Abstract: Based on three-frame synthetic aperture radar (SAR) data derived from ALOS satellite sensor PALSAR, a three-pass differential SAR interferometry (D-InSAR) technique was used to analyze landslide activities in the Wudongde Hydropower Reservoir area at lower Jinsha River, and high accuracy ground displacement values were acquired by this method. The classification of these ground displacement values by sliding velocity and displacement clearly illustrated the ground activity deformation states of various zones in the studied area were clearly obtained, determined some potential moving landslides and active landslides and identified the dangerous zones of landslides. For an active landslide numbered No.L1R-6, the deformation detected by D-InSAR analysis shows an accordance tendency with the one by global positioning system (GPS) monitoring. In the end, single-point errors which existed in the result of D-InSAR technique were analyzed and a grid function error interpolation method of D-InSAR and GPS was proposed to improve the monitoring accuracy of D-InSAR technique.
Abstract: The deformation of roof strata supported by pillars in mined out area was analyzed in consideration of the rheological properties of rock masses and by utilizing the elastic-viscoelastic correspondence principle and numerical Laplace inversion. The roof deflection as a function of time was established, based on which the time-dependent behavior of the roof displacement was elaborated. It is shown that when rock creep properties are taken into account for both the pillars and roof, the roof displacement increases with pro-longing time as expected. Therefore, given a sufficient period of time, the roof deformation can reach a considerable magnitude even for hard rock masses and eventually lead to the collapse of roof strata. As a case, the estimation of failure time was carried out for Xingtai Gypsum Mine in China, in which the feasibility of the proposed method was verified by acceptable agreement between the estimated data and actual field observations.
Abstract: For vibration is an important factor among all influencing factors of coal and gas bursts, gas adsorption experiments of coal were done and crack growth in coal was analyzed under vibration conditions. The mechanism of coal and gas bursts was discussed according to experimental and theoretical results. It is shown that under the action of vibration the gas content of coal and the adsorption ability decrease, and after vibration the time to reach the gas absorption equilibrium in coal and the adsorption equilibrium pressure increase, indicating that vibration makes free gas increase and the gas content of coal reduce. Vibration also leads to the increasing of crack number and crack growth rate, and when the vibration strength arrives at some value a large-scale connected crack network appears. The integrated influence of vibration on the coal and gas system increases the danger of coal and gas bursts.
Abstract: Coal-based roasting reduction-magnetic separation technology for iron extraction from Xuanlong-type iron ores and its relevant influencing factors were investigated. An optimal technological condition for iron extraction from the iron ores was determined with iron concentrate grade and iron recovery rate as evaluation indices. The results show that the iron concentrate grade of 92.53% and the iron recovery rate of 90. 78% can be obtained when the reductant dosage is 30%, the roasting temperature is 1 200℃, the reduction time is 60 min, the percentage of roasting products with a grinding fineness of -45 μm is 96. 19%, and the magnetic field intensity is 111 kA·m-1.
Abstract: Combined with the transformed model equation of rotating magnetic fields and the boundary renewal method, the k-ε turbulent model was used to analyze the flow field in the continuous casting process of steel under the action of a rotating magnetic field. The electromagnetic field makes molten steel whirl in the horizontal plane, decreases the downward velocity and speeds up the vortex. The horizontal rotating velocity decreases gradually downwards from the vertical center of the stirring area. The rotating velocity increases with the increasing of both electric current and frequency, with a distribution of single peak values on the horizontal plane and the maximum occurs near the wall.
Abstract: A method of quenching and atomizing the melting slag simultaneously under a high pressure water jet was put forward. Experiments about cooling and pulverizing the melting steel slag and the melting blast furnace (BF) slag by a high pressure water jet of 8 to 10 MPa were conducted on a self-made slag melting and high pressure water cooling system. The results show that the atomized steel slag can be pulverized with an average particle size of 94.3μm and a composition of glass phase and Ca2SiO4, its reactivity is increased and the compressive strength of its cement samples aged for 28 d is 33.96 MPa, which is 8 MPa higher than that of cement samples from raw steel slag. The quenched BF slag forms flocculent structure, with degraded reactivity. The proposed method is more suitable for steel slag tapping processes than BF slag tapping processes.
