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28 August 2022, Volume 48 Issue 4 Previous Issue    Next Issue

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Materials Science and Engineering

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Simulation on influence of natural convection for dendrite growth based on F-LBM model ZHU Chang-sheng, CAO Ya-xing, LEI Peng, FENG Li, MA Fang-lan 2022, 48 (4):  1-10.  Abstract ( 333 )   PDF (9844KB) ( 249 )   Save Based on the phase field model of binary alloy dendrite growth, a multifaceted alloy phase field model with the external fields such as coupling flow field,temperature field and concentration field is established.Under the natural convection,the single dendrite and multi dendrite are simulated to observe the changes of dendrite morphology,flow field and concentration field during the solidification of the dendrite.It was found that the natural convection iscaused by the change of temperature gradient and concentration gradient,and the symmetry of the dendrite as a whole is broken, the upstream tip growth is promoted and its speed is larger than that of the downstream tip,and the horizontal tip growth speed locate between those of the upstream and downstream tips. The growth speed and concentration of the secondary dendrite arm are basically the same as that of primary dendrite arm,the fluctuation of energy and structure on dendrites is more obvious. In addition,with the increase of anisotropy intensity,the dendrite size becomes larger,the growth rate is accelerated,the main dendrite arm becomes thinner,the internal depression becomes obvious,the tip becomes sharp,the spacing between secondary dendrite arms increases and when the anisotropy intensity of single dendrite is 0.05,there is an obvious “necking” phenomenon,when anisotropy intensity of multi dendrite is 0.03,there is an obvious “necking” phenomenon. References | Related Articles | Metrics

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Effect of process parameters on microstructure and properties of Ni60-Cu/BaF2·CaF2 directional structure coating WANG Yi, YIN Xiang, ZHOU Kai, WANG Xin-min WANG Xin-hua, REN Jun-qiang 2022, 48 (4):  11-18.  Abstract ( 164 )   PDF (3869KB) ( 430 )   Save Ni60-Cu/BaF2·CaF2 directional structure composite coatings were prepared by a combination of oxyacetylene flame spraying + induction remelting + forced cooling. The effects of induction remelting parameters on the microstructure, element distribution and microhardness of Ni60-Cu/BaF2·CaF2 directional structure coatings were studied with a fixed Cu/BaF2·CaF2 content. The research shows that the low induction remelting power (7 kW) can not provide enough heat of fusion for the coating, and can not guarantee the complete melting state of the coating,the too high induction remelting power (15 kW) will provide excessive heat input, which will cause excessive diffusion of matrix elements to the coating, coarse microstructure and reduced hardness.When the induction remelting power is 10 kW, the directional structural coating obtains good microstructure,and the structure is dense and the columnar crystal is obvious, the metallurgical bonding zone between the coating and the substrate is relatively smooth, and the hardness value of the coating is higher. References | Related Articles | Metrics

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Dissipative particle dynamics simulationof the self-assembled structural behavior of complex “star” surface-active polymers LI Hui, WANG Zhen-yu, WANG Ning, WEI Yuan-yuan ZHAO Hai-tao, CHEN Zhen-bin, LIN Qiao-li 2022, 48 (4):  19-24.  Abstract ( 211 )   PDF (3157KB) ( 242 )   Save Surfactant polymers are widely used in medical and chemical fields because of their ability to change the surface tension of solution. The micelles formed by self-assembly surfactant polymers in solution can determine the rheological properties, and a lot of researches have been carried out on the self-assembly behavior of surfactants, among which the factors affecting the formation of self-assembly structure are the focus. Dissipative particle dynamics (DPD) method is applied, the self-assembly structure of multi-arm "star" surfactant polymers is investigated. The effects of various factors on the self-assembly behavior of “star” surfactant polymers are explored by changing the hydrophilicity and hydrophobicity of chain segments, the types of hydrophilic groups and hydrophobic groups, and the structure of surfactant polymers. The results shows that star surfactant polymers can self-assemble into spherical layered columnar/tubular and vesicle micelles. The solvent conditions, length of hydrophobic chain and the type of hydrophilic and hydrophobic groups have significant effects on the morphology of micelles, and the vesicle deformation is obviously affected by the secondary topological structure. The self-assembly mechanism of the surfactant can be used in the research of oil drilling and drug delivery. References | Related Articles | Metrics

