Spherical integral formulas for upward/downward continuation of gravitational gradients onto gravitational gradients     

Michal Šprlák  Josef Sebera  Miloš Val’ko  Pavel Novák 《Journal of Geodesy》2014,88(2):179-197

New integral formulas for upward/downward continuation of gravitational gradients onto gravitational gradients are derived in this article. They provide more options for continuation of gravitational gradient combinations and extend available mathematical apparatus formulated for this purpose up to now. The starting point represents the analytical solution of the spherical gradiometric boundary value problem in the spatial domain. Applying corresponding differential operators on the analytical solution of the spherical gradiometric boundary value problem, a total of 18 integral formulas are provided. Spatial and spectral forms of isotropic kernels are given and their behaviour for parameters of a GOCE-like satellite is investigated. Correctness of the new integral formulas and the isotropic kernels is tested in a closed-loop simulation. The derived integral formulas and the isotropic kernels form a theoretical basis for validation purposes and geophysical applications of satellite gradiometric data as provided currently by the GOCE mission. They also extend the well-known Meissl scheme.  相似文献   

How a Sphagnum fuscum‐dominated bog changed into a calcareous fen: the unique Holocene history of a Slovak spring‐fed mire     

Petra Hájková  Ab Grootjans  Mariusz Lamentowicz  Eliška Rybníčková  Mikuláš Madaras  Věra Opravilová  Dierk Michaelis  Michal Hájek  Hans Joosten  Lesław Wołejko 《第四纪科学杂志》2012,27(3):233-243

In general, mires develop by autogenic succession from more groundwater‐fed to more rainwater‐fed. This study from a calcareous mire in the West Carpathians (Slovakia) describes a similar development in the Early Holocene, followed by a reverse development in the Middle and Late Holocene. Pollen, macrofossil and testate amoeba analyses show that the site started as a minerotrophic open fen woodland. After 10 700 cal a BP autogenic succession led to the accumulation of at least 1 m of Sphagnum fuscum peat. Around 9000 cal a BP, as climate could no longer sustain a stable water regime, the bog desiccated and a fire broke out. The fire removed part of the peat layer and as a consequence relative water levels rose, leading to the establishment of a wet minerotrophic swamp carr with Thelypteris palustris, Equisetum sp. and Alnus sp. with extremely slow peat accumulation. After 600 cal a BP, rapid peat accumulation with calcareous tufa formation resumed as a result of anthropogenic deforestation and hydrological changes in the catchment and resulting increased groundwater discharge. At present the mire still hosts a wealth of relict and endangered plant and animal species typical of calcareous fens and fen meadows. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Local Recovery of Sub-Crustal Stress Due to Mantle Convection from Satellite-to-Satellite Tracking Data     

Michal Šprlák  Mehdi Eshagh 《Acta Geophysica》2016,64(4):904-929

Two integral transformations between the stress function, differentiation of which gives the meridian and prime vertical components of the sub-crustal stress due to mantle convection, and the satellite-to-satellite tracking (SST) data are presented in this article. In the first one, the SST data are the disturbing potential differences between twin-satellites and in the second one the line-of-sight (LOS) gravity disturbances. It is shown that the corresponding integral kernels are well-behaving and therefore suitable for inversion and recovery of the stress function from the SST data. Recovery of the stress function and the stress components is also tested in numerical experiments using simulated SST data. Numerical studies over the Himalayas show that inverting the disturbing potential differences leads to a smoother stress function than from inverting LOS gravity disturbances. Application of the presented integral formulae allows for recovery of the stress from the satellite mission GRACE and its planned successor.  相似文献   

High-frequency QPO modulation in neutron-star and black-hole sources     

Michal Bursa   《New Astronomy Reviews》2008,51(10-12):846

After twelve years have past since the discovery of the first high-frequency quasi-periodic oscillation in Sco X-1, an enormous progress has been made on the observational side and on the field of data analysis. Equal amount of effort has been devoted also to the theoretical aspect of the QPO problem. However, so far no model is able to sufficiently fully explain the mechanism of QPO production. There are two aspects: the question of the QPO origin; and the question of its modulation. In this article, I am focusing solely on the second issue – I discuss ways of how the outgoing flux can be modulated at a level sufficient to match the observational rms amplitudes. Some more space is devoted to my own work in the field.  相似文献   

Analysis of thunderstorm and lightning activity associated with sprites observed during the EuroSprite campaigns: Two case studies     

Serge Soula  Oscar van der Velde  Joan Montany  Torsten Neubert  Olivier Chanrion  Michal Ganot 《Atmospheric Research》2009,91(2-4):514-528

