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Although the unconventional gas has accounted for 40% of the recoverable resource of natural gas, its production contributed only 14% of nature gas supply in 2010. This share of unconventional gas in nature gas provision is expected to rise to 21% and 32% in 2020 and 2035, respectively [1]. To predict the gas permeability through ultra-tight porous media, gas rarefaction effect which enhances permeability should be taken into account. In this work, gas flows through samples of porous media are directly simulated by solving the BGK kinetic equation [2] using Discrete Velocity Method (DVM) and lattice Boltzmann method (LBM) for a wide range of the Knudsen number. While the LBM cannot capture rarefaction effect, the results indicate that the resolution of the velocity grid has little influence on the DVM results for complex geometry, even in the free molecular flow regime.

Colloque avec actes et comité de lecture. Internationale.; International audience; In micro-devices the equivalent mean free path of the gas molecules can be of the same order as the characteristic dimension of these devices. In this case the fluid can be considered to be under rarefied conditions and it cannot be treated as a continuum medium as it usually done by classic fluid mechanics. Depending on their level of rarefaction, micro gas flows often require modeling by means of molecular based approaches. Gas rarefaction induces macroscopic non-equilibrium effects at the interface between gas and solid surfaces for the gas macroscopic parameters, such as viscous and thermal slip and temperature jump at the wall, for the gas velocity and its temperature, respectively. These non-equilibrium phenomena are affected by the specific configuration of the surface of the micro-device, such as surface roughness and materials, and the molecular structure of the gas considered. At the current state of the art, experimental observation on rarefied gas flows is generally limited to stationary flow configurations. Very little experimental efforts on transient rarefied flows have been conducted so far. Our work focuses on the experimental and numerical analysis of time-dependent isothermal rarefied gas flows through a long metallic micro-tube. The experimental methodology was conceived on the basis of the constant volume technique and adapted to measure the evolution with time of a transient mass flow rate through a micro-tube. Furthermore, the characteristic time of each experiment, extracted from the pressure measurements in each reservoir, offered a clear indication on the dynamics of the transient flow as a function of the gas molecular mass and its rarefaction level. Moreover we present an original methodology to extract stationary mass flow rates by using the tube conductance, which can be associated to the characteristic time of the experiment, measured for different mean pressures between two tanks. The measured conductance of the tube and the stationary mass flow rate at the inlet and outlet of the micro-tube was compared to numerical results obtained with the BGK linearized kinetic equation model. The results were obtained in a wide range of rarefaction conditions for nitrogen N2.

In a recent paper by Lasseux, Vald\'{e}s-Parada and Porter (J.~Fluid~Mech. \textbf{805} (2016) 118-146), it is found that the apparent gas permeability of the porous media is a nonlinear function of the Knudsen number. However, this result is highly questionable, because the adopted Navier-Stokes equations and the first-order velocity-slip boundary condition are first-order (in terms of the Knudsen number) approximations of the Boltzmann equation and the kinetic boundary condition for rarefied gas flows. Our numerical simulations based on the Bhatnagar-Gross-Krook kinetic equation and regularized 20-moment equations prove that the Navier-Stokes equations with the first-order velocity-slip boundary condition are only accurate at a very small Knudsen number limit, where the apparent gas permeability is a linear function of the Knudsen number., Comment: a comment paper regarding the application range of the Navier-Stokes equation with the first-order velocity-slip boundary condition in porous media

This paper presents research results on improvement of grading process in the footwear industry, a new grading software which is suitable to manufacturing practices, can reduce deviation and increase productivity in the grading process in comparison with the manual method. According to statistical data of the Ministry of Industry and Trade, the footwear export turnover of the country amounts to $3.56 billions in 2006, exceeding the plan ($3.35 billions) by 6.1%. Vietnam footwear industry is currently the third export earner after petroleum and garment. The projected export turnover in 2010 is $6.5 billions, with the annual increase of 20%. The goal in 2010 is the production of 720 millions of footwear pairs, 80.7 million of bags and 80 sq. meters of tanned leather, which together constitute the industry export turnover of $6.5 billions. The said objectives make indispensable the application CAD/CAM in new technology and modern equipment. Shoes grading is the first component of the CAD/CAM material cutting process in footwear industry. In developed countries shoes grading is performed using specialized software of well-known brands like Lectra RomanCad of Lectra, SCS of Palmel. The said software's are however packaged into integrated systems of high cost. Currently, only a few of Vietnamese footwear companies can afford foreign made shoes grading software. For this reason local CAD/CAM systems in general and shoes grading software in particular are urgently required for having technology upgraded and fabrication equipment modernized.

