检索结果-南通市图书馆

RESEARCH ON ADAPTIVE DATA COMPRESSION METHOD FOR TRIANGULATED SURFACES

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2004年第2期17卷 189-192页

作者： Wang Wen Wu Shixiong Chen Zichen Department of Mechanical Engineering,Zhejiang University,hangzhou 310027, China Department of Mechanical Engineering Zhejiang University Hangzhou 310027

NC code or STL file can be generated directly from measuring data in a fastreverse-engineering mode. Compressing the massive data from laser scanner is the key of the newmode. An adaptive compression method based on triangulated-surfaces model is put forward.Normal-vector angles between triangles are computed to find prime vertices for removal. Ring datastructure is adopted to save massive data effectively. It allows the efficient retrieval of allneighboring vertices and triangles of a given vertices. To avoid long and thin triangles, a newre-triangulation approach based on normalized minimum-vertex-distance is proposed, in which thevertex distance and interior angle of triangle are considered. Results indicate that the compressionmethod has high efficiency and can get reliable precision. The method can be applied in fastreverse engineering to acquire an optimal subset of the original massive data.

关键词： Data compression Reverse engineering Triangulated surfaces

RANDOM COPOLYMER OF PROPYLENE OXIDE AND ETHYLENE OXIDE PREPARED BY DOUBLE METAL CYANIDE COMPLEX CATALYST

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2002年第5期20卷 453-459页

作者： Yi-jun Huang Guo-rong Qi Guan-xi Chen Department of Polymer Science and Engineering, Zhejiang University hangzhou 310027,China Department of Polymer Science and Engineering Zhejiang University Zhangzhou 310027 Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027

Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H-1-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO+PO to initiator moles used, The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.

关键词： propylene oxide ethylene oxide double metal cyanide complex

CNC NON-CONTACT MEASURING SYSTEM FOR FREEFORM SURFACE

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2002年第2期15卷 103-106页

作者： JuHua Wang Wen Chen Zichen Li Jian Wang Hengkui Institute of Production Engineering, Zhejiang University, hangzhou 310027, China Institute of Production Engineering Zhejiang University Hangzhou 310027

Developing CNC measuring method on the base of coordinate machine can makethe best of the hardware resource of CNC system and realize the integration of CAD/CAM/CAT. Based onthe evenly spaced parallel planes scanning, a new adaptive digitizing approach for freeform surfacenamely arc length extrapolation is put forward. By this way, the digitizing approach can be addedto the CNC system, while the system's hardware and software are not changed.

关键词： Reverse engineering Freeform surface digitalization CNC non-contactmeasurement Arc extension

Tetragonal Domain Switching via Reversible tm Phase Transformation

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 1996年第4期12卷 255-260页

作者： Haiyan ZHU and Zhicheng XU(Dept. of Materials Science and Engineering, Zhejiang University, hangzhou 310027, China) Dept. of Materials Science and Engineering Zhejiang University Hangzhou 310027 China

Grinding-induced tm phase transformation and the resultant texture in ceria-yttria-doped tetragonal zirconia polycrystals with varied tetragonality have been studied by XRD. It is observed that the reversible tm phase transformation occurs during grinding and the intensity ratio of I(002)t/I(200)t increases with the transformability. The author proposes that the texture induced by grinding at low temperatures is due to the tetragonal variant reorientation via cyclic,reversible tm phase transformation, termed 'transformational domain switching', instead of the ferroelastic one

关键词： Jun Am Chen Tetragonal Domain Switching via Reversible t m Phase Transformation

Optical Properties of Fullerenated Poly(epoxy propyl carbazole)

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1998年第9期9卷 835-837页

作者： Tao GU Wan Xi CHEN Zhu De XU (Department of Chemistry, Zhejiang University, hangzhou 310027) Department of Chemistry Zhejiang University Hangzhou 310027 China

The optical properties of the fullerenated poly(epoxy propyl carbazole) (PEPC) have been investigated. Compared with pure PEPC, fullerenated PEPC has the same structure in the UV region of the absorption spectrum, and extends the active range to a longer wavelength. The apparent quenching of PEPC fluorescence was observed in the fullerenated polymer and it can be attributed to intramolecular excited state energy transfer.

