Direct determination of the number-weighted mean radius and polydispersity from dynamic light-scattering data

We compare results for the number-weighted mean radius and polydispersity obtained either by directly fitting number distributions to dynamic light-scattering data or by converting results obtained by fitting intensity-weighted distributions. We find that results from fits using number distributions are angle independent and that converting intensity-weighted distributions is not always reliable, especially when the polydispersity of the sample is large. We compare the results of fitting symmetric and asymmetric distributions, as represented by Gaussian and Schulz distributions, respectively, to data for extruded vesicles and find that the Schulz distribution provides a better estimate of the size distribution for these samples.     

Isoconversion method for kinetic analysis of solid-state reactions from dynamic thermoanalytical data

The activation energy for a heterogeneous reaction involving a solid may be obtained from a plot of ₀ ln(d/dt) d against ₀(1/T) d, where represents the fractional conversion of the solid reactant, and T(t) is the (time-dependent) reactant temperature. This new approach to the analysis of dynamic thermoanalytical kinetic data has distinct advantages over existing methods, as it needs to make no assumption about the kinetic model, involves no approximation to the temperature integral, and is easy to implement on the computer.     

一种机械系统动力学响应分析方法

 为了动力学响应分析的通用性及简便性,提出一种新的动力学响应分析方法.将机械系统分解成有序单开链单元,按其正序首先在约束度小于0的单元进行虚拟赋值,然后在其他单元依次进行运动分析,最后可得到维数最低的运动学方程.基于虚功原理导出动力学响应方程通式,对广义速度与广义加速度特殊赋值后通过序单开链法可求出响应方程的各系数,从而确定动力学响应方程.该动力学响应方程的维数等于机械系统自由度,形式简洁,便于求解,平面三自由度并联机构的实例表明了该方法的有效性.     

动态载荷识别位置优化的传递函数相干法

利用多自由度动力学原理对频域载荷识别方法进行分析,对传递函数病态性进行了研究,分析了动态载荷识别方法中响应点位置对传递函数病态性及载荷识别结果的影响.为降低载荷识别误差特别是结构共振频率下的识别误差,基于传递函数的相干分析定义了传递函数相干因子,并提出以最小传递函数相干因子为目标的动态载荷识别位置优化的传递函数相干法....     

Entropy-based method for COP data analysis

Entropy-based data analysis methods have been applied to many science or engineering fields. The centre of pressure (COP) data are often dynamic, non-linear and non-stationary in nature. It is thought that it may be used to analyse COP data, which is often used for evaluating postural stability in ergonomics research. Multi-scale entropy (MSE) and empirical mode decomposition are introduced first; then, three examples are presented to demonstrate the initial applications of the proposed methods, young and elderly subjects: (1) standing with attention; (2) standing with eyes open/closed; and (3) wearing vibratory shoes. The MSE analysis results are compared with traditional COP stabilogram metrics. Based on these applications, MSE can be an effective metric for COP data analysis and other ergonomics research. The cautions of using MSE, including the non-specificity nature and individual baseline variation, are also discussed. There is a good potential for using MSE in ergonomics-related research, especially for ageing ergonomics.     

State space analysis of stochastic response cumulants

The technique of linear state space analysis is extended to allow computation of response cumulants of any order. In particular, equations are derived which govern the evolution of the cumulants for the response of a linear system excited by a delta correlated process, which generally causes nonnormal response. The technique also applies if the excitation can be viewed as the output of a linear filter with a delta correlated input. When applied to find second cumulants (i.e., covariances), the method gives the usual Lyapunov matrix equation. The method is illustrated by formulation of the state space equations for the third-order cumulants of the response of an SDF oscillator.     

Inversion of low-angle elastic light-scattering data with a new method devised by modification of the Chahine algorithm

A new inversion method, devised by modification of the nonlinear iterative method originally proposed by Chahine [J. Opt. Soc. Am. 58, 1634 (1968)] is applied to the inversion of low-angle elastic light-scattering data. The algorithm was tested by computer simulations carried out within the wave-vector range 2.5 x 10(2) -2.5 x 10(4) cm(-1). The particle-size distributions were recovered in the 0.70-77-mum range of radii. Compared with the original method of Chahine, this algorithm is much more stable and reliable with respect to random noise, improves the overall reliability of the fitting, and allows both number and weight particle-size distributions to be retrieved accurately. When the performances of the method are investigated with respect to the noise, the results of the simulations show that the particle-size distributions can be recovered accurately up to noise levels of several rms percent.     

