In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau （QTP） was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing （RS） datasets ...In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau （QTP） was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing （RS） datasets by decision tree method. The spatial resolution of the map is 1 km×1 kin, and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas. The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km2. In the vegetated region, 50,260 km2 is the areas of alpine swamp meadow, 583,909 km2 for alpine meadow, 332,754 km2 for alpine steppe, and 234,828 km2 for alpine desert. This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of highaltitude areas.展开更多
Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its ca...Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its catalytic ability for the thiophene alkylation, xylene alkylation and hexene oligomerization was investigated. The results showed that the acidity of the Hβ zeolite was increased with the decrease of Si/Al2 ratio, but its catalytic ability was not always increased. In fact, it reached the maximal catalytic ability at Si/Al2 ratio of 66, and under the reaction conditions of 60 ℃, 1.5 MPa, WHSV 3.0 h^-1 and time on stream 2 h. At the ratio, the conversion of thiophene, xylene, and oligomerized hexene were 96.6%, 2.7% and 2.8%, respectively. An optimal Si/Al2 ratio exists for the catalytic performance of Hβ zeolite. By investigating the coke deposition of the used Hβ zeolite catalysts, it has been found that the optimal Si/Al2 ratio is attributed to the combined effect of the carbocation activation capability and the hydrogen transformation capability of the Hβ zeolite catalyst.展开更多
Seismic oceanography is a new cross-discipline of reflection seismology and physical oceanography. The biggest difference between seismic oceanography and traditional reflection seismology is its research object of ti...Seismic oceanography is a new cross-discipline of reflection seismology and physical oceanography. The biggest difference between seismic oceanography and traditional reflection seismology is its research object of time-varied seawater. How to estimate the temporal variations of reflectors in water structure and make some corrections in seismic data are basic problems in seismic oceanography research. Here a method of estimation for seawater movement is provided based on the reflectors. The application results of this method to the simulated and field seismic data turn out to be acceptable. As compared with the previous research, this method has the advantages of low-dependence on migration velocity and dip of reflectors, and it is very suitable for correction in a spectral analysis using seismic data, which is very useful in the research of ocean energy budget.展开更多
Five of the seven Phase I beamlines of Shanghai Synchrotron Radiation Facility(SSRF) are based on insertion devices(IDs),which include two wigglers,one elliptically polarized undulator(EPU),and two in-vacuum undulator...Five of the seven Phase I beamlines of Shanghai Synchrotron Radiation Facility(SSRF) are based on insertion devices(IDs),which include two wigglers,one elliptically polarized undulator(EPU),and two in-vacuum undulators.There were some inevitable field integral errors in manufacturing the IDs,and these would affect performance of the storage ring.The integrated multipoles were corrected by using the magic fingers technique.In this paper,we report the correction method based on the simulated-annealing algorithm.The results show that the integrated multipole components were corrected to meet the design specifications.展开更多
We compare the properties of optically dark GRBs, defined by the optical-to-X- ray spectral indexβox 〈 0.5, and normal ones discovered by the Swift satellite before the year 2008 in a statistical way, using data col...We compare the properties of optically dark GRBs, defined by the optical-to-X- ray spectral indexβox 〈 0.5, and normal ones discovered by the Swift satellite before the year 2008 in a statistical way, using data collected from the literature and online databases. Our sample includes 200 long bursts, 19 short bursts, and 10 with measured high redshifts （z ≥ 4）. The ratio of dark bursts is found to be -10% - 20%, and is similar among long bursts, short ones, and the high-z sub-sample. The result for long bursts is consistent with both the pre-Swift sample and studies by other authors on smaller Swift samples. The existence of dark short GRBs is pointed out for the first time. The X-ray derived hydrogen column densities of dark GRBs clearly prefer large values compared with those of normal bursts. This supports the dust extinction scenario as the main cause of dark GRBs. Other possibilities like very high redshifts and non-standard emission mechanisms are less likely, although not fully excluded.展开更多
