Optimized Schwarz waveform relaxation and discontinuous Galerkin time stepping for heterogeneous problems

We design and analyze a Schwarz waveform relaxation algorithm for domain decomposition of advection-diffusion-reaction problems with strong heterogeneities. The interfaces are curved, and we use optimized Robin or Ventcell transmission conditions. We analyze the semi-discretization in time with Discontinuous Galerkin as well. We also show two-dimensional numerical results using generalized mortar finite elements in space

International perspectives on building capacity for planning and health

This paper looks at the integration of health into planning and planning curricula and what we have learnt from international practice in the context of the PLAN-ED (“Educating Planners for the New Challenges of Sustainability, Knowledge and Governance”) project involving staff from four planning schools in the EU and the USA. In Bristol, the project brought together researchers, stakeholders and practitioners from both health and planning, including from local authorities, NGOs and health services to consider how best to progress the capacity building agenda

Enabling Realistic Cross-Layer Analysis based on Satellite Physical Layer Traces

We present a solution to evaluate the performance of transport protocols as a function of link layer reliability schemes (i.e. ARQ, FEC and Hybrid ARQ) applied to satellite physical layer traces. As modelling such traces is complex and may require approximations, the use of real traces will minimise the potential for erroneous performance evaluations resulting from imperfect models. Our Trace Manager Tool (TMT) produces the corresponding link layer output, which is then used within the ns-2 network simulator via the additionally developed ns-2 interface module. We first present the analytical models for the link layer with bursty erasure packets and for the link layer reliability mechanisms with bursty erasures. Then, we present details of the TMT tool and our validation methodology, demonstrating that the selected performance metrics (recovery delay and throughput efficiency) exhibit a good match between the theoretical results and those obtained with TMT. Finally, we present results showing the impact of different link layer reliability mechanisms on the performance of TCP Cubic transport layer protocol

Identification of nonmonotonic behaviors and stick-slip transition in liquid crystal polymers

International audienceThe recent identification of shear-induced phases in the isotropic melts of liquid crystal polymers shows that these materials are expected to display original nonlinear behaviors. We have investigated the flow behavior of a nematic sidechain polymer above its isotropic-nematic transition temperature. Nonlinear rheology and bire-fringence measurements indicate the appearance, above a critical shear rate, of the shear-induced isotropic-nematic phase transition. The rheological behavior of this induced phase is characterized by undamped time-periodic shear stress oscillations. These sustained oscillations are interpreted in terms of a stick-slip mechanism alternating high-friction static state and low-friction kinetic state. PACS number͑s͒: 83.80.Xz, 47.20.Hw, 83.50.Ax, 64.70.Md Polymers are non-Newtonian fluids ͓1͔ whereas liquid crystals do not behave as simple fluids close to phase transitions ͓2͔. When these two complex fluids are coupled to form a melt of sidechain liquid crystal polymers ͑SCLCPs͒, the resulting rheological behavior is expected to be peculiar. The very first flow studies ͓3͔ have indeed indicated that SCLCP melts display strong nonlinear behaviors above the isotropic-nematic transition temperature (T NI). This behavior looks similar to the well-studied shear-induced behavior of giant micelle solutions which display a shear-induced IN transition above T NI ͓4,5͔. The SCLCP shear-induced transition was revealed by flow birefringence and via the existence of a stress plateau in the stress versus shear rate curve. The stress plateau can be explained by entering an unstable flow region; above a critical shear rate, the region is characterized by a decreasing stress with increasing shear rate. The system is then supposed to phase separate into homogeneous bands ͑shear banding͒ to maintain the imposed shear rate ͓5͔. The existence of such nonequilibrium states opens the question of identification of the coupling parameters associated with the critical shear rate. Clearly, the shear induced SCLCP critical times are not associated with the lifetime of the pretransi-tional fluctuations, suggesting a coupling with slower time scales which could be rather consistent with the existence of macroscopic heterogeneities as proposed by Collin et al. ͓6͔. The shear-induced phase conformation of the polymer main chain was also determined using small angle neutron scattering. For a LC polymer characterized in the equilibrium nem-atic phase by a perpendicular main chain/mesogen coupling ͑oblate conformation͒, we observed that the initially perpendicular coupling is inverted in the shear-induced nematic phase to a parallel coupling with the main-chain conforma-tion becoming prolate ͓3͔. This structural rearrangement can be proposed as a working hypothesis to explain the appearance of shear-induced transitions in SCLCP isotropic melts. The purpose of the present paper is to analyze the flow behavior produced above T NI by a SCLCP whose main-chain conformation is already prolate in the equilibrium nematic phase ͓7͔. The experimental techniques used are nonlinear rheology and flow birefringence. A nonequilibrium phase compatible with shear-banding is identified together with the observation of a second nonlinear behavior corresponding to an oscillating regime. The SCLCP chosen, PA 4-CN, is characterized as a prolate nematic polymer ͓7͔. The monomers have been synthesized at the Laboratoire Lé on Brillouin and polymerized by Poly-merExpert via controlled radical polymerization. The polymer described here corresponds to a molecular weight of M W ϭ85 800 and a polydispersity index of Iϭ1.1. This molecular weight corresponds to a nonentangled polymer and no rubbery plateau was found in viscoelastic measurements. This PA 4-CN presents the following succession of me-sophases: Tg-30 °C-N-116 °C-I and corresponds to the formul

