期刊文献+
共找到488篇文章
< 1 2 25 >
每页显示 20 50 100
ESTIMATION OF THE NUMBER OF CORRELATED SOURCES WITH COMMON FREQUENCIES BASED ON POWER SPECTRAL DENSITY 被引量:5
1
作者 LI Ning SGU Tielin 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2007年第4期88-93,共6页
Blind source separation and estimation of the number of sources usually demand that the number of sensors should be greater than or equal to that of the sources, which, however, is very difficult to satisfy for the co... Blind source separation and estimation of the number of sources usually demand that the number of sensors should be greater than or equal to that of the sources, which, however, is very difficult to satisfy for the complex systems. A new estimating method based on power spectral density (PSD) is presented. When the relation between the number of sensors and that of sources is unknown, the PSD matrix is first obtained by the ratio of PSD of the observation signals, and then the bound of the number of correlated sources with common frequencies can be estimated by comparing every column vector of PSD matrix. The effectiveness of the proposed method is verified by theoretical analysis and experiments, and the influence of noise on the estimation of number of source is simulated. 展开更多
关键词 Blind signal number of sources Power spectral density
下载PDF
Numerical Study of Natural Convective Heat Transfer in an Air Filled Square Cavity Heated from Below and Symmetrically Cooled from the Sides with a Partition in the Hot Wall
2
作者 Farah Zemani-Kaci Amina Sabeur-Bendhina 《Fluid Dynamics & Materials Processing》 EI 2023年第2期513-539,共27页
A two-dimensional numerical study of laminar natural convection in a square enclosure filled with air with a wall partially heated on the bottom is presented.The heat source is located on the lower wall with different... A two-dimensional numerical study of laminar natural convection in a square enclosure filled with air with a wall partially heated on the bottom is presented.The heat source is located on the lower wall with different heated widths varied from 20 to 80%(ε=0.2–0.8)of the total width of the lower wall and different heights h=H/4 and H/2 of the partition.The effect of the partition height on the main system dynamics is investigated through solution of the two-dimensional Navier-Stokes equations and the energy equation by means of a finite volume method based on the SIMPLE algorithm.The influence of the Rayleigh number(Ra=10^(3) to 10^(6))and the hot wall length is also examined.It is shown that the average Nusselt number grows whenεincreases and when h decreases.For a given value ofεand h,the average Nusselt number increases as Ra increases.It is concluded that the partition height causes a decrease in the average Nusselt number. 展开更多
关键词 Natural convection square enclosure heat source partial partition nusselt number
下载PDF
Dynamic Direction of Arrival Estimation with an Unknown Number of Sources
3
作者 王荣杰 詹宜巨 周海峰 《Journal of Donghua University(English Edition)》 EI CAS 2016年第3期490-494,共5页
Aiming at source number determination and direction of arrival(DOA) estimation under the case of time-varying source number,a method of DOA estimation with an unknown number of sources was proposed.Firstly,an algorith... Aiming at source number determination and direction of arrival(DOA) estimation under the case of time-varying source number,a method of DOA estimation with an unknown number of sources was proposed.Firstly,an algorithm based on crossvalidation technique was introduced to determine the number of sources.Then dynamic DOAs of source were estimated using an algorithm based on blind source separation(BSS) under the case that number of sources were unknown in advance and it was timevarying.The effectiveness of the proposed method was validated by simulation of time-invariant and time-varying numbers of source.Compared with other conventional methods,the proposed method has superior evaluation performances The proposed method can estimate m(the numbers of sensor) DOAs while other conventional methods estimate less than m DOAs.The R_(mse) of the proposed method in the case of low signal-to-noise ratio(SNR)(equal or lower than 30 dB) is smaller than 0.2 while R_(mse) of other conventional methods are greater than 0.8. 展开更多