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Preparation of nano-ZnO by gentle liquid phase method and its photocatalytic performance LÜ Kang-le, SONG Jun-mi 2022, 48 (4):  25-29.  Abstract ( 171 )   PDF (1386KB) ( 369 )   Save Using ZnCl2 as the zinc source, a flower-like hexagonal wurtzite structure oxygen vacancy-deficient nano-ZnO material composed of zinc oxide particles with a particle size of about 17 nm was prepared by a liquid phase method. The structure, morphology and composition were characterized. The band gap of the prepared ZnO was calculated by UV-Vis absorption spectroscopy. Its photocatalytic properties were investigated using methylene blue. The results show that the oxygen vacancy defect ZnO nanomaterials have good crystallinity and morphology, and the band gap width is 3.17 eV, which is lower than that of ordinary ZnO. When photocatalytic degradation of methylene blue solution for 0.5 h and 2.5 h, the degradation rates are 20% and 80% respectively, and the degradation rate is 4 times higher than that of ordinary Ag nanoparticles doped zinc oxide, indicating that the prepared oxygen vacancy defect ZnO nanomaterials have excellent photocatalytic properties. References | Related Articles | Metrics

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Preparation of nitric acid modified carbon microspheres and its electrochemical performance KOU Yuan-zhe, LIU Hao-rui, ZHAO Lei 2022, 48 (4):  30-35.  Abstract ( 165 )   PDF (2605KB) ( 281 )   Save In order to improve the specific capacity of carbon electrode materials, the polystyrene microspheres synthesized by suspension polymerization were carbonized at high temperature, and then modified carbon microspheres electrode materials were prepared by concentrated HNO3 liquid phase treatment. The morphology and microstructure of the unmodified and modified carbon microspheres were characterized by emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption and desorption apparatus and Fourier transform infrared (FTIR) spectrometer,and the electrochemical properties of the modified carbon microspheres electrode materials were measured by cyclic voltammetry (CV) and constant current charge-discharge method. The results showed that the specific capacity of the modified carbon microspheres was up to 246 F/g at the current density of 0.625 A/g, and even at a high current density of 12.5 A/g, the specific capacity of the modified carbon microspheres was still higher than that of the unmodified carbon microspheres. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Residual strength degradation model of metal material based on gamma process WEI Yao-bing, ZHAO Cheng, ZHANG Zhen, LIU Jian-hui 2022, 48 (4):  36-42.  Abstract ( 281 )   PDF (1341KB) ( 376 )   Save Aiming at the problem of the residual strength of parts under multi-level loading not considering the loading sequence, the Schaff model is revised by introducing the loading sequence influence factor based on the Schaff model, and an equal damage ratio residual strength prediction model considering the effect of the loading sequence is established. With the aid of the shape parameter and size parameter of the Gamma function, the strength degradation process of the part is described. The fatigue test data of 45# steel and 30CrMnSiA are used to verify the accuracy of the model. The results show that the prediction accuracy of the modified equal damage ratio residual strength model is better than that of the Schaff model, and the Gamma process is consistent with the strength degradation process of the parts. References | Related Articles | Metrics

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Study on effect of laminate thickness on bridging and interlaminar fracture toughness ZHANG Yong-gui, MA Qi-wen, LIU Jian-hui 2022, 48 (4):  43-48.  Abstract ( 209 )   PDF (3399KB) ( 509 )   Save Accurate simulation and analysis of delamination propagation behavior of composite laminates is extremely significant for the structural design of laminates. In view of the deficiency that the existing research does not quantitatively describe the relationship between mode Ⅰ interlaminar fracture toughness and laminate thickness, a plane strain model was established with the help of ABAQUS finite element software. The iterative method was used to determine the influence of specimen thickness on the traction separation behavior in the bridging zone by controlling the ratio of the thickness to the layer number. At the same time, considering the cohesive constitutive relationship,when the thickness was 2, 4 and 8 mm,the delamination propagation behavior of unidirectional carbon/epoxy composites was studied by finite element method. The results show that the steady-state fracture toughness become higher with the increase of specimen thickness. However, the initial fracture toughness is independent of specimen thickness. The effect of specimen thickness on interlaminar fracture toughness of laminates is further verified, and the analytical results are in good agreement with the experimental values. References | Related Articles | Metrics

