Network worms that scan random computers have caused billions of dollars in damage to enterprises across the Internet. Earlier research has concentrated on using epidemiological models to predict the number of computers a worm will infect and how long it takes to do so. In this research, one possible approach is outlined for predicting the spatial flow of a worm within the local area network (LAN). The approach in this research is based on the application of mathematical models and variables inherent in plant epidemiology. In particular, spatial autocorrelation has been identified as a candidate variable that helps predict the spread of a worm over a LAN. This research describes the application of spatial autocorrelation to the geography and topology of the LAN and describes the methods used to determine spatial autocorrelation. Also discussed is the data collection process and methods used to extract pertinent information. Data collection and analyses are applied to the spread of three historical network worms on the Virginia Tech campus and the results are described. Spatial autocorrelation exists in the spread of network worms across the Virginia Tech campus when the geographic aspect is considered. If a new network worm were to start spreading across Virginia Tech's campus, spatial autocorrelation would facilitate tracking the geographical locations of the spread. In addition if an infection with a known value of spatial autocorrelation is detected, the characteristics of the worm can be identified without a complete analysis. / Master of Science

Ultrawideband (UWB) is one of the most promising communication technologies in recent times with the promise of high data rates and spectral reuse. This work analyses the outdoor and outdoor-to-indoor propagating characteristics of the UWB pulse, which can be of the order of a few gigahertz in bandwidth. The aim of the thesis is to provide the parameters needed in order to develop a channel model for such cases. The channel model would then play an important role in determining physical layer (PHY) solutions to optimally exploit these characteristics. The measurements carried out on the Virginia Tech campus are used to compute parameters such as path loss, penetration loss and delay statistics. These are carried out in multiple frequency bands and the results are compared across frequency bands to determine effect of different frequency levels on the parameters. Finally the results are analyzed with respect to similar parameters obtained in other measurement campaigns in an attempt to evaluate the performance of Ultrawideband vis-à-vis narrowband systems. / Master of Science

A wireless local area network (LAN) system is proposed to provide mobility for existing data communication services. This thesis presents a physical layer design for a direct sequence spread spectrum ISM band radio LAN system. This radio system employs spread spectrum communication technology and a differential binary phase shift keying/quadrature phase shift keying (BPSK/QPSK) non-coherent receiver to overcome the adverse indoor wireless environment. Moreover, a variable data rate transmission technique is used to dynamically configure the spread spectrum system according to channel performance. This physical layer incorporates the Zilog Z2000 Evaluation Board performing direct sequence spread spectrum processing, a Grayson 900 MHz radio receiver and a transmitter module which was designed and built at Virginia Tech. The transmitted spectrum occupies a 4 MHz bandwidth in the 900 MHz ISM band and this system supports a data rate of up to 363 Kbits/sec. The spread spectrum system design along with detailed descriptions of hardware and control software development are presented. / Master of Science

Spread spectrum techniques offer an alternate solution to the urgency for distributed optical fiber sensors. These techniques are based on the properties of pseudorandom sequences that have triangular autocorrelation functions with peaks only at regions of no delay. This affords an opportunity to give the desired signal a power advantage over many types of interference and noise. A study in employing spread spectrum techniques for multiplexing optical fiber sensors is presented. A mathematical analysis of the system is conducted with due consideration given to performance issues. Simulations in software are conducted to characterize system performance. Hardware developed for this project operates at over 1 Mbps and is capable of simultaneously monitoring four sensors. Real time experiments conducted on these multiplexed sensors affirm the technical feasibility of the system. Configurations for viable applications of the system are also suggested. / Master of Science

Yes / We study liquidity on the London Stock Exchange. We find that the average bid-ask spread declines, but that the skewness of the spread increases. These results are robust to firm size, trading volume and price level. Our findings hold when the bid-ask spread is estimated utilising high frequency data. We find that the bid-ask spread prior to earnings announcements dates is significantly higher than that of post earnings announcements, suggesting that asymmetric information has driven the increase in liquidity skewness. We also find that the effect of earnings announcements is more pronounced in the 2007 global financial crisis, consistent with the notion that extreme market downturns amplify asymmetric information. Our overall evidence also implies that increased competition and transparent trading environments limit market makers' abilities to cross-subsidize bid-ask spreads between periods of high and low levels of asymmetric information. / National Natural Science Foundation of China (No. 71571197)

