The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of...The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of lacustrine loess-like facies,and 5 layers of lacustrine facies.The results of grain-size analysis shows that the palaeo-mobile dune sands,palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands,ranging from 70% to 96%;their silt contents ranged from 4% to 20%,and their clay contents ranged from 1% to 5%;the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form,which is caused by the dominance of the cold,dry East Asian winter monsoon.In contrast,the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands,but have higher silt and clay contents,most of their sand content ranged from 30% to 60%,their silt contents ranged from 35% to 55%,and their clay contents ranged from 6% to 20%.The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm,humid East Asian summer monsoon based on their similarity with modern sediments.The grain-size indicator Mz(mean grain diameter) and the SC/D value in the TMS5e sequence indicate climatic insta-bility at the southern edge of the Tengger Desert during MIS5e,with at least 14 fluctuations between a warm,humid climate and a cold,dry climate,divided into five stages:TMS5e5(139 kyr to 129.3 kyr B.P.),TMS5e4(129.3 kyr to 124 kyr B.P.),TMS5e3(124 kyr to 119.5 kyr B.P.),TMS5e2(119.5 kyr to 116.5 kyr B.P.),and TMS5e1(116.5 kyr to 113.7 kyr B.P.).These correspond roughly to MIS5e5,MIS5e4,MIS5e3,MIS5e2,and MIS5e1,respectively,in the GRIP ice core data.展开更多
Widespread aeolian sediments have been found in the middle reaches of the Yarlung Zangbo River, China. The grain-size characteristics of sediments from Cha’er Section in the area were analyzed. The results show that ...Widespread aeolian sediments have been found in the middle reaches of the Yarlung Zangbo River, China. The grain-size characteristics of sediments from Cha’er Section in the area were analyzed. The results show that the section include one stratum of paleo-mobile dunes, four strata of paleo-semi-fixed dunes, two strata of paleo-fixed dunes, one stratum of sandy immature soils. The paleo-mobile and paleo-semi-fixed dune sand in this section are simi- lar to modern aeolian sand in either grain-size composition or Mz and σ distribution. Compared the above types of dunes each other, the content of sand substance decreases, while the content of silt and clay increases for paleo-fixed dunes and sandy immature soils. Combined with age data for each stratum, the analysis shows that these strata are the products of climate changes and the evolution of aeolian landforms. The evolutionary sequence of the paleoclimate and of aeolian activities in the valley since 8600 yr B.P. reveals four stages: 8600–5700 yr B.P., when the paleoclimate was cold and dry, with strong winds, thereby activating dunes; 5700–3600 yr B.P., when it was warm and wet, with weak winds, causing dunes to undergo soil-forming processes; 3600–1900 yr B.P., when climate shifted from cold-dry with strong winds to warm-wet with weak winds, and activated dunes were fixed again; and 1900 yr B.P. –present, when the climate became fine, with weak winds, fixing dunes again.展开更多
In this paper, we studied the process of dissociation unimolecular of the evaporation of H+2n+1 hydrogen clusters according to size, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The rate constants k(E) were ...In this paper, we studied the process of dissociation unimolecular of the evaporation of H+2n+1 hydrogen clusters according to size, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The rate constants k(E) were determined with the use of statistical theory of unimolecular reactions using various approximations. In our work, we used the products frequencies instead of transitions frequencies in the calculation of unimolecular dissociation rates obtained by three models RRKM. The agreement between the experimental cross section ratio and calculated rate ratio with direct count approximation seems to be reasonable.展开更多
