Numerical study of unsteady flow and heat transfer of circular tangential direction jets flowing over the inner cylinder surface in the annular chamber

In order to understand the dynamics of vortices on heat transfer, the unsteady flow field of tangential direction jets flowing in the annular chamber is numerically investigated by scale-adaptive simulation (SAS). The jet Reynolds number is 332,000 based on the jet’s diameter and inflow velocity for a specific geometric model. The analogy theory is used to obtain the convective heat transfer coefficient distribution on the hub surface. Spectral analysis via fast Fourier transform (FFT) is used to analyze frequency information that flows inside the chamber. The proper orthogonal decomposition (POD) method is performed on the velocity field in the chamber and the convective heat transfer coefficient on the hub surface using a snapshot method. The fast Fourier transform helps find the dominant frequency of the unsteady flow in the chamber. The time sequence of velocity fields on the radial plane shows the presence of cyclic flapping of the jet. The proper orthogonal decomposition analysis indicates that the unsteady periodic flow phenomenon in the chamber and unsteady heat transfer on the hub surface are mainly related to the dynamics of the counter-rotating vortices caused by the jet.     

Steepest-descent method-based adaptive frequency domain equalizer in coherent optical orthogonal frequency division multiplexing with quadrature phase shift keying modulation

An adaptive frequency domain equalizer (A-FDE) in quadrature phase shift keying-coherent optical-orthogonal frequency division multiplexing (QPSK-CO-OFDM) system is proposed in this paper. A-FDE uses steepest descent method to search the optimal equalization parameters. And through applying the adaptive control factor (ACF) to monitor the state of A-FDE, the interference from phase noise (PN) and chromatic dispersion (CD) can be mitigated. The numerical simulation shows that the performance of A-FDE has a remarkable improvement on combating PN and CD comparing with the conventional decision-directed equalizer (DDE). And the A-FDE can achieve the forward-error-correction (FEC) threshold in noisier scenario. Furthermore, because the calculation of ACF only bases on valid data instead of pilot symbols (PSs), A-FDE has low PS overhead merit.     

Electrical properties of interdigitated partially bent like shaped liquid crystalline compound

This article represents the electrical studies of an interdigitated highly skewed N(4-n-pentyloxybenzylidene) 4-n-alkylaniline (5O.16) compound. Interestingly the compound is partially bent like and unsymmetrical in alkyl chain length. Dielectric and impedance spectroscopy studies indicate the coupling between the liquid crystal and the electrical field. Studies were carried out as a function of temperature as well as frequency. Semicircular nature of the Cole–Cole plots indicates the reorientation of the molecule with the applied field. Using the experimental data and the theoretically fitted results the effective equivalent model circuit was designed. Which used to explain the behavior of the compound under the external electric effect and the influence of the electrodes with different variable represent the resistor circuit. However, the effect of the conductivity of temperature and frequency are also reported.     

Orthogonal multiple click reactions in synthetic polymer chemistry

This review highlights the concept of multiple click reaction strategy which is utilized for design and synthesis of well‐defined complex macromolecular structures as well as multifunctionalization of well‐defined polymers. This review examines the click combinations mainly from double to quadruple and additionally from the most frequently used to the least. The present review may also be regarded as an update for recent reviews dealing with specifically double and triple click reaction combinations in synthetic polymer chemistry. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3147–3165     

A dual‐weighted trust‐region adaptive POD 4‐D Var applied to a finite‐volume shallow water equations model on the sphere

In this paper we study solutions of an inverse problem for a global shallow water model controlling its initial conditions specified from the 40‐yr ECMWF Re‐analysis (ERA‐40) data sets, in the presence of full or incomplete observations being assimilated in a time interval (window of assimilation) with or without background error covariance terms. As an extension of the work by Chen et al. (Int. J. Numer. Meth. Fluids 2009), we attempt to obtain a reduced order model of the above inverse problem, based on proper orthogonal decomposition (POD), referred to as POD 4D‐Var for a finite volume global shallow water equation model based on the Lin–Rood flux‐form semi‐Lagrangian semi‐implicit time integration scheme. Different approaches of POD implementation for the reduced inverse problem are compared, including a dual‐weighted method for snapshot selection coupled with a trust‐region POD adaptivity approach. Numerical results with various observational densities and background error covariance operator are also presented. The POD 4‐D Var model results combined with the trust‐region adaptivity exhibit similarity in terms of various error metrics to the full 4D Var results, but are obtained using a significantly lesser number of minimization iterations and require lesser CPU time. Based on our previous and current work, we conclude that POD 4‐D Var certainly warrants further studies, with promising potential of its extension to operational 3‐D numerical weather prediction models. Copyright © 2011 John Wiley & Sons, Ltd.     

