Measuring water velocity in highly turbulent flows: field tests of an electromagnetic current meter (ECM) and an acoustic Doppler velocimeter (ADV)     

B. J. MacVicar  E. Beaulieu  V. Champagne  A. G. Roy 《地球表面变化过程与地形》2007,32(9):1412-1432

Two field tests were completed to compare the performance of an electromagnetic current meter (ECM) with that of an acoustic Doppler velocimeter (ADV) in gravel‐bed rivers. Research was particularly motivated by the need to measure flow properties in highly energetic turbulent flows. Measurements were made at two field sites, one at moderate velocities (up to 70 cm/s) and with moderate turbulence intensities (10–20% of mean flow), and the other in an area of non‐uniform flow that included locations with fast mean velocities (up to 1.75 m/s) and high turbulent intensities (up to 50% of mean flow). Comparison of means, standard deviations, turbulent kinetic energy and Reynolds shear stress confirm the general agreement between the ECMs and ADVs. The general agreement is subject to limitations associated with the sample volume and frequency response of the instruments, and only applies within restricted velocity (up to ≈1.25 m/s) and turbulence intensity ranges (up to ≈0·125 m/s). At higher turbulence intensities, spectral analysis showed anomalous behavior of the ADV signal, especially in the vertical velocity component. Quadrant analysis of the Reynolds stress suggests that these problems occur predominantly in quadrants 1 and 3. Errors in ADV measurements were estimated using four different methods: one that utilized the characteristic noise floor in spectral plots, one based on internal ADV measurements of signal correlation and two techniques that aggregate errors related to various sub‐factors. Estimates were divergent at high flows. Techniques that rely on sub‐factors appeared to underestimate the impact of high turbulence on signal quality. The key conclusion for future field applications is that the older ECM technology provides the more reliable estimates of flow parameters in high turbulence. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Toward cyberinfrastructure to facilitate collaboration and reproducibility for marine integrated ecosystem assessments     

Stace E. Beaulieu  Peter A. Fox  Massimo Di Stefano  Andrew Maffei  Patrick West  Jonathan A. Hare  Michael Fogarty 《Earth Science Informatics》2017,10(1):85-97

There is a growing need for cyberinfrastructure to support science-based decision making in management of natural resources. In particular, our motivation was to aid the development of cyberinfrastructure for Integrated Ecosystem Assessments (IEAs) for marine ecosystems. The IEA process involves analysis of natural and socio-economic information based on diverse and disparate sources of data, requiring collaboration among scientists of many disciplines and communication with other stakeholders. Here we describe our bottom-up approach to developing cyberinfrastructure through a collaborative process engaging a small group of domain and computer scientists and software engineers. We report on a use case evaluated for an Ecosystem Status Report, a multi-disciplinary report inclusive of Earth, life, and social sciences, for the Northeast U.S. Continental Shelf Large Marine Ecosystem. Ultimately, we focused on sharing workflows as a component of the cyberinfrastructure to facilitate collaboration and reproducibility. We developed and deployed a software environment to generate a portion of the Report, retaining traceability of derived datasets including indicators of climate forcing, physical pressures, and ecosystem states. Our solution for sharing workflows and delivering reproducible documents includes IPython (now Jupyter) Notebooks. We describe technical and social challenges that we encountered in the use case and the importance of training to aid the adoption of best practices and new technologies by domain scientists. We consider the larger challenges for developing end-to-end cyberinfrastructure that engages other participants and stakeholders in the IEA process.  相似文献   

Slant Column Measurements of O3 and NO2 During the NDSC Intercomparison of Zenith-Sky UV-Visible Spectrometers in June 1996     

H. K. Roscoe  P. V. Johnston  M. Van Roozendael  A. Richter  A. Sarkissian  J. Roscoe  K. E. Preston  J-C. Lambert  C. Hermans  W. DeCuyper  S. Dzienus  T. Winterrath  J. Burrows  F. Goutail  J-P. Pommereau  E. D'Almeida  J. Hottier  C. Coureul  R. Didier  I. Pundt  L. M. Bartlett  C. T. McElroy  J. E. Kerr  A. Elokhov  G. Giovanelli  F. Ravegnani  M. Premuda  I. Kostadinov  F. Erle  T. Wagner  K. Pfeilsticker  M. Kenntner  L. C. Marquard  M. Gil  O. Puentedura  M. Yela  D. W. Arlander  B. A. Kastad Hoiskar  C. W. Tellefsen  K. Karlsen Tornkvist  B. Heese  R. L. Jones  S. R. Aliwell  R. A. Freshwater 《Journal of Atmospheric Chemistry》1999,32(2):281-314

