Applied Sciences

4013 KiB

Open AccessArticle

Modeling, Simulation, and Performance Analysis of Decoy State Enabled Quantum Key Distribution Systems

by Logan O. Mailloux, Michael R. Grimaila, Douglas D. Hodson, Ryan Engle, Colin McLaughlin and Gerald Baumgartner

Appl. Sci. 2017, 7(2), 212; https://doi.org/10.3390/app7020212 - 22 Feb 2017

Cited by 6 | Viewed by 8055

Abstract

Quantum Key Distribution (QKD) systems exploit the laws of quantum mechanics to generate secure keying material for cryptographic purposes. To date, several commercially viable decoy state enabled QKD systems have been successfully demonstrated and show promise for high-security applications such as banking, government, [...] Read more.

Quantum Key Distribution (QKD) systems exploit the laws of quantum mechanics to generate secure keying material for cryptographic purposes. To date, several commercially viable decoy state enabled QKD systems have been successfully demonstrated and show promise for high-security applications such as banking, government, and military environments. In this work, a detailed performance analysis of decoy state enabled QKD systems is conducted through model and simulation of several common decoy state configurations. The results of this study uniquely demonstrate that the decoy state protocol can ensure Photon Number Splitting (PNS) attacks are detected with high confidence, while maximizing the system’s quantum throughput at no additional cost. Additionally, implementation security guidance is provided for QKD system developers and users. Full article

(This article belongs to the Special Issue Modeling, Simulation, Operation and Control of Discrete Event Systems)

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Figure 1
This is a Quantum Key Distribution (QKD) system context diagram. The sender “Alice” and receiver “Bob” generate shared secret key <math display="inline"> <semantics> <mi>K</mi> </semantics> </math> for use in data encryption/decryption. Reproduced with permission from [<a href="#B9-applsci-07-00212" class="html-bibr">9</a>], Copyright IEEE, 2016. Full article ">Figure 2
The eavesdropper (Eve and Eve′) is shown conducting a Photon Number Splitting (PNS) attack against the QKD system (Alice and Bob). Adapted with permission from [<a href="#B9-applsci-07-00212" class="html-bibr">9</a>], Copyright IEEE, 2016. Full article ">Figure 3
Variation in weak coherent pulse Mean Photon Number (MPN) emitted from Alice’s modeled laser due to expected fluctuations and performance limitations in the modeled decoy state generator (i.e., the variable optical attenuator). The upper and lower Prediction Intervals (PI) are shown to bound the expected performance. Full article ">Figure 4
Simulation results are shown for the for the 50 km decoy state protocol configurations examined when operating under normal conditions. In each configuration studied, the signal and decoy state efficiencies are the same <math display="inline"> <semantics> <mrow> <msup> <mi>η</mi> <mrow> <mi>s</mi> <mi>i</mi> <mi>g</mi> <mi>n</mi> <mi>a</mi> <mi>l</mi> </mrow> </msup> <mo>=</mo> <msup> <mi>η</mi> <mrow> <mi>d</mi> <mi>e</mi> <mi>c</mi> <mi>o</mi> <mi>y</mi> </mrow> </msup> <mo>±</mo> <mo>Δ</mo> </mrow> </semantics> </math> (within expected variation tolerances). Full article ">Figure 5
Simulation results are shown for the 50 km decoy state protocol configurations examined when subject to PNS attacks. In each configuration studied, the signal and decoy state efficiencies are statistically different <math display="inline"> <semantics> <mrow> <msup> <mi>η</mi> <mrow> <mi>s</mi> <mi>i</mi> <mi>g</mi> <mi>n</mi> <mi>a</mi> <mi>l</mi> </mrow> </msup> <mo>≠</mo> <msup> <mi>η</mi> <mrow> <mi>d</mi> <mi>e</mi> <mi>c</mi> <mi>o</mi> <mi>y</mi> </mrow> </msup> <mo>±</mo> <mo>Δ</mo> </mrow> </semantics> </math> (outside expected variation tolerances). Full article ">Figure 6
Simulation results show the optimized decoy state protocol for detecting PNS attacks based on the fielded QKD system [<a href="#B55-applsci-07-00212" class="html-bibr">55</a>]. The inlay details the expected dark count rate complete with outliers to illustrate the modeled noise over the QKD communication channel. Full article ">Figure 7
Simulation results detailing the number of decoy state detections per round of quantum exchange for the optimized decoy state protocol based on the fielded QKD system parameters shown in <a href="#applsci-07-00212-t006" class="html-table">Table 6</a>. Full article ">

329 KiB

Open AccessErratum

Erratum: A CMOS Multiplied Input Differential Difference Amplifier: A New Active Device and Its Applications. Applied Sciences 2017, 7, 106

by Applied Sciences Editorial Office

Appl. Sci. 2017, 7(2), 211; https://doi.org/10.3390/app7020211 - 22 Feb 2017

Viewed by 2990

Abstract

We wish to make the following correction to the published paper [...] Full article

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4107 KiB

Open AccessArticle

Seismic Failure Mechanism of Reinforced Cold-Formed Steel Shear Wall System Based on Structural Vulnerability Analysis

by Jihong Ye, Liqiang Jiang and Xingxing Wang

Appl. Sci. 2017, 7(2), 182; https://doi.org/10.3390/app7020182 - 22 Feb 2017

Cited by 14 | Viewed by 9066

Abstract

A series of structural vulnerability analyses are conducted on a reinforced cold-formed steel (RCFS) shear wall system and a traditional cold-formed steel (CFS) shear wall system subjected to earthquake hazard based on forms in order to investigate their failure mechanisms. The RCFS shear [...] Read more.

A series of structural vulnerability analyses are conducted on a reinforced cold-formed steel (RCFS) shear wall system and a traditional cold-formed steel (CFS) shear wall system subjected to earthquake hazard based on forms in order to investigate their failure mechanisms. The RCFS shear wall adopts rigid beam-column joints and continuous concrete-filled CFS tube end studs rather than coupled-C section end studs that are used in traditional CFS shear walls, to achieve the rigid connections in both beam-column joints and column bases. The results show that: the RCFS and traditional CFS shear wall systems both exhibit the maximum vulnerability index associated with the failure mode in the first story. Therefore, the first story is likely to be a weakness of the CFS shear wall system. Once the wall is damaged, the traditional CFS shear wall system would collapse because the shear wall is the only lateral-resisting component. However, the collapse resistance of the RCFS shear wall system is effectively enhanced by the second defense, which is provided by a framework integrated by rigid beam-column joints and fixed column bases. The predicted collapse mode with maximum vulnerability index that was obtained by structural vulnerability analysis agrees well with the experimental result, and the structural vulnerability method is thereby verified to be reasonable to identify the weaknesses of framed structures and predict their collapse modes. Additionally, the quantitative vulnerability index indicates that the RCFS shear wall system exhibits better robustness compared to the traditional one. Furthermore, the “strong frame weak wallboard” and the “strong column weak beam” are proposed in this study as conceptional designations for the RCFS shear wall systems. Full article

(This article belongs to the Special Issue Applications of Thin-Walled Structures)

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7271 KiB

Open AccessArticle

Overload Control in Smart Transformer-Fed Grid

by Giovanni De Carne, Zhixiang Zou, Giampaolo Buticchi, Marco Liserre and Costas Vournas

Appl. Sci. 2017, 7(2), 208; https://doi.org/10.3390/app7020208 - 20 Feb 2017

Cited by 13 | Viewed by 6552

Abstract

Renewable energy resources and new loads—such as electric vehicles—challenge grid management. Among several scenarios, the smart transformer represents a solution for simultaneously managing low- and medium-voltage grids, providing ancillary services to the distribution grid. However, unlike conventional transformers, the smart transformer has a [...] Read more.

