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An Event Horizon Imager(EHI) mission Concept Utilizing medium Earth Orbit Sub-mm Interferometry

空间科学学报 2021年第2期41卷 211-233页

作者： KUDRIASHOV V mARTIN-NEIRA m ROELOFS F FALCKE H BRINKERINK C BARYSHEV A HOGERHEIJDE m YOUNG A POURSHAGHAGHI H KLEIN-WOLT m mOSCIBRODZKA m DAVELAAR J BARAT I DUESmANN B VALENTA V PERDIGUES ARmENGOL J m DE WILDE D mARTIN IGLESIAS P ALAGHA N van der vorst m Department of Astrophysics/ImAPP Radboud University NijmegenP.O.Box 90106500 GL Nijmegenthe Netherlands ESTEC/ESA Keplerlaan 12201 A2 Noordurigkthe Netherlands mar Planck Institute for Radio Astrorny Auf dem Higel 69D-53121 Bon(Endenich)Germany University of Groningen Landleven 129747 AD Groningenthe Netherlands Leiden Observatory Leiden UniversityPO Box 95132300 RALeidenthe Netherlands Anton Pannekoek Institute for Astronomy University of AmsterdamScience Park 9041098 XHAmsterdamthe Netherlands Center for Computational Astrophysics Flatiron Institute162 Fifth AvenueNew YorkNY 10010USA

Submillimeter interferometry has the potential to image supermassive black holes on event horizon scales,providing tests of the theory of general relativity and increasing our understanding of black hole accretion *** Event Horizon Telescope(EHT) performs these observations from the ground,and its main imaging targets are Sagittarius A~* in the Galactic Center and the black hole at the center of the m87 ***,the EHT is fundamentally limited in its performance by atmospheric effects and sparse terrestrial(u,v)-coverage(Fourier sampling of the image).The scientific interest in quantitative studies of the horizon size and shape of these black holes has motivated studies into using space interferometry which is free of these *** resolution considerations and interstellar scattering effects push the desired observing frequency to bands above 500 *** paper presents the requirements for meeting these science goals,describes the concept of interferometry from Polar or Equatorial medium Earth Orbits(PECmEO) which we dub the Event Horizon Imager(EHI),and utilizes suitable space technology *** this concept,two or three satellites orbit at slightly different orbital radii,resulting in a dense and uniform spiral-shaped(u,v)-coverage over *** local oscillator signals are shared via an inter-satellite link,and the data streams are correlated on-board before final processing on the ***-satellite metrology and satellite positioning are extensively employed to facilitate the knowledge of the instrument position vector,and its time *** European space heritage usable for both the front ends and the antenna technology of such an instrument is *** and future sensors for the required inter-satellite metrology are *** performance estimates and simulation results are given.

关键词： Instrumentation Space VLBI Radio Telescopes

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Two-fluid modeling of Geldart A particles in gas-fluidized beds

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Particuology 2008年第6期6卷 540-548页

作者： m.A. van der Hoef J.A.m. Kuipers Faculty of Science & Technology University of Twente

We have investigated the effect of cohesion and drag models on the bed hydrodynamics of Geldart A particles based on the two-fluid （TF） model. For a high gas velocity U0 = 0.03 m/s, we found a transition from the homogeneous fluidization to bubbling fluidization with an increase of the coefficient C1, which is used to account for the contribution of cohesion to the excess compressibility. Thus cohesion can play a role in the bed expansion of Geldart A particles. Apart from cohesion, we have also investigated the influence of the drag models. When using the Wen and Yu drag correlation with an exponent n = 4.65, we find an under-prediction of the bed expansion at low gas velocities （U0 = 0.009 m/s）. When using a larger exponent （n = 9.6）, as reported in experimental studies of gas-fluidization, a much better agreement with the experimental bed expansion is obtained. These findings suggest that at low gas velocity, a scale-down of the commonly used drag model is required. On the other hand, a scale-up of the commonly used drag model is necessary at high gas velocity （U0 = 0.2 and 0.06 m/s）. We therefore conclude that scaling the drag force represent only an ad hoc way of repairing the deficiencies of the TF model, and that a far more detailed study is required into the origin of the failure of the TF model for simulating fluidized beds of fine powders.

