<p>The Geologic <i>TimeScale Creator </i>(TSCreator) project has compiled a range of paleo-environmental and bio-diversity data which provides the opportunity to explore origination, speciation and extinction events. My PhD research has four major interconnected themes which include the visualization methods of evolutionary tree and the impacts of climate change on the evolution of life in longer and shorter timeframes: <b>(1) </b>Evolutionary range data of planktonic foraminifera and nannofossils over the Cenozoic era have been updated with our latest geological timescale. These evolutionary ranges can be visualized in the form of interactive, extensible evolutionary trees and can be compared with other geologic data columns. <b>(2) </b>A novel approach of integrating morphospecies and lineage trees is proposed to expand the scope of exploration of the evolutionary history of microfossils. It is now possible to visualize morphological changes and ancestor-descendant lineage relationships on TSCreator charts which helps mutual learning of these species based on genetic and bio-stratigraphic studies. <b>(3) </b>These evolutionary datasets have been used to analyze semi-periodic cycles in the past bio-diversity and characteristic rates of turnover. Well-known Milankovitch cycles have been found as the drivers of fluctuations in the speciation and extinction processes. <b>(4) </b>Within a shorter 2000-year time period, global cooling events might have been a factor of human civilization turnover. Using our regional and global cultural turnover time series data, the effect of climate change on human culture has been proposed. The enhancement of the evolutionary visualization system accomplished by this research will hopefully allow academic and non-academic users across the world to research and easily explore Earth history data through publicly available TSCreator program and websites. </p>

Diese Arbeit beschäftigt sich mit den besonderen elektronischen Eigenschaften der Übergangsmetall-Aluminide. In Anlehnung an die Quasikristalle und ihre Approximanten zeigt sich, dass selbst Materialien mit kleinen Einheitszellen die gleichen überraschenden Effekte aufweisen. So gibt es unter den Übergangsmetall-Aluminiden auch semimetallische und halbleitende Verbindungen, auch wenn sie aus klassisch-metallischen Komponenten wie Fe, Al oder Cr bestehen. Diese Eigenschaften sind außerdem mit einem tiefen Pseudogap bzw. Gap in der Zustandsdichte und starken kovalenten Bindungen gekoppelt. Bindungen werden im Rahmen dieser Arbeit durch zwei wesentliche Eigenschaften beschrieben. Erstens durch die Bindungsladung und zweitens durch die energetische Auswirkung der Bindung. Es ergibt sich, dass im Fall halbleitender Übergangsmetall-Aluminide zum einen eine Sättigung von bestimmten Bindungen, wie auch ein bindungs-antibindungs-Wechsel bei der Fermi-Energie vorliegt. Mit der Analyse der Nahordnung in Form der sogenannten lokalen Koordinationspolyeder ist es gelungen, eine einfache Regel für Halbleiter aufzustellen, die Fünffachkoordination für Al. Diese Regel besagt, dass Aluminium-Atome mit ihren drei Valenzelektronen nicht in der Lage sind, mehr als fünf gesättigte Bindungen zu ihren nächsten Übergangsmetall-Nachbarn aufzubauen. In exzellenter Übereinstimmung mit den in Annahme gleichartiger Bindungen theoretisch vorhergesagten Bindungswinkel ergibt sich, dass alle binären Übergangs-Aluminid-Halbleiter für die Al-Atome die gleiche Nahordnung aufweisen. Typische Werte für spezifische Widerstände der untersuchten Materialien bei Raumtemperatur liegen im Bereich von einigen 100µOhm cm, was weit größer ist als einige 10µOhm cm wie im Fall der unlegierten Metalle. Überraschend ist außerdem eine hohe Transportanisotropie mit einem Verhältnis der spezifischen Widerstände bis zu 3.0. Eine wesentliche Errungenschaft der Arbeit kann in der Verknüpfung der Eigenschaft des elektronischen Transports und der Bindungseigenschaften gesehen werden. Die geringen Leitfähigkeiten konnten durch geringe Werte in der Zustandsdichte (DOS) und einem bei gleicher Energie stattfindenden bindungs-antibindungs-Wechsel erklärt werden.

