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Organic substances play an essential role for the formation of stable soil structures. In this context, their physico-chemical properties, interactions with mineral soil constituents and soil-water interactions are particu-larly important. However, the underlying mechanisms contributing to soil particle cementation by swollen or-ganic substances (hydrogels) remains unclear. Up to now, no mechanistic model is available which explains the mechanisms of interparticulate hydrogel swelling and its contribution to soil-water interactions and soil structur-al stability. This mainly results from the lack of appropriate testing methods to study hydrogel swelling in soil as well as from the difficulties of adapting available methods to the system soil/hydrogel.
In this thesis, 1H proton nuclear magnetic resonance (NMR) relaxometry was combined with various soil micro- and macrostructural stability testing methods in order to identify the contribution of hydrogel swelling-induced soil-water interactions to the structural stability of water-saturated and unsaturated soils. In the first part, the potentials and limitations of 1H NMR relaxometry to enlighten soil structural stabilization mechanism and vari-ous water populations were investigated. In the second part, 1H-NMR relaxometry was combined with rheologi-cal measurements of soil to assess the contribution of interparticulate hydrogel swelling and various polymer-clay interactions on soil-water interactions and soil structural stability in an isolated manner. Finally, the effects of various organic and mineral soil fractions on soil-water interactions and soil structural stability was assessed in more detail for a natural, agriculturally cultivated soil by soil density fractionation and on the basis of the experiences gained from the previous experiments.
The increased experiment complexity in the course of this thesis enabled to link physico-chemical properties of interparticulate hydrogel structures with soil structural stability on various scales. The established mechanistic model explains the contribution of interparticulate hydrogels to the structural stability of water-saturated and unsaturated soils: While swollen clay particles reduce soil structural stability by acting as lubricant between soil particles, interparticulate hydrogel structures increase soil structural stability by forming a flexible polymeric network which interconnects mineral particles more effectively than soil pore- or capillary water. It was appar-ent that soil structural stability increases with increasing viscosity of the interparticluate hydrogel in dependence on incubation time, soil texture, soil solution composition and external factors in terms of moisture dynamics and agricultural management practices. The stabilizing effect of interparticulate hydrogel structures further in-crease in the presence of clay particles which is attributed to additional polymer-clay interactions and the incor-poration of clay particles into the three-dimensional interparticulate hydrogel network. Furthermore, the simul-taneous swelling of clay particles and hydrogel structures results in the competition for water and thus in a mu-tual restriction of their swelling in the interparticle space. Thus, polymer-clay interactions not only increase the viscosity of the interparticulate hydrogel and thus its ability to stabilize soil structures but further reduce the swelling of clay particles and consequently their negative effects on soil structural stability. The knowledge on these underlying mechanisms enhance the knowledge on the formation of stable soil structures and enable to take appropriate management practices in order to maintain a sustainable soil structure. The additionally out-lined limitations and challenges of the mechanistic model should provide information on areas with optimization and research potential, respectively.
