检索结果-南通市图书馆

spectrum analysis of interval process model and its application in uncertain vibration analysis

Science China(Technological Sciences) 2024年第8期67卷 2549-2564页

作者： LI JinWu JIANG Chao NI BingYu State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncertainties. This model employs upper and lower bounds instead of precise probability distributions to quantify uncertainty in a parameter at any given time point. It is anticipated to complement the conventional stochastic process model in the coming years owing to its relatively low dependence on experimental samples and ease of understanding for engineers. Building on our previous work, this paper proposes a spectrum analysis method to describe the frequency domain characteristics of an interval process, further strengthening the theoretical foundation of the interval process model and enhancing its applicability for complex engineering problems. In this approach, we first define the zero midpoint function interval process and its auto/cross-power spectral density(PSD) functions. We also deduce the relationship between the auto-PSD function and the auto-covariance function of the stationary zero midpoint function interval process. Next, the auto/cross-PSD function matrices of a general interval process are defined, followed by the introduction of the concepts of PSD function matrix and cross-PSD function matrix for interval process vectors. The spectrum analysis method is then applied to random vibration problems, leading to the creation of a spectrum-analysis-based interval vibration analysis method that determines the PSD function for the system displacement response under stationary interval process excitations. Finally, the effectiveness of the formulated spectrum-analysis-based interval vibration analysis approach is verified through two numerical examples.

关键词： interval process spectrum analysis power spectral density(PSD) time-varying uncertainty uncertain vibration analysis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

spectrum analysis of all parameter noises in repetition-rate laser pulse train

引用

Chinese Optics Letters 2006年第8期4卷 467-469页

作者：汤君华王云才 Physics Department College of Science Taiyuan University of Technology

The theoretical investigation of all parameter noises in repetition-rate laser pulse train was presented. The expression of power spectrum of laser pulse trains with all parameter noises was derived, and the power spectra of pulse trains with different noise parameters were numerically simulated. By comparing the power spectra with and without pulse-width jitter, we noted that pulse-width jitter could not be neglected compared with amplitude noise and timing jitter and contributed a great amount of noise into the power spectrum under the condition that the product of pulse width and angular frequency was larger than 1.

关键词： Computer simulation spectrum analysis Timing jitter

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The spectrum analysis of RMP coils with multiple connection modes and the design of high field side coils on J-TEXT

引用

Plasma Science and Technology 2022年第12期24卷 224-231页

作者： Zhengkang REN Da Li Nengchao WANG Feiyue MAO Zhuo HUANG Song ZHOU Ruo JIA Ying HE Chengshuo SHEN Abba Alhaji BALA Bo RAO Yonghua DING the J-TEXT Team International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China College of Computer Science South-Central Minzu UniversityWuhan 430074People's Republic of China Physics Department Federal University DutseDutse 720101Nigeria

The phase difference Δξ between locked islands(2/1 and 3/1) has been found to influence the heat transport on the thermal quench during disruptions by numerical modeling [Hu Q et al *** 59,016005].To verify this experimentally,a set of resonant magnetic perturbation(RMP) coils is required to excite coupled magnetic islands with different Δξ.The spectrum analysis shows that the current RMP coils on J-TEXT can only produce sufficient 2/1 and 3/1RMP fields with a limited phase difference of Δξ∈[-75°,75°].In order to broaden the adjustable range of Δξ,a set of coils on the high field side(HFS) is proposed to generate 2/1 and 3/1 RMP fields with Δξ=180°.As a result,RMPs with adjustable Δξ∈[-180°,180°] and sufficient amplitudes could be achieved by applying the HFS coils and the low field side(LFS)*** work provides a feasible solution for flexible adjustment of the phase difference between m and m+1 RMP,which might facilitate the study of major disruptions and their control.

