32 research outputs found
De afscheiding van wolfraam uit gasvormige verbindingen en hare toepassing
No full textApplied Science
The simultaneous isolation of multiple high and low frequent T-cell populations from donor peripheral blood mononuclear cells using the major histocompatibility complex I-Streptamer isolation technology
No full textImmunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease
Dislocation networks in precipitation hardened aluminium alloys during plastic deformation: The effects of dislocations on the anelastic behaviour and the evolution of dislocation networks in an AA7075 aluminium alloy.
No full textThe effects of precipitates in the microstructure of an AA7075 aluminium alloy on: the dislocation behaviour, dislocation structure and dislocation structure evolution during plastic deformation were investigated using the physical yield criterion model by van Liempt and Sietsma. The model was in fact applied for the first time to aluminium and an AA7075 aluminium alloy. By constructing an extended Kocks-Mecking plot from the measured tensile and interrupted tensile data the dislocation density, average dislocation segment length and physical yield stress were determined.The aim of the present study was to get a better understanding of the role of precipitates in the evolution of the dislocation structure during plastic deformation. The recovery of anelastic strain during loading and subsequent unloading after plastic deformation was investigated as well. The yield criterion was used to study the anelastic loading, while a constitutive unloading model by Torkabadi et al. was used to study the unloading behaviour. The models were combined to define the fraction of unrecoverable anelastic strain. The anelastic strain is related to springback. Therefore a better understanding of the anelastic strain could be useful for making better predictions of springback after metal forming. The physical yield criterion was further extended by incorporating a continuous uniform dislocation segment length distribution. Insight on the dislocation segment length distribution, and the evolution thereof during plastic deformation, could help to better understand the mechanical behaviour of metals.The evolution of the dislocation structure during plastic deformation is impeded by the presence of precipitates in the microstructure. Therefore, the physical interpretation of α in the Taylor equation which quantifies the dislocation structure, proposed by Arachebelata et al., was modified to incorporate the effects of precipitates in the microstructure. The dislocation structure parameter α should remain constant. However, the average dislocation segment length obtained from the extended Kocks-Mecking plot does not decrease sufficiently to accommodate a constant α. The introduction of the length between precipitates, which is independent from work hardening, into the Taylor equation ensures that α does remain constant, whilst in addition it provides an estimate of the distance between the precipitates. Anelastic strain, caused by reversible glide of dislocations in the pre-yield regime, is introduced into or recovered from the metal during loading and unloading respectively. The anelastic unloading strain determined from the interrupted tensile tests was found to be smaller than what was expected according to the model. Three possible causes were identified: not all Frank-Read sources are at their critical state when unloading is initiated, dislocation loops propagating through the crystal undo portions of the anelastic unloading strain and the retracting dislocations remain stuck behind obstacles whilst retracting under the reducing applied stress. The constitutive model was found to be not suitable for studying the dislocation behaviour during unloading because the change of dislocation segment length with plastic deformation is not accounted for. The development of a physical unloading model is therefore recommended. The distribution of the dislocation segment lengths could explain the non-zero value of the work hardening rate Θ at the abrupt change of slope between the pre and post-yield regime in the extended Kocks-Mecking plot. The value of Θ at this point could be an indication of the distribution width. The continuous uniform distribution is a rather unrealistic description of the dislocation segment length distribution. Therefore, other distribution types are proposed for the further development of the dislocation segment length distribution model of the physical yield criterion.<br/
Yield and flow stress of steel in the austenitic state
No full textThis research was funded by Tata Steel Research and Development and carried out under project no.MC10.07297 in the framework of the Research Program of the Materials innovation institute(M2i).(OLD) MSE-
CityJSON: does (file) size matter?
