An analytical model for performance evaluation of multimedia applications over EDCA in an IEEE 802.11e WLAN

We extend the modeling heuristic of (Harsha et al. 2006. In IEEE IWQoS 06, pp 178 - 187) to evaluate the performance of an IEEE 802.11e infrastructure network carrying packet telephone calls, streaming video sessions and TCP controlled file downloads, using Enhanced Distributed Channel Access (EDCA). We identify the time boundaries of activities on the channel (called channel slot boundaries) and derive a Markov Renewal Process of the contending nodes on these epochs. This is achieved by the use of attempt probabilities of the contending nodes as those obtained from the saturation fixed point analysis of (Ramaiyan et al. 2005. In Proceedings ACM Sigmetrics, `05. Journal version accepted for publication in IEEE TON). Regenerative analysis on this MRP yields the desired steady state performance measures. We then use the MRP model to develop an effective bandwidth approach for obtaining a bound on the size of the buffer required at the video queue of the AP, such that the streaming video packet loss probability is kept to less than 1%. The results obtained match well with simulations using the network simulator, ns-2. We find that, with the default IEEE 802.11e EDCA parameters for access categories AC 1, AC 2 and AC 3, the voice call capacity decreases if even one streaming video session and one TCP file download are initiated by some wireless station. Subsequently, reducing the voice calls increases the video downlink stream throughput by 0.38 Mbps and file download capacity by 0.14 Mbps, for every voice call (for the 11 Mbps PHY). We find that a buffer size of 75KB is sufficient to ensure that the video packet loss probability at the QAP is within 1%.

Relationship between quality certification and financial and non-financial performance of organizations

At present, many countries have either embraced ISO9001 or used it as the basis of their national quality certification systems. However, few studies have been conducted to examine the benefits companies’ gain from achieving and implementing ISO9001 standards (Chikuku et al. 2012; Psomas et al. 2013; Sampaio et al. 2011a,b). Analysis has brought much more confused and uneven results across the countries. Turning to the experience of Malaysia, this country has witnessed a spectacular growth at an average rate of 9.89% per annum of ISO certificates issued to companies operating within its borders (ISO Survey 2012). While many companies rush to be ISO 9001 certified whether this brings about better benefits (both the financial and the non-financial) is still an open question. In this study, the research problems were first formulated from the literature and then a questionnaire survey was conducted to test the hypotheses. A survey was administered to chief executives officers and managers across manufacturing and service organizations in Malaysia. Multivariate analysis and SPSS macro developed by Preacher and Hayes were used as statistical techniques to the financial and non-financial benefits of ISO9001 certification. The survey instrument was a two-page questionnaire comprising three sections. The first section of the questionnaire covered the company’s profile. The second section consisted of 25 items on internal benefits and third section consisted of 7 items on external benefits measured on 1–5 Likert scale to assess the benefits of ISO9001 certification. Total 201 valid responses were received. Results of the study indicate that there was no significant direct relationship between ISO9001 certification and organizational financial performance, while strong statistical evidence was found to support the direct relationship between ISO9001 certification and non-financial performance. The findings of the study discovered that financial performance is actually directly related to two non-financial measures, namely quality performance and local and international business performance, which are directly and significantly influenced by ISO9001 certification. Therefore non-financial performance measures are involved in the mediational process. The findings will assist practitioners in taking right courses of action that make the implementation of this standard more effective. For example, the study findings study suggests that companies should put emphasize on nonfinancial factors to improve their financial performance.

