Abstract: It is the most important research for west coal mining presently to control the derived dynamical disasters of large scale mined-out area. In order to obtain reliable evidence to control the disasters, some characters, causes and essentials were analysed. The result shows that a technology based on digital monitoring and predicting can control the derived dynamical disasters of large scale mined-out area for west coal mines.
Abstract: The spray test was used to investigate the dust pollution of povement in an open-pit mine. The cap-abilites of moisture absorption, moisture releasing and antifreezing of sixteen kinds of mixtures made of two chlorides were tested under natural environment in one day. By comparison, the best one among them was selected.
Abstract: Contrast tests were performed on the flocculating ability of mycobacterium phlei to hematite and quartz with the method of gravity sedimentation. The result indicated that mycobacterium phlei has much stronger flocculating ability to hematite than to quartz because the former can form even larger accumulation and even closer aggregation structure than the later in the mycobacterium phlei syetem.
Abstract: In the laboratory and with a simulated wastewater as samples, the factors influencing the precipitation of ammonia nitrogen from wastewater were investigated with MgCl2 and Na2HPO4 as precipitants. These factors studied include the pH of precipitation, the dosage of precipitants, and the initial NH4+-N concentration of waste-water. The result shows that the pH of precipitation is the key factor and it determines the precipitation rate of NH4+-N, the remaining concentration, the removal rate and the remaining concentration of Mg2+ and PO43-. The optimum pH is 11. When the initial NH4+-N concentration is less than 1 000 mg/L, both the precipitation rate and the residual concentration of NH4+-N decrease with decreasing the initial concentration. When the initial NH4+-N concentration is less than 100 mg/L, the precipitation rate decreases dramatically, but the minimum residual concentration is 5 mg/L and remaining the same.
Abstract: According to the precise level survey on the subsidence of CFG pile composite foundation and the nonlinear fitting trend analysis, the nonlinear relationship between composite foundation subsidece and time was obtained. The properties of creep and uneven subsidence were pointed out under the effect of building deadweight. The importance of harmony between structure and foundation deformation was emphasized in the subsidence
Abstract: A kind of filter with sand as the percolation medium for dust-removing were discussed and designed for isothermal experiment. Through the experiment by this fiter simulating the BF top gas sub-dedusting, the effect of the thickness of the fiter layer and the filtration gas velocity upon the dust-removing efficiency and the pressure loss was investigated. Based on the experimental results, the optimized thickness of the filter layer and the optimized velocity of filtration gas were confirmed.
Abstract: Highly turbulent flow in the shroud nozzle of a ladle can split introduced inert gas into fine bubbles, which enhances the removal of fine inclusions from molten steel. The maximum size of the bubbles was obtained through calculating the energy dissipation rate of liquid flow in the shroud. The pressure distribution of the fluid flow within shroud was analyzed with Bernoulli equation as well. The results by theoretic calculations are agreeable with these by water modeling experiment.
Abstract: The effect of top slag composition on CaO-Al2O3-SiO2 inclusion composition was studied by controlling the condition of deoxidization and composition of top slag in experimental furnace in which the tire cord steel was melt. The content of Al2O3 in inclusion increased with that in top slag increasing while the basicity of top slag was fixed. Plastic inclusion presented while the content of Al2O3 in top slag was below 8%. It is concluded that the composition of the inclusion can be controlled within the plastic area by controlling the condition of deoxidization and the composition of top slag.
Abstract: Using Shirengou ore as raw material, pitch coke as reducing agent, according to the orthogonal experimental theory a experimental study of direct reduction was performed with coke-cover under the condition of open-firing atmosphere. The rational operating parameters of DRI production were obtained. The experimental results also show that DRI product can be produced with Shirengou Ore.
Abstract: It is clarified that the important method to improve the blast temperature from 1000 ℃ to 1 250-1 300℃ is to preheat both auxiliary air and coal gas. The blast furnace temperature can be reached to 1250-1 300℃ by burning single blast stove gas if using high speed burners and a type of external-combustion swirl-flowing hot blast stove to preheat auxiliary combustion air. The calculating results, similar to those determinating experimental data in a middle experiment hot blast stove, proved that there is no eccentric flow in the face of the store energy balls and the flow and temperature fields even.
Abstract: The silicon in high carbon metallurgical melt was tested with a developed Mg2SiO4(s)+MgO(s) silicon sensor. It was found that the phase construction of the auxiliary electrode and the oxygen component in the melt has an obvious effect on the measuring result. A physical model of this silicon sensor was proposed at the first time. The expression of local equilibrium silicon-oxygen potential, related to the oxygen potential of the melt and directly measured results, was derived. The physical meanings of coverage constant and structure constant were described. The structure constant was calculated to be 66.6 by means of fitting the experimental data. The measured oxygen potental, obtained with different silicon sensors whose coverage constant is less than 1, was corrected with the derived expression. The values of local equlibrium oxygen potential are the same. This testified that the physical model conforms to the practice.
