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Performance Assessment (performance + assessment)
Selected AbstractsAssessing Differential Item Functioning in Performance Assessment: Review and RecommendationsEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 3 2000Randall D. Penfield How can we best extend DIF research to performance assessment? What are the issues and problems surrounding studies of DIF on complex tasks? What appear to be the best approaches at this time? [source] The Integrated Performance Assessment (IPA): Connecting Assessment to Instruction and LearningFOREIGN LANGUAGE ANNALS, Issue 3 2006Bonnie Adair-Hauck ABSTRACT: This article reports on Beyond the OPI: Integrated Performance Assessment (IPA) Design Project, a three-year (1997,2000) research initiative sponsored by the U.S. Department of Education International Research and Studies Program. The primary goal of the project was to develop an integrated skills assessment prototype that would measure students' progress towards the Standards for Foreign Language Learning in the 21st Century (National Standards, 1999, 2006). A second goal of the project was to use the assessment prototype as a catalyst for curricular and pedagogical reform. This paper presents the Integrated Performance Assessment (IPA) prototype, illustrates a sample IPA, and discusses how classroom-based research on the IPA demonstrated the washback effect of integrated performance-based assessment on teachers' perceptions regarding their instructional practices. [source] The Generalizability of Scores for a Performance Assessment Scored with a Computer-Automated Scoring SystemJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 3 2000Brian E. Clauser When performance assessments are delivered and scored by computer, the costs of scoring may be substantially lower than those of scoring the same assessment based on expert review of the individual performances. Computerized scoring algorithms also ensure that the scoring rules are implemented precisely and uniformly. Such computerized algorithms represent an effort to encode the scoring policies of experts. This raises the question, would a different group of experts have produced a meaningfully different algorithm? The research reported in this paper uses generalizability theory to assess the impact of using independent, randomly equivalent groups of experts to develop the scoring algorithms for a set of computer-simulation tasks designed to measure physicians' patient management skills. The results suggest that the impact of this "expert group" effect may be significant but that it can be controlled with appropriate test development strategies. The appendix presents multivariate generalizability analysis to examine the stability of the assessed proficiency across scores representing the scoring policies of different groups of experts. [source] Enhanced Performance Assessment of Subspace Model-Based Predictive Controller with Parameters TuningTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2007Qiang Zhang Abstract This study focuses on performance assessment of model predictive control. An MPC-achievable benchmark for the unconstrained case is proposed based on closed-loop subspace identification. Two performance measures can be constructed to evaluate the potential benefit to update the new identified model. Potential benefit by tuning the parameter can be found from trade-off curves. Effect of constraints imposed on process variables can be evaluated by the installed controller benchmark. The MPC-achievable benchmark for the constrained case can be estimated via closed-loop simulation provided that constraints are known. Simulation of an industrial example was done using the proposed method. Cette étude porte sur l'évaluation de la performance du contrôle prédictif par modèles (MPC). On propose un banc d'essai adapté au MPC pour le cas non contraint en se basant sur l'identification de sous-espaces en boucle fermée. Deux mesures de performance sont élaborées pour évaluer l'avantage potentiel de mettre à jour le nouveau modèle identifié. L'avantage potentiel par réglage du paramètre peut s'obtenir à partir des courbes de compromis. L'effet des contraintes imposé sur les variables de procédé peut être évalué par le banc d'essai de contrôleur installé. Le banc d'essai adapté au MPC pour le cas contraint peut être estimé par la simulation en boucle fermée dans la mesure où les contraintes sont connues. On a réalisé la simulation d'un exemple industriel à l'aide de la méthode proposée. [source] Environmental Performance Assessment of China's ManufacturingASIAN ECONOMIC JOURNAL, Issue 1 2010Tao Zhang O47; P28; R15 This paper applies the data envelopment analysis approach to contribute to the debate on the environmental performance of China's manufacturing sector. Regional and periodic differences in environmental efficiency, environmental quantity and environmental change indexes in China's manufacturing sector are examined for the period between 1998 and 2002. Within the framework of data envelopment analysis and distance functions, environmental quantity and environmental change indexes are measured as variants of the