Abstract: Ground penetrating radar(GPR) electromagnetic waves which penetrate through rock and soil mediums and are reflected back carry internal information about the target objects. The GPR basic frequency values of Fourier spectra can be used as a quantitative index of judgment for the structure characteristic of rock and soil mediums. Based on a highway tunnel project with the surrounding rock of quartz sandstone,advanced geological exploration test was carried out in front of the tunnel face with MALA GPR and a 100 MHz shielded antenna. Typical Class Ⅴ,Class Ⅳ and Class Ⅲ quartz sandstone surrounding rock mass were chosen to analyze their waveform graph information characteristic and the Fourier spectrum frequency characteristic during electromagnetic wave propagation in rock mass mediums. The regularity of GPR wave basic frequency values corresponding to the quartz sandstone rock mass medium in a certain sensitive frequency range due to its structure and surrounding environment changes was obtained through field test data analysis. A comparison between the research results and engineering excavation practices shows that it is feasible to invert the basic frequency value characteristic of GPR waves derived from advanced geological exploration for determining the structure characteristics of surrounding rock.
Abstract: The deformation and failure characteristics of total 270 consequent rock slopes under complicated working conditions are investigated by the discrete element method depending on two parameters,structural plane dip angle θ and slope angle α. Different θ and α ranges corresponding to different failure modes are obtained by the statistical method. Moreover,the relationship between the two parameters and the slope stability is attempted based on the shear strength reduction method. The failure mechanism and stability characteristics of consequent rock slopes are revealed. Four deformation and failure modes of consequent rock slopes are proposed according to different deformation and failure characteristics:toe-slip-failure along the structural plane,top-sliding-failure along the structural plane,lower edge uplift bending-shear failure,and upper edge fracturing-fold-bending-failure. Further general rules of the four modes are analyzed and summarized such as occurrences,deformation characteristics and possible failure modes. The safety factor fs of the slopes decreases and subsequently increases with the increase of θ,it reaches a minimum and then rises quickly to a high value and finally slowing down. During the changing process of θ,the safety factor fs will obtain a minimum when θ is approximately equal to α-7. 3°,which corresponds to the worst slope stability.
Abstract: Alkaline leaching bacteria are new efficient strains for processing alkaline minerals. Slurry gradient domestication and ultraviolet mutagenesis were introduced to improve the adaptive capacity to environment and leaching rate of the strains. With the help of Design Expert-8 software,a three-factor three-level Box-Behnken experiment was conducted to investigate the influence of pulp density,initial bacteria inoculation and temperature on the leaching rate. The optimal experimental condition was determined by Design Expert-8 software and a prediction model was proposed in this paper. Comparative experiment was conducted to investigate the differences before and after this improvement experiment under the optimal conditions. The results show that the improved strain can adapt to the pulp condition better. The population of the improved strain can up to 6. 5 ×108mL-1 and the leaching rate reaches to 50. 57%,while the population of the original strain can up to 3 ×108mL-1 and the leaching rate reaches only to 29. 03%.
Abstract: Through analysis of samples taken in the refining process of low carbon and aluminum containing 20Mn2 steel,it was found that the melting point of the refining slag was high,substantial solid CaO and CaO-type inclusions existed in the steel and slag,leading to a decrease in absorption capacity of inclusions in the molten slag. Based on thermodynamic calculations utilizing Fact Sage software,the slag system was investigated and optimized by integrating the control of low-melting-point regions and reactions between slag and steel. The results show that 3% CaF2 addition can decrease the melting temperature of the slag with CaO/Al2O3 mass ratio around 1. 5,and the melting point of the slag exhibits an initial decline and a subsequent rise with increasing CaF2 content. The largest low-melting-point region is obtained through governing the MgO content in a vicinity of 5%. The oxygen content in the steel decreases with increasing CaO/Al2O3 mass ratio in the region of SiO2 exceeding 30%,and decreases with increasing CaO content in the region of SiO2 lower than 30%. The acid-soluble aluminum content increases with increasing Al2O3/SiO2 mass ratio in the region of high SiO2 content and increasing CaO/SiO2 mass ratio in the region of low SiO2 content. According to results from thermodynamic analysis,the optimized slag can be given as 50%-60% CaO,20%-35% Al2O3,5%-10% SiO2,5%-8% MgO,and 0-5% CaF2. Experi-mental results show that the melting point of the optimized slag declines,and there are apparent decreases in the number,area and mean diameter of inclusions in the steel.
