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Sensors, Volume 11, Issue 4 (April 2011) , Pages 3401-4473

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Open AccessArticle
Immunity-Based Diagnosis for a Motherboard
Sensors 2011, 11(4), 4462-4473; https://doi.org/10.3390/s110404462
Received: 18 February 2011 / Revised: 29 March 2011 / Accepted: 14 April 2011 / Published: 18 April 2011
Cited by 4 | Viewed by 4418 | PDF Full-text (470 KB) | HTML Full-text | XML Full-text
Abstract
We have utilized immunity-based diagnosis to detect abnormal behavior of components on a motherboard. The immunity-based diagnostic model monitors voltages of some components, CPU temperatures, and fan speeds. We simulated abnormal behaviors of some components on the motherboard, and we utilized the immunity-based [...] Read more.
We have utilized immunity-based diagnosis to detect abnormal behavior of components on a motherboard. The immunity-based diagnostic model monitors voltages of some components, CPU temperatures, and fan speeds. We simulated abnormal behaviors of some components on the motherboard, and we utilized the immunity-based diagnostic model to evaluate motherboard sensors in two experiments. These experiments showed that the immunity-based diagnostic model was an effective method for detecting abnormal behavior of components on the motherboard. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Distributed Dynamic Host Configuration Protocol (D2HCP)
Sensors 2011, 11(4), 4438-4461; https://doi.org/10.3390/s110404438
Received: 28 February 2011 / Revised: 10 April 2011 / Accepted: 12 April 2011 / Published: 18 April 2011
Cited by 19 | Viewed by 8295 | PDF Full-text (751 KB) | HTML Full-text | XML Full-text
Abstract
Mobile Ad Hoc Networks (MANETs) are multihop wireless networks of mobile nodes without any fixed or preexisting infrastructure. The topology of these networks can change randomly due to the unpredictable mobility of nodes and their propagation characteristics. In most networks, including MANETs, each [...] Read more.
Mobile Ad Hoc Networks (MANETs) are multihop wireless networks of mobile nodes without any fixed or preexisting infrastructure. The topology of these networks can change randomly due to the unpredictable mobility of nodes and their propagation characteristics. In most networks, including MANETs, each node needs a unique identifier to communicate. This work presents a distributed protocol for dynamic node IP address assignment in MANETs. Nodes of a MANET synchronize from time to time to maintain a record of IP address assignments in the entire network and detect any IP address leaks. The proposed stateful autoconfiguration scheme uses the OLSR proactive routing protocol for synchronization and guarantees unique IP addresses under a variety of network conditions, including message losses and network partitioning. Simulation results show that the protocol incurs low latency and communication overhead for IP address assignment. Full article
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Open AccessArticle
Oxidation of Hydrocarbons on the Surface of Tin Dioxide Chemical Sensors
Sensors 2011, 11(4), 4425-4437; https://doi.org/10.3390/s110404425
Received: 2 March 2011 / Revised: 1 April 2011 / Accepted: 6 April 2011 / Published: 15 April 2011
Cited by 10 | Viewed by 5475 | PDF Full-text (428 KB) | HTML Full-text | XML Full-text
Abstract
The paper presents the results of our investigation on the effect of the molecular structure of organic vapors on the characteristics of resistive chemical gas sensors. The sensors were based on tin dioxide and prepared by means of thick film technology. The electrical [...] Read more.
The paper presents the results of our investigation on the effect of the molecular structure of organic vapors on the characteristics of resistive chemical gas sensors. The sensors were based on tin dioxide and prepared by means of thick film technology. The electrical and catalytic examinations showed that the abstraction of two hydrogen atoms from the organic molecule and formation of a water in result of reaction with a chemisorbed oxygen ion, determine the rate of oxidation reactions, and thus the sensor performance. The rate of the process depends on the order of carbon atoms and Lewis acidity of the molecule. Therefore, any modification of the surface centers of a sensor material, modifies not only the sensor sensitivity, but also its selectivity. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle
A Secure Cluster-Based Multipath Routing Protocol for WMSNs
Sensors 2011, 11(4), 4401-4424; https://doi.org/10.3390/s110404401
Received: 9 February 2011 / Revised: 8 April 2011 / Accepted: 11 April 2011 / Published: 15 April 2011
Cited by 17 | Viewed by 6292 | PDF Full-text (3018 KB) | HTML Full-text | XML Full-text
Abstract
The new characteristics of Wireless Multimedia Sensor Network (WMSN) and its design issues brought by handling different traffic classes of multimedia content (video streams, audio, and still images) as well as scalar data over the network, make the proposed routing protocols for typical [...] Read more.
The new characteristics of Wireless Multimedia Sensor Network (WMSN) and its design issues brought by handling different traffic classes of multimedia content (video streams, audio, and still images) as well as scalar data over the network, make the proposed routing protocols for typical WSNs not directly applicable for WMSNs. Handling real-time multimedia data requires both energy efficiency and QoS assurance in order to ensure efficient utility of different capabilities of sensor resources and correct delivery of collected information. In this paper, we propose a Secure Cluster-based Multipath Routing protocol for WMSNs, SCMR, to satisfy the requirements of delivering different data types and support high data rate multimedia traffic. SCMR exploits the hierarchical structure of powerful cluster heads and the optimized multiple paths to support timeliness and reliable high data rate multimedia communication with minimum energy dissipation. Also, we present a light-weight distributed security mechanism of key management in order to secure the communication between sensor nodes and protect the network against different types of attacks. Performance evaluation from simulation results demonstrates a significant performance improvement comparing with existing protocols (which do not even provide any kind of security feature) in terms of average end-to-end delay, network throughput, packet delivery ratio, and energy consumption. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A New HLA-Based Distributed Control Architecture for Agricultural Teams of Robots in Hybrid Applications with Real and Simulated Devices or Environments
Sensors 2011, 11(4), 4385-4400; https://doi.org/10.3390/s110404385
Received: 15 February 2011 / Revised: 2 April 2011 / Accepted: 13 April 2011 / Published: 14 April 2011
Cited by 10 | Viewed by 5866 | PDF Full-text (7940 KB) | HTML Full-text | XML Full-text
Abstract
The control architecture is one of the most important part of agricultural robotics and other robotic systems. Furthermore its importance increases when the system involves a group of heterogeneous robots that should cooperate to achieve a global goal. A new control architecture is [...] Read more.
