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A Novel Optical Code Division Multiple Access Ring Network System for LAN

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The Journal of China Universities of Posts and Telecommunications 2004年第3期11卷 5-9页

作者： WANGYu-Bao GAOYi-Ran MAWen-hua wujian linjin-tong SchoolofTelecommunicationsEngineering BeijingUniversityofpostsandtelecommunicationsBeijing100876P.R.China

In this paper the impact factors on the optical fiber LAN network with ring topology are considered. The couple ratio, the self-ring effect, the Multiple-Access Interference (MAI), and the channel noises are the main factors degrading the system performance. We develop a systematic method that employs the smallest p multiplication method to analyze the optimization of the ring network. The results show that choosing an optimal couple ratio and power control will enhance the system performance dramatically. In addition, the “self-ring” interference and MAI can be suppressed by power control to some extent.

关键词： ring network optimization power control optical code division multiple access

An Acceleration Method for Stationary Iterative Solution to linear System of Equations

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Advances in Applied Mathematics and Mechanics 2012年第4期4卷 473-482页

作者： Qun lin wujian Peng Academy of Math and System Sciences Chinese Academy of SciencesInstitute Computational MathematicsBeijing 100190China School of Mathematics and Information Sciences Zhaoqing UniversityZhaoqingGuangdong 526061China

An acceleration scheme based on stationary iterative methods is presented for solving linear system of *** Chebyshev semi-iterative method which requires accurate estimation of the bounds for iterative matrix eigenvalues,we use a wide range of Chebyshev-like polynomials for the accelerating process without estimating the bounds of the iterative matrix.A detailed error analysis is presented and convergence rates are *** experiments are carried out and comparisons with classical Jacobi and Chebyshev semi-iterative methods are provided.

关键词： Iterative method error analysis recurrence

Effects of litter removal on plant species diversity: a case study in tropical Eucalyptus forest ecosystems in South China

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Journal of Environmental Sciences 2003年第3期15卷 367-371页

作者： PENGShao-lin RENHai wujian-guo LUHong-fang SouthChinaInstituteofBotany ChineseAcademyofSciencesGuangzhou510650China.E-mail:renhai@*** ArizonaStateUniversityWest PhoenixAZ85069USA

The removal of litterfall in the Eucalyptus plantations in South China affected the plant biodiversity in these ecosystems was found based on the field observation and lab analysis. The protection times of species diversity of three Eucalyptus communities were different (Community Ⅰ with no protection, Community Ⅱ with 7-year-protection, Community Ⅲ with 35-year-protection). The total numbers of species in these communities (from Community Ⅰ to Ⅱ to Ⅲ) are 1, 6, and 17, respectively. The results showed that the protection of litterfall from being taken out of the ecosystem is important and can increase plant species diversity. This study combined biomass data, the chemical and physical properties of the soil, and the diversity of microbes in the communities. It is concluded that the mechanism of the effects of litter removal on biodiversity includes three factors: removing the suitable habitat of microbe and animal, decreasing the soil nutrient, and changing the special habitat for the germination and growth of invading plants. These results should have important implications for managing these Eucalyptus forest ecosystems in South China.

关键词： litter removal biodiversity Eucalyptus plantation South China

Preparative Purification and Bioassay of Bt Toxin from Cry1Ab Transgenic Rice

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Chemical Research in Chinese Universities 2004年第5期20卷 579-583页

作者： wujian-min YEQin-fu DepartmentofChemistry FacultyofScienceZhejiangUniversityHangzhou310027P.R.China InstituteofNuclear-AgriculturalScience ZhejiangUniversityHangzhou310029P.R.China

A method of extracting and purifying Cry1Ab protein(Bt toxin) from Cry1Ab transgenic rice was established. Most of the Bt toxin present in the tissue of Cry1Ab transgenic rice was extracted effectively with a solution of 50 mmol/LNa_2CO_3 and NaHCO_3. The crude protein containing Bt toxin was obtained after the pretreatment of Cry1Ab transgenic rice with ultra-filtration, ammonium sulfate precipitation and centrifugation. The dialysed crude protein was futher separated on DEAE Sephadex A-50 columns and Sephadex G-150 columns. The protein bound on DEAE Sephadex A-50 gel was eluted with buffer solution B(10 mmol/L tris-HCl buffer+1.0 mmol/L EDTA, pH=8.0) mixed with 0.1, 0.3, 0.5 and 0.8 mol/L NaCl in a discontinuous gradient elution mode. The peak of the Bt toxin eluted from the columns was identified by ELISA and bioassayed with larvae of tobacco hornworms and silkworms. The purity and the bioactivity of the Bt toxin were determined by means of SDS-PAGE and larvicidal assay, respectively. The purity of the Bt toxin obtained by this method is high, and its insecticidal activity is retained after the toxin is purified.

关键词： Transgenic rice Bt toxin Purification Bioassay

STABILITY ANALYSIS OF COUPLED SYSTEM OF MAGNETIC HEAD AND ULTRA-THIN GAS FILM

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Journal of Hydrodynamics 2005年第2期17卷 134-140页

作者： CHENHai-xia wujian-kang DepartmentofMechanics HuazhongUniversityofScienceandTechnologyWuhan430074China

This paper presents a pressure perturbation equation for the ultra-thin gas film lubrication of magnetic head-disk based on a generalized gas lubrication equation applicable to arbitrary Knudsen number. The gas film pressure of Air Bearing Slider (ABS) was obtained by using the operator-splitting and finite element method. The pressure perturbation equation was solved by the finite element method with unstructured triangle grids to calculate the stiffness and damping coefficients of the gas film. Modal analysis of coupled system of magnetic head and gas film was carried out to obtain natural frequencies, damping rates and mode shapes of the magnetic head vibrations. Vibration stability of Ω-type magnetic head was predicted in this work. Numerical results indicate that the natural frequencies of the coupled system increases as the gas film thickness decreases, and the natural frequencies and damping rate of the coupled vibration modes of heave and pitch motions are much lower than those of uncoupled modes. And it is concluded that the stability of magnetic head is slightly worsened when the disk rotation speed increases.

