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
Daily precipitation and temperature records at 13 stations for the period 1960-2008 were analyzed to identify climatic change and possible effects of urbanization on low-temperature precipitation [LTP, precipitation ...Daily precipitation and temperature records at 13 stations for the period 1960-2008 were analyzed to identify climatic change and possible effects of urbanization on low-temperature precipitation [LTP, precipitation of ≥ 0.1 mm d^-1 occurring under a daily minimum temperature （Tmin） of ≤ 0℃] in the greater Beijing region （B JR）, where a rapid process of urbaniza tion has taken place over the last few decades. The paper provides a climatological overview of LTP in B JR. LTP contributes 61.7% to the total amount of precipitation in B JR in the cold season （November-March）. There is a slight increasing trend [1.22 mm （10 yr）^-1] in the amount of total precipitation for the cold season during 1960-2008. In contrast, the amount of LTP decreases by 0.6 mm （10 yr）^-1. The warming rate of Train in B JR is 0.66℃ （10 yr）^-1. Correspondingly, the frequency of LTP decreases with increasing Tmin by -0.67 times per ℃. The seasonal frequency and amount of LTP in southeast B JR （mostly urban sites） are 17%-20% less than those in the northwestern （rural and montane sites）. The intensity of LTP for the urban sites and northeastern B JR exhibited significant enhancing trends [0.18 and 0.15 mm d^- 1 （10 yr）^- 1, respectively]. The frequency of slight LTP （〈0.2 mm d^-1） significantly decreased throughout B JR [by about -15.74% （10 yr）^-1 in the urban area and northeast B JR], while the contribution of the two heaviest LTP events to total LTP amount significantly increased by 3.2% （10 yr） ^-1.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
In this study, the clear sky hourly global and net solar irradiances at the surface determined using SUNFLUX, a simple parameterization scheme, for three stations （Gaize, Naqu, and Lhasa） on the Tibetan Plateau were...In this study, the clear sky hourly global and net solar irradiances at the surface determined using SUNFLUX, a simple parameterization scheme, for three stations （Gaize, Naqu, and Lhasa） on the Tibetan Plateau were evaluated against observation data. Our modeled results agree well with observations. The correlation coefficients between modeled and observed values were 〉 0.99 for all three stations. The relative error of modeled results, in average was 〈 7%, and the root-mean-square variance was 〈 27 W m-2. The solar irradiances in the radiation model were slightly overestimated compared with observation data; there were at least two likely causes. First, the radiative effects of aerosols were not included in the radiation model. Second, solar irradiances determined by thermopile pyranometers include a thermal offset error that causes solar radiation to be slightly underestimated. The solar radiation absorbed by the ozone and water vapor was estimated. The results show that monthly mean solar radiation absorbed by the ozone is 〈 2% of the global solar radiation （〈 14 W m-2）. Solar radiation absorbed by water vapor is stronger in summer than in winter. The maximum amount of monthly mean solar radiation absorbed by water vapor can be up to 13% of the global solar radiation （95 W m-2）. This indicates that water vapor measurements with high precision are very important for precise determination of solar radiation.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
The existing high-resolution hydrographic data in the western tropical Pacilit; Ocean are used to explore the spatial distribution and primary characteristics of thermohaline intrusions in the thermocline. Statistics ...The existing high-resolution hydrographic data in the western tropical Pacilit; Ocean are used to explore the spatial distribution and primary characteristics of thermohaline intrusions in the thermocline. Statistics show that the vertical scales of intrusions are 20-40 m in the upper thermocline （22.0-26.0δ0） and 40-80 m in the lower thermocline （26.0-27.2δ0）. In the upper thermocline, the most intensive intrusions exist at the equatorial front （EF） where north/sonth Pacilic water masses converge, anti Ihe westward spreading of the north Pacilic tropical waler （NPTW） in the Philippines Sea also produces patches of intrusions surrounding its high-salinity tongue. In the lower thermocline, intrusions are also strong at the tropical front （TF） which is the boundary between the north Pacilic subtropical/tropical waters. At the bottom of the thermocline （at about 27.0δ0）, intrusions mainly exist near the western boundary, which are produced by intermediate water convergence through the advection of subthermocline western boundary Ilows. Most strikingly a ＂C＂-shape distribution of intrusions at around 26.4δ0 is revealed, covering the vicinity of the EF the TE and the Mindanao Current （MC）, i.e., tile western boundary pathway ol the norlh Pacilic subtrnpical cell （STC）. Synoptic section analysis reveals that intrusions are more prominent on the warm/sally flank ot the fronts, implying more cross-front tongues of cold/fresh water. Among the intrusions, those at the EF are of best lateral coherence which implies a unique driving mechanism involving near-inertial velocity perturbations near the equator.