Abstract: A result of safety evaluation was educed according to the rules of credible recognition after a index system in colliery ventilation safety evaluation was established. An unascertained measure model was constructed and the unascertained measure values of all evaluation indexes were calculated. This method can solve a lot of unascertained problems in ventilation system evaluation, and also can analyze the ventilation system quantitatively. Exemplification indicates that the evaluation result is consistent with actual instance if the method of unascertained measure evaluation is applied in colliery ventilation safety evaluation.
Abstract: Located in the northeast of China, there is an overbridge crossing above an expressway. Its right abutment is seated on a rock masses slope with low carrying capacity. The slope and abutment basis had appeared obvious unstable evidence before completion. For the stability of abutment and slope, according to the in-situ situation, some effective reinforcement measures Were adopted, which include middle-high pressure grouting, pre-stressed anchoring, anti-sliding anchoring, etc. The software of FLAC was used to numerically simulate the reinforced structure, and the design parameters were attained. Engineering practice of the abutment-slope system verified effectiveness of the multi-reinforcement.
Abstract: Sawdust cellulose xanthate was prepared from sawdust of the wood machining industry, and the processing parameters were optimized. The effects of the dosage of sawdust cellulose xanthate, reactive time, pH value, temperature on the removal of heavy metal ions in wastewater were investigated. The mechanism of removing heavy metal ions and the stability of sawdust cellulose xanthate were also discussed. The removing rates of heavy metals Cu2+, Ni2+ and Zn2+ by sawdust cellulose xanthate were above 98%, and the mass concentrations of Cu2+, Ni2+ and Zn2+ in the treated wastewater were lower than those in the national standard.
Abstract: The formation of non-isothermal flow in a tundish was investigated in a special designed 2D water modelling system. The critical condition of the formation of non-isothermal flow was proposed to be a number Zb evaluating the sensitivity of tundish flow to temperature difference. CFD simulation of the tracing pattern in a water model described in the initial formation condition of non-isothermal flow. A direct measurement of temperature stratification in a 40 t tundish confirmed the existence of the non-isothermal flow.
Abstract: Electromagnetic stirring process for the round billet mould (450 mm in diameter) in No. 1 Steelmaking Plant of Maanshan Steel in China was analyzed by using mathematical simulation. Orderliness was found out in order to optimize flow path in the round billet mould and make certain reasonable casting parameters. Computational results of electromagnetic stirring process indicated that the magnetic field intensity increases with the stirring frequency decreased and the stirring electric current increased. The electric current intensity does not change magnetic field distribution. The characteristic of magnetic field along the mould vertical direction is strong in the middle and weak at the end of the mould. The optimized processing parameters are the stirring electric current of 350 A and the stirring frequency of 2 Hz.
Abstract: Directional solidification structure was studied under Alternating Current (AC) process. The result indicated that AC field had a refining effect on solidification structure, the effect became more obvious at a higher current, and AC field reduced the solute concentration at solidification interface. Analysis of all field effects showed that interface stability increased with the reduction of interface chemical potential, but interface layer attenuated and interface stability reduced in the situation of increased interface energy, small activity coefficient and oscillation at interface solute, accordingly the stability of cystiform crystals was restrained and columnar cystiform crystals turned refined ones.
Abstract: Healing processing of 16Mn steel samples was carried out. The healing area of internal cracks made by compressing a drilled hole was observed and analyzed. SEM analysis displayed that the fine structure in the healing area is mostly ferrite and there exists many polyangular grains of several hundreds nanometer. Vickers hardness tests showed that the hardness of ferrite in the healing area is higher than that in the matrix, which may result from strengthening of polyangular grains.
Abstract: High temperature mechanical properties of 5 automobile steel grades produced by the EAF steelmaking workshop of Shijiazhuang Iron & Steel Co. Ltd. (Shigang Steel) were investigated by the classical thermal simulating method. Hot ductility and strength curves of these steels were measured with a hot stress/strain test machine. Results in different sampling ways for blooms and a comparison with other results were discussed. The embrittlement and fracture mechanisms o~ these respective steels were clarified based on examination to the fracture surface of specimens with scanning electronic microscope. The relation between bloom quality and high temperature mechanical properties was discussed.
