An invariant in shock clustering and Burgers turbulence

1-D scalar conservation laws with convex flux and Markov initial data are now known to yield a completely integrable Hamiltonian system. In this article, we rederive the analogue of Loitsiansky's invariant in hydrodynamic turbulence from the perspective of integrable systems. Other relevant physical notions such as energy dissipation and spectrum are also discussed.Comment: 11 pages, no figures; v2: corrections mad

Power analysis on smartcard algorithms using simulation

This paper presents the results from a power analysis of the AES and RSA algorithms by\ud simulation using the PINPAS tool. The PINPAS tool is capable of simulating the power\ud consumption of assembler programs implemented in, amongst others, Hitachi H8/300\ud assembler. The Hitachi H8/300 is a popular CPU for smartcards. Using the PINPAS tool, the\ud vulnerability for power analysis attacks of straightforward AES and RSA implementations is\ud examined. In case a vulnerability is found countermeasures are added to the implementation\ud that attempt to counter power analysis attacks. After these modifications the analysis is\ud performed again and the new results are compared to the original results

Modelling bacterial behaviour close to a no-slip plane boundary: the influence of bacterial geometry

We describe a boundary-element method used to model the hydrodynamics of a bacterium propelled by a single helical flagellum. Using this model, we optimize the power efficiency of swimming with respect to cell body and flagellum geometrical parameters, and find that optima for swimming in unbounded fluid and near a no-slip plane boundary are nearly indistinguishable. We also consider the novel optimization objective of torque efficiency and find a very different optimal shape. Excluding effects such as Brownian motion and electrostatic interactions, it is demonstrated that hydrodynamic forces may trap the bacterium in a stable, circular orbit near the boundary, leading to the empirically observable surface accumulation of bacteria. Furthermore, the details and even the existence of this stable orbit depend on geometrical parameters of the bacterium, as described in this article. These results shed some light on the phenomenon of surface accumulation of micro-organisms and offer hydrodynamic explanations as to why some bacteria may accumulate more readily than others based on morphology

Density Matrix Renormalization for Model Reduction in Nonlinear Dynamics

We present a novel approach for model reduction of nonlinear dynamical systems based on proper orthogonal decomposition (POD). Our method, derived from Density Matrix Renormalization Group (DMRG), provides a significant reduction in computational effort for the calculation of the reduced system, compared to a POD. The efficiency of the algorithm is tested on the one dimensional Burgers equations and a one dimensional equation of the Fisher type as nonlinear model systems.Comment: 12 pages, 12 figure

Risico-evaluatie toepassing groen gas in de Nederlandse glastuinbouw

In deze studie worden de mogelijke risico’s die het gebruik van biogas in de glastuinbouw met zich mee kunnen brengen zo goed mogelijk in beeld gebracht. Aan de hand van de samenstellingseisen in de aansluit' en Transport' voorwaarden Gas RNB en de resultaten van biogasanalyses bij vijf verschillende vergistingprojecten is bepaald welke componenten in het gas kunnen voorkomen. Op basis de maximaal toegestane concentratie in het gas is vervolgens een schatting gemaakt van de te verwachte maximale concentratie in de kas, op plantniveau. De verhouding tussen de fytotoxiciteit van de betreffende component en de te verwachte concentratie in de kas bepaald of de component een potentieel risico vormt voor kasgewassen

Orientation dynamics of weakly Brownian particles in periodic viscous flows

Evolution equations for the orientation distribution of axisymmetric particles in periodic flows are derived in the regime of small but non-zero Brownian rotations. The equations are based on a multiple time scale approach that allows fast computation of the relaxation processes leading to statistical equilibrium. The approach has been applied to the calculation of the effective viscosity of a thin disk suspension in gravity waves.Comment: 16 pages, 7 eps figures include

Repair of Full-scale Timber Bridge Chord members by Shear Spiking

The addition of vertically-oriented shear spikes (fiberglass reinforced polymer rods) was shown to increase the effective stiffness of the stringers of a full-scale timber bridge chord specimen. Results found from the flexural load testing of a full-scale timber bridge chord laboratory specimen are presented. Reinforcement was provided with 19 mm diameter shear spikes bonded to the wood by an epoxy resin. The bridge chord specimen was intentionally damaged to simulate degradation. Shear spikes were then installed from the top of the member into pre‑drilled holes to provide horizontal shear resistance and to improve the flexural effective stiffness. Results from the testing showed that with the insertion of five sets of shear spikes the average flexural effective stiffness recovered in the four stringers of the chord was 91.6%

Genetic characterization of HIV-1 subtype G envelope sequences by single genome analysis

Subtype G is the sixth most prevalent subtype of HIV-1 and is responsible for an estimated 1,500,000 infections worldwide. Although systematic analyses of a wide range of HIV-1 envelope sequences and neutralization have been performed, subtype G viruses are severely underrepresented in these studies. There is thus an important need to study subtype G envelope sequences and their neutralization capacities

The Kardar-Parisi-Zhang equation in the weak noise limit: Pattern formation and upper critical dimension

We extend the previously developed weak noise scheme, applied to the noisy Burgers equation in 1D, to the Kardar-Parisi-Zhang equation for a growing interface in arbitrary dimensions. By means of the Cole-Hopf transformation we show that the growth morphology can be interpreted in terms of dynamically evolving textures of localized growth modes with superimposed diffusive modes. In the Cole-Hopf representation the growth modes are static solutions to the diffusion equation and the nonlinear Schroedinger equation, subsequently boosted to finite velocity by a Galilei transformation. We discuss the dynamics of the pattern formation and, briefly, the superimposed linear modes. Implementing the stochastic interpretation we discuss kinetic transitions and in particular the properties in the pair mode or dipole sector. We find the Hurst exponent H=(3-d)/(4-d) for the random walk of growth modes in the dipole sector. Finally, applying Derrick's theorem based on constrained minimization we show that the upper critical dimension is d=4 in the sense that growth modes cease to exist above this dimension.Comment: 27 pages, 19 eps figs, revte