Abstract: The formula of cumulative weight percentage at different particle sizes, which was in the case of composite particle size distribution, was proposed. Based on analyzing the theoretical model of ultrasonic attenuation, the formula was integrated into the ultrasonic attenuation model, and the relation of ultrasonic attenuation to pulp density and particle size was derived. The correlation between ultrasonic attenuation and particle size distribution was given by combining experiments with data analysis, and an inverse parameters optimization method, genetic algorithm, was applied for particle size distribution. The result of inversely calculation shows that its precision is higher.
Abstract: In order to improve the reliability of numerical simulation results, a new backward analysis method for mechanical parameters of slope rocks was developed based on orthogonal design, difference method and artificial neural network. According to orthogonal design, the value levels of the mechanical parameters were chosen, and simulation schemes were arranged; the related analytical samples for neural network were given by FLAC2D calculations; RBF neural network was trained; the physical and mechanical parameters of an open pit slope were analyzed backwards by well-trained RBF neural network and surveyed data about spot displacements. The error between the backward analysis results and the theoretical ones is much little and meets the demand of precision, which indicates that this backward analysis method is feasible and accurate.
Abstract: Four heterotrophic microbes were separated from deep sea floor sediment of the Pacific Ocean. The dissimilatory reduction principles of these heterotrophic microbes were explored after their acclimatization to acid and metals. The results indicate that anaerobic leaching is better than aerobic condition, the optimum pH range is 2.5 to 3, the leaching time is 3 d, and the leaching rate is up to 98%. It shows that dissimilatory reduction of marine nodules with heterotrophic microbes has such advantages as higher leaching rate, no ventilation, lower investment, easier operation and better environment. The solid and organic waste can be treated at the same time coupling valuable metal recovery.
Abstract: Under the laboratorial condition, the kinetic study on reaction of reducing V2O5 by carbon saturated molten iron was carried on using CaO-SiO2-Al2O3-MgO-V2O5 as the base slag. Base on the investigation of the influence of different factors on the reduction rate and degree of the reaction, the reducing reaction mechanism was studied, and the apparent rate constant was calculated under different conditions. The experimental results show that the conditions of high temperature, proper slag basicity, large weight ratio between liquid iron and slag and high initial V2O5 content can make the reducing reaction fast and obtain high reduction degree. Before reaching the balance, the reaction shows as apparent first class reaction. The apparent activation energy is 23.21 kJ· mol-1, which indicates that the limit step of the reaction is the diffusion of V in liquid iron.
Abstract: The microstructure and γ' phase distribution of FGH95 P/M superalloy under different hot extrusions and heat treatments were investigated. OM, SEM and TEM were employed to study the microstructure after heat treatment and γ' phase's dark field images after aging treatment. Tensile properties at room temperature (20℃) and high temperature (650℃) were tested. The microstructure of instant fracture appearance at high temperature was also analyzed. The results show that under the same heat treatment the higher HIP temperature is, the larger γ'phase size during aging treatment is. Heat treatment processing can change the distribution of γ' phase, and salt cooling can increase the total number of γ' phase with middle size and markedly improve the high-temperature plasticity.
Abstract: The oxidation behavior of kovar alloy (Fe-29Ni-17Co) was studied in N2/H2O atmosphere under simulated field condition by weighing method. The weight gain curves of kovar alloy oxidized at 1000℃ in N2 with different dew points were tested, and the results show that these oxidation kinetics obey parabolic rule. The composition and pattern of the oxides were analyzed by XRD and SEM. Thermodynamical calculations reveal that if kovar alloy is oxidized in N2/H2O atmosphere under simulated field condition, external air will infiltrate into the furnace, which increases the partial pressure of oxygen, and the presence of α-Fe2O3 in oxides surface is unavoidable. In the condition of a higher dew point and a longer oxidation time, the quantity of α-Fe2O3 formed will exceed that of Fe3O4.
Abstract: A new Cu80Ni13Fe7 alloy was obtained and rolled into thin tape with a thickness of 0.2 mm successfully. The machining property proved to be better than the conventional Cu60Ni20Fe20 alloy. The elfects of tempering temperature and time on the magnetic properties of the alloy were studied. Better magnetic property of the alloy could be got only under proper tempering condition. After tempered at 635℃ for 1 h, the coercivity Hc, the remnant induction Br and the squareness S of the alloy reached 54.2 kA·m-1, 0.19 T and 0.79, respectively. Magnetic measurements showed that the difference of coercivity between parallel and perpendicular to the rolling direction for the alloy tempered at 635℃ for 1 h, is more significant than those under other tempering conditions. The results indicate that the alloy is a candidate for magnetic scales.