The aim of the experiment is to analyze and view the distribution of gangue withdifferent particle sizes in mine spoil pile cross section.According to the Dimensionalmethod,'Pi'theorem was employed first to ab...The aim of the experiment is to analyze and view the distribution of gangue withdifferent particle sizes in mine spoil pile cross section.According to the Dimensionalmethod,'Pi'theorem was employed first to abbreviate ten physical and mechanical parametersto three dimensionless groups, and then the similarity criterion and coefficient ofthe experiment were determined and calculated based on particle size distribution curve.The similarity model was designed and constructed to represent the process of the minespoil pile.The profile of the final model shows that the small sized particles mainly composethe upper zone of the mine spoil pile, while the bottom of the pile is dominated bybigger sized particles, and the intermediate section presents a zigzag stripe cross-beddingstructure which is composed by small-medium scale particles and medium-large scaleparticles.Each stripe has two critical angles: one is the angle in which gangue particlescan maintain their stability condition, with approximate range from 24° to 26°; and theother is the angle in which particles can stop gliding downwards, approximately varyingfrom 34° to 36°.展开更多
In this paper,a distribution map of gravelly soil liquefaction that was caused by the Wenchuan M8.0 earthquake in China is proposed based on a detailed field investigation and an analysis of geological soil profiles. ...In this paper,a distribution map of gravelly soil liquefaction that was caused by the Wenchuan M8.0 earthquake in China is proposed based on a detailed field investigation and an analysis of geological soil profiles. The geological background of the earthquake disaster region is summarized by compiling geological cross sections and borehole logs. Meanwhile,four typical liquefied sites were selected to conduct sample drillings,dynamic penetration tests (DPT),and shear wave velocity tests,to understand the features of liquefied gravelly soil. One hundred and eighteen (118) liquefied sites were investigated shortly after the earthquake. The field investigation showed:(1) sandboils and waterspouts occurred extensively,involving thousands of miles of farmland,120 villages,eight schools and five factories,which caused damage to some rural houses,schools,manufacturing facilities and wells,etc.; (2) the Chengdu plain is covered by a gravelly soil layer with a thickness of 0 m to 541 m according to the geological cross sections; (3) there were 80 gravelly soil liquefied sites in the Chengdu plain,shaped as five belt areas that varied from 20 km to 40 km in length,and about ten gravelly soil liquefied sites distributed within Mianyang area; and (4) the grain sizes of the sampled soil were relative larger than the ejected soil on the ground,thus the type of liquefied soil cannot be determined by the ejected soil. The gravelly soil liquefied sites are helpful in enriching the global database of gravelly soil liquefaction and developing a corresponding evaluation method in further research efforts.展开更多
The telescopic boom is the main bearing force component of the crane.The rationality of the design will directly affect the performance of the machine and safety.The telescopic boom is a typical thin-walled plate and ...The telescopic boom is the main bearing force component of the crane.The rationality of the design will directly affect the performance of the machine and safety.The telescopic boom is a typical thin-walled plate and shell structure.Its main form of damage is the occurrence of buckling,resulting in decreased carrying capacity,or even a security incident.In order to meet the lifting weight and height,to ensure the stability of the telescopic boom has become a major problem of the designer.There are many factors that affect the critical load of the telescopic boom,including support method,inertia moment,length and material.When the support mode,material and length are determined,the maximum factor affecting the buckling critical load is the inertia moment.In this paper,the influence of the section size on the buckling critical load of the telescopic boom is analyzed by using the inertia moment of section method ande finite element method.And the sensitivity analysis is carried out on this basis.The results of the analysis can provide designers with design reference basis.Then a reasonable cross-sectional size can be used to improve the buckling resistance capacity of the telescopic boom.展开更多
