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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
671

\"Estudos sobre a taxonomia e a distribuição dos peixes da família Myctophidae (Actinopterygii: Myctophiformes) no Sudeste e Sul do Brasil\"

Santos, Andressa Pinter dos 16 April 2003 (has links)
Os peixes da família Myctophidae constituem do ponto de vista ecológico o grupo mais importante da fauna mesopelágica, tanto em número de espécies, quanto em biomassa. Fazem parte da dieta de uma grande variedade de cetáceos e peixes oceânicos. Representam também uma considerável fonte de proteína animal, ainda não diretamente explorada. Além disso, estes peixes tem papel importante na transferência de energia das camadas superficiais oceânicas para as mais profundas através de um comportamento migratório vertical diário de centenas de metros característico. O material deste estudo provém de um Programa de Avaliação do Potencial Sustentável de Recursos Vivos na Zona Econômica Exclusiva (Programa Revizee), no qual foram efetuados arrastos com rede de meia água com o N/Oc. Atlântico Sul, entre as isóbatas de 100 e 1500 m, de 22oS a 35oS, realizados no inverno de 1996, outono e primavera de 1997, e outono e primavera de 1999. As características morfológicas descritivas das 37 espécies coletadas foram analisadas e comparadas com dados morfológicos de exemplares coletados de outras regiões do Atlântico, constantes da literatura. A análise destas comparações mostrou que 17 das espécies apresentaram pelo menos uma diferença morfológica consistente nos caracteres estudados, sugerindo isolamento e diferenciação na área pesquisada. Além disso, informações sobre a distribuição geográfica destas espécies no Atlântico são apresentadas e discutidas frente aos padrões biogeográficos estabelecidos pelos pesquisadores para organismos mesopelágicos do Atlântico. Fica evidente que apesar da contribuição que este trabalho trouxe em relação ao conhecimento destes peixes nesta região, o número de amostras analisadas até hoje no Atlântico Sul ainda é pequeno para que o conhecimento taxonômico e de distribuição dos Myctophidae torne-se conclusivo. / From an ecological point of view the Myctophidae fishes constitute the most important group of the mesopelagic fauna, considering as much as number of species, as biomass. They are part of the diet of a great variety of cetaceans and marine fishes. They also represent a remarkable animal protein source, although not directly exploited. Besides these fishes have important role at energy transference from the upper productive zones to deeper, trophically poorer, through a daily vertical migratory behavior of hundreds of meters. The material of this study results from a Program of Evaluation of the Sustainable Potential of the Livings Resources in the Exclusive Economic Zone (Revizee Program), in which sampling was done using mid water trawl on board R/V Atlântico Sul, between 100 and 1500 meters deep, latitudes between 20oS and 30oS, during winter of 1996, autumn and spring of 1997, and autumn and spring of 1999. The descriptive morphological characteristics of the 37 collected species were analyzed and compared to the morphological data of specimes collected from other regions of Atlantic Ocean, according to the literature. The analysis of these comparisons showed that 17 of the species presented at least one consistent morphological difference in the studied characters, suggesting isolation and differentiation in the studied area. Moreover, information concerning geographical distribution of these species at the Atlantic Ocean are presented and argued front to the biogeographics patterns established by researchers of the mesopelagical ichthyofauna of the referred ocean. It is evident that despite the contribution of the present study to the knowledge of these fishes in this region, the quantity of samples analyzed until now in the South Atlantic Ocean is still small so that the taxonomic knowledge and distribution of the Myctophidae becomes conclusive.
672

New results in probabilistic modeling. / CUHK electronic theses & dissertations collection

January 2000 (has links)
Chan Ho-leung. / "December 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 154-[160]). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
673

