On the practical stability of the triangular points in the restricted three-body problem

This paper contains a proposal of a new way of treating astrodynamical stability problems. A definition of a practical stability and a direct method of its examination are presented. The method has been applied to the triangular points problem for variety of ande values in the case of the linearized equation system as well as in the general one. The results are shown in a form which facilitates the comparison with results published by other authors.     

WIP: A Web‐based program for indexing planar features in quartz grains and its usage

Planar deformation features (PDFs) in quartz are the most important diagnostic features that allow the unambiguous identification of impact structures on Earth. In order to confirm that these features (that are characterized by planar character and form along specific crystallographic planes) are indeed PDFs, they need to be properly investigated and indexed. Following universal‐stage measurements, the process of indexing is usually performed manually, using a Wulff stereonet and following a strict procedure, which is time consuming and error prone. In this article, we present WIP, a new Web‐based program for indexing planar deformation features in quartz. The correctness of our program is shown by its application to measurements that had previously been indexed manually. The observed minor differences, especially in the absolute frequency percentage of PDFs, are negligible and not significant enough to influence the estimation of shock pressure that could be calculated from the indexed results. Usability of this program is shown using the spatial relationships between a statistically significant number of 278 quartz grains with 409 sets of PDFs analyzed within the area (~35 mm²) of a single thin section of a meta‐greywacke from the Bosumtwi impact structure. Our program is not only more accurate and faster than the manual (graphical) method but also removes the human error from the plotting process and allows control of several parameters, such as the value of estimated measurement error used in the indexing calculation or method of aggregated error handling. The program also provides information about the angles between the planes of the measured PDF sets present in a grain, which allows determination of the angles between (for example) indexed {} and {} sets.     

Temperature and heat flux changes at the base of Laurentide ice sheet inferred from geothermal data (evidence from province of Alberta,Canada)

International Journal of Earth Sciences - Using a previously published temperature log of the 2363-m-deep borehole Hunt well (Alberta, Canada) and the results of its previous interpretation, the...     

Longitudinal asymmetry of craters' density distributions on the icy satellites

Crater's density distribution versus satellitographical longitude was searched for seven icy satellites: two of Jupiter (Ganymede and Callisto) and five of Saturn (Mimas, Tethys, Dione, Rhea and Iapetus). Craters were classified according to their size. Four bins of the craters' diameter were used. Density distributions were found in the longitudinal sectors of the near-equatorial stripes that circumscribe the satellites. The size distributions (R-plots) were done independently for each of the eight longitudinal sectors of the satellites. Searching for the leading/trailing (apex/antapex) and the near-side/far-side asymmetry was done. It was found that the crater density is longitudinally asymmetric for all seven satellites being studied. However, the apex–antapex asymmetry is much less pronounced than predicted by theory of Zahnle et al. (2003), for impacts on the satellites by ecliptic comets. We conclude that the impact craters observed on the considered satellites are mostly originated from planetocentric swarm of debris. In that case longitudinal asymmetry is not expected, as stated by Horedt and Neukum, 1984a, Horedt and Neukum, 1984b. However, cratering longitudinal asymmetry that we observe for Mimas perfectly agrees with calculations of Alvarellos et al. (2005). It is very likely that important part of craters on Mimas were formed due to impacts of ejecta originated from crater Herschel.     

GIS‐based multicriteria decision analysis: a survey of the literature

The integration of GIS and multicriteria decision analysis has attracted significant interest over the last 15 years or so. This paper surveys the GIS‐based multicriteria decision analysis (GIS‐MCDA) approaches using a literature review and classification of articles from 1990 to 2004. An electronic search indicated that over 300 articles appeared in refereed journals. The paper provides taxonomy of those articles and identifies trends and developments in GIS‐MCDA.     

