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Performance Issues (performance + issues)
Selected AbstractsNeural Network Modeling of Constrained Spatial Interaction Flows: Design, Estimation, and Performance IssuesJOURNAL OF REGIONAL SCIENCE, Issue 1 2003Manfred M Fischer In this paper a novel modular product unit neural network architecture is presented to model singly constrained spatial interaction flows. The efficacy of the model approach is demonstrated for the origin constrained case of spatial interaction using Austrian interregional telecommunication traffic data. The model requires a global search procedure for parameter estimation, such as the Alopex procedure. A benchmark comparison against the standard origin constrained gravity model and the two,stage neural network approach, suggested by Openshaw (1998), illustrates the superiority of the proposed model in terms of the generalization performance measured by ARV and SRMSE. [source] Performance issues of bandwidth management in ATM networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2003Christos Bouras Abstract In our days, efficient management of the available network resources becomes a critical issue, both from a functional point of view (so that users can be provided with the bandwidth they need), and an economical point of view (so that carriers can satisfactorily and efficiently serve as many customers as possible and at the same time increase their revenue). In this paper we consider a bandwidth control scheme (i.e. managed bandwidth service) for an ATM network infrastructure which is applied to the Greek research and technology network (GRNET). We present some methods that we have tested (in a simulation setting) in order to increase the efficiency of the system and the utilization of the available bandwidth. More specifically, we consider a bandwidth-resizing algorithm for virtual paths, in order to keep the allocated bandwidth very close to the bandwidth actually used. This leads to an increased number of accepted requests and better network utilization. We, also, use the simulation results in order to get an estimation of the effective bandwidth for VBR paths that can be used in call admission. Finally, we consider a semi-offline scheme where requests are gathered and considered for acceptance in regular intervals. Simulation results show an increase in the utilization of resources. As a further improvement, we allow connections to be allocated a little before or after the time initially requested. This leads to further improvement in network utilization. All the improvement schemes were tested with the ATM-TN simulator and the results look promising. Copyright © 2003 John Wiley & Sons, Ltd. [source] Adaptable cache service and application to grid cachingCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2010Laurent d'Orazio Abstract Caching is an important element to tackle performance issues in largely distributed data management. However, caches are efficient only if they are well configured according to the context of use. As a consequence, they are usually built from scratch. Such an approach appears to be expensive and time consuming in grids where the various characteristics lead to many heterogeneous cache requirements. This paper proposes a framework facilitating the construction of sophisticated and dynamically adaptable caches for heterogeneous applications. Such a framework has enabled the evaluation of several configurations for distributed data querying systems and leads us to propose innovative approaches for semantic and cooperative caching. This paper also reports the results obtained in bioinformatics data management on grids showing the relevance of our proposals. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effects of Mixing Granular Iron with Sand on the Kinetics of Trichloroethylene ReductionGROUND WATER MONITORING & REMEDIATION, Issue 2 2009Erping Bi A substantial cost of granular iron permeable reactive barriers is that of the granular iron itself. Cutting the iron with sand can reduce costs, but several performance issues arise. In particular, reaction rates are expected to decline as the percentage of iron in the blend is diminished. This might occur simply as a function of iron content, or mass transfer effects may play a role in a much less predictable fashion. Column experiments were conducted to investigate the performance consequences of mixing Connelly granular iron with sand using the reduction kinetics of trichloroethylene (TCE) to quantify the changes. Five mixing ratios (i.e., 100%, 85%, 75%, 50%, and 25% of iron by weight) were studied. The experimental data showed that there is a noticeable decrease in the reaction rate when the content of sand is 25% by weight (iron mass to pore volume ratio, Fe/Vp = 3548 g/L) or greater. An analysis of the reaction kinetics, using the Langmuir-Hinshelwood rate equation, indicated that mass transfer became an apparent cause of rate loss when the iron content fell below 50% by weight (Fe/Vp = 2223 g/L). Paradoxically, there were tentative indications that TCE removal rates were higher in a 15% sand + 85% iron mixture (Fe/Vp = 4416 g/L) than they were in 100% iron (Fe/Vp = 4577 g/L). This subtle improvement in performance might be due to an increase of iron surface available for contact with TCE, due to grain packing in the sand-iron mixture. [source] Improved adaptive control for the discrete-time parametric-strict-feedback formINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 12 2009Graciela Adriana González Abstract Adaptive control design for a class of single-input single-output nonlinear discrete-time systems in parametric-strict-feedback form is re-visited. No growth restrictions are assumed on the nonlinearities. The control objective is to achieve tracking of a reference signal. As usual, the algorithm derives from the combination of a control law and a parameter estimator (certainty equivalence principle). The parameter estimator strongly lies on the regressor subspace identification by means of an orthogonalization process. Certain drawbacks of previous schemes are analyzed. Several modifications on them are considered to improve the algorithm complexity, control performance and numerical stability. As a result, an alternative control scheme is proposed. When applied to the proposed class of systems, global boundedness and convergence remain as achieved objectives while improving the performance issues of previous schemes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Traffic locality characteristics in a parallel forwarding systemINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2003W. Shi Abstract Due to the widening gap between the performance of microprocessors and that of memory, using caches in a system to take advantage of locality in its workload has become a standard approach to improve overall system performance. At the same time, many performance problems finally reduce to cache performance issues. Locality in system workload is the fact that makes caching possible. In this paper, we first use the reuse distance model to characterize temporal locality in Internet traffic. We develop a model that closely matches the empirical data. We then extend the work to investigate temporal locality in the workload of multi-processor