关键词： resonant magnetic perturbation spectrum analysis phase difference between 2/1 and 3/1 islands

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

LARGE EDDY SIMULATION AND spectrum analysis OF FLOW AROUND TWO SQUARE CYLINDERS ARRANGED SIDE BY SIDE

引用

Applied Mathematics and Mechanics(English Edition) 2004年第8期25卷 903-910页

作者：魏英杰朱蒙生何钟怡 Department of Aerospace Engineering & Mechanics Harbin Institute of Technology Harbin 150001 P.R.China School of Municipal & Environmental Engineering Harbin Institute of Technology Harbin 150090 P.R.China

Large eddy simulation cooperated with the second order full extension ETG(Euler-Taylor-Galerkin) finite element method was applied to simulate the flow around two square cylinders arranged side by side at a spacing ratio of (1.5.) The second order full extension ETG finite element method was developed by Wang and He. By means of Taylor expansion of terms containing time derivative, time derivative is replaced by space derivative. The function of it is equal to introducing an artificial viscosity term. The streamlines of the flow at different moments were obtained. The time history of drag coefficient, lift coefficient and the streamwise velocity on the symmetrical points were presented. Furthermore, the symmetrical problem of the frequency spectrum of flow around two square cylinders arranged side by side were studied by using the spectral analysis technology. The data obtained at the initial stage are excluded in order to avoid the influence of initial condition on the results. The power spectrums of drag coefficient, lift coefficient, the streamwise velocity on the symmetrical points were analyzed respectively. The results show that although the time domain process of dynamic parameters is non-symmetrical, the frequency domain process of them is symmetrical under the symmetrical boundary conditions.

关键词： two square cylinders arranged side by side symmetrical flow around body spectrum analysis large eddy simulation ETG finite element drag coefficient lift coefficient

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

fMRI time series analysis based on stationary wavelet and spectrum analysis

引用

Progress in Natural Science:Materials International 2006年第11期16卷 1171-1176页

作者： ZHI Lianhe~ 1,2,3 , ZHAO Xia~4, SHAN Baoci~1**, PENG Silong~5, YAN Qiang~1, YUAN Xiuli~1 and TANG Xiaowei~ 1,6 (1. Key Laboratory of Nuclear analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 2. Graduate School of Chinese Academy of Sciences, Beijing 100049, China 3. Department of Physics, Zhoukou Normal University, Zhoukou 466100, China 4. Research Imaging Center, University of Texas Health Science Center, San Antonio, Texas 78229, USA 5. National ASIC Design and Engineering Center, Institute of Automation, Chinese Academy of Sciences, Beijing 100049, China 6. Department of Physics, Zhejiang University, Hangzhou 310027, China) [a]Key Laboratory of Nuclear analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing China [b]Graduate School of Chinese Academy of Sciences Beijing China [c]Department of Physics Zhoukou Normal University Zhoukou China [d]Research Imaging Center University of Texas Health Science Center San Antonio Texas USA [e]National ASIC Design and Engineering Center Institute of Automation Chinese Academy of Sciences Beijing China [f]Department of Physics Zhejiang University Hangzhou China

The low signal to noise ratio (SNR) of functional MRI (fMRI) prefers more sensitive data analysis methods. Based on stationary wavelet transform and spectrum analysis, a new method with high detective sensitivity was developed for analyzing fMRI time series, which does not require any prior assumption of the characteristics of noises. In the proposed method, every component of fMRI time series in the different time-frequency scales of stationary wavelet transform was discerned by the spectrum analysis, then the components from noises were removed using the stationary wavelet transform, finally the components of real brain activation were detected by cross-correlation analysis. The results obtained from both simulated and in vivo visual experiments illustrated that the proposed method has much higher sensitivity than the traditional cross-correlation method.

关键词： fMRI stationary wavelet transform spectrum analysis data analysis.

