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Volume 13
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Sensors, Volume 13, Issue 6 (June 2013) – 64 articles , Pages 6882-8059

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603 KiB  
Article
Extending the GMR Current Measurement Range with a Counteracting Magnetic Field
by Tin Yan Poon, Norman Chung Fai Tse and Ricky Wing Hong Lau
Sensors 2013, 13(6), 8042-8059; https://doi.org/10.3390/s130608042 - 21 Jun 2013
Cited by 30 | Viewed by 8567
Abstract
Traditionally, current transformers are often used for current measurement in low voltage (LV) electrical networks. They have a large physical size and are not designed for use with power electronic circuits. Semiconductor-based current sensing devices such as the Hall sensor and Giant Magnetoresistive [...] Read more.
Traditionally, current transformers are often used for current measurement in low voltage (LV) electrical networks. They have a large physical size and are not designed for use with power electronic circuits. Semiconductor-based current sensing devices such as the Hall sensor and Giant Magnetoresistive (GMR) sensor are advantageous in terms of small size, high sensitivity, wide frequency range, low power consumption, and relatively low cost. Nevertheless, the operational characteristics of these devices limit their current measurement range. In this paper, a design based on using counteracting magnetic field is introduced for extending the GMR current measurement range from 9 A (unipolar) to ±45 A. A prototype has been implemented to verify the design and the linear operation of the circuit is demonstrated by experimental results. A microcontroller unit (MCU) is used to provide an automatic scaling function to optimize the performance of the proposed current sensor. Full article
(This article belongs to the Section Physical Sensors)
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<p><b>(a)</b> Schematic cross-section of a GMR layered structure; (<b>b</b>) limited electron path due to scattering.</p> Full article ">
<p>Geometric arrangement of the Helmholtz coil.</p> Full article ">
<p>Wheatstone bridge configuration.</p> Full article ">
<p><b>(a)</b> Simplified circuit diagram; <b>(b)</b> block diagram of the system.</p> Full article ">
<p>Offset output of the sensor.</p> Full article ">
<p>Photo of the prototype current sensor.</p> Full article ">
<p>Linearity of the current sensor (<b>a</b>) with Helmholtz coil and; (<b>b</b>) without Helmholtz coil.</p> Full article ">
<p>(<b>a</b>) Frequency response of the sensor; (<b>b</b>) waveform of the input current and the output of sensor at 50 Hz.</p> Full article ">
<p>Power consumption <span class="html-italic">vs.</span> the input current.</p> Full article ">
972 KiB  
Article
Sequential Fuzzy Diagnosis Method for Motor Roller Bearing in Variable Operating Conditions Based on Vibration Analysis
by Ke Li, Xueliang Ping, Huaqing Wang, Peng Chen and Yi Cao
Sensors 2013, 13(6), 8013-8041; https://doi.org/10.3390/s130608013 - 21 Jun 2013
Cited by 121 | Viewed by 8689
Abstract
A novel intelligent fault diagnosis method for motor roller bearings which operate under unsteady rotating speed and load is proposed in this paper. The pseudo Wigner-Ville distribution (PWVD) and the relative crossing information (RCI) methods are used for extracting the feature spectra from [...] Read more.
A novel intelligent fault diagnosis method for motor roller bearings which operate under unsteady rotating speed and load is proposed in this paper. The pseudo Wigner-Ville distribution (PWVD) and the relative crossing information (RCI) methods are used for extracting the feature spectra from the non-stationary vibration signal measured for condition diagnosis. The RCI is used to automatically extract the feature spectrum from the time-frequency distribution of the vibration signal. The extracted feature spectrum is instantaneous, and not correlated with the rotation speed and load. By using the ant colony optimization (ACO) clustering algorithm, the synthesizing symptom parameters (SSP) for condition diagnosis are obtained. The experimental results shows that the diagnostic sensitivity of the SSP is higher than original symptom parameter (SP), and the SSP can sensitively reflect the characteristics of the feature spectrum for precise condition diagnosis. Finally, a fuzzy diagnosis method based on sequential inference and possibility theory is also proposed, by which the conditions of the machine can be identified sequentially as well. Full article
(This article belongs to the Section Physical Sensors)
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<p>Frequency of crossing over level <span class="html-italic">i</span>.</p> Full article ">
<p>Changes in the clustering centers: (<b>a</b>) at the start of the ACO, (<b>b</b>) after 100 iterations and (<b>c</b>) after 200 iterations. The symbols ○ and □ express the value samples of the SPs in the normal and roller defect states, respectively, and the large symbols ■ and ● represent their respective clustering centers.</p> Full article ">
<p>The axis of the synthetic symptom parameter (SSP).</p> Full article ">
<p>Illustrative example of an SSP: (<b>a</b>) probability distributions of P<sub>1</sub>and P<sub>2</sub> and (<b>b</b>) probability distributions of SSP<sub>NR</sub>.</p> Full article ">
<p>Possibility and probability density functions.</p> Full article ">
<p>Matching examples of the possibility function.</p> Full article ">
<p>Flowchart of the sequential condition diagnosis.</p> Full article ">
<p>Flowchart for condition diagnosis.</p> Full article ">
<p>Experimental setup for the rolling bearing fault diagnosis. (<b>a</b>) Illustration of the rotation machinery and (<b>b</b>) the motor in the field.</p> Full article ">
558 KiB  
Article
Array of Hall Effect Sensors for Linear Positioning of a Magnet Independently of Its Strength Variation. A Case Study: Monitoring Milk Yield during Milking in Goats
by Fernando-Juan García-Diego, Angel Sánchez-Quinche, Paloma Merello, Pedro Beltrán and Cristófol Peris
Sensors 2013, 13(6), 8000-8012; https://doi.org/10.3390/s130608000 - 21 Jun 2013
Cited by 5 | Viewed by 7729
Abstract
In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The [...] Read more.
In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization) by row (position) making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R2 = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)
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<p>Photographs of the electronic system and its location in the proportional meter, <b>(a)</b> front view of the proportional meter whit the electronic circuit attached, <b>(b)</b> view from above of dismounted receiving container, showing part of the array of Hall Effect sensors and the magnet over the pink float.</p> Full article ">
<p>Electronic sketch of the array of sensors, multiplexing and conditioning of the signal.</p> Full article ">
<p><b>(a)</b> Potential in volts (vertical axis) as a function of the position (mm) of the magnet with respect to a sensor in the center of the array (horizontal axis). Graphic in blue corresponds to the magnet without heat treatment, the red one corresponds to the magnet with heat treated. <b>(b)</b> Normalized value of the potential, for both magnet without heat treatment (blue) and treated (red). A value of zero on the horizontal axis indicates coincidence of positions (position of the sensor equal to the magnet position). We have made a zoom to see the difference between both points.</p> Full article ">
<p>Output volume in L <span class="html-italic">vs.</span> predicted volume by the calibration curve (L).</p> Full article ">
<p>Manually measured volume (<span class="html-italic">Vf</span>(<span class="html-italic">real</span>)) and volume estimated by the electronic system and calibration model (<span class="html-italic">Vf</span>(<span class="html-italic">e</span>)) <span class="html-italic">vs.</span> time. The confidence intervals have been plotted for <span class="html-italic">Vf</span>(<span class="html-italic">real</span>) considering a manual measurement error of ±0.05 L.</p> Full article ">
1606 KiB  
Article
Rate-Gyro-Integral Constraint for Ambiguity Resolution in GNSS Attitude Determination Applications
by Jiancheng Zhu, Tao Li, Jinling Wang, Xiaoping Hu and Meiping Wu
Sensors 2013, 13(6), 7979-7999; https://doi.org/10.3390/s130607979 - 21 Jun 2013
Cited by 16 | Viewed by 6714
Abstract
In the field of Global Navigation Satellite System (GNSS) attitude determination, the constraints usually play a critical role in resolving the unknown ambiguities quickly and correctly. Many constraints such as the baseline length, the geometry of multi-baselines and the horizontal attitude angles have [...] Read more.
In the field of Global Navigation Satellite System (GNSS) attitude determination, the constraints usually play a critical role in resolving the unknown ambiguities quickly and correctly. Many constraints such as the baseline length, the geometry of multi-baselines and the horizontal attitude angles have been used extensively to improve the performance of ambiguity resolution. In the GNSS/Inertial Navigation System (INS) integrated attitude determination systems using low grade Inertial Measurement Unit (IMU), the initial heading parameters of the vehicle are usually worked out by the GNSS subsystem instead of by the IMU sensors independently. However, when a rotation occurs, the angle at which vehicle has turned within a short time span can be measured accurately by the IMU. This measurement will be treated as a constraint, namely the rate-gyro-integral constraint, which can aid the GNSS ambiguity resolution. We will use this constraint to filter the candidates in the ambiguity search stage. The ambiguity search space shrinks significantly with this constraint imposed during the rotation, thus it is helpful to speeding up the initialization of attitude parameters under dynamic circumstances. This paper will only study the applications of this new constraint to land vehicles. The impacts of measurement errors on the effect of this new constraint will be assessed for different grades of IMU and current average precision level of GNSS receivers. Simulations and experiments in urban areas have demonstrated the validity and efficacy of the new constraint in aiding GNSS attitude determinations. Full article
(This article belongs to the Section Physical Sensors)
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<p>Geometric depiction of the rate-gyro-integral constraint.</p> Full article ">
<p>Projection vectors and angles on the rotation plane.</p> Full article ">
<p>Success rate varies with threshold at different accuracy levels of gyroscope.</p> Full article ">
<p>Shrinking efficiency varies with threshold at different accuracy of gyroscope.</p> Full article ">
<p>Testing vehicle is set up: (<b>a</b>) plan view; (<b>b</b>) side view.</p> Full article ">
<p>Testing trajectory.</p> Full article ">
<p>Scheme for actual field data processing.</p> Full article ">
<p>Turntable road and locations of 23 GPS epochs for data section F.</p> Full article ">
<p>ζ s for data section F.</p> Full article ">
1483 KiB  
Article
Quantitative Analysis of Fragrance and Odorants Released from Fresh and Decaying Strawberries
by Yong-Hyun Kim, Ki-Hyun Kim, Jan E. Szulejko and David Parker
Sensors 2013, 13(6), 7939-7978; https://doi.org/10.3390/s130607939 - 20 Jun 2013
Cited by 31 | Viewed by 9621
Abstract
The classes and concentrations of volatile organic compounds (VOC) released from fresh and decaying strawberries were investigated and compared. In this study, a total of 147 strawberry volatiles were quantified before and after nine days of storage to explore differences in the aroma [...] Read more.
