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Necessary and sufficient conditions for moderate deviations of dependent random variables with heavy tails

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science china Mathematics 2010年第6期53卷 1421-1434页

作者： liU li school of Mathematics and Statistics,wuhan university,wuhan 430072,china 1. school of Mathematics and Statistics Wuhan University Wuhan 430072 China

This paper studies the moderate deviations of real-valued extended negatively dependent(END) random variables with consistently varying *** moderate deviations of partial sums are first *** results are then used to establish the necessary and sufficient conditions for the moderate deviations of random sums under certain circumstances.

关键词： moderate deviation extended negative dependence consistently varying tail random sum

Sol-gel Preparation and Infrared Radiation Property of Boron-substituted Cordierite Glass-ceramics

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Journal of materials science & technology 2010年第5期26卷 445-448页

作者： Shuming Wang and Fenghua Kuang school of materials science and engineering,university of science & technology Beijing,Beijing 100083,china [a] school of materials science and engineering university of science & technology Beijing Beijing 100083 china

Boron for aluminum substitution in the cordierite structure has been examined by sol-gel preparation of different samples along the compositional junction Mg2Al4-xBxSi5O18 with x=0,0.5,1,*** increasing the x value from 0 to 1.5 the crystallization behavior changed *** amount B2O3 doping can promote the sintering of amorphous cordierite gel,effectively restrain the precipitation of μ-cordierite and enhance the crystallization of α-*** substitution of B3＋ for Al3＋ in cordierite crystal structure can effectively improve the near-infrared spectral emissivity of this cordierite based glass-ceramics.

关键词： Sol-gel Glass-ceramics Infrared radiation B3+ substitution Solid solution

Effects of Fibers on the Dynamic Properties of Asphalt Mixtures

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Journal of wuhan university of technology(materials science) 2007年第4期22卷 733-736页

作者：吴少鹏 Key Laboratory of Silicate materials science and engineering of Ministry of Education(wuhan university of technology)

The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester （SPT） was conducted to study the dynamic modulus （E＇） and phase angle （δ） for the control asphalt mixture and fiber-modified ones at various temperatures and frequencies. Experimental results show that all fiber-modified asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the time- temperature superposition theory at a control temperature （21.1℃）. The fatigue parameter E^＊×sinδ and rutting parameter E^＊/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fiber additives.

关键词： fiber asphalt mixture dynamic modulus phase angle master curve

Mechanical and Thermal Properties of Polysiloxanes and NBR Blend Elastomer

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Journal of wuhan university of technology(materials science) 2006年第4期21卷 92-94页

作者：王雁冰 school of materials science and engineering Wuhan University of Technology Wuhan 430070China

A series of elastomers , based on NBR , polysiloxanes （PS） were prepared and characterized by tensile tests, thermogravimetry （ TG ） and differential scanning calorimetry （ DSC ）. Two kinds of vulcanizing agent, DMDBH （2,5-dimethyl- 2,5-di （ t- butyl perory ） hexane ） and DCP （ dicumylperoxide ） were used to investigate the influence of different vulcanizing agents on properties of PS/ NBR. The addition of PS to NBR was found to improve the thermal stability and decrease the tensile strength of NBR. The tensile strength decreased conshterably while the elongation at break increased obviously with the increase of PS content. The series using DMDBH as vulcanizing agent showed a higher tensile strength and elongation at break than the series using DCP as vulcanizing agent. Simultaneity the thermal stability increased with the increase of PS content.

关键词： NBR polysiloxanes tensile tests thermal stability

Dislocation Densites of Deformed Steel Sheets Based on Positron Annihilation

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International Journal of Minerals,Metallurgy and materials 1998年第1期12卷 47-50页

作者： Yonglin Kang Xianjin Wang (materials science and engineering school, university of science and technology Beijing, Beijing 100083, china) materials science and engineering school University of Science and Technology Beijing Beijing 100083 China

The variation regularity of dislocation densites of some deformed steel sheets under three kinds of strainpaths as uniaxial tension, plane strain and equal biaxial stretching was investigated by means of positron lifetimespectrum and Doppler-broadening techniques. The results show that the increasing rate of dislocation densites isrelated to the plastic strain path. A relationship between the increasing rate of micro-defects, macro-instability andforming limits during the process of steel sheet forming was got based on analyzing the mechanism of dislocationdensity increasing under different stress-strain condihons.

