检索结果-南通市图书馆

Temperature variations recovered from tree-rings in the middle Qilian Mountain over the last millennium

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth {1. 2005年第4期48卷 521-529页

作者： LIU Xiaohong1.2, QIN Dahe1. SHAO Xuemei , CHEN Tuo1.& REN Jiawen1. 1. Cold and Arid Regions Environmental and Engineering Research institute, {1., Lanzhou 730000, china 2. institute of Geographical sciences and Natural Resources Research, {1., Beijing 1.01.1. china 1. Cold and Arid Regions Environmental and Engineering Research institute Chinese Academy of Sciences 730000 Lanzhou China 2. institute of Geographical {1. and Natural Resources Research Chinese Academy of Sciences 100101 Beijing China

Based on the cross-dated tree-ring samples collected from the middle Qilian Moun- tain, a standard ring-width chronology had been developed, which covered the period AD 1.00 to 2000. The correlations between the chronology and climatic records from the nearby meteorological stations indicated that temperature was the dominant climatic factor for tree growth at upper timberline, and the most important climatic factor for the tree growth in the area was the mean temperature from previous December to current April. The temperature variations recovered from the ring-width data showed a cold period during the “Little Ice Age” and the con- tinuous warming during the twentieth century. Comparison between the ring-width chronology and δ1.O records from the Dunde ice core in the Qilian Mountain indicated that there was a con- sistent trend in both time series. A significant correlation existed between our ring-width chro- nology and the Northern Hemispheric temperature, suggesting that the climate changes in the Qilian Mountain were not only driven by regional factors, but also responsive to the global cli- mate.

关键词： middle Qilian Mountain, tree-ring width chronology, temperature variations.

Effect of rock mass structure and block size on the slope stability——Physical modeling and discrete element simulation

在线全文

学校读者我要写书评

暂无评论

Science china(Technological {1.) 2005年第z1期48卷 1-17页

作者： LI Shihai1. LIAN Zhenzhong1.2 & J. G. Wang3 1. institute of Mechanics, {1., Beijing 1.0080, china 2. Graduate School, {1., Beijing 1.0060, china 3. Tropical Marine Science institute, National University of Singapore, Singapore 1.9260 chinese Acad Sci Inst Mech Beijing 100080 Peoples R China chinese Acad Sci Grad Sch Beijing 100060 Peoples R China Natl Univ Singapore Trop Marine Sci Inst Singapore 119260 Singapore

This paper studies the stability of jointed rock slopes by using our improved three-dimensional discrete element methods (DEM) and physical modeling. Results show that the DEM can simulate all failure modes of rock slopes with different joint configurations. The stress in each rock block is not homogeneous and blocks rotate in failure development. Failure modes depend on the configuration of joints. Toppling failure is observed for the slope with straight joints and sliding failure is observed for the slope with staged joints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considering the joints in rock masses, the LEM predicts much higher factor of safety than physical modeling and DEM. The failure mode and factor of safety predicted by the DEM are in good agreement with laboratory tests for any jointed rock slope.

关键词： rock masses, slope stability, DEM simulation, block size effect, joints configuration effect, limit equilibrium method.

STUDY ON THE SYNTHESIS AND PROPERTIES OF POLY(ESTER-IMIDEETHER)MULTIBLOCK COPOLYMERS

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Polymer Science 2000年第1期18卷 9-13页

作者： Zu-yao Shan Zhen-yi Li institute of {1., chinese academy of sciences, Beijing 1.0080, china chinese Acad Sci Inst Chem Beijing 100080 Peoples R China

A new class of poly(ester-imide-ether) multiblock copolymers was synthesized by transes-terification and melt copolymerization of dimethyl terephthalate (DMT) and N-(4-carbomethoxyphenyl)-4-(carbomethoxy)-phthalimide with ethylene glycol (EG) and polytetramethylene glycol (PTMG). The structure of the above copolymers was characterized by H-1.NMR and IR spectroscopy. Some properties of the coplymers were also examined. It was found that their mechanical properties and heat stability, compared with poly(ether-ester) copolymers, were obviously improved.

