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28 December 2020, Volume 46 Issue 6 Previous Issue    Next Issue

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Materials Science and Engineering

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Microstructure, age-hardening behavior and mechanical properties of Mg-7Sn-Zn(Y) alloy BI Guang-li, XU Zuo-cheng, GU Jia-rui, JIANG Jing, JIANG Chun-hong, LI Yuan-dong 2020, 46 (6):  1-8.  Abstract ( 211 )   PDF (7349KB) ( 173 )   Save The microstructure, age-hardening behavior and mechanical properties of Mg-7Sn-Zn(Y) alloy were investigated. The as-cast Mg-7Sn alloy was mainly composed of α-Mg and eutectic(α-Mg+Mg2Sn) phase. The addition of Zn refines Mg2Sn phase, increases volume fraction of Mg2Sn phase and promotes precipitation of Mg2Sn phase on non-basal plane, and thus enhances the ageing hardening capacity of the alloy. The peak-ageing hardness of the Mg-7Sn-1Zn alloy increases from 64.6 HV to 69.7 HV, and the peak-ageing time decreases from 166 h to 142 h. The addition of Zn and Y elements forms the needlelike MgSnY phase. Although the peak-ageing time of the alloy is effectively decreased(166 h to 120 h), the peak-ageing hardness of the alloy reduces.The Mg-7Sn-1Zn alloy exhibits the best mechanical properties,Which was mainly attributed to the precipitation strengthening of fine Mg2Sn phasewith high volume fraction. References | Related Articles | Metrics

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Structure and properties of self-sensitive luminescent composite coatings prepared by detonation gun spraying LI Wen-sheng, ZHAO Wen-jie, CAO Chi, HE Ling, HU Chun-xia, YANG Xiao-tian 2020, 46 (6):  9-15.  Abstract ( 140 )   PDF (4636KB) ( 310 )   Save Wear-resistant and self-sensitive luminescent composite coatings, made of high-aluminum bronze mixed with SrAl2O4:Eu2+,Dy3+ particles, were successfully prepared on steel 45# substrate by using ADM-4D detonation gun spraying device. Structural morphologies and luminous intensities of the composite coatings were observed and analyzed and further friction and wear behaviors of the composite coatings were investigated. Results show that the deposition rate of SrAl2O4 particles in the composite coating increases nearly 78.6% when the oxygen-fuel ratio of the detonation spraying goes up from 1.3 to 2.3, and thus the composite coatings become more densified, and the hardness and the bonding strength increases 24% and 75% respectively as a result. At an oxygen-fuel ratio of 1.3, the proportion of phosphorescent particles deposited effectively on the surface of the composite coatings reaches, up to 9.7%. The macroscopic luminescence intensity of the coatings becomes therefore highest in this case, and consequently the macroscopic indication effect of the coatings excited by UV lamp becomes also the best. The friction coefficient between the composite coatings and the 304 stainless steel increases by nearly 35%, whereas the wear rate decreases by about 47%, when the oxygen-fuel ratio rises up to 2.3. References | Related Articles | Metrics

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Effect of SiO2 coating on luminescence and friction properties of self-sensitive coating prepared by detonation spray HE Ling, ZHAO Fan, LI Wen-sheng, SUN Wei-min, DONG Qi-zheng 2020, 46 (6):  16-21.  Abstract ( 158 )   PDF (7149KB) ( 97 )   Save The SiO2 layer was coated on surface of the strontium aluminate phosphor by sol-gel method. The SrAl2O4∶Eu2+, Dy3+/Cu-14Al-X self-sensing composite coating with different amounts of SiO2 coating was prepared by detonation spraying on steel 45# substrate. The emission spectra and afterglow attenuation curves of strontium aluminate powder along with self-sensing coating were compared in this paper, the corresponding friction coefficient together with wear of the composite coating were also compared, and further the effect of amount of SiO2 coating on the luminescence and tribological behavior of the self-sensing coating was analyzed in details as well. The results show that SiO2 coating can protect strontium aluminate during detonation spraying and improve luminous properties of the coating. With the increase of amount of SiO2 coating, the structure of the composite coating becomes more compacted, and the hardness and wear resistance of the composite coating are improved as a consequence. Under 20% amount of the coating, the hardness of strontium aluminate powders takes 564.5HV, which is 38% higher than that of uncoated strontium aluminate powders. The friction coefficient of the composite coating after being coated is relatively stable due to a certain degree of self-lubricating effect of broken SiO2 coating. The friction coefficient of the composite coating reaches 0.182 at 15% amount of SiO2 coating in this case, which exhibits the best friction performance. References | Related Articles | Metrics

