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Relaying Selection with Network-coded Cooperative Protocols in Aeronautical Communications

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Chinese Journal of Aeronautics 2010年第1期23卷 75-83页

作者： Du Bing,Zhang Jun School of Electronics and Information Engineering,beijing University of Aeronautics and Astronautics,beijing 100191,China School of Electronics and Information Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

In this article, we exploit the idea of network-coded cooperative protocol in aeronautical communications which combines different source nodes＇ information at the relay and joint decoding at the destination. Recently, the network coding in cooperative communications has been categorized into two mainstreams, bit-level and signal-level combinations, which are both discussed in the article. And to be exclusively,multiple access relay channel（MARC） is adopted. The mutual information expressions of both above-cited network-coded protocols are deduced, which prove that without proper selected relays to perform network coding, the spatial diversity of the proposed protocol cannot be obtained. This then leads to search for the selection and grouping algorithms. An adjacency matrix is defined to describe the connectivity of the nodes in one radio contact disk, so that, the selection and grouping of algorithm is equivalent to constructing this adjacency matrix to minimize the system outage probability evaluated in term of the mutual information. Besides, a network-coded cooperative protocol requires the acyclic network, of which the construction is to avoid loop-4 in the matrix. The article ends with simulations to demonstrate the viability of the proposed algorithms.

关键词： communication network coding outage probability mutual information bit-level signal-level

CONVERGENCE RATE OFDISTRIBUTIONS OF TRIMMED SUMS

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Chinese Annals of Mathematics,Series B 1996年第3期17卷 349-364页

作者： QI YONGCHENG CHENG SHIHONG(Department of Probability & Statistics, beijing University, beijing 100871, China) Department of Probability and Statistics Beijing University Beijing 100871 China

The authors first derive the normal expansion of the joint density function of two orderstatistics from the uniform distribution and then, using the approximation, establish a wayto estimate the normal convergence rate for trimmed sums. For applications, the convergencerates for the intermediately trimmed sums and heavily trimmed surns are found out.

关键词： Trimmed sum Order statistics Convergence rate Normal approximation

A WT-STFT combining Algorithm

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International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 315-317页

作者： Xisheng Li, Shaochun Wang (Information Engineering School, University of Science and Technology beijing, beijing 100083, China) Information Engineering School University of Science and Technology Beijing Beijing 100083 China

A fast wavelet packet (WP) algorithm is presented, in which the wavelet transform (WT) and the short-time Fourier transform (STFT) are combined. As WT produces multiresolution of frequency and time, and STFT has a fas... 详细信息

关键词： signal processing, wavelet transform short-time Fourier transform Informatid

The influence of thermal radiation on MHD station-point flow past a stretching sheet with heat generation

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Acta Mechanica Sinica 2011年第4期27卷 502-509页

作者： Jing Zhu.Lian-Cun Zheng.Xin-Xin Zhang Department of Mathematics and Mechanics,University of Science and Technology beijing,100083 beijing,China Thermal Engineering Department,University of Science and Technology beijing,100083 beijing,China Zheng Department of Mathematics and Mechanics University of Science and Technology Beijing Beijing China Thermal Engineering Department University of Science and Technology Beijing Beijing China

This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free stream velocity and stretching velocity, heat source parameter, Prandtl number, thermal radiation parameter, the suction and injection velocity parameter and magnetic parameter and dimensionality index in the series form with the help of homotopy analysis method （HAM）. Convergence of the series is explicitly dis- cussed. In addition, shear stress and heat flux at the surface are calculated.

关键词： Thermal radiation MHD Laminar boundarylayers - Homotopy analysis method

Assessment of the apparent activation energies for gas/solid reactions—carbonate decomposition

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Journal of University of Science and Technology beijing 2003年第2期10卷 25-29页

