Induction in a von Karman flow driven by ferromagnetic impellers

We study magnetohydrodynamics in a von K\'arm\'an flow driven by the rotation of impellers made of material with varying electrical conductivity and magnetic permeability. Gallium is the working fluid and magnetic Reynolds numbers of order unity are achieved. We find that specific induction effects arise when the impeller's electric and magnetic characteristics differ from that of the fluid. Implications in regards to the VKS dynamo are discussed.Comment: 14 pages, 7 figure

Testing Lorentz symmetry with Lunar Laser Ranging

Lorentz symmetry violations can be parametrized by an effective field theory framework that contains both general relativity and the standard model of particle physics called the standard-model extension (SME). We present new constraints on pure gravity SME coefficients obtained by analyzing lunar laser ranging (LLR) observations. We use a new numerical lunar ephemeris computed in the SME framework and we perform a LLR data analysis using a set of 20721 normal points covering the period of August, 1969 to December, 2013. We emphasize that linear combination of SME coefficients to which LLR data are sensitive and not the same as those fitted in previous postfit residuals analysis using LLR observations and based on theoretical grounds. We found no evidence for Lorentz violation at the level of $10^{-8}$ for $\bar{s}^{TX}$, $10^{-12}$ for $\bar{s}^{XY}$ and $\bar{s}^{XZ}$, $10^{-11}$ for $\bar{s}^{XX}-\bar{s}^{YY}$ and $\bar{s}^{XX}+\bar{s}^{YY}-2\bar{s}^{ZZ}-4.5\bar{s}^{YZ}$ and $10^{-9}$ for $\bar{s}^{TY}+0.43\bar{s}^{TZ}$. We improve previous constraints on SME coefficient by a factor up to 5 and 800 compared to postfit residuals analysis of respectively binary pulsars and LLR observations

Coil Quick (RV Sewer Hose Compressor) Device

The purpose of this design project is to design, build, and test an RV sewer hose compactor device that can be used by the project sponsor and marketed to other RV owners. The goal of the RV sewer hose compactor device is to mechanically compress an RV sewer hose from its fully extended length to its fully compressed and storable state. Since a prototype device has already been developed, this project will aim to improve the prototype design to make it smaller, quicker, quieter, and more durable. Additionally, we improved the device to make it more user friendly and have better performance. The project introduction, research, and objectives included in this document define the requirements of this project and the approach taken to fulfill them. The concept design section illustrates the process taken to refine and select a final design and presents the chosen design direction. There is a final design section which describes the structural prototype design. The manufacturing section outlines how we built the structural prototype. The design verification section illustrates our testing of the structural prototype

Electron transport through a metal-molecule-metal junction

Molecules of bisthiolterthiophene have been adsorbed on the two facing gold electrodes of a mechanically controllable break junction in order to form metal-molecule(s)-metal junctions. Current-voltage (I-V) characteristics have been recorded at room temperature. Zero bias conductances were measured in the 10-100 nS range and different kinds of non-linear I-V curves with step-like features were reproducibly obtained. Switching between different kinds of I-V curves could be induced by varying the distance between the two metallic electrodes. The experimental results are discussed within the framework of tunneling transport models explicitly taking into account the discrete nature of the electronic spectrum of the molecule.Comment: 12 pages, 12 figures to appear in Phys. Rev. B 59(19) 199

Analysis of Multijunction solar cells: Electroluminescence study

This paper describes the principle of the study which is based on electroluminescence to extract the parameters characterizing the recombination centers induced by irradiation in a solar cell. This technique is able to provide direct information on each individual junction constituting the multijonctions. The results are compared with those obtained by electrical methods.This paper describes the principle of the study which is based on electroluminescence to extract the parameters characterizing the recombination centers induced by irradiation in a solar cell. This technique is able to provide direct information on each individual junction constituting the multijonctions. The results are compared with those obtained by electrical methods

Turbulent transport of material particles: An experimental study of finite size effects

We use an acoustic Lagrangian tracking technique, particularly adapted to measurements in open flows, and a versatile material particles generator (in the form of soap bubbles with adjustable size and density) to characterize Lagrangian statistics of finite sized, neutrally bouyant, particles transported in an isotropic turbulent flow of air. We vary the size of the particles in a range corresponding to turbulent inertial scales and explore how the turbulent forcing experienced by the particles depends on their size. We show that, while the global shape of the intermittent acceleration probability density function does not depend significantly on particle size, the acceleration variance of the particles decreases as they become larger in agreement with the classical scaling for the spectrum of Eulerian pressure fluctuations in the carrier flow

Preferential Concentration of Free-Falling Heavy Particles in Turbulence

We present a sweep-stick mechanism for heavy particles transported by a turbulent flow under the action of gravity. Direct numerical simulations show that these particles preferentially explore regions of the flow with close to zero Lagrangian acceleration. However, the actual Lagrangian acceleration of the fluid elements where particles accumulate is not zero, and has a dependence on the Stokes number, the gravity acceleration, and the settling velocity of the particles.Fil: Falkinhoff, F.. Universidad de Buenos Aires; Argentina. Universite Lyon 2; FranciaFil: Obligado, M.. Centre National de la Recherche Scientifique; FranciaFil: Bourgoin, M.. Universite Lyon 2; FranciaFil: Mininni, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin