Loading...

Archive

    For Selected: Toggle Thumbnails
    Information & Control
    Scheduling and Analysis of Global EDF for Multi-core Real-time Systems with Cache Partitioning
    LIN Yu-han, YAN Jian, WANG Kan-kan, DENG Qing-xu
    2021, 42 (12):  1673-1680.  DOI: 10.12068/j.issn.1005-3026.2021.12.001
    Abstract ( 712 )   HTML ( 60)   PDF (484KB) ( 360 )  
    Multi-core real-time systems are significantly challenging to analyze due to the unpredictability from extensive contention over shared caches. Therefore, an efficient method, cache partitioning, is introduced into modern multi-core platforms to avoid cache access from co-executing cores, by which the timing predictability are improved. However, the cache space isolation technique may result in unbounded blocking because of the insufficient number of cache partitions. Unfortunately, the existing scheduling and analysis techniques cannot be applied to this situation. gEDFca, a cache-aware preemptive global earliest deadline first(EDF)scheduling algorithm was proposed for multi-core systems. And its analysis method was presented based on linear programming. Besides, a novel optimization algorithm was introduced for further improving schedulability. Evaluations using generation tasks show the proposed analysis method is highly efficient. It also shows that the optimization algorithm yields a significant improvement in schedulability.
    References | Related Articles | Metrics
    A Charge Prediction Method Based on Graph Attention Network: CP-GAT
    ZHAO Qi-hui, LI Da-peng, GAO Tian-han, WEN Ying-you
    2021, 42 (12):  1681-1687.  DOI: 10.12068/j.issn.1005-3026.2021.12.002
    Abstract ( 720 )   HTML ( 32)   PDF (776KB) ( 464 )  
    The task of charge prediction is to predict the charge of a case based on text data. Aiming at the problem that the existing methods do not perform well on similar charges and long tail datasets, a case charge prediction method was proposed based on graph attention network(CP-GAT). Firstly, the case event description text in the judicial document data set and the corresponding legal information of the case are used to establish the heterogeneous graph structure data. The constructed heterogeneous graph contains two types of nodes(word nodes and case nodes), two types of edges(the edges connected by word nodes and word nodes, the edges connected by word nodes and case nodes). The graph attention network was used to extract graph features on the heterogeneous graph constructed based on texts, and finally the obtained feature vector was input into the classifier of charge prediction to get the charge of the case. The experimental results on the CAIL2018 legal dataset show that the charge prediction method based on graph attention network is better than the model used in the comparative experiment, and the accuracy and macro F1 value reach 95.2% and 66.1 respectively, which verifies that the proposed method is conducive to improving the performance of the case charge prediction task.
    References | Related Articles | Metrics
    Feature Selection Algorithm Based on LightGBM
    LI Zhan-shan, YAO Xin, LIU Zhao-geng, ZHANG Jia-chen
    2021, 42 (12):  1688-1695.  DOI: 10.12068/j.issn.1005-3026.2021.12.003
    Abstract ( 2795 )   HTML ( 75)   PDF (419KB) ( 7534 )  
    In order to solve the shortcomings of the following two types of feature selection algorithms, filtering and wrapping based on evolutionary learning, a new wrapping feature selection algorithm LGBFS(LightGBM feature selection) was proposed. First, LightGBM was introduced to construct an gradient boosting tree model for the original features and measure the importance of features; then the proposed LR sequential forward search strategy LRSFFS was combined to select features; finally, the proposed algorithm was compared with nine algorithms in 21 standard datasets. The results show that 16 of the 21 standard data sets of LGBFS have achieved the best classification accuracy, and 18 standard data sets have achieved the best dimensionality reduction rate and the best CPU running time. In addition, time complexity analysis and significance test were carried out. The test shows that LGBFS is significantly different from the six comparison algorithms, and it also shows that LGBFS can balance the calculation efficiency and classification accuracy of feature subsets.