关键词 cross validation direction of arrival(DOA) blind source separation(BSS) principal component analysis number of sources
下载PDF
Thermal partition of two asymmetric discrete heat sources by cold air curtain
4
作者 DENG Quan-wei DENG Qi-hong 《Journal of Central South University of Technology》 2005年第z1期268-273,共6页
A partition solution implemented by a cold air curtain for two asymmetric discrete heat sources in a twodimensional rectangular enclosure was numerically studied. Main attentions were focused on the effects of Reynold... A partition solution implemented by a cold air curtain for two asymmetric discrete heat sources in a twodimensional rectangular enclosure was numerically studied. Main attentions were focused on the effects of Reynolds number, Grashof number, separation distance between heat sources, and buoyancy ratio. It is found that the airflow and heat transfer are not only determined by governing parameters, but also affected by boundary conditions. It is also found that nearly symmetry of flow structure corresponds to nearly thermal partition, and the symmetry can be enhanced when Reynolds number, separation distance and buoyancy ratio increase. In addition, it is observed that there is a minimum Reynolds number for obtaining nearly thermal partition, which increases when Grashof number increases. 展开更多
关键词 COLD air CURTAIN ASYMMETRIC discrete heat sources critical PARTITION REYNOLDS number mixed CONVECTION
下载PDF
Vibration Source Number Estimation of A Shell Structure 被引量:1
5
作者 Cheng Wei He Zhengjia Zhang Zhousuo 《仪器仪表学报》 EI CAS CSCD 北大核心 2013年第S1期142-146,共5页
It has been challenging to correctly separate the mixed signals into source components when the source number is not known a priori.To reveal the complexity of the measured vibration signals,and provide the priori inf... It has been challenging to correctly separate the mixed signals into source components when the source number is not known a priori.To reveal the complexity of the measured vibration signals,and provide the priori information for the blind source separation,in this paper,we propose a novel source number estimation based on independent component analysis(ICA)and clustering evaluation analysis,and then carry out experiment studies with typical mechanical vibration signals from a shell structure.The results demonstrate that the proposed ICA based source number estimation performs stably and robustly for the shell structure. 展开更多
关键词 SOURCE number estimation SOURCE SEPARATION SHELL structure INDEPENDENT component analysis
下载PDF
Eco-environment range in the source regions of the Yangtze and Yellow rivers 被引量:18
6
作者 DING Yongjian,YANG Jianping,LIU Shiyin,CHEN Rensheng,WANG Genxu,SHEN Yongping,WANG Jian,XIE Changwei,ZHANG Shiqing(Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou 730000, China) 《Journal of Geographical Sciences》 SCIE CSCD 2003年第2期172-180,共9页
Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper.... Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper. According to the comprehensive analysis of topographical characteristics, climate conditions, vegetation distribution and hydrological features, the source region ranges for eco-environmental study are defined. The eastern boundary point is Dari hydrological station in the upper reach of the Yellow River. The watershed above Dari hydrological station is the source region of the Yellow River which drains an area of 4.49×10 4 km 2 . Natural environment is characterized by the major topographical types of plateau lakes and marshland, gentle landforms, alpine cold semi-arid climate, and steppe and meadow vegetation in the source region of the Yellow River. The eastern boundary point is the convergent site of the Nieqiaqu and the Tongtian River in the upstream of the Yangtze River. The watershed above the convergent site is the source region of the Yangtze River, with a watershed area of 12.24×10 4 km 2 . Hills and alpine plain topography, gentle terrain, alpine cold arid and semi-arid climate, and alpine cold grassland and meadow are natural conditions in the source region of the Yangtze River. 展开更多
关键词 the source regions of the Yangtze and Yellow rivers eco-environmental range CLC number:X171.1
下载PDF
Estimation of Non-point Source Pollution Loads Under Uncertain Information 被引量:4
7
作者 LI Ruzhong 《Chinese Geographical Science》 SCIE CSCD 2008年第4期348-355,共8页
Many kinds of uncertainties are involved, such as random, fuzzy, grey, unascertained property and so on, in soil erosion process. To exactly predict the non-point source pollution loads, some uncertainties should be t... Many kinds of uncertainties are involved, such as random, fuzzy, grey, unascertained property and so on, in soil erosion process. To exactly predict the non-point source pollution loads, some uncertainties should be taken into consideration. Aiming at the deficiency of present blind number theory being helpless for fuzziness, a novel blind number, i.e. extended-blind number, was introduced by substituting a set of triangular fuzzy numbers (TFNs), expressed as a-cuts, for interval values in present blind number, and the expected value of extended-blind number was also brought forward by referring to the current blind number theory. On the basis of denoting the parameters of Uni- versal Soil Loss Equation (USLE) as extended-blind parameters, a novel USLE model was established for quantitatively evaluating soil erosion loss and non-point source pollution loads. As a case, the uncertain USLE was employed for predicting the soil erosion loss and non-point source pollution loads of absorbed nitrogen and phosphorus in a dis- trict in the Hangbu-Fengle River basin, in the upstream of Chaohu Lake watershed. The results show that it is feasible in theory to extend blind number into fuzzy environment and reliable on conclusion to apply extended-blind number theory for predicting non-point source pollution loads. 展开更多
关键词 non-point source pollution Universal Soil Loss Equation (USLE) triangular fuzzy number (TFN) blind number
下载PDF
Effect of drip irrigation method, nitrogen source, and flushing schedule on emitter clogging 被引量:3
8
作者 Mohamed Yousif Tayel Sabreen Khalil Pibars Hani Abdel-Ghani Mansour 《Agricultural Sciences》 2013年第3期131-137,共7页
Field experiments were carried out at the National Research Center farm, Nubaria area, Behura Governorate, Egypt, to study the effect of nitrogen source, flushing schedule and irrigation method on emitter clogging. Pe... Field experiments were carried out at the National Research Center farm, Nubaria area, Behura Governorate, Egypt, to study the effect of nitrogen source, flushing schedule and irrigation method on emitter clogging. Peanut Giza 5 variety (Arachishy pogaea L.) was planted in sandy soil during two successive growing seasons (2010-2011) in the 1st week of May and harvested after 130 days. Treatments used are: 1) two irrigation methods: surface drip irrigation and sub-surface drip irrigation (SDI;SSDI), 2) nitrogen source (NS):NH4NO3, (NH4)2SO4 and Ca(NO3)2 (NS1, NS2 and NS3) and 3) flushing number (FL) 0, 1 and 4 (FL1, FL2;FL3). The experiments design was split-split plot and three replicates were used. Data obtained were subjected to statistical analysis. The main effects of treatments used on clogging per cent could be written the following