817 resultados para Distributed Denial of Service


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Due to the growing complexity and adaptability requirements of real-time systems, which often exhibit unrestricted Quality of Service (QoS) inter-dependencies among supported services and user-imposed quality constraints, it is increasingly difficult to optimise the level of service of a dynamic task set within an useful and bounded time. This is even more difficult when intending to benefit from the full potential of an open distributed cooperating environment, where service characteristics are not known beforehand and tasks may be inter-dependent. This paper focuses on optimising a dynamic local set of inter-dependent tasks that can be executed at varying levels of QoS to achieve an efficient resource usage that is constantly adapted to the specific constraints of devices and users, nature of executing tasks and dynamically changing system conditions. Extensive simulations demonstrate that the proposed anytime algorithms are able to quickly find a good initial solution and effectively optimise the rate at which the quality of the current solution improves as the algorithms are given more time to run, with a minimum overhead when compared against their traditional versions.

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Wireless Sensor Networks (WSNs) are highly distributed systems in which resource allocation (bandwidth, memory) must be performed efficiently to provide a minimum acceptable Quality of Service (QoS) to the regions where critical events occur. In fact, if resources are statically assigned independently from the location and instant of the events, these resources will definitely be misused. In other words, it is more efficient to dynamically grant more resources to sensor nodes affected by critical events, thus providing better network resource management and reducing endto- end delays of event notification and tracking. In this paper, we discuss the use of a WSN management architecture based on the active network management paradigm to provide the real-time tracking and reporting of dynamic events while ensuring efficient resource utilization. The active network management paradigm allows packets to transport not only data, but also program scripts that will be executed in the nodes to dynamically modify the operation of the network. This presumes the use of a runtime execution environment (middleware) in each node to interpret the script. We consider hierarchical (e.g. cluster-tree, two-tiered architecture) WSN topologies since they have been used to improve the timing performance of WSNs as they support deterministic medium access control protocols.

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Due to the growing complexity and adaptability requirements of real-time embedded systems, which often exhibit unrestricted inter-dependencies among supported services and user-imposed quality constraints, it is increasingly difficult to optimise the level of service of a dynamic task set within an useful and bounded time. This is even more difficult when intending to benefit from the full potential of an open distributed cooperating environment, where service characteristics are not known beforehand. This paper proposes an iterative refinement approach for a service’s QoS configuration taking into account services’ inter-dependencies and quality constraints, and trading off the achieved solution’s quality for the cost of computation. Extensive simulations demonstrate that the proposed anytime algorithm is able to quickly find a good initial solution and effectively optimises the rate at which the quality of the current solution improves as the algorithm is given more time to run. The added benefits of the proposed approach clearly surpass its reducedoverhead.

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A QoS adaptation to dynamically changing system conditions that takes into consideration the user’s constraints on the stability of service provisioning is presented. The goal is to allow the system to make QoS adaptation decisions in response to fluctuations in task traffic flow, under the control of the user. We pay special attention to the case where monitoring the stability period and resource load variation of Service Level Agreements for different types of services is used to dynamically adapt future stability periods, according to a feedback control scheme. System’s adaptation behaviour can be configured according to a desired confidence level on future resource usage. The viability of the proposed approach is validated by preliminary experiments.

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MSC Dissertation in Computer Engineering

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Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de Computadores Especialidade: Robótica e Manufactura Integrada

