Based on climate extreme indices calculated from a high-resolution daily observational dataset in China during 1961–2005,the performance of 12 climate models from phase 6 of the Coupled Model Intercomparison Project(...Based on climate extreme indices calculated from a high-resolution daily observational dataset in China during 1961–2005,the performance of 12 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),and 30 models from phase 5 of CMIP(CMIP5),are assessed in terms of spatial distribution and interannual variability.The CMIP6 multi-model ensemble mean(CMIP6-MME)can simulate well the spatial pattern of annual mean temperature,maximum daily maximum temperature,and minimum daily minimum temperature.However,CMIP6-MME has difficulties in reproducing cold nights and warm days,and has large cold biases over the Tibetan Plateau.Its performance in simulating extreme precipitation indices is generally lower than in simulating temperature indices.Compared to CMIP5,CMIP6 models show improvements in the simulation of climate indices over China.This is particularly true for precipitation indices for both the climatological pattern and the interannual variation,except for the consecutive dry days.The arealmean bias for total precipitation has been reduced from 127%(CMIP5-MME)to 79%(CMIP6-MME).The most striking feature is that the dry biases in southern China,very persistent and general in CMIP5-MME,are largely reduced in CMIP6-MME.Stronger ascent together with more abundant moisture can explain this reduction in dry biases.Wet biases for total precipitation,heavy precipitation,and precipitation intensity in the eastern Tibetan Plateau are still present in CMIP6-MME,but smaller,compared to CMIP5-MME.展开更多
Extreme high temperature(EHT)events are among the most impact-related consequences related to climate change,especially for China,a nation with a large population that is vulnerable to the climate warming.Based on the...Extreme high temperature(EHT)events are among the most impact-related consequences related to climate change,especially for China,a nation with a large population that is vulnerable to the climate warming.Based on the latest Coupled Model Intercomparison Project Phase 6(CMIP6),this study assesses future EHT changes across China at five specific global warming thresholds(1.5℃-5℃).The results indicate that global mean temperature will increase by 1.5℃/2℃ before 2030/2050 relative to pre-industrial levels(1861-1900)under three future scenarios(SSP1-2.6,SSP2-4.5,and SSP5-8.5),and warming will occur faster under SSP5-8.5 compared to SSP1-2.6 and SSP2-4.5.Under SSP5-8.5,global warming will eventually exceed 5℃ by 2100,while under SSP1-2.6,it will stabilize around 2℃ after 2050.In China,most of the areas where warming exceeds global average levels will be located in Tibet and northern China(Northwest China,North China and Northeast China),covering 50%-70%of the country.Furthermore,about 0.19-0.44 billion people(accounting for 16%-41%of the national population)will experience warming above the global average.Compared to present-day(1995-2014),the warmest day(TXx)will increase most notably in northern China,while the number of warm days(TX90p)and warm spell duration indicator(WSDI)will increase most profoundly in southern China.For example,relative to the present-day,TXx will increase by 1℃-5℃ in northern China,and TX90p(WSDI)will increase by 25-150(10-80)days in southern China at 1.5℃-5℃ global warming.Compared to 2℃-5℃,limiting global warming to 1.5℃ will help avoid about 36%-87%of the EHT increases in China.展开更多
Link flooding attack(LFA)is a fresh distributed denial of service attack(DDoS).Attackers can cut off the critical links,making the services in the target area unavailable.LFA manipulates legal lowspeed flow to flood c...Link flooding attack(LFA)is a fresh distributed denial of service attack(DDoS).Attackers can cut off the critical links,making the services in the target area unavailable.LFA manipulates legal lowspeed flow to flood critical links,so traditional technologies are difficult to resist such attack.Meanwhile,LFA is also one of the most important threats to Internet of things(IoT)devices.The introduction of software defined network(SDN)effectively solves the security problem of the IoT.Aiming at the LFA in the software defined Internet of things(SDN-IoT),this paper proposes a new LFA mitigation scheme ReLFA.Renyi entropy is to locate the congested link in the data plane in our scheme,and determines the target links according to the alarm threshold.When LFA is detected on the target links,the control plane uses the method based on deep reinforcement learning(DRL)to carry out traffic engineering.Simulation results show that ReLFA can effectively alleviate the impact of LFA in SDN IoT.In addition,the rerouting time of ReLFA is superior to other latest schemes.展开更多
[Objectives]This study aimed to establish a QAMS(quantitative analysis of multi-components by single-marker)method for simultaneous determination of four phenolic acids,salvianolic acid B,tanshinol,lithospermic acid a...[Objectives]This study aimed to establish a QAMS(quantitative analysis of multi-components by single-marker)method for simultaneous determination of four phenolic acids,salvianolic acid B,tanshinol,lithospermic acid and rosmarinic acid in Radix Salviae Miltiorrhizae by HPLC and conduct methodological investigation.[Methods]Salvianolic acid B,with moderate retention time,good resolution,great response value and easy availability was selected as the internal standard,and the relative retention values and relative correction factors between tanshinol,rosmarinic acid,lithospermic acid and salvianolic acid B were established.The results of QAMS were compared with those of external standard method to verify the accuracy and applicability of QAMS.[Results]There were no significant differences between the calculated values of QAMS and the measured values of external standard method.The relative deviation was less than 3%,and the relative correction factors obtained from the experiment were credible.[Conclusions]QAMS can be used to determine the contents of phenolic acids in Radix Salviae Miltiorrhizae formula granules.展开更多
In order to meet the requirements of on-orbit servicing outside the cabin, a flexible, dexterous hand with easy grasping ability and strong loading capacity is designed. The dexterous hand is comprised of three finger...In order to meet the requirements of on-orbit servicing outside the cabin, a flexible, dexterous hand with easy grasping ability and strong loading capacity is designed. The dexterous hand is comprised of three fingers. Each finger is driven by a set of four linkages. Furthermore, two fingers have a set of axial rotational degrees of freedom. In order to achieve the position control and keep griping stability, the dexterous hand adopts a mechanism of hybrid force/position control. In the end, experimental results demonstrates that the on-orbit servicing dexterous hand has great adaptability and operational capability.展开更多