Renewable energy resources and new loads—such as electric vehicles—challenge grid management. Among several scenarios, the smart transformer represents a solution for simultaneously managing low- and medium-voltage grids, providing ancillary services to the distribution grid. However, unlike conventional transformers, the smart transformer has a very limited overload capability, because the junction temperature—which must always be below its maximum limit—is characterized by a short time constant. In this work, an overload control for smart transformer by means of voltage and frequency variations has been proposed and veriﬁed by means of simulations and experiments. Full article

(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems)

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5861 KiB

Open AccessArticle

Application of the DC Offset Cancellation Method and S Transform to Gearbox Fault Diagnosis

by Xinghui Zhang, Jianmin Zhao, Rusmir Bajrić and Liangliang Wang

Appl. Sci. 2017, 7(2), 207; https://doi.org/10.3390/app7020207 - 20 Feb 2017

Cited by 12 | Viewed by 5913

Abstract

In this paper, the direct current (DC) offset cancellation and S transform-based diagnosis method is verified using three case studies. For DC offset cancellation, correlated kurtosis (CK) is used instead of the cross-correlation coefficient in order to determine the optimal iteration number. Compared [...] Read more.

In this paper, the direct current (DC) offset cancellation and S transform-based diagnosis method is verified using three case studies. For DC offset cancellation, correlated kurtosis (CK) is used instead of the cross-correlation coefficient in order to determine the optimal iteration number. Compared to the cross-correlation coefficient, CK enhances the DC offset cancellation ability enormously because of its excellent periodic impulse signal detection ability. Here, it has been proven experimentally that it can effectively diagnose the implanted bearing fault. However, the proposed method is less effective in the case of simultaneously present bearing and gear faults, especially for extremely weak bearing faults. In this circumstance, the iteration number of DC offset cancellation is determined directly by the high-speed shaft gear mesh frequency order. For the planetary gearbox, the application of the proposed method differs from the fixed-axis gearbox, because of its complex structure. For those small fault frequency parts, such as planet gear and ring gear, the DC offset cancellation’s ability is less effective than for the fixed-axis gearbox. In these studies, the S transform is used to display the time-frequency characteristics of the DC offset cancellation processed results; the performances are evaluated, and the discussions are given. The fault information can be more easily observed in the time-frequency contour than the frequency domain. Full article

(This article belongs to the Special Issue Deep Learning Based Machine Fault Diagnosis and Prognosis)

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2168 KiB

Open AccessArticle

LED Current Balance Using a Variable Voltage Regulator with Low Dropout vDS Control

by Hung-I Hsieh and Hao Wang

Appl. Sci. 2017, 7(2), 206; https://doi.org/10.3390/app7020206 - 20 Feb 2017

Cited by 5 | Viewed by 6652

Abstract

A cost-effective light-emitting diode (LED) current balance strategy using a variable voltage regulator (VVR) with low dropout vDS control is proposed. This can regulate the multiple metal-oxide-semiconductor field-effect transistors (MOSFETs) of the linear current regulators (LCR), maintaining low dropout vDS on the flat [...] Read more.

A cost-effective light-emitting diode (LED) current balance strategy using a variable voltage regulator (VVR) with low dropout vDS control is proposed. This can regulate the multiple metal-oxide-semiconductor field-effect transistors (MOSFETs) of the linear current regulators (LCR), maintaining low dropout vDS on the flat vGS-characteristic curves and making all drain currents almost the same. Simple group LCRs respectively loaded with a string LED are employed to implement the theme. The voltage VVdc from a VVR is synthesized by a string LED voltage NvD, source voltage vR, and a specified low dropout vDS = VQ. The VVdc updates instantly, through the control loop of the master LCR, which means that all slave MOSFETs have almost the same biases on their flat vGS-characteristic curves. This leads to all of the string LED currents being equal to each other, producing an almost even luminance. An experimental setup with microchip control is built to verify the estimations. Experimental results show that the luminance of all of the string LEDs are almost equal to one another, with a maximum deviation below 1% during a wide dimming range, while keeping all vDS of the MOSFETs at a low dropout voltage, as expected. Full article

(This article belongs to the Special Issue Energy Saving)

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2988 KiB

Open AccessArticle

Microwave-Assisted Synthesis of SiC Nanoparticles for the Efficient Adsorptive Removal of Nitroimidazole Antibiotics from Aqueous Solution

by Ali Fakhri, Sahar Rashidi, Mohammad Asif and Ahmed A. Ibrahim

Appl. Sci. 2017, 7(2), 205; https://doi.org/10.3390/app7020205 - 20 Feb 2017

Cited by 26 | Viewed by 4617

Abstract

Environmental pollution caused by the improper disposal of pharmaceuticals is a matter of global concern, and warrants immediate attention. Of particular concern is the aquatic contamination caused by the increasing use of antibiotics, which could give rise to superbugs. While researchers have mainly [...] Read more.

Environmental pollution caused by the improper disposal of pharmaceuticals is a matter of global concern, and warrants immediate attention. Of particular concern is the aquatic contamination caused by the increasing use of antibiotics, which could give rise to superbugs. While researchers have mainly focused on improving the adsorption capacity of mostly activated carbon-based adsorbents, we have developed a non-conventional adsorbent (SiC nanoparticles) in the present work for the adsorptive removal of four different nitroimidazole antibiotics, namely metronidazole (MNZ), dimetridazole (DMZ), ronidazole (RNZ), and tinidazole (TNZ). In addition to the unique properties which are inherent to SiC, the present adsorbent not only possesses a high adsorption capacity, but also shows one of the highest adsorption rates; both of which are prerequisites for an efficient and cost-effective adsorption-based separation technology. Silicon carbide (SiC) nanoparticles, synthesized by a microwave-assisted method, were thoroughly characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and the Brunauer–Emmett–Teller method. The adsorption isotherm data were accurately described by the Langmuir isotherm model. On the other hand, the adsorption kinetics, closely represented by the pseudo-second order kinetic model, were faster than most previously reported adsorbents. The reaction rate constants were 0.0089, 0.0079, 0.0072, and 0.0055 g/(mg min), for MNZ, DMZ, RNZ, and TNZ, respectively. Full article

(This article belongs to the Section Chemical and Molecular Sciences)

