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15 October 2003, Volume 24 Issue 10 Previous Issue    Next Issue
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Synthesis of PB-g-SAN elastomer and its toughening behavior for SAN resins Zhang, Ming-Yao (1); Zuo, Liang (1); Xu, Xin-Feng (2); Zhang, Hui-Xuan (2) 2003, 24 (10):  919-922.  DOI: - Abstract ( 205 )   HTML   PDF (178KB) ( 790 )   A series of PB-g-SAN elastomers in which the polybutadiene (PB) content is 40% were synthesized using seed emulsion polymerization technique to graft-copolymerize styrene and acrylonitrile onto PB latex rubber particles. The effects of tert-dodecyl mercaptan (TDDM) content in monomer mixture on the grafting behavior of styrene-acrylonitrile (SAN) copolymers and the morphology and dynamic mechanical properties of elastomers were studied. It was found that the grafting degree and efficiency of SAN copolymer decrease and the size of SAN glassy sub-inclusions distributed in PB particles increases but the low temperature dynamic shear modulus of elastomer decreases with the increase of TDDM content. In a series of SAN resins blended with the elastomers particles, the increase in toughness of the blends is found more efficient when introducing TDDM into monomer mixture in the process of PB-g-SAN synthesis. References | Related Articles | Metrics

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Mathematical model for cooling control of medium plates Cai, Xiao-Hui (1); Zhang, Dian-Hua (1); Xie, Feng-Guang (2); Wang, Guo-Dong (1) 2003, 24 (10):  923-926.  DOI: - Abstract ( 231 )   HTML   PDF (231KB) ( 972 )   The model showed by the topic was introduced including a difference expression and some models for heat transfer coefficient air/water cooling specific heat and heat conductivity. Applying the finite difference method to the simulation of cooling process, the temperature field along the thickness/width of plate was calculated, as well as the effect of intermittent cooling on the result of cooling control. Simulating results show that the re-reddening time and temperature gradient along thickness increase with plate thickness and the inner temperature of plate decrease evenly if cooling intermittently, with plate surface continuously cooled and re-reddended. The on-line applications revealed that the model can get high accuracy in calculation to meet actual requirements in production. References | Related Articles | Metrics

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Study on compositely bonded magnets Chang, Ying (1); Lian, Fa-Zeng (1); Yu, Xiao-Jun (2) 2003, 24 (10):  927-930.  DOI: - Abstract ( 217 )   HTML   PDF (168KB) ( 559 )   The composite effect of the hybrid magnets bonded by nanocrystalline Nd2Fe14B/Fe3B with ferrite powders was studied, as well as the influence of its variations in magnetic properties, temperature coefficient βjHc of intrinsic coercive force jHc and thermal stability and the composite effect itself on its density and compressive strength. The results show that the composite effect makes its temperature coefficient βjHc and irreversible loss hirr decrease with the thermal stability improved. The effect of the content of ferrite on its magnetic properties at 100°C shows that the remanence Br and maximum magnetic energy product(BH)m decrease but the intrinsic coercive force jHc increases obviously. The composite effect affects its magnetic properties and density obviously but affects compressive strength slightly. References | Related Articles | Metrics

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Effect of HDDR process on properties of Nd2Fe14B-Based Magnetic Powders Fu, Meng (1); Lian, Fa-Zeng (1); Wang, Ji-Jie (1); Yang, Hong-Cai (1) 2003, 24 (10):  931-934.  DOI: - Abstract ( 427 )   HTML   PDF (195KB) ( 905 )   The HDDR (Hydrogenation-disproportionation-desorption-recombination) is a special process to produce Nd2Fe14B -based permanent magnet powder. The effects of HD and/or DR temperature on the properties of high performance Nd-Fe-B magnet powders produced by HDDR process were investigated, with X-ray diffraction (XRD) used to analyze the phase component of the alloy in various treating conditions. The results show that the magnetic properties of the Nd-Fe-B powders are sensitive to either HD or DR temperature and adding the alloying elements Ga and Al into them can improve their magnetic properties. Although the remanence of magnetic powders will be improved by way of eliminating the harmful α-Fe phase, the phase can not be eliminated completely by homogenizing treatment. The major phase Nd2Fe14B is decomposed into three phases, i.e., α-Fe, NdH2 and Fe2B, during HD stage, then the major α-phase grain size becomes finer after DR stage, about 0.28 μm as calculated. References | Related Articles | Metrics