关键词： positron annihilation dislocation steel sheet strain path

Perturbed low-thrust geostationary orbit transfer guidance via polynomial costate estimation

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Chinese Journal of Aeronautics 2024年第3期37卷 181-193页

作者： Zhao li Hengnian li Fanghua JIANG Junfeng li State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control CenterXi’an 710043China school of Aerospace engineering Tsinghua UniversityBeijing 100084China

This paper proposes an optimal,robust,and efficient guidance scheme for the perturbed minimum-time low-thrust transfer toward the geostationary *** Earth’s oblateness perturbation and shadow are taken into *** is difficult for a Lyapunov-based or trajectory-tracking guidance method to possess multiple characteristics at the same time,including high guidance optimality,robustness,and onboard computational *** this work,a concise relationship between the minimum-time transfer problem with orbital averaging and its optimal solution is identified,which reveals that the five averaged initial costates that dominate the optimal thrust direction can be approximately determined by only four initial modified equinoctial orbit elements after a coordinate *** on this relationship,the optimal averaged trajectories constituting the training dataset are randomly generated around a nominal averaged *** polynomial regression models are trained on the training dataset and are regarded as the costate *** the transfer,the spacecraft can obtain the real-time approximate optimal thrust direction by combining the costate estimations provided by the estimators with the current state at any ***,all these computations onboard are *** simulation results show that the proposed guidance scheme possesses extremely high guidance optimality,robustness,and onboard computational efficiency.

关键词： Low thrust Orbital transfer Trajectory optimization Guidance Indirect method Orbital averaging Machine learning Geostationary satellites

Phenomenon of “contact guidance” on the surface with nano-micro-groove-like pattern and cell physiological effects

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Chinese science Bulletin 2009年第18期54卷 3200-3205页

作者： ZHOU Feng 1,2, YUAN lin 1,3, HUANG He 1,2 & CHEN Hong1,2 1 State Key Laboratory of Advanced technology for materials Synthesis and Processing, wuhan 43.070, china 2 school of materials science and engineering, wuhan university of technology, wuhan 43.070, china 3 Biomedical materials Research Center, wuhan university of technology, wuhan 43.070, china State Key Laboratory of Advanced technology for materials Synthesis and Processing Wuhan 430070 China school of materials science and engineering Wuhan University of Technology Wuhan 430070 China Biomedical materials Research Center Wuhan University of Technology Wuhan 430070 China

The topography of material surface has important influence on cell behavior and physiological functions. Groove-like pattern has drawn much attention among various patterns, due to the phenomenon of "contact guidance" induced by this kind of topography. This review mainly focuses on "contact guidance" formation as well as its influence on cell behavior and physiological effects. The possible mechanisms of "contact guidance" formation were discussed. The research trend and the potential applications were also suggested.

关键词：细胞行为生理功能材料表面逻辑效应触指纳米微米生理效应

Research of Environment-friendly Low Emissivity Glass

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Journal of wuhan university of technology(materials science) 2007年第2期22卷 385-387页

作者：余峰 school of Civil engineering and Architecture Wuhan University of Technology

The environment-friendly glasses which integrate function and structure were introduced, among these glasses can save energy very efficiently due to its low infrared emissivity. The fundamental principle of the low emissivity glass and the research progress of this kind glass were analyzed. Meanwhile, high performance and low applied development trend of emissivity glass were reviewed.

关键词： low emissivity glass(Low-E) environment-friendly research progress development trend

Binding materials of Dehydrated Phases of Waste Hardened Cement Paste and Pozzolanic Admixture

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Journal of wuhan university of technology(materials science) 2009年第1期24卷 140-144页

作者：吕林女 school of science Wuhan University of Technology

Fly ash （FA） and ground granulated blast-furnace slag （GGBFS） were added to improve the performances of regenerated binding materials （RBM） which refer to dehydrated phases with rebinding ability of waste hardened cement paste. Flowability tests, compressive strength tests, SEM, TG-DSC, and non-evaporable water content tests were employed to study the performances of the combined binding materials and the interactions between RBM, FA, and GGBFS. Results show that adding FA or GGBFS can improve the workability of RBM paste, and GGBFS has positive effects on strength of RBM. Pozzolanic reactions happen between RBM, FA, and GGBFS. And the activation effect of RBM to FA and GGBFS is superior to that of P.O grade-32.5 cement, especially at earlier ages, because of the high reactive f-CaO existing in RBM. On the advantages of the synergetic effects of RBM and pozzolanic admixtures such as FA and GGBFS, new combined binding materials can be prepared by blending them together.

关键词： combined binding materials dehydrated phase fly ash granulatedblast-furnace slag