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X-ray diffraction pattern of SiC nanoparticles. Full article ">Figure 2
Transmission electron microscopy (TEM) (A) and scanning electron microscopy (SEM) images (B) of SiC nanoparticles. Full article ">Figure 3
Effects of contact time on the adsorption of nitroimidazoles onto SiC NPs (C0 = 30 mg/L, T = 25 °C; adsorbent dose = 0.1 g, pH = 8). Full article ">Figure 4
Effects of initial pH on the adsorption of nitroimidazoles onto SiC NPs (C0 = 30 mg/L, T = 25 °C, adsorbent dose = 0.1 g). Full article ">Figure 5
Langmuir model for nitroimidazole adsorption onto SiC NPs (T = 25 °C; adsorbent dose = 0.1 g, pH = 8). Full article ">Figure 6
Pseudo-second order kinetic model for nitroimidazole adsorption onto SiC NPs (C0 = 30 mg/L, T = 25 °C; adsorbent dose = 0.1 g, pH = 8). Full article ">

2811 KiB

Open AccessArticle

Preliminary Study on the Damping Effect of a Lateral Damping Buffer under a Debris Flow Load

by Zheng Lu, Yuling Yang, Xilin Lu and Chengqing Liu

Appl. Sci. 2017, 7(2), 201; https://doi.org/10.3390/app7020201 - 20 Feb 2017

Cited by 40 | Viewed by 5993

Abstract

Simulating the impact of debris flows on structures and exploring the feasibility of applying energy dissipation devices or shock isolators to reduce the damage caused by debris flows can make great contribution to the design of disaster prevention structures. In this paper, we [...] Read more.

Simulating the impact of debris flows on structures and exploring the feasibility of applying energy dissipation devices or shock isolators to reduce the damage caused by debris flows can make great contribution to the design of disaster prevention structures. In this paper, we propose a new type of device, a lateral damping buffer, to reduce the vulnerability of building structures to debris flows. This lateral damping buffer has two mechanisms of damage mitigation: when debris flows impact on a building, it acts as a buffer, and when the structure vibrates due to the impact, it acts as a shock absorber, which can reduce the maximum acceleration response and subsequent vibration respectively. To study the effectiveness of such a lateral damping buffer, an impact test is conducted, which mainly involves a lateral damping buffer attached to a two-degree-of-freedom structure under a simulated debris flow load. To enable the numerical study, the equation of motion of the structure along with the lateral damping buffer is derived. A subsequent parametric study is performed to optimize the lateral damping buffer. Finally, a practical design procedure is also provided. Full article

(This article belongs to the Special Issue Energy Dissipation and Vibration Control: Modeling, Algorithm and Devices)

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499 KiB

Open AccessArticle

An Adaptive Buffering Scheme for P2P Live and Time-Shifted Streaming

by Eunsam Kim, Taeyoung Kim and Choonhwa Lee

Appl. Sci. 2017, 7(2), 204; https://doi.org/10.3390/app7020204 - 18 Feb 2017

Cited by 4 | Viewed by 4839

Abstract

Recently, P2P streaming techniques have been a promising solution to a large-scale live streaming system because of their high scalability and low installation cost. In P2P live streaming systems, however, it is difficult to manage peers’ buffers effectively, because they can buffer only [...] Read more.

Recently, P2P streaming techniques have been a promising solution to a large-scale live streaming system because of their high scalability and low installation cost. In P2P live streaming systems, however, it is difficult to manage peers’ buffers effectively, because they can buffer only a limited amount of data around a live broadcasting time in the main memory and suffer from long playback lag due to the nature of P2P structures. In addition, the number of peers decreases rapidly as the playback position moves further from this time by performing time-shifted viewing. These situations widen the distribution of peers’ playback positions, thereby decreasing the degree of data duplication among peers. Moreover, it is hard to use each peer’s buffer as the caching area because the buffer area where the chunks that have already been played back are stored can be overwritten at any time by new chunks that will arrive soon. In this paper, we therefore propose a novel buffering scheme to significantly increase data duplication in buffering periods among peers in P2P live and time-shifted streaming systems. In our proposed scheme, the buffer ratio of each peer is adaptively adjusted according to its relative playback position in a group by increasing the ratio of the caching area in its buffer as its playback position moves earlier in time and increasing the ratio of the prefetching area as its playback position moves later. Through extensive simulations, we demonstrate that our proposed adaptive buffering scheme outperforms the conventional buffering technique considerably in terms of startup delay, average jitter ratio, and the ratio of necessary chunks in a buffermap. Full article

(This article belongs to the Special Issue High-Performance and Parallel Computer Systems: Design and Algorithms)

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3554 KiB

Open AccessArticle

Fuzzy Synthetic Evaluation of the Long-Term Health of Tunnel Structures

by Bo Wang, Chencong Mo, Chuan He and Qixiang Yan

Appl. Sci. 2017, 7(2), 203; https://doi.org/10.3390/app7020203 - 17 Feb 2017

Cited by 23 | Viewed by 5622

Abstract

A tunnel is a coupled system of the surrounding rock and the supporting structure. The health status of a tunnel structure is complex and is influenced by various factors. In addition, these factors are coupled and interacted with each other, which calls for [...] Read more.

A tunnel is a coupled system of the surrounding rock and the supporting structure. The health status of a tunnel structure is complex and is influenced by various factors. In addition, these factors are coupled and interacted with each other, which calls for the linguistic description of the tunnel safety level. In this paper, we describe the health status of a highway tunnel structure in terms of four levels: safe; basically safe; potentially unsafe and unsafe. Based on the analysis of the safety characteristics of the tunnel structure and its proposed safety level, this research develops a multi-level fuzzy synthetic evaluation model for the long-term safety evaluation system of a tunnel structure. The Cang Ling Tunnel, which has embedded sensors to measure the stress values of the secondary lining and the contact pressure, is used as an example to study the proposed method. The results show that the structure of the entire Cang Ling Tunnel is in almost a safe condition under the current conditions, which is consistent with the actual operational situation. Full article

(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)

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6766 KiB

Open AccessArticle

Numerical Study on the Asphalt Concrete Structure for Blast and Impact Load Using the Karagozian and Case Concrete Model

by Jun Wu, Liang Li, Xiuli Du and Xuemei Liu

Appl. Sci. 2017, 7(2), 202; https://doi.org/10.3390/app7020202 - 17 Feb 2017

Cited by 18 | Viewed by 6501

Abstract

The behaviour of an asphalt concrete structure subjected to severe loading, such as blast and impact loadings, is becoming critical for safety and anti-terrorist reasons. With the development of high-speed computational capabilities, it is possible to carry out the numerical simulation of an [...] Read more.

