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Required Performance (required + performance)
Selected AbstractsComparison of c-space and p-space particle tracing schemes on high-performance computers: accuracy and performanceINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2002F. Schäfer Abstract The present paper presents a comparison of four different particle tracing schemes which were integrated into a parallel multiblock flow simulation program within the frame of a co-visualization approach. One p-space and three different c-space particle tracing schemes are described in detail. With respect to application on high-performance computers, parallelization and vectorization of the particle tracing schemes are discussed. The accuracy and the performance of the particle tracing schemes are analyzed extensively on the basis of several test cases. The accuracy with respect to an analytically prescribed and a numerically calculated velocity field is investigated, the latter in order to take the contribution of the flow solver's error to the overall error of the particle traces into account. Performance measurements on both scalar and vector computers are discussed. With respect to practical CFD applications and the required performance especially on vector computers, a newly developed, improved c-space scheme is shown to be comparable to or better than the investigated p-space scheme. According to accuracy the new c-space scheme is considerably more advantageous than traditional c-space methods. Finally, an application to a direct numerical simulation of a turbulent channel flow is presented. Copyright © 2002 John Wiley & Sons, Ltd. [source] Operational performance metrics for mars exploration roversJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8-9 2007Edward Tunstel The concept of operational performance metrics and associated measurement issues is explored for deployed robotic systems. The focus is on performance of mobility and robotic arm autonomy exercised on the NASA Mars Exploration Rovers surface mission. This planetary rover mission has been underway for nearly 3 years since January 2004 using two rovers performing separate missions. The autonomy functions of surface navigation, short-distance approach to surface science targets, and robotic placement of armmounted instruments on science targets are considered. Operational metrics that measure performance of these functions relative to system requirements are advocated. Specific metrics are defined and computed using telemetry from the rovers' multiyear operations on Mars and applied to rate performance during their respective missions. An existing methodology is applied to compute metrics with respect to required performance and to aggregate multiple metrics into a composite performance score for each rover. The formulation is augmented to accommodate importance weights that add flexibility in use of the metrics by different potential endusers, e.g., sponsors, program managers, systems engineers, and technologists. A brief example illustrates the application and effect of importance weights on overall rover performance scores. © 2007 Wiley Periodicals, Inc. [source] Optimizing performance of benzoate and phthalate blends for vinyl applicationsJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2005William D. Arendt To achieve required performance, blends of plasticizers are commonly used in flexible vinyl applications. Typically, when fast fusion is required, high solvating phthalates have been utilized in plasticizer blends. Benzoate esters are high solvators and can also be used in these blends. However, even though benzoate plasticizers offer additional performance benefits that can complement general-purpose phthalate performance, most of the literature does not include the use of benzoate plasticizers in blends with phthalates. The purpose of this article is to demonstrate the performance benefits of blending benzoate and phthalate plasticizers. The approach selected to accomplish this task was to develop performance data by utilizing a mixture design approach with DOE (design of experiments) software. A resilient flooring plastisol formulation was selected as the model. The following properties were obtained: degassing, low and high shear viscosity, viscosity stability of the plastisol, gel and fusion characteristics, tensile strength vs. temperature, vinyl heat stability, stain resistance, volatility, and UV stability. The data indicate how to utilize the advantage of benzoates as "process aids" to speed production rates and improve product quality. J. VINYL. ADDIT. TECHNOL. 11:150,154, 2005. © 2005 Society of Plastics Engineers [source] Simulated experimental design used to define the characteristic curves of car shock-absorbersQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 2 2001G. Arcidiacono Abstract This paper introduces a special ,quality' parameter on automotive perspective, i.e. the quality index in order to measure the customer satisfaction with car manoeuvrability. In particular, it describes how the characteristic setting curves of a car shock-absorber can be optimized using subjective customer assessment of three categories of perception: handling, steering quality and ride-comfort. These, called manoeuvrability indices, were used to represent the assessment of customer satisfaction with car manoeuvrability. The characteristic curves for each shock-absorber setting were defined using parameters which uniquely determined their shape. Subsequent analysis was carried out using simulated experimental design which adopts a numeric model of vehicle simulation thereby enabling experimental costs to be reduced. This analysis made it possible to ascertain which setting parameter values provided the best compromise among the three categories of required performance. A codified method of optimization was then developed. This method, which includes the three categories of perception, will be extended to all new projects. Copyright © 2001 John Wiley & Sons, Ltd. [source] A new approach to solving problems of multi-state system reliability optimizationQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 2 2001Gregory Levitin Abstract Usually engineers try to achieve the required reliability level with minimal cost. The problem of total investment cost minimization, subject to reliability constraints, is well known as the reliability optimization problem. When applied to multi-state systems (MSS), the system has many performance levels, and reliability is considered as a measure of the ability of the system to meet the demand (required performance). In this case, the outage effect will be essentially different for units with different performance rate. Therefore, the performance of system components, as well as the demand, should be taken into account. In this paper, we present a technique for solving a family of MSS reliability optimization problems, such as structure optimization, optimal expansion, maintenance optimization and optimal multistage modernization. This technique combines a universal generating function (UGF) method used for fast reliability estimation of MSS and a genetic algorithm (GA) used as an optimization engine. The UGF method provides the ability to estimate relatively quickly different MSS reliability indices for series-parallel and bridge structures. It can be applied to MSS with different physical nature of system performance measure. The GA is a robust, universal optimization tool that uses only estimates of solution quality to determine the direction of search. Copyright © 2001 John Wiley & Sons, Ltd. [source] Design and application of a membrane bioreactor unit to upgrade and enhance the required performance of an installed wastewater treatment plantASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010Teresa Castelo-Grande Abstract Wastewater treatment plants (WWTPs) are nowadays common solutions to improve the quality of streams and soils. However, there are still many issues required to be solved within these plants. We were commissioned to redesign a WWTP in Amarante, Portugal, which was not working properly. Among the several units we have designed, there is a membrane bioreactor representing one of the main units of this remodelled WWTP. The biological treatment stage at the upgraded WWTP will take place in the remodelled primary and secondary settlers and in the remodelled and improved biological reactor. Hence, the primary settler is readapted in such a way that it functions as the anoxic area of the biological treatment, while the aerobic treatment will be sequentially performed at the remodelled biological reactor and at the actual secondary settler. Membrane treatment will be performed by using ultrafiltration membranes. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Fuel Cells, Advanced Reactors and Smart Catalysis: The Exploitation of Ceramic Ion-Conducting MembranesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2003I.S. Metcalfe Abstract Membrane reactors are of great interest in the chemical industries because they offer the possibility of improved yields, improved selectivities and more compact plant. However, a significant barrier to their uptake is the unavailability of membrane systems having the required performance at an acceptable cost. In this paper we will explore the use of one class of membrane that has the potential to deliver high performance at reasonable cost. Ion-conducting ceramic membranes can be used in a wide range of high temperature applications including fuel cells, advanced reactors and even smart catalytic systems. [source] | |||||||||||||