Abstract: A hybrid cluster analysis method based on genetic algorithm (GA) and fuzzy C-means (FCM) algorithm is introduced for the automatic identification of joint sets. The initial cluster centers for FCM are obtained by GA, and then the optimal cluster results can be calculated by FCM on the basis of the work in the first stage. This method eliminates the local optimality disadvantage of FCM and the subjectivity of traditional methods such as pole and contour plots for classifying joints into sets and resolves the conflict between search speed and cluster precision by general GA. The analysis steps, parameters selection, cluster validity and dominant direction determination for identification of joints sets using the hybrid cluster analysis method are discussed based on joint survey data sets.
Abstract: The process of ultra-fine grinding gold concentrate with stirring mills was studied. The effect of main operations on ultra-fine grinding parameters was tested. The results show that the gold concentrate of -20 μm more than 99% can be acquired by optimizing all the parameters in grinding process.
Abstract: A method for preparation of mesoporous composite materials was investigated which is the combination of destructive pore-making technique and organic composite method. The final product made by the method possesses excellent absorbent property for both small inorganic molecules and big organic molecules in polluted water, and it is also a kind of bactericide. By the acid etching technique, many impurities in matrix materials were removed and pore canals were etched. The moisture absorption rate of the semifinished product for 24 h is 2 times as large as that of the raw material, and the adsorption amount for dye is 1.6 times.
Abstract: Based on the Mohr-Coulomb failure criteria, the yield functions were deduced under the passive earth pressure condition. By using of the in-situ test data and assisted by FLAC2D, the numerical analysis of an unstable soil slope located at the No.205 national highway was carried out. The results show that the increment of elastic area and the decrement of lateral displacement in the soil slope after cement-grouting are notable, also the strain-sheared area and the volume strain area tend to dissipation.
Abstract: By analyzing the bottle-neck of desulphurization reacton, a kinetic model applied in refining desurlfurization process was developed based on two kind of calculating reactive modes: both durative contact mode and temporary contact mode. The results show that this model is in good agreement with the experimental data.
Abstract: The three-dimensional flow field, the temperature distribution and the dimensionless inclusion concentration in a T-shape tundish were studied by SIMPLE method. The influences of particles diameter, inner structure of the tundish and the depth of liquid steel on the ratio of removed inclusion particles were discussed. The results indicate that inclusions can be removed easily from liquid steel with double dam and weir in T-shape tundishes.
Abstract: The surface temperature and shell thickness of continuous casts slab were obtained by modeling heat transfer during solidification process. A mathematical model of strain at solid/liquid interface was set up. The strain in the solidifying shell under normal and abnormal operation conditions was gained. The results indicate that strain is small under normal operation conditions and internal cracks never happen. But when the variation of roll gap is above 2 mm, the strain caused is greater than caused by bulging. The total strain exceeds the critical one and internal cracks will appear. It is of great importance to maintain the fine state of continuous casting machine to avoid the appearance of internal cracks.
Abstract: Based on the behavior of filling pressure during semisolid alloy slurry filling process, a mathematic model of slurry flow coupled with apparent viscosity was established. The filling process and filling pressure of thixotropic Al alloys and steel were simulated. It is demonstrated that the filling pressure gradually increases with the course of the filling, in response to flow resistance and gravity and with a range of 0.12 MPa. Semisolid alloy slurry flows in a stable and laminar-type manner within the range of filling velocity. Compared with thixotropic Al alloys, the high melting point of steel leads to the decrease of filling temperature easily, so the increase of apparent viscosity results in casting defects. The simulation results of filling pressure and the experimental results of semisolid brake pump casting show that semisolid casting filled along the radial presents good forming quality.
Abstract: The intermediate transformation microstructure of low-carbon bainite steel was analyzed, which had been deformed in the non-recrystallization temperature range, relaxed for a period of time and cooled by various cooling rates. The influence of relaxation process and cooling rate on the intermediate transformation structure type and microstructure refinement was revealed. The results show that in a slowly cooled sample after relaxation the transformation structure is mainly granular bainite and the effect of relaxation refinement is not marked. But while the cooling rate is fast enough (>10 ℃/s): the main microstructure is lath-like bainite, and relaxation effect can be seen clearly. After relaxation, the lath of bainitic ferrite is more fine and sharp, the morphology of M/A constituent is film-like. Comparing with the non-relaxed sample, it is clearly seen that the relaxation of deformed austenite benefits to obtain ultra-fine lath-like bainite structure. At the same cooling rate, the amount of M/A constituent decreases in the relaxed sample.
