The increasing competition between the companies forces them to develop the production in a continuous manner in order to maintain the competitiveness in the global market, and became as efficient and effective as possible. This master thesis is conducted at Getrag All Wheel Drive Company which is one of the largest suppliers for transmissions and powertrain systems .This Company has worked actively for long time to improve the production flow at the manufacturing departments by using usual methods. Because of the high complex and intersected flow that the company has, the management intended to adopt another approach that takes dynamic information into consideration, therefore, building a simulation model is the solution, where according to Banks et al (2001) the simulation is a duplication of a real-world process or system and its behaviour as it progress during the time, which is a very useful method to evaluate complex systems, instead of using usual mathematical means used tools. The simulation model created by using Banks et al (2001) simulation methodology, and ExtendSim software help. The resulted model used as a tool that provides great assistance to the decision makers, in order to develop the Conwip system which applied in the manufacturing line under study, and to investigate “What if” scenarios. The result of this study obtained after performing two experiments, where the first experiment gives recommendation regarding the optimal upper bound of the total amount of work that can be used in Conwip system, with the use of sensitivity analysis, and the second experiment analyse the overall all effect on the system after separating the paths of high and low volume products. This project proves the powerful side of using the simulation in situations where it’s too hard or even impossible to improve the performance of a manufacturing line i.e. when large number of variables involved and affecting the system.

The results of this thesis concern folding of one-dimensional objects in two dimensions: planar linkages. More precisely, a planar linkage consists of a collection of rigid bars (line segments) connected at their endpoints. Foldings of such a linkage must preserve the connections at endpoints, preserve the bar lengths, and (in our context) prevent bars from crossing. The main result of this thesis is that a planar linkage forming a collection of polygonal arcs and cycles can be folded so that all outermost arcs (not enclosed by other cycles) become straight and all outermost cycles become convex. A complementary result of this thesis is that once a cycle becomes convex, it can be folded into any other convex cycle with the same counterclockwise sequence of bar lengths. Together, these results show that the configuration space of all possible foldings of a planar arc or cycle linkage is connected. These results fall into the broader context of folding and unfolding <I>k</I>-dimensional objects in <i>n</i>-dimensional space, <I>k</I> less than or equal to <I>n</I>. Another contribution of this thesis is a survey of research in this field. The survey revolves around three principal aspects that have received extensive study: linkages in arbitrary dimensions (folding one-dimensional objects in two or more dimensions, including protein folding), paper folding (normally, folding two-dimensional objects in three dimensions), and folding and unfolding polyhedra (two-dimensional objects embedded in three-dimensional space).

This thesis will address several problems in discrete optimization. These problems are considered hard to solve. However, good approximation algorithms for these problems may be helpful in approximating problems in computational biology and computer science. Given an undirected graph G=(V,E) and a family of subsets of vertices S, the minimum crossing spanning tree is a spanning tree where the maximum number of edges crossing any single set in S is minimized, where an edge crosses a set if it has exactly one endpoint in the set. This thesis will present two algorithms for special cases of minimum crossing spanning trees. The first algorithm is for the case where the sets of S are pairwise disjoint. It gives a spanning tree with the maximum crossing of a set being 2OPT+2, where OPT is the maximum crossing for a minimum crossing spanning tree. The second algorithm is for the case where the sets of S form a laminar family. Let b_i be a bound for each S_i in S. If there exists a spanning tree where each set S_i is crossed at most b_i times, the algorithm finds a spanning tree where each set S_i is crossed O(b_i log n) times. From this algorithm, one can get a spanning tree with maximum crossing O(OPT log n). Given an undirected graph G=(V,E), and a family of subsets of vertices S, the minimum crossing perfect matching is a perfect matching where the maximum number of edges crossing any set in S is minimized. A proof will be presented showing that finding a minimum crossing perfect matching is NP-hard, even when the graph is bipartite and the sets of S are pairwise disjoint.

