期刊文献+
共找到9,642篇文章
< 1 2 250 >
每页显示 20 50 100
Sensorimotor Self-Learning Model Based on Operant Conditioning for Two-Wheeled Robot 被引量:1
1
作者 张晓平 阮晓钢 +1 位作者 肖尧 黄静 《Journal of Shanghai Jiaotong university(Science)》 EI 2017年第2期148-155,共8页
Traditional control methods of two-wheeled robot are usually model-based and require the robot’s precise mathematic model which is hard to get. A sensorimotor self-learning model named SMM TWR is presented in this pa... Traditional control methods of two-wheeled robot are usually model-based and require the robot’s precise mathematic model which is hard to get. A sensorimotor self-learning model named SMM TWR is presented in this paper to handle these problems. The model consists of seven elements: the discrete learning time set, the sensory state set, the motion set, the sensorimotor mapping, the state orientation unit, the learning mechanism and the model’s entropy. The learning mechanism for SMM TWR is designed based on the theory of operant conditioning (OC), and it adjusts the sensorimotor mapping at every learning step. This helps the robot to choose motions. The leaning direction of the mechanism is decided by the state orientation unit. Simulation results show that with the sensorimotor model designed, the robot is endowed the abilities of self-learning and self-organizing, and it can learn the skills to keep itself balance through interacting with the environment. © 2017, Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg. 展开更多
关键词 two-wheeled robot sensorimotor model SELF-LEARNING operant conditioning(OC)
原文传递
The skinner automaton: A psychological model formalizing the theory of operant conditioning 被引量:8
2
作者 RUAN XiaoGang WU Xuan 《Science China(Technological Sciences)》 SCIE EI CAS 2013年第11期2745-2761,共17页
Operant conditioning is one of the fundamental mechanisms of animal learning, which suggests that the behavior of all animals, from protists to humans, is guided by its consequences. We present a new stochastic learni... Operant conditioning is one of the fundamental mechanisms of animal learning, which suggests that the behavior of all animals, from protists to humans, is guided by its consequences. We present a new stochastic learning automaton called a Skinner au- tomaton that is a psychological model for formalizing the theory of operant conditioning. We identify animal operant learning with a thermodynamic process, and derive a so-called Skinner algorithm from Monte Carlo method as well as Metropolis algo- rithm and simulated annealing. Under certain conditions, we prove that the Skinner automaton is expedient, 6-optimal, optimal, and that the operant probabilities converge to the set of stable roots with probability of 1. The Skinner automaton enables ma- chines to autonomously learn in an animal-like way. 展开更多
关键词 Learning automata Boltzmann distribution operant conditioning operant learning simulated annealing
原文传递
Automated Pipe Defect Identification in Underwater Robot Imagery with Deep Learning 被引量:1
3
作者 Mansour Taheri Andani Farhad Ameri 《哈尔滨工程大学学报(英文版)》 2026年第1期197-215,共19页
Underwater pipeline inspection plays a vital role in the proactive maintenance and management of critical marine infrastructure and subaquatic systems.However,the inspection of underwater pipelines presents a challeng... Underwater pipeline inspection plays a vital role in the proactive maintenance and management of critical marine infrastructure and subaquatic systems.However,the inspection of underwater pipelines presents a challenge due to factors such as light scattering,absorption,restricted visibility,and ambient noise.The advancement of deep learning has introduced powerful techniques for processing large amounts of unstructured and imperfect data collected from underwater environments.This study evaluated the efficacy of the You Only Look Once(YOLO)algorithm,a real-time object detection and localization model based on convolutional neural networks,in identifying and classifying various types of pipeline defects in underwater settings.YOLOv8,the latest evolution in the YOLO family,integrates advanced capabilities,such as anchor-free detection,a cross-stage partial network backbone for efficient feature extraction,and a feature pyramid network+path aggregation network neck for robust multi-scale object detection,which make it particularly well-suited for complex underwater environments.Due to the lack of suitable open-access datasets for underwater pipeline defects,a custom dataset was captured using a remotely operated vehicle in a controlled environment.This application has the following assets available for use.Extensive experimentation demonstrated that YOLOv8 X-Large consistently outperformed other models in terms of pipe defect detection and classification and achieved a strong balance between precision and recall in identifying pipeline cracks,rust,corners,defective welds,flanges,tapes,and holes.This research establishes the baseline performance of YOLOv8 for underwater defect detection and showcases its potential to enhance the reliability and efficiency of pipeline inspection tasks in challenging underwater environments. 展开更多