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Effect of slotted blade on cavitation performance of axial flow pump ZHAO Wei-guo, XUE Zi-yang, KANG Yan-dong, CHENG Chao, LI Qing-hua 2022, 48 (4):  49-55.  Abstract ( 215 )   PDF (5356KB) ( 517 )   Save In order to investigate the effect of the slotted blade on the cavitation control of the axial flow pump, the 350ZQ-70-H submersible axial flow pump is taken as the research object, and the flow field under different cavitation margins is simulated by steady and unsteady constant values. The velocity vector distribution, pressure distribution, internal void volume fraction and void volume change of the original model and the improved model are compared and analyzed. The results show that the slotted blade can improve the efficiency and head of the axial flow pump, and enhance the performance of the axial flow pump. The slotted blade increases the flow area at the blade inlet, reduces the flow velocity at the blade inlet, improves the pressure distribution in the axial flow pump impeller, and thus suppresses cavitation. In each stage of cavitation, the cavity volume fraction distribution of the slotted model is reduced, especially in the initial stage of cavitation, which is 30.4% lower than the original model, effectively inhibited the development of cavitation and significantly improved the cavitation performance. References | Related Articles | Metrics

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Study on evaluation method of product appearance scheme based on contingency-VIKOR theory LI Fen-qiang, YIN Yue, ZHANG Shu-tao, LU Yan-na, HAN Su-bin 2022, 48 (4):  56-63.  Abstract ( 204 )   PDF (1022KB) ( 330 )   Save Under the premise of the unity of function, material and structure, an evaluation method of product modeling scheme based on competitive analysis and user preference is proposed in order to carry out the evaluation of product appearance scheme effectively, aimed at solving some problems in the process of new product appearance design scheme evaluation, such as strong subjective fuzziness, unreasonable allocation of subjective and objective factors and proportion, which may lead to large errors in the evaluation results. Firstly, the user perceived similarity is obtained by the comprehensive research and analysis of the product model, and the design scheme is preliminarily screened by comparing the similarity between the design scheme and competitive products. Secondly, the comprehensive weight of the product modeling evaluation index is obtained by the entropy weight and the contingency theory. Finally, the overall ranking of product design schemes is calculated by combining the comprehensive weight of product modeling evaluation index with VIKOR method, so as to screen the product innovation schemes with high evaluator satisfaction and low similarity with competitive products in the market. Taking the evaluation of intelligent ejector modeling scheme as an example, the results of different methods are compared to verify the scientific and effectiveness of the proposed method. References | Related Articles | Metrics

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Cleaning and modeling of abnormal data of wind farm power curve CAO Li-xin, LIU Wei-min, GUO Hu-quan 2022, 48 (4):  64-70.  Abstract ( 467 )   PDF (3178KB) ( 759 )   Save The wind speed and power data of wind farms usually contain a large number of abnormal data, which is difficult to reflect the real working conditions of wind turbines, affect the accuracy of wind power prediction, and then cause certain economic losses. To solve this problem, the characteristics of abnormal data are analyzed, a slip-quartile abnormal data elimination method is proposed, and the wind speed power curve of the eliminated data is modeled by using high-order polynomial and Logistic function. Finally, the applicability and effectiveness of this method are verified by variance, root means square error and determination coefficient. The analysis in the example shows that the method is simple, efficient and versatile, and can significantly improve the accuracy of wind turbine power characteristic analysis. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Pressure analysis of nonlinear flow in multiple media of tight oil reservoir KANG Hao, LI Lin-kai, GAO Jian, HOU Mei-ling, LIU Sheng-li, ZHANG Ji-min 2022, 48 (4):  71-75.  Abstract ( 182 )   PDF (1792KB) ( 184 )   Save In order to realize the efficient development of the tight oil reservoirs, the multi-media mathematical model of multiple media tight oil reservoir is established on basis of flow equation analysis. The numerical solution of the model is obtained by the Newton-Raphson iteration method, which is used for the validation of the model. Then, the effects of nonlinear flow parameter, cross flow coefficient, elastic storativity ratio, and boundary conditions on well test curves are studied, respectively. Results show that the nonlinear seepage characteristic mainly affects the material exchange between fracture and matrix. When the cross flow ability between large-small fracture and large fracture-matrix is the same, there is only one caviton on the pressure derivative curve. Otherwise, there will be two cavitons. The increase of matrix storativity ratio lead to the increase of the depth of the two concavities at the same time, but the increase of micro fracture storativity ratio only increases the depth of the first caviton. References | Related Articles | Metrics

