Systems are becoming more complicated, complex, and interrelated. Designers have recognized the need to develop systems from a holistic perspective and design them as Systems-of-Systems (SoS). The design of the SoS, especially in the conceptual design phase, is generally characterized by significant uncertainty. As a result, it is possible for all three types of uncertainty (aleatory, epistemic, and error) and the associated factors of uncertainty (randomness, sampling, confusion, conflict, inaccuracy, ambiguity, vagueness, coarseness, and simplification) to affect the design process. While there are a number of existing SoS design methods, several gaps have been identified: the ability to modeling all of the factors of uncertainty at varying levels of knowledge; the ability to consider both the pernicious and propitious aspects of uncertainty; and, the ability to determine the value of reducing the uncertainty in the design process. While there are numerous uncertainty modeling theories, no one theory can effectively model every kind of uncertainty. This research presents a Hybrid Uncertainty Modeling Method (HUMM) that integrates techniques from the following theories: Probability Theory, Evidence Theory, Fuzzy Set Theory, and Info-Gap theory. The HUMM is capable of modeling all of the different factors of uncertainty and can model the uncertainty for multiple levels of knowledge. In the design process, there are both pernicious and propitious characteristics associated with the uncertainty. Existing design methods typically focus on developing robust designs that are insensitive to the associated uncertainty. These methods do not capitalize on the possibility of maximizing the potential benefit associated with the uncertainty. This research demonstrates how these deficiencies can be overcome by identifying the most robust and opportunistic design. In a design process it is possible that the most robust and opportunistic design will not be selected from the set of potential design alternatives due to the related uncertainty. This research presents a process called the Value of Reducing Uncertainty Method (VRUM) that can determine the value associated with reducing the uncertainty in the design problem before a final decision is made by utilizing two concepts: the Expected Value of Reducing Uncertainty (EVRU) and the Expected Cost to Reducing Uncertainty (ECRU).

An opportunistic large array (OLA) is a form of cooperative diversity in which a large group of simple, inexpensive relays or forwarding nodes operate without any mutual coordination, but naturally fire together in response to energy received from a single source or another OLA. When used for broadcast, OLAs form concentric rings around the source, and have been shown to use less energy than conventional multi-hop protocols. This simple broadcasting scheme, which is already known, is called Basic OLA. The OLA Concentric Routing Algorithm (OLACRA), which is our contribution, takes advantage of the concentric ring structure of broadcast OLAs to limit flooding on the upstream connection. By limiting the node participation, OLACRA saves over 80% of the energy compared to Basic OLA, without requiring GPS, individual node addressing, or inter-node interaction. This thesis analyzes the performance of OLACRA over 'deterministic channels' where transmissions are on non-faded orthogonal channels and on 'diversity channels' where transmissions are on Rayleigh flat fading limited orthogonal channels. The performance of diversity channels is shown to approach the deterministic channel at moderate orders of diversity. Enhancements to OLACRA to further improve its efficiency by flooding in the initial upstream level and limiting the downlink 'step sizes' are also considered. The protocols are tested using Monte Carlo evaluation.