Malmquist quantity index. The overall environmental efficiency of China's manufacturing sector is very low, indicating substantial potential to reduce pollution emissions in China's manufacturing industries. The results and implications of this study can provide helpful information to improve the environmental performance of China's manufacturing sector. [source] Alternative Interpretations of Alternative Assessments: Some Validity Issues in Educational Performance AssessmentsEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 3 2002Lyle F. Bachman The use of alternative assessments has led many researchers to reexamine traditional views of test qualities, especially validity. Because alternative assessments generally aim at measuring complex constructs and employ rich assessment tasks, it becomes more difficult to demonstrate (a) the validity of the inferences we make and (b) that these inferences extrapolate to target domains beyond the assessment itself. An approach to addressing these issues from the perspective of language testing is described. It is then argued that in both language testing and educational assessment we must consider the roles of both language and content knowledge, and that our approach to the design and development of performance assessments must be both construct-based and task-based.1 [source] Performance assessment and simulation fidelity for dummiesEMERGENCY MEDICINE AUSTRALASIA, Issue 6 2008Victoria Brazil No abstract is available for this article. [source] Negotiating the Network: The Contracting Experiences of Community Mental Health Agencies in New ZealandFINANCIAL ACCOUNTABILITY & MANAGEMENT, Issue 2 2001Susan Newberry Structural options for reforming New Zealand'spublicly funded health services included a hierarchy, a market model, or hybrid arrangements such as quasi-markets and networks. A survey of 28 community mental health agencies, contracting with the four regional health authorities, found that three structures emerged: a quasi-market, a coercive network and a beneficent network. Further reforms to the publicly funded health services created a single purchaser and preferred a network structure. Performance assessment of these reformed health services requires assessment of the whole network and not just individual components. The accounting profession, although closely involved in the public sector reforms, appears to have overlooked this task. [source] Performance assessment of a GCM land surface scheme using a fine-scale calibrated hydrological model: an evaluation of MOSES for the Nile BasinHYDROLOGICAL PROCESSES, Issue 11 2009Mohamed Ezzat Elshamy Abstract Land surface schemes (LSSs) represent the interface between land surface and the atmosphere in general circulation models (GCMs). Errors in LSS-simulated heat and moisture fluxes can result from inadequate representation of hydrological features and the derivation of effective surface parameters for large heterogeneous GCM gridboxes from small-scale observations. Previous assessments of LSS performance have generally compared simulated heat and moisture fluxes to observations over a defined experimental domain for a limited period. A different approach has been evaluated in this study, which uses a fine-resolution calibrated hydrological model of the study basin to provide a quasi-observed runoff series for direct comparison with simulated runoff from a selected LSS at GCM scale. The approach is tested on two GCM gridboxes covering two contrasting regions within the Nile Basin. Performance is mixed; output from the LSS is generally compatible with that of the fine-resolution model for one gridbox while it cannot reproduce the runoff dynamics for the other. The results also demonstrate the high sensitivity of runoff and evapotranspiration to radiation and precipitation inputs and show the importance of subtle issues such as temporal disaggregation of climatic inputs. We conclude that the use of a fine-resolution calibrated model to evaluate a LSS has several advantages, can be generalized to other areas to improve the performance of global models and provides useful data that can be used to constrain LSS parameterizations. Copyright © 2009 John Wiley & Sons, Ltd. [source] Performance assessment under field conditions of a rapid immunological test for transgenic soybeansINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2001John Fagan Summary Current market conditions and food regulations make it necessary for international and domestic participants in the agrifood industry to structure supply chains that control the content of genetically modified (GM) material in their products. Tests to detect and/or quantify GM components represent an important tool in maintaining such supply systems. This study assesses the field performance of kits that employ lateral flow immuno-technology to detect soybeans GM to be resistant to the herbicide glyphosate. Operators at 23 grain-handling facilities were paid to conduct analyses on a series of blinded samples containing defined proportions of conventional and transgenic soybeans. The observed rate of false positives was 6.7% in an experiment in which the highest level of GM material was 