Abstract: Iron-based sulfides self-lubricating alloys with different contents of molybdenum were prepared with a medium-frequency induction furnace. The evolution of molybdenum sulfide in these alloys was studied by scanning electron microscope and X-ray diffractometer. The results showed that only FeS formed in the alloy and Mo presented as Fe3Mo2 with a Mo mass fraction of 1.5%. When the mass fraction of Mo was 6.5%, no MoS2 formed, and Mo still presented as Fe3Mo2. When the mass fraction of Mo was 11%, only a small quantity of MoSx could form and great majority of Mo and Fe formed the compound Fe3Mo2. MoSx formed remarkably when the mass fraction of Mo was up to 19.5%. It is difficult for molybdenum sulfides to be formed with Mo mass fractions less than 10%. Annealing treatment is favorable for MoSx formation, but no pure MoSx was found in the above alloys. MoSx is a metastable phase formed through the decomposition of Fe-Mo-S compounds. V, Nb and Ti, which are used to decrease grain size in the alloys, are disadvantageous for the formation of molybdenum sulfides due to their strong bonding force to sulfur. Aluminum used as deoxidant should be added in a small amount.
Abstract: A PVDF2801-based porous polymer electrolyte membrane doped TiO2 micron-particles for lithium ion batteries was prepared. The physical and electrochemical properties of this electrolyte were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), AC impedance method and charge/discharge test. The results indicate that the ionic conductivity of the polymer electrolyte doped 6.5%-TiO2 micron-particles is 1.66×10-3 S· cm-1 at room temperature and the extended intensity is 2.78 MPa. In the battery used the above electrolyte, the discharge capacity of the LiCoO2 is 140.6 mAh· g-1 at 28mA·g-1, and 99.17mAh·g-1 at 280mA·g-1.
Abstract: The average intracranial pressure (ICP) of parietal position for adults is normally about 3.62 kPa. The brain appears to be mild injury as the ICP variation is about 2.5 kPa, moderate injury as the ICP variation is about 3.5 kPa, and severe injury as the ICP variation is about or more than 5 kPa. This paper analyzed the stress and strain on the exterior surface of human skull and the composite structure composed by skull and duramater with the finite-element software MSC-PATRAN/NASTRAN. The experiments were carried out on the strains of porcine skull slices, porcine and human coronal skulls to simulate the actual situation in the human craniocerebra. The results show that the strains of mild injury, moderate injury and severe injury are 1.5×10-6, 2.5×10-6 and 4.0×10-6 respectively. It indicates that the strains on the exterior surface of skull are measurable and all within the range of instrument test. The minitraumatic method to measure ICP is feasible by pasting strain foils on the exterior surface of skull, by which ICP variation can be obtained through the corresponding operation to the strain of skull. Compared with the clinical methods of punching in the skull or puncturing in the spine cord, the strain-electrometric method is safe, simple, minitraumatic, accurate and feasible.
Abstract: To study the lateral movement of pipe strings connected by screwed joints and spherical joints in deep sea, this paper built the models of the pipe strings and made comparison of their horizontal displacements. Under the four-level oceanic condition, the transiently dynamic and kinetic analyses of the pipe strings were carried out by finite element method and virtual prototype technology. The results show that the maximum lateral displacement of pipe strings connected by screwed joints is 2.1 m, and the maximum moment in this system is 8 400 N· m. While the maximum lateral displacement of pipe strings connected by spherical joints is 6.0 m, the moment in this system is zero, and the pipe strings can be considered as flexible pipes which can bear large axial force. Since the lateral movement of buffer periodically changes with time and its period is much longer than that of the waves, materials with better wearability are more suitable for spherical joint-connected pipe strings.
Abstract: The section deflection of an H-beam is not considered in the traditional straightening theory, so it is difficult to get desired straightening effect. A finite element model of one straightening unit was established with ANSYS, the straightening process was simulated and the section deflection of the H-beam was studied. The results show that the section deflection of the H-beam in straightening process should not be neglected, in which web falling plays a dominating role. The main factors which influence web falling include straightening force, gap between roller outside and beam inner side and roller-outside-corner radius, and the varying regulation of web falling is quadratics of the relevant factors. At last, a regressive formula of web falling was presented. In order to obtain an ideal straightening effect, the actual bending deflection should be the sum of the theoretical bending deflection and the web falling.
Abstract: To set up the critical tension model of buckling and find the effective technologic measures to prevent the buckling, the effect and acting mechanism of seven major factors, roll profile, strip shape, strip width, transverse distribution of temperature, weld position, friction on the roll, and total tension, on the transverse distribution of tensile stress in a continuous annealing furnace were simulated by using the finite element method of geometrical nonlinear buckling calculation and the theory of elastic-plastic buckling in the field of stamping. The simulation results show that roll profile and thickness of the strip are the two most remarkable factors influenced on the transverse distribution of tension stress. The relationships between buckling and transverse distribution of tensile stress are revealed, and a valuable technologic measure was provided to control the "heat buckling" and proved to be well effective online.