Abstract: The influence of 0.21% Al (mass fraction) on the kinetics of austenite decomposition in microalloyed steel containing 0.05%C-1.7%Mn-0.4%Si-0.05%Nb-0.03%Ti was studied. The results show that the hardenability of the experimental steel increases apparently by adding 0.21% Al when the cooling rate is in the range of 1~30 ℃/s. For isothermal treated plates at 600 ℃ for 20 min after rolling process, the banding microstructure of the plates containing 0.21% Al is abated or avoided and the overall mechanical properties of the plates is promoted greatly.
Abstract: By using a thermal-simulator Gleeble 1500, CCT curves of an EAF-CSP low carbon Mn-containing steel, which had been deformed in austenite region twice, were determined. The effect of accelerated cooling conditions on the microstructure and mechanical properties of the steel was studied. The steel contains 0.17% C, 1.21% Mn and 0.28% Si (mass fraction): it was found that the Ar3 temperature is lowed by increasing the cooling rate and results in the further grain refinement. The mixture of bainite and ferrite appears while the cooling rate reaches 20 ℃/s and over. The ratio of yield to strength could be decreased by increasing the fraction of bainite. Banding structure of ferrite/pearlite exists in the steel with finishing rolling temperature 790 ℃ and coiling at 550 ℃. Accelerating the cooling rate is an effective way to avoid band structure.
Abstract: A micro-crystalline aluminide coating of 100μm thick was obtained by vibratile electro-pulse deposition on Cr5Mo steel. An Fe-Al intermetallic compound layer forms due to high temperature during instant discharging between alumimum electrodes and specimens, micro-crystalline structure is achieved due to the high cooling rate during deposition, and the coating bonds with the substrate firmly. The experimential results of oxidation in air for 200h at 600 ℃ and sulfuration in flowing 99.98%SO2 for 50h at 600 ℃ and the analysis of SEM and XRD show that the high temperature oxidation and sulfuration resistances of Cr5Mo steel with aluminide coating are greatly improved.
Abstract: The effect of different residual element contents of tin and antimony and rare earth element lanthanum on the impact toughness of 34CrNi3Mo steel with low oxygen and sulfur contents was investigated with JB-30B impact test machine. SEM and EDS were used to study lanthanum effect on the fracture mode of the steel with different tin and antimony contents and the rare earth inclusions. The results show that rare earth metal lanthanum may decrease remarkably the harm of residual elements on the toughness of the steel and combine with residual elements in the steel to form La-Sb intermetallic compound and a little amount of La-Sn intermetallic compound, presenting orderly distribution.
Abstract: The effects of Heat Isostatic Pressing (HIP) sintering on the density, microstructure and magnetic properties of Nd-Fe-B permanent magnets were studied. The results show that compared to conventional magnets, the magnetic properties of HIP sintered ones decrease due to the deterioration of alignment of Nd2Fe14B grains and the lower density of the magnets, which resulted from the existence of more holes in the HIP sintered magnets. It is concluded that HIP sintering is not suitable for producing high performance sintered Nd-Fe-B magnets.
Abstract: A manufacture method of anisotropic NdFeB magnet powders was investigated from sintered bulk magnets by hydrogen decrepitation (HD process): it is found that HD temperature plays a very important role affecting the coercivity of the obtained magnetic powders evidently. This temperature determines the fracture way of bulk magnets during HD process as well. In intergranular fracture way through properly controlled HD temperature, at 220 ℃ for instance, anisotropic magnet powders with a coercivity up to 490 kA/m are obtained after a following annealing treatment at 950 ℃.
Abstract: By means of TGA, SEM (EDX) and XRD, the high temperature corrosion behavior of Ni-Cr-Co base superalloy was studied at 750 ℃ and 775 ℃ in air with water vapor. The results indicate that the kinetic curve of the alloy oxidized at 750 ℃ for 2480 h in air with 10% water vapor obeys a parabolic law at the initial oxidation stage and then follows a linear law. The oxide scale mainly consists of Cr2O3 and the internal oxides, Al2O3 and TiO2, also precipitate in matrix. The protective oxide scale of the alloy oxidized at 775 ℃ for 432 h in air with 5% water vapor is composed of Cr2O3, TiO2 and CoCr2O4 and the internal oxides are Al2O3 and TiO2. The corrosion speed is quickened because of the presence of water vapor. The corrosion procedure is decided by the transmission of the elements through the oxide scale.
Abstract: The method of airflow ultrasonic spray thermochemical process was discussed, which can be used to produce nano-scaled amorphous WO3-CuO composite powders directly. The hot decomposition process and the conversion process from amorphous to micro-crystal of the powders were investigated by XRD, TEM and TG-DSC. The results show that it is feasible to industrially produce nano-scaled WO3-CuO composite powders on a large scale by means of airflow ultrasonic spray thermochemical process. The average particle size of WO3-CuO composite powders is less than 50 nm, and their shape is spherical.
