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Uniaxial Compression Failure Mechanism and Acoustic Emission Characteristics of Granite with Y-Type Composite Joints Peng-hai ZHANG, Qing-shan MA, Xi-ge LIU, Tian-hong YANG Journal of Northeastern University(Natural Science)    2024, 45 (4): 564-572.   DOI: 10.12068/j.issn.1005-3026.2024.04.014 Abstract （1234）   HTML （22）    PDF （8178KB）（154）       Y?type composite joints with different inclination angles are prefabricated in granite specimens using the splitting method， and uniaxial compression experiments are conducted. The effects of the inclination angle of the composite joint on the failure mode， peak strength， surface deformation field， and acoustic emission energy release characteristics are analyzed， and the failure mechanism under different failure modes is explored. The experimental results show that： 1） Rock with Y‐shaped composite joints exhibit three main failure modes： overall failure， wedge ejection failure， and failure along the main joint surface， which vary with joint inclination； 2） The angle of composite joints and the inclination angle of main joints have a negative correlation with rock strength； 3） When the failure mode transitions changes from overall failure to ejection failure and failure along the main joint， the concentrated slip deformation zone shifts from the secondary joint to the main joint， and the high‐energy AE events induce a transition from the main and secondary joint compaction and slip dislocation to the main joint compaction and slip dislocation； 4） As the inclination angle of the main joint increases， the energy released on the main joint surface is higher and the distribution of energy is more uneven. Table and Figures | Reference | Related Articles | Metrics

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Control Mechanism and Early Warning of Rainfall- Induced Landslide Based on NPR Anchor Cable Zhi-gang TAO, Guang-cheng SHI, Xiao-jie YANG, Man-chao HE Journal of Northeastern University(Natural Science)    2024, 45 (4): 573-583.   DOI: 10.12068/j.issn.1005-3026.2024.04.015 Abstract （1203）   HTML （17）    PDF （12091KB）（180）       In order to study the control and the early?warning prediction technology for rainfall?induced landslide， the similar model test was designed by analyzing the spatial and temporal characteristics of slope deformation of Xiongjia Mountain landslide. Using ordinary Poisson’s ratio （PR） anchor cable and negative Poisson’s ratio （NPR） anchor cable as reinforcement materials， the law of rainfall?induced landslide and control mechanism of anchor cable were analyzed by using high?speed photography， pore pressure， earth pressure and anchor cable force sensors， and the evolution law of the Newtonian force during landslide was explored based on field tests. The results show that the sudden drop in pore water pressure is approximately synchronized with the local collapse of slope. NPR anchor force drop abruptly， causing local deformation in slope. The PR anchor cables fail because they cannot withstand large deformation， while the NPR anchor cables have high?stress energy absorption control functions due to the constant resistance and large deformation characteristics， enabling the slope to reach a secondary equilibrium state. The NPR anchor cable exhibits a significant deformation?slip dynamic law characterized by a first sudden increase followed by a sudden drop before the landslide. The field test revealed the Newtonian force evolution law in the whole process of the landslide， and obtained the early?warning time parameters of the Xiongjia Mountain landslide 7.5 h in advance. Table and Figures | Reference | Related Articles | Metrics

