International Professional University of Technology in Nagoya Repository
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Tunable Power Divider With Varactors Based Schiffman Phase Shifters for Antenna Arrays Beam Steering
No full textInternational audienceA tunable power divider appropriate for beam steering phased antenna array in the Ku band is designed in this paper. Varactors based Schiffman phase shifters are added to the power divider of four elements phased array. The proposed phase shifter generates a continuous phase shift variation by adjusting only one control voltages. Thus, the power divider can be able to steer continuously its beam with a maximum steering angle of 18.8° at 12.7 GHz. Various directions of the main beam are obtained by changing the diodes voltages
Friends with Benefits: Implementing Corecursion in Foundational Proof Assistants
No full textInternational audienceWe introduce AmiCo, a tool that extends a proof assistant, Isabelle/ HOL, with flexible function definitions well beyond primitive corecursion. All definitions are certified by the assistant's inference kernel to guard against inconsistencies. A central notion is that of friends: functions that preserve the productivity of their arguments and that are allowed in corecursive call contexts. As new friends are registered, corecursion benefits by becoming more expressive. We describe this process and its implementation, from the user's specification to the synthesis of a higher-order definition to the registration of a friend. We show some substantial case studies where our approach makes a difference
Surface reconstruction by computing restricted Voronoi cells in parallel
No full textInternational audienceWe present a method for reconstructing a 3D surface triangulation from an input point set. The main component of the method is an algorithm that computes the restricted Voronoi diagram. In our specific case, it corresponds to the intersection between the 3D Voronoi diagram of the input points and a set of disks centered at the points and orthogonal to the estimated normal directions. The method does not require coherent normal orientations (just directions). Our algorithm is based on a property of the restricted Voronoi cells that leads to an embarrassingly parallel implementation. We experimented our algorithm with scanned point sets with up to 100 million vertices that were processed within few minutes on a standard computer. The complete implementation is provided
More Results on the Complexity of Domination Problems in Graphs
No full textInternational audienceGiven a graph G = (V, E) and an integer r ≥ 1, we call 'r-dominating code' any subset C of V such that every vertex in V is at distance at most r from at least one vertex in C. We investigate and locate in the complexity classes of the polynomial hierarchy, several problems linked with domination in graphs, such as, given r and G, the existence of, or search for, optimal r-dominating codes in G, or optimal r-dominating codes in G containing a subset of vertices X ⊂ V
A Transfinite Knuth-Bendix Order for Lambda-Free Higher-Order Terms
No full textInternational audienceWe generalize the Knuth-Bendix order (KBO) to higher-order terms without λ-abstraction. The restriction of this new order to first-order terms coincides with the traditional KBO. The order has many useful properties, including transitivity, the subterm property, compatibility with contexts (monotonicity), stability under substitution, and well-foundedness. Transfinite weights and argument coefficients can also be supported. The order appears promising as the basis of a higher-order superposition calculus
Fabricable Tile Decors
No full textInternational audienceRecent advances in 3D printing have made it easier to manufacture customized objects by ordinary users in an affordable manner, and therefore spurred high demand for more accessible methods for designing and fabricating 3D objects of various shapes and functionalities. In this paper we present a novel approach to model and fabricate surface-like objects composed of connected tiles, which can be used as objects in daily life, such as ornaments, covers, shades or handbags.Our method is designed to maximize the efficiency and ease of fabrication. Given a base surface and a set of tile elements as user input, our method generates a tight packing of connected tiles on the surface. We apply an efficient and tailored optimization scheme to pack the tiles on the base surface with fabrication constraints. Then, to facilitate the fabrication process, we use a novel method based on minimal spanning tree to decompose the set of connected tiles into several connected patches. Each patch is articulated and can be developed into a plane. This allows printing with an inexpensive FDM printing process without requiring any supporting structures, which are often troublesome to remove. Finally, the separately printed patches are reassembled to form the final physical object, a shell surface composed of connected user-specified tiles that take the shape of the input base surface. We demonstrate the utility of our method by modeling and fabricating a variety of objects, from simple decorative spheres to moderately complex surfaces, such as a handbag and a teddy bear. Several user controls are available, to distribute different type of tiles over the surface and locally change their scales and orientations
Communications multi-utilisateurs dans les réseaux d’accès radio centralisés : architecture, coordination et optimisation
