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Wed, 24 Feb 2021 13:24:39 +0100Wed, 24 Feb 2021 13:24:39 +0100Development and validation of a gas-liquid two-phase model for industrial computational fluid dynamics applications
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5413
A local algebraic simulation model was developed, to determine the characteristic length scales for dispersed phases. This model includes the Ishii- Zuber drag model, the lift, the wall lubrication force and the turbulent dispersion force as well. It is based on the Algebraic Interface Area Density (AIAD) model from the Helmholtz Zentrum Dresden Rossendorf (HZDR), which provides the morphology detection and the free surface drag model. The developed model is in agreement with the current state of knowledge based on an examination of the theory and of state of science models for interface momentum transfer.
This new simulation model was tested on three different experiments. Two experiments can be found in the literature, the Fabre 1987 and the Hewitt 1987 experiment. And the third simulation is based on a steam drum experiment. This steam drum experiment is designed with ERK Eckrohrkessel GmbH internals and was developed to examine the droplet mass flow out of the turbulent separation stage.
The implementation of all models and tests was performed using Ansys CFX. The first analysis was carried out to reproduce a wavy stratified flow to examine the effects of different simulation model set-ups according to the velocity and kinetic energy profiles, as well as the pressure drop gradient and the water level measured by Fabre 1987. The second analysis was a proof on concept for reproducing the vertical flow pattern by an experiment from Hewitt 1987. The third simulation analysed the water distribution in the steam drum and feeding pipes system as well as the droplet carryover into the gas phase in the turbulent separation region of the drum.
These simulations have shown, that the accuracy of the particle distribution model in interaction with the drag and non-drag forces is able to reproduce horizontal and vertical flow patterns. Higher deviations are recognised for the liquid volume fraction close above the interface. Generally, simulations can now be performed to optimise industrial steam drum designs.Mario Nowitzkidoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5413Wed, 24 Feb 2021 13:24:39 +0100Direct numerical simulation of nonlinear pattern formation on the surface of liquid films
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5431
We investigate the dynamics of a Newtonian liquid layer bounded on one side by a horizontal and planar substrate and on the other side by its free and deformable surface. The system is subjected to a time-periodic gravitation field in lateral or normal direction. Based on a nonlinear coordinate transformation, which maps the time-dependent surface onto a constant domain and thus eliminates the need for tracking the interface, a finite-difference method on staggered grids is presented, allowing direct numerical simulations of the full incompressible Navier-Stokes equations in two and three dimensions. Taking into account the continuity equation, a sparse linear system for the pressure is obtained from the discretized Navier-Stokes equations whose solution satisfies the conservation of momentum and mass, so that pressure corrections can be avoided. In the case of a harmonic force perpendicular to the substrate, we find in high frequency ranges the classical square patterns oscillating subharmonically with half of the driver’s frequency. For a slow excitation, hexagonal Faraday waves emerge oscillating at the forcing frequency. Vertical two-frequency excitations lead to more complex patterns — surface waves having the shape of a square superlattice are found. In the case of a lateral excitation, the formation of coarsening droplets is observed. We show that ratchet-like forces generate a nonvanishing averaged flow rate inducing a preferred direction of motion of the drops. These results correspond well with those of a simplified model based on the lubrication approximation. Our investigations also include systems in Rayleigh-Taylor configuration, where the liquid is located on the underside of the substrate. By considering rigid walls instead of periodic boundaries, wave amplification due to resonance can be studied. The corresponding numerical results are in good agreement with experimentally obtained data.Sebastian Richterdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5431Mon, 22 Feb 2021 10:59:57 +0100Parallel constraint solving for combinatorial problems
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5437
With parallelism becoming the standard in computer design, research on parallel constraint solving technique is of vital importance for enhancing the performance of constraint solving. In this dissertation, we reviewed the literature on exploiting parallelism in constraint solving to help gain insight into the rationale of different types of parallel constraint solving approaches. On this basis, we analyzed the effectiveness of parallel constraint solving, with the focus on obtaining a first solution when solving computationally hard combinatorial problems. We have shown that a well-designed search space splitting method and constraint programming model can enable the embarrassingly parallel search (EPS) to solve some open instances of the social golfer problem that have not been solved by a sequential algorithm. We also observed superlinear speedups when solving these instances, which confirms our theoretical analysis. Besides, we examined two practical constraint optimization problems, including the traveling tournament problem with predefined venues and the talent scheduling problem. Our proposed constraint models outperformed the existing models on the same instances, and the EPS approach could always attain better feasible solutions in terms of the optimal objective value by using more parallel processors. To explore the use of massively parallel processing, we proposed the parallel stochastic portfolio search, which is a simple and non-intrusive way to parallelize different incarnations of a sequential solver. When comparing the existing portfolio to our portfolio approach by solving the same constraint satisfaction problems using the same constraint models, our technique could solve harder and larger instances. The successes of our new parallel approaches are attributed to early diversity; i.e., some diversity early in the search introduced by parallelism can offset early mistakes caused by weak heuristic choices. Unlike the other techniques (e.g., limited discrepancy search) used to overcome early mistakes, the studied two parallel constraint solving approaches not only can explore more nodes simultaneously but also does not sacrifice the guarantee of completeness.
