Abstract: The water physical properties of aquitard at different depths were studied with the aquitard of Tianjin City in China as an example. The results showed the pore water styles of aquitard at different depths and the corresponding deformation mechanisms. For different deformation mechanisms of aquitard, this paper advises using different calculating models to calculate the deformation of aquitard at different depths according to the moisture content of aquitard.
Abstract: The formation process of the system composed of fault band and elastic rock block and the shear displacement distribution across a fault band were modeled numerically by FLAC. The adopted failure criterion was a composite Mohr-Coulomb criterion with tension cut-off and the post-peak constitutive relation of rock was linear strain-softening. Once two shear bands combine to form a fault band, the system is formed, subsequently leading to the decrease in load-carrying capacity of the system. On one side of the fault band, snap-back occurs due to the sharp recovery of elastic strain in strain-softening process, indicating the unstable failure. Nearly uniform displacement distribution is observed outside the fault band. A higher displacement gradient exists within the band and increases with the decrease in load-carrying capacity of the system. Snap-back of the zone far away from the loading end is the earliest. Then, the size of the snap-back zone propagating towards the loading end increases until snap-back of the entire system takes place. The process only needs a few time steps, reflecting the abrupt occurrence of instability of the system. Snap-back of the entire system occurs in the strain-softening stage of a stress-strain curve.
Abstract: The orthogonal experiment method and the associated analysis of the grey theory were used to analyze the results of numerical simulation and to optimize the supporting parameters for a coal mine tunnel affected by two-mining in Yangquan mining area. The designed orthogonal experiment needs 27 numerical simulations including 13 factors with 3 levels for each one. According to the supporting parameters, tunnel stabilization and deformation in the condition of different stresses and supporting parameters were analyzed. Some criteria of tunnel stabilization and deformation to determine a corresponding local optimization scheme were computed. Based on consideration of the supporting cost and difficulty of construction comprehensively, an optimal supporting scheme for the secondary dynamic pressure tunnel was deduced by the associated analysis of the grey theory. The research results were put into use in Yangquan mining area and got the satisfied support effect.
Abstract: The characters of methane emission at the working face No. 14201 in Shaqu Coal Mine were analyzed, the technical parameters to control methane by incline high-position alley pumping were optimized, and its control efficiency was investigated. The results showed that controlling methane in Shaqu Coal Mine by incline high-position alley pumping was very efficient, a great deal of high-concentration methane had been taken out with the pumping system, and this technique supplied a technical guarantee for safe production in the working face.
Abstract: Gas pre-drainage is the main solution to solve gas disaster problems. The efficiency of gas pre-drainage, however, is low by far. The method of controlled blasting was investigated to improve the effect of gas pre-drainage. Such problems as safe ignition in high-gas coal bed, charging technique in a long horizontal borehole, and selection of explosives were solved. After the blasting, the amount of gas selfdrainage is more than 5 times that in the non-blasting area, the efficiency of gas pre-drainage is improved, and pre-drainage time is less than 2/3 of the original time.
Abstract: An FEM simulation using three-dimensional beam element was performed in order to study the causes of cracking on the top of curved prestressed concrete girder bridge piers, where the prestressing tendons were simplified as forces acting on the concrete girder. The results indicate that the direction of moment on the top of a single pillar pier caused by prestressing and that caused by dead load are identical, and the former is 1 order of magnitude higher. These two moments are the main causes of cracking on the top of the piers. By comparative computation, applicable suggestions were proposed to prevent the cracking of a pier.
Abstract: Simulated wastewater and the wastewater from a coke-making factory were used to investigate the crystallization and flotation mechanism of precipitates formed in the precipitation of ammonia nitrogen in wastewater. The results obtained by X ray diffraction show that the precipitates formed in simulated wastewater are non-crystalline, but the precipitates formed in coke-making wastewater are crystalline. Infrared spectrum results show that the pH value at which the flotation of precipitates is carried out influences the mechanism between precipitates and collectors used for flotation of precipitates. The collectors, dodecanoic acid and sodium oleate, physically adsorb on the surface of precipitates at pH 9, but chemical adsorption of the collectors takes place on the surface of precipitates at pH 11. Dodecanoic acid is the best collector for the precipitates formed in simulated wastewater but the best collector for the precipitates formed in cokemaking wastewater is sodium oleate because of different crystallization states in different wastewaters.
Abstract: Detailed information of the hot metal desulfurization process is very important for development of the hot metal pre-treatment technology. A comprehensive theoretical model of CaO particles desulfurization and slag regeneration process was proposed, The reacting behavior of CaO particles was described. The effects of particle size, transfer coefficient and sulfur content on the desulphurization process were invesigated. The results show that the deduced model is feasible and can be used to study the hot metal desulphurization reaction efficiently.
