503 research outputs found
Niet zonder conflicten
No full textDuurzame ontwikkeling in het ingenieursonderwijs blijkt geen snelle conflictloze strategie voor verduurzaming. Met als gevolg dat het breder leren denken van de ingenieur in opleiding nog in de kinderschoenen staat.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.Organisation & Governanc
Characterization of production in different branches of production in different branches spanish industrial activity, by means of time series analysis.
No full textThis work presents a quantitative study of the evolution of spanish industrial activity, measured by the indices of industrial production, by means of Time Series analysis. Univariate ARIMA models with intervention analysis for all the series of these indices have been constructed. The use of Univariate Time Series models to characterise economic phenomena is justified and the type of characterisation made for each industrial branch is described. The procedures for automatic modelling of series are presented. Then the characteristics of the Spanish industrial branches are shown. These results are collected in a diskette for use of researchers.ARIMA model; Intervention analysis; Univariate model; Industrial production; automatic modelling;
Outcome Based Subgroup Analysis: A Neglected Concern.
No full textA subgroup of clinical trial subjects identified by baseline characteristics is a proper subgroup while a subgroup determined by post randomization events or measures is an improper subgroup. Both types of subgroups are often analyzed in clinical trial papers. Yet, the extensive scrutiny of subgroup analyses has almost exclusively attended to the former. The analysis of improper subgroups thereby not only flourishes in numerous disguised ways but also does so without a corresponding awareness of its pitfalls. Comparisons of the grade of angina in a heart disease trial, for example, usually include only the survivors. This paper highlights some of the distinct ways in which outcome based subgroup analysis occurs, describes the hazards associated with it, and proposes a simple alternative approach to counter its analytic bias. Data from six published trials show that outcome based subgroup analysis, like proper subgroup analysis, may be performed in a post-hoc fashion, overdone, selectively reported, and over interpreted. Six hypothetical trial scenarios illustrate the forms of hidden bias related to it. That bias can, however, be addressed by assigning clinically appropriate scores to the usually excluded subjects and performing an analysis that includes all the randomized subjects. A greater level of awareness about the practice and pitfalls of outcome based subgroup analysis is needed. When required, such an analysis should maintain the integrity of randomization. This issue needs greater practical and methodologic attention than has been accorded to it thus far
A decade of ERS satellite orbits and altimetry
No full textThe First European Remote Sensing Satellite, ERS-1, was launched in July 1991, fol- lowed by ERS-2 in April 1995. Both satellites carry a radar altimeter to serve oper- ational applications and scientific research in the fields of geodesy, oceanography, glaciology and meteorology. Together, the satellites have now been operating for over twelve years. This thesis embarks on the a voyage along several milestones in the lifetime of these satellites, and particularly of its altimeters. Both altimeter missions were hampered by a number of misfortunes, ranging from hardware failures, via design mishaps, to a sub-optimally designed ground segment. Yet, the altimeter data, when properly processed and supplied with a precise orbit, can compete favourably with data supplied by specialised altimeter satellites like TOPEX/Poseidon and Jason-1. The upgrading of all altimeter cor- rections and the tweaking of the basic altimeter measurements of range, significant wave height and backscatter coefficient, are essential steps in this process, outlined in this thesis. Having accomplished that, the ERS altimeters allow the monitor- ing of annual, semi-annual and secular changes in sea level, which are important factors in study of climate change. A key role in the processing of altimeter data plays the position of the satellite, and its progress in time, the satellite orbit. The quality of the recovered sea surface height is limited by the precision at which the orbit can be determined. A long journey along several stepwise improvements of the orbit determination process, both in the technique as well as in the modelling, have resulted in the reduction of the orbit error by a factor of 30! A major player in this process was the estab- lishment of a gravity field model tailored to the ERS satellites that, when applied to ERS orbit determination, outperformed any of the previous and contemporary general-purpose models. Yet, it is shown that this model, DGM-E04, is not just a fabrication for the benefit of ERS only, but is equally suitable for the orbit determ- ination of TOPEX/Poseidon and as a long-wavelength geoid model. The calibration of the ERS-1 altimeter in 1991 required, at a time when the orbit errors were still counted in decimetres, if not metres, a short-arc orbit determin- ation technique centred over the calibration site off the coast of Venice. Again, through elaborate surveying, gathering of altimeter corrections and tide gauge measurements, problem solving and elimination of errors, a final absolute range bias of 41.5 cm was established, a value that is still within the error margins of more recent estimates. A timing error in the ERS altimeter data was discovered in 1995 and its cause remained a mystery ever since, especially when the timing error appeared to ex- hibit daily, annual and inter-annual variations as well. Although the exact cause may never be found, the issue is examined in fine detail and a model is constructed to eliminate the timing error for the benefit of the quality of the altimeter data.Aerospace Engineerin
Semi-analytical long-arc satellite orbit computation and the estimation of time-varying gravity parameters
No full textAerospace Engineerin
Creating Circular, Efficient and Symbiotic Cities: And How Higher Education Should Contribute to Create the Solutions that are Required
No full textThe ‘Grand Challenges’ of our times, like climate change, resource depletion, global inequity and the destruction of wildlife and biodiversity can only be addressed by innovating cities. This paper will analyse major options for innovating cities, main barriers for these innovations that are rooted in the paradigms of the experts running urban systems and educational reforms that might contribute overcoming these barriers.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.Organisation & Governanc
No Short-Cut in Assessing Trial Quality: A Case Study.
No full textAssessing the quality of included trials is a central part of a systematic review. Many check-list type of instruments for doing this exist. Using a trial of antibiotic treatment for acute otitis media, Burke et al., BMJ, 1991, as the case study, this paper illustrates some limitations of the check-list approach to trial quality assessment. The general verdict from the check list type evaluations in nine relevant systematic reviews was that Burke et al. (1991) is a good quality trial. All relevant meta-analyses extensively used its data to formulate therapeutic evidence. My comprehensive evaluation, on the other hand, brought to the surface a series of serious problems in the design, conduct, analysis and report of this trial that were missed by the earlier evaluations. A check-list or instrument based approach, if used as a short-cut, may at times rate deeply flawed trials as good quality trials. Check lists are crucial but they need to be augmented with an in-depth review, and where possible, a scrutiny of the protocol, trial records, and original data. The extent and severity of the problems I uncovered for this particular trial warrant an independent audit before it is included in a systematic review
The use of satellites in gravity field determination and model adjustment
No full textAerospace Engineerin
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