2,897 research outputs found

    Space test program of high-voltage solar array-space plasma interactions

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    Future spacecraft, notably the proposed Space Station, will require power systems much larger than have previously been flown. It is recognized that at higher voltages, and at the relatively high plasma density present at low Earth orbital altitudes, undesirable interactions between the high voltage solar array and the space plasma will occur. Space experiments on high voltage solar array space plasma interactions in low Earth orbit are an absolute requirement for confident design of a higher voltage solar array. Experiments are presently being identified to provide the necessary space data for calibration of ground testing, validation of analytical models, and development of design guidelines required for confident design of high voltage solar arrays in space. A proposed flight experiment program which is designed to obtain the required data is summarized

    HR Explorer

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    At the European Laboratory for Particle Physics Research (CERN), Geneva Switzerland we are using OracleHR for managing our human resources since 1995. After the first year of production it became clear that there was a strong need for an easy-to-use Decision Support Tool exploring the data in OracleHR. This paper illustrates an approach which we have adopted to provide on-line management reporting, multi-dimensional analysis, drill-down and slicing & dicing of data, warehoused from OracleHR. The tool offers strong resource management and planning capabilities including career follow-up. The user management and security monitoring are implemented using the Oracle WebServer

    Droplet impact on a thin fluid layer

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    The initial stages of high-velocity droplet impact on a shallow water layer are described, with special emphasis given to the spray jet mechanics. Four stages of impact are delineated, with appropriate scalings, and the successively more important influence of the base is analysed. In particular, there is a finite time before which part of the water in the layer remains under the droplet and after which all of the layer is ejected in the splash jet

    THE TEXAS RICE INDUSTRY COALITION FOR THE ENVIRONMENT (R.I.C.E.): MAIN POINTS FROM SIX FOCUS GROUPS

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    The Texas Rice Industry Coalition for the Environment (R.I.C.E.) was formed in February, 1995. Their stated mission is to build a coalition of interests to foster and strengthen relationships between the rice industry and the natural resources of our rice-producing area in Texas. In June, 1995, a series of six focus groups was conducted. These round table discussions involved two groups of producers (from the East Side and West Side of Houston), two groups of environmentalists in the Houston area, and two groups of non-farming Houstonians (adults and children). These focus groups were structured to elicit opinions from various viewpoints concerning the opportunities, challenges, and priorities of Texas R.I.C.E. The goal of the two producers focus groups conducted on the East Side and the West Side of Houston was to determine whether Texas R.I.C.E.'s activities were widely known and to ascertain producers' viewpoints on the coalition's priorities. Producers were agreed on their key concerns regarding compliance with environmental policy - they face a cost-price squeeze and therefore one-size-fits-all regulations are particularly burdensome. Water quality and quantity were most often mentioned as key factors in the continued viability of the rice industry in Texas. Producers recognize the natural synergy between rice production and waterfowl habitat enhancement, yet they are concerned because waterfowl habitat places increased demands on scarce water. Rice producers are concerned about the public being largely ignorant and uninterested in the environmental benefits of rice production, and they endorsed two-way education between rice producers and environmentalists. No clear consensus emerged in the focus group discussions about the role for Texas R.I.C.E. in lobbying. Some rice producers see education and lobbying as conflicting activities and would prefer for Texas R.I.C.E. to focus on education. Others were positive about collaborative opportunities between rice producers' lobbyists and environmental interest groups' lobbyists. The two environmental focus groups were a mix of bird-watchers, hunters, hikers and conservationists. These environmentalists had a good idea of where rice is grown in Texas and knew that rice production is declining in the state. Their major concerns about the environmental effects from rice production were water usage and water quality, agri-chemical runoff, food and habitat for migratory birds, and trade-offs concerning wetlands. In sum, they appreciated that rice production makes a positive contribution to waterfowl habitat. They were concerned that lost Texas rice acreage will be replaced with urban land uses, thus reducing wildlife habitat benefits. They viewed rice production as being environmentally friendly compared with other types of agricultural production, such as cotton farming. They were favorably impressed that rice producers were taking the initiative to form a coalition. They were anxious to work collaboratively and offered several concrete suggestions about forums and issues for educational campaigns. They suggested that consumptive and non-consumptive users of wildlife habitat (such as hunters and bird-watchers, respectively) should compensate private landowners for allowing access. They acknowledged problems with adversarial attitudes going both ways between environmentalists and rice producers; they brainstormed about how Texas R.I.C.E. could help break down barriers. The general public adult focus group, comprised of non-farming Houstonians, established a general interest and awareness concerning rice production. However, the Houstonians participating in this focus group were uninformed about the waterfowl habitat benefits associated with rice production. They offered positive endorsement of the Texas R.I.C.E. effort and expressed sincere (and specific) interests in educational programming. The general public children focus group included several children from the Clear Lake area south of Houston. These children exhibited a natural inquisitiveness and concern regarding the environment and food safety. They were largely ignorant of commercial agriculture, excepting several recollections of "visits to relatives' farms." They expressed considerable interest in more agricultural-related curriculum being incorporated into their science and/or social studies curricula.Environmental Economics and Policy,