The space manipulator is always designed to have 7 degrees of freedom(Dofs)with the consideration of energy limitation,as well as the flexible moving possibility.Therefore,how to plan the trajectory is important to ...The space manipulator is always designed to have 7 degrees of freedom(Dofs)with the consideration of energy limitation,as well as the flexible moving possibility.Therefore,how to plan the trajectory is important to improve the performance of the manipulator.In this paper,the speed of the end effector is configured as a projecting parameter,when a constant acceleration is applied to adjust the velocity.To implement this trajectory planning strategy,an optimization algorithm through the pseudo inverse of Jacobin matrix is designed,which adjusts the weight functions of joints.According to the functional theory,this algorithm is analyzed and the optimal solution is found in numerous sets of planning.A MATLAB simulation platform is established and the results verity the effectiveness of the algorithm.展开更多
Dear editor,Human-robot collaboration is a research topic that has numerous potential applications, such as in smart cities. An important safety consideration in human-robot collaboration is collision avoidance[1]. Ma...Dear editor,Human-robot collaboration is a research topic that has numerous potential applications, such as in smart cities. An important safety consideration in human-robot collaboration is collision avoidance[1]. Many studies have prioritized collision avoidance of the robot end-effector. However, multi-joint(whole-body) collision avoidance is also very important in complex working scenarios. Several studies have achieved multi-joint collision avoidance by estimating the distance between obstacles and control points placed on the robot body.展开更多
The outbreak of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in late 2019 has negatively affected people's lives and productivity.Because the mode of transmission of SARS-CoV-2 is of great concern,th...The outbreak of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in late 2019 has negatively affected people's lives and productivity.Because the mode of transmission of SARS-CoV-2 is of great concern,this review discusses the sources of virus aerosols and possible transmission routes.First,we discuss virus aerosol collection methods,including natural sedimentation,solid impact,liquid impact,centrifugal,cyclone and electrostatic adsorption methods.Then,we review common virus aerosol detection methods,including virus culture,metabolic detection,nucleic acid-based detection and immunology-based detection methods.Finally,possible solutions for the detection of SARS-CoV-2 aerosols are introduced.Point-of-care testing has long been a focus of attention.In the near future,the development of an instrument that integrates sampling and output results will enable the real-time,automatic monitoring of patients.展开更多
Climate change adaptation and relevant policy-making need reliable projections of future climate.Methods based on multi-model ensemble are generally considered as the most efficient way to achieve the goal.However,the...Climate change adaptation and relevant policy-making need reliable projections of future climate.Methods based on multi-model ensemble are generally considered as the most efficient way to achieve the goal.However,their efficiency varies and inter-comparison is a challenging task,as they use a variety of target variables,geographic regions,time periods,or model pools.Here,we construct and use a consistent framework to evaluate the performance of five ensemble-processing methods,i.e.,multimodel ensemble mean(MME),rank-based weighting(RANK),reliability ensemble averaging(REA),climate model weighting by independence and performance(ClimWIP),and Bayesian model averaging(BMA).We investigate the annual mean temperature(Tav)and total precipitation(Prcptot)changes(relative to 1995–2014)over China and its seven subregions at 1.5 and 2℃warming levels(relative to pre-industrial).All ensemble-processing methods perform better than MME,and achieve generally consistent results in terms of median values.But they show different results in terms of inter-model spread,served as a measure of uncertainty,and signal-to-noise ratio(SNR).ClimWIP is the most optimal method with its good performance in simulating current climate and in providing credible future projections.The uncertainty,measured by the range of 10th–90th percentiles,is reduced by about 30%for Tav,and 15%for Prcptot in China,with a certain variation among subregions.Based on ClimWIP,and averaged over whole China under 1.5/2℃global warming levels,Tav increases by about 1.1/1.8℃(relative to 1995–2014),while Prcptot increases by about 5.4%/11.2%,respectively.Reliability of projections is found dependent on investigated regions and indices.The projection for Tav is credible across all regions,as its SNR is generally larger than 2,while the SNR is lower than 1 for Prcptot over most regions under 1.5℃warming.The largest warming is found in northeastern China,with increase of 1.3(0.6–1.7)/2.0(1.4–2.6)℃(ensemble’s median and range of the 10th–90th percentiles)under 1.5/2℃warming,followed by northern and northwestern China.The smallest but the most robust warming is in southwestern China,with values exceeding 0.9(0.6–1.1)/1.5(1.1–1.7)℃.The most robust projection and largest increase is achieved in northwestern China for Prcptot,with increase of 9.1%(–1.6–24.7%)/17.9%(0.5–36.4%)under 1.5/2℃warming.Followed by northern China,where the increase is 6.0%(–2.6–17.8%)/11.8%(2.4–25.1%),respectively.The precipitation projection is of large uncertainty in southwestern China,even with uncertain sign of variation.For the additional half-degree warming,Tav increases more than 0.5℃throughout China.Almost all regions witness an increase of Prcptot,with the largest increase in northwestern China.展开更多
The SARS–CoV–2 virus is released from an infectious source(such as a sick person)and adsorbed on aerosols,which can form pathogenic microorganism aerosols,which can affect human health through airborne transmission....The SARS–CoV–2 virus is released from an infectious source(such as a sick person)and adsorbed on aerosols,which can form pathogenic microorganism aerosols,which can affect human health through airborne transmission.Efficient sampling and accurate detection of microorganisms in aerosols are the premise and basis for studying their properties and evaluating their hazard.In this study,we built a set of sub-micron aerosol detection platform,and carried out a simulation experiment on the SARS–CoV–2 aerosol in the air by wet-wall cyclone combined with immunomagnetic nanoparticle adsorption sampling and ddPCR.The feasibility of the system in aerosol detection was verified,and the influencing factors in the detection process were experimentally tested.As a result,the sampling efficiency was 29.77%,and extraction efficiency was 98.57%.The minimum detection limit per unit volume of aerosols was 250 copies(102copies/m L,concentration factor 2.5).展开更多
