We studied temperature-dependent amplified spontaneous emission (ASE) in CsPbBr3 perovskite thin films. For temperatures 180-360 K, a narrow-band lasing is observed. However, a new accompanying ASE band appears below 180 K, indicating a more complicated behavior. The two ASE bands are strongly correlated and in competition; they are assigned as exciton and bi-exciton recombination. We estimated the exciton binding energy (E-B = 27.3 meV) and that of the bi-exciton, which is lower than the E-B. The reduced effective mass of the exciton is estimated as mu = 0.11 m(c). This discovery identifies more details of the ASE phenomenon. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Since its initial proposal, steam-assisted gravity drainage (SAGD) has become a key technology of heavy-oil recovery. Due to the large heat loss and high energy consumption in the SAGD process, gas-assisted SAGD is a way to improve the efficiency. In this paper, a two-dimensional (2D) visualization simulation experiment of SAGD is introduced. By adjusting the volume ratio of steam to nitrogen, the proportion for the nitrogen-assisted SAGD process is optimized based on a homogeneous model. The 2D visualization simulation experiment of a heterogeneous model is carried out by adjusting the length of a low-permeability interlayer. The results of the SAGD simulation experiment and nitrogen-assisted SAGD simulation experiment are analyzed. The effect of nitrogen on breaking through and bypassing the low-permeability interlayer is discussed. The experimental results show that the optimal volume ratio of steam to nitrogen is 8:2 in the process of nitrogen-assisted SAGD. At this volume ratio, the sweep efficiency, recovery factor and cumulative oil-steam ratio are the largest, and the recovery factor reaches up to 49.12%. The experimental results for the heterogeneous model with the low-permeability interlayer show that nitrogen can synergistically promote steam to break through the fully occluding interlayer and bypass partially occluding interlayers. Comparing the results of the SAGD simulation with those of the nitrogen-assisted SAGD simulation for the heterogeneous model with the low-permeability interlayer, it is found that the sweep efficiency of steam increases from 34.24% to 43.12%. This result can be explained by the effect of nitrogen on expanding the steam-swept area in the SAGD process and the synergistic action between nitrogen and steam.
The environmental risks and health impacts associated with particulate organophosphate flame retardants (OPFRs), which are ubiquitous in the global atmosphere, have not been adequately assessed due to the lack of data on the reaction kinetics, products, and toxicity associated with their atmospheric transformations. Here, the importance of such transformations for OPFRs are explored by investigating the reaction kinetics, degradation chemical mechanisms, and toxicological evolution of two OPFRs (2-ethylhexyl diphenyl phosphate (EHDP) and diphenyl phosphate (DPhP)) coated on (NH4)(2)SO4 particles upon heterogeneous OH oxidation. The derived reaction rate constants for the heterogeneous loss of EHDP and DPhP are (1.12 +/- 0.22) x 10(-12) and (2.33 +/- 0.14) x 10(-12) cm(3) molecules(-1) s(-1), respectively. Using recently developed real-time particle chemical composition measurements, particulate products from heterogeneous photooxidation and the associated degradation mechanisms for particulate OPFRs are reported for the first time. Subsequent cytotoxicity analysis of the unreacted and oxidized OPFR particles indicated that the overall particle cytotoxicity was reduced by up to 94% with heterogeneous photooxidation, likely due to a significantly lower cytotoxicity associated with the oxidized OPFR products relative to the parent OPFRs. The present work not only provides guidance for future field sampling for the detection of transformation products of OPFRs, but also strongly supports the ongoing risk assessment of these emerging chemicals and most critically, their products.
Abstract Flue gas collection from steam generators and its utilization in enhanced oil recovery (EOR) can reduce CO2 emissions into the atmosphere and improve oil recovery efficiency. Under the environments of flue gas corrosion in oilfields, the effects of corrosion time, temperature, pressure, velocity, and concentrations of O2, SO2, H2O, and NaCl on corrosion rates of steels used for a downhole string were investigated through physical simulation experiments. The corrosion mechanisms were analyzed by component, and the morphology of the corrosion products tested by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the gas phase, the corrosion rates of X70, P110, and N80 notably increase with temperature and O2 concentration. The corrosion rates first increase rapidly with pressure from 1.0 to 3.0 MPa and then remain largely stable. Meanwhile, the corrosion rates of X70, P110, and N80 in the liquid phase first increase and then decrease with temperature and reach maximum values at 90°C. The corrosion rates of X70, P110, and N80 increase notably with velocity and the concentrations of O2, SO2, H2O, and NaCl. The corrosion rate of 13Cr is considerably lower than those of N80, P110, and X70, which shows good corrosion resistance performance. To reduce the flue gas corrosion of a downhole string, the relative humidity of the flue gas should be lower than 0.7, the temperature of the flue gas in the wellbore should avoid the range between 80 and 100°C, the excess air coefficient of the boiler should be kept at a reasonable value to reduce the O2 content in the flue gas, and the flue gas should not be coinjected into wellbores with brine. The injection of flue gas is technically feasible considering the corrosion of downhole string.
Since 1971, it has been known that the atmospheric free radicals play a pivotal role in maintaining the oxidizing power of the troposphere. The existence of the oxidizing power is an important feature of the troposphere to remove primary air pollutants emitted from human beings as well as those from the biosphere. Nevertheless, serious secondary air-pollution incidents can take place due to fast oxidation of the primary pollutants. Elucidating the atmospheric free-radical chemistry is a demanding task in the field of atmospheric chemistry worldwide, which includes two kinds of work: first, the setup of reliable radical detection systems; second, integrated field studies that enable closure studies on the sources and sinks of targeted radicals such as OH and NO3. In this review, we try to review the Chinese efforts to explore the atmospheric free-radical chemistry in such chemical complex environments and the possible link of this fast gas-phase oxidation with the fast formation of secondary air pollution in the city-cluster areas in China.