Abstract: According to eco-environmental characteristics of longitudinal range-gorge region in Yunnan Province, China, an appraisal indicators system of ecological security was established by the analytic hierarchy process method. Based on this system, the comprehensive index method and gray correlation theory were applied to appraise the ecological security state and analyze the key factors of ecological security of the region. The results show that the ecological security state in the region as a whole is good. Main factors which affect ecological security are vegetation overcast rate, population natural growth rate, water quantity change, industry structure, population diathesis, soil losing rate, and exploiture land rate. There are different ecological states in different regions and drainage areas, and the ecological states of west region and Nujiang drainage area are the best. Different measures should be taken to manage eco-environment in the region so as to protect the coordination development of natural, economic and ecological environment.
Abstract: By using the self-developed agglomerate desulphurization processing, the effect of two complex agglomerate reagents on removing fine slime pyrite from high sulfur coal was studied. The synergistic effect of the two reagents was also analyzed. Experiment results showed that there was an obvious synergistic effect of the two complex agglomerate reagents on the removal of pyritic sulfur. The best proportion of the two complex agglomerate reagents was A2B2. The desulphurization rate of 60.40% could be obtained at the best proportion, and the clean coal production rate could be up to 70.08%. It is feasible to use the proposed technique to remove pyrite from high sulfur coal, and the complex reagents have an obvious effect on the coal agglomerate.
Abstract: During Zijinshan copper heap-leaching, lots of pyrite was leached and Fe3+ concentration was higher in solution with chalcocite and covellite leached. The oxidation behavior and mechanism of pyrite bioleaching, especially the chemical oxidation of Fe3+ and the influential factors of pyrite bioleaching were studied. The results showed that the pyrite leaching rate is 5%-8% when the pH value of solution was 1.6 and bacteria was in presence during composite leaching process at the initial stage. The redox potential of solution increases with the bioleaching time prolonging, After 15 d, when the redox potential was 500 mV, the pyrite leaching rate was over 25%. It was indicated that the higher redox potential was an important influential factor in pyrite bioleaching. The research on bioleaching mechanism showed that the indirect action of bacteria gave priority to the direct attack of microbial cells in pyrite bioleaching, and the attachment of bacteria to pyrite surface was synergetic effect to pyrite bioleaching.
Abstract: The corrosion resistance and corrosion behavior of low alloy steels with different carbon contents and different microstructures were investigated and compared with a commercial weathering steel 09CuPCrNi. Optical microscopy and SEM were employed to examine the microstructures of these steels. It was revealed that the dominant microstructure in the steel cooled in water after rolling is lath-like bainite while the microstructure in the steel cooled in air after rolling is the mixture of acicular ferrite, granular bainite, M/A islands and little cementite (pearlite). Cyclic wet-dry test was carried out to evaluate the corrosion resistance of these steels. The results indicate that the corrosion resistance of the low carbon steel with 0.03 96 C or 0.196 C, which was cooled in water after rolling, excels that of 09CuPCrNi steel. Provided with low carbon content, the influence of on the corrosion resistance of the tested steel is not obvious. With a higher carbon content, the bainitic steel with single phase exhibits a higher corrosion resistance than multi-phase steel constituted by ferrite and cementite (pearlite). No marked distinction can be detected in the corro-sion resistance of the steels with different carbon contents when they were cooled in water after rolling. When cooled in air after rolling, the steel with low carbon content exhibits a higher corrosion resistance than the steel with a higher carbon content. Through observations on rust layers with SEM, it can be found that a compact inner rust layer forms in the specimen with excellent corrosion resistance after long corrosion.
Abstract: The reacting mechanism between silane and steel surface, the forming process of silane treating film and the linkage between silane and epoxy resin were studied. The effects of process parameters on the adhesive strength of epoxy/steel interface and the anti-corrosion property of silane treating film were investigated, and their inherent laws were analyzed. The correlativity between the adhesive property and the anti-corrosion property was discussed.
Abstract: The microstructures of X70 dissimilar weld joints were studied by optical microscope and SEM. Galvanic corrosion at different area ratios was investigated in simulated soil solution. The results indicated that the fusion zone was so narrow that no martensite-like structure was found. Fine dendrites were obtained in the weld zone, in which Nb and Mo seriously segregated in interdendritic. The corrosion resistance of the weld zone was excellent because of its passive film. There were coarse bainitic ferrite and nonuniformly distributed strip M-A constituent in the coarse-grained heat-affected zone (CGHAZ), and fine bainite existed in X70 base material. Their corrosion behaviors were not obviously different, but as the anode polarized potential exceeded to 150 mV the polarizability of CGHAZ was relatively high. The cathodic reaction rate was dependent on oxygen diffusion when the weld zone was coupled with X70 pipeline steel. The corrosion current density of X70 pipeline steel increased rapidly with increasing area ratio. The corrosion characteristic was similar to "Catchment Principle". Because of high cathodic potential the weld zone did not suffer corrosion.