The classes and concentrations of volatile organic compounds (VOC) released from fresh and decaying strawberries were investigated and compared. In this study, a total of 147 strawberry volatiles were quantified before and after nine days of storage to explore differences in the aroma profile between fresh strawberries (storage days (SRD) of 0, 1, and 3) and those that had started to decay (SRD = 6 and 9). In terms of concentration, seven compounds dominated the aroma profile of fresh strawberries (relative composition (RC) up to 97.4% by mass, sum concentration): (1) ethyl acetate = 518 mg∙m−3, (2) methyl acetate = 239 mg∙m−3, (3) ethyl butyrate = 13.5 mg∙m−3, (4) methyl butyrate = 11.1 mg∙m−3, (5) acetaldehyde = 24.9 mg∙m−3, (6) acetic acid = 15.2 mg∙m−3, and (7) acetone = 13.9 mg∙m−3. In contrast, two alcohols dominated the aroma profile of decayed samples (RC up to 98.6%): (1) ethyl alcohol = 94.2 mg∙m−3 and (2) isobutyl alcohol = 289 mg∙m−3. Alternatively; if the aroma profiles are re-evaluated by summing odor activity values (ΣOAV); four ester compounds ((1) ethyl butyrate (6,160); (2) ethyl hexanoate (3,608); (3) ethyl isovalerate (1,592); and (4) ethyl 2-methylbutyrate (942)) were identified as the key constituents of fresh strawberry aroma (SRD-0). As the strawberries began to decay; isobutyl alcohol recorded the maximum OAV of 114 (relative proportion (RP) (SRD = 6) = 58.3%). However, as the decay process continued, the total OAV dropped further by 3 to 4 orders of magnitude—decreasing to 196 on SRD = 6 to 7.37 on SRD = 9. The overall results of this study confirm dramatic changes in the aroma profile of strawberries over time, especially with the onset of decay. Full article
(This article belongs to the Special Issue Sensing of Scent, Fragrance, Smell, and Odor Emissions from Biota Sources)
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<p>Illustration of the impinger system for the collection of VOCs emitted from strawberry samples. Labels: (<b>1</b>) 10 L polyester aluminum bag filled with ultra-pure nitrogen; (<b>2</b>) Silicon tubing; (<b>3</b>) Impinger bottle; (<b>4</b>) Aluminum container; (<b>5</b>) Water heated to 25 °C; (<b>6</b>) Heater; (<b>7</b>) Sensor; (<b>8</b>) Temperature regulator; (<b>9</b>) Strawberry slices; (<b>10</b>) Sorbent tube; (<b>11</b>) Mini vacuum pump; and (<b>12</b>) Teflon tubing.</p> Full article ">
<p>Comparison of frequency) pattern and log concentration of strawberry volatiles (compounds sorted by functional group).</p> Full article ">
<p>Plots of correlation between molecular weight and log (odor thresholds (ppbv)) for alldata (n = 62) and optimal fit (n = 54) of the four major VOC groups (Ester, Alcohol, Aldehyde, and Ketone) emitted from strawberry samples.</p> Full article ">
<p>Plots of correlation between molecular weight and log (odor thresholds (ppbv)) for alldata (n = 62) and optimal fit (n = 54) of the four major VOC groups (Ester, Alcohol, Aldehyde, and Ketone) emitted from strawberry samples.</p> Full article ">
<p>Comparison between (odor activity value) OAV and relative proportion (RP) of the major VOCs which had OAV and RP of above 100 and 5%, respectively at storagetime of 0, 1, 3, 6, and 9 days.</p> Full article ">
<p>The linear regression analysis between the response factors (RF) and effective carbon number (ECN) for each atom and function group (e.g., C, H, O, &gt;C=O, -O-, and -CH<sub>3</sub>).</p> Full article ">
<p>Photographs showing strawberry samples in impinge.</p> Full article ">
<p>Relationship between Σodor activity values (OAV) and dilution-to-threshold (D/T) ratio.</p> Full article ">
924 KiB  
Article
Synthesis of Novel CuO Nanosheets and Their Non-Enzymatic Glucose Sensing Applications
by Zafar Hussain Ibupoto, Kimleang Khun, Valerio Beni, Xianjie Liu and Magnus Willander
Sensors 2013, 13(6), 7926-7938; https://doi.org/10.3390/s130607926 - 20 Jun 2013
Cited by 100 | Viewed by 12624
Abstract
In this study, we have developed a sensitive and selective glucose sensor using novel CuO nanosheets which were grown on a gold coated glass substrate by a low temperature growth method. X-ray differaction (XRD) and scanning electron microscopy (SEM) techniques were used for [...] Read more.
In this study, we have developed a sensitive and selective glucose sensor using novel CuO nanosheets which were grown on a gold coated glass substrate by a low temperature growth method. X-ray differaction (XRD) and scanning electron microscopy (SEM) techniques were used for the structural characterization of CuO nanostructures. CuO nanosheets are highly dense, uniform, and exhibited good crystalline array structure. X-ray photoelectron spectroscopy (XPS) technique was applied for the study of chemical composition of CuO nanosheets and the obtained information demonstrated pure phase CuO nanosheets. The novel CuO nanosheets were employed for the development of a sensitive and selective non-enzymatic glucose sensor. The measured sensitivity and a correlation coefficient are in order 5.20 × 102 µA/mMcm2 and 0.998, respectively. The proposed sensor is associated with several advantages such as low cost, simplicity, high stability, reproducibility and selectivity for the quick detection of glucose. Full article
(This article belongs to the Section Chemical Sensors)
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<p>The XRD pattern of CuO nanosheets.</p> Full article ">
<p>The SEM image of CuO nanosheets (<b>a</b>) low magnification image; and (<b>b</b>) high magnification image.</p> Full article ">
<p>The XPS study of CuO nanosheets.</p> Full article ">
<p>Calibration curve of the current <span class="html-italic">versus</span> different scan rate measured in 1.96 mM glucose concentration.</p> Full article ">
<p>The CVs curve of CuO nanosheets based electrode in different concentrations of glucose at the scan rate of 10.00 mV/s.</p> Full article ">
<p>(<b>a</b>) The calibration curve of the current <span class="html-italic">versus</span> glucose concentrations by amperometric measurement at applied potential of 0.50 V; (<b>b</b>) The response time curve of the proposed glucose sensor at applied potential of 0.50 V with successive addition of glucose in 0.10 M NaOH solution.</p> Full article ">
<p>The calibration curve of the proposed glucose sensor in the presence of common interferents.</p> Full article ">
276 KiB  
Article
A Reflective Photonic Crystal Fiber Temperature Sensor Probe Based on Infiltration with Liquid Mixtures
by Ran Wang, Jianquan Yao, Yinping Miao, Ying Lu, Degang Xu, Nannan Luan, Mayilamu Musideke, Liangcheng Duan and Congjing Hao
Sensors 2013, 13(6), 7916-7925; https://doi.org/10.3390/s130607916 - 20 Jun 2013
Cited by 36 | Viewed by 7788
Abstract
In this paper, a reflective photonic crystal fiber (PCF) sensor probe for temperature measurement has been demonstrated both theoretically and experimentally. The performance of the device depends on the intensity modulation of the optical signal by liquid mixtures infiltrated into the air holes [...] Read more.
In this paper, a reflective photonic crystal fiber (PCF) sensor probe for temperature measurement has been demonstrated both theoretically and experimentally. The performance of the device depends on the intensity modulation of the optical signal by liquid mixtures infiltrated into the air holes of commercial LMA-8 PCFs. The effective mode field area and the confinement loss of the probe are both proved highly temperature-dependent based on the finite element method (FEM). The experimental results show that the reflected power exhibits a linear response with a temperature sensitivity of about 1 dB/°C. The sensor probe presents a tunable temperature sensitive range due to the concentration of the mixture components. Further research illustrates that with appropriate mixtures of liquids, the probe could be developed as a cryogenic temperature sensor. The temperature sensitivity is about 0.75 dB/°C. Such a configuration is promising for a portable, low-power and all-in-fiber device for temperature or refractive index monitoring in chemical or biosensing applications. Full article
(This article belongs to the Section Physical Sensors)
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<p>The image of LMA-8 cross section from field emission scanning electron microscopy.</p> Full article ">
<p>The simulated distributions of LMA-8 PCF fundamental modes with the volume ratio of chloroform and ethanol as 9:1, <b>(a)</b> at 0 °C , <b>(b)</b> at 20 °C .</p> Full article ">
<p>The confinement loss and effective mode area as functions of temperature.</p> Full article ">
<p>Scheme of the experimental setup for the LMA-8 PCF sensor probe.</p> Full article ">
<p>Theoretical and experimental loss <b>(a)</b> and linear fitting curves of the experimental loss <b>(b)</b> as functions of temperature with the volume ratio of chloroform and ethanol as 9:1.</p> Full article ">
<p>Theoretical and experimental loss <b>(a)</b> and linear fitting curves of the experimental loss <b>(b)</b> as functions of temperature with pure chloroform.</p> Full article ">
<p>The experimental total loss and linear-fitting curve as functions of temperature in the ultralow range with a 3:7 volume ratio of toluene and ethanol.</p> Full article ">
668 KiB  
Article
Estimation of Melanin and Hemoglobin Using Spectral Reflectance Images Reconstructed from a Digital RGB Image by the Wiener Estimation Method
by Izumi Nishidate, Takaaki Maeda, Kyuichi Niizeki and Yoshihisa Aizu
Sensors 2013, 13(6), 7902-7915; https://doi.org/10.3390/s130607902 - 19 Jun 2013
Cited by 77 | Viewed by 12684
Abstract
A multi-spectral diffuse reflectance imaging method based on a single snap shot of Red-Green-Blue images acquired with the exposure time of 65 ms (15 fps) was investigated for estimating melanin concentration, blood concentration, and oxygen saturation in human skin tissue. The technique utilizes [...] Read more.
A multi-spectral diffuse reflectance imaging method based on a single snap shot of Red-Green-Blue images acquired with the exposure time of 65 ms (15 fps) was investigated for estimating melanin concentration, blood concentration, and oxygen saturation in human skin tissue. The technique utilizes the Wiener estimation method to deduce spectral reflectance images instantaneously from an RGB image. Using the resultant absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin and deoxygenated hemoglobin as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of melanin and total blood are then determined from the regression coefficients using conversion vectors that are numerically deduced in advance by the Monte Carlo simulations for light transport in skin. Oxygen saturation is obtained directly from the regression coefficients. Experiments with a tissue-like agar gel phantom validated the method. In vivo experiments on fingers during upper limb occlusion demonstrated the ability of the method to evaluate physiological reactions of human skin. Full article
(This article belongs to the Special Issue Spectral Imaging at the Microscale and Beyond)
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<p>Experimental configuration for the image acquisitions and the spectral reflectance measurements.</p> Full article ">
<p>Spectral profiles for (<b>a</b>) the RGB-responses of camera and (<b>b</b>) the intensity of illuminant.</p> Full article ">
<p>Photographs of tissue-like agar gel phantom for (<b>a</b>) cross-sectional view and (<b>b</b>) top view.</p> Full article ">
<p>Comparison of the estimated values by the Wiener estimation and the reference values by spectrometer for (<b>a</b>) <span class="html-italic">C<sub>c</sub></span><sub>,</sub> (<b>b</b>) <span class="html-italic">C<sub>tb</sub></span><sub>,</sub> and (<b>c</b>) <span class="html-italic">StO</span><sub>2</sub> in the phantom experiments.</p> Full article ">
<p><span class="html-italic">In vivo</span> results obtained from human fingers under the normal condition for (<b>a</b>) raw RGB image and (<b>b</b>) the estimated images of spectral diffuse reflectance by the Wiener estimation.</p> Full article ">
<p>Comparisons of the estimated reflectance spectra averaged over the ROI (white square area in <a href="#f4-sensors-13-07902" class="html-fig">Figure 4</a>) and the reference spectra measured by spectrometer for (<b>a</b>) pre-occlusion, (<b>b</b>) 300 s after occlusion, and (<b>c</b>) 90 s after deflation of pressure cuff.</p> Full article ">
<p>Typical images of fingers (from top to bottom; <span class="html-italic">C<sub>m</sub></span><sub>,</sub><span class="html-italic">C<sub>tb</sub></span><sub>,</sub> and <span class="html-italic">StO</span><sub>2</sub>) for pre-occlusion, 300 s after occlusion, and 90 s after deflation of pressure cuff.</p> Full article ">
<p>Time courses of (<b>a</b>) <span class="html-italic">C<sub>m</sub></span><sub>,</sub> (<b>b</b>) <span class="html-italic">C<sub>tb</sub></span><sub>,</sub> and (<b>c</b>) <span class="html-italic">StO</span><sub>2</sub> averaged over the ROIs (white squares in <a href="#f6-sensors-13-07902" class="html-fig">Figure 6</a>) are compared with the reference values from the spectrometer recordings. The error bars show the standard deviations (<span class="html-italic">n</span> = 5).</p> Full article ">
499 KiB  
Article
Gait-Based Person Identification Robust to Changes in Appearance
by Yumi Iwashita, Koji Uchino and Ryo Kurazume
Sensors 2013, 13(6), 7884-7901; https://doi.org/10.3390/s130607884 - 19 Jun 2013
Cited by 55 | Viewed by 7737
Abstract
The identification of a person from gait images is generally sensitive to appearance changes, such as variations of clothes and belongings. One possibility to deal with this problem is to collect possible subjects’ appearance changes in a database. However, it is almost impossible [...] Read more.
