Refine
Year of publication
- 2014 (24) (remove)
Document Type
- Doctoral Thesis (24) (remove)
Keywords
- Pestizid (2)
- Pflanzenschutzmittel (2)
- monitoring (2)
- Abdrift (1)
- Annotation (1)
- Anpassung (1)
- Araneae (1)
- Augenbewegung (1)
- Auslese (1)
- Auswahl (1)
Institute
- Fachbereich 7 (8)
- Fachbereich 5 (3)
- Institut für Informatik (3)
- Fachbereich 8 (2)
- Institut für Erziehungswissenschaft (2)
- Institute for Web Science and Technologies (2)
- Fachbereich 6 (1)
- Institut für Anglistik und Amerikanistik (1)
- Institut für Computervisualistik (1)
- Institut für Grundschulpädagogik (1)
The goal of this thesis is the development of methods for augmented image synthesis using 3D photo collections. 3D photo collections are representations of real scenes automatically generated from single photos and describe a scene as a set of images with known camera poses as well as a sparse point-based model of the scene geometry. The main goal is to perform a photo-realistic augmented image synthesis of real and virtual parts, where the real scene is provided as a 3D photo collection. Therefore, three main problems are addressed.
Since the photos may be represented in different device-specific RGB color spaces, a color characterization of the 3D photo collections is necessary to gain correct color information that is consistent with human perception. The proposed novel method automatically transforms all images into a common RGB color space and thereby simplifies color characterization of 3D photo collections.
As a main problem for augmented image synthesis, all environmental lighting has to be known in order to apply illumination to virtual parts that is consistent with the real portions shown in the photos. To solve this problem, two novel methods were developed to reconstruct the lighting from 3D photo collections.
In order to perform image synthesis for arbitrary views on the scene, an image-based approach was developed that generates new views in 3D photo collections making direct use of its point cloud. The novel method creates new views in real-time and allows free-navigation.
In conclusion, the proposed novel methods show that 3D photo collections are a useful representation for real scenes in Augmented Reality and they can be used to perform a realistic image synthesis of real and virtual portions.
This study examined whether positive resource change and two types of baseline stressors would influence general life satisfaction and satisfaction with health at the end of treatment in mothers attending an inpatient rehabilitation or preventive program for mothers, fathers and children. Parenting self-efficacy was included as an indicator of resources while baseline distress was operationalized in terms of parenting-related stressors and depressive symptoms, respectively. Drawing on Hobfoll- conservation of resources theory, it was hypothesized that resource change and baseline stressors would interact in their effect on satisfaction measures at the end of the preventive/rehabilitation program: resource gains were expected to influence satisfaction more strongly in patients who reported higher stress levels at baseline (as compared to patients with lower baseline distress; primary research question). Hypotheses were tested using a sample of N=1724 female prevention and rehabilitation patients by means of structural equation modeling including latent interactions. Results showed that parenting-related stressors were negatively associated with general satisfaction as well as satisfaction with health while resource gains had a small positive effect on satisfaction. There was, however, no significant interaction of parenting-related stressors and positive resource change. When depressive symptoms were included as a measure of baseline distress, they were negatively associated with both facets of satisfaction. In these models, there were only small positive associations of resource gains and satisfaction measures. Again, no interaction effects were found. Additional analyses that comprised both stressor types as predictors showed that the effects of depressive symptoms on satisfaction were more pronounced than the influence of parenting-related stressors; the effects of resource gains were small to negligible. In addition, it was examined whether problem-oriented coping strategies mediated the influence of positive resource change on general life satisfaction and satisfaction with health, respectively (secondary research question). Correlations between coping, resource change and satisfaction were low or not significant. Given this lack of direct associations between the relevant variables, no further path analytic testing was performed; the hypothesized mediating role of problem-oriented coping could thus not be confirmed. All in all, study results show that contrary to the hypotheses derived from conservation of resources theory, the effects of positive resource change and distress indicators on patients" life satisfaction and satisfaction with health were not interdependent.
