Abstract: Based on the comprehensive investigation of characteristics of the regional seismic geology, the spatial variability of rock properties, mining technical conditions and supporting patterns, the deformation and failure modes of broken rock mass roadways were quantitatively analyzed by FLAC3D numerical modeling. It is shown that the fracture depth in the roof, the strength of fractured rock mass and the rationality of supporting patterns have remarkable influences on the stability of the roadways. The analysis results are good consistent with the field monitoring ones, which indicates that the numerical analysis models are correct. Engineering practice indicated that the co-action of reinforced rock mass in the roof and two wails controlled the influence of asymmetric load and rock strength deterioration in two wails, which led to the reduction in asymmetric deformation, squeezed wall slipping and roof failing of the roadways.
Abstract: Aimed at the landslide possibility and influencing factors' uncertainty of high and steep slope in Changba Opencast Mine of China, five potential influencing factors of slope landslide were firstly investigated based on field investigation and monitoring data. The key factors were analyzed by means of orthogonal experiment and the key mechanism paths acting on the slope were discussed. Then the fitting function between the influencing factors and displacement was obtained by regress method. A series of rock strength parameters, their corresponding displacements and safety coefficients were computed out in limit state. In the end, the fitting functions between rock strength parameters and displacement and between safety coefficients and displacement were presented. The results show that the safety coefficients approach 1, which indicates that the slope is in unstable state and the monitoring should be enhanced.
Abstract: The micromechanism of strength increase with curing time for compacted cement-soil was investigated by unconfined compressive strength experiment and microstructure observation. The results show that the unconfined compressive strength increases with increasing curing time, and the extent of the strength gradually decreases and then tends to steady. The strength of 60 d curing time can be used for engineering design of compacted cement soil. The change in strength with curing time substantively is cement hydration from weak to strong, ion exchange and agglomeration between hydrated gelatin and active substance of mixed soil, and induration reaction. The microstructure of hydrated crystals is from floccule and fibre-like to mum-like, finally to gridding. The pore among grains is from large to small. Cement hydration makes dispersed soil grains to agglomerate. With durative cement hydration, soil and hydrated substance agglomerations join each other to form cement-soil concretion by gridding hydrated crystals, which results in the increase of cement-soil strength.
Abstract: Thermal healing processing of Q235 steel with La addition was carried out in order to study the healing mechanism. An inner crack was made by compressing a drilled hole on the sample. The microstructures of samples were analyzed by means of optical microscope and SEM. The results showed that two types of dissipative structures obtained during heating healing for low carbon steel. One type was the dissolution of lamellar pearlite in host and the other was the formation of structure at crack healing zone. It was proposed that low carbon steel with inner cracks was an open system far from the balanced state. The dissipative structure was produced during thermal healing due to the nonlinear condition for reaction diffusion, energy fluctuation, structure fluctuation and composition fluctuation.
Abstract: The Gleehle-1500 thermal/mechanical simulator was used to study static recrystallization in four non-quenched/tempered steels with V-N-microalloying and one non-microalloying base steel. The results show that in the V-N microalloved steel with 0.33% C, the static recrystallization process was retarded markedly in comparison with that in the non-mlcro,alloying steel with the same C content, especially in the range of 820 to 880℃. However, the relationship between C content and static recrystallization was not linear for the microalloyed steels studied. Compared that for the steels with lower or higher C contents, the inter-pass static recrystallization amounts in the 0.33% C steel were always the maximum within the temperature range of 760 to 880℃, though all the five tested steels completed static recrystalllzation under 940℃. Such results indicated that the effect of V-contalning precipitates on the inter-pass static recrystallization process was fairly complex and depended on when the precipitation occurs. When the mass fraction of N increased from 140×10-6 to 210×10-6 and the other compositions were almost the same, the inter-pass static recrystallization amount decreased by 14% to 19% in the temperature range of 820 to 860℃;, showing that the increase of N content would restrain static recrystallization obviously.
Abstract: A manufacturing process bas titanium ed on the accumulative roll-bonding (ARB) technology for TA1/Q235 clad plates was demonstrated. It is found that well-bonded clad plates can be obtained by this process. The bond strength improves as the accumulative deformation and the first pass deformation increase. The surface treatment methods, i.e. rotoblasting and grinding help get a clean, fresh and work-hardening interface, therefore improve the bond strength of TA1/Q235 clad plates. When the rolling temperature is lower than 800℃, the stripped microstructure of Q235 steel can be examined. However, when rolling temperature is higher than 850℃, this kind of stripped microstructure turns into equiaxed grains due to recrystallization. In addition, there are ferrite belts with regular and coarse grains along the joint interface, but the microstructure of TA1 titanium is mainly equiaxed α and Widmannstatten α structures in metallographic analysis. Considering the microstructures of Q235 steel and TA1 titanium and their bonding properties, the ARB temperature should be controlled in the range of 800 to 850℃.