Abstract: The principle for choosing proper interlayer materials to bond dissimilar metals was discussed. An appropriate interlayer was designed and bonding experiment was carried out to join stainless steel panel with aluminum alloy honeycomb core. The function of interlayer was investigated by analyzing the interface microstructure and examining the joint strengths. The effect of processing parameters on the interface microstructure and liquid diffusion bonding was also discussed. The results show that good wetting and spreading properties in the interlayer were attained so that firm metallurgical bonding between stainless steel and aluminum was obtained.
Abstract: MgB2 powder was successfully synthesized by a self-propagating high-temperature method. Thermodynamic calculation and XRD analysis were used to investigate the powder's synthesizing order and transforming relationship between different Mg-B phases. Phase composition and decomposition temperature in the synthesis process were discussed. The results show that MgB2 phase has synthesized without other impurities such as MgB4. The particle size is small and the MgB2 is easy to decompose.
Abstract: The effect of Zr content on the grain size of Mg-gGd-4Y alloys and the grain refinement mechanism of Zr were investigated. The results reveal that Zr can refine grains of the alloys greatly, and the grains become finer with the increase of Zr content. The microstructure analysis shows that there are at least one Zr-rich core in the almost each grain in the alloys with high Zr content, whereas the characteristic Zr-rich cores are not found in the alloy with low Zr content. It is suggested that the grain refinement mechanism of zirconium in the low Zr alloys be different from that in the high Zr alloys: the zirconium works mainly by restricting grain growth in the low Zr alloys, and by generating nucleants in the high Zr alloys.
Abstract: Titania nanoparticles co-doped with Ce3+, Fe3+, Zn2+ were prepared by sol-gel self-combustion synthesis with TiCl4 as the precusor. The products were characterized by X-Ray Diffraction (XRD). The effects of Fe/Ce, (Fe + Ce)/Ti, citric acid/Ti (in mole ratio), calcining temperature and time on phase composition were investigated by the orthogonal experimental method. The results showed that citric acid/Ti, calcining temperature and (Fe + Ce)/Ti affect dominantly on phase composition of the products.
Abstract: SiO2 aerogel was prepared by using waterglass as the Si source, formamide as the catalyst and glycol as the drying chemical controlling additive (DCCA) via sol-gel method and ambient pressure drying. It is revealed that a certain amount of excessive formamide is favorable for preparation of the aerogel with high porosity, while more excessive glycol can deteriorate the formation of nano-porous SiO2 aerogel network. Additionally, the pH value of the reaction system has a strong impact on the microstructure and properties of prepared SiO2 aerogel. The aerogel modified with dimethyldiethoxysilane (DMDEOS) shows an excellent hydrophobic feature. The structure and properties of hydrophobic silica aerogel were analyzed by Fourier transform infrared spectra (FTIR), thermogravimetric (TG) and Differential Scanning Calorimetry (DSC).
Abstract: In order to enhance the thermal stability of TPD (Triphenylamines Derivatives) for hole transport materials and device durability, a series of novel electroluminescent polymers with charge transporting properties were synthesized by condensation polymerization using TPD with di-halide through the Friedel-Crafts reaction, which TPD units were introduced into the main chain of polymers. It was found that all poly-TPD had almost the same structure of energy band as that of TPD itself and had better thermal stability. Some of polymers can transport holes as well as electrons. Their properties for electroluminesence of single layer devices were investigated. The results show that the devices emitted the maximum luminescence of about 36 cd·m-2 at 17 V and the maximum emission of the device was 460 nm.
