Polytechnic Nantes

Nantes, France

Polytechnic Nantes

Nantes, France
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Kraniotis D.,Norwegian Institute of Wood Technology | Langouet N.,Polytechnic Nantes | Orskaug T.,Norwegian Institute of Wood Technology | Nore K.,Norwegian Institute of Wood Technology | Glaso G.,Norwegian Institute of Wood Technology
WCTE 2016 - World Conference on Timber Engineering | Year: 2016

The capacity of hygrothermal materials to buffer the maxima and minima of relative humidity indoors has been discussed and presented during the last years. In particular, the wooden surfaces have the potential to contribute to the reduction of the mechanical ventilation loads and consequently to the energy demand and consumption. In this paper, the hygrothermal performance of a wood-based prefabricated insulating sandwich panel is under investigation. Thermography techniques are employed to monitor the increase of interior surface temperature (3 °C) of the panel when water vapour migrate to the wooden structure. A hygrothermal simulation tool is used and the results are compared with the experimental data. The results show that the temperature increases in the whole inner solid wood component, contributing to reducing the conductive heat losses. Furthermore, state-of-the-art equations are used to quantify the latent heat of sorption in the solid wood. The mathematical calculations show that heat of sorption can counterbalance up to 37.1% of the conductive heat losses through opaque elements during a winter day. Finally, the potential of using the sandwich panel for rehabilitation purposes is presented.

Ammar M.,Artemis | Mitrea M.,Artemis | Boujelben I.,Artemis | Caller P.L.,Polytechnic Nantes
Human Vision and Electronic Imaging 2016, HVEI 2016 | Year: 2016

This paper investigates whether the information related to the human visual saliency is still preserved at the level of the HEVC compressed stream syntax elements. In this respect, a new saliency model, matched to the peculiarities of this emerging standard is defined. It consists of four elementary maps, describing the four main saliency features: intensity, color, orientation and motion. These maps arc defined based on the energies of the luma and chroma coefficients, on the variations of the intra prediction modes and on the energy of motion vectors, respectively. They are ftisioned according to 48 static and static-dynamic pooling formulas. The results are compared to three state-of-the-art uncompressed (pixel) domain as well as to the MPEG-4 AVC compressed domain saliency maps. It is brought to light that the HEVC saliency model outperforms (with singular exceptions) the state-of-the-art uncompressed domain and is as good as MPEG-4 AVC saliency model. We can thus state that, as its MPEG-4 AVC ancestor, although not designed based upon visual saliency principles, the HEVC compression standard preserves this human visual property at the level of its syntax elements.

Faure O.,Institute francais des science et technologies des transports des amenagements et des reseaux Ifsttar | Gauvreau B.,Institute francais des science et technologies des transports des amenagements et des reseaux Ifsttar | Junker F.,Électricité de France | Lafon P.,Institute francais des science et technologies des transports des amenagements et des reseaux Ifsttar | Bourlier C.,Polytechnic Nantes
Applied Acoustics | Year: 2017

Natural grounds can exhibit small scale geometric irregularities, compared to the acoustic wavelength, known as ground roughness. This roughness has a noticeable effect on sound pressure levels and produces a surface wave. In the context of prediction methods improvement for outdoor sound propagation, using an effective impedance appears to be an useful approach to model the effects of surface roughness. Two time-domain numerical methods are considered: finite difference schemes (FDTD), and the transmission line modeling (TLM) method. An effective impedance model for random ground roughness defined by a roughness spectrum, called the SPM model, is exposed. The efficiency of this model for taking into account the mean effects of random roughness on sound pressure levels and for modeling the roughness-induced surface wave is shown, by comparing with results of TLM simulations of propagation above random rough grounds. The direct implementation of the SPM model as a boundary condition in both TLM and FDTD methods is then studied. This approach allows the modeling of ground roughness effects in numerical methods without having to mesh finely the ground roughness profile, allowing easier and faster computations, and more accurate predictions for future impact studies in environmental acoustics. © 2016 Elsevier Ltd

Dahmen M.,Fraunhofer Institute for Laser Technology | Lindner S.,Outokumpu | Monfort D.,Polytechnic Nantes | Petring D.,Fraunhofer Institute for Laser Technology
Physics Procedia | Year: 2016

