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Sensors, Volume 13, Issue 1 (January 2013) – 80 articles , Pages 1-1384

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1435 KiB  
Review
Nucleic Acids for Ultra-Sensitive Protein Detection
by Kris P. F. Janssen, Karel Knez, Dragana Spasic and Jeroen Lammertyn
Sensors 2013, 13(1), 1353-1384; https://doi.org/10.3390/s130101353 - 21 Jan 2013
Cited by 39 | Viewed by 11995
Abstract
Major advancements in molecular biology and clinical diagnostics cannot be brought about strictly through the use of genomics based methods. Improved methods for protein detection and proteomic screening are an absolute necessity to complement to wealth of information offered by novel, high-throughput sequencing [...] Read more.
Major advancements in molecular biology and clinical diagnostics cannot be brought about strictly through the use of genomics based methods. Improved methods for protein detection and proteomic screening are an absolute necessity to complement to wealth of information offered by novel, high-throughput sequencing technologies. Only then will it be possible to advance insights into clinical processes and to characterize the importance of specific protein biomarkers for disease detection or the realization of “personalized medicine”. Currently however, large-scale proteomic information is still not as easily obtained as its genomic counterpart, mainly because traditional antibody-based technologies struggle to meet the stringent sensitivity and throughput requirements that are required whereas mass-spectrometry based methods might be burdened by significant costs involved. However, recent years have seen the development of new biodetection strategies linking nucleic acids with existing antibody technology or replacing antibodies with oligonucleotide recognition elements altogether. These advancements have unlocked many new strategies to lower detection limits and dramatically increase throughput of protein detection assays. In this review, an overview of these new strategies will be given. Full article
(This article belongs to the Section Biosensors)
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<p>When trying to multiplex a typical ELISA, the risk of false positive detection due to immuno reagent cross-talk increases rapidly with increasing amounts of targeted analytes.</p> Full article ">
<p>A schematic overview of the topics under review.</p> Full article ">
<p>Schematic overview of (<b>A</b>) PCR, where an initial dsDNA template is first dehybridized, after which primers anneal to the ssDNA strands. These primers provide a 3′ extendable terminus that is used for polymerase synthesis of the complementary strand. Subsequent discrete cycles of dehybridization and primer extension lead to an exponential increase of amplicon. (<b>B</b>) In RCA, a primer anneals to a circular ssDNA template, often called a padlock probe, polymerase extension at the 3′ primer origin leads to a continuous synthesis of ssDNA amplicon that consists of concatenated complements of the original template, leading to a linear increase of amplicon.</p> Full article ">
<p>Schematic overview of IPCR where dsDNA is coupled to an antibody through the use of various linkers (<b>A</b>). Target binding (<b>B</b>) and subsequent amplification of the dsDNA label allows for sensitive quantification of the target (<b>C</b>).</p> Full article ">
<p>Different strategies for coupling antibodies and DNA for use in IPCR: (<b>I</b>) A Streptavidin-protein A chimera protein was used for labeling of the detection antibody with biotinylated DNA. (<b>II</b>) Universal IPCR uses biotinylated antibodies that are labeled with dsDNA through subsequent incubations with streptavidin and biotinylated dsDNA. (<b>III</b>) Direct coupling of antibodies and dsDNA can in some cases be achieved using chemical methods. (<b>IV</b>) Specialized coupling strategies exist where single- or multiple copies of labeling DNA are encapsulated inside of liposomes, supramolecular constructs or even phages. (<b>V</b>) Using readily available biofunctionalization strategies for micro- and nanoparticles, both the antibody and the labeling dsDNA can be immobilized on the surface of the particles, thus effectively achieving coupling between the two.</p> Full article ">
<p>Schematic representation of self-assembled oligomeric DNA-protein complexes used in IPCR. Mono- and bis-biotinylated dsDNA was mixed with equimolar amounts of streptaidin to generate oligomeric DNA-streptavidin complexes. The resulting DNA-streptavidin networks could be functionalized by coupling with biotinylated antibodies, and after sufficient purification, these functionalized networks could be applied as reagents in IPCR [<a href="#b24-sensors-13-01353" class="html-bibr">24</a>].</p> Full article ">
<p>(<b>A</b>) ScFv consists of the variable regions of the heavy (V<sub>H</sub>) and light chains (V<sub>L</sub>) of whole immunoglobulins, connected with a short linker peptide. (<b>B</b>) When the encoding gene for an ScFv is inserted into the phage genome at the correct location, the ScFv will be expressed on the phage mantle, allowing the phages to selectively bind target proteins. In a phage IPCR assay, target binding can be followed by phage lysis after which the phage DNA can serve as the template for PCR amplification [<a href="#b28-sensors-13-01353" class="html-bibr">28</a>].</p> Full article ">
<p>Overview of the bio-barcode assay. (A) For a specific target, mAb-functionalized MMPs are prepared, along with pAb functionalized DNA-AuNP conjugates. (B) In a typical experiment, an aqueous dispersion of MMP probes is mixed with an aqueous solution of sample. After incubation, the MMPs, having captured the analyte of interest, are concentrated using a magnet. The supernatant is removed, and the MMPs are resuspended. This process is repeated to wash the MMPs. The AuNP probes are then added to the assay solution. The AuNPs reacted with the target immobilized on the MMPs and provide DNA for signal amplification and protein identification. After sufficient washing of the MMP-AuNP sandwich, they are resuspended in pure water at elevated temperature to dehybridize barcode DNA strands from the nanoparticle probe surface. Dehybridized barcode DNA was then separated and collected from the probes with the use of the magnetic separator [<a href="#b30-sensors-13-01353" class="html-bibr">30</a>].</p> Full article ">
<p>Schematic overview of the immuno-RCA assay. (<b>A</b>) DNA labeled antibodies are used in an otherwise standard sandwich immuno assay. (<b>B</b>) Hybridization of a circular DNA probe (<b>C</b>) RCA. (<b>D</b>) The amplified product is labeled through hybridization with fluorescently labeled oligonucleotides, leading to significant signal amplification.</p> Full article ">
864 KiB  
Article
Fluorescent Ratiometric Indicators Based on Cu(II)-Induced Changes in Poly(NIPAM) Microparticle Volume
by John Osambo, W. Rudolf Seitz, Daniel P. Kennedy, Roy P. Planalp, Aaron M. Jones, Randy K. Jackson and Shawn Burdette
Sensors 2013, 13(1), 1341-1352; https://doi.org/10.3390/s130101341 - 21 Jan 2013
Cited by 10 | Viewed by 7240
Abstract
Microparticles consisting of the thermal responsive polymer N-isopropyl acrylamide (polyNIPAM), a metal ion-binding ligand and a fluorophore pair that undergoes fluorescence resonance energy transfer (FRET) have been prepared and characterized. Upon the addition of Cu(II), the microparticles swell or contract depending on [...] Read more.
Microparticles consisting of the thermal responsive polymer N-isopropyl acrylamide (polyNIPAM), a metal ion-binding ligand and a fluorophore pair that undergoes fluorescence resonance energy transfer (FRET) have been prepared and characterized. Upon the addition of Cu(II), the microparticles swell or contract depending on whether charge is introduced or neutralized on the polymer backbone. The variation in microparticle morphology is translated into changes in emission of each fluorophore in the FRET pair. By measuring the emission intensity ratio between the FRET pair upon Cu(II) addition, the concentration of metal ion in solution can be quantified. This ratiometric fluorescent indicator is the newest technique in an ongoing effort to use emission spectroscopy to monitor Cu(II) thermodynamic activity in environmental water samples. Full article
(This article belongs to the Section Chemical Sensors)
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<p>Signaling mechanism in polyNIPAM particle indicators. (<b>a</b>) Cross-linked polyNIPAM particles are functionalized with a Cu(II) binding ligand and a fluorophore pair capable of undergoing FRET. (<b>b</b>) If the Cu(II) binding ligand carries a negative charge, metal ion binding neutralizes the charge causing the particles to shrink, which decreases the distance between the donor and acceptor fluorophores and increases FRET. (<b>c</b>) When a neutral Cu(II) binding ligand is incorporated into the particles, the introduction of charge on the polymer backbone causes the particles to swell. The increased distance between the donor and acceptor fluorophores leads to decreases in FRET.</p> Full article ">Figure 2
<p>SEM images of polyNIPAM polymer indicators. (<b>a</b>) Indicator <b>3</b> containing neutral bipyridine ligand. (<b>b</b>) Indicator <b>4</b> containing iminodiactate esters.</p> Full article ">Figure 3
<p>Changes in emission ratio due to FRET in a charged carboxylate ligand (<b>5</b>) <span class="html-italic">vs.</span> an uncharged ester (<b>4</b>) polyNIPAM indicator as a function of temperature. Cu(II) binding neutralizes charge on the polymer backbone of <b>5</b>, which contain negatively charged carboxylate groups, and causes emission ratio changes that closely resemble that of <b>5</b>, which contains neutral ester groups.</p> Full article ">Figure 4
<p>Emission Intensity ratio <span class="html-italic">vs.</span> [Cu(II)] for indicator <b>3</b> at 25 and 50 °C (MOPS, pH 6.0). The decrease in emission ratio is consistent with reduced FRET as particles swell when charge is introduced on the polymer backbone by bound Cu(II).</p> Full article ">Figure 5
<p>Emission Intensity ratio <span class="html-italic">vs.</span> [Cu(II)] for indicator <b>5</b> at 25 and 50 °C (MOPS, pH 6.0). The increase in emission ratio is consistent with reduced FRET as particles contract as the ligand charge is neutralized on the polymer backbone by Cu(II) binding.</p> Full article ">Figure 6
<p>Synthesis of <b>2</b>.</p> Full article ">
2594 KiB  
Article
Low-Loss Hollow Waveguide Fibers for Mid-Infrared Quantum Cascade Laser Sensing Applications
by Pietro Patimisco, Vincenzo Spagnolo, Miriam S. Vitiello, Gaetano Scamarcio, Carlos M. Bledt and James A. Harrington
Sensors 2013, 13(1), 1329-1340; https://doi.org/10.3390/s130101329 - 21 Jan 2013
Cited by 48 | Viewed by 9830
Abstract
We report on single mode optical transmission of hollow core glass waveguides (HWG) coupled with an external cavity mid-IR quantum cascade lasers (QCLs). The QCL mode results perfectly matched to the hybrid HE11 waveguide mode and the higher losses TE-like modes have [...] Read more.
