Reflectance Spectra of Seven Lunar Swirls Examined by Statistical Methods : A Space Weathering Study

Higher magnetic field in lunar swirls is believed to deflect majority of incoming charged particles away from the lunar-swirl surfaces. As a result, space weathering inside and outside swirls should be different. We wanted to evaluate these differences, therefore we have examined seven swirl areas on the Moon (four mare and three highland swirls). We applied the Modified Gaussian Model to statistical sets of the Moon Mineralogy Mapper spectra. Using Principal Component Analysis (PCA), we were able to distinguish the old (weathered) material from both the fresh crater and swirl materials. The swirls did not follow the same behavior as the fresh material, nor were they fully separable. Additionally, we could distinguish between the mare and highland swirls (mare/highland dichotomy) based on the PCA and histogram plots of the albedo and strength of the 1000-nm absorption band. The mare/highland dichotomy can partially be caused by different FeO content in maria and highlands, which points to the existence of a threshold value that changes the spectral evolution due to space weathering. Slope behavior seemed to be dependent on whether the swirl was on the near- or far-side of the Moon, likely due to shielding of lunar nearside by Earth's magnetotail. Our results thus favor the solar wind stand-off hypothesis in combination with the fine dust transport hypothesis and point to the fact that micrometeoroid impacts generally do not reproduce the same weathering trends as all the space weathering effects together.Peer reviewe

Sub-surface alteration and related change in reflectance spectra of space-weathered materials

Context. Airless planetary bodies are studied mainly by remote sensing methods. Reflectance spectroscopy is often used to derive their compositions. One of the main complications for the interpretation of reflectance spectra is surface alteration by space weathering caused by irradiation by solar wind and micrometeoroid particles. Aims. We aim to evaluate the damage to the samples from H+ and laser irradiation and relate it to the observed alteration in the spectra. Methods. We used olivine (OL) and pyroxene (OPX) pellets irradiated by 5 keV H+ ions and individual femtosecond laser pulses and measured their visible (VIS) and near-infrared (NIR) spectra. We observed the pellets with scanning and transmission electron microscopy. We studied structural, mineralogical, and chemical modifications in the samples. Finally, we connected the material observations to changes in the reflectance spectra. Results. In both minerals, H+ irradiation induces partially amorphous sub-surface layers containing small vesicles. In OL pellets, these vesicles are more tightly packed than in OPX ones. Any related spectral change is mainly in the VIS spectral slope. Changes due to laser irradiation are mostly dependent on the material's melting temperature. Of all the samples, only the laser-irradiated OL contains nanophase Fe particles, which induce detectable spectral slope change throughout the measured spectral range. Our results suggest that spectral changes at VIS-NIR wavelengths are mainly dependent on the thickness of (partially) amorphous sub-surface layers. Furthermore, amorphisation smooths micro-roughness, increasing the contribution of volume scattering and absorption over surface scattering. Conclusions. Soon after exposure to the space environment, the appearance of partially amorphous sub-surface layers results in rapid changes in the VIS spectral slope. In later stages (onset of micrometeoroid bombardment), we expect an emergence of nanoparticles to also mildly affect the NIR spectral slope. An increase in the dimensions of amorphous layers and vesicles in the more space-weathered material will only cause band-depth variation and darkening.Peer reviewe

Selected problems of parallel computer graphics: technical report no. DCSE/TR-2004-02

This thesis gives an overview of parallel techniques used in co mputer graphics. It investigates the problems of work distribution, load balancing, communication traffic reduction and merging of subsolutions. These problems a re discussed in the relation to parallel rendering, the representative of tradition al computer graphics, and the Delaunay triangulation, the representative of the compu tational geometry. The description is illustrated by numerous examples. This thesis also proposes several new parallel algorithms for the construction of Delaunay triangulation suitable for architectures with several processors and the shared memory. The proposed solution was tested and the results are summarized in this thesis. Preliminary proposal of some algorithms suitable for cluster architectures is given in the final part of the thesis

The Relationship between the Apostles Peter and Paul on the Backround of the Early Church History

Katedra biblických věd a starých jazykůDepartment of Biblical Sciences and ancient languagesKatolická teologická fakultaCatholic Theological Facult

