Abstract:Experimental studies of four sandwich walls with the same height but different height-width ratio and different vertical compressive stress, which were subjected to in-plane cyclic loading, were presented and tests results were discussed. Based on actual mechanical characteristics, the vertical and horizontal loads were loaded on the center of the interior walls. The whole process of loading-deforming-damaging-cracking-yielding-failure was observed during the test. The failure characteristics, hysteretic curves, skeleton curves, displacement ductility, bearing capacity, behavior of the tie bar and coordination between two cavity walls were analyzed. The result showed that the interior walls and the outer walls worked together well, and the outer walls were slightly damaged; shear slipping and pinching occurred in the test; shear failure occurred when the ratio of height to width was small and bending-shear failure occurred when the ratio increased and the ultimate bearing capacity of the walls increased with the increase of the axial compressive ratio. The shear capacity of the walls in the test is greater compared with the GB 50003-2001 Code.

Abstract:To address the shortcoming that traditional pavement performance method is subjective and is not suitable to the high-grade road, and intelligent algorithm is fussy to determine the parameters, the pavement condition index(PCI)，pavement ride quality index(RQI)，structure strength index(SSI)，pavement skid resistance index (SRI) and rut depth (RD) were chosen as pavement performance indicators to determine the weight coefficient of each index in the Delphi method. A comprehensive model of pavement performance assessment was established in Delphi-Ideal Point method. At last, some highway pavement performance data were analyzed and computed, and the results were consistent with the actual data, thus proving that the Delphi-Ideal Point method is reliable. This method greatly reduces the weight of subjectivity, and it is feasible and simple, and at the same time, its calculation is easy.

Abstract:Three-dimensional finite element analysis of the consolidation of composite ground was carried out in detail within the influence scope of a single granular column. Due to the different mesh sizes of granular column and soil set, several calculation conditions were gained first. Then, the numerical solutions for consolidation degree and excess pore pressure of different conditions were compared with analytical solution. Subsequently, the significant level of errors caused by different meshing schemes was obtained. It was found that deviations caused by different meshings decreased with the development of consolidation. The gridding of the soil around the granular column was the main source of error within three mesh schemes. The ground mesh in the direction of depth has no obvious effect on the overall consolidation degree, but it had a greater impact on the result of excess pore pressure in the shallow. The gridding of the granular column had little effect on the calculation result of consolidation, so it can be described by one unit in FEM. The above findings can be used to guide the finite element analysis of a reasonable mesh.

Abstract:For round-ended piers of high-speed railway bridges, two kinds of finite element model were set up to calculate the elastic-plastic seismic responses of piers: one was beam element model of the whole bridge which includes the piers and could take into account the influence of vehicle load，and the other was solid model of the piers which could explain the seismic responses of piers. According to the two models and the bending moment-curvature relationship program, the elastic-plastic seismic responses of piers were computed at different earthquake load combination, pier height and vehicle speed. The calculation results have shown that the seismic responses of piers will increase with increment seismic intensity, the influence of vehicle speed and pier height on the responses of the piers is not in a linearly increasing manner, the frequency characteristics of earthquake wave have great influence on the seismic responses of the piers, the piers step into the state of elastic-plasticity and the plastic hinge will be developed at the bottom of piers under rare earthquake. The simplified calculation formula of plastic hinge region length suited to high-speed railway bridge round-ended piers where stirrups are encrypted was presented.

Abstract:To study the effects of the design parameters of a helical intake port on the in-cylinder swirl ratio for an automotive diesel engine, the transit port and in-cylinder flows were simulated with the Converge CFD software. By changing the values of three main design parameters of the intake port, their effects on the in-cylinder swirl ratio were simulated and studied. The results have shown that the in-cylinder swirl ratio achieved the maximum values when the spiral chamber height, the vortex shell cut-off amount and the helical intake port angle were changed to the values of 13 mm, 1.27 mm and 0 degree, respectively. The results also indicated that the effects of the parameters on the swirl ratio were not additive when multiple parameters were varied at the same time. This study has shown that the numerical analysis of multiple design parameters of a helical intake port can be done with the use of the Converge software.

