Abstract: Coal pillar width and gateway location to face result in the differences of stress redistribution and rock seam movement and importantly influence gateway stability and maintenance. According to the geological and mining technical conditions of the No. 1151(3) fully mechanized top-coal caving (FMTC) mining face in Xieqiao Mine and based on the analysis of numerical simulation and in-situ observation, the stress distribution and it's variation laws were investigated at different coal pillar widths. The results show that not only coal pillars' stress distribution laws but also coal entities' stress distribution laws are different with coal pillar width, and both stress distributions are displaced. The maintenance situation of gateway was determined on the stress distributions of coal entity and coal pillar, and the appropriate width of coal pillar is less than the critical displacing stress-width.
Abstract: The electron transfer process of microbe on the mineral surface was studied by the use of a microbe fuel cell. The results indicate that direct contact plays an important role in the process of reducing Fe(OH)3 with Geobacte metallireducens, and the bio-film absorbed on the mineral surface is a key factor. Bio-film formation needs a relative long time. It is an important metabolic way to form bio-film by cell-absorption on the solid surface. Although mediate AQDS accelerates the reduction rate effectively at the early stage, but its effectiveness is not significant after the cell-absorption. So the microbe catalysis mineral oxidation-reduction reaction is influenced by bio-film. Accelerating the film formation on the mineral surface and keeping its stability are very important for the microbe leaching rate.
Abstract: The three-dimensional flow field, temperature distribution, trajectory of inclusions, and removing rate of inclusions in a FTSC tundish were simulated by software FLUENT. The results showed that the flow control devices of double effect pad and dam in the FTSC tundish had a significant influence on improving the flow field and temperature distribution and on increasing the removing rate of inclusions especially small inclusions (d<60μm).
Abstract: Under the use of mould fluxes with different fluorine contents, the change of fluorine ion (F-) concentration in the continuous casting secondary cooling water was investigated in two plants. An experiment was also conducted to understand how the components and the soaking time of fluxes influence the F-concentration of leaching water. The results showed that, when a flux with low fluorine content was used in Plant A, the increase of F- concentration in the secondary cooling water was 1.2-24.3 mg·L-1, and the water behaved in neutrality. While in Plant B, a flux containing high fluorine was used, the increase of F- concentration in the secondary cooling water reached at 57.9 mg·L-1, and the water behaved in acidity. The higher the fluorine content in the fluxes was and the longer the soak time of the fluxes in the water was, the more the fluorine would transfer into the water. Controlling the fluorine in the fluxes less than 2% in mass fraction was helpful to reduce the hazard effects of the mould fluxes on the secondary cooling water. In the researched composition ranges, the basicity (CaO/SiO2) and the Li20 content had not an evident influence on the leaching of fluorine. Increasing the content of B2O3 could reduce the leaching of fluorine from the mould fluxes into the secondary cooling water.
Abstract: Many experimental methods such as electron microscopy and chemical phase analysis were used to study the precipitates of high-strength weather-resisting steel with titanium addition, and the precipitation process was analyzed based on thermodynamics calculations. The results showed that the main particles in the steel were TiC, TiCN, Ti4C2S2 and TiN, and almost TiN particles have precipitated before hot rolling. A large number of nanometer TiC particles distributed on dislocations in ferrite. The size distri- bution of MC phase changed with increasing titanium content. The obvious increase in volume fraction of small scale particles heightened the yield strength of the steel through precipitation strengthening.
Abstract: Aluminum coatings were sprayed on Q235 steel by arc spraying. The failure process was studied through the simulated immersing tests in 3.5% NaCl solution at a fluid velocity of 0.6 m·s-1 and a test temperature of 50 ±1℃. The results showed that there was little difference in the corrosion rates of undamaged and partially damaged samples. Uniform corrosion of the aluminum coatings was slight. Local corrosion occurred on the coatings because of synergism of the occluded cell and the active-passive cell. The main corrosion type was pit corrosion which induced bed separation and pits. Once corrosive solution arrived at the substrate, galvanic corrosion occurred, and aluminum coatings acted as the sacrificial anode protecting the steel substrate from corrosion.
Abstract: By using the orthogonal design method, experiments of extracting iron from slag and making glass-ceramics from secondary slag melt were carried out. The slag-iron separation results were compared at different raw material ratios. The phase composition and characteristics of the glass-ceramics products were analyzed using comprehensive methods such as optical microscope, XRD and physical and chemical properties testing. The feed proportioning and processing were introduced for guiding industrial test.