The goals of engineering and scientific missions for Chang＇E-2 lunar satellite require high detection sensitivity and large imaging dynamic range for the onboard CCD cameras. The TDI CCD image sensor was adopted for ...The goals of engineering and scientific missions for Chang＇E-2 lunar satellite require high detection sensitivity and large imaging dynamic range for the onboard CCD cameras. The TDI CCD image sensor was adopted for the two linear CCD stereo cameras for the first time in the lunar reconnaissance of the world. The design argumentation is described in this paper. The analysis shows that the imagers meet the mission requirements. The satellite was launched on 1 October 2010 at zero window. The cameras obtained images of 7 m resolution on the 100 km orbit for the first time on 24 October 2010, and operated once again on 27 October 2010 to take stereo images of the Sinus Iridum with the resolution better than 1.5 m. On the near-moon-arc of 15 kmxl00 km elliptical orbit, the images are very clear and rich of grey scales, indicating successful completion of the Chang＇E-2 engineering mission. At the present the cameras are acquiring the full lunar surface stereo images with 7 m resolution on the 100 km circular orbit to complete their scientific mission.展开更多
16S rDNA sequencing results from this study and literatures demonstrate that sediment bacteria in the South China Sea （SCS） were very diverse,which contained 22 of the 24 phyla of bacteria investigated from marine s...16S rDNA sequencing results from this study and literatures demonstrate that sediment bacteria in the South China Sea （SCS） were very diverse,which contained 22 of the 24 phyla of bacteria investigated from marine sediment,however,it was very imbalance among stations.So bacterial diversity from 15 samples which covered a wide range of sediment types from 20 to 3 888 m in depth was studied in DGGE （denature gradient gel electrophoresis） in this paper.The DGGE results indicate that both sediment bacterial diversity and diversity difference among stations were significant.Thirty representative and differential fingerprints among samples were recovered and sequenced,phylogenetic analysis indicates that they may belong to Proteobacteria （α-,β-,γ-,δ-,ε-）,Planctomycetes,Firmicutes,Chloroflexi,Acidobacteria,Actinobacteria,Nitrospirae,Gemmatimonadetes,candidate division WS3 and so on,of which,Gemmatimonadetes and candidate division WS3 bacteria were first detected in SCS sediment.This study also shows that bacterial diversity analysis based on DGGE was more potential than traditional 16S rDNA clone library in multiple sample analysis.展开更多
In this paper,short pulse radiation in Shanghai Synchrotron Radiation Facility(SSRF)is generated by the low momentum compaction factor(α_C)optics,and three kinds of the low-α_C optics are found,with the very lowα_C...In this paper,short pulse radiation in Shanghai Synchrotron Radiation Facility(SSRF)is generated by the low momentum compaction factor(α_C)optics,and three kinds of the low-α_C optics are found,with the very lowα_C being adopted by reducing dispersion in the straight section to negative value in the SSRF.Energy acceptance is selected as objective functions in nonlinear optimization rather than the second orderα_C or other nonlinear driving terms.The optimal result is improved step-by-step by randomly setting harmonic sextupole strengths.Two optics modes,i.e.low positiveα_C and low negativeα_C,are analyzed.In order to get a large energy acceptance and only one stable point in longitudinal phase space,the low negativeα_C optics is taken as an operation mode for the short pulse radiation in the SSRF.展开更多
A rapid liquid X-ray diffractometer was used to study the time-averaged and space-averaged structure of aqueous sodium sulfate solutions at 298 and 323 K. Difference radial distribution functions of the solutions were...A rapid liquid X-ray diffractometer was used to study the time-averaged and space-averaged structure of aqueous sodium sulfate solutions at 298 and 323 K. Difference radial distribution functions of the solutions were obtained from accurate diffraction data. The interaction distances of Na+-OH2 and S-H2O in solutions were found to be 0.235 and 0.385 nm, respectively, after deconvolution of superposition peaks by Gaussian multi-peak fitting program. The characteristic distance of the NaSO4-contact ion pairs in higher concentration solutions was determined to be 0.345 nm, suggesting that the Na+ ions coordinated with SO42- ions in the mono-dentate form. Effects of concentration and temperature on the hydration structure of the solutions were discussed in the present paper. With a decrease in concentration, the contributions of the H2O to the diffraction pattern increase, the average coordination number of the Na+ ions hardly changes, while the hydration number of SO42-ions increases slightly. The formation of NaSO4-contact ion pairs becomes easier at higher temperature. The structure of hydrogen bond in dilute solutions is broken to a considerable extent with rising temperature, and the peak at 0.290 nm splits into two peaks at 0.275 and 0.305 nm, respectively.展开更多
