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991.
In this article, a nonspiral plate is investigated numerically by vector diffraction theory to observe the focusing properties of Gaussian beams. Both low- and high-numerical-aperture (NA) optical systems are considered in the investigation. It is found that the parameter of NA and the phase vary rate of the phase plate influence the focal intensity distribution considerably. When a nonspiral plate is used to provide linear phase variation on one half of the Gaussian beam, it may adjust the focal spot considerably and conveniently. Changing the vary rate of the phase plate or the parameter of NA can alter optical intensity distribution; some novel focal spots and focal switch may also occur. 相似文献
992.
993.
In this paper,attention is focused on the intensity moments of the Hermite-Cosh-Gaussian (HChG) laser beams from the zero-order to the fourth-order.The frequently used parameters such as the power in bucket (PIB),the beam width,the curvature radius,the far field divergence,the M2-factor,the Rayleigh length and the kurtosis are calculated in terms of the intensity moments.Figures show the influence of the mode index and the decentered parameter,which are the critical parameters of the HChG beams.Moreover,the center of the gravity of the radiation field and the symmetry are discussed along with the propagation axis.Finally,the power fraction within the beam width defined by the second moments is illustrated with numerical method. 相似文献
994.
Silvia Richter Stepan Kyrsta Jochen Schneider David Hajas Joachim Mayer 《Mikrochimica acta》2006,155(1-2):257-262
Fibre reinforced NiAl offers new possibilities for the development of high strength structural materials of low density applicable
in gas turbines at high operating temperatures. The properties of composite materials are strongly influenced by the strength
of the fibre–matrix interface. In addition, if fibre and matrix differ in their thermal expansion coefficients, a well controlled
interface reaction at high temperature changes is demanded. Therefore, two layers consisting of BN and Hf were embedded between
a sapphire fibre and NiAl and heated at 1350 °C to find a compromise between adhesion and ductility. The control and characterization
of the reaction zone is essential for the development of these new materials. Especially, the characterization of the fibre-coating
interface is a challenge. The different hardness of fibre and coating makes it nearly impossible to use a conventional cross-section
preparation. Further, the small dimension of the reaction zone requires the use of analytical techniques providing high lateral
resolution. In order to accomplish these requirements, a newly developed technique FIB (Focused Ion Beam)-EPMA (Electron Probe
Microanalysis) was combined with XRD (X-ray diffraction). XRD was performed for the identification of the phases. The reaction
zone was exposed by a special FIB preparation technique and examined by surface-sensitive EPMA. This allowed to determine
the spatial distribution of the different phases. 相似文献
995.
Rolf Gengenbach Christian Hahn Wilhelm Schrader Jan Peter Toennies 《Theoretical chemistry accounts》1974,34(3):199-212
Absolute integral cross sections have been measured for n-H2-n-H2 at primary particle velocities between 1270 and 9650 m/sec with a 77 °K target. The number density of target particles was determined with an accuracy of 1% by the method of dynamic expansion. The velocity dependence of the integral cross section was also measured for the isotopic systems n-D2-n-H2 and n-D2-n-D2 at primary beam velocities between 280 and 1170 m/sec with a 15 °K target. All available integral cross section data are compared with literature potentials. A new potential is proposed, which exhibits one bound state for H2-H2.Dedicated to Professor H. Hartmann on his 60th birthday. 相似文献
996.
杨震华 《核聚变与等离子体物理》1988,(2)
本文用宏观处理的方法,研究了强流相对论电子束在等离子体内引起的回流电流效应。通过Fourier变换的方法,求得Maxwell方程组的电场表达式和回流电流的径向表达式。在4στ>>1的极限下,电子束通道内的回流电流和入射的电子束电流基本抵消。最后,比较了回流电流的焦耳热和束电子与等离子体粒子库仑碰撞的能耗值。 相似文献
997.
Yu. A. Borisov Yu. A. Zolotarev E. V. Laskatelev N. F. Myasoedov 《Russian Chemical Bulletin》1998,47(8):1442-1445
Ab initio calculations of molecular and electronic structures of neutral molecules and protonated forms of methionine and its derivatives
in the gaseous phase were carried out by the Hartree-Fock method using the 6–31G* basis set with full geometry optimization. Proton affinities of methionine (1), methionine sulfoxide (2), and methionine
sulfone (3) were calculated for different modes of coordination of the proton. The results of calculations demonstrated that
in protonated forms of 1 and 3, bonding between the proton and the N atom is most favorable, while in protonated form of 2,
bonding between the proton and the O atom of the SO group is most favorable. The proton affinities of the amino acids are
as follows: 223.2 (1), 241.2 (2), and 221.5 (3) kcal mol−1,i.e., methionine sulfoxide 2 exhibits the highest proton affinity in the series of the amino acids under consideration.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1487–1490, August, 1998. 相似文献
998.
Yong Lee 《Optical Review》1996,3(5):303-305
We show by computer simulation that a coupled-cavity-type multilayered structure is suitable for the transmissive compensation of group-velocity dispersion for optical pulses of subpicosecond length, and can thus be used to make a simple, compact, and transmissive dispersion-compensation device. 相似文献
999.
In this paper we further develop the theory of the extended Timoshenko beam model, as first introduced in Part I [5] of this
work, with particular emphasis on applications of the model in formation theory [11], [12]. We begin with formal development
of the equilibrium equations of static formation theory in the context of the extended Timoshenko model, giving a rigorous
discussion of existence, uniqueness, and regularity of weak solutions with appropriate assumptions on the coefficients. We
continue to obtain the fundamental duality relationship in the context of weak solutions and indicate its usefulness in investigations
of approximate formability. Optimal formation problems and corresponding necessary conditions for optimality are discussed.
We conclude with a discussion of a particular problem of joint optimization of controls and actuator densities in the context
of a prismatic extended Timoshenko beam and we present the results of some computational studies.
Accepted 14 November 1996 相似文献
1000.