In this study, we quantified the Chemistry-Process-Structure-Property (CPSP) relations of a Ti-6Al-4V/TiB functionally graded material to assess its ability to withstand large deformations in a high throughput manner. The functionally graded Ti-6Al-4V/TiB alloy was created by using a Laser Engineered Net Shaping (LENS) process. A complex thermal history arose during the LENS process and thus induced a multiscale hierarchy of structures that in turn affected the mechanical properties. Here, we quantified the functionally graded chemical composition; functionally graded TiB particle size, number density, nearest neighbor distance, and particle fraction; grain size gradient; porosity gradient. In concert with these multiscale structures, we quantified the associated functionally graded elastic moduli and overall stress-strain behavior of eight materials with differing amounts of titanium, vanadium, aluminum, and boron with just one experiment under compression using digital image correlation techniques. We then corroborated our experimental stress behavior with independent hardening experiments. This paper joins not only the Process-Structure-Property (PSP) relations, but couples the different chemistries in an efficient manner to effectively create the CPSP relationships for analyzing titanium, aluminum, vanadium, and boron together. Since this methodology admits the CPSP coupling, the development of new alloys can be solved by using an inverse method. Finally, this experimental data now lays down the gauntlet for modeling the sequential CPSP relationships.

No description available.

Yes / The ever-increasing demand for high performance electronic and computer systems has unequivocally called for increased microprocessor performance. However, increasing microprocessor performance requires increasing the power and on-chip power density of the microprocessor, both of which are associated with increased heat dissipation. In recent times, thermal management of electronic systems has gained intense research attention due to increased miniaturization trend in the electronics industry. In the paper, we present a numerical study on the performance of a convective-radiative porous heat sink with functionally graded material for improved cooling of various consumer electronics. For the theoretical investigation, the thermal property of the functionally graded material is assumed as a linear and power-law function. We solved the developed thermal models using the Chebyshev spectral collocation method. The effects of inhomogeneity index of FGM, convective and radiative parameters on the thermal behaviour of the porous heat sink are investigated. The present study shows that increase in the inhomogeneity index of FGM, convective and radiative parameter improves the thermal efficiency of the porous fin heat sink. Moreover, for all values of Nc and Rd, the temperature gradient along the fin of FGM is negligible compared to HM fin in both linear and power-law functions. For comparison, the thermal predictions made in the present study using Chebyshev spectral collocation method agrees excellently with the established results of Runge-Kutta with shooting and homotopy analytical method. / Supported in part from PhD sponsorship of the first author by the Tertiary Education Trust Fund of the Federal Government of Nigeria.

In this dissertation, we developed a mathematical framework for cohomological field theories (CohFTs) in the language of ``QK-manifolds', which unifies the previous ones in (Baulieu and Singer 1988; Baulieu and Singer 1989; Ouvry, Stora, and Van Baal 1989; Atiyah and Jeffrey 1990; Birmingham et al. 1991; Kalkman 1993; Blau 1993). Within this new framework, we classified the (gauge invariant) solutions to the descent equations in CohFTs (with gauge symmetries). We revisited Witten’s idea of topological twisting and showed that the twisted super-Poincaré algebra gives rise naturally to a ``QK-structure'. We also generalized the Mathai-Quillen construction of the universal Thom class via a variational bicomplex lift of the equivariant cohomology. Our framework enables a uniform treatment of examples like topological quantum mechanics, topological sigma model, and topological Yang-Mills theory.

More than one-half of university students in the United States and Canada are not active enough to gain health benefits. Enjoyment of exercise proposes a feasible solution to the absence of motivation surrounding physical activity. The purpose of this study is to compare the differences in reported enjoyment between upper and lower body cycling graded exercise to exhaustion (GXT). Seven university students (23 ± 3 years old; 26 ± 4 kg/m2) performed two randomized graded exercise tests on different days: one for upper body, one for lower body. Feeling Scale (FS) measured the affective response during exercise. Post-exercise enjoyment values were recorded 15 minutes after concluding GXT using the Physical Activity Enjoyment Scale (PACES), which has been shown to be a valid and reliable measure of physical activity enjoyment. Paired t-tests were used to evaluate mean differences between upper and lower body GXT enjoyment scores. Rank biserial correlations and Cohen's d values were used to evaluate effect size for the non-parametric and parametric analyses. Alpha level was set a priori at p < 0.05. Means and standard deviations were calculated for PACES, age, and BMI. No significant differences were found for enjoyment (p=0.162) between upper (104.3 ± 12.6) and lower-body cycling (97.8 ± 15.3). Notable effect sizes were found for the PACES Total and several subscales (Enjoy/Hate, Pleasant, and Contentment). No significant differences were found for the FS at ventilatory threshold (p=0.586) or at maximal aerobic power (p=0.670) between the upper and lower body GXT trials. More research is needed to explore exercise enjoyment across different exercise modes and provide a more particular evaluation of PACES subscales. Further research should aim to compare enjoyment levels across different physical activity levels (e.g., low, moderate, high), between sexes and within diverse populations.

