Abstract: The No. 5 coal of Huating Coal Mine in China is a deep and heavy thick coal seam. In the coal seam, the dependence of excavation and disturbance is very serious, the difference between the maximum and minimum principal stress levels is greater, and there are frequent destabilizations leading to hazards during min-ing. Based on the comparison of the acoustic emission (AE) experiment of coal-rock unstable crack propagation and destabilization with their in-situ measurement, this paper investigated the regularity of various dynamics load and comprehensively analyzed the quantificational destabilization characters including variable dynamical specific energy of tension, resistance to compression, and proportional limit of shear under the complex-variable excavation and geological environment.
Abstract: Based on the assumption of elastic half-space a 2D lumped parameters model was used to simplify soil foundation. An analysis model of soil-structure interaction was constructed based on the soil physical model for mainly studying the interaction between subsoil and superstructure. The seismic responses of both a 5-floors building and a IS-floors building were analyzed. The results obtained from the 2D lumped parameters model of both medium hard site and medium soft site were some valuable conclusions were obtained. compared with those derived from the rigid foundation model.
Abstract: The permeability of saline soil in Zabuye salt lake in China was studied based on the analysis of difference between the results of saline soil in-site test and indoor seepage test. In order to make the tested values of permeability coefficient more accurate, an in-site permeability test method was proposed to evaluate the verti-cal permeability of soil. The formula for calculation of permeability coefficient was established from a mathematical model. An engineering application demonstrated the applied testing method and the formula were reliable.
Abstract: Anaerobic biofilm particles with high activity were developed by the immobilized method of carrier adsorption. The start-up and operation of the reactor, the processing characteristics and the sludge characteristics were investigated. The feasibility of granular sludge replaced by biofilm particles was discussed to resolve the shortage of granular sludge in China. The equipment was applied an anaerobic attached microbial film expanded bed, whose influent was artificial and whose bare carrier was ceramic media with a wet superficial density of 1 310 kg·m-3 and an averaged meter of 0.32 mm. The results showed that start-up of the reactor was successful only in 24 d, the COD volumetric loading rate (OLR) was up to 18 kg·m-3·d-1 and the COD removal efficiency was 70%~80%.
Abstract: The sulfolobus, a thermophilic microorganism, can grow at high temperature up to 65℃. It has good ability to oxidizing element sulfur and ferrous ion and can meet the high temperature demand in dump leaching and chalcopyrite stirring leaching in a reactor. The culture results show that at 75℃the sulfolobus has more adapted to the environment than below and above the temperature. The changing tends of the solution pH,redox potential, SO42- concentration and ferrous oxidation rate with time in bio culture as well as in bioleaching of chalcopyrite concentrate were elucidated. The bioleaching experiments show that using the trained sulfolobus strains at 75℃ in the shake blasting when the slurry mass fraction is below 10%, the chalcopyrite concentrate leaching rate could up to 90% after 150 h leaching. But when slurry mass fraction is up to 15%, after 350 h leaching, the leaching rate is only 80%. It demonstrates that the slurry mass fraction has apparently effect on the leaching results.
Abstract: The microstructure during solidification of high-carbon steel billets was investigated, The results showed that primary dendritic arms in the billets were becoming coarser and shorter with evolvement of solidification. A higher carbon content in the steel was favorable to form short and thick primary dendrites as well as wider primary dendritic arm spacings (PDAS) and coarsening columnar structure. A higher superheat promoted coarse primary dendrites and wider PDAS. With the withdrawal rate slower, it was easy to form narrow PDAS. The greater the secondary cooling water flow ratio, the easier the spindly primary dendrites and narrow PDAS formed. Mole-electromagnetic stirring (M-EMS) greatly reduced the PDAS and dendritic length-to-width ratio. With the increase of M-EMS electric current, the PDAS was reduced obviously.
Abstract: The effects of controlled rolling and controlled cooling parameters on the microstructure and mechanieal properties of high strength automobile beam steels produced by CSP technology were investigated. According to the theory of flexible technology, the processing of automobile beam steels with different strength grades by EAF-CSP technology was developed in Zhujiang Steel, China. The differences of microstructure and strength were analyzed by using scanning electron microscopy and transmission electron microscopy. It is shown that the final microstructure is mainly of polygonal ferrite and some pearlite, and the average ferrite grain size is about 3.7~5.6 μm. With decreasing coiling temperature, the cementite lamella of hot strips is fractured and transformed into discrete cementite particles, which is distributed throughout the ferrite matrix. It is also noticed that some granular bainite appears in the microstructure.