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Geometric Covariance Modeling for Surface Variation of Compliant Parts Based on Hybrid Polynomial Approximation and spectrum analysis

引用

Transactions of Nanjing University of Aeronautics and Astronautics 2014年第3期31卷 314-324页

作者：谭昌柏侯东旭袁园 College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics College of Computer Science Nanjing Institute of Industry Technology

Part variation characterization is essential to analyze the variation propagation in flexible assemblies. Aiming at two governing types of surface variation,warping and waviness,a comprehensive approach of geometric covariance modeling based on hybrid polynomial approximation and spectrum analysis is proposed,which can formulate the level and the correlation of surface variations accurately. Firstly,the form error data of compliant part is acquired by CMM. Thereafter,a Fourier-Legendre polynomial decomposition is conducted and the error data are approximated by a Legendre polynomial series. The weighting coefficient of each component is decided by least square method for extracting the warping from the surface variation. Consequently,a geometrical covariance expression for warping deformation is established. Secondly,a Fourier-sinusoidal decomposition is utilized to approximate the waviness from the residual error data. The spectrum is analyzed is to identify the frequency and the amplitude of error data. Thus,a geometrical covariance expression for the waviness is deduced. Thirdly,a comprehensive geometric covariance model for surface variation is developed by the combination the Legendre polynomials with the sinusoidal polynomials. Finally,a group of L-shape sheet metals is measured along a specific contour,and the covariance of the profile errors is modeled by the proposed method. Thereafter,the result is compared with the covariance from two other methods and the real data. The result shows that the proposed covariance model can match the real surface error effectively and represents a tighter approximation error compared with the referred methods.

关键词： compliant part geometric covariance Legendre polynomial sinusoidal polynomial spectrum analysis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Drawing Tower In-Line Fabrication and the spectrum analysis of Sampled Fiber Grating

引用

Photonic Sensors 2020年第1期10卷 80-87页

作者： Yu ZHENG Wenjing GAO Haihu YU Huiyong GUO Shan JIANG Desheng JIANG National Engineering Laboratory for Fiber Optic Sensing Technology Wuhan University of TechnologyWuhan 430070China WUTOS Technology Co. LtdWuhan 430223China

Sampled fiber grating is a special superstructure fiber Bragg grating with a wide range of applications in many *** this work,based on drawing tower in-line fabrication system,a new preparation method of the sampled fiber grating is proposed and experimentally *** result shows that the obtained sampled fiber gratings possess dense reflection spectra,with a minimum reflection peak interval of only 0.09 *** method exhibits promising application prospect in the fabrication of the high-quality sampled fiber *** the other hand,the spectral characteristics of the sampled fiber grating are analyzed when the sub-grating is affected by the external physical quantities such as,in this paper,*** shift and intensity change in the reflection peak of the spectra indicate that the grating is affected differently by micro strains,due to the different spatial positions along the axis of the sampled fiber *** work is aimed at exploring the potential applications of the sampled fiber grating in quasi-distributed micro-area sensing with the millimeter level.

关键词： Sampled fiber grating drawing tower in-line fabrication spectrum analysis grating array sensing application

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Spectral Characteristics of White Organic Light-emitting Diodes Based on Novel Phosphorescent Sensitizer

引用

Chinese Journal of Chemical Physics 2008年第6期21卷 510-514页

作者： Xiao-qing Tang Jun-sheng Yu Lu Li Wen Wen Ya-dong Jiang State Key Laboratory of Electronic Thin Films and Integrated Devices School of Optoelectronic Information University of Electronic Science and Technology of China Chengdu 610054 China

