In polarization-encoded free-space quantum communications, a transmitter on a satellite and a receiver in a ground station each have a respective polarization zero direction, by which they encode and decode every pola...In polarization-encoded free-space quantum communications, a transmitter on a satellite and a receiver in a ground station each have a respective polarization zero direction, by which they encode and decode every polariza-tion quantum bit required for a quantum com-munication protocol. In order to complete the protocol, the ground-based receiver needs to track and compensate for the polarization zero direction of the satellite-based transmitter. Ex- pressions satisfied by amplitudes of the s-polarization component and the p-polarization component are derived based on a two-mirror model, and a condition satisfied by the reflec- tion coefficients of the two mirrors is given. A polarization tracking principle is analyzed for satellite-to-ground quanaun communications, and quantum key encoding and decoding prin- ciples based on polarization tracking are given. A half-wave-plate-based dynamic polariza- tion-basis compensation scheme is proposed in this paper, and this scheme is proved to be suitable for satellite-to-ground and intersatellite quantum communications.展开更多
Total Cloud Cover （TCC） over China deter- mined from four climate datasets including the Interna- tional Satellite Cloud Climatology Project （ISCCP）, the 40-year Re-Analysis Project of the European Centre for Medi...Total Cloud Cover （TCC） over China deter- mined from four climate datasets including the Interna- tional Satellite Cloud Climatology Project （ISCCP）, the 40-year Re-Analysis Project of the European Centre for Medium-Range Weather Forecasts （ERA-40）, Climate Research Unit Time Series 3.0 （CRU3）, and ground sta- tion datasets are used to show spatial and temporal varia- tion of TCC and their differences. It is demonstrated that the four datasets show similar spatial pattern and seasonal variation. The maximum value is derived from ISCCE TCC value in North China derived from ERA-40 is 50% larger than that from the station dataset; however, the value is 50% less than that in South China. The annual TCC of ISCCP, ERA-40, and ground station datasets shows a decreasing trend during 1984-2002; however, an increasing trend is derived from CRU3. The results of this study imply remarkable differences of TCC derived from surface and satellite observations as well as model simu- lations. The potential effects of these differences on cloud climatology and associated climatic issues should be carefully considered.展开更多
Based on arrival time data of seismic phases of ML≥2. 0 earthquakes measured at Shanxi Digital Seismic Network for the period from January 2001 to October 2014,V_P/ V_S in the Shanxi region is calculated using the Wa...Based on arrival time data of seismic phases of ML≥2. 0 earthquakes measured at Shanxi Digital Seismic Network for the period from January 2001 to October 2014,V_P/ V_S in the Shanxi region is calculated using the Wadati single station and multi-earthquake method,and an investigation is conducted into the variation behavior of V_P/ V_S in the Shanxi region before and after the three earthquakes of MS≥4. 5 in 2010. Our study finds that abnormal V_P/ V_S appeared earlier at distant stations before all of the three earthquakes,which is at the time range from 6 months to 1 year before the earthquakes,and later at near stations,at the time range 10 days to 2 months before earthquakes. Therefore,it s possible to narrow down the scope of the location in earthquake prediction from the distant and near station data. The calculations of Dongshan seismic station indicate that the size of the residual of the origin time has impact on the detail of V_P/ V_S variation,thus,appropriate thresholds should firstly be set for the residuals of origin time at each seismic station in practical application,to ensure scientific and steady V_P/ V_S calculations.展开更多
Environmental design is concerned with the function of people within an environment and their interactions. Subway stations spaces are important examples of public spaces that are in close connection with the social l...Environmental design is concerned with the function of people within an environment and their interactions. Subway stations spaces are important examples of public spaces that are in close connection with the social life of people. Also, the fact that the social interactions and relations between people and city environments are becoming indispensable for subway station space indicates that these spaces play an essential role in urban life. This paper addresses the result of a study conducted by the authors on the influential elements pivotal to the improvement of social interactions in subway stations. The theory of John Lang in Urban design with consideration of social interaction was considered in this study. The objective of the study was to identify the architectural requirements in improving social interaction between people and environment in subway station spaces according to an evidence based design approach. To do so, relevant literature in different disciplines, architecture, urban design, social sustainability and so on, were reviewed Next, the most important environmental factors which contribute to human behavior in public spaces were derived and analyzed. Data of the study were collected via questionnaires filled out by the users of Tehran＇s subway stations. The collected data were analyzed and the architectural elements/requirements for improving social interactions were classified. The results of the study indicate that in the case of architectural requirements, contribution to the improvement of social interactions, design considerations for physical and mental safety, accessibility and lighting are the most important factors.展开更多
