Loading...

Table of Content

    25 March 2009, Volume 37 Issue 3
    Previous Issue    Next Issue
    Materials Science & Technology
    Fluorescence Spectra of Zinc Sulfide Quantum Dots/Polyurethane Nano-Composite
    Li Guang-ji Huang Yu-gang Zhu Zu-zhao Luo Wei-ang Chen Xu-dong
    2009, 37(3):  1-5. 
    Asbtract ( 615 )   PDF (329KB) ( 833 )  
    Related Articles | Metrics

    ZnS quantum dots （QDs） sol surface-modified by mercaptopropionic acid （MPA） was prepared via the aqueous-phase method, and ZnS QDs/polyurethane nano-composite membrane was prepared via film casting. Then, ZnS QDs and the prepared nano-composite membrane were characterized by UV-Vis absorption spectra and fluorescence spectra. UV-Vis absorption spectra show that the size of ZnS QDs, which is 3.0nm at the reflux temperature of 70 ℃ according to the Brus model, keeps unchanged after the purification. Fluorescence spectra show that the increase of reflux temperature results in a great improvement of fluorescence intensity of ZnS QDs, that the emission band of ZnS QDs in water at about 400 nm attributes to the trapped emission arising from the radiative recombination of the trapped carriers caused by the Zn vacancies on QDs surface, and that the emission band of ZnS QDs after the recombination exhibits a redshift from 400 nm to 425 nm.

    Photocatalytic Activity of Nano-Polycrystalline Titania
    Zhu Hong-li Chen Ke-fu Qi De-wei Yang Ren-dang
    2009, 37(3):  6-9. 
    Asbtract ( 634 )   PDF (259KB) ( 1396 )  
    Related Articles | Metrics

    Polycrystalline TiO2 was prepared by means of ultrasonic dispersion, with pure anatase and rutile as the raw materials. The effect of crystal phase composition on the photocatalytic activity of the nano-polycrystalline TiO2 was then investigated. In the investigation, XRD was employed to analyze the crystal phase composition and crystal size, and gas chromatography was employed to evaluate the toluene degradation photo-assisted by the nano-polycrystalline TiO2. Experimental results show that, although the photocatalytic activity of the anatase is better than that of the rutile, an appropriate doping of rutile may improve the photocatalytic activity of nano-polycrystalline TiO2 due to the synergistic effect, and that the nano-polycrystalline TiO2 is of the highest photocatalytic activity when the mass ratio of anatase to rutile is 83： 17.

    Research on Flame Retardancy of Intumescent Halogen-Free Flame-Retardant Polypropylene Using Cone Calorimeter
    Liu Fang Sun Ling Luo Yuan-fang Jia De-min
    2009, 37(3):  10-13,18. 
    Asbtract ( 568 )   PDF (327KB) ( 1208 )  
    Related Articles | Metrics

    Intumescent halogen-free flame-retardant polypropylene was prepared respectively according to the in-situ reaction compatibility method and the direct adding method, and the flame retardancy of the product was then evaluated using a cone calorimeter. The results show that the intumescent halogen-free flame-retardant polypropylene is of excellent flame retardancy greatly affected by the preparation methods, and that, as compared with the direct adding method, the in-situ reaction compatibility method may result in more excellent flame retardancy of the flame- retardant polypropylene, namely the ignition time lasts from 23 s to 27 s, the maximum heat-releasing rate decreases from 298 kW/m2 to 249 kW/m2, the average heat-releasing rate decreases from 125.4 kW/m2 to 86. 5 kW/m2, the total heat release decreases from 148.6 MJ/m2 to 124. 5 MJ/m2, the total smoke release decreases from 372 m2/m2 to 266m2/m2 and the combustion residue increases from 27.5% to 33.9%.