关键词： Gas-fluidized bed Geldart A particles Two-fluid model Cohesive force Drag correlation

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Dispersal of invasive species by drifting

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Current Zoology 2011年第6期57卷 818-827页

作者： m.C. van RIEL G. van der VELDE A. BIJ DE VAATE Radboud University Nijmegen Institute for Water and Wetland Research Department of Animal Ecology and Ecophysiology Section Aquatic Animal Ecology Heyendaalseweg 135 6525 AJ Nijmegen The Netherlands Team Freshwater Ecology DLO-Alterra P.O. Box 47 6700 AA Wageningen The Netherlands Netherlands Centre for Biodiversity Naturalis EO. Box 9517 2300 RA Leiden The Netherlands Waterfauna Hydrobiologisch Adviesbureau Oostrandpark 30 8212 AP Lelystad The Netherlands

Drifting can be an effective way for aquatic organisms to disperse and colonise new areas. Increasing connectivity between European large rivers facilitates invasion by drifting aquatic macroinvertebrates. The present study shows that high abundances of invasive species drift in the headstream of the river Rhine. Dikerogammarus villosus and Chelicorophium cur- vispinum represented up to 90% of the total of drifting macroinvertebrates. Drift activity shows seasonal and diel patterns. most species started drifting in spring and were most abundant in the water column during the summer period. Drift activity was very low during the winter period. Diel patterns were apparent; most species, including D. villosus, drifted during the night. Drifting macroinvertebrates colonised stony substrate directly from the water column. D. villosus generally colonised the substrate at night, while higher numbers of C. curvispinum colonised the substrate during the day. It is very likely that drifting functions as a disper- sal mechanism for crustacean invaders. Once waterways are connected, these species are no longer necessarily dependent on dispersal vectors other than drift for extending their distribution range

关键词： Amphipods Invaders Colonization Drift Daily rhythms Seasonal variation

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The impact of prehospital blood sampling on the emergency department process of patients with chest pain:a pragmatic non-randomized controlled trial

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World Journal of Emergency medicine 2023年第4期14卷 257-264页

作者： Johan L.van Nieuwkerk m.Christien van der Linden Rolf J.Verheul merel van Loon-van Gaalen marije Janmaat Naomi van der Linden Emergency Department Haaglanden Medical Centre&Emergency Medical Services Haaglandenthe Hague 2501 CBthe Netherlands Research and Development Haaglanden Medical Centrethe Hague 2501 CKthe Netherlands Laboratory Services Haaglanden Medical Centrethe Hague 2501 CKthe Netherlands Emergency Department Haaglanden Medical Centrethe Hague 2501 CKthe Netherlands Faculty of Health University of Applied Sciences LeidenLeiden 2300 AJthe Netherlands Faculty of Technology Policy and ManagementDelft University of TechnologyDelft 2628 BXthe Netherlands

BACKGROUND:In patients with chest pain who arrive at the emergency department(ED)by ambulance,venous access is frequently established prehospital,and could be utilized to sample *** blood sampling may save time in the diagnostic *** this study,the association of prehospital blood draw with blood sample arrival times,troponin turnaround times,and ED length of stay(LOS),number of blood sample mix-ups and blood sample quality were ***:The study was conducted from October 1,2019 to February 29,*** patients who were transported to the ED with acute chest pain with low suspicion for acute coronary syndrome(ACS),outcomes were compared between cases,in whom prehospital blood draw was performed,and controls,in whom blood was drawn at the *** analyses were used to assess the association of prehospital blood draw with the time ***:Prehospital blood draw was performed in 100 *** 406 patients,blood draw was performed at the *** blood draw was independently associated with shorter blood sample arrival times,shorter troponin turnaround times and decreased LOS(Pmber of blood sample mix-ups and quality were observed(P>0.05).CONCLUSION:For patients with acute chest pain with low suspicion for ACS,prehospital blood sampling is associated with shorter time intervals,while there were no significant differences between the two groups in the validity of the blood samples.

