The Tunisian Tourism Business: What We Learn About The European Demand?

People from European countries are traditionally the most important sources of tourism for Tunisia. The aim of this paper is to analysis the European tourism demand for Tunisia. we propose a vector autoregression error correction model. The following methodology allows us to analysis the dynamic of Tunisian tourism in both short-term and long-term. Our main results show that the real exchange rate is an important factor explaining long-term overnight stays. A currency depreciation of 10% will increase the number of nights spent by visitors by 12% in the long term, but will have the opposite effect in the short term. However, we show that tourism demand is inelastic to income, indicating the low-cost nature of Tunisian tourism

Data on the fabrication of hybrid calix [4]arene-modified natural bentonite clay for efficient selective removal of toxic metals from wastewater at room temperature

Fresh water resources on the earth are less than 0.2%; meanwhile, around 80% of the freshwater is consumed daily in agriculture, industries, and household activities [1–2]. There is an essential need to develop efficient adsorbents for wastewater treatment [1–6], in this regards, hereafter we present the rationale synthesis and characterization of hybrid natural bentonite clay modified with Calix [4] arene (denoted as B-S-Calix) as efficient adsorbents for toxic metals from wastewater. This is driven by the facile photo-radical thiol-yne addition among the thiolated clay and an alkynylated calix[4]arene. The morphology, surface modifications, and Thermal degradation of B, B-S, and B-S-Calix were investigated using TEM, FTIR, and TGA techniques. The adsorption performance of B, BS and B-S-Calix towards toxic metals including cadmium (II) ion [Cd (II)], zinc (II) ion [Zn(II)], lead(II) ion [Pb(II)], strontium(II) ion [Sr (II)], cobalt(II) ion [Co (II)], copper(II) ion [Cu(II)], and mercury (II) ion [Hg(II)] from wastewater were benchmarked 25 °C. These data are related to the article entitled “hybrid Clay/Calix[4]arene Calix[4]arene-clicked clay through thiol-yne addition for the molecular recognition and removal of Cd(II) from wastewater’’ [7]

Rational synthesis, characterization, and application of environmentally friendly (polymer–carbon dot) hybrid composite film for fast and efficient UV-assisted Cd²⁺ removal from water

Background: Carbon dots (CDs) are of particular interest in numerous applications. However, their efficiency for heavy metal removal from wastewater was not yet reported. Herein, we rationally synthesized CDs from petroleum coke waste via hydrothermal treatment in the presence of ammonia. Results: This drove the formation of outstanding photoluminescent, water-soluble, biocompatible, and high yield of monodispersed sub-5 nm CDs. The CDs are co-doped with high 10% of N and 0.2% of S. The as-prepared CDs possess unprecedented photoluminescent properties over broad pH range making these dots unique efficient pH sensor. Conclusions: Chitosan (CH)–CDs hybrid hydrogel nanocomposite film was further prepared as a platform membrane for the removal Cd2+ metal from wastewater. The as-prepared CH–CDs membranes show relatively good mechanical properties, based on stress resistance and flexibility to facilitate handling. The equilibrium state was reached within 5 min. Intriguingly, the UV-light illuminations enhanced the Cd2+ removal efficiency of the photoluminescent CDs substantially by four times faster under. It was found that adsorption followed pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity at 25 °C was found to be 112.4 mg g−1 at pH 8. This work paves the way to new applications of CDs in water treatment.[Figure not available: see fulltext.]

Personal verification system based on retina and SURF descriptors

International audienceToday, Human recognition, especially based on retina, has been an important and attractive topic of scientific research. Most efforts in Biometrics tend to develop more efficient systems which compromise speed and robustness of authenti-cation. In fact, retinal images often suffer from imperfections such as background intensity variation, affine transformations (translation, rotation, scale changes) variations from pattern to other. These defects can seriously affect features extraction in terms of quality and execution time. In this context, in order to overcome these defects, we propose in this paper a novel retinal verification system based on the Speeded Up Robust Features (SURF) extraction. This feature extraction method is so fast and invariant to the affine transformations such as rotation, scale changes and translation. We employ the Optical Disc interest Ring (ODR) method as a preprocessing step in order to further speed up the system and improve the performance. A subset of the VARIA database is used to evaluate the proposed SURF based system. It compromises a high quality with 100% of verification accuracy rate and a time processing very lower than existing verification systems

: Interest ring extraction around the optical disc for a robust retinal identification