关键词 YOLO8 Underwater robot Object detection Underwater pipelines Remotely operated vehicle Deep learning
在线阅读 下载PDF
Adaptive-length data-driven predictive control for post-operation of space robot non-cooperative target capture with disturbances 被引量:1
4
作者 Peiji WANG Bicheng CAI +2 位作者 Chengfei YUE Yong ZHAO Weiren WU 《Chinese Journal of Aeronautics》 2026年第2期485-498,共14页
This paper solves the problem of model-free dual-arm space robot maneuvering after non-cooperative target capture under high control quality requirements.The explicit system model is unavailable,and the maneuvering mi... This paper solves the problem of model-free dual-arm space robot maneuvering after non-cooperative target capture under high control quality requirements.The explicit system model is unavailable,and the maneuvering mission is disturbed by the measurement noise and the target adversarial behavior.To address these problems,a model-free Combined Adaptive-length Datadriven Predictive Controller(CADPC)is proposed.It consists of a separated subsystem identification method and a combined predictive control strategy.The subsystem identification method is composed of an adaptive data length,thereby reducing sensitivity to undetermined measurement noises and disturbances.Based on the subsystem identification,the combined predictive controller is established,reducing calculating resource.The stability of the CADPC is rigorously proven using the Input-to-State Stable(ISS)theorem and the small-gain theorem.Simulations demonstrate that CADPC effectively handles the model-free space robot post operation in the presence of significant disturbances,state measurement noise,and control input errors.It achieves improved steady-state accuracy,reduced steady-state control consumption,and minimized control input chattering. 展开更多
关键词 Combined control Data-driven predictive control Post operation Predictive control systems Space non-cooperative target capture
原文传递
A radiomics approach for predicting gait freezing in Parkinson's disease based on resting-state functional magnetic resonance imaging indices:A cross-sectional study 被引量:1
5
作者 Miaoran Guo Hu Liu +6 位作者 Long Gao Hongmei Yu Yan Ren Yingmei Li Huaguang Yang Chenghao Cao Guoguang Fan 《Neural Regeneration Research》 2026年第4期1621-1627,共7页
Freezing of gait is a significant and debilitating motor symptom often observed in individuals with Parkinson's disease.Resting-state functional magnetic resonance imaging,along with its multi-level feature indice... Freezing of gait is a significant and debilitating motor symptom often observed in individuals with Parkinson's disease.Resting-state functional magnetic resonance imaging,along with its multi-level feature indices,has provided a fresh perspective and valuable insight into the study of freezing of gait in Parkinson's disease.It has been revealed that Parkinson's disease is accompanied by widespread irregularities in inherent brain network activity.However,the effective integration of the multi-level indices of resting-state functional magnetic resonance imaging into clinical settings for the diagnosis of freezing of gait in Parkinson's disease remains a challenge.Although previous studies have demonstrated that radiomics can extract optimal features as biomarkers to identify or predict diseases,a knowledge gap still exists in the field of freezing of gait in Parkinson's disease.This cross-sectional study aimed to evaluate the ability of radiomics features based on multi-level indices of resting-state functional magnetic resonance imaging,along with clinical features,to distinguish between Parkinson's disease patients with and without freezing of gait.We recruited 28 patients with Parkinson's disease who had freezing of gait(15 men and 13 women,average age 63 years)and 30 patients with Parkinson's disease who had no freezing of gait(16 men and 14 women,average age 64 years).Magnetic resonance imaging scans were obtained using a 3.0T scanner to extract the mean amplitude of low-frequency fluctuations,mean regional homogeneity,and degree centrality.Neurological and clinical characteristics were also evaluated.We used the least absolute shrinkage and selection operator algorithm to extract features and established feedforward neural network models based solely on resting-state functional magnetic resonance imaging indicators.We then performed predictive analysis of three distinct groups based on resting-state functional magnetic resonance imaging indicators indicators combined with clinical features.Subsequently,we conducted 100 additional five-fold cross-validations to determine the most effective model for each classification task and