关键词： Air Bearing Slider (ABS) magnetic head gas film lubrication stability analysis

Development and progress in resistive plate chamber

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Nuclear Science and Techniques 2004年第5期15卷 281-289页

作者： CHENHong-Fang wujian DepartmentofModernPhysics UniversityofScienceandTechnologyofChinaHefei230026

Resistive Plate Chamber (RPC) is a robust and low cost gas detector, which is extensively used in high-energy physics, cosmic and astroparticle physics experiments. Over the past twenty years, as a particle detector, RPC has made remarkable progress. The main achievements, features and results of experiemantal tests including R&D and production of the RPCs by several Chinese groups in recent years are reported in this article.

关键词：雪崩均衡电场电容器多隙气体电离

Identification of the bound residue composition derived from ^(14)C-labeled chlorsulfuron in soil by using LC-MS and isotope tracing method

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Journal of Environmental Sciences 2004年第1期16卷 73-78页

作者： YEQing-fu wujian-min SUNJin-he InstituteofNuclear-AgriculturalScience ZhejiangUniversityHangzhou310029China

A new method for extracting the bound residue(BR) derived from 14 C-labeled chlorsulfuron in soils was developed, and the technique of combining LC-MS with isotope tracing method was subsequently applied to identify the composition of the 14 C-BR in a loamy Fluvent derived from marine deposit. The results showed that the 14 C-[2-amino-4-methoxyl-6-methyl-1,3,5]-triazine, 14 C-[2-amino-4-hydroxyl-6-methyl-1,3,5]-triazine and 14 C-chlorsulfuron parent compound constituted the main composition of the 14 C-BR derived from 14 C-labeled chlorsulfuron in the soil. The radioactive ratio of three compounds accounted for 39.8%, 35.4% and 17.9% of total recovered radioactivity, respectively. However, a small amount(3.6% of total recovered radioactivity) of the complex of 14 C-[2-amino-4-hydroxyl-6-methyl-1,3,5]-triazine might have existed in the 14 C-BR in association with an unknown soil substrate. 2-chlorobenzenesulfonamide was also detected to be one of the components of the BR. The results could well explain the mechanism of phytotoxicity caused by the BR derived from chlorsulfuron in soil. In addition, the mechanism of BR formation in soil was also discussed in details.

关键词： bound residue chlorsulfuron composition identification soil

Bioavailability of bound residue derived from ^(14)C-labeled chlorsulfuron in soil and its mechanism of phytotoxicity

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Journal of Environmental Sciences 2004年第2期16卷 262-267页

作者： YEQing-fu wujian-min SUNJin-he InstituteofNuclearAgriculturalSciences ZhejiangUniversityHangzhou310029China. DepartmentofChemistry ZhejiangUniversityHangzhou310029China

The bioavailability of bound residue(BR) derived from 14 C-labeled chlorsulfuron in soil and effect of the main components of the BR on growth of rape(brassica napus) and rice(Oryza sativa L.) were investigated. The results showed that the BR with the concentration of 0 28 and 0 56 nmol/g air-dried soil, which was calculated by special radioactivity of 14 C-labeled chlorsulfuron parent compound, resulted in significant depression effect on growth of rape seedling. It was assured that the main components(2-amino-4-methoxyl-6-methyl-1,3,5-triazine, 2-amino-4-hydroxyl-6-methyl-1,3,5-triazine, and 2-chloro-benzenesul-f onamide) of the BR did not inhibit the growth of rape and rice. LC-MS analysis demonstrated that the parent compound previously bound to the soil matrix could be again released and transformed into methanol-extractable residue during the course of rape growth. It was concluded that the molecular leading to the phytotoxicity to rape and rice in the BR is still the parent compound.

关键词： chlorsulfuron bound residue bioavailability phytotoxicity mechanism

Effect of Electron Itineracy on Magnetism of S=1／2 Ferromagnetic Ising Model

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Communications in Theoretical Physics 2003年第5期39卷 617-620页

作者： WANGHuai-YU wujian-Hua XUNKun DepartmentofPhysics TsinghuaUniversityBeijing100084China DepartmentofPhysics PekingUniversityBeijing100871China

The effect of electron itineracy on the magnetism of S＝1/2 ferromagnetic Ising model is investigated by introducing a hopping term. The electron Green's function method is used to deal with this Hamiltonian. Here emphasis is made on that the magnetization is caused by the difference between the filling of spin-up and spin-down *** concept is in accordance with that of band structure theory. In the zero band width limit, our results are the same as obtained by spin Green's function method. However, our method achieves more detailed physical information. The spontaneous magnetization, Curie temperature, total energy, and specific heat are calculated and investigated in detail by the densities of states. Hopping term depresses the Curie temperature but remains the order-disorder transformation still to be second order transition. Above the transition point, the energy band is the same as that of tight binding system because exchange interaction has no effect anymore. While under the transition point, the energy band splits into two subbands due to exchange interaction.

关键词： ferromagnetic Ising model electron itineracy energy band order-disorder transition