Parasite distribution and specificity in anuran host complexes

Crosswaite, Matthew John January 1994 (has links)
This study was based on the parasite fauna of three anuran systems. In two of the systems; the spadefoot toads, Scaphiopus bombifrons and S. multiplicatus and the fire and yellow-bellied toads, Bombina bombina and B.variegata, inter-species hybridisation occurs. In the third system an autopolyploid species complex involves the Gray treefrogs, Hyla chrysoscelis and H.versicolor. The status of the Scaphiopus hybrid zone in Arizona was re-assessed by cellulose-acetate gel electrophoresis. Genotypic frequencies were comparable to those previously documented, indicating that a region of 'balanced introgression' may exist. Specimens were collected in areas of host sympatry and the distribution of helminths within hosts of different genetic constitution investigated. From extensive surveys of all three systems, parasite frequency distributions were typically aggregated with no evidence of any change in host genetic predisposition to infection. In addition, the surveys have documented a number of new host and/or parasite locality records for each system. Of particular interest was the discovery of the digenean Clinostomum complanatum in a desert environment, an introduction related to human management of the ecosystem. Particular reference was made to the specificity of the polystomatid monogeneans, Polystoma nearcticum infecting members of the H.chrysoscelis- H.versicolor complex and Neodiplorchis scaphiopodis infecting S.bombifrons and S.multiplicatus. For Polystoma, worms from H.chlysoscelis and H.versicolor could not be separated by morphology, which was supported by preliminary crossinfections. This suggests that P.nearcticum infects both members of this complex. For Neodiplorchis, morphological similarity was confirmed by cross-infections which revealed that N.scaphiopodis can reach sexual maturity and produce fully developed larvae in heterospecific hosts. The neotenic development of P. nearcticum and the initial post-oncomiracidial stages of N.scaphiopodis were documented. Furthermore, certain aspects of transmission dynamics were examined by the experimental infection of H. versicolor tadpoles with P. nearcticum.
674

Earnings variations by educational fields, industries, and occupations in Hong Kong.

January 1998 (has links)
Chi Him Roger Yip. / Thesis submitted in 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 134-137). / Abstract also in Chinese. / Acknowledgment --- p.1 / Abstract --- p.2 / CONTENTS --- p.3 / Chapter Chapter 1 --- Introduction and Overview --- p.5 / Chapter I. --- Age-earnings profiles --- p.6 / Chapter II. --- An overview of the thesis --- p.24 / Chapter Chapter 2 --- Literature Review --- p.25 / Chapter I. --- Human capital as a determinant of earnings --- p.25 / Chapter A. --- The early roots: Adam Smith --- p.25 / Chapter B. --- Rapid development in human capital theory in the late 20th century --- p.27 / Chapter II. --- Empirical labour economics: Mincer's statistical earnings function --- p.29 / Chapter A. --- Development of the statistical earnings function --- p.29 / Chapter B. --- The problem of ability bias --- p.32 / Chapter III. --- Empirical Evidence --- p.34 / Chapter Chapter 3 --- The Data Sets and the Variables Available --- p.37 / Chapter Chapter 4 --- Earnings Variations among Working Men --- p.40 / Chapter I. --- Summary statistics --- p.40 / Chapter II. --- "Earnings Function, and Estimation Results" --- p.42 / Chapter III. --- Summing-up --- p.52 / Chapter Chapter 5 --- The Contribution of Educational Fields to Earnings --- p.53 / Chapter I. --- Summary statistics --- p.53 / Chapter II. --- Earnings functions with educational fields as dummy variables --- p.63 / Chapter III. --- Summing-up --- p.76 / Chapter Chapter 6 --- Earnings Variations by Industries --- p.78 / Chapter I. --- Summary statistics --- p.78 / Chapter II. --- Earnings functions with industries as dummy variables --- p.83 / Chapter III. --- Contribution of educational fields to earnings --- p.90 / Chapter IV. --- Summing-up --- p.106 / Chapter Chapter 7 --- Earnings Variations by Occupations --- p.107 / Chapter I. --- Summary statistics --- p.107 / Chapter II. --- Earnings functions with occupations as dummy variables --- p.112 / Chapter III. --- Contribution of educational fields to earnings --- p.118 / Chapter IV. --- Summing-up --- p.131 / Chapter Chapter 8 --- Conclusion --- p.132 / Bibliography --- p.134
675

