Zhen Cheng

Long-term trend of haze pollution and impact of particulate matter in the Yangtze River Delta, China.

Haze pollution caused by heavy particulate matter (PM) loading brings significant damage in eastern China. Long-term monitoring from 1980 to 2011 and 1-year field measurement in 2011-2012 are used for investigating visibility variation and the impact of PM pollution for the Yangtze River Delta (YRD). It was found that visual range in the YRD endured a sharp reduction from 13.2 km to 10.5 km during 1980-2000. Average mass extinction efficiency (MEE) for inhalable PM (PM10) is 2.25 m(2)/g in 2001-2011, and extinction coefficient due to PM10 is 207 Mm(-1), accounting for 36.2% of total extinction coefficient. MEE of PM2.5 and PM2.5-10 are 4.08 m(2)/g and 0.58 m(2)/g, respectively. Extinction coefficient due to PM2.5 and PM2.5-10 is 198 Mm(-1) (39.6%) and 20 Mm(-1) (4.0%) in 2011-2012. Maximum daily concentration of PM10 and PM2.5 is estimated to be 63 μg/m(3) (RH: 73%) and 38 μg/m(3) (RH: 70%) to keep visual range above 10 km. Fine particulate matter is the key factor for haze pollution improvement in the YRD area.

Mass extinction efficiency and extinction hygroscopicity of ambient PM2.5 in urban China

ABSTRACT The ambient PM2.5 pollution problem in China has drawn substantial international attentions. The mass extinction efficiency (MEE) and hygroscopicity factor (f(RH)) of PM2.5 can be readily applied to study the impacts on atmospheric visibility and climate. The few previous investigations in China only reported results from pilot studies and are lack of spatial representativeness. In this study, hourly average ambient PM2.5 mass concentration, relative humidity, and atmospheric visibility data from China national air quality and meteorological monitoring networks were retrieved and analyzed. It includes 24 major Chinese cities from nine city‐clusters with the period of October 2013 to September 2014. Annual average extinction coefficient in urban China was 759.3±258.3 Mm−1, mainly caused by dry PM2.5 (305.8.2±131.0 Mm−1) and its hygroscopicity (414.6±188.1 Mm−1). High extinction coefficient values were resulted from both high ambient PM2.5 concentration (68.5±21.7 &mgr;g/m3) and high relative humidity (69.7±8.6%). The PM2.5 mass extinction efficiency varied from 2.87 to 6.64 m2/g with an average of 4.40±0.84 m2/g. The average extinction hygroscopic factor f(RH=80%) was 2.63±0.45. The levels of PM2.5 mass extinction efficiency and hygroscopic factor in China were in comparable range with those found in developed countries in spite of the significant diversities among all 24 cities. Our findings help to establish quantitative relationship between ambient extinction coefficient (visual range) and PM2.5 & relative humidity. It will reduce the uncertainty of extinction coefficient estimation of ambient PM2.5 in urban China which is essential for the research of haze pollution and climate radiative forcing. HighlightsData from air quality and meteorological monitoring networks were combined.MEE and hygroscopicity of PM2.5 in China was similar to that of developed countries.High extinction coefficient was dominated by both high PM2.5 and relative humidity.

Long-term atmospheric visibility trends in megacities of China, India and the United States