The control architecture is one of the most important part of agricultural robotics and other robotic systems. Furthermore its importance increases when the system involves a group of heterogeneous robots that should cooperate to achieve a global goal. A new control architecture is introduced in this paper for groups of robots in charge of doing maintenance tasks in agricultural environments. Some important features such as scalability, code reuse, hardware abstraction and data distribution have been considered in the design of the new architecture. Furthermore, coordination and cooperation among the different elements in the system is allowed in the proposed control system. By integrating a network oriented device server Player, Java Agent Development Framework (JADE) and High Level Architecture (HLA), the previous concepts have been considered in the new architecture presented in this paper. HLA can be considered the most important part because it not only allows the data distribution and implicit communication among the parts of the system but also allows to simultaneously operate with simulated and real entities, thus allowing the use of hybrid systems in the development of applications. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle
Boosting-Based On-Road Obstacle Sensing Using Discriminative Weak Classifiers
Sensors 2011, 11(4), 4372-4384; https://doi.org/10.3390/s110404372
Received: 14 January 2011 / Revised: 20 March 2011 / Accepted: 12 April 2011 / Published: 14 April 2011
Cited by 3 | Viewed by 3792 | PDF Full-text (278 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an extension of the weak classifiers derived from the Haar-like features for their use in the Viola-Jones object detection system. These weak classifiers differ from the traditional single threshold ones, in that no specific threshold is needed and these classifiers [...] Read more.
This paper proposes an extension of the weak classifiers derived from the Haar-like features for their use in the Viola-Jones object detection system. These weak classifiers differ from the traditional single threshold ones, in that no specific threshold is needed and these classifiers give a more general solution to the non-trivial task of finding thresholds for the Haar-like features. The proposed quadratic discriminant analysis based extension prominently improves the ability of the weak classifiers to discriminate objects and non-objects. The proposed weak classifiers were evaluated by boosting a single stage classifier to detect rear of car. The experiments demonstrate that the object detector based on the proposed weak classifiers yields higher classification performance with less number of weak classifiers than the detector built with traditional single threshold weak classifiers. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Estimation of Distributed Fermat-Point Location for Wireless Sensor Networking
Sensors 2011, 11(4), 4358-4371; https://doi.org/10.3390/s110404358
Received: 28 February 2011 / Revised: 14 March 2011 / Accepted: 11 April 2011 / Published: 13 April 2011
Cited by 7 | Viewed by 4822 | PDF Full-text (508 KB) | HTML Full-text | XML Full-text
Abstract
This work presents a localization scheme for use in wireless sensor networks (WSNs) that is based on a proposed connectivity-based RF localization strategy called the distributed Fermat-point location estimation algorithm (DFPLE). DFPLE applies triangle area of location estimation formed by intersections of three [...] Read more.
This work presents a localization scheme for use in wireless sensor networks (WSNs) that is based on a proposed connectivity-based RF localization strategy called the distributed Fermat-point location estimation algorithm (DFPLE). DFPLE applies triangle area of location estimation formed by intersections of three neighboring beacon nodes. The Fermat point is determined as the shortest path from three vertices of the triangle. The area of estimated location then refined using Fermat point to achieve minimum error in estimating sensor nodes location. DFPLE solves problems of large errors and poor performance encountered by localization schemes that are based on a bounding box algorithm. Performance analysis of a 200-node development environment reveals that, when the number of sensor nodes is below 150, the mean error decreases rapidly as the node density increases, and when the number of sensor nodes exceeds 170, the mean error remains below 1% as the node density increases. Second, when the number of beacon nodes is less than 60, normal nodes lack sufficient beacon nodes to enable their locations to be estimated. However, the mean error changes slightly as the number of beacon nodes increases above 60. Simulation results revealed that the proposed algorithm for estimating sensor positions is more accurate than existing algorithms, and improves upon conventional bounding box strategies. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Fused Smart Sensor Network for Multi-Axis Forward Kinematics Estimation in Industrial Robots
Sensors 2011, 11(4), 4335-4357; https://doi.org/10.3390/s110404335
Received: 9 March 2011 / Revised: 8 April 2011 / Accepted: 12 April 2011 / Published: 13 April 2011
Cited by 14 | Viewed by 7524 | PDF Full-text (2403 KB) | HTML Full-text | XML Full-text
Abstract
Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that [...] Read more.
Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that decrease the accuracy of the robot position and orientation. To overcome those problems, several sensor fusion methods have been proposed but at expenses of high-computational load, which avoids the online measurement of the joint’s angular position and the online forward kinematics estimation. The contribution of this work is to propose a fused smart sensor network to estimate the forward kinematics of an industrial robot. The developed smart processor uses Kalman filters to filter and to fuse the information of the sensor network. Two primary sensors are used: an optical encoder, and a 3-axis accelerometer. In order to obtain the position and orientation of each joint online a field-programmable gate array (FPGA) is used in the hardware implementation taking advantage of the parallel computation capabilities and reconfigurability of this device. With the aim of evaluating the smart sensor network performance, three real-operation-oriented paths are executed and monitored in a 6-degree of freedom robot. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Non-Contact Plant Growth Measurement Method and System Based on Ubiquitous Sensor Network Technologies
Sensors 2011, 11(4), 4312-4334; https://doi.org/10.3390/s110404312
Received: 14 January 2011 / Revised: 14 March 2011 / Accepted: 12 April 2011 / Published: 13 April 2011
Cited by 4 | Viewed by 5250 | PDF Full-text (2271 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a non-contact plant growth measurement system using infrared sensors based on the ubiquitous sensor network (USN) technology. The proposed system measures plant growth parameters such as the stem radius of plants using real-time non-contact methods, and generates diameter, cross-sectional area [...] Read more.
