Sensors

1894 KiB

Open AccessArticle

Viability Prediction of Ricinus cummunis L. Seeds Using Multispectral Imaging

by Merete Halkjær Olesen, Pejman Nikneshan, Santosh Shrestha, Ali Tadayyon, Lise Christina Deleuran, Birte Boelt and René Gislum

Sensors 2015, 15(2), 4592-4604; https://doi.org/10.3390/s150204592 - 17 Feb 2015

Cited by 48 | Viewed by 9854

Abstract

The purpose of this study was to highlight the use of multispectral imaging in seed quality testing of castor seeds. Visually, 120 seeds were divided into three classes: yellow, grey and black seeds. Thereafter, images at 19 different wavelengths ranging from 375–970 nm [...] Read more.

The purpose of this study was to highlight the use of multispectral imaging in seed quality testing of castor seeds. Visually, 120 seeds were divided into three classes: yellow, grey and black seeds. Thereafter, images at 19 different wavelengths ranging from 375–970 nm were captured of all the seeds. Mean intensity for each single seed was extracted from the images, and a significant difference between the three colour classes was observed, with the best separation in the near-infrared wavelengths. A specified feature (RegionMSI mean) based on normalized canonical discriminant analysis, were employed and viable seeds were distinguished from dead seeds with 92% accuracy. The same model was tested on a validation set of seeds. These seeds were divided into two groups depending on germination ability, 241 were predicted as viable and expected to germinate and 59 were predicted as dead or non-germinated seeds. This validation of the model resulted in 96% correct classification of the seeds. The results illustrate how multispectral imaging technology can be employed for prediction of viable castor seeds, based on seed coat colour. Full article

(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)

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913 KiB

Open AccessArticle

Online Sensor Fault Detection Based on an Improved Strong Tracking Filter

by Lijuan Wang, Lifeng Wu, Yong Guan and Guohui Wang

Sensors 2015, 15(2), 4578-4591; https://doi.org/10.3390/s150204578 - 16 Feb 2015

Cited by 25 | Viewed by 6471

Abstract

We propose a method for online sensor fault detection that is based on the evolving Strong Tracking Filter (STCKF). The cubature rule is used to estimate states to improve the accuracy of making estimates in a nonlinear case. A residual is the difference [...] Read more.

We propose a method for online sensor fault detection that is based on the evolving Strong Tracking Filter (STCKF). The cubature rule is used to estimate states to improve the accuracy of making estimates in a nonlinear case. A residual is the difference in value between an estimated value and the true value. A residual will be regarded as a signal that includes fault information. The threshold is set at a reasonable level, and will be compared with residuals to determine whether or not the sensor is faulty. The proposed method requires only a nominal plant model and uses STCKF to estimate the original state vector. The effectiveness of the algorithm is verified by simulation on a drum-boiler model. Full article

(This article belongs to the Section Physical Sensors)

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1601 KiB

Open AccessArticle

An Instantaneous Low-Cost Point-of-Care Anemia Detection Device

by Jaime Punter-Villagrasa, Joan Cid, Cristina Páez-Avilés, Ivón Rodríguez-Villarreal, Esteve Juanola-Feliu, Jordi Colomer-Farrarons and Pere Ll. Miribel-Català

Sensors 2015, 15(2), 4564-4577; https://doi.org/10.3390/s150204564 - 16 Feb 2015

Cited by 21 | Viewed by 10541

Abstract

We present a small, compact and portable device for point-of-care instantaneous early detection of anemia. The method used is based on direct hematocrit measurement from whole blood samples by means of impedance analysis. This device consists of a custom electronic instrumentation and a [...] Read more.

We present a small, compact and portable device for point-of-care instantaneous early detection of anemia. The method used is based on direct hematocrit measurement from whole blood samples by means of impedance analysis. This device consists of a custom electronic instrumentation and a plug-and-play disposable sensor. The designed electronics rely on straightforward standards for low power consumption, resulting in a robust and low consumption device making it completely mobile with a long battery life. Another approach could be powering the system based on other solutions like indoor solar cells, or applying energy-harvesting solutions in order to remove the batteries. The sensing system is based on a disposable low-cost label-free three gold electrode commercial sensor for 50 µL blood samples. The device capability for anemia detection has been validated through 24 blood samples, obtained from four hospitalized patients at Hospital Clínic. As a result, the response, effectiveness and robustness of the portable point-of-care device to detect anemia has been proved with an accuracy error of 2.83% and a mean coefficient of variation of 2.57% without any particular case above 5%. Full article

(This article belongs to the Section Biosensors)

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2289 KiB

Open AccessArticle

Real-Time Strap Pressure Sensor System for Powered Exoskeletons

by Jesús Tamez-Duque, Rebeca Cobian-Ugalde, Atilla Kilicarslan, Anusha Venkatakrishnan, Rogelio Soto and Jose Luis Contreras-Vidal

Sensors 2015, 15(2), 4550-4563; https://doi.org/10.3390/s150204550 - 16 Feb 2015

Cited by 71 | Viewed by 10643

Abstract

Assistive and rehabilitative powered exoskeletons for spinal cord injury (SCI) and stroke subjects have recently reached the clinic. Proper tension and joint alignment are critical to ensuring safety. Challenges still exist in adjustment and fitting, with most current systems depending on personnel experience [...] Read more.