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RESUMO: Nos últimos anos assistiu-se a um reposicionamento das pessoas portadoras de doença mental na sociedade, no sentido de viverem em pleno os seus direitos, sem restrições. Esta tendência acompanhou as transformações que se têm vivido na forma como os utentes dos serviços de saúde interagem com os mesmos e com os profissionais de saúde, de forma a permitir uma maior autonomização e responsabilização no que concerne ao tratamento da sua doença, a relação que estabelecem com o seu médico, e a participação na avaliação e monitorização da qualidade dos serviços. Mais recentemente, também no mundo científico, esta afirmação se fez sentir, com o surgimento de investigação liderada por utentes, no sentido de estudar de forma adequada questões que partem do seu ponto de vista, e que possibilitem a produção de conhecimento significativa no contexto das suas experiências. Com o presente trabalho pretende-se contribuir para a validação da versão portuguesa do VOICE (Service Users’ Perceptions of Inpatient Care, Views on Inpatient Care) (Evans et al., 2012), instrumento para a avaliação dos serviços de internamento de agudos em psiquiatria, construído a partir de um investigação liderado por utentes e partindo das suas perspectiva. O VOICE é constituído por 19 questões, agrupadas em sete domínios: admissão; cuidados e tratamento; medicação; equipa de técnicos do internamento; terapia e atividades; ambiente e diferenças. O presente estudo envolveu uma amostra de 85 utentes de um serviço de internamento de agudos de uma instituição psiquiátrica do Norte de Portugal. A versão portuguesa do VOICE apresentou boa aceitação por parte dos utentes e boas características psicométricas - a consistência interna foi alta (α = 0,87) e todos, exceto um item (item 6), apresentam elevadas correlações item-total (variando de 0,18 - item 6 a 0,71 - item 11; M = 0,54, DP = 0,15), sugerindo ser um instrumento útil na avaliação dos serviços de internamento de agudos. No futuro torna-se necessário alargar o estudo a outros contextos de internamento e envolvendo amostras mais alargadas.-------------- ABSTRACT: In recent years there has been a gradual process to help people with the experience of mental illness regaining their full rights. Following the advances in the understanding of mental health problems, and the use of medication to help patients overcome symptoms, service-users have become more autonomous and responsible in the way they deal with health professionals, and are now called to participate in assessing and monitoring mental health services and policies. In the context of these transformations we have assisted to the emergence of research led by service-users (in this case of psychiatric and mental health services) in order to emphasize their point of view, and to enable the production of significant knowledge resulting from their experiences, and perceptions. The present study aims to contribute to the dissemination of service-user led research, based on the adaptation and validation of the Portuguese version of the VOICE - Service Users' Perceptions Questionnaire, Views on Inpatient Care. (Evans et al., 2012). The VOICE is composed of 19 questions, grouped in seven domains: admissions, care and treatment, medication, team of technicians during hospitalization, therapy and activities, environment and diversity. The present study involved a sample of 85 inpatient of a psychiatric institution in Northern Portugal. The Portuguese version of the VOICE showed good psychometric properties and was well accepted by patients [high internal consistency (α = 0,87); and high correlation of each item, except item 6, with the total score (ranging from 0.18 on item 6 to 0.71 on item 11; average=0,54; SD=0,15), suggesting it to be a useful tool for assessing inpatient services. In the future there is a need to extend the study to other contexts and include larger samples.

