Bibliography: pages 150-158. / Health care systems all over the world are in crisis. The presenting symptom is a cost spiral that is out of control. Money supply is finite, and if this problem continues the system will eventually collapse. There are a number of causes associated with the problem that are usually analysed by reduction, an approach based upon an assumption of simple linear causal relations. This study shows the problem to be the dialectic opposite, in other words these problems are all interrelated through complex causal interactions. Therefore, the health care system is a complex social system and solutions to its problems may be found in terms of the interactions in such a system. An investigation into the history of the health care system shows that the system started with a simple one on one interaction between patients and physicians. At the time of its initiation, very little empirical knowledge was available about illness. After the renaissance, this changed dramatically with a subsequent increase in the ability to diagnose, but also in the complexity to treat illness. However, modern beliefs about illness and illness processes do not reflect the complexity of this knowledge. Beliefs about both illness and knowledge contribute to the process of diagnosis (medical decision making, or problem solving). Furthermore, the expectations, wants, and needs of patients and physicians, as well as the decision environment, increases the complexity and difficulty of this decision making process. These decisions initiate treatment processes that are ultimately represented in the health care system as cost. Therefore, the patient-physician system as the simplest initial interaction is an event that ultimately affects cost. This system is not functioning efficiently at present and a system of inquiry that can improve it may make a contribution to an improved system, and therefore a saving in cost. Altering the diagnostic system from a linear into a circular process, in other words into a learning system, improves both decision making and the use of knowledge. However, an inquiring system is needed in addition that can enhance the rigour of this process. Charles West Churchman devoted a large part of his work to knowledge and the way we acquire knowledge, in other words inquiring systems. His belief is that problem solving ought to be approached in a comprehensive way in order to minimise the risk for making incorrect decisions. Furthermore, because decisions are made upon incomplete information, the solutions will be the cause of new problems. Therefore, problem solving is a never ending cycle of learning. In order to have as complete information as possible about the problem, we have to: know the history of the problem, take a broad view that includes the environment of the problem (use a systems approach), and consider all the alternative solutions to the problem. Virtually all of our knowledge is based upon underlying assumptions. In order to test the validity of the knowledge we use for inquiry and decision making, it is important to test the assumptions upon which the knowledge is based. This is valid in regard to empirical knowledge as well. Finally, according to Churchman, decision making has to be ethical. Therefore, we have to do all we can to ensure that the implementation of the decision will improve the situation, not only now, but also in the future. The application of Churchman's approach to the patient-physician interaction, assists in the synthesis of a more comprehensive world view of health care and illness. This study shows that this leads to important changes in the negative interactions identified as contributing to the health care crisis. In terms of Churchman's approach, the role of physicians can be seen as managers of illness. Their purpose is therefore to plan for the improvement of illness (the problem) in an ethical way. Such planning should include the values of patients in deciding upon appropriate treatment. It is the submission of this study that only a methodology that is able to address complex human systems, such as a systems approach, and a comprehensive philosophy of inquiry, such as that of C West Churchman is appropriate to address the current problems of the health care system.

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 241-259.

