A simulation study of service differentiation for the bandwidth request scheme in fixed IEEE 802.16 network

Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better.

Impact of denial of service solutions on network quality of service

The Internet has become a universal communication network tool. It has evolved from a platform that supports best-effort traffic to one that now carries different traffic types including those involving continuous media with quality of service (QoS) requirements. As more services are delivered over the Internet, we face increasing risk to their availability given that malicious attacks on those Internet services continue to increase. Several networks have witnessed denial of service (DoS) and distributed denial of service (DDoS) attacks over the past few years which have disrupted QoS of network services, thereby violating the Service Level Agreement (SLA) between the client and the Internet Service Provider (ISP). Hence DoS or DDoS attacks are major threats to network QoS. In this paper we survey techniques and solutions that have been deployed to thwart DoS and DDoS attacks and we evaluate them in terms of their impact on network QoS for Internet services. We also present vulnerabilities that can be exploited for QoS protocols and also affect QoS if exploited. In addition, we also highlight challenges that still need to be addressed to achieve end-to-end QoS with recently proposed DoS/DDoS solutions. © 2010 John Wiley & Sons, Ltd.

A model of service performance enhancement:the role of transactional and transformational leadership

This paper is concerned with the ways in which transactional and transformational leadership styles can improve the service performance of front-line staff. Past literature on services marketing has indicated the importance of leadership but has largely ignored the parallel literature in which leadership styles have been conceptualized and operationalized (e.g., sales management, organizational psychology). This paper seeks to build upon existing services marketing theory by introducing the role of leadership styles in enhancing service performance. Consequently, a conceptual framework of the effect of transactional and transformational leadership styles on service performance, anchored in a crossdisciplinary literature review, is developed. Managerial implications and future research directions are also discussed.

Outcomes of service encounter quality in a business-to-business context

Service encounter quality is an area of growing interest to researchers and managers alike, yet little is known about the effects of face-to-face service encounter quality within a business-to-business setting. In this paper, a psychometrically sound measure of such service encounter quality is proposed, and consequences of this construct are empirically assessed. Both a literature review and a dyadic in-depth interview approach were used to develop a conceptual framework and a pool of items to capture service encounter quality. A mail survey of customers was undertaken, and a response rate of 36% was obtained. Data analysis was conducted via confirmatory factor analysis and structural equation modeling. Findings reveal a four-factor structure of service encounter quality, encompassing professionalism, civility, friendliness and competence dimensions. Service encounter quality was found to be directly related to customer satisfaction and service quality perceptions, and indirectly to loyalty. The importance of these findings for practitioners and for future research on service encounter quality is discussed.

Antecedents and consequences of service quality in consumer evaluation of self-service internet technologies

Advances in technology coupled with increasing labour costs have caused service firms to explore self-service delivery options. Although some studies have focused on self-service and use of technology in service delivery, few have explored the role of service quality in consumer evaluation of technology-based self-service options. By integrating and extending the self-service quality framework the service evaluation model and the Technology Acceptance Model the authors address this emerging issue by empirically testing a comprehensive model that captures the antecedents and consequences of perceived service quality to predict continued customer interaction in the technology-based self-service context of Internet banking. Important service evaluation constructs like perceived risk, perceived value and perceived satisfaction are modelled in this framework. The results show that perceived control has the strongest influence on service quality evaluations. Perceived speed of delivery, reliability and enjoyment also have a significant impact on service quality perceptions. The study also found that even though perceived service quality, perceived risk and satisfaction are important predictors of continued interaction, perceived customer value plays a pivotal role in influencing continued interaction.

