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This dissertation presents three studies on the design and implementation of interactive surface environments. It puts forward approaches to engineering interactive surface prototypes using prevailing methodologies and technologies. The scholarly findings from each study have been condensed into academic manuscripts, which are conferred herewith.
The first study identifies a communication gap between engineers of interactive surface systems (i.e., originators of concepts) and future developers. To bridge the gap, it explores a UML-based framework to establish a formal syntax for modeling hardware, middleware, and software of interactive surface prototypes. The proposed framework targets models-as-end-products, towards enabling a shared view of research prototypes thereby facilitating dialogue between concept originators and future developers.
The second study positions itself to support developers with an open-source solution for exploiting 3D point clouds for interactive tabletop applications using CPU architectures. Given dense 3D point-cloud representations of tabletop environments, the study aims toward mitigating high computational effort by segmenting candidate interaction regions as a preprocessing step. The study contributes a robust open-source solution for reducing computational costs when leveraging 3D point clouds for interactive tabletop applications. The solution itself is flexible and adaptable to variable interactive surface applications.
The third study contributes an archetypal concept for integrating mobile devices as active components in augmented tabletop surfaces. With emphasis on transparent development trails, the study demonstrates the utility of the open-source tool developed in the second study. In addition to leveraging 3D point clouds for real-time interaction, the research considers recent advances in computer vision and wireless communication to realize a modern, interactive tabletop application. A robust strategy that combines spatial augmented reality, point-cloud-based depth perception, CNN-based object detection, and Bluetooth communication is put forward. In addition to seamless communication between adhoc mobile devices and interactive tabletop systems, the archetypal concept demonstrates the benefits of preprocessing point clouds by segmenting candidate interaction regions, as suggested in the second study.
Collectively, the studies presented in this dissertation contribute; 1—bridging the gap between originators of interactive surface concepts and future developers, 2— promoting the exploration of 3D point clouds for interactive surface applications using CPU-based architectures, and 3—leveraging 3D point clouds together with emerging CNN-based object detection, and Bluetooth communication technologies to advance existing surface interaction concepts.
The gradual digitization in the architecture, engineering, and construction industry over the past fifty years led to an extremely heterogeneous software environment, which today is embodied by the multitude of different digital tools and proprietary data formats used by the many specialists contributing to the design process in a construction project. Though these projects become increasingly complex, the demands on financial efficiency and the completion within a tight schedule grow at the same time. The digital collaboration of project partners has been identified as one key issue in successfully dealing with these challenges. Yet currently, the numerous software applications and their respective individual views on the design process severely impede that collaboration.
An approach to establish a unified basis for the digital collaboration, regardless of the existing software heterogeneity, is a comprehensive digital building model contributed to by all projects partners. This type of data management known as building information modeling (BIM) has many benefits, yet its adoption is associated with many difficulties and thus, proceeds only slowly. One aspect in the field of conflicting requirements on such a digital model is the cooperation of architects and structural engineers. Traditionally, these two disciplines use different abstractions of reality for their models that in consequence lead to incompatible digital representations thereof.
The onset of isogeometric analysis (IGA) promised to ease the discrepancy in design and analysis model representations. Yet, that initial focus quickly shifted towards using these methods as a more powerful basis for numerical simulations. Furthermore, the isogeometric representation alone is not capable of solving the model abstraction problem. It is thus the intention of this work to contribute to an improved digital collaboration of architects and engineers by exploring an integrated analysis approach on the basis of an unified digital model and solid geometry expressed by splines. In the course of this work, an analysis framework is developed that utilizes such models to automatically conduct numerical simulations commonly required in construction projects. In essence, this allows to retrieve structural analysis results from BIM models in a fast and simple manner, thereby facilitating rapid design iterations and profound design feedback.
The BIM implementation Industry Foundation Classes (IFC) is reviewed with regard to its capabilities of representing the unified model. The current IFC schema strongly supports the use of redundant model data, a major pitfall in digital collaboration. Additionally, it does not allow to describe the geometry by volumetric splines. As the pursued approach builds upon a unique model for both, architectural and structural design, and furthermore requires solid geometry, necessary schema modifications are suggested.
Structural entities are modeled by volumetric NURBS patches, each of which constitutes an individual subdomain that, with regard to the analysis, is incompatible with the remaining full model. The resulting consequences for numerical simulation are elaborated in this work. The individual subdomains have to be weakly coupled, for which the mortar method is used. Different approaches to discretize the interface traction fields are implemented and their respective impact on the analysis results is evaluated. All necessary coupling conditions are automatically derived from the related geometry model.
The weak coupling procedure leads to a linear system of equations in saddle point form, which, owed to the volumetric modeling, is large in size and, the associated coefficient matrix has, due to the use of higher degree basis functions, a high bandwidth. The peculiarities of the system require adapted solution methods that generally cause higher numerical costs than the standard procedures for symmetric, positive-definite systems do. Different methods to solve the specific system are investigated and an efficient parallel algorithm is finally proposed.
When the structural analysis model is derived from the unified model in the BIM data, it does in general initially not meet the requirements on the discretization that are necessary to obtain sufficiently accurate analysis results. The consequently necessary patch refinements must be controlled automatically to allowfor an entirely automatic analysis procedure. For that purpose, an empirical refinement scheme based on the geometrical and possibly mechanical properties of the specific entities is proposed. The level of refinement may be selectively manipulated by the structural engineer in charge. Furthermore, a Zienkiewicz-Zhu type error estimator is adapted for the use with isogeometric analysis results. It is shown that also this estimator can be used to steer an adaptive refinement procedure.
The intention of this thesis is to analyse the performance of the theory and the practice of the integrated development planning by Cape Town’s local government in two Townships named Nyanga and Philippi between 1999 and 2001. Since then the local government aimed to supply a planning approach that is of an integrative nature, opposed to the disintegrative one during Apartheid before 1994. South Africa’s primary instrument for development is named the Integrated Development Plan (IDP). This instrument is primarily responsible for socioeconomic development but significantly affects and considers spatial planning aspects as well. Between 1999 and 2001 the five selected project cases along the Ingulube Drive in Nyanga and Philippi under the umbrella of the Dignified Places rogramme have been implemented. The study analysis aims to investigate a specific momentum in time, where spatial practice in South Africa began to experience a new, integrative approach. Furthermore, the study is embedded in the planning conventions in Cape Town’s black Townships before, during and after Apartheid. ...
In ten chapters, this thesis presents information retrieval technology which is tailored to the research activities that arise in the context of corpus-based digital humanities projects.