This paper proposes a non-contact plant growth measurement system using infrared sensors based on the ubiquitous sensor network (USN) technology. The proposed system measures plant growth parameters such as the stem radius of plants using real-time non-contact methods, and generates diameter, cross-sectional area and thickening form of plant stems using this measured data. Non-contact sensors have been used not to cause any damage to plants during measurement of the growth parameters. Once the growth parameters are measured, they are transmitted to a remote server using the sensor network technology and analyzed in the application program server. The analyzed data are then provided for administrators and a group of interested users. The proposed plant growth measurement system has been designed and implemented using fixed-type and rotary-type infrared sensor based measurement methods and devices. Finally, the system performance is compared and verified with the measurement data that have been obtained by practical field experiments. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Methodology for the Regulation of Boom Sprayers Operating in Circular Trajectories
Sensors 2011, 11(4), 4295-4311; https://doi.org/10.3390/s110404295
Received: 1 February 2011 / Revised: 23 March 2011 / Accepted: 11 April 2011 / Published: 13 April 2011
Cited by 3 | Viewed by 4730 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
A methodology for the regulation of boom sprayers working in circular trajectories has been developed. In this type of trajectory, the areas of the plots of land treated by the outer nozzles of the boom are treated at reduced rates, and those treated [...] Read more.
A methodology for the regulation of boom sprayers working in circular trajectories has been developed. In this type of trajectory, the areas of the plots of land treated by the outer nozzles of the boom are treated at reduced rates, and those treated by the inner nozzles are treated in excess. The goal of this study was to establish the methodology to determine the flow of the individual nozzles on the boom to guarantee that the dose of the product applied per surface unit is similar across the plot. This flow is a function of the position of the equipment (circular trajectory radius) and of the displacement velocity such that the treatment applied per surface unit is uniform. GPS technology was proposed as a basis to establish the position and displacement velocity of the tractor. The viability of this methodology was simulated considering two circular plots with radii of 160 m and 310 m, using three sets of equipment with boom widths of 14.5, 24.5 and 29.5 m. Data showed as increasing boom widths produce bigger errors in the surface dose applied (L/m2). Error also increases with decreasing plot surface. As an example, considering the three boom widths of 14.5, 24.5 and 29.5 m working on a circular plot with a radius of 160 m, the percentage of surface with errors in the applied surface dose greater than 5% was 30%, 58% and 65% respectively. Considering a circular plot with radius of 310 m the same errors were 8%, 22% and 31%. To obtain a uniform superficial dose two sprayer regulation alternatives have been simulated considering a 14.5 m boom: the regulation of the pressure of each nozzle and the regulation of the pressure of each boom section. The viability of implementing the proposed methodology on commercial boom sprayers using GPS antennas to establish the position and displacement velocity of the tractor was justified with a field trial in which a self-guiding commercial GPS system was used along with three precision GPS systems located in the sprayer boom. The use of an unique central GPS unit should allow the estimation of the work parameters of the boom nozzles (including those located at the boom ends) with great accuracy. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
Open AccessReview
Biological Sensors for Solar Ultraviolet Radiation
Sensors 2011, 11(4), 4277-4294; https://doi.org/10.3390/s110404277
Received: 12 February 2011 / Revised: 2 April 2011 / Accepted: 4 April 2011 / Published: 12 April 2011
Cited by 28 | Viewed by 10376 | PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
Solar ultraviolet (UV) radiation is widely known as a genotoxic environmental agent that affects Earth ecosystems and the human population. As a primary consequence of the stratospheric ozone layer depletion observed over the last decades, the increasing UV incidence levels have heightened the [...] Read more.
Solar ultraviolet (UV) radiation is widely known as a genotoxic environmental agent that affects Earth ecosystems and the human population. As a primary consequence of the stratospheric ozone layer depletion observed over the last decades, the increasing UV incidence levels have heightened the concern regarding deleterious consequences affecting both the biosphere and humans, thereby leading to an increase in scientific efforts to understand the role of sunlight in the induction of DNA damage, mutagenesis, and cell death. In fact, the various UV-wavelengths evoke characteristic biological impacts that greatly depend on light absorption of biomolecules, especially DNA, in living organisms, thereby justifying the increasing importance of developing biological sensors for monitoring the harmful impact of solar UV radiation under various environmental conditions. In this review, several types of biosensors proposed for laboratory and field application, that measure the biological effects of the UV component of sunlight, are described. Basically, the applicability of sensors based on DNA, bacteria or even mammalian cells are presented and compared. Data are also presented showing that on using DNA-based sensors, the various types of damage produced differ when this molecule is exposed in either an aqueous buffer or a dry solution. Apart from the data thus generated, the development of novel biosensors could help in evaluating the biological effects of sunlight on the environment. They also emerge as alternative tools for using live animals in the search for protective sunscreen products. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
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Open AccessArticle
Tightly Coupled Low Cost 3D RISS/GPS Integration Using a Mixture Particle Filter for Vehicular Navigation
Sensors 2011, 11(4), 4244-4276; https://doi.org/10.3390/s110404244
Received: 15 February 2011 / Revised: 2 April 2011 / Accepted: 7 April 2011 / Published: 8 April 2011
Cited by 7 | Viewed by 6279 | PDF Full-text (6698 KB) | HTML Full-text | XML Full-text
Abstract
Satellite navigation systems such as the global positioning system (GPS) are currently the most common technique used for land vehicle positioning. However, in GPS-denied environments, there is an interruption in the positioning information. Low-cost micro-electro mechanical system (MEMS)-based inertial sensors can be integrated [...] Read more.