No full textThe possibilities of 3D city models for the analysis of the built environment are increasingly explored, and there is a continuous development in improvements on their inner workings. They are also used more often on the web, for example for visualisation but it is also possible to query, analyse, and edit data in this way. In this case, the network becomes a potential new bottleneck in time performance. Especially when a 3D city model contains a lot of attributes, there is a rapid increase in file size when the area of study is expanded.This presents challenges in efficiency and in this thesis I focus on the improvement of the inner workings of 3D city models to attempt to relieve this problem, in specific for spreading and using them more efficiently on the web.By investigating and testing different compression techniques on 3D city models stored in the CityJSON format, I have attempted to relieve this problem. CityJSON is already more compact than CityGML and these techniques decrease the file sizes of datasets even further, allowing for faster transmission over a network. But on the other hand, additional steps are needed to process compressed files. The goal of using a compression technique is to result in a net speed gain, meaning that the time that is saved on download time should be larger than the additional time that it costs to process the file before transmission (compressing the data on the server) and after receival (decompressing the data in the client).There are compression techniques for both general and specific purposes, and I have used combinations of them. Amongst these are Draco compression, zlib, CBOR, and a self-created technique. Specific ones are used for the main characteristics that CityJSON datasets have, which are the JSON structure, feature attributes, and feature geometries. To assess the impact that different combinations of compression techniques have, I take uncompressed CityJSON performance as the baseline and have come up with different performance indicators that include several use cases such as visualisation, querying, analysis, and editing.I have benchmarked all combinations of compression techniques on the use cases of these performance indicators. For this I have created two types of server implementations: one with which datasets are compressed beforehand and are processed in the client based on the request made by the user, and one where the data is processed first and only then compressed and transmitted to the server. In the results, you can see the best-performing compression type per use case.The benchmarking is performed on a variety of datasets that are split into four categories: larger datasets, larger datasets without attributes, smaller datasets, and smaller datasets without attributes. This ultimately makes for use cases that are very specific and choosing suitable compression types requires finding out which ones perform relatively well in most cases, and are not difficult to implement in order to keep CityJSON a simple file format. It turns out that Draco compression can give good results in specifc situations, but in general is not good to use. Not only regarding performance, but also from a developer point of view. CBOR, zlib, and a combination of these two are easy to use and generally affect the performance of CityJSON on the web in a good way.https://github.com/jliempt/CityJSON-does-file-size-matter-Geomatic
CityREST: CityJSON in A Database + RESTful Access
No full textWith the increasing demand for 3D city models in various applications, providing efficient access to 3D city models on the web has become very important and valuable. However, there is a lack of web services in which users can directly and effectively access the city objects contained in the 3D city models on the web. Another problem with web services related to 3D city models is that the size of 3D city models can become very large. As a consequence, the browser will not respond immediately until all city objects in the requested 3D city model have arrived. Addi-tionally, although file-based systems are the easiest way of data storage, they have deficiencies in web services that require scalability, efficiency, and flexibility in data access. To fix these is-sues, the goal of this research is to develop the an efficient way of disseminating 3D city models on the web, to discover the method of enabling 3D city models to be parsed incrementally and efficiently by the browser, and to explore a proper database solution for storing 3D city models to support the fast data access.CityJSON has advantages in web applications over the CityGML data format, thus being chosen as the main datasets used in this research. Inspired by OGC API – Feature, a RESTful API for fast access to geospatial features in CityJSON has been developed. The second part of my research is related to the data streaming. CityJSONFeature has been proposed to enable CityJSON to be parsed incrementally on the web. To improve the overall data streaming perfor-mance, I proposed two methods to stream the data from the database to the RESTful API so that the RESTful API can immediately start constructing the first CityJSONFeature and sending it to the user. The third part of my research is to explore a proper database solution for CityJSON datasets to best support the fast data access in the RESTful API. In addition, some