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Logical verification of scientific discovery

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science china(Information sciences) 2010年第4期53卷 677-684页

作者： LI Wei State Key Laboratory of Software Development Environment, school of computer {2. and engineering, Beihang University, beijing 100191, china 1. State Key Laboratory of Software Development Environment School of Computer Science and Engineering Beihang University Beijing 100191 China

This paper shows that the discovery processes of Einstein’s special theory of relativity and Darwin’s theory of evolution of species can be formally verified by R-calculus which is a logical inference system. The aim of R-calculus is to delete the principles of scientific theories which contradict empirical evidence. The paper shows that the special theory of relativity is the only and correct choice for physics to meet the experimental evidence given at the time. As far as the biology of Darwin’s time is concerned, however, the R-calculus has derived three logically correct but different theories, which are all consistent with the empirical evidence provided by Darwin and his principle of natural selection. Darwin’s theory of evolution matches one of the three theories derived by R-calculus. This theory has a logical consequence that is "each species has been independently created is erroneous". But the other two theories support the negation of the above statement. The existence of the other two theories may be a reason of the controversies over Darwin’s theory.

关键词： R-calculus theory of relativity theory of evolution

Complex conforming Delaunay triangulation

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science china(Information sciences) 2010年第6期53卷 1130-1140页

作者： MENG XianHai 1, LI JiGang 1, YANG Qin 1, CAI Qiang 2.& CHEN QiMing 3 1 NLSDE, school of computer {2. and engineering, BeiHang University, beijing 100083, china 2.school of computer {2.s, beijing Technology and Business University, beijing 100037, china 3 school of Mechanical engineering and Automation, BeiHang University, beijing 100083, china 1. NLSDE School of Computer Science and Engineering BeiHang University Beijing 100083 China2. School of Computer Sciences Beijing Technology and Business University Beijing 100037 China3. School of Mechanical Engineering and Automation BeiHang University Beijing 100083 China

A novel algorithm of conforming Delaunay triangulation for curved geometry is presented in the paper.A progress has been made for the problem puzzled Delaunay refinement where curved constraints cannot be accepted as input *** algorithm is based on a new sufficient condition for the existence of constraints in *** requires computing only the intersection between constraints and Voronoi edges or faces instead of the circum-sphere of curved *** the termination of the algorithm when small input angles exist in constraints, a weighted method is applied to ensure that the algorithm can terminate under any *** two-dimensional and three-dimensional results are also *** is shown that the algorithm has the capability of dealing with both linear and nonlinear constraints in a consistent way, without the need of maintaining triangular meshes on face constraints.

关键词： mesh generation Delaunay triangulation conforming curved constraints tetrahedralization weight

Large field of view computed laminography with the asymmetric rotational scanning geometry

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science china(Technological sciences) 2010年第8期53卷 2261-2271页

作者： FU Jian 1,2.,JIANG BaiHong&LI Bin 1 school of Mechanical engineering and Automation,Beihang University,{2.,china 2.Research Center of Digital Radiation Imaging and Biomedical Imaging,Beihang University,{2.,china 1. school of Mechanical engineering and Automation Beihang University Beijing 100191 China2. Research Center of Digital Radiation Imaging and Biomedical Imaging Beihang University Beijing 100191 China

X-ray computed laminography(CL)is used in the fields of industrial inspection and medical *** can provide the internal structure three-dimensional(3D)information of a region of the objects *** is important to the clinical diagnosis and the quality control of flat objects like printed circuit boards,aircraft wings and satellite solar *** the restriction that the imaging region must be within the X-ray beam formed by the X-ray source and the detector,the imaging field of view of CL is limited by the size of detector.A new CL method with an asymmetric rotational cone-beam scanning geometry,called large field of view CL,is presented to overcome the existing *** can extend the imaging region when the imaging spatial resolution keeps the same as that of the conventional *** can also improve the imaging spatial resolution when the imaging region keeps the same as that of the conventional *** asymmetric configuration can be achieved by offsetting the detector from the conventional symmetric *** does not,however,require new detectors and X-ray source nor alter the scanning mechanical *** filtered back-projection(FBP)reconstruction algorithm and the data truncation smoothing functions have been deduced to reconstruct the images directly from the data acquired with this asymmetric *** performed numerical studies and experiments to demonstrate and validate the proposed approach. Results in these studies and experiments confirm that the proposed method can enlarge the imaging region and improve the spatial *** proposed approach may find applications in the CL system with the rotational scanning geometry.

