Abstract: A 3-D dynamic mathematical model of gas explosion flow field was built based on explosion mechanics, explosion dynamic mechanics and thermodynamics. The way of boundary conditions defining was studied by experiment and theory analysis, and the total variation diminishing (TVD) was used to numerically solve the mathematical model. Numerical simulation results show that barricade excitation will be formed in combustion and other areas while the pressure is increased to detonation, and the fields of pressure and velocity around the barricade is greatly changed in the whole area of explosion.
Abstract: In order to characterize the interdependence of all the factors directly in the process of bioleaching polymetallic nodules in deep sea, this paper conducted the aerobic and anaerobic leaching experiments of a microbe catalysis MnO2-FeS2-H2SO4 system. The dynamic model of valuable metals by microbe catalysis leaching under anaerobic condition, that is the shrinking core model, was established using the DLVO theory. In the oxidation-reduction process of polymetallic nodules and pyrites, the Mn-leaching mechanics under anaerobic condition was the circulate transformation between Fe2+ and Fe3+ by microbe catalysis. The microbes absorbed on the surface of mineral and accelerated the reaction process, the mineral particles got small continuously during the reaction. The further study on the experiments indicates that retract model curves fit the experimental ones nicely, which verified the reliability of the model.
Abstract: In order to study the failure mechanism and reinforcement technique of reinforced earth retaining walls, the reinforcement project of a crossroad was taken as an example. The failure mechanism was analyzed firstly. A united measure of shotcrete lining on the surface, pre-stressed anchor and injection was applied. Main problems in construction were discussed and solved. Lastly, the reinforcement effect was simulated with FLAC2D. After the reinforcement, stable stress and little deformation indicate the united measure is effective.
Abstract: A new bio-carrier with large specific surface area was made by combination of both suspended carrier and solid carrier. The specific surface area of this new type of combined ball carrier was 711-1 185 m-1 about 3-5 times as large as than that of suspended carrier. During the advanced treatment process of domestic wastewater, biofilm generated on the surface easily and fast, and microbe was advanced, abundant and difficult to be brushed off. The new carrier with 90% porosity was not easy to be plugged. It is dense biofilm on the surface and abundant protoplast growing in cavities of the zeolite that avail nitrogen removal. Experimental results show that a fluidized bed reactor with the new carrier can treat the secondary effluent very well in stable condition, after the treatment the CODcr concentration of effluent is from 10 mg·L-1 to 36 mg·L-1 with a removal rate in 48%-81% and the NH4+ -N concentration of effluent was no more than 2 mg·L-1 with a removal rate of no lower than 89%. It can be concluded that water quality after treatment can meet the criterion of cooling water quality.
Abstract: Optical microscope, transmission electronic microscopy and mechanical tester were employed to analyze the effect of the composition and processing of Ti microalloyed high strength weathering steel on its microstructure and mechanical properties. The results show that Ti addition has a obvious effect on the yield strength of the experimental steel, the grain size remains unchanged as the Ti content increases in 0.05% -0.08%; the increase in strength is dependent on the content of effective titanium that is related to the contents of titanium, nitrogen and sulfur; under the certain content of effective titanium, precipitation strengthening mainly depends on the cooling rate of the experimental steel.
Abstract: The electrochemical behavior of a fusion bonded epoxy (FBE) coating with linear defects/carbon steel X70 system in 3.5% NaCl solution was studied by electrochemical impedance spectroscopy (EIS) technique. The defects were made on samples at right angle by scribing the sample through the paint down to the bare metal to form a 20 mm×20 mm cross. Experimental results show that corrosion process can be divided into three stages. In the initial stage of eroding, the electrochemical behavior is similar to that of bare steel. In the interim stage, corrosive outgrowth accumulates in the interior of linear defects. It makes pH of solution in the interior of linear defects fall down and causes the coating bonded joint rupture. In the final stage, EIS data show that along the seams, the FBE coating peels off steel substrate. EIS data had been interpreted and discussed in terms of the time dependence of electrical (paint coating) and electrochemical (steel substrate) parameters. The parameters were associated with interracial processes describing deterioration of the carbon steel/fusion bonded epoxy coating with linear defects system.
Abstract: The microstructure and mechanical properties of high Zn Al-Zn-Mg-Cu aluminum alloys prepared by spray forming technology with different aging treatments were investigated. The results showed that strengthening phases precipitated from grain boundary during natural aging treatment, and with the prolong action of aging time the precipitate phases of single aging alloys grew up gradually. The precipitate phases of double aging alloys got coarsened and the precipitate phases of grain boundary were intermittence. The regression-reaging treated alloys possessed fine grain-interior precipitate phases and the discontinuous grain-boundary phases as the same as those of two-step aging alloys. Compared with peak aging alloys, the ultimate tensile strength (UTS) of two-step aging alloys reduced by about 13%, but UTS of regression-reaging treated alloys excelled that of peak aging alloys.
