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ON NUMBER OF LIMIT CYCLES FOR THE QUADRATIC SYSTEMS WITH A WEAK FOCUS AND A STRONG FOCUS 被引量:1
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作者 Zhang Pingguang Zhao ShenqiDept.ofMath.ZhejiangUniv.,Hangzhou310027. 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2001年第2期127-132,共6页
It is proved that the quadratic system with a weak focus and a strong focus has at most one limit cycle around the strong focus, and as the weak focus is a 2nd order(or 3rd order) weak focus the quadratic system ha... It is proved that the quadratic system with a weak focus and a strong focus has at most one limit cycle around the strong focus, and as the weak focus is a 2nd order(or 3rd order) weak focus the quadratic system has at most two(one) limit cycles which have (1,1) distribution ((0,1) distribution). 展开更多
关键词 Quadratic differential system number of limit cycle weak focus strong focus.
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Modification of rock mass rating system:Interbedding of strong and weak rock layers 被引量:7
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作者 Mohammad Mohammadi Mohammad Farouq Hossaini 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2017年第6期1165-1170,共6页
Rock mass classification systems are the very important part for underground projects and rock mass rating(RMR) is one of the most commonly applied classification systems in numerous civil and mining projects. The typ... Rock mass classification systems are the very important part for underground projects and rock mass rating(RMR) is one of the most commonly applied classification systems in numerous civil and mining projects. The type of rock mass consisting of an interbedding of strong and weak layers poses difficulties and uncertainties for determining the RMR. For this, the present paper uses the concept of rock bolt supporting factor(RSF) for modification of RMR system to be used in such rock mass types. The proposed method also demonstrates the importance of rock bolting practice in such rock masses. The geological parameters of the Shemshak Formation of the Alborz Tunnel in Iran are used as case examples for development of the theoretical approach. 展开更多
关键词 Rock mass rating(RMR) strong and weak rock layers Interbedding Rock bolt supporting factor(RSF) Alborz tunnel
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Global existence of weak solutions to a prey-predator model with strong cross-diffusion
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作者 李慧玲 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2009年第6期727-740,共14页
Using finite differences and entropy inequalities, the global existence of weak solutions to a multidimensional parabolic strongly coupled prey-predator model is obtained. The nonnegativity of the solutions is also sh... Using finite differences and entropy inequalities, the global existence of weak solutions to a multidimensional parabolic strongly coupled prey-predator model is obtained. The nonnegativity of the solutions is also shown. 展开更多
关键词 prey-predator model strong cross-diffusion entropy functional existenceof weak solutions Orlicz space
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Strong/weak limits and strong/weak differentials of multi-variable indeterminate forms. I: Deduction and geometric illustration
