Advanced Materials Research Vols. 236-238

Abstract: Nacre is one of the most attractive biological materials for its superior mechanical property which is mainly due to the “brick-mortar” microstructure. Nacre samples are heated in N₂ atmosphere at 200°C, 400°C and 600°C, separately. The microstructures of the fresh and heated samples are characterized by SEM and XRD, and the three-point bending strengths of these samples are tested by universal mechanical testing machine. TG-DSC curves are performed on the fresh nacre and the demineralized one. The results show that biopolymer plays important roles in maintaining the microstructure, toughening mechanism and the phase transformation of aragonite.

Abstract: A series of intramolecular charge transfer (ICT) molecules containing six-membered N-heterocyclic electron acceptors, as well as their phenyl analogue, have been synthesized. The pyrazine derivatives exhibit the largest quantum yield, stokes shift and the longest emission maxima wavelength due to the appropriate electronegativity of pyrazine, while the triazine derivative has much lower quantum yield due to its too strong ICT. The methyl groups at N-heterocyclic rings also have influence on the optical properties by disturbing the molecular dipole moment.

Abstract: This paper, while introduce development trend, basic structure and working principle for auto power steering system, is analyzing on characteristic curve of steering force in steering system. The paper proposed a control mode for electric power steering system, which, analyzing control strategy for power steering system based on control module, providing a new design thought and method for electric power steering system using MATLAB simulation analysis for steering dynamic features of electric power steering system and affects of road obstruction on steering system performance.

Abstract: A new concept of “Sideling Flow” in shell side of shell-and-tube heat exchanger is presented, which is relative to the cross flow, longitudinal flow and helical flow in heat exchanger. A type of new energy saving shell-and-tube heat exchanger with sideling flow in shell side, shutter baffle heat exchanger is invented, which exhibits the significant heat transfer enhancement and flow resistance reducement performance. The “Field Synergy Principle” is adopted to analyze the heat transfer enhancement mechanism of sideling flow, it is indicated that the shutter baffle heat exchanger exhibits the perfect cooperativity between velocity field and temperature grads field. Effects of the structure and processing parameters on the fluid flow and heat transfer are also investigated through numerical simulation, both the correlative equations of heat transfer coefficient and pressure drop in shell side are deduced, which provide references for the design and popularization of this new type heat exchanger.

Abstract: Based on the creative design of nozzle structure, the application fields of the micro-particles production using supercritical fluids (SCF) can be further broaden. According to the analysis of the structural characteristics of the nozzles, a new kind of nozzle with a tunable annular gap is proposed in this research, which includes a cover, movable trays, unmovable trays, seal fittings and connecting components. By virtue of FLUENT software, the flow field of the nozzle in outer mixing mode with two passages is numerically simulated. The effects of the passing length of SCF before mixing and the height of conic convexity on the flow-field are analyzed. The simulation results show that the above length does adverse effect on enhancing mixing extent, however, the smaller height of convexity can help achieve better mixing level. Then the nozzle is redesigned in which a movable tray and an unmovable tray are removed. The improved nozzle has simple and reasonable structure and can do better work on improving gas-liquid mixing extent.

Abstract: In order to enhance the operational safety of tram vehicle and reduce the wear of guide wheels mounted on the vehicle, it is necessary to remove particles such as dusts and silts from tramway surface. The aim of this paper is to evaluate the effectiveness of street vacuum sweeper for sucking up dusts from tramway surface. A numerical model was developed based on dusts removal process. Under different pressure drops across the pickup head of the street vacuum sweeper, the flow field and dusts removal efficiency were analyzed with computational fluid dynamics (CFD) method. The numerical results show that a higher pressure drop can improve the airflow field in the pickup head and results in higher dusts removal efficiency, but higher pressure drop definitely need more energy. Therefore, a balance should be taken into consideration.

Abstract: The multi-layer pressure vessel generates the preload stress during the process of wrapping & clamping. The contact between the wrapped layers and the inner shell is the source of the preload stress. The contact mechanics model shows the primary mechanics relationship, and the contact pressure vessel causes the local settlement. The theory contact pressure has 5% error with simulation value. The experiment values of inner wall are coincided with the theory stresses, and the largest error between the theory and the experiment is below 16.3%.

Abstract: In this article first order second moment and Monte-Carlo methods are used to calculate the reliability of the pipeline under uniform corrosion conditions. The results show that the data obtained by the two methods is almost the same. Reliability assessment shows that the reliability is continuously decrease while the stress of the pipeline is still lower than yield limit of the material. At the 20th year in the pipeline’s life, the reliability is only 0.58, and the pipeline is not safe anymore. So, for the safety of the pipeline, not only the stress should be considered, but also the reliability.

Abstract: The precursors of Cd_xNi_1-xCo_0.2Mn_1.8O₄ (x=0,0.1,0.2,0.3) and Cd_0.2Cu_0.1Ni_0.7Co_0.2Mn_1.8O₄ negative temperature coefficient (NTC) ceramics were prepared at room temperature by the solid reaction. These precursors were calcined and then sintered in air at 1100°C. Influence of the Cd and Cd-Cu doping on the microstructure and electrical properties of the NTC ceramics were investigated by X-ray diffraction and SEM technique. The results showed that Cd doping was conducive to reduce the grain size, increase density, and obtain high thermal stability.

Abstract: N-doped TiO₂ hollow spheres (labeled as NTH) were prepared using hydrophilic colloidal carbon spheres as template in conjunction with the sol-gel method. The hollow spheres were characterized by XRD, SEM, UV-Vis and XPS. Photocatalytic activity of N-doped TiO₂ hollow spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation. The photocatalytic activity of the sample enhanced a lot compared to commercial P25 TiO₂. The apparent rate constant of the N-doped TiO₂ hollow spheres was almost 10 times as that of P25 TiO₂.