103 research outputs found
Knoken in Koksijde: onderzoek van de menselijke skeletresten aangetroffen in de oostelijke pandgang van de abdij Ten Duinen
No full textSchool inspection feedback : unravelling determinants and consequences of teachers\u2019 feedback acceptance
No full textAbstract: Dit proefschrift draagt bij tot het verwerven van een beter inzicht in de manier waarop leraren inspectiefeedback verwerken alvorens zij deze accepteren of bereid zijn ermee aan de slag te gaan. In deze samenvatting situeren we eerst de noodzaak van dit proefschrift om de determinanten van feedbackacceptatie bij leraren te exploreren. Nadien gaan we dieper in op de belangrijkste conclusies uit dit proefschrift. Tot slot geven we een aantal aanbevelingen die de acceptatie van inspectiefeedback en de bereidheid van leraren om met de feedback aan de slag te gaan vergroten
Online wear monitoring of polymer matrix composites with advanced measurement techniques
No full textPolymers are used in bearings due to their self-lubricating ability. These materials are limited in use requiring high bearing capacity and temperature resistance. The loading can be solved by adding reinforcements (fibers, weft structures, ...) resulting in a composite material. These composites typically consist of two different components, a matrix material (polymer, metal or ceramic) and a reinforcing component (fibers, particles, ...). In this work only the polymer matrix composites are discussed, more in particular, polyester and polyphenylene sulfide (PPS). Both matrices are of different nature. Polyester is a thermoset polymer, while the PPS is thermoplastic, which melts with rising temperature. Glass or carbon fibers are used as reinforcements. These composites were subjected to experimental friction and wear tests to evaluate their behaviour for different loads and speeds. Different online measurement techniques were also applied to evaluate the technique for online wear and friction measurements. For this, a test rig was constructed and built.
The first part of the research was to develop this test rig, originating from a basic test setup for friction and wear testing, but with the ability of adding the different advanced measurement techniques. These techniques include acoustic emission, vibration analysis, online camera and temperature measurements. Before adding these sensors to a test rig, one must know the sensors, their size, how they measure, how they need to be fixed for optimal measuring, etc. The implementation of these sensors resulted in a pin on disc setup with composite disc and steel pin, such that a microscope could be added for picturing the wear track that will appear on the composite disc. Optimal positions for the other sensors are on both sides of the pin. To reduce the mounting, the steel pin is constructed as two parts. The first is a mounting pin, on which the sensors could be placed. The second part in the mating contact was chosen to be the ball of a ball bearing, such that the steel contact had always the same initial parameters as roundness, hardness, rounding, etc. which can be expected for ball bearings.
The second component in the test, the disc, was cut out of larger plates via water jet. This excludes the possible influence of temperature (laser cutting). Then, these composite disc was mounted on a disc holder for fixation and excluding the possible rotation of the disc in its holder. The structure of the disc is related to their production method. The glass fiber reinforced polyester plates were made via pultrusion, so a top layer, a non-woven and a zone with unidirectional fibers are available, while the compressionmoulding technique for the carbon fiber reinforced PPS yields a layered structure of different orientation of the 5 harness satin weaves. Wear testing for the polyester resulted in the formation of a polymer film in the wear track, which was continuously formed and deformed due to the rotation and the applied pressure. This results in the particle agglomerates near the edges of the wear track, which oncewere a part of the film. Particles falling from the pin and from the matrix material under the film, made the film keeping its structure and thickness. Once the continuous fibers were reached, the polymer film was removed and fibers became visible. For the thermoplastic PPS, wear only starts after plastic deformation of the upper PPS layer, with break through this layer at different times in relation to the fiber orientation. After this break through a carbon film is formed in the wear track which protects the composite material from further wear. The pin itself gets slightly polished in contact with the glass fibers, while was completely worn after touching the carbon fibers. The look for the behaviour in time yield a further investigation in the appearance of different wear mechanisms. These mechanisms were fiber breakage, fiber pull-out, fiber-matrix debonding, shear deformation of the fibers and edge deformation. Also wear outside the wear track was observed, as a result of particles pressed aside on the original surface. The frictional behaviour is dependent on the wear, the material structure, the contact conditions, speed and load. The formation of the polymer film yields a reduction in friction force of almost 20%. Once the unidirectional fibers were reached due to wear, the orientation with respect to the motion also influenced the frictional behaviour. The parallel fiber orientation results in the lowes friction values, while the perpendicular case was higher. Additionally also the 45° orientations were investigated and yielded a higher coefficient of friction than the perpendicular case. For the PPS material this was also the case. Only the 45° were grouped per two, related to the weft-warp structure of the carbon weaves. Post mortem analysis on the wear tracks, SEM and EDX resulted in a visualization of the wear track and the wear mechanisms. Analysis of the surface structure yields that glass fiber fragments were found in the polymer film, while in the PPS case Fe could be found as loose particles on the film. Online measurements yields variable success in wear monitoring. The acoustic emission, or the measuring of surface waves as a result of energy release within the material, was most promising. This was not only the result of a good measurement technique, but more due to the acquired information about the relation of signal content and wear mechanism out of previous tensile tests. Vibrations were measured with a 3D sensors, which allowed to measure the vibrations as well in the normal direction (wear) as in the frictional direction. In the frictional direction, a relation between amplitude and frequency content and the related friction force could be made, but this was more the result of the larger change in contact geometry. Influences of the fiber orientation could not be detected. The camera which should allow to take online images of the wear track at different stages of the wear test had many difficulties to overcome. The out of focus issue was one of the main problems. Due to the wear of the disc, the microscope should lower with the disc wear only. This was difficult due to the fact that the measured wear was measured as a combined wear of the pin and disc. Temperature measurements wear done with thermocouples and infra red thermometry. The thermocouples had to deal with static loading of the pin (attachment of particles) and resulted in impossible high temperatures. The infra red thermometry gave good results, but to measure the exact contact spot could not be done.