    References | Related Articles | Metrics
    DOA Estimation of Coherent Signals Based on Reconstructed Noise Subspace
    ZHANG Shi, XU Fang-han, SHE Li-huang, LIU Ping-fan
    2021, 42 (12):  1696-1700.  DOI: 10.12068/j.issn.1005-3026.2021.12.004
    Abstract ( 635 )   HTML ( 13)   PDF (447KB) ( 424 )  
    Traditional DOA(direction of arrival) estimation algorithms often fail to deal with coherent signals, so a new DOA estimation method with high accuracy based on reconstructed noise subspace is proposed. This method constructs an augmented matrix as a new covariance matrix by using the auto-covariance and cross-covariance information of uniform liner array, and then, the corresponding noise subspace and the eigen value matrix can be obtained through singular value decomposition on the augmented matrix. To obtain more accurate signal vectors, a new noise subspace can be reconstructed by the eigenvectors associated with the new eigen value matrix. Finally, DOA estimation is completed through spectral peak searching. The proposed algorithm doesnot affect the estimation effect of independent signals. Compared with the IMMUSIC(improved multiple signal classification) algorithm, the proposed algorithm has higher estimation accuracy, especially under the conditions of low signal-to-noise ratio and small signal incidence interval. The simulation results show that even for the conditions of low signal-to-noise ratio and low sampling snapshot number, the improved algorithm can effectively estimate the DOA.
    References | Related Articles | Metrics
    Materials & Metallurgy
    Investigation on Microstructure Evolution of Aviation Bearing Steel During Carburizing Heat Treatment
    JIANG Xia-xia, JIA Tao, WANG Hui, WANG Zhao-dong
    2021, 42 (12):  1701-1708.  DOI: 10.12068/j.issn.1005-3026.2021.12.005
    Abstract ( 852 )   HTML ( 24)   PDF (2080KB) ( 342 )  
    The microstructure evolution of an aviation bearing steel during carburizing heat treatments was analyzed qualitatively and quantitatively by EPMA and XRD. Results show that after carburizing and direct quenching, the microstructures on sample surfaces and near the surfaces include numerous carbides and a small amount of retained austenite, where the carbides are M23C6and M6C. With increasing carburizing depth, the fraction of carbides decreases and the retained austenite increases. After the secondary quenching, the mass fraction of carbon in austenite and martensite increases. This results in a significant increase of retained austenite fraction after quenching, which reaches 22.7% at 0.1mm of the carburized layer. After twice cryogenic and tempering treatments, the mass fraction of carbon in martensite and austenite decreases. Meanwhile, the carbide fraction increases, leading to the increased hardness of the carburized layer.
    References | Related Articles | Metrics
    Effect of Zr Treatment on Nitride in Low Carbon Ti-Microalloyed Steels
    YANG Yong-kun, ZHAN Dong-ping, JIANG Zhou-hua, LEI Hong
    2021, 42 (12):  1709-1716.  DOI: 10.12068/j.issn.1005-3026.2021.12.006
    Abstract ( 556 )   HTML ( 8)   PDF (2077KB) ( 270 )  
    The effect of Zr content on nitrides in low carbon Ti-microalloyed steels was studied by experiment and thermodynamic calculation.The results show that with the increase of Zr content from 0.0020% to 0.0200%, the number density and area proportion of nitrides increase obviously. The type of nitrides gradually changes from TiN to (Tiy,Zr1-y)N and the Zr/Ti atomic ratio in (Tiy,Zr1-y)N increases. The main nitrides in (Tiy,Zr1-y)N gradually changes from TiN to ZrN. The thermodynamic calculation results show that there is no precipitation of TiN, ZrN and other nitrides in the refining process, and nitrides mainly precipitate in the solidification process. When Zr content is 0.0020%, only TiN precipitates during solidification, whereas when Zr content is more than 0.0046%ZrN precipitates at the late stage of solidification. As the temperature decreases, (Tiy,Zr1-y)N fulfills the thermodynamic precipitation conditions. When Zr content increases from 0.0046% to 0.0200%, the precipitation temperature of (Tiy,Zr1-y)N increases, but the ratio of TiN in (Tiy,Zr1-y)N decreases. Finally, when Zr-Ti composite deoxidization is adopted, the mass fraction of Zr in steels should be controlled within the range of 0.0020%~0.0050%.