We report on single mode optical transmission of hollow core glass waveguides (HWG) coupled with an external cavity mid-IR quantum cascade lasers (QCLs). The QCL mode results perfectly matched to the hybrid HE11 waveguide mode and the higher losses TE-like modes have efficiently suppressed by the deposited inner dielectric coating. Optical losses down to 0.44 dB/m and output beam divergence of ~5 mrad were measured. Using a HGW fiber with internal core size of 300 µm we obtained single mode laser transmission at 10.54 µm and successful employed it in a quartz enhanced photoacoustic gas sensor setup. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
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<p>Cross-section of the cylindrical hollow waveguides. The inner part consists of a metallic Ag layer coated by a single dielectric film of AgI or polystyrene (Ps) or by AgI/Ps double dielectric film. The outer part consists of silica with UV acrylate external coating.</p> Full article ">
<p>Schematics of the experimental setup. The laser beam is focused at the waveguide entrance using a ZnSe lens (<b>a</b>) or in a simple back-to-back configuration (<b>b</b>) and detected using a pyroelectric detector equipped with a XY stepper motor.</p> Full article ">
<p>Far field spatial intensity distribution of the λ<sub>b</sub>-QCL. The beam profile has been measured under the experimental configuration of <a href="#f2-sensors-13-01329" class="html-fig">Figure 2(b)</a> without any optics between the laser and the detector stage.</p> Full article ">
<p>Far-Field spatial intensity distribution of the λ<sub>a</sub> (<b>upper row</b>) and λ<sub>b</sub> (<b>lower row</b>) upon exiting a 12 cm long and 1 mm core diameter hollow waveguide having AgI/Ps double dielectric layer and having a single dielectric film of AgI and Ps. The beam profiles have been measured by focusing the QCL beam directly at the center of waveguide by using a ZnSe lens.</p> Full article ">
<p>Far-Field spatial intensity distribution of the λ<sub>a</sub> (<b>upper row</b>) and λ<sub>b</sub> (<b>lower row</b>) upon exiting a 12 cm long and 1 mm bore diameter hollow waveguide having AgI/Ps double dielectric layer and having a single dielectric film of AgI and Ps. The beam profiles have been measured in a back-to-back configuration.</p> Full article ">
<p>Total losses calculated from the ratio of input/output power values for the wavelength λ<sub>a</sub> at the waveguide entrance/exit for Ag/AgI coatings (● symbols) and for AgPs coatings (■ symbols). The dashed lines are linear fits to the data. The reported transmission losses have been estimated from the slope of each linear fit.</p> Full article ">
<p>Schematics of the output divergence angle measurement.</p> Full article ">
<p>Far-field spatial intensity distribution upon exiting a 12 cm long and 1 mm bore diameter hollow waveguide having a single dielectric film of AgI and Ps at L<sub>1</sub> = 1 cm (<b>a</b>) and <span class="html-italic">L</span><sub>2</sub> = 5.1 cm (<b>b</b>) distance from the waveguide exit.</p> Full article ">
<p>Three-dimensional single mode profile of the EC-QCL beam: exiting the hollow fiber (<b>a</b>) and at the focusing plane of the collimator (<b>b</b>). The color map, identical for both panels, is shown in right side of the figure.</p> Full article ">
476 KiB  
Article
Design of the Dual Stone Locating System on an Extracorporeal Shock Wave Lithotriptor
by Yong-Ren Pu, Ioannis Manousakas, Shen-Min Liang and Chien-Chen Chang
Sensors 2013, 13(1), 1319-1328; https://doi.org/10.3390/s130101319 - 21 Jan 2013
Cited by 15 | Viewed by 8891
Abstract
Extracorporeal Shock Wave Lithotriptors are very popular for the treatment of urinary stones all over the world. They depend basically upon either X-ray fluoroscopy or ultrasound scans to detect the stones before therapy begins. To increase the effectiveness of treatment this study took [...] Read more.
Extracorporeal Shock Wave Lithotriptors are very popular for the treatment of urinary stones all over the world. They depend basically upon either X-ray fluoroscopy or ultrasound scans to detect the stones before therapy begins. To increase the effectiveness of treatment this study took advantage of both X-ray and ultrasound to develop a dual stone locating system with image processing modules. Its functions include the initial stone locating mode with stone detection by fluorescent images and the follow-up automatic stone tracking mode made by constant ultrasound scanning. The authors have integrated both apparatus and present the operating principles for both modes. The system used two in vitro experiments to justify its abilities of stone location in all procedures. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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<p>The framework of the dual stone locating system.</p> Full article ">Figure 2
<p>The geometry of the dual stone location apparatus.</p> Full article ">Figure 3
<p>The schematic diagrams of the fluorescent images. On the left, the C-arm is upright; and, on the right, the C-arm rolls at an angle <span class="html-italic">θ</span>.</p> Full article ">Figure 4
<p>The schematic diagram of the stone deviation in the US images.</p> Full article ">Figure 5
<p>The coordinate system of the US probe for stone tracking.</p> Full article ">Figure 6
<p>(<b>a</b>) The phantom with kidney-shaped cavity mounted on the ESWL, and (<b>b</b>) the phantom cap attached with a model stone at the tip.</p> Full article ">Figure 7
<p>The fluorescent images of the phantom (<b>a</b>) before stone location, and (<b>b</b>) after stone location.</p> Full article ">Figure 8
<p>The front (left) and side (right) views of the devices for the <span class="html-italic">in vitro</span> automatic stone tracking experiment.</p> Full article ">Figure 9
<p>The trajectories of the model stone's center in the US images with and without tracking.</p> Full article ">
856 KiB  
Review
Low Frequency Electrical and Magnetic Methods for Non-Destructive Analysis of Fiber Dispersion in Fiber Reinforced Cementitious Composites: An Overview
by Marco Faifer, Liberato Ferrara, Roberto Ottoboni and Sergio Toscani
Sensors 2013, 13(1), 1300-1318; https://doi.org/10.3390/s130101300 - 21 Jan 2013
Cited by 20 | Viewed by 7529
Abstract
Non-destructive analysis of fiber dispersion in structural elements made of Fiber Reinforced Concrete (FRC) and Fiber Reinforced Cementitious Composites (FRCCs) plays a significant role in the framework of quality control and performance prediction. In this paper, the research activity of the authors in [...] Read more.
Non-destructive analysis of fiber dispersion in structural elements made of Fiber Reinforced Concrete (FRC) and Fiber Reinforced Cementitious Composites (FRCCs) plays a significant role in the framework of quality control and performance prediction. In this paper, the research activity of the authors in the aforementioned field all over the last lustrum will be reviewed. A method based on the measurement of the inductance of a probe to be placed on the specimen will be presented and its progressive development will be described. Obtained correlation with actual fiber dispersion, as checked by means of destructive methods, as well as with the mechanical performance of the composite will also be presented, in an attempt to address the significance of the method from an engineering application perspective. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)
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<p>Single winding probe.</p> Full article ">
<p>Single winding probe: flux density predicted by FEM analysis.</p> Full article ">
<p>Two winding probe.</p> Full article ">
<p>Two winding probe: flux density predicted by FEM analysis.</p> Full article ">
<p>schematic view of the test set-up.</p> Full article ">
<p>Magnetic measuring sensor for ND characterization of fiber dispersion and orientation in FRC slabs (<b>a</b>); schematic of the measuring procedure (<b>b</b>); casting of a FRC slab specimen featuring preferential fiber alignment (<b>c</b>); ND estimated fiber dispersion cartography (<b>d</b>) and comparison between ND estimated and destructively assessed local fiber concentration (<b>e</b>).</p> Full article ">
<p>Magnetic measuring sensor for ND characterization of fiber dispersion and orientation in FRC slabs (<b>a</b>); schematic of the measuring procedure (<b>b</b>); casting of a FRC slab specimen featuring preferential fiber alignment (<b>c</b>); ND estimated fiber dispersion cartography (<b>d</b>) and comparison between ND estimated and destructively assessed local fiber concentration (<b>e</b>).</p> Full article ">
<p>Direction of the maximum inductance in each sector of the slab.</p> Full article ">
<p>Support allowing the test of cylindrical specimens.</p> Full article ">
<p>Polar plots of the self-inductance and of the power losses due to the alternating magnetic field measured on two different cylindrical specimens.</p> Full article ">
3110 KiB  
Article
Robot Evolutionary Localization Based on Attentive Visual Short-Term Memory
by Julio Vega, Eduardo Perdices and José M. Cañas
Sensors 2013, 13(1), 1268-1299; https://doi.org/10.3390/s130101268 - 21 Jan 2013
Cited by 8 | Viewed by 7560
Abstract
Cameras are one of the most relevant sensors in autonomous robots. However, two of their challenges are to extract useful information from captured images, and to manage the small field of view of regular cameras. This paper proposes implementing a dynamic visual memory [...] Read more.
Cameras are one of the most relevant sensors in autonomous robots. However, two of their challenges are to extract useful information from captured images, and to manage the small field of view of regular cameras. This paper proposes implementing a dynamic visual memory to store the information gathered from a moving camera on board a robot, followed by an attention system to choose where to look with this mobile camera, and a visual localization algorithm that incorporates this visual memory. The visual memory is a collection of relevant task-oriented objects and 3D segments, and its scope is wider than the current camera field of view. The attention module takes into account the need to reobserve objects in the visual memory and the need to explore new areas. The visual memory is useful also in localization tasks, as it provides more information about robot surroundings than the current instantaneous image. This visual system is intended as underlying technology for service robot applications in real people’s homes. Several experiments have been carried out, both with simulated and real Pioneer and Nao robots, to validate the system and each of its components in office scenarios. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
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<p>Block diagram of the proposed visual system.</p> Full article ">
<p>Modules of the Visual Memory.</p> Full article ">
<p>Differences between Canny+Hough (left) and Solis algorithm (right).</p> Full article ">
<p>3D projection on the image plane (left) and matching between predicted and observed segments (right).</p> Full article ">
<p>Scene situation with three instantaneous images and 3D scene reconstruction.</p> Full article ">
<p>Complex primitives in visual memory: parallelograms with occlusion.</p> Full article ">
<p>P-controller mechanism.</p> Full article ">
<p>Basic diagram of evolutionary algorithm.</p> Full article ">
<p>Image analysis before merging (left) and after merging (right).</p> Full article ">
2769 KiB  
Article
An Aerial-Ground Robotic System for Navigation and Obstacle Mapping in Large Outdoor Areas
by Mario Garzón, João Valente, David Zapata and Antonio Barrientos
Sensors 2013, 13(1), 1247-1267; https://doi.org/10.3390/s130101247 - 21 Jan 2013
Cited by 73 | Viewed by 11982
Abstract
There are many outdoor robotic applications where a robot must reach a goal position or explore an area without previous knowledge of the environment around it. Additionally, other applications (like path planning) require the use of known maps or previous information of the [...] Read more.
There are many outdoor robotic applications where a robot must reach a goal position or explore an area without previous knowledge of the environment around it. Additionally, other applications (like path planning) require the use of known maps or previous information of the environment. This work presents a system composed by a terrestrial and an aerial robot that cooperate and share sensor information in order to address those requirements. The ground robot is able to navigate in an unknown large environment aided by visual feedback from a camera on board the aerial robot. At the same time, the obstacles are mapped in real-time by putting together the information from the camera and the positioning system of the ground robot. A set of experiments were carried out with the purpose of verifying the system applicability. The experiments were performed in a simulation environment and outdoor with a medium-sized ground robot and a mini quad-rotor. The proposed robotic system shows outstanding results in simultaneous navigation and mapping applications in large outdoor environments. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
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Graphical abstract

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<p>Coordinate frames.</p> Full article ">
<p>UGV heading geometry. The angle of interest is given by <span class="html-italic">γ</span> = <span class="html-italic">θ</span> − <span class="html-italic">α</span>.</p> Full article ">
<p>Features extraction procedure example for a ground robot.</p> Full article ">
<p>Test Trajectory for EKF. A trajectory was performed in order to test the performance of the Extended Kalman Filter.</p> Full article ">
<p>Steering Behaviors. Two Behaviors (Seek and Avoid) and their corresponding vectors are shown.</p> Full article ">
<p>UAV and UGV in the proposed environments (<b>a</b>) Simulated environment. (<b>b</b>) Real environment. The blue squares in each figure represent the image acquired from the camera on board the aerial robot.</p> Full article ">
<p>Single obstacle Avoidance. The trajectory of the UGV while performing the avoidance maneuver, and the detected obstacle positions are shown.</p> Full article ">
<p>Obstacle Position Estimation. The green line denotes the UGV position. The blue arrows determine the transformation from each robot position to the center of the obstacle marked with red circles.</p> Full article ">
<p>Obstacle Position (Real <span class="html-italic">vs</span>. Estimated). The red circles denote the estimated obstacle position. The green one shows the real position of the obstacle and the blue is the mean value of the calculated positions. All positions were translated to a common reference frame.</p> Full article ">
601 KiB  
Article
A Comparative Study on Three Different Transducers for the Measurement of Nonlinear Solitary Waves
by Xianglei Ni, Luyao Cai and Piervincenzo Rizzo
Sensors 2013, 13(1), 1231-1246; https://doi.org/10.3390/s130101231 - 18 Jan 2013
Cited by 7 | Viewed by 6853
Abstract
In the last decade there has been an increasing interest in the use of highly- and weakly- nonlinear solitary waves in engineering and physics. Nonlinear solitary waves can form and travel in nonlinear systems such as one-dimensional chains of particles, where they are [...] Read more.
