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.

This Thesis expands on the current developments of the theory of stochastic diffusion processes of rumours. This is done by advancing the current mathematical characterisation of the solution to the Daley-Kendall model of the simple S-I-R rumour to a physical solution of the sub-population distribution over time of the generalised simple stochastic spreading process in social situations. After discussing stochastic spreading processes in social situations such as the simple epidemic, the simple rumour, the spread of innovations and ad hoc communications networks, it uses the three sub-population simple rumour to develop the theory for the identification of the exact sub-population distribution over time. This is done by identifying the generalised form of the Laplace Transform Characterisation of the solution to the three sub-population single rumour process and the inverse Laplace Transform of this characterisation. In this discussion the concept of the Inter-Changeability Principle is introduced. The general theory is validated for the three population Daley-Kendall Rumour Model and results for the three, five and seven population Daley-Kendall Rumour Models are pre- sented and discussed. The α - p model results for pseudo-Maki-Thompson Models are presented and discussed. In subsequent discussion it presents for the first time a statement of the Threshold Problem for Stochastic Spreading Processes in Social settings as well as stating the associated Threshold Theorem. It also investigates limiting conditions. Aspects of future research resulting from the extension of the three subpopulation model to more than three subpopulations are discussed at the end of the thesis. The computational demands of applying the theory to more than three subpopulations are restrictive; the size of the total population that can be considered at one time is considerably reduced. To retain the ability to compute a large population size, with an increase in the number of possible subpopulations, a possible method of repeated application of the three population solution is identified. This is done through the medium of two competing mutually exclusive rumours. The final discussion occurs on future investigation into the existence of limit values, zero states, cyclic states and absorbing states for the M subpopulation case. The generalisation and inversion of the Laplace Transform as well as the consequential statement of the threshold theorem, derivation of the transition probabilities and discussion of the limiting conditions are significant advances in the theory of rumours and similar social phenomena. / Thesis (Ph.D.) -- University of Adelaide, School of Mathematical Sciences, 2008

SUMMARY The topic of final work for Master‘s degree is The Drug Habit Spread Prevention In Correctional Institutions. Due to this topic the main goal of this work is to specify particularities and evaluate the problems of implementing the measures of drug habit prevention in correctional institutions and to give some offers of possible solution of them and of improving underway prevention. Although drug habit prevention, implemented in different spheres and levels has common features, drug habit prevention in correctional institutions has some particularities. It is important that prevention would fulfil the changes of habits and opportunities of using drug in correctional institutions. For attaining this object the up-to-date state of drug habit spread in correctional institutions, tendencies and the reasons are analyzed. The main provision of legal acts, regulating the prevention of drug habit in correctional institutions, is also provided. The particularities of prevention measures applied in Vilnius’ correctional institutions are also investigated. The experience of implementing drug habit prevention measures in some foreign countries is being examined here as well. Summing up of the results are set forth in the conclusion of this work.

[pt] As condições de crédito da economia têm uma influência direta nas decisões de consumo e investimento tomadas pelos agentes, tendo em vista que em geral eles não conseguem captar recursos pagando apenas a taxa básica de juros fixada pela autoridade monetária. Então, deslocamentos na oferta de crédito, interpretados neste trabalho como alterações no spread bancário para uma dada taxa Selic, alteram o preço relativo do consumo futuro e impactam a demanda agregada. Através da estimação de um VAR (Vector Auto Regression) para a economia brasileira encontramos evidência empírica de que deslocamentos na oferta de crédito têm efeito significativo sobre a atividade econômica. Em seguida, estimamos uma função de reação do banco central, e os resultados indicam que a autoridade monetária responde a uma queda no spread bancário elevando sua meta para a taxa Selic, ceteris paribus, de forma a compensar a alteração no trade-off intertemporal dos agentes. / [en] The credit conditions have a direct influence on the investment and consumption decisions made by the agents, considering that they usually can`t borrow paying only the basic interest rate fixed by the monetary authority. That being said, movements in the credit supply, interpreted in this work as changes in the credit spread for a given Selic rate, change the relative price of future consumption and have an impact on aggregate demand. Through the estimation of a VAR (Vector Auto Regression) for the Brazilian economy we find empirical evidence that a shock to the credit supply has a significant impact on economic activity. Afterwards, we estimate a central bank`s reaction function, and the results suggest that the monetary authority responds to a fall in the credit spread by hiking its interest rate target, ceteris paribus, in order to compensate the change in the intertemporal trade-off faced by the agents.

