检索结果-南通市图书馆

Synthesize TiO_2 microspheres self-assembled from nanorods via hydrothermal treatment

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2007年第2期50卷 175-178页

作者： ZHANG YiBing1,2,FENG XinJian3 & JIANG Lei2,3 1 Shangrao Teachers’ College,Shangrao 334001,China 2 national center for Nanoscience and Nanotechnology,Beijing 100080,China 3 Institute of Chemistry,Chinese Academy of Sciences,Beijing 100080,China Shangrao Teachers’ College Shangrao China national center for Nanoscience and Nanotechnology Beijing China Institute of Chemistry Chinese Academy of Sciences Beijing China

The TiO2 microspheres were deposited on the glass substrates under certain conditions via hydro-thermal reaction using 0.15 mol·L?1 TiCl3 saturated NaCl aqueous solution adding urea as an additive. The TiO2 is characterized rutile by results of SEM,TEM and XRD techniques,the TiO2 microspheres are large scale assembled from TiO2 nanorods. The affections on the products by the factors of the con-tents of urea being an additive(the key techniques) ,the reaction temperature,the reaction time and the concentration of TiCl3 were studied. The optimum condition was found,and the mechanism of reac-tions was discussed also.

关键词： TiO2 self-assembly nanorods microsphere hydrothermal reaction

Seasonal water storage change of the Yangtze River basin detected by GRACE

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2006年第5期49卷 483-491页

作者： HU Xiaogong1, CHEN Jianli1,2, ZHOU Yonghong1, HUANG Cheng1 & LIAO Xinhao1 1. center for Astro-geodynamics Research, Shanghai Astronomical Observatory, national Astronomical Observatories, Shanghai 200030, China 2. center for Space Research, University of Texas at Austin, 3925 W. Braker Lane, Suite 200, Austin, TX78750, USA center for Astro-geodynamics Research Shanghai Astronomical Observatory National Astronomical Observatories Shanghai China center for Space Research University of Texas at Austin Austin USA

US-Germany co-sponsered satellite gravimetry mission GRACE (Gravity Recovery And Climate Experiment), launched in March 2002, has been producing monthly time series of Earth gravity models up to degree and order of 120. The GRACE mission consists of two identical satellites flying on an almost polar orbit with an altitude of about 300-500 km and satelite-to-satellite ranging of about 220 km. Thanks to the payloads of space-borne GPS receivers, accelerometers and high-precision K-band satelite-to-satellite ranging mesurements, GRACE gravity models are expected to achieve more than one order of magnitude of improvement over previous models at spatial scales of a few hundred kilometers or larger. Recovery of surface mass re-distribution based on GRACE’s time-varying gravity models is applied to studies in solid Earth geophysics, oceanography, climatology and geodesy. At secular time scales, GRACE is expected to provide valuable information on global ice changes, whose variations have profound influences on global climate, and in particular, on sea level changes. At seasonal time scales, GRACE is expected to reveal surface water changes with an ac- curacy of less than 1 cm, or ocean bottom pressure changes with an accuracy of less than 1 mbar (1 mbar =102 Pa). These surface mass redistribution measurements would impove our understanding of the global and regional mass and energy cycles that are critical to human life. Using 15 GRACE monthly gravity models covering the period from April 2002 to December 2003, this study compares seasonal water storage changes recovered from GRACE data and hydrology models at global and regional scales, with particular focus on the Yangtze River basin of China. Annual amplitude of 3.4 cm of equivalent water height change is found for the Yangtze River basin with maximum in Spring and Autumn, agreeing with two state-of-the-art hydrology models. The differences between GRACE re- sults and model predictions are less than 1-2 cm. We conclude

关键词： GRACE, earth gravity, water storage, Yangtze River basin.

A user-space file system for on-demand legacy desktop software

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2011年第6期54卷 1142-1150页

作者： ZHANG YouHui 1,2 , SU GeLin 1,2 & ZHENG WeiMin 1,2 1 Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China 2 Tsinghua national Laboratory for Information Science and Technology, Tsinghua University, Beijing 100084, China Department of Computer Science and Technology Tsinghua University Tsinghua national Laboratory for Information Science and Technology Tsinghua University

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system accesses into remote visits. Quite a few optimizations are adopted and adjusted to suit the file-access-pattern of on-demand software, including the local cache, metadata/data/software prefetch and content-addressable storage (CAS), to decrease the number of remote visits and/or to overlap IO (input/output) operations with software execution. Detailed access-pattern analyses are also presented. This file system has been implemented and tests show that it is practical for much daily-used software-a local cache of limited size can provide up to 80% hit ratio and the corresponding overhead of running-time is about 37%. Owing to this method, on any compatible and networked computer, a user can use his/her personalized software conveniently although it does not exist on the local host.