    References | Related Articles | Metrics
    Effect of w(CaO)/w(Al2O3) on the Crystallization Properties of CaO-Al2O3-based Mold Flux
    QI Jie, LIU Cheng-jun, ZHANG Jiang-hao, JIANG Mao-fa
    2021, 42 (12):  1717-1723.  DOI: 10.12068/j.issn.1005-3026.2021.12.007
    Abstract ( 469 )   HTML ( 4)   PDF (1936KB) ( 245 )  
    The crystallization properties of CaO-Al2O3-based mold fluxes with different values of w(CaO)/w(Al2O3) were studied by using single hot thermocouple technique(SHTT) and scanning electron microscope and energy dispersive spectrometer(SEM-EDS). The results showed that the crystalline phases were LiAlO2 and CaO·Al2O3 with a lower w(CaO)/w(Al2O3). They were formed due to the charge compensation of Li+ions and Ca2+ ions to aluminum tetrahedral structure with high polymerization degree. Li+ions were preferentially involved, and LiAlO2 preferentially precipitated. With higher w(CaO)/w(Al2O3), the crystalline phase was transformed into LiAlO2 and 3CaO·Al2O3. The reason for the change was that the relative mass fraction of CaO was increased, accordingly, the degree of polymerization of the mold flux was decreased and 3CaO·Al2O3 was formed and precipitated due to the combination of Ca2+ ions and low-polymerization tetrahedral structural unit Q2. As the w(CaO)/w(Al2O3) was increased from 1.13 to 1.82, the crystallization ability was first weakened and then increased. The crystallization ability was the weakest and the strongest when the w(CaO)/w(Al2O3) was 1.50 and 1.82, respectively.
    References | Related Articles | Metrics
    Flow Field and Temperature Rising Characteristics of Butterfly Induction Heating Tundish
    WANG Ning, LI Bao-kuan, QI Feng-sheng, ZHANG Xiao-ming
    2021, 42 (12):  1724-1730.  DOI: 10.12068/j.issn.1005-3026.2021.12.008
    Abstract ( 584 )   HTML ( 5)   PDF (1679KB) ( 284 )  
    In order to solve the problem that induction heating device can not be installed in the tundish of traditional continuous casting equipment, a new butterfly induction heating tundish was designed. A three-dimensional unsteady magnetic-thermal-flow coupling mathematical model was then established to study the effect of electromagnetic field on the flow and temperature fields in the butterfly tundish, revealing the relationship between induction heating power and temperature rising characteristics. The results showed that the induced current formed a closed loop in the tundish and was mainly concentrated in the channel. The eccentric electromagnetic force rendered the steel to spin in the channel with large tangential velocity, and the steel flowing out of the channel moved up to the casting chamber. When the flow rate of tundish was 2t/min and without induction heating, the outlet temperature drop was 7K. However, under induction heating, when the heating power increased from 600kW to 1000kW, the outlet temperature rise was elevated from 8K to 27K.
    References | Related Articles | Metrics
    Mechanical Engineering
    Reliability Sensitivity Analysis of Angular Contact Ball Bearing Skidding
    HUANG Xian-zhen, ZHU Hui-bin, JIANG Zhi-yuan, JIANG Rui
    2021, 42 (12):  1731-1738.  DOI: 10.12068/j.issn.1005-3026.2021.12.009
    Abstract ( 613 )   HTML ( 7)   PDF (820KB) ( 163 )  
    Bearing skidding is likely to cause early failure of the bearings. Traditional methods of bearing skidding analysis claim that the bearing parameters are determined, but they are random in actual working conditions, which may cause larger analysis errors. In order to solve this problem, a reliability analysis model of angular contact ball bearing skidding which takes into account the influence of random factors is proposed. According to the quasi-static analysis of rolling bearings and the criterion of Hirano for bearing skidding, the critical surface of skidding is given, and the limit-state equation of bearing skidding is established based on whether the bearing is skidding or not. The reliability sensitivity analysis is carried out by using Kriging method to evaluate the influence of bearing parameters on bearing skidding. The research results show that the change of ball diameters has the most impact on the bearing skidding, then the raceway diameter and groove curvature radius of the inner and outer raceway take the second place, and the contact angle is the least. The research results may provide the theoretical basis for reducing or avoiding ball bearing skidding.
