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See detailPostulates for Revocation Schemes
Cramer, Marcos UL; Casini, Giovanni UL

in Cramer, Marcos; Casini, Giovanni (Eds.) Principles of Security and Trust. Proceedings of the 6th International Conference POST 2017 (2017, January 18)

In access control frameworks with the possibility of delegating permissions and administrative rights, delegation chains can form. There are di erent ways to treat these delegation chains when revoking ... [more ▼]

In access control frameworks with the possibility of delegating permissions and administrative rights, delegation chains can form. There are di erent ways to treat these delegation chains when revoking rights, which give rise to di erent revocation schemes. Hagstr om et al. [11] proposed a framework for classifying revocation schemes, in which the di erent revocation schemes are de ned graph-theoretically. At the outset, we identify multiple problems with Hagstr om et al.'s de nitions of the revocation schemes, which can pose security risks. This paper is centered around the question how one can systematically ensure that improved de nitions of the revocation schemes do not lead to similar problems. For this we propose to apply the axiomatic method originating in social choice theory to revocation schemes. Our use of the axiomatic method resembles its use in belief revision theory. This means that we de ne postulates that describe the desirable behaviour of revocation schemes, study which existing revocation frameworks satisfy which postulates, and show how all de ned postulates can be satis ed by de ning the revocation schemes in a novel way. [less ▲]

Detailed reference viewed: 183 (39 UL)
See detailPosture éthique et compétences de l'enseignant
Weber, Jean-Marie UL

in Transfert (2006)

Detailed reference viewed: 53 (0 UL)
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See detailPostwachstum finanzieren? Grüne Finanzprodukte für veränderte Produktionslogiken
Dörry, Sabine; Schulz, Christian UL

in Lange, Bastian; Hülz, Martina; Schmid, Benedikt (Eds.) et al Postwachstumsgeographien. Raumbezüge diverser und alternativer Ökonomien (2020)

Detailed reference viewed: 38 (4 UL)
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See detailPostwachstum in den Raumwissenschaften
Schulz, Christian UL

in Akademie fuer Raumforschung und Landesplanung. Nachrichten (2018), 47(4), 11-14

Detailed reference viewed: 174 (5 UL)
See detailPostwachstumsgeographien – Mehr Räume für Alternativen!
Lange, Bastian; Hülz, Martina; Schmid, Benedikt et al

in Corona Blog (2020)

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See detailPostwachstumsgeographien. Konzeptionelle und thematische Eckpunkte der Anthologie
Schulz, Christian UL; Lange, Bastian; Hülz, Martina et al

in Lange, Bastian; Hülz, Martina; Schmid, Benedikt (Eds.) et al Postwachstumsgeographien. Raumbezüge diverser und alternativer Ökonomien (2020)

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See detailPostwachstumsgeographien. Raumbezüge diverser und alternativer Ökonomien
Lange, Bastian; Hülz, Martina; Schmid, Benedikt et al

Book published by Transcript (2020)

Detailed reference viewed: 39 (4 UL)
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See detailPotassium fluoride ex-situ treatment on both Cu-rich and Cu-poor CuInSe2 thin film solar cells
Elanzeery, Hossam UL; Babbe, Finn UL; Melchiorre, Michele UL et al

in IEEE Journal of Photovoltaics (2017), 7(2), 684-689

Detailed reference viewed: 322 (14 UL)
Peer Reviewed
See detail[Potassium restriction and essential hypertension].
Neyses, Ludwig UL

in Deutsche medizinische Wochenschrift (1946) (1992), 117(35), 1341

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See detailPotential Component Leaks in Android Apps: An Investigation into a new Feature Set for Malware Detection
Li, Li UL; Allix, Kevin UL; Li, Daoyuan UL et al

in The 2015 IEEE International Conference on Software Quality, Reliability and Security (QRS 2015) (2015, August)

Detailed reference viewed: 536 (261 UL)
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See detailPotential Contributions to Geoscience from GNSS Observations of the King Edward Point Geodetic Observatory, South Georgia, South Atlantic Ocean
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Ahmed, Furqan UL et al

Poster (2013, September 01)

