Abstract: A space-time unified distribution model of ground fracture ratio caused by mining-induced underground coal fire was proposed based on the theory of random medium movement. The distribution and dynamic change laws of ground line (tension) fracture ratio, areal fracture ratio and shear fracture ratio were revealed through the analysis of an example. The maximum values of these three categories of ground fracture ratio respectively distribute in the ground surface region corresponding to the 20-m inner side from the surrounding boundary, the 4 midpoints of the surrounding boundary, and the 4 marginal endpoints of goaf. With combustion of the coal seam, the line fracture ratio perpendicular to the fire development direction and the areal fracture ratio corresponding to the boundary of goal change according to the half normal curve and stable at the maximum, while the shear fracture ratio, line fracture ratio along the fire development direction and the areal fracture ratio corresponding to the interior of goaf change according to the normal curve.
Abstract: To improve the situation of dust concentration exceeding during side slope drilling in an open-pit mine, according to the theories of gas-solid two-phase flow and gradient transportation, the dust movement, diffusion and sedimentation equations were established based on the analysis of dust movement, diffusion and sedimentation characteristics in the air. Taking S03# slope of an iron mine as an example, the Fluent software for computational fluid mechanics was used for numerical simulation of dust concentration distribution during side slope drilling. In contrast to field measured data, the simulation result almost conforms to the measured data. The research result shows that the dust concentration firstly increases sharply and reaches a maximum value with increasing distance from the drilling position. After that, it decreases quickly to a lower value and then gradually decreases. What is more, when the drilling begins, the dust concentration keeps on rise until a certain value and remains during the whole drilling process. Meanwhile, the dust concentration achieves its minimum value at a wind speed of 3.5 m·s-1, an air pressure of 1 MPa, a drilling depth of 12 m, and a drilling speed of 84 r·min-1.
Abstract: To solve the disadvantages of strong subjectivity for traditional plot methods of grouping discontinuities, such as the pole isodensity map and the occurrence rose graph, and the lack of intuitionism for popular clustering methods, this article introduces a plot method called the membership contour map. Based on the data of the membership matrix obtained through the fuzzy C-mean (FCM) algorithm, the membership contour map is realized by a graphics technique. Due to the full use of membership information in FCM clustering, the membership contour map can show the spatial distribution of the membership degree of each clustering, distinguish discontinuities caused by trivial random factors, and read out clustering centers by the scope form from the membership contour map directly. An application of Sanshandao Gold Mine proves that the membership contour map holds the advantages of both intuitionism and objectivity, and can adapt discontinuities data, which do not have obvious dominant groups.
Abstract: By analyzing the composition and morphology of each layer IF steel clogs on the nozzle, it is found that aggregation and sintering of Al2O3 inclusions is the main reason for nozzle clogging. The effects of different aluminum consumptions on the stopper pole position were compared. When the quantity of aluminum consumption is large, the stopper pole position rises significantly. It may cause the casting accident of molten steel breakout while the quantity of aluminum consumption is more than 3.5 kg·t-1. The average aluminum consumption and average oxygen potential at final deoxidation were defined. As the average aluminum consumption increases, the casting time decreases when a single submerged nozzle is used. When the quantity of average aluminum consumption is over 3.5 kg·t-1, the casting time is less than 50 rain with a single submerged nozzle used. The aluminum consumption tends to increase with the improvement of oxygen potential at final deoxidation. When the oxygen potential at final deoxidation is more than 600×10-6, the aluminum consumption may exceed 3.0 kg·t-1. While the average oxygen potential at final deoxidation is more than 600×10-6, the casting time with a single submerged nozzle is probably less than 50 min.
