Picosecond laser studies of V-T processes in gases and electronic excitation transport in disordered systems

SVL fluorescence spectroscopy was used to study intra- molecular energy transfer from the 0(DEGREES) level of aniline induced by collisions with CO(,2). The populations of eight aniline vibronic growth levels, as a function of CO(,2) pressure, were monitored. Collision gas pressures were adjusted to keep aniline-CO(,2) interactions within the single-collision regime. To first order, collision-induced energy transfer from the 0(DEGREES) level of aniline for CO(,2) as the collision gas follows the same flow pattern as was found in previous studies when Ar, H(,2)O or CH(,3)F were the collision partners(\u271,2);Time-correlated photon counting was used to measure concen- tration dependent fluorescence depolarization for rhodamine 6G in glycerol. Fluorescence decays from these viscous solutions provide data for analyzing the three-dimensional, three-body excitation transport theory developed by Gochanour, Andersen and Fayer for disordered systems(\u273). Solution concentrations of rhodamine 6G range from 1.7 x 10(\u27-4) to 2.4 x 10(\u27-3) M. Differences between optimized theoretical and experimental profiles are shown to be dominated by experimental artifacts arising from excitation trapping by rhodamine 6G aggregates and from self-absorption in solution cells thicker than 10 (mu)m;The two-dimensional, two-body excitation theory developed by Loring and Fayer(\u274) was also examined using time-resolved fluores- cence depolarization techniques. The samples, made up of sub- monolayers of rhodamine 3B adsorbed onto optically flat fused silica yield fluorescence profiles which agree well with profiles developed from the theory for reduced surface coverages up to (TURN)0.4. At higher coverages, excitation trapping by rhodamine 3B aggregates;truncates the depolarization process, yielding apparent reduced coverages which are appreciably lower than the true coverages; (\u271,2,3,4)Please see dissertation for references

Displacement and disparity representations in early vision

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (p. 211-220).by Steven James White.Ph.D

B Physics

I introduce and define Quantum Chromodynamics. I describe various well-known nonperturbative techniques for calculating quantities from the theory and discuss their merits and deficiencies. I then motivate and define a non-relativistic formulation (NRQCD) of the theory. I discuss the mechanics of the extraction of numbers from numerical simulations, and present general arguments as to the expected form of these data. I present results and details of their extraction from simulations of heavy-heavy and heavy-light mesons using NRQCD. I compare these results with those from other calculations and with experimental data, where they exist. I make suggestions for further work. An appendix contains details of the code used in the simulation together with the input parameters of the simulation

ANALOG SIGNAL PROCESSING SOLUTIONS AND DESIGN OF MEMRISTOR-CMOS ANALOG CO-PROCESSOR FOR ACCELERATION OF HIGH-PERFORMANCE COMPUTING APPLICATIONS

Emerging applications in the field of machine vision, deep learning and scientific simulation require high computational speed and are run on platforms that are size, weight and power constrained. With the transistor scaling coming to an end, existing digital hardware architectures will not be able to meet these ever-increasing demands. Analog computation with its rich set of primitives and inherent parallel architecture can be faster, more efficient and compact for some of these applications. The major contribution of this work is to show that analog processing can be a viable solution to this problem. This is demonstrated in the three parts of the dissertation. In the first part of the dissertation, we demonstrate that analog processing can be used to solve the problem of stereo correspondence. Novel modifications to the algorithms are proposed which improves the computational speed and makes them efficiently implementable in analog hardware. The analog domain implementation provides further speedup in computation and has lower power consumption than a digital implementation. In the second part of the dissertation, a prototype of an analog processor was developed using commercially available off-the-shelf components. The focus was on providing experimental results that demonstrate functionality and to show that the performance of the prototype for low-level and mid-level image processing tasks is equivalent to a digital implementation. To demonstrate improvement in speed and power consumption, an integrated circuit design of the analog processor was proposed, and it was shown that such an analog processor would be faster than state-of-the-art digital and other analog processors. In the third part of the dissertation, a memristor-CMOS analog co-processor that can perform floating point vector matrix multiplication (VMM) is proposed. VMM computation underlies some of the major applications. To demonstrate the working of the analog co-processor at a system level, a new tool called PSpice Systems Option is used. It is shown that the analog co-processor has a superior performance when compared to the projected performances of digital and analog processors. Using the new tool, various application simulations for image processing and solution to partial differential equations are performed on the co-processor model

Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers

Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method

Hypercube matrix computation task

The Hypercube Matrix Computation (Year 1986-1987) task investigated the applicability of a parallel computing architecture to the solution of large scale electromagnetic scattering problems. Two existing electromagnetic scattering codes were selected for conversion to the Mark III Hypercube concurrent computing environment. They were selected so that the underlying numerical algorithms utilized would be different thereby providing a more thorough evaluation of the appropriateness of the parallel environment for these types of problems. The first code was a frequency domain method of moments solution, NEC-2, developed at Lawrence Livermore National Laboratory. The second code was a time domain finite difference solution of Maxwell's equations to solve for the scattered fields. Once the codes were implemented on the hypercube and verified to obtain correct solutions by comparing the results with those from sequential runs, several measures were used to evaluate the performance of the two codes. First, a comparison was provided of the problem size possible on the hypercube with 128 megabytes of memory for a 32-node configuration with that available in a typical sequential user environment of 4 to 8 megabytes. Then, the performance of the codes was anlyzed for the computational speedup attained by the parallel architecture

Direct extraction of ∆(_MS) from e(^+)e jet observables

We demonstrate a renormalisation group improved formulation of QCD perturbation theory. At next-to-leading order (NLO) and beyond this permits a direct extraction of the QCD dimensional transmutation parameter, A(_ms) that typifies the one parameter freedom of the theory in the limit of massless quarks. We apply this to a variety of experimental data on e(^+)e" jet observables at NLO. We take into consideration data from PETRA, PEP, TRISTAN, SLC and LEP 1 and 2. In this procedure there is no need to mention, let alone to arbitrarily vary, the unphysical renormalization scale µ, and one avoids the spurious and meaningless "theoretical error" associated with standard a(_8) determinations. An attempt is made to estimate the importance of uncalculated next-to-NLO and higher order perturbative corrections, and power corrections, by studying the scatter in the values of ∆(_MS) obtained for different observables. We also consider large infrared logarithm resummations in these jet observables and present results for the particular cases of the four-jet rate to a next-to-leading logarithm approximation and the distributions for the four-jet variables, "light hemisphere mass" and "narrow jet broadening" to a next-to-next-to-leading logarithm approximation in the perturbative expansion. We apply a simple power correction to these variables and obtain remarkably good fits to the data