Hill stability in the many-body problem     

L. G. Luk’yanov  L. P. Nasonova  G. I. Shirmin 《Astronomy Letters》2003,29(4):274-277

We established a criterion for the Hill stability of motions in the problem of many spherical bodies with a spherical density distribution. The region of Hill stability was determined. The sizes of this region are comparable to the total volume of all of the bodies in the system, which sharply increases the probability of mutual collisions. This result may be considered as a confirmation that a supermassive core can be formed at the center of a globular star cluster. The motions in the n-body problem are shown to be unstable according to Hill.  相似文献   

Size characteristics of sediment in interrill overland flow on a semiarid hillslope,Southern Arizona     

Anthony J. Parsons  Athol D. Abrahams  Shiu-Hung Luk 《地球表面变化过程与地形》1991,16(2):143-152

This study examines the size characteristics of sediment removed from a semiarid hillslope by interrill overland flow. Rainfall simulation experiments were conducted on a runoff plot 18 m wide and 35 m long established on a piedmont hillslope in southern Arizona. The top of the plot coincided with the hillslope divide, and its outlet was located within a shallow rill. Samples of runoff were obtained from two cross-sections located in the interrill portion of the plot upslope of the rill and from a calibrated flume through which was directed interrill overland flow reaching the bottom of the plot. Analyses of sediment contained in these samples showed that sediment in interrill flow is finer than the matrix soil. The fineness of the interrill sediment compared to the matrix soil appears to be due to the inability of interrill overland flow to transport the coarser fraction of the sediment supplied to it by raindrop detachment. This finding implies that the rate of soil erosion in interrill areas is not. as is commonly supposed, limited by the rate at which raindrops can detach sediment but by the rate at which they detach sediment of a size that the overland flow is competent to transport. The relative fineness of sediment eroded from this hillslope is consistent with other evidence for the recent evolution of shrub-covered hillslopes in southern Arizona.  相似文献   

Influence of stratospheric dust layer particles on vertical changes of energy distribution in the shortwave spectrum     

Miroslav Kocifaj  Ján Lukáč 《Studia Geophysica et Geodaetica》1995,39(1):37-48

Summary The aim of this article is the evaluating of the radiation flux changes connected with the changes of atmosphere structure after a volcanic eruption. A situation similar to the after the eruption of volcano El Chichon in 1982 is analyzed. The comparison of the calculated characteristics with measured radiation fluxes indicates good agreement. It is shown that the most important changes in the radiation fluxes are observed in the spectral range of 500–600 nm. The particles in dust layers contribute to increasing the albedo of the Earth-atmosphere system especially in the near infrared part of the spectrum. A shift of the energy maximum in the radiation spectrum of the dust layer in the volcanic atmosphere is also observed.on leave from the Astronomical Institute, Slovak Academy of Sciences  相似文献   

Stochastic Modelling of Mineral Exploration Targets     

Talebi  Hassan  Mueller  Ute  Peeters  Luk J. M.  Otto  Alex  de Caritat  Patrice  Tolosana-Delgado  Raimon  van den Boogaart  K. Gerald 《Mathematical Geosciences》2022,54(3):593-621

Mathematical Geosciences - Mineral deposits are metal enrichment anomalies, occurring as local manifestations of the interplay between various geological processes that operate at a wide range of...  相似文献   

Estimating by inverse modeling the release of radioactive substances (<Superscript>133</Superscript>Xe, <Superscript>131</Superscript>I,and <Superscript>137</Superscript>Cs) into the atmosphere from Fukushima Daiichi nuclear disaster     

T.?I.?BabukhinaEmail author  A.?V.?Gan’shin  R.?V.?Zhuravlev  A.?N.?Luk’yanov  Sh.?Sh.?Maksyutov 《Russian Meteorology and Hydrology》2016,41(5):335-343

The estimate of the release of radioactive substances (¹³³Xe, ¹³¹I, and ¹³⁷Cs) into the atmosphere from the Fukushima Daiichi nuclear disaster is presented. It was obtained using the FLEXPART Lagrangian dispersion model and the data of local ground-based measurements of radiation dose rate. The computation period covers the active phase of the nuclear disaster that lasted 20 days after the tsunami. To get the quantitative characteristics of emissions of radioactive substances, the inverse modeling based on the Bayesian approach is used. The emissions were estimated for three altitudes. The total emissions are equal to 2.1 + 0.4 kg (14 000 + 2700 PBq) for ¹³³Xe, (3.8 + 0.4) x 10^-2 kg (174 + + 18 PBq) for ¹³¹I, and 5.7 + 1.2 kg (18 + 4 PBq) for ¹³⁷Cs that is consistent with the results of other studies. Retrieved emissions were used to provide the forward modeling for mapping the areas of radionuclide deposition. The developed method of retrieving the emission of radioactive substances makes a useful instrument that operationally estimates and localizes the areas of potential pollution in case of nuclear accidents and could be used for making decisions on the population evacuation.  相似文献   