Abstract: The factors influencing the thermal stability of a vanadium phosphate (H3NCH2CH2NH2)4 [VⅢ(H2O)2(VⅣO)8(OH)4(HPO4)4(PO4)4(H2O)2 ]·3H2O (V9P8-en for short) with open-framework were investigated by XPS. The thermal degradation of V9P8-en while heated under Ar and air atmospheres was studied, including the removal of organic templates (en), phase transition and vanadium oxidation states. It is shown that the structure of the compound collapses with decomposition of the organic template before 380 ℃, and the oxidation states of vanadium atoms become variable, i.e. vanadium atoms in VPO skeleton are reduced from V4+ to V3+. As viewed from crystal chemistry, the structure has to be rebuilt because the original coordination environments of V4+ (distorted octahedron or trigonal-bipyramid) cannot match ones of V3+ (regular octahedron). It is concluded that the rational control of pretreatment conditions to maintain the original oxidation states of vanadium will be helpful for the thermal stability of open framework vanadium phosphates.
Abstract: A real-time simulator of Automatic Gauge Control (AGC) for hot-rolling mill based on Digital Signal Processor (DSP) was proposed. The models of the hydraulic cylinder for Automatic Position Control (APC) and the deformation area of each stand were built. The simulator was performed by using parallel processing based on dynamic simulation of the characteristic of the strip and the stands which were coupled by the rolled material, and exchange data with the AGC controller of a computer control system through reflective memory network in a real-time mode. It could be used for developing and real-time testing AGC control strategies in off-line state. When simulated, the dynamic models were executed by a digital signal processing card and exchange data with the AGC controller in a real-time mode.
Abstract: A general equation about scattering intensity of heat radiation wave in medium was derived from viewpoints of the dipole radiation theory. The main factors, which affect the scattering intensity of heat radiation effectively, were ascertained. It was shown that the frequency of incident heat radiation and the swing of a damping oscillator in medium are of vital importance for the heat radiation properties such as reflectivity, absorptivity and transmissivity of medium.
Abstract: In order to suppress electromechanical vibration, to dynamically restrain the disturbance ot a main drive system and not to induce static error by the disturbance, a state space model of two-degree-of-freedom systems was built based on model matching techniques for the main drive system of a roiling mill. The design of an electromechanical vibration controller was converted into a standard H∞ control problem. Then an output feedback H∞ controller was obtained by using LMI approach so as to guarantee the robustness of the main drive system of a roiling mill. Simulated results showed that the controller effectively improved the performance of command following, suppressed electromechanical vibration, and reduced the dynamic speed fall caused by load disturbance.
Abstract: Taking the simple model of an alternating current torque servo system as the control object, a 2-degree of freedom inner model controller based on the H∞ robust controller is devised. Emulation experiments show that compared with a traditional controller both the traceability and robust stability of the new system are improved under variation of parameters, and the negative effect of the variation of parameters is limited.
Abstract: This paper modifies the two-cell immune dynamics differential equation which is showed in a reference. Based on the modified two-cell immune dynamics differential equation, a two-cell immune controller model is proposed to describe immune process. The controller is simple in structure, needs only three regulating parameters and is easy to be realized. Simulated results indicate that it has such fascinating characteristics as one-order integral character, good stabilization to a large pure-lag system, and remembrance character, and its parameters is easy to be regulated.
Abstract: A novel method of tracking a moving object in video sequences was presented. Adaptive background updating based on dynamic information window was used to solve the problem of complicated background, and a novel color model was used to dispel motion shadow. A given moving object with accurate edge was obtained, The centroid of the moving object was calculated and the coordinates were established. The method of 2-stage least squares was adopted to implement tracking the moving object. The results showed that the presented method was promising to track and forecast the motion of a moving object in video sequences.
Abstract: This paper introduces a dynamical learning method using support vector machine (SVM). This method can solve such machine learning problems as the difficulties in gathering training samples and the change of samples with outer environment. It is proved that SVM classifiers can achieve optimal performance after using this method in tracking the change of samples. A bank slip OCR system designed by this method proves the validity.
Abstract: Based on the dynamic dual-diamond model of logistics center site location, the causal and mutual relationship of systematical kinetics was analyzed. The flow charts of systematical kinetics about logistics center location were applied. The dynamic equations and state variables were designed. The basis of the computer simulation algorithm in selection of logistics center sites was structured.
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
