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Performance Prediction (performance + prediction)
Selected AbstractsPerformance prediction for a code with data-dependent runtimesCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 3 2008S. A. Jarvis Abstract In this paper we present a predictive performance model for a key biomedical imaging application found as part of the U.K. e-Science Information eXtraction from Images (IXI) project. This code represents a significant challenge for our existing performance prediction tools as it has internal structures that exhibit highly variable runtimes depending on qualities in the input data provided. Since the runtime can vary by more than an order of magnitude, it has been difficult to apply meaningful quality of service criteria to workflows that use this code. The model developed here is used in the context of an interactive scheduling system which provides rapid feedback to the users, allowing them to tailor their workloads to available resources or to allocate extra resources to scheduled workloads. Copyright © 2007 John Wiley & Sons, Ltd. [source] Performance prediction of a refrigerating machine using R-407C: the effect of the circulating composition on system performanceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2002P. Haberschill Abstract This article presents a steady-state model of a vapour compression refrigerating machine using a ternary refrigerant mixture R-407C. When using a zeotropic mixture in a refrigerant cycle, the circulating composition does not agree with the composition of the original charged mixture. It is mainly due to the temperature glide and the vapour,liquid slip ratio. As a result of the composition shift and its magnitude, the system performance changes depending on the system design, especially the presence of liquid receiving vessels. In this paper, a method that predicts the circulating composition has been associated to a refrigerating machine model. The results obtained with this model show an enrichment in the most volatile components of about 1% for the circulating composition, which is sufficient to decrease the system performance by about 3%. Factors affecting the overall performance have been investigated. The results show a very strong performance dependence on the refrigerant charge. The COP can decrease by 25% when the refrigerant charge is insufficient. An initial charged composition variation of 2% involves variations of the cooling capacity of about 5%. Furthermore, our model was employed to compare the performance for both R-22 and R-407C. The cooling capacity for R-22 is slightly greater in comparison to R-407C and the COP is almost constant. Copyright © 2002 John Wiley & Sons, Ltd. [source] Performance prediction of concentrator solar cells and modules from dark I,V characteristicsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2003I. Antón The indoor performance of concentrator solar cells and modules at operating conditions is a complex task, owing to the required illumination and temperature conditions, and even more so during extensive procedures, such as on a production line. The solution proposed throughout this paper consists of predicting the illumination I,V characteristic of the solar cells, with the dark I,V curve and the photogenerated current as the only input data. As well as this, the technology-dependent components of the series resistance are obtained from the dark characteristics for quality control. Theory and experiments on several types of concentrator cell have been carried out to validate the method. The equipment to be used on a production line has been developed by IES and used by BP Solar to test up to 25 000 cells and 2000 modules for the 480,kWp power plant using the EUCLIDESTM concentrator. Copyright © 2003 John Wiley & Sons, Ltd. [source] A Grid-enabled problem-solving environment for advanced reservoir uncertainty analysisCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 18 2008Zhou Lei Abstract Uncertainty analysis is critical for conducting reservoir performance prediction. However, it is challenging because it relies on (1) massive modeling-related, geographically distributed, terabyte, or even petabyte scale data sets (geoscience and engineering data), (2) needs to rapidly perform hundreds or thousands of flow simulations, being identical runs with different models calculating the impacts of various uncertainty factors, (3) an integrated, secure, and easy-to-use problem-solving toolkit to assist uncertainty analysis. We leverage Grid computing technologies to address these challenges. We design and implement an integrated problem-solving environment ResGrid to effectively improve reservoir uncertainty analysis. The ResGrid consists of data management, execution management, and a Grid portal. Data Grid tools, such as metadata, replica, and transfer services, are used to meet massive size and geographically distributed characteristics of data sets. Workflow, task farming, and resource allocation are used to support large-scale computation. A Grid portal integrates the data management and the computation solution into a unified easy-to-use interface, enabling reservoir engineers to specify uncertainty factors of interest and perform large-scale reservoir studies through a web browser. The ResGrid has been used in petroleum engineering. Copyright © 2008 John Wiley & Sons, Ltd. [source] Computational study of a novel continuous solar adsorption chiller: performance prediction and adsorbent selectionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2007Evan Voyiatzis Abstract