Mechanical Systems and Signal Processing最新文献_第10页

Integrating data-driven reduced order models with Kriging for efficient sensor placement and full-field prediction 整合数据驱动的降阶模型与Kriging有效的传感器放置和全场预测

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-05-02 DOI: 10.1016/j.ymssp.2025.112760

Weizhuo Wang

{"title":"Integrating data-driven reduced order models with Kriging for efficient sensor placement and full-field prediction","authors":"Weizhuo Wang","doi":"10.1016/j.ymssp.2025.112760","DOIUrl":"10.1016/j.ymssp.2025.112760","url":null,"abstract":"<div><div>This paper presents a two-stage methodology for efficient and accurate full-field displacement reconstruction using sparse online measurements derived from high-resolution Digital Image Correlation (DIC) data. The proposed approach integrates Modal Order Reduction and Kriging-based Uncertainty Quantification to address challenges associated with high-dimensional data analysis in structural dynamics.</div><div>In the offline stage, Adaptive Geometric Moment Descriptor (AGMD)-based shape features are used to compress the high-dimensional dataset, identify modal properties, and estimate residual covariance structures. In the online stage, a sparse set of optimally placed sensors, determined via QR decomposition with pivoting, is employed to infer full-field responses through <em>Kriging interpolation</em>, which also provides predictive variances for uncertainty quantification.</div><div>The methodology was demonstrated on a curved plate under random excitation. The results show strong correlations between measured and reconstructed fields using AGMDs and successfully identify multiple full-field vibration modes. In the online stage, the Kriging-predicted full-field responses, informed by an empirically estimated covariance structure from the offline dataset, exhibited better accuracy compared to predictions made using the Generalised Least Squares method (GLS). Validation on temporal sampling data achieved a coverage probability of 94.34% at 95% confidence intervals, highlighting the method’s reliability and robustness.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"234 ","pages":"Article 112760"},"PeriodicalIF":7.9,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143894327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Dynamic modeling and study of slipping and friction characteristics of four-point contact ball bearings under the angular misalignment 角不对中四点接触球轴承滑动和摩擦特性的动力学建模与研究

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-05-02 DOI: 10.1016/j.ymssp.2025.112800

Zihang Li , Haoze Wang , Xilong Ji , Chongyang Wang , Kexin Cao , Lihua Yang

{"title":"Dynamic modeling and study of slipping and friction characteristics of four-point contact ball bearings under the angular misalignment","authors":"Zihang Li , Haoze Wang , Xilong Ji , Chongyang Wang , Kexin Cao , Lihua Yang","doi":"10.1016/j.ymssp.2025.112800","DOIUrl":"10.1016/j.ymssp.2025.112800","url":null,"abstract":"<div><div>Four-Point Contact Ball Bearing (FPCBB) is utilized in aero-engines, wind power and industrial gearboxes due to its ability to withstand axial forces in both directions, its high-speed performance, and its space-efficient design. It has been demonstrated that the structural characteristics of multi-point contact have some advantages, and at the same time increase the friction between the balls and the raceways. In this study, a dynamic model of the FPCBB is developed by considering six degrees of freedom for the ball and cage, and five degrees of freedom for the inner ring, incorporating nonlinear collision and frictional interactions among components. The model accounts for potential multi-point contact between the ball and raceway, as well as the angular misalignment of the inner ring. The maximum error between the experimental and simulated cage speed is only 4.98%, confirming the model’s accuracy. Based on this model, the vibration response of the bearing under angular misalignment, along with frictional characteristics are analyzed. Structural optimization is then performed based on these results. Additionally, the effects of angular misalignment and axial preload are evaluated. The findings indicate that the maximum PV value in the main load area under fixed-pressure preload is approximately 70% of that under locating preload. This study is aimed to provide a theoretical foundation for understanding the dynamic characteristics of these bearings under angular misalignment and for parameter selection in practical service applications.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"234 ","pages":"Article 112800"},"PeriodicalIF":7.9,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143898519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Deep reinforcement learning-based trajectory planning for double pendulum cranes: Design and experiments 基于深度强化学习的双摆起重机轨迹规划：设计与实验

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-05-02 DOI: 10.1016/j.ymssp.2025.112780