关键词： Blood specimen collection Crowding Emergency medical services Troponin

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No evidence for a genetic association between female mating preference and male secondary sexual trait in a Lake Victoria cichlid fish

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Current Zoology 2010年第1期56卷 57-64页

作者： Inke van der SLUIJS Ole SEEHAUSEN Tom J.m.van DOOREN Jacques J.m.van ALPHEN Department of Animal Ecology Institute of Biology Leiden University Department of Biology McGill University Institute of Ecology and Evolution University of Bern Department of Fish Ecology & Evolution Centre of Ecology Eawag Swiss Federal Institute for Aquatic Science and TechnologyEvolution & Biogeochemistry

Sexual selection by female mating preference for male nuptial coloration has been suggested as a driving force in the rapid speciation of Lake Victoria cichlid fish. This process could have been facilitated or accelerated by genetic associations between female preference loci and male coloration loci. Preferences, as well as coloration, are heritable traits and are probably determined by more than one gene. However, little is known about potential genetic associations between these traits. In turbid water, we found a population that is variable in male nuptial coloration from blue to yellow to red. males at the extreme ends of the phenotype distribution resemble a reproductively isolated species pair in clear water that has diverged into one species with blue-grey males and one species with bright red males. Females of the turbid water population vary in mating preference coinciding with the male phenotype distribution. For the current study, these females were mated to blue males. We measured the coloration of the sires and male offspring. Parents-offspring regression showed that the sires did not affect male offspring coloration, which confirms earlier findings that the blue species breeds true. In contrast, male offspring coloration was determined by the identity of the dams, which suggests that there is heritable variation in male color genes between females. However, we found that mating preferences of the dams were not correlated with male offspring coloration. Thus, there is no evidence for strong genetic linkage between mating preference and the preferred trait in this population [Current Zoology 56 （1）： 57-64 2010].

关键词： Speciation Sexual selection mate choice Genetic association Cichlid fish Lake Victoria

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Skin tribology:Science friction?

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Friction 2013年第2期1卷 130-142页

作者： E.van der HEIDE X.ZENG m.A.mASEN Laboratory for Surface Technology and Tribology Faculty of Engineering TechnologyUniversity of TwenteDrienerlolaan 57522 NB EnschedeThe Netherlands TNO De Rondom 15612 AP EindhovenThe Netherlands

The application of tribological knowledge is not just restricted to optimizing mechanical and chemical engineering *** fact,effective solutions to friction and wear related questions can be found in our everyday *** important part is related to skin tribology,as the human skin is frequently one of the interacting surfaces in relative *** seem to solve these problems related to skin friction based upon a trial-and-error strategy and based upon on our sense for *** question of course rises whether or not a trained tribologist would make different choices based upon a science based strategy?In other words:Is skin friction part of the larger knowledge base that has been generated during the last decades by tribology research groups and which could be referred to as Science Friction?This paper discusses the specific nature of tribological systems that include the human skin and argues that the living nature of skin limits the use of conventional *** tribology requires in vivo,subject and anatomical location specific test *** predictive friction models can only partially be applied to predict in vivo skin *** reason for this is found in limited understanding of the contact mechanics at the asperity level of product-skin interactions.A recently developed model gives the building blocks for enhanced understanding of friction at the micro *** largely simplified power law based equations are currently available as general engineering ***,the need for friction control is illustrated by elaborating on the role of skin friction on discomfort and *** texturing and polymer brush coatings are promising directions as they provide way and means to tailor friction in sliding contacts without the need of major changes to the product.