In the last decade there has been an increasing interest in the use of highly- and weakly- nonlinear solitary waves in engineering and physics. Nonlinear solitary waves can form and travel in nonlinear systems such as one-dimensional chains of particles, where they are conventionally generated by the mechanical impact of a striker and are measured either by using thin transducers embedded in between two half-particles or by a force sensor placed at the chain’s base. These waves have a constant spatial wavelength and their speed, amplitude, and duration can be tuned by modifying the particles’ material or size, or the velocity of the striker. In this paper we propose two alternative sensing configurations for the measurements of solitary waves propagating in a chain of spherical particles. One configuration uses piezo rods placed in the chain while the other exploits the magnetostrictive property of ferromagnetic materials. The accuracy of these two sensing systems on the measurement of the solitary wave’s characteristics is assessed by comparing experimental data to the numerical prediction of a discrete particle model and to the experimental measurements obtained by means of a conventional transducer. The results show very good agreement and the advantages and limitations of the new sensors are discussed. Full article
(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)
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<p>Schematic diagram of the experimental setup.</p> Full article ">
<p>Sensing technologies used in this study. (<b>a</b>) Bead sensor formed by a thin piezoelectric crystal embedded between two half particles, (<b>b</b>) commercial piezo rod, (<b>c</b>) magnetostrictive sensor formed by a coil and a bridge magnet, (<b>d</b>) Schematic diagram of one magnetostrictive sensor assembled with the tube filled with spherical particles.</p> Full article ">
<p>Schematic diagram of the one-dimensional discrete element model. The <span class="html-italic">c<sub>1</sub>, c<sub>2</sub></span>, …, <span class="html-italic">c<sub>N</sub></span> indicates the points of contact between two neighboring particles. When the presence of the piezo rod is modeled, the spheres 13 and 18 are replaced by solid rods.</p> Full article ">
<p>Discrete particle model results showing the temporal force profile for all threesensing configurations at contact points: (<b>a</b>) <span class="html-italic">c<sub>8</sub></span>, (<b>b</b>) <span class="html-italic">c<sub>11</sub></span>, (<b>c</b>) <span class="html-italic">c<sub>12</sub></span>, and (<b>d</b>) <span class="html-italic">c<sub>13</sub></span>.</p> Full article ">
<p>Discrete particle model results showing the temporal force profile at some contact points (dashed lines) and as measured by three sensors (solid lines): (<b>a</b>) bead sensor, (<b>b</b>) piezo rod, (<b>c</b>) magnetostrictive sensor.</p> Full article ">
<p>Discrete particle model results showing the temporal force profile at some contact points (dashed lines) and as measured by three sensors (solid lines): (<b>a</b>) bead sensor, (<b>b</b>) piezo rod, (<b>c</b>) magnetostrictive sensor.</p> Full article ">
<p>Typical waveforms measured by the bead sensors.</p> Full article ">
<p>(<b>a</b>) Experimental results for bead sensors, (<b>b</b>) comparison of experimental and numerical results for bead sensors, (<b>c</b>) experimental results for cylindrical sensors, (<b>d</b>) comparison of experimental and numerical results for cylindrical sensors, (<b>e</b>) experimental results formagnetostrictive sensors, (<b>f</b>) comparison of experimental and numerical results for magnetostrictive sensors.</p> Full article ">
294 KiB  
Article
A Network Access Control Framework for 6LoWPAN Networks
by Luís M. L. Oliveira, Joel J. P. C. Rodrigues, Amaro F. De Sousa and Jaime Lloret
Sensors 2013, 13(1), 1210-1230; https://doi.org/10.3390/s130101210 - 18 Jan 2013
Cited by 25 | Viewed by 9223
Abstract
Low power over wireless personal area networks (LoWPAN), in particular wireless sensor networks, represent an emerging technology with high potential to be employed in critical situations like security surveillance, battlefields, smart-grids, and in e-health applications. The support of security services in LoWPAN is [...] Read more.
Low power over wireless personal area networks (LoWPAN), in particular wireless sensor networks, represent an emerging technology with high potential to be employed in critical situations like security surveillance, battlefields, smart-grids, and in e-health applications. The support of security services in LoWPAN is considered a challenge. First, this type of networks is usually deployed in unattended environments, making them vulnerable to security attacks. Second, the constraints inherent to LoWPAN, such as scarce resources and limited battery capacity, impose a careful planning on how and where the security services should be deployed. Besides protecting the network from some well-known threats, it is important that security mechanisms be able to withstand attacks that have not been identified before. One way of reaching this goal is to control, at the network access level, which nodes can be attached to the network and to enforce their security compliance. This paper presents a network access security framework that can be used to control the nodes that have access to the network, based on administrative approval, and to enforce security compliance to the authorized nodes. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
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<p>6LoWPAN network architecture.</p> Full article ">
<p>6LoWPAN neighbor discovery address registration.</p> Full article ">
<p>Node remote reprogramming mechanisms.</p> Full article ">
<p>Access control decision process.</p> Full article ">
714 KiB  
Article
Customized Multiwavelets for Planetary Gearbox Fault Detection Based on Vibration Sensor Signals
by Hailiang Sun, Yanyang Zi, Zhengjia He, Jing Yuan, Xiaodong Wang and Lue Chen
Sensors 2013, 13(1), 1183-1209; https://doi.org/10.3390/s130101183 - 18 Jan 2013
Cited by 32 | Viewed by 8623
Abstract
Planetary gearboxes exhibit complicated dynamic responses which are more difficult to detect in vibration signals than fixed-axis gear trains because of the special gear transmission structures. Diverse advanced methods have been developed for this challenging task to reduce or avoid unscheduled breakdown and [...] Read more.
Planetary gearboxes exhibit complicated dynamic responses which are more difficult to detect in vibration signals than fixed-axis gear trains because of the special gear transmission structures. Diverse advanced methods have been developed for this challenging task to reduce or avoid unscheduled breakdown and catastrophic accidents. It is feasible to make fault features distinct by using multiwavelet denoising which depends on the feature separation and the threshold denoising. However, standard and fixed multiwavelets are not suitable for accurate fault feature detections because they are usually independent of the measured signals. To overcome this drawback, a method to construct customized multiwavelets based on the redundant symmetric lifting scheme is proposed in this paper. A novel indicator which combines kurtosis and entropy is applied to select the optimal multiwavelets, because kurtosis is sensitive to sharp impulses and entropy is effective for periodic impulses. The improved neighboring coefficients method is introduced into multiwavelet denoising. The vibration signals of a planetary gearbox from a satellite communication antenna on a measurement ship are captured under various motor speeds. The results show the proposed method could accurately detect the incipient pitting faults on two neighboring teeth in the planetary gearbox. Full article
(This article belongs to the Section Physical Sensors)
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<p>Schematic of an elementary planetary gear set having three planet gears.</p> Full article ">
<p>(<b>a</b>) Decomposition (<span class="html-italic">r</span> = 2) of MWT. (<b>b</b>) Reconstruction (<span class="html-italic">r</span> = 2) of MWT.</p> Full article ">
<p>(<b>a</b>) Decomposition (<span class="html-italic">r</span> = 2) of MWT. (<b>b</b>) Reconstruction (<span class="html-italic">r</span> = 2) of MWT.</p> Full article ">
<p>The decomposition of redundant multiwavelet transform. (<b>a</b>) Decomposition of redundant multiwavelet transform. (<b>b</b>) Zero-padding of filter banks.</p> Full article ">
<p>The algorithm of improved neighboring coefficients.</p> Full article ">
<p>Hermite spline multiscaling functions and multiwavelet functions. (<b>a</b>) Multiscaling functions. (<b>b</b>) Multiwavelet functions.</p> Full article ">
<p>The flow chart of the proposed method.</p> Full article ">
<p>The flow chart of the customized multiwavelets.</p> Full article ">
<p>The transmission mechanism of the azimuth axis.</p> Full article ">
<p>The testing framework of the SCA of a measurement ship.</p> Full article ">
1043 KiB  
Article
A Wireless Sensor Network-Based Portable Vehicle Detector Evaluation System
by Seong-eun Yoo
Sensors 2013, 13(1), 1160-1182; https://doi.org/10.3390/s130101160 - 17 Jan 2013
Cited by 19 | Viewed by 9607
Abstract
In an upcoming smart transportation environment, performance evaluations of existing Vehicle Detection Systems are crucial to maintain their accuracy. The existing evaluation method for Vehicle Detection Systems is based on a wired Vehicle Detection System reference and a video recorder, which must be [...] Read more.
In an upcoming smart transportation environment, performance evaluations of existing Vehicle Detection Systems are crucial to maintain their accuracy. The existing evaluation method for Vehicle Detection Systems is based on a wired Vehicle Detection System reference and a video recorder, which must be operated and analyzed by capable traffic experts. However, this conventional evaluation system has many disadvantages. It is inconvenient to deploy, the evaluation takes a long time, and it lacks scalability and objectivity. To improve the evaluation procedure, this paper proposes a Portable Vehicle Detector Evaluation System based on wireless sensor networks. We describe both the architecture and design of a Vehicle Detector Evaluation System and the implementation results, focusing on the wireless sensor networks and methods for traffic information measurement. With the help of wireless sensor networks and automated analysis, our Vehicle Detector Evaluation System can evaluate a Vehicle Detection System conveniently and objectively. The extensive evaluations of our Vehicle Detector Evaluation System show that it can measure the traffic information such as volume counts and speed with over 98% accuracy. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
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<p>(<b>a</b>) Overall system description (<b>b</b>) System description with network connections.</p> Full article ">
<p>Network architecture of TSN.</p> Full article ">
<p>Addressing Scheme for Level-based Static Routing.</p> Full article ">
<p>Timing diagram of the synchronization procedure of T-Sensor nodes to the T-sink node.</p> Full article ">
<p>Procedure for T-Sensor node to synchronize its local software time tick to the received Sync_Req broadcast message.</p> Full article ">
<p>Overall operation procedure of T-Sensor node S/W.</p> Full article ">
<p>Overall flow of event detection in a T-Sensor node.</p> Full article ">
<p>Refined data, D(k), gathered by prototype hardware.</p> Full article ">
<p>TAR, TACCR0 register alignment for synchronized periodic timer interrupt in two different T-Sensor nodes.</p> Full article ">
112 KiB  
New Book Received
Antenna Systems and Electronic Warfare Applications. Edited by Richard A. Poisel, Artech House, 2012; 1036 pages. Price: £129.00, ISBN 978-1-60807-484-6
by Shu-Kun Lin
Sensors 2013, 13(1), 1158-1159; https://doi.org/10.3390/s130101158 - 17 Jan 2013
Viewed by 5848
Abstract
This comprehensive book serves as a one-stop resource for practical EW antenna system know-how. Supported with over 700 illustrations and nearly 1,700 equations, this authoritative reference offers you detailed explanations of all the important foundations and aspects of this technology. Moreover, you get [...] Read more.
This comprehensive book serves as a one-stop resource for practical EW antenna system know-how. Supported with over 700 illustrations and nearly 1,700 equations, this authoritative reference offers you detailed explanations of all the important foundations and aspects of this technology. Moreover, you get an in-depth treatment of a wide range of antenna system applications. Full article
(This article belongs to the Section Chemical Sensors)
123 KiB  
New Book Received
Electronic Warfare Target Location Methods, Second Edition. Edited by Richard A. Poisel, Artech House, 2012; 422 pages. Price: £99.00, ISBN 978-1-60807-523-2
by Shu-Kun Lin
Sensors 2013, 13(1), 1151-1157; https://doi.org/10.3390/s130101151 - 17 Jan 2013
Cited by 1 | Viewed by 6419
Abstract
Describing the mathematical development underlying current and classical methods of geolocating electronic systems that are emitting, this newly revised and greatly expanded edition of a classic Artech House book offers practical guidance in electronic warfare target location. The Second Edition features a wealth [...] Read more.