Marknadskommunikation mot sitt segment

EKLUND, SUSANNE, IVARSSON JÖNSSON, AMANDA January 2013 (has links)
Idag blir konkurrensen allt hårdare på marknaden, inte minst sagt i modebranschen. Företag tar till alla olika sorters konkurrensstrategier för att just de skall sticka ut från mängden. Här följer en studie inriktat på en av dessa konkurrensstrategier, nämligen marknadskommunikation. Kommunicerar man fel på den hårt konkurerande marknaden idag kan det få förödande effekter. Man måste som sändare av budskapet veta vem mottagaren är. För att nå framgång i modebranschen är det därför viktigt att positionera sig på marknaden så att man differentierar sig från sina konkurrenter. För att differentiera sig måste du hitta ditt eget sätt att kommunicera till ditt segment. Marknadskommunikationens första prioritering är att ge rätt associationer till företagets varumärke, göra företaget attraktivt på marknaden och även att bygga upp och förmedla ett så kallat mervärde. För att få en verklig och realistisk överblick över problemet har vi valt att undersöka hur företaget Wakakuu kommunicerar med sitt segment. Vi har utifrån detta kunnat analysera hur det ser ut i teorin och hur det ser ut i praktiken. Wakakuu är ett företag som har en framgångsrik webbshop och en showroombutik belägen i Hovås, söder om Göteborg. Svenska modebranschens omsättning var 206 miljarder kronor år 2011. 43 % av den totala omsättningen står butikshandeln för och 4 % står e-handeln för. (Svensk handel 2013) Butikshandeln utgör som sagt en stor del av den totala marknaden och detta var en av anledningen till att vi ville samarbeta med en butik. Vi har studerat hur Wakakuu arbetar för att nå ut till deras segment, kvinna 20-30 år, som finns på deras webbshop men ej i deras fysiska butik, för att få detta segment till den fysiska butiken. För att ta reda på detta har vi studerat deras kommunikationskanaler och påverkande faktorer som utgör om en butik blir vald eller ej. Syftet med vår uppsats är att ta reda på hur ett modeföretag kommunicerar med sitt segment. Vi vill undersöka hur kommunikationsprocessen går till. Slutligen kommer vi att analysera vårt resultat och vår teori, vi vill kunna dra paralleller mellan teorin och praktiken. Vi har kommit fram till att Wakakuu har svårigheter med att nå ut till den yngre kundgruppen, kvinna 20-30 år. I de sociala medier som Wakakuu använder för att kommunicera finns den yngre kundgruppen. Dock ser vi ingen positiv effekt utifrån denna kommunikationsprocess. Vi drar här slutsatsen att Wakakuus kommunikation inte når ut ur det informationsbrus som vi lever i, och det uppkommer för många störningar innan kommunikationen når konsumenten att de inte får någon positiv effekt. Vi har också kommit fram till att Wakakuus läge och pris är påverkande faktorer till varför Wakakuu inte väljs utav konsumenten. / Program: Butikschef, textil och mode
676

Economic dependency and income distribution in Puerto Rico 1950-1977

Corrada-Guerrero, Rafael January 1979 (has links)
Thesis. 1979. Ph.D.--Massachusetts Institute of Technology. Dept. of Urban Studies and Planning. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Vita. / Bibliography: leaves 228-242. / by Rafael Corrada Guerrero. / Ph.D.
677

Further experimental investigations into electric charging in fuel filtration

Wexler, Anthony Howard January 1978 (has links)
Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Anthony H. Wexler. / M.S.
678

Property Testing and Probability Distributions: New Techniques, New Models, and New Goals

Canonne, Clement Louis January 2017 (has links)
In order to study the real world, scientists (and computer scientists) develop simplified models that attempt to capture the essential features of the observed system. Understanding the power and limitations of these models, when they apply or fail to fully capture the situation at hand, is therefore of uttermost importance. In this thesis, we investigate the role of some of these models in property testing of probability distributions (distribution testing), as well as in related areas. We introduce natural extensions of the standard model (which only allows access to independent draws from the underlying distribution), in order to circumvent some of its limitations or draw new insights about the problems they aim at capturing. Our results are organized in three main directions: (i) We provide systematic approaches to tackle distribution testing questions. Specifically, we provide two general algorithmic frameworks that apply to a wide range of properties, and yield efficient and near-optimal results for many of them. We complement these by introducing two methodologies to prove information-theoretic lower bounds in distribution testing, which enable us to derive hardness results in a clean and unified way. (ii) We introduce and investigate two new models of access to the unknown distributions, which both generalize the standard sampling model in different ways and allow testing algorithms to achieve significantly better efficiency. Our study of the power and limitations of algorithms in these models shows how these could lead to faster algorithms in practical situations, and yields a better understanding of the underlying bottlenecks in the standard sampling setting. (iii) We then leave the field of distribution testing to explore areas adjacent to property testing. We define a new algorithmic primitive of sampling correction, which in some sense lies in between distribution learning and testing and aims to capture settings where data originates from imperfect or noisy sources. Our work sets out to model these situations in a rigorous and abstracted way, in order to enable the development of systematic methods to address these issues.
679

