Sensors

560 KiB

Open AccessArticle

Handmade Task Tracking Applied to Cognitive Rehabilitation

by José M. Cogollor, Charmayne Hughes, Manuel Ferre, Javier Rojo, Joachim Hermsdörfer, Alan Wing and Sandra Campo

Sensors 2012, 12(10), 14214-14231; https://doi.org/10.3390/s121014214 - 22 Oct 2012

Cited by 19 | Viewed by 9286

Abstract

This article presents research focused on tracking manual tasks that are applied in cognitive rehabilitation so as to analyze the movements of patients who suffer from Apraxia and Action Disorganization Syndrome (AADS). This kind of patients find executing Activities of Daily Living (ADL) [...] Read more.

This article presents research focused on tracking manual tasks that are applied in cognitive rehabilitation so as to analyze the movements of patients who suffer from Apraxia and Action Disorganization Syndrome (AADS). This kind of patients find executing Activities of Daily Living (ADL) too difficult due to the loss of memory and capacity to carry out sequential tasks or the impossibility of associating different objects with their functions. This contribution is developed from the work of Universidad Politécnica de Madrid and Technical University of Munich in collaboration with The University of Birmingham. The Kinect^TM for Windows^© device is used for this purpose. The data collected is compared to an ultrasonic motion capture system. The results indicate a moderate to strong correlation between signals. They also verify that Kinect^TM is very suitable and inexpensive. Moreover, it turns out to be a motion-capture system quite easy to implement for kinematics analysis in ADL. Full article

(This article belongs to the Section Physical Sensors)

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706 KiB

Open AccessArticle

Mobile Mapping of Sporting Event Spectators Using Bluetooth Sensors: Tour of Flanders 2011

by Mathias Versichele, Tijs Neutens, Stephanie Goudeseune, Frederik Van Bossche and Nico Van de Weghe

Sensors 2012, 12(10), 14196-14213; https://doi.org/10.3390/s121014196 - 22 Oct 2012

Cited by 21 | Viewed by 7071

Abstract

Accurate spatiotemporal information on crowds is a necessity for a better management in general and for the mitigation of potential security risks. The large numbers of individuals involved and their mobility, however, make generation of this information non-trivial. This paper proposes a novel [...] Read more.

Accurate spatiotemporal information on crowds is a necessity for a better management in general and for the mitigation of potential security risks. The large numbers of individuals involved and their mobility, however, make generation of this information non-trivial. This paper proposes a novel methodology to estimate and map crowd sizes using mobile Bluetooth sensors and examines to what extent this methodology represents a valuable alternative to existing traditional crowd density estimation methods. The proposed methodology is applied in a unique case study that uses Bluetooth technology for the mobile mapping of spectators of the Tour of Flanders 2011 road cycling race. The locations of nearly 16,000 cell phones of spectators along the race course were registered and detailed views of the spatiotemporal distribution of the crowd were generated. Comparison with visual head counts from camera footage delivered a detection ratio of 13.0 ± 2.3%, making it possible to estimate the crowd size. To our knowledge, this is the first study that uses mobile Bluetooth sensors to count and map a crowd over space and time. Full article

(This article belongs to the Section Remote Sensors)

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Mobile sensor deployment during the race. Top: schematic overview of the methodology, bottom: actual deployment (1: Bluetooth sensor, 2: video camera, 3: GPS unit). Full article ">
Tour of Flanders, 2011 edition. Top: spatial view of the official track and the trajectory of the mobile platform. Bottom: elevation profile of the mobile platform trajectory (NASA Shuttle Radar Topography Mission elevation data). In both cases, the speed of the mobile platform is shown in a color scale ranging from red (temporary stops) to blue (more than 80 km/h). The 18 official climbs are shown as triangles in the spatial view and solid vertical lines in the elevation profile (non covered climbs excluded). The dashed vertical lines represent the cobblestoned segments, the dotted vertical line the first provision point, and the dashed-dotted line the village of the tour. Full article ">
Mobile Bluetooth detection process investigation: (a) experimental setup showing both mobile phones (A, B) and the two passing scenarios (1: sensor facing phones, 2: sensor not facing phones); (b) effect of sensor type, speed, and phone distance (both the mean and standard deviations, as well as the individual values of all combinations are shown; both error bars and individual data points are offset from their real x-value for visual clarity); (c) effect of sensor placement on mobile platform at a speed of 60 km/h. Full article ">
Mobile Bluetooth detection process investigation: (a) experimental setup showing both mobile phones (A, B) and the two passing scenarios (1: sensor facing phones, 2: sensor not facing phones); (b) effect of sensor type, speed, and phone distance (both the mean and standard deviations, as well as the individual values of all combinations are shown; both error bars and individual data points are offset from their real x-value for visual clarity); (c) effect of sensor placement on mobile platform at a speed of 60 km/h. Full article ">
Number of detected phones along 1 km long segments of the trajectory followed by the mobile platform as an indicator of crowdedness. Top: spatial view using a yellow-to-red color scale to depict the number of phones, class breaks according to the Jenks natural breaks optimization [<a href="#b32-sensors-12-14196" class="html-bibr">32</a>]. The background shows the population density of statistical sectors in the area, colored in a grey-scale, once again according to Jenks natural breaks. Bottom: one-dimensional view. Full article ">
Real-life influence of mobile platform speed on four trajectory segment characteristics: (a) number of detected phones (log scale), (b) number of detections/number of detected phones (log scale), (c) sensor overlap, (d) mean RSSI. Full article ">
Scatter plot of statistical population density versus number of detected phones over each 1 km long segment of the trajectory. Full article ">

1047 KiB

Open AccessArticle

Intelligent Color Vision System for Ripeness Classification of Oil Palm Fresh Fruit Bunch

by Norasyikin Fadilah, Junita Mohamad-Saleh, Zaini Abdul Halim, Haidi Ibrahim and Syed Salim Syed Ali

Sensors 2012, 12(10), 14179-14195; https://doi.org/10.3390/s121014179 - 22 Oct 2012

Cited by 74 | Viewed by 12834

Abstract

Ripeness classification of oil palm fresh fruit bunches (FFBs) during harvesting is important to ensure that they are harvested during optimum stage for maximum oil production. This paper presents the application of color vision for automated ripeness classification of oil palm FFB. Images [...] Read more.

Ripeness classification of oil palm fresh fruit bunches (FFBs) during harvesting is important to ensure that they are harvested during optimum stage for maximum oil production. This paper presents the application of color vision for automated ripeness classification of oil palm FFB. Images of oil palm FFBs of type DxP Yangambi were collected and analyzed using digital image processing techniques. Then the color features were extracted from those images and used as the inputs for Artificial Neural Network (ANN) learning. The performance of the ANN for ripeness classification of oil palm FFB was investigated using two methods: training ANN with full features and training ANN with reduced features based on the Principal Component Analysis (PCA) data reduction technique. Results showed that compared with using full features in ANN, using the ANN trained with reduced features can improve the classification accuracy by 1.66% and is more effective in developing an automated ripeness classifier for oil palm FFB. The developed ripeness classifier can act as a sensor in determining the correct oil palm FFB ripeness category. Full article

(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)

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876 KiB

Open AccessArticle

Developing a Reading Concentration Monitoring System by Applying an Artificial Bee Colony Algorithm to E-Books in an Intelligent Classroom

by Chia-Cheng Hsu, Hsin-Chin Chen, Yen-Ning Su, Kuo-Kuang Huang and Yueh-Min Huang

Sensors 2012, 12(10), 14158-14178; https://doi.org/10.3390/s121014158 - 22 Oct 2012

Cited by 41 | Viewed by 8599

Abstract

A growing number of educational studies apply sensors to improve student learning in real classroom settings. However, how can sensors be integrated into classrooms to help instructors find out students’ reading concentration rates and thus better increase learning effectiveness? The aim of the [...] Read more.

