Modified nodal analysis and the incorporation of multiphase, coupled networks

As a note to an original presentation ("Modified nodal analysis: an essential addition to electrical circuit theory and analysis", see ibid., vol.11, no.3, p.84-92, 2002), this paper adds a further, final comment on the efficacy of modified nodal analysis (MNA) in handling multi-phase, coupled impedance networks typical of which are multi-conductor transmission lines and cables in which the electrical length is short so that the network elements are discrete lumped impedances.     

Electromechanical analysis of an asymmetric piezoelectric/elastic laminate structure: theory and experiment

The electromechanical characteristics of an asymmetric piezoelectric/elastic laminated actuator are investigated by electroelasticity and experiments. The axial expansion-bending coupled motion of the system is separated into quasi-axial expansion and quasi-bending by its physical significance of vibration modes. General formulation of calculations for the mechanical, electrical, and electromechanical characteristics of the structure are presented via parametric analysis. Finally, the displacement sensitivity and the frequency response of displacement and electrical current are experimentally measured for this piezoelectric/elastic laminated specimen. Close agreement between theoretical and experimental results confirms the validity of the theory.     

Effects of fluoropolymer addition to an epoxy on scratch depth and recovery

Samples were prepared by addition of a fluorinated poly(aryl ether ketone) (12F-PEK) to a commercial epoxy resin and curing at either 24 °C or 70 °C. The concentrations of fluoropolymer in the samples were 0, 5, 10, 20, 30, 40, and 50%. Phase inversion facilitates the formation of more and more smooth surfaces for scratch testing with increasing fluoropolymer concentration. A progressively increasing load from 0.03 N to 12 N was administered with a diamond tip to the surfaces of the samples; depths were determined within ±7.5 nm. The original scratch depth is a function of the fluoropolymer concentration. Scratch recovery (healing) reaches values up to 95%. Plots of the residual depth versus concentration of the fluoropolymer at 4, 6, 8, and 10 N reveal minima for all forces and both temperatures. Addition of only 5% or 10% 12F-PEK improves the scratch recovery significantly. The results are explained by changes of material morphology with the fluoropolymer concentration. Electronic Publication     

Local bifurcation and instability theory applied to formability analysis

The design and optimization of both sheet metal formed parts and processes are nowadays carried out virtually making use of numerical tools by finite element analysis. Such virtual try-out approach contributes with significant savings in terms of money, time and effort in the design, production and process set-up of deep drawn parts. The analysis of either forming success operation or surface defects, in each of the development phases, is generally performed by means of the material’s forming limit diagram (FLD), since it allows to define a safe region that reduces the probability of: (i) necking; (ii) wrinkling and (iii) large deformation occurrence. However, the FLD represented in the strain space is known to present some disadvantages. To overcome this problem, Ito and Goya proposed a local bifurcation criterion that defines the critical state for a local bifurcation to set in as a function of the stress level to work-hardening rate ratio, leading to a FLD represented in the stress space. This suggests that the FLD obtained is completely objective in the sense that it is completely independent of the strain or stress history paths (Ito et al. 2000). In this work the Ito and Goya model is used to evaluate formability, as well as fracture mode and direction on the deep drawing of a square cup. Since the analysis is performed based on the stress state, it is also possible to determine an instability factor that “measures” the degree of acceleration by current stress for the local bifurcation mode towards fracture. The selected example highlights the potential use of the criterion which, once combined with the finite element analysis, can undeniably improve the mechanical design of forming processes.     

Modified texture and room temperature formability of magnesium alloy sheet by Li addition

The effect of Li addition on the mechanical responses of magnesium alloy sheets was examined in correlation with the concurrent microstructure and texture evolution. The basal texture was drastically weakened and the basal pole rotated to the transverse direction (TD) owing to the Li addition. The Mg alloy sheet containing lithium element exhibited larger uniform elongation and its Erichsen value (IE) increased by?~?59 %. Enhanced the ambient formability of the extruded Mg alloy sheet fabricated by Li addition was accomplished by the tilted weak basal texture. The microstructure evolution and properties were characterized and compared.     

Grey system theory trends from 1991 to 2018: a bibliometric analysis and visualization

Scientometrics - Grey system theory has rapidly developed in recent years, and it has solved real-world problems in various scientific fields successfully. However, there is a lack of bibliometric...     

Laser applications to chemical and environmental analysis: an introduction

This issue of Applied Optics features papers on the application of laser technology to chemical and environmental analysis. Many of the contributions to this issue, although not all, result from papers presented at the 1996 OSA Topical Meeting on Laser Applications to Chemical and Environmental Analysis, which was held in Orlando, Florida, in March 1996. This successful meeting, with nearly 100 participants, continued the tradition of earlier Laser Applications to Chemical Analysis (LACA) meetings. The title change reflects an expended scope and an even greater emphasis on environmental analysis than the previous four LACA meetings.     

