Abstract: Taking Laohutai Coal Mine in Fushun of northeastern China as an engineering background,an application study of strong mining-induced seismicity prediction was carried out on the basis of the load/unload response ratio(LURR) theory.It is shown that when the load/unload response magnitude adopts the mining-induced seismicity of 0 ≤ ML ≤ 0.5,the forecasting efficacy is very good in all mining depths and the average forecasting reliability of the staged peak magnitude is 0.72.When ML ≥ 1.4,the response magnitude is direct proportion to mining depth,and is generally 0.5 to 1.0 lower than the predicted magnitude,while the average forecasting reliability of the staged peak magnitude is 0.60.When 0.6 ≤ ML<1.4,there might be a mixture of two mining-induced seismicities with different mechanisms,which is not suitable to the load/unload response magnitude due to its wide randomness.With the increase of mining depth,the in-situ stress intensity is higher,and the prediction is better.According to universal tests in Fuxin Coal Field and Mentougou Mine,the forecasting reliability is 0.8 and 0.73,respectively.The results indicate that the LURR theory and methods have a good ability and a broad application in predicting strong mining-induced seismicity.
Abstract: The spatial and temporal distributions of acoustic emission(AE) during the deformation of granite samples containing an inhomogeneous fault were studied under confinement using particle flow code software(PFC2D).The results show that with the enhance of confining pressure,failure peak loads of rock samples increase and the failure mode changes from instability to gradual failure.The time asynchrony between AE peak values and ultimate failure in rock samples was found.The former which occurs when the failure load decreases approximately to 90% of its peak value is much later than the latter.Before rock failure there is a relatively quiet period of AE.AE temporal sequence is significantly affected by confining pressure and the relatively quiet period of AE may extend with the confining pressure increase.It is found that the phenomena of strain energy is absorbed during the relatively quiet period of AE through strain energy tracking,validating that damage healing exists in the rock failure process.
Abstract: Leaching processes and sulfur speciation on the surface of pyrite leached by the moderate thermophiles of Sulfobacillus thermosulfidooxidans were investigated by scanning electron microscopy,X-ray diffraction and sulfur K-edge X-ray absorption near edge structure spectroscopy.The results show that Sulfobacillus thermosulfidooxidans can significantly improve the leaching of pyrite and the leaching rate is up to 5.3 g·L-1 after the process for 24 d.The surface of the mineral is obviously corrupted after leaching for 24 d with microbes and on the surface there are some visible crystalline floccules.Leaching products were found accumulating during the leaching process and the main composition is jarosite.The sulfur K-edge spectra indicates that the sulfur components are composed by pyrite and jarosite,whose mass fractions are 34.8% and 65.2%,respectively.
Abstract: The mechanism of action of nucleating agent was studied during the direct reduction of low grade hematite pellets in Central South China.The results show that the nucleating barrier is reduced by over 50% by adding a nucleating agent in the hematite pellets,which can effectively improve the nucleating of metal iron grains during the direct reduction.Because of the nucleating agent,the apparent activation energy of the hematite pellets decreases from 18.10 kJ·mol-1 to 10.15 kJ·mol-1,dropping by 43.92%.The lower the apparent activation energy,the easier the reduction reaction takes place.It is concluded that the nucleating agent can efficiently improve the direct reduction and upgrade the metallization degree of the reduced pellets.
Abstract: Vanadium-bearing titanomagnetite concentrates were reduced isothermally by adding pulverized coal and additives.Some factors which influence the metallization degree,such as reaction temperature,reaction time,C-to-Fe molar ratio and additives,were investigated.The enhanced reduction mechanism of additives was also discussed.The results show that reaction temperature,reaction time,C-to-Fe molar ratio and additives have great effect on the metallization degree.Under the condition of the reaction temperature of 1 200℃ and the reaction time of 120 min,the maximum metallization degree is 84.5% without any additive.Using Na2CO3 or CaF2 as an additive,the reduction of vanadium-bearing titanomagnetite concentrates can be promoted.With the addition of 3.0% Na2CO3 or CaF2,the metallization degree of vanadium-bearing titanomagnetite concentrates can reach up to 96.5% and 93.3% after the samples are heated at 1 200℃ for 120 min,respectively.
