<p> A two-part scheme for the design of wideband linear phase SAW filters is proposed. The design uses curved finger interdigital transducers, and extension of slanted finger design, to compensate for circuit effects and eliminate the need for matching. Theory is combined with distortion minimizing techniques to realize devices which satisfy INTELSAT filter specifications. </p> <p> Basic SAW theory is reviewed. and curved finger theory presented, while methods of distortion minimization are both reviewed and proposed. Experimental results which illustrate and support the theory given are included. </p> / Thesis / Master of Engineering (MEngr)

<p> The subject of this thesis is the design, fabrication and comparative testing of two prototype L-band ferrite digital latching phase shifters. One phaser is a variation of a design published by G.T. Roome and H.A. Hair, "Thin Ferrite Devices for Microwave Integrated Circuits", IEEE Trans. Microwave Theory Tech, vol. MTT-16 pp. 411-420, July 1968. The second design is original and is experimentally and theoretical compared to the first phaser. A comparative study was made because of technological difficulties in making these devices. Insertion losses of 2dB and an order of magnitude less than possible phase shift occurred because of inadequate production facilities. Thus, the comparative study gave a common mode error to the published device and the new device.</p> <p> Also, the theory of ferrite microwave phasers and a discussion of a particular system application which prompted this study are included in this thesis.</p> / Thesis / Master of Engineering (MEngr)

The human brain is considered to be the most complex and powerful information-processing device in the known universe. The fundamental concepts behind the physics of complex systems motivate scientists to investigate the human brain as a collective property emerging from the interaction of thousand agents. In this dissertation, I investigate the emergence of cooperation-induced properties in a system of interacting units. I demonstrate that the neural network of my research generates a series of properties such as avalanche distribution in size and duration coinciding with the experimental results on neural networks both in vivo and in vitro. Focusing attention on temporal complexity and fractal index of the system, I discuss how to define an order parameter and phase transition. Criticality is assumed to correspond to the emergence of temporal complexity, interpreted as a manifestation of non-Poisson renewal dynamics. In addition, I study the transmission of information between two networks to confirm the criticality and discuss how the network topology changes over time in the light of Hebbian learning.

This thesis describes a Master of science research program of duration May, I960 to April, 1961 inclusive. It represents part of an extensive research program designed to investigate the thermodynamic aspects of phase transformations. A great deal of effort has been devoted to the application of multicomponent diffusion theory to (de)carburisation, pearlite, and segregation reactions; particularly in ferrous alloys. This fundamental research program is here extended to a general study of the morphological aspects of phase transformation interfaces. Substantially all industrial metallurgical phase transformations are accompanied by the development of non-planar morphologies with attendant segregation. Previous investigations have demonstrated that the factors controlling the type and degree of morphological development are varied and complex. It is apparent that the structural character of an interface is determined, to a large extent, by the system’s phasial constitution in terms of the concentration, temperature, and pressure variables. Therefore, an examination of the relation between these parameters and the structural form of non-planar interfaces was suggested as a potentially valuable field of endeavour. / Thesis / Master of Science (MSc)

This thesis makes a novel contribution to the state-of-the-art literature on EHD melting enhancement of PCMs showing the effects of electroconvection flow and solid extraction during the melting process. The details of the contribution made by this work have been disseminated in the form of three journal publications, which have been integrated into this sandwich Ph.D. thesis. / Latent heat thermal energy storage plays an important role in bridging the gap between the energy supply and consumer demands. The latent heat storage systems use phase change materials (PCMs) which are characterized by their high latent heat and therefore lead to higher energy densities. However, one major disadvantage of PCMs is their low thermal conductivities which affects the rates of charging and discharging. Electrohydrodynamics (EHD) offers an opportunity as an active heat transfer enhancement method which can significantly enhance the melting rates while being able to control the heat transfer as per the system’ needs with a very low power consumption. The application of EHD in two-phase solid liquid systems results in generating electroconvection flow in the liquid medium which increases the heat transfer coefficient and decreases the melting time. The main objective of the current work is to study the heat transfer enhancement and the role of EHD forces during the melting of phase change materials (PCMs) under constant temperature boundary conditions. There are two main investigations performed in the current study. First is experimentally studying the EHD melting enhancement of PCMs while applying high voltages through two rows of electrodes embedded inside the PCM. Moreover, in the experiments, solid extraction was investigated using high-speed imaging conducted at various locations with respect to the electrodes. In the second investigation, PCM melting in a rectangular cavity under the effect of EHD and constant temperature boundary conditions is studied numerically. The flow field, temperature field, and phase field are simulated during the melting process until a steady state condition is reached. Additionally, the effect of the applied voltage and temperature boundaries on the electroconvection flow is illustrated. Experimentally, the EHD melting enhancement of paraffin wax is examined under different applied DC voltage magnitudes and polarities, and different temperature gradients. In addition, the role of EHD forces was investigated by applying DC and AC square waves with different frequencies and offset values. The results showed that the melting enhancement increases with a nonlinear relation with voltages, wherein the maximum effective thermal conductivity was found to be 0.95 W/m-K at -10 kV in comparison with the value of 0.2 W/m-K for the pure liquid paraffin wax, with an enhancement ratio of 4.75. The Coulomb force was concluded to be the dominant EHD force in the study while the dielectrophoretic effect was negligible. Characterization of solid extraction was performed by measuring the intensity of extraction, and the size and velocity of dendrites after extraction at different applied voltages and temperature boundaries for different phase change materials having different mushy zone thickness. For paraffin wax, solid extraction was detected for all the applied DC voltages. Small dendrites were observed to be pulled out from the mushy zone melt front and rise upwards in a rotational manner. The extraction intensity was found to be high at locations of high Coulomb force near the electrodes. In addition, solid extraction measurements showed that the size and velocity of the extracted dendrites increase alongside the applied voltage while the velocity decreases at higher temperature boundaries. Finally, it was found that the existence of a large mushy zone results in higher solid extraction intensities. A numerical model was conducted using the finite element method to investigate the EHD melting of PCMs. In the model, the non-autonomous charge injection assumption is used with the Coulomb force being the only electrical body force considered. First, phase-change modeling is conducted to simulate the melting of paraffin wax without EHD under constant temperature boundary conditions until a steady-state condition is achieved. Next, the whole set of coupled EHD equations is introduced to the model to simulate the EHD melting process. The results revealed that two electroconvection cells were generated between each two successive electrodes in the liquid PCM. The EHD flow leads to the redistribution of the temperature field which enhances the heat transfer. EHD melting continues until a steady-state condition is regained after one hour of EHD time, at which point the enhancement ratio was found to be 2.33 at 6 kV. The influence of the applied voltages and temperature boundaries on the electroconvection flow showed that the fluid velocity increases significantly by increasing the voltage while it decreases under higher temperature gradients across the liquid region. This thesis makes a novel contribution to the state-of-the-art literature on EHD melting enhancement of PCMs showing the effects of electroconvection flow and solid extraction during the melting process. The details of the contribution made by this work have been disseminated in the form of three journal publications, which have been integrated into this sandwich Ph.D. thesis. / Thesis / Doctor of Philosophy (PhD)

