Le conservatisme conditionnel des entreprises françaises cotées

Appliqué au contexte français, cette étude a pour objet d’attribuer au conservatisme conditionnel une évidence empirique. Pour ce faire, le modèle de Basu (1997) et le modèle de Khan & Watts (2009) sont utilisés pour détecter cette pratique comptable. En outre, des investigations sont menées pour montrer que le degré de conservatisme a diminué après l’adoption de l’IFRS en 2005 ; que le degré de conservatisme est tributaire du marché de cotation, de la taille et du secteur d’activité de l’entreprise. A partir d’un panel non cylindré de 331 entreprises françaises cotées à l’Euronext Paris durant la période allant de 2000 à 2015, les résultats obtenus révèlent que seules les entreprises cotées sur le marché réglementé Eurolist (Compartiments A, B et C) sont conservatrices. Ce conservatisme a diminué après l’adoption obligatoire des normes IFRS. La taille et le secteur d’activité auquel appartient l’entreprise sont des déterminants du conservatisme conditionnel

Fenton and solar photo-Fenton processes for the removal of chlorpyrifos insecticide in wastewater

The degradation of chlorpyrifos in water by Fenton (H2O2/Fe2+) and solar photo-Fenton (H2O2/Fe2+/solar light) processes was investigated. A laboratory-scale reactor was designed to evaluate and select the optimal oxidation condition. The degradation rate is strongly dependent on pH, temperature, H2O2 dosing rate, and initial concentrations of the insecticide and Fe2+. The kinetics of organic matter decay was evaluated by means of chemical oxygen demand (COD) measurement. Overall kinetics can be described by a pseudo-second-order rate equation with respect to COD. The optimum conditions were obtained at pH 3, H2O2 dosing rate 120 mg·min–1, [Fe2+]0 5.0 mM, initial COD 1 330 mg·l–1 and 35°C for the Fenton process. However, in the solar photo-Fenton process, the degradation rate increased significantly. To achieve 90% of COD removal, the solar photo-Fenton process needs 50% less time than that used in the Fenton process which translates to a 50% gain of H2O2

Les implications différentielles du conservatisme conditionnel sur la persistance des accruals et leurs composants : Application au contexte français

L’intérêt de cet article est de tester les implications différentielles du conservatisme conditionnel sur la persistance des accruals et leurs composants dans le contexte français. L’échantillon de l’étude est un panel non cylindré de 331 entreprises françaises cotées à l’Euronext Paris durant la période allant de 2000 à 2015. Les résultats montrent que le conservatisme conditionnel augmente la persistance des accruals. Une analyse en trois composants des accruals révèle que le conservatisme augmente seulement la persistance des accruals d’exploitation (Wakil & Alam, 2014). Le test de sensibilité des résultats aux sous composants (Actif et Passif) des accruals confirme le constat initial mais révèle que le conservatisme réduit la persistance respective du composant passif financier (fiable) et du composant passif d’exploitation non courant (peu fiable)

Electrochemical behavior of Auramine O dye in aqueous solutions at lead dioxide electrode

Electrochemical behavior of Auramine O (AO) was studied by galvanostatic electrolysis at lead dioxide (Ta/PbO2) anodes. The influence of operating parameters, such as current density, initial concentration of AO, temperature and initial pH value was investigated. The oxidation kinetics of the AO was followed by HPLC, UV / visible spectrophotometry and the measurement of chemical oxygen demand (COD). The experimental results showed that the electrochemical process was suitable for almost completely removing COD, due to the production of the hydroxyl radicals at the anode surface. The oxidation of AO is dependent on its initial concentration, current density, temperature and pH. COD decay follows a pseudo first-order kinetic and the process was under mass transport control. The HPLC analysis showed that the main AO oxidation products formed during electrolysis are the hydroquinone (HQ) representing the reduced form of benzoquinone (BQ) and carboxylic acids (CA).  The proposed AO anodic oxidation into (BQ) is mainly based on an alternance of indirect monoelectronic discharge by the mediation of hydroxyl radicals and hydrolysis steps. The electrochemical oxidation of AO can be used as an economically adequate way for a pre-treatment of waters containing this dye followed by biological treatment

