Abstract: An microscopical experimental method was brought out to study the flow law and flow rules of gas-liquid-sold complex flow in condensate reservoirs with wax deposition. Real porous media were modeled by the phantom micro-model with similar pore structure. The experiments were carried out in porous media at high temperature and high pressure to observe the forming, distribution and flow rules of gas-liquid-sold complex flow. The results show the adsorption and migration laws of wax deposition, three-phase flow pattern, phase change and distribution characteristics of porous media. It is difficult to accumulate for the condensate in big pores. The flow mode of the condensate includes mainly eight styles:schlepping by gas, pulse flow, crawling along pore wall, interface flow, plug flow, rivulet flow, continuous flow, and little liquid droplets assembling with bigger liquid droplets and liquid flow. The results also indicate that wax deposition adsorbs at pore surfaces. Some is from gas phase and adsorbs on the surfaces of porous media with sheet, the other is from liquid phase with flock and affects the flow. Pore structures are affected by solid wax precipitation. The smaller the pore structure, the more the wax adsorption, and the resistance of the gas-liquid-solid flow increases.
Abstract: The support vector method was applied to classify rock quality, and the indexes often used in engineering such as rock quality designation, integrity coefficient, uniaxial saturated compressive strength, and friction factor of structural planes were adopted as discriminant parameters. The radial basis kernel function was selected to train samples, the optimized model parameters were determined by cross-validation, and a model of rock quality ranks was established. In comparison with the existing multi-classification model based on support vector machine constructed by a one-against-all method, the multi-classification model constructed by the pairwise method proposed in this paper may obviously reduce the indivisible region, that is, extraordinarily improves the model accuracy. Applications of this model to engineering show that the result of this model agrees with that of engineering that the classification method of rock quality ranks is effective.
Abstract: The problem of fuzzy multi-objective ore blending was put forward. According to the linguistic preference information of managers and the satisfaction degree of decision makers, a fuzzy multi-objective optimum algorithm was designed to effectively deal with ore blending optimization. The algorithm was modified from optimum and importance models, and had the characteristics of effectiveness, flexibility, and sensitivity, which were verified by different ore blending needs of a certain mine.
Abstract: A fuzzy comprehensive evaluation method for evaluating the foundation stability of new buildings above work-out areas was proposed on the basis of the theory of fuzzy mathematics. A lot of factors that influence foundation stability were analyzed, and the evaluation elements were determined. A method for determining the subjection degree of primary factors was presented. The analytic hierarchy process was used to determine a judgment matrix, which distributes weight coefficients for every factor rationally. Based on the proposed method, a fuzzy comprehensive evaluation model was constructed, and the corresponding relation between the evaluation indexes and the level of foundation stability was obtained. The method was verified with three examples.
Abstract: At present there is no design standard in designing large steel SCR (selective catalytic reduction) reactors. According to numerical analysis on the structure of a steel SCR reactor, the stress and deformation as well as weak position of whole construction are obtained. The results derived from geometric linear analysis and geometric nonlinear analysis are compared. According to the results, the data based on geometric linear analysis are conservative, and the stress distribution is more homogeneous when large deformation is considered. It turns out that the rational design of the reactor structure has a surplus to meet the needs of safety and the use function of the reactor.
Abstract: To study the rheological properties of filling slurry, using the principle of hydrodynamics, a gravity flow test through a L-shaped pipe was carried out and the mechanical properties of slurry flow in the pipe was analyzed. The results indicated that the flow resistance and filling rate were depended on slurry concentration, flow rate and pipe diameter, among which slurry concentration was the predominant influencing factor. Under the condition of reasonable filling rates at which the gravity flow of slurry can be achieved, after determining the flow rate and pipe diameter based on filling ability, the slurry concentration can be adjusted in the filling station to obtain excellent results in transportation, sedimentation, anti-eduction, dehydration and drainage, concretion and mechanical properties.