By the work presented in this thesis, the CH4 emissions of the River Saar were quantified in space and time continuously and all relevant processes leading to the observed pattern were identified. The direct comparison between reservoir zones and free-flowing intermediate reaches revealed, that the reservoir zones are CH4 emission hot spots and emitted over 90% of the total CH4. On average, the reservoir zones emitted over 80 times more CH4 per square meter than the intermediate reaches between dams (0.23 vs. 19.7 mol CH4 m-2 d-1). The high emission rates measured in the reservoir zones fall into the range of emissions observed in tropical reservoirs. The main reason for this is the accumulation of thick organic rich sediments and we showed that the net sedimentation rate is an excellent proxy for estimating ebullitive emissions. Within the hot spot zones, the ebullitive flux enhanced also the diffusive surface emissions as well as the degassing emissions at dams.
To resolve the high temporal variability, we developed an autonomous instrument for continuous measurements of the ebullition rate over long periods (> 4 weeks). With this instrument we could quantify the variability and identify the relevant trigger mechanisms. At the Saar, ship-lock induces surges and ship waves were responsible for over 85% of all large ebullition events. This dataset was also used to determine the error associated with short sampling periods and we found that with sampling periods of 24 hours as used in other studies, the ebullition rates were systematically underestimated by ~50%. Measuring the temporal variability enabled us to build up a conceptual framework for estimating the temporal pattern of ebullition in other aquatic systems. With respect to the contribution of freshwater systems to the global CH4 emissions, hot spot emission sites in impounded rivers have the potential to increase the current global estimate by up to 7%.
Web 2.0 provides technologies for online collaboration of users as well as the creation, publication and sharing of user-generated contents in an interactive way. Twitter, CNET, CiteSeerX, etc. are examples of Web 2.0 platforms which facilitate users in these activities and are viewed as rich sources of information. In the platforms mentioned as examples, users can participate in discussions, comment others, provide feedback on various issues, publish articles and write blogs, thereby producing a high volume of unstructured data which at the same time leads to an information overload. To satisfy various types of human information needs arising from the purpose and nature of the platforms requires methods for appropriate aggregation and automatic analysis of this unstructured data. In this thesis, we propose methods which attempt to overcome the problem of information overload and help in satisfying user information needs in three scenarios.
To this end, first we look at two of the main challenges of sparsity and content quality in Twitter and how these challenges can influence standard retrieval models. We analyze and identify Twitter content features that reflect high quality information. Based on this analysis we introduce the concept of "interestingness" as a static quality measure. We empirically show that our proposed measure helps in retrieving and filtering high quality information in Twitter. Our second contribution relates to the content diversification problem in a collaborative social environment, where the motive of the end user is to gain a comprehensive overview of the pros and cons of a discussion track which results from social collaboration of the people. For this purpose, we develop the FREuD approach which aims at solving the content diversification problem by combining latent semantic analysis with sentiment estimation approaches. Our evaluation results show that the FREuD approach provides a representative overview of sub-topics and aspects of discussions, characteristic user sentiments under different aspects, and reasons expressed by different opponents. Our third contribution presents a novel probabilistic Author-Topic-Time model, which aims at mining topical trends and user interests from social media. Our approach solves this problem by means of Bayesian modeling of relations between authors, latent topics and temporal information. We present results of application of the model to the scientific publication datasets from CiteSeerX showing improved semantically cohesive topic detection and capturing shifts in authors" interest in relation to topic evolution.
In the recent years, Software Engineering research has shown the rise of interest in the empirical studies. Such studies are often based on empirical evidence derived from corpora - collections of software artifacts. While there are established forms of carrying out empirical research (experiments, case studies, surveys, etc.), the common task of preparing the underlying collection of software artifacts is typically addressed in ad hoc manner.
In this thesis, by means of a literature survey we show how frequently software engineering research employs software corpora and using a developed classification scheme we discuss their characteristics. Addressing the lack of methodology, we suggest a method of corpus (re-)engineering and apply it to an existing collection of Java projects.
We report two extensive empirical studies, where we perform a broad and diverse range of analyses on the language for privacy preferences (P3P) and on object-oriented application programming interfaces (APIs). In both cases, we are driven by the data at hand, by the corpus itself, discovering the actual usage of the languages.
