Technische Universität Bergakademie Freiberg: Qucosa
Not a member yet
1431 research outputs found
Sort by
Socially aware robot navigation: Evaluating the impact of human field of view
No full textThis paper presents a concept for socially aware robot navigation with a focus on avoiding the human field of view (FOV). The aim is to improve user acceptance, minimize hu- man discomfort and reduce impairment of concentration in the workplace, aspects often measured through subjective comfort and distraction metrics. For this purpose, a navigation concept is developed that integrates the human viewing direction into a costmap for navigation. Three different ways of modeling the environment around a human are implemented and then tested for comparison. The implementation for ROS2 is tested with a real robot, the Husky A200, equipped with the ZED2i camera. The concept and each variant are tested with test persons in a realistic working environment and evaluated in a user study. The results show a slight improvement in socially aware navigation by integrating the viewing areas into a costmap
Management of a quarry, waste stockpile & surrounded forests to a sustainable CO2 sink and biodiverse ecosystem: A guideline for a mining company in the alpine region
Full text linkThis study focuses on the environmental impacts of quarrying and emphasizes sustainable land management to mitigate greenhouse gas emissions and support biodiversity. It aligns with the Paris Agreement and Sustainable Development Goals (SDGs), focusing on responsible resource extraction and ecosystem restoration. Key legislation, such as the Mineral Resources Act and EU Nature Restoration Law, guides sustainable practices for habitat conservation. After quarrying, land is rehabilitated through recultivation (for agricultural or forestry use) or renaturation (restoring natural ecosystems). Forests, especially in Austria, are highlighted for their significant role in carbon sequestration. Management approaches like proforestation, reduced-impact logging, and “Proforestation Light” maximize carbon storage and biodiversity. Biodiversity monitoring assesses the health of ecosystems affected by quarrying, with restored sites benefiting both climate and ecological stability. The study uses advanced methods, including terrestrial laser scanning and ArcGIS, to analyze quarry and forest data, enabling accurate CO₂ sequestration calculations. The OMYA quarry case study illustrates how reclaimed lands can enhance carbon absorption and support biodiversity. Overall, rehabilitated quarries can contribute to climate goals and sustainable development when managed with a focus on ecological health.:I. TABLE OF CONTENTS
1 INTRODUCTION XII
1.1 DANKSAGUNG XII
1.2 MOTIVATION 1
1.3 RESEARCH QUESTIONS 3
1.4 DESIGN OF THE STUDY 4
1.5 GREENHOUSE GASES & THE GREENHOUSE EFFECT 5
1.6 THE PARIS AGREEMENT & THE SUSTAINABLE DEVELOPMENT GOALS 7
1.7 LEGISLATION 9
1.7.1 Mineral Resources Act 9
1.7.2 Fauna Flora Habitat Directive 10
1.7.3 Nature Conservation Act 11
1.7.4 The Forest Act 13
1.7.5 EU Nature Restoration Law 14
1.8 RECULTIVATION, RENATURATION & OPEN PIT MINING 16
1.8.1 Recultivation 17
1.8.2 Renaturation 17
1.8.3 Usage forms of former quarries 18
1.8.4 Open Pit Mining 20
1.8.4.1 Advantages & Disadvantages of open pit mining 21
1.8.4.2 Waste rock dumps & backfillings 25
1.9 FORESTS & FOREST MANAGEMENT APPROACHES 27
1.9.1 Forests in Austria 27
1.9.2 Different Tree Types in Austria 27
