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91.
用于投影显示的分色合色膜系的消偏振设计 总被引:3,自引:3,他引:0
由于斜入射时,光学薄膜存在一定的偏振效应,将产生S-和P-偏振光的光谱分离.在Philips棱镜系统中,分色合色膜系通常分色时对S-光应用,合色时则对P-光应用.从提高光能利用率、减少杂散光和增加系统对比度等因素综合考虑,要求分色合色膜系的S-和P-偏振光的分离尽可能小.新设计方法采用宽带法布里-珀罗薄膜干涉滤光片中心波长两侧的干涉带作为长波通或短波通截止滤光片,可实现S-和P-偏振分量的分离几乎为零. 相似文献
92.
The scattering behavior of P-waves in piezoelectric composites with 1–3 connectivity is studied. The method of wave function expansion is adopted for the theoretical derivations. Analytical expressions are obtained for the distributions of mechanical displacement in z-direction along the circumferences of piezoelectric cylinders. These solutions are used to study the influence of each element of the stiffness matrix and the piezoelectric matrix on the various resonant modes of vibration. Numerical results obtained indicate that perturbations of the elements c44 and e15 significantly affect resonant frequencies and amplitudes, perturbations of c11 and c12 have pronounced effects on resonant modes of high frequencies also. However, the resonant modes are not so sensitive to the perturbations of c13, e31 and e33. The dynamic characteristics of 1–3 connectivity piezoelectric composites exposed here are meaningful for the design and manufacture of sensor/actuator elements by this kind of composites as well as the on-line health monitoring of the mechanical properties variations of the composites itself. 相似文献
93.
G Budak 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,88(4):525-532
The X-ray absorption jump factor and jump ratio of Gd, Dy, Ho and Er were measured with a Si(Li) detector by attenuation, with Gd, Dy, Ho and Er foil, a Compton peak produced by the scattering of the Am-241 Gamma rays. Al was chosen as secondary exciter. The experimental absorption jump factors and jump ratios are compared with the theoretical estimates of WinXcom (Radiat. Phys. Chem. 60 (2001) 23), McMaster (Compilation of X-ray cross sections UCRL-50174, 1969; Sec. II. Rev. I), Broll (X-ray Spectrom 15 (1986) 271), Hubbel and Seltzer (NISTIR (1995) 5632) and Budak (Radiat. Meas. accepted for publication). The present results constitute the first measurement for this combination of energy and elements, and good agreement is obtained between experiment and theory. 相似文献
94.
Woonghee Tim Huh 《Operations Research Letters》2004,32(3):212-216
This paper studies the NP-hard problem of finding a minimum size 2-edge connected spanning subgraph (2-ECSS). An algorithm is given that on an r-edge connected input graph G=(V,E) finds a 2-ECSS of size at most |V|+(|E|−|V|)/(r−1). For r-regular, r-edge connected input graphs for r=3, 4, 5 and 6, this gives approximation guarantees of and , respectively. 相似文献
95.
We present a framework aimed to reveal directed interactions of activated brain areas using time-resolved fMRI and vector autoregressive (VAR) modeling in the context of Granger causality. After describing the underlying mathematical concepts, we present simulations helping to characterize the conditions under which VAR modeling and Granger causality can reveal directed interactions from fluctuations in BOLD-like signal time courses. We apply the proposed approach to a dynamic sensorimotor mapping paradigm. In an event-related fMRI experiment, subjects performed a visuomotor mapping task for which the mapping of two stimuli (“faces” vs “houses”) to two responses (“left” or “right”) alternated periodically between the two possible mappings. Besides expected activity in sensory and motor areas, a fronto-parietal network was found to be active during presentation of a cue indicating a change in the stimulus-response (S-R) mapping. The observed network includes the superior parietal lobule and premotor areas. These areas might be involved in setting up and maintaining stimulus-response associations. The Granger causality analysis revealed a directed influence exerted by the left lateral prefrontal cortex and premotor areas on the left posterior parietal cortex. 相似文献
96.
Jian-pingOu Fu-jiZhang 《应用数学学报(英文版)》2003,19(3):505-510
An m-restricted edge cut is an edge cut that separates a connected graph into a disconnected one with no components having order less than m. m-restrict edge connectivity λm is the cardinality of a minimum m-restricted edge cut. Let G be a connected k-regular graph of order at least 2m that contains m-restricted edge cuts and X be a subgraph of G. Let θ(X) denote the number of edges with one end in X and the other not in X and ξm=min{θ(X) ;X is a connected vertex-induced subgraph of order m}.It is proved in this paper that if G has girth at least m/2 2,then λm≤ξm.The upper bound of λm is sharp. 相似文献
97.
Let G be a graph, $ \{a, b, c\}\subseteq V(G) $, and
$ \{a', b', c'\}\subseteq V(G) $ such that $ \{a, b, c\}\neq \{a', b', c'\} $. We say that
$ (G, \{a, c\}, \{a', c'\}, (b, b')) $ is an obstruction if, for
any three vertex disjoint paths from {a, b, c} to
{a', b', c'} in G, one path is
from b to b'. In this paper
we characterize obstructions. As a consequence, we show that no obstruction can be 8-connected,
unless b = b' or {a, c} = {a', c'}.AMS Subject Classification: 05C38. 相似文献
98.
In this paper the question of what classes A of T
0-spaces should be paired with classes of domains in order that all function spaces [AB] for AA and B are -compact domains is considered. It is shown that core compact spaces are paired with bounded complete domains and a class of topological spaces called RW-spaces (with finitely many components) is paired with the class of -compact pointed L-domains (L-domains). 相似文献
99.
A non-conforming finite element method with anisotropic mesh grading for the Stokes problem in domains with edges 总被引:5,自引:0,他引:5
The solution of the Stokes problem in three-dimensional domainswith edges has anisotropic singular behaviour which is treatednumerically by using anisotropic finite element meshes. Thevelocity is approximated by CrouzeixRaviart (nonconformingP1 ) elements and the pressure by piecewise constants. Thismethod is stable for general meshes (without minimal or maximalangle condition). Denoting by Ne the number of elements in themesh, the interpolation and consistency errors are of the optimalorder h Ne1/3 which is proved for tensor product meshes.As a by-product, we analyse also nonconforming prismatic elementswith P1 [oplus ] span {x32} as the local space for the velocitywhere x3 is the direction of the edge. 相似文献
100.