Deployment of mobile nodes in a region of interest is a critical issue in building a mobile sensor network because it affects cost and detection capabilities of the system. The deployment of mobile sensors in essence is the movement of sensors from an initial position to a final optimal location. Considerable attention has recently been given to this deployment issue. Many of the distributed deployment schemes use the potential field method. In most cases, the negative gradient of the potential function becomes the feedback control input to a node. This assumes that the potential function is differentiable over the entire region. This assumption is valid primarily when the topology of the network is fixed. In this research, we analyze the stability of a network that uses piecewise smooth potential functions. A gravitation-like force is proposed to deploy a group of agents and to form a certain configuration. We use a nonsmooth version of the Lyapunov stability theory and LaSalle’s invariance principle to show asymptotic stability of the network which is governed by discontinuous dynamics. We propose a hierarchical structure using potential fields for mobile sensor network deployment. A group of mobile nodes first form a cluster using a potential field method and then cluster heads are used to establish a hexagonal structure that employs a higher level potential field. We consider specifically the problem of deploying a mobile sensor network so that a certain area coverage is realized and maintained. And we propose an algorithm for main taining the desired coverage that assumes the availability of a stochastic sensor model. The model reflects the decline of the sensor accuracy as the distance increases from the sensor. It is further assumed that each node’s sensor has a different sensing range to represent sensor performance deterioration due to power decay. The network deployment scheme combines artificial forces with individual sensor ranges. The validity and the effectiveness of the proposed algorithm are compared to the conventional methods in simulations. Simulation results confirm the effectiveness of the proposed algorithms with respect to a defined performance metric.

A distributed sensor using an optical fiber for detecting and locating intruders over long perimeters (>10 km) is described. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (φ−OTDR). Light pulses from a cw laser operating in a single longitudinal mode and with low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. In laboratory tests with 12 km of fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on φ−OTDR traces were characterized. In field tests in which the sensing element is a single mode fiber in a 3-mm diameter cable buried in an 8 to 18 inch deep, 4 inch wide trench in clay soil, detection of intruders on foot up to 15 ft from the cable line was achieved. In desert terrain field tests in which the sensing fiber is in a 4.5-mm diameter cable buried in a 1 ft deep, 2.5 ft wide trench filled with loose sand, high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km in real time. In a final series of field tests in clay soil, phase changes produced by the steps of a person walking up to 15 ft away from the buried cable were observed, and vehicles traveling at 10 mph were consistently detected up to 300 ft away. Based on these results, this technology may be regarded as a candidate for providing low-cost perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.

Mobile sinks are vital in many wireless sensor applications for efficient data collection, data querying, and localized sensor reprogramming. Mobile sinks prolong the lifetime of a sensor network. However, when sensor networks with mobile sinks are deployed in a hostile environment, security became a critical issue. They become exposed to varieties of malicious attacks. Thus, anti threats schemes and security services, such as mobile sink?s authentication and pairwise key establishment, are essential components for the secure operation of such networks. Due to the sensors, limited resources designing efficient security schemes with low communication overhead to secure communication links between sensors and MS (Mobile Sink) is not a trivial task. In addition to the sensors limited resources, sink mobility required frequent exchange of cryptography information between the sensors and MS each time the MS updates its location which imposes extra communication overhead on the sensors. In this dissertation, we consider a number of security schemes for WSN (wireless sensor network) with MS. The schemes offer high network?s resiliency and low communication overhead against nodes capture, MS replication and wormhole attacks. We propose two schemes based on the polynomial pool scheme for tolerating nodes capture: the probabilistic generation key pre-distribution scheme combined with polynomial pool scheme, and the Q-composite generation key scheme combined with polynomial pool scheme. The schemes ensure low communication overhead and high resiliency. For anti MS replication attack scheme, we propose the multiple polynomial pools scheme that provide much higher resiliency to MS replication attack as compared to the single polynomial pool approach. Furthermore, to improve the network resiliency against wormhole attack, two defensive mechanisms were developed according to the MS mobility type. In the first technique, MS uses controlled mobility. We investigate the problem of using a single authentication code by sensors network to verify the source of MS beacons, and then we develop a defensive approach that divide the sensor network into different authentication code?s grids. In the second technique, random mobility is used by MS. We explore the use of different communication channels available in the sensor hardware combined with polynomial pool scheme.

TiO2 is a fascinating material proving its usefulness in a wide range of applications. In photocatalytic and gas sensitization applications, it has been utilized as a stable semiconductor for the organic matter of waste water cleaning and impetus on environmental consciousness the need for highly efficient combustion engines, controlled industrial processes and monitoring the hazardous gas level in the environment. Nanocrystalline TiO2 modified with Nb incorporation has been produced by LPD technique that deposited at 40 oC with (NH4)2TiF6 for 0.2 M, and 0.6 M for boric acid and a few mount of Nb solution. The deposition rate can be controlled perfectly about 40-50 nm/h. The addition of Nb stabilizes the anatase phase and retards the grain growth during high temperature annealing. XRD and RAMAN spectra of undoped and Nb doped samples show that the undoped one has converted to rutile at 900 oC, meanwhile the doped one remains anatase phase. Nanocrystalline films stabilize at 800 oC with grain size of about 7 nm have successfully been synthesized by the additives of Nb, which appear to be an adequate dopant to improve the photocatalytic and gas sensor performances. The ability of niobium introduction is of retarding the anatase to rutile transformation and hindering its grain growth.

