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正倒锥体结构上冰力谱分析实验研究 被引量:6
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作者 曲月霞 李广伟 +1 位作者 李志军 王永学 《海洋工程》 CSCD 北大核心 2001年第3期38-42,共5页
利用研制的新型非冻结可破碎合成模型冰材料 ,进行了冰排与正倒锥体结构物作用的物理模拟试验研究 ,试验中观察记录了冰排的破碎过程并测量了作用于锥体结构物上的冰力。通过快速傅立叶变换方法由所测得的冰力时程曲线得到冰力频谱 ,分... 利用研制的新型非冻结可破碎合成模型冰材料 ,进行了冰排与正倒锥体结构物作用的物理模拟试验研究 ,试验中观察记录了冰排的破碎过程并测量了作用于锥体结构物上的冰力。通过快速傅立叶变换方法由所测得的冰力时程曲线得到冰力频谱 ,分析并讨论了冰排速度、锥体结构物的水线直径、锥角以及冰排弯曲破坏方向等对冰力频谱因子的影响。 展开更多
关键词 冰力频谱 特征频率 尖度因子 快速傅立叶变换 零阶矩 海冰 正倒锥体结构
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Shape Measures for the Distribution of a Qualitative Variable
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作者 José Moral de la Rubia 《Open Journal of Statistics》 2023年第4期619-634,共16页
There are several shape measures for quantitative variables, some of which can also be applied to ordinal variables. In quantitative variables, symmetry, peakedness, and kurtosis are essential properties to evaluate t... There are several shape measures for quantitative variables, some of which can also be applied to ordinal variables. In quantitative variables, symmetry, peakedness, and kurtosis are essential properties to evaluate the deviation from assumptions, particularly normality. They aid in selecting the most appropriate method for estimating parameters and testing hypotheses. Initially, these properties serve a descriptive role in qualitative variables. Once defined, they can be considered to check for non-compliance with assumptions and to propose modifications for testing procedures. The objective of this article is to present three measures of the shape of the distribution of a qualitative variable. The concepts of qualitative asymmetry and peakedness are defined. The measurement of the first concept involves calculating the average frequency difference between qualitative categories matched by frequency homogeneity or proximity. For the second concept, the peak-to-shoulder difference and the qualitative percentile kurtosis are taken into consideration. This last measurement is a less effective option than the peak-to-shoulder difference to measure peakedness. A simulated example of the application of these three measures is given and the paper closes with some conclusions and suggestions. 展开更多
关键词 SYMMETRY peakedness Descriptive Measures Nominal Measurement Scale Qualitative Variables
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Shape Measures for the Distribution of a Qualitative Variable
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作者 José Moral de la Rubia 《Open Journal of Endocrine and Metabolic Diseases》 2023年第4期619-634,共16页
There are several shape measures for quantitative variables, some of which can also be applied to ordinal variables. In quantitative variables, symmetry, peakedness, and kurtosis are essential properties to evaluate t... There are several shape measures for quantitative variables, some of which can also be applied to ordinal variables. In quantitative variables, symmetry, peakedness, and kurtosis are essential properties to evaluate the deviation from assumptions, particularly normality. They aid in