Made available in DSpace on 2014-12-17T15:55:00Z (GMT). No. of bitstreams: 1 VivianeSFN_DISSERT.pdf: 1830875 bytes, checksum: cab92fad26402f8ffafa1b30a4f983b4 (MD5) Previous issue date: 2012-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Water is essential to life and all living organisms and their supply is necessary for economic development and quality of life of human populations, but their quality has been altered by human actions. In semi-arid northeast, the water is an issue of concern, especially its quality. This region is common to the construction of reservoirs that capture rain water, streams and temporary rivers in search of ease this situation, being intended for various purposes. Water scarcity is a limiting factor for the economic and social development of the region and contributes to the maintenance of waterborne diseases. About 80% of diseases that occur in developing countries are infected by waterborne pathogens. Therefore, this study aimed to determine in two environments that are part of semil?nticos Armando Ribeiro Gon?alves reservoir, and a stretch of the river Assu, all located in the semiarid RN, the occurrence of opportunistic pathogenic bacteria; check the conceptions of teachers and health workers about the issues "waterborne diseases" and "bacteria" and a diagnosis of diarrheal diseases that affect the population in some municipalities of the semi-arid region of RN from a survey of epidemiological data. For identification of bacteria using commercial kits and the diagnosis of diarrheal disease was based on information from databases. The previous conceptions of teachers and health workers were obtained through questionnaires. The results confirmed the presence of opportunistic bacteria in the studied area, showing the importance of monitoring water quality. There was an under-reporting of cases of diarrhea pointing out flaws in the monitoring of Diarrheal Diseases and indicating the need to improve it. It was felt also the need to implement educational activities on topics dealt with both with teachers and health workers, since they were identified misconceptions on the subject / A ?gua ? essencial ? vida e a todos os organismos vivos e o seu suprimento ? necess?rio para o desenvolvimento econ?mico e para a qualidade de vida das popula??es humanas, mas sua qualidade vem sendo alterada pelas a??es antr?picas. No semi?rido nordestino, a ?gua ? uma quest?o preocupante, especialmente a sua qualidade. Nessa regi?o ? comum a constru??o de reservat?rios, que captam ?guas de chuvas, c?rregos e rios tempor?rios, na busca de amenizar essa situa??o, sendo destinados para diversas finalidades. A escassez de ?gua ? limitante para o desenvolvimento econ?mico e social da regi?o e contribui com a manuten??o das doen?as de veicula??o h?drica. Cerca de 80% das doen?as que ocorrem em pa?ses em desenvolvimento s?o veiculadas pela ?gua contaminada por microrganismos patog?nicos. Nesse contexto, este trabalho objetivou determinar, em dois ambientes semil?nticos que fazem parte do reservat?rio Armando Ribeiro Gon?alves, e em um trecho do rio Assu, todos localizados no semi-?rido potiguar, a ocorr?ncia de bact?rias patog?nicas oportunistas; verificar as concep??es de professores e agentes de sa?de a respeito dos temas doen?as de veicula??o h?drica e bact?rias , e realizar um diagn?stico das doen?as diarr?icas que acometem a popula??o de alguns munic?pios do semi-?rido do RN a partir do levantamento de dados epidemiol?gicos. Para identifica??o das bact?rias utilizaram-se kits comerciais, e o diagn?stico das doen?as diarr?icas foi realizado com base em informa??es de bancos de dados. As concep??es pr?vias de professores e agentes de sa?de foram obtidas por meio da aplica??o de question?rios. Os resultados confirmaram a presen?a de bact?rias oportunistas nos ambientes estudados, evidenciando a import?ncia de vigil?ncia da qualidade da ?gua. Verificou-se uma sub-notifica?ao de casos de diarr?ias apontando falhas no Monitoramento das Doen?as Diarr?icas, e indicando a necessidade de aprimor?-lo. Percebeu-se, ainda, a necessidade de implementa??o de atividades educativas sobre os temas abordados, tanto com os professores como com os agentes de sa?de, uma vez que foram identificadas concep??es equivocadas sobre o tema

Location-sharing services have become increasingly popular with the proliferation of smartphones and online social networks. People share their locations with each other to record their daily lives or satisfy their social needs. At the same time, inappropriate disclosure of location information poses threats to people's privacy. One of the reasons why people fail to protect their location privacy is the difficulty of using the current mechanisms to manually configure location-privacy settings. Since people's location-privacy preferences are context-aware, manual configuration is cumbersome. People's incapability and unwillingness to do so lead to unexpected location disclosures that violate their location privacy. In this thesis, we investigate the feasibility of using recommender systems to help people protect their location privacy. We examine the performance of location-privacy recommender systems and compare it with the state-of-the-art. We also conduct online user studies to understand people's acceptance of such recommender systems and their concerns. We revise our design of the systems according to the results of the user studies. We find that user-based collaborative filtering can accurately recommend location-privacy preferences and outperform the state-of-the-art when training data are insufficient. From users' perspective, their acceptance of location-privacy recommender systems is affected by the openness and the context of recommendations and their privacy concerns about the systems. It is feasible to use data obfuscation or decentralisation to alleviate people's concerns and meanwhile keep the systems robust against malicious data attacks.

