Doctor of Philosophy

dissertationAccording to a UN report, more than 50% of the total world's population resides in urban areas and this fraction is increasing. Urbanization has a wide range of potential environmental impacts, including those related to the dispersion of potentially dangerous substances emitted from activities such as combustion, industrial processing or from deliberate harmful releases. This research is primarily focused on the investigation of various factors which contribute to the dispersion of certain classes of materials in a complex urban environment and improving both of the fundamental components of a fast response dispersion modeling system - wind modeling and dispersion modeling. Specifically, new empirical parameterizations have been suggested for an existing fast response wind model for street canyon flow fields. These new parameterizations are shown to produce more favorable results when compared with the experimental data. It is also demonstrated that the use of Graphics Processing Unit (GPU) technology can enhance the efficiency of an urban Lagrangian dispersion model and can achieve near real-time particle advection. The GPU also enables real-time visualizations which can be used for creating virtual urban environments to aid emergency responders. The dispersion model based on the GPU architecture relies on the so-called "simplified Langevin equations (SLEs)" for particle advection. The full or generalized form of the Langevin equations (GLEs) is known for its stiffness which tends to generate unstable modes in particle trajectory, where a particle may travel significant distances in a small time step

SYSTEM AND METHOD FOR A PRIVATE VEHICLE SHARING SERVICE

The present disclosure is directed to a subscription and/or membership based private vehicle sharing service. A user can purchase a subscription that allows the user to utilize the private vehicle sharing service for a particular amount of use over a given period. The unit measurement of the amount of use can be distance-based and/or tripbased. Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure

INDO-US RELATIONS: PAST TO PRESENT

India and the US are the two most important democratic courtiers in the world. The US is the oldest modern democratic country whereas India is the largest democratic country in the modern world and any sort of positive cooperation between the two great democracies is bound to create a new world order and balance promising peace and tranquility especially in all volatile South China Sea and Asia-pacific region. It will also contribute in maintaining peace throughout the world

Design of High Performance Modified Wave pipelined DAA Filter with Critical Path Approach

In this paper, a new high speed control circuit is proposed which will act as a critical path for the data which will go from input to output to improve the performance of wave pipelining circuits The wave pipelining is a method of high performance circuit designs which implements pipelining in logic without the use of intermediate registers. Wave pipelining has been widely used in the past few years with a great deal of significant features in technology and applications. It has the ability to improve speed, efficiency, economy in every aspect which it presents. Wave pipelining is being used in wide range of applications like digital filters, network routers, multipliers, fast convolvers, MODEMs, image processing, control systems, radars and many others. In previous work, the operating speed of the wave-pipelined circuit can be increased by the following three tasks: adjustment of the clock period, clock skew and equalization of path delays. The path-delay equalization task can be done theoretically, but the real challenge is to accomplish it in the presence of various different delays. So, the main objective of this paper is to solve the path delay equalization problem by inserting the control circuit in wave pipelined based circuit which will act as critical path for the data that moves from input to output. The proposed technique is evaluated for DSP applications by designing 4- tap FIR filter using Distributed arithmetic algorithm (DAA). Then comparison of this design is done with 4-tap FIR filter designs using conventional pipelining and non pipelining. The synthesis and simulation results based on Xilinx ISE Navigator 12.3 shows that wave pipelined DAA based filter is faster by a factor of 1.43 compared to non pipelined one and the conventional pipelined filter is faster than non pipelined by factor of 1.61 but at the cost of increased logic utilization by 200 %. So, the wave-pipelined DA filters designed with the proposed control circuit can operate at higher frequency than that of non-pipelined but less than that of pipelined. The gain in speed in pipelined compared to that of wavepipelined is at the cost of increased area and more dissipated power. When latency is considered, wavepipelined design filters with the proposed scheme are having the lowest latency among three schemes designed

