Issued also as thesis PH. D)--Columbia University.

Thesis (Ph. D.)--Columbia University, 1917. / Reproduction of original from Harvard Law School Library.

Thesis--Wisconsin. / Includes bibliographical references (leaves 105-110).

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Abstract Environmental concern and tighter public regulations have created new pressures to reduce effluent loading from kraft pulp bleaching during the past decades. This trend has forced both pulp mills and the related engineering industries to develop and optimise equipment for the pulping processes which fulfils these demands. New pulp washers and washing systems connected with the introduction of new oxygen-based reagents have in particular provided considerably improved tools for reusing process water and thereby essentially reducing effluent discharge or even allowing the implementation of a totally closed water circulation system in kraft pulp bleaching. This study was performed mainly on a laboratory scale at the University of Oulu, but some pilot-scale tests were also performed to confirm the findings of the laboratory-scale evaporation test. Another aim of the pilot-scale tests was to produce enough concentrate for further processing. Conditions were strictly controlled in all the experiments in order to ensure that conclusions could be reached regarding the phenomena examined. The results reported here indicate that the amounts of transition metal ions such as iron, copper or manganese in the process water or water to be recirculated should be kept as low as possible during chlorine dioxide or peracetic acid bleaching, as even a small amount (<<5 ppm) markedly reduced pulp quality and increased reagent consumption. The results also show that evaporation can be used as a method for purifying acidic effluent from both chlorine dioxide and peracetic acid bleaching, and that the resulting condensates were free of transition metals and clean enough for reuse in both bleaching processes. The purity of the condensates was further improved by neutralising the feed pH of the acidic effluents from the bleach plant before evaporation. The results also indicate that the chloride ions in the concentrate arising from evaporation of the acidic effluent from chlorine dioxide bleaching can be removed by a combined acidification/re-evaporation system.

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This research evaluates crime prevention effects/impact of open-street closed circuit television (CCTV) surveillance systems as installed in the selected areas (research sites) of the cities of Johannesburg and Tshwane in the Gauteng Province of South Africa on crimes occurring in these surveilled areas. Currently, CCTV surveillance systems are a common sight in many of the urban areas of South Africa.The principal aim of this study was to explore the evaluation of CCTV for crime prevention, reduction and control. The results show that, despite a lack of empirical evidence as to the value of CCTV surveillance systems in preventing or reducing crime, there is strong public support for these systems and that the foundation for much of this support lies in the perceptions/feelings of members of the public of greater safety generated in areas with CCTV coverage. The method of sampling used was a purposive non-probability sampling approach. Participants were selected for interviews based on their knowledge and experience of CCTV systems. The results show that, despite this lack of empirical evidence, CCTV appears to be a viable option for crime prevention and control when integrated with evidence-based strategies rather than as a stand-alone tactic in order to achieve crime control benefits. / Criminology and Security Science / M. Tech. (Security Management)

Supply chain management has evolved over the course of history in order to provide faster and efficient service to those companies that follow its principles. As there have been advances in technology and changes in the way business is conducted across the globe, supply chains also have had to change in order to remain effective. With greater attention paid to resource depletion, environmental impact, and waste reduction; the concept of closed-loop supply chains has garnered the attention of managers who look to make their production processes more efficient. Finding ways to judge the performance of these supply chains is critical to managers. By identifying key performance measures, they are able to gauge how their closed-loop process is performing as well as identify areas for improvement.

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A dynamic real-time optimization (DRTO) formulation with closed-loop prediction is used to coordinate distributed model predictive controllers (MPCs) by rigorously predicting the interaction between the distributed MPCs and full plant response in the DRTO formulation. This results a multi-level optimization problem and that is solved by replacing the MPC quadratic programming subproblems by their equivalent Karush-Kuhn-Tucker (KKT) first-order optimality conditions to yield a single-level mathematical program with complementarity constraints (MPCC). The proposed formulation is able to perform both target tracking and economic optimization with significant performance improvement over decentralized control, and similar performance to centralized MPC. A linear dynamic case study illustrates the performance of the proposed strategy for coordination of distributed MPCs for different levels of plant interaction,. The method is thereafter applied to a nonlinear integrated plant with recycle, where its performance in both set-point target tracking and economic optimization is demonstrated. Subsequently, this study presents two techniques for approximation of the closed-loop prediction within the DRTO formulation - a hybrid closed-loop formulation and an input clipping formulation. The hybrid formulation generates closed-loop predictions for a limited number of time intervals along the DRTO prediction horizon, followed by an open-loop optimal control formulation extended to rest of the horizon. The input clipping formulation utilizes an unconstrained MPC optimization formulation for each distributed MPC, coupled with the application of an input saturation mechanism. The performance of the approximation techniques is evaluated through application to case studies based on linear and nonlinear dynamic plant models respectively. The approximation techniques are demonstrated to be more computationally efficient than than the rigorous counterpart without significant loss in performance. The performance of the proposed DRTO formulation can be further improved by the introduction of nonlinearity. The nonlinear dynamic plant model is firstly introduced in the DRTO formulation while maintaining the linear formulation for the distributed MPCs. The performance of resulting formulation is demonstrated and compared against the linear counterpart. The nonlinear MPC formulation is then included in both lower-level control implementation and DRTO formulation. By reformulating the Lagrangian of the nonlinear MPC optimization subproblems, the nonlinear MPC formulation is successfully implemented in the DRTO formulation. The performance of such DRTO formulation is further improved and shown using a nonlinear case study. The conclusion of this study is summarized and the potential directions of this research such as large-scale applications, variation of MPC implementations, and robust model-based control are outlined and explained in the end. / Thesis / Master of Applied Science (MASc)