    Large droplet impact on water layers

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    The impact of large droplets onto an otherwise undisturbed layer of water is considered. The work, which is motivated primarily with regard to aircraft icing, is to try and help understand the role of splashing on the formation of ice on a wing, in particular for large droplets where splash appears, to have a significant effect. Analytical and numerical approaches are used to investigate a single droplet impact onto a water layer. The flow for small times after impact is determined analytically, for both direct and oblique impacts. The impact is also examined numerically using the volume of fluid (VOF) method. At small times there are promising comparisons between the numerical results, the analytical solution and experimental work capturing the ejector sheet. At larger times there is qualitative agreement with experiments and related simulations. Various cases are considered, varying the droplet size to layer depth ratio, including surface roughness, droplet distortion and air effects. The amount of fluid splashed by such an impact is examined and is found to increase with droplet size and to be significantly influenced by surface roughness. The makeup of the splash is also considered, tracking the incoming fluid, and the splash is found to consist mostly of fluid originating in the layer

    The extension and exploitation of the inventory and order based production control system archetype from 1982 to 2015

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    In 1994, through classic control theory, John, Naim and Towill developed the ‘Automatic Pipeline, Inventory and Order-based Production Control System’ (APIOBPCS) which extended the original IOBPCS archetype developed by Towill in 1982 ─ well-recognised as a base framework for a production planning and control system. Due to the prevalence of the two original models in the last three decades in the academic and industrial communities, this paper aims to systematically review how the IOBPCS archetypes have been adopted, exploited and adapted to study the dynamics of individual production planning and control systems and whole supply chains. Using various databases such as Scopus, Web of Science, Google Scholar (111 papers), we found that the IOBPCS archetypes have been studied regarding the a) modification of four inherent policies related to forecasting, inventory, lead-time and pipeline to create a ‘family’ of models, b) adoption of the IOBPCS ‘family’ to reduce supply chain dynamics, and in particular bullwhip, c) extension of the IOBPCS family to represent different supply chain scenarios such as order-book based production control and closed-loop processes. Simulation is the most popular method adopted by researchers and the number of works based on discrete time based methods is greater than those utilising continuous time approaches. Most studies are conceptual with limited practical applications described. Future research needs to focus on cost, flexibility and sustainability in the context of supply chain dynamics and, although there are a few existing studies, more analytical approaches are required to gain robust insights into the influence of nonlinear elements on supply chain behaviour. Also, empirical exploitation of the existing models is recommended

    A systematic review of research into the management of manufacturing capabilities

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    Our study aims to explore the past and present knowledge related to the management of manufacturing capabilities and to assess the extent to which our knowledge of this field has developed. It places specific emphasis on the philosophical foundations of the field, while also providing a set of directions for future research. A systematic review is applied, covering 104 articles. The authors unfold a strong dominance of the positivist paradigm, and call for a more balanced and informed approach in philosophical and, more specifically, methodological selection by scholars. In terms of the research content, a strong bias exists towards measuring the impact that certain manufacturing capabilities, and various configurations of these, may have on key performance indicators, such as cost. Our review warns on the dangers of following a dominant paradigmatic stance and on the limitations of researching a limited area of the complex and dynamic manufacturing capabilities arena
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