The presentation is structured by a conceptual research process that is introduced in Chapter 1. The process distinguishes a set of five research activities: research question generation, corpus acquisition, research question modeling, corpus annotation, and result dissemination. Each of these research activities elicits different information retrieval tasks with special challenges, for which algorithmic approaches are presented after an introduction of the core information retrieval concepts in Chapter 2.
A vital concept in many of the presented approaches is the keyquery paradigm introduced in Chapter 3, which represents an operation that returns relevant search queries in response to a given set of input documents. Keyqueries are proposed in Chapter 4 for the recommendation of related work, and in Chapter 5 for improving access to aspects hidden in the long tail of search result lists.
With pseudo-descriptions, a document expansion approach is presented in Chapter 6. The approach improves the retrieval performance for corpora where only bibliographic meta-data is originally available. In Chapter 7, the keyquery paradigm is employed to generate dynamic taxonomies for corpora in an unsupervised fashion.
Chapter 8 turns to the exploration of annotated corpora, and presents scoped facets as a conceptual extension to faceted search systems, which is particularly useful in exploratory search settings. For the purpose of highlighting the major topical differences in a sequence of sub-corpora, an algorithm called topical sequence profiling is presented in Chapter 9.
The thesis concludes with two pilot studies regarding the visualization of (re)search results for the means of successful result dissemination: a metaphoric interpretation of the information nutrition label, as well as the philosophical bodies, which are 3D-printed search results.
Exploratory Research into Transformation Processes of Former Industrial Complexes of Leipziger Baumwollspinnerei (Leipzig) and Mattatoio di Testaccio (Rome); New Meanings of Industrial Heritage
Physical manifestations of the Industrial Revolution left a permanent imprint on the complexion of cities. Abandonment that followed the deindustrialization contributed to an estrangement, turning derelict industrial spaces and run‐down factories into a ballast to conjure with. At present, industrial heritage management applies flexibility and creativity, partially overcoming the essentially traditional paradigm of heritage preservation. This approach permits sustainable conservation – utilization and integration of disused industrial constructs in the contemporary urban landscape. Being a part of the European cultural stock, industrial heritage is an exciting and unique setting from many perspectives. It is defined and consumed by many markets, ranging from the industrial heritage tourism to the market of special events and festivals. Reused industrial buildings and factories come into view as products of post‐industrial societies, fitting to the Western post‐industrial (consumer) culture, offering a field of activities that are at an interface between the industrial history and contemporary socio‐cultural milieu.
Alteration of values, growth of new roles and definitions of industrial heritage, generated by functional restructuring, is a subject which is often left behind the general discussion about sustainable conservation and adaptive reuse of industrial heritage. Yet, in the modified state, industrial heritage is very complex to understand and to define.
By conducting a desk and a case study research of former industrial complexes – Leipziger Baumwollspinnerei and Mattatoio di Testaccio, this doctoral thesis aims to identify industrial heritage as a contemporary (post‐industrial) concept. Observation of ideas, values and definitions that emerge as a consequence of the transformation and re‐conceptualization of industrial heritage are intended to raise awareness and appreciation of industrial heritage in the full richness of its contemporary interpretation.
Although it is impractical to avert subsequent natural disasters, advances in simulation science and seismological studies make it possible to lessen the catastrophic damage. There currently exists in many urban areas a large number of structures, which are prone to damage by earthquakes. These were constructed without the guidance of a national seismic code, either before it existed or before it was enforced. For instance, in Istanbul, Turkey, as a high seismic area, around 90% of buildings are substandard, which can be generalized into other earthquakeprone regions in Turkey. The reliability of this building stock resulting from earthquake-induced collapse is currently uncertain. Nonetheless, it is also not feasible to perform a detailed seismic vulnerability analysis on each building as a solution to the scenario, as it will be too complicated and expensive. This indicates the necessity of a reliable, rapid, and computationally easy method for seismic vulnerability assessment, commonly known as Rapid Visual Screening (RVS). In RVS methodology, an observational survey of buildings is performed, and according to the data collected during the visual inspection, a structural score is calculated without performing any structural calculations to determine the expected damage of a building and whether the building needs detailed assessment. Although this method might save time and resources due to the subjective/qualitative judgments of experts who performed the inspection, the evaluation process is dominated by vagueness and uncertainties, where the vagueness can be handled adequately through the fuzzy set theory but do not cover all sort of uncertainties due to its crisp membership functions. In this study, a novel method of rapid visual hazard safety assessment of buildings against earthquake is introduced in which an interval type-2 fuzzy logic system (IT2FLS) is used to cover uncertainties. In addition, the proposed method provides the possibility to evaluate the earthquake risk of the building by considering factors related to the building importance and exposure. A smartphone app prototype of the method has been introduced. For validation of the proposed method, two case studies have been selected, and the result of the analysis presents the robust efficiency of the proposed method.
Die Arbeit leistet einen wissenschaftlichen Beitrag zur Erforschung der Einsatzmöglichkeiten eines Immobilienportfoliomanagements für öffentliche museale Schlösserverwaltungen in Deutschland. Insbesondere wird ein für deren Organisation spezifisches Modell zur Investitionssteuerung herausgearbeitet und dessen Anwendbarkeit in der Praxis mit Experten diskutiert.
Due to the significant number of immigrants in Europe, especially Germany, integration is an ongoing subject of debate. Since the 1970s, with the emergence of the discussions on ‘place,’ it has also been realized that the immigrant experience is associated with location. Nevertheless, due to the challenges in capturing the place and migration relevance, there is a gap in understanding the role of the migrant’s geography of experiences and its outcomes (Phillips & Robinson, 2015).
This research aims to investigate the extent to which both the process of objective integration and the socio-spatial practices of high-skilled Iranian immigrants in Berlin outline and influence their sense of belonging to Berlin as the new “home.” The embedded mixed-method design had employed for this study. The quantitative analysis through Pearson’s correlation technique measured the strength of the association between Iranians’ settlement distribution and the characteristics of Berlins’ districts. The quantitative analysis provides contextual data to get a greater level of understanding of the case study’s interaction with place. The units of place intend to demonstrate the case study’s presence and possible interaction with places around their settlement location that relatively shapes their perception. The qualitative analysis comprises ethnographic fieldwork and semi-structured in-depth interviews with a homogeneous sample of Iranian immigrants in Berlin that provide data on individual and ethnic behaviors and trajectories and analyze the complex interactions between the immigrant’s experience and the role of place.
