Abstract: The subsidence characteristics of horizontally-sliced mechanized top-caving mining are different from those of either flat seam mining or steep-inclined middle-thick seam mining. Similar material model test was used to simulate the rock mass movement of steep-inclined super-thick coal seam of a coal mine. The results revealed the law of strata movement and ground deformation due to horizontally-sliced mechanized top-caving mining at a greater depth of steeply-inclined seam, which would provide a guide to real mining.
Abstract: Water jet breaking soil effect is determined by water jet parameters and soil parameters. Water jet parameters decide the water jet impact force, while soil parameters do the soil critical destructive force. Based on analyzing the dynamic property and breaking soil mechanism of water jet, the internal relationship between water jet parameters and soil parameters was discovered and the theoretical equation of water jet breaking soil was established. This equation solves the problem hard to precisely select parameters during the process of water jet breaking soil.
Abstract: The common finite element analysis software ANSYS was adopted as the running environment. Member cross section areas of the lattice grid structure were taken as the discrete design variables. The total weight was considered as the objective function. The restrain conditions such as strength, rigidity, stability and cross section dimensions were considered. The one-dimensional search method and the modified stress ratio method were selected as the optimization method. Optimization of the lattice grid structure was conducted. The calculated results show that the optimal method has easy principle and big convergence rate. It can reduce the cost of a project on the base of guaranteeing safety, and can get a better optimal result.
Abstract: Transient phenomena often happen in an operating water distribution system (WDS). Large pressure fluctuation generated by the transient is harmful to the system. This paper studied the simulation model, boundary conditions and analysis solution for simulating the whole situation of the transient process. A computation method was proposed based on the model of transient condition. The method's feasibility was approved by an example.
Abstract: This paper proposed a determination method for 8 organophosphorus pesticides residues of dichlorvos, methamidophos, acephate, phorate, omethoate, dimethoate, parathionmethyl and chlorpyriphos in leek. The 8 organophosphorus pesticides were separated from each other through DB-608 capillary column and determined by flame photometric detector, and the recoveries ranged 70%~119%. The lowest determination concentrations of the 8 organophosphorus pesticides are 0.01~0.02 μg·mL-1 This method is rapid and sensitive, and meets the demands of actual application.
Abstract: Subgrain and micrograin structures of Q235 steel were obtained by the process of equal channel angular pressing (ECAP) at room temperature with the route Bc that samples were rotated 90(and kept the direction unaltered after ECAP. The microstructure evolution of four surfaces was observed after ECAP deformation. It is shown that the microstructure of ECAP deforming Q235 steel is thinned with the increase of deformation pass, and the thinning degree of the first pass is the greatest. The appearances of four surfaces are different: Surface S is mainly dislocation cells; Surface R appears the cross of deforming bands in the second pass; there are equiaxed grains on Surface T after two passes, and the grain boundaries of equiaxed grains are very clear after four passes, with an average grain size of about 0.25μm; On Surface L are equiaxed grains after four passes, and the grain boundaries are not clear. After eight passes, all surfaces are clear equiaxed grains, the average grain size is about 0.20μm. The subgrain and micrograin structures of Q235 steel can obtain by means of ECAP.
Abstract: The shaping behavior of an iron-based alloy consisting Fe-Mo-B pre-alloyed powder was studied during warm compaction (WC) and liquid sintering. The effect of compacting temperature and pressure on the green density was discussed. The density and microstructure of samples with different amounts of Fe-Mo-B pre-alloyed powder before and after sintering were compared. The results show that compared with compaction at room temperature the green density was obviously increased by WC, e.g. at 120 ℃ the green density of the alloy containing 10 % and 15.4 % Fe-Mo-B increase 0.34g·cm-3 and 0.32 g·cm-3, respectively. The raw material powder with Fe-Mo-B pre-alloyed powder causes liquid-phase sintering, which can improve densification of the material and obtain typical bainite. The highest density reaches 7.49 g·cm-3 after sintering, with a relative density of 97.74 %.
