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Design and Implementation of a Load Balancing Web Server ClusterTseng, Jin-Shan 02 September 2005 (has links)
The Internet has become popular and many traditional services have changed into web service stage by stage. The web server with single architecture is no longer satisfying a large number of user requests and the cluster-based web server architecture becomes another suitable solution. Dispatch mechanism play an important role in web server cluster and there are many load balancing policies have been proposed recently. But, these research has only simulation, performance of these policies operate in a real system is unknown. In these simulation all has an assumption that web traffic is heavy-tailed distribution. However, in our experience, the assumption has changed. Web content has become large because network bandwidth increasing and more and more large files like video¡Baudio and tail software, etc. coming in. We defined this web traffic is a data-intensive workload.
In this study, we use a real and data-intensive web site to measure and compare these scheduling policies.
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QoS Performance Management in Mixed Wireless NetworksAstatke, Yacob 10 1900 (has links)
ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / This paper presents a model for Quality of Service (QoS) management in a mix of fixed Ground Station (GS) and ad-hoc telemetry networks, and introduces an enhanced clustering scheme that jointly optimizes the performance of the network using multiple distance measures based on the location of the wireless nodes and the traffic level. It also demonstrates that a "power" performance measure is an effective tool for modeling and managing QoS in Mixed Networks. Simulation results show that significant QoS performance improvements can be obtained and maintained even under severe traffic conditions.
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Quality of control and real-time scheduling : allowing for time-variations in computer control systemsSanfridson, Martin January 2004 (has links)
The majority of computers around us are embedded in productsand dedicated to perform certain tasks. A specific task is thecontrol of a dynamic system. The computers are ofteninterconnected by communication networks forming a distributedsystem. Vehicles and manufacturing equipment are two types ofmechatronic machines which often host dedicated computercontrol systems. A research problem is how the real-timebehaviour of the computer system affects the application,especially the control of the dynamic system. If the internal or external conditions varies over time, itbecomes difficult to assign a fixed resource reservation thatwill work well in all situations. In general, the more time anapplication gets of a resource, the better its gauged orperceived quality will be. A strategy is to alter the resourcereservation when the condition changes. This can be constructedas a negotiation between competing applications, a method forwhich the termquality of control, QoC, has been coined. Scalability isthe ability to change the structure and configuration of asystem. It promotes evolving systems and a can help manage acomplex product family. An architecture for a QoC middleware ontop of a scalable computer system, has been proposed. As aquality measureof a control application, the well-knownweighted quadratic loss function used in optimal control, hasbeen revised to encompass a subset of the so called timingproperties. The timing properties are the periods and thedelays in the control loop, including time-varying period anddelay. They are the interface between control and computerengineering, from a control engineering viewpoint. The qualitymeasure can be used both offline and on-line given a model ofthe sampled-data system and an appropriate description of thetiming properties. In order to use a computer system efficiently and toguarantee its responsiveness, real-time scheduling is a must.In fixed priority scheduling each task arrives periodically andhas a fixed priority. A task with a high priority can preempt alow priority task and gain access to the resource. Thebest-case response time characterizes the delays in the system,which is useful from a control viewpoint. A new algorithm tocalculate thebest-caseresponsetime has been derived. It is based on ascheduling scenario which yields a recurrence equation. Themodel is dual to the well-known worst-case response timeanalysis. Besides the dynamic fixed priority scheduling algorithm,optimal control usingstatic schedulinghas been studied, assuming a limitedcommunication. In the static schedule, which is constructedpre-runtime, each task is assigned a time window within aschedule repeated in eternity. The optimal scheduling sequenceis sought by optimizing the overall control performance. Aninteresting aspect is that the non-specified control periodfalls out as a result of theoptimal schedule. The time-varying delay is accountedfor in the control design. Keywords:Real-time scheduling, sampled-data control,performance measure, quality of control, limited communication,time-varying delay, jitter.
