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31.
Dense comb-like reflective spectrum is available for a sampled fiber Bragg grating (SFBG) by using multiple-phase-shift (MPS) technique. The expressions for the reflection-peak bandwidths of a uniform SFBG based on MPS technique are derived through Fourier transform of the index modulation. The new expressions can be used to accurately calculate the reflection-peak bandwidths as taking the parameters into account, such as the duty cycle and the “AC” index change. The simulation spectrum based on the transfer matrix method agrees well with the theoretical analysis. 相似文献
32.
Free-standing thick films of spinel ferrite, Ni0.89−xCu0.11ZnxFe2O4 with x=0.55 and 0.60, were prepared as fillers to fabricate electromagnetic composites. Compared to those made with conventional spherical fillers, the composites made with thick film fillers showed enhanced static permeability (μ′0) and maximum imaginary permeability (μ″max). At the same time, complex permittivity (ε′ and ε″) were almost unchanged. A relative bandwidth WR of 7–8 was achieved, which is about 75% of the theoretical maximum relative bandwidth. These composites are potential candidates as electromagnetic attenuation materials with ultrabroad absorption bandwidth in L and S bands. 相似文献
33.
The bandwidth of a graph is the minimum, over vertex labelings with distinct integers, of the maximum difference between
labels on adjacent vertices. Kuang and McDiarmid proved that almost all n-vertex graphs have bandwidth . Thus the sum of the bandwidths of a graph and its complement is almost always at least ; we prove that it is always at most 2n−4 log 2
n+o(log n). The proofs involve improving the bounds on the Ramsey and Turán numbers of the “halfgraph”.
Received: September 2, 1998?Final version received: November 29, 1999 相似文献
34.
Choongrak Kim Byeong U. Park Woochul Kim Chiyon Lim 《Annals of the Institute of Statistical Mathematics》2003,55(2):359-367
Estimation of a survival function from randomly censored data is very important in survival analysis. The Kaplan-Meier estimator
is a very popular choice, and kernel smoothing is a simple way of obtaining a smooth estimator. In this paper, we propose
a new smooth version of the Kaplan-Meier estimator using a Bezier curve. We show that the proposed estimator is strongly consistent.
Numerical results reveal the that proposed estimator outperforms the Kaplan-Meier estimator and its kernel weighted smooth
version in the sense of mean integrated square error.
This research is supported by the Korea Research Foundation (1998-015-d00047) made in the program year of 1998. 相似文献
35.
Bootstrap bandwidth selection in kernel density estimation from a contaminated sample 总被引:4,自引:0,他引:4
In this paper we consider kernel estimation of a density when the data are contaminated by random noise. More specifically
we deal with the problem of how to choose the bandwidth parameter in practice. A theoretical optimal bandwidth is defined
as the minimizer of the mean integrated squared error. We propose a bootstrap procedure to estimate this optimal bandwidth,
and show its consistency. These results remain valid for the case of no measurement error, and hence also summarize part of
the theory of bootstrap bandwidth selection in ordinary kernel density estimation. The finite sample performance of the proposed
bootstrap selection procedure is demonstrated with a simulation study. An application to a real data example illustrates the
use of the method.
This research was supported by ‘Projet d’Actions de Recherche Concertées’ (No. 98/03-217) from the Belgian government. Financial
support from the IAP research network nr P5/24 of the Belgian State (Federal Office for Scientific, Technical and Cultural
Affairs) is also gratefully acknowledged. 相似文献
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The Hales numbered n-dimensional hypercube exhibits interesting recursive structures in n. These structures lead to a very simple proof of the well-known bandwidth formula for hypercubes proposed by Harper, whose proof was thought to be surprisingly difficult. Harper also proposed an optimal numbering for a related problem called the antibandwidth of hypercubes. In a recent publication, Raspaud et al. approximated the hypercube antibandwidth up to the third-order term. In this paper, we find the exact value in light of the above recursive structures. 相似文献