The interplay between different self-organized electronically ordered states and their relation to unconventional electronic properties like superconductivity constitutes one of the most exciting challenges of modern condensed matter physics. In the present thesis this issue is thoroughly investigated for the prototypical layered material 1T-TaS2 both experimentally and theoretically. At first the static charge density wave order in 1T-TaS2 is investigated as a function of pressure and temperature by means of X-ray diffraction. These data indeed reveal that the superconductivity in this material coexists with an inhomogeneous charge density wave on a macroscopic scale in real space. This result is fundamentally different from a previously proposed separation of superconducting and insulating regions in real space. Furthermore, the X-ray diffraction data uncover the important role of interlayer correlations in 1T-TaS2. Based on the detailed insights into the charge density wave structure obtained by the X-ray diffraction experiments, density functional theory models are deduced in order to describe the electronic structure of 1T-TaS2 in the second part of this thesis. As opposed to most previous studies, these calculations take the three-dimensional character of the charge density wave into account. Indeed the electronic structure calculations uncover complex orbital textures, which are interwoven with the charge density wave order and cause dramatic differences in the electronic structure depending on the alignment of the orbitals between neighboring layers. Furthermore, it is demonstrated that these orbital-mediated effects provide a route to drive semiconductor-to-metal transitions with technologically pertinent gaps and on ultrafast timescales. These results are particularly relevant for the ongoing development of novel, miniaturized and ultrafast devices based on layered transition metal dichalcogenides. The discovery of orbital textures also helps to explain a number of long-standing puzzles concerning the electronic self-organization in 1T-TaS2 : the ultrafast response to optical excitations, the high sensitivity to pressure as well as a mysterious commensurate phase that is commonly thought to be a special phase a so-called “Mott phase” and that is not found in any other isostructural modification.

Im Rahmen des Bundesxzellenzclusters MERGE EXC 1075 an der TU Chemnitz erfolgte die Entwicklung einer neuartigen großserientauglichen Technologie zur Herstellung faserverstärkter Thermoplastbauteile. Für die Demonstration der Technologie wurde eine Pilotanlage realisiert, die zum Ablegen des Thermoplasttapes über eine Verlegeeinheit – einen sog. Tapelegekopf – verfügt. Mit Abschluss des Legeprozesses wird das Halbzeug, das aus einer angebremsten Spule abgezogen wird, abgeschnitten und der Prozess wird von neuem begonnen. Für das Schneiden des Materials haben Voruntersuchungen gezeigt, dass konturierte Klingen erforderlich sind, um ein Verlaufen des Bandes zu vermeiden. Darüber hinaus hat sich als zweckmäßig erwiesen eine zusätzliche Fixierung vorzunehmen. Dies verbessert die Schnittqualität und Zuverlässigkeit des Systems. Aufgrund enger Bauraumrestriktionen wurde entschieden die Schneidbewegung und das Fixieren zwangläufig synchronisiert auf einen Antrieb zurück zu führen. Hierfür wurden zwei ungleichmäßige Rastgetriebe synthetisiert, ausgelegt sowie in weiteren Entwicklungsstufen auskonstruiert, gefertigt und getestet. Mit der Inbetriebnahme des Gesamtanlagensystems erfolgte ebenfalls der Funktionsnachweis dieses mechanisch zwangläufigen Schneidsystems, das im Rahmen des Vortrags vorgestellt wird. Diese Arbeiten entstanden im Rahmen des Bundesexzellenzclusters EXC 1075 „Technologiefusion für multifunktionale Leichtbaustrukturen“ und wurde von der Deutschen Forschungsgemeinschaft gefördert. Die Autoren danken für die finanzielle Unterstützung.

CHARLES UNIVERSITY FACULTY OF SOCIAL SCIENCES Institute of Political Studies Department of International Security Studies Contemporary Challenges of Space Debris Removal: Overview and Outlook Abstract in English Author: Eliška Vojáková Study programme: Security Studies Supervisor: Mgr. Bohumil Doboš, Ph.D. Year of the defence: 2021 Abstract The sustainability of the outer space environment is necessary for all actors to execute all existing and future human space operations safely. While the severe negative consequences of the uncontrolled space debris population are not new, government agencies and intergovernmental organizations' initiatives to lessen the predicament continue to be insufficient. Scientific research and simulation models show that mere mitigation measures cannot stop the ongoing degradation of the outer space environment polluted from the past space missions. Instead, research supports the development of space projects designed with a primary objective to remove debris from space. National administrations attempt to cooperate at the international level to formulate uniform debris mitigation standards and hold each other mutually accountable for worsening the space debris situation. However, joint public international missions to actively remove debris remain unthinkable. The privatization...