A growing number of educational studies apply sensors to improve student learning in real classroom settings. However, how can sensors be integrated into classrooms to help instructors find out students’ reading concentration rates and thus better increase learning effectiveness? The aim of the current study was to develop a reading concentration monitoring system for use with e-books in an intelligent classroom and to help instructors find out the students’ reading concentration rates. The proposed system uses three types of sensor technologies, namely a webcam, heartbeat sensor, and blood oxygen sensor to detect the learning behaviors of students by capturing various physiological signals. An artificial bee colony (ABC) optimization approach is applied to the data gathered from these sensors to help instructors understand their students’ reading concentration rates in a classroom learning environment. The results show that the use of the ABC algorithm in the proposed system can effectively obtain near-optimal solutions. The system has a user-friendly graphical interface, making it easy for instructors to clearly understand the reading status of their students. Full article

(This article belongs to the Section Physical Sensors)

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1344 KiB

Open AccessArticle

Numerical Study of Opto-Fluidic Ring Resonators for Biosensor Applications

by Han Keun Cho and Jinwoo Han

Sensors 2012, 12(10), 14144-14157; https://doi.org/10.3390/s121014144 - 22 Oct 2012

Cited by 10 | Viewed by 6334

Abstract

The opto-fluidic ring resonator (OFRR) biosensor is numerically characterized in whispering gallery mode (WGM). The ring resonator includes a ring, a waveguide and a gap separating the ring and the waveguide. Dependence of the resonance characteristics on the resonator size parameters such as [...] Read more.

The opto-fluidic ring resonator (OFRR) biosensor is numerically characterized in whispering gallery mode (WGM). The ring resonator includes a ring, a waveguide and a gap separating the ring and the waveguide. Dependence of the resonance characteristics on the resonator size parameters such as the ring diameter, the ring thickness, the waveguide width, and the gap width between the ring and the waveguide are investigated. For this purpose, we use the finite element method with COMSOL Multiphysics software to solve the Maxwell’s equations. The resonance frequencies, the free spectral ranges (FSR), the full width at half-maximum (FWHM), finesse (F), and quality factor of the resonances (Q) are examined. The resonant frequencies are dominantly affected by the resonator diameter while the gap width, the ring thickness and the waveguide width have negligible effects on the resonant frequencies. FWHM, the quality factor Q and the finesse F are most strongly affected by the gap width and moderately influenced by the ring diameter, the waveguide width and the ring thickness. In addition, our simulation demonstrates that there is an optimum range of the waveguide width for a given ring resonator and this value is between ~2.25 μm and ~2.75 μm in our case. Full article

(This article belongs to the Section Biosensors)

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The schematic of (a) the multi-channel OFRR and (b) a section view. Full article ">
A photograph of a fabricated OFRR. Full article ">
Electric fields distributions for the ring-waveguide coupling part (d = 100 μm, t = 3 μm, w = 2 μm, g = 0 μm); (a) the regular plots and (b) the magnified plots. (Off-resonance (a-1,b-1); first-order resonance (a-2,b-2); second-order resonance (a-3,b-3)). Full article ">
Resonance spectra of the ring for the OFRR (d = 100 μm, t = 3 μm, w = 2 μm, g = 0 nm). The large peaks are for the first-order resonances while the small peaks are for the second-order resonances. Full article ">
Effects of the ring diameter on the resonance characteristics (t = 3 μm, w = 2 μm, g = 0 μm). Displayed four data sets are obtained from adjacent resonance peaks, respectively. Full article ">
Effects of the ring thickness on the resonance characteristics (d = 100 μm, w = 2 μm, g = 0 μm). Displayed four data sets are obtained from adjacent resonance peaks, respectively. Full article ">
Effects of the waveguide width on the resonance characteristics (d = 100 μm, t = 3 μm, g = 0 μm). Displayed four data sets are obtained from adjacent resonance peaks, respectively. Full article ">
Effect of the waveguide width on FWHM (d = 100 μm, g = 0 μm). Full article ">
Effects of the gap width on the resonance characteristics (d = 100 μm, t = 3 μm, w = 2 μm). Displayed four data sets are obtained from adjacent resonance peaks, respectively. Full article ">

1585 KiB

Open AccessArticle

An Embedded Real-Time Red Peach Detection System Based on an OV7670 Camera, ARM Cortex-M4 Processor and 3D Look-Up Tables

by Mercè Teixidó, Davinia Font, Tomàs Pallejà, Marcel Tresanchez, Miquel Nogués and Jordi Palacín

Sensors 2012, 12(10), 14129-14143; https://doi.org/10.3390/s121014129 - 22 Oct 2012

Cited by 14 | Viewed by 11596

Abstract

This work proposes the development of an embedded real-time fruit detection system for future automatic fruit harvesting. The proposed embedded system is based on an ARM Cortex-M4 (STM32F407VGT6) processor and an Omnivision OV7670 color camera. The future goal of this embedded vision system [...] Read more.

This work proposes the development of an embedded real-time fruit detection system for future automatic fruit harvesting. The proposed embedded system is based on an ARM Cortex-M4 (STM32F407VGT6) processor and an Omnivision OV7670 color camera. The future goal of this embedded vision system will be to control a robotized arm to automatically select and pick some fruit directly from the tree. The complete embedded system has been designed to be placed directly in the gripper tool of the future robotized harvesting arm. The embedded system will be able to perform real-time fruit detection and tracking by using a three-dimensional look-up-table (LUT) defined in the RGB color space and optimized for fruit picking. Additionally, two different methodologies for creating optimized 3D LUTs based on existing linear color models and fruit histograms were implemented in this work and compared for the case of red peaches. The resulting system is able to acquire general and zoomed orchard images and to update the relative tracking information of a red peach in the tree ten times per second. Full article

(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)

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1141 KiB

Open AccessArticle

Automatic Suppression of Intense Monochromatic Light in Electro-Optical Sensors

by Gunnar Ritt and Bernd Eberle

Sensors 2012, 12(10), 14113-14128; https://doi.org/10.3390/s121014113 - 19 Oct 2012

Cited by 24 | Viewed by 8050

Abstract

Electro-optical imaging sensors are widely distributed and used for many different tasks. Due to technical improvements, their pixel size has been steadily decreasing, resulting in a reduced saturation capacity. As a consequence, this progress makes them susceptible to intense point light sources. Developments [...] Read more.

Electro-optical imaging sensors are widely distributed and used for many different tasks. Due to technical improvements, their pixel size has been steadily decreasing, resulting in a reduced saturation capacity. As a consequence, this progress makes them susceptible to intense point light sources. Developments in laser technology have led to very compact and powerful laser sources of any wavelength in the visible and near infrared spectral region, offered as laser pointers. The manifold of wavelengths makes it difficult to encounter sensor saturation over the complete operating waveband by conventional measures like absorption or interference filters. We present a concept for electro-optical sensors to suppress overexposure in the visible spectral region. The key element of the concept is a spatial light modulator in combination with wavelength multiplexing. This approach allows spectral filtering within a localized area in the field of view of the sensor. The system offers the possibility of automatic reduction of overexposure by monochromatic laser radiation. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany 2012)

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480 KiB

Open AccessArticle

Detection of Interference Phase by Digital Computation of Quadrature Signals in Homodyne Laser Interferometry

by Simon Rerucha, Zdenek Buchta, Martin Sarbort, Josef Lazar and Ondrej Cip

Sensors 2012, 12(10), 14095-14112; https://doi.org/10.3390/s121014095 - 19 Oct 2012

Cited by 40 | Viewed by 9250

Abstract

We have proposed an approach to the interference phase extraction in the homodyne laser interferometry. The method employs a series of computational steps to reconstruct the signals for quadrature detection from an interference signal from a non-polarising interferometer sampled by a simple photodetector. [...] Read more.

