Abstract: According to discrete characteristics of deformation, an evolution model of deformation in mine rock-mass was built by using cellular automaton (CA). In order to measure the complex process of deformation in mine-rock body, the change probability of cellular rock and the influence coefficient were defined. Simulation tests were carried out and the experimental results were analyzed by use of R/S analysis. It is shown that discrete degree can be taken as the criterion of rock-mass stability.
Abstract: The strength weakening controlling mechanism of rock bursts in coal mines was put forward. The strength of coal and rock mass can be weakened through deep hole relieving shot, so the ability of energy accumulation is reduced, and a large amount of elastic energy accumulated in coal and rock mass is released, which makes it sure that the elastic energy accumulated in coal and rock mass do not exceed the minimum energy induced rock burst. Simultaneously, electromagnetic emission (EME) is used to check out the effect of eliminating or reducing the danger of rock bursts. The validity of this kind of control technology is fully proofed by the engineering practice of 9202 high-danger working face in Sanhejian Coal Mine and 6303 danger working face in Jining No. 3 Coal Mine in China.
Abstract: Dust and smoke were not efficiently reduced under mines by common water-stemming. Based on the analysis of the dust-reduction mechanism of water-stemming, the surface tension and humid capacity of different concentrations of solutions water-stemming were measured in the laboratory, and efficient water-stemming were developed. The results of explosive comparative tests under mines show that the dust density was efficiently reduced by the efficient water-stemming. It is worthy of being used widely, particularly for blasting mines.
Abstract: The water after final filtering at the sewage plant of Xibaipo Power Plant in Hebei Province, China was selected as original water. The effects of different ozonation technics used to deal with organic contamination were investigated. The results of captive testing and dynamic testing showed that, when UV and active carbon were used as synergetic catalyzer in ozonation process (in an OUC reactor), the effects of organic contaminations oxidation degradation were improved markedly, the same as the availability of ozone.
Abstract: An experimental study was made on the character of oxidized round spots in electrical steel in order to determine the forming procedure of surface defects. The results showed that nice oxidized round spots could form in hot rolling cracks of Q steel and W20 steel when the temperature is over 1170℃ and 1160℃ respectively using the thermal simulator Gleeble 1500. Oxidized round spots in casting blank cracks in a heater by simulator experiment were crassitude. Desilication of the casting blank cracks were more obvious than that of hot rolling cracks by energy spectrum analysis. There was great difference in pattern, layer thickness and adjacent desilication of oxidized round spots. Such discrepancy can be set as a reference to determine the formation procedure of defects in electrical steel.
Abstract: Based on the measured data of mould temperature and heat flux, a three-dimensional transient heat-transfer model was developed to simulate the temperature field of a round billet in continuous casting, and the solid fraction and shell thickness of the billet were calculated. The results agree with the measured data, which indicates that the real process conditions can be well reflected by the model. The effects of casting speed and pouring temperature on the shell thickness were discussed, and the comparison of the model with experiential formulas in calculating the shell thickness was also carried out.
Abstract: The effect of Ti-containing complex inclusions on the microstructure refinement of non-quenched and tempered steel was studied by using SEM and EDS. The room temperature tensile strength and absorbed-infracture energy of the tested steel were tested, and the fractography was observed. The results show that Ticontaining complex inclusions act as the nuclei for intra-granular ferrites and refine austenite grains, and with Ti added, the area proportion of ductile fracture is increased. The toughness of the studied steel is enhanced by about 50% while keeping the same strength level.
Abstract: In order to study the linking between metal magnetic memory signal of ferromagnetic materials and stress, based on wavelet analysis the metal magnetic memory signal was decomposed into two parties, i.e., the large-scale approach and the detail section. The correlation dimension of the detail section was calculated and the relation of the correlation dimension to stress was investigated. It is shown that with increasing stress the correlation dimension decreases.
Abstract: The slip stress acting on straight screw and edge dislocations in surface layer of pure aluminum was investigated based on the analysis of dislocation image force. The size of low dislocations' density area of the surface layer and the critical slip distance of the dislocations induced by image stress effects were calculated theoretically. The relationship between critical climb distance and temperature of straight edge dislocation was discussed. The relatively stable dislocation configuration around the surface layer was indicated.