Weili Ding , Heng Zhang , Changchun Hua , Biao Lu

{"title":"Deep reinforcement learning-based trajectory planning for double pendulum cranes: Design and experiments","authors":"Weili Ding , Heng Zhang , Changchun Hua , Biao Lu","doi":"10.1016/j.ymssp.2025.112780","DOIUrl":"10.1016/j.ymssp.2025.112780","url":null,"abstract":"<div><div>Since cranes usually possess double pendulum dynamics, the mass of the payload often changes and there are frequently lifting/lowering operations simultaneously. Moreover, most crane systems are driven by motors, whose velocities and accelerations are often limited. To solve the above problems, this paper proposes a deep reinforcement learning (DRL) reference trajectory generation method based on virtual–physical joint training. Firstly, a DRL module based on deep deterministic policy gradient (DDPG), along with a double pendulum crane dynamic model and an adaptive controller, are established within the virtual environment for training the reference trajectory. When the reward reaches the threshold, the training is switched to the physical environment to further optimize the reference trajectory, realizing the swing suppression of the hook and the payload. In addition, to satisfy the performance of the drive motors, velocity and acceleration thresholds are set to constrain the performance of the drive motors. Finally, in view of the fact that the operation process of the double pendulum crane is divided into payload transportation and payload loading/unloading, an event-triggering mechanism is designed to switch different control policies in accordance with different operation processes, thus reducing the consumption of computing resources. Through experiments on the actual double pendulum crane and comparison with the existing reference trajectories and input shapers, the superiority of this method is demonstrated.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"234 ","pages":"Article 112780"},"PeriodicalIF":7.9,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143894326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Wave propagation characteristics of controllable gyroscopic chiral metamaterials 可控陀螺手性超材料的波传播特性

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-05-01 DOI: 10.1016/j.ymssp.2025.112811

Zhenkun Guo , Duo Zhu , Guoqing Jiang , Junyuan Zheng , Yanxue Wang , Jihou Yang

{"title":"Wave propagation characteristics of controllable gyroscopic chiral metamaterials","authors":"Zhenkun Guo , Duo Zhu , Guoqing Jiang , Junyuan Zheng , Yanxue Wang , Jihou Yang","doi":"10.1016/j.ymssp.2025.112811","DOIUrl":"10.1016/j.ymssp.2025.112811","url":null,"abstract":"<div><div>This paper investigates the dispersion characteristics and wave propagation of triangular and concave hexagonal gyroscopic metamaterials. The theory derivations of the dispersion relations are presented and validated through numerical simulations. Group velocity, phase velocity, and wave transmission with different gyroscope torques are analyzed, revealing how the gyroscope torque influences the wave propagation characteristics in the triangular structures. The results indicate that the gyroscope torque breaks the time inverse symmetry, inducing chirality in the triangular structure, and wave predominantly propagates along the spring direction on both low and high frequency dispersion surfaces. On this basis, the concave hexagonal gyroscopic metamaterial is proposed by introducing a transverse long spring, which exhibits two geometric special nodes. Four distinct dispersion surfaces with unique propagation characteristics are generated in the analysis of wave propagation. It is found that the propagation intensity on the first and second dispersion surfaces is highly sensitive to the direction of the gyroscope torque, while wave propagation characteristics of the third and fourth dispersion surfaces exhibit an opposite relationship, in which the Dirac cone is discovered. These findings emphasize that varying the gyroscope torque can achieve the same wave propagation characteristics with different frequencies or change wave propagation with the same frequencies, offering valuable insights for designing metamaterial structures with precise torque distribution control.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"233 ","pages":"Article 112811"},"PeriodicalIF":7.9,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143892401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Nonlinear vibrations of cantilevered circular cylindrical shells partially filled with liquid presenting large-amplitude sloshing 部分充液的悬臂圆柱壳的非线性振动

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-05-01 DOI: 10.1016/j.ymssp.2025.112787

Hamid Reza Moghaddasi , Marco Amabili

{"title":"Nonlinear vibrations of cantilevered circular cylindrical shells partially filled with liquid presenting large-amplitude sloshing","authors":"Hamid Reza Moghaddasi , Marco Amabili","doi":"10.1016/j.ymssp.2025.112787","DOIUrl":"10.1016/j.ymssp.2025.112787","url":null,"abstract":"<div><div>While fully numerical studies on nonlinear sloshing of liquids in various elastic and rigid containers exist, analytical studies on partially filled circular cylindrical elastic shells are limited to small-amplitude (linear) sloshing of the free liquid surface. In this study, for the first time, large-amplitude nonlinear vibrations of thin elastic shells, with clamped-free (cantilevered) boundary conditions, are coupled to large-amplitude sloshing liquid. The shell is modeled according to the Flügge-Lur’e-Byrne nonlinear shell theory. The liquid velocity potential satisfies the Laplace equation in the domain, and nonlinear boundary conditions are imposed at the free sloshing surface. Using the Lagrange multipliers method to satisfy the nonlinear boundary conditions for the liquid, the Lagrange equations of the system are made stationary. The effects of the liquid level inside the shell and nonlinearity at the free surface are investigated through frequency–response curves around resonances. It was observed that the sloshing nonlinearity often intensifies the softening behavior of the system in comparison to linear sloshing, and an increase in the liquid level inside the shell can have the same effect. Also, in contrast to some literature, it was found that there is a significant difference between considering nonlinear or linear sloshing during large amplitude vibrations of the shell, even when the free-surface oscillation amplitude is small.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"233 ","pages":"Article 112787"},"PeriodicalIF":7.9,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143892399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Automated Operational Modal Analysis of self-excited vibrations in turning 车削自激振动的自动运行模态分析