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作者 宋光世 《Journal of Chongqing University》 CAS 2003年第2期104-108,共5页
Strong and weak limits as well as strong and weak differentials of multi-variable indeterminate forms are discussed based on the thorough exploration of differentiation to solve the strong and weak limits and differen... Strong and weak limits as well as strong and weak differentials of multi-variable indeterminate forms are discussed based on the thorough exploration of differentiation to solve the strong and weak limits and differentials of unitary indeterminate forms. The fruit of this work is going to be reported in three parts. The first part presents the standard analysis on this subject which supplements, systematizes and advances L. Hospital抯 principles on differential calculus by applying special ,general, and limit guaranteeing theories together with K(t) and XhK0 theories. The combination of theoretical analysis and geometric signification makes the derivation intuitional, visual and easy to perceive. 展开更多
关键词 strong limit weak limit strong differential weak differential indeterminate form multi-variable special form general form
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WEAKLY ALGEBRAIC REFLEXIVITY AND STRONGLY ALGEBRAIC REFLEXIVITY
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作者 Tao Changli Lu Shijie Chen PeixinDept.ofAppl.Math.,ShandongUniv.ofSci.andTech.,Taian271019,China,Dept.ofMath.,ZhejiangUniv.,Hangzhou310027,China 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2002年第2期193-198,共6页
Algebraic reflexivity introduced by Hadwin is related to linear interpolation.In this paper,the concepts of weakly algebraic reflexivity and strongly algebraic reflexivity which are also related to linear interpolat... Algebraic reflexivity introduced by Hadwin is related to linear interpolation.In this paper,the concepts of weakly algebraic reflexivity and strongly algebraic reflexivity which are also related to linear interpolation are introduced.Some properties of them are obtained and some relations between them revealed 展开更多
关键词 linear interpolation algebraic reflexivity weakly algebraic reflexivity strongly algebraic REFLEXIVITY surperreflexivity
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Checking weak and strong optimality of the solution to interval convex quadratic program
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作者 XIA Meng-xue LI Miao-miao +1 位作者 ZHANG Ben LI Hao-hao 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2021年第2期172-186,共15页
In this paper,we investigate three canonical forms of interval convex quadratic pro-gramming problems.Necessary and suficient conditions for checking weak and strong optimality of given vector corresponding to various... In this paper,we investigate three canonical forms of interval convex quadratic pro-gramming problems.Necessary and suficient conditions for checking weak and strong optimality of given vector corresponding to various forms of feasible region,are established respectively.By using the concept of feasible direction,these conditions are formulated in the form of linear systems with both equations and inequalities.In addition,we provide two specific examples to illustrate the efficiency of the conditions. 展开更多
关键词 interval convex quadratic program weakly optimal solution strongly optimal solution feasible directions
