检索结果-南通市图书馆

Trend,seasonal and diurnal variations of atmospheric CO_2 in beijing

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2002年第24期47卷 2050-2055页

作者： WANG Yuesi, WANG Changke, GUO Xueqing, LIU Guangren & HUANG YaoLAPC, Institute of atmospheric physics, Chinese Academy of Sciences, beijing 100083, China department of Chemistry, Capital Normal{4., beijing 100037, China LAPC Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China department of Chemistry Capital Normal University Beijing China

The concentration of atmospheric CO2 in beijing increased rapidly at a mean growth rate of 3.7%·a-1 from 1993 to 1995. After displaying a peak of (4.9.7±25.9) μmol·mol-1 in 1995, it decreased slowly. Both the almost stable anthropogenic CO2 source and increasing biotic CO2 sink contribute to the drop of CO2 concentration from 1995 to 2000. The seasonal variation of CO2 concentration exhibits a clear cycle with a maximum in winter, averaging (4.6.8± 20.6)μmol·mol-1, and a minimum in summer, averaging (369.1±6.1)μmol·mol-1. The seasonal variation of CO2 concentration is mainly controlled by phenology. The mean diurnal variation of atmospheric CO2 concentration for a year in beijing is highly clear: daily maximum CO2 concentration usually occurs at night, but daily minimum CO2 concentration does in the daytime, with a mean diurnal difference more than 34.7μmol·mol-1. It has been revealed that the interannual variations of atmospheric CO2 concentration in winter and autumn regulated the

关键词： atmospheric CO2 annual variation seasonal variation diurnal variation urban environment.

The refined theory of deep rectangular beams based on general solutions of elasticity

在线全文

学校读者我要写书评

暂无评论

Science China(physics,Mechanics & Astronomy) 2006年第3期49卷 291-303页

作者： GAO Yang1 & WANG Minzhong2 1. College of Science, China Agricultural university, beijing 100083, China 2. State Key Laboratory for Turbulence and Complex Systems and department of Mechanics and Engi- neering Science, peking university,{4., China College of Science China Agricultural University Beijing 100083 China State Key Laboratory for Turbulence Complex Systems department of Mechanics Engineering Science Peking University Beijing 100871 China

The problem of deducing one-dimensional theory from two-dimensional the- ory for a homogeneous isotropic beam is investigated. Based on elasticity theory, the re- fined theory of rectangular beams is derived by using Papkovich-Neuber solution and Lur’e method without ad hoc assumptions. It is shown that the displacements and stresses of the beam can be represented by the angle of rotation and the deflection of the neutral surface. Based on the refined beam theory, the exact equations for the beam without transverse surface loadings are derived and consist of two governing differential equations: the fourth-order equation and the transcendental equation. The approximate equations for the beam under transverse loadings are derived directly from the refined beam theory and are almost the same as the governing equations of Timoshenko beam theory. In two ex- amples, it is shown that the new theory provides better results than Levinson’s beam the- ory when compared with those obtained from the linear theory of elasticity.

关键词： deep rectangular beams,the refined theory,Papkovich-Neuber solution,Lur'e method,governing equation

Current Flows in Pulsar Magnetospheres

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2006年第2期6卷 217-226页

作者： Ren-Xin Xu Xiao-Hong Cui Guo-Jun Qiao department of Astronomy School of Physics Peking University Beijing 100871

The global structure of current flows in pulsar magnetosphere is investigated, with rough calculations of the circuit elements. It is emphasized that the potential of the critical field lines （the field lines that intersect the null surface at the light cylinder radius） should be the same as that of interstellar medium, and that pulsars whose rotation axes and magnetic dipole axes are parallel should be positively charged, in order to close the pulsar＇s current flows. The statistical relation between the radio luminosity and pulsar＇s electric charge （or the spindown power） may hint that the millisecond pulsars could be low-mass bare strange stars.

关键词： pulsars: general - stars: neutron - dense matter

在线全文

学校读者我要写书评

暂无评论

质谱仪中带电粒子运动的双波描述

物理学报 1996年第5期45卷 729-735页

作者：黄湘友北京大学物理系北京100871

一个已知能量的带电粒子在质谱仪中于何时何地进入和离开磁场,如何用量子力学来计算是个很有意思的问题。这一体系的双波描述给出类似于经典力学的结果,但粒子能量取量子化分立值。

关键词：质谱仪带电粒子运动双波

A Method of Calculating Ice Water Content Using Data of Two Dimensional Cloud Particle Images from PMS

在线全文

学校读者我要写书评

暂无评论

A Method of Calculating Ice Water Content Using Data of Two ...

中国气象学会2004.年会

作者： Shen Ning~1 Xin Huolin~2 Zhao Chunsheng~1 Zhao Zengliang~1 (1 department of atmospheric Science, School of physics, peking university,{4., China 2 department of physics, School of physics, peking university,{4., China)

＜正＞An inverse calculation of ice water content （IWC） of clouds from PMS two dimensional cloud images is described in this paper. This study provides an algorithm to refine the observed aspect ratios of different shape categories. Expectation of 2-D cloud particles’ pro ected area and that of the IWC are calculated with respect to various particle shapes and different size distributions. It is shown that the formula of inverse calculation from assembly average of 2-D cloud images to the mean IWC of cloud particles is obtainable;and the aspect ratios of different shape categories could be *** of spherical approximation are also studied quantitatively.

