Abstract: Through statistical analysis of random experiments, there is a function of porosity 3lnφ-2ln(1-φ) that approximately follows a normal distribution. In the test particle size range of 30 to 180 ram, the expectation and variance of this function value increase with an increase in grain size of rock blocks. On the basis of deriving the subsidence hypersurface equation of a basic roof, a continuous inhomogeneous distribution model and a random inhomogeneous distribution model of porosity in the combustion space area (CSA) are deduced. For a rectangular coal fire space, the porosity in the shallow and edge side of CSA is large, but in the middle region is small. In the x-y plane, the porosity contour appears a side lying U-shaped distribution, and the porosity presents negative exponent attenuation with an increase in distance entering CSA along the x axis. In addition, the overall trend of the porosity of continuous distribution and random distribution is the same, but the difference is that the porosity described by the random distribution model has a certain stochastic volatility. The random distribution model of porosity has been used in a numerical simulation of the temperature field in a fire zone, and the accuracy of simulation and the applicability of this porosity model are verified by infrared temperature measurements.
Abstract: The psychology and physiology of miners would be damaged if they continue to stay in uncomfortable environments for long time. When waiting for rescue in emergency refuge facilities, numerous factors can affect comfortable feelings of miners. In this paper, four crucial factors, including oxygen concentration, carbon dioxide concentration, temperature and relative humidity, were selected as the study objects. Adopting the grading method, a series of human live experiments were performed to obtain vote data under both a single and multiple environmental variables. The functional relation between human comfort degree and environmental variables were got by statistically analyzing these vote data. A mathematical model was proposed to predict the human comfort degree of miners in refuge confined space. The allowable ranges of oxygen level, carbon dioxide level, temperature and relative humidity along with their controlling principles were discussed in the end.
Abstract: Kriging interpolation is a widely used low-pass filter interpolation method, but it cannot reconstruct the high-frequency, low-frequency and partial information of original information. Fractal interpolation using self-similarity, which can retain original information, overcomes the limitations of Kriging interpolation low-pass filters, thereby improving the interpolation accuracy. On the basis of the traditional fractal interpolation algorithm and in combination with geological spatial information, this paper introduces a four-dimensional space fractal interpolation algorithm suitable for ore grade estimation. The interpolation algorithm is applied to molybdenum ore grade estimation and then compared with the Kriging interpolation algorithm. The results show that the interpolation algorithm is superior to the Kriging interpolation algorithm.
Abstract: To explore the characteristics of the effect of ore particle size on the capillary flow of solution in an ore heap, solution capillary rise experiments of two groups of ore particles, mono-size and non-uniform, were performed with an established capillary rise experimental device. The relationship of solution capillary rise height with time and the corresponding fitting equations were obtained. The regularity of solution rise velocity with time was analyzed. It is found that at the beginning of the experiment, the ore heap solution rises quickly; with the increase of time, the solution rise velocity decreases and eventually drops to zero; the maximum solution rise height and velocity have negative correlation with ore particle size. Immobile solution content inside the ore heap formed by capillary action increases with the decreasing of average particle size, and a wide range area of immobile solution will form when the content of fine particles in the ore heap is too much, which can influence the solution seepage of the ore heap.
Abstract: As a deoxidizer for steelmaking,Al has a problem of oxidation loss when it is added into liquid steel,which leads to a lower utilization rate of Al. At the same time,the high melting point and irregular shape of the deoxidization products make it difficult to remove Al2O3 inclusions from molten steel effectively,which causes nuzzle clogging and steel quality deteriorative. A new kind of complex deoxidizer which takes Al as the effective deoxidization component and a low melting point slag including Al2O3-SiO2-MgO-CaO as the carrier was investigated to improve the deoxidization utilization rate of Al and make the deoxidization products eliminate quickly from molten steel. Experiment results showed that the complex deoxidizer not only guaranteed the dissolved oxygen content in molten steel below 10×10-6,but also made the deoxidization inclusions fewer and smaller. Compared with Al deoxidization,the purity of steel was significantly improved and an excellent deoxidization effect was presented.