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Strong and Weak Property of Travelling Wave Front Solutions for a Class of Degenerate Parabolic Equations
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作者 李正元 刘迎东 叶其孝 《Northeastern Mathematical Journal》 CSCD 2001年第2期195-204,共10页
In this paper we study the strong and weak property of travelling wave front solutions for a class of degenerate parabolic equations. How the strong and weak property changes under the effects of wave speed and reacti... In this paper we study the strong and weak property of travelling wave front solutions for a class of degenerate parabolic equations. How the strong and weak property changes under the effects of wave speed and reaction diffusion terms are showed. 展开更多
关键词 degenerate parabolic equation strong traveling wave front solution weak traveling wave front solution convergence or divergence propety of integral
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Key Technical Points of Wheat Moisture-resistant Strain Sowing and Management of Promoting Seedlings from Weak to Strong in Daiyue District
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作者 Juqing GE 《Plant Diseases and Pests》 CAS 2022年第2期27-29,共3页
According to the meteorological conditions of sowing period and the characteristics of seedling in each key growth period,the measures of rushing drainage,rushing harvest stubble,rushing sow,implementing late sowing,s... According to the meteorological conditions of sowing period and the characteristics of seedling in each key growth period,the measures of rushing drainage,rushing harvest stubble,rushing sow,implementing late sowing,strengthening field management before winter and in spring are taken in Daiyue District during the autumn planting period of wheat,which reduce the influence of natural disasters and increase the yield of wheat. 展开更多
关键词 Moisture-resistant strain Late sowing technique Field management Promoting seedlings from weak to strong
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DIRECT TITRATION OF VERY WEAK ACIDS(BASES)IN AQUEOUS SOLUTION WITH STRONG BASES(ACIDS)USING VISUAL END-POINT INDICATION WITHOUT INDICATOR
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作者 Shu Ping BI Guang Yu ZHANG Hone GAO (H.Kao) Chemistry Department,Nanjing University,Nanjing,210008 《Chinese Chemical Letters》 SCIE CAS CSCD 1991年第2期153-154,共2页
This paper reports a new method of titration for very weak acids and bases using the appearance of incisions on oscillopolarogram to indicate the end-point.This method has the advantages of rapidity,simplicity,no indi... This paper reports a new method of titration for very weak acids and bases using the appearance of incisions on oscillopolarogram to indicate the end-point.This method has the advantages of rapidity,simplicity,no indicator needed as well as good precision. 展开更多
关键词 DIRECT TITRATION OF VERY weak ACIDS ACIDS)USING VISUAL END-POINT INDICATION WITHOUT INDICATOR BASES)IN AQUEOUS SOLUTION WITH strong BASES
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INTERACTION OF STRONG AND WEAK SINGULARITIES FOR HYPERBOLIC SYSTEM OF CONSERVATION LAWS IN MULTIDIMENSIONAL SPACE
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作者 陈恕行 《Acta Mathematica Scientia》 SCIE CSCD 1990年第3期298-302,共5页
