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    20 July 2004, Volume 32 Issue 7
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    Mechanical Properties of Low-temperature Sintered Al2O3/3Y-TZP Composites
    Rao Ping-gen, Wu Jian-qing, Ye Jian-dong, et al
    2004, 32(7):  1-4. 
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    The m(Al2O3)∶m(3Y-TZP)=85∶15 composites were prepared by mixing the high-activity low-temperature sinterable Al2O3 with ZrO2(x(Y2O3)=3%)powders .The powder compacts were then sintered at 1350 ～ 1500 ℃for 2 hours in air .A relative density more than 0 .99 was achieved for the samples sintered at a lower temperature of 1425 ℃.The phase compositions and microstructures of the samples were investigatd by X-ray diffraction and a scan-ning electron microscope ,respectively .The effects of the phase composition and the microstructure on the mechanical properties of the Al2O3/3Y-TZP composites were also studied .The results indicate that the composites sintered at 1 425 ℃is of optimum mechanical properties, that is , a bending strength of 856 MPa , a fracture toughness of 7.4MPa°m1/2 and a Vickers hardness of 16.4GPa . 
    Tensile Strength and Its Prediction Model of Al2O3f+Cf/ZL109 Hybrid Composites at Room Temperature
    Du Jun, Liu Yao-hui, Yu Si-rong, et al
    2004, 32(7):  5-9. 
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    Alumina and carbon short fibers reinforced Al-12Si aluminum alloy ( Al2O3f +Cf/ZL109) hybrid composites were fabricated by squeeze casting .The tensile strength of the hybrid composites at room temperature was experimentally and theoretically analyzed .The rule-of-mixture (ROM)model to predict the tensile strength of the composite was then developed and modified, based on the effects of comprehensive factors on the property of metal-matrix composites, including the length change regularities of the two fibres, the respective tensile beha-vior and mechanism of the two fibres, the dislocation-strengthening resulting from thermal stress and the dispersion-strengthening of the fibres .Furthermore, a new model was established for the prediction of the tensile strength of the hybrid composites at room temperature .The theoretical tensile strength predicted by the new mo-del agrees well with the experimental results .
    PTCR Effect of BaPbO3 Ceramic with Al Electrode
    Li Jing-run Li Zhi-cheng Xu Yong-bo
    2004, 32(7):  10-14. 
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    A series of La-doped ceramics was prepared with the materials of BaCO3-PbO powders in order to obtain the ceramics with high Curie point, low electrical resistivity and PTCR（Positive Temperature Coefficient of Resistivity）．It is found from experiments that as-sintered ceramics are of very low electrical resistivities and show the same conductor feature as metal conductors, that the BaPbO3-based ceramic body with Al electrode displays the PTCR characteristic which can be improved by adjusting the La content．Microstructures of the ceramics were then analyzed by using scanning electron microscopy and transmission electron microscopy．The analytical results reveal that the low resistivity of the ceramic surface layer results from the nanosized BaPbO3 orthorhombic phase which is of metallic properties, and that the ceramic interior is composed of the ferroelectric phase with domain structures, thus causing the PTCR effect in the ceramic body with Al electrode when the surface layer is removed．
    Combat Channel Errors Algorithm Combining Multiple Description Coding and Error Concealment for Video
    Liu Jie-ping Yu Ying-lin
    2004, 32(7):  15-19. 
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    In this paper, the MD-SPIHT algorithm was extended to video sequence, and a combat channel errors algorithm combining MDC（Multiple Description Coding） with ECN（Error Concealment） was presented for v-i deo in order to improve the robustness of the video transmission．In this new algorithm‚the wavelet coefficients are divided into different groups according to their spatia-l temporal relationships after the wavelet transformation, and each group was independently encoded by using the3D-SPIHT algorithm, thus creation multiple description is which are transmitted through multiple independent channels．In addition, every description embedded bit-streams, and this makes it feasible to encode with quality scalability．When the end-user receives few descriptions, a low-quality image can be reconstructed according to the received descriptions‚followed by the recovery of the lost wavelet tree by error concealment method．Simulation tests were finally carried out aiming at multiple sequences, with the conclusion that the proposed algorithm can effectively increase the robustness in video transmission．
    Improvement of a Typical Circuit Unit in Integrated Filters
    Tu Yong-jun Lin Tu-sheng
    2004, 32(7):  20-22,27. 
