Non-linear viscoelastodynamic equations of three-dimensional rotating structures in finite displacement and finite element discretization

This paper deals with the non-linear viscoelastodynamics of three-dimensional rotating structure undergoing finite displacement. In addition, the non-linear dynamics is studied with respect to geometrical and mechanical perturbations. On part of the boundary of the structure, a rigid body displacement field is applied which moves the structure in a rotation motion. A time-dependent Dirichlet condition is applied to another part of the boundary. For instance, this corresponds to the cycle step of a helicopter rotor blade. A surface force field is applied to the third part of the boundary and depends on the time history of the structural displacement field. For example, this might corresponds to general unsteady aerodynamics forces applied to the structure. The objective of this paper is to model the non-linear dynamic behavior of such a rotating viscoelastic structure undergoing finite displacements, and to allow small geometrical and mechanical (mass, constitutive equations) perturbations analysis to be performed. The model is constructed by the introduction of a reference configuration which is deduced from the non-linear steady boundary value problem. A constitutive equation deduced from the Coleman and Noll theory concerning the viscoelasticity in finite displacement is used. Thereafter, the weak formulation of the boundary value problem is constructed and discretized using the finite element method. In order to simplify the mathematical study of the equations, multilinear forms are introduced in the algebraic calculation and their mathematical properties are presented.     

Gas chromatography-mass spectrometry and high-performance liquid chromatography-tandem mass spectrometry in quantifying fatty acids

This critical overview covers current analytical methods and future developments in quantitative determination of fatty acids (FAs), emphasizing sample extraction, derivatization and instrumental analysis with gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS²). We compare the benefits and the drawbacks of these two analytical techniques.We consider the well-established GC/MS method with pre-derivatization to be a traditional technique in terms of highly standardized sample-preparation procedures, affordability and readily available library searching for compound identification. However, the complicated derivatization steps required prior to instrumental analysis with GC/MS take a long time, with loss and transformation of FAs, low recovery and poor reproducibility.HPLC/MS² without derivatization shows the benefits of simple, mild sample-processing conditions, satisfactory recovery, short running time and high selectivity and sensitivity, which may allow it to become a viable alternative to GC/MS for the analysis of FAs in the years ahead.     

Desirability-based optimization and its sensitivity analysis for the perindopril and its impurities analysis in a microemulsion LC system

In the current paper the application of multiobjective optimization (MOOP) technique, via Derringer's desirability function, to a microemulsion liquid chromatographic (MELC) method is described. Chromatographic separation of perindopril tert-butylamine and its four impurities was selected as the case study. Central composite design (CCD) with fractional factorial design, ± 0.5 α star design and four replications in central point was applied for a response surface study, in order to examine in depth the effects of the most important factors. As factors that influence the system mostly (i) content of ethyl acetate and (ii) butyl acetate in composite internal phase, (iii) content of sodium dodecyl sulfate (surfactant) and (iv) n-butanol (co-surfactant), as well as (v) pH of the mobile phase were selected. Retention factor of (a) perindoprilat and (b) impurity Y 31 and (c) resolution factor for impurities Y 32 and 33 were chosen for simultaneous optimization. By adjustment of the importance coefficients and weights, according to defined objectives, the optimal mobile phase composition was predicted to be: 0.24% w/v butyl acetate, 0.3% w/v ethyl acetate, 2% w/v SDS, 7.75% w/v n-butanol and pH of the mobile phase 3.7. The sensitivity analysis of desirability function for these optimal conditions was conducted for the first time in LC separations, by applying a sensitivity procedure. The performed sensitivity analysis confirmed that the higher overall desirability does not necessarily mean a better solution. The accuracy of prediction might be affected if the optimal levels of input variables, achieved from several design points, end up with equal settings and different corresponding overall desirability. In our study this was not the issue, which confirmed the adequacy of predicted optimum.     

Determining Type II sensitivity ranges of the fractional assignment problem

This paper proposes iterative labeling algorithms to determine the Type II sensitivity ranges of the fractional assignment problem. Unlike the traditional sensitivity range which keeps the current optimal basis remaining optimal, the Type II sensitivity range is the range that keeps the current optimal assignment remaining optimal. Focusing only on the non-degenerate basic variables makes the Type II sensitivity range more practical. Three cases of perturbation, each with two kinds, are discussed. An example is presented to demonstrate the proposed algorithms.     

声表面波气体传感器研究进展*

基于声表面波技术的气体传感器包括采用敏感膜和结合气相色谱两种方式。比较而言,采用敏感膜的声表面波气体传感器体积小、功耗低,适应小型化毒气报警器的发展要求,但可检测的气体种类少、灵敏度低、存在交叉干扰问题;声表面波与气相色谱联用的气体分析仪灵敏度高、可检测气体种类多、很好地解决交叉干扰问题,特别适合于复杂大气背景条件下的气体成分分析。本文从传感器响应机理分析与物理功能结构两方面出发介绍了两类声表面波气体传感器的研究进展情况。     

Revisiting parametric multi-terminal problems: Maximum flows, minimum cuts and cut-tree computations

Given an undirected network, the multi-terminal network flows analysis consists in determining the all pairs maximum flow values. In this paper, we consider an undirected network in which some edge capacities are allowed to vary and we analyze the impact of such variations on the all pairs maximum flow values. We first provide an efficient algorithm for the single parametric capacity case, and then propose a generalization to the case of multiple parametric capacities. Moreover, we provide a study on Gomory–Hu cut-tree relationships.     

惠斯通电桥的灵敏度

讨论了电桥灵敏度S与桥臂的阻值以及检流计内阻Rg之间的关系，并且给出了在限定条件下S的极大值。     

形状优化设计敏度分析的参数法

本文对形状优化设计问题中的敏度分析,提出了一种解析算法,较好地解决了二维等参元的敏度分析计算问题。算例表明,方法是有效、可行的。     

Self-marking phase-stepping electronic speckle pattern interfometry (ESPI) for 3D displacement measurement on cathode ray tube (CRT)-panels

This study demonstrates the feasibility of applying phase-shifting electronic speckle pattern interfometry to measure the deformation field of the front panel of a cathode ray tube, to support analysis to enhance the implosion-resistance capacity under violent collapse. Two effects, the air exhaustion and shrink band constraint effects, are comprehensively investigated. The angle of an adjustable mirror is switched, to provide three sensitivity vectors that are required in 3D-displacement measurement. A Fourier filtration is employed to remove speckle noise and establish a noise-free phase map. Inconsistent points are identified and masked to prevent any possible divergence during phase unwrapping. The results show that the accuracy of this method is satisfactory.     

一维大气边界层光学折射率结构常数数值模式的敏感性分析

 提出了一种大气光学折射率结构常数的数值模式。通过敏感性分析发现，对折射率结构常数有显著影响的参数是：一年中的不同日期、土壤的热容量和含水量、雪地和水面上、云量等，风速大小几乎对折射率结构常数没有什么影响。