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基于DSP56F805的PWM实现

微特电机 2004年第1期32卷 18-20页

作者：奚正平中国科学院电工研究所北京100080

介绍了脉宽调制技术和DSP5 6F80 5内置的PWM模块 ,并通过编程实例和实验、仿真结果说明了该模块的应用方法。

关键词： DSP56F805 PWM 脉宽调制电气传动系统永磁同步电机矢量控制

Identification and Practical Application of Silicate-dissolving Bacteria

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Agricultural sciences in china 2002年第1期1卷 81-85页

作者： LIN Qi-mei, RAO Zheng-hua, SUN Yan-xing, YAO Jun and XING Li-jun( Department of Soil and Water sciences , china Agricultural University, beijing 100094 institute of Plant Nutrition and Resources , beijing academy of Agricultural and Forestry sciences, beijing 100081 ) Department of Soil and Water sciences China Agricultural University Beijing 100094 institute of Plant Nutrition and Resources Beijing Academy of Agricultural and Forestry Sciences Beijing 100081

Slime-forming bacteria were isolated from soils, rock surface and earthworm intestine, and their effects on dissolving silicate minerals and tomato growth were examined. One of the bacteria, Bacillus mucilaginosus RGBc13, had particularly strong ability to form slime and dissolve silicates. RGBc13 could also colonize and develop in both non-rhizosphere and rhizosphere soil. Total number of slime-forming bacteria increased from 2.9 × 103 cfu·g-1and 8.4 × 103 cfu·g-1 to 9.6 × 106 cfu·g-1 and 6.0 × 107 cfu·g-1 in the non-rhizosphere and rhizosphere soils respectively. Potassium and phosphorus nutritional conditions in the rhizosphere were markedly improved through inoculation of this bacterium. Available K and P respectively increased from 25. 86 and 3. 63mg · kg-1 in the non-rhizosphere soil to 91. 23 and 5. 74mg · kg-1 in the rhizosphere soil. Tomato biomass increased by 125%, K and P uptakes were more than 150%, greater than the non-inoculation. Thus, there is a potential in applying RGBcl3 for improving plant K and P nutrition.

关键词： Silicate-dissolving bacteria Silicates Tomato

An improvement on summer regional climate simulation over East china: Importance of data assimilation of soil moisture

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chinese Science Bulletin 2010年第9期55卷 867-873页

作者： HU YaMin1,2,3, DING YiHui4 & LIAO Fei2 1 institute of Tropical and Marine Meteorology, china Meteorological Administration, Guangzhou 510080, china 2 Guangdong Climate Center, Guangzhou 510080, china 3 chinese academy of Meteorological sciences, beijing 100081, china 4 National Climate Center, china Meteorological Administration, beijing 100081, china

The Newtonian relaxation is used to assimilate data from the Second Global Soil Wetness Project (GSWP2) into the initial field for soil moisture in a regional climate model (i.e., BCC_RegCM 1.0, hereinafter called RegCM). The results show that different nudging parameters can improve the simulation of the air temperature and the precipitation to some extent in summertime season over East china. When the nudging intensity is 0.5 and nudging duration is 5 days, the result is desirable. Introducing the data assimilation of soil moisture into RegCM, the amelioration is not only in the spatial distribution pattern but also in the magnitude of the temperature and the precipitation. More specifically, the assimilation experiments have corrected the systematical cold bias of the air temperature and the precipitation on the low side, which is much closer to the observation compared with the control experiment. On the whole, the assimilation experiments shed light on the fact that the simulated bias in the original RegCM may be affected by the description of soil moisture in the land surface process. Therefore, the effect of soil moisture in RegCM should be paid more attention in the future.

