Abstract: The seam angle is 64°+ and the mining level height is 54 m at the + 579E2EB1+2 top-coal-caving working face in Weihuliang Mine in northwestern China. Theoretical analysis, numerical calculation and field test were used to study roof collapse and gas overlimit in mined-out area during mining on the working face. The results show that fast mining, control symmetrical top-coal caving in dipping and strike directions, optimizing the ventilation system, and the initiative in preventing gas are valid for safety mining.
Abstract: In order to solve decentralized management and poor sharing in the emergency rescue management information of coal mines, an information management system was developed by B/S model, adopting Oracle as the database. The computer integration and system structure of mine emergency rescue were discussed. The information classification, functions, design of B/S model, and implementation process of the system were described. A system for emergency rescue of coal mines was established for No. 12 Coal Mine of Pingdingshan Coal Mining Group Co. Ltd.
Abstract: In order to investigate the effect of underground complex environmental factors on the identification of forecast indicators for coal and gas outburst fatalness and meet the need of determining forecast indicators, the value of drilling cuttings weight and desorption index for drill cuttings were focused on, which were applied in coal and gas outburst controlling. The relation between desorption indexes for drill cuttings was discussed. After analyzing common factors which affect the error of single-index measurement, some attentions in mensuration and measures to reduce the error were put forward in preventing coal and gas outburst.
Abstract: Adsorption and removal tests of SO2 in simulated industrial flue gas were done with polyacrylonitrile activated carbon fiber (PAN-ACF) in the fluidized state: Some influencing factors such as the flux and temperature of flue gas, mass concentration of SO2 and volume fraction of vapor in flue gas, recycle ratio of ACF, and mass flux of new ACF on the desulfuration efficiency of PAN-ACF were investigated. The results show that PAN-ACF has a better desulfurization performance. Its desulfuration efficiency decreases with increasing the flux and temperature of flue gas and the mass concentration of SO2, increases first and decreases later with increasing the volume fraction of vapor in flue gas, and increases with increasing the recycle ratio of ACF and the mass flux of new ACF.
Abstract: Bioleaching test of Ziiinshan copper sulfide ore in a shake flask was conducted at different temperatures. Bacteria culture from Zijinshan copper mine bioheap was applied in this test. The highest copper leaching rate of 87.62 % in 10 d was achieved at 30 ℃. Microbial community at 15 ℃ and 30 ℃ was analyzed by denaturing gradient gel electrophoresis. The dominant bacteria groups at 15℃ and 30 ℃ are Leptospirillum ferriphilum and Acidithiobacillus thiooxidans respectively, together with Acidithiobacillus caldus accounting high proportion at both the temperatures. The change in microbial community with temperature is correlated with its characteristics.
Abstract: The enrichment mechanism of Cu, As and Sn in HSLA continuously cast slabs and medium plates were studied by scanning electron microscope and X-ray energy dispersive spectroscopy (X-EDS). It is shown that Cu, As and Sn are simultaneous enriched in the scale and the scale/steel matrix interface of continuously cast slabs. There are Cu, As and Sn enriched phases in the scale/steel matrix interface of medium plates, and the contents of Cu, As and Sn in the steel matrix are large than those in the scale. The contents of Cu, AS and Sn at grain boundaries of hot rolled plates are more than those in grains. Segregation of Cu, AS and Sn at austenite grain boundaries and selective oxidation of Fe result in enrichment of Cu, As and Sn, reheating in the reheating furnace exacerbates the enrichment, and the penetration and diffusion of Cu, As and Sn toward the steel matrix deteriorates the hot ductility of steel tremendously, which lead to lots of surface microcracks in medium plates. The effect meehanism of Cu, As and Sn enriched phases on the surface microcracks was analyzed.
Abstract: Wet-dry cyclic accelerated corrosion tests together with XRD, SEM, EDS and N2 adsorption technology were employed to investigate the corrosion behavior and corrosion products of a low carbon hainite steel. The steel was subjected to three kinds of atmospheric environments, i.e. marine environment, industrial environment and marine industrial environment, which were simulated by corresponding solutions. It is found that the corrosion rates of the low carbon bainite steel are lower than that of the commercial weathering steel 09CuPCrNi in all the three kinds of environments. The corrosion rates of the hainite steel in the three kinds of environments are also different. In the environment containing both Cl- and SO32- the corrosion is the most serious, while in the environment only containing SO32- the corrosion is the lightest. The distinction of corrosion products in the three kinds of environments is neglectable, while the compact degree of rust layers formed in different environments is obviously different. The more compact the rust layer is, the lower corrosion rate the steel exhibits. There is no serious selective corrosion in the bainite steel for the corrosion has little effect on its tensile mechanical properties.