We also presented a hypertree decomposition method that builds a degenerate decomposition tree for a given constraint network, in which each node of the decomposition tree possesses and executes a subset of constraints of the given constraint network. The usefulness of our proposed parallel techniquedepends on whether we can find an efficient way to join the results of each node.Ke Liudoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5437Thu, 18 Feb 2021 15:29:27 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2021,3 (15.02.2021)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5428
Habilitationsordnung der Fakultät 4 – Soziale Arbeit, Gesundheit und Musik vom 12. Februar 2021periodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5428Mon, 15 Feb 2021 19:51:29 +0100Parallel constraint solving for combinatorial problems
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5399
With parallelism becoming the standard in computer design, research on parallel constraint solving technique is of vital importance for enhancing the performance of constraint solving. In this dissertation, we reviewed the literature on exploiting parallelism in constraint solving to help gain insight into the rationale of different types of parallel constraint solving approaches. On this basis, we analyzed the effectiveness of parallel constraint solving, with the focus on obtaining a first solution when solving computationally hard combinatorial problems. We have shown that a well-designed search space splitting method and constraint programming model can enable the embarrassingly parallel search (EPS) to solve some open instances of the social golfer problem that have not been solved by a sequential algorithm. We also observed superlinear speedups when solving these instances, which confirms our theoretical analysis. Besides, we examined two practical constraint optimization problems, including the traveling tournament problem with predefined venues and the talent scheduling problem. Our proposed constraint models outperformed the existing models on the same instances, and the EPS approach could always attain better feasible solutions in terms of the optimal objective value by using more parallel processors. To explore the use of massively parallel processing, we proposed the parallel stochastic portfolio search, which is a simple and non-intrusive way to parallelize different incarnations of a sequential solver. When comparing the existing portfolio to our portfolio approach by solving the same constraint satisfaction problems using the same constraint models, our technique could solve harder and larger instances. The successes of our new parallel approaches are attributed to early diversity; i.e., some diversity early in the search introduced by parallelism can offset early mistakes caused by weak heuristic choices. Unlike the other techniques (e.g., limited discrepancy search) used to overcome early mistakes, the studied two parallel constraint solving approaches not only can explore more nodes simultaneously but also does not sacrifice the guarantee of completeness.
We also presented a hypertree decomposition method that builds a degenerate decomposition tree for a given constraint network, in which each node of the decomposition tree possesses and executes a subset of constraints of the given constraint network. The usefulness of our proposed parallel techniquedepends on whether we can find an efficient way to join the results of each node.Ke Liudoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5399Thu, 11 Feb 2021 11:44:13 +0100Development of Ni-based superalloy metal matrix composites, featuring high creep resistance
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5398
The increasing demand for competitive, whilst also environment-friendly airplane travel, compels the design of highly efficient engines in the aeronautical field. A potential for improvement of traditional polycrystalline Ni-based superalloys, aiming higher creep resistance, was investigated. The approach adopted the concept of metal matrix composites (MMCs) to incorporate a rigid discontinuous phase, in the form of particles, to a γ’-strengthened Ni-based superalloy. In order to make the concept feasible, different microstructures resulting from diverse manufacturing techniques were investigated. By using distinct mixing and sintering methods, powders of Inconel X-750 and TiC were combined to form composites containing 15 vol.% of reinforcing particles. Powders were prepared with low and high energy milling processes, and formed by uniaxial pressure sintering and spark plasma sintering methods. Non-reinforced variants and composites had microstructures thoroughly examined at their initial state and after long isothermal aging treatments. Selected variants were further submitted to tensile and compression creep tests at temperatures between 700 and 800 °C, in the stress range of 200 to 500 MPa.
