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Gebze, Turkey

Mkhinini N.,Laboratoire Of Meteorologie Dynamique | Coimbra A.L.S.,UME | Stegner A.,Laboratoire Of Meteorologie Dynamique | Arsouze T.,Laboratoire Of Meteorologie Dynamique | And 2 more authors.
Journal of Geophysical Research C: Oceans | Year: 2015

We analyzed 20 years of AVISO data set to detect and characterize long-lived eddies, which stay coherent more than 6 months, in the eastern Mediterranean Sea. In order to process the coarse gridded ( 1/8°) AVISO geostrophic velocity fields, we optimized a geometrical eddy detection algorithm. Our main contribution was to implement a new procedure based on the computation of the Local and Normalized Angular Momentum (LNAM) to identify the positions of the eddy centers and to follow their Lagrangian trajectories. We verify on two mesoscale anticyclones, sampled during the EGYPT campaign in 2006, that our methodology provides a correct estimation of the eddy centers and their characteristic radius corresponding to the maximal tangential velocity. Our analysis reveals the dominance of anticyclones among the long-lived eddies. This cyclone-anticyclone asymmetry appears to be much more pronounced in eastern Mediterranean Sea than in the global ocean. Then we focus our study on the formation areas of long-lived eddies. We confirm that the generations of the Ierapetra and the Pelops anticyclones are recurrent and correlated to the Etesian wind forcing. We also provide some evidence that the smaller cyclonic eddies formed at the southwest of Crete may also be induced by the same wind forcing. On the other hand, the generation of long-lived eddies along the Libyo-Egyptian coast are not correlated to the local wind-stress curl but surprisingly, their initial formation points follow the Herodotus Trough bathymetry. Moreover, we identify a new formation area, not discussed before, along the curved shelf off Benghazi. © 2014. American Geophysical Union. All Rights Reserved.

Hallstrom J.,MIKES | Bergman A.,SP | Dedeoglu S.,UME | Elg A.,SP | And 6 more authors.
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2012

This paper describes design principles of a wideband HVDC reference divider. The modular divider will be used for traceable calibration of HVDC measuring systems up to 1000 kV in customers' laboratories. The first priority in the design was the accuracy of HVDC measurements. In addition the divider was designed to have wide bandwidth, both to enable measurement of ripple voltages and to prevent damage during possible flashovers. © 2012 IEEE.

Otal P.,LNE | Morgado I.,LNE | Steindl D.,BEV | Medina Martin N.,CEM | And 12 more authors.
PTB - Mitteilungen Forschen und Prufen | Year: 2011

Fifteen European metrological institutes have compared their approaches to estimate the effective area parameters resulting from the calibration of pressure balances by cross-floating. The methods in estimating these parameters and the associated uncertainties are tested by applying four calibration data sets simulated numerically, two in gas (up to 10 MPa) and two in oil (up to 500 MPa). The performance of the methods is evaluated in terms of robustness and ability to estimate the uncertainties of the effective area parameters.

Kocas I.,UME | Sabuga W.,PTB | Bergoglio M.,INRIM - Istituto Nazionale di Ricerca Metrologica | Eltawil A.E.,Nis | And 4 more authors.
PTB - Mitteilungen Forschen und Prufen | Year: 2011

The regional key comparison EURAMET.M.P-K13 for pressure measurements in liquid media from 50 MPa to 500 MPa was piloted by the TÜBİTAK UME Pressure Group Laboratories, Turkey. The transfer standard was a DH-Budenberg pressure balance with a free deformation piston-cylinder unit of 2 mm2 nominal effective area. Seven laboratories from the EURAMET region, namely PTB, INRIM, NIS, SMU, IMT and NPL, and one laboratory from the APMP region, NMISA, participated in this comparison. PTB participated in this comparison as a link between this comparison, previous 500 MPa comparison EUROMET 881 and 500 MPa CCM key comparison CCM.P-K13. All participants' results with exception of only one value at 500 MPa at were found to be consistent with each other and with the calculated reference value, within their claimed uncertainties, at all pressures. The results are therefore considered to be satisfactory.

Chabassier J.,French Institute for Research in Computer Science and Automation | Chaigne A.,UME
20th International Congress on Acoustics 2010, ICA 2010 - Incorporating Proceedings of the 2010 Annual Conference of the Australian Acoustical Society | Year: 2010

Construction of a physical model for the grand piano implies complex and multidimensional phenomena. We present a model of piano strings coupled to a soundboard, and its numerical approximation. Measurements on piano strings and bridge show phantom partials and a time precursor that both cannot be explained by the linear scalar string model. A classical model of nonlinear strings has been written by Morse & Ingard, it implies to consider the longitudinal displacement as well as the standard transversal displacement of the string, in a nonlinear coupled system. Various approximate (polynomial) models have been written from this one, by expanding the nonlinearity (a square root term) around the rest position of the string. We provide a mathematical justification of the most used model. Transmission of the string motion to the rest of the structure is essential from the acoustical point of view. We use a modal approach for the soundboard, and we write a nonstandard reciprocal coupling condition between strings and soundboard at the bridge. Numerical approximation of such a nonlinear, multidimensional and coupled problem is a difficult issue. We use an energy approach to achieve stability, which leads to an innovating implicit numerical scheme.

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