1% and 22.3% in a second experiment in which the highest level of GM material was 10%. This difference may be attributed to increased risk of cross-contamination with the higher level of transgenic material used in the second study. Samples containing 0.01% GM material were reported as genetically modified 6.70% of the time, while samples containing 0.1, 0.5 and 1% GM material were classified as genetically modified 29.5, 67.7 and 68.2% of the time, respectively. Thus, the frequencies of false negatives were 93.3, 70.5, 33.3 and 31.8% for samples containing 0.01, 0.1, 0.5 and 1.0% GM material. Samples containing 10% GM material were correctly reported as genetically modified in all cases. These results lead to the conclusion that the kit under study is useful in screening for lots of soybeans that contain high levels of GM material, but that, as a field tool, it is not effective in monitoring for GM material at the level of 1.0% or lower. Statistical and immunochemical analyses were carried out in order to assess the relative contributions of various factors to the error observed in these studies. These analyses indicated that limitations in operator performance, not defects in test kit materials, were the primary contributors, while sample size may play a secondary role. As both operator performance and sample size are independent of the specific characteristics of the test kit used in this study, it appears justifiable to generalize conclusions obtained here to other similar test systems. [source] Performance assessment of a UASB,anoxic,oxic system for the treatment of tomato-processing wastesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2006Alpesh Gohil Abstract An upflow anaerobic sludge blanket (UASB),anoxic,oxic system was used to achieve biochemical oxygen demand, NH4 and total suspended solids (TSS) criteria of 15, 1 and 15 mg dm,3 at 1.17 days of system hydraulic retention time during treatment of tomato-processing waste. The incorporation of an anoxic tank was found to affect the improvement in sludge-settling characteristics, as reflected by about 25,33% reduction in the sludge volume index, along with final effluent TSS and soluble biochemical oxygen demand concentrations of 13 and 9 mg dm,3, respectively, which met the discharge criteria. Despite incomplete denitrification, sludge settleability was very good (sludge volume index < 60 cm3 g,1) owing to reduction in volatile suspended solids/TSS ratio from 0.75 to 0.6 as a result of higher alkalinity in the UASB effluent. Also in this study, phosphorus release was observed in the anoxic tank, predominantly due to abundance of acetic acid in the UASB effluent. A phosphate release of 5.4 mg P dm,3 was observed in the anoxic tank with subsequent P uptake in the following aerobic stage. Copyright © 2006 Society of Chemical Industry [source] Performance assessment in health care providers: a critical review of evidence and current practiceJOURNAL OF NURSING MANAGEMENT, Issue 8 2007KAREN E. STC. Aim, To evaluate methods of performance assessment through an international literature review and a survey of current practice. Background, Over the past two decades health care organizations have focussed on promoting high quality care in conjunction with retaining motivated staff. Cognisant of such initiatives, we sought to evaluate assessment methods for qualified staff according to their utility in the working environment. Methods, A systematic literature search was completed and each paper independently reviewed. All health care organizations in Northern Ireland submitted details of their performance assessments. Each was critically appraised using a utility index. Results, Performance was not universally defined. A broad range of assessments were identified, each method had advantages and disadvantages. Although many lacked rigorous testing, areas of good practice were also noted. Conclusions, No single method is appropriate for assessing clinical performance. Rather, this study endorses proposals for a multi-method strategy to ensure that performance assessment demonstrates all attributes required for effective nursing and midwifery practice. [source] Performance assessment of hanging funnel-and-gate structures designed by reverse particle tracking for capturing polluted groundwaterREMEDIATION, Issue 3 2007Paul F. Hudak The objective of this study was to evaluate the capability of partially penetrating (hanging) funnel-and-gate structures, designed using reverse flow trajectories, for capturing plumes of contaminated groundwater. Linear capture structures, comprised of two slurry cutoff walls on either side of a permeable gate, were positioned perpendicular to regional groundwater flow in a hypothetical unconfined aquifer. A four-step approach was used for each of two simulated settings: (1) a numerical mass transport model generated a contaminant plume originating from a source area; (2) a particle-tracking model projected groundwater flow paths upstream from a treatment gate; (3) the structure was widened and deepened until bounding path lines contained the plume; and (4) mass transport simulation tested the ability of the structure to capture the plume. Results of