Polyunsaturated fatty acid requirements of murine colon adenocarcinomas

The polyunsaturated fatty acid (PUFA) requirements of three transplantable murine colon adenocarcinomas, the MAC13, MAC16 and MAC26, were evaluated in vitro and in vivo. When serum concentrations became growth limiting in vitro, proliferation of the MAC13 and MAC26 cell lines was stimulated by linoleic acid (LA) at 18μM and arachidonic acid (AA) at 16 or 33μM respectively. This was not demonstrated by the MAC16 cell line. MAC13 and MAC26 cells were found to be biochemically fatty acid deficient as measured by the formation of Mead acid (20:3 n-9), but the MAC16 cells were not. In vivo the growth of the MAC26 tumour was stimulated by daily oral administration of LA between 0.4-2.0g/kg. There was a threshold value of 0.4g/kg for the stimulation of MAC26 tumour growth, above which there was no further increase in tumour growth, and below which no increase in tumour growth was observed. This increased tumour growth was due to the stimulation of tumour cell proliferation in all areas of the tumour, with no effect on the cell loss factor. The growth of the MAC13, MAC16, and MAC26 cell lines in vitro were more effectively inhibited by lipoxygenase (LO) inhibitors than the cyclooxygenase inhibitor indomethacin. The specific 5-LO inhibitor Zileuton and the leukotriene D4 antagonist L-660,711 were less effective inhibitors of MAC cell growth in vitro than the less specific LO inhibitors BWA4C, BWB70C and CV6504. Studies of the hyroxyeicosatetraenoic acids (HETEs) produced from exogenous AA in these cells, suggested that a balance of eicosanoids produced from 5-LO, 12-LO and 15-LO pathways was required for cell proliferation. In vivo BWA4C, BWB70C and CV6504 demonstrated antitumour action against the MAC26 tumour between 20-50mg/kg/day. CV6504 also inhibited the growth of the MAC 13 tumour in vivo with an optimal effect between 5-10mg/kg/day. The antitumour action against the MAC16 tumour was also accompanied by a reduction in the tumour-induced host body weight loss at 10-25mg/kg/day. The antitumour action of CV6504 in all three tumour models was partially reversed by daily oral administration of 1.0g/kg LA. Studies of the AA metabolism in tumour homogenates suggested that this profound antitumour action, against what are generally chemoresistant tumours, was due to inhibition of eicosanoid production through LO pathways. As a result of these studies, CV6504 has been proposed for stage I./II. clinical trials against pancreatic cancer by the Cancer Research Campaign. This will be the first LO inhibitor entering the clinic as a therapeutic agent.

Ecological studies on:(a) the use of colonisation samplers in relation to biological surveillance of river water quality (b) the requirements of freshwater gastropoda

Some of the factors affecting colonisation of a colonisation sampler, the Standard Aufwuchs Unit (S. Auf. U.) were investigated, namely immersion period, whether anchored on the bottom or suspended, and the influence of riffles. It was concluded that a four-week immersion period was best. S. Auf. U. anchored on the bottom collected both more taxa and individuals than suspended ones. Fewer taxa but more individuals colonised S. Auf. U. in the potamon zone compared to the rhithron zone with a consequent reduction in the values of pollution indexes and diversity. It was concluded that a completely different scoring system was necessary for lowland rivers. Macroinvertebrates colonising S. Auf. U. in simulated streams, lowland rivers and the R. Churnet reflected water quality. A variety of pollution and diversity indexes were applied to results from lowland river sites. Instead of these, it was recommended that an abbreviated species - relative abundance list be used to summarise biological data for use in lowland river surveillance. An intensive study of gastropod populations was made in simulated streams. Lynnaea peregra increased in abundance whereas Potamopyrgas jenkinsi decreased with increasing sewage effluent concentration. No clear-cut differences in reproduction were observed. The presence/absence of eight gastropod taxa was compared with concentrations of various pollutants in lowland rivers. On the basis of all field work it appeared that ammonia, nitrite, copper and zinc were the toxicants most likely to be detrimental to gastropods and that P. jenkinsi and Theodoxus fluviatilis were the least tolerant taxa. 96h acute toxicity tests of P. jenkinsi using ammonia and copper were carried out in a flow-through system after a variety of static range finding tests. P. jenkinsi was intolerant to both toxicants compared to reports on other taxa and the results suggested that these toxicants would affect distribution of this species in the field.

An investigation into the nature, determinants, and dynamics of service quality expectations

On the basis of a review of the substantive quality and service marketing literature current knowledge regarding service quality expectations was found either absent or deficient. The phenomenon is of increasing importance to both marketing researchers and management and was therefore judged worthy of scholarly consideration. Because the service quality literature was insufficiently rich when embarking on the thesis three basic research issues were considered namely the nature, determinants, and dynamics of service quality expectations. These issues were first conceptually and then qualitatively explored. This process generated research hypotheses mainly relating to a model which were subsequently tested through a series of empirical investigations using questionnaire data from field studies in a single context. The results were internally consistent and strongly supported the main research hypotheses. It was found that service quality expectations can be meaningfully described in terms of generic/service-specific, intangible/tangible, and process/outcome categories. Service-specific quality expectations were also shown to be determined by generic service quality expectations, demographic variables, personal values, psychological needs, general service sophistication, service-specific sophistication, purchase motives, and service-specific information when treating service class involvement as an exogenous variable. Subjects who had previously not directly experienced a particular service were additionally found to revise their expectations of quality when exposed to the service with change being driven by a sub-set of identified determinants.

