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111.
Collecting marine data during hydroacoustic research surveys is a complex task, which not only consists of measurements but also analysis, validation, and interpretation of information acquired by various sensors. Automatic integration, visualization, and processing of collected data allow for a more precise investigation of the researched phenomena. The paper presents a dedicated Web-based system for fusion and dissemination of data from satellite imagery, hydrological measurements using CTD probes, acoustic surveys by multibeam systems, side-scan sonars and singlebeam echosounders, as well as live radar feed and oil spill spread models. The system has been designed as a tool for supporting research using the aforementioned techniques. 相似文献
112.
113.
In urbanized areas, particularly in lowland terrains and floors of large river valleys, the natural land configuration is often hard to recognize due to a long history of human activity. Accordingly, archaeological works in cities, which supply knowledge on settlement conditions, are usually accompanied by geological and geomophological research. Lately, data from light detection and ranging (LiDAR) have become a valuable source of information on urban land configuration. Geophysical methods are also becoming increasingly popular in background studies. The paper presents a method of using and linking these sources of spatial information about landforms in such areas. The main aim is to identify to what extent these complementary sources of data and the proposed method can be used in such a specific environment to reconstruct natural, buried terrain morphology. The city of Wroc?aw in Central Europe serves as an example. To this end geomorphometric studies were conducted with the use of digital elevation models (DEMs) based on LiDAR scanning and derivated land-surface parameters—SAGA Wetness Index, Channel Network Base Level and Altitude above Channel Network. The study also involved determining morphological edges and measurements of the meanders of the Odra, as well as expanding information on the spatial distribution of alluvia and the structure of slope breaks. To this end, geophysical measurements were conducted using the Two-Dimensional Electrical Resistivity Tomography method. Additionally, five typical sequences of man-made ground present within the perimeter of the city were distinguished. As a result, a map of the main landforms of Wroc?aw is presented. Finally, we argue that although high resolution DEM and derivate land-surface parameters are very useful in terrain analysis, places with thick man-made ground or strongly levelled areas must be recognized by geoarchaeological excavations or geological bore holes. The geophysical survey is useful to identify buried morphological edges and older relief elements in open areas. 相似文献
114.
Smectite suspensions, at low solids contents, are known to be naturally high in volume with diverse structural properties. The changing structural properties of smectite aqueous suspensions in the absence and presence of calcium ions were investigated using an acoustosizer and an advanced cryo-SEM technique to further understand and thereby control their environmental impact.In the absence of Ca(II) ions, smectite particles are present as a colloidally stable sol due to electrical double layer repulsion of the negatively charged platelets. The smectite network is observed to be extended throughout the suspension via clay platelets networking with an edge–edge (EE) orientation due to high basal surface repulsion. After the initial addition of Ca(II) ions, the smectite negative zeta potential reduces and the smectite platelets coagulate forming 2 µm aggregates. The platelets are randomly orientated, lettuce-like, coagulated aggregates with a high presence of both edge–edge (EE) and edge–face (EF) orientations. After equilibration, the smectite platelets forming an orientated honeycomb cellular structure comprised of face–face (FF) multiply sheet aggregates. The voids in the cellular structure are larger than prior to Ca(II) addition, measured at 2–8 µm.The changing structural properties of a smectite suspension in the absence and presence of Ca(II) greatly influence smectite stability and in turn, mineral processing and/or environmental management. Adequate time is required to allow suppression of the initial swelling of the smectite, full Ca(II) exchange and platelet aggregation. 相似文献
115.
While it is well-known that texture can be used to classify very high resolution (VHR) data, the limits of its applicability have not been unequivocally specified. This study examines whether it is possible to divide satellite images into two classes associated with “low” and “high” texture values in the initial stage of processing VHR images. This approach can be effectively used in object-oriented classification. Based on the panchromatic channel of KOMPSAT-2 images from five areas of Europe, datasets with down-sampled pixel resolutions of 1, 2, 4, 8, and 16 m were prepared. These images were processed using different texture analysis techniques in order to discriminate between basic land cover classes. Results were assessed using the normalized feature space distance expressed by the Jeffries–Matusita distance. The best results were observed for images with the highest resolution processed by the Laplacian filter. Our research shows that a classification approach based on the idea of “low” and “high” textures can be effectively applied to panchromatic data with a resolution of 8 m or higher. 相似文献
116.