ascending orders: SDI 3 2 1, NS1 2 3. Concerning the 1st interaction the following ascending orders denote their effects on clogging percent: SDI × FL3 2 1, SDI × NS1 2 3, SSDI × FL3 2 1, SSDI × NS1 2 3, FL1 × NS1 1 × NS2 1 × NS3, FL2 × NS1 2 × NS2 2 × NS3 and FL3 × NS1 3 × NS2 3 × NS3. The differences between any two treatments and/or any two interactions in clogging percent were significant at the 5% level. The effect of the 2nd interaction on clogging percent was significant at the 5% level. The maximum value of clogging (20.18%) and the lowest one (3.9%) were archived in the interactions: SSDI × FL1 × NS3 and SDI × FL3 × NS1, respectively. 展开更多
关键词 IRRIGATION METHOD Nitrogen Source FLUSHING number Water and Soil Analysis EMITTER CLOGGING
下载PDF
Entropy analysis of unsteady magneto-nanofluid flow past accelerating stretching sheet with convective boundary condition 被引量:1
9
作者 S.DAS S.CHAKRABORTY +1 位作者 R.N.JANA O.D.MAKINDE 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2015年第12期1593-1610,共18页
The unsteady laminar magnetohydrodynamics (MHD) boundary layer flow and heat transfer of nanofluids over an accelerating convectively heated stretching sheet are numerically studied in the presence of a transverse m... The unsteady laminar magnetohydrodynamics (MHD) boundary layer flow and heat transfer of nanofluids over an accelerating convectively heated stretching sheet are numerically studied in the presence of a transverse magnetic field with heat source/sink The unsteady governing equations are solved by a shooting method with the Runge-Kutta- Fehlberg scheme. Three different types of water based nanofluids, containing copper, aluminium oxide, and titanium dioxide, are taken into consideration. The effects of the pertinent parameters on the fluid velocity, the temperature, the entropy generation num- ber, the Bejan number, the shear stress, and the heat transfer rate at the sheet surface are graphically and quantitatively discussed in detail. A comparison of the entropy generation due to the heat transfer and the fluid friction is made with the help of the Bejan number. It is observed that the presence of the metallic nanoparticles creates more entropy in the nanofluid flow than in the regular fluid flow. 展开更多
关键词 unsteady MHD flow NANofLUID heat source/sink entropy generation Bejan number
下载PDF
A new source number estimation method based on the beam eigenvalue 被引量:2
10
作者 JIANG Lei CAI Ping YANG Juan WANG Yi-ling XU Dan 《Journal of Marine Science and Application》 2007年第1期41-46,共6页
Most source number estimation methods based on the eigenvalues are decomposed by covariance matrix in MUSIC algorithm. To develop the source number estimation method which has lower signal to noise ratio and is suitab... Most source number estimation methods based on the eigenvalues are decomposed by covariance matrix in MUSIC algorithm. To develop the source number estimation method which has lower signal to noise ratio and is suitable to both correlated and uncorrelated impinging signals, a new source number estimation method called beam eigenvalue method (BEM) is proposed in this paper. Through analyzing the space power spectrum and the correlation of the line array, the covariance matrix is constructed in a new way, which is decided by the line array shape when the signal frequency is given. Both of the theory analysis and the simulation results show that the BEM method can estimate the source number for correlated signals and can be more effective at lower signal to noise ratios than the normal source number estimation methods. 展开更多
关键词 source number estimation DOA estimation beam eigenvalue MUSIC
下载PDF
Combined heat and mass transfer by mixed convection MHD flow along a porous plate with chemical reaction in presence of heat source 被引量:1
11
作者 J.ZUECO S.AHMED 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2010年第10期1217-1230,共14页
