Abstract: The characteristics of three-phase foam in mine fire control were introduced, its covering and inhibition were analyzed, and experiments on extinguishing the top fire in a porous medium were carried out. The results show that three-phase foam can cover the whole goaf and prevent everywhere fire by pervasion and accumulation. According to the characteristics of goaf and three-phase foam, technical parameters, such as diffused distance of three-phase foam, length between working face and pipe bottom and durative time for spontaneous combustion of coal, were deduced. Based on them, three-phase foam was applied in the workface N2 703 of Daxing coal mine in China, and laying pipes in advance in goaf was carried out. The effect of application shows that three-phase foam can successfully prevent spontaneous combustion of coal in the working face.
Abstract: Based on the analysis and numerical simulation of ancient landslide revivification, an effective reinforcement measure of micro anti-slide piles combined with pressure grouting, unloading soil and pressing the slope toe was adopted to ensure the road and the cutting slope against slippery. With a practical example, the mechanical analysis and numerical simulation of a micro anti-slide piles are carried out and the result shows that the maximum axial force takes place in the middle and the maximum shear stress is in the 1/3-2/5 height of the pile.
Abstract: Long-term deflection computations of two typical built-up beams in a actual project were carried out by a built-up beam long-term deflection computational method considering contraction, creep and composition plane slipping. The crag earth project analysis software FLAC3D was used to the built-up beam slip-surface simulation, and the calculated, measured and computer simulated data were compared subsequently. The results show that the proposed method is fit for calculating the long-term deflection. Some advices are also proposed for the design and construction of composite beams.
Abstract: 25Cr5MoA/Q235 steel clad plates were prepared with the composite slabs heated to the temperature between 800℃ and 1 100℃, held at each temperature for 30 min, rolled one pass and reduced from 50% to 70%. Their bonding shear strengths were tested by the electron universal testing machine CMT4105 and the metallographic microstructures of their interfaces were observed by optical microscope and SEM. The results show that the rolling temperature between 900℃ and 1000℃ is favorable to the bonding of the steels and pass reduction is crucial to the bonding strength. When the pass reduction becomes large, cleaner and more activated new interfaces will be obtained and the grains will The gradient metallographic changes of grains can be refined, as a result the bonding strength can be enhanced. also raise the bonding strength of the clad plates.
Abstract: B-contained (0.004% -0.006%) and B-free SPHD hot strips produced by CSP process were chosen as experimental materials. The mechanical properties, microstructure, precipitates, dislocation density and grain orientation of the two different kinds of specimens were analyzed by tensile tests, metallographic observations, SEM analysis, TEM and EBSD observations. The results showed that the addition of micro-alloying element B into SPHD hot strips made ferrite grains evidently coarse, large precipitates were found, the dislocation density decreased, and all these caused the yield strength to reduce. The crystallographic orientation was analyzed and observed by EBSD. The orientations among neighboring grains both of the B-contained and B-free steel were mainly large angle grain boundaries, however, a great deal of subgrains were found in the B-free steel.
Abstract: The microstructure evolution of a Fe3Al-based alloy was investigated by uniaxial compression tests on a Gleeble 1500 hot simulation test machine at 850℃ and a strain rate of 10-3s-1. The results indicated that under the present deformation conditions the dynamic recrystallization of the Fe3Al-based alloy occurred. At low strain, the nuclei of dynamic recrystallization formed by bulging of initial grain boundaries, i.e. discontinuous dynamic recrystallization occurred; but the growth of the nuclei became more difficult with increasing strain. At large strain, finer dynamic recrvstallized grains formed by the process of continuous dynamic recrystallization.
Abstract: Using Ni46 alloy powder as the raw material, the erosive wear resistance of stainless steel was improved with Ni-based alloy coating onto the stainless steel by plasma cladding. The coating's microstructure was studied and its microhardness was measured using an HVS1000 micro-hardness tester. The erosive wear resistance of the coating in a slurry erosion tester was investigated. The results show that the mechanical properties of metal materials influenced their erosive wear resistance:the larger the hardness value of the material is, the better the anti erosive wear properties are. On the same experimental condition, the erosive wear rates of the materials follow this rule:Ni-based coating > 0Cr13Ni5Mo > 1Cr18Ni9Ti. The improvement in erosion resistance can be attributed to the solution strengthening of γ-Ni matrix and the presence of large amounts of borides and carbides which withstood the impingement of slurry erosion.
Abstract: Three samples with mottle (Hu-ban-wen) were analyzed by using SEM, XRD and microscope. The matrix of these samples was cast and then heated. Distinct interface between the matrix and mottle existed. The mottle layer was high tin bronze and the thickness was about 20-40μm. SnO2 and Cu41Sn11 were main composition of the mottle layer. Some experiments were carried out by using the methods of coating with Cu-Sn alloy solution and hot-tinning. Clear boundary and columnar crystal growing could be seen clearly by all these methods and varied thickness of the coating was caused by different heating conditions. The result shows that the mottle is artificial, the columnar crystal growing from substrate to coating should be caused by dissolving and diffusion of copper into liquid tin and δ phase maybe caused by hot-tinning and annealing.