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Optimization and research of loaded roll gap model of complex roll system based on influence function method LI Jun-chen, HUANG Xu-tao, MA Guo-cai, WANG Jun-wei, PAN Ji-xiang, RUAN Qiang 2020, 46 (6):  22-27.  Abstract ( 166 )   PDF (3203KB) ( 287 )   Save Accurate shape control theory is of great significance to improve the quality of strip rolling. At the same time, the efficient prediction of roll gap becomes an important part of the shape control theory. Aiming at the problem of online computation of roll gap in a complex roll system, this paper presents a new and efficient calculation method to predict the roll gap numerically. The method is based on the influence function method which is widely used in simple roll systems, and combined also with the idea of establishing stiffness matrix like that used in finite element method. The matrix can be solved by matrix iteration so as to predict the roll gap. Through the pre-processing of the contact pressure vector Ψ between rolls, the efficient presupposition of an initial value may be realized. Therefore, the efficiency and accuracy of the new prediction method are further improved. By comparing the proposed prediction method with the finite element method, it is found that the calculation time of this method is much less than that of the finite element method, while the accuracy approaches greatly to that of the finite element method. The maximum error resulting from this method is only 1.6%, which meets requirements of the on-line calculation indeed. References | Related Articles | Metrics

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Effect of compression/diameter ratio on pure copper butt cold-welded welded joints HUANG Yong, YANG Xiao-juan, RAN Xiao-long 2020, 46 (6):  28-32.  Abstract ( 189 )   PDF (3491KB) ( 354 )   Save Cold pressing welding has outstanding advantages in the connection of functional materials because it does not have melting zone and welding heat affected zone. In this investigation, the butt cold pressing welding for pure copper rod was tested with compression/diameter ratio of the rod as a single variable, and conditions for obtaining better strength of welded joint were discussed in combination with numerical calculations of rod strain and microstructure analysis of joint deformation process. The results show that with the increase of the compression/diameter ratio of the pure copper rod, the effective plastic strain of each region of the welded joint increases, and therefore the maximum effective plastic strain at the joint interface goes up from 2.6 to 2.9. With the increase of strain, the proportion of recrystallized grains increases, and the tensile strength of the joint exhibits a stepwise increasing. References | Related Articles | Metrics

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Study on high speed welding technology of DP-TIG LIU Zi-gang, CHEN Fei, TANG Hai-hong, CHEN Liang 2020, 46 (6):  33-37.  Abstract ( 199 )   PDF (4638KB) ( 290 )   Save Deep Penetration TIG welding (DP-TIG welding) takes the advantage of deep penetration welding and has great advantages in the field of thick plate welding. In order to expand applications of DP-TIG welding in the field of high-speed welding of thin plates, the high-speed welding process of thin plates made of low carbon steel and stainless steel was investigated in this research by adjusting welding current, welding speed, tungsten cone angle, gas composition and other process parameters. The experimental results show that compared with conventional TIG welding, the welding speed of low carbon steel plate with 2 mm thickness is increased by 75%, and for stainless steel plate with 3 mm thickness, the welding speed is increased by more than 2 times. Moreover, with the decrease of tungsten electrode angle, the welding speed can be further improved. If a certain amount of H2 is introduced into the shielding gas, the maximum welding speed of stainless steel DP-TIG welding may be improved further to a certain extend. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Vibration characteristics and stress distribution of MW grade composite wind turbine blades AN Zong-wen, GAO Xing-feng, MA Qiang, KOU Hai-xia 2020, 46 (6):  38-42.  Abstract ( 233 )   PDF (2546KB) ( 419 )   Save In view of the unreasonable lamination in the finite element model of wind turbine blades at present, taking a 1.5 MW wind turbine blade as the research object, Solidworks software is used to generate three-dimensional model of blades, which is then imported into thelarge-scale finite element software Abaqus, and the zonal lamination can be generated according to the theory of blade lamination.The finite element model of the blade is used to make it closer to the true lamination condition of the blade. In the finite element numerical calculation, vibration characteristics of the blades and stress distributions in the blades under the limit wind speed of 50 m/s are analyzed. Our predicted results show that the established blade lamination model meets the design requirements in terms of mode, strength and rigidity. The dangerous section of the blade is located at about 1/3 from the tip of the blade, and the stress is mainly distributed at 1/3~2/3 from the tip of a blade, and the main bearing structure is the main beam and web of a blade. References | Related Articles | Metrics