The initial process of coal and gas sudden outburst is studied in the article when under the influence of rock and gas pressure the part of a coal seam layer(a coal section)is squeezed out from the mouth of the future...The initial process of coal and gas sudden outburst is studied in the article when under the influence of rock and gas pressure the part of a coal seam layer(a coal section)is squeezed out from the mouth of the future outburst cavity in a jump-like manner into the working.Geo-mechanical criterion for a part of a coal seam layer outsqueezing in the form of the relation of active(squeezing out)and passive(preventing the outsqueezing)forces is defined in the article.Based on it,the geophysical criterion is defined by expressing basic physical parameters through geo-physical ones:the current stress is defined by spectral-acoustic method through the ratio of high frequency and low-frequency components of an acoustic signal,which is generated into a face working space by the mining equipment operating in the face;in-situ gas pressure is defined by gas analytical method by the concentration of methane in the atmosphere of the working;the strength of the most broken coal layer is defined by a strength measuring device(a device for measuring the depth of a steal cone punched into the coal by a spring mechanism).This paper studies the influence of acoustic,strength and filtrating and collecting properties of a face working space on the limit value of an obtained geophysical criterion of pre-outburst squeezing of a coal‘‘plug”out of the mouth of the future outburst cavity into the working.展开更多
This study is based on both a generic and species level investigation of the individual size of the latest Permian conodont Neogondolella Pa elements collected from Meishan Section A, Changxing, Zhejiang Province. In ...This study is based on both a generic and species level investigation of the individual size of the latest Permian conodont Neogondolella Pa elements collected from Meishan Section A, Changxing, Zhejiang Province. In this study, an obvious size reduction of Neogondolella Pa elements within bed 24e of the upper Changxing Limestone is recognized. The size variation of the Neogon- dolella occurs simultaneously with some important events including the negative shift of δ 13C, change in the ratio of the abundance of cyanobacterial biomarkers versus that of other general bacterial biomarkers and the shallowing of the sea water. Through the investigation of the paleoenvironmental changes and the analysis of the paleoecology of the conodont genus Neogondolella, the authors propose that the major factors for the size reduction of species of the conodont genus Neogondolella are food shortages caused by the mass extinction, the shallowing of the sea water as well as the in- crease in opacity of the sea water during the end Permian. The same phenomenon of Neogondolella size reduction is also observed in preliminary research from the same horizon at Shangsi Section, Sichuan Province. All the evidence suggests that there was a mass extinction that occurred at the horizon of bed 24e, and the evidence supports the viewpoint of a multi-phase mass extinction during the Permian and Triassic transition in South China.展开更多
基金Foundation item:Under the auspices of State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences (No.SKLLQG0901,SKLLQG1013)Research Fund for the Doctoral Program of Higher Education of China (No.20094407120004)
文摘The TMS5e sequence from the Tumen section,at the southern edge of Tengger Desert in the northwestern China,is synchronous with Marine Isotope Stage 5e(MIS5e).It consists of 16 layers of aeolian dune sands,11 layers of lacustrine loess-like facies,and 5 layers of lacustrine facies.The results of grain-size analysis shows that the palaeo-mobile dune sands,palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands,ranging from 70% to 96%;their silt contents ranged from 4% to 20%,and their clay contents ranged from 1% to 5%;the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form,which is caused by the dominance of the cold,dry East Asian winter monsoon.In contrast,the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands,but have higher silt and clay contents,most of their sand content ranged from 30% to 60%,their silt contents ranged from 35% to 55%,and their clay contents ranged from 6% to 20%.The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm,humid East Asian summer monsoon based on their similarity with modern sediments.The grain-size indicator Mz(mean grain diameter) and the SC/D value in the TMS5e sequence indicate climatic insta-bility at the southern edge of the Tengger Desert during MIS5e,with at least 14 fluctuations between a warm,humid climate and a cold,dry climate,divided into five stages:TMS5e5(139 kyr to 129.3 kyr B.P.),TMS5e4(129.3 kyr to 124 kyr B.P.),TMS5e3(124 kyr to 119.5 kyr B.P.),TMS5e2(119.5 kyr to 116.5 kyr B.P.),and TMS5e1(116.5 kyr to 113.7 kyr B.P.).These correspond roughly to MIS5e5,MIS5e4,MIS5e3,MIS5e2,and MIS5e1,respectively,in the GRIP ice core data.