1.9.3 CO₂ sequestration of forests 38
1.9.4 Forest Restoration 38
1.9.5 Sustainable Forest Management 40
1.9.6 Proforestation 42
1.9.7 Reduced Impact Logging 45
1.9.8 Ecosystem Reclamation Approach 45
1.9.9 The “Proforestation Light” approach 47
1.10 BIODIVERSITY 50
1.10.1 Biodiversity Monitoring 50
1.10.2 Relationship between Biodiversity & Quarries 54
2 RESEARCH METHODOLOGY 55
2.1 TERRESTRIAL LASER SCANNING 56
2.2 METHODOLOGY OF LASER SCAN IN THE CASE STUDY QUARRY 57
2.2.1 ArcGIS 66
2.2.2 Sampling 68
2.3 THE CO₂ CALCULATION 73
2.4 CARBON SEQUESTRATION POTENTIAL OF OMYAS FORESTS 76
3 THE CASE STUDY 79
3.1 OMYA – QUARRY & SURROUNDINGS 79
3.2 RESEARCH QUESTIONS & CONCLUSION 85
3.2.1 Research Question 1 85
3.2.2 Research Question 2 87
3.2.3 Research Question 3 90
3.2.4 Research Question 4 92
3.2.5 Research Question 5 93
3.2.6 Conclusion 97
4 SOURCE DIRECTORY 100
5 APPENDIX 10
Swelling behavior of expansive geomaterials: Finite element and machine learning approaches
No full textThis thesis presents a collection of research related to the application of numerical modeling and machine learning techniques in geotechnical engineering, particularly focusing on the swelling behavior of clay-sulfate rocks and expansive soils. The swelling of these materials poses significant challenges to the stability of infrastructures such as tunnels, foundations, and roads. Traditional numerical models for swelling processes often struggle with computational demands and the complexity of capturing coupled processes.
To address these challenges, this work explores the application of a variety of machine learning techniques for predicting key geotechnical parameters. These include the solubility of sulfate minerals, swelling potential, maximum swelling pressure, water retention and unsaturated hydraulic conductivity of clay soils. The research also investigates the development of hydro-mechanical models based on finite element method for simulating swelling phenomena in clay-sulfate rocks, using data from laboratory and field settings to validate the models.
Key contributions include the development of neural network models that outperform traditional empirical methods in predicting swelling potential and pressures in soils, offering improved accuracy and robustness in various geotechnical scenarios. Additionally, the implementation of advanced machine learning models and the integration of uncertainty quantification methods, such as Monte Carlo simulations, provide a more reliable prediction framework for subsurface engineering applications. A significant part of the thesis focuses on the coupled hydro-mechanical modeling of swelling in clay-sulfate formations, using the laboratory data and the case study of Staufen in Southwest Germany, where the proposed models have demonstrated their ability to replicate real-world swelling behavior and inform risk mitigation strategies.
By integrating various modeling techniques, this thesis provides novel insights into the complex behavior of expansive soils and clay-sulfate rocks. It contributes to the development of more efficient and reliable predictive models for use in geotechnical engineering, thereby enhancing the stability and safety of structures impacted by swelling phenomena
Seismic site characterization in and around the COSC-1 drillhole