We have proposed an approach to the interference phase extraction in the homodyne laser interferometry. The method employs a series of computational steps to reconstruct the signals for quadrature detection from an interference signal from a non-polarising interferometer sampled by a simple photodetector. The complexity trade-off is the use of laser beam with frequency modulation capability. It is analytically derived and its validity and performance is experimentally verified. The method has proven to be a feasible alternative for the traditional homodyne detection since it performs with comparable accuracy, especially where the optical setup complexity is principal issue and the modulation of laser beam is not a heavy burden (e.g., in multi-axis sensor or laser diode based systems). Full article

(This article belongs to the Special Issue Laser Sensing and Imaging)

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Polarising laser interferometer with quadrature detection unit for homodyne detection: the interferometer employs the polarising divider, the reference corner cube reflector CCref and measurement reflector CCmeas. The output beam is compound from two beams with a different polarisation. The detection unit splits the beam into two detection branches on the non-polarising divider NP In the first branch, the polarising beam splitter PBS1 adjusts the polarisation to a single plane so that the interference occurs and is observed by photodetectors D1, D1′ (mutually in an opposite phase). In the second branch, one of the wave components is retarded by the retarder plate RP The photodetectors D2, D2′ observe the interference that occurs due to rotation of the polarisation plane on the polarising beam splitter PBS2. The subtracter SI produces the signal Ix as a difference between signals D1 and D1′, the subtracter S2 produces Iy from D2, D2′ in the same way. Full article ">
Detection of the unwanted phase shift δa: the known instantaneous values Ix, Iy are projected to phasors K⃗x, K⃗y that form the angles φ (equal to the immediate interference phase) and φ′ = φ − π/2 + δa with axis x (a); a combination of K⃗x and K⃗y forms phasor K⃗xy (b). Since there exists such φ such that K⃗xy is parallel to axis x, the real angle α = π/2 + δa can be calculated using law of cosines. Full article ">
Experimental setup scheme: the interferometer employs the polarising divider, the reference corner cube CCref and measurement corner cube CCmeas. The laser input is attenuated by a neutral density absorption niters ND, collimated by an optical expander EXP and its polarisation plane is rotated by the half-wave plate λ/2. The interferometer output is split into two detection branches by the non-polarising divider NP In the first branch, the interference occurs on the polariser POL and the intensity is observed by a photodetector PD. In the second branch, the signal from the interferometer is processed by the reference quadrature detection unit QDU. The acquisition and control hardware drives the modulation of the laser source optical frequency and evaluates the signals from both the photodetector and the quadrature detection unit. Full article ">
Evaluation of single experimental cycle: the X- and Y-axis signals from quadrature detection unit, i.e., the 〈Ĩx(τ, t)〉 and 〈Ĩy(τ, t)〉 (refer to <a href="#FD30" class="html-disp-formula">Equation (30)</a>), with scale linearity compensation applied (a); X- and Y-axis signals reconstructed by proposed method, i.e., 〈Ĩx(τ, t)〉 and Id (<a href="#FD35" class="html-disp-formula">Equation (35)</a>), reconstructed from the signal observed by the photodetector with the phase shift removal and scale linearization applied (b) and the phase determination error, PDE (c). Full article ">
Experimental results: the red points show the periodic error, i.e., the dependence of the mean phase determination error on immediate interference phase; the blue error bars indicate the interval of radius of standard deviation around the mean PDE at each corresponding point i (ni ≈ 1,485) Full article ">
Experimental results: the red points show the dependence of the mean phase determination error on the path length difference; the blue error bars indicate the interval of radius of standard deviation around the mean PDE at each corresponding point i (ni ≈ 2,670) Full article ">

966 KiB

Open AccessArticle

Refractive Index Compensation in Over-Determined Interferometric Systems

by Josef Lazar, Miroslava Holá, Ondřej Číp, Martin Čížek, Jan Hrabina and Zdeněk Buchta

Sensors 2012, 12(10), 14084-14094; https://doi.org/10.3390/s121014084 - 19 Oct 2012

Cited by 26 | Viewed by 6881

Abstract

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from [...] Read more.

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup. Full article

(This article belongs to the Section Physical Sensors)

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Principal schematics of the inteferometric system with two countermeasuring interferometers and an interferometer monitoring overall length LC. LA, LB: particular lengths determining the position of the moving carriage. Full article ">
Configuration with corner-cube reflectors measuring directly the overall length and two particular displacements. CC: corner-cube reflector, PBS: polarizing beamsplitter, NP: non-polarizing plane, λ/2: half-wave plate, F: fiber-optic light delivery, OA, OB, OC: outputs. Full article ">
Recording of the variations of the interferometers A (red line), B (yellow line), and overall length measuring C (blue line) together with the sum of A and B (green line) over time in a closed thermal box. Full article ">
Recording of the variations of the interferometers A (red line), B (yellow line), and overall length measuring C (blue line) together with the sum of A and B (green line) over time in under laboratory environment. Full article ">
Recording of a slow refractive index drift evaluated from measurement of air temperature, pressure, humidity and CO2 content (blue line) and polynomial approximation (red line). Full article ">
Recording of the output from the interferometer C, responding to variations of the overall optical length. Full article ">

636 KiB

Open AccessArticle

FPGA-Based Multiprocessor System for Injection Molding Control

by Benigno Muñoz-Barron, Luis Morales-Velazquez, Rene J. Romero-Troncoso, Carlos Rodriguez-Donate, Miguel Trejo-Hernandez, Juan P. Benitez-Rangel and Roque A. Osornio-Rios

Sensors 2012, 12(10), 14068-14083; https://doi.org/10.3390/s121014068 - 18 Oct 2012

Cited by 4 | Viewed by 12225

Abstract

The plastic industry is a very important manufacturing sector and injection molding is a widely used forming method in that industry. The contribution of this work is the development of a strategy to retrofit control of an injection molding machine based on an [...] Read more.

The plastic industry is a very important manufacturing sector and injection molding is a widely used forming method in that industry. The contribution of this work is the development of a strategy to retrofit control of an injection molding machine based on an embedded system microprocessors sensor network on a field programmable gate array (FPGA) device. Six types of embedded processors are included in the system: a smart-sensor processor, a micro fuzzy logic controller, a programmable logic controller, a system manager, an IO processor and a communication processor. Temperature, pressure and position are controlled by the proposed system and experimentation results show its feasibility and robustness. As validation of the present work, a particular sample was successfully injected. Full article

(This article belongs to the Section Sensor Networks)

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Graphical abstract

677 KiB

Open AccessArticle

Cooperative Suction by Vertical Capillary Array Pump for Controlling Flow Profiles of Microfluidic Sensor Chips

by Tsutomu Horiuchi, Katsuyoshi Hayashi, Michiko Seyama, Suzuyo Inoue and Emi Tamechika

Sensors 2012, 12(10), 14053-14067; https://doi.org/10.3390/s121014053 - 18 Oct 2012

Cited by 11 | Viewed by 8680

Abstract

A passive pump consisting of integrated vertical capillaries has been developed for a microfluidic chip as an useful component with an excellent flow volume and flow rate. A fluidic chip built into a passive pump was used by connecting the bottoms of all [...] Read more.