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Quality of control and real-time scheduling : allowing for time-variations in computer control systemsSanfridson, Martin January 2004 (has links)
<p>The majority of computers around us are embedded in productsand dedicated to perform certain tasks. A specific task is thecontrol of a dynamic system. The computers are ofteninterconnected by communication networks forming a distributedsystem. Vehicles and manufacturing equipment are two types ofmechatronic machines which often host dedicated computercontrol systems. A research problem is how the real-timebehaviour of the computer system affects the application,especially the control of the dynamic system.</p><p>If the internal or external conditions varies over time, itbecomes difficult to assign a fixed resource reservation thatwill work well in all situations. In general, the more time anapplication gets of a resource, the better its gauged orperceived quality will be. A strategy is to alter the resourcereservation when the condition changes. This can be constructedas a negotiation between competing applications, a method forwhich the term<i>quality of control</i>, QoC, has been coined. Scalability isthe ability to change the structure and configuration of asystem. It promotes evolving systems and a can help manage acomplex product family. An architecture for a QoC middleware ontop of a scalable computer system, has been proposed.</p><p>As a<i>quality measure</i>of a control application, the well-knownweighted quadratic loss function used in optimal control, hasbeen revised to encompass a subset of the so called timingproperties. The timing properties are the periods and thedelays in the control loop, including time-varying period anddelay. They are the interface between control and computerengineering, from a control engineering viewpoint. The qualitymeasure can be used both offline and on-line given a model ofthe sampled-data system and an appropriate description of thetiming properties.</p><p>In order to use a computer system efficiently and toguarantee its responsiveness, real-time scheduling is a must.In fixed priority scheduling each task arrives periodically andhas a fixed priority. A task with a high priority can preempt alow priority task and gain access to the resource. Thebest-case response time characterizes the delays in the system,which is useful from a control viewpoint. A new algorithm tocalculate the<i>best-caseresponse</i>time has been derived. It is based on ascheduling scenario which yields a recurrence equation. Themodel is dual to the well-known worst-case response timeanalysis.</p><p>Besides the dynamic fixed priority scheduling algorithm,optimal control using<i>static scheduling</i>has been studied, assuming a limitedcommunication. In the static schedule, which is constructedpre-runtime, each task is assigned a time window within aschedule repeated in eternity. The optimal scheduling sequenceis sought by optimizing the overall control performance. Aninteresting aspect is that the non-specified control periodfalls out as a result of the<i>optimal schedule</i>. The time-varying delay is accountedfor in the control design.</p><p><b>Keywords:</b>Real-time scheduling, sampled-data control,performance measure, quality of control, limited communication,time-varying delay, jitter.</p>
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The impact of inter-company network technology on correlations between supply chain drivers and performance measuresWu, Gang, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2009 (has links)
This research aims to examine how, and to what extent, the advanced network technology such as custom-built large-scale network, or internet-based technology contribute to the correlations between supply chain drivers and performance measures. The uniqueness of the research is to use network technology as a leverage factor, instead of merely one of the supply chain drivers, to analyse how it would impact on the correlations between supply chain drivers and performance measures. Through literature review, we identified the key drivers in supply chain and the key performance indicators as independent and dependent variables respectively for data analysis in the research. We consider the utilisation of network technology as a selection variable in the analysis. We also proposed a set of research questions and hypotheses resulting from the literature review. The subsequent data analyses attempted to find answers for these questions and test the validity of the hypotheses. This was achieved by a field survey for 1035 major Australian firms through a structured questionnaire. The response rate of the survey was 20.8%. All these data were analysed with statistical models such as reliability test, multi-collinearity test, MANOVA procedures, factor analysis, and multiple regression modelling to validate whether the survey was robust and how the leverage factor (network technology) would impact on the correlations between supply chain drivers and performance measures. Each research question and hypothesis was reviewed, validated, and concluded based on the results from data analysis. The key findings from the data analysis support the perception that the network technologies with their external customers and suppliers dramatically affect the correlations between supply chain drivers and performance measures. Statistically it actually determines whether the supply chain will success or fail when comparing firms using the technologies with firms not using them. In general, the impact on the correlations is directional and positive. A set of validated theoretical models was also proposed to depict the dynamics between supply chain variables under the influence of network technology. Implications of the findings are also provided in the thesis.
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The effect of explanations and monetary incentives on effort allocation decisionsGuymon, Ronald Nathan 01 January 2008 (has links)
In this study I examine the joint effect of explanations and monetary incentives on employees' effort allocation decisions in a multi-action setting. A rich literature in economics indicates that monetary incentives substantially influence employees' decisions. This literature demonstrates that the size of the incentive for a given performance measure should consider the measure's sensitivity, congruence and precision. Research in psychology demonstrates the decision influencing effects of explanations (a non-monetary factor) on employees' decisions through perceptions of fairness. I expect that effort allocation decisions are influenced both by explanations and monetary incentives: I hypothesize that providing reasonable and complete explanations substantively alter agents' action choices relative to a setting with monetary incentives alone. Using student subjects in experiments, I find that monetary incentives matter. Moreover, for sizeable monetary incentives, providing a detailed explanation modifies behavior favorably relative to when an unclear explanation is provided. However, for all of the considered monetary incentives, merely requesting a desired course of action is also enough to modify behavior favorably. This study contributes to the accounting literature by providing evidence of a decision influencing benefit associated with the use of explanations such as causal maps employed by firms adopting the balanced scorecard. This study also contributes to the organizational justice literature by providing evidence regarding the interaction effect of multiple antecedents of justice.
