The Spatiotemporal Distribution Characteristics of Cloud Types and Phases in the Arctic Based on CloudSat and CALIPSO Cloud Classification Products

The cloud type product 2B-CLDCLASS-LIDAR based on CloudSat and CALIPSO from June 2006 to May 2017 is used to examine the temporal and spatial distribution characteristics and interannual variability of eight cloud types(high cloud, altostratus, altocumulus, stratus, stratocumulus, cumulus, nimbostratus, and deep convection) and three phases(ice,mixed, and water) in the Arctic. Possible reasons for the observed interannual variability are also discussed. The main conclusions are as follows:(1) More water clouds occur on the Atlantic side, and more ice clouds occur over continents.(2)The average spatial and seasonal distributions of cloud types show three patterns: high clouds and most cumuliform clouds are concentrated in low-latitude locations and peak in summer;altostratus and nimbostratus are concentrated over and around continents and are less abundant in summer;stratocumulus and stratus are concentrated near the inner Arctic and peak during spring and autumn.(3) Regional averaged interannual frequencies of ice clouds and altostratus clouds significantly decrease, while those of water clouds, altocumulus, and cumulus clouds increase significantly.(4) Significant features of the linear trends of cloud frequencies are mainly located over ocean areas.(5) The monthly water cloud frequency anomalies are positively correlated with air temperature in most of the troposphere, while those for ice clouds are negatively correlated.(6) The decrease in altostratus clouds is associated with the weakening of the Arctic front due to Arctic warming, while increased water vapor transport into the Arctic and higher atmospheric instability lead to more cumulus and altocumulus clouds.

Influence of Bayer Red Mud on the Operational and Mechanical Characteristics of Composite Cement Mortar

The aim of this study is to enhance the value and utilization of red mud generated in the Bayer process by preparing composite cement mortars.The effects of two different types of Bayer red mud with varying physical and chemical characteristics on the fluidity,mechanical strength,mineral composition,and microstructure of the composite cement mortar were systematically evaluated.The results showed that the optimal addition of red mud A was 10 wt%,while it was 20 wt% for red mud B.The mechanical properties of the composite cement mortar met the standards for P·O42.5 cement.Furthermore,the composite mortar with the addition of red mud B showed higher flexural and compressive strengths compared to the composite mortar with red mud A.This improvement is attributed to the smaller particle size of red mud B,which filled the micro-pores and increased the compactness of the cement stone,as well as its higher content of Na_(2)O,K_(2)O,and other free alkalis,which resulted in more obvious alkali activation,accelerating the hydration of the active minerals in the slurry.

The Observed Near-Surface Energy Exchange Processes over Arctic Glacier in Summer

Under Arctic warming,near-surface energy transfers have significantly changed,but few studies have focused on energy exchange over Arctic glacier due to limitations in available observations.In this study,the atmospheric energy exchange processes over the Arctic glacier surface were analyzed by using observational data obtained in summer 2019 in comparison with those over the Arctic tundra surface.The energy budget over the glacier greatly differed from that over the tundra,characterized by less net shortwave radiation and downward sensible heat flux,due to the high albedo and icy surface.Most of the incoming solar radiation was injected into the glacier in summer,leading to snow ice melting.During the observation period,strong daily variations in near-surface heat transfer occurred over the Arctic glacier,with the maximum downward and upward heat fluxes occurring on 2 and 6 July 2019,respectively.Further analyses suggested that the maximum downward heat flux is mainly caused by the strong local thermal contrast above the glacier surface,while the maximum upward heat transfer cannot be explained by the classical turbulent heat transfer theory,possibly caused by countergradient heat transfer.Our results indicated that the near-surface energy exchange processes over Arctic glacier may be strongly related to local forcings,but a more in-depth investigation will be needed in the future when more observational data become available.

