Phase-field modelling of fracture in single crystal plasticity

We propose a phase-field model for ductile fracture in a single crystal within the kinematically linear regime, by combining the theory of single crystal plasticity as formulated in Gurtin et al. (2010) and the phase-field formulation for ductile fracture proposed by Ambati et al. (2015) . The model introduces coupling between plasticity and fracture through the dependency of the so-called degradation function from a scalar global measure of the accumulated plastic strain on all slip systems. A viscous regularization is introduced both in the treatment of plasticity and in the phase-field evolution equation. Testing of the model on two examples for face centred cubic single crystals indicates that fracture is predicted to initiate and develop in the regions of the maximum accumulated plastic strain, which is in agreement with phenomenological observations. A rotation of the crystallographic unit cell is shown to affect the test results in terms of failure pattern and corresponding global and local response

Mock galaxy catalogs using the quick particle mesh method

Sophisticated analysis of modern large-scale structure surveys requires mock catalogs. Mock catalogs are used to optimize survey design, test reduction and analysis pipelines, make theoretical predictions for basic observables and propagate errors through complex analysis chains. We present a new method, which we call "quick particle mesh", for generating many large-volume, approximate mock catalogs at low computational cost. The method is based on using rapid, low-resolution particle mesh simulations that accurately reproduce the large-scale dark matter density field. Particles are sampled from the density field based on their local density such that they have N-point statistics nearly equivalent to the halos resolved in high-resolution simulations, creating a set of mock halos that can be populated using halo occupation methods to create galaxy mocks for a variety of possible target classes.Comment: 13 pages, 16 figures. Matches version accepted by MNRAS. Code available at http://github.com/mockFactor

LA FIN DE LA DÉMOCRATIE LIBÉRALE TELLE QUE NOUS L’AVONS CONNUE?

