767 research outputs found
Crustal accretion at the Reykjanes Ridge, 61°–62°N
No full textWe report results of a seismic, gravity, and magnetic survey of the Reykjanes Ridge spreading center at 61°–62°N, about 600 km from the center of the Iceland mantle plume. Anomalously shallow water on the ridge crest enabled us to record seismic refractions on a 2.4 km hydrophone streamer. The velocity within layer 2A is 2.4 ± 0.3 km s−1, and its mean thickness is 400 ± 100 m. The velocity at the base of layer 2A is 3.3 ± 0.3 km s−1 on the ridge axis, increasing with crustal age to ∼4.0 km s−1 at 1.5 Ma and ∼4.5 km s−1 at 5 Ma. Assuming that seismic layer 2A on the ridge axis is also the extrusive layer, i.e., the magnetic source layer, we have successfully modeled the variations in amplitude of the magnetic field. The best magnetic model includes enhanced magnetization within layer 2A at the sites of recent volcanic activity as independently recognized in side-scan sonar data. We also present a full crustal seismic model, based on wide-angle seismic recordings on digital ocean bottom hydrophones and disposable sonobuoys. The seismic model is complemented by gravity modeling, which further suggests that the ridge crest is in isostatic equilibrium. The zero age crust is 10.0 km thick, while crust of age 5 Ma is 7.8 km thick. These crustal thicknesses are greater than those of normal oceanic crust, which we attribute to the presence of anomalously hot asthenospheric mantle beneath the spreading center. We suggest that the variation in thickness between 0 Ma and 5 Ma crust is caused by temporal variation in the plume-fed asthenospheric temperature beneath the Reykjanes Ridge
Nouvelle méthode syntagmatique de vectorisation appliquée au self-organizing map des textes vietnamiens
No full text@inproceedings{CN-NGUYEN-2004, author = {Nguyen D.T.}, title = {Nouvelle méthode syntagmatique de vectorisation appliquée au self-organizing map des textes vietnamiens}, booktitle = {RECIRAL'04}, year = {2004}, address = {Fès, Maroc}, month = {avril} }National audienc
Combined use of the GGSFT data base and on Board Marine Collected Data to Model the Moho Beneath the Powell Basin, Antarctica
No full textThe Powell Basin is a small oceanic basin located at the NE end of the Antarctic Peninsula developed during the Early Miocene and mostly surrounded by the continental crusts of the South Orkney Microcontinent, South Scotia Ridge and Antarctic Peninsula margins. Gravity data from the SCAN 97 cruise obtained with the R/V Hespérides and data from the Global Gravity Grid and Sea Floor Topography (GGSFT) database (Sandwell and Smith, 1997) are used to determine the 3D geometry of the crustal-mantle interface (CMI) by numerical inversion methods. Water layer contribution and sedimentary effects were eliminated from the Free Air anomaly to obtain the total anomaly. Sedimentary effects were obtained from the analysis of existing and new SCAN 97 multichannel seismic profiles (MCS). The regional anomaly was obtained after spectral and filtering processes. The smooth 3D geometry of the crustal mantle interface obtained after inversion of the regional anomaly shows an increase in the thickness of the crust towards the continental margins and a NW-SE oriented axis of symmetry coinciding with the position of an older oceanic spreading axis. This interface shows a moderate uplift towards the western part and depicts two main uplifts to the northern and eastern sectors
Mapping the Landscape: A Bibliometric Analysis of CALIBER 2022 Convention Publications
No full textThe present study examines the authorship patterns, collaboration levels, and various other parameters such as gender, author designation, institutional affiliation, and geographical distribution of the conference papers presented at CALIBER 2022 by employing an array of bibliographic analysis techniques. The analysis is based on a dataset consisting of 45 papers authored by 100 individuals and found that authors hailing from Uttar Pradesh emerged as the foremost contributors. The study also found that universities emerged as the most prolific contributors, responsible for the publication of 71.00 per cent of the articles within the designated time frame
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Aerial remote sensing surveys progress report: Helicopter geophysical survey of the Oak Ridge Reservation
No full textThe 35,252 acre Department of Energy Oak Ridge Reservation (ORR) in the western portion of the Appalachian Valley and Ridge Province in Tennessee, has been a nuclear production and development facility for50 years. Contaminants in the many waste sites on the ORR include a wide variety of radioactive isotopes as well as many organic and inorganic compounds. The locations, geometry, and contents of many of these waste sites are reasonably well known, while others are poorly known or unknown. To better characterize the reasonably well known sites and search for additional potentially environmentally hazardous sites, a two-phase aerial survey of the ORR was developed. Phase I began in March 1992 and consisted of aerial radiation, multispectral scanner, and photographic (natural color and color infrared) surveys. Phase II began in November 1992 and is described in this report. Phase II consisted of helicopter electromagnetic (HEM), magnetic, and gamma radiation surveys. Targets of the survey included both man-made (drums, trench boundaries, burn pits, well heads) and geologic (fractures, faults, karst features, geologic contacts) features. The Phase II survey has three components: testing, reconnaissance, and high-resolution data acquisition. To date, the testing and reconnaissance data acquisition have been completed, and some of the data have been processed. They indicate that: (1) magnetic and HEM data are complementary and do not always highlight the same anomaly; (2) under favorable circumstances, helicopter magnetometer systems are capable of detecting groups of four or more 55-gal drums at detector altitudes of 15 m or less; (3) HEM data provide data that compare favorably with surface data collected over burial trenches, (4) well casings may be related to magnetic monopole anomalies, as would be expected; and (5) changes in HEM and magnetic anomaly character are related to lithologic changes and may be used to track contacts between known outcrops
INTERFACIAL AREA BY ALPHA OR BETA DOSIMETRY--A FEASIBILITY STUDY
No full textOak Ridge National Lab., Tenn. A survey of chemical radiolysis methods of measuring interfacial area by means of short range particle irradiation of a liquid interface indicated the most promising system was an aqueous solution of polonium210 in contact with a benzene solution of tetrachloroethylene. Experimentally, the rate of chloride liberation was quite low, and when measured by activation analysis, the specific rate of chloride production was subject to a very large relative error. (auth
