Abstract: Rock burst was easily happened at chain pillars face. According to the mechanism analysis of rock burst, the between hydraulic mining face and drying mining cracks in the loaded coal mass under the condition of high-energy unstable development would lead to rock burst happening, and would bring forward controlling principle of rock burst that impel crack in coal mass to develop stably and decease energy storied in unit coal mass by lengthening the unloaded area, for controlling of the rock burst at chain pillar between hydraulic mining face and drying mining face. Under this condition, the preventive measure was increasing the porosity of coal mass and deceasing the circulating channels of gas and air. Based on the principle, the preventive scheme was put forward by stage and combining water infusion with grouting. Project practice proved that the scheme was effective.
Abstract: The excavation process of the tunnel construction in metro line No. 5 adjacent to Yuting Bridge in Beijing was modeled by 3D-ANSYS numerical code. The influence of the excavation on the bridge's platform and ground environment was analyzed. The computed results were compared with measured data. It is shown that the influence of the excavation on the bridge's platform andground environment is in the range of the allowable value following the design. Any additional prior consolidating measure is not needed.
Abstract: The sponge iron making with iron sludge produced during DSD acid-making can be used for not only general metallurgy but also iron-carbon bed to treat DSD acid oxidation wastewater. It is pointed out that under the condition of the temperature of 1120℃, the reaction time of 16 min and the carbon content of 27%, the metal transformation rate of sponge iron used for general metallurgy is up to 90%. But the optimal carbon content is 29% for iron sponge to treat DSD acid oxidation wastewater. Under condition of the wastewater's pH value of 3 to 5 and the reaction time of 40 min, the removal rates of CODCr and color are 68% and 90%, respectively. The BOD/COD ratio is up to 0.425 when DSD oxidation acid water is treated with sponge iron. As Fe3C and other materials contained in sponge iron formed so innumerable micro-batteries between iron and other elements to oxidate and deoxidize the organics in wastewater, the pollutants became degradable and the biodegradation of wastewater was promoted. The micro-sponge-shape of sponge iron is so developed that its special surface area is greater and its activity is higher, so it is the best alternative of general iron powder.
Abstract: The treatment of car-washing wastewater by using membrane bioreactor (MBR) was investigated. The influences of operating pressure and environmental factors on the membrane's filtration function were analyzed combining with theoretical calculations. In the meiobar range, membrane resistance was the dominant role, independent of operating terms. In the middle pressure range, concentration difference-polarized resistance was the dominant role, depending much on operating terms. In the high pressure range, gelatin resistance was the dominant role. The influences of the operating pressure was small on the membrane flux, and the mem-brane's separating characteristics were related much with mud concentration, membrane flow velocity and etc. This study showed that when MBR was used to dispose car-washing wastewater, there was a critical pressure in MBR. When the operating pressure was higher than the critical pressure, the membrane flux was changed slightly, but membrane surface pollution was increased distinctly. Therefore when MBR was designed, the operating pressure was a key parameter. The influences of environmental factors such as temperature, pH and hydraulic retention time on the membrane's filtration function were investigated.
Abstract: In order to study the mechanism of the oxidative leaching of marmatite, the slurry of synthetic marmatite was selected as the research object. The electrochemical behavior of marmatite in sulfuric acid leaching was investigated by the three-electrode method. The experimental results proved the intermediate product of H2S in the leaching of marmatite. The results also showed that oxygen, element sulfur disperser as well as chloride ions could accelerate the electrochemical oxidation of marmatite in sulfuric acid. The electrochemical oxidation of sphalerite was retarded but that of marmatite was promoted with the increase of acidity. Marmatite was much easier to be oxidized through electrochemistry than sphalerite. The electrochemical oxidation of marmatite should not be neglected in the sulfuric acid leaching.
Abstract: Rare earth fluorides were synthesized with RE2O3 and NH4HF2 under atmospheric pressure and vacuum in RE2O3-NH4HF2 systems, the reactions in the systems were studied, and a new mechanism for the synthesis of REF3 was proposed. Powder La2O3, Gd2O3 started to react with NH4HF2 at low temperature, and the products were RENH4F4(RE=La, Gd), NH4F, NH3 and H2O. RENH4F4 was decomposed to REF3 and NH4F at high temperature, accompanied with the volatilization and decomposition of NH4F. The whole process could be divided into three steps of synthesis, decomposition and deammoniation. The initial and final temperatures of the reactions were reduced under vacuum. The combination process of synthesis under atmospheric pressure at low temperature and decomposition and deammoniation under vacuum at high temperature should be applied to the preparation of rare earth fluorides.