Abstract: The relationship among the inierostructure, precipitation behavior and mechanical properties of China low activation martensitic (CLAM) steel was studied by optical microscopy, transmission electron microscopy (TEM) and chemical phase analysis. It is shown that the quenched microstructure is martensite, but after being tempered at 760℃ the mierostrueture transforms into finer and more homogeneous sorbite. The tensile strength, yield strength and elongation of the steel at room temperature are 697 MPa, 652 MPa and 24.4%, respectively; however, at 600℃ their values are 453 MPa, 452 MPa and 23%, respectively. The ductile-brittle transition temperature (DBTT) is -60℃. The second phase particles, sized from 30 to 70 nm, mainly are M23C6 and Ta(C, N) with FCC crystal structures. The particles, mostly distributed at grain boundaries but few dispersively in grains, can produce precipitation strengthening, as the key strengthening mechanism of the steel.
Abstract: The hot deformation behavior of 9Cr reduced activation martensitic steel was investigated by compression testing on a Gleeble-1500D simulator in the temperature range of 950 to 1200℃ and the strain rate range of 10-2 to 10 s-1, and the microstructural evolution was analyzed by metallography. Based on measured data in the strain range of 0.15 to 0.8, material parameters in the Arrhenius-type hyperbolic-sine equation were solved by using regression analysis methods and then used to fit the deformation. A constitutive equation which relates the flow stress to temperature, strain rate and strain was established by mathematical methods. The values of peak stress, critical stress, peak strain, critical strain and grain size for dynamic recrystallization (DRX) were determined from the true strain-true stress curves and their equations related to the Zener-Hollomon parameter were obtained.
Abstract: Through the analysis of hot rolling processes by establishing a vaporizing combustion zone, it was found that the oil-water mixture kept liquid and there was not enough time to reach its burning point both in the entry vaporizing combustion zone and deformation zone. Oil film strength tests, friction coefficient tests and long grinding experiments were carried out on a four-ball machine. Wear scars showed that when the mass concentration of the rolling oil in water was more than 2 g·L-1, the lubrication regime was boundary lubrication, in which the lubrication effects depended on the strength of oil films, not oil concentration. Rolling lubrication in production with an oil mass concentration of 2 g·L-1 was tested; it proved the above-mentioned research results. The rolling force was effectively decreased and the cooling water pollution was minimal at the same time. It was recommended that the mass concentration of the rolling oil should be less than 10 g·L-1 for different rolling products and processes; otherwise the rolling oil residues might cause the cooling water polluted.
Abstract: Copper powders were prepared by electro-deposition with an inert anode. The effects of Cu2+ mass concentration, H2SO4 mass concentration, current density, electrolyte temperature and scraping interval on the median particle diameter of copper powders were investigated. The results show that high quality copper powders with a normal particle size distribution and dendritic micromorphologies were obtained under the optimum conditions of the Cu2+ mass concentration of 15 g·L-1, the H2SO4 mass concentration of 140g·L-1, the current density of 1 800 A· m-2, the electrolyte temperature of 35℃, the scraping interval of 30 min, the circulation rate of 14 L·h-1 and the interpolar distance of 4.5 cm. It is advantageous to the decrease in cell voltage to increase the Cu2+ mass concentration, H2SO4 mass concentration and electrolyte temperature. The increases of Cu2+ mass concentration, electrolyte temperature and scraping interval help improving the current efficiency. A higher current density, a higher H2SO4 mass concentration and a lower Cu2+ mass concentration are beneficial to obtain copper powders with small particle size.
Abstract: The film-forming mechanism of stearic acid modified SnAgCu alloy powders by vacuum evaporation was researched. Scanning electronic microscope (SEM) and transmission electronic microscope (TEM) were used to observe the morphology and structure of the coated powders. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were adopted to test the transmission absorption spectrum and photoelectron energy of the coated powders. The results indicate that uniform and compact coatings whose thickness was 5 to 10 nm could be obtained. The growth mechanism of stearic acid coatings on SnAgCu alloy powders was a process of physical adsorption and followed the Volmer-Weber model. The essence of the process was the transformation between vapor and liquid and the growth of crystals.