    References | Related Articles | Metrics
    Research on Transmitted Torque Calculation Method of Permanent Magnet Eddy-Current Couplers
    CHENG Xi-kang, LIU Wei, SUN Ming-hao, LUO Wei-qi
    2021, 42 (12):  1739-1746.  DOI: 10.12068/j.issn.1005-3026.2021.12.010
    Abstract ( 700 )   HTML ( 9)   PDF (1290KB) ( 395 )  
    As a kind of driving device, the effective calculation of transmitted torque for permanent magnet eddy-current couplers is a significant index to evaluate the transmission performance. For a permanent magnet eddy current coupler with 6 pole pairs and 1450r/min rated input speed, firstly, according to the geometry, finite element method is used to simulate the magnetic field lines and to obtain the magnetic path distribution. Also, through the analysis of leakage fluxes boundary condition, the leakage magnetic resistance and effective magneto motive force are obtained. Secondly, the coordinate system of eddy current on the conductor disk is established. According to the law of skin depth and ampere loop, the magnetic induction intensity equation is constructed which considers the continuity and symmetry of magnetic field distribution. Then, based on the mathematical relationship between eddy-current density and conductivity of the conductor disk, the analytical result of transmitted torque is presented accounting for the three-dimensional end effect. Finally, a prototype test platform and a three-dimensional finite element analytical model are built to verify the method. The results show that the proposed method has good accuracy within the range of speed slip in a certain operation where the relative error is within 6%. Moreover, some reasonable suggestions are put forward for the design optimization of permanent magnet eddy-current couplers.
    References | Related Articles | Metrics
    Resources & Civil Engineering
    Experimental Study of the Inclined Slices Sublevel Caving Method in Xingshan Iron Mine
    QIAO Xia-liang, REN Feng-yu, CAO Jian-li, SHI Hong-wei
    2021, 42 (12):  1747-1752.  DOI: 10.12068/j.issn.1005-3026.2021.12.011
    Abstract ( 525 )   HTML ( 14)   PDF (1535KB) ( 267 )  
    The orebody in Xiaoxingshan mining area of Xingshan iron mine is layered inclined thick.Originally, the sublevel caving method without sill pillar was used for mining with drift perpendicular to strike, resulting in high ore loss and dilution, serious underground pressure behavior at hanging wall side of drift, large amount of roadway support engineering, and so on.Therefore, the inclined slices sublevel caving method is proposed. Along the deepening direction, orebody is mined according to the inclined line from the hanging wall to the footwall.An induced caving drift was arranged in each orebody slices.Current sublevel ore is caved, meanwhile the orebody near the hanging wall is also induced to cave naturally, and the caved ore is mined by the recovery drift set in the footwall surrounding rock. This method conforms to the movement law of ore caving in the inclined orebody, reduces the total cost of development and cut engineering.The experimental stope has been mined since May 2019, and now two sublevels has been mined, the ore recovery rate increased from 74% to85.6%, and the dilution rate has been reduced from 18% to 15%. New method has achieved good technical and economic indexes.
    References | Related Articles | Metrics
    Collaborative Monitoring of Open Pit Mine Induced Large Scale Landslide with LiDAR DEM and Time Series SAR Data
    WEI Lian-huan, LIU Shan-jun, YANG Tian-hong, ZHAO Ye
    2021, 42 (12):  1753-1760.  DOI: 10.12068/j.issn.1005-3026.2021.12.012
    Abstract ( 656 )   HTML ( 14)   PDF (5473KB) ( 321 )  
    A collaborative monitoring scheme combining pixel offset tracking(POT) and multi-temporal interferometry (MTI) is proposed, where POT is used during rapid-movement period and MTI is used during slow-movement period. Targeting at the spatial inconsistency between the azimuth-line of sight(Az-LOS) measurements and downslope landslide displacements, a light detection and ranging(LiDAR) digital elevation model(DEM) based conversion method from Az-LOS to downslope direction is also proposed and adopted in the long-term displacement monitoring of the large scale landslide on the south slope in Fushun west open pit mine. By comparing the estimated downslope displacements with GPS measurements, mean error of decimeter level is achieved.