Abstract: An integrated mathematical model for predicting microstructure evolution in high carbon wire rods during high speed hot rolling and controlled cooling was developed on the base of laboratory research and industrial validation tests. It consisted of many sub-models such as critical strain, static and dynamic recrystallization of austenite, volume fraction of transformed austenite, interlamellar spacing of pearlite, microstructure-to-property relations. Based on these models, a simulating software, which could run on PC computers, was programmed to numerically simulate the physical metallurgy process for high-speed wire production including the temperature distribution, evolution of austenite grains, final microstructure and mechanical properties. The predicted results are agreeable well with the measured ones by industrial tests.
Abstract: Stress corrosion cracking (SCC) of 3Cr17Ni7Mo2SiN and 00Cr22Ni5Mo3N (2205) stainless steels in acidic hydrogen sulfide solutions was investigated by slow strain rate tensile test and U-bent specimen immersing test. The time to SCC failure of 2205 stainless steel was much longer than that of 3Cr17Ni7Mo2SiN stainless steel. 2205 stainless steel was highly susceptible to SCC at a lower pH level in saturated H2S solution, and its SCC susceptibility sharply decreased with increasing pH value or decreasing H2S concentration in solution. 3Cr17Ni7Mo2SiN stainless steel showed a high susceptibility to SCC in solution with a HES concentration higher than 103 mg·L-1 and pH≤4.5. However, the susceptibility varied slightly with the change of pH value and H2S concentration. SCC of 3Cr17Ni7Mo2SiN stainless steel initiated in an intergranular mode, which transformed into transgranular cracking as the SCC propagated further. For 2205 stainless steel, SCC originated at the place where hydrogen-induced cracking (HIC) occurred along the ferrite/austenite matrix boundaries firstly, and then propagated transgranularly.
Abstract: Precipitation of nitrides and carbides in high nitrogen austenitic stainless steels after solution treatment and aging was investigated by using a physicochemical phase analysis method. The character, particle size distribution, content and structural formulae of phases in the alloy were determined. It is shown that the precipitate is mostly M23C6 carbide in 1Cr22Mn15N0.6 steel and (CrFe)2N1-x nitride in 1Cr22Mn15N0.9 steel respectively, and its volume fraction increases with prolonging the aging time.
Abstract: Rolling process parameters of DH36 high strength ship plate steel in Baosteel were simulated and optimized with a selfdeveloped and designed large-specimen plane strain thermo-mechanical simulator. The flow stress was measured in the process of deformation. Microstructure observations, round stick tension and Charpy V-notch impact tests of simulated specimens were carried out. The results show that large-specimen plane strain simulation technology not only meets the requirement of microstructure analysis like a general thermo-simulation system, but also the mechanical properties of the specimens can be analyzed after simulation. Experimental data show that the simulated ship plate steel provides with excellent mechanical properties.
Abstract: Axial compression test was carried out by using a Gleeble-1500 thermal strain-stress simulator with spring steel 60Si2Mn as experimental material. The microstructural evolution and mechanical properties of the metal in semi-solid state are investigated during deformation. The results show that the flow stress of semi-solid samples at the liquid-solid zone is relative low, no other than 10 MPa. A strain-softening phenomenon appears with the deformation proceeding and the influence of deformation rate on the flow stress is comparative complex. The deformation behaviour of solid phase is different from that of liquid phase. The microstructural morphology has close relationship with deformation temperature, deformation degree and deformation rate.
