Abstract: In order to gain ideal parameters of boreholes along coal seam for methane drainage, based on the gas flow theory in coal seam and the law of mass conservation, a mathematical model of the flow equation for draining methane through boreholes was established to study the methane flow field around drainage boreholes along coal seam. No. 5213 working face of Xinzhuangzi Coal Mine was taken as the field for simulating methane flow with MATLAB software. The simulation result was compared with actual drainage effect of the mine. Finally, the methane drainage parameters suitable to coal seam of the mine were obtained through analysis. The parameters can be applied and popularized in Huainan Mining Area with similar conditions of coal seam storage, which is beneficial to safety production for high methane mines.
Abstract: Based on the physical and chemical properties of saline soil, a method of salinization treatment and a combined method of salinization treatment with RCC were used to improve the anti-permeability and strength property of saline soil located in the bottom of salt field. The results of in-situ permeability testing and indoor physical-mechanical testing show that the anti-permeability and strength property of saline soil after treatment have been markedly improved. All the two measures can meet the requirements of project design.
Abstract: In order to analyze the effects of valley topography on the seismic responses of soil sites, the linear and equivalent-linear seismic responses of a valley with a span length of 500 m were calculated by applying the direct finite element method, respectively. As the span of the valley is large, the discrepancy of seismic responses of the soil sites was compared under uniform excitation and traveling wave excitation. At the same time, based on the wave propagation theory, the seismic responses of layered soil were evaluated for discussing the valley topography effect. The results show that the valley topography effect will lead to considerable vertical motion. Comparing with uniform excitation, the horizontal acceleration response is decreased and the vertical acceleration response is increased when under the excitation of traveling waves.
Abstract: Considering the complexity of time history analysis on each curved bridge pier whose maximum response relies on the seismic angle, a relationship between the curvature at the bottom of the pier and the seismic response was presented based on the principle of Pushover method. The formula to calculate the critical angle was gained with non-liner Pushover method. Through the ease of a curved bridge, the critical angle to the seismic response of the curved bridge was calculated with the non-linear statically analytical method. The results of dynamical time history analysis in the range from 0° to 180° indicate that the formula is accurate to determine the critical angle to the seismic response of curved bridges.
Abstract: In order to study the aseismie performance of long-strut-braced steel frames, a shaking table test was carried out for a vertical irregular high-rise steel structure model with a total height of 4.56 m, The 59.2 t 1/12-scale model structure, which is mainly supported by V-shaped concrete-filled steel tube struts, was built to obtain the dynamic characteristics, foundation and column-end reactions. The E1 Centro earthquake records and artificial waves were adopted to investigate the dynamic responses, Structure acceleration and displacement responses under the excitations of seven-degree frequent, basic, and rare earthquakes were tested. As a result, the model exhibits considerable torsional effects; the displacements of protrudent parts are relatively greater. Compared with single directional excitation, the torsional responses in three-dimensional exciting conditions are more intense. Based on the similitude theory and experimental results, the seismic responses of the prototype structure were deduced and some suggestions for improving aseismic vulnerabilities were proposed.
Abstract: Low carbon Mn-Mo-Nb-Cu-Zr-B steel was designed, which was processed by thermo-mechanical controlling and cooled at medium cooling rate, and the microstructures including an abundant of lath bainite, a number of granular bainite and a bit of acicular ferrite were obtained. The yield strength of the as-rolled steel plate exceeds the 850MPa grade, which meets the need for the mechanical properties of X120 pipe line steel. As 0. 015% Zr (mass faction) was added in the steel, a number of complex Zr-bearing carbonitrides with irregular shape were observed by TEM, and their size ranged from 80 nm to 200 nm; considering anomalous shape, they formed at high temperature and had high melting points. The size of Zr-bearing precipitates would reduce when the reheat temperature exceeded 1200℃ because of some amounts of Ti and Nb in the precipitates dissolving, which is better for controlling the austenite grain coarsening. Whereas, quasi-elliptic Zr-free carbonitrides would dissolve even vanish when reheating. Zr-bearing precipitates distributing evenly can block the moving of grain boundaries effectively when reheating, which is the predominant reason that the tendency of austenite grain growth of Zr-bearing steel is lower than that of Zr-free steel. A conclusion should be obtained that 0.015% Zr (mass fraction) addition can improve the weld properties of low carbon Mn-Mo-Nb-Cu-Zr-B steel.