    References | Related Articles | Metrics
    Classification-Dispersion Flotation of Fine Mixed Magnetic Concentrate
    LI Dong, ZHONG He-dong, YIN Wan-zhong, HU Yang
    2021, 42 (12):  1761-1767.  DOI: 10.12068/j.issn.1005-3026.2021.12.013
    Abstract ( 502 )   HTML ( 6)   PDF (892KB) ( 128 )  
    The Donganshan mixed magnetic concentrate was separated through the pre-classification-enhanced dispersion flotation process, and the corresponding mechanism was investigated by the sedimentation test, zeta potential test, and turbidity measurement. Under the optimum conditions, a concentrate iron grade of 66.24% and iron recovery of 79.47% can be obtained by the closed circuit of classification-dispersion flotation, in which the recovery of concentrate iron is increased by 4.47% compared with the dispersion flotation results. The sedimentation and turbidity test indicate that the dispersant citric acid and particle size distribution can influence the dispersion state of the hematite-quartz mixture suspension. The adsorption of citric acid onto the hematite surface will increase the electrostatic repulsive force between the mineral particles. The narrow fraction flotation obtained by optimizing particle size distribution can decrease the detrimental hetero-aggregation, which is beneficial to the subsequent flotation separation, which is also supported by the DLVO theory and the agglomeration dynamics.
    References | Related Articles | Metrics
    Effect of Pore Structure on Mechanical Properties and Fracture Mechanism of Porous Materials
    JIA Peng, XU Xue-tong, HUANG Fei, YANG Qi-yao
    2021, 42 (12):  1768-1774.  DOI: 10.12068/j.issn.1005-3026.2021.12.014
    Abstract ( 806 )   HTML ( 10)   PDF (954KB) ( 847 )  
    In order to study the effect of pore structure on the mechanical properties, fracture mechanism and durability of altered rock porous materials, the uniaxial compression and freeze-thaw cycle experiments were carried out on two types of porous materials with different pore structures. Meanwhile, numerical simulation was conducted to analyze the failure process and failure mechanism of the two porous materials under uniaxial compression. The results show that the pore structure has a significant effect on the mechanical properties of porous materials. The larger the porosity, the lower the compressive strength and the higher the energy absorption. The 10-cycle freeze-thaw experiments in the range of ±25℃ show that when the porosity is small and closed, the frost resistance of the material increases due to the particle falling and filling of the pore wall by the freeze-thaw effect, and when the porosity is small, the crack propagation under uniaxial compression mainly extends from both ends of the specimen to the middle of the specimen, forming a continuous main tensile crack with few secondary cracks; when the porosity is large, a large number of microcracks will appear under compression with many secondary cracks.
    References | Related Articles | Metrics
    Load Transfer Model of Pile-Soil Interface Based on the Disturbed State Concept
    JIA Yu, ZHANG Jia-sheng, ZHANG Fei, LIAO Xiang-ying
    2021, 42 (12):  1775-1781.  DOI: 10.12068/j.issn.1005-3026.2021.12.015
    Abstract ( 524 )   HTML ( 3)   PDF (876KB) ( 132 )  
    Based on the disturbed state concept(DSC), it is assumed that the shear strength of the relative intact(RI)part of the pile-soil interface obeys the linear elastic theory, and the shear strength of the fully adjusted(FA)part obeys the ideal plastic theory, so that the pile-soil interface load transfer model can be established.A large-scale direct shear test was carried out on the pile-soil interface, which shows that the strain exhibits softening characteristics during the shear process between the pile and red clay interface, and the softening phenomenon becomes more significant with the increase of the normal stress.The strain exhibits slightly hardening characteristics during the shearing process between the pile and silty clay interface. The shear stress-shear displacement curves(τ-s curves) calculated by using the pile-soil interface load transfer model is in good agreement with the τ-s curves obtained from the direct shear test, which proved that the load transfer model of pile-soil interface based on DSC has a good accuracy and applicability.