关键词： computed laminography image reconstruction reconstruction algorithm imaging field of view imaging spatial resolution

A New Scheme and Microstructural Model for 3D Full 5-directional Braided Composites

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Chinese Journal of Aeronautics 2010年第1期23卷 61-67页

作者： Zhang Fan,Liu Zhenguo,Wu Zhe,Tao Guoquan school of Aeronautic science and {2.,beijing University of Aeronautics and Astronautics,beijing 100191,china [a] school of Aeronautic science engineering Beijing University of Aeronautics Astronautics Beijing 100191 China

Three-dimensional（3 D）braided composites are a kind of advanced ones and are used in the aeronautical and astronautical fields more widely. The advantages, usages, shortages and disadvantages of 3D braided composites are analyzed, and the possible approach of improving the properties of the materials is presented, that is, a new type of 3D full 5-directional braided composites is developed. The methods of making this type of preform are proposed. It is pointed out that the four-step braiding which is the most possible to realize industrialized production almost has no effect on the composites＇ properties. By analyzing the simulation model,the advantages of the material compared with the 3D 4-directional and 5-directional materials are presented. Finally, a microstructural model is analyzed to lay the foundation for the future theoretical analysis of these composites.

关键词： 3D braided fabrics four-step braiding 3D full 5-directional braided composites preform microstructure

Research progress in the inner surface modification of metal tubes by plasma processing

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Progress in Natural science:Materials International 2006年第11期16卷 1119-1126页

作者： ZHANG Guling~ 1,2.**, WU Xingfang~1, GU Weichao~2. CHEN Guangliang~2. FENG Wenran~2. NIU Erwu~2. LI Li~2. L Guohua~2. CHEN Huan~2. FAN Songhua~2. LIU Chizi~2.and YANG Size~2.1. school of Material science and {2., University of science and Technology beijing, beijing 100083, china 2. beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of sciences, beijing 100080, china) school of Material science and {2. University of Science and Technology Beijing Beijing 100083 China beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China

The recent progress in inner surface hardening of tubes by plasma processing is summerized. Several techniques of inner surface plasma source ion implantation and deposition are introduced, and their advantages and disadvantages are discussed. The basic principles, technical features and new progress of inner surface plasma source ion implantation methods for metal tubes, which were developed in our laboratory, are described in detail. And perspectives of the future technical development for inner surface ion implantation of tubes are presented.

关键词： PSII metal tubes inner surface surface modification.

A formal semantics for program debugging

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science china(Information sciences) 2012年第1期55卷 133-148页

作者： LI Wei1&LI Ning1,2.1State Key Laboratory of Software Development Environment,school of computer {2. and engineering,Beihang University,beijing 100191,china 2.5} Ship Research and Development Academy,beijing 100192.china 1. State Key Laboratory of Software Development Environment School of Computer Science and Engineering Beihang University Beijing 100191 China2. China Ship Research and Development Academy Beijing 100192 China

This work aims to build a semantic framework for automated debugging.A debugging process consists of tracing,locating,and fixing processes *** first two processes are accomplished by a tracing procedure and a locating procedure,*** tracing procedure reproduces the execution of the failed test case with well-designed data structures and saves necessary information for locating *** locating procedure will use the information obtained from the tracing procedure to locate ill-designed statements and to generate a system of fix-equations,whose solution will be used to fix the bugs.A structural operational semantics is given to define the functions of the tracing and locating *** of them are proved to *** main task of fixing process is to solve the *** turns out that for a given failed test case,there exist four types of fix-equations and three dierent solutions:1)The bug is solvable,i.e.,there exists a solution of the system of fix-equations,and the program can be repaired.2.There exists a structural design error in the program,i.e.,the system of fix-equations generated at each round of the locating procedure is solvable,but a new bug will arise when the old bug is being fixed.3)There exists a logical design error,and the system of fix-equations is not solvable.