An exact and a numerical solutions to the problem of a steady mixed convective MHD flow of an incompressible viscous electrically conducting fluid past an infinite vertical porous plate with combined heat and mass tra... An exact and a numerical solutions to the problem of a steady mixed convective MHD flow of an incompressible viscous electrically conducting fluid past an infinite vertical porous plate with combined heat and mass transfer are presented.A uniform magnetic field is assumed to be applied transversely to the direction of the flow with the consideration of the induced magnetic field with viscous and magnetic dissipations of energy.The porous plate is subjected to a constant suction velocity as well as a uniform mixed stream velocity.The governing equations are solved by the perturbation technique and a numerical method.The analytical expressions for the velocity field,the temperature field,the induced magnetic field,the skin-friction,and the rate of heat transfer at the plate are obtained.The numerical results are demonstrated graphically for various values of the parameters involved in the problem.The effects of the Hartmann number,the chemical reaction parameter,the magnetic Prandtl number,and the other parameters involved in the velocity field,the temperature field,the concentration field,and the induced magnetic field from the plate to the fluid are discussed.An increase in the heat source/sink or the Eckert number is found to strongly enhance the fluid velocity values.The induced magnetic field along the x-direction increases with the increase in the Hartmann number,the magnetic Prandtl number,the heat source/sink,and the viscous dissipation.It is found that the flow velocity,the fluid temperature,and the induced magnetic field decrease with the increase in the destructive chemical reaction.Applications of the study arise in the thermal plasma reactor modelling,the electromagnetic induction,the magnetohydrodynamic transport phenomena in chromatographic systems,and the magnetic field control of materials processing. 展开更多
关键词 MHD perturbation technique network simulation method Eckert number mixed convection induced magnetic field viscous dissipation heat source/sink
下载PDF
Non-Aligned Stagnation Point Flow of a Casson Fluid Past a Stretching Sheet in a Doubly Stratified Medium 被引量:1
12
作者 N.Vijaya G.Venkata Ramana Reddy Y.Hara Krishna 《Fluid Dynamics & Materials Processing》 EI 2019年第3期233-251,共19页
This paper investigates the problem of oblique hydro magnetic stagnation point flow of an electrically conducting Casson fluid over stretching sheet embedded in a doubly stratified medium in the presence of thermal ra... This paper investigates the problem of oblique hydro magnetic stagnation point flow of an electrically conducting Casson fluid over stretching sheet embedded in a doubly stratified medium in the presence of thermal radiation and heat source/absorption with first order chemical reaction.It is assumed that the fluid impinges on the wall obliquely.Similarity variables were used to convert the partial differential equations to ordinary differential equations.The transformed ordinary differential equations are solved numerically using Runge-Kutta-Fehlberg method with shooting technique.It is observed that a boundary layer is formed when the stretching velocity of the surface is less than the in viscid free stream velocity at a point decreases with increase in the non-Newtonian rheology parameter.The augmentation of the temperature is observed with the magnetic parameter,heat source parameter and thermal radiation parameter while a reverse effect with thermal stratification number,Prandtl number and the velocity ratio parameter.Influence of Skin friction coefficient,Nusselt number and Sherwood number on the flow configurations for different values of pertinent parameters are portrayed graphically and discussed.Numerical results are compared with the published results and are found to be in good agreement with previously published results as special cases of present problem.The mass concentration is seen to be decrease with Schmidt number,chemical reaction parameter and solutal stratification number. 展开更多