Abstract: The as-cast structure and microstructure obtained after heat-treatment in the α+γ field of a Ti-46Al-8Nb-2Mn-0.2B alloy were studied. Optical and SEM observations show that the γ phase segregation region is not the grain boundary of the alloy but part of the α + γ lamella. The Al content at the γ phase segregation region is a little more than the α + γ lamella matrix, but it can play an important role in stabilizing the lamella and does harm to the break-up at the γ phase segregation region. By obtaining near γ microstructure firstly in the alloy and then heat-treating it in the middle region of the α + γ field, the duplex microstructure with a grain size of 40μm can be formed, but a little of β phase still exists.
Abstract: Constant strain bend and slow strain rate tests (SSRT) were used to investigate the resistance to sulfide stress corrosion cracking (SSCC) of 16Mn and 16Mn hydrogen-induced cracking (HIC) resistance steels and their welded seams in acid solutions with saturated hydrogen sulfide gas, The results show that all of sampies are sensitive to SSCC in the acidic solutions with H2S. The mechanism of cracking is HIC and most cracks are transgranular type. The resistance to SSCC of 16Mn(HIC) steel with low content elements C, Mn, P and S is better than that of 16Mn steel. Otherwise, the welded seams have less resistance to SSCC than their matrix because of big crystals, inclusions, vacancies and defects produced in the process of welding, but the work of post welding heat treatment (PWHT) can increase the resistance of their welded seams.
Abstract: Corrosion tests of N80 steel under different CO2 partial pressures at 65℃ and 90℃ were carried out by a self-made high-temperature high-pressure autoclave. The mass losses of the steel under different CO2 partial pressures were measured. The morphologies of the corrosion scale and the descaled N80 steel were observed by SEM, and the thickness of the scale was measured. Electrochemical polarization curve and impedance spectroscopy analysis (EIS) were employed to study the corrosion behavior of N80 pre-corroded under different CO2 partial pressures at two temperatures. The results show that as the CO2 partial pressure increases, the protection property of the scale becomes better, but the corrosion rate increases because of the increase in solution corrosivity. The local defects of the corrosion scale are responsible for the pitting corrosion of metal matrix, the increase in CO2 partial pressure makes for reducing the defects. Compared with 65℃, the protection property of the corrosion scale is more sensitive to the change of CO2 partial pressure at 90℃.
Abstract: A bulk nanocrystalline Al-Zn-Mg-Cu alloy was produced by cryomilling and spark plasma sintering. The grain size, the microstrain, phase transformation and microstructure of this alloy were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the bulk nanocrystalline 7000 aluminum alloy prepared by spark plasma sintering has two types of distinctive nanostructures-primarily equiaxed grains with diameters of 50-100 nm, and a few of larger grains with diameters of 200-400 nm. The precipitate of second phases, mainly including η (MgZn2) and a few θ (Al2Cu) and S(Al2CuMg), and recrystallization of the bulk nanocrystalline 7000 aluminum alloy were found during the consolidation process by SPS
Abstract: The surface of an up-conversion luminescence material was modified with carboxyl group in the way of grafting modification. The influencing factors including reaction time, buffer solution and finishing agent's mass were investigated by experiment. This modification method has resolved the problem that when an up-conversion luminescence material is used as fluorescence labeling, it cannot covalently fix biological activity molecules directly. The experimental results show that when the reaction time is 4 h, the PB buffer solution is pH=9.0 and 0.50 mol·L-1, agent to original materials is activity carboxyl group. the volume of adding the buffer solution is 50 mL, and the mass ratio of finishing 12, the surface of an up-conversion luminescence material is mostly modified with
Abstract: Silica aerogels modified and unmodified with trimethylchlorosilane (TMCS) were prepared by using tetraethoxysilane (TEOS) as the silica source via a two-step sol-gel method combined with supercritical CO2 drying. The water absorption of two kinds of silica aerogels was measured and the effect of heat treatment temperature on the water absorption of the unmodified silica aerogel was investigated. The silica aerogel modified with trimethylchlorosilane (TMCS) exhibits excellent hydrophobic behavior. For the unmodified silica aerogel, the water absorption increases apparently with heat-treated temperature in the range of 300-500℃, and tends to be almost unchangeable in the range of 500-700℃. After heat-treated at 800℃, the water absorption in-creases remarkably again, whereas after heat-treated at 1 000℃ it decreases significantly due to vitrification of the silica aerogel. The water absorption process of the silica aerogel can be divided into three stages:quick weight gain, slow weight gain and saturation. The relationship between the water absorption of the silica aerogel and its micro and chemical structures was evaluated by differential scanning calorimetry (DSC)/thermogravimetry (TG), infrared spectra (IR), and N2 absorption techniques.
Abstract: The hysteresis loop technique was applied to investigate the thixotropic behavior of semi-solid AlSi6Mg2 aluminum alloy slurries using a Couette type viscometer. The experimental results show that, under cyclic shear deformation, the thixotropy degree of semi-solid AlSi6Mg2 alloy increases with increasing resting time, solid fraction, maximum shear rate, and decreasing time to reach the maximum shear rate.
