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A theorem of Hsu-Robbins type for negatively associated sequence 被引量:2
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作者 苏淳 《Chinese Science Bulletin》 SCIE EI CAS 1996年第6期441-446,共6页
The sequence of negatively associated random variables (r.v.’s) are widely used in thereliability theory and multivariate statistical analysis, so it is significant to investigate thelimit properties of those sequences.
关键词 NA SEQUENCES COMPLETE CONVERGENCE mixed MOMENTS of high-orders.
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A Fast Manual Picking of Small Parts High Volume Orders
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作者 Kemal Taljanovic AdnanSalihbegovic AlicaPandzo 《通讯和计算机(中英文版)》 2012年第10期1097-1103,共7页
关键词 人工采摘 大批量 小零件 订单 成本最小化 周期时间 生产效率 高精确度
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Experimental analysis of the mechanism of high-order polygonal wear of wheels of a high-speed train 被引量:27
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作者 Yue WU Xing DU +2 位作者 He-ji ZHANG Ze-feng WEN Xue-song JIN 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2017年第8期579-592,共14页
This paper presents a detailed investigation, via field experiment, into the mechanism of high-order polygonal wear of wheels of a new type of high-speed train. The investigation was carried out during the performance... This paper presents a detailed investigation, via field experiment, into the mechanism of high-order polygonal wear of wheels of a new type of high-speed train. The investigation was carried out during the performance acceptance test of the train and its initial commercial operation. The investigation covered the performance acceptance test of 150 000 km and the commercial operation of about 150 000 km. In the performance acceptance test of the first stage of about 70 000 km, at 200-250 km/h with full loading and sometimes overloading by 30%, the serious polygonal wear of 23-order took place on all the wheels of the train, and was measured and analyzed in detail. All the potygonized wheels were re-profiled because the polygonal wear had caused strong vibration and damage to the train parts. After re-profiling, the vibration of the train and track and the wear status of the wheels were measured and analyzed at different test mileages according to the polygonal wear situation of the wheels. The measured vibration of the train includes the accelerations at different positions of a motor car and a trail car. The vibration modes of the key parts of the bogies of the two cars were calculated. Meanwhile, the track resonant frequencies were investigated at the site. The purpose of the above tests and analysis is try to find the frequency of work mode matching the passing frequency of the high-order wheel polygon. The present investigation shows that one of the working models causes the formation and development of the high-order wheel polygonal wear. The growth of this wear was effectively reduced through the frequent changing of the running speed of the train operating on the way back and forth every day. 展开更多
关键词 high-speed train WHEEL high-order polygonal wear Field test Model analysis System resonance frequency
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Controllability of multi-agent systems based on agreement protocols 被引量:20
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作者 WANG Long JIANG FangCui +1 位作者 XIE GuangMing JI ZhiJian 《Science in China(Series F)》 2009年第11期2074-2088,共15页
