In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult....In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult.Unfortunately,there are few studies on the failure and support mechanism of the surrounding rocks in the excavation of supported tunnel,while most model tests of super-large-span tunnels focus on the failure characteristics of surrounding rocks in tunnel excavation without supports.Based on excavation compensation method(ECM),model tests of a super-large-span tunnel excavation by different anchor cable support methods in the initial support stage were carried out.The results indicate that during excavation of super-large-span tunnel,the stress and displacement of the shallow surrounding rocks decrease,following a step-shape pattern,and the tunnel failure is mainly concentrated on the vault and spandrel areas.Compared with conventional anchor cable supports,the NPR(negative Poisson’s ratio)anchor cable support is more suitable for the initial support stage of the super-large-span tunnels.The tunnel support theory,model test materials,methods,and the results obtained in this study could provide references for study of similar super-large-span tunnels。展开更多
Since the inaugural international collaboration under the framework of the Collaboratory for the Study of Earthquake Predictability(CSEP)in 2007,numerous forecast models have been developed and operated for earthquake...Since the inaugural international collaboration under the framework of the Collaboratory for the Study of Earthquake Predictability(CSEP)in 2007,numerous forecast models have been developed and operated for earthquake forecasting experiments across CSEP testing centers(Schorlemmer et al.,2018).Over more than a decade,efforts to compare forecasts with observed earthquakes using numerous statistical test methods and insights into earthquake predictability,which have become a highlight of the CSEP platform.展开更多
Earth’s near space,located in the region between 20 and 100 km above sea level,is characterized by extreme conditions,such as low temperature,low atmospheric pressure,harsh radiation,and extreme dryness.These conditi...Earth’s near space,located in the region between 20 and 100 km above sea level,is characterized by extreme conditions,such as low temperature,low atmospheric pressure,harsh radiation,and extreme dryness.These conditions are analogous to those found on the surface of Mars and in the atmosphere of Venus,making Earth’s near space a unique natural laboratory for astrobiological research.To address essential astrobiological questions,teams from the Chinese Academy of Sciences(CAS)have developed a scientific balloon platform,the CAS Balloon-Borne Astrobiology Platform(CAS-BAP),to study the effects of near space environmental conditions on the biology and survival strategies of representative organisms in this terrestrial analog.Here,we describe the versatile Biological Samples Exposure Payload(BIOSEP)loaded on the CAS-BAP with respect to its structure and function.The primary function of BIOSEP is to expose appropriate biological specimens to the harsh conditions of near space and subsequently return the exposed samples to laboratories for further analysis.Four successful flight missions in near space from 2019 to 2021 have demonstrated the high reliability and efficiency of the payload in communicating between hardware and software units,recording environmental data,exposing sample containers,protecting samples from external contamination,and recovering samples.Understanding the effects of Earth’s near space conditions on biological specimens will provide valuable insights into the survival strategies of organisms in extreme environments and the search for life beyond Earth.The development of BIOSEP and associated biological exposure experiments will enhance our understanding of the potential for life on Mars and the habitability of the atmospheric regions of other planets in the solar system and beyond.展开更多
Huaihe River Basin(HRB) is located in China’s north-south climatic transition zone,which is very sensitive to global climate change.Based on the daily maximum temperature,minimum temperature,and precipitation data of...Huaihe River Basin(HRB) is located in China’s north-south climatic transition zone,which is very sensitive to global climate change.Based on the daily maximum temperature,minimum temperature,and precipitation data of 40 meteorological stations and nine monthly large-scale ocean-atmospheric circulation indices data during 1959–2019,we present an assessment of the spatial and temporal variations of extreme temperature and precipitation events in the HRB using nine extreme climate indices,and analyze the teleconnection relationship between extreme climate indices and large-scale ocean-atmospheric circulation indices.The results show that warm extreme indices show a significant(P < 0.05) increasing trend,while cold extreme indices(except for cold spell duration) and diurnal temperature range(DTR) show a significant decreasing trend.Furthermore,all extreme temperature indices show significant mutations during 1959-2019.Spatially,a stronger warming trend occurs in eastern HRB than western HRB,while maximum 5-d precipitation(Rx5day) and rainstorm days(R25) show an increasing trend in the southern,central,and northwestern regions of HRB.Arctic oscillation(AO),Atlantic multidecadal oscillation(AMO),and East Atlantic/Western Russia(EA/WR) have a stronger correlation with extreme climate indices compared to other circulation indices.AO and AMO(EA/WR) exhibit a significant(P < 0.05) negative(positive)correlation with frost days and diurnal temperature range.Extreme warm events are strongly correlated with the variability of AMO and EA/WR in most parts of HRB,while extreme cold events are closely related to the variability of AO and AMO in eastern HRB.In contrast,AMO,AO,and EA/WR show limited impacts on extreme precipitation events in most parts of HRB.展开更多
In this paper,by choosing some appropriate test functions,we prove the Weyl’s lemma for triharmonic functions based on the new type of mean value formulas.