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<p>The present-day sedimentary rock record on Mars provides insights into the early surface and subsurface geologic processes. Understanding the sediment characteristics in different environments can help to constrain the climate regimes, potential for habitability, and provide a record of ancient surface processes. The research presented in this dissertation uses complementary remote sensing techniques and datasets from rovers at the surface, satellites in orbit, and at terrestrial analogs that are relevant to current Mars exploration to better characterize alteration through water-rock alteration at multiple scales.</p><p>The martian field site for this work is Mt. Sharp, a 5-kilometer-high mountain in Gale crater that is predominantly composed of fluviolacustrine strata overlain by aeolian strata. At the rover-scale, the effects of large clay-mineral rich deposits were characterized using landscape- and hand lens-scale visible images from the Mastcam and MAHLI instruments, and multispectral visible/near-infrared images from Mastcam (445-1013 nm). Detailed analysis of the observed textures and spectral properties showed that the clay-rich deposits preserve the early surface environment, based on their lack of diagenetic features. While the regions immediately surrounding the clay-rich deposit experienced prolonged exposure to water, leading to enhanced alteration zones, and destroying characteristics from the early environment but providing insight into later water-rock processes.</p><p>At the orbital-scale, three visually distinct, dark-toned, and erosion-resistant layers were mapped and characterized using visible to short wave infrared hyperspectral (700-2650 nm) and image data. Two of these units have been identified as either aeolian or lacustrine through in situ rover investigations and the third unit will not be explored in situ so its origin can only be constrained through orbital analyses. We conducted a comparison of the morphological and spectral properties of the two known units to constrain whether their respective environments can be differentiated from orbit and apply this knowledge to the unknown third unit. The composition of all three units is similar, dominated by mafic minerals, suggesting a similar sediment source. The morphology is distinct between the lacustrine and aeolian units, with the unknown unit having similar morphology as the lacustrine unit, suggesting similar environments. We propose that the lacustrine unit in this study likely represent short-timescale transitions between wet and dry environments, where mafic sands are exposed to water prior to burial and lithification. While in the aeolian unit, most water-rock interactions occur upon lithification and later diagenesis. This has climatic implications in terms of the presence of surface water as these units were deposited as part of the original Mt. Sharp strata (i.e., the lacustrine unit) while some mantling existing topography (i.e., the aeolian and unknown units), representing similar processes but at a much later time.</p><p>The terrestrial analog field site for this dissertation was conducted in Iceland which represents a cold and wet/icy climate. We characterized sediments produced through glaciovolcanism and how they are sorted and altered through transport from source to sink along to characterize unique identifiers of glaciovolcanism that can be determined with Mars-relevant techniques. Decorrelation stretched visible images and lab visible/near-infrared reflectance and thermal-infrared emission data sets (400-2500 nm and 1200-400 cm-1, respectively) show that it is possible to differentiate sediments from glaciovolcanic and subaerial volcanic systems. In some glaciovolcanic systems, a high glass abundance (50-90 %) is observed in sediment grains due to the erosion of hyaloclastite and hyalotuff, deposits that form in water- and ice-magma interactions. These glass grains did not readily breakdown physically or chemically during transport, suggesting that they could still be observed on the martian surface today and be used to identify possible glaciovolcanic deposits.</p><p>The research described in this thesis improves the understanding of different geologic environments using remote sensing techniques and their climatic implications. This will help to better constrain early environments on Mars and identify areas where water may have been present through the rock record, as observed from the surface and from orbit.</p>

No description available.