Abstract: 60 % SiCp/Al composites with a relative density of 98.7 % were successfully prepared by the combination of ceramic injection molding for the preparation of SiC preforms with monosized particles and aluminum pressureless infiltration technique. The composites' microstructures were uniform and dense observed by SEM. The coefficients of thermal expansion of the composites in the current work ranged from 7.10×10-6 to 7.75×10-6 K-1 as the temperature from 100 ℃ to 400 ℃, and the thermal conductivity was 170 W·m-1·K-1. Both were suit the technique requirement for electronic packaging.
Abstract: The multiaxial fatigue behavior of the notched specimens and thin wall tube specimens of GH4169 super alloy was investigated. Symmetric axial-torsional strain was controlled in fatigue tests at a high temperature of 650 ℃ by using a MTS 809 tension-torsional servo-controlled electro-hydraulic testing machine with proportional and non-proportional loading. The phases between axial strain and torsional strain were 0° in-phase (proportional) and 45°, 90° out-of-phase (non-proportional) respectively. Based on the critical approach, a model for multiaxial fatigue life prediction was established by combining maximum shear strain and normal strain on the critical plane, and the effect of stress state under the multiaxial cyclic loading condition on the fatigue life was taken into account. The results of life prediction show that the new fatigue life prediction model is validated with the experimental.
Abstract: This paper investigated the galvanic corrosion behavior and laws of AZ91D, AM50 and AM60 cast magnesium alloys coupled with four materials of Q235 carbon steel, H62 brass, 316L stainless steel and LY12 aluminum alloy under atmospheric exposure in Qingdao and Wuhan of China for three, six, fifteen, twenty, twenty-seven months. The results show that the magnesium alloys act as the anode and their corrosion rates obviously increase when coupled with the four materials used in this test. The atmospheric galvanic effects of the magnesium alloys coupled with Q235 carbon steel and 316L stainless steel are larger than those of others, while that of the magnesium alloy/LY12 aluminum alloy couple is the smallest. The atmospheric galvanic effect in Qingdao is obviously higher than in Wuhan. Among the experimental magnesium alloys the maximum atmospheric galvanic effect was found in the test of AZ91D, while AM50 the minimum.
Abstract: A model was developed to predict the hot rolling parameters such as rolling force, torque and power etc. For various flow stress equations were coupled which take into account of chemical composition, temperature, strain, strain rate and austenite grain size, the model can automatically calculate the rolling parameters based on input process parameters and calculated strain, strain rate in every pass. According to the real measured data this model can adjust its output. Compared with the mill data of Panzhihua Iron and Steel Company, the model is in a good agreement with no more than 10 % deviation.
Abstract: The occurrence probability and existence form of internal defects in rolled pieces during threeroll and two-roll cross wedge rolling were compared and analyzed by finite element numerical simulation.The reason that the internal defects little occur at the center points and fissure takes an annular form during three-roll rolling was expounded based on the state of stress and strain at the center of rolled pieces. It is indicated that three-roll cross wedge rolling process has a distinct advantage in the forming quality of the center of rolled pieces.
Abstract: In order to master the SmartCrown system for profile and flatness control first applied on a 1700mm tandem cold roiling mill, the SmartCrown work roll wear pattern was obtained on the basis of large amount of measured roll contours. A prediction wear model of the SmartCrown work roils was built up by using genetic algorithm. The effect of the roll wear contour pattern on profile and flatness performance was analyzed by the developed three-dimensional finite element analysis model of a roll stacks system with ANSYS software. A new rolling strategy was brought forward for application of the new SmartCrown system.
Abstract: Based on lots of video observation tests, there are three motion states of grinding medium in a mill tube, including projection, revolution and autorotation. The movement cycle of grinding medium departing from and contacting with the inner liner is equal to the vibrating period. By building an impulse transfer model, the distribution laws of impulse transfer, energy transfer and energy dissipation are discussed, and the mechanism of the vibrating mill is revealed. Finally, this paper proposes the ways to reduce the inertia region in the grinding tube and to improve the efficiency of grinding.