Abstract:The interaction of a piezoelectric screw dislocation in the matrix with interface effects under remote anti-plane shear stresses and in-plane electric loads in transversely isotropic piezoelectric solids was investigated. By using the complex variable method, the general solutions to the problem were given. With the aid of the Peach-Koehler formula, the explicit expressions of the image force acting on the screw dislocations were given. The results have indicated that the influence of the interface stress on the motion and the equilibrium of the dislocation near the inhomogeneity become significant when the radius of the inhomogeneity is reduced to nanometer scale. If the dislocation is located in the matrix, the positive interface effects can repel it. The soft inhomogeneity can also repel the screw dislocation near the inhomogeneity when the positive interface effect is considered.

Abstract:To cope with the problem of overheating of rear-mounted engine cabin, based on a type of hybrid vehicle, a coupled model for the cooling system of rear-mounted engine cabin was established by using the coupling 3D/1D model. Through the process of coupled calculation, the convection heat transfer coefficient of engine surfaces and the flow coefficient of engine cabin in different ambient temperatures and driving speeds were studied. In addition, the general laws of the heat transfer coefficient and the flow coefficient were summarized and empirical equations were provided. All the results proved basic parameters for the establishment of one-dimensional model and theoretical basis for the design of the engine cabin. By analyzing the heat flow field, it was found that convection heat transfer coefficient and flow field changed noticeably with different layouts of engine cabin. The increase of the area of ventilated grille in the rear of engine cabin or adjusting the layout of radiator reasonably can improve the uniformity of the heat flow field and enhance the capacity of convective heat transfer of engine surfaces.

Abstract:This paper introduced the topology of five-level neutral point clamped (NPC) H-Bridge inverter and its operating principle, and proposed a new algorithm of space vector pulse width modulation (SVPWM), which can be applied to the five-level inverter. In this algorithm, the reference voltage position is located by twelve judging rules, and in order to avoid the abrupt change of output voltage vectors during the process of desired vector changing from one section to another, the method that made the output vector changes of the two adjacent triangles in the opposite direction is used. In this paper, the implementation approaches and concrete steps for the algorithm used to control the five-level inverter were studied with simulation. The simulation results have shown that the proposed algorithm is correct and effective, the harmonics of inverter output voltage are significantly reduced and the amplitude of fundamental voltage also increase significantly, compared with the traditional SPWM method.

Abstract:A new direct-contact dehumidifying economizer was developed, in which the packed mass was set for the recovery of waste heat in the flue gas exhausted from gas-fired boiler. An investigation of the heat and mass transfer process in the packed mass section and the design model was carried out to build and improve the economizer designing method. A set of differential equations were developed in which the flue gas temperature tg was used as an independent variable and the Lewis Number Le, the wet specific heat CH of mainstream flue gas and CHi of the flue gas on the phase interface between the flue gas and water were included. The differential equation set can be used to calculate the parameter distribution in the heat and mass transfer process in the packed mass section and the packed mass section height. The calculation results agree well with the experimental measurement. This has proved that the calculation method developed can be applied in the design and analysis of the new direct-contact dehumidifying economizer.

Abstract:The effects of deep cryogenic treatment in different holding times combined with the traditional HSS heat treatment processes on the microstructure and hardness of M42 HSS were investigated with metallurgical microscope, SEM and Hervey hardness tester. The process included: quenching+deep cryogenic treatment, quenching+deep cryogenic treatment+tempering and quenching+tempering+deep cryogenic treatment. The results have shown that deep cyogenic teatment in 24 h after quenching can obviously refine grain size, improve the hardness of M42 HSS,and significantly promote the transformation of retained austenite to martensite and the precipitation of dispersion distribution carbide, and meanwhile result in the change of the shape of martensite which is different from the conventional heat treatment.Deep cryogenic treatment before tempering can reduce the temperature of secondary hardening, where the peak temperature declined to 450 ℃ compared with 525 ℃ of the process without the deep cryogenic treatment. The hardness of secondary hardening peak is 998.2HV,which is 5% higher than that of the process without the deep cryogenic treatment. The effect of deep cryogenic treatment after tempering on the microstructure and the hardness of M42 HSS is not obvious.