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 intention of this work is to consider the stable isotopic compositions of oxygen and deuterium in rainfall, surface water and groundwater along the Yellow River in the North China Plain(NCP). This demonstrated tha...The intention of this work is to consider the stable isotopic compositions of oxygen and deuterium in rainfall, surface water and groundwater along the Yellow River in the North China Plain(NCP). This demonstrated that the δ~18O values in groundwater varied from –10.17 to –6.85‰, with mean value of –8.76‰, and that the δD ranged from –68.7 to –58.0‰, with mean value of –63.4‰, respectively. The δ~18O values in surface water varied from –8.36 to 1.32‰, with mean value of –6.8‰, and δD ranged from –64.4 to –35.1‰, with mean value of –57.6‰, respectively. Further, The range of Cl-values of groundwater varied from 5.9 to 340.5 mg/L and that values ranged from 30.1 to 81.9 mg/L in surface water samples and Na^+ value changed from 27.4 to 321 mg/L in groundwater, while that in surface water varied from 24.8 to 50.5 mg/L. Most of the points fall below the GMWL, but are close to the LMWL. Therefore the results indicated that the groundwaters along the Yellow River were influenced by rainfall in heavy events and surface water.展开更多
This paper proposes a low power wake-up baseband circuit used in Chinese Electronic Toll Collection (ETC) system. To reduce the static power consumption, a low power biasing strategy is proposed. The proposed circuit ...This paper proposes a low power wake-up baseband circuit used in Chinese Electronic Toll Collection (ETC) system. To reduce the static power consumption, a low power biasing strategy is proposed. The proposed circuit is fabricated in TSMC 0.18 μm technology with an area of 0.09 mm 2 . Its current consumption is only 2.1 μA under 1.8 V power supply. It achieves a sensitivity of 0.95 mV at room temperature with a variation of only ±28% over -35℃ to 105℃.展开更多
The Tropical Cyclone Genesis Potential Index （GPI） was employed to investigate possible impacts of global warming on tropical cyclone genesis over the western North Pacific （WNP）. The outputs of 20th century clima...The Tropical Cyclone Genesis Potential Index （GPI） was employed to investigate possible impacts of global warming on tropical cyclone genesis over the western North Pacific （WNP）. The outputs of 20th century climate simulation by eighteen GCMs were used to evaluate the models＇ ability to reproduce tropical cyclone genesis via the GPI. The GCMs were found in general to reasonably reproduce the observed spatial distribution of genesis. Some of the models also showed ability in capturing observed temporal variation. Based on the evaluation, the models （CGCM3.1-T47 and IPSL-CM4） found to perform best when reproducing both spatial and temporal features were chosen to project future GPI. Results show that both of these models project an upward trend of the GPI under the SRES A2 scenario, however the rate of increase differs between them.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
According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be desig...According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.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
The properties of norfloxacin(NFX)and its 4?-N-acetyl derivative(ANFX)are investigated in different pH aqueous solutions and H2O-CH3CN mixed solutions,to determine the effects of pH and polarity on their ground and ex...The properties of norfloxacin(NFX)and its 4?-N-acetyl derivative(ANFX)are investigated in different pH aqueous solutions and H2O-CH3CN mixed solutions,to determine the effects of pH and polarity on their ground and excited states.The triplet states of NFX and ANFX are affected more by pH than by polarity.The pH dependence of the NFX and ANFX triplet states is likely due to the different quantum yields of different protonated forms.Steady-state fluorescence,time-resolved fluorescence,and laser flash photolysis experiments at different pH values provide clear evidence of the involvement of different intramolecular charge-transfer pathways in the singlet states of NFX and ANFX.The different electron-donating capacities of 1-N,1?-N,and 4?-N under different conditions determine the major pathway.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supported by National Natural Science Foundation of China(Grant No.41075063)Chinese Academy of Sciences Strategic Priority Research Program(Grant No.XDA05090000)National Basic Research Program of China(Grant No.2012CB956200)