Abstract: TiAl based alloys from the prealloyed powder of Ti-47.5Al-2.5V-1.0Cr were prepared by spark plasma sintering (SPS), and the relationship among sintering temperature, microstructure and mechanical properties was studied. The results showed that the TiAl based-alloy with high density and uniform microstructure could be obtained by SPS. In addition, the microstructure changed with sintering temperature, as a result, the mechanical properties changed with the microstructure. The finer the microstructure was, the higher the strength and ductility at room temperature became. For specimens sintered at 1100℃, the finer duplex microstructure was achieved. The specimens exhibited better compressive properties at room temperature with a compressive strength of 3 321 MPa and a compression ratio of 35.2%.
Abstract: The hot compression behaviors of AZ31 magnesium alloy at 250~400℃ and a strain rate of 0.5~3,0 s-1 were investigated by means of isothermal compression test on a Gleeble-1500 thermal mechanical simulator. The true strain-true stress curves of AZ31 alloy under different deformation conditions were obtained, The microstructure after deformation was observed by optical microscopy. The results showed that dynamic recrystallization was a main mechanism responsible for grain refinement under the test conditions and was influenced by deformation parameters.
Abstract: The electrode alloy La0.7Mg0.3Ni2.5Co0.5 prepared by the spark plasma sintering (SPS) technology was used to investigated the improvement in electrochemical properties of La-Mg-Ni hydrogen storage alloys, The experimental results indicated that the maximum discharge capacities of the electrode alloys respectively prepared by SPS and vacuum medium-frequency induction melting were close, Using the SPS technology would decrease the weakening rate of capacity of the electrode alloy, After 150 cycles, the retention rate of capacity was 61.8% for the SPS technology, but 39.6% for the induction melting method, At the same time, the SPS technology would also increase the discharge medium voltage, broaden the discharge platform, and decrease the gradient of the platform.
Abstract: Fully dense nanocrystalline Cu with an average grain size of 56 nm was synthesized by a direct-current electrodeposition technique. Tensile tests performed at room temperature indicated that both the strength and the ductility of the nanocrystalline Cu increased by the increment of strain rate, especially a pronounced strain rate dependence of tensile ductility was observed. As the strain rate was raised from 1.04×10-5s-1 to 1.04 s-1, the fracture strain increased from 23.2% to 39.4%, and the ultimate tensile strength increased from 309 MPa to 451 MPa. Two reasons might be responsible for this phenomenon. First, the strain hardening behavior increased with increasing strain rate, resulting in an enhanced uniform elongation. Second, the collective grain-rotations were revealed when the nanocrystalline Cu necked at a higher strain rate, which contributed to the increase of strain after instability.
Abstract: Nanosized tungsten powder with a mean particle size of 60 nm, which was prepared by catalysis-gel process, was used as raw material. After compacted with a steel die, the green compact was sintered in hydrogen in order to investigate its shrinkage kinetic curve. The changes of grain size and relative density during sintering at different temperatures for different sintering time were tested. It is shown that the compact of nanosized tungsten powder starts to shrink at 200℃ and stops shrinking at 1 300℃. The highest shrinkage rate occurs at 1225℃. From 1 000℃ to 1200℃, the relative density increases by 24%. After sintered at 1200℃ for 120 min, the average grain size is 5μm, and the relative density is 95%.
Abstract: The transition metal Rh is highly active in surface-enhanced Raman scattering (SERS) under ultraviolet activation. The electrochemical deposition behavior of Rh3+ on Au electrode was studied using cyclic voltammetry (CV) and a layer of Rh was prepared on Au substrate by constant potential step method. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and electrochemical method were employed to characterize the Rh layer. The experimental results show that a uniform Rh layer has been obtained on Au surface. Electrochemical measurements demonstrate that the resulting Rh layer exhibits the same electrochemical properties as those of bulk Rh in sulfuric solution. The rough Rh substrate was prepared by using the following strategy:firstly, a rough Au substrate was prepared by electrochemical method, and then a layer of Rh was electrochemically deposited on the rough Au surface. The obtained Rh film has the roughness similar to that of Au substrate and exhibits good SERS activity when using pyridine as the probe molecule.
Abstract: The standard formation free energies at different temperatures of compounds in a Mo-Si-B ternary system were calculated. The adiabatic temperatures and the molten ratios of Mo5SiB2(T2 phase) at different initial temperatures for the reaction of synthesizing Mo5SiB2 were obtained, The results showed that it was feasible to synthesize in-situ Mo5SiB2 from the elemental powders. Mo5SiB2 could not be synthesized using the SkIS (self-propagating high-temperature synthesis) mode of combustion. In contrast, the explosion mode of combustion (in-situ reactively hot-pressing) was acceptable. The adiabatic temperature and the molten ratio of Mo5SiB2 were relative to the initial temperature.
