Analysis and Comparison of SMAC and TMAC Protocol for Energy Efficient Dynamic Topology in Sensor Network

In the era of wireless communication, wireless sensor is one of the best technologies we are witnessing. In case of environmental monitoring, tactical systems and different tracking applications, wireless sensors are being used. Here, the corresponding nodes operate on incomplete power and thus the energy comes into play to operate these entire networks. Managing the energy and its utilization is vital for TCP/IP protocol suite which is MAC layer’s application. Thus keeping in mind the above challenges, the techniques used are increasing the sleep duration, over hearing and ideal listening, collision of packet and eliminating hidden terminal problem. This paper is oriented towards the comparison of energy consumption by SMAC and TMAC protocol. The characteristics of TMAC and SMAC protocols were explored keeping real transmission conditions intact, like variable transmission bit rate, dynamic topology and mobile sensors in network. TMAC and SMAC protocols are contention based protocols and are designed to keep the energy consumption low using duty cycle

Discrete Element Method (DEM) Analysis of Non-Cohesive Granular Material Flow in Hoppers

Hoppers, silos and bins are expected to store material and provide unrestricted and uniform flow of the same in mate-rial processing plants. Traditionally, the material flow from hopper is analyzed assuming the solid mass as contin-uum. However, the behavior of particulate solids deviates significantly from a continuous system, due to fluctuation in its bulk material properties (e.g. bulk density) throu-ghout the process. In the present work, a numerical techn-ique called discrete element method (DEM) is used to analyze granular material flow from hopper. DEM tracks the _trajectories of individual particles as they interact with their neighboring particles and hopper walls. These interactions ultimately translate to the overall displace-ment of the particles. The scheme is repeated in small time intervals covering the complete duration of the proc-ess. Here the simulations are limited to non-cohesive sphe-rical granular material. Material flow is studied as a function of hopper geometry. This article involves visua-lization and flow rate analysis of coarse particles for different hopper design

Self-Similar Distributions of Fine Particles Produced in Non-Linear Batch Grinding

A parametric approach is described for tracking the evolut-ion of particle size distribution with time in batch grinding in micron and sub-micron range. The approach is based on an asymptotic self-similarity solution to populat-ion balance equation of grinding. The possible presence of non-linearity in the fine grinding regime is captured by a modification to the model formulation scheme. It is assu-med that the breakage rate is a function of the grind time and therefore, indirectly of the time-dependent mean, median or a percentile size. It is shown that the self-similar character is preserved under a wide class of functions that can in principle describe the non-linear characteristics of the comminution process. The resulting parametric model describes the evolution of particle spectra. Several sets of published data are employed to validate the model

Band offsets of metal oxide contacts on TlBr radiation detectors

Metal oxides are investigated as an alternative to metal contacts on thallium bromide (TlBr) radiation detectors. X-ray photoelectron spectroscopy studies of SnO 2/TlBr and ITO/TlBr devices indicate that a type-II staggered heterojunction forms between TlBr and metal oxides upon contacting. By using the Kraut method of valence band offset (VBO) determination, the VBOs of SnO 2/TlBr and ITO/TlBr heterojunctions are determined to be 1.05 ± 0.17 and 0.70 ± 0.17 eV, respectively. The corresponding conduction band offsets are then found to be 0.13 ± 0.17 and 0.45 ± 0.17 eV, respectively. The I-V response of symmetric In/SnO 2/TlBr and In/ITO/TlBr planar devices is almost Ohmic with a leakage current of less than 2.5 nA at 100 V

Quasiparticle spectroscopy in technologically-relevant niobium using London penetration depth measurements

London penetration depth was measured in niobium foils, thin films, single crystals, and superconducting radio-frequency (SRF) cavity pieces cut out from different places. The low-temperature (T<Tc/3) variation, sensitive to the low-energy quasiparticles with states inside the superconducting gap, differs dramatically between different types of samples. With the help of phenomenological modeling, we correlate these different behaviors with known pair-breaking mechanisms and show that such measurements may help distinguish between different pair-breaking mechanisms, such as niobium hydrides and two-level systems (TLS). The conclusions also apply to SRF cavities when tracking the temperature-dependent quality factor and the resonant frequency