The increasing demand for ultra-high strength steels in vehicle manufacturing leads to the application of new alloys. This poses a challenge on joining especially by fusion welding. A stainless high manganese steel sheet with excellent strength and deformation properties stands in the centre of the development. Similar and dissimilar welds with a metastable austenitic steel and a hot formed martensitic stainless steel were performed. An investigation of the mixing effects on the local microstructure and the hardness delivers the metallurgical features of the welds. Despite of carbon contents above 0.4 wt.% none of the welds have shown cracks. Mechanical properties drawn from tensile tests deliver high breaking forces enabling a high stiffness of the joints. The results show the potential for the application of laser beam welding for joining in assembly of structural parts. © 2016 The Authors.

Bolteau S.,Energi and Kylanalys AB | Rogstam J.,Energi and Kylanalys AB | Tazi M.,Polytechnic Nantes
Refrigeration Science and Technology | Year: 2016

Ice rinks have a high coinciding cooling and heating demand which turns them into ideal heat recovery applications. Using carbon dioxide (CO2) as a refrigerant in a trans-critical refrigeration system allows the ice rink to be self-sufficient in terms of heat. High temperatures can be supplied which in combination with a suitable heating system design can result in very high heat recovery performance. This study is based on the system solution used in the Gimo ice rink, first of its kind in Europe, using a 100% CO2 trans-critical system, with direct expansion. This system is designed with a temperature cascade on the heat recovery side to fit the CO2 properties. This implies a low return temperature from the heating system to increase the sub-cooling and thus the system efficiency. To further improve efficiency and the return from the heat recovery system a geothermal storage equips the installation as well. A numerical model has been created using real data from the field which allows to compare actual operating parameters with the desired optimal values. The aim is to find the optimum control of the head pressure and the sub-cooling to reach the maximum overall efficiency at all conditions. The results suggests that the heat recovery coefficient of performance is in the range 3.5-4, which is in line with or exceeds most conventional heat pumps considering the relatively high supply temperature of 60°C. An advantage is that this system solution does not need supplementary heat or heating equipment - one system covers the complete refrigeration and heating function. © 2016, International Institute of Refrigeration. All rights reserved.

Paseta L.,University of Zaragoza | Potier G.,Polytechnic Nantes | Abbott S.,Abbott Laboratories | Abbott S.,University of Leeds | Coronas J.,University of Zaragoza
Organic and Biomolecular Chemistry | Year: 2015

Hansen solubility parameters (HSP) have found their greatest use in the evaluation of solvent-polymer chemical interactions. Given their great interest among the scientific community, host-guest interactions in metal-organic frameworks (MOFs), with organic and inorganic moieties, could benefit from a HSP approach. In this work we have initiated the application of HSP to the study of caffeine encapsulation in MOFs ZIF-8 and NH2-MIL-88B(Fe). However, the availability of HSP for MOFs is nearly zero. As a first step to evaluating the potential of HSP for rational design we have made the simplifying assumption that the HSP distance of the caffeine-ligand interaction (i.e. ignoring the metal and the MOF structure) dominates the ability to form a MOF host-guest system. Although much work remains to be done, the first indications are that this approach has much potential. © The Royal Society of Chemistry 2015.

Paseta L.,University of Zaragoza | Potier G.,Polytechnic Nantes | Sorribas S.,University of Zaragoza | Sorribas S.,University of Manchester | Coronas J.,University of Zaragoza
ACS Sustainable Chemistry and Engineering | Year: 2016

Besides the substitution or minimization of the use of harmful solvents, one essential goal of chemistry is to try to avoid their use altogether whenever possible. In the case of the synthesis of MOFs (metal-organic frameworks), this can only be achieved by finding alternatives to conventional processes. An example is the approach described here which involves working at high pressure (at 0.31 GPa) without using a solvent. This has evident advantages over mechanochemical synthesis by grinding or milling (also a solventless process) where the sample is submitted to attrition. The present paper reports the simple high pressure synthesis of the ZIF (zeolitic imizadolate framework) ZIF-8. This methodology enables fast synthesis of MOF materials and offers new insights into their industrial implementation. In addition, this technique could be applied to the synthesis of other MOFs and even COFs (covalent organic frameworks). © 2016 American Chemical Society.

