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De Graaf, Martin (author), Sarna, K. (author), Brown, Jessica (author), Tenner, Elma V. (author), Schenkels, Manon (author), Donovan, D.P. (author)The interactions between aerosols and clouds are among the least understood climatic processes and were studied over Ascension Island. A ground-based UV polarization lidar was deployed on Ascension Island, which is located in the stratocumulus-to-cumulus transition zone of the southeastern Atlantic Ocean, to infer cloud droplet sizes and droplet...journal article 2023
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De Graaf, Maartje M.A. (author), Perugia, Giulia (author), Fosch-Villaronga, Eduard (author), Lim, Angelica (author), Broz, F. (author), Short, Elaine Schaertl (author), Neerincx, M.A. (author)Discrimination and bias are pressing issues of many AI and robotics applications. These outcomes may derive from limited datasets that do not fully represent society as a whole or from the AI scientific community's western-male configuration bias. Although being a pressing issue, understanding how robotic systems can replicate and amplify...conference paper 2022
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van Riet, T.C.T. (author), De Graaf, Willem M. (author), van Antwerpen, R. (author), van Frankenhuyzen, J. (author), De Lange, Jan (author), Kober, J. (author)a measurement setup is proposed that, for the first time, is capable of capturing the combination of high forces and subtle movements exerted during tooth removal procedures in high detail and in a reproducible manner by using robot technology. The outcomes of a design process from a collaboration between clinicians, mechanical and software...conference paper 2020
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Griffin, Debora (author), Sioris, Christopher (author), Chen, Jack (author), Dickson, Nolan (author), Kovachik, Andrew (author), De Graaf, Martin (author), Nanda, Swadhin (author), Veefkind, j. Pepijn (author), Dammers, Enrico (author)Before the launch of the TROPOspheric Monitoring Instrument (TROPOMI), only two other satellite instruments were able to observe aerosol plume heights globally, the Multi-angle Imaging SpectroRadiometer (MISR) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The TROPOMI aerosol layer height is a potential game changer, since it...journal article 2020
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Nanda, Swadhin (author), De Graaf, Martin (author), Veefkind, j. Pepijn (author), Ter Linden, Mark (author), Sneep, Maarten (author), De Haan, Johan (author), Levelt, Pieternel Felicitas (author)To retrieve aerosol properties from satellite measurements of the oxygen A-band in the near-infrared, a line-by-line radiative transfer model implementation requires a large number of calculations. These calculations severely restrict a retrieval algorithm's operational capability as it can take several minutes to retrieve the aerosol layer...journal article 2019
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Nanda, S. (author), Veefkind, j. Pepijn (author), De Graaf, Martin (author), Sneep, Maarten (author), Stammes, Piet (author), De Haan, Johan F. (author), Sanders, Abram F.J. (author), Apituley, Arnoud (author), Tuinder, Olaf (author), Levelt, Pieternel Felicitas (author)This paper presents a weighted least squares approach to retrieve aerosol layer height from top-of-atmosphere reflectance measurements in the oxygen A band (758-770g nm) over bright surfaces. A property of the measurement error covariance matrix is discussed, due to which photons travelling from the surface are given a higher preference over...journal article 2018
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Nanda, S. (author), De Graaf, Martin (author), Sneep, Maarten (author), De Haan, Johan F. (author), Stammes, Piet (author), Sanders, Abram F.J. (author), Tuinder, Olaf (author), Veefkind, j. Pepijn (author), Levelt, Pieternel Felicitas (author)Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been...journal article 2018
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De Graaf, S. (author), Hoogendoorn, S.P. (author), Barmentlo, H. (author)Vrijwel alle gemeenten en regio’s gebruiken strategische verkeersmodellen om hun mobiliteitsbeleid vorm te geven. Deze modellen, zelfs de multimodale, houden echter onvoldoende rekening met fiets- en voetgangersstromen. Vooral nu het bereikbaarheidsbelang van fietsen steeds groter wordt, is dat een vervelend probleem. Hoog tijd dus om werk te...journal article 2015
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Ayerden, N.P. (author), Ghaderi, M. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)The design, fabrication and characterization of a highly integrated optical gas sensor is presented. The gas cell takes up most of the space in a microspectrometer and is the only component that has so far not been miniaturized. Using the tapered resonator cavity of a linear variable optical filter as a gas cell enables ultimate miniaturization,...conference paper 2015