关键词： friction bio-tribology skin soft tissue surface texture brush coatings

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Competition for shelter between four invasive gobiids and two native benthic fish species

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Current Zoology 2011年第6期57卷 844-851页

作者： N. van KESSEL m. DORENBOSCH m.R.m. DE BOER R.S.E.W. LEUVEN G. van der VELDE Radboud University Nijmegen Institute for Water and Wetland Research Department of Animal Ecology and Ecophysiology EO. Box 9010 6500 GL Nijmegen The Netherlands Radboud University Nijmegen Institute for Water and Wetland Research Department of Environmental Science P.O. Box 9010 6500 GL Nijmegen The Netherlands Natuurbalans - Limes Divergens P.O. Box 31070 6503 CB Nijmegen The Netherlands Netherlands Institute of Ecology （NIOO - KNAW） EO. Box 50 6700 AB Wageningen The Netherlands Netherlands Centre for Biodiversity Naturalis EO. Box 9517 2300 RA Leiden The Netherlands

Recent invasions by non-native gobiid fish species that are ongoing in the Western European rivers Rhine and meuse, will lead to interactions with native benthic fish species. Since both non-native gobiids and native benthic species are bottom dwelling species with a preference for shelter during at least part of their life cycle, it is likely that competition for shelter will occur between these non-native and native species when shelter is a limiting factor. To investigate the importance of this mecha- nism for species replacements, various habitat choice experiments were conducted between two common native benthic fish spe- cies （Cottus perifretum and Barbatula barbatula） and four invasive non-native gobiid species （Proterorhinus semilunaris, Neogo- bius melanostomus, N. kessleri and N. fluviatilis）. The first series of single specimen experiments determined the habitat choice of each individual fish species. In a second series of competition experiments, shifts in habitat choice in comparison with the previ- ously observed habitat choice, were determined when a native benthic fish species co-occurred with non-native gobiid species. Native C. perifretum displayed a significant shift in habitat choice in co-occurrence with the gobiids N. kessleri or P. semilunaris. C. perifretum was outcompeted and moved from the available shelter place to less preferred habitat types. During the competition experiments no change in habitat choice of B. barbatula was shown. Our study therefore suggests that competition for shelter is likely to occur in rivers invaded by N. kessleri and P. semilunaris at sites where shelter is limiting

关键词： Bullhead Exotic species Habitat choice Invasive gobies Rivers Rhine and meuse Stone loach

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Colour-ring wear and loss effects in citizen science mark-resighting studies

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Avian Research 2019年第2期10卷 148-162页

作者： Andrew m.Allen Bruno J.Ens martijn van de Pol Henk van der Jeugd magali Frauendorf Henk-Jan van der Kolk Kees Oosterbeek Jeroen Nienhuis Eelke Jongejans Department of Animal Ecology and Physiology Radboud University6500 GL NijmegenThe Netherlands Sovon Dutch Centre for Field Ornithology 6503 GANijmegen and Sovon-Texel1790 AB Den BurgThe Netherlands Department of Animal Ecology Netherlands Institute of Ecology NIOOKNAW6708 PB WageningenThe Netherlands Dutch Centre for Avian migration and Demography 6700 AB WageningenThe Netherlands Centre for Avian Population Studies WageningenThe Netherlands