A comprehensive analysis was conducted using techniques such as EBSD, XRD Rietveld refinement, EDS and TEM to evaluate the development of γ’, η and TiC phases, determining the achievable microstructures with each fabrication method and establishing their evolution after aging treatments over times up to 1000 h. Likewise, creep properties were analyzed by obtaining parameters such as creep exponents, threshold stresses and activation energies. A creep life estimation was conducted with the use of a Monkman-Grant relationship and a Larson-Miller parametrization. Lastly, the potential for a reduction in creep strain rates in a working turbine blade, considering the density of investigated materials as a parameter, was evaluated.
All produced composites presented power law creep, with dislocations surpassing γ’ particles by climb. The variant produced by high energy ball milling and spark plasma sintering exhibited the highest creep rates, resulting from intense diffusion through grain boundaries. It also presented η phase after long isothermal aging, which affects negatively the creep resistance. Contrastingly, in the variant produced by low mixing combined with pressure sintering the lowest creep rates were observed. It was proposed that reinforcing TiC particles effectively acted as a load bearing phase, counterbalancing the adverse effects of the intergranular diffusion in the refined microstructure. Furthermore, a higher microstructural stability was observed in this variant, resulting from limited interaction between TiC particles and the matrix during fabrication.Georges Lemosdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5398Tue, 09 Feb 2021 09:35:16 +0100Beschleunigung der Verdichterkennfeldberechnung mithilfe von Methoden des maschinellen Lernens
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5395
In der heutigen Triebwerksentwicklung ist die Verwendung komplexer und zeitaufwändiger numerischer Strömungssimulationsverfahren (3D-CFD) unerlässlich. Dies gilt auch und insbesondere für den Bereich der Verdichterkennfeldberechnung, welcher viele zeitintensive 3D-CFD Berechnungen benötigt. Dabei sind zur qualitativen Beurteilung eines Verdichterentwurfs sowohl Betriebspunkte wie, Reiseflug, Start und Landung, hinreichend genau abzubilden, als auch die kritischen, den Verdichterarbeitsbereich limitierenden Betriebsgrenzen Pumpen und Sperren zu detektieren. Bisherige Arbeiten zur automatisierten Verdichterkennfeldberechnung basieren auf strukturierten Berechnungen von verschiedenen Drehzahllinien, auf welchen jeweils isoliert Pump- und Sperrgrenze gesucht werden. Durch die Beschränkung auf einzelne Drehzahlen wird jedoch nicht der gesamte Charakter des Kennfeldes erfasst, so dass unbekannte Betriebsbereiche aus linearer Interpolation abgeleitet werden müssen. Ein zusätzlicher Nachteil solcher auf einzelne Drehzahllinien fixierten Methoden ist ihre geringe Parallelisierbarkeit.
Der Fokus dieser Arbeit liegt daher auf der Entwicklung eines effizienten Verfahrens zur Erfassung des gesamten Verdichterkennfeldes. Die zwei wesentlichen Anforderungen an das Verfahren sind erstens die Reduktion der Anzahl der notwendigen CFD-Berechnungen zur hinreichend genauen Beschreibung des Verdichterkennfeldes sowie zweitens die Beschleunigung jeder einzelnen 3D-CFD-Berechnung. Zu diesem Zweck wird zur Kennfeldberechnung eine Strategie vorgeschlagen, welche sich von der üblichen strukturierten Berechnung einzelner Drehzahllinien löst und stattdessen mit unstrukturierten, zufällig bestimmte Stützstellen arbeitet. Dabei wird ein zweiphasiges Verfahren entwickelt, bei dem zunächst die Pump- und Sperrlinien in ihrer Gesamtheit mit einer iterativen, hoch parallelisierbaren, auf Support-Vector-Machine beruhenden Strategie bestimmt werden. Als nächster Schritt wird mit Methoden der statistischen Versuchsplanung eine ausreichende Dichte von Stützstellen innerhalb der Betriebsgrenzen des Verdichters generiert. Abschließend werden auf Basis aller verwendeten Stützstellen Antwortflächen für Verdichterdruckverhältnis, Wirkungsgrad und Eintrittsmassenstrom aufgebaut.