作者： Jianhua Liu and Jiayun ZhangMetallurgical Engineering School, University of Science and Technology beijing, beijing 100083, China Metall. Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The guidelines for assessing the apparent activation energies of gas/solidreactions have been proposed based on the experimental results from literatures. In CO_2 free inletgas flow, CaCO_3 decomposition between 950 and 1250 K with thin sample layer could be controlled bythe interfacial chemical reaction with apparent activation energy E = (215+-10) KJ/mol and E=(200+-10) kJ/mol at T = 813 to 1020 K, respectively. With relatively thick sample layer between 793and 1273 K, the CaCO_3 decomposition could be controlled by one or more steps involvingself-cooling, nucleation, intrinsic diffusion and heat transfer of gases, and E could vary between147 and 190 kJ/mol. In CO_2 containing inlet gas flow (5 percent-100 percent of CO_2), E wasdetermined to be varied from 949 to 2897 kJ/mol. For SrCO_3 and BaCO_3 decompositions controlled bythe interfacial chemical reaction, E was (213+-15) kJ/mol (1000-1350K) and (305+-15) kJ/mol(1260-1400 K), respectively

关键词： assessment activation energy decomposition carbonate

CALCULATING MODELS OF MASS ACTION CONCENTRATIONSFOR MATTES (Cu_2S-FeS-SnS)INVOLVING EUTECTIC

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 392-397页

作者： J. Zhang (Department of Metallurgy, University of Science and Technology beijing, beijing 100083, China) Univ of Science and Technology Beijing Beijing China

Based on the facts that cations and anions of molten salts and binary basic oxide solid solutions do not separate from each other as well as that the electric conductivities of mattes are greater than that of salts and basic oxide solid solutions, the calculating models of mass action concentrations for binary and ternary mattes involving eutectic have been formulated. The results of calculation agree well with the values measured;this in turn shows that the calculating models can reftect the structural characteristics of the mattes concerned.

关键词： matte activity eutectic mass action concentration

Tribological Performance of TiB_2-Ni Composite Coating Deposited by APS

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稀有金属材料与工程 2012年第S1期41卷 481-486页

作者： Zhu Hongbin,Li Hui,Li Zhuoxin beijing University of Technology,beijing 100124,China beijing Univ Technol Beijing 100124 Peoples R China

TiB2-Ni composite powders were prepared by pressurized hydrogen reduction cladding with different proportion of *** coatings were then prepared by *** microstructures and the phase composition of the powders as well as the deposited coatings were analyzed by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The coatings were tested using a ring-on-disc tribometer from ambient temperature to 300°C.A sprayed Cr3C2-NiCr coating was tested as a *** morphologies of the worn surface of the coatings were observed and *** is found that the TiB2-Ni composite coatings present higher friction coefficient than that of the Cr3C2-NiCr coating at room temperature due to the adhesive wear mechanism,whereas the main wear mechanism of Cr3C2-NiCr coating is rupture and ***,at high temperature,the friction coefficient of the TiB2-Ni composite coating decreases as a result of B2O3 solid lubricant,which alleviates the adhesive wear on ***,the TiB2-Ni composite coating greatly reduces the mass loss of the boron cast iron.

关键词： TiB2-Ni composite coating APS wear behavior

Comparison of Some Methods on Prediction of Activity Interaction Coefficient

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International Journal of Minerals,Metallurgy and Materials 1998年第1期12卷 13-15页

作者： Changxiang Xiang Ningxin Zhang (Applied Science School, University of Science and Technology beijing, beijing 100083, China) Applied Science School University of Science and Technology Beijing Beijing 100083 China

Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and ageneral solution model, a new model for prediction of activity interaction coefficient ε is proposed. The calculatedresults are better in agreement with the experimental values than the two previous models. The related theories andmodels are discussed according to the degree of agreement with experimental values.

关键词： Miedema's semiempirical formation enthalpy model activity interaction coefficient free volume theory similarity coefficient

Autonomous Path Planning For Robot Manipulators in Manufacturing Environment

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International Journal of Minerals,Metallurgy and Materials 1998年第2期12卷 104-107页

作者： Wei Wang Yang Yang Kui Yuan Information Engineering School, UST beijing, beijing 100083, China Information Engineering School UST Beijing Beijing 100083 China

A robot intelligent path planning system(RIPPS), which can be used as a robot off-line programming tool was introduced in this paper. C-space modeling and path search are key parts of the system. A fast C-space modeling is presented based on critical collision joint angle(CCJA), C-obstacle boundary can be computed by the feature points of obstacles. A modified A* algorithm is used for path search, although the path is slightly sub-optimal, a tremendous speed increase is achieved. RIPPS runs on a Silicon Graphic 4D/70 workstation, simulation results show that the system is efficient and practical for robot collision-free autonomous path planning in a structured and known environment.

关键词： robot path plalanning A~* algorithm