Assistive and rehabilitative powered exoskeletons for spinal cord injury (SCI) and stroke subjects have recently reached the clinic. Proper tension and joint alignment are critical to ensuring safety. Challenges still exist in adjustment and fitting, with most current systems depending on personnel experience for appropriate individual fastening. Paraplegia and tetraplegia patients using these devices have impaired sensation and cannot signal if straps are uncomfortable or painful. Excessive pressure and blood-flow restriction can lead to skin ulcers, necrotic tissue and infections. Tension must be just enough to prevent slipping and maintain posture. Research in pressure dynamics is extensive for wheelchairs and mattresses, but little research has been done on exoskeleton straps. We present a system to monitor pressure exerted by physical human-machine interfaces and provide data about levels of skin/body pressure in fastening straps. The system consists of sensing arrays, signal processing hardware with wireless transmission, and an interactive GUI. For validation, a lower-body powered exoskeleton carrying the full weight of users was used. Experimental trials were conducted with one SCI and one able-bodied subject. The system can help prevent skin injuries related to excessive pressure in mobility-impaired patients using powered exoskeletons, supporting functionality, independence and better overall quality of life. Full article

(This article belongs to the Section Physical Sensors)

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1978 KiB

Open AccessArticle

Design and Simulation of Material-Integrated Distributed Sensor Processing with a Code-Based Agent Platform and Mobile Multi-Agent Systems

by Stefan Bosse

Sensors 2015, 15(2), 4513-4549; https://doi.org/10.3390/s150204513 - 16 Feb 2015

Cited by 9 | Viewed by 8334

Abstract

Multi-agent systems (MAS) can be used for decentralized and self-organizing data processing in a distributed system, like a resource-constrained sensor network, enabling distributed information extraction, for example, based on pattern recognition and self-organization, by decomposing complex tasks in simpler cooperative agents. Reliable MAS-based [...] Read more.

Multi-agent systems (MAS) can be used for decentralized and self-organizing data processing in a distributed system, like a resource-constrained sensor network, enabling distributed information extraction, for example, based on pattern recognition and self-organization, by decomposing complex tasks in simpler cooperative agents. Reliable MAS-based data processing approaches can aid the material-integration of structural-monitoring applications, with agent processing platforms scaled to the microchip level. The agent behavior, based on a dynamic activity-transition graph (ATG) model, is implemented with program code storing the control and the data state of an agent, which is novel. The program code can be modified by the agent itself using code morphing techniques and is capable of migrating in the network between nodes. The program code is a self-contained unit (a container) and embeds the agent data, the initialization instructions and the ATG behavior implementation. The microchip agent processing platform used for the execution of the agent code is a standalone multi-core stack machine with a zero-operand instruction format, leading to a small-sized agent program code, low system complexity and high system performance. The agent processing is token-queue-based, similar to Petri-nets. The agent platform can be implemented in software, too, offering compatibility at the operational and code level, supporting agent processing in strong heterogeneous networks. In this work, the agent platform embedded in a large-scale distributed sensor network is simulated at the architectural level by using agent-based simulation techniques. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Sensors and Applications)

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563 KiB

Open AccessArticle

Use of Multispectral Imaging in Varietal Identification of Tomato

by Santosh Shrestha, Lise Christina Deleuran, Merete Halkjær Olesen and René Gislum

Sensors 2015, 15(2), 4496-4512; https://doi.org/10.3390/s150204496 - 16 Feb 2015

Cited by 49 | Viewed by 8204

Abstract

Multispectral imaging is an emerging non-destructive technology. In this work its potential for varietal discrimination and identification of tomato cultivars of Nepal was investigated. Two sample sets were used for the study, one with two parents and their crosses and other with eleven [...] Read more.

Multispectral imaging is an emerging non-destructive technology. In this work its potential for varietal discrimination and identification of tomato cultivars of Nepal was investigated. Two sample sets were used for the study, one with two parents and their crosses and other with eleven cultivars to study parents and offspring relationship and varietal identification respectively. Normalized canonical discriminant analysis (nCDA) and principal component analysis (PCA) were used to analyze and compare the results for parents and offspring study. Both the results showed clear discrimination of parents and offspring. nCDA was also used for pairwise discrimination of the eleven cultivars, which correctly discriminated upto 100% and only few pairs below 85%. Partial least square discriminant analysis (PLS-DA) was further used to classify all the cultivars. The model displayed an overall classification accuracy of 82%, which was further improved to 96% and 86% with stepwise PLS-DA models on high (seven) and poor (four) sensitivity cultivars, respectively. The stepwise PLS-DA models had satisfactory classification errors for cross-validation and prediction 7% and 7%, respectively. The results obtained provide an opportunity of using multispectral imaging technology as a primary tool in a scientific community for identification/discrimination of plant varieties in regard to genetic purity and plant variety protection/registration. Full article

(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)

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1546 KiB

Open AccessArticle

Architecture of a Service-Enabled Sensing Platform for the Environment

by Alexander Kotsev, Francesco Pantisano, Sven Schade and Simon Jirka

Sensors 2015, 15(2), 4470-4495; https://doi.org/10.3390/s150204470 - 13 Feb 2015

Cited by 20 | Viewed by 8586

Abstract

Recent technological advancements have led to the production of arrays of miniaturized sensors, often embedded in existing multitasking devices (e.g., smartphones, tablets) and using a wide range of radio standards (e.g., Bluetooth, Wi-Fi, 4G cellular networks). Altogether, these technological evolutions coupled with the [...] Read more.

Recent technological advancements have led to the production of arrays of miniaturized sensors, often embedded in existing multitasking devices (e.g., smartphones, tablets) and using a wide range of radio standards (e.g., Bluetooth, Wi-Fi, 4G cellular networks). Altogether, these technological evolutions coupled with the diffusion of ubiquitous Internet connectivity provide the base-line technology for the Internet of Things (IoT). The rapid increase of IoT devices is enabling the definition of new paradigms of data collection and introduces the concept of mobile crowd-sensing. In this respect, new sensing methodologies promise to extend the current understanding of the environment and social behaviors by leveraging citizen-contributed data for a wide range of applications. Environmental sensing can however only be successful if all the heterogeneous technologies and infrastructures work smoothly together. As a result, the interconnection and orchestration of devices is one of the central issues of the IoT paradigm. With this in mind, we propose an approach for improving the accessibility of observation data, based on interoperable standards and on-device web services. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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1009 KiB

Open AccessReview

Mining Personal Data Using Smartphones and Wearable Devices: A Survey

by Muhammad Habib ur Rehman, Chee Sun Liew, Teh Ying Wah, Junaid Shuja and Babak Daghighi

Sensors 2015, 15(2), 4430-4469; https://doi.org/10.3390/s150204430 - 13 Feb 2015

Cited by 80 | Viewed by 15453

Abstract

The staggering growth in smartphone and wearable device use has led to a massive scale generation of personal (user-specific) data. To explore, analyze, and extract useful information and knowledge from the deluge of personal data, one has to leverage these devices as the [...] Read more.

