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Incremental support vector machine algorithm based on multi-kernel learning 被引量:7
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作者 Zhiyu Li Junfeng Zhang Shousong Hu 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2011年第4期702-706,共5页
A new incremental support vector machine (SVM) algorithm is proposed which is based on multiple kernel learning. Through introducing multiple kernel learning into the SVM incremental learning, large scale data set l... A new incremental support vector machine (SVM) algorithm is proposed which is based on multiple kernel learning. Through introducing multiple kernel learning into the SVM incremental learning, large scale data set learning problem can be solved effectively. Furthermore, different punishments are adopted in allusion to the training subset and the acquired support vectors, which may help to improve the performance of SVM. Simulation results indicate that the proposed algorithm can not only solve the model selection problem in SVM incremental learning, but also improve the classification or prediction precision. 展开更多
关键词 support vector machine (SVM) incremental learning multiple kernel learning (MKL).
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Learning control of nonhonolomic robot based on support vector machine
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作者 冯勇 葛运建 +1 位作者 曹会彬 孙玉香 《Journal of Central South University》 SCIE EI CAS 2012年第12期3400-3406,共7页
A learning controller of nonhonolomic robot in real-time based on support vector machine(SVM)is presented.The controller includes two parts:one is kinematic controller based on nonlinear law,and the other is dynamic c... A learning controller of nonhonolomic robot in real-time based on support vector machine(SVM)is presented.The controller includes two parts:one is kinematic controller based on nonlinear law,and the other is dynamic controller based on SVM.The kinematic controller is aimed to provide desired velocity which can make the steering system stable.The dynamic controller is aimed to transform the desired velocity to control torque.The parameters of the dynamic system of the robot are estimated through SVM learning algorithm according to the training data of sliding windows in real time.The proposed controller can adapt to the changes in the robot model and uncertainties in the environment.Compared with artificial neural network(ANN)controller,SVM controller can converge to the reference trajectory more quickly and the tracking error is smaller.The simulation results verify the effectiveness of the method proposed. 展开更多
关键词 nonhonolomic robot learning control support vector machine nonlinear control law dynamic control
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A Novel Kernel for Least Squares Support Vector Machine
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作者 冯伟 赵永平 +2 位作者 杜忠华 李德才 王立峰 《Defence Technology(防务技术)》 SCIE EI CAS 2012年第4期240-247,共8页
Extreme learning machine(ELM) has attracted much attention in recent years due to its fast convergence and good performance.Merging both ELM and support vector machine is an important trend,thus yielding an ELM kernel... Extreme learning machine(ELM) has attracted much attention in recent years due to its fast convergence and good performance.Merging both ELM and support vector machine is an important trend,thus yielding an ELM kernel.ELM kernel based methods are able to solve the nonlinear problems by inducing an explicit mapping compared with the commonly-used kernels such as Gaussian kernel.In this paper,the ELM kernel is extended to the least squares support vector regression(LSSVR),so ELM-LSSVR was proposed.ELM-LSSVR can be used to reduce the training and test time simultaneously without extra techniques such as sequential minimal optimization and pruning mechanism.Moreover,the memory space for the training and test was relieved.To confirm the efficacy and feasibility of the proposed ELM-LSSVR,the experiments are reported to demonstrate that ELM-LSSVR takes the advantage of training and test time with comparable accuracy to other algorithms. 展开更多
关键词 计算技术 理论 方法 自动机理论
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Parameter selection of support vector machine for function approximation based on chaos optimization 被引量:18
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作者 Yuan Xiaofang Wang Yaonan 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第1期191-197,共7页
The support vector machine (SVM) is a novel machine learning method, which has the ability to approximate nonlinear functions with arbitrary accuracy. Setting parameters well is very crucial for SVM learning results... The support vector machine (SVM) is a novel machine learning method, which has the ability to approximate nonlinear functions with arbitrary accuracy. Setting parameters well is very crucial for SVM learning results and generalization ability, and now there is no systematic, general method for parameter selection. In this article, the SVM parameter selection for function approximation is regarded as a compound optimization problem and a mutative scale chaos optimization algorithm is employed to search for optimal paraxneter values. The chaos optimization algorithm is an effective way for global optimal and the mutative scale chaos algorithm could improve the search efficiency and accuracy. Several simulation examples show the sensitivity of the SVM parameters and demonstrate the superiority of this proposed method for nonlinear function approximation. 展开更多
关键词 learning systems support vector machines (SVM) approximation theory parameter selection optimization.
