Direct conversion of methane to methanol by electrochemical methods

A convenient method for methane(CH_(4))direct conversion to methanol(CH_(3)OH)is of great significance to use methane-rich resources,especially clathrates and stranded shale gas resources located in remote regions.Theoretically,the activation of CH_(4) and the selectivity to the CH_(3)OH product are challenging due to the extreme stability of CH_(4) and relatively high reactivity of CH_(3)OH.The state-of-the-art‘methane reforming-methanol synthesis’process adopts a two-step strategy to avoid the further reaction of CH_(3)OH under the harsh conditions required for CH_(4) activation.In the electrochemical field,researchers are trying to develop conversion pathways under mild conditions.They have found suitable catalysts to activate the C–H bonds in methane with the help of external charge and have designed the electrode reactions to continuously generate certain active oxygen species.These active oxygen species attack the activated methane and convert it to CH_(3)OH,with the benefit of avoiding over-oxidation of CH_(3)OH,and thus obtain a high conversion efficiency of CH_(4) to CH_(3)OH.This mini-review focuses on the advantages and challenges of electrochemical conversion of CH4 to CH_(3)OH,especially the strategies for supplying electro-generated active oxygen species in-situ to react with the activated methane.

Recent Progress in Atmospheric Chemistry Research in China: Establishing a Theoretical Framework for the “Air Pollution Complex”

Atmospheric chemistry research has been growing rapidly in China in the last 25 years since the concept of the“air pollution complex”was first proposed by Professor Xiaoyan TANG in 1997.For papers published in 2021 on air pollution(only papers included in the Web of Science Core Collection database were considered),more than 24000 papers were authored or co-authored by scientists working in China.In this paper,we review a limited number of representative and significant studies on atmospheric chemistry in China in the last few years,including studies on(1)sources and emission inventories,(2)atmospheric chemical processes,(3)interactions of air pollution with meteorology,weather and climate,(4)interactions between the biosphere and atmosphere,and(5)data assimilation.The intention was not to provide a complete review of all progress made in the last few years,but rather to serve as a starting point for learning more about atmospheric chemistry research in China.The advances reviewed in this paper have enabled a theoretical framework for the air pollution complex to be established,provided robust scientific support to highly successful air pollution control policies in China,and created great opportunities in education,training,and career development for many graduate students and young scientists.This paper further highlights that developing and low-income countries that are heavily affected by air pollution can benefit from these research advances,whilst at the same time acknowledging that many challenges and opportunities still remain in atmospheric chemistry research in China,to hopefully be addressed over the next few decades.

Advances of research on high-speed railway catenary

The interaction between the catenary and pantograph is one of the most crucial factors that determine the train operation in high-speed railway. The bad state of catenary is able to directly influence the power supply safety of traction power system. In this paper, four aspects on the catenary research of high-speed railway are reviewed in detail, namely the solution methods for catenary equilibrium state, the dynamic modeling methods of catenary, the non-contact detection methods of catenary, and the static and dynamic evaluation methods of catenary. In addition, their recent advances are described. For the low solution accuracy of the initial equilibrium state of cate- nary, the structure finding method with multi-objective constraint and nonlinear finite element procedure are introduced to solve the problem. For the catenary＇s dynamic modeling, considering the influence of environmental wind on the catenary, environmental wind simula- tions and wind tunnel tests are used to obtain the aerodynamic coefficients and build the wind field along the catenary for analysis of its wind vibration characteristics. In order to improve the detection accuracy of non-contact detection for the catenary, the deep learning theory and real-time detection algorithms should be adopted in the future. In view of the lack of dynamic assessment method for the catenary, the modern spectrum evaluation, timefrequency analysis, big data technology and their combi- nations will be the important means for future catenary evaluation.

Simulation of atmospheric aerosols in East Asia using modeling system RAMS-CMAQ:Model evaluation

The modeling system RAMS-CMAQ is applied in this paper to East Asia to simulate the temporo-spatial concentration distributions of atmospheric aerosols. For evaluating its performances, modeled concentrations of aerosols such as sulfate, nitrate, ammonium, black carbon and organic carbon were compared with observations obtained in East Asia on board of two aircrafts in the springtime of 2001. The comparison showed generally good agreement, and, in particular, that the modeling system captured most of the important observed features, including vertical gradients of the aerosols of the Asian outflow over the western Pacific. The evaluation results provide us with much confidence for further use of the modeling system to investigate the transport and transformation processes of atmospheric aerosols over East Asia and to assess their impacts on the Earth＇s radiation budget.

Chemical properties and origin of dust aerosols in Beijing during springtime

Ground observation of dust aerosols was conducted in Beijing in the spring of 2005 in order to investigate the element composition and origin of mineral dust. Mass concentrations of most mineral elements of particles increased during dust events. Mineral elements were predominant in the sums of total element loadings in both dusty and non-dusty days. Mg, Si, Fe, A1 or Ti can be used as an indicator of dust outflow; C1 can be viewed as an evidence of dust particles mixing with anthropogenic emissions. Mineral and pollutant elements showed a bimodal mass particle-size distribution （MSD） in non-dusty days, and a trimodal distribution in dusty days, but their peak concentrations fell in different size stages. Zn and S were mainly enriched in fine particles, whereas C1 was enriched in medium particles, but most mineral elements and Cu were enriched in coarse particles. Mineral elements were dominated by crustal material in dusty even non-dusty days, but pollutant elements were from non-crustal material including local and remote sources. Back trajectory analysis indicated that dust particles in Beijing mainly originated from the Gobi and desert regions of Mongolian and northern China.

Simulation of the direct effects of dust aerosol on climate in East Asia

The results from some general circulation models show distinct radiative forcing （RF） by dust aerosol, which potentially has an effect on climate change. The direct RF and regional climatic effects of dust aerosol over the East Asian region are investigated in this study using NCAR＇s Community Atmospheric Model version 3.1. The negative RF at the top of the atmosphere （TOA） and the surface （SRF） has been revealed except for some high-albedo regions, which leads to a decrease in the surface air temperature and brings an increase of atmospheric radiative heating under both clear- and all-sky conditions. The decrease in the surface air temperature can be found over a wide region that includes the Indian peninsula and northwest China. It accompanies an increase in eastern China and the Korean peninsula, and temperature changes are not limited to regions with a large dust optical depth. A belt of vapor increase is revealed from the Indian peninsula extending east to northern China, while vapor content evidently deceases in southwest China. An increase in precipitation can also be found in the belt of increased vapor accompanying the reduction of precipitation across the regions to the south of 30~N. The pattern of rainfall change helps to offset the trend of increasing wetness in the south and increasing dryness in the north of China in recent years.