The identification of a person from gait images is generally sensitive to appearance changes, such as variations of clothes and belongings. One possibility to deal with this problem is to collect possible subjects’ appearance changes in a database. However, it is almost impossible to predict all appearance changes in advance. In this paper, we propose a novel method, which allows robustly identifying people in spite of changes in appearance, without using a database of predicted appearance changes. In the proposed method, firstly, the human body image is divided into multiple areas, and features for each area are extracted. Next, a matching weight for each area is estimated based on the similarity between the extracted features and those in the database for standard clothes. Finally, the subject is identified by weighted integration of similarities in all areas. Experiments using the gait database CASIA show the best correct classification rate compared with conventional methods experiments. Full article
(This article belongs to the Section Physical Sensors)
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<p>(<b>a</b>) An example of average images in the database; (<b>b</b>) An example of average images of subjects with a shoulder bag.</p> Full article ">
<p>Affine moment invariant <span class="html-italic">A</span><sub>1</sub> in a gait sequence.</p> Full article ">
<p>Estimation of matching weights.</p> Full article ">
<p>Examples of silhouette images of the CASIA-B dataset.</p> Full article ">
<p>Examples of silhouette images of the CASIA-C dataset.</p> Full article ">
<p>Correct classification rates by the proposed method (CASIA-B).</p> Full article ">
<p>Correct classification rates by the proposed method and the method without matching weights.</p> Full article ">
<p>Correct classification rates by the proposed method (CASIA-C).</p> Full article ">
<p>Examples of silhouette images: (<b>a</b>) CASIA-B-BG and (<b>b</b>) CASIA-B-CL.</p> Full article ">
642 KiB  
Article
In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics
by Thomas Leeuw, Emmanuel S. Boss and Dana L. Wright
Sensors 2013, 13(6), 7872-7883; https://doi.org/10.3390/s130607872 - 19 Jun 2013
Cited by 72 | Viewed by 23141
Abstract
Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made [...] Read more.
Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger. Full article
(This article belongs to the Section Chemical Sensors)
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<p>Sensor components and geometry. The detector is placed at 90° to the light source to minimize the amount of excitation light scattered toward the detector.</p> Full article ">
<p>Emission spectrum from LED420L and percent transmission of Roscolux filter #19.</p> Full article ">
<p>Transimpedance amplifier using OP07 and 5 GΩ resistors.</p> Full article ">
<p>Radiance at 425 nm of blue LED over time. The LED should be allowed to run for at least 1.5 minutes to allow the output to stabilize.</p> Full article ">
<p>Cross calibration using extracted chlorophyll <span class="html-italic">a</span> from spinach leaves (<b>Left</b>) and live <span class="html-italic">Thalassiosira weissflogii</span> cells (<b>Right</b>). Regression equation, coefficient of determination, and root mean squared error (RMSE) are included in each plot.</p> Full article ">
<p>Sensor response to water turbidity. The figure shows counts returned by the sensor when placed in a mixture of deionized water and varying amounts of bentonite clay.</p> Full article ">
<p>Time series of chlorophyll <span class="html-italic">a</span> concentration measured in the Damariscotta River Estuary during first deployment (04/03/12–04/04/12). Vertical lines show time of high and low tide.</p> Full article ">
<p>Comparison of chlorophyll <span class="html-italic">a</span> concentration measured by WetLabs WETStar and the constructed fluorometer in The Damariscotta River Estuary (08/01/12–08/02/12). The outputs from both sensors were normalized to extracted chlorophyll <span class="html-italic">a</span> measurements taken from water collected during the deployment.</p> Full article ">
<p>Roscolux filter booklet from Edmund Optics (included in the total price of the fluorometer). A booklet contains over 200 filters, each with a graph showing percent transmission. These can be used over the light source or detector to measure fluorescence from numerous other substances in addition to chlorophyll <span class="html-italic">a</span>.</p> Full article ">
598 KiB  
Article
Recovery of Odorants from an Olfactometer Measured by Proton-Transfer-Reaction Mass Spectrometry
by Michael Jørgen Hansen, Anders Peter S. Adamsen and Anders Feilberg
Sensors 2013, 13(6), 7860-7871; https://doi.org/10.3390/s130607860 - 19 Jun 2013
Cited by 26 | Viewed by 7829
Abstract
The aim of the present study was to examine the recovery of odorants during the dilution in an olfactometer designed according to the European standard for dynamic olfactometry. Nine odorants in the ppmv-range were examined including hydrogen sulfide, methanethiol, dimethyl sulfide, [...] Read more.
The aim of the present study was to examine the recovery of odorants during the dilution in an olfactometer designed according to the European standard for dynamic olfactometry. Nine odorants in the ppmv-range were examined including hydrogen sulfide, methanethiol, dimethyl sulfide, acetic acid, propanoic acid, butanoic acid, trimethylamine, 3-methylphenol and n-butanol. Each odorant was diluted in six dilution steps in descending order from 4,096 to 128 times dilutions. The final recovery of dimethyl sulfide and n-butanol after a 60-second pulse was only slightly affected by the dilution, whereas the recoveries of the other odorants were significantly affected by the dilution. The final recoveries of carboxylic acids, trimethylamine and 3-methylphenol were affected by the pulse duration and the signals did not reach stable levels within the 60-second pulse, while sulfur compounds and n-butanol reach a stable signal within a few seconds. In conclusion, the dilution of odorants in an olfactometer has a high impact on the recovery of odorants and when olfactometry is used to estimate the odor concentration, the recoveries have to be taken into consideration for correct measurements. Full article
(This article belongs to the Special Issue Sensing of Scent, Fragrance, Smell, and Odor Emissions from Biota Sources)
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<p>Schematic drawing of the experimental setup.</p> Full article ">
<p>Recovery of odorants in the outlet tubing of an olfactometer as a function of the dilution factor.</p> Full article ">
<p>Development in the recovery during a 60-second pulse for selected odorants in an olfactometer. The odorants were introduced to the olfactometer after 10 s and the pulse stopped after 70 s.</p> Full article ">
<p>PTR-MS response time for individual odorants measured with a 1.2 m PEEK sampling line heated to 60 °C. The PTR-MS response time was defined as the time to reach 90% of the final concentration when changing from a highly diluted sample to an undiluted sample (relative time = 10 s).</p> Full article ">
<p>Correlation between the concentration of dimethyl sulfide measured in the outlet tubing from the olfactometer and in the nose cone where the human nose is placed.</p> Full article ">
2217 KiB  
Article
Combination of RGB and Multispectral Imagery for Discrimination of Cabernet Sauvignon Grapevine Elements
by Roemi Fernández, Héctor Montes, Carlota Salinas, Javier Sarria and Manuel Armada
Sensors 2013, 13(6), 7838-7859; https://doi.org/10.3390/s130607838 - 19 Jun 2013
Cited by 35 | Viewed by 8670
Abstract
This paper proposes a sequential masking algorithm based on the K-means method that combines RGB and multispectral imagery for discrimination of Cabernet Sauvignon grapevine elements in unstructured natural environments, without placing any screen behind the canopy and without any previous preparation of the [...] Read more.
This paper proposes a sequential masking algorithm based on the K-means method that combines RGB and multispectral imagery for discrimination of Cabernet Sauvignon grapevine elements in unstructured natural environments, without placing any screen behind the canopy and without any previous preparation of the vineyard. In this way, image pixels are classified into five clusters corresponding to leaves, stems, branches, fruit and background. A custom-made sensory rig that integrates a CCD camera and a servo-controlled filter wheel has been specially designed and manufactured for the acquisition of images during the experimental stage. The proposed algorithm is extremely simple, efficient, and provides a satisfactory rate of classification success. All these features turn out the proposed algorithm into an appropriate candidate to be employed in numerous tasks of the precision viticulture, such as yield estimation, water and nutrients needs estimation, spraying and harvesting. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)
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<p>(<b>a</b>) Proposed acquisition system; (<b>b</b>) Filter wheel layout.</p> Full article ">
<p>Narrow band images of grapevine leaves. (<b>a</b>) Image at 635 nm; (<b>b</b>) Image at 750 nm.</p> Full article ">
<p>Spectral signatures.</p> Full article ">
<p>Cabernet Sauvignon vineyard.</p> Full article ">
<p>(<b>a</b>) Sensor rig close-up; (<b>b</b>) Set-up for data acquisition.</p> Full article ">
<p>Step 1. <b>(a)</b> Image acquired with the optical filter whose centre wavelength is 635 nm; (<b>b</b>) K-means result: 2 clusters representing the background and the foreground.</p> Full article ">
<p>Steps 2–3. <b>(a)</b> Background mask (mask 1) obtained after morphological procedure; <b>(b)</b> RGB image with background mask.</p> Full article ">
<p>Steps 5–6. <b>(a)</b> K-means clustering applied to the ‘a*b*’ space; <b>(b)</b> Fruits mask (mask 2).</p> Full article ">
<p>Step 8. <b>(a)</b> 880 nm image with background and fruits masked; <b>(b)</b> Stems mask (mask 3).</p> Full article ">
645 KiB  
Article
A Wireless Monitoring Sub-nA Resolution Test Platform for Nanostructure Sensors
by Chi Woong Jang, Young Tae Byun, Taikjin Lee, Deok Ha Woo, Seok Lee and Young Min Jhon
Sensors 2013, 13(6), 7827-7837; https://doi.org/10.3390/s130607827 - 19 Jun 2013
Cited by 3 | Viewed by 6226
Abstract
We have constructed a wireless monitoring test platform with a sub-nA resolution signal amplification/processing circuit (SAPC) and a wireless communication network to test the real-time remote monitoring of the signals from carbon nanotube (CNT) sensors. The operation characteristics of the CNT sensors can [...] Read more.
