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将超声反射CT(URCT)方法与最大似然估计方法相结合,用于对多体目标定位和对物体形状参数进行估计,给出了迭代方法及模拟结果,并作了某些讨论。  相似文献
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采用三维时域有限差分法,数值研究了等高、等体积下不同形状金属纳米颗粒的局域表面等离子体的共振性质及其规律,得到了面形状因子对共振波长的影响关系。研究表明,沿偏振方向的形状变化对共振波长偏移有重要贡献,在空气中,确定金属纳米结构局域表面等离子体共振波长的形状参数L可采用偏振方向上的纵横比和面形状因子描述,L可以拟合为纵横比和面形状因子乘积的线性函数。得到了等高、等体积下不同形状金属纳米颗粒的局域表面等离子体共振的电场能量和共振波长的关系,面形状因子越小,形状越尖锐,电场能量越高,共振波长红移。研究结果为进一步了解金属纳米颗粒的局域表面等离子体共振性质提供有益的参考。  相似文献
3.
In this paper we analyze the upper tail of the size distribution of Italian companies with limited liability belonging to the CEBI database. Size is defined in terms of net worth.In particular, we show that the largest firms follow a power law distribution, according to the well-known Pareto law, for which we give estimates of the shape parameter. Such a behavior seems to be quite persistent over time, view that for almost 20 years of observations, the shape parameter is always in the vicinity of 1.8.The power law hypothesis is also positively tested using graphical and analytical methods.  相似文献
4.
雪粒径的形状因素对积雪的反射光谱曲线影响较大,如何有效地刻画雪粒径的形状参数成为研究的热点.渐进辐射传输模型被广泛地应用于雪粒径反演,其对雪粒径形状的描述只采用了2个值(3.62对应于片状雪粒径,4.53为球形雪粒径),较难描述积雪的形状参数,同时为了反演积雪的雪粒径,这两个形状参数必须被提前固定,这大大降低了雪粒径的反演精度,为此提出了一种基于光谱库的雪粒径及形状参数反演算(LUTMA).首先利用渐进辐射传输模型建立不同粒径,不同形状参数的光谱库,然后采用光谱角指指标进行匹配,最终获取积雪的粒径与形状参数.实验表明,基于光谱库的雪粒径及形状参数反演新方法与实测数据较为吻合.  相似文献
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杨娟  赖晓明  彭刚  卞保民  陆建 《物理学报》2009,58(5):3008-3013
提出悬浮颗粒质量子集的概念,并将其推广为与计数测量信号幅度档对应的等效质量子集概念.根据统计学原理,进一步建立了悬浮颗粒质量子集颗粒平均体积的分形测度模型.基于悬浮颗粒群不同质量子集的几何形貌结构分布具有统计自相似性的特征,推导出计数法颗粒质量测量中与信号幅度档对应的颗粒等效质量计算公式,建立起计数法悬浮颗粒质量测量的基础理论模型. 关键词: 分形测度 形貌参数 质量测量 质量子集  相似文献
6.
Pulse stacking is an effective method to generate a long-shaped pulse from short pulses. In this paper, we study all-fiber coherent pulse stacking systematically; we show that the time delays and phase differences between the short pulses are the key parameters of the stacked pulse. The permitted variation of the time delay and phase difference are obtained. The ability of the stacker to produce arbitrary pulse shapes is discussed.  相似文献
7.
Teik-Cheng Lim 《Molecular physics》2013,111(12):1589-1597
A potential energy function that is reducible to the Lennard–Jones, Morse, Buckingham and Linnett potential functions by prescribing 0 and 1 to its two type-parameters is herein centralized at 0.5 for both the type-parameters. Assessment on the potential's suitability is made herein by parameterization of its shape parameters for a sampling of noble gases, small molecules (including diatoms), Buckminsterfullerene, polymers and metals for both bonded and non-bonded interactions. Comparison between the parameterized potential with other sources exhibit good agreement. A preliminary map of shape parameter product versus the shape parameter ratio was plotted to observe the distribution of bonded and non-bonded interactions within the framework of the multi-functional potential. Due to the wide ranging applicability of this new potential function for quantifying covalent and metallic bonds as well as intermolecular interactions for small and large molecules, it is herein proposed that extensive parameterization to be performed for this potential function. The use of a single potential function across various types of bonding and molecular sizes will aid the development of multi-scale analysis due to the smooth transition of energy quantification from one scale to another.  相似文献
8.
Radial basis functions (RBFs) have become a popular method for interpolation and solution of partial differential equations (PDEs). Many types of RBFs used in these problems contain a shape parameter, and there is much experimental evidence showing that accuracy strongly depends on the value of this shape parameter. In this paper, we focus on PDE problems solved with a multiquadric based RBF finite difference (RBF-FD) method. We propose an efficient algorithm to compute the optimal value of the shape parameter that minimizes the approximation error. The algorithm is based on analytical approximations to the local RBF-FD error derived in [1]. We show through several examples in 1D and 2D, both with structured and unstructured nodes, that very accurate solutions (compared to finite differences) can be achieved using the optimal value of the constant shape parameter.  相似文献
9.
本文主要讨论浅海水平不变波导中的低频声传播问题,为环境适配声纳设计奠定基础。通过仿真分析了海水及海底环境参数对传播损失的影响,根据仿真及实验结果,建立了声速剖面随机扰动及海面、海底起伏条件下的声强分布概率模型,并利用模型中的形状参数α和尺度参数β,提出了局部蒙特卡洛模拟加曲线拟合的声场敏感性分析方法。仿真及实验结果表明声场传播损失服从伽马分布,良好水文条件下10 km距离的声场能量起伏也达到10 d B,随着距离增加,声场敏感性增加。本文所提出方法通过对近场声场的测量和统计实现对远场声场敏感性的预报,与全声场蒙特卡洛模拟相比计算量减小一个数量级。  相似文献
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