Abstract: An approach for fabricating sintered stainless steel with high green strength and sintered density by gelcasting was presented. The effects of gelcasting process parameters such as monomer content, ratio of monomer/cross-linker in premixed solution, solid loading of slurry, and initiator content on the green strength and sintered density of stainless steel were investigated. The results show that the appropriate process parameters of 316L stainless steel gelcasting are as follows, monomer mass fraction 18%-22%, ratio of monomer/cross-linker 90:1-240:1, solid loading 52%-55%, and initiator content 0.8%-1.4% (based on the mass of monomer). Under the above condition, complex-shaped stainless steel parts with green strength more than 30.0 MPa, sintered density more than 97% and mechanical properties slightly less than those of parts by metal powder injection molding (MIM) were obtained.
Abstract: Theoretical and experimental studies on the production of M-based amorphous alloy powders by close-coupled gas atomization were carried out. The particle size, surface morphology and microstructure of the atomized powders were analyzed by XRD, SEM, TEM and DTA. The critical cooling rate for glass formation and corresponding powder diameter of the M-based alloy were determined in terms of the breakup mode and cooling behavior of melt during atomization. It is indicated that there are amorphous particles in the atomized M-based powders, which are basically below 26μm in diameter. The critical cooling rate for glass formation of the M-based alloy is about 106 K·s-1 Melt atomization is such a complicated process that powders form under the coupling interaction of breakup and solidification, where rapid solidification (>104 K·s-1) restrains the breakup of melt; meanwhile, the breakup mode of melt has great influences on solidification. The present close-coupled gas atomization can only produce the mixture powders of crystal and amorphous particles.
Abstract: The microstructure and mechanical properties of a new corrosion-resistant alloy C-22HS with high strength under standard heat treatment condition were studied by means of thermodynamic calculations, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and mechanical properties testing. The results indicate that C-22HS alloy under standard heat treatment condition is composed of equiaxed grains with different sizes. Major precipitations in C-22HS alloy are granular (Mo, Cr)6C and dispersed distributing strengthening phase Ni2(Mo, Cr). It is shown that C-22HS alloy under standard heat treatment condition possesses not only a higher strength but also a better plasticity and impact toughness. Its yield strength is much higher than that of C-22 alloy at room temperature or high temperature.
Abstract: The effects of the amount of Si added to Al-8Mg alloy on the microstructure and thermal conductivity of pressureless infiltrated SiCp/Al composites were investigated. The results show that Si addition to matrix can reduce the porosity of the infiltrated composites by the improvement of SiC/Al wettability, suppress the SiC/Al interracial reaction and increase the relative density of the infiltrated composites. Without Si addition to At-SMg alloy, the composites exhibited a lower thermal conductivity and relative density because of poor wettability and severe interracial reaction. With increasing the Si content to 12%, the interracial reaction was suppressed and the thermal conductivity of the composites is the maximum. With further increasing Si content, the thermal conductivity of the composites decreased because the thermal conductivity of matrix itself decreased.
Abstract: Host doped (Y,Rn)2O2S:Sm3+,Ti4+,Mg2+ (Rn=La, Gd, Lu, Ga, Al) red phosphors were prepared by solid state method. Their chief emission peaks are in the red-orange range coming from the energy transition of 4G5/2→6H7/2 and host-doping has little effluence on the emitting spectra. Afterglow results show that the semi diameter of doped ions has some effect on the longlasting property. When the doped ion is a little smaller than Y3+, the afterglow time will increase. When two ions are doped, two smaller ions doping will promote the long-lasting property; if one ion is larger than Y3+, it will shorten the long-lasting time. The presumable mechanism was also discussed.
Abstract: The alkali earth chlorosilicate of Sr8Si4O12Cl8:Eu3+,M3+(M3+=Sm3+,Al3+) was synthesized by the high temperature solid state method. The excitation and emission spectra were measured and the luminescent properties of red-photoluminescence were investigated. The effects of Sm3+ and Al3+ ions on the luminescence of Eu3+ ions and the relation of relative luminescence intensity to its composition were analyzed. The results show that M3+ (M=Sm3+, Al3+) ions can sensitize Eu3+ ions in Sr8Si4O12Cl8, with the relative luminescence intensity increasing 7.3% and 40.5%, respectively. The luminescence intensity reaches to the maximum when the molar fractions of Eu3+ and Sm3+ (Al3+) are 8% and 5% (18%), respectively.
Abstract: To solve the problems of the low strength of silica aerogel and the high thermal conductivity of xonotlite, silica sol was prepared with TEOS through sol-gel process, and then xonotlite-silica aerogel nanoporous super insulation materials dried by supercritical drying technique were prepared with silica sol compounded into xonotlite. A transient hot-apparatus was used to measure the thermal conductivity of samples at normal temperature in an environmental pressure range of 1.01×105~1×10-2 Pa, and the effect of preparation condition on the thermal conductivity of the composite materials was studied. It is indicated that the thermal conductivity of the composite materials decrease with decreasing unit weight of xonotlite and increasing composite mass growth rate, but they experience the changeable process from decrease to increase with increasing unit weight of silica aerogel.
