Cookies Policy
The website need some cookies and similar means to function. If you permit us, we will use those means to collect data on your visits for aggregated statistics to improve our service. Find out More
Accept Reject
  • Menu
Publications

2018

Point spread function reconstruction coupling AO telemetry and focal plane images

Authors
Beltramo Martin, O; Correia, CM; Neichel, B; Fusco, T; Ragland, S; Wizinowich, PL;

Publication
ADAPTIVE OPTICS SYSTEMS VI

Abstract
Scientific exploitation in ground-based astronomy is improved thanks to adaptive optics (AO) that restore diffraction-limit angular resolution. Besides, the ultimate data interpretation is delivered by post-processing techniques that usually relies on a Point spread function (PSF) model. Nevertheless, existing methods to constrain this model based on standard pipeline encounter the spatial and time variations of the AO PSF. In order to improve accuracy on key science observables, such as photometry and astrometry, alternative methods are investigated, such as PSF reconstruction (PSF-R), designed to estimate the PSF from AO control-loop data and key atmosphere and system parameters. We aim in this paper at retrieving directly these relevant inputs we need to reconstruct the PSF using an hybrid approach, that couples AO telemetry with focal plane images, named as Focal plane profiling and reconstruction (FPPR). It adjusts atmosphere parameters (the C2n (h) profile) and optical gains in the system. We describe the FPPR method that is applied to on-sky Keck images in engineering mode operated with either natural or laser guide star and show we get 1% of accuracy on respectively the Strehl-ratio and the PSF FWHM reconstruction.

2018

Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole

Authors
Abuter, R; Amorim, A; Anugu, N; Bauböck, M; Benisty, M; Berger, JP; Blind, N; Bonnet, H; Brandner, W; Buron, A; Collin, C; Chapron, F; Clénet, Y; Du Foresto, VC; De Zeeuw, PT; Deen, C; Delplancke Ströbele, F; Dembet, R; Dexter, J; Duvert, G; Eckart, A; Eisenhauer, F; Finger, G; Schreiber, NMF; Fédou, P; Garcia, P; Lopez, RG; Gao, F; Gendron, E; Genzel, R; Gillessen, S; Gordo, P; Habibi, M; Haubois, X; Haug, M; Haußmann, F; Henning, T; Hippler, S; Horrobin, M; Hubert, Z; Hubin, N; Rosales, AJ; Jochum, L; Jocou, L; Kaufer, A; Kellner, S; Kendrew, S; Kervella, P; Kok, Y; Kulas, M; Lacour, S; Lapeyrère, V; Lazareff, B; Le Bouquin, JB; Léna, P; Lippa, M; Lenzen, R; Mérand, A; Müler, E; Neumann, U; Ott, T; Palanca, L; Paumard, T; Pasquini, L; Perraut, K; Perrin, G; Pfuhl, O; Plewa, PM; Rabien, S; Ramírez, A; Ramos, J; Rau, C; Rodríguez Coira, G; Rohloff, RR; Rousset, G; Sanchez Bermudez, J; Scheithauer, S; Schöller, M; Schuler, N; Spyromilio, J; Straub, O; Straubmeier, C; Sturm, E; Tacconi, LJ; Tristram, KRW; Vincent, F; Von Fellenberg, S; Wank, I; Waisberg, I; Widmann, F; Wieprecht, E; Wiest, M; Wiezorrek, E; Woillez, J; Yazici, S; Ziegler, D; Zins, G;

Publication
ASTRONOMY & ASTROPHYSICS

Abstract
The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU approximate to 1400 Schwarzschild radii, the star has an orbital speed of approximate to 7650 km s(-1), such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Delta lambda/lambda approximate to 200 km s(-1)/c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 +/- 0.09 vertical bar(stat) +/- 0.151 vertical bar(sys). The S2 data are inconsistent with pure Newtonian dynamics.

2018

The impact of knowledge management factors in organizational sustainable competitive advantage

Authors
Torres, AI; Ferraz, SS; Santos Rodrigues, H;

Publication
JOURNAL OF INTELLECTUAL CAPITAL

Abstract
Purpose The purpose of this paper is to empirically test the relations among different knowledge management (KM) factors, such as human capital (HC), processes and information systems (IS) on organizational sustainable competitive advantage (CA), within the SMEs context. Design/methodology/approach Structured questionnaires were distributed to CEOs and managers of Portuguese organizations through an electronic survey. Partial least squares software was utilized to analyze the data. Findings The measurement model results identify and validate the dimensions of HC, processes and IS representing the KM construct. The structural model results demonstrate that HC and processes have a direct and significant impact on organizational CA, on the customer and financial dimensions, respectively. IS indirectly and significantly influence organizational CA, mediated by HC and processes. Research limitations/implications The sample size includes mostly service business and SMEs. Other organizations sectors, such as industry, should be analyzed in order to develop a comparative cross-sectorial study. Practical implications This study establishes suggestions for managers to make legitimate decisions concerning investments on knowledge assets and organizational capabilities that can foster business growth and sustainable CA within a SMEs context. Originality/value The authors propose a mediation mechanism showing that the relationship between IS and sustainable CA is not direct, but it is mediated by HC and processes. This mechanism points out some critical issues for the strategic knowledge and intellectual capital assets, as a source of organizational CA.

2018

Purchase' Portfolio Optimization of Power Supply Company with Distributed PV Considering EVs

Authors
Ren, H; Zhang, A; Li, K; Wang, F; Li, Y; khah, MS; Catalão, JPS;

Publication
IEEE Industry Applications Society Annual Meeting, IAS 2018, Portland, OR, USA, September 23-27, 2018

Abstract
In recent years, with the vigorous development of the new energy industry in the world, distributed photovoltaics (PV) have strongly penetrated the international energy markets at exponential growth rates, and a large number of electric vehicles (EVs) have been used mainly driven by policies. The use of EVs and distributed PV would lead to an increase in load uncertainty. Hence, a new day-ahead portfolio optimization model for a power supply company with distributed PV considering EVs was developed. The model contains risks depending on market price fluctuation and load uncertainty caused by EVs load, conventional load and distributed PV's output, considering the expected cost of errors, and helping to determine an optimal quantity of power to be obtained from distributed PV's output and different electricity markets. This paper analyses the efficient frontier of conditional value-at-risk (CVaR) and the influence of different EVs market penetration levels and distributed PV's output on the portfolio strategy. © 2018 IEEE

2018

ReoLive: Analysing Connectors in Your Browser

Authors
Cruz, R; Proença, J;

Publication
Software Technologies: Applications and Foundations - STAF 2018 Collocated Workshops, Toulouse, France, June 25-29, 2018, Revised Selected Papers

Abstract

2018

Blended Mobility: a way for the Sustainable Internationalization of Higher Education

Authors
Escudeiro, N; Escudeiro, P;

Publication
SIXTH INTERNATIONAL CONFERENCE ON TECHNOLOGICAL ECOSYSTEMS FOR ENHANCING MULTICULTURALITY (TEEM'18)

Abstract
Modern economy requires engineers to excel in collaborative and communication skills at an international setting. However, these competences are not usually addressed in most engineering curricula. In the Multinational Undergraduate Team Work course, MUTW, students develop their capstone project as members of an international team while working at their home institutions. Team members are geographically spread to assure heterogeneous teams and to promote international cooperation. This paradigm can be applied in any project/internship course unit. The results from the pilot editions that ran between 2009 and 2011 support our initial hypothesis that MUTW significantly promotes students' soft skills without requiring costly and time consuming changes to prior degree curricula.

  • 1641
  • 4188