关键词： IWC PMS cloud particle projected area

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

两维方格形复合介质中导电性的渗流临界指数

物理学报 1995年第3期44卷 451-459页

作者：包科达尹光俊北京大学物理系北京100871

在方格形、圆形和四边星形复合介质导电性的严格数值解基础上,分析和研究了这三种几何形态在渗流阈值附近的导电特性,并求得了它们的导电临界指数,分别为0.356,0.675和0.209.它们不仅在数值上较之分立网络系统的导电临界指数有相当大的... 详细信息

在方格形、圆形和四边星形复合介质导电性的严格数值解基础上,分析和研究了这三种几何形态在渗流阈值附近的导电特性,并求得了它们的导电临界指数,分别为0.356,0.675和0.209.它们不仅在数值上较之分立网络系统的导电临界指数有相当大的差别,而且没有普适性.建议用文中的(3)和(12)式概括两元性和非两元性复合材料的有效电导率.引进了作为复合介质微结构函数的幂指数m,并证明临界指数等于临界幂指数的倒数,它的数值完全由复合介质的几何形态所决定.

关键词：方格形复合介质导电性渗流临界指数二维

Interannual variability of Antarctic Oscillation and its influence on East Asian climate during boreal winter and spring

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 554-560页

作者： FAN Ke1,2,3 & WANG Huijun2 1. Nansen-Zhu International Research Center, Institute of atmospheric physics, Chinese Academy of Sciences, beijing 100029, China 2. department of atmospheric Science, Yunnan university, Kunming 650091, China 3. Graduate university of the Chinese Academy of Sciences, beijing 10004., China 1. Nansen-Zhu International Research Center Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China 2. department of atmospheric Science Yunnan University Kunming 650091 China 3. Graduate university of the Chinese Academy of Sciences Beijing 100049 China

The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean me- ridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.

关键词： Antarctic Oscillation, Eurasian west wind, meridional teleconnection, mean meridional circulation.

Debating about the climate warming

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第1期16卷 1-6页

作者： WANG Shaowu1, LUO Yong2, ZHAO Zongci2, DONG Wenje2 and YANG Bao3 (1.department of atmospheric Sciences, School of physics, peking university,{4., China 2. Laboratory for Climate Studies, China Meteorological Administration, beijing 100081, China 3. Institute of Cold and Arid Regions Environmental and Engineering, Chinese Academy of Sciences, Lanzhou 730000, China) [a] department of atmospheric Sciences School of Physics Peking University Beijing China [b] Laboratory for Climate Studies China Meterological Administration Beijing China [c] Institute of Cold and Arid Regions Environmental and Engineering Chinese Academy of Sciences Lanzhou China

Debating about the climate warming is reviewed. Discussions have focused on the validity of the temperature reconstruction for the last millennium made by Mann et al. Arguments against and for the reconstruction are introduced. Temperature reconstructions by other authors are examined, including the one carried out by Wang et al. in 1996. It is concluded that: (1) Ability of reproducing temperature variability of time scale less than 10 a is limited, so no sufficient evidence proves that the 1990s was the warmest decade, and 1998 was the warmest year over the last millennium. (2) All of the temperature reconstructions by different authors demonstrate the occurrence of the MWP (Medieval Warm Period) and LIA (Little Ice Age) in low frequency band of temperature variations, though the peak in the MWP and trough in LIA varies from one reconstruction to the others. Therefore, terms of MWP and LIA can be used in studies of climate change. (3) The warming from 1975 to 2000 was significant, but we do not know if it was the strongest for the last millennium, which needs to be proved by more evidence.

关键词： climate warming MWP LIA the 20th century.

A Parameterization of Bowen Ratio with Respect to Soil Moisture Availability

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Advances in atmospheric Sciences 1995年第4期12卷 449-474页

作者： Ye Zhuojia and Roger A. Pielke (Institute of atmospheric physics, Chinese Academy of Sciences, beijing 100029, China)(Colorado State university,{4. of atmospheric Science, Fort Collins, Colorado 80523, USA) Institute of atmospheric physics ChineseAcademyof Scienced Colorado Stateuniversity Department of Atmospheric Science

The Bowen ratio (B) is impacted by 5 environmental elements: soil moisture availabillity, m, the ratio of resistances between atmosphere and soil pores, atmospheric relative humidity, h,atmospheric stability, △T, and enviD ronment temperature. These impacts have been investigated over diverse surfaces, including bare soil, free water surface, and vegetation covered land, using an analytical approach. It was concluded that: (a) B is not a continuous function. The singularity exists at the condition αhcb = h, occurring preferably in the following conditions f weak turbulence, stable stratified stability, dry soil, and humid air, where hcb, defined by Eq.(11) is a critical variable. The existence of a singularity makes the dependence of B on the five variables very complicated. The value of B approaches being inversely proportional to m under the conditions m≥mfc (the soil capacity) and / *** proportional coefficient changes with season and latitude with relatively high values in winter and over the poles; (b) B is nearly independent of during the day. The impact of m on B is much larger as compared to that of on B; (c) when h increases, the absolute value of B also increases; (d) over bare soil,when the absolute surface net radiation increases, the absolute value of B will increase. The impact of RN on B is larger at night than during the day, and (e) over plant canopy, the singularity and the dependdes of B on m,rα, and h are modified as compared to that over bare *** (i) during the daytime unstable condition, m exerts an even stronger impact on B; at night, however,B changes are weak in response to the change in m; (ii) the value of B is much more sensitive in response to the changes of turbulent intensity; (iii) the B response to the variation of h over a vegetation covered area is weaker; and (iv) the singularity exists at the condition hcp=h instead of αhcb=h as over bare soil, where hcp is defined by Eq.(4.). The formulas derived over bare soil also hol

关键词： Bowen ratio parameterization Soil moisture availability Plant canopy