Young Binary Stars and Associated Disks

The typical product of the star formation process is a binary star. Binaries have provided the first dynamical measures of the masses of pre-main-sequence (PMS) stars, providing support for the calibrations of PMS evolutionary tracks. Surprisingly, in some star-forming regions PMS binary frequencies are higher than among main-sequence solar-type stars. The difference in PMS and main-sequence binary frequencies is apparently not an evolutionary effect; recent attention has focussed on correlations between binary frequency and stellar density or cloud temperatures. Accretion disks are common among young binary stars. Binaries with separations between 1 AU and 100 AU have substantially less submillimeter emission than closer or wider binaries, suggesting that they have truncated their disks. Evidence of dynamical clearing has been seen in several binaries. Remarkably, PMS binaries of all separations show evidence of circumstellar disks and continued accretion. This suggests that the circumstellar disks are replenished from circumbinary disks or envelopes. The frequent presence of disks suggests that planet formation can occur in binary environments, and formation of planets in wide binaries is already established by their discovery. Circumbinary disk masses around very short period binaries are ample to form planetary systems such as our own. The nature of planetary systems among the most common binaries, with separations between 10 AU and 100 AU, is less clear given the observed reduction in disk mass, though they may have disk masses adequate for the formation of terrestrial-like planets.Comment: 32 pages, including 6 Postscript figures (TeX, uses psfig.sty); to appear in "Protostars & Planets IV". Gif figures with captions and high-res Postscript color figure available at http://hven.swarthmore.edu/~jensen/preprints/ppiv.htm

Optimization of the bi-oleothermal treatment process for wood preservation and fireproofing

The bi-oleothermal© process (combination of oil and heat treatment) is a well mastered alternative method for wood protection. However, the fire behavior and resistance to decay of bi-oleothermally treated wood are not good enough to ensure performance which meets the service standards for outdoor applications such as cladding or decking expected by the market. The aim of the present research project has been to improve this performance by optimizing the linseed oil formulations used at the impregnation stage. Different formulations combining linseed oil, fungicides, insecticides and/or fire retardants were tested under laboratory conditions in order to assess the resistance of oil-treated wood to molds, decay fungi, longhorn beetles, subterranean termites and fire. The results showed that the investigated biological organisms exhibit different levels of susceptibility to oil based formulations. Additionally, the collected data suggested that some inhibition processes might occur between the oil and the active ingredients, lowering the biocide effect of the final formulation. Subsequently, chemical analyses were performed in order to identify the active ingredients both in the oil formulations used for the second bath and inside the treated wood. The measured concentrations of active ingredients were then compared to the expected target values to determine the possible fate of the biocides in the oil formulations (degradation, migration into wood, interaction between the different components). (Résumé d'auteur

Linear Haskell: practical linearity in a higher-order polymorphic language

Linear type systems have a long and storied history, but not a clear path forward to integrate with existing languages such as OCaml or Haskell. In this paper, we study a linear type system designed with two crucial properties in mind: backwards-compatibility and code reuse across linear and non-linear users of a library. Only then can the benefits of linear types permeate conventional functional programming. Rather than bifurcate types into linear and non-linear counterparts, we instead attach linearity to function arrows. Linear functions can receive inputs from linearly-bound values, but can also operate over unrestricted, regular values. To demonstrate the efficacy of our linear type system - both how easy it can be integrated in an existing language implementation and how streamlined it makes it to write programs with linear types - we implemented our type system in GHC, the leading Haskell compiler, and demonstrate two kinds of applications of linear types: mutable data with pure interfaces; and enforcing protocols in I/O-performing functions

Lidar Measurement Bias Estimation via Return Waveform Modelling in a Context of 3D Mapping

In a context of 3D mapping, it is very important to get accurate measurements from sensors. In particular, Light Detection And Ranging (LIDAR) measurements are typically treated as a zero-mean Gaussian distribution. We show that this assumption leads to predictable localisation drifts, especially when a bias related to measuring obstacles with high incidence angles is not taken into consideration. Moreover, we present a way to physically understand and model this bias, which generalises to multiple sensors. Using an experimental setup, we measured the bias of the Sick LMS151, Velodyne HDL-32E, and Robosense RS-LiDAR-16 as a function of depth and incidence angle, and showed that the bias can go up to 20 cm for high incidence angles. We then used our modelisations to remove the bias from the measurements, leading to more accurate maps and a reduced localisation drift.Comment: IEEE Copyrights: 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work

Metastable states of a flux line lattice studied by transport and Small Angle Neutron Scattering

Flux Lines Lattice (FLL) states have been studied using transport measurements and Small Angle Neutron Scattering in low T$_c$ materials. In Pb-In, the bulk dislocations in the FLL do not influence the transport properties. In Fe doped NbSe$_{2}$, transport properties can differ after a Field Cooling (FC) or a Zero Field Cooling (ZFC) procedure, as previously reported. The ZFC FLL is found ordered with narrow Bragg Peaks and is linked to a linear V(I) curve and to a superficial critical current. The FC FLL pattern exhibits two Bragg peaks and the corresponding V(I) curve shows a S-shape. This can be explained by the coexistence of two ordered FLL slightly tilted from the applied field direction by different superficial currents. These currents are wiped out when the transport current is increased.Comment: accepted for publication in Phys. Rev.

A new optical set-up for on-line following up the crystallization of polymers at high cooling rates

International audienceA new experimental procedure, named " Polymer High Cooling - Optics " and whose performance has been improved, is presented. It allows us to monitor on-line the quiescent crystallization of a polymer film under high and constant cooling rates. With such a set-up, two cooling control modes are available resulting into a range of relatively moderate (from 30 to 500°C/min) and a range of high (from 500 to 1600°C/min) constant cooling rates. The crystallization experiments are observed by polarized light microscopy. Preliminary results are presented. They are obtained on the α-modification of one industrial grade of isotactic polypropylene, under relatively moderate constant cooling rates. Two relevant crystallization parameters are captured, the temperature of crystallization together with the spherulitic growth kinetics versus cooling rate. Accurate data are obtained. As well, they are in good agreement with comparable literature results compiled by Janeschitz-Kriegl [Macromolecules, 2006]. The obtained results seem to match the Hoffman and Lauritzen theory. These discussions validate our " Polymer High Cooling - Optics " set-up in relatively moderate constant cooling rates. Next step is to demonstrate the suitability of this first generation set-up for higher constant cooling rates

Why pinning by surface irregularities can explain the peak effect in transport properties and neutron diffraction results in NbSe2 and Bi-2212 crystals?

The existence of a peak effect in transport properties (a maximum of the critical current as function of magnetic field) is a well-known but still intriguing feature of type II superconductors such as NbSe2 and Bi-2212. Using a model of pinning by surface irregularities in anisotropic superconductors, we have developed a calculation of the critical current which allows estimating quantitatively the critical current in both the high critical current phase and in the low critical current phase. The only adjustable parameter of this model is the angle of the vortices at the surface. The agreement between the measurements and the model is really very impressive. In this framework, the anomalous dynamical properties close to the peak effect is due to co-existence of two different vortex states with different critical currents. Recent neutron diffraction data in NbSe2 crystals in presence of transport current support this point of view