A passive pump consisting of integrated vertical capillaries has been developed for a microfluidic chip as an useful component with an excellent flow volume and flow rate. A fluidic chip built into a passive pump was used by connecting the bottoms of all the capillaries to a top surface consisting of a thin layer channel in the microfluidic chip where the thin layer channel depth was smaller than the capillary radius. As a result the vertical capillaries drew fluid cooperatively rather than independently, thus exerting the maximum suction efficiency at every instance. This meant that a flow rate was realized that exhibited little variation and without any external power or operation. A microfluidic chip built into this passive pump had the ability to achieve a quasi-steady rather than a rapidly decreasing flow rate, which is a universal flow characteristic in an ordinary capillary. Full article

(This article belongs to the Special Issue Microfluidic Devices)

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Schematic illustrations of a fluidic chip including a passive pump composed of an integrated vertical capillary array and its suction profile. (A) Definitions of position and the notations are summarized in the top and side view illustrations. (B) Fluid can propagate in the area of the main flow channel and the junction zone except at the bottoms of the capillaries when d < rc. (C) A quasi-steady flow is realized after the B stage. (D) No quasi-steady flow is realized if d < rc is not satisfied. (E) Comparison with a surface tension pump. (F) Time-series imagery of the suction profile of 4-mm-long capillaries in a 3 × 5 arrangement in a square lattice and 2 mm apart; d, rc, and ri were 0.05, 0.2, and 1.5 mm, respectively. (G) A fluidic chip with a highly integrated vertical capillary array provided a large volume sample for actual sensor application. The main flow channel (not shown) was surrounded by capillaries and an inlet to realize a large flow volume on a small footprint. Sample fluid injected into the inlet propagates in the main channel and branches to the right and left junction zones. The capillaries were arranged in a hexagonal lattice and were 0.35 mm apart. There were 816 capillaries, and the capillary length, d, rc, and ri were 4, 0.05, 0.14 and 1.5 mm, respectively. Image obtained after several refill operations. Full article ">
Structure of fluidic chip (A–D) and setup for flow rate measurement (E). An inlet (3 mm diameter) and a vertical capillary (0.4 mm diameter) array were opened in the thick (4 mm) acrylic resin plate (A). 15 capillaries were arranged in a square lattice and 2 mm apart. A flow channel was opened in a thin (0.05 mm-thick) two-sided adhesive film (B). The bottom of the device was a 1 mm-thick acrylic resin plate (C). The assembled flow device is shown in (D). Liquid fronts in the inlet and capillaries were observed and recorded from the side of the fluidic chip using a video camera. All the capillaries can be observed without any overlaps from an oblique direction. Individual capillaries are identified by the numbers shown in (E). These numbers are common throughout this paper. Full article ">
Screen shots of a computational fluidic dynamics simulation. (A) Channel depth d is smaller than the capillary radius r (d < r). Time is 0.17 s. All capillaries waited to draw fluid up until the junction zone was full. (B) The channel depth and capillary radius are the same (d = r). Time is 0.1 s. The fluid front propagated in both capillaries and the junction zone concurrently. Full article ">
(A) Height of fluid front in each capillary obtained by experiment in <a href="#f1-sensors-12-14053" class="html-fig">Figure 1(F)</a> as a function of time after fluid injection. The numbers in the figure are capillary identification labels (See <a href="#f2-sensors-12-14053" class="html-fig">Figure 2(E)</a>). (B) Sum of fluid front heights of all capillaries in A as a function of time after fluid injection. The irregular disorganized suction pattern of A was subject to the fact that the increase rate of the sum is constant as shown in B. Full article ">
Height of fluid front in each capillary (A,C) and sum of fluid fronts of all capillaries (B,D) obtained by CFD simulations as a function of time. The numbers in the figures are capillary identification labels. There are 4-mm-long capillaries in a 3 × 5 arrangement in a square lattice and 0.6 mm apart. rc and ri were 0.1 and 1.5 mm, respectively. d was 0.075 mm in A and B and 0.1 mm in C and D. The two different slopes in D means that there was no clear separation in the flow profile transition. Full article ">
Linear velocity profiles at a height of d/2 from the bottom in the region of the detection area obtained by simulations. The flow rate fluctuation was confined to the second stage (before 0.17 s) and after that a quasi-steady flow was observed with the fluidic chip where d < rc, (d = 0.075 mm, black). Simulation conditions were the same except that the gravitational acceleration constant was zero (red). The flow rate fluctuation remained for almost the entire period and the flow rate decreased slightly (d = 0.1 mm). Full article ">
Color depth change of a capillary in the presence of the pullback phenomenon. The color depth corresponds to the liquid front height. A certain capillary exhibited its maximum color depth at 10 s. This value decreased immediately and returned to the value. Full article ">
Velocity of fluid front in each capillary calculated using the data in <a href="#f5-sensors-12-14053" class="html-fig">Figure 5(A)</a>. A negative velocity indicates the pullback phenomenon. Capillaries #4, 11, 7 and 14 exhibit their maximum negative velocity at 0.22, 0.33, 0.34, and 0.41 s, respectively. Full article ">

397 KiB

Open AccessArticle

Thermoresponsive Magnetic Nano-Biosensors for Rapid Measurements of Inorganic Arsenic and Cadmium

by Mohammad Shohel Rana Siddiki, Shun Shimoaoki, Shunsaku Ueda and Isamu Maeda

Sensors 2012, 12(10), 14041-14052; https://doi.org/10.3390/s121014041 - 18 Oct 2012

Cited by 14 | Viewed by 8431

Abstract

Green fluorescent protein-tagged sensor proteins, ArsR-GFP and CadC-GFP, have been produced as biosensors for simple and low-cost quantification of As(III) or Cd(II). In this study, the sensor protein-promoter DNA complexes were reconstructed on the surfaces of magnetic particles of different sizes. After the [...] Read more.

Green fluorescent protein-tagged sensor proteins, ArsR-GFP and CadC-GFP, have been produced as biosensors for simple and low-cost quantification of As(III) or Cd(II). In this study, the sensor protein-promoter DNA complexes were reconstructed on the surfaces of magnetic particles of different sizes. After the surface modification all the particles could be attracted by magnets, and released different amounts of GFP-tagged protein, according to the metal concentrations within 5 min, which caused significant increases in fluorescence. A detection limit of 1 µg/L for As(III) and Cd(II) in purified water was obtained only with the nanoparticles exhibiting enough magnetization after heat treatment for 1 min. Therefore, thermoresponsive magnetic nano-biosensors offer great advantages of rapidity and sensitivity for the measurement of the toxic metals in drinking water. Full article

(This article belongs to the Special Issue Biosensors and Rapid Testing Bio-Analytical Platforms for Food and Water Analysis)

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614 KiB

Open AccessArticle

A Hybrid Sensing Approach for Pure and Adulterated Honey Classification

by Norazian Subari, Junita Mohamad Saleh, Ali Yeon Md Shakaff and Ammar Zakaria

Sensors 2012, 12(10), 14022-14040; https://doi.org/10.3390/s121014022 - 17 Oct 2012

Cited by 78 | Viewed by 10065

Abstract

This paper presents a comparison between data from single modality and fusion methods to classify Tualang honey as pure or adulterated using Linear Discriminant Analysis (LDA) and Principal Component Analysis (PCA) statistical classification approaches. Ten different brands of certified pure Tualang honey were [...] Read more.