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Time series online prediction algorithm based on least squares support vector machine 被引量:8
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作者 吴琼 刘文颖 杨以涵 《Journal of Central South University of Technology》 EI 2007年第3期442-446,共5页
Deficiencies of applying the traditional least squares support vector machine (LS-SVM) to time series online prediction were specified. According to the kernel function matrix's property and using the recursive cal... Deficiencies of applying the traditional least squares support vector machine (LS-SVM) to time series online prediction were specified. According to the kernel function matrix's property and using the recursive calculation of block matrix, a new time series online prediction algorithm based on improved LS-SVM was proposed. The historical training results were fully utilized and the computing speed of LS-SVM was enhanced. Then, the improved algorithm was applied to timc series online prediction. Based on the operational data provided by the Northwest Power Grid of China, the method was used in the transient stability prediction of electric power system. The results show that, compared with the calculation time of the traditional LS-SVM(75 1 600 ms), that of the proposed method in different time windows is 40-60 ms, proposed method is above 0.8. So the improved method is online prediction. and the prediction accuracy(normalized root mean squared error) of the better than the traditional LS-SVM and more suitable for time series online prediction. 展开更多
关键词 time series prediction machine learning support vector machine statistical learning theory
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Support vector machine based nonlinear model multi-step-ahead optimizing predictive control 被引量:9
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作者 钟伟民 皮道映 孙优贤 《Journal of Central South University of Technology》 EI 2005年第5期591-595,共5页
A support vector machine with guadratic polynomial kernel function based nonlinear model multi-step-ahead optimizing predictive controller was presented. A support vector machine based predictive model was established... A support vector machine with guadratic polynomial kernel function based nonlinear model multi-step-ahead optimizing predictive controller was presented. A support vector machine based predictive model was established by black-box identification. And a quadratic objective function with receding horizon was selected to obtain the controller output. By solving a nonlinear optimization problem with equality constraint of model output and boundary constraint of controller output using Nelder-Mead simplex direct search method, a sub-optimal control law was achieved in feature space. The effect of the controller was demonstrated on a recognized benchmark problem and a continuous-stirred tank reactor. The simulation results show that the multi-step-ahead predictive controller can be well applied to nonlinear system, with better performance in following reference trajectory and disturbance-rejection. 展开更多
关键词 nonlinear model predictive control support vector machine nonlinear system identification kernel function nonlinear optimization
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Elastic Multiple Kernel Learning 被引量:6
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作者 WU Zheng-Peng ZHANG Xue-Gong 《自动化学报》 EI CSCD 北大核心 2011年第6期693-699,共7页
(MKL ) 多重核学习被建议处理核熔化。MKL 听说线性联合几个核并且解决同时与联合的核联系的支持的向量机器(SVM ) 。MKL 的当前的框架鼓励核联合系数的稀少。核的重要部分什么时候是增进知识的,强迫稀少,趋于选择仅仅一些核并且可以... (MKL ) 多重核学习被建议处理核熔化。MKL 听说线性联合几个核并且解决同时与联合的核联系的支持的向量机器(SVM ) 。MKL 的当前的框架鼓励核联合系数的稀少。核的重要部分什么时候是增进知识的,强迫稀少,趋于选择仅仅一些核并且可以忽略有用信息。在这份报纸,我们建议学习的有弹性的多重核(EMKL ) 完成适应的核熔化。EMKL 使用混合规则化功能损害稀少和非稀少。MKL 和 SVM 能被认为是 EMKL 的特殊情况。为 MKL 问题基于坡度降下算法,我们建议一个快算法解决 EMKL 问题。模拟数据集上的结果证明 EMKL 的表演有利地比作 MKL 和 SVM。我们进一步把 EMKL 用于基因集合分析并且得到有希望的结果。最后,我们学习比作另外的非稀少的 MKL 的 EMKL 的理论优点。 展开更多
关键词 《自动化学报》 期刊 摘要 编辑部
