129 research outputs found

    Technology for large space systems: A bibliography with indexes (supplement 10)

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    The bibliography lists 408 reports, articles and other documents introduced into the NASA scientific and technical information system to provide helpful information to the researcher, manager, and designer in technology development and mission design in the area of large space system technology. Subject matter is grouped according to systems, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

    Aeronautical Engineering: A continuing bibliography, 1982 cumulative index

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    This bibliography is a cumulative index to the abstracts contained in NASA SP-7037 (145) through NASA SP-7037 (156) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, contract, and report number indexes

    Assessing plant design with regards to MPC performance using a novel multi-model prediction method

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    Model Predictive Control (MPC) is nowadays ubiquitous in the chemical industry and offers significant advantages over standard feedback controllers. Notwithstanding, projects of new plants are still being carried out without assessing how key design decisions, e.g., selection of production route, plant layout and equipment, will affect future MPC performance. The problem addressed in this Thesis is comparing the economic benefits available for different flowsheets through the use of MPC, and thus determining if certain design choices favour or hinder expected profitability. The Economic MPC Optimisation (EMOP) index is presented to measure how disturbances and restrictions affect the MPC’s ability to deliver better control and optimisation. To the author’s knowledge, the EMOP index is the first integrated design and control methodology to address the problem of zone constrained MPC with economic optimisation capabilities (today's standard in the chemical industry). This approach assumes the availability of a set of linear state-space models valid within the desired control zone, which is defined by the upper and lower bounds of each controlled and manipulated variable. Process economics provides the basis for the analysis. The index needs to be minimised in order to find the most profitable steady state within the zone constraints towards which the MPC is expected to direct the process. An analysis of the effects of disturbances on the index illustrates how they may reduce profitability by restricting the ability of an MPC to reach dynamic equilibrium near process constraints, which in turn increases product quality giveaway and costs. Hence the index monetises the required control effort. Since linear models were used to predict the dynamic behaviour of chemical processes, which often exhibit significant nonlinearity, this Thesis also includes a new multi-model prediction method. This new method, called Simultaneous Multi-Linear Prediction (SMLP), presents a more accurate output prediction than the use of single linear models, keeping at the same time much of their numerical advantages and their relative ease of obtainment. Comparing the SMLP to existing multi-model approaches, the main novelty is that it is built by defining and updating multiple states simultaneously, thus eliminating the need for partitioning the state-input space into regions and associating with each region a different state update equation. Each state’s contribution to the overall output is obtained according to the relative distance between their identification point, i.e., the set of operating conditions at which an approximation of the nonlinear model is obtained, and the current operating point, in addition to a set of parameters obtained through regression analysis. Additionally, the SMLP is built upon data obtained from step response models that can be obtained by commercial, black-box dynamic simulators. These state-of-the-art simulators are the industry’s standard for designing large-scale plants, the focus of this Thesis. Building an SMLP system yields an approximation of the nonlinear model, whose full set of equations is not of the user’s knowledge. The resulting system can be used for predictive control schemes or integrated process design and control. Applying the SMLP to optimisation problems with linear restrictions results in convex problems that are easy to solve. The issue of model uncertainty was also addressed for the EMOP index and SMLP systems. Due to the impact of uncertainty, the index may be defined as a numeric interval instead of a single number, within which the true value lies. A case of study consisting of four alternative designs for a realistically sized crude oil atmospheric distillation plant is provided in order to demonstrate the joint use and applicability of both the EMOP index and the SMLP. In addition, a comparison between the EMOP index and a competing methodology is presented that is based on a case study consisting of the activated sludge process of a wastewater treatment plant

    Cattle vector-borne disease occurrence and management and climate change experiences in pastoral communities in Northern Tanzania

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    The livestock sector is vital to Tanzanian economy, and pastoralists largely depend on livestock production for their livelihood. The Vector-Borne Diseases (VBDs) of cattle, East Coast fever (ECF) and African animal trypanosomosis (AAT), whose occurrence are known to be influenced by climatic conditions, cause substantial cattle production losses in pastoralist communities that may be heightened with climate change. However, little is documented on pastoralists’ experiences and observations on climate change and ECF and AAT occurrence. Further, information on management practices for ECF and AAT is outdated following privatisation of veterinary services in Tanzania. This research employed 10 randomly selected villages of Monduli District in Northern Tanzania in 2014-2015. The study explored pastoralist indigenous knowledge of the relationship between climate parameters (temperature and rainfall) and ECF and AAT using participatory epidemiology approaches. The study also quantified the seasonal prevalence of Theileria parva and trypanosome infection in 960 cattle during the wet and dry seasons. Entomological surveys for brown ear ticks (Rhipicephalus appendiculatus) and tsetse flies (Glossina spp.) were also carried out. Assessment of management practices for ECF and AAT, seasonal movements and wildlife interactions in Maasai ecosystem were investigated. This research was the first to explore pastoralists’ understanding, observation and experiences on climate parameters and ECF and AAT. The findings on seasonal prevalence of T. parva and trypanosome infection will help inform decision-making on current and future cattle VBD control strategies. In addition, the information gathered from this thesis will inform the design and implementation of active surveillance, better control and preventive strategies to manage vectors and cattle vector-borne diseases in a changing climate in pastoral communities

    Guaranteed set-based controller design for hybrid dynamical systems

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