Sharif Digital Repository

In this paper, a hierarchical routing protocol for wireless sensor networks is introduced that aims at reducing the energy imbalance among sensor nodes by integrating the distance of the nodes from the base station into clustering policies. Moreover, the proposed routing protocol does not need any centralized support from a certain node which is at odds with aiming to establish a scalable routing protocol. Mobility management is a salient feature of this protocol that guarantees reliable communications between mobile and static nodes. A simulator was developed in the MATLAB environment to evaluate the performance of this protocol. Simulations on two different network configurations are used... 

Energy consumption is one of the most important design criteria in Wireless Sensor Networks. Sensor nodes are expected to be battery-equipped. Due to their working environments, recharging or replacing batteries for each node is difficult and uneconomical. So prolonging the service lifetime of sensor nodes is a critical issue. The MAC protocol for WSNs plays a very important role in the control of energy consumption. Many of proposed MAC protocols attempt only to prolong the network lifetime for energy-efficiency. In this paper, we are going to reduce end-to-end latency in addition to extending the network lifetime. To reach this purpose, we propose a new adaptively ProLong MAC protocol... 

The prime shortcoming of Wireless Sensor Networks (WSNs) is their energy constraint. The main energy consumer in a sensor node is its radio transmitter. One of the most effective methods to reduce the data transmission rate is data prediction. By data prediction, the amount of transmitted data is reduced; which results in energy saving and the longevity of the network life. Environmental variations almost have similar effects on different sensor sources in a sensor device. So, considering the correlation between different sources reduces the noise impact and increases data prediction accuracy. In this paper, temporal and multi-source correlations are used, to reduce data transmission in... 

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... 

A low-power wide-range CMOS temperature sensor architecture is proposed for RFID and Sensor Networks based on temperature-to-frequency conversion using supply voltage controlled sub-threshold ring oscillator. The principles of operation are investigated and proved via simulation results. Most errors are canceled out by this ratio-metric design. An inaccuracy of -0.84°C to +0.34°C occurs over a range of -40°C to 80°C after using a novel in-field digital two-point calibration. The entire sensor consumes less than 93nW to 305nW over the temperature range and can be digitally reconfigured for setting sample rate and resolution in a tradeoff. © 2016 IEEE  

Semiconductor gas sensors have been developed so far on empirical bases, but now recent innovative materials for advancing gas sensor technology have been made available for further developments. Two-dimensional (2D) materials have gained immense attention since the advent of graphene. This attention inspired researchers to explore a new family of potential 2D materials. The superior structural, mechanical, optical and electrical properties of 2D materials made them attractive for next-generation smart device applications. There are considerable improvements and research studies on graphene, molybdenum disulfide (MoS2), tungsten disulfide (WS2), tin sulfide (SnS2), black phosphorus and other... 

Low-power wireless stand-alone sensors that can operate without any wiring have received significant attention in sensor network applications. These devices harvest environmental energy resources to supply their power and transfer their collected data using wireless RF links. In many instances, the power supplied from the environment is far less than the power required by the sensor device. In this case, the main solution is to accumulate energy on a storage element, and when enough energy is stored, the sensor node is instantaneously activated using an undervoltage lockout (UVLO) circuit. During this short time burst, the sensor performs the required acquisition, transmits the results, and... 

Resolver, as an electromagnetic sensor, is widely used in many industrial applications. It can detect the position of the rotary part of the electric machines precisely. In commercial resolvers, excitation winding is connected to the High-Frequency (HF) AC source. The amplitude-modulated voltages induced in signal windings need to be demodulated in order to calculate the envelope of the output signals and detect the position accordingly. On the other hand, in PM-resolver, signal windings are replaced by Hall-effect sensors to measure the DC magnetic ux, which is produced by permanent magnets. In this study, the performance of both AC and DC ux resolvers is investigated under di erent... 

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... 

This paper presents closed loop simulation of a CMOS-MEMS force sensor for biomedical applications employing an optimal proportional-integral-derivative controller. Since the dynamic behavior of the sensor under investigation is nonlinear the iterative feedback tuning approach was proposed for optimal gains tuning of the proposed controller. Simulation results presented in this research illustrate that the proposed controller suppresses the undesired in-plane vibration induced by environment or gripper 40 times faster than the nonlinear controller proposed in the literature. To suppress the maximum input disturbance the maximum voltage was approximately 18 V which was less than the pull-in... 

Localization is a crucial problem in wireless sensor networks and most of the localization algorithms given in the literature are non-adaptive and designed for fixed sensor networks. In this paper, we propose a learning based localization algorithm for mobile wireless sensor networks. By this technique, mobility in the network will be discovered by two crucial methods in the beacons: position and distance checks methods. These two methods help to have accurate localization and constrain communication just when it is necessary. The proposed method localizes the nodes based on connectivity information (hop count), which doesn't need extra hardware and is cost efficient. The experimental... 

By fabrication of several bolometric detectors on the YBCO film made of Metal-Organic Deposition (MOD) and the effect of pattering and film parameters on the optical responsivity of transition edge sensors is investigated. The low cost nonfluorine (MOD) method has been applied to fabricate YBCO thin films with different patterning parameters. The measurement results of the optical responsivity versus modulation frequency up to 100 KHz for these devices are reported  

In this paper, LQG/LTR controller is designed for attitude control of the geostationary satellite at nominal mode. Usage actuator is the reaction wheel and control torque is determined by the LQR regulator. LQR controller signal has good performance, if all states are considered in feedback, but does not include model and sensors noises. Usage sensors are sun and earth sensors and EKF is used for estimation of noisy states. Then, LQG and LQG/LTR controllers are designed based on the estimated states, and are compared with LQR controller. The results show that robustness and performance of LQG/LTR are better than LQG and its control overshoot is smaller than LQR. The term that is provided in... 

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 operates successfully, the active nodes must maintain both sensing coverage and network connectivity. It has been 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 first we consider a rectangular region A = a * b, such that Rs≤a, Rs≤b where Rs is the sensing range of node, and put a constraint on minimum allowed distance between nodes (... 

Sensor networks with sensing, data processing and communicating capabilities have a broad spectrum of applications. Based on application requirements, various network configurations can be designed. One such robust configuration is a hybrid wired-cum-wireless sensor network that is composed of a wireless sensor network and a wired backbone which are inter-connected via access points. In this paper, the joint problem of configuring a hybrid wired-cum-wireless sensor network, position-constrained cluster head and access point placement is proposed. The design considers real wireless communication limitations, optimum locations of access points and cluster heads, and hybrid transmission... 

The concepts of thermal radiation heat transfer are not tangible for many students. Experiments relied on various parameters can clarify the concepts of this mode of heat transfer.A lab-scale set up is described to study the thermal radiation heat transfer experiments. An electrical circuit of the thermopile sensor is designed and manufactured to provide experimental data.The validity of Inverse Square, Stefan-Boltzmann, and Kirchhoff Laws are investigated experimentally in the setup. Results indicate that, it is necessary to consider temperature shifts in the thermopile cold junction which is a potential source of error. Therefore, the output voltage, corresponding to the sensor... 

Many applications that utilise wireless sensor networks (WSNs) require essentially secure communication. However, WSNs suffer from some inherent weaknesses because of restricted communication and hardware capabilities. Key management is the crucial important building block for all security goals in WSNs. Most existing researches tried to assign keys assuming homogeneous network architecture. Recently, a few key management models for heterogeneous WSNs have been proposed. In this study, the authors propose a dynamic key management framework based on elliptical curve cryptography and signcryption method for heterogeneous WSNs. The proposed scheme has network scalability and sensor node (SN)...