in the 2 µm waveband into titanium dioxide waveguides. Error-free transmissions have been experimentally achieved taking advantage of a 23-dB insertion loss fiber-to-fiber grating-based injection test-bed platform. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Embedded metal gratings in TiO<sub>2</sub> layout; (<b>b</b>) Numerical simulations of the coupling efficiency for one facet as a function of the width <span class="html-italic">w<sub>1</sub></span> of the grating lines for the following parameters: <span class="html-italic">h</span><sub>bottom</sub> = 70 nm, <span class="html-italic">h<sub>Au</sub></span> = 5 nm, <span class="html-italic">h</span><sub>top</sub> = 234 nm, <span class="html-italic">Λ</span> = 1900 nm at the central wavelength of our laser source (1.98 µm). The results for the transverse electric (TE) mode are compared to those for the transverse magnetic (TM) mode. The circles highlight the values where the efficiencies of both modes are equal. The green circle corresponds to the best value; (<b>c</b>) Corresponding coupling efficiency per facet for the TE and TM modes as a function of the wavelength (for <span class="html-italic">w</span><sub>1</sub> = 700 nm—green circle on panel (b)).</p> Full article ">Figure 2
<p>(<b>a</b>) Sketch of the cross-section of the 304-nm strip waveguides. Corresponding mode profile of the electric field and associated effective index for (<b>b</b>) a multimode waveguide (width, 8 µm) and (<b>c</b>) a subwavelength waveguide (width, 1.6 µm). Subplot (<b>b1</b>) corresponds to the fundamental TE mode, whereas subplot (<b>b2</b>) is related to fundamental TM mode.</p> Full article ">Figure 3
<p>Images of (<b>a</b>) a subwavelength waveguide and (<b>b</b>) a large waveguide considered as a slab. Insets 1 show scanning electron microscopy (SEM) pictures of embedded metal grating on one end of the waveguides whereas insets 2 show optical images of the waveguides. Contrary to the slab, the subwavelength waveguide is equipped with tapers. Insets 3 correspond to SEM pictures of the subwavelength that has a width of 1.65 µm (<b>a3</b>), and the slab which is actually 8.0 µm wide (<b>b3</b>).</p> Full article ">Figure 4
<p>Total insertion losses as a function of the injected wavelength for an MM waveguide (grey curve) and an SM waveguide (black curve) obtained with the amplified spontaneous emission (ASE) source (for <span class="html-italic">w</span><sub>1</sub> = 630 nm). The oscillations of short period on the grey curve are due to a Perot–Fabry effect. The grey dashed line corresponds to the central wavelength of the laser source used in the next section.</p> Full article ">Figure 5
<p>Experimental setup for a 10-Gbit/s 2-µm optical transmission. CW: continuous wave; IM: intensity modulator; PC: polarization controller; PRBS: pseudorandom binary sequence; TDFA: thulium-doped fiber amplifier; VOA: variable optical attenuator; PM: power meter; OSA: optical spectrum analyzer; PD: photodiode; BERT: bit error rate tester (model MU181040A, Anritsu Corporation, Atsugi-shi, Japan).</p> Full article ">Figure 6
<p>(<b>a</b>) Eye diagrams for the back-to-back configuration and after transmission in the 1.65 μm wide waveguide (panels 1 and 2 respectively). In both cases, eyes diagrams were recorded for error-free measurements; (<b>b</b>) Bit-Error-Rate (BER) as a function of optical signal-to-noise ratio (OSNR) for the two previously described waveguides. On the graph, the black points of measurements are associated with back-to-back configuration. The crosses are used for BER measurements for TiO<sub>2</sub> devices (red for the 1.65-µm SM wide waveguide and blue for the 8-µm wide MM waveguide).</p> Full article ">
5789 KiB  
Article
Comparative Study of Stator Configurations of a Permanent Magnet Linear Oscillating Actuator for Orbital Friction Vibration Actuator
by Jianhui Hu, Meng Zhao, Jibin Zou and Yong Li
Appl. Sci. 2017, 7(6), 630; https://doi.org/10.3390/app7060630 - 17 Jun 2017
Cited by 5 | Viewed by 3976
Abstract
A PM orbital friction vibration actuator (OFVA) which composes four linear oscillating actuators (LOA) is proposed in this paper. This paper presents the design, analysis, and experimental validation of stator configuration of a permanent magnet LOA to improve its thrust force characteristics. First, [...] Read more.
A PM orbital friction vibration actuator (OFVA) which composes four linear oscillating actuators (LOA) is proposed in this paper. This paper presents the design, analysis, and experimental validation of stator configuration of a permanent magnet LOA to improve its thrust force characteristics. First, the magnetized topology and the coil configuration are interpreted. The optimization design goal of the LOA was established and the end effects of the actuator are illustrated. The influences of stator design parameters on the performance of LOA were investigated and the optimal parameters have been identified with reference to the thrust force density and thrust force ripple. Results showed that a quasi‐Halbach magnetized E‐cored LOA with obtrapezoid teeth has the best electromagnetic performances of all the LOAs examined here. Finally, the predicted thrust force characteristics were validated by measurements on a prototype actuator. Full article
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<p>Proposed a permanent magnet (PM) orbital friction vibration actuators (OFVA).</p> Full article ">Figure 2
<p>Topology of short stroke single-phase quasi-Halbach PM linear oscillating actuators (LOA). (<b>a</b>) C-core with one slot in stator; (<b>b</b>) E-core with two slots in stator.</p> Full article ">Figure 3
<p>Cross-section of the E-cored LOA.</p> Full article ">Figure 4
<p>Thrust forces of initial LOA over the stroke range.</p> Full article ">Figure 5
<p>Variations of thrust force and its fluctuation with <span class="html-italic">h<sub>s</sub></span>.</p> Full article ">Figure 6
<p>Variations in thrust force and its fluctuation with <span class="html-italic">h</span><sub>1</sub>.</p> Full article ">Figure 7
<p>Variations in thrust force and its fluctuation with <span class="html-italic">h</span><sub>2</sub>.</p> Full article ">Figure 8
<p>Variations of thrust force and its fluctuation with <span class="html-italic">b</span><sub>0</sub>.</p> Full article ">Figure 9
<p>Variations in thrust force and its fluctuation with <span class="html-italic">b</span><sub>1</sub>.</p> Full article ">Figure 10
<p>Variations in thrust force and its fluctuation with <span class="html-italic">b</span><sub>2</sub>.</p> Full article ">Figure 11
<p>Variations in thrust force and its fluctuation with <span class="html-italic">b</span><sub>3</sub>.</p> Full article ">Figure 12
<p>Variations in thrust force and its fluctuation with <span class="html-italic">b<sub>e</sub></span>.</p> Full article ">Figure 13
<p>Variations in thrust force and its fluctuation with <span class="html-italic">b<sub>m0</sub></span>.</p> Full article ">Figure 14
<p>Variations in thrust forces with position.</p> Full article ">Figure 15
<p>Prototype LOA.</p> Full article ">Figure 16
<p>Schematic diagram of experimental device.</p> Full article ">Figure 17
<p>Variations in thrust forces with ampere-turns.</p> Full article ">
4848 KiB  
Article
Experimental Study and Numerical Simulation of a Laminated Reinforced Concrete Shear Wall with a Vertical Seam
by Jianbao Li, Yan Wang, Zheng Lu and Junzuo Li
Appl. Sci. 2017, 7(6), 629; https://doi.org/10.3390/app7060629 - 17 Jun 2017
Cited by 45 | Viewed by 7082
Abstract
In this paper, 12 laminated reinforced concrete shear walls are designed for cyclic loading tests. Seismic performance of laminated reinforced concrete shear walls with vertical seams are evaluated by the failure mode, deformability, hysteresis curve, stiffness degradation, and energy dissipation capacity. In addition, [...] Read more.
In this paper, 12 laminated reinforced concrete shear walls are designed for cyclic loading tests. Seismic performance of laminated reinforced concrete shear walls with vertical seams are evaluated by the failure mode, deformability, hysteresis curve, stiffness degradation, and energy dissipation capacity. In addition, two different construction measures and construction techniques are designed to study their influence on the wall behavior, which provides a reference for the construction of laminated reinforced concrete shear walls. The numerical simulation of the specimen is carried out with ABAQUS, which is in good agreement with the experimental results. These results provide a technical basis for the design, application, and construction of the laminated reinforced concrete shear wall structure. Full article
(This article belongs to the Special Issue The Industrialization of the Building Construction Process)
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<p>Drawing of the laminated reinforced concrete shear wall: (<b>a</b>) frontal view of specimen PCF-A (including type I and II); (<b>b</b>) frontal view of specimen PCF-C (including type I and II); (<b>c</b>) reinforcement drawing of PCFI-A; (<b>d</b>) reinforcement drawing of PCFII-A; (<b>e</b>) reinforcement drawing of PCFI-C; and (<b>f</b>) reinforcement drawing of PCFII-C. Note: PCF-A and PCF-C are specimen numbers whose details are listed in <a href="#applsci-07-00629-t001" class="html-table">Table 1</a>.</p> Full article ">Figure 2
<p>Sensor placement: (<b>a</b>) displacement meters of PCF-A; (<b>b</b>) displacement meters of PCF-C; (<b>c</b>) strain gauges of PCFI-A; (<b>d</b>) strain gauges of PCFII-A; (<b>e</b>) strain gauges of PCFI-C; and (<b>f</b>) strain gauges of PCFII-C.</p> Full article ">Figure 2 Cont.