This thesis is composed of theoretical, experimental, and numerical studies. In Part I, it discusses fundamental challenges of the discrete element method, provides a set of algorithms for addressing them, and presents performance gains of an improved algorithm on a target computer platform. A new contact detection and force resolution algorithm based upon (i) the fast common-plane (FCP) algorithm, (ii) using axisaligned bounding boxes (AABBs) to perform a proximity search, (iii) estimating the time of collision, and (iv) accurate resolution of contact points is presented. Benchmark simulations indicate an order of magnitude increase in performance is achievable for a relatively small number of elements. A new parallel discrete element algorithm is presented which combines the domain decomposition, object-oriented, and perfectly parallel strategies of parallelism to eliminate the drawbacks of parallel discrete element algorithms put forth by past studies. A significant speed-up is observed in comparison to past studies in trials conducted on a NUMA-based SMP computer. In Part II, various applications of the discrete element method are reviewed, with an emphasis on ice-structure interaction. The conical design of the Kulluk drillship is of particular interest due to its success in operating in the Beaufort Sea from 1975- 1993 and its subsequent purchase and recommission by Shell in 2006. Three previous experimental studies and a unique set of full-scale data measurements form the basis for comparison of a concurrent experimental and numerical investigation. The results of a model scale experiment at the NRC-IOT are analyzed and presented, followed by results of the numerical simulations. A 1:40 scale replica of the Kulluk platform in level ice produces results which are consistent with past experiments and confirm expected trends as well as different regimes of results dependent on the ductile/brittle behavior of ice. The numerical setup models the full-scale platform in three dimensions with a 24-sided rigid conical structure, ice as an elastic brittle material with plate-bending elements, and platform mooring through the implementation of a spread mooring algorithm. Numerical results are in agreement with past results for ice thickness of less than 1.2m, confirming that the initial design goal of the Kulluk was achieved while still overestimating the loads in comparison to the full-scale data set. Two explanations are presented for the non-conformity of the experimental and numerical predictions to the full-scale data results.

There is increasing pressure from animal rights organizations (AROs) on restaurant chains, food retailers, and meat processors to implement more stringent farm animal welfare (FAW) requirements for their suppliers. In the United States, AROs have recently initiated successful ballots to phase out confinement practices in several states. In Canada AROs have been pressuring both public and private sector stakeholders to improve FAW. Are FAW issues, however, paramount in the minds of Canadian consumers? Is the demand for more stringent FAW protocols primarily determined by a subset of consumers with very strong preferences or does it signal a more fundamental underlying change in consumer and societal preferences? Given the credence nature of FAW, who do consumers trust (i.e., government vs. private industry vs. independent third parties) in the market place for the provision of FAW quality assurances? What are the determinants of trust in these organizations for providing accurate information about animal welfare?<p> In order to answer these questions, a stated preference consumer survey encompassing FAW issues specific to the Canadian pork sector was tested on two samples of consumers in summer 2008, namely: a general population sample (GPS) across Canada and a sample of AROs members. Consumers participated in a purchase experiment where they had to chose between pork chops characterized by combinations of different levels of FAW attributes (i.e., housing system, gestation stalls, and use of antibiotics), quality verifying organization, and price. Multinomial Logit and Latent Class Logit Models were used to analyse the survey data.<p> Surprisingly, outdoor system does not seem to resonate well with Canadians, as both the GPS and the members of the AROs discounted this attribute. As expected, the AROs members have much stronger preferences for the other FAW attributes than have consumers in the GPS. Nevertheless, significant heterogeneity exists within consumer preferences. Five classes of consumers were identified in the GPS with respect to their preferences for FAW. At one end of the spectrum are the FAW sensitive consumers (12.3%) that have higher willingness-to-pay (WTP) for FAW, while at the other end of the spectrum Price Conscious consumers (18.3%) do not exhibit any WTP for FAW. The other three classes (69.4%) comprise respondents with mixed perceptions regarding FAW. Government and Third Party verification of FAW quality assurances had the strongest influence on consumers preferences in both samples. As well, scientific experts in FAW along with the above two organizations are the most credible in providing information about the welfare of pigs. The extent to which these organizations are knowledgeable about the welfare of pigs is the most important factor enhancing consumers trust. Results from this study suggest that there are potential marketing opportunities for pork chops sourced from pigs raised on farms where sows are kept in groups, and where credible quality assurances can be established, that private industry could consider. As well, the results suggest that consumers would derive benefits from the government taking a more active role with respect to validating FAW quality assurances.

