Abstract: Chengchao Iron Mine of Wuhan Iron and Steel Corporation was taken as the engineering background. Drilling monitor and similar material model test were used to study the regular and mechanism of capping rock collapse during orebody caving. Firstly, based on the condition of orebody occurrence, strata's structure and mining process, two drill-holes were designed to monitor the protess of capping rock collapse. Secondly, based on the similar model theory, according to sections and geometry sizes a similar material model was built to study the characters of strain, displacement and deformation through the data collection methods of pressure cells, percent meters and photogrammetry. The collusions reveal the elementary mechanism of capping rock collapse and the rules of ground subsidence during the caving process by non-pillar sublevel caving.
Abstract: In order to investigate the aseismie performance of a kind of newly developed frame structure with dense grid of slender concrete columns in walls, a quasi-static test under reciprocating lateral loads was conducted for a full-scale two-storied modal frame and the experimental results were introduced. As a comparative study, the static elastoplastic push-over analyses were performed using different softwares of ABAQUS, SAP2000 and PKPM. Compared with the experimental results, the analyzed FEM models exhibited the same crack propagation patterns in walls, and the plastic hinge points also coincided with the experimental results. Finally, a capacity spectrum was obtained to evaluate the aseismic performance of the experimental model; its aseismic performance under eight-degree rare earthquake was evaluated. It is concluded that the aseismic performance of the frame structure with dense grid of concrete columns is considerably good.
Abstract: Two efficient polyphosphate accumulating organisms, A and E, were screened from the returned sludge which comes from the final sedimentation tank in Beijing Gaobeidian Sewage Treatment Plant. At the same time, the reversing dilution plate separation technology was identified to be beneficial to screening the polyphosphate accumulating organisms. Observations of their morphological, physiological and biochemical features indicate that they are acinetobacter sp. By experiment, the optimal choices for carbon of the polyphosphate accumulating organisms A and E are CH3COONa and C5H8NNaO4, respectively. Experimental data show the best growth conditions of polyphosphate accumulating organisms in reducing carbon concentrations, i.e. less than COD 100 mg·L-1:the optimal pH values and temperatures of the polyphosphate accumulating organisms A and E are 8 and 7, 20℃ and 25℃, respectively. Metal ions Mg2+, K+ and Mn2+ can be helpful to accumulate polyphosphate. The effect of oxygen on the phosphate accumulating microorganisms was discussed, and the characteristics of P removal in anaerobic condition and P uptake in aerobic condition could be observed.
Abstract: Dyeing wastewater was treated with a two-stage system of hydrolysis acidification and food chain reactor (FCR). The influences of hydraulic retention time (HRT) on the removal efficiency of COD, chromaticity, NH3-N and anilin were examined, and the mechanism and efficiency of nitrogen removal at the optimum HRT were discussed. When HRT was 30 h, the average removal ratios of COD, chromaticity, TN, NH3-N and anilin were 93.3%, 81.9%, 79.9%, 98.1% and 74.8%, respectively. The effluent average concentrations of COD, chromaticity, TN, NH3-N and anilin all met the first level of China Textile and Dyeing Industry Water Pollutants Discharge Standard (GB 4287—92). It is shown that this system, which not only removes both color and organic matter effectively, but also has great removal effect on nitrogen, can be used in treating high-and middle-concentration dyeing wastewater.
Abstract: Based on a dynamical research on deoxidation and desulfurization of molten steel with calcium treatment, it is found that when solid calcium particles are fed into molten steel, some dissolve and the others become bubbles reacting with oxygen and sulfur. The bigger the diameter of the calcium particle is, the bigger the residenee time and average flotation speed of the bubble in molten steel are, and the less the mass transfer coefficients of deoxidation and desulfurization are. The residence time and flotation speed have hardly relationship with temperature in the steelmaking temperature range, but the mass transfer coefficient becomes large with increasing temperature. With increasing the contents of oxygen and sulfur in molten steel, the optimal diameter of calcium particles enlarges. The usage of calcium decreases with increasing particle size at a given depth of molten steel and oxygen and sulfur contents. Calcium particles of less than 0. 002 m in diameter will be wholly utilized under the condition of the temperature of 1823 K, the mass fraction of[S] of 0.012% and the depth of molten steel of 3 m. The conversion rate of calcium is 84.4% when the particle diameter is in the range of 0. 002 to 0.003 m.