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Ghaderi, M. (author), Ayerden, N.P. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)The design and CMOS-compatible fabrication of airgap-based optical filters in a surface micromachining process with sacrificial release using thevapour phase is presented. An airgap-dielectric layer combination offers a higher refractive index contrast, as compared to the conventional all-dielectriclayer based filters, which results in a higher...conference paper 2015
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- Wu, Y. (author), De Graaf, M. (author), Menenti, M. (author) journal article 2015
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Ghaderi, M. (author), Ayerden, N.P. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)In CMOS-compatible optical filter designs, SiO2 is often used as the low-index material, limiting the optical contrast (nHi/nLo) to about 2. Using the air as low-index material improves the optical contrast by about 50%, thus increasing the reflectivity and bandwidth at a given design complexity. The design and fabrication of a 4-layered air...journal article 2014
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Silva, M.F. (author), Rodrigues, J.A. (author), Oliveira, M.J. (author), Fernandes, A.R. (author), Pereira, S. (author), Costa, C.G. (author), Ghaderi, M. (author), Ayerden, P. (author), Goncalves, L.M. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author), Correia, J.H. (author)This paper presents the design, fabrication and characterization of two Fabry Perot type optical filters (415 nm and 540 nm) for enabling Narrow Band Imaging (NBI) in medical devices (MD). The two-colour illumination should satisfy a highly specific optical design, which is composed of a thin-film optical filter stack of titanium dioxide (TiO2)...journal article 2014
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Ayerden, N.P. (author), Ghaderi, M. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)A set-up for optical gas composition measurement based on absorption spectroscopy is composed of a white light source, a gas cell and a spectrometer. The Fabry-Perot optical filter is suitable for miniaturization of this system, as it is composed of only two reflectors with a transparent layer in-between. Varying the width of this optical...journal article 2014
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De Graaf, M. (author), Bellouin, N. (author), Tilstra, L.G. (author), Haywood, J. (author), Stammes, P. (author)The aerosol direct radiative effect (DRE) of African smoke was analyzed in cloud scenes over the southeast Atlantic Ocean, using Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite observations and Hadley Centre Global Environmental Model version 2 (HadGEM2) climate model simulations. The observed mean DRE...journal article 2014
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- Boogaard, F.C. (author), De Graaf, R. (author), Dionisio Pires, M. (author) journal article 2014
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Boog, M.C. (author), Erasmus, V. (author), De Graaf, J.M. (author), Van Beeck, E.H.E. (author), Melles, M. (author), Van Beeck, E.F. (author)Background The introduction of alcohol-based hand rub dispensers has had a positive influence on compliance of healthcare workers with the recommended guidelines for hand hygiene. However, establishing the best location for alcohol-based hand rub dispensers remains a problem, and no method is currently available to optimize the location of these...journal article 2013
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Emadi, A. (author), Wu, H. (author), De Graaf, G. (author), Wolffenbuttel, R.F. (author)This paper presents the design, fabrication and characterization of Infra-Red (IR) Linear Variable Optical Filter (LVOF)-based micro-spectrometers. Two LVOF microspectrometer designs have been realized: one for operating in the 1400 nm to 2500 nm wavelength range and another between 3000 nm and 5000 nm. The IR LVOFs have been fabricated in an IC...journal article 2013
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De Graaf, K. (author)Stuur specifieker op kwaliteit van onderhoud. Verzamel niet meer informatie, maar de juiste informatie op het juiste moment. Leg dit zo vast dat zowel technische medewerkers als bestuurders grip krijgen op onderhoudskwaliteit.conference paper 2013
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De Graaf, R. (author), Van der Duin, P.M. (author)Since many of today's problems are becoming ever more complex, the way we look for and manage innovations to solve these problems should also be innovated. We introduce the ‘Collective Innovation’ approach to deal with these kind of ‘wicked problems’ that require the input of many different parties. Furthermore, in Collective Innovation it is...journal article 2013