Abstract: The space between blast-holes is the main factor influencing on the desensitization of industrial explosives. The relation of pressure desensitization to the space between explosive charges was analyzed and ideally modeled. Two concepts of critical dead-pressing space and critical desensitization space were introduced and discussed based on the practice and it is reasonable to depict the relation by the two concepts. It is shown that the two concepts are helpful for understanding the desensitization of explosives and guidable to design blasting holes in millisecond blasting.
Abstract: Based on field observations of the high-density digital seismograph and tidal deformation network of a meso-scale seismological experimental site, the data of strong mining-induced earthquake process were analyzed by the seismological method and wavelet tool. Believable b values and η values were tested, and frequency seismological anomalies and fixed point tidal deformation anomalies were found before strong mining-induced earthquake in the short-term and impending stages. The extraction method of anomalous information and the forecast of strong mining-induced earthquake in the short-term and impending stages were discussed.
Abstract: A dustproof method, adding dust-sticking bar to infusion, was studied. This method can reduce contact angle and shorten wetting time. The contact angle and the wetting time of seven coal samples in the dust-sticking bar's solution with different concentrations were analyzed to obtain the critical surface tension of the seven coal samples. It was concluded that the wetting effect of coal seam infusion primarily lies on the surface tension of injected water. By this method, the dust of coal seam can be greatly decreased and the adding technical process is simple, convenient and practical.
Abstract: The equation of soil bore enlarging with water jet was established based on the water jet theory and soil mechanical theory. Through indoor simulation test, the relationship between water jet parameters and bore-enlarging effect was studied. The results showed that the equation of soil bore enlarging with water jet is correct. Increasing the water jet flow quantity has more obvious effect on bore enlarging than increasing the water jet pressure. The experimental parameter βs is mainly related to the lifting speed and the rotational speed of the drill pipe.
Abstract: An unsaturated clay slope, with multi-sloping angles, successively consists of loose layers of unsaturated clay, strongly weathered sandstone intermingled by mudstone, moderately weathered sandstone as well as lightly weathered sandstone. The slide interfaces were determined by geophysical approaches and the original slope was reconstructed. The sub-slope masses were classified based on the varieties of sloping angle. A force recursive principle was used to calculate the stability coefficient of the sub-slope masses. The influencing factors such as sloping, water content, cohesion, internal frictional angle, hydrostatic pressure, seismic force as well as train load were analyzed. The step length, range and correlation of the above-mentioned factors were discussed and coupling equations were established to reflect the relationships between density, cohesion, internal frictional angle and water content, as well as the relationship between internal frictional angle and cohesion. The sensitivity of the slope stability was analyzed and susceptive factors were determined when the above-mentioned factors were taken as independent and dependent respectively. The results show that internal frictional angle, cohesion, sloping and water content are the principal susceptive factors influencing the stability of the slope. It can fade the influencing extent of water content and cohesion to the slope stability if the above-mentioned factors are taken as independent variables without considering their correlation.
Abstract: The anchoring mechanism of a Pre-stressed Anchor Cable under Dispersive Pressure (PACDP) was studied with FLAC software. Compared with a Pre-stressed Anchor Cable under Concentrated Tension (PACCT), the PACDP has several advantages and is more suitable for supporting soft rock with large deformation. The peak value of axial stress of the PACDP is only 1/n of that of the PACCT, where n is the number of supporters and the grouted part is in compression. The peak value of shear stress between the grouted part and the drilling wall of the PACDP is also smaller than that of PACCT and evenly distributed along the axis of the anchor. The PACDP can provide a larger anchoring force than the PACCT. It is concluded that pre-stressed anchoring under dispersive pressure is an effective way to enhance the anchoring force and improve the mechanical conditions by suitably increasing the number of grouted parts.
Abstract: The single-point ramming process of loess road foundation was simulated by the finite element method. The distributions of stress, displacement and pressure in the foundation during dynamic consolidation were provided with a sample of Han-Chang Expressway. Computational results were compared with the measured data at the consolidation site. It is shown that the numerical simulation can exactly reveal the change of physical and mechanical parameters of the collapsible loess foundation during dynamic consolidation.