Darbe atlikta detali aktualių straipsnių, nagrinėjančių įvairių veiksnių įtaka skolos vertybinių popierių pajamingumui, apžvalga. Išskirti keli pagrindiniai pajamingumo pokyčius lemiantys veiksniai: likvidumas, kredito rizika bei bendra makroekonominė padėtis. Siekiant įvertinti nagrinėjamų veiksnių įtaką skolos vertybinių popierių pajamingumo pokyčiams, sukurti vektorinės autoregresijos modeliai skolos vertybinių popierių portfeliams, apibendrinantiems skirtingas skolos vertybinių popierių klases. Palyginus modeliavimo rezultatus, pateikiamos baigiamojo darbo išvados. Darbą sudaro 18 dalių: įvadas, tikslas, uždaviniai, aktualumas, literatūros apžvalga, pagrindiniai skolos vertybinių popierių rinką charakterizuojantys rodikliai, statistiniai metodai, modelio aprašymas, kintamujų aprašymas bei transformacijos, statistinė analizė, trendo išskyrimas, stacionarumo patikrinimas, modeliavimas, modelių palyginimas bei scenarijų analizė, išvados, literatūros sąrašas. / A brief survey of relevant researches on different factors’ impact on bonds’ yields is provided in master thesis. Several main factors were identified: liquidity, credit risk and macroeconomic environment. In order to measure the impact of distinguished factors on the yields’ changes vector autoregressive models for fixed income securities portfolios, generalizing different asset classes, were created. The modeling results are described and analyzed, conclusions are made Structure: introduction, goal, task, relevance, literature overview, the main indicators of sixed income securities market, statistical methods, models’ describtion, variables’ description and transformations, statistical analysis, elimination of the trend, stacionarity check, modeling, models’ comparison and scenario analysis, conclusions, references.

Credit spread is the extra risk-reward that an investor is bearing for investing in corporate bonds instead of government bonds. Structural models, which are simple in their framework, fail to explain the occurring credit spread and underestimate the predicted credit spread. Hence, the need for new models and exploration of systematic and idiosyncratic variables arose. The present paper aims to investigate if the predictability of lower-medium investment grade bonds and non-investment grade bonds credit spread can be improved by incorporating systematic and idiosyncratic variables into a fixed effect panel data regression model, and whether the selected variables’ significance has high influence on credit spread or not. Initial results showed that fixed effect panel data regression model underperforms the structural models and under predicts the actual credit spread. The applied model explained 13.5% of the lower-medium investment grade bonds credit spread and 8.5% of non-investment grade bonds. Further, systematic variables have higher influence on lower-medium investment grade bonds and idiosyncratic variables have higher influence on non-investment grade bonds. The predictability of credit spread can be improved by employing correct explanatory variables which are selected based on the characteristics of the sample size.