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Influence of volute outlet position on performance of low specific speed centrifugal pump ZHAO Wei-guo, LI Shang-sheng, PAN Xu-wei, WANG Heng 2020, 46 (6):  43-51.  Abstract ( 242 )   PDF (5899KB) ( 333 )   Save In order to study the influence of volute outlet position on the performance of a low specific speed centrifugal pump, the outlet position of the volute is adjusted on the premise of ensuring that the base circle of the volute, the area and shape of the first eight sections, the outlet diameter of the volute and the center height keep the same. Three types of volute A, B and C are designed respectively as a result. Based on Reynolds averaging method and RNG k-ε turbulence model, the numerical calculation of a centrifugal pump with a specific rotating speed of 46 is carried out by taking clear water as a medium. The results show that the change trend of external characteristics of the centrifugal pump is basically the same under three different outlet positions, but the highest efficiency is different from each other. At each operating condition, the efficiency of type C is higher than that of type A and B. The higher efficiency region for the three types tends to shift to heavy operating conditions. For the three types of volute centrifugal pumps, the static pressure distribution, turbulent kinetic energy distribution and streamline distribution at inlet of the impeller are roughly the same under their respective working conditions, while the three distributions in outlet of the impeller and flow passage of the volute vary greatly. It has been illustrated that changing outlet position of the volute has little effect on flow field at inlet of the impeller, but affects mainly the change of the flow field both at outlet of the impeller and in the volute channel. References | Related Articles | Metrics

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Ultrasonic three-dimensional visualization nondestructive testing system based on UML YAN Chang-feng, ZHANG Luo-dan, LI Yan-jun, WANG Wen-bin 2020, 46 (6):  52-59.  Abstract ( 222 )   PDF (2437KB) ( 352 )   Save In order to meet the needs of 3D reconstruction using ultrasonic point cloud data in industrial NDT, a modeling method for ultrasonic 3D visualization NDT system based on combination of UML and component technology is proposed in this paper. By analyzing the system requirements and using the modeling method of the combination of UML and component technology, the ultrasonic 3D visual NDT system model is then established. This system model includes the model of system architecture, requirement, use case, static class, system sequence, activity and component deployment. A prototype of the ultrasonic 3D visual NDT software system is therefore developed, and the effectiveness of the modeling method is verified by examples. The development practice of the system model proves that the ultrasonic 3D visualization system based on the combination of UML and component technology has a lot of advantages of reasonable structure design, strong reusability, maintainability and expandability, which does provide an experimental basis and experimental platform for developing 3D reconstruction algorithm of ultrasonic point cloud and for using 3D visualization system in industrial NDT. References | Related Articles | Metrics

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Design and numerical simulation analysis of holding down   spring for floating cup axial piston pump YANG Guo-lai, GAO Wen-tao, DONG Ji-cheng, CHEN Chen, WU Cai-e 2020, 46 (6):  60-65.  Abstract ( 208 )   PDF (2581KB) ( 379 )   Save The unique structure of a floating cup floating on drum plate in a floating cup axial piston pump leads to possibility of the floating cup overturning. In this study, combined with structural characteristics of the floating cup pump, both the trajectory of the floating cup on the drum plate and the situation that the floating cup overturns under the action of centrifugal force and leads further to stuck in the process of motion are analyzed respectively. The analysis shows that a compression spring may prevent the floating cup from tilting from the drum plate and does not affect the normal movement of the floating cup. The design of the compression spring is also introduced, including the optimum spring radius, the adequate position and size of the plunger hole on the compression spring. Finally, the compression spring is then analyzed numerically by finite element method, and the results show that it is necessary to optimize and improve the structure around the screw hole of the compression spring. References | Related Articles | Metrics