This research proposes the architecture of motor driver IC for the application of small BLDC motors. Both analog and digital mixed-mode techniques are employed here to design BLDC fan motor driver IC. The controlling method of this motor driver IC mainly utilizes analog approach. Besides, in order to prevent any damages on motors due to abnormal operations, digital control circuit is also involved in this IC. This motor driver IC is used in heat-sinking fan on notebooks as well as on the motors with very small impedance, so the IC is designed to be able to work in low supply voltage, and has high driving capability at the output stage. Via the feedback signal generated by the Hall sensor, it controls the motor driver IC so that the IC can supply current accordingly to stator coil. Therefore, the purpose of controlling motors is then achieved.

Electrostatic Assisted Vapor Deposition method was adopted to deposit SnO2 thin films in this work using either SnCl4 or DBTDC (C12H24O4Sn) as precursors. Appropriate deposition parameters were identified for deposition of porous and dense films . A post-deposition calcination of 600¢XC/2h yielded well crystalline rutile phase. Electrical resistance measurement indicated that the most porous films ,derived from the precursor solution of ethanol solvent, were not continuous. Instead, films derived from precursor solution of mixed ethanol-carbitol solvent were less porous allowing stable resistance values to be measured. A detection sensitivity of 2.55 for 100ppm CO gas was obtained from films derived from a 30% ethanol-70% carbitol solution. A higher sensitivity of 6.55 was obtained from films derived from solutions containing Di-n-butyltin diacetate (DBTDC) as precursor.

Two new stepped-frequency continuous wave (SFCW) radar sensor prototypes, based on a coherent super-heterodyne scheme, have been developed using Microwave Integrated Circuits (MICs) and Monolithic Millimeter-Wave Integrated Circuits (MMICs) for various surface and subsurface applications, such as profiling the surface and subsurface of pavements, detecting and localizing small buried Anti-Personnel (AP) mines and measuring the liquid level in a tank. These sensors meet the critical requirements for subsurface and surface measurements including small size, light weight, good accuracy, fine resolution and deep penetration. In addition, two novel wideband microstrip quasi-TEM horn antennae that are capable of integration with a seamless connection have also been designed. Finally, a simple signal processing algorithm, aimed to acquire the in-phase (I) and quadrature (Q) components and to compensate for the I/Q errors, was developed using LabView. The first of the two prototype sensors, named as the microwave SFCW radar sensor operating from 0.6-5.6-GHz, is primarily utilized for assessing the subsurface of pavements. The measured thicknesses of the asphalt and base layers of a pavement sample were very much in agreement with the actual data with less than 0.1-inch error. The measured results on the actual roads showed that the sensor accurately detects the 5-inch asphalt layer of the pavement with a minimal error of 0.25 inches. This sensor represents the first SFCW radar sensor operating from 0.6-5.6-GHz. The other sensor, named as the millimeter-wave SFCW radar sensor, operates in the 29.72-35.7-GHz range. Measurements were performed to verify its feasibility as a surface and sub-surface sensor. The measurement results showed that the sensor has a lateral resolution of 1 inch and a good accuracy in the vertical direction with less than  0.04-inch error. The sensor successfully detected and located AP mines of small sizes buried under the surface of sand with less than 0.75 and 0.08 inches of error in the lateral and vertical directions, respectively. In addition, it also verified that the vertical resolution is not greater than 0.75 inches. This sensor is claimed as the first Ka-band millimeter-wave SFCW radar sensor ever developed for surface and subsurface sensing applications.

A large-scale distributed wireless sensor network is composed of a large collection of small low-power, unattended sensing devices equipped with limited memory, processors, and short-range wireless communication. The network is capable of controlling and monitoring ambient conditions, such as temperature, movement, sound, light and others, and thus enable smart environments. Energy efficient data dissemination is one of the fundamental services in large-scale wireless sensor networks. Based on the study of the data dissemination problem, we propose two efficient data dissemination schemes for two categories of applications in large-scale wireless sensor networks. In addition, our schemes provide spatial-based multi-resolution data dissemination for some applications to achieve further energy efficiency. Analysis and simulation results are given to show the performance of our schemes in comparison with current techniques.

Wireless sensor network consists of a large number of sensors, which are capable of sensing, communication and data processing. In wireless sensor network, predictable or unpredictable death of sensor nodes may cause coverage and connectivity problems of the original network. In order to compensate the loss of coverage and connectivity, we propose a region-based movement scheme that divides the neighboring sensors of the dead sensor into a number of regions. The neighboring sensors are moved to repair the regions respectively by using the least mobility distance, and their existing coverage and connectivity are not jeopardized. Our work has better performance of maintaining coverage and connectivity of the network. By the results, our work can decrease the average mobility distance and coverage deterioration substantially.

In this thesis, we consider a distributed detection problem in wireless sensor networks (WSNs) using ultrawide bandwidth (UWB) communications. Due to the severe restrictions on power consumption, energy efficiency becomes a critical design issue in WSNs. UWB technology has low-power transceivers, low-complexity and low-cost circuitry which are well suited to the physical layer requirements for WSNs. In a typical parallel fusion network, local decisions are made by local sensors and transmitted through a wireless channel to a fusion center, where the final decision is made. In this thesis, we control the number of UWB pulses to achieve the energy efficient distributed detection. We first theoretically characterize the performance of distributed detection using UWB communications. Both AWGN and fading channels are considered. Based on the analysis, we then obtain the minimum number of the pulses per detection to meet the required performance. To achieve a near-optimal design, we further propose a multiple access technique based on the random number of UWB pulses. Finally, the performance evaluation is provided to demonstrate the advantage of our design.