this study suggest that designing funnel-and-gate structures using reverse particle tracking may result in too small a structure to capture a contaminant plume. This practice generally ignores effects of hydrodynamic dispersion, which may enlarge plumes such that contaminants move beneath or around a capture structure. This bypassing effect may be considerable even for low values of dispersivity. Particle-tracking approaches may also underestimate the amount of time required to reduce contaminant concentrations to acceptable levels. © 2007 Wiley Periodicals, Inc. [source] Performance assessment of next-generation wireless mobile systemsBELL LABS TECHNICAL JOURNAL, Issue 4 2009Krishna Balachandran The deployment of third generation (3G) systems such as Universal Mobile Telecommunications System (UMTS) and code division multiple access (CDMA) 1X is now ubiquitous. Furthermore, several operators have already deployed evolved 3G systems such as high speed packet access (HSPA) and 1× evolution data optimized (1× EV-DO). These 3G and evolved 3G systems are based on spread spectrum technologies. Now the industry has begun to focus on next-generation wireless systems based on orthogonal frequency division multiplexing (OFDM) technology, flat-Internet Protocol (IP) architectures, and advanced multiple input-multiple output (MIMO) capabilities. These next-generation technologies, primarily are: 3rd Generation Partnership Project (3GPP)-based evolved UMTS terrestrial radio access network (EUTRAN), also called Long Term Evolution (LTE); 3rd Generation Partnership Project 2 (3GPP2)-based Ultra Mobile Broadband (UMB); and Institute of Electrical and Electronics Engineers (IEEE) 802. 16e-based Worldwide Interoperability for Microwave Access (WiMAX). These technologies are in the final specifications to initial deployment phases in selected markets. This paper provides an overview and performance analysis of these next-generation technologies based on their initial releases. Additionally, a comparative performance analysis of these technologies is also presented. © 2009 Alcatel-Lucent. [source] Long-Term Monitoring and Identification of Bridge Structural ParametersCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2009Serdar Soyoz This three-span 111-m long bridge is instrumented with 13 acceleration sensors at both the superstructure and the columns. The sensor data are transmitted to a server computer wirelessly. Modal parameters of the bridge, that is, the frequencies and the modal shapes were identified by processing 1,707 vibration data sets collected under traffic excitations, based on which the bridge structural parameters, stiffness and mass, and the soil spring values were identified by employing the neural network technique. The identified superstructure stiffness at the beginning of the monitoring was 97% of the stiffness value based on the design drawings. In the identified modal frequencies, a variation from ,10% to +10% was observed over the monitoring period. In the identified stiffness values of the bridge superstructure, a variation from ,3% to +3% was observed over the monitoring period. Based on the statistical analysis of the collected data for each year, 5% decrease in the first modal frequency and 2% decrease in the superstructure stiffness were observed over the 5-year monitoring period. Probability density functions were obtained for stiffness values each year. Stiffness threshold values for the collapse of the bridge under the operational loading can be determined. Then the number of years can be assessed for which the area under the proposed probability density functions is greater than the threshold value. So the information obtained in this study is valuable for studying aging and long-term performance assessment of similar bridges. [source] Impact of the international program for quality assessment and standardization for immunological measures relevant to HIV/AIDS: QASICYTOMETRY, Issue 2 2002Francis Mandy Abstract Measurements of CD4 T-cell levels are essential for the assessment of human immunodeficiency virus (HIV) disease course, clinical staging, epidemiological studies, and decisions regarding prophylactic therapies against opportunistic infection. Until now, only in the industrialized countries was T-cell subset monitoring considered a practical option to assess disease progression. The Quality Assessment and Standardization for Immunological Measures Relevant to HIV/AIDS (QASI) program was established in 1997 to meet performance assessment for immunophenotyping laboratories in countries where such service is not available. The QASI program is provided at no cost to any laboratory in a resource-poor setting that wishes to participate. This report describes the beneficial impact of participation in the QASI program. Carefully selected commercial stabilized whole blood preparations were sent regularly to participating laboratories. Participants reported the T-cell subset values they obtained by flow cytometry. Once the aggregate mean values for the T-cell subsets were established for the shipment, a comprehensive and confidential report was sent to each laboratory. The results from five consecutive shipments