Abstract: The graph-theory method was used to build a mathematical model of the optimum rescue route during mine fire time and an improved Dijkstra algorithm was brought forward to calculate it. Then each step of the Dijkstra algorithm was discussed, and the residence and moving time-temperature function was fitted. Finally, taking the mine hazard emergency rescue system of Dong-pang mine as an example, through operation the decision maker can get the optimum rescue route on the Dongpang mine tunnel distribution sketch map. The software realizes the requirement of visualization with high efficiency and provides powerful technical support for mine fire rescue.
Abstract: The horizontal deformation of a cantilever anti-slide pile or an embeded anti-slide pile is less than that of landslide due to large pile diameter and stiffness, which leads to local cracking of the slope. On the basis of analyzing the stress and deformation of a cantilever anti-slide pile and an embeded anti-slide pile, the anchor anti-slide pile was put forward to reinforce subgrade landslide. As an embeded anti-slide structure, it solved not only the unreasonable stress problem of a cantilever anti-slide pile but also the local cracking problem of the slope. The stress of the anchor anti-slide pile was simulated with FLAC software in subgrade reinforcement engineering.
Abstract: The subsurface flow wetland reactor model for sewage treatment was studied by approximating the Michaelis-Menten equation into a nonlinear power law function of two orders. The analytical solutions were obtained in terms of a rapid convergent power series by utilizing the Adomain decomposition technique. The mathematical technique employed in this paper is also of significance in studying the problems when the Michaelis-Menten equation is approximated by other nonlinear functions.
Abstract: The vapor pressures of zinc and its chloride from a FeO-CaO-SiOE-Al2O3 slag system were measured by Knudsen effusion method under the conditions with varying parameters such as temperature and slag composition. The results show that the vapor pressures of metallic Zn and ZnCl2 increase with increasing temperature. For ZnCl2, the logarithm of vapor pressure is a linear function of the reciprocal of temperature. The slag basicity exhibits the different effects on the vapor pressures of metallic Zn and ZnCl2. The former increases with increasing slag basicity, while the latter decreases. A high FeO content in the slag tends to increase the vapor pressures of metallic Zn and ZnCl2.
Abstract: The microstructure characteristics of F40 type hull structure steel and the effect of microstructure on its low-temperature toughness were studied by OM, SEM, TEM, and EBSD. The mechanism of low-temperature toughness was also analyzed. It is shown that the micro-alloyed steel possesses high strength and excellent low-temperature toughness due to a mixed microstructure of acicular ferrite and quasi-polygonal ferrite. The grain boundaries between the two microstructures and the grain boundaries between acicular ferrites are the large boundary, which is pronounced to inhibit cleavage crack propagation and improve the crack propagation energy. The mixed microstructure shows the capability to attain such an excellent low-temperature toughness that the Charpy-V impact energy can reach 138 J at -80℃.
Abstract: The corrosion behavior of X70 steel in Dagang saline-alkaline soil with 20%-34% water content was studied by polarization curve measurement and electrochemical impedance spectroscopy (EIS). It is shown that the corrosion behavior of X70 steel is strongly dependent on the water content in soil. Local corrosion occurred at the water content of 25%, and general corrosion took place when the water content was more than 30%. With increasing water content, the corrosion current density increased to a maximum at the water content of 25% and then decreased. The low-frequency inductance loop emerged at the water content of 20%. It disappeared with increasing water content and a single capacitive impedance loop was observed.
Abstract: The influence of chloride ions (Cl-) on the corrosion resistance of X80 pipeline steel in 0.5 mol·L-1 NaHCO3 solution was discussed by potentiodynamic polarization technique, and the corrosion mechanism was investigated by capacitance The results show that Cl- enhances the occurrence of pitting corrosion of X80 pipeline steel in 0.8mol·L-1 NaHCO3, and the density and size of corrosion pits increase with increasing Cl- concentration. Mott-Schottky results indicated that the value of donor density of the passive film increases with increasing Cl- concentration, which enhances the potential sites of film local breakdown and corrosion initiation. It is concluded that the addition of Cl- decreases the corrosion resistance of X80 pipeline steel in 0.5 mol·L-1 NaHCO3 solution.