A novel solar adsorption chiller intended for domestic use is presented. The chiller can be integrated with existing solar systems based on flat plate collectors, and, contrary to commercial chillers, it operates continuously. A detailed analysis of both the simple and the heat-integrated cycle is carried out so as to select the optimal adsorbent and operating conditions. The employed integral thermodynamic model takes into account the inert masses that limit the performance of the chiller, such as the metal frame, the thermo-fluid, and the non-adsorbed steam, by introducing heat capacity effects. Given the adsorption equilibrium data, the energy balances, the performance, and the useful thermal loads of the system can be calculated at any operating conditions. The results indicate that silica gel Type A is a more efficient adsorbent compared to silica gel Type RD or Type 3A. Furthermore, the total porosity has a slight effect on system performance, while optimal operation can be achieved when the condenser temperature is less than 326 K and the evaporator temperature greater than 280 K. Copyright © 2006 John Wiley & Sons, Ltd. [source] An engineering approach to dynamic prediction of network performance from application logsINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 3 2005Zalal Uddin Mohammad Abusina Network measurement traces contain information regarding network behavior over the period of observation. Research carried out from different contexts shows predictions of network behavior can be made depending on network past history. Existing works on network performance prediction use a complicated stochastic modeling approach that extrapolates past data to yield a rough estimate of long-term future network performance. However, prediction of network performance in the immediate future is still an unresolved problem. In this paper, we address network performance prediction as an engineering problem. The main contribution of this paper is to predict network performance dynamically for the immediate future. Our proposal also considers the practical implication of prediction. Therefore, instead of following the conventional approach to predict one single value, we predict a range within which network performance may lie. This range is bounded by our two newly proposed indices, namely, Optimistic Network Performance Index (ONPI) and Robust Network Performance Index (RNPI). Experiments carried out using one-year-long traffic traces between several pairs of real-life networks validate the usefulness of our model.,Copyright © 2005 John Wiley & Sons, Ltd. [source] Rotationally symmetric FDTD for wideband performance prediction of TM01 DR filtersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2002Andrew R. Weily Abstract The generalized perfectly matched layer (GPML) coupled with rotationally symmetric (RS)-FDTD method has been utilized to extract the S-parameters for several probe-coupled TM01 dielectric resonator (DR) filters to directly obtain the theoretical wideband spurious performance. The computationally efficient (RS)-FDTD method has also been used to obtain accurate filter parameters for TE01 and TM01 dielectric resonators loaded in cylindrical cavities. The RS-FDTD method combined with digital filtering and the Matrix Pencil technique are used to analyze the resonant frequencies, inter-resonator coupling, and external Q values. When perturbation theory is used with RS-FDTD, accurate values of unloaded Q are obtained. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 259,271, 2002. [source] Relationship Between Work Performance and Personality Traits in Hong Kong Organizational SettingsINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 1 2006Graham P. Tyler Four hundred and thirty-seven employees from four Hong Kong organizations completed the Traditional Chinese versions of the Fifteen Factor Personality Questionnaire Plus (15FQ+) and the Cross-Cultural Personality Assessment Inventory (CPAI-2) (indigenous scales) and provided objective and memory-based recent performance appraisal scores. A number of significant bivariate correlations were found between personality and performance scores. Hierarchical multiple regression analyses revealed that a number of the scales from the 15FQ+ contributed to significantly predicting four of the performance competency dimensions, but that the CPAI-2 indigenous scales contributed no incremental validity in performance prediction over and above the 15FQ+. Results are discussed in the light of previous research and a call made for continued research to further develop and increase the reliability of the Chinese instruments used in the study and to enable generalization of the findings with confidence. [source] Analysis of stirred tanks with two-zone modelsAICHE JOURNAL, Issue 10 2009Ville Alopaeus Abstract Stirred tank turbulence and fluid flow characteristics are analyzed based on a two-zone model. Instead of using the zonal model for stirred tank performance prediction as often proposed in the literature, the zoning is used here as a tool for mixing analysis. A systematic zoning approach is proposed, where the tank is divided into two nested regions. By gradually increasing the inner zone volume, continuous curves can be obtained for turbulent energy dissipation distribution and pumping numbers between the zones as functions of the zone sizes. It is shown here that these curves can be used as a powerful tool for visualizing stirred tank performance. They can be used, e.g., in impeller performance comparisons and analysis of mixing characteristics with changing rheology, or to examine various numerical aspects related to stirred tank CFD modeling. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Modeling and design of vapor-phase biofiltration for chlorinated volatile organic compoundsAICHE JOURNAL, Issue 9 2002Walter Den A mathematical model was developed for biofilter design and performance prediction with reference to the purification of contaminated gas streams. The model incorporated important aspects such as mass transfer, biodegradation, and adsorption processes. A systematic modeling protocol incorporated the development of a scale-up strategy based on dimensional analysis and similitude. Trichloroethylene (TCE) was employed as the model contaminant for biofiltration testing and model verification. The biokinetic and adsorption parameters for the contaminant were determined independently from a series of minibiofilter and miniadsorber column experiments, specifically designed to simulate the actual biofilter operational regimes in a miniature scale. Bench-scale biofilter experiments employing granular activated carbon columns indicated the good predictive capability of the model for the removal of TCE. Dynamic simulation studies were performed to assess the transient- and steady-state behavior of the model under various operating conditions. Model sensitivity was studied to evaluate the influence of adsorption equilibrium, transport and biological parameters on the biofilter dynamics. The results demonstrated that the biofilter performance was greatly influenced by the Monod coefficients and the biofilm thickness. [source] RF characteristics of spaceborne antenna mesh reflecting surfaces: Application of periodic method of momentsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2005Amane Miura Abstract This paper describes a numerical-analysis methodology for RF characterization of various mesh reflecting surfaces used as the reflector surface of spaceborne antennas. Two mesh reflecting surfaces, which demonstrate different polarization characteristics, are studied. Because the mesh reflecting surface has a periodic weaving structure, periodic MoM with RWG basis and testing functions is applied, which allows only one periodic cell of mesh surface to be simulated. The analysis of transmission and reflection losses indicated that Single Satin mesh was much better than Single Atlas mesh, in terms of independence of transmission or reflection loss on polarization. This is because Single Satin mesh model has denser strips than the Single Atlas mesh model. Therefore, for any polarization direction, there is always at least one strip with its axis along or nearly along the incident electric field. The methodology and results presented in this paper are useful for accurate performance prediction of mesh reflector antennas. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 365,370, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21171 [source] Dynamic mechanical properties of extruded nylon,wood compositesPOLYMER COMPOSITES, Issue 4 2008Jianmin Chen Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon,wood composite in under-the-hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon,wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (Tg), physical aging effects, long-term performance prediction, and comparisons to similar products. The storage modulus of the nylon,wood composite was found to be more temperature stable than pure nylon 66. The Tg range of the nylon,wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon,wood composites have good temperature-dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon,wood composite with other similar products shows that nylon,wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Grouping Pavement Condition Variables for Performance Modeling Using Self-Organizing MapsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2001Nii O. Attoh-Okine Different modeling techniques have been employed for the evaluation of pavement performance, determination of structural capacity, and performance predictions. The evaluation of performance involves the functional analysis of pavements based on the history of the riding quality. The riding comfort and pavement performance can be conveniently defined in terms of roughness and pavement distresses. Thus different models have been developed relating roughness with distresses to predict pavement performance. These models are too complex and require parsimonious equations involving fewer variables. Artificial neural networks have been used successfully in the development of performance-prediction models. This article demonstrates the use of an artificial intelligence neural networks self-organizing maps for the grouping of pavement condition variables in developing pavement performance models to evaluate pavement conditions on the basis of pavement distresses. [source] A standards-based Grid resource brokering service supporting advance reservations, coallocation, and cross-Grid interoperabilityCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 18 2009Erik Elmroth Abstract The problem of Grid-middleware interoperability is addressed by the design and analysis of a feature-rich, standards-based framework for all-to-all cross-middleware job submission. The architecture is designed with focus on generality and flexibility and builds on extensive use, internally and externally, of (proposed) Web and Grid services standards such as WSRF, JSDL, GLUE, and WS-Agreement. The external use provides the foundation for easy integration into specific middlewares, which is performed by the design of a