To make oral test accurately reflect the actual English spoken ability of candidates and play its role in guiding and promoting the improvement of English learners in the teaching, we must ensure that the design of sc...To make oral test accurately reflect the actual English spoken ability of candidates and play its role in guiding and promoting the improvement of English learners in the teaching, we must ensure that the design of scientific questions, the feasibility and validity of judgments to make an accurate and fair measurement of testers' language ability.展开更多
A new approach to improve the test efficiency of random testing is presented in this paper. In conventional random testing, each test pattern is selected randomly regardless of the tests previously generated. This pap...A new approach to improve the test efficiency of random testing is presented in this paper. In conventional random testing, each test pattern is selected randomly regardless of the tests previously generated. This paper introduces the concept of random like testing. The method provided appears to have the same concepts as used in random testing,but actually takes an opposite way to it in order to improve the efficiency of random testing.In a random like testing sequence, the total distance among all test patterns is chosen to be maximal so that the fault sets detected by one test pattern are as different as possible from that detected by the tests previously applied. The procedure to construct a random like testing sequence (RLTS) is described in detail. Theorems to justify the effectiveness and usefulness of the procedure presented are developed. Experimental results on benchmark circuits as well as on other circuit are also given to evaluate the performance of the new approach.展开更多
基金supported by the Innovation Fund Research Project of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK202201)the Foundation for the Opening of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK2129)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z020007)。
文摘In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult.Unfortunately,there are few studies on the failure and support mechanism of the surrounding rocks in the excavation of supported tunnel,while most model tests of super-large-span tunnels focus on the failure characteristics of surrounding rocks in tunnel excavation without supports.Based on excavation compensation method(ECM),model tests of a super-large-span tunnel excavation by different anchor cable support methods in the initial support stage were carried out.The results indicate that during excavation of super-large-span tunnel,the stress and displacement of the shallow surrounding rocks decrease,following a step-shape pattern,and the tunnel failure is mainly concentrated on the vault and spandrel areas.Compared with conventional anchor cable supports,the NPR(negative Poisson’s ratio)anchor cable support is more suitable for the initial support stage of the super-large-span tunnels.The tunnel support theory,model test materials,methods,and the results obtained in this study could provide references for study of similar super-large-span tunnels。
基金granted by the National Natural Science Foundation of China(Grant No.42004038)Earthquake Tracking Orientation Tasks of CEA(Grant No.2024020104)+1 种基金the Special Fund of IEFCEA(Grant No.CEAIEF2022030206)the China Scholarship Council(CSC)exchange program(Grant No.202204190019)。
文摘Since the inaugural international collaboration under the framework of the Collaboratory for the Study of Earthquake Predictability(CSEP)in 2007,numerous forecast models have been developed and operated for earthquake forecasting experiments across CSEP testing centers(Schorlemmer et al.,2018).Over more than a decade,efforts to compare forecasts with observed earthquakes using numerous statistical test methods and insights into earthquake predictability,which have become a highlight of the CSEP platform.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA17010505)
文摘Earth’s near space,located in the region between 20 and 100 km above sea level,is characterized by extreme conditions,such as low temperature,low atmospheric pressure,harsh radiation,and extreme dryness.These conditions are analogous to those found on the surface of Mars and in the atmosphere of Venus,making Earth’s near space a unique natural laboratory for astrobiological research.To address essential astrobiological questions,teams from the Chinese Academy of Sciences(CAS)have developed a scientific balloon platform,the CAS Balloon-Borne Astrobiology Platform(CAS-BAP),to study the effects of near space environmental conditions on the biology and survival strategies of representative organisms in this terrestrial analog.Here,we describe the versatile Biological Samples Exposure Payload(BIOSEP)loaded on the CAS-BAP with respect to its structure and function.The primary function of BIOSEP is to expose appropriate biological specimens to the harsh conditions of near space and subsequently return the exposed samples to laboratories for further analysis.Four successful flight missions in near space from 2019 to 2021 have demonstrated the high reliability and efficiency of the payload in communicating between hardware and software units,recording environmental data,exposing sample containers,protecting samples from external contamination,and recovering samples.Understanding the effects of Earth’s near space conditions on biological specimens will provide valuable insights into the survival strategies of organisms in extreme environments and the search for life beyond Earth.The development of BIOSEP and associated biological exposure experiments will enhance our understanding of the potential for life on Mars and the habitability of the atmospheric regions of other planets in the solar system and beyond.
