Radiation hardening of Rare-Earth doped fiber amplifiers

We investigated the radiation hardening of optical fiber amplifiers operating in space environments. Through a real-time analysis in active configuration, we evaluated the role of Ce in the improvement of the amplifier performance against ionizing radiations. Ce-codoping is an efficient hardening solution, acting both in the limitation of defects in the host glass matrix of RE-doped optical fibers and in the stabilization of lasing properties of the Er3+-ions. On the one hand, in the nearinfrared region, radiation induced attenuation measurements show the absence of radiation induced P-related defect species in host glass matrix of the Ce-codoped active fibers; on the other hand, in the Ce-free fiber, the higher lifetime variation shows stronger local modifications around the Er3+-ions with the absence of Ce

Radiation hardening techniques for rare-earth based optical fibers and amplifiers

Er/Yb doped fibers and amplifiers have been shown to be very radiation sensitive, limiting their integration in space. We present an approach including successive hardening techniques to enhance their radiation tolerance. The efficiency of our approach is demonstrated by comparing the radiation responses of optical amplifiers made with same lengths of different rare-earth doped fibers and exposed to gamma-rays. Previous studies indicated that such amplifiers suffered significant degradation for doses exceeding 10 krad. Applying our techniques significantly enhances the amplifier radiation resistance, resulting in a very limited degradation up to 50 krad. Our optimization techniques concern the fiber composition, some possible pre-treatments and the interest of simulation tools used to harden by design the amplifiers. We showed that adding cerium inside the fiber phosphosilicate-based core strongly decreases the fiber radiation sensitivity compared to the standard fiber. For both fibers, a pre-treatment with hydrogen permits to enhance again the fiber resistance. Furthermore, simulations tools can also be used to improve the tolerance of the fiber amplifier by helping identifying the best amplifier configuration for operation in the radiative environment

Ставлення істориків українських земель другої половини XIX — початку XX ст. до релігії та церкви

У статті показані головні підходи істориків того періоду до важливих суспільних явищ, підкреслені відмінності підходи позитивістів та прихильників інших наукових парадигм.The article shows the main approaches of historians of that period to these important social phenomena, stresses the differences between the approaches of the positivists and supporters of other scientific paradigms

The Roles of the S3MPC: Monitoring, Validation and Evolution of Sentinel-3 Altimetry Observations

The Sentinel-3 Mission Performance Centre (S3MPC) is tasked by the European Space Agency (ESA) to monitor the health of the Copernicus Sentinel-3 satellites and ensure a high data quality to the users. This paper deals exclusively with the effort devoted to the altimeter and microwave radiometer, both components of the Surface Topography Mission (STM). The altimeters on Sentinel-3A and -3B are the first to operate in delay-Doppler or SAR mode over all Earth surfaces, which enables better spatial resolution of the signal in the along-track direction and improved noise reduction through multi-looking, whilst the radiometer is a two-channel nadir-viewing system. There are regular routine assessments of the instruments through investigation of telemetered housekeeping data, calibrations over selected sites and comparisons of geophysical retrievals with models, in situ data and other satellite systems. These are performed both to monitor the daily production, assessing the uncertainties and errors on the estimates, and also to characterize the long-term performance for climate science applications. This is critical because an undetected drift in performance could be misconstrued as a climate variation. As the data are used by the Copernicus Services (e.g., CMEMS, Global Land Monitoring Services) and by the research community over open ocean, coastal waters, sea ice, land ice, rivers and lakes, the validation activities encompass all these domains, with regular reports openly available. The S3MPC is also in charge of preparing improvements to the processing, and of the development and tuning of algorithms to improve their accuracy. This paper is thus the first refereed publication to bring together the analysis of SAR altimetry across all these different domains to highlight the benefits and existing challenges

Les sécheresses du Nordeste brésilien

Note portant sur l’auteur Note portant sur l’auteur Note portant sur l’auteur Le Nordeste brésilien qui comprend actuellement 36 millions d’habitants soit près du tiers de la population du pays, a toujours été éprouvé par les sécheresses. Mais ce n’est pas tant la faible quantité d’eau précipitée annuellement qui est la cause principale des sécheresses, mais plutôt l’irrégularité des précipitations au cours d’une même année. Dans la zone semi-aride, où la pluviométrie moyenne annuelle varie e..