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Criteria for measuring resilience of youth-owned small retail businesses in selected rural areas of Vhembe District, South AfricaKativhu, Simbarashe 16 May 2019 (has links)
PhDRDV / Institute for Rural Development / In South Africa, various government and private sector-led initiatives have been directed
towards promoting youth involvement in small retail businesses. This was designed to counter
the high unemployment and poverty rates among youth. However, high failure rates of the
initiatives consistently frustrate these noble efforts. Even though this is the case, neither
attributes of youth-run small retail business resilience nor the factors that predispose them to
the high failure rates are well-known. This situation demands taking urgent action to foster
resilience in the youth-run small retail business sector. Thus, the current study focused on
identifying the major threats and strengths to business and determining a set of objective
criteria and indices for use in measuring resilience. Potential resilience strategies were also
sought. The study was conducted in Vhembe District of Limpopo Province in South Africa. An
explorative mixed research approach was employed. Participants were selected using both
snowball and cluster sampling procedures. Data were collected using semi-structured
interview guides and questionnaires. Qualitative data were analysed using Atlas ti version 8
software techniques such as network diagrams and code primary document tables. For each
objective, in-depth results were obtained, further interrogated in a survey and analysed using
the Statistical Package for Social Sciences software (IBM SPSS; version 25) in the
subsequent phase. The main statistical techniques utilised were Principal Component
Analysis (PCA) and Kruskal-Wallis tests. Significance was determined at P< 0.5.
Results from PCA test reviewed three major threats to small retail business resilience that
included poor infrastructure (28.54 %), financial infrastructure (20.97 %) and competition
(14.94 %). The three factor structure accounted for a total variance of 64.46 %. Poor
infrastructure and financial inadequacy threats did not vary with distance from the urban area
(P > 0.05) while competition significantly varied with distance from the urban area (P< 0.05).
With regard to strengths, PCA analysis produced a four factor structure that explained a total
variance of 54.59 %. The four major strengths included marketing ability (16.97 %), good
customer care (14.42 %), business knowledge (12.08 %) and commitment (11.13 %).
A six dimension criteria for measuring small retail business resilience was established using
PCA. The six dimensions encompassed security measures (18.01 %), outsourcing abilities
(13. 70 %), marketing strategies (10.07), risk management (8.54 %), financial management
(8.43 %) and innovation (7.89 %). The six factor structure explained a total variance of 66.67
%. These resilience pillars were related to threat detection, prevention and adaptation
business mechanisms. Four resilience dimensions (security measures, marketing abilities,
risk management and innovation) were similar across distance variations from the urban area
(P> 0.05). However, significant differences between urban and rural areas were observed in
two variables, that is, joining business alliances (P=0.012) linked to outsourcing abilities and
keeping money away from the business premise (P=0.034) associated with financial
management.
Resilience indices were further developed utilising the six building blocks of the criteria. The
indices for measuring small retail business resilience were expressed in the formula: R1= ƒ
(SM1, OA1, MS1, RM1, FM1, I1, S1) + e where SM=Security Measures; OA= Outsourcing
Abilities; MS= Marketing Strategies; OM=Risk Management; FM= Financial Management; I=
Innovation; S= Subjective resilience dimensions and 1= particular time; e= error. The
assumption underpinning these indices was that, small retail business resilience is not
observable and thus it can be measured through assessing each dimension separately at a
particular time. The outcomes reflected that, measuring youth-owned small retail businesses
resilience encompasses a clear understanding of area specific threats and the subsequent
customised performance measures. Resilience dimensions may change with time due to
socio-economic changes, government policies and local conditions. As such, it is crucial to
constantly assess youth small retail businesses in order to determine their current status and
changes in resilience components. Current strategies and potential interventions for promoting
small business resilience were also reviewed. Small retailers were currently utilising strategies
such as business collaboration, specialisation and stock diversification. To, address the
weaknesses associated with presently utilised strategies, potential interventions that
encompassed financial support, provision of cheap stands, need for financial assistance and
provision of business training and infrastructure upgrades were proposed.