Abstract: The influencing factors on triangular zone cracks were obtained by analyzing the database of sulphur printing results of continuously cast slabs. The result indicates that triangular zone cracks get worse with the increasing of sulpher content, superheat, casting speed and width of the slab. On the basis of that, the responding control principles were proposed as follows. The content of carbon should be near to the lower limit 0.13%. When the content of sulphur is between 0.015% and 0.020%, the content of manganese should be between 0.375% and 0.50% to assure the ratio of manganese to sulphur is above 25. The superheat of steel in tundish should be below 25 ℃ and the casting speed below 1.3 m/min. It is very necessary to improve the intensity of secondary cooling in the narrow side of a wider slab and ansure the precision of continuously cast machine.
Abstract: The temperature of the bottom surface of a tundish was calculated by using an one-dimensional steady-state heat transfer model. The relationship between the temperature of the bottom surface and the damage degree of the tundish lining was established. It was found that the temperature rises with the increase of damage degree. Practical examinations proved that the temperature of the bottom surface rises with the increase of tundish age, and both the detection of damage degree and the quantitative analysis of tundish lining can be carried out by the infrared image technology.
Abstract: In order to improve the statistics of 3D grain microstructure models, a large-scale 3D digital model of microstructures of polycrystalline materials was implemented using Monte Carlo Potts simulation. The quantitative characterization and 3D visualizing of the model were carried out. The results show that the grain size distribution and the grain face number distribution in this model can be fitted approximately by the lognormal function, with an average grain face number of 13.8±0.1, very similar to the polycrystalline microstructure in real material.
Abstract: A class of partial differential equations (PDE) which describe three-dimension steady state crystal growth for concentration were studied. Because there exists far-field condition, their exact solution or numerical solution can not be derived based on known results about PDE. By using variables separation in the complex number field, the real analytical solution in the form of Fourier series was obtained. The result shows that the concentration in the solid-liquid interface is exponentially damped oscillation.
Abstract: A theoretic equation of deformation work, phase transformation temperature, initial grain size and metal structure was analyzed, and a method of controlling the precipitation of σ phase was provided. On this basis, the properties and microstructures of SAF2205 duplex stainless steel during isothermal hot tensile tests were investigated by means of stepped isothermal tension. The result shows that, with the method of fast cooling and temperature-changed isothermal hot tension, the precipitation of σ phase can happen during the deformation, and the tiny and dispersed σ phase can limit the growth of the grains. In order to realize the strain-induced precipitation of σ phase and the superplastic deformation of duplex stainless steel in lower temperatures, a faster cooling velocity needs to be applied.
Abstract: The microstructure of in-situ reactive spray formed 7075+XTiC (the volume fraction X=0,1.15%, 1.73%, 2.91%, 4.48%, 5.95%) after heat treatment at 610℃ and 620℃ for 30min were observed using SEM. The grain size was measured by a mean linear intercept method to analyze the effect of different volume fractions of in-situ TiC particles on the semi-solid microstrucrure of spray formed 7075 alloy. It was shown that at 610℃ the pinning effect was significant when the volume fraction of in-situ TiC particles was up to 2.91%, which made micro-structures of the alloy keep as-spray formed characteristics and could meet the requirement of subsequent semi-solid processing. If that of in-situ TiC particles exceeded 2.91%, the grain size was further decreased, but the number of dispersoids and particles at grain boundaries evidently increased with net-shaped distribution. When that was less than 2.91%, the grain grew abnormally at local areas, resulting in the homogenization reduction of grain structure.
Abstract: The alloys containing Mo-12Si-8.5B and Mo-28Si-8.5B respectively were prepared by the in-situ synthesis reaction of the elemental powders of Mo, Si and B by hot-pressing. The microstructures and the annealing processing were investigated by optical microscopy, polariscopy, scanning election microscopy (SEM), and X-ray diSractometry (XRD). The fracture toughness of the alloys at room temperature were determined to be 7.7 and 4.1 MPa·m1/2 respectively. The mechanism for toughening at ambient temperature was discussed.
Abstract: The Nd-Fe-B Ribbons of 0.1-0.4 mm thick were fabricated by using single roll melt spinning in replace of the traditional casting method. The relationship among the technological parameters, the thickness of ribbons and the microstructure is obtained. In order to fabricate the Nd-Fe-B ribbons of 0.25-0.35 mm thick, the optimum technological parameters should be controlled in the following range. The rolling velocity is about 10m/s, the jet pressure is 0.08-0.10 MPa, and the gap between the roll and the nozzle is (2±0.5) mm. The microstructure of the ribbon of 0.3 mm thick is mainly composed of lamellar Nd2Fe14B phase, which grows in the preferred orientation of <410>, and the spacing between the Nd-rich phases is 5 nm. For the ribbon of 0.4mm thick, the amount of α-Fe is obviously higher than that of Nd2Fe14B, and the preferred orientation is <008>. The microstructure of the ribbon of 0.1 mm thick is composed of fine equiaxed grains, but that of the ribbon of 0.4mm thick, of thick equiaxed grains.