Methods for the estimation of a stationary battery\'s capacity with enfasis on security aplications.

Neste projeto, é proposto métodos diferentes para medir a capacidade e o envelhecimento de baterias estacionárias com ênfase em aplicações de segurança. Para tanto, é primeiro descrito a importância de baterias em diversas aplicações, principalmente as baterias de íons de lítio. Um estudo das características elétricas e químicas de baterias de íons de lítio é apresentado, mostrando entre outras coisas as causas eletroquímicas do envelhecimento. Além disso, as diferentes técnicas para o monitoramento de sistemas são mostradas. Neste projeto pretende-se usar redes neurais, lógica fuzzy e adaptatividade para estimar a capacidade de uma bateria usando os valores da resistência e capacitância interna. Os dados recolhidos são apresentados e analisados. Os diferentes métodos são comparados e as vantagens e desvantagens de cada método são discutidas.This project proposes different methods for measuring the capacity and aging of stationary batteries on security sistems. For this, it is first described batteries\' important role on many applications, especially concerning lithium-ion batteries. A study of electrical and chemical characteristics of lithium-ion batteries is presented, showing among other things the electrochemical causes for aging. Furthermore, different techniques for Battery Management System (BMS) are shown. In this project we intend to use a neural network, fuzzy logic and adaptability to estimate the battery\'s capacity using the internal resistance and capacitance values. The data collected is presented and analyzed. In the end, each method is compared with one another

Subseasonal coastal-trapped wave propagations in the Southeastern Pacific and Atlantic Oceans : 2. Wave characteristics and connection with the equatorial variability

The objective of this study is to compare the characteristics of the oceanic teleconnection with the linear equatorial dynamics of two upwelling systems along the southwestern South American and African continents at subseasonal time scales (<120 days). Altimetric data analysis shows that the coastal variability remains coherent with the equatorial signal until 27 degrees S in the southeastern Pacific (SEP), while in the southeastern Atlantic (SEA) it fades out south of 12 degrees S. To explain this striking difference, our methodology is based on the experimentation with twin regional model configurations of the SEP and SEA Oceans. The estimation of free Coastal-Trapped Waves (CTWs) modal structures and associated contribution to coastal variability allows inferring and comparing the characteristics of each CTW mode in the two systems; namely, their forcings, amplitude, dissipation rate, and scattering. Results show that the Pacific subseasonal equatorial forcing is only 20% larger than in the Atlantic, but important differences in the relative contribution of each baroclinic mode are reported. The first baroclinic mode dominates the eastern equatorial Pacific variability, while in the eastern equatorial Atlantic, the second mode is the most energetic. This leads to a drastic increase in the dissipation and scattering of the remotely forced CTW in the SEA sector, compared to the coastal SEP. Concomitantly, south of 15 degrees S, the subseasonal coastal wind stress forcing is substantially more energetic in the SEA and participates in breaking the link between the equatorial forcing and the coastal variability. Our results are consistent with the solutions of a simple multimode CTW model. Plain Language Summary The Humboldt and the Benguela upwelling systems are connected to the equatorial variability. Part of the incoming eastward equatorial wave energy is transmitted southward along the South American and African coasts as Coastal-Trapped Waves, where they imprint on the ecosystem variability. At subseasonal time scales (<120 days), altimetry reveals that the coastal variability remains coherent with the equatorial signal until 27 degrees S in the southeastern Pacific, while in the Atlantic counterpart it fades out south of 12 degrees S. To explain this striking difference, we compare the characteristics of coastal waves between the two systems: their forcing at the equator, their dissipation and scattering along their propagation, and the energization by the coastal wind stress. We use a variety of ocean models of different complexity ranging from regional general circulation models to simple linear coastal models. Results show that the difference between the two systems regarding the connection with the equatorial variability can be attributed to the distinct characteristics of their equatorial forcing. The latter favors fast and weakly dissipative coastal wave in the Humboldt. Off southwestern Africa, the equatorially-forced coastal-trapped waves dissipate at approximate to 13 degrees S and the subseasonal coastal wind stress forcing which is energetic south of 15 degrees S, participates in breaking the link between the equatorial and coastal variabilities