<p>Sensor placement: (<b>a</b>) displacement meters of PCF-A; (<b>b</b>) displacement meters of PCF-C; (<b>c</b>) strain gauges of PCFI-A; (<b>d</b>) strain gauges of PCFII-A; (<b>e</b>) strain gauges of PCFI-C; and (<b>f</b>) strain gauges of PCFII-C.</p> Full article ">Figure 3
<p>Fabrication of the laminated reinforced concrete wall: (<b>a</b>) fabrication of the prefabricated part; (<b>b</b>) fabrication of the cast-in-place part; and (<b>c</b>) the connector between the bottom beam and the specimen.</p> Full article ">Figure 4
<p>Test loading: (<b>a</b>) test setup; and (<b>b</b>) load process. Note: N is recycling times, and Δ is displacement increment.</p> Full article ">Figure 5
<p>Hysteretic curves (<b>a</b>–<b>f</b>) and standardized skeleton curves (<b>g</b>–<b>i</b>).</p> Full article ">Figure 5 Cont.
<p>Hysteretic curves (<b>a</b>–<b>f</b>) and standardized skeleton curves (<b>g</b>–<b>i</b>).</p> Full article ">Figure 6
<p>The calculation diagram of equivalent viscous damping coefficient.</p> Full article ">Figure 7
<p>Stiffness degradation curves: (<b>a</b>) PCFI-A; (<b>b</b>) PCFI-C; and (<b>c</b>) PCFII-C.</p> Full article ">Figure 8
<p>Constitutive model of the reinforcement.</p> Full article ">Figure 9
<p>Stress-Strain relationship of concrete under uniaxial tension: (<b>a</b>) the stress-strain relationship; and (<b>b</b>) the stress-plastic strain relationship.</p> Full article ">Figure 10
<p>Strain distribution and crack profile: (<b>a</b>) the strain distribution of the cast-in-place wall; (<b>b</b>) the crack profile of the cast-in-place wall; (<b>c</b>) the strain distribution of the whole wall; (<b>d</b>) the crack profile of the whole wall; (<b>e</b>) the strain distribution of the seam wall; and (<b>f</b>) the crack profile of the seam wall.</p> Full article ">Figure 10 Cont.
<p>Strain distribution and crack profile: (<b>a</b>) the strain distribution of the cast-in-place wall; (<b>b</b>) the crack profile of the cast-in-place wall; (<b>c</b>) the strain distribution of the whole wall; (<b>d</b>) the crack profile of the whole wall; (<b>e</b>) the strain distribution of the seam wall; and (<b>f</b>) the crack profile of the seam wall.</p> Full article ">Figure 11
<p>Displacement-base shear curve: (<b>a</b>) the whole laminated shear wall; and (<b>b</b>) the laminated shear wall with a vertical seam.</p> Full article ">Figure 12
<p>Average experimental results and the calculated results of specimens in the two groups.</p> Full article ">
3253 KiB  
Article
Entropy Analysis for Damage Quantification of Hysteretic Dampers Used as Seismic Protection of Buildings
by Elisabet Suarez, Andrés Roldán, Antolino Gallego and Amadeo Benavent-Climent
Appl. Sci. 2017, 7(6), 628; https://doi.org/10.3390/app7060628 - 17 Jun 2017
Cited by 13 | Viewed by 5453
Abstract
Relative wavelet energy entropy (RWEE) is proposed to detect and quantify damage to hysteretic dampers used for the passive seismic control of building structures. Hysteretic dampers have the role of dissipating most of the energy input of an earthquake. Minor or moderate earthquakes [...] Read more.
Relative wavelet energy entropy (RWEE) is proposed to detect and quantify damage to hysteretic dampers used for the passive seismic control of building structures. Hysteretic dampers have the role of dissipating most of the energy input of an earthquake. Minor or moderate earthquakes do not exhaust the energy dissipation capacity of the dampers, yet they damage them. For this reason, continuous or periodic damper-health evaluation is required to decide if they need to be replaced. Such evaluation calls for the application of efficient structural health monitoring techniques (SHM). This paper focuses on the well-known vibration technique, which is applied to a particular type of hysteretic damper called Web Plastifying Damper (WPD), patented by the University of Granada. Vibration signals, properly recorded by piezoelectric sensors attached around the damaged area of the dampers, are decomposed by means of wavelet packet analysis. Then, the relative wavelet energy entropy of these decompositions is used to calculate the proposed index. Validation of RWEE for this particular application involved dampers installed in two different specimens of reinforced concrete structures subjected to earthquake sequences of increasing intensity. When compared with a well-established mechanical energy-based damage index, results demonstrate that RWEE is a successful and low-cost technique for reliable in-situ monitoring of dampers. Full article
(This article belongs to the Section Mechanical Engineering)
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<p>(<b>a</b>) Instrumented I-sections in a particular Web Plastifying Damper (WPD) damper; (<b>b</b>) I-section instrumented with two piezoelectric transducers (PZT), one acting as actuator (input signal) and one acting as sensor (output signal); (<b>c</b>) Connection of the PZT transducers to the electronic system; (<b>d</b>) Installation of the dampers in the building.</p> Full article ">Figure 2
<p>Deformation of an I-section segment of a WPD.</p> Full article ">Figure 3
<p>Response signal obtained from the vibration tests.</p> Full article ">Figure 4
<p>Schematic representation of three Wavelet Packet Transform (WPT) levels of a signal.</p> Full article ">Figure 5
<p>Overview of test models and set-up on the shaking table. (<b>a</b>) Frame with dampers (FD) specimen; (<b>b</b>) Flat-slab with dampers (SD) specimen.</p> Full article ">Figure 6
<p>Accelerations of the seismic simulations applied to the structures FD (<b>a</b>) and SD (<b>b</b>).</p> Full article ">Figure 7
<p>Wavelet energy of one I-section of the ground floor of specimen FD. (<b>a</b>) Complete frequency range; (<b>b</b>) Zoom around the 25 kHz natural frequency.</p> Full article ">Figure 8
<p>Wavelet energy of one I-section of the ground floor of specimen SD. (<b>a</b>) Complete frequency range; (<b>b</b>) Zoom around the 25 kHz natural frequency.</p> Full article ">Figure 9
<p>The relative wavelet energy entropy index (RWEE) vs. mechanical damage index (ID) for each I-section of the dampers of FD.</p> Full article ">Figure 10
<p>RWEE vs. ID for each I-section of the dampers of SD.</p> Full article ">Figure 11
<p>RWEE vs. ID for dampers of specimens FD and SD.</p> Full article ">
2430 KiB  
Review
Spatial Audio for Soundscape Design: Recording and Reproduction
by Joo Young Hong, Jianjun He, Bhan Lam, Rishabh Gupta and Woon-Seng Gan
Appl. Sci. 2017, 7(6), 627; https://doi.org/10.3390/app7060627 - 16 Jun 2017
Cited by 78 | Viewed by 18530
Abstract
With the advancement of spatial audio technologies, in both recording and reproduction, we are seeing more applications that incorporate 3D sound to create an immersive aural experience. Soundscape design and evaluation for urban planning can now tap into the extensive spatial audio tools [...] Read more.
With the advancement of spatial audio technologies, in both recording and reproduction, we are seeing more applications that incorporate 3D sound to create an immersive aural experience. Soundscape design and evaluation for urban planning can now tap into the extensive spatial audio tools for sound capture and 3D sound rendering over headphones and speaker arrays. In this paper, we outline a list of available state-of-the-art spatial audio recording techniques and devices, spatial audio physical and perceptual reproduction techniques, emerging spatial audio techniques for virtual and augmented reality, followed by a discussion on the degree of perceptual accuracy of recording and reproduction techniques in representing the acoustic environment. Full article
(This article belongs to the Special Issue Spatial Audio)
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<p>Schematic illustration of soundscape design process, types of acoustic environment and required techniques.</p> Full article ">Figure 2
<p>Examples of spherical microphone array (from left to right) from Nokia OZO with 8 microphones, Dysonics Randomic with 8 channels, Eigenmike with 32 channels, B&amp;K with 36 channels, and VisiSonics with 64 channels.</p> Full article ">Figure 3
<p>Brüel &amp; Kjær 4101 Binaural microphone worn on the ear.</p> Full article ">Figure 4
<p>Dummy heads (from left to right): KEMAR, Brüel &amp; Kjær 4128 HATS, Head Acoustics HMS III, and Neumann KU-100. Note that Neumann KU-100 dummy head is torso-free.</p> Full article ">Figure 5
<p>Binaural microphones from 3Dio, Free space binaural microphones.</p> Full article ">Figure 6
<p>Ambisonics microphones (from left to right): Sennheiser AMBEO, Core Sound TetraMic, and SoundField SPS200.</p> Full article ">Figure 7
<p>Evolution of spatial audio reproduction systems.</p> Full article ">Figure 8
<p>(<b>Left</b>) AR setup with spatial audio from rendered virtual sound objects for in situ environments. (<b>Right</b>) A lab-based VR setup from omni-directional camera recordings and a reproduced acoustic environment using spatial audio from ambisonic microphone recordings and rendered virtual sound objects [<a href="#B97-applsci-07-00627" class="html-bibr">97</a>].</p> Full article ">
5265 KiB  
Article
A Wireless Sensor Network Using GNSS Receivers for a Short-Term Assessment of the Modal Properties of the Neckartal Bridge
by Timo Kumberg, Sascha Schneid and Leonhard Reindl
Appl. Sci. 2017, 7(6), 626; https://doi.org/10.3390/app7060626 - 16 Jun 2017
Cited by 17 | Viewed by 5522
Abstract
In this article, we present a novel structural health monitoring system based on a wireless sensor network for GNSS (global navigation satellite system) receivers. The GNSS network presented here consists of three GNSS rover stations and one base station that are deployed at [...] Read more.