Abstract: A series of fluorinated Schiff base ester liquid crystals, 4-(4-alkyl-trans-cyclohexyl)-bensoic acid 4-[(2, 3, 4-trifluorophenylimino)-methyl]-phenyl ester, were synthesized. Their chemical structures were identified by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR); their mesomorphic properties were studied by polarized optical microscopy (POM) and differential scanning calorimeter (DSC). It was found that all the four compounds showed nematic and smectic properties and possessed high clearing point over 300℃. And with the increase of the length of alkyl chain, the thermal range of nemarie phase and clearing point temperatures decreased, while the smectic-nematic transition temperature and thermal range of smectic phase increased, but their melting point temperatures showed no distinct regularity.
Abstract: In order to improve the rolled quality of pipe stretch-reducing process, reduce energy consumption, exactly control finishing temperature, and thus offer scientific set values to pipe tapping temperature, based on analyzing the mechanism of heat transfer, a mathematical model of heat transfer in pipe stretch-reducing process is derived, in which the boundary conditions in the processes of descaling, rolling and air cooling are provided. The equation of deformation heat in rolling deformation zone is also obtained using the variation principle of plastic material. The results indicate that the effect of deformation heat on the steel pipe's thermal distribution should not be ignored. The mathematical model provided can present the pipe's temperature fluctuation and agree well with the testing values in the process of stretch-reducing. Accordingly, the model can be used in the parameter analysis and technologic optimization of the processes of steel pipe reheating and stretch-reducing.
Abstract: A set of separate heat pipe (SHP) with water as medium was built. The flow and condensation of vapor with non-condensable and high partial pressure air in the SHP were measured in the experiment. The physical model of the flow and condensation of vapor-air mixture was studied and the related numeral model was founded. Except for the mass, momentum and energy conservation equations, the diffusion and condensation equations were added to calculate the distribution of the mixture in the mathematical model. The numerical result agrees well with the experimental data, and the deviation is between 8% and 15%.
Abstract: Microstructure evolution of coarse particles in fluidized bed combustion (FBC) was investigated by SEM technology, diagram processing technology and physical absorption method. It was found that the quantity of micro-pores increased when their sizes were less than 400 pixels in diagram for bituminous coal, but never changed when their sizes were larger than 400 pixels. The specific surface area of coarse particles obviously increased with increasing combustion time during fluidized bed combustion.
Abstract: After the discussion of information systems and production management modes, based on the advanced planning and scheduling theory a system architecture model of integrated steel production planning and scheduling was presented for make-to-order production management in iron and steel enterprises. In the model, an inventory matching model of hot rolling strips was established for the inventory matching problem of integrated production management, and a capability planning model which considered the constraints of working procedure in steel production processes and the constraints of equipment capacity was established for the capability matching problem of integrated production management. The production planning and scheduling methods and their whole relationship were researched from the points of view of available-to-promise and capacity-to-promise and production scheduling.
Abstract: Fuzzy edge images exist in non-contract width measurement of hot rolling strips based on image processing. They would result in inaccurate image edge detecting, which has a bad effect on the accuracy of width measurement. In order to accurately confirm the location of edge and eliminate the impact of fuzzy edge on the accuracy of width measurement, edge operators were developed, and a dual-template method was presented and applied based on the analysis and comparison of various operators. The new method was successfully applied to measure the width of hot rolling strips on line, and steady and exacter measuring results were gained. It was verified by experiments that the dual-template method can accurately measure the width of hot rolling strips whose images edge is fuzzy.
Abstract: Aiming at the tracking control problem of hydraulic position servo systems with nonlinear time-varying feature, a design method of filtered-X hydraulic position adaptive inverse control was presented based on adaptive inverse control. A transform domain variable step-size normalized least mean square (NLMS) algorithm was provided to overcome the shortage of traditional adaptive filter algorithms for filtered-X structure. The algorithm was used to in plant modeling, inverse plant modeling and controller design for a hydraulic position adaptive system. Simulation result shows filtered-X hydraulic position adaptive inverse control has the good performances of speediness tracking and strong robust.
Abstract: An adaptive genetic algorithm for the optimum path planning problem of a mobile robot was proposed. The research project was carried out from four aspects:a geometry obstacle avoiding algorithm was developed to generate initial population; the crossover, mutation, improving and deletion operators which base on heuristic knowledge were designed for path planning; a new kind of fuzzy logic control algorithm was adopted to self-adaptively adjust the probabilities of crossover and mutation; simulation studies in both off-line and on-line environments were implemented. The simulation results show that the adaptive genetic algorithm has advantages such as rapid search speed, high search quality and strong self-adaptability. It is a new approach for solving the optimum path planning problem of a mobile robot.
Abstract: Based on the quadratic stability theory, the robust H∞ control problem for uncertain discrete-time systems with timedelay was deal with. The problem of robust H∞ control with memory state feedback was discussed by linear matrix inequality approach. The sufficient condition for a robust H∞ controller was derived. An H∞ state feedback controller was designed and the controller could be solved by one LMI. An illustrative example was presented to prove the correctness of this method.
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
