检索结果-南通市图书馆

Chinese Science Bulletin 1999年第5期44卷 398-411页

作者： LU Guxian, CHEN Jing, LIU Ruixun and LI Xiaobo Institute of Geomechanics , beijing 100081, china Electron Microscopy Laboratory,{{2., beijing 100871, china Department of Geology,{{2., beijing 100871, china Institute of Geological Information , beijing 100037, china Institute of Geomechanics Beijing China Electron Microscopy Laboratory Peking University Beijing China Department of Geology Peking University Beijing China Institute of Gelogical Information Beijing China

The knowledge that hydrostatic pressure is equal to the gravity value of the overlying rocks in studying a dynamic state of certain underground site is argued. It is suggested that the stress field T in the crust is a combination or superposition of total hydrostatic pressure P with differential stress σ,and the total hydrostatic pressure P at any point in the crust comprises two parts: one is spherical stress tensor PG caused by the gravity, and the other is spherical stress tensor Ps caused by tectonic stress; therefore P could not be attributed to the gravity of overlying rocks only. The results obtained by a finite-element simulation indicate that the tectono-original additional hydrostatic pressures Ps decrease gradually from the compressive zone （pcS） to the shear zone (PSHs)and to the tensile zone （PTs）, i.e.Pcs>PsHs>PTs in the same depth. On the basis of the above-mentioned research, the method of measurement and calculation of metallogenetic depth corrected by Ps is

关键词： formation depth tectonic additional hydrostatic pressure Dabie UHPM zone coesite-bearing eclogite expansion-cracking texture tectonic physicochemistry.

r-matrix and algebraic-geometric symplectic map

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1999年第2期44卷 114-118页

作者： QIAO ZhijunInstitute of Mathematics and School of Mathematical Sciences, peking university, beijing 100871,{{2. Institute of Mathematics and School of Mathematical Sciences Peking University Beijing China

A new Lax matrix is introduced for the integrable symplectic map (ISM), and the non-dynamical(i. e. constant) r-matrix of ISM is obtained. Moreover, an effective approach is systematically presented to construct the explicit solution(here, the explicit solution means algebraic-geometric solution expressed by the Riemann-Theta function) of a soliton system or nonlinear evolution equation from Lax matrix, r-matrix, and the theory of nonlinearization through taking the Toda lattice as an example. The given algebraic-geometric solution of the Toda lattice is almost-periodic and includes the periodic and finite-band solution.

关键词： symplectic map r-matrix algebraic-geometric solution.

The LIL Convergence for Stationary Linear Random Field

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 1996年第4期12卷 385-397页

作者： He Shuyuan Department of Probability and Statistics peking university beijing, {{2. china Department of Probability and Statistics Peking University Beijing China

Let Y={Y_n;n∈N^2. be a stationary linear random field generated by a two- dimensional martingale difference. Where N^2.denotes the two dimensional integer lattice. The main purpose of this paper is to obtain the LIL ... 详细信息

关键词： Stationary linear random field 1/4 Martingale difference LIL convergency.

OBLIQUE DERIVATIVE PROBLEMS FOR SECOND ORDER NONLINEAR MIXED EQUATIONS WITH DEGENERATE LINE

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2008年第3期28卷 604-612页

作者：闻国椿 School of Mathematical Sciences Peking University

The present article deals with oblique derivative problems for some nonlinear mixed equations with parabolic degeneracy, which include the Tricomi problem as a special case. First, the formulation of the problems for the equations is given; next, the representation and estimates of solutions for the above problems are obtained; finally, the existence of solutions for the problems is proved by the successive iteration and the compactness principle of solutions of the problems. In this article, the author uses the complex method, namely, the complex functions in the elliptic domain and the hyperbolic complex functions in hyperbolic domain are used.

关键词： Oblique derivative problems nonlinear mixed equations parabolic degeneracy

Fluxes of NH_3 and HNO_3 over heathland in the Netherlands:implications for chemical interactions

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 1997年第1期9卷 49-58页

作者： Zhang Yuanhang Center of Environmental Sciences,peking university,{{2. 100871,china Center of Environmental Sciences Peking University Beijing 100871 China

The surface exchange of NH_3 and HNO_3 gases over heathland was measured with the aerodynamic gradient method in Leende,the Netherlands during April 2. and May 9,*** to reactions in the system NH_3,HNO_3 and NH_4NO_3,the NH_3 deposition flux is overestimated,while HNO_3 shows apparent emission fluxes mostly during the field *** reveal that NH_3 gradients are influenced slightly by HNO_3 and the HNO_3 gradients are strongly controlled by the NH_3.A clear relationship between NH_3 and HNO_3 gradient is suggested by the Leende experiment. Before the late afternoon,NH_3 deposition gradients will cause HNO_3 upward gradients,meanwhile the NH_3 gradients themselves will become *** the HNO_3 upward gradient reaches maxi- mum,the NH_3 deposition gradients will be enlarged or the emission gradients depressed,while the HNO_3 upward gradients become smaller.

