Synoptic patterns identified by an automated procedure employing principal- component analysis and a two-stage cluster analysis, and backward trajectory analysis clustered by the HYSPLIT4.9 model were used to examine ...Synoptic patterns identified by an automated procedure employing principal- component analysis and a two-stage cluster analysis, and backward trajectory analysis clustered by the HYSPLIT4.9 model were used to examine air quality patterns over¨ Uru¨mqi, China, one of the most heavily polluted cities in the world. Six synoptic patterns representing different atmospheric circulation patterns and air-mass characteristics were classified during the winter heating periods from 2001 to 2008, and seven trajectory clusters representing different paths of air masses arriving at ürümqi were calculated during the winter heating periods from 2005 to 2008. Then air quality was evaluated using these two approaches, and significant variations were found across both synoptic patterns and trajectory clusters. The heaviest air-pollution episodes occurred when ürümqi was either in an extremely cold, strong anticyclone or at the front of a migrating cyclone. Both conditions were characterized by with light winds, cold, wet surface air, and relatively dry upper air. ürümqi was predominately influenced by air masses from the southwest and from local areas. Air pollution index （API） levels were highest for air masses originating from the southwest with a longer path or for the local area, because of transport from semi-desert/desert regions by strong winds and because of local heavy pollution emissions, respectively. The interactions between these two analytical approaches showed that poor diffusion conditions, together with local circulation, enhanced air pollution, besides, regional air-mass transport caused by strong winds contributed to serious air quality under relatively good diffusion conditions.展开更多
The Shaerqiaoke Gravel, more than 400 m in thickness, on the north piedmont of the Tianshan Mountains, is located at the exit of the Urümqi River Valley and belongs to the Molasse construction of the Tianshan Mou...The Shaerqiaoke Gravel, more than 400 m in thickness, on the north piedmont of the Tianshan Mountains, is located at the exit of the Urümqi River Valley and belongs to the Molasse construction of the Tianshan Mountains. Another uplift event with the tectonic boundary expansion ended the deposition of the Shaerqiaoke Gravel, and resulted in folding, faulting and down-erosion in the frontier of the deposit. The ESR dating indicates that the top of the Shaerqiaoke Gravel accumulated before 1148 kaBP, probably responding to the Kunlun-Huanghe movement of the Qinghai-Tibetan plateau. After that time, erosion-deposition cycle occurred and 9 terraces developed. The TL and ESR dating techniques were employed to date these terraces, and the results indicate that Terrace 3 was formed at MIS 6. Terrace 2 at Houxia also developed simultaneously. Terraces 5 and 6 were accumulated in 338 kaBP and 562-591 kaBP, respectively. The oldest glaciation, named Gao Wangfeng, correlates to MIS 12.展开更多
Natural cosmogenic tritium or artificial tritium from thermonuclear tests takes the form of HTO to circulate. Before thermonuclear tests, the tritium content in precipitation was meagre, mean value 5—10 TU. After 195...Natural cosmogenic tritium or artificial tritium from thermonuclear tests takes the form of HTO to circulate. Before thermonuclear tests, the tritium content in precipitation was meagre, mean value 5—10 TU. After 1954, however, great influence has apparently been exerted by artificial tritium from numerous thermonuclear tests. In 1963,展开更多
Current glacier recession under the global warming has aroused world-wide attention.Initiated from 1958,the observations show that over the past 50 years,the glacier has changed remarkably in the aspects of snow-firn ...Current glacier recession under the global warming has aroused world-wide attention.Initiated from 1958,the observations show that over the past 50 years,the glacier has changed remarkably in the aspects of snow-firn stratigraphy,ice formation zone,ice temperature,area and terminus position,etc.These changes are apparently the results of temperature rise in this area.The glacier recession continued throughout the entire observed time period,and showed an accelerated tendency since 1985.Meltwater runoff also increased 84.2% over the last 20 years.展开更多
数学教学质量评估系统(Mathematical Quality of Instruction)是由美国密西根大学研发的一项数学课堂评价工具,该系统从数学内容丰富度、学生行为处理、错误和不严密性及学生有意义学习参与度四个领域评估数学课堂教学质量。本文介绍数...数学教学质量评估系统(Mathematical Quality of Instruction)是由美国密西根大学研发的一项数学课堂评价工具,该系统从数学内容丰富度、学生行为处理、错误和不严密性及学生有意义学习参与度四个领域评估数学课堂教学质量。本文介绍数学教学质量评估系统基本框架、建构过程和特点,分析模型价值,探讨该评估模型所带来的启示:强调教师对数学本身知识的掌握、生成性教学和有意义学习。展开更多