Abstract: According to the solidified characteristic of peritectic steel for wide and thick slabs, mold fluxes with high basicity, high crystallization rate, low crystallization temperature and low heat flux density were developed and experimentally studied on 3# Caster at BaoSteel. The trial results of 4 casting times showed that experimental strands produced with the developed mold fluxes had not surface longitudinal cracks, but the surface longitudinal crack ratio of strands produced with original mold fluxes was 5%. The developed mold fluxes can prevent surface longitudinal cracks in wide and thick slabs effectively.
Abstract: The static and dynamic CCT curves of low carbon bainite steel microalloyed with Nb, V, Ti, Mo and Cr were tested with a Formaster-Digital dilatometer and a Gleeble-1500 thermo-mechanical simulator, respectively. The transformation microstructures were observed by SEM and TEM. It is shown that the transformation microstructures are bainite after continuous cooling when the cooling rate is more than 10℃·s-1 due to the fact that alloy additions inhibit the transformation from austenite to ferrite, which results in excellent strength; in addition, deformation promotes bainite transformation, and the start temperature and final temperature of bainite transformation are 610 to 668℃ and 520 to 551℃, respectively.
Abstract: The hot ductility of SS400, Q235B, Q345B steels produced by CSP process was investigated with a Gleeble 1500 testing machine, the results show that the steels have two low ductility zones. The first zone was founded in the range from Tm to 1310℃ and the second zone in the range from 850 to 725℃. Low ductility and strength in the first zone is due to the presence of liquid films in interdendritic regions which result from sulfur, phosphorus and oxygen segregation between dendrites. The two main reasons for low ductility in the second zone are AIN precipitation and network-shape ferrite formation at grain boundaries. Based on the results, some measures were given to improve the hot ductility of medium carbon steel for preventing slab cracks.
Abstract: Microsegregation and homogenization of superalloy GH105 ingots were studied by optical microscope, scanning electron microscopy and EDAX. The results show that the severe segregated elements are Ti and Mo, and the segregation degree can be reduced by a two-stage heat-treatment of homogenization. The homogenization process can be effectively predicted by the homogenizing equation, which agrees with experimental results as a whole, while there are some errors between experimental results and those predicted by the residual segregation parameter model.
The effects of alloy elements on the precipitation behaviors of equilibrium phases in new type nickel-based powder metallurgy (P/M) superalloys at aging temperature were studied systematically by a thermodynamic calculation method. The calculation results show that the equilibrium precipitation phases of René 104 are γ', MC, M23C6, M3B2 and TCP phases. Cr and Co contents mainly influence the precipitation behaviors of TCP phases and the precipitation temperature of γ' phase. Cr content also plays a role in the precipitation behaviors of M23C6 and M3B2. The suggested content of Cr is 13%. Mo and W contents influence the precipitation behaviors of TCP phases and M3B2. The mass ratios of Al/Ti and Nb/Ta affect the precipitation behaviors of γ' phase. It suggests controlling the values of Al/Ti and Nb/Ta to be unity in order to make γ' phase having desire strengthen effect. C and B contents significantly influence the precipitation volumes of carbides and borides; they can restrain the precipitation of TCP phases indirectly. Zr content influences the precipitation behaviors of MC and M23C6. Besides, it is revealed that the composition optimization and design trend of the 3rd generation P/M turbine disc superalloys is with more Co, less Cr and to obtain a smaller lattice mismatch by adjusting the contents of alloy elements.
Abstract: Nano-composite alloy Nd4.5Fe77B18.5 was prepared by melt quench, annealed under Ar gas protection. The best magnetization properties of the sample were attained by annealing at 660℃ for 10 min. The micromagnetic behavior of the sample is much more complex and full of various interactions because of nanostructure and dual phase composition. The first order reversal curves (FORC) diagram was employed to research the magnetization mechanism and characterize inner interactions. The experimental FORC diagram shows that there are apparent reversible magnetization and irreversible magnetization, coupling each other characterized by the negative peak. The asymmetry and migration of the irreversible peak show strong interactions among magnetic moments, and the whole magnet shows demagnetizing effect, which is proved by the δM curve method.