This paper investigates the controllability of multi-agent systems based on agreement protocols. First, for a group of single-integrator agents, the controllability is studied in a unified framework for both networks ... This paper investigates the controllability of multi-agent systems based on agreement protocols. First, for a group of single-integrator agents, the controllability is studied in a unified framework for both networks with leader-following structure and networks with undirected graph. Some new necessary/sufficient conditions for the controllability of networks of single-integrator agents are established. Second, we prove that, under the same topology and same prescribed leaders, a network of high-order dynamic agents is completely controllable if and only if so is a network of single-integrator agents. Third, how the selection of leaders and the coupling weights of graphs affect the controllability is analyzed. Finally, some numerical simulations are presented to demonstrate the effectiveness of the theoretical results. 展开更多
关键词 multi-agent systems CONTROLLABILITY structural controllability agreement protocols high-order dynamic agents GRAPHS
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交错网格任意阶导数有限差分格式及差分系数推导 被引量:17
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作者 杨庆节 刘财 +3 位作者 耿美霞 冯晅 郭智奇 刘洋 《吉林大学学报(地球科学版)》 EI CAS CSCD 北大核心 2014年第1期375-385,共11页
交错网格有限差分算法以其高效、精确、实用等优点在地震波数值模拟中得到广泛应用。目前交错网格有限差分的精度已达到时间4阶、空间2 N阶;然而在求空间三次导数时,差分格式实际上并未达到所谓的2 N阶精度,而是采用了低阶的差分格式及... 交错网格有限差分算法以其高效、精确、实用等优点在地震波数值模拟中得到广泛应用。目前交错网格有限差分的精度已达到时间4阶、空间2 N阶;然而在求空间三次导数时,差分格式实际上并未达到所谓的2 N阶精度,而是采用了低阶的差分格式及差分系数,这样有利于提高大尺度空间正演时的计算效率;但从计算精度的角度考虑,有必要推导出准确的满足2 N阶精度的交错网格有限差分格式及差分系数,以得到更高精度的正演结果。笔者利用Taylor公式展开首次推导出了可导函数任意次导数的任意偶数阶精度的差分近似式及相应的差分系数,从而完善了常规高精度交错网格有限差分算法。采用新推导的交错网格有限差分格式得到的正演波形与解析解进行了对比,证明了新推导的差分格式的正确性,并与常规差分格式的正演波形进行了比较,结果显示,新推导出的交错网格有限差分格式模拟结果稳定性好,精度更高。 展开更多
关键词 交错网格 差分格式 差分系数 高精度
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求解泊松方程的紧致高阶差分方法 被引量:11
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作者 田振夫 《西北大学学报(自然科学版)》 CAS CSCD 1996年第2期109-114,共6页
基于Hermite插值法的基本思想,提出了求解二维泊松(Poisson)方程的紧致高阶差分方法,得到了一般形式的四阶和六阶差分紧致格式。通过数值实验证明了格式的良好性态。
关键词 泊松方程 差分方法 精度 紧致格式
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Generation of isolated attosecond pulses in bowtie-shaped nanostructure with three-color spatially inhomogeneous fields 被引量:13
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作者 薛山 杜洪川 +1 位作者 夏月 胡碧涛 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第5期386-393,共8页
We theoretically investigate high-order harmonic generation in a two-color multi-cycle inhomogeneous field combined with a 27th harmonic pulse. By considering a bowtie-shaped gold nanostructure, the spatiotemporal pro... We theoretically investigate high-order harmonic generation in a two-color multi-cycle inhomogeneous field combined with a 27th harmonic pulse. By considering a bowtie-shaped gold nanostructure, the spatiotemporal profiles of enhanced plasmonic fields are obtained by solving the Maxwell equation using finite-domain time-difference method. Based on quantum-mechanical and classical models, the effect of 27th harmonic pulse, temporal profile of enhanced plasmonic field and inhomogeneity on supercontinuum generation are analyzed and discussed. As a result, broadband supercontinuum can be generated from our approach with optimized gap size of nanostructure. Moreover, these results are not sensitively dependent on the relative phase in the two-color field. 展开更多
关键词 surface plasmon resonances high-order harmonics attosecond pulse 27th harmonic pulse
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基于“金课”建设标准的翻转课堂教学模式建构研究 被引量:13
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作者 姬彦红 《教育教学论坛》 2020年第1期265-267,共3页
在狠抓新时代高校本科教育工作的大背景下,如何提升翻转课堂教学模式的教学效果,打造具有“高阶性、创新性、挑战度”的“金课”,成为当前高等教育改革的热点问题。文章分析了翻转课堂教学模式实践中存在的问题,从课前准备、课中组织、... 在狠抓新时代高校本科教育工作的大背景下,如何提升翻转课堂教学模式的教学效果,打造具有“高阶性、创新性、挑战度”的“金课”,成为当前高等教育改革的热点问题。文章分析了翻转课堂教学模式实践中存在的问题,从课前准备、课中组织、课后提升三个阶段探讨了如何构建基于“金课”建设标准的翻转课堂教学模式,以期为提升高等教育质量提供有益借鉴。 展开更多
关键词 翻转课教学模式 “金课”建设 高阶性 创新性 挑战度