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Support Vector Machine:A Novel Tool for Mineral Prospectivity Mapping 被引量:1
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作者 Renguang Zuo~1,Gang Chen~2 1.State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China. 2.Faculty of Information Engineering,China University of Geosciences(Wuhan),Wuhan 430074,China 《地学前缘》 EI CAS CSCD 北大核心 2009年第S1期289-289,共1页
Support Vector Machine(SVM) was demonstrated as a potentially useful tool to integrate multi-variables and to produce a predictive map for mineral deposits. The e 1071,a free R package,was used to construct a SVM with... Support Vector Machine(SVM) was demonstrated as a potentially useful tool to integrate multi-variables and to produce a predictive map for mineral deposits. The e 1071,a free R package,was used to construct a SVM with radial kernel function to integrate four evidence layers and to map prospectivity for Gangdese porphyry copper deposits.The results demonstrate that the predicted prospective target area for Cu occupies 20.5%of the total study area and contains 52.4%of the total number of known porphyry copper deposits.The results obtained 展开更多
关键词 support vector machine kernel function prospectivity NEURAL Network TIBET
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Support Vector Machine-Based Nonlinear System Modeling and Control 被引量:1
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作者 张浩然 韩正之 +1 位作者 冯瑞 于志强 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2003年第3期53-58,共6页
This paper provides an introduction to a support vector machine, a new kernel-based technique introduced in statistical learning theory and structural risk minimization, then presents a modeling-control framework base... This paper provides an introduction to a support vector machine, a new kernel-based technique introduced in statistical learning theory and structural risk minimization, then presents a modeling-control framework based on SVM. At last a numerical experiment is taken to demonstrate the proposed approach's correctness and effectiveness. 展开更多
关键词 support vector machine Statistical learning theory Nonlinear systems Modeling and control.
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Multiclassification algorithm and its realization based on least square support vector machine algorithm
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作者 Fan Youping Chen Yunping +1 位作者 Sun Wansheng Li Yu 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2005年第4期901-907,共7页
As a new type of learning machine developed on the basis of statistics learning theory, support vector machine (SVM) plays an important role in knowledge discovering and knowledge updating by constructing non-linear... As a new type of learning machine developed on the basis of statistics learning theory, support vector machine (SVM) plays an important role in knowledge discovering and knowledge updating by constructing non-linear optimal classifter. However, realizing SVM requires resolving quadratic programming under constraints of inequality, which results in calculation difficulty while learning samples gets larger. Besides, standard SVM is incapable of tackling multi-classification. To overcome the bottleneck of populating SVM, with training algorithm presented, the problem of quadratic programming is converted into that of resolving a linear system of equations composed of a group of equation constraints by adopting the least square SVM(LS-SVM) and introducing a modifying variable which can change inequality constraints into equation constraints, which simplifies the calculation. With regard to multi-classification, an LS-SVM applicable in multi-dassiftcation is deduced. Finally, efficiency of the algorithm is checked by using universal Circle in square and twospirals to measure the performance of the classifier. 展开更多
关键词 control theory control engineering artificial intelligence machine learning support vector machine.