The present study provided a criteria and resilience indices that can be used by policy
implementers, development agencies and funders to determine resilience drivers, monitor
changes in resilience attributes over time and identify necessary interventions in the small
retail sector. This assists decision makers to make pre-informed decisions before providing
support to youth small retailers. The use of participatory research methods in the present study
helped to ground the work in the youth small retail sector and thus, contributing to community
engagement practices. The use of mixed study approaches has been consistently
recommended in studies related to resilience measurement methods. As a result, the mixed
research methods utilised in the present study provides directions for future replication in
studies aimed at developing approaches for measuring resilience in the small business sector.
Lastly, the simplicity of the criteria and indices make it easier for small retail business owners
and other practitioners to use in future. / NRF
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Investigation of automated vehicle effects on drivers behavior and traffic performanceAria, Erfan January 2016 (has links)
Advanced Driver Assistance Systems (ADAS) offer the possibility of helping drivers to fulfill their driving tasks. Automated vehicles are capable of communicating with surrounding vehicles (V2V) and infrastructure (V2I) in order to collect and provide essential information about driving environment. Studies have proved that automated vehicles have a potential to decrease traffic congestion on road networks by reducing the time headway, enhancing the traffic capacity and improving the safety margins in car following. Furthermore, vehicle movement and drivers behavior of conventional vehicles will be affected by the presence of automated vehicles in traffic networks. Despite different encouraging factors, automated driving raises some concerns such as possible loss of situation awareness, overreliance on automation and degrading driving skills in absence of practice. Moreover, coping with complex scenarios, such as merging at ramps and overtaking, in terms of interaction between automated vehicles and conventional vehicles need more research. This thesis work aims to investigate the effects of automated vehicles on drivers behavior and traffic performance. A broad literature review in the area of driving simulators and psychological studies was performed to examine the automated vehicle effects on drivers behavior. Findings from the literature survey, which has been served as setup values in the simulation study of the current work, reveal that the conventional vehicles, which are driving close to the platoon of automated vehicles with short time headway, tend to reduce their time headway and spend more time under their critical time headway. Additionally, driving highly automated vehicles is tedious in a long run, reduce situation awareness and can intensify driver drowsiness, exclusively in light traffic. In order to investigate the influences of automated vehicles on traffic performance, a microscopic simulation case study consisting of different penetration rates of automated vehicles (0, 50 and 100 percentages) was conducted in VISSIM software. The scenario network is a three-lane autobahn segment of 2.9 kilometers including an off-ramp, on-ramp and a roundabout with some surrounding urban roads. Outputs of the microscopic simulation in this study reveal that the positive effects of automated vehicles on roads are especially highlighted when the network is crowded (e.g. peak hours). This can definitely count as a constructive point for the future of road networks with higher demands. In details, average density of autobahn segment remarkably decreased by 8.09% during p.m. peak hours in scenario with automated vehicles. Besides, Smoother traffic flow with less queue in the weaving segment was observed. Result of the scenario with 50% share of automated vehicles moreover shows a feasible interaction between conventional vehicles and automated vehicles. Meaningful outputs of this case study, based on the input data from literature review, demonstrate the capability of VISSIM software to simulate the presence of automated vehicles in great extent, not only as an automated vehicle scenario but also a share of them, in traffic network. The validity of the output values nonetheless needs future research work on urban and rural roads with different traffic conditions.
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Tarptautinės funkcionavimo, negalumo ir sveikatos klasifikacijos bei kanadietiško veiklos atlikimo testo panaudojimas, vertinant asmenų patyrusių galvos smegenų infarktą, veiklą / International Classification for Health, Disability and Functioning (ICF) and Canadian Occupational Performance Measure (COPM) use in evaluation people’s employment after head brain infarctionKarbauskaitė, Lina 21 June 2010 (has links)
Darbo tikslas – įvertinti, Tarptautinės funkcionavimo, negalumo ir sveikatos klasifikacijos, bei Kanadietiško veiklos atlikimo testo tinkamumą, vertinant asmenų patyrusių galvos smegenų infarktą, veiklą. Nustatyti, šių dviejų testų sąsajas ir skirtumus. Pacientus vertinant reabilitacijos laikotarpiu, po paguldymo reabilitacijos skyriuje praėjus 1-3 dienoms ir pakartotinis vertinimas atliktas po dviejų savaičių. Veiklos ir dalyvumo sutrikimų nustatymas- svarbus, paskiriant reabilitacijos specialistus ir sudarant reabilitacijos gydymo planą. / Final aim of master work - to explore International Classification for Health, Disability and Functioning (ICF) and Canadian Occupational Performance Measure (COPM) use in evaluation people’s employment after head brain infarction. To clarify these two tests conjunction and differences. Assess the patients in rehabilitation period then they come for the medical treatment in 1-3 day’s period and repeated after two weeks. Operational problems determination is important of rehabilitation professionals and the appointment of the conclusion of the rehabilitation treatment plan.