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-04-30 DOI: 10.1016/j.ymssp.2025.112705

Ali Ebrahimi-Tirtashi, Keivan Ahmadi

引用次数: 0

A neural network-based air-coupled ultrasonic damage detection method for composite honeycomb sandwich structure 基于神经网络的复合材料蜂窝夹层结构空气耦合超声损伤检测方法

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-04-30 DOI: 10.1016/j.ymssp.2025.112789

Jian-Hao Wu , Jin-Shui Yang , Xue-Yi Zhang , Lan-Ling Fu , Shuang Li , Lin-Zhi Wu , Rüdiger Schmidt , Kai-Uwe Schröder

{"title":"A neural network-based air-coupled ultrasonic damage detection method for composite honeycomb sandwich structure","authors":"Jian-Hao Wu , Jin-Shui Yang , Xue-Yi Zhang , Lan-Ling Fu , Shuang Li , Lin-Zhi Wu , Rüdiger Schmidt , Kai-Uwe Schröder","doi":"10.1016/j.ymssp.2025.112789","DOIUrl":"10.1016/j.ymssp.2025.112789","url":null,"abstract":"<div><div>Fiber reinforced composites have been widely used due to their excellent mechanical properties and designability, but the damage forms of composite materials are more complex compared to metals. Regular non-destructive testing (NDT) is crucial to ensure the reliability of equipment during use. Air-coupled ultrasound testing (ACUT), which uses air as the coupling agent, has the advantages of non-contact, simple equipment, and no pollution, and is widely used in NDT of composite material structures. However, the difference in acoustic impedance between the specimen and air results in poor accuracy of ACUT detection, and the analysis of the results is influenced by the experience of the technical personnel. To address this issue, a neural network-based method for damage detection and imaging has been proposed. Firstly, ACUT was used to detect pre-embedded defects at different depths within the composite honeycomb sandwich structure, and the original ultrasonic signals were obtained. Then, based on the pattern of sudden changes in signal amplitude at the defect boundary, detailed signal classification and defect area division were carried out by superimposing the results of damage area judgment under different thresholds. Finally, the signals after augmentation were input into neural networks to identify the state of the structure, and the prediction results are output to a pixel matrix to form a detection image. The results demonstrate that the trained neural network has a high classification accuracy; Even when faced with unseen data, the network still has strong robustness and generalization. Compared with traditional methods, neural networks only require A-scan signals to achieve state prediction, without the need for signal comparison in different states and relying on human experience, which can effectively improve recognition efficiency and reliability.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"233 ","pages":"Article 112789"},"PeriodicalIF":7.9,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A degradation assessment method for industrial robot in flexible manufacturing systems based on multiple physics-informed neural network 基于多物理信息神经网络的柔性制造系统工业机器人退化评估方法

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-04-30 DOI: 10.1016/j.ymssp.2025.112793

Shijie Wang , Jianfent Tao , Qinchent Jiang , Wei Chen , Chengliang Liu , Pengcheng Xia

{"title":"A degradation assessment method for industrial robot in flexible manufacturing systems based on multiple physics-informed neural network","authors":"Shijie Wang , Jianfent Tao , Qinchent Jiang , Wei Chen , Chengliang Liu , Pengcheng Xia","doi":"10.1016/j.ymssp.2025.112793","DOIUrl":"10.1016/j.ymssp.2025.112793","url":null,"abstract":"<div><div>With the expansion of industrial robot applications, degradation monitoring is valuable for manufacturing systems. The article develops a framework to predict the remaining useful life (RUL) of industrial robots, which is called Physical-Informed Channel-Attention-Inception-Unet (PICAIU), it can be used to evaluate the reducer degradation. In order to improve the training efficiency and prediction accuracy, it embeds knowledge of robot dynamics and servo controller into a data-driven neural network, adding channel-attention mechanism to the Inception-Unet to fuse motion and power feature, thereby obtaining accurate motor current estimates. Based on the aging experimental data of robot harmonic gear transmission, relevant life curves have been established, which can be used to evaluate other robots. We conducted a series of experiments to discuss the robustness and generalization of the proposed method. The ablation experiments showed that the introduction of physical information constraints improved training efficiency and convergence accuracy, effectively alleviating the sample size requirement of channel self-attention mechanism. The RUL prediction error was 26% lower than the best baseline model. Under the same batch size conditions, PICAIU only need 42% training rounds of the corresponding baseline model to let fitting error be lower than 10%, saving training time and sample costs significantly. Through cross validation with two robots, when generalizing from a rich dataset to poor dataset, the prediction error is only 6.4%, which has potential prospects in real industrial scenarios with relatively few samples.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"233 ","pages":"Article 112793"},"PeriodicalIF":7.9,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Local resonances in free and continuous welded rails 自由和连续焊轨的局部共振

