Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May 23, 2007). PDF text: 114 p. ; 0.53 Mb UMI publication number: AAT 3237060. Includes bibliographical references. Also available in microfilm and microfiche formats.

Uma das propriedades fÃsicas mais utilizadas para a implementaÃÃo da tecnologia quÃntica à a polarizaÃÃo da luz. Entretanto, uma vez que a polarizaÃÃo da luz à frÃgil, à essencial que seja utilizado um sistema de correÃÃo de erro quÃntico a fim de tornar a informaÃÃo quÃntica viÃvel na polarizaÃÃo de um fÃton. Um mÃtodo de correÃÃo da polarizaÃÃo proposto para fÃtons isolados divide o canal em subcanais de tal forma que somente a variaÃÃo nesses subcanais destrÃi a informaÃÃo. Para isso, variaÃÃes rÃpidas devem acontecer no momento em que dois pulsos Ãpticos atravessam o subcanal. Neste trabalho analisa-se um modelo estatÃstico que usa o grau de despolarizaÃÃo da luz como uma probabilidade do subcanal sofrer pequenas variaÃÃes no perÃodo de tempo entre a passagem de dois pulsos. Para modelar as variaÃÃes dos parÃmetros do canal, utiliza-se o mÃtodo probabilÃstico de Poisson aplicado a eventos raros. Realiza-se uma estimativa usando mÃtodos numÃricos que mede o grau de polarizaÃÃo da luz para fazer uma previsÃo de como seria o comportamento na prÃtica do sistema de correÃÃo de erro quÃntico estudado. / One of the most used physical properties to implement quantum technology is the polarization of the light. However, since the polarization of the light is fragile, it is essential that a quantum error correction system is used to make quantum information feasible in the polarization of a photon. A method of correction of polarization proposed for isolated photons divides the channel into sub-channels in such a way that only the variation in those sub-channels destroys the information. Therefore, rapid changes must occur in the moment that two optical pulses pass through the sub-channel. This work analyses a statistical model that uses the degree of depolarization of the light as a probability for the sub-channel to undergo minute variations in the time between the passage of two pulses. To model the variations of the parameters of the channel, it is used the probabilistic method of Poisson, applied to rare events. An estimate can be done using numerical methods which measures the degree of polarization of the light to predict how would be the behavior in the practice of the quantum error correction system studied.

M.Ing. / In practice, channels with only insertions and deletions are rare. More commonly, additive errors are also present. Therefore, additional redundancy bits are added to the encoded data stream to allow for insertion/deletion correction. In this dissertation, moment balancing templates are used to add a single insertion/deletion capability to an arbitrary additive-error-correcting code. Moment balancing can be used for systematic encoding of number-theoretic codes. The selection of a particular additive-error-correcting codebook has potential influence on the moment balancing template. In direct relation to this, partition distributions of linear sets are considered and their connection to moment balancing templates illustrated. As an alternative to fixed length moment balancing templates, a variable length approach to moment balancing is also considered. It is shown that variable length moment balancing templates result in better performance, in terms of redundancy, than the optimal fixed length moment balancing template. It is assumed that the boundaries of variable length Levenshtein codewords are known. To implement the variable length template in practice, multiple markers are needed. The delimitation of variable length codeword boundaries with these markers leads to longer marker sequences as compared with the fixed length templates.

M.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

The purpose of this study is to examine the role and locations of “magnetic centers” which evolve, or are established , form the flow of information and the lines of authority on a university campus. It is believed that the certain individuals are centers of information, “magnetic centers,” and they draw messages from other individuals at all levels in the communications network of the structure of structures of an institution. By doing this they exert influence through a filtering process of the flow of information they receive and disseminate. These magnetic connectors may or may not be recognized by other individuals within the organization. Based on the assumption that there are certain individuals who could be classified as magnetic centers the following questions were considered: (1) Are there magnetic centers in the structure or structures of a university?; (2) Are these individuals magnetic centers established because of their position or because of other characteristics held in common?; (3) Are the centers permanent in the structure? If there is more than one structure, which structure appears to be more permanent?; (4) Which structure dominates in the number of recognized magnetic centers?; (5) Do the recognized magnetic centers have common procedures for getting information?; (6) Are there magnetic centers which are not recognized by other individuals in the structure or structures? Are there ascertainable reasons for their non-recognition?

Why is the term information in English an uncountable noun, whereas in information theory it is a well-defined quantity? Since the amount of information can be quantified, what is the meaning of a fraction of that amount? This dissertation introduces a quasi-entropy matrix which developed from Claude Shannon's information measure as an analytical tool for behavioral studies. Such matrix emphasizes the role of relative characteristics of individual level data across different collections. The real challenge in the big data era is never the size of the dataset, but how data lead scientists to individuals rather than arbitrarily divided statistical groups. This proposed matrix, when combining with other statistical measures, provides a new and easy-to-do method for identifying pattern in a well-defined system because it is built on the idea that uneven probability distributions lead to decrease in system entropy. Although the matrix is not superior to classical correlation techniques, it allows an interpretation not available with traditional standard statistics. Finally, this matrix connects heterogeneous datasets because it is a frequency-based method and it works on the modes of data rather than the means of values. It also visualizes clustering in data although this type of clustering is not measured by the squared Euclidean distance of the numerical attributes.

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