Cognitive Approach to e-Learning in Sciences and Technologies

This article describes the approach adopted and the results obtained by the international team developing WBLST (Web Based Learning in Sciences and Technologies) a Web-based application for e-learning, developed for the students of “UVPL: Université Virtuelle des Pays de la Loire”. The developed e-learning system covers three levels of learning activities - content, exercises, and laboratory. The delivery model is designed to operate with domain concepts as relevant providers of semantic links. The aim is to facilitate the overview and to help the establishment of a mental map of the learning material. The implemented system is strongly based on the organization of the instruction in virtual classes. The obtained quality of the system is evaluated on the bases of feedback form students and professors

Analysis of Self-Mixing Moderate and Strong Feedback Regimes for Mechatronics Applications

L'utilisation des lasers est répandue dans le domaine de l'instrumentation. Cependant, le fonctionnement de tels dispositifs peut être perturbé par le phénomène de rétro-injection optique (ou self-mixing) auquel est soumis la diode laser. Cette sensibilité du laser à la rétro-injection optique offre de nombreux avantages, notamment pour la mesure de déplacements, de vitesse ou de distance. Dans ce travail, nous introduisons le phénomène de self-mixing avant d'effectuer un état de l'art des différentes applications de ce type de capteurs. Le régime de fonctionnement de rétro-injection optique modérée est d'abord étudié en détails en introduisant la notion de perte de pics; en l'interprétant et en étudiant son effet sur différentes méthodes de mesure de déplacement. Nous étudions ensuite le régime de forte rétro-injection optique en analysant son aspect statistique et l'effet des différents paramètres sur cet aspect. Un capteur de déplacement relatif opérant dans ce régime est alors conçu et réalisé. Après l'avoir caractérisé, l'application de ce capteur était étendue à l'analyse modale où il avait l'avantage majeur de donner une image très fidèle du déplacement en temps réel sans traitement de signal complexe. Ce capteur est alors utilisé pour caractériser une plaque encastrée et pour détecter les impacts dans des poutres en fibre de carbone. ABSTRACT : Lasers have been widely used in different types of applications such as telecommunications, CD/DVD readers or for sensing purposes. A major drawback in their use is the optical feedback caused by an obstacle in their direction of propagation. This light reinjected in the active area modifies the emission properties of laser diodes and obliges the developers to consider adding isolators increasing thereby the complexity and the price of such systems. However this optical feedback induces a variation in the emission power and frequency in function with the distance to the reflector. This phenomenon, more commonly known as self-mixing, is used in different types of displacement, velocity and vibration sensors. In this work, the physical theory of the self-mixing effect is introduced and then a state of the art of its main applications in the different fields of instrumentation is accomplished. A detailed study of the self-mixing signal in the moderate feedback regime is achieved introducing the effect of "loss of peaks", its physical interpretation, mechanisms and effect on different types of displacement measurement. Afterwards, the discrepancy concerning the strong feedback regime was cleared out showing that it may be used for relative displacement measurement. A detailed study of this regime covers its statistical aspect and the influence of different parameters on this aspect. Finally, the self-mixing sensor under strong feedback was introduced in modal analysis applications after being characterized. It was applied to study a clamped plate or to detect damage in carbon fiber CFBs. This type of sensors proved its major advantage of simplicity providing a direct image of the displacement without the need of any advanced signal processing. This facilitates its duplication where an array of sensors was used in different experiments

High-performance FPGA implementation of the secure hash algorithm 3 for single and multi-message processing

