High entropy alloys (HEAs) based on refractory elements have shown a great potential for high temperature structural applications. In particular, the ones containing Al, exhibits a microstructure similar to the γ-γ' in Ni-based superalloys. While these alloys exhibit impressive strengths at room temperature (RT) and at elevated temperatures, the continuous B2 matrix in these alloys is likely to be responsible for their brittle behavior at RT. Phase stability of five such alloys are studied by thermo-mechanical treatments and characterization techniques using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Two of these alloys showed an inverted microstructure, where the disordered BCC phase becomes continuous, and therefore, they were characterized in detail using SEM, TEM, atom probe tomography (APT) and synchrotron x-ray diffraction experiments. The phenomenon of phase inversion lead to a better combination of strength and ductility as compared to the non-inverted microstructure.To enhance the stability of B2 intermetallic phase which provides the strength when present in a BCC matrix, multicomponent B2 phase compositions stable at 1000°C in some of the above studied alloys, were melted separately. The aim was to establish a single phase B2 at 1000°C and understand the mechanical behavior of these single-phase multicomponent B2 intermetallic …

High entropy alloys (HEAs) are a relatively new class of solid solution alloys that contain multiple principal elements to take advantage of their high configurational entropy, sluggish diffusion, lattice distortion, and the cocktail effect. In recent development, work hardening mechanisms known as twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) have been found active in Al0.3CoCrFeNi (molar fraction) and Fe50Mn30Co10Cr10 (at %) HEA compositions. Friction-stir processing was done to increase the mechanical properties and improve the microstructure of the alloys for the purpose of high strain rate performance. Quasi-static tensile tests as well as top-hat geometry Split-Hopkinson pressure bar tests were conducted to view the mechanical properties as well as view the microstructural evolution at dynamic strain rates. Overall, the Al0.3CoCrFeNi condition after friction-stir processing and heat treatment has proved to have the best mechanical properties, and selecting from the conditions in this study, Al0.3CoCrFeNi has better shear localization resistance.

The current study examined associations between perceived family functioning, sibling relational dynamics, and individual's self-reported personal adjustment and internalizing problems among 8- to 11-year old children. Path analyses revealed significant direct effects between conflictual family functioning and children's psychological well-being (p < 0.05). Further, sibling conflict was found to indirectly affect these associations. Finally, significant interactions between family functioning and sibling dynamics were found suggesting that congruent relational dynamics at multiple levels of the family system had a cumulative impact on the child's well-being. Findings from the current study highlight the unique contributions of sibling relationships to the family and the child providing evidence for targeting the sibling relationship in clinical interventions and future family research.

Mental health stigma has been identified as a barrier to help-seeking in the United States. Research suggests that insecure attachment may contribute to higher mental health stigma and lower help-seeking behavior. This may be particularly salient in military personnel who tend to report higher mental health stigma than the general population. Evidence suggests that both supportive and destructive military leadership are related to service members' attitudes toward seeking help. In the current study, a sample of military service members and veterans (N = 232) completed an online survey regarding mental health stigma, military leadership experiences, attachment strategies, and mental health help-seeking behaviors. Findings indicated that destructive and supportive leadership experiences were significantly related to self and public stigma, and self-stigma mediated the relationship between destructive and supportive leadership experiences and likelihood to seek help. Attachment anxiety predicted higher self and public stigma, while attachment avoidance predicted high self-stigma but low public stigma, with high self-stigma partially mediating the relationship between attachment avoidance and help seeking.

This mixed-methods dissertation used an explanatory sequential design to examine art and mathematics preservice teachers' perceptions and attitudes towards integrating art and mathematics (IAM) after an IAM workshop. The conceptual framework of this study has its basis in three theoretical sources: constructivism, multiple intelligence theory, and semiotics. Each of these sources provides a conceptual lens to examine art integration in the curriculum and the teacher's role in facilitating this instructional process. Participants of this study included two sub-groups at a large university in Saudi Arabia. The first sub-group was preservice teachers of art education. The second sub-group was preservice teachers of mathematics. Quantitative and qualitative results indicated that the IAM workshop had positive impacts on art and mathematics preservice teachers' attitudes and perceptions of IAM. Participants attributed more value to art, were more willing to apply IAM, and felt that there was less barriers for applying IAM. The study also indicated differences between art and mathematics preservice teachers' attitudes towards IAM. The differences were due more to art value than willingness or barriers. After the IAM workshop, mathematics preservice teachers put more emphasis on the importance of art to mathematics, especially with respect to making mathematics a more enjoyable subject.

Accurate assessment of sleep-wake patterns is important for sleep researchers and clinicians. Actigraphs are low-cost, non-intrusive, wrist-worn activity detectors used to estimate sleep-wake patterns in a natural environment for several nights. Although actigraphy shows good sensitivity (sleep detection), it has consistently demonstrated poor specificity (wakefulness detection while lying in bed relatively motionless). Because insomnia is characterized by wakefulness in bed, actigraphy may not be a valid objective measure of wakefulness for this group. It is possible that refinement of actigraphy software settings for sleep/wake algorithms might improve specificity. The current studies investigated this hypothesis by comparing wake parameters from 48 combinations of actigraphy settings to determine which sleep/wake algorithms best inform insomnia diagnosis and treatment. In the first study, none of the 48 actigraphy setting combinations consistently discriminated between adults with insomnia (n = 69) and non-insomnia (n = 80) on all three wake parameters, and no setting clearly discriminated between groups for the composite variable, total wake time. Similarly, in the second study, no setting combinations consistently discriminated between adults treated for insomnia (n = 18) and controls with untreated insomnia (n = 26) on all three wake parameters. Although two setting combinations discriminated between groups for the composite …

Lithium-sulfur (Li-S) batteries are faced with practical drawbacks of poor cycle life and low charge efficiency which hinder their advancements. Those drawbacks are primarily caused by the intrinsic issues of the cathodes (sulfur) and the anodes (Li metal). In attempt to resolve the issues found on the cathodes, this work discusses the method to prepare a binder-free three-dimensional carbon nanotubes-sulfur (3D CNTs-S) composite cathode by a facile and a scalable approach. Here, the 3D structure of CNTs serves as a conducting network to accommodate high loading amounts of active sulfur material. The efficient electron pathway and the short Li ions (Li+) diffusion length provided by the 3D CNTs offset the insulating properties of sulfur. As a result, high areal and specific capacities of 8.8 mAh cm−2 and 1068 mAh g−1, respectively, with the sulfur loading of 8.33 mg cm−2 are demonstrated; furthermore, the cells operated at a current density of 1.4 mA cm−2 (0.1 C) for up to 150 cycles. To address the issues existing on the anode part of Li-S batteries, this work also covers the novel approach to protect a Li metal anode with a thin layer of two-dimensional molybdenum disulfide (MoS2). With the protective layer of MoS2 …