Abstract: The treatment of coking wastewater was researched by ultrasonic wave. The influences of irradiation time, ultrasonic power, initial pH value of coking wastewater, initial concentrations of chemical oxygen demand (CODCr) and ammonium (NH4+), and dissolved gas on the removal of CODCr and NH4+ were investigated systematically. The ultrasonic treatments of coking wastewater combined with oxidants were comparatively analyzed. The results show that the ultrasonic treatment combined with H2O2 or Fenton reagent had a synergetic effect, and then the removal rates of CODCr, and NH4+ greatly increase. The order of removal rate is the following:ultrasonic treatment + Fenton 〉 ultrasonic treatment + H2O2 〉 Fenton 〉 ultrasonic treatment 〉 H2O2. According to the analysis results of GC-MS, the removal process of CODCr and NH4+ was preliminary studied. It is found that the proportions of non-biodegradation organisms, such as naphthalene, anthracene and quinoline, obviously decreased in treated coking wastewater.
Abstract: The thermodynamic analysis and experiments of inclusions formation in a Ti-Al-O system in molten steel at 1 873 K were investigated. The results show that in the Ti-Al-O system the equilibrium between Al and O can be obtained instantly and the content of[O] is determined by the amount of Al. The formation of composite inclusions in the Ti-Al-O system depends on aTi/aAl values. According to thermodynamic data, the stable section in the phase diagram of composite inclusions (Al2O3-Ti3O5-Ti2O3) in the Ti-Al-O system was calculated. The composition of inclusions changes from Al2O3 to Ti3O5 as the aTi/aAl value increases. When the molten steel contains high amount of[O], it is very easy to form Ti3O5 inclusions. The experimental results agree well with thermodynamic data.
Abstract: According to the laws of simultaneous equilibria and mass conservation, the logarithm concentration-pH diagram of a Ca-Mo-P-H2O system, the logarithm eoncentration-pH diagrams of total calcium and total molybdenum at different total phosphate concentrations, and the stabile area of calcium molybdate at 25℃ were obtained on the basis of thermodynamic data. The results show that the stabile areas of H2MoO4(s), CaMoO4(s), Ca5(OH) (PO4)3(s) and Ca(OH)2(s) are distinguished orderly with increasing pH values at a constant total phosphate concentration. Calcium molybdate can be easily decomposed since the stabile area of calcium molybdate shrinks or even disappears with increasing total phosphate concentration; at the same time, the total molybdenum concentration increases, and the total calcium concentration decreases. However, high phosphate concentration is unnecessary for calcium molybdate can be decomposed at a very low phosphate concentration. Compared to carbonate, phosphate is more propitious to the decomposition of calcium molybdate.
Abstract: Based on the fact that the formation of sodium aluminium hydrosilicates can be avoided on the experimental condition of high liquid-to-solid ratio (20:1), the secondary reaction process is divided into two sections according to the characteristics of dynamic process during clinker-leaching. One of the two processes, namely, the process of SiO2 dissolving into sodium aluminate solution was detailedly researched. Through processing all data with a fitting kinetic model, the corresponding kinetic equation was deduced. The results demonstrate that the process has an apparent activation energy of 24.86 kJ· mol-1, which serves as an indication that corresponding reactions of this process can easily happen. Since the effect of Al2O3 mass concentration in sodium aluminate solution is more than those of Na2CO3 mass concentration and NaOH mass concentration greatly, it can be considered that the reaction between calcium silicate in clinker and NaAl(OH)4 is the main reason to result in SiO2 entering into sodium aluminate solution.
Abstract: Cr12 ferritic stainless steels with different amounts of cerium were obtained, their high temperature oxidation resistance was tested according to the standard HB 5258-2000, oxidation phenomena and products phase analysis were studied by SEM and XRD, and thermodynamic calculations of the formation of oxidation products were carried out. Experimental results show that the oxidation analysis results consist with the thermodynamic calculation ones. The primary oxidation product is M3O4 type spinel oxide at lower temperatures of 600℃, 700℃ and 800℃, which has good protective capability, and this protective film can be accelerated by adding cerium. As the result, the oxidation rate can be decreased at these temperatures. At 900℃, the primary oxidation product is M2O3 type oxide, which has poor protective capability, and cerium-containing steels with refined grain size are oxidized faster at the beginning. Whereas cerium can improve the adherence between oxide and substrate, prevents materials from being further quick oxidized in the later period. The oxidation mechanism was well explained by reactive element effect and grain size effect.