    Preparation and Characterization of Inclusion Complex of α-Cyclodextrin and PELA
    Zhao Yao-ming Sun Wei-xiang
    2009, 37(3):  14-18. 
    Asbtract ( 599 )   PDF (309KB) ( 760 )  
    Related Articles | Metrics

    Poly [ ethylene glycol-b- （L-lactide） ] （PELA） was synthesized, with monomethoxypolyethylene glycol （MPEG）, stannous octoate and L-lactide as the materials. The product then reacted with α-cyclodextrin to form an inclusion complex. Moreover, the structure and properties of the complex were characterized by infrared spectrosco- py （IR）, differential scanning calorimetry （DSC）, X-ray diffractometry （XRD） and 1H nuclear magnetic resonance （1H NMR） spectroscopy. It is shown that PELA polymer chains are included inside the molecular tube formed by multiple α-cyclodextrin molecules aligning into close-packed hexagonal crystalline structures, that there is no crystallization and melting behaviors in the complex because the chain motion of PELA is confined by α-cyclo- dextrin molecules, and that the molar ratio of ot-cyclodextrin to the repeating unit of polyethylene glycol block in the inclusion complex is 1 ： 4. 7. In conclusion, PELA is capable of forming inclusion complex with α-cyclodextrin.

    Preparation of Chloroprene Latex Modified with Vinyl Monomers via Emulsion Graft Polymerization and Corresponding Mechanism
    Zhang Kai Shen Hui-fang Zhang Xin-ya Lan Ren-hua Chen Huan-qin
    2009, 37(3):  19-24. 
    Asbtract ( 622 )   PDF (441KB) ( 1774 )  
    Related Articles | Metrics

    Two kinds of vinyl monomers, namely methyl methacrylate （MMA） and styrene （St）, were grafted onto chloroprene latex （CRL） via emulsion polymerization under the action of redox initiator. The effects of the emulsification system, the initiation system, the mass ratio of monomer to polymer, the monomer composition and the reaction temperature on the monomer conversion and the grafting efficiency were then investigated. Moreover, the mechanism of emulsion grafting was analyzed. The results indicate that, in the optimal grafting conditions, that is, a polymerization temperature of 50 ℃, a reaction time of 5.5 h, an initiator （ tea-butyl hydroperoxide/tetraethylenepen- tamine） dosage of O. 5% （based on the dry weight of CRL）, a mass ratio of monomer to polymer of 3： 5, a mass ratio of methyl methacrylate to styrene of 3： 2, and a emulsifier （ sodium dodecylbenzenesulfonate） dosage of 1.5 % （ based on the dry weight of monomers）, the monomer conversion and grafting efficiency of the polymerization with dropwise-added monomers respectively reach 99.6% and 54. 9%. FFIR and gel content analysis confirm that MMA and St are successfully grafted onto the main chain of CRL. The results also show that the adhesive obtained from the graft eopolymer prepared in the optimal conditions is of excellent adhesion properties for PVC leatheroid, SBS rubber and sponge, that the active points of the polymerization locate on the surface of latex particles, and that the grafting process is surface-controlled.

    A Novel Joining-Compounding Technology of 3D Co-Continuous Ceramic Skeleton
    Wang Juan Chen Wei-ping He Zeng-xian Huang Dan
    2009, 37(3):  25-28. 
    Asbtract ( 518 )   PDF (349KB) ( 902 )  
    Related Articles | Metrics

    Based on the screen printing mechanism, a novel process to fabricate the complex-shaped ceramic skeleton of 3D co-continuous ceramic-metal composite was investigated by joining 99% Al2O3 ceramic in the green state with ceramic slurry. The microstructures of the jointing interface were then characterized by means of SEM, and the effect of sintering temperature on the mechanical properties of the skeleton was also analyzed. The results indicate that the hole-blockage of skeleton can be successfully overcome by the new process, and that the skeleton sintered at 1450 ℃ is of the optimal bending strength and an interlayer thickness of about 250 μm at the joint.

    Effect of Y-doping Technology on Properties of Y-BT Ceramics
    Liu Yong Zhuang Zhi-qiang Wang Xin
    2009, 37(3):  29-33. 
    Asbtract ( 554 )   PDF (327KB) ( 1090 )  
    Related Articles | Metrics

    Y-doped nano-crystalline barium titanate （Y-BT） powders were prepared via the heterogeneous-nucleation surface-coating method and the chemical-mixing method, respectively. The prepared powders and the sintered ceramic samples were then characterized by means of differential scanning calorimetry, thermogravimetry, induc- tively-coupled plasma-atomic emission spectrometry and scanning electron microscopy. Moreover, the effect of Y dosage on the room-temperature resistivity of the Y-BT ceramics prepared with different methods was discussed. The results show that, as compared with the Y-BT powders prepared via the chemical mixing method, the powders pre- pared via the coating method have more homogeneous Y distribution, more uniform crystal size and more accurate stoichiometric ratio, and that the corresponding Y-BT ceramic possesses good semiconducting properties at a Y dosage of only 0. 1% and achieves more minimum room-temperature resistivity at a low temperature.