The staggering growth in smartphone and wearable device use has led to a massive scale generation of personal (user-specific) data. To explore, analyze, and extract useful information and knowledge from the deluge of personal data, one has to leverage these devices as the data-mining platforms in ubiquitous, pervasive, and big data environments. This study presents the personal ecosystem where all computational resources, communication facilities, storage and knowledge management systems are available in user proximity. An extensive review on recent literature has been conducted and a detailed taxonomy is presented. The performance evaluation metrics and their empirical evidences are sorted out in this paper. Finally, we have highlighted some future research directions and potentially emerging application areas for personal data mining using smartphones and wearable devices. Full article

(This article belongs to the Section Physical Sensors)

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688 KiB

Open AccessCorrection

Correction: Tang, C. Y. and Chen, X.Y. A Class of Coning Algorithms Based on a Half-Compressed Structure. Sensors 2014, 14, 14289–14301

by Chuanye Tang and Xiyuan Chen

Sensors 2015, 15(2), 4425-4429; https://doi.org/10.3390/s150204425 - 13 Feb 2015

Cited by 3 | Viewed by 4775

Abstract

Due to an oversight by MDPI and the authors, the following numerical corrections were not made in the originally published article [1]. MDPI-Sensors and the authors would like to apologize for any inconvenience brought to the readers.[...] Full article

(This article belongs to the Special Issue Optical Gyroscopes and Navigation Systems)

1230 KiB

Open AccessArticle

A High Resolution On-Chip Delay Sensor with Low Supply-Voltage Sensitivity for High-Performance Electronic Systems

by Duo Sheng, Hsiu-Fan Lai, Sheng-Min Chan and Min-Rong Hong

Sensors 2015, 15(2), 4408-4424; https://doi.org/10.3390/s150204408 - 13 Feb 2015

Cited by 3 | Viewed by 5597

Abstract

An all-digital on-chip delay sensor (OCDS) circuit with high delay-measurement resolution and low supply-voltage sensitivity for efficient detection and diagnosis in high-performance electronic system applications is presented. Based on the proposed delay measurement scheme, the quantization resolution of the proposed OCDS can be [...] Read more.

An all-digital on-chip delay sensor (OCDS) circuit with high delay-measurement resolution and low supply-voltage sensitivity for efficient detection and diagnosis in high-performance electronic system applications is presented. Based on the proposed delay measurement scheme, the quantization resolution of the proposed OCDS can be reduced to several picoseconds. Additionally, the proposed cascade-stage delay measurement circuit can enhance immunity to supply-voltage variations of the delay measurement resolution without extra self-biasing or calibration circuits. Simulation results show that the delay measurement resolution can be improved to 1.2 ps; the average delay resolution variation is 0.55% with supply-voltage variations of ±10%. Moreover, the proposed delay sensor can be implemented in an all-digital manner, making it very suitable for high-performance electronic system applications as well as system-level integration. Full article

(This article belongs to the Section Physical Sensors)

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2051 KiB

Open AccessArticle

A Soft-Hard Combination-Based Cooperative Spectrum Sensing Scheme for Cognitive Radio Networks

by Nhu Tri Do and Beongku An

Sensors 2015, 15(2), 4388-4407; https://doi.org/10.3390/s150204388 - 13 Feb 2015

Cited by 28 | Viewed by 7155

Abstract

In this paper we propose a soft-hard combination scheme, called SHC scheme, for cooperative spectrum sensing in cognitive radio networks. The SHC scheme deploys a cluster based network in which Likelihood Ratio Test (LRT)-based soft combination is applied at each cluster, and weighted [...] Read more.

In this paper we propose a soft-hard combination scheme, called SHC scheme, for cooperative spectrum sensing in cognitive radio networks. The SHC scheme deploys a cluster based network in which Likelihood Ratio Test (LRT)-based soft combination is applied at each cluster, and weighted decision fusion rule-based hard combination is utilized at the fusion center. The novelties of the SHC scheme are as follows: the structure of the SHC scheme reduces the complexity of cooperative detection which is an inherent limitation of soft combination schemes. By using the LRT, we can detect primary signals in a low signal-to-noise ratio regime (around an average of −15 dB). In addition, the computational complexity of the LRT is reduced since we derive the closed-form expression of the probability density function of LRT value. The SHC scheme also takes into account the different effects of large scale fading on different users in the wide area network. The simulation results show that the SHC scheme not only provides the better sensing performance compared to the conventional hard combination schemes, but also reduces sensing overhead in terms of reporting time compared to the conventional soft combination scheme using the LRT. Full article

(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)

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1200 KiB

Open AccessArticle

A Stationary North-Finding Scheme for an Azimuth Rotational IMU Utilizing a Linear State Equality Constraint

by Huapeng Yu, Hai Zhu, Dayuan Gao, Meng Yu and Wenqi Wu

Sensors 2015, 15(2), 4368-4387; https://doi.org/10.3390/s150204368 - 13 Feb 2015

Cited by 7 | Viewed by 6530

Abstract

The Kalman filter (KF) has always been used to improve north-finding performance under practical conditions. By analyzing the characteristics of the azimuth rotational inertial measurement unit (ARIMU) on a stationary base, a linear state equality constraint for the conventional KF used in the [...] Read more.

