Lifetime of the Hα chromospheric network     

Rogers  Ernest H. 《Solar physics》1970,13(1):57-77

Time-lapse photographs of the H chromospheric network were taken at 3-sec intervals with a -Å filter centered at H + 0.65 Å, where the network appears as a system of dark mottles. A nearly continuous sequence of 62 hr duration was made possible by summertime operation of the telescope at Thule Air Base, Greenland, 10° above the Arctic Circle. A quiet region was followed across the center of the disc. The life history of the network, as determined by measurement of the cross-correlation of selected photographs taken at intervals ranging between 3 sec and 29 hr, shows a rather complicated behavior. Initially the correlation falls off quite rapidly, dropping from 0.97 at 3 sec to 0.60 at about 7 min. Thereafter, the decline becomes increasingly more gradual, reaching a value of 0.24 at 4 hr. From this point the correlation falls off quite slowly. A least-squares fit to that portion of the cross-correlation curve for time differences greater than 4 hr yields a mean (1/e) life of 25.0 ± 1.6 hr and a value for twice the half-life of 38.8 ± 4.0 hr. This rate of decline is believed to be characteristic of the lifetime of the chromospheric network. The rapid initial loss of correlation appears to be due to a redistribution of the features, seen in the red wing of the H line, along the network.  相似文献   

COCORP deep seismic reflection traverses of the U.S. Cordillera     

Christopher J. Potter  Richard W. Allmendinger  Ernest C. Hauser  Jack E. Oliver 《Geophysical Journal International》1987,89(1):99-104

Summary. COCORP seismic reflection traverses of the U.S. Cordillera at 40°N and 48.5°N latitude reveal some fundamental similarities as well as significant differences in reflection patterns. On both traverses, autochthonous crust beneath thin-skinned thrust belts of the eastern part of the Cordillera is unreflective; immediately to the west the Cordilleran interior is very reflective above a flat, prominent reflection Moho. Mesozoic accreted terranes in the western part of the orogen are underlain on both traverses by very complex reflection patterns, in constrast to more easily deciphered patterns beneath areas of Cenozoic accretion. The prominent reflection Moho beneath the orogenic interior on both transects probably evolved through a combination of magmatic and deformational processes during Cenozoic extension. The main differences between the two traverses lie in the reflection patterns of the middle and lower crust in the Cordilleran interior; these differences are probably related to the way Cenozoic extension was accommodated at depth. Laminated middle and lower crust above the reflection Moho in the western Basin and Range (40°N) may be related to magmatism, ductile pure shear and large-scale transposition during Cenozoic extension. By contrast, beneath the eastern Basin and Range (40°N), and the orogenic interior in the NW United States (48.5°N), Cenozoic extension was probably accommodated along dipping deformation zones throughout the crust.  相似文献   

On the stable stratification of the nocturnal lower troposphere inferred from lidar observations over Pune,India     

P. Ernest Raj  P. C. S. Devara 《Boundary-Layer Meteorology》1993,65(1-2):197-205

The nocturnal structure of the lower troposphere is studied using aerosol profile data (50–2800 m AGL) obtained with a bistatic, continuous wave, Argon ion lidar system during October 1986–September 1989 at Pune (18°32 N, 73°51 E, 559m AMSL), India. The top of the nocturnal groundbased inversion is taken as the height above ground where the negative vertical gradient in aerosol concentration first reaches a maximum. During the post-sunset period over this station, this height is as low as 160m and frequently lies around 550m. Greater heights are observed in pre-monsoon months and smaller ones during the southwest monsoon season. Positive vertical gradients in aerosol concentration, indicative of stable/elevated layers, appear frequently around 750m. Temporal variations of aerosol concentration gradients in two adjacent air layers, 920–1000m and 100–1100m, provide evidence that stability increases downward in the early night hours.  相似文献   

AN INDEX OF ELIGIBILITY STANDARDS FOR WELFARE BENEFITS     

Ernest H. Wohlenberg 《The Professional geographer》1976,28(4):381-384

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Laboratory Tests on Thin Spray-On Liner Penetrated Rock Joints in Direct Shear     

Qiuqiu Qiao  Jan Nemcik  Ian Porter  Ernest Baafi 《Rock Mechanics and Rock Engineering》2015,48(5):2173-2177

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Laboratory Investigation of the Resistance of Tailings and Natural Sediments to Cyclic Loading     

Africa M. Geremew  Ernest K. Yanful 《Geotechnical and Geological Engineering》2012,30(2):431-447

A number of cyclic triaxial tests were carried out on mine tailings and natural sediment samples under undrained conditions to investigate their resistance to cyclic loading. The tests were performed on more than 100 samples with a cyclic shear stress ratio ranging from 0.10 to 0.40 under varying void ratio and the same confining pressure. It was observed that the axial strain and excess pore water pressure increased with the number of loading cycles while the effective stress decreased with increasing number of loading cycles. The liquefaction resistance of the tailings was also observed to be higher than that of natural soils with similar particle size distribution, void ratio and plasticity index. It was observed that the influence of specific gravity on the cyclic strength of mine tailings is significant. The results showed that the cyclic resistance of the tailings was not strongly influenced by plasticity index for low plasticity tailings. A boundary relationship between void ratio and normalized cyclic resistance ratio was established based on the results.  相似文献   

