http://hdl.handle.net/1957/16561 2013-05-25T14:40:11Z 2013-05-25T14:40:11Z Rebhuhn, Carrie M. http://hdl.handle.net/1957/38662 2013-05-20T19:36:12Z 2013-05-13T00:00:00Z

A multiagent approach to identifying innovation in design components Rebhuhn, Carrie M. Innovation is a key element for a product to achieve market success, but identifying it within product or even defining the term is a difficult task. Identifying innovation has been approached in many different ways. Experts in design engineering may identify innovative designs based on an analysis of a product's functions, and statistical techniques may be used to evaluate innovation within a set of products. While there are numerous ways to recognize innovation in a product, there is no straightforward way of identifying how much each component within a product contributes to its innovation. Multiagent systems face an analogous problem; though the performance of a system may be easily assessed, the complex interactions of the agents makes using this system performance to reward each agent ineffective. Difference rewards provide a mechanism for a multiagent system to better quantify the impact of an agent on the system's performance. We introduce the Creative Agents for Repository-Reliant Innovation Engineering (CARRIE) algorithm, which frames the problem of creating a design as supervised learning within a multiagent system. Agents simulate the design process by selecting components to create a product from their training data, and receive external evaluations based on the product-level innovation score. In order to propagate this score to the component selections, the CARRIE algorithm incorporates difference rewards to identify components that positively or negatively impact the overall innovation score within a set of products. Traditional application of the difference reward requires a way to calculate a system’s performance, and then a way to recalculate this performance when an agent is removed in simulation. This presents a problem when we only have the numerical evaluation of the innovation in a product to use as a system performance score, and no indication of how this innovation score was obtained. For this reason, the CARRIE algorithm uses a method by which we can calculate the system score based on the novelty scores of the components in a product. This enables the computation of the difference reward in this domain without actually having a mathematical formulation of an arbitrary system reward. Graduation date: 2013

2013-05-13T00:00:00Z Mehravaran, Yasaman http://hdl.handle.net/1957/38553 2013-05-13T16:57:14Z 2013-04-17T00:00:00Z

Hybrid Flowshop Scheduling with Dual Resources in a Supply Chain; Hybrid flowshop scheduling with dual resources in a supply chain Mehravaran, Yasaman This dissertation addresses a hybrid-flow shop scheduling problem with dual resource constraints in a supply chain. Most of the traditional scheduling problems deal with machine as the only resource. However, other resources such as labor is not only required for processing jobs but are often constrained. Considering the second resource (labor) makes the scheduling problems more realistic and practical to implement in industries. In this research labor has different skill levels and the skill level required to perform the setup could be different from that needed to perform the run. The setup time is sequence-dependent, and job release times and machine availability times are dynamic. Also machine skipping is allowed. In tactical supply chain decisions such as scheduling, the goal is to minimize the cost of producer. However, when looking at the whole network, minimizing the cost of the producer alone may not lead to minimizing the cost of the whole supply chain. In fact the coordination between the producer and other entities in the network can minimize the cost. In this dissertation coordination between producer and customers is considered in order to make effective scheduling decisions. The goal of this research is to minimize the work-in-process inventory for the producer and maximize customers' service level to maintain producer-customers coordination. A linear mixed-integer mathematical programming model is proposed and CPLEX solver is used to find solutions for generated example problems with branch-and-bound technique. As the problem is NP-hard in the strong sense three different meta-search heuristic algorithms based on tabu search are developed in order to quickly solve the scheduling problems. A total of 243 examples were generated in small, medium and large size problems. Search algorithms performance in small size problems can be assessed by comparing them with the optimal solution from branch-and-bound method. However, in medium and large size problems, branch-and-bound method cannot find the optimal solution and therefore for assessing the performance of search algorithms three different lower bounding methods are proposed. The first method is based on Logic-Based Benders Decomposition and the second and third methods are two different variations of iterative selective linear programming (LP) relaxation called fractional LP relaxation and positive LP relaxation. An experimental analysis based on a nested-factorial design with blocking is developed in order to identify statistically significant differences between the effectiveness and efficiency of the lower bounding methods and search algorithms. The results showed that the proposed search algorithms and lower bounding methods are very effective and efficient. On average the developed lower bounding methods tighten the lower bound found by branch-and-bound by 11.93%. The quality of search algorithms is the same as the upper bound found by branch-and-bound. However, the search algorithms are on average 3.8 times faster than the branch-and-bound method. Graduation date: 2013