The Kalman filter (KF) has always been used to improve north-finding performance under practical conditions. By analyzing the characteristics of the azimuth rotational inertial measurement unit (ARIMU) on a stationary base, a linear state equality constraint for the conventional KF used in the fine north-finding filtering phase is derived. Then, a constrained KF using the state equality constraint is proposed and studied in depth. Estimation behaviors of the concerned navigation errors when implementing the conventional KF scheme and the constrained KF scheme during stationary north-finding are investigated analytically by the stochastic observability approach, which can provide explicit formulations of the navigation errors with influencing variables. Finally, multiple practical experimental tests at a fixed position are done on a postulate system to compare the stationary north-finding performance of the two filtering schemes. In conclusion, this study has successfully extended the utilization of the stochastic observability approach for analytic descriptions of estimation behaviors of the concerned navigation errors, and the constrained KF scheme has demonstrated its superiority over the conventional KF scheme for ARIMU stationary north-finding both theoretically and practically. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems)

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1594 KiB

Open AccessArticle

A Choline Oxidase Amperometric Bioassay for the Detection of Mustard Agents Based on Screen-Printed Electrodes Modified with Prussian Blue Nanoparticles

by Fabiana Arduini, Viviana Scognamiglio, Corrado Covaia, Aziz Amine, Danila Moscone and Giuseppe Palleschi

Sensors 2015, 15(2), 4353-4367; https://doi.org/10.3390/s150204353 - 13 Feb 2015

Cited by 12 | Viewed by 6998

Abstract

In this work a novel bioassay for mustard agent detection was proposed. The bioassay is based on the capability of these compounds to inhibit the enzyme choline oxidase. The enzymatic activity, which is correlated to the mustard agents, was electrochemically monitored measuring the [...] Read more.

In this work a novel bioassay for mustard agent detection was proposed. The bioassay is based on the capability of these compounds to inhibit the enzyme choline oxidase. The enzymatic activity, which is correlated to the mustard agents, was electrochemically monitored measuring the enzymatic product, hydrogen peroxide, by means of a screen-printed electrode modified with Prussian Blue nanoparticles. Prussian Blue nanoparticles are able to electrocatalyse the hydrogen peroxide concentration reduction at low applied potential (−50 mV vs. Ag/AgCl), thus allowing the detection of the mustard agents with no electrochemical interferences. The suitability of this novel bioassay was tested with the nitrogen mustard simulant bis(2-chloroethyl)amine and the sulfur mustard simulants 2-chloroethyl ethyl sulfide and 2-chloroethyl phenyl sulfide. The bioassay proposed in this work allowed the detection of mustard agent simulants with good sensitivity and fast response, which are excellent premises for the development of a miniaturised sensor well suited for an alarm system in case of terrorist attacks. Full article

(This article belongs to the Section Chemical Sensors)

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18030 KiB

Open AccessArticle

Illumination-Invariant and Deformation-Tolerant Inner Knuckle Print Recognition Using Portable Devices

by Xuemiao Xu, Qiang Jin, Le Zhou, Jing Qin, Tien-Tsin Wong and Guoqiang Han

Sensors 2015, 15(2), 4326-4352; https://doi.org/10.3390/s150204326 - 12 Feb 2015

Cited by 12 | Viewed by 7309

Abstract

We propose a novel biometric recognition method that identifies the inner knuckle print (IKP). It is robust enough to confront uncontrolled lighting conditions, pose variations and low imaging quality. Such robustness is crucial for its application on portable devices equipped with consumer-level cameras. [...] Read more.

We propose a novel biometric recognition method that identifies the inner knuckle print (IKP). It is robust enough to confront uncontrolled lighting conditions, pose variations and low imaging quality. Such robustness is crucial for its application on portable devices equipped with consumer-level cameras. We achieve this robustness by two means. First, we propose a novel feature extraction scheme that highlights the salient structure and suppresses incorrect and/or unwanted features. The extracted IKP features retain simple geometry and morphology and reduce the interference of illumination. Second, to counteract the deformation induced by different hand orientations, we propose a novel structure-context descriptor based on local statistics. To our best knowledge, we are the first to simultaneously consider the illumination invariance and deformation tolerance for appearance-based low-resolution hand biometrics. Settings in previous works are more restrictive. They made strong assumptions either about the illumination condition or the restrictive hand orientation. Extensive experiments demonstrate that our method outperforms the state-of-the-art methods in terms of recognition accuracy, especially under uncontrolled lighting conditions and the flexible hand orientation requirement. Full article

(This article belongs to the Section Physical Sensors)

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1327 KiB

Open AccessArticle

An Overview of Distributed Microgrid State Estimation and Control for Smart Grids

by Md Masud Rana and Li Li

Sensors 2015, 15(2), 4302-4325; https://doi.org/10.3390/s150204302 - 12 Feb 2015

Cited by 66 | Viewed by 8982

Abstract

Given the significant concerns regarding carbon emission from the fossil fuels, global warming and energy crisis, the renewable distributed energy resources (DERs) are going to be integrated in the smart grid. This grid can spread the intelligence of the energy distribution and control [...] Read more.

