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Affinities and functional morphology of the Middle Cambrian ornamented tubules from West Hunan,china

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Progress in Natural Science:Materials International 2004年第10期14卷 67-71页

作者： ZHU Caifa 1,2. and DONG Xiping 1 (1.school of Earth and Space Sciences,peking University,{2.100871,china 2.University of Petroleum,{2.102.49,china) peking Univ Sch Earth & Space Sci Beijing 100871 Peoples R China Univ Petr Beijing 102249 Peoples R China

Problematic phosphatic tubular microfossils with ornamented sculptures are documented to exist in limestones of the up-per Middle Cambrian Huaqiao Formation at the Paibi section and the Wangcun section in West Hunan,*** morphological pat-terns,including Ornamented Tube Form I and Ornamented Tube Form II are *** on the analysis of the preservation,wall structure and composition of the fossils,it is deduced that these ornamented tubes may represent carapace spines of some Cambrian arthro-pods with phosphatic carapaces,such as bradoriid *** of functional morphology indicates that the sclerites may rather be considered of a defensive than grasping function on the original organism body.

关键词： Middle Cambrian ornamented tubes affinities functional morphology West Hunan

The localization of 1-cohomology of transitive Lie algebroids

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Science china Mathematics 2006年第2期49卷 277-288页

作者： CHEN Zhuo & LIU Zhangju Department of Mathematics, Capital Normal University, beijing 100037, china {2. of Mathematical Science, peking University, beijing 100871, china 1. Department of Mathematics Capital Normal University Beijing 100037 China 2. school of Mathematical Science Peking University Beijing 100871 China

For a transitive Lie algebroid A on a connected manifold M and its representation on a vector bundle F, we define a morphism of cohomology groups rk: Hk(A,F) → Hk(Lx,Fx), called the localization map, where Lx is the adjoint algebra at x ∈ M. The main result in this paper is that if M is simply connected, or H (LX,FX) is trivial, then T is injective. This means that the Lie algebroid 1-cohomology is totally determined by the 1-cohomology of its adjoint Lie algebra in the above two cases.

关键词： transitive Lie algebroid representation cohomology localization.

A novel endorectal RF coil for high resolution MRI and spectroscopy of the prostate

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Progress in Natural Science:Materials International 2005年第5期15卷 472-476页

作者： ZHANG Hongjie 1,2. SONG Xiaoyu1, WANG Xiaoying3, XU Pingfang1 and BAO Shanglian1*(1. beijing Key Laboratory of Medical physics & Engineering, {2. University, beijing 100871, china 2. Navy General Hospital, beijing 100037, china 3. {2. University First Hospital, beijing 100034, china) beijing Key Laboratory of Medical physics & Engineering Peking University Beijing 100871 China Navy General Hospital Beijing 100037 China peking University First Hospital Beijing 100034 China

The diagnosis of prostate diseases by magnetic resonance imaging (MRI) in vivo is sometimes difficult for the lower signal to noise ratio (SNR). To increase the SNR of the prostate image, we designed a RF coil that can be inserted into rectum and was named endorectal coil. The properties of RF coil were evaluated using a network analyzer. Moreover the images and spectroscopy of a special phantom were acquired and the results were compared to those of the commercial TORSO coil (G.E. Medical Systems, USA). Our coil gave a significantly higher SNR at the region of interest (ROI). The achieved high local SNR and resulting high spatial resolution would add more anatomic and biochemical information to the diagnosis of prostate diseases.

关键词： MRI RF coil endorectal coil.

ON THE CENTRAL RELAXING SCHEME Ⅱ: SYSTEMS OF HYPERBOLIC CONSERVATION LAWS

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Journal of Computational Mathematics 2001年第6期19卷 571-582页

作者： Hua-zhong Tang (school of Mathematical Sciences, peking University, {2., china) (LSEC,ICMSEC Academy of Mathematics and Systems Sciences, Chinese Academy of Sciences, beijing 100080, china) school of Mathematical Sciences Peking University Beijing 100871 China

This paper continues to study the central relaxing schemes for system of hyperbolic conservation laws, based on the local relaxation approximation. Two classes of relaxing systems with stiff source term are introduced to approximate system of conservation laws in curvilinear coordinates. Based on them, the semi-implicit relaxing schemes are con- structed as in [6, 12. without using any linear or nonlinear Riemann solvers. Numerical experiments for one-dimensional and two-dimensional problems are presented to demon- strate the performance and resolution of the current schemes.

关键词： Hyperbolic conservation laws The relaxing system The central relaxing schemes The Euler equations.

Source time-function as discriminant using empirical Green's function

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Science china Earth Sciences 2005年第12期48卷 2118-2122页

作者： HE Yongfeng1,2.& CHEN Xiaofei1 1. Department of Geophysics, school of Earth & Space Sciences, {2. University, beijing 100871, china 2. North-West Institute of Nuclear Technology, Xi’an 71002., china 1. Department of Geophysics School of Earth & Space Sciences Peking University 100871 Beijing China 2. North-West Institute of Nuclear Technology 710024 Xi’an China

The source mechanism of underground nuclear explosions is remarkably different from that of earthquakes in both spatial radiation pattern and source time-function (STF). Small underground nuclear explosions can be used as empirical Green’s functions (EGF) to isolate the source-time spectrum of a large suspected earthquake occurred in a Nuclear Test Site (target area) by the spectral division method. As this study shows, with high-quality data, the quotient spectrum can be transformed to the time domain, yielding the apparent far-field source-time function of the large suspected event. The relative source time-function (RSTF) of a nuclear ex-plosion is usually a simple pulse with a duration of about 1 s., while an earthquake’s is more complicated with a series of pulses and a longer duration. The RSTF can be used as a nice dis-criminant to distinguish the nature earthquakes from underground nuclear explosions in target areas.