Generalized Inversion Method has been used to estimate the spatial variation of site effects,using the digital data of SH-waves recorded by 63 stations in the Capital Circle Region of China from 2001 to 2006.We gained...Generalized Inversion Method has been used to estimate the spatial variation of site effects,using the digital data of SH-waves recorded by 63 stations in the Capital Circle Region of China from 2001 to 2006.We gained the site effects of all stations participating in the calculation.We found that the site effect of rock was stabile and about 1.0 from 1.0Hz to 10.0Hz,while the site effect of deposit was high in low frequencies,about 3 ～ 7 from 1.0Hz to 8.0Hz,and the site effect was protuberant at about 5.0Hz,then fell as the frequency increased.The result shows the shape and intensity of station site effects are mainly influenced by the lithology below the station,and possibly also by the local geological structure.展开更多
After the Yushu M S 7.1 earthquake on April 14,2010,a large number of aftershocks were recorded by the surrounding permanent network and temporary seismic stations.Due to the distribution of stations,knowledge about v...After the Yushu M S 7.1 earthquake on April 14,2010,a large number of aftershocks were recorded by the surrounding permanent network and temporary seismic stations.Due to the distribution of stations,knowledge about velocity structure,the reliability of seismic phases,and so on,the location result from conventional method is usually of low precision,from which it is difficult to recognize the spatial and temporal distribution and the trends of aftershock activity.In this paper,by using teleseismic waveforms recorded by permanent station,the seismic velocity structure beneath the vicinity is obtained from receiver function stacking and inversion methods.And the Yushu earthquake sequences are relocated from seismic phase data by HypoDD.The results show that the Yushu M S 7.1 earthquake occurred at 13 km depth;the aftershock sequences were distributed mainly in the NWW along the Garzê-Yushu fault,and most aftershocks were concentrated in a 100 km length and 5-20 km depth.Combined with the velocity structure,it can be inferred that the earthquake mainly destroys the high-velocity layer of the upper crust.In the west of the seismic fault near(33.3°N,96.2°E),the aftershock sequences were distributed like a straight column,suggesting there was a comminuted break from 25km depth to the ground.展开更多
As a main constituent of geological body, the rock masses have distinct differences from other materials, one of which is that rock masses are initially stressed in their natural states. Hence, it is an extremely chal...As a main constituent of geological body, the rock masses have distinct differences from other materials, one of which is that rock masses are initially stressed in their natural states. Hence, it is an extremely challenging and significant research project to know the present residual stress of the rock masses in the earth's crust. Although some regularities of distribution of in-situ rock stresses can be deduced, the basic means to study the state of rock stress is in-situ stress measurement. After a brief review of several measuring methods of in-situ 3D rock stress, a new one, borehole wall stress relief method (BWSRM) to determine the in-situ 3D rock stress tensor in a single drilled borehole was proposed. Based on the principle of in-situ rock stress measurement with BWSRM, an original geostress measuring instrument was designed and manufactured. Preliminary experiments for determination of in-situ stress orientation and magnitude were carried out at an experimental tunnel in Jinping Ⅱ hydropower station in China, where the buried depth of overburden was about 2430 m. The results showed that it was feasible to measure the in-situ 3D rock stresses with BWSRM presented in this paper. The BWSRM has a broad prospect for in-situ 3D rock stress measurements in practical rock engineering.展开更多
A dedicated 24 h S/X dual-band geodetic very long baseline interferometry(VLBI) experiment was conducted in January 2015 with the goal of improving the position estimates for the Chinese Deep Space Station Kashi. Prev...A dedicated 24 h S/X dual-band geodetic very long baseline interferometry(VLBI) experiment was conducted in January 2015 with the goal of improving the position estimates for the Chinese Deep Space Station Kashi. Previously, the position estimates had been only accurate to ~20 cm, which is insufficient for future Chinese deep space explorations. The experiment design and data reduction are described with special emphasis on the limited frequency ranges of Kashi for bandwidth synthesis. A narrowed multi-band delay search window based on post-fit residuals was utilized to resolve the sub-ambiguities due to the drop of a frequency channel in fringe fit, which saved ~22% of the observations from the affected baseline. Final position estimates of Kashi were obtained from the global solution by using more than 5300 international VLBI sessions from August 1979 to September 2015, and estimates were found to be accurate to about 10, 25, and 20 mm in the X, Y, and Z components. Various statistical tests were run, and the estimates and precisions are believed to be reliable.展开更多
基金supported by the Scientific Research Fund of Heilongjiang Provincial Education Department of China under Grant No.12511119
文摘In polarization-encoded free-space quantum communications, a transmitter on a satellite and a receiver in a ground station each have a respective polarization zero direction, by which they encode and decode every polariza-tion quantum bit required for a quantum com-munication protocol. In order to complete the protocol, the ground-based receiver needs to track and compensate for the polarization zero direction of the satellite-based transmitter. Ex- pressions satisfied by amplitudes of the s-polarization component and the p-polarization component are derived based on a two-mirror model, and a condition satisfied by the reflec- tion coefficients of the two mirrors is given. A polarization tracking principle is analyzed for satellite-to-ground quanaun communications, and quantum key encoding and decoding prin- ciples based on polarization tracking are given. A half-wave-plate-based dynamic polariza- tion-basis compensation scheme is proposed in this paper, and this scheme is proved to be suitable for satellite-to-ground and intersatellite quantum communications.