Abstract: The effects of strain aging on the microstructure evolution and internal friction of F40 hull structure steel were studied by SEM, TEM and multi-functional internal friction apparatus. The result showed that there was no obvious change in microstructure during the process of strain aging, displaying better mierostructure stability. A peak was found in the curve of internal friction to temperature, which can be attributed to C trapping on dislocations and dislocation motion. The strain aging phenomenon induced an increase in hardness associated with ductility loss and large toughness reduction. This trend is attributed to dislocation configurations and the interaction between interstitial carbon and dislocations.
Abstract: A thermo-mechanical finite element model was established for the developed continuous dieless drawing process equipment by using DEFORM finite element software. The temperature field and stress field in the continuous dieless drawing process of NiTi shape memory alloy wires were analyzed through the thermo-mechanical coupling simulation. The effects of distance between heater and cooler, cooling water flow-rate and drawing speed on the diameter of wires were investigated. The results were well consistent with the experimental ones.
Abstract: Clad steel pipes of 20Cr/1Cr18Ni9Ti were prepared by centrifugal casting and extruding. The interracial microstructure of the preproduction clad steel pipes was analyzed by SEM and the mechanical properties were tested by tensile test and thermal cycling test. The results show that the clad steel pipes get completely metallurgical bonding interface with greatly increased bonding strength and their processability and service performance are improved due to transversal area in the interface. It is indicated that not only the centrifugal casting and extruding process can be used to produce the clad steel pipes with better microstructure and properties, but also its working procedure is simple and its production cost is low.
Abstract: Ultrasonic field was introduced into the solidification process of industrial pure aluminum. The mechanism of grain refinement by ultrasonic was discussed. The effects of ultrasonic power and melt temperature range subjected to ultrasonic vibration on the solidification structure of casting ingots were studied. The experiment results showed that the solidification structures of aluminum melt were all refined remarkably by ultrasonic treatment due to ultrasonic cavitation effect and acoustic stream effect. The structure refinement was improved when the ultrasonic power increased, the refining effect was the best at the ultrasonic power of 170 W, but it would be decreased if the ultrasonic power continuously increased. The similar law was found in investigating the influence of temperature range applying vibration on the solidification structure, and the grain refinement can reach an optimum degree at a reasonable temperature applying ultrasonic.
Abstract: The effects of friction on metallic rheology and mechanical parameters during plane strain compression were studied. Based on the 2-D and 3-D thermo-mechanical coupled finite element theory, the mechanical parameters, lateral spread and deformed metal flow pattern were calculated in different friction conditions by using MSC/Superform finite element software. The metallic deformation law was analyzed with pure aluminium at room temperature on a self-developed large specimen plane strain thermomechanical simulator under different friction conditions at top and bottom interfaces. The results show that the deformation load enhances and the lateral spread lessens with increasing friction coefficient. The difference in friction coefficient at top and bottom interfaces results in U-type deformed specimens, and the inhomogeneity of deformation is more severe when the difference between top and bottom friction coefficients increases.
Abstract: High temperature tensile experiments were earned out to investigate the effect of hydrogen on the superplastic deformation behavior of Ti-6Al-4V titanium alloy. The influence of hydrogen on the microstructure evolution of the alloy was analyzed by OM, SEM, TEM, and XRD. The results show that the amount of 13 phase in the hydrogenated alloy increases with increasing hydrogen content, and martensite begins to form while the mass content of hydrogen reaches to 0.2% and becomes coarser with the increase in hydrogen content. A reasonable hydrogen content can improve the superplastic behavior such as increasing the m value and lowering the flow stress and temperature. The addition of 0.1% hydrogen in Ti-6Al-4V alloy ean result in a decrease in peak flow stress of 53% and a decrease in deformation temperature of 6012. Due to addition of hydrogen the dislocation density of the hydrogenated alloy after deformation is lower than that of the unhydrogenated alloy.
