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   

Plasma-neutral gas interaction in cosmical physics     

B. Lehnert 《Astrophysics and Space Science》1978,55(1):25-37

The influence of plasma-neutral gas interaction on cosmical phenomena is discussed. with applications to steady and non-steady phenomena in cool interstellar and interplanetary clouds, in the photospheres, chromospheres, prominences and filaments of the Sun and other stars, in the planetary ionospheres, as well as in certain cosmogonical theories Special attention is given to filamentary structures of hot plasmas embedded in cooler regions, and to the internal properties of cool partially ionized clouds.Paper dedicated to Professor Hannes Alfvén on the occasion of his 70th birthday, 30 May, 1978.  相似文献   

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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Alternative validation method of satellite gradiometric data by integral transform of satellite altimetry data     

Michal Šprlák  Eliška Hamáčková  Pavel Novák 《Journal of Geodesy》2015,89(8):757-773

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Quantitative imaging of the Permo‐Mesozoic complex and its basement by frequency domain waveform tomography of wide‐aperture seismic data from the Polish Basin     

Michal Malinowski  Stéphane Operto 《Geophysical Prospecting》2008,56(6):805-825

In this study we present the workflow and results of 2D frequency domain waveform tomography applied to the global‐offset seismic data acquired in central Poland along a 50‐km long profile during the GRUNDY 2003 experiment. The waveform tomography method allows full exploitation of the wide‐aperture content of these data and produces in a semi‐automatic way both the detailed P‐wave velocity model and the structural image (i.e., perturbations in respect to the starting model). Thirteen frequencies ranging from 4 to 16 Hz were inverted sequentially, gradually introducing higher wavenumbers and more details into the velocity models. Although the data were characterised by relatively large shot spacings (1.5 km), we obtained clear images both of the Mesozoic and Permian sedimentary cover. Velocity patterns indicated facies changes within the Jurassic and Zechstein strata. A high velocity layer (ca. 5500 m/s) was found near the base of Triassic (Scythian), which made the imaging of a deeper layer difficult. Nevertheless, we were able to delineate the base of the Permian (i.e., base of the Rotliegend), which was not possible to derive from conventional common‐depth‐point processing, as well as some deeper events, attributed to the Carboniferous. The sub‐Permian events formed a syn‐form which favoured our previous interpretation of a depression filled with Upper Carboniferous molasse. The validity of the waveform tomography‐derived model was confirmed by well‐log data. Forward ray‐tracing modelling and synthetic seismograms calculations provided another justification for the key structures present in the waveform tomography model.  相似文献   

Late quaternary paleogeography of Middle Europe and the Northcentral United States: A framework for comparative studies of prehistoric man-land relationships     

John Bower  Michal Kobusiewicz 《Geoarchaeology》1988,3(2):117-125

The work summarized in this paper is an important component of a larger study concerned with the responses of prehistoric hunting-gathering cultures to long term environmental change. the general approach involves comparing cultural systems and their transformations in Middle Europe and the northcentral United States during the late Pleistocene and early Holocene transition from glacial to interglacial conditions. This paper is specifically aimed at identifying ecological factors that may help account for similarities and differences in the cultural successions on opposite sides of the Atlantic. We conclude that, despite broadly similar environmental histories in both regions, important differences are evident in, for example, trajectories of climatic amelioration. These, together with differences in human demography, can be seen to have contributed toward shaping divergent cultural adaptations in Europe and North America.  相似文献