Reynolds Number Effects on Thrust Coefficients and PIV for Flapping Wing Micro Air Vehicles

For the last several years the Air Force Institute of Technology (AFIT) has conducted research in aerodynamics for flapping wing micro air vehicles (MAVs). The focus of this research was to augment this effort by measuring thrust, velocity, and torque in tanks of water and glycerin using a scale and a reaction torque cell. The results for different flapping mechanisms are compared to a rotating propeller with the goal of elucidating the design trade space between rotorcraft and flapping wings at Reynolds numbers less than 100,000. In addition, flow visualization and quantitative velocity data were captured in the wake of the flapping wing. One flapping-wing mechanism was designed to incorporate a coupled 4-bar planar and 4-bar spatial linkage system to prescribe motion which included both flapping and rotation. Thrust and velocity data were found to follow the general trends for a flapping wing with passive rotation. The passive rotation angle setting was found to alter thrust and velocity patterns

Molybdenum Disulfide Nanodisks For Photoelectrochemical Hydrogen Evolution

Current strategies of energy production and conversion continue to emit CO2 at a rate that is extremely likely to warm the planet 1.5°C by 2052, and energy sourced from renewables needs to increase 95% by 2050 in the most relaxed reductions emissions scenarios. Photoelectrochemical (PEC) hydrogen evolution from MoS2/p-Si is introduced as a technology that can directly convert solar energy to chemical energy without the use of rare earth metals. The mechanisms of both hydrogen evolution from 2H-MoS2 edge sites and semiconductor photocatalysis are discussed. Colloidal lithography using masks of polystyrene (PS) nanospheres, electron-beam deposition, and chemical vapor deposition were used to control the diameter (200–500 nm), thickness (1.5–9.5 nm) and areal density (1.8–20.9%) of MoS2 nanodisks on p-Si, which were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and image processing techniques. The PEC performances of bare p-Si and MoS2/p-Si were analyzed using linear scan voltammetry (LSV) and chronoamperometry (CA). Replacing Ga-In with Au as the back contact for p-Si in PEC testing was found to reduce the magnitude of the overpotential at -10 mA cm-2 from -593 to -390 mV due to Schottky barrier removal. 200 nm MoS2 and 500 nm MoS2 nanodisks on p-Si further decreased the overpotential at 10 mA cm-2 from -390 mV to -234 and -172 mV, respectively, and produced short-circuit currents of -0.45 mA cm-2 and -0.80 mA cm-2, respectively. The stability of MoS2/p-Si photocathode performance was found to depend on the thickness of e-beam deposited Mo, with a 31 and 134 mV decrease in overpotential measured for 500 nm MoS2 nanodisks produced from 1 nm and 4 nm Mo, respectively. Finally, the in situ observation of hydrogen evolution from bare p-Si was demonstrated, and images were collected bubbles on the microscale. Future work involves optimizing the thickness of MoS2 to meet state-of-the-art performance parameters and investigating the conditions under which the growth of insulating SiO2 affects photocathode performance

Affective and cognitive components of job satisfaction: Scale development and initial validiation.

Job satisfaction is one of the most commonly studied variables in the organizational literature. It is related to a multitude of employee-relevant variables including but not limited to performance, organizational commitment, and intent to quit. This study examined two new instruments measuring the components of affect and cognition as they relate to job satisfaction. It further proposed including an evaluative (or true attitudinal) component to improve the prediction of job satisfaction. Results provide some evidence of both two and three factor structures of affect and cognition. This study found minimal support for the inclusion of evaluation in the measurement of job satisfaction. Affect was found to be the single best predictor of job satisfaction, regardless of the satisfaction measure used. Further development is needed to define the factor structures of affect and cognition as well as the role of these factors and evaluation in the prediction of job satisfaction