No full textIn future mobile networks denser deployment of radio access points is planned to satisfy demand of higher throughput, but an increased number of mobile users can suffer from inter-cell interference. Fortunately, the centralization of base-band processing offered by Cloud Radio Access Network (C-RAN) architecture enables coordination and joint physical layer processing between cells. To make practical deployment of these techniques possible, we have to study C-RAN in an end-to-end view regarding several aspects: the functional architecture of a deployment, the multi-cell coordination strategy, the implementation of multi-user signal processing and possibilities for optimization to increase operational efficiency.In this thesis, first, we propose an architecture defining the placement of base-band processing functions between the distributed remote units and the central processing unit. The aim of this design is to enable multi-cell processing both on the uplink and the downlink while requiring low data rate between the involved entities. Secondly, we study how low latency coordination can be realized inside the central unit using software defined networking adapted to radio access networks. Our demonstration through a real-time prototype deployment shows the feasibility of the proposed control framework. Finally, we investigate adaptive allocation of fronthaul rate that is used for transferring quantized base-band symbols for users participating in uplink multi-cell reception in order to exploit interference between them. We propose an optimization model that includes the cost of fronthaul tranmissions and aims to maximize the gain of network operators from multi-user transmissions in C-RAN. We solve the optimization problem for different fronthaul pricing models, in a scenario where real-time and accurate channel estimates are available and in another where only channel statistics are exploited. Using our method - fitting in the architecture that we have defined - cost efficiency of fronthaul usage can be significantly improved.Dans les réseaux mobiles du future, un déploiement plus dense des points d’accés radio est prévu pour satisfaire la demande accrue de débit, mais les terminaux utilisateurs peuvent être affectés par une interférence inter-cellulaire plus forte. Par chance, la centralisation des traitements de signal en bande de base dans l’achitecture Cloud RAN (C-RAN) offre la possibilité de la coordination et du traitement conjoint de plusieurs cellules. Pour réellement permettre de déployer ces techniques, une étude bout-à-bout du CRAN est nécessaire selon plusieurs aspects, notamment l’architecture fonctionnelle, la stratégie de coordination, l’implémentation du traitement de signal multiutilisateur et les optimisations possibles pour un fonctionnement plus efficace.Dans cette thèse, nous proposons en premier une architecture qui définit le placement des fonctions du traitement en bande de base entre les unités distribuées et le serveur central. Le but de ce design est de permettre la réalisation des fonctions multi-utilisateurs en transmettant avec la moins de débit possible sur les liens de fronthaul reliant les différentes entités. Dans un second temps, nous présentons comment il est possible de coordiner les différentes cellules servies par le C-RAN en utilisant le concept de réseaux définis par logiciels adapté pour les réseaux d’accès radio. Nous avons mis en place un prototype démontrant la faisabilité de la méthode de contrôle proposée. Finalement, nous étudions l’allocation adaptative du débit sur les liens de fronthaul transportant les symboles numériques quantifiés des utilisateurs en besoin de traitement multi-cellulaire sur la voie montante pour exploiter l’interférence entre eux. Nous proposons un modèle d’optimisation qui inclut le coût des transmissions fronthaul pour maximiser ainsi le gain obtenu par l’opérateur du réseau où la communication multiutilisateur a lieu. Nous réalisons l’optimisation pour différents modèles de coût et en utilisants deux types de données: d’abord les estimations de canal supposées parfaites et disponibles en temps réel, puis seulement les statistiques du canal. Nous montrons que la méthode d’optimisation proposée permet d’exploiter plus efficacement les liens de fronthaul dans l’architecture précedemment définie
Integrating hyper-parameter uncertainties in a multi-fidelity Bayesian model for the estimation of a probability of failure
No full textInternational audienceA multi-fidelity simulator is a numerical model, in which one of the inputs controls a trade-off between the realism and the computational cost of the simulation. Our goal is to estimate the probability of exceeding a given threshold on a multi-fidelity stochastic simulator. We propose a fully Bayesian approach based on Gaussian processes to compute the posterior probability distribution of this probability. We pay special attention to the hyper-parameters of the model. Our methodology is illustrated on an academic example
Information Flow Tracking for Linux Handling Concurrent System Calls and Shared Memory
No full textInternational audienceInformation flow control can be used at the Operating System level to enforce restrictions on the diffusion of security-sensitive data. In Linux, information flow trackers are often implemented as Linux Security Modules. They can fail to monitor some indirect flows when flows occur concurrently and affect the same containers of information. Furthermore, they are not able to monitor the flows due to file mappings in memory and shared memory between processes. We first present two attacks to evade state-of-the-art LSM-based trackers. We then describe an approach, formally proved with Coq to perform information flow tracking able to cope with concurrency and in-memory flows. We demonstrate its implementability and usefulness in Rfblare, a race condition-free version of the flow tracking done by KBlare
Automatic biomechanical graph matching CT-CBCT fusion
No full textInternational audienceImage-guided hepatic surgery is progressively becoming a standard for certain interventions. However, limited dose radiation requirements result in lower quality images, making it difficult to localize tumors and other structures of interest. In this paper we propose an automatic registration method exploiting the matching of the vascular trees, visible in both pre and intra-operative images. The graphs are automatically matched using an algorithm combining a Gaussian Process Regression and biomechanical model. This process is automatic, does not require any initialization and handles large intra-operative deformations