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Numerical calculation on temperature field of FGH95 alloy droplet during rapid solidification

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Journal of University of science and technology beijing 2003年第3期10卷 51-54页

作者： Huanming Chen and Benfu Hu Materials science and Engineering School, University of science and technology beijing, beijing 100083,china Physics and Electrical information Engineering School, Ningxia University, Yinchuan 750021,china Univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China Ningxia Univ Phys & Elect Informat Engn Sch Yinchuan 750021 Peoples R China

The temperature field of FGH95 alloy droplet atomized by plasma rotatingelectrode processing (PREP) during solidification has been calculated through numerical analysisbased on equivalent sensible heat capacity method. And thus the relational curves among temperaturegradient of solid-liquid interface, moving velocity of solid-liquid interface and solid fractionduring solidification have been presented. The results indicate that the relation between averagetemperature gradient of solid-liquid interface and droplet size, and the relation between averagemoving velocity of solid-liquid interface and droplet size can be expressed during solidification.

关键词： FGH95 alloy droplet temperature field numerical calculation

Investigation on Self-Q-Switched Er3+-Doped Fiber Lasers

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Chinese Journal of Lasers 1995年第3期B4卷 211-216页

作者： SUN Junqiang HUANG Dexiu(Department of Optoelectronic EngineeringHuazhong University of science and technology, Wuhan 430074, china)LI Zaiguang(national laboratory of Laser technology, Wuhan 430074, china) Huazhong Univ of science and Technology Wuhan China

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关键词： changeable nonlinear refraction index self-Q-switching

An algorithm to compute maximal contractions for Horn clauses

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science china(information sciences) 2011年第2期54卷 244-257页

作者： LUO Jie & LI Wei State Key laboratory of Software Development Environment, School of Computer science and technology, Beihang University, beijing 100191, china 1. State Key laboratory of Software Development Environment School of Computer Science and Technology Beihang University Beijing 100191 China

In the theory of belief revision, the computation of all maximal subsets (maximal contractions) of a formula set with respect to a set of facts is one of the key problems. In this paper, we try to solve this problem by studying the algorithm to compute all maximal contractions for Horn clauses. First, we point out and prove the conversion relationship between minimal inconsistent subsets of union of the formula set and the set of facts and maximal contractions of the formula set with respect to the set of facts. Second, we prove a necessary condition of a set of Horn clauses to be minimal inconsistent. Then, based on these two conclusions, we propose an interactive algorithm to enumerate all minimal inconsistent subsets of a given set of Horn clauses and a second algorithm to compute maximal contractions from these minimal inconsistent subsets. Finally, we proposed an interactive algorithm to compute maximal contractions for Horn clauses by composing the above two algorithms.

关键词： maximal contraction minimal inconsistent set minimal subtraction Horn clause

Spectral Estimation based on Filter Bank and Cepstrum Thresholding for Cognitive Radios

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china Communications 2009年第1期6卷 92-98页

作者： Cao Zhiping, Bi Guangguo, Zhang Zaichen national Mobile Communication Research laboratory, School of information science and Engineering, Southeast University, Nanjing 210096, china national Mobile Communication Research laboratory School of Information Science and Engineering Southeast University Nanjing 210096 China

Spectrum sensing plays an important role in cognitive radio (CR). Nonparametric spectrum estimation is considered as a feasible candidate for CR. Some filter bank based periodogram algorithms, such as Thomson’s multitaper spectral estimator, can achieve fine spectral dynamic range1 but have large estimation variance. On the other hand, recently, Cepstrum Thresholding is proposed to reduce the variance of periodogram estimation. In this paper, we combine these two methods to achieve spectral dynamic range and variance request at the same time.

关键词： spectrum analysisfifilter bank cepstrum thresholding.

Prediction-based guidance algorithm for high-lift reentry vehicles

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science china(information sciences) 2011年第3期54卷 498-510页

作者： ZHANG Zhao 1,2 & HU Jun 1 1 beijing Institute of Control Engineering, beijing 100190, china 2 science and technology on Space Intelligent Control laboratory, beijing 100190, china 1. beijing Institute of Control Engineering Beijing 100190 China2. Science and Technology on Space Intelligent Control Laboratory Beijing 100190 China

In this work, we propose a pseudo four-degrees-of-freedom (DOF) prediction based guidance algo- rithm specifically for high-lift reentry vehicles. The algorithm is composed mainly of three parts. First, at the beginning of each guidance cycle, the 4-DOF predictor is called upon to predict the final downrange, crossrange, and heading errors. Then, the magnitude of the bank angle is determined from the downrange error, using the proportional-integral (PI) control method. Finally, two bank angle reversal time points are determined to minimize the crossrange and heading errors. Compared with traditional predictor-corrector guidance, the algorithm proposed does not require iterative procedures which significantly decreases the computational burden for the on-board computer and makes the implementation practical. Simulation results for dispersion tests demonstrated that our algorithm is computationally efficient and robust against uncertainties and disturbances.

