Security and privacy are among the growing concerns of a Vehicular Ad hoc Network (VANET) which requires a high degree of liability from its participants. In this dissertation, We address security, anonymity and privacy challenges of VANETs in the light of the IEEE standards for vehicular communications. VANET provides a variety of road-safety and other applications through wireless devices installed in vehicles and roadside infrastructure. A roadside infrastructure in VANET is generally public, and is prone to several different malicious attacks including node compromise, impersonation, and false message delivery attacks. Therefore, a user of a VANET must verify the integrity of a message that is delivered from a roadside infrastructure. On the other hand, a vehicle-originated message should be anonymous in order to ensure user-privacy in a VANET. However, a vehicle must not be able to take advantage of its anonymity for any misbehavior like sending false messages or malicious updates to other vehicles or a roadside infrastructure. We use proxy signature, identity-based signature, and elliptic curve cryptosystems to provide authentication for infrastructure generated messages, and anonymous authentication for vehicle originated messages. Authentication in a dense traffic condition is a challenge for a receiving entity as it incurs a processing delay at the receiving end. We address this issue with a dynamic approach that selectively verifies received messages based on a message's MAC-layer priority and a sender's information relevance. This approach makes a trade-off between priority and fairness in vehicular message authentication. We develop a network simulator to measure the impact of our authentication schemes over a WAVE protocol stack. Also, we investigate how some of the MAC-layer weaknesses may impair the security of a VANET. Our solutions are lightweight, bandwidth friendly and compatible to the current standards of vehicular communications.

Security and privacy are among the growing concerns of a Vehicular Ad hoc Network (VANET) which requires a high degree of liability from its participants. In this dissertation, We address security, anonymity and privacy challenges of VANETs in the light of the IEEE standards for vehicular communications. VANET provides a variety of road-safety and other applications through wireless devices installed in vehicles and roadside infrastructure. A roadside infrastructure in VANET is generally public, and is prone to several different malicious attacks including node compromise, impersonation, and false message delivery attacks. Therefore, a user of a VANET must verify the integrity of a message that is delivered from a roadside infrastructure. On the other hand, a vehicle-originated message should be anonymous in order to ensure user-privacy in a VANET. However, a vehicle must not be able to take advantage of its anonymity for any misbehavior like sending false messages or malicious updates to other vehicles or a roadside infrastructure. We use proxy signature, identity-based signature, and elliptic curve cryptosystems to provide authentication for infrastructure generated messages, and anonymous authentication for vehicle originated messages. Authentication in a dense traffic condition is a challenge for a receiving entity as it incurs a processing delay at the receiving end. We address this issue with a dynamic approach that selectively verifies received messages based on a message's MAC-layer priority and a sender's information relevance. This approach makes a trade-off between priority and fairness in vehicular message authentication. We develop a network simulator to measure the impact of our authentication schemes over a WAVE protocol stack. Also, we investigate how some of the MAC-layer weaknesses may impair the security of a VANET. Our solutions are lightweight, bandwidth friendly and compatible to the current standards of vehicular communications.

This thesis considers the use of two U-series nuclides – 231 Pa and 230 Th – as proxies for studying ocean circulation. A total of six water-column profiles of 231 Pa, 230 Th, and 232 Th have been measured from two regions of the southwestern Indian Ocean: the Madagascar and Mascarene Basins; and the southeastern continental margin of South Africa. Measurement by MC-ICP-MS of 10 litre water samples is possible for samples with as little as 4 and 2 fg of 231 Pa and 230 Th and yields typical uncertainties of 6% and 14% respectively. These profiles show that the scavenging and advection histories of water masses can affect their 231 Pa concentration, with distinct variations superimposed on a general increase in concentration with depth due to reversible scavenging. A 1D particle scavenging model is used to show that sedimentary (231 Paxs /230 Thxs )0 is most representative of the (231 Pa/230 Th) of the bottom most water mass at any one locality, although in turn this water mass (231 Pa/230 Th) will be dependent not only on its advection and scavenging history but also the 231 Pa and 230 Th concentrations of the overlying water masses during advection. Acknowledgment that sedimentary (231 Paxs /230 Thxs )0 is “set” by the bottommost water mass is important for interpretation of scenarios where changes in depth of circulation, as well as circulation strength, may have occurred. A record of sedimentary (231 Paxs /230 Thxs )0 has been recovered from a 6 m Kasten core from the Mascarene Basin covering the past 140 ka, in order to reconstruct flow of AABW into the basin. The (231 Paxs /230 Thxs )0 measured is below the production ration of 0.093 and shows no significant variation. This indicates that (231 Paxs /230 Thxs )0 is sensitive to changes in particle productivity and circulation at this location and that there has been little or no change in either environmental variable over the last full interglacial-glacial cycle. This finding is in contrast to other ocean basins, particularly the North Atlantic, where large changes in circulation are observed.