selecting the most appropriate method for estimating parameters and testing hypotheses. Initially, these properties serve a descriptive role in qualitative variables. Once defined, they can be considered to check for non-compliance with assumptions and to propose modifications for testing procedures. The objective of this article is to present three measures of the shape of the distribution of a qualitative variable. The concepts of qualitative asymmetry and peakedness are defined. The measurement of the first concept involves calculating the average frequency difference between qualitative categories matched by frequency homogeneity or proximity. For the second concept, the peak-to-shoulder difference and the qualitative percentile kurtosis are taken into consideration. This last measurement is a less effective option than the peak-to-shoulder difference to measure peakedness. A simulated example of the application of these three measures is given and the paper closes with some conclusions and suggestions. 展开更多
关键词 SYMMETRY peakedness Descriptive Measures Nominal Measurement Scale Qualitative Variables
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基于GWO-VMD算法的齿轮故障自适应特征提取
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作者 崔乐晗 于洋 《装备环境工程》 CAS 2023年第2期117-124,共8页
目的 齿轮产生故障时,利用其声发射信号进行自适应特征提取后诊断。方法 利用变分模态分解方法(VMD)对齿轮发生故障时的声发射信号进行分解。在现实状况中,采集声发射原信号噪声干扰大,导致特征提取准确度低,并且模态分解时参数需要人... 目的 齿轮产生故障时,利用其声发射信号进行自适应特征提取后诊断。方法 利用变分模态分解方法(VMD)对齿轮发生故障时的声发射信号进行分解。在现实状况中,采集声发射原信号噪声干扰大,导致特征提取准确度低,并且模态分解时参数需要人为调试设定。鉴于此,引入灰狼优化算法(GWO),对模态分解个数k和二次惩罚因子α自适应选择最优参数后,对信号分解得到本征模态函数(IMF)。通过相关系数选出最佳IMF作为特征分量,计算其峭度和样本熵。结果 计算了各分量的相关系数,选取与原始信号最为相近的分量,分别计算其峭度和样本熵。分解后,齿轮故障声发射信号峭度高于正常的情况,而样本熵则偶然性表现为正常情况下的值大于故障条件下的值。结论 采用支持向量机对特征向量集进行分类识别,对比改进后的试验结果,GWO-VMD结合峭度–样本熵的方法能够有效地提取故障特征,判断齿轮状态是否健康。 展开更多
关键词 齿轮 声发射信号 变分模态分析 灰狼优化 峭度 样本熵 支持向量机
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MINIMUM ENTROPY DECONVOLUTION OF ONE-AND MULTI-DIMENSIONAL NON-GAUSSIAN LINEAR RANDOM PROCESSES
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作者 程乾生 《Science China Mathematics》 SCIE 1990年第10期1153-1162,共10页
The minimum entropy deconvolution is considered as one of the methods for decomposing non-Gaussian linear processes. The concept of peakedness of a system response sequence is presented and its properties are studied.... The minimum entropy deconvolution is considered as one of the methods for decomposing non-Gaussian linear processes. The concept of peakedness of a system response sequence is presented and its properties are studied. With the aid of the peakedness, the convergence theory of the minimum entropy deconvolution is established. The problem of the minimum entropy deconvolution of multi-dimensional non-Gaussian linear random processes is first investigated and the corresponding theory is given. In addition, the relation between the minimum entropy deconvolution and parameter method is discussed. 展开更多
关键词 NON-GAUSSIAN LINEAR RANDOM processes minimum ENTROPY DECONVOLUTION peakedness.
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广义偏斜t分布的APARCH模型与应用
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作者 罗彬 《科教文汇》 2011年第3期203-204,共2页