Automation Technique and Computer Technology

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Mechanical resonance suppression of permanent magnet servo system based on shaft torque compensation BAO Guang-qing, DU He-xuan, QI Wu-gang 2022, 48 (4):  76-82.  Abstract ( 193 )   PDF (2877KB) ( 689 )   Save Flexible drive will cause mechanical resonance in the AC permanent magnet servo system and degrade the dynamic performance and control accuracy of the system. Therefore, a Kalman filter-based resonance suppression method for shaft torque compensation is proposed. In this method, the shaft torque estimation value of the flexible drive device is obtained by Kalman filter, which is converted into a current signal and compensated to the given current loop, so as to eliminate the influence of the flexible transmission on the motor speed and improve the dynamic performance of the system. Finally, the effectiveness of the method is verified by simulation. References | Related Articles | Metrics

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Investigation on obstacle detection and recognition of façade-cleaning robot based on convolutional neural network GUO Run-lan, SHI Fang-qing, FAN Ya-qiong, HE Zhi 2022, 48 (4):  83-89.  Abstract ( 207 )   PDF (4742KB) ( 539 )   Save Combined with the working principle of the robot and the application of convolutional neural network (CNN) of image classification, a wall obstacle detection and recognition algorithm based on CNN is proposed. Firstly, with the goal of accurate recognitionof wall obstacles, the image database of wall obstacles is constructed, and then the simplified VGG-16 network is optimized to obtain a CNN model, which is suitable for accurate recognition of wall obstacles. On this basis, the network is designed to be composed of an input layer, four convolutional layers, two pooling layers, a fully-connected layer and an output layer. Further, the training samples are convolved using 3×3 convolution kernels, and the acquired feature maps are pooled in 2×2 domains. After repeating the above operations, the optimal network model is obtained by learning and the network model parameters are further determined. The experimental results show that the recognition accuracy of obstacles can reach 99.0%, which has good recognition ability. References | Related Articles | Metrics

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An evaluation method of critical nodes in complex network based on accurate k-shell LU Peng-li, XU Xing-zhou 2022, 48 (4):  90-98.  Abstract ( 260 )   PDF (3023KB) ( 301 )   Save Critical nodes are the core elements of complex networks and can play a critical role in maintaining structural stability and information transmission. The k-shell is a common measure index of node importance. But due to its shortcomings such as destroying the overall structure information of the network and ignoring the influence of neighboring nodes, it is difficult to ensure that each node can be quantitatively distinguished. In order to improve the accuracy of node identification, this paper firstly improves the decomposition process of k-shell and proposes the Ak (accurate k-shell). Considering the influence of local feature information and global structure information on nodes in the network, the Ak is applied to the gravity centrality and the AGC (accurate gravity centrality) is proposed, subsequently. Because of the good expansibility for Shannon entropy in informatics has good expansibility in the identification of key nodes in the network,the MC (mixed centrality) is finally proposed to evaluate the importance of nodes pluralistically by combining Shannon entropy of neighborhood centrality, neighborhood Ak and AGC. Under 7 kinds of real networks, a series of experiments on the monotonicity and accuracy of MC and other node evaluation indexes in terms of monotonicity and accuracy were conducted. The experimental results show that MC has better performance in identifying key nodes. References | Related Articles | Metrics

