Thesis (Ph.D.)--Duquesne University, 2005. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 203-209) and index.

A thorough review of the literature on the model reduction of linear, time-invariant, dynamical systems in both the frequency and time domains is presented. Particular attention is paid to the least-squares extension of the classical method of Padé approximation. An account is given of the development of apparently different approaches of least-squares parameter- matching Padé model reduction applied to continuous-time and discrete-time systems. These approaches are shown to be related via a unifying theory. From the formulation it is possible to show several interesting features of the least-squares approach which lead to a fuller understanding of exactly how the reduced model approximates the full system. An error index is derived in the general continuous-time case and it is shown that a range of system parameter preservation options are available. Using the theory developed in the continuous-time case a non-uniqueness property of the method is proven. An ‘optimal’ least-squares method based on the approach and the introduction of weighting for the system parameters are both investigated. The unifying theory is extended to the discrete-time case where an important new stability preservation property is proved and is shown to provide the basis for a new least- squares Padé method. This method uses transformations between the z- and 5-planes to guarantee stable reduced order models approximating stable high order continuous-time systems. The application of least-squares Padé approximation is further extended to the multivariable case with particular attention given to the factors affecting the levels of order reduction achieved. Appropriate numerical examples are used to illustrate the main points of the thesis and graphs of the impulse and step responses are used throughout to visually highlight the accuracy of approximation.

I argue in this thesis that qualitative duration (viewed in opposition to the construct of quantitative clock-time) can be experienced through performance encounters that challenge smooth consumption. In a socially accelerated culture, where to do more in less time is the measure of a productive life, one’s connection with the ‘real’ time of duration is diminished. To challenge this premise, I have used an autoethnographic approach to explore an experience of duration conceived via the work of French philosopher Henri Bergson, who posits that “pure duration [is that which] excludes all idea of juxtaposition, reciprocal externality, and extension” (Bergson, 1903/1999, p. 26). In other words, Bergson asserts that duration defies quantitative measurement. I argue that the Bergsonian experience of duration offers a pause from social acceleration and effects a transformation for the spectator in the form of peak-experience, flow, and communitas.

The dynamic business environment has prompted the companies to improve their competitiveness in terms of manufacturing efficiencies by exploring faster, better and cheaper modes of product development. In this concern, different approaches are configured such as lean manufacturing, just in time and lead time reduction. The study focuses on a critical investigation into the reduction of Lead Time within discrete manufacturing in Kurdistan region of Iraq and the reasons behind this research, that area has evolved gradually as well as the government has an action plan for national recovery and development of reconstruction, where lead-time has become a major issue in manufacturing industry. Specifically, current research study aims at contributing to the strand by focusing on a critical investigation into the reduction of lead time within discrete manufacturing in Kurdistan region of Iraq, where lead-time has become a major issue in manufacturing industry. Mainly, the study has the goals of developing reliable techniques for reducing the lead time through application of assessment survey, capacity planning and key performance indicators in order to implement and control the manufacturing processes. The rationale behind the present study is consisted of economic development within the region, which has attracted a large number of foreign direct investments, but the expanded lead time is causing hurdles with the lack of a strategic plan for resolving the issue which has not keenly addressed in literature so current study would be beneficial for both the stakeholders such as researchers relying on literature and for practitioners as well. In order to conduct the analysis, current research applies the mixture of quantitative and qualitative research. Specifically, for quantitative analysis, a survey is conducted using questionnaires as data collection tool and SPSS analysis for exploring the cause and effect relationship. Mainly, the data are collected from eight Kurdistan based manufacturers. On the contrary, the qualitative analysis is conducted through the case studies. The development of a comprehensive conceptual framework has been applied for focusing on quick response manufacturing both at batch and mass production level. The framework is a contribution to academic knowledge. Through the outcomes of the study, specific factors which are explored to be the main causes of extension in lead time include ineffective forecasting for material requirements, capacity planning, inaccurate demand analysis, decreased resource efficiency and shipment delays. As the most effective solution to these issues, the findings explained that the lot for lot technique is much better than the fixed period requirements which are mostly used in the Iraq region. Moreover, just in time manufacturing strategy and closed loop capacity is also proven to be fruitful along with the splitting order tactic. It is concluded from the findings of this study that the basic issue lies with management in different areas like in human resource, quality, information acquiring, technological developments and operational efficiency. So, it is recommended to the practitioners to higher efficient management squad at the most basic level to eradicate the root cause of the lead time issue. This research will provide new simple strategies for reducing manufacturing lead-time because this is particularly important, as it can be used to provide guidance to industry practitioners on how to reduce manufacturing lead time.