個人目前服務於國內上市金融控股公司，有感於匯率波動對多數公司的財務報表損益有著深遠的影響，故興起一股想進一步了解匯率避險的方法，及是否有其他更合適的辦法來降低避險成本。 全球匯市近期動盪加劇，讓壽險公司國外投資避險操作難度升高，過去常用的「一籃子貨幣避險」，今年失靈並嚴重衝擊壽險業第一季獲利。因傳統避險方法會影響國外投資獲利，因此多數壽險公司長期採用一籃子貨幣避險，即同時持有各種外幣，透過外幣間的自然升貶值來抵銷匯兌風險。但近期國際匯率波動加大，2月英鎊、歐元貶幅都比新台幣還兇，讓一籃子貨幣避險嚴重失靈。 本研究主要是想探討當利差縮窄到一定程度後，要利用替代避險工具會有其困難度，特別是傳統CS避險成本也大幅下降狀況。但因壽險資金若一開始匯出時，未使用傳統CS避險方式，日後要再增加CS避險部位，則央行並不會同意。故實際上雖然2009年以後，使用替代避險並不容易達到避險目的，但還是有部分壽險公司持續使用，原因為無法以CS或NDF來取代。同時CS期間短、成本不低，必須實際支付成本，該點亦是壽險公司考量主因。 故在從事海外投資時，如何規避匯率風險便成了海外投資的最重要課題了。 / I was currently serving the domestic market of financial holding companies, and realized the exchange rate fluctuations on the financial statements of most companies have a profound impact on the profit and loss. Because the rise of an exchange rate hedge, I like to know if there are other more appropriate ways to reduce hedging costs. Increased volatility in global currency markets recently, so that life insurance companies to hedge foreign investment in the difficulty, in the past used the basket hedge caused a serious impact on the first quarter earnings of life insurance . For traditional hedging methods will affect the profitability of foreign investment, so most life insurance companies to hedge long-term use of a basket of currencies, which also holds a variety of foreign currency through currency depreciation between the natural rise to offset the exchange risk. But the recent increase of international exchange rate fluctuations, especially Pound and Euro depreciated than NTD also fierce, so that a serious failure of a basket hedging. This study is to investigate when the spread narrowed to a certain extent, to the use of alternative hedging tool has its difficulty, especially in the traditional hedging costs also declined substantially CS condition. But if the beginning of the life insurance funds remitted when the CS is not the traditional way of hedging, increased again in future CS hedge position, the central bank will not agree. Although it is in fact after 2009, the use of alternative hedging is not easy to achieve hedging purposes, but still some life insurance companies continue to use, because CS or NDF can not be replaced. During the same time, the short term CS, the cost is not low and you must actually pay the cost, the point is also the main reason for life insurance companies to consider. Therefore, when engaged in overseas investment, how to avoid exchange rate risk has become the most important issue of overseas investment .

Univ., Diss. u.d.T.: Kyriakakis, Konstantinos: Die Überwachung des Managements einer US-amerikanischen Aktiengesellschaft durch institutionelle Anleger--Osnabrück, 2000. / Nebent.: Überwachung des Managements durch institutionelle Anleger.

