Qualitative features of matrix pencils and DAEs arising in circuit dynamics

The dynamical behaviour of nonlinear electrical circuits is usually modelled in the time domain by differential-algebraic equations (DAEs). The differential-algebraic formalism drives qualitative analyses based on linearization to a matrix pencil setting. In this context, the present paper performs a spectral analysis of matrix pencils and DAEs arising in nonlinear circuit theory. Specifically, the non-singularity, hyperbolicity and asymptotic stability of equilibria are addressed in terms of circuit topology. The differential-algebraic framework puts the results beyond those already known for state-space models, unfeasible in many actual problems. The topological conditions arising in this qualitative study are proved independent of those supporting the index, and therefore they apply to both index-1 and index-2 configurations. The approach illustrates how graph theory, matrix analysis and DAE theory interact in the dynamical study of nonlinear circuits.     

On the stability of solutions of autonomous index-I tractable and quasilinear index-2 tractable DAEs

Conclusion We have seen that the stationary solutions of the regularized equations are asymptotically stable if the stationary solution of the original quasilinear index-2 tractable DAE is so. In other words, the given regularizations supply a solution sharing the stability properties of the solution of the unperturbed equation.     

Using MCRDR based Agile approach for expert system development

Various expert system development approaches were proposed but most of them cannot deal with two problems: the difficulty of analysis and maintenance. Rather than to spend time waiting any longer, it is better to find an alternative solution from other research fields. In computer software development area, researchers have been suffering from the difficulty of maintenance and analysis, just as the researchers in the expert system development field. To solve this issue, researchers in the software used both agile software development and business rules approach: agile software development is for overcoming the the difficulty of analysis, and business rules approach is for reducing issues in the maintenance. There is a big opportunity that those two approaches can also be solve the two issues in the expert system development field. The paper describes requirements of the approach based on agile software development and the business rules approach. As a result, we consider and specify why the Multiple Classification Ripple Down Rules is the novel approach for the expert system development.     

Semistate models of electrical circuits including memristors

In this paper we present several semistate or differential‐algebraic models arising in nodal analysis of nonlinear circuits including memristors. The goal is to characterize the tractability index of these models under strict passivity assumptions, a key issue for the numerical simulation of circuit dynamics. We show that the main model, which combines memristors' fluxes and charges, is index two. From a technical point of view, this result is based on the use of a projector along the image of the leading matrix, in contrast to previous index analyses. For charge‐controlled memristors, the elimination of fluxes yields an index one system in topologically nondegenerate circuits, and an index two model otherwise. Analogous results are also proved to hold for flux‐controlled memristors. Our framework accommodates coupling effects among resistors, memristors, capacitors and inductors. Copyright © 2010 John Wiley & Sons, Ltd.     

Energy Scales in the Local Magnetic Excitation Spectrum of YBa2Cu3O6+y

The wave-vector integrated dynamical spin susceptibility _2D() of YBa ₂ Cu ₃ O _6+y cuprates is considered. _2D is calculated in the superconducting state from a renormalized mean-field theory of the t–t–J-model, based on the slave-boson formulation. Besides the well-known 41 meV resonance a second, much broader peak ('hump') appears in Im _2D. It is caused by particle-hole excitations across the maximum gap ⁰ . In contrast to the resonance, which moves to lower energies when the hole filling is reduced from optimal doping, the position of this 'hump' at 2 ⁰ stays almost unchanged. The results are in reasonable agreement with inelastic neutronscattering experiments.     

The Sandia Fracture Challenge: blind round robin predictions of ductile tearing

Existing and emerging methods in computational mechanics are rarely validated against problems with an unknown outcome. For this reason, Sandia National Laboratories, in partnership with US National Science Foundation and Naval Surface Warfare Center Carderock Division, launched a computational challenge in mid-summer, 2012. Researchers and engineers were invited to predict crack initiation and propagation in a simple but novel geometry fabricated from a common off-the-shelf commercial engineering alloy. The goal of this international Sandia Fracture Challenge was to benchmark the capabilities for the prediction of deformation and damage evolution associated with ductile tearing in structural metals, including physics models, computational methods, and numerical implementations currently available in the computational fracture community. Thirteen teams participated, reporting blind predictions for the outcome of the Challenge. The simulations and experiments were performed independently and kept confidential. The methods for fracture prediction taken by the thirteen teams ranged from very simple engineering calculations to complicated multiscale simulations. The wide variation in modeling results showed a striking lack of consistency across research groups in addressing problems of ductile fracture. While some methods were more successful than others, it is clear that the problem of ductile fracture prediction continues to be challenging. Specific areas of deficiency have been identified through this effort. Also, the effort has underscored the need for additional blind prediction-based assessments.     

Impact of managed care on independent practice and professional ethics: A survey of independent practitioners.

Managed care significantly affects the service delivery patterns, business structures, ethics, and professional concerns of independent practitioners. This survey assessed psychologists' perceptions of the effects of managed care on practice and ethics. Most respondents reported significant increases in dependence on managed care services for income. Negative effects included loss of control over ethical decisions and potential harm to patients from erosion of confidentiality. A majority of respondents reported encountering ethical concerns not addressed by the American Psychological Association ethics code. Findings suggest directions for practice development, for public policy addressing confidentiality, and for clarification of ethical responsibilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What we know about offenders who drive under the influence: analysis of court case file reviews

This paper presents findings from a quantitative study about alcohol-impaired drivers in Utah. The University of Utah's Social Research Institute conducted a retrospective case file evaluation about the adjudication and sanctioning phases associated with driving under the influence (DUI) to determine Utah's response to DUI crime from arrest forward. Although Utah driver's license and court systems are on the cutting edge of dealing with DUI offenders, we found a variety of limitations for analysis due to data collection and entry. Therefore, it is difficult to develop a thorough understanding about the process of dealing with DUI offenders and the effectiveness of court actions and treatments. The purpose of this paper is to provide recommendations about how to ensure more accurate data collection about impaired drivers.