This paper presents a comparison between data from single modality and fusion methods to classify Tualang honey as pure or adulterated using Linear Discriminant Analysis (LDA) and Principal Component Analysis (PCA) statistical classification approaches. Ten different brands of certified pure Tualang honey were obtained throughout peninsular Malaysia and Sumatera, Indonesia. Various concentrations of two types of sugar solution (beet and cane sugar) were used in this investigation to create honey samples of 20%, 40%, 60% and 80% adulteration concentrations. Honey data extracted from an electronic nose (e-nose) and Fourier Transform Infrared Spectroscopy (FTIR) were gathered, analyzed and compared based on fusion methods. Visual observation of classification plots revealed that the PCA approach able to distinct pure and adulterated honey samples better than the LDA technique. Overall, the validated classification results based on FTIR data (88.0%) gave higher classification accuracy than e-nose data (76.5%) using the LDA technique. Honey classification based on normalized low-level and intermediate-level FTIR and e-nose fusion data scored classification accuracies of 92.2% and 88.7%, respectively using the Stepwise LDA method. The results suggested that pure and adulterated honey samples were better classified using FTIR and e-nose fusion data than single modality data. Full article

(This article belongs to the Section Chemical Sensors)

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E-nose setup for headspace evaluation of honey, sugar and adulteration sample. Full article ">
(a) All Pure Tualang honey and sugar solutions for full spectra range (650 cm−1 to 4,000 cm−1). (b) All AG honey sample for full spectra range (650 cm−1 to 4,000 cm−1). (c) AG samples for spectra range from 750 cm−1 to 1,500 cm−1. Full article ">
(a) All Pure Tualang honey and sugar solutions for full spectra range (650 cm−1 to 4,000 cm−1). (b) All AG honey sample for full spectra range (650 cm−1 to 4,000 cm−1). (c) AG samples for spectra range from 750 cm−1 to 1,500 cm−1. Full article ">
All Agromas honey brand sample with the corrected peak height. Full article ">
Low-level fusion scheme. Full article ">
Intermediate-level or feature-level fusion scheme. Full article ">
PCA plot of normalized E-nose data. Full article ">
LDA plot of normalized E-nose data. Full article ">
PCA plot of normalized FTIR data. Full article ">
LDA plot of normalized FTIR data. Full article ">

1148 KiB

Open AccessArticle

Temperature and Relative Humidity Estimation and Prediction in the Tobacco Drying Process Using Artificial Neural Networks

by Víctor Martínez-Martínez, Carlos Baladrón, Jaime Gomez-Gil, Gonzalo Ruiz-Ruiz, Luis M. Navas-Gracia, Javier M. Aguiar and Belén Carro

Sensors 2012, 12(10), 14004-14021; https://doi.org/10.3390/s121014004 - 17 Oct 2012

Cited by 38 | Viewed by 9440

Abstract

This paper presents a system based on an Artificial Neural Network (ANN) for estimating and predicting environmental variables related to tobacco drying processes. This system has been validated with temperature and relative humidity data obtained from a real tobacco dryer with a Wireless [...] Read more.

This paper presents a system based on an Artificial Neural Network (ANN) for estimating and predicting environmental variables related to tobacco drying processes. This system has been validated with temperature and relative humidity data obtained from a real tobacco dryer with a Wireless Sensor Network (WSN). A fitting ANN was used to estimate temperature and relative humidity in different locations inside the tobacco dryer and to predict them with different time horizons. An error under 2% can be achieved when estimating temperature as a function of temperature and relative humidity in other locations. Moreover, an error around 1.5 times lower than that obtained with an interpolation method can be achieved when predicting the temperature inside the tobacco mass as a function of its present and past values with time horizons over 150 minutes. These results show that the tobacco drying process can be improved taking into account the predicted future value of the monitored variables and the estimated actual value of other variables using a fitting ANN as proposed. Full article

(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)

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1287 KiB

Open AccessArticle

Physically-Based Reduced Order Modelling of a Uni-Axial Polysilicon MEMS Accelerometer

by Aldo Ghisi, Stefano Mariani, Alberto Corigliano and Sarah Zerbini

Sensors 2012, 12(10), 13985-14003; https://doi.org/10.3390/s121013985 - 17 Oct 2012

Cited by 10 | Viewed by 7371

Abstract

In this paper, the mechanical response of a commercial off-the-shelf, uni-axial polysilicon MEMS accelerometer subject to drops is numerically investigated. To speed up the calculations, a simplified physically-based (beams and plate), two degrees of freedom model of the movable parts of the sensor [...] Read more.

In this paper, the mechanical response of a commercial off-the-shelf, uni-axial polysilicon MEMS accelerometer subject to drops is numerically investigated. To speed up the calculations, a simplified physically-based (beams and plate), two degrees of freedom model of the movable parts of the sensor is adopted. The capability and the accuracy of the model are assessed against three-dimensional finite element simulations, and against outcomes of experiments on instrumented samples. It is shown that the reduced order model provides accurate outcomes as for the system dynamics. To also get rather accurate results in terms of stress fields within regions that are prone to fail upon high-g shocks, a correction factor is proposed by accounting for the local stress amplification induced by re-entrant corners. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)

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1201 KiB

Open AccessArticle

Floating Chip Mounting System Driven by Repulsive Force of Permanent Magnets for Multiple On-Site SPR Immunoassay Measurements

by Tsutomu Horiuchi, Tatsuya Tobita, Toru Miura, Yuzuru Iwasaki, Michiko Seyama, Suzuyo Inoue, Jun-ichi Takahashi, Tsuneyuki Haga and Emi Tamechika

Sensors 2012, 12(10), 13964-13984; https://doi.org/10.3390/s121013964 - 17 Oct 2012

Cited by 7 | Viewed by 6662

Abstract

We have developed a measurement chip installation/removal mechanism for a surface plasmon resonance (SPR) immunoassay analysis instrument designed for frequent testing, which requires a rapid and easy technique for changing chips. The key components of the mechanism are refractive index matching gel coated [...] Read more.

We have developed a measurement chip installation/removal mechanism for a surface plasmon resonance (SPR) immunoassay analysis instrument designed for frequent testing, which requires a rapid and easy technique for changing chips. The key components of the mechanism are refractive index matching gel coated on the rear of the SPR chip and a float that presses the chip down. The refractive index matching gel made it possible to optically couple the chip and the prism of the SPR instrument easily via elastic deformation with no air bubbles. The float has an autonomous attitude control function that keeps the chip parallel in relation to the SPR instrument by employing the repulsive force of permanent magnets between the float and a float guide located in the SPR instrument. This function is realized by balancing the upward elastic force of the gel and the downward force of the float, which experiences a leveling force from the float guide. This system makes it possible to start an SPR measurement immediately after chip installation and to remove the chip immediately after the measurement with a simple and easy method that does not require any fine adjustment. Our sensor chip, which we installed using this mounting system, successfully performed an immunoassay measurement on a model antigen (spiked human-IgG) in a model real sample (non-homogenized milk) that included many kinds of interfering foreign substances without any sample pre-treatment. The ease of the chip installation/removal operation and simple measurement procedure are suitable for frequent on-site agricultural, environmental and medical testing. Full article

(This article belongs to the Section Biosensors)

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2091 KiB

Open AccessArticle

Implementation of Obstacle-Avoidance Control for an Autonomous Omni-Directional Mobile Robot Based on Extension Theory

by Neng-Sheng Pai, Hung-Hui Hsieh and Yi-Chung Lai

Sensors 2012, 12(10), 13947-13963; https://doi.org/10.3390/s121013947 - 16 Oct 2012

Cited by 8 | Viewed by 8909

Abstract

The paper demonstrates a following robot with omni-directional wheels, which is able to take action to avoid obstacles. The robot design is based on both fuzzy and extension theory. Fuzzy theory was applied to tune the PMW signal of the motor revolution, and [...] Read more.