The striations of the reverberation spectrum in the time-frequency distribution were observed in a shallow water acoustic experiment in 2002. A model following the coherent reverberation model developed in 2002 is pre...The striations of the reverberation spectrum in the time-frequency distribution were observed in a shallow water acoustic experiment in 2002. A model following the coherent reverberation model developed in 2002 is presented to explain the observed striations. To examine the consistency between the measured data and numerical predictions, we have used a method based on Radon transform for determining the slope of the striations to the measured reverberation data and numerical predictions. The results indicate that the previously developed coherent reverberation model can predict the interference structure of the reverberation intensity in the time-frequency distribution.展开更多
Traditional studies on potential yield mainly referred to attainable yield： the maximum yield which could be reached by a crop in a given environment. The new concept of crop yield under average climate conditions wa...Traditional studies on potential yield mainly referred to attainable yield： the maximum yield which could be reached by a crop in a given environment. The new concept of crop yield under average climate conditions was defined in this paper, which was affected by advancement of science and technology. Based on the new concept of crop yield, the time series techniques relying on past yield data was employed to set up a forecasting model. The model was tested by using average grain yields of Liaoning Province in China from 1949 to 2005. The testing combined dynamic n-choosing and micro tendency rectification, and an average forecasting error was 1.24%. In the trend line of yield change, and then a yield turning point might occur, in which case the inflexion model was used to solve the problem of yield turn point.展开更多
Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distri...Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distribution maintained by pitch-angle scattering, the model calculates the electron flux by following bounce-averaged electric field, gradient, and curvature drift in the time dependent electric and magnetic field, meanwhile it counts the electron loss caused by pitch angle scattering. Using the model, the clectron flux distribution during a magnetic storm was calculated and compared with the observation data from the geosynchronous orbit. It is shown that the model can successfully reproduce most of the major electron flux enhancements observed at the geosynchronous orbit and generally tracks the satellite data well. The rms errors of the modeled logarithm of flux are between 0.5-1.0.展开更多
A three-layer structure of n-type organic semiconductors （PTCDA/PTCDA：PCBM/PCBM） is successfully identified as pho- toanode for photoelectrochemical water oxidation during the overall splitting of water into hydrog...A three-layer structure of n-type organic semiconductors （PTCDA/PTCDA：PCBM/PCBM） is successfully identified as pho- toanode for photoelectrochemical water oxidation during the overall splitting of water into hydrogen/oxygen in a nearly stoi- chiometric ratio （H2：O2 = 2：1） under visible irradiation （2 〉 420 nm）. A possible charge separation mechanism under visible light illumination was also proposed.展开更多
Forward secrecy is an important security property in key agreement protocol. Based on Ham＇s protocol, in this paper a new authenticated Diffie-Hellman key agreement protocol with half forward secrecy is proposed. Thi...Forward secrecy is an important security property in key agreement protocol. Based on Ham＇s protocol, in this paper a new authenticated Diffie-Hellman key agreement protocol with half forward secrecy is proposed. This protocol is also based on a single cryptographic assumption, and is user authentication and shared key authentication. More importantly, our protocol provides forward secrecy with respect to one of the parties. For this reason, besides the advantages of Ham＇s protocol, in practice, our protocol can reduce the damages resulted from the disclosure of the user＇s secret key and it is very beneficial to today＇s communication with portable devices.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.41101055)the Hundred Talents Program of the Chinese Academy of Sciences granted to Tonghua Wu (Grant No.51Y251571)the “National Basic Research Program of China (973 Program)” (Grant No.2010CB951402)
文摘In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau （QTP） was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing （RS） datasets by decision tree method. The spatial resolution of the map is 1 km×1 kin, and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas. The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km2. In the vegetated region, 50,260 km2 is the areas of alpine swamp meadow, 583,909 km2 for alpine meadow, 332,754 km2 for alpine steppe, and 234,828 km2 for alpine desert. This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of highaltitude areas.