以股权分置改革以来上证指数的日收益为样本,基于广义偏斜t分布的APARCH模型进行样本内拟合。与现有研究大多发现股市收益率具有尖峰厚尾的结果有所不同,本文发现中国上证指数的收益率经APARCH模型拟合后表现出负偏斜且尖峰薄尾的高阶... 以股权分置改革以来上证指数的日收益为样本,基于广义偏斜t分布的APARCH模型进行样本内拟合。与现有研究大多发现股市收益率具有尖峰厚尾的结果有所不同,本文发现中国上证指数的收益率经APARCH模型拟合后表现出负偏斜且尖峰薄尾的高阶矩特征。 展开更多
关键词 偏斜 峰度 高阶矩 APARCH
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基于PCF重构的北斗B1C信号无模糊捕获算法
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作者 王鹏 张展豪 +1 位作者 金志威 徐庆 《河北大学学报(自然科学版)》 CAS 北大核心 2023年第3期320-329,共10页
针对B1C信号自相关函数存在多峰性会导致基带信号处理过程中存在模糊性问题,提出一种基于伪相关函数(pseudo-correlation function,PCF)重构的无模糊捕获算法,对互相关函数进行重构消除副峰并提高主峰峰值,将B1C信号的数据和导频分量进... 针对B1C信号自相关函数存在多峰性会导致基带信号处理过程中存在模糊性问题,提出一种基于伪相关函数(pseudo-correlation function,PCF)重构的无模糊捕获算法,对互相关函数进行重构消除副峰并提高主峰峰值,将B1C信号的数据和导频分量进行联合捕获提高捕获灵敏度,同时引入降采样和FFT并行捕获策略降低计算复杂度.仿真结果分析表明:改进算法可以实现B1C信号捕获,改进算法在提高主峰的同时,完全消除了副峰,实现了B1C信号捕获的无模糊性.其捕获时间相比其他算法缩短近1/2,在信噪比高于13 dB时,主峰比例均值趋于稳定,最高相比Filtered法提高67.74%,在捕获概率为0.9时联合捕获载噪比低于导频单通道捕获1.8 dB·Hz,并在较低载噪比情况下较其他算法具有更好的适应能力. 展开更多
关键词 B1C信号捕获 多峰性 伪相关函数 联合捕获 降采样
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多维条件下的单峰定理研究 被引量:3
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作者 肖江波 《经济研究导刊》 2010年第31期12-13,共2页
对著名经济学家邓肯·布莱克的单峰定理进行深入研究,一维条件下,个体为单峰偏好可以解决"投票悖论"。将单峰偏好分析从一维条件扩展到二维条件直至N维条件,探讨N维条件下单峰定理是否适用。
关键词 社会选择 单峰偏好 投票悖论
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无线网络服务过程建模及突发特性
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作者 房曙光 董育宁 张晖 《中国科技论文》 CAS 北大核心 2012年第4期257-262,共6页
现代无线通信系统所具有的复杂结构使得系统服务过程建模及服务质量(QoS)分析具有很高计算复杂度。对于以合理精度预测网络QoS而言,过于精准的系统服务过程模型是不必要的,所构建模型应能反映系统服务过程对网络QoS产生的影响。无线通... 现代无线通信系统所具有的复杂结构使得系统服务过程建模及服务质量(QoS)分析具有很高计算复杂度。对于以合理精度预测网络QoS而言,过于精准的系统服务过程模型是不必要的,所构建模型应能反映系统服务过程对网络QoS产生的影响。无线通信系统服务过程的突发特性对网络QoS具有重要影响,笔者分析了过程突发特性的描述方法,详细说明了尖度因子函数对过程突发特性的描述及相应表达式,在此基础上给出一个基于尖度因子函数构建切换批伯努利过程马尔可夫模型的方法,并通过数值分析对其有效性和准确性予以了验证。 展开更多
关键词 无线网络 服务质量 系统建模 突发特性 尖度因子函数
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92417型轴承检测门限值探讨
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作者 袁新宇 周安平 《内燃机车》 北大核心 2003年第5期44-46,共3页
通过对383台次DF4B型机车中修待装牵引电动机92417型轴承的检测数据的统计分析,结合本段检修、运用特点,确定出92417型轴承较为合理的检测门限值,为该型轴承的检测提供了判定依据。
关键词 DF4B型机车 牵引电动机 92417型轴承 检测 门限值 检修
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单峰偏好下马斯金单调性与联盟防策略的等价性
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作者 李江峰 刘宗谦 《经济数学》 2008年第1期64-73,共10页
本文证明了在单峰偏好域上Maskin单调性与防策略条件是等价的,并进一步证明了Maskin单调性与联盟防策略是等价的.从而推广了Muller-Satterthwaite(1977)在无限制强序域上得到的结论.在此基础上,利用Mollin(1980)在单峰偏好域上提出的防... 本文证明了在单峰偏好域上Maskin单调性与防策略条件是等价的,并进一步证明了Maskin单调性与联盟防策略是等价的.从而推广了Muller-Satterthwaite(1977)在无限制强序域上得到的结论.在此基础上,利用Mollin(1980)在单峰偏好域上提出的防策略社会选择函数特征化定理,证明了在单峰偏好域上能够突破Muller-Satterthwaite不可能性定理所预示的消极结论. 展开更多
关键词 Maskin单调性 防策略 联盟防策略 单峰偏好域
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General expressions of peaked traveling wave solutions of CH-γ and CH equations 被引量:10
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作者 ZHANG WenlingDepartment of Mathematics and Physics, National Natural Science Foundation of China, Beijing 100085, China 《Science China Mathematics》 SCIE 2004年第6期862-873,共12页