Computer Assisted Spectrophotometric Analysis of Three Component Mixtures (Caffeine Mixtures and Codeine Mixtures)

Abstract

Two mixtures (caffeine mixture (I) and codeine mixture (II)) of 3-components, containing acetaminophen and salicylamide as majors, have been assayed using different computer-assisted spectrophotometric methods. These methods are the Unique Absorbance Method (UAM), the Unique Orthogonal Function Method (UOFM), and Unique Fourier Function Method (UFFM), and also their correspondences under the least squares approach. The parameters have been optimized for the accurate determination of the minor component caffeine in mixture (I). In mixture (II), however. codeine has been extracted - in two steps-prior to the correction of interferences from the major components acetaminophen and salicylamide.     

PBL节点初始平动刚度计算及设计参数优化

为研究钢桁腹混凝土组合箱梁中PBL(Perfobond Leiste)节点的初始平动刚度及其影响因素,首先基于组件法,运用卡氏第二定理推导出考虑了开孔钢板与混凝土间的界面剪切力和混凝土榫贡献的PBL节点的初始平动刚度表达式,其次以某工程实例为背景,结合有限元模型验证所推公式的合理性;在此基础上分析了混凝土强度、腹杆直径、腹杆壁厚、开孔钢板开孔孔径和开孔钢板厚度等构造参数对初始平动刚度的影响,并利用正交分析法对以上5个参数进行优化组合。研究结果表明,本文方法计算的PBL节点初始平动刚度结果与有限元计算结果间的误差在8.0%以内;相较运用解三角形计算腹杆平动位移的方法,采用卡氏第二定理不仅可以简化计算,还可以减小解三角形过程中因多次计算变形带来的误差累积;腹杆刚度对PBL节点整体平动刚度的贡献最大,可达到82.5%;保持原设中的混凝土强度不变,将腹杆直径增加20 mm,将钢腹杆壁厚增加4 mm,将开孔钢板开孔孔径增加4 mm,将开孔钢板厚度增加4 mm,可以将PBL节点理论初始平动刚度提高约25.7%。     

随机结构正交展开分析的Ritz动力聚缩法

针对随机结果正交展开理论计算上的弱点 ,本文在分析扩阶矩阵特性的基础上 ,于 Ritz模态向量子空间中对扩阶方程实现动力聚缩 ,大大提高了正交展开理论对实际工程问题的分析能力。分析实例表明 :即使结构参数具有很大变异性 (如δ =0 .4 )时 ,该算法依然能理想地与 Monte Carlo法模拟结果相吻合 ,计算时间则远远小于 Monte Carlo模拟法。同时 ,分析例证再一次强化了在结构动力分析中考虑结构参数随机性的必要性     

A Three‐Factor Product Construction for Mutually Orthogonal Latin Squares

It is well known that mutually orthogonal latin squares, or MOLS, admit a (Kronecker) product construction. We show that, under mild conditions, “triple products” of MOLS can result in a gain of one square. In terms of transversal designs, the technique is to use a construction of Rolf Rees twice: once to obtain a coarse resolution of the blocks after one product, and next to reorganize classes and resolve the blocks of the second product. As consequences, we report a few improvements to the MOLS table and obtain a slight strengthening of the famous theorem of MacNeish.     

Zero sets of bivariate Hermite polynomials

We establish various properties for the zero sets of three families of bivariate Hermite polynomials. Special emphasis is given to those bivariate orthogonal polynomials introduced by Hermite by means of a Rodrigues type formula related to a general positive definite quadratic form. For this family we prove that the zero set of the polynomial of total degree n+m$n+m$ consists of exactly n+m$n+m$ disjoint branches and possesses n+m$n+m$ asymptotes. A natural extension of the notion of interlacing is introduced and it is proved that the zero sets of the family under discussion obey this property. The results show that the properties of the zero sets, considered as affine algebraic curves in R²${\mathbb{R}}^2$, are completely different for the three families analyzed.