2,149 research outputs found
Development of the TanDEM-X Calibration Concept: Analysis of Systematic Errors
No full textThe TanDEM-X mission, result of the partnership
between the German Aerospace Center (DLR) and Astrium
GmbH, opens a new era in spaceborne radar remote sensing. The first bistatic satellite synthetic aperture radar mission is formed by flying the TanDEM-X and TerraSAR-X in a closely controlled helix formation. The primary mission goal is the derivation of a high-precision global digital elevation model (DEM) according to High-Resolution Terrain Information (HRTI) level 3 accuracy.
The finite precision of the baseline knowledge and uncompensated radar instrument drifts introduce errors that may compromise the height accuracy requirements. By means of a DEM calibration, which uses absolute height references, and the information provided by adjacent interferogram overlaps, these height errors can be minimized. This paper summarizes the exhaustive studies of the nature of the residual-error sources that have been carried out during the development of the DEM calibration concept.
Models for these errors are set up and simulations of the resulting DEM height error for different scenarios provide the basis for the development of a successful DEM calibration strategy for the TanDEM-X mission
TOPS Imaging with TerraSAR-X: Mode Design and Performance Analysis
No full textThis paper reports about the performed investigations for the implementation of the wide swath TOPS imaging mode with TerraSAR-X. The TOPS mode overcomes the limitations imposed by the ScanSAR mode by steering the antenna along-track during the acquisition of a burst. In this way, a uniform signal to noise ratio (SNR) is achieved, and consequently, scalloping and an azimuth-dependent distributed target ambiguity ratio (DTAR) are avoided. However, the use of electronically steered antennas leads to a quantization of the steering law and a non-ideal pattern for squinted angles (grating lobes and main lobe reduction). The former provokes spurious peaks, while the latter introduces a slight scalloping and DTAR deterioration. These effects are analyzed and quantified for TerraSAR-X and a TOPS system design approach is presented. Next, the requirements concerning interferometry are investigated. Finally, several results are shown with TerraSAR-X data, including a comparison between the TOPS and ScanSAR modes and the reporting of first TOPS interferometric results
CLIVAR Exchanges - VAMOS: Joint Edition of the Newsletter of the Climate Variability and Predictability Project (CLIVAR) Exchanges and the CLIVAR Variability of the American Monsoon Systems Project (VAMOS)
No full textOn the continuity of the group inverse in C*-Algebras
No full text[EN] Let {a_n} be a sequence of group invertible elements of a unital C* algebra A that converges to a. We present some equivalent conditions for the group invertibility of a and for the convergence of {a^#_n} to a#.The first author was supported by the Universidad Politecnica de Valencia (PAID-06-12). The second author is supported by Grant No. 174007 of the Ministry of Science, Technology and Development, Republic of Serbia. The third author is supported by the Guangxi Natural Science Foundation 2013 GXNS-FAA019008, the key project of Education Department of Guangxi 201202ZD031 Project and by national science foundation of China 11361009.Benítez López, J.; Cvetkovic-Ilic, D.; Liu, X. (2014). On the continuity of the group inverse in C*-Algebras. Banach Journal of Mathematical Analysis. 8(2):204-213. https://doi.org/10.15352/bjma/1396640064S2042138
Swamp dredge: Research into grunge
No full textFor this project I have researched grunge music and created a body of work influenced by this genre. During my extended contextual research into the genre, I looked at both the artists and producers. I wrote/co-wrote the songs, played some of the instruments and produced the recordings. These are now available for download on www.soundcloud.com/swampdredg
The Titanic sunk, so what? Project manager response to unexpected events
No full textProjects are inherently uncertain and face unexpected events, from small changes
in scope to unforeseen client's bankruptcy. This paper studies how project
managers respond to such events and how successful and unsuccessful responses
differ from the perspective of the practitioner. We analysed 44 unexpected
events faced by 22 experienced project managers in defence and defence-related
organisations. The project managers compared two unexpected events that they
faced, one that they considered the response successful and the other
unsuccessful. We identified three pillars supporting successful responses to
unexpected events: (1) responsive and functioning structure at the
organisational level, (2) good interpersonal relationship at the group level and
(3) competent people at the individual level. The events and respective
responses analysed suggest that improvement in project management can be
achieved by better managing these three pillars, allowing project and programme
managers to "create their own luck". (C) 2009 Elsevier Ltd and IPMA. All rights
reserved
Authorisation in Grid Computing
No full textThis paper briefly surveys how authorisation in Grid computing has evolved during the last few years, and presents the latest developments in which Grid applications can utilise a policy controlled authorisation infrastructure to make decisions about which users are allowed to perform which actions on which Grid resources. The paper describes the Global Grid Forum SAML interface for connecting policy based authorisation infrastructures to Grid applications, and then describes the PERMIS authorisation infrastructure which has implemented this interface. The paper concludes with suggestions about how this work will evolve in the future
Ultra-high photon flux high-harmonic generation
No full textWe present a highly stable, easy-to-use HHG source delivering a record photon flux of >1011 photons/s at 69eV-75eV, being tunable to approx. 100eV which will be used for future photon-hungry applications.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ImPhys/Optic
The effect of intervening conditions on the management of project risk
No full textPurpose – The purpose of this paper is to highlight the main findings of a
successfully defended doctoral thesis that studied factors or interventions
causing the discrepancy between how adequate project risks should be managed and
how project risks are actually managed. Design/methodology/approach – The
approach involved interviews and a survey using questionnaires gathered data
from project managers about their experiences with project risk management
during two phases of fieldwork. The first phase included in-depth interviews
with information technology (IT) project managers in order to explore patterns
involving risk mediators and their influence on project risk management. A web-
based survey was used in the second phase for the purpose of testing these
patterns on a wider range of project managers. Findings – Specific risk-related
interventions strongly influence the effective use of project risk management:
project managers tended to deny, avoid, ignore risks and to delay the management
of risk. Risks were perceived as discomforting, not agreed upon. IT project
managers were unaware of risks and considered them to be outside their scope of
influence and preferred to let risks resolve themselves rather than proactively
engaging with them. As a consequence, factors such as the lack of awareness of
risks by IT project managers appeared to constrain the application of project
risk management with the result that risk had an adverse influence on the
outcome of IT projects. Practical implications – The underlying rational
assumptions of project risk management and the usefulness of best practice
project risk management standards as a whole need to be questioned because of
the occurrence of interventions such as the lack of information. IT project
managers should first prevent risk-related interventions from influencing the
use of project risk management. However, if this is not possible, they should be
prepared to adapt to risks influencing the project outcome. Originality/value –
The paper contradicts the myth of a “self-evidently” correct project risk
management approach. It defines interventions that constrain project manager’s
ability to man
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