Different techniques (weight loss, electrochemical, and spray
corrosion measurements) have been used to evaluate four sarcosine derivatives to inhibit corrosion and one commercial compound as synergist. The basic metal was low carbon steel CR4 tested at different conditions. As working media mainly neutral water and 0.1 M NaCl was applied. The protective film was formed on the steel surface via direct absorption of the tested substances during the immersion process. A highly improved corrosion protection with direct correlation to the molecular weight and carbon chain length of the tested compounds was detected. The protection of steel CR4 against corrosion in 0.1 M NaCl enhanced with increasing concentration of selected sarcosine compounds. The best inhibitor throughout all tested concentrations and all evaluation systems was Oleoylsarcosine (O) with efficiencies up to 97 % in potentiodynamic polarization (PP), 83 % electrochemical impedance spectroscopy (EIS), and 85 % weight loss (WL) at 100 mmol/L as highest concentration tested here. The second best inhibitor was Myristoylsarcosine (M) with efficiencies up to 82 % in PP, 69 % in EIS, and 75 % in WL at highest concentration. The inhibitor with the shortest hydrocarbon chain in this series is Lauroylsarcosine (L). It showed lowest effects to inhibit corrosion compared to O and M. The efficiencies of L were a bit more than 50 % at 75 and 100 mmol/L and less than 50 % at 25 and 50 mmol/L in all used evaluation systems. Furthermore, the overall efficiency is promoted with longer dip coating times during the steel CR4 immersion as shown for 50 mmol/L for all present derivatives. This survey indicated 10 min as best time in respect of cost and protection efficiency. The commercial inhibitor Oley-Imidazole (OI) improved significantly the effectiveness of compound Cocoylsarcosine (C), which contains the naturally mixture of carbon chain lengths from coconut oil (C8 - C18), and enhanced protection when used in combination (C+OI, 1:1 molar ration). In this system the efficiency increased from 47 % to 91 % in PP, from 40 % to 84 % in EIS, and from 45 % to 82 % in WL at highest concentration. Spray corrosion tests were used to evaluate all present sarcosine substances on steel CR4 in a more realistic system. The best inhibitor after a 24 h test was O followed by the combination C+OI and M with efficiencies up to 99 %, 80 %, and 79 %, respectively. The obtained results indicate a good stability of the protective film formed by the present inhibitors even after 24 h. All evaluation systems used in the current investigation were in good agreement and resulted in the same inhibitor sequence. Furthermore, the adsorption process of the tested compounds is assumed to follow the Langmuir type isotherm. Response surface methodology (RSM) is an optimization method depending on Box- Behnken Design (BBD). It was used in the current system to find the optimum efficiency for inhibitor O to protect steel CR4 against corrosion in salt water. Four independent variables were used here: inhibitor concentration (A), dip coating time (B), temperature (C), and NaCl concentration (D); each with three respective levels: lower (-1), mid (0), and upper (+1). According to the present result, temperature has the greatest effect on the protection process as individual parameter followed by the inhibitor concentration itself. In this investigation an optimum efficiency of 99 % is calculated by the following parameter and level combination: upper level (+1) for inhibitor concentration, dip coating time, and NaCl concentration while lower level (-1) for temperature.
Soil organic matter (SOM) is a key component responsible for sequestration of organic molecules in soil and regulation of their mobility in the environment. The basic structure of SOM is a supramolecular assembly responding dynamically to the environmental factors and the presence of interacting molecules. Despite of the advances in the understanding of sorption processes, the relation between sorbate molecules, SOM supramolecular structure and its dynamics is limited. An example of a dynamic nature of SOM is a physicochemical matrix aging that is responsible for SOM structural arrangement. The underlying process of the physicochemical aging is the formation of water molecule bridges (WaMB) between functional groups of molecular segments. Since WaMB influence the stiffness of SOM structure, it was hypothesized that formation of WaMB contributes to the sequestration of organic molecules. However, this hypothesis has not been tested experimentally until now. Furthermore, the knowledge about the influence of organic molecules on WAMB is based solely on computer modeling studies. In addition, the influence of organic molecules on some physical phases forming SOM is not well understood. Especially, the interactions between organic molecules and crystalline phases represented by aliphatic crystallites, are only presumed. Thus, the investigation of those interactions in unfractioned SOM is of high importance.
In order to evaluate the involvement of WaMB in the sequestration of organic molecules and to increase our understanding about interactions of organic chemicals with WaMB or aliphatic crystallites, the following hypotheses were tested experimentally. 1) Similarly to crystalline phases in synthetic polymers, aliphatic crystallites, as a part of SOM, cannot be penetrated by organic molecules. 2) The stability of WaMB is determined by the ability of surrounding molecules to interact with water forming WaMB. 3) WaMB prevent organic molecules to leave the SOM matrix and contribute thus to their immobilization. In order to test the hypotheses 1 and 2, a set of experiments including treatment of soils with chosen chemicals was prepared. Interaction abilities of these chemicals were characterized using interaction parameters from the Linear Solvation Energy Relationship theory. WaMB characteristics were monitored using Differential Scanning Calorimetry (DSC) allowing to measure the WaMB thermal stability and the rigidity of SOM matrix; which in turn was determined by the heat capacity change. In addition, DSC and 13C NMR spectroscopy assessed thermal properties and the structure of aliphatic crystallites. The spiking of samples with a model compound, phenol, and measurements of its desorption allowed to link parameters of the desorption kinetics with WaMB characteristics.