Interdepartmental decision-making in theory and practice: an overview

This paper examines a special class of behaviour in organizations, namely, social relations between managers of functionally interdependent departments. It is organized around three topics : (1) A discussion of the problem of interdepartmental relations. (2) An overview of theoretical and applied findings on this problem. (3) Some views on the form of future research on this problem.     

Application of interval analysis and evidence theory to fault location

The technique of fast fault clearance for railway power transmission lines is an urgent and noticeable problem. According to the segmented structure characteristic of the lines, a novel fault location scheme based on the interval analysis and evidence theory is proposed. First, the interval model is addressed. The interval analysis is applied to deduce three interval algorithms, which implement interval location. Then, in terms of the characteristic of interval set, the difference matrix of deviation degree is used to represent quantitatively the degree of similarity between interval numbers, and construct an expression of basic probability assignment function. Finally, the evidence theory is introduced to combine the results of three interval algorithms and infer the fault segmented interval. The simulated results and practical application have effectively verified the accuracy and reliability of the proposed location scheme, which is suitable for all segmented structure lines.     

C-K design theory: an advanced formulation

C-K theory is a unified Design theory and was first introduced in 2003 (Hatchuel and Weil 2003). The name “C-K theory” reflects the assumption that Design can be modelled as the interplay between two interdependent spaces with different structures and logics: the space of concepts (C) and the space of knowledge (K). Both pragmatic views of Design and existing Design theories define Design as a dynamic mapping process between required functions and selected structures. However, dynamic mapping is not sufficient to describe the generation of new objects and new knowledge which are distinctive features of Design. We show that C-K theory captures such generation and offers a rigorous definition of Design. This is illustrated with an example: the design of Magnesium-CO₂ engines for Mars explorations. Using C-K theory we also discuss Braha and Reich’s topological structures for design modelling (Braha and Reich 2003). We interpret this approach as special assumptions about the stability of objects in space K. Combining C-K theory and Braha and Reich’s models opens new areas for research about knowledge structures in Design theories. These findings confirm the analytical and interpretative power of C-K theory.

Stress analysis of imperfect composite laminates with an interlaminar bonding theory

Delamination is a major damage mode in laminated composites since it can cause severe structural degradation. Based on an interlaminar shear stress continuity theory and a linear shear slip theory, a so-called Interlayer Shear Slip Theory was presented in a previous study. This theory was verified to be feasible for shearing-mode delamination analysis. However, in order to account for opening-mode delamination in laminated composites, the continuity of interlaminar normal stress and the modelling of normal separation on the composite interface should also be considered. The present study gives a complete discussion on the Interlaminar Bonding Theory. The effects of interlaminar bonding condition on the laminate deformation and stress distribution are also presented. It is concluded from numerical results that the present theory is suitable for analysis of composite laminates with imperfect interfaces.     

Fixed-point iteration to nonlinear finite element analysis. Part I: Mathematical theory and background

This paper sets the stage for the implementation of the Fixed-Point Iteration (FPI) to nonlinear finite element analysis as an alternative to the existing Newton-Raphson Method (NRM) or its derivatives. The superiority of the former method over the latter one is such that it enables one to obtain nonlinear structural static or dynamic responses without inverting the structural stiffness matrix. In the first part of the paper, a new convergence correction/acceleration factor has been developed for the FPI when applied to a single nonlinear algebraic equation. This new factor causes the iteration function of the equation under consideration to rotate about an axis that passes through one of its fixed points or roots. Using this observation, the slope of the iteration function can be adjusted in the neighbourhood of a specific root to ensure the convergence of the FPI. It is found that the optimum choice of the new factor corresponds to a zero slope, evaluated at the root, of the iteration function. The rate of convergence and the error estimate of this form of the FPI is developed and compared with the NRM. The equilibrium positions of a nonlinear loaded softening spring have been obtained by both methods as an illustrative numerical example to measure the effect of the new factor on the convergence rate. The second part of the paper extends the above concept to find the solution of a linear system of algebraic equations using the FPI. This leads to a better diagonal approximate inverse for the Jacobi iteration, or method of simultaneous displacements. If the elements of the solution vector of a specific system are all equal, the new Jacobi iteration becomes an exact method and the solution is obtained in one iteration. The concept is also extended to the Gauss-Seidel iteration, or method of successive displacements. Systems involving symmetric as well as nonsymmetric coefficient matrices have been used as numerical examples and are presented. For future implementation to nonlinear finite element analysis, the active column or the skyline (or the non-zero profile) FPI algorithms are developed for programming considerations.     