Ubiquitous computing refers to providing a global computing service where the user access seamlessly resources. User tracking is one of the most important location-aware applications for maintaining the service even with the users' mobility.Unlike outdoor localization technologies like GPS, indoor localization systems have to encounter many problems such as interferences from external sources, low cost and low latency infrastructure requirements, and high accuracy in a limited space.Our localization approaches associate with technologies that are currently equipped in mobile devices, including NFC technology and inertial sensors and Wireless LAN. The aim of this thesis is to design simple and effective architecture ensuring two requirements: a high accuracy and an adaptation to the multiple scenarios. Therefore, our proposed system does not address to the fingerprint technique and learning machine algorithms. In this thesis, we propose three approaches as follows:- The NFC-tagging approach is an instant on-the-spot localization with almost zero-latency- A combination of accelerometer and magnetometer in the sensors-based approach permits to characterize the user's movement- The signal-strength-based approach using the similarity of radio conditions between the neighbors can update in real time the radio map for long period localization.We analyze the performance of the proposed approaches based on rigorous simulation and experimentation tests. We then implement the proposed approaches in a wireless testbed with Android smartphone. Although the implementation is not a final product, the current application can be used to evaluate the feasibility and the performance of the proposed approaches., L'objectif de nos travaux de recherche est de concevoir une architecture simple et efficace veiller à deux exigences suivantes: une grande précision (au niveau de la pièce) ; une adaptation aux plusieurs scénarios. La thèse contribue aux études pour les systèmes de localisation en intérieur en combinant des approches basées sur la caractérisation de mouvement, la communication courte portée et de l'intensité du signal. La combinaison de ces approches proposées permettent de minimiser la défaillance de chacune approche. En effet, notre système de localisation propose une combinaison des technologies qui sont actuellement équipé en terminaux mobiles, y compris la technologie de WLAN, NFC et des capteurs (accéléromètre et magnétomètre). Voici nos trois approches proposées : Premièrement, nous proposons l'approche basée sur NFC-étiquetage qui fournit un service simple et efficace pour une localisation en intérieur. En touchant une étiquette disséminées dans l'environnement intérieur, l'utilisateur peut connaître sa position réelle qui est même à celle d’étiquette. Cette approche est très pratique car la localisation se fait automatiquement en approchant le terminal mobile de l'utilisateur à l’étiquette. L'approche basée sur NFC-étiquetage, cependant, nécessite l'intervention régulière de l'utilisateur qui n'est pas prédictive et donc peut poser des problèmes sur la validité des informations. Alors, l'information de localisation n’est fiable que dans un certain intervalle de temps depuis le dernier étiquetage. La valeur de cet intervalle de temps (ex. t secondes) sera ajustée selon les scénarios de déploiement. Deuxièmement, nous améliorons la qualité de l'approche précédente en développant la deuxième approche basée sur des capteurs qui combine l'accéléromètre et le magnétomètre pour estimer la distance de déplacement de l'utilisateur. Avec l'objectif de permettre à l'utilisateur de tenir son terminal mobile commodément dans la main (multi-positions), la deuxième approche fournit un service de localisation caractérisant le degré de mouvement à l'utilisateur pour déterminer si l'utilisateur est au même endroit depuis le dernier étiquetage. Pour une longue trajectoire, cette approche permet de détecter que l'utilisateur a déjà déplacé à un autre endroit. Finalement, afin de surmonter les inconvénients de deux approches précédentes, nous proposons la troisième approche basée sur l'intensité du signal en utilisant la similarité des conditions radio entre proches voisins. Nous proposons une combinaison de la technologie NFC et WLAN pour construire la cartographie d'intensité du signal. La communication à courte portée NFC permet au système d’obtenir correctement les informations de position. Cette combinaison peut récupérer les données de l'intensité du signal radio à et les attribuer à une position connue sur la cartographie, sans exiger de phases hors ligne pour enregistrer l'intensité du signal radio.

A progressive die is an effective tool for efficient and economical production of sheet metal parts in large quantities. Nowadays, progressive die designers still spend much of their time on choosing better layouts among feasible ones. This study employs Pro/Web.Link, Hyper Text Markup Language (HTML) and JavaScript to develop an application which helps evaluate automatically strip layouts in Pro/Engineer software environment. This paper proposes solutions for calculating total evaluation score of the strip layout based on four factors: station number factor, moment balancing factor, strip stability factor and feed height factor.

International audience

Dans ce rapport, nous présentons la mise en oeuvre d'un service contextuel et multimodal, permettant la diffusion d'information dans les musées. Ce service proactif (1) capture des profils de visiteurs se trouvant dans le même voisinage physique, (2) réalise l'adaptation de l'information en fonction de l'utilisateur visé, et enfin (3) distribue automatiquement les informations vers différents équipements, des guides électroniques utilisés par les visiteurs jusqu'aux écrans d'affichage disséminés dans le musée.