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近年來，標準化的媒體訪問控制（MAC）協議，在無線局域網（WLAN）和無線傳感器網絡（WSNs）中起著重要的作用。其中具有分佈式協調功能 (DCF) 的IEEE 802.11協議目前是一種最流行的WLAN標準，它包括MAC層和物理層的規範；而規範了PHY-MAC 的IEEE 802.15.4協議，也成為了促進部署各種商業用途的無線傳感器網絡的一個重要的里程碑。IEEE 802.11 DCF和802.15.4 MAC協議的核心是使用與防撞載波偵聽多路訪問協議 （CSMA/CA）。 / 雖然對這類MAC協議的研究已經持續了幾十年，但是研究者們仍然無法對這些無線網絡進行全面徹底的性能分析。 / 鑑於這種原因，我們在這篇論文中提出了一種通用馬爾可夫狀態空間模型，用於分析基於CSMA/ CA的MAC協議。每個節點的輸入緩衝器被模擬為一個Geo/G/1隊列，我們用了馬爾可夫鏈來描述每一個隊頭封包（HOL）的服務時間分佈。在本篇文章裡，這種馬爾可夫模型理論被運用於分析在非飽和條件下，基於概率指數補償的調度算法的兩種網絡：在理想信道和非理想信道條件下的IEEE 802.11 DCF網絡，以及IEEE 802.15.4網絡。 / 從這個排隊模型中，我們獲得了網絡穩態下吞吐量的特性方程，數據包平均分組接入延遲以及排隊延遲。此外，對於IEEE802.15.4網絡，通過馬爾可夫模型我們也得到每個節點的能量消耗的準確表達。 / 在這篇論文中，我們闡述了對於MAC網絡的吞吐量和排隊延遲方面的穩定條件。基於這兩個穩定條件，我們能夠得出兩種區域：穩定的吞吐量區域和有界延遲區域，並發現它們與補償調度算法和總輸入量有著密切的關係。另外我們證明了這種指數補償演算法同樣適合龐大用戶量的網絡。 / 對於802.11 DCF網絡，我們發現基於RTS / CTS訪問機制的網絡性能受到總輸入量和轉播因子的影響比基於基本訪問機制的網絡來的小。此外，經過對比理想和非理想信道下網絡性能的表現，我們發現傳輸錯誤對網絡的吞吐量和延遲也會產生重大影響。對於IEEE802.15.4網絡，我們的研究結果證實在穩定的吞吐區域內，單個節點的能耗較少。 / 最後，我們將這種方法擴展到基於競爭窗口補償模型中，對比分析證明了概率補償演算法的模型可以有效地用於分析實際中基於競爭窗口機制的無線網絡。 / In recent years, the standardized Media Access Control (MAC) protocol plays an important role in wireless local area networks (WLANs) and wireless sensor networks (WSNs). The IEEE 802.11 protocol with distributed coordination function (DCF) is the most popular standard in WLANs that includes specifications for both MAC and physical layers, whereas the IEEE 802.15.4 PHY-MAC specifications represents a significant milestone in promoting deployment of WSNs for a variety of commercial uses. The core of the 802.11 DCF and 802.15.4 MAC protocols is the Carrier-Sense Multiple-Access protocol with Collision Avoidance (CSMA/CA). / Although the studies of such kinds of MAC protocols have been lasted for several decades, a thorough network performance analysis of these wireless networks still cannot be tackled in the existing works. / In light of this concern, we propose a generic Markov state space model of the MAC protocols with CSMA/CA for contention resolution in this thesis. The input buffer of each node is modeled as a Geo/G/1 queue, and the service time distribution is derived from a Markov chain describing the state transitions of head-of-line (HOL) packets. This Markov model is well demonstrated by the IEEE 802.11 DCF networks in either ideal channels or imperfect channels, and IEEE 802.15.4 networks, with probabilistic exponential backoff scheduling algorithm under non-saturated condition. / With this queueing model, we obtain the steady state characteristic equation of network throughput as well as the mean packet access and queueing delays of packets. Moreover, for the IEEE 802.15.4 networks, the accurate expressions of energy consumptions for each node can also be obtained through this Markov model. / In this dissertation, we specify the stability conditions in terms of throughput and queueing delay for MAC networks. These two stable conditions enable us to derive two kinds of regions: the stable throughput region and the bounded delay region, which is dependent on the backoff scheduling algorithm and the aggregate input traffic. We prove that the stable regions still exist even for an infinite population with exponential backoff. / For the IEEE 802.11 DCF networks, it depicts that the network performance of RTS/CTS access scheme is less dependent on the aggregate input rate and retransmission factor than that of the Basic access mechanism. Additionally, with the comparison of the networks performance under ideal and imperfect channels, we also show that the transmission errors have a significant impact on both throughput and delay of networks. For the IEEE 802.15.4 networks, our results confirm that the energy consumption of a single node is kept small within its stable throughput region. / Last but not least, we extend our approach to the contention-window-based backoff model, and depict that the probabilistic backoff model can serve as a good analytical model for the practical contention window mechanism. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Yin, Dongjie. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 151-160). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chapter Chapter 1 --- Introduction of IEEE Standard MAC Protocols --- p.1 / Chapter 1.1 --- Medium Access Control (MAC) Protocols --- p.2 / Chapter 1.1.1 --- Medium access control in wireless LANs --- p.3 / Chapter 1.1.2 --- Medium access control in wireless sensor networks --- p.6 / Chapter 1.2 --- Backoff Scheduling Algorithms for Contention Resolution --- p.8 / Chapter 1.3 --- Our Methodologies --- p.11 / Chapter 1.3.1 --- Multi-queue-singer-server system --- p.11 / Chapter 1.3.2 --- State space of Markov chain for MAC protocols --- p.15 / Chapter 1.4 --- Contributions --- p.19 / Chapter 1.4.1 --- The Markov state space model of MAC protocols --- p.20 / Chapter 1.4.2 --- Stability analysis of networks --- p.20 / Chapter 1.4.3 --- Probabilistic exponential backoff and window-based exponential backoff --- p.21 / Chapter 1.5 --- Dissertation Overview --- p.22 / Chapter Chapter 2 --- IEEE 802.11 Distributed Coordination Function --- p.24 / Chapter 2.1 --- Introduction and Overview of IEEE 802.11 DCF --- p.25 / Chapter 2.1.1 --- Principle of IEEE 802.11 DCF protocols --- p.25 / Chapter 2.1.2 --- Historical background of IEEE 802.11 DCF --- p.26 / Chapter 2.1.3 --- Contributions of our works --- p.29 / Chapter 2.2 --- Queuing Model of HOL Packet for the 802.11 DCF --- p.31 / Chapter 2.2.1 --- Alternating renewal process of channel --- p.31 / Chapter 2.2.2 --- Queuing model of input buffer --- p.34 / Chapter 2.3 --- Stable Throughput Region for the 802.11 DCF --- p.42 / Chapter 2.3.1 --- Stable throughput condition --- p.43 / Chapter 2.3.2 --- Stable throughput region of exponential backoff --- p.45 / Chapter 2.4 --- Bounded Delay Region for IEEE 802.11 --- p.52 / Chapter 2.4.1 --- Bounded delay condition --- p.52 / Chapter 2.4.2 --- Bounded delay region of exponential backoff --- p.53 / Chapter 2.5 --- Window-based Exponential Backoff --- p.57 / Chapter 2.6 --- Conclusion --- p.63 / Chapter Chapter 3 --- IEEE 802.11 DCF in Presence of Non-Ideal Transmission Channel --- p.65 / Chapter 3.1 --- Introduction of IEEE 802.11 DCF with Error-Prone --- p.66 / Chapter 3.1.1 --- Collision and error control in 802.11 DCF --- p.66 / Chapter 3.1.2 --- Historical background --- p.69 / Chapter 3.2 --- Queuing Model of Input Buffer for the 802.11 DCF with Error-Prone Channels --- p.71 / Chapter 3.3 --- Stability Analysis --- p.83 / Chapter 3.3.1 --- Stability analysis of network throughput --- p.83 / Chapter 3.3.2 --- Stability analysis of queueing delay --- p.91 / Chapter 3.4 --- Conclusion --- p.96 / Chapter Chapter 4 --- Performance Analysis of IEEE 802.15.4 Beacon-Enabled Mode --- p.97 / Chapter 4.1 --- Introduction --- p.98 / Chapter 4.1.1 --- Principle of IEEE 802.15.4 protocols --- p.98 / Chapter 4.1.2 --- Historical background of IEEE 802.15.4 --- p.101 / Chapter 4.1.3 --- Contributions of our works --- p.103 / Chapter 4.2 --- Queuing Model of Input Buffer for IEEE 802.15.4 --- p.105 / Chapter 4.2.1 --- Queuing model of input buffer --- p.106 / Chapter 4.2.2 --- Stable conditions of exponential backoff --- p.113 / Chapter 4.3 --- Analysis of Uplink Traffic without Acknowledgement --- p.116 / Chapter 4.4 --- Analysis of Acknowledged Uplink Traffic --- p.122 / Chapter 4.5 --- Analysis of Power Consumption of Each Node --- p.127 / Chapter 4.5.1 --- Power consumption of non-acknowledgement mode --- p.129 / Chapter 4.5.2 --- Power consumption of acknowledgement mode --- p.130 / Chapter 4.6 --- Simulation and Numerical Results --- p.132 / Chapter 4.7 --- Conclusion --- p.137 / Chapter Chapter 5 --- Summary and Future Works --- p.139 / Chapter 5.1 --- Contribution Summary --- p.140 / Chapter 5.2 --- Future Works --- p.142 / Chapter Appendix A --- Service Time Distribution for the Ideal 802.11 DCF with Exponential Backoff --- p.145 / Chapter Appendix B --- Throughput of802.11 DCF with Window-Based Backoff Scheme --- p.146 / Chapter Appendix C --- Service Time Distribution for the 802.11 DCF under Error-Prone Channels with Exponential Backoff --- p.147 / Chapter Appendix D --- Service Time Distribution for the IEEE 802.15.4 with Exponential Backoff --- p.150 / Bibliography --- p.151