Abstract: This paper studied the effect of B additive on the electrochemical properties of hydrogen storage alloys with the Co mass fraction less than 5% and designed non-stoichiometry cast alloys Mm(NiCoMnAlB)5+χ(χ=0.02, 0.03, 0.05, 0.1, 0.2, 0.3). The results show that the activation performance and high ratio discharge property are improved, but the discharge capacity is reduced. Microstructure analysis approves that B additive in the alloys forms secondary phase CeCo4B, which can improve high ratio discharge property. Special software MASTE was used to optimize the composition. It is found when the addition of B is 0.1 in atom ratio the comprehensive properties are the best. A new alloy composition Mm (NiCoMnAlB)5.08 was predicted, and the electrochemical properties were proved by experiment.
Abstract: A series of glass/NiO(lnm)/[Co(0.4nm)/Pt(0.5nm)]3/Pt(xnm)/[Co(0.4nm)/Pt(0.5 nm)]3 samples with different Pt interlayer thicknesses were prepared by magnetron sputtering to determine the ferromagnetic coupling between Co layers across the Pt layer. The measured results of major and minor hysteresis loops show that the ferromagnetic coupling between the top and bottom Co/Pt multilayer decreases monotonously with the increase of Pt layer thickness and disappears as the Pt layer thickness over 4 nm. In addition to the ferromagnetic coupling, there exists a weak biquadratic coupling, which induces the broad transition of the bottom Co/Pt multilayer.
Abstract: The effects of high temperature solid state synthesis condition on the structure, micro-morphology, pore diameter distribution and electrochemical properties of spinel Li4Ti5Ol2 for an Li4Ti5O12/C hybrid electrochemical capacitor were investigated by XRD, SEM, BET and charge/discharge tests. The results show that the Li4Ti5O12 sample obtained at 800℃ for 2 h has rich mesopores and exhibits better electrochemical properties. Its BET surface area reaches 4.4 m2·g-1 the specific capacity reaches approximately 150 mAh·g-1 when charged and discharged at 175 mÅg-l and the power performance and cyclelife is superior.
Abstract: Pure and Ce-doped nano-TiO2 particles were prepared by a sol-gel process and characterized and explained by UV-Vis and XRD spectra. Being a model reaction, the photocatalytic degradation of methyl orange aqueous solution in the present of CeO2/TiO2 nano-particles was investigated with a high pressure mercury lamp as the light source. The results show that rare-earth Ce doped makes the reflective spectral characteristic of nano-TiO2 move to the visible region with a red shift to 500 nm, and is favorable to enhancing the absorption of visible and UV light of nano-TiO2. A few Ce4+ doped enter into the crystal lattices of TiO2, but a lot of Ce4+ doped disperse into TiO2 or cover onto TiO2 as the form of CeO2 with small size. It is indicated that rare-earth Ce doped increases its photocatalytic activity, and the optimum molar fraction of Ce in CeO2/TiO2 is 2.0%.
Abstract: Cermet Composites ZrO2(3Y)/WC-20% Co with different ZrO2(3Y) contents were prepared by normal vacuum hot isostatic pressing. The mechanical properties of the composites such as hardness, bending strength and impact toughness were tested, and SEM was used to characterize the microstructures and components. The phase transformation contents of m-ZrO2(3Y) to t-ZrO2(3Y) before and after mechanical tests were measured by X-ray diffraction quantitative phase analysis. The experimental results show that the ZrO2(3Y) particles are spherical particles with different sizes in WC-20% Co matrix and distribute uniformly in Co phases and WC phases. The bending strength and impact toughness of the cermet composites are improved remarkably, but little in hardness.
Abstract: A temperature and phase transformation coupling finite element model was established to calculate the temperature field of hot rolled strip cooled on the run-out table along thickness and width direction. In this model, each metal phase's physical parameters such as density, heat conduct coefficient, specific heat etc were considered to be functions of temperature and the linear mean value of all phases was used during calculation. Based on TTT curves of the material studied, Avrami function and Scheil additivity rule were used to calculate the latent heat of phase transformation, and the coupling solving of temperature and phase transformation was carried out. The results of simulation indicate that temperature difference exists along the thickness direction of strip and non-uniform temperature distribution along the width direction of strip, which match well with actual measurement on spot.
