Hao Wu

This work presents a novel InGaAs/InP avalanche photodiode fabricated in the separate absorption, grading, charge, and multiplication configuration operated at non-cryogenic conditions under low-frequency ramp gating. An optimized three stage InP multiplication layer of 1μ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> thickness offers extended linear mode operation by reducing the punch-through voltage and indefinitely increasing the avalanche threshold voltage. A large background dark current is observed following steady, and linear multiplication in approximately direct relationship with the ramp gating. For 1310 nm short-wave infrared, normal incidence pulsed illumination at instant-to-peak voltage ratios of (0.11,0.2,0.6,0.89,0.98,0.9), a sort of negative differential resistance is incorporated into the device in a qualitative sense, owing to the illumination induced switching/variations in the intrinsic values of electron and hole avalanche coefficients in the multiplication region. Under fixed illumination, an interesting deduction from the transient photo response is the slow quenching phenomenon prolonging ~120 μ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> for all the electrical field establishments in the device. The related measurement scheme paves the way for futuristic ramp-driven InGaAs/InP APDs for detecting SWIR wavelengths under required low power consumption environments.

Activated carbon (AC) adsorption is an effective method for abatement of volatile organic compounds (VOCs) in coal-fired power plants. The adsorption behaviors of VOCs (toluene and chlorobenzene) for ACs (coconut shell-based AC (CSAC) and wood-based AC (WAC)) under medium-high temperature (MHT: 90–150 °C) conditions were investigated in a fixed-bed reactor. The results indicated that the adsorption capacity of VOCs was reduced with increasing temperature. CSAC had a higher adsorption capacity and adsorption rate for the two VOCs than WAC at the same adsorption temperature. The adsorption capacity of toluene was within the range of 13.9–49.9 mg/g, while that for chlorobenzene was 26–80.3 mg/g. The content of oxygen-containing groups on the AC surface was increased with acid modification and decreased with alkali modification. The adsorption capacity of AC was improved to varying degrees after chemical modification. Adsorption was mainly controlled by physical adsorption, whereas the effects of chemisorption became evident with increasing temperature. The interactions between oxygen-containing groups and VOCs were more beneficial for improving adsorption capacity than π–π interactions. The pseudofirst-order kinetic model better described the adsorption of VOCs by ACs. The MHT conditions promoted the intraparticle diffusion; lower VOC concentration resulted in the external mass transfer of AC becoming the adsorption rate-limiting step. Increasing the external surface area and micropore volume of AC and enriching the content of surface oxygen-containing groups were useful in enhancing the VOC removal efficiency.