Satellite navigation systems such as the global positioning system (GPS) are currently the most common technique used for land vehicle positioning. However, in GPS-denied environments, there is an interruption in the positioning information. Low-cost micro-electro mechanical system (MEMS)-based inertial sensors can be integrated with GPS and enhance the performance in denied GPS environments. The traditional technique for this integration problem is Kalman filtering (KF). Due to the inherent errors of low-cost MEMS inertial sensors and their large stochastic drifts, KF, with its linearized models, has limited capabilities in providing accurate positioning. Particle filtering (PF) was recently suggested as a nonlinear filtering technique to accommodate for arbitrary inertial sensor characteristics, motion dynamics and noise distributions. An enhanced version of PF called the Mixture PF is utilized in this study to perform tightly coupled integration of a three dimensional (3D) reduced inertial sensors system (RISS) with GPS. In this work, the RISS consists of one single-axis gyroscope and a two-axis accelerometer used together with the vehicle’s odometer to obtain 3D navigation states. These sensors are then integrated with GPS in a tightly coupled scheme. In loosely-coupled integration, at least four satellites are needed to provide acceptable GPS position and velocity updates for the integration filter. The advantage of the tightly-coupled integration is that it can provide GPS measurement update(s) even when the number of visible satellites is three or lower, thereby improving the operation of the navigation system in environments with partial blockages by providing continuous aiding to the inertial sensors even during limited GPS satellite availability. To effectively exploit the capabilities of PF, advanced modeling for the stochastic drift of the vertically aligned gyroscope is used. In order to benefit from measurement updates for such drift, which are loosely-coupled updates, a hybrid loosely/tightly coupled solution is proposed. This solution is suitable for downtown environments because of the long natural outages or degradation of GPS. The performance of the proposed 3D Navigation solution using Mixture PF for 3D RISS/GPS integration is examined by road test trajectories in a land vehicle and compared to the KF counterpart. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
SMS-Based Medical Diagnostic Telemetry Data Transmission Protocol for Medical Sensors
Sensors 2011, 11(4), 4231-4243; https://doi.org/10.3390/s110404231
Received: 10 February 2011 / Revised: 28 March 2011 / Accepted: 2 April 2011 / Published: 8 April 2011
Cited by 8 | Viewed by 4936 | PDF Full-text (345 KB) | HTML Full-text | XML Full-text
Abstract
People with special medical monitoring needs can, these days, be sent home and remotely monitored through the use of data logging medical sensors and a transmission base-station. While this can improve quality of life by allowing the patient to spend most of their [...] Read more.
People with special medical monitoring needs can, these days, be sent home and remotely monitored through the use of data logging medical sensors and a transmission base-station. While this can improve quality of life by allowing the patient to spend most of their time at home, most current technologies rely on hardwired landline technology or expensive mobile data transmissions to transmit data to a medical facility. The aim of this paper is to investigate and develop an approach to increase the freedom of a monitored patient and decrease costs by utilising mobile technologies and SMS messaging to transmit data from patient to medico. To this end, we evaluated the capabilities of SMS and propose a generic communications protocol which can work within the constraints of the SMS format, but provide the necessary redundancy and robustness to be used for the transmission of non-critical medical telemetry from data logging medical sensors. Full article
Open AccessCommunication
Applying Rprop Neural Network for the Prediction of the Mobile Station Location
Sensors 2011, 11(4), 4207-4230; https://doi.org/10.3390/s110404207
Received: 5 January 2011 / Revised: 17 March 2011 / Accepted: 1 April 2011 / Published: 8 April 2011
Cited by 10 | Viewed by 5386 | PDF Full-text (555 KB) | HTML Full-text | XML Full-text
Abstract
Wireless location is the function used to determine the mobile station (MS) location in a wireless cellular communications system. When it is very hard for the surrounding base stations (BSs) to detect a MS or the measurements contain large errors in non-line-of-sight (NLOS) [...] Read more.
Wireless location is the function used to determine the mobile station (MS) location in a wireless cellular communications system. When it is very hard for the surrounding base stations (BSs) to detect a MS or the measurements contain large errors in non-line-of-sight (NLOS) environments, then one need to integrate all available heterogeneous measurements to increase the location accuracy. In this paper we propose a novel algorithm that combines both time of arrival (TOA) and angle of arrival (AOA) measurements to estimate the MS in NLOS environments. The proposed algorithm utilizes the intersections of two circles and two lines, based on the most resilient back-propagation (Rprop) neural network learning technique, to give location estimation of the MS. The traditional Taylor series algorithm (TSA) and the hybrid lines of position algorithm (HLOP) have convergence problems, and even if the measurements are fairly accurate, the performance of these algorithms depends highly on the relative position of the MS and BSs. Different NLOS models were used to evaluate the proposed methods. Numerical results demonstrate that the proposed algorithms can not only preserve the convergence solution, but obtain precise location estimations, even in severe NLOS conditions, particularly when the geometric relationship of the BSs relative to the MS is poor. Full article
(This article belongs to the Special Issue Adaptive Sensing)
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Open AccessArticle
Can Infrared Spectroscopy Be Used to Measure Change in Potassium Nitrate Concentration as a Proxy for Soil Particle Movement?
Sensors 2011, 11(4), 4188-4206; https://doi.org/10.3390/s110404188
Received: 11 March 2011 / Revised: 6 April 2011 / Accepted: 7 April 2011 / Published: 7 April 2011
Cited by 10 | Viewed by 6085 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text
Abstract
Displacement of soil particles caused by erosion influences soil condition and fertility. To date, the cesium 137 isotope (137Cs) technique is most commonly used for soil particle tracing. However when large areas are considered, the expensive soil sampling and analysis present [...] Read more.