Abstract: Al-1%Si segments with 5 mm in diameter were held at different temperatures for 12 h and quenched. The recrystallization mechanism of the material was investigated by contrasting recrystallization texture after different-temperature heat treatment. An optimal heat-treated process was proposed, by which the original tissue with orbicular crystals of the material can be transformed into single crystals with high extended rate and electrical conductivity.
Abstract: SiCp and binder were mixed together and SiCp preforms were prepared by warm pressing, thermal debinding and pre-sintering. The relations of the performances such as size variation, porosity and strength of the performs with process parameters were investigated. The microstructure of the performs was observed by SEM. The results show that SiCp preforms with suitable strength and porosity for preparing SiCp/Al composites can be obtained by controlling effectively the process parameters such as compaction, debinding and pre-sintering.
Abstract: A two-dimension steady temperature fluctuation mathematical model is studied. The solution of the model is proved to be existential, unique and steady. The temperature solution of the mathematical model shows an exponentially descendent and oscillatory pattern with respect to the crystal growth direction. It theoretically confirms that the horizontal melt convection condition accelerates temperature fluctuation and results in a large number of nuclei.
Abstract: By using Laplace inverse transformation method, a two-dimensional time-dependent partial differential equation for crystal growth is analyzed and the solution is obtained. The uniqueness of the solution is proved. An example is presented.
Abstract: Major influencing factors on the emissivity of coatings are analyzed microscopically and macroscopically respectively. A blackbody model was proposed. It is proved that the decrease of the particle size of coatings can increase the emissivity of the coatings both theoretically and practically.
Abstract: The radiative heat transfer of one-dimensional plane-parallel slabs under radiative equilibrium was investigated by Discrete Ordinate Method (DOM): The selection of angular quadrature schemes, which is very important to the accuracy and calculation time of DOM, was studied. The accuracy of the SN approximation quadrature scheme, Fiveland's angular quadrature scheme with equal weights FN and Gauss angular quadrature scheme GN was analyzed. It shows that the accuracy and computation time of DOM increases with the increase of the order of each quadrature scheme. The accuracy of DOM is different from each other for the three quadrature schemes with the same order and FN is the best one among them. As a conclusion, FN is recommended in DOM calculations.
Abstract: A weak feature signals identification method based on local projection and wavelet transform is introduced. Experiment indicates that the local projective algorithm can separate background signals and weak feature signals into different orthogonal sub-spaces. Wavelet transform is effective for noise reduction of sharp and break signals. The algorithm which combines the local projective and wavelet transform has an excellent effect on identifying weak feature signals in nonlinear time series.
Abstract: An artificial immune response model based on biological immune response mechanism was proposed, which is made up of four procedures: antigen matching, clone selection, mutation and affinity maturation. The diversity of antibodies, achieved by clone and mutation process, can make the built system possess self-adaptive capability. Knowledge acquisition results from affinity maturation. The model needs few operating parameters and is easy to stable. When applied to data analysis the model has fascinating ability to enhance data compression ratio and data recognition ratio.
Abstract: The regression parameters estimation exprssions of a random-fuzzy linear regression model are deduced. It is proved that they are an unbiased estimator. The formulae for calculating the numerical characteristics of regression parameters estimation and the correlation coefficients of the regression equation are derived. Based on the experimental data of triaxial compression tests, the calculated results are more realistic and reasonable compared with the linear regression method.
Abstract: Based on the principle of two-point measurement method, a measuring technique for thermal para-meters of living tissue by using three-point temperature measurements was proposed. The corresponding theoretical model was established. The effects of thermal conductivity blood perfusion and volumetric heat capacity on the temperature variation were analyzed through numerical calculations. The results of sensitivity analysis show that the sensitivity coefficients of these thermal parameters are linearly independent each other, and thereby can be measured simultaneously by using this three-point method.
Abstract: Based on the general objective of a developmental planning for teacher team, the management-by-objective system for optimizing teacher team is derived by mathematical method. A quantitative measurement to control teacher team structure next year is found according to the change every year. The corresponding policy is proposed so as to achieve the goal structure of teacher team gradually.
Abstract: The forming process of technological innovation motives in enterprises is discussed as so to review economic factor, technological factor and social factor, which control the forming, the continuing and the recycling of the motives, and the influencing mechanism of the factors. It is considered that the inherent motivity of technological innovation depends on the most profit and the absolute competition advantage in meeting the social needs. Other factors such as environmental factor constraint factor in resources and competitive factor also play important roles.
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