Abstract: A comprehensive mathematical model for simulating the reacting flow and heat transfer process in a reheating furnace was developed. The model includes the k-ε two-equation model for turbulenct flow, the six-flux model for radiative heat transfer and the EBU turbulent gaseous combustion model for gaseous reaction. The governing equations are solved by the SIMPLER algorithm. Detailed and reasonable results of the distributions of velocity, temperature and concentration were obtained.
Abstract: In the sintering process of iron ores, the fluidity of sintering liquid phase created by iron ores reacting with CaO is one of the important indexes that evaluate whether the sintering mixture can consolidate effectively. 10 kinds of imported iron ore fines were used to investigate the fluidity of liquid phase in iron ores and analyze its influential factors by the minitype sintering method and the viscosity evaluation method based on flow area. The effect of the fluidity of liquid phase in iron ores on the realistic sintering process was discussed. The results indicate that different iron ores have different fluidities of liquid phase in sintering conditions due to their inherent characteristics.
Abstract: Deep dephosphorization experiment was carried out in the laboratory by BaO-CaO-CaF2 flux to obtain ultra-low phosphorus steel. The result showed that the P content of the tested steel could decrease from about 0.01% to 0.005% or even lower to 0.002% with a dephosphorization ratio of 50% by use of this kind of flux. It is found that the oxidizability of steel has significant effect on dephosphoriztion when using the BaO-CaO-CaF2 flux. The phosphate capacity of the used system varied from 1018 to 1019.35 in 1813~1893 K and increased with the increase of BaO content.
Abstract: By using a thermomechanical simulator, the laws of continuous cooling transformation and microstructure evolution of TRIP steel produced by TSCR were investigated. It is found that the phase transition temperature during continuous cooling is lower and decreases with the increase of cooling rate, which is beneficial to lower the finishing temperature. A higher heating-up temperature suppresses phase transformation, on the contrary, deformation can promote it. Bainite was found when the cooling rate surpassed 10℃/s.
Abstract: By using TEM the strain-induced precipitation of Nb(CN) during deformation of under cooled austenite was investigated in Nb-microalloyed steel. The results showed that at 1200℃ all of Nb were dissolved and there were no Nb(CN) precipitates formed during cooling until down to 760℃. During deformation-enhanced ferrite transformation the Nb(CN) of dynamic precipitation required an incubation period, but compared with isothermal transformation it reduced significantly. Only when the strain increased to 0.69, Nb(CN) began to precipitate on dislocation nodes and grain boundaries. The volume fraction of Nb(CN) precipitates increased with the increase of strain but their coarsening was not significant. It is shown that the measured grain size is in good agreement with the calculated value.
Abstract: Ti-6Al-4V compacts were prepared by metal injection molding and binders in the compacts were debound by solvent debinding and heat debinding. The microstructure and mechanical properties of the alloy under the conditions of vacuum sintering and hot isostatic pressing (HIP) sintering were investigated. The results showed the specimens by vacuum sintering had a typical Widmannstatten microstructure, which possessed coarser prior β-grains and secondary platelet α+β-phase, but the alloy had a more microporosity and a lower tensile strength and ductility. After HIP treatment, prior β-grains and secondary platelet α+β-phase became fine and uniform, and the alloy possessed a less microporosity and a higher tensile strength and ductility.
Abstract: A physical and a mathematic model of solute grain boundary segregation were developed which synthetically took account of both equilibrium and non-equilibrium grain boundary segregation, transformation of segregated solute to precipitates and cooling rate. The adsorption and adsorptivity of grain boundaries and extended disordered zones in the vicinity of grain boundaries to solute atoms were considered. The evolution of boron grain boundary segregation during cooling from 1150℃ to 640℃ in the Fe-40%Ni-B alloy with 0.0010% boron was simulated. The simulated results show that the boron enrichment factor of the boundary zones increases fast at the beginning of cooling, then relatively even, indicating the back diffusion of segregated boron atoms. After boron precipitates appearing, the enrichment factor increases fast again. Good agreement between experimental and simulated results was achieved.