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Preparation of boron carbide by magnesium reducing-SHS Zhang, Ting-An (1); Dou, Zhi-He (1); Yang, Huan (1); Ding, Qian-Li (1) 2003, 24 (10):  935-938.  DOI: - Abstract ( 265 )   HTML   PDF (225KB) ( 1036 )   It was suggested that B4C micropowder would be produced by self-propagating high-temperature synthesis (SHS), with taking B4O and C raw materials and Mg powder as reducing agent, which has many advantages such as simple process, high purity and fine granularity of product. The adiabatic temperature of the B2O3-Mg-C reaction system was calculated in order to verify the feasibility of the SHS reaction. The results of X-ray diffraction analysis of the products show that B4C will be gained through SHS and there is little C in the product. It is found that the B4C grain is very fine by SEM, and it is observed that in B4C powder the single crystal is fully growing together with incompletely growing polycrystal by electronic diffraction patterns. Purity of B4C is shown not lower than 98% by spectrum analysis, while it is slightly lower by chemical analysis. Special attention is paid to the reaction mechanism of SHS. References | Related Articles | Metrics

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Effect of additives on particle size and strength of aluminum hydroxide decomposed with seed crystal used Zhao, Su (1); Bi, Shi-Wen (1); Yang, Yi-Hong (1); Xie, Yan-Li (1) 2003, 24 (10):  939-941.  DOI: - Abstract ( 310 )   HTML   PDF (201KB) ( 1058 )   In the decomposition process of sodium aluminate solutions with seed crystal added into it, first relevant additives can play an important role in improving the particle size and strength of product, i.e., aluminate hydroxide. The additives used were divided into two kinds: one was used to increase the product's particle size, including the additives H1, F, I and G, the other was to improve the strength, including L, I, F, G, H2, H3 and H5. The relationship between the particle size and strength of the product was investigated. The results show that the higher the percentage of number of particles with size from 45 to 105 μm is, the higher the strength will be, as well as more even particle distribution. The mechanism of additives as discussed revealed that on the surface of A1(OH)3 particles the oleophilic group of surface active agent will form oil films to bind together fine A1(OH)3 particles closely so as to increase both the particle size and strength. References | Related Articles | Metrics

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Investigation on copper removal from molten steel in vacuum Yan, Li-Yi (1); Pei, Li-Miao (1); Li, Guang-Tian (1) 2003, 24 (10):  942-944.  DOI: - Abstract ( 260 )   HTML   PDF (126KB) ( 565 )   The investigation was done through thermodynamic analysis and orthogonal designed lab tests to determine the optimal conditions for copper removal from molten steel on the principle of vacuum metallurgy. The effects of vacuum tightness, copper removal reagents selected and their amounts, melting temperature and removing duration on the removal rate were studied. The results show that adding such reagent as either MgO or CO(NH2)2 into molten steel can remove copper obviously to the criterion w(Cu)<0.2% which most of steel grades require. However, by a comparison made for copper removal rates, CO(NH2)2 is better than MgO under the same conditions. The removal rate will increase greatly with the increase of reagent amount, removing duration and melting temperature. Copper can be cleaned out best in steel if in a 40 min removing duration 0.7% of CO(NH2)2 is used as copper removal reagent. Based on the lab test, an industrial test scheme was envisaged preliminarily. References | Related Articles | Metrics

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Measurement of turbulence velocity of dust in a 20 L-Sphere Li, Xin-Guang (1); Zhang, Ping (1); Radandt, S. (2); He, Ji-Cheng (3) 2003, 24 (10):  952-955.  DOI: - Abstract ( 369 )   HTML   PDF (113KB) ( 753 )   A 20 L-Sphere, as one of the typical measurement set-ups, was used to measure and test the parameters of dust explosion characteristics. In respect to both the characteristic parameters and the violence of dust explosion, the RMS turbulent velocity plays an important role. So, a Laser-Doppler anemometer was applied to the measurement and testing of the velocity of dust particles in a 20 L-Sphere, with all the resulting data processed and discussed. The time-dependent curves of RMS turbulent velocity of dust particles at different positions were therefore obtained, thus providing data for the comparison between minimum ignition energies at different apparatus and also providing a basis for the verification of mathematical models of dust explosion. Such RMS values will benefit applying the data measured to industrial uses. References | Related Articles | Metrics