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Microscopic Failure Characteristics of Sandstones with Different Composition and Microstructures Da-zeng SUN, Wen ZHAO, Xing-liang XU, Xin WANG Journal of Northeastern University(Natural Science)    2024, 45 (4): 584-591.   DOI: 10.12068/j.issn.1005-3026.2024.04.016 Abstract （1182）   HTML （18）    PDF （5822KB）（266）       In order to study the interconnection between macroscopic and microscopic failure characteristics of different textured sandstones， three types of sandstones from Xianghualing mining area were analyzed using petrographic analysis， sedimentary phase discrimination， and uniaxial compression and shear tests to observe the microscopic structural characteristics. The results show that compressive strength of terrestrial sedimentary quartz sandstone is the largest， followed by feldspathic sandstone， and marine sedimentary glauconitic sandstone is the smallest. In uniaxial compression， quartz sandstone and feldspathic sandstone exhibit brittle failure on a macroscopic scale， while glauconitic sandstone shows ductile failure with softening characteristics. On the microscopic scale， quartz sandstone undergoes intergranular failure with a smooth surface， while feldspathic sandstone experiences intergranular and transgranular failure with a small scallop?shaped surface and minimal adhering debris， and glauconitic sandstone displays a flat?granular composite fracture surface with obvious grain crushing and pronounced scratches. The failure characteristics are jointly controlled by the grains， cemented material and structural weak planes. The shear test microscopically shows that the quartz sandstone occurs has transgranular failure first and then intergranular failure， with uneven surface， scrapes and debris， while the feldspathic sandstone occurs transgranular failure mainly and intergranular failure， with partially flat surface， scrapes and debris. The glauconitic sandstone simultaneously exhibits intergranular and transgranular failure， resulting in a smooth surface with almost no abrasion or debris. The microscopic failure characteristics are influenced by the grain strength and cementing materials. Table and Figures | Reference | Related Articles | Metrics

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Ferrite Phase Transformation Model of DP600 Hot Rolled Dual-Phase Steel Under ESP Process Xiao-guang ZHOU, Xin MA, Shan JIANG, Zhen-yu LIU Journal of Northeastern University(Natural Science)    2024, 45 (4): 483-489.   DOI: 10.12068/j.issn.1005-3026.2024.04.004 Abstract （1172）   HTML （24）    PDF （1445KB）（204）       In order to establish ferrite phase transformation kinetics mathematical model of DP600 hot rolled dual-phase steel under the ESP process condition， the isothermal phase transformation and continuous cooling phase transformation experiments were conducted on the experimental steel by using the dynamic phase transformation dilatometer. Based on the measured ferrite phase transformation incubation time and ferrite volume fraction， the incubation time of ferrite phase transformation was calculated by combining classical nucleation theory above the deformation temperature， and the incubation time of ferrite phase transformation below the deformation temperature was calculated by fitting ? G_{\mathrm{V}} according to the experimental data. Considering the influence of cooling rate， the additivity rule was modified and based on this， the starting temperature and volume fraction of ferrite phase transformation under continuous cooling conditions were calculated. The results showed that the calculated starting temperature and volume fraction of ferrite phase transformation using the modified phase transformation model are in good agreement with the measured values， which can be used to predict the ferrite phase transformation behavior of DP600 dual-phase steel under the ESP process. Table and Figures | Reference | Related Articles | Metrics

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Regulation of Secondary Carbide Characteristics and Its Effect on Wear Resistance of High Carbon High Alloy Martensitic Steel Jin-zhe JIANG, Yue LIU, Chun-ming LIU Journal of Northeastern University(Natural Science)    2024, 45 (4): 490-498.   DOI: 10.12068/j.issn.1005-3026.2024.04.005 Abstract （1161）   HTML （28）    PDF （2514KB）（277）       The size and content of secondary carbide have an important effect on the mechanical properties and wear resistance of high carbon high alloy martensitic steel. In this paper， the evolution behavior of secondary carbide during forging and spheroidizing annealing process were studied by scanning electron microscope and transmission electron microscope， and its effects on mechanical properties and wear resistance of high carbon high alloy martensitic steel were also studied with abrasion wear testing machine. The results show that spheroidizing annealing significantly increases the content and size of secondary carbide in forged and air?cooled steel. The secondary carbide refine the austenite grain size by pinning grain boundary and reduce the solid solution content of alloying elements in martensite， which effectively improves the impact toughness of experimental steel. The micron?sized secondary carbide and ductile martensite matrix hinder abrasive cutting and reduce the microscopic fracture on worn surface effectively， which improves the wear resistance of experimental steel. Table and Figures | Reference | Related Articles | Metrics

