Hybrid Analysis of Nonlinear Circuits: DAE Models with Indices Zero and One

We extend in this paper some previous results concerning the differential-algebraic index of hybrid models of electrical and electronic circuits. Specifically, we present a comprehensive index characterization which holds without passivity requirements, in contrast to previous approaches, and which applies to nonlinear circuits composed of uncoupled, one-port devices. The index conditions, which are stated in terms of the forest structure of certain digraph minors, do not depend on the specific tree chosen in the formulation of the hybrid equations. Additionally, we show how to include memristors in hybrid circuit models; in this direction, we extend the index analysis to circuits including active memristors, which have been recently used in the design of nonlinear oscillators and chaotic circuits. We also discuss the extension of these results to circuits with controlled sources, making our framework of interest in the analysis of circuits with transistors, amplifiers, and other multiterminal devices.     

Beyond instrument selection: Cultural considerations in the psychological assessment of U.S. Latinas/os.

Currently the second largest U.S. ethnic group, U.S. Latinas/os are projected to continue increasing as a proportion of the U.S. population over the next century. The culturally competent psychological evaluation of U.S. Latinas/os requires both the use of instruments that are adequately validated in that population and the adequate consideration of culturally linked factors known to influence the assessment process and its findings. This article makes foundational recommendations in this second area, organizing them along 4 stages of professional practice in psychological assessment. Consultation with qualified professionals is discussed as being important in ensuring the accurate and ethical psychological assessment of U.S. Latinas/os at all stages of professional practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prologue

Optimization and Engineering -     

Product-type and presmoothed hazard rate estimators with censored data

Two new classes of nonparametric hazard estimators for censored data are proposed in this paper. One is based on a formula that expresses the hazard rate of interest as a product of the hazard rate of the observable lifetime and the conditional probability of uncensoring. The second class follows presmoothing ideas already used by Cao et al. (J Nonparametr Stat 17:31–56, 2005) for the cumulative hazard function. Asymptotic representations for some estimators in these classes are obtained and used to prove their limit distributions. Finally, a simulation study illustrates the comparative behavior of the estimators studied along the paper.     

A new cobalt oxide electrodeposit bath for solar absorbers

A study was carried out in a Hull cell in order to optimize the deposition conditions of cobalt xide (black cobalt) in an electrolytic bath, which uses cobalt nitrate for direct obtention of black cobalt. Thermal stability of the material was surveyed on several samples of black cobalt prepared on stainless-steel with a thickness of approximately of 2.5 μm. It was found that the optical properties change, in respect to the initial values, with time of treatment until an equlibrium is reached. This equilibrium depends on the substrate and the temperature of the treatment used.     

Structure and mechanical properties of blends of two thermotropic copolyesters

Blends of two thermotropic copolyesters, poly(ethylene terephthalate/p‐hydroxy benzoic acid) (20/80), EB, and poly(p‐hydroxy benzoic acid/2,6‐hydroxy naphthoic acid) (73/27), BN, were obtained in the melt state by direct mixing in an injection machine throughout the full composition range. They comprised an almost pure EB phase and a BN‐rich phase that contained some reacted EB. Important synergisms with most of the values above those of the two pure blend components were found at most compositions in the modulus of elasticity and the tensile strength. The synergisms appeared to be due to the concomitant effect mainly of an orientation of the components higher in the blends than in the pure components, and to a lesser extent, of a blending‐induced specific volume decrease.     

A cobweb bidding model for competitive electricity markets

The new competitive framework that has been established in several electricity markets all over the world has changed the way that electric companies attain benefits. Under this new scenario, generation companies need to develop bidding models not only for the sake of achieving a feasible dispatch of their units, but also for maximizing their benefits. This paper presents a new bidding strategies model which considers the global policy of a company, but also specifies the bid of each generating unit. The proposed model produces a maximum price bid and an optimal bidding quantity by means of an iterative procedure using the generating company's residual demand curve. It is based on an economic principle known as the cobweb theorem, frequently used to study stability in trading markets. A realistic case study from the Spanish daily electric market is presented to illustrate the methodology     

Camera Autocalibration and the Calibration Pencil

We study the geometric object given by the set of lines incident with the absolute conic. We see that this object is given by a pencil of quadrics of P ⁵, which is characterized. We describe some of its most relevant properties for the camera autocalibration problem. Finally, we illustrate the applicability of the theory proposing a linear algorithm for the metric upgrading of a projective calibration of a set of ten or more cameras with varying parameters and known skew and aspect ratio.This revised version was published online in June 2005 with correction to CoverDate     

Subterranean wine cellars of Central-Spain (Ribera de Duero): An underground built heritage to preserve

From the dawn of civilization, human beings have exploited the underground space provided by natural or excavated caves for the purpose of habitation and as storage space for different agricultural produce.Throughout the Mediterranean countryside, and particularly in many rural areas of the Iberian Peninsula, an ancestral example of that underground architecture survives through the ages: the subterranean wine cellars. These human-excavated caves, originally devoted to the winemaking and vintage processes, are placed near the villages in groups of several tens of constructions, giving rise to outstanding visual landscapes.This paper is concerned with the formal and functional features of this vernacular subterranean architecture. By a research carried out in one of the most traditional winemaking regions of Spain – Ribera de Duero – the characteristics, excavation techniques and typological classification of the caves are discussed. Moreover, the problem caused by the obsolescence and consequent dereliction of these subterranean constructions is shown here and several alternative uses are examined to preserve this underground heritage.     

Crack opening conditions at ‘corner nodes’ in FE analysis with cracking along mesh lines

On the basis of a recent work proposed by the authors on a double-minimization method for evaluating inter-element forces and stresses transmitted across mesh lines, the crack opening conditions at a corner node of the FE mesh, from where several lines (potential cracks) emanate, is examined in this paper. The study is developed locally as a post-processing step of a standard displacement-based FE calculation, in terms of an always-increasing external (macroscopic) load factor μ. The cracking laws for each potential crack line are assumed rigid-plastic with hyperbolic failure criterion in terms of normal and shear components of the stress traction at that point. It is observed that, as μ increases, in general such point may undergo up to four phases of evolution until a crack can effectively open through it. First, while stress tractions across mesh lines at the point are all below cracking criterion, forces may be evaluated with the double minimization method recently proposed. Second, cracking criterion is reached for one of the lines only. Stress evaluation requires a modified minimization method with one (hyperbolic) constraint; however, crack still does not open at the node because of the lack of kinematic continuity. Third, cracking criterion is satisfied for a second of the lines converging at the nodal point. Stress tractions may then be calculated with a system of equations involving the two hyperbolic constraints alone and no minimization is needed. But in general the through crack cannot open yet at this stage because of non-coincident flow rules, until either (i) a third line reaches the cracking criterion, or (ii) these get reoriented to exhibit parallel directions in the global reference system. Two simple examples of application are provided which illustrates the development of the various cracking stages and shows different situations that may take place.