Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 7123. Adviser: Carolyn Beck. Includes bibliographical references (leaves 82-87) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 7070. Adviser: Sheldon Jacobson. Includes bibliographical references (leaves 107-114) Available on microfilm from Pro Quest Information and Learning.

Thesis (PH.D.) -- Syracuse University, 2004. / "Publication number AAT 3149061."

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 4034. Adviser: Sheldon H. Jacobson. Includes bibliographical references (leaves 123-128) Available on microfilm from Pro Quest Information and Learning.

<p> Univariate cubic <i>L</i>¹ spline fits have been successful to preserve the shapes of 2D data with abrupt changes. The reason is that the minimization of <i>L</i>¹ norm of the data is considered, as opposite to <i>L</i>² norm. While univariate <i>L</i>¹ spline fits for 2D data are discussed by many, bivariate <i>L</i>¹ spline fits for 3D data are yet to be fully explored. This thesis aims to develop bicubic <i>L</i>¹ spline fits for 3D data approximation. This can be achieved by solving a bi-level optimization problem. One level is bivariate cubic spline interpolation and the other level is <i> L</i>¹ error minimization. In the first level, a bicubic interpolated spline surface will be constructed on a rectangular grid with necessary first and second order derivative values estimated by using a 5-point window algorithm for univariate <i>L</i>¹ interpolation. In the second level, the absolute error (i.e. <i> L</i>¹ norm) will be minimized using an iterative gradient search. This study may be extended to higher dimensional cubic <i>L</i>¹ spline fits research.</p><p>

<p> The development of expected-distance formulas for multi-dock-door, unit-load warehouse configurations is the focus of the dissertation. From formulations derived, the width-to-depth ratios minimizing expected distances are obtained for rectangle-shaped, unit-load warehouse configurations. Partitioning the storage region in the warehouse into three classes, the performance of a multi-dock-door, unit-load warehouse is studied when storage regions can be either rectangle-shaped or contour-line-shaped. </p><p> Our first contribution is the development of formulas for expected distance traveled in storing and retrieving unit loads in a rectangle-shaped warehouse having multiple dock doors along one warehouse wall and storage racks aligned perpendicular to that wall. Two formulations of the optimization problem of minimizing expected distance are considered: a discrete formulation and a continuous formulation with decision variables being the width and depth of the warehouse for single- and dual-command travel. Based on dock door configurations treated in the literature and used in practice, three scenarios are considered for the locations of dock doors: 1) uniformly distributed over the entire width of a wall; 2) centrally located on a wall with a fixed distance between adjacent dock doors; and 3) not centrally located on a wall, but with a specified distance between adjacent dock doors. </p><p> Our second contribution is the investigation of the effect on the optimal width-to-depth ratio (shape factor) of the number and locations of dock doors located along one wall or two adjacent walls of the warehouse. Inserting a middle-cross-aisle in the storage area, storage racks are aligned either perpendicular or parallel to warehouse walls containing dock doors. As with the warehouse having storage racks aligned perpendicular to the warehouse wall, discrete and continuous formulations of the optimization problem are developed for both single- and dual-command travel and three scenarios for dock-door locations are investigated. </p><p> Our final contribution is the analysis of the performance of a unit-load warehouse when a storage region or storage regions can be either rectangle-shaped or contour-line-shaped. Particularly, we consider two cases for the locations of dock doors: equally spaced over an entire wall of the warehouse and centrally located on a wall, but with a specified distance between adjacent dock doors. Minimizing expected distance, the best rectangle-shaped configuration is determined and its expected distance is compared with the expected distance in its counterpart contour-line-shaped configuration.</p><p>

Many wake-up calls have been received for emergency response, due to natural disasters such as hurricanes, fires or man-made incidents, for example: oil and chemical spills, city bombings, and the terrorist attacks of 9-11. The emergency responders need to work in a coordinated, well-planned manner to best mitigate the impact of an emergency incident. Simulation systems as valuable tools provide a wider range of training at a much lower expense for emergency preparedness and response, and can be used for vulnerability assessment, organizing, educating and decision support. This is identified as the only feasible approach when it is difficult to emulate real-life experiences. This thesis presents an emergency evacuation training simulation, taking the demonstrative example of the SITE building of the University of Ottawa. The objective of the research is to design a multi-user distributed simulator to conduct the safety training in the scenarios of emergent evacuation. The real-time interaction and collaboration, in the simulation, among the users are achieved over HLA/RTI, the IEEE standard for distributed simulation and modeling.