    Preparation and Structural Characteristics of Activated Carbon Composite Enwrapped by Microfibers
    Zhang Hui-ping Gao Lian-lian Yan Ying
    2009, 37(3):  34-37. 
    Asbtract ( 520 )   PDF (252KB) ( 865 )  
    Related Articles | Metrics

    A new kind of activated carbon composite enwrapped by microfibers was prepared via the wet papermaking process and the sintering process, by using bamboo fibers, ceramic fibers and micron-sized activated carbon as the materials. The apparent structure of the composite was then analyzed by means of SEM, finding that the junctures of ceramic fibers are completely sintered together to form a three-dimension network, and that activated carbon is well enwrapped by the microfibrous network. Moreover, the nitrogen adsorption isotherms and pore size distributions of both the original activated carbon and the composite were measured using an ASAP-2020 adsorption apparatus. The results show that the BET specific surface areas of the original activated carbon and the composite are re- spectively 690 m2/g and 428 m2/g, and that the activated carbon enwrapped in the composite keeps a high BET specific surface area of 638 m2/g, which is 92.5% of the original.

    Theoretical Analysis of Filling Process in Metal-Powder Dynamic Injection Molding
    Liu Bin Luo Jie-wen Peng Man-hua Qu Jin-ping Gao Wei
    2009, 37(3):  38-42. 
    Asbtract ( 635 )   PDF (276KB) ( 881 )  
    Related Articles | Metrics

    Based on the continuum theory and the process in metal injection molding is analyzed, and power law model, the effect of vibration field on the filling a physical model and the corresponding mathematical model, which are suitable for the isothermal feedstocks filling a center-gated disk-shaped mold under vibration field, are built. Then, by solving the mathematical model, the equations describing the velocity distribution, the edge posi- tion and the mold entrance pressure in the filling process are deduced. Experimental results indicate that, in the filling process with constant average injection flowrate and vibration frequency, the mold entrance pressure wavelike increases with the vibration amplitude. Moreover, it is found that the theoretical values of mold pressure accord well with the experimental ones, meaning that the theoretical calculation is correct.

    Microwave-Absorbing Properties of La0. 8 Sr0. 2 Mn0. 86 Fe0. 14-x CoxO3
    Bei Cheng-xun Wang Da Yao Ruo-he Li Bin
    2009, 37(3):  43-46. 
    Asbtract ( 515 )   PDF (251KB) ( 967 )  
    Related Articles | Metrics

    La0.8Sr0.2Mn0.86Fe0.14-xCoxO3（ X = O. 01, 0. 02, 0. 03 ） crystal powders were synthesized via the sol-gel method, and the crystal structure of the product was characterized by means of XRD. Then, the complex permittivity and permeability of the product in the frequency range of 2 - 18 GHz were measured using a microwave vector network analyzer. Moreover, the curves describing the relationship between the microwave reflectivity and the frequency were obtained according to the measured data. The results show that, with a thickness of 1.80 mm, La0.8Sr0.2Mn0.86Fe0.13Co0.01O3 is of an absorption peak height of 27. 9 dB and an absorption bandwidth in 2 -18 GHz of 5.3 GHz, while with a thickness of 2.00mm, the height decreases to 26dB and the bandwidth to 4. 9GHz. According to the tangents of both electric loss and magnetic loss angles, the microwave absorption attributes to both the dielectric and the magnetic loss, especially the former. It is also indicated that the doping of Fe and Co changes the double-exchange of Mn^3＋--O--Mn^4＋ system and the electromagnetic parameters of the material, thus improving the microwave-absorbing properties.