关键词： N-(4-carbomethoxyphenyl)-4-(carbomethoxy)-phthalimide polyester-polyether copolymer poly-(ester-imidether) multiblock copolymer imide modification

Climatic and environmental changes over the last millennium recorded in the Malan ice core from the northern Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Science china Earth {1. 2006年第10期49卷 1079-1089页

作者： WANG Ninglian1.2, YAO Tandong2,1. PU Jianchen1. ZHANG Yongliang1.& SUN Weizhen1.1. Key Laboratory of Cryosphere and Environment, Cold and Arid Regions Environmental and Engineering Research institute, {1., Lanzhou 730000, china 2. institute of Tibetan Plateau Research, {1., Beijing 1.0085, china 1. Key Laboratory of Cryosphere and Environment Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China 2. institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China

In this paper, climatic and environmental changes were reconstructed since 1.29A.D. based on the Malan ice core from Hol Xil, the northern Tibetan Plateau. The record of δ 1.O in the Malan ice core indicated that the warm-season air temperature variations displayed a general increase trend, the 20th-century warming was within the range of natural climate variability, and the warmest century was the 1.th century while the warmest decade was the 1.1.s, over the entire study period. The “Medieval Warm Epoch” and “Little Ice Age” were also reflected by the ice core record. The dust ratio in the Malan ice core is a good proxy for dust event frequency. The 870-year record of the dust ratio showed that dust events occurred much frequently in the 1.th century. Comparing the variations of δ 1.O and the dust ratio, it is found that there was a strong negative correlation between them on the time scales of 1.1.1.2 years. By analyses of all the climatic records of ice cores and tree rings from the northern Tibetan Plateau, it was revealed that dust events were more frequent in the cold and dry periods than in the warm and wet periods.

关键词： the Tibetan Plateau, the Malan ice core, climate changes, dust event frequency.

The lepton flavor violating signal of the extra gauge boson Z′in photon-photon collision at the ILC

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 1992-1997页

作者： LIU GuoLi 1.2 1.Physics Department,Zhengzhou University,Zhengzhou 450001.china 2 Kavli {1. for Theoretical Physics china,chinese academy of sciences,Beijing 1.01.0,china 1. Physics Department Zhengzhou University Zhengzhou 450001 China2. Kavli Institute for Theoretical Physics China Chinese Academy of Sciences Beijing 100190 China

The hitherto unconstrained lepton flavor mixings,induced by the new gauge boson Z ,which are the prediction of many new physics models,such as topcolor-assisted technicolor (TC2) models and flavor-universal TC2 models,may lead to the lepton flavor violating productions of τμˉ,τeˉ and μeˉ in photon-photon collision at the proposed International Linear Collider (ILC).Through a comparative analysis of these processes,we find that the better channel to probe the new physics models is the production of τμˉ or τeˉ which occurs at a much higher rate than μeˉ production due to the large mixing angle and the large flavor changing coupling,and may reach the detectable level of the ILC for a large part of the parameter *** the rates predicted by the Standard Model are far below the detectable level,these processes may serve as a sensitive probe for such new physics models.

关键词： new gauge boson Z lepton flavor violating processes photon-photon

Novel gaseous transient species:generation and characterization

在线全文

学校读者我要写书评

暂无评论

Science china {1. 2007年第2期50卷 145-169页

作者： ZENG XiaoQing1.2 & WANG DianXun1. State Key Laboratory for Structural chemistry of Unstable and Stable Species,{1. of chemistry,chinese academy of Sci-ences,Beijing 1.0080,china 2 Graduate School of chinese academy of sciences,Beijing 1.0039,china 1. State Key Laboratory for Structural chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China 2. Graduate School of chinese academy of sciences Beijing 100039 China

Due to special properties of transient species, such as short-lived, unstable, reactive, and even explosive, the generation and subsequent characterization is a great challenge for experimental chemists. In our laboratory, systematic researches have been carried out to investigate novel transient species: reactive halogen species (RHS), short-lived free radicals, and metastable pseudohalogen compounds, based on the successive technical improvements on the Hel Photoelectron spectroscopy (PES). In this review, the topic mainly focuses on innovative methods of generating novel transient species, and subsequent geometric and electronic structure characterizations of these species combined with quantum chemical calculations.

