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Investigation　of　Low－repetition－rate　Pulse　Amplification　in　Pr3＋－doped　Fiber　Amplifier

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Chinese Journal of Lasers 1996年第5期B5卷 403-408页

作者： YANG Bac MING Hai TAO Weidong XIE Jianping (department of Physics, university of {2. and technology of china,hefei 2.002., china) Univ of science and technology of China Hefei China

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关键词： Pr￣(3+)-doped fiber amplifier low-repetition-rate pulse

Existence of unbiased estimate of regression parameters in simple linear EV models

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science china Mathematics 2005年第7期48卷 915-928页

作者： LIU Jixue & CHEN Xiru department of Statistics and Finance, university of science and technology of china,{2., china department of Mathematics, Graduate School of Chinese Academy of sciences, Beijing 100049, china department of Statistics and Finance University of Science and Technology of China Hefei 230026 China department of Mathematics Graduate School Chinese Academy of Sciences Beijing 100049 China

It is well known that for one-dimensional normal EV regression model X = x+ u,Y =α+βx+e, where x, u, e are mutually independent normal variables and Eu=Ee=0, the regression parameters a and β are not identifiable without some restriction imposed on the parameters. This paper discusses the problem of existence of unbiased estimate for a and β under some restrictions commonly used in practice. It is proved that the unbiased estimate does not exist under many such restrictions. We also point out one important case in which the unbiased estimates of a and β exist, and the form of the MVUE of a and β are also given.

关键词： EV regression model unbiased estimate identiflability.

Jackson’s theorem in Q_p spaces

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science china Mathematics 2010年第2期53卷 367-372页

作者： CHEN YingWei 1 & REN GuangBin 1, 2. 1 department of Mathematics, university of science and technology of china,{2., china 2.department of Mathematics, university of Aveiro, P-3810-193 Aveiro, Portugal 1. department of Mathematics University of Science and Technology of China Hefei 230026 China2. Department of Mathematics University of Aveiro P-3810-193 Aveiro Portugal

A Jackson type inequality in Q p spaces is established, i.e., for any f (z) = Σ∞ j=0 ajzj ∈ Qp , 0≤p 1, and k-1 ∈ N,where ω(1/k, f, Q p ) is the modulus of continuity in Q p spaces and C(a) is an absolute const... 详细信息

关键词： Q p space BMOA polynomial approximation

Facile synthesis of dendrimer-like star-branched poly(isopropylacrylamide) via combination of click chemistry and atom transfer radical polymerization

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science china Chemistry 2010年第12期53卷 2520-2527页

作者： WAN XueJuan,XU Jian & LIU ShiYong CAS Key Laboratory of Soft Matter Chemistry department of Polymer science and Engineering,{2. National Laboratory for Physical sciences at the Microscale,university of science and technology of china,{2. 2.002.,china 1. CAS Key Laboratory of Soft Matter Chemistry department of Polymer science and Engineering Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China Hefei 230026 China

We report a facile synthesis method of dendrimer-like star-branched poly(N-isopropylacrylamide) (PNIPAM) via the combination of click chemistry and atom transfer radical polymerization (ATRP) by employing the arm-first ***,the α-azido-ω-chloro-heterodifunctionalized building block,N3-PNIPAM-Cl (G0-Cl),was synthesized via ATRP by 3-azidopropyl 2.chloropropionate as the *** advantage of click chemistry,the first generation (G1) of dendrimer-like star-branched PNIPAM,G1-(Cl)3,was facilely prepared via the click coupling reaction between G0-Cl and *** the construction of second generation (G2. dendrimer-like star-branched PNIPAM,G2.(Cl)6,terminal chloride moieties of G1-(Cl)3 were first converted to azide,and then reacted with excess tripropargylamine to give G1-(alkynyl)6 ;G2.(Cl)6 was subsequently prepared via click reaction between G1-(alkynyl) 6 and *** permeation chromatography (GPC) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry were employed to confirm the successful construction of dendrimer-like star-branched *** unique thermal phase transition behavior of this dendrimer-like star-branched polymer in aqueous solutions was further investigated by turbidimetry and micro-differential scanning calorimetry (Micro-DSC).

关键词： dendrimer-like branched ATRP click chemistry

Three-Dimensional and Cross-sectional Characteristics of Normal Grain Growth Based on Monte Carlo Simulation

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International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 129-133,139页

作者： Xiaoyan Song Guoquan Liu(Material science and Engineering School, university of science and technology Beijing, Beijing 100083, china)(department of Materials science and Engineering, Hebei university of technology, Tianjin 300130, china) Material science and Engineering School University of Science and Technology Beijing Beijing 100083 China departments of Materials science and Engineering Hebei University of Technology Tianjin 300130 China

An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of normal grain growth was done. It was found that the time exponent of grain growth determined from cross-section exhibits the same rule of increasing slowly with time and approaching the theoretical value n = 0.5 of steadygrain growth as the three-dimensional (3-D) system. From change of the number of grains per unit area with timemeasured in cross-section, the state of 3-D normal grain growth may be predicted. The gtain size distribution incross-section is different from that in 3-D system and can not express the evolution characteristic of the 3-D distribution. Furthermore, there exists statistical connection between the topological parameters in cross-section and thosein three-dimensions.