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Effect of water retaining agent on two-dimensional infiltration of sandy loam soil moisture ZHAO Wen-ju, CAO Qiang-zhong, CAO Tao-hong, HU Jun-hong 2020, 46 (6):  66-71.  Abstract ( 155 )   PDF (2694KB) ( 240 )   Save In order to reveal the effect of amount of water-retaining agent on the two-dimensional infiltration of water into soils with and without sand cover, this study took a bare soil test group for comparison, the effects of different water-retaining agent dosage (0, 0.1%, 0.2%, 0.5%) on soil water infiltration under conditions of sand cover and non-sand cover were studied through a simulated single-point source infiltration experiment. The results show that the regularity of soil water infiltration under the two different conditions is basically the same. In the early stage of infiltration, with the increase of the amount of water-retaining agent, the smaller the infiltration rate is, the greater the cumulative infiltration is. The difference between the horizontal and vertical movement of the wetting front is not significant, while the horizontal and vertical ratio of the wetting body is not significant as well. The infiltration rate and cumulative infiltration in the middle stage of infiltration are consistent with those in the initial stage of infiltration, but both the horizontal ratio and vertical ratio of the wetting body increase in the horizontal direction and decrease in the vertical direction as a contrast. In the later stage of infiltration, the infiltration rate basically tends to be stable, and the cumulative infiltration continues to increase. The Kostiakov infiltration model can characterize the regularity of two-dimensional infiltration of water into sandy loam by the water-retaining agent. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Preparation of Ni and NiO nanoparticle composite structure and study on lithium storage performance ZHANG Qing-tang, BAI Yong-bao, MA Yan-hui, TANG Xi-xiu 2020, 46 (6):  72-76.  Abstract ( 221 )   PDF (2670KB) ( 235 )   Save Ni and NiO nanocomposite (Ni@NiO)as well as NiO were prepared by low temperature pyrolysis in air atmosphereusing C4H6O4Ni·4H2O and Ni(NO3)2·6H2O as raw materials. The microstructure and electrochemical properties of the two samples were characterized by XRD, SEM, cyclic voltammetry and galvanostatic charge-discharge method. Results from the characterizations show that both materials contain NiO crystals. Ni@NiO is formed by stacking spherical particles with a particle size of 20~110 nm, and NiO is composed of irregular micro-particles. Ni@NiO has better lithium storage performance. When the voltage keeps a range of 0~3 V and the current keeps a range of 0.1 A/g, the first charge specific capacity of Ni@NiO reaches as high as 827.7 mAh/g, and the first coulomb efficiency becomes 77.1% as a consequence. References | Related Articles | Metrics

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Preparation and adsorption properties of corncob based biochar WEI Hui-ge, LI Dai-yuan, MA Jun-hui, ZHOU Deng-feng, CUI Da-peng 2020, 46 (6):  77-84.  Abstract ( 587 )   PDF (2593KB) ( 501 )   Save Using agricultural waste corncob as raw material, biochar with low cost and high performance was prepared by hydrothermal carbonization (HTC) at different temperatures. The biochar has mesoporous structure and abundant oxygen-containing functional groups on its surface, such as —OH, C ==O, C—O and so on. Methylene blue (MB) was used as model adsorbent to further study the adsorption properties of the biochar. Results from the study of adsorption kinetics show that the adsorption behavior is in accordance with the pseudo second-order kinetics model, and the biochar obtained under the hydrothermal condition of 225 ℃ has the maximum adsorption capacity (41.37 mg/g) and the maximum adsorption rate. The adsorption equilibrium data agree well with the Langmuir isotherm model, indicating that the adsorption of MB on biochar belongs to monolayer adsorption, and the interaction between oxygen-containing functional groups on the surface of the biochar and the MB molecule is helpful to the adsorption process. References | Related Articles | Metrics

Automation Technique and Computer Technology

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Co-design of CPS dual security control and communication under DoS attack LI Wei, WEI Kai-feng, LI Ya-jie, SHI Ya-hong 2020, 46 (6):  85-97.  Abstract ( 214 )   PDF (2132KB) ( 250 )   Save In view of a class of CPS with actuator failure and DoS attacks, this paper studies the cooperative design of CPS dual security control and communication on the basis of concept of edge computation combined with event-triggered communication mechanism. Firstly, based on the resource allocation of edge computing, the CPS dual security control architecture under the discrete event trigger mechanism is proposed, meanwhile transforming the finite energy DoS attack into a special delay, and the closed-loop CPS model under fault and attack is established under the scheme of discrete event triggering. Secondly, the appropriate Lyapunov-Krasovskii functional with the aid of the time-delay system theory and using affine Bessel-Legendre and other inequalities are both constructed. The robust observer of state and fault estimation under DoS attack and the dual security control and communication collaborative design method under DoS attack are presented respectively. Finally, the effectiveness and feasibility of present theoretical results in this paper are verified by the simulation of four-tank water tank system. References | Related Articles | Metrics

