Sharif Digital Repository

In this paper, a "Game Theory" approach for finding an optimal path in a "Wireless Sensor Network" is discussed. WSN is one of the most interesting research fields in the communication networks, and is the center of attention in recent years. In our model, a pricing and payment technique is presented to obtain an optimal path in a WSN by considering reliability, energy and traffic load. The proposed algorithm is able to find a path which improves network lifetime, load distribution and path reliability  

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),... 

We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I–V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal–interface–semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100–40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration... 

Pd–WO3 nanostructures were incorporated on graphene oxide (GO) and partially reduced graphene oxide (PRGO) sheets using a controlled hydrothermal process to fabricate effective hydrogen gas sensors. Pd–WO3 nanostructures showed ribbon-like morphologies and Pd–WO3/GO presented an irregular nanostructured form, while Pd–WO3/PRGO exhibited a hierarchical nanostructure with a high surface area. Gas sensing properties of thin films of these materials were studied for different hydrogen concentrations (from 20 to 10,000 ppm) at various temperatures (from room temperature to 250 °C). Although adding GO in the Pd–WO3, after hydrothermal process could increase the film conductivity, gas sensitivity... 

Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol–gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti–C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time... 

Topology of a mobile wireless sensor/ad hoc network is prone to link breakages due to node mobility which compels the periodic re-construction of the topology in so called ""hello"" intervals. The problem addressed in this paper is determining the maximum ""hello"" interval preserving the connectivity of a homogeneous topology with high probability. In order to study the optimum ""hello"" interval, statistical topology lifetime (STL) is formally defined as a value of ""hello"" interval that ensures statistical connectivity with a given threshold. Temporal properties of the topology are studied based on two phenomena; one concerning a connectivity phase transition with time and the other one... 

In many wireless sensor network applications, nodes are mobile, while many protocols proposed for these networks assume a static network. Thus, it is important to evaluate if a traditional protocol designed for a static network can tolerate different levels of mobility. This paper provides an analytic model to investigate the effect of mobility on a well-known cluster-based protocol, LEACH. The model evaluates data loss after construction of the clusters due to node mobility, which can be used to estimate a proper update interval to balance the energy and data loss ratio. Thus, the results can help the network designer to adjust the topology update interval given a value of acceptable data... 

Processor allocation in todays many core MPSoCs is a challenging task, especially since the order and requirements of incoming applications are unknown during design stage. To improve network performance, balance the workload across processing cores, or mitigate the effect of hot processing elements in thermal management methodologies, task migration is a method which has attracted much attention in recent years. Runtime task migration was first proposed in multicomputer with load balancing as the major objective. However, specific NoC properties such as limited amount of communication buffers, more sensitivity to implementation complexity, and tight latency and power consumption constraints... 

This paper investigates a class of mobile wireless sensor networks that are unconnected most of the times; we refer to them as delay-tolerant wireless sensor networks (DTWSN). These networks inherit their characteristics from both delay tolerant networks (DTN) and traditional wireless sensor networks. After introducing DTWSNs, three main problems in the design space of these networks are discussed: routing, data gathering, and neighbor discovery. A general protocol is proposed for DTWSNs based on opportunistic broadcasting in delay-tolerant networks with radio device on-off periods. Three performance measures are defined in the study: the energy for sending queries to ask for data from... 

In this article, the state estimation for Automotive Slip Angle considering the measurement noise in sensor is addressed. Realtime measurement of the slip angle is applicable to many active vehicle safety applications, such as rollover prevention and yaw stability control. As the sensors that measure slip angle directly are expensive, the method to extract slip angle from other available sensors in vehicle is considered. First from the simplified nonlinear dynamic system of vehicle, a Piecewise Affine (PWA) model with calculated uncertainties is obtained. The uncertainties are the result of nonlinear system deviation from PWA model. Then using the PWA model, a Stochastic Robust Hybrid... 

Co-deposition of RF-sputtering and RF-PECVD from acetylene gas and Au target were used to prepare sensor chip of gold nanoparticles (Au NPs). Deposition conditions were optimized to reach a Localized Surface Plasmon Resonance (LSPR) sensor chip of Au NPs with particle size less than 10 nm. The RF power was set at 180 W and the initial gas pressure was set at 0.035 mbar. Transmission Electron Microscopy (TEM) images and Atomic Force Microscopy (AFM) data were used to investigate particles size and surface morphology of LSPR sensor chip. The Au and C content of the LSPR sensor chip of Au NPs was obtained from X-ray photoelectron spectroscopy (XPS). The hydrogenated amorphous carbon (a-C:H)... 