This paper describes the changes made from Cal Poly’s initial railgun system, the Mk. 1 railgun, to the Mk. 1.1 system, as well as the design, fabrication, and testing of a newer and larger Mk. 2 railgun system. The Mk. 1.1 system is developed as a more efficient alteration of the original Mk. 1 system, but is found to be defective due to hardware deficiencies and failure, as well as unforeseen efficiency losses. A Mk. 2 system is developed and built around donated hardware from the Naval Postgraduate School. The Mk. 2 system strove to implement an efficient, augmented, electromagnetic railgun and projectile system capable of firing an approximate 1g aluminum projectile to speeds exceeding 2 km/s. A novel three part projectile is proposed to mitigate rail and projectile degradation. Projectile and sabot system kinematic equations are derived and the projectile is designed and tested along with Mk. 2 barrel. A numerical electromechanical model is developed to predict the performance of the Mk. 2 system and projectile assembly, and predicts a final velocity for the fabricated system exceeding 3.5 km/s and an efficiency as high as 24%. Testing of the Mk. 2 system showed catastrophic failure of the projectile during initial acceleration, resulting in very short acceleration times and distance, low velocity projectiles, and low efficiencies. During further testing of various projectile configurations, the barrel structure failed due to a large internal arc. Future work for the Mk. 2 system is discussed, a revised external barrel structure suggested, and a solid, more conventional solid chevron projectile design suggested.

Quantum chemical calculations at BP86/TZVPP//BP86/SVP have been carried out for the Nheterocylic carbene and analogues complexes (tetrylene) [(CO)4W-NHE] (W4-NHE) with E = C – Pb. The tetrylene complexes W4-NHE possess end-on-bonded NHE ligands (E = C, Si), while for E = Ge and Sn, they possess slightly side-on-bonded ligands. The strongest side-on-bonded ligand when E = Pb has a bending angle of 102.9°. The trend of the bond dissociations energies (BDEs) for the W-E bond is W4-NHC > W4-NHSi > W4-NHGe > W4-NHSn > W4-NHPb. Analysis of the bonding situation suggests that the NHE ligands in W4-NHE are strong σ-donors and weak π-donors. This is because the tetrylenes have only one lone-pair orbital available for donation. The polarization of the W-E bond and the hybridization at atom E explain the trend in the bond strength of the tetrylene complexes W4-NHE. The W-E bonds of the heavier systems W4-NHE are strongly polarized toward atom E giving rise to rather weak electrostatic attraction with the tungsten atom which is the main source for the decreasing trend of the bond energies. The theoretical calculations suggest that transition-metal complexes tetrylenes [(CO)4W-{NHE}] (E = C – Pb) should be synthetically accessible compounds with tetrylenes NHE act as two-electron-donor ligands in complexes. / Phân tích cấu trúc và bản chất liên kết hóa học của hợp chất với kim loại chuyển tiếp chứa phối tử N-heterocyclic carbene và các đồng đẳng (tetrylene) [(CO)4W–NHE] (W4-NHE) với E = C – Pb sử dụng tính toán hóa lượng tử ở mức BP86/TZVPP//BP86/SVP. Cấu trúc của phức W4-NHE cho thấy các phối tử NHE với E = C, Si tạo với phân tử W(CO)4 một góc thẳng α = 180,0°, trong khi đó các phức W4-NHE thì phối tử NHE với E = Ge – Pb tạo liên kết với nhóm W(CO)4 một góc cong α < 180,0° và góc cong càng trở nên nhọn hơn khi E = Pb (α = 102.9°). Năng lượng phân ly liên kết của liên kết W-E giảm dần: W4-NHC > W4-NHSi > W4-NHGe > W4-NHSn > W4-NHPb. Tính toán hóa lượng tử trong phức [(CO)4W-{NHE}] (E = C – Pb) cho thấy phối tử tetrylene là chất cho electron. Điều này có thể do phối tử tetrylene chỉ giữ lại một cặp electron tại nguyên tử E để đóng vai trò là chất cho điện tử. Độ bền liên kết của phức W4-NHE được giải thích nhờ vào độ phân cực của liên kết W-E và sự lai hóa của nguyên tử trung tâm E. Nguyên nhân chính làm giảm dần năng lượng liên kết là do liên kết W-E của các phức nặng hơn W4-NHE bị phân cực mạnh về phía nguyên tử E dẫn đến lực hút tĩnh điện với nguyên tử W yếu dần. Hệ phức nghiên cứu được coi là hợp chất điển hình cho các nghiên cứu thực nghiệm.