Biometrics: Effectiveness and Applications within the Blended Learning Environment

Learning methods have been benefited by a large act of recent systems based on the merging of several models of teaching. Blended learning philosophy has undergone a deep change with the internalization of new engineering sciences such as biometric. While it is known that passwords or PIN should never be stored in the clear, biometric technologies are becoming the foundation of an all-inclusive array of highly secure identification and personal verification solutions. In this paper, we present an in depth discussion the effectiveness of applying different types of biometrics in blended learning environments. We outline an implementation and report the effectiveness of the fingerprint model as a secure biometric method on a database consisting of 13000 students. Keywords: Blended learning, biometrics, e-learning, fingerprint matching, information technology

Prevalence of menopausal hot flashes in Lebanon: A cross-sectional study

Background: Menopausal hot flashes or vasomotor symptoms are prevalent and could be debilitating in postmenopausal women. There is controversy regarding the risk factors for hot flashes, some of which may vary from one country or culture to another. Objective: To shed light on this matter by assessing the prevalence of hot flashes, their effect on quality of life, and their association with certain factors such as physical exercise, caffeine, spicy food consumption, dietary intake, smoking, alcohol, etc. Materials and Methods: A large cross-sectional study was conducted among 627 Lebanese women, aged 45-67 yr using a well-developed and comprehensive questionnaire, in order to better assess the prevalence of hot flashes, focusing on their characteristics, association with various factors, severity, and effect on the women’s quality of life. Results: 62.5% of participants experienced hot flashes. A statistically significant difference was noted between women who experience hot flashes and their counterparts with respect to smoking, body mass index, spicy food consumption, education level, age, menstrual status, and parity. An association was not found with physical activity or other dietary factors. Conclusion: As an alternative for hormone therapy, clinicians should consider lifestyle changes to help manage hot flashes, which impose a tremendous physical and social toll on the women experiencing them. Key words: Menopause, Diet, Body mass index, Quality of life, Smoking

The measurement of revenue inefficiency over time: An additive perspective

In this paper, we measure and decompose revenue inefficiency over time while accounting for all sources of technical inefficiencies. Our proposed decomposition exploits the dual relationship between the weighted additive distance function and revenue inefficiency in Aparicio et al. [1]. With the aid of the Luenberger indicator, we decompose this indicator into productivity change, and overall allocative change components. The importance of such decomposition is that it provides a complete picture of the sources of productivity change, thus obtaining a slack free allocative component. Finally, the model is ap- plied to the French wine sector to illustrate its practicality: we track how revenue inefficiency evolves in French wine regions over the 2004–2013 period, before and after the implementation of Common Market Organization policies in Europe in 200

Étude et réalisation de photodétecteurs de type APD Geiger pixellisés à très haute sensibilité pour l'astronomie gamma très haute énergie