Given the significant concerns regarding carbon emission from the fossil fuels, global warming and energy crisis, the renewable distributed energy resources (DERs) are going to be integrated in the smart grid. This grid can spread the intelligence of the energy distribution and control system from the central unit to the long-distance remote areas, thus enabling accurate state estimation (SE) and wide-area real-time monitoring of these intermittent energy sources. In contrast to the traditional methods of SE, this paper proposes a novel accuracy dependent Kalman filter (KF) based microgrid SE for the smart grid that uses typical communication systems. Then this article proposes a discrete-time linear quadratic regulation to control the state deviations of the microgrid incorporating multiple DERs. Therefore, integrating these two approaches with application to the smart grid forms a novel contributions in green energy and control research communities. Finally, the simulation results show that the proposed KF based microgrid SE and control algorithm provides an accurate SE and control compared with the existing method. Full article

(This article belongs to the Section Sensor Networks)

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413 KiB

Open AccessArticle

Development of an Immunochromatographic Strip for Rapid Detection of Pantoea stewartii subsp. stewartii

by Min Feng, Dezhao Kong, Wenbing Wang, Liqiang Liu, Shanshan Song and Chuanlai Xu

Sensors 2015, 15(2), 4291-4301; https://doi.org/10.3390/s150204291 - 12 Feb 2015

Cited by 39 | Viewed by 7622

Abstract

A rapid, simple, sensitive, and specific immunochromatographic test strip was developed for the detection of Pantoea stewartii subsp. stewartii (Pss) in corn seed which was soaked overnight and then centrifuged for precipitate re-dissolved as samples. A pair of sensitive monoclonal antibodies for the [...] Read more.

A rapid, simple, sensitive, and specific immunochromatographic test strip was developed for the detection of Pantoea stewartii subsp. stewartii (Pss) in corn seed which was soaked overnight and then centrifuged for precipitate re-dissolved as samples. A pair of sensitive monoclonal antibodies for the immunochromatographic test strip was generated by mice immunization and cell fusion. Under optimized conditions, the lower detection limit of the strips for Pss was 1 × 10⁵ cfu/mL both in 0.01 M phosphate buffer solution and corn seed samples, with no cross-reactivity with other common plant pathogens. The developed strip is useful and rapid for the detection of Pss in corn seed samples. Full article

(This article belongs to the Special Issue Immunosensors 2014)

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516 KiB

Open AccessArticle

An Accurate Link Correlation Estimator for Improving Wireless Protocol Performance

by Zhiwei Zhao, Xianghua Xu, Wei Dong and Jiajun Bu

Sensors 2015, 15(2), 4273-4290; https://doi.org/10.3390/s150204273 - 12 Feb 2015

Cited by 8 | Viewed by 5306

Abstract

Wireless link correlation has shown significant impact on the performance of various sensor network protocols. Many works have been devoted to exploiting link correlation for protocol improvements. However, the effectiveness of these designs heavily relies on the accuracy of link correlation measurement. In [...] Read more.

Wireless link correlation has shown significant impact on the performance of various sensor network protocols. Many works have been devoted to exploiting link correlation for protocol improvements. However, the effectiveness of these designs heavily relies on the accuracy of link correlation measurement. In this paper, we investigate state-of-the-art link correlation measurement and analyze the limitations of existing works. We then propose a novel lightweight and accurate link correlation estimation (LACE) approach based on the reasoning of link correlation formation. LACE combines both long-term and short-term link behaviors for link correlation estimation. We implement LACE as a stand-alone interface in TinyOS and incorporate it into both routing and flooding protocols. Simulation and testbed results show that LACE: (1) achieves more accurate and lightweight link correlation measurements than the state-of-the-art work; and (2) greatly improves the performance of protocols exploiting link correlation. Full article

(This article belongs to the Section Sensor Networks)

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429 KiB

Open AccessArticle

Simultaneous 2D Strain Sensing Using Polymer Planar Bragg Gratings

by Manuel Rosenberger, Waltraud Eisenbeil, Bernhard Schmauss and Ralf Hellmann

Sensors 2015, 15(2), 4264-4272; https://doi.org/10.3390/s150204264 - 12 Feb 2015

Cited by 30 | Viewed by 7048

Abstract

We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG) fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive [...] Read more.

We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG) fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive strain at various angles. It is shown that the sensitivity of the PPBG strongly depends on the angle between the optical waveguide into which the grating is inscribed and the direction along which the mechanical load is applied. Additionally, a 2D PPBG fabricated by writing two Bragg gratings angularly displaced from each other into a single polymer platelet is bonded to a stainless steel plate. The two reflected wavelengths exhibit different sensitivities while tested toward tensile and compressive strain. These characteristics make 2D PPBG suitable for measuring multi-axial tensile and compressive strain. Full article

(This article belongs to the Special Issue Optical Sensors for Chemical, Biological and Industrial Applications)

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1646 KiB

Open AccessArticle

Differential Wide Temperature Range CMOS Interface Circuit for Capacitive MEMS Pressure Sensors

by Yucai Wang and Vamsy P. Chodavarapu

Sensors 2015, 15(2), 4253-4263; https://doi.org/10.3390/s150204253 - 12 Feb 2015

Cited by 18 | Viewed by 9141

Abstract

We describe a Complementary Metal-Oxide Semiconductor (CMOS) differential interface circuit for capacitive Micro-Electro-Mechanical Systems (MEMS) pressure sensors that is functional over a wide temperature range between −55 °C and 225 °C. The circuit is implemented using IBM 0.13 μm CMOS technology with 2.5 [...] Read more.

We describe a Complementary Metal-Oxide Semiconductor (CMOS) differential interface circuit for capacitive Micro-Electro-Mechanical Systems (MEMS) pressure sensors that is functional over a wide temperature range between −55 °C and 225 °C. The circuit is implemented using IBM 0.13 μm CMOS technology with 2.5 V power supply. A constant-g_m biasing technique is used to mitigate performance degradation at high temperatures. The circuit offers the flexibility to interface with MEMS sensors with a wide range of the steady-state capacitance values from 0.5 pF to 10 pF. Simulation results show that the circuitry has excellent linearity and stability over the wide temperature range. Experimental results confirm that the temperature effects on the circuitry are small, with an overall linearity error around 2%. Full article

(This article belongs to the Section Physical Sensors)

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Open AccessArticle

Ionizing Radiation Detectors Based on Ge-Doped Optical Fibers Inserted in Resonant Cavities

by Saverio Avino, Vittoria D'Avino, Antonio Giorgini, Roberto Pacelli, Raffaele Liuzzi, Laura Cella, Paolo De Natale and Gianluca Gagliardi

Sensors 2015, 15(2), 4242-4252; https://doi.org/10.3390/s150204242 - 12 Feb 2015

Cited by 9 | Viewed by 7737

Abstract

The measurement of ionizing radiation (IR) is a crucial issue in different areas of interest, from environmental safety and industrial monitoring to aerospace and medicine. Optical fiber sensors have recently proven good candidates as radiation dosimeters. Here we investigate the effect of IR [...] Read more.

