期刊文献+
共找到2,151篇文章
< 1 2 108 >
每页显示 20 50 100
An Efficient Method for Local Buckling Analysis of Stiffened Panels 预览
1
作者 WANG Xinwei YUAN Zhangxian 《南京航空航天大学学报:英文版》 EI CSCD 2019年第1期17-25,共9页
The local buckling of stiffened panels is one of possible failure modes and concerned by engineers in the preliminary design of lightweight structures. In practice,a simplified model,i.e.,a rectangular plate with elas... The local buckling of stiffened panels is one of possible failure modes and concerned by engineers in the preliminary design of lightweight structures. In practice,a simplified model,i.e.,a rectangular plate with elastically restrained along its unloaded edges,is established and the Ritz method is usually employed for solutions. To use the Ritz method,however,the loaded edges of the plate are usually assumed to be simply supported. An empirical correction factor has to be used to account for clamped loaded edges. Here,a simple and efficient method,called the quadrature element method(QEM),is presented for obtaining accurate buckling behavior of rectangular plates with any combinations of boundary conditions, including the elastically restrained conditions. Different from the conventional high order finite element method(FEM),non?uniformly distributed nodes are used,and thus the method can achieve an exponential rate of convergence. Formulations are worked out in detail. A computer program is developed. Improvement of solution accuracy can be easily achieved by changing the number of element nodes in the computer program. Several numerical examples are given. Results are compared with either existing solutions or finite element data for verifications. It is shown that high solution accuracy is achieved. In addition,the proposed method and developed computer program can allow quick analysis of local buckling of stiffened panels and thus is suitable for optimization routines in the preliminary design stage. 展开更多
关键词 LOCAL BUCKLING QUADRATURE ELEMENT METHOD elastically restrained stiffened PANEL
在线阅读 下载PDF
Quasi-static and dynamical analyses of a thermoviscoelastic Timoshenko beam using the differential quadrature method 预览
2
作者 Qiang LYU Jingjing LI Nenghui ZHANG 《应用数学和力学:英文版》 SCIE EI CSCD 2019年第4期549-562,共14页
The quasi-static and dynamic responses of a thermoviscoelastic Timoshenko beam subject to thermal loads are analyzed.First,based on the small geometric de-formation assumption and Boltzmann constitutive relation,the g... The quasi-static and dynamic responses of a thermoviscoelastic Timoshenko beam subject to thermal loads are analyzed.First,based on the small geometric de-formation assumption and Boltzmann constitutive relation,the governing equations for the beam are presented.Second,an extended differential quadrature method(DQM)in the spatial domain and a differential method in the temporal domain are combined to transform the integro-partial-differential governing equations into the ordinary dif-ferential equations.Third,the accuracy of the present discrete method is verified by elastic/viscoelastic examples,and the effects of thermal load parameters,material and geometrical parameters on the quasi-static and dynamic responses of the beam are dis-cussed.Numerical results show that the thermal function parameter has a great effect on quasi-static and dynamic responses of the beam.Compared with the thermal relaxation time,the initial vibrational responses of the beam are more sensitive to the mechanical relaxation time of the thermoviscoelastic material. 展开更多