evaluated the performance of the model using the area under the receiver operating characteristic curve.The results showed that when differentiating patients with Parkinson's disease who had freezing of gait from those who did not have freezing of gait,or from healthy controls,the models using only the mean regional homogeneity values achieved the highest area under the receiver operating characteristic curve values of 0.750(with an accuracy of 70.9%)and 0.759(with an accuracy of 65.3%),respectively.When classifying patients with Parkinson's disease who had freezing of gait from those who had no freezing of gait,the model using the mean amplitude of low-frequency fluctuation values combined with two clinical features achieved the highest area under the receiver operating characteristic curve of 0.847(with an accuracy of 74.3%).The most significant features for patients with Parkinson's disease who had freezing of gait were amplitude of low-frequency fluctuation alterations in the left parahippocampal gyrus and two clinical characteristics:Montreal Cognitive Assessment and Hamilton Depression Scale scores.Our findings suggest that radiomics features derived from resting-state functional magnetic resonance imaging indices and clinical information can serve as valuable indices for the identification of freezing of gait in Parkinson's disease. 展开更多
关键词 amplitude of low-frequency fluctuation degree centrality feedforward neural network freezing of gait machine learning parahippocampal gyrus Parkinson's disease receiver operating characteristic regional homogeneity resting-state functional magnetic resonance imaging
暂未订购
Lipschitz Estimates for the Commutators of Fractional Hardy and Hardy-Littlewood-Pólya Operators on Grand p-adic Variable Herz Spaces
6
作者 常云鹏 武江龙 《数学进展》 北大核心 2026年第2期419-430,共12页
In this article,we prove the boundedness for commutators of fractional Hardy and Hardy-Littlewood-Pólya operators on grand p-adic variable Herz spaces,where the symbols of the commutators belong to Lipschitz spaces.
关键词 p-adic field fractional Hardy operator Hardy-Littlewood-Pólya operator grand variable Herz space commutator
原文传递
Hyponormal Block Toeplitz Operators on the Weighted Bergman Space with Circulant Symbols
7
作者 FU Guangyang ZHOU Jiang 《数学进展》 北大核心 2026年第1期183-191,共9页
In this paper,we present a necessary and sufficient condition for hyponormal block Toeplitz operators T on the vector-valued weighted Bergman space with symbolsΦ(z)=G^(*)(z)+F(z),where F(z)=∑^(N)_(i)=1 A_(i)z^(i)and... In this paper,we present a necessary and sufficient condition for hyponormal block Toeplitz operators T on the vector-valued weighted Bergman space with symbolsΦ(z)=G^(*)(z)+F(z),where F(z)=∑^(N)_(i)=1 A_(i)z^(i)and G(z)=∑^(N)_(i)=1 A_(−i)z^(i),A_(i)ae culants. 展开更多
关键词 block Toeplitz operator hyponormal weighted Bergman space CIRCULANT COMMUTATOR
原文传递
Hybrid Controller for Steady Speed of Agricultural Machinery on Slopes
8
作者 WU Caicong XU Haisong GAO Xingyu 《农业机械学报》 北大核心 2026年第2期416-426,共11页
Steady speed control of agricultural machinery can improve operating quality and efficiency.To address the impact of farmland slope variations on the speed stability of unmanned operation agricultural machinery,a hybr... Steady speed control of agricultural machinery can improve operating quality and efficiency.To address the impact of farmland slope variations on the speed stability of unmanned operation agricultural machinery,a hybrid control method was proposed.This method included a hybrid controller composed of a slope-based controller and a proportional-integral-derivative(PID)controller.The speed of agricultural machinery was influenced by longitudinal forces,which were divided into two parts:one part was slope-related forces and conventional resistance,and the other was hard-to-estimate forces,such as sliding friction.For the first part,a slope-based controller was designed;for the second part,a PID controller was implemented.By combining these two controllers,the system can dynamically adjust the throttle opening and the brake master cylinder pressure,ensuring steady speed travel on sloping farmland.Simulation tests at a target speed of 7 km/h demonstrated that the proposed controller maintained a stable speed,achieving a root mean square error of 0.13 km/h and a mean absolute percentage error of 1.6%.Field tests on a practical experimental platform validated the method’s effectiveness,with results showing consistent control performance across varying slope conditions.The proposed controller demonstrated superior control performance.Experimental data verified that this method can achieve precise control of the agricultural machinery’s movement speed,meeting the stability requirements for agricultural operations. 展开更多
关键词 farmland slope PID controller steady speed control agricultural machinery unmanned operation
在线阅读 下载PDF
Cooperative robust parallel operation of multiple actuators
