Filling a silo with a mixture of grains: Friction-induced segregation

We study the filling process of a two-dimensional silo with inelastic particles by simulation of a granular media lattice gas (GMLG) model. We calculate the surface shape and flow profiles for a monodisperse system and we introduce a novel generalization of the GMLG model for a binary mixture of particles of different friction properties where, for the first time, we measure the segregation process on the surface. The results are in good agreement with a recent theory, and we explain the observed small deviations by the nonuniform velocity profile.Comment: 10 pages, 5 figures, to be appear in Europhys. Let

Description of two new species of the groundstreak genus Arzecla Duarte et Robbins, 2010 (Lepidoptera: Lycaenidae: Theclinae: Eumaeini) from Colombia = Описание двух новых видов рода Arzecla Duarte et Robbins, 2010 (Lepidoptera: Lycaenidae: Theclinae: Eumaeini) из Колумбии

Two species of Arzecla Duarte et Robbins, 2010 are described from Colombia, namely: Arzecla straboris Bálint, sp. n. (type locality: El Aguila, Manizales, Caldas), and Arzecla straelena Bálint, sp. n. (type locality: Cerro Ingrumá, Riosucio, Caldas), both on the basis of a single male specimen. New species possess a combination of characters, unique in the genus, hence they are easy to identify. A  checklist with biogeographic and country indications and a key for identification based on wing characters for all described Arzecla species is provided. Specimens examined for comparative purpose are listed as an Appendix. Eleven figures

Autonomic SLA-Aware service virtualization for distributed systems

Cloud Computing builds on the latest achievements of diverse research areas, such as Grid Computing, Service-oriented computing, business processes and virtualization. Managing such heterogeneous environments requires sophisticated interoperation of adaptive coordinating components. In this paper we introduce an SLA-aware Service Virtualization architecture that provides non-functional guarantees in the form of Service Level Agreements and consists of a three-layered infrastructure including agreement negotiation, service brokering and on demand deployment. In order to avoid costly SLA violations, flexible and adaptive SLA attainment strategies are used with a failure propagation approach. We demonstrate the advantages of our proposed solution with a biochemical case study in a Cloud simulation environment. © 2011 IEEE

Generalizations of the clustering coefficient to weighted complex networks

The recent high level of interest in weighted complex networks gives rise to a need to develop new measures and to generalize existing ones to take the weights of links into account. Here we focus on various generalizations of the clustering coefficient, which is one of the central characteristics in the complex network theory. We present a comparative study of the several suggestions introduced in the literature, and point out their advantages and limitations. The concepts are illustrated by simple examples as well as by empirical data of the world trade and weighted coauthorship networks.Comment: 4 pages, 1 table, 3 figures; revised versio

Piling and avalanches of magnetized particles

We performed computer simulations based on a two-dimensional Distinct Element Method to study granular systems of magnetized spherical particles. We measured the angle of repose and the surface roughness of particle piles, and we studied the effect of magnetization on avalanching. We report linear dependence of both angle of repose and surface roughness on the ratio $f$ of the magnetic dipole interaction and the gravitational force (\emph{interparticle force ratio}). There is a difference in avalanche formation at small and at large interparticle force ratios. The transition is at $f_c \approx 7$. For $f < f_c$ the particles forming the avalanches leave the system in a quasi-continuous granular flow (\emph{granular regime}), while for $f > f_c$ the avalanches are formed by long particle clusters (\emph{correlated regime}). The transition is not sharp. We give plausible estimates for $f_c$ based on stability criteria.Comment: 9 pages, 7 figure

Emergence of communities in weighted networks

Topology and weights are closely related in weighted complex networks and this is reflected in their modular structure. We present a simple network model where the weights are generated dynamically and they shape the developing topology. By tuning a model parameter governing the importance of weights, the resulting networks undergo a gradual structural transition from a module free topology to one with communities. The model also reproduces many features of large social networks, including the "weak links" property.Comment: 4 pages, 5 figure

Different sensing mechanisms in single wire and mat carbon nanotubes chemical sensors

Chemical sensing properties of single wire and mat form sensor structures fabricated from the same carbon nanotube (CNT) materials have been compared. Sensing properties of CNT sensors were evaluated upon electrical response in the presence of five vapours as acetone, acetic acid, ethanol, toluene, and water. Diverse behaviour of single wire CNT sensors was found, while the mat structures showed similar response for all the applied vapours. This indicates that the sensing mechanism of random CNT networks cannot be interpreted as a simple summation of the constituting individual CNT effects, but is associated to another robust phenomenon, localized presumably at CNT-CNT junctions, must be supposed.Comment: 12 pages, 5 figures,Applied Physics A: Materials Science and Processing 201

Whey separation using TiO₂-modified ultrafiltration membrane

Nowadays, the membrane filtration technique is a commonly used method for the separation of whey. The most significant limitation of membrane applications is fouling, which causes flux decline. During this work, regenerated cellulose membranes covered by TiO2-nanoparticles were investigated and applied to the separation of whey solution. Experiments were carried out in a dead-end ultrafiltration cell, and the changes in filtration parameters and the photocatalytic effects of the UV irradiated TiO2 modified membrane surface on the membrane fouling were examined. Our results showed that the water flux decreased with increasing TiO2 layer thickness, but the retention of turbidity and of COD increased. After separation, the membrane surface was cleaned by UV irradiation by means of photocatalytic oxidation. It was found that the original flux was recoverable, while the retention of the membrane decreased after cleaning

Male secondary sexual characters in Aphnaeinae wings (Lepidoptera: Lycaenidae)

Male secondary sexual characters have been discovered on the hindwing verso of genera Aphnaeus Hübner, [1819], Cigaritis Donzel, 1847, Lipaphnaeus Aurivillius, 1916 and Pseudaletis Druce, 1888 representing the Palaeotropical subfamily Aphnaeinae Lycaenidae: Lepidoptera). Relevant wing parts are illustrated, described, and some observations on the organs are briefly annotated. With an appendix and 14 figures