Trust-based security for the OLSR routing protocol

The trust is always present implicitly in the protocols based on cooperation, in particular, between the entities involved in routing operations in Ad hoc networks. Indeed, as the wireless range of such nodes is limited, the nodes mutually cooperate with their neighbors in order to extend the remote nodes and the entire network. In our work, we are interested by trust as security solution for OLSR protocol. This approach fits particularly with characteristics of ad hoc networks. Moreover, the explicit trust management allows entities to reason with and about trust, and to take decisions regarding other entities.In this paper, we detail the techniques and the contributions in trust-based security in OLSR. We present trust-based analysis of the OLSR protocol using trust specification language, and we show how trust-based reasoning can allow each node to evaluate the behavior of the other nodes. After the detection of misbehaving nodes, we propose solutions of prevention and countermeasures to resolve the situations of inconsistency, and counter the malicious nodes. We demonstrate the effectiveness of our solution taking different simulated attacks scenarios. Our approach brings few modifications and is still compatible with the bare OLSR.     

Combining FDI and AI approaches within causal-model-based diagnosis.

This paper presents a model-based diagnostic method designed in the context of process supervision. It has been inspired by both artificial intelligence and control theory. AI contributes tools for qualitative modeling, including causal modeling, whose aim is to split a complex process into elementary submodels. Control theory, within the framework of fault detection and isolation (FDI), provides numerical models for generating and testing residuals, and for taking into account inaccuracies in the model, unknown disturbances and noise. Consistency-based reasoning provides a logical foundation for diagnostic reasoning and clarifies fundamental assumptions, such as single fault and exoneration. The diagnostic method presented in the paper benefits from the advantages of all these approaches. Causal modeling enables the method to focus on sufficient relations for fault isolation, which avoids combinatorial explosion. Moreover, it allows the model to be modified easily without changing any aspect of the diagnostic algorithm. The numerical submodels that are used to detect inconsistency benefit from the precise quantitative analysis of the FDI approach. The FDI models are studied in order to link this method with DX component-oriented reasoning. The recursive on-line use of this algorithm is explained and the concept of local exoneration is introduced.     

Linear amphiphilic diblock copolymers of lactide and 2-dimethylaminoethyl methacrylate using bifunctional-initiator and one-pot approaches

Linear amphiphilic diblock copolymers of polylactide (PLA) and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) were synthesized by atom transfer radical polymerization (ATRP) of DMAEMA followed by ring-opening polymerization (ROP) of LLA using the bifunctional initiator, 2′-hydroxyethyl 2-bromoisobutyrate. NMR showed that the resulting PLA block was racemic and a quaternization/precipitation technique showed that there were significant amounts of racemic PLA homopolymer. In addition, simultaneous ATRP of DMAEMA and ROP of l-lactide by tin octoate were conducted at varied temperatures, indicating 90 °C as a suitable compromise temperature; this one-pot process also led to racemization and P(L)LA homopolymer. The racemization was attributed to reversible deprotonation of LLA by the N(CH₃)₂ moiety of (P)DMAEMA and the PLA homopolymer impurity was related to in situ formation of lactoyl lactate (LA–LA) due to nucleophilic ring opening of lactide by the amino moieties of (P)DMAEMA. The methods presented can be useful for the preparation of PDMAEMA–b–PLA/PLA composites in a two-step process or in a single step, one-pot process.     

Analytic Tangent Irradiance Environment Maps for Anisotropic Surfaces

Environment‐mapped rendering of Lambertian isotropic surfaces is common, and a popular technique is to use a quadratic spherical harmonic expansion. This compact irradiance map representation is widely adopted in interactive applications like video games. However, many materials are anisotropic, and shading is determined by the local tangent direction, rather than the surface normal. Even for visualization and illustration, it is increasingly common to define a tangent vector field, and use anisotropic shading. In this paper, we extend spherical harmonic irradiance maps to anisotropic surfaces, replacing Lambertian reflectance with the diffuse term of the popular Kajiya‐Kay model. We show that there is a direct analogy, with the surface normal replaced by the tangent. Our main contribution is an analytic formula for the diffuse Kajiya‐Kay BRDF in terms of spherical harmonics; this derivation is more complicated than for the standard diffuse lobe. We show that the terms decay even more rapidly than for Lambertian reflectance, going as l^–3, where l is the spherical harmonic order, and with only 6 terms (l = 0 and l = 2) capturing 99.8% of the energy. Existing code for irradiance environment maps can be trivially adapted for real‐time rendering with tangent irradiance maps. We also demonstrate an application to offline rendering of the diffuse component of fibers, using our formula as a control variate for Monte Carlo sampling.     