Abstract: Efforts were focused on the improvement of fusibility of selective laser sintering (SLS) ceramic powders by the approach of coating some low melt-point binders on them. Methylmethacrylate monomer and butylmethacrylate monomer were synthesized and prepared as sintering binder. The infrared spectrum and DSC/TG method were employed to analyze the copolymer. The results showed the main composition of the copolymer is polymethylmethacrylate and polybutylmethacrylate, the glass transition temperature is 102.0℃ and the heat decomposition was beyond 80% between 300-400℃. The self-made copolymer and the inorganic binder NH4H2PO4 were mixed together by a proper proportion. The binders were used to coat Si3N4 ceramic powders by mechanical mixing and spray drying. The coated powders were sintered successfully by SLS.
Abstract: The hydrodynamic force of lifting pipes in a 1 km pilot-scale mining system of polymetallic nodules is determined by many parameters. Based on the integrated design parameters of the 1 km pilotscale mining system, the suitable wave theory was selected and all kinds of parameters were presented. A numerical integration procedure was formulated for calculation of the hydrodynamic force according to the Morison equation. The relationship among the force, time and depth below ocean surface was finally studied. At the same depth below ocean surface, the total hydrodynamic force is varied with increasing time as a function of sine. While at the specified time, the total hydrodynamic force is decreased with increasing depth below ocean surface. The lapse rate is particularly fast from 0 to 200 m in depth. The maximum of hydrodynamic force is 3. 790 kN.
Abstract: Due to various nonlinear factors in vehicle suspension, the time domain method applicable to solve a nonlinear model can obtain more accurate ride analysis results. Considering the limitation of single software, the concurrent simulation technique was adopted to analyze the ride performance of a nonlinear vehicle model. The nonlinear vehicle model was built using mechanical system simulation software ADAMS. The road surface model, tire model and driver model were constructed using S function in the MATLAB/Simulink. With the randomly generated road data as input, the simulation model was built and run under the MATLAB/Simulink. The results were imported to ADAMS. An example of ride analysis based on co-simulation was given, anti the root mean square value of weighted acceleration on sprung mass and tire dynamic loads was calculated according to the data of time history response. The results of ride analysis show that the co-simulation approach is reasonable and reliable and turns out to be adequate for time-domain ride analysis of a nonlinear vehicle model.
Abstract: Two aspects realizing the self-protect ability of a blast furnace cooling system with copper stave, adherent dross capability and adherent dross condition, were mainly discussed. Based on the copper stave in practice, a three-dimension heat transfer mathematical model of copper stave was established. Integration of the calculation with practice experience shows that the copper stave is more suitable for high loaded heat zone. The copper stave can provide with better adherent dross capability; but at the same time, only if having better adherent dross condition, the copper stave self-protect ability can be realized to get longevity and high productivity. The various elements of adherent dross condition were also analyzed.
Abstract: A new method of oxygen enrichment from air by use of gradient magnetic fields was introduced, A magnetic space with open borders was formed by two opposite magnetic poles of two permanent magnets with certain distance, A field intensity gradient, which points at the interior of the magnetic space, existed near the borders. When oxygen molecules in air outflowed via the borders, they would be fettered by the magnetizing force. So oxygen was enriched in the magnetic space, especially at the far end away from the air inlet, The most outstanding characteristic of this method was to be able to effectively avoid the re-mixing caused by gas turbulence, Brown motion and diffusion. Neodymium-iron-boron permanent magnets were adopted and the size was 78 mm×38 mm×30 mm. The size of the formed magnetic space was 78 mm×38 mm×1 mm, The experimental results showed that the highest oxygen volume fraction in the magnetic space appeared at the farthest border apart from the air inlet. The airflow ratio of inlet to outlet had an optimal value(air inlet ≤ 60 mL·min-1) which made the highest oxygen volume fraction. Under the experimental conditions in this study, it should be about 2.0, When the airflows of inlet and outlet were up to 40 mL·min-1 and 20 mL·min-1, respectively, the increment of oxygen volume fraction at the outlet reached 0. 65%.