关键词 TIMOSHENKO beam THERMOVISCOELASTICITY thermal load dynamic response differential QUADRATURE method(DQM)
在线阅读 下载PDF
QSM-IDM -A novel quadrature spatial modulation based on interleaving division multiplexing for multiple antenna system 预览
3
作者 Sherif K. El Dyasti Esam A.A. Hagras Hadia El-Hennawy 《数字通信与网络:英文版》 2019年第3期183-188,共6页
Quadrature Spatial Modulation (QSM) is a high spectral efficiency Multiple-Input Multiple Output (MIMO) technique used to improve the spectral efficiency of wireless communication systems. The main concept of QSM is t... Quadrature Spatial Modulation (QSM) is a high spectral efficiency Multiple-Input Multiple Output (MIMO) technique used to improve the spectral efficiency of wireless communication systems. The main concept of QSM is to extend the spatial constellation of the conventional Spatial Modulation (SM) in both the in-phase and quadrature components of the data symbol. In this paper, because QSM-based on Interleaxdng Division Multiplexing (IDM) has not been introduced in the literature as a multiple antenna system, we introduced a novel scheme, called QSM system based on Interleaving Division Multiplexing (QSM-IDM). The antenna sets are also applied to a spreader, before being used to assign an antenna number for information transmission. Analysis and simulations for a flat fading channel show that the proposed QSM-IDM method significantly outperforms the original QSM system with the same data rate, while maintaining a relatively acceptable complexity. The obtained simulation results show that the conducted analysis yields significant improvements for the accuracy of the proposed scheme, with satisfactory complexity. 展开更多
关键词 Interleaver DIVISION MULTIPLEXING (IDM) MULTIPLE Input MULTIPLE Output (MIMO) Spatial MODULATION (SM) QUADRATURE Spatial MODULATION (QSM)
在线阅读 免费下载
Blast response in concrete beam with nanoparticles utilising Newmark method
4
作者 P. Polita 《机电液工程学报》 2019年第1期2-3,共2页
The project focuses on the dynamic analysis of concrete beams reinforced with silica-nanoparticles under blast loading. The structure is located at two boundary conditions. The effective composite properties are obtai... The project focuses on the dynamic analysis of concrete beams reinforced with silica-nanoparticles under blast loading. The structure is located at two boundary conditions. The effective composite properties are obtained utilising Mori-Tanak theory. The structure is simulated with sinusoidal shear deformation theory. Applying strains and stress, the beam energies are derived and utilising principal of Hamilton, the final equations are calculated. Using method of differential quadrature (DQM) and Newmark, the structure dynamic deflection is obtained. The influences of volume fraction and agglomeration of silica nanoparticles, parameters of geometrical, boundary condition and blast load on the dynamic deflection are studied. 展开更多
关键词 concrete BEAM NANOPARTICLES NEWMARK method differential QUADRATURE (DQM)
计算Cauchy主值积分的高精度公式
5
作者 陈传希 金国祥 《高等学校计算数学学报》 CSCD 北大核心 2019年第3期224-233,共10页
1引言Gauss型求积公式使求积公式精度最大化。
关键词 CAUCHY principal value INTEGRALS Gauss-Kronrod QUADRATURE FORMULAE ALGEBRAIC accuracy
Buckling analysis of functionally graded plates partially resting on elastic foundation using the differential quadrature element method 预览
6
作者 Arash Shahbaztabar Koosha Arteshyar 《力学学报:英文版》 SCIE EI CAS CSCD 2019年第1期174-189,I0005共17页