关键词： fullerene (fullerenated) PEPC (poly(epoxy propyl carbazole)) optical properties

EFFECTS OF STOICHIOMETRIC RATIO ON STRUCTURE AND ELECTRODE PERFORMANCE OF HYDROGEN STORAGE ALLOYS

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 1998年第3期8卷 72-76页

作者： Chen Weixiang Department of Materials Science and Engineering, Zhejiang University, hangzhou 310027, P. R. China Department of Materials Science and Engineering Zhejiang University Hangzhou 310027 China

１ＩＮＴＲＯＤＵＣＴＩＯＮＮｉｃｋｅｌｍｅｔａｌｈｙｄｒｉｄｅ（Ｎｉ／ＭＨ）ｂａｔｅｒｉｅｓｅｍｐｌｏｙｉｎｇａｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｏｙａｓｔｈｅｎｅｇａｔｉｖｅｍａｔｅｒｉａｌｈａｖｅａｔｒａｃｔ... 详细信息

１ＩＮＴＲＯＤＵＣＴＩＯＮＮｉｃｋｅｌｍｅｔａｌｈｙｄｒｉｄｅ（Ｎｉ／ＭＨ）ｂａｔｅｒｉｅｓｅｍｐｌｏｙｉｎｇａｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｏｙａｓｔｈｅｎｅｇａｔｉｖｅｍａｔｅｒｉａｌｈａｖｅａｔｒａｃｔｅｄｍｕｃｈａｔｅｎｔｉｏｎｂｅ?..

关键词： hydrogen storage alloy stoichiometric ratio structure thermodynamic property

Synthesis and electrochemical performance of YF_3-coated LiMn_2O_4 cathode materials for Li-ion batteries

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2011年第1期30卷 39-43页

作者： CAO Jina CAO Gaoshao YU Hongming XIE Jian ZHAO Xinbing Department of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China

Spinel LiMn2O4 cathodes were coated with 1 mol% YF3.X-ray diffraction（XRD） analyses showed that Y and/or F did not enter the lattice of the LiMn2O4 crystal.Transmission electron microscopy（TEM） showed that a compact YF3 layer of 5-20 nm in thickness was coated onto the surface of LiMn2O4 particles.Scanning electron microscopy（SEM） observation showed that the YF3 coating caused the agglomeration of LiMn2O4 particles.The cycling test demonstrated that the YF3 coating can improve the electrochemical performance of LiMn2O4 at both 20 and 55°C.Moreover,YF3-coated LiMn2O4 exhibited an improved rate capability compared with the uncoated one at high rates over 5C.The immersion test in electrolytes showed that YF3-coated LiMn2O4 is more erosion resistant than the uncoated one.

关键词： lithium batteries coatings cathodes electrochemical properties

The Coupled-mode Theory of Grating-assisted Parallel Optical Fiber Cores

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 2002年第1期11卷 52-57页

作者： ZHU Songlin ZHANG Xianmin CHEN Kangsheng (Department of Information & Electronic Engineering, Zhejiang University, hangzhou 310027, China) Department of Information & Electronic Engineering Zhejiaiig University Hangzhou 310027

A new coupled-mode formulation is developed for grating-assisted parallel optical fiber cores. The theory is derived from the scalar wave equation by perturbation method. The diffraction caused by grating and coupler in the grating region are both considered. Based on the theory, various experimental phenomena in grating-assisted parallel optical fiber cores can be simulated accurately.

关键词： fiber grating coupled-mode directional coupler

Constructing a quasi-Legendre basis based on the C-Bézier basis

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第6期15卷 559-563页

作者： HUANG Yu* and WANG Guozhao(Department of Mathematics, Zhejiang University, hangzhou 310027, China) Department of Mathematics Zhejiang University Hangzhou 310027 China

In the space Γ_n=span｛sint,cost,1,t,t2,…,t n-2 ｝, a C-Bézier basis is constructed by an integral approach. However, the C-Bézier basis is not orthogonal. For some applications, we construct an orthogonal basis based on the C-Bézier basis, which has remarkable properties similar to that of the Legendre basis. Then we derive the transformation matrices that convert the C-Bézier basis and the orthogonal basis into each other. As an example of application, we apply this orthogonal basis to the degree reduction approximation of the C-Bézier curves.

关键词： C-Bézier basis orthogonal basis basis transformations degree reduction.