Design and Implementation of Interface of "Projects" Module

Práce popisuje vytvoření modulu Projekty do redakčního systému OpenCMS, napsaného v programovacím jazyce Java. Součástí modulu je i možnost získávání a importu dat z jiných systémů používaných na Západočeské univerzitě. Modul bude nasazen jako součást nových webových stránek Katedry informatiky a výpočetní techniky a bude sloužit pro správu projektů na této katedře a k jejich následnému zobrazení návštěvníkovi webových stránek.Katedra informatiky a výpočetní technikyObhájenoThe purpose of this bachelor thesis is to develop the plugin Projects into the content management system OpenCMS in the programming language Java. As a part of the plugin is also possibility to gather and to import data from other information systems used at the University of West Bohemia in Pilsen. This plugin will be deployed as a part of the web pages at the Department of Computer Science and Engineering. The plugin will serve for managing projects at the department and presentation of this projects to public at the departments web pages

Rychlá a realistická metoda virtuálního modelování svalů

Tento článek popisuje simulaci pohybu svalů v reálném čase, která je založena na inverzní kinematice, kde je apriorní umístění kosti známé a tvar svalu je počítán metodou pozičně orientované dynamiky (PBD). Metoda je srovnatelná a konkurenceschopná s již existujícími metodami, navíc je vylepšena o některé nové vlastnosti, jako je respektování svalové anizotropie, rychlá detekce kolize atd. Výsledná svalová deformace v reálném čase je ve většině případů vizuálně věrohodná.This paper describes a real-time simulation of muscle movement that is based on inverse kinematics where bone placement is known apriori and muscle shape is calculated by a modified position-based dynamics (PBD) method. The method is comparable and competitive with the others, moreover, it is enhanced with some novel features like approach for respecting muscle anisotropy, really fast simplistic collision detection, etc. This real-time simulation presents visual plausibility of resulting muscle deformation in most cases

Automatické generování 3D geometrie složitých svalů pro personalizované muskuloskeletální modely

Geometrickou reprezentaci svalů ve výpočetních modelech muskuloskeletálního systému typicky představuje série úseček, jejichž anatomie je založena na měřeních provedených na několika málo kadaverických studií, což omezuje možnosti personalizace a posouzení geometrických modelů svalů. Pro překonání tohoto metodologického omezení navrhujeme novou, plně automatickou techniku, která z geometrie povrchu svalu a jeho úponových oblastí dokáže vygenerovat libovolný počet tzv. line of action (vláken) tvořených uživatelsky definovaným počtem úseků. Tato vlákna mohou být začleněna do standardních muskuloskeletálních modelů a využita v biomechanických simulacích. Tato metodologie byla aplikována na čtyři svaly v okolí kyčelního kloubu (iliacus, psoas, gluteus maximus a gluteus medius), extrahovaných z MRI snímků kadavera, pro které byly vytvořeny vysoce diskretizované reprezentace a použity pro simulaci funkčních úloh. Momenty sil jednotlivých vláken byly validovány vůči měřením a modelům stejných svalů z literatury se slibnými výsledky. Lze proto očekávat, že navržený přístup zlepší anatomické reprezentace kosterních svalů v personalizovaných biomechanických modelech a aplikacích FE.The geometrical representation of muscles in computational models of the musculoskeletal system typically consists of a series of line segments. These muscle anatomies are based on measurements from a limited number of cadaveric studies that recently have been used as atlases for creating subject-specific models from medical images, so potentially restricting the options for personalisation and assessment of muscle geometrical models. To overcome this methodological limitation, we propose a novel, completely automated technique that, from a surface geometry of a skeletal muscle and its attachment areas, can generate an arbitrary number of lines of action (fibres) composed by a user-defined number of straight-line segments. These fibres can be included in standard musculoskeletal models and used in biomechanical simulations. This methodology was applied to the surfaces of four muscles surrounding the hip joint (iliacus, psoas, gluteus maximus and gluteus medius), segmented on magnetic resonance imaging scans from a cadaveric dataset, for which highly discretised muscle representations were created and used to simulate functional tasks. The fibres' moment arms were validated against measurements and models of the same muscles from the literature with promising outcomes. The proposed approach is expected to improve the anatomical representation of skeletal muscles in personalised biomechanical models and finite element applications