Les communications par satellites sont l’aboutissement de recherches menées dans les domaines de télécommunications et des technologies spatiales depuis plus de 50 ans. Les premiers satellites souffraient d’un coût exorbitant pour des performances très limitées. Les avancées technologiques apparues dans ces domaines ont permis de rendre ce rapport satisfaisant et commercialement viable ce qui a permis de multiplier leurs lancements et ainsi de mettre en place de véritables réseaux de satellites. À ce jour, il existe de nombreuses constellations de satellites géostationnaires et d’orbites basses utilisées à des fins civiles ou militaires. De manière générale, le routage au sein de ces constellations s’effectue suivant un pré-calcul des routes existantes qui est alors utilisé sur une période donnée et rafraîchi si besoin. Ce type de routage n’étant optimal que sur des topologies déterministes, nous sommes donc amenés à considérer d’autres solutions si l’on relaxe cette hypothèse. L’objectif de cette thèse est d’explorer les alternatives possibles au routage pré-calculé. En tant que piste potentielle, nous proposons de vérifier l’adéquation des protocoles de routage à réplication issus du monde des réseaux tolérants au délai, DTN, aux constellations de satellites. Afin de nous offrir un cadre d’étude pertinent à la vue de cet objectif, nous nous focalisons sur une constellation particulière à caractère quasi-déterministe n’offrant pas une connectivité directe entre tous les nœuds du système. Dans une deuxième partie nous nous intéressons à la modélisation du protocole de routage Binary Spray and Wait. Nous développons un modèle capable de déterminer théoriquement la distribution du délai d’acheminement pour tout type de réseau, homogène et hétérogène. / Satellite communication is the achievement of more than 50 years of research in the fields of telecommunications and space technologies.First satellites had exorbitant costs for very limited performances. Technological advances occurred in these areas have helped them to become commercially feasible and satisfying. This enable the increase of satellite launches and thus, building complete satellite networks.Today, there are many GEO or LEO satellite constellations used for civilian or military applications. In general, routing in these constellations is done by pre-computing existing routes. These routes are then used for a given period and refreshed if needed. This type of routing is optimal only on deterministic topologies as a consequence we need to consider other solutions if we relax this assumption. The objective of this thesis is to explore alternatives to pre-computed routing. As a potential solution, we propose to assess the suitability of replication based routing protocols issued from the world of delay tolerant networks, DTN. To provide a relevant framework to study this topic, we focus on a particular constellation that present a quasi-deterministic nature and do not provide direct connectivity between all nodes of the system. In a second part, we focus on the modeling of the Binary Spray and Wait, routing protocol. We develop a model that can theoretically determine the distribution of end-to-end delay for any type of network, homogeneous and heterogeneous. Finally, we present a possible use of this model to conduct more in-depth theoretical analysis.

Made available in DSpace on 2015-04-11T14:03:00Z (GMT). No. of bitstreams: 1 Polianny Almeida Lima.pdf: 1135711 bytes, checksum: 18018c30e2dd4e938af7eadcae042cbe (MD5) Previous issue date: 2013-03-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Standard networking technologies are based on typical assumptions such as the existence of connectivity end-to-end between source and destination for the entire period of communication, low error rates, retransmission mechanisms to repair errors, and relatively small communication delays. If one or more of these assumptions are not achieved in practice, blinks occur in communication, creating challenges that must be overcome to ensure the successful transmission. In this context, came the delay-tolerant networks and disconnection (DTN - Delay Tolerant Networks), an emerging technology for communications when there is no network infrastructure and disconnections may occur frequently due to the mobility of nodes. To bypass the problem of disconnections, DTN networks use the concept of persistent storage, which becomes a problem because the nodes have limited capacity of the buffers. The question is how to select the messages that remain in buffers longer considering the unpredictable mobility of nodes, short contacts between pairs of nodes, storage nodes achieved by finite and so on. This paper proposes a buffer management that transmits messages adaptively based on entropy variation of mobility network. / Tecnologias de redes tradicionais baseiam-se em suposições típicas, como a existência de conectividade fim a fim entre origem e destino durante todo o período de comunicação, baixas taxas de erros, mecanismos de retransmissão para reparar erros, e atrasos de comunicação relativamente pequenos. Caso uma ou mais dessas suposições não sejam alcançadas na prática, ocorrem intermitências na comunicação, criando desafios que devem ser superados a fim de garantir o sucesso na transmissão. Nesse contexto, surgiram as redes tolerantes a atraso e desconexão (DTN - Delay Tolerant Networks), uma tecnologia emergente para comunicações quando não há infraestrutura de rede e desconexões podem ocorrer com frequência devido à mobilidade dos nodos. Para contornar o problema das desconexões, as redes DTN utilizam o conceito de armazenamento persistente, o que se torna um problema, pois os nodos tem capacidade de buffers limitada. A questão é selecionar as mensagens que ficarão nos buffers por mais tempo levando em consideração a mobilidade imprevisível dos nodos, contatos de curta duração entre pares de nodos, armazenamento finito realizado pelos nodos e assim por diante. Este trabalho apresenta uma proposta de gerenciamento de buffer que transmite mensagens de forma adaptativa baseada na variação de entropia de mobilidade da rede.