We have constructed a wireless monitoring test platform with a sub-nA resolution signal amplification/processing circuit (SAPC) and a wireless communication network to test the real-time remote monitoring of the signals from carbon nanotube (CNT) sensors. The operation characteristics of the CNT sensors can also be measured by the ISD-VSD curve with the SAPC. The SAPC signals are transmitted to a personal computer by Bluetooth communication and the signals from the computer are transmitted to smart phones by Wi-Fi communication, in such a way that the signals from the sensors can be remotely monitored through a web browser. Successful remote monitoring of signals from a CNT sensor was achieved with the wireless monitoring test platform for detection of 0.15% methanol vapor with 0.5 nA resolution and 7 Hz sampling rate. Full article
(This article belongs to the Special Issue Nanotube and Nanowire Sensors)
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<p>(<b>a</b>) The 4-channel CNT sensor (14 × 12 mm<sup>2</sup>), (<b>b</b>) schematic of electrical characteristics measurement setup (red-lined area shows the structure of the red-lined square in (a)), (<b>c</b>) <span class="html-italic">I<sub>SD</sub></span>-<span class="html-italic">V<sub>SD</sub></span> measurements, and (<b>d</b>) <span class="html-italic">I<sub>SD</sub></span>-<span class="html-italic">V<sub>G</sub></span> measurements.</p> Full article ">
<p>The signal amplification and processing circuits (SAPC); (<b>a</b>) block diagram and (<b>b</b>) circuit boards (250 × 80 mm<sup>2</sup>).</p> Full article ">
<p>(<b>a</b>) Block diagram and (<b>b</b>) photograph of the wireless monitoring test platform.</p> Full article ">
<p>Experimental setup for detection and calibration of concentration of methanol vapor; (<b>a</b>) open glove box, (<b>b</b>) closed glove box, and (<b>c</b>) measurement devices and vapor control devices (<b>1</b>: hot plate, <b>2</b>: methanol solution, <b>3</b>: CNT sensor, <b>4</b>: Bluetooth module, <b>5</b>: SAPC, <b>6</b>: gas sampling pump, <b>7</b>: methanol detector tube, and <b>8</b>: digital thermometer).</p> Full article ">
<p>(<b>a</b>) <span class="html-italic">I<sub>SD</sub></span>-<span class="html-italic">V<sub>SD</sub></span> measurement of the CNT sensors by high resolution current meter (HRCM) and the SAPC and (<b>b</b>) calibration graph of <span class="html-italic">I<sub>SD</sub></span> from the SAPC by <span class="html-italic">I<sub>SD</sub></span> from HRCM.</p> Full article ">
<p>Methanol vapor detection in the glove box; (<b>a</b>) the SAPC current value of the CNT sensor and the methanol vapor concentration according to the control of the methanol vapor flow and (<b>b</b>) electrical current variation against the methanol vapor concentration.</p> Full article ">
<p>Methanol vapor detection with the SAPC and the CNT sensor in the actual field test using a cotton bud moistened with the methanol solution (the first peak for 0.25 % and the second peak for 0.15 % methanol vapor concentration indicated by the arrows).</p> Full article ">
1007 KiB  
Article
Enhanced Electronic Properties of Pt@Ag Heterostructured Nanoparticles
by Anh Thi Ngoc Dao, Derrick M. Mott, Koichi Higashimine and Shinya Maenosono
Sensors 2013, 13(6), 7813-7826; https://doi.org/10.3390/s130607813 - 18 Jun 2013
Cited by 21 | Viewed by 9204
Abstract
Platinum coated by silver nanoparticles was synthesized, which displays a unique structure where polycrystalline platinum particles are completely encapsulated in continuous monocrystalline silver shells. These particles display accentuated electronic properties, where the silver shells gain electron density from the platinum cores, imparting enhanced [...] Read more.
Platinum coated by silver nanoparticles was synthesized, which displays a unique structure where polycrystalline platinum particles are completely encapsulated in continuous monocrystalline silver shells. These particles display accentuated electronic properties, where the silver shells gain electron density from the platinum cores, imparting enhanced properties such as oxidation resistance. This electron transfer phenomenon is highly interfacial in nature, and the degree of electron transfer decreases as the thickness of silver shell increases. The nanoparticle structure and electronic properties are studied and the implication to creating sensing probes with enhanced robustness, sensitivity and controllable plasmonic properties is discussed. Full article
(This article belongs to the Special Issue Multimetallic Nanoparticles for Chemical/Biological Sensing Applications)
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<p>TEM images of platinum nanoparticles with a size of 4.5 (<b>A</b>); 31.3 (<b>B</b>); and 99.3 (<b>C</b>) nm.</p> Full article ">
<p>TEM images of a platinum core particle (39.8 nm) (<b>A</b>) and Pt@Ag particles with an optimal silver shell thickness of 1.3 (<b>B</b>); 5.2 (<b>C</b>); and 9.1 (<b>D</b>) nm.</p> Full article ">
<p>STEM-HAADF image (<b>A</b>) and the corresponding EDS elemental maps for silver L line (<b>B</b>); platinum M line (<b>C</b>); and an overlay of the two maps (<b>D</b>) for a single Pt<sub>25.7</sub>@Ag<sub>8.1</sub> NP.</p> Full article ">
<p>UV-Vis spectra for platinum core particle (39.8 nm) and Pt<sub>39.8</sub>@Ag<sub>y</sub> particles with an optimal silver shell thickness of 1.4; 5.2; and 9.1 nm.</p> Full article ">
<p>XRD pattern of platinum seeds (4.5 nm), platinum NPs (25.7 nm) and Pt<sub>25.7</sub>@Ag<sub>8.1</sub> NPs. The reference peak positions for fcc phase platinum and silver are also shown.</p> Full article ">
<p>HRTEM images of a bare platinum (25.7 nm) NP (<b>A</b>) and for a Pt<sub>25.7</sub>@Ag<sub>8.1</sub> NP (<b>B</b>).</p> Full article ">
<p>XPS spectra for platinum core particle (39.8 nm) and Pt<sub>39.8</sub>@Ag<sub>y</sub> particles with an optimal silver shell thickness of 1.3; 5.2; and 9.1 nm. The inserted graphs show the Pt 4f<sub>7/2</sub> and 4f<sub>5/2</sub> peaks (solid curves) and the fitting with the asymmetric G-L mixed function (circles).</p> Full article ">
<p>XPS spectra for platinum core particle (39.8 nm) (<b>A</b>) and Pt<sub>39.8</sub>@Ag<sub>y</sub> particles with an optimal silver shell thickness of 1.3 (<b>B</b>); 5.2 (<b>C</b>); and 9.1 (<b>D</b>) nm. The inserted graphs show the Pt 4f<sub>7/2</sub> and 4f<sub>5/2</sub> peaks (solid curves) and the fitting with the asymmetric G-L mixed function (circles).</p> Full article ">
<p>The Pt 4f and Ag 3d peak energy shift plotted as a function of silver shell thickness for Pt<sub>39.8</sub>@Ag<span class="html-italic"><sub>y</sub></span> (<span class="html-italic">y</span> = 1.3, 5.2, and 9.1 nm) NPs. The peak energy shift Δ<sub>BE</sub> = BE<sub>core-shell</sub> − BE<sub>Pt</sub> (or BE<sub>Ag</sub>).</p> Full article ">
1128 KiB  
Article
Performance Evaluation of UHF RFID Technologies for Real-Time Bus Recognition in the Taipei Bus Station
by Chung-Ming Own, Da-Sheng Lee, Ti-Ho Wang, De-Jun Wang and Yu-Lun Ting
Sensors 2013, 13(6), 7797-7812; https://doi.org/10.3390/s130607797 - 18 Jun 2013
Cited by 5 | Viewed by 7798
Abstract
Transport stations such as airports, ports, and railways have adopted blocked-type pathway management to process and control travel systems in a one-directional manner. However, this excludes highway transportation where large buses have great variability and mobility; thus, an instant influx of numerous buses [...] Read more.
Transport stations such as airports, ports, and railways have adopted blocked-type pathway management to process and control travel systems in a one-directional manner. However, this excludes highway transportation where large buses have great variability and mobility; thus, an instant influx of numerous buses increases risks and complicates station management. Focusing on Taipei Bus Station, this study employed RFID technology to develop a system platform integrated with modern information technology that has numerous characteristics. This modern information technology comprised the following systems: ultra-high frequency (UHF) radio-frequency identification (RFID), ultrasound and license number identification, and backstage graphic controls. In conclusion, the system enabled management, bus companies, and passengers to experience the national bus station’s new generation technology, which provides diverse information and synchronization functions. Furthermore, this technology reached a new milestone in the energy-saving and efficiency-increasing performance of Taiwan’s buses. Full article
(This article belongs to the Section Physical Sensors)
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<p>Bus station platform layout types, (<b>a</b>) the straight-line layout; (<b>b</b>) the zigzag layout; (<b>c</b>) the obtuse-angle layout; (<b>d</b>) the leaving-type layout.</p> Full article ">
<p>(<b>a</b>) Traffic on Chengde Road; (<b>b</b>) roadside bus stop signs. Each bus company has a different sign; (<b>c</b>) Crowds of boarding passengers on Chengde Road; and (<b>d</b>) Taipei Bus Station ticket counters.</p> Full article ">
<p>Taipei Bus Station floor plan.</p> Full article ">
<p>Framework of the RFID management system.</p> Full article ">
<p>Function of the RFID reader regarding the lanes and platform.</p> Full article ">
<p>RFID reader equipment on the lanes and platforms; (<b>a</b>) is the infrared projector; (<b>b</b>) is the automatic UHF RFID tag on a bus; (<b>c</b>) is the UHF RFID reader; and (<b>d</b>) is a schematic diagram showing the RFID signal between the platform and the bus.</p> Full article ">
<p>The functional block diagram of the UHF RFID active tag.</p> Full article ">
<p>Process of ultrasound and vehicle plate identification.</p> Full article ">
<p>The actual ultrasound transmitter is located approximately 1m from the buses.</p> Full article ">
300 KiB  
Article
Power Measurement Methods for Energy Efficient Applications
by Guilherme Calandrini, Alfredo Gardel, Ignacio Bravo, Pedro Revenga, José L. Lázaro and F. Javier Toledo-Moreo
Sensors 2013, 13(6), 7786-7796; https://doi.org/10.3390/s130607786 - 18 Jun 2013
Cited by 13 | Viewed by 6363
Abstract
Energy consumption constraints on computing systems are more important than ever. Maintenance costs for high performance systems are limiting the applicability of processing devices with large dissipation power. New solutions are needed to increase both the computation capability and the power efficiency. Moreover, [...] Read more.
Energy consumption constraints on computing systems are more important than ever. Maintenance costs for high performance systems are limiting the applicability of processing devices with large dissipation power. New solutions are needed to increase both the computation capability and the power efficiency. Moreover, energy efficient applications should balance performance vs. consumption. Therefore power data of components are important. This work presents the most remarkable alternatives to measure the power consumption of different types of computing systems, describing the advantages and limitations of available power measurement systems. Finally, a methodology is proposed to select the right power consumption measurement system taking into account precision of the measure, scalability and controllability of the acquisition system. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)
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<p>Measurement Systems Methods.</p> Full article ">
<p>Measurement System Diagram (<b>a</b>) IPS based (<b>b</b>) <span class="html-italic">Ad-hoc</span> System.</p> Full article ">
<p>Measurement Testbench.</p> Full article ">
<p>Testbench of Internal RAPL <span class="html-italic">vs.</span> External Measurements.</p> Full article ">
496 KiB  
Article
Impedimetric DNA Biosensor Based on a Nanoporous Alumina Membrane for the Detection of the Specific Oligonucleotide Sequence of Dengue Virus
by Jiajia Deng and Chee-Seng Toh
Sensors 2013, 13(6), 7774-7785; https://doi.org/10.3390/s130607774 - 17 Jun 2013
Cited by 74 | Viewed by 9461
Abstract
A novel and integrated membrane sensing platform for DNA detection is developed based on an anodic aluminum oxide (AAO) membrane. Platinum electrodes (~50–100 nm thick) are coated directly on both sides of the alumina membrane to eliminate the solution resistance outside the nanopores. [...] Read more.