Abstract: Based on the coexistence theory of slag structure,a calculating model of action concentration was established for the slag system CaO-MnO-SiO2.The effects of basicity B and temperature on the action concentration of MnO,NMnO,were analyzed.The results show that the calculated values of NMnO are in good agreement with the measured activity values of aMnO,indicating that this calculating model can wholly embody the characteristics of the slag system.NMnO increases with the basicity when B<2.0,and reaches the maximum value when B is 2.0,then decreases with the basicity when B>2.0.In the range of low basicity,the influence of basicity on NMnO is more apparent.No obvious influence of temperature on NMnO was observed.
Abstract: The characteristics of subsurface hooks in continuous cast LCAK steel head slabs were investigated.The results show that the hook characteristics have significant correlations with each other,e.g.the mean hook length,thickness and depth increase with the rise of hook angle.The hook characteristics increase when the oscillation mark depth increases and the casting speed decreases.With the increase of casting length,the mean hook length,depth and thickness decrease,and when the casting length exceeds 7.9 m the hook characteristics remain stable.However the mold heat extraction has a reverse trend,thus with the increase of heat extraction the hooks become shorter.Finally a hook formation mechanism was proposed.It is suggested that meniscus freezing occurred during two stages,the late stage of the positive strip period and the earlier stage of the negative strip period.The mechanism could explain the phenomena that the hook root deviates from the valley of the oscillation mark,and then the main factors affecting hook characteristics were discussed.
Abstract: A secondary cooling control model based on effective-speed and effective-superheat was developed to solve the problem of the frequent fluctuations of casting speed and temperature,which can lead to great fluctuations of slab surface temperature under secondary cooling control.The new model can well control the surface temperature of slabs without on-line calculating the temperature values,while it only needs on-line calculating the values of effective-speed and effective-superheat by existing parameter control models.Computer simulation indicates that this control model has good adaptability to the variation of casting speed and superheat,meets the requirements of modern continuous casting production and can be operated simply and conveniently.
Abstract: Based on the composition of X70 pipeline steel produced in Shougang Group,the phase structure,the precipitation temperature of phases and the precipitation behaviour of Nb at different temperatures were analyzed by calculation with Thermo-Calc software.The effect rules of Nb and C contents on the precipitation behaviour of Nb were studied.The precipitation temperature of Nb in the steel was analyzed by thermal simulation and scanning electron microscopy(SEM).It is indicated that precipitation phases in the steel are the carbonitrides of Ti and Nb,alloying cementite,Ti4C2S2,MnS,AlN,M7C3 and Mo carbides.The Nb precipitation phase mainly consists of the elements of Nb and C,and in the Nb precipitation phase,Ti and N are dissolved.With increasing Nb and C contents,the precipitation temperature of the Nb alloy phase rises and the precipitated Nb content at the same temperature increases.
Abstract: Frictional wear behavior under the condition of friction coupling with deformation between a DC54 hot-dipped galvanized steel strip and a sliding block made of quench tempering DC53 cold-work die steel was studied on a self-made tester of friction coupling with deformation.Stress distributions along the thickness direction and the rubbing surface of the DC54 hot-dipped galvanized steel strip were calculated by a finite element method.The results showed plastic deformation was the key effect factor of frictional wear behavior under this test condition.With increasing load,friction between the strip and the sliding block increased and the wear got severer.
Abstract: The crack propagation of GH864 alloy with different solution temperatures and stabilization treatments was studied.The percentages of crack initiation period,propagation period and final fracture period in the whole fatigue failure process were calculated by analyzing the microstructure,fracture morphology and lga-lgNi/Nf,da/dN-a and da/dN-N curves.The influence of microstructural factors on the percentages of each period was analyzed.The result shows that with increasing solution temperature,the grain size of GH864 alloy enlarges,the crack growth rate decreases,meanwhile the percentage of crack initiation period decreases but the percentage of crack propagation period increases.With the time prolonging and the temperature rising in the stabilization process,the amount of carbides precipitated at grain boundaries increases,thereby the crack propagation rate decreases,but the percentage of crack initiation period is gradually increasing.