In June 1996, 16 UV-visible sensors from 11 institutes measured spectra of the zenith sky for more than 10 days. Spectra were analysed in real-time to determine slant column amounts of O3 and NO2. Spectra of Hg lamps and lasers were measured, and the amount of NO2 in a cell was determined by each spectrometer. Some spectra were re-analysed after obvious errors were found. Slant columns were compared in two ways: by examining regression analyses against comparison instruments over the whole range of solar zenith angles; and by taking fractional differences from a comparison instrument at solar zenith angles between 85° and 91°. Regression identified which pairs of instruments were most consistent, and so which could be used as universal comparison instruments. For O3, regression slopes for the whole campaign agreed within 5% for most instruments despite the use of different cross-sections and wavelength intervals, whereas similar agreement was only achieved for NO2 when the same cross-sections and wavelength intervals were used and only one half-day's data was analysed. Mean fractional differences in NO2 from a comparison instrument fall within ±7% (1-sigma) for most instruments, with standard deviations of the mean differences averaging 4.5%. Mean differences in O3 fall within ±2.5% (1- sigma) for most instruments, with standard deviations of the mean differences averaging 2%. Measurements of NO2 in the cell had similar agreement to measurements of NO2 in the atmosphere, but for some instruments measurements with cell and atmosphere relative to a comparison instrument disagreed by more than the error bars.  相似文献   

Deep-sea mining of seafloor massive sulfides     

Porter Hoagland  Stace Beaulieu  Maurice A. Tivey  Roderick G. Eggert  Christopher German  Lyle Glowka  Jian Lin 《Marine Policy》2010

The potential emergence of an ocean mining industry to exploit seafloor massive sulfides could present opportunities for oceanographic science to facilitate seafloor mineral development in ways that lessen environmental harms.  相似文献   

Phytoplankton distribution and productivity in a highly turbid, tropical coastal system (Bach Dang Estuary, Vietnam)     

Rochelle-Newall EJ  Chu VT  Pringault O  Amouroux D  Arfi R  Bettarel Y  Bouvier T  Bouvier C  Got P  Nguyen TM  Mari X  Navarro P  Duong TN  Cao TT  Pham TT  Ouillon S  Torréton JP 《Marine pollution bulletin》2011,62(11):2317-2329

Phytoplankton diversity, primary and bacterial production, nutrients and metallic contaminants were measured during the wet season (July) and dry season (March) in the Bach Dang Estuary, a sub-estuary of the Red River system, Northern Vietnam. Using canonical correspondence analysis we show that phytoplankton community structure is potentially influenced by both organometallic species (Hg and Sn) and inorganic metal (Hg) concentrations. During March, dissolved methylmercury and inorganic mercury were important factors for determining phytoplankton community composition at most of the stations. In contrast, during July, low salinity phytoplankton community composition was associated with particulate methylmercury concentrations, whereas phytoplankton community composition in the higher salinity stations was more related to dissolved inorganic mercury and dissolved mono and tributyltin concentrations. These results highlight the importance of taking into account factors other than light and nutrients, such as eco-toxic heavy metals, in understanding phytoplankton diversity and activity in estuarine ecosystems.  相似文献   

Efficient analysis in planet transit surveys     

A. Schwarzenberg-Czerny  J.-Ph. Beaulieu 《Monthly notices of the Royal Astronomical Society》2006,365(1):165-170

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A late Pleistocene long pollen record from Lake Urmia, NW Iran   总被引：4，自引：0，他引：4  

Morteza Djamali  Jacques-Louis de Beaulieu  Madjid Shah-hosseini  Valrie Andrieu-Ponel  Philippe Ponel  Abdolhossein Amini  Hossein Akhani  Suzanne A.G. Leroy  Lora Stevens  Hamid Lahijani  Simon Brewer 《Quaternary Research》2008,69(3):413-420