No full textThe Scandinavian Caledonides were formed from the collision of Baltica and Laurentia during the Palaeozoic era and were comparable in size to the present-day Himalayas. Over 400 million years of erosion, along with uplift and extension, have left geological structures near the surface that were deeply buried during the Caledonian orogeny. The COSC project aims to study these structures, particularly the far-transported allochthons and the crystalline Precambrian basement, using two deep boreholes. COSC-1, drilled to a depth of 2.5 km, revealed the anisotropic Seve Nappe Complex. Several surface and borehole seismic experiments were conducted after drilling. In this thesis, a seismic depth imaging workflow is presented that helped to characterize the vicinity of the COSC-1 borehole. The focus is on including anisotropic seismic velocities in a Kirchhoff pre-stack depth migration approach. The results of this study offer detailed insights into the structural complexity of the region. The findings not only validate previous interpretations but also pave the way for future geological and geophysical research
Systematische Untersuchungen zur Thermodynamik und Stabilität ausgewählter Metallborhydride der 1. bis 5. Gruppe des Periodensystems der Elemente
Full text linkIm Rahmen der Dissertation wurden die Borhydride von Ca, Sr, Ba, Y, La, Zr und Hf hergestellt und deren thermodynamische Daten durch kalorimetrische Messungen ermittelt. Weiterhin wurden DFT-Berechnungen und verschiedene Korrelationen zur Ergänzung der experimentellen Datenbasis eingesetzt. Es folgte ein Vergleich aller ermittelten Daten mit abgeschätzten Werten. Auf Basis der bestimmten thermodynamischen Daten erfolgten umfangreiche Berechnungen zum Zersetzungsverhalten der Boranate, welche mit den experimentellen Befunden verglichen wurden. Weiterhin wurden Gleichgewichtsberechnungen zur Rehydrierbarkeit der reinen Boranate genutzt, um Aussagen zu deren Eignung als Wasserstoffspeichermaterialien abzuleiten. Abschließend wurden Berechnungen zum Design von reaktiven Hydridmischungen anhand des thermodynamischen Tunens ausgeführt, wobei aussichtsreiche Kandidaten in der Gruppe der untersuchten Erdalaklimetallboranate für experimentelle Untersuchungen identifiziert werden konnten.:Abbildungsverzeichnis XII
Tabellenverzeichnis XV
Verzeichnis der Schemata XVII
Abkürzungs- und Symbolverzeichnis XVIII
1 Einleitung 1
2 Stand der Literatur 5
2.1 Allgemeines 5
2.2 Synthese 6
2.3 Bindungsmotive und Kristallstruktur 8
2.4 Aussagen zum Zersetzungsverhalten und zur Rehydrierbarkeit 9
2.5 Verfügbarkeit thermodynamischer Daten der betrachteten Boranate und mögliche Korrelationen zur Abschätzung 21
2.6 Zusammenfassung und Ableitungen für die eigene Arbeit 31
3 Experimenteller Teil 32
3.1 Synthese 32
3.2 Charakterisierungsmethoden 36
3.3 Berechnungen 40
4 Erdalkaliboranate 42
4.1 Synthese von Calcium-, Strontium- und Bariumboranat 42
4.2 Untersuchung der thermischen Zersetzung von Calcium- und Strontiumboranat 47
4.3 Versuche zur Bestimmung der Bildungsenthalpie von Calcium- und Strontiumbo-
ranat 51
4.4 Bestimmung der Wärmekapazitätsfunktionen von Calcium- und Strontiumboranat 52
4.5 Absolute Standardentropie von Calcium- und Strontiumboranat 57
4.6 Thermodynamische Berechnungen zum Zersetzungsverhalten von Calcium- und
Strontiumboranat 57
4.7 Bestimmung thermodynamischer Daten von Bariumboranat 60
4.8 Thermodynamische Betrachtungen zu Bariumboranat 63
4.9 Fazit 64
5 Übergangsmetallboranate 66
5.1 Yttriumboranat, Y(BH4)3 66
5.2 Lanthanboranat, La(BH4)3 75
5.3 Zirkonium- und Hafniumboranat, Zr(BH4)4 und Hf(BH4)4 78