Impact de la variabilité climatique et du barrage Nangbéto sur l'hydrologie du système Mono-Couffo (Afrique de l'Ouest)     

Ernest Amoussou  Pierre Camberlin  Gil Mahé 《水文科学杂志》2013,58(4):805-817

Résumé

En Afrique tropicale, de nombreuses études sur la variabilité climatique montrent qu'une tendance à la sécheresse s'est manifestée à partir de la fin des années 1960. Cette sécheresse a affecté aussi l'hydrosystème Mono-Couffo, en Afrique de l'Ouest, avec une persistance remarquable qui s'est répercutée sur les écoulements. Depuis 1988, avec la mise en eau du barrage de Nangbéto, qui coïncide avec une légère reprise pluviométrique dans les années 1990, on assiste à une modification du régime hydrologique du Mono à Athiémé. Les méthodes statistiques appliquées aux données mensuelles de pluie et débit de la période 1961–2000 ont permis de constater que les déficits pluviométriques des décennies 1970 et 1980 ont engendré des déficits de l'écoulement. Mais, avec la légère reprise pluviométrique (2%) de 1988 à 2000, on assiste à un excédent d'écoulement de 37% sur le Mono à Athiémé à régime « artificiel » depuis 1988; et, par contre, pas d'excédent (0,1%) sur le Couffo à Lanta à régime « naturel ».

Editeur Z.W. Kundzewicz

Citation Amoussou, E., Camberlin, P. et Mahé, G., 2012. Impact de la variabilité climatique et du barrage Nangbéto sur l'hydrologie du système Mono-Couffo (Ouest Afrique). Hydrological Sciences Journal, 57 (4), 805–817.  相似文献   

Motional modes of dilatational waves in elastic porous media containing two immiscible fluids     

Wei-Cheng Lo  Garrison Sposito  Ernest Majer  Chao-Lung Yeh 《Advances in water resources》2010

Numerical simulations of dilatational waves in an elastic porous medium containing two immiscible viscous compressible fluids indicate that three types of wave occur, but the modes of dilatory motion corresponding to the three waves remain uncharacterized as functions of relative saturation. In the present paper, we address this problem by deriving normal coordinates for the three dilatational waves based on the general poroelasticity equations of Lo et al. 2005 [13]. The normal coordinates provide a theoretical foundation with which to characterize the motional modes in terms of six connecting coefficients that depend in a well defined way on inertial drag, viscous drag, and elasticity properties. Using numerical calculations of the connecting coefficients in the seismic frequency range for an unconsolidated sand containing water and air as a representative example relevant to hydrologic applications, we confirm that the dilatational wave whose speed is greatest corresponds to the motional mode in which the solid framework and the two pore fluids always move in phase, regardless of water saturation, in agreement with the classic Biot theory of the fast compressional wave in a water-saturated porous medium. For the wave which propagates second fastest, we show, apparently for the first time, that the solid framework moves in phase with water, but out of phase with air [Mode (III)], if the water saturation is below about 0.8, whereas the solid framework moves out of phase with both pore fluids [Mode (IV)] above this water saturation. The transition from Mode (III) to Mode (IV) corresponds to that between the capillarity-dominated region of the water retention curve and the region reflecting air-entry conditions near full water saturation. The second of the two modes corresponds exactly to the slow compressional wave in classic Biot theory, whereas the first mode is possible only in a two-fluid system undergoing capillary pressure fluctuations. For the wave which has the smallest speed, the dilatational mode is dominated by the motions of the two pore fluids, which are always out of phase, a result that is consistent with the proposition that this wave is caused by capillary pressure fluctuations.  相似文献   

DISTRIBUTION OF CCRMP, NIST, AND USGS REFERENCE MATERIAL DATA IN THE LITERATURE (1950 - 1989)     

Ernest S. GLADNEY  Iwan ROELANDTS 《Geostandards and Geoanalytical Research》1996,20(1):45-55

Publication patterns of CCRMP, NIST, and USGS reference materials are traced over the past 40 years by literature source, analytical method employed, and constituents measured. This is the first update to our 1987 paper which covered the period 1951 - 1985.  相似文献   

1988 COMPILATION OF ELEMENTAL CONCENTRATION DATA FOR USGS AGV-1, GSP-1 AND G-2     

Ernest S. GLADNEY  Elizabeth A. JONES  Eric J. NICKELL  Iwan ROELANDTS 《Geostandards and Geoanalytical Research》1992,16(2):111-300

Concentration data on up to 90 individual constituents in USGS AGV-1, GSP-1, and G-2 have been collected from 1270 journal articles and technical reports. These data are summarized in consensus (mean) values with uncertainties expressed as +/- one standard deviation. Mean values are also calculated as a function of analytical procedure and all raw data are given in the tables. Recommended values are proposed based upon data criteria used by NIST (National Institute of Standards and Technology, formerly the National Bureau of Standards or NBS).  相似文献