During February 2013 the King Edward Point (KEP) Geodetic Observatory was established in South Georgia, South Atlantic Ocean, through a University of Luxembourg funded research project and in ... [more ▼]

During February 2013 the King Edward Point (KEP) Geodetic Observatory was established in South Georgia, South Atlantic Ocean, through a University of Luxembourg funded research project and in collaboration with the United Kingdom’s National Oceanography Centre, British Antarctic Survey and Unavco, Inc. Due to its remote location in the South Atlantic Ocean, as well as, being one of few subaerial exposures of the Scotia plate, South Georgia Island has been a key location for a number of global monitoring networks, e.g. seismic, geomagnetic and oceanic. However, no geodetic monitoring station has been established, e.g. by the International Global Navigation Satellite System (GNSS) Service (IGS) community, despite the lack of such observations from this region. In this study we will present an evaluation of the GNSS observations from the KEP Geodetic Observatory for the period from February to August 2013. We calculate multipath and positioning statistics and compare these to those from IGS stations. The on-site meteorological data is compared to those from the nearby KEP meteorological station and global numerical weather models, and the impact of these data sets on delay and integrated water vapour estimates will be evaluated. We will discuss the installation in terms of its potential contributions to sea level observations using tide gauges and satellite altimetry, studies of tectonics, glacio-isostatic adjustment and atmospheric processes. [less ▲]

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See detailPotential energy landscape of monolayer-surface systems governed by repulsive lateral interactions: The case of (3 x 3)-I-Pt(111)
Tkatchenko, Alexandre UL; Batina, Nikola; Galvan, Marcelo

in PHYSICAL REVIEW LETTERS (2006), 97(3),

Combined density functional theory (DFT) and Monte Carlo (MC) approach is applied to study the potential energy landscape of four iodine atoms adsorbed on the Pt(111) surface in a (3x3) unit cell. Three ... [more ▼]

Combined density functional theory (DFT) and Monte Carlo (MC) approach is applied to study the potential energy landscape of four iodine atoms adsorbed on the Pt(111) surface in a (3x3) unit cell. Three critical points were identified: (3x3)-sym and (3x3)-asym, corresponding to structures well known from experimental studies, while the third one (3x3)-zigzag is a new structure not reported before. An interaction model fitted to DFT calculations allows us to explain the difference between arrangements of iodine monolayer in vacuum, air, and solution environments as a result of different repulsion regimes. [less ▲]

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See detailThe potential of including the UK in comparisons with other European countries in research on teenage pregnancy
Franz, Anke; Worrell, Marcia; Gilvarry, Catherine et al

in Critical Social Policy (2009), 29

This article is a response to Arai (2003) ‘British policy on teenage pregnancy and childbearing: The limitations of comparisons with other European countries’ (Critical Social Policy 23: 89–102). It ... [more ▼]

This article is a response to Arai (2003) ‘British policy on teenage pregnancy and childbearing: The limitations of comparisons with other European countries’ (Critical Social Policy 23: 89–102). It discusses the arguments put forward by Arai there that cross-cultural comparisons in the area of teenage pregnancy are often problematic due to the unique demographics of the UK. While Arai’s considerations are important for cross-cultural research, they need to be more sensitive to the differences between countries included in these comparisons. Our article illustrates the potential value of cross-cultural research, using Germany as an exam- ple, and concludes that, as long as countries for such comparisons are cho- sen carefully, the merit of cross-cultural research on topics such as teenage pregnancy far exceeds its limitations. [less ▲]

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See detailThe potential of Language Technology and AI
Schommer, Christoph UL

Speeches/Talks (2020)

Detailed reference viewed: 130 (3 UL)
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See detailThe Potential of Precipitable Water Vapour Measurements from Global Navigation Satellite Systems in Luxembourg
Ahmed, Furqan UL

Doctoral thesis (2015)

The primary objectives of this research were to investigate the potential of precipitable water vapour (PWV) estimates derived from Global Navigation Satellite Systems (GNSS) measurements, firstly, for ... [more ▼]