L'astronomie gamma des Très Hautes Energies utilise jusqu'à aujourd'hui exclusivement comme détecteurs le Photomultiplicateur à Tube (PMT) pour capter les faibles flux lumineux des gerbes atmosphériques. Mais une alternative commence à apparaitre : les photodiodes à avalanche polarisées en mode Geiger appelées APD-Geiger. Le PMT est un détecteur conçu dans les années 70 qui présente certes de nombreux avantages mais qui souffre également d'inconvénients comme la taille, le coût, le poids ou encore la sensibilité aux champs magnétiques et surtout la difficulté à réaliser une pixellisation en matrice. Les APD-Geiger, sont des dispositifs à semi-conducteur composés d'une jonction PN intégrée dans une technologie spéciale pour la détection de très faible flux lumineux grâce à leur polarisation au delà de la tension d'avalanche. Les APD-Geiger présentent un gain de photoélectrons très élevé (~106), bien que dépendant fortement de la tension de polarisation au delà de l'avalanche. Ces photodiodes présentent de nombreux avantages par rapport aux photomultiplicateurs, notamment du point de vue de leur miniaturisation pour des applications basées sur l'imagerie, comme la détection de flashs Tcherenkov en astronomie gamma. Dans cette thèse, nous présentons l'étude, la conception et la réalisation de cette structure technologique basée sur du Silicium. Cette structure a montré sa fiabilité pour la détection de faibles flux lumineux avec une tension de claquage de 12V et un courant de fuite ne dépassant pas 10pA au claquage. Nous avons également mis au point, différents modèles physiques et électriques indispensables aux démarches d'optimisation technologiques ainsi qu'au développement des circuits de commande et de lecture, i.e. la base de toute technologie d'imagerie. Le travail présenté ici consiste en l'étude, la conception et la réalisation d'une matrice de pixels à haute sensibilité. Un projet de télescope Cerenkov basé sur cette technologie innovante est finalement présenté.Very High Energy gamma ray astronomy uses till now exclusively as detector the Photomultiplier Tube (PMT) to collect weak light flux of atmospheric showers. But an alternative is now emerging: Avalanche Photodiodes polarized in Geiger mode called "Geiger-APD". The PMT is a detector designed in the 70's which presents many advantages but also suffers from several drawbacks: size, weight, cost, sensitivity to magnetic field but especially difficulty to realize its pixilation in matrix. Geiger-APDs are semi-conductor devices made of PN junction integrated in a special technology to detect very low light flux, thanks to the polarization beyond the avalanche voltage. Geiger-APD presents very high photoelectron gain (˜106) strongly dependant on the polarization voltage beyond avalanche. These photodiodes present many advantages with respect to PMT, mainly as concerns miniaturization for applications based on imaging, such as the detection of Cerenkov flashes in gamma ray astronomy. In this thesis, we present the study, the design and the realization of a technological structure, based on Silicon. This structure has shown reliability to detect weak luminous flux with breakdown voltage at 12V and dark current below 10pA at breakdown. We also developed several models, physical and electrical, necessary to the technological optimization, as well to the development of control and readout circuits, i.e. the basis of any imaging technology. The work presented here consists in the study, the design and the realization of a matrix of high sensitivity pixels. A project of a Cerenkov telescope based on this innovative technology is also presented

Heat exchanger fouling in phosphoric acid concentration: analysis of field data

International audienceThe main problem in concentrating phosphoric acid is due to fouling on the tube-side of the heat exchangers. The deposits of fouling can create a significant resistance to heat transfer .Therefore regular cleaning of heat exchangers is necessary. In this investigation, a large number of heat exchanger data were collected from shell and tube heat exchangers of industrial phosphoric acid concentration unit using the measurements of the operating parameters over a period of one year. The overall heat transfer coefficients and fouling resistances were evaluated at different times. Therefore, the experimental data of fouling resistances were compared with Kern and Seaton predictive model. The predictions of the model are in good agreement with the plant data

Dark Count rate measurement in Geiger mode and simulation of a photodiode array, with CMOS 0.35 technology and transistor quenching.

International audienceSome decades ago single photon detection used to be the terrain of photomultiplier tube (PMT), thanks to its characteristics of sensitivity and speed. However, PMT has several disadvantages such as low quantum efficiency, overall dimensions, and cost, making them unsuitable for compact design of integrated systems. So, the past decade has seen a dramatic increase in interest in new integrated single-photon detectors called Single-Photon Avalanche Diodes (SPAD) or Geiger-mode APD. SPAD detectors fabricated in a standard CMOS technology feature both single-photon sensitivity, and excellent timing resolution, while guarantying a high integration. SPAD are working in avalanche mode above the breakdown level. When an incident photon is captured, a very fast avalanche is triggered, generating an easily detectable current pulse. In this work, we investigate the design of SPAD detectors using the Austriamicrosystems 0.35 μm CMOS Opto technology. A series of different SPADs has been fabricated and benchmarked in order to evaluate a future integration into a SPAD- based image sensor. The main characteristics of each SPAD operating in Geiger-mode are reported: current voltage, breakdown voltage as a function of temperature. From this first set of results, a detailed study of the Dark Count Rate (DCR) has been conducted. Our results show a dark count rate increase with the size of the photodiodes and the temperature (at T=22.5°C, the DCR of a 10μm-photodiode is 2020 count.s-1 while it is 270 count.s-1 at T=- 40°C for a overvoltage of 800mV). We found that the adjustment of overvoltage is very sensitive and depends on the temperature. The temperature will be adjusted for the subsequent experiments. A mathematical model is presented for reproduce the DCR of a single photodiode. We simulated the noise (DCR) of array of 32x32 photo-detectors. Our results show, of course an increase of DCR of 1024, but especially, the probability of having two pulses simultaneously is 0 (without light). By studying these probabilities of occurrence of the pulses, we think we can reduce the DCR of 50% with a statistical method and reduce the crosstalk of 90%. This study is realized in order to prepare the first digital matrices sensor in Geiger mode