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271.
272.
HaiMing Wang [Wang HaiMing, Long range optical triangulation utilising collimated probe beam. Optics and Lasers in Engineering, 23(11), 1995, 41–52] studied the influences of the size of the object spot on the image spot in laser triangulation measuring. This paper points out that the study method of HaiMing Wang is inappropriate from two points of view. The size and relative power density distribution of the image spot can be calculated either when assuming the object spot is an ideal point, which emits a uniform spherical wave over the object, or when assuming that the object surface is a light scattering surface. Both the conditions show that the size of the image spot is much bigger than that of HaiMing Wang’s. 相似文献
273.
A temperature distribution sensing system based on the reflection spectrum of a 70 mm apodized chirped fiber Bragg grating has been demonstrated. Reflection variations created by the Fabry-Perot effect due to the intra-grating wavelength shift are presented. By fitting a parametric transfer matrix model of the grating response to measured spectra, the temperature change, position and width of a localized temperature change are obtained. This system is particularly attractive of its simplicity, high spatial resolution and ability in measuring a non-monotonic distribution. Experiments to measure two localized heating regions along the grating indicate that the technique is promising for measuring more complex temperature profiles. 相似文献
274.
The theoretical and technique results of a 1D focusing linear Bragg–Fresnel optics working at 18 nm X-ray radiation are given in the present paper. A theoretical method describing its optical performances is introduced briefly, the parameters of the diffraction pattern are presented. The preparation of multilayer mirrors, the decision of X-ray absorber layer thickness and the fabrication process of the diffraction pattern are described. The studied results of thermal and chemical stabilities for Mo/Si multilayer structure are shown. Some measured results for the 1D focusing linear Bragg–Fresnel optics are given. 相似文献
275.
杂多阴离子的NMR和ESR研究:Ⅱ磷钼钒杂多酸及其镧盐的NMR 总被引:1,自引:0,他引:1
具有Keggin结构的磷钼钒杂多酸及其盐是有效的氧化剂.本文通过磷钼钒杂多酸及其镧盐的~(31)p,~(51)V,~(139)La,~(17)O及~1H的NMR测定,并结合红外和差热分析,说明镧的引入对Keggin结构没有影响,但镧对水分子有强的作用力,使阴离子之间存在更多的水分子,从而对催化氧化活性产生了影响. 相似文献
276.
Single-mode condition for silicon rib waveguides with trapezoidal cross-section was obtained using a numerical method based on imaginary-distance beam propagation method with non-uniform discretization. Both quasi-transverse-electric and quasi-transverse-magnetic modes were investigated. Simulated single-mode condition is given by a modified equation. Comparison with reported results shows that the Marcatili’s method is in a better agreement with our results. 相似文献
277.
对掺Cr~(3 )乙酰丙酮铝单晶的(001),(100)和(110)晶面进行晶面旋转EPR扫描,得到共振磁场随旋转角度变化的实验图形,根据本征插方法编写的程序,对实验谱图进行投合,得到下述顺磁参数,D=0.5870±O.005cm~(-1),E=-0.00490±0.0001cm~(-1),g~2=g_y=1.965土0.001,g_r=1.984±0.001. 相似文献
278.
ZHOU Jun RAN Hong RAO Jun LIU Yong ZHANG Jinsong SONG Shaodong LU Zhihong CHEN Gangyu 《核工业西南物理研究院年报(英文版)》2004,(1):62-64
Electron cyclotron resonance heating and electron cyclotron current drive (ECRH/ECCD) have developed significantly in recent years such as Tore Supra, JT-60U , Heliotron j. It has many advantages over other means of heating and current drive. Firstly, the launcher can be located far away from the plasma. Secondly, the fact that the ECRH/ECCD power can be injected as narrow Gaussian beams, giving rise to highly localized power deposition, makes ECRH/ECCD an ideal candidate for local MHD control. 相似文献
279.
On the generalized Busemann-Petty problem 总被引:1,自引:0,他引:1
The generalized Busemann-Petty problem asks whether the origin-symmetric convex bodies in ℝ
n
with a larger volume of all i-dimensional sections necessarily have a larger volume. As proved by Bourgain and Zhang, the answer to this question is negative
if i > 3. The problem is still open for i = 2, 3. In this article we prove two specific affirmative answers to the generalized Busemann-Petty problem if the body with
a smaller i-dimensional volume belongs to given classes. Our results generalize Zhang’s specific affirmative answer to the generalized
Busemann-Petty problem.
This work was supported, in part, by the National Natural Science Foundation of China (Grant No. 10671117) 相似文献
280.
Inequalities for Edge Lengths and Volumes of Two Simplexes 总被引:2,自引:0,他引:2
Leng Gangsong 《Geometriae Dedicata》1997,68(1):43-48
In this paper, a class of geometric inequalities for the edge lengths and volumes of two n-dimensional simplexes are established. As a corollary, a generalization to several dimensions of the Neuberg–Pedoe inequality is given. 相似文献