Analog of the surfaces of zero velocity in the restricted elliptic,parabolic, and hyperbolic three-body problem     

L. G. Luk’yanov 《Astronomy Letters》2010,36(11):823-833

The surfaces of minimum energy have been constructed in the noncircular restricted three-body problem, which are a generalization of the surfaces of zero velocity known in the circular problem. The Hill stability, conditional stability, and instability criteria have been established. Some astronomical applications of the results obtained are considered.  相似文献   

Assessing water quality in Marine Protected Areas from Southern California, USA     

Schiff K  Luk B  Gregorio D  Gruber S 《Marine pollution bulletin》2011,62(12):2780-2786

Despite the regulatory mandate to maintain “natural water quality”, there are ?271 storm drain discharges that potentially threaten the 14 designated marine water quality protected areas in Southern California called Areas of Special Biological Significance (ASBS). After sampling 35 site-events, the geomean concentrations of total suspended solids, nutrients, total and dissolved trace metals, and polycyclic aromatic hydrocarbons in the ocean following storm events were similar between reference drainages and ASBS discharge sites. Concentrations of chlorinated hydrocarbons were nondetectable and no post-storm sample exhibited significant toxicity to the endemic purple sea urchin (Strongylocentrotus purpuratus) near ASBS discharge sites. A reference-based threshold was developed and, despite the similarities in average concentrations, there were some individual ASBS discharge sites that were greater than reference background. Cumulatively across all ASBS, the constituents that were most frequently greater than the reference-based threshold were nutrients and general constituents, followed by dissolved and total trace metals.  相似文献   

Spectral,Photometric, and Dynamic Analysis of Eight Draconid Meteors     

Jiří Borovička  Pavel Koten  Lukáš Shrbený  Rostislav Štork  Kamil Hornoch 《Earth, Moon, and Planets》2014,112(1-4):15-31

A Draconid meteor shower outburst was observed from on board two scientific aircraft deployed above Northern Europe on 8th October 2011. The activity profile was measured using a set of photographic and video cameras. The main peak of the activity occurred around 20:15 ± 0:0.5 UT which is consistent with the model prediction as well as with the IMO network visual observations. The corrected hourly rates reached a value of almost 350. The brighter meteors peaked about 15–20 min earlier than the dimmer ones. This difference can be explained by different directions of the ejection of the meteoroids from the parent comet. One of the instruments was even able to detect meteors connected with the material ejected from the parent comet before 1900 and thus confirmed the prediction of the model, although it was based on uncertain pre-1900 cometary data. Another small peak of the activity, which was caused by material ejected during the 1926 perihelion passage of the parent comet, was detected around 21:10 UT. The mass distribution index determined using the narrow field-of-view video camera was 2.0 ± 0.1. This work shows that the observation of meteor outbursts can constrain the orbital elements, outgassing activity and existence of jets at the surface of a comet.  相似文献   

Origin and geodynamic relationships of the Late Miocene to Quaternary alkaline basalt volcanism in the Pannonian basin,eastern–central Europe     

Szabolcs Harangi  M. Éva Jankovics  Tamás Sági  Balázs Kiss  Réka Lukács  Ildikó Soós 《International Journal of Earth Sciences》2015,104(8):2007-2032

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Lead Isotopic Composition in Biogenic Certified Reference Materials Determined by Different ICP‐based Mass Spectrometric Techniques          下载免费PDF全文

Jana Ďurišová  Lukáš Ackerman  Ladislav Strnad  Vladislav Chrastný  Jan Borovička 《Geostandards and Geoanalytical Research》2015,39(2):209-220

This work presents data for the radiogenic Pb isotopic ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) in nine biogenic certified reference materials (NIST SRM 1515, 1566b, 1570a, 1573a, 1575a; BCR 100, BCR 101, BCR 670 and IAEA 359), which are suitable for analytical quality control in environmental research. The results were obtained using three different types of ICP‐based mass spectrometer (quadrupole‐based/magnetic sector field single‐collector ICP‐MS instruments and a multi‐collector ICP‐MS) and applying different mass bias correction procedures (calibrator‐sample bracketing and external Tl normalisation) with and without Pb separation from the matrix using ion exchange chromatography. In the majority of the samples, the measurements from all three of the ICP‐MS instruments were in agreement within ± 0.1%, despite the lower analytical precision of the single‐collector ICP‐MS instruments. We demonstrate that the presence of the sample matrix did not significantly influence the Pb isotopic ratios measured by magnetic sector field ICP‐MS, whereas the use of the two different mass bias corrections resulted in a systematic difference of 0.09% for the ²⁰⁸Pb/²⁰⁶Pb ratio.  相似文献