Magnequench International, Inc., USA (MQI) announced in August that it had filed lawsuits against Polymag of Bellport, New York and Pacific Century of Chantilly, Virginia for infringing one of its
基金supported by the National Basic Research Program (also called 973 Program) of China (Grant No 2007CB407303)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No KZCX2-YW-Q02-03)
文摘Synoptic patterns identified by an automated procedure employing principal- component analysis and a two-stage cluster analysis, and backward trajectory analysis clustered by the HYSPLIT4.9 model were used to examine air quality patterns over¨ Uru¨mqi, China, one of the most heavily polluted cities in the world. Six synoptic patterns representing different atmospheric circulation patterns and air-mass characteristics were classified during the winter heating periods from 2001 to 2008, and seven trajectory clusters representing different paths of air masses arriving at ürümqi were calculated during the winter heating periods from 2005 to 2008. Then air quality was evaluated using these two approaches, and significant variations were found across both synoptic patterns and trajectory clusters. The heaviest air-pollution episodes occurred when ürümqi was either in an extremely cold, strong anticyclone or at the front of a migrating cyclone. Both conditions were characterized by with light winds, cold, wet surface air, and relatively dry upper air. ürümqi was predominately influenced by air masses from the southwest and from local areas. Air pollution index （API） levels were highest for air masses originating from the southwest with a longer path or for the local area, because of transport from semi-desert/desert regions by strong winds and because of local heavy pollution emissions, respectively. The interactions between these two analytical approaches showed that poor diffusion conditions, together with local circulation, enhanced air pollution, besides, regional air-mass transport caused by strong winds contributed to serious air quality under relatively good diffusion conditions.
基金This work was supported by the Foundation of the Tianshan Glaciology Station, the Chinese Academy of Sciences (Grant No. 9905)the National Natural Science Foundation of China (Grant Nos. 49971080 and 49731010)the Cold and Arid Regions Environment
文摘The Shaerqiaoke Gravel, more than 400 m in thickness, on the north piedmont of the Tianshan Mountains, is located at the exit of the Urümqi River Valley and belongs to the Molasse construction of the Tianshan Mountains. Another uplift event with the tectonic boundary expansion ended the deposition of the Shaerqiaoke Gravel, and resulted in folding, faulting and down-erosion in the frontier of the deposit. The ESR dating indicates that the top of the Shaerqiaoke Gravel accumulated before 1148 kaBP, probably responding to the Kunlun-Huanghe movement of the Qinghai-Tibetan plateau. After that time, erosion-deposition cycle occurred and 9 terraces developed. The TL and ESR dating techniques were employed to date these terraces, and the results indicate that Terrace 3 was formed at MIS 6. Terrace 2 at Houxia also developed simultaneously. Terraces 5 and 6 were accumulated in 338 kaBP and 562-591 kaBP, respectively. The oldest glaciation, named Gao Wangfeng, correlates to MIS 12.
文摘Natural cosmogenic tritium or artificial tritium from thermonuclear tests takes the form of HTO to circulate. Before thermonuclear tests, the tritium content in precipitation was meagre, mean value 5—10 TU. After 1954, however, great influence has apparently been exerted by artificial tritium from numerous thermonuclear tests. In 1963,
基金This research was supported by the Knowledge Innovation Project of the Chinese Academy of Sciences(KZCX2-YW-127)and the National Natural Science Foundation of China(40631001,40571033,40371028,J0630966).
文摘Current glacier recession under the global warming has aroused world-wide attention.Initiated from 1958,the observations show that over the past 50 years,the glacier has changed remarkably in the aspects of snow-firn stratigraphy,ice formation zone,ice temperature,area and terminus position,etc.These changes are apparently the results of temperature rise in this area.The glacier recession continued throughout the entire observed time period,and showed an accelerated tendency since 1985.Meltwater runoff also increased 84.2% over the last 20 years.
文摘数学教学质量评估系统(Mathematical Quality of Instruction)是由美国密西根大学研发的一项数学课堂评价工具,该系统从数学内容丰富度、学生行为处理、错误和不严密性及学生有意义学习参与度四个领域评估数学课堂教学质量。本文介绍数学教学质量评估系统基本框架、建构过程和特点,分析模型价值,探讨该评估模型所带来的启示:强调教师对数学本身知识的掌握、生成性教学和有意义学习。
文摘Magnequench International, Inc., USA (MQI) announced in August that it had filed lawsuits against Polymag of Bellport, New York and Pacific Century of Chantilly, Virginia for infringing one of its