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RESUMO: Este estudo procurou documentar a perspectiva (s) dos utentes de saúde mental e das associações de prestadores de cuidados sobre a prestação, o papel e a contribuição de serviços de saúde mental da comunidade tal como foram percebidos por um número de informadores-chave, incluindo os utentes do serviço mentais e os próprios prestadores de cuidados. O caso específico da Sociedade Saúde Mental do Gana (MEHSOG) foi o foco deste estudo. O modelo foi o de um estudo de caso, utilizando discussões de grupo e entrevistas com informadores-chave como instrumentos de recolha de dados. Estas ferramentas de colheita de dados foram complementadas por observações dos participantes e pela revisão de documentos da MEHSOG e dos vários grupos de apoio da comunidade de auto-ajuda que compõem a associação nacional. O estudo revelou que os utentes dos serviços de saúde mental e seus prestadores de cuidados constituem um importante grupo de partes interessadas na prestação de serviços de saúde mental da comunidade e no desenvolvimento de políticas que tenham em conta as necessidades e os direitos das pessoas com doença mental ou epilepsia. O envolvimento da MEHSOG promove a mobilização de membros e famílias relacionadas com a doença mental de beneficiar de serviços de tratamento bem organizados com um impacto significativo na melhoria da saúde e da participação dos utentes dos serviços e seus prestadores de cuidados primários em processos de tomada de decisão da família e na comunidade processos de desenvolvimento. Os utentes dos serviços por beneficiarem de tratamento, e os prestadores de cuidados primários, por se tornarem mais livres e menos sobrecarregados com a responsabilidade de cuidar, podem passar a envolver-se mais em atividades que melhoramo seu estado, o de suas famílias e das comunidades. A advocacia dos membros da MEHSOG para conseguir que a “Mental Health Bill” se transforme numa Lei foi também um desenvolvimento significativo resultante da participação ativa dos utentes do serviço em chamar a atenção para uma nova e inclusiva legislação de saúde mental para o Gana. Entre os fatores e oportunidades que permitiram aos utentes dos serviços de saúde mental e aos prestadores de cuidados primários de pessoas com doença mental apoiar activamente a prestação de serviços de saúde mental comunitária e o desenvolvimento de políticas conta-se a contribuição da sociedade civil do Gana, particularmente o movimento da deficiência, e os esforços anteriores de ONGs em saúde mental e dos profissionais de saúde mental para ter uma nova lei em saúde mental. Observámos um certo número de desafios e barreiras que actuam de forma a limitar a influência dos utentes dos serviços de saúde mental na provisão da saúde mental comunitária e no desenvolvimento de políticas. Entre elas o estigma social contra a doença mental e pessoas com doença mental ou epilepsia e seus cuidadores primaries é um factor chave. O estigma tem alterado a percepção e as análises do público em geral, especialmente dos profissionais de saúde e das autoridades políticas afetando a priorização dos problemas de saúde mental nas políticas e programas. Outro desafio foi a deficiente infra-estrutura disponível para apoiar serviços de saúde mentais que assegurem aos utentes permanecerem em bom estado de saúde e bem-estar para serem advogados de si próprios. A recomendação do presente estudo é que os movimentos de utentes dos serviços de saúde mental são importantes e que eles precisam de ser apoiados e encorajados a desempenhar o seu papel como pessoas com experiência vivida para contribuir para a organização e prestação de serviços de saúde mental, bem como para a implementação, monitorização e avaliação de políticas e programas. ------------------------------------ ABSTRACT: This study sought to document the perspective(s) of mental health users and care-givers associations in community mental health service provision and their role and contribution as it was perceived by a number of key informants including the mental service users and care-givers themselves. The specific case of the Mental Health Society of Ghana (MEHSOG) was the focus of this study. A case study approach was used to with Focus Group Discussions and Key Informants Interviews being the data collection tools that were used. These data collection tools were complemented by participant observations and review of documents of the MEHSOG and the various community self-help peer support groups that make up the national association. The study revealed that mental health service users and their care-givers constitute an important stakeholder group in community mental health service provision and development of policies that factor in the needs and rights of persons with mental illness or epilepsy. MEHSOG’s involvement in mobilising members and education families to come forward with the relations with mental illness to benefit from treatment services were well made a significant impact in improving the health and participation of service users and their primary carers in family decision-making processes and in community development processes. Service users, on benefiting from treatment, and primary care-givers, on becoming freer and less burdened with the responsibility of care, move on to engage in secure livelihoods activities, which enhanced their status in their families and communities. The advocacy MEHSOG members undertook in getting the mental health Bill become Law was also noted as significant development that was realised as a result of active involvement of service users in calling for a new and inclusive mental health legislation for Ghana. Enabling factors and opportunities that enabled mental health service users and primary care-givers of people with mental illness to actively support community mental health service provision and policy development is with the vibrant civil society presence in Ghana, particularly the disability movement, and earlier efforts by NGOs in mental health in Ghana long-side mental health professionals to have a new law in mental health. A number of challenges were also noted which were found to limit the extent to which mental health service users can be influential in community mental health service provision and policy development. Key among them was the social stigma against mental illness and people with mental illness or epilepsy and their primary carers. Stigma has affected perceptions, analyses of the general public, especially health practitioners and policy authorities that it has affected their prioritisation of mental health issues in policies and programmes. Another challenge was the poor infrastructure available to support enhanced mental health care services that ensure mental health service users remain in a good state of health and wellbeing to advocate for themselves. The recommendation from the study is that mental health service user movements are important and need to be supported and encouraged to play their role as persons with lived experience to inform organisation and provision of mental health services as well as design and implementation, monitoring and evaluation of policies and programes.

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Distributed data aggregation is an important task, allowing the de- centralized determination of meaningful global properties, that can then be used to direct the execution of other applications. The resulting val- ues result from the distributed computation of functions like count, sum and average. Some application examples can found to determine the network size, total storage capacity, average load, majorities and many others. In the last decade, many di erent approaches have been pro- posed, with di erent trade-o s in terms of accuracy, reliability, message and time complexity. Due to the considerable amount and variety of ag- gregation algorithms, it can be di cult and time consuming to determine which techniques will be more appropriate to use in speci c settings, jus- tifying the existence of a survey to aid in this task. This work reviews the state of the art on distributed data aggregation algorithms, providing three main contributions. First, it formally de nes the concept of aggrega- tion, characterizing the di erent types of aggregation functions. Second, it succinctly describes the main aggregation techniques, organizing them in a taxonomy. Finally, it provides some guidelines toward the selection and use of the most relevant techniques, summarizing their principal characteristics.

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This paper analyzes both theoretically and empirically the relationship between distance and frequency of scheduled transportation services. We study the interaction between a monopoly firm providing high-speed scheduled service and personal trans- portation (i.e., car). Most interestingly, the carrier chooses to increase frequency of service on longer routes when competing with personal transportation because provid- ing a higher frequency (at extra cost) it can also charge higher fares that can boost its profits. However, when driving is not a relevant option, frequency of service de- creases for longer flights consistently with prior studies. An empirical application of our analysis to the European airline industry con?rms the predictions of our theoretical model.