ABSTRACT Millions of premature deaths worldwide every year mostly in China and India are contributed by the poor air quality. The atmospheric visibility is a proven indicator of the ambient air quality. In this study, nine megacities were selected, including Beijing, Shanghai and Guangzhou from China, Chicago, Los Angeles (LA) and New York City (NYC) from the United States, and Mumbai, Chennai and Jaipur from India. The data of visibility, aerosol optical depth (AOD), and meteorological factors from 1973 to 2015 were collected. The temporal variations of annual and monthly percentages of bad days (visibility < 5 km) and good days (visibility > 15 km) were evaluated. Visibility of Chicago, LA and NYC gradually improved during the past 43 years and has reached a very good level (good day percentages: 75–88%; bad day percentages: 0 – 4%). Conversely, visibility in Mumbai, Chennai and Jaipur continued deteriorating and suffered an extremely poor visibility situation in recent years (good day percentages: 0; bad day percentages: 6–100%). Likewise, visibility in Beijing, Shanghai and Guangzhou has experienced the worsening period during the industrial development from 1970s and turned better after the 1990s. A strong seasonal pattern of bad day percentages of each year were observed in most cities, especially in the winter, which is caused by the fossil fuel combustion for heating, relatively high relative humidity, and other unfavorable meteorological conditions. The low visibility events occurred more frequently in days with low wind speeds and specific wind directions, further explaining the seasonal patterns of visibility. With population growth from the period of 2000–2010 to the period of 2011–2015, AOD and bad day percentages both increased in Mumbai, Chennai, Jaipur and Beijing while others were relatively stable. This study demonstrated that the macro‐control of pollution emissions could effectively reduce air deterioration. The relationships among visibility variation, meteorological, pollutant and population factors provide valuable scientific support for public health researches, air quality managements (monitoring and forecasting), and clean energy initiatives. HighlightsThe 40‐year visibility trend analysis of nine populated cities in China, India and the United States.The relationships of visibility with meteorological factors and human activities are investigated.The temporal variations of visibility indicate positive impacts of various air quality management policies.

Superconductor based neuron single electron transistor

Abstract We have proposed a new functional superconductor single electron transistor called neuron superconducting single electron transistor (Neuron — SuSET), which simulates the function of biological neurons. The new transistor is capable of executing a weighted sum calculation of multiple input signals and threshold operation based on the results of the weighted summation, The basic structure and the variable threshold characteristics of the Neuron — SuSET are described based on the semiclassical model.

Insights into extinction evolution during extreme low visibility events: Case study of Shanghai, China

Apportionment of ambient extinction coefficient is essential for quantifying the causes of visibility degradation. Previous studies focused on either seasonal or episode-average extinction coefficients. The extinction evolution during different types of low visibility events was still unclear and seldom investigated. In this study, hourly-resolution apportionment of ambient extinction coefficient, including dry extinction coefficient and hygroscopic portion, during three low visibility events (i.e., dust storm, autumn and winter haze) and one clear episode was retrieved through online measurement in Shanghai, China. PM2.5 soil and coarse particles contributed 90% of PM10 mass and 62% of total extinction coefficient throughout the dust storm event. Secondary inorganic aerosol and organic matter dominated the autumn and winter haze events, accounting for 52% and 31% of PM2.5 mass, 35% and 27% of extinction coefficient, respectively. Hygroscopic enhancement by inorganic particles contributed another 22-27% of extinction coefficient during the two haze events. However, higher relative humidity elevated the extinction percentage of inorganic aerosol and hygroscopic enhancement during the autumn haze, and the percentage of organic matter decreased correspondingly. In contrast, the extinction of each contributor increased proportionally and the percentages could keep at a stable level during the winter haze. Furthermore, the mass extinction efficiency of major PM2.5 chemical components was found to increase with the accumulation of mass loading. These findings indicated the importance of reducing the mass level of organic matter and secondary inorganic aerosol during the autumn or winter haze events. The control of precursors of sulfur and nitrogen oxides seemed more effective for visibility improvement during the autumn events with higher relative humidity.

The capacitor and the mesoscopic tunnel junction in series coupled superconducting single electron transistor

Abstract The capacitor and the mesoscopic tunnel junction (CMTJ) in series coupled superconducting single electron transistor (CMTJ — SuSET) is proposed, The gate — control characteristics of the drain current (I D ) — drain voltage (V DD ) and drain current (I D ) — gate voltage (V GG ) of the CMTJ — SuSET are studied by means of the Monte Carlo simulation based on the semiclassical model. The memory effect of the CMTJ — SuSET is also discussed.