A novel and integrated membrane sensing platform for DNA detection is developed based on an anodic aluminum oxide (AAO) membrane. Platinum electrodes (~50–100 nm thick) are coated directly on both sides of the alumina membrane to eliminate the solution resistance outside the nanopores. The electrochemical impedance technique is employed to monitor the impedance changes within the nanopores upon DNA binding. Pore resistance (Rp) linearly increases in response towards the increasing concentration of the target DNA in the range of 1 × 10−12 to 1 × 10−6 M. Moreover, the biosensor selectively differentiates the complementary sequence from single base mismatched (MM-1) strands and non-complementary strands. This study reveals a simple, selective and sensitive method to fabricate a label-free DNA biosensor. Full article
(This article belongs to the Special Issue Novel Tools in Electrochemical Sensing)
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<p>(<b>a</b>) Scheme of DNA immobilization procedure; (<b>b</b>) Schematics of nanoporous alumina membrane for impedimetric biosensing of DNA target; (<b>c</b>) The equivalent circuit model for fitting the impedimetric experimental data.</p> Full article ">
<p>Differential pulse voltammetry current signal response of the integrated nanoporous membrane sensor toward increasing concentration of complementary DNA target from 10<sup>−12</sup> to10<sup>−6</sup> M.</p> Full article ">
<p>Nyquist plots of (<b>a</b>) integrated nanoporous membrane electrode grafted with DNA probe, (<b>b</b>) unmodified nanoporous membrane electrode in response toward increasing concentrations of target DNA (10<sup>−12</sup>∼10<sup>−6</sup> M), (<b>c</b>) 200 nm pore size membrane sensor grafted with DNA probe toward increasing concentration of DNA targets (10<sup>−10</sup>∼10<sup>−6</sup> M).</p> Full article ">
<p>Calibration plot of pore resistance against the logarithm of complementary target DNA concentration.</p> Full article ">
<p>(<b>a</b>) Nyquist plots of ssDNA probe grafted nanoporous alumina membrane after exposure to noncomplementary target sequence (MM-21), single base mismatched target sequence (MM-1) and complementary target sequence. Each measurement step was followed by a denaturing step; (<b>b</b>) Bar chart illustrating the <span class="html-italic">R</span><sub>p</sub> values obtained from the impedance responses of the integrated nanoporous membrane sensor after consecutive steps of incubation with DNA targets followed by a regeneration step; (<b>c</b>) Nyquist plots of unmodified nanoporous alumina membrane in response to noncomplementary target sequence (MM-21), single base mismatched target sequence (MM-1) and complementary target sequence, following the same procedure and order as (a).</p> Full article ">
667 KiB  
Article
Robust Vehicle Detection under Various Environmental Conditions Using an Infrared Thermal Camera and Its Application to Road Traffic Flow Monitoring
by Yoichiro Iwasaki, Masato Misumi and Toshiyuki Nakamiya
Sensors 2013, 13(6), 7756-7773; https://doi.org/10.3390/s130607756 - 17 Jun 2013
Cited by 58 | Viewed by 12195
Abstract
We have already proposed a method for detecting vehicle positions and their movements (henceforth referred to as “our previous method”) using thermal images taken with an infrared thermal camera. Our experiments have shown that our previous method detects vehicles robustly under four different [...] Read more.
We have already proposed a method for detecting vehicle positions and their movements (henceforth referred to as “our previous method”) using thermal images taken with an infrared thermal camera. Our experiments have shown that our previous method detects vehicles robustly under four different environmental conditions which involve poor visibility conditions in snow and thick fog. Our previous method uses the windshield and its surroundings as the target of the Viola-Jones detector. Some experiments in winter show that the vehicle detection accuracy decreases because the temperatures of many windshields approximate those of the exterior of the windshields. In this paper, we propose a new vehicle detection method (henceforth referred to as “our new method”). Our new method detects vehicles based on tires’ thermal energy reflection. We have done experiments using three series of thermal images for which the vehicle detection accuracies of our previous method are low. Our new method detects 1,417 vehicles (92.8%) out of 1,527 vehicles, and the number of false detection is 52 in total. Therefore, by combining our two methods, high vehicle detection accuracies are maintained under various environmental conditions. Finally, we apply the traffic information obtained by our two methods to traffic flow automatic monitoring, and show the effectiveness of our proposal. Full article
(This article belongs to the Section Physical Sensors)
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<p>Thermal images and a visible light image in snow and thick fog: (<b>a</b>) thermal image (back side view), (<b>b</b>) thermal image (front side view), and (<b>c</b>) visible light image (front side view).</p> Full article ">
<p>The infrared thermal camera and the notebook personal computer on a pedestrian bridge.</p> Full article ">
<p>A frame of thermal images.</p> Full article ">
<p>An example of spatio-temporal images.</p> Full article ">
<p>Some examples of the positive sample images.</p> Full article ">
<p>Some vehicle detection results in thermal images.</p> Full article ">
<p>One frame of the visible light images taken in August.</p> Full article ">
<p>A thermal image in which the temperatures of the windshields similar to those of the exterior of the windshields.</p> Full article ">
<p>The flowchart of our new method.</p> Full article ">
17714 KiB  
Article
Design of a Wearable Sensing System for Human Motion Monitoring in Physical Rehabilitation
by Lara González-Villanueva, Stefano Cagnoni and Luca Ascari
Sensors 2013, 13(6), 7735-7755; https://doi.org/10.3390/s130607735 - 17 Jun 2013
Cited by 34 | Viewed by 10997
Abstract
Human motion monitoring and analysis can be an essential part of a wide spectrum of applications, including physical rehabilitation among other potential areas of interest. Creating non-invasive systems for monitoring patients while performing rehabilitation exercises, to provide them with an objective feedback, is [...] Read more.
Human motion monitoring and analysis can be an essential part of a wide spectrum of applications, including physical rehabilitation among other potential areas of interest. Creating non-invasive systems for monitoring patients while performing rehabilitation exercises, to provide them with an objective feedback, is one of the current challenges. In this paper we present a wearable multi-sensor system for human motion monitoring, which has been developed for use in rehabilitation. It is composed of a number of small modules that embed high-precision accelerometers and wireless communications to transmit the information related to the body motion to an acquisition device. The results of a set of experiments we made to assess its performance in real-world setups demonstrate its usefulness in human motion acquisition and tracking, as required, for example, in activity recognition, physical/athletic performance evaluation and rehabilitation. Full article
(This article belongs to the Collection Sensors for Globalized Healthy Living and Wellbeing)
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Graphical abstract

Graphical abstract
Full article ">
<p>Proposed system architecture for human motion tracking and analysis.</p> Full article ">
<p>Details of the HenesisWiModule. (<b>a</b>) Size comparison; (<b>b</b>) Example of packaging.</p> Full article ">
<p>Structure of the data packet.</p> Full article ">
<p>Communication protocol with data synchronization.</p> Full article ">
<p>The proposed system, how to wear it and sample signals from one of the slave modules.</p> Full article ">
<p>Coordinate reference system. (<b>a</b>) Human body reference axes; (<b>b</b>) Sensor coordinate system; (<b>c</b>) Cartesian and spherical coordinate systems.</p> Full article ">
<p>Zoom of the data for the synchronization test. (<b>a</b>) Best case: perfect synchronization; (<b>b</b>) Worst case: de-synchronization of two data samples.</p> Full article ">
<p>The twelve poses of the Sun Salutation sequence.</p> Full article ">
<p>State diagram of the FFSM for the reduced cycle of the Sun Salutation.</p> Full article ">
1159 KiB  
Article
Geometric Feature-Based Facial Expression Recognition in Image Sequences Using Multi-Class AdaBoost and Support Vector Machines
by Deepak Ghimire and Joonwhoan Lee
Sensors 2013, 13(6), 7714-7734; https://doi.org/10.3390/s130607714 - 14 Jun 2013
Cited by 235 | Viewed by 15834
Abstract
Facial expressions are widely used in the behavioral interpretation of emotions, cognitive science, and social interactions. In this paper, we present a novel method for fully automatic facial expression recognition in facial image sequences. As the facial expression evolves over time facial landmarks [...] Read more.
Facial expressions are widely used in the behavioral interpretation of emotions, cognitive science, and social interactions. In this paper, we present a novel method for fully automatic facial expression recognition in facial image sequences. As the facial expression evolves over time facial landmarks are automatically tracked in consecutive video frames, using displacements based on elastic bunch graph matching displacement estimation. Feature vectors from individual landmarks, as well as pairs of landmarks tracking results are extracted, and normalized, with respect to the first frame in the sequence. The prototypical expression sequence for each class of facial expression is formed, by taking the median of the landmark tracking results from the training facial expression sequences. Multi-class AdaBoost with dynamic time warping similarity distance between the feature vector of input facial expression and prototypical facial expression, is used as a weak classifier to select the subset of discriminative feature vectors. Finally, two methods for facial expression recognition are presented, either by using multi-class AdaBoost with dynamic time warping, or by using support vector machine on the boosted feature vectors. The results on the Cohn-Kanade (CK+) facial expression database show a recognition accuracy of 95.17% and 97.35% using multi-class AdaBoost and support vector machines, respectively. Full article
(This article belongs to the Section Physical Sensors)
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<p>Overall block diagram of the landmark initialization and tracking process.</p> Full article ">
<p>Examples of the result of facial landmark tracking.</p> Full article ">
<p>Example of landmark tracking sequences before (<b>First</b> row) and after (<b>Second</b> row) normalization.</p> Full article ">
<p>Maximum intensity frame of each facial expression prototype.</p> Full article ">
<p>The first few (20, 40, 60, 80, and 100) features selected using multi-class AdaBoost. A blue dot indicates a feature vector extracted only from that landmark tracking result, as the expression evolves over time; whereas a red line connecting two landmarks indicates the feature vector extracted from that pair of landmarks tracking result, as the expression evolves over time.</p> Full article ">
<p>The first few (20, 40, and 60) features selected by AdaBoost for each class of facial expression. A red dot indicates a feature vector extracted from the tracking result of that landmark, as the facial expression evolves over time, whereas a red line connecting two landmarks indicates a feature vector extracted from the tracking result of those pair of landmarks, as the facial expression evolves over time.</p> Full article ">
<p>Grouping of landmarks into different regions according to the facial geometry.</p> Full article ">
<p>Recognition accuracy under different numbers of AdaBoost selected features.</p> Full article ">
<p>Average confusion score of week classifiers in percentages, for the recognition of each class of facial expressions.</p> Full article ">
1282 KiB  
Review
Integration of Biosensors and Drug Delivery Technologies for Early Detection and Chronic Management of Illness
by Mpho Ngoepe, Yahya E. Choonara, Charu Tyagi, Lomas Kumar Tomar, Lisa C. Du Toit, Pradeep Kumar, Valence M. K. Ndesendo and Viness Pillay
Sensors 2013, 13(6), 7680-7713; https://doi.org/10.3390/s130607680 - 14 Jun 2013
Cited by 68 | Viewed by 15045
Abstract
Recent advances in biosensor design and sensing efficacy need to be amalgamated with research in responsive drug delivery systems for building superior health or illness regimes and ensuring good patient compliance. A variety of illnesses require continuous monitoring in order to have efficient [...] Read more.
