210 research outputs found
MedRoBERTa.nl: A Language Model for Dutch Electronic Health Records
No full textThis paper presents MedRoBERTa.nl as the first Transformer-based language model for Dutch medical language. We show that using 13GB of text data from Dutch hospital notes, pre-training from scratch results in a better domain-specific language model than further pre-training RobBERT. When extending pre-training on RobBERT, we use a domain-specific vocabulary and re-train the embedding look-up layer. We show that MedRoBERTa.nl, the model that was trained from scratch, outperforms general language models for Dutch on a medical odd-one-out similarity task. MedRoBERTa.nl already reaches higher performance than general language models for Dutch on this task after only 10k pre-training steps. When fine-tuned, MedRobERTa.nl outperforms general language models for Dutch in a task classifying sentences from Dutch hospital notes that contain information about patients' mobility levels.</p
Sacred building back to the residents
No full textThe transformation of the St Jozef Church in Amsterdam West into a cultural center for the Robbert Scott neighborhood.R-MITArchitectureArchitecture and The Built Environmen
Subsonic near-surface P-velocity and low S-velocity observations using propagator inversion
No full textDetailed knowledge of near-surface P- and S-wave velocities is important for processing and interpreting multicomponent land seismic data because (1) the entire wavefield passes through and is influenced by the near-surface soil conditions, (2) both source repeatability and receiver coupling also depend on these conditions, and (3) near-surface P- and S-wave velocities are required for wavefield decomposition and demultiple methods. However, it is often difficult to measure these velocities with conventional techniques because sensitivity to shallow-wave velocities is low and because of the presence of sharp velocity contrasts or gradients close to the earth's free surface. We demonstrate that these near-surface P- and S-wave velocities can be obtained using a propagator inversion. This approach requires data recorded by at least one multicomponent geophone at the surface and an additional multicomponent geophone at depth. The propagator between them then contains all information on the medium parameters governing wave propagation between the geophones at the surface and at depth. Hence, inverting the propagator gives local estimates for these parameters. This technique has been applied to data acquired in Zeist, the Netherlands. The near-surface sediments at this site are unconsolidated sands with a thin vegetation soil on top, and the sediments considered are located above the groundwater table. A buried geophone was positioned 1.05 m beneath receivers on the surface. Propagator inversion yielded low near-surface velocities, namely, 270 ± 15 m/s for the compressional-wave velocity, which is well below the sound velocity in air, and 150 ± 9 m/s for the shear velocity. Existing methods designed for imaging deeper structures cannot resolve these shallow material properties. Furthermore, velocities usually increase rapidly with depth close to the earth's surface because of increasing confining pressure. We suspect that for this reason, subsonic near-surface P-wave velocities are not commonly observed
Deconvolution of land seismic data for source and receiver characteristics and near-surface structure
No full textSeismic reflection methods are widely used for the detection of hydrocarbons in subsurface structures up to several kilometers depth. However, since most data are acquired at or close to the Earth's surface, it is essential to understand the influence of the near-surface on the acquired data in order that its effects are not interpreted as pertaining to the reservoir. The near-surface effect on seismic data has two main origins: (i) near-surface wave propagation and (ii) wavefield acquisition. Wavefield acquisition comprises both wavefield excitation and wavefield measurement, i.e. source and receiver effects.
Since both P- and S-wave velocities are observed to vary rapidly close to the Earth's surface, wave propagation in the near-surface is often very complex. In order to improve our understanding of near-surface wave propagation, we investigated and developed methods to determine near-surface P- and S-wave velocities. For this purpose, we used dense recording geometries including buried geophones, since these material properties cannot be resolved with a conventional acquisition geometry using geophones only at the free surface. One of the methods developed is based on the estimation and inversion of the propagator matrix, and therefore referred to as propagator inversion. The propagator inversion was applied to data which we acquired in Zeist, The Netherlands. We obtained a low near-surface P velocity, namely 270 ± 15 m/s, which is well below the sound velocity in air, and 150 ± 9 m/s for the S velocity. The buried geophone was located at approximately 1.0 m depth, thus the obtained velocities are only representative of the top meter of the near-surface.
The second part of this thesis is devoted to the influence of wavefield acquisition. Corrections for source and receiver perturbations are necessary when their behaviour changes within a given survey, and should be performed in the early stages of processing. However, existing techniques, such as surface-consistent deconvolution, require prior processing before even they can be applied. We developed an alternative approach to compensate for source and receiver amplitude perturbations which has the advantage of being purely a raw data preprocessing step. It is applicable to the whole seismic trace, and does not impose additional assumptions on the subsurface. The approach is based on reciprocity of the medium response. This implies that differences between normal and reciprocal traces can be attributed to the source and receiver perturbations. We successfully demonstrated the procedure to compensate for these perturbations on both synthetic and field data. The field data were acquired in Manistee County, Michigan (courtesy of WesternGeco). Along the acquisition line, near-surface conditions change from moist-to-wet sediments to dry sands. The obtained source corrections are strongly correlated to these changing near-surface conditions, whereas the receiver corrections vary more strongly from geophone to geophone.
