32,027 research outputs found
Stability of rock on slopes under wave attack: Comparison and analysis of datasets Van der Meer [1988] and Van Gent [2003]
No full textIn VAN GENT [2004] graphs were presented in which the datasets of VAN DER MEER [1988] and VAN GENT ET AL. [2003] were compared, but in this comparison a number of parameters were not correctly transformed into a comparable format. In this M.Sc. thesis after an extensive analysis to the datasets all parameters of the datasets of Van der Meer were transformed into the same format as the parameters used by Van Gent. In the same way the dataset of THOMPSON & SHUTTLER [1975], which formed the basis of the work of Van der Meer, was treated. The inclusion of correction factors for the effects of stone roundness from LATHAM ET AL. [1988] gave remarkable effects on a certain part of the dataset of Van der Meer which showed more damage than average. After this still differences could be seen between the datasets of Van der Meer and Van Gent. Using the statistical T-test these differences are approved. Explanations for the differences found between the datasets of Van der Meer and Van Gent can be found in the fact that most of the tests of Van Gent. were done with shallow foreshores where Van der Meer did most tests with deep water conditions. Tests by a number of M.Sc. students at Delft University of Technology showed that tests with identical spectra, but with different foreshore slope angles show different damage patterns. In the dataset of Van Gent also the 1:30 foreshore slopes on average show more damage than the 1:100 slopes. In further research the influence of the foreshore should be incorporated in the stability formulae by a foreshore Iribarren parameter. Also a detailed investigation to the effects of wave breaking on shallow foreshores is needed. For this the complete dataset of Van Gent needs to be available and accessible.Hydraulic EngineeringCivil Engineering and Geoscience
Doorbraakvrije dijken: Opzet doorbraakvrije zeedijken en voorlopige conclusies sterkte binnentaluds bij golfoverslag
No full textIn het kader van WV21 wordt door Deltares en een werkgroep gekeken naar doorbraakvrije dijken. Er wordt gekeken naar de definitie van doorbraakvrij en daarnaast naar hoe doorbraakvrije dijken er zouden moeten uitzien ten opzichte van de huidige dijken. In dit kader is aan Van der Meer Consulting gevraagd specifiek uitwerking te geven aan doorbraakvrije zee- en meerdijken en is gevraagd voorlopige conclusies op te stellen naar aanleiding van de proeven met de golfoverslagsimulator omtrent de sterkte van binnentaluds van dijken tegen golfoverslag. Deze uitwerking en het maken van voorlopige conclusies is gedaan door meerdere personen/bedrijven hierbij te betrekken, namelijk de projectgroep voor de proeven bij de Boonweg in Friesland en de proeven in Zeeland (Deltares zelf, Infram, Royal Haskoning en Alterra) en Infram ten aanzien van doorbraakvrije zeedijken. Vanuit observaties van de golfoverslagproeven (zie appendix 1 voor een fotorapportage met beschrijving) is één hoofdconclusie met betrekking tot doorbraakvrije dijken naar voren gekomen. Gesteld wordt dat het aannemelijk lijkt dat een binnentalud van klei met gras bij een overslag van 30 l/s per m of minder nooit door erosie zal bezwijken. Dit betekent dat in veel extremere omstandigheden dan de huidige maatgevende belasting, een huidige zee- of meerdijk niet door overslag zal bezwijken. Om het faalmechanisme infiltratie door golfoverslag en afschuiven van het binnentalud uit te sluiten, dient een doorbraakvrije zee- of meerdijk een binnentalud van 1:3 te hebben. Als kostenalternatief kan ook gekeken worden naar een binnentalud van 1:5. Omdat de huidige zee- en meerdijken al voor hoge stormvloeden en hoge golven zijn of worden ontworpen, lijkt het relatief gezien geen grote ingreep om deze dijken bestand te maken voor een veel zwaardere storm met een veel kleinere kans van voorkomen. En deze dijk zodoende doorbraakvrij te maken. Als meer golfoverslag wordt toegestaan in zeer extreme omstandigheden (tot ver boven de huidige maatgevende omstandigheden), en wanneer een zee- of meerdijk moet worden verbeterd, dan is het niet een grote stap om deze dijk, ook voor de komende 50 jaar, doorbraakvrij te maken. Bekledingen moeten dan iets dikker worden dan wat nu volgt uit het huidige ontwerpproces en ze moeten iets hoger op het talud worden aangebracht en de dijk moet mogelijk iets hoger
Anemia and erythropoietin in heart failure
No full textNa een hartinfact krijgen veel patiënten te maken met hartfalen; een verminderde pompfunctie van het hart. Peter van der Meer ontdekte dat EPO de hartfunctie van patiënten kan verbeteren. Verder blijkt de prognose duidelijk slechter te zijn wanneer patiënten naast hartfalen ook bloedarmoede hebben. Voor sporters is EPO (erythropoëtine) aantrekkelijk, omdat het de hoeveelheid rode bloedcellen en daarmee de zuurstofopname verhoogt. EPO is vooral vanuit het wielrennen bekend. Van der Meer laat zien dat EPO bij hartproblemen kan zorgen voor een kleiner infarct en een verbeterde hartfunctie: bij ratten verbetert de knijpkracht van het hart en ontstaan er meer bloedvaatjes in de hartspier, waardoor er waarschijnlijk een betere zuurstofuitwisseling plaatsvindt. De promovendus verwacht een snelle toepassing bij patiënten omdat EPO veilig is; het wordt al decennia lang aan patiënten met bloedarmoede gegeven.