An analysis of single wire earth return (SWER) system for rural electrification

The primary objective of this investigation was to determine the general applicability of Single Phase Earth Return(SWER) system for rural electrification where the load density is low, for example electrification of farms and small villages in emerging nations. The limitations of SWER system of distribution are many and it is necessary to make judicious use of such transmission. In this investigation the construction costs of transmission and distribution by SWER system is compared with single phase and three phase systems for loads of 25KVA and 50KVA. Phase converters are required to operate a three phase motor on a single phase supply. Three different types of static phase converters are discussed and their merits and costs are compared. Four different types of grounding systems are discussed in this study. The heating of earth electrodes due to continuous ground current flowing through the electrodes is investigated. Co-ordination of SWER systems with telecommunication lines is discussed in detail. Danger to humans and animals due to potential gradient at the surface of the earth in the vicinity of the grounding system caused by continuous ground current is also investigated in this study --Abstract, page ii

Material properties analysis of graphene base transistor (GBT) for VLSI analog circuits design

Graphene base transistor’s (GBT) analysis has been reviewed in this paper. This study has been focused on work carried out by other authors for GBT physics. Here prominence has been given to material properties and their effects on GBT for VLSI analog circuit design to operate in high frequency range of THz. Various papers in literature have been reported for the implementation of designs with different emitter and collector materials. Materials properties are the controlling parameters to decide cut-off frequency (f­T), trans-conductance, gain and off current (Ioff) in GBT. The implemented results of literatures signify that the electron affinity and work function of emitter and collector are the dominant factors for flow of charges from emitter to collector. Dependency of these two parameters on dielectric constant and thickness of emitter-base insulator (EBI) and base collector insulator (BCI) that are tantalum pentoxide (Ta2O5), carbon-doped silicon oxide (SiCOH) and SiO2 has been studied. Effects of collector and BCI thickness have been investigated in detail to scrutinize base leakage current by the virtue of back scattering in collector-BCI interface. Small signal equivalent circuit model for GBT have also been studied by including parasitic capacitance behaviour between graphene Dirac-point potential with respect to graphene fermi level, emitter, EBI, BCI and collector fermi level potential