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Experimental analysis on vibration of rotor system with oil-film instability fault Han, Qing-Kai (1); Ren, Yun-Peng (1); Liu, Ke (1); Wen, Bang-Chun (1) 2003, 24 (10):  959-961.  DOI: - Abstract ( 333 )   HTML   PDF (110KB) ( 1435 )   Experiments were carried out to investigate the oil-film instability fault behaviors, including oil-film whirling and oscillating, on a special-designed test rig for single-span rotor system. The rotor shaft vibration responses were measured in the processes of both stable and speed up-down running. When the oil-film is oscillating, in the time-domain the rotor vibration is featured with complex multi-period and the center routes of rotor shaft are all of irregularly diffused curves. The sub-frequency, i.e. , 0.44 times the frequency, is shown obviously in both the power-density and holographic spectra. An analysis of time-frequency domain when the rotor running up and down, as indicated by 3-D frequency spectrogram and time-frequency indexing chart, revealed the progress how a rotor oil-film changes from whirling to oscillating state. Results of the experiment and analysis are of importance to further study on the faults due to oil-film instability and the implementation of monitoring and predicting of rotating machines. References | Related Articles | Metrics

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On the pedestal looseness of dynamic oil film-rotor system Zhang, Jing (1); Li, He (1); Wen, Bang-Chun (1) 2003, 24 (10):  962-965.  DOI: - Abstract ( 176 )   HTML   PDF (185KB) ( 646 )   With a nonlinear non-steady oil-film force model newly developed by Zhang Wen et al for short bearings, the complicated motion of rotor-bearing system with pedestal loosened on one side was analyzed using numerical simulation and other methods. The motion in periodical, quasi-periodical and chaotic forms in the system, which take place while the speed ratio changes, was discussed. The results show that a triple-frequency motion is found even though in the higher speed range if a pedestal is loosened in the system. Moreover, peculiar moving path of loosened journal center and phase path of slightly shaking pedestal is found. A theoretic base is thus provided to diagnose effectively the fault of pedestal looseness in a rotor-bearing system. References | Related Articles | Metrics

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Reliability design of vehicle axles on Bayes Wang, Tie (1); Zhang, Guo-Zhong (1); Zhou, Shu-Wen (1) 2003, 24 (10):  966-969.  DOI: - Abstract ( 254 )   HTML   PDF (173KB) ( 737 )   Reliabilities of force condition analysis of vehicle axles and Bayes statistics are both discussed with the intention of determining the axle diameter on given reliability basis and vice versa, the posterior expectation of Bayes statistics is simplified in order in sequence: (1) converting the non-normal distribution into equivalent normal one by use of conventional approaches to reliability; (2) calculating the prior and posterior parameters of normal distribution by use of the characteristics of exponent group in conjugate distribution; (3) getting numerical solutions with very high convergence by use of symbolic integration by substitution and Newton-Ralphson iteration method. The solution is verified through an instance. The algorithm is implemented on computer with VB programming, thus avoiding out-of-date methods and rationalizing conventional design procedure. In particular the method proposed here applies to the personalized/specialized designs to which the classical statistics method is unavailable, and it may provide more accurate solutions than traditional methods for those designs which will be changed frequently or poor in either experimental or in-site data. References | Related Articles | Metrics

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Experimental investigation on nonlinear vibration characteristics of rotor-bearing system with rub-impact fault Liu, Chang-Li (1); Yao, Hong-Liang (1); Zhang, Xiao-Wei (1); Wen, Bang-Chun (1) 2003, 24 (10):  970-973.  DOI: - Abstract ( 286 )   HTML   PDF (260KB) ( 925 )   An experimental setup was developed to investigate nonlinear vibration characteristics of rotor bearing system with rub-impact fault. It is found that in a system where the effect of oil film force is comparatively small, the rub-impact action will cause the system to form sub-and super-harmonic vibration components, whereas in a system supported by sliding bearings a lot of super-harmonic vibration components will form because the very thin clearance between rotor and stator causes them to rub and impact each other before oil film whirl. In case the clearance is comparatively thick, they will rub and impact each other after oil film whirl and the rub-impact effect will be very small on the system at that moment with a maximum effect of oil film force in bearing on the system. References | Related Articles | Metrics

