Canonical Elements for Collision Orbits     

Scott Tremaine 《Celestial Mechanics and Dynamical Astronomy》2001,79(3):231-233

I derive a set of canonical elements that are useful for collision orbits (perihelion distance approaching zero at fixed semimajor axis). The coordinates are the mean anomaly and the two spherical polar angles at aphelion.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

California's New Ground Water Management Law     

Scott W. Horsley 《Ground Water Monitoring & Remediation》1994,14(4):114-115

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A method for stratigraphic correlation of several boreholes     

Douglas M. Hawkins 《Mathematical Geology》1984,16(4):393-406

The borehole slotting method previously proposed by Gordon and Reyment for two boreholes may be extended to three or more boreholes, but soon becomes computationally intractable. We propose another method based on the mixture model of cluster analysis, the computational labor of which increases linearly with the number of boreholes. This method produces profiles of the unknown strata to which the individual boreholes are easily matched by the two-borehole slotting method.  相似文献   

Binary Plankton Image Classification     

Xiaoou Tang Feng Lin Scott Samson Andrew Remsen 《Oceanic Engineering, IEEE Journal of》2006,31(3):728-735

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Mineralogical interpretation of reflectance spectra of Eros from NEAR near‐infrared spectrometer low phase flyby     

Lucy A. Mcfadden  Dennis D. Wellnitz  Matthew Schnaubelt  Michael J. Gaffey  J. F. Bell  Noam Izenberg  Scott Murchie  Clark R. Chapman 《Meteoritics & planetary science》2001,36(12):1711-1726

Abstract— High signal‐to‐noise near‐infrared spectrometer (NIS) spectra acquired during the low phase flyby of the near‐Earth asteroid rendezvous (NEAR) mission to 433 Eros are analyzed to determine mineral chemistry and proportions of mafic silicates across the asteroid's surface at 2.68 × 5.50 km spatial resolution. Spectral band parameters are derived, and compared with those of laboratory samples of known mineral composition, grain size distribution and terrestrial, meteoritic and lunar pyroxene spectral properties. The NIS derived band parameters are consistent with ordinary chondrite meteorites. We invoke the presence of a clinopyroxene component in the spectra, which is consistent with ordinary chondrite mineralogy and/or some degree of partial melting of ordinary chondritic material. Spectra measured across the surface of Eros can reveal small but real spectral variations. Most relative spectra are uniform to within 1–2%. Some areas suggest compositional variations of a few percent. Spectral slope variations of a few percent are seen indicating a non‐uniform distribution of materials affecting the slope parameter but with no resolved absorption bands. We find no correlation of slope with viewing geometry or compositional variation. The band parameter values do not consistently indicate a specific ordinary chondrite class but Eros is definitely undifferentiated with possible compositional variations of no more than 1–2%.  相似文献   

The hydrocarbons in the Isla Vista marine seep environment     

Daniel H. Stuermer  Robert B. Spies  Paul H. Davis  Douglas J. Ng  Clarence J. Morris  Sharon Neal 《Marine Chemistry》1982,11(5):413-426

Hydrocarbon analyses on samples of sediment, interstitial water, and dissolved and particulate fractions of the water column from the vicinity of the Isla Vista seep near Santa Barbara, California, are presented. The results demonstrate that a very heterogeneous distribution of hydrocarbon composition and concentration exists in the seep environment and that the life-style and feeding habits of the organisms in this environment will have a dramatic effect on their hydrocarbon exposure.  相似文献   

De Draconis: Spectroscopic orbit,rotation effect and physical model     

Douglas P. Hube  Janet S. Couch 《Astrophysics and Space Science》1982,81(1-2):357-368

New spectroscopic observations are used for the determination of orbital elements and for a study of the rotation effect of DE Draconis. The primary component is found to rotate much faster than the synchronous rate and with its axis of rotation possibly inclined with respect to the perpendicular to the orbital plane. The system is fully detached and the stars are relatively young and unevolved.  相似文献   

An entry model for the Tagish Lake fireball using seismic,satellite and infrasound records     

Peter G. Brown  Douglas O. ReVelle  Edward Tagliaferri  Alan R. Hildebrand 《Meteoritics & planetary science》2002,37(5):661-675

