Abstract: In order to improve the full-flow state of backfilling pipelines in deep mines, full-flow ratio was put forward to regard as a quantitative index to describe the full-flow state of the filling system. At the same time a mathematical model of full-flow ratio was deduced based on the hydraulic transmission theory and its influence factors were also analysed in theory by using the mathematical model. It is found that reducing the pipe diameter or increasing the slurry flow velocity is the best way to increase the full-flow ratio. On the basis of the pipe two-phase flow theory, a mathematical expression about the relationship of the pipe diameter, velocity, and full-flow ratio was also established, which provides a theoretical basis of selecting the best conveying parameters for the filling system. A local reform, replacing Ф150 mm pipes with Ф85 mm pipes and increasing the flux to 80 m3·h-1 simultaneously, was carried out in a deep mine filling system. The results show that the full-flow ratio of such system is able to be improved by 6 times and the pipe wearing can be reduced effectively.
Abstract: The effects of parameters including solution pH value, initial Cu2+ concentration, contact time, spent shiitake substrate dosage, and temperature on the adsorption of Cu2+ on the spent shiitake substrate were studied, and the adsorption mechanisms were also analyzed. As the initial pH value lowers, the adsorption capacity decreases. The adsorption of Cu2+ on the spent shiitake substrate follows well by the Langmuir and Freundlich equilibrium adsorption models. The maximum adsorption capacity of Cu2+ is 33.11 mg·g-1. The equilibrium time is 1 h. The adsorption kinetic data fit the pseudo-second-order model very well with the correlation coefficient of 0.9995. The adsorbent dosage is optimized to 10 g·L-1. Raising the temperature leads to an extreme drop of adsorption capacity. Thermodynamic studies indicate that the biosorption process is exothermic and can react spontaneously more easily at lower temperatures. By means of scanning electron microscopy and Zeta potentials, it is found that the adsorption of Cu2+ on the spent shiitake substrate is mainly a physical process at lower pH values, while a chemical one at higher pH values.
The bioleaching of a high alkaline copper oxide ore from Yunnan Province in southwest China was carried out in a shake flask with ammonia-producing bacteria Provideneia JAT-1. It is found that temperature, liquid-solid ratio, species and concentration of the leaching aid, and initial bacteria inoculation have significant impact on the copper leaching rate. When the temperature is 30℃, the liquid-solid mass ratio is 7:1, the concentration of ammonium sulfate as the leaching aid is 0.024 mol·L-1, and the initial bacteria inoculation is 20%, the bioleaching for 144 h yields a copper recovery of 42.35%. The result of phase analysis shows that the copper leaching rate of secondary sulphide copper in the ore is the highest.
Abstract: In view of the importance of heat state judgment for calcium carbide smelting, the concept of furnace heat index was presented by analyzing the smelting features. A calculation model of furnace heat index was established based on the two-stage thermal equilibrium, and a prediction model of hot calcium carbide temperature was constructed by using a BP neural network. Both the models can effectively judge the furnace heat state. Simulation results show that there is a significant linear correlation between hot calcium carbide temperature and heat surplus, and it is feasible to consider furnace heat index as a heat state's sign. The hit rate to hot calcium carbide temperature predicted by the prediction model reaches 86.7%.
Abstract: Massive CaO(CaS)-Al2O3-MgO complex inclusions were found in 40Cr casting billet samples based on systematic sampling during the processes of before LF-after LF-tundish-continuous casting and electron microscopy analysis on inclusion morphology, size and composition. The formation of CaO(CaS)-Al2O3 complex inclusions was the-oretically calculated in the CaO-CaS-Al2O3 ternary phase diagram obtained by Factsage; the composition and formation process of CaO(CaS)-Al2O3-MgO complex inclusions were studied by further stroke treatment on surface scan distribu-tion. Factsage calculations show that the contents of components in the liquid region of the CaO-CaS-Al2O3 ternary phase diagram are 32% to 58% CaO, 0% to 5% CaS, and 42% to 65% Al2O3. The CaO content increases and the CaS content decreases gradually after calcium treatment. In combination with the scanning plane distribution of inclusions, it is found that the CaO(CaS)-Al2O3-MgO complex inclusions are xCaO·yAl2O3+mMgO·nAl2O3+Al2O3+CaS. Moreover, Ca can make Al2O3 become CaO-Al2O3 while the inclusions have very high CaS content after calcium treatment. Along with calcium treatment carrying on, CaS will gradually transform into CaO-Al2O3 from the inner to the outward.