In this study, we present fabrication and characterization of a gas ionization sensor based on high aspect ratio one-dimensional CuO nanowires as the field enhancing medium. Self-organized arrays of CuO nanowires have been synthesized based on a low-cost thermal oxidation method and integrated into a gas ionization sensor (GIS). The self-organized arrays of CuO nanowires have been employed to detect the identity of several gas species such as He, Ar and CO at ambient temperature and pressure. The sharp nanoscale size of CuO tips provide very high electric fields at moderate voltages (less than 100 V) and provoke the breakdown of different gases. The reduced breakdown current of the metal... 

For the first time, a new platform based on electrochemical growth of Au nanoparticles on aligned multi-walled carbon nanotubes (A-MWCNT) was developed for sensitive lable-free DNA detection of the TP53 gene mutation, one of the most popular genes in cancer research. Electrochemical impedance spectroscopy (EIS) was used to monitor the sequence-specific DNA hybridization events related to TP53 gene. Compared to the bare Ta or MWCNT/Ta electrodes, the synergistic interactions of vertically aligned MWCNT array and gold nanoparticles at modified electrode could improve the density of the probe DNA attachment and resulting the sensitivity of the DNA sensor greatly. Using EIS, over the extended... 

The existing methods in attitude control of satellites are based on using the estimate of satellite attitude, which is usually generated by using multiple vector measurements. In this paper we propose an output feedback controller that directly uses a single vector measurement and does not use an attitude estimator. The output feedback gain is computed by solving a generalized Riccati differential equation (GRDE). The existence of a solution to the GRDE depends on a uniform controllability condition  

Herein, we present the large scale fabrication of carbon nanotubes (CNT) electrodes supported on flexible polymeric sheets by subsequent multilayer inkjet printing of a silver layer for electrical connection, CNT layers as active electrode material and an insulation layer to define a stand-alone CNT active electrode area with high accuracy. Optical and electrochemical characterization using several redox mediators demonstrates the reproducibility of the electrode surfaces and their functionality even with a single inkjet printed CNT layer. These electrodes are targeted to the clinical sector for the determination of the antioxidant power (AOP) of biologically relevant fluids by... 

The growing interest in applications of Wireless Multimedia Sensor Networks (WMSNs) imposes new challenges on congestion control protocols in such networks. In this paper, we propose a new content-aware cross layer WMSN Congestion Control Protocol (WCCP) by considering the characteristics of multimedia content. WCCP employs a Source Congestion Avoidance Protocol (SCAP) in the source nodes, and a Receiver Congestion Control Protocol (RCCP) in the intermediate nodes. SCAP uses Group of Picture (GOP) size prediction to detect congestion in the network, and avoids congestion by adjusting the sending rate of source nodes and distribution of the departing packets from the source nodes. In... 

The first usage of dihexadecyl hydrogen phosphate (DHP)-modified highly oriented multi-walled carbon nanotube (MWCNTs) forests in a sensor configuration was developed to investigate the electrochemical oxidation and determination of simvastatin (SV) in pharmaceutical dosage forms. Synthesis of well-aligned MWCNTs on a conductive Ta substrate by catalytic vapor deposition technique using a common chemical, ethylenediamine, and without being plasma-aided was reported. The electrochemical behavior and oxidation of SV at the aligned MWCNTs/DHP/Ta electrode were discussed in detail through cyclic voltammetry and differential pulse voltammetry. This modified electrode showed considerably higher... 

Although, the optical flow sensors which are used in optical mouse have high resolution in measuring displacement, their error refrain us from a precise and reliable measurement. Besides, these sensors require calibration based on the surface. Their error has different sources and the most important is surface texture in micro level. In this research, we have worked to find surface conditions on which sensor measurement is more precise. For this aim, we used an 800 DPI low cost optical flow sensor. For making different surface textures and grains, we printed different textures with 600 and 1200DPI resolution on white paper with certain length. Then we used optical flow sensor for measuring...