Abstract: A kind of filter with sand as the percolation medium for dust-removing was discussed and designed for isothermal and high temperature experiments. The aim of this study was to evaluate the performance of the granular filter designed for hot gas cleaning up. The effect of temperature on the characteristic of the granular bed filter at high temperature was investigated, and the formulae of dust removal efficiency and pressure drop with temperature were obtained. The experimental results are similar with the formulae. With the increase of temperature, the dust-removing efficiency and pressure drop become higher during the dust-removal process.
Abstract: A new control solution to finishing automatic width control (FAWC) and automatic gauge control (AGC) is proposed based on active disturbance rejection controller (ADRC) because the plant is of serious decoupling, large time-delay, uncertainty, many disturbances and nonlinear etc. A new kind of static and dynamic decoupling way based on extended state observer (ESO) is presented to eliminate the coupling between FAWC and AGC. In order to produce the fast transient response of the time-delay system, the proposed ADRC consists of the ESO and nonlinear state error feedback (NLSEF) without tracking differentiator (TD). The performance of NLSEF is improved by using a nonlinear function and the order of ADRC is lower than the routine ADRC. Simulation results show that the designed controller not only has good decoupling performance, but also ensures good robustness and adaptability under modeling uncertainty and external disturbance.
Abstract: The cooperation mechanism between a continuous descaling and cold-rolling mill (CDCM) and its downstream machines, which is the bottleneck in cold rolling production management, is under consideration. The production changeover policy for the CDCM is studied to assure the continuity of production and to reduce both the inventories of work in process and the changeover frequency in production. A mathematical model is built to determin the order and lot size on the CDCM. A heuristic algorithm and three changeover rules are developed to solve practical problems. Computational results show the algorithm's effectiveness and adaptability with the data obtained from production practices.
Abstract: In a context of modern capital market, the first issue that must be solved in a firm's equity financing is to determine the systematic risk of equity capital compared with the entire market, and further to obtain the reasonable level of rate of return to equity investors. This paper used a rolling method to measure theβ coefficients of equity capitals in 30 listed A-share steel making companies in China. The results by the rolling method are more stable compared with the ones by traditional measurement methods, which means the results are more relevant to the financial decision-making for listed A-share companies.
Abstract: A self-adaptive genetic algorithm was proposed and successfully applied for the shortest path planning of vehicles. The encoding scheme, crossover and mutation operators were specifically designed for shortest path planning problems in the proposed genetic algorithm. A new online self-adaptive adjustment strategy for crossover and mutation probabilities was also investigated in order to improve the search speed and search quality of genetic algorithm. The comparison of the proposed genetic algorithm with Dijkstra and A* algorithms was carried out. Simulation results under 5 different circumstances show that the proposed genetic algorithm can decrease the searching time for shortest path compared with Dijkstra algorithm and obtain more shortest paths than A* algorithm.
Abstract: The economic model was applied to solve the QoS (quality of service) guarantees problem, and a utility model expressed in multi-QoS attributes was presented, which can be used to dynamically allocate resource in the Grid. A multi-QoS attributes-based joint utility function scheduling (JUFS) algorithm under the deadline and budget constrain was proposed. The performance of the algorithm was evaluated through a series of simulations. Comparisons with other economic and non-economic algorithms show that the performance of the JUFS algorithm matches well with the service on demand in the Grid.
Abstract: To solve the power circuit parameter design of the direct power control (DPC) system of three phase boost-type PWM rectifiers, the power control model of a PWM rectifier is established based on it model in the synchronouscoordinate. According to the power control model and the features of the DPC system of three phase boost-type PWM rectifiers, it is deduced that inductance on the AC side depends on power, the width of power hysteresis comparators, and switching average frequency. DC voltage is determined by AC voltage, inductance on the AC side, and load. DC capacitor relies on the pulsation of DC voltage, power, inductance on the AC side, and load. A design method of inductance on the AC side, DC voltage and DC capacitor of the power circuit based on many factors is proposed. The design method is proved feasible by simulation and experiment.
Abstract: A humanoid robot joint was established. Two pieces of Mckibben muscles were used to actuate the joint. The force characteristic of Mckiben muscles was introduced simply. The relationship between Mckibben muscle length and the joint angle was calculated. The maximum of the joint angle was discussed in view of force analysis. The influence of connective position and structure parameters on the maximum of the joint angle was analyzed. The comparison between the artificial joint and human's was conducted. The result shows that both the contraction ratio of Mckibben muscles and the structure parameters of the joint have great influence on the joint angle. The appropriate connection position with the inboard Mckibben muscle can make the joint angle get its maximum.
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