Abstract: The friction wear behaviors of 316L stainless steel/Y-PSZ (partially yttria-stabilized zirconia) metal-ceramics compos-ites fabricated by means of powder metallurgy were evaluated under dry-sliding condition on a high-speed block-on-ring contact wear test machine MRH-3, and were contrasted to those of T10 steel (HRC 45). The effects of the volume fraction (30% -50%) and particle size (10.8-51.6μm) of 316L and the rotary speed (200-280 r·min-1) of the friction ring on the wear resistance of 316L/Y-PSZ composites were investigated. The results show that the wear resistance of the composites decrease with the increase of 316L content and particle size, or with the increase of the rotary speed of the friction ring. The wear resistance of fabricated 316L/Y-PSZ composites is better than that of T10 steel under the experimental conditions in this work except for few cases. Furthermore, the wear resistance of the fabricated 316L/Y-PSZ composites with a 316L volume fraction of 30% and a 316L particle size 10.8μm is 3.0-3.2 times as large as that of T10 steel under the experimental conditions in this work. The abrasion mechanism of 316L/Y-PSZ composites is mainly composed of the desquamation of 316L particles and the delamination of Y-PSZ matrix.
Abstract: Glass-coated pure copper micro-wires were fabricated by the melting spinning method. The mechanical properties of both glass-coated pure copper micro-wires and pure copper fibers were evaluated and the fracture morphology was observed, The results show that the ultimate tensile load of the glass-coated pure copper micro-wire with 45 μm in diameter and 7.5 μm in thickness of glass layer is 0.268 N, and the load of the micro-wire with 27 μm in diameter and 6.0 μm in thickness of glass layer is 0.237 N. The tensile stress-strain curves of pure copper fibers exhibit low work hardening rate. The ratio of yield strength to tensile strength is above 0.75. The tensile strength of pure copper fibers increases with the diameter of copper fibers decreasing. The average tensile strength of the copper fiber with 10μm in diameter is 547.9 MPa and the elongation is about 2.5%.The tensile fracture mode of pure copper fibers is slip-elongation rupture.
Abstract: Fine aluminium was extruded by using self-developed continuous variable cross-section extruding equipment, and the microstructure of samples was studied. The results showed that the grain size is different in every section along the extruding direction owing to the different extrusion rate. The grain size is fined with increasing extrusion rate. The phenomenon is more obvious in a sin-gle cross-section extruded sample. The grains on the same section are not nonuniform. In the same section, the grain size is increased from outer part to center of the sample. The grains are mostly smaller in the outer part but bigger at the center. Some grains are very big, and the reason is that some grains recrystallize during heat treatment. The research gives the microstructural evolvement rule of extrusions in continuous variable cross-section extrusion.
Abstract: An Al-Zn-Mg-Cu alloy containing 2% Mn (mass fraction) was prepared by spray forming method and hot extrusion. The microstructure and mechanical properties of the spray-deposited Al alloy were studied by optical microscopy, scanning electron microscopy, X-ray diffraction, and tensile tests. The results show that the Al alloy has uniformly fine recrystallized grains with an average size of 8μm after hot extrusion and solid solution treatment. MnAl6 particles were precipitated at grain boundaries during the spray forming process, most of the MnAl6 particles were plastically deformed to some extent along the direction of extrusion during the hot extrusion process, and some large MnAl6 particles were fragged. The effect of solution treatment on the size of MnAl6 particles is negligible but the spheroidization of rod-like/plate-like particles occurred at the corner of these particles. The spheroidization of MnAl6 particles is benefit to the decrease of stress or strain concentration which would induce microcracks. When aged at 120℃ for 24 h, the tensile strength of the Al alloy was increased up to 775 MPa with an elongation of 4.3%, and the fracture surface consisted mainly of dimples with a size lower than 500 nm.
Abstract: Remelting tests at different cooling rates for Waspaloy alloy were performed and the effect of cooling rate on the segregation behavior and the liquid density of Waspaloy alloy during solidification process was systematically investigated by SEM and EDAX. The results show that the element segregation decreases with increasing cooling rate and Ti segregation is the most serious during solidification which is a positive segregation element and congregates in interdendritic area. The liquid density exhibits an in-version trend due to the element segregation. The maximum liquid density inversion occurs near the solidification temperature of 1 300℃.
Abstract: The AlxTiVCrMnFeCoNiCu high-entropy alloys, designed by using the strategy of high entropy of mixing, were investigated on room-temperature mechanical properties. The four alloys have the compressive strength higher than 1.3 GPa and the compressive strength of AlTiVCrMnFeCoNiCu alloy reaches 2.4 GPa. Besides, both AlTiVCrMnFeCoNiCu and Al2TiVCrMnFeCoNiCu alloys exhibit compressive plasticity. For the alloy system, the microhardness in both dendrite and interden-drite area increase with increasing Al content. Such excellent room-temperature mechanical properties should be attributed to the solution strengthening, the dispersion strengthening of nano-scale particles, and the structure transformation from ductile face-centered cubic phases to strong body-centered cubic phases.