Gravimetric approach to the standard addition method in instrumental analysis. 1

A mathematical formulation for a gravimetric approach to the univariate standard addition method (SAM) is presented that has general applicability for both liquids and solids. Using gravimetry rather than volumetry reduces the preparation time, increases design flexibility, and makes increased accuracy possible. SAM has most often been used with analytes in aqueous solutions that are aspirated into flames or plasmas and determined by absorption, emission, or mass spectrometric techniques. The formulation presented here shows that the method can also be applied to complex matrixes, such as distillate and residual fuel oils, using techniques such as X-ray fluorescence (XRF) or combustion combined with atomic fluorescence or absorption. These techniques, which can be subject to matrix-induced interferences, could realize the same benefits that have been demonstrated for dilute aqueous solutions.     

Bayesian approach to the analysis of fluorescence correlation spectroscopy data I: theory

Fluorescence correlation spectroscopy (FCS) is a powerful tool to infer the physical process of macromolecules including local concentration, binding, and transport from fluorescence intensity measurements. Interpretation of FCS data relies critically on objective multiple hypothesis testing of competing models for complex physical processes that are typically unknown a priori. Here, we propose an objective Bayesian inference procedure for testing multiple competing models to describe FCS data based on temporal autocorrelation functions. We illustrate its performance on simulated temporal autocorrelation functions for which the physical process, noise, and sampling properties can be controlled completely. The procedure enables the systematic and objective evaluation of an arbitrary number of competing, non-nested physical models for FCS data, appropriately penalizing model complexity according to the Principle of Parsimony to prefer simpler models as the signal-to-noise ratio decreases. In addition to eliminating overfitting of FCS data, the procedure dictates when the interpretation of model parameters are not justified by the signal-to-noise ratio of the underlying sampled data. The proposed approach is completely general in its applicability to transport, binding, or other physical processes, as well as spatially resolved FCS from image correlation spectroscopy, providing an important theoretical foundation for the automated application of FCS to the analysis of biological and other complex samples.     

Hierarchical task analysis vs. cognitive work analysis: comparison of theory,methodology and contribution to system design

The cognitive work analysis framework continues to attract increasing attention from the human factors and ergonomics community. Conversely, hierarchical task analysis has been, and remains, the most popular of all human factors and ergonomics methods. This article compares the two approaches in terms of their theoretical underpinning, methodological approach and potential contributions to system design and evaluation. To do this, recent analyses, involving both approaches, of a military rotary wing mission planning software tool are compared and contrasted in terms of their methodological procedure and analysis outputs. The findings indicate that, despite the very different theoretical and methodological nature of the two approaches, and also the entirely different analyses derived, the two methods provide highly complementary outputs. In conclusion, it is argued that there is benefit in applying both approaches to inform the design and/or evaluation of the same product or system.     

Elution-extrusion countercurrent chromatography: theory and concepts in metabolic analysis

Elution-extrusion countercurrent chromatography (EECCC) takes full advantage of the liquid nature of the stationary phase in CCC by combining regular chromatographic elution with stationary-phase extrusion. EECCC is shown to be a three-stage process consisting of classical elution (I), sweeping elution (II), and extrusion (III). After only two column volumes of solvent, it rapidly yields a high-resolution chromatogram that covers an extended polarity range of solutes. As hydrophilicity/lipophilicity balance is a crucial discriminatory property of analytes in highly complex mixtures such as metabolomic samples, the precise determination of CCC distribution constants (KD) is vital to the analysis of metabolomes and other complex biological matrixes. This work builds the EECCC concept by performing a full theoretical treatment and providing equations for retention volumes, peak widths, resolution factors, and distribution constants. Experimental validation utilizes natural products standards that resemble the zero to infinity range of the polarity continuum. EECCC extends the "sweet spot" of high resolution in CCC and provides access to the otherwise practically unapproachable high-KD portion of the high-resolution chromatograms in CCC. Its improved capabilities of KD targeting make EECCC a promising tool for the specific analysis of "small" molecules in complex samples such as in metabolomic fingerprinting and footprinting.     

Application of Griffith's theory to analysis of progressive fracture

Macroscopic fracture criteria based on Griffith's theory and its modification by McClintock and Walsh are used in conjunction with the finite element method to simulate progressive fracture in structural elements. A piecewise linear model with variable load increments is developed to predict crack growth. Comparison of results of calculation with experimental data shows that the procedure can successfully predict initiation, propagation and arrest of macroscopic cracks and also model the influence of progressive fracture on the load-deformation behavior of structural elements.