The secure hash function has become the default choice for information security, especially in applications that require data storing or manipulation. Consequently, optimized implementations of these functions in terms of Throughput or Area are in high demand. In this work we propose a new conception of the secure hash algorithm 3 (SHA-3), which aim to increase the performance of this function by using pipelining, four types of pipelining are proposed two, three, four, and six pipelining stages. This approach allows us to design data paths of SHA-3 with higher Throughput and higher clock frequencies. The design reaches a maximum Throughput of 102.98 Gbps on Virtex 5 and 115.124 Gbps on Virtex 6 in the case of the 6 stages, for 512 bits output length. Although the utilization of the resource increase with the increase of the number of the cores used in each one of the cases. The proposed designs are coded in very high-speed integrated circuits program (VHSIC) hardware description language (VHDL) and implemented in Xilinx Virtex-5 and Virtex-6 A field-programmable gate array (FPGA) devices and compared to existing FPGA implementations

Efficiency of two decoders based on hash techniques and syndrome calculation over a Rayleigh channel

The explosive growth of connected devices demands high quality and reliability in data transmission and storage. Error correction codes (ECCs) contribute to this in ways that are not very apparent to the end user, yet indispensable and effective at the most basic level of transmission. This paper presents an investigation of the performance and analysis of two decoders that are based on hash techniques and syndrome calculation over a Rayleigh channel. These decoders under study consist of two main features: a reduced complexity compared to other competitors and good error correction performance over an additive white gaussian noise (AWGN) channel. When applied to decode some linear block codes such as Bose, Ray-Chaudhuri, and Hocquenghem (BCH) and quadratic residue (QR) codes over a Rayleigh channel, the experiment and comparison results of these decoders have shown their efficiency in terms of guaranteed performance measured in bit error rate (BER). For example, the coding gain obtained by syndrome decoding and hash techniques (SDHT) when it is applied to decode BCH (31, 11, 11) equals 34.5 dB, i.e., a reduction rate of 75% compared to the case where the exchange is carried out without coding and decoding process

Space Cooling Using Geothermal Single-Effect Water/Lithium Bromide Absorption Chiller

Abstract This research is proposed to fully investigate the performance of a single‐effect water/lithium bromide absorption chiller driven by geothermal energy. Since absorption cycles are considered as low‐grade energy cycles, this innovative idea of rejecting fluid from a single‐flash geothermal power plant with low‐grade energy would serve as efficient, economical, and promising technology. In order to examine the feasibility of this approach, a residential building which is located in Sharjah, UAE, considered to evaluate its cooling capacity of 39 kW which is calculated using MATLAB software. Based on the obtained cooling load, modeling of the required water/lithium bromide single‐effect absorption chiller machine is implemented and discussed. A detailed performance analysis of the proposed model under different conditions is performed using Engineering Equation Solver software (EES). Based on the obtained results, the major factors in the design of the proposed system are the size of the heat exchangers and the input heat source temperature. The results are presented graphically to find out the geofluid temperature and mass flow and solution heat exchanger effectiveness effects on the chiller thermal performance. Moreover, the effects of the size of all components of the absorption chiller on the cooling load to meet the space heating are presented. The thermal efficiency of the single‐flash geothermal power plant is about 13% when the power plant is at production well temperature 250℃, separator pressure 0.24 MPa, and condenser pressure 7.5 kPa. The results show that the coefficient of performance (COP) reaches about 0.87 at solution heat exchanger effectiveness of 0.9, when the geofluid temperature is 120℃

Zur mathematischen Modellierung des kapillaren Anstiegs - Dissipative Mechanismen und nicht-lineare Oszillationen

Ausgehend von der Beschreibung des kapillaren Anstiegs nach Bosanquet, wird das Modell erweitert und untersucht. Die Erweiterungen beinhalten dabei die Einführung eines dynamischen Kontaktwinkels und die Betrachtung der Energiedissipation in der Nähe der Kontaktlinienregion. Die daraus resultierenden Differentialgleichungen werden mathematisch analysiert. Diese Analyse beinhaltet die Existenz und das asymptotische Verhalten einer Lösung, sowie den Regimewechsel von einer monoton steigenden zu einer oszillierenden Lösung. Des Weiteren werden die Lösungen numerisch analysiert und mit Experimenten verglichen

