724 research outputs found
General Algorithm For Improved Lattice Actions on Parallel Computing Architectures
Quantum field theories underlie all of our understanding of the fundamental
forces of nature. The are relatively few first principles approaches to the
study of quantum field theories [such as quantum chromodynamics (QCD) relevant
to the strong interaction] away from the perturbative (i.e., weak-coupling)
regime. Currently the most common method is the use of Monte Carlo methods on a
hypercubic space-time lattice. These methods consume enormous computing power
for large lattices and it is essential that increasingly efficient algorithms
be developed to perform standard tasks in these lattice calculations. Here we
present a general algorithm for QCD that allows one to put any planar improved
gluonic lattice action onto a parallel computing architecture. High performance
masks for specific actions (including non-planar actions) are also presented.
These algorithms have been successfully employed by us in a variety of lattice
QCD calculations using improved lattice actions on a 128 node Thinking Machines
CM-5.
{\underline{Keywords}}: quantum field theory; quantum chromodynamics;
improved actions; parallel computing algorithms
Architecture des milieux
Cities do not wait on architecture to evolve - neither forethought nor attention are necessary for them to show extraordinary growth and energy. But contemporary political discussion directly addresses our living conditions and environment: how can we answer new social and ecological problems without renewing our thoughts on architecture and urban planning, or examining associated practices?Die Stadt im Werden erinnert uns tÀglich an die Tatsache: ausdehnen und verwandeln kann sich eine Stadt ganz gut ohne Architektur! Die aktuelle politische Debatte befragt jedoch ganz direkt unser Lebensumfeld. Ohne völliges Umdenken was Urbanismus und Architektur anbelangt geht es nicht. Die Architektur der Milieus bringt eine Hypothese um diese Kollektivarbeit zu nÀhren: zugleich reparieren und neu fundieren
Thermo-mechanical analysis of GaAs devices under temperature-humidity-bias testing
International audienceAccelerated life tests on microelectronic devices are needed to estimate their degradation under severe environment. THB (Temperature Humidity Bias) [1] at 85°C and 85%RH (relative humidity) is commonly used for reliability studies. Empirical acceleration laws, used for THB test take into account the temperature change (from 22°C to 85°C), but they do not quantify its impact of the corresponding thermo-elastic stress which it adds to the residual stress in the die and of possible microstructure changes. The aim of this work is to determine the thermo-mechanical stresses induced in the active layer of a Gallium Arsenide (GaAs) chip by the THB test. They are due to the mismatch in Coefficients of Thermal Expansion (CTE) between the stack of thin film materials used as metallurgic interconnection and the intermediate dielectric layers above the active area of the chip. To estimate this stress, fist layers thicknesses measurement have been made with various techniques; second few configurations have been used to simulate heating and finally " complete " 2D Finite Element Analysis (FEA) has been performed. Elastic and thermo-physical materials data come from the literature. The results indicate compression of metal gate (Ti/Al/Au) and tensile stress concentration in the SiNx passivation layer. The outcomes is compared with THB test results from [2] and suggests that stress induced by heating must be considered to explain failure during THB test
The space of cultural practices: from the construction of social space to the study of subgroups through specific class analysis.
Quels sont les dĂ©terminants sociaux des orientations culturelles et, en particulier, quel est lâeffet de la position de classe sur les diffĂ©rences observĂ©es dans lâunivers des pratiques culturelles? Le prĂ©sent article revisite cette question dĂ©sormais classique de sociologie de la culture et de sociologie de la stratification, Ă partir de donnĂ©es dâune enquĂȘte par questionnaire menĂ©e en France en 2003 (âParticipation culturelle et sportiveâ). En mobilisant une dĂ©marche systĂ©mati-que dâanalyse gĂ©omĂ©trique des donnĂ©es, il sâagit ici de discuter empiriquement lâimportance de lâeffet de lâappartenance de classe, telle quâelle peut ĂȘtre saisie Ă partir de nomenclatures socio--professionnelles Ă diffĂ©rents niveaux dâagrĂ©gation. Une fois dĂ©terminĂ© lâeffet de lâappartenance de classe et Ă©valuĂ© son importance selon divers critĂšres, on Ă©tudie dans un second temps les variations sociales Ă lâintĂ©rieur de trois groupes sociaux particuliers, afin de montrer que lâon peut interprĂ©ter sociologiquement la diversitĂ© de pratiques culturelles au sein de diffĂ©rentes catĂ©gories sociales, voire Ă des niveaux encore plus fins.What are the social determinants of cultural orientations and, in particular, what is the effect of class position on the differences observed in the universe of cultural practices? This article revisits this classic question of the sociology of culture and the sociology of stratification, based on the data of a survey conducted in France in 2003 ("Cultural and sports participation"). Mobilizing a systematic approach based on geometric data analysis, the aim of this article is to discuss empirically the importance of class belonging effect, as it can be understood from socio-professional nomenclatures at different levels of aggregation. Once the effect of class belonging has been determined and its importance according to various criteriaassessed, the social variations within three social groups are examined, in order to show that it is possible to interpret sociologically the diversity of cultural practices within different social categories, possibly even in more refined levels.Quais sĂŁo as determinantes sociais das orientaçÔes culturais