9
作者 XU Liang XU Xiang LIU Tao 《控制理论与应用》 北大核心 2026年第1期3-11,共9页
This paper studies cooperative robust parallel operation of multiple actuators over an undirected communication graph.The plant is modeled as an uncertain linear system,and the actuators are linear and identical.Based... This paper studies cooperative robust parallel operation of multiple actuators over an undirected communication graph.The plant is modeled as an uncertain linear system,and the actuators are linear and identical.Based on the internal model principle,a distributed dynamic output feedback control law is proposed to achieve both robust output regulation of the closed-loop system and plant input sharing among the actuators.A practical example of five motors cooperatively driving an uncertain shaft under an external load torque is presented to show the effectiveness of the proposed control law. 展开更多
关键词 cooperative parallel operation multiple actuators robust output regulation CONSENSUS
在线阅读 下载PDF
Estimates for p-adic fractional integral operator with rough kernels on grand p-adic Herz-type spaces
10
作者 XIA Xiaoxi ZHOU Jiang 《中山大学学报(自然科学版)(中英文)》 北大核心 2026年第2期153-159,共7页
The goal of this paper is to establish the boundedness of the p-adic fractional integral operator with rough kernel I_(β,Ω′)^(p)and its commutators generated by b∈Λ_(γ)(Q_(p)^(n))(0<γ<1)and the I_(β,Ω′... The goal of this paper is to establish the boundedness of the p-adic fractional integral operator with rough kernel I_(β,Ω′)^(p)and its commutators generated by b∈Λ_(γ)(Q_(p)^(n))(0<γ<1)and the I_(β,Ω′)^(p) on grand p-adic Herz spaces. 展开更多
关键词 Lipschitz spaces grand p-adic Herz spaces p-adic fractional integral operator COMMUTATORS
在线阅读 下载PDF
Inverse Scattering Problem on a Star-shaped Graph with Robin Boundary Conditions
11
作者 WU Dongjie 《数学进展》 北大核心 2026年第2期369-384,共16页
This work deals with an inverse scattering problem for the Schrodinger operator on a star-shaped graph with one semi-infinite branch.Using the high-frequency asymptotic behaviour of the reflection coefficient,first we... This work deals with an inverse scattering problem for the Schrodinger operator on a star-shaped graph with one semi-infinite branch.Using the high-frequency asymptotic behaviour of the reflection coefficient,first we provide the identifiability of the geometry of this star-shaped graph:the number of edges and their lengths.Under some assumptions on the geometry of the graph,the main result states that the measurement of one reflection coefficient,together with the scattering data corresponding to the infinite branch,associated with Robin boundary conditions at the external nodes of the graph,can uniquely determine the parameters of the boundary conditions and the potentials on the whole interval which is already known in a half-interval. 展开更多
关键词 inverse scattering Schrödinger operator reflection coefficient
原文传递
Mixed Quasi-martingale Hardy Spaces
12
作者 ZHANG Chuanzhou LI Shimeng HE Zhibin 《应用数学》 北大核心 2026年第1期221-231,共11页
In this article,we conduct a study on mixed quasi-martingale Hardy spaces that are defined by means of the mixed L_(p)-norm.By utilizing Doob’s inequalities,we explore the atomic decomposition and quasi-martingale in... In this article,we conduct a study on mixed quasi-martingale Hardy spaces that are defined by means of the mixed L_(p)-norm.By utilizing Doob’s inequalities,we explore the atomic decomposition and quasi-martingale inequalities of mixed quasi-martingale Hardy spaces.Moreover,we furnish sufficient conditions for the boundedness ofσ-sublinear operators in these spaces.These findings extend the existing conclusions regarding mixed quasi-martingale Hardy spaces defined with the help of the mixed L_(p)-norm. 展开更多
关键词 Mixed quasi-martingale Hardy space Atomic Decomposition σ-sublinear operator
在线阅读 下载PDF
DEPRESSION OF RETRIEVAL OF AN OPERANT CONDITIONING IN RATS BY ENKEPHALIN
13
作者 张世仪 齐慧新 王玢 《Chinese Science Bulletin》 SCIE EI CAS 1991年第2期158-162,共5页
It is established that opioid peptides are involved in the regulation of various physiological processes including the higher function of the brain. We have reported that peripheral administration of enkephalin impair... It is established that opioid peptides are involved in the regulation of various physiological processes including the higher function of the brain. We have reported that peripheral administration of enkephalin impaired memory retention in mice. This effect was reversed by naloxone. We further found that bestatin, an aminopeptidase inhibitor, when injected peripherally or into amygdala introduced memory impairment which mimiced the effect of enkephalin. The present study examined the influence of hippocampal and peripheral enkephalin on operant defence conditioning in rats, with an attempt to detect the action of central enkephalin on memory. 展开更多
关键词 ENKEPHALIN BESTATIN operant DEFENSE conditioning.