Abstract: SEM, TEM and X-ray diffraction methods were used to observe and analyze the microstructure, phase distribution and composition distribution of Cu and Mo-containing (Ni-A) and Cu and Mo-free (Ni-B) Ni-based alloy spray-welding coatings. The micro-Vickers hardness of the matrix and the heat-effected, combined and coating areas was measured. The thermal fatigue process was actualized by an induction heater to investigate the phase morphology and composition distribution and the phenomenon of thermal cracks appearing and spreading. Experimental results show that there exists needle Cr-rich phase with excellent thermal fatigue property in both Ni-A and Ni-B coatings. Ni-A coating can be divided into two areas:one is round-shaped Cr-rich phase which distributes near the matrix uniformly and the other is needle-shaped Cr-rich phase which distributes near the surface with a distance of about 200μm away from the outer surface of the coating. The volume of the needle-shaped Cr-rich phase is smaller than that of the roundshaped Cr-rich phase by several ten times. Compared with Ni-A coating, Ni-B coating has only needle-shaped Cr rich phase distributing in the spray coating uniformly. The thermal fatigue property of Ni-A coating is better than that of Ni-B because of a transition area in Ni-A coating. The results obtained by EDS analysis show that there is almost no diffusion of elements in Ni-A and Ni-B coatings during the thermal experiment and the two types of coatings have excellent thermal stability.
Abstract: Based on the traditional oxidation process, 4H-SiC MOS capacitors were fabricated by wet re-oxidation annealing (wet-ROA). The oxide film quality was analyzed by I-V characteristics testing and the Flower-Nordheim (F-N) tunneling current model. The SiO2/SiC interface trap density was calculated by the Terman method. The structures of SiO2/SiC interfaces, which were obtained by different processes, were analyzed by XPS. The SiO2/SiC interface fabricated by wet-ROA, with 10 MV·cm-1 in the breakdown field strength of oxide film, 2.46 eV in the barrier height of SiO2/SiC, 1011 eV-1·cm-2 in the interface trap density, can meet the reliability requirement in fabricating devices.
Abstract: N-doped TiO2 photocatalyst was prepared by calcination of hydrated titanium dioxide in ambient atmosphere at 600℃ for 2 h, which was obtained by using saturated urea solutions as precipitant. The photocatalytic properties of the obtained yellow sampies were studied using reactive brilliant red X-3B, 2, 4-dichlorophenol and CH3COO- as model pollutants. XPS results indicated that nitrogen was doped into TiO2 lattice in the form of Ti-N chemical bond. UV-Vis results showed that the sample could absorb the visible light wavelength above 400 nm. Photocatalytic results revealed that X-3B and 2, 4-dichlorophenol could be degraded by N/TiO2 photocatalysis when using a fluorescent lamp of 420 nm in main wavelength as the light source, while CH3COO- could not be degraded, however, CH3COO- could be degraded by N/TiO2 photocatalysis under UV irradiation. The wavelength of excitation illumination has great influence on the oxidative power of N/TiO2 photocatalysis.
Abstract: Anode materials for hydrogen production by electrolyzing seawater were investigated. The electrodes with γ-MnO2 type oxide coatings were prepared by anodic electrodeposition on the base of Ti/IrO2. MnV, MnCr, MnMoFe and MnFeV electrodes were obtained by doping other elements in electrodeposition solution. The results of testing in simulated seawater indicated that the doped elements obviously enhanced the selective performance of electrodes for evolving oxygen and restraining chlorine. The oxygen evolution efficiency of MnFeV was as high as 100%, which can meet the requirement of selectivity in electrolyzing seawater. The results of structure analysis show that a mix-oxide Mn(Fe, V)O2 with γ-MnO2 structure was formed after adding Cr, Fe and V to the manganese oxide electrodes. These elements existed in Mn(Fe,V)O2 in the form of Mn4+, V5+, and Fe3+. The doped Fe and V can refine grains and increase the deformation energy, thus the electrocatalystic properties for evolving oxygen of electrodes were improved effectively.