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Material Removal Mechanism During Ultrasonic Vibration Assisted Grinding AISI 304 with Single CBN Grain Zhen-yu YANG, Ping ZOU, Liang ZHOU, An-qi WANG Journal of Northeastern University(Natural Science)    2024, 45 (7): 1011-1019.   DOI: 10.12068/j.issn.1005-3026.2024.07.013 Abstract （1161）   HTML （2）    PDF （5703KB）（127）       In order to explain the removal mechanism of abrasive cutting materials under ultrasonic action， the single grain grinding process was analyzed， and the mathematical model of undeformed cutting thickness and the fixed velocity ratio （vs/vw） of abrasive and workpiece was established. The single grain tests of conventional grinding （CG）， tangential ultrasonic vibration assisted grinding （TUVAG） and radial ultrasonic vibration assisted grinding （RUVAG） with a fixed speed ratio were carried out on AISI 304 specimens. The results showed that the specimens are removed by plastic deformation under the action of CG and TUVAG at the fixed speed ratio， but the ultrasound significantly improves the material removal rate. The material removal method of the specimen under RUVAG was closely related to the value of the maximum undeformed cutting thickness agmax. When agmax is less than 0.8 μm， the specimen was removed in the form of brittle fracture. After that， with the increase of agmax， the specimen was removed in the form of plastic deformation. Table and Figures | Reference | Related Articles | Metrics

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Mechanism and Efficiency of Combined Longitudinal-Torsional Vibration-Assisted Rock Drilling Da-yong GAO, Jian-yong LIN, Ya-ting TIAN, Hong-liang YAO Journal of Northeastern University(Natural Science)    2024, 45 (4): 555-563.   DOI: 10.12068/j.issn.1005-3026.2024.04.013 Abstract （1142）   HTML （15）    PDF （2491KB）（109）       In response to the limitations posed by singular longitudinal or torsional vibration‐assisted rock drilling， a combined longitudinal‐torsional vibration‐assisted rock drilling scheme was proposed. Firstly， the theoretical model of the scheme is analyzed. Then， DEM （discrete element method ） simulations using EDEM （event driven execution manager） software are conducted to simulate the drilling mechanism and effects on rocks under various conditions. Results indicate that the addition of combined longitudinal‐torsional vibration assistance decreases the maximum resultant force on the drill bit by 36.45%， 9.34% and 32.84%， respectively， compared to zero vibration， longitudinal vibration， and torsional vibration schemes. Moreover， drilling speeds increase by 26.02%， 4.27% and 16.13%， respectively. Finally， experimental validation of the proposed scheme’s drilling performance reveals a 35.48% reduction in the drill head’s support strain and a 31.25% increase in the drilling speed when compared to solely adding torsional vibration assistance. It is demonstrated that the combined longitudinal‐torsional vibration‐assisted method can significantly enhance the efficiency of rock drilling. Table and Figures | Reference | Related Articles | Metrics

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Effect of Feeding Steel Strip Carbon Content on Macrosegregation Distribution in Large Continuous Casting Round Bloom Yu-chao YAO, Zhong-qiu LIU, Wen-jie RONG, Bao-kuan LI Journal of Northeastern University(Natural Science)    2024, 45 (4): 499-506.   DOI: 10.12068/j.issn.1005-3026.2024.04.006 Abstract （1067）   HTML （21）    PDF （1891KB）（178）       Feeding a cold steel strip into continuous casting （CC） mold is an effective method to improve the center quality of large round bloom. A liquid‐columnar‐equiaxed solidification three‐phase volume averaged solidification model was developed to explore the effect of feeding strip carbon content on solidification structure and macrosegregation distribution of large CC round bloom in this paper. The results show that the carbon content of feeding steel strip has a significant effect on the growth of equiaxed crystals and columnar crystals. Under the condition of both low and high strip carbon contents， the effect of feeding steel strip on increasing equiaxed grain volume fraction will be reduced. The solute concentration and distribution in the casting bloom can be directly affected by regulating the solute concentration of steel strip. The steel strip with 1.0 times the carbon content of casting steel （ r_{\mathrm{C}} =1.0） has the best improvement effect on the large CC round bloom， with the radial extreme difference of carbon content and macrosegregation index of the bloom being 0.165 7% and 38.36%， respectively. Table and Figures | Reference | Related Articles | Metrics