This study considered using a relatively new method to study soil-tool wear which could drastically reduce the time and associated costs of traditional wear studies. The goal was to utilize discrete element method (DEM) simulations to recreate the results of a circular soil bin test in order to develop a relationship that could be used to predict wear under different conditions. Through the application of DEM, simulations could be used to study different materials or designs intended to result in improved wear performance.<p> Three replications of aluminum cylindrical bars were worn during 400 km of travel in a circular soil bin. Wear was quantified by measuring the change in radius of the cylinders at 18-degree intervals around their circumference. Mass data were also obtained to provide an overall average of wear occurring on the bar and to validate the radii measurements.<p> The DEM simulations were executed using EDEM software. Conditions present in the physical soil bin trials were simulated by recreating components in the soil bin and incorporating soil properties that were directly measured, using representative soil samples. Forces exerted on the bar by the soil and the relative velocities between the soil and tool were used to generate a relationship to predict wear of the bar. The wear equation was verified using a portion of the experimental data from the soil bin.<p> The wear model showed promise in predicting the amount of wear recorded in the soil bin through the application of DEM-predicted compressive forces and relative velocities between the tool and soil particles. The Archard equation for wear was modified to create a non-linear equation. Plotting the measured wear against the wear predicted from the fitted equation produced a trendline with a slope of 0.65. Although a perfect correlation would have produced a slope of 1, the model was able to predict a large portion of the wear that occurred. Refinement of the model could further be achieved with changes in the design of the geometry used in the simulation and through verification of force predictions with experimental data. Because of the variable nature of wear, additional replications of tools in the soil bin would have increased the number of data points available to create the model and reduced the impact of outlying data. With these recommended improvements, the wear model has the ability to very accurately predict the wear of a cylindrical bar.

<p>The goal of this dissertation is to provide a coherent and computationally feasible basis for the analysis of the dynamics of both housing supply and demand from a microeconomics perspective. The dissertation includes two papers which incorporate unique micro data with new methodological approaches to examine housing market dynamics. The first paper models the development decisions of land owners as a dynamic discrete choice problem to recover the primitives of housing supply. The second paper develops a new methodology for dynamically estimating the demand for durable goods, such as housing, when the choice set is large.</p><p>In the first paper, using the new data set discussed above, I develop and estimate the first dynamic microeconometric model of supply. Parcel owners maximize the discounted sum of expected per-period profits by choosing the optimal time and nature of construction. In addition to current profits, the owners of land also take into account their expectations about future returns to development, balancing expected future prices against expected future costs. This forward looking behavior is crucial in explaining observed aggregate patterns of construction. Finally, the outcomes generated by the parcel owners' profit maximizing behavior, in addition to observable sales prices, allow me to identify the parameters of the per-period profit function at a fine level of geography.</p><p>By modeling the optimal behavior of land owners directly, I can capture important aspects of profits that explain both market volatility and geographic differences in construction rates. In particular, the model captures both the role of expectations and of more abstract costs (such as regulation) in determining the timing and volatility of supply in way that would not be possible using aggregate data. The model returns estimates of the various components of profits: prices, variable costs, and the fixed costs of building, which incorporate both physical and regulatory costs.</p><p>Estimates of the model suggest that changes in the value of the right-to-build are the primary cause of house price appreciation, that the demographic characteristics of existing residents are determinants of the cost environment, and that physical and regulatory costs are pro-cyclical. Finally, using estimates of the profit function, I explain the role of dynamics in determining the timing of supply by distinguishing the effects of expected future cost changes from the effects of expected future price changes. A counterfactual simulation suggest that pro-cyclical costs, combined with forward looking behavior, significantly dampen construction volatility. These results sheds light on one of the empirical puzzles of the housing market - what determines the volatility of housing construction?</p><p>In the second paper, I outline a tractable model of neighborhood choice in a dynamic setting along with a computationally straightforward estimation approach. The approach allows the observed and unobserved features of each neighborhood to evolve in a completely flexible way and uses information on neighborhood choice and the timing of moves to recover semi-parametrically: (i) preferences for housing and neighborhood attributes, (ii) preferences for the performance of the house as a financial asset, and (iii) moving costs. In order to accommodate a number of important features of housing market, this approach extends methods developed in the recent literature on the dynamic demand for durable goods in a number of key ways. The model and estimation approach are applicable to the study of a wide set of dynamic phenomena in housing markets and cities. These include, for example, the analysis of the microdynamics of residential segregation and gentrification within metropolitan areas. More generally, the model and estimation approach can be easily extended to study the dynamics of housing and labor markets in a system of cities.</p> / Dissertation

