Search results for " Cooling"
showing 10 items of 278 documents
Relating morphology to nanoscale mechanical properties: from crystalline to mesomorphic iPP
2005
Abstract A nanoindentation technique using an atomic force microscope (AFM) was applied to characterize the mechanical behaviour of several isotactic polypropylene (iPP) samples. The samples were solidified from the melt with a CCT (continuous cooling transformation) procedure spanning a wide range of cooling rates thanks to a fast quenching apparatus developed by the authors. The influence of instrumental parameters on the nanoscale mechanical properties (indentation depth, Young's modulus) shows that for modulus determination one has to rely on simpler methods of force curve analysis based on trace curve alone. Structure homogeneity up to the scale of macroscopic samples used to evaluate …
Wide Temperature Operation of 40-Gb/s 1550-nm Electroabsorption Modulated Lasers
2006
Electroabsorption modulated lasers (EMLs) exploiting the quantum confined Stark effect need thermoelectric coolers to achieve stable output power levels and dynamic extinction ratios. Temperature-independent operation is reported between 20/spl deg/C and 70/spl deg/C for InGaAlAs-InP-based monolithically integrated 1550-nm EMLs exploiting a shared active area at 40 Gb/s by actively controlling the electroabsorption modulator bias voltage. Dynamic extinction ratios of at least 8 dB and fiber-coupled mean modulated optical power of at least 0.85 mW are obtained over the mentioned temperature range.
Residual stresses in friction stir welded parts of complex geometry
2011
Residual stresses play a key role on the mechanics underlying the fatigue crack growth propagation of welded joints. Indeed, compressive residual stresses may induce a beneficial enhancement of the fatigue life under loading condition whereas tensile residual stresses may act to increase the stress distribution at crack tip, resulting in a life-threatening condition of the welded structure. In-process distortion and final geometry of welded joints are also affected by residual stresses. In this paper, the longitudinal residual stress distributions in friction stir welding (FSW) joints were investigated for butt and skin–stringer geometries, including lap and T configurations. To measure res…
Laser frequency stabilization by magnetically assisted rotation spectroscopy
2011
Abstract We present a method of Doppler-free laser frequency stabilization based on magnetically assisted rotation spectroscopy (MARS) which combines the Doppler-free velocity-selective optical pumping (VSOP) and magnetic rotation spectroscopy. The stabilization is demonstrated for the atomic rubidium transitions at 780 nm. The proposed method is largely independent of stray magnetic fields and does not require any modulation of the laser frequency. Moreover, the discussed method allows one to choose between locking the laser exactly to the line center, or with a magnetically-controlled shift to an arbitrary frequency detuned by up to several natural linewidths. This feature is useful in ma…
Electron refrigeration in hybrid structures with spin-split superconductors
2017
Electron tunneling between superconductors and normal metals has been used for an efficient refrigeration of electrons in the latter. Such cooling is a nonlinear effect and usually requires a large voltage. Here we study the electron cooling in heterostructures based on superconductors with a spin-splitting field coupled to normal metals via spin-filtering barriers. The cooling power shows a linear term in the applied voltage. This improves the coefficient of performance of electron refrigeration in the normal metal by shifting its optimum cooling to lower voltage, and also allows for cooling the spin-split superconductor by reverting the sign of the voltage. We also show how tunnel couplin…
Investigation into the gas mixing effect in ECRIS plasma using Kα and optical diagnostics
2018
Mixing a lighter gas species into the plasma of an ECRIS is known to enhance high charge state production of the heavier gas species. With this investigation, Kα diagnostics, optical emission spectroscopy and the measured charge state distribution of the extracted beam were combined to shed more light on the physics governing this phenomenon. Kα diagnostics data from two ion sources, the JYFL 14 GHz ECRIS and the GTS at iThemba LABS, are presented to gain confidence on the observed trends. The results seem to favor ion cooling as the most likely mechanism responsible for the favorable influence of the gas mixing.Mixing a lighter gas species into the plasma of an ECRIS is known to enhance hi…
Potential and limits of water-cooled Pb–17Li blankets and divertors for a fusion power plant
2000
Abstract Blankets and divertors are key components of a fusion power plant. They have a large impact on the overall plant design, its performance and availability, and on the cost of electricity. The water-cooled Pb–17Li (WCLL) blanket uses reduced activation ferritic–martensitic steel as structural material. It was previously validated under numerous aspects such as TBR, mechanical and thermo-mechanical stability, thermal–hydraulics, MHD, safety and others. This was done assuming the specifications for a European DEMOnstration reactor which were fixed back in 1989. A WCLL blanket would best be combined with a water-cooled divertor so that a single coolant could be used for the entire react…
Data fusion analysis applied to different climate change models: An application to the energy consumptions of a building office
2019
Abstract The paper aims to achieve the modelling of climate change effects on heating and cooling in the building sector, through the use of the available Intergovernmental Panel on Climate Change forecasted data. Data from several different climate models will be fused with regards to mean air temperature, wind speed and horizontal solar radiation. Several climatic models data were analysed ranging from January 2006 to December 2100. Rather than considering each model in isolation, we propose a data fusion approach for providing a robust combined model for morphing an existing weather data file. The final aim is simulating future energy use for heating and cooling of a reference building a…
Comparison between the energy performance of a ground coupled water to water heat pump system and an air to water heat pump system for heating and co…
2008
Abstract The investigation presented in this article was aimed at demonstrating the technical and economical feasibility of using ground source heat pump systems in mixed climate applications, where cooling requirements are dominant. We show an experimental comparison between a ground coupled heat pump system and a conventional air to water heat pump system, focussing at the heating and cooling energy performance. A direct comparison could be made as both systems are linked, in parallel, to the same building with exactly the same loads and climatic conditions. For a whole climatic season the results obtained show that the geothermal system saves, in terms of primary energy consumption, a 43…
Iron-clay interactions: Detailed study of the mineralogical transformation of claystone with emphasis on the formation of iron-rich T-O phyllosilicat…
2014
International audience; Iron-minerals-water interactions are of primary importance in the contexts of underground structure engineering (e.g. reactive barriers or deep geological storage) and for the understanding of secondary alteration processes in primitive meteorites. To improve our understanding of these systems, we determine the mineralogical transformations induced by the association of iron and silicates during a cooling through an experimental simulation of iron-clay interactions with a step-by-step procedure in the range of 90 degrees C to 40 degrees C. The run products and solutions are well characterised, by means of different techniques (X-ray diffraction, scanning and transmis…