In this article, we present a novel structural health monitoring system based on a wireless sensor network for GNSS (global navigation satellite system) receivers. The GNSS network presented here consists of three GNSS rover stations and one base station that are deployed at the Neckartal bridge on the Autobahn A81 in southwest Germany. The newly-developed GNSS sensor nodes support satellite data logging up to a sampling rate of 20 Hz. Due to the ultra-low-power consumption achieved by the wake-up receiver during inactive periods, the nodes offer a lifetime from 20 to almost 200 days, without energy harvesting and depending on the satellite data logging period. By performing differential post-processing, precise positioning information in the millimeter range could be achieved. Using the GNSS sensors, we determined resonant frequencies at 0.33 Hz and 1.31 Hz, mainly in the lateral direction of the bridge. To verify the GNSS results, we placed an accelerometer on the bridge. The frequencies detected by the acceleration sensor correspond well to the frequencies found by the GNSS sensors, although the accelerometer measured further higher frequencies as it is probably more sensitive to small amplitudes. Full article
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
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<p>Schematic of a wireless sensor node including the basic components, power supply, sensing, processing and communication. The communication unit consists of the main radio and a wake-up receiver.</p> Full article ">Figure 2
<p>Schematic of a low-frequency wake-up message on-off-keying modulated on the high-frequency carrier signal.</p> Full article ">Figure 3
<p>(<b>a</b>) Schematic of the GNSS (global navigation satellite system) wireless sensor node. (<b>b</b>) Photo of the GNSS sensor node.</p> Full article ">Figure 4
<p>Structure of a range data log.</p> Full article ">Figure 5
<p>States of the sensor nodes separated into active periods (<math display="inline"> <semantics> <msub> <mi>t</mi> <mrow> <mi>l</mi> <mi>o</mi> <mi>g</mi> </mrow> </msub> </semantics> </math>) and (<math display="inline"> <semantics> <msub> <mi>t</mi> <mrow> <mi>c</mi> <mi>o</mi> <mi>m</mi> </mrow> </msub> </semantics> </math>) and the idle period (<math display="inline"> <semantics> <msub> <mi>t</mi> <mrow> <mi>i</mi> <mi>d</mi> <mi>l</mi> <mi>e</mi> </mrow> </msub> </semantics> </math>) during a time interval (<math display="inline"> <semantics> <msub> <mi>t</mi> <mrow> <mi>i</mi> <mi>n</mi> <mi>t</mi> </mrow> </msub> </semantics> </math>).</p> Full article ">Figure 6
<p>The lifetime of the GNSS sensor node plotted over an increasing number of logging and communications intervals in 24 h assuming a battery capacity of 40 Ah and no energy harvesting. The black curve depicts the case of 4-Hz logging, and the red curve assumes 20-Hz logging linked to longer transmission periods.</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic drawing of the base station; (<b>b</b>) Photo of the GSM (global system for mobile communications) base station node.</p> Full article ">Figure 8
<p>Data packet consisting of eight control bytes required by the routing algorithm and one to 246 payload bytes.</p> Full article ">Figure 9
<p>Schematic of the wake-up multi-hop routing protocol.</p> Full article ">Figure 10
<p>The structure of the payload to be transmitted in a routing packet. The payload consists of a length field, type of sensor, the number of the current packet, the total number of packets belonging to this GNSS message, the measurement timestamp and the GNSS message (part or complete) itself.</p> Full article ">Figure 11
<p>Geometry of single differencing with the known position of receiver <span class="html-italic">A</span> and the unknown position of receiver <span class="html-italic">B</span>. Both receiver measure their distance <math display="inline"> <semantics> <mi>ρ</mi> </semantics> </math> to the same satellite <span class="html-italic">j</span>.</p> Full article ">Figure 12
<p>Geometry of double differencing with the known position of receiver <span class="html-italic">A</span> and the unknown position of receiver <span class="html-italic">B</span>. Both receiver measure their distance <math display="inline"> <semantics> <mi>ρ</mi> </semantics> </math> to satellites <span class="html-italic">j</span> and <span class="html-italic">k</span>.</p> Full article ">Figure 13
<p>Photo of the Neckar Valley bridge near Weitingen in southwest Germany.</p> Full article ">Figure 14
<p>Deployment of the wireless sensor network consisting of three rover nodes, a reference node, two relay nodes and the GSM base station.</p> Full article ">Figure 15
<p>(<b>a</b>) Photo of a GNSS antenna attached to the side of the steel bridge by magnets. (<b>b</b>) Photo of the relay node on top of the first pillar.</p> Full article ">Figure 16
<p>Position E2 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-displacements over time as measured by the GNSS sensor.</p> Full article ">Figure 17
<p>Position E3 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-displacements over time as measured by the GNSS sensor.</p> Full article ">Figure 18
<p>Position E4 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-displacements over time as measured by the GNSS sensor.</p> Full article ">Figure 19
<p>Position E2 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-residuals over time.</p> Full article ">Figure 20
<p>Position E3 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-residuals over time.</p> Full article ">Figure 21
<p>Position E4 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-residuals over time.</p> Full article ">Figure 22
<p>Position E2 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-frequencies over significance as measured by the GNSS sensor.</p> Full article ">Figure 23
<p>Position E3 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-frequencies over significance as measured by the GNSS sensor.</p> Full article ">Figure 24
<p>Position E4 (<b>a</b>) <span class="html-italic">x</span>-, (<b>b</b>) <span class="html-italic">y</span>- and (<b>c</b>) <span class="html-italic">z</span>-frequencies over significance as measured by the GNSS sensor.</p> Full article ">Figure 25
<p>Spectra of the GNSS sensor at position E4 in directions (<b>a</b>) <span class="html-italic">x</span>, (<b>b</b>) <span class="html-italic">y</span> and (<b>c</b>) <span class="html-italic">z</span>.</p> Full article ">Figure 26
<p>Spectra of the acceleration sensor at the position E4 in directions (<b>a</b>) <span class="html-italic">x</span>, (<b>b</b>) <span class="html-italic">y</span> and (<b>c</b>) <span class="html-italic">z</span>.</p> Full article ">
992 KiB  
Article
Large Earthquake Magnitude Prediction in Chile with Imbalanced Classifiers and Ensemble Learning
by Manuel Jesús Fernández-Gómez, Gualberto Asencio-Cortés, Alicia Troncoso and Francisco Martínez-Álvarez
Appl. Sci. 2017, 7(6), 625; https://doi.org/10.3390/app7060625 - 16 Jun 2017
Cited by 18 | Viewed by 4618
Abstract
This work presents a novel methodology to predict large magnitude earthquakes with horizon of prediction of five days. For the first time, imbalanced classification techniques are applied in this field by attempting to deal with the infrequent occurrence of such events. So far, [...] Read more.
This work presents a novel methodology to predict large magnitude earthquakes with horizon of prediction of five days. For the first time, imbalanced classification techniques are applied in this field by attempting to deal with the infrequent occurrence of such events. So far, classical classifiers were not able to properly mine these kind of datasets and, for this reason, most of the methods reported in the literature were only focused on moderate magnitude prediction. As an additional step, outputs from different algorithms are combined by applying ensemble learning. Since false positives are quite undesirable in this field, due to the social impact that they might cause, ensembles have been designed in order to reduce these situations. The methodology has been tested on different cities of Chile, showing very promising results in terms of accuracy. Full article
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<p>General flowchart of the proposed methodology.</p> Full article ">Figure 2
<p>Proposed methodology, based on imbalanced classifiers and ensemble learning.</p> Full article ">
1718 KiB  
Article
Efficiency Evaluation of Operation Analysis Systems Based on Dynamic Data Envelope Analysis Models from a Big Data Perspective
by Yixin Sun, Xiaobao Yu, Zhongfu Tan, Xiaofei Xu and Qingyou Yan
Appl. Sci. 2017, 7(6), 624; https://doi.org/10.3390/app7060624 - 16 Jun 2017
Cited by 13 | Viewed by 4444
Abstract
The operating environment of power grid enterprises is complex with a range of monitoring indicators. To grasp the overall operational status in time and find the key affecting factors, Balanced Scorecard Card (BSC), Interpretive Structural Model (ISM), Principal component analysis (PCA) should be [...] Read more.