<p>This dissertation considers incentives arising from equilibrium influences that affect the sequence of decisions that lead to family formation. The first chapter examines how state regulations directly aimed at abortion providers affect the market for abortion in the United States. Estimates from a dynamic model of competition among abortion providers show that regulations' main impact is on the fixed costs of entry for providers. Simulations indicate that the removal of regulations would promote entry and competition among abortion providers, and because abortions are found to be price sensitive, this would lead to increases in the number of abortions observed. The second chapter tests if an important negative externality of abortion access exists, namely whether abortion access makes prospective fathers more likely to leave pregnant women. Designing a number of empirical tests, I confirm that in some areas where abortion is more accessible women who give birth are more likely to be single mothers, rather than sharing parental responsibility with the biological father. The final chapter, which is joint work with Peter Arcidiacono and Marjorie McElroy, examines how gender ratios influence bargaining power in romantic relationships between men and women. Gender ratios, by influencing the prospects of matching, allow us to estimate preferences for various match characteristics and activities. We find men prefer sexual relationships more than women at high school ages, and that men and women trade off their preferred partner for an increased chance of matching.</p> / Dissertation

The approaches for discretizing the direction variable in particle transport calculations are the discrete-ordinates method and function-expansion methods. Both approaches are limited if the transport solution is not smooth. Angular discretization errors in the discrete-ordinates method arise from the inability of a given quadrature set to accurately perform the needed integrals over the direction ("angular") domain. We propose that an adaptive discrete-ordinate algorithm will be useful in many problems of practical interest. We start with a "base quadrature set" and add quadrature points as needed in order to resolve the angular flux function. We compare an interpolated angular-flux value against a calculated value. If the values are within a user specified tolerance, the point is not added; otherwise it is. Upon the addition of a point we must recalculate weights. Our interpolatory functions map angular-flux values at the quadrature directions to a continuous function that can be evaluated at any direction. We force our quadrature weights to be consistent with these functions in the sense that the quadrature integral of the angular flux is the exact integral of the interpolatory function (a finite-element methodology that determines coefficients by collocation instead of the usual weightedresidual procedure). We demonstrate our approach in two-dimensional Cartesian geometry, focusing on the azimuthal direction The interpolative methods we test are simple linear, linear in sine and cosine, an Abu-Shumays “base” quadrature with a simple linear adaptive and an Abu-Shumays “base” quadrature with a linear in sine and cosine adaptive. In the latter two methods the local refinement does not reduce the ability of the base set to integrate high-order spherical harmonics (important in problems with highly anisotropic scattering). We utilize a variety of one-group test problems to demonstrate that in all cases, angular discretization errors (including "ray effects") can be eliminated to whatever tolerance the user requests. We further demonstrate through detailed quantitative analysis that local refinement does indeed produce a more efficient placement of unknowns. We conclude that this work introduces a very promising approach to a long-standing problem in deterministic transport, and we believe it will lead to fruitful avenues of further investigation.

The promise and potential of controllers that can reconfigure themselves in the case of control effector failures and uncertainties, and yet guarantee stability and provide satisfactory performance, has led to fault tolerant control being an active area of research. This thesis addresses this issue with the design of two fault tolerant nonlinear Structured Adaptive Model Inversion control schemes for systems with fixed magnitude discrete controls. Both methods can be used for proportional as well as discrete controls. However, discrete controls constitute a different class of problems than proportional controls as they can take only binary values, unlike proportional controls which can take many values. Two nonlinear control laws based on Structured Adaptive Model Inversion are developed to tackle the problem of control failure in the presence of plant and operating environment uncertainties. For the case of redundant actuators, these control laws can provide a unique solution. Stability proofs for both methods are derived and are presented in this thesis. Fault Tolerant Structured Adaptive Model Inversion that has already been developed for proportional controls is extended here to discrete controls using pulse width modulation. A second approach developed in this thesis is Fault Tolerant Control Allocation. Discrete control allocation coupled with adaptive control has not been addressed in the literature to date, so Fault Tolerant Control Allocation for discrete controls is integrated with SAMI to produce a system which not only handles discrete control failures, but also accounts for uncertainties in the plant and in the operating environment. Fault tolerant performance of both controllers is evaluated with non real-time nonlinear simulation for a complete Mars entry trajectory tracking scenario, using various combinations of control effector failures. If a fault is detected in the control effectors, the fault tolerant control schemes reconfigure the controls and minimize the impact of control failures or damage on trajectory tracking. The controller tracks the desired trajectory from entry interface to parachute deployment, and has an adaptation mechanism that reduces tracking errors in the presence of uncertainties in environment properties such as atmospheric density, and in vehicle properties such as aerodynamic coefficients and inertia. Results presented in the thesis demonstrate that both control schemes are capable of tracking pre-defined trajectories in the presence of control failures, and uncertainties in system and operating environment parameters, but with different levels of control effort.