forwarding systems by comparing locality under different packet scheduling schemes. Our simulations show that for systems with hash-based schedulers, caching can be an effective way to improve forwarding performance. Based on flow-level traffic characteristics, we further discuss the relationship between load-balancing and hash-scheduling, which yields insights into system design. Copyright © 2003 John Wiley & Sons, Ltd. [source] Contrasting Institutional and Performance Accounts of Environmental Management Systems: Three Case Studies in the UK Water & Sewerage Industry*JOURNAL OF MANAGEMENT STUDIES, Issue 4 2007Anja Schaefer abstract This paper presents results from a longitudinal, qualitative study into the adoption of environmental management systems (EMS) in three companies in the UK water & sewerage industry. Based on institutional theory and the literature on EMS, four factors related to the adoption of EMS are identified: external and internal institutional forces, environmental performance issues, and economic performance issues. While previous literature has often assumed a balance of performance and institutional factors or a preponderance of performance factors, the results of this study indicate that institutional forces are the predominant drivers. The results further indicate that environmental performance issues become less important over time, whereas institutional drivers and economic performance rationales increase in importance over time. While conforming to institutional pressures can result in improved economic performance of a company, adoption of environmental management systems mostly on the basis of institutional and economic factors has wider repercussions for the state of corporate environmental management and progress towards greater ecological sustainability of business. [source] Validity of the Alcohol Use Disorders Identification Test in College StudentsALCOHOLISM, Issue 6 2004Patricia K. Kokotailo Background: High-risk alcohol use among college students is associated with accidents, partner violence, unwanted sexual encounters, tobacco use, and performance issues. The identification and treatment of high-risk drinking students is a priority for many college campuses and college health centers. The goal of this study was to test the psychometric properties of the Alcohol Use Disorders Identification Test (AUDIT) in college students. Methods: A convenience sample of students coming into a college health clinic was asked to complete the 10-question AUDIT and then participate in a research interview. The interview focused on assessing students for alcohol abuse and dependence by using the Composite International Diagnostic Interview Substance Abuse Module and timeline follow-back procedures to assess a 28-day drinking history. Results: A total of 302 students met the eligibility criteria and agreed to participate in the study. The sample consisted of 185 females (61%) and 117 males (39%), with a mean age of 20.3 years. Forty students were abstinent, 88 were high-risk drinkers, and 103 met criteria for a 12-month history of dependence. Receiver operator curves demonstrated that the AUDIT had the highest area under the cure for detecting high-risk alcohol use (0.872) and the lowest for identifying persons with a lifetime history of alcohol abuse or dependence (0.775). An AUDIT cutoff score of 6 or greater demonstrated a sensitivity of 91.0% and a specificity of 60.0% in the detection of high-risk drinkers. Conclusions: The AUDIT has reasonable psychometric properties in sample of college students using student health services. This study supports the use of the AUDIT in this population. [source] Theory development and convergence of human resource fields: Implications for human performance technologyPERFORMANCE IMPROVEMENT QUARTERLY, Issue 3 2010Yonjoo Cho PhD This study examines major theory developments in human resource (HR) fields and discusses implications for human performance technology (HPT). Differentiated HR fields are converging to improve organizational performance through knowledge-based innovations. Ruona and Gibson (2004) made a similar observation and analyzed the historical evolution and convergence of three HR-related fields: human resource management (HRM), human resource development (HRD), and organization development (OD). A field left out in their analysis is HPT. Many learning professionals recognize HPT as a more comprehensive approach to improving organizational performance issues (Molenda & Pershing, 2008; Pershing, 2006). However, little research has been done to advance the theory development of HPT and discuss its relationships within HR fields. This study adds a new perspective to that of Ruona and Gibson's historical analysis of HR fields by examining convergence issues from a theory development perspective. [source] Continuously improving PSM effectiveness,A practical roadmapPROCESS SAFETY PROGRESS, Issue 2 2006Steve Arendt Vice President Abstract PSM practices and formal management systems have been in place in many companies for more than 20 years. PSM is widely credited for perceived reductions in major accident risk and in improved chemical industry performance. Nevertheless, many companies continue to be challenged by resource pressures, inadequate management system audit results, and stagnant process safety incident performance. While most companies claim to advocate Continuous Improvement, few have actually put substance into these words and succeeded in practice. This is partly because there is no clear vision of what PSM performance and continuous improvement are. This article defines the following function: PSM Effectiveness = f [PSM performance + PSM efficiency] Continuous improvement can address performance issues or efficiency issues or both. Companies are seeking new ways to improve process safety management activities. This article defines these terms and gives examples and lessons that show ways companies are improving performance, efficiency, and effectiveness. © American Institute of Chemical Engineers Process Saf Prog, 2006 [source] Blind drunk: the effects of alcohol on inattentional blindnessAPPLIED COGNITIVE PSYCHOLOGY, Issue 5 2006Seema L. Clifasefi Alcohol consumption is a major contributor to road accidents. While it is likely that perceptual processing deficits contribute to poorer driving performance among intoxicated individuals, we know little about alcohol's role in particular perceptual processes. For instance, we know that even sober individuals can fail to detect unexpected salient objects that appear in their visual fields, a phenomenon known as inattentionalblindness (IB; Mack & Rock, 1998). We were interested in whether these visual errors become more or less likely when subjects are under the influence of alcohol or just think that they are drunk. We told half our subjects that they had received alcohol, and half that they had received a placebo. This information was either true or false. Intoxicated subjects (regardless of what they were told) were more likely to show ,blindness' to an unexpected object in their visual field. This finding has practical implications for human performance issues such as driving and eyewitness memory, and theoretical implications for visual cognition. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||