Abstract: The effects of BN content on the thermal conductivity, hardness and microstructure of AlN-BN composite ceramics prepared by ceramic injection molding (CIM) and pressureless sintering, as well as the rheological characteristics of the mixtures were discussed. The results showed that the mixtures had good fluidity and low temperature dependence of viscosity, suitable for ceramic injection molding. It was found that the thermal conductivity, relative density and hardness of the ceramics decreased with increasing BN content, which was attributed to the low conductivity and hardness of BN self and its card house structure generated during the sintering that can delay the densification process of the composite ceramics. In view of the demand on the thermal conductivity and hardness, a better content of BN in AlN-BN composite ceramics is thought to be from 10% to 15%, at which, the thermal conductivity of the composite ceramics is more than 120 W·m-1·K-1, the hardness in HRA is less than 80, and the relative density is more than 90%.
Abstract: The oxidation behavior and mechanism of SiAlON materials at high temperature have been a hot issue in the field of materials. Studies on the oxidation of SiAlON materials in literatures were reviewed and the oxidation behaviors of monophase and mutiphase SiAlON materials were compared. The influencing factors and oxidation mechanism were also discussed. The problems existing in the oxidation of SiAlON materials were pointed out.
Abstract: Using KClO3 as inner oxidant, MnZn-ferrite powder was synthesized by a self-propagating high-temperature synthesis (SHS) process in normal air atmosphere. The properties of the powder were investigated by XRD, SEM and VSM. The effects of combustion synthesis parameters were also analyzed. The results show that, with the Fe value k=0.6 and the inner oxidant value m=0.43 the combustion velocity is 1.93 mm ·s-1, and the highest combustion temperature is 1593 K. The powder possesses good magnetic properties, σs=64.44A·m2·kg-1,σr=1.349 A·m2·kg-1, Hc=0.24 kA·m-1, and the mean particle diameter is 1.42 μm.
Abstract: A high amorphous content Fe-based amorphous coating was prepared by the activated combustion high-velocity air-fuel (AC-HVAF) spraying method. According to the thermodynamic transformation theory of amorphous alloys, the crystallization of the fractional crystallized amorphous alloy is the transformation of residual amorphous phase, and its transformation enthalpy should be proportional to the phase content of residual amorphous phase. The coating was crystallized by different heat treatment methods. The nanocrystal content in the heated treating coatings and the fractional transformation enthalpy were measured by DSC analysis. The crystallization of the coating was detected. The experimental result basically matched with the data of theoretic forecasting.
Abstract: The microwave response of YBa2Cu3O7/LaAlO3 (YBCO/LAO) and YBa2Cu3O7/MgO (YBCO/MgO) superconducting thin films was studied by microstrip resonator technique. Microwave characteristics of the superconducting films were analyzed by the temperature dependence of resonant frequency, load quality factor and insert loss. The penetration depth at 0 K can be attained as:λ0=265 nm for YBCO/LAO and λ0=280 nm for YBCO/MgO. The microwave surface resistance Rs of YBCO/LAO and YBCO/MgO was also investigated by microstrip resonator.
Abstract: A mixture of H2, CH4 and Ar gas was used as feed gas under gas recycling condition. Diamond films with different thicknesses were deposited on molybdenum substrates by a 100 kW DC arc plasma jet CVD system at 850 and 950℃. The morphology, quality, orientation and residual stress of diamond films were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The results show that the quality of diamond films increases and the residual stress in diamond films decreases with increasing film thickness at 850℃. Diamond films with good growth stability were obtained and the tensile residual stress in diamond films was observed. The diamond film of 110μm in thickness deposited at 850℃ has a better growth stability, a higher quality and a smaller residual stress than the diamond film of 120 μm in thickness deposited at 950℃ when the flow rate of reaction gases is kept unchanged.
Abstract: Atomic displacement fluctuation in a graphene under dual laser fields was studied by a moatttea functional integral approach. It was shown that when the field strength and the frequency were fixed, the atomic displacement fluctuation was tuned by the phase difference between dual laser fields. It was realized that the rate of change of the atomic displacement fluctuation took its positive value in measurable time ranges. This corresponded to a phonon amplification effect. The mechanism of generating the phonon amplification was discussed.
