Optimization of Piezoelectric Electrical Generators Powered by Random Vibrations

This paper compares the performances of a vibrationpowered electrical generators using PZT piezoelectric ceramic associated to two different power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented and implemented with a particular power conditioning circuit topology. Theoretical predictions and experimental results show that the nonlinear processing technique may increase the power harvested by a factor up to 4 compared to the Standard optimization technique. Properties of this new technique are analyzed in particular in the case of broadband, random vibrations, and compared to those of the Standard interface.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Search for the disappearance of muon antineutrinos in the NuMI neutrino beam

We report constraints on muon antineutrino oscillation parameters that were obtained by using the two MINOS detectors to measure the 7% antineutrino component of the NuMI neutrino beam. In the Far Detector, we select 130 events in the charged-current muon antineutrino sample, compared to a prediction of 136.4 +/- 11.7(stat) ^{+10.2}_{-8.9}(syst) events under the assumption |dm2bar|=2.32x10^-3 eV^2, snthetabar=1.0. A fit to the two-flavor oscillation approximation constrains |dm2bar|<3.37x10^-3 eV^2 at the 90% confidence level with snthetabar=1.0

The Magnetic Distortion Calibration System of the LHCb RICH1 Detector

The LHCb RICH1 detector uses hybrid photon detectors (HPDs) as its optical sensors. A calibration system has been constructed to provide corrections for distortions that are primarily due to external magnetic fields. We describe here the system design, construction, operation and performance.Comment: 9 pages, 14 figure

Characterization Of Epoxy-Coated Oxide Films Using Acoustic Microscopy

An adhesive joint consisting of aluminum adherends bonded with an epoxy adhesive is composed of three main layers. The adherends are usually a few millimeters thick with a layer of epoxy adhesive between one and three hundred microns thick between them. The surfaces of the adherends are typically pre-treated to produce a thin film of porous aluminum oxide, which has a honeycomb-like structure. The epoxy adhesive may then penetrate into these honeycomb cells or pores. The resulting layer between the adhesive and adherend is therefore a micro-composite and it is typically of the order of one micron in thickness. The use of the surface pre-treatment is a major factor in increasing the durability of the adhesive joint when it is exposed to water. Additionally, joints which have been in use for some time, especially ones which have been subject to environmental attack, usually experience a failure along the plane of this film. Therefore, characterization of this epoxy/oxide interlayer is very important in understanding adhesive joints and how they are affected by environmental factors. Unfortunately, not much is known about their mechanical properties

Radio emission of extensive air shower at CODALEMA: Polarization of the radio emission along the v*B vector

Cosmic rays extensive air showers (EAS) are associated with transient radio emission, which could provide an efficient new detection method of high energy cosmic rays, combining a calorimetric measurement with a high duty cycle. The CODALEMA experiment, installed at the Radio Observatory in Nancay, France, is investigating this phenomenon in the 10^17 eV region. One challenging point is the understanding of the radio emission mechanism. A first observation indicating a linear relation between the electric field produced and the cross product of the shower axis with the geomagnetic field direction has been presented (B. Revenu, this conference). We will present here other strong evidences for this linear relationship, and some hints on its physical origin.Comment: Contribution to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009. 4 pages, 8 figures. v2: Typo fixed, arxiv references adde

The relationship between auroral hiss at high altitudes over the polar caps and the substorm dynamics of aurora

Strong variations of intensity and cutoff frequency of the auroral hiss were observed by INTERBALL-2 and POLAR satellites at high altitudes, poleward from the auroral oval. The hiss intensifications are correlated with the auroral activations during substorms and/or pseudo-breakups. The low cutoff frequency of auroral hiss increases with the distance between the aurora and the satellite footprint. Multicomponent wave measurements of the hiss emissions on board the POLAR spacecraft show that the horizontal component of the Poynting flux of auroral hiss changes its direction in good accordance with longitudinal displacements of the bright auroras. The vertical component of the Poynting flux is directed upward from the aurora region, indicating that hiss could be generated by upgoing electron beams. This relationship between hiss and the aurora dynamics means that the upgoing electron beams are closely related to downgoing electron beams which produce the aurora. During the auroral activations the upgoing and downgoing beams move and change their intensities simultaneously.<br><br> <b>Keywords.</b> Magnetospheric physics (Auroral phenomena; Plasma waves and instabilities; Storms and substorms

Optimization of organized silicon nanowires growth inside porous anodic alumina template using hot wire chemical vapor deposition process

International audienceA Hot Wire assisted Chemical Vapor Deposition (HWCVD) process has been developed for producing highdensity arrays of parallel, straight and organized silicon nanowires (SiNWs) inside vertical Porous Anodic Alumina (PAA) templates, exploring temperatures ranging from 430 °C to 600 °C, and pressures varying between 2.5 and 7.5 mbar. In order to prevent parasitic amorphous silicon (a-Si) deposit and to promote the crystalline SiNWs growth, we used a tungsten hot wire to partially crack H2 into atomic hydrogen, which acts like a selective etchant regarding a-Si. Here we describe the optimization route we followed to limit the deposit of a-Si onto the surface of the porous membrane and on the walls of the pores, which led to the possibility to grow SiNWs inside the PAA membranes. Such an approach has high potentialities for device realization, like PIN junctions, FETs or electrodes for Li-ion batteries

Evidence of pervasive biologically functional secondary-structures within the genomes of eukaryotic single-stranded DNA viruses

Single-stranded DNA (ssDNA) viruses have genomes that are potentially capable of forming complex secondary-structures through Watson-Crick base-pairing between their constituent nucleotides. A few of the structural elements formed by such base-pairings are, in fact, known to have important functions during the replication of many ssDNA viruses. What is unknown, however, is (i) whether numerous additional ssDNA virus genomic structural elements predicted to exist by computational DNA folding methods actually exist, and (ii) whether those structures that do exist have any biological relevance. We therefore computationally inferred lists of the most evolutionarily conserved structures within a diverse selection of animal- and plant-infecting ssDNA viruses drawn from the families Circoviridae, Anelloviridae, Parvoviridae, Nanoviridae andGeminiviridae, and analysed these for evidence of natural selection favouring the maintenance of these structures. While we find evidence that is consistent with purifying selection being stronger at nucleotide sites that are predicted to be base-paired than it is at sites predicted to be unpaired, we also find strong associations between sites that are predicted to pair with one another and site pairs that are apparently coevolving in a complementary fashion. Collectively, these results indicate that natural selection actively preserves much of the pervasive secondary-structure that is evident within eukaryote-infecting ssDNA virus genomes and, therefore, that much of this structure is biologically functional. Lastly, we provide examples of various highly conserved but completely uncharacterised structural elements that likely have important functions within some of the ssDNA virus genomes analysed here

Air fluorescence measurements in the spectral range 300-420 nm using a 28.5 GeV electron beam

Measurements are reported of the yield and spectrum of fluorescence, excited by a 28.5 GeV electron beam, in air at a range of pressures of interest to ultra-high energy cosmic ray detectors. The wavelength range was 300 - 420 nm. System calibration has been performed using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air at 304 K the yield is 20.8 +/- 1.6 photons per MeV.Comment: 29 pages, 10 figures. Submitted to Astroparticle Physic