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Dynamic social network differential privacy protection based on B+ tree index LIU Zhen-peng, WANG Shuo, HE Yu-peng, LI Xiao-fei 2020, 46 (6):  98-103.  Abstract ( 140 )   PDF (787KB) ( 218 )   Save The dynamic updating speed of social network is getting faster and faster. Aiming at the slow iteration speed of differential privacy protection methods in current social network, a differential privacy protection method of dynamic social network based on B+ tree index is proposed. By using the edge of B+ tree index social network graph, according to the characteristics of differential privacy parallelism combination, the index data of B+ tree are divided, and the data are assigned with different epsilon and epsilon ratios and added with Laplace noise, so as to achieve the overall high efficiency and strong local protection after data privacy. During the iteration, the efficient index of B+ tree is used to quickly locate the information to be updated, so as to realize the rapid iteration of differential privacy protection of dynamic social network. Experiments show that the B+ tree index effectively improves the iteration speed of differential privacy protection in dynamic social networks, and the parallelism of differential privacy improves the utility of data. This method effectively solves the problem of slow iteration of differential privacy protection in social networks. References | Related Articles | Metrics

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Precise regression prediction method based on coarse-to-fine and feature selection and its application in second language acquisition LIN Yu-ping, LONG Hong, SONG Pan-pan, LI Xiao-mian 2020, 46 (6):  104-111.  Abstract ( 157 )   PDF (1094KB) ( 265 )   Save To deal with the problem of uneven data distribution and the situation that many factors easily cause inaccurate prediction, this paper proposes an accurate regression prediction method combining coarse to fine and feature selection. First of all, this paper puts forward a prediction method from coarse-to-fine, which uses decision trees to roughly classify the sub-intervals of the prediction target for overcoming the problem that direct prediction may be difficult to accurately fit due to uneven data distribution and large prediction intervals. Next, taking into account of the small amount of data and the circumstance that many feature factors may cause over-fitting and some redundant features may affect the prediction accuracy of the model, this paper proposes a regression prediction method based on feature selection to improve the prediction accuracy. Compared with the traditional regression model, the experimental results on the data set of English achievement of college students and their personality factors have proved that the method from coarse-to-fine and feature selection proposed in this paper has higher precision and better stability. More flexible and feasible syllabus based on proposed method could be laid out to tackle students’ personality traits problem to enhance their competition capability and thus impel English education in China in the future. References | Related Articles | Metrics

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Robust economic dispatch of active distribution networks with distributed energy storage systems LU Yu-jiao, YOU Qing-shan, LIN Lin-xin-yan, LI Bo 2020, 46 (6):  112-118.  Abstract ( 167 )   PDF (1268KB) ( 418 )   Save To address the impacts of uncertainty of wind outputs on the power system operation, this paper proposes a robust optimization economic dispatch method in the active distribution network. The model is built on a worst-best theory that integrates Latin hyper cube sampling method for generating wind output scene set to represent uncertainty of wind outputs. The aims of the model is to minimize the operation costs for distributed energy storage and micro turbine, and purchase costs from the upper grid. The particle swarm optimization algorithm based on random mutation is used to solve the model, and the optimized results with the least operating cost in extreme scenarios can be obtained. The proposed approach is implemented on a 33-bus distribution system. Our results demonstrate that optimized dispatch can satisfy all of the constraints within forecast error of wind outputs. The comparison of the determined economic dispatch method demonstrate that the proposed method is more robust. References | Related Articles | Metrics

Architectural Sciences

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Influence of blasting vibration of Guanlinzi tunnel on the existing down-traversing road DENG Xiang-hui, XIA Dao-hong, WANG Rui, ZHANG Yong-jie 2020, 46 (6):  119-124.  Abstract ( 143 )   PDF (2028KB) ( 266 )   Save In blasting construction of a new tunneldowntraversing the existing road, vibrations produced by the blasting are very easy to cause damage to upper pavement structure or even failure of the structure. Taking the new Guanlinzi Tunnel of Bao-Han Highway as an example, the finite element method is used to simulate the peak vibration velocity, pavement stress and pavement displacement of ten key points of the pavement. Combined with monitoring results taking from on-site blasting vibration and vibration velocity, the influence of blasting vibration on the existing road is compared and analyzed in this paper. The main research conclusions are as follows:the peak blasting velocity of the ten key points occurs during cut blasting. Both the road surface stress and the road surface displacement of the existing road are small, which is not enough to cause damage of the existing road.According to results of our numerical simulation and field tests, the existing road safety can be ensured when the peak value of combined velocity caused by vibrations on upper pavement surface of the underpass is less than 0.035 m/s. References | Related Articles | Metrics