Recent advances in biosensor design and sensing efficacy need to be amalgamated with research in responsive drug delivery systems for building superior health or illness regimes and ensuring good patient compliance. A variety of illnesses require continuous monitoring in order to have efficient illness intervention. Physicochemical changes in the body can signify the occurrence of an illness before it manifests. Even with the usage of sensors that allow diagnosis and prognosis of the illness, medical intervention still has its downfalls. Late detection of illness can reduce the efficacy of therapeutics. Furthermore, the conventional modes of treatment can cause side-effects such as tissue damage (chemotherapy and rhabdomyolysis) and induce other forms of illness (hepatotoxicity). The use of drug delivery systems enables the lowering of side-effects with subsequent improvement in patient compliance. Chronic illnesses require continuous monitoring and medical intervention for efficient treatment to be achieved. Therefore, designing a responsive system that will reciprocate to the physicochemical changes may offer superior therapeutic activity. In this respect, integration of biosensors and drug delivery is a proficient approach and requires designing an implantable system that has a closed loop system. This offers regulation of the changes by means of releasing a therapeutic agent whenever illness biomarkers prevail. Proper selection of biomarkers is vital as this is key for diagnosis and a stimulation factor for responsive drug delivery. By detecting an illness before it manifests by means of biomarkers levels, therapeutic dosing would relate to the severity of such changes. In this review various biosensors and drug delivery systems are discussed in order to assess the challenges and future perspectives of integrating biosensors and drug delivery systems for detection and management of chronic illness. Full article
(This article belongs to the Section Biosensors)
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<p>Routes of obtaining biomarkers for a variety of illnesses. 1. Spinal fluid [<a href="#b11-sensors-13-07680" class="html-bibr">11</a>]; 2. Saliva [<a href="#b12-sensors-13-07680" class="html-bibr">12</a>]; 3. Breath [<a href="#b13-sensors-13-07680" class="html-bibr">13</a>]; 4. Urine [<a href="#b14-sensors-13-07680" class="html-bibr">14</a>]; 5. Blood [<a href="#b15-sensors-13-07680" class="html-bibr">15</a>]; 6. Sweat [<a href="#b16-sensors-13-07680" class="html-bibr">16</a>]; 7.Nucleotides [<a href="#b17-sensors-13-07680" class="html-bibr">17</a>].</p> Full article ">
<p>Schematic depicting functional principles of a biosensor.</p> Full article ">
<p>A schematic depicting antibodies and antigens as immunosensor prototypes and genome probe as genosensor prototype (Adapted from [<a href="#b53-sensors-13-07680" class="html-bibr">53</a>]).</p> Full article ">
<p>Amperometric immunosensor based on a new electrochemical detection scheme (adapted from [<a href="#b75-sensors-13-07680" class="html-bibr">75</a>]).</p> Full article ">
<p>A schematic depicting the prototype label free immunosensor (adapted from [<a href="#b80-sensors-13-07680" class="html-bibr">80</a>]).</p> Full article ">
<p>Mechanism of bioreporters (adapted from [<a href="#b81-sensors-13-07680" class="html-bibr">81</a>]).</p> Full article ">
<p>A schematic depicting the basic mechanism of glucose sensor [<a href="#b43-sensors-13-07680" class="html-bibr">43</a>]. Commercial glucose biosensors: Ultimate EZ Smart Plus test strips (EZ Smart) and Contour blood glucose test strips (Bayer Healthcare LCC).</p> Full article ">
<p>A schematic showing an immobilized enzyme biosensor (adapted from [<a href="#b96-sensors-13-07680" class="html-bibr">96</a>]). Commercial cholesterol biosensors: CardioChek Cholesterol meter and Cholesterol Biometer cholesterol (Polymer Technology Systems, Inc.).</p> Full article ">
<p>Functionalized nanoparticles used in imaging biosensors (adapted from [<a href="#b99-sensors-13-07680" class="html-bibr">99</a>]).</p> Full article ">
600 KiB  
Article
Voltammetric Determination of Cocaine in Confiscated Samples Using a Carbon Paste Electrode Modified with Different [UO2(X-MeOsalen)(H2O)]·H2O Complexes
by Laura Siqueira De Oliveira, Ana Paula Dos Santos Poles, Marco Antonio Balbino, Matheus Manoel Teles de Menezes, José Fernando De Andrade, Edward Ralph Dockal, Heloísa Maria Tristão and Marcelo Firmino De Oliveira
Sensors 2013, 13(6), 7668-7679; https://doi.org/10.3390/s130607668 - 14 Jun 2013
Cited by 36 | Viewed by 8892
Abstract
A fast and non-destructive voltammetric method to detect cocaine in confiscated samples based on carbon paste electrode modified with methoxy-substituted N,N'-ethylene-bis(salcylideneiminato)uranyl(VI)complexes, [UO2(X-MeOSalen)(H2O)]·H2O, where X corresponds to the positions 3, 4 or 5 of the methoxy group on [...] Read more.
A fast and non-destructive voltammetric method to detect cocaine in confiscated samples based on carbon paste electrode modified with methoxy-substituted N,N'-ethylene-bis(salcylideneiminato)uranyl(VI)complexes, [UO2(X-MeOSalen)(H2O)]·H2O, where X corresponds to the positions 3, 4 or 5 of the methoxy group on the aromatic ring, is described. The electrochemical behavior of the modified electrode and the electrochemical detection of cocaine were investigated using cyclic voltammetry. Using 0.1 mol·L−1 KCl as supporting-electrolyte, a concentration-dependent, well-defined peak current for cocaine at 0.62 V, with an amperometric sensitivity of 6.25 × 104 μA·mol·L−1 for cocaine concentrations ranging between 1.0 × 10−7 and 1.3 × 10−6 mol·L−1 was obtained. Chemical interference studies using lidocaine and procaine were performed. The position of the methoxy group affects the results, with the 3-methoxy derivative being the most sensitive. Full article
(This article belongs to the Special Issue Novel Tools in Electrochemical Sensing)
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<p>Chemical structure of cocaine.</p> Full article ">
<p>Structural representations of the ligands and complexes used in this study.</p> Full article ">
<p>(<b>a</b>) Influence of the concentration of procaine and (<b>b</b>) lidocaine standard samples on the electrochemical response of the electrode modified with [UO<sub>2</sub>(3-MeO-salen)(H<sub>2</sub>O)]·H<sub>2</sub>O.</p> Full article ">
<p>Influence of the concentration cocaine standard samples in the electrochemical response of the electrode modified with [UO<sub>2</sub>(5-MeO-salen)(H<sub>2</sub>O)]·H<sub>2</sub>O.</p> Full article ">
<p>Influence of the concentration of procaine (<b>a</b>) and lidocaine (<b>b</b>) standard samples on the electrochemical response of the electrode modified with [UO<sub>2</sub>(5-MeO-salen)(H<sub>2</sub>O)]·H<sub>2</sub>O.</p> Full article ">
917 KiB  
Article
CrossVit: Enhancing Canopy Monitoring Management Practices in Viticulture
by Alessandro Matese, Francesco Primo Vaccari, Diego Tomasi, Salvatore Filippo Di Gennaro, Jacopo Primicerio, Francesco Sabatini and Silvia Guidoni
Sensors 2013, 13(6), 7652-7667; https://doi.org/10.3390/s130607652 - 13 Jun 2013
Cited by 16 | Viewed by 8483
Abstract
A new wireless sensor network (WSN), called CrossVit, and based on MEMSIC products, has been tested for two growing seasons in two vineyards in Italy. The aims are to evaluate the monitoring performances of the new WSN directly in the vineyard and collect [...] Read more.
A new wireless sensor network (WSN), called CrossVit, and based on MEMSIC products, has been tested for two growing seasons in two vineyards in Italy. The aims are to evaluate the monitoring performances of the new WSN directly in the vineyard and collect air temperature, air humidity and solar radiation data to support vineyard management practices. The WSN consists of various levels: the Master/Gateway level coordinates the WSN and performs data aggregation; the Farm/Server level takes care of storing data on a server, data processing and graphic rendering; Nodes level is based on a network of peripheral nodes consisting of a MDA300 sensor board and Iris module and equipped with thermistors for air temperature, photodiodes for global and diffuse solar radiation, and an HTM2500LF sensor for relative humidity. The communication levels are: WSN links between gateways and sensor nodes by ZigBee, and long-range GSM/GPRS links between gateways and the server farm level. The system was able to monitor the agrometeorological parameters in the vineyard: solar radiation, air temperature and air humidity, detecting the differences between the canopy treatments applied. The performance of CrossVit, in terms of monitoring and reliability of the system, have been evaluated considering: its handiness, cost-effective, non-invasive dimensions and low power consumption. Full article
(This article belongs to the Section Sensor Networks)
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<p>Illustration of the on-going implementation of the in-field data acquisition network. MGL = Master/Gateway Level; NL = Node Level; FSL = Farm Server Level; NL2MGL = Node Level to Master/Gateway Level connection; MGL2FSL = Master/Gateway Level to Farm Server Level connection; NL2MGL = Node Level to Master/Gateway Level connection.</p> Full article ">
<p>Node Level.</p> Full article ">
<p>Block diagram of the hardware connections and software operation.</p> Full article ">
<p>(<b>a</b>) Data transmission test at San Nicolò vineyard. The isosignal lines represent the RSSI values; (<b>b</b>) Data transmission test at Ponte di Piave vineyard. The isosignal lines represent the RSSI values.</p> Full article ">
<p>Daily cycle of air temperature (max) (°C) at the two vineyards A (Ponte Piave) and B (San Nicolò) in the three field treatments applied: NP, no pruning (gray dotted line); PM mechanical pruning (gray solid line); PMa manual pruning (black dotted line). Master (black solid line) is the air temperature measured outside the vineyard. All the values are hourly averages of two years of observations from April to September.</p> Full article ">
<p>Daily cycle of solar radiation (W·m<sup>−2</sup>) at the two vineyards (<b>A</b>) (Ponte Piave) and (<b>B</b>) (San Nicolò) in the three field treatments applied: NP, no pruning (gray dotted line); PM mechanical pruning (gray solid line); PMa manual pruning (black dotted line). Master (black solid line) is the solar radiation measured outside the vineyard. All the values are hourly averages of two years of observations from April to September.</p> Full article ">
<p>Daily cycle of relative air humidity (%) at the two vineyards (A) (Ponte Piave) and (B) (San Nicolò) in the three field treatments applied: NP, no pruning (gray dotted line); PM mechanical pruning (gray solid line); PMa manual pruning (black dotted line). Master (black solid line) is the relative humidity measured outside the vineyard. All the values are hourly averages of two years of observations from April to September.</p> Full article ">
1284 KiB  
Article
Development of a Control System for the Teat-End Vacuum in Individual Quarter Milking Systems
by Ulrich Ströbel, Sandra Rose-Meierhöfer, Hülya Öz and Reiner Brunsch
Sensors 2013, 13(6), 7633-7651; https://doi.org/10.3390/s130607633 - 13 Jun 2013
Cited by 10 | Viewed by 7447
Abstract
Progress in sensor technique and electronics has led to a decrease in the costs of electronic and sensor components. In modern dairy farms, having udders in good condition, a lower frequency of udder disease and an extended service life of dairy cows will [...] Read more.