关键词： debugging operational semantics failed test case fix-equations

Development and Application of High Performance X80 Line Pipe for the 2.(nd) West-East Gas Pipeline

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Journal of Iron and Steel Research International 2011年第S1期18卷 39-48页

作者： LI He-lin 1 , HUO Chun-yong 1 , JI Ling-kang 1, 2., LI Yang 1, 3 (1. CNPC Tubular Goods Research Institute, Xi’an 710065, china 2. . school of Material {2. and engineering, Xi’an Jiaotong University, Xi’an 710049, china 3. school of Material {2. and engineering, University of {2. and Technology beijing, beijing 100083, china) CNPC Tubular Goods Res Inst Xian 710065 Peoples R China Xi An Jiao Tong Univ Sch Mat Sci & Engn Xian 710049 Peoples R China Univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China

It is the development tendency of gas pipeline to improve strength of line pipe and transmission pressure, which is an important symbol of the progress of gas pipeline technology. The 2.d West-East Gas Pipeline (the 2.nd WEGP) is the largest-scale X80 high pressure gas pipeline project in the world. Through the joint development project by Pipeline Company, research institute, and steel company, a series of achievements of technology have been obtained, which makes it possible to apply pressure of 12.MPa and X80 LSAW and HSAW pipe for the 2.nd WEGP. Specifications of X80 steel and pipe have been issued based on API 5L. High performance X80 steel and pipe have been developed and meets the Specification. General design conception of applying HSAW pipe and LSAW pipe on gas transmission trunk line with large diameter and high pressure has been established. Failure control of the 2.nd WEGP has been carried out to avoid failure and reduce the lost which based on analysis of pipeline failure mode. In this paper, research and development of high performance X80 welded pipe, establishment of technical route of joint application of HSAW and LSAW steel pipe and key technology of failure control are emphatically discussed.

关键词： 2.nd WEGP acicular ferrite failure control arrest toughness strain-based design

Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

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Journal of Wuhan University of Technology(Materials science) 2009年第4期24卷 515-519页

作者：张津 school of Materials science & {2. University of Science and Technology Beijing College of Materials science & engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance

Effects of chitosan/collagen substrates on the behavior of rat neural stem cells

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science china(Life sciences) 2010年第2期53卷 215-222页

作者： YANG ZhaoYang1,MO LinHong2.DUAN HongMei2.& Li XiaoGuang1,2.1 school of Biological science and Medical {2.,Beihang University,beijing 100191,china 2.beijing Institute for Neuroscience,Capital Medical University,beijing 100069,china 1. school of Biological science and Medical {2. Beihang University Beijing 100191 China2. Beijing Institute for Neuroscience Capital Medical University Beijing 100069 China

Spinal cord and brain injuries usually lead to cavity *** transplantation by combining stem cells and tissue engineering scaffolds has the potential to fill the cavities and replace the lost neural *** chitosan and collagen have their unique *** this study,the effects of chitosan and collagen on the behavior of rat neural stem cells (at the neurosphere level) were tested in vitro in terms of cytotoxicity and supporting ability for stem cell survival,proliferation and *** the serum-free condition,both chitosan membranes and collagen gels had low cytotoxicity to *** is,cells migrated from neurospheres,and processes extended out from these neurospheres and the differentiated *** with the above two materials,chitosan-collagen membranes were more suitable for the co-culture with rat neural stem cells,because,except for low cytotoxicity and supporting ability for the cell survival,in this group,a large number of cells were observed to migrate out from neurospheres,and the differentiating percentage from neurospheres into neurons was significantly *** modification of chitosan-collagen membranes may shed light on in vivo nerve regeneration by transplanting neural stem cells.

关键词： chitosan collagen neural stem cells biocompatibility differentiation