State-of-the-Art on the Marine Current Turbine System Faults

This chapter deals with the state of the art on the marine current turbine (MCT) system faults. Indeed, the MCT structure consists of a marine turbine, a generator (permanent magnet synchronous generator (PMSG) or doubly fed induction generator (DFIG)), and a PWM power converter. Nevertheless, these systems are exposed to functional and environmental severe conditions. Firstly, the power increase leads to a higher current and/or voltage. Second, the installation of the MCT system under the sea and the existence of the swell and wave imply harmonic current speeds. In fact, several faults (related to the turbine, the generator, the blades, and the converters) can occur in the MCT system. Most of these faults generate the speed and the torque oscillations, which can lead to mechanical vibrations and the rapid destruction of the insulating material generator. Consequently, MCT system performances can be degraded

Etude Nationale sur la détection des jeunes talents sportifs en Algérie

L’objectif principal de cette étude est d’évaluer de la croissance morpho-fonctionnelle des enfants scolarisés et de déterminer les profils morphologiques, selon les différentes willayas du territoire national âgés de 06 à12 ans. L’établissement des références nationales seront un support pour la détection des jeunes talents sportifs et leur formation en fonction des différentes régions du territoire nationa

Marine Current Turbine System Post-Fault Behavior under an Open Circuit Fault

This paper describes the modeling and simulation of a Permanent Magnet Synchronous Generator (PMSG) based Marine Current Turbine (MCT) under converter faulty conditions. The modeling of the generator is represented in the d-q reference frame. The Proportional Integral (PI) controllers are used for the direct current, the quadratic current, and the speed Control. The faulty mode describes an open-circuit fault in the generator-side converter. Simulations results show that the dynamic performances and the power generation of the MCT are highly degraded due to the fault

Nonlinear modeling of trapping and thermal effects on GaAs and GaN MESFET/HEMT devices

A novel nonlinear model for MESFET/HEMT devices is presented. The model can be applied to low power (GaAs) and high power (GaN) devices with equal success. The model provides accurate simulation of the static (DC) and dynamic (Pulsed) I-V characteristics of the device over a wide bias and ambient temperature range (from -70ºC to +70ºC) without the need of an additional electro-thermal sub-circuit. This is an important issue in high power GaN HEMT devices where self-heating and current collapse due to traps is a more serious problem. The parameter extraction strategy of the new model is simple to implement. The robustness of the model when performing harmonic balance simulation makes it suitable for RF and microwave designers. Experimental results presented demonstrate the accuracy of the model when simulating both the small-signal and large-signal behavior of the device over a wide range of frequency, bias and ambient temperature operating points. The model described has been implemented in the Advanced Design System (ADS) simulator to validate the proposed approach without convergence problems.The authors would like to thank the Spanish Ministry of Science and Innovation (MICINN) by the financial support provided through projects CSD2008-00068, TEC2008-06684-C03-01 and TEC2011-29126-C03-01

Caracterización en DC de transistores HEMT de GaN

AlGaN/GaN HEMT’s exhibit very promising properties for high frequency applications where high power generation is necessary. As for former devices (GaAs MESFET, etc), good models are required to predict the different figures of merit at the design stage. In this sense purpose, this paper presents a procedure to extract the parameters of the rectifying Schottky junction along with a method to obtain the values of the parasitic resistances in GaN, HEMT’s. Virgin and aged devices are considered in the performed measurements to take into account the thermal stress influence in the device behavior. The obtained results will show the validity of the different presented approaches, being the same consistent with the presented in other referenced works

Caracterización de niveles trampa en transistores HEMT de GaN

This work presents the description of trapping effects in GaN HEMT’s. Two different effects will be considered: gate-lag and drain-lag, describing their physical origin. Virgin and aged devices will be used as test vehicles to study the dependence on the manufacturing process of the devices electrical behaviour. From a macroscopic point of view, both phenomena are quite different, so whilst gate-lag depends on Vgs voltage, drain-lag depends on the Vds one. Considering differences between virgin and aged devices, a conclusion about the dependence of trap levels on both thermal and electrical stress could be extracted