were analyzed. The coefficient of variation decreased from 7.2% to 4.7% and from 14.2% to 8.8% for percent and absolute CD4 T-cell counts, respectively. With the implementation of the QASI program using commercial stabilized whole blood specimens, it is possible to reduce interlaboratory error. This study illustrates that a quality assessment program can improve the overall performance of laboratories. Reducing interlaboratory variation can enhance significantly the effectiveness of multicenter HIV vaccine or drug trial evaluation. Cytometry (Clin. Cytometry) 50:111,116, 2002. © 2002 Wiley-Liss, Inc. [source] Structural performance assessment under near-source pulse-like ground motions using advanced ground motion intensity measuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2008Polsak Tothong Abstract This paper demonstrates the effectiveness of utilizing advanced ground motion intensity measures (IMs) to evaluate the seismic performance of a structure subject to near-source ground motions. Ordinary records are, in addition, utilized to demonstrate the robustness of the advanced IM with respect to record selection and scaling. To perform nonlinear dynamic analyses (NDAs), ground motions need to be selected; as a result, choosing records that are not representative of the site hazard can alter the seismic performance of structures. The median collapse capacity (in terms of IM), for example, can be systematically dictated by including a few aggressive or benign pulse-like records into the record set used for analyses. In this paper, the elastic-based IM such as the pseudo-spectral acceleration (Sa) or a vector of Sa and epsilon has been demonstrated to be deficient to assess the structural responses subject to pulse-like motions. Using advanced IMs can be, however, more accurate in terms of probabilistic response prediction. Scaling earthquake records using advanced IMs (e.g. inelastic spectral displacement, Sdi, and IM1I&2E; the latter is for the significant higher-mode contribution structures) subject to ordinary and/or pulse-like records is efficient, sufficient, and robust relative to record selection and scaling. As a result, detailed record selection is not necessary, and records with virtually any magnitude, distance, epsilon and pulse period can be selected for NDAs. Copyright © 2008 John Wiley & Sons, Ltd. [source] Seismic vulnerability assessment using regional empirical dataEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2006Ahmet Yakut Abstract This article presents a procedure developed for the seismic performance assessment of low- to mid-rise reinforced concrete buildings in Turkey. The past performance of reinforced concrete buildings during major earthquakes have been compiled and analysed comprehensively using statistical procedures in order to study the empirical correlation between the significant damage inducing parameters and the observed damage. A damage database of nearly 500 representative buildings experiencing the 1999 Kocaeli and Düzce earthquakes have been used and discriminant functions expressing damage score in terms of six damage inducing parameters have been developed. In order to extrapolate the procedure to other regions that are likely to be subjected to major earthquakes a new approach that takes into account different local soil conditions, site-to-source distance and the magnitude of the earthquake has been introduced. The procedure has been applied to a pilot area in Istanbul to estimate expected damage distribution under a credible scenario earthquake. Copyright © 2006 John Wiley & Sons, Ltd. [source] Inelastic spectra for infilled reinforced concrete framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2004Matja Abstract In two companion papers a simplified non-linear analysis procedure for infilled reinforced concrete frames is introduced. In this paper a simple relation between strength reduction factor, ductility and period (R,µ,T relation) is presented. It is intended to be used for the determination of inelastic displacement ratios and of inelastic spectra in conjunction with idealized elastic spectra. The R,µ,T relation was developed from results of an extensive parametric study employing a SDOF mathematical model composed of structural elements representing the frame and infill. The structural parameters, used in the proposed R,µ,T relation, in addition to the parameters used in a usual (e.g. elasto-plastic) system, are ductility at the beginning of strength degradation, and the reduction of strength after the failure of the infills. Formulae depend also on the corner periods of the elastic spectrum. The proposed equations were validated by comparing results in terms of the reduction factors, inelastic displacement ratios, and inelastic spectra in the acceleration,displacement format, with those obtained by non-linear dynamic analyses for three sets of recorded and semi-artificial ground motions. A new approach was used for generating semi-artificial ground motions compatible with the target spectrum. This approach preserves the basic characteristics of individual ground motions, whereas the mean spectrum of the whole ground motion set fits the target spectrum