Hydrodynamic and mass transfer efficiency of ceramic foam packing applied to distillation.

In addition to a high void volume and specific area, solid foams possess other properties (low density, good thermal, mechanical, electrical, and acoustical behaviour) that make them attractive for applications such as heat exchangers and reformers. Applications using foams as catalysts or structured catalyst supports have demonstrated higher performance than classical catalysts. Several studies have explored the hydrodynamic behaviour of foams in monophasic and counter current systems and have reported very low pressure drops. This paper describes the application of ceramic foam to distillation. The β-SiC foam contains 5 pores per inch (PPI) with a 91% void volume and a surface area of 640 m2/m3. Performance parameters including pressure drop for the dry and wet packing, flooding behaviour, and dynamic liquid hold-up were measured in a column of 150 mm internal diameter. The mass transfer efficiency in terms of the height equivalent to theoretical plate (HETP) was determined by total reflux experiments using a mixture of n-heptane and cyclohexane at atmospheric pressure. The experimental results were used to develop a set of correlations describing pressure drop and liquid hold-up in terms of a dimensionless number. The hydrodynamic performance and mass transfer efficiency were compared with classical packing materials used in distillation

Detecting induced subgraphs

An s-graph is a graph with two kinds of edges : subdivisible edges and real edges. A realisation of an s-graphB is any graph obtained by subdividing subdivisible edges of B into paths of arbitrary length (at least one). Given an s-graph B, we study the decision problem Pi(B) whose instance is a graph G and whose question is "Does G contain a realisation of B as an induced subgraph ?".Detection, induced, subgraph.

A mesomodel for localisation and damage computation in laminates

International audienceThe basic aspects of a material mesomodel dedicated to composite laminates and capable of simulating complete fracture phenomena are discussed. Attention is focused herein on damage computation and, in particular, on the description of localisation phenomena. Both quasi-static and dynamic loadings are considered

Side-channel Analysis of Gr{\o}stl and Skein

International audienceIn this work, a detailed study of two finalists of the SHA-3 competition from the side-channel analysis point of view is provided. For both functions when used as a MAC, this paper presents detected strategies for performing a power analysis. Besides the classical HMAC mode, two additionally proposed constructions, the envelope MAC for Grøstl and the Skein-MAC for Skein are analyzed. Consequently, examples of software countermeasures thwarting first-order DPA or CPA are given. For the validation of our choices, HMAC-Grøstl, HMAC-Skein as well as the countermeasures were implemented on a 32-bit ARM-based smart card, and power analysis attacks were mounted in practice on both unprotected and protected implementations. Finally, the performance difference between both versions is discussed

Exact Capacity Scaling of Extended Wireless Networks

n source and destination pairs randomly located in an area extending linearly with n want to communicate with each other. Signals transmitted from one user to another at distance r apart are subject to a power attenuation of r^{-alpha} and random phase changes. Classical multihop architectures that decode and forward packets can deliver a sqrt{n}-scaling of the aggregate throughput, while recently proposed hierarchical cooperation achieves n^{2-alpha/2}-scaling, which is superior to multi-hop for alpha4, while the moderate-attenuation regime (2 2. Our result shows that the mentioned schemes are scaling-optimal, namely that no other scheme can beat hierarchical cooperation when alpha 3. The key ingredient is a careful evaluation of the scaling of the cut-set bound

Electrical detection of plasmon-induced isomerization in molecule-nanoparticle network devices

We use a network of molecularly linked gold nanoparticles (NPSAN: nanoparticles self-assembled network) to demonstrate the electrical detection (conductance variation) of a plasmon-induced isomerization (PII) of azobenzene derivatives (azobenzene bithiophene : AzBT). We show that PII is more efficient in a 3D-like (cluster-NPSAN) than in a purely two-dimensional NPSAN (i.e., a monolayer of AzBT functionalized Au NPs). By comparison with usual optical (UV-visible light) isomerization of AzBT, the PII shows a faster (a factor about 10) isomerization kinetics. Possible PII mechanisms are discussed: electric field-induced isomerization, two-phonon process, plasmon-induced resonant energy transfer (PIRET), the latter being the most likely.Comment: Final manuscript with supporting informatio

Périgueux – Porte de Mars

La Porte de Mars est une porte urbaine dans l’enceinte antique tardive de la Cité à Périgueux qui comporte une entrée charretière flanquée de deux tours en grand appareil ornées de pilastres, coiffés d’un grand entablement. Ce décor austère et l’utilisation exclusive du grand appareil ont toujours intrigué, peut-être à cause d’un contexte d’élaboration tardif, jugé à tort peu propice aux manifestations grandioses de constructions monumentales. L’enceinte constitue une parure et un symbole de ..