To avoid dangerous climate change impact, the Paris Agreement sets out two ambitious goals: to limit the global warming to be well below 2 ℃ and to pursue effort for the global warming to be below 1.5 ℃ above the ...To avoid dangerous climate change impact, the Paris Agreement sets out two ambitious goals: to limit the global warming to be well below 2 ℃ and to pursue effort for the global warming to be below 1.5 ℃ above the pre-industrial level. As climate change risks may be region-dependent, changes in magnitude and probability of extreme precipitation over China are investigated under those two global warming levels based on simulations from the Coupled Model Inter-Comparison Projects Phase 5. The focus is on the added changes due to the additional half a degree warming from 1.5 ℃ to 2 ℃ . Results show that regional average changes in the magnitude do not depend on the return periods with a relative increase around 7% and 11% at the 1.5 ℃ and 2 ℃ global warming levels, respectively. The additional half a degree global warming adds an additional increase in the magnitude by nearly 4%. The regional average changes in term of occurrence probabilities show dependence on the return periods, with rarer events(longer return periods) having larger increase of risk. For the 100-year historical event, the probability is projected to increase by a factor of 1.6 and 2.4 at the 1.5 ℃ and 2 ℃ global warming levels, respectively.The projected changes in extreme precipitation are independent of the RCP scenarios.展开更多
The external source/sink of potential vorticity (PV) is the original driving force for the atmospheric circulation. The relationship between surface PV generation and surface PV density forcing is discussed in detail ...The external source/sink of potential vorticity (PV) is the original driving force for the atmospheric circulation. The relationship between surface PV generation and surface PV density forcing is discussed in detail in this paper. Moreover, a case study of the extreme winter freezing rain/snow storm over South China in January 2008 is performed, and the surface PV density forcing over the eastern flank of the Tibetan Plateau (TP) has been found to significantly affect the precipitation over South China in this case. The TP generated PV propagated eastward in the middle troposphere. The associated zonal advection of positive absolute vorticity resulted in the increasing of cyclo-nic relative vorticity in the downstream region of the TP. Ascending air and convergence in the lower troposphere developed, which gave rise to the development of the southerly wind. This favored the increasing of negative meridio-nal absolute vorticity advection in the lower troposphere, which provided a large-scale circulation background conducive to ascending motion such that the absolute vorticity advection increased with height. Consequently, the ascending air further strengthened the southerly wind and the vertical gradient of absolute vorticity advection between the lower and middle troposphere in turn. Under such a situation, the enhanced ascending, together with the moist air transported by the southerly wind, formed the extreme winter precipitation in January 2008 over South China.展开更多
A weighting scheme jointly considering model performance and independence(PI-based weighting scheme) is employed to deal with multi-model ensemble prediction of precipitation over China from 17 global climate models. ...A weighting scheme jointly considering model performance and independence(PI-based weighting scheme) is employed to deal with multi-model ensemble prediction of precipitation over China from 17 global climate models. Four precipitation metrics on mean and extremes are used to evaluate the model performance and independence. The PIbased scheme is also compared with a rank-based weighting scheme and the simple arithmetic mean(AM) scheme. It is shown that the PI-based scheme achieves notable improvements in western China, with biases decreasing for all parameters. However, improvements are small and almost insignificant in eastern China. After calibration and validation, the scheme is used for future precipitation projection under the 1.5 and 2℃ global warming targets(above preindustrial level). There is a general tendency to wetness for most regions in China, especially in terms of extreme precipitation. The PI scheme shows larger inhomogeneity in spatial distribution. For the total precipitation PRCPTOT(95 th percentile extreme precipitation R95 P), the land fraction for a change larger than 10%(20%) is 22.8%(53.4%)in PI, while 13.3%(36.8%) in AM, under 2℃ global warming. Most noticeable increase exists in central and east parts of western China.展开更多
Northeastern China has experienced a significant increase in summer compound hot and dry events(CHDEs),posing a threat to local agricultural production and sustainable development.This study investigates the detectabl...Northeastern China has experienced a significant increase in summer compound hot and dry events(CHDEs),posing a threat to local agricultural production and sustainable development.This study investigates the detectable anthropogenic signal in the long-term trend of CHDE and quantifies the contribution of different external forcings.A probability-based index(PI)is constructed through the joint probability distribution to measure the severity of CHDE,with lower values representing more severe cases.Response of CHDE to external forcing was assessed with simulations from the Coupled Model Intercomparison Project phase 6(CMIP6).The results show a significant increase in the severity of CHDE over northeastern China during the past decades.The trend of regional averaged PI is-0.28(90%confidence interval:-0.43 to-0.13)per 54 yr and it is well reproduced in the historical forcing simulations.The attribution method of optimal fingerprinting was firstly applied to a two-signal configuration with anthropogenic forcing and natural forcing;the anthropogenic impact was robustly detected and it explains most of the observed trend of PI.Similarly,three-signal analysis further demonstrated that the anthropogenic greenhouse gases dominantly contribute to the observed change,while the anthropogenic aerosol and natural forcing have almost no contribution to the observed changes.For a compound event concurrently exceeding the 95 th percentile of surface air temperature and precipitation reversal in the current period,its likelihood exhibits little change at 1.5℃global warming,but almost doubled at 2.0℃global warming.展开更多