small set of plugins for each middleware. Currently, plugins are provided for integration into Globus Toolkit 4 and NorduGrid/ARC. The internal use of standard formats facilitates customization of the job submission service by replacement of custom components for performing specific well-defined tasks. Most importantly, this enables the easy replacement of resource selection algorithms by algorithms that address the specific needs of a particular Grid environment and job submission scenario. By default, the service implements a decentralized brokering policy, striving to optimize the performance for the individual user by minimizing the response time for each job submitted. The algorithms in our implementation perform resource selection based on performance predictions, and provide support for advance reservations as well as coallocation of multiple resources for coordinated use. The performance of the system is analyzed with focus on overall service throughput (up to over 250 jobs per min) and individual job submission response time (down to under 1,s). Copyright © 2009 John Wiley & Sons, Ltd. [source] Affirmative action, duality of error, and the consequences of mispredicting the academic performance of african american college applicantsJOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 1 2002Jeryl L. Mumpower The implications of different potential affirmative action policies depend on three factors: selection rate from the applicant pool, base rate of qualified applicants, and accuracy of performance predictions. A series of analyses was conducted under various assumptions concerning affirmative action plans, causes of racial differences in average college admissions test scores, and racial differences in accuracy of performance predictions. Evidence suggesting a lower level of predictive accuracy for African Americans implies that, under a program of affirmative action, both proportionately more false positives (matriculated students who do not succeed) and proportionately more false negatives (rejected applicants who could have succeeded) will be found among African American applicants. Unless equivalent levels of predictive accuracy are achieved for both groups, no admission policy can be fair simultaneously to majority group applicants and African American applicants. © 2002 by the Association for Public Policy Analysis and Management. [source] Design of a Protective Cage for an Intravascular Axial Flow Blood Pump to Mechanically Assist the Failing FontanARTIFICIAL ORGANS, Issue 8 2009Amy L. Throckmorton Abstract Currently, no long-term mechanical bridge-to-transplant or bridge-to-recovery therapeutic alternative exists for failing single ventricles. A blood pump that would augment pressure in the cavopulmonary circulation is needed, and would lead to a reduction in elevated systemic venous pressure, and improve cardiac output. Thus, we are developing a collapsible, percutaneously inserted, axial flow blood pump to support the cavopulmonary circulation in adult patients with a failing single ventricle physiology. This collapsible axial flow pump is designed for percutaneous positioning. The outer protective cage will be designed with radially arranged filaments as touchdown surfaces to protect the vessel wall from the rotating components. This study examined the geometric characteristics of the protective cage of filaments and the impeller through the development and numerical analysis of 13 models. A blood damage analysis was also performed on selected geometric models to assess the probability of blood trauma. All models demonstrated an acceptable hydraulic performance by delivering 2,6 L/min at a rotational speed of 6000,10 000 rpm and generating pressure rise of 5,20 mm Hg. Expected trends in the hydraulic performance of the pump models were found. This study represents the initial first design phase of the impeller and protective cage of filaments. Validation of these flow and performance predictions will be completed in the next round of experimental testing with blood bag evaluation. [source] Strategy Generalization Across Orientation Tasks: Testing a Computational Cognitive ModelCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 5 2008Glenn Gunzelmann Abstract Humans use their spatial information processing abilities flexibly to facilitate problem solving and decision making in a variety of tasks. This article explores the question of whether a general strategy can be adapted for performing two different spatial orientation tasks by testing the predictions of a computational cognitive model. Human performance was measured on an orientation task requiring participants to identify the location of a target either on a map (find-on-map) or within an egocentric view of a space (find-in-scene). A general strategy instantiated in a computational cognitive model of the find-on-map task, based on the results from Gunzelmann and Anderson (2006), was adapted to perform both tasks and used to generate performance predictions for a new study. The qualitative fit of the model to the human data supports the view that participants were able to tailor a general strategy to the requirements of particular spatial tasks. The quantitative differences between the predictions of the model and the performance of human participants in the new experiment expose individual differences in sample populations. The model provides a means of accounting for those differences and a framework for understanding how human spatial abilities are applied to naturalistic spatial tasks that involve reasoning with maps. [source] | ||||||||||||||||