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991.
992.
In studying the multiple scattering of acoustic waves by a half-space of distributed discrete scatterers, the quasicrystalline approximation(QCA) approach together with the hole correction (HC) or the pair distribution functions (PDF) have been used extensively, in which a system of simultaneous equations must be solved to determine the effective propagation constant and the expansion coefficients of the coherent exciting field. In this paper, we analyse the same problem under Foldy's approximation (EFA) by using the so-called modified T-matrix approach (MTMA) which was first proposed by Twersky. Two equations in a considerably simple and clear form are obtained for determining the effective propagation constant and the amplitude of the coherent transmitted field, as the scatterers are identical spheres. The numerical results in the low-frequency limit are also discussed in brief. 相似文献
993.
The study of focused ion beam (FIB) milling for making etched facet and semiconductor/air distributed Bragg reflector (DBR) facets of AlGaInP-based red laser diodes (LD) is presented in this letter. For the Ga ion beam current of 100 pA at fixed accelerated voltage 30 kV, FIB milling rate of GaAs was found to be 0.46 μm3/nC. As a trade-off between high reflectivity and enough technical tolerance, the combination of third Bragg orders of semiconductor wall and air gap was chosen. The deeply etched mirror and distributed Bragg reflector facet consisting of pairs of semiconductor wall/air gap on laser diodes (LD) cavity facets with vertical sidewall on AlGaInP LDs were fabricated by focused Ga ion beam milling. Comparison of the AlGaInP LD with the mirrors between cleaved and FIB made facet was given and discussed. 相似文献
994.
René Schoof 《Mathematische Annalen》2003,325(3):413-448
For every conductor f{1,3,4,5,7,8,9,11,12,15} there exist non-zero abelian varieties over the cyclotomic field Q(ζ
f
) with good reduction everywhere. Suitable isogeny factors of the Jacobian variety of the modular curve X
1
(f) are examples of such abelian varieties. In the other direction we show that for all f in the above set there do not exist any non-zero abelian varieties over Q(ζ
f
) with good reduction everywhere except possibly when f=11 or 15. Assuming the Generalized Riemann Hypothesis (GRH) we prove the same result when f=11 and 15.
Received: 19 April 2001 / Revised version: 21 October 2001 / Published online: 10 February 2003 相似文献
995.
Hu Lanying Ren Yong 《Annals of Differential Equations》2007,23(4):416-421
In this paper,we derive the continuous dependence on the terminal condition of solutions to nonlinear reflected backward stochastic differential equations involving the subdifferential operator of a lower semi-continuous,proper and convex function under non-Lipschitz condition by means of the corollary of Bihari inequality. 相似文献
996.
本文介绍了利用超声振动能量制取超细金属粉末的超声雾化方法,提出了超声制粉雾化室,等离子枪,阴极、阳极喷咀及换能器振动系统的最佳尺寸和工作参数,给出了实验结果及制得的粉末显微结构照片.实验结果表明,用本文所述方法制得的金属粉末组成为:-80目粉占84呢,-120目粉占63.7啪,而用PREP方法制得的粉末分别占19.5%和11.7%,由此看来,用本方法制取超细金属粉,在粒度组成方面优于PREP方法.文中还对粉末冷却速度做了估算,得到了粉末平均冷却速度大于1×10_5k/5 相似文献
997.
Wing-Sum Cheung Jingli Ren Patricia J.Y. Wong Dandan Zhao 《Journal of Mathematical Analysis and Applications》2007,330(2):900-915
In this paper, we investigate a second-order nonlinear difference equation with sign-changing nonlinearity subject to two different sets of nonlocal boundary conditions. The explicit expressions of the associated Green's functions are presented. By using a recently developed fixed point theorem, we establish sufficient conditions for the existence of multiple positive solutions of the boundary value problem. 相似文献
998.
It has been proved that if a rectangle is dissected into three congruent pieces,then those pieces must themselves be rectangles. In the present paper this result is generalized to the case of parallelogram. 相似文献
999.
Qing-Quan Jiang Wei Ren Jian Tang Xiao-Feng Liu 《International Journal of Theoretical Physics》2007,46(6):1449-1454
Applying the semi-classical quantum tunneling model, we have studied the Hawking radiation via tunneling from a cylindrically
symmetric black hole. The derived results show that the tunneling rate of at the event horizon of the black hole is related
to Bekenstein–Hawking entropy and the factual radiation spectrum is not strictly pure thermal, but is consistent with the
underlying unitary theory.
PACS numbers: 04.20.-s, 97.60.Lf. 相似文献
1000.