Abstract: The effect of slag composition on the[C] content of ultra-low carbon steel at the end of smelting was investigated by the coexistence theory,dynamics analysis and experimental verification. A regression model of end-point[C] content was established with temperature and slag composition in a temperature range from 1853 K to 1973 K. The results show that the Fe O activity is little affected by temperature,while it is mainly affected by slag composition. However,the decarburization kinetics is mainly affected by slag composition and temperature. The end-point[C] content increases with increasing slag basicity,but it quickly decreases with increasing Fe O content in slag,so the end-point Fe O mass fraction in slag should be controlled in 12%-18%. In addition,the increment value of[C] is less than 0. 01% with the Mg O mass fraction in slag from 7% to 13%. The results also show that the end-point[C]mass fraction decreases with increasing temperature. Compared with industrial results,the average error rate of the regression model for the end-point[C] content in the ultra-low carbon steel is ±15. 25%,and the hit rate to[C] content predicted by the regression model reaches 69. 19% with a control precision of ±0. 01% for heats of the experiment.
Abstract: In order to solve the problem of lead removal from crude antimony in the traditional antimony refining process,NaPO3 was introduced as a lead elimination reagent to generate phosphate slag and the slag was removed by floating on the surface of liquid antimony. The reaction mechanisms were clarified by thermogravimetric-differential thermal analysis and X-ray diffraction analysis and removal of Pb from crude Sb was investigated by condition experiment. It is found that PbO and NaPO3 begin an endothermic reaction at 590℃ and mainly form NaPb4(PO4)3 and NaPbPO4 below 850℃ and above 850℃,respectively. The reaction products of the mixture of PbO,Sb2O3 and NaPO3 show that NaPO3 preferentially reacts with PbO when NaPO3 is insufficient,and amorphous antimony glass will generate only with enough NaPO3. Single-factor experiments were taken with NaNO3 as an oxidizing agent under nitrogen.Reaction time,temperature,NaPO3 and NaNO3 amounts were considered for smelting results. Under the optimal condition,the content of lead in refined antimony is 0. 047% and 98. 90% of lead is removed.
Abstract: Temperature fluctuations exist on the slab surface due to unstable heat flux during repeated contact and departure between the hot slab surface and the relatively cold supporting rollers in the secondary cooling zone. Considering thermal oscillations,hot ductility test under different thermal conditions was carried out on J55 microalloyed steel. The results show that at a temperature higher than 850℃,the hot ductility under the oscillating condition is lower than that under the isothermal condition,but it is on the contrary when the temperature equals or falls below 850℃. By analyzing results from experiment and from literature comprehensively,for the microalloyed steel,it is inferred that there exists a critical temperature a bit higher than the Ae3 temperature. Above this critical temperature the hot ductility under the isothermal condition is higher than that measured by the more accurate oscillating way,while below it the result is opposite. This conclusion is meaningful to determine the straightening temperature for microalloyed steel production during continuous casting.
Abstract: The microstructure of hot-rolled dual-phase steel was studied by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The volume fraction of each phase in the dual-phase steel was determined by Image-Pro Plus software. A microstructure-based model was deduced for the stress-strain relationship of the dual-phase steel according to the mixing rule of multiphase materials and the Swift equation. Then the model was verified by the strain-stress curves of DP590 and DP780 steels obtained from uniaxial tensile testing. The results show that the model expounds the relationship between the microstructural parameters and macroscopic mechanical properties,and it is able to accurately describe the deformation behavior of materials and well predict the tensile curve of hot rolled dual-phase steel.
Abstract: In order to study the effects of deformation conditions and initial grain size on the dynamic recrystallization behavior of316 LN austenitic stainless steel,single pass hot compression tests were conducted on a Gleeble-1500 D thermal-mechanical simulator with the deformation temperature of 900-1200℃,the strain rate of 0. 001-10 s-1,the true strain of 0. 1-0. 9 and the initial grain size of 122-297 μm. It is obtained that the ratio of critical strain to peak strain and the ratio of critical stress to peak stress are 0. 38 and 0. 89,respectively. A dynamic recrystallization kinetic model and a grain size evolution model were established based on experimental data. In addition,the developed models were modified for DEFORM-3D finite element simulation. It can be found that the simulated values by the modified model and experimental data agree well,indicating that the modified models have good accuracy.
Abstract: The effects of dissolved oxygen(DO) and temperature on the stress corrosion cracking(SCC) of 06Cr17Ni12Mo2 Ti stainless steel(SS) in supercritical water environments were investigated by slow strain rate tensile tests(SSRT). It is found that the SCC susceptibility of the stainless steel is observed in 450℃ and 550℃ supercritical water environments containing different amounts of dissolved oxygen(0/200/2000 μg·kg-1). The effect of dissolved oxygen on the SCC susceptibility is more remarkable with increasing amount of dissolved oxygen. However,the SCC susceptibility decreases with the increase of temperature. In 650℃ supercritical water environments containing different amounts of dissolved oxygen(0/200/2000 μg·kg-1),ductile fracture can be found,but the SCC susceptibility is not observed. In these environments,the effect of DO is negligible.