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Numerical analysis of the effect of horizontal boundary constrains on the buried pipes under static loading SUN Wen-jun, SONG Yang, XIAO Cheng-zhi, SUN Wen-jie, LIU Qian 2020, 46 (6):  125-130.  Abstract ( 147 )   PDF (4903KB) ( 315 )   Save Based on model test results, the influence of model size on the mechanical and deformation properties of a buried pipeline under static load is studied by finite element numerical simulation software. The numerical results showed that when the distance between outside wall of the pipeline and horizontal boundary falls into the range of less than 25D(D, pipe diameter), the ultimate bearing capacity of soil gradually increases with the increase of the model size in horizontal direction.The variation regularity of pipeline radial deformation ratio in the process of loading is obviously different while the model size is different.Under the action of surface static load, the pipeline is mainly subjected to circumferential pressure. And due to the arch effect of soils at the top of the pipeline, the earth pressure around the pipeline reaches the highest at side of the pipeline, the second at top of the pipeline, and the smallest at bottom of the pipeline.Regularities for bearing capacity of the soils at top of the pipeline, for the force for the pipeline to take and for the deformation the pipeline maintain basically the same when the horizontal expansion of the outer wall of the model box exceeds 20D. References | Related Articles | Metrics

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Engineering application of prefabricated concrete-filled tube bracing in deep excavation for shield shaft GUO Xue-yuan, ZHANG Ming-ju, WU Li-wei, HAN Liu-tao 2020, 46 (6):  131-136.  Abstract ( 229 )   PDF (1213KB) ( 219 )   Save In view of reality of small working surface and large depth of foundation pit when a deep foundation pit is excavated in shield shaft, a prefabricated concrete filled tube (PCFT) internal bracing structure is presented. The PCFT internal bracing consists of lightweight aggregate concrete members and anchors composed of double-limb rectangular steel tubes, and assembled by high-strength bolts.Taking the deep foundation pit project of a shield shaft in Beijing Metro Line 17 as background, research on the design and application of PCFT internal bracing foundation pit support were carried out. In the study, the information monitoring of supporting axial force, retaining pile deformation, pile top displacement and surface settlement was also carried out. The design technology of PCFT internal bracing is summarized and optimized later in engineering practice. The implementation effect and monitoring results show that erection construction technology of PCFT internal bracing is simple and easy. On the basis of effectively controlling the stability of the foundation pit and the safety of the surrounding environment, the PCFT internal bracing greatly improves the safety and convenience of shield shaft deep foundation pit construction. References | Related Articles | Metrics

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Properties and modify mechanism of tourmaline anionic powder modified asphalt ZHU Qu-ping 2020, 46 (6):  137-142.  Abstract ( 141 )   PDF (1178KB) ( 220 )   Save In order to investigate the pavement properties of tourmaline anionic powder modified asphalt, modified asphalt with different contents of tourmaline anionic powder were prepared by a high speed shear method, then, the high and low-temperature performance, viscosity-temperature property were studied by means of the conventional physical performance test, multiple stress creep recovery test (MSCR), bending beam rheometry (BBR) and Brookfield viscosimeter test, respectively. The microstructure, chemical composition and thermal properties of the modified asphalt were characterized and analyzed by means of X-ray powder diffraction (XRD), Fourier infrared spectrometer (FT-IR), optical microscope and differential scanning calorimetry (DSC) so as to investigate the modification mechanism of tourmaline anionic powder from a microscopic perspective. The results show that tourmaline anionic powder can significantly improve the high and low-temperature performance and viscosity-temperature properties of asphalt by virtue of its excellent thermoelectric and piezoelectric properties. Moreover, tourmaline anionic powder can be dispersed uniformly in the base asphalt and form a kind of cavernous network structure, which can effectively improve the technical performance of asphalt. Compared with base asphalt, both the Tg and ΔH are sigificantly improved, and the modified asphalt exhibit a better thermal stability. There is only physical interaction between tourmaline anionic powder and asphalt. References | Related Articles | Metrics