The primary objectives of this research were to investigate the potential of precipitable water vapour (PWV) estimates derived from Global Navigation Satellite Systems (GNSS) measurements, firstly, for short-term weather forecasting based on numerical weather prediction (NWP) in Luxembourg and its surroundings and, secondly, for monitoring climate on regional and global scales. The suitability of real-time (RT) zenith total delay (ZTD) estimates obtained from three different precise point positioning (PPP) software packages was assessed by comparing them with the state-of-the-art product from the International GNSS Service (namely the IGS Final troposphere product) as well as collocated radiosonde (RS) observations. It was found that the RT-PPP ZTD estimates from two of the three software packages meet the threshold requirements for NWP nowcasting. The biases between the RT-PPP ZTD and the reference ZTD were found to be stable over time for all the RT-PPP ZTD solutions. A millimetre-level impact on the RT-PPP ZTD estimates was also observed when integer ambiguities were resolved. The impact of assimilating GNSS-derived near real-time (NRT) ZTD in the Applications of Research to Operations at Mesoscale (AROME) NWP model using a three-dimensional, variational (3D-VAR) assimilation scheme on the quality of weather forecasts for Luxembourg was studied. It was found that the assimilation of GNSS-derived ZTD systematically improves the atmospheric humidity short-range forecasts in comparison to other water vapour observing systems (radio soundings, satellite radiances, surface networks). Examination of several case studies revealed the ability of the ZTD observations to modify the intensity and location of predicted precipitation in accordance with previous studies. The addition of ZTD from the dense GNSS network in Wallonie (Belgium) was also found to be beneficial by improving the prediction of rainfall patterns in Luxembourg. The 2D maps of IWV obtained from the hourly NRT system were compared with cloud distribution and precipitation maps from satellite and weather radar data, respectively, and a good agreement in the location of the front system was found. A rise in IWV was recorded during a precipitation event in Luxembourg and it was shown that by observing the IWV change over the ground-based GNSS stations in Luxembourg in NRT, it is possible to determine the speed and direction of the passing fronts and hence storms can also be tracked. A 5-year long global reprocessed GNSS data set containing over 400 ground-based GNSS stations and based on the double differencing strategy has been used to validate the ZTD estimates obtained from the climate reanalysis model of the European Centre for Medium-range Weather Forecasts (ECMWF) namely the ECMWF ReAnalysis-Interim (ERA-Interim) in different climate zones. It was found that the correlation coefficient between the GNSS-derived ZTD observations and the ZTD modeled by ERA-Interim ranges from 0.87 to 1.00. Higher correlation coefficients were found for the stations belonging to the climate zones with lower amount of water vapour. Furthermore, it was found that the mean, SDev and RMS of the differences depends on periodicity in the residuals, altitude of the stations in a particular zone as well as the topographic variation in the zone. Monthly and seasonal means of GNSS-derived ZTD (ZTDgnss) were computed using a global ZTDgnss dataset consisting of 19-years of data and over 400 stations to study the climate variability in different climate zones. In terms of seasonal means, it was found that the climate zones in the northern hemisphere have ZTD maxima in Boreal Summer (June-July-August) whereas those in the southern hemisphere have ZTD maxima in Austral Summer (December-January-February). Monthly and seasonal variability in ZTDgnss was also studied for the locations of 6 ground-based GNSS (SPSLux) stations in Luxembourg. It was found that all the 6 SPSLux stations experience the same monthly and seasonal variability of ZTDgnss. In terms of monthly variation, it was found that the maxima in ZTDgnss occurs around the month of July for all the 6 SPSLux stations whereas in terms of seasonal variation, the location of maxima was found to be in Summer (June-July-August). The suitability of the ZTD derived using precise point positioning (PPP) strategy for climate monitoring applications was studied through its comparison with the ZTD estimates derived using double differenced positioning (DDP) using a global network of 114 stations and duration of 1 year. The mean differences between the two were found to be ranging from -3.35 to 2.37 mm over different climate zones. Furthermore, correlation coefficients ranging from 0.90 and 1.00 were found between the ZTD obtained using the two processing strategies. It was found that use of higher elevation cut-off angles and tropospheric mapping functions based on NWP improves the agreement between the PPP and DDP solutions. [less ▲]

Detailed reference viewed: 251 (17 UL)