This research uncovers that Iranian highly skilled immigrants are successful in integrating objectively; However, in regards to their state of belonging, it illustrated the following: The role of socio-ethnic culture of the case study in denotation of home and belonging; Iranian high-skilled immigrants’ efforts towards reaching a level of upward mobility overshadow their attempt to shape social and spatial interaction with Berliners and Berlin itself, which manifests both in their perception and use of urban space; and finally, the identification practice and the boundary-making as an act of reassurance and self-protection against the generalization of adjacent nationalities, demonstrated in the intersection of demographical settlement distribution of Iranians in Berlin and the ethnic diversity, impact the sense of belonging and place-making.
Modern immersive telepresence systems enable people at different locations to meet in virtual environments using realistic three-dimensional representations of their bodies. For the realization of such a three-dimensional version of a video conferencing system, each user is continuously recorded in 3D. These 3D recordings are exchanged over the network between remote sites. At each site, the remote recordings of the users, referred to as 3D video avatars, are seamlessly integrated into a shared virtual scenery and displayed in stereoscopic 3D for each user from his or her perspective.
This thesis reports on algorithmic and technical contributions to modern immersive telepresence systems and presents the design, implementation and evaluation of the first immersive group-to-group telepresence system in which each user is represented as realistic life-size 3D video avatar. The system enabled two remote user groups to meet and collaborate in a consistent shared virtual environment. The system relied on novel methods for the precise calibration and registration of color- and depth- sensors (RGBD) into the coordinate system of the application as well as an advanced distributed processing pipeline that reconstructs realistic 3D video avatars in real-time. During the course of this thesis, the calibration of 3D capturing systems was greatly improved. While the first development focused on precisely calibrating individual RGBD-sensors, the second stage presents a new method for calibrating and registering multiple color and depth sensors at a very high precision throughout a large 3D capturing volume. This method was further refined by a novel automatic optimization process that significantly speeds up the manual operation and yields similarly high accuracy. A core benefit of the new calibration method is its high runtime efficiency by directly mapping from raw depth sensor measurements into an application coordinate system and to the coordinates of its associated color sensor. As a result, the calibration method is an efficient solution in terms of precision and applicability in virtual reality and immersive telepresence applications. In addition to the core contributions, the results of two case studies which address 3D reconstruction and data streaming lead to the final conclusion of this thesis and to directions of future work in the rapidly advancing field of immersive telepresence research.
Der Einsatz ungeeigneter Materialien ist eine der häufigsten Ursachen für Bauwerksschäden. Da die Beseitigung dieser Schäden oft mit hohen Kosten verbunden ist, besteht in der Baupraxis der Bedarf an einer Identifizierungsmethode für eingesetzte Baustoffe. Daneben wäre eine Kenntnis der in einem Bauwerk vorliegenden Materialien auch für Instandhaltungsarbeiten hilfreich.
Die Identifizierung der in einem Festbeton oder Festmörtel vorliegenden Zementart gilt auch gegenwärtig noch als schwierig oder sogar unmöglich. Die Schwierigkeiten ergeben sich in erste Linie daraus, dass die Hydratationsprodukte verschiedener Zementarten oft nur geringe Unterschiede in ihrer chemischen und mineralogischen Zusammensetzung aufweisen und die Hydratationsmechanismen bei einigen Zementarten noch nicht vollständig erforscht sind.
Primäres Ziel der vorliegenden Arbeit war es zu untersuchen, ob anhand des Mineralphasenbestandes, der sich während einer thermischen Behandlung von Zementsteinen einstellt, eine Identifizierung der vorliegenden Zementart möglich ist. Weiterhin sollte die Übertragbarkeit dieser Ergebnisse auf Betone und Mörtel eingeschätzt werden.
Zur Schaffung von Identifizierungsmerkmalen wurden die (angereicherten) Zementsteine bei Temperaturen im Bereich zwischen 600 °C und 1400 °C thermisch behandelt. An den getemperten Proben wurde der Mineralphasenbestand mittels Röntgendiffraktometrie bestimmt. Mit der gleichen Methode wurden die Ausgangszemente und die (angereicherten) Zementsteine untersucht. Aus der Gegenüberstellung der nachgewiesenen Mineralphasen konnten die gesuchten Identifizierungsmerkmale abgeleitet werden. Um den Einfluss der Gesteinskörnungen auf die Identifizierungsmöglichkeiten gesondert zu erfassen, wurde das Versuchsprogramm auf 3 Abstraktionsebenen angelegt. Für die Auswertung der Ergebnisse wurden die Proben zu Klassen zusammengefasst, welche jeweils charakteristische Zusammensetzungen der Ausgangszemente repräsentieren. Für die Analyseergebnisse wurden die klassenspezifischen die Mittel- und Grenzwerte bestimmt.
Als die effektivste Methode zur Anreicherung der Zementsteinmatrix aus Mörtel- und Betonproben erwies sich die Kombination aus einer Zerkleinerung in einem Laborbackenbrecher. Die fein partikulären Fraktionen, welche Zementsteingehalte von 70-80 Ma.-% aufwiesen, wurden als Analyseproben verwendet. Es zeigte sich aber auch, dass das Anreicherungsergebnis von der Gesteinskörnungsart abhängt. Bei Laborbetonen mit einer Kalkstein-Gesteinskörnung wurde mit der gleichen Methode lediglich eine Anreicherung des Zementsteins auf etwa 50 Ma.-% erreicht.
Die Untersuchungen auf Abstraktionsebene 1 lieferten die Erkenntnis, dass der Hydratationsprozess der Klinkerphasen, der Klinkerphasengemische sowie des Hüttensandes, auch in Gegenwart des Sulfatträgers für Behandlungstemperaturen im Bereich des Klinkerbrandes vollständig reversibel ist. Im Hinblick auf die Identifizierungsmöglichkeiten wurde 1100 °C als optimale Behandlungstemperatur ermittelt, da hier eine Schmelzphasenbildung ausgeschlossen werden kann.