Abstract— We present instrumental observations of the Tagish Lake fireball and interpret the observed characteristics in the context of two different models of ablation. From these models we estimate the pre‐atmospheric mass of the Tagish Lake meteoroid to be ?56 tonnes and its porosity to be between 37 and 58%, with the lowest part of this range most probable. These models further suggest that some 1300 kg of gram‐sized or larger Tagish Lake material survived ablation to reach the Earth's surface, representing an ablation loss of 97% for the fireball. Satellite recordings of the Tagish Lake fireball indicate that 1.1 times 10¹² J of optical energy were emitted by the fireball during the last 4 s of its flight. The fraction of the total kinetic energy converted to light in the satellite pass band is found to be 16%. Infrasonic observations of the airwave associated with the fireball establish a total energy for the event of 1.66 ± 0.70 kT TNT equivalent energy. The fraction of this total energy converted to acoustic signal energy is found to be between 0.10 and 0.23%. Examination of the seismic recordings of the airwave from Tagish Lake have established that the acoustic energy near the sub‐terminal point is converted to seismic body waves in the upper‐most portion of the Earth's crust. The acoustic energy to seismic energy coupling efficiency is found to be near 10^?6 for the Tagish Lake fireball. The resulting energy estimate is near 1.7 kT, corresponding to a meteoroid 4 m in diameter. The seismic record indicates extensive, nearly continuous fragmentation of the body over the height intervals from 50 to 32 km. Seismic and infrasound energy estimates are in close agreement with the pre‐atmospheric mass of 56 tonnes established from the modeling. The observed flight characteristics of the Tagish Lake fireball indicate that the bulk compressive strength of the pre‐atmospheric Tagish Lake meteoroid was near 0.25 MPa, while the material compressive strength (most appropriate to the recovered meteorites) was closer to 0.7 MPa. These are much lower than values found for fireballs of ordinary chondritic composition. The behavior of the Tagish Lake fireball suggests that it represents the lowest end of the strength spectrum of carbonaceous chondrites or the high end of cometary meteoroids. The bulk density and porosity results for the Tagish Lake meteoroid suggest that the low bulk densities measured for some small primitive bodies in the solar system may reflect physical structure dominated by microporosity rather than macroporosity and rubble‐pile assemblages.  相似文献   

Antipodean Contrasts: National Parks in New Zealand and Europe     

Douglas G. Pearce  Gerard Richez 《New Zealand geographer》1987,43(2):53-59

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The MESSENGER mission to Mercury: scientific objectives and implementation     

Sean C. Solomon  Ralph L. McNutt  Jr.  Robert E. Gold  Mario H. Acua  Daniel N. Baker  William V. Boynton  Clark R. Chapman  Andrew F. Cheng  George Gloeckler  James W. Head III  Stamatios M. Krimigis  William E. McClintock  Scott L. Murchie  Stanton J. Peale  Roger J. Phillips  Mark S. Robinson  James A. Slavin  David E. Smith  Robert G. Strom  Jacob I. Trombka  Maria T. Zuber 《Planetary and Space Science》2001,49(14-15)

Mercury holds answers to several critical questions regarding the formation and evolution of the terrestrial planets. These questions include the origin of Mercury's anomalously high ratio of metal to silicate and its implications for planetary accretion processes, the nature of Mercury's geological evolution and interior cooling history, the mechanism of global magnetic field generation, the state of Mercury's core, and the processes controlling volatile species in Mercury's polar deposits, exosphere, and magnetosphere. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission has been designed to fly by and orbit Mercury to address all of these key questions. After launch by a Delta 2925H-9.5, two flybys of Venus, and two flybys of Mercury, orbit insertion is accomplished at the third Mercury encounter. The instrument payload includes a dual imaging system for wide and narrow fields-of-view, monochrome and color imaging, and stereo; X-ray and combined gamma-ray and neutron spectrometers for surface chemical mapping; a magnetometer; a laser altimeter; a combined ultraviolet–visible and visible-near-infrared spectrometer to survey both exospheric species and surface mineralogy; and an energetic particle and plasma spectrometer to sample charged species in the magnetosphere. During the flybys of Mercury, regions unexplored by Mariner 10 will be seen for the first time, and new data will be gathered on Mercury's exosphere, magnetosphere, and surface composition. During the orbital phase of the mission, one Earth year in duration, MESSENGER will complete global mapping and the detailed characterization of the exosphere, magnetosphere, surface, and interior.  相似文献