The operating environment of power grid enterprises is complex with a range of monitoring indicators. To grasp the overall operational status in time and find the key affecting factors, Balanced Scorecard Card (BSC), Interpretive Structural Model (ISM), Principal component analysis (PCA) should be applied. This paper proposed several grid enterprise operators and monitoring indicator systems (which include achievement indicators and driver indicators), and applied PCA for verification and evaluation. The achievement indicators mainly reflected the effectiveness of business operations, which included corporate value, social value, customer value, and so on. Driver indicators mainly reflected the core resources and operations process management of business operations, which have a direct impact on the achievement indicators. The driver and achievement indicators were used as input and output indicators for the provinces to assess the efficiency of operations, and appropriate measures were proposed for improvement. The results showed that the dynamic data envelopment analysis (DEA) model could reflect the time lag of the grid enterprises operating investment and income much better than the other two methods, and the static changes compared to assess efficiency had an average around 4%. Full article
(This article belongs to the Special Issue Simulation, Analysis, Optimization and New Challenges of District Heating and Cooling Networks)
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<p>Basic workflow of the Interpretive Structural Model (ISM).</p> Full article ">Figure 2
<p>Adjacency matrix.</p> Full article ">Figure 3
<p>Reachability matrix.</p> Full article ">Figure 4
<p>Relationship diagram of the operational monitoring index.</p> Full article ">Figure 5
<p>Comprehensive trend of operational performance driving index and achievement index.</p> Full article ">Figure 6
<p>A comparison of the efficiency evaluation results.</p> Full article ">Figure 7
<p>Evaluation comparison of static efficiency and dynamic efficiency.</p> Full article ">
5705 KiB  
Article
Combined CFD-Stochastic Analysis of an Active Fluidic Injection System for Jet Noise Reduction
by Mattia Barbarino, Mario Ilsami, Raffaele Tuccillo and Luigi Federico
Appl. Sci. 2017, 7(6), 623; https://doi.org/10.3390/app7060623 - 16 Jun 2017
Cited by 12 | Viewed by 6114
Abstract
In the framework of DANTE project (Development of Aero-Vibroacoustics Numerical and Technical Expertise), funded under the Italian Aerospace Research Program (PRORA), the prediction and reduction of noise from subsonic jets through the reconstruction of turbulent fields from Reynolds Averaged Navier Stokes (RANS) calculations [...] Read more.
In the framework of DANTE project (Development of Aero-Vibroacoustics Numerical and Technical Expertise), funded under the Italian Aerospace Research Program (PRORA), the prediction and reduction of noise from subsonic jets through the reconstruction of turbulent fields from Reynolds Averaged Navier Stokes (RANS) calculations are addressed. This approach, known as Stochastic Noise Generation and Radiation (SNGR), reconstructs the turbulent velocity fluctuations by RANS fields and calculates the source terms of Vortex Sound acoustic analogy. In the first part of this work, numerical and experimental jet-noise test cases have been reproduced by means RANS simulations and with different turbulence models in order to validate the approach for its subsequent use as a design tool. The noise spectra, predicted with SNGR, are in good agreement with both the experimental data and the results of Large-Eddy Simulations (LES). In the last part of this work, an active fluid injection technique, based on extractions from turbine and injections of high-pressure gas into the main stream of exhausts, has been proposed and finally assessed with the aim of reducing the jet-noise through the mixing and breaking of the turbulent eddies. Some tests have been carried out in order to set the best design parameters in terms of mass flow rate and injection velocity and to design the system functionalities. The SNGR method is, therefore, suitable to be used for the early design phase of jet-noise reduction technologies and a right combination of the fluid injection design parameters allows for a reduction of the jet-noise to 3.5 dB, as compared to the baseline case without injections. Full article
(This article belongs to the Special Issue Advances in Vibroacoustics and Aeroacustics of Aerospace and Automotive Systems)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Representation of the wave vector <math display="inline"> <semantics> <mrow> <msub> <mi mathvariant="bold-italic">k</mi> <mi>n</mi> </msub> </mrow> </semantics> </math> and velocity direction vector <math display="inline"> <semantics> <mrow> <msub> <mi mathvariant="bold-italic">σ</mi> <mi>n</mi> </msub> </mrow> </semantics> </math> and definition of the stochastic angles (Adapted from [<a href="#B13-applsci-07-00623" class="html-bibr">13</a>]).</p> Full article ">Figure 2
<p>Two-point space correlation of a jet plume. (<b>a</b>) First approach based on blobs structure; (<b>b</b>) Second approach based on an adaptive Cartesian mesh.</p> Full article ">Figure 3
<p>Computational domain (Adapted from Andersson [<a href="#B7-applsci-07-00623" class="html-bibr">7</a>]).</p> Full article ">Figure 4
<p>(<b>a</b>) Mesh used for the Reynolds Averaged Navier Stokes (RANS) jet flow simulation; (<b>b</b>) Contour plots of the RANS solution. Mean velocity on the top and turbulent kinetic energy on the bottom.</p> Full article ">Figure 5
<p>The vertical dashed lines indicate lines along which profiles of time-averaged quantities were extracted (Adapted from Andersson [<a href="#B7-applsci-07-00623" class="html-bibr">7</a>]).</p> Full article ">Figure 6
<p>(<b>a</b>) Centerline profile of the axial velocity; (<b>b</b>) Axial profiles of turbulence intensity. (Dotted black lines: experimental results; continuous red line: <span class="html-italic">K</span>-ε model; dashed green line: <span class="html-italic">K</span>-ω SST model; dotted-dashed blue line: LES).</p> Full article ">Figure 7
<p>(<b>a</b>) Radial profiles of axial velocity; (<b>b</b>) Radial profiles of <span class="html-italic">uv</span> correlation. The profiles have been staggered according to their axial location. (Dotted black lines: experimental results; continuous red line: <span class="html-italic">K</span>-ε model; dashed green line: <span class="html-italic">K</span>-ω SST model; dotted-dashed blue line: LES).</p> Full article ">Figure 8
<p>(<b>a</b>) 3D acoustic domain; (<b>b</b>) 3D contour plot of turbulent kinetic energy.</p> Full article ">Figure 9
<p>Position of the microphones (Adapted from Andersson [<a href="#B7-applsci-07-00623" class="html-bibr">7</a>]).</p> Full article ">Figure 10
<p>(<b>a</b>) Power spectra of far-field pressure signal for a few observer locations on the inner arc, <math display="inline"> <semantics> <mrow> <mn>30</mn> <msub> <mi>D</mi> <mi>j</mi> </msub> </mrow> </semantics> </math>. The Power Spectral Density (PSD) spectra have been staggered by multiplying the amplitude by a factor <math display="inline"> <semantics> <mrow> <msup> <mn>10</mn> <mrow> <mn>2</mn> <mi>n</mi> </mrow> </msup> </mrow> </semantics> </math>, where <math display="inline"> <semantics> <mrow> <mi>n</mi> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mfrac> <mrow> <mi>θ</mi> <mo>−</mo> <mn>20</mn> </mrow> <mrow> <mn>40</mn> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mi>θ</mi> </semantics> </math> being the angle from the jet axis; (<b>b</b>) Overall Sound Pressure Level Directivity.</p> Full article ">Figure 11
<p>(<b>a</b>) Power spectra of far-field pressure signal for a few observer locations on the outer arc, <math display="inline"> <semantics> <mrow> <mn>30</mn> <msub> <mi>D</mi> <mi>j</mi> </msub> </mrow> </semantics> </math>. The PSD spectra have been staggered by multiplying the amplitude by a factor <math display="inline"> <semantics> <mrow> <msup> <mn>10</mn> <mrow> <mn>2</mn> <mi>n</mi> </mrow> </msup> </mrow> </semantics> </math>, where <math display="inline"> <semantics> <mrow> <mi>n</mi> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mfrac> <mrow> <mi>θ</mi> <mo>−</mo> <mn>20</mn> </mrow> <mrow> <mn>40</mn> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mi>θ</mi> </semantics> </math> being the angle from the jet axis; (<b>b</b>) Overall Sound Pressure Level Directivity.</p> Full article ">Figure 12
<p>Sound radiation from the jet. Real part of the acoustic pressure [Pa] at 700 Hz.</p> Full article ">Figure 13
<p>Sketch of the active Fluidic Injection System.</p> Full article ">Figure 14
<p>Sketch of the low frequency turbulence region.</p> Full article ">Figure 15
<p>Sketch of the exhaust plumes emitted from a jet engine without (on the top) and with fluid injection (on the bottom).</p> Full article ">Figure 16
<p>Turbulent kinetic energy levels [m<sup>2</sup>/s<sup>2</sup>] for the injection patterns tested.</p> Full article ">Figure 17
<p>Comparison between the different injection patterns in terms of velocity and turbulence intensity. (<b>a</b>) Centerline profile of the axial velocity; (<b>b</b>) Axial profiles of turbulence intensity.</p> Full article ">Figure 18
<p>Turbulent velocity difference, Δ????<sub>????????????????</sub> [m/s] between the baseline case and the 4th test in the whole domain of interest.</p> Full article ">Figure 19
<p>(<b>a</b>) Overall Sound Pressure Level Directivity on the inner arc; (<b>b</b>) Overall Sound Pressure Level Directivity on the outer arc.</p> Full article ">
419 KiB  
Article
Application of Matched-Filter Concepts to Unbiased Selection of Data in Pump-Probe Experiments with Free Electron Lasers
by Carlo Callegari, Tsukasa Takanashi, Hironobu Fukuzawa, Koji Motomura, Denys Iablonskyi, Yoshiaki Kumagai, Subhendu Mondal, Tetsuya Tachibana, Kiyonobu Nagaya, Toshiyuki Nishiyama, Kenji Matsunami, Per Johnsson, Paolo Piseri, Giuseppe Sansone, Antoine Dubrouil, Maurizio Reduzzi, Paolo Carpeggiani, Caterina Vozzi, Michele Devetta, Davide Faccialà, Francesca Calegari, Mattea Carmen Castrovilli, Marcello Coreno, Michele Alagia, Bernd Schütte, Nora Berrah, Oksana Plekan, Paola Finetti, Eugenio Ferrari, Kevin Charles Prince and Kiyoshi Uedaadd Show full author list remove Hide full author list
Appl. Sci. 2017, 7(6), 621; https://doi.org/10.3390/app7060621 - 16 Jun 2017
Cited by 2 | Viewed by 4860
Abstract
Pump-probe experiments are commonly used at Free Electron Lasers (FEL) to elucidate the femtosecond dynamics of atoms, molecules, clusters, liquids and solids. Maximizing the signal-to-noise ratio of the measurements is often a primary need of the experiment, and the aggregation of repeated, rapid, [...] Read more.