Zur Reduktion der Rechenzeit jeder einzelnen 3D-CFD Rechnung werden unterschiedliche Methoden zur Erzeugung von Startlösungen betrachtet. In diesem Rahmen werden Initialisierungsansätze aus reduzierten Strömungsmodellen und aus der Superposition von bereits bekannten Strömungslösungen auf Basis der Methode der Proper-Orthogonal-Decomposition (POD) untersucht.
Als Validierung wird abschließend das entwickelte Verfahren zur Kennfeldberechnung in Kombination mit dem POD-Initialisierungsansatz erfolgreich auf die Analyse eines 4.5- stufigen Forschungsverdichters angewendet.Dmitrij Ivanovdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5395Mon, 08 Feb 2021 15:13:41 +0100Training of artificial neuronal networks with nonlinear optimization techniques
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5404
Machine learning is a field that has been the object of study of many researchers around the globe during the last decades. Very often to solve machine learning challenges like classification problems for example, one needs to train an artificial neural network. To train this network a certain loss function has to be minimized. There is a ubiquitous approach to achieve this which consists of using variants of the stochastic gradient descent combined with the backpropagation algorithm. In our work, we aimed at testing a rather non-conventional scheme consisting of making use of the solvers a software called AMPL offers.Thierry Tchouto Mbatchoubachelorthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5404Thu, 04 Feb 2021 14:25:03 +0100Plattform Innenstadt - Zurück zu multifunktionalen Zentren, 10 Lausitzer Kleinstädte - individuell, flexibel, wandlungsfähig
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5343
Die vorliegende Publikation präsentiert Ergebnisse von 20 Studierenden des Masterstudiengangs Stadtplanung aus dem Projekt „Plattform Innenstadt - Zurück zu multifunktionalen Zentren“ im Sommersemester 2020 am Fachgebiet Stadtmanagement der BTU Cottbus-Senftenberg.
Das Projekt befasste sich mit zehn ausgewählten Lausitzer Kleinstädten. Der Fokus lag dabei auf strukturellem Wandel in der Region sowie im Einzelhandel im Besonderen und den daraus resultierenden Wirkungen auf die Innenstädte.
Eingebunden war das Projekt in einen bundesweiten Wettbewerb des Wissensnetzwerks Stadt und Handel e.V. (WSH). Daran beteiligten sich insgesamt vier Hochschulen mit unterschiedlichen Fachrichtungen und Themen, zum Beispiel Städtebau,Stadtplanung oder Betriebswirtschaft.
Eine Vielzahl an Lösungsansätzen und eine große Bandbreite von Ergebnissen wurden in Austausch gebracht. Dabei konnten die Studierenden Erfahrungen sammeln und die Untersuchungsgegenstände auf neue Art methodisch und didaktisch angehen.studythesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5343Tue, 02 Feb 2021 11:10:54 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2021,2 (27.01.2021)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5397
Erste Änderungssatzung zur Allgemeinen Prüfungs- und Studienordnung für Master-Studiengänge (AMbl. 14/2016) vom 26. Januar 2021periodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5397Wed, 27 Jan 2021 12:08:32 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2021,1 (27.01.2021)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5396
Erste Änderungssatzung zur Allgemeinen Prüfungs- und Studienordnung für Bachelor-Studiengänge (AMbl. 13/2016)vom 26. Januar 2021periodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5396Wed, 27 Jan 2021 12:03:24 +0100Beiträge zur Landnutzungsgeschichte in der Niederlausitz und im Erzgebirge
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5388
In diesem Band sind verschiedene Beiträge zur Landnutzungsgeschichte in der Niederlausitz und im Erzgebirge zusammengefasst. Die ersten vier Beiträge befassen sich mit historischen Ackerfluren und Wölbäckern in der Niederlausitz. Archäologische Untersuchungen, in Kontext gestellt mit archivalischen Quellen und historischen Karten, geben gemeinsam mit dem Einsatz naturwissenschaftlicher Methoden und Visualisierungen hochauflösender LiDAR-Daten neue Einblicke in die ehemalige Landnutzung. Der fünfte Beitrag aus dem Erzgebirge beschreibt die Nutzung von ehemaligen Meilerplätzen als Quellengattung der Montanarchäologie.bookhttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5388Wed, 27 Jan 2021 10:10:59 +0100On bilevel optimization problems in infinite-dimensional spaces
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5375
In this thesis we consider bilevel optimization problems in infinite-dimensional spaces. In particular, we are interested in providing first-order necessary optimality conditions. We consider bilevel optimization problems both in abstract Banach spaces and in some special situations. This includes the optimal control of the obstacle problem, which is a typical bilevel optimization problem in Sobolev spaces, as well as a class of inverse optimal control problems. We obtain optimality conditions for these more specific optimization problems by applying our results from the abstract setting.
