Dissertation Defense Announcements

Thermal stress has been identified as one of the major failure causes in the power module. It is generated from the mechanical strain by severely varying temperatures at different loci in the power module and the different coefficients of the thermal expansion of materials, where the varying temperatures result from the real-time power loss across the power converter. This thermal stress accelerates the degradation of semiconductor devices, downgrades the system quality and efficiency, and eventually causes catastrophic system breakdowns and extensive economic losses. Therefore, this research is dedicated to investigating both local control level methods and system level strategies to ameliorate the real-time power loss in order to reduce the thermal stress in the power module, thereby extend the component lifetime and enhance the system reliability. A finite-control-set model predictive control (FCS-MPC) is introduced and deductively investigated from the local control level. Its variable switching frequency property is derived through the geometry analysis on the voltage vector space. It realizes the switching frequency variation autonomously by the loading power. By taking advantage of this property, the power loss is leveled in the real-time operation by FCS-MPC, and a more mitigated thermal profile is acquired compared with the one by the conventional controller. Furthermore, a centralized thermal stress oriented dispatch (TSOD) system level strategy is proposed for multiple paralleled distributed energy resource systems, which helps to reduce the thermal stress in the power module of paralleled converters. It is thermal stress oriented and takes effect according to the real-time junction temperature variation, the health condition of the individual converter, and the system operation. Two local control level methods, the switching frequency variation and the reactive power injection, are imported separately as the dispatch algorithm to generate the expected power loss. Dealing with the varying mission profile, the more mitigated thermal profiles are achieved for all converters with the assistance of the proposed TSOD strategy.

Family business leaders often include preserving socioemotional wealth (SEW) and successful intergenerational succession efforts in their list of primary non-economic goals, yet most next-generation family members seek careers outside of the family business.
This research aims to understand how internal family dynamics affect the development of psychological ownership feelings towards the family business in next-generation family members. The moderating effect of gender, as socially constructed, was also explored.
Data was collected using a snowball technique and an anonymous online survey (n=161) and was analyzed using regression analysis. Next-generation family members were encouraged to participate regardless of their ownership of, or employee status within, the business. The family dynamics measured were cognitive cohesion, emotional cohesion, adaptability, communication, intergenerational attention to needs, and authority. Findings are included, followed by discussion, limitations, and future directions for research. Currently, family business scholars have a limited understanding of how and when psychologically related micro-factors manifest in next-generation family members; however, relationships have been identified between a business family's internal dynamics and the development of certain attitudes, beliefs, and feelings held by their next-generation family members. Despite this research's similarities to past examples in the SEW and related literature streams, no support was found for this study's hypothesized relationships. Additional empirical research is necessary to understand when and how a business family's internal dynamics influence the manifestation of psychological ownership feelings in their next-generation family members.

With the introduction of job embeddedness theory, turnover research shifted away from the precursors of why people leave and focused on why people stay. Distinct from similar constructs, such as job satisfaction and organizational commitment, job embeddedness includes community-related issues in addition to job-related issues. While existing literature has evaluated alternate ways to measure the job embeddedness construct, variable-centered approaches continue to be utilized. This approach implicitly assumes that being high or low on job embeddedness perceptions in the form of an overall composite indicates that individuals perceive each aspect and their attachment ties similarly. Thus, this study advances the job embeddedness theoretical framework by engaging in a person-centered approach. This study found that the presumed underlying factors used to measure job embeddedness were best represented by a six-factor model through confirmatory factor analysis. In addition, this study conducted a latent profile analysis to examine patterns in response indicators within the sample data and found that distinct job embeddedness profiles emerged. These profiles showed unique patterns of job-based and non-job-based experiences that relate to staying on the job. Lastly, this study examined each job embeddedness profile and compared them with respect to job satisfaction, organizational commitment, and turnover intentions.

The Tax Cuts and Jobs Act of 2017 (TCJA) provides a novel context in which to examine the effects of U.S. taxation of foreign earnings on the behavior of multi-national corporations (MNCs). Prior to the TCJA, the U.S. levied taxes on an MNC’s worldwide earnings, deferred until firms repatriated the funds to U.S. The worldwide taxation and deferral until repatriation led to firms holding significant amounts of cash offshore. By 2017, there was an estimated $2.8 trillion of repatriatable funds “trapped” offshore. Prior legislation intended to encourage repatriation offered temporary “tax holiday” measures. The TCJA lowered corporate tax rates for all firms and eliminated future U.S. tax on repatriated earnings after payment of a one-time transition tax, creating a “permanent tax holiday” for foreign earnings. I examine the relationship between pre-TCJA foreign cash holdings disclosed by MNCs and their shareholder payout and investment behavior in the two years immediately following enactment of the TCJA. Similar to research into the effects of the temporary tax holidays in prior legislation, I find share repurchases in the post-TCJA period are associated with pre-TCJA foreign cash holdings. I further find that MNCs disclosing pre-TCJA foreign cash holdings increased research and development and capital expenditures in the second year following the TCJA. These findings indicate that the foreign earnings provisions of the TCJA may have had some longer-term effects in line with its legislative intent. This contrasts in some ways with the findings of prior research and should be of interest to policymakers, particularly as the current U.S. administration considers changes to the corporate tax regime, while also providing a basis for future research.