南北朝以前陕西天文人物     

刘次沅  窦忠 《时间频率学报》1994

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Mercurian volcanism questioned     

Don E. Wilhelms 《Icarus》1976,28(4):551-558

The Mariner 10 television team has argued that extensive plains on Mercury were formed by volcanism and compared them with the demonstrably lunar maria. I believe, however, that in stratigraphic relations, surface morphology, and albedo contrast, the Mercurian plains more closely resemble the lunar light plains. These lunar plains were interpreted as volcanic on the basis of data comparable to that available to the Mariner 10 investigators but have been shown by the Apollo missions to be of impact origin. The plains on Mercury might also be formed of impact materials, perhaps of impact melt or other basin ejecta that behaved more like a fluid when emplaced that did lunar basin ejecta.  相似文献   

WELL FIELD CONTAMINATION NEAR BALD KNOB,ALLEGANY COUNTY,MARYLAND     

Don W. Duckson 《The Professional geographer》1981,33(4):445-449

A case study from Allegany County, Maryland illustrates that, in the absence of a baseline of water quantity and quality established prior to coal mining, resolution of conflicts is neither fully possible nor equitable.  相似文献   

Temperature Dependence of Single-Crystal Spinel (MgAl₂O₄) Elastic Constants from 293 to 423°K Measured by Light-Sound Scattering in the Raman-Nath Region     

Hsi-Ping Liu  R. N. Schock  Don L. Anderson 《Geophysical Journal International》1975,42(1):217-250

Summary. The temperature dependence of single-crystal elastic constants of synthetic stoichiometric MgAl₂O₄ spinel has been measured by the light-sound scattering technique in the Raman-Nath region. The crystal is set into forced vibration by a single crystal LiNbO₃ transducer coupled to one crystal face. A He-Ne Laser beam is diffracted by the stress-induced birefringence inside the crystal. The diffraction angle is determined from the distance between two spots exposed on a photographic plate by the first order diffracted beams as measured by a microdensitometer. The sound wavelength inside the crystal is then inferred from the laser diffraction angle. Combining the sound wavelength with the measured transducer frequency, the velocity inside the crystal is determined typically to a precision of 0·05 per cent. In this method, the measurement of velocity is not dependent on either the determination of sample length or on phase shifts at sample-transducer interface. Velocities of four pure modes, L //[001], T //[001], L //[110], and T //[110]( P //[1 1 0] are measured in the temperature range between 293 and 423 °K. A linear temperature dependence is fit to the data by a least square method. Values obtained at 25 °C from this linear fit are
The temperature dependence of the adiabatic elastic constants and bulk and shear (VRH average) moduli is computed using the density and literature value of thermal expansion coefficient. Values obtained are:
A comparison with previous measurements by pulse superposition and ultrasonic interferometry methods is made. Disagreement, when present, is discussed in terms of the separate measuring techniques. Finally, the present method, with its possibility for further improvement, is evaluated as a new method to measure temperature and pressure dependence of elastic constants.  相似文献   

Leonard Medal Citation for Robert M. Walker     

Don Burnett 《Meteoritics & planetary science》1994,29(4):434-435

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The structure of the lowermost mantle determined by short-period P-wave amplitudes     

Larry J. Ruff  Don V. Helmberger 《Geophysical Journal International》1982,68(1):95-119

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Morgan, W.B. and Moss, R.P. Fuelwood and rural energy production and supply in the humid tropics : Dun Laoghaire: Tycooly International, 1981. Natural resources and the environment series, vol. 4, 224 pp. £21 hardback; £15.70 paperback     

Don Scott-Kemmis 《Applied geography (Sevenoaks, England)》1983,3(4):345-346

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Salinity Threatens the Viability of Agriculture and Ecosystems in Western Australia   总被引：3，自引：1，他引：3  

Richard George  Don McFarlane  Bob Nulsen 《Hydrogeology Journal》1997,5(1):6-21

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川滇及其邻区强震连续活动的地域图象研究   总被引：1，自引：2，他引：1  

黄圣睦  董瑞英 《四川地震》1997,(4):8-14

侧重分析了川滇及共邻区强度连续活动的不同地域分布图象，根据强震间的构造成因联系，将它们分为两种类型，主震－晚期强震和先期强震－后期强震。后一类又可分为两个亚类，由前兆性中强震条带联系的先、后期强震和相关构造带联系的先、后期强震。从整体连续强震活动图象变化特征上反映出强震及其晚期强震活动的可预测性，因而可供强震中期预报参数。  相似文献   

Channel bed steps and pool shapes along Soda Creek, Three Sisters Wilderness, Oregon     

Don W. Duckson  Jr.  Linda J. Duckson 《Geomorphology》2001,38(3-4)

Field study of bedrock step–pool systems along the upper reaches of Soda Creek in the Three Sisters Wilderness of Oregon shows strong correlation between several form variables (shape) and channel slope. Although step height and step length showed no regular spacing and variable correlation with channel slope, length to height ratios demonstrated strong negative correlations: steep slopes (20% to 80%) featured greater step height and shorter pool lengths than did flatter channel slopes. Correlations between step height to length ratios and channel slope varied between three lithologies. Explained variations ranged from 0.984 for the oldest channel steps developed in basalt, to 0.982 for steps of intermediate age developed in andesite, to 0.964 for the youngest steps developed in dacite. Sample size was 57, 40, and 33, respectively. The frequency of pool shape classes did not vary by lithology, but specific shape classes developed under differing slope conditions by rock type. All pool classes have adjusted (developed) their form to maximize resistance to flow H/L/S, and they have done so in remarkably uniform fashion.  相似文献