The paper demonstrates a following robot with omni-directional wheels, which is able to take action to avoid obstacles. The robot design is based on both fuzzy and extension theory. Fuzzy theory was applied to tune the PMW signal of the motor revolution, and correct path deviation issues encountered when the robot is moving. Extension theory was used to build a robot obstacle-avoidance model. Various mobile models were developed to handle different types of obstacles. The ultrasonic distance sensors mounted on the robot were used to estimate the distance to obstacles. If an obstacle is encountered, the correlation function is evaluated and the robot avoids the obstacle autonomously using the most appropriate mode. The effectiveness of the proposed approach was verified through several tracking experiments, which demonstrates the feasibility of a fuzzy path tracker as well as the extensible collision avoidance system. Full article

(This article belongs to the Section Physical Sensors)

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1376 KiB

Open AccessReview

A Review on Architectures and Communications Technologies for Wearable Health-Monitoring Systems

by Víctor Custodio, Francisco J. Herrera, Gregorio López and José Ignacio Moreno

Sensors 2012, 12(10), 13907-13946; https://doi.org/10.3390/s121013907 - 16 Oct 2012

Cited by 122 | Viewed by 14772

Abstract

Nowadays society is demanding more and more smart healthcare services that allow monitoring patient status in a non-invasive way, anywhere and anytime. Thus, healthcare applications are currently facing important challenges guided by the u-health (ubiquitous health) and p-health (pervasive health) paradigms. New emerging [...] Read more.

Nowadays society is demanding more and more smart healthcare services that allow monitoring patient status in a non-invasive way, anywhere and anytime. Thus, healthcare applications are currently facing important challenges guided by the u-health (ubiquitous health) and p-health (pervasive health) paradigms. New emerging technologies can be combined with other widely deployed ones to develop such next-generation healthcare systems. The main objective of this paper is to review and provide more details on the work presented in “LOBIN: E-Textile and Wireless-Sensor-Network-Based Platform for Healthcare Monitoring in Future Hospital Environments”, published in the IEEE Transactions on Information Technology in Biomedicine, as well as to extend and update the comparison with other similar systems. As a result, the paper discusses the main advantages and disadvantages of using different architectures and communications technologies to develop wearable systems for pervasive healthcare applications. Full article

(This article belongs to the Special Issue Body Sensor Networks for Healthcare and Pervasive Applications)

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97 KiB

Open AccessArticle

Organic Electroluminescent Sensor for Pressure Measurement

by Yu Matsuda, Kaori Ueno, Hiroki Yamaguchi, Yasuhiro Egami and Tomohide Niimi

Sensors 2012, 12(10), 13899-13906; https://doi.org/10.3390/s121013899 - 16 Oct 2012

Cited by 14 | Viewed by 7525

Abstract

We have proposed a novel concept of a pressure sensor called electroluminescent pressure sensor (ELPS) based on oxygen quenching of electroluminescence. The sensor was fabricated as an organic light-emitting device (OLED) with phosphorescent dyes whose phosphorescence can be quenched by oxygenmolecules, and with [...] Read more.

We have proposed a novel concept of a pressure sensor called electroluminescent pressure sensor (ELPS) based on oxygen quenching of electroluminescence. The sensor was fabricated as an organic light-emitting device (OLED) with phosphorescent dyes whose phosphorescence can be quenched by oxygenmolecules, and with a polymer electrode which permeates oxygen molecules. The sensor was a single-layer OLED with Platinum (II) octaethylporphine (PtOEP) doped into poly(vinylcarbazole) (PVK) as an oxygen sensitive emissive layer and poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate) (PEDOT:PSS) as an oxygen permeating polymer anode. The pressure sensitivity of the fabricated ELPS sample was equivalent to that of the sensor excited by an illumination light source. Moreover, the pressure sensitivity of the sensor is equivalent to that of conventional pressure-sensitive paint (PSP), which is an optical pressure sensor based on photoluminescence. Full article

(This article belongs to the Section Chemical Sensors)

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1530 KiB

Open AccessArticle

Frequency Identification of Vibration Signals Using Video Camera Image Data

by Yih-Nen Jeng and Chia-Hung Wu

Sensors 2012, 12(10), 13871-13898; https://doi.org/10.3390/s121013871 - 16 Oct 2012

Cited by 8 | Viewed by 8705

Abstract

This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. [...] Read more.

This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system. Full article

(This article belongs to the Section Physical Sensors)

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1975 KiB

Open AccessArticle

Thermography and Sonic Anemometry to Analyze Air Heaters in Mediterranean Greenhouses

by Alejandro López, Diego L. Valera, Francisco Molina-Aiz and Araceli Peña

Sensors 2012, 12(10), 13852-13870; https://doi.org/10.3390/s121013852 - 16 Oct 2012

Cited by 4 | Viewed by 7375

Abstract

The present work has developed a methodology based on thermography and sonic anemometry for studying the microclimate in Mediterranean greenhouses equipped with air heaters and polyethylene distribution ducts to distribute the warm air. Sonic anemometry allows us to identify the airflow pattern generated [...] Read more.

The present work has developed a methodology based on thermography and sonic anemometry for studying the microclimate in Mediterranean greenhouses equipped with air heaters and polyethylene distribution ducts to distribute the warm air. Sonic anemometry allows us to identify the airflow pattern generated by the heaters and to analyze the temperature distribution inside the greenhouse, while thermography provides accurate crop temperature data. Air distribution by means of perforated polyethylene ducts at ground level, widely used in Mediterranean-type greenhouses, can generate heterogeneous temperature distributions inside the greenhouse when the system is not correctly designed. The system analyzed in this work used a polyethylene duct with a row of hot air outlet holes (all of equal diameter) that expel warm air toward the ground to avoid plant damage. We have observed that this design (the most widely used in Almería’s greenhouses) produces stagnation of hot air in the highest part of the structure, reducing the heating of the crop zone. Using 88 kW heating power (146.7 W∙m⁻²) the temperature inside the greenhouse is maintained 7.2 to 11.2 °C above the outside temperature. The crop temperature (17.6 to 19.9 °C) was maintained above the minimum recommended value of 10 °C. Full article

(This article belongs to the Section Physical Sensors)

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795 KiB

Open AccessArticle

Synthesis of ZnO Nanostructures for Low Temperature CO and UV Sensing

by Muhammad Amin, Umair Manzoor, Mohammad Islam, Arshad Saleem Bhatti and Nazar Abbas Shah

Sensors 2012, 12(10), 13842-13851; https://doi.org/10.3390/s121013842 - 16 Oct 2012

Cited by 37 | Viewed by 7708

Abstract

In this paper, synthesis and results of the low temperature sensing of carbon monoxide (CO) gas and room temperature UV sensors using one dimensional (1-D) ZnO nanostructures are presented. Comb-like structures, belts and rods, and needle-shaped nanobelts were synthesized by varying synthesis temperature [...] Read more.

In this paper, synthesis and results of the low temperature sensing of carbon monoxide (CO) gas and room temperature UV sensors using one dimensional (1-D) ZnO nanostructures are presented. Comb-like structures, belts and rods, and needle-shaped nanobelts were synthesized by varying synthesis temperature using a vapor transport method. Needle-like ZnO nanobelts are unique as, according to our knowledge, there is no evidence of such morphology in previous literature. The structural, morphological and optical characterization was carried out using X-ray diffraction, scanning electron microscopy and diffused reflectance spectroscopy techniques. It was observed that the sensing response of comb-like structures for UV light was greater as compared to the other grown structures. Comb-like structure based gas sensors successfully detect CO at 75 °C while other structures did not show any response. Full article

(This article belongs to the Section Chemical Sensors)

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778 KiB

Open AccessArticle

Non-Contact Translation-Rotation Sensor Using Combined Effects of Magnetostriction and Piezoelectricity

by Bintang Yang, Qingwei Liu, Ting Zhang, Yudong Cao, Zhiqiang Feng and Guang Meng

Sensors 2012, 12(10), 13829-13841; https://doi.org/10.3390/s121013829 - 15 Oct 2012

Cited by 7 | Viewed by 8342

Abstract

Precise displacement sensors are an important topic in precision engineering. At present, this type of sensors typically have a single feature of either translation or rotation measurement. They are also inconvenient to integrate with the host devices. In this report we propose a [...] Read more.