Thesis (M.B.A.)--University of Hong Kong, 1983.

No description available.

Over the last thirty years, Materials Requirements Planning (MRP) based systems have become commonplace within batch manufacturing environments, but are still widely held to be under performing. This research hypothesises that there may be inherent problems associated with the application due to uncertainties that exist within dynamic operating environments. Research has highlighted both the absence of any business model that uses a structured and systematic approach to deal with uncertainty holistically and the lack of any widely used, consistent performance measures to allow comparison of research results. The industrial need for such a holistic approach became apparent from survey work, which showed MRP under-performed in the presence of uncertainty even when numerous Buffering and Dampening (BAD) approaches were applied. A business model of uncertainty that structures the causes and effects of uncertainty as a hierarchy of four levels has been proposed, to be verified and validated through industrial survey and simulation respectively. The relationship between causes and effects in the business model has been verified from survey results using Analysis of Variance (ANOVA), which identified twenty-three significant uncertainties within Mixed-Mode (MM) operating environments. Using a multi-product, multi-level dependent demand MRP simulation model within an MM operating environment driven by planned order release, an experimental programme has been carried out that showed finished products delivered late to be insensitive as a performance measure. Parts Delivered Late (PDL) was found to be more sensitive and has been adopted as the preferred measure. ANOVA on the simulation results validated the cause-and-effect relationships, showing that the higher the level of uncertainty, the worse was delivery performance. Individual uncertainties produced effects that were not discretely recognised in the literature. `Knock-on' effects are created by uncertainties delaying the issue of batches and affected particular Bill of Materials chains. `Compound' effects are caused by uncertainties affecting resource availability and also induced consequent knock-on effects. Simulation results also showed that late deliveries from suppliers, machine breakdowns, unexpected or urgent changes to schedules affecting machines and customer design changes are the most significant uncertainties within the parameter levels modelled. Several significant two-way and three-way interactions were found. The business model of uncertainty represents a practical and pragmatic attempt to act as a diagnostic tool to identify significant underlying causes affecting PDL for MM companies using MR1, enabling more effective application of suitable BAD approaches. Using the business model to drive a continuous improvement programme that monitored both levels of uncertainty and PDL would allow internal and external benchmarking for the efficacy of BAD approaches and for the reduction of uncertainties.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 95-105). Also available via the Internet.

Thesis (Ph. D.)--Northwestern University, 1977. / Vita. Includes bibliographical references (leaves 422-431).

As humans we find communicating natural and compelling. Over the centuries we have created many innovations which enable and improve communication between people; during the past decade mobile phone networks have brought about a technological revolution in this area. Never before have people been so connected to one another. Today we have the ability to communicate with almost anyone, anytime, anywhere. Our increased connectivity and reachability also leads to new issues and challenges that we need to deal with. When we phone someone we expect an instant connection, and when this does not occur it can be frustrating. On the other hand it is equally disruptive to receive a call when one is busy with an important task or in a situation where communication is inappropriate. Social protocol dictates that we try to minimize such situations for the benefit of others nearby and for ourselves. This management of communications is a constant and difficult task. Using presence – which signals a person’s availability and willingness to communicate – is a solution to this problem. Such information can benefit communication partners by increasing the likelihood of a successful connection and decreasing disruptions. This research addresses the problem of staying connected while keeping control over mobile communications. It adopts a design-science research paradigm, with the primary research artifact being a model for privacy-aware presence management in mobile communications. As part of the model development knowledge contributions are made in several ways. Existing knowledge about the problem area is extended through a quantitative analysis of mobile communications management. This analysis uses a novel survey, collecting useful empirical data for future research. This includes how people currently manage their communications and what features they expect from a potential “call management” system. The examination and use of presence standards, as a foundation for the model, provides a comparison of the main presence technologies available today. A focus on privacy features identifies several shortcomings in standards which, if addressed, can help to improve and make these standards more complete. The model stresses the privacy of potentially sensitive presence information. A unique perspective based on social relationship theories is adopted. The use of relationship groups not only makes logical sense but also assists in the management of presence information and extends existing standards. Finally, the evaluation of the model demonstrates the feasibility of a practical implementation as well the ability to extend the model in next generation mobile networks. Thus the model presents a solid foundation for the development of future services. In these ways the proposed model contributes positively towards balancing efficient mobile communications with the need for privacy-awareness.