A concurrent approach to automated manufacturing process planning

textWith the increasing demand of fast-paced and hybrid manufacturing processes in modern industry, it is desirable to expedite the iterations between design and manufacturing through intelligent computational techniques. In this research, we propose a concurrent approach of this kind to streamline the design and manufacturing processes. With this approach, a CAD design is automatically analyzed in terms of its manufacturability in the early design stage. If the part is manufacturable, a set of process plans optimized in time, cost, fixture quality and tolerance satisfaction are reported in real time. If the part is not manufacturable, the potential design changes are provided for better manufacturing. In the approach, the geometric information of 3D models and the empirical knowledge in manufacturing processes, fixtures, and tolerances are combined and encapsulated into a graph-grammar based reasoning. The reasoning systematically extracts meaningful manufacturing details that later constitute complete process plans for any given solid model. The plans are then evaluated and optimized using a specially designed multi-objective best first search technique. The complete approach enables a concurrent and efficient manufacturability analysis tool that closely resembles real manufacturing planning practice. Numerous case studies with real engineering parts are presented to characterize the novelty and contributions of this approach. The optimality of the suggested plans is verified through computational comparisons, and the practicality of the plans is validated with hands-on implementations on the shop floor.Mechanical Engineerin

Essays on economics of information, contract and experimentation

This thesis consists of three chapters. In the first chapter, I explore a two-period economy with a three-tier hierarchy in which the principal without full commitment decides how and when to motivate a productive intermediary (agent one) to privately sub-contract and collaborate with another agent (agent two) on a project with uncertain quality. The dynamic moral hazard problem arises due to the agents’ hidden effort choice and the opportunity for future work. Besides free riding, the agent one’s exclusion and over-investment incentives need to be considered due to his private sub-contract option. Both the dominant incentive constraint in the optimal short term contract and the principal’s investment decision depend on the project’s value-cost ratio, the level of synergy in the partnership and the amount of patience. In general, the principal under-invests and stops earlier compared to the first-best outcome. However, there exist scenarios in which agent one always over-invests when the individual work is motivated, and the principal might compromise to motivate a higher effort level by over-investing relative to the static game, especially if the synergy is positive but small and the project’s value-cost ratio is medium. In a two-tier hierarchy, the principal can be weakly better off, but the inefficiency caused by agent one’s private link to the other agent still exists. In the second chapter, I study how a principal motivates an uninformed agent to learn about, and reveal, his quality through private experiments. The principal commits to a reward scheme and she aims to assign the rewards to correspond as closely as possible to the quality of the agent. To get a high reward, the agent experiments privately and discloses the results selectively. I show that the optimal reward scheme features an increasing step function: the initial steps encourage a potential good type agent to continue experiments after early successes; the later steps are designed to deter a bad type agent from over-experimentation after a failure, and the scheme becomes flat when enough successes are reported. If the agent’s incentives to deviate from the intended path of experimentation are weak, a one-step function is optimal: the agent receives a bonus if he reports enough successes; otherwise, he only gets a non-negative compensation. I characterise the conditions where the principal achieves the same efficiency level relative to a public information environment. The third chapter is an extension of the second chapter. I consider a situation in which an uninformed agent persuades a principal for a high reward through costly private experimentation. I show the existence of three types of equilibria as well as their conditions: no-experiment equilibrium, separating equilibria with learning and pooling equilibria with learning. The participation threshold determines the upper bound of the entire set of equilibria, and the over-experimentation determines the boundary between the separating and pooling equilibria with learning. As the agent’s value-cost ratio or prior belief increases, the set of separating equilibria with learning shrinks but the set of pooling equilibria with learning expands. Moreover, when the agent can pre-commit to report a specific number of successes to prove his quality, he tends to commit to a number that is as small as possible

A Case of Severe Pleural Effusion and Pulmonary Dysfunction Associated with Occupational Exposure to Asphalt Tar Smoke is Reported

Asphalt and tar transportation personnel are often exposed to the polluted air environment of asphalt fumes, tar and diesel exhaust. This long-term occupational exposure can adversely affect lung function, causing fibrosis, pleural effusion, and inflammation. This paper reports a case of pleural effusion in a 35-year-old male who had been engaged in asphalt paving and transportation for 5 years. There was no occupational exposure protection during the working period. The patient had dyspnea, expectoration, and pleural effusion for more than 1 month. After admission, thoracic drainage and pleural cauterization dissection were performed, and the symptoms were relieved. However, pulmonary fibrosis and visceral pleural thickening are challenging to reverse, and patients still have pulmonary dysfunction and the risk of continuing to develop lung consolidation. Therefore, the personnel engaged in asphalt and tar transportation should be well-protected to reduce occupational exposure

Establishment of the model system between phytochemicals and gene expression profiles in Macrosclereid cells of Medicago truncatula

Macrosclereid cells, which are a layer in the seed coat of Medicago truncatula, accumulate large amounts of phytochemicals during their development. But little is known about the complex and dynamic changes during macrosclereid cell development. To characterize the phytochemicals and the related gene expression during the development of M. truncatula macrosclereid cells, a high performance liquid chromatography-mass spectrometry (HPLC-MS) assay and microarray study were conducted on transcriptome changes from macrosclereid cell during seed development. A total of 16 flavonoids by HPLC-MS and 4861 genes exhibited significant differences at transcript levels by microarray analysis were identified for macrosclerid cells at six different time points during seed development. 815 abiotic and biotic stress genes, 223 transcriptional factors (TFs), and 155 annotated transporter proteins exhibited differential expression during the development of macrosclereid cells. A total of 102 genes were identified as involved in flavonoid biosynthesis, phenypropanoid biosynthesis, and flavone and flavonol biosynthesis. We performed a weighted gene co-regulatory network (WGCNA) to analyze the gene-flavonoid association and rebuilt the gene regulatory network during macrosclereid cell development. Our studies revealed that macrosclereid cells are, beside as the first barrier of defense against diseases, an excellent model system to investigate the regulatory network that governs flavonoid biosynthesis

Microlensing effect of charged spherically symmetric wormhole

We systematically investigate the microlensing effect of charged spherically symmetric wormhole, where the light source is remote from the throat. Remarkably, there will be at most three images by considering the charge part. We study all situations including three images, two images, and one image, respectively. The numerical result shows that the range of total magnification is from $10^5$ to $10^{-2}$ depending on various metrics. In the case of three images, there will be two maximal values of magnification (a peak, and a gentle peak) when the contribution via mass is much less than that of charge. However, we cannot distinguish the case that forms three images or only one image as the total magnification is of order $10^5$. Finally, our theoretical investigation could shed new light on exploring the wormhole with the microlensing effect.Comment: 10 pages, 9 figure

Extremum Seeking Based Fault-Tolerant Cooperative Control for Multiagent Systems

We propose a novel fault-tolerant cooperative control strategy for multiagent systems. A set of unknown input observers for each agent are constructed for fault detection. Then a real-time adaptive extremum seeking algorithm is utilized for adaptive approximation of fault parameter. We prove that the consensus can be still reached by regulating the interconnection weights and changing the connection topology of the fault agent. A numerical simulation example is given to illustrate the feasibility and effectiveness of the proposed method