Abstract: The corrosion behavior of D32 steel for offshore platforms was studied at the splash zone with polarization curves and electric impedance spectroscopy (EIS). Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were employed to analyze the corrosion rusts. Because of different microstructures, components and cover degrees of the corrosion rusts, the samples at the immersion zone corroded a little more seriously than those at the seawater, whereas the samples at the splash zone corroded much more seriously than those at the immersion zone. It was due to the rust layer and calcium magnesium layer formed on the surface of the steel that the Warburg impedance appeared in the Nyquist figure at the immersion zone and splash zone of Qingdao and Chengdao seawater.
Abstract: The microstructure of X100 pipeline steel produced by steckel mill was observed by SEM and TEM. Electron backscattered diffraction (EBSD) was employed to investigate the relationship between effective grain size and low-temperature toughness. The size distribution and strengthening effect of precipitation in X100 pipeline steel were quantitatively analyzed through physicochemical phase analysis technology. The results show that the microstructure of X100 pipeline steel mainly consists of granular bainite with plenty of M/A islands dispersing in the matrix or on grain boundaries. The effective grain size of X100 pipeline steel is refined to about 2μm. The refinement of effective grains and the reduction of microstructure orientation are two effective ways to improve the low-temperature toughness. The average size of precipitation particles in X100 pipeline steel is refined to 45.4 nm. Since the total mass fraction of precipitation particles is about 0. 062%, the strengthen effect of precipitation is only about 52 MPa, which does not contribute much to the yield strength.
Abstract: Simulation was made using CFD software Fluent to calculate the flow field of aluminum alloy melt sonicated in a crucible. The results showed that large-scale Eckart acoustic streaming formed in the liquid phase zone under the radiator's face, driven by radiation force which formed as a result of acoustic pressure gradient due to viscous attenuation. The maximum axial velocity appeared around the centre of the liquid phase zone in the axial line of the radiator's face, and it did not increase linearly with the driving force increasing. Experiment results showed that a borderline in the area from the radiator's face to the boundary of the ingot formed by acoustic streaming. The solidification structure of one side of the borderline was absolutely different from the other's. The structures of the side under the radiator's face were all well refined by the duple action of cavitation and acoustic streaming, while the other side's were coarse and dendritic.
Abstract: The effects of running conditions such as operating temperature, heat exchange quality between bars and ambient, and current capacity on the conductivity of copper cladding aluminum (CCA) flat bars were analyzed by a numerical analysis method. The results show that the rate of power loss increasing is smaller than that of direct current resistance increasing due to operating temperature rising. When the sectional configuration of cladding layers is the same, the mean current density which CCA fiat bars can carry decreases with the sectional area increasing. CCA flat bars can replace copper fiat bars when their direct current resistance is the same. This saves copper resource and reduces cost, at the same time the carrying capacity of bars increases. The power loss and operating temperature of CCA flat bars are lower than those of copper fiat bars.
Taking glass-coated Fe69Co10Si8B13 alloy microwires as an example, the dependences of sizes, microstructure and mechanical properties of microwires on drawing speed and cooling condition were analyzed, and the tensile fracture mechanism of the microwires under different cooling conditions was discussed. The results show that, with the drawing speed increasing from 5 m· min-1 to 400 m· min-1, the diameters of microwires and core-wires decrease from 95.2 μm and 22.7 μm to 14.5 μm and 7.2 μm respectively, and the tensile strength of core-wire increases from 1305 MPa to 5 842 MPa. As the cooling distance is less than 20 mm, the sizes and mechanical properties of microwires decrease drastically with the cooling distance increasing, but the influences of cooling distance on them are not obvious as the distance exceeding 20 mm. As water cooling is applied and the drawing speed exceeds 5 m· min-1, all the core-wires are amorphous. Applying air cooling, the drawing speed should exceed 20 m· min-1 to obtain amorphous core-wires. The core-wires exhibit brittle fracture mode accompanied by uneven plastic flow and the brittle tendency increases with the cooling distance increasing.
Abstract: Twisted nematic (TN) liquid crystal display mode cells doped with single-walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT) were prepared. The effects of SWNT and MWNT on the driving voltage, contrast ratio and response time of TN liquid crystal display mode cells were investigated with a liquid crystal display parameters tester. It was found that the addition of SWNT and MWNT remarkably decreased the driving voltage and decreased the contrast ratio significantly. The fieldon response time (ton) and field-off response time (toff) of TN liquid crystal display mode cells doped with SWNT were higher than those of pure TN liquid crystal display mode cells. For TN liquid crystal display mode cells doped with MWNT, toff was reduced, but the variation of ton had no obvious rules.