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Assessment of Two Turbulence Models and Some Compressibility Corrections for Hypersonic Compression Corners by High-order Difference Schemes 被引量:12
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作者 TU Guohua DENG Xiaogang MAO Meiliang 《Chinese Journal of Aeronautics》 SCIE EI CSCD 2012年第1期25-32,共8页
The Spalart-Allmaras (S-A) turbulence model, the shear-stress transport (SST) turbulence model and their compressibility corrections are revaluated for hypersonic compression comer flows by using high-order differ... The Spalart-Allmaras (S-A) turbulence model, the shear-stress transport (SST) turbulence model and their compressibility corrections are revaluated for hypersonic compression comer flows by using high-order difference schemes. The compressibility effect of density gradient, pressure dilatation and turbulent Mach number is accounted. In order to reduce confusions between model uncertainties and discretization errors, the formally fifth-order explicit weighted compact nonlinear scheme (WCNS-E-5) is adopted for convection terms, and a fourth-order staggered central difference scheme is applied for viscous terms. The 15° and 34° compression comers at Mach number 9.22 are investigated. Numerical results show that the original SST model is superior to the original S-A model in the resolution of separated regions and predictions of wall pressures and wall heat-flux rates. The capability of the S-A model can be largely improved by blending Catris' and Shur's compressibility corrections. Among the three corrections of the SST model listed in the present paper, Catris' modification brings the best results. However, the dissipation and pressure dilatation corrections result in much larger separated regions than that of the experiment, and are much worse than the original SST model as well as the other two corrections. The correction of turbulent Mach number makes the separated region slightly smaller than that of the original SST model. Some results of low-order schemes are also presented. When compared to the results of the high-order schemes, the separated regions are smaller, and the peak wall pressures and peak heat-flux rates are lower in the region of the reattachment points. 展开更多
关键词 AERODYNAMICS high-order weighted compact nonlinear scheme hypersonic compression comers turbulence models compressibility corrections shock/boundary layer interactions shock waves
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Selection of optimal window length using STFT for quantitative SNR analysis of LFM signal 被引量:11
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作者 Qingbo Yin Liran Shen +2 位作者 Mingyu Lu Xiangyang Wang Zhi Liu 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2013年第1期26-35,共10页
An adaptive approach to select analysis window param- eters for linear frequency modulated (LFM) signals is proposed to obtain the optimal 3 dB signal-to-noise ratio (SNR) in the short- time Fourier transform (S... An adaptive approach to select analysis window param- eters for linear frequency modulated (LFM) signals is proposed to obtain the optimal 3 dB signal-to-noise ratio (SNR) in the short- time Fourier transform (STFT) domain. After analyzing the instan- taneous frequency and instantaneous bandwidth to deduce the relation between the window length and deviation of the Gaus- sian window, high-order statistics is used to select the appropriate window length for STFT and get the optimal SNR with the right time-frequency resolution according to the signal characteristic under a fixed sampling rate. Computer simulations have verified the effectiveness of the new method. 展开更多
关键词 window length selection quantitative signal-to-noise ratio instantaneous bandwidth high-order statistics.
