Thesis (M.S.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references (leaves [70]-72).

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 10, 2007) Vita. Includes bibliographical references.

The traveling salesperson (or, salesman) problem (TSP) is a well known and important combinatorial optimization problem. The goal is to find the shortest tour that visits each city in a given list exactly once and then returns to the starting city. Despite this simple problem statement, solving the TSP is difficult since it belongs to the class of NP-complete problems. The importance of the TSP arises besides from its theoretical appeal from the variety of its applications. Typical applications in operations research include vehicle routing, computer wiring, cutting wallpaper and job sequencing. The main application in statistics is combinatorial data analysis, e.g., reordering rows and columns of data matrices or identifying clusters. In this paper, we introduce the R package TSP which provides a basic infrastructure for handling and solving the traveling salesperson problem. The package features S3 classes for specifying a TSP and its (possibly optimal) solution as well as several heuristics to find good solutions. In addition, it provides an interface to Concorde, one of the best exact TSP solvers currently available. (authors' abstract)

Smith, T.H.C., Prof.

This thesis describes the design of two particular types of conventional distributed amplifiers and treats a proposed split-band amplifier. The method used for the conventional designs is an iterative synthesis process developed at Stanford University in 1952. The objective was to investigate the possibility of producing distributed amplifiers of superior performance. Only amplifiers with a flat amplitude response were considered since the calculating equipment available was inadequate for the computations involved in producing amplifiers with other types of response characteristics. Three designs of one form of conventional distributed amplifier were carried out. These were amplifiers with ladder networks for delay lines and with both delay lines identical except for a possible difference in impedance level. None of the three amplifiers had theoretical characteristics which justified an attempt to construct them. The other conventional amplifier was one employing ladder-like networks for the delay lines with each of the lines symmetrical about the mid-point of its length and with both lines identical except for a possible difference in impedance level. An attempt to design one of these amplifiers produced new information beyond that reported in the original work at Stanford University. Furthermore, when using the iterative technique to design this amplifier, there seemed to be reasonable doubt as to whether or not the process was always convergent. No definite opinion on the matter was formulated since it would have required that the calculations be continued through more cycles of iteration than could reasonably be carried out with the computing equipment at hand. Finally, a proposed split-band amplifier was investigated and its theoretical gain-bandwidth characteristics were compared with those of a conventional distributed amplifier. It showed a slight advantage, but this was far outweighed by certain serious inherent disadvantages and the project was discontinued. The investigation has shown that it is impractical to carry out the calculations involved in the iterative prodecure when using a hand calculator. Also, some doubt as to the general convergence of the iterative synthesis process has been raised. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

O presente trabalho descreve os processos de preparação do aluminato de bário e cálcio, material emissor de elétrons, empregados nos catodos do tipo impregnado para utilização em uma válvula de microondas do tipo TWT. Os catodos investigados constituem-se de uma pastilha de tungstênio porosa impregnada com aluminato de bário e cálcio com proporção molar 5:3:2. Para a síntese do aluminato, utilizaram-se três diferentes métodos: reação em estado sólido, precipitação e cristalização. A termogravimetria auxiliou na consolidação dos procedimentos de preparação dos aluminatos de modo a definir os parâmetros de pirólise/calcinação. Verificou-se que a técnica que apresentou melhores características de síntese foi o método da cristalização, pois esta apresentou uma menor temperatura de formação do aluminato (800ºC) em atmosfera oxidante (O2), quando comparada às técnicas de reação em estado sólido e de precipitação (temperatura de 1000ºC em atmosfera redutora – H2). Utilizou-se o conceito da distribuição da função trabalho prática (PWFD) de Miram para a caracterização termiônica dos catodos impregnados. Empregando-se este método, foi possível traçar o perfil termiônico do catodo com aluminato de bário e cálcio. As curvas PWFD apresentaram a função trabalho média do catodo aluminato de, aproximadamente, 2,00 eV. / In the present work it is described the barium calcium aluminate manufacture processes employed to produce impregnated cathodes to be used in a traveling-wave tube (TWT). The cathodes were developed using a tungsten body impregnated with barium and calcium aluminate with a 5:3:2 proportion (molar). Three different processes were investigated to obtain this material: solid-state reaction, precipitation and crystallization. Thermal analysis, thermogravimetry specifically, supported to determine an adequate preparation procedure (taking into account temperature, time and pirolisys atmosphere). It was verified that the crystallization showed a better result when compared to those investigated (solid-state reaction and precipitation techniques – formation temperature is about 1000ºC in hydrogen atmosphere), whereas it presented the lower formation temperature (800ºC) in oxidizing atmosphere (O2). It was used the practical work function distribution theory (PWFD) of Miram to characterize thermionic impregnated cathode. The PWFD curves were used to characterize the barium-calcium aluminate cathode. PWFD curves shown that the aluminate cathode work function is about 2,00 eV.