Abstract: SEM and image analysis technique were used to investigate the morphology, chemical composition and size distribution of inclusions and the effect of holding time on the size distribution of inclusions in a non-quenched and tempered steel deoxidized by Ti. The results showed that the deoxidation product of Ti in liquid steel could become the nucleus of MnS in solidification of liquid steel. After adding Ti, inclusions in the steel were finely distributed. A proper holding time could make inclusions fine. The grains were fine after adding Ti in the steel.
Abstract: A mathematical model of RH-MFB process was developed. The temperature of molten steel can be calculated by Delphi program. The results show that the temperature of molten steel declines drastically in the beginning of refining, and the speed of temperature drop is approximately 3 ℃·min-1 in the first 10 min. Al addition, blowing oxygen, alloy addition and the initial temperature of the vacuum vessel wall have more effect on the temperature of molten steel. A comparison between the calculated and measured temperatures shows that the values with average errors in ±5℃ is by 80 % for predicting the temperature of molten steel at the end-point of RH-MFB process.
Abstract: The precipitates in X70 acicular ferrite pipeline steel were investigated by transmission electron microscope. There are two typical precipitates in X70 pipeline steel. One is cubic shaped compound precipitates Ti(Nb)NC with the size of 50 nm~1 μm, in which TiN plays the main role and the ratio of Ti/Nb reaches 5~12. The other is spherical shaped Nb(Ti)C with the size less than 20 nm, in which NbC is the main phase with the ratio of Nb/Ti within 1-6.37. The spherical shaped precipitates exist in multigrains proved by electron diffraction. The cubic shaped precipitates formed above 1 150 ℃, and varied scarcely during the process afterwards. The spherical (ellipsoidal) shaped precipitates emerged almost totally in the range of 900 ℃ to 1 100 ℃, and kept coherent or semi-coherent relationship with the matrix. The precipitate of V was not obviously observed reminding the weak effect of V in steel. The results from the high-temperature ductility and strength curves show that the precipitation started at 1 050 ℃ and the amount of the precipitates reach the highest within the temperature range of 900 ℃-50 ℃ in the condition of no deformation.
Abstract: The corrosion inhibition and adsorption behavior of urotropine (UP) for steel in a 1 mol·L-1 hydrochloric acid solution were studied by electrochemical impedance spectroscopy (EIS) and open circuit potential measurements (OCPM). The results of EIS showed that with increasing UP concentration, adsorption film formed gradually on the surface of the electrode and the charge transmission resistance increased. When the concentration of UP is 0.01 mol·L-1, the maximum of inhibition efficiency was observed. When the concentration of UP was greater than 0.01 mol·L-1, UP desorbed from the steel surface and made inhibition efficiency decreased. The results of OCPM indicated that the difference of corrosion potential before and after the addition of UP was linear with the reciprocal of temperature. The adsorption heat was -35 kJ·mol-1, the mode of adsorption was physical adsorption, and UP was an anodic inhibitor.
Abstract: This paper investigated the galvanic corrosion behavior and laws of AZ91D magnesium alloy coupled with other four metals (Q235 carbon steel, H62 brass, LF21 aluminum alloy, and 356# cast aluminum) in ethylene glycol solution and the difference before and after inorganic-organic salt compounds were added into the solution as an inhibitor, and then discussed the effect of this inhibitor. It was found that not only uniform corrosion was reduced but also pit corrosion was abated effectively by adding the inhibitor of inorganic-organic salt compounds into the ethylene glycol solution system. By scouting the change of electrochemical parameters and mapping the polarization curves it was found that cathodic control was replaced by anodic control in the process of galvanic corrosion and the effect on anode was more obvious.
Abstract: SiCp/Al composites with 63 % SiC in volume fraction were successfully prepared by powder injection molding and pressureless infiltration. The effects of major processing parameters on the properties of SiC preforms and SiCp/Al composites were investigated. The results showed that SiC preforms prefired at 1100 ℃ or lower temperature exhibited high open porosity, which is over 97.9 % of the whole porosity. The SiO2 film resulting from the oxidation of SiCp at high temperature can remarkably enhance the wettability of SiCp by Al alloy liquid, leading to a significant increase in density of the composites. After optimization of the processing parameters, the SiC performs were well wetted by Al alloy liquid. As a result, an SiCp/Al composite with a higher relative density of over 97 % was obtained.