文摘Daily precipitation and temperature records at 13 stations for the period 1960-2008 were analyzed to identify climatic change and possible effects of urbanization on low-temperature precipitation [LTP, precipitation of ≥ 0.1 mm d^-1 occurring under a daily minimum temperature （Tmin） of ≤ 0℃] in the greater Beijing region （B JR）, where a rapid process of urbaniza tion has taken place over the last few decades. The paper provides a climatological overview of LTP in B JR. LTP contributes 61.7% to the total amount of precipitation in B JR in the cold season （November-March）. There is a slight increasing trend [1.22 mm （10 yr）^-1] in the amount of total precipitation for the cold season during 1960-2008. In contrast, the amount of LTP decreases by 0.6 mm （10 yr）^-1. The warming rate of Train in B JR is 0.66℃ （10 yr）^-1. Correspondingly, the frequency of LTP decreases with increasing Tmin by -0.67 times per ℃. The seasonal frequency and amount of LTP in southeast B JR （mostly urban sites） are 17%-20% less than those in the northwestern （rural and montane sites）. The intensity of LTP for the urban sites and northeastern B JR exhibited significant enhancing trends [0.18 and 0.15 mm d^- 1 （10 yr）^- 1, respectively]. The frequency of slight LTP （〈0.2 mm d^-1） significantly decreased throughout B JR [by about -15.74% （10 yr）^-1 in the urban area and northeast B JR], while the contribution of the two heaviest LTP events to total LTP amount significantly increased by 3.2% （10 yr） ^-1.
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.
基金supported by the National Natural Science Foundation of China(GrantNos.40905038,40921003,40775020,and40905071)
文摘In this study, the clear sky hourly global and net solar irradiances at the surface determined using SUNFLUX, a simple parameterization scheme, for three stations （Gaize, Naqu, and Lhasa） on the Tibetan Plateau were evaluated against observation data. Our modeled results agree well with observations. The correlation coefficients between modeled and observed values were 〉 0.99 for all three stations. The relative error of modeled results, in average was 〈 7%, and the root-mean-square variance was 〈 27 W m-2. The solar irradiances in the radiation model were slightly overestimated compared with observation data; there were at least two likely causes. First, the radiative effects of aerosols were not included in the radiation model. Second, solar irradiances determined by thermopile pyranometers include a thermal offset error that causes solar radiation to be slightly underestimated. The solar radiation absorbed by the ozone and water vapor was estimated. The results show that monthly mean solar radiation absorbed by the ozone is 〈 2% of the global solar radiation （〈 14 W m-2）. Solar radiation absorbed by water vapor is stronger in summer than in winter. The maximum amount of monthly mean solar radiation absorbed by water vapor can be up to 13% of the global solar radiation （95 W m-2）. This indicates that water vapor measurements with high precision are very important for precise determination of solar radiation.
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The National Natural Science Foundation of China under contract No.40890152the National Basic Research Program of China under contract No.2012CB417401
文摘The existing high-resolution hydrographic data in the western tropical Pacilit; Ocean are used to explore the spatial distribution and primary characteristics of thermohaline intrusions in the thermocline. Statistics show that the vertical scales of intrusions are 20-40 m in the upper thermocline （22.0-26.0δ0） and 40-80 m in the lower thermocline （26.0-27.2δ0）. In the upper thermocline, the most intensive intrusions exist at the equatorial front （EF） where north/sonth Pacilic water masses converge, anti Ihe westward spreading of the north Pacilic tropical waler （NPTW） in the Philippines Sea also produces patches of intrusions surrounding its high-salinity tongue. In the lower thermocline, intrusions are also strong at the tropical front （TF） which is the boundary between the north Pacilic subtropical/tropical waters. At the bottom of the thermocline （at about 27.0δ0）, intrusions mainly exist near the western boundary, which are produced by intermediate water convergence through the advection of subthermocline western boundary Ilows. Most strikingly a ＂C＂-shape distribution of intrusions at around 26.4δ0 is revealed, covering the vicinity of the EF the TE and the Mindanao Current （MC）, i.e., tile western boundary pathway ol the norlh Pacilic subtrnpical cell （STC）. Synoptic section analysis reveals that intrusions are more prominent on the warm/sally flank ot the fronts, implying more cross-front tongues of cold/fresh water. Among the intrusions, those at the EF are of best lateral coherence which implies a unique driving mechanism involving near-inertial velocity perturbations near the equator.