A palynological study based on two 100-m long cores from Lake Urmia in northwestern Iran provides a vegetation record spanning 200 ka, the longest pollen record for the continental interior of the Near East. During both penultimate and last glaciations, a steppe of Artemisia and Poaceae dominated the upland vegetation with a high proportion of Chenopodiaceae in both upland and lowland saline ecosystems. While Juniperus and deciduous Quercus trees were extremely rare and restricted to some refugia, Hippophaë rhamnoides constituted an important phanerophyte, particularly during the late last glacial period. A pronounced expansion in Ephedra shrub-steppe occurred at the end of the penultimate late-glacial period but was followed by extreme aridity that favoured an Artemisia steppe. Very high lake levels, registered by both pollen and sedimentary markers, occurred during the middle of the last glaciation and late part of the penultimate glaciation. The late-glacial to early Holocene transition is represented by a succession of Hippophaë, Ephedra, Betula, Pistacia and finally Juniperus and Quercus. The last interglacial period (Eemian), slightly warmer and moister than the Holocene, was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern European pollen sequences.  相似文献   

Difference imaging photometry of blended gravitational microlensing events with a numerical kernel     

M. D. Albrow  K. Horne  D. M. Bramich  P. Fouqué  V. R. Miller  J.-P. Beaulieu  C. Coutures  J. Menzies  A. Williams  V. Batista  D. P. Bennett  S. Brillant  A. Cassan  S. Dieters  D. Dominis Prester  J. Donatowicz  J. Greenhill  N. Kains  S. R. Kane  D. Kubas  J. B. Marquette  K. R. Pollard  K. C. Sahu  Y. Tsapras  J. Wambsganss  M. Zub 《Monthly notices of the Royal Astronomical Society》2009,397(4):2099-2105

The numerical kernel approach to difference imaging has been implemented and applied to gravitational microlensing events observed by the PLANET collaboration. The effect of an error in the source-star coordinates is explored and a new algorithm is presented for determining the precise coordinates of the microlens in blended events, essential for accurate photometry of difference images. It is shown how the photometric reference flux need not be measured directly from the reference image but can be obtained from measurements of the difference images combined with the knowledge of the statistical flux uncertainties. The improved performance of the new algorithm, relative to isis2 , is demonstrated.  相似文献   

The Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue: MASH     

Quentin A. Parker  A. Acker  D. J. Frew  M. Hartley  A. E. J. Peyaud  F. Ochsenbein  S. Phillipps  D. Russeil  S. F. Beaulieu  M. Cohen  J. Köppen  B. Miszalski  D. H. Morgan  R. A. H. Morris  M. J. Pierce  A. E. Vaughan 《Monthly notices of the Royal Astronomical Society》2006,373(1):79-94

We present the Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue (MASH) of over 900 true, likely and possible new Galactic planetary nebulae (PNe) discovered from the AAO/UKST Hα survey of the southern Galactic plane. The combination of depth, resolution, uniformity and areal coverage of the Hα survey has opened up a hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. Away from the Galactic bulge the new PNe are typically more evolved, of larger angular extent, of lower surface brightness and more obscured (i.e. extinguished) than those in most previous surveys. We have also doubled the number of PNe in the Galactic bulge itself and although most are compact, we have also found more evolved examples. The MASH catalogue represents the culmination of a seven-year programme of identification and confirmatory spectroscopy. A key strength is that the entire sample has been derived from the same, uniform observational data. The 60 per cent increase in known Galactic PNe represents the largest ever incremental sample of such discoveries and will have a significant impact on many aspects of PN research. This is especially important for studies at the faint end of the PN luminosity function which was previously poorly represented.  相似文献   

Mass segregation in young compact clusters in the Large Magellanic Cloud – III. Implications for the initial mass function     

R. de Grijs  G. F. Gilmore  A. D. Mackey  M. I. Wilkinson  S. F. Beaulieu  R. A. Johnson  B. X. Santiago 《Monthly notices of the Royal Astronomical Society》2002,337(2):597-608

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