The observed intensity, frequency, and duration(IFD) of summer wet spells, defined here as extreme events with one or more consecutive days in which daily precipitation exceeds a given threshold(the 95th percentile...The observed intensity, frequency, and duration(IFD) of summer wet spells, defined here as extreme events with one or more consecutive days in which daily precipitation exceeds a given threshold(the 95th percentile), and their future changes in RCP4.5 and RCP8.5 in the late 21st century over China, are investigated by using the wet spell model(WSM) and by extending the point process approach to extreme value analysis. Wet spell intensity is modeled by a conditional generalized Pareto distribution, frequency by a Poisson distribution, and duration by a geometric distribution, respectively. The WSM is able to realistically model summer extreme rainfall spells during 1961–2005, as verified with observations at 553 stations throughout China. To minimize the impact of systematic biases over China in the global climate models(GCMs) of the Coupled Model Intercomparison Project Phase 5(CMIP5), five best GCMs are selected based on their performance to reproduce observed wet spell IFD and average precipitation during the historical period. Furthermore, a quantile–quantile scaling correction procedure is proposed and applied to produce ensemble projections of wet spell IFD and corresponding probability distributions. The results show that in the late 21st century, most of China will experience more extreme rainfall and less low-intensity rainfall. The intensity and frequency of wet spells are projected to increase considerably, while the duration of wet spells will increase but to a much less extent. The IFD changes in RCP8.5 are in general much larger than those in RCP4.5.展开更多
Although the tumor suppressor P53 is known to regulate a broad network of signaling pathways,it is still unclear how certain drugs influence these P53 signaling netw orks.Here,we used a comprehensive singlecell multio...Although the tumor suppressor P53 is known to regulate a broad network of signaling pathways,it is still unclear how certain drugs influence these P53 signaling netw orks.Here,we used a comprehensive singlecell multiomics view of the effects of ginsenosides on cancer cells.Transcriptome and proteome profiling revealed that the antitumor activity of ginsenosides is closely as sociated with P53 protein.A miRNA-proteome interaction network revealed that P53 controlled the transcription of at least 38 proteins,and proteomemetabolome profiling analysis revealed that P53 regulated proteins involved in nucleotide metabolism,amino acid metabolism and"Warburg effect".The results of integrative multiomics analysis revealed P53 protein as a potential key target that influences the anti-tumor activity of ginsenosides.Furthermore,by applying affinity mass spectrometry(MS)screening and surface plasmon resonance fragment library screening,we confirmed that 20(S)-protopanaxatriol directly targeted adj acent regions of the P53 DNA-binding pocket and promoted the stability of P53-DNA interactions,which further induced a series of omics changes.展开更多
The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 ...The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 stations in East China during 1961-2013 is classified into six patterns: the South China(SC) pattern, the southern Yangtze River(SY) pattern, the Yangtze-Huai River(YH) pattern, the North China(NC) pattern, the overall wetter(OW) pattern, and the overall drier(OD) pattern. Features of the transition probability matrix of the first four patterns reveal that 1) the NC pattern is the most persistent, followed by the YH, and the SY is the least one; and 2) there exists a SY-SC-SY-YH-NC propagation process for the rain belt over East China during the flood season. The intraseasonal variability in the occurrence frequency of each pattern determines its start and end time. Furthermore,analysis of interdecadal variability in the occurrence frequency of each pattern in recent six decades has identified three obvious interdecadal variations for the SC, YH, and NC patterns in the mid-late 1970 s, the early 1990 s, and the late 1990 s. After 2000, the patterns concentrated in the southern region play a dominant role, and thus there maintains a "flooding in the south and drought in the north" rainfall distribution in eastern China. In summary, the HMM provides a unique approach for us to obtain both spatial distribution and temporal variation features of flood-season rainfall.展开更多
Using space stations for a large number of observation, exploration, and research is a necessary way to fully develop spacetechnology. It is a necessary means of space experiment to install the extravehicular experime...Using space stations for a large number of observation, exploration, and research is a necessary way to fully develop spacetechnology. It is a necessary means of space experiment to install the extravehicular experimental load by using the loadplate. However, the extravehicular environment is full of danger, which poses a threat to the health and even safety ofastronauts. Using robots to replace astronauts to complete this task can effectively reduce the threat to astronauts. Aimingat the problem that the configurations of existing space robots have difficulty in balancing the contradiction betweencomplexity and dexterity, our previous work proposes a 12-DOF 3-arm robot and preliminarily explores the feasibility ofits large-scale ability. This paper focus on the 8-DOF redundant dexterous manipulator composed of 2 of the robot arms.In view of the difficulties in solving the inverse kinematics of the redundant manipulator, the challenges of complexenvironmental lighting, and difficulties of matching multiple groups of holes and pins in the load plate assembly task, theresearch on the autonomous assembly of the load plate is carried out. The main work is as follows: (a) A variable D-Hparameter inverse kinematics solution method is proposed, which lays a foundation for humanoid dexterous operationplanning of the robot. (b) An autonomous operation method based on visual guidance and variable parameter admittancecontrol is proposed. Finally, the safety and robustness of the robot in the autonomous assembly of the load plate withmultipins and holes are successfully verified by experiments.展开更多
基金This research was supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0603804 and 2018YFC1507704)the Natural Science Foundation of China(Grant No.41805048).