During the summers of 2003 to 2006 sprites were observed over thunderstorms in France by cameras on mountain tops in Southern France. The observations were part of a larger coordinated effort, the EuroSprite campaigns, with data collected simultaneously from other sources including the French radar network for precipitation structure, Meteosat with images of cloud top temperature and the Météorage network for detection of cloud-to-ground (CG) flash activity. In this paper two storms are analyzed, each producing 27 sprite events. Both storms were identified as Mesoscale Convective Systems (MCS) with a trailing stratiform configuration (ST) and reaching a maximum cloud area of ~ 120,000 km². Most of the sprites were produced while the stratiform area was clearly developed and during periods of substantial increase of rainfall in regions with radar reflectivity between 30 and 40 dBZ. The sprite-producing periods followed a maximum in the CG lightning activity and were characterized by a low CG flash rate with a high proportion of + CG flashes, typically around 50%. All sprites were associated with + CGs except one which was observed after a − CG as detected by the Météorage network. This − CG was estimated to have − 800 C km charge moment change. The peak current of sprite-producing + CG (SP + CG) flashes was twice the average value of + CGs and close to 60 kA with little variation between the periods of sprite activity. The SP + CG flashes were further characterized by short time intervals before a subsequent CG flash (median value < 0.5 s) and with clusters of several CG flashes which suggest that SP + CG flashes often are part of multi-CG flash processes. One case of a lightning process associated with a sprite consisted of 7 CG flashes.  相似文献   

Field Test of Enhanced Remedial Amendment Delivery Using a Shear‐Thinning Fluid          下载免费PDF全文

Michael J. Truex  Vince R. Vermeul  David T. Adamson  Mart Oostrom  Lirong Zhong  Rob D. Mackley  Brad G. Fritz  Jake A. Horner  Tim C. Johnson  Jonathan N. Thomle  Darrell R. Newcomer  Chris D. Johnson  Michal Rysz  Tom W. Wietsma  Charles J. Newell 《Ground Water Monitoring & Remediation》2015,35(3):34-45

Heterogeneity of hydraulic properties in aquifers may lead to contaminants residing in lower‐permeability zones where it is difficult to deliver remediation amendments using conventional injection processes. The focus of this study is to examine use of a shear‐thinning fluid (STF) to improve the uniformity of remedial amendment distribution within a heterogeneous aquifer. Previous studies have demonstrated the significant potential of STFs for improving remedial amendment delivery in heterogeneous aquifers, but quantitative evaluation of these improvements from field applications is lacking. A field‐scale test was conducted that compares data from successive injection of a tracer in water followed by injection of a tracer in an STF to evaluate the impact of the STF on tracer distribution uniformity in the presence of permeability contrasts within the targeted injection zone. Data from tracer breakthrough at multiple depth‐discrete monitoring intervals and electrical resistivity tomography (ERT) showed that inclusion of STF in the injection solution improved the distribution of the injected fluid within the targeted treatment zone. One improvement was a reduction in the movement of injected fluids through high‐permeability pathways, as evidenced by slower breakthrough of tracer at monitoring locations where breakthrough in baseline tracer‐only injection data was faster. In addition, STF‐amended injection solutions arrived faster and to a greater extent in monitoring locations within low‐permeability zones. ERT data showed that the STF injection covered a higher percentage of a two‐dimensional cross section within the injection interval between the injection well and a monitoring well about 3 m away.  相似文献   

Port engineering: 3rd edition,by P. Bruun. Gulf Publishing Company,Houston, 1981, xi + 787 pp., US $79.95.     

J.B. Herbich 《Coastal Engineering》1985,9(1):99

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Application of Tracking Technologies to the Study of Pedestrian Spatial Behavior*     

Noam Shoval  Michal Isaacson 《The Professional geographer》2006,58(2):172-183

Research into human spatial behavior has tended to rely solely on evidence provided by the research subjects themselves. Subjects' accounts of where they were and for how long were logged and integrated into time‐space diaries. In the past few years, a number of studies have exploited advanced tracking technologies instead of the traditional diary technique, however these were mostly transport studies focusing on vehicular movement. This article explores the implementation of tracking technologies as a tool for gathering data on pedestrian spatial behavior. The article considers two of the principal tracking technologies available today: satellite navigation systems and land‐based navigation systems. The makeup and properties of each technology are detailed, and their potential as data‐gathering tools on pedestrian spatial behavior is evaluated.  相似文献   

Power-law spectra of 1–2 GHz narrowband dm-spikes   总被引：3，自引：0，他引：3  

Karlický  Marian  Jiřička  Karel  Sobotka  Michal 《Solar physics》2000,194(1):165-174

Twelve examples of clouds of narrowband dm-spikes, observed by the Ondejov radiospectrograph in the 1–2 GHz frequency range, are analyzed. After transforming of the frequency scales to heights in the solar atmosphere, the indices of the power-law power spectra are determined. The derived power-law indices are scattered in a broad range of values (–0.80––2.85). In some cases they considerably deviate from the previously found value of –5/3. A change of the power-law index above logk2.5 was also found in some cases. In the two longest events the time evolution of their power spectra as well as their indices were studied. While in most parts of the radio spectra the spectral index remains constant, in one part its absolute value increases with the spike intensity increase. Finally, the results, especially the broad range of power-law indices, are briefly discussed.  相似文献   

Passive Seismic Structure Imaging of a Coal Mine by Ambient Noise Seismic Interferometry on a Dense Array     

GU Ning  Michal CHAMARCZUK  GAO Ji  Michal MALINOWSKI  ZHANG Haijiang 《《地质学报》英文版》2021,95(Z1):37-39

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