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Short-term traffic flow prediction model based on IFA optimized RBF neural network CAO Jie, ZHANG Min, ZHANG Hong, CHEN Zuo-han, HOU Liang 2022, 48 (4):  99-104.  Abstract ( 202 )   PDF (1281KB) ( 292 )   Save Aiming at the problem of low accuracy of prediction results caused by the extremely strong uncertainty of short-term traffic flow data, a short-term traffic flow prediction model(IFA-RBF) based on the improved firefly algorithm (IFA) optimized RBF neural network is proposed. By introducing linear decreasing inertial weight and chaos mechanism, the model improves the shortcoming of being trapped into local extremes and lack of population diversity in the later stage of FA. IFA is used to optimize the connection weight and basis function width of the RBF neural network is used to improve the prediction accuracy of the RBF network. Experimental results show that compared with Elman, BP, RBF and FA-RBF models, the constructed model has higher prediction accuracy, and the predicted value has higher fitting degree with the real value. References | Related Articles | Metrics

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Study on hyper-ellipsoidal Bayesian network method for evaluating reliability of pantograph system QI Jin-ping, ZHOU Ya-hui, WANG Kang, LI Shao-xiong 2022, 48 (4):  105-110.  Abstract ( 141 )   PDF (661KB) ( 227 )   Save Aiming at the characteristic of complex polymorphism of the pantograph system and the difficulty in expressing the accuracy of the failure probability, and the current situation that the existing research is mainly stuck in the fuzzy Bayesian network combined with the evidence theory, the hyper-ellipsoidal Bayesian network is introduced for the first time into the reliability analysis of pantograph, which avoids the extreme value of the fuzzy Bayesian network interval and further defines the probability value interval of the root node. Then the hyper-ellipsoidal Bayesian network is used to solve the reliability parameters such as leaf node failure rate, sensitivity and posterior probability of the pantograph system under different fault states, and the high-risk events of the system are found out. Compared with the fuzzy Bayesian network, it can be seen that the interval of the hyper-ellipsoidal Bayesian network is smaller, which verifies the correctness and practicability of the new method. References | Related Articles | Metrics

Architectural Sciences

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Performance of different steel-reinforced concrete filled steel tubular composite members under transverse impact load DANG Li-rong, LIU Xin-wen, ZHANG Lin-zhi, CAO Xu-dong, QI Sheng-wang 2022, 48 (4):  111-118.  Abstract ( 177 )   PDF (3421KB) ( 344 )   Save The numerical model of steel-reinforced concrete-filled steel tubular composite members under transverse impact load was established in ABAQUS, and the correctness of the model was verified through previous transverse impact tests. The effect of three different profiled steel on the transverse impact performance of concrete-filled steel tubular (CFST) members were compared. The mid-span deflection, impact force and sectional moment of the composite members during impact were analyzed, and the influence of parameters of profiled steel on the impact resistance of specimens was discussed. The results demonstrate that the overall deformation of the CFST members under the transverse impact load can be reduced by reinforcing the section steel, and impact resistance of the membersincreases. When the profiled steel ratio is same, the composite specimens with I-shaped profiled steel have the best impact resistance. The profiled section form has a significant influence on the bending moment distribution of composite members. When the profiled steel ratio remains constant, the impact resistance of the specimen gradually increases with the increase of the profiled steel web height, and the outspread section form of the profiled steel is more favorable for impact resistance. The distribution position of the angle steel has a certain influence on the impact resistance of the specimen, and the impact resistance increase with the profiled steel ratio. References | Related Articles | Metrics