Durch eine Gegenüberstellung der chemischen Zusammensetzung der Ausgangszemente und des Phasenbestandes nach der Temperung konnte nachgewiesen werden, dass bei reinen Zementsteinen grundsätzlich alle Bestandteile an der Reaktion, die während der thermischen Behandlung bei 1100 °C stattfindet, beteiligt sind. Der sich einstellende Phasen bestand ist nur von der chemischen Zusammensetzung der Probe und dabei besonders von derem CaO-Gehalt abhängig. Empirisch wurde eine Prioritätenfolge für die Phasenbildung ermittelt. Daraus geht hervor, dass bevorzugt CaO-reiche Phasen, wie Aluminatferritphase, Belit und Ye‘elimit entstehen und dass überschüssiger Kalk als freies CaO vorliegt. Nur wenn der CaO-Gehalt der Probe nicht für die vollständige Bildung der – in der Summe – kalkreichsten Phasen ausreicht, entstehen partiell oder vollständig kalkärmere Phasen, wie Merwinit und Melilith. Basierend auf den Prioritäten zur Phasenbildung wurde ein Satz von Berechnungsgleichungen aufgestellt, mit denen der CaO-Typ aus der Phasenzusammensetzung der bei 1100 °C getemperten Probe bestimmt werden kann. CaO-Typen repräsentieren Bereiche für die chemische Zusammensetzung der Ausgangsprobe, welche bei der Temperaturbehandlung zu einer charakteristischen qualitativen Phasenzusammensetzung führen. Die CaO-Typen der marktüblichen Zementarten wurden anhand der in der Norm EN 197 festgelegten Bereiche für die Zusammensetzung der Zemente aus ihren Hauptbestandteilen sowie der aus der Fachliteratur ermittelten Bereiche für die chemische Zusammensetzung dieser Hauptbestandteile ermittelt. Damit kann für die Zementarten der Phasenbestand vorhergesagt werden, welcher sich während der Temperaturbehandlung des entsprechenden Zementsteins einstellt. Ein Vergleich mit dem gemessenen Phasenbestand erlaubt so die Identifizierung der Zementart.
Die Übertragbarkeit der durch die Untersuchungen an den Zementsteinen gewonnenen Erkenntnisse und die daraus abgeleiteten Identifizierungsmöglichkeiten auf Zementsteine, welche aus quarzsandhaltigen Normmörteln angereichert wurden, konnte nachgewiesen werden. Dabei wurde eine leichte Verschiebung des Phasenbestandes hin zu kalkärmeren Phasen beobachtet, welche auf die Reaktionsbeteiligung eines Teils der in den Proben enthaltenen Restgesteinskörnung zurückzuführen ist. Die Unterscheidungsmöglichkeiten zwischen den Zementarten blieben jedoch überwiegend erhalten.
Bei Betonen nimmt der Einfluss der Gesteinskörnung auf den Phasenbestand deutlich zu und kann zum Teil nicht mehr vernachlässigt werden. Die Identifizierungsmöglichkeiten müssen deshalb nach der chemischen Zusammensetzung und der Reaktivität der Gesteinskörnung differenziert ermittelt werden. Dazu sind weitere Untersuchungen notwendig.
Für Zementsteine, zementsteinreiche Systeme sowie Mörtel und Betone mit wenig reaktiven Gesteinskörnungen kann die Zementart bereits mit der in dieser Arbeit vorgestellten Methode identifiziert werden. In Fällen, für die sich die Bereiche der chemischen Zusammensetzung mehrerer Zementarten überschneiden, kann es dabei notwendig sein, zusätzliche chemische bzw. mineralogische Untersuchungen durchzuführen, z. B. am unbehandelten Zementstein.
The thesis investigates at the computer aided simulation process for operational vibration analysis of complex coupled systems. As part of the internal methods project “Absolute Values” of the BMW Group, the thesis deals with the analysis of the structural dynamic interactions and excitation interactions. The overarching aim of the methods project is to predict the operational vibrations of engines.
Simulations are usually used to analyze technical aspects (e. g. operational vibrations, strength, ...) of single components in the industrial development. The boundary conditions of submodels are mostly based on experiences. So the interactions with neighboring components and systems are neglected. To get physically more realistic results but still efficient simulations, this work wants to support the engineer during the preprocessing phase by useful criteria.
At first suitable abstraction levels based on the existing literature are defined to identify structural dynamic interactions and excitation interactions of coupled systems. So it is possible to separate different effects of the coupled subsystems. On this basis, criteria are derived to assess the influence of interactions between the considered systems. These criteria can be used during the preprocessing phase and help the engineer to build up efficient models with respect to the interactions with neighboring systems. The method was developed by using several models with different complexity levels. Furthermore, the method is proved for the application in the industrial environment by using the example of a current combustion engine.
Problem definition and research objectives
1. The production of Portland cement clinker causes approx. 5% to 8% of the annual man-made CO2 emissions. This is due to the usage of mainly fossil fuel (approx. 40 % of the total CO2) and because of the decarbonation of limestone as a main component of the raw meal (approx. 60 % of the total CO2).
2. Various strategies are applied in order to reduce the green-house gas-emissions, such as optimizing the process of clinker production, the use of alternative fuel and the partial substitution of the clinker in blended cement by so-called SCM (supplementary cementitious materials). Hereby blast-furnace slag, fly ash and limestone are the most used materials.
3. Quaternary systems containing three SCM simultaneously besides Portland cement contribute to the reduction of CO2 emissions due to the decrease of the clinker content. In addition, such systems allow to use blast-furnace slag and fly ash in the most economical way and provide the possibility to account for shortages of SCM on the market.
4. Blast-furnace slag and fly ash show similarities in their principal chemical compositions such that similar hydrates are formed during their reaction in presence of Portland cement. Compared to ternary systems based on blast-furnace slag or fly ash besides limestone, quaternary systems that contain both, blast-furnace slag and fly ash, simultaneously besides limestone, are expected to perform similar in terms of phase assemblage and strength development.
5. The use of SCM as cement replacing materials is limited due to their generally slower reaction compared to neat cement which also leads to lower strength development, especially in the early stage of the hydration up to 28 d. To account for this it is necessary to study the reactivity of SCM such as blast-furnace slag and fly ash in detail in order to develop strategies to enhance the reactivity and thereby the strength development of SCM-containing systems.
6. The early hydration of clinker phases is studied in detail, mainly in diluted systems. It is unclear if processes that were found to control the reaction of such model systems are also prevailing in concentrated cement pastes under realistic water-to-solid ratios. Deeper insight to this aspect is needed to better understand interactions of neat Portland cement and SCM in the first hours of hydration.
State-of-the-art
7. Increasing Ca-concentrations lead to decreasing dissolution rates of C3S and C2S in diluted systems.
8. The hydration kinetics of C3S is controlled by the interplay of undersaturation with respect to C3S and oversaturation with respect to C-S-H.
9. Increasing Al-concentrations lead to a retardation of the hydration of C3S. It is unclear if the uptake of aluminum in C-S-H to form C-(A)-S-H which has a significantly lower growth rate than pure C-S-H or a retarding effect of Al on the dissolution of C3S causes this phenomenon.
10. The surface of limestone provides excellent conditions for the nucleation and growth of C-S-H such that significantly more C-S-H nuclei are formed in presence of limestone compared to other SCM.