Abstract: An all-vanadium redox-flow battery (VRB) typically uses carbon felt as the electrode material in order to enhance the reactive current. The carbon felt made by polyaerylonitrile-based polymers can be heat-treated to increase the number of surface oxide sites and to improve its crystallinity and conductivity. It was examined in VRB that the over potentiality was mainly caused by positive pole reactions. The heat treatment of positive felt could decrease the cell's resistance dramatically, but that of negative felt induced low hydrogen evolution over potentiality and low current efficiency. With raw felt as the negative pole material and heat-treated felt as the positive pole material the test cell could get the optimal energy efficiency.
Abstract: A 6-DOF rigid multi-body handling stability model of an articulated dump truck (ADT) was developed by Roberson-Wittenburg method. XAD250 yaw velocity gain curves under no-load and full-load states were calculated with the software MATLAB. From the curves it was found that the no-load ADT had larger under steer than the full-load one. Some parameters were calculated such as tire lateral stiffness, centroid position of every segment, and suspension system parameter, which influence the handling stability of an ADT.
Abstract: By the fractal method, mathematical models for particle number variation, particle surface area profile and particle mass distribution were established to predict and control the particle-size distribution of coal grinding at any grinding time. The particle number variation can be used to describe the main range of particle diameter. The surface area profile can be used to predict the energy consumption in grinding process. The particle mass distribution could be used to calculate the specific stacking density of particles or the slurry concentration. These models were proved to be valid by comparison of the fractal particle-size distribution with practical measurement.
Abstract: This paper described a kind of ultrasonic ranging system which employs a new driving circuit and low-noise programmable amplifier. The design of signal-to-noise ratio (SNR) in the circuit was raised to make measurement more stable and reliable. An efficient central ellipse algorithm for estimating the echo peak positions of ultrasonic sampling was presented to find the accurate receive time of echo by searching the peak of energy bursts, which is base on the theories of energy centrobaric correction method and least square method in the ultrasonic ranging system. A comparison of experimental results shows that the proposed algorithm's relative error is approximately 0.2%, which is more accuracy than the envelope detector or the cubic fitted multiple regression equation method, as a result it is suitable for higher accuracy industrial applications.
Abstract: In cluster, the performance of an interconnection network exhibits significant effect on that of the whole cluster system. The interconnection network is required to possess the characteristics of high bandwidth, low delay and high reliability. Traditional interconnection network access technologies are almost based on the peripheral component interface (PCI). This paper proposed a design ideology of access based on DDR DIMM interface and presented a design of the network interface on FPGA. The access bandwidth could be increased by reading and writing memory directly. Parts of the communication protocols were downloaded into the network interface card (NIC) to improve the parallel of calculation and communication. Measurements indicate that excluding the upper layer protocol, the access bandwidth of the NIC can reach to 3120 Mbps. An implementation approach of the NIC for FPGA was put forward and was simulated on an XC2VP20 FPGA chip of Xilinx Corporation.
Abstract: For the two different cases that the upper bound of network-induced delays is longer or less than one sampling period in a continuous-time networked control system (NCS), by discretizing the model of a continuous-time system and applying the augmented state-space method to the model, a uniform discrete-time jump model governed by Markov chains was presented. The parameters of the model reflected both the length of the delays and computation precision, so this model had more widely adaptability. The existing theory of a jump linear system was applied to analysis the necessary and sufficient conditions guaranteeing the system's stability. An interior-point algorithm was applied to design stabilizing controllers, and an approach to get the feasible initial solution of the interior-point algorithm was proposed. This improved algorithm stated above was applied effectively to the networked control and design of a cart and inverted pendulum with random delays.
Abstract: The orthogonal Kautz function was used to obtain the approximate model of a system. An adaptive predictive functional control algorithm using the Kautz model was designed. The stability of the algorithm was analyzed, and the sufficient condition to make a closed-loop system stable was presented based on the Lyapunov stability theory. Simulation results show that the proposed algorithm is effective, which can describe the system exactly and reach a high degree of control performance.
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