Abstract: Si3N4 particle-reinforced 316L stainless steel composites were prepared by powder injection molding(PIM) using water-soluble binders.It is shown that a water-soluble binder mainly consisting of polyoxymethylene(PEG),polyvinyl butyral(PVB) and stearic acid(SA) exhibits a better water-soluble degreasing performance.After degreasing injection parts in water for 6 h,the total binder removal rate is 55% and the PEG removal rate is 78.6%.The sintered composites have a uniform microstructure and excellent properties with a relative density of 95.2%,a hardness of HRB 79.8 and a tensile strength of 620 MPa.And the hardness and tensile strength are 5% and 20.4% higher than the Si3N4 particle-reinforced 316L stainless steel produced by PIM with a paraffin wax-based binder,respectively.
Abstract: MgAlON-bonded magnesia,magnesia-alumina spinel and corundum materials were prepared by reaction sintering.The influence of different major phases on the formation temperature of single MgAlON bonding phase and that of volume expansion caused by chemical reactions and the vapouring of oxides on the sintering of the materials were studied.The results show that athough the mixed powders used to form MgAlON bonding phase have the same composition and the same amount,the temperatures at which single MgAlON bonding phase forms in MgAlON-bonded magnesia,magnesia-alumina spinel and corundum samples are different,and rise in turn.On the matter of MgAlON-bonded magnesia samples,the volume expands significantly and a big amount of MgO vapours during the sintering process,magnesia grains bond loosely with the matrix in the fired samples,and thus the samples have low bulk density and low compressive strength.For MgAlON-bonded corundum samples,the volume expands slightly and a small amount of oxides vapours during the sintering process,corundum grains bond tightly with the matrix in the fired samples,and therefore the samples have high bulk density and high compressive strength.As to MgAlON-bonded magnesia-alumina spinel samples,the volume expansion and the amount of oxides vapoured during the sintering process,the bonding between grains and the matrix in the fired samples,and the bulk density and compressive strength of the fired samples are all between those of the above two kinds of samples.
Abstract: The modification of multi-walled carbon nanotubes(MWCNTs) was carried out with a mixed acid of concentrated sulfuric acid and nitric acid at a volume ratio of 3:1.The morphology,specific surface area and surface functional groups of the resulting MWCNTs were analyzed by field emission scanning electron microscopy(FE-SEM),surface area analysis and X-ray photoelectron spectroscopy(XPS),respectively.The electrochemical properties of the MWCNTs were studied by cyclic voltammetry and galvanostatic charge-discharge tests.The results indicate that after oxidation by acid,the lengths of the MWCNTs are shortened,and the specific surface area is enlarged and the contents of surface nitrogen-and oxygen-containing functional groups increase.This leads to the enhancement of electrochemical properties of the MWCNTs,and the specific capacitance of MWCNTs can increase from 7 F·g-1 to 66 F·g-1.
Abstract: After surface cleaning,weld combining and vacuumizing to 1×10-3 Pa,Q345 continuous casting slabs were processed by conventional control rolling(CCR) and recrystallization control rolling(RCR).The mechanical properties of the clad rolling plates were tested by shear,tensile and cold bending tests,and the microstructures and combining boundaries were observed by scanning electron microscope(SEM).The results show that the mechanical properties of the clad rolling plates produced by the two rolling processes are all qualified.Compared with CCR process,RCR process provides a better bonding effect and the plate has better property homogeneity in the thickness direction.The clad rolling process in the experimental condition involves the mechanical meshing mechanism and the recrystallization mechanism.
Abstract: Thermal-mechanical coupled numerical simulation of GH4169 alloy during cross wedge rolling(CWR) was carried out using the finite element software DEFORM-3D.The metal flowing and temperature distribution of rolled pieces,and the rolling force and torque between the rolled piece and the roller were obtained and comparatively analyzed with 45# steel.The results show that the axial metal flowing of GH4169 during CWR is different from that of 45# steel,and the axial metal flowing at the surface substantially lags behind that at the center.All the energetic parameters are much greater than 45# steel's,and the maximum value is 2.15 times that of 45# steel.Meantime the deformation temperature is always higher than 45# steel's,and the maximum temperature rise is 6.21% more than that of 45# steel.
