ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Cambridge University Press  (14,879)
  • 2020-2023  (19)
  • 1980-1984  (9,518)
  • 1965-1969  (5,342)
Collection
Years
Year
  • 1
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Xu, L., Roberts, M., Elder, K., Hansman, R., Gagnon, A., & Kurz, M. Radiocarbon in dissolved organic carbon by UV oxidation: an update of procedures and blank characterization at NOSAMS. Radiocarbon, 64(1), (2022): 195-199, https://doi.org/10.1017/rdc.2022.4.
    Description: This note describes improvements of UV oxidation method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). The procedural blank is reduced to 2.6 ± 0.6 μg C, with Fm of 0.42 ± 0.10 and δ13C of –28.43 ± 1.19‰. The throughput is improved from one sample per day to two samples per day.
    Description: We gratefully acknowledge support from the U.S. National Science Foundation, via NSF-OCE-1755125.
    Keywords: Blank ; Dissolved organic carbon ; Radiocarbon ; UV-oxidation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2022-06-22
    Description: Pliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area.
    Description: Published
    Description: 853 - 872
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: active faults ; seismic faults ; Earthquakes ; strike-slip faults ; inner Northern Apennines ; solid earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    facet.materialart.
    Unknown
    Cambridge University Press
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McNichol, A., Key, R., & Guilderson, T. Global ocean radiocarbon programs. Radiocarbon, (2022): 1–13, https://doi.org/10.1017/rdc.2022.17.
    Description: The importance of studying the radiocarbon content of dissolved inorganic carbon (DI14C) in the oceans has been recognized for decades. Starting with the GEOSECS program in the 1970s, 14C sampling has been a part of most global survey programs. Early results were used to study air-sea gas exchange while the more recent results are critical for helping calibrate ocean general circulation models used to study the effects of climate change. Here we summarize the major programs and discuss some of the important insights the results are starting to provide.
    Description: Authors received funding from the National Science Foundation OCE-85865400 (APM) and a Woods Hole Oceanographic Technical Staff Award (APM).
    Keywords: Dissolved inorganic carbon ; Ocean models ; Oceanography ; Radiocarbon
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Druffel, E., Beaupre, S., Grotheer, H., Lewis, C., McNichol, A., Mollenhauer, G., & Walker, B. Marine organic carbon and radiocarbon – present and future challenges. Radiocarbon, (2022): 1-17, https://doi.org/10.1017/RDC.2021.105.
    Description: We discuss present and developing techniques for studying radiocarbon in marine organic carbon (C). Bulk DOC (dissolved organic C) Δ14C measurements reveal information about the cycling time and sources of DOC in the ocean, yet they are time consuming and need to be streamlined. To further elucidate the cycling of DOC, various fractions have been separated from bulk DOC, through solid phase extraction of DOC, and ultrafiltration of high and low molecular weight DOC. Research using 14C of DOC and particulate organic C separated into organic fractions revealed that the acid insoluble fraction is similar in 14C signature to that of the lipid fraction. Plans for utilizing this methodology are described. Studies using compound specific radiocarbon analyses to study the origin of biomarkers in the marine environment are reviewed and plans for the future are outlined. Development of ramped pyrolysis oxidation methods are discussed and scientific questions addressed. A modified elemental analysis (EA) combustion reactor is described that allows high particulate organic C sample throughput by direct coupling with the MIniCArbonDAtingSystem.
    Keywords: CSRA ; Dissolved organic carbon ; Methodology ; Organic carbon ; Radiocarbon
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Priscu, J. C., Kalin, J., Winans, J., Campbell, T., Siegfried, M. R., Skidmore, M., Dore, J. E., Leventer, A., Harwood, D. M., Duling, D., Zook, R., Burnett, J., Gibson, D., Krula, E., Mironov, A., McManis, J., Roberts, G., Rosenheim, B. E., Christner, B. C., Kasic, K., Fricker, H. A., Lyons, W. B., Barker, J., Bowling, M., Collins, B., Davis, C., Gagnon, A., Gardner, C., Gustafson, C., Kim, O-S., Li, W., Michaud, A., Patterson, M. O., Tranter, M., Ryan Venturelli, R., Trista Vick-Majors, T., & Elsworth, C. Scientific access into Mercer Subglacial Lake: scientific objectives, drilling operations and initial observations. Annals of Glaciology, 62(85–86), (2021): 340–352, https://doi.org/10.1017/aog.2021.10.
    Description: The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes 〉0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.
    Description: This material is based upon work supported by the US National Science Foundation, Section for Antarctic Sciences, Antarctic Integrated System Science program as part of the interdisciplinary (Subglacial Antarctic Lakes Scientific Access (SALSA): Integrated study of carbon cycling in hydrologically-active subglacial environments) project (NSF-OPP 1543537, 1543396, 1543405, 1543453 and 1543441). Ok-Sun Kim was funded by the Korean Polar Research Institute. We are particularly thankful to the SALSA traverse personnel for crucial technical and logistical support. The United States Antarctic Program enabled our fieldwork; the New York Air National Guard and Kenn Borek Air provided air support; UNAVCO provided geodetic instrument support. Hot water drilling activities, including repair and upgrade modifications of the WISSARD hot water drill system, for the SALSA project were supported by a subaward from the Ice Drilling Program of Dartmouth College (NSF-PLR 1327315) to the University of Nebraska-Lincoln. J. Lawrence assisted with manuscript preparation. Finally, we are grateful to C. Dean, the SALSA Project Manager, and R. Ricards, SALSA Project Coordinator at McMurdo Station, for their organizational skills, and B. Huber of Lamont-Doherty Earth Observatory for providing the SBE39 PT sensors and the Nortek Aquadopp current meter and assisting with interpretation of the data. B. Huber also provided helpful input on programing and calibrating the SBE19PlusV2 6112 CTD.
    Keywords: Antarctic glaciology ; Basal ice ; Biogeochemistry ; Glacial sedimentology ; Subglacial lakes
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    facet.materialart.
    Unknown
    Cambridge University Press
    In:  EPIC3Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, ,, IPCC AR6 WGII, https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_FinalDraft_Chapter03.pdf, Cambridge University Press
    Publication Date: 2022-08-23
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , NonPeerReviewed
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    facet.materialart.
    Unknown
    Cambridge University Press
    In:  EPIC3Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, IPCC AR6 WGII, Climate Change 2022: Impacts, adaptation and vulnerability. Contribution of the WGII to the 6th assessment report of the intergovernmental panel on climate change, IPCC AR6 WGII, https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_FinalDraft_Chapter02.pdf, Cambridge University Press, 5 p., pp. 22-26
    Publication Date: 2022-06-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2022-07-20
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tan, S., Pratt, L. J., Voet, G., Cusack, J. M., Helfrich, K. R., Alford, M. H., Girton, J. B., & Carter, G. S. Hydraulic control of flow in a multi-passage system connecting two basins. Journal of Fluid Mechanics, 940, (2022): A8, https://doi.org/10.1017/jfm.2022.212.
    Description: When a fluid stream in a conduit splits in order to pass around an obstruction, it is possible that one branch will be critically controlled while the other remains not so. This is apparently the situation in Pacific Ocean abyssal circulation, where most of the northward flow of Antarctic bottom water passes through the Samoan Passage, where it is hydraulically controlled, while the remainder is diverted around the Manihiki Plateau and is not controlled. These observations raise a number of questions concerning the dynamics necessary to support such a regime in the steady state, the nature of upstream influence and the usefulness of rotating hydraulic theory to predict the partitioning of volume transport between the two paths, which assumes the controlled branch is inviscid. Through the use of a theory for constant potential vorticity flow and accompanying numerical model, we show that a steady-state regime similar to what is observed is dynamically possible provided that sufficient bottom friction is present in the uncontrolled branch. In this case, the upstream influence that typically exists for rotating channel flow is transformed into influence into how the flow is partitioned. As a result, the partitioning of volume flux can still be reasonably well predicted with an inviscid theory that exploits the lack of upstream influence.
    Description: This work was supported by the National Science Foundation under grants OCE-1029268, OCE-1029483, OCE-1657264, OCE-1657795, OCE-1657870 and OCE-1658027.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    facet.materialart.
    Unknown
    Cambridge University Press
    In:  EPIC3Antarctic Science, Cambridge University Press, 33(6), pp. 575-595, ISSN: 0954-1020
    Publication Date: 2022-01-13
    Description: The waters along the West Antarctic Peninsula (WAP) have experienced warming and increased freshwater inputs from melting sea ice and glaciers in recent decades. Challenges exist in understanding the consequences of these changes on the inorganic carbon system in this ecologically important and highly productive ecosystem. Distributions of dissolved inorganic carbon (CT), total alkalinity (AT) and nutrients revealed key physical, biological and biogeochemical controls of the calcium carbonate saturation state (Ωaragonite) in different water masses across the WAP shelf during the summer. Biological production in spring and summer dominated changes in surface water Ωaragonite (ΔΩaragonite up to +1.39; ∼90%) relative to underlying Winter Water. Sea-ice and glacial meltwater constituted a minor source of AT that increased surface water Ωaragonite (ΔΩaragonite up to +0.07; ∼13%). Remineralization of organic matter and an influx of carbon-rich brines led to cross-shelf decreases in Ωaragonite in Winter Water and Circumpolar Deep Water. A strong biological carbon pump over the shelf created Ωaragonite oversaturation in surface waters and suppression of Ωaragonite in subsurface waters. Undersaturation of aragonite occurred at 〈 ∼1000 m. Ongoing changes along the WAP will impact the biologically driven and meltwater-driven processes that influence the vulnerability of shelf waters to calcium carbonate undersaturation in the future.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in [Schiller, C. M., Whitlock, C., Elder, K. L., Iverson, N. A., & Abbott, M. B. Erroneously old radiocarbon ages from terrestrial pollen concentrates in Yellowstone Lake, Wyoming, USA. Radiocarbon, 63(1), (2021): 321-342, https://doi.org/10.1017/RDC.2020.118.
    Description: Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study.
    Description: This research was supported by NSF Grant No. 1515353 to C. Whitlock and sampling in Yellowstone National Park was conducted under permits YELL-SCI-0009 and YELL-SCI-5054.
