Iterative Quantization Using Codes On Graphs

We study codes on graphs combined with an iterative message passing algorithm for quantization. Specifically, we consider the binary erasure quantization (BEQ) problem which is the dual of the binary erasure channel (BEC) coding problem. We show that duals of capacity achieving codes for the BEC yield codes which approach the minimum possible rate for the BEQ. In contrast, low density parity check codes cannot achieve the minimum rate unless their density grows at least logarithmically with block length. Furthermore, we show that duals of efficient iterative decoding algorithms for the BEC yield efficient encoding algorithms for the BEQ. Hence our results suggest that graphical models may yield near optimal codes in source coding as well as in channel coding and that duality plays a key role in such constructions.Comment: 10 page

SBI Intervention: An Old Problem- A New Perspective

This research effort attempted to determine if SB/ intervention would change the perception of business problems by not only the business owner but also the student consultants. This focus further to encompassed firms that could be classified in either Stage I or Stage II of development. Even though there were no changes in perception by student consultants, and mixed results of whether stage development affected perceptual differences, strong support was given to the proposition that owners, overall, did change their perception of existing problems after SBI intervention

Halles Alstom : les bienfaits de la proximité

Une cinquantaine « d’entreprises créatives » se sont regroupées depuis 2005 au sein des anciennes Halles Alstom sur l’Île de Nantes, au cœur du futur Quartier de la création. Leur proximité géographique, mais aussi leurs affinités, leur ont permis de tisser des liens marchands et non-marchands. À l’évidence, un « effet cluster » est à l’œuvre

On Hadamard Type Inequalities Involving Several Kind of Convexity

In this paper, we not only give the extensions of the results given in [7] by Gill et al. for log-convex functions, but also obtain some new Hadamard type inequalities for log-convex, m-convex and (alpha,m)-convex functions.Comment: This paper is published in Journal of Inequalities and Application

A continuum model accounting for the effect of the initial and evolving microstructure on the evolution of dynamic recrystallization

Laser assisted forming is a process which is increasingly being adopted by the industry. Application of heat by a laser to austenitic stainless steel (ASS) sheet provides local control over formability and strength of the material. The hot forming behavior of ASS is characterized by significant dynamic recovery and dynamic recrystallization. These two processes lead to a softening stress-strain response and have a significant impact on the microstructure of the material. Most of the research performed on hot forming of ASS focuses on dynamic recrystallization and then specifically on the behavior of the annealed state, consisting of relatively large equiaxed austenite grains. However, in industry it is common to use cold rolled ASS sheet which is a mixture of austenite and martensite. Application of a laser heat treatment to the cold rolled grades of ASS induces a socalled ‘reverse’ transformation of martensite to austenite which, depending on the exact time-temperature combinations, leads to an austenite grain size in the range of nanoto micrometer. It is known from experiments that the effect of initial grain size on dynamic recrystallization is significant, especially on the initial stages of recrystallization. Therefore any continuum model capable of describing hot forming of cold rolled ASS should include the effect of the initial grain size. In this work a physically based continuum model for dynamic recrystallization is presented which accounts for the effect of the initial and evolving grain size on the evolution of dynamic recrystallization. It is shown that the initial grain size can be accounted for by incorporating its effect on the availability of preferred nucleation sites, i.e. grain edges. The new model is compared to experimental results and it is shown that the model correctly predicts accelerated recrystallization with decrease in grain size and that there is a weak dependence of the dynamically recrystallized grain size on the initial grain size. Furthermore predicted recrystallized grain sizes are in good agreement with the experimentally measured values

Mobile Bipolarons in the Adiabatic Holstein-Hubbard Model in 1 and 2 dimensions

The bound states of two electrons in the adiabatic Holstein-Hubbard model are studied numerically in one and two dimensions from the anticontinuous limit. This model involves a competition between a local electron-phonon coupling (with a classical lattice) which tends to form pairs of electrons and the repulsive Hubbard interaction $U \geq 0$ which tends to break them. In 1D, the ground-state always consists in a pair of localized polarons in a singlet state. They are located at the same site for U=0. Increasing U, there is a first order transition at which the bipolaron becomes a spin singlet pair of two polarons bounded by a magnetic interaction. The pinning mode of the bipolaron soften in the vicinity of this transition leading to a higher mobility of the bipolaron which is tested numerically. In 2D, and for any $U$, the electron-phonon coupling needs to be large enough in order to form small polarons or bipolarons instead of extended electrons. We calculate the phase diagram of the bipolaron involving first order transitions lines with a triple point. A pair of polarons can form three types of bipolarons: a) on a single site at small $U$, b) a spin singlet state on two nearest neighbor sites for larger $U$ as in 1D and c) a new intermediate state obtained as the resonant combination of four 2-sites singlet states sharing a central site, called quadrisinglet. The breathing and pinning internal modes of bipolarons in 2D generally only weakly soften and thus, they are practically not mobile. On the opposite, in the vicinity of the triple point involving the quadrisinglet, both modes exhibit a significant softening. However, it was not sufficient for allowing the existence of a classical mobile bipolaron (at least in that model)

L’entreprise sociale – SCIC entre intégration et tensions : le cas du secteur culturel

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