Abstract: The effects of 0%, 1%, 3% and 5% mish-metal additions on the microstructure and properties of an as-cast Mg-9Y-0.6Zr (WK90) alloy were investigated by optical microscope, X-ray diffractometer (XRD), scanning electron microscope (SEM), differential scanning calorimeter (DSC) and mechanical tester. The results indicate that the microstructure of the as-cast alloy is composed of α-Mg and little eutectic structure. After adding mish-metal, the eutectic structure increases markedly. When the mish-metal contents are 0%, 1% and 3%, the eutectic structure is in a single form, and there are the layered eutectic structure and the divorced eutectic structure when the mish-metal content is 5%. The areas of low temperature endothermic peaks in the DSC curves of WK90 alloy with different mish-metal contents increase and at last are separated with adding mish-metal, which is decided by the quantity and type of eutectic structure. The as-cast alloy with a mish-metal addition of 3% and the extruded alloy with a mish-metal addition of 1% have the best ultimate tensile strength under their own states. The influence reasons are not only grain size but also the distribution and the morphology of the divorced eutectic structure.
Abstract: Micro IrO2-pH electrodes were prepared under three heat treatment conditions:700℃ furnace cooling, 870℃ air cooling and 870℃ furnace cooling. Their linear response range and response time were compared. The results indicate that heat treatment conditions have significant effect on the uniformity of iridium oxide films and the open potential stability and response time of the electrodes. After both 700℃ furnace cooling and 870℃ air cooling, the oxide films have rough surfaces, non-uniform porosities and crevices; whereas after 870℃ furnace cooling, the oxide films appear with improved characteristics, such as a more uniformity, a shorter response time and a better linearity of open potential. It is concluded that during iridium oxidation, iridium is oxidized by O2 in air with high temperature Li2CO3 as a solvent. The H+ response is caused by the reaction of hydrous iridium oxide on the electrode and H+ ions in the solution, resulting in the transition of Ir4+ and Ir3+.
Abstract: LiFePO4/carbon nanotube (CNT) composite cathode materials were synthesized by a sol-gel-microwave method. The effects of microwave time and CNT content on the electrochemical properties of LiFePO4/CNT were studied and the crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the samples with better electrochemical performance are obtained when the CNT content in LiFePO4/CNT is 2% and the microwave time is 18 rain. When charge-discharge cycling at 0.1 C, the initial specific discharge capacity is 142 mAh·g-1 and the specific capacity at the 10th cycle is 136mAh·g-1.
Abstract: The effects of sand-to-cementitious materials ratio (S/C), water-to-cementitious materials ratio (W/C), fiber species and using a reduction additive on the shrinkage distortion of fiber-reinforced high-ductility cementitious composites (ECC) were investigated. Experimental results show that the shrinkage strain of ECC reduces with increasing S/C and enlarges with increasing W/C. Chinese PVA fibers effectively control the early stage shrinkage distortion of ECC, but Japanese PVA fibers of high Young's modulus have great effect on the final stage shrinkage distortion of ECC. Hybrid fibers can better control the shrinkage distortion of ECC than Chinese or Japanese PVA fibers separately when the W/C is 0.40. The shrinkage strain probably reduces 200×10-6 by using a reduction additive, and the reduction additive can also effectively control the shrinkage distortion of ECC at the W/C of 0.40.
Abstract: Metallurgical radar was developed which can be used in high temperature and hash production environments. It adopted an improved frequency-modulated continuous wave principle and enhanced the real-time performance of solid material level measurement. An intelligent time-varying threshold signal processing method was proposed to solve the radar ranging accuracy problem caused by the change of solid material surface reflection coefficient in a blast furnace. Measurement results in a solid-powder state material surface simulation environment in the laboratory shows that the measurement tracking delay of the metallurgical radar is within 0.2 s, and the maximum average tracking error is less than 0.05%. Field test results show that the average measurement error is 0.95%, indicating that the metallurgical radar is capable of stable material surface tracking in real-time and can meet the requirements of BF monitoring.