We extend the differential quadrature element method (DQEM) to the buckling analysis of uniformly in-plane loaded functionally graded (FG) plates fully or partially resting on the Pasternak model of elastic support. M... We extend the differential quadrature element method (DQEM) to the buckling analysis of uniformly in-plane loaded functionally graded (FG) plates fully or partially resting on the Pasternak model of elastic support. Material properties of the FG plate are graded in the thickness direction and assumed to obey a power law distribution of the volume fraction of the constituents. To set up the global eigenvalue equation, the plate is divided into sub-domains or elements and the generalized differential quadrature procedure is applied to discretize the governing, boundary and compatibility equations. By assembling discrete equations at all nodal points, the weighting coefficient and force matrices are derived. To validate the accuracy of this method, the results are compared with those of the exact solution and the finite element method. At the end, the effects of different variables and local elastic support arrangements on the buckling load factor are investigated. 展开更多
关键词 Differential QUADRATURE element method Pasternak elastic support Critical BUCKLING load Functionally GRADED plates
在线阅读 下载PDF
Spectral method for multidimensional Volterra integral equation with regular kernel
7
作者 Yunxia WEI Yanping CHEN +1 位作者 Xiulian SHI Yuanyuan ZHANG 《中国数学前沿:英文版》 SCIE CSCD 2019年第2期435-448,共14页
This paper is concerned with obtaining an approximate solution for a linear multidimensional Volterra integral equation with a regular kernel. We choose the Gauss points associated with the multidimensional Jacobi wei... This paper is concerned with obtaining an approximate solution for a linear multidimensional Volterra integral equation with a regular kernel. We choose the Gauss points associated with the multidimensional Jacobi weight function ω(x)=∏di=1(1-xi)^α(1+xi)^β,-1<α,β<1/d-1/2 (d denotes the space dimensions) as the collocation points. We demonstrate that the errors of approxima te solution decay exponentially. Numerical results are presen ted to demonstrate the effectiveness of the Jacobi spectral collocation method. 展开更多
关键词 MULTIDIMENSIONAL Volterra integral equation JACOBI COLLOCATION discretization: MULTIDIMENSIONAL Gauss QUADRATURE formula
Error bounds of a quadrature formula with multiple nodes for the Fourier-Chebyshev coefficients for analytic functions
8
作者 Aleksandar V.Pejcev Miodrag M.Spalevic 《中国科学:数学英文版》 SCIE CSCD 2019年第9期1657-1668,共12页
Three kinds of effective error bounds of the quadrature formulas with multiple nodes that are generalizations of the well-known Micchelli-Rivlin quadrature formula, when the integrand is a function analytic in the reg... Three kinds of effective error bounds of the quadrature formulas with multiple nodes that are generalizations of the well-known Micchelli-Rivlin quadrature formula, when the integrand is a function analytic in the regions bounded by confocal ellipses, are given. A numerical example which illustrates the calculation of these error bounds is included. 展开更多
关键词 error bound QUADRATURE formula with MULTIPLE NODES analytic function
高速编码器在流量计量中的应用 预览
9
作者 杨智 裴锐 《仪器仪表用户》 2019年第9期45-47,共3页
详细分析的X2控制器用于高速IO测量的4种测量方式:累加计数、正交计数、频率计数和脉宽计数.通过对X2控制器编程实现了欧姆龙编码器累积脉冲、旋转方向、旋转圈数的计量,进而验证了高速编码器用于工业流量计量的可行性.工业编码器可靠性... 详细分析的X2控制器用于高速IO测量的4种测量方式:累加计数、正交计数、频率计数和脉宽计数.通过对X2控制器编程实现了欧姆龙编码器累积脉冲、旋转方向、旋转圈数的计量,进而验证了高速编码器用于工业流量计量的可行性.工业编码器可靠性强,应用灵活,可以有效地提升容积式流量计的现场计量效率. 展开更多
关键词 编码器 X2控制器 累积 频率 正交 脉冲
在线阅读 下载PDF
On-node lattices construction using partial Gauss–Hermite quadrature for the lattice Boltzmann method
10
作者 叶欢锋 干则成 +1 位作者 匡波 杨燕华 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第5期175-180,共6页