Estudio y caracterización del efecto kink en transistores HEMT de GaN

Using as test vehicles virgin and aged GaN HEMT devices, a study of the kink effect evolution with the applied electric field and ambient temperature has been performed. The obtained results lead to a physics explanation of the kink effect origin as well as its dependence on ambient temperature. Experimental results, showing the different effects taking place in the transistor, will be reported for several GaN devices operating at different electric field and temperature conditions

Efectos térmicos y trampa en los transistores AlGaN/GaN HEMT

Traps effects (due to the presence of surface-state densities and deep-levels) in AlGaN/GaN HEMT devices cause slow current transients referred as gate-lag and drain-lag effects that become a cause of so called current collapse. Current collapse is a reversible reduction of drain-current when both the gate and drain voltages are changed abruptly. This effect cause important deviation between DC and dynamic I/V characteristics that limits the output power of the device at high frequencies. In addition, traps state depends on thermal and illumination conditions of the device. Energy from the illumination and temperature supports the electrons captured in traps states to overcome the energy-barrier to the conduction band. In order to improve the device performance and reliability, understanding the current collapse effects is critical, and it must be taken into account when an accurate large-signal dynamic model is needed. In this paper, drain-current collapse due to gate-lag and drain-lag effects as well as the effects of temperature on traps state are characterised based on pulsed measurements technique

Status of HIV and hepatitis C virus infections among prisoners in the Middle East and North Africa: review and synthesis.

INTRODUCTION: The status of HIV and hepatitis C virus (HCV) infections among incarcerated populations in the Middle East and North Africa (MENA) and the links between prisons and the HIV epidemic are poorly understood. This review synthesized available HIV and HCV data in prisons in MENA and highlighted opportunities for action. METHODS: The review was based on data generated through the systematic searches of the MENA HIV/AIDS Epidemiology Synthesis Project (2003 to December 15, 2015) and the MENA HCV Epidemiology Synthesis Project (2011 to December 15, 2015). Sources of data included peer-reviewed publications and country-level reports and databases. RESULTS AND DISCUSSION: We estimated a population of 496,000 prisoners in MENA, with drug-related offences being a major cause for incarceration. Twenty countries had data on HIV among incarcerated populations with a median prevalence of 0.6% in Afghanistan, 6.1% in Djibouti, 0.01% in Egypt, 2.5% in Iran, 0% in Iraq, 0.1% in Jordan, 0.05% in Kuwait, 0.7% in Lebanon, 18.0% in Libya, 0.7% in Morocco, 0.3% in Oman, 1.1% in Pakistan, 0% in Palestine, 1.2% in Saudi Arabia, 0% in Somalia, 5.3% in Sudan and South Sudan, 0.04% in Syria, 0.05% in Tunisia, and 3.5% in Yemen. Seven countries had data on HCV, with a median prevalence of 1.7% in Afghanistan, 23.6% in Egypt, 28.1% in Lebanon, 15.6% in Pakistan, and 37.8% in Iran. Syria and Libya had only one HCV prevalence measure each at 1.5% and 23.7%, respectively. There was strong evidence for injecting drug use and the use of non-sterile injecting-equipment in prisons. Incarceration and injecting drugs, use of non-sterile injecting-equipment, and tattooing in prisons were found to be independent risk factors for HIV or HCV infections. High levels of sexual risk behaviour, tattooing and use of non-sterile razors among prisoners were documented. CONCLUSIONS: Prisons play an important role in HIV and HCV dynamics in MENA and have facilitated the emergence of large HIV epidemics in at least two countries, Iran and Pakistan. There is evidence for substantial but variable HIV and HCV prevalence, as well as risk behaviour including injecting drug use and unprotected sex among prisoners across countries. These findings highlight the need for comprehensive harm-reduction strategies in prisons