excellently. In the parametric study, the R,µ,T relation was determined by assuming a constant reduction factor, while the corresponding ductility was calculated for different ground motions. The mean values proved to be noticeably different from the mean values determined based on a constant ductility approach, while the median values determined by the different procedures were between the two means. The approach employed in the study yields a R,µ,T relation which is conservative both for design and performance assessment (compared with a relation based on median values). Copyright © 2004 John Wiley & Sons, Ltd. [source] Assessing Differential Item Functioning in Performance Assessment: Review and RecommendationsEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 3 2000Randall D. Penfield How can we best extend DIF research to performance assessment? What are the issues and problems surrounding studies of DIF on complex tasks? What appear to be the best approaches at this time? [source] Zero-sequence-based relaying technique for protecting power transformers and its performance assessment using unsupervised learning ANNEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2006Guzmán Díaz Abstract In this paper a simple and robust new relaying technique for protecting transformers from internal winding faults is proposed. Based on the measurement of zero sequence current inside a delta winding, the technique greatly simplifies the conventional differential relaying arrangement when a delta winding is available. Despite the number of windings of the transformer and the location of the fault, only measurement of induced zero sequence current within the delta winding is needed. Since the proposed technique has been shown to be prone to generate false pick-up signals during inrush, a simple restraining criterion is proposed and analysed. Additionally, use of projection techniques based on self-organizing maps (SOM) is proposed in this paper as a valuable tool for analysing multivariable data which are generated from the huge number of possible combinations existing between switching instant and fault location. Finite element simulations and laboratory tests have been combined into SOM to validate the proposed relaying technique and the restraining criterion. Copyright © 2005 John Wiley & Sons, Ltd. [source] Adaptive group detection for DS/CDMA systems over frequency-selective fading channels,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2003Stefano Buzzi In this paper we consider the problem of group detection for asynchronous Direct-Sequence Code Division Multiple Access (DS/CDMA) systems operating over frequency-selective fading channels. A two-stage near-far resistant detection structure is proposed. The first stage is a linear filter, aimed at suppressing the effect of the unwanted user signals, while the second stage is a non-linear block, implementing a maximum likelihood detection rule on the set of desired user signals. As to the linear stage, we consider both the Zero-Forcing (ZF) and the Minimum Mean Square Error (MMSE) approaches; in particular, based on the amount of prior knowledge on the interference parameters which is available to the receiver and on the affordable computational complexity, we come up with several receiving structures, which trade system performance for complexity and needed channel state information. We also present adaptive implementations of these receivers, wherein only the parameters from the users to be decoded are assumed to be known. The case that the channel fading coefficients of the users to be decoded are not known a priori is also considered. In particular, based on the transmission of pilot signals, we adopt a least-squares criterion in order to obtain estimates of these coefficients. The result is thus a fully adaptive structure, which can be implemented with no prior information on the interfering signals and on the channel state. As to the performance assessment, the new receivers are shown to be near-far resistant, and simulation results confirm their superiority with respect to previously derived detection structures. Copyright © 2003 AEI. [source] Exergetic performance assessment of a pilot-scale heat pump belt conveyor dryerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010Zafer Erbay Abstract In this study, olive leaves were dried in a pilot-scale heat pump (HP) belt conveyor dryer as a thin layer. Drying experiments were carried out at the drying air temperature range of 45,55°C with the drying air velocity range of 0.5,1.5,m,s,1. The performance of the system and the process was evaluated using exergy analysis method. The exergy loss and flow diagram (the so-called Grassmann diagram) of the dryer system was presented to give quantitative information regarding the proportion of the exergy input that is dissipated in the various system components. Effects of the drying air temperature and the velocity on the performance of the drying process were discussed. The actual coefficient of performance values were obtained to be 2.37 for the HP unit and 2.31 for the overall system, respectively. The most important component of the system for improving the efficiency