Abstract: Hot-rolled TRIP steel with 0.038% Nb was thermomechanically processed on a Gleeble simulation test machine. The microstructural evolution and the precipitation behavior of Nb were analyzed by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The amount of Nb in solution/precipitation was quantitatively measured by inductively coupled plasma optical emission spectrometry (ICP-OES). After austenization at 1250℃ for 5 rain, about 70% of added Nb is dissolved into austenite. During hot deformation in the austenitic recrystallized region above 1000℃, only 3% of dissolved Nb precipitates, which is too little to retard static recrystallization of austenite, and then the austenite grain size is markedly refined. Before hot deformation in the austenitie non-recrystallized region at 900℃, the fraction of precipitated Nb is up to 9%, which retards static recrystallization of austenite after hot deformation and results in pancaked austenite grains. Hot deformation in the austenitic non-recrystallized region accelerates the γ→α transformation and refines the ferrite grains. After controlled-cooling to 650℃, there are still 48% and 40% of added Nb in solution after thermomechnical processing for reerystallized austenite and deformed austenite, respectively.
Abstract: Nuclear grade stainless steel welding joints were prepared by laser beam welding (LBW) at different welding speeds. Optical microscopy and scanning electron microscopy were subsequently used to study the weld penetration ratio, δ/γ ratio, micro structure, and phase composition. The hardness distribution was examined with a micro-Vickers hardness tester. When this welding speeds up, the weld penetration ratio and δ-ferrite content within the welding seam increase, the island and lath-shaped microstructures enlarge at the cost of the worm-like one, and the average hardness value in the weld area becomes greater.
A method was presented to predict phase change behavior and liquid film evolution on specimens by combining the Eulerian wall film (EWF) model of two-phase flow with the self-defined formula of dew amount. Firstly, a self-built environmental test chamber was used to carry out condensation physical tests, and simulated tests were respectively performed based on the EWF model and the single-phase flow model. It is found that the EWF model is more accurate than the single-phase flow model due to necessary consideration of the phase change process. Then, a self-defined formula was established to calculate the dew amount and it was verified by the physical tests. Finally, under the premise that simulated and tested temperatures, relatively humidity curves and dew amounts show good agreement, the changing process of liquid films on specimen surfaces was predicted, and the simulation prediction of liquid film shape on specimen surfaces is in consistent with in-situ video imaging morphology during the physical tests.
Abstract: Electrochemical impedance spectroscopy (EIS) was used to study the corrosion behavior of electroless nickel immersion gold processing printed circuit boards (PCB-ENIG) in a simulated electrolyte solution (0.1 mol. L-1 NaHSO3), and the morphology, composition of corrosion products as well as the failure mechanism of the plating layer were analyzed with the aid of stereo microscopy and scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). It is found that the corrosion resistance of PCB-ENIG in NaHSO3 solution is relative poor. Partial discolor appears in PCB-ENIG just immersing for 12 h, along with micro-crack generation. The electrolyte can directly erode the Cu substrate through micro-cracks, forming dendritic crystalline products around these micro-cracks, whose main composition should be Cu2S. Continuous generation of these corrosion products results in large transverse shear stress between the Ni intermediate layer and Cu substrate, and eventually bubbling and shedding of the Ni plating layer occur.
Abstract: Copper nanoparticles with uniform size and morphology were prepared on indium tin oxide (ITO) substrates by an electrochemical method. CuSO4·5H2O and polyvinylpyrrolidone (PVP) were used as a precursor and a capping agent, respectively. The effect of the concentration of the precursor, the type and concentration of the capping agent, and the potential of electrochemical deposition on the morphology and density of products were studied. A CuO film was obtained by a heat treatment of the as-prepared Cu nanoparticles. Test results show that the CuO film exhibits high photoelectrochemical activity toward water splitting for hydrogen generation.
Abstract: Natural clinoptilolite was modified by different concentrations of hydrochloric acid. Systemic investigations were performed on the channel characteristics, chemical composition, surface potential, and cation exchange behavior of the modified clinoptilolite. It is found that the surface of the modified clinoptilolite becomes loose and rough, the contents of K+, Na+, Ca2+, and Mg2+ slightly decrease, the surface negative charges increases, and the cation exchange capacity decreases to some extent. The specif-ic surfaee area and total pore volume are improved and the maximum values of them increase from 35.97 m2·g-1 and 0.0761 m3·g-1 to 64.46 m2·g-1 and 0.1156 m3·g-1, respectively. The distribution of micropores, mesopores, and macropores is obviously impacted, and the type of zeolite cavities is determined to be uneven slits by the hysteresis loop shape, indicating that this aeid modification cannot change zeolite cavities.
