Abstract: The law of stress distribution and its variation in rock roadway before and after excavation were studied so as to probe clearly the mechanism of impacting disasters in coal mines. Based on original in-situ stress data, rock damage modes under different rock characteristics and stress states were obtained by indoor rock mechanics simulation test. According to the location of rupture sources, impacting disasters had been divided into rock burst, pressure bump and mine earthquake. The mechanism, process and macro-characteristics of the three kinds of impacting disasters were analyzed.
Abstract: To meet the needs of development and construction of digital mines, a Web-based framework of a mine and typical disaster 3D simulation system was designed with object-oriented design and programming methodology. This system framework consists of three main function modules:core function module, data management module, and ancillary module. With Web and visualization technology, a browser/server (B/S) based technique for a mine and typical disaster 3D simulation system was realized. After data collection from a gold mine in China and data treatment the terrain, orebody, and underground excavations were simulated with the technique mentioned above based on the B/S mode.
Abstract: Based on the mechanism of coal and gas outburst and the physical characters of outburst process, in combination with a coal mine safety monitoring system, early warning indexes were proposed by the time series of methane concentration and coal temperature. An early warning model of coal and gas outburst was built by globe information system (GIS) technology and artificial neural network. Taking 17180 working face for an example, the early warning model was tested in an exact mine. The result shows that the model can provide technical support for early warning of coal and gas outburst.
Abstract: Acoustic emission (AE) characteristics of a sandstone sample in fatigue failure process were analyzed by AE testing and its fatigue damage evolution rule was studied. Based on the AE characteristics and the damage evolution rule, in consideration of the three-stage rule of irreversible deformation development of rock, the whole fatigue process can he divided into four stages. Fatigue damage failure of rock has the burst characteristic, and the damage accelerates to evolve in the failure stage. Experiment results show that, if rock's fatigue failure is monitored and forecasted by AE, it enters into the failure stage when the damage amount is about 0.4 and into the disabled stage when the damage amount is about 0.3, respectively.
Abstract: The analytical solution to the post-peak slope of the stress-strain curve of a uniaxially compressive concrete specimen subjected to single shear failure in the form of the shear band exhibiting linear strain-softening behavior beyond the peak stress was generalized as the nonlinear case. Prior to the peak stress, the Scott model was adopted to describe the nonlinear constitutive relation. The nonlinear strain-softening constitutive relation was back-calculated from the derived post-peak slope of the shortest normal concrete specimen. Using the assessed post-peak constitutive relation, the stress-strain curves of other longer normal concrete specimens were predicted. The predicted post-peak stress-strain curves are size-dependent and agree with previous experiments. The assessed average plastic shear strain in the shear band is extraordinarily greater than the maximum axial strain measured in uniaxial compression. If the measured post-peak stress-axial strain curve is seen as a constitutive relation, then the post-peak ductility of concrete columns will be greatly underestimated.
Abstract: The processing and mechanism of the improvement in pelletization of Brazilian specularite by high-pressure roller grinding (HPRG) were investigated. SEM observations show that after being pretreated by HPRG in a closed flow path at an optimized cyclic loading, the specific surface area of Brazilian specularite increases greatly and its ballability is dramatically improved. The pellet feed composed of 70% specularite and 30% magnetite was pretreated by HPRG at 71%-product cyclic loading in a closed flow path, mixed with 2.4% bentonite and balled for 15 min under the 8% moisture. Experimental results show that all indexes of green pellets are much higher than those of the pellets made of the same feed without the pretreating. The drop number is up to 4.5 times from the 0.5m height, the compression strength is 10.25 N per pellet, and the thermal shock temperature is 455℃. The compression strength of fired pellets was tested up to 2690.88 N per pellet by preheating at 1050℃ for 10 min and by roasting at 1280℃ for 12 min, which meets the demand of strength for commercial pellets.
Abstract: The enrichment of boron in refractory low-grade paigeite was researched by the technology of reductive roasting, magnetic separation, and fine ore direct-to-furnace. Carbon was matched according to the chemical equivalent of C/O=1 (atom ratio). Roasting experiments were carried out in a muffle furnace in order to investigated the changes of paigeite grade and recovery in the range of 500 to 1450℃. The result shows that iron grains increase with raising roasting temperature. The grade of ore concentrate powder can be reached 14.29% at 1 200℃, which can meet the challenges of the paigeite chemical industry (ω(B2O3) ≥ 12%. Over 1200℃ the boron recovery can be reached 14.29%. Little changes in boron grade and recovery take place when the roasting temperature is more than 1350℃. It is concluded that the roasting temperature is determined in the range of 1200 to 1350℃, which can not only satisfy high boron recovery, but also meet the requirement of boron grade in the paigeite chemical industry.