基金supported by the "Strategic Priority Research Program" of the Chinese Academy of Sciences(XDA05100300)the National Basic Research Program of China(2013CB955801)the National Natural Science Foundation of China(41175030)
文摘Total Cloud Cover （TCC） over China deter- mined from four climate datasets including the Interna- tional Satellite Cloud Climatology Project （ISCCP）, the 40-year Re-Analysis Project of the European Centre for Medium-Range Weather Forecasts （ERA-40）, Climate Research Unit Time Series 3.0 （CRU3）, and ground sta- tion datasets are used to show spatial and temporal varia- tion of TCC and their differences. It is demonstrated that the four datasets show similar spatial pattern and seasonal variation. The maximum value is derived from ISCCE TCC value in North China derived from ERA-40 is 50% larger than that from the station dataset; however, the value is 50% less than that in South China. The annual TCC of ISCCP, ERA-40, and ground station datasets shows a decreasing trend during 1984-2002; however, an increasing trend is derived from CRU3. The results of this study imply remarkable differences of TCC derived from surface and satellite observations as well as model simu- lations. The potential effects of these differences on cloud climatology and associated climatic issues should be carefully considered.
基金co-funded by the China Earthquake Science and Technology Spark Plan Project(XH12008YXH13004)+1 种基金the Youth Backbone Project of China Earthquake Administration(20140305)Shanxi Foundation for Basic Research,China(2013011029)
文摘Based on arrival time data of seismic phases of ML≥2. 0 earthquakes measured at Shanxi Digital Seismic Network for the period from January 2001 to October 2014,V_P/ V_S in the Shanxi region is calculated using the Wadati single station and multi-earthquake method,and an investigation is conducted into the variation behavior of V_P/ V_S in the Shanxi region before and after the three earthquakes of MS≥4. 5 in 2010. Our study finds that abnormal V_P/ V_S appeared earlier at distant stations before all of the three earthquakes,which is at the time range from 6 months to 1 year before the earthquakes,and later at near stations,at the time range 10 days to 2 months before earthquakes. Therefore,it s possible to narrow down the scope of the location in earthquake prediction from the distant and near station data. The calculations of Dongshan seismic station indicate that the size of the residual of the origin time has impact on the detail of V_P/ V_S variation,thus,appropriate thresholds should firstly be set for the residuals of origin time at each seismic station in practical application,to ensure scientific and steady V_P/ V_S calculations.
文摘Environmental design is concerned with the function of people within an environment and their interactions. Subway stations spaces are important examples of public spaces that are in close connection with the social life of people. Also, the fact that the social interactions and relations between people and city environments are becoming indispensable for subway station space indicates that these spaces play an essential role in urban life. This paper addresses the result of a study conducted by the authors on the influential elements pivotal to the improvement of social interactions in subway stations. The theory of John Lang in Urban design with consideration of social interaction was considered in this study. The objective of the study was to identify the architectural requirements in improving social interaction between people and environment in subway station spaces according to an evidence based design approach. To do so, relevant literature in different disciplines, architecture, urban design, social sustainability and so on, were reviewed Next, the most important environmental factors which contribute to human behavior in public spaces were derived and analyzed. Data of the study were collected via questionnaires filled out by the users of Tehran＇s subway stations. The collected data were analyzed and the architectural elements/requirements for improving social interactions were classified. The results of the study indicate that in the case of architectural requirements, contribution to the improvement of social interactions, design considerations for physical and mental safety, accessibility and lighting are the most important factors.