Abstract: Accumulative roll bonding (ARB) industrial experiments of Q235 plain carbon steel and L2 pure Al were carried out with a multi-function hot-rolling mill. The effects of deformation temperature, reduction and cycle pass on the tensile strength, stress-to-strain relation, microhardness and plasticity of these two metal mate-rials were investigated, and the reasons for these effects were analyzed. The results indicated that Q235 plain carbon steel and L2 pure Al could be well-bonded themselves by ARB process without the addition of any strengthening elements, their tensile strength increased, but their plasticitv decreased in a certain extent.
Abstract: The eight-stand hot continuous rolling of seamless steel tubes with an inner free floating mandrel was successfully simulated by using three-dimensional thermo-mechanical coupled elastoplastic FEM after the fi-nite element model was constructed with the friction, heat-transferring and contact boundary conditions. The stress, strain and temperature distributions as well as rolling force during the hot continuous mandrel rolling were obtained from the finite element analysis. The simulated rolling force is in good agreement with the measured one. The characteristics of the velocity of floating mandrel as well as the changes in outer diameter and wall thickness of the tube shell were also investigated in detail.
Abstract: The fact that the metallurgical properties of natural lump ores were not insufficiently comprehensive and thorough grasped is obstructing the technology development of using lump ores in a modern blast furnace. Through analyzing and inspecting each metallurgical property of natural lump ores from main habitats in the world by experiment, the article indicates that the lump ores' metallurgical properties can meet a modern blast-furnace except the softening and melting properties. And the interaction between the sinter and the lump ores was found in the high temperature zone of the blast furnace, which can obviously improve the softening and melting properties of the lump ores. The blast burden structure also can be optimized by the interaction.
Abstract: The main cause of deformation of a converter shell is temperature rising of the converter shell, a economical and effective method to reduce the temperature and creep deformation is adopting a heat insulation layer of asbestos board. The temperature field and thermal stress of shells with different thicknesses of asbestos board at different temperatures were obtained for an 80 t converter at Chongsteel in China by heat transfer mathematical modeling. The calculated temperatures were in conformity with the measured data. When the thickness of asbestos board reaches 30 mm, the shell temperature could be controlled below 360℃, which is lower than the creep temperature of the shell material, and the thermal expansion stress of the shell is only 50 96 of that without asbestos board.
Abstract: To provide a theory for the optimized design of a U-tube ground heat exchanger used in ground source heat pumps, CFD software was used to simulate the processes of flow and heat transfer in the U-tube ground heat exchanger. The results show that the heat transfer efficiency of the U-tube ground heat exchanger increases with the increasing distance between two tubes and with the increasing heat conductivity of backfilling soil. The effect of the distance between two tubes and the heat conductivity of backfilling soil on the U-tube ground heat exchanger's efficiency are a very complex nonlinear relation. When the hole-depth is deeper than 80 m, the temperature rise ratio of two tubes increases rapidly and the heat losing between two tubes increases. In practical operation, the hole-depth is better not to be too deep.
Abstract: Aimed at the maximum of economic benefit and mineral resource recovery benefit during iron deposit mining, the ore grade index of Baiyunebo Iron Mine in China was optimized by constructing three system models, including ore reserves model, mineral processing model and technological economic analysis model, and by adopting fuzzy comprehensive evaluation. The results showed that the cut-off grade of magnetite ore in Baiyunebo Iron Mine should be readjusted from 20% to 15%. As a result, the mine economic benefit could be increased more than 120 410 000 yuan RMB and the iron concentrate recovery was more than 91.54×104 t.
Abstract: The essence of both automatic shape control (ASC) and automatic gauge control (AGC) is the controlling of loaded gap between rolls, so the closed control loops of ASC and AGC are coupled. The coupling between ASC and AGC holds down improvement of the combined controlling quality of ASC and AGC heavily. After the coupled process control model was developed, a feedback decoupling controller was proposed to decouple the model. The simulation result is perfect and indicates that the cross coupling between ASC and AGC especially the disturbance from AGC to ASC was depressed, which ensures the quality of the decoupling controller.
Abstract: In surface inspection of medium and heavy plates, defects recognition based on texture analysis suffers from mutative illuminations and scales. An illumination invariant texture analysis method named structure spectrum was proposed and applied to recognition of surface defects on medium and heavy plates. Compared with other textural features such as gray level co-occurrence matrix, Laws texture energy, and Fourier power spectrum, higher classification rates were made by structure spectrum for classification of pits, scars and inclusions.
Abstract: To make an efficient path-finding engine, a heuristic optimization path-finding algorithm was proposed for resolving the time and space complexity problems of a searching algorithm in a large application system. The algorithm was based on the classical Dijkstra algorithm and introduced the decision mechanism in AI into path-finding. To decrease the number of nodes to search, cost-function was incorporated into this algorithm and used to decide the path-finding policy, that was, which nodes were searched firstly. The condition of getting the optimal solution from this algorithm was put forward and proved. These two algorithms were tested comparatively.
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