Our main approach for deriving optimality conditions in the abstract setting utilizes the relaxation of a reformulation of the bilevel optimization problem via the optimal value function. We also introduce the so-called normal-cone-preserving operators and show how this concept can be applied.
We also consider other topics that arise in this context. For instance, we investigate the so-called limiting normal cone to a complementarity set in Sobolev spaces. This complementarity set plays a central role in the context of the optimal control of the obstacle problem. The limiting normal cone is a concept which appears in the area of variational analysis and generalizes the usual normal cone from convex analysis. We also investigate in which spaces Legendre forms and Legendre-* forms can exist. We show that if a Legendre-* form exists in a reflexive Banach space or a space with a separable predual space, then this space is already isomorphic to a Hilbert space. We also consider a discretization of a bilevel optimization problem in Lebesgue spaces. We present both theoretical error estimates and numerical experiments.
The new results in this thesis are illustrated by examples and counterexamples. In order to present the topics in a self-contained way, we review some known concepts and their basic properties. A particular focus for this is on the definitions and properties from the area of capacity theory.Felix Harderdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5375Thu, 21 Jan 2021 15:53:13 +0100Studies on the influence of mechanical stress on the properties of silicon sensor modules for the ATLAS Phase-II Upgrade
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5323
The subject of this thesis is the development and test of silicon strip detectors for the high luminosity upgrade of the tracking detector of the ATLAS experiment at the Large Hadron Collider. Special emphasis is devoted to the understanding of the impact of mechanical stress on the electrical properties and the particle detection performance of detector modules.
First simulations were done to estimate the maximum expected stress on a sensor when operated at -30 °C within the future silicon strip tracking detector ITk, at ATLAS. The maximum stress in a worst case scenario is expected to be 27 MPa. Tensile strength tests were done to estimate the maximum stress which can be applied to a silicon strip sensor. Silicon shards, with a thickness and dopand concentration corresponding to the ITk sensor specifications break at >23 MPa, wafers at >700 MPa and sensors at ~ 400 MPa. The huge variations lead to the assumption, that the tensile stregth, which is highly dependent on the quality of the crystal lattice, is due to different cutting technology. Wafers, irradiated with a fluence equivalent of a lifetime dose of an ITk sensor, show no stress dependency of the youngs modulus. The tensile strength of irradiated wafers is decreased by ~ 6,6 %. No damage on silicon sensors from mechanical stress is expected for sensor modules installed it the ITk.
The electrical properties of silicon strip sensors were studied for applied mechanical stress on ATLAS07 sensors up to 60 MPa. The specifications of the sensors are similar to the specification of strip sensors in the future silicon strip tracker barrel region of the ATLAS detector. The leakage current changes at 50 MPa by -1.7 %, the bias resistance by +0.8 % and the interstrip resistance by -25 %. The depletion voltage and the implant resistance are not affected by mechanical stress. Except for the interstrip resistance the results can be explained by piezoresistive effects.
Silicon strip modules were build and studied in particle test beams. These modules consists of an ATLAS07 or an ATLAS12 sensor and an analogue readout to study the influence of stress on the module performance. The sensor module noise is independent from the applied stress. An effect of stress on the signal strength was seen. The ATLAS07 sensor module signal strength was decreased and the ATLAS12 sensor module signal strength was increased with a slope of ~0,6 MPa^-1. The average cluster size of the ATLAS07 sensor module was increased by 0,25 % MPa^-1 and the average cluster size of the ATLAS12 sensor module was decreased by 0,06 % MPa^-1 with applied stress.Martin Steglerdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5323Tue, 19 Jan 2021 16:25:54 +0100Learning from the Past, Designing for the Future: Sustainability of the Mediterranean Vernacular
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5309
With climate change and the depleting ozone layer, awareness about protecting the environment is increasing and “Sustainable Architecture” is becoming an essential part of the architectural future of cities. However, sustainable buildings of today are being built with high cost, high tech systems which can be reduced by taking advantage of past technologies and systems. The brilliance of vernacular architecture and the way man adapted to his surroundings fascinated me and inspired me to do further research on the sustainable characteristics of vernacular settlements of the Mediterranean area in order to determine if these characteristics can be applied to present and future architecture in an innovative way to create sustainable buildings with least possible energy consumption.