was determined to be the compressor. Exergetic efficiencies of the drying of olive leaves were in the range of 67.45,81.95%. It was obtained that they increased as the drying air temperature decreased and the drying air velocity increased. Copyright © 2009 John Wiley & Sons, Ltd. [source] A review on advances in alkali metal thermal to electric converters (AMTECs)INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2009Shuang-Ying Wu Abstract The alkali metal thermal to electric converter (AMTEC) is one of the most promising technologies for direct conversion of thermal energy to electricity and has been receiving attention in the field of energy conversion and utilization in the past several decades. This paper aims to present a comprehensive review of the state of the art in the research and development of the AMTEC, including its working principles and types, historical development and applications, analytical models, working fluids, electrode materials, as well as the performance and efficiency improvement. The current two major problems encountered by the AMTEC, the time-dependent power degradation and relatively low efficiency compared to its theoretical value, are discussed in depth. In addition, a brief comparison of the AMTEC with other direct thermal to electric converters (DTECs), such as the thermoelectrics converter (TEC), thermionics converter, and thermophotovoltaics converter, is given, and combinations of different DTECs to further improve DTECs' power generation and overall conversion efficiency are demonstrated. Future research and development directions and the issues that need to be further investigated are also suggested. It is believed that this comprehensive review will be beneficial to the design, simulation, analysis, performance assessment, and applications of various types of AMTECs. Copyright © 2009 John Wiley & Sons, Ltd. [source] Exergetic performance evaluation of a combined heat and power (CHP) system in TurkeyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2007Ozgur Balli Abstract This study deals with the exergetic performance assessment of a combined heat and power (CHP) system installed in Eskisehir city of Turkey. Quantitative exergy balance for each component and the whole CHP system was considered, while exergy consumptions in the system were determined. The performance characteristics of this CHP system were evaluated using exergy analysis method. The exergetic efficiency of the CHP system was accounted for 38.16% with 49 880 kW as electrical products. The exergy consumption occurred in this system amounted to 80 833.67 kW. The ways of improving the exergy efficiency of this system were also analysed. As a result of these, a simple way of increasing the exergy efficiency of the available CHP system was suggested that the valves-I,III and the MPSC could be replaced by a 3500 kW-intermediate pressure steam turbine (IPST). If the IPST is installed to the CHP system (called the modified CHP (MCHP) system), the exergetic efficiency of the MCHP system is calculated to be 40.75% with 53 269.53 kW as electrical products. The exergy consumption is found to be 77 444.14 kW in the MCHP system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Exergetic performance assessment of a ground-source heat pump drying systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2007Ebru Hancioglu Kuzgunkaya Abstract In evaluating the efficiency of heat pump (HP) systems, the most commonly used measure is the energy (or first law) efficiency, which is modified to a coefficient of performance (COP) for HP systems. However, for indicating the possibilities for thermodynamic improvement, energy analysis is inadequate and exergy analysis is needed. This study presents an exergetic assessment of a ground-source (or geothermal) HP (GSHP) drying system. This system was designed, constructed and tested in the Solar Energy Institute of Ege University, Izmir, Turkey. The exergy destructions in each of the components of the overall system are determined for average values of experimentally measured parameters. Exergy efficiencies of the system components are determined to assess their performances and to elucidate potentials for improvement. COP values for the GSHP unit and overall GSHP drying system are found to range between 1.63,2.88 and 1.45,2.65, respectively, while corresponding exergy efficiency values on a product/fuel basis are found to be 21.1 and 15.5% at a dead state temperature of 27°C, respectively. Specific moisture extraction rate (SMER) on the system basis is obtained to be 0.122 kg kW,1 h,1. For drying systems, the so-called specific moisture exergetic rate (SMExR), which is defined as the ratio of the moisture removed in kg to the exergy input in kW h, is also proposed by the authors. The SMExR of the whole GSHP drying system is found to be 5.11 kg kW,1 h,1. Copyright © 2006 John Wiley & Sons, Ltd. [source] Distribution-based anomaly detection in 3G mobile networks: from theory to practiceINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2010Alessandro D'Alconzo The design of anomaly detection (AD) methods for network traffic has been intensively investigated by the research community