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Removal Mechanism and Effect of Parameters on Grinding Force in Grinding SiC Ceramics Yun-guang ZHOU, Chuan-chuan TIAN, Shu-hai WANG, Han CHEN Journal of Northeastern University(Natural Science)    2024, 45 (4): 548-554.   DOI: 10.12068/j.issn.1005-3026.2024.04.012 Abstract （1060）   HTML （13）    PDF （1695KB）（217）       In order to explore the removal mechanism and influence law of grinding force in grinding SiC ceramics， the simulation model of single abrasive striking SiC ceramics was established based on the SPH（smoothed particle hydrodynamics） method， and the crack generation and propagation mechanism during grinding SiC ceramics were analyzed； the effect of grinding velocity （vs）， feeding rate （vw） and grinding depth （ap） on the removal mechanism， the normal grinding force and tangential grinding force of grinding SiC ceramics were analyzed by the single factor experiment. The results showed that the abrasives striking the workpiece lead to the generation of the median cracks and the transverse cracks. With the increase of abrasive pressing depth， the transverse crack expands to the material surface， and when the transverse crack expands to the material surface， the brittle fracture occurs. With the increase of vs， the decrease of vw and ap， and the decrease of the area and depth of the pits on the grinding surface， the plastic removal area becomes larger， and the normal grinding force and tangential grinding force both decrease. These results may provide an important basis for high‐efficiency and low‐damage machining of SiC ceramic components. Table and Figures | Reference | Related Articles | Metrics

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Critical Fluidization Characteristics of Iron Ore in Fluidized Bed Reactor Zhi-ming LI, Yue-xin HAN, Yong-sheng SUN, Zhi-dong TANG Journal of Northeastern University(Natural Science)    2024, 45 (4): 592-599.   DOI: 10.12068/j.issn.1005-3026.2024.04.017 Abstract （943）   HTML （15）    PDF （1622KB）（170）       The U‐type reaction chamber is a core component of suspension roasting equipment， the critical fluidization characteristics of materials have both theoretical and practical significance. Therefore， this paper built a cold test system， and conducted research using hematite powder and aluminum oxide powder as materials to study the influence of aeration air volume， material properties on the critical fluidization characteristics， and modified empirical formula of critical fluidization characteristics based on the test. The results show that the critical fluidization gas velocity increases with the increase in particle size and density of materials. The critical fluidization velocity decreases with the increase of the aeration air volume under the condition of a fixed bed in the loosening chamber， the modified formula fits well with the experimental results and can be used to predict fluidization behavior. The research results are helpful to realize the integration of suspension roasting technology and equipment， and also have certain guiding significance for industrial applications. Table and Figures | Reference | Related Articles | Metrics

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Hybrid Denoising Algorithm for Medical CT Sequence Images Jin-lin CHEN, Pei-xin YUAN Journal of Northeastern University(Natural Science)    2024, 45 (4): 464-473.   DOI: 10.12068/j.issn.1005-3026.2024.04.002 Abstract （942）   HTML （32）    PDF （2210KB）（274）       The medical CT sequence images dopes noise for various reasons. Denoising can effectively improve image quality. The common algorithms are used for single image， while the CT sequence images have high similarity between adjacent images. Therefore， this paper proposes a hybrid denoising algorithm based on the structural similarity. Firstly， a histogram is drawn according to the maximum and minimum gray value. Secondly， relevant threshold parameters are set to calculate the window width and window level， and then conduct window adjustment. Thirdly， the structural similarity of the target image and its adjacent images are calculated. Finally， BM3D and Gaussian filtering algorithms are mixed for three images according to structural similarity. Experimental results show that the algorithm can improve the mean square error， peak signal?to?noise ratio and structural similarity， which effectively improves the image quality. Table and Figures | Reference | Related Articles | Metrics