Biotechnological potential of Ulva ohnoi epiphytic bacteria: enzyme production and antimicrobial activities

Seaweed surfaces harbor diverse epibiotic bacterial communities with functions related to morphogenesis, host health, and defense. Among seaweed holobionts, culturable strains can represent innovative sources of bioactive compounds and enzymes. The global industrial demand for microbial enzymes is continually growing in order to improve certain manufacturing processes with new perspectives of industrial exploitation. In this regard, the present study focuses on the enzymatic production and the antimicrobial activities of culturable epibiotic bacteria of Ulva from the Tunisian coast. Culturable associated bacteria were isolated and molecular identification was realized by 16S rRNA gene sequencing. For each strain, eight enzymatic activities were investigated: amylase, hemolysis, DNase, cellulase, lecithinase, lipase, gelatinase, and chitinase. The antimicrobial activity of Ulva-associated bacteria was evaluated against seven pathogenic bacteria, Escherichia coli, Vibrio anguillarum, Vibrio alginoliticus, Pseudomonas aeruginosa, Aeromonas hydrophila, Salmonella typhymurium, and Staphylococcus aureus, and one yeast, Candida albicans. The antibiotic resistance of isolated strains was determined for 15 commonly used antibiotics. The phylogenetic analysis revealed that the isolates belonged to Alphaproteobacteria (3), Gammaproteobacteria (5), Actinobacteria (3), and Firmicutes (4) phyllum. The majority of the isolates (66%) produced simultaneously more than one enzyme. Hemolysis was produced by 46.6% of isolates, while DNase was produced by 33% of strains. On the other hand, 13% of strains produced lecithinase, gelatinase, cellulase, and lipase. No chitinase was produced by the isolated bacteria. In addition, 60% of isolates displayed antimicrobial activity against at least one pathogenic strain. All Ulva ohnoi-associated bacteria were resistant to at least seven commonly used antibiotics. These results highlighted the occurrence of several enzymatic activities within Ulva-associated bacteria that can have potential uses in the industrial sector

Utilisation des données biométriques pour la régénération des clés cryptobiométriques révocables