Abstract: Three porous carbide ceramics (Cr3C2, TiC and WC) were successfully prepared through a reactive sintering process by reducing their oxides (Cr2O3, TiO2 and WO3) with methane. The surface and cross section morphologies of sintered products were examined by scanning electron microscopy, the microstruetures were characterized, and the reaction dynamics was studied by X-ray diffraction analysis. It is found that the preparation temperatures of porous TiC and WC ceramics should he 1200℃ and 1000℃, respectively, below which intermediates will be produced in the sintering process. The average sizes of both the ceramic struts and pores for porous Cr3C2 ceramics prepared by reactive sintering increase with an increase in sintering temperature.
Abstract: Blast furnace slag, tailing and coal fly ash were used as starting materials for preparing glass-ceramics by the sintering method based on their characteristics and without adding any other nucleating and chemical agents. The effects of CaO/SiO2 mass ratio and crystallization temperature on the crystaltransition, crystallization behavior and main mechanical properties of slag glass-ceramics with 10% Al2O3were systematically investigated by differential thermal analysis, X-ray diffraction and scanning electron microscopy. When the CaO/SiO2 mass ratio increases, the crystallization activation energy decreases, the Si-O tetrahedral bonding strength decreases, the particle movement strengthens, and the crystallization onset temperature and the crystallization temperature decrease. The glass samples with a CaO/SiO2 mass ratio of 0.4, sintered at 886℃ for 1 h as a nucleation process and at 982℃ for 1 h as a crystalli-zation process, possess the best performance with the bending strength of 103.59 MPa, the microhardness of 5.3 GPa and the acid and alkali resistances of 0.25% and 〈 0.1% (mass loss rate) respectively. Moreover, the major phase of the glass ceramics is diopside.
Abstract: Reverse-mode polymer-stabilized cholesteric texture (R-PSCT) films were prepared from ultraviolet polymerization-induced phase separation in a mixture of 1,4-di[4-(6-acryloyloxyhexyloxy) benzoyloxy] -2-methylbenzene (C6M)/(S)-4'-(2-methyl-butyl) biphenyl-4-earbonitrile (CB15)/2,2-dimethopxy-1,2-diphenyl-ethanone (IRC,651)/SLC 1717. The effects of curing temperature and ultraviolet (UV) irradiance on the electro-optical properties of R-PSCT films were studied. When the curing temperature increases or the ultraviolet irradianee decreases, the driving voltage, the contrast ratio and the on-state response time decrease, but the off-state response time increases. The R-PSCT film prepared at a curing temperature of 293 K and an ultraviolet irradiance of 0.75 mW·cm-2 has better electro-optical properties.
Abstract: Based on ultraviolet (UV) accelerated aging tests, aging processes were tracked to study the effects of nano-TiO2 antiaging agent on the surface aging behaviors and anti-aging ability of ethylene-propylene-diene monomer (EPDM). The anti-aging mechanism was also analyzed by Fourier transform infrared spectroscopy (FT-IR) and UV absorption spectroscopy. When the aging time prolongs, the surfaces of EPDM become rough, the chromatic aberration and the glossiness loss increase, the surface carbonyl index rises, while the rate of UV absorbance declines. FT-IR results demonstrate that with coating SiO2, the photocatalytic degradation reaction of nano-TiO2 is inhibited and the aging process of EPDM is postponed. After adding nano-TiO2 anti-aging agent, the hole density decreases, the chromatic aberration and glossiness loss declines by 0.97 and 22.29%, respectively, the surface carbonyl index descends by 0.06, and the rate of UVabsorbance increases by 3.92%. The anti-aging ability of EPDM enhances.
Abstract: The forming process of shafts by cross wedge rolling (CWR) was presented by numerical simulation and rolling experiment. The metal deformation characteristics of roiled pieces were studied from the view of area reduction. It is found that the cut-off point between rolled pieces with light area reduction and conventional area reduction is roughly at 35%. Comparative analysis was mainly focused on the deformation rule of rolled pieces with light area reduction and conventional area reduction. The results show that the main deformation of roiled pieces with light area reduction is near the outer while that with conventional area reduction is inside. A more uneven axial tensile deformation exists in rolled pieces with light area reduction than in rolled pieces with conventional area reduction, leading to a heavier cross section elliptical deformation in rolled pieces with light area reduction.
