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失速起始检测的平均数值差分方法 被引量:11
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作者 张朴 祝雪平 李应红 《航空动力学报》 EI CAS CSCD 北大核心 2003年第4期546-548,共3页
为在压气机整机进入深度失速前检测到失速起始信号,提出了一种基于平均数值差分的短周期扰动检测方法。应用该方法对某轴流式压气机压力测量数据进行了分析。结果表明,平均数值差分方法可准确地在该压气机深度失速前0.02~0.05s检测到... 为在压气机整机进入深度失速前检测到失速起始信号,提出了一种基于平均数值差分的短周期扰动检测方法。应用该方法对某轴流式压气机压力测量数据进行了分析。结果表明,平均数值差分方法可准确地在该压气机深度失速前0.02~0.05s检测到失速起始信号,具有一定的工程应用价值。 展开更多
关键词 航空发动机 失速起始 短周期扰动 试验 平均数值差分方法
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星际湍流介质中二阶矩方程的数值差分方法及其应用 被引量:1
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作者 张民 吴振森 +1 位作者 杨廷高 张延冬 《电波科学学报》 EI CSCD 2001年第2期185-188,共4页
详细分析了湍流介质中二阶矩方程的数值差分方法。利用不同的波结构函数模型 ,计算了平面脉冲波在湍流介质中传播的双频互相关函数的实部和虚部 ,直接应用于脉冲展宽、脉冲强度等问题的计算中。为应用于脉冲波传播特性分析 ,提供必要的... 详细分析了湍流介质中二阶矩方程的数值差分方法。利用不同的波结构函数模型 ,计算了平面脉冲波在湍流介质中传播的双频互相关函数的实部和虚部 ,直接应用于脉冲展宽、脉冲强度等问题的计算中。为应用于脉冲波传播特性分析 ,提供必要的理论基础和方法。同时 ,也可以推广应用到处理复宗量函数的同类偏微分方程问题中。 展开更多
关键词 脉冲波 湍流介质 双频互相关函数 数值差分方法 二阶矩方程 星际湍流介质
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非线性系统随机响应计算的纽马克差分——等效线性化综合数值方法
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作者 夏宜凉 张森文 《江汉大学学报(社会科学版)》 1993年第6期46-50,共5页
作者应用分段等效线性化思想与Newmark差分格式结合,提出了用于非线性系统受随机激励时响应方差计算的NSL方法,将线性系统的Newmark差分格式推广用于非线性系统。并与SCD—SL方法进行了比较。
关键词 非线性系统随机响应 白噪音 分段线性化 纽马克差分等效线性化综合数值方法 中心差分等效线性化综合数值方法
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求解非线性伏尔泰拉积分方程的有限差分方法(英文) 被引量:1
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作者 苟斐斐 刘建军 +1 位作者 刘卫东 罗莉涛 《中国科学院大学学报(中英文)》 CSCD 北大核心 2016年第3期329-333,共5页
研究一类典型的伏尔泰拉积分方程的数值求解方法.通过数值差分离散积分方程,然后将积分方程演化为非线性代数方程组,通过迭代推进求解此类积分方程.分析这种求解方法的代数精度,证明此数值解法的精度高达Δt^2阶,可以满足工程计算需要.... 研究一类典型的伏尔泰拉积分方程的数值求解方法.通过数值差分离散积分方程,然后将积分方程演化为非线性代数方程组,通过迭代推进求解此类积分方程.分析这种求解方法的代数精度,证明此数值解法的精度高达Δt^2阶,可以满足工程计算需要.通过数值仿真验证,数值解与解析解的误差为10^(-5).如果采用更高阶的数值积分离散方式,可以获得更高阶精度. 展开更多
关键词 伏尔泰拉积分方程 非线性 数值差分方法 差分
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螺槽内塑料熔体传热及温度的数值模拟 被引量:3
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作者 李凌丰 茅旭飞 +1 位作者 管灵波 张振然 《机械工程学报》 EI CAS CSCD 北大核心 2013年第14期23-30,共8页
用数值方法模拟塑料加工过程中的熔体可以了解其流动与传热历史,进而提高塑化性能,改善制品质量。针对熔融塑料在螺槽中的流动与传热,结合运动方程和本构方程,建立多因素同时作用下的能量守恒数学模型,模型通过热对流项、热传导项、黏... 用数值方法模拟塑料加工过程中的熔体可以了解其流动与传热历史,进而提高塑化性能,改善制品质量。针对熔融塑料在螺槽中的流动与传热,结合运动方程和本构方程,建立多因素同时作用下的能量守恒数学模型,模型通过热对流项、热传导项、黏性耗散热项的共同作用描述传热与温度分布的动态过程和稳定状态特性。利用有限差分法离散偏微分方程,构造线性方程组,根据初始条件和边界条件,并借助数值计算方法,求解得到三维流道的温度模拟结果。分析模拟结果,得到螺槽内塑料熔体的温度、热对流、热传导、黏性耗散热的分布及变化规律,据此可以更深入地理解塑化过程及其影响因素。在同样条件下比较,模拟结果与商品化软件的计算结果是一致的,验证了所提方法的正确性。 展开更多
关键词 塑料熔体流动 传热 能量守恒 有限差分数值计算方法
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简支梁结构裂纹损伤的数值分析及仿真 被引量:1
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作者 刘大任 侯祥林 高岳阳 《沈阳建筑大学学报(自然科学版)》 EI CAS 2006年第3期379-382,共4页
目的解决实际工程中梁结构裂纹损伤问题.方法对工程中梁结构动力学方程利用差分数值分析方法,得出其差分方程并编制计算机程序对典型结构的不同深度裂纹计算响应数据和绘制响应的仿真曲线.结果通过结构的响应数据和仿真曲线找出结构损... 目的解决实际工程中梁结构裂纹损伤问题.方法对工程中梁结构动力学方程利用差分数值分析方法,得出其差分方程并编制计算机程序对典型结构的不同深度裂纹计算响应数据和绘制响应的仿真曲线.结果通过结构的响应数据和仿真曲线找出结构损伤的固有特性,并将差分数值方法与实验测试结果和有限元计算结果对比,表明差分算法是具有计算量小、并可有效地反映梁裂纹损伤状况.结论通过与有限元计算结果和实验测试结果的对比分析,可知笔者提出的差分方法确为一直接的、计算简便、有效地解决复杂结构问题的方法.能够为建立诊断样本提供理论计算依据. 展开更多
关键词 简支梁 结构损伤 响应 差分数值方法 仿真
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双地下物质变化区参数解算方法研究
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作者 董冬辉 程向明 +2 位作者 张桢君 王建成 冒蔚 《天文学报》 CAS CSCD 北大核心 2022年第3期85-95,共11页