The behaviour of an asphalt concrete structure subjected to severe loading, such as blast and impact loadings, is becoming critical for safety and anti-terrorist reasons. With the development of high-speed computational capabilities, it is possible to carry out the numerical simulation of an asphalt concrete structure subjected to blast or impact loading. In the simulation, the constitutive model plays a key role as the model defines the essential physical mechanisms of the material under different stress and loading conditions. In this paper, the key features of the Karagozian and Case concrete model (KCC) adopted in LSDYNA are evaluated and discussed. The formulations of the strength surfaces and the damage factor in the KCC model are verified. Both static and dynamic tests are used to determine the parameters of asphalt concrete in the KCC model. The modified damage factor is proposed to represent the higher failure strain that can improve the simulation of the behaviour of AC material. Furthermore, a series test of the asphalt concrete structure subjected to blast and impact loadings is conducted and simulated by using the KCC model. The simulation results are then compared with those from both field and laboratory tests. The results show that the use of the KCC model to simulate asphalt concrete structures can reproduce similar results as the field and laboratory test. Full article

(This article belongs to the Special Issue Advanced Asphalt Materials and Paving Technologies)

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3550 KiB

Open AccessArticle

Comparative Interactions of Dihydroquinazolin Derivatives with Human Serum Albumin Observed via Multiple Spectroscopy

by Yi Wang, Meiqing Zhu, Jia Liu, Risong Na, Feng Liu, Xiangwei Wu, Shisuo Fan, Zhen Wang, Dandan Pan, Jun Tang, Qing X. Li, Rimao Hua and Shangzhong Liu

Appl. Sci. 2017, 7(2), 200; https://doi.org/10.3390/app7020200 - 17 Feb 2017

Cited by 9 | Viewed by 4731

Abstract

The interactions of dihydroquinazolines with human serum albumin (HSA) were studied in pH 7.4 aqueous solution via fluorescence, circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopic techniques. In this work, 6-chloro-1-(3,3-dimethyl-butanoyl)-2(un)substitutedphenyl-2,3-dihydroquinazolin-4(1H)-one (PDQL) derivatives were designed and synthesized to study the impact of [...] Read more.

The interactions of dihydroquinazolines with human serum albumin (HSA) were studied in pH 7.4 aqueous solution via fluorescence, circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopic techniques. In this work, 6-chloro-1-(3,3-dimethyl-butanoyl)-2(un)substitutedphenyl-2,3-dihydroquinazolin-4(1H)-one (PDQL) derivatives were designed and synthesized to study the impact of five similar substituents (methyl, methoxy, cyano, trifluoromethyl and isopropyl) on the interactions between PDQL and HSA using a comparative methodology. The results revealed that PDQL quenched the intrinsic fluorescence of HSA through a static quenching process. Displacement experiments with site-specific markers revealed that PDQL binds to HSA at site II (subdomain IIIA) and that there may be only one binding site for PDQL on HSA. The thermodynamic parameters indicated that hydrophobic interactions mainly drove the interactions between PDQL and HSA. The substitution using five similar groups in the benzene ring could increase the interactions between PDQL and HSA to some extent through the van der Waals force or hydrogen bond effects in the proper temperature range. Isopropyl substitution could particularly enhance the binding affinity, as observed via comparative studies Full article

(This article belongs to the Section Chemical and Molecular Sciences)

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Graphical abstract
Full article ">Figure 1
Synthetic route for 6-chloro-1-(3,3-dimethyl-butanoyl)-2-(un)substituted phenyl-2,3-dihydroquinazolin-4(1H)-one (PDQL). Full article ">Figure 2
Fluorescence quenching spectra of HSA in the presence of different concentrations of PDQL at 298 K. λex = 280 nm; the HSA concentration was 1.0 × 10−6 M; (a–i) PDQL concentrations (×10−6 M) were 0.000, 1.333, 2.667, 4.000, 5.333, 6.667, 8.000, 9.333 and 10.667, respectively. (x) 1.0 × 10−6 M PDQL only. Full article ">Figure 3
The Stern-Volmer plots for the fluorescence quenching of HSA by PDQL. Full article ">Figure 4
Modified Stern-Volmer plots of PDQL-HSA systems. Full article ">Figure 5
Far-UV circular dichroism (CD) spectra of the PDQL-HSA system: CHSA = 1.0 × 10−6 M and 1.0 × 10−6 M HSA + 2.0 × 10−6 M PDQL. Full article ">Figure 6
FTIR spectra of free HSA (1.0 × 10−5 M) and the PDQL-HSA complex ((PDQL) = 2.0 × 10−5 M). Full article ">

4115 KiB

Open AccessArticle

Surface Quality of Staggered PCD End Mill in Milling of Carbon Fiber Reinforced Plastics

by Guangjun Liu, Hongyuan Chen, Zhen Huang, Fei Gao and Tao Chen

Appl. Sci. 2017, 7(2), 199; https://doi.org/10.3390/app7020199 - 17 Feb 2017

Cited by 24 | Viewed by 6446

Abstract

Machined surface quality determines the reliability, wear resistance and service life of carbon fiber reinforced plastic (CFRP) workpieces. In this work, the formation mechanism of the surface topography and the machining defects of CFRPs are proposed, and the influence of milling parameters and [...] Read more.

Machined surface quality determines the reliability, wear resistance and service life of carbon fiber reinforced plastic (CFRP) workpieces. In this work, the formation mechanism of the surface topography and the machining defects of CFRPs are proposed, and the influence of milling parameters and fiber cutting angles on the surface quality of CFRPs is obtained, which can provide a reference for extended tool life and good surface quality. Trimming and slot milling tests of unidirectional CFRP laminates are performed. The surface roughness of the machined surface is measured, and the influence of milling parameters on the surface roughness is analyzed. A regression model for the surface roughness of CFRP milling is established. A significance test of the regression model is conducted. The machined surface topography of milling CFRP unidirectional laminates with different fiber orientations is analyzed, and the effect of fiber cutting angle on the surface topography of the machined surface is presented by using a digital super depth-of-field microscope and scanning electron microscope (SEM). To study the influence of fiber cutting angle on machining defects, the machined topography under different fiber orientations is analyzed. The slot milling defects and their formation mechanism under different fiber cutting angles are investigated. Full article

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5517 KiB

Open AccessArticle

Experimental Investigation on Soft Galloping and Hard Galloping of Triangular Prisms

by Jijian Lian, Xiang Yan, Fang Liu, Jun Zhang, Quanchao Ren and Xu Yang

Appl. Sci. 2017, 7(2), 198; https://doi.org/10.3390/app7020198 - 17 Feb 2017

Cited by 25 | Viewed by 4716

Abstract

The studies currently on soft galloping (SG) and hard galloping (HG) are scarce. In this study, SG and HG of spring-mounted triangular prisms in a water channel are investigated experimentally. A power take-off system (PTO), a spring system, additional weights, and different triangular [...] Read more.

The studies currently on soft galloping (SG) and hard galloping (HG) are scarce. In this study, SG and HG of spring-mounted triangular prisms in a water channel are investigated experimentally. A power take-off system (PTO), a spring system, additional weights, and different triangular prisms were used to achieve the variations in damping coefficient c, system stiffness K, oscillation mass m and section aspect ratios α, respectively. The present paper proves that the VIV (vortex-induced vibration) lower branch can be observed in the SG response. In SG response, VIV branches are incomplete while the galloping branch is complete, and galloping can be self-initiated only in the self-excited region. On the contrary, in HG response, VIV branches are complete, the galloping branch is incomplete, and galloping can only be initiated by external excitation at a velocity exceeding the critical velocity. As c and m increase, or K and α decrease, the oscillation mode of a triangular prism gradually transitions from SG to CG (critical galloping), and continues to HG. The amplitude in VIV branch is the main reason causing the onset of galloping in SG response. A critical damping coefficient c_c, which is dependent on m, K and α, is proposed to predict the occurrences of SG, CG and HG. When c < c_c, SG occurs; when c > c_c, HG occurs; when c = c_c, CG occurs. Full article

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6165 KiB

Open AccessArticle

Surrogate Based Optimization of Aerodynamic Noise for Streamlined Shape of High Speed Trains

by Zhenxu Sun, Ye Zhang and Guowei Yang

Appl. Sci. 2017, 7(2), 196; https://doi.org/10.3390/app7020196 - 17 Feb 2017

Cited by 21 | Viewed by 7536

Abstract

Aerodynamic noise increases with the sixth power of the running speed. As the speed increases, aerodynamic noise becomes predominant and begins to be the main noise source at a certain high speed. As a result, aerodynamic noise has to be focused on when [...] Read more.