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-04-30 DOI: 10.1016/j.ymssp.2025.112783

Yuning Wu , Keping Zhang , Xiangdong He , Peng Zhang , Ranting Cui , John S. Popovics , Xuan Zhu

{"title":"Local resonances in free and continuous welded rails","authors":"Yuning Wu , Keping Zhang , Xiangdong He , Peng Zhang , Ranting Cui , John S. Popovics , Xuan Zhu","doi":"10.1016/j.ymssp.2025.112783","DOIUrl":"10.1016/j.ymssp.2025.112783","url":null,"abstract":"<div><div>Local vibrational resonances associated with zero-group velocity (ZGV) and cutoff frequency points in dispersion curves have been extensively investigated in plate structures. These local resonances are identified as sharp and spatially localized peaks in amplitude spectra. Because local resonances can be used for nondestructive evaluation (NDE) and structural health monitoring (SHM) of waveguide structures, it is important to understand their characteristics in engineering structures. While previous studies primarily focused on plate and pipe structures, this study examines local resonances in continuous welded rail (CWR), which is widely used in modern railway systems. First, we implement semi-analytical finite element (SAFE) analysis and fully discretized finite element (FDFE) models to predict and identify ZGV and cutoff frequency points and associated local resonances in a free rail. Experimental data are then collected using surface-bonded piezoelectric patches as excitation sources in a section of free rail and CWR at a revenue-service railroad site for frequencies up to 80 kHz. The dispersion relations and local resonance spectra from numerical simulations demonstrate reasonable agreement with experimental results from both specimens, and the detectability and excitability of local resonances are discussed. Additional experimental tests reveal important energy trapping and localized minimum frequency behaviors for ZGV and cutoff frequency resonances in CWR, and furthermore the influences of rail support conditions on local resonance behavior are studied.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"233 ","pages":"Article 112783"},"PeriodicalIF":7.9,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Thermal error mechanism model and transient thermal characteristics analysis of direct-drive rotary axis transmission system of CNC machine tools 数控机床直驱转轴传动系统热误差机理模型及瞬态热特性分析

IF 7.9 1区工程技术

Mechanical Systems and Signal Processing Pub Date : 2025-04-29 DOI: 10.1016/j.ymssp.2025.112792

Hainan Zhang , Sitong Xiang , Nong Li , Jianguo Yang

{"title":"Thermal error mechanism model and transient thermal characteristics analysis of direct-drive rotary axis transmission system of CNC machine tools","authors":"Hainan Zhang , Sitong Xiang , Nong Li , Jianguo Yang","doi":"10.1016/j.ymssp.2025.112792","DOIUrl":"10.1016/j.ymssp.2025.112792","url":null,"abstract":"<div><div>The direct-drive rotary axis is an important component of precision five-axis machine tools, and its transient thermal characteristics are crucial in improving machining accuracy. This study proposed a direct-drive rotary axis transmission system thermal error mechanism modelling method based on the theory of heat conduction and thermoelasticity. In contrast to traditional modelling methods, both the temperature field and thermal deformation are also mechanism models here. We first simplify the rotary axis moving parts into equivalent hollow cylinders and develop a mechanism model of the heating and cooling transient temperature field based on variable separation and eigenfunction expansion method. Then, based on the features that the direct-drive axis heat source and boundary conditions are approximately symmetrical about the central axis, a thermoelastic potential-based transmission system thermal error mechanism model is established. According to temperature rise and interference compressive stress, this model calculates thermal error. Both experimental and simulation results validate the accuracy of the proposed mechanism model in predicting actual temperature changes along with thermal error of the rotary axis in real time. This work lays the groundwork for active control or compensation of thermal errors in direct-drive rotating parts such as CNC machine tool turntables and spindles.</div></div>","PeriodicalId":51124,"journal":{"name":"Mechanical Systems and Signal Processing","volume":"233 ","pages":"Article 112792"},"PeriodicalIF":7.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0