    Chemistry & Chemical Engineering
    Numerical Simulation of Heat-Transfer Characteristics of Swirling Impinging Jet with Micro-Aperture
    Wang Chang-hong Zhu Dong-sheng Tu Juan Wang Nan
    2009, 37(3):  47-52. 
    Asbtract ( 639 )   PDF (388KB) ( 1048 )  
    Related Articles | Metrics

    In this paper, the heat transfer of swirling impinging jet is numerically simulated, and the effects of injection aperture, injection distance, swirling angular velocity and flow-field distribution characteristics on the surface heat-transfer coefficient and the average heat-transfer effect are analyzed. The results indicate that, with the same Reynolds number, the average heat-transfer effect of the jet from 3 mm-diameter nozzle is better than that from the 6 mm-diameter one, that the average heat-transfer coefficient of the jet form big-diameter nozzle is more greatly affected by the swirling angular velocity, that the maximum heat-transfer coefficient decreases as the swirling angu- lar velocity increases, with the peak value moving away from the stagnation point, and that the curve of average heat-transfer coefficient becomes more fiat as the swirling angular velocity increases, meaning that the swirling resuits in uniform heat transfer.

    Numerical Simulation of Heat and Mass Transfer in Plate-Type Evaporative Condenser
    Guo Chang-qing Zhu Dong-sheng Jiang Xiang Wu Zhi-fiang Zhang Jing-wei
    2009, 37(3):  53-57. 
    Asbtract ( 582 )   PDF (309KB) ( 2061 )  
    Related Articles | Metrics

    By considering the momentum source term of surface tension as well as the source term of heat and mass transfer in gas-liquid two-phase flow, a computational model based on the Volume of Fluid （VOF） algorithm was established to describe the heat and mass transfer of two-phase falling film in a plate-type evaporative condenser. Then, the model was used to quantitatively analyze the influences of wall heat flux, inlet liquid temperature and air velocity on the temperature distribution and on the relative relationship between the latent heat transfer density and the sensible one at the gas-liquid interface. The results indicate that the temperatures of liquid membrane and air both increase with the wall heat flux, that the temperature gradient is discontinuous at the gas-liquid interface, that the heat transfer at the gas-liquid interface is mainly the latent heat transfer caused by water evaporation and is assisted by the sensible heat transfer caused by the air, that the heat transfer resistance is mainly due to the water membrane, and that the mass transfer improves with the air velocity.

    Heat-Transport Capability of Pulsating Heat Pipes for Microcapsule Fluid
    Wang Shuang-feng Lin Zi-rong Zhang Wei-bao
    2009, 37(3):  58-61,66. 
    Asbtract ( 596 )   PDF (306KB) ( 1538 )  
    Related Articles | Metrics

    A four-turn pulsating heat pipe （PHP） was made from a copper tube with its outer diameter of 2. 5 mm and inner diameter of 1.3mm. The startup characteristics of the PHP were then investigated at various liquid-filling rates of 40% -80%, respectively with 3% FS-39E microcapsule fluid, ethanol and water as the working fluids. Moreover, the effects of working fluid and liquid-filling rate on the heat-transport capability were analyzed. The re- suhs show that the startup of PHP is related to the liquid-filling id, and that, as compared with ethanol and water, 3% FS-39E range of PHP, and particularly high heat-transport capability. at a high liquid-filling rate, the rate, the thermal driving force and the working flumicrocapsule liquid may result in a broader working PHP possesses excellent startup characteristics and

    Utilization of Cryogenic Energy of LNG in Ethylene Cryogenic Separation Process
    Li Ya-jun Yin Hua
    2009, 37(3):  62-66. 
    Asbtract ( 694 )   PDF (348KB) ( 1163 )  
    Related Articles | Metrics

    In the conventional ethylene cryogenic separation process, the compression refrigeration system consumes a lot of cryogenic energy. In order to solve this problem, the cryogenic energy of liquefied natural gas （LNG） is applied to ethylene cryogenic separation process to reduce the compression refrigeration load. Experimental results of a ethylene cryogenic separation system with an annual output of 300kt/a indicate that the utilization rate of LNG cryogenic energy in the separation process reaches 76. 5%, and that LNG provides a cryogenic energy of 22472 kW, which results in a direct compression power saving of 11968 kW and greatly reduces the energy consumption of ethylene cryogenic separation process.