    Keywords: AMS dating ; Chronology ; Contamination ; Paleoecology ; Pine
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baker, M. G., Aster, R. C., Wiens, D. A., Nyblade, A., Bromirski, P. D., Gerstoft, P., & Stephen, R. A. Teleseismic earthquake wavefields observed on the Ross Ice Shelf. Journal of Glaciology, 67(261), (2021): 58-74, https://doi.org/10.1017/jog.2020.83.
    Description: Observations of teleseismic earthquakes using broadband seismometers on the Ross Ice Shelf (RIS) must contend with environmental and structural processes that do not exist for land-sited seismometers. Important considerations are: (1) a broadband, multi-mode ambient wavefield excited by ocean gravity wave interactions with the ice shelf; (2) body wave reverberations produced by seismic impedance contrasts at the ice/water and water/seafloor interfaces and (3) decoupling of the solid Earth horizontal wavefield by the sub-shelf water column. We analyze seasonal and geographic variations in signal-to-noise ratios for teleseismic P-wave (0.5–2.0 s), S-wave (10–15 s) and surface wave (13–25 s) arrivals relative to the RIS noise field. We use ice and water layer reverberations generated by teleseismic P-waves to accurately estimate the sub-station thicknesses of these layers. We present observations consistent with the theoretically predicted transition of the water column from compressible to incompressible mechanics, relevant for vertically incident solid Earth waves with periods longer than 3 s. Finally, we observe symmetric-mode Lamb waves generated by teleseismic S-waves incident on the grounding zones. Despite their complexity, we conclude that teleseismic coda can be utilized for passive imaging of sub-shelf Earth structure, although longer deployments relative to conventional land-sited seismometers will be necessary to acquire adequate data.
    Description: This research was supported by NSF grants PLR-1142518, 1141916, 1142126, 1246151, 1246416 and OPP-1744852 and 1744856.
    Keywords: Glacier geophysics ; Ice shelves ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Publication Date: 2022-05-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tison, J.-L., Maksym, T., Fraser, A. D., Corkill, M., Kimura, N., Nosaka, Y., Nomura, D., Vancoppenolle, M., Ackley, S., Stammerjohn, S., Wauthy, S., Van der Linden, F., Carnat, G., Sapart, C., de Jong, J., Fripiat, F., & Delille, B. Physical and biological properties of early winter Antarctic sea ice in the Ross Sea. Annals of Glaciology, 61(83), (2020): 241–259, https://doi.org/10.1017/aog.2020.43.
    Description: This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
    Description: S. Stammerjohn was supported by the PIPERS and LTER Programs of the U.S. National Science Foundation, ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado) and ANT-0823101 (H. Ducklow, LDEO/Columbia University), respectively. Steve Ackley (UTSA) was supported by the PIPERS program of the U.S. National Science Foundation ANT-1341717 and by NASA Grant 80NSSC19M0194 to the Center for Adv. Meas. in Extreme Environments at UTSA.Ted Maksym (WHOI) was supported by the PIPERS program of the U.S. National Science Foundation ANT-1341513. This research was supported by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Fanny Van der Linden, Sarah Wauthy, Gauthier Carnat, Célia Sapart and Bruno Delille are PhD students, postdoctoral researchers and research associate, respectively, of the Belgian F.R.S.-FNRS. This work was also supported by the Australian Government's Cooperative Research Centre program through the Antarctic Climate & Ecosystems Cooperative Research Centre, and by the Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001). Daiki Nomura was supported by grants from the Japan Society for the Promotion of Science (#17H04715) and the National Institute for Polar Research through Project Research KP-303 (ROBOTICA) and #28-14.
    Keywords: Antarctic glaciology ; biogeochemistry ; sea ice
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Roberts, Mark L., Elder, Kathryn L., Jenkins, William J., Gagnon, Alan R., Xu, Li, Hlavenka, Joshua D., & Longworth, Brett E. C-14 Blank Corrections for 25-100 mu G samples at the National Ocean Sciences AMS Laboratory. Radiocarbon, 61(5), (2019): 1403-1411, Doi: 10.1017/RDC.2019.74.
    Description: Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0–1.5 and mass range 6 μg–2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently “blank correct” measured unknowns in the mass range 25–100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented.
    Description: This work is supported by a Cooperative Agreement (OCE-1755125) with the U.S. National Science Foundation.
    Keywords: AMS ; AMS dating ; Blank corrections
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Publication Date: 2022-10-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baker, M. G., Aster, R. C., Anthony, R. E., Chaput, J., Wiens, D. A., Nyblade, A., Bromirski, P. D., Gerstoft, P., & Stephen, R. A. Seasonal and spatial variations in the ocean-coupled ambient wavefield of the Ross Ice Shelf. Journal of Glaciology, 65(254), (2019): 912-925, doi:10.1017/jog.2019.64.
    Description: The Ross Ice Shelf (RIS) is host to a broadband, multimode seismic wavefield that is excited in response to atmospheric, oceanic and solid Earth source processes. A 34-station broadband seismographic network installed on the RIS from late 2014 through early 2017 produced continuous vibrational observations of Earth's largest ice shelf at both floating and grounded locations. We characterize temporal and spatial variations in broadband ambient wavefield power, with a focus on period bands associated with primary (10–20 s) and secondary (5–10 s) microseism signals, and an oceanic source process near the ice front (0.4–4.0 s). Horizontal component signals on floating stations overwhelmingly reflect oceanic excitations year-round due to near-complete isolation from solid Earth shear waves. The spectrum at all periods is shown to be strongly modulated by the concentration of sea ice near the ice shelf front. Contiguous and extensive sea ice damps ocean wave coupling sufficiently so that wintertime background levels can approach or surpass those of land-sited stations in Antarctica.
    Description: This research was supported by NSF grants PLR-1142518, 1141916, 1142126, 1246151 and 1246416. JC was additionally supported by Yates funds in the Colorado State University Department of Mathematics. PDB also received support from the California Department of Parks and Recreation, Division of Boating and Waterways under contract 11-106-107. We thank Reinhard Flick and Patrick Shore for their support during field work, Tom Bolmer in locating stations and preparing maps, and the US Antarctic Program for logistical support. The seismic instruments were provided by the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at New Mexico Tech. Data collected are available through the IRIS Data Management Center under RIS and DRIS network code XH. The PSD-PDFs presented in this study were processed with the IRIS Noise Tool Kit (Bahavar and others, 2013). The facilities of the IRIS Consortium are supported by the National Science Foundation under Cooperative Agreement EAR-1261681 and the DOE National Nuclear Security Administration. The authors appreciate the support of the University of Wisconsin-Madison Automatic Weather Station Program for the data set, data display and information; funded under NSF grant number ANT-1543305. The Ross Ice Shelf profiles were generated using the Antarctic Mapping Tools (Greene and others, 2017). Regional maps were generated with the Generic Mapping Tools (Wessel and Smith, 1998). Topography and bathymetry data for all maps in this study were sourced from the National Geophysical Data Center ETOPO1 Global Relief Model (doi:10.7289/V5C8276M). We thank two anonymous reviewers for suggestions on the scope and organization of this paper.
    Keywords: Antarctic glaciology ; Ice shelves ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Publication Date: 2022-10-21
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Stammerjohn, S., Maksym, T., Smith, M., Cassano, J., Guest, P., Tison, J., Delille, B., Loose, B., Sedwick, P., DePace, L., Roach, L., & Parno, J. Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign. Annals of Glaciology, 61(82), (2020): 181-195, doi:10.1017/aog.2020.31.
    Description: The Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.
    Description: NSF supported PIPERS award numbers: ANT-1341717 (S.F. Ackley, UTSA); ANT-1341513 (E. Maksym, WHOI); ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado); ANT-1341725 (P. Guest, NPS). P. Sedwick was supported by NSF ANT-1543483. S.F. Ackley was also supported by NASA Grant 80NSSC19M0194 to the Center for Advanced Measurements in Extreme Environments at UTSA. S. Stammerjohn was also supported by the LTER Program under NFS award number ANT-0823101 (H. Ducklow, LDEO/Columbia University). Additional support was by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Bruno Delille is a research associate of the F.R.S.-FNRS. Terra-Sar-X quicklook imagery was coordinated by Kathrin Hoeppner at DLR, and Andy Archer (with the Antarctic Support Contractor) provided selected (cloud-free) MODIS scenes and daily maps of AMSR2 sea-ice concentration.
    Keywords: Atmosphere/ice/ocean interactions ; Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hughen, K. A., & Heaton, T. J. Updated Cariaco Basin C-14 calibration dataset from 0-60 cal kyr BP. Radiocarbon, 62(4), (2020): 1001-1043, doi:10.1017/RDC.2020.53.
    Description: We present new updates to the calendar and radiocarbon (14C) chronologies for the Cariaco Basin, Venezuela. Calendar ages were generated by tuning abrupt climate shifts in Cariaco Basin sediments to those in speleothems from Hulu Cave. After the original Cariaco-Hulu calendar age model was published, Hulu Cave δ18O records have been augmented with increased temporal resolution and a greater number of U/Th dates. These updated Hulu Cave records provide increased accuracy as well as precision in the final Cariaco calendar age model. The depth scale for the Ocean Drilling Program Site 1002D sediment core, the primary source of samples for 14C dating, has been corrected to account for missing sediment from a core break, eliminating age-depth anomalies that afflicted the earlier calendar age models. Individual 14C dates for the Cariaco Basin remain unchanged from previous papers, although detailed comparisons of the Cariaco calibration dataset to those from Hulu Cave and Lake Suigetsu suggest that the Cariaco marine reservoir age may have shifted systematically during the past. We describe these recent changes to the Cariaco datasets and provide the data in a comprehensive format that will facilitate use by the community.
    Description: K.A. Hughen was supported by funds from U.S. NSF grant #OCE-1657191, and by the Investment in Science Fund at WHOI. T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9, “Improving the Measurement of Time Using Radiocarbon”.
    Keywords: Calibration ; Climate ; Radiocarbon
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Publication Date: 2022-10-20
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ackley, S. F., Perovich, D. K., Maksym, T., Weissling, B., & Xie, H. Surface flooding of Antarctic summer sea ice. Annals of Glaciology, 61(82), (2020): 117-126, doi:10.1017/aog.2020.22.