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Optimization of Argon Bottom Blowing During Electric Heating Stage of LF Refining Process Ning WANG, De-yue QIN, Bao-kuan LI, Jia-qi ZHAO Journal of Northeastern University(Natural Science)    2024, 45 (4): 507-513.   DOI: 10.12068/j.issn.1005-3026.2024.04.007 Abstract （932）   HTML （22）    PDF （2094KB）（263）       During the electric heating stage of the LF （lalde furnace） refining process， dual?nozzle equi?flow argon blowing is often used. This paper proposes a bottom blowing method of dual?nozzle non?equi?flow argon blowing. A 1∶4 non?isothermal water model experimental platform was designed based on a 135 t ladle in a steel plant. Under the same total flow rate， temperature homogenization experiments were conducted with bottom blowing ratios of 1∶1， 2∶1 and 3∶1. The results show that the minimum dimensionless temperature difference and the best homogenization effect were observed at each monitoring point when the bottom blowing ratio was 2∶1. The coupling mathematical model for flow and heat transfer was established to verify the experimental results. The results show that under the same total flow rate， the proportion of flow dead zone was 14.1%， 9.1%， and 9.8% respectively when the bottom blowing ratio was 1∶1， 2∶1 and 3∶1， and the proportion of temperature dead zone was 6.2%， 2.6%， and 0.3%， respectively. The 2∶1 non?equi?flow bottom blowing method has advantages in active flow field and promotes the temperature uniformity. Table and Figures | Reference | Related Articles | Metrics

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Research on Event-Triggered Control of Heterogeneous Cooperative Vehicle Platoons Considering Time Delay Chuan-yin TANG, Ji-feng XIA, Ming-li ZHANG, Long-jie WU Journal of Northeastern University(Natural Science)    2024, 45 (4): 540-547.   DOI: 10.12068/j.issn.1005-3026.2024.04.011 Abstract （905）   HTML （13）    PDF （2339KB）（233）       To address the problem of heterogeneity and time delay caused by mixed traffic， a heterogeneous cooperative event‐triggered control method with time delay for autonomous driving platoons was proposed. Firstly， a heterogeneous vehicle delay model taking into account mixed traffic was established. Secondly， the event‐triggered controller in different modes was designed based on PID（proportional?integral?derivative） control and model predictive control（MPC）. Thirdly， under urban and emergency conditions， the proposed controller was simulated and analyzed. Finally， a real‐car experiment was conducted based on the Jetson Nano model car. The simulation and experiment results illustrated that the proposed event‐triggered control method strikes a better balance between control accuracy and calculation speed under different circumstances. In the emergency situations with communication delay， it can still maintain lower errors. Table and Figures | Reference | Related Articles | Metrics

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Elastic Modulus and Dynamic Evolution of Fracture in Double-Fractured Sandstone Under Cyclic Loading Shu-hong WANG, Xian-peng ZHUANG, Fei WANG, Qian-bai ZHAO Journal of Northeastern University(Natural Science)    2024, 45 (3): 361-371.   DOI: 10.12068/j.issn.1005-3026.2024.03.008 Abstract （872）   HTML （23）    PDF （4183KB）（253）       In order to study the changes in elastic modulus and the dynamic evolution of cracks in sandstones with different inclination angles of rock bridges under cyclic loading， uniaxial cyclic loading and unloading tests， along with PFC2D simulations were carried out on sandstone specimens with rock bridge inclination angles of 15°， 45°， 75°， 90° and 105° when the fissure inclination angle was fixed at 45°. The results show that a significant strengthening of the elastic modulus of sandstone with different fissures due to cyclic loading. There is a correlation between the stress‐strain curve and the instantaneous microcrack evolution curve of specimens obtained from discrete element simulation under cyclic loading. The rock bridge inclination angle has an influence on the damage mode of sandstone， and the dynamic crack evolution in the PFC2D simulation can reasonably reflect the initiation location and growth direction of cracks in the rock. The damage defined based on the number of microcracks， corresponds well to the damage pattern， with the maximum original damage at a rock bridge inclination angle of 45°. Table and Figures | Reference | Related Articles | Metrics

