Sharif Digital Repository

One of the most important applications of wireless sensor networks is data collection. This paper proposes as efficient approach for data collection in wireless sensor networks by introducing Member Forward List. This list includes the nodes with highest priority for forwarding the data. When a node fails or dies, this list is used to select the next node with higher priority. The benefit of this node is that it prevents the algorithm from repeating when a node fails or dies. The results show that Member Forward List decreases power consumption and latency in wireless sensor networks  

Pure and Pd-doped WO3 Nanocrystalline tungsten oxide films on alumina substrates were prepared via sol-gel method from peroxopolytungstic acid. AFM, XRD, SEM, XPS methods were used to determine the surface morphology, grain size and layer composition. XRD analysis showed WO3 nanocrystalline particles in monoclinic phase and with average size of about 333nm, which was consistent with SEM analysis results. Sensing properties of samples toward H2 gas was studied. The sensitivity of WO3 nanocrystalline films was about 4 at 2300ppm (0.2%) H2 gas. Introducing Pd to the system led to an increase in the sensitivity about 2 orders of magnitude. The sensitivity of Pd: WO3 was about 400 at 2300ppmH2  

In this article, two possible applications of prism-based probes for liquid-switching, level-sensing, and as a refractometer are described. Theoretical formulation is developed for the emergent intensity for each system and possible range of operation for each system is reported. By comparing the theoretical investigations, some hints are given in optimum usage of prism in each case. Variation of the beam divergence, incident angle, and prism glass index are major parameters that are considered in this investigation. The obtained results are compared with some available experimental results and practical points concerning the effective application of each geometry is reported. Theoretical... 

The potentiometric response characteristics with respect to salicylate anion of several membrane electrodes based on iron(II) tetraphenylporphyrin chloride (FeTPPCl) and derivatives with electrophilic and nucleophilic substituents, incorporated into plasticized polyvinylchloride (PVC) membranes were investigated. Complexes tetraphenyl porphyrin iron(III) chloride (FeTPPCl; A), tetrakis (4-methoxyphenyl) porphyrin iron(III) chloride (Fe(TOCH 3PP)Cl; B), tetrakis (2,6-dichlorophenyl) porphyrin iron(III) chloride (Fe(TDClPP)Cl; C), tetrakis (4-nitrophenyl) porphyrin iron(III) chloride (Fe(TNO2PP)Cl; D), and tetrakis (pentafluorophenyl) porphyrin iron(III) chloride (Fe(TPFPP)Cl; E) were used as... 

In many industries there is a need for a flexible system, which is capable of picking up some objects of various shapes, weights, and colors with arbitrarily position and orientation. Such system requires recognition and guiding sub-systems. The recognition system includes target function for the recognition sub-system and relation between object characteristics and recognition target. The laser sensor system can be used for such object recognition. Wire-based telemetry and control systems can cause many problems in shop floors and factories, and so there has been a strong growth of interest in wireless guidance like vehicles equipped with laser guiding and navigation systems. This article... 

Design and operation of an optical fiber sensor based on the light leakage from one fiber to another one causing intensity modulation are reported. Performance of this sensor is tested as a liquid level sensor for different liquids and the experimental results are reported. The dry and wet signals for this probe are measured for a series of measurements and important factors concerning sensor operation are described. The precision of measured values, reproducibility of the results (1.3%), and the stability of sensing operation as a function of time at different launching powers are also reported (0.8%). The reported results are promising and verify the successful operation of such a device... 

Sound source localization has always been one of the most challenging subjects in different fields of engineering, one of the most important of which being tracking of flying objects. This article focuses on sound source localization using fuzzy fusion and a beamforming method. It proposes a new fuzzy-based algorithm for localizing a sound source using distributed sensor nodes. Eight low-cost sensor nodes have been constructed in this study each of which consists of a microphone array to capture sound waves. Each node is able to record audio signals synchronously on an SD card to evaluate different algorithms offline. However, the sensor nodes are designed to be able to estimate the location... 

Wireless Sensor Network (WSN) should be capable of fulfilling its mission, in a timely manner. Therefore, we propose a quantitative real-time model for multihop WSN. "Real-time degree" describes the percentage of real-time data that the network can deliver on time from any source to its destination. Most of network properties are considered as random variables and a queuing-theory based model is derived. In this model, the effect of network load on the packets ' delay and the "real-timeliness" of the network are considered. Simulation results are used to validate the proposed model. The simulation results agree very well with the model. © 2007 IEEE  

Privacy preservation in wireless sensor networks has drawn considerable attention from research community during last few years. Emergence of single-owner, multi-user commercial sensor networks along with hostile and uncontrollable environment of such networks, makes the security issue in such networks of a great importance. This paper concentrates on token-based privacy preservation schemes. A possible attack on such schemes has been introduced. Two different approaches has been utilized to mitigate the attack. We present mathematical models for it's effects and overheads. The results have been verified using extensive simulations  

TNT: Silicon microcantilevers modified with a three-dimensional layer of vertical titanium dioxide nanotubes can be used in micromechanical sensors with optical signal detection to detect low levels of explosives such as 2,4,6-trinitrotoluene (TNT) in the gas phase, even in the presence of other volatile impurities such as n-heptane and ethanol  

Gas sensors have been fabricated based on field ionization from titanium oxide nanotubes grown on titanium foil. Ordered nanaotube arrays of titanium oxides were grown by the anodization method. We measured breakdown voltages and discharge currents of the device for various gases. Our gas ionization sensors (GIS) presented good sensitivity, selectivity, and short response time. The GISs based on TiO2 nanotube arrays showed lower breakdown voltage, higher discharge current, and good selectivity. An excellent response observed for Ar compared to other gases. Besides, by introducing 2 % CO and 4 % H2 to N2 flow gas, the amount of breakdown voltage shifts about 20 and 70 volts to the lower... 