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Barriers, determinants and enablers of market orientation :|bimpact on business performance for small to medium enterprises in South Africa / Jobo DubihlelaDubihlela, Jobo January 2012 (has links)
Small and medium enterprises (SMEs) are recognised as important for the economic success of countries all over the world because of their contribution to the gross domestic product (GDP), to innovation, to export revenue, to the provision of goods and services to society and large enterprises, to social stability, to employment creation, and to the improvement of economic welfare. These organisations operate within an economic environment characterised by volatility, highly demanding dynamism and tough competition, which often seriously threaten their performance and their survival. The South African business environment in general is constantly changing in the face of an unreceptive economic environment and a subtle political setting which breeds a highly competitive market. For SMEs to withstand the hazards of such a precarious and unfavourable competitive climate, they need to engage in market-oriented strategies. While market orientation research in large organisations has been studied etensively, little attention has been paid to the market orientation of SMEs. Market orientation models have been developed and tested only for developed countries, which recognise the substantial importance of market orientation in the modern business arena. Despite its importance, market orientation and its implementation and relationship with business performance has not been widely researched in developing economies. This need for a market orientation model that is applicable to developing countries underlies this research, the principal purpose of which is to develop a market orientation–business performance conceptual model and test it in a developing country setting. For this purpose, the researcher applied the market orientation constructs as guided by various proponents in the field. Market orientation was identified from the large body of literature and a conceptual framework of market orientation–business performance was proposed. The conceptual framework considered barriers to market orientation, determinants and enablers of market orientation and market orientation with its dimensions (customer emphasis, information generation, intelligence dissemination and intelligence responsiveness or taking action) and economic and non-economic performance as consequences. This framework was then tested in order to identify the link between barriers to market orientation, determinants of market orientation, overall market orientation and business performance. Such efforts have been observed in previous market orientation literature but those studies did not distinguish barriers from determinants. The objective of this study was to establish the relationship between market orientation and the performance of SMEs measured by financial and non-financial measures of business performance. It also sought to ascertain the barriers to market orientation and the determinants/enablers of market orientation and their relationship with market orientation. Another objective was to examine the extent to which SMEs in South Africa have adopted market-oriented practices. A quantitative method was used. Surveys were conducted with 273 SMEs respondents, which were identified using a convenience sampling method. Data from owners/managers of these SMEs were collected using structured questionnaires. This study is different from previous studies on various grounds. Firstly, this study on market orientation is particularly focused on SMEs. Secondly, this study considered barriers to market orientation and determinants of market orientation separately, as having two divergent effects on market orientation. Thirdly, this study considered both the economic and non-economic performance measures as business performance indicators, factorising all the dimensions and modelling the relationship structures. Finally, this study was conducted in a developing economy (South Africa) where limited market orientation studies have been carried out with emphasis on market orientation among SMEs. Quantitative research methods were used to arrive at a valid and convergent conclusion about market orientation and its relationship with business performance. For this purpose, quantitative survey data were obtained from officials of both marketing and non-marketing departments of SMEs in the Vaal Triangle (South Africa). The hypotheses of the study were tested using t-tests statistics, analysis of variance (ANOVA), confirmatory factor analysis (CFA), and structural equation modelling (SEM) goodness of fit. The findings of the study supported the hypotheses of the study and confirmed the applicability of the proposed market orientation framework. The findings also indicated that the market orientation of SMEs in South Africa is determined by four fundamental factors (top management emphasis, market-based reward system, inter-departmental connectedness and management risk posture). In addition, the findings identified four key barriers to market orientation (centralisation and formalisation, inter-departmental conflict, competitive intensity and turbulence). The study also found a significant effect of market orientation on business performance. The findings of this study are consistent with those of previous market orientation studies undertaken in developed countries. At the final stage, the first conceptual model of market orientation–business performance applicable to SMEs in a developing country (South Africa) was offered on the basis of the findings of this study. This conceptual model provides insights and groundwork for further research. Therefore, in order to verify its generic application, it is hoped that this model will be used as a starting point for further studies and be tested in other countries in the world, both developed and developing. / PhD (Business Management)|cNorth-West University, Vaal Triangle Campus|d2013
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