Om bloedarmoede bij hartfalenpatiënten te kunnen voorkomen, zocht Van der Meer naar de oorzaak. Hij laat zien dat de beenmergcellen minder goed delen en dat dit te maken heeft met het eiwit Ac-SDKP. Wanneer dit eiwit bij patiënten verhoogd is, kan dit leiden tot bloedarmoede. Opvallend is dat een medicamenteuze behandeling met ACE-remmers juist bloedarmoede kan opwekken. De promovendus verwacht dat dit gevolgen kan hebben voor de huidige behandeling van hartpatiënten
Guidance on erosion resistance of inner slopes of dikes from 3 years of testing with the Wave Overtopping Simulator
No full textThe Wave Overtopping Simulator was developed in 2006 and destructive tests have been performed in February and March of 2007, 2008 and 2009 and will probably be continued in 2010. The tests show the behaviour of various inner slopes of dikes, embankments or levees under simulation of wave overtopping, up to a mean overtopping discharge of 125 l/s per m. In 2010 a Technical Report on strength of inner slopes of dikes against wave overtopping will be written, leading to new guidelines for the required five-yearly safety assessment of flood defence assets in the Netherlands. This paper will give a mid-term review and first guidance, based on 3 years of destructive testing. Till summer 2009 15 sections of dikes at 5 different locations in the Netherlands have been tested. The paper will give guidance to practical engineers, based on observations and analysis from all the testing so far. It also discusses the possible modifications in safety assessment.SB
Rock Armour Slope Stability under Wave Attack; the Van der Meer Formula revisited
No full textThe Van der Meer formula for rock slope stability under wave attack has been in use now in research and design for more than thirty years. This paper takes the original formula as a basis and then explores into a larger field of application, as investigated by various authors, or includes improved insights in parameters to be used. The spectral period has become the leading wave period over the mean or peak period in the field of wave overtopping. First the Van der Meer formula has been rewritten to include this spectral wave period, based on original data.
A guideline how to compare new research in extending application areas has been developed, including how to come to a modification of the formula. First the essence of the Van der Meer formula is given, such as a gradually developing damage curve according to a power function and the relationship between damage development and storm duration. Each new research should be validated for these relationships before a direct comparison is possible. Such comparison can be done along graphs of damage versus the breaker parameter (including wave period and slope angle), including the original data of the Van der Meer formula.
Possible modifications to the formula are best described if using multiplication coefficients for plunging and surging waves that directly show the influence on the original formula by the deviation from the value 1.0. Two significant investigations have then been re-analysed along the developed guidelines, one on rock shape and one on rock placing.
The research on rock shape was performed with a significant thinner armour layer, so it actually included two effects: rock shape and a thinner armour layer. The two effects have been divided and can be described by adjusted multiplication coefficients.