关键词： soil moisture Newtonian relaxation data assimilation regional climate simulation

Influence of valence electron structures of phase and biphase interfaces of sulfides on hot brittleness in steel

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Science china(Technological sciences) 2004年第4期47卷 488-504页

作者： LIU Yan1,3, LIU Zhilin1, ZHANG Chengwei1,2 & ZHOU Yingchun1 1. Liaoning institute of Technology, Jinzhou 121001, china 2. china National Oil and Gas Exploration and Development Corporation, beijing 100011, china 3. College of Science, Northeastern University, Shengyang 110006, china 1. Liaoning institute of Technology 121001 Jinzhou China 2. College of Science Northeastern University 110006 Shengyang China 3. china National Oil and Gas Exploration and Development Corporation 100011 Beijing China

This paper calculates the electron structures of phase of FeS, MnS and their biphase interface electron structures with austenite in steel. The precipitation and the transformation of FeS and MnS are investigated through studying the valence electron pair numbers on the strongest bond n A with the structure formation factor S. The continuity of electron density and its relation with stress are explored in the biphase interfaces with the electron density difference απ Using n A, S, απ we explain the reason why FeS can bring about hot brittleness in steel and the physical mechanism why MnS may eliminate or inhibit hot brittleness, based on which satisfying results are obtained by calculating several rare-earth sulfides.

关键词： valence electron structure, sulfide, hot brittleness, and rare earth.

Tribology properties of plasma sprayed nanostructured and conventional WC-Co coatings under water environment

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Tribology properties of plasma sprayed nanostructured and co...

Variation of Non-Metallic Inclusions Composition in X80 Pipeline Steel Refined by High Basicity Slag

Fifth International Conference on Surface Engineering

作者： Xiaoqin Zhao1 2 Jianjim Chen1 Huidi Zhou1 1 State Key Laboratory of Solid Lubrication Lanzhou institute of Chemical Physics chinese academy of sciences Lanzhou 730000 china 2 Graduate School chinese academy of sciences beijing 100039 china

WC-Co cermet has wide applications in machinery industries as a wear-resisitance *** fabrication of Nanostructured coatings would be more encouraging in tribological surface *** this paper,the nanostructured and conventional WC-Co coatings were depsited on 1Cr18Ni9Ti stainless steel substrate using an atmospheric plasma spray *** microstructures and tribology properties in water environment were comparatively *** was found that the as-sprayed WC-Co coating were composed of WC as the major phase and W2C,WC1-X,and W3Co3C as the minor *** nanostructured WC-Co coating had much higher hardness and more uniform *** water environment,both the nanostructured and conventional WC-Co coatings had the similar friction coefficient under the same ***,nanostructured WC-Co coating had better wear resistance than conventional WC-Co coating no matter sliding against Si3N4 ball or stainless steel *** wear mechanism of nanostructured WC-Co coating is adhesion under 20 N and brittle flake with fatigue abrasion under 150N sliding against Si3N4 ball,while when the Si3N4 ball was replaced by stainless steel ball,the friction coefficient and the wear rate were effectively reduced,and the wear mechanism was adhesion under 20 N and split by crack under 150 *** WC-Co coating was more wear-resistance than the conventional one in water environment,and the friction coefficient and wear rate could be effectively reduced when rubbing against stainless steel ball.

关键词： Plasma spraying WC-Co coating water environment tribolobgy

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Journal of Iron and Steel Research International 2011年第S1期18卷 563-566页

作者： LI Qiang 1,WANG Xin-hua 1,LI Hai-bo 2,HUANG Fu-xiang 1,YANG Jun 1,WANG Wan-jun 1 (1.School of Metallurgical and Ecological,University of Science and Technology beijing,beijing 100083,china 2.Shousteel Research institute,beijing 100039,china) Univ Sci & Technol beijing Sch Met & Ecol Beijing 100083 Peoples R China Shousteel Res Inst Beijing 100039 Peoples R China

The transformation of inclusions was studied when control technology of refining top slag in ladle furnace was used in X80 pipeline *** amount of aluminum was added to experimental heats for final deoxidation during BOF tapping,and then the refining top slag with high basicity and strong reducibility was adopted to transform Al 2 O 3 to inclusions with low melting *** results show that the composition of inclusions changes in order of "Al 2 O 3 → MgO-Al 2 O 3 system→ CaO-MgO-Al 2 O 3 system→ CaO-Al 2 O 3 system".And the inclusions after LF refining are liquid or semi-liquid state at the temperature of steelmaking,which are easily removable to obtain high cleanliness steel by collision,agglomeration and flotation.