基金the National 973 Project of China(No.2005CB221403)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant:DICP K2007D3)
文摘Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its catalytic ability for the thiophene alkylation, xylene alkylation and hexene oligomerization was investigated. The results showed that the acidity of the Hβ zeolite was increased with the decrease of Si/Al2 ratio, but its catalytic ability was not always increased. In fact, it reached the maximal catalytic ability at Si/Al2 ratio of 66, and under the reaction conditions of 60 ℃, 1.5 MPa, WHSV 3.0 h^-1 and time on stream 2 h. At the ratio, the conversion of thiophene, xylene, and oligomerized hexene were 96.6%, 2.7% and 2.8%, respectively. An optimal Si/Al2 ratio exists for the catalytic performance of Hβ zeolite. By investigating the coke deposition of the used Hβ zeolite catalysts, it has been found that the optimal Si/Al2 ratio is attributed to the combined effect of the carbocation activation capability and the hydrogen transformation capability of the Hβ zeolite catalyst.
基金The National Major Fundamental Research and Development Project of China under contract No. 2011CB403503the National Natural Science Foundation of China under contract Nos 41076024 and 91028002
文摘Seismic oceanography is a new cross-discipline of reflection seismology and physical oceanography. The biggest difference between seismic oceanography and traditional reflection seismology is its research object of time-varied seawater. How to estimate the temporal variations of reflectors in water structure and make some corrections in seismic data are basic problems in seismic oceanography research. Here a method of estimation for seawater movement is provided based on the reflectors. The application results of this method to the simulated and field seismic data turn out to be acceptable. As compared with the previous research, this method has the advantages of low-dependence on migration velocity and dip of reflectors, and it is very suitable for correction in a spectral analysis using seismic data, which is very useful in the research of ocean energy budget.
文摘Five of the seven Phase I beamlines of Shanghai Synchrotron Radiation Facility(SSRF) are based on insertion devices(IDs),which include two wigglers,one elliptically polarized undulator(EPU),and two in-vacuum undulators.There were some inevitable field integral errors in manufacturing the IDs,and these would affect performance of the storage ring.The integrated multipoles were corrected by using the magic fingers technique.In this paper,we report the correction method based on the simulated-annealing algorithm.The results show that the integrated multipole components were corrected to meet the design specifications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10673014 and 10873017)by the National Basic Research Program of China (Grant No. 2009CB824800)
文摘We compare the properties of optically dark GRBs, defined by the optical-to-X- ray spectral indexβox 〈 0.5, and normal ones discovered by the Swift satellite before the year 2008 in a statistical way, using data collected from the literature and online databases. Our sample includes 200 long bursts, 19 short bursts, and 10 with measured high redshifts （z ≥ 4）. The ratio of dark bursts is found to be -10% - 20%, and is similar among long bursts, short ones, and the high-z sub-sample. The result for long bursts is consistent with both the pre-Swift sample and studies by other authors on smaller Swift samples. The existence of dark short GRBs is pointed out for the first time. The X-ray derived hydrogen column densities of dark GRBs clearly prefer large values compared with those of normal bursts. This supports the dust extinction scenario as the main cause of dark GRBs. Other possibilities like very high redshifts and non-standard emission mechanisms are less likely, although not fully excluded.
