排序方式: 共有36条查询结果,搜索用时 56 毫秒
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F/1.3抛物面零检验补偿器设计 总被引:4,自引:1,他引:3
根据会聚光路中使用的Offner补偿器和平行光路中使用的两片式补偿器的要求,设计出了四个针对F/1.3抛物面的补偿器,并从剩余波像差、公差要求、加工工艺性、装调等方面对它们的性能做出比较,确定了三个可用于实际补偿检验的设计结果,其剩余波像差均小于/35。所述补偿器的设计方法和要求具有普遍性,设计结果也可用于同类型主镜补偿器的设计。 相似文献
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Nonparametric inference with generalized likelihood ratio tests 总被引:2,自引:0,他引:2
The advance of technology facilitates the collection of statistical data. Flexible and refined statistical models are widely
sought in a large array of statistical problems. The question arises frequently whether or not a family of parametric or nonparametric
models fit adequately the given data. In this paper we give a selective overview on nonparametric inferences using generalized
likelihood ratio (GLR) statistics. We introduce generalized likelihood ratio statistics to test various null hypotheses against nonparametric alternatives.
The trade-off between the flexibility of alternative models and the power of the statistical tests is emphasized. Well-established
Wilks’ phenomena are discussed for a variety of semi- and non-parametric models, which sheds light on other research using
GLR tests. A number of open topics worthy of further study are given in a discussion section.
This invited paper is discussed in the comments available at: , , , , , , , , .
The work was supported by the NSF grants DMS-0354223, DMS-0532370 and DMS-0704337.
The paper was initiated when Jiancheng Jiang was a research fellow at Princeton University. 相似文献
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Torsional rigidity of a circular bar with multiple circular inclusions using the null-field integral approach 总被引:1,自引:1,他引:0
In this article, a systematic approach is proposed to calculate the torsional rigidity and stress of a circular bar containing
multiple circular inclusions. To fully capture the circular geometries, the kernel function is expanded to the degenerate
form and the boundary density is expressed into Fourier series. The approach is seen as a semi-analytical manner since error
purely attributes to the truncation of Fourier series. By collocating the null-field point exactly on the real boundary and
matching the boundary condition, a linear algebraic system is obtained. Convergence study shows that only a few number of
Fourier series terms can yield acceptable results. Finally, torsion problems are revisited to check the validity of our method.
Not only the torsional rigidities but also the stresses of multiple inclusions are also obtained by using the present approach. 相似文献
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For the point null hypothesis testing problem it is shown that, in some situations, the classical evidence againstH
0, expressed in terms of the p-value, is in the range of Bayesian measures of evidence. In these situations, it is therefore
possible to reconcile measures of evidence between Bayesian and frequentist approaches. More specifically, for the class of
unimodal, symmetric and nonincreasing prior distributions, it is shown that the infimum of the posterior probability ofH
0 is numerically equal to thep value. The discrepancy which appears in the literature dedicated to this subject until now, is due to the form of the mixed
distribution and not due to its use as a prior. 相似文献
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Håkan Wirdelius 《Journal of Nondestructive Evaluation》1992,11(1):29-39
A model of a compressional ultrasonic transducer is implemented into a T-matrix method-based solution to a crack scattering problem. The probe can act both as a receiver and as a transmitter, and it is modeled as an acoustic piston-like source. A previous solution by the null field approach is applied and is here used to model a crack that is partly closed due to an external background pressure. Numerical calculations of the signal response when the crack is penny-shaped are performed and compared with results from a program based on the Geometrical Theory of Diffraction, and the agreement is generally found to be very good. 相似文献
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Peter Olsson 《Journal of Nondestructive Evaluation》1986,5(3-4):161-168
A recent modification of the null field approach is adapted to the study of scattering of elastic waves by fluid-filled nonplanar cracks. The fluid-filled crack is modeled as a surface over which friction-free boundary conditions apply. A closed surface is formed by adding a fictitious surface, on which latter surface boundary conditions of welded contact are applied. The surface fields on the closed surface are expanded in vector spherical harmonics in a manner which takes the edge conditions into account. Some numerical results on farfield quantities, such as scattering cross sections and backscattering amplitudes (both in the frequency and time domains), are presented for rotationally symmetric cracks. 相似文献
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The influence of annealing temperature (Ta = 300-900 K) on optical properties of the Au (4 nm)/Co (3 nm)/Cu (6-12 nm)/Co (20 nm)/SiO2/Si spin-valve structures was studied. The model of Co, Au, and Cu atom interdiffusion was proposed based on the experimental data analysis. The formation of solid solutions at the thin layer interfaces Au/Co and Cu/Co was studied, and as a result the most intensive formation of solid solutions was identified at annealing temperature of Ta = 750 K. The optical parameters of the samples were calculated using the genetic algorithm. The spin-valve systems remain relatively unperturbed until 750 K, but the optical properties change significantly from 750 to 900 K. It can be explained by the formation of the interphase in multilayer thin film systems. 相似文献