946 resultados para Dependent Failures, Interactive Failures, Interactive Coefficients, Reliability, Complex System


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Engineering assets are often complex systems. In a complex system, components often have failure interactions which lead to interactive failures. A system with interactive failures may lead to an increased failure probability. Hence, one may have to take the interactive failures into account when designing and maintaining complex engineering systems. To address this issue, Sun et al have developed an analytical model for the interactive failures. In this model, the degree of interaction between two components is represented by interactive coefficients. To use this model for failure analysis, the related interactive coefficients must be estimated. However, methods for estimating the interactive coefficients have not been reported. To fill this gap, this paper presents five methods to estimate the interactive coefficients including probabilistic method; failure data based analysis method; laboratory experimental method; failure interaction mechanism based method; and expert estimation method. Examples are given to demonstrate the applications of the proposed methods. Comparisons among these methods are also presented.

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With the application of GIS methodologies to spatial data, researchers can now identify patterns of occurrence for many social problems including health-issues and crime. Further more, since this type of data also contains clues as to the underlying causes of social problems, it can be used to make well-educated and consequently, more effective policy decisions.

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Virtual training systems are attracting paramount attention from the manufacturing industries due to their potential advantages over the conventional training practices. Significant cost savings can be realized due to the shorter times for the development of different training-scenarios as well as reuse of existing designed engineering (math) models. In addition, use of computer based virtual reality (VR) training systems can shorten the time span from computer aided product design to commercial production due to non-reliance on the hardware parts for training. Within the aforementioned conceptual framework, a haptically enabled interactive and immersive virtual reality (HIVEx) system is presented. Unlike existing VR systems, the presented idea tries to imitate real physical training scenarios by providing comprehensive user interaction, constrained within the physical limitations of the real world. These physical constrains are imposed by the haptics devices in the virtual environment. As a result, in contrast to the existing VR systems that are capable of providing knowledge generally about assembly sequences only, the proposed system helps in cognitive learning and procedural skill development as well, due to its high physically interactive nature.

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Yeast phosphatidylinositol-transfer protein (Sec14p) is essential for Golgi secretory function and cell viability. This requirement of Sec14p is relieved by genetic inactivation of the cytidine diphosphate-choline pathway for phosphatidycholine (PtdCho) biosynthesis. Standard phenotypic analyses indicate that inactivation of the phosphatidylethanolamine (PtdEtn) pathway for PtdCho biosynthesis, however, does not rescue the growth and secretory defects associated with Sec14p deficiency. We now report inhibition of choline uptake from the media reveals an efficient “bypass Sec14p” phenotype associated with PtdEtn-methylation pathway defects. We further show that the bypass Sec14p phenotype associated with PtdEtn-methylation pathway defects resembles other bypass Sec14p mutations in its dependence on phospholipase D activity. Finally, we find that increased dosage of enzymes that catalyze phospholipase D-independent turnover of PtdCho, via mechanisms that do not result in a direct production of phosphatidic acid or diacylglycerol, effect a partial rescue of sec14-1ts-associated growth defects. Taken together, these data support the idea that PtdCho is intrinsically toxic to yeast Golgi secretory function.

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Thesis--University of Illinois at Urbana-Champaign.

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Thesis (M.S.)--University of Illinois at Urbana-Champaign.

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3D geographic information system (GIS) is data and computation intensive in nature. Internet users are usually equipped with low-end personal computers and network connections of limited bandwidth. Data reduction and performance optimization techniques are of critical importance in quality of service (QoS) management for online 3D GIS. In this research, QoS management issues regarding distributed 3D GIS presentation were studied to develop 3D TerraFly, an interactive 3D GIS that supports high quality online terrain visualization and navigation. ^ To tackle the QoS management challenges, multi-resolution rendering model, adaptive level of detail (LOD) control and mesh simplification algorithms were proposed to effectively reduce the terrain model complexity. The rendering model is adaptively decomposed into sub-regions of up-to-three detail levels according to viewing distance and other dynamic quality measurements. The mesh simplification algorithm was designed as a hybrid algorithm that combines edge straightening and quad-tree compression to reduce the mesh complexity by removing geometrically redundant vertices. The main advantage of this mesh simplification algorithm is that grid mesh can be directly processed in parallel without triangulation overhead. Algorithms facilitating remote accessing and distributed processing of volumetric GIS data, such as data replication, directory service, request scheduling, predictive data retrieving and caching were also proposed. ^ A prototype of the proposed 3D TerraFly implemented in this research demonstrates the effectiveness of our proposed QoS management framework in handling interactive online 3D GIS. The system implementation details and future directions of this research are also addressed in this thesis. ^

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The IEEE Subcommittee on the Application of Probability Methods (APM) published the IEEE Reliability Test System (RTS) [1] in 1979. This system provides a consistent and generally acceptable set of data that can be used both in generation capacity and in composite system reliability evaluation [2,3]. The test system provides a basis for the comparison of results obtained by different people using different methods. Prior to its publication, there was no general agreement on either the system or the data that should be used to demonstrate or test various techniques developed to conduct reliability studies. Development of reliability assessment techniques and programs are very dependent on the intent behind the development as the experience of one power utility with their system may be quite different from that of another utility. The development and the utilization of a reliability program are, therefore, greatly influenced by the experience of a utlity and the intent of the system manager, planner and designer conducting the reliability studies. The IEEE-RTS has proved to be extremely valuable in highlighting and comparing the capabilities (or incapabilities) of programs used in reliability studies, the differences in the perception of various power utilities and the differences in the solution techniques. The IEEE-RTS contains a reasonably large power network which can be difficult to use for initial studies in an educational environment.

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Treatment as prevention has mobilized new opportunities in preventing HIV transmission and has led to bold new UNAIDS targets in testing, treatment coverage and transmission reduction. These will require not only an increase in investment but also a deeper understanding of the dynamics of combining behavioural, biomedical and structural HIV prevention interventions. High-income countries are making substantial investments in combination HIV prevention, but is this investment leading to a deeper understanding of how to combine interventions? The combining of interventions involves complexity, with many strategies interacting with non-linear and multiplying rather than additive effects. Discussion: Drawing on a recent scoping study of the published research evidence in HIV prevention in high-income countries, this paper argues that there is a gap between the evidence currently available and the evidence needed to guide the achieving of these bold targets. The emphasis of HIV prevention intervention research continues to look at one intervention at a time in isolation from its interactions with other interventions, the community and the socio-political context of their implementation. To understand and evaluate the role of a combination of interventions, we need to understand not only what works, but in what circumstances, what role the parts need to play in their relationship with each other, when the combination needs to adapt and identify emergent effects of any resulting synergies. There is little development of evidence-based indicators on how interventions in combination should achieve that strategic advantage and synergy. This commentary discusses the implications of this ongoing situation for future research and the required investment in partnership. We suggest that systems science approaches, which are being increasingly applied in other areas of public health, could provide an expanded vocabulary and analytic tools for understanding these complex interactions, relationships and emergent effects. Conclusions: Relying on the current linear but disconnected approaches to intervention research and evidence we will miss the potential to achieve and understand system-level synergies. Given the challenges in sustaining public health and HIV prevention investment, meeting the bold UNAIDS targets that have been set is likely to be dependent on achieving systems level synergies.