Applications of boundry vorticity dynamics to flow simulation, airfoil design, and flow control

This dissertation is dedicated to the study of applications of the boundary vorticity dynamics theoryThe vorticity generation mechanism from solid boundaries is studied firstThe development of a two-dimensional viscous solver and an airfoil inverse design tool is conducted next. Finally, a new flow control method called BVF cutting is introduced and tested. Various source terms of the vorticity generation rate, i.e., boundary vorticity flux (BVF), are studied based on the tangential momentum balance on a solid surface. The direct connection between BVF and aerodynamic forces is rederived. The constraint of BVF imposed by the vorticity conservation is formulated and clarified. Two aerodynamic tools are developed in terms of BVF: A numerical Navier-Stokes (N-S) solver for two-dimensional incompressible steady or unsteady flows by using stream function-vorticity variables, with the BVF as the Neumann boundary condition; and an inverse design tool to develop airfoils with improved performance, in which the BVF is used as the objective function in the Euler limit of a viscous flow. An extensive validation of the N-S solver is conducted, and examples of improved airfoils are given mainly for the purpose of enhancing their lift coefficients and delaying the stall angles of attack. By reexamining the flow separation in terms of BVFtwo possible ways to imple- ment the BVF cutting method are examined, one of which is proved very effective. Enlightened by these, the most idealized objective for flow control is found. A principle for the perfect controlled flow and a guideline to judge the effectiveness of a flow control is proposed

The Relationships between Parenting Stress, Child Characteristics, Parenting Self-Efficacy, and Social Support in Parents of Children with Autism in Taiwan

Children with autism often place increased demands on their families due to the nature of their disorders. Research has repeatedly shown that parents of children with autism experience higher levels of stress and lower levels of overall well-being than parents of children with other disabilities, or parents of typical children. Compared to research on Western families of children with autism, research on Taiwanese families is limited. In addition, the role of parenting self-efficacy and social support and their relationship with parenting stress has remained unclear in the field of autism. The purpose of this study was to compare parenting stress (as measured by the Parenting Stress Index and the Family Stress and Coping Interview-Adapted) in parents of primary school-age children with autism (6-12 years) and parents of adolescent children with autism (13-18 years) in Taiwan. This study also explored the relative contribution of the children's characteristics, including autism severity, communication skills, socialization skills, daily living skills, and problem behaviors, as well as parenting self-efficacy and social support in relation to parenting stress among parents of children with autism in Taiwan. Moreover, the mediating and moderating effects of parenting self-efficacy and social support on the relationship between behavior problems and parenting stress were also examined. Lastly, some qualitative data were reported at the end of this study to expand the understanding of the sources of stress that Taiwanese parents of children with autism may be experiencing. A total of seventy-nine parents of children with autism between the ages of six and eighteen years old participated in the study. In addition to face-to-face interviews, the participants completed four self-report measures and a demographic questionnaire. The results of Independent Samples t-tests showed no significant differences on the two parenting stress measures between parents of school-aged children with autism and parents of adolescent children with autism in Taiwan. The results of correlational analyses revealed that parenting self-efficacy, social support, autism severity, and behavior problems were significantly correlated with parenting stress for Taiwanese parents of children with autism. Moreover, in stepwise regression analyses, parenting self-efficacy, social support, and behavior problems were found to be the best set of predictors of parenting stress for Taiwanese parents of children with autism. A series of multiple regression analyses indicated that both parenting self-efficacy and social support demonstrated partial mediation as they both mediated the relationship between behavior problems and parenting stress among Taiwanese parents of children with autism. However, both parenting self-efficacy and social support failed to moderate the relationship between behavior problems and parenting stress. Lastly, qualitative data were reported based on responses to an open-ended question requesting parents to list the most important aspects that they would like to see change in rearing their children with autism

Preparation of Mesoporous Tin Oxide for Electrochemical Applications

Mesoporous tin oxide stable up to 500 °C has been prepared for the first time using both cationic and neutral surfactants

Preparation of Mesoporous Yttria-Stabilized Zirconia (YSZ) and YSZ-NiO Using a Triblock Copolymer as Surfactant

