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1.
凑合反推法──流体力学变分原理建立的一条新途径   总被引:6,自引:0,他引:6  
凑合反推法是刘商联系统方法[1]的进一步发展,应用这种方法可以方便地构造各种亚广义变分原理及广义变分原理,并可以消除临界变分现象.对于任何二维守恒型流体力学方程,作者推导得到了其广义变分通用公式.几个实例证明这种方法是有效的、简单的,并具有普遍的意义.  相似文献
2.
基于爆轰波原理声源定位方法初探   总被引:5,自引:0,他引:5  
基于弹丸发射时所发出的爆轰波,利用传感器接收时差信息,从而确定声源位置。本文建立了该声源定位反问题的物理和数学模型,并依据该模型寻求适当的数值解法,最后针对延拓-广义逆法声源定位问题进行了演算和简要分析。  相似文献
3.
姚磊华 《计算物理》2005,22(4):311-318
遗传算法在处理非线性优化问题时具有较好的全局搜索性能,但在局部搜索时搜索效率不高,解的精度亦不高,高斯牛顿法在处理非线性优化问题时的性质正好和遗传算法相反,利用遗传算法和高斯牛顿法的优点,用改进的遗传算法和高斯牛顿法联合反演地下水数值模型参数.首先用遗传算法求出地下水模型参数的初值,然后利用这组初值用高斯牛顿法进行数值模型参数的反演,并以一非均质各向同性三维承压非稳定流理想模型为例,结合有限元法讨论了用遗传算法和高斯牛顿法联合反演地下水数值模型参数的过程.计算结果表明,联合参数反演方法,具有收敛速度快、解的精度高的特点,在地下水渗流和水资源评价等领域可广泛应用.  相似文献
4.
We introduce a purely anharmonic lattice model with specific double-well on-site potential, which admits traveling compacton-like solitary wave solutions by the inverse method with the help of Mathematica. By properly choosing the shape of the solitary wave solution of the system, we can calculate the parameters of the specific on-site potential. We also found that the localization of the compacton is related to the nonlinear coupling parameter Cnl and the potential parameter V0 of the on-site potential, and the velocity of the propagation of the compacton is determined by the localization parameter q and the potential parameter V0. Numerical calculation results demonstrate that the narrow compacton is unstable while the wide compacton is stable when they move along the lattice chain.  相似文献
5.
A multiple scattering inversion procedure for the aerosol extinction coefficient profile retrieval and error assessment in the oxygen A-band, for passive remote sensing instruments, has been developed. The procedure has been applied to SCIAMACHY nadir simulated measurements to investigate its effectiveness in the troposphere.The inversion procedure consists of a multiple scattering Forward Model, an inversion method and a complete sensitivity and error assessment tool. The Forward Model is based on LIDORT code; the inversion method, the sensitivity study and the complete error assessment are based on Optimal Estimation. The sensitivity and error analysis has been derived to investigate the profile retrieval errors due to the uncertainty of different aerosol optical properties, molecular and surface parameters.The analysis confirms that the profile retrieval accuracy and vertical resolution are strongly dependent on the oxygen A-band spectral resolution. The moderately high SCIAMACHY spectral resolution (0.4 nm in the oxygen A-band) results in distinguishing a maximum of three aerosol layers in troposphere. The SCIAMACHY tropospheric aerosol profile retrieval is shown to be highly sensitive to aerosol optical properties as phase function and single scattering albedo. The sensitivity study reveals an improvement of information content increasing the solar zenith angle and decreasing the surface albedo. As regards the forward model, negligible errors occur as the number of streams exceeds 6.  相似文献
6.
High temperature oxidation of metals leads to residual stresses both in the metal and in the growing oxide. In this work, the evolution of this residual stresses is theoretically predicted in the growing oxide layers. The origin of these stresses is based on a microstructural model. Using experimental results providing from the oxidation kinetics, and an analysis proposed to describe the growth strain occurring in the thin layers, a set of equations is established allowing determining the stresses evolution with oxidation time. Then, the model is compared with experimental results obtained on both α-Fe and phosphated α-Fe, oxidised at different temperatures. Numerical data are extracted from experiments either with an asymptotic formulation or with an inverse method. These two methods give good agreement with experiments and allow extracting the model parameters.  相似文献
7.
(GaN/GaAlN/GaN)//Al2O3(00.1) HEMT heterostructures have been studied by X-ray scattering techniques, transmission electron microscopy and atomic force microscopy. X-ray reflectometry has been used to determine with a high accuracy both the individual layer thicknesses and the interfacial roughness, in spite of the weak electronic density contrast between layers. From the Fourier inversion method and using a simulation software, the roughness of the interface corresponding to the two-dimensional electron gas location has been determined equal to 0.5 nm. Both high resolution X-ray diffraction and transmission electron microscopy experiments have shown the excellent crystallinity of the heterostructures. Finally, the surface morphology has been inferred using atomic force microscopy experiments.  相似文献
8.
Antimonide-based superlattices dedicated to the elaboration of opto-electronic devices have been studied by X-ray scattering techniques. In particular, specular and non-specular X-ray reflectometry experiments have been performed on two MBE-samples elaborated with different shutter sequences at the interfaces. The results have shown a limitation of the incorporation of Sb species in the subsequent InAs layer for one of the samples, as expected.Then, a study on a InGaAs-cap layer/(InGaAs/AlAsSb)N superlattice grown on a InGaAs/InP buffer layer by both specular X-ray reflectometry and High resolution X-ray diffraction is reported. In particular, the results have revealed the presence of a highly disturbed thin-layer on top of the MOVPE-made GaInAs, whose presence has been explained by In-concentration modification during the desoxidation procedure at the surface of the MOVPE-made GaInAs.Beside the results on the Sb-based heterostructures, the use of X-ray scattering metrology as a routinely working non-destructive testing method has been emphasized.  相似文献
9.
In this paper, we present an inverse method based on experimental measurements of bidirectional reflection and transmission (BRDF and BTDF). Silica wool samples are studied by using an optic spectroscopy apparatus comprising a goniometric device and a grating monochromator. The inverse method allows, by means of a least-squares model, the determination of the radiative properties of the medium: albedo, optical thickness and phase function coefficients. A new phase function model taking into account Henyey and Greenstein functions associated with a Lorentz function is used. Our results achieved with the inverse method are compared to those obtained by the Mie theory.  相似文献
10.
陆 鹏  邹欣晔  王耀俊 《应用声学》2002,21(4):21-23,40
本文采用超声双透射技术测量了水中各向同性金属板的超声透射频谱,将透射频谱的理论值与实验值实现最佳拟合,具体反演得到了金属板的杨氏模量和泊松比。  相似文献
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