经典天体测量仪器以铅垂线为基准测量本地的天文经纬度,因而能探测到本地铅垂线的偏转.本地铅垂线的偏转代表着测站周围重力场的变化,而这一变化与地下物质的再分布相关,由此有望帮助了解地下物质变化的情况.将本地的铅垂线偏转(Plumb L... 经典天体测量仪器以铅垂线为基准测量本地的天文经纬度,因而能探测到本地铅垂线的偏转.本地铅垂线的偏转代表着测站周围重力场的变化,而这一变化与地下物质的再分布相关,由此有望帮助了解地下物质变化的情况.将本地的铅垂线偏转(Plumb Line Variation,PLV)与地下物质变化联系起来,建立了双质量体模型.在97°E-107°E和21°N-29°N范围内,考虑了3480个包含正、负质量变化(相对地质背景)的质量体组合算例,并利用差分进化(Differential Evolutionary,DE)算法进行了解算.解算得到的质量体相对于模拟值的位置误差小于米量级,质量误差小于10^(11) kg,结果精度较高. 展开更多
关键词 天体测量学 方法:数值:差分进化算法 铅垂线偏转 地下质量扰动
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特高压直流输电线路塔基边坡的稳定性分析 被引量:5
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作者 谢寿平 刘志鹏 +4 位作者 罗红明 王大庆 杨桦 刘凯 苏云鹏 《安全与环境工程》 CAS 北大核心 2019年第6期172-177,共6页
山区输电线路工程塔基一般修建于自然边坡上,塔基边坡的稳定状态是涉及输电线路工程安全的关键技术问题。以甘肃酒泉—湖南±800 kV特高压直流输电线路工程5535#塔基边坡为例,采用三维有限差分数值模拟方法,利用FLAD 3D软件对塔基... 山区输电线路工程塔基一般修建于自然边坡上,塔基边坡的稳定状态是涉及输电线路工程安全的关键技术问题。以甘肃酒泉—湖南±800 kV特高压直流输电线路工程5535#塔基边坡为例,采用三维有限差分数值模拟方法,利用FLAD 3D软件对塔基和塔基边坡的稳定性进行了分析。结果表明:塔基在荷载作用下,桩顶位置产生了向坡外向下的位移,桩端位置产生了向坡内的位移,且桩水平位移最大值为4.025 mm,处于桩水平变形允许范围内;塔基荷载作用对边坡的应力总体影响不大,局部范围内应力有所增加,且仅在坡顶局部出现拉破坏,坡顶以下坡体处于弹性变形范围,未形成整体变形失稳的破坏区,对边坡的整体稳定性影响较小;建议对塔基边坡坡顶进行适当的加固处理,以满足特高压直流输电线路工程安全运行的要求。 展开更多
关键词 输电线路 塔基边坡 稳定性分析 三维有限差分数值模拟方法
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Effects of liquefaction-induced large lateral ground deformation on pile foundations 被引量:5
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作者 王艳丽 程展林 王勇 《Journal of Central South University》 SCIE EI CAS 2013年第9期2510-2518,共9页
The pile-soil system interaction computational model in liquefaction-induced lateral spreading ground was established by the finite difference numerical method.Considering an elastic-plastic subgrade reaction method,n... The pile-soil system interaction computational model in liquefaction-induced lateral spreading ground was established by the finite difference numerical method.Considering an elastic-plastic subgrade reaction method,numerical methods involving finite difference approach of pile in liquefaction-induced lateral spreading ground were derived and implemented into a finite difference program.Based on the monotonic loading tests on saturated sand after liquefaction,the liquefaction lateral deformation of the site where group piles are located was predicted.The effects of lateral ground deformation after liquefaction on a group of pile foundations were studied using the fmite difference program mentioned above,and the failure mechanism of group piles in liquefaction-induced lateral spreading ground was obtained.The applicability of the program was preliminarily verified.The results show that the bending moments at the interfaces between liquefied and non-liquefied soil layers are larger than those at the pile's top when the pile's top is embedded.The value of the additional static bending moment is larger than the peak dynamic bending moment during the earthquake,so in the pile foundation design,more than the superstructure's dynamics should be considered and the effect of lateral ground deformation on pile foundations cannot be neglected. 展开更多
关键词 liquefaction-induced lateral spreading ground pile foundation large post-liquefaction deformation finite difference method
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Two Unconditional Stable Schemes for Simulation of Heat Equation on Manifold Using DEC
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作者 谢正 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第2期321-324,共4页
