Hund and pair-hopping signature in transport properties of degenerate nanoscale devices

We investigate the signature of a complete Coulomb interaction in transport properties of double-orbital nanoscale devices. We analyze the specific effects of Hund exchange and pair hopping terms, calculating in particular stability diagrams. It turns out that a crude model, with partial Coulomb interaction, may lead to a misinterpretation of experiments. In addition, it is shown that spectral weight transfers induced by gate and bias voltages strongly influence charge current. The low temperature regime is also investigated, displaying inelastic cotunneling associated with the exchange term, as well as Kondo conductance enhancement.Comment: 5 pages, 4 figure

Identification of rolling resistance as a shape parameter in sheared granular media

Using contact dynamics simulations, we compare the effect of rolling resistance at the contacts in granular systems composed of disks with the effect of angularity in granular systems composed of regular polygonal particles. In simple shear conditions, we consider four aspects of the mechanical behavior of these systems in the steady state: shear strength, solid fraction, force and fabric anisotropies, and probability distribution of contact forces. Our main finding is that, based on the energy dissipation associated with relative rotation between two particles in contact, the effect of rolling resistance can explicitly be identified with that of the number of sides in a regular polygonal particle. This finding supports the use of rolling resistance as a shape parameter accounting for particle angularity and shows unambiguously that one of the main influencing factors behind the mechanical behavior of granular systems composed of noncircular particles is the partial hindrance of rotations as a result of angular particle shape.Comment: Soumis a Physical Review E; Statistical, Nonlinear, and Soft Matter Physics http://link.aps.org/doi/10.1103/PhysRevE.84.01130

Conditions for requiring nonlinear thermoelectric transport theory in nanodevices

In this paper, we examine the conditions under which the nonlinear transport theory is inescapable, when a correlated quantum dot is symmetrically coupled to two leads submitted to temperature and voltage biases. By detailed numerical comparisons between nonlinear and linear currents, we show that the claimed nonlinear behavior in a temperature gradient for the electric current is not so genuine, and the linear theory made at the operating temperature $\bar{T}= (T_H+T_C)/2$ is unexpectedly robust. This is demonstrated for the single impurity Anderson model, in different regimes: resonant tunneling, Coulomb blockade and Kondo regimes

« La dame Comptabilité », une analogie au service de la vulgarisation comptable : de la circulation sanguine à la santé de l'entreprise

Comment rendre accessible à un public non formé les documents comptables et de gestion ? Cet article analyse un exemple de vulgarisation, datant de 1933, qui repose sur une analogie avec la circulation sanguine. Pour ce faire, le travail de recherche a consisté à établir un état des connaissances comptables diffusées entre 1900 et 1933 pour mettre en perspective le document étudié. Si l'auteur prend des libertés avec l'anatomie, l'analogie apparaît pertinente puisqu'elle permet de faire le lien avec la notion de santé de l'entreprise : santé de l'entreprise sur laquelle jouent les évènements et les choix des dirigeants, apparence de santé grâce à des manipulations comptables. Il semble également que sur cette période que l'analogie ne soit utilisée que dans le cadre de la vulgarisation.Analogie; vulgarisation; histoire de la comptabilité; période 1900-1933; circulation sanguine

Internal friction and absence of dilatancy of packings of frictionless polygons

By means of numerical simulations, we show that assemblies of frictionless rigid pentagons in slow shear flow possess an internal friction coefficient (equal to 0.183 ± 0.008 with our choice of moderately polydisperse grains) but no macroscopic dilatancy. In other words, despite side-side contacts tending to hinder relative particle rotations, the solid fraction under quasistatic shear coincides with that of isotropic random close packings of pentagonal particles. Properties of polygonal grains are thus similar to those of disks in that respect. We argue that continuous reshuffling of the force-bearing network leads to frequent collapsing events at the microscale, thereby causing the macroscopic dilatancy to vanish. Despite such rearrangements, the shear flow favors an anisotropic structure that is at the origin of the ability of the system to sustain shear stress

Bonded-cell model for particle fracture

Particle degradation and fracture play an important role in natural granular flows and in many applications of granular materials. We analyze the fracture properties of two-dimensional disklike particles modeled as aggregates of rigid cells bonded along their sides by a cohesive Mohr-Coulomb law and simulated by the contact dynamics method. We show that the compressive strength scales with tensile strength between cells but depends also on the friction coefficient and a parameter describing cell shape distribution. The statistical scatter of compressive strength is well described by the Weibull distribution function with a shape parameter varying from 6 to 10 depending on cell shape distribution. We show that this distribution may be understood in terms of percolating critical intercellular contacts. We propose a random-walk model of critical contacts that leads to particle size dependence of the compressive strength in good agreement with our simulation data

Status and distribution of non-volant small mammals in Universiti Putra Malaysia, Bintulu Sarawak Campus (UPMKB)

This paper presents basic distribution data on non-volant small mammals derived from four sampling periods (2006-2009) in UPMKB. A total of 22 species belonging to families Tupaiidae, Sciuridae, Muridae, Viverridae, Manidae, Tarsiidae, Felidae and Cercopithecidae were captured and recorded. Planted Forest showed the highest number of species (14), followed by Nirwana Forest (11 species), Campus Zone Area (10 species), and Forestry Park (5 species). Two (2) species have been classified as Totally Protected while seven (7) species are protected under the Sarawak Wildlife Protection Ordinance, 1998. Mapping of the total area showed that the Campus Zone Area contained the highest diversity and the number of non-volant small mammals as compared to other sites in UPMKB. Thus, conservation effort of the area should be given higher priority to ensure that the biodiversity of the area is maintained