White organic light-emitting diodes were fabricated by using a novel phosphorescence bis（1,2-diphenyl-1H-benzoimidazole）iridium（acetylacetonate）[（pbi）2Ir（acac）] as sensitizer and a fluorescent dye of 4- （dicyanomethylene）-2-t-butyl-6-（1,1,7,7-tetramethyljulolidyl-9-enyl）-4H-pyran （DCJTB） codoped into a carbazole polymer of poly（N-vinylcarbazole）（PVK）. Through characterizing the UV-Vis absorption spectra, the photoluminescence spectra of （pbi）2Ir（acac） and DCJTB, and the electroluminescence spectral properties of the WOLEDs, the energy transfer mechanisms of the codoped polymer system were deduced. The results demonstrate that the luminescent spectra with different intensity of （pbi）2Ir（acac） and DCJTB were co-existent in the EL spectra of the blended system, which is ascribed to an incomplete energy transfer process in the EL process. The efficient Forster and Dexter energy transfer between the host and the guests enabled a strong yellow emission from （pbi）2Ir（acac） and DCJTB, where （pbi）2Ir（acac） plays an important role as a phosphorescent sensitizer for DCJTB. With the blue emitting-layer of N,N＇-diphenyl-N,N＇-bis（1- naphthyl）（1,1＇-biphenyl）-4,4＇-diamine, the codoped system device achieved white emission. The codoped system showed that its Commissions Internationale de 1＇Eclairage coordinates were more independent of the variation of bias voltage than those of phosphorescent doped PVK systems.

关键词： White organic light-emitting diode Phosphorescent sensitizer spectrum analysis

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Spectral baseline estimation using penalized least squares with weights derived from the Bayesian method

引用

Nuclear Science and Techniques 2022年第11期33卷 144-157页

作者： Qian Wang Xin-Liang Yan Xiang-Cheng Chen Peng Shuai Meng Wang Yu-Hu Zhang Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China Van Swinderen Institute University of GroningenGroningen 9747 AAThe Netherlands

The penalized least squares(PLS)method with appropriate weights has proved to be a successful baseline estimation method for various spectral *** can extract the baseline from the spectrum while retaining the signal peaks in the presence of random *** algorithm is implemented by iterating over the weights of the data *** this study,we propose a new approach for assigning weights based on the Bayesian *** proposed method provides a self-consistent weighting formula and performs well,particularly for baselines with different curvature *** method was applied to analyze Schottky spectra obtained in 86Kr projectile fragmentation measurements in the experimental Cooler Storage Ring(CSRe)at *** provides an accurate and reliable storage lifetime with a smaller error bar than existing PLS *** is also a universal baseline-subtraction algorithm that can be used for spectrum-related experiments,such as precision nuclear mass and lifetime measurements in storage rings.

关键词： Penalized least squares Baseline correction Bayesian rule spectrum analysis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Mission segment division of the whole aeroengine loading spectrum based on flight actions

引用

Chinese Journal of Aeronautics 2022年第2期35卷 164-174页

作者： Yu JIN Zhigang SUN Yingdong SONG Xin LIN Xuming NIU Junjie DING Jiangsu Province Key Laboratory of Aerospace Power System College of Energy and Power EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Aero-engine Thermal Environment and StructureMinistry of Industry and Information TechnologyNanjing 210016China State Key Laboratory of Mechanics and Control Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

This paper studies on a division method of the whole aeroengine loading spectrum flight mission segment and rotor speed mission segment,which is based on the actual flight actions and related to the flight operations of aeroengine and is suitable for the variable-speed aeroengines such as turbojet and *** the research,the aeroengine loading spectrum operation-related mission segments can be divided,which can provide important data basis for the life research on the structures which are sensitive to flight maneuver(such as the main shaft,large gearbox and installation section),lay a foundation for the simulation,compilation and prediction of the whole aeroengine loading ***,based on the summary of basic flight actions in actual flight,the division of flight mission segment was realized by ***,the aeroengine rotor speed mission segments,associated with flight actions and missions,were divided based on the flight mission segment division ***,the efficiency and accuracy of the mission segment division results were verified by adopting measured loading spectrum ***,the characteristics of speed mission segment division results were compared and analyzed in tables and *** comparison results show that the characteristics of similar speed mission segments are similar,while the characteristics of different speed mission segments are *** the shapes of similar mission segments vary to the change of flight actions and operations,which can reflect the operation-related feature of the segments.

关键词： Aircraft engine Flight mission segment Mission segment division Rotor speed mission segment spectrum analysis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：