Through the increasing availability of access to the web, more and more interactions between people take place in online social networks, such as Twitter or Facebook, or sites where opinions can be exchanged. At the same time, knowledge is made openly available for many people, such as by the biggest collaborative encyclopedia Wikipedia and diverse information in Internet forums and on websites. These two kinds of networks - social networks and knowledge networks - are highly dynamic in the sense that the links that contain the important information about the relationships between people or the relations between knowledge items are frequently updated or changed. These changes follow particular structural patterns and characteristics that are far less random than expected.
The goal of this thesis is to predict three characteristic link patterns for the two network types of interest: the addition of new links, the removal of existing links and the presence of latent negative links. First, we show that the prediction of link removal is indeed a new and challenging problem. Even if the sociological literature suggests that reasons for the formation and resolution of ties are often complementary, we show that the two respective prediction problems are not. In particular, we show that the dynamics of new links and unlinks lead to the four link states of growth, decay, stability and instability. For knowledge networks we show that the prediction of link changes greatly benefits from the usage of temporal information; the timestamp of link creation and deletion events improves the prediction of future link changes. For that, we present and evaluate four temporal models that resemble different exploitation strategies. Focusing on directed social networks, we conceptualize and evaluate sociological constructs that explain the formation and dissolution of relationships between users. Measures based on information about past relationships are extremely valuable for predicting the dissolution of social ties. Hence, consistent for knowledge networks and social networks, temporal information in a network greatly improves the prediction quality. Turning again to social networks, we show that negative relationship information such as distrust or enmity can be predicted from positive known relationships in the network. This is particularly interesting in networks where users cannot label their relationships to other users as negative. For this scenario we show how latent negative relationships can be predicted.
Mathematical Modelling of GIS Tailored GUI Design with the Application of Spatial Fuzzy Logic
(2014)
This PhD thesis is situated within the framework of the Research-Group Learning and Neurosciences (ReGLaN)-Health and Logistics project. The goal of this project is the optimisation of health service delivery in the rural areas of South Africa. Cooperation takes place between ReGLaN-Health and Logistics and the South African Council for Scientific and Industrial Research (CSIR) Meraka Institute, with Prof Dr Dr Marlien Herselman of Pretoria, South Africa, as the central contact person. This thesis deals with the mathematical modelling of Geographic Information System (GIS)-tailoredrnGraphical User Interface (GUI) design with the application of spatial fuzzy logic. This thesis considers the mathematical visualisation of risk and resource maps for epidemiological issues using GIS and adaptive GUI design for an Open Source (OS) application for digital devices. The intention ofrnthis thesis is to provide spatial decision support tailored to different user groups. In order for the GUI elements to be evaluated and initialised, empirical teaching-learning-research on dealing with geomedia and GUI elements was conducted.
This study explored the question whether greenhouse gas mitigation projects in Namibia could be initiated through local economic development programmes. In particular, research was done on whether the Clean Development Mechanism (CDM) of the Kyoto Protocol could play an essential role in the promotion of such mitigation projects.
In a first step supporting and inhibiting factors (potential for mitigation projects, business and investment climate, institutions, etc.) were discussed, which have a negative or positive influence on mitigation projects. In a second step the mind-set of climate and energy experts as well as of local economic development experts and practitioners was analysed with regard to the research questions. To this end, 229 questionnaires, 28 interviews and the output of a focus group discussion with 20 participants were evaluated. Additionally, the author conducted a real life case study to investigate the practicability of initiating greenhouse gas mitigation projects through local economic development efforts. Parallel to the development of an economic development strategy in the Namibian region of Otjozondjupa, the potential for greenhouse gas mitigation projects was explored. Based on the outcome of this investigation project ideas were developed and their potential socio-economic impact was evaluated. Promising projects were then included into the development strategy.
Due to various factors such as the complexity of CDM, low greenhouse gas emissions in Namibia, the low price of emission rights and insufficient financial means it is unlikely that CDM projects can be initiated through local economic development initiatives in Namibia. However, many stakeholders consider the idea of interlinking mitigation projects and local economic development initiatives favourably as long as such projects support the broader objectives of those initiatives. This research has shown that locally initiated mitigation projects do not contribute much to employment or income generation at the local level in Namibia. Thus, national strategic objectives should be considered, such as improving access to electricity to all strata of society or becoming less dependent on electricity imports. This requires, however, that local economic development strategies also cover the energy sector, that local governments are willing and capacitated to initiate mitigation projects, that national and local public institutions work together more closely, that national and local economic framework conditions are improved so as to attract private investments, and that the experiences and interests of the relevant stakeholders are considered throughout the project development process.