In this paper we study the interaction of strong and weak singularities for hyperbolic system of conservation laws in multidimensional space. Under the assumption of transversal intersect of the shock front with the b... In this paper we study the interaction of strong and weak singularities for hyperbolic system of conservation laws in multidimensional space. Under the assumption of transversal intersect of the shock front with the bicharacteristics bearing weak singularities we proved a theorem on regularity propagation across the shock front. 展开更多
关键词 INTERACTION OF strong AND weak SINGULARITIES FOR HYPERBOLIC SYSTEM OF CONSERVATION LAWS IN MULTIDIMENSIONAL SPACE
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The strong versus weak theory debate in the UK advertising industry
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作者 Ziying Li 《致富时代(下半月)》 2010年第4期211-213,共3页
关键词 广告业 广告宣传 广告理论 广告策划
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部分包覆钢-混凝土组合梁柱节点抗震性能试验研究 被引量:1
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作者 刘宏欣 贾水钟 +4 位作者 李杰 李亚明 张仪放 蔡艳清 潘法超 《建筑结构》 北大核心 2024年第4期18-23,共6页
为研究不同连接构造的部分包覆钢-混凝土组合梁柱节点(PEC梁柱节点)的抗震性能,对2个PEC梁柱节点试件进行了拟静力加载试验,研究了低周往复荷载作用下PEC梁柱节点试件的破坏现象、滞回曲线、骨架曲线、延性、耗能能力和刚度退化等抗震... 为研究不同连接构造的部分包覆钢-混凝土组合梁柱节点(PEC梁柱节点)的抗震性能,对2个PEC梁柱节点试件进行了拟静力加载试验,研究了低周往复荷载作用下PEC梁柱节点试件的破坏现象、滞回曲线、骨架曲线、延性、耗能能力和刚度退化等抗震性能。结果表明:强轴连接PEC梁柱节点的滞回曲线呈梭形和弓形,在达到极限承载力后仍能保持一定的延性和耗能能力;弱轴连接PEC梁柱节点牛腿与梁间的焊缝处发生破坏,未展现出预期的耗能能力,PEC梁仍在弹塑性状态,没有达到极限状态;PEC梁柱节点核心区混凝土替换为加劲肋板后,试件仍具有较好的承载力、延性和耗能能力,刚度退化规律无明显变化,且强轴连接节点与弱轴连接节点刚度变化规律基本一致;PEC柱牛腿设计过短会导致焊缝连接处断裂,试件延性和耗能能力得不到发挥,剩余刚度较大。 展开更多
关键词 部分包覆钢-混凝土组合梁柱节点 强轴连接 弱轴连接 破坏模式 抗震性能
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鄂尔多斯盆地本溪组碎屑障壁海岸砂体微相南北变化
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作者 孟祥振 窦天财 +4 位作者 蒲仁海 高小平 刘刚 宋明 樊宇洁 《西北大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第3期555-568,共14页
在延长探区近1500口钻井资料的基础上,进行大量岩心和薄片观察以及砂厚和砂地比统计,探究鄂尔多斯盆地本溪组的砂体微相类型、平面形态和分布的沿岸变化及其控制因素。结果表明,延长气田本溪组总体均为中小潮差环境下的陆源碎屑障壁海... 在延长探区近1500口钻井资料的基础上,进行大量岩心和薄片观察以及砂厚和砂地比统计,探究鄂尔多斯盆地本溪组的砂体微相类型、平面形态和分布的沿岸变化及其控制因素。结果表明,延长气田本溪组总体均为中小潮差环境下的陆源碎屑障壁海岸沉积,但南部的甘泉—富县地区波浪作用较弱,形成了典型的障壁砂坝和障壁后沉积。北部延安—靖边南地区波浪作用较强,形成了改造障壁、浅滩和下切谷充填潮道3种主要微相砂体。障壁砂体呈平行岸线的带状或串珠状排列,近源和近岸分布;浅滩砂体呈多个分散的卵圆形远源远岸分布;潮道带砂体充填则受控于古地貌凹槽。该研究结果对延长气田和类似环境的储层识别和评价具有重要的指导意义。 展开更多
关键词 强波浪型障壁 弱波浪型障壁 浅滩 潮道 砂体规模与形态
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“组强村弱”结构下的征地博弈及启示--基于赣西H村的考察
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作者 王波 《山西农业大学学报(社会科学版)》 2024年第4期115-124,共10页
延续既有征地研究中利益博弈的视角,研究发现“村庄治理结构”是影响征地博弈样态的独立因素。区别于将行政村默认为利益博弈中的村级主体,研究关注“组强村弱”治理结构下小组作为博弈主体的征地实践。基于赣西H村的实证分析发现,“组... 延续既有征地研究中利益博弈的视角,研究发现“村庄治理结构”是影响征地博弈样态的独立因素。区别于将行政村默认为利益博弈中的村级主体,研究关注“组强村弱”治理结构下小组作为博弈主体的征地实践。基于赣西H村的实证分析发现,“组弱村强”治理结构的产生与村庄分布形态、宗族认同和土地集体所有等因素有关。它对征地博弈的影响在于:对外博弈中,小组因一致行动能力而具备更强的议价能力;在组内博弈中,小组具备排除行政能力干预、自主决定利益分配的空间,这种宽松的环境加剧了利益分化的群体之间的利益博弈。以小组为单位进行的双层博弈导致村庄公共利益消失、村庄认同弱化以及村庄矛盾激化等一系列后果,动摇了村社共同体的根基,由此产生的纠纷矛盾对基层治理能力提出挑战。 展开更多
关键词 组强村弱 治理结构 利益博弈 征地
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基于数据驱动的红外弱小机动目标检测与跟踪
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作者 陈华杰 钱逸凡 +2 位作者 龙翔 许啸 吴浩宇 《电光与控制》 CSCD 北大核心 2024年第12期64-71,105,共9页
针对复杂背景下红外弱小目标检测跟踪中目标特征缺失、强杂波干扰等问题,基于多帧的处理方法引入了目标运动特征来提升性能,然而针对无人机等新型强机动目标,现有的基于机理模型的多帧处理方法难以覆盖其复杂多变的运动形态,导致其检测... 针对复杂背景下红外弱小目标检测跟踪中目标特征缺失、强杂波干扰等问题,基于多帧的处理方法引入了目标运动特征来提升性能,然而针对无人机等新型强机动目标,现有的基于机理模型的多帧处理方法难以覆盖其复杂多变的运动形态,导致其检测跟踪的效果并不理想。对此,以多帧的处理方法为基础框架,提出了一种复杂背景下基于数据驱动的红外弱小机动目标检测跟踪方法:首先采用MPCM算法对弱小目标进行增强;其次将多帧的增强结果投影到二维子空间,构建基于YOLO的二维轨迹检测模型;最后将二维检测结果进行三维时空回溯,构建基于LSTM的三维轨迹检测模型。构建检测模型时,在实测图像的基础上进行了数据增广,使得训练样本尽量覆盖目标的各种运动形态;在二维子空间上,利用高性能YOLO检测网络,快速剔除大量杂波;在三维时空上,利用LSTM时序网络对少量难剔除的杂波进行精细化筛除。与多种算法的对比实验结果表明,所提方法在耗时上能满足实时性要求,同时,在多个场景下的平均跟踪精度能达到86.6%,虚警率仅有9.2%,ROC曲线下的AUC值能达到0.9820。 展开更多