This thesis aims to regenerate crypto-biometric keys (cryptographic keys obtained with biometric data) that are resistant to quantum cryptanalysis methods. The challenge is to obtain keys with high entropy to have a high level of security, knowing that the entropy contained in biometric references limits the entropy of the key. Our choice was to exploit facial biometrics.We first created a state-of-the-art face recognition system based on public frameworks and publicly available data based on DNN embedding extractor architecture and triplet loss function. We participated in two H2020 projects. For the SpeechXRays project, we provided implementations of classical and cancelable face biometrics. For the H2020 EMPATHIC project, we created a face verification REST API. We also participated in the NIST SRE19 multimedia challenge with the final version of our classical face recognition system.In order to obtain crypto-biometric keys, it is necessary to have binary biometric references. To obtain the binary representations directly from face images, we proposed an original method, leveraging autoencoders and the previously implemented classical face biometrics. We also exploited the binary representations to create a cancelable face verification system.Regarding our final goal, to generate crypto-biometric keys, we focused on symmetric keys. Symmetric encryption is threatened by the Groover algorithm because it reduces the complexity of a brute force attack on a symmetric key from 2N à 2(N/2). To mitigate the risk introduced by quantum computing, we need to increase the size of the keys. To this end, we tried to make the binary representation longer and more discriminative. For the keys to be resistant to quantum computing, they should have double the length.We succeeded in regenerating crypto-biometric keys longer than 400bits (with low false acceptance and false rejection rates) thanks to the quality of the binary embeddings. The crypto-biometric keys have high entropy and are resistant to quantum cryptanalysis, according to the PQCrypto project, as they satisfy the length requirement. The keys are regenerated using a fuzzy commitment scheme leveraging BCH codes.Ce travail de thèse vise à régénérer des clés crypto-biométriques (clés cryptographiques obtenues avec des données biométriques) résistantes aux méthodes de cryptanalyse quantique. Le défi est d'obtenir des clés avec une haute entropie pour avoir un haut niveau de sécurité, sachant que l'entropie contenue dans les références biométriques limite l'entropie de la clé. Notre choix a été d'exploiter la biométrie faciale.Nous avons d'abord créé un système de reconnaissance faciale de pointe basé en utilisant des bases de données publiques. Notre architecture utilise des réseaux de neurones profonds avec une fonction de perte‘Triplet loss'. Nous avons participé à deux Projets européens H2020 pour lesquelles nous avons fournit des adapations de notres systeme de reconnaise de visage. Nous avons également participé au challenge multimédia NIST SRE19 avec la version finale de notre système classique de reconnaissance faciale qui a donnée d'excellents résultats.Pour obtenir des clés crypto-biométriques, il est nécessaire de disposer de références biométriques binaires. Pour obtenir les représentations binaires directement à partir d'images de visage, nous avons proposé une méthode novatrice tirant parti des auto-encodeurs et la biométrie faciale classique précédemment mise en œuvre. Nous avons également exploité les représentations binaires pour créer un système de vérification de visage cancelable.Concernant notre objectif final, générer des clés crypto-biométriques, nous nous sommes concentrés sur les clés symétriques. Le chiffrement symétrique est menacé par l'algorithme Groover parce qu'il réduit la complexité d'une attaque par force brute de 2(N/2).. Pour atténuer le risque introduit par l'informatique quantique, nous devons augmenter la taille des clés. Pour cela, nous avons essayé de faire la représentation binaire plus longue et plus discriminante.Nous avons réussi à régénérer des clés crypto-biométriques de plus de 400 bits grâce à la qualité des plongements binaires. Les clés crypto-biométriques ont une haute entropie et résistent à la cryptanalyse quantique selon le PQCrypto projet car ils satisfont à l'exigence de longueur. Les clés sont régénérées à l'aide d'un schéma de "fuzzy commitment" en utilisant les codes BCH

State-of-the-art face recognition performance using publicly available software and datasets

International audienceWe are interested in the reproducibility of face recognition system. By reproducibility we mean : is the scientific community, and are the researchers from different sides, capable of reproducing the last published results by a big company, that has at its disposal huge computational power and huge proprietary databases ? With the constant advancements in GPU computation power and availibility of open-source software, the reproducibility of published results should not be a problem. But, if architectures of the systems are private and databases are proprietary, the reproducibility of published results can not be easily attained. To tackle this problem, we focus on training and evaluation of face recognition systems on publicly available data and software. We are also interested in comparing the best Deep Neural Net (DNN) based results a baseline "classical" System. This paper exploits the OpenFace open-source system to generate a deep convolutional neural network model using publicly available datasets. We study the impact of the size of the datasets, their quality and compare the performance to a classical face recognition approach. Our focus is to have t fully reproducible model. To this end, we used publicly available datasets (FRGC, MS-celeb-IM, MOBIO, LFW) as well publicly available sofware (OpenFace) to train our model in order to do face recognition. Our best trained model achieves 97.52% accuracy on the Labelled in the Wild dataset (LFW) dataset which is lower than Google's best reported results of 99,96% but slightly better than Facebook reported result of 97,35%. We also evaluated our best model on the challenging video dataset MOBIO and report competitive results with the best reported results on this databas

Utilisation des données biométriques pour la régénération des clés cryptobiométriques révocables