Mesoporous yttria-stabilized zirconia (YSZ) and YSZ-NiO have been prepared for the first time using Pluronic P103 as a structure-directing agent and inorganic chlorides as precursors in a nonaqueous medium. After being fired at 500°C for 2 h, mesostructured YSZ has a BET surface area of about 146 m2 g-1, with an average pore size of 3.8 nm, while mesostructured YSZ-NiO has a BET surface area of about 108 m2 g-1, with an average pore size of 4.5 nm

Redox Stable Anodes for Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) can convert chemical energy from the fuel directly to electrical energy with high efficiency and fuel flexibility. Ni-based cermets have been the most widely adopted anode for SOFCs. However, the conventional Ni-based anode has low tolerance to sulfur-contamination, is vulnerable to deactivation by carbon build-up (coking) from direct oxidation of hydrocarbon fuels, and suffers volume instability upon redox cycling. Among these limitations, the redox instability of the anode is particularly important and has been intensively studied since the SOFC anode may experience redox cycling during fuel cell operations even with the ideal pure hydrogen as the fuel. This review aims to highlight recent progresses on improving redox stability of the conventional Ni-based anode through microstructure optimization and exploration of alternative ceramic-based anode materials

Employee-Oriented Corporate Social Responsibility (CSR) and Employees Performance, within the Mining Sector

Several researches have highlighted the responses of the employees towards the Corporate Social responsibility (CSR) within various business sectors,whereas few studies payed attention to the employees within the mining sector,this paper seeks to investigate the linkage between the employee-oriented CSR and their performance, basically the study focused on a sample of 300 employees of the mining sector in the Democratic Republic of the Congo. The relationship was tested by estimating a linear regression model, the study assessed the mediation mechanism of job satisfaction and organizational commitment.The empirical results showed an evidence of a positive relationship between Employee-oriented Corporate Social Responsibility and job performance, CSR practices towards employees would increase the employee satisfaction, which significantly predicts their job performance, therefore, Employee-oriented Corporate Social Responsibility indirectly impact job performance through mediating mechanism of job satisfaction and organizational commitment.The authors recommended the mining firms to initiate CSR initiatives that involve the workers participation. Keywords: Mining Sector, Corporate Social Responsibility, Human Resources Management,Job perfomance,Job satisfaction, Organizational Commitment. DOI: 10.7176/EJBM/12-24-07 Publication date:August 31st 202

Characteristics of the Hydrogen Electrode in High Temperature Steam Electrolysis Process

YSZ-electrolyte supported solid oxide electrolyzer cells (SOECs) using LSM-YSZ oxygen electrode but with three types of hydrogen electrode, Ni–SDC, Ni–YSZ and LSCM–YSZ have been fabricated and characterized under different steam contents in the feeding gas at 850°C. Electrochemical impedance spectra results show that cell resistances increase with the increase in steam concentrations under both open circuit voltage and electrolysis conditions, suggesting that electrolysis reaction becomes more difficult in high steam content. Pt reference electrode was applied to evaluate the contributions of the hydrogen electrode and oxygen electrode in the electrolysis process. Electrochemical impedance spectra and over potential of both electrodes were measured under the same testing conditions. Experimental results show that steam contents mainly affect the behavior of the hydrogen electrode but have little influence on the oxygen electrode. Further, contribution from the hydrogen electrode is dominant in the electrolysis process for Ni–based SOECs, but this contribution decreases for LSCM–based SOECs

Foreign investment & growth in emerging economies: panel ARDL analysis

Recently, the contributory role of foreign investment growth in Africa has been considered by researchers and policymakers. Studies in this area are not yet clear. Besides, foreign direct investment has emerged as a determining factor of economic growth. Concerning this evidence, the current study tries to investigate the contributions of foreign direct investment on economic growth or for developing the economy of Africa. This study used yearly panel data for the period 1995-2015 for 5 developing the economy of Africa. The results of Panel ARDL indicate that foreign direct investment has a positive effect on economic growth as well as a positive sign of trade openness, inflation, and labor. The study also stresses that, for increasing economic growth, there is a need to seek more foreign investments, increase trade openness and inflation, and at the same time, to improve the employment condition in the selected African developing countries