Pump-probe experiments are commonly used at Free Electron Lasers (FEL) to elucidate the femtosecond dynamics of atoms, molecules, clusters, liquids and solids. Maximizing the signal-to-noise ratio of the measurements is often a primary need of the experiment, and the aggregation of repeated, rapid, scans of the pump-probe delay is preferable to a single long-lasting scan. The limited availability of beamtime makes it impractical to repeat measurements indiscriminately, and the large, rapid flow of single-shot data that need to be processed and aggregated into a dataset, makes it difficult to assess the quality of a measurement in real time. In post-analysis it is then necessary to devise unbiased criteria to select or reject datasets, and to assign the weight with which they enter the analysis. One such case was the measurement of the lifetime of Intermolecular Coulombic Decay in the weakly-bound neon dimer. We report on the method we used to accomplish this goal for the pump-probe delay scans that constitute the core of the measurement; namely we report on the use of simple auto- and cross-correlation techniques based on the general concept of “matched filter”. We are able to unambiguously assess the signal-to-noise ratio (SNR) of each scan, which then becomes the weight with which a scan enters the average of multiple scans. We also observe a clear gap in the values of SNR, and we discard all the scans below a SNR of 0.45. We are able to generate an average delay scan profile, suitable for further analysis: in our previous work we used it for comparison with theory. Here we argue that the method is sufficiently simple and devoid of human action to be applicable not only in post-analysis, but also for the real-time assessment of the quality of a dataset. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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<p>(<b>a</b>) Three representative delay scans and (<b>b</b>) their autocorrelation curves. We use the autocorrelation curves (<math display="inline"> <semantics> <mrow> <mi>q</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math> excluded) as a criterion to classify scans as good (black), drifting (red), or pure noise (blue). The autocorrelation curve of a good scan is well approximated by a gaussian (green). In panel (<b>a</b>), traces have been offset for clarity, and the shaded curve is the weighed average Equation (<a href="#FD7-applsci-07-00621" class="html-disp-formula">7</a>); in panel (<b>b</b>), the green curve is a gaussian fit of the black autocorrelation trace; the gray curve is the same, scaled to the height of the red autocorrelation trace (white-noise peak excluded). The calculated signal-to-noise ratio <math display="inline"> <semantics> <mrow> <mo>(</mo> <mi>S</mi> <mi>N</mi> <mi>R</mi> <mo>)</mo> </mrow> </semantics> </math> for the three scans are 1.30, 0.52, and 0.20.</p> Full article ">Figure 2
<p>(<b>a</b>) Signal-to-noise ratio plotted versus scan index. (<b>b</b>) Same data as (<b>a</b>) sorted by increasing value, to highlight the gap between <math display="inline"> <semantics> <mrow> <mi mathvariant="italic">SNR</mi> <mo>&gt;</mo> <mn>0.25</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi mathvariant="italic">SNR</mi> <mo>&lt;</mo> <mn>0.45</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 3
<p>Single-shot ion-TOF trace (gray) and average over <math display="inline"> <semantics> <mrow> <mn>12</mn> <mo>,</mo> <mn>200</mn> </mrow> </semantics> </math> shots (red). One in three shots is a blank shot (no gas sample), which is subtracted from the average to eliminate spurious signals, such as that at <math display="inline"> <semantics> <mrow> <mi>m</mi> <mo>/</mo> <mi>z</mi> <mo>=</mo> <mn>28</mn> </mrow> </semantics> </math> in the single shot spectrum, due to residual nitrogen gas. Note that for <math display="inline"> <semantics> <mrow> <mi>m</mi> <mo>/</mo> <mi>z</mi> <mo>&gt;</mo> <mn>25</mn> </mrow> </semantics> </math> both spectra are magnified by a factor 5.</p> Full article ">Figure 4
<p>Schematic representation of the generation of a delay scan <math display="inline"> <semantics> <mrow> <mo>{</mo> <msub> <mi>S</mi> <mi>i</mi> </msub> <mo>}</mo> </mrow> </semantics> </math>, as a function of pump-probe delay <math display="inline"> <semantics> <mrow> <mo>{</mo> <msub> <mi>d</mi> <mi>i</mi> </msub> <mo>}</mo> </mrow> </semantics> </math> from single-shot data <math display="inline"> <semantics> <msub> <mi>a</mi> <mi>j</mi> </msub> </semantics> </math>. The green (red) dots symbolize shots that pass (fail) the filter conditions.</p> Full article ">
2790 KiB  
Article
ANN Sizing Procedure for the Day-Ahead Output Power Forecast of a PV Plant
by Francesco Grimaccia, Sonia Leva, Marco Mussetta and Emanuele Ogliari
Appl. Sci. 2017, 7(6), 622; https://doi.org/10.3390/app7060622 - 15 Jun 2017
Cited by 49 | Viewed by 5746
Abstract
Since the beginning of this century, the share of renewables in Europe’s total power capacity has almost doubled, becoming the largest source of its electricity production. In 2015 alone, photovoltaic (PV) energy generation rose with a rate of more than 5%; nowadays, Germany, [...] Read more.
Since the beginning of this century, the share of renewables in Europe’s total power capacity has almost doubled, becoming the largest source of its electricity production. In 2015 alone, photovoltaic (PV) energy generation rose with a rate of more than 5%; nowadays, Germany, Italy, and Spain account together for almost 70% of total European PV generation. In this context, the so-called day-ahead electricity market represents a key trading platform, where prices and exchanged hourly quantities of energy are defined 24 h in advance. Thus, PV power forecasting in an open energy market can greatly benefit from machine learning techniques. In this study, the authors propose a general procedure to set up the main parameters of hybrid artificial neural networks (ANNs) in terms of the number of neurons, layout, and multiple trials. Numerical simulations on real PV plant data are performed, to assess the effectiveness of the proposed methodology on the basis of statistical indexes, and to optimize the forecasting network performance. Full article
(This article belongs to the Special Issue Computational Intelligence in Photovoltaic Systems)
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<p>Mean normalized mean absolute error (<span class="html-italic">NMAE<sub>%</sub></span>) as a function of the number of neurons, with Levenberg–Marquardt training algorithm set for a faster convergence. Comparable mean <span class="html-italic">NMAE<sub>%</sub></span> in yellow, with 95% interval of confidence, with the minimum in red.</p> Full article ">Figure 2
<p>Mean <span class="html-italic">NMAE<sub>%</sub></span> as a function of the number of neurons, with Levenberg–Marquardt training algorithm set for a slower convergence. Comparable mean <span class="html-italic">NMAE<sub>%</sub></span> in yellow, with 95% interval of confidence, with the minimum in red.</p> Full article ">Figure 3
<p><span class="html-italic">NMAE<sub>%</sub></span> of ten random ensemble (grey lines) as a function of the growing number of trials. The artificial neural network (ANN) has 120 neurons and an “LM fast” training algorithm. The mean of the ten ensemble forecasts <math display="inline"> <semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>N</mi> <mi>M</mi> <mi>A</mi> <mi>E</mi> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> <mi>p</mi> </msub> </mrow> </semantics> </math> is in red, the mean <span class="html-italic">NMAE<sub>%</sub></span> of one thousand forecasts is the dashed green line, and the ensemble <span class="html-italic">NMAE<sub>%</sub></span> of one thousand forecasts is the dash-dotted blue line.</p> Full article ">Figure 4
<p><span class="html-italic">NMAE<sub>%</sub></span> of ten random ensemble (grey lines) as a function of the growing number of trials. The artificial neural network (ANN) has 120 neurons and a “Levenberg–Marquardt (LM) slow” training algorithm. The mean of the ten ensemble forecasts <math display="inline"> <semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>N</mi> <mi>M</mi> <mi>A</mi> <mi>E</mi> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> <mi>p</mi> </msub> </mrow> </semantics> </math> is in red, the mean of one thousand forecasts is the dashed green line, and the ensemble <span class="html-italic">NMAE<sub>%</sub></span> of one thousand forecasts is the dash-dotted blue line.</p> Full article ">Figure 5
<p>Mean <span class="html-italic">NMAE<sub>%</sub></span> of 50 different forecasts as a function of the hidden layers’ sizes, with a constant ratio of neurons.</p> Full article ">Figure 6
<p>Comparison between the mean <span class="html-italic">NMAE<sub>%</sub></span> and the ensemble <span class="html-italic">NMAE<sub>%</sub></span> of 50 trials as a function of the hidden layers’ sizes, kept with a constant ratio of neurons.</p> Full article ">
5667 KiB  
Article
Experimental Investigations of Composite Adsorbent 13X/CaCl2 on an Adsorption Cooling System
by Huizhong Zhao, Shaolong Jia, Junfeng Cheng, Xianghu Tang, Min Zhang, Haoxin Yan and Wenting Ai
Appl. Sci. 2017, 7(6), 620; https://doi.org/10.3390/app7060620 - 14 Jun 2017
Cited by 13 | Viewed by 4428
Abstract
A new experimental device which tests the adsorption performance of the 13X/CaCl2 composite adsorbent under vacuum conditions was established. In this device, heat transfer characteristics in the adsorbent bed have a great influence on the adsorbent performance, the temperature of the bottom [...] Read more.