Abstract: In order to eliminate the hazard effects of the leaching of fluorine in mold fluxes,this paper introduces a mold flux with high Al2O3 content. The effects of Al2O3 content on the concentration of F- ions and the pH value of leaching water were investigated,and the dependence of Al2O3 on the structure of mold fluxes was analyzed by X-ray photoelectron spectroscopy(XPS). When the mass fraction of Al2O3 is 4%,the concentration of F- ions in leaching water is about 22.8 to 35.4 mg·L-1,and the pH range is between 4.0 and 9.5. The F- concentration and the pH range initially reduces and then slightly rises again as the Al2O3 content increases from 4% to 34%. The XPS spectra show that the Al-F bond forms in the mold flux when the Al2O3 content increases. This can restrain the dissolution of fluorine in water. Controlling the content of Al2O3 between 16% and 34%,the F- concentration in leaching water is about 4.0 to 10.0 mg·L-1,and the pH range is between 6.5 and 7.5. This is helpful to reduce the hazard effects of the leaching of fluorine in mold fluxes.
Abstract: Dialysis was utilized to separate gelatin whose relative molecular mass is over 3500 from a simulated copper electrolyte,and the concentration of separated gelatin was determined with a bicinchoninic acid(BCA) method. The impact of H2SO4 concentration and temperature on gelatin degradation was investigated. It was found that Cu2+ hardly affected the stability of gelatin. Increases in electrolyte temperature and H2SO4 concentration exacerbated gelatin degradation. For constant temperature,when the H2SO4 concentration increased by 15 g·L-1 in the range of 150 to 180 g·L-1,the reaction rate constant of gelatin degradation enlarged by 1.2 times. For constant H2SO4 concentration,raising the temperature by 5℃ in the range of 55 to 70℃ increased the reaction rate constant of gelatin degradation by 1.5 times. For copper electrolysis production,when the concentration of H2SO4 in the copper electrolyte was 150 to 180 g·L-1and the temperature was 60 to 65℃,it could be estimated that the residence time of the electrolyte in the electrolytic cell was 3 to 4 h and the gelatin degradation rate in the electrolyte reached to 50% to 80%. A complete cycle of the electrolyte in the copper electrolysis system took about 6 h,and at this moment the gelatin degradation rate in the electrolyte reached to 70% to 90%.
Abstract: In view of serious shortcomings existing in a traditional secondary lead pyrometallurgical process such as high smelting temperature,large energy consumption and low concentration of SO2 fume together with lead vapor pollution,a low-temperature alkaline and sulfur-fixing smelting process of secondary lead was proposed in this work based on a thermodynamic analysis of the NaOHC-PbSO4-ZnO low-temperature alkaline system. The effects of NaOH amount,smelting temperature,coke amount and ZnO addition on the alkaline and sulfur-fixing smelting of spent lead-acid battery colloid sludge(hereinafter referred to as colloid sludge) which was used as the test material were investigated by single factor experiments. The optimum conditions were determined as follows:m(NaO H)/m(colloid sludge)=60%,temperature 860℃,m(coke)/m(colloid sludge)=10%,and m(ZnO)=m(theoretic). Under these above-mentioned optimum conditions,the average direct recovery ratio of lead was 99.09%,the average grade of crude lead was 98.86%,and the average sulfur-fixing rate for ZnO was 93.37%. XRD spectra indicated that sulfur contained in the material was mainly fixed in the solid residue in the form of zinc sulfide,most of NaO H was converted into Na2CO3,and no SO2 emission existed in the smelting process.
Abstract: Continuous cooling transformation curves were established and the influence of finish rolling temperature on the microstructure was investigated for a titanium-microalloyed dual phase steel through simulation experiment. A feasible process based on simulation experiment was obtained and confirmatory experiment was performed. It was found that pro-eutectoid ferrite could form in the steel when the cooling rate was less than 5℃·s-1 at a temperature of 625 to 725℃. The amount of ferrite and martensite increased firstly and then decreased slightly with the increasing of finishing rolling temperature. A higher hardness of ferrite was obtained at a higher finish rolling temperature because of precipitation strengthening. Better performance with a tensile strength of 672 MPa and a yield ratio of 0.61 was obtained for the steel when the finish rolling and slow cooling temperatures were 840℃ and 700℃,respectively. The amount of this precipitation strengthening was about 78.5 MPa based on calculations.
Abstract: The microstructures and mechanical properties of a modified 310 austenitic stainless steel during isothermal aging at 700℃ were investigated by using scanning electron microscopy(SEM) and transmission electron microscopy(TEM),tensile testing at ambient temperature and 700℃,and micro-hardness testing. It was found that massive block(Cr,Fe,Mo)23C6,(Cr,Fe)23C6 carbides,σ-phase and a small quantity of χ-phase formed on grain boundaries and within grains in the tested steel after aging at 700℃ for 1000 h. Precipitates significantly strengthened the mechanical properties of the tested steel at room temperature. The strength increased and the hardness raised by 20 Hv,while the elongation still remained above 30%. However,at high temperature,the effect of precipitation strengthening was weakened,and the ductility slightly decreased. Fracture surface and cross-sectional microstructural analysis after tensile testing showed that the high temperature tensile fracture mode after aging for 1000 h was ductile fracture; neither cracks nor holes were observed; but the room temperature tensile fracture was brittle,and there were some cracks and holes in σ-phase near the fracture. Finally,from the ductile-brittle transition of σ-phase and the difference in strength between room temperature and 700℃,this article discussed the reason for crack and hole forming in the stretching process at room temperature as well as the different effects of aging on the mechanical properties at room temperature and high temperature.