基金sponsored by the Special Foundation of China Earthquake Administration (2007-8-26)
文摘Generalized Inversion Method has been used to estimate the spatial variation of site effects,using the digital data of SH-waves recorded by 63 stations in the Capital Circle Region of China from 2001 to 2006.We gained the site effects of all stations participating in the calculation.We found that the site effect of rock was stabile and about 1.0 from 1.0Hz to 10.0Hz,while the site effect of deposit was high in low frequencies,about 3 ～ 7 from 1.0Hz to 8.0Hz,and the site effect was protuberant at about 5.0Hz,then fell as the frequency increased.The result shows the shape and intensity of station site effects are mainly influenced by the lithology below the station,and possibly also by the local geological structure.
基金supported by Institute of Geophysics,China Earthquake Administration(Grant No.DQJB10B04)
文摘After the Yushu M S 7.1 earthquake on April 14,2010,a large number of aftershocks were recorded by the surrounding permanent network and temporary seismic stations.Due to the distribution of stations,knowledge about velocity structure,the reliability of seismic phases,and so on,the location result from conventional method is usually of low precision,from which it is difficult to recognize the spatial and temporal distribution and the trends of aftershock activity.In this paper,by using teleseismic waveforms recorded by permanent station,the seismic velocity structure beneath the vicinity is obtained from receiver function stacking and inversion methods.And the Yushu earthquake sequences are relocated from seismic phase data by HypoDD.The results show that the Yushu M S 7.1 earthquake occurred at 13 km depth;the aftershock sequences were distributed mainly in the NWW along the Garzê-Yushu fault,and most aftershocks were concentrated in a 100 km length and 5-20 km depth.Combined with the velocity structure,it can be inferred that the earthquake mainly destroys the high-velocity layer of the upper crust.In the west of the seismic fault near(33.3°N,96.2°E),the aftershock sequences were distributed like a straight column,suggesting there was a comminuted break from 25km depth to the ground.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50579037, 50639080, 50979054)the Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering (Grant No. SKLZ0901)
文摘As a main constituent of geological body, the rock masses have distinct differences from other materials, one of which is that rock masses are initially stressed in their natural states. Hence, it is an extremely challenging and significant research project to know the present residual stress of the rock masses in the earth's crust. Although some regularities of distribution of in-situ rock stresses can be deduced, the basic means to study the state of rock stress is in-situ stress measurement. After a brief review of several measuring methods of in-situ 3D rock stress, a new one, borehole wall stress relief method (BWSRM) to determine the in-situ 3D rock stress tensor in a single drilled borehole was proposed. Based on the principle of in-situ rock stress measurement with BWSRM, an original geostress measuring instrument was designed and manufactured. Preliminary experiments for determination of in-situ stress orientation and magnitude were carried out at an experimental tunnel in Jinping Ⅱ hydropower station in China, where the buried depth of overburden was about 2430 m. The results showed that it was feasible to measure the in-situ 3D rock stresses with BWSRM presented in this paper. The BWSRM has a broad prospect for in-situ 3D rock stress measurements in practical rock engineering.
基金supported by China’s Lunar Exploration Key Techniques Research Program (Grant No. TY3Q20100009)
文摘A dedicated 24 h S/X dual-band geodetic very long baseline interferometry(VLBI) experiment was conducted in January 2015 with the goal of improving the position estimates for the Chinese Deep Space Station Kashi. Previously, the position estimates had been only accurate to ~20 cm, which is insufficient for future Chinese deep space explorations. The experiment design and data reduction are described with special emphasis on the limited frequency ranges of Kashi for bandwidth synthesis. A narrowed multi-band delay search window based on post-fit residuals was utilized to resolve the sub-ambiguities due to the drop of a frequency channel in fringe fit, which saved ~22% of the observations from the affected baseline. Final position estimates of Kashi were obtained from the global solution by using more than 5300 international VLBI sessions from August 1979 to September 2015, and estimates were found to be accurate to about 10, 25, and 20 mm in the X, Y, and Z components. Various statistical tests were run, and the estimates and precisions are believed to be reliable.