Abstract: Resistance sintering under ultra-high pressure was developed to fabricate Mo-Cu alloys containing copper of 25%-75% in volume fraction. Consolidation was carried out under pressures of 2-10 GPa and an input power of 15 kW for 65 s. The densification effect and mechanical properties of these Mo-Cu alloys were investigated. The results show that these composites have high density and their mechanical properties are well. It is concluded that resistance sintering under ultra-high pressure is one of the fabrication methods which can avoid inhomogeneous structure and abnormal grain growth.
Abstract: Li4Ti5O12(M1) was obtained by solid reaction process with LiNO3 and TiO2 as reactants. XRD analysis indicates that the main phase of the produced powder is Li4Ti5O12 compound oxide with spinel structure. The initial discharge capacity of M1 at 35 mA·g-1 reaches 170 mAh·g-1, which is comparable to the theoretical capacity, and the first coulombic efficiency is 92%. M1 performs well when it charges and discharges with high current density, and the discharge capacities reach 151, 140 and 115 mAh·g-1 at 175, 350 and 875 mA·g-1, respectively. The discharge capacities of M1, comparing with that of ME prepared by conventional solid-state sintering of LiOH and TiO2, increase by 5%, 10% and 26% at 175, 350 and 875 mA·g-1, respectively. Cyclic voltammogram suggests that the electrode of M1 has low polarization, good reversibility and high electrochemical activity. The charge transfer resistances of M1 measured through AC impedance are 16 and 2012 after lithium insertion and extraction, respectively.
Abstract: The PtSn/C catalyst was prepared by the low-temperature solid phase reaction method. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) were used to characterize the crystallinity and particle size of the catalyst. The results indicate that the PtSn/C and Pt/C catalyst prepared by the same low-temperature solid phase reaction method both have platinum fcc structure. The addition of Sn can increase the lattice parameter of Pt. Compared with the Pt/C catalyst prepared by the same method, the PtSn/C catalyst shows a higher dispersion and a smaller particle size and its mean particle size is about 4.8 nm, therefore the PtSn/C catalyst has a higher active specific surface area. The results of electrochemical measurements demonstrate that the PtSn/C catalyst has a better electrocatalytic activity for the methanol oxidation than Pt/C catalyst.
Abstract: After AgSnO2 powders prepared by hydrothermal method being pressed and sintered, AgSnO2 contact materials were obtained. X-ray diffraction, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis were used for the AgSnO2 powders. It is indicated that AgSnO2 composite powders with finer size and spherical can be prepared by hydrothermal method by means of the co-precipitation of Ag and SnO2 in aqueous systems. As a result of changing the combination states of silver and tin oxide, the tin oxide crystals show preferred orientation in (110) plate by X-ray diffraction. Microstructure analysis by optical micrograph shows that the AgSnO2 composite bulks have the microstructure with SnO2 particles dispersed on the silver matrix equably.
Abstract: Mg(OH)2-coated Al(OH)3 composite flame-retardant was prepared with a chemical compound technique. SEM, X-ray energy dispersion spectroscopy (X-EDS) and XRD were used to investigate the composite flame-retardant, and the results show that the particles of fine Al(OH)3 powder are rough and coated with Mg(OH)2 nanoparticles in the composite flame-retardant. The specific surface area of particles increase from 3. 797 9 m2·g-1 to 15. 941 4 m2·g-1 by coating. EVA products filled with the composite retardant have superior flame retardancy (the oxygen index is 39.0) and mechanical properties (the tensile strength is 10.2 MPa, the elongation at break is 180%) to those with uncoated Al(OH)3 and the physical mixture of Al(OH)3 and Mg(OH)2. Thermal analysis (TG-DTA) demonstrates that the composite flame-retardant could increase the decomposition temperature and burning residue rate of the EVA products, bate the thermal cracking of polyethylene's main chain effectively, and promote the charring.
Abstract: The phonon amplification effect occurring in a single-walled nanotube was discussed, and the change rates of phonon population at different temperatures were calculated by using a time-dependent-perturbation method. It is shown that the optical phonon population increases nonlinearly with increasing laser field and the rate decreases as the temperature increases. At a definite temperature, the more intense the laser field is, the more remarkable the phonon amplification effect is, and a reasonable interpretation on this phenomenon was presented.
Abstract: The roll contour variation characteristics of conventional backup and work rolls, self-developed VCR (varying contact backup rolls) and ASR (asymmetry self-compensating work rolls) were investigated by industrial test results. The finite element models of three typical roll contour configurations, i.e. conventional backup/work rolls, VCR/conventional work rolls, and VCR/ASR, were developed to calculate the roll stack deformation. The flatness control performance of these roll contour configurations was analyzed. In comparison with the conventional roll contour configuration, the crown control range by roll bending force enhances by 12.79% and the roll gap stiffness increases by 25.30%. The peak values of roll contact pressure in the prophase and anaphase rolling service drop by 40.23% and 41.40%, respectively. The application of VCR/ASR configuration gives better strip profile and flatness quality, an increase in coil number within the rolling campaign and a significant alleviated effect of severe work roll wear contour on the performance of edge drop control in a 1 700 mm hot strip mill at WIS(G)CO of China.