    Analysis of Benzene/Ethanol Extractives from Flesh and Old Eucalyptus urophydis Chips by Py-GC/MS
    Peng Wan-xi Wu Shu-bin Wu Yi-qiang Chen Hong
    2009, 37(3):  67-74. 
    Asbtract ( 719 )   PDF (495KB) ( 873 )  
    Related Articles | Metrics

    The extraction of Eucalyptus urophydis （E. urophydis） wood consumes a lot of bleaching agents and other additives, aggravates the environmental pollution due to wastewater, and causes a great consumption of extractives. In order to solve these problems, Py-GC/MS was used to analyze the main chemical components of benzene/ ethanol extractives from flesh and old E. urophydis chips. The results show that there are 145 compounds in the benzene/ethanol extractives from flesh E. urophydis chip, including 1-phenanthrenecarboxylic acid, 1,2,3,4,4α, 9,10, 10α-octahydro-1,4α-dimethyl-7-（ 1-methylethyl ）-, methyl ester （ 19.49% ）, 3,7-dihydroxy-9-methoxy-1- methyl-6H-dibenzo [ B, D ] pyran- 6-one （ 5.01% ）, 1-phenanthrenecarboxylic acid, 1,2,3,4,4α, 9,10,10a-octa- hydro-1,4α-dimethyl-7-（ 1-methylethyl） （4. 47% ）, ergosta-4,6,22-trien-3β-ol （4. 07% ）, phenol ,2,6-dimethoxy （3. 94% ） , hexadecanoic acid （2. 96% ）, acetic acid （2.86%）, ethanone ,1-（3-methoxyphenyl） （2. 83% ）, phenol ,2- methoxy （2.47%）, germanicol （2. 00% ）, etc. , and that there are 55 compounds in the extractives from old E. urophydis chip, including ergosta-4,6,22-trien-3β-ol （23.33%）, brucine （9.61%）, chol-8 （14）-en-24-ol, （5β） （6.86%）, oleic acid （6. 14% ）, phenol, 2-methyl （5.63%）, 1-mercapto-2-heptadecanone （4. 06% ）, 2,4- dibenzyl-5,8-dimethoxy-6-methyl-l-naphthol （3.86%）, hexadecanoic acid （3.65%）,β-sitosterol （3.12%）, 4- chloro-2-fluoroaniline （2. 29% ）, 9,19-cycloergost-24 （28） -en-3-ol,4,14-dimethyl-, （3β,4α ,5α） （2. 19% ）, 7- heptadecene, 17-chloro （2.09%）, etc. It is indicated that the benzene/ethanol extractives from both fresh and old E. uropydis chips are of potential application prospects in the fields of biological energy, biological medicine, cosmetic, skin care and flavor.

    Preparation and Characteristics of Magnetic Nano-Composite Fiber and Magnetic Paper
    Tang Ai-min Zhang Hong-wei Chen Gang Tian Ying-zi Liu Ying-yao
    2009, 37(3):  75-80. 
    Asbtract ( 561 )   PDF (414KB) ( 1196 )  
    Related Articles | Metrics

    In this paper, first, cellulose/magnetic nano-composite fibers were prepared via in-situ compounding, with spruce fibers as the raw material. Next, the products were characterized by means of XRD, FFIR, SEM and AFM, finding that magnetic particles are compounded mainly on spruce fiber surface and but very little in fiber lumen, with their crystalline form of γ-Fe2O3 and with a diameter of 20 -100nm. Then, the magnetic characteristics of the products were measured by SQUID, showing that the prepared magnetic nano-composite fibers are both super- paramagnetic and ferromagnetic, with a saturation magnetization of 14. 7 emu/g （fiber）. Finally, the magnetic nano-composite fibers were added in a papermaking system in different ways, and a kind of multi-layer composite magnetic paper with orientationally-distributed nano-composite fibers was prepared. As compared with the paper made completely from magnetic fibers, the prepared composite paper is of higher whiteness and strength as well as better magnetic characteristics.