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Early test facilities and analytic methods for radiation shielding: Proceedings
No full textThis report represents a compilation of eight papers presented at the 1992 American Nuclear Society/European Nuclear Society International Meeting. The meeting is of special significance since it commemorates the fiftieth anniversary of the first controlled nuclear chain reaction. The papers contained in this report were presented in a special session organized by the Radiation Protection and Shielding Division in keeping with the historical theme of the meeting. The paper titles are good indicators of their content and are: (1) The origin of radiation shielding research: The Oak Ridge experience, (2) Shielding research at the hanford site, (3) Aircraft shielding experiments at General Dynamics Fort Worth, 1950-1962, (4) Where have the neutrons gone , a history of the tower shielding facility, (5) History and evolution of buildup factors, (6) Early shielding research at Bettis atomic power laboratory, (7) UK reactor shielding: then and now, (8) A very personal view of the development of radiation shielding theory
Eastern Iran in the Achaemenid Period
No full textThe author deals with the archaeological evidence of the Achaemenid period in eastern Iran. This evidence is limited, rare and contradictory with regard to the historical importance of the eastern provinces of the Empire. The territorial extent of the Achaemenid Empire is ambiguous too and in this regard the cultural background of the different provinces, as well as relationships between center and periphery, were crucial factors affecting the visibility of the Achaemenid empire in its eastern-most regions. Similarly, the geographic definition of ‘eastern Iran’ requires clarification as well because, as a geomorphological unit. Thus at least four different aspects of interpretation should be considered when considering the evidence of the Achaemenid empire in the east:
1. the dynastic - identifiable by inscriptions, coins and seals
2. the ethnic - possibly detectable on both physical anthropological and cultural grounds
3. the political/imperial - recognizable both in macroscopic architectural and art historical remains and in the material traces of settlement patterns and economic investments, e.g. to secure the water supply
4. the chronological - interpretable in the differing horizons connected to the period of Achaemenid political-dynastic dominion in the area
Landscape design methods in architecture
No full textLandscape has been used as a metaphor or conceptual reference for an increasing amount of excellent architectural projects in the last two decades. The phenomenon seems to be a substantial innovation of architecture with an interesting potential for artistic, social and ecological gains. To be able to better understand and critically review these projects, it is important to better understand the notion of landscape. How can we better understand the idea of landscape and its design methods for application in architecture? To answer this central question we try to find a working definition of relevant landscape design methods in this paper. Only thereafter may we ask how these landscape methods are applied to the theory and practice of architecture, and what knowledge can be derived from built examples for future practical and theoretical use in the field. This paper is part of the larger study ‘Architecture with Landscape Methods’ with more case studies. This paper however is mainly based on literature study. Currently the author is analyzing four crucial projects from 1990-present in CAD and GIS based analytical case studies. One or two of these cases will illustrate the subject to the audience in the author's poster presentation at IFLA2012.UrbanismArchitectur
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Status of Preconceptual Design of the Advanced High-Temperature Reactor (AHTR)
No full textA new reactor plant concept is presented that combines the benefits of ceramic-coated, high-temperature particle fuel with those of clean, high-temperature, low-pressure molten salt coolant. The Advanced High-Temperature Reactor (AHTR) concept is a collaboration of Oak Ridge National Laboratory, Sandia National Laboratories, and the University of California at Berkeley. The purpose of the concept is to provide an advanced design capable of satisfying the top-level functional requirements of the U.S. Department of Energy Next Generation Nuclear Plant (NGNP), while also providing a technology base that is sufficiently robust to allow future development paths to higher temperatures and larger outputs with highly competitive economics. This report summarizes the status of the AHTR preconceptual design. It captures the results from an intense effort over a period of 3 months to (1) screen and examine potential feasibility concerns with the concept; (2) refine the conceptual design of major systems; and (3) identify research, development, and technology requirements to fully mature the AHTR design. Several analyses were performed and are presented to quantify the AHTR performance expectations and to assist in the selection of several design parameters. The AHTR, like other NGNP reactor concepts, uses coated particle fuel in a graphite matrix. But unlike the other NGNP concepts, the AHTR uses molten salt rather than helium as the primary system coolant. The considerable previous experience with molten salts in nuclear environments is discussed, and the status of high-temperature materials is reviewed. The large thermal inertia of the system, the excellent heat transfer and fission product retention characteristics of molten salt, and the low-pressure operation of the primary system provide significant safety attributes for the AHTR. Compared with helium coolant, a molten salt cooled reactor will have significantly lower fuel temperatures (150-200-C lower) for the equivalent temperature of heat delivered to either the power conversion system or a hydrogen production plant. Using a comparative cost analysis, the construction costs per unit output are projected to be 50-55% of the costs for modular gas-cooled or sodium-cooled reactor systems. This is primarily a consequence of substantially larger power output and higher conversion efficiency for the AHTR. The AHTR has a number of unique technical challenges in meeting the NGNP requirements; however, it appears to offer advantages over high-temperature helium-cooled reactors and provides an alternative development path to achieve the NGNP requirements. Primary challenges include optimizing the core design for improved response to transients, designing an internal blanket to thermally protect the reactor vessel, and engineering solutions to high-temperature refueling and maintenance
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