Compensation of the recorded data for the source and receiver perturbations resulted in a significant improvement of the signal-to-noise ratio, both on prestack and poststack data. Finally, the receiver response we found did not agree with the generally accepted damped harmonic oscillator model, implying that this model need to be revised
Het huisvesten van kennis: Een plek die ons stimuleert zo vrij mogelijk te denken
No full textRobbert Dijkgraaf is sinds mei 2008 voorzitter van de Koninklijke Nederlandse Akademie van Wetenschappen. Hij is cum laude gepromoveerd, staat bekend als een briljant wetenschapper die de wetenschap toegankelijk maakt voor een groter publiek. FMI trad in gesprek met hem over wetenschappelijk denken en de huisvesting die hier het beste bij past.Real Estate and Housin
Coll., Die Welt des Islams, vol. 54, n°1, 2014
No full textChristoph Schumann
Author: Thomas Philipp Source: Volume 54, Issue 1, pp 1 –3 Materials for a History of Hungarian Academic Orientalism: The Case of Gyula Germanus Author: Adam Mestyan Source: Volume 54, Issue 1, pp 4 –33 Franz Rosenthal’s Half an Autobiography
Author: Hinrich Biesterfeldt Source: Volume 54, Issue 1, pp 34 –105 Post-Islamism in Distress? A Critical Evaluation of the Theory in Islamist-Dominated Egypt (11 February 2011-3 July 2013)
Author: Robbert A.F.L. Wolteri..
Cryostat Control: Real time control for a cryogenic refrigerator
No full textIn order to measure the spectrum of radio emissions from galaxies and other deep space objects, a new superconducting spectrometer, working at very cold temperatures close to the absolute zero, is developed. An advanced cooling system called a cryostat is used to cool down the spectrometer. The cool down of the cryostat involves the control of multiple sensors and actuators connected to the cryostat to achieve a final temperature below 250 millikelvin. A software program is used for this purpose. As extra hardware components have been added to the cryostat, the existing program does no longer fulfill the requirements. For this reason a new software program, which can monitor temperatures of all components and start control processes, is developed. The developed program consists of a client server structure. The server handles the logic of the cryostat using several controllers. It can send data to a native client, which is the graphical user interface, or a REST API. The native client displays sensor readouts received from the server and allows full control of server, which means it can start the cool down process as well as manual control processes. The REST API allows the user to have full control over the server using a Python script to achieve measurements which cannot be done from the native client. The increased automation, improved control and ability to integrate with external Python scripts allow the user to focus on the essential parts of an experiment making the developed program an improvement over the previous program
Three Way Duels: Infinite Games on the Unit Square
No full textWith the growing wealth and economy of a country, there are an increasing amount of small and big businesses. Every company has its own marketing strategy that it uses in order to lure customers away from their competition and increase their sales. Choosing the perfect time to advertise or discount several products is of essence for a company to gain more money than their competition. These type of marketing games are all slight variations of duels. The purpose of this report is to research how this duel is played most optimal when there are two or more participants. Several types of two-player duels shall be analysed first in order to understand and analyse a three-player duel.Applied Mathematic
Proving functional correctness of monadic programs using separation logic
No full textInteraction trees are an active development in representing effectful and impure pro- grams in the Coq proof assistant. Examples of programs they can represent are programs that use: mutable state, concurrency and general recursion. Besides representing these programs we also want to reason about and verify these programs using separation logic. That is the purpose of this thesis. More technically speaking interaction trees are new way to do shallow embeddings in the Coq proof assistant. They are a coinductive variant of the free monad and come with the usual constructions of events and event handlers. The aim of interaction trees is to represent impure programs and potentially non-terminating programs in their environment. Interaction trees are, in contrast to relational operational semantics, executable by interpretation or program extraction. Interaction trees come with a framework for reasoning about their behavior based on equivalency up to weak bisimulation. An open problem is to reason about interaction trees utilizing a separation logic rather than weak bisimulation. We developed Pothos as a solution to this problem. Pothos has an Iris based concurrent separation logic for interaction trees. We address the problem in a non-extensible setting, with mutable state, non-termination and concur- rency as our chosen effects. Pothos inherits all the executable properties from interaction trees and includes a novel relation of Iris’s step-index with coinductive types. We have proven our logic to be sound and include a case study of a spin lock library. The case study shows that our logic is both non-trivial and can utilize the standard Iris patterns for concurrency.Computer Scienc
Sonar target enhancement by shrinkage of incoherent wavelet coefficients
No full textBackground reverberation can obscure useful features of the target echo response in broadband low-frequency sonar images, adversely affecting detection and classification performance. This paper describes a resolution and phase-preserving means of separating the target response from the background reverberation noise using a coherence-based wavelet shrinkage method proposed recently for de-noising magnetic resonance images. The algorithm weights the image wavelet coefficients in proportion to their coherence between different looks under the assumption that the target response is more coherent than the background. The algorithm is demonstrated successfully on experimental synthetic aperture sonar data from a broadband low-frequency sonar developed for buried object detection.</p
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