Smithsonian Institution''s Global Volcanism Network     

Luke Jensen 《Bulletin of Volcanology》2001,63(4):293-294

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Lateral coherence in isotropic turbulence and in the natural wind     

L. Kristensen  N. O. Jensen 《Boundary-Layer Meteorology》1979,17(3):353-373

A short review of experimental findings is given, followed by a theoretical derivation, based on Taylor's hypothesis, of formulas for lateral coherences. It is assumed that the flow is stationary and homogeneous. Explicit formulas are derived assuming an energy spectrum pertaining to the inertial subrange. Even when the last assumption is not fulfilled, there are only four different types of non-zero velocity coherences. These four coherences correspond to the combinations uu, vv, ww, and uv, where u, v, and w are the longitudinal, the transversal, and the vertical component of the turbulent velocity with respect to the direction of the horizontal mean wind velocity U. In the case of small displacements relative to the scale of turbulence, the coherences are shown to be universal functions of the non-dimensional frequency nD/¦U¦, where n is the frequency and D the lateral displacement. It is shown that these theoretical formulas for spectral coherences are in good agreement with atmospheric data. Finally, the role of the scale of the turbulence is discussed.  相似文献   

Methodology and exploration for sandstone-type uranium deposits     

H. A. Qidwai  M. L. Jensen 《Mineralium Deposita》1979,14(2):137-152

Mobility of uranium with ground water in near surface earth conditions and its association with sandstone formations of continental depositional environments require an increase in the understanding and application of depositional characteristics in exploration. This paper, therefore, summarizes significant relationships of uranium geochemistry in the supergene environments and depositional characteristics of fluvial, deltaic, and lacustrine environments and their influence on exploration that may aid in the expeditious search for sandstone-type uranium deposits throughout the world.  相似文献   

Zur Spur-für Spur-Korrektur in der Seismik     

Dr. phil. K. D. Jensen 《Pure and Applied Geophysics》1959,44(1):74-82

Zusammenfassung Der nachfolgende Aufsatz diskutiert erneut die Frage der Korrekturen bei der Auswertung seismischer Filme. Die vom Verfasser vorgeschlagene Methode ist auf alle Verfahren der angewandten Seismik anwendbar und kann zur Entlastung des Wissenschaftlers von jedem Zeichner oder Rechner gehandhabt werden.

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Summary The following lines discuss anew the problem of the corrections while interpreting seismic records. The method recommended by the author applied to all methods of the applied seismics and can be performed by any drawer or calculator in order to relieve the scientist.

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Atmospheric Disturbances that Generate Intermittent Turbulence in Nocturnal Boundary Layers     

Jielun Sun  Donald H. Lenschow  Sean P. Burns  Robert M. Banta  Rob K. Newsom  Richard Coulter  Stephen Frasier  Turker Ince  Carmen Nappo  Ben B. Balsley  Michael Jensen  Larry Mahrt  David Miller  Brian Skelly 《Boundary-Layer Meteorology》2004,110(2):255-279

Using the unprecedented observational facilities deployed duringthe 1999 Cooperative Atmosphere-Surface Exchange Study (CASES-99),we found three distinct turbulent events on the night of 18October 1999. These events resulted from a density current,solitary wave, and internal gravity wave, respectively. Our studyfocuses on the turbulence intermittency generated by the solitarywave and internal gravity wave, and intermittent turbulenceepisodes associated with pressure change and wind direction shiftsadjacent to the ground. Both the solitary and internal gravitywaves propagated horizontally and downward. During the passage ofboth the solitary and internal gravity waves, local thermal andshear instabilities were generated as cold air was pushed abovewarm air and wind gusts reached to the ground. These thermal andshear instabilities triggered turbulent mixing events. Inaddition, strong vertical acceleration associated with thesolitary wave led to large non-hydrostatic pressure perturbationsthat were positively correlated with temperature. The directionaldifference between the propagation of the internal gravity waveand the ambient flow led to lateral rolls. These episodic studiesdemonstrate that non-local disturbances are responsible for localthermal and shear instabilities, leading to intermittentturbulence in nocturnal boundary layers. The origin of thesenon-local disturbances needs to be understood to improve mesoscalenumerical model performance.  相似文献   

Groundwater recharge and evapotranspiration for two natural ecosystems covered with oak and heather     

U. L. Ladekarl  K. R. Rasmussen  S. Christensen  K. H. Jensen  B. Hansen 《Journal of Hydrology》2005,300(1-4):76-99

The evapotranspiration and groundwater recharge from two natural areas with high (oak) and low (heath) vegetation were estimated by calibrating a semi-physical numerical soil water and heat model to fit 8 and 7 years of TDR-measurements of water content, respectively. The measurements were made between the surface and 7 m depth. For the oak stand, the estimated annual recharge for the years 1992–1999 is 390 mm, the evaporation from soil and interception is 205 mm, and the transpiration is 285 mm. For the heath area estimation was carried out for the years 1993–1999. However, the heath was struck by a heavy beetle attack in 1994, which strongly affected the vegetation and thus the water balance for the following 3 years. For years not affected, the estimated recharge is 733 mm (about 50% larger than for the oak stand for the same years), the evaporation is 316 mm, and the transpiration is 128 mm. The estimated recharge values compare fairly well to estimates obtained from bromide tracer experiments. However, the recharge estimates obtained from the tracer experiments are very uncertain. The uncertainty is mainly due to spatial heterogeneity making the three replicate samples taken here for each time and depth insufficient.