    Fluidization Investigation and CFD Simulation of Medium-Consistency Pulp Suspensions
    Chen Qi-feng Chen Guang-xue Chen Ke-fu
    2009, 37(3):  81-84,99. 
    Asbtract ( 717 )   PDF (345KB) ( 1374 )  
    Related Articles | Metrics

    High shear stress is employed to fluidize medium-consistency （MC） pulp suspensions, and the corre- sponding fluidization motion is investigated. The results indicate that the energy in the fluidization process dissipates in the form of heat, which may result in the temperature rising of pulp suspensions, that the fluidization of MC pulp suspensions exhibits turbulent flow of smaller floes, possessing the dynamic characteristics of Newtonian fluid, and that there exists dynamic coupling and balancing between the floeculation and dispersion of fibers. A CFD simulation of the fluidization process of MC pulp suspensions is finally performed based on the Eulerian multiphase flow model and the Reynolds time average-based hybrid turbulent model. The simulated results accord well with the experimental ones.

    Performances of PAN/PS Blend Membrane Under Action of Electric Field
    Xiao Kai-jun Yuan Liang Liu Wen-shan Li Lin Zhou Xian-hong Yin Yu-rong
    2009, 37(3):  85-89. 
    Asbtract ( 588 )   PDF (313KB) ( 874 )  
    Related Articles | Metrics

    The separation performances of polyacrylonitrile/polysulphone （PAN/PS） blend membrane under the action of an external DC electric field were investigated by measuring the membrane flux, the retention rate as well as the decline and recovery of the flux, with bovine serum albumin （67000 in relative molecular mass） as the ultra- filtration object. The results show that both the flux and the retention rate of the blend membrane increase in an ex- ternal positive electric field, that the flux and the retention rate increase respectively by 85% and by 1.1% in ＋ 120V/cm electric field, that the flux decreases from 57. 14% to 26. 33% in ＋60V/cm electric field, and that the flux recovery rate reaches more than 90% due to the self-cleaning by electric field. It is thus concluded that an external electric field may improve the separation performances and increase the flux, retention rate and anti-fouling property of the blend membrane.

    Effect of Hydrochloric Acid in Organic Alcohol on Properties of Potato Starch
    Luo Zhi-gang Xie Xian-hua Xu Zhong-yue
    2009, 37(3):  90-93，98. 
    Asbtract ( 557 )   PDF (357KB) ( 1086 )  
    Related Articles | Metrics

    Potato starch was modified by hydrochloric acid, respectively with anhydrous methanol, ethanol, 2-propanol and 1-butanol as the solvents. The physicochemical properties of potato starch before and after the modification were then investigated. The results show that, with the increase in carbon atom number of the organic alcohols from methanol to 1-butanol, fissures occurring on the surface of acid-modified starch granules develop into frag- ments, and the freeze-thaw stability, the viscosity and the swelling ratio all decrease, but the transparency and the solubility increases. It is thus concluded that the sensitivity of potato starch to acid hydrolysis increases with the carbon atom number of the organic alcohols from methanol to 1-butanol.

    Architecture & Civil Engineering
    Development of Digital Monitoring System of Strong Motion for Long-Span Bridges
    He Zhi-yong Lan Yan-liang Dai Shao-ping
    2009, 37(3):  94-98. 
    Asbtract ( 586 )   PDF (345KB) ( 1125 )  
    Related Articles | Metrics

    Both the observation of strong motion of bridges and the vibration monitoring of bridge structures help to reach the final goal of reducing the earthquake disaster. In this paper, based on the earthquake response analyses of cable bridges, the scheme of a digital strong-motion monitoring system for long-span bridges is investigated in terms of the choice of monitoring sections, the main technical indexes, the early-warning system of strong motion, the data processing of observed strong-motion data and the submission of reports, etc. The proposed system not only offers accurate and quantitative ground acceleration data for post-earthquake relief and structural seismic design codes but also provides an effective means for avoiding the earthquake disaster, revealing the working state and removing the hidden danger of bridges.

    Decision-Making Model for Bridge Inspection and Maintenance Based on Benefit Maximization
    Han Da-jian Pan Ling
    2009, 37(3):  99-103. 
    Asbtract ( 598 )   PDF (341KB) ( 728 )  
    Related Articles | Metrics

    In this paper, a dynamic model to determine the inspection and maintenance strategy of bridges is set up based on Bayes analysis method. The proposed model follows the process from information collection to data analysis and further to decision-making. It provides more sufficient data for the decision-making by combining the prior information with the inspection results. The authors also make an example analysis considering two inspection methods and four maintenance schemes, and determine the best inspection time and scheme to maximize the net inspection benefit in a benchmark period. Finally, the best maintenance scheme for the possible inspection results is determined based on the principle of minimizing the maintenance cost.