Enabling Realistic Cross-Layer Analysis based on Satellite Physical Layer Traces

We present a solution to evaluate the performance of transport protocols as a function of link layer reliability schemes (i.e. ARQ, FEC and Hybrid ARQ) applied to satellite physical layer traces. As modelling such traces is complex and may require approximations, the use of real traces will minimise the potential for erroneous performance evaluations resulting from imperfect models. Our Trace Manager Tool (TMT) produces the corresponding link layer output, which is then used within the ns-2 network simulator via the additionally developed ns-2 interface module. We first present the analytical models for the link layer with bursty erasure packets and for the link layer reliability mechanisms with bursty erasures. Then, we present details of the TMT tool and our validation methodology, demonstrating that the selected performance metrics (recovery delay and throughput efficiency) exhibit a good match between the theoretical results and those obtained with TMT. Finally, we present results showing the impact of different link layer reliability mechanisms on the performance of TCP Cubic transport layer protocol.Comment: 6 pages, 5 figures and 1 table. Submitted at PIMRC 201

Risikomanagement im öffentlichen Sektor

Bei der Erfüllung seiner Aufgaben ist der öffentliche Sektor einer Vielfalt von Chancen und Risiken ausgesetzt. Gleichzeitig verfügt der öffentliche Sektor bislang nicht über anerkannte Standards im Risikomanagement. Das Interne Kontrollsystem (IKS) vermag das Risikomanagement nicht zu ersetzen. Konzepte und Begriffe im Risikomanagement sind uneinheitlich und lückenhaft. Konsolidierungsregeln (Vergleichbarkeit, Korrelation, Aggregation) für ein integriertes Risikomanagement auf der Ebene der Exekutive (sog. Corporate-Ebene) fehlen im öffentlichen Sektor, obwohl der Staat mit seinen hierarchischdezentralen Strukturen einer besonders ausgeprägten Konsolidierungsproblematik gegenübersteht. Diese Situation erschwert die Führung von öffentlichen Verwaltungen (Governance) sowie einen nachhaltigen, effizienten und effektiven Umgang mit öffentlichen Mitteln. Das Projekt entwickelt im Rahmen der in der INTOSAI-Richtlinie 9130 für ein umfassendes Risikomanagement festgelegten Prinzipien (2007) für eine schweizerische Grossstadt ein mit dem IKS abgestimmtes Risikomanagement. Es untersucht den dafür erforderlichen kulturellen Veränderungsprozess und evaluiert die Einführung eines integrierten Risikomanagements in einer schweizerischen Grossstadt

Size and polydispersity effect on the magnetization of densely packed magnetic nanoparticles

The magnetic properties of densely packed magnetic nanoparticles (MNP) assemblies are investigated from Monte Carlo simulations. The case of iron oxide nanoparticles is considered as a typical example of MNP. The main focus is put on particle size and size polydispersity influences on the magnetization curve. The particles are modeled as uniformly magnetized spheres isolated one from each other by a non magnetic layer representing the organic coating. A comparison with recent experimental results on $\gamma-$Fe$_2$O$_3$ powder samples differing by their size is given.Comment: To be published in the Journal of Applied Physics, to be found at http://jap.aip.org