挂架载荷的动态标定及其数据处理方法研究

研究武器系统挂架载荷的动态标定及其数据处理方法,为挂架载荷力值的测量提供标定模型。采用对挂架上一特征点施加标准的脉冲和阶跃激励,测量应变片对激励的响应输出,通过非参数拟合,获得标定样本数据库,根据最近邻域法确定未知受力值。结果表明,基于非参数拟合的标定方法,可较好地解决复杂环境下应变片输出的噪声干扰,从而提高测量数据的稳健性。     

The analysis of the Generalized-α method for non-linear dynamic problems

 This paper presents the consistency and stability analyses of the Generalized-α methods applied to non-linear dynamical systems. The second-order accuracy of this class of algorithms is proved also in the non-linear regime, independently of the quadrature rule for non-linear internal forces. Conversely, the G-stability notion which is suitable for linear multistep schemes devoted to non-linear dynamic problems cannot be applied, as the non-linear structural dynamics equations are not contractive. Nonetheless, it is proved that the Generalized-α methods are endowed with stability in an energy sense and guarantee energy decay in the high-frequency range as well as asymptotic annihilation. However, overshoot and heavy energy oscillations in the intermediate-frequency range are exhibited. The results of representative numerical simulations performed on relatively simple single- and multiple-degrees-of-freedom non-linear systems are presented in order to confirm the analytical estimates. Received 1 April 2001     

Superelement method for transient dynamic analysis of structural systems

A superelement algorithm for the transient dynamic analysis of structural systems is presented. The method represents a generalization of existing static and dynamic superelement (substructure) algorithms. Natural frequencies and modal shapes of a fixed boundary substructure are used to obtain equations of motion of a superelement. An implicit time-stepping algorithm is presented for the numerical solution of a resulting superelement system of equations of motion. Numerical examples are given to illustrate the presented approach. The method is believed to be effective for large-scale problems of structural analysis.     

A simple method for dynamic scientometrics using lexical analysis

Techniques for studying problematic networks in science and technology are principally derived either from citation analyses or from lexical methods. The former have been the object of many developments and improvements. A considerable range of applications exists within the practical constraint of their being limited to fields covered by the ISI databases. For the latter, the co-word method has a register of applications that up until now have been more specialized in the sociology of science as it is done, but it has in principle no field limitations. An important question is whether we can extend the application range of this analytical method to take in longer periods, and in particular to deal with historiography either on a large scale (at the level of a research field) or on a small scale (at the level of a process of discovery or invention). Here we propose a way of rendering lexical methods dynamic, more particularly through developing a rudimentary but precise technique to aid historiographical analysis. This method ofcritical variations is illustrated in a working example.     

Resonance light-scattering method for the determination of labetalol using uranyl acetate and aniline blue

A sensitive and convenient method for determining labetalol has been developed based on resonance light-scattering using ternary complex of aniline blue (AB), uranyl ion (UO₂²⁺) and labetalol. At pH 6.0–7.0, labetalol reacted with AB and UO₂²⁺ to form an ion-association complex that resulted in considerable resonance light-scattering (RLS) characterized with a peak at 356 nm. The RLS was successfully applied to the determination of labetalol. The intensity of RLS (I_RLS) at 356 nm linearly depended on the concentration of labetalol ranging from 4.0 × 10^? 7 to 2.4 × 10^? 4 mol L^? 1. The lower detection limit was 2.1 × 10^? 7 mol L^? 1. The present method is highly selective to labetalol and can successfully be applied to the determination of labetalol in human urine.     

Robust design for multiple dynamic quality characteristics using data envelopment analysis

The Taguchi method is extensively adopted in various industries to continuously improve product design in response to customer requirements. The dynamic system of the Taguchi method is frequently implemented to design products with flexible applications. However, Taguchi's dynamic system can be employed only for individual quality characteristic, and the relationship between the quality characteristic and the signal factor is assumed to be linear. Because of these restrictions, Taguchi's dynamic system is ineffective for multiple quality characteristics or when the quality characteristic has a nonlinear relationship with the signal factor. This study describes a novel procedure for optimizing a dynamic system based on data envelopment analysis. The proposed procedure overcomes the limitations of Taguchi's dynamic system. Two cases are analyzed to demonstrate the effectiveness of the proposed procedure. The results show that the proposed procedure can enhance multiple dynamic quality characteristics. Copyright © 2008 John Wiley & Sons, Ltd.     

Particle sizing in strongly turbid suspensions with the one-beam cross-correlation dynamic light-scattering technique

The utility of the one-beam cross-correlation dynamic light-scattering system for sizing small particles in suspension was previously limited by its small-intensity signal-to-baseline ratio for strongly turbid suspensions. We describe three improvements in the optical system and sample cell that raise the ratio to a value comparable with that of other cross-correlation dynamic light-scattering systems. These improvements are (i) using a square cross-sectional sample cell to minimize the attenuation of the incident beam and singly scattered light, (ii) placing a 200-microm-wide slit between the sample cell and the detector fibers to mask off the region of weak single scattering and strong multiple scattering from the detectors' field of view, and (iii) aligning the center of the detectors' field of view with the region of strongest single scattering. We analyze a number of suspensions of polystyrene latex spheres with a diameter between 65 and 562 nm in water using this improved one-beam instrument and find that the measured radius is determined in a 2-min data collection time to better than +/-10% for volume fractions of the suspended polystyrene latex spheres up to a few percent.     