A concise theoretical framework,the partial Gauss–Hermite quadrature (pGHQ),is established to construct on-node lattices of the lattice Boltzmann (LB) method under a Cartesian coordinate system.Compared with the exis... A concise theoretical framework,the partial Gauss–Hermite quadrature (pGHQ),is established to construct on-node lattices of the lattice Boltzmann (LB) method under a Cartesian coordinate system.Compared with the existing approaches,the pGHQ scheme has the following advantages: extremely concise algorithm,unifies the constructing procedure for symmetric and asymmetric on-node lattices,and covers a full-range quadrature degree of a given discrete velocity set.We employ the pGHQ scheme to search the local optimal and asymmetric lattices for {n = 3,4,5,6,7} moment degree equilibrium distribution discretization on the range [-10,10].The search reveals a surprising abundance of available lattices.Through a brief analysis,the discrete velocity set shows a significant influence on the positivity of equilibrium distributions,which is considered as one of the major impacts of the numerical stability of the LB method.Hence,the results of the pGHQ scheme lay a foundation for further investigations to improve the numerical stability of the LB method by modifying the discrete velocity set.It is also worth noting that pGHQ can be extended into the entropic LB model,even though it was proposed for the Hermite polynomial expansion LB theory. 展开更多
关键词 equilibrium distribution DISCRETIZATION PARTIAL Gauss–Hermite QUADRATURE
Numerical Simulation of MHD Peristaltic Flow with Variable Electrical Conductivity and Joule Dissipation Using Generalized Differential Quadrature Method
11
作者 Muhammad Qasim Zafar Ali +1 位作者 Abderrahim Wakif Zoubair Boulahia 《理论物理通讯:英文版》 SCIE CAS CSCD 2019年第5期509-518,共10页
In this paper, the MHD peristaltic flow inside wavy walls of an asymmetric channel is investigated, where the walls of the channel are moving with peristaltic wave velocity along the channel length. During this invest... In this paper, the MHD peristaltic flow inside wavy walls of an asymmetric channel is investigated, where the walls of the channel are moving with peristaltic wave velocity along the channel length. During this investigation,the electrical conductivity both in Lorentz force and Joule heating is taken to be temperature dependent. Also, the long wavelength and low Reynolds number assumptions are utilized to reduce the governing partial differential equations into a set of coupled nonlinear ordinary differential equations. The new set of obtained equations is then numerically solved using the generalized differential quadrature method(GDQM). This is the first attempt to solve the nonlinear equations arising in the peristaltic flows using this method in combination with the Newton-Raphson technique. Moreover, in order to check the accuracy of the proposed numerical method, our results are compared with the results of built-in Mathematica command NDSolve. Taking Joule heating and viscous dissipation into account, the effects of various parameters appearing in the problem are used to discuss the fluid flow characteristics and heat transfer in the electrically conducting fluids graphically. In presence of variable electrical conductivity, velocity and temperature profiles are highly decreasing in nature when the intensity of the electrical conductivity parameter is strengthened. 展开更多
关键词 peristaltic flow MHD VARIABLE electrical CONDUCTIVITY Joule DISSIPATION GENERALIZED differential QUADRATURE method(GDQM)
