Experimental wooden frame house for the validation of whole building heat and moisture transfer numerical models

An experimental investigation has begun concerning the hygrothermal behaviour of wooden frame houses. The experimental set-up, consisting in a full-scale wooden frame house exposed to natural exterior climate is presented in the paper. It is located in Grenoble (South-East of France), and is equipped with over 150 sensors in order to collect a large amount of data (temperatures, relative humidity). The experimental data presented in the paper enable to get better understanding of coupled hygrothermal phenomena, and can be used to allow the validation of numerical models for heat, air and moisture transfers in wooden frame buildings. The analysed results demonstrate the importance of temperature-driven moisture diffusion from hygroscopic panelling.     

Scanning electron microscope investigations of highly conducting organic composites

Scanning electron microscope (SEM) investigation of the highly conducting organic composites of general formulae (BEDT-TTF) _x /(AuI) and (BEDT-TTF) _x /(AuI₃), where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, obtained by direct charge-transfer (CT) reaction in the solid state is performed. The granular structure of the composites with domination of three types of the grains: (BEDT-TTF)₂I₃, (BEDT-TTF)₂AuI₂ and Au, is suggested. The changes in the composite structure caused by their composition and/or thermal treatment are connected with the d.c. electrical conductivity of the samples.     

Results of the Los Alamos free-electron laser experiment

A free-electron laser (FEL) amplifier experiment to test the performance of a tapered wiggler at high optical power has been successfully completed. A well-separated two-component electron energy distribution has been obtained that is characteristic of a tapered wiggler. Energy distribution spectra and extraction efficiencies have been measured as a function of initial electron energy, energy spread, emittance, optical power, and spatial and temporal misalignments of the laser and electron beams. A maximum efficiency of ∼ 4 percent was measured, and good agreement of efficiency with a one-dimensional theory was obtained.     

Optical performance of the Los Alamos free-electron laser

During a year of oscillator experiments, the Los Alamos free-electron laser has demonstrated high-power and diffraction-limited output capabilities with a factor-of-4 wavelength tunability in the infrared. A conventional,L-band RF linear accelerator produced a 100 μs long, 2000 pulse train of 35 ps wide electron-beam pulses with peak currents to 50 A and nominal energy of 20 MeV. Small-signal gain in excess of 40 percent was generated in a 1 m, plane-polarized, uniform-period undulator for wavelengths between 9 and 11 μm. Best performance included an electron-energy extraction efficiency of 1 percent, 10 MW peak output power, and a corresponding average power of 6 kW over a 90 μs pulse train. A Strehl ratio of 0.9 characterized the output spatial beam quality. By reducing the electron energy by a factor of 2, the wavelength was tuned continuously from 9 to 35 μm.     

A second order turbulence model for the prediction of air movement and heat transfer in a ventilated room

A full-scale test room is used to investigate experimentally and numerically the velocity and temperature fields in the case of a mechanical ventilation. Detailed fields are measured for three cases of ventilation air temperature: an isothermal case, a hot case, and a cold case. The experimental data are used to test two turbulence models: a first order k-ε realizable turbulence model and a second order quadratic RSM (Reynolds Stress Model) turbulence model. The RSM model predicts the temperature and velocity fields better than the k-ε turbulence model. In particular, global values of velocity and temperature coming from experiments are in good agreement with the RSM turbulence model. This conclusion is confirmed using a turbulence analysis based on Lumley triangles.     

SEraMic: A semi-automatic method for the segmentation of grain boundaries

The SEraMic method, implemented in the SEraMic plugin for Fiji or ImageJ software, was developed to calculate a segmented image of a ceramic cross section that shows the grain boundaries. This method was used to accurately and automatically determine grain boundary positions and further assess the grain size distribution of monophasic ceramics, metals, and alloys. The only required sample preparation is polishing the cross section to a mirror-like finish. The SEraMic method is based on at least six backscattered electron scanning electron microscopy images of a unique region of interest with various tilt angles ranging from -5° to +5°, which emphasises the orientation contrasts of the grains. Because the orientation contrast varies with the incident beam angle on the sample, the set of images contains information related to all the grain boundaries. The SEraMic plugin automatically calculates and builds a segmented image of the grain boundaries from the set of tilted images. The SEraMic method was compared with classical thermal etching methods, and it was applied to determine the grain boundaries in various types of materials (oxides, phosphates, carbides, and alloys). The method remains easy to use and accurate when the average grain diameter is greater than or equal to 0.25 μm.     

Theoretical studies of UV-preionized transverse discharge KrF and ArF lasers

A theoretical model has been developed to examine the behavior of UV preionized, fast transverse discharge, rare-gas halide lasers. The model integrates the time dependent circuit equations for the discharge, the kinetic equations for the important atomic and molecular species and electrons, and the equations describing the growth of the spontaneous and stimulated emission. Results of KrF and ArF are compared with those in a companion experimental paper by Sze and Loree. The effects of various self-absorption mechanisms in the laser media are discussed, along with the possible impact of several uncertainties regarding the fundamental processes occurring in such lasers.     

Proposal for a new hybrid control strategy of a solar desiccant evaporative cooling air handling unit

Correctly controlled solar desiccant evaporative cooling is an interesting option for achieving savings in building air-conditioning consumption. The operation of this system (open loop cooling cycle) is strongly influenced by indoor and outdoor air conditions. This influence is characterized using numerical simulations. First the air conditioned room and the cooling system are simulated using a validated model of the desiccant wheel. Then the influence of each parameter of the desiccant air handling unit is evaluated. The third step is to assess the system cooling power for each operating mode with fluctuating outdoor and indoor air conditions. This allows for making relevant choices for a new control strategy taking into account both indoor and outdoor air conditions. This control strategy is tested for a whole cooling season and compared to a reference compression system with promising results, allowing for energy savings of about 40% for French climate.