基金Under the auspices of National Natural Science Foundation of China (No. 40671185)National Key Technologies R&D Program of China (No. 2006BAD26B03)
文摘Widespread aeolian sediments have been found in the middle reaches of the Yarlung Zangbo River, China. The grain-size characteristics of sediments from Cha’er Section in the area were analyzed. The results show that the section include one stratum of paleo-mobile dunes, four strata of paleo-semi-fixed dunes, two strata of paleo-fixed dunes, one stratum of sandy immature soils. The paleo-mobile and paleo-semi-fixed dune sand in this section are simi- lar to modern aeolian sand in either grain-size composition or Mz and σ distribution. Compared the above types of dunes each other, the content of sand substance decreases, while the content of silt and clay increases for paleo-fixed dunes and sandy immature soils. Combined with age data for each stratum, the analysis shows that these strata are the products of climate changes and the evolution of aeolian landforms. The evolutionary sequence of the paleoclimate and of aeolian activities in the valley since 8600 yr B.P. reveals four stages: 8600–5700 yr B.P., when the paleoclimate was cold and dry, with strong winds, thereby activating dunes; 5700–3600 yr B.P., when it was warm and wet, with weak winds, causing dunes to undergo soil-forming processes; 3600–1900 yr B.P., when climate shifted from cold-dry with strong winds to warm-wet with weak winds, and activated dunes were fixed again; and 1900 yr B.P. –present, when the climate became fine, with weak winds, fixing dunes again.
文摘In this paper, we studied the process of dissociation unimolecular of the evaporation of H+2n+1 hydrogen clusters according to size, using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The rate constants k(E) were determined with the use of statistical theory of unimolecular reactions using various approximations. In our work, we used the products frequencies instead of transitions frequencies in the calculation of unimolecular dissociation rates obtained by three models RRKM. The agreement between the experimental cross section ratio and calculated rate ratio with direct count approximation seems to be reasonable.
基金Supported by the National Natural Science Foundation of China(50874102,50974070)
文摘The aim of the experiment is to analyze and view the distribution of gangue withdifferent particle sizes in mine spoil pile cross section.According to the Dimensionalmethod,'Pi'theorem was employed first to abbreviate ten physical and mechanical parametersto three dimensionless groups, and then the similarity criterion and coefficient ofthe experiment were determined and calculated based on particle size distribution curve.The similarity model was designed and constructed to represent the process of the minespoil pile.The profile of the final model shows that the small sized particles mainly composethe upper zone of the mine spoil pile, while the bottom of the pile is dominated bybigger sized particles, and the intermediate section presents a zigzag stripe cross-beddingstructure which is composed by small-medium scale particles and medium-large scaleparticles.Each stripe has two critical angles: one is the angle in which gangue particlescan maintain their stability condition, with approximate range from 24° to 26°; and theother is the angle in which particles can stop gliding downwards, approximately varyingfrom 34° to 36°.
基金Fundamental Research Funds of Institute Engineering Mechanics and Earthquake Under Grant No.2009B01 and No.200708001 National Natural Science Foundation of China Under Grant No.90715017 International Corporation Project of Science and Technology Administration of China Under Grant No.2009DFA71720
文摘In this paper,a distribution map of gravelly soil liquefaction that was caused by the Wenchuan M8.0 earthquake in China is proposed based on a detailed field investigation and an analysis of geological soil profiles. The geological background of the earthquake disaster region is summarized by compiling geological cross sections and borehole logs. Meanwhile,four typical liquefied sites were selected to conduct sample drillings,dynamic penetration tests (DPT),and shear wave velocity tests,to understand the features of liquefied gravelly soil. One hundred and eighteen (118) liquefied sites were investigated shortly after the earthquake. The field investigation showed:(1) sandboils and waterspouts occurred extensively,involving thousands of miles of farmland,120 villages,eight schools and five factories,which caused damage to some rural houses,schools,manufacturing facilities and wells,etc.; (2) the Chengdu plain is covered by a gravelly soil layer with a thickness of 0 m to 541 m according to the geological cross sections; (3) there were 80 gravelly soil liquefied sites in the Chengdu plain,shaped as five belt areas that varied from 20 km to 40 km in length,and about ten gravelly soil liquefied sites distributed within Mianyang area; and (4) the grain sizes of the sampled soil were relative larger than the ejected soil on the ground,thus the type of liquefied soil cannot be determined by the ejected soil. The gravelly soil liquefied sites are helpful in enriching the global database of gravelly soil liquefaction and developing a corresponding evaluation method in further research efforts.
