Stability of Intershaft Squeeze Film Dampers

Intershaft squeeze film dampers were investigated for damping of dual rotor aircraft jet engines. It was thought that the intershaft damper would enhance the stability of the rotor-bearing system. Unfortunately, it was determined that the intershaft squeeze film damper was unstable above the engine's first critical speed. Here, a stability analysis of rotors incorporating intershaft squeeze film dampers is discussed. A rotor model consisting of two Jeffcott rotors with two intershaft squeeze film dampers was investigated. Examining the system characteristic equation for the conditions at which the roots indicate an ever-growing unstable motion results in the stability conditions. The cause of the instability is identified as the rotation of the oil in the damper clearance. Several proposed configurations of intershaft squeeze film dampers are discussed, and it is shown that the intershaft dampers are stable supercritically only with a configuration in which the oil film does not rotate

Increasing blood donation in Egypt

Blood donation is becoming a critical national demand of emergency especially after Egypt’s revolution on the 25th of January 2011, and should be a high priority for the Ministry of Health (MOH) officials in order to save patients in need. This thesis investigated current barriers and possible incentives that would motivate more citizens to donate their blood. It explored factors that influence educated Egyptians’ decisions to donate blood, such as guidelines set before donating, efficiency of donation centers’ personnel, awareness regarding health gains, and the opportunity to rescue others. As a result of a qualitative and quantitative research, recommendations were formulated that could guide the MOH such as adjusting policies, equipping blood donation centers more appropriately, and promoting campaigns to increase willingness to donate blood in Egypt. Results in brief showed that face-to-face communication proved to be the most successful publicity measure. In addition, when doing campaigns, the government and the ministry have to be transparent regarding the phases of blood donation process and should take care to approach people coming from different social and educational backgrounds through proper methods. The most common barriers were fear of: pain, lack of hygiene and fear of getting infected, but lack of donations is also because of recent governmental policies: forbidding paid blood donation and monopolizing blood donation. The survey findings to an extent supported a conclusion that confidence in personal physical capabilities as well as trust in the blood donation staff efficiency and the process as a whole would lead to a rise in the willingness to donate blood

The effect of extreme confinement on the nonlinear-optical response of quantum wires

This work focuses on understanding the nonlinear-optical response of a 1-D quantum wire embedded in 2-D space when quantum-size effects in the transverse direction are minimized using an extremely weighted delta function potential. Our aim is to establish the fundamental basis for understanding the effect of geometry on the nonlinear-optical response of quantum loops that are formed into a network of quantum wires. Using the concept of leaky quantum wires, it is shown that in the limit of full confinement, the sum rules are obeyed when the transverse infinite-energy continuum states are included. While the continuum states associated with the transverse wavefunction do not contribute to the nonlinear optical response, they are essential to preserving the validity of the sum rules. This work is a building block for future studies of nonlinear-optical enhancement of quantum graphs (which include loops and bent wires) based on their geometry. These properties are important in quantum mechanical modeling of any response function of quantum-confined systems, including the nonlinear-optical response of any system in which there is confinement in at leat one dimension, such as nanowires, which provide confinement in two dimensions