Abstract:A series of Mg-9Al-1Zn-xNd (AZ91Nd) was prepared by adding Mg-Nd master alloy into AZ91 under the protection of CO2+SF6. The density and distribution of galvanic corrosion currents of the AZ91Nd magnesium alloys were investigated by galvanic corrosion tests, electrochemical analysis and X-ray photoelectron spectroscopy (XPS). The XPS results indicated that Nd was incorporated into corrosion film in the form of Nd2O3 during the corrosion. The electrochemical analysis indicated that the addition of Nd increased the corrosion potential and impedance. The corrosion tests indicated that Nd could decrease the current density, improve the uniformity of the current distribution. As a result, the local corrosion of AZ91Nd was effectively restrained and the galvanic corrosion resistance was enhanced. The enhancement of the galvanic corrosion resistance was mainly attributed to the increase of corrosion potential and impedance resulting from the incorporation of Nd2O3 in the corrosion film.

Abstract:This paper studied the water volume of the Dongting Lake by using Terra/MODIS satellite data, water level and lake bottom DEM (Digital Elevation Model). As water has a high absorption rate in the near infrared and infrared band, the water area of the Dongting Lake was extracted by setting thresholds on NDVI (Normalized Difference Vegetation Index) and NIR (Near InfraRed). A water level distribution map was obtained by interpolating the water level data from hydrological stations. The volume of the Dongting Lake was estimated by using the water area map, the water level distribution map and the lake bottom DEM. The hydrological response of the Dongting Lake on the Three Gorges was studied by using the water level, area, and volume data. The result has shown that the method mentioned above can be used for water volume estimation of the Dongting Lake. The water area, water volume and water level have a high correlation. The water level of Chenglingji and water volume of the Dongting Lake was fitted by cubic curve, and the coefficients of the determination of the fitting curves were 0.915 and 0.928, respectively. The Three Gorges Project has shown the ability of flood storage after interception, and the cumulative water volume ratio of flood season decreased year by year from 2004 to 2006. At the same time, during late summer and early autumn, the impoundment of the Three Gorges Project causes the decrease of water discharged, which increases the drought of the Dongting Lake.

Abstract:This paper analyzed the energy efficiency of small-sized coal-fired Combined Heat and Power(CHP) at part heat-load, and presents the “low heat-load Triangle” based on heat-load duration diagram. The energy efficiency of coal-fired CHP in the “low heat-load Triangle” is much lower than separate generation because the heat-load is so little. Therefore, it is an effective way to improve the energy efficiency of CHP plant by minimizing the “low heat-load Triangle”. Separate generation instead of coal-fired cogeneration can be a better scenario in this special area. The study of the CHP district heating in 9 cities of different latitudes in China has shown that distributed gas boilers can be used in the “Triangle Areas”, which can lead to a visible energy saving. But the energy saving rate has a remarkable difference among cities of different latitudes. So the cogeneration and separate generation sources should be reasonably matched for utilization so that the energy saving rate can be considerably enhanced.

Abstract:A class of inverse eigenvalue problem for periodic arrow-like matrices constructed by spectral data and its properties were discussed. The necessary and sufficient conditions for the solvability and uniqueness of the problem were obtained, followed by a feasible numerical algorithm according to Boley and Lanczos' algorithm.

Abstract:Implied volatilities are more efficient in the long-term prediction of volatilities than the series models. Solving the implied volatility is a typical PDE inverse problem. The traditional Tikhonov regularization method may over-smooth the solution. Considering the jump, overnight, weed-end effect of the volatility and the advantage of the total variation regularization which preserve the edge of the restored image, we put the problem of determining the implied volatility into a parabolic equation of the terminal problem under the Black-Scholes theoretical framework, propose the total variation regularization method and prove the existence to the solution.

Abstract:Considering that the entropy method and the objective criterion compromise solution ranking (VIKOR) method have advantages in solving multi-criteria decision problems, this paper used the two methods to evaluate public works' project risk and to overcome the difficulty resulting from the fixed weight method and the diversity of the decision-making. By selecting six construction projects of Changsha invested by the government for sample analysis, the results have shown that this method for the evaluation of public project risks is feasible and effective.

Abstract:We divided accounting information quality affecting factors for enterprises' countermeasures to anti-dumping into six dimensions and constructed structural equation models of factors through field interviews. Then, we did empirical tests on the reliability and influence of each factor based on 231 valid samples. The empirical results have shown that the direct influence degree of accounting officers' professional abilities ranks first, followed by the information acquisition capabilities, accounting government capabilities, China's accounting standards internationalization and the independent audit level outside the enterprises. The Composite Index of enterprises' obtaining information through the internet on the accounting information quality also reaches the 0.5 level, which have shown that the set of six-dimensional factors influence significantly accounting information quality affecting factors for enterprises' countermeasures to anti-dumping.