    References | Related Articles | Metrics
    Reliability Study of Prefabricated Box Culvert Components Based on Probability Density Evolution Method
    KANG Yu-mei, LI Jia-qi, LIU Zi-ao, YU Jia-yue
    2021, 42 (12):  1782-1789.  DOI: 10.12068/j.issn.1005-3026.2021.12.016
    Abstract ( 460 )   HTML ( 7)   PDF (1300KB) ( 319 )  
    The calculation accuracy and efficiency of reliability analysis of prefabricated box culvert components are studied using the probability density evolution method based on the actual project. Firstly, the function of prefabricated box culvert is established, the generalized probability density evolution equation of the function is derived, and the finite difference method is used to solve the problem. Secondly, the probability density function is integrated to get the failure probability of components, and then the corresponding reliability index is obtained. Finally, it is compared with Monte Carlo method to analyze the applicability of probability density evolution method. The results show that: in the process of solving the reliability of prefabricated box culvert components, the probability density evolution method fully considers the randomness of component parameters and the probability relationship between sample points based on the relationship between physical system and stochastic system. Compared with Monte Carlo method, probability density evolution method can avoid random convergence effectively, and improve the accuracy and efficiency of calculation under the premise of guaranteeing the unique result.
    References | Related Articles | Metrics
    Study on Excess Sludge Disintegration by High Pressure Jet Impingement Stream
    XIE Yuan-hua, YANG Dai-en, BAI Bing, ZHU Tong
    2021, 42 (12):  1790-1796.  DOI: 10.12068/j.issn.1005-3026.2021.12.017
    Abstract ( 479 )   HTML ( 6)   PDF (862KB) ( 139 )  
    Excess sludge is rich in bacteria, viruses, and organics matter, potentially causing secondary pollution. Sludge disintegration is beneficial to the recovery of organic matter and treatment of harmful substances. Sludge disintegration by high pressure jet impingement stream was investigated. The optimal range of three factors including impinged distance,impinged time, and impinged pressure were determined at a distance of 5cm, a time of 20~25min, and a pressure of around 13.79MPa. Response surface methodology(RSM)was used to analyze the disintegration effects and energy consumption. Disintegration energy ratio(DER)of soluble chemical oxygen demand(SCOD)was the evaluation index of RSM. Considering both disintegration effects and DERSCOD, 5~6cm, 15~20min and 13.79MPa were suggested. This study provides new insights into physical sludge disintegration.
    References | Related Articles | Metrics
    Management Science
    Underlying Mechanisms of the Effectiveness of Brand Placement in Movies
    YE Guo-quan, GUO Fu, LI Feng-xiang, HU Ming-cai
    2021, 42 (12):  1797-1804.  DOI: 10.12068/j.issn.1005-3026.2021.12.018
    Abstract ( 582 )   HTML ( 10)   PDF (541KB) ( 434 )  
    According to the limited capacity model of attention, persuasion knowledge model and elaboration likelihood model of persuasion, the theoretical models between brand prominence, need for cognition and brand responses(i.e. brand memory, brand attitude and purchase intention)were constructed. By conducting an eye-tracking experiment, the underlying mechanisms between brand prominence, need for cognition and brand responses were unraveled. The results showed that, brand prominence can significantly positively affect brand memory, but significantly negatively affect brand attitude and purchase intention; attention allocation and activation of conceptual persuasion knowledge play intermediary roles between brand prominence and brand memory; attention allocation, activation of conceptual and attitudinal persuasion knowledge play intermediary roles between brand prominence and brand attitude and purchasing intention; these influential mechanisms of brand prominence on brand responses were significant only for viewers high in need for cognition.
    References | Related Articles | Metrics