文摘The goals of engineering and scientific missions for Chang＇E-2 lunar satellite require high detection sensitivity and large imaging dynamic range for the onboard CCD cameras. The TDI CCD image sensor was adopted for the two linear CCD stereo cameras for the first time in the lunar reconnaissance of the world. The design argumentation is described in this paper. The analysis shows that the imagers meet the mission requirements. The satellite was launched on 1 October 2010 at zero window. The cameras obtained images of 7 m resolution on the 100 km orbit for the first time on 24 October 2010, and operated once again on 27 October 2010 to take stereo images of the Sinus Iridum with the resolution better than 1.5 m. On the near-moon-arc of 15 kmxl00 km elliptical orbit, the images are very clear and rich of grey scales, indicating successful completion of the Chang＇E-2 engineering mission. At the present the cameras are acquiring the full lunar surface stereo images with 7 m resolution on the 100 km circular orbit to complete their scientific mission.
基金The State Principal and Basic Research and Development Program of the Ministry of Sciences and Technology of China under contract No.2010CB833801the National Supportive Project under contract No.2006BAB19B02Hundred Talents Program of Chinese Academy of Science
文摘16S rDNA sequencing results from this study and literatures demonstrate that sediment bacteria in the South China Sea （SCS） were very diverse,which contained 22 of the 24 phyla of bacteria investigated from marine sediment,however,it was very imbalance among stations.So bacterial diversity from 15 samples which covered a wide range of sediment types from 20 to 3 888 m in depth was studied in DGGE （denature gradient gel electrophoresis） in this paper.The DGGE results indicate that both sediment bacterial diversity and diversity difference among stations were significant.Thirty representative and differential fingerprints among samples were recovered and sequenced,phylogenetic analysis indicates that they may belong to Proteobacteria （α-,β-,γ-,δ-,ε-）,Planctomycetes,Firmicutes,Chloroflexi,Acidobacteria,Actinobacteria,Nitrospirae,Gemmatimonadetes,candidate division WS3 and so on,of which,Gemmatimonadetes and candidate division WS3 bacteria were first detected in SCS sediment.This study also shows that bacterial diversity analysis based on DGGE was more potential than traditional 16S rDNA clone library in multiple sample analysis.
文摘In this paper,short pulse radiation in Shanghai Synchrotron Radiation Facility(SSRF)is generated by the low momentum compaction factor(α_C)optics,and three kinds of the low-α_C optics are found,with the very lowα_C being adopted by reducing dispersion in the straight section to negative value in the SSRF.Energy acceptance is selected as objective functions in nonlinear optimization rather than the second orderα_C or other nonlinear driving terms.The optimal result is improved step-by-step by randomly setting harmonic sextupole strengths.Two optics modes,i.e.low positiveα_C and low negativeα_C,are analyzed.In order to get a large energy acceptance and only one stable point in longitudinal phase space,the low negativeα_C optics is taken as an operation mode for the short pulse radiation in the SSRF.