Hot corrosion behaviors of DZ466 alloy at 850℃ and 950℃ were investigated by using a NaCl/Na2SO4salt-deposit method. It is found that there are three corrosion layers on the alloy. The outer and the middle layers consist of(Ni,Co) O oxide and(Ni,Co) Cr2O4 with a spinel structure,respectively. The innermost layer is an inner corrosion layer,which consists of Ni3S2 at 850℃,and the internal oxidation Al2O3 can be produced close to the middle layer at 950℃. The same hot corrosion mechanism is shown at 850℃ and 950℃. The destruction of the oxidation film continuity is a key reason for hot corrosion of the alloy. The hot corrosion weight gain curves obey a parabolic law at the two temperatures,the rate constants are 3.1×10-11g2·cm-4·s-1 and 1.5 × 10-9g2·cm-4·s-1,and the hot corrosion activation energies are 179.2 and 138.3 kJ ·mol-1at 850℃ and 950℃,respectively.
Abstract: The creep fracture behavior of a[011] oriented single crystal nickel base superalloy was investigated in the temperature range of 750 to 980℃ and the stress scope of 200 to 680 MPa. The fracture surfaces and longitudinal sections of crept specimens were examined by scanning electron microscopy(SEM). It is found that under different initial stresses at 750℃ and 870℃,creep cracks seem always to initiate at the γ'/γ interface on the interdendritic sub-boundary and propagate along the sub-boundary trace,and their cleavage planes expand along〈110〉and〈100〉on the(011) plane. But under different stresses at 980℃,creep cracks initiate at inherent casting pores and slowly propagate perpendicular to the axis of stress applied up to the final fast fracture. After observing the longitudinal sections of specimens crept under different stresses at 750℃ and 870℃,it is feasible for the area fraction of irregularγ' phase in the sub-boundary to characterize the creep damage level before collapsing of the superalloy along the[011]direction at the moderated and low temperatures.
Abstract: Oxide dispersion strengthening(ODS) copper has the characteristics of both high strength and high conductivity. The porosity is an important factor influencing the electrical conductivity. 0.9Al2O3/Cu powder was compacted by a high velocity compaction(HVC) technique. The influence of impact velocity on the green density of Al2O3 dispersion strengthening copper was studied,and the green density of 8.46 g·cm-3 was got at the impact velocity of 9.4 m·s-1. The dependence of the electrical conductivity on sintering temperature was investigated. The results from sintering steps showed that the higher the sintering temperature was,the higher the electrical conductivity was at the same green density level. Fracture surface and SEM observations indicated that the samples were inadequately sintered at the sintering temperature of 950℃,with particle boundaries and some pores being visible obviously. When the sintering temperature rose up to 1080℃,the pores tended to spheroidize,the particle boundaries disappeared,and the dimples appeared on the fracture surface,showing a typical plastic fracture characteristic. The electrical conductivity of the sintered compacts was measured to be 71.3% IACS.
Abstract: Carbon fiber carrying Fe0(PCF-ZVI) was prepared by the electrodeposition method. The carbon fiber carrying Fe0 was characterized by scanning electron microscope/energy dispersive spectroscopy(SEM/EDS) and X-ray diffraction(XRD),and its performance was investigated to apply in chromium(VI) removal. It was shown that the carbon fiber carrying Fe0 had good effect on chromium(VI) removal in aqueous solutions. The removal efficiency could be up to 99.96% at the Fe0/C mass ratio of 2:1,the Fe0 dosage of 2 g·L-1,the initial Cr(VI) concentration of 20 mg·L-1,pH 5,and the reaction time of 40 min. The reaction process was fitted by the pseudo first order reduction kinetics model. The relationship between the rate of reduction and the reaction temperature accorded with the Arrhenius law,and the reaction activation energy was 20.683 kJ ·mol-1.