Made available in DSpace on 2016-04-26T20:48:37Z (GMT). No. of bitstreams: 1 Vania Vieira Ramos.pdf: 3565329 bytes, checksum: 41f89b0eea4fb985e067c0ad56f80b3f (MD5) Previous issue date: 2012-10-23 / The interest rate is one of the main instruments of monetary policy for the control of the economy, especially for that countries, like Brazil, that use the Inflaction Target System. Brazil presents one of the world's highest interest rates. This hampers the development and the heating of the economy as a whole, as the credit takers, individuals and legal entities, especially those considered "good payers", feel discouraged to seek for financial institutions, because the charge to be paid at the end of a contract of credit is exorbitant. Moreover, the inertia of high interest rates of the Brazilian banking system led foreign banks with branches here, to the same behavior of domestic banks, and this behavior does not bring stimulus to the credit, as not brought competitiveness for the Brazilian banking sector. In this regard, this work tries to make a comparative study between high interest rates used in Brazil, by private domestic and foreign banks, and public national banks, with the latter, are financial institutions that have political, economic and social conditions to drive a significant drop in interest rates and stimulate development. The first chapter is the Theoretical Framework, it sought to understand the concept of economic development and its relationship with credit. The second chapter is a historical chapter on the interest rate practiced in Brazil from 1990 to 2010. This chapter, aimed to build a history of the Brazilian interest rate, making a comparison between the interest rates charged by major private banks (domestic and foreigners) - Bradesco, Itau, Banco Santander and HSBC in Brazil, U.S., Spain and England. In this same chapter we tried to investigate what the main impacts of the practice of high interest rates on the Brazilian economy. And at the end of this chapter, held a brief study of the legal issue behind the high interest rates in place in Brazil today. The third chapter is called: National Public Banks: Solutions with Subsidized Interest Rate and Microcredit, and seeks to understand the role of public banks in the lending scenario in Brazil. To this end, we evaluated case by case, the main role of public institutions providing credit. Among the key findings, we have that foreign banks has not pushed down the interest rate as was assumed when the financial openness. This role falls to the national public banks which, in the Brazilian context, possess sufficient market power to exert influence on the final interest rate and spread, thus ensuring the efficient transmission of monetary policy / A taxa de juros é um dos principais instrumentos de Política Monetária para controle da economia, principalmente para aqueles países, como o Brasil, que utilizam o regime de Metas de Inflação. O Brasil apresenta uma das maiores taxas de juros do mundo. Isso dificulta o desenvolvimento e o aquecimento da economia como um todo, na medida em que os tomadores de crédito, tanto pessoas físicas quanto pessoas jurídicas, principalmente, aqueles considerados bons pagadores , sentem-se desestimulados a procurar as instituições financeiras, pois o encargo a ser pago ao final de um contrato de operação de crédito é exorbitante. Ademais, a inércia de juros altos do sistema bancário brasileiro levou os bancos estrangeiros, com filiais aqui, ao mesmo comportamento dos bancos nacionais e esse comportamento não trouxe nem estímulo ao crédito e nem competitividade ao setor bancário brasileiro. Neste sentido, este trabalho busca fazer um estudo comparativo entre as altas taxas de juros praticadas no Brasil, pelos bancos nacionais e estrangeiros privados e os bancos nacionais públicos, sendo que estes últimos, são as instituições financeiras que têm condições políticas, econômicas e sociais de conduzir uma queda considerável na taxa de juros e estimular o desenvolvimento. O primeiro capítulo é o Referencial Teórico, nele procurou-se entender o conceito de desenvolvimento econômico e a sua relação com o crédito. O segundo capítulo é um capítulo histórico sobre a Taxa de Juros Praticada no Brasil de 1990 a 2010. Neste capítulo, buscou-se construir um histórico da taxa de juros brasileira, fazendo-se uma comparação entre as taxas de juros praticadas pelos principais bancos privados brasileiros (nacionais e estrangeiros) Bradesco, Itaú, Santander e HSBC no Brasil, nos EUA, na Espanha e na Inglaterra. Neste mesmo capítulo procurou-se investigar quais os principais impactos da prática de altas taxas de juros sobre o desenvolvimento econômico brasileiro. E no final deste capítulo, realizou-se um breve estudo sobre a questão jurídica por trás das altas taxas de juros em prática no Brasil na atualidade. O terceiro capítulo chama-se: Bancos Nacionais Públicos: Soluções com Taxa de Juros Subsidiada e Microcrédito, e procura entender o papel dos bancos públicos no cenário creditício brasileiro. Para tanto, avaliou-se caso a caso, o papel das principais instituições públicas fornecedoras de crédito. Entre as principais conclusões tem-se que os bancos estrangeiros não pressionaram para baixo a taxa de juros como foi suposto quando da abertura financeira. Este papel cabe aos bancos públicos que, no contexto brasileiro, possuem poder de mercado suficiente para exercer influência sobre a taxa de juros final e o spread, garantindo portanto a eficiência na transmissão da política monetária

Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2016-10-07T13:06:42Z No. of bitstreams: 1 Darci Pereira Corsi.pdf: 1039054 bytes, checksum: 5adde395b12bddf3345aeb5f3dffa2e5 (MD5) / Made available in DSpace on 2016-10-07T13:06:42Z (GMT). No. of bitstreams: 1 Darci Pereira Corsi.pdf: 1039054 bytes, checksum: 5adde395b12bddf3345aeb5f3dffa2e5 (MD5) Previous issue date: 2016-08-04 / Statement of Value Added (SVA), is an accounting and financial report, required by law and legal for companies in the form of anonymous public companies, and large companies economic form of limited partnerships, and recommended to the other juridical types of companies, by regulators of accounting. The SVA was created from the inserter of Brazil in the international harmonization process of accounting information system, whose main goal is to qualify the information about business performance to users of accounting system, thus following the new conceptual framework of accounting, which in turn follows the economic global changes, social and business management. The Value Statement added, is based on information contained in the statement of income for the exercise, so that the revenues net of inputs acquired from third parties, and also deducted by the accounting adjustment expenses, in accordance with the basic assumption of competence produces the added value, which is the first part of the report, and thus producing the "GDP" of the business unit and the second part shows the distribution of this wealth to forming agents under the headings: staff salaries; government compensation through taxes, fees and contributions; payment of debt, through financial charges, rents and others; return on equity, through interest on equity, dividends and retained profit. The Statement of value added is an important tool in the accounting information system, which contributes to social and economic analysis of the company, producing indicators for the sector, region and the country. The paper describes the concepts and monetary training of all items report components, appraises the economic agents who participate in the formation and distribution of the wealth produced by a company, including reviewing the economic and legal aspects of a company. The paper presents the three models of the SVA presents an analysis of the added value produced by a company in the commercial sector, and one of the insurance industry, demonstrating the report's usefulness in economic and financial analysis of such companies, since they are economic entities, with different operating object and generate different nomenclatures for the items that underlie the preparation of the statement of value added. Finally the paper analyzes, through the statement of added value, the behavior of the allowance for doubtful accounts, the largest Brazilian financial institutions, which is a significant component in the composition of the spread, set by the Central Bank of Brazil / Demonstração do valor adicionado (DVA), é um relatório contábil e financeiro, exigido por diploma e legal, para empresas sob forma de sociedades anônimas de capital aberto, e para empresas de grande porte econômico sob forma de sociedades limitadas, e recomendado para os demais tipos juridicos de empresas, pelos orgaõs reguladores da contabilidade. A DVA, foi criada a partir da insersão do Brasil no processo de harmonização internacional do sistema de informação contábil, cujo objetivo principal é o de qualificar as informações sobre o desempenho empresarial aos usuários do sistema contábil, acompanhando assim a nova estrutura conceitual da contabilidade, que por sua vez segue as transformações globais econômicas, sociais e de gestão empresarial. A Demonstração do Valor adicionado, tem por base a informações contidas na Demonstração do resultado do Exercício DRE, de forma que as receitas auferidas deduzidas dos insumos adquiridos de terceiros, e deduzidas também pelas despesas de ajuste contábeis, em concordância com o pressuposto básico da competência, produz o valor adicionado, que é a primeira parte do relatório, e assim produzindo o “PIB” da unidade empresarial e na segunda parte, demonstra a distribuição dessa riqueza aos agentes formadores sob as rubricas: remuneração do pessoal; remuneração do governo, através dos impostos, taxas e contribuições; remuneração do capital de terceiros, atraves dos encargos financeiros, alugueis e outros; remuneração do capital próprio, atraves dos juros sobre o capital próprio, dividendos, e retenções do lucro. A Demonstração do valor adicionado é um importante instrumento do sistema de informação contabil, que contribui para análise sócial e econômica da empresa, produzindo indicadores para o setor, região e para o país. O trabalho descreve os conceitos e formação monetária de todas as rubricas componentes do relatório, conceitua os agentes economicos, que participam da formação e distribuiçao da riqueza produzida por uma empresa, inclusive revisando os aspectos econômicos e juridícos de uma empresa. O trabalho apresenta os tres modelos da DVA, apresenta uma análise do valor adicionado produzido por uma empresa do setor comercial, e outra do setor de seguros, demonstrando a utilidade do relatório na análise economica e financeira dessa empresas, uma vez que são entidades economicas, com objeto de exploração distintos e geram nomenclaturas distintas para as rubricas que fundamentam a elaboração da demonstração do valor adicionado. E finalmente o trabalho analisa, por meio da demonstração do valor adicionado, o comportamento da provisão para crédito de liquidação duvidosa, das maiores instituições financeiras brasileira, que é um significativo componente na composição do spread bancário, definido pelo banco central do Brasil

Spread spectrum techniques have a number of different applications, including range finding, synchronisation, anti-jamming systems and multiple access communication systems. In each of these applications the properties of the resulting systems depend heavily on the family of spreading sequences employed. As such, the design of spreading sequences is an important area of research. Two areas of spreading sequence design are of particular interest in this work, combination techniques and Interference Free Window (IFW) sequences. Combination techniques allow a new sequence family to be constructed by combining two or more existing families. Such an approach allows some of the desirable properties of the components to be maintained, whilst mitigating the components' disadvantages. In addition, it can facilitate the construction of large families at a greatly reduced computational cost. Combination families are considered through the construction of two new classes of sequences, modified Unified Complex Hadamard Transform (UCHT) sequences, and combination Oppermann sequences, respectively based on UCHT sequences and periodic Oppermann sequences. Numerical optimisation techniques are employed to demonstrate the favourable performance of sequences from these classes compared to conventional families. Second, IFW sequences are considered. In systems where approximate, but not perfect, synchronisation between different users can be maintained, IFW sequences can be employed to greatly reduce both interference between users and interference resulting from multipath spread of each user's signal. Large Area Synchronous (LAS) sequences are a class of sequences which both result from combination techniques and exhibit an IFW. LAS sequences are produced by combining Large Area (LA) sequences and LS sequences. They have been demonstrated to be applicable to multiple access communication systems, particularly through their use in LAS2000, which was proposed for third generation mobile telephony. Work to date has been restricted to only a very small range of examples of these families. In order to examine a wider range of LAS sequences, the construction and resulting properties of LA and LS families are considered. The conditions an LA family must satisfy are codified here, and algorithms which can be used to construct LA families with given parameters are presented. The construction of LS sequences is considered, and relationship between each of the parameters used in this construction and the properties of the final family is examined. Using this expanded understanding of both these sequence families, a far wider range of LAS families, potentially applicable to a wider range of applications, can be considered. Initially, the merits of proposed sequences are considered primarily through their correlation properties. Both maximum and mean squared correlation values are considered, depending on the context. In order to demonstrate their practical applicability, combination Oppermann, modified UCHT and LAS sequences are employed in a simulated communications system, and the resulting bit error rates are examined.