It is well known that the excess noise factor of an avalanche photodiode (APD), which is a measure of its gain fluctuation, can be reduced by decreasing the thickness of the avalanche multiplication region. This noise reduction is attributable to the increased importance of the dead-space effect in thin layers, which prevents a carrier from impact ionizing before it travels a sufficient distanc...

Introduction: The head scatter factor (Sc) is important to measurements radiation beam and beam modeling of treatment planning systems used for advanced radiation therapy techniques. This study aimed to investigate the design of a mini-phantom to measurement variations in collimator Sc in the presence of shielding blocks for shaping the beam using different field sizes. <str...

In a superconductor, absorption of photons with an energy below the superconducting gap leads to redistribution of quasiparticles over energy and thus induces a strong nonequilibrium quasiparticle energy distribution. We have measured the electrodynamic response, quality factor, and resonant frequency of a superconducting aluminium microwave resonator as a function of microwave power and temper...

Solvent ordering at an interface can be studied by multiple-quantum NMR. Quantitative studies of (2)H2O ordering require clean double-quantum (2Q) filtration and an analysis of 2Q buildup curves that accounts for relaxation and, if randomly oriented samples are used, the distribution of residual couplings. A pulse sequence with absorption mode detection is extended for separating coherences by ...

Simultaneous transmission infrared (IR) absorption and photoluminescence (PL) spectroscopies are used to reveal the correlation of free electron and defect densities during the stepwise annealing of ZnO nanocrystals in high vacuum. For increasing annealing temperatures between 700 and 1000 K, the free electron density increases with a negligible increase in PL yield. With increased annealing te...

impact is one of the most important subjects which always have been considered in mechanical science. nature of impact is such that which makes its control a hard task. therefore it is required to adopt a safe and secure mechanism for transferring the impact to other vulnerable parts of a structure, when it is necessary. one of the best methods of absorbing impact energy is using thin-walled tu...