The method of research was based upon a general analysis of the passive design (solar and wind) characteristics of a town or settlement in Mediterranean climate starting from its site elements such as topography, vegetation, water. After that its urban structure, such as the geometry, block and street orientation and dimensions. Following that, the dwelling characteristics like dwelling shape, orientation and dimensions and finally the thermal regulating elements found in these dwellings, such as windows and vegetation. These elements were given a score according to their contribution to energy savings in buildings. Four case studies were chosen: two vernacular case studies from the region of study (the Mediterranean Coasts) and two modern case studies inspired by the Mediterranean vernacular. The analysis was repeated in the same sequence mentioned: Site, Settlement, Dwelling, Element, for the actual performance of each case study. The elements were given a number of points out of the score assigned for each element in the general analysis.
A total score and rating for each case study resulted from this analysis. The objective of these scores were to compare the performance of the vernacular case studies to the vernacular inspired case studies in terms of energy savings. The final scores displayed comparable results between both types of case studies meaning that when these modern settlements were designed with an influence from the Mediterranean vernacular, their performance in energy savings was close to that of a vernacular settlement. That means that it is possible to design settlements which are influenced by vernacular settlements and can even defeat them by following the general guidelines of the vernacular passive design characteristics in addition to modern tools and innovative methods. These guidelines can be reflected in a handbook and rating system which can become a simple step by step guide for architects and planners to design sustainable settlements without the need for expensive and complicated rating systems and consultants.Najla Elattassidoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5309Tue, 19 Jan 2021 15:32:29 +0100A reflection on methodological approaches to assessing and implementing social sustainability in historical public spaces
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/4902
In this paper, through a literature review, I clarify the meaning of public space and reflect on theoretical approaches to and methods of assessing the ability of historic public spaces to enhance social sustainability. I explain how the definition of public space and approaches to urban planning share concepts with social sustainability.
Finally, reflecting on examples of empirical research that attempt to
link physical and social components of public spaces, I point out the
methodological strengths and weaknesses in the field.Solmaz Yadollahibookparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/4902Tue, 19 Jan 2021 08:55:29 +0100Experiments on nonlinear waves in homogeneous flows with free upper surface and time-dependent forcing
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5386
The linear-theory assumption is a fundamental approach for the study of waves in fluids. The governing equations are linearized by assuming the perturbations are small so that the consequences of nonlinear terms are negligible. Nevertheless, if a wave approaches a critical level, in which the wave amplitude grows so as to create an instability of the background flow, the assumption of linearity may not hold any longer. In this case, the nonlinear terms are required to be taken into consideration.
In this thesis, two experimental setups have been proposed for the study of two scenarios, in which the nonlinear effects become significant and a traditional linear solution is no longer valid.
The first experiment focuses on an inertially oscillating rotating fluid. In the thesis, we present experimental results from a system that is simpler than classical precession experiments but still shows very similar wave interactions and a collapse to turbulence. This system consists of a partly filled rotating annulus that rotates about its symmetry axis slightly tilted with respect to the gravity vector.
In the experiments, we find a resonant collapse when the forcing frequency corresponds with a resonant frequency of the rotating tank. Two types of instability can be triggered: a parametric triadic instability, in which two free Kelvin modes arise and form a triad with the forced Kelvin mode, and a shear-type instability related to the nonlinearly excited geostrophic flow. The latter instability gives rise to a barotropic mode that interacts with the forced mode and generates secondary modes. We also observed dependency of the mode frequencies on the Ekman number, which can, at least partly, be explained by a Doppler shift due to the mean flow. Finally, we try to connect our data to a low-order dynamical system based on the weakly nonlinear theory that describes the main features of single triad interaction in precession experiments.