A novel bat coronavirus with a polybasic furin-like cleavage site

The current pandemic of COVID-19 caused by a novel coronavirus,severe acute respiratory syndrome coronavirus-2(SARS-CoV-2),threatens human health around the world.Of particular concern is that bats are recognized as one of the most potential natural hosts of SARS-CoV-2;however,coronavirus ecology in bats is still nascent.Here,we performed a degenerate primer screening and next-generation sequencing analysis of 112 bats,collected from Hainan Province,China.Three coronaviruses,namely bat betacoronavirus(Bat CoV)CD35,Bat CoV CD36 and bat alpha-coronavirus CD30 were identified.Bat CoV CD35 genome had 99.5%identity with Bat CoV CD36,both sharing the highest nucleotide identity with Bat Hp-betacoronavirus Zhejiang2013(71.4%),followed by SARS-CoV-2(54.0%).Phylogenetic analysis indicated that Bat CoV CD35 formed a distinct clade,and together with Bat Hp-betacoronavirus Zhejiang2013,was basal to the lineage of SARS-CoV-1 and SARS-CoV-2.Notably,Bat CoV CD35 harbored a canonical furin-like S1/S2 cleavage site that resembles the corresponding sites of SARS-CoV-2.The furin cleavage sites between CD35 and CD36 are identical.In addition,the receptor-binding domain of Bat CoV CD35 showed a highly similar structure to that of SARS-CoV-1 and SARS-CoV-2,especially in one binding loop.In conclusion,this study deepens our understanding of the diversity of coronaviruses and provides clues about the natural origin of the furin cleavage site of SARS-CoV-2.

Ecological health analysis of wetlands in the middle reaches of Yangtze River under changing environment

Changes in wetland ecosystems have a critical impact on the local ecology and species diversity.Different development scenarios and policies are key factors influencing their changes.Therefore,we studied changes of wetlands in the middle Yangtze River basin(MYRB)in 2001-2020,and a patch-generated land use simulation(PLUS)model and random forest(RF)method were applied to predict and analyze the changes under different scenarios in the MYRB in the future(i.e.2035-2095).The results indicated that:(1)The regions with high wetland proportions were concentrated in the central and eastern MYRB in 2001-2020,with a 1.5%decrease in overall wetland area;(2)The RF could simulate the future ecological quality with training and testing accuracies of 0.98 and 0.92,respectively;(3)Remote Sensing Ecological Index(RSEI)less than 0.5 in the central and eastern regions and 13.3%reduction in the northwest in the SSP245 scenario.In general,the study provides a basis for future regional studies of ecosystem quality and provides data to support wetland conservation and management.

Effect of Support Height on Microstructure and Mechanical Properties of Selective Laser Melting Ti-15Mo Alloy

In this research,for the first time,the Ti-15Mo alloy generated via selective laser melting(SLM)with many different support heights was examined.With the increase of the support height,the risks of forming microcracks and small holes increase while the ductility of the sample decreases.The grain sizes of the samples decrease with an increase in support height because of the more efficient heat dissipation rate during the SLM process.The average grain sizes of the samples are 36.95±0.7μm(5 mm-sample I),35.24±0.7μm(10 mm-sample II)and 33.91±0.7μm(15 mm-sample III),respectively.As the support height increases,the intensity of(111)texture increases and the misorientation angles gradually decrease.The ultimate tensile strength,yield strength and ductility of the three samples are 970±13 MPa,769±12 MPa and 9.78%±1.5%(sample I),1051±11 MPa,932±11 MPa and 7.17%±2%(sample II),1123±14 MPa,1089±9 MPa and 5.4%±1.4%(sample III),respectively.The decrease in grain size,increase in dislocation density and enhancement of the(111)texture are all conducive to achieving the higher strength.

Synergistic effects of non-thermal plasma-assisted catalyst and ultrasound on toluene removal

A wire-mesh catalyst coated by La0.8Sr0.2MnO3 was combined with a dielectric barrier discharge （DBD） reactor for toluene removal at atmospheric pressure. It was found that toluene removal efficiency and carbon dioxide selectivity were enhanced in the catalytic packed-bed reactor. In addition, ozone and nitrogen monoxide from the gas effluent byproducts decreased. This is the first time that ultrasound combined with plasma has been used for toluene removal. A synergistic effect on toluene removal was observed in the plasma-assisted ultrasound system. At the same time, the system increased toluene conversion and reduced ozone emission.

Historical Changes and Future Projections of Extreme Temperature and Precipitation along the Sichuan-Tibet Railway

