International Professional University of Technology in Nagoya Repository
Not a member yet
15131 research outputs found
Sort by
Annotated multisemantics to prove Non-Interference analyses
No full textInternational audienceThe way information flows into programs can be difficult to track. As non-interference is a hyperproperty relating the results of several executions of a program, showing the correctness of an analysis is quite complex. We present a framework to simplify the certification of the correction proof of such analyses. The key is capturing the non-interference property through an annotated semantics based on the execution of the program and not simply its result. The approach is illustrated using a small While language. CCS CONCEPTS • Security and privacy → Formal methods and theory of security
Sur l'efficacité des systèmes de formes normales de fonctions Booléennes
No full textNational audienceIn this paper we compare various normal form representations of Boolean functions. We extend the study of [3] pertaining to the comparison of the asymptotic efficiency of representations produced by normal form systems (NFSs). We identify some properties, such as as-sociativity, linearity, quasi-linearity and symmetry, that allow the efficiency of the corresponding NFSs to be compared. We illustrate these results by comparing well-known NFSs such as the DNF, CNF, polynomial (PNF) representations, as well as the Median Normal Form (MNF) and Sheffer Normal Form (SNF). We obtain in particular that NFSs generated by a single connective are polynomially as efficient as those generated by several connectives. As for the MNF, it is as efficient as any other NFS.Dans cet article, nous comparons différentes représen-tations des fonctions Booléennes à l'aide de systèmes de formes normales. Nous étendons les travaux de [3] sur l'étude asymptotique de l'efficacité des représentations produites par des systèmes de formes normales (Normal Form Systems–NFSs). Nous identifions certaines proprié-tés, comme l'associativité, la linéarité, la quasi-linéarité et la symétrie, qui nous permettent de comparer l'effica-cité des NFSs correspondantes. Nous illustrons ces résul-tats en comparant des NFSs usuelles telles que la DNF, CNF, les représentations polynomiales, ainsi que la forme normale médiane (MNF) et celle dite de Sheffer (SNF). Nous obtenons en particulier que les NFSs générés par un seul connecteur sont polynomialement aussi efficace que ceux générés par plusieurs. La MNF, quand à elle, est aussi efficace que n'importe quel autre système
Real-Time Selective Video Encryption based on the Chaos System in Scalable HEVC Extension
No full textInternational audienceIn this paper we propose a real-time selective video encryption solution in the scalable extension of High Effciency Video Coding(HEVC) standard, referred to as SHVC. The proposed scheme encrypts a set of sensitive SHVC parameters with a minimum delayand complexity overheads. The encryption process is performed at the CABAC binstring level and fulfils both constant bitrate andformat compliant video encryption requirements. In addition, it preserves all SHVC functionalities, including bitstream extractionfor mid-network adaptation and error resilience.We compare the performance of three selective SHVC encryption schemes: the first scheme encrypts only the lowest SHVC layer,the second encrypts all layers and the last scheme encrypts only the highest layer. The performance of the proposed schemes isassessed over different video encryption criteria, at different scalability configurations and various High Definition (HD) videosequences. Experimental results showed that encrypt only the lowest layer or all layers enables a high security level, while encryptingonly the highest layer leads to a perceptual encryption solution, by slightly decreasing the highest layer quality. Moreover, theprocessing complexity of the proposed solution is assessed in the context of a real-time SHVC decoder. The complexity overheadremains low and does not exceed 6% of the real-time decoding of SHVC video sequences
MOL 2017, the 15th Meeting on the Mathematics of Language: Proceedings of the conference
No full textInternational audienc
The GNUnet System
No full textGNUnet is an alternative network stack for building secure, decentralized and privacy-preserving distributed applications. Our goal is to replace the old insecure Internet protocol stack. Starting from an application for secure publication of files, it has grown to include all kinds of basic protocol components and applications towards the creation of a GNU internet.This habilitation provides an overview of the GNUnet architecture, including the development process, the network architecture and the software architecture. The goal of Part 1 is to provide an overview of how the various parts of the project work together today, and to then give ideas for future directions. The text is a first attempt to provide this kind of synthesis, and in return does not go into extensive technical depth on any particular topic. Part 2 then gives selected technical details based on eight publications covering many of the core components. This is a harsh selection; on the GNUnet website there are more than 50 published research papers and theses related to GNUnet, providing extensive and in-depth documentation. Finally, Part 3 gives an overview of current plans and future work
Tribocorrosion behavior of bio-functionalized highly porous titanium
No full textInternational audienceTitanium and its alloys are widely used in orthopedic and dental implants, however, some major clinical concerns such as poor wear resistance, lack of bioactivity, and bone resorption due to stress shielding are yet to be overcome. In order to improve these drawbacks, highly porous Ti samples having functionalized surfaces were developed by powder metallurgy with space holder technique followed by anodic treatment. Tribocorrosion tests were performed in 9 g/L NaCl solution using a unidirectional pin-on-disc tribometer under 3 N normal load, 1 Hz frequency and 4 mm track diameter. Open circuit potential (OCP) was measured before, during and after sliding. Worn surfaces investigated by field emission gun scanning electron microscope (FEG-SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Results suggested bio-functionalized highly porous samples presented lower tendency to corrosion under sliding against zirconia pin, mainly due to the load carrying effect given by the hard protruded oxide surfaces formed by the anodic treatment