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Experimental investigation on permeability evolution of brittle rock in failure process Yang, Tian-Hong (1); Xu, Tao (1); Feng, Qi-Yan (2); Tang, Chun-An (1) 2003, 24 (10):  974-977.  DOI: - Abstract ( 203 )   HTML   PDF (188KB) ( 1055 )   A large number of permeability tests of different brittle rocks were conducted using an electro-hydraulic servo-controlled MTS 815.02 testing machine to investigate the permeability evolution characteristics of brittle rock in compressive deformation and failure process corresponding to the complete stress-strain path. Laboratory tests show that the permeability of brittle rock relates closely to the state of stress in rock and the permeability of brittle rock in post-peak stress-strain region is much higher than that in pre-peak stress-strain region. Moreover, the sharp increase or sudden jump of permeability frequently occurs in the post-peak stress-strain region due to the catastrophic changes of microstructure of rock in compression. Based on the experimental results of permeability evolution tests for different brittle rocks, the piecewise stress-permeability fitting curves for brittle rocks in compression were obtained to offer reliable experimental evidence for the numerical model of coupled stress-permeability regarding the permeability evolution of brittle rock in compressive failure. References | Related Articles | Metrics

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Coupling effect of bidirectional earthquake on multi-storey structures on isolated frictional base Gu, Wei (1); Li, Yi (1); Liu, Bin (1) 2003, 24 (10):  986-989.  DOI: - Abstract ( 254 )   HTML   PDF (173KB) ( 412 )   A kinematic differential equation and criterion to discriminate sliding from joggling state were developed by virtue of an interstorey shearing model with multi-degree of freedom considered for those multi-storey masonry structures which are built on an isolated frictional base and under the action of earthquake in both horizontal and vertical directions, which a numerical analysis is made to the influence of vertical action on earthquake-isolated structures. The results show that the vertical action enables the lower storeys especially the ground or 1st storey to displace. Thus, the interstorey shear and displacing acceleration will increase and go on further with the higher peak value of vertical acceleration when the earthquake intensity is increasing. It is also possible that the sliding displacement amplitude will increase then. So, it is highly recommended that the influence of vertical earthquake action on such structures shall be taken into account in high-intensity earthquake regions. References | Related Articles | Metrics

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Hybrid genetic algorithm for optimum design of building structures Zhang, Yan-Nian (1); Liu, Bin (1); Guo, Peng-Fei (2) 2003, 24 (10):  990-993.  DOI: - Abstract ( 245 )   HTML   PDF (243KB) ( 1437 )   A hybrid genetic algorithm (HGA) composed of the standard genetic algorithm (SGA) and unidirectional searching algorithm (USA) is proposed, taking their advantages of time saving, high efficiency and powerfully local searching capability of USA, as well as the global searching capability of genetic algorithm (GA). The results by exemplification show that this method can not only be used directly to work out the optimum structural design with discrete variables to constrain both stress and cross-section area but deal with the discrete structural optimization featured with multi-loading, multi-constraints and multi-variables. HGA, as an efficient optimal method having advantages of both SGA and USA without their disadvantages, is superior to either one. References | Related Articles | Metrics

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Polyphenal composite placed in site as new thermal-insulation roofing Zhao, Gang (1); Zhu, Fu-Sheng (1); Zhou, Qing (2); Ma, Bin (3) 2003, 24 (10):  994-997.  DOI: - Abstract ( 258 )   HTML   PDF (164KB) ( 726 )   A cellular polyphenal composite was picked out as a new thermal-insulation roofing that shall be placed in site after a series of investigations including such factors as choice of raw materials, work process, techno-economical assessment, environment friendly requirement and energy saving. The new roofing process can combine the thermal insulation together with sloping layer even combine the insulation, leveling layer, sloping layer with air gapping layer, thus not only simplifying the roof construction and work process but making the roof better at thermal insulation properties with reasonable cost. The commercial applications revealed that the new processing could save about half of the cost. References | Related Articles | Metrics

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- - 2003, 24 (10):  998-1001.  DOI: - Abstract ( 243 )   HTML   PDF (283KB) ( 874 )   - References | Related Articles | Metrics

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- - 2003, 24 (10):  1002-1005.  DOI: - Abstract ( 271 )   HTML   PDF (194KB) ( 1028 )   - References | Related Articles | Metrics

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- - 2003, 24 (10):  1006-1009.  DOI: - Abstract ( 214 )   HTML   PDF (178KB) ( 717 )   - References | Related Articles | Metrics

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- - 2003, 24 (10):  1010-1013.  DOI: - Abstract ( 217 )   HTML   PDF (185KB) ( 675 )   - References | Related Articles | Metrics

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- - 2003, 24 (10):  1014-1017.  DOI: - Abstract ( 181 )   HTML   PDF (190KB) ( 829 )   - References | Related Articles | Metrics

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- - 2003, 24 (10):  1018-1020.  DOI: - Abstract ( 275 )   HTML   PDF (148KB) ( 592 )   - References | Related Articles | Metrics