    Description: The surface flooding of Antarctic sea ice in summer covers 50% or more of the sea-ice area in the major summer ice packs, the western Weddell and the Bellingshausen-Amundsen Seas. Two CRREL ice mass-balance buoys were deployed on the Amundsen Sea pack in late December 2010 from the icebreaker Oden, bridging the summer period (January–February 2011). Temperature records from thermistors embedded vertically in the snow and ice showed progressive increases in the depth of the flooded layer (up to 0.3–0.35 m) on the ice cover during January and February. While the snow depth was relatively unchanged from accumulation (〈10 cm), ice thickness decreased by up to a meter from bottom melting during this period. Contemporaneous with the high bottom melting, under-ice water temperatures up to 1°C above the freezing point were found. The high temperature arises from solar heating of the upper mixed layer which can occur when ice concentration in the local area falls and lower albedo ocean water is exposed to radiative heating. The higher proportion of snow ice found in the Amundsen Sea pack ice therefore results from both winter snowfall and summer ice bottom melt found here that can lead to extensive surface flooding.
    Description: This work was supported by the National Science Foundation grant to UTSA, ANT-0839053-Sea Ice System in Antarctic Summer (S.F. Ackley, H. Xie and B. Weissling), and to WHOI, ANT-1341513 (T. Maksym), and by the NASA Center for Advanced Measurements in Extreme Environments or NASA-CAMEE at UTSA, NASA #80NSSC19M0194 (S.F. Ackley, H. Xie, B.Weissling).
    Keywords: Ice/ocean interactions ; Sea ice ; Sea-ice growth and decay ; Snow/ice surface processes
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Reimer, P. J., Austin, W. E. N., Bard, E., Bayliss, A., Blackwell, P. G., Ramsey, C. B., Butzin, M., Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Hajdas, I., Heaton, T. J., Hogg, A. G., Hughen, K. A., Kromer, B., Manning, S. W., Muscheler, R., Palmer, J. G., Pearson, C., van der Plicht, J., Reimer, R. W., Richards, D. A., Scott, E. M., Southon, J. R., Turney, C. S. M., Wacker, L., Adolphi, F., Buentgen, U., Capano, M., Fahrni, S. M., Fogtmann-Schulz, A., Friedrich, R., Koehler, P., Kudsk, S., Miyake, F., Olsen, J., Reinig, F., Sakamoto, M., Sookdeo, A., & Talamo, S. The Intcal20 Northern Hemisphere radiocarbon age calibration curve (0-55 cal kBP). Radiocarbon, 62(4), (2020): 725-757, doi:10.1017/RDC.2020.41.
    Description: Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.
    Description: We would like to thank the National Natural Science Foundation of China grants NSFC 41888101 and NSFC 41731174, the 111 program of China (D19002), U.S. NSF Grant 1702816, and the Malcolm H. Wiener Foundation for support for research that contributed to the IntCal20 curve. The work on the Swiss and German YD trees was funded by the German Science foundation and the Swiss National Foundation (grant number: 200021L_157187). The operation in Aix-en-Provence is funded by the EQUIPEX ASTER-CEREGE, the Collège de France and the ANR project CARBOTRYDH (to EB). The work on the correlation of tree ring 14C with ice core 10Be was partially supported by the Swedish Research Council and the Knut and Alice Wallenberg foundation. M. Butzin was supported by the German Federal Ministry of Education and Research (BMBF) as Research for Sustainable Development (FONA; http://www.fona.de) through the PalMod project (grant number: 01LP1505B). S. Talamo and M. Friedrich are funded by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No. 803147-RESOLUTION, awarded to ST). CA. Turney would like to acknowledge support of the Australian Research Council (FL100100195 and DP170104665). P. Reimer and W. Austin acknowledge the support of the UKRI Natural Environment Research Council (Grant NE/M004619/1). T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9. Other datasets and the IntCal20 database were created without external support through internal funding by the respective laboratories. We also would like to thank various institutions that provided funding or facilities for meetings.
    Keywords: Calibration curve ; Radiocarbon ; IntCal20
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Heaton, T. J., Koehler, P., Butzin, M., Bard, E., Reimer, R. W., Austin, W. E. N., Ramsey, C. B., Grootes, P. M., Hughen, K. A., Kromer, B., Reimer, P. J., Adkins, J., Burke, A., Cook, M. S., Olsen, J., & Skinner, L. C. Marine20-the marine radiocarbon age calibration curve (0-55,000 cal BP). Radiocarbon, 62(4), (2020): 779-820, doi:10.1017/RDC.2020.68.
    Description: The concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-average marine record of radiocarbon from 0–55 cal kBP and serves as a baseline for regional oceanic variation. Marine20 is intended for calibration of marine radiocarbon samples from non-polar regions; it is not suitable for calibration in polar regions where variability in sea ice extent, ocean upwelling and air-sea gas exchange may have caused larger changes to concentrations of marine radiocarbon. The Marine20 curve is based upon 500 simulations with an ocean/atmosphere/biosphere box-model of the global carbon cycle that has been forced by posterior realizations of our Northern Hemispheric atmospheric IntCal20 14C curve and reconstructed changes in CO2 obtained from ice core data. These forcings enable us to incorporate carbon cycle dynamics and temporal changes in the atmospheric 14C level. The box-model simulations of the global-average marine radiocarbon reservoir age are similar to those of a more complex three-dimensional ocean general circulation model. However, simplicity and speed of the box model allow us to use a Monte Carlo approach to rigorously propagate the uncertainty in both the historic concentration of atmospheric 14C and other key parameters of the carbon cycle through to our final Marine20 calibration curve. This robust propagation of uncertainty is fundamental to providing reliable precision for the radiocarbon age calibration of marine based samples. We make a first step towards deconvolving the contributions of different processes to the total uncertainty; discuss the main differences of Marine20 from the previous age calibration curve Marine13; and identify the limitations of our approach together with key areas for further work. The updated values for ΔR, the regional marine radiocarbon reservoir age corrections required to calibrate against Marine20, can be found at the data base http://calib.org/marine/.
    Description: We would like to thank Jeremy Oakley and Richard Bintanja for informative discussions during the development of this work. T.J. Heaton is supported by a Leverhulme Trust Fellowship RF-2019-140\9, “Improving the Measurement of Time Using Radiocarbon”. M Butzin is supported by the German Federal Ministry of Education and Research (BMBF), as Research for Sustainability initiative (FONA); www.fona.de through the PalMod project (grant numbers: 01LP1505B, 01LP1919A). E. Bard is supported by EQUIPEX ASTER-CEREGE and ANR CARBOTRYDH. Meetings of the IntCal Marine Focus group have been supported by Collège de France. Data are available on the PANGAEA database at doi:10.159/ANGAEA.914500.
    Keywords: Bayesian modeling ; calibration ; carbon cycle ; computer model ; marine environment
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Publication Date: 1984-01-01
    Description: The following radiocarbon date list contains dates of samples measured since our previous list (R, 1982, v 24, p 352–371). As before, age calculations are based on the Libby half-life (5570 ± 30) yr and reported in years before 1950. The modern standard is 0.95 of the NBS oxalic acid activity. Sample pretreatment, combustion, and counting technique are essentially the same as described in R, 1971, v 13, p 135–140, supplemented by new techniques for groundwater processing (R, 1979, v 21, p 131–137).
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Publication Date: 1984-01-01
    Description: We demonstrate the feasibility of pulse time of arrival information for early detection of periodic events in low level counting. Time of arrival data allows us to apply time series analysis and serial correlation tests which, in graphic form, give the user an illustrative view of the parameters affecting the validity of counting statistics. The decision to discontinue counting can already be made on the basis of less than 100 counts from the time information alone if more than 10 of these are non-Poisson periodic counts. The analyses also serve as a means of quality control for low level counting, being directly based upon the interval distribution of the Poisson process.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Publication Date: 1984-01-01
    Description: This series reports some of the measurements made since publication of the last list (R, 1981, v 23, p 94–135). Also included are a number of earlier dates previously withheld pending submitter evaluation. For some the authors have been unable to obtain appropriate comment. References to other publication of these dates are given where known.Acetylene proportional gas counting methods essentially remain as described in Saskatchewan II (R, 1960, v 2, p 73). Bone dating is carried out on soluble collagen extract (Longin, 1971) since 1978.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Publication Date: 1984-01-01
    Description: Facilities for radiocarbon dating were established at the University of Frankfurt/Main in the Institute of Anthropology. The Radiocarbon Laboratory provides assistance to the Amino-Acid-Dating Laboratory. This list reports on 14C dates measured up to September 1983.The laboratory is installed in the basement of a three-story building and is equipped with a 2L copper proportional counter filled to 1013 mbar with purified CO2. The counter is protected against cosmic and surrounding radiation by a 3.5 ton lead shield and a copper multiwire anticoincidence ring-counter flushed with purified 90Ar/10CH4. Electronics are of the commercial NIM type. Charcoal and wood samples are treated by standard acid-alkali-acid methods. Bone samples are treated according to the collagen methods described by Berger, Horney, and Libby (1964), Longin (1971), Protsch (1972; 1975), and Protsch and Berger (1973).