The measurement of ionizing radiation (IR) is a crucial issue in different areas of interest, from environmental safety and industrial monitoring to aerospace and medicine. Optical fiber sensors have recently proven good candidates as radiation dosimeters. Here we investigate the effect of IR on germanosilicate optical fibers. A piece of Ge-doped fiber enclosed between two fiber Bragg gratings (FBGs) is irradiated with gamma radiation generated by a 6 MV medical linear accelerator. With respect to other FBG-based IR dosimeters, here the sensor is only the bare fiber without any special internal structure. A near infrared laser is frequency locked to the cavity modes for high resolution measurement of radiation induced effects on the fiber optical parameters. In particular, we observe a variation of the fiber thermo-optic response with the radiation dose delivered, as expected from the interaction with Ge defect centers, and demonstrate a detection limit of 360 mGy. This method can have an impact in those contexts where low radiation doses have to be measured both in small volumes or over large areas, such as radiation therapy and radiation protection, while bare optical fibers are cheap and disposable. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors)

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340 KiB

Open AccessReview

Microbial Biofilm as a Smart Material

by Christian Garde, Martin Welch, Jesper Ferkinghoff-Borg and Thomas Sams

Sensors 2015, 15(2), 4229-4241; https://doi.org/10.3390/s150204229 - 12 Feb 2015

Cited by 5 | Viewed by 5788

Abstract

Microbial biofilm colonies will in many cases form a smart material capable of responding to external threats dependent on their size and internal state. The microbial community accordingly switches between passive, protective, or attack modes of action. In order to decide which strategy [...] Read more.

Microbial biofilm colonies will in many cases form a smart material capable of responding to external threats dependent on their size and internal state. The microbial community accordingly switches between passive, protective, or attack modes of action. In order to decide which strategy to employ, it is essential for the biofilm community to be able to sense its own size. The sensor designed to perform this task is termed a quorum sensor, since it only permits collective behaviour once a sufficiently large assembly of microbes have been established. The generic quorum sensor construct involves two genes, one coding for the production of a diffusible signal molecule and one coding for a regulator protein dedicated to sensing the signal molecules. A positive feedback in the signal molecule production sets a well-defined condition for switching into the collective mode. The activation of the regulator involves a slow dimerization, which allows low-pass filtering of the activation of the collective mode. Here, we review and combine the model components that form the basic quorum sensor in a number of Gram-negative bacteria, e.g., Pseudomonas aeruginosa. Full article

(This article belongs to the Special Issue Smart Materials for Switchable Sensors)

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1817 KiB

Open AccessArticle

Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices

by Cuong M. Nguyen, Smitha Rao, Xuesong Yang, Souvik Dubey, Jeffrey Mays, Hung Cao and Jung-Chih Chiao

Sensors 2015, 15(2), 4212-4228; https://doi.org/10.3390/s150204212 - 12 Feb 2015

Cited by 31 | Viewed by 8741

Abstract

Flexible iridium oxide (IrO_x)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrO_x electrodes with long lifetime, high stability [...] Read more.

Flexible iridium oxide (IrO_x)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrO_x electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 µm × 500 µm, and 100 µm × 100 µm were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrO_x electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrO_x pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrO_x reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans. Full article

(This article belongs to the Special Issue Sol-Gel Based Sensors and Devices)

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2065 KiB

Open AccessArticle

Wearable Sensor-Based Rehabilitation Exercise Assessment for Knee Osteoarthritis

by Kun-Hui Chen, Po-Chao Chen, Kai-Chun Liu and Chia-Tai Chan

Sensors 2015, 15(2), 4193-4211; https://doi.org/10.3390/s150204193 - 12 Feb 2015

Cited by 91 | Viewed by 12517

Abstract

Since the knee joint bears the full weight load of the human body and the highest pressure loads while providing flexible movement, it is the body part most vulnerable and susceptible to osteoarthritis. In exercise therapy, the early rehabilitation stages last for approximately [...] Read more.

Since the knee joint bears the full weight load of the human body and the highest pressure loads while providing flexible movement, it is the body part most vulnerable and susceptible to osteoarthritis. In exercise therapy, the early rehabilitation stages last for approximately six weeks, during which the patient works with the physical therapist several times each week. The patient is afterwards given instructions for continuing rehabilitation exercise by him/herself at home. This study develops a rehabilitation exercise assessment mechanism using three wearable sensors mounted on the chest, thigh and shank of the working leg in order to enable the patients with knee osteoarthritis to manage their own rehabilitation progress. In this work, time-domain, frequency-domain features and angle information of the motion sensor signals are used to classify the exercise type and identify whether their postures are proper or not. Three types of rehabilitation exercise commonly prescribed to knee osteoarthritis patients are: Short-Arc Exercise, Straight Leg Raise, and Quadriceps Strengthening Mini-squats. After ten subjects performed the three kinds of rehabilitation activities, three validation techniques including 10-fold cross-validation, within subject cross validation, and leave-one-subject cross validation are utilized to confirm the proposed mechanism. The overall recognition accuracy for exercise type classification is 97.29% and for exercise posture identification it is 88.26%. The experimental results demonstrate the feasibility of the proposed mechanism which can help patients perform rehabilitation movements and progress effectively. Moreover, the proposed mechanism is able to detect multiple errors at once, fulfilling the requirements for rehabilitation assessment. Full article

