检索结果-南通市图书馆

The effect of discharge conditions of ICP etching reactor on plasma parameters

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第6期25卷 769-776页

作者： Yijia Lu Yaosong Chen Yiran An LTCS, college of Engineering, peking university,100871 beijing, china LTCS College of Engineering Peking University Beijing China

This study investigated the inductively coupled plasma etching reactor and RF coils developed by North Microelectronic Corporation. Full three dimensional simulations were made at different discharge conditions. The simulations examined and compared the distribution and non-uniformity of several plasma parameters at a fixed position upon the wafer at different pressures and coil currents. These parameters included electron density, electron temperature and power deposition. The results demonstrate that the electron density, power deposition and uniformity increase with either higher pressure or stronger coil currents, while the electron temperature decreases at this condition. Coil number increase can reduce the non-uniformity of parameters in the spatial distribution. The linear relationship between power deposition and electron density does not always exist. The comparison between simulation results and experiment results is also presented in the paper.

关键词： Inductively coupled plasma. Electron densityElectron temperature ~ Power deposition - RF coils

Totally geodesic submanifolds of maximal rank in symmetric spaces

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2004年第2期47卷 264-271页

作者： ZHU Fuhai & LIANG KeSchool of Mathematical sciences and LMAM, peking university, beijing 100871, china college of Mathematical sciences and LPMC, Nankai university, Tianjin 300071, china School of Mathematical sciences and LMAM Peking University Beijing China college of Mathematical sciences and LPMC Nankai University Tianjin China

We gave a complete list of totally geodesic submanifolds of maximal rank in symmetric spaces of noncompact type. The compact cases can be obtained by the duality.

关键词： totally geodesic submanifold, Lie triple system, maximal rank.

LDFF,the large molecular weight DNA fragmentation factor,is responsible for the large molecular weight DNA degradation during apoptosis in Xenopus egg extracts

在线全文

学校读者我要写书评

暂无评论

Cell Research 2004年第2期14卷 134-140页

作者： Zhi Gang LU, Chuan Mao ZHANG~*, Zhong He ZHAI~* Department of Cell Biology and Genetics, college of life sciences, peking university, beijing 100871, china. Department of Cell Biology and Genetics College of Life Sciences Peking University Beijing China

DNA degradation is a biochemical hallmark in apoptosis. It has been demonstrated in many cell types that there are two stages of DNA fragmentation during the apoptotic execution. In the early stage, chromatin DNA is cut into large molecular weight DNA fragments, although the responsible nuclease(s) has not been recognized. In the late stage, the chromatin DNA is cleaved further into short oligonucleosomal fragments by a well-characterized nuclease in apoptosis, the caspase-activated DNase (CAD/DFF40). In this study, we demonstrate that large molecular weight DNA fragmentation also occurs in Xenopus egg extracts in apoptosis. We show that the large molecular weight DNA fragmentation factor (LDFF) is not the Xenopus CAD homolog XCAD. LDFF is activated by caspase-3. The large molecular weight DNA fragmentation activity of LDFF is Mg2+-dependent and Ca2+-independent, can occur in both acidic and neutral pH conditions and can tolerate 45℃ treatment. These results indicate that LDFF in Xenopus egg extr

关键词： apoptosis caspase-activated DNase (CAD) large molecular weight DNA fragmentation factor (LDFF).

china's energy, environment and policy perspective

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2000年第3期12卷 270-274页

作者： ZHANG Shi\|qiu (Center for Environmental sciences, peking university, beijing 100871, china) Center for Environmental sciences Peking University Beijing 100871 China

This paper discusses the specific features of the energy in china, and addresses those key challenges in china is that the co\|exist of (1) higher total energy production and lower per capita level; (2) lower per capita energy resources level with unrational energy consumption structure; (3) lower energy utilization efficiency and higher energy conservation potential; and (4) unequal distribution of energy resources. It reviews the key environmental problems related to the feature of energy production and consumption. Based on the analysis, the author furthers addresses the policy and actions needed.

关键词： energy energy production energy consumption environment policy

A quantitative program for Hadwiger's covering conjecture

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第9期53卷 2551-2560页

作者： ZONG Chuanming School of Mathematical sciences,peking university,beijing 100871,china School of Mathematical sciences Peking University Beijing China

In 1957,Hadwiger made a conjecture that every n-dimensional convex body can be covered by 2n translates of its *** to now,this conjecture is still open for all n *** 1933,Borsuk made a conjecture that every n-dimensional bounded set can be divided into n + 1 subsets of smaller *** to now,this conjecture is open for 4 n *** this article we encode the two conjectures into continuous functions defined on the spaces of convex bodies,propose a four-step program to attack them,and obtain some partial results.