Polymer Nanocomposite Membranes for Selective Ion Transport Applications

Soft materials are indispensable components of energy storage and conversion technologies necessary for the renewable energy transition. Two key examples are electrolytes used in solid-state batteries and ion-exchange membranes used in electrolysis and electrodialysis. The figures of merit for these applications are often summarized using upper-bound relationships, which define the best possible combination of performance metrics for a given material. A promising route to break the upper-bound and to improve upon the state-of-the-art is engineering materials at the nanoscale. Two commonly employed strategies are the use of block copolymers and polymer nanocomposites. In the former, the sequence of different monomers along the backbone of the polymer chain is varied; in the latter, ceramic nanoparticles are mixed with polymers and processed to achieve different dispersion states. In both of these classes of materials, the self-assembly of molecular and colloidal components controls the structure and function of the resulting material. This dissertation investigates these structure-property relationships in model soft nanomaterials, namely colloids, polymer nanocomposites, and ion-exchange membranes, using experiments, molecular dynamics simulations, and theory. The dissertation can be divided into three parts. The first, Chapters 2 and 3, investigates polymer and polymer nanocomposite electrolytes for applications in solid-state Li batteries. Chapter 2 investigates the coarse-graining and force field parameterization of polymer electrolytes for molecular dynamics simulations. Chapter 3 reports the experimental characterization of polymer nanocomposite electrolytes, with a key focus on understanding how the particle dispersion state affects the ionic conductivity and mechanical reinforcement of the composite. The second part, Chapters 4 and 5, studies fundamental structure-property relationships in two types of polymer nanocomposites. In Chapter 4, the surface chemistry of hydrophilic silica nanoparticles is altered to promote miscibility in organic solvents and in semicrystalline polymers. In these "bare" nanocomposites, the particles are stabilized against aggregation via the adsorption of a polymer bound layer, which is quantitatively studied via small angle X-ray scattering. In Chapter 5, the surface-modified particles are densely grafted with polymer chains via surface-initiated polymerization to obtain matrix-free polymer grafted nanoparticle films. The collective dynamics of the nanoparticle cores in these self-supporting films, where all of the polymer is grafted to the particle surface, is then measured using X-ray photocorrelation spectroscopy at a variety of temperatures. In Chapters 6 and 7, random copolymer chemistries are used to create cation- and anion-exchange membranes, respectively, with controlled ion-exchange capacity and swelling behavior. The key finding of Chapter 6 is that water-lean cation-exchange membranes selectively transport ions with low free energies of hydration, allowing the design of specific-ion selective electrodialysis stacks for Li+ recovery applications. The analogous properties of anion-exchange membranes are suggested as an avenue for future research

The Multicultural Study of Psychopathy: An Examination of Latin American Differences

Psychopathy is a personality disorder that is composed of characteristics that include poverty of empathy, lack of anxiety or fear, impulsive actions, and manipulation of others. The definition and measurement of psychopathy has changed over time and remains controversial. Ethnicity is an under researched area of psychopathy. In particular, previous psychopathy research has focused primarily on European American men. Despite increased attention to differences between African Americans and European Americans, Latin Americans continue to be overlooked, with only a small number of studies examining psychopathy among individuals from Latin ethnicities. The current study is among the first to examine psychopathy traits among Latino males. Features of Latin American culture that may affect psychopathy traits were explored, including interpersonal protective factors, increased egocentrism, machismo (culturally based masculinity), and interpersonal violence. This research was conducted with Latin American and European American male undergraduates. Results indicate that there are differences in psychopathy traits at the global scale and subscale level. In addition, machismo and psychopathy traits are moderately related. Psychopathy traits, machismo, and the interaction are predictive of violence in European Americans. However, psychopathy traits, machismo, and the interaction were less reliably predictive of violence in Latin Americans. Psychopathy traits in Latin Americans may not be related to correlates of psychopathy traits (i.e. aggression and violence). Overall, culturally based differences are significant and future research should give culture a more significant role

Multicultural study of psychopathy: An examination of Latin American differences

Psychopathy is a personality disorder that is composed of characteristics that include poverty of empathy, lack of anxiety or fear, impulsive actions, and manipulation of others. The definition and measurement of psychopathy has changed over time and remains controversial. Ethnicity is an under researched area of psychopathy. In particular, previous psychopathy research has focused primarily on European American men. Despite increased attention to differences between African Americans and European Americans, Latin Americans continue to be overlooked, with only a small number of studies examining psychopathy among individuals from Latin ethnicities. The current study is among the first to examine psychopathy traits among Latino males. Features of Latin American culture that may affect psychopathy traits were explored, including interpersonal protective factors, increased egocentrism, machismo (culturally based masculinity), and interpersonal violence. This research was conducted with Latin American and European American male undergraduates. Results indicate that there are differences in psychopathy traits at the global scale and subscale level. In addition, machismo and psychopathy traits are moderately related. Psychopathy traits, machismo, and the interaction are predictive of violence in European Americans. However, psychopathy traits, machismo, and the interaction were less reliably predictive of violence in Latin Americans. Psychopathy traits in Latin Americans may not be related to correlates of psychopathy traits (i.e. aggression and violence). Overall, culturally based differences are significant and future research should give culture a more significant role