Abstract: According to the special characters of a multi-roll cold tandem mill, a roiling force prediction model based on fuzzy algorithm and cerebellum model articulation controller (CMAC) combined with the traditional model was designed to improve the precision of rolling force prediction. By comparing the values of the traditional rolling force model and the prediction model by CMAC with the measured ones, the precision of the prediction model by the fuzzy CMAC is much better than that of the traditional roiling force model and is more suitable for online use of a multi-roll cold tandem mill controlled by computer, which also meets manufacturing requirement of the field and receives better control effect of the shape and thickness.
Abstract: A nonlinear dynamic model of horizontal vibration was derived based on the analysis of friction state on rolling contact interface. The effects of the transform of friction state on the horizontal movement of a roll were discussed. Phase portrait technique was used to analyze the horizontal motion of a roll and determine a limit circle which could describe the path of sticking-sliding motion. The dynamic characteristics and mechanism of horizon chatter were analyzed. The critical parameters able to divide up the sticking-sliding motion requisition in the parameters plane were deduced.
Abstract: For the distance between the drive motor and roll of a rolling mill is long and the rigid of its spindle is limited, the normal control of current and speed closed loops leads easily to the phenomena of electromechanical vibration and broken strip as the strip is rolled at high speed. In order to solve the problem, aiming at the characteristics of the approximate model of a main drive system, the uncertain external load disturbance and unmodeled dynamics were regarded as one integrated disturbance. Electromechanical vibration controllers were designed based on extended state observer (ESO) and auto-disturbance-rejection control (ADRC) technology respectively. Simulated results show that the two controllers effectively improve the performances of command following, electromechanical vibration suppression, and robustness to parameter variation. ESO and ADRC were utilized in electromechanical vibration control of the main drive system of a rolling mill, their validity and superiority were verified in comparison with the conventional PI controller and the state feedback controller based on reduced-order state observer.
Abstract: As kind of new fuzzy to large torque ripple in direct torque control (DTC) of induction motors at low speed, a neural networks (FNN) approach was proposed based on the merits that fuzzy control absorbs man's empirical thinking and neural networks have self-organization and self-study ability. The new approach achieved inverter switch's duty ratio control and made torque ripple minimum. The problem that BP algorithm easily gets into local minimum was solved by using least square method for the training of fuzzy neural networks. By comparing traditional DTC approach with FNN duty ratio control scheme, the effectiveness of FNN duty ratio control scheme was verified.
Abstract: The pressure equalization process of miniature pressure swing adsorption (PSA) for oxygen generating was experimentally investigated by changing the switching pressure, pressure equalization time, ratio of height to diameter, inlet and outlet pressure of an absorber. The experimental results show that, under the experimental conditions, the oxygen purity increases first and then decreases with increasing switching pressure, and with the change in time of pressure equalization the best switching pressure is constant. As the time of pressure equalization increasing, the oxygen purity also increases at the beginning then decreases. There must be a best time of pressure equalization, which is decided by the absorber's structure. The bigger the ratio of height to diameter of the absorber is, the longer the best time of pressure equalization is. In the absorber of air flowing in, the pressure increases rapidly during the pressure equalization process, but its change is slow after the pressure equalization process. The pressure curves at the inlet and outlet are parallel.
Abstract: In order to improve the flexibility of assembly and expansion in simulation of rolling process on computer, MATLAB/Simulink was used as a basic platform, which is often adopted in control systems. A transfer function model building for main rolling equipment was denoted by the simple block diagram with input and output interface, and dispatched and constituted freely as practice equipment, then various control systems was built. The visualize simulation method for rolling was developed, which can study the model independently and assemble different control schemes easily. Several hydraulic AGC systems were simulated under the same initial condition, and the result shows that the dynamic set AGC is more steadily.
Abstract: A new method of designing BP neural networks based on immune genetic algorithm (IGA) was proposed. The mechanisms of diversity maintaining and antibody density regulation exhibited in a biological immune system were introduced into IGA based on genetic algorithm (GA). The proposed algorithm overcame the problems of GA on search efficiency, individual diversity and premature, and enhanced the convergent performance effectively. In order to solve the problem of random initial weights, simulated annealing algorithm for diversity was used to initialize weight vectors, and the detailed design steps of the algorithm were given. Simulated results show that the BP neural networks designed by IGA have better performance in Convergent speed and global convergence compared with hybrid genetic algorithm.
Abstract: The grid information service system is a very important part of grid computing. An old grid information service system needs to be reconstructed as a result of the combination of grid and web service. This paper discussed quondam grid information service systems such as MDS, R-GMA and Hawkeye and substantially analyzed the specification of open grid services architecture (OGSA). An OGIS (grid information system based on OGSA) with forest structure was constructed, the functions and means of realization of OGIS modules were presented, and the key technologies and solutions to OGIS were described. OGIS provides an effective blue print for developing a grid information service system.
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