Abstract: Basic glass with stable properties was prepared from molten blast furnace slag by using the melting method. The heat treatment regime of glass-ceramics was determined by differential thermal analysis of the basic glass. Optimum heat treatment parameters were selected and the crystal growth pattern of glass-ceramics was analyzed by X-ray diffraction and scanning electron microscopy.The results show that the optimum heat treatment parameters of glass-ceramics are the nucleation temperature of 850℃ for 1.5 h and the crystallization temperature of 935℃ for 1 h. The crystallization grows from the surface to interior gradually. The mechanical properties of the prepared glass-ceramics,such as bending strength,acid and alkali resistance,and hardness,are better than those of ordinary marble.
Abstract: The technological characteristics of a top gas recycling-oxygen blast furnace determine that in comparison with a traditional blast furnace the combustion condition of pulverized coal in the raceway has great changes. A mathematical model of pulverized coal flow and combustion in the blowpipe-tuyere-raceway bottom is developed in this paper. The influences of entry modes,oxygen enrichment,recycling gas temperature,H2O and CO2 contents on the burnout of pulverized coal are investigated by this model. The results indicate that an entry mode with the premixing of recycling gas and oxygen is obviously better than two other modes with recycling gas and oxygen entering alone. When the oxygen content changes from 80% to 90% the coal burnout increases from 87.525% to 93.402%. The effect of recycling gas temperature is not significant. The maximum gas temperature along the tuyere axis decreases by 124 K with the increasing of H2O content in the recycling gas by 5%,and it drops by 113 K for CO2.
Abstract: Wall thickness uniformity is an important quality criterion of railway hollow shafts by multi-wedge synchrostep cross wedge rolling. The stable rolling condition of railway hollow shafts in this rolling process is analyzed,and a flattening instability criterion is presented. Based on this result,a rigid-plastic finite element model of hollow railway shafts by multi-wedge synchrostep rolling is established with DEFORM-3D software,the influence of processing parameters such as broadening angle and forming angle on the wall thickness uniformity is discussed,and the change law of wall thickness is obtained by changing these processing parameters. The bigger the forming angle,the more uniform the wall thickness is; the bigger the spreading angle,the more uniform the wall thickness is,but when the spreading angle is more than 10°,the wall thickness uniformity will decrease. A 1:5 ratio high-speed railway hollow shaft is rolled based on multi-wedge synchrostep cross wedge rolling experiment. Rolling torque measurements and wall thickness comparisons between experimental and simulated results show that the relative error is controlled within 10%,which verifies the validity of this finite element model.
Abstract: A new approach of dimensional synthesis is introduced for Watt-I six-bar rigid-body guidance mechanisms. Through establishing the mechanism solution-region,this approach can get all feasible solutions for the finite separated four-position problem of the rigid-body in the end. This paper firstly gives the solution-curve formula and recommends the methods of solution-curve mapping and forming plane solution-region. After that,a circle and branch defects decision is proposed for this type of mechanism. Through this defect decision,the feasible region of no-defect mechanism solutions is acquired,which makes a designer be able to get much better mechanisms that meet much more design requirements,avoid the blindness of selecting mechanisms and improve the design efficiency. Finally,the synthesis process of the approach presented in this paper is illustrated through a synthesis example,which proves the practicability and effectiveness of this approach.
Abstract: This paper presents a novel fast neighbor searching method. By using this method,fluid simulation based on smooth particle hydrodynamics(SPH) can be parallelized easily and run on graphic processing unit(GPU) with high efficiency. The neighbor searching method can search two or more kinds of particles,while saving their information in the same background grid. Ghost boundary particles are introduced to improve the accuracy of boundaries,which can enhance the fidelity of the fluid simulation. Experiments show that the proposed method is more efficient than the traditional SPH method based on GPU.
Abstract: A class of fractional-order hyperchaotic system is introduced and its basic dynamical properties are investigated by means of theoretical analysis and numerical simulation. Systemic sensitivity to the orders of all involved derivatives is analyzed by stud-ying the Lyapunov exponent spectrum and bifurcation diagram. The class of fractional-order system presents hyperchaos, chaos, and periodic behaviors when the fractional orders vary continuously. Based on synchronization of the fractional-order hyperchaotic system and the theory of spread spectrum communication, we propose a new scheme for general spread spectrum communication. In contrast to PN code in the traditional CDMA communication, the scheme uses the chaotic signal sequence as a spread spectrum address code of direct sequence spread spectrum communication. Then, a circuit of spread spectrum communication based on the fractional-order hy-perchaotic system is designed. The validity and feasibility of this scheme are certificated in Multsim platform.
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