A new experimental device which tests the adsorption performance of the 13X/CaCl2 composite adsorbent under vacuum conditions was established. In this device, heat transfer characteristics in the adsorbent bed have a great influence on the adsorbent performance, the temperature of the bottom outside bed is very close to the temperature of the bottom inside bed and the temperature difference between them at the end of heating and cooling are 5.66 °C and 0.303 °C, respectively. The following conclusions could be drawn: the equilibrium water uptake of composite adsorbent CA10X (zeolite 13X impregnated with 10 wt % CaCl2 solution) was increased 5.7% compared with that of 13X, and the water uptake was 0.37 g/g. The composite adsorbent CA10X has a better performance in the adsorption refrigeration system. Full article
(This article belongs to the Special Issue Simulation, Analysis, Optimization and New Challenges of District Heating and Cooling Networks)
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<p>13X/CaCl<sub>2</sub> composite adsorbent.</p> Full article ">Figure 1 Cont.
<p>13X/CaCl<sub>2</sub> composite adsorbent.</p> Full article ">Figure 2
<p>Schematic diagram of adsorbent performance testing device. 1—adsorbent bed, 2—absorbent channel, 3—heating furnace, 4—temperature controller, 5—air inlet valve, 6—air inlet, 7—blower, 8—air outlet valve, 9—air outlet, 10—Flange, 11—vacuum ball valve 1, 12—vacuum ball valve 2, 13—pressure transmitter, 14—vacuum ball valve 3, 15—vacuum ball valve 4, 16—evaporator/condenser, and 17—vacuum pump.</p> Full article ">Figure 3
<p>Photograph of adsorbent performance testing device.</p> Full article ">Figure 4
<p>Temperature rate of the adsorbent bed.</p> Full article ">Figure 5
<p>Temperature changes of the adsorbent bed.</p> Full article ">Figure 6
<p>Variation of temperature and pressure in the process of thermal vacuuming.</p> Full article ">Figure 7
<p>Variation of temperature and pressure in the process of pumping out air of the evaporator/condenser.</p> Full article ">Figure 8
<p>Variation of temperature and pressure during the adsorption process.</p> Full article ">Figure 9
<p>Variation of temperature and pressure during the desorption process.</p> Full article ">Figure 10
<p>Equilibrium water uptake changes with time.</p> Full article ">Figure 11
<p>Equilibrium water uptakes changes with temperature.</p> Full article ">
10063 KiB  
Article
Simulation Investigation on Combustion Characteristics in a Four-Point Lean Direct Injection Combustor with Hydrogen/Air
by Jianzhong Li, Li Yuan and Hukam C. Mongia
Appl. Sci. 2017, 7(6), 619; https://doi.org/10.3390/app7060619 - 14 Jun 2017
Cited by 11 | Viewed by 7829
Abstract
To investigate the combustion characteristics in multi-point lean direct injection (LDI) combustors with hydrogen/air, two swirl–venturi 2 × 2 array four-point LDI combustors were designed. The four-point LDI combustor consists of injector assembly, swirl–venturi array and combustion chamber. The injector, swirler and venturi [...] Read more.
To investigate the combustion characteristics in multi-point lean direct injection (LDI) combustors with hydrogen/air, two swirl–venturi 2 × 2 array four-point LDI combustors were designed. The four-point LDI combustor consists of injector assembly, swirl–venturi array and combustion chamber. The injector, swirler and venturi together govern the rapid mixing of hydrogen and air to form the mixture for combustion. Using clockwise swirlers and anticlockwise swirlers, the co-swirling and count-swirling swirler arrays LDI combustors were achieved. Using Reynolds-Averaged Navier–Stokes (RANS) code for steady-state reacting flow computations, the four-point LDI combustors with hydrogen/air were simulated with an 11 species and 23 lumped reaction steps H2/Air reaction mechanism. The axial velocity, turbulence kinetic energy, total pressure drop coefficient, outlet temperature, mass fraction of OH and emission of pollutant NO of four-point LDI combustors, with different equivalence ratios, are here presented and discussed. As the equivalence ratios increased, the total pressure drop coefficient became higher because of increasing heat loss. Increasing equivalence ratios also corresponded with the rise in outlet temperature of the four-point LDI combustors, as well as an increase in the emission index of NO EINO in the four-point LDI combustors. Along the axial distance, the EINO always increased and was at maximum at the exit of the dump. Along the chamber, the EINO gradually increased, maximizing at the exit of chamber. The total temperature of four-point LDI combustors with different equivalence ratios was identical to the theoretical equilibrium temperature. The EINO was an exponential function of the equivalence ratio. Full article
(This article belongs to the Special Issue Clean Energy and Fuel (Hydrogen) Storage)
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<p>Geometric definition of four-point lean direct injection (LDI) combustor.</p> Full article ">Figure 2
<p>Schematic diagram of the co-swirling and count-swirling swirler arrays of four-point LDI combustors.</p> Full article ">Figure 3
<p>Mesh for a four-point LDI combustor.</p> Full article ">Figure 4
<p>Axial velocity profiles and contours compared for co-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 4 Cont.
<p>Axial velocity profiles and contours compared for co-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 5
<p>Axial velocity profiles and contours compared for count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 5 Cont.
<p>Axial velocity profiles and contours compared for count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 6
<p>Turbulence kinetic energy contours compared for count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 6 Cont.
<p>Turbulence kinetic energy contours compared for count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 6 Cont.
<p>Turbulence kinetic energy contours compared for count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 7
<p>Total pressure drop coefficient profiles and contours compared between co-swirling and count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 8
<p>Total temperature profiles and contours compared between co-swirling and count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">Figure 9
<p>EI<sub>NO</sub> profiles compared between co-swirling and count-swirling four-point LDI combustors with different equivalence ratios.</p> Full article ">
1122 KiB  
Article
Iridescent Perfect Absorption in Critically-Coupled Acoustic Metamaterials Using the Transfer Matrix Method
by Noé Jiménez, Jean-Philippe Groby, Vincent Pagneux and Vicent Romero-García
Appl. Sci. 2017, 7(6), 618; https://doi.org/10.3390/app7060618 - 14 Jun 2017
Cited by 22 | Viewed by 5890
Abstract
The absorption performance of a locally-reacting acoustic metamaterial under oblique incidence is studied. The metamaterial is composed of a slotted panel, each slit being loaded by an array of Helmholtz resonators. The system is analytically studied using the transfer matrix method, accounting for [...] Read more.