11. The reactivity of blast-furnace slag and fly ash depends on the particle size as well as on the intrinsic reactivity of especially the amorphous phases.
12. An increase in network modifying oxides (e.g. CaO) in the chemical composition of amorphous (calcium)aluminosilicates leads to an increasingly depolymerized network which in turn causes increasing reactivity. The role of amphoteric oxides (Al2O3, Fe2O3) that can be present as network modifying oxides as well as network forming oxides is not completely solved.
13. CO2-containing AFm-phases are thermodynamically more stable than monosulfoaluminate. This indirectly stabilizes the voluminous ettringite which causes a higher total volume of hydrates and lower porosity whereby higher compressive strength is reached.
14. Only a few percent of limestone in blended cement reacts chemically dependent on the Al2O3 available for reaction. Al2O3 that is provided by the reaction of Portland cement but also by the dissolution of SCM, especially by fly ash, reacts to form hemicarboaluminate which is transformed to monocarboaluminate as the hydration proceeds.
Methodology
15. The influence of SCM on the early hydration of Portland cement in binary (including blast-furnace slag or fly ash or limestone or quartz) and ternary (including fly ash and limestone) systems was investigated applying isothermal calorimetry and analysis of the pore solution chemistry. Calculated saturation indices and solubility products of relevant phases were correlated with heat development. Based on the gained data it was reviewed if mechanisms that control the hydration of pure phases in diluted systems are also prevailing in cement pastes under realistic conditions.
16. The influence of the chemical composition of synthetic glasses on their dissolution at high pH was investigated in highly diluted systems using ion chromatography. Pozzolanity tests were conducted on pastes using simplified model systems and glass-blended Portland cements. The process of the glass dissolution was investigated by isothermal calorimetry and by thermogravimetry. Correlation of experimentally determined total bound water with bound water determined by mass balance calculations as a function of amount of glass reacted allowed to estimate the degree of glass reaction in the pastes. Further on selective dissolution experiments were carried out to crosscheck the results of the bound water/mass balance approach.
17. The reaction kinetics of quaternary pastes containing blast-furnace slag and fly ash simultaneously in the presence of limestone were investigated up to 28 d using isothermal calorimetry and chemical shrinkage measurements. In addition strength tests on mortar bars were carried out.
18. Pastes of quaternary blends were also investigated in terms of hydrate assemblage at ages of up to 182 d. Thermodynamic calculations regarding total volume of hydrates as a function of limestone and fly ash/blast-furnace slag content were conducted. The calculations were supported by thermogravimetric determination of bound water and portlandite content as well as qualitative X-ray diffraction. The results were correlated with strength tests on mortar bars.
19. The pore solutions of hydrated quaternary blends were extracted and investigated by means of ion chromatography at ages of up to 728 d. Based on the ion concentrations in the solutions saturation indices were calculated for relevant phases. In order to gain better insight to the blast-furnace slag reaction sulphate speciation was carried out at two blast furnace slag levels (20 and 30 wt.%) for selected samples up to 91 d of hydration and at 91 d for the whole matrix under investigation.
Main results
20. Investigations on the early hydration kinetics of binary systems showed a higher heat flow in presence of SCM compared to neat Portland cement. This is caused by the higher surface area that is available for the nucleation of hydrates and by the lower (over)saturation with respect to C-S-H. An increase in the Ca-concentration in the pore solution did not cause lower dissolution rates of C3S as was reported for pure phases in diluted systems. The highest dissolution was observed in the presence of limestone, i.e. at the highest Ca-concentration. The general trend of the reaction rate is inversely related to the degree of undersaturation with respect to C3S. The more undersaturated the faster the observed reaction. The presence of increasing Al-concentrations caused a retardation of the reaction which is in line with investigations on pure phases in diluted systems. Higher sulphate concentrations could be detected for the fly ash containing blend which possibly hindered ettringite precipitation and results in higher Al-concentrations. Correspondingly the low sulphate concentrations lead to lower Al-concentrations in the presence of quartz, blast-furnace slag and limestone compared to fly ash.
21. The early hydration kinetics of quaternary systems is significantly accelerated in the presence of limestone while fly ash leads to retardation. Compared to reference systems containing inert quartz, investigations by means of isothermal calorimetry and chemical shrinkage revealed an acceleration caused by blast-furnace slag. Additions of fly ash, limestone or mixtures thereof introduced another acceleration but differences are too small to be significant and clear distinguishing between the various SCM is not possible.
22. Investigations on the reactivity of synthetic glasses showed that increasing amounts of network modifying oxides caused an increase in reactivity and dissolution rates. The results reveal that Al2O3 acts mainly as network modifying oxide in all investigated glasses. Experimentally determined bound water (thermogravimetric experiments) in model systems and blended cements can be compared with bound water determined by mass balance calculations carried out as a function of the amount of glass reacted. This enables to estimate the degree of glass reaction.
23. The actual content of blast-furnace slag, fly ash or limestone does not exert significant influence on the development of compressive strength up to 7 d. At later ages thermodynamic calculations predict a degree of CaCO3 reaction of 2 to 5 wt.%. This leads to the formation of hemicarbonate and monocarbonate whereby ettringite is indirectly stabilized. As a result the total amount of solids is increased and compressive strength shows a slight maximum. Hereby the degree of CaCO3 reaction depends on the Al2O3 available for reaction which is not only provided by the dissolution of Portland cement but especially by the dissolution of the fly ash.
24. In general the presence of blast-furnace slag and fly ash in the presence of limestone exerts little influence on the hydrate assemblage. The substitution of some of the blast-furnace slag by fly ash leads to a slight decrease of portlandite and C-S-H and gives rise to the formation of more monocarbonate and hemicarbonate. Portlandite is consumed in a pozzolanic reaction with the fly ash whereby C-S-H is formed. However, the low reactivity of the fly ash causes a decrease in the amount of C-S-H formed. Thereby a lower total volume of hydrates is generated which is in line with slightly lower compressive strength in case of increasing fly ash content. The overall influence is small and all systems investigated reach strength class 42.5 N according to EN 196-1.
25. Corresponding to the investigations of the hydrate assemblage the pore solution chemistry of quaternary systems showed only small variations. Depending on the fly ash content the highest variations are observed for aluminium, i.e. increasing fly ash content leads to higher Al-concentrations. Another effect of increasing fly ash contents is an increasing undersaturation with respect to portlandite and a decreasing undersaturation with respect to strätlingite indicating the dissolution of portlandite.