Displacement of soil particles caused by erosion influences soil condition and fertility. To date, the cesium 137 isotope (137Cs) technique is most commonly used for soil particle tracing. However when large areas are considered, the expensive soil sampling and analysis present an obstacle. Infrared spectral measurements would provide a solution, however the small concentrations of the isotope do not influence the spectral signal sufficiently. Potassium (K) has similar electrical, chemical and physical properties as Cs. Our hypothesis is that it can be used as possible replacement in soil particle tracing. Soils differing in texture were sampled for the study. Laboratory soil chemical analyses and spectral sensitivity analyses were carried out to identify the wavelength range related to K concentration. Different concentrations of K fertilizer were added to soils with varying texture properties in order to establish spectral characteristics of the absorption feature associated with the element. Changes in position of absorption feature center were observed at wavelengths between 2,450 and 2,470 nm, depending on the amount of fertilizer applied. Other absorption feature parameters (absorption band depth, width and area) were also found to change with K concentration with coefficient of determination between 0.85 and 0.99. Tracing soil particles using K fertilizer and infrared spectral response is considered suitable for soils with sandy and sandy silt texture. It is a new approach that can potentially grow to a technique for rapid monitoring of soil particle movement over large areas. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
Open AccessReview
Recent Progress in Brillouin Scattering Based Fiber Sensors
Sensors 2011, 11(4), 4152-4187; https://doi.org/10.3390/s110404152
Received: 6 February 2011 / Revised: 25 March 2011 / Accepted: 30 March 2011 / Published: 7 April 2011
Cited by 280 | Viewed by 11617 | PDF Full-text (648 KB) | HTML Full-text | XML Full-text
Abstract
Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency [...] Read more.
Brillouin scattering in optical fiber describes the interaction of an electro-magnetic field (photon) with a characteristic density variation of the fiber. When the electric field amplitude of an optical beam (so-called pump wave), and another wave is introduced at the downshifted Brillouin frequency (namely Stokes wave), the beating between the pump and Stokes waves creates a modified density change via the electrostriction effect, resulting in so-called the stimulated Brillouin scattering. The density variation is associated with a mechanical acoustic wave; and it may be affected by local temperature, strain, and vibration which induce changes in the fiber effective refractive index and sound velocity. Through the measurement of the static or dynamic changes in Brillouin frequency along the fiber one can realize a distributed fiber sensor for local temperature, strain and vibration over tens or hundreds of kilometers. This paper reviews the progress on improving sensing performance parameters like spatial resolution, sensing length limitation and simultaneous temperature and strain measurement. These kinds of sensors can be used in civil structural monitoring of pipelines, bridges, dams, and railroads for disaster prevention. Analogous to the static Bragg grating, one can write a moving Brillouin grating in fibers, with the lifetime of the acoustic wave. The length of the Brillouin grating can be controlled by the writing pulses at any position in fibers. Such gratings can be used to measure changes in birefringence, which is an important parameter in fiber communications. Applications for this kind of sensor can be found in aerospace, material processing and fine structures. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada)
Open AccessReview
Bioinspired Principles for Large-Scale Networked Sensor Systems: An Overview
Sensors 2011, 11(4), 4137-4151; https://doi.org/10.3390/s110404137
Received: 17 January 2011 / Revised: 21 March 2011 / Accepted: 23 March 2011 / Published: 7 April 2011
Cited by 17 | Viewed by 6233 | PDF Full-text (783 KB) | HTML Full-text | XML Full-text
Abstract
Biology has often been used as a source of inspiration in computer science and engineering. Bioinspired principles have found their way into network node design and research due to the appealing analogies between biological systems and large networks of small sensors. This paper [...] Read more.
Biology has often been used as a source of inspiration in computer science and engineering. Bioinspired principles have found their way into network node design and research due to the appealing analogies between biological systems and large networks of small sensors. This paper provides an overview of bioinspired principles and methods such as swarm intelligence, natural time synchronization, artificial immune system and intercellular information exchange applicable for sensor network design. Bioinspired principles and methods are discussed in the context of routing, clustering, time synchronization, optimal node deployment, localization and security and privacy. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
Open AccessArticle
A Lightweight Data Integrity Scheme for Sensor Networks
Sensors 2011, 11(4), 4118-4136; https://doi.org/10.3390/s110404118
Received: 10 March 2011 / Accepted: 6 April 2011 / Published: 7 April 2011
Cited by 32 | Viewed by 4884 | PDF Full-text (345 KB) | HTML Full-text | XML Full-text
Abstract
Limited energy is the most critical constraint that limits the capabilities of wireless sensor networks (WSNs). Most sensors operate on batteries with limited power. Battery recharging or replacement may be impossible. Security mechanisms that are based on public key cryptographic algorithms such as [...] Read more.
Limited energy is the most critical constraint that limits the capabilities of wireless sensor networks (WSNs). Most sensors operate on batteries with limited power. Battery recharging or replacement may be impossible. Security mechanisms that are based on public key cryptographic algorithms such as RSA and digital signatures are prohibitively expensive in terms of energy consumption and storage requirements, and thus unsuitable for WSN applications. This paper proposes a new fragile watermarking technique to detect unauthorized alterations in WSN data streams. We propose the FWC-D scheme, which uses group delimiters to keep the sender and receivers synchronized and help them to avoid ambiguity in the event of data insertion or deletion. The watermark, which is computed using a hash function, is stored in the previous group in a linked-list fashion to ensure data freshness and mitigate replay attacks, FWC-D generates a serial number SN that is attached to each group to help the receiver determines how many group insertions or deletions occurred. Detailed security analysis that compares the proposed FWC-D scheme with SGW, one of the latest integrity schemes for WSNs, shows that FWC-D is more robust than SGW. Simulation results further show that the proposed scheme is much faster than SGW. Full article
Open AccessArticle
A Distance-Aware Replica Adaptive Data Gathering Protocol for Delay Tolerant Mobile Sensor Networks
Sensors 2011, 11(4), 4104-4117; https://doi.org/10.3390/s110404104
Received: 9 February 2011 / Revised: 18 March 2011 / Accepted: 21 March 2011 / Published: 6 April 2011
Cited by 17 | Viewed by 4720 | PDF Full-text (571 KB) | HTML Full-text | XML Full-text
Abstract
In Delay Tolerant Mobile Sensor Networks (DTMSNs) that have the inherent features of intermitted connectivity and frequently changing network topology it is reasonable to utilize multi-replica schemes to improve the data gathering performance. However, most existing multi-replica approaches inject a large amount of [...] Read more.