Abstract: According to production data of a 1580 rolling mill, an integrated method combining finite element analysis and neural networks was presented for hot rolling. In the method, plastic deformation during the rolling process was firstly modeled by a finite element method, and then a neural network provided parameter adjustment for the finite element model, so the integrated model had the advantages of neural network and finite element methods. At the same time, intelligent chaos particle swarm optimization (CPSO) was used to optimize weights and thresholds of the network. A comparison between simulation results and actual production data proved the validity of the integrated model.
Abstract: A three-dimensional elastic-plastic finite element model (FEM) of horizontal rolling integration was established with ANSYS/LS-DYNA analysis software. The process of muhi-pass and continuous reversing horizontal rolling was simulated by a small-scale restart method. The changes in width spread of equal-thickness intermediate slabs while adopting different rolling schedules and of different thickness intermediate slabs while rolling various strip specifications were analyzed by the model. Simulation results of different rolling pass-schedules showed that rolling schedules affected the width spread of intermediate slabs slightly, but they may consume different energies, leading to different rolling forces and force moments. The small-scale restart method not only can keep rolling processes continuous, but also ean avoid the complexity of repeated modeling by a model updating method.
Abstract: Based on current cooling methods commonly used to cool the outer surface by a low pressure pipe jet and the inner surface by a high pressure axial jet, numerical simulations with finite element software ANSYS were performed to study the temperature field of large-caliber seamless steel pipes during quenching. The considered factors are the diameter of steel pipes, the rotation speed of steel pipes and the wetting angle of cooling water. Numerical results reveal that pipe diameter has little influence on the cooling uniformity. The radial cooling uniformity of steel pipes is the best under the condition of the rotation speed of no less than 60 r·min-1 and the wetting angle of about 270o.
Abstract: Given frame points, the point on the expectant straight-line and the direction of the task straight-line, this paper presents a syntbesis method of approximate straigbt-line four-bar linkages, which has four-point contact with its tangent. The traditional synthesis methods are difficult to obtain the optimal mechanism since only parts of the mechanism solutions are synthesized. After solution regions are determined, an infinite number of mechanism solutions satisfied the designers' needs can be expressed on a finite coordinate ptane. The mechanism property graphs are displayed to enable the designers to find out all the mechanism types and properties more intuitively for getting the optimal mechanism directly. So the problem of blindness of choosing mechanisms is solved efficiently, and the design period will be shortened.
Abstract: The mechanism of impact compaction and asphalt rubber formation as well as the function of asphalt rubber stress absorbing membrane interlayer (AR-SAMI) in pavement structure are analyzed separately. A composite engineering application test of impact compaction, asphalt rubber and AR-SAMI was carried out based on the strong-foundation and thin-pavement theory. It is shown that the mechanism of impact compaction on rockfill embankment placed on a weak muddy soil foundation is the combined action of dynamic compression and dynamic consolidation; the formation mechanism of asphalt rubber is that both physical and chemical reactions take place when crumbed rubber and base bitumen are mixed together at high temperature, but physical swelling is the main process; AR-SAMI is applied for the purpose of absorbing stress, resisting reflective cracks, proofing water and improving the adhesion between road structure layers. Composite engineering applications of the technology have performed very well.
Abstract: Based on Conley index theory, the shock wave solutions of a class of nonlinear reaction-diffusion equations were studied. Considering the diffusion coefficient as a system parameter, the existence of heteroclinic orbits of ordinary differential equations satisfied by traveling wave solutions is analyzed by using Conley index and Morse decompositions. The existence of saddle-focus and saddle-crunode style shock wave solutions of the reaction-diffusion equations is proved on the basis of an idea that the solitary waves and shock waves of partial differential equations correspond to the homoclinic orbits and heteroclinic orbits of ordinary differential equations. In particular, the existence and uniqueness of saddle-saddle style shock wave solutions are proved by using connection matrixes and transition matrixes, which are computed with Conley packages and Maple software by programming.
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