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高阶差值筛选鬼成像方案研究 被引量:11
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作者 陈超 赵生妹 《光学学报》 EI CAS CSCD 北大核心 2014年第6期83-89,共7页
鬼成像提供了一种运用常规手段难以获得清晰图像的方法,能够解决一些常规成像技术不易解决的问题,是近些年来量子光学领域的前沿和热点之一。提出了一种基于少量数据预处理的差值筛选鬼成像恢复重建方法。该方法利用闲置光路测得的强度... 鬼成像提供了一种运用常规手段难以获得清晰图像的方法,能够解决一些常规成像技术不易解决的问题,是近些年来量子光学领域的前沿和热点之一。提出了一种基于少量数据预处理的差值筛选鬼成像恢复重建方法。该方法利用闲置光路测得的强度值和桶探测器测得的强度值的差值作为筛选门限,并且只选取少量差值进行预处理而无需对所有差值求平均得到筛选门限。将该方法应用于高阶鬼成像方案,分析高阶差值筛选鬼成像方案的可见度、峰值信噪比和阶数N的关系。研究结果表明,该方案可获得与对应鬼成像性能相当的成像质量,但重建时间明显少于对应鬼成像方案。随着阶数N的增加,成像可见度得到提高;当N足够大时理论上可见度可以接近1。同时可见度的增加将以峰值信噪比为代价,当阶数N由2阶增加到9阶时,图像的峰值信噪比下降了26.3%。 展开更多
关键词 成像系统 鬼成像 对应鬼成像 高阶 可见度
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Developing Hybrid cell-edge and cell-node Dissipative Compact Scheme for Complex Geometry Flows 被引量:10
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作者 DENG XiaoGang JIANG Yi +2 位作者 MAO MeiLiang LIU HuaYong TU GuoHua 《Science China(Technological Sciences)》 SCIE EI CAS 2013年第10期2361-2369,共9页
Developing high resolution finite difference scheme and enabling the use of this scheme on complex geometry are the aims of this study.High resolution has been achieved by Dissipative Compact Schemes(DCS),however,acco... Developing high resolution finite difference scheme and enabling the use of this scheme on complex geometry are the aims of this study.High resolution has been achieved by Dissipative Compact Schemes(DCS),however,according to the recent research,applications of DCS on complex geometry may have serious problem for that the Geometric Conservation Law(GCL)is not satisfied,and this may cause numerical instability.To cope with this problem,a new scheme named Hybrid cell-edge and cell-node Dissipative Compact Scheme(HDCS)has been formulated.The formulation of the HDCS contains two steps.First,a new central compact scheme is formulated for the purpose of conveniently fulfilling the GCL,and then dissipation is added on the central scheme by high-order dissipative interpolation of cell-edge variables.The solutions of Euler and Navier-Stokes equations show that the HDCS can be applied successfully on complex geometry,while the DCS may suffer numerical instabilities.Moreover,high resolution of the HDCS may be observed in the test of scattering of acoustic waves by multiple cylinders. 展开更多
关键词 high-order compact scheme Hybrid cell-edge and cell-node Dissipative Compact Scheme (HDCS) Weighted CompactNonlinear Scheme (WCNS) Complex Geometry Geometric Conservation Law (GCL)
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Calibration of a γ-Re_θ transition model and its validation in low-speed flows with high-order numerical method 被引量:9
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作者 Wang Yuntao Zhang Yulun +1 位作者 Li Song Meng Dehong 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2015年第3期704-711,共8页
Abstract Based on the Reynolds-averaged Navier--Stokes (RANS) equations and structured grid technology, the calibration and validation of Y-Reo transition model is preformed with fifth-order weighted compact nonline... Abstract Based on the Reynolds-averaged Navier--Stokes (RANS) equations and structured grid technology, the calibration and validation of Y-Reo transition model is preformed with fifth-order weighted compact nonlinear scheme (WCNS), and the purpose of the present work is to improve the numerical accuracy for aerodynamic characteristics simulation of low-speed flow with transition model on the basis of high-order numerical method study. Firstly, the empirical correlation functions involved in the Y-Reo transition model are modified and calibrated with experimental data of turbulent flat plates. Then, the grid convergence is studied on NLR-7301 two-element airfoil with the modified empirical correlation. At last, the modified empirical correlation is validated with NLR-7301 two-element airfoil and high-lift trapezoidal wing from transition location, velocity pro- file in boundary layer, surface pressure coefficient and aerodynamic characteristics. The numerical results illustrate that the numerical accuracy of transition length and skin friction behind transition location are improved with modified empirical correlation function, and obviously increases the numerical accuracy of aerodynamic characteristics prediction for typical transport configurations in low-speed range. 展开更多
