Nakajima varieties and repetitive algebras

We realize certain graded Nakajima varieties of finite Dynkin type as orbit closures of repetitive algebras of Dynkin quivers. As an application, we obtain that the perverse sheaves introduced by Nakajima for describing irreducible characters of quantum loop algebras are isomorphic to the intersection cohomology sheaves of these orbit closures.Comment: 26 pages, v2 : Minor corrections. Final version to appear in PRIMS (Publications of the Research Institute for Mathematical Sciences, Kyoto

Weyl group action and semicanonical bases

Let U be the enveloping algebra of a symmetric Kac-Moody algebra. The Weyl group acts on U, up to a sign. In addition, the positive subalgebra U^+ contains a so-called semicanonical basis, with remarkable properties. The aim of this paper is to show that these two structures are as compatible as possible

Modeling Study of the Low-Temperature Oxidation of Large Methyl Esters

This study focuses on the automatic generation by the software EXGAS of kinetic models for the oxidation of large methyl esters using a single set of kinetic parameters. The obtained models allow to well reproduce the oxidation of n-decane / methyl palmitate mixture in a jet-stirred reactor. This paper also presents the construction and a comparison of models for methyl esters from C7 up to C17 in terms f conversion in a jet-stirred reactor and of ignition delay time in a shock tube. This comparison study showed that methyl esters larger than methyl octanoate behave similarly and have very close reactivities.Comment: European Combustion Meeting 2009, Vienne : Autriche (2009

Experimental and modeling study of the low-temperature oxidation of large alkanes

This paper presents an experimental and modeling study of the oxidation of large linear akanes (from C10) representative from diesel fuel from low to intermediate temperature (550-1100 K) including the negative temperature coefficient (NTC) zone. The experimental study has been performed in a jet-stirred reactor at atmospheric pressure for n-decane and a n-decane/n-hexadecane blend. Detailed kinetic mechanisms have been developed using computer-aided generation (EXGAS) with improved rules for writing reactions of primary products. These mechanisms have allowed a correct simulation of the experimental results obtained. Data from the literature for the oxidation of n-decane, in a jet-stirred reactor at 10 bar and in shock tubes, and of n-dodecane in a pressurized flow reactor have also been correctly modeled. A considerable improvement of the prediction of the formation of products is obtained compared to our previous models. Flow rates and sensitivity analyses have been performed in order to better understand the influence of reactions of primary products. A modeling comparison between linear alkanes for C8 to C16 in terms of ignition delay times and the formation of light products is also discussed

Les risques assumables : récidive et libération conditionnelle

Les décisions de remise en liberté conditionnelle reposent sur une évaluation du risque de récidive qui s’élabore autour des antécédents d’arrestations ou de condamnations du détenu. Les risques de récidive « réels » ne sont jamais vraiment étudiés. La présente étude fait état d’une enquête auprès d’un échantillon d’étudiants universitaires (N =274) sur les chances de récidive qu’ils jugeraient acceptables ou « assumables » dans une décision de libération conditionnelle. Confrontée à des mises en situation très spécifiques, la règle adoptée par les répondants semble être une règle de prépondérance : lorsque les chances de récidive sont jugées prépondérantes (70 % ou plus), ils ne prennent pas le risque de libérer le détenu ; lorsqu’elles sont jugées faibles (30 à 40 %), ils acceptent de courir ce risque. L’étude dégage le profil des décisions déviantes (trop prudentes et trop imprudentes).Parole decision-making relies on known or official odds of re-arrest or re-conviction to assess acceptable rates of official recidivism of parolees. Actual odds of recidivism however are not well researched. The paper uses a sample of undergraduate students to explore what an incoming cohort of future parole agents view as acceptable odds of actual criminal recidivism. The survey presents subjects with specific vignettes and detailed assessments of the case. Findings indicate that most subjects favour parole even though chances of recidivism are estimated to be relatively important (30 to 40%). Deviant decisions (excessively imprudent or excessively prudent) are identified and analysed.Las decisiones de libertad condicional se basan en una evaluación del riesgo de reincidencia que se elabora en torno a los antecedentes de arrestos o condenas del detenido. Los riesgos “reales” de reincidencia no son nunca realmente estudiados. El presente estudio da cuenta de una encuesta realizada a partir de una muestra de estudiantes universitarios (N = 274) sobre los riesgos de reincidencia que juzgarían aceptables o “asumibles” en una decisión de puesta en libertad condicional. Confrontada a escenarios muy específicos, la regla adoptada por los encuestados parece ser una regla de preponderancia : cuando las posibilidades de reincidencia son juzgadas preponderantes (70 % o más), no corren el riesgo de liberar al detenido ; cuando son juzgadas bajas (30 a 40 %), aceptan correr el riesgo. El estudio pone de manifiesto un perfil de decisiones desviantes (demasiado prudentes o imprudentes)