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111.
与传统的优化方法相比,遗传算法以其极强的鲁棒性、随机搜索特性以及优化结果的全局性等特点而在工程优化中得到越来越广泛的应用.标准遗传算法中使用的二进制编码类似于生物染色体的组成,使算法易于用生物遗传学理论加以解释,同时也使交叉、变异等遗传操作易于实现.此外,使用二进制编码还有助于充分发挥算法隐含的并行性.本文对传统遗传算法加以改进,在二进制编码下引入分段进化的概念,再配以高效的交叉、变异算子,充分发挥二进制编码固有优势的同时在很大程度上提高了算法的优化效率,并与Euler方程数值解法相结合,对机翼外形进行了气动优化设计.优化后机翼的升阻比有了显著提高,表明建立的优化模型是合理有效的. 相似文献
112.
为提高带外挂物大展弦比直机翼的颤振速度,基于假设模态法提出一种带集中质量弯扭组合梁模态分析手段,结合片条理论考察外挂物不同质量及布置形式对机翼颤振特性的影响。首先,基于弯扭组合梁建立带外挂物大展弦比直机翼的结构动力学模型,并利用假设模态法得到其弯曲和扭转模态。其次,引入片条理论近似计算有限翼展升力面的气动力,调整外挂物的质量、数目及其在机翼展向和弦向的相对位置,得到外挂物对机翼颤振特性的影响规律。最后,利用在机翼前缘附近悬吊小质量外挂物可提高机翼颤振速度的优势,探究颤振速度恢复方法并提出颤振速度恢复的优化问题,使得携带外挂物的机翼与不携带外挂物的机翼颤振速度基本相同。研究结果表明,外挂物的不同悬挂方式可引起机翼颤振模态的跳转,在以俯仰为颤振主模态的机翼上可调整外挂物位置以恢复原机翼的颤振速度。 相似文献
113.
Abstarct The Cp)2Ni2Fe(CO)3(µ3-C2H2) and Cp)2Ni2Fe(CO)3(µ3-C2H2) (B) complexes have been synthesized and spectroscopically characterized. An accurate X-ray study and a comparison with related structures shows that the substituents of the alkyne ligands exert considerable effects on the bonding parameters.Crystal data for complex A, monoclinic space group P21/n,a = 8.418(1),b = 15.779(2),c = 14,493(1) Å, = 91.64(1)°,Z = 4, 2753 observed reflections,R = 0.022; crystal data for complex B, monoclinic space group C2/c,a = 16.2189(7),b = 7.445(3),c = 25.745(5) Å, = 103.74(3),Z=8, 1853 observed reflections,R = 0.051. 相似文献
114.
A class of Baire spaces, which contains many known examples and variations thereof, is described and it is shown that no space in this class contains a dense metrizable Gδ-subspace. This gives a class of semi-metrizable spaces which are not σ-spaces. We discuss the existence of Lindelöf semi-metrizable spaces which are not σ-spaces. This is of interest since the only known examples require the use of CH. 相似文献
115.
High Altitude, Long Endurance (HALE) aircraft can achieve sustained, uninterrupted flight time if they use solar power. Wing morphing of solar powered HALE aircraft can significantly increase solar energy absorbency. An example of the kind of morphing considered in this paper requires the wings to fold so as to orient a solar panel to be hit more directly by the sun's rays at specific times of the day. An example of the kind of morphing considered in this paper requires the wings to fold so as to orient a solar panel that increases the absorption of solar energy by decreasing the angle of incidence of the solar radiation at specific times of the day. In this paper solar powered HALE flying wing aircraft are modeled with three beams with lockable hinge connections. Such aircraft are shown to be capable of morphing passively, following the sun by means of aerodynamic forces and engine thrusts. The analysis underlying NATASHA (Nonlinear Aeroelastic Trim And Stability of HALE Aircraft), a computer program that is based on geometrically exact, fully intrinsic beam equations and a finite-state induced flow model, was extended to include the ability to simulate morphing of the aircraft into a “Z” configuration. Because of the “long endurance” feature of HALE aircraft, such morphing needs to be done without relying on actuators and at as near zero energy cost as possible. The emphasis of this study is to substantially demonstrate the processes required to passively morph a flying wing into a Z-shaped configuration and back again. 相似文献
116.
R. Hartmann 《国际流体数值方法杂志》2013,72(8):883-894
Discontinuous Galerkin (DG) methods allow high‐order flow solutions on unstructured or locally refined meshes by increasing the polynomial degree and using curved instead of straight‐sided elements. DG discretizations with higher polynomial degrees must, however, be stabilized in the vicinity of discontinuities of flow solutions such as shocks. In this article, we device a consistent shock‐capturing method for the Reynolds‐averaged Navier–Stokes and k‐ ω turbulence model equations based on an artificial viscosity term that depends on element residual terms. Furthermore, the DG method is combined with a residual‐based adaptation algorithm that targets at resolving all flow features. The higher‐order and adaptive DG method is applied to a fully turbulent transonic flow around the second Vortex Flow Experiment (VFE‐2) configuration with a good resolution of the vortex system.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
117.
The static rolling aerodynamics of a finned slender body is numerically studied in this paper.Simulation results show a nonlinear uprising of the rolling moment when the angle of attack is greater than 20°in subsonic flows.Asymmetric vortex break down phenomenon on the"horizontal"rudders is found to be responsible for this phenomenon.By introducing the geometric-equivalent angle of attack and geometric-equivalent sweep angle,the cause of the nonlinear rolling moment characteristics can be explained by the delta wing vortex breakdown analysis. 相似文献
118.
119.
Let be the additive group of 1×n row vectors over . For an n×n matrix T over and , the affine transformation FT,ω of sends x to xT+ω. Let α be the cyclic group generated by a vector . The affine transformation coset pseudo-digraph has the set of cosets of α in as vertices and there are c arcs from x+α to y+α if and only if the number of zx+α such that FT,ω(z)y+α is c. We prove that the following statements are equivalent: (a) is isomorphic to the d-nary (n−1)-dimensional De Bruijn digraph; (b) α is a cyclic vector for T; (c) is primitive. This strengthens a result conjectured by C.M. Fiduccia and E.M. Jacobson [Universal multistage networks via linear permutations, in: Proceedings of the 1991 ACM/IEEE Conference on Supercomputing, ACM Press, New York, 1991, pp. 380–389]. Under the further assumption that T is invertible we show that each component of is a conjunction of a cycle and a De Bruijn digraph, namely a generalized wrapped butterfly. Finally, we discuss the affine TCP digraph representations for a class of digraphs introduced by D. Coudert, A. Ferreira and S. Perennes [Isomorphisms of the De Bruijn digraph and free-space optical networks, Networks 40 (2002) 155–164]. 相似文献
120.
The dynamic aspects along the normal vibrational motions of the lowest frequencies in the oxidized, radical, and reduced
states of flavin (isoalloxazine) have been studied. In comparison with the twist motions in the oxidized state, the butterfly
motions in the radical and reduced states turned out to bring more significant variations to the frontier molecular orbital
energies and to the charge distributions on the atoms of the pyrazine ring in isoalloxazine. It can be considered that the
electron transfers from and to the isoalloxazine ring can be adjusted or controlled by these variations. In the reduced states
the electron release from the molecule, and in the radical states the electron release from or acceptance by the molecule,
could be impelled by the butterfly motions, while in the oxidized state the electron acceptance by the molecule could be accelerated
slightly by the twist motion.
Received: 30 September 1998 / Accepted: 20 January 1999 / Published online: 7 June 1999 相似文献