关键词： dry deposition ammonia nitric acid equilibrium,fluxes.

SYNTHESIS AND PROPERTIES OF NEW MESOGEN-JACKETED LIQUID CRYSTALLINE POLYMERS

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2期18卷 139-148页

作者： Qi-ding Mi Qi-feng Zhou Department of Polymer Science & Engineering, College of Chemistry peking university, beijing 100871,{{2. peking Univ Coll Chem Dept Polymer Sci & Engn Beijing 100871 Peoples R China

Some new mesogen-jacketed liquid crystalline polymers (MJLCP) with polymer backbones, spacers, and mesogenic units of different structures were synthesized by radical polymerization. The mesomorphic behavior of these polymers was examined using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Their liquid crystallinity is influenced by the variation of polymer backbone, spacer, mesogenic unit and its terminal groups. The results show that 1) a more flexible polymer main-chain is more favorable to the formation of a liquid crystal phase, while 2. a flexible spacer will decrease the 'Jacket Effect' and the liquid crystallinity and 3) a subtle modification of the terminal groups on the mesogenic unit may also have a significant influence on properties of the polymers.

关键词： mesogen-jacketed liquid crystalline polymers polymer backbones spacers mesogenic units liquid crystallinity

Frontal genesis of moisture atmosphere during the early 2.08 persistent freezing-rain event in southern china

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2010年第3期53卷 454-464页

作者： QIAN WeiHong1 & FU JiaoLan1,2.1 Department of Atmospheric Sciences, School of Physics, peking university,{2.,{2. 2.National Meteorological Center of CMA, beijing, 100081,{2. 1. Department of Atmospheric Sciences School of Physics Peking University Beijing 100871 China2. National Meteorological Center of CMA Beijing 100081 China

From January 10 to February 2. 2.08, a severe and persistent freezing-rain event occurred in southern and southwestern{2.. Here we use an observational analysis to compare the persistent freezing-rain event in the early 2.08 with the winter precipita- tion in the late 2.07 over south of the Yangtze River (Jiangnan). The persistent freezing-rain event was directly linked to the activity of quasi-stationary front. The gradient of equivalent temperature (ET) can well indicate the frontal genesis of moist atmosphere (moisture front) and its activity as well as its relationship with precipitation belt. The precipitation types (snow and freezing rains) are related to the vertical structure of moisture front. The inversion profile of ET vertical distribution is a typical synoptic condition that caused the freezing-rain event. The horizontal gradient of ET with a criterion of 10℃ / 100 km, which reflects the accumulation and release of atmospheric energy, can be applied to predict the precipitation 5-10 days in advance.

关键词： freezing-rain event frontal genesis extended-range weather forecast winter Jiangnan

A　Diference　Scheme　with　Anti－difusion　Terms　to　Improve　the　Computation　of　Contact　Discontinuities　and　the　Study　of　Weak　Discontinuities　in　Compresible　Flow

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1996年第4期1卷 42-51页

作者： Chunguang XU (College of Mathematical Science ,peking university,{{2.) College of Mathematical Science peking university beijing 100871 USA

Ａｂｓｔｒａｃｔ：ＴｈｅｉｎｖｅｓｔｉｇａｔｉｏｎｏｆＭａｃｈｒｅｆｌｅｃｔｉｏｎｆｏｒｍｅｄａｆｔｅｒｔｈｅｉｍｐｉｎｇｅｍｅｎｔｏｆａｗｅａｋｐｌａｎｅｓｈｏｃｋｗａｖｅｏｎａｗｅｄｇｅ，ｗｉｔｈｓｈｏｃｋＭａｃ... 详细信息