26. The total concentration of sulfur in the pore solution is controlled by sulphate (SO42–) while the concentrations of sulphite (SO32–) and thiosulphate (S2O32–) were very low. Up to 2 d of hydration about 90 % of the total sulphur is present as SO42–. After 91 d this value is reduced to about 36 % while about 28 % are present as S2O32–. In general higher blast-furnace slag content leads to higher concentrations of sulphite and thiosulphate after 7 d.
Eine zielführende Anwendung von Zusatzmitteln bei der Ausführung anspruchsvoller Betonbauten setzt einen hohen Kenntnisstand bezüglich der Wirkungsmechanismen und Interaktionen der einzelnen Betonkomponenten voraus. In der vorliegenden Arbeit wurden einige Aspekte der Zementhydratation in Abhängigkeit von der Fließmittelzugabe diskutiert. Im Ergebnis liefern die Teile eins und zwei der vorliegenden Arbeit einen Beitrag dazu, Veränderungen der Fließfähigkeit von Zementleim in Abhängigkeit der Zementhydratation und Fließmittelzugabe besser zu verstehen. Es konnte so z.B. gezeigt werden, dass Bildung langprismatischer Kristalle (z.B. Syngenit, Gips) die Fließfähigkeit von Zementleim und Beton vermindert. Infolge anhaltender Scherung von Zementleimen / Betonen mit langprismatischen Kristallen wird ein Zuwachs an Fließfähigkeit erzielt. Elektronenmikroskopische Untersuchungen zeigen, dass dies darauf zurückzuführen ist, dass die Kristalle in eine Vorzugsorientierung relativ zur Scherbewegung rotieren. Weiterhin wurde der Mechanismus einer so genannten Zement-Fließmittel-Inkompatibilität aufgezeigt. Durch diese Erweiterung des Kenntnisstandes zum Einfluss von Fließmitteln auf die Zementhydratation ist es möglich der Zement-Fließmittel-Inkompatibilität durch gezielte Auswahl des Zementes vorzubeugen. Dabei ist besonders darauf zu achten, dass der Zement ein ausgewogenes Verhältnis an zur Reaktion zur Verfügung stehendem C3A und Menge / Löslichkeit des Abbindereglers besitzt. Fließmittel verändern nicht nur die Verarbeitungseigenschaften sondern auch die Festigkeit und Dauerhaftigkeit von Zementstein und Beton. Im dritten Teil der vorliegenden Arbeit wird daher der Einfluss der Fließmittel und deren verflüssigender Wirkung auf die Festigkeitsentwicklung von Zementstein und C3S untersucht. Es konnte gezeigt werden, dass durch die dispergierende Wirkung der Fließmittel auch ohne Verminderung des Wasserzementwertes, eine Verdichtung des Zementsteingefüges erzielt werden kann. Es konnte weiterhin gezeigt werden, dass durch die Erhöhung der Partikelpackungsdichte am Anfang der Hydratation die Ausbildung der festigkeitsgebenden C-S-H Phasen verändert wird. Ein dichteres Verwachsen dieser nanostrukturierten C-S-H Phasen ermöglicht einen zusätzlichen Festigkeitszuwachs.
Reine Calciumsulfatbindemittel weisen eine hohe Löslichkeit auf. Feuchteinwirkung führt zudem zu starken Festigkeitsverlusten. Aus diesem Grund werden diese Bindemittel ausschließlich für Baustoffe und -produkte im Innenbereich ohne permanenten Feuchtebeanspruchung eingesetzt. Eine Möglichkeit, die Feuchtebeständigkeit zu erhöhen, ist die Beimischung puzzolanischer und zementärer Komponenten. Diese Mischsysteme werden Gips-Zement-Puzzolan-Bindemittel (kurz: GZPB) genannt.
Mischungen aus Calciumsulfaten und Portlandzementen allein sind aufgrund der treibenden Ettringitbildung nicht raumbeständig. Durch die Zugabe von puzzolanischen Stoffen können aber Bedingungen im hydratisierenden System geschaffen werden, welche eine rissfreie Erhärtung ermöglichen. Hierfür ist eine exakte Rezeptierung der GZPB notwendig, um die GZPB-typischen, ettringitbedingten Dehnungen zeitlich zu begrenzen. Insbesondere bei alumosilikatischen Puzzolanen treten während der Hydratation gegenüber rein silikatischen Puzzolanen deutlich höhere Expansionen auf, wodurch die Gefahr einer potenziellen Rissbildung steigt. Für die Erstellung geeigneter GZPB-Zusammensetzungen bedarf es daher einer Methodik, um raumbeständig erhärtende Systeme sicher von destruktiven Mischungen unterscheiden zu können.
Sowohl für die Rezeptierung als auch für die Anwendung der GZPB existieren in Deutschland keinerlei Normen. Darüber hinaus sind die Hydratationsvorgänge sowie die entstehenden Produkte nicht konsistent beschrieben. Auch auf die Besonderheiten der GZPB mit alumosilikatischen Puzzolanen wird in der Literatur nur unzureichend eingegangen.
Ziel war es daher, ein grundlegendes Verständnis der Hydratation sowie eine sichere Methodik zur Rezeptierung raumbeständig und rissfrei erhärtender GZPB, insbesondere in Hinblick auf die Verwendung alumosilikatischer Puzzolane, zu erarbeiten. Darüber hinaus sollte systematisch der Einfluss der Einzelkomponenten auf Hydratation und Eigenschaften dieser Bindemittelsysteme untersucht werden. Dies soll ermöglichen, die GZPB für ein breites Anwendungsspektrum als Bindemittel zu etablieren, und somit vorteilhafte Eigenschaften der Calciumsulfate (geringe Schwindneigung, geringe CO2-Emission etc.) mit der Leistungs-fähigkeit von Zementen (Wasserbeständigkeit, Festigkeit, Dauerhaftigkeit etc.) zu verbinden.
Als Ausgangsstoffe der Untersuchungen zu den GZPB wurden Stuckgips und Alpha-Halbhydrat als Calciumsulfatbindemittel in unterschiedlichen Anteilen im GZPB verwendet. Die Puzzolan-Zement-Verhältnisse wurden ebenfalls variiert. Als Puzzolan kam für den Großteil der Untersuchungen ein alumosilikatisches Metakaolin zum Einsatz. Als kalkspendende Komponente diente ein reiner Portlandzement.