基金supported by the National Natural Science Foundation of China (51575370)Natural Science Foundation of Shanxi Province (201901D111236)Nanchong 2023 Municipal Science and Technology Plan Project (23YYJCYJ0023)。
文摘The telescopic boom is the main bearing force component of the crane.The rationality of the design will directly affect the performance of the machine and safety.The telescopic boom is a typical thin-walled plate and shell structure.Its main form of damage is the occurrence of buckling,resulting in decreased carrying capacity,or even a security incident.In order to meet the lifting weight and height,to ensure the stability of the telescopic boom has become a major problem of the designer.There are many factors that affect the critical load of the telescopic boom,including support method,inertia moment,length and material.When the support mode,material and length are determined,the maximum factor affecting the buckling critical load is the inertia moment.In this paper,the influence of the section size on the buckling critical load of the telescopic boom is analyzed by using the inertia moment of section method ande finite element method.And the sensitivity analysis is carried out on this basis.The results of the analysis can provide designers with design reference basis.Then a reasonable cross-sectional size can be used to improve the buckling resistance capacity of the telescopic boom.
基金the grant of Russian Science Foundation (project No. 17-17-01143)
文摘The initial process of coal and gas sudden outburst is studied in the article when under the influence of rock and gas pressure the part of a coal seam layer(a coal section)is squeezed out from the mouth of the future outburst cavity in a jump-like manner into the working.Geo-mechanical criterion for a part of a coal seam layer outsqueezing in the form of the relation of active(squeezing out)and passive(preventing the outsqueezing)forces is defined in the article.Based on it,the geophysical criterion is defined by expressing basic physical parameters through geo-physical ones:the current stress is defined by spectral-acoustic method through the ratio of high frequency and low-frequency components of an acoustic signal,which is generated into a face working space by the mining equipment operating in the face;in-situ gas pressure is defined by gas analytical method by the concentration of methane in the atmosphere of the working;the strength of the most broken coal layer is defined by a strength measuring device(a device for measuring the depth of a steal cone punched into the coal by a spring mechanism).This paper studies the influence of acoustic,strength and filtrating and collecting properties of a face working space on the limit value of an obtained geophysical criterion of pre-outburst squeezing of a coal‘‘plug”out of the mouth of the future outburst cavity into the working.
基金supported by the National Natural Science Foundation of China(Grant No.40232025)the GeoTurn Group of China University of Geosciences.
文摘This study is based on both a generic and species level investigation of the individual size of the latest Permian conodont Neogondolella Pa elements collected from Meishan Section A, Changxing, Zhejiang Province. In this study, an obvious size reduction of Neogondolella Pa elements within bed 24e of the upper Changxing Limestone is recognized. The size variation of the Neogon- dolella occurs simultaneously with some important events including the negative shift of δ 13C, change in the ratio of the abundance of cyanobacterial biomarkers versus that of other general bacterial biomarkers and the shallowing of the sea water. Through the investigation of the paleoenvironmental changes and the analysis of the paleoecology of the conodont genus Neogondolella, the authors propose that the major factors for the size reduction of species of the conodont genus Neogondolella are food shortages caused by the mass extinction, the shallowing of the sea water as well as the in- crease in opacity of the sea water during the end Permian. The same phenomenon of Neogondolella size reduction is also observed in preliminary research from the same horizon at Shangsi Section, Sichuan Province. All the evidence suggests that there was a mass extinction that occurred at the horizon of bed 24e, and the evidence supports the viewpoint of a multi-phase mass extinction during the Permian and Triassic transition in South China.