The second experiment concerns the study of undular bores (or tidal bores), in which the nonlinearity plays an important role. An experiment has been performed in which undular bores are produced in an open circular channel. More specifically, two different cases have been investigated: a single bore case with a rigid boundary setup and a bore colliding case with a periodic lateral boundary setup. Bores are generated by abruptly releasing a barrier that separates fluids with different surface levels. Up to our knowledge, this is the first experimental study of undular bores in a circular channel. For a setup without barriers, this geometry accomplishes in a natural way the periodic lateral boundary conditions, which is very often used in numerical simulations. The experimental results have been compared with the nonlinear numeric simulations and achieved an excellent agreement.Wenchao Xudoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5386Mon, 18 Jan 2021 15:31:56 +0100Anthropogenetische Geomorphologie - Geomorphologie im Anthropozän : Virtuelle Jahrestagung des Arbeitskreises für Geomorphologie 2020,
28./29. September 2020, BTU Cottbus - Senftenberg
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5363
In diesem Band finden sich das Programm und die Kurzfassungen der Beiträge zur Jahrestagung 2020 des Deutschen Arbeitskreises für Geomorphologie, die am 28. und 29.9.2020 als virtuelle Konferenz stattgefunden hat. Die Tagung wurde von der Brandenburgischen Technischen Universität Cottbus-Senftenberg (BTU) ausgerichtet und von 120 Teilnehmer*innen besucht. Das Tagungsthema lautete „Anthropogenetische Geomorphologie – Geomorphologie im Anthropozän“ und befasste sich mit der aktuell unter verschiedenen Aspekten diskutierten Frage des Einflusses des Menschen auf seine natürliche Umgebung. Die Lausitz bietet mit den Bergbauaktivitäten eine Vielzahl von Beispielen von tiefgreifenden Veränderungen der Erdoberflächenformen durch menschliche Einflüsse. Die insgesamt 23, auf zwei Themenblöcke aufgeteilten Vorträge sowie 21 Posterbeiträge in drei thematischen Sessions zeigten darüber hinaus zahlreiche weitere Beispiele aus verschiedenen Regionen weltweit. Der internationale Charakter der Tagung wurde durch die große Zahl englischsprachiger Beiträge unterstrichen.conferenceobjecthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5363Mon, 21 Dec 2020 08:51:44 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2020,20 (17.12.2020)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5342
Neufassung der fachspezifischen Prüfungs- und Studienordnung für den Master-Studiengang Umweltingenieurwesen vom 15. Dezember 2020periodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5342Fri, 18 Dec 2020 11:49:26 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2020,19 (17.12.2020)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5341
Fachspezifische Prüfungs- und Studienordnung für den Master-Studiengang Physics vom 14. Dezember 2020periodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5341Fri, 18 Dec 2020 11:36:55 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2020,18 (17.12.2020)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5340
Bekanntmachung: Aufhebung des Bachelor-Studiengangs Verfahrenstechnik sowie des Master-Studiengangs Nachwachsende Rohstoffe und Erneuerbare Energienperiodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5340Fri, 18 Dec 2020 10:44:21 +0100Application of the One-Dimensional Turbulence model to electrohydrodynamically enhanced internally forced convective flows
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5338
This thesis is an attempt to assess some of the effects that electroquasistatic body forces exert on turbulent internally forced convective flows. In order to do that, a stochastic turbulence model is employed, namely, the One-Dimensional Turbulence (ODT) model.
The reduced dimensionality of ODT demands a reduction of the Navier-Stokes equations (and in this case, also the Maxwell equations), into a 1-D system. This is done by performing an asymptotic analysis in terms of the nondimensional numbers of the flow. Also, a validation step due to the relative novel character of the cylindrical ODT formulation is done for an incompressible and constant properties flow regime and a variable density flow regime. The validation is presented for both the temporal (T-ODT) and a novel spatial (S-ODT) formulation in both planar and cylindrical geometries. Results in the constant property case show that wall normal (and radial) profiles, in both the T-ODT and S-ODT formulations, show good agreement with each other and to the data of Direct Numerical Simulations (DNSs). For the evaluated variable density heated pipe flow, gradients at the wall can be better reproduced with S-ODT.