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基于SPSO优化Multiple Kernel-TWSVM的滚动轴承故障诊断 被引量:7
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作者 徐冠基 曾柯 柏林 《振动.测试与诊断》 EI CSCD 北大核心 2019年第5期973-979,1130,共8页
双子支持向量机(twin support vector machine,简称TWSVM)的核函数选择对其分类性能有着重要影响,TWSVM其核函数一般是局部核函数或者全局核函数,这两种核函数的泛化能力和分类性能不能兼顾。笔者利用综合加权的高斯局部核函数和多项式... 双子支持向量机(twin support vector machine,简称TWSVM)的核函数选择对其分类性能有着重要影响,TWSVM其核函数一般是局部核函数或者全局核函数,这两种核函数的泛化能力和分类性能不能兼顾。笔者利用综合加权的高斯局部核函数和多项式全局核函数方法组成双核函数来改进TWSVM以提高其泛化能力和分类性能,并采用简化粒子群优化(simple particle swarm optimization,简称SPSO)方法来对权值和参数进行优化,提出了SPSO优化Multiple Kernel-TWSVM模型,将该模型应用到滚动轴承故障诊断模式识别中。实验结果表明,双核TWSVM比单核TWSVM和反向传播(back propagation,简称BP)神经网络具有更高的分类准确率。 展开更多
关键词 滚动轴承 故障诊断 相空间重构 简化粒子群优化 双核双子支持向量机
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Fault diagnosis model based on multi-manifold learning and PSO-SVM for machinery 被引量:6
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作者 Wang Hongjun Xu Xiaoli Rosen B G 《仪器仪表学报》 EI CAS CSCD 北大核心 2014年第S2期210-214,共5页
Fault diagnosis technology plays an important role in the industries due to the emergency fault of a machine could bring the heavy lost for the people and the company. A fault diagnosis model based on multi-manifold l... Fault diagnosis technology plays an important role in the industries due to the emergency fault of a machine could bring the heavy lost for the people and the company. A fault diagnosis model based on multi-manifold learning and particle swarm optimization support vector machine(PSO-SVM) is studied. This fault diagnosis model is used for a rolling bearing experimental of three kinds faults. The results are verified that this model based on multi-manifold learning and PSO-SVM is good at the fault sensitive features acquisition with effective accuracy. 展开更多
关键词 FAULT diagnosis multi-manifold learning particle SWARM optimization support vector machine
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Kernel matrix learning with a general regularized risk functional criterion 被引量:3
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作者 Chengqun Wang Jiming Chen +1 位作者 Chonghai Hu Youxian Sun 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2010年第1期72-80,共9页
Kernel-based methods work by embedding the data into a feature space and then searching linear hypothesis among the embedding data points. The performance is mostly affected by which kernel is used. A promising way is... Kernel-based methods work by embedding the data into a feature space and then searching linear hypothesis among the embedding data points. The performance is mostly affected by which kernel is used. A promising way is to learn the kernel from the data automatically. A general regularized risk functional (RRF) criterion for kernel matrix learning is proposed. Compared with the RRF criterion, general RRF criterion takes into account the geometric distributions of the embedding data points. It is proven that the distance between different geometric distdbutions can be estimated by their centroid distance in the reproducing kernel Hilbert space. Using this criterion for kernel matrix learning leads to a convex quadratically constrained quadratic programming (QCQP) problem. For several commonly used loss functions, their mathematical formulations are given. Experiment results on a collection of benchmark data sets demonstrate the effectiveness of the proposed method. 展开更多
关键词 kernel method support vector machine kernel matrix learning HKRS geometric distribution regularized risk functional criterion.
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Improved adaptive pruning algorithm for least squares support vector regression 被引量:4
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作者 Runpeng Gao Ye San 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2012年第3期438-444,共7页
As the solutions of the least squares support vector regression machine (LS-SVRM) are not sparse, it leads to slow prediction speed and limits its applications. The defects of the ex- isting adaptive pruning algorit... As the solutions of the least squares support vector regression machine (LS-SVRM) are not sparse, it leads to slow prediction speed and limits its applications. The defects of the ex- isting adaptive pruning algorithm for LS-SVRM are that the training speed is slow, and the generalization performance is not satis- factory, especially for large scale problems. Hence an improved algorithm is proposed. In order to accelerate the training speed, the pruned data point and fast leave-one-out error are employed to validate the temporary model obtained after decremental learning. The novel objective function in the termination condition which in- volves the whole constraints generated by all training data points and three pruning strategies are employed to improve the generali- zation performance. The effectiveness of the proposed algorithm is tested on six benchmark datasets. The sparse LS-SVRM model has a faster training speed and better generalization performance. 展开更多
关键词 least squares support vector regression machine (LS- SVRM) PRUNING leave-one-out (LOO) error incremental learning decremental learning.