Abstract: This article is focused on the effect of temperature on the corrosion electrochemical behavior of 13Cr martensitic stainless steel under a high temperature and high CO2 partial pressure environment. Cyclic polarization(CP) measurements,electrochemical impedance spectroscopy(EIS),Mott-Schottky plot measurements,ZSIMPWIN software,and scanning electron microscopy(SEM) are used in this study. The results show that the stability of passive films formed on the 13Cr stainless steel surface decreases with increasing temperature under a high temperature and high CO2 partial pressure environment. This leads to increases in the corrosion rate and pitting susceptibility.
Abstract: The microstructure of as-cast GH625 alloy was investigated on the basis of experimental methods such as Thermo-Calc software,scanning electron microscopy and energy dispersive spectroscopy. The effect of casting temperature on the microstructure was also analyzed by comparing different samples. The microstructure of as-cast GH625 alloy is a dendritic structure and M6C carbides accompanied with δ phase precipitate in the interdendritic area. Both primary dendrite arm spacing(λ1) and second dendrite arm spacing(λ2) increase with the increase of casting temperature; however,the microsegregation is affected by both diffusion distance and diffusion time. The comprehensive interaction of these two factors leads to the greatest microsegregation degree of Nb at 1420℃,which contributes to δ phase precipitation in the interdendritic area. As a result,diffusion distance and diffusion time should be comprehensively considered in making the casting process,so as to choose a proper casting temperature(or cooling rate).
Abstract: A series polycrystalline samples of Sr14(Cu1-xZnx)24O41(x=0,0. 01,0. 02,0. 03) were prepared by standard solidstate reactions. X-ray diffraction(XRD) patterns show that a single phase can be achieved in all samples and their lattice parameters have weak fluctuation with the change of doping content x. X-ray photo-electron spectroscopy results show that the valence of copper ions in Sr14Cu24O41 is + 2 and Zn doping has no effect on the valence of copper ions. Magnetic susceptibility measurements in a temperature range from 10 to 300 K show that Zn doping decreases the magnetic susceptibility of the Sr14Cu24O41 system. Experimental fitting results show that the contribution to magnetic susceptibility of the Curie-Weiss term,the value of coupling energy in dimers JD,the number of dimers NDand the number of free Cu2+ ion spins in the CuO2 spin chain per formula unit NF all decrease with the increase of doping content x. Further analysis indicates that the number of Zn2+ ions which substitute Cu2+ ions in dimers is less than the number of Zn2+ ions which substitute free Cu2+ ions. Electrical resistivity measurements show that the Sr14Cu24O41 system is semiconducting,Zn doping decreases the electrical resistivity of the Sr14Cu24O41 system,and the decreasing level increases with the increase of doping content x,but no metal-insulator transition occurs in this system. We think that the decrease in electrical resistivitymaybe results from decoupling of dimers in the spin chain due to Zn2+ ion doping. It means that the charge order super structure is destroyed,so more holes are released and transferred into the spin ladder then participate in conducting.
Abstract: Room-temperature synthesis of ZnS was controlled at the oil-water liquid-liquid interface. Combining with polymer films which were modified by hydroxyl-terminated self-assembled monolayers(SAMs) as flexible substrates,nanocrystalline ZnS films were fabricated on the substrates. X-ray diffraction analysis indicates that the ZnS films have a hexagonal wurtzite structure,which is the high-temperature polymorph of sphalerite. Scanning electron microscopy and transmission electron microscopy observations show that the ZnS films consist of nanoparticles with the diameter of 30-50 nm. Photocatalytic degradation of methyl orange by these products under UV-light irradiation was observed,which confirmed the photocatalytic degradation ability of the nanocrystalline ZnS films to organics. In view of the results,a facile one-step method,combining the oil-water interface with the SAMs-modified substrate,was proposed for fabricating the wurtzite ZnS functional films without any additive at room temperature. The relationship between photocatalytic performance and the morphology of the products was also discussed.