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    Nonlinear distortion‚one of the primary constraints in filter design and manufacture‚is due to the nonlinearity between the elementary components and the circuit units in filter topological structures．In this paper‚the nonlinearity of a typical circuit unit（Schaumann component） was investigated and the analytical equations of the nonlinearity were deduced．On the basis of which‚an improved circuit of the component was presented．In this circuit‚a symmetrical balanceable structure containing two components is adopted to perform the algebraic addition of output signals‚and the circuit nonlinearity is lessened by the selection of the partial voltage on either of the components‚thus obtaining optimal linearity．These proposed analytical equations are of great use to the nonl-i nearity analysis of the Gm-C filters constructed‚with the circuit units proposed above and their deduced method being applicable to other similar circuits．
    Controllability and Reachability of the Hybrid Dynamic System in Buck Converter
    Hu Zong-bo Zhang Bo Deng Wei-hua
    2004, 32(7):  23-27. 
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    The concepts of hybrid dynamic system (HDS)and switched linear system (SLS)were introduced into studying the controllability and reachability of Buck converter .In this paper , the switched linear system model of Buck converter was first built , and then the controllability and reachability definitions and theorems of the switched linear system with the same systematic matrix and different input matrices were presented according to the characteristics of the switched linear system model for Buck converters .Afterwards, the controllability and reachability of Buck converter was strictly proved based on the switched linear system model .Finally , the relationship among the controllability , reachability and output controllability was discussed and it is pointed out that the three items are in good concordance. Moreover , the controllability of Buck converter was verified by experiments, there by concluding that , with load current step , the output of Buck converter is completely controllable and is kept stable in the designed reference .This is in concordance with the controllability analysis result of Buck converter as a switched linear system model .The proposed method is also adaptable to the investigation of the controllability and reachability of other power converters .
    LU Decomposition of Jacobi Array for Harmonic Elimination PWM Model by FPGA
    Wu Shu-quan Wang Qian Xie Yun-xiang
    2004, 32(7):  28-31,85. 
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    In the solution of the harmonic elimination PWM model for inverted power supply‚the inverse calculation of Jacobi matrix is the main factor affecting the solving speed．In this paper‚to accelerate the solving speed of Jacobi matrix‚the Gausssian elimination was briefly analyzed‚on the basis of which a circuit structure of LU decomposition realized by a two-dimension systolic array was constructed．The structure was then modeled and simulated by VHDL language and its validity was verified by FPGA experiments．The results show that the proposed structure can be used to realize the rapid LU decomposition of the matrix‚thus effectively improving the rea-l time property of the solution of the harmonic elimination model． 
    Shielding Technology to Restrain Computer Information Leakage
    Yu A-i min Lai Sheng-li
    2004, 32(7):  32-35. 
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    Electromagnetic radiation is an important influencing factor of computer information leakage．The technology to enhance the efficiency of electromagnetic shieding is one of the important technologies to resolve the problem of electromagnetic radiation．In this paper‚according to the theory of shield technology‚the electromagnetic performance of common shielding materials was analyzed‚and the shielding efficiencies of iron and tin were analyzed and calculated． Then‚tinning film with high reflection loss and iron with high absorption loss were selected to make a ferrous case film of electrolytic tinning．The shielding test of the case was carried out in an anechoic room in the EMC authentication center of Guangzhou Testing＆Inspection Institute for Household Electrical Appliance．The results show that the ferrous case with a film thickness of only0．18mm can effectively shield the electromagnetic radiation and avoid the imformation leakage of computers．
    An Improved General Test Paper-generating Model and Its Intelligent Algorithm
    Tian Xiang Xiao Ren-yue Xiong Yun-hui Deng Fei-qi
    2004, 32(7):  36-40. 
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    To overcome the common trouble that the papers generated by many test paper bank systems are unsatisfactory to teachers‚the usability of the generated paper was analyzed‚and an improved model was proposed‚which adds in the usability constraints on“avoiding overlapping knowledge points”‚“evenly distributing the question types‚contents‚ and difficulty levels”and“avoiding the repeat of questions in test papers”．Accordingly‚to solve the model‚an intelligent algorithm was presented based on a heuristic index called satisfiability degree．The improved model and its algorithm were used to generate papers for several test paper banks published by the Higher Education Press．The results show that the model is widely applicable to science‚engineering and medicine test paper banks．Moreover‚it completely avoids overlapping knowledge points‚decreases the paper-generating error and the uneven degree of question distribution． 
    Biobleaching of Reed Kraft Pulp with Laccase-mediator System
    He Wei Zhan Hua-i yu Chen L-i hui
    2004, 32(7):  41-46. 
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    Two laccase-mediator systems（LMSA and LMSB） respectively consisted of laccase（EC1．10．3．2） A as well as laccase B and their mediator of1-hydroxybenzotriazole（HBT） were used to biobleach reed kraft pulp which was then extracted with soda．Kappa number and viscosity of the bleached pulps were determined．The results confirm that the LMS biobleaching exhibits excellent delignification selectivity．Higher level of delignification was obtained in LMSB stage than in LMSA stage．UV-Vis absorption spectra of laccases A and B reveal that laccase B contains less aromatic amino acid residues than laccase A does‚which makes laccase B less vulnerable to HBT·attack．So the reaction between HBT·and the residual lignin in LMSB biobleaching becomes easier．This is the reason for the more excellent delignification efficiency of LMSB compared to LMSA． 
    Distribution of Phase Holdups in the Adsorption Process of Activated Carbon Fibers with Fluidization
    Zhang Xiao-ping Chen Shui-xie
    2004, 32(7):  47-50. 