As a conclusion, all the applied measurements have there qualities and difficulties. In the presented work we achieved to implement all sensors on a test rig, and performed tests, in order to determine the qualities of each sensor. Most of the analysis of the gathered data is done after testing. As general conclusions, on could say that the implementation of the different online techniques is rather complex. One does not only need to take into account the pure technical and constructive reasons, but also the acquisition and storage of the data, and not to forget the data processing. The materials used in this work are not directly related to bearing application, but resulted in knowledge about film formation. Another result is that wear and wear particles not necessary have a negative influence on the frictional behaviour. The exceptional behaviour of the carbon fiber reinforced PPS opens perspectives as construction-bearing material. For the frictional behaviour, the 45° orientation has the highest coefficient of friction, which is a unique finding due to use of a composite disc
The influence of the Big 5 personality traits on young people’s political consumer behavior
No full textsponsorship: The author wants to thank the Research Foundation Flanders for their generous support on this project (Grant No 1209511N, G032810N, G0A2312N). (Research Foundation Flanders|1209511N, Research Foundation Flanders|G032810N, Research Foundation Flanders|G0A2312N)status: Publishe
Legal history in Belgium
No full textThis article deals with the situation of legal history in Belgium. However, it is neither a survey of the research done by Belgian legal historians nor a bibliography of Belgian legal history. For that, the reader can be referred to John Gilissen’s 1971 bibliography[[he author would like to thank Prof. G. Martyn, B. Debaenst, B. Vandael and B. Quintelier for their remarks
De voorlopers van de Onze-Lieve-Vrouw Hemelvaartkerk te Hofstade (Aalst, prov. Oost-Vlaanderen). Archeologisch noodonderzoek en fysisch-antropologische studie
No full textIn het najaar van 2004 werd in Hofstade, deelgemeente van de stad Aalst, gestart met de installatie van een nieuw verwarmingssysteem in de parochiekerk Onze-Lieve-Vrouw Hemelvaart. Het kleinschalige archeologische onderzoek hierbij toonde nogmaals het belang aan van een degelijke archeologische begeleiding van zelfs beperkte ingrepen in het bodemarchief van kerken. De hier in Hofstade uitgevoerde opgraving bracht niet alleen de resten van de romaanse voorloper van de huidige kerk aan het licht, maar leverde ook aanwijzingen op voor de aanwezigheid van een nog ouder kerkgebouw. In een breder perspectief kan de aanwezigheid van een kerk met apsis bijdragen tot een beter inzicht in de verspreiding en vormgeving van deze kleinere kerken in het grensgebied tussen de twee grote cultuurgebieden van de romaanse kunst, de Maas-Rijnregio en het Scheldegebied .
Omwille van de kwantiteit, kwaliteit en ruime periodisering kan uit het fysisch-antropologische onderzoek eerder anekdotische informatie naar voor worden gebracht. De voorlopige resultaten van het skeletonderzoek bieden wel aanwijzingen, maar geen finale integratie van de gegevens in een globaal archeologisch verhaal. Toch waren er enkele interessante resultaten met betrekking tot de samenstelling en algemene gezondheidsstatus binnen de onderzoekspopulatie. De meeste onderzochte individuen zijn van het mannelijke geslacht. De vormen van gewrichtsslijtage aan de wervelkolom en grote gewrichten zijn vermoedelijk te wijten aan het verouderingsproces, maar er bestaat ook een duidelijk verband tussen aangetroffen schouderartrose en de opvallende robuustheid van de opperarmbeenderen bij een aantal mannen. Dit kan op een bovengemiddeld gebruik van de arm- en schouderspieren (bv. bij zwaar labeur) wijzen.
De resultaten van dit onderzoek kunnen bij eventuele toekomstige ingrepen binnen de kerk of op het omliggende kerkhof als basis dienen om voorafgaandelijk een onderzoeksstrategie te bepalen om zo tot een beter inzicht in de ontstaansevolutie van de kerk te komen
Experimental extrapolation model for friction and wear of polymers on different testing scales
No full textFeiten en normen in het moreel relativisme debat
No full textDe hier besproken versie van moreel relativisme houdt in dat we moeten verdragen dat andere mensen morele oordelen hebben die niet verenigbaar zijn met onze eigen oordelen. Bepaalde filosofen verwijzen recent naar de nieuwste bevindingen in de moraalpsychologie om een haalbare versie van dit moreel relativisme te verdedigen. Ik evalueer één van deze redeneringen en argumenteer dat de besproken versie, hoewel zij niet in tegenspraak is met de werking van ons morele vermogen, beperkt is door haar eigen normatieve vooronderstellingen. De besproken auteur maakt dus succesvol gebruik van empirische informatie zoals deze verkregen door experimentele filosofen; daarbij ziet hij echter de eigen niet-empirische, normatieve vooronderstellingen over het hoofd.The here discussed version of moral relativism entails that we should tolerate that other people endorse moral judgments that are incompatible with the judgments we ourselves endorse. Certain philosophers refer in their recent work to the newest findings in moral psychology to defend a feasible version of moral relativism. I evaluate one of these reasonings and argue that the version under discussion, though not incompatible with the workings of our moral sense, is limited by its normative presuppositions. Thus, the mentioned author successfully employs empirical information such as acquired by experimental philosophers; however, in the process, he neglects his own non-empirical presuppositions
Influence of re-adhesion on the wear and friction of glass fiber reinforced polyester composites.
No full text- …