Progress in sensor technique and electronics has led to a decrease in the costs of electronic and sensor components. In modern dairy farms, having udders in good condition, a lower frequency of udder disease and an extended service life of dairy cows will help ensure competitiveness. The objective of this study was to develop a teat-end vacuum control system with individual quarter actor reaction. Based on a review of the literature, this system is assumed to protect the teat tissue. It reduces the mean teat-end vacuum in the maximum vacuum phase (b) to a level of 20 kPa at a flow rate of 0.25 L/min per quarter. At flow rates higher than 1.50 L/min per quarter, the teat-end vacuum can be controlled to a level of 30 kPa, because in this case it is desirable to have a higher vacuum for the transportation of the milk to the receiver. With this system it is possible for the first time to supply the teat end with low vacuum at low flow rates and with higher vacuum at increasing flow rates in a continuous process with a three second reaction-rate on individual quarter level. This system is completely automated. Full article
(This article belongs to the Section Physical Sensors)
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<p>Test set-up with Multilactor<sup>®</sup> (MULTI), vacuum control valve (VCV) and the artificial teat [<a href="#b26-sensors-13-07633" class="html-bibr">26</a>].</p> Full article ">
<p>A drawing of the vacuum control valve (VCV), tosgether with an example for the twelve sliding cores, which were used for the tests [<a href="#b26-sensors-13-07633" class="html-bibr">26</a>].</p> Full article ">
<p>Vacuum changes as a function of time for Line-a: machine vacuum; Line-b: pulsation chamber vacuum; and Line-c: teat-end vacuum at flow rates of 0.5 (<b>a</b>) and 1.2 L/min per quarter (<b>b</b>) in MULTI, measured at the rear left quarter, without control [<a href="#b26-sensors-13-07633" class="html-bibr">26</a>].</p> Full article ">
<p>Characteristic curve of mean teat-end vacuum in b-phase depending on the boreholes in the sliding cores and on the liquid flow rate per udder quarter [<a href="#b26-sensors-13-07633" class="html-bibr">26</a>].</p> Full article ">
<p>Characteristic curve of mean teat-end vacuum in d-phase, depending on the diameter of the boreholes in the sliding cores and depending on the liquid flow rate per udder quarter [<a href="#b26-sensors-13-07633" class="html-bibr">26</a>].</p> Full article ">
<p>Vacuum behaviour in MULTI, depending on the flow rate per minute, per udder quarter, with the four possible models of the developed vacuum control system [<a href="#b26-sensors-13-07633" class="html-bibr">26</a>].</p> Full article ">
<p>Block diagram for the vacuum control system. This system is fully integrated into the herd management system of the Impulsa AG (modified according to [<a href="#b32-sensors-13-07633" class="html-bibr">32</a>]).</p> Full article ">
1298 KiB  
Article
Novel Magnetic Sensing Approach with Improved Linearity
by Marco Fontana, Fabio Salsedo and Massimo Bergamasco
Sensors 2013, 13(6), 7618-7632; https://doi.org/10.3390/s130607618 - 13 Jun 2013
Cited by 28 | Viewed by 7470
Abstract
This paper introduces a novel contactless sensing principle conceived for measuring the rotation angle of a shaft. The sensor is based on a smart combination of low-cost components that can be effectively integrated in a mechanical assembly of a rotary joint. The working [...] Read more.
This paper introduces a novel contactless sensing principle conceived for measuring the rotation angle of a shaft. The sensor is based on a smart combination of low-cost components that can be effectively integrated in a mechanical assembly of a rotary joint. The working principle is based on the relative rotation of a small diametrically magnetized cylindrical or annular magnet and at least one Hall effect sensor. One of the main strengths of the new sensing principle is to be adaptable to any assigned dimensions and encumbrances without typical design limitations given by the use of standard components. A numerical model is developed for predicting the sensor output characteristic on the base of the concept of magnetic charge. Such a model is validated against results from laboratory experiments. The parameters that define the geometry and layout of the sensor are optimized in order to maximize linearity over an assigned angular range of measurement. Two examples of mechatronic systems that employ the new sensing principle are presented in order to show the possibility of obtaining with the new principle a compact/integrated sensor-design. Full article
(This article belongs to the Section Physical Sensors)
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<p>(<b>a</b>) Scheme of the distribution of the equivalent magnetic charge on the cylindrical surfaces of the cylindrical and annular magnets; (<b>b</b>) scheme of the geometry of the model employed for the solution.</p> Full article ">
<p>Layout of the sensing principle (<b>a</b>) traditional sensing with sinusoidal-like output (<b>b</b>) modified layout with eccentricity.</p> Full article ">
<p>Estimated measured radial component of component <span class="html-italic">B⃗</span> <span class="html-italic">versus</span> angle. Plots refer to cylindrical magnet with <span class="html-italic">M⃗</span> = [0,1<span class="html-italic">T</span>,0], radius R<sub>c</sub> = 6 mm, thickness <span class="html-italic">h</span> = 6 mm, measurement radius is <span class="html-italic">ρ</span> = 10mm and eccentricity values (<b>a</b>) <span class="html-italic">e<sub>c</sub></span> = 0; (<b>b</b>) <span class="html-italic">e<sub>c</sub></span> = 1 mm; (<b>c</b>) <span class="html-italic">e<sub>c</sub></span> = 2 mm</p> Full article ">
<p>Estimated linearity error <span class="html-italic">E<sub>l</sub></span> versus eccentricity computed for three different range of measure. Plot refers to cylindrical magnet with <span class="html-italic">M⃗</span> = [0,1<span class="html-italic">T</span>,0], radius <span class="html-italic">R<sub>c</sub></span> = 6 mm, thickness <span class="html-italic">h</span> = 6 mm, measurement radius is <span class="html-italic">r<sub>m</sub></span> = 10 mm.</p> Full article ">
<p>(<b>a</b>) Estimated optimum eccentricity in function of the radius of measurement in a range <span class="html-italic">α<sub>m</sub></span> = <span class="html-italic">π</span>/2; (<b>b</b>) Estimated ratio between the optimum eccentricity and the radius of measurement. Both plots refer to cylindrical magnet with <span class="html-italic">M⃗</span> = [0,1<span class="html-italic">T</span>,0], radius <span class="html-italic">R<sub>c</sub></span> = 6 mm, thickness <span class="html-italic">h</span> = 6 mm, measurement radius is <span class="html-italic">r<sub>m</sub></span> = 10 mm, in a range <span class="html-italic">α<sub>m</sub></span> = <span class="html-italic">π</span>/2.</p> Full article ">
<p>Graphical scheme of the optimization procedure.</p> Full article ">
<p>Alternative layouts (<b>a</b>) <span class="html-italic">Layout A</span> with a single HS allows ranges up to 180°; (<b>b</b>) <span class="html-italic">Layout B</span> allows 360° of measurement with 2 HS; (<b>c</b>) <span class="html-italic">Layout C</span> allows 360° of measurement with three HS with improved linearity.</p> Full article ">
<p>Scheme of the experimental setup employed for the validation of the model and the optimization procedure.</p> Full article ">
<p>Plot of the experimental results (<span class="html-italic">r<sub>m</sub></span> = 14 mm) (<b>a</b>) comparison between theoretical and experimental values of the measured induction field (<b>b</b>) comparison between theoretical and experimental optimal values.</p> Full article ">
1054 KiB  
Article
Two Phase Non-Rigid Multi-Modal Image Registration Using Weber Local Descriptor-Based Similarity Metrics and Normalized Mutual Information
by Feng Yang, Mingyue Ding, Xuming Zhang, Yi Wu and Jiani Hu
Sensors 2013, 13(6), 7599-7617; https://doi.org/10.3390/s130607599 - 13 Jun 2013
Cited by 15 | Viewed by 8259
Abstract
Non-rigid multi-modal image registration plays an important role in medical image processing and analysis. Existing image registration methods based on similarity metrics such as mutual information (MI) and sum of squared differences (SSD) cannot achieve either high registration accuracy or high registration efficiency. [...] Read more.
Non-rigid multi-modal image registration plays an important role in medical image processing and analysis. Existing image registration methods based on similarity metrics such as mutual information (MI) and sum of squared differences (SSD) cannot achieve either high registration accuracy or high registration efficiency. To address this problem, we propose a novel two phase non-rigid multi-modal image registration method by combining Weber local descriptor (WLD) based similarity metrics with the normalized mutual information (NMI) using the diffeomorphic free-form deformation (FFD) model. The first phase aims at recovering the large deformation component using the WLD based non-local SSD (wldNSSD) or weighted structural similarity (wldWSSIM). Based on the output of the former phase, the second phase is focused on getting accurate transformation parameters related to the small deformation using the NMI. Extensive experiments on T1, T2 and PD weighted MR images demonstrate that the proposed wldNSSD-NMI or wldWSSIM-NMI method outperforms the registration methods based on the NMI, the conditional mutual information (CMI), the SSD on entropy images (ESSD) and the ESSD-NMI in terms of registration accuracy and computation efficiency. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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<p>Two phase non-rigid multi-modal image registration.</p> Full article ">
<p>Differential excitation of Weber local descriptor.</p> Full article ">
<p>The square symmetric neighborhoods with different <span class="html-italic">R</span> for extracting WLD features. (<b>a</b>) The neighborhood with <span class="html-italic">R</span> = 1. (<b>b</b>) The neighborhood with <span class="html-italic">R</span> = 2.</p> Full article ">
<p>Entropy image and WLD with different <span class="html-italic">R</span> of the various MR images. (<b>a</b>) deformed T1 image; (<b>b</b>) Entropy image of (a); (<b>c</b>) WLD with <span class="html-italic">R</span> = 1 of (<b>a</b>); (<b>d</b>) WLD with <span class="html-italic">R</span> = 2 of (a); (<b>e</b>) WLD with <span class="html-italic">R</span> = 3 of (a); (<b>f</b>) deformed PD image; (<b>g</b>) Entropy image of (f); (<b>h</b>) WLD with <span class="html-italic">R</span> = 1 of (f); (<b>i</b>) WLD with <span class="html-italic">R</span> = 2 of (f); (<b>j</b>) WLD with <span class="html-italic">R</span> = 3 of (f); (<b>k</b>) original T2 image; (<b>l</b>) Entropy image of (k); (<b>m</b>) WLD with <span class="html-italic">R</span> = 1 of (k); (<b>n</b>) WLD with <span class="html-italic">R</span> = 2 of (k); (<b>o</b>) WLD with <span class="html-italic">R</span> = 3 of (k).</p> Full article ">
<p>Distance measures for T1 and T2 weighted MR images. (<b>a</b>) Distance versus rotation angles; (<b>b</b>) Distance versus translation in <span class="html-italic">x</span> direction (mm); (<b>c</b>) Distance versus translation in <span class="html-italic">y</span> direction (mm).</p> Full article ">
<p>Landmarks in the deformed T1, deformed PD and original T2 images. (<b>a</b>) Landmarks in the Deformed T1; (<b>b</b>) Landmarks in the Deformed PD; (<b>c</b>) Landmarks in the original T2.</p> Full article ">
<p>TRE<span class="html-italic"><sub>l</sub></span> (in mm) for the wldNSSD and wldWSSIM using various patch sizes. (<b>a</b>) wldNSSD; (<b>b</b>) wldWSSIM.</p> Full article ">
<p>Time (in seconds) for the wldNSSD and wldWSSIM using various patch sizes. (<b>a</b>) wldNSSD; (<b>b</b>) wldWSSIM.</p> Full article ">
<p>Comparison of registration precision with different γ for wldWSSIM and wldNSSD. (<b>a</b>) wldWSSIM; (<b>b</b>)wldNSSD.</p> Full article ">
<p>Comparison of registration precision with different γ for wldWSSIM and wldNSSD. (<b>a</b>) wldWSSIM; (<b>b</b>)wldNSSD.</p> Full article ">
1669 KiB  
Review
Aspects of the Application of Cavity Enhanced Spectroscopy to Nitrogen Oxides Detection
by Jacek Wojtas, Janusz Mikolajczyk and Zbigniew Bielecki
Sensors 2013, 13(6), 7570-7598; https://doi.org/10.3390/s130607570 - 10 Jun 2013
Cited by 38 | Viewed by 12434
Abstract
This article presents design issues of high-sensitive laser absorption spectroscopy systems for nitrogen oxides (NOx) detection. Examples of our systems and their investigation results are also described. The constructed systems use one of the most sensitive methods, cavity enhanced absorption spectroscopy [...] Read more.