Band offsets of metal oxide contacts on TlBr radiation detectors

Metal oxides are investigated as an alternative to metal contacts on thallium bromide (TlBr) radiation detectors. X-ray photoelectron spectroscopy studies of SnO 2/TlBr and ITO/TlBr devices indicate that a type-II staggered heterojunction forms between TlBr and metal oxides upon contacting. By using the Kraut method of valence band offset (VBO) determination, the VBOs of SnO 2/TlBr and ITO/TlBr heterojunctions are determined to be 1.05 ± 0.17 and 0.70 ± 0.17 eV, respectively. The corresponding conduction band offsets are then found to be 0.13 ± 0.17 and 0.45 ± 0.17 eV, respectively. The I-V response of symmetric In/SnO 2/TlBr and In/ITO/TlBr planar devices is almost Ohmic with a leakage current of less than 2.5 nA at 100 V

STRATEGIC APPROACHES TOWARDS SOLVING CRITICAL CHALLENGES IN CRYSTAL GROWTH OF DETECTOR GRADE Cd0.9Zn0.1Te INCLUDING MELT MIXING TECHNIQUES

Over the last few decades Cadmium Zinc Telluride (CZT) has emerged as a novel material for radiation detection in homeland security as well as medical applications and as substrates for epitaxial growth of infrared detector, Mercury Cadmium Telluride. There are, however, several critical issues regarding the bulk growth of CZT which renders it unsuitable or cost ineffective for these applications. These challenges can be summarized as non-uniformity (due to Zinc and intentional dopant segregation), longer growth times (because of lower thermal conductivity of the melt), Tellurium (Te) secondary phases (SP), unstable growth interface (due to lower thermal conductivity and higher heat of fusion) and non-stoichiometric growth conditions. Systematic approaches towards solving these problems will be discussed along with the consequences and future research directions.By application of a proper mixing technique to the CZT melt, most inhomogeneity problems that are common in growth techniques using non rotating crucibles can be overcome. A unique custom made ampoule rotation system was developed for mixing the CZT melt by applying several rotation parameters. Experiments were performed with different growth temperature profiles, rotation parameters and charge/dopant concentrations. Improvements in Zinc distribution profiles and the shape of the liquid/solid interface during the growth process were determined by room temperature photoluminescence (RT-PL) mapping of radial and longitudinal-cut CZT wafers. SP diameters were limited to a maximum of 10 µm after application of ampoule rotation, with distribution maxima at 6 µm. Growth interface studies revealed several unique features which will be discussed in the dissertation. The spectral, optical and electrical properties of the detectors fabricated from all these growths will be presented. The statistical variations of different properties along the grown ingots will be discussed

Essays on International Economics

My dissertation consists of two essays, which focus on international finance and trade that are encapsulated within the realm of international economics. My first essay tests whether the effects of financial system liberalization in Singapore can be identified using indicators of exchange market pressure. First, I calculate exchange market pressure (EMP) index for the Singapore dollar relative to US dollar for two separate periods 1991-1997 and 1998-2008. During 1991-1997, Monetary Authority of Singapore heavily regulated Singapore financial markets. However, post 1997 MAS started to liberalize Singapore financial system. In view of such structural changes in the financial system, we estimate a VAR model incorporating EMP and obtain impulse response functions to identify how MAS changes its policy approach in response to high EMP during two periods. My second essay explores the impact of the Dominican Republic - Central American Free Trade Agreement (ACFAT-DR) on U.S. imports and determines whether the enactment of such an agreement caused trade creation or trade diversion. More specifically, it investigates whether or not there was any significant increase in U.S. import flows from Central America due to enactment of the agreement. Using disaggregate data we estimate fixed effect regression models and find that U.S. imports increased due to tariff liberalization under CAFTA-DR agreement without causing any trade diversion

Development of multiobjective management models for coastal aquifers

Management models are developed and solved that are based on the advective-dispersive density-dependent miscible flow and transport processes in the aquifer. Various conflicting objectives of aquifer management are considered in this study. Two optimization models incorporating multiple objectives of coastal aquifer management are formulated. These models are solved for a hypothetical three-dimensional aquifer system for transient flow and transport conditions. The obtained solution results demonstrate potential feasibility of using the embedding technique for the development of multiple-objective coastal aquifer management models. In general, a planned, spatially and temporally, varying pumping strategy, obtained as solutions of an embedded optimization model, is shown to be a viable management method for beneficial exploitation and salinity control of a coastal aquifer. The potential feasibility of these management models for evolving a transient spatially dependent pumping strategy to facilitate beneficial exploitation of the aquifer and to control or remediate contamination due to seawater intrusion is also demonstrated