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Stability analysis of high fill slope with loess under earthquake and rainfall infiltration YUAN Zhong-xia, LI De-peng, YE Shuai-hua 2022, 48 (4):  119-125.  Abstract ( 287 )   PDF (2951KB) ( 365 )   Save In order to investigate the effect of earthquake and rainfall infiltration on the stability of loess high fill subgrade slope, a dynamic seismic calculation, complete fluid-solid coupling calculation and strength reduction calculation are used to analyze and compare the loess high fill slope in use. The displacement time history, acceleration power spectrum, suction, effective stress and minimum safety factor of slope soil are used to study the effect of earthquake and rainfall infiltration conditions on the stability of loess high fill slopes. The results show that the effect of earthquake on the surface soil of loess high fill slope is greater than that on the base soil. The influence range of rainfall infiltration on the slope soil is surface soil and shallow soil. Rainfall infiltration reduces the suction and effective stress of the surface soil of the slope, while the local suction of the shallow soil is increased. In the process of rainfall, the effective stress of slope surface soil is decreased, the effective stress of the shallow soil is increased first and then decreases gradually. After the earthquake, the infiltration of the slope causes the change of the most dangerous slip surface area of the slope, the rainfall rate and rainfall duration have an impact on the minimum safety factor, and the minimum safety factor of the slope is decreased after the rainfall. This study provides a reference for the study of the stability of loess high-filled slope under 3D conditions of earthquakes and rainfall infiltration. References | Related Articles | Metrics

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Experimental study on repair of concrete cracks by microbial action CAO Hui, ZANG Yang, FENG Qiong, KANG Kai-wei YE Hu-zi, GOU Bao-xia, LIU Jun-jun 2022, 48 (4):  126-131.  Abstract ( 439 )   PDF (4574KB) ( 451 )   Save Microbial mineralization can effectively heal concrete cracks and therefore achieving the purpose of repairing concrete structures. In this paper, concrete specimens with cracks were taken as the research object. Bacillus pasteurii was used as the healing agent to repair the concrete specimens under different crack conditions, i.e. with width of 0.2 mm, 0.3 mm and 0.6 mm and depth of 20 mm and 30 mm, respectively. Through crack observation, ultrasonic testing, compressive strength testing and microscopic morphology analysis, the repair effects of the selected microorganism on concrete cracks were evaluated. The results show that Bacillus pasteurii can repair the surface cracks of concrete effectively. The supply of oxygen provides the necessary environmental condition for the mineralization of microorganisms inside the cracks. As the depth of the crack increases, the repair effect of Bacillus pasteurii decreases, and as the width increases, the mineralization effect of microorganisms in the cracks is weakened. References | Related Articles | Metrics

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Influence of freeze-thaw cycles-dynamic water scouring cycles on the characteristic parameters of intermittently graded asphalt mixture DANG Zhi-rong, NIAN Teng-fei, LIU Zong-cheng, JIANG Ji-bin YANG Hai-li, SHI Guo-xiong 2022, 48 (4):  132-137.  Abstract ( 232 )   PDF (3053KB) ( 374 )   Save Under the long-term action of water, temperature and load, the service life of asphalt pavement is significantly reduced. In order to explore the decay law of asphalt mixture road performance, a dynamic water scour simulation test device for asphalt mixtures was independently developed. The asphalt mix Marshall specimens were subjected to multiple freeze-thaw cycles-dynamic water scouring cycles to analyze the change law of asphalt mix characteristics parameters, combined with CT slice scanning to explore the law of internal structural changes of asphalt mixes. The results show that each characteristic parameter shows a faster growth or decay in the pre-freeze-thaw cycle-dynamic water scour cycle. Under the action of applied dynamic water pressure, the internal water absorption of asphalt mixture will gradually increase to the full water state, and the micro-open pores inside the asphalt mixture specimens will undergo structural and morphological changes. The splitting strength of the asphalt mixture was reduced by up to 65.44% after 12 freeze-thaw cycles-dynamic water scouring cycles. The research results provide a theoretical basis for further understanding of the water damage mechanism of asphalt pavements. References | Related Articles | Metrics