Influence of hysteresis on the transient hygrothermal response of a hemp concrete wall

Building envelopes with bio-materials like hemp concrete are currently undergoing an increasing development due to their low environmental impact and their interesting hygrothermal properties. This kind of hygroscopic material is characterized by a hysteretic behaviour. In this paper, the influence of such behaviour on the hygrothermal response of a building wall is discussed. An experimental facility is designed to measure temperature and relative humidity within a hemp concrete wall submitted to climatic variations. This facility provides a set of experimental data suited for benchmarking. Numerical simulations are performed with a hysteresis model implemented in a heat and moisture transfer model. Comparisons between numerical and experimental results show that hysteresis modelling is relevant to simulate the hygrothermal response of the wall. The discussion is extended to the influence of the initial moisture content.     

Fast in situ 3D nanoimaging: a new tool for dynamic characterization in materials science

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CrimeSPOT: A language and runtime for developing active wireless sensor network applications

Advances in wireless sensing and actuation technology allow embedding significant amounts of application logic inside wireless sensor networks. Such active WSN applications are more autonomous, but are significantly more complex to implement. Event-based middleware lends itself to implementing these applications. It offers developers fine-grained control over how an individual node interacts with the other nodes of the network. However, this control comes at the cost of event handlers which lack composability and violate software engineering principles such as separation of concerns. In this paper, we present CrimeSPOT as a domain-specific language for programming WSN applications on top of event-driven middleware. Its node-centric features enable programming a node’s interactions through declarative rules rather than event handlers. Its network-centric features support reusing code within and among WSN applications. Unique to CrimeSPOT is its support for associating application-specific semantics with events that carry sensor readings. These preclude transposing existing approaches that address the shortcomings of event-based middleware to the domain of wireless sensor networks. We provide a comprehensive overview of the language and the implementation of its accompanying runtime. The latter comprises several extensions to the Rete forward chaining algorithm. We evaluate the expressiveness of the language and the overhead of its runtime using small, but representative active WSN applications.     

Robust detection of outliers for projection-based face recognition methods

In this paper, the impact of outliers on the performance of high-dimensional data analysis methods is studied in the context of face recognition. Most of the existing face recognition methods are based on PCA-like methods: faces are projected into a lower dimensional space in which similarity between faces is supposed to be more easily evaluated. These methods are, however, very sensitive to the quality of the face images used in the training and in the recognition phases. Their performance significantly drops when face images are not well centered or taken under variable illumination conditions. In this paper, we study this phenomenon for two face recognition methods, namely PCA and LDA2D, and we propose a filtering process that allows the automatic selection of noisy face images which are responsible for the performance degradation. This process uses two techniques. The first one is based on the recently proposed robust high-dimensional data analysis method called RobPCA. It is specific to the case of recognition from video sequences. The second technique is based on a novel and effective face classification technique. It allows isolating still face images that are not very precisely cropped, not well-centered or in a non-frontal pose. Experiments show that this filtering process significantly improves recognition rates by 10 to 30%.

Kinetics of Multi‐Step Redox Processes by Time‐Resolved In Situ X‐ray Diffraction

The kinetics of redox reactions of iron oxide in oxygen carrier 50Fe₂O₃/MgAl₂O₄ are examined using different time‐resolved techniques. Reduction kinetics are studied by H₂ temperature‐programmed reduction (H₂‐TPR) monitored by time‐resolved in situ XRD. In contrast to conventional TPR, in situ XRD distinguishes the three‐stage reduction of Fe₂O₃ → Fe₃O₄ → FeO → Fe. It also shows that the oxidation of Fe → Fe₃O₄ by CO₂ has no intermediate crystalline phases, explaining why its kinetics can easily be investigated by conventional CO₂ temperature‐programmed oxidation (CO₂‐TPO). A shrinking core model which takes into account solid state diffusion allows describing the experimental data.