Navier–Stokes computation of transonic vortices over a round leading edge delta wing

A 3D Navier–Stokes solver has been developed to simulate laminar compressible flow over quadrilateral wings. The finite volume technique is employed for spatial discretization with a novel variant for the viscous fluxes. An explicit three-stage Runge–Kutta scheme is used for time integration, taking local time steps according to the linear stability condition derived for application to the Navier–Stokes equations. The code is applied to compute primary and secondary separation vortices at transonic speeds over a 65° swept delta wing with round leading edges and cropped tips. The results are compared with experimental data and Euler solutions, and Reynolds number effects are investigated.     

Microstructures and Optical Properties of Scales of Butterfly Wings

This paper describes the mechanism generating the beautiful wing colors of various male butterflies and the relationship between the wing material and the color appearance. The microstructure of the scales covering the upper surface of the wings was analyzed with the aid of a scanning electron microscope. The basic mechanism of color generation of structurally colored scales is determined for the first time in accordance with the theory of optical interference in thin film layers using a model of wing scales. Optical properties were found in relation to the three-dimensional spectral reflectance of the samples, and differences were observed between the brightness perceived in subjective evaluations and calculated values based on the reflective spectra of the structurally colored wings. The results of this study suggest that the microroughness of the upper wing surface may influence the perceived gloss of structurally colored wings.     

An analysis of coating-efficiency as a measure for capillary column performance

Summary An expression is proposed for the value of the Coating-Efficiency C. E. starting from the Golay-equation, extended to situations of appreciable pressure drop by Giddings. A comparison is made between the coating-efficiency following this theory and the simplified expression for coating-efficiency as generally used in the literature, that neglects the effects of resistance to mass transfer in the liquid phase and the pressure drop. It is shown that the complete equation from the coating-efficiency explains the observations made in practice. Application of the theory described will lead to a better check on film formation in capillary columns.     

基于改进排序遗传算法的径向基函数神经网络色谱峰解析

构造了以塔板模型为基函数的径向函数神经网络（P－RBFNN），为了使P－RBFNN具有结构重组能力，又在网络学习算法中引入鲁棒（Rubust)和随机全局最优的两阶段排序遗传算法：结构学习和进化。P－RBFNN结合改进的排序遗传算法很适合组分数未知的色谱（含重叠）峰解析。     

The determination of the plate count for large molecules under reversed-phase gradient conditions

The true performance of HPLC columns in the gradient separation of macromolecules can be assessed by measuring the true plate count, if we know the retention factor of the analyte at the point of elution. We are demonstrating in this short communication how this can accomplished in a straightforward fashion. The procedure used here is a significant simplification over previous approaches, and enables the chromatographer to do so without complex algebra or additional experiments.     

ARGO-YBJ detector simulation using GEANT4

'G4argo', a GEANT4-based simulation package for the ARGO-YBJ detector, is described in this paper. G4argo incorporates in the simulation the true RPC time resolution and another 0.5 ns time uncertainty which is introduced from the offline calibration of TDC. In addition, the correct RPC geometry and the true materials for the ARGO-YBJ experimental hall are implemented. As a result, G4argo simulation shows a very good agreement with real data.     

结构参数对串联微环谐振腔编解码器性能的影响

光码分多址系统中, 光编解码器是影响系统性能的关键因素之一.自相关峰值旁瓣比(P/W)、自互相关峰值比(P/C)是衡量编解码器性能的两个重要指标.以硅基SOI微环谐振腔为载体, 提出了一种串联三环阵列的二维相干OCDMA编解码器模型.详细研究了耦合系数、损耗系数、阵列间距以及通道间隔对微环谐振腔编解码器性能的影响.结果表明, 半径为50 μm的微环, 环与直波导间耦合系数在0.6–0.7之间, 环与环间耦合系数在0.1–0.2之间, 损耗系数 < 2 dB/cm, 阵列间距大于3 mm, 通道间隔在25–36 GHz间时, 编解码器能够获得良好的性能.     

Parameter extension for combined hybrid finite element methods and application to plate bending problems

Based on a weighted average of the modified Hellinger-Reissner principle and its dual, the combined hybrid finite element (CHFE) method was originally proposed with a combination parameter limited in the interval (0, 1). In actual computation this parameter plays an important role in adjusting the energy error of discretization models. In this paper, a novel expression of the combined hybrid variational form is used to show the relationship between the resultant method and some Galerkin/least-squares stabilized finite scheme for plate bending problems. The choice of combination parameter is then extended to (−∞, 0) ? (0, 1). Existence, uniqueness and convergence of the solution of discrete schemes are proved, and the advantage of the parameter extension in computation is discussed. As an application, improvement of Adini’s rectangular element by the CHFE approach is performed.     

CFD analysis of an oscillating wing at various reduced frequencies

The effect of various reduced frequencies has been examined for an oscillating aspect ratio 10 NACA 0015 wing. An unsteady, compressible three‐dimensional (3D) Navier–Stokes code based on Beam and Warming algorithm with the Baldwin–Lomax turbulence model has been used. The code is validated for the study against published experimental data. The 3D unsteady flow field is simulated for reduced frequency values of 0.1, 0.2 and 0.3 for a fixed mean angle of attack position and fixed amplitude. The type of motion is sinusoidal harmonic. The force coefficients, pressure distributions and flow visualization show that at the given conditions the flow remains attached to the wing surface even at high angles of attack with no clear separation or typical light‐to‐deep category of dynamic stall. Increased magnitude of hysteresis and higher gradients are seen at higher reduced frequencies. The 3D effects are even found at midspan locations. In addition, the rate of decrease in lift near the wing tips compared with the wing root is not much like in the static cases. Copyright © 2008 John Wiley & Sons, Ltd.     

Multi-mode parametric excitation of a simply supported plate under time-varying and non-uniform edge loading

In this study, multi-mode parametric excitation of a simply supported plate under time-varying and non-uniform edge loading is modeled and the solution is found. Equations for multi-mode parametric excitation of a simply supported plate are derived using stress distributions within the plate as well as on the edges, considering both the effects of non-uniform edge loading and the non-linearity caused by the large deflection. The multi-mode equations are coupled by first-order linear terms, even in the case of simply supported boundary conditions, due to the non-uniform edge loading. The perturbation solutions of two-mode parametric excitation are examined by the method of multiple scales. For the edge loading, which consists of a uniform term as well as a non-uniform one, equations could be coupled or de-coupled by parametric excitation terms, and the numbers and values of the resonance frequencies of the parametric excitations could also differ, depending on whether the non-uniform term of the edge loading is time-varying or not. In addition to the resonant frequencies of the case when only the uniform term of the edge loading is time-varying, there are additional combination resonances at the vicinity of the sum of two natural frequencies of each mode when the non-uniform term of the non-uniform edge loading is time-varying.