Abstract: The morphology of silicon was studied in corundum silicon-nitride composites after nitridation at different temperatures. The results showed that silicon was wrapped by flocculant O'-Sialon at 1300℃. Silicon grains were broken and silicon nitride formed inside the grains at 1400℃. All silicon was nitrided into O'-Sialon or silicon nitride without any silicon left at 1500℃. Impurities from silicon such as CaO, Fe2O3 were aggregated at 1600℃.
Abstract: The conductivity of several perovskite-type and similar perovskite-type oxide materials was investigated. The experimental results showed that the conductivities of La0.8Sr0.2MnO3, La0.8Sr0.2 Ni0.1Mn0.9O3, La0.8Sr0.2 Ce0.1Mn0.9O3 and SrFe0.5Co0.5O3 are approximative and all arrive at 10-1 S·cm-1. LaLiMnOy and LaLi0.5MnOy, whose stabilities in molten carbonate are excellent, are different in conductivity. The former is more than 1 S·cm-1, which meets the need of cathode materials of MCFC, and the latter is only 10-2 S·cm-1. A much higher activation energy of 0.191 eV should be the reason that the conductivity of LaLi0.5MnOy is lower.
Abstract: Magnetic drum coating material was prepared by using the magnetic slurry inunction process and the influence of component on the property of coating material was investigated. A high-performance magnetic drum whose diameter is 30-40 mm was ultimately manufactured with this material. The magnetic drum was magnetized and recorded 128 and 256 magnetic poles. A metal film magnetoresistance transducer was used to detect the distributing magnetic field of the drum surface and the signal was transformed to an oscillograph and an arithmometer by a magnifying and plastic circuit. It is shown that the output signal waveform is fine and the count is integrated.
Abstract: The measurement of roving evenness based on a capacitive evenness tester is usually off-line. An on-line measurement of the evenness of finish woolen web based on computer image processing was proposed. Compared with the capacitive evenness tester, the computer image processing can satisfactorily control the evenness of finish woolen web in the whole production process.
Abstract: The paper proposed a gas film thickness distribution formula involved gas film thickness error, round and cylindrical errors. The effect of tolerance on the performance of an externally pressurized air journal bearing was studied by the finite element method. It is shown that round and cylindrical errors have less effect on the load-carrying capacity of the bearing, and an average film thickness error of 5% may result in a load-carrying change of 10%.
Abstract: A dynamic model of involute gears with asymmetric teeth was proposed based on the analysis of mesh characteristics when the gears transmitting. The numerical integral and numerical simulation method were used to study nonlinear vibration. Considering the time-variant mesh stiffness when the gears transmitting, the vibration characteristics were compared between gears with symmetric teeth and with asymmetric teeth. The results showed that under the same condition the gears with asymmetric teeth had better dynamic characteristics than those with symmetric teeth.
Abstract: The main optical parameters of Confocal Fabry-Perot Interferometers (CFPI), including free spectral range, minimum resolvable frequency difference (instrumental bandpass), finesse, spectral resolving power, were discussed. According to the requirement and feature of laser-ultrasonic detection, a CFPI used in laboratory was designed and fabricated. The CFPI's cavity length and operation point were controlled by a micro-single computer. Laser-ultrasonic non-contact detection is carried out successfully with the CFBI.
Abstract: Aimed at the difficulty to extract the fault information of a low speed shaft in a large gearbox, wavelet analysis was used to realize the local analysis of signals in a time and frequency domain simultaneously. The signals were dissembled to a series of compactly supported wavelet bases non-redundantly and without leaking. The saltation coefficient of wavelet analysis was regarded as a characteristic value to predict a sudden accident and the changing trend of the coefficient was figured out. The results showed that wavelet transform could capture the characteristics in a time domain and the evolvement procedure of a fault. The trend graph of the coefficient could effectively predict the development trend of a fault and avoid a sudden accident.