Ce travail de thèse vise à régénérer des clés crypto-biométriques (clés cryptographiques obtenues avec des données biométriques) résistantes aux méthodes de cryptanalyse quantique. Le défi est d'obtenir des clés avec une haute entropie pour avoir un haut niveau de sécurité, sachant que le l'entropie contenue dans les références biométriques limite l'entropie de la clé. Notre choix a été d'exploiter la biométrie faciale.Nous avons d'abord créé un système de reconnaissance faciale de pointe basé en utilisant des bases de données publiques. Notre architecture utilise des réseaux de neurones profonds avec une fonction de perte‘Triplet loss'. Nous avons participé à deux Projets européens H2020 pour lesquelles nous avons fournit des adapations de notres systeme de reconnaise de visage. Nous avons également participé au challenge multimédia NIST SRE19 avec la version finale de notre système classique de reconnaissance faciale qui a donnée d'excellents résultats.Pour obtenir des clés crypto-biométriques, il est nécessaire de disposer de références biométriques binaires. Pour obtenir les représentations binaires directement à partir d'images de visage, nous avons proposé une méthode novatrice tirant parti des auto-encodeurs et la biométrie faciale classique précédemment mise en œuvre. Nous avons également exploité les représentations binaires pour créer un système de vérification de visage cancelable.Concernant notre objectif final, générer des clés crypto-biométriques, nous nous sommes concentrés sur les clés symétriques. Le chiffrement symétrique est menacé par l'algorithme Groover parce qu'il réduit la complexité d'une attaque par force brute de 2(N/2).. Pour atténuer le risque introduit par l'informatique quantique, nous devons augmenter la taille des clés. Pour cela, nous avons essayé de faire la représentation binaire plus longue et plus discriminante.Nous avons réussi à régénérer des clés crypto-biométriques de plus de 400 bits grâce à la qualité des plongements binaires. Les clés crypto-biométriques ont une haute entropie et résistent à la cryptanalyse quantique selon le PQCrypto projet car ils satisfont à l'exigence de longueur. Les clés sont régénérées à l'aide d'un schéma de "fuzzy commitment" en utilisant les codes BCH.This thesis aims to regenerate crypto-biometric keys (cryptographic keys obtained with biometric data) that are resistant to quantum cryptanalysis methods. The challenge is to obtain keys with high entropy to have a high level of security, knowing that the entropy contained in biometric references limits the entropy of the key. Our choice was to exploit facial biometrics.We first created a state-of-the-art face recognition system based on public frameworks and publicly available data based on DNN embedding extractor architecture and triplet loss function. We participated in two H2020 projects. For the SpeechXRays project, we provided implementations of classical and cancelable face biometrics. For the H2020 EMPATHIC project, we created a face verification REST API. We also participated in the NIST SRE19 multimedia challenge with the final version of our classical face recognition system.In order to obtain crypto-biometric keys, it is necessary to have binary biometric references. To obtain the binary representations directly from face images, we proposed an original method, leveraging autoencoders and the previously implemented classical face biometrics. We also exploited the binary representations to create a cancelable face verification system.Regarding our final goal, to generate crypto-biometric keys, we focused on symmetric keys. Symmetric encryption is threatened by the Groover algorithm because it reduces the complexity of a brute force attack on a symmetric key from 2N à 2(N/2). To mitigate the risk introduced by quantum computing, we need to increase the size of the keys. To this end, we tried to make the binary representation longer and more discriminative. For the keys to be resistant to quantum computing, they should have double the length.We succeeded in regenerating crypto-biometric keys longer than 400bits (with low false acceptance and false rejection rates) thanks to the quality of the binary embeddings. The crypto-biometric keys have high entropy and are resistant to quantum cryptanalysis, according to the PQCrypto project, as they satisfy the length requirement. The keys are regenerated using a fuzzy commitment scheme leveraging BCH codes

On the Security of Authenticated Group Key Agreement Protocols

The group key agreement protocol enables to derive a shared session key for the remote members to communicate securely. Recently, several attempts are made to utilize group key agreement protocols for secure multicasting in Internet of Things. This paper contributes to identify the security vulnerabilities in the existing protocols, to avoid them in future constructions. The protocols presented by Gupta and Biswas have been found insecure to ephemeral secret key leakage (ESL) attack and also, malicious insiders can impersonate an honest participant. Additionally, the protocol presented by Tan is also ESL-insecure. We also present a fix to the Tan's protocol to make it secure.info:eu-repo/semantics/publishe

Potential of three local marine microalgae from Tunisian coasts for cadmium, lead and chromium removals

International audienc