Cette thèse se propose de déterminer les facteurs explicatifs des spreads des rendements obligataires souverains d’un échantillon de pays de la zone euro, lors des crises survenues au cours de la dernière décennie, et d’étudier l’impact de ces crises sur la dynamique du marché obligataire souverain, et sur son interaction avec le marché boursier et celui des CDS. L’identification des déterminants des spreads de chaque pays fait appel aux modèles de type GARCH, et aux modèles à effets fixes et aléatoires pour l’ensemble de l’échantillon. L’étude de la contagion emploie les modèles MS-VAR et DCC-MVGARCH. Les résultats montrent que la variance des spreads est expliquée principalement par le risque global et celui relatif à la liquidité. Les spreads des pays périphériques apparaissent plus sensibles aux facteurs de risque que ceux du cœur. Les coefficients des facteurs de risque sont aussi trouvés plus significatifs lors des périodes de crise des sub-primes et de la zone euro. Pour l’étude des interactions entre les marchés financiers de la zone euro, les tests menés ont permis de mettre en lumière la présence de phénomènes de contagion et de « fuite vers la qualité ». / This thesis focuses on explaining the determinants of sovereign bond yield spreads in selected euro area countries during the financial crises of last decade. It examines the impact of those turmoil periods on sovereign bond market dynamics, and on its interactions with stock and CDS markets. GARCH-type models are used to identify determinants explaining spreads of each country, while panel data analyzed within fixed and random effects models, and run on crisis and non-crisis periods, identify whole sample determinants. To assess contagion effect, both MS- VAR and DCC-MVGARCH models are used. Results suggest that global risk and liquidity factors are the significant drivers of the spreads volatility. For the periphery countries in the euro zone, spreads are found to be more responsive to explanatory risk factors than those of the core countries. The role of these factors is also found stronger during the sub-prime and euro area crises. The analyses of the financial markets interactions within the euro area demonstrate the existence of a contagion effect, as well as a “flight to quality” phenomenon.

nÃo hà / O mercado bancÃrio brasileiro passou por uma sÃrie de transformaÃÃes durante a dÃcada de 1990, as quais tiveram um impacto sobre as formas de atuaÃÃo dos bancos afetando diretamente aspectos relacionados à eficiÃncia, lucratividade/rentabilidade e exposiÃÃo ao risco sistÃmico dos bancos. A partir de meados da dÃcada de 1990, com a implementaÃÃo e consolidaÃÃo do Plano Real, ocorreram mudanÃas na economia brasileira visando um cenÃrio de estabilidade econÃmica a partir da contenÃÃo da inflaÃÃo e outras polÃticas econÃmicas visando tal cenÃrio. Nessa perspectiva, apÃs esse processo de reestruturaÃÃo, observou-se um ambiente de maior concentraÃÃo do setor bancÃrio brasileiro. Esse estudo investigou a relaÃÃo entre concentraÃÃo bancÃria e spread bancÃrio, assim como um conjunto de fatores explicativos que influenciam variaÃÃes nesse spread bancÃrio. Os resultados do modelo economÃtrico divergiram da hipÃtese central levantada nesta pesquisa, de que uma estrutura mais concentrada poderia contribuir para uma reduÃÃo do spread bancÃrio geral. De acordo com esta pesquisa a concentraÃÃo poderia se mostrar negativamente relacionada com spread atravÃs de um aumento da eficiÃncia dos processos e reduÃÃes de perdas, inclusive com reduÃÃo indireta dos nÃveis de inadimplÃncia. Todavia, o que se observou atravÃs da evidÃncia economÃtrica foi a existÃncia de uma relaÃÃo positiva entre essas duas variÃveis no modelo analisado nessa pesquisa, isso pode ser observado a partir do coeficiente estimado positivo para a relaÃÃo entre o spread bancÃrio e a medida de concentraÃÃo bancÃria representada pela variÃvel MSCB1 no modelo economÃtrico. / The Brazilian banking market has undergone a series of transformations during the 1990s, which had an impact on the ways of acting banks directly affecting aspects related to efficiency, profitability / return and exposure to systemic risk of banks. From the mid-1990s, with the implementation and consolidation of the Real Plan, there were changes in the Brazilian economy for a scenario of economic stability from containing inflation and other economic policies to such a scenario. From this perspective after this restructuring process, there was a higher concentration of the Brazilian banking sector environment. This study investigated the relationship between bank concentration and banking spread as well as a set of explanatory factors that influence variations that banking spread. The results of the econometric model diverged from the central hypothesis in this research, that a more concentrated structure could contribute to a reduction in the general banking spread. According to this research the concentration could prove negatively related to spread through increased process efficiency and loss reduction including indirect reduction in default levels. But what was observed by econometric evidence was the existence of a positive relationship between these two variables in the model analyzed in this research, it can be seen from the positive estimated coefficient for the relationship between the banking spread and the measure represented bank concentration by MSCB1 variable in the econometric model.