S-nets: A Petri net based model for performance evaluation of real-time scheduling algorithms

A new class of nets, called S-nets, is introduced for the performance analysis of scheduling algorithms used in real-time systems Deterministic timed Petri nets do not adequately model the scheduling of resources encountered in real-time systems, and need to be augmented with resource places and signal places, and a scheduler block, to facilitate the modeling of scheduling algorithms. The tokens are colored, and the transition firing rules are suitably modified. Further, the concept of transition folding is used, to get intuitively simple models of multiframe real-time systems. Two generic performance measures, called �load index� and �balance index,� which characterize the resource utilization and the uniformity of workload distribution, respectively, are defined. The utility of S-nets for evaluating heuristic-based scheduling schemes is illustrated by considering three heuristics for real-time scheduling. S-nets are useful in tuning the hardware configuration and the underlying scheduling policy, so that the system utilization is maximized, and the workload distribution among the computing resources is balanced.

Performance analysis of beacon-less IEEE 802.15.4 multi-hop networks

We develop an approximate analytical technique for evaluating the performance of multi-hop networks based on beacon-less CSMA/CA as standardised in IEEE 802.15.4, a popular standard for wireless sensor networks. The network comprises sensor nodes, which generate measurement packets, and relay nodes which only forward packets. We consider a detailed stochastic process at each node, and analyse this process taking into account the interaction with neighbouring nodes via certain unknown variables (e.g., channel sensing rates, collision probabilities, etc.). By coupling these analyses of the various nodes, we obtain fixed point equations that can be solved numerically to obtain the unknown variables, thereby yielding approximations of time average performance measures, such as packet discard probabilities and average queueing delays. Different analyses arise for networks with no hidden nodes and networks with hidden nodes. We apply this approach to the performance analysis of tree networks rooted at a data sink. Finally, we provide a validation of our analysis technique against simulations.

Holistic Measures for Evaluating Prediction Models in Smart Grids

The performance of prediction models is often based on ``abstract metrics'' that estimate the model's ability to limit residual errors between the observed and predicted values. However, meaningful evaluation and selection of prediction models for end-user domains requires holistic and application-sensitive performance measures. Inspired by energy consumption prediction models used in the emerging ``big data'' domain of Smart Power Grids, we propose a suite of performance measures to rationally compare models along the dimensions of scale independence, reliability, volatility and cost. We include both application independent and dependent measures, the latter parameterized to allow customization by domain experts to fit their scenario. While our measures are generalizable to other domains, we offer an empirical analysis using real energy use data for three Smart Grid applications: planning, customer education and demand response, which are relevant for energy sustainability. Our results underscore the value of the proposed measures to offer a deeper insight into models' behavior and their impact on real applications, which benefit both data mining researchers and practitioners.

A fast and accurate performance analysis of beaconless IEEE 802.15.4 multi-hop networks

We develop an approximate analytical technique for evaluating the performance of multi-hop networks based on beaconless IEEE 802.15.4 ( the ``ZigBee'' PHY and MAC), a popular standard for wireless sensor networks. The network comprises sensor nodes, which generate measurement packets, relay nodes which only forward packets, and a data sink (base station). We consider a detailed stochastic process at each node, and analyse this process taking into account the interaction with neighbouring nodes via certain time averaged unknown variables (e.g., channel sensing rates, collision probabilities, etc.). By coupling the analyses at various nodes, we obtain fixed point equations that can be solved numerically to obtain the unknown variables, thereby yielding approximations of time average performance measures, such as packet discard probabilities and average queueing delays. The model incorporates packet generation at the sensor nodes and queues at the sensor nodes and relay nodes. We demonstrate the accuracy of our model by an extensive comparison with simulations. As an additional assessment of the accuracy of the model, we utilize it in an algorithm for sensor network design with quality-of-service (QoS) objectives, and show that designs obtained using our model actually satisfy the QoS constraints (as validated by simulating the networks), and the predictions are accurate to well within 10% as compared to the simulation results in a regime where the packet discard probability is low. (C) 2015 Elsevier B.V. All rights reserved.

Structural Design under Seismic Risk Using Multiple Performance Objectives

Structural design is a decision-making process in which a wide spectrum of requirements, expectations, and concerns needs to be properly addressed. Engineering design criteria are considered together with societal and client preferences, and most of these design objectives are affected by the uncertainties surrounding a design. Therefore, realistic design frameworks must be able to handle multiple performance objectives and incorporate uncertainties from numerous sources into the process.