In Delay Tolerant Mobile Sensor Networks (DTMSNs) that have the inherent features of intermitted connectivity and frequently changing network topology it is reasonable to utilize multi-replica schemes to improve the data gathering performance. However, most existing multi-replica approaches inject a large amount of message copies into the network to increase the probability of message delivery, which may drain each mobile node’s limited battery supply faster and result in too much contention for the restricted resources of the DTMSN, so a proper data gathering scheme needs a trade off between the number of replica messages and network performance. In this paper, we propose a new data gathering protocol called DRADG (for Distance-aware Replica Adaptive Data Gathering protocol), which economizes network resource consumption through making use of a self-adapting algorithm to cut down the number of redundant replicas of messages, and achieves a good network performance by leveraging the delivery probabilities of the mobile sensors as main routing metrics. Simulation results have shown that the proposed DRADG protocol achieves comparable or higher message delivery ratios at the cost of the much lower transmission overhead than several current DTMSN data gathering schemes. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A New Approach to Visual-Based Sensory System for Navigation into Orange Groves
Sensors 2011, 11(4), 4086-4103; https://doi.org/10.3390/s110404086
Received: 6 February 2011 / Revised: 30 March 2011 / Accepted: 31 March 2011 / Published: 6 April 2011
Cited by 6 | Viewed by 4429 | PDF Full-text (2597 KB) | HTML Full-text | XML Full-text
Abstract
One of the most important parts of an autonomous robot is to establish the path by which it should navigate in order to successfully achieve its goals. In the case of agricultural robotics, a procedure that determines this desired path can be useful. [...] Read more.
One of the most important parts of an autonomous robot is to establish the path by which it should navigate in order to successfully achieve its goals. In the case of agricultural robotics, a procedure that determines this desired path can be useful. In this paper, a new virtual sensor is introduced in order to classify the elements of an orange grove. This proposed sensor will be based on a color CCD camera with auto iris lens which is in charge of doing the captures of the real environment and an ensemble of neural networks which processes the capture and differentiates each element of the image. Then, the Hough’s transform and other operations will be applied in order to extract the desired path from the classification performed by the virtual sensory system. With this approach, the robotic system can correct its deviation with respect to the desired path. The results show that the sensory system properly classifies the elements of the grove and can set trajectory of the robot. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle
Determination of Moisture Content in Oil Palm Fruits Using a Five-Port Reflectometer
Sensors 2011, 11(4), 4073-4085; https://doi.org/10.3390/s110404073
Received: 8 March 2011 / Revised: 5 April 2011 / Accepted: 5 April 2011 / Published: 6 April 2011
Cited by 18 | Viewed by 5947 | PDF Full-text (428 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone [...] Read more.
This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone reflectometer consists of a PC, a microwave source, diode detectors and an analog to digital converter. All the measurement and data acquisition were done using Agilent VEE graphical programming software. The relectometer can be used with any reflection based microwave sensor. In this work, the application of the reflectometer as a useful instrument to determine the moisture content in oil palm fruits using monopole and coaxial sensors was demonstrated. Calibration equations between reflection coefficients and moisture content have been established for both sensors. The equation based on phase measurement of monopole sensor was found to be accurate within 5% in predicting moisture content in the fruits when compared to the conventional oven drying method. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
Open AccessArticle
Bromocresol Green/Mesoporous Silica Adsorbent for Ammonia Gas Sensing via an Optical Sensing Instrument
Sensors 2011, 11(4), 4060-4072; https://doi.org/10.3390/s110404060
Received: 20 January 2011 / Revised: 18 March 2011 / Accepted: 18 March 2011 / Published: 6 April 2011
Cited by 29 | Viewed by 6633 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text
Abstract
A meso-structured Al-MCM-41 material was impregnated with bromocresol green (BG) dye and then incorporated into a UV-Vis DRA spectroscopic instrument for the online detection of ammonia gas. The absorption response of the Al-MCM-41/BG ammonia sensing material was very sensitive at the optical absorption [...] Read more.
A meso-structured Al-MCM-41 material was impregnated with bromocresol green (BG) dye and then incorporated into a UV-Vis DRA spectroscopic instrument for the online detection of ammonia gas. The absorption response of the Al-MCM-41/BG ammonia sensing material was very sensitive at the optical absorption wavelength of 630 nm. A high linear correlation was achieved for ppmv and sub-ppmv levels of ammonia gas. The response time for the quantitative detection of ammonia gas concentrations ranging from 0.25 to 2.0 ppmv was only a few minutes. The lower detection limit achieved was 0.185 ppmv. The color change process was fully reversible during tens of cycling tests. These features together make this mesoporous Al-MCM-41 material very promising for optical sensing applications. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
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Open AccessArticle
Detection, Composition and Treatment of Volatile Organic Compounds from Waste Treatment Plants
Sensors 2011, 11(4), 4043-4059; https://doi.org/10.3390/s110404043
Received: 23 February 2011 / Revised: 18 March 2011 / Accepted: 1 April 2011 / Published: 6 April 2011
Cited by 30 | Viewed by 7396 | PDF Full-text (290 KB) | HTML Full-text | XML Full-text
Abstract
Environmental policies at the European and global level support the diversion of wastes from landfills for their treatment in different facilities. Organic waste is mainly treated or valorized through composting, anaerobic digestion or a combination of both treatments. Thus, there are an increasing [...] Read more.