Abstract: In situ tensile tests in scanning electron microscope (SEM) were carried out using single-edge notched specimens of no larger than 0.5 mm in thickness made of CL60 wheel steel with or without hydrogen charging. Observations under optical microscope (OM) were also done to a wedge opening-loading (WOL) specimen with a thickness of 30 mm which was precracked. The result shows that, for the thinner specimen, plastic deformation occurs firstly in proeutectoid ferrite and then grows along the prior austenite grain boundary, and then, a microcrack initiates and propagates preferentially at the interface of proeutectoid ferrite and pearlite colony. The process of deformation and fracture is almost same each other for both specimens with and without hydrogen, except that the microcrack initiates more frequently by way of inclusion separating and shelling from matrix for the specimen with hydrogen. The fracture surface fractograph of the thinner specimen is ductile fracture. However, for the thicker specimen (WOL), plastic deformation and cracking mainly occurs in the pearlite colony, which results in cleavage fracture.
Abstract: Hydrogen permeation tests in a classical permeation cell, where a steel membrane is separating two electrolytic solutions, were used to characterize the effects of pH value, NH4+ and CO2 on the corrosion process of steels in H2S solutions. The results show that the detection of hydrogen diffusion through the steels is totally controlled by inclusions in metals and vacancies and defects produced in the process of welding. The steady state permeation current decreases with increasing pH value and increases with the concentration of aggressive NH4+ increasing. But the influence of CO2 on the steady state permeation current is related to the pH value of solutions.
Abstract: The crystal structure change of LixCoO2(0.5<x<1) during delithiating process was studied in order to optimize the electrochemical property of the Li-ion battery cathode material LiCoO2.LixCoO2 samples with different lithium contents were prepared by chemically extracting lithium from LiCoO2 with Na2S2O8. The crystal structures of these samples were then analyzed by X-ray diffraction and electron diffraction. From X-ray diffraction, the lattice parameter c of LixCoO2(0.5<x<1) changes with Li content. The results of electron diffraction indicate that the ordered arrangement of lithium and vacancy in LixCoO2(0.5<x<1) which cannot he detected by XRD leads to significant change in crystal structure and the corresponding crystal structure model was proposed. Phase transformation exhibits voltage plateau in the charge and discharge curves of a Li-ion battery with LiCoO2 cathode.
Abstract: An in-situ reinforcing phase (Cr,Fe)7C3 ceramal composite coating was fabricated on the substrate of a 0.45% carbon steel using Fe-Cr-C elemental powder blending by reactive plasma clad process. The microstructure and micro-hardness of the coating were evaluated by SEM, XRD, EDS and micro-hardness instrument, the room temperature and high temperature wear properties were evaluated under dry sliding wear test conditions, and the wear mechanism was discussed. The results indicated that the reactive plasma clad ceramal composite coating has a rapidly solidified microstructure consisting of primary (Cr,Fe)7C3 and (Cr,Fe)7C3/γ-Fe eutectics, with excellent wear properties under both room-temperature and high-temperature sliding wear test conditions.
Abstract: Nitrate replaced alkoxide and alcohol solvent omitted, a TEOS-KNO3-Al(NO3)3-H2O system turned into gel in 5~12 min with pH adjusted by aqua ammonia. Dried gel treated at 862℃, pure and homogeneous kalsilite powder was prepared with an average particle size of 8μm. The TEOS hydrolysis reaction was catalyzed by H+ released from aluminum nitrate hydrolysis firstly, and then promoted again by OH- with the addition of aqua ammonia. The gelation time was shortened greatly owing to the catalysis mode of acid first and alkali second. A penta-coordination Al was detected by 27Al NMR analyzing the dried aluminosilicate gel.
Abstract: The problems about the variation in center temperature of discharged region and the relationship between crater shape and electrical parameters in the process of electric discharge texturing on the surface of a work roll was studied. The developing process of discharging channel and the distribution of heat flux were analyzed. A thermal conduction model of single channel spark per pulse was presented. By combining the methods of integral transform and finite difference this model was solved. The change of transient temperature at the center spark point upon the roll surface was discussed under the condition of different peak current, and the relation of crater shape to peak current and pulse duration was also deduced. Finally, the calculated values were compared with the experimental ones. The result showed that they were in good agreement. The developed model and adopted method were valid and could be used for simulation of the developing process of geometric topography on roll surface.
Abstract: Rolling force and rolling moment are the important parameters when cross rolling wedges mills forming automobile semi-axes was designed. The changes of rolling force and rolling moment are complicated in the rolling course due to the mutual restriction relation between main wedge and side wedge in the process of multi-wedge cross rolling wedges (MCRW) forming automobile semi-axes. The LS-DYNA finite element soft-ware was adopted to simulate the process of MCWR rolling automobile semi-axes by setting up a finite element model. The rule was obtained that the rolling force and rolling moment change with every factor in the rolling course.