Abstract: The deformation characteristic and interface microstructure of TA1/Q235 during deformation process were studied with accumulative roll-bonding (ARB) technology. It was found that the difference of deformation between TA1 and Q235 enlarged with increasing total strain. When the true strain exceeded 1.0, the difference kept about 1.0. An abrupt change point of the TA1 ' s strain was observed between 850℃ and 900℃, and rose with increasing the difference of radial deformation. When the deformation temperature was less than 850 ℃, obvious deformation microstructure appeared on the side of Q235, which was vertical to the compression direction. When the deformation temperature is between 850℃ and 900℃, obvious ferrite columnar grains were found. The ferrite columnar grains regularly arranged on the side of Q235, and nearly all of them were vertical to the interface. As the temperature increased, the ferrite grains became coarsening. Under the condition of the cumulative deformation less than 1.5 and the deformation temperature of 850℃, the thickness of intermetallic compounds was 0.7 to 1 μm ; when the cumulative deformation increased to 2.0, its thickness was about 1.7 μm. When the cumulative deformation was 1.0 and the deformation temperature is between 700℃and 850 ℃, the thickness of interface compounds was 0.8 to 1 μm. But when the deformation temperature was 900℃ the thickness increased more than one time, and was 2.3 μm when the deformation temperature is 950℃.
Abstract: The room temperature tensile properties of Mo-30Cu alloy was investigated and its fracture morphology was observed Cold rolling test was carried out to study the change in microstructure of Mo-30Cu alloy with different deformations The results showed that the room fracture of Mo-30Cu alloy was composed fracture of copper binder, separation of molybdenum/copper binder interfaces, and cleavage of molybdenum particles. Cleavage of molybdenum particles and separation of molybdenum-copper binder interfaces made cracks in Mo-30Cu alloy during cold rolling at room temperature.
Abstract: The phase-field method was adopted to investigate the effects of noise, initial crystal nuelei's radius, anisotropy and super-cooling degree on the simulation of dendritic growth in Al-Si alloys. The results show that if the initial crystal nucleus is not melted, its size has nothing to do with the simulation results. With the coefficient of interfaeial anisotropic strength increasing, the dendritic tip's growing speed increases linearly, while its radius decreases parabolically. The lower the sub-cooling degree is, the more difficult it is to find secondary dendrites. As a result, the influencing factors in phase-field simulation have important impact on dendritic growth simulation.
Abstract: Electrodeposited Ni-Fe permalloy foils was annealed under hydrogen atmosphere at 850, 1000 and 1 150 ℃ for 5 h, respectively. The microstructures of cross-sections and surfaces were observed by SEM and optical microscope, the crystal structure was studied by XRD, and the direct-current magnetic properties were measured by direct-current magnetic properties testing equipment. The results indicate that when the annealing temperature is between 850 and 1 150 ℃, the direct-current magnetic properties improve with increasing temperature. After annealing, the crystals of the permalloy foils grow up rapidly and present obvious preferred orientation.
Abstract: Soft magnetic alloy Ta/Ni0.65Co0.35 films, whose magnetostriction coefficient is close to zero, were selected as sensitive layer. The effects of heat treatment on the microstructure and the anisotropie magnetoresistance (AMR) properties of Ta/Ni65Co35 films were investigated. A magnetic resistance element with Barber electrode structure was made and its output characteristics were tested. The results show that vacuum annealing can be effective in reducing the stress and impurity defect distribution in the films, increase the grain size, reduce the scattering of grain boundaries to conduction electrons, and make the AMR value effectively improve. Vacuum magnetic annealing is conducive to raising the films' uniaxial anisotropy and make the AMR value of the films and the sensitivity of the magnetic sensor element increase.
Abstract: CuInSe2 thin films were prepared by selenization of electrodeposited Cu-In precursors on Ti substrate under constant current with a carbon rod worked as anode. The phase composition and its influencing factors of Cu-In precursor films and CuInSe2 thin films were studied. The results show that controlling deposition parameters can change the phase composition of Cu-In precursor films. When the atomic ratio of Cu/In is less than 1, the precursors containing the Culn phase and the Cu2In phase are obtained at a lower concentration of InCl3, a lower concentration ratio of H3Cit to CuCl2 and a higher current density. Stoichiometric CuInSe2 films with a single chalcopyrite phase are synthesized from Cu-In precursors containing the Culn phase and the Cu2In phase. The CuSe phase occurs in addition to the CuInSe2 chalcopyrite phase in Cu-rich CuInSe2 films synthesized from Cu-In precursors with only the Culn phase. Cu-In precursors with both the Culn and Cu2In phases are favorable for CuInSe2 films.