Describing the mathematical development underlying current and classical methods of geolocating electronic systems that are emitting, this newly revised and greatly expanded edition of a classic Artech House book offers practical guidance in electronic warfare target location. The Second Edition features a wealth of additional material including new chapters on time delay estimation, direction finding techniques, and the MUSIC algorithm. This practical resource provides you with critical design information on geolocation algorithms, and establishes the fundamentals of existing algorithms as a launch point for further algorithm development. You gain an in-depth understanding of key target location methods that you can effectively apply to your work in the field. You discover triangulation algorithms that offer a highly efficient way to geolocate targets when the real estate on the sensor systems is adequate to support an antenna array. The book also presents quadratic geolocation techniques that can be implemented with extremely modest antennas — frequently a single dipole or monopole. Moreover, this authoritative volume details methods for geolocating the source of high frequency signals with a single sensor site. Full article
(This article belongs to the Section Chemical Sensors)
121 KiB  
New Book Received
Introduction to Modern EW Systems. Edited by Andrea De Martino, Artech House, 2012; 417 pages. Price: £119.00, ISBN 978-1-60807-207-1
by Shu-Kun Lin
Sensors 2013, 13(1), 1146-1150; https://doi.org/10.3390/s130101146 - 17 Jan 2013
Cited by 1 | Viewed by 6113
Abstract
Master the latest electronic warfare (EW) techniques and technologies related to on-board military platforms with this authoritative resource. You gain expert design guidance on technologies and equipment used to detect and identify emitter threats, giving you an advantage in the never-ending chess game [...] Read more.
Master the latest electronic warfare (EW) techniques and technologies related to on-board military platforms with this authoritative resource. You gain expert design guidance on technologies and equipment used to detect and identify emitter threats, giving you an advantage in the never-ending chess game between sensor guided weapons and EW systems. This unique book offers you deeper insight into EW systems principles of operation and their mathematical descriptions, arming you with better knowledge for your specific design applications. Full article
(This article belongs to the Section Chemical Sensors)
713 KiB  
Article
Characterization of a New Heat Dissipation Matric Potential Sensor
by Luzius Matile, Roman Berger, Daniel Wächter and Rolf Krebs
Sensors 2013, 13(1), 1137-1145; https://doi.org/10.3390/s130101137 - 17 Jan 2013
Cited by 15 | Viewed by 7704
Abstract
Soil moisture sensors can help to reduce the amount of water needed for irrigation. In this paper we describe the PlantCare soil moisture sensor as a new type of heat dissipation sensor, its calibration and the correction for temperature changes. With the PlantCare [...] Read more.
Soil moisture sensors can help to reduce the amount of water needed for irrigation. In this paper we describe the PlantCare soil moisture sensor as a new type of heat dissipation sensor, its calibration and the correction for temperature changes. With the PlantCare sensor it is possible to measure the matric potential indirectly to monitor or control irrigation. This sensor is based on thermal properties of a synthetic felt. After a defined heating phase the cooling time to a threshold temperature is a function of the water content in the synthetic felt. The water content in this porous matrix is controlled by the matric potential in the surrounding soil. Calibration measurements have shown that the sensor is most sensitive to −400 hPa and allows lower sensitivity measurements to −800 hPa. The disturbing effect of the temperature change during the measurement on the cooling time can be corrected by a linear function and the differences among sensors are minimized by a two point calibration. Full article
(This article belongs to the Section Physical Sensors)
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<p>(<b>A</b>) PlantCare sensor (diameter 15 mm). (<b>B</b>) PlantCare sensor without box and synthetic felt.</p> Full article ">
<p>Relative Temperature <span class="html-italic">T′</span> = <span class="html-italic">(T</span> − <span class="html-italic">T<sub>a</sub>)</span>/<span class="html-italic">(T<sub>h</sub></span> − <span class="html-italic">T<sub>a</sub>)</span> as a function of time during the measurement with a PlantCare heat dissipative sensor in a wet and a dry soil (solid and dashed lines). The effect of changes of the ambient temperature <span class="html-italic">dT<sub>a</sub></span>/<span class="html-italic">dt</span> on the cooling time <span class="html-italic">t</span> is illustrated in the enlarged circles. (<span class="html-italic">T<sub>a</sub></span>: ambient temperature, <span class="html-italic">T<sub>h</sub></span>: peak temperature after heating phase at <span class="html-italic">t<sub>o</sub></span>, <span class="html-italic">T′<sub>t</sub></span>: threshold temperature).</p> Full article ">
<p>Calibration of the signals of 7 sensors with simultaneous tensiometer readings expressed as absolute cooling time <span class="html-italic">t</span> fitted with <a href="#FD3" class="html-disp-formula">Equation (3)</a> (<b>A</b>) and as normalized cooling time <span class="html-italic">t<sub>n</sub></span> fitted with <a href="#FD2" class="html-disp-formula">Equation (2)</a> (<b>B</b>). The threshold temperature was 18% (<a href="#f2-sensors-13-01137" class="html-fig">Figure 2</a>).</p> Full article ">
<p>(<b>A</b>) Calibration of the PlantCare sensor signals in a pressure plate apparatus (circles) expressed as absolute cooling time <span class="html-italic">t</span> fitted with <a href="#FD3" class="html-disp-formula">Equation (3)</a> and (<b>B</b>) as normalized cooling time <span class="html-italic">t<sub>n</sub></span> fitted with <a href="#FD2" class="html-disp-formula">Equation (2)</a>. The threshold temperature was 18% (<a href="#f2-sensors-13-01137" class="html-fig">Figure 2</a>).</p> Full article ">
<p>Correction factor <span class="html-italic">k</span> as a function of the cooling time <span class="html-italic">t</span> for a threshold value of 18% (<a href="#f2-sensors-13-01137" class="html-fig">Figure 2</a>) and the 4 substrates (organic substrate, sand, clay loam and sandy substrate).</p> Full article ">
<p>(<b>a</b>) Variations of soil temperature <span class="html-italic">T</span> (top) and (<b>b</b>) cooling time <span class="html-italic">t</span>; uncorrected (solid line) and corrected for temperature changes (circles). The sensors were placed in an irrigated apple plantation in a depth of 25 cm.</p> Full article ">
801 KiB  
Article
Using an Automatic Resistivity Profiler Soil Sensor On-The-Go in Precision Viticulture
by Roberta Rossi, Alessio Pollice, Maria-Paz Diago, Manuel Oliveira, Borja Millan, Giovanni Bitella, Mariana Amato and Javier Tardaguila
Sensors 2013, 13(1), 1121-1136; https://doi.org/10.3390/s130101121 - 16 Jan 2013
Cited by 28 | Viewed by 10868
Abstract
Spatial information on vineyard soil properties can be useful in precision viticulture. In this paper a combination of high resolution soil spatial information of soil electrical resistivity (ER) and ancillary topographic attributes, such as elevation and slope, were integrated to assess the spatial [...] Read more.
Spatial information on vineyard soil properties can be useful in precision viticulture. In this paper a combination of high resolution soil spatial information of soil electrical resistivity (ER) and ancillary topographic attributes, such as elevation and slope, were integrated to assess the spatial variability patterns of vegetative growth and yield of a commercial vineyard (Vitis vinifera L. cv. Tempranillo) located in the wine-producing region of La Rioja, Spain. High resolution continuous geoelectrical mapping was accomplished by an Automatic Resistivity Profiler (ARP) on-the-go sensor with an on-board GPS system; rolling electrodes enabled ER to be measured for a depth of investigation approximately up to 0.5, 1 and 2 m. Regression analysis and cluster analysis algorithm were used to jointly process soil resistivity data, landscape attributes and grapevine variables. ER showed a structured variability that matched well with trunk circumference spatial pattern and yield. Based on resistivity and a simple terrain attribute uniform management units were delineated. Once a spatial relationship to target variables is found, the integration of point measurement with continuous soil resistivity mapping is a useful technique to identify within-plots areas of vineyard with similar status. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
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<p>(<b>a</b>) Picture of the DC recording resistivity meter (ARP<sup>©</sup>, Automatic Resistivity Profiling. GEOCARTA, Paris, France) towed by a ground vehicle; (<b>b</b>) schematic representation of the multiple system: R: resistivity meter; I: injection wheel; V1, V2 and V3: receiving wheels (<b>c</b>) maps of resistivity distribution at the three consecutive exploration depth (V1 = 0−0.5 m; V2 = 0−1.0 m; V3 = 0−2.0 m).</p> Full article ">
<p>Field measurement locations (<b>a</b>) aerial photograph of the field with the position of plant measurement sites (red dots: center of each plant measurement block). (<b>b</b>) electrical resistivity transects with average ER values for layer 1 (0–50 cm depth). (<b>c</b>) scheme of a typical plant block with the three vines (in red) used for measurements.</p> Full article ">
<p>(<b>a</b>) Frequency distribution of trunk girth, (<b>b</b>) yield and (<b>c</b>) soil electrical resistivity (ER). All plant and ER data corresponded to 65 experimental sampled blocks of regular grid.</p> Full article ">
<p>Interpolated maps (<b>left</b>) of ER measured by the ARP system in the three soil layers (V<sub>1</sub> = 0–0.5, V<sub>2</sub> = 0–1 and V<sub>3</sub> = 0–2 m depth). Interpolated map (<b>right</b>) of the first layer (0–0.5 m) overlaid on the digital elevation model (DEM) of the experimental vineyard.</p> Full article ">
<p>Empirical variograms of (<b>a</b>) trunk girth, (<b>b</b>) yield and (<b>c</b>) soil electrical resistivity (ER) overlaid by theoretical variogram models.</p> Full article ">
<p>Interpolated maps of (<b>a</b>) trunk girth (cm), (<b>b</b>) yield (Kg/vine) and (<b>c</b>) top-layer (0–0.5 m) soil electrical resistivity (Ohm·m).</p> Full article ">
<p>Map of residuals (<b>left</b>) and empirical semivariogram of residuals (<b>right</b>) of the linear multiple regression model for trunk girth.</p> Full article ">
<p>Boxplots of trunk girth and ER with increasing number of clusters (<b>left</b>) and uniform management zones maps derived by the clustering analysis (<b>right</b>). Top: management zone 1: blue; management zone 2: black. Bottom: management zone 1: blue; management zone 2: green; management zone 3: blue.</p> Full article ">
877 KiB  
Article
A New Curb Detection Method for Unmanned Ground Vehicles Using 2D Sequential Laser Data
by Zhao Liu, Jinling Wang and Daxue Liu
Sensors 2013, 13(1), 1102-1120; https://doi.org/10.3390/s130101102 - 16 Jan 2013
Cited by 48 | Viewed by 7729
Abstract
Curb detection is an important research topic in environment perception, which is an essential part of unmanned ground vehicle (UGV) operations. In this paper, a new curb detection method using a 2D laser range finder in a semi-structured environment is presented. In the [...] Read more.