Abstract: ZnO films, with rapid reversible transition properties of super-hydrophobicity and super-hydrophilicity under vacuum ultraviolet (VUV) irradiation, were prepared by a simple and low-temperature solution method by controlling the pH value with hydrofluoric acid. The surface of the film exhibits hierarchical structure with nanostructure on the micro-spheres mimicking to the taro leaf surface. The fresh film shows the water contact angle (WCA) of 151°,turning into a super-hydrophilic (WCA〈5°) one after 30 min VUV irradiation. The super-hydrophilic film can be recovered to super-hydrophobic through being placed in the dark for 6 d. The wettability of the film can be reversibly switched circularly by the alternation of VUV irradiation and dark storage. The transition from super-hydrophobic to super-hydrophilic is more quickly than that of the past reports due to the use of VUV and the special hierarchical structure of the ZnO film surface. This study is expected to promote the applications of ZnO materials in micro-fluidic devices.
Abstract: Equivalent moles of KMnO4 and Mn(CH3COO)2 were used to prepare a weak-crystalline α-MnO2 supercapacitor electrode material via a mechanochemical route. An assembled symmetrical supercapacitor was tested by galvanostatic charging-discharging within 1.2 V at 200 mA·g-1. The structure and electrochemical performances of the electrode material were identified by XRD, cyclic voltammetry and AC impedance both before and after charging-discharging. The slope of the charge-discharge curve was analyzed for the first time. It suggests that the supercapacitor exhibits both double-layer capability and pseudocapacitance property. Mn3O4, an electrochemical inert, has formed in the charging-discharging process. During cycling, redox peaks disappeared gradually in the cyclic voltammetry diagram, and the pseudocapacitance property disappeared in the discharge curve, then the discharge curve was dosed to the ideal line of double-layer capacitance; the specific capacity and equivalent series resistance of the MnO2 supercapacitor changed accordingly, the maximum specific capacity of the MnO2 electrode reached as high as 416 F·g-l, and retained 220 F·g-1 after nearly 500 cycles.
Abstract: Based on the microstructure features of xonotlite-aerogel composite insulation material, a three dimensional unit cell model was developed for the coupled heat transfer of gas and solid in the material. The effective thermal conductivities of xonotlite-type calcium silicate, aerogel and xonotlite-aerogel composite insulation material were compared by model calculation. The results show that the density of xonotlite-type calcium silicate has great influence on the effective thermal conductivity of xonotlite-aerogel composite insulation material, but the density of aerogel has little influence. The effective thermal conductivity of xonotlite-aerogel composite insulation material is apparently lower than those of xonotlite-type calcium silicate and aerogel at an elevated temperature.
Abstract: Photo-alignment materials were prepared from ladder-like polysiloxane materials containing dual photo-reactive groups. The effects of solution concentration, irradiance and irradiation time on the photo-alignment behavior of the ladder-like polysiloxane film were investigated by polarized optical microscopy (POM) and the crystal rotation method. It was found that photo-reactive groups were prone to form homeotropic alignment with the increase of the solution concentration, and then it could induce liquid crystal molecules to form homeotropic alignment. The isomerization and reorientation both in and out of plane of azobenzene groups could be achieved within a suitable irradiance range, and then it was beneficial to the formation of in-plane alignment of liquid crystal molecules. Increasing the irradiation time availed the formation of in-plane alignment of liquid crystals molecules.
Abstract: Butanone 1,2-pmpanediol ketal was synthesized from butanone and 1,2-propanediol in the presence of H3PW6Mo6O40/MCM-48. The effects of the molar ratio of hutanone to 1,2-propanediol, catalyst dosage and reaction time on the yield of hutanone 1, 2-propanediol ketal were investigated. The catalytic activity of H3PW6Mo6O40/MCM-48 was discussed by the orthogonal experiment. The results show that H3PW6Mo6O40/MCM-48 is an excellent catalyst for synthesizing butanone 1,2-propanediol ketal and the yield can be up to reach 81.0% under the condition that the molar ratio of butanone to 1,2-propanediol is 1:1.4, the mass percent of catalyst is 0.2% of feed stocks, and the reaction time is 1.0h.