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Research on Identifying the Psychological Load of Operators in Hazardous Operations Based on Physiological Signals Rui HAO, Xin ZHENG, Yi-lin LI Journal of Northeastern University(Natural Science)    2024, 45 (4): 600-608.   DOI: 10.12068/j.issn.1005-3026.2024.04.018 Abstract （852）   HTML （21）    PDF （1185KB）（223）       To identify the psychological load of operators in hazardous operations and improve the reliability of man‐machine systems， the psychological load was induced by the detonation of energy?containing materials， and the heart rate， EEG （electroencephalogram）， and eye movement signals of 30 subjects were collected for psychological load identification under the resting state and psychological load. Firstly， the paired t‐test and rank sum test were used to statistically analyze the collected heart rate， EEG and eye movement signals. Eight EEG， three eye movement， and nine heart rate features were significantly changed under the resting state and psychological load. Secondly， Pearson correlation analysis， maximum relevance minimum redundancy （MRMR） algorithm and principal component analysis （PCA） were applied to reduce dimension of the physiological indexes obtained from the preliminary selection. Finally， the physiological indicators obtained after dimensionality reduction based on the above three methods were used for psychological load identification by Logistic Regression， KNN， SVM， XG‐Boost， Decision Tree， and Random Forest machine learning methods. The results showed that the Random Forest machine learning method has better identification performance （ACC=0.917， SN=1.0， SP=0.857， F1=0.909， AUC=0.971） based on MRMR’s psychological load feature selection results. The current research provides a theoretical basis for the effective identification of the psychological load of operators in hazardous operations. Table and Figures | Reference | Related Articles | Metrics

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Jacobi-like Joint Diagonalization Algorithm Based on QR Decomposition Ce JI, Ye LI, Bo-qun LI Journal of Northeastern University(Natural Science)    2024, 45 (3): 305-313.   DOI: 10.12068/j.issn.1005-3026.2024.03.001 Abstract （815）   HTML （79）    PDF （2170KB）（409）       In order to improve the blind separation performance of approximate joint diagonalization of real matrix sets and to avoid trivial solutions， a Jacobi?like joint diagonalization algorithm based on QR decomposition is proposed. Using the numerical stability of QR decomposition， the Jacobi rotation matrix is used to decompose the separation matrix into the product of several elementary triangular matrices and orthogonal matrices. The structure of Jacobi rotation matrix and the related elements of the target matrix transformation are used to obtain the optimal parameters. The high-dimensional minimization problem is iteratively transformed into a series of low-dimensional sub-problems， which enhances the recovery accuracy of the source signal. The algorithm complexity is reduced by solving the simplified Frobenius-norm objective function. The simulation results of mixed electrocardiogram （ECG） signals show that compared with QRJ2D， LUCJD and EGJLUD， the proposed algorithm has certain advantages in separation accuracy and convergence speed. Table and Figures | Reference | Related Articles | Metrics

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A Method for Anomaly Detection and Fault Diagnosis of Elevator Door Machine Yu-chuan FAN, Bo FAN, Zhuo CHEN, Xiao-shun ZHANG Journal of Northeastern University(Natural Science)    2024, 45 (6): 761-768.   DOI: 10.12068/j.issn.1005-3026.2024.06.001 Abstract （799）   HTML （78）    PDF （1731KB）（561）       A method for anomaly detection and fault diagnosis of elevator door machine operation is proposed. Firstly， the opening and closing door curve is spearated from the operation data of the elevator door machine and divided it into 10 operating segments， and the data characteristics of each section is extracted. Secondly， an anomaly detection method based on boxplot is proposed， and the accumulated data characteristics of each running section are used for anomaly diagnosis. In order to prevent the diagnostic error caused by the data not satisfying the normal distribution， the normality test method of the feature data of the door machine is added， and the Box-Cox transformation is performed on the data that does not meet the normal distribution. Finally， the segmented feature data of the elevator door is extracted， and the extreme learning machine（ELM） is used to train the classification model for three faults： door knife jamming fault， overall resistance increase fault and synchronous belt loosening fault. Experiments have verified that the proposed anomaly detection method and fault diagnosis method have high accuracy and value of application and promotion. Table and Figures | Reference | Related Articles | Metrics