Abstract: The kinetic processes of recrystallization and precipitation in low carbon steels with different Nb contents were studied by stress-relaxation method. The effects of Nb solute drag and its precipitation on the recovery and recrystallization behavior were analyzed by the experiment and theoretical model. When the Nb content increases, the nose temperature of precipitation kinetic curves (PTT) rises, but the time of precipitation corresponding to the nose temperature changes a little, which is about 20 to 30 s. The precipitation can obviously restrain the recrystallization process, and increasing the Nb content makes the non-recrystallized temperature rise. The Nb solute drag can inhibit the mobility of grain boundaries, lead to the decreasing mobility rate of grain boundaries, and finally cause the process of recrystallization retarded. The recrystallized activation energy is linear with the square root of Nb mass fraction.
Abstract: 30MnB5 hot stamping steel was quenched and tempered at different temperatures. The effects of tem-pering temperature on the microstructure and mechanical properties were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, and tensile testing. The best mechanical properties were obtained after the steel being tempered at 200℃ for 2 min, which are the tensile strength of 1774 MPa, the total elongation of 8%, and the product of tensile strength and elongation more than 14 GPa.%. It can meet the require-ment for automotive structural parts after hot stamping. The mechanical properties non-monotonically change with tempering temperature. The microstructure of the steel tempered at 200℃ is lath martensite and ε-carbides, and the dislocation density decreases slightly. The ε-carbide particles with the size of about 100 nm in length are needle-like distributed in martensite laths and pinned with dislocations. When the tempering temperature increases, the recovery and recrystallization of lath martensite occur, the lath boundary becomes more and more obscure, and the dislocation density decreases sharply. Furthermore, some of the lath martensite transforms into equiaxed ferrite, and the ε-carbides gradually convert into low-boundary-layer-energy spheroidal cementite, which is coarsened to about 200 nm. Owing to these, the interaction between carbides and dislocations largely weakens.
Abstract: The effects of annealing time on the microstructure and mechanical properties of a cold rolled medium-manganese TRIP steel 0.1C-7Mn were analyzed on a CCT-AY-Ⅱ heat treatment system for thin steel sheet. The microstructure and composition of the steel obtained through different annealing processes were investigated by means of scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, and energy dispersive X-ray spectroscopy. The amount of retained austenite in the steel was determined by X-ray diffraction analysis and the mechanical properties were measured by tensile testing. The steel annealed at 650℃ for 3 min has the best comprehensive mechanical properties, with the tensile strength of 1329 MPa, the total elongation of 21.3%, and the product of tensile strength and elongation of 28 GPa.%. It is believed that the high plasticity is provided by the TRIP effect of metastable austenite together with ultra-fine grained ferrite. The high strength is caused by martensite which is directly transformed from austenite in the cooling process during annealing and obtained during the tensile deformation attributed to the TRIP effect.
Abstract: The microstructural evolution of undercooled austenite in C-Mn-Si TRIP steel and C-Mn-Al-Si TRIP steel during hot deformation was investigated by hot uniaxial compression testing on a Gleeble-1500 hot simulator, and the influences of alloying elements and processing parameters on the dynamic transformation of undereooled austenite were analyzed. It is found that the dynamic transformation kinetics of undercooled austenite in C-Mn-Si TRIP steel and C-Mn-Al-Si TRIP steel is faster obviously than the isothermal transformation kinetics of undercooled austenite. In comparison with C-Mn-Si TRIP steel, the A3 temperature of C-Mn-AI-Si TRIP steel is elevated markedly by the substitution of 1% Al for Si, and the dynamic transformation of undercooled austenite in C-Mn-AI-Si TRIP steel is faster at the same processing conditions. But the averave size of ferrite grains fomred by the dynamic transformation in C-Mn-Si TRIP steel is finer. The refinement of austenite grains before the dynamic transformation is of benefit to the development of the dynamic transformation of undercooled austenite. Increasing the deformation temerature or the strain rate of undercooled austenite during hot deformation has a retarding effect on the dynamic transformation of undercooled austenite, but this effect is not marked.