Abstract: According to flying gauge change (FGC) characteristics of a tandem cold rolling mill (TCM), a speed control strategy of the FGC stand with the strip tension set-point before FGC as a control target was put forward. Based on the developed analytic mathematic models of strip elastic deformation under tension between stands, the speed control rule of the FGC stand was derived under the condition of small gauge change by single step, and the speed of the other stands having finished the FGC process was calculated based on the constant mass flow principle. When the dimensions or material properties of two kinds of strips varied great, the method using wedge was also took to carry out FGC, and the control rules of rolling speed and gauge set-point for every thickness of the wedge were derived and calculated by using the developed strategy. The deviations of strip thickness produced by FGC were limited in the stands before and behind the FGC point, and the interference of the FGC stand to the others was eliminated, then the process control for FGC could be implemented easier.
Abstract: A sort of system for faults detection and diagnosis based on the immunology principle was presented. Initial detectors were produced at random combining negative selection of self-patterns which response normal working situation of detecting objects. The learning and memory of non-self-patterns which response abnormal working situation of detecting objects were realized using the mechanism of evolution leaning based on the artificial immune theory. The corresponding zones of different faults on states space were distinguished and marked using the results of evolution learning and information warehouse of faults. Regarding the set of each era antibodys mutated in the system learning as a random series, the condition of convergence of the series and a proof were presented. The algorithm's astringency was proved. Appling the method in detection and diagnosis for faults of gear case of machine tools, the experimental results indicate that the method is effective.
Abstract: Based on the Biot-Savart law, spatial filtering technology and two-dimensional Fourier transform, the inverse problem of magnetic field to current distribution was researched. The inverse method was applied to the real magnetic field data measured by a high-temperature superconducting quantum interference device (SQUID), and the magnetic field was produced by a lead with current and vortex around a columniform crack. The inverse results, especially how to select the filtering frequency in a Fourier space, were discussed. The results show that a larger cutoff frequency can improve the spatial resolution of the current image, but increase the noise signal. If a smaller cutoff frequency is selected, much of the noise can be eliminated, but the resulted inverse signal will be anamorphic, and the spatial resolution is decreased. Using the magnetic field data excited by vortex around a column form defect, the inversed current result can give the information about the location and the form of the defect exactly.
Abstract: As an angle displacement generation mechanism for example, the process of choosing design variables, noise factors and quality targets was given. A mathematical model of robust design for angle displacement generation based on the tolerance was established. The result of design was given and compared with that of the original projects. It is shown that the robustness of movement precision can be insured and the larger tolerances of each rod of the mechanism can be determined by this method, so the manufacturability can be improved and the cost can be reduced.
Abstract: To make AS/RS planning more scientific and reasonable, the set theory was used to describe an AS/RS system, the goal of AS/RS was quantified and the rule of AS/RS planning was pointed out. The whole process of AS/RS planning was partitioned to three phases:prime planning, particular planning, and working planning. The simulation method suitable for each phase was carried out to satisfy planning requirements of each phase. A three-phase integrated simulation platform was built to integrate planning information and simulation information of each phase and to reduce data redundancy and increase efficiency. Simulation software was selected to suit to the integrated simulation platform, and a simulation example is carried out to prove the effect of all the work above.
Abstract: To improve intelligent level and coordinative ability, cooperate with distributed grid services, and adapt to dynamic computing environment and variable user demands in the grid, cooperative intelligent grid (CIG) was proposed. CIG was based on OGSA, and the applied theory and methodology of distributed artificial intelligence and distributed coordinating control to improve the existing grid services' cooperativity and provide services to grid users more efficiently and accurately. The concept of CIG was introduced first, and followed by the description of the architecture of CIG, then the principles and methods for constructing an open and dynamic CIG with respect to the community/federal policy-driven system structure. The domain-adapting medium service collaboration mechanism and rational negotiation mechanism were discussed. CIG can effectively organize coordination, negotiation and collaboration among grid entities and improve the automation degree and abstract administrative levels of grid service composition.
Abstract: Based on the Petri net theory, ECA rules was researched and a basic Petri net model was established. Special research was made on how to use a Petri net to express compound event ECA rules, and an extended Petri net system was put forward. Considering the feature of ECA rules in general, the Petri net model based on an ECA rule system reflects the system feature of ECA rules in all aspects. Through forming the reachability tree and transition sequence, the ECA rule system and its action feature can be understood clearly, and rationality verification on the rule system is convenient to make and to help a system administrator to analyze and manage it.
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