Curb detection is an important research topic in environment perception, which is an essential part of unmanned ground vehicle (UGV) operations. In this paper, a new curb detection method using a 2D laser range finder in a semi-structured environment is presented. In the proposed method, firstly, a local Digital Elevation Map (DEM) is built using 2D sequential laser rangefinder data and vehicle state data in a dynamic environment and a probabilistic moving object deletion approach is proposed to cope with the effect of moving objects. Secondly, the curb candidate points are extracted based on the moving direction of the vehicle in the local DEM. Finally, the straight and curved curbs are detected by the Hough transform and the multi-model RANSAC algorithm, respectively. The proposed method can detect the curbs robustly in both static and typical dynamic environments. The proposed method has been verified in real vehicle experiments. Full article
(This article belongs to the Section Physical Sensors)
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<p>Flowchart of the new curb detection method.</p> Full article ">Figure 2
<p>The local DEM in static environment.</p> Full article ">Figure 3
<p>The schematic of the laser scanning on the road.</p> Full article ">Figure 4
<p>The local DEM in dynamic environment. (<b>a</b>) The bad result. (<b>b</b>) The result of our approach.</p> Full article ">Figure 5
<p>The results of the curb candidate detection. (<b>a</b>) The local DEM. (<b>b</b>) The curb candidate points in the local DEM.</p> Full article ">Figure 6
<p>The accumulated results of the curb candidates. (<b>a</b>) The local DEM. (<b>b</b>) The accumulated curb candidate points in the local DEM.</p> Full article ">Figure 7
<p>The flowchart of the multi-model RANSAC algorithm.</p> Full article ">Figure 8
<p>The iterative number of the RANSAC algorithm.</p> Full article ">Figure 9
<p>The position of the laser range finder.</p> Full article ">Figure 10
<p>The running route of the vehicle in first experiment. (<b>a</b>) The experimental site in the Google map. (<b>b</b>) The position of four scenes.</p> Full article ">Figure 11
<p>The result of the straight curb detection. (<b>a</b>) Scene 1. (<b>b</b>) The results of Hough transform. (<b>c</b>) The final curb detection results in the local DEM.</p> Full article ">Figure 12
<p>The result of the curb detection. (<b>a</b>) Scene 2. (<b>b</b>) The data cluster results of the curb candidate points. (<b>c</b>) The final curb detection results in the local DEM.</p> Full article ">Figure 13
<p>The curb detection in typical dynamic environment. (<b>a</b>) Scene 3. (<b>b</b>) The accumulated results of the curb candidates. (<b>c</b>) The final curb detection results in the local DEM.</p> Full article ">Figure 14
<p>The contrastive result of the curb detection. (<b>a</b>) The bad curb detection result. (<b>b</b>) The result of our method.</p> Full article ">Figure 15
<p>The contrastive result of the curved curb detection. (<b>a</b>) Data cluster result in Scene 5. (<b>b</b>) The bad curb detection result. (<b>c</b>) The result of our method. (<b>d</b>) Data cluster result in Scene 6. (<b>e</b>) The bad curb detection result. (<b>f</b>) The result of our method.</p> Full article ">Figure 15 Cont.
<p>The contrastive result of the curved curb detection. (<b>a</b>) Data cluster result in Scene 5. (<b>b</b>) The bad curb detection result. (<b>c</b>) The result of our method. (<b>d</b>) Data cluster result in Scene 6. (<b>e</b>) The bad curb detection result. (<b>f</b>) The result of our method.</p> Full article ">Figure 16
<p>The execution time of our algorithm.</p> Full article ">Figure 17
<p>The curb detection results in the second experiment. (<b>a</b>) The entire curb detection results in the global coordinate system. (<b>b</b>) The enlarged result in the top rectangle in <a href="#f17-sensors-13-01102" class="html-fig">Figure 17(a)</a>. (<b>c</b>) The enlarged result in the bottom rectangle in <a href="#f17-sensors-13-01102" class="html-fig">Figure 17(a)</a>.</p> Full article ">
1284 KiB  
Article
Monolithic Composite “Pressure + Acceleration + Temperature + Infrared” Sensor Using a Versatile Single-Sided “SiN/Poly-Si/Al” Process-Module
by Zao Ni, Chen Yang, Dehui Xu, Hong Zhou, Wei Zhou, Tie Li, Bin Xiong and Xinxin Li
Sensors 2013, 13(1), 1085-1101; https://doi.org/10.3390/s130101085 - 16 Jan 2013
Cited by 9 | Viewed by 9459
Abstract
We report a newly developed design/fabrication module with low-cost single-sided “low-stress-silicon-nitride (LS-SiN)/polysilicon (poly-Si)/Al” process for monolithic integration of composite sensors for sensing-network-node applications. A front-side surface-/bulk-micromachining process on a conventional Si-substrate is developed, featuring a multifunctional SiN/poly-Si/Al layer design for diverse sensing functions. [...] Read more.
We report a newly developed design/fabrication module with low-cost single-sided “low-stress-silicon-nitride (LS-SiN)/polysilicon (poly-Si)/Al” process for monolithic integration of composite sensors for sensing-network-node applications. A front-side surface-/bulk-micromachining process on a conventional Si-substrate is developed, featuring a multifunctional SiN/poly-Si/Al layer design for diverse sensing functions. The first “pressure + acceleration + temperature + infrared” (PATIR) composite sensor with the chip size of 2.5 mm × 2.5 mm is demonstrated. Systematic theoretical design and analysis methods are developed. The diverse sensing components include a piezoresistive absolute-pressure sensor (up to 700 kPa, with a sensitivity of 49 mV/MPa under 3.3 V supplied voltage), a piezoresistive accelerometer (±10 g, with a sensitivity of 66 μV/g under 3.3 V and a −3 dB bandwidth of 780 Hz), a thermoelectric infrared detector (with a responsivity of 45 V/W and detectivity of 3.6 × 107 cm·Hz1/2/W) and a thermistor (−25–120 °C). This design/fabrication module concept enables a low-cost monolithically-integrated “multifunctional-library” technique. It can be utilized as a customizable tool for versatile application-specific requirements, which is very useful for small-size, low-cost, large-scale sensing-network node developments. Full article
(This article belongs to the Section Physical Sensors)
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<p>Schematic of four sensing-structure types (cross-section view).</p> Full article ">Figure 2
<p>(<b>a</b>) Schematic of the prototype “pressure + acceleration + temperature + infrared” (PATIR) composite sensor design (cap not shown here). (<b>b</b>) The absolute-pressure sensor with the stress-distribution in pressure-sensing diaphragm. (<b>c</b>) The accelerometer with stress-distribution analysis along the beam. (<b>d</b>) The infrared detector (cross-section view) with simulated temperature distribution.</p> Full article ">Figure 3
<p>The developed single-side-integrated process flow for the prototype PATIR composite sensor.</p> Full article ">Figure 4
<p>Photos showing the prototype PATIR composite sensor: (<b>a</b>) and (<b>f</b>) full views, (<b>b</b>) thermistor, (<b>c</b>) piezoresistive absolute-pressure sensor, (<b>d</b>) piezoresistive accelerometer, (<b>e</b>) thermoelectric infrared detector.</p> Full article ">Figure 5
<p>Measurement results of the PATIR composite sensor. (<b>a</b>) Output response of the absolute-pressure sensor under pressure inputs. (<b>b</b>) Output response of the accelerometer under acceleration loads. (<b>c</b>) Frequency response of the accelerometer. (<b>d</b>) Self-test response of the accelerometer. The inset illustrates the principle of the developed self-test technique. (<b>e</b>) Real-time responses of the circular-membrane and square-membrane infrared detectors under the blackbody radiation signal. (<b>f</b>) Frequency response of the circular-membrane infrared detector. (<b>g</b>) Real-time response of the circular-membrane infrared detector when a human body passing by with 2 m distance. (<b>h</b>) Output response of the thermistor under temperature inputs.</p> Full article ">
303 KiB  
Article
Development of a Portable Taste Sensor with a Lipid/Polymer Membrane
by Yusuke Tahara, Kenichi Nakashi, Ke Ji, Akihiro Ikeda and Kiyoshi Toko
Sensors 2013, 13(1), 1076-1084; https://doi.org/10.3390/s130101076 - 16 Jan 2013
Cited by 35 | Viewed by 9823
Abstract
We have developed a new portable taste sensor with a lipid/polymer membrane and conducted experiments to evaluate the sensor’s performance. The fabricated sensor consists of a taste sensor chip (40 mm × 26 mm × 2.2 mm) with working and reference electrodes and [...] Read more.
We have developed a new portable taste sensor with a lipid/polymer membrane and conducted experiments to evaluate the sensor’s performance. The fabricated sensor consists of a taste sensor chip (40 mm × 26 mm × 2.2 mm) with working and reference electrodes and a portable sensor device (80 mm × 25 mm × 20 mm). The working electrode consists of a taste-sensing site comprising a poly(hydroxyethyl)methacrylate (pHEMA) hydrogel layer with KCl as the electrolyte layer and a lipid/polymer membrane as the taste sensing element. The reference electrode comprises a polyvinyl chloride (PVC) membrane layer with a small hole and a pHEMA layer with KCl. The whole device is the size of a USB memory stick, making it suitable for portable use. The sensor’s response to tannic acid as the standard astringency substance showed good accuracy and reproducibility, and was comparable with the performance of a commercially available taste sensing system. Thus, it is possible for this sensor to be used for in-field evaluations and it can make a significant contribution to the food industry, as well as in various fields of research. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2012)
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<p>(<b>a</b>) Fabricated taste sensor chip. (<b>b</b>) Structure of the working electrode. (<b>c</b>) Structure of the reference electrode.</p> Full article ">Figure 2
<p>Block diagram of portable taste sensor device.</p> Full article ">Figure 3
<p>Potential variation of the fabricated reference electrode. The experiment was carried out in the reference solution.</p> Full article ">Figure 4
<p>Response of the portable taste sensor to tannic acid. (<b>a</b>) Relative values. (<b>b</b>) CPA values.</p> Full article ">
358 KiB  
Article
G-Quadruplex DNAzyme Molecular Beacon for Amplified Colorimetric Biosensing of Pseudostellaria heterophylla
by Zhenzhu Zheng, Jing Han, Wensheng Pang and Juan Hu
Sensors 2013, 13(1), 1064-1075; https://doi.org/10.3390/s130101064 - 16 Jan 2013
Cited by 18 | Viewed by 8101
Abstract
With an internal transcribed spacer of 18 S, 5.8 S and 26 S nuclear ribosomal DNA (nrDNA ITS) as DNA marker, we report a colorimetric approach for authentication of Pseudostellaria heterophylla (PH) and its counterfeit species based on the differentiation of the nrDNA [...] Read more.
With an internal transcribed spacer of 18 S, 5.8 S and 26 S nuclear ribosomal DNA (nrDNA ITS) as DNA marker, we report a colorimetric approach for authentication of Pseudostellaria heterophylla (PH) and its counterfeit species based on the differentiation of the nrDNA ITS sequence. The assay possesses an unlabelled G-quadruplex DNAzyme molecular beacon (MB) probe, employing complementary sequence as biorecognition element and 1:1:1:1 split G-quadruplex halves as reporter. In the absence of target DNA (T-DNA), the probe can shape intermolecular G-quadruplex structures capable of binding hemin to form G-quadruplex-hemin DNAzyme and catalyze the oxidation of ABTS2− to blue-green ABTS•− by H2O2. In the presence of T-DNA, T-DNA can hybridize with the complementary sequence to form a duplex structure, hindering the formation of the G-quadruplex structure and resulting in the loss of the catalytic activity. Consequently, a UV-Vis absorption signal decrease is observed in the ABTS2−-H2O2 system. The “turn-off” assay allows the detection of T-DNA from 1.0 × 10−9 to 3.0 × 10−7 mol·L−1 (R2 = 0.9906), with a low detection limit of 3.1 × 10−10 mol·L−1. The present study provides a sensitive and selective method and may serve as a foundation of utilizing the DNAzyme MB sensor for identifying traditional Chinese medicines. Full article
(This article belongs to the Section Biosensors)
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<p>Working principle of the 1:1:1:1 split G-quadruplex DNAzyme MB sensor for PH nrDNA ITS.</p> Full article ">Figure 2
<p>Absorbance spectra of the H<sub>2</sub>O<sub>2</sub> mediated ABTS<sup>2−</sup> colorimetric system. (<b>a</b>) probe-1 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>b</b>) probe-1 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>), T-DNA (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>c</b>) probe-2 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>d</b>) probe-2 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>), T-DNA (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>e</b>) probe-3 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>f</b>) probe-3 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>), T-DNA (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>g</b>) probe-4 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); (<b>h</b>) probe-4 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>), T-DNA (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>).</p> Full article ">Figure 3
<p>CD spectra of (<b>a</b>) probe-1 (1.0 × 10<sup>−6</sup> mol·L<sup>−1</sup>), (<b>b</b>) probe-2 (1.0 × 10<sup>−6</sup> mol·L<sup>−1</sup>), (<b>c</b>) probe-3 (1.0 × 10<sup>−6</sup> mol·L<sup>−1</sup>), (<b>d</b>) probe-4 (1.0 × 10<sup>−6</sup> mol·L<sup>−1</sup>), (<b>e</b>) probe-4 (1.0 × 10<sup>−6</sup> mol·L<sup>−1</sup>) + T-DNA (1.0 × 10<sup>−6</sup> mol·L<sup>−1</sup>).</p> Full article ">Figure 4
<p>(<b>A</b>) Absorbance spectra of the H<sub>2</sub>O<sub>2</sub> mediated ABTS<sup>2−</sup> colorimetric system with probe-4 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>); T-DNA (a) 1.0 × 10<sup>−9</sup>; (b) 3.0 × 10<sup>−9</sup>; (c) 5.0 × 10<sup>−9</sup>; (d) 8.0 × 10<sup>−9</sup>; (e) 5.0 × 10<sup>−8</sup>; (f) 1.0 × 10<sup>−7</sup> and (g) 3.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>. Inset: visual color changes of the systems with different concentrations of T-DNA. (<b>B</b>) Absorbance value at 419 nm of the colorimetric system with probe-4 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>) <span class="html-italic">versus</span> T-DNA concentration. Inset: derived calibration curve.</p> Full article ">Figure 5
<p>Absorbance value at 419 nm of the G-quadruplex DNAzyme MB colorimetric system containing probe-4 (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>) in the presence of T-DNA (1.0 × 10<sup>−7</sup> mol·L<sup>−1</sup>) or C-DNA (1.0 × 10<sup>−7</sup> mol·L<sup>1</sup>) respectively.</p> Full article ">
407 KiB  
Article
A Novel Scheme for DVL-Aided SINS In-Motion Alignment Using UKF Techniques
by Wanli Li, Jinling Wang, Liangqing Lu and Wenqi Wu
Sensors 2013, 13(1), 1046-1063; https://doi.org/10.3390/s130101046 - 15 Jan 2013
Cited by 87 | Viewed by 8543
Abstract
In-motion alignment of Strapdown Inertial Navigation Systems (SINS) without any geodetic-frame observations is one of the toughest challenges for Autonomous Underwater Vehicles (AUV). This paper presents a novel scheme for Doppler Velocity Log (DVL) aided SINS alignment using Unscented Kalman Filter (UKF) which [...] Read more.