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Study on Rheology of RBC by Coupled Model in Fluid-Solid-Electrics Multi-physical Fields HU Sheng, WANG Yang-cheng, LYU Xiao-yong Journal of Northeastern University(Natural Science)    2023, 44 (12): 1673-1679.   DOI: 10.12068/j.issn.1005-3026.2023.12.001 Abstract （794）   HTML （47）    PDF （1490KB）（432）       The study of the mechanical deformation of red blood cell (RBC) suffered from fluid stress becomes more mature， but is insufficient for multi-physical fields， which involve the combination of electrical， acoustic， optical and thermal fields. Using COMSOL finite element software， a coupled model including three physical fluid-solid-electrics fields is built to study the migration simulation of two different RBC shapes with respect to spherocyte and normocyte. Compared to coupled model only involved in fluid-solid fields， the von Mises stress of spherocyte suffered from is greater than that of the normocyte when the electroosmotic flow generated by the electric field drives the cell migration. The effect of electroosmotic flow at 180μm/s leads to the RBC shape evolving into a “C” gesture. The spherocyte and normocyte have a different direction of rotation when they come across a pin obstacle due to the different shape. Regarding the coupled model with multi-physical fields presented， the motion trajectories of two cells reveal the possibility of separating different shaped cell relying on electroosmosis. Reference | Related Articles | Metrics

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Reliability Analysis of FRP-Concrete-Steel Tubular Composite Column Under Axial Compression Hai-yang GAO, Lian-guang WANG, Bai-ling CHEN Journal of Northeastern University(Natural Science)    2024, 45 (3): 430-438.   DOI: 10.12068/j.issn.1005-3026.2024.03.016 Abstract （780）   HTML （15）    PDF （2272KB）（158）       Several existing FRP-confined concrete strength models were evaluated by using 85 FRP?concrete?steel DSTC（double‐skin tubular column） axial compression test data as statistical samples. Finally， Teng’s model was selected for reliability analysis， and the optimal probability distributions of strength model error and resistance were determined. The reliability of DSTC was calculated using the JC method. The results show that the reliability index increases with the increase of steel tube strength， hollow ratio and steel ratio， while it is not significantly influenced by concrete strength. The increase in FRP confining stress leads to the decrease in reliability index. Based on the target reliability index of 3.7， a new expression of resistance partial factor is proposed for DSTC. Table and Figures | Reference | Related Articles | Metrics

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Numerical Simulation of Molten Steel Flow, Heat Transfer and Solidification in Slab Mold Under Composite Magnetic Field Ren WEI, Zhi-jian SU, Yi-da DU, Yan-bin WANG Journal of Northeastern University(Natural Science)    2024, 45 (4): 514-522.   DOI: 10.12068/j.issn.1005-3026.2024.04.008 Abstract （774）   HTML （15）    PDF （1631KB）（187）       In view of the merits and the insurmountable technical defects of the electromagnetic stirring （EMS） process and electromagnetic braking （EMBr） process， a split type composite magnetic field combining EMS and EMBr is applied in this paper to control the flow field and temperature field in slab continuous casting mold. In this process， a ruler structure of EMBr is proposed. A three‐dimensional numerical simulation model of the molten steel flow and heat transfer with coupled solidification in slab mold under magnetic field is established. The effect of the composite magnetic field on the molten steel flow， heat transfer and solidification in mold is analyzed. The results show that， after applying the composite magnetic field， the velocities of the upward flow and the downward flow in the mold decrease obviously， the impact depth of the main stream of molten steel on the narrow surface rises， the upward flow moves down slightly as a whole， and the molten steel on the meniscus forms a clockwise circulation flow. The overall temperature distribution in the mold becomes more homogeneous， and the temperature on the meniscus is almost the same as that without magnetic field. The solidified shell at the outlet of the mold is more uniform， and its thickness is increased compared with that without magnetic field. The washing intensity of molten steel jet on the primary solidification shell near the narrow surface is reduced. Table and Figures | Reference | Related Articles | Metrics