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Research on application of stress equivalent method in single beam static load test JIANG Guo-fu, ZHUO Xiao-li, JIANG Jin-yi, HAO Tian-zhi 2022, 48 (4):  138-143.  Abstract ( 212 )   PDF (2367KB) ( 376 )   Save The determination of static test load of single beam usually takes the loading efficiency of control bending moment as the control objective, and the conventional method is “moment equivalent method”. However, the actual stress characteristics of single beam do not conform to the stress state of the completed bridge, which makes the calculation value of test load distorted. In order to solve the above problem, this paper proposes a more practical “stress equivalence method”. By using MIDAS/Civil finite element software, the stress state of precast box girder with different spans is calculated, and the calculation results of “stress equivalent method” and “moment equivalent method” are compared and analyzed. The results shows that the “stress equivalent method”, that is, the superimposed stress or the bending moment calculated by the inverse superposition stress as the control index in the static load test, is closer to the actual stress state of the structure. Compared with the bending moment calculated by the “moment equivalent method” as the calculation method of controlling internal force, the “stress equivalent method” is about 12% less, which can reduce the misjudgment of load test, and has certain guiding significance for the load test of single beam of similar bridges. References | Related Articles | Metrics

Scientific

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A characterization of FC-projective modules over triangular matrix rings WU De-jun, FU Jia-hui 2022, 48 (4):  144-151.  Abstract ( 182 )   PDF (614KB) ( 242 )   Save Let T=A0 UB be a formal triangular matrix ring, where A and B are rings and U is a (B, A)-bimodule. Equivalent characterizations of left T-modules of finite cogeneration and finite corepresentation on the formal triangular matrix ring are given. Furthermore, a characterization of FC-projective left T-modules over the formal triangular matrix ring is given. As an application, the FC-projective dimensions of left T-modules are discussed. References | Related Articles | Metrics

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A model of single-specie with time lag and contraception control LI Qiu-ying 2022, 48 (4):  152-156.  Abstract ( 156 )   PDF (507KB) ( 167 )   Save Based on ecological security, sterile technology has gradually become the development direction of rodent control, which can control rodent population more permanently and thoroughly than poison. Combined with the valid period of sterilant, a single-species population under sterility control is established. After the discussion of the conditions for the existence of equilibrium points, the necessary and sufficient conditions are obtained for guaranteeing global asymptotic stability of the zero equilibrium points, and the sufficient condition is obtained for guaranteeing global asymptotic stability of the positive equilibrium point. In the end, the effects of contraception control and the valid period of sterilant on the dynamics of the pest population are analyzed. References | Related Articles | Metrics

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On the f-complexity and cross-correlation of some binary sequences LIANG Jia-yi, XUE Pan 2022, 48 (4):  157-162.  Abstract ( 188 )   PDF (541KB) ( 320 )   Save The binary sequences constructed using the Legendre symbols has strong pseudo-randomness. In this paper, based on Legendre symbol and the estimation of character sums of polynomials and exponential, two kinds of binary sequences families with good pseudo-randomness are constructed, both of which have great f-complexity and little cross-correlation measure. References | Related Articles | Metrics

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Interaction of collinear double cracks in superconductor slab with inclusions ZHAO Yu-feng, XU Tao 2022, 48 (4):  163-167.  Abstract ( 136 )   PDF (2198KB) ( 323 )   Save A YBCO superconducting slab model with circular inclusion and longitudinal through collinear crack is established. Under the action of Lorentz force generated by external magnetic field, the interaction between two collinear cracks in YBCO superconductor with inclusion is studied, and the Bean model is used to describe the electromagnetic behavior of the superconductor. The stress intensity factor (SIF) at the crack tip is determined and the related magnetoelastic stress analysis is conducted. The results show that the size of external magnetic field, viscous magnetic flux flow velocity v0, inclusion size, crack length, inclusion radius and the ratio of inclusion to matrix Young’s modulus all have an effect on the stress intensity factor. References | Related Articles | Metrics

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Measuring the topological charge of vortex beams with three-slit interference XU Quan-xue, ZHENG Si-min, YUAN Cai-fu, WANG Tao 2022, 48 (4):  168-172.  Abstract ( 193 )   PDF (1470KB) ( 450 )   Save The distribution of interference fringes in the interference field of vortex beams after three slit interference is studied, and the effect of topological charge number on the fringe distribution is discussed on the different conditions with topological charge number of integer and fraction. It is shown that unlike the plane wave, the fringes of the vortex beam move along the lateral direction after three-slit interference, and the magnitude and direction of lateral displacement of the fringes are related to the value of topological charge. References | Related Articles | Metrics