To predict the heat diffusion in a given region over time, it is often necessary to find the numerical solution for heat equation. However, the computational domain of classical numerical methods are limited to fiat s... To predict the heat diffusion in a given region over time, it is often necessary to find the numerical solution for heat equation. However, the computational domain of classical numerical methods are limited to fiat spacetime. With the techniques of discrete differential calculus, we propose two unconditional stable numerical schemes for simulation heat equation on space manifold and time. The analysis of their stability and error is accomplished by the use of maximum principle. 展开更多
关键词 discrete exterior calculus discrete manifold heat equation
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Mechanical analysis of fixed geosynthetic technique of GRPS embankment
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作者 张军 郑俊杰 马强 《Journal of Central South University》 SCIE EI CAS 2013年第5期1368-1375,共8页
To overcome the deficiencies of conventional geosynthetic-reinforced and pile-supported (GRPS) embankment, a new improvement technique, fixed geosynthetic technique of GRPS embankment (FGT embankment), was developed a... To overcome the deficiencies of conventional geosynthetic-reinforced and pile-supported (GRPS) embankment, a new improvement technique, fixed geosynthetic technique of GRPS embankment (FGT embankment), was developed and introduced. Based on the discussion about the load transfer mechanism of FGT embankment, a simplified check method of the requirement of geosynthetic tensile strength and a mechanical model of the FGT embankment were proposed. Two conditions, the pile cap and pile beam conditions are considered in the mechanical model. The finite difference method is used to solve the mechanical model owing to the complexity of the differential equations and the soil strata. Then, the numerical procedure is programmed. Finally, a field test is conducted to verify the mechanical model and the calculated results are in good agreement with field measured data. 展开更多
关键词 mechanical model load transfer mechanism fixed geosynthetic technique GRPS embankment field test
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Numerical Solution of Some Diffusion Problems in 3-Layered 3D Domain
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作者 Harijs Kalis Ilmars Kangro Aigars Gedroics 《Journal of Mathematics and System Science》 2013年第6期309-318,共10页
In this paper we consider averaging and finite difference methods for solving the 3-D boundary-value problem in a multilayered domain. We consider the metal concentration in the 3 layered peat blocks. Using experiment... In this paper we consider averaging and finite difference methods for solving the 3-D boundary-value problem in a multilayered domain. We consider the metal concentration in the 3 layered peat blocks. Using experimental data the mathematical model for calculating the concentration of metal at different points in peat layers is developed. A specific feature of these problems is that it is necessary to solve the 3-D boundary-value problems for the partial differential equations (PDEs) of the elliptic type of second order with piece-wise diffusion coefficients in the three layer domain. We develop here a finite-difference method for solving a problem of the above type with the periodical boundary condition in x direction. This procedure allows reducing the 3-D problem to a system of 2-D problems by using a circulant matrix. 展开更多
关键词 3D diffusion problem finite difference method averaged method heavy metals Ca Fe peat bog.