Made available in DSpace on 2016-03-15T19:31:18Z (GMT). No. of bitstreams: 1 Adilson Aderito da Silva.pdf: 1146737 bytes, checksum: 8cd5e83fb0f914d05834ba4cd0ffbb5b (MD5) Previous issue date: 2009-03-03 / Fundo Mackenzie de Pesquisa / Based on the transaction cost reasoning this doctoral dissertation proposed a model that theorizes on the relationship between uncertainty, bounded rationality, asset specificity, opportunism and vertical integration in supply chains. An extensive literature review was conducted in three basic fields: transaction cost economics; organizational theory; and strategy to better understand the definition of those variables and their theoretical relationship. The review also helped to identify scales used in previous research to measure the research variables. The identified scales were then back translated and adapted to be used in this research. The research instrument was pre-tested and then it was made available on the internet from April to October 2008 and managers from industrial organizations classified in the D section in the Brazilian SIC and also listed in the database of FIESP (São Paulo State Industry Association) were asked to participate in the survey. The section D includes industries that perform physical, chemical and biological transformation of inputs into new products. From the population we selected only firms classified by the association as medium or large sizes which resulted in a target of three thousand potential subjects. Electronic messages which explained the survey proposal and instructions to fill in the questionnaire were sent through the internet. All those that not answered the first message received another message few days later and they were again contacted by phone. Due to the nature of the study only middle managers and directors working in the target firms were asked to answer the questionnaire. Some 111 good responses were available in the end of data collection process and they represent 87 different firms and 14 economic activities the collected data were analyzed using the EQS 6.1 software, which allowed the validation of the research constructs through SEM. The use of this methodology represented an innovation in the research field, because it gives the possibility to include more variables in the basic model, and they are simultaneously considered in the search of explanations for vertical integration. This choice brought important methodological contributions to the research field. Validation of the uncertainty construct as multidimensional derived from three types of uncertainty. The second contribution was to test the construct bounded rationality as a second order latent variable and in the first order were used two types of uncertainty effect and response. The third contribution refers to the level of refinement introduced by the use of the EQS software and structural equation modeling. This approach allowed us to verify the validation of the theoretical model. The statistical significance of most tested direct and indirect relationships among constructs confirmed the proposed theoretical model. Another finding derived from the data is that the explanation of degree of vertical integration in supply chain has to consider all research constructs included in the model to interact together. So no single construct in the TCT can explain alone the vertical integration. / Neste trabalho um modelo teórico para testar o relacionamento entre incerteza, racionalidade limitada, especificidade dos ativos, o comportamento oportunista e o grau de integração vertical em cadeias de suprimentos foi proposto e testado. Para tal foi realizada uma revisão na literatura de Teorias das Organizações, Teoria dos Custos de Transação e Economia visando fundamentar os conceitos subjacentes nessas variáveis latentes e identificar escalas com indicadores que se apresentaram confiáveis em estudos prévios. A partir dessa revisão, elaborou-se um instrumento para a coleta de dados que ficou disponível on-line entre os meses de abril a outubro de 2008. O universo da pesquisa foi definido pelo conjunto de empresas da indústria de transformação classificadas na seção D do CNAE (2004) constantes na base da Federação das Indústrias do Estado de São Paulo - FIESP envolvendo a transformação física, química ou biológica de materiais, substâncias ou componentes para a obtenção de novos produtos. Nesse universo foram selecionadas e convidadas para participar da pesquisa 3000 empresas. O convite foi efetuado, num primeiro momento, a partir do envio de mensagens eletrônicas contendo os objetivos, as instruções e o link de acesso à pesquisa e, num segundo momento, o convite foi ratificado junto aos respondentes por meio de contatos telefônicos. Dada a sua natureza, a pesquisa de campo foi limitada àqueles que desempenhavam funções de Gerentes ou de Diretores em suas empresas, resultando numa amostra com 111 respondentes, que representaram 87 empresas em 14 setores de atividades econômicas. Os dados