5.4 Niob- und Tantalboranat, Nb(BH4)x und Ta(BH4)x 89
5.5 Fazit 91
6 Aktualisierung von Korrelationen basierend auf den ermittelten Werten 92
6.1 Annahmen und Vorbetrachtungen 92
6.2 Abschätzung der Bildungsenthalpie 92
6.3 Abschätzung der absoluten Entropie 94
6.4 Zusammenstellung der ermittelten Daten und Fazit 95
7 Vorschläge für reaktive Mischungen auf Grundlage des thermodynamischen Tunens 97
7.1 Vorbetrachtungen 97
7.2 Mischungen der Boranate mit Metallhydriden 98
7.3 Mischungen der Boranate untereinander 99
7.4 Fazit 101
8 Zusammenfassung und Ausblick 102
Literatur 108
Anhang 119
A.1 Zusammenstellung der Literaturangaben zu Zersetzungstemperaturen und -enthalpien 119
A.2 Thermodynamische Literaturdaten der untersuchten Boranate 121
A.3 Weitere Angaben zu den Korrelationen 122
A.4 Details der durchgeführten Synthesen 123
A.4.1 Übersicht der eingesetzten Chemikalien 123
A.4.2 Metathesen in der Flüssigphase 125
A.4.3 Mechanochemische Metathesen 127
A.4.4 Direkte Metathesen 128
A.4.5 Desolvatisierung der hergestellten Boranat-Solvat-Komplexe 129
A.4.6 Zersetzung der Boranate im Rohrofen 130
A.4.7 Reaktive Mischungen aus Boranaten und Aluminium-Pulver 131
A.5 Auflistung aller mittels TG-DSC-MS/FTIR untersuchten Proben inklusive relevanter Parameter 132
A.6 Zusammenstellung thermodynamischer Daten aus der Literatur aller in dieser Arbeit verwendeten Verbindungen 133
A.7 Kristallographische Daten von Zr(BH4)4 und Hf(BH4)4 135
A.8 Ergebnisse der NMR-Messungen von Zr(BH4)4 und Hf(BH4)4 136
A.8.1 Zr(BH4)4 136
A.8.2 Hf(BH4)4 13
Mass transfer during biopolymer aerogel production: measurement and modeling
Full text linkThis thesis aims to measure and model diffusive mass transfer processes during all three steps of biopolymer aerogel production using 1-D Raman spectroscopy: gelation in aqueous media, solvent exchange to an organic solvent, and supercritical drying using CO2.
For the gelation step, the CO2 induced gelation of pectin gels was investigated. It could be shown that the liquid gelling solution likely solidifies immediately upon contact with CO2 and that therefore diffusion is the only relevant mass transfer mechanism.
Solvent exchange and supercritical drying of cylindrical gel monoliths were exemplarily analyzed using agar and whey protein isolate gels. A convective mass transfer model that includes both, diffusion and advection due to volume changes upon mixing was implemented with the effective diffusion coefficient being the sole fit parameter. It was shown that advection can play a decisive role during supercritical drying due to the high excess volume of the CO2+EtOH system.
In order to calculate the excess volume during supercritical drying, non-saturated binary mixture densities were experimentally determined for the four binary systems of CO2+EtOH, acetone, acetonitrile and DMSO from 308-333 K and 6-12 MPa over the whole composition range in the single-phase region.
Tortuosity factors derived from the experimentally determined effective diffusion coefficients during solvent exchange and supercritical drying differed by a factor of two, although the gels did not show any shrinkage. This contradiction could be attributed to an incorrect prediction of the binary diffusion coefficient of EtOH+CO2 in common aerogel literature. Stepwise supercritical drying was then employed to experimentally analyze the true composition dependency of the binary diffusion coefficient of EtOH+CO2.