Abstract: In order to improve the wettability of molten glass on diamond particles, copper coatings on the surfaces of diamond particles should be oxidized in certain atmosphere to obtain Cu2O coatings with eertain thickness. Thermodynamic calculations for the oxidation of copper coatings on diamond surfaces were carried out and the oxidation process was determined to be proceeded at 650℃ in N2/H2O atmosphere with a dew point of 20℃. The dynamic research results showed that the oxidation of copper coatings on diamond surfaees followed a parabolic rule and the parabolic rate constant was 1.127 5 ×10-12g2·cm-4·min-1 in this condition. On this base, the oxidation time was chosen as 40 min. XRD results showed that the oxidized copper coatings on the surfaces of diamond partides were only composed of Cu and Cu2O, without any CuO.
Abstract: The organic and inorganic component transformation of a mesoporous composite material in preparation process was analyzed based on the infrared spectrograms and X-ray diffraction patterns of raw materials, semifinished products, and end products. The change of components and their rations in the material were educed to judge the crystal lattice change of organic ion exchanged products. A transformation mechanism of components in the material was proposed according to FTIR analysis, X-ray analysis and TEM analysis. Driving force species and their alteration mechanism for the organic ion exchanging reaction were postulated from the view points of acting force and thermodynamics.
Abstract: The electrochemical impedance spectroscopy of an activated carbon/activated carbon supercapacitor and an asymmetric supercapacitor before and after activation process was studied. The asymmetric supercapacitor consisted of spinal LiMn2O4(LMO) as a positive electrode and activated carbon (AC) as a negative electrode. After activation process, its resistance at high frequency (10 kHz) has almost no change, but its capacitance at low frequency is greatly increased; its frequency behavior is quite different from that of the AC/AC supercapacitor as a result of the LMO positive electrode. The impedance spectroscopy of the asymmetric supercapacitor before and after the activation process was studied in terms of complex capacitance and complex power, and the relaxation time constant was determined. The impedance behaviors of the AC/AC supercapacitor and the LMO/AC asymmetric supercapacitor were compared, showing the effect of the LMO positive electrode on the frequency response characteristics of a supercapacitor.
Abstract: UV accelerated ageing was performed on acrylic polyurethane anticorrosive coatings; gloss and color difference testing, SEM and FTIR analysis incorporated with EIS were used to analyze their photoaging behavior. The results indicate that the photoaging of acrylic polyurethane coatings can be sensitively detected by gloss measurement; on the basis of contact angle and color difference, there are three processes during the photoaging of acrylic polyurethane, i.e. prophase (slow photoaging), metaphase (quick photoaging) and anaphase (slow photoaging). The chemical changes of the coatings show that UV irradiation causes the breaking of O—CH and C—N bands, which is considered the main reason of acrylic polyurethane photodegradation. Compared the results of surface analysis with those of EIS, it can be found that the corrosion resistance of acrylic polyurethane has declined obviously before visible photodegradation.
Abstract: The degree of cure and temperature are coupled during the pultrusion of carbon fiber reinforced plastics (CFRP). The models of unsteady temperature field and curing were established according to the curing kinetics and heat transfer theory. Kinetic parameters needed for simulation were obtained from differential scanning calorimetry (DSC) experiment. The finite element method, finite different method and indirect decoupling method based on ANSYS were implemented to simulate degree-of-cure profiles in CFRP during pultrusion. A fiber Bragg grating (FBG) sensor, encapsulated in the aluminum capillary, was employed to monitor the temperature of CFRP on real-time from which the real-time degree of cure was calculated. The degree of cure of CFRP was also measured by using Sorbitic extraction. It is found that the simulated results are in good agreement with the experimental ones.
Abstract: A full scale water modeling experiment was carried out for slag entrapment in a CSP funnel-shaped mould with a bifurcated SEN. The structures of the mould and SEN cause meniscus dynamic distortion phenomena of the free surface in the mould which result in periodical mould slag entrapment. The emergent distortion of the bath surface causes short time continuous entrapment by shear force and the appearance of entrapping effectual vortices. Among casting parameters, casting speed has the greatest influence on slag entrapment. The transient behaviors of movement of entrapped slag drops in the CSP mould were also studied. It is shown that periodical slag entrapment leads to a larger distribution difference of large inclusions in the casting direction of slabs.