Geosocial gauge: a system prototype for knowledge discovery from social media

The remarkable success of online social media sites marks a shift in the way people connect and share information. Much of this information now contains some form of geographical content because of the proliferation of location-aware devices, thus fostering the emergence of geosocial media – a new type of user-generated geospatial information. Through geosocial media we are able, for the first time, to observe human activities in scales and resolutions that were so far unavailable. Furthermore, the wide spectrum of social media data and service types provides a multitude of perspectives on real-world activities and happenings, thus opening new frontiers in geosocial knowledge discovery. However, gleaning knowledge from geosocial media is a challenging task, as they tend to be unstructured and thematically diverse. To address these challenges, this article presents a system prototype for harvesting, processing, modeling, and integrating heterogeneous social media feeds towards the generation of geosocial knowledge. Our article addresses primarily two key components of this system prototype: a novel data model for heterogeneous social media feeds and a corresponding general system architecture. We present these key components and demonstrate their implementation in our system prototype, GeoSocial Gauge.     

Lithosphere thermal structure at the eastern margin of the Bohemian Massif: a case petrological and geophysical study of the Nied?wied? amphibolite massif (SW Poland)

The crustal section beneath amphibolite Nied?wied? Massif (Fore-Sudetic Block in NE Bohemian Massif), modelled on the basis of geological and seismic data, is dominated by gneisses with subordinate granites (upper and middle crust) and melagabbros (lower crust). The geotherm was calculated based on the chemical analyses of the heat-producing elements in the rocks forming the crust and the measurements of their density and heat conductivity. The results were verified by heat flow calculations based on temperature measurements from 1,600?m deep well in the Nied?wied? Massif and by temperature–depth estimates in mantle xenoliths coming from the nearby ca. 4.5?My basanite plug in Lutynia. The paleoclimate-corrected heat flow in the Nied?wied? Massif is 69.5?mW?m^?2, and the mantle heat flow is 28?mW?m^?2. The mantle beneath the Massif was located marginally relative to the areas of intense Cenozoic thermal rejuvenation connected with alkaline volcanism. This results in geotherm which is representative for lithosphere parts located at the margins of zones of continental alkaline volcanism and at its waning stages. The lithosphere–asthenosphere boundary (LAB) beneath Nied?wied? is located between 90 and 100?km depth and supposedly the rheological change at LAB is not related to the appearance of melt.     

Harvesting ambient geospatial information from social media feeds

Social media generated from many individuals is playing a greater role in our daily lives and provides a unique opportunity to gain valuable insight on information flow and social networking within a society. Through data collection and analysis of its content, it supports a greater mapping and understanding of the evolving human landscape. The information disseminated through such media represents a deviation from volunteered geography, in the sense that it is not geographic information per se. Nevertheless, the message often has geographic footprints, for example, in the form of locations from where the tweets originate, or references in their content to geographic entities. We argue that such data conveys ambient geospatial information, capturing for example, people’s references to locations that represent momentary social hotspots. In this paper we address a framework to harvest such ambient geospatial information, and resulting hybrid capabilities to analyze it to support situational awareness as it relates to human activities. We argue that this emergence of ambient geospatial analysis represents a second step in the evolution of geospatial data availability, following on the heels of volunteered geographical information.     

Sublimation-driven evolution of the local radius and the moment of inertia of a long-period comet

In this paper we intend to analyze how the sublimation of ice from cometary nuclei affects changes of the moments of inertia. Our aim is to show general trends for different orientations of cometary nucleus’ rotation axis. Thus we apply numerical model of a hypothetical homogeneous and initially spherical nucleus composed of water ice and dust. As an example we present simulations for a model comet of the orbital elements and the nucleus size the same as determined for C/1995 O1 Hale-Bopp, a widely analyzed long-period comet. We calculated water production from the nucleus and changes of the shape (initially spherical) and of the moment of inertia versus time. Simulations are performed for the full range (0–90°) of inclinations I of the rotation axis. The second paramater related to the orientation of the rotation axis is the argument Φ (0–360°). The heat conductivity of the nucleus spans over the vast range, 0.04–4 W m⁻¹ K⁻1.