Report on IAU colloquium no. 39 “the relationships of comets,minor planets and meteorites”     

John R. Dickel 《Icarus》1977,32(2):251-254

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The relationship of wind stress to heat flux divergence of Texas-Louisiana shelf waters     

Paul C. Etter  William F. Ulm  John D. Cochrane 《Continental Shelf Research》1985,4(5):547-552

Monthly, multi-annual mean heat budgets are calculated for waters overlying the Texas-Louisiana shelf. Heat storage rates are calculated on the basis of a volumetric temperature-salinity census; unpublished data from Bunker are consulted to determine surface heat exchanges. Monthly heat flux divergences, calculated as residuals in the heat budget equation, show divergence of heat during the months of June and July, the upwelling season for much of the Texas-Louisiana coast, and convergence of heat during the rest of the year when winds conducive to downwelling prevail.  相似文献   

Analyzing Radar Meteor Trail Echoes using the Fresnel Transform Technique: A Signal Processing Viewpoint     

Arnab Roy  John F. Doherty  John D. Mathews 《Earth, Moon, and Planets》2007,101(1-2):27-39

Several techniques have been proposed for measuring speeds of meteoroids observed using radars. A recent technique involves the use of Fresnel transforms to accurately determine the speed of a meteoroid producing the trail. We follow a numerical modeling approach to analyze this technique in detail. Our studies indicate that high sensitivity to background noise levels might be a possible shortcoming of the Fresnel transform method. A matched filtering approach is presented as an alternative to alleviate this sensitivity to the noise problem. Performance of the two techniques is compared using numerical modeling and data from a 30 MHz radar.  相似文献   

Geographers,Maps, And Campus Map Collections     

John V. Bergen 《The Professional geographer》1972,24(4):310-316

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Sedimentological,geomorphological and dynamic context of debris-mantled glaciers,Mount Everest (Sagarmatha) region,Nepal     

Michael J. Hambrey  Duncan J. Quincey  Neil F. Glasser  John M. Reynolds  Shaun J. Richardson  Samuel Clemmens 《Quaternary Science Reviews》2009,28(11-12):1084

This paper presents the sediment, landform and dynamic context of four avalanche-fed valley glaciers (Khumbu, Imja, Lhotse and Chukhung) in the Mount Everest (Sagarmatha) region of Nepal. All four glaciers have a mantle of debris dominated by sandy boulder-gravel that suppresses melting to an increasing degree towards the snout, leading to a progressive reduction in the overall slope of their longitudinal profile. Prominent lateral–terminal moraine complexes, also comprising sandy bouldergravel, enclose the glaciers. These terminal moraines originally grew by accretion of multiple sedimentary facies of basal glacial and supraglacial origin, probably by folding and thrusting when the glaciers were more dynamic during the Little Ice Age. The four glaciers are in various stages of recession, and demonstrate a range of scenarios from down-wasting of the glacier tongue, through morainedammed lake development, to post-moraine-dam breaching. Khumbu Glacier is at the earliest stage of supraglacial pond formation and shows no sign yet of developing a major lake, although one is likely to develop behind its >250 m high composite terminal moraine. Imja Glacier terminates in a substantial body of water behind a partially ice-cored moraine dam (as determined from geophysical surveys), but morphologically appears unlikely to be an immediate threat. Chukhung Glacier already has a breached moraine and a connected debris fan, and therefore no longer poses a threat. Lhotse Glacier has an inclined, free-draining tongue that precludes hazardous lake development. From the data assembled, a conceptual model, applicable to other Himalayan glaciers, is proposed to explain the development of large, lateral-terminal moraine complexes and associated potentially hazardous moraine dams. – 2008 Elsevier Ltd. All rights reserved.  相似文献   

Bedrock aquifers and population growth in the Denver Basin, Colorado, USA     

John E. Moore Robert G. Raynoldse Marieke Dechesne 《《幕》》2007,30(2):115-118

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The zoo hypothesis     

John A. Ball 《Icarus》1973,19(3):347-349

Extraterrestrial intelligent life may be almost ubiquitous. The apparent failure of such life to interact with us may be understood in terms of the hypothesis that they have set us aside as part of a wilderness area or zoo.  相似文献   

grommet: an N-body code for high-resolution simulations of individual galaxies     

John Magorrian 《Monthly notices of the Royal Astronomical Society》2007,381(4):1663-1671

This paper presents a fast, economical particle-multiple-mesh N -body code optimized for large- N modelling of collisionless dynamical processes, such as black hole wandering or bar–halo interactions, occurring within isolated galaxies. The code has been specially designed to conserve linear momentum. Despite this, it also has variable softening and an efficient block-time-step scheme: the force between any pair of particles is calculated using the finest mesh that encloses them both (respecting Newton's third law) and is updated only on the longest time-step of the two (which conserves momentum). For realistic galaxy models with   N ≳ 10⁶  , it is faster than the fastest comparable tree code by factors ranging from ∼2 (using single time-steps) to ∼10 (multiple time-steps in a concentrated galaxy).  相似文献   

The spin and shape of dark matter haloes in the Millennium simulation of a Λ cold dark matter universe     

Philip Bett  Vincent Eke  Carlos S. Frenk  Adrian Jenkins  John Helly  Julio Navarro 《Monthly notices of the Royal Astronomical Society》2007,376(1):215-232

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CHRISTALLERIAN NETWORKS IN THE LÖSCHIAN ECONOMIC LANDSCAPE     

John U. Marshall 《The Professional geographer》1977,29(2):153-159

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