Ａｂｓｔｒａｃｔ：ＴｈｅｉｎｖｅｓｔｉｇａｔｉｏｎｏｆＭａｃｈｒｅｆｌｅｃｔｉｏｎｆｏｒｍｅｄａｆｔｅｒｔｈｅｉｍｐｉｎｇｅｍｅｎｔｏｆａｗｅａｋｐｌａｎｅｓｈｏｃｋｗａｖｅｏｎａｗｅｄｇｅ，ｗｉｔｈｓｈｏｃｋＭａｃｈｎｕｍｂｅｒＭｓｎｅａｒ１，ｉｓｓｔｉｌａｎｏｐｅｎｐｒｏｂｌｅｍ［１２］．Ｉｔ＇ｓｄｉｆｉｃｕｌｔｆｏｒｓｈｏｃｋｔｕｂｅｅｘｐｅｒｉｍｅｎｔｓｗｉｔｈｉｎｔｅｒｆｅｒｏｍｅｔｅｒｔｏｄｅｔｅｃｔｃｏｎｔａｃｔｄｉｓｃｏｎ－ｔｉｎｕｉｔｉｅｓ，ｉｆｉｔｉｓｔｏｏｗｅａｋ；ａｌｓｏｄｉｆｉｃｕｌｔｔｏｃａｔｃｈｗｉｔｈｄｕｅａｃｃｕｒａｃｙｔｈｅｔｒａｎｓｉｔｉｏｎｃｏｎｄｉｔｉｏｎｂｅｔｗｅｅｎＭａｃｈｒｅｆｌｅｃｔｉｏｎａｎｄｒｅｇｕｌａｒｒｅｆｌｅｃｔｉｏｎ．Ｔｈｅｉｎｔｅｒｅｓｔｔｏｔｈｉｓｐｈｅｎｏｍｅｎｏｎｉｓｃｏｎｔｉｎ－ｕｉｎｇ，ｅｓｐｅｃｉａｌｙｆｏｒｗｅａｋｓｈｏｃｋｓ，ｂｅｃａｕｓｅｔｈｅｒｅｗａｓｓｙｓｔｅｍａｔｉｃｄｉｓｃｒｅｐａｎｃｙｂｅｔｗｅｅｎｓｉｍ－ｐｌｉｆｉｅｄｔｈｒｅｅｓｈｏｃｋｔｈｅｏｒｙｏｆｖｏｎＮｅｕｍａｎｎ［８］ａｎｄｓｈｏｃｋｔｕｂｅｒｅｓｕｌｔ

关键词： weak reflection Mach reflection anti-diffusion

Recursive equations for compound distribution with the severity distribution of the mixed type

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 Mathematics 2005年第5期48卷 594-609页

作者： YANG Jingping, CHENG Shihong & WU Qin LMAM, Department of Financial Mathematics, peking university, beijing 100871,{{2. 1. LMAM Department of Financial Mathematics Peking University 100871 Beijing China

In this paper, recursive equations are obtained for compound distribution with the number of claims belonging to (a, b)-family and the severity distribution of the mixed type. Numerical methods to solve these equation... 详细信息

关键词： recursive equation compound distribution (a b)-family severity distribution of the mixed type.

Pollution characteristics of atmospheric fine particles and their secondary components in the atmosphere of Shenzhen in summer and in winter

在线全文

学校读者我要写书评

暂无评论

Science china Chemistry 2006年第5期49卷 466-474页

作者： NIU Yuwen1,2.HE Lingyan1,2.HU Min2.ZHANG Jing2.& ZHAO Yunliang2.1. Shenzhen Graduate School of peking university,Shenzhen 518055,china 2. State Joint Key Laboratory of Environmental Simulation and Pollution Control,College of Environmental Sciences,{2. university,beijing 100871,china 1. Shenzhen Graduate School of peking university Shenzhen 518055 China 2. State Joint Key Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences Peking University Beijing 100871 China

Two field measurements for atmospheric fine particles were conducted in Baoan district of Shenzhen during the summer and winter in 2.04. Totally 30 sets of 2. h samples were collected, and then the mass concentrations and chemical compositions were determined. The seasonal varia- tions and secondary pollution characteristics of fine particles during the sampling periods were dis-cussed with meteorological factors. The results show that seasonal variations of atmospheric particles are significant in Shenzhen. The average mass concentrations of PM2.5 and PM10 in summer were 35 μg·m-3 and 57 μg·m-3, respectively, and those in winter were 99 μg·m-3 and 135 μg·m-3, respec-tively. The concentrations of both PM2.5 and PM10 in winter increased 184% and 137%, respectively, compared to those in summer. PM2.5 accounted for 61% and 75% of PM10 in summer and in winter, respectively, indicating severe fine particle pollution in Shenzhen. During the summer and winter sampling periods, the mean OC/EC ratios were 3.4 and 1.6, respectively. The estimated secondary organic carbon (SOC) averagely accounted for 56% and 6% of the total OC in summer and in winter, respectively, which implies a major contribution of SOC to OC in summer. During the continuous high temperature period in summer, both the concentrations and fractions of secondary aerosol compo-nents in PM2.5 were highly elevated, suggesting severe secondary pollution again. The prevailing wind was from South china Sea in summer, and the air quality was good. The prevailing wind in winter was from china's Mainland to the north, and the polluted air mass led to poor air quality.

关键词： PM2.5, mass concentration, secondary pollution, seasonal variation, Shenzhen.