Das Untersuchungsprogramm gliederte sich in 4 Teile. Zuerst wurde anhand von CaO- und pH-Wert-Messungen in Suspensionen sowie dem Längenänderungsverhalten von Bindemittelleimen verschiedener Zusammensetzungen eine Vorauswahl geeigneter GZPB-Rezepturen ermittelt. Danach erfolgten, ebenfalls an Bindemittelleimen, Untersuchungen zu den Eigenschaften der als geeignet eingeschätzten GZPB-Mischungen. Hierzu zählten Langzeitbetrachtungen zur rissfreien Erhärtung bei unterschiedlichen Umgebungsbedingungen sowie die Festigkeitsentwicklung im trockenen und feuchten Zustand. Im nächsten Schritt wurde anhand zweier exemplarischer GZPB-Zusammensetzungen (mit silikatischen und alumosilikatischen Puzzolan) die prinzipiell mögliche Phasenzusammensetzung unter Variation des Puzzolan-Zement-Verhältnisses (P/Z-Verhältnis) und des Calciumsulfatanteils im thermodynamischen Gleichgewichtszustand berechnet. Hier wurde im Besonderen auf Unterschiede der silikatischen und alumosilikatischen Puzzolane eingegangen. Im letzten Teil der Untersuchungen wurden die Hydratationskinetik der GZPB sowie die Gefügeentwicklung näher betrachtet. Hierfür wurden die Porenlösungen chemisch analysiert und Sättigungsindizes berechnet, sowie elektronenmikropische, porosimetrische und röntgenografische Untersuchungen durchgeführt. Abschließend wurden die Ergebnisse gesamtheitlich interpretiert, da die Ergebnisse der einzelnen Untersuchungsprogramme miteinander in Wechselwirkung stehen.
Als hauptsächliche Hydratationsprodukte wurden Calciumsulfat-Dihydrat, Ettringit und
C-(A)-S-H-Phasen ermittelt, deren Anteile im GZPB neben dem Calciumsulfatanteil und dem Puzzolan-Zement-Verhältnis auch deutlich vom Wasserangebot und der Gefügeentwicklung abhängen. Bei Verwendung von alumosilikatischen Puzzolans kommt es wahrscheinlich zur teilweisen Substitution des Siliciums durch Aluminium in den C-S-H-Phasen. Dies erscheint aufgrund des Nachweises der für diese Phasen typischen, folienartigen Morphologie wahrscheinlich. Portlandit wurde in raumbeständigen GZPB-Systemen nur zu sehr frühen Zeitpunkten in geringen Mengen gefunden.
In den Untersuchungen konnte ein Teil der in der Literatur beschriebenen, prinzipiellen Hydratationsabläufe bestätigt werden. Bei Verwendung von Halbhydrat als Calciumsulfatkomponente entsteht zuerst Dihydrat und bildet die Primärstruktur der GZPB. In dieses existierende Grundgefüge kristallisieren dann das Ettringit und die C-(A)-S-H-Phasen. In den GZPB sorgen entgegen der Beschreibungen in der Literatur nicht ausschließlich die
C-(A)-S-H-Phasen zur Verbesserung der Feuchtebeständigkeit und der Erhöhung des Festigkeitsniveaus, sondern auch das Ettringit. Beide Phasen überwachsen im zeitlichen Verlauf der Hydratation die Dihydratkristalle in der Matrix und hüllen diese – je nach Calciumsulfatanteil im GZPB – teilweise oder vollständig ein. Diese Umhüllung sowie die starke Gefügeverdichtung durch die C-(A)-S-H-Phasen und das Ettringit bedingen, dass ein lösender Angriff durch Wasser erschwert oder gar verhindert wird. Gleichzeitig wird die Gleitfähigkeit an den Kontaktstellen der Dihydratkristalle verringert.
Eine rissfreie und raumbeständige Erhärtung ist für die gefahrlose Anwendung eines GZPB-Systems essentiell. Hierfür ist die Kinetik der Ettringitbildung von elementarer Bedeutung. Die gebildete Ettringitmenge spielt nur eine untergeordnete Rolle. Selbst ausgeprägte, ettringitbedingte Dehnungen und hohe sich bildende Mengen führen zu frühen Zeitpunkten, wenn die Dihydratkristalle noch leicht gegeneinander verschiebbar sind, zu keinen Schäden. Bleibt die Übersättigung bezüglich Ettringit und somit auch der Kristallisationsdruck allerdings über einen langen Zeitraum hoch, genügen bereits geringe Ettringitmengen, um das sich stetig verfestigende Gefüge stark zu schädigen.
Die für die raumbeständige Erhärtung der GZPB notwendige, schnelle Abnahme der Ettringitübersättigung wird hauptsächlich durch die Reaktivität des Puzzolans beeinflusst. Die puzzolanische Reaktion führt zur Bindung des aus dem Zement stammenden Calciumhydroxid durch die Bildung von C-(A)-S-H-Phasen und Ettringit. Hierdurch sinkt die Calcium- und Hydroxidionenkonzentration in der Porenlösung im Verlauf der Hydratation, wodurch auch die Übersättigung bezüglich Ettringit abnimmt. Je höher die Reaktivität des Puzzolans ist, desto schneller sinkt der Sättigungsindex des Ettringits und somit auch der Kristallisationsdruck. Nach Unterschreiten eines noch näher zu klärendem Grenzwert der Übersättigung stagnieren die Dehnungen. Das Ettringit kristallisiert bzw. wächst nun bevorzugt in den Poren ohne eine weitere, äußere Volumenzunahme zu verursachen.
Um eine schadensfreie Erhärtung des GZPB zu gewährleisten, muss gerade in der frühen Phase der Hydratation ein ausreichendes Wasserangebot gewährleistet werden, so dass die Ettringitbildung möglichst vollständig ablaufen kann. Andernfalls kann es bei einer Wiederbefeuchtung zur Reaktivierung der Ettringitbildung kommen, was im eingebauten Zustand Schäden verursachen kann. Die Gewährleistung eines ausreichenden Wasserangebots ist im GZPB-System nicht unproblematisch. In Abhängigkeit der GZPB-Zusammensetzung können sich große Ettringitmengen bilden, die einen sehr hohen Wasserbedarf aufweisen. Deshalb kann es, je nach verwendeten Wasser-Bindemittel-Wert, im Bindemittelleim zu einem Wassermangel kommen, welcher die weitere Hydratation verlangsamt bzw. komplett verhindert. Zudem können GZPB-Systeme teils sehr dichte Gefüge ausbilden, wodurch der Wassertransport zum Reaktionsort des Ettringits zusätzlich behindert wird.