Environmental policies at the European and global level support the diversion of wastes from landfills for their treatment in different facilities. Organic waste is mainly treated or valorized through composting, anaerobic digestion or a combination of both treatments. Thus, there are an increasing number of waste treatment plants using this type of biological treatment. During waste handling and biological decomposition steps a number of gaseous compounds are generated or removed from the organic matrix and emitted. Different families of Volatile Organic Compounds (VOC) can be found in these emissions. Many of these compounds are also sources of odor nuisance. In fact, odors are the main source of complaints and social impacts of any waste treatment plant. This work presents a summary of the main types of VOC emitted in organic waste treatment facilities and the methods used to detect and quantify these compounds, together with the treatment methods applied to gaseous emissions commonly used in composting and anaerobic digestion facilities. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
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Open AccessArticle
Surface Plasmon Resonance Based Biosensors for Exploring the Influence of Alkaloids on Aggregation of Amyloid-β Peptide
Sensors 2011, 11(4), 4030-4042; https://doi.org/10.3390/s110404030
Received: 16 February 2011 / Revised: 16 March 2011 / Accepted: 28 March 2011 / Published: 6 April 2011
Cited by 16 | Viewed by 4788 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
The main objective of the presented study was the development of a simple analytical tool for exploring the influence of naturally occurring compounds on the aggregation of amyloid-β peptide (Aβ40) in order to find potential anti-neurodegenerative drugs. The gold discs used [...] Read more.
The main objective of the presented study was the development of a simple analytical tool for exploring the influence of naturally occurring compounds on the aggregation of amyloid-β peptide (Aβ40) in order to find potential anti-neurodegenerative drugs. The gold discs used for surface plasmon resonance (SPR) measurements were modified with thioaliphatic acid. The surface functionalized with carboxylic groups was used for covalent attaching of Aβ40 probe by creation of amide bonds in the presence of EDC/NHS. The modified SPR gold discs were used for exploring the Aβ40 aggregation process in the presence of selected alkaloids: arecoline hydrobromide, pseudopelletierine hydrochloride, trigonelline hydrochloride and α-lobeline hydrochloride. The obtained results were discussed with other parameters which govern the phenomenon studied such as lipophilicity/ hydrophilicy and Aβ40-alkaloid association constants. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
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Open AccessArticle
Intelligent Method for Diagnosing Structural Faults of Rotating Machinery Using Ant Colony Optimization
Sensors 2011, 11(4), 4009-4029; https://doi.org/10.3390/s110404009
Received: 9 March 2011 / Revised: 1 April 2011 / Accepted: 6 April 2011 / Published: 6 April 2011
Cited by 2 | Viewed by 4413 | PDF Full-text (552 KB) | HTML Full-text | XML Full-text
Abstract
Structural faults, such as unbalance, misalignment and looseness, etc., often occur in the shafts of rotating machinery. These faults may cause serious machine accidents and lead to great production losses. This paper proposes an intelligent method for diagnosing structural faults of rotating [...] Read more.
Structural faults, such as unbalance, misalignment and looseness, etc., often occur in the shafts of rotating machinery. These faults may cause serious machine accidents and lead to great production losses. This paper proposes an intelligent method for diagnosing structural faults of rotating machinery using ant colony optimization (ACO) and relative ratio symptom parameters (RRSPs) in order to detect faults and distinguish fault types at an early stage. New symptom parameters called “relative ratio symptom parameters” are defined for reflecting the features of vibration signals measured in each state. Synthetic detection index (SDI) using statistical theory has also been defined to evaluate the applicability of the RRSPs. The SDI can be used to indicate the fitness of a RRSP for ACO. Lastly, this paper also compares the proposed method with the conventional neural networks (NN) method. Practical examples of fault diagnosis for a centrifugal fan are provided to verify the effectiveness of the proposed method. The verification results show that the structural faults often occurring in the centrifugal fan, such as unbalance, misalignment and looseness states are effectively identified by the proposed method, while these faults are difficult to detect using conventional neural networks. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessArticle
An Intelligent Tool for Activity Data Collection
Sensors 2011, 11(4), 3988-4008; https://doi.org/10.3390/s110403988
Received: 8 February 2011 / Revised: 14 March 2011 / Accepted: 30 March 2011 / Published: 6 April 2011
Cited by 2 | Viewed by 4917 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
Activity recognition systems using simple and ubiquitous sensors require a large variety of real-world sensor data for not only evaluating their performance but also training the systems for better functioning. However, a tremendous amount of effort is required to setup an environment for [...] Read more.
Activity recognition systems using simple and ubiquitous sensors require a large variety of real-world sensor data for not only evaluating their performance but also training the systems for better functioning. However, a tremendous amount of effort is required to setup an environment for collecting such data. For example, expertise and resources are needed to design and install the sensors, controllers, network components, and middleware just to perform basic data collections. It is therefore desirable to have a data collection method that is inexpensive, flexible, user-friendly, and capable of providing large and diverse activity datasets. In this paper, we propose an intelligent activity data collection tool which has the ability to provide such datasets inexpensively without physically deploying the testbeds. It can be used as an inexpensive and alternative technique to collect human activity data. The tool provides a set of web interfaces to create a web-based activity data collection environment. It also provides a web-based experience sampling tool to take the user’s activity input. The tool generates an activity log using its activity knowledge and the user-given inputs. The activity knowledge is mined from the web. We have performed two experiments to validate the tool’s performance in producing reliable datasets. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
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Open AccessArticle
Metallo-Graphene Nanocomposite Electrocatalytic Platform for the Determination of Toxic Metal Ions
Sensors 2011, 11(4), 3970-3987; https://doi.org/10.3390/s110403970
Received: 13 February 2011 / Revised: 20 March 2011 / Accepted: 23 March 2011 / Published: 1 April 2011
Cited by 100 | Viewed by 6017 | PDF Full-text (1049 KB) | HTML Full-text | XML Full-text
Abstract
A Nafion-Graphene (Nafion-G) nanocomposite solution in combination with an in situ plated mercury film electrode was used as a highly sensitive electrochemical platform for the determination of Zn2+, Cd2+, Pb2+ and Cu2+ in 0.1 M acetate buffer [...] Read more.