Made available in DSpace on 2016-03-15T19:26:40Z (GMT). No. of bitstreams: 1 Renato Cesar Ottoni Barbosa.pdf: 619600 bytes, checksum: 054e4613399521a88c4dcef695505075 (MD5) Previous issue date: 2008-11-14 / Fundo Mackenzie de Pesquisa / This paper aims to test the determinants of banking spread in panel of countries. Using the database of World Bank Survey Doing Business , we were able to construct proxies for the level of informational asymmetry in the markets. Our results suggest that markets with very low degree of asymmetry have on average lower spread from 2% to 4% per year compared to other markets. These results came from low risk interest rates, although it is supposed that larger reductions could be obtained for higher risk credit portfolios. This result is obtained from an econometric model and seems to be statically robust. However, new studies must be done before any final conclusion can be stated. Our sample has a very short time dimension and new tests must be done with this database as soon as more information becomes available. / Um grande esforço de pesquisa tem sido feito para avaliar quais seriam os determinantes de spread bancário. Utilizando indicadores de assimetria informacional construídos a partir da pesquisa do Banco Mundial Doing Business , investiga-se o papel que a assimetria de informação gera nos spreads bancários. Os resultados encontrados neste trabalho sugerem que a existência de um menor grau de assimetria informacional nos mercados de crédito reduz o spread bancário. Esta conclusão foi obtida a partir da análise de taxas de empréstimo prime. O efeito seria na casa de 2% a 4% de redução permanente no spread. Conjectura-se que maiores reduções poderiam ser obtidas para outras modalidades de crédito de maior risco. A relação foi obtida a partir de modelos econométricos de dados de painel com efeitos estáticos e parece ser robusta do ponto de vista estatístico. Contudo, novos estudos que trabalhem com uma amostra mais longa temporalmente devem ser feitos para confirmar esta relação, à medida que tais dados estejam disponíveis.