    Seismic Response Control of Self-Anchored Suspension Bridge with Viscous Dampers
    Song Xu-ming Dai Gong-lian Zeng Qing-yuan
    2009, 37(3):  104-108,113. 
    Asbtract ( 602 )   PDF (382KB) ( 1200 )  
    Related Articles | Metrics

    By taking the Sanchaji Xiangjiang bridge as is established based on the seismic dynamic equation the research object, a spatial nonlinear finite element model of bridge. The proposed model is then used to analyze the effects of the parameters and location of viscous damper on the mitigation to seismic response of self-anchored suspension bridge. The results indicate that the longitudinal displacements of the girder and the pylon top as well as the longitudinal moment of the pylon bottom are quite great under the action of earthquake, that appropriate damper parameters help to effectively reduce the displacement and internal force of the bridge, that the installation position of the damper greatly affects the seismic response, and that the variations of internal force and displacement in different control sections should be fully considered in the installation of viscous dampers.

    Buckling of Corrugated Steel Web in Composite Box-Girder Bridge Under the Action of Eccentric Loading
    Shan Cheng-lin
    2009, 37(3):  109-113. 
    Asbtract ( 653 )   PDF (323KB) ( 1219 )  
    Related Articles | Metrics

    A spatial finite element model of prestressed-concrete composite box-girder bridge With corrugated steel web is established. The model is then used to analyze the effects of dimension parameters of the steel web on the critical buckling load coefficient and buckling mode of the web under the action of bending-torsion coupling action. The results indicate that the buckling of corrugated steel web under the action of mid-span eccentric loading always happens on the loading side, that the increment of anti-buckling capability of the steel web for the box-girders with different height-span ratios basically keeps unchanged when the corrugation angle of steel web is less than 20°, but increases with the corrugation angle when the angle is more than 20° and when the height-span ratio decreases, that the anti-buckling capability of the steel web with different thickness increases with the corrugation angle, the increment increasing with the angle when the angle is more than 20° and when the web thickness increases, that the increments of anti-buckling and anti-torsion abilities are basically consistent for the box-girders with different heightspan ratios at a certain corrugation angle and a increasing thickness, and that the anti-torsion capability of box-girder significantly decreases with the height-span ratio when the corrugation angle is less than 20° but linearly increases with the ratio when the angle is more than 20°..

    Fatigue Damage of Reactive Powder Concrete
    Yu Zi-ruo An Ming-zhe
    2009, 37(3):  114-119. 
    Asbtract ( 606 )   PDF (382KB) ( 757 )  
    Related Articles | Metrics

    In order to reveal the fatigue damage mechanism and to establish a fatigue damage model of reactive powder concrete, axial equiamplitute pulsating loads are imposed to reactive powder concrete prism specimens, and the failure pattern and macro-crack evolution of the specimens at four different stress levels are observed. Then, the development of longitudinal strain with the loading is measured. The results show that the fatigue damage of reactive powder concrete develops from a nucleation stage to a stable stage and further to an instability stage, and that there is no macro-damage till the cyclic number of load exceeds a threshold. Moreover, a damage variable is defined according to the cumulative residual plastic strain, and some fatigue damage curves are plotted according to the experimental data. Finally, based on the theory of damage mechanics, a fatigue damage model of reactive powder concrete with simplicity and rationality is established for engineering application, with its parameters being also determined.

    Fire-Resistant Performance of High-Strength Concrete Columns with Different Decorative Materials
    Wu Bo Li Jie Huang Yu-long Wang Fan
    2009, 37(3):  120-126,131. 
    Asbtract ( 565 )   PDF (528KB) ( 1013 )  
    Related Articles | Metrics

    Eight high-strength concrete columns with different decorative materials were tested following the ISO834 standard heating process, and the influence of decorative materials on the explosive spalling of concrete was discussed. Then, the internal temperature fields of the specimens were analyzed, and the results were finally compared with the measured ones. It is indicated that, with the addition of decorative materials, the explosive spalling of concrete delays but the spalling becomes more serious, that two-layer insulation plates significantly prevent high- strength concrete from explosive spalling, and that, by converting decorative materials into equivalent concrete, the influence of decorative materials on the temperature field in specimen section can be well revealed.

