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Performance Study (performance + study)
Selected AbstractsPerformance study of a partial gasification pressurized combustion topping gas cycle and split rankine combined cycle: Part II,Exergy analysisINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2003S. De Abstract In addition to the energy analysis in part I of this paper, an exergy analysis of an advanced combined cycle is presented in this part of the paper to identify the major causes of thermodynamic imperfections. The exergy loss and exergetical efficiency of each of the components of the plant are investigated for variations of design and operating parameters. This is done to explore the possible improvements in the second law performance of this plant. Copyright © 2003 John Wiley & Sons, Ltd. [source] Performance study of modified ZSM-5 as support for bimetallic chromium,copper catalysts for VOC combustionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004Ahmad Zuhairi Abdullah Abstract The catalytic performance of bimetallic chromium,copper supported over untreated ZSM-5 (CrCu/Z), ZSM-5 treated with silicon tetrachloride (Cr,Cu/SiCl4 -Z) and ZSM-5 treated with steam (Cr,Cu/H2O-Z) is reported. The activity is based on the combustion of ethyl ethanoate and benzene at a feed concentration of 2000 ppm and a gas hourly space velocity (GHSV) of 32 000 h,1. Due to higher reactivity and larger molecular size compared with that of water molecules, SiCl4 reacted at the external surface of ZSM-5 crystals. Cr,Cu/SiCl4 -Z and Cr,Cu/H2O-Z both gave slightly lower conversion and carbon dioxide yield compared with Cr,Cu/Z. This was attributed to larger active metal crystallites formed in the mesopores and narrowing pore mouth and pore intersection by extraframework species. Cr,Cu/SiCl4 -Z and Cr,Cu/H2O-Z both had reduced concentration and strength of acid sites, thus making them less susceptible to deactivation by coking. The coke accumulated by these two catalysts was relatively softer and more easily decomposed in oxygen during catalyst regeneration. Copyright © 2004 Society of Chemical Industry [source] Performance study of heptane reforming in the dense ceramic membrane reactorsAICHE JOURNAL, Issue 1 2008Wenliang Zhu Abstract Heptane reforming was investigated in three dense ceramic membrane reactors, where the membranes were modified differently with reforming catalyst. Each reactor displayed distinctive catalytic behavior. The reactor with a bare membrane showed low catalytic activity and low oxygen permeation flux (JO2), but gave stable performance. The left two membranes reactors modified with catalyst both displayed shift processes at the preliminary stage of membrane reaction, not only in JO2 but also in the selectivity of all products. Moreover, the membrane reactor with more catalyst gave higher performance in the case of JO2 and CO selectivity. The observed shift phenomena are due to the activation of catalyst on the membrane surface, and the different amounts of catalyst produce different impaction on the membrane reactions. On the basis of the results in three membrane reactors, a reaction pathway of hydrocarbon reforming in dense ceramic membrane reactor is proposed. Being some different from combustion and reforming mechanism (CRR), hydrocarbon reforming in dense ceramic membrane reactor has its own characteristics. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] A performance study of job management systemsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2004Tarek El-Ghazawi Abstract Job Management Systems (JMSs) efficiently schedule and monitor jobs in parallel and distributed computing environments. Therefore, they are critical for improving the utilization of expensive resources in high-performance computing systems and centers, and an important component of Grid software infrastructure. With many JMSs available commercially and in the public domain, it is difficult to choose an optimum JMS for a given computing environment. In this paper, we present the results of the first empirical study of JMSs reported in the literature. Four commonly used systems, LSF, PBS Pro, Sun Grid Engine/CODINE, and Condor were considered. The study has revealed important strengths and weaknesses of these JMSs under different operational conditions. For example, LSF was shown to exhibit excellent throughput for a wide range of job types and submission rates. Alternatively, CODINE appeared to outperform other systems in terms of the average turn-around time for small jobs, and PBS appeared to excel in terms of turn-around time for relatively larger jobs. Copyright © 2004 John Wiley & Sons, Ltd. [source] Circle hooks, ,J' hooks and drop-back time: a hook performance study of the south Florida recreational live-bait fishery for sailfish, Istiophorus platypterusFISHERIES MANAGEMENT & ECOLOGY, Issue 2 2007E. D. PRINCE Abstract, This study evaluates the performance of two types of non-offset circle hooks (traditional and non-traditional) and a similar-sized ,J' hook commonly used in the south Florida recreational live-bait fishery for Atlantic sailfish, Istiophorus platypterus (Shaw). A total of 766 sailfish were caught off south Florida (Jupiter to Key West, FL, USA) to assess hook performance and drop-back time, which is the interval between the fish's initial strike and exertion of pressure by the fisher to engage the hook. Four drop-back intervals were examined (0,5, 6,10, 11,15 and >15 s), and hook performance was assessed in terms of proportions of successful catch, undesirable hook locations, bleeding events and