Two-dimensional (2D) materials have properties that are often different from their three-dimensional (3D) bulk form. Many of these materials are stable at ambient conditions, which allows them to be integrated with other 2D- or 3D-materials to form heterostructures. Integration of various dimensional materials attains unique electrical and optical properties that aid in developing novel electronic devices. The interface of the heterogeneous integration of these films can exhibit a weak van der Waals-like bonding. In this thesis, an advanced characterization (from atomic to millimeter resolution) of various dimensional materials with weakly bonded interfaces is developed and employed to understand their behavior at scale. First, a large-area single-crystal cadmium telluride thin film is grown incommensurately and strain-free to a sapphire substrate despite a significant 3.7% lattice mismatch. The film remarkably delaminates as a bulk single crystal film due to an atomically thin tellurium that spontaneously forms at the interface. Aberration-corrected electron microscopy and spectroscopy reveal both the van der Waals-like structure and bonding at the film/substrate interface. Second, a large-area atomically thin gallium is intercalated at the interface of epitaxial graphene. Correlative microscopy workflows are applied to understand the thickness uniformity and area coverage of the 2D–gallium over few millimeters of the sample. Utilizing multiple correlative methods, SEM image contrast is found to be directly related to the presence of the intercalated gallium. The origin of the SEM contrast is investigated as a function of the surface potential. Then, the heterostructure characterization is scaled up over a few square millimeter areas by segmenting SEM images, each acquired with nanometer-scale resolution. Additionally, transmission electron microscopy is applied to investigate the interface of gallium–SiC, the gallium air–stability, and the role of the substrate on the heteroepitaxial growth of 2D–gallium, which charts a path for further development of these materials. / Thesis / Doctor of Philosophy (PhD)

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Introduction: A task-associated analysis of ammonia and particulate matter concentrations was conducted on swine farms in breeding and gestation barns. The purpose of this study was to determine if specific tasks performed by workers increase concentrations of ammonia and particulate matter exposure. Methods: An exploratory, descriptive design was used to determine if swine confinement workers have increased ammonia and particulate matter exposure when performing assigned tasks in breeding and gestation barns. A convenience sample of 8 workers volunteered from among all breeding and gestation workers (n=24). Data collection occurred in the morning at each of the 8 farms and continued until tasks were completed (~4 hrs). Analysis of covariance (ANCOVA) was computed to determine if the type of task or type of barn was related to workers' exposure to ammonia or particulate matter. Results: Ammonia levels were below the sensitivity of the instrument (<0.1) except on 1 morning when the ammonia concentration was recorded at 8 ppm. However, concentrations above 0.1 ppm lasted for less than 5 minutes. Consequently, this variable was not included in the analysis. Correlation analysis was used to answer the 1st research question. The results suggested a statistically significant decrease in particulate matter as the number of operating fans increased. Analysis of covariance (ANCOVA) was used to answer the last 2 research questions. The results suggested a significant interactive effect between the type of confinement barn and the type of tasks workers were performing. The barn types differed by the number of exhaust fans and the type of animal waste disposal system. Conclusions: Occupational health nurses can use study results to implement interventions to minimize worker exposures. These results indicate that understanding the relationship between building design and type of work tasks along with the importance of proper ventilation may minimize worker exposure to harmful particulate matter in SCBs during the summer months.

Yes / Recycled aggregate concrete filled stainless steel tube (RAC-FSST) is a new type of composite member combining the advantage of stainless steel and RAC. In this paper, a total of twenty-four RAC-FSST stub columns were tested under axial load, considering the influences of coarse recycled aggregate (CRA) content, steel ratios and compressive strengths of RAC. The obtained results, including the failure patterns, responses of axial load vs. deformation, stress states of external stainless steel tube and inner RAC and confinement effects, were systematically analyzed. Results indicated that all specimens presented good ductility and high residual strengths after reaching the maximum axial load. The elastic stiffness of RAC-FSSTs obviously declined with the increasing CRA content, while the strain at the ultimate load was larger. The inclusion of CRA could advance the occurrence of the confinement and lead to lower confining stress. Based on the experimental results, an analytical model with consideration of confinement action was developed to predict the axial response of RAC-FSST stub columns. Besides, the current design provisions for the normal CFST and RAC-FST members were employed to evaluate their applicability to RAC-FSSTs. In general, the design rules EN 1994-1-1:2004, GB 50936-2014 and T/CECS 625-2019 gave a conservative and relatively accurate prediction on ultimate strength of RAC-FSST stub columns. / This work was supported by the National Natural Science Foundation.

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This Masters Thesis is a response to the personal willingness of obtaining something positive from the global crisis, caused by Covid-19. In such a situation, an understanding of the role of light in domiciles is appropriate not only functionally, but emotionally, as new ways of living in space are introduced. Indeed, flexibility has turned to be a claimed characteristic in the house, as well as access to daylight and outdoor spaces. Those aspects are to be considered positive in the near future. Nevertheless, what can be considered as positive light and the extent to which it is related to flexibility is a factor to study.  How positive light can be achieved is also a factor to consider. Throughout this project, positive light will be defined under the exceptional circumstances of quarantine. The distribution of a survey, a discussion of architectural theories, as well as a study of positive light in my personal home will be carried out in order to gain an insight into its definition.