Aerodynamic noise increases with the sixth power of the running speed. As the speed increases, aerodynamic noise becomes predominant and begins to be the main noise source at a certain high speed. As a result, aerodynamic noise has to be focused on when designing new high-speed trains. In order to perform the aerodynamic noise optimization, the equivalent continuous sound pressure level (SPL) has been used in the present paper, which could take all of the far field observation probes into consideration. The Non-Linear Acoustics Solver (NLAS) approach has been utilized for acoustic calculation. With the use of Kriging surrogate model, a multi-objective optimization of the streamlined shape of high-speed trains has been performed, which takes the noise level in the far field and the drag of the whole train as the objectives. To efficiently construct the Kriging model, the cross validation approach has been adopted. Optimization results reveal that both the equivalent continuous sound pressure level and the drag of the whole train are reduced in a certain extent. Full article

(This article belongs to the Special Issue Advances in Vibroacoustics and Aeroacustics of Aerospace and Automotive Systems)

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3869 KiB

Open AccessArticle

Dielectric Characterization of Chinese Standard Concrete for Compressive Strength Evaluation

by Kwok L. Chung, Lei Yuan, Songtao Ji, Li Sun, Chengping Qu and Chunwei Zhang

Appl. Sci. 2017, 7(2), 177; https://doi.org/10.3390/app7020177 - 17 Feb 2017

Cited by 34 | Viewed by 8337

Abstract

Dielectric characterization of concrete is essential for the wireless structural health monitoring (SHM) of concrete structures. Guo Biao (GB) concrete refers to the concrete mixed and cast in accordance with the Chinese standard. Currently, China is the largest producer and consumer of concrete [...] Read more.

Dielectric characterization of concrete is essential for the wireless structural health monitoring (SHM) of concrete structures. Guo Biao (GB) concrete refers to the concrete mixed and cast in accordance with the Chinese standard. Currently, China is the largest producer and consumer of concrete in the world. However, minimal attention has been paid to the dielectric properties of GB concrete. This paper presents the results of the dielectric constant of GB concrete, where three regression models have been used to present the measurement data from 10 MHz to 6 GHz. The objective is to provide a data set of nominal values of the dielectric constant for ordinary GB concrete. The final goal is to facilitate a compressive strength evaluation via the measured dielectric constant. Measurements of the dielectric constant and compressive strength for five types of ordinary concrete have been undertaken, after 28 days of curing. As the main contribution in this work, the correlation model between the compressive strength and dielectric constant of GB concrete is realized. Full article

(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)

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A big picture illustrating the cross-disciplinary work for compressive strength evaluation, using the dielectric constant of 28-day cement concrete. Full article ">Figure 2
Photographs for GB concrete mixing and casting: (a) anchor type of concrete mixer; (b) elimination of entrapped air from specimens using vibration table. Full article ">Figure 3
Experimental setup of dielectric constant measurement. Full article ">Figure 4
Measured average compressive strength and standard deviation versus w/c ratio. Full article ">Figure 5
Average values of the measured dielectric constant versus frequency. Full article ">Figure 6
Dielectric characterization of GB concrete via curve fitting to measured data using the first-order exponential model, Debye model, and Jonscher model, expressed in (a) linear scale; (b) log-frequency scale. Full article ">Figure 7
Dielectric constant versus water-to-cement ratio of GB concrete. Full article ">Figure 8
Compressive strength versus dielectric constant of GB concrete, (a) at various frequencies; (b) at 2.45 GHz with both the standard deviations from measurement. Full article ">

2548 KiB

Open AccessArticle

Simulation of Hybrid Photovoltaic Solar Assisted Loop Heat Pipe/Heat Pump System

by Nannan Dai, Xinyi Xu, Shuhong Li and Zheng Zhang

Appl. Sci. 2017, 7(2), 197; https://doi.org/10.3390/app7020197 - 16 Feb 2017

Cited by 26 | Viewed by 6712

Abstract

A hybrid photovoltaic solar assisted loop heat pipe/heat pump (PV-SALHP/HP) water heater system has been developed and numerically studied. The system is the combination of loop heat pipe (LHP) mode and heat pump (HP) mode, and the two modes can be run separately [...] Read more.

A hybrid photovoltaic solar assisted loop heat pipe/heat pump (PV-SALHP/HP) water heater system has been developed and numerically studied. The system is the combination of loop heat pipe (LHP) mode and heat pump (HP) mode, and the two modes can be run separately or compositely according to the weather conditions. The performances of independent heat pump (HP) mode and hybrid loop heat pipe/heat pump (LHP/HP) mode were simulated and compared. Simulation results showed that on typical sunny days in spring or autumn, using LHP/HP mode could save 40.6% power consumption than HP mode. In addition, the optimal switchover from LHP mode to HP mode was analyzed in different weather conditions for energy saving and the all-year round operating performances of the system were also simulated. The simulation results showed that hybrid LHP/HP mode should be utilized to save electricity on sunny days from March to November and the system can rely on LHP mode alone without any power consumption in July and August. When solar radiation and ambient temperature are low in winter, HP mode should be used Full article

(This article belongs to the Special Issue Sciences in Heat Pump and Refrigeration)

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7686 KiB

Open AccessArticle

Time-Sequential Working Wavelength-Selective Filter for Flat Autostereoscopic Displays

by René De la Barré, Roland Bartmann, Silvio Jurk, Mathias Kuhlmey, Bernd Duckstein, Arno Seeboth, Detlef Lötzsch, Christian Rabe, Peter Frach, Hagen Bartzsch, Matthias Gittner, Stefan Bruns, Gerhard Schottner and Johanna Fischer

Appl. Sci. 2017, 7(2), 194; https://doi.org/10.3390/app7020194 - 16 Feb 2017

Cited by 4 | Viewed by 6347

Abstract

A time-sequential working, spatially-multiplexed autostereoscopic 3D display design consisting of a fast switchable RGB-color filter array and a fast color display is presented. The newly-introduced 3D display design is usable as a multi-user display, as well as a single-user system. The wavelength-selective filter [...] Read more.