Abstract: Finite element method was used to numerically simulate spring-back in multi-point forming (MPF). By contrasting two forming modes of multi-point die (MPD) and multi-point press (MPP), the influence of different forming modes on spring-back was analyzed. Firstly figuration was simulated by explicit method, and then implicit method was imported to calculate the spring-back of the spherical parts of 1 mm and 2 mm in thickness. The results indicate that when forming a figuration piece of 400 mm in curvature and 1 mm in thickness by the MPD forming mode of 10×10 array without hold blank, its spring-back value is 1.22 mm up to the most. But under the same condition, the spring-back value only is 0.24 mm by MPP. Namely the spring-back value of a metal sheet by MPP is 1/5 that by MPD. Moreover the spring back value is approximately 0 when forming a spherical part of 2 mm in thickness by MPP. It is concluded that MPP is better for MPF than MPD, and spring back value is sharply reduced.
Abstract: A new environmental friendly catalyst, I2/Pana, was prepared. The catalytic activities of I2/ PAn in synthesizing 2-methyl-2-ethoxycarbonylmethyl-1, 3-dioxolane, 2, 4-dimethyl-2-ethoxycarhonylmethyl-1, 3-dioxolane, cyclohexanone ethylene ketal, cyclohexanone 1, 2-propanediol ketal, butanone ethylene ketal, butanone 1, 2-propanediol ketal, 2-phenyl-1, 3-dioxolane, 4-methyl-2-phenyl-1, 3-dioxolane, 2-propyl-1, 3-dioxolane, and 4-methyl-2-propyl-1, 3-dioxolane were reported. It is demonstrated that I2/PAn is an excellent catalyst. Various factors concerned in these reactions were investigated. An optimum condition was found, that is, the molar ratio of aldehyde/ketone to glycol is 1/1.6, the mass ratio of the catalyst used to the reactants is 0.2 %, and the reaction time is 1.0 h. Under the optimum condition, the yields of these 10 kinds of acetals/ketals are 47.3%-94.2%.
Abstract: The traditionally used parameter for accessing the surface such as surface roughness has a very limited value in relating the functional properties of bearing and lubricant retention capabilities to the surface of rolls and steel sheets. This paper proposed some functional characteristic parameters of 2-D profiles and 3-D surfaces and presented their calculating methods. By comparing with surface roughness and analyzing the surface of electrical discharge textured rolls with these parameters, it is proved that these parameters more concretely and exactly show the functional properties of surface topography.
Abstract: Work roll wear contours and wear profiles were analyzed on the basis of large amount of measured work roll contour patterns and processing parameters. The method of building wear calculation functions for center portion abrasion and marginal abrasion respectively was used to develop a work roll wear prediction mathematical model for the 1700mm hot strip mill of Wuhan Iron and Steel (Group) Co. by using genetic algorithm. The calculated results of the prediction model are in good agreement with the measured ones and can be applied to guide production in practice.
Abstract: A control model was proposed for the secondary water cooling in continuous slab casting in a steel plant. Based on the heat transfer theory and the reasonable analysis and hypothesis of operating conditions, a differential equation of heat transfer was established. Numerical calculation method was used to solve the differential equation, and the water distribution under different operating conditions was obtained by using regression method. The simulation and a production test proved the availability of the control model, and the cooling parameters derived from the control model was verified in production practice of 16Mn type steel.
Abstract: A robust approach based on μ synthesis is proposed on the analysis of a dynamic set AGC model and engineering practice in hot strip mill. Even thought there is perturbation in stiffness, the performance of the system with the approach satisfies the request all the time. By introducing the fictive uncertainty characterizing the system capability and the main loop theorem, the problem that design a controller to satisfy the performance request with the model perturbation inside is transformed into the robust stability problem of an augmented system. Compared with H∞ method, this method is more effective because of its design target more really reflecting the control target. In the end, simulation with the practical data proves the dynamic set AGC system with the method can achieve more robust performance than that of H∞ method.
Abstract: Based on the keystone of genetic algorithm (GA), improvements are made to simple genetic algorithm (SGA) in two aspects. The theory of fuzzy control and the niche technique are introduced into the GA, for the purpose of enhancing the population diversity and maintaining the best part of each generation. In order to avoid premature convergence and occurrence of minimal deceptive problems, which is caused by the niche technique, fuzzy control is presented for the controlling of the crossover probability Pc and mutation probability Pm. Above all, that is the new type of algorithm-fuzzy controlled niche genetic algorithm (FNGA). Through comparisons to FGA and NGA with the optimization of several functions, the result of the new algorithm shows its feasibilityand reliability.
Abstract: This paper discusses least squares support vector machines (LSSVM) in the time series forecasting problem. Kernel principal component analysis (KPCA) is proposed to calculate principal component. Least squares support vector machines are applied to predict time series. Experimental results show that the performance of LSSVM with feature extraction using KPCA is much better than that without feature extraction. In comparison with PCA, there is also superior Derforrnance in KPCA.
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