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Classification of hyperspectral remote sensing images based on simulated annealing genetic algorithm and multiple instance learning 被引量:3
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作者 高红民 周惠 +1 位作者 徐立中 石爱业 《Journal of Central South University》 SCIE EI CAS 2014年第1期262-271,共10页
A hybrid feature selection and classification strategy was proposed based on the simulated annealing genetic algonthrn and multiple instance learning (MIL). The band selection method was proposed from subspace decom... A hybrid feature selection and classification strategy was proposed based on the simulated annealing genetic algonthrn and multiple instance learning (MIL). The band selection method was proposed from subspace decomposition, which combines the simulated annealing algorithm with the genetic algorithm in choosing different cross-over and mutation probabilities, as well as mutation individuals. Then MIL was combined with image segmentation, clustering and support vector machine algorithms to classify hyperspectral image. The experimental results show that this proposed method can get high classification accuracy of 93.13% at small training samples and the weaknesses of the conventional methods are overcome. 展开更多
关键词 hyperspectral remote sensing images simulated annealing genetic algorithm support vector machine band selection multiple instance learning
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深埋长大隧道地温预测的机器学习算法对比研究 被引量:1
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作者 周权 罗锋 +1 位作者 柴波 周爱国 《安全与环境工程》 北大核心 2025年第1期137-147,共11页
地热对隧道施工、工程结构及运营安全等均有较大的危害,随着我国基础设施建设布局西移,隧道建设的地质条件愈发复杂,隧道埋深和长度不断增加,隧道施工期高温热害问题频发。针对传统地温预测方法中预测精度不高、数据运用不充分,单一机... 地热对隧道施工、工程结构及运营安全等均有较大的危害,随着我国基础设施建设布局西移,隧道建设的地质条件愈发复杂,隧道埋深和长度不断增加,隧道施工期高温热害问题频发。针对传统地温预测方法中预测精度不高、数据运用不充分,单一机器学习模型解译性差等问题,以A隧道为研究对象,将决策树(decision tree,DT)、支持向量机(support vector machine,SVM)、随机森林(random forest,RF)进行耦合,提出了基于DT-SVM-RF模型的深埋长大隧道地温预测方法。