undesirable release condition associated with physical hook damage and trauma. In terms of hook performance, the traditionally-shaped circle hook had the greatest conservation benefit for survival after release. In addition, this was the only hook type tested that performed well during each drop-back interval for all performance metrics. Conversely, ,J' hooks resulted in higher proportions of undesirable hook locations (as much as twofold), bleeding and fish released in undesirable condition, particularly during long drop-back intervals. Non-traditional circle hooks had performance results intermediate to the other hook types, but also had the worst performance relative to undesirable release condition during the first two drop-back intervals. Choice of hook type and drop-back interval can significantly change hook wounding, and different models of non-offset circle hooks should not be assumed to perform equivalently. [source] Large-scale parallel finite-element analysis using the internet: a performance studyINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2005Ryuji Shioya Abstract This paper describes a parallel finite-element system implemented using the domain decomposition method on a cluster of remote computers connected via the Internet. This technique is also readily applicable to a grid computing environment. A three-dimensional finite-element elastic analysis involving more than one million degrees of freedom was solved using this system, and a good approximate solution was obtained with high parallel efficiency of over 90% using remote computers located in three different countries. Copyright © 2005 John Wiley & Sons, Ltd. [source] Performance analysis of IEEE 802.11 DCF with stochastic reward nets,INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2007R. Jayaparvathy Abstract In this paper, we present a performance study to evaluate the mean delay and the average system throughput of IEEE 802.11-based wireless local area networks (WLANs). We consider the distributed co-ordination function (DCF) mode of medium access control (MAC). Stochastic reward nets (SRNs) are used as a modelling formalism as it readily captures the synchronization between events in the DCF mode of access. We present a SRN-based analytical model to evaluate the mean delay and the average system throughput of the IEEE 802.11 DCF by considering an on,off traffic model and taking into account the freezing of the back-off counter due to channel capture by other stations. We also compute the mean delay suffered by a packet in the system using the SRN formulation and by modelling each station as an M/G/1 queue. We validate our analytical model by comparison with simulations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Achieving performance enhancement in IEEE 802.11 WLANs by using the DIDD backoff mechanismINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2007P. Chatzimisios Abstract Wireless local area networks (WLANs) based on the IEEE 802.11 standards have been widely implemented mainly because of their easy deployment and low cost. The IEEE 802.11 collision avoidance procedures utilize the binary exponential backoff (BEB) scheme that reduces the collision probability by doubling the contention window after a packet collision. In this paper, we propose an easy-to-implement and effective contention window-resetting scheme, called double increment double decrement (DIDD), in order to enhance the performance of IEEE 802.11 WLANs. DIDD is simple, fully compatible with IEEE 802.11 and does not require any estimation of the number of contending wireless stations. We develop an alternative mathematical analysis for the proposed DIDD scheme that is based on elementary conditional probability arguments rather than bi-dimensional Markov chains that have been extensively utilized in the literature. We carry out a detailed performance study and we identify the improvement of DIDD comparing to the legacy BEB for both basic access and request-to-send/clear-to-send (RTS/CTS) medium access mechanisms. Copyright © 2006 John Wiley & Sons, Ltd. [source] Phase-contrast X-ray imaging with a large monolithic X-ray interferometerJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2000Tohoru Takeda To increase the field of view for large objects in phase-contrast X-ray imaging, a large monolithic X-ray interferometer has been fabricated using an available silicon ingot of diameter 10,cm. A performance study of this interferometer has been carried out using a synchrotron X-ray source. The view size of the interference pattern obtained with this interferometer was 25,mm wide and 15,mm high and its visibility was 79%. Various structures of a sliced human hepatocellular carcinoma were identified as necrosis, hemorrhagic necrosis, normal liver tissue and blood vessel. The performance of this interferometer was sufficient for phase-contrast X-ray imaging. [source] Review of an instructor computation model for Navy learning centers and a Navy instructor workweek analysis for facilitated self-paced instructionPERFORMANCE IMPROVEMENT, Issue 3 2008Monica Huff CPT The purpose of the performance study was to review a proposed U.S. Navy Learning Center instructor computation (ICOMP) model for calculating the number of instructors required for teaching courses at Navy training sites. Based on recommendations from the initial analysis, a workweek breakdown was conducted for facilitated self-paced instructors. Findings improved the application of an ICOMP for the U.S. Navy and advanced the understanding of instructors' workweek requirements and duties. [source] | |||||||||||||