Thermoluminescence properties of gamma-irradiated nano-structure hydroxyapatite.

The suitability of nano-structured hydroxyapatite (HAP) for use as a thermoluminescence dosimeter was investigated. HAP samples were synthesized using a hydrolysis method. The formation of nanoparticles was confirmed by X-ray diffraction and average particle size was estimated to be ~30 nm. The glow curve exhibited a peak centered at around 200 °C. The additive dose method was applied and this showed that the thermoluminescence (TL) glow curves follow first-order kinetics due to the non-shifting nature of Tm after different doses. The numbers of overlapping peaks and related kinetic parameters were identified from Tm -Tstop through computerized glow curve deconvolution methods. The dependence of the TL responses on radiation dose was studied and a linear dose response up to 1000 Gy was observed for the samples.

Motion of a density current head in a diverging channel.

Velocity of density current head in the diverging channel, where a river enters a dam reservoir, lake, or sea, is a key parameter when evaluating the extent to which suspended material travels, and determining the type and distribution of sediment in the reservoir. Effects of the channel degree of divergence on the density current head velocity were experimentally evaluated. Experiments were conducted in a 6.0m long and 0.72m wide flume at two slopes of 0.009 and 0.016. Head velocity was measured at three diverging degrees of 8, 12, 26, also in a uniform cross section channel 0.2m wide for various discharges. For the same slope and density current discharge, results showed that head velocity is higher in the diverging channels compared to that in the uniform cross section channel. As the channel degree of divergence was increased, the head velocity also increased. The increase of head velocity was insignificant beyond 12 degrees of divergence. In consent to the previous studies, the current head velocity increased as the bed slope increased. Using theory of dimensional analysis supported by experiments, a mathematical model was developed to calculate the head velocity for a variety of slopes and degrees of divergence.