We use qualitative analysis and numerical simulation to study peaked traveling wave solutions of CH-γ and CH equations. General expressions of peakon and periodic cusp wave solutions are obtained. Some previous resul... We use qualitative analysis and numerical simulation to study peaked traveling wave solutions of CH-γ and CH equations. General expressions of peakon and periodic cusp wave solutions are obtained. Some previous results become our special cases. 展开更多
关键词 peaked traveling waves general expressions numerical simulations
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Peaked wave solutions of CH-r equation 被引量:2
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作者 郭柏灵 刘正荣 《Science China Mathematics》 SCIE 2003年第5期696-709,共14页
In this paper the qualitative analysis methods of planar autonomous systems and numerical simu-lation are used to investigate the peaked wave solutions of CH-r equation. Some explicit expressions of peakedsolitary wav... In this paper the qualitative analysis methods of planar autonomous systems and numerical simu-lation are used to investigate the peaked wave solutions of CH-r equation. Some explicit expressions of peakedsolitary wave solutions and peaked periodic wave solutions are obtained, and some of their relationships arerevealed. Why peaked points are generated is discussed. 展开更多
关键词 CH-r equation peaked WAVE solutions BIFURCATION of PHASE portraits.
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Proton acceleration from picosecond-laser interaction with a hydrocarbon target
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作者 杨宇晨 黄太武 +2 位作者 蒋轲 郁明阳 周沧涛 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第2期77-85,共9页
As an intense picosecond laser pulse irradiates a hydrocarbon target,the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target.We investigate the effect of the lase... As an intense picosecond laser pulse irradiates a hydrocarbon target,the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target.We investigate the effect of the laser and hydrocarbon target parameters on proton acceleration with two/threedimensional particle-in-cell simulations.It is found that the resulting two-ion species plasma can generate a multiple peaked charge-separation field that accelerates the protons.In particular,a smaller carbon-to-hydrogen ratio,as well as the thinner and/or lower density of the target,leads to a larger sheath field and thus proton beams with a larger cutoff energy and smoother energy spectrum.These results may be useful in achieving high-flux quasi-monoenergetic proton beams by properly designing the hydrocarbon target. 展开更多
关键词 picosecond laser pulse proton acceleration multiple peaked charge-separation field carbon-to-hydrogen ratio
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Explicit Peaked Wave Solutions to the Generalized Camassa-Holm Equation 被引量:2
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作者 Zhen-hui Xu Xi-qiang Liu 《Acta Mathematicae Applicatae Sinica》 SCIE CSCD 2010年第2期277-282,共6页
By constructing auxiliary differential equations, we obtain peaked solitary wave solutions of the generalized Camassa-Holm equation, including periodic cusp waves expressed in terms of elliptic functions.