Diffusion imaging captures the movement of water molecules in tissue by applying varying gradient fields in a magnetic resonance imaging (MRI)-based setting. It poses a crucial contribution to in vivo examinations of neuronal connections: The local diffusion profile enables inference of the position and orientation of fiber pathways. Diffusion imaging is a significant technique for fundamental neuroscience, in which pathways connecting cortical activation zones are examined, and for neurosurgical planning, where fiber reconstructions are considered as intervention related risk structures.
Diffusion tensor imaging (DTI) is currently applied in clinical environments in order to model the MRI signal due to its fast acquisition and reconstruction time. However, the inability of DTI to model complex intra-voxel diffusion distributions gave rise to an advanced reconstruction scheme which is known as high angular resolution diffusion imaging (HARDI). HARDI received increasing interest in neuroscience due to its potential to provide a more accurate view of pathway configurations in the human brain.
In order to fully exploit the advantages of HARDI over DTI, advanced fiber reconstructions and visualizations are required. This work presents novel approaches contributing to current research in the field of diffusion image processing and visualization. Diffusion classification, tractography, and visualizations approaches were designed to enable a meaningful exploration of neuronal connections as well as their constitution. Furthermore, an interactive neurosurgical planning tool with consideration of neuronal pathways was developed.
The research results in this work provide an enhanced and task-related insight into neuronal connections for neuroscientists as well as neurosurgeons and contribute to the implementation of HARDI in clinical environments.
Field margins are often the only remaining habitats of various wild plant species in agricultural landscapes. However, due to their proximity to agricultural fields, the vegetation of field margins can be affected by agrochemicals applied to the crop fields. The aim of this thesis was to investigate the individual and combined effects of herbicide, insecticide and fertilizer inputs on the plant community of a field margin. Therefore, a 3-year field experiment with a randomized block design including seven treatments (H: herbicide, I: insecticide, F: fertilizer, H+I, F+I, F+H and F+H+I) and one control was conducted on a low-production meadow. Each treatment was replicated 8 times in 8 m x 8 m plots with a distance of 2 m between each plot. The fertilizer rates (25 % of the field rate) and pesticide rates (30 % of the field rate) used for the plot applications were consistent with realistic average input rates (overspray + drift) in the first meter of a field margin directly adjacent to a wheat field.
The study revealed that fertilizer and herbicide misplacements in field margins are major factors that affect the natural plant communities of these habitats. In total, 20 of the 26 abundant species on the study site were significantly affected by the fertilizer and herbicide treatment. The fertilizer promoted plants with high nutrient uptake and decreased the frequencies of small species. The herbicide caused a nearly complete disappearance of three species directly after the first application, whereas sublethal effects (e.g., phytotoxic effects and reduced seed productions of up to 100 %) were observed for the other affected species. However, if field margins are exposed to repeated agrochemical applications over several years, then such sublethal effects (particularly reproduction effects) also reduce the population size of plant species significantly, as observed in this study.
Significant herbicide-fertilizer interaction effects were also detected and could not be extrapolated from individual effects. The fertilizer and herbicide effects became stronger over time, leading to shifts in plant community compositions after three years and to a 15 % lower species diversity than in the control. The insecticide significantly affected the frequencies of two plant species (1 positively and 1 negatively). The results of the experiment suggest that a continuous annual agrochemical application on the study site would cause further plant community shifts and would likely lead to the disappearance of certain affected plants. A clear trend of increasing grass dominance at the expense of flowering herbs was detected. This finding corresponds well with monitoring data from field margins near the study site.
Although herbicide risk assessment aims to protect non-target plants in off-field habitats from adverse effects, reproduction effects and combined effects are currently not considered. Furthermore, no regulations for fertilizer applications next to field margins exist and thus, fertilizer misplacements in field margins are likely to occur and to interact with herbicide effects.
Adaptations of the current risk assessment, a development of risk mitigation measures (e.g., in-field buffers) for the application of herbicides and fertilizers, and general management measures for field margins are needed to restore and conserve plant diversity in field margins in agricultural landscapes.