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Numerical Solution of Klein-Gordon Equation on Manifold Using DEC
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作者 谢正 叶征 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第8期287-291,共5页
In physics,the Klein-Gordon equation describes the motion of a quantum scalar or pseudoscalar field.Itis important to find actual values of its solutions in general timespace manifold.The paper deals with description ... In physics,the Klein-Gordon equation describes the motion of a quantum scalar or pseudoscalar field.Itis important to find actual values of its solutions in general timespace manifold.The paper deals with description ofdiscrete exterior calculus method for solving this equation numerically on space manifold and the time.The analysis ofstable condition and error for this method is also accomplished. 展开更多
关键词 MANIFOLD Klein-Gordon equation Laplace operator discrete exterior calculus
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Determining the Effective Refractive Index of AIGaAs-GaAs Slab Waveguide Based on Analytical and Finite Difference Method
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作者 All Cetin Ercan Ucgun M .Selami Kilickaya 《Journal of Physical Science and Application》 2012年第9期381-385,共5页
Optical waveguide is the main element in integrated optics. Therefore many numerical methods are used on these elements of integrated optics. Simulation response of an optical slab waveguide used in integrated optics ... Optical waveguide is the main element in integrated optics. Therefore many numerical methods are used on these elements of integrated optics. Simulation response of an optical slab waveguide used in integrated optics needs such numerical methods. These methods must be precise and useful in terms of memory capacity and time duration. In this paper, we study basic analytical and finite difference methods to determine the effective refractive index of AIGaAs-GaAs slab waveguide. Also, appropriate effective refractive index value is obtained with respect to number of grid points and number of matrix sizes. Finally, the validity of the obtained values by both methods is compared to using waveguide type. 展开更多
关键词 Numerical approximation and analysis computational techniques simulations optical constants.