在线阅读 下载PDF
A hierarchical and role-driven digital twin system with applications to complex chemical process operation
14
作者 Xinyu Tao Runjie Yao +3 位作者 Lingyu Zhu Changrui Xie Muqian Zhang Xi Chen 《Chinese Journal of Chemical Engineering》 2026年第1期302-313,共12页
Digital twin technology brings more opportunities and challenges to chemical engineering in both academic and industry.A complex process could have multiple digitalization needs,including simulation,monitoring,operato... Digital twin technology brings more opportunities and challenges to chemical engineering in both academic and industry.A complex process could have multiple digitalization needs,including simulation,monitoring,operator training,etc.;thus,a hierarchical digital twin would be a comprehensive solution to that.In this study,a novel and general framework of the digital twin is proposed for operations in process industry.With the hierarchical structure,the framework can handle various tasks driven by different roles in process industry,including managers,engineers,and operators.To complete these tasks,the framework consists of three modules:OAS(Operation Analysis System),OMS(Operation Monitoring System),and OTS(Operator Training System).Each module focuses on one unique type of demand from the staff,as well as interactions among them enabling efficient data sharing.Based on the hierarchical framework,a digital twin system is applied for one complex industrial nitration process,which successfully enhances the operation efficiency and safety in several industrial scenarios with different demands. 展开更多
关键词 Digital twin Hierarchical framework Role-driven Process operation Process modeling&optimization Operator training system
在线阅读 下载PDF
A Testing Ground
15
作者 LI NAN 《China Today》 2026年第2期44-47,共4页
Hainan’s special customs operations are expected to significantly reduce the institutional costs of foreign goods flowing into Hainan,enabling the island to function as a gateway for global goods.DAVID Adrian Janke,a... Hainan’s special customs operations are expected to significantly reduce the institutional costs of foreign goods flowing into Hainan,enabling the island to function as a gateway for global goods.DAVID Adrian Janke,a British citizen operating a translation company in Haikou,capital of Hainan Province in south China,witnessed surging orders as special customs operations got underway in the island province on December 18. 展开更多
关键词 reduce institutional costs global goods foreign goods special customs operations HAINAN customs operations institutional costs translation company
在线阅读 下载PDF
Aligning with Global Rules The Hainan FTP is China's new model for institutional opening-up
16
作者 Yu Yunquan 《China Report ASEAN》 2026年第3期24-25,共2页
The Hainan Free Trade Port (FTP) is a key step for China to advance high-standard opening-up and seize a more active role in economic globalization. After early trials, a policy framework has taken shape, and islandwi... The Hainan Free Trade Port (FTP) is a key step for China to advance high-standard opening-up and seize a more active role in economic globalization. After early trials, a policy framework has taken shape, and islandwide special customs operations mark a shift from design to full implementation.As of January 18, island-wide special customs operations in Hainan FTP had been in place for a month. The first month ran smoothly, with more efficient flow of goods, people, and capital.This reflects China’s institutional opening-up and, amid slowing global growth, has injected fresh vitality into the regional and global economy. 展开更多
关键词 free trade port Special Customs Operations economic globalization policy framework Hainan Free Trade Port Institutional Opening up customs operations Regional Economy
在线阅读 下载PDF
Lines Across Horizons Hainan's island-wide special customs operations are redefining boundaries to elevate opening-up
17
作者 Yang Hangjun 《China Report ASEAN》 2026年第3期16-19,共4页
On December 18,2025, Hainan Free Trade Port (Hainan FTP) officially began islandwide special customs operations.Although only two months have passed since this landmark step, the shift is already visible everywhere—f... On December 18,2025, Hainan Free Trade Port (Hainan FTP) officially began islandwide special customs operations.Although only two months have passed since this landmark step, the shift is already visible everywhere—from the bustling flow of international passengers at Haikou Meilan International Airport to the steady stream of cargo vessels calling at Yangpu Port, and even in the sustained attention investors are paying to “Hainan-related” stocks.Together, these signals point to one clear conclusion:China’s largest special economic zone has entered a new phase of development. 展开更多