In-motion alignment of Strapdown Inertial Navigation Systems (SINS) without any geodetic-frame observations is one of the toughest challenges for Autonomous Underwater Vehicles (AUV). This paper presents a novel scheme for Doppler Velocity Log (DVL) aided SINS alignment using Unscented Kalman Filter (UKF) which allows large initial misalignments. With the proposed mechanism, a nonlinear SINS error model is presented and the measurement model is derived under the assumption that large misalignments may exist. Since a priori knowledge of the measurement noise covariance is of great importance to robustness of the UKF, the covariance-matching methods widely used in the Adaptive KF (AKF) are extended for use in Adaptive UKF (AUKF). Experimental results show that the proposed DVL-aided alignment model is effective with any initial heading errors. The performances of the adaptive filtering methods are evaluated with regards to their parameter estimation stability. Furthermore, it is clearly shown that the measurement noise covariance can be estimated reliably by the adaptive UKF methods and hence improve the performance of the alignment. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
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<p>DVL-aided IMU alignment scheme.</p> Full article ">
<p>Fixing of experimental devices.</p> Full article ">
<p>Alignment flowchart.</p> Full article ">
<p>Heading error comparison with different initial heading errors.</p> Full article ">
<p>Convergence time comparison with different initial heading errors.</p> Full article ">
<p>Heading error comparison with extra large initial heading errors.</p> Full article ">
<p>Estimation of measurement noise covariance with different window sizes by innovation-based AUKF.</p> Full article ">
<p>Estimation of measurement noise covariance with different window sizes by residual-based AUKF.</p> Full article ">
<p>Estimation of measurement noise covariance with different initial <span class="html-italic">R</span> values by innovation-based AUKF.</p> Full article ">
2061 KiB  
Review
A Flexible Sensor Technology for the Distributed Measurement of Interaction Pressure
by Marco Donati, Nicola Vitiello, Stefano Marco Maria De Rossi, Tommaso Lenzi, Simona Crea, Alessandro Persichetti, Francesco Giovacchini, Bram Koopman, Janez Podobnik, Marko Munih and Maria Chiara Carrozza
Sensors 2013, 13(1), 1021-1045; https://doi.org/10.3390/s130101021 - 15 Jan 2013
Cited by 73 | Viewed by 16102
Abstract
We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant’Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is [...] Read more.
We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant’Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is completely modular and scalable, allowing one to cover areas of any sizes and shapes, and to measure different pressure ranges. In this work we present the main application areas for this technology. A first generation of the system was used to monitor human-robot interaction in upper- (NEUROExos; Scuola Superiore Sant’Anna) and lower-limb (LOPES; University of Twente) exoskeletons for rehabilitation. A second generation, with increased resolution and wireless connection, was used to develop a pressure-sensitive foot insole and an improved human-robot interaction measurement systems. The experimental characterization of the latter system along with its validation on three healthy subjects is presented here for the first time. A perspective on future uses and development of the technology is finally drafted. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)
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<p>Overview of the PSP1: (<b>a</b>) specific scheme of the 1 × 8 array of sensitive elements of the PSP 1.0 and PSP1.1; (<b>b</b>) scheme of the transduction principle; (<b>c</b>) 3D design of the PSP1.1 (adapted from [<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]).</p> Full article ">Figure 2
<p>Cross section of the PSP1.1 (adapted from [<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]).</p> Full article ">Figure 3
<p>Finite element simulation of PSP1.1: (<b>a</b>) un-deformed structure; the rigid flat indenter is transparent brown, the silicone structure is grey and the PCB is green; (<b>b</b>) total deformation representation; (<b>c</b>) total stress representation (adapted from [<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]).</p> Full article ">Figure 4
<p>Force (or pressure) <span class="html-italic">vs.</span> output voltage of the PSP1 1 × 8 array of sensitive elements: (<b>a</b>) PSP1.0; (<b>b</b>) PSP1.1 (adapted from [<a href="#b33-sensors-13-01021" class="html-bibr">33</a>,<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]. (a) is a slightly adapted reprinted graphics from [<a href="#b33-sensors-13-01021" class="html-bibr">33</a>], ©2011, with permission from Elsevier).</p> Full article ">Figure 4 Cont.
<p>Force (or pressure) <span class="html-italic">vs.</span> output voltage of the PSP1 1 × 8 array of sensitive elements: (<b>a</b>) PSP1.0; (<b>b</b>) PSP1.1 (adapted from [<a href="#b33-sensors-13-01021" class="html-bibr">33</a>,<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]. (a) is a slightly adapted reprinted graphics from [<a href="#b33-sensors-13-01021" class="html-bibr">33</a>], ©2011, with permission from Elsevier).</p> Full article ">Figure 5
<p>Overview of the second-generation PSP sensitive element: (<b>a</b>) dimension of the sensitive element, (<b>b</b>) transduction principle (adapted from [<a href="#b39-sensors-13-01021" class="html-bibr">39</a>], ©2011 IEEE. Reprinted with permission).</p> Full article ">Figure 6
<p>Cross section of the PSP2 silicone cover; the geometrical parameters are: cover thickness T, height of the curtain H1, pyramidal frustum height H2, square base size B1, square top-face size B2.</p> Full article ">Figure 7
<p>3D FE simulations of PSP2.1: (<b>a</b>) simulation environment: in blue the rigid indenter, in grey the silicone structure, in green the PCB; (<b>b</b>) map of the total deformation, (<b>c</b>) cross-section of the pyramidal frustum showing the sinking effect.</p> Full article ">Figure 8
<p>Characterization of the sensitive element of PSP2.0: (<b>a</b>) quasi-static force-to-deformation characterization; (<b>b</b>) quasi-static force-to-voltage curve (adapted from [<a href="#b39-sensors-13-01021" class="html-bibr">39</a>], ©2011 IEEE. Reprinted, with permission).</p> Full article ">Figure 9
<p>Results of the PSP2.1 characterization: (<b>a</b>) quasi-static force-to-deformation loading-unloading, averaged over three iterations (black line is the loading phase, grey line is the unloading phase); (<b>b</b>) all fitting curves of loading-unloading cycles at seven different levels of loading speed (namely, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1 mm/s); (<b>c</b>) quasi-static force-to-voltage curve (blue dots are experimental data, black line is the smoothing spline).</p> Full article ">Figure 10
<p>The NEUROExos platform equipped with two PSPs 1.0. (<b>a</b>) PSP placement onto inner-side of exoskeleton inner-shells; front (<b>b</b>) and lateral (<b>c</b>) view of a subject wearing the NEUROExos (adapted from [<a href="#b33-sensors-13-01021" class="html-bibr">33</a>], ©2011, with permission from Elsevier).</p> Full article ">Figure 11
<p>NEUROExos joint trajectory, front- and back-side PSP1.0 pressure profiles during a prototypical rehabilitation task, with and without the user <span class="html-italic">reaction</span>. Top panel reports: the reference trajectory of the rehabilitation task (dashed line), the “no action” trajectory (gray line), and the “pre-defined action” performed by the subject (black line). Middle and bottom panels report respectively front- and back-side PSP1.0 pressure profiles: the “no action” condition is the gray line, the “pre-defined action” is the black line. Pressure profiles are averaged over ten sinusoidal motions and reported along with standard-deviation contour (dotted line). We assume that the elbow is fully extended when the joint angle is equal to zero (figure adapted from [<a href="#b33-sensors-13-01021" class="html-bibr">33</a>], ©2011, with permission from Elsevier).</p> Full article ">Figure 12
<p>(<b>a</b>) Overview of the LOPES exoskeleton; (<b>b</b>) right-leg thigh cuff sensorized with six PSPs 1.1; (<b>c</b>) schematic view of the right-leg sensorized cuff (adapted from [<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]).</p> Full article ">Figure 13
<p>Test of PSP1.1 on the LOPES: profiles of right hip flexion-extension angle, total interaction force measured by the load cell, and the force estimated by three of the six PSPs (<span class="html-italic">i.e.</span>, “Front 1”, “Front 2”, “Rear 1”). Data are shown for two conditions: transparent and viscous field (figure adapted from [<a href="#b37-sensors-13-01021" class="html-bibr">37</a>]).</p> Full article ">Figure 14
<p>PSP2.0-based pressure-sensitive insoles. (<b>a</b>) Overview of the pressure-sensitive insole on the bench; (<b>b</b>) two pressure-sensitive insoles integrated into normal sneaker shoes.</p> Full article ">Figure 15
<p>Gait phases recognition through the pressure-sensitive insole for both left (top panel) and right (bottom panel) feet.</p> Full article ">Figure 16
<p>New PSP2.1-based LOPES sensorized cuffs. (<b>a</b>) Overview of the 8 × 4 and 4 × 4 sensitive arrays; (<b>b</b>) sensorized thigh cuff; (<b>c</b>) sensorized shank and ankle cuffs; (<b>d</b>) overview of the LOPES with all of the six cuffs endowed with PSPs 2.1.</p> Full article ">Figure 17
<p>Hip kinematic and dynamic variables for Subject #1: right-leg hip flexion-extension joint angle and torque, and total force recorded by front- (F-S) and back-side (B-S) thigh-cuff PSPs. Data are averaged over 20 gait cycles (solid line), and shown along with the standard deviation contour (shadowed), for three conditions: (<b>a</b>) gait velocity is 2.5 km/h, with assistive torque; (<b>b</b>) gait velocity is 4 km/h, with assistive torque; (<b>c</b>) gait velocity is 4 km/h without assistive torque.</p> Full article ">
11521 KiB  
Article
Registration of 3D and Multispectral Data for the Study of Cultural Heritage Surfaces
by Camille Simon Chane, Rainer Schütze, Frank Boochs and Franck S. Marzani
Sensors 2013, 13(1), 1004-1020; https://doi.org/10.3390/s130101004 - 15 Jan 2013
Cited by 14 | Viewed by 8019
Abstract
We present a technique for the multi-sensor registration of featureless datasets based on the photogrammetric tracking of the acquisition systems in use. This method is developed for the in situ study of cultural heritage objects and is tested by digitizing a small canvas [...] Read more.