Individually placed rock with three points of contact, or placed with a dense packing, increase stability significantly and may always be seen as a good measure. The damage curve, however, is not gradually developing, but shows a kind of brittle failure. Direct comparison with the Van der Meer formula is not possible then. A brittle failure needs a safety coefficient, showing for design similar stone sizes as with the formula
Design of the US Wave Overtopping Simulator
No full textThe US Wave Overtopping Simulator has to simulate overtopping discharges up to 2 cfs/s/ft for wave conditions of respectively 8 ft with a peak period of 14 s and 3 ft with a period of 6 s. This requires a Simulator which is in size about three times larger than the existing Dutch one. This report describes the theory of waves overtopping the crest of a levee, the design of the Simulator, how to operate it and possible ways to measure hydraulics during testing. We know a lot about wave overtopping over levees, but still there are discrepancies between various formulae. First the existing theory is given about wave overtopping discharge and individual wave overtopping volumes. This leads to the distributions of wave overtopping volumes that have to be simulated by the Simulator. Then flow velocities, flow depths and flow times or durations of overtopping wave volumes at the crest of a levee have been discussed, including re-analysis of existing work and some recent research. The conclusion is that using the equations in an integration, to calculate the wave overtopping volume, the volumes are much too large, indicating that at least flow depth andflow time predictions are too large. For this reason the Simulator will mainly be based on flow velocity and the given peak periods of the waves. Good experience is available with Simulators up to a size of about 6 m3/m width. The majority of all overtopping wave volumes will be limited to this size. It is for this reason that the US Simulator has been designed with an inner Simulator, comparable to the existing sizes, and an outer Simulator, giving the maximum capacity of 16 m3/m. The outer Simulator will only be used for the very large overtopping wave volumes. The mechanical design has been described and this design has been discussed during a visit to CSU, in order to start fabrication of the Simulator. The Dutch test set-ups at various locations have been described with their improvements every consecutive year. The operation of the Simulator by a steering file and PLC has been given, first by description of the Dutch Simulator and then by possible modifications and improvements for the US Simulator. Finally, experiences to measure flow depth and front velocity of overtopping waves have been described and possible ways of improvements, which will be performed in the Netherlands and tested in February/March 2010. If successful, these kind of measurements can also be developed at CSU
Hyper IgD syndrome and type AA amyloidosis.
No full textContains fulltext :
80421.pdf (Publisher’s version ) (Open Access)RU Radboud Universiteit Nijmegen, 29 januari 2009Promotores : Meer, J.W.M. van der, Drenth, J.P.H. Co-promotor : Simon, A.179 p
Rock Armour Slope Stability under Wave Attack; the Van der Meer Formula revisited
No full textThe Van der Meer formula for rock slope stability under wave attack has been in use now in research and design for more than thirty years. This paper takes the original formula as a basis and then explores into a larger field of application, as investigated by various authors, or includes improved insights in parameters to be used. The spectral period has become the leading wave period over the mean or peak period in the field of wave overtopping. First the Van der Meer formula has been rewritten to include this spectral wave period, based on original data.
A guideline how to compare new research in extending application areas has been developed, including how to come to a modification of the formula. First the essence of the Van der Meer formula is given, such as a gradually developing damage curve according to a power function and the relationship between damage development and storm duration. Each new research should be validated for these relationships before a direct comparison is possible. Such comparison can be done along graphs of damage versus the breaker parameter (including wave period and slope angle), including the original data of the Van der Meer formula.
Possible modifications to the formula are best described if using multiplication coefficients for plunging and surging waves that directly show the influence on the original formula by the deviation from the value 1.0. Two significant investigations have then been re-analysed along the developed guidelines, one on rock shape and one on rock placing.
The research on rock shape was performed with a significant thinner armour layer, so it actually included two effects: rock shape and a thinner armour layer. The two effects have been divided and can be described by adjusted multiplication coefficients.
Individually placed rock with three points of contact, or placed with a dense packing, increase stability significantly and may always be seen as a good measure. The damage curve, however, is not gradually developing, but shows a kind of brittle failure. Direct comparison with the Van der Meer formula is not possible then. A brittle failure needs a safety coefficient, showing for design similar stone sizes as with the formula
Design construction and calibration of a wave overtopping simulator
No full textDesign, construction and calibration of wave overtopping simulatorFloodsit
Agave segurae D. Guillot & Van Der Meer, un taxón nuevo dentro del grupo Americanae, naturalizado en la Comunidad Valenciana
No full textEn este artículo describimos un taxón nuevo dentro del género Agave L., grupo Americanae, que denominamos Agave segurae D. Guillot & Van Der Meer, naturalizado en la Comunidad Valenciana
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