关键词： target-area, empirical Green's function, RSTF.

Status of study on biological and toxicological effects of nanoscale materials

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Science china Chemistry 2005年第5期48卷 385-394页

作者： WANG Bing1, FENG Weiyue1, ZHAO Yuliang1, XING Gengmei1, CHAI Zhifang1, WANG Haifang2.& JIA Guang3 1. Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials (Nanosafety Lab), Institute of High Energy physics, Chi-nese Academy of Sciences, beijing 100049, {2. 2. College of Chemistry and Molecular Engineering, peking University, beijing 100871, {2. 3. Department of Occupational and Environmental Health Sciences, school of Public Health, peking University, beijing 100083, {2. 1. Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials (Nanosafety Lab) Institute of High Energy Physics Chinese Academy of Sciences 100049 Beijing China 2. College of Chemistry and Molecular Engineering Peking University 100871 Beijing China 3. Department of Occupational and Environmental Health Sciences School of Public Health Peking University 100083 Beijing China

Because the physical and chemical properties of nanosized materials mostly differ from the existing microsized materials, their potential impacts on human health and the envi-ronment will be topics under the serious discussions in press and in a number of international scientific journals. We analyze and summarize the existing data of the experimental study on the biological activities and adverse effects of nanoscale materials/particles including single wall carbon nanotubes, multi wall carbon nanotubes, titanium oxide and iron powders. Though some biological behaviors of nanoscale materials observed cannot be understood on the basis of the current knowledge, as the existing data are mostly preliminary, it is too early to make some ex-clusive conclusions on biological activities (or the toxicity) of any of nanoscale materials. The experimental techniques, the current topics, and the future research directions for this new re-search field are also discussed.

关键词： nanomaterials, single wall carbon nanotubes, multi wall carbon nanotubes, titanium oxide and iron, biological activity and toxicological effect.

A SQP optimization method for shimming a permanent MRI magnet

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Progress in Natural Science:Materials International 2009年第10期19卷 1439-1443页

作者： Zhe Jina,Xing Tangb,Bin Menga,Donglin Zu b,Weimin Wanga,a Institute of Quantum Electronics,school of Electronics Engineering and Computer Science,peking University,{2.,china b Institute of Heavy Ion physics,beijing Key Laboratory of Medical physics and Engineering,school of physics,peking University,{2.,china [a]Institute of Quantum Electronics School of Electronics Engineering and Computer Science Peking University Beijing 100871 China [b]Institute of Heavy Ion physics Beijing Key Laboratory of Medical Physics and Engineering School of Physics Peking University Beijing 100871 China

Based on the sequential quadratic programming(SQP) method,a new approach is presented in this paper to gain a uniform magnetic field for a permanent MRI magnet with biplanar ***,the adopted shimming piece is modeled as a magnetic dipole moment to calculate its effect on the background field over the imaging region of ***,the SQP method is utilized to determine the ideal solution for the shimming ***,the ideal solution is discrete,and the quantization error control technique is used for special *** new method helps to reduce the inhomogeneity from 12.4.5 ppm to 2..4 ppm over a 36 cm diameter spherical volume(DSV),within hours in practical shimming work.

关键词： Magnetic resonance imaging(MRI) Field shimming Sequential quadratic programming(SQP) Permanent MRI magnet

Is the PhyloCode better than Linnaean system?—— New development and debate on biologi-cal nomenclatural issues

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Chinese Science Bulletin 2003年第3期48卷 308-312页

作者： GAO Keqin & SUN Yuanlin school of Earth and Space Sciences, peking University, {2., china school of Earth and Space Sciences Peking University Beijing 100871 China

The Linnaean system provides ultimate means governing biological nomenclature and classification. With series of modification, this system has admirably served bio-logical sciences for some 2.0 years. The new PhyloCode, however, advocates the phylogenetic nomenclature that radically alternates the current nomenclatural rules. The new proposals upset many systematic biologists and have provoked hot debate on nomenclatural issues. Binomial no-menclature and hierarchical classification are the key com-ponents of the Linnaean system. Proposed abandonment of these in the PhyloCode is widely criticized for it would not help to promote systematics but create chaos. It is not the Linnaean system but the phylogenetic nomenclature that should be abandoned.

关键词：生物分类生物命名法林奈系统系统代码法特点

Towards a degradation-based mechanism for adaptive overload control

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Science china(Information Sciences) 2012年第12期55卷 2708-2722页

作者： WANG ZiYou 1,2.ZHOU MingHui 1,2.& MEI Hong 1,2.1 Software Institute,school of Electronics Engineering and Computer Science,peking University,{2.,china 2.Key Laboratory of High Confidence Software Technologies(peking University),Ministry of Education,{2.,china 1. Software Institute School of Electronics Engineering and Computer Science Peking University Beijing 100871 China 2. Ministry of Education Key Laboratory of High Confidence Software Technologies (Peking University) Beijing 100871 China

Uncontrolled overload is one of the major causes of the system's decline in reliability and performance for web *** also harms the construction of trustworthy *** paper presents a degradationbased mechanism to adaptively control overload in complex,dynamic web *** our mechanism,the bottlenecks in the application's performance are determined by internally monitoring the performance and resource utilization state of the application,which is decomposed into a set of *** locating the bottlenecks,two decision algorithms are proposed to dynamically and adaptively generate proper degradation plans without *** degrading the service which consumes critical resources and has a low priority from the perspective of business logic,the application can keep providing key services even when overload *** implement a prototype and conduct a case study on a wiki *** also evaluate our approach and demonstrate its effectiveness in simulated overload *** handling overload,we make a breakthrough in building trustworthy software in an open,dynamic and rapidly changing environment.

关键词： overload service degradation resource monitoring performance management