在分析隧道综合测井、地应力及岩石热物理试验、航空物探数据后,选取深度、声波波速等10个影响因子作为模型的输入,采用随机交叉验证和空间交叉验证对模型的鲁棒性、泛化能力进行检验,构建LASSO回归、随机森林、互信息3种回归模型,分析10个影响因子的特征重要性排序。结果表明:在测试集上多元线性回归、支持向量机、人工神经网络和决策树-支持向量机-随机森林(decision tree-support vector machinerandom forest,DT-SVM-RF)模型决定系数(R^(2))分别为0.76、0.91、0.88、0.93,均方误差MSE分别为17.64、6.25、8.46、5.20,DT-SVM-RF模型具有相对更优的预测性能,深度、岩石导温系数、岩石导热系数、最大水平主应力特征较为重要,说明DT-SVM-RF模型能有效地提高地温预测的准确率。研究结果可为类似隧道地温预测提供一种精度更高的可行新思路。 展开更多
关键词 隧道热害 隧道安全 多元线性回归 支持向量机(SVM) 随机森林(RF) 人工神经网络(ANN) 特征选择
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基于物理驱动支持向量机方法的地震作用下结构动力响应求解 被引量:2
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作者 杜轲 吴文贤 +1 位作者 林志鹏 骆欢 《振动与冲击》 北大核心 2025年第3期284-290,共7页
物理驱动机器学习是一种将物理原理融入机器学习框架的前沿方法。通过引入物理知识,该方法旨在使模型更为贴合实际世界的物理规律和约束,以提高模型在学习过程中对数据本质特征的准确捕捉。该研究使用了一种以支持向量机为基础的物理驱... 物理驱动机器学习是一种将物理原理融入机器学习框架的前沿方法。通过引入物理知识,该方法旨在使模型更为贴合实际世界的物理规律和约束,以提高模型在学习过程中对数据本质特征的准确捕捉。该研究使用了一种以支持向量机为基础的物理驱动方法,用于精确计算结构的动力响应。该算法通过最小化多输出最小二乘支持向量机的目标函数,实现了对回归模型参数的精准拟合。同时,通过在特征空间中引入系统动态平衡方程和初始条件的物理约束,无需事先训练数据即可有效计算结构的动力响应。随后开展在地震动荷载作用下的单自由度体系和二层剪切框架多自由度体系的动力响应,并将所用方法与传统方法的结果进行了对比。分析结果表明,提出的物理驱动机器学习方法在精度和大时间步长性能方面均显著优于传统方法。 展开更多
关键词 机器学习 支持向量机 物理驱动 无标记数据 结构动力响应分析
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电力变压器内部故障的递进分层诊断方法 被引量:1
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作者 咸日常 李云淏 +4 位作者 刘焕国 王昭璇 张海强 胡玉耀 王玮 《电网技术》 北大核心 2025年第4期1726-1734,I0079,I0080,共11页
电力变压器内部故障成因复杂、种类繁多,精确诊断难度大,现有诊断技术大多滞留于故障定性阶段。为实现多类型故障的精准定位,该文通过建立多状态量与故障特征之间的递进映射关系,提出一种改进灰狼算法与最小二乘支持向量机耦合的电力变... 电力变压器内部故障成因复杂、种类繁多,精确诊断难度大,现有诊断技术大多滞留于故障定性阶段。为实现多类型故障的精准定位,该文通过建立多状态量与故障特征之间的递进映射关系,提出一种改进灰狼算法与最小二乘支持向量机耦合的电力变压器故障递进分层诊断方法。首先介绍改进灰狼算法与最小二乘支持向量机的原理,建立电力变压器故障递进分层、自动诊断及定位模型;其次基于300组电力变压器的状态量,利用核主成分分析法进行降维处理,选取线性无关的特征状态量,依据DL/T 1685—2017《油浸式变压器状态评价导则》进行离散化处理,借助算法模型递进分层、自动诊断:第一层诊断故障回路、第二层确定故障部位、第三层明确故障原因,得到各分类器的诊断准确率及惩罚系数和核函数参数的最优组合解,并与其他算法模型的故障诊断结果进行分析对比;最后以实际故障案例验证方法的有效性。结果表明:该文所提诊断模型比其他方法拥有更高准确率和更快的运算速度。 展开更多
关键词 电力变压器 改进灰狼算法 最小二乘支持向量机 多状态量 内部故障 递进分层诊断
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多策略改进COA算法优化LSSVM的变压器故障诊断研究 被引量:1
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作者 李斌 白翔旭 《电工电能新技术》 北大核心 2025年第4期112-119,共8页