A new approach to the identification problem of linear continuous-time time-invariant systems from input-output measurements is presented. Both parametric and nonparametric system models are considered. The new approach is based on the use of continuous-time functions, the modal functions, defined in terms of the system output, the output derivatives and the state variables under the assumption that the order n of the observable system is known a priori. The modal functions are obtained by linear filtering operations of the system output, the output derivatives and the state variables so that the modal functions are independent of the system instantaneous state. In this case, the modal functions are linear functions of the input exponential modes, and they contain none of the system exponential modes unlike the system general response which contains modes from both the system and the input. The filters parameters, the modal parameters are estimated using linear regression techniques. The modal functions and the modal parameters of the output and its derivatives are used to identify parametric input-output and state models of the system. The coefficients of the system characteristic polynomial are obtained by solving n algebraic equations formed from the estimates of the modal parameters. Estimates of the parameters associated with the system zeros are obtained by solving another set of linear algebraic equation. The system frequency response and step response are estimated using the output modal function. The impulse response is obtained by filtering the estimated step response using the output first derivative modal parameters. A new method is presented to obtain the system poles as the eigenvalues of a data matrix formed from the system free response. The coefficients of the system characteristic polynomial are obtained from the data matrix through a simple recursive equation. This method has some important advantages over the well known Prony's method. The state modal functions are used to obtain a minimum-time observer that gives the continuous-time system state as a direct function of input-output samples in n sampling intervals. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

M.Com. (Industrial Psychology) / It is in the interest of the modern organisation to have control over the physical passage of time. The passage of time impl ies change and it is often the way in which change is handled that determines the success or failure of the organisation. Although the manager has a wide variety of means at his disposal with which he can manipulate concrete physical time within his managerial functions, it is especially his ability to move psychologically in time, either to the past or to the future, that enables him to control the passage of time. The manager's ability to orientate himself towards should, therefore, play an important part in the successful execution of his managerial functions. The importance of time orientation in management is not only self evident, but time orientation itself is increasingly receiving attention as a fundamental determinant of human behavior...

Due to the need for advanced computer-controlled functionality in distributed embedded systems the requirements on network communication are becoming overly intricate. This dissertation targets the requirements that are concerned with real-time guarantees, run-time adaptation, resource utilization and flexibility during the development. The Flexible Time-Triggered Switched Ethernet (FTT-SE) and Hard Real-Time Ethernet Switching (HaRTES) network architectures have emerged as two promising solutions that can cater for these requirements. However, these architectures do not support multi-hop communication as they are originally developed for single-switch networks. This dissertation presents a fundamental contribution in multi-hop real-time communication over the FTT-SE and HaRTES architectures targeting the above mentioned requirements. It proposes and evaluates various solutions for scheduling and forwarding the traffic through multiple switches in these architectures. These solutions preserve the ability of dynamic adaptation without jeopardizing real-time properties of the architectures. Moreover, the dissertation presents schedulability analyses for the timeliness verification and evaluation of the proposed solutions as well as several protocols to support run-time adaptation in the multi-hop communication. Finally, the work led to an end-to-end resource reservation framework, based on the proposed multi-hop architectures, to support flexibility during the development of the systems. The efficiency of the proposed solutions is evaluated on various case studies that are inspired from industrial systems.

<p> The following study is an attempt to design a minimum-time digital position controller. </p> <p> The. investigation of the theoretical problem of the minimum time position control leads to a survey of stepping motors, which seem to provide a natural solution to the problem. However the permanentic d.c. motor is shown to be more suitable. Approximate switching characteristics are derived from the mathematical models chosen. </p> <p> Quantizing the shaft position, a digital controller is practically implemented and the experimental results confirm the theory. </p> <p> To solve the trickiest problem of measuring the velocity of the shaft, a new concept of digital tachometer is derived and implemented. Providing a very high precision and resolution, the new tachometer proved itself much better than any other instrument available now, and its direct application to the controller simplifies the latter and improves it considerably. </p> / Thesis / Doctor of Philosophy (PhD)

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Yes / Purpose: To compare full-time occlusion (FTO) and part-time occlusion (PTO) therapy in the treatment of amblyopia, with the secondary aim of evaluating the minimum number of hours of part-time patching required for maximal effect from occlusion. Methods: A literature search was performed in PubMed, Scopus, Science Direct, Ovid, Web of Science and Cochrane library. Methodological quality of the literature was evaluated according to the Oxford Center for Evidence Based Medicine and modified Newcastle-Ottawa scale. Statistical analyses were performed using Comprehensive Meta-Analysis (version 2, Biostat Inc., USA). Results: The present meta-analysis included six studies (three randomized controlled trials [RCTs] and three non-RCTs). Pooled standardized difference in the mean changes in the visual acuity was 0.337 [lower and upper limits: 0.009, 0.683] higher in the FTO as compared to the PTO group; however, this difference was not statistically significant (P ¼ 0.056, Cochrane Q value ¼ 20.4 (P ¼ 0.001), I2 ¼ 75.49%). Egger's regression intercept was 5.46 (P ¼ 0.04). The pooled standardized difference in means of visual acuity changes was 1.097 [lower and upper limits: 0.68, 1.513] higher in the FTO arm (P < 0.001), and 0.7 [lower and upper limits: 0.315, 1.085] higher in the PTO arm (P < 0.001) compared to PTO less than two hours. Conclusions: This meta-analysis shows no statistically significant difference between PTO and FTO in treatment of amblyopia. However, our results suggest that the minimum effective PTO duration, to observe maximal improvement in visual acuity is six hours per day.