文摘Based on climate extreme indices calculated from a high-resolution daily observational dataset in China during 1961–2005,the performance of 12 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),and 30 models from phase 5 of CMIP(CMIP5),are assessed in terms of spatial distribution and interannual variability.The CMIP6 multi-model ensemble mean(CMIP6-MME)can simulate well the spatial pattern of annual mean temperature,maximum daily maximum temperature,and minimum daily minimum temperature.However,CMIP6-MME has difficulties in reproducing cold nights and warm days,and has large cold biases over the Tibetan Plateau.Its performance in simulating extreme precipitation indices is generally lower than in simulating temperature indices.Compared to CMIP5,CMIP6 models show improvements in the simulation of climate indices over China.This is particularly true for precipitation indices for both the climatological pattern and the interannual variation,except for the consecutive dry days.The arealmean bias for total precipitation has been reduced from 127%(CMIP5-MME)to 79%(CMIP6-MME).The most striking feature is that the dry biases in southern China,very persistent and general in CMIP5-MME,are largely reduced in CMIP6-MME.Stronger ascent together with more abundant moisture can explain this reduction in dry biases.Wet biases for total precipitation,heavy precipitation,and precipitation intensity in the eastern Tibetan Plateau are still present in CMIP6-MME,but smaller,compared to CMIP5-MME.
基金supported by the National Key Research and Development Program of China(2017YFA0603804)the National Natural Science Foundation of China(41831174 and 41430528)+1 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX19_1026)Guwei ZHANG was supported by the China Scholarship Council(NO.201908320503)。
文摘Extreme high temperature(EHT)events are among the most impact-related consequences related to climate change,especially for China,a nation with a large population that is vulnerable to the climate warming.Based on the latest Coupled Model Intercomparison Project Phase 6(CMIP6),this study assesses future EHT changes across China at five specific global warming thresholds(1.5℃-5℃).The results indicate that global mean temperature will increase by 1.5℃/2℃ before 2030/2050 relative to pre-industrial levels(1861-1900)under three future scenarios(SSP1-2.6,SSP2-4.5,and SSP5-8.5),and warming will occur faster under SSP5-8.5 compared to SSP1-2.6 and SSP2-4.5.Under SSP5-8.5,global warming will eventually exceed 5℃ by 2100,while under SSP1-2.6,it will stabilize around 2℃ after 2050.In China,most of the areas where warming exceeds global average levels will be located in Tibet and northern China(Northwest China,North China and Northeast China),covering 50%-70%of the country.Furthermore,about 0.19-0.44 billion people(accounting for 16%-41%of the national population)will experience warming above the global average.Compared to present-day(1995-2014),the warmest day(TXx)will increase most notably in northern China,while the number of warm days(TX90p)and warm spell duration indicator(WSDI)will increase most profoundly in southern China.For example,relative to the present-day,TXx will increase by 1℃-5℃ in northern China,and TX90p(WSDI)will increase by 25-150(10-80)days in southern China at 1.5℃-5℃ global warming.Compared to 2℃-5℃,limiting global warming to 1.5℃ will help avoid about 36%-87%of the EHT increases in China.
基金supported by the Fundamental Research Funds under Grant 2021JBZD204ZTE industry-university research cooperation fund project “Research on network identity trusted communication technology architecture”State Key Laboratory of Mobile Network and Mobile Multimedia Technology
文摘Link flooding attack(LFA)is a fresh distributed denial of service attack(DDoS).Attackers can cut off the critical links,making the services in the target area unavailable.LFA manipulates legal lowspeed flow to flood critical links,so traditional technologies are difficult to resist such attack.Meanwhile,LFA is also one of the most important threats to Internet of things(IoT)devices.The introduction of software defined network(SDN)effectively solves the security problem of the IoT.Aiming at the LFA in the software defined Internet of things(SDN-IoT),this paper proposes a new LFA mitigation scheme ReLFA.Renyi entropy is to locate the congested link in the data plane in our scheme,and determines the target links according to the alarm threshold.When LFA is detected on the target links,the control plane uses the method based on deep reinforcement learning(DRL)to carry out traffic engineering.Simulation results show that ReLFA can effectively alleviate the impact of LFA in SDN IoT.In addition,the rerouting time of ReLFA is superior to other latest schemes.
基金Supported by High-level Entrepreneurial and Innovative Talent(Team)Project 2015.
文摘[Objectives]This study aimed to establish a QAMS(quantitative analysis of multi-components by single-marker)method for simultaneous determination of four phenolic acids,salvianolic acid B,tanshinol,lithospermic acid and rosmarinic acid in Radix Salviae Miltiorrhizae by HPLC and conduct methodological investigation.[Methods]Salvianolic acid B,with moderate retention time,good resolution,great response value and easy availability was selected as the internal standard,and the relative retention values and relative correction factors between tanshinol,rosmarinic acid,lithospermic acid and salvianolic acid B were established.The results of QAMS were compared with those of external standard method to verify the accuracy and applicability of QAMS.[Results]There were no significant differences between the calculated values of QAMS and the measured values of external standard method.The relative deviation was less than 3%,and the relative correction factors obtained from the experiment were credible.[Conclusions]QAMS can be used to determine the contents of phenolic acids in Radix Salviae Miltiorrhizae formula granules.
基金Supported by the National Natural Science Foundation of China(61733001,61573063,61503029,U1713215)
文摘In order to meet the requirements of on-orbit servicing outside the cabin, a flexible, dexterous hand with easy grasping ability and strong loading capacity is designed. The dexterous hand is comprised of three fingers. Each finger is driven by a set of four linkages. Furthermore, two fingers have a set of axial rotational degrees of freedom. In order to achieve the position control and keep griping stability, the dexterous hand adopts a mechanism of hybrid force/position control. In the end, experimental results demonstrates that the on-orbit servicing dexterous hand has great adaptability and operational capability.
基金Supported by the National High Technology Research of China(2015AA043101,2015BAF10B02)Basic Scientific Research(B2220133017)National Natural Science Foundation of China(61503029,61573063)
文摘The space manipulator is always designed to have 7 degrees of freedom(Dofs)with the consideration of energy limitation,as well as the flexible moving possibility.Therefore,how to plan the trajectory is important to improve the performance of the manipulator.In this paper,the speed of the end effector is configured as a projecting parameter,when a constant acceleration is applied to adjust the velocity.To implement this trajectory planning strategy,an optimization algorithm through the pseudo inverse of Jacobin matrix is designed,which adjusts the weight functions of joints.According to the functional theory,this algorithm is analyzed and the optimal solution is found in numerous sets of planning.A MATLAB simulation platform is established and the results verity the effectiveness of the algorithm.