关键词： pseudo 4-DOF prediction-based guidance high-lift reentry vehicle

Stability analysis of a hypersonic vehicle controlled by the characteristic model based adaptive controller

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science china(information sciences) 2012年第10期55卷 2243-2256页

作者： ZHANG Zhao 1,2 & HU Jun 1 1 beijing Institute of Control Engineering,beijing 100190,china 2 science and technology on Space Intelligent Control laboratory,beijing 100190,china 1. beijing Institute of Control Engineering Beijing 100190 China2. Science and Technology on Space Intelligent Control Laboratory Beijing 100190 China

The closed loop attitude stability of a hypersonic vehicle controlled by the characteristic model-based all-coefficient adaptive controller is studied in this paper,and an algorithm based on the computation of induced matrix 1-norm or ∞-norm is *** of all,the Taylor series expansion is applied to discretize the inputoutput description of the attitude dynamics of the *** obtained difference equations have the same structure as characteristic model;thus the intervals which contain all possible values of certain characteristic model parameters are *** the linear feedback controller is used in the feedback loop,with some conservation,the closed loop system is viewed as a class of interval time-varying systems defined by a number of free time-varying *** free parameters take values from predefined *** sufficient and necessary condition for the stability of this class of system is ***,a sufficient condition for the stability of hypersonic vehicle attitude control loop is proposed and demonstration example is *** method proposed checks up the stability of the closed loop system by evaluating a finite number of matrix norms,and overcomes the difficulties brought by the time-varying nature of the characteristic model and parameter estimation.

关键词： characteristic model hypersonic vehicle interval time-varying system stability test attitude control

Molecular dynamics simulation on thermodynamic properties of Pb-Ag alloys

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Rare Metals 2010年第3期29卷 323-326页

作者： JIA Guobin,LIU Yuanyuan,YANG Bin,and LIU Dachun national Engineering laboratory of Vacuum Metallurgy,Kunming University of science and technology,Kunming 650093,china national Engineering laboratory of Vacuum Metallurgy Kunming University of Science and Technology Kunming China

Molecular dynamics simulation was used to simulate the thermodynamic properties of three binary alloys,Pb-Ag （1：1）,Pb-Ag （4：1）,and Pb-Ag （9：1）.The energy functions,such as excess free energy,cohesive energy,and formation energy,were *** calculated values agree well with the experimental *** atomic interactions were analyzed in macroscopic and microcosmic views and both are consistent well.

关键词： molecular dynamics energy function generalized embedded atom method Pb-Ag alloy

A new theorem to synchronization of unified chaotic systems via adaptive control

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Journal of University of science and technology beijing 2003年第6期10卷 72-75页

作者： Lequan Min and Jianyi JingApplied science School, University of science and technology beijing, beijing 100083, china Univ Sci & Technol beijing Appl Sci Sch Beijing 100083 Peoples R China

Chaos synchronization has been applied in secure communication, chemicalreaction, biological systems, and information processing. A new theorem to synchronization ofunified chaotic systems via adaptive control is proposed. The constructive theorem provides thedesign scheme for adaptive controller such that a respond system can synchronize with respect to anuncertain drive system. One example for discontinuous chaotic system is proposed to illustrate theeffectiveness and feasibility.

关键词： uncertain chaotic system adaptive control synchronization Chua's circuit

Interface-directed sol-gel:direct fabrication of the covalently attached ultraflat inorganic oxide pattern on functionalized plastics

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science china Chemistry 2010年第1期53卷 173-182,287-288页

作者： GAN ShengHua,YANG Peng & YANG WanTai State Key laboratory of Chemical Resource Engineering College of Materials science and Engineering,beijing University of Chemical technology,beijing 100029,china 1. State Key laboratory of Chemical Resource Engineering College of Materials science and Engineering Beijing University of Chemical Technology Beijing 100029 China

For plastic electronics and optics,the fabrication of smooth,transparent and stable crack-free inorganic oxide films(and patterning) on flexible polymeric substrates with strong bonding strength and controllable thickness from nanometers to micrometers is a key but still remains a *** versatile inorganic oxides,silica oxide film as SiOx is especially important because this semiconductor material could provide crucial properties in devices or serve as a base layer for further multilayer *** this paper,we describe a new interface-directed sol-gel method to fabricate flexible high quality silicon oxide film onto commodity *** resulting crack-free silica film has strong covalent bonding with polymer substrates,homogeneous morphology with ultralow roughness,highly optical transparency,tunable thickness from nm to μm,and easy patterning *** fabrication strategy relies on a novel photocatalytic oxidation reaction by photosensitive ammonium persulfate(APS),which is able to fabricate highly reactive hydroxyl monolayer surface on inert polymeric *** kind of hydroxylated surface could serve as nucleation and growth sites to initiate surface sol-gel *** a result,well-defined SiOx film deposition(gelation) occurs,and patterned hydroxylation regions could be easily utilized to induce the formation of patterned oxide film *** strategy also excludes the requirements of clean room and vacuum devices so as to fulfill low-cost and fast fabrication *** application examples from such high quality SiOx layer onto plastics are given but should not be limited within *** is that oxygen permeation rate of SiOx deposited polymer film decreases 25 times than pristine polymer substrate,which is good for the potential packaging *** other one is that silanization monolayer,for example,3-aminopropyltriethoxysilane(APTES),could be successfully constructed onto silica layer through classical silanization reac

关键词： surface patterning silicon oxide sol-gel polymer surface modification functional coatings