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Publication Date: 1984-01-01
    Description: The following list consists of dates for archaeologic and geologic samples mostly measured from June 1982 to June 1983. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16). Dates are expressed in radiocarbon years relative to ad 1950 based on the Libby half-life for 14C of 5570 yr, and are corrected for isotopic fractionation (δ13C values are relative to PDB). No corrections have been made for natural 14C variations. The modern reference standard is NBS oxalic acid (SRM 4990). Errors quoted with dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (± 1σ). Descriptions, comments, and references to publications are based on information supplied by submitters.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Publication Date: 1984-01-01
    Description: This radiocarbon laboratory began operation in 1980 using the benzene scintillation method. The benzene synthesizer is essentially identical with that of Ikeda (1976). A liquid scintillation counter is Aloca LSC-LB1. Samples dated are wood, charcoal, shell, and coral.Pretreatment of wood and charcoal is a standard acid-alkali procedure, using 2% HCl and 2% NaOH at elevated temperatures. Charcoal is further heated in concentrated HNO3 for one hour, diluted in water, stands one night, and is washed and dried. Pretreated wood and charcoal are carbonized before combustion. The combustion products are passed over CuO, and are collected in an ammonium hydroxide bubbler system, and precipitated with calcium chloride.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Publication Date: 1984-01-01
    Description: A sodium bicarbonate solution with a 10-fold activity compared to oxalic acid is used as a secondary standard in the Heidelberg 14C Laboratory. All routine checks and counter tests are greatly facilitated because of the high activity of the solution.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Publication Date: 1984-01-01
    Description: Procedures and equipment used in the University of Wisconsin laboratory have been described in previous date lists. Except as otherwise indicated, wood, charcoal, and peat samples are pretreated with dilute NaOH-Na4P2O7 and dilute H3PO4 before conversion to the counting gas methane; marls and lake cores are treated with acid only. Very calcareous materials are treated with HCl instead of H3PO4. Pretreatment of bone varies with the condition of the bone sample; solid bone with little deterioration is first cleaned manually and ultrasonically. The bone is treated with 8% HCl for 15 minutes, then dilute NaOH-Na4P2O7 for 3 hours at room temperature, washed until neutral, and the collagen extracted according to Longin (1971). Charred bone is treated with dilute HCl, NaOH-Na4P2O7, and then dilute HCl again.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    Publication Date: 1984-01-01
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Publication Date: 1984-01-01
    Description: Radiocarbon dating provides the principal chronometric data for the Middle and Upper Palaeolithic, Epipalaeolithic, and Chalcolithic periods in the southern Levant. It is a secondary source of dating evidence for the Early Bronze age, when archaeological correlations with Syria and especially Egypt become available. For the Middle and Late Bronze age, Iron age, Persian, Hellenistic, Roman, and Byzantine periods, 14C dating has only limited value because the technique is less precise than the normally available archaeologic and historic materials.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    Publication Date: 1984-01-01
    Description: The Radiocarbon Laboratory of the Archaeological and Ethnographical Museum in Lódź was established to meet the growing demand for radiocarbon dating of archaeologic and geologic samples. The liquid scintillation technique based on the Polish liquid scintillation counter with a single photomultiplier began operation in 1966. The base for the measurements was ethylbenzene. In 1974 new facilities for the determination of radiocarbon assays were installed. The proportional counter and the electronics supplied by Nuclear Enterprises became routine counting equipment two years later.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Publication Date: 1984-01-01
    Description: This list contains the results of measurements of 167 groundwater samples made between September 1979 and December 1982. An additional 175 samples were measured, but these were submitted without detailed information, such as sampling depth, well location, etc; therefore, they were excluded from the following list.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Publication Date: 1984-01-01
    Description: A major collective effort was made to develop a data base for establishing the relationship between 14C and calendric ages (Stuiver, 1982). The early “cosmic schwung” fit between the two ages (Suess, 1970a, p 310) and the 10,350 yr period of the grand trend (Suess, 1970b, p 596) have recently been replaced by the period of 12,100 yr (Suess, 1980). The period of the grand trend was estimated by correlating the data with an a priori postulated sine function (Suess, 1970, p 596), or more recently a polynomial fit of the sixth degree was used (Klein et al, 1982). In the detrended data, periods (wiggles) of between 2400 yr and 104 yr were identified by conventional time series analysis. This approach could not be used to estimate the period of the grand trend, because the time series includes less than one cycle, whereas several cycles are required in order to get a meaningful result.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Publication Date: 1984-01-01
    Description: This list reports measurements made on archaeologic and geologic samples by our laboratory from June 1982 to December 1983. Results of measurements made during that period which lack review by submitters will be reported in a subsequent date list. Sample preparation techniques and benzene synthesis remain as described previously (R, 1982, v 24, p 344–351). For low organic samples, such as sediments, we now use a combustion tube assembly. These samples are burned under oxygen flow in a quartz tube. To absorb sulfur and break up nitrous compounds, we pass combustion gases through a 50% mixture of MnO2 and CuO wire heated to ca 500°C. The gas is then bubbled through a distilled water and KMnO4 solution to remove chlorides before being introduced into our standard dry ice and CO2 traps.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Publication Date: 1984-01-01
    Description: Measurements have continued with the same proportional counter system, pretreatment procedure, methane preparation and measurement, and calculation, as described previously (R, 1970, v 12, p 298–318). Uncertainties quoted are single standard deviations. No 13C/12C ratios were measured. Sample descriptions have been prepared in cooperation with submitters.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Publication Date: 1984-01-01
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Publication Date: 1984-01-01
    Description: This date list includes most of the archaeologic and geologic samples dated in this laboratory since publication of our last date list (R, 1981, v 23, p 227–240), as well as some samples dated previously which lacked adequate sample information.All samples were pretreated with 3N HCl and some, where noted, were given additional pretreatment with 2% NaOH for the removal of possible humic acid contaminants.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Publication Date: 1984-01-01
    Description: This list consists of dates of soil samples from selected soil profiles in Tunisia, Sudan, and Argentina. The profiles from Tunisia were taken to elucidate ages of typic paleosols of paleoclimatic significance. The Sudan profiles increase our understanding of pedogenesis of Sudanese Vertisols. The existence of pedoturbation in these profiles is further explored and questioned. The profiles of Argentina were dated to supplement information from chemical and micromorphological studies.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Publication Date: 1984-01-01
    Description: Selected stable carbon isotope measurements published in Radiocarbon over a 12-year period have been abstracted, plotted, and summarized, to give more reliable estimates of the mean value and range of δ13C for five classes of natural material (human bone collagen, non-human animal bone collagen, plant materials, wood, and charcoal), and to provide a firmer base line for stable carbon isotope dietary and environmental studies.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Publication Date: 1984-01-01
    Description: Very incautiously, after printing 25 volumes of Radiocarbon, the editors have authorized some personal reminiscence. Like all “Quaternary scientists”—no better collective name is available for our strange profession—I have been engaged in historiography, writing about history, for many years. In 1946, when natural radiocarbon was discovered, my subject, the sedimentary history of lakes, was only one of several kinds of historical record that needed, and soon received, a new reading. At the time, not all custodians of other kinds of record were ready to agree that new readings were conceivable, let alone necessary. The record of their persuasion—some of which has been written by Greg Marlowe (1980) in “W F Libby and the Archaeologists”—is part of the history of historiography. To the bibliography of this dangerously abstract subject I venture to add some minor footnotes. They come, not from historical research like Marlowe's, but from a leaky, selective memory.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Publication Date: 1984-01-01
    Description: Most of the 14C measurements reported here were made between October 1982 and October 1983. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36–37; 1976, v 18, p 290; 1980, v 22, p 1045).Age calculations are based on a contemporary value equal to 95% of the activity of NBS oxalic acid standard (No. 4990A) and on the conventional half-life for 14C of 5568 yr. Results are reported in years before 1950 (years bp). Errors quoted with the dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (±σ).
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Publication Date: 1984-01-01
    Description: Manuscripts of 14C papers and date lists should follow the recommendations in “Suggestions to Authors of the Reports of the US Geological Survey,” 6th ed, 1978, Superintendent of Documents, Government Printing Office, Washington, DC 20402. All copy, including the references, must be typewritten in double space: manuscripts must be submitted in duplicate. Computer print-out sheets may be used in letter-quality printing form. Manuscripts should be checked with meticulous care before they are submitted, for the author, not the editor, is finally responsible for errors other than those made by the printer. Revised manuscripts must be submitted in duplicate along with the original edited manuscript.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Publication Date: 1984-01-01
    Description: Although acid leaching of shell carbonates prior to 14C assay is usually desirable, under some circumstances it can worsen contamination by preferentially dissolving unaltered shell and thus increasing the proportion of secondary carbonate. The risk can be eliminated by monitoring the progress of leaching with the help of microscopy and x-ray diffraction.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    Publication Date: 1984-01-01
    Description: Bomb 14C has been used as a tracer for CO2 in ocean surface water to study CO2 exchange between atmosphere and ocean. Using ordinary cargo ships for sampling, we have been able to cover some parts of the Atlantic, Pacific, and Indian Oceans for certain periods. A total number of 520 samples from 89 locations were measured during the last 15 years. The data are presented both in tables and graphs. A maximum 14C concentration (Δ14C) of ca 20% was observed in temperate northern latitudes, and a few per cent lower at southern latitudes. A seasonal trend in the 14C variation, with summer maximum and winter minimum, was observed both in downwelling and upwelling areas.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Publication Date: 1984-01-01
    Description: The reinstallment, operation, and the 14C measurements reported here were made since 1976 in the LATYR, the Radiocarbon Dating Laboratory of the Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata. Sample preparation is preceded by careful visual separation and hand removal of gross impurities. This is followed in all cases (charcoal, wood) with successive washings of the sample with boiling 2% HCl and 1% NaOH solution for removal of carbonates and humic acids. Thereafter, it is washed with distilled water and acidified to pH = 3. Individual variations in the pretreatment are not described in the date list, but they are usually reported directly to the collector together with the data obtained.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Publication Date: 1984-12-01
    Description: The stability of steady isothermal flow of one-dimensional Newtonian fibres is considered. Bifurcation theory yields a stable supercritical Hopf bifurcation, with frequency decreasing for increasing winder speeds near the critical winder speed. A new Chebyshev expansion procedure is used with time-marching to obtain accurate numerical solutions valid far from the critical point. Our numerical solution agrees well with our analytical solution near the critical winder speed, but differs significantly from those of previous numerical models. There is qualitative agreement with a previous isothermal experiment for oscillation amplitude but not for oscillation frequency. These comparisons are discussed. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Publication Date: 1984-12-01