In this study, a multi-criteria based design framework for structural design under seismic risk is explored. The emphasis is on reliability-based performance objectives and their interaction with economic objectives. The framework has analysis, evaluation, and revision stages. In the probabilistic response analysis, seismic loading uncertainties as well as modeling uncertainties are incorporated. For evaluation, two approaches are suggested: one based on preference aggregation and the other based on socio-economics. Both implementations of the general framework are illustrated with simple but informative design examples to explore the basic features of the framework.

The first approach uses concepts similar to those found in multi-criteria decision theory, and directly combines reliability-based objectives with others. This approach is implemented in a single-stage design procedure. In the socio-economics based approach, a two-stage design procedure is recommended in which societal preferences are treated through reliability-based engineering performance measures, but emphasis is also given to economic objectives because these are especially important to the structural designer's client. A rational net asset value formulation including losses from uncertain future earthquakes is used to assess the economic performance of a design. A recently developed assembly-based vulnerability analysis is incorporated into the loss estimation.

The presented performance-based design framework allows investigation of various design issues and their impact on a structural design. It is a flexible one that readily allows incorporation of new methods and concepts in seismic hazard specification, structural analysis, and loss estimation.

Production planning of multi-stage multi-option seru production systems with sustainable measures

With the concerns over climate change and the escalation in worldwide population, sustainable development attracts more and more attention of academia, policy makers, and businesses in countries. Sustainable manufacturing is an inextricable measure to achieve sustainable development since manufacturing is one of the main energy consumers and greenhouse gas contributors. In the previous researches on production planning of manufacturing systems, environmental factor was rarely considered. This paper investigates the production planning problem under the performance measures of economy and environment with respect to seru production systems, a new manufacturing system praised as Double E (ecology and economy) in Japanese manufacturing industries. We propose a mathematical model with two objectives minimizing carbon dioxide emission and makespan for processing all product types by a seru production system. To solve this mathematical model, we develop an algorithm based on the non-dominated sorting genetic algorithm II. The computation results and analysis of three numeral examples confirm the effectiveness of our proposed algorithm. © 2014 Elsevier Ltd. All rights reserved.

The performance and persistence of exchange-traded funds: evidence for iShares MSCI country-specific ETFs

The aim of this paper is to investigate the performance and persistence of 20 iShares MSCI country-specific exchange-traded funds (ETFs) in comparison with S&P 500 index over the period July 2001 to June 2006. There are several studies analysing mutual funds performance in past years, but very little is known about ETFs. In our analysis the Sharpe, Treynor and Sortino ratios are used as risk-adjusted performance measures. To evaluate performance persistence and therefore if there is any relationship among past performance and future performance, we apply to the Spearman Rank Correlation Coefficient and the Winner-loser Contingency Table. The main findings are at two levels. First, ETFs can beat the U.S. market index based on risk-adjusted performance measures. Second, there is evidence of ETFs performance persistence based on annual return.

Performance Management in the UK Public Sector: addressing multiple stakeholder complexity

Purpose The aim of this paper is to explore the issues involved in developing and applying performance management approaches within a large UK public sector department using a multiple stakeholder perspective and an accompanying theoretical framework. Design/methodology/approach An initial short questionnaire was used to determine perceptions about the implementation and effectiveness of the new performance management system across the organisation. In total, 700 questionnaires were distributed. Running concurrently with an ethnographic approach, and informed by the questionnaire responses, was a series of semi-structured interviews and focus groups. Findings Staff at all levels had an understanding of the new system and perceived it as being beneficial. However, there were concerns that the approach was not continuously managed throughout the year and was in danger of becoming an annual event, rather than an ongoing process. Furthermore, the change process seemed to have advanced without corresponding changes to appraisal and reward and recognition systems. Thus, the business objectives were not aligned with motivating factors within the organisation. Research limitations/implications Additional research to test the validity and usefulness of the theoretical model, as discussed in this paper, would be beneficial. Practical implications The strategic integration of the stakeholder performance measures and scorecards was found to be essential to producing an overall stakeholder-driven strategy within the case study organisation. Originality/value This paper discusses in detail the approach adopted and the progress made by one large UK public sector organisation, as it attempts to develop better relationships with all of its stakeholders and hence improve its performance. This paper provides a concerted attempt to link theory with practice.