Abstract: The electrochemical behavior of welded joints of used Q235 pipeline steel was investigated in soil simulation solution. Polarization curves of various micro-areas were measured and related electrochemical parameters were acquired. The results show that the sequence of free corrosion potential from lower to higher or the sequence of free corrosion current density from higher to lower is melt run, incomplete normalized zone, overheated zone, normalized zone, tempered zone, base metal, and weld metal. These micro-areas of a welded joint compose a multiple electrode system when exposed to the same electrolyte. Melt run and incomplete normalized zone suffer corrosion dissolution firstly as the anode of a galvanic cell composed of a complex multiple electrode system, while weld area and base metal are subjected to cathodic protection as the cathode of the galvanic cell.
Abstract: The corrosion behavior of Q235 steel in Dagang soil with a 20% water content at different temperatures was studied by the means of polarization curve, linear polarization and electrochemical impedance spectroscopy (EIS). The results indicate that at the range of 20 to 70℃, with increasing temperature the corrosion current density Icorr increases, and the linear polarization resistance Rp and the charge transfer resistance Rt depress. At the range of 100 to 200 mV of anodic polarization, the electrode reaction of Q235 steel is blocked, and the slops of E to lgI curves exponentially decrease with increasing temperature. The value of B which is calculated by the corrosion current density Icorr and the linear polarization resistance Rp is bigger than the one which accounts for active uniformity corrosion, and keeps constant at about 44.2 mV. Due to the control of diffusion process, the linear polarization resistances Rp is much bigger than the charge transfer resistance R t obtained from equivalent circuit simulation of EIS technology.
Abstract: Four ancient solder samples were examined by using optical microscope, scanning electron microscope (SEM), X-ray energy dispersive spectrometry (EDS), and X-ray diffraction spectrometry (XRD). Among these samples, three were unearthed from the tombs of the Warring State period (the 5th-3rd centuries BC) at Gaozhuang, Huaiyin, Jiangsu Province of China and one from the tomb of the Eastern Han Dynasty (the 1st-3rd centuries AD) at Shitang, Mianyang, Sichuan Province of China. The results show that all the solders are made of Pb-Sn alloys. One of the Gaozhuang samples contains 68.1% Pb and 21.4% Sn, and its microstructure consists of α and β phases. This sample was taken from a bronze Jian vessel leg, but it seems to have not been involved in welding. The other two samples that were clearly involved in welding contain not only Pb and Sn, but also Cu, and the Cu contents are 1.6% and 3.8%, respectively. It is pointed out that Cu in these two solder samples resulted from the dissolution of Cu into the molten Pb-Sn solder. At the interface between the liquid solder and the bronze substrate, a scallop-type layer of Cu-Sn inter-metallic compound (Cu6Sn5) formed and grew. Some irregular pieces of Cu6Sn5 also formed within the bulk solder.
Abstract: The effects of sealing atmosphere, sealing temperature, and sealing time on the surface appearance, leakage rate, bonding strength, bending frequency, and height of glass along the pins were investigated for glass to Kovar sealing. The results indicated that sealing atmosphere had an important impact on the surface appearance, and the extent of glass spattering was more serious as increasing the oxidizability of sealing atmosphere. With the extending of sealing time or the increasing of sealing temperature, the bonding strength between single oxide film (single FeO or single Fe3O4) and glass gradually increased, and the bending frequency almost maintained. The bonding strength between hilayer oxide film (FeO + Fe3O4 or Fe3O4 + Fe2O3) and glass was relatively higher and increased more quickly, however the bending frequency sharply decreased. The height of glass along the pins was not related to the type of the oxide; it reduced gradually with increasing sealing temperature, and also decreased rapidly with increasing sealing time until 140μm. The recommended sealing conditions included that the sealing atmosphere was weak reductive gas, the sealing temperature was about 980℃ and the sealing time was between 20 and 30 min.