Abstract: Oxide scales on the surface of 700 MPa grade high strength steel produced by CSP process were studied in this paper. It is found that along the length direction of the coil, the oxide scales on the head and the middle mostly consist of magnetite-iron eutectoid, but the oxide scale on the tail is a double-layered structure with the outer layer of Fe2O3 and the inner layer of Fe3O4. Along the width direction of the coil, the oxide scale is thick at the edge, and it thins as far away from the edge. The percentage of Fe2O3 and Fe3O4 phase decreases and the proportion of magnetite-iron eutectoid increases from the edge to the width center. When the distance is over 300 mm apart from the edge the oxide scale entirely consists of magnetite-iron eutectoid. In comparison with SPHC steel produced by CSP, the oxide scale thickness of 700 MPa grade high strength steel produced by CSP is less sensitive to strip thickness.
Abstract: The effects of Hf content on the microstructure, dendrite microsegregation and precipitated phase of FGH96 superalloy powders were investigated by scanning electron microscopy, transmission electron microscopy with energy-dispersive spectrometry, and carbon extraction method. It is found that Hf content can change the proportion of dendrite, cellular and microcrystal structures. The microstructures of the superalloy powders mainly depend on cooling rate and the ratio of thermal gradient to solid/liquid interface velocity. Nb, Ti, Zr and Al elements enrich between the dendrite arms, but Co, Cr, W and Ni elements enrich in the dendrite axis for all FGH96 superalloy powders with different Hf contents. The dendrite microsegregations of Ti, Nb, Zr and Hf elements are the least when the mass fraction of Hf is 0.3%. Hf is more sensitive to the oxygen content than the carbon of the rapidly solidified powder particles, and forms the stable oxide of HfO2 firstly.
Abstract: Due to the poor pressing formability of AZ31 magnesium alloy sheets at room temperature, the magne-sium alloy sheets were obtained by rolling at different temperatures and their forming limit diagram (FLD) was drawn by the test of hemispherical punch bulging at room temperature. The effects of rolling temperature on the microstructure and room-temperature formability of the magnesium alloy sheets were analyzed. It is found that the room-temperature formability of the magnesium alloy sheets not only depends on grain size, but also depends on grain orientation. The weakening of the basal texture can significantly improve the performance of bulging forming, and grain size plays a decisive role on the room-temperature formability of the magnesium alloy sheets at the similar basal texture intensity.
Abstract: The forming process of 4Cr9Si2 martensite heat-resistant steel during cross wedge rolling was simulated by means of rigid-plastic finite element software DEFROM-3D. The effect of stretching angle on the internal quality of work pieces was analyzed on the basis of simulated results. It is found that the center of work pieces endures three-dimensional tensile stresses at the beginning of the wedging stage. The increases of the tensile stress maxima and duration time resulting from the reduction of stretching angle lead to will accelerate by decreasing the stretching angle, resulting a higher possibility of internal defects. The axial metal flow in the decrease of work piece diameter for center symmetry after the wedging stage and the increase of axial force, and finally those factors make the central cross section of work pieces decrease. On the contrary, the surface spiral will increase by increasing the stretching angle, but the influence is not obviously. Rolling experiments were carried out to verify the correctness of the finite element method and the reliability of simulated results.
Abstract: A new recognition method of surface defects based to the characteristics of continuous casting slabs. Sample images were on Contourlet transform was proposed according decomposed into multiple subbands with different scales and directions by Contourlet transform. The Contourlet coefficients of subbands and the textural features of sample images were combined into a high-dimensional feature vector. Supervised kernel locality preserving projection (SKLPP) was applied to the high-dimensional feature vector for dimension reduction, which resulted in a low-dimensional feature vector. The resulted feature vector was inputted to a support vector machine (SVM) for recognition of surface defects. The method was tested with sample images from an industrial production line, including cracks, scales, non-uniform illumination, and slags. The test results show that the recognition rate of these sample images is 94.35%, which is better than that by Gabor wavelet.
Abstract: A novel Fourier descriptor based on multi-level triangular area functions (MTA) was proposed for shape retrieval. For each point on the shape contour, MTA values were derived from unequal-arc-length partitions of the shape contour. The MTA can finely capture the global features and local contour variations of the contour and their low-frequency Fourier coefficients were regarded as the feature vector for shape description. The image retrieval performance of the proposed method was evaluated on the standard MPEG-7 shape database and compared with those of Fourier descriptors derived from the centroid distance function, area function, farthest point distance function, angular radius function, arc-height radius complex function, and the combined Fourier descriptor. Experimental results demonstrate that the proposed method reaches the highest precision at the same recall value and has low complexity among these descriptors, showing its effectiveness.