Abstract: In a system consisted of semiconductor silicon wafer (Si), diffusion resistant layer (Cr-Ni alloy) and metal contact material (Cu), diffusion couples were formed at Si/(Cr-Ni) and (Cr-Ni)/Cu, respectively. The phases formed due to interracial reactions in both the diffusion couples were investigated experimentally and the apparent phase contact sequences were obtained at 950℃. Based on phase equilibrium calculations of the Cr-Cu-Ni and the Cr-Ni-Si ternary systems, the phase formation driving forces for interfacial reactions of the diffusion couples were analyzed theoretically. The step-by-step phase formation sequences were obtained to simulate microstructure evolutions in the diffusion couples. The thermodynamic predictions are in accord with the experimental observations.
Abstract: A kind of Fe-Ti-C composite powder for reactive spraying was prepared with ferrotitanium and sucrose as raw materials. TiC/Fe composite coatings were synthesized and deposited by reactive plasma spraying (RPS). XRD, SEM and EDS were employed to analyze the composition and microstructure of the composite powder and coatings. The wear resistance properties of the coatings were also tested. The results show that the particles of Fe-Ti-C composite powder for RPS are uniform without any impurity and the bonding strength among the raw material particles is strong. TiC/Fe composite coatings by RPS are composed of layers in which round TiC particles are dispersed within the Fe-alloy matrix. The size of round TiC particles is mostly less than 0.5 μm. The wearing capacity of TiC/Fe composite coatings with 53 % TiC is 25 times that of the substrate (45 steel) in a SRV tester.
Abstract: Acrylic polyurethane varnish coatings were exposed in two artificial weathering environments produced by a fluorescent UV/eondensation weathering device and a xenon lamp light exposure/weathering equipment for different periods of time. The results showed that the xenon exposure program affected the thickness loss and gloss loss more seriously than the UV/condensation. However, yellow index measurements and low frequency impedance revealed that a greater degradation was caused by the UV/condensation, which was in agreement with the result obtained from FTIR analysis. In the two accelerated weathering environments, the low frequency impedance modulus of intact coatings decreased exponentially with the increase in ageing time, and correlated with the changes in other properties of ageing coatings. It can be used to predict the lifetime of the coatings.
Abstract: The concept of amplitude modulation energy ratio coefficient was defined and an algorithm for the coefficient was explained on the base of cyclostationarity analysis on the mathematical model of gear damage vibration signals. Simulation analysis indicates that the method based on cumulant cyclic correlation is effective in suppressing additive stationary noise and in extracting modulation information. Experimental data of localized gear damage was analyzed and the results show that the energy ratio coefficient increases with increasing damage degree in slightly localized gear damage. This coefficient can be used to indicate the localized gear damage degree.
Abstract: With the principle that ozone generates when air is exposed to strong UV radiation, UV-radiated air flowed into a thermobalance to react with pulverized coal. The thermal analysis method was used to study the effect of ozone on coal combustion. It is showed that small amount of ozone can advance the burning time and the weightlessness time of pulverized coal. Dynamics analysis reveals that ozone decreases the activation energy of pulverized coal combustion reaction. Thermodynamic calculations show that the higher the temperature is, the more easily the oxygen atoms are stimulated by oxygen molecules exposed to UV radiation. The idea is proposed that strong UV-radiated hot blast air flow should be used to increase the combustion efficient of injected coal for a blast furnace.
Abstract: To cut down the time and space complexity and improve the efficiency of the attribute reduction algorithm based on Skowron's discernibility matrix, the definitions of a simplified discernibility matrix and corresponding attribute reduction were provided. It is proved that attribute reduction based on the simplified discernibility matrix is equivalent to that based on the old one. By the foundation of a simplified decision table, a function which can measure the frequency of a condition attribute in the simplified discernibility matrix was defined. An algorithm for the above function was designed. Its time and space complexity are O (|U/C|). Then an efficient algorithm of attribute reduction based on Skowron's discernibility matrix was designed with the new function. Its time complexity is cut down to O(|C||U|) + O(|C|2|U/C|), and space complexity to O(|U|). Finally, an example was used to illustrate the effectiveness of the new algorithm.
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
