Search results for "s.r.l.s."
showing 10 items of 213 documents
Model-assisted ultrasonic calibration using intentionally embedded defects for in-process weld inspection
2021
Abstract Automated in-process Non-Destructive Testing (NDT) systems are rapidly gaining traction within the manufacturing industry as they reduce manufacturing time and costs. When considering calibration and verification of such systems, creating defects of known geometry and nature during the deposition of a weld can: (I) help examine the capability of the automated system to detect and characterise defects, (II) be used to form a database of signals associated with different defect types to train intelligent defect classification algorithms, and (III) act as a basis for in-process gain calibration during weld inspection at high temperatures, where the ultrasound beam can be skewed as a r…
More Dubious Dead Sea Scrolls
2021
Abstract In the course of the last eighteen years more than 75 new “Dead Sea Scrolls” fragments have surfaced on the antiquities market. These are commonly referred to as post-2002 Dead Sea Scrolls-like fragments. A growing number of scholars regard a substantial part of them as forgeries. In this article, we will discuss four more dubious fragments, but this time from the 20th Century—or at least from pre-2002. Two of the fragments have been known since the late nineties and are published in the DJD series. One was published in Revue de Qumran (2003), and one in Gleanings from the Caves (2016). All four are today accepted as part of the Dead Sea Scrolls dataset even though they are unprove…
Laser Cladding of TiC for Better Titanium Components
2011
Pure commercial titanium is widely used because of its high corrosion resistance and lower cost compared with other titanium alloys, in particular when there is no high wear requirements. Nevertheless, the wear resistance is poor and surface damage usually occurs in areas under contact loadings. Laser cladding is a suitable technique for manufacturing precise and defect free coatings of a dissimilar material with higher wear and corrosion resistance. In this work a good understanding of laser metal deposition mechanisms allowed to obtain defect free coatings of Ti6Al4V and TiC metal matrix composite (MMC) using a flash lamp pumped Nd:YAG laser of 1 kW. A complete investigation of the proces…
Effect of gaseous impurities and the laser optics
2004
The impurities into the volume of a material appear while the elaboration process of the considered material. If a material is non-homogenous, even if we machine this material by means of a classical technology we could remark some differences in the machining process like cutting, drilling a.s.o. even in the process of welding. The impurities may be gaseous or solid. Each kind of impurity has another effect for the classical tool, or for a non-traditional tool i.e. a kind of concentrated energy. Each kind of medium has another reaction versus laser beam, because each medium has other physical characteristics. The modifications of characteristics require modifications of photon beam paramet…
Coexistence of quasi-CW and SBS-boosted selfQ-switched pulsing in ytterbium-doped fiber laser with low Q-factor cavity
2020
We report the results of an experimental study of an ytterbium-doped fiber laser with low Q-factor cavity. We demonstrate that the laser operates in two randomly alternating sub-regimes, quasi-CW (QCW) and self-Q-switching (SQS), the latter ignited by stimulated Brillouin scattering (SBS). We show that probability of each sub-regime depends on pump power: QCW dominates slightly above the laser threshold while SQS pulsing prevails at higher pump powers. We also discuss the featuring details of QCW sub-regime and its role in instabilities (jittering) of SBS-boosted SQS pulsing as well as the statistical properties of the latter.
Alma Mater: 2013/ Ziema
2013
Andra Čudare. Gribu saprast, kas ir aiz debess malas ; Indra Gleizde. Kā var nepatikt Gēte? Daudzšķautņainā personība Valdis Bisenieks; Gita Siliņa. Zinātne un kultūra viena otrai palīdz; Andra Čudare. Svētā Četrvienība Teoloģijas fakultātē; LU Preses centrs. 14 uzņēmumi zem viena jumta; Leonardo Patačini. No Buenosairesas līdz Rīgai; Lauma Abramoviča, Evija Ansonska, Ilze Jansone, Jeļena Poļakova, Kristīne Zaksa. Aizrautība ārpus Universitātes sienām; Aija Taimiņa. Rīgas pirmajai tipogrāfijai – 425; Katrīna Žukova. Japāna ienāk Universitātes sporta zālē; Mikus Žagata. «Austrums» – cauri trim gadsimtiem un kontinentiem; LU Preses centrs. Katru ceturtdienu paver mākoņa malu; Aktuāli notikumi…
Characterizations of convex approximate subdifferential calculus in Banach spaces
2016
International audience; We establish subdifferential calculus rules for the sum of convex functions defined on normed spaces. This is achieved by means of a condition relying on the continuity behaviour of the inf-convolution of their corresponding conjugates, with respect to any given topology intermediate between the norm and the weak* topologies on the dual space. Such a condition turns out to also be necessary in Banach spaces. These results extend both the classical formulas by Hiriart-Urruty and Phelps and by Thibault.
Modelling of laser beam texturing process: experimental and numerical approaches
2007
The aim of this work is to reache a better control of the laser beam surface texturing process on three materials: 304L, TA6V and AA6056 alloys. For this purpose, two complementary methods, experimental and numerical modelling, have been used. As a result of the experimental design approach, it was observed that the laser surface texturing process of 304L and TA6V alloys is strongly influenced by the pulse energy and frequency. In order to obtain a surface roughness Sa < 5 µm for the highest possible productivity it is necessary to work with an energy of 5 mJ and a frequency ranging between 10 and 12 kHz. Unfortunately, for aluminium alloy AA6056, it is necessary to make a choice between ha…
Self-focusing in Terbium Gallium Garnet using Z-scan
1998
International audience; When illuminated near its resonance with an Ar ion laser beam (lambda=488 nm), laser induced thermal self-focusing is observed in Terbium Gallium Garnet. The crystal exhibits a strong intensity dependent refractive index change Dn. The Z-scan technique is used to study the beam waist change due to Dn. The refractive index is found to be well described by a quadratic spatial distribution model. Both the sign and the distribution coefficient of Dn are determined.
Très longs épisodes secs hivernaux dans le bassin méditerranéen : variabilité spatio-temporelle et impact sur la production céréalière en Espagne.
2018
This study concerns the long winter sequences without rain at the whole Mediterraneanbasin scale. Objectives are (i) to define theses extreme events as geographical and climatological objectscharacterized by a location, a spatial extension and a temporal length and (ii) measured impacts of these eventson the cereal production in Spain. 76 events of very long dry spells (eVLDS) are detected over the 1957-2013period. These eVLDS are grouped into 4 typical recurrent configurations at the Mediterranean basin scale: North-East, West, Scattered & Localised and South-East. The eVLDS have a greater impact on barley, wheat and oatyields (winter crops grown through rainfed agriculture) than rainfall …