International audienceL’identification des personnes est devenue un service d’exigence croissante pour la maitrise des risques liés au contrôle d’accès physique à des milieux hautement sécurisés (coffre-fort, base militaire, etc.). De nos jours, les technologies d’authentification biométrique apparaissent comme dominantes pour la reconnaissance automatique des personnes. En effet, des caractéristiques biométriques distinctives et mesurables comme l’iris, l’empreinte digitale, la forme de visage, l’ADN, la rétine etc., sont de plus en plus utilisées. La plupart des efforts dans les systèmes d'authentification ont tendance à développer des environnements plus sûrs et difficiles à falsifier. Dans ce contexte, le motif des vaisseaux rétinien est unique, universel, invariable dans le temps et très difficile à falsifier. Il est considéré comme un des caractéristiques biométriques les plus efficaces pour l'authentification personnelle. Par ailleurs, en raison des processus d'acquisition modernes, les images de fond de l’œil ne sont pas illuminées de manière uniforme, souvent floues et peu contrastées et sont parfois surexposées ce qui réduit généralement le taux d'identification. En outre, la rétine a une structure dense d’information sur les vaisseaux ce qui augmente le temps d'exécution du système de reconnaissance. Afin de surmonter ces problèmes, nous avons proposé un système de reconnaissance basé sur une nouvelle méthode nommée "ODR" (Optical Disc interest Ring). Elle consiste, dans un premier temps, à améliorer la qualité de contraste de l'image rétinienne acquise. Ensuite, le centre de disque optique est détecté comme référence pour l’extraction d’un anneau d’intérêt autour de ce centre. La sélection de cette région d’intérêt permet de maintenir une haute densité d'information rétinienne nécessaire pour assurer une meilleure qualité d’identification et de réduire considérablement les temps de calcul.Pour son évaluation, la méthode ODR a été intégrée dans un système d’identification basé sur une caractérisation locale et invariante telles que SIFT (Scale Invariant Feature Transform) et SURF (Speeded Up Robust Features). Un taux de reconnaissance de 99.8% est obtenu avec des images rétiniennes saines de la base VARIA. Nous utiliserons dans nos futurs travaux d’autres bases rétiniennes, notamment médicales telles que STARE et DRIVE. Ces bases contiennent des images rétiniennes affectées par différentes anomalies comme la cataracte, le glaucome, le diabète l’hypertension et l'artériosclérose. Ces pathologies rétiniennes provoquent des lésions et des exsudats, au niveau de la rétine, qui peuvent influencer la phase de détection de disque optique. Comme perspectives, nous allons étudier la robustesse de la méthode ODR en présence de ces anomalies et nous proposerons, si nécessaire, de nouveaux traitements adaptés au contexte des images rétiniennes pathologiques

The asymmetric relationship between returns and implied volatility : evidence from global stock markets

Published online: 19 May 2017We investigate the asymmetric relationship between returns and implied volatility for 20 developed and emerging international markets. In particular we examine how the sign and size of return innovations affect the expectations of daily changes in volatility. Our empirical findings indicate that the conditional contemporaneous return-volatility relationship varies not only based on the sign of the expected returns but also upon their magnitude, according to recent results from the behavioral finance literature. We find evidence of an asymmetric and reverse return-volatility relationship in many advanced, Asian, Latin-American, European and South African markets. We show that the US market displays the highest reaction to price falls, Asian markets present the lowest sensitivity to volatility expectations, while the Euro area is characterized by a homogeneous response both in terms of direction and impact. These results may be safely attributed to cultural and societal characteristics. An extensive quantile regression analysis demonstrates that the detected asymmetric pattern varies particularly across the extreme distribution tails i.e., in the highest/lowest quantile ranges. Indeed, the classical feedback and leverage hypotheses appear not plausible, whilst behavioral theories emerge as the new paradigm in real-world applications

Human identification system based on the detection of optical Disc Ring in retinal images

International audienceRetinal identification is being studied as a hot research topic in the biometric field. Many factors such as the poor quality of retinal images and the huge execution time can seriously affect the performance of the retinal identification systems. In this context, in order to compromise the quality and the processing time, this paper presents a human identification system based on a new preprocessing method of retinal images that we call optical Disc Ring detection method. The proposed ODR method consists of three phases: image quality improvement in order to enhance the contrast of input retinal image, the optical disc center detection and the extraction of an interest ring around the detected center which contains the densest retinal information. This proposed method was integrated in an identification system based on SIFT features and evaluated using a subset of the VARIA retinal database. The correct identification rate was found to be 99.89% while the reached execution time is very lower than other existing identification systems

Retinal Identification System based on Optical Disc Ring Extraction and New Local SIFT-RUK Descriptor

International audiencePersonal recognition based on retina has been an attractive topic of scientific research. A common challenge of retinal identification system is to ensure a high recognition rate while maintaining a low mismatching FMR rate and execution time. In this context, this paper presents a retinal identification system based on a novel local feature description. The proposed system is composed of three stages, firstly we enhance the retinal image and we select a ring around the optical disc as an interest region by using our recently proposed Optical Disc Ring ODR method. Secondly, in order to reduce the mismatching rate and speed up the matching step, we propose in this paper an original alternative local description based on the Remove of Uninformative SIFT Keypoints, that we call SIFT-RUK. Finally, the generalization of Lowe’s matching technique (g2NN test) is employed. Experiments on the VARIA database are done to evaluate the performance of our proposed SIFT-RUK feature-based identification system. We show that we obtain a high performance with 99.74% of identification accuracy rate without any mismatching (0% of False Matching Rate FMR) and with a low matching processing time compared to existing identification systems