(This article belongs to the Section Physical Sensors)

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2742 KiB

Open AccessArticle

Compressive SAR Imaging with Joint Sparsity and Local Similarity Exploitation

by Fangfang Shen, Guanghui Zhao, Guangming Shi, Weisheng Dong, Chenglong Wang and Yi Niu

Sensors 2015, 15(2), 4176-4192; https://doi.org/10.3390/s150204176 - 12 Feb 2015

Cited by 8 | Viewed by 5942

Abstract

Compressive sensing-based synthetic aperture radar (SAR) imaging has shown its superior capability in high-resolution image formation. However, most of those works focus on the scenes that can be sparsely represented in fixed spaces. When dealing with complicated scenes, these fixed spaces lack adaptivity [...] Read more.

Compressive sensing-based synthetic aperture radar (SAR) imaging has shown its superior capability in high-resolution image formation. However, most of those works focus on the scenes that can be sparsely represented in fixed spaces. When dealing with complicated scenes, these fixed spaces lack adaptivity in characterizing varied image contents. To solve this problem, a new compressive sensing-based radar imaging approach with adaptive sparse representation is proposed. Specifically, an autoregressive model is introduced to adaptively exploit the structural sparsity of an image. In addition, similarity among pixels is integrated into the autoregressive model to further promote the capability and thus an adaptive sparse representation facilitated by a weighted autoregressive model is derived. Since the weighted autoregressive model is inherently determined by the unknown image, we propose a joint optimization scheme by iterative SAR imaging and updating of the weighted autoregressive model to solve this problem. Eventually, experimental results demonstrated the validity and generality of the proposed approach. Full article

(This article belongs to the Section Physical Sensors)

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2630 KiB

Open AccessArticle

Characterization of a Field Spectroradiometer for Unattended Vegetation Monitoring. Key Sensor Models and Impacts on Reflectance

by Javier Pacheco-Labrador and M. Pilar Martín

Sensors 2015, 15(2), 4154-4175; https://doi.org/10.3390/s150204154 - 11 Feb 2015

Cited by 26 | Viewed by 6197

Abstract

Field spectroradiometers integrated in automated systems at Eddy Covariance (EC) sites are a powerful tool for monitoring and upscaling vegetation physiology and carbon and water fluxes. However, exposure to varying environmental conditions can affect the functioning of these sensors, especially if these cannot [...] Read more.

Field spectroradiometers integrated in automated systems at Eddy Covariance (EC) sites are a powerful tool for monitoring and upscaling vegetation physiology and carbon and water fluxes. However, exposure to varying environmental conditions can affect the functioning of these sensors, especially if these cannot be completely insulated and stabilized. This can cause inaccuracy in the spectral measurements and hinder the comparison between data acquired at different sites. This paper describes the characterization of key sensor models in a double beam spectroradiometer necessary to calculate the Hemispherical-Conical Reflectance Factor (HCRF). Dark current, temperature dependence, non-linearity, spectral calibration and cosine receptor directional responses are modeled in the laboratory as a function of temperature, instrument settings, radiation measured or illumination angle. These models are used to correct the spectral measurements acquired continuously by the same instrument integrated outdoors in an automated system (AMSPEC-MED). Results suggest that part of the instrumental issues cancel out mutually or can be controlled by the instrument configuration, so that changes induced in HCFR reached about 0.05 at maximum. However, these corrections are necessary to ensure the inter-comparison of data with other ground or remote sensors and to discriminate instrumentally induced changes in HCRF from those related with vegetation physiology and directional effects. Full article

(This article belongs to the Section Remote Sensors)

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500 KiB

Open AccessArticle

Efficient Evaluation of Wireless Real-Time Control Networks

by Peter Horvath, Mark Yampolskiy and Xenofon Koutsoukos

Sensors 2015, 15(2), 4134-4153; https://doi.org/10.3390/s150204134 - 11 Feb 2015

Cited by 12 | Viewed by 6108

Abstract

In this paper, we present a system simulation framework for the design and performance evaluation of complex wireless cyber-physical systems. We describe the simulator architecture and the specific developments that are required to simulate cyber-physical systems relying on multi-channel, multihop mesh networks. We [...] Read more.

In this paper, we present a system simulation framework for the design and performance evaluation of complex wireless cyber-physical systems. We describe the simulator architecture and the specific developments that are required to simulate cyber-physical systems relying on multi-channel, multihop mesh networks. We introduce realistic and efficient physical layer models and a system simulation methodology, which provides statistically significant performance evaluation results with low computational complexity. The capabilities of the proposed framework are illustrated in the example of WirelessHART, a centralized, real-time, multi-hop mesh network designed for industrial control and monitor applications. Full article

(This article belongs to the Special Issue Cyber-Physical Systems)

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1147 KiB

Open AccessReview

Augmenting the Senses: A Review on Sensor-Based Learning Support

by Jan Schneider, Dirk Börner, Peter Van Rosmalen and Marcus Specht

Sensors 2015, 15(2), 4097-4133; https://doi.org/10.3390/s150204097 - 11 Feb 2015

Cited by 80 | Viewed by 13589

Abstract

In recent years sensor components have been extending classical computer-based support systems in a variety of applications domains (sports, health, etc.). In this article we review the use of sensors for the application domain of learning. For that we analyzed 82 sensor-based [...] Read more.