Abstract: The calculation formulas of general curvature radius and tooth face contact stress of the unsymmetric gear with double pressure angles were proposed at the upper and lower points of single and double teeth mesh areas and the pitch point. The given parameters were calculated by analytic method. Parametric design programs of the total tooth models of unsymmetric and symmetric involute gears were developed by Autolisp language, and the total models were transferred into ANSYS and calculated by finite element method. Compared with the standard involute gear, the two methods showed that the unsymmetric involute gear could efficiently improve the tooth face contact strength. Considering the time-variant mesh stiffness and curvature radius of mesh points, the change of tooth face contact stress in one engagement period was demonstrated.
Abstract: A robust mathematical design model based on the response surface method was established for steering trapezoid mechanism. In the model, movement precision during steering course was chosen as the objective function; kingpins distance, axles distance, trapezoid mechanism's bottom angle and steering arm length were defined as the design variables; minimum transmission angle and maximum angle error were considered as the restraint condition. Steering mechanism of a truck was optimum designed by adopting the method of Monte Carlo optimization design with distribution parameters. The results of fixed optimization design and Monte Carlo optimization design were compared. It is shown that the minimum transmitted angle derived from the Monte Carlo optimization design method is larger and the system has well transmitted performance and steering performance while the difference of steering error is small, furthermore movement precision is assured when design variables are little varied.
Abstract: In robust optimization mechanical design, uncertainty variables are often assumed to be stochastic variables complying with special distribution and these uncertainty variables' original data are discarded, in the succedent optimization design model. That method cannot often reflect these uncertain variables' essence, consequently a far-from-fact conclusion is obtained. In order to describe these uncertain variables actually, the uncertain variables in mechanical design were expressed in blind number and the relation between variables was expressed in the operation rule of blind number. Combining the blind number theory and the robust design method, a robust optimization design model was built. Using this model in optimization design of an air driving reversing device, the result is better than that from traditional robust design. The method based on blind number is a kind of discrete numerical calculation method, and the example unfurls its flexible fully and proves that this optimization method is reasonable and practicable.
Abstract: Using Lennard-Jones pair potential, the thermal conductivity of nitrogen in a cubic pore of 20 nm in length was calculated by equilibrium molecular dynamics (MD) simulation at 300 K and 0.1 MPa. The distributions of velocity component and speed of molecules calculated by the simulation and the Maxwell distribution equation fit very well. The mean free path of the molecules was strictly confined by the wall size of the nanoscale pore. The thermal conductivity of nitrogen in the nanoscale pore was determined by the Green-Kubo method and separately compared with the experimental and theoretic data in the literatures. The simulation result is close to the experimental one and only about one third of the value in the free space under the same conductions.
Abstract: Based on the research of ear recognition with independent component analysis (ICA), a new compound structure classifier (CSCER) ear recognition model was proposed. The model made rough classification to the human ears first according to their geometric features, then ICA was used to extract the algebra features and support vector machine (SVM) was for detailed classification, finally the results were achieved, which was in accordance with human natural recognition process. The model overcame the single ICA disadvantages of costing too much time and with too many features, also avoided losing structure feature when ear images were preprocessed. The experiment shows that the model can achieve high recognition rate and is suitable for complex ear image libraries.
Abstract: Traditional key word filtering technology meets people's common need, but the flexibility and effect is too limited to recognize or filter the transformed key words. Semantic elements were applied to net monitor and a new key word filter method was proposed. This method could recognize and filter the transformed key words effectively. The filter time was O(L) rather than general O(LN), where L was the length of text and N was the size of Keyword-base. It means this algorithm costs constant time even if N is hundreds of thousands or millions. It is very practical in net monitor and information filter.
Abstract: A multi-agent-based grid service discovery framework was put forward, in which agents were distinguished into three categories:service-agent, request-agent and service-discovery-agent. A service description language based on fuzzy Petri nets (FPN-SDL) was proposed as a specification to publish or request for a service, it used possibility transition to represent a service or request, input places and output places to denote conditions before and after performing the service respectively, and possibility and necessity to quantify the confidence levels that the service could satisfy a request. At last this paper presented a semantic-based service matchmaking that can find an appropriate service for a request and support partial matching, and illuminated these through an example of the vehicle maintenance service system.
Abstract: An area-first design method for multifunctional and reconfigurable large number calculators was brought forward. Based on the addition algorithm, the design was optimized by the method of scan chain control and iterative invoke and realized 14 kinds of large-number operations such as addition, subtraction, multiplication, division, module addition, module multiplication, module exponential, etc. Every operation supported the data length from 8 bits to 2 048 bits, which afforded security chip users' maneuverability, and reduced the time and cost of coding remarkably. Under the speed restriction of architecture, operations reused the same logic units as possible and the design just contained 13 887 gats, which could meet the requirement of area-first design completely.
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