In-plane dynamics of a fluid-conveying corrugated pipe supported at both ends 预览
12
作者 Yingjie WANG Qichang ZHANG +1 位作者 Wei WANG Tianzhi YANG 《应用数学和力学:英文版》 SCIE EI CSCD 2019年第8期1119-1134,共16页
The dynamics and stability of fluid-conveying corrugated pipes are investigated. The flow velocity is assumed to harmonically vary along the pipe rather than with time. The dimensionless equation is discretized with t... The dynamics and stability of fluid-conveying corrugated pipes are investigated. The flow velocity is assumed to harmonically vary along the pipe rather than with time. The dimensionless equation is discretized with the differential quadrature method (DQM). Subsequently, the effects of the mean flow velocity and two key parameters of the corrugated pipe, i.e., the amplitude of the corrugations and the total number of the corrugations, are studied. The results show that the corrugated pipe will lose stability by flutter even if it has been supported at both ends. When the total number of the corrugations is sufficient, this flutter instability occurs at a micro flow velocity. These phenomena are verified via the Runge-Kutta method. The critical flow velocity of divergence is analyzed in detail. Compared with uniform pipes, the critical velocity will be reduced due to the corrugations, thus accelerating the divergence instability. Specifically, the critical flow velocity decreases if the amplitude of the corrugations increases. However, the critical flow velocity cannot be monotonously reduced with the increase in the total number of the corrugations. An extreme point appears, which can be used to realize the parameter optimization of corrugated pipes in practical applications. 展开更多
关键词 fluid-structure interaction fluid-conveying corrugated pipe differential QUADRATURE method (DQM) bifurcation FLUTTER
在线阅读 下载PDF
基于正交定向耦合器组合的微波功率测量方法 预览
13
作者 杜百廷 林宏翔 +1 位作者 黄贵荣 刘伟 《电子学报》 CSCD 北大核心 2018年第5期1222-1226,共5页
定向耦合器广泛应用于微波系统的功率测量.但定向耦合器的方向隔离度有限,两个方向的耦合输出信号存在一定程度地串扰,影响功率测量的准确性.为了解决这一问题,本文提出一种正交耦合测量方法.该方法采用一对相位差为90°的定向... 定向耦合器广泛应用于微波系统的功率测量.但定向耦合器的方向隔离度有限,两个方向的耦合输出信号存在一定程度地串扰,影响功率测量的准确性.为了解决这一问题,本文提出一种正交耦合测量方法.该方法采用一对相位差为90°的定向耦合器同时测量功率,通过对测量结果的计算处理,可消除方向串扰的影响.推导了正反向传输功率与正交耦合器组合功率测量值的关系,分析了正交偏差所产生的误差.为了确定耦合器的正交状态,提出了一种准确测量两个定向耦合器之间相位差的方法.实测表明正交耦合方法可有效提高功率和驻波比测量的准确性. 展开更多
关键词 微波系统 微波功率测量 定向耦合器 隔离度 正交
在线阅读 下载PDF
基于迭代积分卡尔曼PHD滤波多目标跟踪 预览 被引量:1
14
作者 穆祥强 王朝英 +1 位作者 危璋 孔云波 《现代防御技术》 北大核心 2016年第4期95-100,共6页
在多目标跟踪环境下,通过对数值积分卡尔曼概率假设密度滤波器(QK-PHD)的误差分析,提出一种迭代QK-PHD算法。该算法基本思想是将一步预测作为第1次迭代的初始值,通过量测更新得到状态估计,然后将此状态估计作为下一步迭代的初始均值... 在多目标跟踪环境下,通过对数值积分卡尔曼概率假设密度滤波器(QK-PHD)的误差分析,提出一种迭代QK-PHD算法。该算法基本思想是将一步预测作为第1次迭代的初始值,通过量测更新得到状态估计,然后将此状态估计作为下一步迭代的初始均值和方差。通过多次迭代后滤波输出精度更高方差更小。Matlab仿真结果表明,在不明显增加计算时间的基础上,迭代QK-PHD比QK-PHD的跟踪效果更加明显,滤波输出精度更高。 展开更多
关键词 迭代 多目标跟踪 状态估计 数值积分 卡尔曼滤波 概率假设密度滤波
在线阅读 下载PDF
基于 CFD -PBM积分矩量法旋风分离器中颗粒聚团的数值模拟 预览 被引量:3
15
作者 郑建祥 许帅 王京阳 《流体机械》 CSCD 北大核心 2016年第11期30-35,14共7页
为了得到颗粒聚团对旋风分离器分离性能的影响,在不同入口颗粒浓度与入口气速下研究其对分离效率的影响。采用雷诺应力模型(RSM)计算湍流流场,通过群体平衡模型(PBM)耦合 CFD 对颗粒相进行数值计算。研究结果表明:时间为2 s 时... 为了得到颗粒聚团对旋风分离器分离性能的影响,在不同入口颗粒浓度与入口气速下研究其对分离效率的影响。采用雷诺应力模型(RSM)计算湍流流场,通过群体平衡模型(PBM)耦合 CFD 对颗粒相进行数值计算。研究结果表明:时间为2 s 时,旋风分离器内的聚团作用已经趋于稳定,颗粒粒径在1.5μm 到3μm 范围的颗粒在旋风分离器内基本无法被捕集,而粒径大于5μm 的颗粒其分离效率接近于100%;随着入口颗粒浓度的增加,总体分离效率增加,而增加入口气体速度,对分离效率的影响并不是很大。 展开更多
关键词 旋风分离器 群体平衡模型(PBM) 积分矩量法(QMOM) 颗粒聚团 population BALANCE model(PBM) QUADRATURE method of moments(QMOM)
在线阅读 下载PDF
某大型振动试验工装研究 预览
16
作者 王朋 《电子机械工程》 2016年第5期16-19,共4页