2013-04-17T00:00:00Z Vejdani Noghreiyan, Hamid Reza http://hdl.handle.net/1957/38476 2013-05-06T23:31:00Z 2013-05-02T00:00:00Z

Control of spring-mass running robots Vejdani Noghreiyan, Hamid Reza We seek the control strategies that are applicable on legged robots and control them to run in real world as robust and efficient as animals. To achieve this goal, we need to understand the principles of legged locomotion and the control policies that animals use during running. In this study we tried to understand these principles by investigating birds' running experiments, and hypothesized their possible control policies that are important for real machines. We proposed two types of flight phase control techniques inspired from ground running birds for spring-mass running robots and derived mathematical formulas for the optimum design of the passive elements in these robots. For the control policies, we focused on flight phase because adjusting the leg parameters during the flight is very energy efficient and also the overall behavior of the system is very sensitive to the landing conditions that are determined during the flight phase of running. We first considered the change of the leg angle as the only control parameter during the flight phase. In the proposed control policies, three objective functions i) leg peak force, ii) axial impulse and iii) leg actuator work, all from passive stance phase, were considered to be regulated during running. It turned out that with a simple swing leg policy (constant leg angular acceleration), all the three objective functions can be nearly regulated at the same time, meaning that both goals of damage avoidance and energy efficiency can be fulfilled at once. After that, we investigated the effect of the leg length in addition to the leg angle on the dynamics of the spring-mass running robots. This control policy retains the steady state running by providing the equilibrium gait for each stride. The leg length and leg angle together make it possible for the robot to retain the steady state in the presence of a disturbance while limit the increase of the leg force which if increases may break the leg. In all of the control policies, the robot is purely passive during the stance phase and therefore the dynamics of the system comes from the passive dynamics of the system. Finally, we investigated the effect of the passive dynamics elements on the initiation of running. We derived mathematical formulas that determine the required stiffness and damping for the actuator to achieve the maximum possible performance given the physical limitations of the system. Graduation date: 2013

2013-05-02T00:00:00Z Pawar, Supriya V. http://hdl.handle.net/1957/38204 2013-05-24T19:02:03Z 2013-03-21T00:00:00Z

Fabrication of precipitation-hardened aluminum microchannel cooling plates for adsorption-based hydrogen storage systems Pawar, Supriya V. The need for clean and renewable fuel such as hydrogen is driven by a growing worldwide population and increasing air pollution from fossil fuels. One of the major barriers for the use of hydrogen in automotive industry is the storage of hydrogen. Physisorption is the most promising storage technique due to its high storage density, reversibility and rapid sorption kinetics besides being safe and volume-efficient. A major challenge for physisorption is the need to manage the heat of adsorption at cryogenic temperatures. In this thesis, a 6061 aluminum microchannel cooling plate is designed to remove the equivalent heat flux required by the adsorption of hydrogen within an adsorption bed. Therefore, the objective of this thesis is to determine whether laser welding and heat treating strategies can be developed for a 6061 aluminum microchannel cooling plate as part of a larger hydrogen storage thermal management system. Key manufacturing process requirements include controlling the hermeticity, strength and dimensional stability of the heat-treated weld joint. A hermetic microchannel cooling plate was successfully laser welded and heat treated using free convection in air to quench the solution heat treatment. The weld strength and warpage obtained were within acceptable limits. Experimental testing of the fabricated microchannel cooling plate showed acceptable percent error with an experimental heat removal rate within 13.4% of computational fluid dynamics (CFD) analyses and an average pressure drop error of 25%. Calculations show that the cooling plate developed could support a hydrogen storage thermal management system taking up 5.0% and 10.3% of the system displacement volume and mass, respectively. Graduation date: 2013

2013-03-21T00:00:00Z