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

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Displaying articles 1-64
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Open AccessArticle Extending the GMR Current Measurement Range with a Counteracting Magnetic Field
Sensors 2013, 13(6), 8042-8059; https://doi.org/10.3390/s130608042
Received: 12 April 2013 / Revised: 6 June 2013 / Accepted: 14 June 2013 / Published: 21 June 2013
Cited by 6 | PDF Full-text (603 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Sequential Fuzzy Diagnosis Method for Motor Roller Bearing in Variable Operating Conditions Based on Vibration Analysis
Sensors 2013, 13(6), 8013-8041; https://doi.org/10.3390/s130608013
Received: 8 April 2013 / Revised: 27 May 2013 / Accepted: 10 June 2013 / Published: 21 June 2013
Cited by 6 | PDF Full-text (972 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle 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
Sensors 2013, 13(6), 8000-8012; https://doi.org/10.3390/s130608000
Received: 26 April 2013 / Revised: 10 June 2013 / Accepted: 11 June 2013 / Published: 21 June 2013
Cited by 3 | PDF Full-text (558 KB) | HTML Full-text | XML Full-text
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
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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
Open AccessArticle Rate-Gyro-Integral Constraint for Ambiguity Resolution in GNSS Attitude Determination Applications
Sensors 2013, 13(6), 7979-7999; https://doi.org/10.3390/s130607979
Received: 3 May 2013 / Revised: 31 May 2013 / Accepted: 12 June 2013 / Published: 21 June 2013
Cited by 11 | PDF Full-text (1606 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle Quantitative Analysis of Fragrance and Odorants Released from Fresh and Decaying Strawberries
Sensors 2013, 13(6), 7939-7978; https://doi.org/10.3390/s130607939
Received: 18 April 2013 / Revised: 7 June 2013 / Accepted: 13 June 2013 / Published: 20 June 2013
Cited by 14 | PDF Full-text (1483 KB) | HTML Full-text | XML Full-text
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
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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
Open AccessArticle Synthesis of Novel CuO Nanosheets and Their Non-Enzymatic Glucose Sensing Applications
Sensors 2013, 13(6), 7926-7938; https://doi.org/10.3390/s130607926
Received: 6 May 2013 / Revised: 7 June 2013 / Accepted: 14 June 2013 / Published: 20 June 2013
Cited by 39 | PDF Full-text (924 KB) | HTML Full-text | XML Full-text
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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Open AccessArticle A Reflective Photonic Crystal Fiber Temperature Sensor Probe Based on Infiltration with Liquid Mixtures
Sensors 2013, 13(6), 7916-7925; https://doi.org/10.3390/s130607916
Received: 19 April 2013 / Revised: 15 May 2013 / Accepted: 7 June 2013 / Published: 20 June 2013
Cited by 20 | PDF Full-text (276 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle Estimation of Melanin and Hemoglobin Using Spectral Reflectance Images Reconstructed from a Digital RGB Image by the Wiener Estimation Method
Sensors 2013, 13(6), 7902-7915; https://doi.org/10.3390/s130607902
Received: 30 April 2013 / Revised: 12 June 2013 / Accepted: 17 June 2013 / Published: 19 June 2013
Cited by 31 | PDF Full-text (668 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Gait-Based Person Identification Robust to Changes in Appearance
Sensors 2013, 13(6), 7884-7901; https://doi.org/10.3390/s130607884
Received: 28 April 2013 / Revised: 10 June 2013 / Accepted: 14 June 2013 / Published: 19 June 2013
Cited by 21 | PDF Full-text (499 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics
Sensors 2013, 13(6), 7872-7883; https://doi.org/10.3390/s130607872
Received: 2 May 2013 / Revised: 14 June 2013 / Accepted: 17 June 2013 / Published: 19 June 2013
Cited by 28 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text | Supplementary Files
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)
Open AccessArticle Recovery of Odorants from an Olfactometer Measured by Proton-Transfer-Reaction Mass Spectrometry
Sensors 2013, 13(6), 7860-7871; https://doi.org/10.3390/s130607860
Received: 11 April 2013 / Revised: 8 June 2013 / Accepted: 13 June 2013 / Published: 19 June 2013
Cited by 16 | PDF Full-text (598 KB) | HTML Full-text | XML Full-text
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
Open AccessArticle Combination of RGB and Multispectral Imagery for Discrimination of Cabernet Sauvignon Grapevine Elements
Sensors 2013, 13(6), 7838-7859; https://doi.org/10.3390/s130607838
Received: 6 May 2013 / Revised: 13 June 2013 / Accepted: 17 June 2013 / Published: 19 June 2013
Cited by 17 | PDF Full-text (2217 KB) | HTML Full-text | XML Full-text
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
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Graphical abstract

Open AccessArticle A Wireless Monitoring Sub-nA Resolution Test Platform for Nanostructure Sensors
Sensors 2013, 13(6), 7827-7837; https://doi.org/10.3390/s130607827
Received: 9 May 2013 / Revised: 9 June 2013 / Accepted: 13 June 2013 / Published: 19 June 2013
Cited by 1 | PDF Full-text (645 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Enhanced Electronic Properties of Pt@Ag Heterostructured Nanoparticles
Sensors 2013, 13(6), 7813-7826; https://doi.org/10.3390/s130607813
Received: 2 May 2013 / Revised: 11 June 2013 / Accepted: 14 June 2013 / Published: 18 June 2013
Cited by 9 | PDF Full-text (1007 KB) | HTML Full-text | XML Full-text
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
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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
Open AccessArticle Performance Evaluation of UHF RFID Technologies for Real-Time Bus Recognition in the Taipei Bus Station
Sensors 2013, 13(6), 7797-7812; https://doi.org/10.3390/s130607797
Received: 18 April 2013 / Revised: 7 June 2013 / Accepted: 8 June 2013 / Published: 18 June 2013
Cited by 4 | PDF Full-text (1128 KB) | HTML Full-text | XML Full-text
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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