    Description: A class of compressible laminar boundary-layer flows subject to adverse pressure gradients of different magnitude is studied using a finite-element—differential method in which the assumed solutions are represented by classical cubic spline functions. The numerical integration process for the reduced initial-value problem has been carried out directly to at least one integration step upstream of the separation point, and very accurate numerical results have been obtained for a large number of integration steps extremely close to separation. The skin-friction and heat-transfer coefficients for nearly zero-heat-transfer, cooled-wall and heated-wall cases, computed under the assumption of constant Prandtl number Pr = 1.0 as well as Pr = 0.72, have clearly exhibited the same distinctive behaviour near separation. It is deduced that Buckmaster's series expansions for the solution near separation, derived on the assumptions of cooled wall and Pr — 1.0, are valid for all the cases considered. By matching the numerical results with Buckmaster's expansions, accurate distributions of skin friction and heat transfer have been obtained up to the separation point. Moreover, the importance of Prandtl number on the solution is evidenced from the numerical results presented. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Publication Date: 1984-12-01
    Description: A linearized potential-flow analysis is presented for predicting the unsteady airloads produced by the vibrations of turbomachinery blades operating at transonic Mach numbers. The unsteady aerodynamic model includes the effects of blade geometry, non-zero mean-pressure variation across the blade row, high-frequency blade motion, and shock motion within the framework of a linearized frequency-domain formulation. The unsteady equations are solved using an implicit least-squares finite-difference approximation which is applicable on arbitrary grids. A numerical solution for the entire unsteady flow field is determined by matching a solution determined on a rectilinear-type cascade mesh, which covers an extended blade-passage region, to a solution determined on a detailed polar-type local mesh, which covers and extends well beyond the supersonic region(s) adjacent to a blade surface. Results are presented for cascades of double-circular-arc and flat-plate blades to demonstrate the unsteady analysis and to partially illustrate the effects of blade geometry, inlet Mach number, blade-vibration frequency and shock motion on unsteady response. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Publication Date: 1984-12-01
    Description: This paper describes the results of experiments conducted on a circular jet simultaneously excited by two different acoustic tones. By varying the phase between two signals at harmonically related frequencies, control can be exercised on the process of harmonic generation-sometimes the process being virtually destroyed. This is shown to be so for both harmonic and subharmonic generation, but the latter is more difficult to control. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Publication Date: 1984-12-01
    Description: We present experimental results on the modified Stokes force F exerted on a sphere in magnetic levitation whose position is kept fixed by an optical feedback system. A Newtonian liquid moves at a constant velocity U relative to the sphere. We consider the motion in two different situations. (i) When the sphere approaches a wall perpendicular to U, the increase in IFl due to lubrication agrees quantitatively with theoretical results such as those of Brenner (1961) and Maude (1961), obtained neglecting the unsteadiness of the flow field. (ii) In the complementary situation of a sphere moving along the axis of a cylindrical tube, our results expressed as a function of the eccentricity of the trajectory and of the ratio of the two radii confirm and extend previous theoretical analyses. They show in particular the existence of a minimum of |F| away from the axis of the cylinder and a sharp increase in | F| when the sphere approaches the sidewall. By comparing with the results for a sphere moving parallel to a flat wall, we analyse the effect of the curvature of the cylindrical tube. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Publication Date: 1984-12-01
    Description: The transition from diffusion-dominated to inertia-dominated behaviour in the transport of condensable heavy molecules carried in a continuum subsonic He jet that impinges on a solid surface is studied experimentally. The Stokes number S, or ratio between the heavy-molecule relaxation time and the fluid-dynamic time, is varied in the interval 0 ≲S ≲ 1 by changing the jet Mach number at a constant value of the Reynolds number. Although the heavy species departs considerably from equilibrium at all but the smallest values of S, the helium jet is always near equilibrium conditions. At values of S of order unity the observed rate of deposition at the stagnation point asymptotes to a value some six times greater than in the diffusion region (where S →0), implying that the process is governed by the large inertia of the heavy species, very much like in aerosol impactors. As a result, it is argued that the concept of pressure diffusion is unsuitable to explain the observed behaviour. An approximate theoretical description of the transport process is given for the region S ≪ 1 where the kinetic problem is amenable to a hydrodynamic treatment. Finally, the analogy with the inertia-dominated behaviour of aerosols is used to assess the relative merits of various aerodynamics schemes aiming at separating isotopes. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    Publication Date: 1984-12-01
    Description: The ionization relaxation and radiative cooling of weakly unsteady shock waves in krypton and xenon is examined. We find that, besides radiation energy loss, the shock-tube boundary layers and shock attenuation strongly influence the radiative-cooling region. Calculations taking these effects into account are in excellent agreement with experimental values of electron densities. The contribution of line radiation to total radiation energy loss is obtained, and amounts to about 54% at temperatures of 10000 K in krypton. For xenon, first comparisons indicate a similar result. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Publication Date: 1984-12-01
    Description: The vortex loop observed in flow-visualization studies of boundary-layer transition has been investigated by mapping the instantaneous velocity and vorticity fields. All three velocity components have been measured with hot-film anemometers at numerous grid points in a measuring volume centred on the location where the vortex loop appears in flow-visualizaton studies. The instantaneous vorticity field has been computed from the velocity field, and the vortex loop is revealed in the longitudinal component of vorticity. The loop propagates downstream at approximately the primary disturbance wavespeed. The fluid in the outer part of the boundary layer travels faster, and flows over the loop. This forms the inflexional high-shear layer, which breaks down into the hairpin vortices. The magnitude of the vorticity in the high-shear layer is actually about three times larger than that in the loop. These two regions of vorticity are distinguished by the direction of the instantaneous vorticity vectors, i.e. the vectors in the high-shear layer run in the spanwise direction, while the vectors in the vortex loop run primarily in the downstream direction. This also explains why the loop cannot be detected with simple Əu/Əy measurements. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Publication Date: 1984-12-01
    Description: This paper we investigate some effects of a boundary forcing on 2-dimensional cellular patterns in instabilities above threshold. Boundary forcing is modelled as an inhomogeneous boundary condition on the slowly varying amplitude A, i.e. A = λ eiϕ0on boundaries. The relevant range is A—0(ε1/2), where e is the relative distance to the linear-instability threshold. A wavenumber-selection mechanism then occurs, resulting in a band of selected wavenumbers of width proportional to λ A. For large values of λε-1/2 it is shown that no stationary solution exists outside the band of Eckhaus-stable wavenumbers (Eckhaus 1965). For finite geometries of size L, a nonlinear analogue of 'quantization' of modes is investigated. The amplitude equation (equivalent to a space-dependent Ginzburg-Landau model) is analysed by an expansion in powers of exp (—L/£), where £ is the coherence length. The range A = 0(e) is also investigated. A correction to previous theories of wavenumber selection through boundaries (Cross, Daniels, Hohenberg & Siggia 1983a; Pomeau & Zaleski 1981) is calculated. The latter results are general and assume only the existence of a higher-order stationary amplitude equation, which is recast in a form consistent with its boundary conditions. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Publication Date: 1984-12-01
    Description: This paper reports an experimental study of a meandering water stream upon an inclined smooth hydrophobic surface. It was found that the sinuosity (ratio of the total stream length to the length of the projection of the stream on the line of maximum slope of the surface) increases with both increasing discharge rate and surface slope. It was observed that the meandering pattern is not always stable: once the discharge rate exceeds the upper critical value, the meandering pattern becomes unstable, whereas, when the discharge rate is smaller than the lower critical value, the water stream becomes discontinuous, and normally forms droplets, sliding successively down the sloping surface. It was found that, with increasing surface slope, the upper critical value decreases exponentially, while the lower critical value decreases only gradually. It was found that, when a system of stable meanders is formed on the surface, the meander loops are smoothly curved, swinging gradually from left-handed to right-handed deflections from the line of fastest descent, and vice versa, with an almpst constant amplitude and wavelength. The stable meandering pattern migrates gradually down the sloping surface. The observations showed that the central axis of the meandering stream does not coincide with the locus of the highest points of the stream, the highest points being displaced towards the outside of each bend: the cross-sectional profile of the stream is thus usually asymmetrical. It was found that the cross-sectional area of the stream varies cyclically, with one increase and one decrease associated with each bend of the stream. This cyclic variation is repeated many times along the length of the stream, with each point of maximum cross-sectional area located close to a bend. A secondary reversing spiral flow was observed in the stream, and it was found that the sense of rotation of the flow is reversed at each bend. A plausible mechanism of these stream meanders is proposed on the basis of the present results, involving the existence of hysteresis of the contact angle between water and Plexiglas, the presence of asymmetrical surface-tension forces on the stream, and the acceleration and deceleration of the stream as it swings from loop to loop. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Publication Date: 1984-12-01
    Description: The hydrodynamics and heat/mass transport associated with condensation on a moving drop have been investigated for the intermediate Reynolds-number range of drop motion (Re = 0(100)). The drop environment is a mixture of saturated vapour and a non-condensable. The formulation entails a simultaneous solution of the quasi-steady elliptic partial differential equations that describe the flow field and transport in the gaseous phase, and the motion inside the liquid drop. The heat transport inside the drop is treated as a transient process. Results are reported for the interfacial velocities, drag, external and internal flow structure, heat flux, drop growth rate and temperature—time history inside the drop. The results obtained here have been compared with experimental data where available, and these show excellent agreement. The results reveal several novel features. The surface-shear stress increases with condensation. The pressure level in the rear of the drop is higher. As a consequence, the friction drag is higher and the pressure drag is lower. The total drag coefficient increases with condensation rate for small values of drop size or temperature differential, and it decreases for large values of these parameters. The volume of the separated-flow region in the rear of the drop decreases with condensation. At very high rates of condensation, the recirculatory wake is completely suppressed. Condensation also delays the appearance of the weak secondary internal vortex motion in the drop. The heat and mass fluxes are significantly affected by the presence of the non-condensable in the gaseous phase and by the circulation inside the drop. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Publication Date: 1984-12-01