基金supported in part by the National Key Research and Development Program of China(2018YFB1305300)the China Postdoctoral Science Foundation(2020TQ0039,2021M700425)the National Natural Science Foundation of China(61733001,62103054,U2013602,61873039,U1913211,U1713215)。
文摘Dear editor,Human-robot collaboration is a research topic that has numerous potential applications, such as in smart cities. An important safety consideration in human-robot collaboration is collision avoidance[1]. Many studies have prioritized collision avoidance of the robot end-effector. However, multi-joint(whole-body) collision avoidance is also very important in complex working scenarios. Several studies have achieved multi-joint collision avoidance by estimating the distance between obstacles and control points placed on the robot body.
基金the NSFC(Nos.61701176 and 62071119)Macao FDCT(No.0065/2020/A2)+5 种基金Natural Science Foundation of Hunan Province of China(Nos.2022JJ50052,2018JJ3130 and 2020JJ5145)Hunan Key R&D Projects(No.2021SK2003)Nanjing Important Science&Technology Specific Projects(No.2021-11005)2022 Special Project for the Construction of Innovative Provinces to Fight the COVID-19 Outbreak(No.2022SK2115)Open Funding of State Key Laboratory of Oral Diseases(No.SKLOD2022OF05)Shenzhen Innovation and Entrepreneurship Program Innovation and Entrepreneurship Special Project(No.20220624181237005).
文摘The outbreak of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in late 2019 has negatively affected people's lives and productivity.Because the mode of transmission of SARS-CoV-2 is of great concern,this review discusses the sources of virus aerosols and possible transmission routes.First,we discuss virus aerosol collection methods,including natural sedimentation,solid impact,liquid impact,centrifugal,cyclone and electrostatic adsorption methods.Then,we review common virus aerosol detection methods,including virus culture,metabolic detection,nucleic acid-based detection and immunology-based detection methods.Finally,possible solutions for the detection of SARS-CoV-2 aerosols are introduced.Point-of-care testing has long been a focus of attention.In the near future,the development of an instrument that integrates sampling and output results will enable the real-time,automatic monitoring of patients.
基金supported by the National Natural Science Foundation of China(Grant No.42275184)the National Key Research and Development Program of China(Grant No.2017YFA0603804)the Postgraduate Research and Practice Innovation Program of Government of Jiangsu Province(Grant No.KYCX22_1135).
文摘Climate change adaptation and relevant policy-making need reliable projections of future climate.Methods based on multi-model ensemble are generally considered as the most efficient way to achieve the goal.However,their efficiency varies and inter-comparison is a challenging task,as they use a variety of target variables,geographic regions,time periods,or model pools.Here,we construct and use a consistent framework to evaluate the performance of five ensemble-processing methods,i.e.,multimodel ensemble mean(MME),rank-based weighting(RANK),reliability ensemble averaging(REA),climate model weighting by independence and performance(ClimWIP),and Bayesian model averaging(BMA).We investigate the annual mean temperature(Tav)and total precipitation(Prcptot)changes(relative to 1995–2014)over China and its seven subregions at 1.5 and 2℃warming levels(relative to pre-industrial).All ensemble-processing methods perform better than MME,and achieve generally consistent results in terms of median values.But they show different results in terms of inter-model spread,served as a measure of uncertainty,and signal-to-noise ratio(SNR).ClimWIP is the most optimal method with its good performance in simulating current climate and in providing credible future projections.The uncertainty,measured by the range of 10th–90th percentiles,is reduced by about 30%for Tav,and 15%for Prcptot in China,with a certain variation among subregions.Based on ClimWIP,and averaged over whole China under 1.5/2℃global warming levels,Tav increases by about 1.1/1.8℃(relative to 1995–2014),while Prcptot increases by about 5.4%/11.2%,respectively.Reliability of projections is found dependent on investigated regions and indices.The projection for Tav is credible across all regions,as its SNR is generally larger than 2,while the SNR is lower than 1 for Prcptot over most regions under 1.5℃warming.The largest warming is found in northeastern China,with increase of 1.3(0.6–1.7)/2.0(1.4–2.6)℃(ensemble’s median and range of the 10th–90th percentiles)under 1.5/2℃warming,followed by northern and northwestern China.The smallest but the most robust warming is in southwestern China,with values exceeding 0.9(0.6–1.1)/1.5(1.1–1.7)℃.The most robust projection and largest increase is achieved in northwestern China for Prcptot,with increase of 9.1%(–1.6–24.7%)/17.9%(0.5–36.4%)under 1.5/2℃warming.Followed by northern China,where the increase is 6.0%(–2.6–17.8%)/11.8%(2.4–25.1%),respectively.The precipitation projection is of large uncertainty in southwestern China,even with uncertain sign of variation.For the additional half-degree warming,Tav increases more than 0.5℃throughout China.Almost all regions witness an increase of Prcptot,with the largest increase in northwestern China.