关键词： reactive halogen species radicals pseudohalogen compounds Hel Photoelectron Spectroscopy (PES) quantum chemical calculations

Application of three-dimensional discrete element face-to-face contact model with fissure water pressure to stability analysis of landslide in Panluo iron mine

在线全文

学校读者我要写书评

暂无评论

Science china(Technological {1.) 2005年第z1期48卷 146-156页

作者： ZHANG Lei1.2, WEI Zuoan1. LIU Xiaoyu1.& LI Shihai1.1.institute of Mechanics, {1., Beijing 1.0080, china 2.Graduate School, {1., Beijing 1.0060, china chinese Acad Sci Inst Mech Beijing 100080 Peoples R China chinese Acad Sci Grad Sch Beijing 100060 Peoples R China

Three-dimensional discrete element face-to-face contact model with fissure water pressure is established in this paper and the model is used to simulate three-stage process of landslide under fissure water pressure in the opencast mine, according to the actual state of landslide in Panluo iron mine where landslide happened in 1.90 and was fathered in 1.99. The calculation results show that fissure water pressure on the sliding surface is the main reason causing landslide and the local soft interlayer weakens the stability of slope. If the discrete element method adopts the same assumption as the limit equilibrium method, the results of two methods are in good agreement; while if the assumption is not adopted in the discrete element method, the critical φ numerically calculated is less than the one calculated by use of the limit equilibrium method for the sameC. Thus, from an engineering point of view, the result from the discrete element model simulation is safer and has more widely application since the discrete element model takes into account the effect of rock mass structures.

关键词： face-to-facecontactmodel, fissure water pressure, three-dimensional discrete element method,landslide.

Monte Carlo calculation method on low energy electronscattering in polybasic medium

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 1998年第2期43卷 171-174页

作者： TAN Zhenyu 1.and HE Yancai 2 1. College of Electric Power, Shandong University of Technology, Jinan 250061. china 2. Shanghai {1. of Ceramics, chinese academy of sciences, Shanghai 200050, china College of Electric Power Shandong University of Technology Jinan China Shanghai institute of Ceramics Chinese Academy of Sciences Shanghai China

A novel Monte Carlo method of simulating low energy electron (LEE) scattering in polybasic medium is presented. The Mott cross section is adopted to describe the elastic scattering of LEE, and a mean cross section idea is proposed instead of usual determination of the scattering center. The Joy’’s modified Bethe equation is used to calculate energy loss of LEE. The scattering processes of LEE in bulk PMMA have been simulated. And the electron backscattering coefficients, the electron interaction range and energy dissipation distribution of LEE in bulk PMMA have been calculated and compared with those calculated by the method of determining scattering center.

关键词： low_energy electron scattering Monte Carlo method cross_section.

Evaluation criteria for gas source rocks of marine carbonate in china

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第9期15卷 810-817页

作者： WANG Zhaoyun1.*, ZHAO Wenzhi1.and WANG Yunpeng2(1. Research institute of Petroleum Exploration & Development,Petro{1., Beijing 1.0083, {1. 2. Guangzhou institute of Geochemistry, chinese academy of sciences, Guangzhou 51.640, {1.) Research institute of Petroleum Exploration & Development PetroChina Beijing 100083 China. Guangzhou institute of Geo{1. Chinese Academy of Sciences Guangzhou 510640 China

Hydrocarbon generating and expulsion simulation experiments are carried out using samples artifically matched between the acid-dissolved residue of relatively low-maturity limestone and the original sample. This work makes up for the insufficiency of source rock samples with high abundance of organic matters and low maturity in china. The organic carbon content of the 1. prepared samples varies between 0.1.% and 0.74%. Pyrolysis data and simulation experiment results of hydrocarbon generating and expulsion, which were obtained by a high-temperature and high-pressure open system, indicate that the lower limit of organic carbon content for marine carbonate rock to generate and expel hydrocarbons is 0.23%—0.31.. In combination with the numerical analysis of organic carbon in marine carbonate rocks from Tarim Basin, Sichuan Basin, Ordos Basin and North china, as well as the contribution of these gas source rocks to the discovered gas pools, we think that the organic carbon criterion for carbonate gas source rocks should be 0.3%.

关键词： carbonate gas source rock gas-generating efficiency evaluation criteria simulation experiment.