<p> In deterministic computer experiments, a computer code can often be run at different levels of complexity/fidelity and a hierarchy of levels of code can be obtained. The higher the fidelity and hence the computational cost, the more accurate output data can be obtained. Methods based on the co-kriging methodology Cressie (2015) for predicting the output of a high-fidelity computer code by combining data generated to varying levels of fidelity have become popular over the last two decades. For instance, Kennedy and O&rsquo;Hagan (2000) first propose to build a metamodel for multi-level computer codes by using an auto-regressive model structure. Forrester et al. (2007) provide details on estimation of the model parameters and further investigate the use of co-kriging for multi-fidelity optimization based on the efficient global optimization algorithm Jones et al. (1998). Qian and Wu (2008) propose a Bayesian hierarchical modeling approach for combining low-accuracy and high-accuracy experiments. More recently, Gratiet and Cannamela (2015) propose sequential design strategies using fast cross-validation techniques for multi-fidelity computer codes. </p><p> This research intends to extend the co-kriging metamodeling methodology to study steady-state simulation experiments. First, the mathematical structure of co-kriging is extended to take into account heterogeneous simulation output variances. Next, efficient steady-state simulation experimental designs are investigated for co-kriging to achieve a high prediction accuracy for estimation of steady-state parameters. Specifically, designs consisting of replicated longer simulation runs at a few design points and replicated shorter simulation runs at a larger set of design points will be considered. Also, design with no replicated simulation runs at long simulation is studied, along with different methods for calculating the output variance in absence of replicated outputs. </p><p> Stochastic co-kriging (SCK) method is applied to an M/M/1, as well as an M/M/5 queueing system. In both examples, the prediction performance of the SCK model is promising. It is also shown that the SCK method provides better response surfaces compared to the SK method.</p><p>

The selection of right process, use of optimal machining parameters and specification of best tolerance parameters have been recognized by industry as key issues to ensure product quality and reduce production cost. The three issues have thus attracted a great deal of attention over last several decades. However, they are often addressed separately in existing publications. In reality, the three issues are closely interrelated. Analyzing the three issues in isolation will inevitably lead to inconsistent, infeasible, or conflicting decisions. To avoid the drawbacks, an integrated approach is proposed to jointly solve process selection, machining parameter optimization, and tolerance design problems. The integrated problem is formulated as a bi-criterion model to handle both tangible and intangible costs. The model is solved using a modified Chebyshev goal programming method to achieve a preferred compromise between the two conflicting criteria. The application of the proposed bi-criterion approach has been demonstrated by first using the single component single part feature case. The integrated approach is then extended to the multiple components multiple part features case (the assembly case). Examples are provided to illustrate the application of the two models and the solution procedure. The results have shown that the decisions on process selection, machining parameter selection and tolerance design can be made simultaneously using the models.

In metal cutting processes, chatter has been recognized as one of the main factors that limit machining productivity and affect product quality. Two different categories of chatter were classified by researchers, i.e., regenerative chatter and non-regenerative chatter, and in this thesis the former is mainly studied. Over the past few decades, though various chatter detection and suppression methods have been developed, their industrial acceptance is still very limited. This research work presents a new system for on-line chatter detection and suppression. Its detection module implements a statistical index to identify chatters by performing wavelet transform and conducting statistical analysis of positive wavelet transform modulus maxima (WTMM). To suppress chatter, two versions of fuzzy control modules, i.e., plain fuzzy control and self-regulating fuzzy control have been implemented. Unlike the previous chatter suppression systems, the new suppression module features two-way adjustment, i.e., both increasing and decreasing the amount of adjustment. Along with the use of single or multi-output control variables to suppress chatter, productivity is preserved as much as possible. The proposed system is implemented on a SERVO 2000 milling machine. Extensive tests have been carried out. The experimental results show that the wavelet-based chatter detection index can not only detect the existence of chatters but also distinguish the severity levels. The new chatter suppression module works reasonably well in most tests. However, its performance is adversely affected in the presence of non-regenerative vibrations due to the lack of workpiece or clamping rigidity. Further improvements need to be carried out for industrial applications.