Rasilo P.,Aalto University | Rasilo P.,Ghent University | Lemesle M.-A.,Polytechnic Nantes | Belahcen A.,Aalto University | And 2 more authors.
IEEE Transactions on Energy Conversion | Year: 2014

An interior permanent-magnet (PM) motor is modeled by a combined analytical-numerical approach, in which the relationships between the stator currents and flux linkages are identified with static finite-element (FE) analysis. In addition to the previous approaches using the current space vector as the state variable, new models are also developed using the flux-linkage space vector, which leads to more convenient time-integration of the voltage equations. In order to account for the zero-sequence effects in delta connection, the models also include either the zero-sequence flux or current as an additional state variable. Finally, the possibilities of deriving the required quantities as partial derivatives of the magnetic field energy are discussed. The energy-based approaches avoid inaccuracies related to torque computation and thus allow better satisfying the power balance in the state-space model. We show the ability of the developed state-space models to predict the currents and torque equally to a nonlinear time-stepping FE model with much less computational burden. The results are validated by means of measurements for a prototype machine in both star and delta connections. In addition, we also demonstrate the effect of the zero-sequence current on the torque ripple in case of a delta-connected stator winding. © 1986-2012 IEEE.

Battisti F.,Third University of Rome | Bosc E.,Polytechnic Nantes | Carli M.,Third University of Rome | Le Callet P.,Polytechnic Nantes | Perugia S.,Third University of Rome
Signal Processing: Image Communication | Year: 2015

Depth-Image-Based-Rendering (DIBR) techniques are essential for three-dimensional (3D) video applications such as 3D Television (3DTV) and Free-Viewpoint Video. However, this process is based on 3D warping and can induce serious distortions whose impact on the perceived quality is far different from the one experienced in the 2D imaging processes. Since quality evaluation of DIBR-synthesized views is fundamental for the design of perceptually friendly 3D video systems, an appropriate objective quality metric targeting the assessment of DIBR-synthesized views is momentous. Most of the 2D objective quality metrics fail in assessing the visual quality of DIBR-synthesized views because they have not been conceived for addressing the specificities of DIBR-related distortions. In this paper, a new full-reference objective quality metric, 3DSwIM (3D Synthesized view Image Quality Metric), dedicated to artifacts detection in DIBR-synthesized view-points is presented. The proposed scheme relies on a comparison of statistical features of wavelet subbands of two input images: the original image and the DIBR-based synthesized image. A registration step is included before the comparison step so that best matching blocks are always compared to ensure "shifting-resilience". In addition, a skin detection step weights the final quality score in order to penalize distorted blocks containing "skin-pixels" based on the assumption that a human observer is most sensitive to impairments affecting human subjects. Experimental tests show that the proposed method outperforms the conventional 2D and DIBR-dedicated quality metrics under test. © 2014 Elsevier B.V. Al lrights reserved.

Andriyana A.,University of Malaya | Ch'ng S.Y.,University of Selangor | Brulliard V.,CNRS Research Institute in Civil Engineering and Mechanics | Verron E.,CNRS Research Institute in Civil Engineering and Mechanics | Le Corre S.,Polytechnic Nantes
Constitutive Models for Rubber IX - Proceedings of the 9th European Conference on Constitutive Models for Rubbers, ECCMR | Year: 2015

Elastomer is a unique material capable to absorb fluid molecule when in contact with liquid. In this case, the incorporation of filler such as carbon black into elastomers is known to increase their network stiffness and hence restrict the resulting amount of equilibrium swelling exhibited by the elastomers. However, when the elastomers are simultaneously subjected to complex mechanical loading, the role of filler in the corresponding coupled mechanical deformation-liquid diffusion in elastomers is not well established. The present contribution focuses on the development of a continuum model to predict the equilibrium swelling of carbon black filled elastomers in solvents in the presence of static mechanical deformation. To this end, the fluid-solid mixture is viewed as a single, homogenized continuum body. The proposed model is implemented into commercial finite element analysis software ABAQUS to simulate the equilibrium swelling of elastomers in the absence (stress-free swelling) and in the presence (constrained swelling) of mechanical loading. It is shown that the model gives a qualitatively good agreement with experimental observations. © 2015 Taylor and Francis Group.

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