Unidirectional travelling wave operation of a mode-locked Nd:glass ring laser
Abstract The development of unidirectional mode-locked pulses in a Nd:glass ring laser is studied for various combinations of active and passive mode-locking and pulse direction discrimination elements.
Characterization of pulsed Nd:YAG active/passive mode-locked laser
The influence of the distance of an active modulator to one of the resonator's end mirrors is investigated both theoretically and experimentally and is found not to be critical for high-gain lasers. The effect of the active modulator on the pulse length of an active/passive mode-locked Nd:YAG laser is discussed qualitatively. Threshold, stability, pulse length, and output energy are investigated experimentally with respect to their dependence on modulation power of the active modulator, dye concentration of the passive modulator, and resonator length mismatch. At a repetition rate of 10 Hz the best achievable stability for the pulse-train energy was ± 1 percent with a single pulse length of 25 ps. The resonator length has to be maintained with an accuracy of\pm 100 \mum.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.