基金supported by the NSFC(Nos.61701176 and 62071119)Macao FDCT(No.0065/2020/A2)+4 种基金Natural Science Foundation of Hunan Province of China(Nos.2022JJ50052,2018JJ3130 and 2020JJ5145)Hunan Key R&D Projects(No.2021SK2003)Nanjing Important Science&Technology Specific Projects(No.2021-11005)2022 Special Project for the Construction of Innovative Provinces to Fight the COVID-19 Outbreak(No.2022SK2115)Open Funding of State Key Laboratory of Oral Diseases(No.SKLOD2022OF05)。
文摘The SARS–CoV–2 virus is released from an infectious source(such as a sick person)and adsorbed on aerosols,which can form pathogenic microorganism aerosols,which can affect human health through airborne transmission.Efficient sampling and accurate detection of microorganisms in aerosols are the premise and basis for studying their properties and evaluating their hazard.In this study,we built a set of sub-micron aerosol detection platform,and carried out a simulation experiment on the SARS–CoV–2 aerosol in the air by wet-wall cyclone combined with immunomagnetic nanoparticle adsorption sampling and ddPCR.The feasibility of the system in aerosol detection was verified,and the influencing factors in the detection process were experimentally tested.As a result,the sampling efficiency was 29.77%,and extraction efficiency was 98.57%.The minimum detection limit per unit volume of aerosols was 250 copies(102copies/m L,concentration factor 2.5).
基金supported by the National Key R&D Program of China(Grant 2017YFA0603804)the State Key Program of National Natural Science Foundation of China(41230528)+1 种基金the China Scholarship Council(CSC)under the State Scholarship Fundsupported by the French ANR Project China-Trend-Stream
文摘To avoid dangerous climate change impact, the Paris Agreement sets out two ambitious goals: to limit the global warming to be well below 2 ℃ and to pursue effort for the global warming to be below 1.5 ℃ above the pre-industrial level. As climate change risks may be region-dependent, changes in magnitude and probability of extreme precipitation over China are investigated under those two global warming levels based on simulations from the Coupled Model Inter-Comparison Projects Phase 5. The focus is on the added changes due to the additional half a degree warming from 1.5 ℃ to 2 ℃ . Results show that regional average changes in the magnitude do not depend on the return periods with a relative increase around 7% and 11% at the 1.5 ℃ and 2 ℃ global warming levels, respectively. The additional half a degree global warming adds an additional increase in the magnitude by nearly 4%. The regional average changes in term of occurrence probabilities show dependence on the return periods, with rarer events(longer return periods) having larger increase of risk. For the 100-year historical event, the probability is projected to increase by a factor of 1.6 and 2.4 at the 1.5 ℃ and 2 ℃ global warming levels, respectively.The projected changes in extreme precipitation are independent of the RCP scenarios.
基金Supported by the China Meteorological Administration Special Public Welfare Research Fund for the Third Tibetan Plateau Atmospheric Science Experiment(GYHY201406001)Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDY-SSW-DQC018)National Natural Science Foundation of China(41730963,91437219,and 91637312)
文摘The external source/sink of potential vorticity (PV) is the original driving force for the atmospheric circulation. The relationship between surface PV generation and surface PV density forcing is discussed in detail in this paper. Moreover, a case study of the extreme winter freezing rain/snow storm over South China in January 2008 is performed, and the surface PV density forcing over the eastern flank of the Tibetan Plateau (TP) has been found to significantly affect the precipitation over South China in this case. The TP generated PV propagated eastward in the middle troposphere. The associated zonal advection of positive absolute vorticity resulted in the increasing of cyclo-nic relative vorticity in the downstream region of the TP. Ascending air and convergence in the lower troposphere developed, which gave rise to the development of the southerly wind. This favored the increasing of negative meridio-nal absolute vorticity advection in the lower troposphere, which provided a large-scale circulation background conducive to ascending motion such that the absolute vorticity advection increased with height. Consequently, the ascending air further strengthened the southerly wind and the vertical gradient of absolute vorticity advection between the lower and middle troposphere in turn. Under such a situation, the enhanced ascending, together with the moist air transported by the southerly wind, formed the extreme winter precipitation in January 2008 over South China.
基金Supported by the National Key Research and Development Program of China (2017YFA0603804, 2016YFA0600402, and 2018YFC1507704)。
文摘A weighting scheme jointly considering model performance and independence(PI-based weighting scheme) is employed to deal with multi-model ensemble prediction of precipitation over China from 17 global climate models. Four precipitation metrics on mean and extremes are used to evaluate the model performance and independence. The PIbased scheme is also compared with a rank-based weighting scheme and the simple arithmetic mean(AM) scheme. It is shown that the PI-based scheme achieves notable improvements in western China, with biases decreasing for all parameters. However, improvements are small and almost insignificant in eastern China. After calibration and validation, the scheme is used for future precipitation projection under the 1.5 and 2℃ global warming targets(above preindustrial level). There is a general tendency to wetness for most regions in China, especially in terms of extreme precipitation. The PI scheme shows larger inhomogeneity in spatial distribution. For the total precipitation PRCPTOT(95 th percentile extreme precipitation R95 P), the land fraction for a change larger than 10%(20%) is 22.8%(53.4%)in PI, while 13.3%(36.8%) in AM, under 2℃ global warming. Most noticeable increase exists in central and east parts of western China.
基金Supported by the National Key Research and Development Program of China(2018YFC1507704,2017YFA0603804)National Natural Science Foundation of China(41905078)。
文摘Northeastern China has experienced a significant increase in summer compound hot and dry events(CHDEs),posing a threat to local agricultural production and sustainable development.This study investigates the detectable anthropogenic signal in the long-term trend of CHDE and quantifies the contribution of different external forcings.A probability-based index(PI)is constructed through the joint probability distribution to measure the severity of CHDE,with lower values representing more severe cases.Response of CHDE to external forcing was assessed with simulations from the Coupled Model Intercomparison Project phase 6(CMIP6).The results show a significant increase in the severity of CHDE over northeastern China during the past decades.The trend of regional averaged PI is-0.28(90%confidence interval:-0.43 to-0.13)per 54 yr and it is well reproduced in the historical forcing simulations.The attribution method of optimal fingerprinting was firstly applied to a two-signal configuration with anthropogenic forcing and natural forcing;the anthropogenic impact was robustly detected and it explains most of the observed trend of PI.Similarly,three-signal analysis further demonstrated that the anthropogenic greenhouse gases dominantly contribute to the observed change,while the anthropogenic aerosol and natural forcing have almost no contribution to the observed changes.For a compound event concurrently exceeding the 95 th percentile of surface air temperature and precipitation reversal in the current period,its likelihood exhibits little change at 1.5℃global warming,but almost doubled at 2.0℃global warming.
