Highly reliable and selective ethanol sensor based on α-Fe2O3 nanorhombs working in realistic environments

A highly reliable and selective ethanol gas sensor working in realistic environments based on alpha-Fe2O3(α-Fe2O3)nanorhombs is developed. The sensor is fabricated by integrating α-Fe2O3 nanorhombs onto a low power microheater based on micro-electro-mechanical systems(MEMS) technology. The α-Fe2O3 nanorhombs, prepared via a solvothermal method, is characterized by transmission electron microscopy(TEM), Raman spectroscopy, x-ray diffraction(XRD), and x-ray photoelectron spectroscopy(XPS). The sensing performances of the α-Fe2O3 sensor to various toxic gases are investigated. The optimum sensing temperature is found to be about 280℃. The sensor shows excellent selectivity to ethanol.For various ethanol concentrations(1 ppm-20 ppm), the response and recovery times are around 3 s and 15 s at the working temperature of 280℃, respectively. Specifically, the α-Fe2O3 sensor exhibits a response shift less than 6% to ethanol at280℃ when the relative humidity(RH) increases from 30% to 70%. The good tolerance to humidity variation makes the sensor suitable for reliable applications in Internet of Things(IoT) in realistic environments. In addition, the sensor shows great long-term repeatability and stability towards ethanol. A possible gas sensing mechanism is proposed.

Comparison of Aerosol Effects on Simulated Spring and Summer Hailstorm Clouds

Numerical simulations are carried out to investigate the effect of cloud condensation nuclei（CCN） concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are simulated, a spring case and a summer case, in a semiarid region of northern China, with the Regional Atmospheric Modeling System. The results are used to investigate the differences and similarities of the CCN effects between spring and summer hailstorms. The similarities are：（1） The total hydrometeor mixing ratio decreases, while the total ice-phase mixing ratio enhances, with increasing CCN concentration;（2） Enhancement of the CCN concentration results in the production of a greater amount of small-sized hydrometeor particles, but a lessening of large-sized hydrometeor particles;（3） As the CCN concentration increases, the supercooled cloud water and rainwater make a lesser contribution to hail, while the ice-phase hydrometeors take on active roles in the growth of hail;（4） When the CCN concentration increases, the amount of total precipitation lessens,while the role played by liquid-phase rainfall in the amount of total precipitation reduces, relatively, compared to that of icephase precipitation. The differences between the two storms include：（1） An increase in the CCN concentration tends to reduce pristine ice mixing ratios in the spring case but enhance them in the summer case;（2） Ice-phase hydrometeor particles contribute more to hail growth in the spring case, while liquid water contributes more in the summer case;（3） An increase in the CCN concentration has different effects on surface hail precipitation in different seasons.

Impact of emission reduction on aerosol-radiation interaction during heavy pollution periods over Beijing-Tianjin-Hebei region in China

In December 2015,the Beijing-Tianjin-Hebei(BTH) region experienced several episodes of heavy air pollution.The government immediately issued emergency control measures to reduce the pollution,which provided a good opportunity to explore the impact of emission reduction on aerosol-radiation interaction.In this study,four tests were conducted,including the basel simulation with emission reduction and aerosol-radiation interaction on,the base2 simulation with emission reduction and aerosol-radiation interaction off,the scenariol simulation without emission reduction and aerosol-radiation interaction on and the scenario2 simulation without emission reduction and aerosol-radiation interaction off.We find that the aerosol-radiation interaction decreased the downward shortwave radiation and the temperature at 2 m,reduced the planetary boundary layer height(PBLH) in the region,and increased the relative humidity at 2 m,which is favorable for pollution accumulation.Our results revealed that the interaction effect due to emission reductions increased downward shortwave radiation by an average of 0-5 W/m2,leading to increase in surface temperature of 0-0.05℃,increase in the daytime mean PBL high of 0-8 m,and decrease in daytime mean relative humidity at 2 m of 0.5%.We found that if there were aerosol-radiation interaction,it would enhance the effectiveness of emission control measures on air pollution control.The enhance of PM2.5(particulate matter less than 2.5 um),PM10(particulate matter less than 10 um),and NO2(nitrogen dioxide) emission reduction effects reached7.62%,6.90%,11.62%,respectively,over this region.