Designing a safety management support system using open architecture databases: the requirements of information representation in the support of managers' risk-related decision-making

This research was conducted at the Space Research and Technology Centre o the European Space Agency at Noordvijk in the Netherlands. ESA is an international organisation that brings together a range of scientists, engineers and managers from 14 European member states. The motivation for the work was to enable decision-makers, in a culturally and technologically diverse organisation, to share information for the purpose of making decisions that are well informed about the risk-related aspects of the situations they seek to address. The research examined the use of decision support system DSS) technology to facilitate decision-making of this type. This involved identifying the technology available and its application to risk management. Decision-making is a complex activity that does not lend itself to exact measurement or precise understanding at a detailed level. In view of this, a prototype DSS was developed through which to understand the practical issues to be accommodated and to evaluate alternative approaches to supporting decision-making of this type. The problem of measuring the effect upon the quality of decisions has been approached through expert evaluation of the software developed. The practical orientation of this work was informed by a review of the relevant literature in decision-making, risk management, decision support and information technology. Communication and information technology unite the major the,es of this work. This allows correlation of the interests of the research with European public policy. The principles of communication were also considered in the topic of information visualisation - this emerging technology exploits flexible modes of human computer interaction (HCI) to improve the cognition of complex data. Risk management is itself an area characterised by complexity and risk visualisation is advocated for application in this field of endeavour. The thesis provides recommendations for future work in the fields of decision=making, DSS technology and risk management.

The role and training requirements of scaffolders with regard to access scaffolding safety

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A rule based model for the objective determination of the e-business requirements of a manufacturing organisation

The starting point of this research was the belief that manufacturing and similar industries need help with the concept of e-business, especially in assessing the relevance of possible e-business initiatives. The research hypotheses was that it should be possible to produce a systematic model that defines, at a useful level of detail, the probable e-business requirements of an organisation based on objective criteria with an accuracy of 85%-90%. This thesis describes the development and validation of such a model. A preliminary model was developed from a variety of sources, including a survey of current and planned e-business activity and representative examples of e-business material produced by e-business solution providers. The model was subject to a process of testing and refinement based on recursive case studies, with controls over the improving accuracy and stability of the model. Useful conclusions were also possible as to the relevance of e-business functions to the case study participants themselves. Techniques were evolved to synthesise the e-business requirements of an organisation and present them at a management summary level of detail. The results of applying these techniques to all the case studies used in this research were discussed. The conclusion of the research was that the case study methodology employed was successful. A model was achieved suitable for practical application in a manufacturing organisation requiring help with a requirements definition process.

Market orientation of service networks:direct and indirect effects on sustained competitive advantage

Market orientation is an organization-wide concept that helps explain sustained competitive advantage (SCA). Since networks become ever more important, especially in the service sector, there is need to expand the concept of MO to a network setting. In line with Narver and Slater (1990), the concept of Market Orientation of Networks (MONW) is developed. This study indicates how MONW relates to the resource-based view (RBV) of the firm and the industrial organization (IO) view in explaining SCA. It is argued that MONW has direct and indirect effects on SCA. More precisely, the antecedent effect of MONW to resources and industry structure is considered.

Pragmatic development of service based real-time change data capture

This thesis makes a contribution to the Change Data Capture (CDC) field by providing an empirical evaluation on the performance of CDC architectures in the context of realtime data warehousing. CDC is a mechanism for providing data warehouse architectures with fresh data from Online Transaction Processing (OLTP) databases. There are two types of CDC architectures, pull architectures and push architectures. There is exiguous data on the performance of CDC architectures in a real-time environment. Performance data is required to determine the real-time viability of the two architectures. We propose that push CDC architectures are optimal for real-time CDC. However, push CDC architectures are seldom implemented because they are highly intrusive towards existing systems and arduous to maintain. As part of our contribution, we pragmatically develop a service based push CDC solution, which addresses the issues of intrusiveness and maintainability. Our solution uses Data Access Services (DAS) to decouple CDC logic from the applications. A requirement for the DAS is to place minimal overhead on a transaction in an OLTP environment. We synthesize DAS literature and pragmatically develop DAS that eciently execute transactions in an OLTP environment. Essentially we develop effeicient RESTful DAS, which expose Transactions As A Resource (TAAR). We evaluate the TAAR solution and three pull CDC mechanisms in a real-time environment, using the industry recognised TPC-C benchmark. The optimal CDC mechanism in a real-time environment, will capture change data with minimal latency and will have a negligible affect on the database's transactional throughput. Capture latency is the time it takes a CDC mechanism to capture a data change that has been applied to an OLTP database. A standard definition for capture latency and how to measure it does not exist in the field. We create this definition and extend the TPC-C benchmark to make the capture latency measurement. The results from our evaluation show that pull CDC is capable of real-time CDC at low levels of user concurrency. However, as the level of user concurrency scales upwards, pull CDC has a significant impact on the database's transaction rate, which affirms the theory that pull CDC architectures are not viable in a real-time architecture. TAAR CDC on the other hand is capable of real-time CDC, and places a minimal overhead on the transaction rate, although this performance is at the expense of CPU resources.