Liquidity is a measure of the ease with which an asset can be converted into cash. In a perfectly liquid market, conversion is instantaneous and does not incur costs. Amihud and Mendelson (1986:224) proposed that illiquidity increases the expected return on an investment (liquidity premium) and simultaneously lengthens the holding period. These two effects are known respectively as the “spread-return relationship” and the “clientele effect” and have theoretical as well as practical implications. From a theoretical perspective it may help to explain the gap between the capital asset pricing model (which assumes that markets are perfectly liquid) and the associated empirical evidence; which thus far has been rather poor. From a practical perspective, liquidity will influence stakeholders’ decisions and market competitiveness (Amihud&Mendelson, 1991:61-64). The relevant stakeholders are governments, stock exchange regulators, corporations, investors and financial intermediaries. Emerging economies such as the South African economy typically have less liquid markets than the developed world. While this may be attractive for investors looking for higher returns, Amihud and Mendelson (1991:61) are of the opinion that liquid markets are more generally favoured by investors. Constantinides (1986:842-858), also proposes a model for liquidity, but found the liquidity premium to be of lesser importance than that proposed by Amihud and Mendelson (1986:223-231) but also supports the suggestion that investors will favour liquid markets. Although it is by no means a perfect proxy, a security’s bid-ask spread has been found to be an attractive and effective measure of liquidity. It has been found to correlate with beta as well as market capitalisation and several other variables commonly used in capital markets research. Because of this correlation the effect of the bid-ask spread cannot be studied in isolation when regression techniques are employed (Ramanathan, 1998:166). This is particularly problematic because empirical evidence for beta, which is arguably the most important independent variable in financial cross sectional relationships, is weak. Beta has to be estimated and so it is not clear if real markets do not support CAPM theory or if beta cannot be estimated with the required accuracy. All of the common independent variables used in empirical capital markets research are correlated to beta, and for this reason it cannot be established if these variables have a real effect or if they are simply serving as a proxy for the difference between the real and the estimated beta. Various strategies have been proposed to increase the accuracy of beta estimation and these are discussed in detail in this research. Successes with these strategies have been mixed. A second problem encountered in the empirical research base relating to the CAPM is that in the theory the cross-sectional relationship is between expected market return (which cannot be observed due to the vast number of real investments beyond those listed on exchanges) and beta, whereas empirical research makes use of actual return on a market proxy and beta. In order for the actual return to approach the expected return, empirical studies have to be conducted over extended periods. Accurate data for such periods are generally lacking and severe macro-economic changes such as wars, may also affect rational economic behaviour. It has to be kept in mind that the entire CAPM theory flows from the simple assumption that investors aim to achieve the highest return per unit of risk, and so a rejection of beta is a rejection of rational investor behaviour. Liquidity however, addresses one of the assumptions of CAPM, namely that markets are perfectly liquid; which obviously is not met in real markets and so CAPM models expanded for liquidity should be a reasonably fundamental starting point for all empirical capital markets research. The current empirical evidence for the spread-return relationship is inconclusive. While some researchers have found a significant relationship, others have questioned the ability of the methodology to differentiate a true relationship from the ‘proxy for errors in the estimated beta’ problem. Deductions (as explained in section 4.3) that have been made from the research of Marshall and Young (2003:176-186) in particular, provide strong evidence that at least some of the relationship is due to the ‘errors in estimated beta’ problem. Little empirical work has been done on the clientele effect. Atkins and Dyl (1997:318-321) found a significant relationship between holding period and bid-ask spread, although their approach was somewhat unorthodox in the sense that portfolio formation was not done and the effect of beta was not tested. This study tests empirically both the spread-return relationship and the clientele effect on the Johannesburg Stock Exchange over the period stretching from January 2002 to June 2007. The methodology of Fama and Macbeth (1973:614-617) as well as the aggregated beta of Dimson (1979:203-204) were mainly used, with some modifications as suggested by other researchers. With regard to the spread-return relationship, the findings of this study do not support theoretical expectations. This may be due to the short time period that was used as well as the difficulty in estimating beta. To the contrary, very significant evidence for the clientele effect was found, with little to no influence from market capitalisation and beta, which is as expected. Further investigation into the spread-return relationship is required. If a liquidity premium is not present, foreign investors will favour liquid developed markets above the JSE. This implies that efforts of exchange regulators and the government to decrease illiquidity will lead to foreign portfolio investment inflow into the South African economy. / Dissertation (MBA)--University of Pretoria, 2008. / Graduate School of Management / unrestricted

abstract: Land-use change has arguably been the largest contributor to the emergence of novel zoonotic diseases within the past century. However, the relationship between patterns of land-use change and the resulting landscape configuration on disease spread is poorly understood as current cross-species disease transmission models have not adequately incorporated spatial features of habitats. Furthermore, mathematical-epidemiological studies have not considered the role that land-use change plays in disease transmission throughout an ecosystem. This dissertation models how a landscape's configuration, examining the amount and shape of habitat overlap, contributes to cross-species disease transmission to determine the role that land-use change has on the spread of infectious diseases. To approach this, an epidemiological model of transmission between a domesticated and a wild species is constructed. Each species is homogeneously mixed in its respective habitat and heterogeneously mixed in the habitat overlap, where cross-species transmission occurs. Habitat overlap is modeled using landscape ecology metrics. This general framework is then applied to brucellosis transmission between elk and cattle in the Greater Yellowstone Ecosystem. The application of the general framework allows for the exploration of how land-use change has contributed to brucellosis prevalence in these two species, and how land management can be utilized to control disease transmission. This model is then extended to include a third species, bison, in order to provide insight to the indirect consequences of disease transmission for a species that is situated on land that has not been converted. The results of this study can ultimately help stakeholders develop policy for controlling brucellosis transmission between livestock, elk, and bison, and in turn, could lead to less disease prevalence, reduce associated costs, and assist in population management. This research contributes novelty by combining landscape ecology metrics with theoretical epidemiological models to understand how the shape, size, and distribution of habitat fragments on a landscape affect cross-species disease transmission. The general framework demonstrates how habitat edge in single patch impacts cross-species disease transmission. The application to brucellosis transmission in the Greater Yellowstone Ecosystem between elk, cattle, and bison is original research that enhances understanding of how land conversion is associated with enzootic disease spread. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics for the Life and Social Sciences 2020