We present a technique for the multi-sensor registration of featureless datasets based on the photogrammetric tracking of the acquisition systems in use. This method is developed for the in situ study of cultural heritage objects and is tested by digitizing a small canvas successively with a 3D digitization system and a multispectral camera while simultaneously tracking the acquisition systems with four cameras and using a cubic target frame with a side length of 500 mm. The achieved tracking accuracy is better than 0.03 mm spatially and 0.150 mrad angularly. This allows us to seamlessly register the 3D acquisitions and to project the multispectral acquisitions on the 3D model. Full article
(This article belongs to the Section Physical Sensors)
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<p>Acquisition overview. An edge detection was performed to improve image readability.</p> Full article ">
<p>Gom Atos III in the target frame acquiring the cross-stitch canvas.</p> Full article ">
<p>Relative position of the tracking cameras (dark gray) and target frame for all the acquisition positions.</p> Full article ">
<p>Spatial (blue squares) and angular (green circles) tracking accuracy compared with the best-case scenario simulation results (<b>a</b>) and to the tracking goal (<b>b</b>).</p> Full article ">
<p>3D registration. First row: successive projection of each mesh. Bottom image: all meshes.</p> Full article ">
<p>Multispectral/3D registration.</p> Full article ">
<p>Closeup of the multispectral / 3D registration. (<b>a</b>) shows the inaccuracy of the 3D to multispectral registration while (<b>b</b>) highlights the seamless multispectral registration.</p> Full article ">
460 KiB  
Review
Monitoring Ion Activities In and Around Cells Using Ion-Selective Liquid-Membrane Microelectrodes
by Seong-Ki Lee, Walter F. Boron and Mark D. Parker
Sensors 2013, 13(1), 984-1003; https://doi.org/10.3390/s130100984 - 15 Jan 2013
Cited by 27 | Viewed by 10425
Abstract
Determining the effective concentration (i.e., activity) of ions in and around living cells is important to our understanding of the contribution of those ions to cellular function. Moreover, monitoring changes in ion activities in and around cells is informative about the [...] Read more.
Determining the effective concentration (i.e., activity) of ions in and around living cells is important to our understanding of the contribution of those ions to cellular function. Moreover, monitoring changes in ion activities in and around cells is informative about the actions of the transporters and/or channels operating in the cell membrane. The activity of an ion can be measured using a glass microelectrode that includes in its tip a liquid-membrane doped with an ion-selective ionophore. Because these electrodes can be fabricated with tip diameters that are less than 1 μm, they can be used to impale single cells in order to monitor the activities of intracellular ions. This review summarizes the history, theory, and practice of ion-selective microelectrode use and brings together a number of classic and recent examples of their usefulness in the realm of physiological study. Full article
(This article belongs to the Special Issue Ultramicroelectrode Electrochemistry - Theory and Applications)
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<p>(<b>a</b>) Two compartments that contain equal numbers of ions, separated by a semi-permeable membrane. (<b>b</b>) Two compartments that differ ten-fold in ion content, separated by a semi-permeable membrane. (<b>c</b>) Model of an ISM based on <a href="#f1-sensors-13-00984" class="html-fig">Figure 1(A)</a>. (<b>d</b>) Model of ISM calibration.</p> Full article ">
<p>Example calibration plot for an intracellular Na<sup>+</sup>-selective microelectrode gathered using NaCl solutions.</p> Full article ">
<p>Micrograph of blunt-tipped and sharp-tipped microelectrodes taken with a M205A Stereomicroscope (Leica Microsystems, Buffalo Grove, IL, USA). Blue arrows show ionophore-cocktail meniscus.</p> Full article ">
<p>Schematic of microelectrode holder/ISM assembly.</p> Full article ">
<p>Schematic of electrical configuration required to monitor the ion-selective response of an ISM (brown circuit). Amp = Amplifier, Diff amp = Differential Amplifier. The blue circuit represents optional components required to simultaneously monitor membrane potential (<span class="html-italic">V</span><sub>m</sub>) during intracellular recordings. Faraday shielding is also necessary, but not shown.</p> Full article ">
810 KiB  
Article
Applications of Flexible Ultrasonic Transducer Array for Defect Detection at 150 °C
by Jeanne-Louise Shih, Kuo-Ting Wu, Cheng-Kuei Jen, Chun-Hsiung Chiu, Jing-Chi Tzeng and Jiunn-Woei Liaw
Sensors 2013, 13(1), 975-983; https://doi.org/10.3390/s130100975 - 15 Jan 2013
Cited by 17 | Viewed by 8925
Abstract
In this study, the feasibility of using a one dimensional 16-element flexible ultrasonic transducer (FUT) array for nondestructive testing at 150 °C is demonstrated. The FUT arrays were made by a sol-gel sprayed piezoelectric film technology; a PZT composite film was sprayed on [...] Read more.
In this study, the feasibility of using a one dimensional 16-element flexible ultrasonic transducer (FUT) array for nondestructive testing at 150 °C is demonstrated. The FUT arrays were made by a sol-gel sprayed piezoelectric film technology; a PZT composite film was sprayed on a titanium foil of 75 µm thickness. Since the FUT array is flexible, it was attached to a steel pipe with an outer diameter of 89 mm and a wall thickness of 6.5 mm at 150 °C. Using the ultrasonic pulse-echo mode, pipe thickness measurements could be performed. Moreover, using the ultrasonic pulse-echo and pitch-catch modes of each element of FUT array, the defect detection was performed on an Al alloy block of 30 mm thickness with a side-drilled hole (SDH) of f3 mm at 150 °C. In addition, a post-processing algorithm based on the total focusing method was used to process the full matrix of these A-scan signals of each single transmitter and multi-receivers, and then the phase-array image was obtained to indicate this defect- SDH. Both results show the capability of FUT array being operated at 150 °C for the corrosion and defect detections. Full article
(This article belongs to the Section Physical Sensors)
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<p>(<b>a</b>) Configuration of FUT array: aperture (A<sub>FUT</sub>), element size (E<sub>FUT</sub>), height (H<sub>FUT</sub>), gap (G<sub>FUT</sub>) and pitch (P<sub>FUT</sub>). (<b>b</b>) Top and (<b>c</b>) bottom view of a 1D 16-element FUT array on a 75 μm thick Ti foil.</p> Full article ">Figure 1 Cont.
<p>(<b>a</b>) Configuration of FUT array: aperture (A<sub>FUT</sub>), element size (E<sub>FUT</sub>), height (H<sub>FUT</sub>), gap (G<sub>FUT</sub>) and pitch (P<sub>FUT</sub>). (<b>b</b>) Top and (<b>c</b>) bottom view of a 1D 16-element FUT array on a 75 μm thick Ti foil.</p> Full article ">Figure 2
<p>Schematic of TFM for pitch-catch signals of the <span class="html-italic">i</span>th transmitter and the <span class="html-italic">j</span>th receiver.</p> Full article ">Figure 3
<p>(<b>a</b>) Schematic and (<b>b</b>) experimental setup for ultrasonic measurements of FUT array on a metal block at 150 °C.</p> Full article ">Figure 4
<p>(<b>a</b>) Ultrasonic pulse-echo measurements of FUT array (element size: 6 mm × 3 mm, gap: 1 mm) for a steel pipe of OD: 89 mm with 6.5 mm thickness at 150 °C, where (<b>b</b>) is the signal of element 5 and (<b>c</b>) the signal of element 9.</p> Full article ">Figure 5
<p>(<b>a</b>) The pulse-echo signal <span class="html-italic">A</span><sub>44</sub>, (<b>b</b>) the pitch-catch signal <span class="html-italic">A</span><sub>45</sub>, and (<b>c</b>) the synthesized signal <span class="html-italic">S</span><sub>4</sub> of the target point (10 mm, 13.5 mm) for 8-elements FUT array (element size: 10 mm × 2 mm, gap: 1 mm) inspecting an Al alloy block with a SDH of ϕ3 mm at the middle at 150 °C.</p> Full article ">Figure 6
<p>The pitch-catch signal <span class="html-italic">A</span><sub>12</sub> of the target point (0, 30 nm).</p> Full article ">Figure 7
<p>TFM images of (<b>a</b>) 8-elements FUT array (element size: 10 mm × 2 mm, gap: 1 mm) and (<b>b</b>) 7-elements FUT array (element size: 9 mm ×2 mm, gap: 0.5 mm) inspecting an Al alloy block of 30 mm thickness with a SDH of ϕ3 mm at the middle at 150 °C. Dashed circle: SDH.</p> Full article ">
576 KiB  
Article
C59N Peapods Sensing the Temperature
by Yongfeng Li, Toshiro Kaneko and Rikizo Hatakeyama
Sensors 2013, 13(1), 966-974; https://doi.org/10.3390/s130100966 - 15 Jan 2013
Cited by 4 | Viewed by 6018
Abstract
We report the novel photoresponse of nanodevices made from azafullerene (C59N)-encapsulated single-walled carbon nanotubes (C59N@SWNTs), so called peapods. The photoconducting properties of a C59N@SWNT are measured over a temperature range of 10 to 300 K under a [...] Read more.
We report the novel photoresponse of nanodevices made from azafullerene (C59N)-encapsulated single-walled carbon nanotubes (C59N@SWNTs), so called peapods. The photoconducting properties of a C59N@SWNT are measured over a temperature range of 10 to 300 K under a field-effect transistor configuration. It is found that the photosensitivity of C59N@SWNTs depends very sensitively on the temperature, making them an attractive candidate as a component of nanothermometers covering a wide temperature range. Our results indicate that it is possible to read the temperature by monitoring the optoelectronics signal of C59N@SWNTs. In particular, sensing low temperatures would become more convenient and easy by giving a simple light pulse. Full article
(This article belongs to the Special Issue Nanotube and Nanowire Sensors)
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<p>(<b>a</b>) A TEM image of C<sub>59</sub>N@SWNTs. (<b>b</b>) EDX of C<sub>59</sub>N@SWNTs.</p> Full article ">
<p>(<b>a</b>) Schematic illustration of FET configuration with a SWNT as current channel. (<b>b</b>) An AFM image of C<sub>59</sub>N@SWNT-FET.</p> Full article ">
<p>(<b>a</b>) <span class="html-italic">I<sub>DS</sub></span>-<span class="html-italic">V<sub>G</sub></span> curve measured with <span class="html-italic">V<sub>DS</sub></span> = 1 V for a pristine SWNT-FET device. (<b>b</b>) <span class="html-italic">I<sub>DS</sub></span>-<span class="html-italic">V<sub>G</sub></span> curve measured with <span class="html-italic">V<sub>DS</sub></span> = 1 V for a C<sub>59</sub>N@SWNT-FET device.</p> Full article ">
<p>(<b>a</b>) <span class="html-italic">I<sub>DS</sub>-V<sub>G</sub></span> characteristics (<span class="html-italic">V<sub>DS</sub></span> = 1 V) of a C<sub>59</sub>N@SWNT-FET device measured without and with light (400 nm) illumination at room temperature 300 K. (<b>b</b>) <span class="html-italic">I<sub>DS</sub>-V<sub>G</sub></span> characteristics (<span class="html-italic">V<sub>DS</sub></span> = 0.5 V) of a C<sub>59</sub>N@SWNT-FET device measured without and with light (400 nm) illumination at low temperature of 10 K.</p> Full article ">
<p><span class="html-italic">I</span><sub>DS</sub>-<span class="html-italic">V</span><sub>G</sub> characteristics (<span class="html-italic">V<sub>DS</sub></span> = 0.5 V) measured at 10 K for an <span class="html-italic">n</span>-type C<sub>59</sub>N@SWNT with a light pulse (400 nm) at <span class="html-italic">V<sub>G</sub></span> = 21 V and 26 V.</p> Full article ">
<p><span class="html-italic">I</span><sub>DS</sub> measured as a function of time at 10 K under exposure of a light pulse (400 nm) for a C<sub>59</sub>N@SWNT-FET device with <span class="html-italic">V</span><sub>DS</sub> = 0.5 V.</p> Full article ">
<p>Photoinduced currents observed during tracing the <span class="html-italic">I</span><sub>DS</sub>-<span class="html-italic">V</span><sub>G</sub> curves upon a light pulse at (<b>a</b>) 10 K, (<b>b</b>) 90 K, (<b>c</b>) 140 and (<b>d</b>) 300 K, respectively.</p> Full article ">
<p>Variation of photoinduced current (Δ<span class="html-italic">I</span><sub>DS</sub>/<span class="html-italic">I</span><sub>DS</sub>) measured with temperature under exposure of a light pulse (400 nm).</p> Full article ">
550 KiB  
Article
Surface Plasmon Resonance Sensor Based on Polymer Photonic Crystal Fibers with Metal Nanolayers
by Ying Lu, Cong-Jing Hao, Bao-Qun Wu, Mayilamu Musideke, Liang-Cheng Duan, Wu-Qi Wen and Jian-Quan Yao
Sensors 2013, 13(1), 956-965; https://doi.org/10.3390/s130100956 - 15 Jan 2013
Cited by 73 | Viewed by 7985
Abstract
A large-mode-area polymer photonic crystal fiber made of polymethyl methacrylate with the cladding having only one layer of air holes near the edge of the fiber is designed and proposed to be used in surface plasmon resonance sensors. In such sensor, a nanoscale [...] Read more.