coletados foram processados com o software EQS 6.1 que permitiu operacionalizar e validar os construtos propostos por meio da Modelagem por Equações Estruturais. A utilização dessa metodologia de análise representou um avanço em relação aos estudos anteriores, pois possibilitou a inclusão de um número maior de variáveis latentes no modelo de mensuração para avaliar o grau de integração vertical em cadeias de suprimentos. Nesse sentido o estudo trouxe contribuições metodológicas importantes no campo da pesquisa empírica em Teorias das Organizações e Teoria dos Custos de Transação. A primeira foi a validação do construto de incerteza como um construto multidimensional que subsiste em incerteza de estado, de efeito e de resposta. A segunda foi operacionalização do pressupostode racionalidade limitada como um construto de segunda ordem a partir das incertezas de efeito e de resposta. A terceira contribuição está relacionada ao nível de refinamento introduzido pelo processamento dos dados com o EQS 6.1 por meio de Equações Estruturais. A partir dessa abordagem foi possível verificar que a validação do modelo proposto, foi suportada pelos dados empíricos. As significâncias estatísticas dos efeitos diretos e indiretos entre os construtos propostos confirmaram empiricamente o relacionamento entre: incerteza, racionalidade limitada; especificidade dos ativos; e, comportamento oportunista. Estes conceitos, que são apresentados como pressupostos e dimensões básicas na Teoria dos Custos de Transação, são relevantes para explicar o grau de integração vertical em cadeias de suprimentos somente se considerados conjuntamente.

Made available in DSpace on 2016-08-17T14:53:21Z (GMT). No. of bitstreams: 1 Marcio Rodrigo Melo Martins.pdf: 1449274 bytes, checksum: c55738b6ff5f13795eaa87e218fa536c (MD5) Previous issue date: 2012-04-13 / FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO / An opportunistic grid computing environment takes advantage of idle computing cycles of regular computers and workstations that can be spread across several administrative domains for running high performance applications. Opportunistic grids are usually constructed from personal computers that do not need to be dedicated for executing grid applications. The grid workload must coexist with local applications executions, submitted by the nodes regular users. Thus, its execution environment is typically dynamic, heterogeneous and unpredictable failures occur frequently. In addition, the resources of an opportunistic grid can be used at any time for the execution of local tasks, making it difficult to preview the conclusion of the tasks running on the grid nodes. These characteristics hinder the successful execution of applications for which there are time restrictions related to its completion. This thesis presents a management mechanism specifically designed for opportunistic grid computing environments for handling the execution of applications with time deadlines set by users during their submission to the system. The proposed mechanism is based on a dynamic scheduling and rescheduling approach and was evaluated using a simulated model considering various typical scenarios of opportunistic grids. The results demonstrated the benefits of the proposed approach in comparison to traditional scheduling approaches applied in opportunistic grids. / Um ambiente de computação de grade oportunista aproveita ciclos ociosos de computadores e estações de trabalho que podem ser distribuídos por vários domínios administrativos para a execução de aplicações de alto desempenho. Grades oportunistas geralmente são construídas a partir de computadores pessoais que não precisam ser dedicados para a execução de aplicações em grade. Neste tipo de grade, a carga de trabalho deve coexistir com execuções de aplicações locais submetidos pelos usuários dos nós que a compõe. Assim, seu ambiente de execução é tipicamente dinâmico, heterogêneo e imprevisível e falhas ocorrem com frequência. Além disso, os recursos de uma grade oportunista podem ser usados a qualquer momento para a execução de tarefas locais, o que torna difícil prever a conclusão das tarefas em execução nos nós da grade. Essas características dificultam a execução bem sucedida de aplicações para as quais existem restrições de tempo relacionada com a sua conclusão. Este trabalho apresenta um mecanismo de gerenciamento da execução de aplicações projetado especificamente para ambientes de computação de grade oportunista cujas aplicações possuem prazos de execução (deadline) definidos pelos usuários durante sua submissão ao sistema. O mecanismo proposto é baseado em uma abordagem dinâmica de escalonamento e reescalonamento de aplicações e foi avaliado através de um modelo de simulação levando-se em consideração vários cenários típicos de grades oportunistas. Os resultados demonstraram os benefícios da abordagem proposta em comparação com abordagens de escalonamento de aplicações tradicionalmente utilizadas em grades oportunistas.