Especially when solvent exchange is performed in onesingle step, unwanted shrinkage of the gel matrix can occur. It was shown that shrinkage leads to a heterogeneous density distribution of the gel network with a compaction towards its center. Most of the shrinkage takes place during the very beginning of solvent exchange when EtOH can be detected in the outermost layers only and that further shrinkage is prevented by a sharp increase in gels stiffness
Effect of N2–H2 Ratio during Conventional Plasma Nitriding of Intermetallic FeAl40 Alloy on Electrochemical Corrosion Parameters in Sulphuric Acid
Full text linkThe intermetallic alloy FeAl40 was plasma nitrided at 575 ∘C for 4 h while varying the N2–H2 gas mixture with nitrogen contents fN2 between 0.1 and 0.9. The effect of the gas mixture on the resulting structure of the nitrided FeAl40 and the associated electrochemical corrosion behaviour in a 0.25 M H2SO4 (pH = 0.3) electrolyte were investigated using different complementary analytical methods such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray spectroscopy, electron probe microanalysis (EPMA), electrochemical polarisation and electrochemical impedance spectroscopy. Nitriding significantly changed the corrosion mechanism of FeAl40 alloys in acidic environments, ranging from consistently high material loss in untreated base material to strongly inhibited material loss. This phenomenon was the result of a corrosion product layer formed on nitrided FeAl40 during the corrosion process. Therefore, plasma nitriding reduced the corrosion rate to about 5–7 mm/year compared with 22 mm/year of the untreated FeAl40 base material. A high nitrogen content in the N2–H2 plasma of more than fN2 = 0.3 ensured the formation of protective nitrided layers on FeAl40. In addition, an approach to explaining the effect of the nitrided layer on FeAl materials was presented on the basis of thermodynamic considerations
Interplay between Habit Plane and Orientation Relationship in an Electron Backscatter Diffraction Analysis: Using the Example of η′-Al8Fe3 in η-Al5Fe2
No full textThe Al5Fe2 intermetallic rouses interest due to its rapid formation at the interface between iron/steel and aluminum by reactive interdiffusion. Only in the last few years have the differently ordered states of that intermetallic been elucidated (η′, η″, η‴ and ηm). In the present work, the microstructural characteristics of the plate-shaped η′-Al8Fe3 phase regions in a η‴/η-phase matrix were investigated, determining the habit planes from two-dimensional electron backscatter diffraction (EBSD) maps. Within an η grain, there are altogether four variants of η′ with four characteristically crystallographic equivalent habit planes with respect to η. These habit planes have been determined based on their traces measured for differently oriented η containing the η′ plates, applying different methods. One method in particular makes use of the connection between orientation relationship and habit planes. Using these methods, the habit planes were determined as {hkl}η and {hkl}η′, both with {1 1.8 2.5}η/η′. Thus, essential characteristics of the microstructure are provided for further analysis of the phase transformation of the η phase to the η′-Al8Fe3 phase
Verbesserte Synthese von 3-Isocyanatopropyltrialkoxysilanen für die industrielle Anwendung
No full textDie kontinuierliche Thermolyse von Alkyl-3-trialkoxysilylpropylcarbamaten ist die im industriellen Maßstab genutzte Synthese von 3-Isocyanatopropyltrialkoxysilanen. Die Produktausbeute und -qualität wird dabei von vielen Einflussfaktoren bestimmt. Im Rahmen dieser Arbeit wurden der Druck, die Reaktortemperatur, der verwendete Kolonnentyp, die Geschwindigkeit der Eduktzufuhr und die Reinheit des Ausgangsstoffes als wesentliche Faktoren erkannt. Systematische Versuche zur Stabilisierung des Thermolyseprozesses wurden durchgeführt. Außerdem wurde der Einfluss verschiedener LEWIS-Säuren auf den Prozess untersucht.
Eine alternative, bislang nicht etablierte Synthese von 3-Isocyanatopropyl-trialkoxysilanen über die Hydrosilylierung von Allylisocyanat mit Triethoxy- und Trimethoxysilan in Gegenwart von Übergangsmetallkatalysatoren wurde ebenfalls untersucht. Eine rasche Deaktivierung der Katalysatoren erwies sich als charakteristisch für diese Reaktion. Maßnahmen zur Verlängerung der Katalysatoraktivität wurden untersucht und gefunden
Particle Transport Velocity in Vertical Transmission with an Airlift Pump
No full textThis paper presents the optimal conditions for fast transfer of solid particle with an airlift pump. The experimental examinations were carried out in an airlift pump with a length of 5.64 m and an inner diameter of 0.102 m in order to determine the impact of submergence ratio, air flow, and physical particle properties, such as shape, size, and density, on the vertical velocity of the particle in detail. The results showed that with the same air flow, the maximum particle velocity was achieved when the churn flow regime is established with a submergence ratio close to 0.89. However, in bubble and slug flow, it is not possible to carry a large particle in the dimensions of centimeters. Furthermore, in a churn flow, the velocity of the particle exceeds the velocity of pumped water; hence, water is not the only particle carrier in a vertical three-phase flow