关键词 Magnetic parameter heat source prandtl number chemical reaction casson fluid free stream stagnation flow parameters
下载PDF
Iterative Solution of Regularization to Ill-conditioned Problems in Geodesy and Geophysics 被引量:5
13
作者 Yongwei GU Qingming GUI +1 位作者 Xuan ZHANG Songhui HAN 《Journal of Geodesy and Geoinformation Science》 2019年第1期59-65,共7页
In geodesy and geophysics,many large-scale over-determined linear equations need to be solved which are often ill-conditioned.When the conjugate gradient method is used,their ill-conditioning effects to the solutions ... In geodesy and geophysics,many large-scale over-determined linear equations need to be solved which are often ill-conditioned.When the conjugate gradient method is used,their ill-conditioning effects to the solutions must be overcome,which is studied in this paper.Through the regularization ideas,the conjugate gradient method is improved,and the regularization iterative solution based on controlling condition number is put forward.Firstly by constructing the interference source vector,a new equation is derived with ill-condition diminished greatly,which has the same solution to the original normal equation.Then the new equation is solved by conjugate gradient method.Finally the effectiveness of the new method is verified by some numerical experiments of airborne gravity downward to the earth surface.In the numerical experiments the new method is compared with LS,CG and Tikhonov methods,and its accuracy is the highest. 展开更多
关键词 ILL-CONDITION REGULARIZATION condition number interference source vector ITERATION
下载PDF
Repercussion of Hall effect and nonlinear radiation on Couette-Poiseuille flow of Casson-Williamson fluid through upright microchannel
14
作者 B.J.GIREESHA L.ANITHA 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2022年第12期1951-1964,共14页
The main aim of the present work is to investigate the flow and heat transport properties of non-Newtonian Casson-Williamson fluid through an upright microchannel along with entropy generation analysis,and explore the... The main aim of the present work is to investigate the flow and heat transport properties of non-Newtonian Casson-Williamson fluid through an upright microchannel along with entropy generation analysis,and explore the effects of convective boundary conditions,Couette-Poiseuille flow,and nonlinear radiation.The movement of liquid is scrutinized with the Hall effect and exponential heat source.The rheological characteristics of the Casson-Williamson fluid model are also considered.By considering the desirable similarity variables,the equations of motion are reduced to nonlinear ordinary differential equations.The Runge-Kutta-Fehlberg fourth-fifth order method along with the shooting method is adopted to solve these dimensionless expressions.The detailed investigation is pictorially displayed to show the influence of effective parameters on the entropy generation and the Bejan number.One of the major tasks of the exploration is to compare the Casson fluid and the Williamson fluid.The results show that the rate of heat transfer in the Casson fluid is more remarkable than that in the Williamson fluid. 展开更多
关键词 entropy generation Bejan number convective boundary condition Hall effect nonlinear radiation exponential heat source
下载PDF
Method of militarysoftware securityand vulnerability testing based on process mutation
15
作者 金丽亚 王荣辉 肖庆 《Journal of Measurement Science and Instrumentation》 CAS 2013年第3期228-230,共3页
