Computationally efficient representation of statistically described material microstructure for tractable forming simulations

The purpose of this project is to reduce a large statistical distribution of metal microstructure orientations to a manageable distribution to be used in metal forming simulations. Microstructure sensitive simulations at the macro-scale are impractical, because with so many state variables associated with material microstructure data, these simulations are extremely computationally expensive. The goal was to develop a framework to accurately model plastic material response while repre- senting the material microstructure in a more compact form, reducing 106 or more microstructure orientations to a significantly smaller statistical distribution of representative orientations. This will significantly increase the computational efficiency and make the design process known as mi- crostructure sensitive design (MSD) feasible for industry applications. This framework is applied to metals with both cubic and hexagonal structure to validate this approach for slip and twinning deformation mechanisms. Performing microstructure sensitive metal-forming simulations is widely recognized as a computational challenge because of the need to store large sets of state variables related to microstructure data. This makes the investigation of the accuracy of smaller, representative data sets in these simulations profitable. The project accomplished two main goals; the development of an effective fitting algorithm to generate compacted data sets and validation of the framework for data compaction on metals with cubic structure, and hexagonal symmetry, with and without twinning. The research was applied to oxygen-free high-conductivity copper (OFHC Cu) and 6016 aluminum (Al-6016) for application of the framework to cubic metals. An anisotropic (clock-rolled) zirconium (Zr) texture was used to develop the framework for hexagonal metals. The minimum accurate data set for cubic was determined to be 825 orientations and for hexagonal metals, considering twinning and absence of twinning, the minimum number was 1600 orientations. This compaction method will increase the computational speed of microstructure sensitive forming simulations by several orders of magnitude, contributing to the computational feasibility of microstructure informed design

Computationally efficient representation of statistically described material microstructure for tractable forming simulations

The purpose of this project is to reduce a large statistical distribution of metal microstructure orientations to a manageable distribution to be used in metal forming simulations. Microstructure sensitive simulations at the macro-scale are impractical, because with so many state variables associated with material microstructure data, these simulations are extremely computationally expensive. The goal was to develop a framework to accurately model plastic material response while representing the material microstructure in a more compact form, reducing 106 or more microstructure orientations to a significantly smaller statistical distribution of representative orientations. This will significantly increase the computational efficiency and make the design process known as microstructure sensitive design (MSD) feasible for industry applications. This framework is applied to metals with both cubic and hexagonal structure to validate this approach for slip and twinning deformation mechanisms. Performing microstructure sensitive metal-forming simulations is widely recognized as a computational challenge because of the need to store large sets of state variables related to microstructure data. This makes the investigation of the accuracy of smaller, representative data sets in these simulations profitable. The project accomplished two main goals; the development of an effective fitting algorithm to generate compacted data sets and validation of the framework for data compaction on metals with cubic structure, and hexagonal symmetry, with and without twinning. The research was applied to oxygen-free high-conductivity copper (OFHC Cu) and 6016 aluminum (Al-6016) for application of the framework to cubic metals. An anisotropic (clock-rolled) zirconium (Zr) texture was used to develop the framework for hexagonal metals. The minimum accurate data set for cubic was determined to be 825 orientations and for hexagonal metals, considering twinning and absence of twinning, the minimum number was 1600 orientations. This compaction method will increase the computational speed of microstructure sensitive forming simulations by several orders of magnitude, contributing to the computational feasibility of microstructure informed design

Opinion disparity in hypergraphs with community structure

The division of a social group into subgroups with opposing opinions, which we refer to as opinion disparity, is a prevalent phenomenon in society. This phenomenon has been modeled by including mechanisms such as opinion homophily, bounded confidence interactions, and social reinforcement mechanisms. In this paper we study a complementary mechanism for the formation of opinion disparity based on higher-order interactions, i.e., simultaneous interactions between multiple agents. We present an extension of the planted partition model for uniform hypergraphs as a simple model of community structure and consider the hypergraph SIS model on a hypergraph with two communities where the binary ideology can spread via links (pairwise interactions) and triangles (three-way interactions). We approximate this contagion process with a mean-field model and find that for strong enough community structure, the two communities can hold very different average opinions. We determine the regimes of structural and infectious parameters for which this opinion disparity can exist and find that the existence of these disparities is much more sensitive to the triangle community structure than to the link community structure. We show that the existence and type of opinion disparities are extremely sensitive to differences in the sizes of the two communities.Comment: 14 pages, 8 figure

Toward an Understanding of the Economics of Charity: Evidence from a Field Experiment

This study develops theory and uses a door-to-door fundraising field experiment to explore the economics of charity. We approached nearly 5000 households, randomly divided into four experimental treatments, to shed light on key issues on the demand side of charitable fundraising. Empirical results are in line with our theory: in gross terms, our lottery treatments raised considerably more money than our voluntary contributions treatments. Interestingly, we find that a one standard deviation increase in female solicitor physical attractiveness is similar to that of the lottery incentive¡ªthe magnitude of the estimated difference in gifts is roughly equivalent to the treatment effect of moving from our theoretically most attractive approach (lotteries) to our least attractive approach (voluntary contributions).

A Study on How to Avoid a Layoff and How People Recover From a Layoff

This project addresses the topic of layoffs. More specifically, it addresses if the factors of commitment training and performance affect investment in an employee. Investment was used because of the link that it displays to layoffs. Also, it addresses alternatives that an employee can take after being laid off. In order to gather data to address these topics, a web-based survey was designed. This survey was distributed to the graduate students at WPI. The results showed that commitment plays the largest, and possibly the only significant, role in determining investment, and that most of the survey responders primarily seek some kind of income after being laid off

DNA Fingerprinting

This IQP analyzed DNA fingerprinting technology. Different procedures of DNA analysis, including RFLP and PCR, and the progression from analysis of VNTRs to STRs were discussed. The methods used for collecting, handling, storing and processing forensic evidence were enumerated. The development of legal precedent to permit the use of DNA evidence in the courtroom was reviewed with particular emphasis for landmark court cases and the evidence assessment systems set forth by presiding judges. The ethics of DNA databases with relation to informed consent for taking DNA samples, public discourse about the pitfalls of DNA fingerprinting, privacy rights in relation cold-hit techniques, the retention of DNA samples, and the use of private corporations to analyze DNA fingerprints were examined

The Hidden Benefits of Control: Evidence from a Natural Field Experiment

An important dialogue between theorists and experimentalists over the past few decades has raised the study of the interaction of psychological and economic incentives from academic curiosity to a bona fide academic field. One recent area of study within this genre that has sparked interest and debate revolves around the “hidden costs” of conditional incentives. This study overlays randomization on a naturally-occurring environment in a series of temporally-linked field experiments to advance our understanding of the economics of charity and test if such “costs” exist in the field. This approach permits us to examine why people initially give to charities, and what factors keep them committed to the cause. Several key findings emerge. First, there are hidden benefits of conditional incentives that would have gone undetected had we maintained a static theory and an experimental design that focused on short run substitution effects rather than dynamic interactions. Second, we can reject the pure altruism model of giving. Third, we find that public good provision is maximized in both the short and long run by using conditional, rather than unconditional, incentives.