This thesis investigates the potential of the bivalve Arctica islandica (Linnaeus, 1767) from fjordic sites in NW Scotland for reconstructing past marine environmental /climatic variability. Using dendrochronological and sclerochronological techniques, six master chronologies were created which when compared show little common variability between the sites, indicating no common response to regional scale forcing. The chronologies were compared to local and regional scale SST and land based datasets, with no significant, time stable responses to climate found. It is clear the growth/climate response of A. islandica from these sites is complex, potentially due to the shallow nature of the sample sites, direct local drivers such as food availability and, potentially, anthropogenic activity in the region. Geochemical analyses of the shell material were undertaken to examine the timing and magnitude of the radiocarbon bomb-peak and the stable carbon isotope signature of the oceanic Suess Effect. The timing of the radiocarbon bomb-peak in Loch Etive does not appear to match previously published results from other marine locations and are a potentially serious challenge to the assumption that A. islandica GI are always annual features. Results comparing δ¹³C values and the age of the specimen when these values are incorporated into the shell material strongly indicate an ontogenetic control over δ¹³C, meaning the Suess Effect could not be effectively investigated. To take these ontogenetic influences into account it is suggested that any data from the juvenile period of shell life is not used. Analysis of shell biometrics and morphology indicate significant relationships between shell age and height and age and weight, however the errors for these are large (±78 years and ±80 years respectively). These results indicate that despite large errors shell height, as a predictor of age, has the potential to be used for in situ population studies.

Made available in DSpace on 2016-06-02T19:05:18Z (GMT). No. of bitstreams: 1 DissPVCC.pdf: 3610389 bytes, checksum: 207fb73eb90d6ef70e9232d6b9d02a92 (MD5) Previous issue date: 2003-05-26 / Financiadora de Estudos e Projetos / The computational Grid concept allows resource sharing in large scale. This work introduces the ProGrid system, an architecture for computational Grids, whose communication and resource management infrastructure is used transparently by the applications. Unlike other grid approaches, this work relies on the use of proxy servers to perform additional communications and authentication procedures on behalf of client applications. The purpose of this mechanism is to enable parallel applications to be executed in geographically distributed environments interlinked by an open communication network, such as the Internet, meeting the security requisites desirable for computational grids. To reach such objectives, a generic architecture for ProGrid was developed, that is divided in a group services layers. This work was focused in the implementation of layers responsible by the secure communication and for the controlled sharing of available resources. / O conceito de grade computacional permite o compartilhamento de recursos computacionais em larga escala. Este trabalho apresenta o sistema ProGrid, uma arquitetura para Grades Computacionais, na qual a infra-estrutura de comunicação e o gerenciamento de recursos são usados transparentemente pelas aplicações. Diferentemente de outras grades, este trabalho utilizou uma abordagem baseada em servidores Proxy para realizar os processos adicionais de comunicação e autenticação em nome da aplicação cliente. O propósito deste mecanismo é habilitar a execução de aplicações paralelas em ambientes geograficamente distribuídos interconectados por um canal de comunicação aberto, como a Internet, atendendo os requisitos de segurança desejáveis nas Grades Computacionais. Para alcançar tais objetivos, desenvolveu-se uma arquitetura genérica para o ProGrid , que é dividida em um conjunto de camadas de serviços. Este trabalho focou-se na implementação das camadas responsáveis pela comunicação segura e pelo compartilhamento controlado dos recursos disponíveis.