auxiliary data is added into the database to improve the RESTful API’s capabilities with efficient data filtering and streaming.To evaluate the efficiency of the implemented methodology, a systematic benchmarking has been performed on three aspects: 1) the database schema, 2) the two streaming methods, and 3) the performance difference between the DBMS and the file system. The results show that in most use cases the DBMS can better support the RESTful API than the file system with the help of the built-in query and index mechanism. In addition, the overall streaming performance is largely improved when adding data streaming from the DBMS to the RESTful API. Lastly, based on the benchmarks, an optimal database schema has been chosen to support the RESTful API with fast data access, efficient data filtering and streaming.Geomatic
LoD2 voor alle 10 miljoen BAG-panden in Nederland
No full text3D-toepassingen gaan vaak gepaard met de wens om gebouwen met dakvormen te modelleren. Na jaren onderzoek en ontwikkeling hebben we in Delft een methode gerealiseerd die volledig automatisch dakvormen (LoD2)reconstrueert uit puntenwolken en 2D-pandpolygonen. Met deze methode hebben we 3D-modellen gegenereerd voor alle 10 miljoen BAG-panden in Nederland, de eerste open 3D-dataset op dit detailniveau. Niet alle toepassingen zijn gebaat bij dit detailniveau. Daarom reconstrueren we in hetzelfde proces ook andere detailniveaus. Het volledig automatisch proceszorgt ook in de toekomst voor consistentie als nieuwe modellen worden geconstrueerd met actuele input-data. Bovendien monitoren we verschillende kwaliteitsparameters die gebruikers kunnen helpen bij de juiste toepassing van de data.Urban Data Scienc
Kwalitatief interviewen, kunst en kunde
No full textHet kwalitatieve interview heeft veel weg van een goed gesprek. Wat maakt iemand tot een goede gesprekspartner? Dat hij luistert met aandacht, meedenkt en meevoelt met het vertelde en je uit laat spreken. Kortom: een invoelende ruimte biedt en belangstellend is. Is zo iemand vanzelf een goede interviewer? Nee, want alhoewel hiermee de basis is gelegd voor een deel van de kunst waar de titel van dit boek naar verwijst, heeft een interviewer additionele kennis en vaardigheden nodig. Dat is de kunde, die in dit boek uitgebreid besproken wordt. Een interview is allereerst een vraaggesprek met een welbepaald informatiedoel. En pas als de vaardigheden van de goede gesprekspartner samenkomen met de kunde van de onderzoeker, is er sprake van de interviewkunst waar in de titel naar verwezen wordt. In deel I van het boek (geschreven door Jeanine Evers en Fijgje de Bo er) worden uitgebreid allerlei technische kwesties van het interviewen besproken in samenhang met het improviserende karakter van een goed kwalitatief interview. In deel II wordt door auteurs met verschillende disciplinaire achtergronden gesproken over het interviewen van specifieke groepen respondenten (Nico Baakman over elites, Hans Krober en Jeroen Zomerplaag over verstandelijk gehandicapten, Jacomine de Lange over ouderen, Ilse van Liempt over gesmokkelde migranten) en over bepaald soort interviews (Ad van Fessem over focusgroepen in marktonderzoek, Frank van Gemert over interviews bij etnografisch veldwerk, Ellis Jonker over biografische interviews, Ilja Maso over hermeneutische interviews en Stef Scagliola over oral history interviews bij (ex-)militairen. Dit boek is geschikt voor elke onderzoeker die kwalitatieve interviews wil gaan toepassen, alsmede voor onderwijs in kwalitatief interviewen
Smart(phone) travelling: understanding the use and impact of mobile technology on irregular migration journeys
No full textThis article analyses how mobile technology impacts on irregular migrants' journeys. It is based on trajectory ethnography with 11 Afghan, Iranian and Syrian migrants whom the first author met in Turkey and Greece in the spring of 2015. These migrants were followed (partly digitally) to Serbia, Hungary, Germany, Sweden and the Netherlands. We argue that the method of trajectory ethnography is a useful tool that allows us to understand how mobile technology shapes and facilitate parts of the journey - like, for example, decisions on routes and modes of travel, final destinations and the financing of irregular migration. This methodology leads to a more nuanced understanding of irregular migration because it enables us to capture the complex dynamics involved in irregular migration processes and to reflect on decisions taken within the process
Quantification of dislocation structures from anelastic deformation behaviour
No full textAbstractThe pre-yield deformation behaviour (i.e., at stresses below the yield stress) of two materials, pure iron and a low-alloy steel, and its anelastic nature are analysed at room temperature, before and after the dislocation structures are varied by plastic deformation. It is shown, based on tensile experiments, that this behaviour can be explained by limited reversible glide of dislocations without essential changes in the dislocation structure. Moreover, a physically-based model that characterises the dislocation structure by two variables, the dislocation density and the effective dislocation segment length, is used to quantitatively describe this deformation behaviour. The model validity is further evaluated by comparison with dislocation densities from X-Ray Diffraction measurements