Adaptative ranked-order vectorial speckle filtering in polarimetric SAR images : Comparaison with a class of filters

Speckle appearing in synthetic aperture radar (SAR) images is generated by coherent processing of radar signals . It hampers perception and extraction of fine details in the image . That is why speckle reducing is necessary before images analysis . In this paper, we have studied and tested several linear and non linear vectorial methods (Novak, Lee, Russell) to remove speckle in SAR images. Russell's method has proved its efficiency and simplicity of implementation, it is not adaptive . So we have generalized Russell's method to make it adaptive by pixel . Adaptivity is based on the generalization of local scalar variation towards a case of a vectorial variation, on one hand, and on local and global statistic analysis of the latter, on the other hand . To evaluate the performance of a filtering method, we propose criteria that join the two qualities, smoothing and edge preservation . A comparative study with several vectorial filtering methods show that the proposed method provides the best results according to the proposed criteria.La présence du bruit de chatoiement multiplicatif (speckle) dans les images radar à ouverture synthétique (ROS), causé par la cohérence de l'onde radar, rend difficile la perception et l'extraction des détails fins qui s'y trouvent. C'est pourquoi, avant d'effectuer l'analyse d'image, le filtrage du speckle pour réduire son influence est un traitement nécessaire. Dans cet article, nous avons étudié et testé différentes méthodes de filtrage vectorielles linéaires et non linéaires (Novak, Lee, Russel) pour réduire le bruit de speckle du signal d'images ROS. Le filtrage d'ordre vectoriel de Russel semble intéressant par son efficacité et par la simplicité de sa mise en oeuvre. Néamoins, il présente l'inconvénient d'être non adaptatif. C'est pourquoi, en étendant ce filtrage, nous l'avons rendu adaptatif en fonction des caractéristiques du voisinage. Cette adaptativité s'appuie d'une part, sur la généralisation de la notion de coefficient de variation scalaire au cas vectoriel et d'autre part, sur l'analyse statistique locale et globale de ce dernier. Un critère global d'évaluation des performances des filtres est proposé. Il combine les deux caractéristiques antagonistes d'une méthode de filtrage, capacité de lissage dans les zones homogènes et préservation des contours. Une comparaison quantitative, selon le critère proposé, sur les méthodes de filtrage vectoriel, citées plus haut, montre l'intérêt de la méthode proposée

Comparative Antiviral Activity of Remdesivir and Anti-HIV Nucleoside Analogs against Human Coronavirus 229E (HCoV-229E)

Remdesivir is a nucleotide prodrug that is currently undergoing extensive clinical trials for the treatment of COVID-19. The prodrug is metabolized to its active triphosphate form and interferes with the action of RNA-dependent RNA polymerase of SARS-COV-2. Herein, we report the antiviral activity of remdesivir against human coronavirus 229E (HCoV-229E) compared to known anti-HIV agents. These agents included tenofovir (TFV), 4′-ethynyl-2-fluoro-2′-deoxyadenosine (EFdA), alovudine (FLT), lamivudine (3TC), and emtricitabine (FTC), known as nucleoside reverse-transcriptase inhibitors (NRTIs), and a number of 5′-O-fatty acylated anti-HIV nucleoside conjugates. The anti-HIV nucleosides interfere with HIV RNA-dependent DNA polymerase and/or act as chain terminators. Normal human fibroblast lung cells (MRC-5) were used to determine the cytotoxicity of the compounds. The study revealed that remdesivir exhibited an EC50 value of 0.07 µM against HCoV-229E with TC50 of \u3e 2.00 µM against MRC-5 cells. Parent NRTIs were found to be inactive against (HCoV-229E) at tested concentrations. Among all the NRTIs and 5′-O-fatty acyl conjugates of NRTIs, 5′-O-tetradecanoyl ester conjugate of FTC showed modest activity with EC50 and TC50 values of 72.8 µM and 87.5 µM, respectively. These data can be used for the design of potential compounds against other coronaviruses