Abstract: The titanium alloy surface was polished in a recently self-developed electrolyte. The morphology of the polished alloy surface was characterized by optical microscopy (OM) and atomic force microscopy (AFM). The electrolyte was made of alcohol, lactic acid, perchloric acid and sodium perchlorate instead of those poisonous compositions such as hydrofluoric acid, methanol and chromate. The alloy surface was polished in the solutions containing perchloric acid of 5 96, 10% and 15% in volume fraction at different current densities of 20, 25 and 30 A·dm-2, respectively. The corrosion rate was estimated by using weight loss method. The thickness of the removed surface layer was dependent upon polishing time, current density and the concentration of perchloric acid. It was shown that the 5% perchloric acid and 20 A·dm2 current density were good to electropolishing of the titanium alloy.
Abstract: Nd12.3-xDyxFe79.7Nb0.8Zr0.8Cu0.4B6(x=0,0.5,1.5,2.5) prealloys were annealed for about 10h at high temperature (1 050℃). Then, the NdFeB single-phase alloys were smashed into fine grains and oriented in bonding materials to make them solidified. Magnetization curves in the direction of parallel(//c) and perpendicular(⊥ c) to the magnetic field were measured, and the intersection point of the two curves was considered as magnetic anisotropy. With increasing Dy content, the magnetic anisotropy of the aligned alloys increased distinctly. The maximum magnetic anisotropy was about 7 536 kA·m-1 obtained at a Dy atomic fraction of 2.5%; with every 1% increase of Dy addition, the anisotropy was elevated about 200——300 kA·m-1.
Abstract: A perovskite-type composite oxide Ba1.0Co0.7Fe0.2Nb0.1O3-δ(BCFN) was successfully synthesized by solid state reaction with BaCO3, Co3O4, Fe2O3 and Nb2O5 powders as raw materials. The synthetical process and morphology of BCFN fine particles were studied by non-isothermal thermogravimetry and differential scanning calorimetry (DSC), X-ray diffraction analysis, and scanning electron microscope. The results show that during the synthesis process, BaCO3、BaFeO2.9 and BasNb4O15 phases firstly appeared, and after 10 h sintering at 1473 K, a cubic perovskite-type oxide Ba1.0Co0.7Fe0.2Nb0.1O3-δ was synthesized. The overall reaction process is considered involving two stages. The first stage is addition reaction between BaCO3 and CO3O4, Fe2O3, Nb2O5 particles and the second is solid solution reaction between BaCoO3 and BaFeO2.9, Ba5Nb4O15 phases formed in the first stage. Oxygen escaping was observed during the second stage.
Abstract: Magnetic coal-based activated carbons (MCAC) were prepared from Datong bituminous coal in the presence of different amounts of Fe3O4. Their pore structures were characterized by N2 adsorption isotherm, and their iodine value, methylene blue value and magnetic properties were determined. The results show that Fe3O4 in the raw material is of importance to mesopores formation, and the ratio of mesopore volume reaches up to 76.0% when the mass fraction of Fe3O4 in the raw material is 10%. The iodine value decreases by 25.5% and the methylene blue value increases by 79.9% for the activated carbon with 7% Fe3O4 compared with common activated carbon without additives. A proper amount of Fe3O4 in the raw material makes it possible to grant the activated carbon with a higher magnetism and a bigger magnetoconductivity:MCACs derived from the raw materials containing 4% Fe3O4 and 7% Fe3O4 possess the magnetizations greater than common activated carbon by 24.4 times and 44.5 times, respectively.
Abstract: Magnetic earboxymethyl chitosan (MCMCS) nanoadsorbent was prepared for adsorption of palladium and platinum. Chitosan was first carboxymethylated and then grafted on the surface of Fe3O4 nanoparticles through carbodiimide activation. The results showed that MCMCS had the diameter of about 20 nm, the mass content of Fe3O4 of 36%, and the saturation magnetization of 25.74 × 10-3 A· m2·g-1. The main adsorption mechanism was the electrostatic attraction of protonated amine groups and Pd(Pt)-Cl anionic complexes at pH 2. The saturated adsorption capacity was 3.2 mmol· g-1 for Pd and 2.7 mmol·g-1 for Pt, respectively. The competition adsorption between Pd and Pt was observed, Pd and Pt competed for the same adsorption active sites, and the affinity of MCMCS for Pd was greater than that for Pt. The desorption efficiency of more than 68% for both Pd and Pt was achieved using 0.5 mol·L-1 thiourea as eluant, while the highest selectivity was observed with 5 mol· L-1 ammonia.