Understanding New Product Project Performance

Purpose – The purpose of this paper is to summarize the accumulated body of knowledge on the performance of new product projects and provide directions for further research. Design/methodology/approach – Using a refined classification of antecedents of new product project performance the research results are meta-analyzed in the literature in order to identify the strength and stability of predictor-performance relationships. Findings – The results reveal that 22 variables have a significant relationship with new product project performance, of which only 12 variables have a sizable relationship. In order of importance these factors are the degree of organizational interaction, R&D and marketing interface, general product development proficiency, product advantage, financial/business analysis, technical proficiency, management skill, marketing proficiency, market orientation, technology synergy, project manager competency and launch activities. Of the 34 variables 16 predictors show potential for moderator effects. Research limitations/implications – The validity of the results is constrained by publication bias and heterogeneity of performance measures, and directions for the presentation of data in future empirical publications are provided. Practical implications – This study helps new product project managers in understanding and managing the performance of new product development projects. Originality/value – This paper provides unique insights into the importance of predictors of new product performance at the project level. Furthermore, it identifies which predictor-performance relations are contingent on other factors.

Developing management capability within a horizontal supply chain in performance measurement deployment and evolution: A Dynamic Capabilities and Goal Theory perspective

Complex collaboration in rapidly changing business environments create challenges for management capability in Utility Horizontal Supply Chains (UHSCs) involving the deploying and evolving of performance measures. The aim of the study is twofold. First, there is a need to explore how management capability can be developed and used to deploy and evolve Performance Measurement (PM), both across a UHSC and within its constituent organisations, drawing upon a theoretical nexus of Dynamic Capability (DC) theory and complementary Goal Theory. Second, to make a contribution to knowledge by empirically building theory using these constructs to show the management motivations and behaviours within PM-based DCs. The methodology uses an interpretive theory building, multiple case based approach (n=3) as part of a USHC. The data collection methods include, interviews (n=54), focus groups (n=10), document analysis and participant observation (reflective learning logs) over a five-year period giving longitudinal data. The empirical findings lead to the development of a conceptual framework showing that management capabilities in driving PM deployment and evolution can be represented as multilevel renewal and incremental Dynamic Capabilities, which can be further understood in terms of motivation and behaviour by Goal-Theoretic constructs. In addition three interrelated cross cutting themes of management capabilities in consensus building, goal setting and resource change were identified. These management capabilities require carefully planned development and nurturing within the UHSC. 

A gestão do risco em instituições bancárias: uma análise com recurso a medidas de avaliação da performance ajustadas ao risco

Dissertação de Mestrado apresentado ao Instituto de Contabilidade e Administração do Porto para a obtenção do grau de Mestre em Auditoria sob orientação do Mestre Carlos Mota

Key performance indicators and the balanced scorecard at the Luxury Brand Hotels of Pestana Group

Traditional approaches to evaluate performance in hotels, have mainly used financial measures. Building on Speckbacher et al. (2003), this Work Project aims to design and propose a Balanced Scorecard Type II as a performance measurement/management system for the hospitality industry based on data collected at the Luxury Brand Hotels of Pestana Group. The main contribution is to better align the vision, strategy and financial and non-financial performance measures in this category of hotels, in particular those of Pestana Group, and by doing so, lead their managers to focus on what is really critical and, consequently improve the overall performance.