Marek Gierliski rzej A. Zdziarski Juri Poutanen Paolo S. Coppi Ken Ebisawa W. Neil Johnson 《Monthly notices of the Royal Astronomical Society》1999,309(2):496-512
We present X-ray/ γ -ray spectra of Cyg X-1 observed during the transition from the hard to the soft state and in the soft state by ASCA , RXTE and CGRO /OSSE in 1996 May and June. The spectra consist of a dominant soft component below ∼2 keV and a power-law-like continuum extending to at least ∼800 keV. We interpret them as emission from an optically thick, cold accretion disc and from an optically thin, non-thermal corona above the disc. A fraction f ≳0.5 of total available power is dissipated in the corona.
We model the soft component by multicolour blackbody disc emission taking into account the torque-free inner-boundary condition. If the disc extends down to the minimum stable orbit, the ASCA RXTE data yield the most probable black hole mass of MX ≈10 M⊙ and an accretion rate, , locating Cyg X-1 in the soft state in the upper part of the stable, gas-pressure-dominated, accretion-disc solution branch.
The spectrum of the corona is well modelled by repeated Compton scattering of seed photons from the disc off electrons with a hybrid, thermal/non-thermal distribution. The electron distribution can be characterized by a Maxwellian with an equilibrium temperature of kTe ∼30–50 keV, a Thomson optical depth of τ ∼0.3 and a quasi-power-law tail. The compactness of the corona is 2≲ℓh ≲7, and a presence of a significant population of electron–positron pairs is ruled out.
We find strong signatures of Compton reflection from a cold and ionized medium, presumably an accretion disc, with an apparent reflector solid angle, Ω/2π∼0.5–0.7. The reflected continuum is accompanied by a broad iron K α line. 相似文献
We model the soft component by multicolour blackbody disc emission taking into account the torque-free inner-boundary condition. If the disc extends down to the minimum stable orbit, the ASCA RXTE data yield the most probable black hole mass of M
The spectrum of the corona is well modelled by repeated Compton scattering of seed photons from the disc off electrons with a hybrid, thermal/non-thermal distribution. The electron distribution can be characterized by a Maxwellian with an equilibrium temperature of kT
We find strong signatures of Compton reflection from a cold and ionized medium, presumably an accretion disc, with an apparent reflector solid angle, Ω/2π∼0.5–0.7. The reflected continuum is accompanied by a broad iron K α line. 相似文献
117.
Exact cylindrically-symmetric solutions of Sen equations both with and without the source term in Lyra geometry are presented. It is found that the exterior vacuum solution, when continuously joined to the interior solution describing the uniform density cylinder of finite radius, may represent a cosmic string. The rate of light deflection that is independent of the impact parameter suggests that the solution has the gravitational lensing property, and for typical values of the linear mass density it yields predictions similar to general relativity. 相似文献
118.
Physical evolution of Jupiter family (JF) comets is considered as a simultaneous process of erosion and fading. Dynamical effects are limited to discrete changes of the perihelion distance, that result in changes of the evaporation rate. Assuming that the JF comet population is in a steady state, a distribution function of this population in the two dimensional phase space consisting of radius and active fraction of the nucleus surface is found as the solution of a set of kinetic equations, each one of them for a different perihelion distance. With use of the distribution function some statistical properties of the comet population, like the total number of comets in the considered region of the phase space, the number of objects that evaporate or get dormant per unit time, etc., are obtained. The cumulative distribution function with respect to the absolute brightness is calculated and compared with the observed one as a check on the considered models. 相似文献
119.
120.
Multicolour photometry of the polar AM Her was obtained during 3 observational seasons (1994/95/96). The star was in its high
state for most of the observations. It was in its low state in '96 April. It was established that these two states differ
not only in the average light level but in the larger amplitudes of variations at low state than at high state. Moreover the
energy distributions of the two states differ in the stronger dependence of the flux on ν at high state than at low state.
The Fourier analysis of the photometric data shows variability with the spectroscopic (orbital) period. The amplitudes of
this variability in all colours are about two times bigger at low state than at high state. An attempt to explain the photometric
behaviour of AM Her by a model of dominant emission of two hot spots at the magnetic poles of the white dwarf was made and
the spot parameters were determined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献