Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
2 results
Search Results
Item SOCIOTECHNICAL NETWORK MODELING TO QUANTITATIVELY ANALYZE THE IMPACT OF BLOCKCHAIN ON THE RISK OF PROCURING COUNTERFEIT ELECTRONICS(2024) Akhavantaheri, Hirbod; Sandborn, Peter PS; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation develops sociotechnical agent-based network modeling to quantitatively analyze the impact of blockchain and other related policies on the supply-chain risk associated with the procurement of counterfeit electronics in critical systems. Safety-critical, mission-critical, and infrastructure-critical systems (e.g., aerospace, transportation, defense, and power generation) are forced to source parts from a supply chain that they do not control over exceptionally long periods of time. Critical systems are exposed to the dual risks of the impacts of system failure and the exposure to the vagaries of the marketplace over decades. Therefore, critical-systems operators, manufacturers, and sustainers, must implement policies and technologies to reduce the risk of obtaining counterfeit parts. Several policies, ranging from debarment and claw back to “hop counting,” have been considered and used to mitigate such risks. One technology that critical-system operators, manufacturers, and sustainers could adopt is distributed digital ledger (i.e., blockchain) for the supply chain. This dissertation does not focus on how such a blockchain could be implemented but rather on how (and if) blockchain for the supply chain can provide value for verifying the authenticity of parts when prolonged periods of time (decades) elapse between part manufacturing and part sourcing. Additionally, during a part’s ownership changes, supply-chain actors may choose to participate in the distributed ledger based on individual incentives and can recuse themselves from such participation later. The lack of complete participation may affect the designed functionality, and the consequences of lack of participation need to be understood. Using a comprehensive supply-chain model, it can be shown that blockchain for supply chain can reduce the prevalence of counterfeit electronics in the supply chain of critical systems by up to 70%. However, such a reduction requires near complete participation by all supply-chain stakeholders, which is not likely. Due to the relatively high cost of ownership transfer on a blockchain, and the indirect cost of supply-chain information disclosure, a high participation rate is not anticipated. Although blockchain can have benefits in other aspects of supply chain, it may not be a viable solution to combat the counterfeit electronics problem.Item Generating Feasible Spawn Locations for Autonomous Robot Simulations in Complex Environments(2022) Ropelato, Rafael Florian; Herrmann, Jeffrey W; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Simulations have become one of the main methods in the development of autonomous robots. With the application of physical simulations that closely represent real-world environments, the behavior of a robot in a variety of situations can be tested in a more efficient manner than performing experiments in reality. With the implementation of ROS (Robot Operating System), the software of an autonomous system can be simulated separately without an existing robot. In order to simulate the physical environment surrounding the robot, a physics simulation has to be created through which the robot navigates and performs tasks. A commonly used platform for such simulations is Unity which provides a wide range of simulation capabilities as well as an interface for ROS. In order to perform multi-agent simulations or simulations with varying initial locations for the robot, it is crucial to find unobstructed spawn locations to avoid undesirable situations with collisions upon start of the simulation. For this purpose, multiple methods were implemented with this research, in order to generate feasible spawn locations within complex environments. Each of the three applied methods generates a set of valid spawn positions, which can be used to design simulations with varying initial locations for the agents. To assess the performance and functionality of these approaches, the algorithms were applied to several environments varying in complexity and scale. Overall, the implemented approaches performed very well in the applied environments, and generated mainly correctly classified locations which are suitable to spawn a robot. All approaches were tested for performance and compared in respect to their fitness to be applied to environments of varying complexity and scale. The resulting algorithms can be considered a efficient solutions to prepare simulations with multiple initial locations for robots and other test objects.