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

Quantum systems with finite Hilbert space are considered. Position and mo- mentum states and their relation through a Fourier transform, displacement in the position-momentum phase-space, and symplectic transformations are introduced and their properties are studied. Symplectic Sp(2l;Zp) trans- formations in l-partite finite system are explicit constructed. The general method is applied to bi-partite and tri-partite systems. The effect of these transformations on the correlations is discussed. Entanglement calculations between the subsystems in a bi-partite system and a tri-partite system are presented. The effect of measurements is also studied.

This thesis describes the design, fabrication and characterisation of an infrared optical waveguide phase modulator. The modulator was fabricated in GaAs utilizing a carrier-concentration-reduction rib waveguide structure with a Schottky diode contact to allow the application of an electric field across the waveguide region. Measurements of the phase modulation are presented with results agreeing with the theoretical predictions of an electrooptic coefficient of 1.2 x 10-12 m/V at 1.15 //m. Fabrication techniques and problems are thoroughly discussed. The second part of this thesis consists of measurements of the quantum confined stark shift in an AlGaAs-GaAs multiple quantum well p-i-n diode structure. The results show useful changes in absorption with applied electric field. Transmission measurements as a function of applied field are presented for TE polarized light in a waveguiding geometry as well as photocurrent measurements in the same geometry and with light incident perpendicular to the MQW layers. Reasonable agreements for the relative field induced shifts of the excitonic feature are found but the absolute position of the feature is blue shifted by 7 meV with respect to the theoretically predicted position. / Thesis / Master of Engineering (ME)

No description available.

In this dissertation, an increased thermal capacitance (ITC) and thermal storage management (TSM) system was simulated to reduce building energy consumption, specifically energy related to heating, cooling and domestic hot water. An increased thermal capacitance allows phase shift and amplitude reduction of heat flow fluctuations associated with the building’s internal temperature response due to weather. An adaptive allocation and control of the added capacitance through TSM significantly improves the benefits of the extra capacitance. This dissertation was conducted in three parts: (1) a first-order analysis of the ITC/TSM applied to a micro-building; (2) a transient simulation of the ITC/TSM with PCM implementation for tank volume control; and (3) a parameter study on the ITC/TSM system with added complexities such as the inclusion of DHW and a multiple story residential building. The first-order analysis was used for transient simulation comparison, as simple models are much more suitable for real time implementation in actual control systems. A first order study on a small residential building is also used to establish the merit of the ITC/TSM concept before integrating into a more complex analysis. This study determined that the ITC/TSM could potentially provide savings but required a very large thermal mass. The ITC/TSM system was then coupled with phase change materials (PCMs), which enable thermal energy storage volume reduction. The transient energy modeling software, TRNSYS, is used to simulate the building’s thermal response and energy consumption, as well as the ITC/TSM system and controls. Four temperature-controlled operating regimes are used for the ITC/TSM operations: building shell circulation, heat exchanger circulation, solar panel circulation, and storage. After this, 125 simulations were conducted to design and optimize the ITC/TSM. The three parameters of interest were: tank volume size, solar panel size, and mass flowrate. Domestic hot water usage was also included as another energy savings opportunity. Results for the parameter study showed that savings are optimized when the solar panel and the hot water tank are size together. If they are not sized simultaneously, the temperature of the large thermal capacitance is not adequately controlled. For all simulations conducted in the parameter study, the building energy usage was reduced significantly.