关键词 free trade port Special Customs Operations Hainan Free Trade Port Islandwide Special Customs Operations International Passengers cargo vessels INVESTORS Opening up
在线阅读 下载PDF
Improvement of a Dual-Polarization Radar Operator for Ice-phase Microphysical Terms
18
作者 Ji-Won LEE Ki-Hong MIN GyuWon LEE 《Advances in Atmospheric Sciences》 2026年第3期550-564,共15页
Dual-polarization(dual-pol)radar variables provide information about the quantity,type,size,and water content of hydrometeors.Assimilating these dual-pol radar variables into numerical weather prediction models can en... Dual-polarization(dual-pol)radar variables provide information about the quantity,type,size,and water content of hydrometeors.Assimilating these dual-pol radar variables into numerical weather prediction models can enhance forecast accuracy.Observation operators are essential for radar data assimilation.This study focuses on applying a realistic dual-pol radar observation operator to more accurately calculate dual-pol radar variables.Previously reported dual-pol radar observation operators tended to overestimate radar variables near 0℃ in convective precipitation and simulate unrealistic dual-pol radar variables in subfreezing regions.To address this,the improved operator(KNU dual-pol radar observation operator;K-DROP)limits the distribution of mixed-phase hydrometeors,which have both solid and liquid properties,in areas with strong updrafts and downdrafts,improving the overestimation of radar variables near the melting layer.Additionally,by applying the observed snow axis ratio during winter to K-DROP,the issue of differential reflectivity(Z_(DR))being calculated as a constant value in subfreezing regions has been improved.By incorporating the observed maximum radius of hydrometeors into K-DROP,the overestimation of reflectivity(Z_(H))in subfreezing regions,the overestimation of Z_(DR)in warm regions,and the underestimation of specific differential phase(K_(DP))in subfreezing regions and overestimation in warm regions,are improved.Compared to previous operators,the enhanced version reported in the present work produces more realistic dual-pol radar variables. 展开更多
关键词 dual-polarization radar operator observation operator radar data assimilation remote sensing
在线阅读 下载PDF
CHINESE MEDIA
19
《China Report ASEAN》 2026年第1期6-9,共4页
China launches island-wide special customs operations in Hainan FTP.China launched island-wide special customs operations in the Hainan Free Trade Port(FTP),the world’s largest FTP by area,on December 18,2025,allowin... China launches island-wide special customs operations in Hainan FTP.China launched island-wide special customs operations in the Hainan Free Trade Port(FTP),the world’s largest FTP by area,on December 18,2025,allowing freer entry of overseas goods,expanding zerotariff coverage,and introducing more business-friendly measures. 展开更多
关键词 business friendly measures zero tariff special customs operations free trade port ftp customs operations hainan free trade port
在线阅读 下载PDF
Hainan FTP:A New Step to Align with International Rules in Opening-Up
20
作者 YU YUNQUAN 《China Today》 2026年第3期32-33,共2页
The Hainan Free Trade Port’s implementation of special customs operations marks a significant stride in China’s institutional opening-up,spurring global trade and investment flows.THE Hainan Free Trade Port(FTP)repr... The Hainan Free Trade Port’s implementation of special customs operations marks a significant stride in China’s institutional opening-up,spurring global trade and investment flows.THE Hainan Free Trade Port(FTP)represents a significant step forward in China’s pursuit of high-standard opening-up and greater engagement in economic globalization. 展开更多
关键词 implementation special customs operations Special Customs Operations free trade port's Global Trade Hainan Free Trade Port free trade port ftp represents Institutional Opening Up Investment Flows
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部