3D printing technology, which has its origins in rapid prototyping, is increasingly used to build functional devices. Although 3D printing technology has been well developed for thermoplastic polymers and metals, it is still in the research phase for soft polymeric materials such as silicones. Silicones are an industrially vital polymer characterized by a broad spectrum of chemical and physical properties for several smart applications, including on skin printing, smart sensors, multigradient material, and soft actuators. Extrusion-based multimaterial printing is one of the 3D printing techniques that have been adapted due to its compatibility to process silicone-based materials for constructing various functional devices. However, there are several challenges such as achieving on the fly mixing at low Reynolds numbers regime, achieving fast switching while using Newtonian/non-Newtonian inks, and achieving multimaterial printing on nonplanar surfaces. The development of suitable and robust printheads that are able to tackle those challenges can expand the application of this technology to a wide range of fields. In this thesis, several deposition-controlled printhead designs have been created for 3D printing multifunctional devices using an understanding of microfluidics. The established printhead can be controlled to formulate different multigradient structures through on the fly mixing during the material printing. Moreover, the developed printhead can be adapted to print multi viscous inks with high switching rates up to 50 Hz. Through the developed system, the printhead was able to track topologies in real-time, allowing objects to be printed over complex substrates. These new capabilities were applied to fabricate functional structures in order to demonstrate the potential of the developed printhead approaches that can be used in various applications, including smart sensors, soft robotics and multigradient objects. / Thesis / Doctor of Philosophy (PhD) / 3D printing techniques, such as extrusion-based multimaterial printing, have recently been utilized to process silicones due to their versatility in different smart applications, including multigradient material and soft actuators. Although it represents significant progress, there are still several challenges, including the proper mixing during printing with a laminar flow regime, the fast switching between different inks, and the printing over complex topographies. Therefore, various printhead designs have been developed in this thesis to tackle these challenges. In particular, a mixer printhead has been designed to allow mixing during printing for building multigradient objects. Also, a scalable printhead has been developed to allow fast switching for creating pixelated structures. Finally, a simple mechanical system has achieved multimaterial printing over various nonplanar surfaces. To the best of the author's knowledge, the developed printheads can be used in many fields, such as soft robotics and smart devices.

A hydrocode and an explicit finite element code were used to evaluate functionally graded material impacts, meteor impacts, and split Hopkinson pressure bar specimens. Modeling impacts of functionally graded projectiles revealed that density was the primary material characteristic controlling the shock wave profile. A parametric study of material order for functionally graded armor showed that arranging the weaker material in front created the greater stopping power. By modeling an array of meteor impact scenarios, deformation and stress were shown to occur at great depths and possibly cause tectonic movement, like subduction. Three proposed Hopkinson specimens, which were designed to produce either shear or tensile reactions under compressive loading, were evaluated. For two of these specimens, improved stress and strain equations were presented.

No description available.

No description available.

The material taught in a Formal Languages course is mathematical in nature and requires students to practice proofs and algorithms to understand the content. Traditional Formal Languages textbooks are heavy on prose, and homework typically consists of solving many paper exercises. Some instructors make use of finite state machine simulators like the JFLAP package. JFLAP helps students by allowing them to build models and apply various algorithms on these models, which improves student interaction with the studied material. However, students still need to read a significant amount of text and practice problems by hand to achieve understanding. Inspired by the principles of the Programmed Instruction (PI) teaching method, we seek to develop a new Formal Languages eTextbook capable of conveying these concepts more intuitively. The PI approach has students read a little, ideally a sentence or a paragraph, and then answer a question or complete an exercise related to that information. Based on the question response, students can continue to other information frames or retry to solve the exercise. Our goal is to present all algorithms using algorithm visualizations and produce proficiency exercises to let students demonstrate understanding. To evaluate the pedagogical effectiveness of our new eTextbook, we conduct time and performance evaluations across two offerings of the course CS4114 Formal Languages and Automata. In time evaluation, the time spent by students looking at instructional content with text and visualizations versus with PI frames is compared to determine levels of student engagement. In performance evaluation, students grades are compared to assess learning gains with text and paper exercises only, with text, visualizations with exercises, and with PI frames. / Doctor of Philosophy / Theory textbooks in computer science are hard to read and understand. Traditionally, instructors use books that are heavy on mathematical prose and paper exercises. Sometimes, instructors use simulators to allow students to create, simulate, and test models. Previously, we found that students tend to skip reading the text presented in the books. This leads to less understanding of the topics taught in the course. To increase student engagement, we developed a new eTextbook for the Formal Languages course. We used pedagogy based on Programmed Instruction, presenting the content in the form of short bits of prose followed by the related question. If students can solve the question correctly, this means that they understood the content and are ready to move forward. To help both instructors and students, we developed a new Formal Languages simulator named OpenFLAP. OpenFLAP allows instructors to create many exercises, and OpenFLAP can grade these exercises automatically.