基金Supported by the National Natural Science Foundation of China(Grant No.20873172)Prior Special Fund of the Major State Basic Research Development of China(Grant No.2008CB617612)
文摘A rapid liquid X-ray diffractometer was used to study the time-averaged and space-averaged structure of aqueous sodium sulfate solutions at 298 and 323 K. Difference radial distribution functions of the solutions were obtained from accurate diffraction data. The interaction distances of Na+-OH2 and S-H2O in solutions were found to be 0.235 and 0.385 nm, respectively, after deconvolution of superposition peaks by Gaussian multi-peak fitting program. The characteristic distance of the NaSO4-contact ion pairs in higher concentration solutions was determined to be 0.345 nm, suggesting that the Na+ ions coordinated with SO42- ions in the mono-dentate form. Effects of concentration and temperature on the hydration structure of the solutions were discussed in the present paper. With a decrease in concentration, the contributions of the H2O to the diffraction pattern increase, the average coordination number of the Na+ ions hardly changes, while the hydration number of SO42-ions increases slightly. The formation of NaSO4-contact ion pairs becomes easier at higher temperature. The structure of hydrogen bond in dilute solutions is broken to a considerable extent with rising temperature, and the peak at 0.290 nm splits into two peaks at 0.275 and 0.305 nm, respectively.
基金supported by the National Natural Science Foundation of China (Grant No. 10734100)
文摘The striations of the reverberation spectrum in the time-frequency distribution were observed in a shallow water acoustic experiment in 2002. A model following the coherent reverberation model developed in 2002 is presented to explain the observed striations. To examine the consistency between the measured data and numerical predictions, we have used a method based on Radon transform for determining the slope of the striations to the measured reverberation data and numerical predictions. The results indicate that the previously developed coherent reverberation model can predict the interference structure of the reverberation intensity in the time-frequency distribution.
基金Supported by Agricultural Poor-helping Monopoly of Graduate University of Chinese Academy of Science (40641002)
文摘Traditional studies on potential yield mainly referred to attainable yield： the maximum yield which could be reached by a crop in a given environment. The new concept of crop yield under average climate conditions was defined in this paper, which was affected by advancement of science and technology. Based on the new concept of crop yield, the time series techniques relying on past yield data was employed to set up a forecasting model. The model was tested by using average grain yields of Liaoning Province in China from 1949 to 2005. The testing combined dynamic n-choosing and micro tendency rectification, and an average forecasting error was 1.24%. In the trend line of yield change, and then a yield turning point might occur, in which case the inflexion model was used to solve the problem of yield turn point.
基金supported by the National Natural Science Foundation of China(Grant No.40704032)
文摘Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distribution maintained by pitch-angle scattering, the model calculates the electron flux by following bounce-averaged electric field, gradient, and curvature drift in the time dependent electric and magnetic field, meanwhile it counts the electron loss caused by pitch angle scattering. Using the model, the clectron flux distribution during a magnetic storm was calculated and compared with the observation data from the geosynchronous orbit. It is shown that the model can successfully reproduce most of the major electron flux enhancements observed at the geosynchronous orbit and generally tracks the satellite data well. The rms errors of the modeled logarithm of flux are between 0.5-1.0.
基金supported by the National Natural Science Foundation of China (20920102034,20877076 & 20907056)the Major State Basic Research Development Program of China (2010CB933503 &2007CB613306)
文摘A three-layer structure of n-type organic semiconductors （PTCDA/PTCDA：PCBM/PCBM） is successfully identified as pho- toanode for photoelectrochemical water oxidation during the overall splitting of water into hydrogen/oxygen in a nearly stoi- chiometric ratio （H2：O2 = 2：1） under visible irradiation （2 〉 420 nm）. A possible charge separation mechanism under visible light illumination was also proposed.
基金Supported by the National Natural Science Foundation of China (60873233)the Nature Science Foundation of Shaanxi Province, China (2006F19)the Technology Research Program of Xi’an, China (CXY08016)
文摘Forward secrecy is an important security property in key agreement protocol. Based on Ham＇s protocol, in this paper a new authenticated Diffie-Hellman key agreement protocol with half forward secrecy is proposed. This protocol is also based on a single cryptographic assumption, and is user authentication and shared key authentication. More importantly, our protocol provides forward secrecy with respect to one of the parties. For this reason, besides the advantages of Ham＇s protocol, in practice, our protocol can reduce the damages resulted from the disclosure of the user＇s secret key and it is very beneficial to today＇s communication with portable devices.