A time-sequential working, spatially-multiplexed autostereoscopic 3D display design consisting of a fast switchable RGB-color filter array and a fast color display is presented. The newly-introduced 3D display design is usable as a multi-user display, as well as a single-user system. The wavelength-selective filter barrier emits the light from a larger aperture than common autostereoscopic barrier displays with similar barrier pitch and ascent. Measurements on a demonstrator with commercial display components, simulations and computational evaluations have been carried out to describe the proposed wavelength-selective display design in static states and to show the weak spots of display filters in commercial displays. An optical modelling of wavelength-selective barriers has been used for instance to calculate the light ray distribution properties of that arrangement. In the time-sequential implementation, it is important to avoid that quick eye or eyelid movement leads to visible color artifacts. Therefore, color filter cells, switching faster than conventional LC display cells, must distribute directed light from different primaries at the same time, to create a 3D presentation. For that, electric tunable liquid crystal Fabry–Pérot color filters are presented. They switch on-off the colors red, green and blue in the millisecond regime. Their active areas consist of a sub-micrometer-thick nematic layer sandwiched between dielectric mirrors and indium tin oxide (ITO)-electrodes. These cells shall switch narrowband light of red, green or blue. A barrier filter array for a high resolution, glasses-free 3D display has to be equipped with several thousand switchable filter elements having different color apertures. Full article

(This article belongs to the Special Issue Optical Modulators and Switches)

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4003 KiB

Open AccessArticle

Comparison of Oil Spill Classifications Using Fully and Compact Polarimetric SAR Images

by Yuanzhi Zhang, Yu Li, X. San Liang and Jinyeu Tsou

Appl. Sci. 2017, 7(2), 193; https://doi.org/10.3390/app7020193 - 16 Feb 2017

Cited by 32 | Viewed by 6194

Abstract

In this paper, we present a comparison between several algorithms for oil spill classifications using fully and compact polarimetric SAR images. Oil spill is considered as one of the most significant sources of marine pollution. As a major difficulty of SAR-based oil spill [...] Read more.

In this paper, we present a comparison between several algorithms for oil spill classifications using fully and compact polarimetric SAR images. Oil spill is considered as one of the most significant sources of marine pollution. As a major difficulty of SAR-based oil spill detection algorithms is the classification between mineral and biogenic oil, we focus on quantitatively analyzing and comparing fully and compact polarimetric satellite synthetic aperture radar (SAR) modes to detect hydrocarbon slicks over the sea surface, discriminating them from weak-damping surfactants, such as biogenic slicks. The experiment was conducted on quad-pol SAR data acquired during the Norwegian oil-on-water experiment in 2011. A universal procedure was used to extract the features from quad-, dual- and compact polarimetric SAR modes to rank different polarimetric SAR modes and common supervised classifiers. Among all the dual- and compact polarimetric SAR modes, the π/2 mode has the best performance. The best supervised classifiers vary and depended on whether sufficient polarimetric information can be obtained in each polarimetric mode. We also analyzed the influence of the number of polarimetric parameters considered as inputs for the supervised classifiers, onto the detection/discrimination performance. We discovered that a feature set with four features is sufficient for most polarimetric feature-based oil spill classifications. Moreover, dimension reduction algorithms, including principle component analysis (PCA) and the local linear embedding (LLE) algorithm, were employed to learn low dimensional and distinctive information from quad-polarimetric SAR features. The performance of the new feature sets has comparable performance in oil spill classification. Full article

(This article belongs to the Special Issue Polarimetric SAR Techniques and Applications)

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2708 KiB

Open AccessArticle

Recognition Algorithm Based on Improved FCM and Rough Sets for Meibomian Gland Morphology

by Fengmei Liang, Yajun Xu, Weixin Li, Xiaoling Ning, Xueou Liu and Ajian Liu

Appl. Sci. 2017, 7(2), 192; https://doi.org/10.3390/app7020192 - 16 Feb 2017

Cited by 12 | Viewed by 4819

Abstract

To overcome the limitation of artificial judgment of meibomian gland morphology, we proposed a solution based on an improved fuzzy c-means (FCM) algorithm and rough sets theory. The rough sets reduced the redundant attributes while ensuring classification accuracy, and greatly reduced the amount [...] Read more.

To overcome the limitation of artificial judgment of meibomian gland morphology, we proposed a solution based on an improved fuzzy c-means (FCM) algorithm and rough sets theory. The rough sets reduced the redundant attributes while ensuring classification accuracy, and greatly reduced the amount of computation to achieve information dimension compression and knowledge system simplification. However, before this reduction, data must be discretized, and this process causes some degree of information loss. Therefore, to maintain the integrity of the information, we used the improved FCM to make attributes fuzzy instead of discrete before continuing with attribute reduction, and thus, the implicit knowledge and decision rules were more accurate. Our algorithm overcame the defects of the traditional FCM algorithm, which is sensitive to outliers and easily falls into local optima. Our experimental results show that the proposed method improved recognition efficiency without degrading recognition accuracy, which was as high as 97.5%. Furthermore, the meibomian gland morphology was diagnosed efficiently, and thus this method can provide practical application values for the recognition of meibomian gland morphology. Full article

(This article belongs to the Special Issue Smart Healthcare)

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2782 KiB

Open AccessArticle

FE Model Updating on an In-Service Self-Anchored Suspension Bridge with Extra-Width Using Hybrid Method

by Zhiyuan Xia, Aiqun Li, Jianhui Li and Maojun Duan

Appl. Sci. 2017, 7(2), 191; https://doi.org/10.3390/app7020191 - 16 Feb 2017

Cited by 10 | Viewed by 4422

Abstract

Nowadays, many more bridges with extra-width have been needed for vehicle throughput. In order to obtain a precise finite element (FE) model of those complex bridge structures, the practical hybrid updating method by integration of Gaussian mutation particle swarm optimization (GMPSO), Kriging meta-model [...] Read more.

Nowadays, many more bridges with extra-width have been needed for vehicle throughput. In order to obtain a precise finite element (FE) model of those complex bridge structures, the practical hybrid updating method by integration of Gaussian mutation particle swarm optimization (GMPSO), Kriging meta-model and Latin hypercube sampling (LHS) was proposed. By demonstrating the efficiency and accuracy of the hybrid method through the model updating of a damaged simply supported beam, the proposed method was applied to the model updating of a self-anchored suspension bridge with extra-width which showed great necessity considering the results of ambient vibration test. The results of bridge model updating showed that both of the mode frequencies and shapes had relatively high agreement between the updated model and experimental structure. The successful model updating of this bridge fills in the blanks of model updating of a complex self-anchored suspension bridge. Moreover, the updating process enables other model updating issues for complex bridge structures Full article

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3244 KiB

Open AccessArticle

Block Recovery Rate-Based Unequal Error Protection for Three-Screen TV

by Hojin Ha and Eun-Seok Ryu

Appl. Sci. 2017, 7(2), 186; https://doi.org/10.3390/app7020186 - 16 Feb 2017

Viewed by 4239

Abstract

This paper describes a three-screen television system using a block recovery rate (BRR)-based unequal error protection (UEP). The proposed in-home wireless network uses scalable video coding (SVC) and UEP with forward error correction (FEC) for maximizing the quality of service (QoS) over error-prone [...] Read more.