Abstract: The substitution of iron ore tailing powders(IP) for fly ash as mineral admixtures was studied in the development of engineered cementitious composites(ECC). The focus was placed on the effect of IP content on the tensile properties and compressive strength of ECC. The mechanical properties of ECC with IP were also compared with those of traditional ECC with fly ash. Experimental results show that it is feasible to use IP as mineral admixtures to produce high-ductile ECC. ECC with IP exhibits a lower strength performance but a higher ductility under tensile load than ECC with fly ash at the same addition of mineral admixtures. ECC with an IP/cement mass ratio of 1. 2-2. 2 shows a 28-d compressive strength of 36. 7-54. 2 MPa,which meets the compressive strength requirement of normal concrete structures,and a 28-d tensile ductility of 3. 4%-4. 3%. The amount of iron ore tailings in those mixtures accounts for 66. 6%-77. 0% of the total solid matrix ingredients of ECC.
Abstract: The compressive properties and energy absorption properties of polypropylene(PP) composites filled with hollow glass beads(HGB) and powdered nitrile butadiene rubber(PNBR) respectively were studied by uniaxial compression tests. The energy absorption capacity of the studied materials was verified by impact toughness based on pendulum impact tests. Scanning electron microscopy was used to observe the microstructure of the fracture surfaces. It is found that HGB increases the stiffness but lowers the ductility of polypropylene,while PNBR is on the contrary. The stress response degree of PNBR/PP is the lowest as absorbing the same energy. The design stress of HGB/PP should be higher than that of PNBR/PP according to energy-absorption efficiency. The maximum value in the ideal energy-absorption efficiency curve occurs at the yield stage. Impact test results show that HGB and PNBR can improve the energy-absorption capability of polypropylene.
Abstract: Cross laminated timber(CLT),a new generation of engineered wood-based product,is gaining attention in the North American market,but it has not been introduced and spread in China yet. In the paper,the mechanical properties of CLT are introduced in details,and the production technology,design methods and research progress are summarized as well. What's more,an experimental study on CLT flexible connection in seismic performance is done. The results show that the failure with all fasteners pulled out is disclosed as an ideal ductility failure. Highly nonlinear,stiffness degradation,strength degradation and pinching are illustrated in the hysteresis curves of connection. An excellent connector in ductility and load capacity is presented by test data analysis.
Abstract: The equilibrium adsorption characteristics of nitrogen adsorbents were tested and a suitable nitrogen adsorbent was selected for producing oxygen by rapid vacuum pressure swing adsorption. Due to low oxygen concentration in the product obtained by traditional rapid pressure swing adsorption,an improved pressurization step with raffinate was developed and experimentally studied in a rapid vacuum pressure swing adsorption system for producing oxygen. The results show that combined pressurization with raffinate and feed gas can effectively improve the oxygen concentration in the product during the rapid vacuum pressure swing adsorption process. The pressure and oxygen concentration of raffinate for pressurizing are key parameters to influence the oxygen concentration in the product,and a higher concentration oxygen product can be obtained by taking an appropriate pressure and a higher oxygen concentration of raffinate. The 90% oxygen can be generated by combined pressurization with raffinate and feed gas during the rapid vacuum pressure swing adsorption process with an adsorption pressure of 240 k Pa and a desorption pressure of 60 k Pa,and the adsorbent productivity is 325. 08 L·h-1·kg-1.
Abstract: This paper introduces a parameter self-tuning algorithm based on dynamic response time series data mining to solve the parameter self-tuning difficulty of a linear active disturbance rejection controller(LADRC). In the algorithm,two gain signal loops' dynamic response of linear state error feedback(LSEF) is used as the parameter adjustment object. Through the parameters auto-tuned by NLJ algorithm and the process data recorded,the control parameter adjustment policy based on association mining is applied to LADRC parameter auto-tuning. To verify the actual effect of the parameter self-tuning method in this paper,a hydraulic automatic position control(HAPC) system is used as the control object. Step response simulation and Monte Carlo experiment show that the dynamic response of the system which is combined by HAPC and the controller is better,the robustness is stronger,the adjustment time is shorter than NLJ algorithm,and the overshoot is also less than the traditional LADRC controller. It is considered as a practical LADRC controller parameter self-tuning method.
Abstract: In order to study the effect of external stimulus duration on the emotional state transition of people,firstly,the Gross emotional regulation process and the finite state machine are used to describe the emotional state transition process. Then the emotional enhancement factor is introduced according to different stimulus durations. The external stimulus duration is associated with the state transition matrix to determine its effect on the emotional state transition. Finally,simulation analysis was done for the proposed algorithm. The results show that the impact of external stimulation on the emotional state transition will be bigger with the increase of stimulus duration,but the rate of increase slows down gradually. The algorithm can effectively describe the relationship between the stimulus duration and emotional state transition matrix.
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