Abstract: After industrially tracing and testing the shifting positions of continuously variable crown(CVC) work rolls for a 2 250 mm hot strip production line,it was found that CVC work rolls always worked at the limit positions.The analysis showed that the quadratic crown control capability of the CVC work roll contour declined quadratically with decreasing strip width,leading to an insufficient crown control capability to narrow strip steel,and so did SmartCrown work rolls.A new advanced variable crown(AVC) work roll was proposed,whose quadratic crown and quartic crown vary linearly with roll shifting positions.With the quartic crown control capability increasing,the quadratic crown control capability varies slowly with strip width,indicating that the new contour can improve the crown control capability of a wide strip or super wide strip rolling mill for different strip widths.
Abstract: A path-scanning algorithm was proposed for processing functionally gradient materials(FGM).The algorithm first slices the functionally gradient materials and disperses each continuous material distribution layer to numbers of sub-regions with a uniform distribution material.After processing each sub-region separately,the process of FGM objects meeting the accuracy requirements was obtained.An actual example of path planning was presented and the algorithm's validity was verified.
Abstract: In gas separation by adsorption,the gas flow in an adsorber is virtually a variable mass flow.The velocity distribution in an adsorber was investigated by a two-dimensional model with consideration of radial porosity and mass variation caused by sorption.Four conclusions are drawn as follows.(1) Porous media themselves have a role in the gas distribution that they make the gas flow uniformly.But the adsorbent in the feed end is greatly affected by entrance effect,in this region the velocity is in a W-shaped distribution,and some parts of the region are in a fluidization state.(2) During the adsorption step there is a greater change in velocity located at the mass transfer zone,while in the other three steps the change in velocity is approximately linear along the bed.(3) During the depressurization step there is a higher velocity in the bed,which blasts the sorbent and causes the sorbent's attrition and pulverization,so it is better to control the rate of depressurization.(4) Mass variation has important effect on the pressure and velocity,so it can not be easily ignored.
Abstract: Suitable conditions for biodiesel synthesis by the transesterification of lipid were studied by using microalgal oil extracted from Chlorella USTB-01 cells as feedstock and bronsted acid ionic liquid([C4MIm]HSO4) as a catalyst.Gas chromatograph-mass spectrometry(GC-MS) was used to determine fatty acids in the microalgal oil and its derived biodiesel.The results indicate that breaking the algae cell wall by grinding can significantly improve the extraction yield of algal lipid using Soxhlet extraction method;among the solvents tested,petroleum ether is the best solvent for the extraction.The major components of Chlorella USTB-01 oil are fatty acids containing C16 and C18.The optimum conditions for synthesizing the microalgae biodiesel are as follows:the molar ratio of methanol to the microalgae oil is 9:1,the dosage of the catalyst accounts for 8% of the mass of the microalgae oil,the reaction temperature is 150℃ and the reaction time is 6 h.Under this condition,the yield of biodiesel can reach 64%.GC-MS analysis shows that biodiesel from Chlorella USTB-01 oil is mainly composed of methyl esters of saturated fatty acid(C16:0) and unsaturated fatty acid(C18:2).The product is feasible to supplement fossil diesel fuel.
Abstract: Most intrusion detection systems produce large amounts of alert information,which affect system management to some extent and lead to high misstatement rate,and thereby influence the intrusion detection.To solve this problem,a calculation method for alert credibility based on the peer correlation is proposed over P2P overlay networks,where peers need the association after receiving a series of intrusion alarm to integrate the alarm information and extract the effective alarm information.According to different associated objects,the peer correlation includes the alert correlation and the trust correlation.The effectiveness of intrusion alert information can be judged through the alert correlation,and the credibility of the peer producing the alarm can be measured through the trust correlation.A correlation algorithm is also given.Simulations show that the dual correlation algorithm can improve the accuracy of intrusion detection alerts.
Abstract: A simple bilinear stress-strain model of fiber-reinforced polymer(FRP) confined concrete was used to analyze the approximate cross-sectional ductility of undamaged circular columns strengthened with hybrid FRP under seismic loads.The effect of reinforcement corrosion on the sectional ductility was considered by the loss of rebar cross-sectional area,the reduction of rebar's mechanical properties and the degradation of interface bonding between rebar and concrete.Then,a simple analytical model was established to estimate the ductility of potential plastic hinge regions.Finally,a non-iterative displacement-based seismic design program for reinforced concrete corroded columns strengthened with hybrid FRP was presented on the basis of the simple analytical model.
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