    Application of Conjugate Gradient Method to Parameter Identification of Dirichlet Series of BP2 Model
    Huang Juan Zhou Jian-chun
    2009, 37(3):  127-131. 
    Asbtract ( 573 )   PDF (281KB) ( 1087 )  
    Related Articles | Metrics

    This paper investigates the parameter identification and fitting methods for large-scale structures to predict the concrete creep in an exponential form. In the investigation, first, the international standard BP2 model of concrete creep is employed to construct a common degenerate-kernel Dirichlet series as the basis function. Next, in view of the fact that the actual parameters are more than the unknown variables in the fitting process, the least square method is used to transform the inconsistent equation group into a normal one. Then, the normal equation group is solved by means of the conjugate gradient method. Finally, based on the presented techniques, program is worked out to identify the parameters of Dirichlet series of BP2 model. It is found that the fitted results accord well with the original ones, the relative error being less than ± 3 %. The recommended Dirichlet series of BP2 model is suitable for the tracking and analysis of long-term creep behavior of large-scale structures. Also, it provides a reference for the performance evaluation of existing structures.

    Traffic & Transportation Engineering
    Optimization of New Airport Location and Airline Rate Considering Suppliers＇ Profit and Users＇ Utility
    Yang Zhong-zhen Wang Lu Chen Gang
    2009, 37(3):  132-137. 
    Asbtract ( 450 )   PDF (407KB) ( 1134 )  
    Related Articles | Metrics

    In this paper, first, the airport choice behavior of users and the airline rating strategy of suppliers are analyzed. Next, based on the theory about users＇ choice of service facilities and a road-railway integrated network, a model to calculate the probability of airport choice is constructed, and a model to estimate the total market share of regional air transport is built by extending the model for a single airline. Then, for the purpose of minimizing the total cost of regional air transport, the models of airport choice and market share estimation are combined to estab- lish the models of new airport location and the corresponding airline rate considering the mutual benefits to suppliers and users. Finally, the data from Liaoning province are used to make a test. The results show that the proposed models accurately illustrate the interaction between the airport choice behavior and the market share of airport, and that they help to determine the location of a new airport and the corresponding average airline rate maximizing both the income and the market share.

    Automatic Matching of Image Feature Points of Accident Vehicle
    Tao Ze-ming Pei Yu-long
    2009, 37(3):  138-143. 
    Asbtract ( 557 )   PDF (380KB) ( 1099 )  
    Related Articles | Metrics

    As the common automatic matching is difficult to meet the requirements of stereo matching for traffic accident investigation, a new automatic matching method of image feature points of accident vehicle is proposed, and the corresponding model is established based on the SIFY theory and the BP neural network. Some experiments are then performed to verify the proposed model. The results show that the proposed method is suitable for the automatic matching of any selected object in a stereopair, and the matching results can be used as a reference to the precise matching. It is also indicated that the proposed method greatly improves the efficiency of stereo keypoint selection and accelerates the measurement in stereovision system. Moreover, as an efficient technology, it provides a reference for the identification of vehicles with covered license.

    Car-Following Model Based on TSK Model
    Tao Cheng Huang Sheng-guo
    2009, 37(3):  144-148. 
    Asbtract ( 607 )   PDF (327KB) ( 1143 )  
    Related Articles | Metrics

    In order to improve the calibration accuracy of the traditional car-following model based on fuzzy reasoning, this paper proposes a new model based on the TSK model. In this model, an improved genetic algorithm-based learning algorithm is adopted for the identification of TSK model, and the situation with insufficient sub-group data point is specially considered. Moreover, some real car-following data are collected by GPS for the establishment and validation of the TSK model. It is found that the experimental results accord well with the theoretical ones, and that the accuracy increases by one order of magnitude, meaning that the application of TSK model to the car-following model is feasible.

News
 
More>>
Featured Article
More>>
Most Read
More>>
Most Download
More>>
Most Cited
More>>
Links
More>>