基金National Key Research and Development Program of China(2017YFA0603804)China Meteorological Administration Special Public Welfare Research Fund(GYHY201306024)National Natural Science Foundation of China(41230528)
文摘The observed intensity, frequency, and duration(IFD) of summer wet spells, defined here as extreme events with one or more consecutive days in which daily precipitation exceeds a given threshold(the 95th percentile), and their future changes in RCP4.5 and RCP8.5 in the late 21st century over China, are investigated by using the wet spell model(WSM) and by extending the point process approach to extreme value analysis. Wet spell intensity is modeled by a conditional generalized Pareto distribution, frequency by a Poisson distribution, and duration by a geometric distribution, respectively. The WSM is able to realistically model summer extreme rainfall spells during 1961–2005, as verified with observations at 553 stations throughout China. To minimize the impact of systematic biases over China in the global climate models(GCMs) of the Coupled Model Intercomparison Project Phase 5(CMIP5), five best GCMs are selected based on their performance to reproduce observed wet spell IFD and average precipitation during the historical period. Furthermore, a quantile–quantile scaling correction procedure is proposed and applied to produce ensemble projections of wet spell IFD and corresponding probability distributions. The results show that in the late 21st century, most of China will experience more extreme rainfall and less low-intensity rainfall. The intensity and frequency of wet spells are projected to increase considerably, while the duration of wet spells will increase but to a much less extent. The IFD changes in RCP8.5 are in general much larger than those in RCP4.5.
基金supported by International Cooperation and Exchange of the National Natural Science Foundation of China(No.81761168039)Macao Science and TechnologyDevelopment 345 Fund(No.015/2017/AFJ,China)National Key Research and Development Program of China(Nos.2018YFC1704800 and 2018YFC1704805)
文摘Although the tumor suppressor P53 is known to regulate a broad network of signaling pathways,it is still unclear how certain drugs influence these P53 signaling netw orks.Here,we used a comprehensive singlecell multiomics view of the effects of ginsenosides on cancer cells.Transcriptome and proteome profiling revealed that the antitumor activity of ginsenosides is closely as sociated with P53 protein.A miRNA-proteome interaction network revealed that P53 controlled the transcription of at least 38 proteins,and proteomemetabolome profiling analysis revealed that P53 regulated proteins involved in nucleotide metabolism,amino acid metabolism and"Warburg effect".The results of integrative multiomics analysis revealed P53 protein as a potential key target that influences the anti-tumor activity of ginsenosides.Furthermore,by applying affinity mass spectrometry(MS)screening and surface plasmon resonance fragment library screening,we confirmed that 20(S)-protopanaxatriol directly targeted adj acent regions of the P53 DNA-binding pocket and promoted the stability of P53-DNA interactions,which further induced a series of omics changes.
基金Supported by the National Natural Science Foundation of China(41675081)National Key Research and Development Program of China(2017YFA0603804)
文摘The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 stations in East China during 1961-2013 is classified into six patterns: the South China(SC) pattern, the southern Yangtze River(SY) pattern, the Yangtze-Huai River(YH) pattern, the North China(NC) pattern, the overall wetter(OW) pattern, and the overall drier(OD) pattern. Features of the transition probability matrix of the first four patterns reveal that 1) the NC pattern is the most persistent, followed by the YH, and the SY is the least one; and 2) there exists a SY-SC-SY-YH-NC propagation process for the rain belt over East China during the flood season. The intraseasonal variability in the occurrence frequency of each pattern determines its start and end time. Furthermore,analysis of interdecadal variability in the occurrence frequency of each pattern in recent six decades has identified three obvious interdecadal variations for the SC, YH, and NC patterns in the mid-late 1970 s, the early 1990 s, and the late 1990 s. After 2000, the patterns concentrated in the southern region play a dominant role, and thus there maintains a "flooding in the south and drought in the north" rainfall distribution in eastern China. In summary, the HMM provides a unique approach for us to obtain both spatial distribution and temporal variation features of flood-season rainfall.
基金This research was partially supported by the National Key Research and Development Program of China(2018YFB1305300)the National Natural Science Foundation of China(61733001,61873039,U1713215,U1913211,U2013602).
文摘Using space stations for a large number of observation, exploration, and research is a necessary way to fully develop spacetechnology. It is a necessary means of space experiment to install the extravehicular experimental load by using the loadplate. However, the extravehicular environment is full of danger, which poses a threat to the health and even safety ofastronauts. Using robots to replace astronauts to complete this task can effectively reduce the threat to astronauts. Aimingat the problem that the configurations of existing space robots have difficulty in balancing the contradiction betweencomplexity and dexterity, our previous work proposes a 12-DOF 3-arm robot and preliminarily explores the feasibility ofits large-scale ability. This paper focus on the 8-DOF redundant dexterous manipulator composed of 2 of the robot arms.In view of the difficulties in solving the inverse kinematics of the redundant manipulator, the challenges of complexenvironmental lighting, and difficulties of matching multiple groups of holes and pins in the load plate assembly task, theresearch on the autonomous assembly of the load plate is carried out. The main work is as follows: (a) A variable D-Hparameter inverse kinematics solution method is proposed, which lays a foundation for humanoid dexterous operationplanning of the robot. (b) An autonomous operation method based on visual guidance and variable parameter admittancecontrol is proposed. Finally, the safety and robustness of the robot in the autonomous assembly of the load plate withmultipins and holes are successfully verified by experiments.