In recent years sensor components have been extending classical computer-based support systems in a variety of applications domains (sports, health, etc.). In this article we review the use of sensors for the application domain of learning. For that we analyzed 82 sensor-based prototypes exploring their learning support. To study this learning support we classified the prototypes according to the Bloom’s taxonomy of learning domains and explored how they can be used to assist on the implementation of formative assessment, paying special attention to their use as feedback tools. The analysis leads to current research foci and gaps in the development of sensor-based learning support systems and concludes with a research agenda based on the findings. Full article

(This article belongs to the Special Issue HCI In Smart Environments)

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1951 KiB

Open AccessArticle

Development and Integration of a Solar Powered Unmanned Aerial Vehicle and a Wireless Sensor Network to Monitor Greenhouse Gases

by Alexander Malaver, Nunzio Motta, Peter Corke and Felipe Gonzalez

Sensors 2015, 15(2), 4072-4096; https://doi.org/10.3390/s150204072 - 11 Feb 2015

Cited by 122 | Viewed by 13969

Abstract

Measuring gases for environmental monitoring is a demanding task that requires long periods of observation and large numbers of sensors. Wireless Sensor Networks (WSNs) and Unmanned Aerial Vehicles (UAVs) currently represent the best alternative to monitor large, remote, and difficult access areas, as [...] Read more.

Measuring gases for environmental monitoring is a demanding task that requires long periods of observation and large numbers of sensors. Wireless Sensor Networks (WSNs) and Unmanned Aerial Vehicles (UAVs) currently represent the best alternative to monitor large, remote, and difficult access areas, as these technologies have the possibility of carrying specialized gas sensing systems. This paper presents the development and integration of a WSN and an UAV powered by solar energy in order to enhance their functionality and broader their applications. A gas sensing system implementing nanostructured metal oxide (MOX) and non-dispersive infrared sensors was developed to measure concentrations of CH₄ and CO₂. Laboratory, bench and field testing results demonstrate the capability of UAV to capture, analyze and geo-locate a gas sample during flight operations. The field testing integrated ground sensor nodes and the UAV to measure CO₂ concentration at ground and low aerial altitudes, simultaneously. Data collected during the mission was transmitted in real time to a central node for analysis and 3D mapping of the target gas. The results highlights the accomplishment of the first flight mission of a solar powered UAV equipped with a CO₂sensing system integrated with a WSN. The system provides an effective 3D monitoring and can be used in a wide range of environmental applications such as agriculture, bushfires, mining studies, zoology and botanical studies using a ubiquitous low cost technology. Full article

(This article belongs to the Section Remote Sensors)

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405 KiB

Open AccessArticle

Extracting Association Patterns in Network Communications

by Javier Portela, Luis Javier García Villalba, Alejandra Guadalupe Silva Trujillo, Ana Lucila Sandoval Orozco and Tai-hoon Kim

Sensors 2015, 15(2), 4052-4071; https://doi.org/10.3390/s150204052 - 11 Feb 2015

Cited by 3 | Viewed by 5971

Abstract

In network communications, mixes provide protection against observers hiding the appearance of messages, patterns, length and links between senders and receivers. Statistical disclosure attacks aim to reveal the identity of senders and receivers in a communication network setting when it is protected by [...] Read more.

In network communications, mixes provide protection against observers hiding the appearance of messages, patterns, length and links between senders and receivers. Statistical disclosure attacks aim to reveal the identity of senders and receivers in a communication network setting when it is protected by standard techniques based on mixes. This work aims to develop a global statistical disclosure attack to detect relationships between users. The only information used by the attacker is the number of messages sent and received by each user for each round, the batch of messages grouped by the anonymity system. A new modeling framework based on contingency tables is used. The assumptions are more flexible than those used in the literature, allowing to apply the method to multiple situations automatically, such as email data or social networks data. A classification scheme based on combinatoric solutions of the space of rounds retrieved is developed. Solutions about relationships between users are provided for all pairs of users simultaneously, since the dependence of the data retrieved needs to be addressed in a global sense. Full article

(This article belongs to the Special Issue Sensor Computing for Mobile Security and Big Data Analytics)

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4220 KiB

Open AccessArticle

Digitization and Visualization of Greenhouse Tomato Plants in Indoor Environments

by Dawei Li, Lihong Xu, Chengxiang Tan, Erik D. Goodman, Daichang Fu and Longjiao Xin

Sensors 2015, 15(2), 4019-4051; https://doi.org/10.3390/s150204019 - 10 Feb 2015

Cited by 42 | Viewed by 14355

Abstract

This paper is concerned with the digitization and visualization of potted greenhouse tomato plants in indoor environments. For the digitization, an inexpensive and efficient commercial stereo sensor—a Microsoft Kinect—is used to separate visual information about tomato plants from background. Based on the Kinect, [...] Read more.

This paper is concerned with the digitization and visualization of potted greenhouse tomato plants in indoor environments. For the digitization, an inexpensive and efficient commercial stereo sensor—a Microsoft Kinect—is used to separate visual information about tomato plants from background. Based on the Kinect, a 4-step approach that can automatically detect and segment stems of tomato plants is proposed, including acquisition and preprocessing of image data, detection of stem segments, removing false detections and automatic segmentation of stem segments. Correctly segmented texture samples including stems and leaves are then stored in a texture database for further usage. Two types of tomato plants—the cherry tomato variety and the ordinary variety are studied in this paper. The stem detection accuracy (under a simulated greenhouse environment) for the cherry tomato variety is 98.4% at a true positive rate of 78.0%, whereas the detection accuracy for the ordinary variety is 94.5% at a true positive of 72.5%. In visualization, we combine L-system theory and digitized tomato organ texture data to build realistic 3D virtual tomato plant models that are capable of exhibiting various structures and poses in real time. In particular, we also simulate the growth process on virtual tomato plants by exerting controls on two L-systems via parameters concerning the age and the form of lateral branches. This research may provide useful visual cues for improving intelligent greenhouse control systems and meanwhile may facilitate research on artificial organisms. Full article

(This article belongs to the Section Physical Sensors)

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Sensors, Volume 15, Issue 2 (February 2015) – 125 articles , Pages 2232-4604

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