    Description: Some new exact relations are derived between integral properties of a progressive irrotational gravity wave of finite amplitude in deep water. In particular it is shown that the Eulerian-mean angular momentum AEis directly proportional to the Lagrangian T—V, through the relation Ae= 2C(T-V)/g, where c is the phase speed and g denotes the acceleration due to gravity. Moreover, for waves of constant length, the differential relation dAB= 2(3T-V)dc/g also holds. In a wave of limiting steepness it was shown previously that the level of action yais very nearly equal to the crest level ymax-This is further discussed, and is shown to be probably a numerical coincidence. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Publication Date: 1984-12-01
    Description: Turbulent spots formed artificially in a Blasius boundary layer have been investigated over a finite width extending across the plane of symmetry of the spots. Hot wires were used to measure the local mean and fluctuating parts of the downstream and spanwise velocity components, and the third component was computed. The results are presented in contour diagrams, and are compared with previous published work. The values of energy thickness in the spots are computed from the contours of downstream velocity. The spots are found to consist of an upper part containing most of the turbulence, moving over a lower layer whose contribution to the energy thickness is small. When, near the rear of the spot, the energy thickness decreases to the value in Blasius flow, the two parts recombine, and the flow slowly regains the Blasius velocity profile. The spots grow by entrainment of laminar fluid, and the physical principles governing this process are discussed. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Publication Date: 1984-12-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    Publication Date: 1984-12-01
    Description: We consider the motion of a sphere or a slender body in the presence of a plane fluid-fluid interface with an arbitrary viscosity ratio, when the fluids undergo a linear undisturbed flow. First, the hydrodynamic relationships for the force and torque on the particle at rest in the undisturbed flow field are determined, using the method of reflections, from the spatial distribution of Stokeslets, rotlets and higher-order singularities in Stokes flow. These fundamental relationships are then applied, in combination with the corresponding solutions obtained in earlier publications for the translation and rotation through a quiescent fluid, to determine the motion of a neutrally buoyant particle freely suspended in the flow. The theory yields general trajectory equations for an arbitrary viscosity ratio which are in good agreement with both exact-solution results and experimental data for sphere motions near a rigid plane wall. Among the most interesting results for motion of slender bodies is the generalization of the Jeffrey orbit equations for linear simple shear flow. © 1984, Cambridge University Press 1984. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    Publication Date: 1984-11-01
    Description: Longitudinal and transverse components of the velocity were simultaneously measured for various vertical locations at 20 off-centreline positions in turbulent spots artificially generated in a zero-pressure-gradient laminar boundary layer. Global ensemble-averaged velocity diagrams and vertical vorticity contours were computed in similarity coordinates ξ = (x—x0)/(U∞ (t-t0)) and ξ =z /(U∞(t—t0)) for different heights η = y/δ above the plate. This global averaging technique inadequately describes the spot, which is not a single large vortex structure. A discriminative averaging technique was developed to construct a statistically most-probable spot with sufficient resolution to include some of the largest substructures detected in visual studies. Four eddies were identified in vertical slices of the central region of the spot, while several rows appeared in the plan view. These features of the velocity and vorticity contours of the statistically most-probable spot exhibit similarities with structures observed in flow visualizations. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Publication Date: 1984-12-01
    Description: This paper extends previous theoretical work on inextensible sails in two ways. First, the asymptotic expansion of sail camber in terms of the small angle of attack a is continued to include terms of order a3because only at this order can one obtain information about the longitudinal static stability of a sail aerofoil. Secondly, to describe aerofoils such as those found in pterodactyl or bat wings, we also consider pretensioned membranes which acquire camber by stretching the surface material, or bending the supporting structure. Approximate formulae are derived for the aerodynamic coefficients in the limits of large and small tension, and the effect of sail and structural flexibility on these coefficients is discussed. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Publication Date: 1984-11-01
    Description: Turbulent airflow over a Stokes water-wave train of small amplitude is studied numerically based on the two-equation closure model of Saffman & Wilcox (1974) together with appropriate boundary conditions on the wave surface. The model calculates, instead of assuming, the viscous sublayer flow, and it is found that the energy transfer between wind and waves depends significantly on the flow being hydraulically rough, transitional or smooth. Systematic computations have yielded a simple approximate formula for the fractional rate of growth per radian, with δi= 0.04 for transitional or smooth flow and δi= 0.06 for rough flow, where p is density of airwthat of water, UAwind speed at one wavelength height and c the wave phase velocity. This formula is in good agreement with most existing data from field experiments and from wave-tank experiments. In the case of waves travelling against wind, the corresponding values are δt— —0.024 for transitional and smooth flow, and δt= —0.04 for rough flow. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    Publication Date: 1984-11-01
    Description: This paper involves a numerical simulation of the final stages of transition to turbulence in plane channel flow at a Reynolds number of 1500. Three-dimensional incompressible Navier-Stokes equations are numerically integrated to obtain the time evolution of two-and three-dimensional finite-amplitude disturbances. Computations are performed on the CYBER-203 vector processor for a 32 x 51 x 32 grid. Solutions indicate the existence of structures similar to those observed in the laboratory and characteristic of the various stages of transition that lead to final breakdown. In particular, evidence points to the formation of a A-shaped vortex and the subsequent system of horsehoe vortices inclined to the main flow direction as the primary elements of transition. Details of the resulting flow field after breakdown indicate the evolution of streaklike formations found in turbulent flows. Although the flow field does approach a steady state (turbulent channel flow), the introduction of subgrid-scale terms seems necessary to obtain fully developed turbulence statistics. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Publication Date: 1984-11-01
    Description: High-speed schlieren cinéphotography of the firing of a high-energy plasma-jet igniter reveal turbulent structures similar in appearance to laboratory models of thermals or turbulent puffs. Measurements of the growth rates of these features together with those of their impulse and thermal energy confirm this similarity. A simple model based on the entrainment assumption gives a good description of the motion of the element and also of the decay of the internal temperature. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Publication Date: 1984-11-01
    Description: A geometrical condition sufficient for uniqueness in two-dimensional time-periodic linear water-wave problems is derived, and some examples are given. The technique can be seen as a generalization of work by John (1950), who established uniqueness for surface-piercing bodies that have the property that vertical lines down from the free surface do not intersect the body. The paper is in two parts. Part 1 provides a review of current knowledge on the topic of uniqueness, and gives a simple form of John’s proof. Part 2 describes the recent progress, in which the ideas of John’s proof are extended so that uniqueness can be demonstrated for surface-piercing bodies that do not satisfy John’s geometrical criterion. In fact the new technique proves uniqueness for a large class of problems involving floating bodies, submerged bodies and multiple-body systems. However, the present work still does not constitute a general proof of uniqueness for all configurations. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Publication Date: 1984-11-01
    Description: Spectral models for turbulent pressure fluctuations are developed by directly Fourier transforming the integral solution to the Poisson equation for a homogeneous constant-mean-shear flow. The turbulence-turbulence interaction is seen to possess the well-known k-7/3inertial subrange and to dominate the high-wavenumber region. The turbulence-mean-shear contribution is seen to be dominant in the energy-containing range and falls off as k-11/3the inertial subrange. The subrange constants and the mean-square pressure fluctuation are evaluated using a spectral model for the velocity. A spectral analysis of the velocity contamination of a pressure probe is also presented. Results are compared with spectral measurements with a static-pressure probe in the mixing layer of an axisymmetric jet. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Publication Date: 1984-11-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Publication Date: 1984-10-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Publication Date: 1984-10-01
    Description: Numerical solutions are presented of the governing equations for three plane flows: the laminar free jet; the developing turbulent free jet; and the turbulent impinging jet for different ratios h/b of the nozzle height h above the plate to the nozzle width b. The accuracy of the numerical procedure is demonstrated by comparing the solution of the Navier-Stokes equations for the laminar-flow case with their analytical boundary-layer solution. For turbulent flows these equations are solved after Reynolds averaging. Closure is achieved by a two-equation turbulence model in conjunction with three alternative algebraic expressions for the turbulent stresses. The capabilities of such an approach are illustrated by the extent and consistency of the predictions and the satisfactory agreement of the measurable quantities with the more reliable experimental data in the literature. The limitations of the models employed, evident from their lack of universality, are discussed in the light of their derivation from more complex ‘single-point’ closures. Features of the flows studied of interest include: the near-nozzle behaviour of a ‘finite’ laminar free jet; the potential core and transition regions of a turbulent free jet, along with the fully developed similarity profiles; the enhanced heat-transfer characteristics of impinging jet flows; and the similarity of the developing wall jet after impingement to the standard wall-jet configuration. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Publication Date: 1984-10-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    Publication Date: 1984-10-01
    Description: Head-on collision of two (KdV) solitary waves at the interface of an inviscid two-fluid system of rigid upper and lower boundaries is investigated by a perturbation method. We obtain the third-order solution and find a dispersive wavetrain trailing behind each emerging solitary wave. The wavetrain is of the same polarity (depression/ elevation) as the main wave. Furthermore, the energy and amplitude of the wave train are decreasing in time as long as it is still attached to the main wave. This implies an increase in energy of the main wave. Up to the third order of accuracy the solitary wave emerging from a head-on collision retains its initial profile save for a phase shift. This phase shift is found to be amplitude dependent to the second order. The transfer of energy from the wavetrain to the main wave explains the slow recovery of the incident profiles in existing numerical results on the head-on collision of two solitary waves at the surface of an infinite channel. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    Publication Date: 1984-10-01
    Description: Two-and three-dimensional non-stationary viscous-fluid flows in a plane channel are considered. By means of efficient computational algorithms for direct integration of the incompressible Navier-Stokes equations the evolution of these flows over large time intervals is simulated. Classes of two-and three-dimensional non-stationary flows with stationary integral characteristics (the flow rate, mean pressure gradient, total energy of pulsations etc.) were found. Such flows are called secondary flows. Two-dimensional secondary flows have only qualitative similarity to turbulent flows observed in experiments. Three-dimensional secondary flows agree very well, even quantitatively, with turbulent flows. The principal characteristics of turbulent flows such as drag coefficient, mean-velocity profile, the distributions of the pulsation velocity components and some others are reproduced in three-dimensional secondary flows with good accuracy. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Publication Date: 1984-10-01