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 intention of this work is to consider the stable isotopic compositions of oxygen and deuterium in rainfall, surface water and groundwater along the Yellow River in the North China Plain(NCP). This demonstrated that the δ~18O values in groundwater varied from –10.17 to –6.85‰, with mean value of –8.76‰, and that the δD ranged from –68.7 to –58.0‰, with mean value of –63.4‰, respectively. The δ~18O values in surface water varied from –8.36 to 1.32‰, with mean value of –6.8‰, and δD ranged from –64.4 to –35.1‰, with mean value of –57.6‰, respectively. Further, The range of Cl-values of groundwater varied from 5.9 to 340.5 mg/L and that values ranged from 30.1 to 81.9 mg/L in surface water samples and Na^+ value changed from 27.4 to 321 mg/L in groundwater, while that in surface water varied from 24.8 to 50.5 mg/L. Most of the points fall below the GMWL, but are close to the LMWL. Therefore the results indicated that the groundwaters along the Yellow River were influenced by rainfall in heavy events and surface water.
基金Supported by the CAS/SAFEA International Partnership Program for Creative Research TeamsNational Natural Science Foundation of China (No. 61106025)
文摘This paper proposes a low power wake-up baseband circuit used in Chinese Electronic Toll Collection (ETC) system. To reduce the static power consumption, a low power biasing strategy is proposed. The proposed circuit is fabricated in TSMC 0.18 μm technology with an area of 0.09 mm 2 . Its current consumption is only 2.1 μA under 1.8 V power supply. It achieves a sensitivity of 0.95 mV at room temperature with a variation of only ±28% over -35℃ to 105℃.
基金supported by the Chinese Academy of Sciences under (Grant Nos.KZCX2-YW-Q1-02 and KZCX2-YW-Q11-05)the Major State Basic Research Development Program of China (973 Pro-gram) (Grant No.2009CB421407)the National Natural Science Foundation of China (Grant Nos. 40631005,40775049, and 40805029)
文摘The Tropical Cyclone Genesis Potential Index （GPI） was employed to investigate possible impacts of global warming on tropical cyclone genesis over the western North Pacific （WNP）. The outputs of 20th century climate simulation by eighteen GCMs were used to evaluate the models＇ ability to reproduce tropical cyclone genesis via the GPI. The GCMs were found in general to reasonably reproduce the observed spatial distribution of genesis. Some of the models also showed ability in capturing observed temporal variation. Based on the evaluation, the models （CGCM3.1-T47 and IPSL-CM4） found to perform best when reproducing both spatial and temporal features were chosen to project future GPI. Results show that both of these models project an upward trend of the GPI under the SRES A2 scenario, however the rate of increase differs between them.
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.
基金supported by the National Natural Science Foundation of China(Grant No.51010007)China Scholarship Council(CSC)
文摘According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.
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 the National Natural Science Foundation of China(10675158)
文摘The properties of norfloxacin(NFX)and its 4?-N-acetyl derivative(ANFX)are investigated in different pH aqueous solutions and H2O-CH3CN mixed solutions,to determine the effects of pH and polarity on their ground and excited states.The triplet states of NFX and ANFX are affected more by pH than by polarity.The pH dependence of the NFX and ANFX triplet states is likely due to the different quantum yields of different protonated forms.Steady-state fluorescence,time-resolved fluorescence,and laser flash photolysis experiments at different pH values provide clear evidence of the involvement of different intramolecular charge-transfer pathways in the singlet states of NFX and ANFX.The different electron-donating capacities of 1-N,1?-N,and 4?-N under different conditions determine the major pathway.