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The model for searching slope space slip surface based on three-dimensional displacement interpolation LI Zhong, WANG Hong-xing, ZHANG Xi 2020, 46 (6):  143-147.  Abstract ( 152 )   PDF (3562KB) ( 248 )   Save The determination of the location of the most dangerous slip surface is a key work in the study of side slope stability. The change of displacement characteristics of rock and soil in the process of slope instability is the most intuitive manifestation of stability state of the side slope. In this research, the displacement field of the side slope is numerically simulated by finite element method. The imported numerical simulation results are developed through coding by a kind of programming software. The spatial displacement interpolation algorithm is then adopted to realize an accurate and efficient search to the most dangerous slip surface on the side slope. Finally, the rationality of the proposed method and coded program is verified by a classical example of 3D side slope. This method does not need to assume the shape and position of slip surface, and the predicted result is reliable and meanwhile easy to program. References | Related Articles | Metrics

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Experiment on mix proportion of ceramic recycled concrete based on orthogonal design QIAO Hong-xia, PENG Kuan, CHEN Ke-fan, LI Jiang-chuan, Hong Fen 2020, 46 (6):  148-152.  Abstract ( 154 )   PDF (660KB) ( 426 )   Save In order to improve the recycling efficiency of ceramics, ceramic particles and ceramic powder were reused as aggregates and admixtures for ceramic-recycled concrete. By using test method of the orthogonal design and taking ceramic powder, ceramic particles, recycled fine aggregate, fly ash and silica fume as five factors, and setting further four levels for each factor, sixteen groups of mix proportion schemes are designed in this paper. Tests of compression and thermal conductivity are carried out respectively. The physical and mechanical parameters such as strength and thermal conductivity of the ceramic-recycled concrete are obtained therefore, and the optimal mix ratio is found as a result. The test results show that the best mix ratio is as follows: the mass fraction of ceramic powder is 10%, the mass fraction of ceramic particles is 20%, the mass fraction of recycled fine aggregate is 40%, the mass fraction of fly ash is 15%, and the mass fraction of silica fume is 5%. References | Related Articles | Metrics

Scientific

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Projectively coresolved Gorenstein flat complexes WU De-jun, ZHAO Zi-hong 2020, 46 (6):  153-158.  Abstract ( 162 )   PDF (761KB) ( 319 )   Save The concept of projectively coresolved Gorenstein flat complex is introduced. Over an arbitrary associate ring R, it is proven that G is a projectively coresolved Gorenstein flat complex if and only if each R-module Gm is a projective coresolved Gorenstein flat module for all m∈Z.Meanwhile, basic properties of projectively coresolved Gorenstein flat complexes are studied, and the relationship between projectively coresolved Gorenstein flat dimension of complex G and projectively coresolved Gorenstein flat dimension of each R-module Gm is discussed. References | Related Articles | Metrics

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Characterization for high dimensional semi-orthogonal wave packet frames CHEN Huan, CHEN Qing-jiang 2020, 46 (6):  159-167.  Abstract ( 120 )   PDF (765KB) ( 245 )   Save The existence of semi-orthogonal wave packet frames in the space of L2(Rn) is studied, and the characteristics of semi-orthogonal wave packet frames in the space of L2(R2) are characterized as well. The necessary and sufficient conditions for wave packet systems composed of several wavelet functions to form wave packet Basel frames are established. The equivalent condition for the wave packet frame to be a semi-orthogonal frame is obtained as well. References | Related Articles | Metrics

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Application of stress-strength interference theory in butt welds WEI Yao-bing, ZHANG Ru-peng, LIU Jian-hui, WANG You-liang 2020, 46 (6):  168-172.  Abstract ( 182 )   PDF (1495KB) ( 250 )   Save In order to solve the problem of whether the bearing capacity of steel bridge meets the actual demand, a method of applying stress-strength interference theory to the numerical analysis of butt weld of steel bridge is proposed in this paper. First of all, through static analysis of whole structure of the steel bridge, the stress states at different positions of main girder of the steel bridge can be obtained. Secondly, the reliability of butt weld under static loading is analyzed by the stress-strength interference theory. Finally, taking the butt welding of Q345 steel as an example, the feasibility of the proposed method is verified. The reliability of the butt weld with residual stress is predicted numerically as well. References | Related Articles | Metrics