The absorption performance of a locally-reacting acoustic metamaterial under oblique incidence is studied. The metamaterial is composed of a slotted panel, each slit being loaded by an array of Helmholtz resonators. The system is analytically studied using the transfer matrix method, accounting for the viscothermal losses both in the resonator elements and in the slits, allowing the representation of the reflection coefficient in the complex frequency plane. We show that by tuning the geometry of the metamaterial, perfect absorption peaks can be obtained on demand at selected frequencies and different angles of incidence. When tilting the incidence angle, the peaks of perfect absorption are shifted in frequency, producing an acoustic iridescence effect similar to the optic iridescence achieved by incomplete band gap. Effectively, we show that in this kind of locally-reacting metamaterial, perfect and omnidirectional absorption for a given frequency is impossible to achieve because the metamaterial impedance does not depend on the incidence angle (i.e., the impedance is a locally reacting one). The system is interpreted in the complex frequency plane by analysing the trajectories of the zeros of the reflection coefficient. We show that the trajectories of the zeros do not overlap under oblique incidence, preventing the observation of perfect and omnidirectional absorption in locally reacting metamaterials. Moreover, we show that for any locally resonant material, the absorption in diffuse field takes a maximal value of 0.951, which is achieved by a material showing perfect absorption for an incidence angle of 50.34 degrees. Full article
(This article belongs to the Section Acoustics and Vibrations)
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<p>(<b>a</b>) Scheme of the deep-subwavelength absorbing panel under oblique incidence, the inset shows the geometrical parameters of the Helmholtz resonators (HRs); (<b>b</b>) Scheme of the unit cell that composes the metamaterial.</p> Full article ">Figure 2
<p>(<b>a</b>) Absorption of the metamaterial using <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> HR as a function of the frequency for incidence angles <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>20</mn> <mo>∘</mo> </msup> <mo>,</mo> <msup> <mn>80</mn> <mo>∘</mo> </msup> <mo>,</mo> <mn>87</mn> <mo>.</mo> <msup> <mn>7</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>b</b>) Angle-dependent absorption obtained using transfer matrix method (TMM; continuous lines) and Equation (<a href="#FD10-applsci-07-00618" class="html-disp-formula">10</a>) (circles) at frequencies <math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>250</mn> <mo>,</mo> <mn>300</mn> <mo>,</mo> <mn>350</mn> </mrow> </semantics> </math> Hz; (<b>c</b>) Map of the absorption as a function of the frequency and incidence angle.</p> Full article ">Figure 3
<p>Complex frequency representation of the reflection coefficient for the metamaterial with <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> HR, in logarithmic colour scale, for different angles of incidence. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>20</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>80</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>c</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <mn>87</mn> <mo>.</mo> <msup> <mn>7</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>d</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>→</mo> <msup> <mn>90</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>. The trajectories of the poles and the zeros of the reflection coefficient as the incidence angle is increased are plotted in coloured lines, corresponding to the blueish and reddish colour bars, respectively.</p> Full article ">Figure 4
<p>(<b>a</b>) Absorption of the metamaterial using <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>3</mn> </mrow> </semantics> </math> HRs as a function of the frequency, for incidence angles <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>20</mn> <mo>∘</mo> </msup> <mo>,</mo> <msup> <mn>65</mn> <mo>∘</mo> </msup> <mo>,</mo> <msup> <mn>85</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>b</b>) Angle-dependent absorption obtained using TMM (continuous lines) and Equation (<a href="#FD10-applsci-07-00618" class="html-disp-formula">10</a>) (circles) at frequencies <math display="inline"> <semantics> <mrow> <mi>f</mi> <mo>=</mo> <mn>290</mn> <mo>,</mo> <mn>350</mn> <mo>,</mo> <mn>410</mn> </mrow> </semantics> </math> Hz; (<b>c</b>) Map of the absorption as a function as the frequency and incidence angle.</p> Full article ">Figure 5
<p>Complex frequency representation of the reflection coefficient for the metamaterial with <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>3</mn> </mrow> </semantics> </math> HRs, in logarithmic colour scale, for different angles of incidence. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>0</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>b</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>65</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>c</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <msup> <mn>85</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>; (<b>d</b>) <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>→</mo> <msup> <mn>90</mn> <mo>∘</mo> </msup> </mrow> </semantics> </math>. The trajectories of the poles and the zeros of the reflection coefficient as the incidence angle is increased are plotted in coloured lines, corresponding to the blueish and reddish colour bars, respectively.</p> Full article ">Figure 6
<p>(<b>a</b>) Angle-dependent absorption of the optimal diffuse-field absorber using TMM (continuous line) and Equation (<a href="#FD10-applsci-07-00618" class="html-disp-formula">10</a>), at <math display="inline"> <semantics> <mrow> <msub> <mi>f</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>300</mn> </mrow> </semantics> </math> Hz; (<b>b</b>) Absorption in diffuse field as a function of the critical coupling angle. The maximum absorption in diffuse field is <math display="inline"> <semantics> <mrow> <msub> <mi>α</mi> <mrow> <mi>diff</mi> <mo>,</mo> <mspace width="0.166667em"/> <mi>MAX</mi> </mrow> </msub> <mo>=</mo> <mn>0.952</mn> </mrow> </semantics> </math>, and is achieved for a structure critically-coupled at <math display="inline"> <semantics> <mrow> <msub> <mi>θ</mi> <mi>PA</mi> </msub> <mo>,</mo> <mi>diff</mi> <mo>=</mo> <mn>50.34</mn> <mo>°</mo> </mrow> </semantics> </math>.</p> Full article ">
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Article
Synthesis and Biophysical Insights into the Binding of a Potent Anti-Proliferative Non-symmetric Bis-isatin Derivative with Bovine Serum Albumin: Spectroscopic and Molecular Docking Approaches
by Ali Saber Abdelhameed, Ahmed H. Bakheit, Mostafa S. Mohamed, Wagdy M. Eldehna, Hatem A. Abdel-Aziz and Mohamed I. Attia
Appl. Sci. 2017, 7(6), 617; https://doi.org/10.3390/app7060617 - 14 Jun 2017
Cited by 20 | Viewed by 4425
Abstract
As part of the research endeavors to combat cancer, a non-symmetric bis-isatin derivative (compound 3) was synthesized and showed a significant anti-proliferative potency. The current study provides a comprehensive characterization of the interaction of compound 3 with the drug-transporting protein bovine serum [...] Read more.
As part of the research endeavors to combat cancer, a non-symmetric bis-isatin derivative (compound 3) was synthesized and showed a significant anti-proliferative potency. The current study provides a comprehensive characterization of the interaction of compound 3 with the drug-transporting protein bovine serum albumin (BSA) via the use of spectroscopic tools along with molecular docking studies. Fluorescence spectral measurements showed that the BSA intrinsic fluorescence can be significantly quenched by the addition of compound 3 and the formation of a non-fluorescent complex. Further measurements revealed a static type of quenching with Stern–Volmer and Linweaver–Burk constants of 105. The thermodynamic parameters of the binding were calculated to be ΔS° 105.09 ± 5.32 with ΔH° of −0.72 ± 0.71 and negative ΔG° values. In addition, synchronous fluorescence and 3D fluorescence spectroscopy suggested that compound 3 did not induce conformational changes in BSA. Site competition experiments revealed that compound 3 competes with warfarin within the BSA binding domain (Sudlow site I). This was further confirmed by the molecular docking results showing a binding energy of −25.93 kJ/mol for compound 3-BSA. Hence, the observed results in the present study assumed that the compound 3-BSA binding is spontaneous, involving electrostatic forces and hydrogen bonding. Full article
(This article belongs to the Section Chemical and Molecular Sciences)
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<p>Chemical structures of some anticancer agents bearing an isatin nucleus.</p> Full article ">Figure 2
<p>Chemical structure of the title compound <b>3</b>.</p> Full article ">Figure 3
<p>Emission spectra of (<b>1</b>) BSA (1.5 μM) and the BSA-compound <b>3</b> system succeeding the addition of compound <b>3</b> at the concentrations of (<b>2</b>) 0.65 μM; (<b>3</b>) 1.0 μM; (<b>4</b>) 1.5 μM; (<b>5</b>) 3.0 μM; (<b>6</b>) 4.5 M; (<b>7</b>) 6.0 μM; (<b>8</b>) 9.0 μM; (<b>9</b>) 12.0 μM; (<b>10</b>) 18 μM; (<b>11</b>) 25 μM.</p> Full article ">Figure 4
<p>Stern–Volmer (<b>a</b>) and Lineweaver–Burk (<b>b</b>) plots at various temperatures.</p> Full article ">Figure 5
<p>Plots of log [(<span class="html-italic">F</span><sub>0</sub> − <span class="html-italic">F</span>)/<span class="html-italic">F</span>] vs. log [<span class="html-italic">Q</span>] for the compound <b>3</b>-BSA interaction at different temperatures.</p> Full article ">Figure 6
<p>An exothermic Van’t Hoff plot for compound <b>3</b>-BSA binding.</p> Full article ">Figure 7
<p>UV spectra of (<b>a</b>) 1.5 μMBSA; (<b>b</b>) 20 μM compound <b>3</b>; (<b>c</b>) compound <b>3</b> (3.0 μM) + BSA (1.5 μM); (<b>d</b>) compound <b>3</b> (6.0 μM) + BSA (1.5 μM); (<b>e</b>) compound <b>3</b> (9.0 μM) + BSA (1.5 μM); (<b>f</b>) compound <b>3</b> (12 μM) + BSA (1.5 μM).</p> Full article ">Figure 8
<p>Spectra of the synchronous fluorescence of BSA (1.5 μM) with the addition of compound <b>3</b> (1–11) = (0–25 μM) at Δλ = 15 nm (<b>a</b>) Δλ = 60 nm (<b>b</b>).</p> Full article ">Figure 9
<p>3D spectra of BSA (1.5 μM) in (<b>a</b>) absence and (<b>b</b>) presence of compound <b>3</b> (12.0 μM).</p> Full article ">Figure 10
<p>Contour plot of the fluorescence intensity spectra of BSA (<b>a</b>) compound <b>3</b>-BSA system (<b>b</b>).</p> Full article ">Figure 11
<p>Stern–Volmer correlation derived from the BSA interaction with compound <b>3</b> at 298 K in the presence of WAR and IBP as the site markers.</p> Full article ">Figure 12
<p>(<b>a</b>) A schematic demonstration, and (<b>b</b>) A cartoon illustration of the amino acids included in compound <b>3</b>-BSA binding within the BSA site I binding pocket.</p> Full article ">Scheme 1
<p>Synthesis of the target compound <b>3</b>. <span class="html-italic">Reagents and conditions</span>: (i) Benzyl bromide, K<sub>2</sub>CO<sub>3</sub>, DMF, RT, 18 h; (ii) 5-Bromo-3-hydrazonoindolin-2-one, catalytic amount of glacial acetic acid, ethanol, reflux, 6 h.</p> Full article ">
2325 KiB  
Article
Smartphones as a Light Measurement Tool: Case of Study
by Jose-Maria Gutierrez-Martinez, Ana Castillo-Martinez, Jose-Amelio Medina-Merodio, Juan Aguado-Delgado and Jose-Javier Martinez-Herraiz
Appl. Sci. 2017, 7(6), 616; https://doi.org/10.3390/app7060616 - 14 Jun 2017
Cited by 31 | Viewed by 10485
Abstract
In recent years, smartphones have become the main computing tool for most of the population, making them an ideal tool in many areas. Most of these smartphones are equipped with cutting-edge hardware on their digital cameras, sensors and processors. For this reason, this [...] Read more.