    Description: Moderate-amplitude axisymmetric oscillations of charged inviscid drops held together by surface tension are calculated by a multiple-timescale expansion. The corrections to the drop shape and velocity caused by mode coupling at second order in amplitude are predicted for two-, three-and four-lobed motions of drops with net charge up to the Rayleigh limit Qc= 4π1/2. Resonant oscillations between four-and six-lobed motions occur for total charge values near Qr= (32/3π)1/2and are analysed. Both frequency and amplitude modulation of the oscillation are predicted for drop motions starting from general initial deformations. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Publication Date: 1984-10-01
    Description: The process of three-dimensional distortion of previously two-dimensional disturbances was investigated in a rectangular channel. For the first time the three-dimensional structures at the breakdown station of the two-dimensional wave were studied by flow visualization. It was shown that the structures have forms identical with A-shaped vortices in a boundary layer of the flat plate. The spanwise spacing of the A-shaped vortices is quite independent of the mean-flow velocity and of the frequency of artificial disturbances. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Publication Date: 1984-10-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Publication Date: 1984-09-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    Publication Date: 1984-10-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    Publication Date: 1984-10-01
    Description: We consider the time evolution of a layer of fresh water placed on top of a layer of salt water in a laboratory tank when denser salt water is supplied to a nozzle at the free surface. The inflow is carried out slowly so as to form a pure plume, which at first does not penetrate through the interface. The two basic processes that govern the time evolution of the initially fresh-water layer are the filling-box process (Baines & Turner 1969) and the entrainment through the end of the plume which impinges upon the density interface. A theoretical model that takes these two processes into account is presented, with the numerical solution of the asymptotic state, valid at large times. The asymptotic solution and experiment are in good agreement; the theory describes well the vertical buoyancy profile, the change in buoyancy difference across the interface with time, and the time when the plume begins to penetrate through the interface. The entrainment rate obtained from changes in thickness of the upper layer with time can be expressed as a function of the Froude number. The functional dependence is close to Fr3at small values of Fr, and it approaches a finite limit as Fr increases. The buoyancy flux across the interface, which is non-dimensionalized by the rate of buoyancy input, also changes as a function of Fr, taking a maximum value of 0.168 at Fr = 0.46 and decreasing sharply at larger and smaller Froude numbers. These values agree well with those found from field observations and experiments on the entrainment at the boundary of convectively mixed layers. It is pointed out that some earlier results of Baines (1975) are not consistent with the model presented here. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Publication Date: 1984-09-01
    Description: We use a numerical method that was described in Part 1 (Marcus 1984a) to solve the time-dependent Navier-Stokes equation and boundary conditions that govern Taylor-Couette flow. We compute several stable axisymmetric Taylor-vortex equilibria and several stable non-axisymmetric wavy-vortex flows that correspond to one travelling wave. For each flow we compute the energy, angular momentum, torque, wave speed, energy dissipation rate, enstrophy, and energy and enstrophy spectra. We also plot several 2-dimensional projections of the velocity field. Using the results of the numerical calculations, we conjecture that the travelling waves are a secondary instability caused by the strong radial motion in the outflow boundaries of the Taylor vortices and are not shear instabilities associated with inflection points of the azimuthal flow. We demonstrate numerically that, at the critical Reynolds number where Taylor-vortex flow becomes unstable to wavy-vortex flow, the speed of the travelling wave is equal to the azimuthal angular velocity of the fluid at the centre of the Taylor vortices. For Reynolds numbers larger than the critical value, the travelling waves have their maximum amplitude at the comoving surface, where the comoving surface is defined to be the surface of fluid that has the same azimuthal velocity as the velocity of the travelling wave. We propose a model that explains the numerically discovered fact that both Taylor-vortex flow and the one-travelling-wave flow have exponential energy spectra such that In [E(k)] ∝ k1where k is the Fourier harmonic number in the axial direction. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Publication Date: 1984-09-01
    Description: A study is made of some numerical calculations of two-dimensional and geostrophic turbulent flows. The primary result is that, under a broad range of circumstances, the flow structure has its vorticity concentrated in a small fraction of the spatial domain, and these concentrations typically have lifetimes long compared with the characteristic time for nonlinear interactions in turbulent flow (i.e. an eddy turnaround time). When such vorticity concentrations occur, they tend to assume an axisymmetric shape and persist under passive advection by the large-scale flow, except for relatively rare encounters with other centres of concentration. These structures can arise from random initial conditions without vorticity concentration, evolving in the midst of what has been traditionally characterized as the cascade of isotropic, homogeneous, large-Reynolds-number turbulence: the systematic elongation of isolines of vorticity associated with the transfer of vorticity to smaller scales, eventually to dissipation scales, and the transfer of energy to larger scales. When the vorticity concentrations are a sufficiently dominant component of the total vorticity field, the cascade processes are suppressed. The demonstration of persistent vorticity concentrations on intermediate scales smaller than the scale of the peak of the energy spectrum and larger than the dissipation scales does not invalidate many of the traditional characterizations of two-dimensional and geostrophic turbulence, but I believe it shows them to be substantially incomplete with respect to a fundamental phenomenon in such flows. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Publication Date: 1984-09-01
    Description: Oblique wave groups consist of waves whose straight parallel lines of constant phase are oblique to the straight parallel lines of constant group phase. Numerical solutions for periodic oblique wave groups with envelopes of permanent shape are calculated from the equations for irrotational three-dimensional deep-water motion with nonlinear upper free-surface conditions. Two distinct families of periodic wave groups are found, one in which the waves in each group are in phase with those in all other groups, and the other in which there is a phase difference of π between the waves in consecutive groups. It is shown that some analytical solutions for oblique wave groups calculated from the nonlinear Schrodinger equation are in error because they ignore the resonant forcing of certain harmonics in two dimensions. Particular attention is given to oblique wave groups whose group-to-wave angle is in the neighbourhood of the critical angle tan1√1/2, corresponding to waves on the boundary wedge of the Kelvin ship-wave pattern. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Publication Date: 1984-08-01
    Description: A nonlinear analysis of Bénard-Marangoni convection in a horizontal fluid layer of infinite extent is proposed. The nonlinear equations describing the fields of temperature and velocity are solved by using the Gorkov-Malkus-Veronis technique, which consists of developing the steady solution in terms of a small parameter measuring the deviation from the marginal state. This work generalizes an earlier paper by Sehluter, Lortz & Busse wherein only buoyancy-driven instabilities were handled. In the present work both buoyancy and temperature-dependent surface-tension effects are considered. The band of allowed steady states of convection near the onset of convection is determined as a function of the Marangoni number and the wavenumber. The influence of various dimensionless quantities like Rayleigh, Prandtl and Biot numbers is examined. Supercritical as well as subcritical zones of instability are displayed. It is found that hexagons are allowable flow patterns. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    Publication Date: 1984-08-01
    Description: The inviscid compressible instability of columnar-vortex flows to three-dimensional perturbations with large wavenumbers is considered. The sufficient conditions for instability obtained are compared with recently published results for incompressible fluids. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    Publication Date: 1984-08-01
    Description: Results are presented of an experimental study on the transition to geostrophic turbulence, and the detailed behaviour within the turbulence regime, in a rotating, laterally heated annulus of fluid. Both spatial and temporal characteristics are examined, and the results are presented in the form of wavenumber and frequency spectra as a function of a single external parameter, the rotation rate. The transition to turbulence proceeds in a sequence of steps from azimuthally symmetric (no waves present) to chaotic flow. The sequence includes doubly periodic flow (amplitude vacillation), semiperiodic flow (structural vacillation), and a transition zone where the characteristics undergo a gradual change to chaotic behaviour. The spectra in the transition zone are characterized by a gradual merging of the background signal with the spectral peaks defining regular wave flow as the rotation rate is increased. Within the geostrophic turbulence regime, the wavenumber spectra are characterized by a broad peak at the baroclinic scale and a power dependence of energy density on wavenumber at the high-wavenumber end of the spectrum. Our data reveal a significant dependence of the slope on the thermal Rossby number, ranging from — 4.8 at Rot = 0.17 to —2.4 at RoT= 0.02. The frequency spectra also show a power dependence of the energy density on frequency at the high-frequency end of the spectrum. We find a nominal —4 power which does not appear to be sensitive to changes in Rossby or Taylor number. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Publication Date: 1984-09-01
    Description: In this paper we apply a formalism introduced in a previous paper to write down a self-consistent set of equations for the functions that describe the near-equilibrium time behaviour of random oceanic internal waves. These equations are based on the direct-interaction approximation. The self-consistent equations are solved numerically (using the Garrett-Munk spectrum as input) and the results are compared to parameters obtained in the weak-interaction approximation (WIA). The formalism points out that an extra parameter that is implicitly vanishingly small in the WIA has a significant effect on decay rates when computed self-consistently. We end by mentioning possible future self-consistent calculations that would improve upon our own. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    Publication Date: 1984-10-01
    Description: Local measurements have been carried out in a mercury-nitrogen two-phase flow using the hot-film anemometric technique, in a cylindrical pipe with electrically insulated walls. The flow was turbulent (Re = 63000) and in the bubbly regime (〈a〉 ≈ 0.03). The maximum intensity of the magnetic field was 0.94 T. Processing of the hot-film signal provided in this medium, for the first time, simultaneous quantitative data for the local time-averaged velocity of the liquid-phase turbulent fluctuations, as well as local void fractions. These data were checked against those obtained, for the same conditions, using a double conductivity probe. The latter also provided information on the bubble velocity and average bubble size. Turbulence spectra were also measured. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Publication Date: 1984-09-01
    Description: A cylinder containing liquid with a free surface is subjected to a vertical oscillation of amplitude εg/ω2and frequency 2ω, where ω is within 0(εω) of the natural frequency of a particular (primary) mode in the surface-wave spectrum and 0 〈 ε ≪1. A Lagrangian formulation, which includes terms of second and fourth order in the primary mode and second order in the secondary modes (which are excited by the primary mode), together with the method of averaging, leads to a Hamiltonian system for the slowly varying amplitudes of the primary mode. The fixed points (which correspond to harmonic motions) and phase-plane trajectories and their perturbations due to linear damping are determined. It is shown that ε 〉 δ, where δ is the damping ratio (actual/critical) of the primary mode, is a necessary condition for subharmonic response of that mode. Explicit results are given for the dominant axisymmetric and antisymmetric modes in a circular cylinder. Internal resonance, in which a pair of modes have frequencies that approximate ω and 2ω, is discussed separately, and the fixed points and their stability for the special case ω2= 2ω1are determined. Internal resonance for ω2 = ω1 is discussed in an appendix. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    Publication Date: 1984-09-01