红外耳温计分度方法及数据分析

研制了一种专门用于红外耳温计分度的双孔黑体空腔,并用研制的黑体空腔对红外耳温计在37℃和41℃进行了分度实验.实验结果表明,此黑体空腔的空腔发射率已达到0.999,完全能作为红外耳温计分度的标准辐射源.最后对实验结果进行了不确定度的评定.     

A recursive method for the dynamic analysis of mechanical systems in spatial motion

Summary. In the present study, a recursive method for generating the equations of motion of mechanical systems that undergo spatial motion is presented. The method uses the force and moment equations to generate the rigid body equations of motion in terms of the Cartesian coordinates of a dynamically equivalent constrained system of particles, without introducing any rotational coordinates and the corresponding rotation matrices. For the open loop case, the equations of motion are generated recursively along the serial chains. Closed loop systems are transformed to open loop systems by cutting suitable kinematic joints and introducing cut-joint constraints. The method is simple and suitable for computer implementation. An example is chosen to demonstrate the generality and simplicity of the developed formulation.     

区间随机桁架结构动力特性分析方法研究

摘 要：针对区间随机桁架结构的动力特性分析,提出了一种区间随机有限元方法。当结构的物理参数和几何尺寸同时具有区间随机性时,利用区间因子法和随机因子法建立了结构的刚度矩阵和质量矩阵;从结构振动的瑞利商表达式出发,利用区间运算推导了结构动力特性区间随机变量的计算式;进而利用随机变量的矩法和代数综合法,推导出了结构特征值的数字特征的计算式。最后通过算例分析了区间随机桁架结构参数的区间随机性对其动力特性的影响,计算结果表明该方法是可行和有效的。
     

A new array decomposition method for multiway data analysis

In chemometrics, two-way singular value decomposition (SVD), CANDECOMP-PARAFAC decomposition (PARAFAC), and Tucker decomposition (TUKER) are three main array decomposition methods. There are disadvantages with the three methods. If multiway data are indeed multilinear, PARAFAC and TUCKER can provide more robust and interpretable models compared to two-way SVD. However, PARAFAC is sometimes numerically unstable, and TUCKER cannot guarantee the uniqueness of an approximate solution. This paper proposes a new array decomposition model with multiple bilinear structure. Then, utilizing this model, a new method, called multiple bilinear decomposition (MBD), is proposed as a generalization of two-way SVD. An algorithm is established to successively decompose an array without a full decomposition, which is not based on alternating least squares. Theoretically, the proposed method has an advantage over PARAFAC and TUCKER in its three important properties, including orthonormality of loading vectors, closed-form decomposition, and successive decomposition of variation. The simulation results based on orthogonal PARAFAC models show that the proposed method outperforms PARAFAC with respect to accuracy and robustness of loading estimate and data-fitting of model, even though the former does not use the priori information of multilinear structure. And, especially in the simulation under no noise, the equivalence of loading estimates indicates that as a successive decomposition, MBD is a superior alternative to PARAFAC.     

Local estimation of directional emissivity of light-scattering volumes using the Monte-Carlo method

A method is described for the calculation of directional emissivity of volumes of arbitrary geometry filled with radiating, absorbing, and scattering medium. The high efficiency of Monte-Carlo simulation method based on local sampling algorithm is demonstrated. The problem of test solutions is discussed, which are used for estimating the Monte-Carlo simulation algorithms. Results are given of calculation of spectral directional emissivity of model jet of a solid-propellant engine.     

动力模型拟静力修正方法及误差分析

摘 要：为了降低动力模型修正过程中的计算复杂程度,提出了拟静力模型修正方法。借助特征载荷的概念,将基于动力测量信息的动力模型转化为静力模型进行修正,避免了模型修正过程中特征值和特征向量的计算。利用样条插值方法,解决了测量信息与计算信息间的匹配问题。采用复域灵敏度分析方法对修正过程中的参数灵敏度进行计算,提高了修正过程中的计算效率。研究了测量误差对修正结果的影响,给出了修正参数的统计特性,为评估修正结果的可靠性提供了基础。通过数值算例对提出的方法进行了验证,结果表明本文的方法是有效可靠的。利用建立的方法对润扬大桥北汊斜拉桥桥塔模型进行了修正,修正结果较为精确可靠。