基金Under the auspices of National Natural Science Foundation of China(No.52279016,51909106,51879108,42002247,41471160)Natural Science Foundation of Guangdong Province,China(No.2020A1515011038,2020A1515111054)+1 种基金Special Fund for Science and Technology Development in 2016 of Department of Science and Technology of Guangdong Province,China(No.2016A020223007)the Project of Jinan Science and Technology Bureau(No.2021GXRC070)。
文摘Huaihe River Basin(HRB) is located in China’s north-south climatic transition zone,which is very sensitive to global climate change.Based on the daily maximum temperature,minimum temperature,and precipitation data of 40 meteorological stations and nine monthly large-scale ocean-atmospheric circulation indices data during 1959–2019,we present an assessment of the spatial and temporal variations of extreme temperature and precipitation events in the HRB using nine extreme climate indices,and analyze the teleconnection relationship between extreme climate indices and large-scale ocean-atmospheric circulation indices.The results show that warm extreme indices show a significant(P < 0.05) increasing trend,while cold extreme indices(except for cold spell duration) and diurnal temperature range(DTR) show a significant decreasing trend.Furthermore,all extreme temperature indices show significant mutations during 1959-2019.Spatially,a stronger warming trend occurs in eastern HRB than western HRB,while maximum 5-d precipitation(Rx5day) and rainstorm days(R25) show an increasing trend in the southern,central,and northwestern regions of HRB.Arctic oscillation(AO),Atlantic multidecadal oscillation(AMO),and East Atlantic/Western Russia(EA/WR) have a stronger correlation with extreme climate indices compared to other circulation indices.AO and AMO(EA/WR) exhibit a significant(P < 0.05) negative(positive)correlation with frost days and diurnal temperature range.Extreme warm events are strongly correlated with the variability of AMO and EA/WR in most parts of HRB,while extreme cold events are closely related to the variability of AO and AMO in eastern HRB.In contrast,AMO,AO,and EA/WR show limited impacts on extreme precipitation events in most parts of HRB.
基金Supported by National Natural Science Foundation of China(Grant Nos.11801006 and 12071489).
文摘In this paper,by choosing some appropriate test functions,we prove the Weyl’s lemma for triharmonic functions based on the new type of mean value formulas.
文摘To make oral test accurately reflect the actual English spoken ability of candidates and play its role in guiding and promoting the improvement of English learners in the teaching, we must ensure that the design of scientific questions, the feasibility and validity of judgments to make an accurate and fair measurement of testers' language ability.
文摘A new approach to improve the test efficiency of random testing is presented in this paper. In conventional random testing, each test pattern is selected randomly regardless of the tests previously generated. This paper introduces the concept of random like testing. The method provided appears to have the same concepts as used in random testing,but actually takes an opposite way to it in order to improve the efficiency of random testing.In a random like testing sequence, the total distance among all test patterns is chosen to be maximal so that the fault sets detected by one test pattern are as different as possible from that detected by the tests previously applied. The procedure to construct a random like testing sequence (RLTS) is described in detail. Theorems to justify the effectiveness and usefulness of the procedure presented are developed. Experimental results on benchmark circuits as well as on other circuit are also given to evaluate the performance of the new approach.