This paper describes a three-screen television system using a block recovery rate (BRR)-based unequal error protection (UEP). The proposed in-home wireless network uses scalable video coding (SVC) and UEP with forward error correction (FEC) for maximizing the quality of service (QoS) over error-prone wireless networks. For efficient FEC packet assignment, this paper proposes a simple and efficient performance metric, a BRR which is defined as a recovery rate of temporal and quality layer from FEC assignment by analyzing the hierarchical prediction structure including the current packet loss. It also explains the SVC layer switching scheme according to network conditions such as packet loss rate (PLR) and available bandwidth (ABW). In the experiments conducted, gains in video quality with the proposed UEP scheme vary from 1 to 3 dB in Y-peak signal-to-noise ratio (PSNR) with corresponding subjective video quality improvements. Full article

(This article belongs to the Special Issue Selected Papers from the International Multi-Conference on Engineering and Technology Innovation 2015 (IMETI2015))

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4000 KiB

Open AccessArticle

Self-Tuning Fuzzy Control for Seismic Protection of Smart Base-Isolated Buildings Subjected to Pulse-Type Near-Fault Earthquakes

by Dahai Zhao, Yang Liu and Hongnan Li

Appl. Sci. 2017, 7(2), 185; https://doi.org/10.3390/app7020185 - 16 Feb 2017

Cited by 12 | Viewed by 6414

Abstract

Pulse-type near-fault earthquakes have obvious long-duration pulses, so they can cause large deformation in a base-isolated system in contrast to non-pulse-type near-fault and far-field earthquakes. This paper proposes a novel self-tuning fuzzy logic control strategy for seismic protection of a base-isolated system, which [...] Read more.

Pulse-type near-fault earthquakes have obvious long-duration pulses, so they can cause large deformation in a base-isolated system in contrast to non-pulse-type near-fault and far-field earthquakes. This paper proposes a novel self-tuning fuzzy logic control strategy for seismic protection of a base-isolated system, which can operate the control force of the piezoelectric friction damper against different types of earthquakes. This control strategy employs a hierarchic control algorithm, in which a higher-level supervisory fuzzy controller is implemented to adjust the input normalization factors and output scaling factor, while a sub-level fuzzy controller effectively determines the command voltage of the piezoelectric friction damper according to current level of earthquakes. The efficiency of the proposed control strategy is also compared with uncontrolled and maximum passive cases. Numerical results reveal that the novel fuzzy logic control strategy can effectively reduce the isolation system deformations without the loss of potential advantages of base-isolated system. Full article

(This article belongs to the Special Issue Energy Dissipation and Vibration Control: Modeling, Algorithm and Devices)

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1363 KiB

Open AccessArticle

Design and Cooling Performances of an Air Conditioning System with Two Parallel Refrigeration Cycles for a Special Purpose Vehicle

by Moo-Yeon

Appl. Sci. 2017, 7(2), 190; https://doi.org/10.3390/app7020190 - 15 Feb 2017

Cited by 3 | Viewed by 8843

Abstract

The objective of this study is to design and briefly investigate the cooling performances of an air conditioning system for a special purpose vehicle under various experimental conditions. An air conditioning system with two parallel refrigeration cycles consisting of two compressors and two [...] Read more.

The objective of this study is to design and briefly investigate the cooling performances of an air conditioning system for a special purpose vehicle under various experimental conditions. An air conditioning system with two parallel refrigeration cycles consisting of two compressors and two condensers for satisfying the required cooling performance of the special purpose vehicle was tested under extremely hot weather conditions and high thermal load conditions and then optimized by varying the refrigerant charge amount. The optimum refrigerant charge amount of the tested air conditioning system was 1200 g with the consideration of the cooling speed and cooling capacity. The indoor temperatures of the suggested air conditioning system at the refrigerant charge amounts of 1200 g, 1400 g, and 1600 g were 24.7 °C, 25.2 °C, and 26.4 °C, respectively, at the elapsed time of 300 s. The cooling time required to reach a 15.0°C inner temperature in the suggested air conditioning system increased by 13.3% with the decrease of the refrigerant charge amount from 1600 g to 1200 g. The cooling capacity and the coefficient of performance (COP) of the suggested air conditioning system increased by 37.9% and 10.9%, respectively, due to a decrease of the refrigerant charge amount from 1600 g to 1200 g. The observed cooling performance characteristics of the air conditioning system with two parallel refrigeration cycles means it could be suitable for cabin cooling of special purpose vehicles. In addition, the designed special air conditioning system with two parallel refrigeration cycles for a special purpose vehicle was built to ensure a sufficient cooling performance for equipped passengers. Full article

(This article belongs to the Section Energy Science and Technology)

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10162 KiB

Open AccessReview

Innovative Hyperspectral Imaging-Based Techniques for Quality Evaluation of Fruits and Vegetables: A Review

by Yuzhen Lu, Yuping Huang and Renfu Lu

Appl. Sci. 2017, 7(2), 189; https://doi.org/10.3390/app7020189 - 15 Feb 2017

Cited by 89 | Viewed by 12726

Abstract

New, non-destructive sensing techniques for fast and more effective quality assessment of fruits and vegetables are needed to meet the ever-increasing consumer demand for better, more consistent and safer food products. Over the past 15 years, hyperspectral imaging has emerged as a new [...] Read more.

New, non-destructive sensing techniques for fast and more effective quality assessment of fruits and vegetables are needed to meet the ever-increasing consumer demand for better, more consistent and safer food products. Over the past 15 years, hyperspectral imaging has emerged as a new generation of sensing technology for non-destructive food quality and safety evaluation, because it integrates the major features of imaging and spectroscopy, thus enabling the acquisition of both spectral and spatial information from an object simultaneously. This paper first provides a brief overview of hyperspectral imaging configurations and common sensing modes used for food quality and safety evaluation. The paper is, however, focused on the three innovative hyperspectral imaging-based techniques or sensing platforms, i.e., spectral scattering, integrated reflectance and transmittance, and spatially-resolved spectroscopy, which have been developed in our laboratory for property and quality evaluation of fruits, vegetables and other food products. The basic principle and instrumentation of each technique are described, followed by the mathematical methods for processing and extracting critical information from the acquired data. Applications of these techniques for property and quality evaluation of fruits and vegetables are then presented. Finally, concluding remarks are given on future research needs to move forward these hyperspectral imaging techniques. Full article

(This article belongs to the Special Issue Applications of Hyperspectral Imaging for Food and Agriculture)

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1821 KiB

Open AccessArticle

Strain Transfer Analysis of a Clamped Fiber Bragg Grating Sensor

by Li Sun, Chuang Li, Jun Li, Chunwei Zhang and Xiaosu Ding

Appl. Sci. 2017, 7(2), 188; https://doi.org/10.3390/app7020188 - 15 Feb 2017

Cited by 39 | Viewed by 4880

Abstract

Clamped fiber Bragg grating (FBG) sensors have been widely applied in engineering strain measurements due to their advantages of high flexibility and efficiency. However, due to the existence of the interlayer, the strain measured by the encapsulated FBG sensor is not equal to [...] Read more.