Background: Ring wear and loss may have important consequences for mark-recapture studies that aim to estimate survival trends. Our study quantifies the rates of wear and loss from a long-running colour-ringing project of the Eurasian Oystercatcher (Haematopus ostralegus) in the Netherlands. methods: Our analysis included 8909 colour-ringed oystercatchers with 118,071 resightings, predominantly ringed and observed by citizen scientists. We quantified how ring wear and loss may vary with ring colour and age, and how this may impact resighting probabilities. We then determined how ring loss may impact survival estimates and resighting probabilities of mark-recapture models by simulating four scenarios of how citizen scientists may resight and report birds with lost colour rings. Results: Annual rates of colour ring loss averaged 2.5% compared with 1% for ring wear, but lost rings also had a higher reporting probability (31.2%) than worn rings (10.3%). Lost rings may not directly impact survival estimates since 50% of oystercatchers with lost rings could still be uniquely identified. Ring wear and loss rapidly increased between 10 and 15 years after ringing. Rates of ring loss were comparable amongst ring colours, but the wear rate appeared higher for red and white rings compared to other colours. Rates of ring wear and loss varied significantly amongst different regions in our study, which were characterised as having different habitat features. Differential rates of ring wear may have important implications for studies conducted over large geographical scales or of multiple species. Conclusions: Based on simulations of ring loss in our population, estimates of apparent survival may be 0.3–1.2% lower whilst the impact of ring wear was deemed even lower. We developed a table of recommendations containing advice for ring fitting, data collection, study design, and mark-recapture analyses, so that future colour-ringing studies can benefit from our experiences in collecti

关键词： Bias Bird migration Citizen science Colour-ring mark-recapture Shorebirds Survival

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Gas–solid interaction force from direct numerical simulation (DNS) of binary systems with extreme diameter ratios

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Particuology 2009年第4期7卷 233-237页

作者： S. Sarkar S.H.L. Kriebitzsch m.A. van der Hoef J.A.m. Kuipers Department of Science and Technology University of Twente P.O. Box 217 7500 AE Enschede The Netherlands

Fluid-particle systems as commonly encountered in chemical, metallurgical and petroleum industries are mostly polydisperse in nature. However, the relations used to describe fluid-particle interactions are originally derived from monodisperse systems, with ad hoc modifications to account for polydispersity. In previous work it was shown that for bidisperse systems with moderate diameter ratios of 1：2 to 1：4, this approach leads to discrepancies, and a correction factor is needed. In this work we demonstrate that this correction factor also holds for more extreme diameter ratios of 1：5, 1：7 and 1： 10, although the force on the large particles is slightly overestimated when using the correction factor. The main origin of the correction is that the void surrounding the large particles becomes less in case ofa bidisperse mixture, as compared to a monodisperse system with the same volume fraction. We further investigated this discrepancy by calculating the volume per particle by means of Voronoi tessellation.

关键词： Bidisperse Fluid-particle interaction force Lattice Boltzmann simulation Direct numerical simulation

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Indentation of elastically soft and plastically compressible solids

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Acta mechanica Sinica 2015年第4期31卷 473-480页

作者： A.Needleman V.Tvergaard E.van der Giessen Department of materials Science and Engineering Texas A&M University College Station Department of mechanical Engineering The Technical University of Denmark Zernike Institute for Advanced materials University of Groningen

The effect of soft elasticity, i.e., a relatively small value of the ratio of Young＇s modulus to yield strength and plastic compressibility on the indentation of isotropically hardening elastic-viscoplastic solids is investigated. Calcu- lations are carried out for indentation of a perfectly sticking rigid sharp indenter into a cylinder modeling indentation of a half space. The material is characterized by a finite strain elastic-viscoplastic constitutive relation that allows for plas- tic as well as elastic compressibility. Both soft elasticity and plastic compressibility significantly reduce the ratio of nomi- nal indentation hardness to yield strength. A linear relation is found between the nominal indentation hardness and the log- arithm of the ratio of Young＇s modulus to yield strength, but with a different coefficient than reported in previous studies. The nominal indentation hardness decreases rapidly for small deviations from plastic incompressibility and then decreases rather slowly for values of the plastic Poisson＇s ratio less than 0.25. For both soft elasticity and plastic compressibility, the main reason for the lower values of indentation hardness is related to the reduction in the hydrostatic stress level in the material below the indenter.

关键词： Plasticity Compressibility Indentation Finite element analysis

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