Precise displacement sensors are an important topic in precision engineering. At present, this type of sensors typically have a single feature of either translation or rotation measurement. They are also inconvenient to integrate with the host devices. In this report we propose a new kind of sensor that enables both translation and rotation measurement by using the combined effect of magnetostriction and piezoelectricity. As a proof of concept, we experimentally realized a prototype of non-contact translation-rotation precise sensor. In the current research stage, through both theoretical and experimental study, the non-contact displacement sensor is shown to be feasible for measuring both translation and rotation either in coarse or fine measurement. Moreover, owing to its compact, rigid structure and fewer components, it can be easily embedded in host equipment. Full article

(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)

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916 KiB

Open AccessArticle

Two Proximal Skin Electrodes — A Respiration Rate Body Sensor

by Roman Trobec, Aleksandra Rashkovska and Viktor Avbelj

Sensors 2012, 12(10), 13813-13828; https://doi.org/10.3390/s121013813 - 15 Oct 2012

Cited by 43 | Viewed by 10227

Abstract

We propose a new body sensor for extracting the respiration rate based on the amplitude changes in the body surface potential differences between two proximal body electrodes. The sensor could be designed as a plaster-like reusable unit that can be easily fixed onto [...] Read more.

We propose a new body sensor for extracting the respiration rate based on the amplitude changes in the body surface potential differences between two proximal body electrodes. The sensor could be designed as a plaster-like reusable unit that can be easily fixed onto the surface of the body. It could be equipped either with a sufficiently large memory for storing the measured data or with a low-power radio system that can transmit the measured data to a gateway for further processing. We explore the influence of the sensor’s position on the quality of the extracted results using multi-channel ECG measurements and considering all the pairs of two neighboring electrodes as potential respiration-rate sensors. The analysis of the clinical measurements, which also include reference thermistor-based respiration signals, shows that the proposed approach is a viable option for monitoring the respiration frequency and for a rough classification of breathing types. The obtained results were evaluated on a wireless prototype of a respiration body sensor. We indicate the best positions for the respiration body sensor and prove that a single sensor for body surface potential difference on proximal skin electrodes can be used for combined measurements of respiratory and cardiac activities. Full article

(This article belongs to the Special Issue Body Sensor Networks for Healthcare and Pervasive Applications)

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876 KiB

Open AccessArticle

Source Localization with Acoustic Sensor Arrays Using Generative Model Based Fitting with Sparse Constraints

by Jose Velasco, Daniel Pizarro and Javier Macias-Guarasa

Sensors 2012, 12(10), 13781-13812; https://doi.org/10.3390/s121013781 - 15 Oct 2012

Cited by 33 | Viewed by 7815

Abstract

This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed [...] Read more.

This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies. Full article

(This article belongs to the Section Physical Sensors)

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850 KiB

Open AccessReview

Italian Contributions to the Development of Continuous Glucose Monitoring Sensors for Diabetes Management

by Giovanni Sparacino, Mattia Zanon, Andrea Facchinetti, Chiara Zecchin, Alberto Maran and Claudio Cobelli

Sensors 2012, 12(10), 13753-13780; https://doi.org/10.3390/s121013753 - 12 Oct 2012

Cited by 30 | Viewed by 12249

Abstract

Monitoring glucose concentration in the blood is essential in the therapy of diabetes, a pathology which affects about 350 million people around the World (three million in Italy), causes more than four million deaths per year and consumes a significant portion of the [...] Read more.

Monitoring glucose concentration in the blood is essential in the therapy of diabetes, a pathology which affects about 350 million people around the World (three million in Italy), causes more than four million deaths per year and consumes a significant portion of the budget of national health systems (10% in Italy). In the last 15 years, several sensors with different degree of invasiveness have been proposed to monitor glycemia in a quasi-continuous way (up to 1 sample/min rate) for relatively long intervals (up to 7 consecutive days). These continuous glucose monitoring (CGM) sensors have opened new scenarios to assess, off-line, the effectiveness of individual patient therapeutic plans from the retrospective analysis of glucose time-series, but have also stimulated the development of innovative on-line applications, such as hypo/hyper-glycemia alert systems and artificial pancreas closed-loop control algorithms. In this review, we illustrate some significant Italian contributions, both from industry and academia, to the growth of the CGM sensors research area. In particular, technological, algorithmic and clinical developments performed in Italy will be discussed and put in relation with the advances obtained in the field in the wider international research community. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)

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An example of the “smart” CGM sensor architecture: cascade of a commercial CGM sensor (black box) and three software modules working in real time for denoising, enhancement and prediction. The denoising module receives in input raw CGM data and returns a smoothed CGM time-series. The enhancement module processes the smoothed CGM data and produces a more accurate CGM profile. The prediction module forecasts the future glucose values, from which “preventive” alerts can be generated before critical hypoglycemic/hyperglycemic events occur. Full article ">
Denoising. Example of real-time application of the algorithm in [<a href="#b59-sensors-12-13753" class="html-bibr">59</a>] to a representative Glucoday® time-series measured in a diabetic volunteer. Original (blue) and denoised (red) CGM profiles are shown. The black horizontal line represents the hypoglycaemic threshold. Full article ">
Enhancement. Example of real-time application of the algorithm in [<a href="#b66-sensors-12-13753" class="html-bibr">66</a>] to a representative DexCom® SevenPlus® time-series measured in a diabetic volunteer. The gray rectangle highlights the two SMBG values (magenta triangles) and the portion of CGM data (blue line) used by the algorithm to estimate the internal regressor parameters. Original CGM data (blue line) and enhanced glucose profile (green line) are then shown against BG references (red stars), collected in parallel using a laboratory instrument. Full article ">
Prediction for alert generation (simulation context). (A). Hypoglycemic alert generated on the basis of CGM data. CGM data before (black line) and after (blue dashed line) the carbohydrates ingestion (blue arrow) in response to alert (blue bell) generated at hypoglycemic threshold crossing. (B). Hypoglycemic alert generated on the basis of predicted CGM data. CGM data before (black line) and after (red dashed line) the carbohydrates ingestion (red arrow) in response to alert (red bell) generated when predicted CGM (red line) exceeds hypoglycemic threshold. Full article ">
(A) Identification of the model allowing to estimate glucose concentration from the 150 signals returned by the Solianis Monitoring AG Multisensor system. The inlaid graphs show, for a real subject, the time-course for the 16 representative channels numbered as 105–120 (left) and the reference BG glucose concentration levels measured in parallel (open bullets, right). (B) Example of estimated glucose profiles during model test for a representative experimental session with the PLS (blue line) and with the LASSO (green line) models against BG samples [<a href="#b129-sensors-12-13753" class="html-bibr">129</a>]. Full article ">

1112 KiB

Open AccessArticle

On-Site Sensor Recalibration of a Spinning Multi-Beam LiDAR System Using Automatically-Detected Planar Targets

by Chia-Yen Chen and Hsiang-Jen Chien

Sensors 2012, 12(10), 13736-13752; https://doi.org/10.3390/s121013736 - 12 Oct 2012

Cited by 30 | Viewed by 8227

Abstract

This paper presents a fully-automated method to establish a calibration dataset from on-site scans and recalibrate the intrinsic parameters of a spinning multi-beam 3-D scanner. The proposed method has been tested on a Velodyne HDL-64E S2 LiDAR system, which contains 64 rotating laser [...] Read more.