Abstract: Three-dimensional surface flexible roll bending was introduced and compared with traditional roll bending and multipoint forming. The flexible roll bending equipment was researched and the corresponding experimental equipment was developed. A finite element model of flexible roll bending was established to simulate the forming process and satisfactory simulated results were gained. The flexible roll bending of sheet metals made of two kinds of materials was simulated and their different forming effects were analyzed.
Abstract: On the basis of analyzing the structure and abrasion of a traditional gyratory crusher's chamber profile, its crushing capacity was defined by computing the flux ratio of every section along the chamber height. The chamber profile was geometrically described by means of a thrice spline curve. The chamber profile target function was built with productivity and nip angle as constraint conditions, then the gyratory crusher's chamber profile was designed and its curves were protracted. A test scheme was set down to meet the aluminum ore crushing demand. After the crushing test of aluminum ore with the optimized chamber profile and new linings, it is shown that the crushing capacity, the certified ratio of crushing products and the working life of linings are better than those with the traditional chamber profile.
Abstract: Aiming at the present situation of air separation units in a steel plant, a rational method of calculating the costs of oxygen, nitrogen and argon was proposed by considering the air separation process and the energy consumption of air-separation products, and was used to calculate the energy consumption and the apportioning proportion of air-separation products. The presented method can not only solve the problem that the energy consumption of single product cannot be accurately calculated because oxygen, nitrogen and argon are by-products one another, but also eliminate the disadvantage that the apportioning proportion is arbitrarily controlled.
Abstract: The trajectory function of a single aerosol particle in a dilute gas system close to a wall was theoretically studied with consideration of different forces such as gravity-buoyancy, particle-wall interaction and Brownian force. The results indicate that there is a wall effect layer in which the particle shows a different dynamic characteristic from that in unlimited space. The wall effect layer is about 50 radii of the particle, which is much higher than the effective range of particle-waU interaction, about 1 radius. Finally, associated discussion was made to understand the effects of surface characteristic and particle size on the wall effect layer.
Abstract: The simultaneous measurement of multiple thermal parameters of living tissues is of great significance for medical clinical applications. A parameter estimation method using improved genetic algorithm (GA) was proposed to simultaneously estimate the multiple thermal parameters of living tissues. In the method the real-coded GA was designed, the selection, crossover and mutation operators were improved, and the niche mechanism was applied to improve the capability of global optimization. The simulation and experimental researches of a dynamic phantom and a human forearm indicate that it is feasible and effective to simultaneously estimate the multiple thermal parameters of living tissues with high accuracy by the proposed method.
Abstract: Despite the increase in use of supplier evaluation, there still exist some limitations for the single evaluation method to deal with all the criteria. In order to avoid the limitations and realize the reasonable supplier evaluation with both qualitative and quantitative criteria, a synthetic supplier qualification selection method was presented based on the classification of supplier selection criteria, This method synthesizes the advantages of severaI methods including group-AHP, fuzzy evaluation, TOPSIS, and entropy methods and can make suppliers' evaluation more reasonable. An example of a real coke supplier selection from an iron and steel corporation is also presented to illustrate the proposed method.
Abstract: A fuzzy reaching law was proposed to eliminate the "crawling" and "flat top" problem of servo systems because of nonlinear friction, a sliding mode controller based on the T-S fuzzy model reaching law was designed, and the simulation and experimental tests were carried out. The results demonstrate the controller not only can effectively eliminate "crawling" and "flat top" phenomena and enhance the tracking accuracy of servo systems, but also can decrease the chattering of conventional reaching law sliding mode controllers significantly and improve control quality. Owing to the good fitness of this controller, it can be used in servo systems with high control performance.
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