Property Testing of Boolean Function

Xie, Jinyu January 2018 (has links)
The field of property testing has been studied for decades, and Boolean functions are among the most classical subjects to study in this area. In this thesis we consider the property testing of Boolean functions: distinguishing whether an unknown Boolean function has some certain property (or equivalently, belongs to a certain class of functions), or is far from having this property. We study this problem under both the standard setting, where the distance between functions is measured with respect to the uniform distribution, as well as the distribution-free setting, where the distance is measured with respect to a fixed but unknown distribution. We obtain both new upper bounds and lower bounds for the query complexity of testing various properties of Boolean functions: - Under the standard model of property testing, we prove a lower bound of \Omega(n^{1/3}) for the query complexity of any adaptive algorithm that tests whether an n-variable Boolean function is monotone, improving the previous best lower bound of \Omega(n^{1/4}) by Belov and Blais in 2015. We also prove a lower bound of \Omega(n^{2/3}) for adaptive algorithms, and a lower bound of \Omega(n) for non-adaptive algorithms with one-sided errors that test unateness, a natural generalization of monotonicity. The latter lower bound matches the previous upper bound proved by Chakrabarty and Seshadhri in 2016, up to poly-logarithmic factors of n. - We also study the distribution-free testing of k-juntas, where a function is a k-junta if it depends on at most k out of its n input variables. The standard property testing of k-juntas under the uniform distribution has been well understood: it has been shown that, for adaptive testing of k-juntas the optimal query complexity is \Theta(k); and for non-adaptive testing of k-juntas it is \Theta(k^{3/2}). Both bounds are tight up to poly-logarithmic factors of k. However, this problem is far from clear under the more general setting of distribution-free testing. Previous results only imply an O(2^k)-query algorithm for distribution-free testing of k-juntas, and besides lower bounds under the uniform distribution setting that naturally extend to this more general setting, no other results were known from the lower bound side. We significantly improve these results with an O(k^2)-query adaptive distribution-free tester for k-juntas, as well as an exponential lower bound of \Omega(2^{k/3}) for the query complexity of non-adaptive distribution-free testers for this problem. These results illustrate the hardness of distribution-free testing and also the significant role of adaptivity under this setting. - In the end we also study distribution-free testing of other basic Boolean functions. Under the distribution-free setting, a lower bound of \Omega(n^{1/5}) was proved for testing of conjunctions, decision lists, and linear threshold functions by Glasner and Servedio in 2009, and an O(n^{1/3})-query algorithm for testing monotone conjunctions was shown by Dolev and Ron in 2011. Building on techniques developed in these two papers, we improve these lower bounds to \Omega(n^{1/3}), and specifically for the class of conjunctions we present an adaptive algorithm with query complexity O(n^{1/3}). Our lower and upper bounds are tight for testing conjunctions, up to poly-logarithmic factors of n.
680

A novel N-phase multi-modular series HVDC tap

Tang, Yunpeng January 2017 (has links)
High-voltage direct-current (HVDC) transmission has higher efficiency and lower expenses for the long-distance bulk-power transmission. A HVDC tap is one type of the multi-terminal HVDC systems which transfers a small amount of power from the HVDC line to the nearby communities with no access to the electricity. Developed from the 1960s, HVDC taps can be summarised into series taps and parallel taps, between which series taps are considered to be more promising on the use of devices and the cost. The conventional series taps have some evident drawbacks, which a modular multilevel based series tap may overcome. Here a novel n-phase Multi-Modular Series HVDC Tap (MMST) is proposed to realise the utilisation of the modular multilevel structure into the series tap and improve the performance of typical series taps. In this PhD thesis the theoretical analysis and the parameter design of two-phase and three-phase MMSTs based on the South-West HVDC Link in Sweden have been carried out. The control strategy for the n-phase MMST, including the load current control, the mean capacitor voltage control and the DC link voltage control, has been designed. In order to verify the feasibility of the proposed topology and the validity of the presented control strategy, simulations have been validated using a low power prototype. The simulation and experimental results indicate that the MMST offers better performance when compared to the conventional series taps.

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