Abstract: Spray cooling of a high-temperature steel plate was simulated by using finite element method. The effects of surface-to-nozzle distance and steel plate's surface temperature on spray cooling heat transfer coefficient were analyzed. The simulation results show that on condition that other parameters retain constant, the heat transfer coefficient increases totally with decreasing jet space (200~500mm) and decreases totally with the surface temperature increasing when the surface temperature of the plate in 1050~1 200K.
Abstract: Dynamic characteristics of a full power hydraulic brake system are directly related to the safe travel performances of vehicles. On the basis of the structure and performance analysis of a serial hydraulic brake valve, a simulating model of responding characteristics in a full power hydraulic brake system was established, and the simulation analysis of various structure parameters of the braking valve affecting the dynamic characteristics of the system was conducted. Experiments were conducted to verify the simulating model, to learn the affecting laws of many different brake means of vehicles on response characteristics of the system. The quality of the deigned brake system and its parts for construction vehicles has, through industrial utilization, met the requirement of ISO 3450.
Abstract: A SRN model for a two-node hot-standby cluster of process control system in process industry was constructed, in which a precise description about the system status and behavior of permanent failure and intermittent failure was proposed and both raid share and image share were considered. The availability of the system was simulated and analyzed using SPNP package. The results showed that image share could obviously enhance the availability of the system compared with raid share in the same condition. Reducing the time of failure discovery and increasing the speed of failure repair could also improve the availability.
Abstract: Sinusoidal waveform of magnetic flux is needed to obtain high-exactitude AC properties measurement results of soft magnets. A new mode to achieve the condition by digital feedback of harmonic compensation was introduced, the waveform of magnetic.flux was analyzed, and the harmonic content in the wave was obtained. The waveform with the same altitude and opposite phase to the harmonic was supplied to the waveform-framing unit, and then the harmonic in output wave was counteracted. Measurement results of electrical steels showed that, after feedback, even at a peak value of induction up to 1.87 T, the form factor fulfilled the condition.
Abstract: The basic theory of direct torque control (DTC) for interior permanent magnet synchronous motors (IPMSM) was studied. A new approach to direct torque control of an interior permanent magnet synchronous motor was presented to decrease torque ripple. In order to improve the static and dynamic performance of the system, a fuzzy logic idea was introduced into the system. In the fuzzy direct torque control system, the flux error and the flux error change were both properly divided into several fuzzy subsets. The acting time of the selected voltage vector and reverse voltage vector were modulated based on fuzzy inference. A speed estimation scheme was integrated with the proposed DTC scheme in order to achieve a fully sensorless high-performance IPMSM drive. The scheme not only maintains constant switching frequency, but also reduces torque ripple, particularly at low speed. Simulation illustrates the operation and performance of the proposed fuzzy-logic-based controller.
Abstract: For different engineering applications, neural networks varied in scale, topology, transfer functions and learning algorithms. A reconfigurable approach for neural hardware implementation was proposed, which was not only flexible to meet those changes, also with the fast prototyping ability for market requirements. Three kinds of reconfigurable processing units were presented based on the analysis of neural network's reeonfiguration. A reconfigurable systolic architecture was put forward and the method of mapping BP networks into this architecture was introduced. Implementation issues were discussed with an example. The results showed that a high learning speed of 432 M CUPS(Connections Updated Per Second)was achieved (working at 100 MHz using 22 multipliers) at a reasonable cost.
Abstract: A constructive theorem of generalized synchronization for discrete chaos systems is established. Based on the theorem, a generalized chaotic synchronization discrete system was constructed. Combining this system with the Henon chaotic mapping designs a digital image encryption scheme, which can successfully encrypt and decrypt gray-scale images without any lost. The scheme is sensitive to perturbations of the parameters and initial conditions of the chaos system. Any perturbations which are larger than 10-15 will make corresponding decryptions become impossible. The key space of the scheme is as large as 1076. The analysis of key space and key parameter sensitivity shows that the scheme has sound security. Numerical simulations reveal that the scheme is effective in network communication.
Abstract: In order to simulate the Chinese character acquisition process, this paper set up a multilayer selforganizing maps (SOM) network model based on improved Kohonen network. The model's output maps, which adapt modified algorithm and expand neuron's neighborhood, were connected via associative links updated by Hebbian learning. After training the model could learn Chinese character architecture successfully and also do well in Chinese character component recognition. The simulation results demonstrated that the feasibility of further research in Chinese character acquisition and even Chinese language learning with this model was possible.
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