Abstract: Polymer dispersed liquid crystal (PDLC) films were prepared from photo-polymerization of a p-allyloxycholesterolbenzoate (ACB)/2-hydroxyethyl methacrylate (HEMA)/liquid crystal (LC)/photoinitiator (IRG-651)/glass spacer (SP-220) mixture by ultraviolet (UV) irradiation. It was found that the contrast ratio of PDLC films was remarkable increased with the addition of ACB although ACB did not participate in polymerization. Under the condition that the UV irradiance (365.0 nm) was 15.0 mW· cm-2, the curing temperature was 303.2 K, and the UV irradiation time was 10.0 min. When the mass fractions of ACB/HEMA/LC/IRG-651/SP-220 were 6.2%/18.5%/74.0%/0.3%/1.0%, the PDLC films with high contrast ratio and better electro-optical properties were obtained.
Abstract: For the problem of strip deformation during tension leveling, a mathematical model was proposed based on the plate bending theory. The Mises yielding criterion, elastic perfect-plastic material, plane strain assumption and the assumption of cross section keeping a plane were used during modeling. Limitations, which appear in previous similar research based on the beam bending theory, did not exist in the proposed model. By the proposed model, stress and strain in the thickness direction could be calculated, and strip deformation during tension leveling could be characterized more accurately. Calculation results of an example show that that the proposed model based on the plate bending theory agree with fact much better than the model based on the beam bending theory.
Abstract: The mechanism of heat conduction in polyfoam-fly ash thermal insulation materials (FP) was studied with a finite element software ANSYS. The numerical simulation results of heat conductivity are agreeable with the measured ones, indicating that the finite element method can be applied to numerical simulation of heat conduction in FP materials. Based on the results of analysis, some measures were proposed for design and preparation of thermal insulation materials.
Abstract: The common LMS (least mean square) adaptive filtering algorithm is difficult to harmonize three performance indices, i.e. initial convergent speed, time-varying track ability, and constringent precision, while modeling the system. In order to solve this problem a region-varying and step size-varying LMS algorithm was put forward, and its algorithmic astringency was proved by the Lyapunoy Function. It is shown that the algorithm gives attention to the three performance indices above and can be applied to modeling the system and the inverse system in a field of control.
Abstract: A measure of local community structure was defined, and an mining algorithm of local community structure based on the minimal increment of link degree of a community was presented for resolving the time complexity problems of finding local community structure in complex networks. The algorithm ran in time O (kd) for general graphs, where d is the mean degree and k is the number of vertices to be explored. In order to determine its performance and calculation precision, the algorithm was compared with the classical local community identification approach, Clauset algorithm. Experimental results show that mining results of the algorithm are as effective as those of Clauset algorithm on the whole, and the algorithm is much faster than Clauset algorithm.
Abstract: A weighted fuzzy clustering algorithm based on the neighbor potential function for wireless sensor networks is proposed to solve clustering problems in the case of network topology stability in the metallurgical industry. The potential function of neighbor nodes is used to optimize the network clustering, which enhances the load balance factor and ensures cluster heads being well scattered. Simulation experiments illustrate that compared with LEACH, the proposed algorithm is able to significantly prolong the networks lifetime by 93.6%.
Abstract: Considering the theories of matter-element and vague set, a model of matter-element decision making under vague environment was proposed. The definition of vague sets was introduced and the compound vague matter-element was defined. The positive-ideal solution and negative-ideal solution of scheme matter-element were established by an improved order function of vague values. According to the similarity measure of vague values, the distances between scheme matter-element and ideal matter-element were calculated, and the best scheme could be selected by the rule of closeness degree. A numerical example is given to apply the proposed method, and the result shows that the proposed method is available for vague and uncertain decision making problems.
Abstract: An extension application of plant management information systems was studied with the help of mobile equipment. PDA (personal digital assistant) was applied in plant management, the architecture of plant management information systems was opened up, the business process was improved in plant time-check, checking of maintenance spare part storage and intendance of maintenance, and the data traffic between PDA and PC was achieved. Application results of an example show that using PDA in plant management can effectively expand the application range of plant management information systems.
Abstract: Lacking of flexibility was found in previous logistics information systems, and using the technology of web services a practical design workflow and modeling method was proposed based on a thoroughly research and analysis of the service-oriented architecture (SOA) theory. It was discussed to implement the "order treatments" workflow on the flat of a cross-language and cross-operation system by combination, arrangement and coordination of business process execution language (BPEL). Web services based on SOA for a local logistics information system and for a heterogeneous platform were realized. Because of SOA, the logistics information system is easily browsed on every business platform. SOA accelerates the application developing process and also permits a un-programmer to create and reuse information technology resources.
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