关键词： on-demand software software as a service user-space file system cloud storage

The Unsymmetrical Delay Compensation in WDM time Transmission Using Optical Fiber

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

The Unsymmetrical Delay Compensation in WDM Time Transmissio...

Dynamics of morphological changes for mitochondrial fission and fusion

第三届中国卫星导航学术年会

作者： Li Xiaofeng 1,2,3 ,Liang Shuangyou 1,2 ,Chen Faxi 1,2 ,Zhao Kan 1,2 ,Zhang Shougang 1,2 1.national time service center,Chinese Academy of Sciences.Xi’an,Shaanxi,710600, China 2 Key Laboratory of time and Frequency Primary Standards,national time service center, Chinese Academy of Sciences.Xi’an,Shaanxi,710600,China 3 Graduate University of Chinese Academy of Sciences.Beijing,100049,China

The transmission of optical wave in fiber is analyzed,and the asymmetry of transmission delay which results from phenomena of chromatic dispersion is computed under the condition of DWDM（density WDM）and SWDM（sparse WDM）.Then we proposed a scheme of DWDM transmission delay compensation in time transmission using optical *** theoretical calculation shows that when calculated on 50km transmission range,the time difference when using two waves of wavelength difference of 1nm is nearly three orders of magnitude less than when using two waves of wavelength of 1550nm and 1310nm.

关键词： time transmission optical fiber time delay compensation WDM

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第4期53卷 680-689页

作者： WANG ShiQi 1,2,4 , FU ChangLiang 1,2 , ZHANG Yan 1,2 , CHEN Quan 3 & LONG Mian 1,2 1 Key Laboratory of Microgravity (national Microgravity Laboratory), Beijing 100190, China 2 center for Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China 3 State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China 4 Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China Key Laboratory of Microgravity (national Microgravity Laboratory) Beijing China Chinese Academy of Sciences Center for Biomechanics and Bioengineering Institute of Mechanics Beijing China (GRID:grid.9227.e) (ISNI:***) Chinese Academy of Sciences Institute of Vertebrate Paleontology and Paleoanthropology Beijing China (GRID:grid.9227.e) (ISNI:***) Key Laboratory of Microgravity (national Microgravity Laboratory) Beijing China (GRID:grid.9227.e) Chinese Academy of Sciences Center for Biomechanics and Bioengineering Institute of Mechanics Beijing China (GRID:grid.9227.e) (ISNI:***) Chinese Academy of Sciences State Key Laboratory of Biomembrane and Membrane Biotechnology Institute of Zoology Beijing China (GRID:grid.9227.e) (ISNI:***)

Mitochondria experience continuous fusion and fission in a living cell, but their dynamics remains poorly quantified. Here a theoretical model was developed, upon a simplified population balance equation (PBE), to predict the morphological changes induced by mitochondrial fission and fusion. Assuming that both fission and fusion events are statistically independent, the survival probability of mitochondria staying in the fission or fusion state was formulated as an exponentially-decayed function with time, which depended on the time-dependent distribution of the mitochondrial volume and the fission and fusion rates. Parametric analysis was done for two typical volume distributions. One was Gamma distribution and the other was Gaussian distribution, derived from the measurements of volume distribution for individual mitochondria in a living cell and purified mitochondria in vitro. The predictions indicated that the survival probability strongly depended on morphological changes of individual mitochondria and was inversely correlated to the fission and fusion rates. This work provided a new insight into quantifying the mitochondrial dynamics via monitoring the evolution of the mitochondrial volume.

关键词： mitochondria morphology fission fusion dynamics modeling

Reconstruction of precipitation variation from tree rings in recent 1000 years in Delingha, Qinghai

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2005年第7期48卷 939-949页

作者： SHAO Xuemei1, HUANG Lei1, LIU Hongbin2, LIANG Eryuan1, FANG Xiuqi3 & WANG Lili1 1. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China 2. national Climate center, Beijing 100081, China 3. Beijing Normal University, Beijing 100875, China Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing 100101 China national Climate center Beijing 100081 China Beijing Normal University Beijing 100875 China