关键词： convex body Hadwiger’s conjecture Banach-Mazur metric β-net Borsuk’s conjecture

The regular representation and regular covariant representation of crossed products of Woronowicz C^(*)-algebras

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第9期48卷 1245-1259页

作者： ZHANG Xiaoxia~(1,2) & GUO Maozheng~(1,3) 1. School of Mathematical sciences,peking university,beijing 100871,china 2. Department of Mathematics,Yantai university,Yantai 264005,china 3. LMAM,peking university,beijing 100871,china School of Mathematical sciences Peking University Beijing China Department of Mathematics Yantai University Yantai China LMAM Peking University Beijing China

In this paper,it is shown that the regular representation and regular covariant representation of the crossed products A×α G correspond to the twisted multiplicative unitary operators,where A is a Woronowicz C~*-algebra acted upon by a discrete group ***,it is also shown that the regular covariant C~*-algebra is the Woronowicz C~*-algebra which corresponds to a multiplicative ***,an explicit description of the multiplicative unitary operator for C(SU_q(2) )×α (?) is given in terms of those of the Woronowicz C~*-algebra C(SU_q(2) ) and the discrete group G.

关键词： multiplicative unitary operator, Woronowicz C*-algebra, crossed product.

Mixed uncertainty analysis of polycyclic aromatic hydrocarbon inhalation and risk assessment in ambient air of beijing

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2008年第4期20卷 505-512页

作者： college of Environmental sciences and Engineering, peking university, beijing 100871, china GUO Huaicheng LIU Yong HUANG Kai WANG Zhen ZHAN Xinye 不详 School of Natural Resources and Environment University of Michigan Ann Arbor 48109 USA Department of Civil and Resource Engineering Dalhousie University Halifax NS B3JIZ1 Canada

This article presents the application of an integrated method that estimates the dispersion of polycyclic aromatic hydrocarbons （PAHs） in air, and assesses the human health risk associated with PAHs inhalation. An uncertainty analysis method consisting of three components were applied in this study, where the three components include a bootstrapping method for analyzing the whole process associated uncertainty, an inhalation rate （IR） representation for evaluating the total PAH inhalation risk for human health, and a normally distributed absorption fraction （AF） ranging from 0% to 100% to represent the absorption capability of PAHs in human body. Using this method, an integrated process was employed to assess the health risk of the residents in beijing, china, from inhaling PAHs in the air. The results indicate that the ambient air PAHs in beijing is an important contributor to human health impairment, although over 68% of residents seem to be safe from daily PAH carcinogenic inhalation. In general, the accumulated daily inhalation amount is relatively higher for male and children at 10 years old of age than for female and children at 6 years old. In 1997, about 1.73% cancer sufferers in beijing were more or less related to ambient air PAHs inhalation. At 95% confidence interval, approximately 272-309 individual cancer incidences can be attributed to PAHs pollution in the air. The probability of greater than 500 cancer occurrence is 15.3%. While the inhalation of ambient air PAHs was shown to be an important factor responsible for higher cancer occurrence in beijing, while the contribution might not be the most significant one.

关键词： polycyclic aromatic hydrocarbons (PAHs) uncertainty analysis human health risk

A brief account on the study of the insulin crystal structure In retrospect:Forty years after the determination of insulin’s crystal structure by Chinese scientists

在线全文

学校读者我要写书评

暂无评论

Science china(life sciences) 2010年第1期53卷 13-15页

作者： WANG Da-Cheng1 & GU XiaoCheng2 1 National Laboratory of Macromolecules,Institute of Biophysics,Chinese Academy of sciences,beijing 100101,china 2 college of life sciences,peking university,beijing 100871,china National Laboratory of Macromolecules Institute of Biophysics Chinese Academy of Sciences Beijing China college of life sciences Peking University Beijing China

"Standards there as high as achieved elsewhere";news delivered to the world by Science in china Approximately forty years ago when china was undergoing a period of great difficulty, Science in china,

关键词： A brief account on the study of the insulin crystal structure In retrospect

Research progress in gecko locomotion and biomimetic gecko-robots

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第1期17卷 1-5页

作者： DAI Zhendong and SUN Jiurong ( Institute of Bio-inspired Structure and Surface Engineering, Nanjing university of Aeronautics and Astronautics, Nanjing 210016, china college of life sciences, peking university, beijing 100871, china) Institute of Bio-inspired Structure and Surface Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China college of life sciences Peking University Beijing 100871 China

Geckos are known for their excellent ability to climb walls and run on ceilings. Previous studies of the gecko's locomotive and adhesive mechanisms, its neuro-sensory and neuro-modulatory systems, its fabrication of artificial setae array, and other related developments, have inspired further research on gecko-based and gecko-like robots. Key research findings in this area are reviewed in the present paper.

关键词： gecko locomotion biomimetic modulation gecko-like robot.