The theoretical fault-lines in liberal democratic theory have always been located in at least two important sites: that of process or procedure, and that of outcome. As to the former, the problem has been that of trying to ensure that the “will of the people” – or at least of the relevant people, the eligible voters – gets to be expressed through meaningful, practical mechanisms. According to the consensus shared by most mainstream liberal democratic theorists of the recent past, elections to representative bodies and subsequent votes by the winners of these elections are such mechanisms. But of course at every turn we constantly find instances of elected governments thwarting the majority views of the same body of individuals by which they were originally elected. Liberal democratic theory says that, as long as the appropriate procedures for manifesting the majority (or, in some instances, mere plurality) will of the people concerning who is to represent them were followed, then the representatives are justified in voting against the apparent will of the people. But this is a clear practical contradiction. As for the the question of outcome, here recent liberal democratic theory has dug an even deeper hole for itself by abandoning the notion of a common good, to which at least some earlier theorists in this tradition still subscribed. Liberal democratic theory has ultimately denied itself any critical function with respect to outcomes. Instead, it is forced to ratify every outcome, however clearly misguided or even tragic it may be, as long as it is the product of the accepted authoritative set of procedures and institutions. Surely the new theoretical direction will need to come to grips with all the elements mostly absent from the Rawlsian approach and from the writings of most of Rawls’ liberal democratic fellow travelers: power, violence, domination, ideology, decision, interpretation, political expression, revolution, history, economy, biopolitics. New models for social and political philosophy are desperately needed!Theoretisch befanden sich die falschen Linien in der Theorie der liberalen Demokratie schon immer an mindestens zwei wichtigen Stellen: im Prozess oder Prozedere und im Resultat. Was das Erste betrifft, so bestand das Problem darin, dass versucht wurde sicherzustellen, dass der „Wille des Volkes“ – oder zumindest der der relevanten Menschen, der wählbaren Wähler – durch anschauliche, praktische Mechanismen zum Ausdruck kommt. Entsprechend dem Konsens der bedeutendsten Theoretiker der liberalen Demokratie in der neueren Vergangenheit gelten als solche Mechanismen die Wahlen für Repräsentativorgane und die nachfolgenden Stimmen der Wahlsieger. Doch auf jedem Schritt stoßen wir auf Instanzen der gewählten Regierungen, die die Mehrheitsansichten desselben Personenkreises, von dem sie ursprünglich gewählt worden waren, preisgeben. Die Theorie der liberalen Demokratie besagt, dass solange angebrachte Verfahren zum Ausdruck des Willens der Mehrheit angewandt werden (oder in einigen Fällen, der bloßen Mehrzahl) im Hinblick darauf, wer sie vertreten soll, die Vertreter berechtigt sind, gegen den manifesten Willen des Volkes zu stimmen. Doch dies ist natürlich ein offensichtlicher Widerspruch. Was die Frage der Resultate betrifft, so hat sich die neueste Theorie der liberalen Demokratie eine noch tiefere Grube gegraben, da sie sich vom Begriff des Allgemeinwohls abgewandt hat, zu dem zumindest einige frühere Theoretiker in dieser Tradition standen. Die Theorie der liberalen Demokratie hat sich letztlich selbst jegliche kritische Funktion in Bezug auf die Resultate abgesprochen. Statt dessen ist sie gezwungen, jedes Ergebnis zu ratifizieren, ohne Rücksicht darauf, wie offensichtlich es irreführend oder sogar tragisch sein mag, solange es das Erzeugnis einer akzeptierten autoritativen Bündels von Verfahren und Institutionen ist. Eine neue theoretische Richtung wird sicherlich gegen alle Elemente ankämpfen müssen, die größtenteils im Rawlsschen Ansatz und den Schriften der meisten seiner liberaldemokratischen Mitläufer fehlen: mit Macht, Gewalt, Domination, Ideologie, Entschlüssen, Deutungen, politischem Ausdruck, Revolution, Geschichte, Ökonomie, Biopolitik. Was wir dringend brauchen, sind neue Modelle sozialer und politischer Philosophie!Les failles dans la théorie de la démocratie libérale ont été toujours localisées dans au moins deux sphères importantes : celle de la procédure et celle des résultatst. En ce qui concerne la première, le problème réside dans le fait que l’on tâche que «la volonté du peuple» – ou du moins celle du peuple pertinent, des électeurs éligibles – s’exprime à travers des mécanismes signifiants et pratiques. Suivant le consenus partagé jusqu’à récemment par la plupart des théoriciens orthodoxes de la démocratie libérale, les élections à des cops représentatifs et les votes ultérieurs des gagnants de ces élections constituent de tels mécanismes. Or, on constate à tout bout de champ que différentes instances des pouvoirs élus agissent à l’encontre de l’opinion des groupements de personnes qui les ont élus. La théorie de la démocratie libérale dit que, tant que l’on respecte les procédures appropriées permettant l’expression majoritaire (ou, à certaines instances, seulement plurielle) de la volonté du peuple quant à ceux qui le représenteront, les représentants sont légitimés à voter contre la volonté apparente du peuple. Or, c’est une pure condradiction pratique. En ce qui concerne la question des résultats, la théorie récente de la démocratie libérale s’est creusé là une fosse encore plus profonde en abandonnant le concept de bien commun, auquel souscrivaient du moins quelques-uns des théoriciens plus traditionnels. La théorie de la démocratie libérale a finalement renoncé à toute fonction critique à l’égard des résultats. Par contre, elle est obligée de ratifier tout résultat, quelque déplorable ou même tragique qu’il puisse être, tant qu’il soit le produit de l’ensemble habilité des procédures et des institutions admises. Or, la nouvelle orientation théorique devra s’attaquer à tous les éléments qui sont absents dans l’approche rawlsienne et dans les écrits de la plupart des disciples libéraux de Rawls : pouvoir, violence, domination, idéologie, décision, interprétation, expression politique, révolution, histoire, économie, biopolitique. On a désespérément besoin de nouveaux modèles opour la philosophie sociale et politique

Canadian Forces In-Flight Acoustic Emission Monitoring Program

A crack growing in the forward wing trunnion of a CF100 aircraft was monitored for over 60 flying hours. Acoustic emission data was detected which indicated that during climb, following take-off,the 3mm crack made unstable advances on a few occasions. The detected crack advances produced about 1mm2 of new fracture surface

Decreasing Opportunities for Low-Wage Workers: The Role of the Nondiscrimination Law for Employer-Provided Health Insurance

As of 1978, the favorable tax treatment of fringe benefits, including health insurance, has been regulated via a nondiscrimination clause such that low-wage, full-time workers must be offered health insurance (and other benefits) that are offered to higher-wage workers by the firm. Part-time workers may be excluded from coverage, however, creating incentives for firms to hire some types of workers part time to deny them coverage. We hypothesize that firms will hire fewer workers whose relative costs have increased, that is, low-wage workers. These workers will be less likely to work for firms that offer coverage, and those that do will be more likely to work part time without being eligible for the firm’s health insurance benefits. We use the 1988 and 1993 Employee Benefits Supplements to the Current Population Surveys and an employer premium imputation to examine these hypotheses. Both the descriptive and multivariate analysis are consistent with our hypotheses. We predict the probability of working for a firm that offers health insurance to decrease as premiums increase for both high- and low-wage workers. An increase in the premium is also associated with a decrease in the probability of part-time work, but an even greater decrease in the joint probability of part-time work with eligibility for health insurance.