After validating the model, ODT is applied first into a planar configuration which emulates the flow in a wire-plate Electrostatic Precipitator (ESP). For this flow, the additional input energy due to the electroquasistatic body force has an effect on the modification of the bulk velocity, and subsequently, the skin friction coefficient. Some qualitative DNS trends are confirmed with ODT, such as the localized increase of the Reynolds stress, as a consequence of increased eddy activity close to the discharge electrodes. Next, the results of ODT simulations in a cylindrical wire-tube ESP are presented. Here, ODT results are compared to experimental results. ODT results for global integral quantities such as the streamwise pressure gradient and the Nusselt number enhancement ratio are able to match in a reasonable way the experimental results. The competing relevance between the EHD contribution to turbulence by momentum, and by affecting the temperature and density due to the Joule heating effect is also analyzed, showing the leading order relevance of the former one. Specifically for the Nusselt number results, the sensitivity of the EHD flow to transition effects is shown to be very significant.
This thesis may open the door to a vast new field of phenomena which can not only serve for the further validation of the ODT model against DNSs or experiments, but also for the real use of ODT in applications which are so far inaccessible for traditional DNSs.Juan Ali Medina Mendezdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5338Thu, 17 Dec 2020 15:52:34 +0100Quantitative empirical studies on sustainable consumption
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5333
The overall research goal of this doctoral thesis is to better understand the determinants of sustainable purchase behaviour. By approaching several context-specific subgoals in a series of four quantitative empirical studies, major research gaps in the field of sustainable consumption are addressed. The first article examines the market potential for social banking in Germany. By means of an experimental survey using adaptive conjoint analysis, a sample of 2896 German social banking customers and a population-representative sample of 641 German conventional banking customers are compiled. Logistic regression modelling reveals that social banking customers differ significantly from their conventional counterparts regarding several consumer characteristics. The results further indicate a large untapped market potential ranging between 10 and 26% of the German population in 2011. The second article investigates the phenomenon of the attitude-behaviour gap in the context of sustainable clothing. Based on survey data of 1085 female German consumers, a structural equation model is estimated to assess how large the possible gap between a positive attitude towards sustainable clothing and the corresponding purchase behaviour is. Apart from a considerable attitude-behaviour gap, the article indicates that a positive attitude, self-transcendence values, as well as an affinity to online and catalogue shopping, significantly enhance sustainable clothing purchases. Self-enhancement values and, remarkably, a preference for durability constitute purchase barriers. The third article studies the influence of product lifetime labelling by the example of electrical appliances. Using choice-based conjoint analysis, experimental survey data is collected from a population-representative sample of 499 German consumers. Hierarchical Bayes utility modelling suggests a decreasing positive effect of the label on purchase decisions and a deterioration of the purchase influence of existing brands. Structural equation modelling indicates, for instance, that the preference for a long product lifetime is fostered by a respective positive attitude and subjective norm. However, the attitude only exerts a significant influence if it is driven by personal rather than environmental gains. The fourth article sheds light on the effects of favourable and unfavourable environmental product information. The analysis draws on data gained from a survey-based experiment conducted among a population-representative sample of 524 German consumers. Using a two-level structural equation model, the results document that the negative effect caused by unfavourable product carbon footprint information on consumers’ willingness to pay is significantly stronger than the positive effect caused by respective favourable information. Furthermore, consumers tend to not substantially differentiate between different high-range degrees of positive or negative environmental information.Kathleen Jacobsdoctoralthesishttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5333Tue, 15 Dec 2020 16:22:05 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2020,17 (26.11.2020)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5308
Promotionsordnung der Fakultät für Gesundheitswissenschaften in Gründung, gemeinsame Fakultät der Universität Potsdam, der Medizinischen Hochschule Brandenburg Theodor Fontane und der Brandenburgischen Technischen Universität Cottbus–Senftenbergperiodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5308Thu, 26 Nov 2020 13:36:55 +0100Amtliches Mitteilungsblatt der BTU Cottbus–Senftenberg, 2020,16 (26.11.2020)
https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5307
Gründungsfakultätsordnung der Fakultät für Gesundheitswissenschaften in Gründung, gemeinsame Fakultät der Universität Potsdam, der Medizinischen Hochschule Brandenburg CAMPUS GmbH (gemeinnützig) Theodor Fontane und der Brandenburgischen Technischen Universität Cottbus–Senftenbergperiodicalparthttps://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/5307Thu, 26 Nov 2020 13:19:55 +0100