Hållbarhet är i fokus och hållbara investeringar är en förutsättning för att utvecklingen av det globala hållbarhetsarbetet ska lyckas. Ett hållbart investeringsalternativ är gröna obligationer, som idag är en efterfrågad produkt av investerare. Obligationsmarknaden används av företag som ett alternativ till finansiering i form av banklån. Här möts företag och investerare i syfte att utbyta pengar mot räntebärande värdepapper, där investeraren erhåller ränteutbetalningar för sitt utlånade kapital. År 2008 emitterades världens första gröna obligation och utvecklingen i antal emitterade gröna obligationer har sedan dess varit extraordinär. Gröna obligationer är likt konventionella obligationer ett räntebärande värdepapper, med skillnaden att emissionskapitalet för gröna obligationer är avsett att användas till att minska miljö- och klimatpåverkan. Genom en investering i gröna obligationer är investeraren med och finansierar gröna projekt och bidrar till en mer hållbar utveckling. Tidigare forskning har lett till varierande slutsatser där majoriteten antyder att det finns en premie förknippat med gröna obligationer. Många av de tidigare forskningarna har studerat obligationsmarknaden på global nivå. Denna studie avser att undersöka premiens förhållande på den svenska obligationsmarknaden och se huruvida svenska bolag emitterar gröna obligationer till en lägre avkastning. Syftet med studien är att påvisa huruvida det finns skillnader i spread mellan gröna obligationer och konventionella obligationer på den svenska obligationsmarknaden. Detta förhållande undersöks genom en kvantitativ studie som bygger på en deduktiv ansats. I studien används en matchningsmetod för att studera fenomenet om en premie för gröna obligationer existerar. Gröna och konventionella obligationers spread jämförs inom bolagen och resultatet sammanfattas i en övergripande marknadsanalys. De slutsatser som dras av studien är att det inte finns någon statistiskt signifikant skillnad mellan gröna och konventionella obligationers spread, och därmed att gröna obligationer inte emitteras med en sämre avkastning än jämförbara konventionella obligationer. Från denna studie drar vi därmed slutsatsen att gröna obligationer på den svenska obligationsmarknaden inte emitteras med någon premie. / Sustainability is in focus and sustainable investments are a prerequisite for the progress of global sustainability work. Green bonds are an example of a sustainable investment alternative and is today a sought-after product by investors. The bond market is used by companies as an alternative to financing projects through bank loans. Organizations and investors meet for the purpose of exchanging money for interest-bearing securities, where the investor receives interest payments for his lent capital. In 2008, the world's first green bond was issued and the development in the number of issued green bonds since then has been extraordinary. Like conventional bonds, green bonds are an interest-bearing security, with the difference that the issued capital for green bonds is intended to be used to reduce the environmental and climate impact. Through an investment in green bonds, the investor participates in and finances green projects and contributes to a more sustainable development. Previous research has led to varying conclusions where the majority suggest that there is a premium associated with green bonds. Many of the previous researches have studied the bond market on a global level. This study intends to examine the premium relationship in the Swedish bond market and conclude whether or not Swedish companies issue green bonds at a lower return. The purpose of the study is to demonstrate whether there are differences in spreads between green bonds and conventional bonds in the Swedish bond market. This relationship is investigated through a quantitative study based on an deductive approach. The study uses a matching method to study the phenomenon of a premium for green bonds. The spreads of green and conventional bonds are compared within the companies and the results are summarized in an overall market analysis. The first conclusion drawn from this study is that there is no statistically significant difference between the spread of green and conventional bonds, seen across the entire Swedish bond market. This indicates that green bonds are not issued with a lower return than comparable conventional bonds. The second conclusion drawn from this study is that green bonds in the Swedish bond market are not issued with any premium. The study shows that green bonds are as profitable as conventional bonds from the same company, and also lead to a more diversified portfolio. This paper is written in Swedish.