Abstract: Based on the principle of steel ball forming by skew rolling, a finite element model of steel ball forming by skew rolling was established by using software DEFORM-3D. This FEM model was proved to be reliable by contrast with laboratory experiment results. Using the data of FEM results, the metal flow laws in both the radial and axial directions were studied. It is found that metal deformation accumulates in a periodic oscillation way. In the axial direction, deformation at the connecting neck is the most severe, both the radial and axial deformation are larger at the location closer to the connecting neck. In the cross sections, smaller radial compression and larger axial elongation were found at the location closer to the center in the front semi-sphere. Differently, there are smaller axial deformation and radial compression at the location closer to the center in the back semi-sphere.
Abstract: A mathematical model to describe the wave-shaped defect generation and stretching process of thin strips is established by using ABAQUS to study the stress characteristics and deformation behavior of strips under initial strain. Influencing factors on the straightening effect are analyzed in the tension straightening process. The deformation process of wave-shaped defects is divided into a generation phase, a stretching stage, and an elastic recovery phase. The elastic-buckling wave of thin steel strips and the elastic-plastic-buckling wave of aluminum strips as two typical wave-shaped forms are focused on to investigate the change of wave steepness and system energy. During the process of tension straightening, the number and height of the elastic-buckling wave both change, while the height of the elastic-plastic-buckling wave does continuously only. After straightening, the residual stress distribution of the elastic-buckling wave is similar to the initial stress distribution, while the residual stress distribution of the elastic-plastic-buckling wave makes a significant difference. The steepness of the residual wave increases with the increase of initial wave steepness and decreases with the increase of strip thickness. The straightening effect of the elastic-plastic-buckling wave is more significant.
Abstract: An analytical model of air-gap flux density and the Lorenz force law were used to establish radial and tangential electro-magnetic force models in the spherical coordinate system for the stator coils. Then, a finite element model of the stator casing and coil holder was applied to compute the strain of the coil holder caused by electromagnetic force, and the influences of the stator casing's thickness, the diameter and the length of the coil holder's connecting rod on this strain were analyzed. Finally, the finite element method and the analytical method were used to analyze a prototype motor and their results were compared, which verified the validity and accuracy of the analytical models. This analysis shows that when the stator casing becomes thin or the connecting rod slenderizes, the strain of the stator coil holder produced by electromagnetic force increases linearly within a certain range and then grows significantly.
Abstract: This article introduces an efficient eye detection method based on gray intensity information and support vector machines (SVM). Firstly, using the evidence that gray intensity variation in the eye region is obvious, an eye variance filter (EVF) was constructed. Within the selected eye search region, the eye variance filter was used to find out eye candidate regions. Secondly, a trained support vector machine classifier was employed to detect the precise eye location among these eye candidate regions. Lastly, the eye center, i. e., iris center, could be located by the proposed gray intensity information rate. The proposed method was evaluated on the BioID, FERET, and IMM face databases, respectively. The correct rates of eye detection on face images without glasses are 98.2%, 97.8% and 98.9% respectively and that with glasses is 94.9%. The correct rates of eye center localization are 90.5%, 88.3% and 96.1%, respectively. Compared with state-of-the-art methods, the proposed method achieves good detection performance.
Abstract: The basic definition and the characteristics of three service principals of reverse supply chain service for the iron and steel industry is analyzed according to the reverse supply chain process of the iron and steel industry. Based on this work, a two-hierarchical and three-dimensional reverse supply chain service process model is built for the iron and steel industry. A three-dimensional service space is constructed, including services abstraction, service organization and collaborative operation, and service network control and service value-added. In the space, the first hierarchical service response constituted by the three stages of service programme matching and decision-making, and the second hierarchical service response constituted by the two stages of service function realization are accomplished. The key technology of service process realization including service modularization, service knowledge acquisition and sharing, and service modular intelligent matching is discussed. Finally, the feasibility of the model is proved by a case of scrap steel reverse supply service for one iron and steel enterprise.
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