Abstract: Due to the characteristic of high tension during cold rolling and the transverse flow in cold rolling different from hot rolling, the Shohet criterion, which is universally used in hot rolling, is not applicable to cold rolling. The formation mechanism of cold rolled strip shapes under high tension was analyzed and a method to calculate the allowable variation of strips' transverse profile was proposed for cold rolling based on the buckling criterion. The allowable variation of transverse profiles of product strips and the required transverse profile range of incoming strips can be calculated by using the method. This method has been successfully applied in a domestic tandem cold mill and the transverse profile range of incoming strips suggested is more practicable and complete than before.
Abstract: In order to reduce the deviation of online forecast for gap, an online calculation model of roll vertical stiffness called the fast calculation model of roll bounce was established on the base of the influence function method. This model does not need complicated experiment for compensation. Its calculation accuracy as well as calculation speed was improved. With the data from a 1580 hot tandem rolling system in Rizhao Rolling Mill, off-line calculations were done to analyze the influence of strip width on the roll vertical stiffness, and the results were compared with the ones by using traditional width compensation models. It takes 20 ms to calculate in every condition with the proposed model and the precision is improved, indicating that the model can be used online in a rolling mill.
Abstract: In order to solve the poor load capacity of oil film bearings during the start-up process of tandem cold rolling mills, based on the hydrostatic bearing theory, a load bearing capacity model for oil film was established. The influences of screw-down tilting, hydraulic pump power and restrictor's hydraulic resistance on the hydrostatic pressure bearing-spindle system were calculated. The results show screw-down tilting is the basic reason of the problem. When there is an obliquity between the shaft sleeve and bush which is caused by screw-down tilting, the load capacity of the bearing drops suddenly. Minimizing the obliquity between the shaft sleeve and bush is essential to keep the kelmet working constantly. The results of calculation have already served as the guidance to make relative measures and achieved good effect.
Abstract: An incompressible laminar flow in a semi-infinite porous channel with expanding or contracting wails is considered. Following the self-similarity transformation, the Navier-Stokes equations are reduced to a fourth-order non-linear differential equation. The resulting equation is then solved asymptotically for large suction Reynolds number. The influences of expansion rate and Reynolds number on the fluid are obtained. When the wall contracts, the boundary layer becomes thinner; and when the wall expands, the boundary layer becomes thicker. It appears that flow reversal begins when the ratio of expansion rate to suction Reynolds number exceeds 1.
Abstract: In order to reduce the possibility of fire hazards in oxygen-enriched atmosphere, the burning rate of thin materials such as filter paper, cotton fabric and Dacron khaki in low barometric pressure and oxygen-enriched atmosphere was studied experimentally. The results show that the burning rate increases significantly with increasing altitude when the partial pressure of oxygen is constant. It is indicated that fire hazards will be caused in high altitude if the oxygen partial pressure is increased up to the oxygen partial pressure under the condition of the standard atmospheric pressure. The maximum safe concentration for oxygen-enrichment in high altitude was obtained from the analysis of experiment results.
Abstract: The absolute stability of multi-functional Lurie indirect control systems with multiple operators and unbounded coefficients was studied. The systems were regarded as large-scale systems. Based on the decomposition technique, the considered systems were partitioned into some isolated subsystems. By making use of the Lyapunov functions of subsystems, the Lyapunov function of Lurie indirect control systems was constructed, and some stability criteria of Lurie indirect control systems were contained. The results were also extended into large-scale indirect control Lurie systems with multiple operators and unbounded coefficients.
Abstract: The performance of routing protocols was studied in vehicular Ad hoc networks (VANETs) based on the Manhattan mobility model. Integrated with the AODV routing protocol, an analytical model was proposed, which was able to quantificationally measure the route breaking rate and routing overhead of VANETs. It is indicated by the analytical model that classic routing protocols in mobile Ad hoc networks can cause serious declination in the performance of VANETs; therefore, a direction based AODV routing protocol (DBAP) was proposed. The vehicle's moving direction was used in DBAP as its auxiliary parameter in routing discovery process, which remarkably improved the routing stability. Simulations show the validity of this model and prove DBAP's lower route breaking rate and routing overhead as well as its significantly improved performance in VENETs in comparison with AODV in urban vehicular environment.
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
