共查询到17条相似文献,搜索用时 93 毫秒
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三维声波方程逆问题的共轭梯度法求解 总被引:3,自引:2,他引:1
考虑一个完整的三维声波方程的逆问题.通过构造一个表面声压偏差平方和形式的目标泛函,把声波方程的逆问题转化为一个控制声学特性参数分布使得目标泛函达到最小伍的优化问题.采用共轭梯度法来求解这个优化问题.通过引入一个对偶函数u(x,t),文中用微扰法求得了目标泛函梯度值的解析表达式,从而克服了以往用共轭梯度法求解偏微分方程控制的优化问题时计算目标活函梯度的困难,大大压缩了共轭梯度法计算目标泛函梯度的时间,而且提高了梯度值的计算精度.还进一步进行了反演声学特性参数三维分布的数值仿真计算.共轭梯度法完整解决了三维声波方程的逆问题. 相似文献
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本文基于BP神经网络方法结合蒙特卡洛和BEER定律辐射传输模拟方法建立了联合反演各向异性散射介质的辐射特性参数模型。首先采用半球透射率结合半球反射率反演模型反演了各向同性介质的吸收系数和散射系数,在此基础上增加准直透射率,建立了联合反演各向异性介质的吸收系数、散射系数和散射不对称因子三参数联合反演模型。反演结果表明该模型能准确反演出介质辐射特性参数,具有实用意义。此外,为了检验测量误差对模型的反演准确性的影响,分别在不同程度测量误差情况下进行反演,结果显示测量误差对散射不对称因子反演值影响较大。 相似文献
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提出双曲传热反问题热物性参数和边界条件多宗量联合反演的一般数值求解模式,考虑了非均质和分布参数的影响,时域上采用时域精细算法进行离散,建立了便于敏度分析的有限元正演模型.由最小二乘原理建立反演模型,应用共轭梯度法进行求解.探讨了时间步长和测量误差对反演结果的影响,并进行了数值验证. 相似文献
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本文以超短脉冲激光照射参与性介质的光学成像为研究背景,分别构建了短脉冲激光在参与性介质内的频域辐射传输正问题模型和根据边界探测所得频域信号重建介质内部光学参数的逆问题模型。在瞬态辐射传输方程的基础上,利用傅里叶变换得到频域辐射传输方程,采用有限体积法求解频域传输方程,模拟超短脉冲激光在二维参与性介质内传输的过程,得到介质边界的出射频域辐射信号。选取共轭梯度法作为反演算法,采用伴随差分模型求解目标函数梯度,重建了二维非均匀参与性介质内不同位置内含物的光学参数分布。结果表明,基于频域辐射传输方程的伴随差分模型能够较为准确地反演多维参与性介质内的光学参数。 相似文献
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采用共轭梯度法的管内壁温度导热反问题求解 总被引:4,自引:0,他引:4
建立了采用共轭梯度法的非稳态二维导热反问题数学模型,并利用FORTRAN语言编写了程序进行计算求解,由同心圆管外壁温度随时间的变化得到管内壁温度随时间的变化.计算结果表明,计算值与准实验值吻合,共轭梯度法能够准确地计算得到管内壁不同位置温度随时间的变化. 相似文献
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Hongwu Fan Bingxi LiLidan Yang Ruzhu Wang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(1):85-95
An inverse radiation analysis is presented for estimating the temperature and the heat load distributions of the heating surface from the temperature and the heat flux measurements of the heated object. The Monte Carlo method is employed to solve the direct radiation problem. The inverse radiation problem is solved using the conjugate gradient and singular value decomposition methods. The measured data are simulated by adding random errors to the exact solution of the direct problem. The effects of the measurement errors on the accuracy of the inverse analysis are investigated. The study shows that the heat load distribution of the heating surface can be estimated accurately for the exact and noisy data. And the conjugate gradient method is better than the singular value decomposition method since the former can obtain more accurate results if the measurement errors are the same. 相似文献
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Hongwu Fan Bingxi LiLidan Yang Ruzhu Wang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(1):75-83
A new inverse radiation analysis is presented for estimating the heat rate and temperature distributions in the combustion region from the information of the temperature and heat flux profiles of wall elements in the system. The Monte Carlo method is employed to solve the radiative heat transfer equation. The inverse radiation problem is posed as a minimization problem of the least squares criterion, which is solved by the conjugate gradient method. The performance of the present technique of inverse analysis is evaluated and the effects of the errors of the absorption coefficient, emissivity and convective heat transfer coefficient on the inverse analysis are investigated. The results show that the present technique is robust and yields accurate estimation even with noisy measurement. 相似文献
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An Effective Multigrid Preconditioned CG Algorithm for Millimeter Wave Scattering by an Infinite Plane Metallic Grating 总被引:1,自引:0,他引:1
An effective multigrid based preconditioned conjugate gradient method is developed to solve electromagnetic large matrix problem for millimeter wave scattering application. By using multigrid technique we restrict the large matrix equation to a relative smaller matrix and which can be solved rapidly. The solution is prolonged as the initial guess for the conjugate gradient (CG) method. Numerical results show that our developed method can reach five times improvement of computational complexity. 相似文献
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R. S. Chen D. G. Fang K. F. Tsang Edward K. N. Yung 《International Journal of Infrared and Millimeter Waves》2000,21(9):1541-1560
An effective wavelet based multigrid preconditioned conjugate gradient method is developed to solve electromagnetic large matrix problem for millimeter wave scattering application. By using wavelet transformation we restrict the large matrix equation to a relative smaller matrix and which can be solved rapidly. The solution is prolonged as the new improvement for the conjugate gradient (CG) method. Numerical results show that our developed wavelet based multigrid preconditioned CG method can reach large improvement of computational complexity. Due to the automaticity of wavelet transformation, this method is potential to be a block box solver without physical background. 相似文献
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A proper selection of the pulse parameters is essential to achieve desired temperature at the material surface. This leads to obtain the required metallurgical changes in the surface vicinity when a time-varying laser pulse is used in a heating process such as surface modification. In this paper, the conjugate gradient method (CGM) for parameter estimation is successfully applied to estimate the unknown laser pulse parameters for those purposes during laser heating process. The determination of the pulse parameters is treated as a one-dimensional, transient, non-linear inverse heat conduction problem (IHCP). Based on a sensitivity analysis, the inverse problem is solved as an optimization problem comparing a desired temperature at the surface and a calculated one where the objective function is minimized by CGM. The method has been applied to a test case of a heating process on steel, appropriate pulse parameters and desired temperature distribution can also be returned. 相似文献