为解决变压器故障诊断准确率低的问题,本文提出一种多策略改进浣熊优化算法(ICOA)与最小二乘支持向量机(LSSVM)相结合的变压器故障诊断方法。首先,通过核主成分分析(KPCA)将变压器故障数据集进行特征提取,降低故障数据维度;其次,应用混... 为解决变压器故障诊断准确率低的问题,本文提出一种多策略改进浣熊优化算法(ICOA)与最小二乘支持向量机(LSSVM)相结合的变压器故障诊断方法。首先,通过核主成分分析(KPCA)将变压器故障数据集进行特征提取,降低故障数据维度;其次,应用混沌映射、透镜反向学习、Levy飞行等策略对浣熊优化算法(COA)进行优化,提高全局寻优能力;然后,应用ICOA算法进行LSSVM参数寻优,构建ICOA-LSSVM故障诊断模型;最后,将特征提取后的数据导入ICOA-LSSVM中并与其他模型对比。实验结果表明所提方法准确率为96.19%,相比其他诊断模型具有更高的故障诊断精度。 展开更多
关键词 变压器故障诊断 浣熊优化算法 核主成分分析 最小二乘支持向量机
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机器学习模型在急性前循环大血管闭塞性缺血性卒中机械取栓术后预后预测中的应用
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作者 杨潇 刘松 +3 位作者 国晶晶 田超 韩彤 靳松 《中国现代神经疾病杂志》 北大核心 2025年第8期761-770,共10页
目的基于真实世界临床数据,评估未加权机器学习模型对急性前循环大血管闭塞性缺血性卒中患者行机械取栓术后预后的预测效能,筛选最优模型,并评估类别加权策略与最优模型预测效能的差异。方法纳入2023年5月至2024年9月在天津市环湖医院... 目的基于真实世界临床数据,评估未加权机器学习模型对急性前循环大血管闭塞性缺血性卒中患者行机械取栓术后预后的预测效能,筛选最优模型,并评估类别加权策略与最优模型预测效能的差异。方法纳入2023年5月至2024年9月在天津市环湖医院行血管内机械取栓术的191例急性前循环大血管闭塞性缺血性卒中患者,收集其临床资料如入院时美国国立卫生研究院卒中量表(NIHSS)评分。同时回顾分析入院时头部平扫CT、多时相CT血管成像(mCTA)和CT灌注成像(CTP)资料,采用mCTA评估侧支循环状态;采用Alberta脑卒中计划早期CT评分(ASPECTS)基于平扫CT评估大脑中动脉供血区早期缺血性改变;采用CTP评估脑灌注状态,获得Mismatch体积、Tmax>4 s体积、Tmax>6 s体积、Tmax>8 s体积、Tmax>10 s体积。以术后90 d改良Rankin量表(mRS)评分作为预后评估指标(>2分为神经功能预后不良)。采用最小绝对收缩和选择算子(LASSO)回归进行特征筛选,分别采用逻辑回归、随机森林、支持向量机、决策树、k近邻和极端梯度提升算法构建未加权预后预测模型。通过受试者工作特征曲线及曲线下面积(AUC)、校准曲线及Brier分数、决策曲线分析评估模型预测效能,筛选最优模型,采用Shapley加法解释对最优模型进行特征重要性分析;同时评估类别加权策略与该最优模型预测效能的差异。结果通过十折交叉验证最小偏差准则确定LASSO回归最优λ值为0.064,筛选出4个特征变量,即ASPECTS评分、Tmax>10 s体积、入院时NIHSS评分及侧支循环不良。采用分层抽样将所有患者按7∶3比例随机分配至训练集(133例)和测试集(58例),基于上述6种机器学习算法及4个特征变量,建立未加权预测模型。在未加权模型中,除外过拟合的随机森林与极端梯度提升模型,Delong检验显示其余模型的AUC值两两比较差异无统计学意义(均P>0.05);但未加权支持向量机模型的Brier分数最低(0.16),提示其校准能力最强;在参考阈值概率15%~30%范围内,未加权支持向量机模型的决策曲线最高,提示具有最佳临床适用性。类别加权与未加权支持向量机模型的AUC值、灵敏度、特异度、准确率、阳性预测值和阴性预测值比较差异无统计学意义(均P>0.05);但与未加权支持向量机模型相比,类别加权支持向量机模型的Brier分数较高(0.17对0.16),提示其校准能力减弱。结论在真实世界急性前循环大血管闭塞性缺血性卒中队列中,未加权支持向量机模型可以准确预测机械取栓术后神经功能不良结局,无需依赖类别加权,且该方法具有较高的临床转化潜力。 展开更多
关键词 缺血性卒中 血栓切除术 机器学习 支持向量机 预后
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