In recent years, smartphones have become the main computing tool for most of the population, making them an ideal tool in many areas. Most of these smartphones are equipped with cutting-edge hardware on their digital cameras, sensors and processors. For this reason, this paper discusses the possibility of using smartphones as an accessible and accurate tool, focusing on the measurement of light, which is an element that has a high impact on human behavior, which promotes conformance and safety, or alters human physiology when it is inappropriate. To carry out this study, three different ways to measure light through smartphones have been checked: the ambient light sensor, the digital camera and an external Bluetooth luxmeter connected with the smartphone. As a result, the accuracy of these methods has been compared to check if they can be used as accurate measurement tools. Full article
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<p>Flow chart of mobile application to obtain luminance through the digital camera.</p> Full article ">Figure 2
<p>Device used as a light diffusor.</p> Full article ">Figure 3
<p>Alcalux device—second prototype.</p> Full article ">Figure 4
<p>Alcalux sensor board.</p> Full article ">Figure 5
<p>Ambient light sensor vs. luxmeter accuracy.</p> Full article ">Figure 6
<p>Ambient light sensor vs. calibrated ambient light sensor vs. luxmeter accuracy.</p> Full article ">Figure 7
<p>Calibrated ambient light sensor vs. luxmeter accuracy.</p> Full article ">Figure 8
<p>Sony Xperia M2’s Ambient light sensor vs. BQ Aquaris X5’s Ambient light sensor vs. luxmeter accuracy.</p> Full article ">Figure 9
<p>Digital camera vs. luxmeter accuracy.</p> Full article ">Figure 10
<p>Digital camera vs. calibrated digital camera vs. luxmeter accuracy.</p> Full article ">Figure 11
<p>LG Nexus 5’s digital damera vs. BQ Aquaris X5’s Digital camera vs. luxmeter accuracy.</p> Full article ">Figure 12
<p>External sensor device (Alcalux) vs. luxmeter accuracy.</p> Full article ">
2203 KiB  
Article
Non-Pulse-Leakage 100-kHz Level, High Beam Quality Industrial Grade Nd:YVO4 Picosecond Amplifier
by Zhenao Bai, Zhenxu Bai, Zhijun Kang, Fuqiang Lian, Weiran Lin and Zhongwei Fan
Appl. Sci. 2017, 7(6), 615; https://doi.org/10.3390/app7060615 - 14 Jun 2017
Cited by 12 | Viewed by 6604
Abstract
A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2 [...] Read more.
A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2O4 (BBO) crystal Pockels cells in both the pulse picker and regenerative amplifier, the seed pulse leakage of the output is suppressed effectively with an adjustable repetition rate from 200 to 500 kHz. Through one stage traveling-wave amplifier, a maximum output power of 24.5 W is generated corresponding to the injected regenerative amplified power of 9.73 W at 500 kHz. The output pulse duration is 16.9 ps, and the beam quality factor M2 is measured to be 1.25 with near-field roundness higher than 99% at the full output power. Full article
(This article belongs to the Special Issue Solid State Lasers Materials, Technologies and Applications)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Diagram of the non-leakage 100-kHz Nd:YVO<sub>4</sub> picosecond regenerative amplifier. The inset is the illustration of the setup.</p> Full article ">Figure 2
<p>Average output power and pulse energy of the amplifier in dependence on the repetition rate of (<b>a</b>) regenerative amplifier output; and (<b>b</b>) final amplifier output.</p> Full article ">Figure 3
<p>Oscilloscope trace of the regenerative amplified pulse train (<b>a</b>) 4 μs/div; and (<b>b</b>) 10 ns/div.</p> Full article ">Figure 4
<p>Measured (<b>a</b>) autocorrelation trace (Gaussian fitting) for the amplified pulse; and (<b>b</b>) beam quality factor <span class="html-italic">M</span><sup>2</sup> (insert: near-field beam intensity distribution).</p> Full article ">
3536 KiB  
Article
Terawatt-Isolated Attosecond X-ray Pulse Using a Tapered X-ray Free Electron Laser
by Sandeep Kumar, Alexandra S. Landsman and Dong Eon Kim
Appl. Sci. 2017, 7(6), 614; https://doi.org/10.3390/app7060614 - 13 Jun 2017
Cited by 4 | Viewed by 4950
Abstract
High power attosecond (as) X-ray pulses are in great demand for ultrafast dynamics and high resolution microscopy. We numerically demonstrate the generation of a ~230 attosecond, 1.5 terawatt (TW) pulse at a photon energy of 1 keV, and a 115 attosecond, 1.2 TW [...] Read more.
High power attosecond (as) X-ray pulses are in great demand for ultrafast dynamics and high resolution microscopy. We numerically demonstrate the generation of a ~230 attosecond, 1.5 terawatt (TW) pulse at a photon energy of 1 keV, and a 115 attosecond, 1.2 TW pulse at a photon energy of 12.4 keV, using the realistic electron beam parameters such as those of Korean X-ray free electron laser (XFEL) in a tapered undulator configuration. To compensate the energy loss of the electron beam and maximize its radiation power, a tapering is introduced in the downstream section of the undulator. It is found that the tapering helps in not only amplifying a target radiation pulse but also suppressing the growth of satellite radiation pulses. Tapering allows one to achieve a terawatt-attosecond pulse only with a 60 m long undulator. Such an attosecond X-ray pulse is inherently synchronized to a driving optical laser pulse; hence, it is well suited for the pump-probe experiments for studying the electron dynamics in atoms, molecules, and solids on the attosecond time-scale. For the realization of these experiments, a high level of synchronization up to attosecond precision between optical laser and X-ray pulse is demanded, which can be possible by using an interferometric feedback loop. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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<p>(Color online) Schematic layout for the terawatt (TW)-attosecond X-ray free electron laser (XFEL) [<a href="#B29-applsci-07-00614" class="html-bibr">29</a>], (<b>a</b>) ESASE section; (<b>b</b>) SASE undulator; (<b>c</b>) Chicane-mirror system; (<b>d</b>) single undulator module (UM4); (<b>e</b>) a small magnet chicane for e-beam delay followed by single undulator module (UM5); and (<b>f</b>) a small magnet chicane for e-beam delay.</p> Full article ">Figure 2
<p>Working principle of the scheme: the alignment process between the current profile of electron bunch (consisting of nine blue spikes produced by ESASE in <a href="#applsci-07-00614-f001" class="html-fig">Figure 1</a>a) and the radiation profile (consisting of nine red spikes) at different locations of <a href="#applsci-07-00614-f001" class="html-fig">Figure 1</a>.</p> Full article ">Figure 3
<p>(<b>a</b>) The current modulation of a 10 GeV electron beam for hard X-ray amplification; the black-dashed line shows the spoiled section of the current profile and the red-dashed line shows the unspoiled section. (<b>b</b>) The longitudinal phase space plot showing energy modulation of the electrons along the electron bunch after the interaction with the optical laser (<a href="#applsci-07-00614-f001" class="html-fig">Figure 1</a>a).</p> Full article ">Figure 4
<p>The radiation amplification along the undulator for hard X-ray case. Snapshot of the radiation pulse (<b>a</b>) after 3 UMs; (<b>b</b>) after 8 UMs; (<b>c</b>) after 13 UMs in a uniform undulator; and (<b>d</b>) after 13 UMs when a tapering is considered in UM9-UM13. A single isolated 130 attosecond FWHM, 1.2 TW radiation pulse is obtained in a tapered undulator.</p> Full article ">Figure 5
<p>(<b>a</b>) Undulator parameter K for a stepwise tapering, and (<b>b</b>) the electron beam energy spread at the undulator entrance and exit for hard X-ray case.</p> Full article ">Figure 6
<p>(<b>a</b>) The average radiation power and the power fluctuations for 10 different random seeds for a uniform and a tapered undulator. (<b>b</b>) Power spectrum of the radiation output for hard X-ray case (inset shows the temporal profiles of the radiation powers).</p> Full article ">Figure 7
<p>(<b>a</b>) Current modulation of an electron beam of 3.15 GeV energy. The dashed-black line shows the spoiled section, and the red line is the unspoiled section of the current profile. The snapshot of the radiation pulse amplification (<b>b</b>) after 3 UMs; (<b>c</b>) after 13 UMs in a uniform undulator; and (<b>d</b>) after 13 UMs in a tapered undulator.</p> Full article ">Figure 8
<p>(<b>a</b>) Stepwise tapering in the undulator parameter K for the attosecond-TW XFEL in soft X-ray region, and (<b>b</b>) variation of the electron beam energy spread along the undulator.</p> Full article ">Figure 9
<p>(<b>a</b>) The average radiation power for 10 different random seeds along the uniform undulator (black line) and along the tapered undulator (red line) in the soft X-ray case, and (<b>b</b>) the power spectra for the uniform undulator (black line) and for the tapered undulator (red line).</p> Full article ">
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