In confined bulk crystal growth techniques such as the traveling heater method, base materials in an ampoule are melted and resolidified as a single crystal. During this process, flow control is desired so that the resulting alloy semiconductors are uniform in composition and have minimal defects. Such control allows for tuned lattice parameters and bandgap energy, properties necessary to produce custom materials for specific electro-optical applications. For ternary alloys, bulk crystal growth methods suffer from slow diffusion rates between elements, severely limiting growth rates and reducing uniformity. Exposing the electrically conducting melt to an external alternating magnetic field can accelerate the mixing. A rotating magnetic field (RMF) can be used to stir the melt in the azimuthal direction, which reduces temperature variations and controls the shape at the solidification front. A traveling magnetic field (TMF) imposes large body forces in the radial and axial directions, which helps reduce the settling of denser components and return them to the growth front. In either case, mixing is desired, but turbulence is not. At large magnetic Taylor numbers the flow becomes unstable to first laminar and then turbulent transitions. It is imperative that crystal growers know when these transitions will occur and how the flow physics is affected. Here, the melt driven by electromagnetic forces is analyzed through the use of 3D numerical simulations of the flow field up to and beyond the point of laminar instability. The analysis aims to emulate laboratory conditions for generating electromagnetic forces for both types of alternating magnetic fields and highlights the differences between laboratory forces and the analytical approximations that are often assumed. Comparisons are made between the resulting forces, flow fields, and points of instability as the frequency of the alternating field varies. Critical Taylor numbers and the resulting unstable flow fields are compared to the results from linear stability theory.

How potential tourists sort out intriguing resorts or wherever could fulfill their necessities among all the tourism destinations, it¡¦s what tourism marketers eager to know and their intention to guide the tourists. In terms of touristic necessities, besides the general factors such as distance, timing, traffic ways and the cost, tourists would more and more value the image and slant on resorts while choosing tourism destination. They would decide where they want to go by acquiring more information about the credit and image of the resorts, and determine whether they would travel there again by the hands-on traveling experiences and impression. This study has at fist referred to some relevant literatures about the tourists¡¦ impressions and slants on the tourism destination and the segmental marketing, then based on the resources and attributes of Moalin national scenic area to build up measurement and questionnaire for traveling image, so as to carry positive investigation around Taiwan and base on non-residents¡¦ impression for Moalin to segmentalize its potential tourism market. There were totally 900 questionnaires issued and 666 were returned (the valid returning rate was 78%). Then by factor analysis, the images and slants of scenic resorts were divided into four constructs, including ¡§natural landscapes¡¨, ¡§history and culture¡¨, ¡§social environment¡¨ and ¡§agricultural and forestry leisured activity¡¨. Furthermore, the imagery factors of resorts were used to be variables of market segmentation and the potential tourist market was divided into 3 factorial segments as factors of ¡§traveling experiences¡¨, ¡§motives for traveling¡¨ and ¡§cognition on impediments to traveling¡¨. The factors of motives for traveling were especially extracted by factor analysis and ramified into 8 clusters such as factors of ¡§enjoying touring experience¡¨, ¡§molding peaceful temperament¡¨, ¡§calling out friends¡¨, ¡§work-out for health¡¨; as well as the four factors for cognition on impediments to traveling such as ¡§experience and safety¡¨, ¡§travel-mate¡¨, ¡§substantial reasons¡¨ and ¡§environment and equipment¡¨. The author also used traveling images, demographic variables and some relevant data about traveling experiences to describe the characteristic and difference among those market segmentations. In the end, the results were sorted out and described according to the characteristic and difference among those market segmentations, so as to work out suggestions for marketing strategies as reference for relevant industries and tourism agency to choose adequate niche market and efficient market strategy.

O presente trabalho descreve os processos de preparação do aluminato de bário e cálcio, material emissor de elétrons, empregados nos catodos do tipo impregnado para utilização em uma válvula de microondas do tipo TWT. Os catodos investigados constituem-se de uma pastilha de tungstênio porosa impregnada com aluminato de bário e cálcio com proporção molar 5:3:2. Para a síntese do aluminato, utilizaram-se três diferentes métodos: reação em estado sólido, precipitação e cristalização. A termogravimetria auxiliou na consolidação dos procedimentos de preparação dos aluminatos de modo a definir os parâmetros de pirólise/calcinação. Verificou-se que a técnica que apresentou melhores características de síntese foi o método da cristalização, pois esta apresentou uma menor temperatura de formação do aluminato (800ºC) em atmosfera oxidante (O2), quando comparada às técnicas de reação em estado sólido e de precipitação (temperatura de 1000ºC em atmosfera redutora – H2). Utilizou-se o conceito da distribuição da função trabalho prática (PWFD) de Miram para a caracterização termiônica dos catodos impregnados. Empregando-se este método, foi possível traçar o perfil termiônico do catodo com aluminato de bário e cálcio. As curvas PWFD apresentaram a função trabalho média do catodo aluminato de, aproximadamente, 2,00 eV. / In the present work it is described the barium calcium aluminate manufacture processes employed to produce impregnated cathodes to be used in a traveling-wave tube (TWT). The cathodes were developed using a tungsten body impregnated with barium and calcium aluminate with a 5:3:2 proportion (molar). Three different processes were investigated to obtain this material: solid-state reaction, precipitation and crystallization. Thermal analysis, thermogravimetry specifically, supported to determine an adequate preparation procedure (taking into account temperature, time and pirolisys atmosphere). It was verified that the crystallization showed a better result when compared to those investigated (solid-state reaction and precipitation techniques – formation temperature is about 1000ºC in hydrogen atmosphere), whereas it presented the lower formation temperature (800ºC) in oxidizing atmosphere (O2). It was used the practical work function distribution theory (PWFD) of Miram to characterize thermionic impregnated cathode. The PWFD curves were used to characterize the barium-calcium aluminate cathode. PWFD curves shown that the aluminate cathode work function is about 2,00 eV.