A large-mode-area polymer photonic crystal fiber made of polymethyl methacrylate with the cladding having only one layer of air holes near the edge of the fiber is designed and proposed to be used in surface plasmon resonance sensors. In such sensor, a nanoscale metal film and analyte can be deposited on the outer side of the fiber instead of coating or filling in the holes of the conventional PCF, which make the real time detection with high sensitivity easily to realize. Moreover, it is relatively stable to changes of the amount and the diameter of air holes, which is very beneficial for sensor fabrication and sensing applications. Numerical simulation results show that under the conditions of the similar spectral and intensity sensitivity of 8.3 × 10−5–9.4 × 10−5 RIU, the confinement loss can be increased dramatically. Full article
(This article belongs to the Section Physical Sensors)
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<p>(<b>a</b>) Structure diagram of the large-mode-area plastic photonic crystal fiber; (<b>b</b>) Optical field distribution of the fundamental mode.</p> Full article ">
<p>(<b>a</b>) Relationship between wavelength and attenuation constant of the fundamental mode of the hollow-core large-mode-area PCF. The black and red curves represent the refractive indices of the samples are 1.33 and 1.335 (Δλpeak ≈ 6 nm), respectively; (<b>b</b>) Intensity detection sensitivity curve.</p> Full article ">
<p>Structure diagram of the improved large-mode-area plastic PCF with 125 μm diameter and seven air holes.</p> Full article ">
<p>(<b>a</b>) Relationship between wavelength and attenuation constant of the fundamental mode of the PMMA PCF. The red and blue curves represent the refractive indices of the samples are 1.33 and 1.335 (Δ<span class="html-italic">λ</span>peak ≈ 6 nm), respectively; (<b>b</b>) Intensity detection sensitivity curve.</p> Full article ">
<p>(<b>a</b>) the improved structure diagram of the large-mode-area plastic PCF with 125 μm diameter and more air holes; (<b>b</b>) Optical field distribution of the fundamental mode.</p> Full article ">
<p>(<b>a</b>) Relationship between wavelength and attenuation constant of the fundamental mode of the PMMA PCF. The black and red curves represent the refractive indices of the samples are 1.33 and 1.335 (Δ<span class="html-italic">λ</span><sub>peak</sub> ≈ 6nm), respectively; (<b>b</b>) Intensity detection sensitivity curve.</p> Full article ">
<p>(<b>a</b>) The comparison of attenuation constant of the fundamental mode of different diameters of the air holes (<b>b</b>) The comparison of intensity detection sensitivity curves.</p> Full article ">
<p>Loss spectra of the structure of <a href="#f5-sensors-13-00956" class="html-fig">Figure 5(a)</a> at different silver layer thickness (t<sub>Ag</sub> = 30 nm, 40 nm, 50 nm). Analyte refractive index (n<span class="html-italic"><sub>a</sub></span> = 1.33).</p> Full article ">
322 KiB  
Review
Odor Sampling: Techniques and Strategies for the Estimation of Odor Emission Rates from Different Source Types
by Laura Capelli, Selena Sironi and Renato Del Rosso
Sensors 2013, 13(1), 938-955; https://doi.org/10.3390/s130100938 - 15 Jan 2013
Cited by 78 | Viewed by 10114
Abstract
Sampling is one of the main issues pertaining to odor characterization and measurement. The aim of sampling is to obtain representative information on the typical characteristics of an odor source by means of the collection of a suitable volume fraction of the effluent. [...] Read more.
Sampling is one of the main issues pertaining to odor characterization and measurement. The aim of sampling is to obtain representative information on the typical characteristics of an odor source by means of the collection of a suitable volume fraction of the effluent. The most important information about an emission source for odor impact assessment is the so-called Odor Emission Rate (OER), which represents the quantity of odor emitted per unit of time, and is expressed in odor units per second (ou∙s−1). This paper reviews the different odor sampling strategies adopted depending on source type. The review includes an overview of odor sampling regulations and a detailed discussion of the equipment to be used as well as the mathematical considerations to be applied to obtain the OER in relation to the sampled source typology. Full article
(This article belongs to the Special Issue Odor Detection: Electronic Nose, Olfactometer, and Advanced Instrumentation)
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<p>Scheme of sampling by means of vacuum pump.</p> Full article ">
<p>Scheme of sampling from an active surface source.</p> Full article ">
<p>Principle of hood sampling on a passive surface source.</p> Full article ">
800 KiB  
Article
Quasi-Real Time Estimation of Angular Kinematics Using Single-Axis Accelerometers
by Alessio Caroselli, Fabio Bagalà and Angelo Cappello
Sensors 2013, 13(1), 918-937; https://doi.org/10.3390/s130100918 - 15 Jan 2013
Cited by 16 | Viewed by 8353
Abstract
In human movement modeling, the problem of multi-link kinematics estimation by means of inertial measurement units has been investigated by several authors through efficient sensor fusion algorithms. In this perspective a single inertial measurement unit per link is required. This set-up is not [...] Read more.
In human movement modeling, the problem of multi-link kinematics estimation by means of inertial measurement units has been investigated by several authors through efficient sensor fusion algorithms. In this perspective a single inertial measurement unit per link is required. This set-up is not cost-effective compared with a solution in which a single-axis accelerometer per link is used. In this paper, a novel fast technique is presented for the estimation of the sway angle in a multi-link chain by using a single-axis accelerometer per segment and by setting the boundary conditions through an ad hoc algorithm. The technique, based on the windowing of the accelerometer output, was firstly tested on a mechanical arm equipped with a single-axis accelerometer and a reference encoder. The technique is then tested on a subject performing a squat task for the knee flexion-extension angle evaluation by using two single-axis accelerometers placed on the thigh and shank segments, respectively. A stereo-photogrammetric system was used for validation. RMSEs (mean ± std) are 0.40 ± 0.02° (mean peak-to-peak range of 147.2 ± 4.9°) for the mechanical inverted pendulum and 1.01 ± 0.11° (mean peak-to-peak range of 59.29 ± 2.02°) for the knee flexion-extension angle. Results obtained in terms of RMSE were successfully compared with an Extended Kalman Filter applied to an inertial measurement unit. These results suggest the usability of the proposed algorithm in several fields, from automatic control to biomechanics, and open new opportunities to increase the accuracy of the existing tools for orientation evaluation. Full article
(This article belongs to the Section Physical Sensors)
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<p>(<b>a</b>) IP model and (<b>b</b>) IP model with misalignment of the sensitive axis of the SAA.</p> Full article ">Figure 2
<p>Algorithm structure.</p> Full article ">Figure 3
<p>Mechanical Inverted Pendulum.</p> Full article ">Figure 4
<p>Two-links model for the knee flexion-extension angle estimation.</p> Full article ">Figure 5
<p>Residual error between the encoder output and sway angle estimated from the accelerometer output in the mechanical inverted pendulum.</p> Full article ">Figure 6
<p>(<b>a</b>) Window size <span class="html-italic">vs.</span> algorithm speed. (<b>b</b>) Window size <span class="html-italic">vs.</span> RMSE [%].</p> Full article ">Figure 7
<p>Residual error of the knee flexion-extension angle estimated by the quasi-real time algorithm and the EKF fusing accelerometers and gyroscope outputs. The angle estimated by stereo-photogrammetry was used as reference.</p> Full article ">
3867 KiB  
Article
Evaluation of a 433 MHz Band Body Sensor Network for Biomedical Applications
by Saim Kim, Christian Brendle, Hyun-Young Lee, Marian Walter, Sigrid Gloeggler, Stefan Krueger and Steffen Leonhardt
Sensors 2013, 13(1), 898-917; https://doi.org/10.3390/s130100898 - 14 Jan 2013
Cited by 25 | Viewed by 8653
Abstract
Body sensor networks (BSN) are an important research topic due to various advantages over conventional measurement equipment. One main advantage is the feasibility to deploy a BSN system for 24/7 health monitoring applications. The requirements for such an application are miniaturization of the [...] Read more.
Body sensor networks (BSN) are an important research topic due to various advantages over conventional measurement equipment. One main advantage is the feasibility to deploy a BSN system for 24/7 health monitoring applications. The requirements for such an application are miniaturization of the network nodes and the use of wireless data transmission technologies to ensure wearability and ease of use. Therefore, the reliability of such a system depends on the quality of the wireless data transmission. At present, most BSNs use ZigBee or other IEEE 802.15.4 based transmission technologies. Here, we evaluated the performance of a wireless transmission system of a novel BSN for biomedical applications in the 433MHz ISM band, called Integrated Posture and Activity NEtwork by Medit Aachen (IPANEMA) BSN. The 433MHz ISM band is used mostly by implanted sensors and thus allows easy integration of such into the BSN. Multiple measurement scenarios have been assessed, including varying antenna orientations, transmission distances and the number of network participants. The mean packet loss rate (PLR) was 0.63% for a single slave, which is comparable to IEEE 802.15.4 BSNs in the proximity of Bluetooth orWiFi networks. Secondly, an enhanced version is evaluated during on-body measurements with five slaves. The mean PLR results show a comparable good performance for measurements on a treadmill (2.5%), an outdoor track (3.4%) and in a climate chamber (1.5%). Full article
(This article belongs to the Section Sensor Networks)
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<p>Functional units on the circuit board of an IPANEMA node generation 2.</p> Full article ">
<p>Drawing showing the difference in size between (<b>a</b>) the MedIT BSN; (<b>b</b>) the IPANEMA BSN nodes generation 2 and (<b>c</b>) generation 2.5. Both IPANEMA 2 and 2.5 fit into the same housing.</p> Full article ">
<p>IPANEMA star-shaped network with three sensor slaves and one master module. Data are relayed to a PDA that can send the data over a WiFi or UMTS connection to a back-end server.</p> Full article ">
<p>TDMA scheme of the IPANEMA generation 2.5 nodes.</p> Full article ">
<p>Diagram of the data interception setup of the master and slave node. A terminal program called <span class="html-italic">Hterm</span> is used to record the serial data stream.</p> Full article ">
<p>Antenna orientation for measurement of the packet loss rate of IPANEMA generation 2 nodes. The double-headed arrows represent the master antenna and the single-headed arrows represent the slave antenna. Black arrows represent antennas on the top of the circuit board, and grey arrows the antennas on the bottom of the circuit board.</p> Full article ">
<p>Position of the IPANEMA generation 2.5 sensor nodes on the body.</p> Full article ">
<p>Measured power spectrum of the MSK modulated signal with a PN-generated random payload and a resolution bandwidth (RBW) of 50 kHz.</p> Full article ">
<p>Measured spectrogram of the transmission of one packet. First, the sync word was sent to signalize the transmission of a new packet to the receiver and to ensure that the channel was clear. This was done by switching between 0 and 1. Then, the protocol header was sent, including information such as packet size and recipient address. The actual payload was marked with four flag bytes (0×0000 0×FFFF, and vice versa) before and after, with a visible spectrum shift. The transmission was concluded with the checksum.</p> Full article ">
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