Abstract: Band gap characteristics of the photonic crystals with triangular lattice of air cylinders and triangular lattice of dielectric cubes were comparatively studied by means of plane wave method. 2D photonic crystal with triangular lattice of air cubes was put forward and the influence of dielectric constant on the band gap width was analyzed. The results show that the band gap width of photonic crystal with triangular lattice of air cylinders is much wider than that of photonic crystal with triangular lattice of dielectric cubes when the photonic crystals are made of the same material. For photonic crystal with triangular lattice of air cubes, theoretical calculations show that two complete photonic band gaps occur and the relative dielectric constant more than 12.0 for the appearance of two gaps. The two band gap width reaches its maximal value when the relative dielectric constant is 19.0.
Abstract: In order to resolve technique problems in sectional multi-point forming, the forming process was simulated by a finite element software, in which dynamic-explicit formulation was used to analyze the loading processes and implicit algorithm formulation for the unloading processes. The forming surface of transition area was designed by non-uniform rational B-surface (NURBS), and the width of transition area that has effect on the quality of sectional forming parts was discussed. It is shown that when simulated with an appropriate design of transition area, sectional forming parts possess a better quality than one-step forming parts.
Abstract: The dissymmetry of flatness control in the vertical direction is the characteristic of a DSR (dynamic shape roll) mill. By constructing the finite element model for whole rolls, the flatness control behavior was numerically calculated by using ANSYS software. After evaluating the flatness control behavior and the vertical dissymmetrical characteristic of a DSR mill in China, the reason for dissymmetry was pointed out, and the measures of moderating the dissymmetrical harms to shape was proposed.
Abstract: Line-scan CCD cameras were used as surface image acquisition devices for hot-rolled strips to avoid problems produced by surface inspection systems based on area-scan CCD cameras. Linear laser was used as the illumination device for homogeneous illumination from long distance under the environment of high temperature. The precision of image acquisition could be higher than 0.5 mm with line-scan CCD cameras and linear laser. A new concept of defect detection was proposed to avoid the disturbance of scales, water and un-homogeneous illumination on the surface of hot-rolled strips. Different detection algorithms were developed for different types of defects. Up to now, detection algorithms for longitudinal cracks and edge cracks were developed, and the detection rate were higher than 95%.
Abstract: The improved principal component analysis (PCA) was introduced to the monitoring of mould processes during slab continuous casting. Based on analyzing the measured mould friction data, simulation results show that the improved PCA can avoid the conservation of Q statistical test and effectively identify the change in the Hotelling T2 test which may caused by process fault or variation in operating condition. Compared with the conventional PCA, the improved PCA is more effective and sensible in fault diagnosis and process monitoring.
Abstract: Regarding the characteristics of gear vibration, a compound over-complete time-frequency dictionary was designed. Basis pursuit, which is effective in matching the characteristic structure of signals globally and extracting the time-frequency information directly, was employed to analyze the vibration signals of both a healthy gearbox and a faulty one. Periodic impacts characterizing the vibration of localized damaged gears were extracted in the joint time-frequency domain, and gear tooth pitting was identified. In comparison with traditional time-frequency analysis methods, such as short time Fourier transform and wavelet transform, basis pursuit is effective in detecting gear damage.
Abstract: The independent control of instantaneous active power and reactive power is obtained based on the power control mathematical model of voltage-type PWM rectifiers in synchronous dq coordinates and power feedforward decoupling. In order to overcome the defects of current control strategy, direct power control strategy and nonlinear control strategy for voltage-type PWM rectifiers, a new control strategy using inner power loop and outer voltage square loop is proposed. Good tracking properties of dc voltage and power of voltage-type PWM rectifiers are obtained by using the new strategy. The system using the new strategy has many advantages, such as fast response, good stability, load disturbance resistance, and simpler structure, The design method for a system controller is given. The new control strategy is proved feasible by Simulink simulation under nominal load and load disturbance.
Abstract: An algorithm of mass-target image matching for vision measurement in mass chip production was put forward to carry out multi-window self-construction. Spiral character chain was used to modify maximum close distance (MCD) for improving the speed and robustness. Experimental results confirm that the assignment of recognizing mass chips is achieved by the algorithm. Beside the advantages of high speed and precision, it is flexible compared with other algorithms.
Abstract: To solve the bad transient response of a conventional adaptive Kalman filter, multiple Kalman filters based on different noise covariances and a conventional adaptive Kalman filter (AKF) were used to form a multiple model adaptive Kalman filter (MMAKF) by using a switching index function. Compared with a conventional AKF, the MMAKF could improve the transient response greatly without losing the characteristic of the conventional AKF.
Abstract: The problem of robust H∞ control was discussed for a class of uncertain systems with delayed state and control. A state feedback controller was designed in terms of linear matrix inequality (LMI). It stabilized the systems and simultaneously guaranteed a pre-specified H∞ disturbance attenuation constraint for all admissible uncertainties.
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