    Description: Experiments on shock-wave attenuation in a porous tube have shown that attenuation is a function of distance from the origin and the rate of cross-mass flow per unit area. It is a linear function of distance if the cross-mass flow rate per unit area is held constant. In a tube with solid walls the relationship between attenuation, mass extraction rate per unit area and distance is similar to that in a proous tube. The ratio of the local attenuation to the local cross-mass flow, or mass extraction rate, per unit area is the same linear function of distance in both sets of experiments. The mechanism of attenuation is therefore also identical. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    Publication Date: 1984-09-01
    Description: The stability properties of steady two-dimensional solutions describing convection in a horizontal fluid layer heated from below with stress-free boundaries are investigated in the neighbourhood of the critical Rayleigh number. The region of stable convection rolls as a function of the wavenumber a and the Rayleigh number R is bounded towards higher a by the monotonic skewed varicose instability, while towards low wavenumbers stability is limited by the zigzag instability or by the oscillatory skewed varicose instability. Only for a limited range of Prandtl numbers, 0.543 〈 P 〈 ∞, does a finite domain of stability exist. In particular, convection rolls with the critical wavenumber ∝care always unstable. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    Publication Date: 1984-09-01
    Description: This report presents a numerical study of the two-dimensional, steady and inviscid flow of a perfect gas past wedge profiles with detached shock waves for free-stream Mach numbers between 1.05 and 1.44. Utilizing the hodograph transformation, a boundary-value problem for the mixed flow is formulated in the hodograph plane and subsequently solved by a finite-difference scheme, iterating respectively between the elliptic and hyperbolic regions. The use of boundary-fitted coordinates and a graded lattice failed to achieve satisfactory results, owing to either convergence difficulties or numerical inaccuracies introduced through the coordinate generator. On the other hand, Cartesian coordinates presented no convergence problems and yielded accurate results. After transforming the solution back to the physical plane, the flow field between the shock wave and the limiting Mach wave is determined. A comparison of the results with experiments and other theories shows a good agreement both for the pressure distribution on the wedge and for the shock stand-off distance. Also of special interest is a quantitative comparison of the results with the small-disturbance theory (solution of the Tricomi equation) and the limiting case of the free-stream Mach number 1. Moreover, an example of the flow past round-nosed wedges, with and without an angle of attack, is treated using the inverse method. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    Publication Date: 1984-09-01
    Description: Experiments were conducted to investigate the response of a rigid two-dimensional elastically mounted smooth circular cylinder, with oscillations restricted to a plane normal to the incident flow, as influenced by the vicinity of an identical fixed body placed inside the wake. The static lift and drag coefficients, as well as the vibration amplitude and frequency of the upstream cylinder as functions of relative position of the pair of cylinders are given. Most measurements were carried out under two conditions of free-stream turbulence. Whilst turbulence decreased the magnitude of drag coefficients, it had no appreciable effect on lift coefficients. The forces on the upstream body were found to be influenced by the proximity to the downstream one in a significant way only when the streamwise spacing is less than two diameters. In the dynamic tests, two kinds of instability, namely a vortex-resonance and galloping, were observed, with the latter only occurring when the downstream cylinder was well submerged in the near wake of the upstream one. The vortex-shedding frequency was always found to lock to oscillation frequency. Whereas the vibration characteristics remained essentially unaffected with changing turbulence intensity, the galloping amplitudes were observed to be sensitive to cylinders aspect ratio. A quasi-steady theory was developed to predict the galloping behaviour. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    Publication Date: 1984-09-01
    Description: Observations of the flow of a two-layer fluid resulting from the motion of a towed streamlined two-dimensional obstacle are described in some detail. The experiments were designed to further our understanding of the factors governing the nature and magnitude of upstream disturbances in the general flow of stratified fluid over two-dimensional topography, and predictions for arbitrary two-dimensional flows are made from the results of these experiments. In particular, the relationship between uniformly stratified flow and single-layer flow over topography is suggested. Most of the observed features of interest in these experiments are nonlinear in character. Relatively complete descriptions of the observed flows are presented over a wide range of parameter values, and the phenomena observed include upstream undular and turbulent bores, bores with zero energy loss, rarefactions (in which the interface height changes monotonically over a transition region of continuously increasing length), and downstream hydraulic drops and jumps. Their properties are shown to be broadly consistent with predictions from a two-layer hydrostatic model based on continuity and momentum considerations, which employs jump criteria and rarefaction equations where appropriate. Bores occur because of nonlinear steepening when the layer containing the obstacle is thinner than the other, and rarefactions occur when this layer thickness is comparable with or greater than that of the other layer. The speed and amplitude of the upstream bores are governed by nonlinear effects, but their character is determined by a balance between nonlinear steepening, wave dispersion and interfacial friction when the bore is non-turbulent. Experimental evidence is presented for two types of hysteresis or multiple equilibria situations where two different flow states may exist for the same external steady conditions. In the first of these hysteresis types, the upstream flow may be supercritical or consist of an upstream bore state. It is analogous to the type anticipated for single-layer flow by Baines & Davies (1980) and described numerically by Pratt (1983), but it is only found experimentally for part of the expected parameter range, apparently because of interfacial stress effects. The second hysteresis type is new, and involves the presence or absence of a downstream hydraulic drop and following jump. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    Publication Date: 1984-09-01
    Description: The stability of the two-dimensional flow induced by the transverse oscillation of a cylinder in a viscous fluid is investigated in both the linear and weakly nonlinear regimes. The major assumption that is made to simplify the problem is that the oscillation frequency is large, in which case an unsteady boundary layer is set up on the cylinder. The basic flow induced by the motion of the cylinder depends on two spatial variables, and is periodic in time. The stability analysis of this flow to axially periodic disturbances therefore leads to a partial differential system dependent on three variables. In the high-frequency limit the linear stability problem can be reduced to a system dependent only on a radial variable and time. Furthermore, the coefficients of the differential operators in this system are periodic in time, so that Floquet theory can be used to reduce this system further to a coupled infinite system of ordinary differential equations together with uncoupled homogeneous boundary conditions. The eigenvalues of this system are found numerically and predict instability entirely consistent with the experiments with circular cylinders performed by Honji (1981). Results are given for cylinders of elliptic cross-section, and it is found that for any given eccentricity the most dangerous configuration is when the cylinder oscillates parallel to its minor axis. Some discussion of nonlinear effects is also given, and for the circular cylinder it is shown that the steady-streaming boundary layer of the basic flow is significantly altered by the instability. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    Publication Date: 1984-09-01
    Description: The bottom boundary layer under a progressive water wave is studied using Saffman's turbulence model. Saffman's equations are analysed asymptotically for the case Re≫ 1, where Re is a Reynolds number based on a characteristic magnitude of the orbital velocity and a characteristic orbital displacement. Approximate solutions for the mass-transport velocity at the edge of the boundary layer and for the bottom stress are obtained, and Taylor's formula for the rate of energy dissipation is verified. The theoretical results are found to agree well with observations for sufficiently large Reynolds numbers. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    Publication Date: 1984-09-01
    Description: Flows occurring between parallel rotating disks have recently been generalized by Parter & Rajagopal (1984) to include solutions that are not axisymmetric. They prove existence, whereas in the present paper we report, for the first time, numerical results for two cases: (i) rotation about a common axis, and (ii) rotation about distinct axes. Calculations were performed for two values of the Ekman number E = v /d2ω at the relative disk rotations of s= 0.8, s= 0 and s= 0.25, where s= ω2/ω1. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    Publication Date: 1984-08-01
    Description: The problem of thermoacoustic heating at the closed end of a tube, in which small gas oscillations are maintained, leads in the case of adiabatic walls, and within the framework of a linear theory of the oscillations and a second order theory of the heating effect, to singular behaviour of the equilibrium temperature at the tube end. Two cases are discussed: one with vanishing viscosity and one with viscosity tending to infinity. The singularities turn out to be similar in character and integrable in both cases. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    Publication Date: 1984-07-01
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    Publication Date: 1984-07-01
    Description: Experiments have been made on quasi two dimensional sails of small camber and at small incidence. Four excess length ratios have been tested at a Reynolds number of 1.2 × 105. The results for lift, tension, centre of lift, maximum camber and its position, and leading and trailingedge membrane angles have been compared with existing inviscid theories and show poor agreement in general. This is attributed to leading and trailingedge flow separations as indicated by supplementary flow visualization experiments. The optimum incidences in particular are much greater than the theoretical value of 0°. Luffing occurs at slightly negative incidences and appears to be a dynamic instability. The highest lift-to-drag ratio obtained was 16.5 on a membrane with an excess length ratio of 0.03. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    Publication Date: 1984-07-01
    Description: The interference of passive thermal fields produced by two (and more) line sources in decaying grid turbulence is studied by using the inference method described by Warhaft (1981) to determine the cross correlation coefficient p between the temperature fluctuations produced by the sources. The evolution of p as a function of downstream distance, for 0.075 〈 d/l 〈 10, where d is the wire spacing and l is the integral lengthscale of the turbulence, is determined for a pair of sources located at various distances from the grid. It is found that p may be positive or negative (thereby enhancing or diminishing the total temperature variance) depending on the line source spacing, their location from the grid and the position of measurement. It is also shown that the effects of a mandoline (Warhaft & Lumley 1978) may be idealized as the interference of thermal fields produced by a number of line sources. Thus new light is shed on the rate of decay of scalar variance dissipation. The thermal field of a single line source is also examined in detail, and these results are compared with other recent measurements. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    Publication Date: 1984-07-01
    Description: A stability theory for the steady swirling flow above an infinite rotating disk immersed in an otherwise unbounded rigidly rotating fluid is developed in order to corroborate the various numerical computations considered for this problem. An analysis of the initial value problem for linearized time dependent perturbations on the steady state similarity solutions shows that the disturbance equations have a stable continuum spectrum which, under certain conditions, exhibits only algebraic decay in time. In addition, a numerical analysis on the discrete spectrum shows that there are unstable eigenvalues for certain rotational rates of the disk relative to the fluid at infinity. The results obtained are in good agreement with the large time behaviour of the corresponding solutions of the unsteady similarity equations. © 1984, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...