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808 results on '"Mostafavi M"'

1. Accurate Sea Surface heights from Sentinel-3A and Jason-3 retrackers by incorporating High-Resolution Marine Geoid and Hydrodynamic Models

Author

Mostafavi M., Delpeche-Ellmann N., and Ellmann A.

Subjects
baltic sea, geoid, tide gauge, hydrogeodesy, hydrodynamic model, jason-3, retracker, satellite altimetry, sea surface height, sentinel-3a, Geodesy, QB275-343
Abstract

One of the major challenges of satellite altimetry (SA) is to produce accurate sea surface heights data up to the shoreline, especially in geomorphologically complex sea areas. New advanced re-tracking methods are expected to deliver better results. This study examines the achievable accuracy of Sentinel-3A (S3A) and Jason-3 (JA3) standard retrackers (Ocean and MLE4) with that of improved retrackers adapted for coastal and sea ice conditions (ALES+ SAR for S3A and ALES+ for JA3). The validation of SA data was performed by the integration of tide gauges, hydrodynamic model and high-resolution geoid model. The geoid being a key component that links the vertical reference datum of the SA with other utilized sources. The method is tested in the eastern section of Baltic Sea. The results indicate that on average reliable sea surface height (SSH) data can be obtained 2–3 km from the coastline for S3A (for both Ocean and ALES+SAR) whilst an average distance of 7–10 km for JA3 (MLE4 and ALES+) with a minimum distance of 3–4 km. In terms of accuracy, the RMSE (with respect to a corrected hydrodynamic model) of S3A ALES+ SAR and Ocean retrackers based SSH were 4–5 cm respectively, whereas with the JA3 ALES+ and MLE4 associated SSH RMSE of 6–7 cm can be achieved. The ALES+ and ALES+ SAR retrackers show SSH improvement within a range of 0.5–1 cm compared to the standard retrackers. This assessment showed that the adaptation of localized retrackers for the Baltic Sea (ALES+ and ALES+SAR) produced more valid observation closer to the coast than the standard retrackers and also improved the accuracy of SSH data.

Published
2021
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5. Scintillating crystals for the Neutral Particle Spectrometer in Hall C at JLab

Author

Horn, T., Berdnikov, V. V., Ali, S., Asaturyan, A., Carmignotto, M., Crafts, J., Demarque, A., Ent, R., Hull, G., Ko, H. -S., Mostafavi, M., Munoz-Camacho, C., Mkrtchyan, A., Mkrtchyan, H., Trung, T. Nguyen, Pegg, I. L., Rindel, E., Somov, A., Tadevosyan, V., Trotta, R., Zhamkochyan, S., Wang, R., and Wood, S. A.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment, Nuclear Experiment
Abstract

This paper discusses the quality and performance of currently available PbWO$_4$ crystals of relevance to high-resolution electromagnetic calorimetry, e.g. detectors for the Neutral Particle Spectrometer at Jefferson Lab or those planned for the Electron-Ion Collider. Since the construction of the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) and early PANDA (The antiProton ANnihilations at DArmstadt) electromagnetic calorimeter (ECAL) the worldwide availability of high quality PbWO$_4$ production has changed dramatically. We report on our studies of crystal samples from SICCAS/China and CRYTUR/Czech Republic that were produced between 2014 and 2019., Comment: 20 pages, 30 figures

Published
2019
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15. Semihypergroup Actions by using the Generalized Permutations.

Author

DAVVAZ, B. and MOSTAFAVI, M.

Subjects
PERMUTATIONS, RESPECT
Abstract

An ordered hypergroupoid is a hypergroupoid together with a partial order such that satisfies the monotone condition. In this paper, we introduce the notion of semihypergroup actions on ordered hypergroupoids. Some results in this respect are investigated. In particular, we prove that if S is a commutative semihypergroup acting on an ordered hypergroupoid H, then there exists a commutative semihypergroup S acting on the ordered hypergroupoid ... in such a way that $H$ is embedded in H. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Quantifying Absolute Dynamic Topography by Synergy of Satellite, Geoid and Hydrodynamic Model

Author

Mostafavi, M., Delpeche Ellmann, N., and Ellmann, A.

Abstract

Accurate determination of absolute dynamic topography (ADT) has been mostly under-utilized because of limited access to high resolution geoid models. However, quantification of ADT is essential for advancing in realistically understanding ocean dynamic (e.g., ocean current patterns, sea level trends etc.). Most importantly it allows conformity of a stable vertical reference datum to be used amongst nations. As a result, this study develops and explores a method that derives ADT by employing both a geodetic and oceanographic approach. The geodesy approach utilizes multi-satellite along track satellite altimetry (SA) data in conjunction with the NKG2015 geoid model (developed by Baltic Sea countries). For the oceanographic approach the vertical datum of HDMs are often undisclosed, thus a method is applied using geoid referred tide gauges (TG), that corrects the HDM. The study site is that of the entire Baltic Sea for the period 2017‒2019.The statistical results showed average discrepancies between SA and HDM within range of ±20 cm; RMSE between 6‒ 9 cm and a standard deviation between 2‒16 cm. The method employed different sources; thus it identified problems with SA, HDM, TG, and geoid. For instance, possible geoid problems were discovered in the eastern Baltic Sea whereas for SA the northern Baltic sea-ice may be problematic. The comparison also revealed that SA along-track data has potential to show more realistic variation of ADT compared to that of HDM (which tended to generate a smooth surface). Also, in most cases, the HDM tended to underestimate the ADT., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023
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46. Investigating the mechanical behaviour of Fukushima MCCI using synchrotron Xray tomography and digital volume correlation

Author

Paraskevoulakos, C., Forna-Kreutzer, J.P., Hallam, K.R., Jones, C.P., Scott, T.B., Gausse, C., Liu, D., Reinhard, C., Corkhill, C.L., and Mostafavi, M.

Abstract

A primary target towards the clean-up operation of the Fukushima disaster is the retrieval of Molten Core-Concrete Interaction (MCCI) products, presently residing on the basement of the damaged nuclear reactor Units 1–3. MCCI is a fusion of materials, composed of both nuclear fuel cladding and neighbouring structural components. Determining the currently unknown, physical and mechanical properties of MCCI is essential for successful and timely retrieval. In this paper, we aim to experimentally quantify the mechanical properties of a material fabricated to resemble MCCI. A small-scale representative specimen was mechanically tested using Hertzian indentation stepwise loading. Synchrotron X-ray computed tomography was conducted at several loading stages to reveal the sample microstructure and mechanical degradation. The acquired tomograms were analysed by digital volume correlation to measure full-field displacements and strains developed within the sample volume. Young’s modulus and Poisson ratio were determined via this combined methodology.

Published
2022

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