Die Konzeption raumbeständiger GZPB-Systeme muss anhand mehrerer aufeinander aufbauender Untersuchungen erfolgen. Zur Vorauswahl geeigneter Puzzolan-Zementverhältnisse eignen sich die Messungen der CaO-Konzentration und des pH-Wertes in Suspensionen. Als alleinige Beurteilungsgrundlage reicht dies allerdings nicht aus. Zusätzlich muss das Längenänderungs-verhalten beurteilt werden. Raumbeständige Mischungen mit alumosilikatischen Puzzolanen zeigen zu frühen Zeitpunkten starke Dehnungen, welche dann abrupt stagnieren. Stetige – auch geringe – Dehnungen weisen auf eine destruktive Zusammensetzung hin.
Mit diesem mehrstufigen Vorgehen können raumbeständige, stabile GZPB-Systeme konzipiert werden, so dass die Zielstellung der Arbeit erreicht wurde und ein sicherer praktischer Einsatz dieser Bindemittelart gewährleistet werden kann.
Modern digital material approaches for the visualization and simulation of heterogeneous materials allow to investigate the behavior of complex multiphase materials with their physical nonlinear material response at various scales. However, these computational techniques require extensive hardware resources with respect to computing power and main memory to solve numerically large-scale discretized models in 3D. Due to a very high number of degrees of freedom, which may rapidly be increased to the two-digit million range, the limited hardware ressources are to be utilized in a most efficient way to enable an execution of the numerical algorithms in minimal computation time. Hence, in the field of computational mechanics, various methods and algorithms can lead to an optimized runtime behavior of nonlinear simulation models, where several approaches are proposed and investigated in this thesis.
Today, the numerical simulation of damage effects in heterogeneous materials is performed by the adaption of multiscale methods. A consistent modeling in the three-dimensional space with an appropriate discretization resolution on each scale (based on a hierarchical or concurrent multiscale model), however, still contains computational challenges in respect to the convergence behavior, the scale transition or the solver performance of the weak coupled problems. The computational efficiency and the distribution among available hardware resources (often based on a parallel hardware architecture) can significantly be improved. In the past years, high-performance computing (HPC) and graphics processing unit (GPU) based computation techniques were established for the investigationof scientific objectives. Their application results in the modification of existing and the development of new computational methods for the numerical implementation, which enables to take advantage of massively clustered computer hardware resources. In the field of numerical simulation in material science, e.g. within the investigation of damage effects in multiphase composites, the suitability of such models is often restricted by the number of degrees of freedom (d.o.f.s) in the three-dimensional spatial discretization. This proves to be difficult for the type of implementation method used for the nonlinear simulation procedure and, simultaneously has a great influence on memory demand and computational time.
In this thesis, a hybrid discretization technique has been developed for the three-dimensional discretization of a three-phase material, which is respecting the numerical efficiency of nonlinear (damage) simulations of these materials. The increase of the computational efficiency is enabled by the improved scalability of the numerical algorithms. Consequently, substructuring methods for partitioning the hybrid mesh were implemented, tested and adapted to the HPC computing framework using several hundred CPU (central processing units) nodes for building the finite element assembly. A memory-efficient iterative and parallelized equation solver combined with a special preconditioning technique for solving the underlying equation system was modified and adapted to enable combined CPU and GPU based computations.
Hence, it is recommended by the author to apply the substructuring method for hybrid meshes, which respects different material phases and their mechanical behavior and which enables to split the structure in elastic and inelastic parts. However, the consideration of the nonlinear material behavior, specified for the corresponding phase, is limited to the inelastic domains only, and by that causes a decreased computing time for the nonlinear procedure. Due to the high numerical effort for such simulations, an alternative approach for the nonlinear finite element analysis, based on the sequential linear analysis, was implemented in respect to scalable HPC. The incremental-iterative procedure in finite element analysis (FEA) during the nonlinear step was then replaced by a sequence of linear FE analysis when damage in critical regions occured, known in literature as saw-tooth approach. As a result, qualitative (smeared) crack initiation in 3D multiphase specimens has efficiently been simulated.
Rapid urbanisation that is not accompanied by socio-economic development strains the capacity of local and national governments to provide even basic services such as shelter. Informal settlements i.e. settlements not built or developed according to the formal regulations have become a solution to many urban dwellers in developing countries. In Tanzania informal settlements accommodate people from low, middle and high income groups. The study explores the nature of potentials and challenges posed by the existence of mixed socio-economic groups in informal settlements, including an assessment of what can be done to optimise utilisation of potentials and mitigation of conflicts. Using a case study strategy, the study was conducted in Dar es Salaam city focusing on Makongo mixed informal settlement.
The results show that mixed informal settlements are as a result of several factors including uncoordinated energies of people. The urban development forces that bring change in the development of the city are stronger than the public states capacity to coordinate and manage them. Informal settlements also offer user-friendly land tenure, flexibility in house construction and proximity to livelihoods. Other factors include the nature of socio-economic living patterns and extension of urban boundaries. Community members operate using social norms. Advantages of mixed informal settlements include availability of plots according to needs and affordability while a disadvantage is, people of different socio-economic groups perceive problems differently.
For policies to be effective, their formulation should be derived from what is happening on the ground i.e. addressing informal settlements according to their heterogeneity. Moreover, empowered local authorities can assist in implementing national development plans; also actors in land development including government institutions, non-governmental institutions, financial institutions, private sector, professionals, political leaders, research institutions, policy-makers and training institutions need to recognise, understand and respect each other’s roles, and pull resources together to minimise problems related to informality in land development; utilise potentials and minimise challenges in mixed informal settlements in Dar es Salaam.
Key words: Informal settlements, land development, urbanisation
Lettenkeuper- und Schilfsandsteine sind in Thüringen weit verbreitet und wurden häufig als Werk- und Bildhauersandsteine verwendet. Die überwiegend tonig-ferritisch gebundenen Steine sind stark witterungsanfällig. Inzwischen droht ein unwiederbringlicher Substanzverlust an vielen denkmalpflegerisch wertvollen Gebäuden und an plastischen Bildwerken. Die Dissertation gibt einen Überblick über die Vorkommen, Eigenschaften und Schadbilder dieser Sandsteine in Thüringen. Konservierungsmaßnahmen, die in Thüringen in den vergangenen 20 Jahren an Lettenkeuper- und Schilfsandsteinen vorgenommen wurden, werden ausgewertet und neue Erkenntnisse zur Konservierung dieser Sandsteine vorgestellt.
This cumulative dissertation investigates aspects of consumer decision making in hedonic contexts and its implications for the marketing of media goods through a series of three empirical studies. All three studies take place within a common theoretical framework of decision making models, applying parts of the framework in novel ways to solve real-world marketing research problems (study 1 and 2), and examining theoretical relationships between variables within of the framework (study 3). One notable way in which the studies differ is their theoretical treatment of the hedonic component of decision making, i.e. the role and conceptualization of emotions.