Abstract: It was carried out successfully to microarc electrodeposit ceramic coatings on the anode and cathode of AZ91D magnesium cast alloy with AC pulse method. The thicknesses, morphologies, composition and micro-structures of the coatings were studied by scanning electron microscopy (SEM) and X ray diffraction (XRD). Rare earth element as Ce can deposit in the anode and cathode ceramic coatings on AZ91D cast alloy besides that both electrodes have formed the same characteristic ceramic coatings. By comparing the electrochemical impendence spectroscopies (EIS) and potentiodynamic scanning polarization curves of the anode and cathode coatings, it was found that microarc oxidation (MAO) coatings on the anode and cathode of AZ91D have better corrosion resistance than that of bare AZ91D magnesium cast alloy.
Abstract: In consideration on the on-line R-value measurement of aluminum deep drawing sheets, the selection of initial slip systems was analyzed according to the activation process of the slip systems during plastic deformation. Initial R values of the 3104 aluminum sheet in different directions were calculated. It was shown that texture is the most important effect factor for determining R value, of which initial R value is the key part. The textures existing in the 3104 sheet decide that R0 is the lowest and R90 is the highest. The calculation indicates that the {111} fiber texture can increase the deep draw-ability drastically while the earring effect is obviously reduced.
Abstract: In accordance with such characters of the electrode control system in ladle furnace as the high non-linearity, time-variant, uncertainty of the model, output response time delay serious, and multivariable input and output coupling, an internal model control strategy based on real-time identification on line by neural network was presented. The control strategy applies neural network decoupline control and the chaos algorithm to the improved BP algorithm and speeds up the training of neural network. The validity of the control strategy is verified by simulation analysis.
Abstract: On the basis of the computer-aided design/computer-aided process planning (CAD/CAPP) integration information model of cross wedge rolling tools (CWRT), a machining features sequencing algorithm for CWRT was constructed with the creative decision-making method based on knowledge and VC++ object-oriented programming technique. Through properly arranging subtasks and defining constraints at different stages, the feasibility and agility of tool process planning were guaranteed. The practicability of this machining features sequencing algorithm was proved by analyzing a typical CWRT.
Abstract: Six items were proposed for evaluating the shape control performances of a mill, including adjustable area and transversal stiffness of loaded roll gap, shape control efficacy curve, edge drop, average contact force between rollers, and its distribution ununiformity. The finite element models of several types of famous mills, such as HC, CVC, PC and DSR, were developed to calculate the roll. The deformation and control performances of these mills were analysed detailedly.
Abstract: Based on Maxwell equations, a model for describing the electromagnetic field in a slab was developed. To meet the need of numerical calculation the model was discretized and simplified. A simulation was conducted by means of the finite element method. The contour plot of the electromagnetic field was presented and analyzed. When the other parameters unchanged, the fundamental relationships between the frequency and Lorenz force and between the electrical current and Lorenz force were established respectively.
Abstract: The change of entry gauge is very large when the flying gauge varies in tandem cold rolling mills, and the speed of identification convergence with a traditional self-adaptive controller is slower than that of parameters changing. In order to deal with this problem, an adaptive multi-model control method was proposed, by which simulations on a 5-stand tandem cold rolling mill were carried out. It is found that the system has a satisfied speed, stability and precision.
Abstract: A simple recurrent neural network named as diagonal recurrent neural network was studied. To overcome the slow convergence of BP algorithm, the recursive prediction error (RPE) algorithm was proposed, which can train both the weight and the bias. A given model was identified by using diagonal recurrent neural network trained with RPE algorithm, and the model of a phosphating temperature control system was established. Both simulation and experiment demonstrate the effectiveness of the proposed algorithm.
Abstract: The key structure of an Ac excited grid frequency synchronized machine (AEGFSM) was presented. The simulation of AEGFSM, cyclo-converter, field-oriented vector control algorithm was done according to their discrete mathematical model. An AEGFSM sample drived was fabricated. Simulation results are in excellent agreement with the experimental under the typical working condition. It is concluded that AEGFSM drives have the high-quality dynamic performances as DC drives and provide an applicable solution of middle-voltage freqency-variable drives.
Abstract: To develop a special miniature PSA oxygen concentrator for SARS patients, the effects of operating parameters, such as production duration, purge-to-product ratio, product flowrate, length-to-diameter ratio of the columns and properties of adsorbents, on the product purity and recovery of the miniature PSA oxygen system were experimentally investigated. The experimental results show that, under miniaturization conditions for PSA process, the optimal production duration is 12 s and the purge-to-product ratio is 0.5. The product purity decreases and the recovery increases when the product flowrate increase. When the product purity is above 90%, the product recovery is about 19%. The properties of adsorbent has significant influences on performances. The product purity increases with the length-to-diameter ratio of column increasing and the proper value of the ratio is between 3.7 and 4.0.
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