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    The axial distribution of phase holdups in the adsorption process of the sisa- l based activated carbon fibers in various operating conditions was determined by measuring the pressure drop and sampling．The experiments were car-ried out in a three-phase fluidized bed with the height of1200mm and the internal diameter of40mm．The results indi -cate that‚at a certain gas velocity and a liquid velocity‚the gas holdup increases with the increase of bed height‚while the liquid and solid holdups decrease gradually‚and that‚at a certain liquid velocity‚the mixing extent in the bed im-proves with the increase of gas velocity‚while at a certain gas velocity‚the segregation extent in the bed increases with liquid velocity．The obtained results provide a basis for the scale-up and operation of the recovery of noble metals by activated carbon fibers in fluidized beds．
    Preparation of Chloramphenicol Molecularly Imprinted Solid-phase Extraction Cartridge and the Optimization of Extraction Conditions
    Chen Xiao-xia Yue Zhen-feng Zheng Wei-ping Xie Li-qi Liang Shi-zhong
    2004, 32(7):  51-55. 
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     The molecularly imprinted solid-phase extraction （SPE） cartridge of chloramphenicol（CAP） was prepared by adopting molecular imprinting technique‚and its absorption ability as well as desorption conditions was investigated‚on the basis of which the working conditions of SPE cartridge‚including the solvent for CAP‚the rinse and elution con-ditions‚were ascertained．The results indicate that‚compared to the traditional C18cartridges‚the molecularly imprinted solid-phase extraction cartidge is of great advantages‚that is‚it can use methano- l water solution with high methanol content as the rinse solution‚acetonitrile-water solution with40％（volume fraction） acetonitrile as the elution solution‚and it is of a greater cartridge capacity than C18cartridges．All these advantages make it possible to apply the SPE car-tridge to the CAP detection of actual bio-products‚thus resolving the problems existing in the CAP residue detection at present．
    Realization and Performance of Refrigeration System Coupling Adsorption with Absorption
    Zhou Guang-ying Zhu Dong-sheng
    2004, 32(7):  56-59. 
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    To overcome the low refrigeration coefficient in the adsorption and absorption refrigeration cycles and to overcome the high vacuum or high pressure in the adsorption cycle resulted from the single-component working medi -um as the adsorbate‚a new refrigeration cycle coupling adsorption with absorption was developed based on the princi -ples and characteristics of adsorption and absorption cycles．In this new cycle‚13X molecular sieve‚calcium chloride and silica gel are respectively selected as adsorbents‚and the binary components of NH 3 and H 2 O are used as working mediums．The influences of desorption temperature and ammonia content on the coefficient of performance were also analyzed．The results show that‚compared to the single-component working medium‚the coefficient of performance of the binary coupling system is improved by more than2times‚and that the novel refrigeration cycle can run in ambient pressure when the condensation process with vapor desorption is used as the absorption process．This work provides a theoretical basis for developing refrigerators with high efficiency and low cost．
    Investigation into the Transverse Initial Cracking in Cross-ply Laminates
    Zeng Qing-dun Zhang Ning
    2004, 32(7):  60-64. 
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    The transverse initial cracking of the cross-ply laminates in90°ply by the action of the tensile loads in0° ply direction was studied by establishing a layering shear -lag model conjunct with the linear elastic fracture mechanics．The initial failure strains resulting from the thermally residual effect were then obtained．The calculated results are in a good agreement with those of the existing experiments and those obtained by finite element me-thod．The proposed model and methods supply a new way to carry out the failure analysis of fiber -reinforced composite laminate‚and the obtained results provide a theoretical basis for the further analysis of the multiple failure and ultimate fracture of lami -nates．
    Initiation and Propagation Laws of the Glass Cracks in Specimens Subject to Normal Loading by Under the Action of Symmetric Wedges
    Wan Zhen-ping, Liu Ya-jun, Tang Yong, et al
    2004, 32(7):  65-69. 
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    With more and more applications of glass in advanced science fields‚the demand for glass machining preci -sion increases greatly．More and more attention is paid to glass cutting because of high efficiency‚low cost and precise glass parts with various shapes．In order to improve the machining precision of the part surfaces and to facilitate the tooldesign and cutting parameter selection‚the initiation and propagation laws of glass cracks in specimens subject to nor-mal loading by symmetric wedges were investigated．The research results show that the initiation and propagation laws are the same with the interior symmetric wedge angles of30°～120°‚while the laws are different with the interior sym-metric wedge angles equal to or more than150°．The relationship between the medial crack length and the normal load-ing was also investigated when specimens are indented by symmetrical wedges with the interior angles of30°～120°．
    Three-Axis ECM System for Machining Blades
    Shi Xian-chuan Zhu Di Li Zhi-yong
    2004, 32(7):  70-73. 