To solve the problems caused by military software security issues,this paper firstly introduces a new software fault injection technique,namely main static fault injection method:program mutation.And then source code ... To solve the problems caused by military software security issues,this paper firstly introduces a new software fault injection technique,namely main static fault injection method:program mutation.And then source code for testing this algorithm is put forward.On this basis buffer overflow testing based on program mutation is conducted.Finally several military software source codes for buffer overflow testing are tested using deficiency tracking system(DTS)tool,Experimental results show the effectiveness of the proposed algorithm. 展开更多
关键词 military software testing fault injection buffer overflow source code scanningCLC number:TP311.562 Document code:AArticle ID:1674-8042(2013)03-0228-03
下载PDF
基于盲源分离的工业谐波源负荷分类识别方法 被引量:2
16
作者 张逸 陈书畅 +1 位作者 刘必杰 林才华 《中国电机工程学报》 EI CSCD 北大核心 2024年第10期3850-3861,I0009,共13页
针对传统谐波源辨识方法无法实现工业用户谐波源具体类型的非侵入式识别的问题,该文提出一种基于盲源分离的工业谐波源负荷分类识别方法。该方法仅依据工业用户进线处电压、电流数据即可实现谐波源负荷具体类型的非侵入式识别。首先,从... 针对传统谐波源辨识方法无法实现工业用户谐波源具体类型的非侵入式识别的问题,该文提出一种基于盲源分离的工业谐波源负荷分类识别方法。该方法仅依据工业用户进线处电压、电流数据即可实现谐波源负荷具体类型的非侵入式识别。首先,从负荷等值阻抗模型入手,建立工业用户多负荷等值阻抗并联电路模型;其次,采用集合经验模态分解与奇异值分解相结合的方法确定构成用户进线处监测点综合等值阻抗信号的源阻抗信号数目;然后,采用快速独立分量分析实现将谐波源负荷等值阻抗信号从综合负荷等值阻抗信号中分离;最后,将分离出谐波源负荷等值阻抗信号频率特征与典型谐波源负荷进行匹配,进而实现分类识别。仿真与实测实验结果均表明,所提方法能够准确识别工业用户所含多种谐波源负荷的具体类型,具有较好的可行性和实用性。 展开更多
关键词 谐波源识别 负荷等值阻抗 盲源分离 源信号数目估计
下载PDF
双源CT电子密度/有效原子序数(Rho/Z)在孤立性肺结节中的诊断价值 被引量:1
17
作者 黄梅萍 兰长青 王洁 《现代医用影像学》 2024年第1期43-47,共5页
目的:探讨双源CT(DSCT)双能量技术电子密度/有效原子序数(Rho/Z)在孤立性肺结节中良恶性的诊断价值。方法:回顾性收集130例双能量平扫及增强的孤立性肺结节患者,其中恶性组68例,良性组62例,利用Rho/Z应用程序对平扫及增强静脉期图像进... 目的:探讨双源CT(DSCT)双能量技术电子密度/有效原子序数(Rho/Z)在孤立性肺结节中良恶性的诊断价值。方法:回顾性收集130例双能量平扫及增强的孤立性肺结节患者,其中恶性组68例,良性组62例,利用Rho/Z应用程序对平扫及增强静脉期图像进行评估,记录参数Rho、Z和双能量指数(DEI)值,比较两组间的差异,对于有统计学差异的参数,将绘制受试者工作特性(ROC)曲线,以评估其诊断效能。结果:平扫时,恶性组Rho (31.1±22.33)HU明显高于良性组(24.69±20.91)HU,两组之间存在显著统计学差异(P=0.003<0.05),Z与DEI在两组间差异无统计学意义(P>0.05);增强静脉期,恶性组Rho (35.3±20.85)HU明显高于良性组(24.73±17.93)HU,两组之间可见显著统计学差异(P=0.001<0.05),Z与DEI在两组间差异均无统计学意义(P>0.05)。在两组的鉴别诊断中,平扫及增强静脉期Rho的ROC曲线下面积分别为0.652、0.696。结论:DSCT双能量技术Rho/Z有一定特征,有助于孤立性肺结节的诊断。 展开更多
关键词 双源CT 电子密度 有效原子系数 双能量指数 肺结节
下载PDF
动态变化混叠模型下盲源分离中的源数估计
18
作者 白琳 温媛媛 李栋 《电讯技术》 北大核心 2024年第3期396-401,共6页
在进行欠定盲分离时,特别是对于源信号数目及混合矩阵动态变化的情况,常规的欠定盲分离及源数估计方法不能对源信号数目的变化时刻做出判断,因此很难实现动态变化的源信号数目实时和准确的估计。针对这个问题,提出了一种动态变化混叠模... 在进行欠定盲分离时,特别是对于源信号数目及混合矩阵动态变化的情况,常规的欠定盲分离及源数估计方法不能对源信号数目的变化时刻做出判断,因此很难实现动态变化的源信号数目实时和准确的估计。针对这个问题,提出了一种动态变化混叠模型下欠定盲源分离中的源数估计方法。首先,建立动态变化混叠情形下盲源分离的数学模型及动态标识矩阵。其次,基于构建的动态标识矩阵统计和判断动态源信号数目的变化情况。最后,通过分段时间内多维观测矢量采样点聚类区间局部峰值统计,实现动态变化混叠模型下盲源分离中的源信号数目的有效估计。仿真结果表明,该方法能有效实现动态变化混叠模型下欠定盲源分离中的源数估计,并且信号估计效果良好。 展开更多
关键词 欠定盲源分离 源数估计 标识矩阵
下载PDF
《打枣谱》若干问题考论
19
作者 张艳 《农业考古》 北大核心 2024年第4期180-188,共9页
陶宗仪编纂、陶珽续编的《说郛》120卷本中的《打枣谱》1卷,汇集枣名70多种,作者署名为元代柳贯。经考证,文中出现赤斤蒙古卫、哈密等明代地名,作者为元代柳贯之说值得存疑;所收枣品种数量应为64种,而非目前流传的75种说、73种说、72种... 陶宗仪编纂、陶珽续编的《说郛》120卷本中的《打枣谱》1卷,汇集枣名70多种,作者署名为元代柳贯。经考证,文中出现赤斤蒙古卫、哈密等明代地名,作者为元代柳贯之说值得存疑;所收枣品种数量应为64种,而非目前流传的75种说、73种说、72种说和37种说;《打枣谱》首次出现的枣名应为10种,而非《中国果树志》(枣卷)统计的42种。《打枣谱》涉及笔记文献几十种,广泛汇集各类枣名,堪称我国第一部有关枣的“专著”,其补阙之功及文献价值不应被忽略。 展开更多
关键词 《打枣谱》 作者署名 品种数量 枣名来源 首次辑录
下载PDF
基于UBSS算法的电力系统低频振荡辨识方法 被引量:1
20
作者 夏远洋 李啸骢 +2 位作者 徐俊华 刘治理 刘源 《中国电机工程学报》 EI CSCD 北大核心 2024年第13期5073-5083,I0005,共12页
低频振荡监测和分析对电力系统故障诊断和电网恢复至关重要。该文提出一种基于欠定盲源分离原理的低频振荡模式辨识方法,包括欠定盲源分离(underdetermined blind source separation,UBSS)和希尔伯特变换(Hilbert transform,HT)。首次... 低频振荡监测和分析对电力系统故障诊断和电网恢复至关重要。该文提出一种基于欠定盲源分离原理的低频振荡模式辨识方法,包括欠定盲源分离(underdetermined blind source separation,UBSS)和希尔伯特变换(Hilbert transform,HT)。首次系统地提出并论证含欠定盲源分离、模式定阶和振荡参数的辨识方法。提出的UBSS-HT方法利用能量比函数确定故障时刻,利用贝叶斯信息准则(Bayesian information criterion,BIC)实现模式定阶,阐述维度空间理论,论证构建虚拟多通道的可行性,通过盲源分离来实现源信号分离,最后通过HT在希尔伯特空间来辨识振荡参数。通过大量的系统建模仿真和现场录波数据试验评估所提方法的性能,验证该方法的有效性、准确性和抗干扰能力。 展开更多
关键词 欠定盲源分离 低频振荡 能量比函数 维度变换 源数估计
下载PDF
上一页 1 2 25 下一页 到第
使用帮助 返回顶部