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This paper presents a theoretical and empirical analysis of the relationship be- tween frequency of scheduled transportation services and their substitutability with personal transportation (using distance as a proxy). We study the interaction between a monopoly firm providing a high-speed scheduled service and private transportation (i.e., car). Interestingly, the carrier chooses to increase the frequency of service on longer routes when competing with personal transportation because by providing higher frequency (at extra cost) it can also charge higher fares which can boost its profits. However, in line with the results of earlier studies, frequency decreases for longer flights when driving is not a viable option. An empirical application of our analysis to the European airline industry confirms the predictions of our theoretical model. Keywords: short-haul routes; long-haul routes; flight frequency; distance JEL Classification Numbers: L13; L2; L93

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This paper studies the effects of service offshoring on the skill composition of labor demand, using novel comparable data for nine Western European countries between 1990 and 2004. The empirical analysis delivers three main results. First, service offshoring is skill-biased, because it increases the demand for high and medium skilled labor and decreases the demand for low skilled labor. Second, the effects of service offshoring are similar to those of material offshoring, both qualitatively and quantitatively. Third, the economic magnitude of these effects is not large.

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AbstractDigitalization gives to the Internet the power by allowing several virtual representations of reality, including that of identity. We leave an increasingly digital footprint in cyberspace and this situation puts our identity at high risks. Privacy is a right and fundamental social value that could play a key role as a medium to secure digital identities. Identity functionality is increasingly delivered as sets of services, rather than monolithic applications. So, an identity layer in which identity and privacy management services are loosely coupled, publicly hosted and available to on-demand calls could be more realistic and an acceptable situation. Identity and privacy should be interoperable and distributed through the adoption of service-orientation and implementation based on open standards (technical interoperability). Ihe objective of this project is to provide a way to implement interoperable user-centric digital identity-related privacy to respond to the need of distributed nature of federated identity systems. It is recognized that technical initiatives, emerging standards and protocols are not enough to guarantee resolution for the concerns surrounding a multi-facets and complex issue of identity and privacy. For this reason they should be apprehended within a global perspective through an integrated and a multidisciplinary approach. The approach dictates that privacy law, policies, regulations and technologies are to be crafted together from the start, rather than attaching it to digital identity after the fact. Thus, we draw Digital Identity-Related Privacy (DigldeRP) requirements from global, domestic and business-specific privacy policies. The requirements take shape of business interoperability. We suggest a layered implementation framework (DigldeRP framework) in accordance to model-driven architecture (MDA) approach that would help organizations' security team to turn business interoperability into technical interoperability in the form of a set of services that could accommodate Service-Oriented Architecture (SOA): Privacy-as-a-set-of- services (PaaSS) system. DigldeRP Framework will serve as a basis for vital understanding between business management and technical managers on digital identity related privacy initiatives. The layered DigldeRP framework presents five practical layers as an ordered sequence as a basis of DigldeRP project roadmap, however, in practice, there is an iterative process to assure that each layer supports effectively and enforces requirements of the adjacent ones. Each layer is composed by a set of blocks, which determine a roadmap that security team could follow to successfully implement PaaSS. Several blocks' descriptions are based on OMG SoaML modeling language and BPMN processes description. We identified, designed and implemented seven services that form PaaSS and described their consumption. PaaSS Java QEE project), WSDL, and XSD codes are given and explained.

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In this paper, we consider the ATM networks in which the virtual path concept is implemented. The question of how to multiplex two or more diverse traffic classes while providing different quality of service requirements is a very complicated open problem. Two distinct options are available: integration and segregation. In an integration approach all the traffic from different connections are multiplexed onto one VP. This implies that the most restrictive QOS requirements must be applied to all services. Therefore, link utilization will be decreased because unnecessarily stringent QOS is provided to all connections. With the segregation approach the problem can be much simplified if different types of traffic are separated by assigning a VP with dedicated resources (buffers and links). Therefore, resources may not be efficiently utilized because no sharing of bandwidth can take place across the VP. The probability that the bandwidth required by the accepted connections exceeds the capacity of the link is evaluated with the probability of congestion (PC). Since the PC can be expressed as the CLP, we shall simply carry out bandwidth allocation using the PC. We first focus on the influence of some parameters (CLP, bit rate and burstiness) on the capacity required by a VP supporting a single traffic class using the new convolution approach. Numerical results are presented both to compare the required capacity and to observe which conditions under each approach are preferred

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The purpose of resource management is the efficient and effective use of network resources, for instance bandwidth. In this article, a connection oriented network scenario is considered, where a certain amount of bandwidth is reserved for each label switch path (LSP), which is a logical path, in a MPLS or GMPLS environment. Assuming there is also some kind of admission control (explicit or implicit), these environments typically provide quality of service (QoS) guarantees. It could happen that some LSPs become busy, thus rejecting connections, while other LSPs may be under-utilised. We propose a distributed lightweight monitoring technique, based on threshold values, the objective of which is to detect congestion when it occurs in an LSP and activate the corresponding alarm which will trigger a dynamic bandwidth reallocation mechanism