Essays on accounting conservatism, corporate social responsibility, and corporate governance

This thesis consists of three essays on accounting conservatism, corporate social responsibility, and corporate governance. The first essay examines the influence of accounting conservatism on trade credit, particularly under the background of the recent global financial crisis. The second essay investigates whether suppliers value customer firms’ corporate social responsibility activities by exploring the influence of customer firms’ social performance on trade credit. The third essay examines how the heterogeneous credit crunch shock that took place during the recent global financial crisis moderated the effectiveness of corporate governance on deterring expropriation by controlling shareholders and improving firm performance.Accounting conservatism and trade credit / Yanlei Zhang. -- Do suppliers value socially responsible customers / Yanlei Zhang, Juan M. García Lara and Josep A. Tribó. -- Heterogeneous credit crunch shock and the effectiveness os corporate governance / Yanlei Zhang, María GutiérrezPrograma Oficial de Doctorado en Empresa y Finanzas / Business and FinancePresidente: Miguel Ángel García Cestona; Secretario: Beatriz García Osma; Vocal: Juan Pedro Sánchez Ballest

Numerical simulation and optimization of Al alloy cylinder body by low pressure die casting

Shrinkage defects can be formed easily at Critical location during low pressure die casting (LPDC) of aluminum alloy cylinder body. It has harmful effect on the products. Mold fi lling and solidifi cation process of a cylinder body was simulated by using of Z-CAST software. The casting method was improved based on the simulation results. In order to create effective feeding passage, the structure of casting was modifi ed by changing the location of strengthening ribs at the bottom, without causing any adverse effect on the part’s performance. Inserting copper billet at suitable location of the die is a valid way to create suitable solidifi cation sequence that is benefi cial to the feeding. Using these methods, the shrinkage defect was completely eliminated at the critical location

Bubble Flow Analysis of High Speed Cylindrical Roller Bearing under Fluid-Solid Thermal Coupling

Heat generation model of high speed cylindrical roller bearing is constructed by calculating the local friction in the bearing. Bubble flow calculation model of roller bearing considering fluid-solid thermal coupling is constructed based on two-body fluid model and k-ε turbulent model, in which diameter and size of bubbles, breakup, and coalescence model of bubbles are considered. Using dynamic mesh method, a new method for evaluating bearing temperature is set up treating the rolling elements as moving heat sources. Based on these models and finite element method, bubble flow of a high speed roller bearing is studied based on FLUENT software. The numerical study reveals the relationship between velocity of bearing, air volume fraction, and velocity and pressure of oil-air flow. An increase of air content in the oil produces a lower pressure at the bearing outlet while the exit fluid velocity increases. When fluid-solid thermal coupling effect is considered, velocity and pressure at outlet of the bearing both become larger, while temperature of bearing is lower than that without coupling. In comparison, the coupling effects on flow pressure and temperature are obvious. For a given rotating speed, there is an optimal value for air volume fraction, such that temperature rise of the bearing reaches the lowest value. Experiments verify the outcomes of the method presented in this paper

Positive solutions for second-order differential equations with singularities and separated integral boundary conditions

We study the existence of positive solutions for second-order differential equations with separated integral boundary conditions. The nonlinear part of the equation involves the derivative and may be singular for the second and third space variables. The result ensures existence of a positive solution when the parameters are in certain ranges. The proof depends on general properties of the associated Green’s function and the Krasnosel’skii–Guo fixed point theorem applied to a perturbed Hammerstein integral operator. Both numerical and analytical examples are constructed to illustrate applications of the theorem to a group of equations. The result generalizes previous work