This paper presents a fully-automated method to establish a calibration dataset from on-site scans and recalibrate the intrinsic parameters of a spinning multi-beam 3-D scanner. The proposed method has been tested on a Velodyne HDL-64E S2 LiDAR system, which contains 64 rotating laser rangefinders. By time series analysis, we found that the collected range data have random measurement errors of around ±25 mm. In addition, the layered misalignment of scans among the rangefinders, which is identified as a systematic error, also increases the difficulty to accurately locate planar surfaces. We propose a temporal-spatial range data fusion algorithm, along with a robust RANSAC-based plane detection algorithm to address these issues. Furthermore, we formulate an alternative geometric interpretation of sensory data using linear parameters, which is advantageous for the calibration procedure. The linear representation allows the proposed method to be generalized to any LiDAR system that follows the rotating beam model. We also confirmed in this paper, that given effective calibration datasets, the pre-calibrated factory parameters can be further tuned to achieve significantly improved performance. After the optimization, the systematic error is noticeable lowered, and evaluation shows that the recalibrated parameters outperform the factory parameters with the RMS planar errors reduced by up to 49%. Full article

(This article belongs to the Special Issue Laser Sensing and Imaging)

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641 KiB

Open AccessArticle

Computational Design of a Carbon Nanotube Fluorofullerene Biosensor

by Tamsyn A. Hilder, Ron J. Pace and Shin-Ho Chung

Sensors 2012, 12(10), 13720-13735; https://doi.org/10.3390/s121013720 - 12 Oct 2012

Cited by 7 | Viewed by 6870

Abstract

Carbon nanotubes offer exciting opportunities for devising highly-sensitive detectors of specific molecules in biology and the environment. Detection limits as low as 10⁻¹¹ M have already been achieved using nanotube-based sensors. We propose the design of a biosensor comprised of functionalized carbon [...] Read more.

Carbon nanotubes offer exciting opportunities for devising highly-sensitive detectors of specific molecules in biology and the environment. Detection limits as low as 10⁻¹¹ M have already been achieved using nanotube-based sensors. We propose the design of a biosensor comprised of functionalized carbon nanotube pores embedded in a silicon-nitride or other membrane, fluorofullerene-Fragment antigen-binding (Fab fragment) conjugates, and polymer beads with complementary Fab fragments. We show by using molecular and stochastic dynamics that conduction through the (9, 9) exohydrogenated carbon nanotubes is 20 times larger than through the Ion Channel Switch ICS^TM biosensor, and fluorofullerenes block the nanotube entrance with a dissociation constant as low as 37 pM. Under normal operating conditions and in the absence of analyte, fluorofullerenes block the nanotube pores and the polymer beads float around in the reservoir. When analyte is injected into the reservoir the Fab fragments attached to the fluorofullerene and polymer bead crosslink to the analyte. The drag of the much larger polymer bead then acts to pull the fluorofullerene from the nanotube entrance, thereby allowing the flow of monovalent cations across the membrane. Assuming a tight seal is formed between the two reservoirs, such a biosensor would be able to detect one channel opening and thus one molecule of analyte making it a highly sensitive detection design. Full article

(This article belongs to the Section Biosensors)

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(A) Schematic of the (9, 9) exohydrogenated carbon nanotube with hydrogen atoms shown in light grey; (B) Free energy profile along the axial coordinate for potassium (K+) and chloride (Cl−) ions; (C) Dwell histogram of potassium ions in the absence of an applied electric potential. Full article ">
(A) Current-voltage profile for potassium ions at an ionic concentration of 500 mM, and (B) Current-concentration profile for potassium ions at an applied potential of 200 mV. Data points represent the average of five sets of simulations, each simulation lasting 0.8 μs. Error bars represent one standard error of the mean and error bars smaller than the data points are not shown. Full article ">
Fluorofullerene PMF. PMF profile for the unbinding of the C60F36 and C60F60 fluorofullerenes from the (9, 9) exohydrogenated carbon nanotube. Full article ">
Illustration of the bound configuration of C60F60 to the carbon nanotube. (A) top view and (B) side view. Full article ">
Schematic representation of the carbon nanotube-fluorofullerene biosensor. (A) In the absence of analyte (orange) all nanotube pores are blocked by fluorofullerene (red)—Fab fragment (purple) conjugates. (B) Analyte is injected into the sample, and binds to the Fab fragments on the fluorofullerene and polymer bead (blue) floating in solution. The flow from the injected analyte solution is sufficient to pull a fluorofullerene from its docked position and potassium current is observed. Full article ">

1051 KiB

Open AccessArticle

Spectral Regression Based Fault Feature Extraction for Bearing Accelerometer Sensor Signals

by Zhanguo Xia, Shixiong Xia, Ling Wan and Shiyu Cai

Sensors 2012, 12(10), 13694-13719; https://doi.org/10.3390/s121013694 - 12 Oct 2012

Cited by 76 | Viewed by 11015

Abstract

Bearings are not only the most important element but also a common source of failures in rotary machinery. Bearing fault prognosis technology has been receiving more and more attention recently, in particular because it plays an increasingly important role in avoiding the occurrence [...] Read more.

Bearings are not only the most important element but also a common source of failures in rotary machinery. Bearing fault prognosis technology has been receiving more and more attention recently, in particular because it plays an increasingly important role in avoiding the occurrence of accidents. Therein, fault feature extraction (FFE) of bearing accelerometer sensor signals is essential to highlight representative features of bearing conditions for machinery fault diagnosis and prognosis. This paper proposes a spectral regression (SR)-based approach for fault feature extraction from original features including time, frequency and time-frequency domain features of bearing accelerometer sensor signals. SR is a novel regression framework for efficient regularized subspace learning and feature extraction technology, and it uses the least squares method to obtain the best projection direction, rather than computing the density matrix of features, so it also has the advantage in dimensionality reduction. The effectiveness of the SR-based method is validated experimentally by applying the acquired vibration signals data to bearings. The experimental results indicate that SR can reduce the computation cost and preserve more structure information about different bearing faults and severities, and it is demonstrated that the proposed feature extraction scheme has an advantage over other similar approaches. Full article

(This article belongs to the Section Physical Sensors)

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Open AccessArticle

In Tube Integrated Electronic Nose System on a Flexible Polymer Substrate

by Thomas Kinkeldei, Christoph Zysset, Niko Münzenrieder, Luisa Petti and Gerhard Tröster

Sensors 2012, 12(10), 13681-13693; https://doi.org/10.3390/s121013681 - 12 Oct 2012

Cited by 7 | Viewed by 7418

Abstract

The fabrication of electronic devices, such as gas sensors on flexible polymer substrates, enables the use of electronics in applications where conventional devices on stiff substrates could not be used. We demonstrate the development of a new intra-tube electronic-nose (e-nose) gas sensor device [...] Read more.

The fabrication of electronic devices, such as gas sensors on flexible polymer substrates, enables the use of electronics in applications where conventional devices on stiff substrates could not be used. We demonstrate the development of a new intra-tube electronic-nose (e-nose) gas sensor device with multiple sensors fabricated and integrated on a flexible substrate. For this purpose, we developed a new method of fabricating a sensor array of four gas sensors on a flexible polymer substrate. The method allowed the use of lithography techniques to pattern different polymers with a broad range of solubility parameters. Conductive polymer composites were used as a gas sensitive layer due to the high stretchability of the material. Each of the 30 e-nose devices on one substrate was designed to fit on a polymer strip with a width of 2 mm. A single e-nose strip was successfully integrated into the inlet tube of a gas-measurement apparatus with an inner-tube diameter of 3 mm. Using the e-nose, we were able to differentiate between four different volatile solvent vapors. The tube-integrated e-nose outperformed a chamber-integrated e-nose of the same type in terms of response time and flow-rate influences. The sensor array inside the tube showed a faster response time and detected short pulses of analyte exposure compared to the same sensor array outside of the tube. We measured gas flow rates from 1,000 to 30 sccm without significant changes in sensor performance using this intra-tube e-nose prototype. The tube could be bent to radii < 15 mm with a sensor performance similar to an unbent sensor. Full article

(This article belongs to the Section Chemical Sensors)

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Sensors, Volume 12, Issue 10 (October 2012) – 70 articles , Pages 12870-14231

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