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A numerical error analysis method and its application on a 4RRR parallel kinematic machine
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作者 刘大炜 Wang Liping +2 位作者 Li Tiemin Tang Limin Guo Zhiping 《High Technology Letters》 EI CAS 2010年第4期345-351,共7页
To guarantee the accuracy of error analysis and evaluate the manufacturing tolerance s influence,anumerical error analysis method for parallel kinematic machines (PKMs) is presented in this paper.Quasi-Newton method a... To guarantee the accuracy of error analysis and evaluate the manufacturing tolerance s influence,anumerical error analysis method for parallel kinematic machines (PKMs) is presented in this paper.Quasi-Newton method and genetic algorithm are introduced for the forward kinematic solution.Based onthe inverse and forward kinematic solutions,the end-effector s error calculation procedure is developed.To solve the accuracy problem caused by the length and angular parameters' different units,a normalizationmethod is proposed based on the manufacturing tolerance.Comparison between the error analysis resultscalculated by the traditional method and the numerical method for a 4RRR PKM shows that,this numericalerror analysis method is more accurate,simpler,and can evaluate the machine s real error basedon the manufacturing tolerance. 展开更多
关键词 parallel kinematic machine (PKMs) error analysis error normalization quasi-Newton method genetic algorithm
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Numerical Homogenization of the Elliptic Problem with Rapidly Varying Tensor or Boundary Condition
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作者 Jack Urombo Ephraim Makoni 《Journal of Mathematics and System Science》 2014年第6期421-432,共12页
Homogenization is concerned with obtaining the average properties of a material. The problem on its own has no easy solution, except in cases like the periodic case, when it can be obtained in closed form. In this pap... Homogenization is concerned with obtaining the average properties of a material. The problem on its own has no easy solution, except in cases like the periodic case, when it can be obtained in closed form. In this paper we consider a numerical solution of the elliptic homogenization problem for the case of rapidly varying tensor or boundary conditions. The method makes use of an adaptive finite element method to correctly capture the rapid change in the tensor or boundary condition. In the numerical experiments we vary the mesh size and do a posteriori error analysis on test problems. 展开更多
关键词 2. Homogenization Elliptic equation
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Improved modal truncation error in the directly analytical method for damage identification of frame structures
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作者 Yang Youfa Xu Dian +1 位作者 Huang Jing Liang Wenguang 《Engineering Sciences》 EI 2010年第4期91-96,共6页
The damage identification is made by the numerical simulation analysis of a five-storey-and-two-span RC frame structure, using improved and unimproved direct analytical method respectively; and the fundamental equatio... The damage identification is made by the numerical simulation analysis of a five-storey-and-two-span RC frame structure, using improved and unimproved direct analytical method respectively; and the fundamental equations were solved by the minimal least square method (viz. general inverse method). It demonstrates that the feasibility and the accuracy of the present approach were impoved significantly, compared with the result of unimproved damage identification. 展开更多
关键词 frame structures the directly analytical method damage identification the modal truncation error the minimal least square method
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Joint semiparametric mean-covariance model in longitudinal study 被引量:3
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作者 MAO Jie ZHU ZhongYi 《Science China Mathematics》 SCIE 2011年第1期145-164,共20页
Semiparametric regression models and estimating covariance functions are very useful for longitudinal study. To heed the positive-definiteness constraint, we adopt the modified Cholesky decomposition approach to decom... Semiparametric regression models and estimating covariance functions are very useful for longitudinal study. To heed the positive-definiteness constraint, we adopt the modified Cholesky decomposition approach to decompose the covariance structure. Then the covariance structure is fitted by a semiparametric model by imposing parametric within-subject correlation while allowing the nonparametric variation function. We estimate regression functions by using the local linear technique and propose generalized estimating equations for the mean and correlation parameter. Kernel estimators are developed for the estimation of the nonparametric variation function. Asymptotic normality of the the resulting estimators is established. Finally, the simulation study and the real data analysis are used to illustrate the proposed approach. 展开更多
关键词 generalized estimating equation kernel estimation local linear regression modified Cholesky decomposition semiparametric varying-coefficient partially linear model
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The ONAD method for solving the SH-wave equation and simulation of the SH-wave propagation in the Earth's mantle
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作者 LI XiaoXiao YANG DingHui TONG Ping 《Science China Earth Sciences》 SCIE EI CAS 2013年第6期913-921,共9页
The optimal nearly-analytic discrete(ONAD) method is a new numerical method developed in recent years for solving the wave equation.Compared with other methods,such as popularly-used finite-difference methods,the ONAD... The optimal nearly-analytic discrete(ONAD) method is a new numerical method developed in recent years for solving the wave equation.Compared with other methods,such as popularly-used finite-difference methods,the ONAD method can effectively suppress the numerical dispersion when coarse grids are used.In this paper,the ONAD method is extended to solve the 2-dimensional SH-wave equation in the spherical coordinates.To investigate the accuracy and the efficiency of the ONAD method,we compare the numerical results calculated by the ONAD method and other methods for both the homogeneous model and the inhomogeneous IASP91 model.The comparisons indicate that the ONAD method for solving the SH-wave equation in the spherical coordinates has the advantages of less numerical dispersion,small memory requirement for computer codes,and fast calculation.As an application,we use the ONAD method to simulate the SH-wave propagating between the Earth's surface and the core-mantle boundary(CMB).Meanwhile,we investigate the SH-wave propagating in the mantle through analyzing the wave-field snapshots in different times and synthetic seismograms. 展开更多
关键词 numerical dispersion spherical coordinates SH wave ONAD method MANTLE
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