机载雷达振动试验是机载雷达研制过程中不可缺少的过程之一,而振动工装设计的合理性决定了振动试验的真实性和可靠性。传统工装设计忽略了振动正交耦合的影响,使雷达天线单元处于过试验状态,严重时会毁坏雷达天线单元。文中通过有限元... 机载雷达振动试验是机载雷达研制过程中不可缺少的过程之一,而振动工装设计的合理性决定了振动试验的真实性和可靠性。传统工装设计忽略了振动正交耦合的影响,使雷达天线单元处于过试验状态,严重时会毁坏雷达天线单元。文中通过有限元仿真和试验分析了某机载雷达天线单元振动工装的振动特性。结果表明,该振动试验工装的固有频率和振动传递率均满足设计和试验要求,但正交耦合现象较为明显。最后对该工装提出了设计改进措施,可为今后类似振动工装的设计和研究提供有益的参考。 展开更多
关键词 机载雷达 振动试验 工装 正交耦合
在线阅读 下载PDF
Adaptive digital backward propagation based on variance of intensity noise
17
作者 蒋林 闫连山 +5 位作者 陈智宇 易安林 盘艳 潘炜 罗斌 李桂芳 《中国光学快报:英文版》 SCIE EI CAS CSCD 2015年第11期20-23,共4页
An adaptive digital backward propagation(ADBP) algorithm is proposed and experimentally demonstrated based on the variance of the intensity noise. The proposed algorithm can self-determine the unknown nonlinear coeffi... An adaptive digital backward propagation(ADBP) algorithm is proposed and experimentally demonstrated based on the variance of the intensity noise. The proposed algorithm can self-determine the unknown nonlinear coefficient γ and the nonlinear compensation parameter ξ. Compared to the scheme based on the variance of phase noise, the proposed algorithm can avoid the repeated frequency offset compensation and carrier phase recovery. The simulation results show that the system’s performance compensated by the proposed method is comparable to conventional ADBP schemes. The performance of the proposed algorithm is simulated in40/112 Gb/s polarization-division multiplexing(PDM)-quadrature phase-shift keying(QPSK) and 224 Gb/s PDM-16-quadrature amplitude modulation(QAM) systems and further experimentally verified in a 40 Gb/s PDM-QPSK coherent optical communication system over a 720 km single-mode fiber. 展开更多
关键词 BACKWARD QUADRATURE COMPENSATION MULTIPLEXING COMP
超低电压正交压控振荡器设计 被引量:1
18
作者 李静 刘辉华 《微电子学与计算机》 CSCD 北大核心 2014年第2期161-164,共4页
提出一种新的低压正交压控振荡器(QVCO)结构,该结构由两个完全相同的低压压控振荡器经过背栅耦合方式实现.背栅耦合方式使压控振荡器实现正交的输出时钟并且降低了功耗和输出相位噪声.该设计中的QVCO电路采用中芯国际0.13μm1P8M... 提出一种新的低压正交压控振荡器(QVCO)结构,该结构由两个完全相同的低压压控振荡器经过背栅耦合方式实现.背栅耦合方式使压控振荡器实现正交的输出时钟并且降低了功耗和输出相位噪声.该设计中的QVCO电路采用中芯国际0.13μm1P8M标准CMOS工艺,可以工作在0.35V的电源电压下,总的功耗为1.75mw,输出时钟频率为5.34GHz,偏离主频1MHz处的相位噪声为-110.5dBc/Hz,对应该相位噪声的FOM(Figure-Of-Merit)为-187.48dBc/Hz,频率调谐范围为4.92~5.34GHz.该QVCO可以在更低的电源电压下实现低的相位噪声,且拥有较高的FOM值. 展开更多
关键词 低压 正交 压控振荡器 背栅耦合
附加相位噪声测试技术研究 预览
19
作者 王崇 鹿森 《电光系统》 2014年第1期44-47,共4页
为精确测量频率控制器件的相位噪声,文章简单介绍了相位噪声的定义,详细介绍了附加相位噪声的测试过程,给出了实际的测试结果,指出了附加相位噪声测试过程中的一些注意事项,希望对附加相位噪声测试人员有一定的借鉴意义。
关键词 附加相位噪声 相位检波器 正交 频率控制器件
在线阅读 下载PDF
Enabling technologies and challenges for transmission of 400 Gb/s signals in 50 GHz channel grid
20
作者 Xiang ZHOU 《中国光电子学前沿:英文版》 CSCD 2013年第1期30-45,共16页
This paper reviewed the recent progress in transmission of 400Gb/s, wavelength-division-multiplexed (WDM) channels for optical networks based on the standard 50GHz grid. modulation, coding, and line We discussed the... This paper reviewed the recent progress in transmission of 400Gb/s, wavelength-division-multiplexed (WDM) channels for optical networks based on the standard 50GHz grid. modulation, coding, and line We discussed the enabling system technologies, as well as the existing challenges. It is shown that, 400 Gb/s per channel signal can be transmitted on the standard 50 GHz ITU-T grid at 8.4 b/ds/Hz net spectral efficiency (SE) over meaningful transmission reach for regional and metropolitan applications. However, further studies are needed to fully understand the potential for meeting the requirements of long-haul transmission applications. 展开更多
关键词 modulation coherent QUADRATURE amplitudemodulation (QAM) fiber capacity RECONFIGURABLE opticaladd DROP MULTIPLEXER (ROADM) optical filtering Nyquistpulse shaping
上一页 1 2 108 下一页 到第
使用帮助 返回顶部 意见反馈