We study Hydrogen sulfide gas detection properties of pure and 1% copper oxide added WO3 thin films. The spin coated deposits on alumina substrates were annealed at 500 C for 1 hour in order to improve the crystallinity of the films. The sensitivity of pure tungsten oxide is poor even at temperatures of about 100 C but the doped samples exhibit good response to H2S gas. Our data show sensitivity of about 1500 in 10 ppm diluted gas in air at 100 C. The films are sensitive to the gas even at 250 ppb (sensitivity about 2) H2S concentration at 100 C but with rather long recovery time. Crystal structure, morphology and chemical composition of samples were studied by X-Ray diffraction (XRD),... 

Operation of two different optical fiber sensor designs for distance measurements with a good sensitivity, resolution, and wide dynamic range is reported. Design is based on the intensity modulation due to reflectance measurement from a target surface. Two reported designs are fabricated with a triple-fiber assembly, in which one uses a double-transmitter, while another one uses a double-receiver fiber design. Reflection signals from different targets are tested with these sensors and results for the mirror and A4 paper surfaces are described. The response curve for both experiments starts from a near zero level, shows a maximum at a certain distance and gradually drops to the background... 

The number of humidity outputs on the cap of a cylindrical capacitance sensor is optimized by designing three different probes with direct and indirect windows. The time interval is measured within which 30- 70 % humidity can influence the dielectric constant and conductivity of the capacitance when exposed to a range of relative humidity. It is then compared with a simple set-up including a simplified equivalent circuit. The direct probes had four and double outputs on the window of the cylindrical capacitive sensor while the indirect probe had a thin plastic layer only. We observed that the dielectric constant and its conductivity depend closely to the humidity outgoing pathway and also to... 

As in many other methods that have integrated nanoparticles (NPs), the chemical nose/tongue strategy has also progressed greatly since the entrance of NPs into this field. The fascinating tunable physicochemical properties of NPs have made them powerful candidates for array-based sensing platforms and have enabled the development of real-time, sensitive and portable systems that are able to target complex mixtures of analytes. In particular, the unique optical properties of NPs have a key role in providing promising array-based sensing approaches. This review will describe the main aspects and processes of most common NP-based optical sensor arrays. The fundamental steps in the design of a... 

The problem of latency in data acquisition, which is specific to the case of mobile wireless sensor networks, has been introduced and investigated. In this regard, the properties of the so-called Data Acquisition Latency Error, and the way it affects the performance of the respective localization schemes in a mobile network were discussed through both theoretical analysis and simulations. Moreover, a weighted version of lateration scheme was introduced and shown to outperform the traditional one, while tracking a mobile node. This work is to the best of our knowledge the first to have addressed the aforementioned problem in mobile wireless sensor networks, and to have offered a solution for... 

We propose a range-free localization framework in which a network of randomly deployed acoustic sensors can passively use natural acoustic phenomena within its environment to localize itself. We introduce a novel approach for registration of sensors observations which takes advantage of a clustering technique on triplets of associated observations. A Bayesian filtering method is employed to incrementally improve system state estimation as more observations become available. To the best of our knowledge this is the first work done on range-free passive acoustic localization. Simulation experiments of the proposed algorithms are presented. © 2008 IEEE  

In this work, we have examined the distributed consensus averaging problem from a novel point of view considering the need for privacy and anonymity. We have proposed a method for incorporating security into the scalable average consensus mechanisms proposed in the literature. Random Offsets Method (ROM) is lightweight, transparent and flexible since it is not based on cryptography, does not require any change in the fusion system and can be used optionally by some nodes who care about their privacy. In this method, which is based on noisiflcation of nodes' information, we achieve robustness against n - 1 colluding adversaries in a network of n nodes, which is maximum level of robustness... 

Sensor networks are systems of many small units that work together to monitor a given environment. A mixed sensor network is composed of a collection of static and mobile nodes that has sensing, computation, communication, and locomotion capabilities. Sensor mobility can be used to compensate for the lack of sensors and improve network coverage. This paper aims to describe an algorithm called Coin for mixed sensor network deployment in an unknown environment by using a small number of mobile sensors. It allows the network to achieve maximum coverage with minimum energy consumption. Our solution includes distributed schemes for: 1) determining the exact size of a coverage hole; 2) determining... 

Sensor network deployment is very challenging due to hostile and unpredictable nature of usage environments. In this letter, we propose two methods for the self-deployment of mobile sensors. The first one is a randomized solution that provides both simplicity and applicability to different environments. Inspired by simulated annealing, it improves both speed and energy conservation of the deployment process. The other method is suggested for environments where sensors form a connected graph, initially. At the cost of this extra limitation, we gain considerable improvements. © 2006 IEEE