关键词 Aerodynamic characteristicsFinite difference scheme high-order method Laminar to turbulenttransition RANS
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一类非线性项前系数可变号的高阶Duffing方程的周期解存在性问题 被引量:8
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作者 李晓静 鲁世平 《系统科学与数学》 CSCD 北大核心 2009年第8期1079-1087,共9页
利用Fourier级数理论,伯努利数理论和重合度理论研究了一类具偏差变元的高阶泛函微分方程x^((m))(t)+β(t)g(x(t-τ(t)))=p(t)的周期解问题,得到了周期解存在性的新结论,有意义的是非线性项前的系数β(t)可变号,但是,周期解先验界估计... 利用Fourier级数理论,伯努利数理论和重合度理论研究了一类具偏差变元的高阶泛函微分方程x^((m))(t)+β(t)g(x(t-τ(t)))=p(t)的周期解问题,得到了周期解存在性的新结论,有意义的是非线性项前的系数β(t)可变号,但是,周期解先验界估计方法与已有工作不同. 展开更多
关键词 高阶 DUFFING方程 重合度 周期解.
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Simulating Study of Dynamic Load Spectra Identification Method of Machinery in Cepstrum Domain 被引量:9
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作者 HONG Cong-hua QIAO Shu-yun WU Miao 《Journal of China University of Mining and Technology》 EI 2006年第1期22-24,共3页
Based on the platform of Matlab and the theory of digital signal processing, we propose a method in the cepstrum domain for dynamic load spectra identification of machinery. We demonstrate that the dynamic load spectr... Based on the platform of Matlab and the theory of digital signal processing, we propose a method in the cepstrum domain for dynamic load spectra identification of machinery. We demonstrate that the dynamic load spectra can be identified from the response signal of the system, based on cepstra. An ARMA model is built based on the harmonic retrieval by high-order spectra. The coefficients of a Green function are determined and the window width can be estimated. Finally the effectiveness of the method is validated by simulation results. 展开更多
关键词 CEPSTRUM dynamic load spectrum identification high-order spectra simulation
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A method for static aeroelastic analysis based on the high-order panel method and modal method 被引量:9
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作者 YANG Chao ZHANG BoCheng +1 位作者 WAN ZhiQiang WANG YaoKun 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第3期741-748,共8页
A method for static aeroelastic analysis based on the high-order panel method and modal method is presented. The static aeroelastic characteristics of flexible wings are investigated using this method. Three-dimension... A method for static aeroelastic analysis based on the high-order panel method and modal method is presented. The static aeroelastic characteristics of flexible wings are investigated using this method. Three-dimensional aerodynamic models of flexible wings are constructed based on the geometry of wing configuration, and the modal method is adopted to achieve the fluid-structure coupling. The static aeroelastic characteristics of the AGARD445.6 wing and a low-aspect-ratio wing are investigated in this study. The influences of elastic structural deformation on aerodynamic forces are studied with an emphasis analyzing the aerodynamic coefficients, wing root loads, structural deformation and pressure distribution of different sections, and results are compared with the results from wind-tunnel tests and the elastic results based on experimental aerodynamic forces. It is concluded that aerodynamic forces can be accurately calculated with the high-order panel method. The method presented in this study is feasible, credible and efficient. Comprehensive static aeroelastic characteristics can be provided by the method for early phases of aircraft design. 展开更多