A Nafion-Graphene (Nafion-G) nanocomposite solution in combination with an in situ plated mercury film electrode was used as a highly sensitive electrochemical platform for the determination of Zn2+, Cd2+, Pb2+ and Cu2+ in 0.1 M acetate buffer (pH 4.6) by square-wave anodic stripping voltammetry (SWASV). Various operational parameters such as deposition potential, deposition time and electrode rotation speed were optimized. The Nafion-G nanocomposite sensing platform exhibited improved sensitivity for metal ion detection, in addition to well defined, reproducible and sharp stripping signals. The linear calibration curves ranged from 1 µg L−1 to 7 µg L−1 for individual analysis. The detection limits (3σ blank/slope) obtained were 0.07 µg L−1 for Pb2+, Zn2+ and Cu2+ and 0.08 µg L−1 for Cd2+ at a deposition time of 120 s. For practical applications recovery studies was done by spiking test samples with known concentrations and comparing the results with inductively coupled plasma mass spectrometry (ICP-MS) analyses. This was followed by real sample analysis. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessCommunication
Novel Mechano-Luminescent Sensors Based on Piezoelectric/Electroluminescent Composites
Sensors 2011, 11(4), 3962-3969; https://doi.org/10.3390/s110403962
Received: 21 February 2011 / Revised: 17 March 2011 / Accepted: 31 March 2011 / Published: 1 April 2011
Cited by 9 | Viewed by 4756 | PDF Full-text (679 KB) | HTML Full-text | XML Full-text
Abstract
A high-sensitivity mechano-luminescent sensor was fabricated on the basis of piezoelectric/electroluminescent composites. The working principle of this mechano-luminescent sensor was elucidated by analyzing the relationship between the piezoelectric-induced charges and the electroluminescent effects. When a stress is applied on the piezoelectric layer, electrical [...] Read more.
A high-sensitivity mechano-luminescent sensor was fabricated on the basis of piezoelectric/electroluminescent composites. The working principle of this mechano-luminescent sensor was elucidated by analyzing the relationship between the piezoelectric-induced charges and the electroluminescent effects. When a stress is applied on the piezoelectric layer, electrical charges will be induced at both the top and bottom sides of the piezoelectric layer. The induced electrical charges will lead to a light output from the electroluminescent layer, thus producing a mechano-luminescence effect. By increasing the vibration strength or frequency applied, the mechano-luminescence output can be obviously enhanced. Mechano-luminescence sensors have potential in smart stress-to-light devices, such as foot-stress-distribution-diagnosis systems and dynamic-load-monitors for bridge hanging cables. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Time-Frequency Analyses of Tide-Gauge Sensor Data
Sensors 2011, 11(4), 3939-3961; https://doi.org/10.3390/s110403939
Received: 21 February 2011 / Revised: 19 March 2011 / Accepted: 31 March 2011 / Published: 1 April 2011
Cited by 18 | Viewed by 5466 | PDF Full-text (1046 KB) | HTML Full-text | XML Full-text
Abstract
The real world phenomena being observed by sensors are generally non-stationary in nature. The classical linear techniques for analysis and modeling natural time-series observations are inefficient and should be replaced by non-linear techniques of whose theoretical aspects and performances are varied. In this [...] Read more.
The real world phenomena being observed by sensors are generally non-stationary in nature. The classical linear techniques for analysis and modeling natural time-series observations are inefficient and should be replaced by non-linear techniques of whose theoretical aspects and performances are varied. In this manner adopting the most appropriate technique and strategy is essential in evaluating sensors’ data. In this study, two different time-series analysis approaches, namely least squares spectral analysis (LSSA) and wavelet analysis (continuous wavelet transform, cross wavelet transform and wavelet coherence algorithms as extensions of wavelet analysis), are applied to sea-level observations recorded by tide-gauge sensors, and the advantages and drawbacks of these methods are reviewed. The analyses were carried out using sea-level observations recorded at the Antalya-II and Erdek tide-gauge stations of the Turkish National Sea-Level Monitoring System. In the analyses, the useful information hidden in the noisy signals was detected, and the common features between the two sea-level time series were clarified. The tide-gauge records have data gaps in time because of issues such as instrumental shortcomings and power outages. Concerning the difficulties of the time-frequency analysis of data with voids, the sea-level observations were preprocessed, and the missing parts were predicted using the neural network method prior to the analysis. In conclusion the merits and limitations of the techniques in evaluating non-stationary observations by means of tide-gauge sensors records were documented and an analysis strategy for the sequential sensors observations was presented. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Multi-Hop Localization Algorithm Based on Grid-Scanning for Wireless Sensor Networks
Sensors 2011, 11(4), 3908-3938; https://doi.org/10.3390/s110403908
Received: 6 January 2011 / Revised: 18 March 2011 / Accepted: 18 March 2011 / Published: 31 March 2011
Cited by 10 | Viewed by 4471 | PDF Full-text (911 KB) | HTML Full-text | XML Full-text
Abstract
For large-scale wireless sensor networks (WSNs) with a minority of anchor nodes, multi-hop localization is a popular scheme for determining the geographical positions of the normal nodes. However, in practice existing multi-hop localization methods suffer from various kinds of problems, such as poor [...] Read more.
For large-scale wireless sensor networks (WSNs) with a minority of anchor nodes, multi-hop localization is a popular scheme for determining the geographical positions of the normal nodes. However, in practice existing multi-hop localization methods suffer from various kinds of problems, such as poor adaptability to irregular topology, high computational complexity, low positioning accuracy, etc. To address these issues in this paper, we propose a novel Multi-hop Localization algorithm based on Grid‑Scanning (MLGS). First, the factors that influence the multi-hop distance estimation are studied and a more realistic multi-hop localization model is constructed. Then, the feasible regions of the normal nodes are determined according to the intersection of bounding square rings. Finally, a verifiably good approximation scheme based on grid-scanning is developed to estimate the coordinates of the normal nodes. Additionally, the positioning accuracy of the normal nodes can be improved through neighbors’ collaboration. Extensive simulations are performed in isotropic and anisotropic networks. The comparisons with some typical algorithms of node localization confirm the effectiveness and efficiency of our algorithm. Full article
(This article belongs to the Section Physical Sensors)
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