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    Evolution and Berry Phase of High-spin Particles in a Rotating Magnetic Field
    Hu Lian Yan Yu-zhen
    2004, 32(7):  74-77. 
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    The evolution and Berry phase of the particles with the spin of1／2in a magnetic field can be found direct -ly by Schrödinger equation‚but mathematical difficulties will come forth as to high-spin particles．According to the characteristic that there are energy level spaces among spin particles‚the method of trial wavefunction was adopted to solve the Schrödinger equation describing the evolution of spin particles in a rotating magnetic field with a adiabatic ap-proximation‚thus obtaining the wavefunction of system evolution and the Berry phase of the system after an evolution period．The proposed method is characterized by avoiding high-order differential equations and simplifying the calculation when it is applied to high-spin particles．
    Two Kinds of Solitary Wave Solutions to the KdV-mKdV Equation Obtained by Hyperbolic Function Method
    Zhu Yan-juan
    2004, 32(7):  78-80. 
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    A united hyperbolic function method to find the solitary wave solutions to nonlinear evolution equations was proposed‚and two kinds of solitary wave solutions to the combined KdV-mKdV equation were obtained by this method．As a special example‚two kinds of solitary wave solutions to the mKdV equation can be obtained‚and the bel- lshaped solution to the KdV equation was also given．The proposed method is based on the fact that the solitary wave solutions are essentially of a localized nature．In this method‚the solitary wave solutions to a nonlinear wave equation are denoted as the polynomials of hyperbolic functions‚and the nonlinear wave equation is changed into nonlinear alge-braic equations．So the hyperbolic function method is simple and effective when used to study the solitary wave solu-tions of the nonlinear evolution equation．
    Existence of Multiple Solutions to the Conjugate Boundary Value Problem of the n-th Order Differential Equation with Deviating Arguments
    YangWen-shu Weng Pei-xuan
    2004, 32(7):  81-85. 
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    The existence of multiple positive solutions to a class of （k‚n-k） conjugate boundary value problem of the n-th order differential equation with deviating arguments is investigated．By a transform‚the discussed problem is firstly changed into a fixed-point problem of a completely continuous operator‚and by using the fixed-point index theorem in cones and the evaluation of Green functions‚two group of sufficient conditions are then obtained to guarantee the exis-tence of two positive solutions to the problem．The results are the extension of those of the corresponding boundary val -ue problem for the ordinary differential equation without deviating argument．The applicability of the obtained theorems is proved by an examlpe at last．
    Best Constant in Weighed Sobolev-Hardy Inequality
    Yao Yang-xin Shen Yao-tian Qu Jun-heng
    2004, 32(7):  86-88. 
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    To the weighed Sobolev-Hardy inequality containing a positive constant C‚the main obstacle is that the method used to the case β＝0does not works anywhere when β≠0．That is to say‚when β＝0‚the method of Schwarz symmetrization can be employed‚but there is no reason to believe that the Schwarz symmetrization still diminishes the weighed L p -gradient or increases the weighed L p∗-norm of a function．So another approach must be found to the Sobolev-Hardy inequality．In this paper‚by Bliss lemma‚it is proved that there exists a best constant C such that the weighed Sobolev-Hardy inequality is right．

    Control Analysis of the Tension in Suspenders of a Spatial Tied-arch Bridge
    Li Xin-ping Zhong Jian-cong
    2004, 32(7):  89-92. 
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    Effect of the Freeze-thaw Cycle on the Protein Denaturation of Starry Triggerfish ( Abalistes Stellaris)Surimi
    Zhou Ai-mei Soottawat Benjiakul Zeng Qing-xiao
    2004, 32(7):  93-96. 
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    The effect of the freeze-thaw cycle on the protein denaturation of starry triggerfish surimi was investigated‚with the measurement items of the salt solubility and Ca2＋-ATPase activity of the proteins‚the breaking force‚deformation‚expressible water and whiteness of surimi gels．The results show that the salt solubility and Ca2＋-ATPase activity of the proteins in the white meat surimi and the whole meat surimi decrease as the number of the freeze-thaw cycle increases‚which suggests that the proteins undergo denaturation．The breaking force‚deformation and water -holding ability of the surimi gels also decrease with the number of the freeze-thaw cycle‚except the whiteness．Therefore‚freezing-thawing should be avoided to ensure the prime quality of triggerfish surimi in the production process．
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