Friction stir processing (FSP) has recently become an effective microstructural modifications technique. Reported results showed that for different alloys, FSP produces very fine equiaxed and homogeneous grain structure. FSP is considered to be a new processing technique and more experimental and analytical investigations are needed to advance the industrial utilization of FSP. Most of the work that has been done in the friction stir processing field is experimental and limited modeling activities have been conducted. Attempts to develop a predictive model to correlate the resulting microstructure with process parameters are scarce. In this work, commercial 5052 Aluminum alloy sheets are friction stir processed at different rotational and translational speeds. The effects of process parameters on the resulting microstructure and mechanical properties are investigated. The results show that FSP produces very fine and homogenous grain structure, and it is observed that smaller grain size structure is obtained at lower rotational speeds. It is also observed that the hardness of the processed sheet depends strongly on the rotational and translational speeds and varies widely within the processed region. The results suggest that the temperature achieved during processing plays an important role in determining the microstructure and properties of the processed sheet. In addition, a new modeling approach based on experiments and theory is proposed to predict the grain size of the friction stir processed material as a function of process parameters. The proposed approach involves determination of the strain rate distribution in the processed (deformation) zone based on the velocity fields of the material and correlating the strain rate distribution with the average grain size of the resulting microstructure using Zener-Holloman parameter.

Bone is a 3D dynamic and unique tissue that structurally adapts in response to mechanical stimuli. Comparative skeletal morphology is commonly utilized to infer ancient hominins' modes of locomotion; however, instances of remarkable gross similarity despite different modes of locomotion do occur. A common cited example is the similarity between the skeletal elements of bipedal human (Homo sapiens) hands/feet and quadrupedal black bear (Ursus americanus) front/hind paws. Through novel 3D Micro-CT and 2D histomorphology analysis, this thesis tests the hypothesis that a 3D microscopic analysis of biomechanically regulated cortical bone structures provides a more representative and accurate means to infer a species' mode of locomotion. Micro-CT data were collected at the mid-diaphysis of human (n=5) and bear (n=5) third metacarpal/metatarsal pairs and compared with independent and paired t-tests, Pearson correlation coefficients and Bland-Altman plots. Bone microarchitecture is quantifiable in 3D and accessible through non-destructive Micro-CT. Interspecies variation was present, however no significant cortical differences between elements of humans and bears was found. Histological inspection revealed further variation between and within species and element. A key limitation was sample size and further investigation of the relationship between mechanical loading and mode of locomotion is warranted.

This dissertation is motivated by two major factors. First, there have been no direct studies conducted for the relationship between market integrity and market efficiency and the driving forces behind the cross-sectional variations in market quality. Second, a better understanding the relationships among market integrity, market efficiency and other mechanism design factors for securities exchanges will facilitate securities exchanges achieve a satisfactory level of market quality. This dissertation consists of three chapters. In Chapter 1, a review of literature on market manipulation will be given. A series of common securities market manipulation strategies and corresponding market surveillance alerts will be explained and defined. In Chapter 2, we develop a testable hypothesis that market manipulation as proxied by the incidence of ramping alerts would raise transaction cost for completing larger trades. We find ramping alert incidence positively related to effective spreads in 8 of 10 turnover deciles from most liquid to thinnest-trading securities. The magnitude of the increase in effective spreads when ramping manipulation incidence doubles is economically significant, 30 to 40 basis points in many moderate liquidity deciles. This compares with an average effective spread of 72 basis points for index-listed securities in the most efficient electronic markets worldwide. In Chapter 3, In Chapter 3 of this thesis, we test the correlation between the levels of market integrity as proxied by the incidence of ramping alerts and a combination of proxies for factors from the following four potential drivers deciding the market quality across securities exchanges: ??? Securities Markets Trading Regulations ??? Securities Markets Technologies ??? Securities Market Infrastructure ??? Securities Market Participants The model we developed to test the correlation between the proxies for level of market integrity and seven proxies for the four potential drivers were estimated with Ordinary Least Square (OLS) and Two-stage Least Square (2SLS) error structures assumed, respectively to learn the most about the possible endogeneity of spreads and volatility. By performing Hausman-Wu specification tests, we concluded that simultaneity bias in the thickly-traded deciles is not material for the AI-Volatility and AI-Spread equation pairs. Subsequently, we used the PROBIT model to analyse the probability of adopting RTS across the 240 securities exchange deciles and the likelihood proves to be systematically related to four determinants in our sample. Finally we estimate the structural equations to investigate possible cross-equation correlation of the disturbances with either seemingly unrelated regression (SURL) estimation. Our findings are three-fold. Firstly, in the moderately-traded deciles, we find that the presence of a closing auction (CloseAucDum) reduces the incidence of ramping alerts. Trade-based manipulation proves more difficult when a manipulator???s counterparties can use closing auctions to unwind their intraday exposures. The RTS dummy variable is significantly positively related to alert incidence. In the absence of any panel data on the dynamic effects of adopting RTS, what we are observing in cross section is the perceived vulnerability of certain exchanges to manipulation and their consequent adoption of RTS plus the regulatory regimes required to have a salutary effect on market integrity. Second, in the moderately-traded deciles, we find that the closing auctions and more regulations in pursuit of market integrity lower quoted spreads. RTS and a regulation specifically prohibiting ramping indicate in cross-section the perceived likelihood of more ramping. Thirdly, in terms of the probability of the deployment of a real-time surveillance system, the estimations again differ by liquidity decile grouping. In the moderately-traded deciles, higher alert incidence, the presence of DMA, and higher FDI again increase the likelihood of adopting a real-time surveillance system. Our findings have a couple of policy implications for many securities exchanges in terms of market design and market surveillance. First, the exhibited relationship between alert incidence and effective spreads indicates trade-based manipulation has a significant impact on execution costs. Therefore, the prevention of securities market manipulation not only serves the indirect purpose of improving an exchange???s reputation for market integrity but also contributes directly to achieving a more efficient marketplace. Second, our results indicate that some market design changes can enhance the regulatory efforts to prevent securities market manipulations. For example, to prevent manipulators from marking the closing price, some exchanges could choose to adopt a closing auction or a random closing time, which would make manipulation more costly. Nevertheless, no securities exchange can be designed perfectly. Consequently, exchange and broker-level surveillance backed by effective regulatory enforcement is a necessary and pivotal complement to good design choices.

Thesis (M.Ch.E.)--University of Delaware, 2008. / Principal faculty advisors: Norman J. Wagner, Dept. of Chemical Engineering; and Eric W. Kaler, College of Engineering. Includes bibliographical references.

Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Arun Gokhale; Committee Member: Dr. Hamid Garmestani; Committee Member: Dr. Karl Jacob; Committee Member: Dr. Meilin Liu; Committee Member: Dr. Steve Johnson.

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 68-73).

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [239]-246).

Thesis (Ph.D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Gokhale, Arun; Committee Member: Gall, Kenneth; Committee Member: Garmestani, Hamid; Committee Member: Kurtis, Kimberly; Committee Member: Thadhani, Naresh

Thesis (M.S.)--Ohio State University, 2009. / Title from first page of PDF file. Includes vita. Includes bibliographical references (p. 108-109).

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 41-43).