The analyses of TDR-measurements and tracer data showed that water front movement depends on the antecedent soil water content. Some layers are bypassed, especially at low water contents, and at high soil water contents preferential flow was observed at the heath site.  相似文献   

Three-Dimensional Numerical Modeling of Steam Override Observed at a Full-Scale Remediation of an Unconfined Aquifer     

Jacob Gudbjerg  Tom Heron  Torben O. Sonnenborg  Karsten H. Jensen 《Ground Water Monitoring & Remediation》2005,25(3):116-127

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Observation of DMSO and CH3S(O)OH from the gas phase reaction between DMS and OH     

S. Sørensen  H. Falbe-Hansen  M. Mangoni  J. Hjorth  N. R. Jensen 《Journal of Atmospheric Chemistry》1996,24(3):299-315

Products and mechanisms have been investigated for the reactions between dimethylsulfide (DMS) and dimethylsulfoxide (DMSO) and the hydroxyl radical (OH) in the presence of NO_x. All of the experiments were performed in a 480 L reaction chamber, applying Fourier transform infrared spectroscopy (FT-IR) and ion chromatography as the analytical techniques.In addition to the sulfur containing products that are known to be produced from the gas phase reaction between DMS and OH (SO₂, dimethylsulfone, methylsulfonyl peroxynitrate, methanesulfonic acid, H₂SO₄), DMSO and methanesulfinic acid (CH₃S(O)OH) were also observed as products. Only SO₂, DMSO₂ and methylsulfonyl peroxynitrate were found as sulfur containing products in the reaction between DMSO and OH. Based on these new results we propose a mechanism for the atmospheric oxidation of DMS and DMSO by OH radical.  相似文献   

Effect of monochloramine on isolated fulvic acid     

James N. Jensen  J. Donald Johnson  Jessica St Aubin  Russell F. Christman 《Organic Geochemistry》1985,8(1):71-76

Monochloramine is interesting both as a selective oxidant of fulvic acid and as a drinking water disinfectant. In this study, the controlled reaction of aquatic fulvic acid with monochloramine did not result in products detectable by ether extraction-gas chromatography-flame ionization detection techniques. Evidence of a reaction was shown by bleaching of the fulvic acid solution (decreased absorbance at 465 nm) and chlorine substitution. Chlorine-containing products were quantified by the total carbon adsorbable organic halide (TOX) parameter. Bleaching and organic chlorine formation were much less extensive than in the reaction of free chlorine with fulvic acid. Monochloramine was shown to produce an organic chlorine fraction more hydrophilic and with higher molecular size than that produced by chlorine and fulvic acid. Results suggest that monochloramine may be useful tool for the investigation of certain humic functionalities because it reacts rather selectively and to a small extent with aquatic fulvic acid.  相似文献   

Detection of Cyclic Patterns Using Wavelets: An Example Study in the Ormskirk Sandstone, Irish Sea     

Nestor A. Rivera  S. Ray  Jerry L. Jensen  Andrew K. Chan  Walter B. Ayers 《Mathematical Geology》2004,36(5):529-543

This study shows how wavelet analysis can be used on well log and drill core data to identify cyclicity in sedimentary sequences. Three possible methods for determining wavelength were investigated: the Morlet wavelet, the Fourier transform, and the semivariogram. When applied to several hypothetical signals similar to those observed in petrophysical measurements in hydrocarbon reservoirs, all three methods could identify the presence of cyclicity. Only the wavelet scalogram, however, gave a clear indication of when the cyclic element was present and where frequency changes occurred in the signal. To illustrate the wavelet analysis, we processed well log and core data from a well in the Ormskirk Sandstone and determined the wavelet coefficients for each zone and the wavelengths of the strongest cyclicities. The cyclicities observed corresponded well with sedimentary features of the formation (e.g., channels and channel sets). Also, ratios of the cyclicity wavelengths corresponded with ratios of the Milankovitch precession, obliquity, and eccentricity periods. This result is in agreement with other investigators, who have proposed that Milankovitch-driven climate changes exercised an important control on Ormskirk Sandstone deposition.  相似文献