关键词 The generalized Camassa-Holm equation periodic cusp wave explicit peaked wave solution
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Two kinds of peaked solitary waves of the KdV,BBM and Boussinesq equations 被引量:4
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作者 LIAO ShiJun 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第12期2469-2475,共7页
It is well-known that the celebrated Camassa-Holm equation has the peaked solitary waves,which have been not reported for other mainstream models of shallow water waves.In this letter,the closed-form solutions of peak... It is well-known that the celebrated Camassa-Holm equation has the peaked solitary waves,which have been not reported for other mainstream models of shallow water waves.In this letter,the closed-form solutions of peaked solitary waves of the KdV equation,the BBM equation and the Boussinesq equation are given for the first time.All of them have either a peakon or an anti-peakon.Each of them exactly satisfies the corresponding Rankine-Hogoniot jump condition and could be understood as weak solution.Therefore,the peaked solitary waves might be common for most of shallow water wave models,no matter whether or not they are integrable and/or admit breaking-wave solutions. 展开更多
关键词 solitary waves peaked crest PROGRESSIVE DISCONTINUITY weak solution
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Peaked Periodic Wave Solutions to the Broer–Kaup Equation
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作者 江波 毕勤胜 《Communications in Theoretical Physics》 SCIE CAS CSCD 2017年第1期22-26,共5页
By qualitative analysis method, a sufficient condition for the existence of peaked periodic wave solutions to the Broer–Kaup equation is given. Some exact explicit expressions of peaked periodic wave solutions are al... By qualitative analysis method, a sufficient condition for the existence of peaked periodic wave solutions to the Broer–Kaup equation is given. Some exact explicit expressions of peaked periodic wave solutions are also presented. 展开更多
关键词 qualitative analysis Broer–Kaup equation periodic peaked wave solution
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PEAKED WAVE SOLUTIONS TO A GENERALIZED HYPERELASTIC-ROD WAVE EQUATION
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作者 Xie Shaolong Wang Lin Rui Weiguo 《Annals of Differential Equations》 2007年第1期96-103,共8页
We study peaked wave solutions of a generalized Hyperelastic-rod wave equation describing waves in compressible hyperelastic-rods by using the bifurcation theory of planar dynamical systems and numerical simulation me... We study peaked wave solutions of a generalized Hyperelastic-rod wave equation describing waves in compressible hyperelastic-rods by using the bifurcation theory of planar dynamical systems and numerical simulation method. The existence domain of the peaked solitary waves are found. The analytic expressions of peaked solitary wave solutions are obtained. Our numerical simulation and qualitative results are identical. 展开更多
关键词 solitary waves BIFURCATION homoclinic orbit peaked solitary wave
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On the Cauchy problem and peakons of a two-component Novikov system 被引量:1
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作者 Changzheng Qu Ying Fu 《Science China Mathematics》 SCIE CSCD 2020年第10期1965-1996,共32页
We study a two-component Novikov system,which is integrable and can be viewed as a twocomponent generalization of the Novikov equation with cubic nonlinearity.The primary goal of this paper is to understand how multi-... We study a two-component Novikov system,which is integrable and can be viewed as a twocomponent generalization of the Novikov equation with cubic nonlinearity.The primary goal of this paper is to understand how multi-component equations,nonlinear dispersive terms and other nonlinear terms affect the dispersive dynamics and the structure of the peaked solitons.We establish the local well-posedness of the Cauchy problem in Besov spaces B^s/p,r with 1 p,r+∞,s>max{1+1/p,3/2}and Sobolev spaces H^s(R)with s>3/2,and the method is based on the estimates for transport equations and new invariant properties of the system.Furthermore,the blow-up and wave-breaking phenomena of solutions to the Cauchy problem are studied.A blow-up criterion on solutions of the Cauchy problem is demonstrated.In addition,we show that this system admits single-peaked solitons and multi-peaked solitons on the whole line,and the single-peaked solitons on the circle,which are the weak solutions in both senses of the usual weak form and the weak Lax-pair form of the system. 展开更多
关键词 two-component Novikov system Hamiltonian structure Camassa-Holm type equation WELLPOSEDNESS peaked soliton
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Orbital Stability of Peakons for the Modified Camassa–Holm Equation
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作者 Ji LI 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2022年第1期148-160,共13页
In this paper,we investigate the orbital stability of the peaked solitons(peakons)for the modified Camassa–Holm equation with cubic nonlinearity.We consider a minimization problem with an appropriately chosen constra... In this paper,we investigate the orbital stability of the peaked solitons(peakons)for the modified Camassa–Holm equation with cubic nonlinearity.We consider a minimization problem with an appropriately chosen constraint,from which we establish the orbital stability of the peakons under H^(1)∩W^(1,4)norm. 展开更多
关键词 STABILITY peaked solitary waves modified Camassa–Holm equation variational problem concentration compactness
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