Orientadores: Saul Barisnik Suslick, Denis Jose Schiozer / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica, Instituto de Geociências / Made available in DSpace on 2018-08-12T08:07:04Z (GMT). No. of bitstreams: 1 Avansi_GuilhermeDaniel_M.pdf: 1362823 bytes, checksum: 732bf257c2ca9c9de80531fdd59770e5 (MD5) Previous issue date: 2008 / Resumo: O processo tradicional de estratégia de produção demanda muitas simulações, devido ao alto número de variáveis e combinações. Devido à impossibilidade de investigar todas as alternativas, processos tradicionais levam a resultados sub-ótimos. Processos automatizados podem resolver em partes esse problema, porém o tempo computacional se eleva devido ao acréscimo do número de simulações geradas no processo. Dentro desta perspectiva, este trabalho propõe uma metodologia de aplicação de metamodelos no processo de estratégia de produção e na avaliação econômica de campos de petróleo, possibilitando um número maior de alternativas e aumentando as chances de melhores decisões na escolha da estratégia de produção de campos de petróleo, sendo que metamodelos já foram utilizados em outras áreas (análise de risco, ajuste de histórico etc.). Os metamodelos estudados e aplicados envolvem: métodos estatísticos; planejamento estatístico; metodologia de superfície de resposta e teste de consistência. Os metamodelos utilizados neste trabalho mostraram que podem ser utilizados para seleção de estratégias de produção, trazendo uma opção adicional ao processo além de encontrar soluções que não são observadas pelos métodos tradicionais, e que permitiu mudar a decisão utilizada no processo de avaliação econômica em um amplo espaço de solução / Abstract: The traditional process of production strategy demands many simulations due to the high number of variables and possibilities. Sub-optimal results can be obtained from manual processes; Automatic processes can mitigate this problem but the computational effort increases as a result of the number of simulations generated in the process. Thus, the objective of this work is an attempt of application of proxy models in the production strategy optimization and in the economic evaluation in petroleum fields, allowing the selection of production strategy evaluating a higher number of alternatives and increasing the chances to find better solutions. Proxies have been used in important applications such as risk analysis, history matching etc. The applied proxy models combine the following components: statistics methods, experimental planning, the response surface methodology and consistency checking. We have shown that proxy models can be used in a definition of production strategy, bringing an additional option in the process. The advantage is to find solutions that are not investigated by the traditional methods; proxy models create new possibilities to change a decision used in an economic evaluation process in a wider solution space / Mestrado / Reservatórios e Gestão / Mestre em Ciências e Engenharia de Petróleo

The purpose of this paper is to evaluate the possibility of paleoentomology as a proxy in garden archaeology research. Garden contexts can prove difficult to identify and interpret due to the many changes the contexts go through during their activity period. Mixing of materials, harvesting and cultivation of many different plants will affect the environmental data that is retrieved from them and thus our interpretation of horticulture. This essay looks at the contexts and materials involved in the gardening process; irrigation sources, fertilizer, garden plant macrofossils and modern ecological insect and host plant relationships. The goal is to suggest a conceptual indicator group of insect and plant species that could aid in the identification of garden context and the in situ growth of relic plants. Paleoentomological information from the relating contexts (middens, composts, wells etc.) and other indicator groups have been included along with the ecological data in order to get a more complex picture over the garden contexts and their varying content. For instance, many of the plants found in garden soils are recorded as host plants to several insect species. This paper argues that investigation of these relationships can aid garden archaeology and further our understanding of herbivorous insects’ and associated species’ relationships to plant domestication in pre-history.

The conceptual rainfall-runoff model Hysim is used to estimate the flow in ungauged catchments in Scotland by Scottish Water. However, there are non-quantified uncertainties associated with the outcomes of the modelling strategy used. In order to identify and quantify these uncertainties it was necessary to use the framework of proxy-basin validation in order to evaluate the performance of different modelling strategies.   The proxy-basin validation test requires hydrologically analogous catchments for the evaluation of models, a Region Of Influence regionalisation method was used in order group selected catchments by Q95(%MF). Four groups of four catchments were established, which covered Q95(%MF) 5-7%, 7-9%, 9-11% and 11-13%.   The allocation of “donor catchment” and “target catchment” for each Q95(%MF) group was accomplished through discussion with Scottish Water with respect to existing Scottish Water modelled catchments. A single donor catchment and three target catchments were therefore indicated for each group.   Two modelling strategies were developed by the study; the first full transposition method used the entire optimised parameter-set from the donor catchment with the exception of the target catchment’s “catchment area” parameter. The second partial transposition method used the entire optimal parameter-set with the exception of the target catchment’s “interception storage”, “time to peak”, “rooting depth” and “catchment area” parameters.    It was found that the full transposition method had the least uncertainty associated its use for flow estimation when the parameter-set was derived from a donor catchment calibration that was excellent. Contrarily, it was found that the partial transposition model method had the least uncertainty associated with flow estimation for parameter-sets that were derived from a relatively poor donor catchment calibration.   Encouraged by this testing framework, this study has suggested the use of catalogue of donor parameter-sets that can be used to estimate flow for catchments that are hydrologically similar. This strategy of hydrological modelling has been recommended to improve existing Scottish Water Hysim methodology.