La gestion des eaux a pendant longtemps été associée à des préoccupations sanitaires afin d'éviter la dissémination de maladie hydrique. Au cours du temps, l'aspect sanitaire a été remplacé par des préoccupations environnementales. A ce jour, des questions sur les potentiels risques sanitaires dues aux ouvrages de gestion des eaux sont récurrentes. Dans ce travail, nous nous sommes intéressés au comportement d'un bassin sec de rétention de l'est lyonnais en étudiant les liens existant entre la présence de bactéries pathogènes opportunistes, le fonctionnement hydraulique et la capacité de piégeage des polluants de ce bassin. Pour cela, nous avons réalisé 6 campagnes de prélèvements sur un an et demi. Les prélèvements ont été caractérisés au niveau physico-chimique et microbiologique (A. caviae, P. aeruginosa, Nocardia, E. coli, coliformes, entérocoques). Les caractéristiques physico-chimiques trouvées sont comparables à celles obtenues dans des bassins similaires. L'ensemble du bassin est régulièrement contaminé par les bactéries suivies (0 à 1.92E+07 UFC/g sec). Des concentrations plus fortes en été et un apport par les pluies ont pu être observés. Des analyses de corrélation de type Pearson ont mis en évidence de rares liens entre la présence de bactéries et de polluants chimiques, comme par exemple entre P. aeruginosa et les HAPs. Une corrélation entre les Nocardia et des caractéristiques sédimentaires (teneur en masse organique volatile et densité) a aussi pu être observée. Une étude plus poussée sur le genre Nocardia a permis: d'isoler pour la première fois en France des N. cyriacigeorgica dans l'environnement, de mettre au point une qPCR (spécifique de cette espèce) utilisable en milieu complexe et de développer un test rapide sur nématode afin de connaitre la virulence d'isolats bactériens au niveau du SNC / Water management has been associated during a long time with health concerns to prevent the spread of waterborne disease. Over time, the health aspect was replaced by environmental concerns. Nowadays, questions about the potential health risks due to water management structures are recurrent. In this work, we studied the behavior of a dry retention basin at the eastern part of Lyon, in particular the links between the presence of opportunistic pathogenic bacteria, the hydraulic behaviour and the trapping capacity of pollutants in the basin. For that purpose, we carried out 6 sampling campaigns during a year and a half. The samples were characterized at a physicochemical and microbiological level (A. caviae, P. aeruginosa, Nocardia, E. coli, coliforms, enterococci). The physicochemical characteristics found are comparable to those obtained in similar basins. The entire basin is regularly contaminated by bacteria followed (0 to 1.92E +07 CFU/g dm). Higher concentrations in summer and during rain periods were observed. Pearson correlation analysis revealed some rare links between the presence of bacteria and chemical pollutants, such as between P. aeruginosa and PAHs. A correlation between Nocardia and sedimentary characteristics (volatile organic content and mass density) was also observed. For the first time in France, further study on the genus Nocardia has permitted: to isolate N. cyriacigeorgica in the environment, to develop a qPCR (specific of this species) used in complex environments and to develop a quick test on nematode in order to identify the virulence of bacterial isolates in the NSC

Magister Public Health - MPH / Antiretroviral therapy (ART) improves the quality of lives of people living with HIV/AIDS by suppressing HIV replication and improving the patient’s immunity. An improved immunity will help prevent patients from contracting opportunistic infections. Adherence to ART is vital to obtain good clinical outcome for patients. Defaulting ART leads to increase in viral load, decreased host immunity, development of HIV drug resistant strains, exposure to opportunistic infections and ultimately death. HIV positive patients who are on ART face many challenges in adhering to their medications, these challenges act as barriers to their adherence to treatment. This study explores the barriers that adult patients in a hospital in Eastern Cape of South Africa face while on treatment. These barriers include individual factors, socio-economic factors, health service factors, medical regimen factors.