e, em particular, qual Ă© o efeito da po-sição de classe sobre as diferenças observadas no universo das prĂĄticas culturais? O presente artigo revisita essa questĂŁo doravante clĂĄssica da sociologia da cultura e da sociologia da estratificação, a partir dos dados de uma pesquisa por questionĂĄrio, realizada na França em 2003 (âParticipação cultural e esportivaâ). Mobilizando uma abordagem sistemĂĄtica de anĂĄlise geomĂ©trica dos dados, trata-se aqui de discutir empiricamente a importĂąncia do efeito de pertencimento de classe, tal como pode ser apreendida a partir de nomenclaturas socioprofissionais em diferentes nĂveis de agregação. Uma vez determinado o efeito do pertencimento de classe e avaliada sua importĂąncia de acordo com diversos critĂ©rios, estudaremos, em seguida, as variaçÔes sociais no interior de trĂȘs grupos sociais em particular, a fim de mostrar que Ă© possĂvel interpretar sociologicamente a diversidade de prĂĄticas culturais no seio de diferentes categorias sociais, eventualmente em nĂveis ainda mais finos
Approches par maillage conforme en mécanique non-linéaire de la rupture : méthode G-theta et modÚle de zone cohésive
National audienceOn prĂ©sente deux approches pour la fissuration en eÌlastoplasticiteÌ : l'une baseÌe sur l'introduction d'une grandeur eÌnergeÌtique caractĂ©ristique de la fissuration pertinente dans ce contexte, l'autre associant remaillage adaptatif et prĂ©diction de trajet de fissuration pour un modeÌle cohĂ©sif. Ces approches, mises en Ćuvre dans le code aux eÌleÌments finis Zset/Zebulon, sont eÌvalueÌes sur des problĂšmes reprĂ©sentatifs simples.See http://hal.archives-ouvertes.fr/docs/00/59/29/29/ANNEX/r_905JKSQE.pd
Development of compositional-gradient metallic alloys for combinatorial investigation of microstructures
International audienc
Infrared Behavior of the Gluon Propagator on a Large Volume Lattice
The first calculation of the gluon propagator using an order a^2 improved
action with the corresponding order a^2 improved Landau gauge fixing condition
is presented. The gluon propagator obtained from the improved action and
improved Landau gauge condition is compared with earlier unimproved results on
similar physical lattice volumes of 3.2^3 \times 6.4 fm^4. We find agreement
between the improved propagator calculated on a coarse lattice with lattice
spacing a = 0.35 fm and the unimproved propagator calculated on a fine lattice
with spacing a = 0.10 fm. This motivates us to calculate the gluon propagator
on a coarse large-volume lattice 5.6^3 \times 11.2 fm^4. The infrared behavior
of previous studies is confirmed in this work. The gluon propagator is enhanced
at intermediate momenta and suppressed at infrared momenta. Therefore the
observed infrared suppression of the Landau gauge gluon propagator is not a
finite volume effect.Comment: 8 pages, 4 figures, minor typos corrected and repsonse to referees
comment
Use of space-resolved in-situ high energy X-ray diffraction for the characterization of the compositional dependence of the austenite-to-ferrite transformation kinetics in steels
In-situ high energy X-Ray diffraction (HEXRD) was used on compositionally graded steels to study the effect of substitutional elements on ferrite growth kinetics in Fe-C-X and Fe-C-X-Y systems. Two systems have been selected to illustrate the applicability of the combinatorial approach in studying such transformations, Fe-C-Mn and Fe-C-Mn-Mo. Comparison between the measured ferrite growth kinetics using HEXRD and the predicted ones using Para-Equilibrium (PE) and Local Equilibrium with Negligible Partitioning (LENP) models indicates that the fractions reached at the stasis of transformation are lower than the predicted ones. Experiments indicated a deviation of measured kinetics from both PE and LENP models when increasing Mn and decreasing Mo (in Fe-C-Mn-Mo system). The large amount of data that can be obtained using this approach can be used for validating existing models describing ferrite growth kinetics
Scaling behavior of the overlap quark propagator in Landau gauge
The properties of the momentum space quark propagator in Landau gauge are
examined for the overlap quark action in quenched lattice QCD. Numerical
calculations are done on three lattices with different lattice spacings and
similar physical volumes to explore the approach of the quark propagator toward
the continuum limit. We have calculated the nonperturbative momentum-dependent
wave function renormalization function Z(p) and the nonperturbative mass
function M(p) for a variety of bare quark masses and perform an extrapolation
to the chiral limit. We find the behavior of Z(p) and M(p) are in reasonable
agreement between the two finer lattices in the chiral limit, however the data
suggest that an even finer lattice is desirable. The large momentum behavior is
examined to determine the quark condensate.Comment: 9 pages, 5 figures, Revtex 4. Streamlined presentation, additional
data. Final versio
Inventaire de la faune apiforme (Hymenoptera, Apoidea) des quartiers Myosotis et Engeland Ă Uccle (Bruxelles, Belgique)
peer reviewedCe travail prĂ©sente lâinventaire des abeilles sauvages (Hymenoptera Apoidea) observĂ©es dans lâancien quartier Myosotis et le nouveau quartier Engeland de la commune dâUccle Ă Bruxelles. Via une campagne dâĂ©chantillonnage dans les deux quartiers, 708 spĂ©cimens ont Ă©tĂ© capturĂ©s ou observĂ©s appartenant Ă 58 espĂšces diffĂ©rentes des 6 familles dâabeilles sauvages de Belgique. La faune apiforme capturĂ©e reprĂ©sente 14% de la faune belge et 28% de la faune bruxelloise. On y retrouve 10 espĂšces mono ou oligolectiques et 5 espĂšces font lâobjet dâenjeux de conservation spĂ©cifiques selon la liste rouge des abeilles de Belgique. Quelques recommandations de gestion de conservation sont discutĂ©es dans ce travail en vue de favoriser au maximum la richesse de ces anthophiles pour la commune dâUccle
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