Abstract: Three-dimensional numerical simulations on the magnetic field in an electromagnetic soft-contact continuous casting mold were carried out through the finite element software ANSYS. The effects of molten steel level in mold on the distributions of magnetic field and electromagnetic force were analyzed. The results show that the magnetic induction density, B , is mainly distributed at the profile-surface of molten steel. If the molten steel level is below the coil top, the maximum value of B is near the top surface of molten steel and falls gradually along the withdrawing direction. If the molten steel level is above the coil top, the maximum value of B is moving toward the centre of the coil as the molten steel level is rising. The distributing character of electromagnetic force is mostly consistent with that of B .
Abstract: Experiments of a real aspect water model were conducted to study the influence of process factors on the characteristic parameters of unstable fluid flow in a continuous thin slab casting mould by using a wave gauge and the particle trajectory visualization method. The results show that the characteristic parameters of fluid flow vary with a certain periodicity. With increasing casting speed, the average jet impinging position and the average circumfluence center descend and the average wave height increases; more-over, the variation ranges of the jet impinging position, the circumfluence center and the wave height increase, the variation period decreases and the fluid flow becomes more unsteady. With increasing immersion depth of the submerged entry nozzle (SEN), the average jet impinging position and the average circumfluence center descend and the average wave height decreases; in addition, the variation ranges of the jet impinging position, the circumfluence center and the wave height decrease, the variation period increases and the turbulent flow becomes gradually calmness. With increasing SEN outlet angle downwards, the average jet impinging position and the average circumfluence center descend and the average wave height decreases; for a larger SEN outlet angel, even though the characteristic fluid flow moving range is larger, the variation period is greater and the level fluctuation becomes relatively stable.
Abstract: Both shape control and uniform roll wear for schedule-free rolling should be realized in the downstream stands of the finishing trains of hot rolling, and the edge drop of some special steel grades such as silicon steel and container steel is large. It is much difficult to get the target crown by conventional shape control means. The asymmetry work roll with a special curve at one roll body end was developed. The top work roll and bottom work roll are placed anti-symmetrically. As the roll axial position is changed, the variation in strip crown is over 150μm. In order to control the strip edge profile efficaciously, a relevant shifting strategy of this roll was designed. At the same time, the wear contour of the work roll can be improved and it is helpful for schedule-free rolling. The application of the asymmetry work roll in the 1700ASP product line of Ansteel shows the crown of silicon steel is reduced by 29.8 96 and the crown of high strength steel can be controlled below 50 μm stably.
Abstract: A design procedure based on FEM was presented, which is combined with topological optimization, design optimization and probabilistic design technology. Compared with traditional design, this procedure can avoid some blindness work, the design progress is more efficiency, and the design result is more reliable. It was successfully applied in the development of a large-scale off-highway vehicle frame.
Abstract: The traditional linear control theory can not meet the system requirement of a permanent synchronous motor (PMSM) for its motion control is a coupling and nonlinear control system and measurement noise also exists in the control system. A method to estimate the rotor position of PMSM was presented based on fluctuating high-frequency voltage signal injection and Kalman rotor-position-estimator. When a fluctuating high-frequency voltage signal was injected into stator winding, the corresponding current signal containing the information of rotor position was demodulated and delivered into the Kalman rotor-position-estimator. Then the rotor position would be detected accurately. Simulation results verified the method can track the rotor position accurately, even though system noise and measurement noise exist in the control system.
Abstract: The relationship between organizational learning capability and firm performance was quantificationally examined based on reviewing the theories on organizational learning and its qualitative relation with firm performance. The sample of this study had 394 companies in China. Data analysis showed that organizational learning capability has positive direct significant impact on administrative and technical innovation, but indirect significant impact on performance by administrative and technical innovation.
Abstract: A class of uncertain composite system was concerned with the decentralized robust feedback stabilization problem. A sufficient condition for decentralized stabilization feedback stabilization was derived by the Riccati matrix inequality techniques. By using the linear matrix inequality techniques, the design scheme of quadratically decentralized stabilization was proposed. Finally, simulation results show that the scheme is effective.
Abstract: A structure model was used to analyze the relations between concepts in knowledge structure and parse the medical records of traditional Chinese medicine to gain connotative rules of treatment based on syndrome differentiation effectively. The analytic results of medical record examples show that the structure model gained by structural analysis can not only discover many un-known relations by few scattered existing information, but also protrude existing structural relations. The picture analysis of structure displays the correlation degree and importance of symptoms, and the results have been validated by medical records and affirmed by experts.
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