Using seven well-replicated Qilian juniper (Sabina przewalskii Kom.) ring-width chronologies developed at Zongwulong and Shalike Mts. in the northeastern part of the Qaidam Basin annual precipitation from previous July to current June in the recent 1000 years was re- constructed for Delingha. The reconstruction can capture 63.1% of precipitation variance and the equation was stable over time. For the reconstructed precipitation, wet periods occurred in AD1520—1633 and 1933—2001, whereas dry intervals in 1429—1519 and 1634—1741. In ad- dition, the magnitude in precipitation variation was lower before 1430 with about 15 mm, but it increased to 30 mm during the period of 1430 to 1850. After 1850, the precipitation variance de- creased again. In contrast to the increase in temperature, a decrease in annual precipitation was evident since the 1990s. The agreement in low-frequency variation between the reconstruction and the glacier accumulation and particulate content in Dunde ice cores during the recent several hundred years suggested that the precipitation reconstructed in this study was rather reliable, and represented a regional signal. This 1000-year reconstruction could benefit our understanding of climatic variation in decadal to century-scale in this region, and provide basic data to climate models and to prediction of future climate in the 21st century.

关键词： northeastern part of the Qaidam Basin tree-ring width series of Qilian juniper precipitation reconstruction in 1000 years.

Comparison of degradation reactions of Acid Yellow 61 in both oxidation processes of H_2O_2/UV and O_3

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2001年第3期13卷 304-310页

作者： WANG Yi zhong 1, A.Yedeler 2, A. Kettrup 2(1 Research center for Eco Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 2 GSF Institute of Ecological Chemistry, Neuherberg, Postfach 1129, 85758 Neuherberg, Germany) Research center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China

The comparison of degradation of Acid Yellow 61 as a model dye compound in both oxidation processes of H 2O 2/UV and O 3 has been studied. When the decolorization rate of Acid Yellow 61 in both reactions presented similar, it was found there are some differences from the results of AOX removal and production of inorganic ions and organic acids. The results reveal that the H 2O 2/UV has beneficial effect on mineralization than O 3 only for degradation of Acid Yellow 61 solution and it is possible for enhancement of method efficiency by taking longer reaction time and addition of high concentration of oxidants.

关键词： oxidation process H 2O 2/UV O 3 dye compound

Research on the Monitoring System of CNC Grinding Process Based on Acoustic Emission

在线全文

学校读者我要写书评

暂无评论

武汉理工大学学报 2006年第S1期28卷 310-313页

作者： HU Zhongxiang1,TENG Jiaxu1,YANG Junwei1,HUO Xiaojing2,SHI Xiaojun1 (1.national Key Laboratory for Remanufacturing,Beijing 100072,China 2.M&E Engineering College of Hebei Agricultural University,Baoding 071001,China) national Key Laboratory for Remanufacturing Beijing 100072China M&EEngineering College of Hebei Agricultural University Baoding 071001China

Using on-line monitoring during the CNC grinding process,the hazard case such as the crushing of grinding wheel and various safety accidents could be avoided,and the optimum time for dressing and replacing grinding wheel could also be determined,and hence,the service life of the grinding wheel could be prolonged and grinding quality could be improved. To overcome the limitation of some traditional techniques in which some parameters including the grinding power and force,torque and so on were monitored,the acoustic emission (AE) technique,which provides high sensitivity and responding speed,were developed in the present paper. The mechanism of AE during grinding was reviewed. Moreover,a virtual AE monitoring system,which could monitor the grinding state under different working conditions during the grinding,has been developed based on the Virtual Instruments technique. Some experiments were also performed on the internal grinder. The results showed that the AE signals became stronger with increasing the main shaft speed and grinding depth or decreasing the distance between the AE sensor and grinding area.

关键词： on-line monitoring virtual instruments CNC grinding acoustic emission

AN EMBEDDED BOUNDARY METHOD FOR ELLIPTIC AND PARABOLIC PROBLEMS WITH INTERFACES AND APPLICATION TO MULTI-MATERIAL SYSTEMS WITH PHASE TRANSITIONS

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2010年第2期30卷 499-521页

作者： Shuqiang Wang Roman Samulyak Tongfei Guo Department of Applied Mathematics and Statistics Stony Brook University Stony Brook NY 11794 USA Computational Science center Brookhaven National Laboratory Upton NY 11973 USA

The embedded boundary method for solving elliptic and parabolic problems in geometrically complex domains using Cartesian meshes by Johansen and Colella （1998, J. Comput. Phys. 147, 60） has been extended for elliptic and parabolic problems with interior boundaries or interfaces of discontinuities of material properties or solutions. Second order accuracy is achieved in space and time for both stationary and moving interface problems. The method is conservative for elliptic and parabolic problems with fixed interfaces. Based on this method, a front tracking algorithm for the Stefan problem has been developed. The accuracy of the method is measured through comparison with exact solution to a two-dimensional Stefan problem. The algorithm has been used for the study of melting and solidification problems.

关键词： embedded boundary method elliptic interface problem front tracking Ste-fan problem