Sharif Digital Repository

A large number of random key pre-distribution (RKD) schemes have been proposed in the literature to secure wireless sensor network applications, relying on symmetric key cryptography. However, sensor nodes are exposed to physical compromise by adversaries, who target the symmetric keys stored at each node. With the stolen keys in their possession, the adversaries are then able to compromise communication links between benign nodes. Here, the big challenge arises: how to increase resilience of RKD schemes for wireless sensor networks to node capture, while maintaining the flexibility and low-cost features of RKD? We propose the idea of key splitting to address this problem, without the need... 

the failure in cluster at a high level can bring up great damages to the system in wireless sensor networks where clustering techniques are used. Certain methods have been reported in the literature in recovering the sensors from a failure cluster. One of the most important methods is to recover the sensors in run-time and without clustering. But it is so much ideal to suppose that all the sensors will be recovered. In this paper, we proposed a method that can operate on the remained sensors that are not recovered. © 2009 IEEE  

The manner of organizing the sensors in the wireless sensor network for increasing the capability and optimized using of the sensors is of great importance. Hence considering coverage parameter in every Wireless Sensor Network (WSN) is extremely essential and critical. The matter of overlapping covered area by sensors in 2D space had been considered until now. This paper is suggested a pattern in which no more are the sensors located at the same surface, but using the 3D geometrical figures like cube, pyramid and etc, in which the sensors were spreading about the different surfaces. Locating the sensors on the different surfaces can be useful under conditions where the space is not in same... 

In Minimally Invasive Surgery (MIS) the operation is performed through introducing surgery instruments, graspers, scissor into the body. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum by surgeon and to measure the transmitted response to the tissue/organ. © 2009 IEEE  

An effective approach for energy conservation in wireless sensor networks is scheduling sleep intervals for extraneous nodes while the remaining nodes stay active to provide continuous service. For the sensor network to operate successfully the active nodes must maintain both sensing coverage and network connectivity, It proved before if the communication range of nodes is at least twice the sensing range, complete coverage of a convex area implies connectivity among the working set of nodes. In this paper we consider a rectangular region A =a *b , such that Rs ≤ a, Rs ≤ b where Rs is the sensing range of nodes. and put a constraint on minimum allowed distance between nodes( Rs ). according... 

In this study, design and operation of a cylindrical capacitive sensor based on the dielectric and reactance capacitance changes of the gap medium is reported. The proposed system was used to determine the electrical properties of different water liquids as a result of the capacitance variations. For capacitance measurement, the cylindrical gap can be filled up by water liquids under study, the electrical characteristics of different water liquids, mixture of ethanol and water, mixture of methanol and water, mixture of petroleum and water and other liquid mixtures were studied. In this research a big difference about 16200 nF was noticed in the measured capacitance of the corresponding... 

Design and operation of an optical fiber sensor based on the intensity modulation is reported in this article. Two distinct mechanisms are considered for the optical power loss and the sensor operation is explained in terms of these effects. The dominant loss mechanism is found to be the evanescent loss and based on this phenomenon the optical fiber sensor is designed. Performance of this sensor is tested as a liquid level sensor for water 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 the design and operation of sensor are described. The precision of measured values, reproducibility... 

A wireless Ad-hoc sensor network consists of a number of sensors spread across a geographical area as a collection of sensors that form an ad-hoc wireless network. Sensors are very tiny devices that their primary function is to sense the target, convert the signal into a suitable data format, and pass on the data to a command node. These sensor nodes are very heavily constrained in processing power, and have a limited energy supply. Since energy is such a scarce resource, several algorithms have been developed at the routing and MAC layers to utilize energy efficiently and extend the lifetime of the network. First layer of the sensor networks is the infrastructure layer and there is no... 

A SEnsor Network with Mobile Agents (SENMA) is an architecture proposed for large scale sensor networks in which the access point moves above the network and gathers information from a limited number of nodes. However, the performance of such system is limited by estimation errors and packet errors due to collision. In this paper, we first derive the equations of distortion in a general scenario and use this model to obtain four best node positions in order to achieve min-max estimation error in a square. In addition, an opportunistic MAC is proposed that considers both collision effects and estimation error based on Channel State Information (CSI). As the simulation results show the... 