in recent years. However, less attention has been devoted to the issues which eventually arise when deploying such tools in a real operational context. We designed a statistical based change detection algorithm for identifying deviations in distribution time series. The proposed method has been applied to the analysis of a large dataset from an operational 3G mobile network, in the perspective of the adoption of such a tool in production. Our algorithm is designed to cope with the marked non-stationarity and daily/weekly seasonality that characterize the traffic mix in a large public network. Several practical issues emerged during the study, including the need to handle incompleteness of the collected data, the difficulty in drilling down the cause of certain alarms, and the need for human assistance in resetting the algorithm after a persistent change in network configuration (e.g. a capacity upgrade). We report on our practical experience, highlighting the key lessons learned and the hands-on experience gained from such an analysis. Finally, we propose a novel methodology based on semi-synthetic traces for tuning and performance assessment of the proposed AD algorithm. Copyright © 2010 John Wiley & Sons, Ltd. [source] An Examination of Rater Drift Within a Generalizability Theory FrameworkJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2009Polina Harik The present study examined the long-term usefulness of estimated parameters used to adjust the scores from a performance assessment to account for differences in rater stringency. Ratings from four components of the USMLE® Step 2 Clinical Skills Examination data were analyzed. A generalizability-theory framework was used to examine the extent to which rater-related sources of error could be eliminated through statistical adjustment. Particular attention was given to the stability of these estimated parameters over time. The results suggest that rater stringency estimates obtained at a point in time and then used to adjust ratings over a period of months may substantially decrease in usefulness. In some cases, over several months, the use of these adjustments may become counterproductive. Additionally, it is hypothesized that the rate of deterioration in the usefulness of estimated parameters may be a function of the characteristics of the scale. [source] Tax performance: a comparative studyJOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 6 2004Joweria M. Teera This paper seeks to analyse tax performance across countries, utilizing what Musgrave (1969) referred to as the stochastic approach, where tax performance is analysed by comparisons with the average performance. The regression approach to tax performance assessment is used and a tax effort index is constructed. Among the variables that are identified to be important determinants of tax shares is a measure of tax evasion. The tax effort indices obtained show that generally the upper middle-income and high-income OECD groups are making better use of their tax bases to increase revenue. There are also economies of scale with respect to population density. Copyright © 2004 John Wiley & Sons, Ltd. [source] Comparison of closed loop vs. manual administration of propofol using the Bispectral index in cardiac surgeryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2009J. AGARWAL Background: In recent years, electroencephalographic indices of anaesthetic depth have facilitated automated anaesthesia delivery systems. Such closed-loop control of anaesthesia has been described in various surgical settings in ASA I,II patients (1,4), but not in open heart surgery characterized by haemodynamic instability and higher risk of intra-operative awareness. Therefore, a newly developed closed-loop anaesthesia delivery system (CLADS) to regulate propofol infusion by the Bispectral index (BIS) was compared with manual control during open heart surgery. Methods: Forty-four adult ASA II,III patients undergoing elective cardiac surgery under cardiopulmonary bypass were enrolled. The study participants were randomized to two groups: the CLADS group received propofol delivered by the CLADS, while in the manual group, propofol delivery was adjusted manually. The depth of anaesthesia was titrated to a target BIS of 50 in both the groups. Results: During induction, the CLADS group required lower doses of propofol (P<0.001), resulting in lesser overshoots of BIS (P<0.001) and mean arterial blood pressure (P=0.004). Subsequently, BIS was maintained within ± 10 of the target for a significantly longer time in the CLADS group (P=0.01). The parameters of performance assessment, median absolute performance error (P=0.01), wobble (P=0.04) and divergence (P<0.001), were all significantly better in the CLADS group. Haemodynamic stability was better in the CLADS group and the requirement of phenylephrine in the pre-cardiopulmonary bypass period as well as the cumulative dose of phenylephrine used were significantly higher in the manual group. Conclusion: The automated delivery of propofol using CLADS was safe, efficient and performed better than manual administration in open heart surgery. [source] | |||||||||||||||||||||||||||||||||||||||||||