Probabilistic Analysis of Rumor Spreading Time
No full textThe context of this work is the well studied dissemination of information in large scale distributed networks through pairwise interactions. This problem, originally called rumor mongering, and then rumor spreading has mainly been investigated in the synchronous model. This model relies on the assumption that all the nodes of the network act in synchrony, that is, at each round of the protocol, each node is allowed to contact a random neighbor. In this paper, we drop this assumption under the argument that it is not realistic in large scale systems. We thus consider the asynchronous variant, where at random times, nodes successively interact by pairs exchanging their information on the rumor. In a previous paper, we performed a study of the total number of interactions needed for all the nodes of the network to discover the rumor. While most of the existing results involve huge constants that do not allow us to compare different protocols, we provided a thorough analysis of the distribution of this total number of interactions together with its asymptotic behavior. In this paper we extend this discrete-time analysis by solving a conjecture proposed previously and we consider the continuous-time case, where a Poisson process is associated to each node to determine the instants at which interactions occur. The rumor spreading time is thus more realistic since it is the real time needed for all the nodes of the network to discover the rumor. Once again, as most of the existing results involve huge constants, we provide tight bound and equivalent of the complementary distribution of the rumor spreading time. We also give the exact asymptotic behavior of the complementary distribution of the rumor spreading time around its expected value when the number of nodes tends to infinity
The Meshfree Finite Volume Method with application to multi-phase porous media models
No full textInternational audienceNumerical methods form a cornerstone of the analysis and investigation of mathematical models for physical processes. Many classical numerical schemes rely on the application of strict meshing structures to generate accurate solutions, which in some applications are an infeasible constraint. Within this paper we outline a new meshfree numerical scheme, which we call the Meshfree Finite Volume Method (MFVM). The MFVM uses interpolants to approximate fluxes in a disjoint finite volume scheme, allowing for the accurate solution of strong-form PDEs. We present a derivation of the MFVM, and give error bounds on the spatial and temporal approximations used within the scheme. We present a wide variety of applications of the method, showing key features, and advantages over traditional meshed techniques. We close with an application of the method to a non-linear multi-phase wood drying model, showing the potential for solving numerically challenging problems
A relevant and robust vacuum-drying model applied to hardwoods
No full textInternational audienceA robust mathematical model was developed to simulate the heat and mass transfer process that evolves during vacuum-drying of four commercially important Australian native hardwood species. The hardwood species investigated were spotted gum (Corymbia citriodora), blackbutt (Eucalyptus pilularis), jarrah (Eucalyptus marginata), and messmate (Eucalyptus obliqua). These species provide a good test for the model based on their extreme diversity between wood properties and drying characteristics. The model uses boundary condition data from a series of vacuum-drying trials, which were also used to validate predictions. By using measured diffusion coefficient values to calibrate empirical formula, the accuracy of the model was greatly improved. Results of a sensitivity analysis showed that the model outputs provide excellent agreement with experimental observation despite the large range of species behaviour and variation in wood properties. This study confirms that the drying rate is significantly improved as a direct result of the enhanced convective and diffusive transfer along the board thickness. Contrary to softwood, it appears that longitudinal migration provides only a secondary effect. Not only is the model able to predict the heat and mass transfer behaviour of a range of hardwood species, it is also flexible enough to predict the behaviour for both conventional and vacuum-drying scenarios. The outcomes of this work provide the hardwood industry with a well-calibrated predictive drying tool that can be used to optimise drying schedules
An Adaptive Metamodel-Based Subset Importance Sampling approach for the assessment of the functional failure probability of a thermal-hydraulic passive system
No full textInternational audienceAn Adaptive Metamodel-Based Subset Importance Sampling (AM-SIS) approach, previously developed by the authors, is here employed to assess the (small) functional failure probability of a thermal-hydraulic (T-H) nuclear passive safety system. The approach relies on an iterative Importance Sampling (IS) scheme that efficiently couples the powerful characteristics of Subset Simulation (SS) and fast-running Artificial Neural Networks (ANNs). In particular, SS and ANNs are intelligently employed to build and progressively refine a fully nonparametric estimator of the ideal, zero-variance Importance Sampling Density (ISD), in order to: (i) increase the robustness of the failure probability estimates and (ii) decrease the number of expensive T-H simulations needed (together with the related computational burden).The performance of the approach is thoroughly compared to that of other efficient Monte Carlo (MC) techniques on a case study involving an advanced nuclear reactor cooled by helium