Abstract: In order to roundly and scientifically evaluate overall benefit in coal enterprises, an evaluation index system of overall benefit in coal enterprises was established based on the definite selection principle of evaluation indexes and the characteristics of coal enterprises, and the evaluation of overall benefit in coal enterprises was studied by means of the entropy coefficient method. The analysis of applied results of an coal enterprise shows that the evaluation index system of overall benefit in coal enterprises is reasonable and the model of multifactor comprehensive evaluation based on entropy is suitable to evaluate overall benefit in coal enterprises.
Abstract: Based on the connotation of ecosystem health in a mining area and an index system for assessment established, the status quo of ecosystem health was assessed by the fuzzy theory and its tread in development was predicted by the grey theory. The non-linear theory was applied to assess the stabilities of the ecosystem and a comprehensive assessment method was proposed. The results show that the situation of ecosystem health in the investigated mining area is sub-healthy. It is necessary to adjust and control the situation and some measures were recommended.
Abstract: According to the production scheduling problem in the dual-line continuous casting production of thin slab continuous casting and hot rolling, two production organization modes were proposed. A simulation model was designed to analyze the execution process of scheduling. Based on the simulation result some suggestions were made for selecting the production organization mode of a continuous casting and continuous rolling enterprise.
Abstract: Based on the advantage competition theory a dynamic dual-diamond model was proposed to locate logistics centers. It quantitatively dealt with the problem of logistics center location by several methods including the factor analysis method for selecting the section and location genes, the analytic hierarchy process and the cluster analysis method for designing the index system of logistics center location. The calculated result of logistics center location in Beijing matches the tenth five-development-program of China.
Abstract: A new algorithm for filling up in complete data was presented according to rough sets. In this method, the main purpose was emphasizing the decision rules, the main means was selecting the important breaking points, and the iterative constraint was the quality of classification. Numerical illustration and database experiments show that the algorithm did not generate conflict rules,but highlighted them.
Abstract: An improved Dijkstra's and an improved A* algorithm were proposed based on the analysis of their drawbacks. In the traditional Dijkstra's algorithm, the distance between two unconnected nodes is infinite and some relative calculations are useless. The improved Dijkstra's algorithm proposed that the connection between nodes should be tested at first so that it can decrease the computing overhead to a great extent. When the traditional A* algorithm is used in practice, its efficiency is not satisfied. The improved A* algorithm includes such steps as the following:firstly, the original optimum path should be planned by the traditional A* algorithm; secondly the nodes in the original optimum path; should be blocked in turn and the traditional A* algorithm is used again in order to look for another new optimum path, finally, these new optimum paths should be compared with the original one so that the final optimum path can be selected. Simulation results show that the improved Dijkstra's algorithm can enhance the calculation efficiency and the improved A* algorithm can find the more optimum path.
Abstract: An efficient method based on Singular Value Decomposition (SVD) for the computation of Lyapunov exponent is presented. This method is applicable not only to discrete systems but also to continuous systems, and it does not require frequent reorthogonalization. Numerical calculations show that the method is stable and has a higher computing efficiency, and the results are credible.
Abstract: Difference-controlled Cellular Neural Networks (CNN) can realize some complex operations more convenient than standard CNN. To improve the stability and realizability of existent median filters based on difference-controlled CNN, a pseudo median filter based on difference-controlled CNN (CNN PM-filter) was presented. In order to reduce image blur caused by filtering, a selective CNN PM-filter was studied too. The results of signal/noise ratio and correlation degree show that the stability and realizability of the two filters in paper were improved. The CNN PM-filter's performance is a little better than a standard median filter; the selective CNN PM-filter can suppress impulse noise and simultaneously reduce image blur effectively.
Abstract: The direct power control (DPC) principle of three-phase boost-type PWM rectifiers based on the mathematical model of PWM rectifiers was analyzed. The effect of the hysteresis wide of power hysteresis comparators on the properties of the PWM rectifiers was discussed. Since the hysteresis wide is widened for decreasing switching frequency and energy loss, which causes the pulsation of instantaneous active power and direct current voltage, a control strategy with the dead zone of sector borders was proposed for eliminating the mistakes of selecting switch vectors on sector borders and improving the waveforms of instantaneous active power and direct current voltage. Simulink simulation shows the feasibility of the control strategy.
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