关键词 红外弱小目标 复杂背景 强机动目标 数据驱动 二维子空间 三维时空
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FT-粗糙集模型的一些性质
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作者 张纪平 周缪娟 李进金 《泉州师范学院学报》 2024年第2期1-9,共9页
T-粗糙集是Pawlak粗糙集理论发展过程中的一个重要模型,已成功应用于数据挖掘等诸多领域.FT-粗糙集模型能够在保持数据的完整性下处理连续型数据,是对仅能处理离散型数据的T-粗糙集模型上的发展.文章引入模糊近似空间(X,Y,T)一对模糊集... T-粗糙集是Pawlak粗糙集理论发展过程中的一个重要模型,已成功应用于数据挖掘等诸多领域.FT-粗糙集模型能够在保持数据的完整性下处理连续型数据,是对仅能处理离散型数据的T-粗糙集模型上的发展.文章引入模糊近似空间(X,Y,T)一对模糊集的弱逆和强逆定义,用量化方法研究FT-粗糙集的一些性质,得到模糊技能映射在析取模型、合取模型下分别生成的知识结构;用量化方法与矩阵表示探究FT-粗糙集模糊集值映射在并、交运算下的性质. 展开更多
关键词 FT-粗糙集 模糊近似空间 下逆和上逆 弱逆和强逆
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冀东金厂峪金矿剪切带控矿规律及找矿建议
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作者 鄂建新 缪广 +2 位作者 宁腾霄 郭运晨 张强 《世界有色金属》 2024年第1期82-84,共3页
冀东金厂峪金矿为典型受构造作用控制的矿床,金矿体主要产于NNE向脆-韧性片理化带内的强变形带之中,直接控矿构造为叠加于强变形带之上的NNE向燕山期脆性断裂构造。本文在详细的野外调查基础上进行了构造分期配套,建立了弱变形域控岩+... 冀东金厂峪金矿为典型受构造作用控制的矿床,金矿体主要产于NNE向脆-韧性片理化带内的强变形带之中,直接控矿构造为叠加于强变形带之上的NNE向燕山期脆性断裂构造。本文在详细的野外调查基础上进行了构造分期配套,建立了弱变形域控岩+强变形带赋矿的透镜体控矿模式,结合矿体赋存和矿化富集规律总结,提出了韧脆性片理化带深部、两侧次级平行构造等找矿方向。 展开更多
关键词 冀东 金厂峪金矿 脆-韧性变形 片理化带 强变形带 弱变形域
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中国竞技篮球风格的守正与创新—兼论中国男篮竞技水平提升策略
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作者 霍子文 毕仲春 +2 位作者 赵映辉 崔鲁祥 张戈 《上海体育大学学报》 CSSCI 北大核心 2024年第5期1-10,40,共11页
秉持守正创新原则探讨中国竞技篮球风格,旨在探索中国竞技篮球高质量发展路径。对中国竞技篮球传统中的“以弱胜强”理念进行考辨,认为“以弱胜强”突出强调“立足弱队”与“敢打必胜”的辩证统一,是关于中国竞技篮球最为根本独到、积... 秉持守正创新原则探讨中国竞技篮球风格,旨在探索中国竞技篮球高质量发展路径。对中国竞技篮球传统中的“以弱胜强”理念进行考辨,认为“以弱胜强”突出强调“立足弱队”与“敢打必胜”的辩证统一,是关于中国竞技篮球最为根本独到、积极有为的认知定位和策略思想。运用“快”与“变”的动力学核心观点阐述“在快速基础上以变打快”的逻辑创新,认为“在快速基础上以变打快”必须置于高质量对抗条件下。由之,形成可有效统摄现有表述的中国竞技篮球风格新构念:以弱胜强,在快速基础上、高质量对抗条件下以变打快。围绕新构念的实践深化,探讨中国男篮的技战术打法创新、竞技保障建议和精神面貌臧否。 展开更多
关键词 中国竞技篮球 风格 以弱胜强 技战术 竞技保障 精神面貌
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基于AdaBoost算法的新能源汽车电机异常故障检测 被引量:1
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作者 倪龙飞 白倩 张治斌 《计算机仿真》 2024年第4期97-101,共5页
新能源汽车的电机系统包含许多复杂的部件和子系统,部件之间的相互作用使得异常故障的检测变得复杂,而电机异常故障检测主要采用人工检测方式,即通过耳朵听声音,用眼睛观察,用手触摸找出故障位置,导致故障检测精度较低。因此,提出AdaBo... 新能源汽车的电机系统包含许多复杂的部件和子系统,部件之间的相互作用使得异常故障的检测变得复杂,而电机异常故障检测主要采用人工检测方式,即通过耳朵听声音,用眼睛观察,用手触摸找出故障位置,导致故障检测精度较低。因此,提出AdaBoost算法下新能源汽车电机异常故障检测方法。通过传感器采集电机信号,采用距离相似度、模糊隶属度函数提取信号特征,借助遗传算法的编码操作、交叉操作及其变异操作获取关键信号特征,运用自适应增强(Adaptive Boosting,AdaBoost)算法将信号特征分成正常信号和异常故障,以此实现对新能源汽车电机异常故障检测。实验结果表明,所提算法电机异常故障检测精度高,且耗时短。 展开更多
关键词 弱分类器 强分类器 遗传算法 新能源汽车 电机异常故障检测
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ALIF-NLM轴承微弱故障特征提取方法
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作者 汪应 宋宇博 朱大鹏 《机械强度》 CAS CSCD 北大核心 2024年第5期1026-1035,共10页
针对强噪声背景下滚动轴承早期微弱故障特征难以提取的问题,结合自适应局部迭代滤波(Adaptive Local Iterative Filter,ALIF)和非局部均值(Non-Local Means,NLM)去噪方法的优势,提出了一种ALIF-NLM轴承微弱故障特征提取方法。首先,构建... 针对强噪声背景下滚动轴承早期微弱故障特征难以提取的问题,结合自适应局部迭代滤波(Adaptive Local Iterative Filter,ALIF)和非局部均值(Non-Local Means,NLM)去噪方法的优势,提出了一种ALIF-NLM轴承微弱故障特征提取方法。首先,构建了加权峭度-能量比准则来筛选ALIF分解的本征模态函数(Intrinsic Mode Function,IMF)分量并重构信号。其次,结合峭度对冲击信号的敏感性同能量熵对信号能量分布均匀性和复杂程度的评价性能构建最小能量熵-峭度比指标,并以该指标为适应度函数,利用粒子群优化(Particle Swarm Optimization,PSO)算法实现了NLM方法中参数组合的自适应选取。最后,利用自适应NLM对重构信号进行故障特征提取。仿真和试验分析结果表明,该方法能有效提取出强噪声背景下的滚动轴承微弱故障特征信息。 展开更多
关键词 强噪声 滚动轴承 自适应局部迭代滤波 粒子群优化 非局部均值去噪 微弱特征提取
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