Based on multiresource high-resolution in situ and satellite merged observations along with model simulations from the Coordinated Regional Climate Downscaling Experiment(CORDEX),this study first investigated historical changes in extreme temperature and precipitation during the period of 1979-2018 in areas along the Sichuan-Tibet Railway,and then projected the future changes in the frequency and intensity of extreme temperature and precipitation under the RCP(Representative Concentration Pathway)4.5 and 8.5 scenarios.This paper is expected to enhance our understanding of the spatiotemporal variability in the extreme temperature and precipitation along the Sichuan-Tibet Railway,and to provide scientific basis to advance the Sichuan-Tibet Railway construction and operation.The results show that temperatures in the Sichuan-Tibet region display a noticeable warming trend in the past 40 years,and the increase of minimum temperature is significantly higher than that of maximum temperature in the northwest of the region.Significant increase of precipitation is found mainly over the northwest of the Tibetan Plateau.Except for Lhasa and its surrounding areas,precipitation over other areas along the Sichuan-Tibet Railway shows no significant change in the past 40 years,as indicated in five datasets;however,precipitation along the railway has shown a remarkable decrease in the past 20 years in the TRMM satellite dataset.The warm days and nights have clearly increased by 6 and 5 day decade1-for 1979-2019,while cold days and nights have markedly decreased by about 6.6 and 3.6 day decade-1,respectively.In the past 20 years,the areas with increased precipitation from very wet days and extremely wet days are mainly distributed to the north of the Sichuan-Tibet Railway,while in the areas along the railway itself,the very wet days and extremely wet days are decreasing.Under RCPs 4.5 and 8.5,the temperature in the Sichuan-Tibet region will increase significantly,and the frequency of extreme high(low)temperature events in the late 21 st century(2070-2099)will greatly increase(decrease)by about 50%-80%(10%)compared with occurrences in the late 20 th century(1970-1999).Meanwhile,the frequency of very wet days and extremely wet days in the Sichuan-Tibet region will increase by about 2%-19% and 2%-5%,respectively,and the areas along the Sichuan-Tibet Railway will be affected by more extreme high temperature and extreme precipitation events.

Simultaneous determination of six steroidal saponins and one ecdysone in Asparagus filicinus using high performance liquid chromatography coupled with evaporative light scattering detection

A high-performance liquid chromatography coupled with an evaporative light scattering detector(HPLC-ELSD)has been developed to evaluate the quality of Asparagus filicinus through a simultaneous determination of six steroidal saponins and one ecdysone,including aspafiliosides A,B,C,E,G,filiasparoside A and 20-hydroxyecdysone.With a C_(18) analytical column,the seven analytes were separated efficiently using acetonitrile-water as the mobile phase in a gradient program.The method limits of detection ranged 0.1250.225μg,and the method limits of quantitation ranged 0.408-0.720μg,respectively.The intra-and inter-day precisions of the method were evaluated and were all less than 3%.All the recoveries for the spiked analytes ranged 95.16%-100.61%.The proposed method was succesfully applied to quantify the seven components in thirteen samples from different localities in China.

Atmospheric Structure Observed over the Antarctic Plateau and Its Response to a Prominent Blocking High Event

Studies on the atmospheric structure over the Antarctic Plateau are important for better understanding the weather and climate systems of polar regions.In the summer of 2017,an observational experiment was conducted at Dome-A,the highest station in Antarctica,with a total of 32 profiles obtained from global positioning system(GPS)radiosondes.Based on observational data,the atmospheric temperature,humidity,and wind structures and their variations are investigated,and compared with those from four other stations inside the Antarctic circle.Distinguished thermal and dynamic structures were revealed over Dome-A,characterized by the lowest temperature,the highest tropopause,the largest lapse rate,and the most frequent temperature and humidity inversion.During the experiment,a prominent blocking event was identified,with great influence on the atmospheric structure over Dome-A.The blocking high produced a strong anticyclone that brought warm and moist air to the hinterland of the Antarctic Plateau,causing a much warmer,wetter,and windier troposphere over the Dome-A station.Meanwhile,a polar air mass was forced out of the Antarctic,formed a cold surge extending as far as southern New Zealand and affected the weather there.Our results proved that there would be a direct interaction between the atmosphere over the hinterland of the Antarctic Plateau and mid latitudes with the action of a blocking high.Further studies are needed to explore the interaction between the atmospheric systems over the Antarctic and mid latitudes under intense synoptic disturbance,with longterm data and numerical modeling.

Research on Effective Teaching Based on the BOPPPS Model Under the Background of Engineering Education Professional Certification

According to the general requirement of the engineering education professional certification and aiming at the problem of how to develop undergraduates with the ability to solve complex engineering problems by teaching research and curriculum construction,a new effective teaching model is built by analyzing the relationship between BOPPPS and effective teaching.Our contributions are as follows:we combine professional training objectives with curriculum characteristics,focus on the importance of participating in the main position of students in learning,and emphasize that students’participatory interaction and feedback and diversified assessment methods for evaluation are adopted to focus on the development and improvement of the comprehensive quality of students and classroom teaching quality and teaching effect to ensure the effectiveness of teaching.The practice in the Oracle database course proves that the teaching mode proposed in this paper can effectively improve the teaching effect,and it plays a positive role in strengthening students’practical abilities to solve practical engineering problems.