关键词： transformation of inclusions high basicity top slag removal of inclusions X80 pipeline steel

Image universal steganalysis based on best wavelet packet decomposition

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Science china(Information sciences) 2010年第3期53卷 634-647页

作者： LUO XiangYang1,2, LIU FenLin1, YANG ChunFang1 & WANG DaoShun2 1Information Science and Technology institute, Zhengzhou 450002, china 2Department of Computer Science and Technology, Tsinghua University, beijing 100084, china 1. Information Science and Technology institute Zhengzhou 450002 China2. Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Based on the best wavelet packet decomposition of images, a new universal steganalysis method with high detection correct ratio is proposed. First, the best wavelet packet decomposition of image based on the Shannon entropy information cost function is made. Second, high order absolute characteristic function moments of histogram extracted from the coefficient subbands obtained by best wavelet packet decomposition are regarded as features. Finally, these features are processed and a back-propagation (BP) neural network is designed to classify original and stego images. Three different steganalysis algorithms for three different cases of background and application condition are presented. To validate the performance of the proposed method, a series of experiments are made for six kinds of typical steganography methods, i.e. LSB, LTSB, PMK, Jsteg, F5 and JPHide. Results show that, the average detection accuracy of the proposed method exceeds at least 6.4% and up to 15.4% and has a better universal performance than its closest competitors. Furthermore, the proposed method can provide reference for designing the pattern recognition and classification algorithm based on best wavelet packet decomposition.

关键词： steganography digital images universal steganalysis best wavelet packet decomposition BP neural network

DIFFERENCE SCHEMES WITH NONUNIFORM MESHES FOR NONLINEAR PARABOLIC SYSTEM

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Journal of Computational Mathematics 1996年第4期14卷 319-335页

作者： Y.L. Zhou(Laboratory of Computational Physics, Centre for Nonlinear Studies, institute of AppliedPhysics and Computational Mathematics, beijing, china) INST APPL PHYS & COMPUTAT MATH CTR NONLINEAR STUDIESLAB COMPUTAT PHYSBEIJING 100088PEOPLES R CHINA

The boundary value problem for the nonlinear parabolic system is solved by the finite difference method with nonuniform meshes. The existence and a priori estemates of the discrete vector solutions for the general difference schemes with unequal meshsteps are established by the fixed point technique. The absolute and relative convergence of the discrete vector solution are justified by a series of a priori estimates. The analysis of mentioned problems are based on the assumption of heuristic character concerning the existence of the unique smooth solution for the original problem of the nonlinear parabolic system.

关键词： Math QT DIFFERENCE SCHEMES WITH NONUNIFORM MESHES FOR NONLINEAR PARABOLIC SYSTEM

The discrete multiple-parameter fractional Fourier transform

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Science china(Information sciences) 2010年第11期53卷 2287-2299页

作者： LANG Jun, TAO Ran& WANG Yue Department of Electronic Engineering, beijing institute of Technology, beijing 100081, china 1. Department of Electronic Engineering Beijing Institute of Technology Beijing 100081 China

As a generalization of the Fourier transform (FT), the fractional Fourier transform (FRFT) has many applications in the areas of optics, signal processing, information security, etc. Therefore, the efficient discrete computational method is the vital fundament for the application of the fractional Fourier transform. The multiple-parameter fractional Fourier transform (MPFRFT) is a generalized fractional Fourier transform, which not only includes FRFT as special cases, but also provides a unified framework for the study of FRFT. In this paper, we present in detail the discretization method of the MPFRFT and define the discrete multiple-parameter fractional Fourier transform (DMPFRFT). Then, we utilize the tensor product to define two-dimensional multiple-parameter fractional Fourier transform (2D-MPFRFT) and the corresponding two-dimensional discrete multiple-parameter fractional Fourier transform (2D-DMPFRFT). Finally, as an application, a novel image encryption method based on 2D-DMPFRFT is proposed. Numerical simulations are performed to demonstrate that the proposed method is reliable and more robust to blind decryption than several existing methods.

关键词： multiple-parameter fractional Fourier transform fractional Fourier transform image encryption information security