关键词： Monte Carlo simulation normal grain growth three-dimension cross-section characteristics

Dynamic damage and stress-strain relations of ultra-high performance cementitious composites subjected to repeated impact

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science china(Technological sciences) 2010年第6期53卷 1520-1525页

作者： LAI JianZhong1 & SUN Wei2.1 department of Materials science and Engineering,Nanjing {2. of science and technology,Nanjing 2.0094,china 2.College of Materials science and Engineering,Southeast {2.,Nanjing 2.1189,china 1. department of Materials science and Engineering Nanjing University of Science and Technology Nanjing 210094 China2. College of Materials Science and Engineering Southeast University Nanjing 211189 China

Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste *** dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity *** show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume *** stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation *** effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were *** show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.

关键词： ultra-high performance cementitious composites (UHPCC) split Hopkinson pressure bar (SHPB) repeated impact damage stress-strain

Preparation and Gas Permeation of Supported γ-Al_2._3 Membranes Used as Substrate Layer for Microporous Membranes

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Journal of Wuhan university of technology(Materials {2.) 2005年第3期20卷 27-30页

作者：韦奇 department of Materials science & Engineering University of Science & Technology of China College of Materials science & Engineering Beijing University of Technology Beijing 100022China

γ-Al2.3 membranes were successfidly deposited on the top of porous α-Al2.3 support by sol-gel process and characterized by means of XRD , SEM, N2.adsorption and gas permeation. The γ-Al2.3 membranes, free of pin-holes and cracks, adhere tightly to the supports and have a thlekness of about 7μm. When sintered at 400 ℃ , γ-Al2.3 membranes have a rutrrow pore size distribution, with a pore diameter of 3.6nm, and the transport of both H2.and CO2.in supported γ-Al2.3 membrane is governed by Knudsen mechanism, with H2.permeance of 3.3× 10^-6 molm^-2.a^-1s^-1 and H2. CO2.permselectivity close to the ideal Knudsen value at 50 ℃ . The γ-Al2.3 membranes are suitable for being used as the substrates of microparoas membranes .

关键词： supported γ-Al2.3 membranes hydrogen separation gas transport

A multicast routing algorithm with multiple trees

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Journal of Systems Engineering and Electronics 2005年第2期16卷 426-432页

作者： Cui Xunxue 1,2., Gao Wei3 & Fang Hongyu41. New Star Research Institute of Applied technology, hefei 2.0031, P. R.{2. 2. Jiangsu Key Laboratory of Computer Information Processing technology,Soochow university, Suzhou 2.5006, P. R.{2. 3. department of Electronic Engineering and Information science,university of science and technology of{2.,{12., P. R.{2. 4. School of Electronic science and technology, Anhui university, hefei 2.0039, P. R.{2. New Star Research Institute of Applied technology Hefei 230031 P. R. China 2. Jiangsu Key Laboratory of Computer Information Processing technology Soochow University Suzhou 215006 P. R. China department of Electronic Engineering and Information science University of Science and Technology of China Hefei 230027 P. R. China School of Electronic science and technology Anhui University Hefei 230039 P. R. China

Quality of service (QoS) multicast routing has continued to be a very important research topic in the Internet. A method of multicast routing is proposed to simultaneously optimize several parameters based on multiobjective genetic algorithm, after the related work is reviewed. The contribution lies on that the selection process of such routing is treated with multiobjective optimization. Different quality criterions in IP network are taken into account for multicast communications. A set of routing trees is generated to approximate the Pareto front of multicast problem. Multiple trees can be selected from the final set of nondominated solutions, and applied to obtain a good overall link cost and balance traffic distribution according to some simulation results.

关键词： multicast routing quality of service multiobjective optimization genetic algorithms.

The Degree of Symmetry of Certain Compact Smooth Manifolds II

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Chinese Annals of Mathematics,Series B 2007年第2期28卷 195-204页

作者： Bin XU department of Mathematics, university of science and technology of china,{2., china Chern Institute of Mathematics, Nankai university, Tianjin 300071, china department of Mathematics, Johns Hopkins university, Baltimore, MD 2.2.8, USA. department of Mathematics University of Science and Technology of ChinaHefei 230026 China

We give the sharp estimates for the degree of symmetry and the semi-simple degree of symmetry of certain compact fiber bundles with non-trivial four dimensional fibers in the sense of cobordism, by virtue of the rigidity theorem of harmonic maps due to Schoen and Yau (Topology, 18, 1979, 361-380). As a corollary of this estimate, we compute the degree of symmetry and the semi-simple degree of symmetry of CP2.V, where V is a closed smooth manifold admitting a real analytic Riemannian metric of non-positive curvature. In addition, by the Albanese map, we obtain the sharp estimate of the degree of symmetry of a compact smooth manifold with some restrictions on its one dimensional cohomology.

关键词： Degree of symmetry Fiber bundle Cobordism Non-positive Curvature Harmonic map First cohomology