Abstract: With a mixture of oxygen and nitrogen as the subject investigated, the direct simulation Monte-Carlo method was applied to simulate the flow of paramagnetic and diamagnetic mixed gas in high gradient magnetic fields. The simulated results were compared with the existing experimental ones, and the reliability of the program was demonstrated. It was shown that the increment of oxygen concentration increased from 0.12% to 1.89% when the product of magnetic field and gradient varied from 100T2·m-1 to 1 000 T2·m-1. The increment of oxygen concentration reduced from 0.4 % to 0.1% when the temperature varied from 273 K to 333 K. The increment rose from 0.12 % to 0.59 % when the initial oxygen concentration varied from 20 96 to 30 %. The change in pressure did not almost influence the oxygen concentration.
Abstract: Aiming at the characteristics of the production of wire rods, how to choose control objects and control charts in the production process was discussed based on the method of statistics process control (SPC). A practical SPC analysis system was designed and carried into execution. Some concerned problems were given in practical use and the factual effect of SPC theory applied in the production of wire rods was demonstrated.
Abstract: This paper studied the problem of robust active queue management (AQM) controller design in Internet congestion control. The problem was first reduced to a robust stabilization one based on the linear model of transmission control protocol (TCP) and the AQM design objectives. A sufficient existence condition of the output feedback controller was then obtained and its design method was provided using linear matrix inequality (LMI) approach. Finally, a design example was given and the simulation was performed. The simulated results show that the proposed controller is feasible and valid for it possesses not only robustness for all the network parameters but fast settling process.
Abstract: In order to mine frequent episodes from an event sequence efficiently, an algorithm based on generalized suffix-tree was proposed to discover and store frequent episodes, which uses the concept of generalized suffix and contains only frequent episodes' nodes. The occurrence list of frequent episodes was used layer-upon-layer to improve the efficiency of the tree. The algorithm make full use of the order character of an event sequence and may discover the variety of frequent episodes. Experimental results show that the proposed algorithm is superior in runtime to Apriori-like frequent episodes mining algorithm.
Abstract: A ear recognition method was proposed which combines the shape feature of outer ear contour with the structural feature of inner ear. The longest axis of auricle contour, which is the line crossing through the two points that have the longest distance on auricle contour, was firstly extracted after edge detection. Then least squares fitting polynomials were used to approximate the auricle curves. The coefficients of the polynomial functions were taken as the feature vector of outer ear contour. The longest axis intersects with the inner ear curves at several points. The ratio of the section length between the intersection points to the longest axis acts as the feature vector of inner ear. Owe to relevant invariability of the longest axis, the feature vectors extracted in the method are invariant to scale, parallel move and rotation. Experiment results prove robustness of this method.
Abstract: In order to solve the investment decision-making problem of an enterprise without sufficient capital, the principal component analysis method was used to study the multi-project assessment and selection of fund-limited projects, and the diagnostic analysis and computation of the projects were also carried out. The computed results were compared with those by traditional decision-making assessment methods, and the validity and reliability of this multi-aspect statistical analysis method were probed to provide a foundation for the multi-project investment decision-making of fund-limited enterprises.
Abstract: This paper analyzed the knowledge diffusion model proposed by Xu Yu and considered the model follows an increase rule that is the same with the condition of accruement. However, in parallelism with the accruement, when the factor of effort of knowledge diffusion by the managers in corporation is considered, the model cannot explain the knowledge diffusion rule. The mechanism in the course of knowledge diffusion was analyzed and the knowledge diffusion model was modified. The modified model concerns the factor of the manager's effort and concludes that the knowledge-non-owned would be requested to receive correlative train, so knowledge diffusion would keep to the first-fast-then-slow rule in the course of diffusion.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