Clamped fiber Bragg grating (FBG) sensors have been widely applied in engineering strain measurements due to their advantages of high flexibility and efficiency. However, due to the existence of the interlayer, the strain measured by the encapsulated FBG sensor is not equal to the strain of the host material, which causes strain measurement errors. In this paper, the strain transfer analysis of a clamped FBG sensor based on the shear-lag theory is conducted to improve the accuracy of strain measurements. A novel theoretical model for the axial strain distribution of a clamped FBG sensor is proposed. It is also discussed how the gauge ratio and interlayer thickness affect the strain transfer rate. The accuracy of the proposed theoretical model is verified by experimental tensile tests. The theoretical value of the strain transfer rate matches well with the tested value. Full article

(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)

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2325 KiB

Open AccessArticle

Subcritical Water Extraction of Ursolic Acid from Hedyotis diffusa

by Shangzhen Xiao, Xingjun Xi, Fei Tang, Juan Dai, Jing Liu, Jiandu Lei and Luying Wang

Appl. Sci. 2017, 7(2), 187; https://doi.org/10.3390/app7020187 - 15 Feb 2017

Cited by 10 | Viewed by 6283

Abstract

An efficient and environmental-friendly extraction method has been developed for extraction of ursolic acid (UA) from Hedyotis diffusa by using subcritical water extraction (SWE). The experiments were carried out at different particle sizes (20–100 mesh), extraction temperature (120–200 °C), extraction time (10–50 min), [...] Read more.

An efficient and environmental-friendly extraction method has been developed for extraction of ursolic acid (UA) from Hedyotis diffusa by using subcritical water extraction (SWE). The experiments were carried out at different particle sizes (20–100 mesh), extraction temperature (120–200 °C), extraction time (10–50 min), solvent/solid ratio (20–40 mL/g), and extraction pressure (0.6–3.0 MPa). Response surface methodology (RSM) was employed to optimize SWE conditions, and the maximum UA yield was 6.45 mg/g material. Optimal conditions are as follows: Particle size of 80 mesh, extraction temperature at 157 °C and a solvent/solid ratio of 30 mL/g. The model of experimental response was proved to predict the experimental results very well and demonstrated that UA yield was mainly depended on solvent/solid ratio, followed by particle size and temperature. The purified extract was analyzed by electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). The acquired precursor ion was m/z 455.3532, which is consistent with calculated value of UA. Furthermore, different extraction methods, including maceration extraction, heat reflux extraction, ultrasonic extraction, microwave-assisted extraction, and SWE were comparatively analyzed, which indicated that SWE was a time-saving, cost-saving and environment-friendly extraction technology for extraction of UA from Hedyotis diffusa. Full article

(This article belongs to the Section Chemical and Molecular Sciences)

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770 KiB

Open AccessArticle

Calculation of Receiver Sensitivities in (Orthogonal) Subcarrier Multiplexing Microwave-Optical Links

by Fernando A. Gutiérrez, Eamonn P. Martin, Philip Perry, Andrew D. Ellis and Liam P. Barry

Appl. Sci. 2017, 7(2), 184; https://doi.org/10.3390/app7020184 - 15 Feb 2017

Cited by 1 | Viewed by 4486

Abstract

Microwave-based all-analogue (orthogonal) subcarrier multiplexing (SCM) permits a direct processing of baseband data at Gbit/s while achieving low power consumption, low latency, low cost, and tolerance to dispersion. A key figure of merit in any SCM link is the sensitivity in the receiver, [...] Read more.

Microwave-based all-analogue (orthogonal) subcarrier multiplexing (SCM) permits a direct processing of baseband data at Gbit/s while achieving low power consumption, low latency, low cost, and tolerance to dispersion. A key figure of merit in any SCM link is the sensitivity in the receiver, which depends on the transmitter, the link and the receiver. By analysing the impact of the nonlinearities of an optical IQ modulator in the presence of optical noise, sensitivities are mathematically estimated as a function of the optical modulation index (OMI) at the transmitter. The results are verified with simulations achieving a good agreement with the mathematical model. The theoretical model provided can be employed as a tool to predict the best achievable sensitivities and the optimum OMI in broadband SCM and orthogonal SCM links. Full article

(This article belongs to the Special Issue Optical Modulators and Switches)

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3855 KiB

Open AccessArticle

Towards a Hybrid Approach to Context Reasoning for Underwater Robots

by Xin Li, José-Fernán Martínez and Gregorio Rubio

Appl. Sci. 2017, 7(2), 183; https://doi.org/10.3390/app7020183 - 15 Feb 2017

Cited by 19 | Viewed by 5460

Abstract

Ontologies have been widely used to facilitate semantic interoperability and serve as a common information model in many applications or domains. The Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs) project, aiming to facilitate coordination and cooperation between heterogeneous underwater vehicles, also [...] Read more.

Ontologies have been widely used to facilitate semantic interoperability and serve as a common information model in many applications or domains. The Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs) project, aiming to facilitate coordination and cooperation between heterogeneous underwater vehicles, also adopts ontologies to formalize information that is necessarily exchanged between vehicles. However, how to derive more useful contexts based on ontologies still remains a challenge. In particular, the extreme nature of the underwater environment introduces uncertainties in context data, thus imposing more difficulties in context reasoning. None of the existing context reasoning methods could individually deal with all intricacies in the underwater robot field. To this end, this paper presents the first proposal applying a hybrid context reasoning mechanism that includes ontological, rule-based, and Multi-Entity Bayesian Network (MEBN) reasoning methods to reason about contexts and their uncertainties in the underwater robot field. The theoretical foundation of applying this reasoning mechanism in underwater robots is given by a case study on the oil spill monitoring. The simulated reasoning results are useful for further decision-making by operators or robots and they show that the consolidation of different reasoning methods is a promising approach for context reasoning in underwater robots. Full article

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5794 KiB

Open AccessFeature PaperArticle

Improving Liquid Entry Pressure of Polyvinylidene Fluoride (PVDF) Membranes by Exploiting the Role of Fabrication Parameters in Vapor-Induced Phase Separation VIPS and Non-Solvent-Induced Phase Separation (NIPS) Processes

by Faisal Abdulla AlMarzooqi, Muhammad Roil Bilad and Hassan Ali Arafat

Appl. Sci. 2017, 7(2), 181; https://doi.org/10.3390/app7020181 - 14 Feb 2017

Cited by 57 | Viewed by 10738

Abstract

Polyvinylidene fluoride (PVDF) is a popular polymer material for making membranes for several applications, including membrane distillation (MD), via the phase inversion process. Non-solvent-induced phase separation (NIPS) and vapor-induced phase separation (VIPS) are applied to achieve a porous PVDF membrane with low mass-transfer [...] Read more.

Polyvinylidene fluoride (PVDF) is a popular polymer material for making membranes for several applications, including membrane distillation (MD), via the phase inversion process. Non-solvent-induced phase separation (NIPS) and vapor-induced phase separation (VIPS) are applied to achieve a porous PVDF membrane with low mass-transfer resistance and high contact angle (hydrophobicity). In this work, firstly, the impacts of several preparation parameters on membrane properties using VIPS and NIPS were studied. Then, the performance of the selected membrane was assessed in a lab-scale direct-contact MD (DCMD) unit. The parametric study shows that decreasing PVDF concentration while increasing both relative humidity (RH) and exposure time increased the contact angle and bubble-point pore size (BP). Those trends were investigated further by varying the casting thickness. At higher casting thicknesses and longer exposure time (up to 7.5 min), contact angle (CA) increased but BP significantly decreased. The latter showed a dominant trend leading to liquid entry pressure (LEP) increase with thickness. Full article

(This article belongs to the Special Issue Membrane Distillation)

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