This article presents design issues of high-sensitive laser absorption spectroscopy systems for nitrogen oxides (NOx) detection. Examples of our systems and their investigation results are also described. The constructed systems use one of the most sensitive methods, cavity enhanced absorption spectroscopy (CEAS). They operate at different wavelength ranges using a blue—violet laser diode (410 nm) as well as quantum cascade lasers (5.27 µm and 4.53 µm). Each of them is configured as a one or two channel measurement device using, e.g., time division multiplexing and averaging. During the testing procedure, the main performance features such as detection limits and measurements uncertainties have been determined. The obtained results are 1 ppb NO2, 75 ppb NO and 45 ppb N2O. For all systems, the uncertainty of concentration measurements does not exceed a value of 13%. Some experiments with explosives are also discussed. A setup equipped with a concentrator of explosives vapours was used. The detection method is based either on the reaction of the sensors to the nitrogen oxides directly emitted by the explosives or on the reaction to the nitrogen oxides produced during thermal decomposition of explosive vapours. For TNT, PETN, RDX and HMX a detection limit better than 1 ng has been achieved. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
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<p>Cavity ring down spectroscopy idea.</p> Full article ">
<p>The scheme of the CEAS setup.</p> Full article ">
<p>NO<sub>2</sub> absorption spectrum (<b>a</b>) and dependence of the detection limit on the cavity length and the reflectivity of mirrors <span class="html-italic">R</span> (<b>b</b>).</p> Full article ">
<p>N<sub>2</sub>O absorption spectrum.</p> Full article ">
<p>NO absorption spectrum.</p> Full article ">
<p>Illustration of matching the laser emission wavelength and cavity mirrors reflectivity.</p> Full article ">
<p>Block diagram of NO<sub>x</sub> sensor.</p> Full article ">
<p>Example of photodetectors detectivity.</p> Full article ">
<p>PMT equivalent scheme.</p> Full article ">
1064 KiB  
Article
Accurate Human Tissue Characterization for Energy-Efficient Wireless On-Body Communications
by Mónica Vallejo, Joaquín Recas, Pablo García Del Valle and José L. Ayala
Sensors 2013, 13(6), 7546-7569; https://doi.org/10.3390/s130607546 - 10 Jun 2013
Cited by 55 | Viewed by 8625
Abstract
The demand for Wireless Body Sensor Networks (WBSNs) is rapidly increasing due to the revolution in wearable systems demonstrated by the penetration of on-the-body sensors in hospitals, sports medicine and general health-care practices. In WBSN, the body acts as a communication channel for [...] Read more.
The demand for Wireless Body Sensor Networks (WBSNs) is rapidly increasing due to the revolution in wearable systems demonstrated by the penetration of on-the-body sensors in hospitals, sports medicine and general health-care practices. In WBSN, the body acts as a communication channel for the propagation of electromagnetic (EM) waves, where losses are mainly due to absorption of power in the tissue. This paper shows the effects of the dielectric properties of biological tissues in the signal strength and, for the first time, relates these effects with the human body composition. After a careful analysis of results, this work proposes a reactive algorithm for power transmission to alleviate the effect of body movement and body type. This policy achieves up to 40.8% energy savings in a realistic scenario with no performance overhead. Full article
(This article belongs to the Special Issue Select papers from UCAmI & IWAAL 2012 - the 6th International Conference on Ubiquitous Computing and Ambient Intelligence & 4th International Workshop on Ambient Assisted Living (UCAmI & IWAAL 2012))
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<p>Experimental Setup.</p> Full article ">
<p>RSSI <span class="html-italic">vs.</span> Distance for LOS/NLOS links in anechoic chamber.</p> Full article ">
<p>NLOS due to four-layered porcine tissue in outdoor environment. (<b>a</b>) Shimmer nodes; (<b>b</b>) Samsi nodes.</p> Full article ">
<p>RSSI <span class="html-italic">vs.</span> Distance for LOS/NLOS links in outdoor environment.</p> Full article ">
<p>Homogeneous and layered biological tissue: fat tissues.</p> Full article ">
<p>Homogeneous and layered biological tissue: muscle tissues.</p> Full article ">
<p>RSSI measures of four subjects with Shimmer node at −10 dBm.</p> Full article ">
<p>Node Position.</p> Full article ">
<p>Power variations for Subject 1 L1/P2.</p> Full article ">
1081 KiB  
Article
Deployment and Validation of a Smart System for Screening of Language Disorders in Primary Care
by María Luisa Martín-Ruiz, Miguel Angel Valero Duboy and Iván Pau de la Cruz
Sensors 2013, 13(6), 7522-7545; https://doi.org/10.3390/s130607522 - 10 Jun 2013
Cited by 15 | Viewed by 9440
Abstract
Neuro-evolutive development from birth until the age of six years is a decisive factor in a child’s quality of life. Early detection of development disorders in early childhood can facilitate necessary diagnosis and/or treatment. Primary-care pediatricians play a key role in its detection [...] Read more.
Neuro-evolutive development from birth until the age of six years is a decisive factor in a child’s quality of life. Early detection of development disorders in early childhood can facilitate necessary diagnosis and/or treatment. Primary-care pediatricians play a key role in its detection as they can undertake the preventive and therapeutic actions requested to promote a child’s optimal development. However, the lack of time and little specific knowledge at primary-care avoid to applying continuous early-detection anomalies procedures. This research paper focuses on the deployment and evaluation of a smart system that enhances the screening of language disorders in primary care. Pediatricians get support to proceed with early referral of language disorders. The proposed model provides them with a decision-support tool for referral actions to trigger essential diagnostic and/or therapeutic actions for a comprehensive individual development. The research was conducted by starting from a sample of 60 cases of children with language disorders. Validation was carried out through two complementary steps: first, by including a team of seven experts from the fields of neonatology, pediatrics, neurology and language therapy, and, second, through the evaluation of 21 more previously diagnosed cases. The results obtained show that therapist positively accepted the system proposal in 18 cases (86%) and suggested system redesign for single referral to a speech therapist in three remaining cases. Full article
(This article belongs to the Special Issue Select papers from UCAmI & IWAAL 2012 - the 6th International Conference on Ubiquitous Computing and Ambient Intelligence & 4th International Workshop on Ambient Assisted Living (UCAmI & IWAAL 2012))
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<p>Knowledge Base System Development Methodology. This figure summarizes the empirical design methodology for the construction of the KBS (Pegasus).</p> Full article ">
<p>Pegasus general use case model.</p> Full article ">
<p>Pegasus general system architecture.</p> Full article ">
<p>Ontology of the system in Protégé. This figure shows Ontology of system in Protégé for the classes of months 2 and 3.</p> Full article ">
<p>Inference in Protégé for questions about 2 month-old child.</p> Full article ">
<p>Inference in Protégé for questions about 2 month-old child.</p> Full article ">
<p>Gades web tool deployment.</p> Full article ">
<p>Pegasus web tool deployment.</p> Full article ">
<p>Language therapist realizing the system verification (Gades).</p> Full article ">
576 KiB  
Article
Early Improper Motion Detection in Golf Swings Using Wearable Motion Sensors: The First Approach
by Sara Stančin and Sašo Tomažič
Sensors 2013, 13(6), 7505-7521; https://doi.org/10.3390/s130607505 - 10 Jun 2013
Cited by 24 | Viewed by 8338
Abstract
This paper presents an analysis of a golf swing to detect improper motion in the early phase of the swing. Led by the desire to achieve a consistent shot outcome, a particular golfer would (in multiple trials) prefer to perform completely identical golf [...] Read more.
This paper presents an analysis of a golf swing to detect improper motion in the early phase of the swing. Led by the desire to achieve a consistent shot outcome, a particular golfer would (in multiple trials) prefer to perform completely identical golf swings. In reality, some deviations from the desired motion are always present due to the comprehensive nature of the swing motion. Swing motion deviations that are not detrimental to performance are acceptable. This analysis is conducted using a golfer’s leading arm kinematic data, which are obtained from a golfer wearing a motion sensor that is comprised of gyroscopes and accelerometers. Applying the principal component analysis (PCA) to the reference observations of properly performed swings, the PCA components of acceptable swing motion deviations are established. Using these components, the motion deviations in the observations of other swings are examined. Any unacceptable deviations that are detected indicate an improper swing motion. Arbitrarily long observations of an individual player’s swing sequences can be included in the analysis. The results obtained for the considered example show an improper swing motion in early phase of the swing, i.e., the first part of the backswing. An early detection method for improper swing motions that is conducted on an individual basis provides assistance for performance improvement. Full article
(This article belongs to the Section Physical Sensors)
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<p>Position of the measurement sensor on the right-handed golfer's leading arm during the golf ball address.</p> Full article ">
<p>The specifically designed wearable 3D accelerometer and gyroscope motion sensor with its intrinsic coordinate system axis.</p> Full article ">
<p>Golfer's leading arm angular velocities <span class="html-italic">ω<sub>x</sub></span>, <span class="html-italic">ω<sub>y</sub></span>, and <span class="html-italic">ω<sub>z</sub></span> and accelerations <span class="html-italic">a<sub>x</sub></span>, <span class="html-italic">a<sub>y</sub></span>, and <span class="html-italic">a<sub>z</sub></span> for one extracted swing sequence obtained using a wearable 3D motion sensor. The sensor-intrinsic x axis coincided with the longitudinal axis of the golfer's leading arm, while the y and z axes referred to the lateral and vertical arm axes, respectively.</p> Full article ">
<p>Reference and test observations of the golfer's leading arm rotation around its intrinsic longitudinal axis during the first 0.625 s of the backswing. All reference observations refer to properly performed swings. Test observations 1–5 refer to an improperly performed swing, and 6 refers to a properly performed swing. The desired motion is obtained as the mean of the reference observations.</p> Full article ">
<p>Acceptable and test deviations from the desired swing motion.</p> Full article ">
<p>The variance of the acceptable deviations from the desired motion covered with the obtained principal components in logarithmic scale. The last four components each cover less than 1% of the variance. These components, covering 2.08% of the variance, were attributed to noise and/or different artefacts and teased from the first nine components. In sum, the first nine components cover the remaining 97.02% of the variance.</p> Full article ">
<p>PCA coefficients of the test deviations from the desired swing motion. For test observations 1, 2, 3, and 5, at least one coefficient exceeds the acceptable range, indicating improper motion in the associated swings.</p> Full article ">
<p>Acceptable and test observation residual deviations in time domain. Acceptable deviations residuals represent deviations in properly performed swings attributed to noise and/or different artefacts. The deviation residuals for test observations 1–5, for which improper motion was detected, considerably exceed acceptable deviations residuals. Consistently positive values in the second half of the considered swing interval for test observations 1–4 indicate a typical improper motion in the associated swings.</p> Full article ">
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