关键词 aeroelasticity flight loads high-order panel method modal method experimental aerodynamic forces
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矩形薄板屈曲分析的高阶有限条传递矩阵法 被引量:9
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作者 葛威延 何斌 +1 位作者 安逸 刘冬梅 《应用力学学报》 CAS CSCD 北大核心 2018年第3期558-563,共6页
针对矩形薄板屈曲,基于基尔霍夫板理论,采用半解析有限条法和含有中间节线的高阶有限条法推导条元的控制方程。在此基础上,根据传递矩阵形成单元传递方程和系统传递矩阵,形成了分析薄板屈曲临界力和屈曲模态的矩形薄板屈曲分析的高阶有... 针对矩形薄板屈曲,基于基尔霍夫板理论,采用半解析有限条法和含有中间节线的高阶有限条法推导条元的控制方程。在此基础上,根据传递矩阵形成单元传递方程和系统传递矩阵,形成了分析薄板屈曲临界力和屈曲模态的矩形薄板屈曲分析的高阶有限条传递矩阵法。采用该方法分析了两种边界条件下四边受压矩形板的屈曲临界力,并与理论解和有限元解比较,实例证明该方法有效。此方法在有限条传递矩阵法的基础上可进一步提高计算精度。 展开更多
关键词 屈曲 薄板 传递矩阵 高阶有限元法 高阶
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Full-Order Sliding Mode Control for High-Order Nonlinear System Based on Extended State Observer 被引量:7
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作者 CHEN Qiang TAO Liang NAN Yurong 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2016年第4期978-990,共13页
In this paper, a full-order sliding mode control based on extended state observer(FSMC+ESO) is proposed for high-order nonlinear system with unknown system states and uncertainties.The extended state observer(ESO) is ... In this paper, a full-order sliding mode control based on extended state observer(FSMC+ESO) is proposed for high-order nonlinear system with unknown system states and uncertainties.The extended state observer(ESO) is employed to estimate both the unknown system states and uncertainties so that the restriction that the system states should be completely measurable is relaxed,and a full-order sliding mode controller is designed based on the ESO estimation to overcome the chattering problem existing in ordinary reduced-order sliding mode control. Simulation results show that the proposed method facilitates the practical application with respect to good tracking performance and chattering elimination. 展开更多
关键词 Extended state observer full-order sliding mode control high-order nonlinear system
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两点边值问题的混合型高精度紧致差分格式 被引量:8
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作者 梁昌弘 马廷福 葛永斌 《宁夏大学学报(自然科学版)》 CAS 2017年第1期1-4,共4页
借助显式紧致格式和隐式紧致格式的思想,构造了求解两点边值问题的一种混合型紧致格式.该格式仅用到3个点上的未知函数值及其一阶导数值,而一阶导数值利用四阶Padé格式进行计算.格式整体具有四阶精度,数值实验结果验证了其精确性... 借助显式紧致格式和隐式紧致格式的思想,构造了求解两点边值问题的一种混合型紧致格式.该格式仅用到3个点上的未知函数值及其一阶导数值,而一阶导数值利用四阶Padé格式进行计算.格式整体具有四阶精度,数值实验结果验证了其精确性和可靠性. 展开更多
关键词 两点边值问题 紧致格式 高精度 混合型 对流扩散反应
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High-Order Radial Derivatives of Harmonic Function and Gravity Anomaly 被引量:8
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作者 Ziqing Wei 《Journal of Physical Science and Application》 2014年第7期454-467,共14页
The first through ninth radial derivatives of a harmonic function and gravity anomaly are derived in this paper. These derivatives can be used in the analytical continuation application. For the downward continuation ... The first through ninth radial derivatives of a harmonic function and gravity anomaly are derived in this paper. These derivatives can be used in the analytical continuation application. For the downward continuation of gravity anomaly, the Taylor series approach developed in the paper is equivalent theoretically to but more efficient and storage-saving computationally than the well-known gradient operator approach. Numerical simulation shows that Taylor series expansion constructed by the derived formulas for the radial derivatives of gravity disturbance is still convergent for height up to 4 km. 展开更多
关键词 Harmonic function gravity anomaly gravity disturbance high-order radial derivative analytical continuation.
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