Evaluation of ambiguity success rates based on multi-frequency GPS and Galileo

The precise positioning applications have long been carried out using dual frequency carrier phase and code observables from the Global Positioning System (GPS). The carrier phase observables are very precise in comparison to the code ones, the reason phase observables play an important role in precise geodetic applications. The carrier phase observables can have precision of about 3 millimeters. However the precision of the estimated parameter of interest, say the receiver position, depends upon the correct resolution of integer ambiguities present in the carrier phase observables. Significant contributions have been made in the last couple of decades towards integer ambiguity estimation to make precise positioning applications possible, using GPS carrier phase and code data from geodetic receivers.Precise positioning applications have been successful in the past, but at the cost of time taken to correctly resolve the integer ambiguities. This delay in integer ambiguity estimation is caused due to the presence of various propagation and hardware related effects present in the observables of GPS or in that case, any other Global Navigation System. The propagation errors related to the atmosphere are significant for medium to long baseline lengths. Among the atmospheric errors, the ionosphere is found to have profound effect on the process of integer ambiguity estimation. With the aid of permanent reference networks, corrections for ionosphere could be interpolated and further transferred to the user with an aim to enhance users ambiguity resolution and fulfill the aim of an efficient and reliable precise positioning.With the advancement of Global Navigation Satellite Systems (GNSS) several of the limiting factors which degrade users ambiguity resolution are seen to be met. The relatively poor precision of the code data in comparison to the phase data, is foreseen to improve for third GPS frequency, also called as GPS L5. Also most of the frequencies on Galileo system would have improved code precision.The ionosphere which has been a major blockade in fast integer ambiguity resolution, for long baseline lengths, would also benefit in a multi-frequency, multi-GNSS scenario. Since a GNSS model, in which the ionosphere is considered unknown and estimated, gains strength with addition of a frequency. The addition of L5 on GPS and availability of up to four frequencies on Galileo system would strengthen the GNSS model which would be beneficial when ionosphere is parameterized for estimation. This study aims at understanding the above mentioned and other possible benefits of the future GPS and Galileo system.The benefits that the future GPS and Galileo can bring to precise applications can be evaluated in terms of correct resolution of integer ambiguities present in the carrier phase data and further by understanding the contribution of the ambiguity resolution towards improvement of fixed-precision of the parameters of interest. The correct resolution of ambiguities was judged by computing the probability of correct integer bootstrap along with LAMBDA decorrelation method. The decorrelation of the ambiguity Variance Covariance matrix resulted the probability of Integer Bootstrap to correspond to lower bounds for the probability of Integer Least Square. The ambiguities were considered to be successfully resolved only after a minimum of 0.999 probability could be obtained from Integer Bootstrap. While all the ambiguities collectively contributed to give 0.999 Ambiguity Success Rate (ASR) it was termed as full Ambiguity Resolution (AR). In scenarios when full AR took large number of epochs to give 0.999 ASR, only a subset of ambiguities were fixed which met the 0.999 ASR criteria. This approach is known as Partial AR (PAR). PAR solution was accepted only when the resolved subset of ambiguities could contribute to give a minimum value of fixed-precision for the parameters of interest. Since this research involves future GPS and Galileo system, GNSS observables, real or simulated were not used. Instead simulations were done based on model assumptions, that is the functional and the stochastic model.This research work focuses on understanding the benefits of multi-frequency GPS and Galileo to its core. This was done by planning multiple scenarios of GNSS frequencies, GNSS combinations, atmospheric considerations, latitudinal variations and baseline orientations. With the aid of this multiple scenario simulation, an estimate for time taken for successful AR and the fixed-precision of parameters of interest obtained after successful AR could be computed for a range of possible situations. When a multi-GNSS scenario consisting of future GPS and Galileo was considered, there have been challenges while a mathematical model for multi-GNSS was being formed. The design of the multi-GNSS mathematical model accounted for the Inter System Biases (ISB’s) which surface while different GNSS systems use the same reference satellite. While a rank defect between the ISB’s and the ionosphere was detected, it was mitigated by choosing an appropriate S-Basis. To make the simulation software robust and realistic, accounting for setting and rising satellites and change of reference satellite was implemented. With the above considerations a multi-GNSS, multi-frequency simulation software was developed in MATLAB programming language. The results have been obtained based on assumption in the functional and stochastic models. In real practice unmodelled errors have an impact on ASR and time to fix the integer ambiguities to its correct solution due to multipath , insufficient knowledge of the stochastic model, etcetera.Presented below are some of the important findings of this study.The Geometry Free model does not gain strength with the addition of satellites. Since with addition of a satellite a receiver-satellite range is added to the unknowns. Also for a combined GPS and Galileo system, the Geometry Free model does not have a coupling parameter in the unknowns, say troposphere or receiver coordinates. Hence while the mathematical model is formed, from a single system to a combined system, the model does not gain strength. Hence a multi-GNSS constellation would not help to reduce the time-to-fix integer ambiguities for a Geometry Free model.The permanent reference networks can benefit from an integrated GPS and Galileo system. The precision of the ionospheric estimates with a permanent network could reach 2cm instantaneously, almost any time of the day by using quadruple frequency (L1pE1q, L5pE5aq, L2,E5b) GPS and Galileo combined system with the aid of PAR.While the user aims at performing relative positioning using a permanent network, the benefits from a combined GPS and Galileo system are immense. For a user with low-end single frequency receiver, for short baseline lengths ( 10Km), obtaining its receiver positions with 2cm precision for north- and east-components and 6cm precision for the up-component would be possible instantaneously using a combined GPS and Galileo. While the user is equipped with ionospheric corrections from the network, all the ambiguities could be resolved in a short time with a combined GPS and Galileo quadruple frequency system (L1pE1q, L5pE5aq, L2,E5b). The findings from this simulation study shows that, while ionosphere corrections are given to the user, all the ambiguities could be successfully resolved (full AR) within 20 epochs (1 second sampling) by using quadruple frequency from an integrated GPS and Galileo system