Advanced Materials Research Vols. 217-218

Abstract: Water absorbing and releasing property of lightweight aggregate (LWA) in concrete and its influence on microstructure of interfacial zone as well as frost-resistance of combined aggregate prepared with different water absorption LWA and w/b ratios were investigated. The results show that, as for concrete with low w/b ratio, the 28d frost-resistance of concrete prepared with high water absorption LWA is worse, however with the increase of curing age, the 90d frost-resistance of concrete improves obviously, which is due to the water releasing of LWA that leads to the recovery of its air entraining effect as well as the densification and thicken of interfacial zone. So the LWA with moderate water absorption should be selected to prepare the low w/b ratio concrete. As for concrete with high w/b ratio, the frost-resistance of concrete prepared with low water absorption LWA is the best. This is account for the dense shell of ceramsite that could reduce the soakage from loose cement paste under frozen pressure.

Abstract: A new SVM (Support Vector Machine) classifier-combination model, based on Hierarchical Partition approach, for enterprise credit assessment is proposed in this paper. Enterprise credit assessment is essentially an ordinal classification (or ranking), and the popular multi-classification technique does not deal with the ordinal information in the sample data. Hierarchical Partition approach makes use of the ordinal characteristics to simplify the structure of classifiers, as well as to decrease the training and testing time. It can also be used to solve the problems where the imbalance sample distribution and different loss-costs among different ranks present. Experimental results show that the generalization ability of the new model using Hierarchical Partition approach are better than that of neural network model and traditional 1-vs-1 combined SVM model.

Abstract: In order to solve the problem of collision in engineering field, the dynamic equation of collision system was established based on FEM(finite element method) and contact element model. The present method can account for the influence of the nonlinear contact stiffness as well as the energy loss during collision process. Collision had been simulated using FEM and MSM(mode superposition method) separately with various contact stiffness, sphere masses and impact velocities. The results indicate that FEM can be used to solve the problem of collision. The two groups of time history curves of contact load have almost the same shape. Compared with the results by MSM, collision durations are relatively decreased by about 7%, and difference of peak value is no more than 4%. The method can be used for collision between two complex structures with nonlinear reaction. So, it has a wider application to simulation of collision damage in engineering field.

Abstract: According to a test for chloride ion erosion in concrete under designed manual climate environment, distributions of chlorine ion concentration in pure bending concrete of short-chopped basalt fiber RC beam and check RC beam without fiber with different flexural loads are analyzed in this paper, and diffusion coefficients of compression and tensile concrete are fitted on the basis of Fick’s second law. Analysis results show that erosion-resisting properties for chloride ion of the basalt fiber compression and tensile concrete in the pure flexural region are increased

Abstract: Chitosan has prompted the continuous impetus for the development of safe and effective drug delivery systems because of its unique physicochemical and biological characteristics. In this study, PEG-chitosan microspheres loaded with levofloxacin for carrying drugs were prepared by the emulsion cross-linking method. The effect of drug process, the emulsifier, the amount of crosslinking agent, stirring speed, temperature, crosslinking time on the prepare experiment were studied. The effect of the quantity of chitosan and PEG, the mass ratio of chitosan and levofloxacin on the drug loading and release ability were studied in drug release experiments too.

Abstract: a novel fibrous catalyst containing palladium nano-particles was produced via electrospinning technique. The fibrous catalyst was characterized by scanning electron microscopy and transmission electron microscopy respectively, the results showed that the diameter of fiber was about 200 nm and the palladium (Pd) particles were in the range of 30~40 nm. The catalyst was tested in hydrogenations of α-olefins, cyclohexene and nitrobenzol in ethanol at room temperature under 1 atmosphere hydrogen. The results showed that the titled catalyst had high activity in the hydrogenations of α-olefins, cyclohexene and nitrobenzol.

Abstract: The infiltration corrosion characteristics of concrete have been studied by determining the seepage coefficient and CaO and SiO2 dissolutions of concrete. The results show that, under the infiltration corrosion of soft water, the infiltration coefficient of concrete decreases gradually with the corrosion time prolonging, but finally goes to a special value. The CaO and SiO2 accumulative dissolutions increase with the time prolonging, and also finally go to a special value. The amount of CaO dissolved by seepage water can be used to evaluate the erosion durability of concrete. The common concrete in this paper is durable at the action of soft water erosion.

Abstract: The fracture properties of 20g steel used as one of boiler materials, after undergoing the heat treatment of short period high temperature and thermal shock, are investigated by evaluating their fracture toughness using the crash opening displacement (COD) and three-point bending test experiment. Meanwhile, the orthogonal test consisting of five temperature stages and four different durations of thermal shock is used to explore the relationships between fracture toughness and temperature or duration. The experimental conclusions show that thermal shock plays a more significant role on affecting the fracture properties, compared with the factor of temperature. Reducing the duration, especially at the high temperature, is useful to inhibit the decrease of fracture toughness. The ranger analysis illustrates that the lower temperature does not have the beneficial effect on the fracture behaviors. Furthermore, the experimental results facilitate providing the valuable reference on the effective safely management of utilize boiler.

Abstract: (HAp/SiO2)/Ti biocomposites were prepared by the powder metallurgy method. The phase compositions and the in vitro bioactivity of such biocomposites were systematically characterized. The XRD result shows that the phase compositions of (HAp/SiO2)/Ti composites are mainly composed of Ca4O(PO4)2 (TTCP), Ti, TiO2 and CaO. The synthesized (HAp/SiO2)/Ti biocomposites exhibit a good bioactivity, for example, after the samples are immersed in SBF solution only for 24 hours, the bone-like layer consisting of spherical apatite crystal clusters has deposited on the surface of the samples. The density and thickness of the apatite layer increases with increasing immersion time. The formation process and mechanisms of bone-like apatite layer are also discussed.

Abstract: The tensile deformation microstructures of an extruded AZ31 Mg alloy were examined at temperatures ranging from room temperature to 250°C over a strain rate range from 10-4 s-1 to 10-2 s-1. It is found that the strain rate has an enhanced effect on the tensile flow behavior of AZ31 Mg alloy with increasing temperature, which is closely related to the changes of deformation microstructures. The tensile deformation of AZ31 Mg alloy is mainly accommodated by twinning and slipping at room temperature and 100°C, and the amount of deformation twins reduces with increasing temperature and decreasing strain rate. However, discontinuous dynamic recrystallization (DRX) occurs primarily at grain boundaries, and nearly no deformation twins form, as the temperature is as high as 250°C. With decreasing strain rate, more significant DRX takes place with an increasing DRX grain size. The tensile deformation of AZ31 Mg alloy at 250°C is thus primarily controlled by slipping and DRX.