Abstract: Based on the basic principle of fluid mechanics, three-dimensional finite volume models of a slab continuous casting mold and a submerged entry nozzle (SEN) were established by Fluent software. When the nozzle was off-center and clogging, the flow characteristics of fluid and temperature field distribution in the mold were investigated. The results showed that while the nozzle was off-center, circulation flows in both sides of the mold were asymmetric and there were vortexes in the free surface. The temperature in the side which was near to the nozzle was higher than that in the other side. When one port of the nozzle was clogging, molten steel from the other port enhanced and the velocity of surface flow from the other port would increase, with vortexes in the free surface. Fresh molten steel from the clogging port reduced and the temperature near to the clogging port was relatively low.
Abstract: A mathematical model of dynamic pressure in a mould flux channel was established, and the pressure fluctuation rule was simulated. The effects of mould flux channel shape parameters, continuous casting technical parameters and mould flux viscosity on the pressure were researched. The results indicate that the flux channel pressure comes to the negative maximum and positive maximum when the mould oscillation velocity reaches the maximum upward velocity and the maximum downward velocity, respectively. The parameters of mould flux channel shape have important effect on the pressure. Both the positive pressure and negative pressure are depressed greatly with the increases of flux channel entrance and exit widths. But the increase of flux channel length makes the pressure large. Both the withdrawal speed and mould oscillation velocity influence the flux channel pressure. With increasing withdrawal speed, the maximum of negative pressure is enlarged, while the maximum of positive pressure is depressed. The increases of mould oscillation velocity and flux viscosity make the maximums of positive pressure and negative pressure enhanced.
Abstract: An inherent problem was introduced when measuring the magnetic properties of high coercivity hard magnetic materials with an existent static BH tracer (hysteresisograph) and the reason why the problem happens was discussed. To deal with the problem a pulsed field magnetometer (PFM) system based on the f-2f method, which could generates 8 756 kA· m-1 magnetic field, was designed and applied to measure the whole hysteresis loop of high coercivity hard magnetic materials. The technical advantages, structure and eddy current effect correction of the system were also introduced. It can be approved, from a large quantity of measurement results, that the long term repeatability of the system is very good. The deviation of magnetic properties, i.e. remanence Br, intrinsic coercivity HcJ, magnetic flux density coercivity HcB, and maximum energy product (BH)max, measured with a PFM compared with that measured with a national standard static BH tracer is within 1% for low coercivity hard magnets. For high coercivity hard magnets the system could measure the whole hysteresis loop and solve the high coercivity problem that a static BH tracer could not avoid.
Abstract: A mathematical model of multi-objective optimal design based on robust was established in order to find the least change spring's stiffness, maximal inherent frequency and minimal spring mass. Random factors in the optimal design were considered synthetically. The mathematical model was compiled into a programmer and computed into the result in MATLAB. A hydraulic valve spiral spring design example shows that the designed target can be improved by multi-objective robust optimal design and the dynamic response characteristics of the hydraulic valve were enhanced in a certain extent.
Abstract: The relationship of the hierarchic system, the non-hierarchic system and their subsystems was studied in multidisciplinary design optimization (MDO). The mixed system was divided into four structures. A method of multidisciplinary mixed collaborative design optimization (MMCDO) was made by establishing the collaborative rules of variables and objective functions. An application of the MMCDO method to optimal design of a micro-machined gyroscope shows satisfactory results.
Abstract: Marangoni convection induced by surface tension gradient along the liquid of finite thickness was researched. It is assumed that the surface tension is a quadratic function of temperature, the under surface temperature is constant, and the super surface temperature is a linear function of horizontal distance. The Marangoni convection boundary layer problem was solved by an efficient transformation and asymptotic expansion technique, and the analytical approximate solution to this Marangoni convection was obtained. The effects of Marangoni number and Prandtl number on the velocity and temperature boundary layers were discussed and the associated transfer mechanism was analyzed in detail.
Abstract: Emotional energy and related parameters describing emotional state were analyzed based on the psychological energy of psycho-dynamics. An emotional energy distributing configuration model and an emotional state probability description space were studied according to the energy balance law. The hidden Markov chain algorithm of excitation transition process was implemented to specify emotional state transferring process. By means of MATLAB simulation, the changing law of emotional state was further studied. Finally, a comprehensive research platform of emotional robot heads was built. It was also found that the results simulated by the emotional energy model were in perfect agreement with the experimental ones of an emotional robot head, demonstrating the validity of the model.
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