Abstract: Considering the bad efficiency and convergence of multi-objective evolutionary algorithms, this article introduces an elite-recombination-based hybrid multi-objective evolutionary algorithm (ERHMEA). In the algorithm, the multi-objective optimization problem was decomposed into multiple single-objective optimization problems and generated the only elite solution with the genetic-algorithm-based elite recombination strategy. Strategies such as regional population initialization, improved local search and selection mechanisms, optimized subgroup based packet crossover and adaptive multiple mutation operator, and chaos optimization based restart mechanism effectively overcome the inherent defects of elite preservation, as well as the multi-objective evolutionary algorithm (MEA) existing target space solution crowding, slow convergence, prematurity, and other issues. Multi-objective test functions analysis and experimental simulation prove the effectiveness and superiority of the proposed algorithm.
Abstract: According to the market environment and operational characteristics of underground metal mines, a market requirement planning model for mineral products was established by incorporating business intelligence (BI) with combination forecasting firstly. Based on the analysis results of the market requirement plamfing model, a mining-excavation planning model was constructed by using the theory and technology of multi-objective programming, expert systems, and time Petri nets extended with price information, and a calculation method to minimize the production cost was put forward. The calculation results of an underground metal mine show that the mining-excavation planning model can effectively optimize the production planning for the mining enterprise, help to achieve the purpose of enhancing the market competitiveness, and decline the operation cost.
Abstract: A symbol system was proposed for the eco-industrial symbiosis network equilibrium model, which is beneficial to decreasing the consumption of virgin materials and reducing emissions generated by industrial activities. In light of the complex eco-industrial symbiosis network structure with multi-products (semi-products, finished products, by-products, wastes and useful materials) and multi-levels (industrial producers, industrial consumers, industrial decom-posers, and demand markets), we described the optimizing behavior of various decision-makers, derived the equilibrium conditions, and established the eco-industrial symbiosis network equilibrium model as a variational inequality problem. The properties of the corresponding variational inequality were discussed under some reasonable assumptions. Finally, the eco-industrial symbiosis network equilibrium model was illustrated with a numerical example to verify its rationality.
Abstract: According to the features of business background and service processes, a performance management frame of service processes was established for bonded port zones (BPZ). A performance evaluation model illustrated with the relative performance system of key indexes from a certain service process of BPZ was proposed on the basis of the performance management frame. In view of the timeliness features of BPZ service processes, a real-time grey prediction method was presented, which was used to carry out the real-time performance prediction of service processes, and the methodology was validated through a real-life case. The performance system of key indexes for BPZ patterns considers both the business layer and IT layer, avoiding one-sidedness of most of the evaluation methods. The real-time performance prediction method effectively supports the close-loop business management of BPZ and is also suitable for wide application in other industries.
The pile-soil load share ratio, pile-soil stress ratio and inter-pile soil deep-seated deformation of compos-ite foundations, which include sand-gravel columns, rammed soil-cement columns and CFG piles composite ground, were measured by indoor model test. The bearing and deformation character of composite foundations were comparatively analyzed between the pile materials. An effective pile length or effective composite soil thickness exists in composite foundations with sand-gravel columns and rammed soil-cement columns. When the pile length of sand-gravel columns exceeds the effective pile length, the effect of improving the load bearing capacity, increasing the compression modulus, and decreasing the deformation is not obvious. It is inadvisable to design the pile length exceeding the effective pile length, except for treating liquefiable foundations, but the sand-gravel columns should not be too long. There is a significant correlation between the effective pile length of rammed soil-cement columns and the compressive strength of pile body; the design of pile body is dependent on the pile strength, and the load bearing capacity of a single pile derived from the pile strength should be not less than that provided by the resistance of soil around piles and pile-end soil. The CFG piles have high pile strength and small compression, and the side resistance can play along the whole pile length. The tip resistance works well when the pile tip penetrating into a good bearing layer. It is advisable to prioritize selecting a good pile-tip bearing layer for design.
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