This paper proposes a new medium-access control (MAC) protocol designed for wireless sensor networks. A wireless sensor network is an array of large number of sensors interconnected by a multi-hop ad-hoc network. The primary objective for the sensor network is achieving to low-power consumption while latency is usually less important compare to traditional wireless networks. This characteristic of sensor network motivates the design of new MAC layer so that power consumption is reduced. In this paper, a novel traffic-aware algorithm based on distributed node schedule management (DMD) protocol is introduced that utilizes distributed dynamic node scheduling strategy to dramatically increase... 

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... 

Access to a prototype during R&D can play a crucial role in early identification of the weaknesses in the design. Under circumstances that a particular commercial subsystem with the exact required specific features is unavailable, the realization of such a prototype can be delayed. In this paper, an example of rapid prototyping for a dual-channel biosignal data acquisition system based on the open-source concept is described. The selected biosignal is the finger photoplethysmogram. Except for Matlab, all other software components are open-source. The hardware design of the optical sensor utilized to record the signals is also open-source, making the system extremely affordable with the... 

Wireless sensor networks include small nodes which have sensing ability; calculation and connection extend themselves everywhere soon. Such networks have source limitation on connection, calculation and energy consumption. So, since the nodes have limited energy in sensor networks, the optimized energy consumption in these networks is of more importance and has created many challenges. The previous works have shown that by organizing the network nodes in a number of clusters, the energy consumption could be reduced considerably. So the lifetime of the network would be increased. In this paper, we used the Queen-bee algorithm to create energy efficient clusters in wireless sensor networks.... 

Attempts to simulate compressible flows with moderate Mach number to relatively high ones using Lattice Boltzmann Method (LBM) have been made by numerous researchers in the recent decade. The stability of the LBM is a challenging problem in the simulation of compressible flows with different types of embedded discontinuities. The present study proposes an approach for simulation of inviscid flows by a compressible LB model in order to enhance the robustness using a combination of Essentially NonOscillatory (ENO) scheme and Shock-Detecting Sensor (SDS) procedure. A sensor is introduced with adjustable parameters which is active near the discontinuities and affects less on smooth regions. The... 

Localization of sensor nodes has become a fundamental requirement for many applications over Wireless Sensor Networks (WSNs). In this paper, we propose a range-free approach based on the Received Signal Strength (RSS) changes. A discrete and probabilistic localization method is offered to localize a moving beacon relative to sensor nodes. In this method we came to a more reliable and accurate result without increasing the number of sectors. We achieved a considerable improvement in localization reliability by defining the primary and secondary sectors and utilizing a Kalman approach for making decisions. The decision making process is based on the allocated probabilities given to each of... 

Although many complex real-world networks are weighted, unweighted networks are used in many applications such as sensor networks. In this Letter it is shown using properly weighted networks the performance can be greatly enhanced by reducing the time necessary for the average consensus. Random geographical models are adapted as network models and a method based on mutually coupled phase oscillators is used for providing average consensus over the network. The consensus time is calculated by numerically solving the network's differential equations and monitoring the average error. The simulation results on some sample networks show that the consensus time is dramatically reduced when the... 

Design and operation of three different optical sensors based on the intensity modulation are reported in this article. These sensors are measuring absence or presence of any liquid and the measurement variable is refractive index and optical absorption. Reported devices can also check the presence of air bubbles in the liquid flow line. Performance of these sensors is tested as a liquid flow monitoring device while using different light sources. Sensor #1 uses a simple cell with the long transmitter and receiver optical fibers. Sensor #2 utilizes a small cell assembly that includes the short transmitter and receiver fibers. Sensor #3 employs a quartz flow cell with the direct light... 

In this paper, the vibration of a constant thickness circular plate made of functionally graded material (FGM) is controlled by implementing two piezoelectric layers as a sensor and an actuator. Assuming that the material properties of FGM plate vary only in the thickness direction according to the power law manner, the governing differential equations are derived based on the Reissner-Mindlin plate theory (RMPT). Moreover, in a parallel work another set of differential equations are also derived using classical plate theory (CPT). Then for two different kinds of plate boundary conditions these coupled differential equations are solved using separation of variable technique and obtained...