The investigation showed that the WaMB stability is significantly reduced by the presence of molecules with H-donor/acceptor interaction abilities. The matrix rigidity associated with WaMB was mainly influenced by the McGowan’s volume of surrounding molecules, suggesting the importance of dispersion forces. The desorption kinetics of phenol followed a first order model with two time constants. Both of them showed a relation with WaMB stability, which supports the hypothesis that WaMB contribute to the physical immobilization of organic molecules. The experiments targeted to the crystallites revealed their structural change from the ordered to the disordered state, when in contact with organic chemicals. This manifested in their melting point depression and the decrease of overall crystallinity. Described structural changes were caused by molecules interacting with specific as well as non-specific forces, which suggests that aliphatic crystallites can be penetrated and modified by molecules with a broad range of interaction abilities.
This work shows that chosen organic molecules interact with constituents of SOM as exemplified on WaMB and aliphatic crystallites, and cause measurable changes of their structure and properties. These findings show that the relevance of aliphatic crystallites for sorption in soil may have been underestimated. The results support the hypothesis that physicochemical matrix aging significantly contributes to the immobilization of organic chemicals in SOM.
The term “Software Chrestomaty” is defined as a collection of software systems meant to be useful in learning about or gaining insight into software languages, software technologies, software concepts, programming, and software engineering. 101companies software chrestomathy is a community project with the attributes of a Research 2.0 infrastructure for various stakeholders in software languages and technology communities. The core of 101companies combines a semantic wiki and confederated open source repositories. We designed and developed an integrated ontology-based knowledge base about software languages and technologies. The knowledge is created by the community of contributors and supported with a running example and structured documentation. The complete ecosystem is exposed by using Linked Data principles and equipped with the additional metadata about individual artifacts. Within the context of software chrestomathy we explored a new type of software architecture – linguistic architecture that is targeted on the language and technology relationships within a software product and based on the megamodels. Our approach to documentation of the software systems is highly structured and makes use of the concepts of the newly developed megamodeling language MegaL. We “connect” an emerging ontology with the megamodeling artifacts to raise the cognitive value of the linguistic architecture.
Homonegative discrimination such as the denial of leadership qualities and higher salaries concern not only lesbians and gay men but also individuals who were perceived as lesbian or gay (Fasoli et al., 2017). Hence, it is assumed that especially straight people become victims of homonegative discrimination (Plöderl, 2014). The perception of sexual orientation is indeed stereotype-driven (e.g., Cox et al., 2015) but there is a lack of knowledge on how accurate stereotypes are – particularly those referring to speech. Despite a variety of sociophonetic and social psychological research related to sexual orientation and gender, an encompassing understanding is missing on how sexual orientation is expressed and perceived.
The present thesis aims to fill these gaps. The two major aims of the present work are a) the examination of the accuracy of speech stereotypes in the context of sexual orientation and b) the development of a model on how sexual orientation is interpersonally construed. Overall, the present thesis comprises five manuscripts with the following aspects in common: They integratively deal with social psychological and sociophonetic perspectives, share a social identity approach, and primarily center speech instead of facial appearance. Moreover, mostly German and German native speaking participants, respectively, have been investigated.
Manuscript 1 establishes the Traditional Masculinity/Femininity-Scale as a reliable and valid instrument for assessing gender-role self-concept. The invention was necessary because existing scales insufficiently represented the self-ascribed masculinity/femininity yet (e.g., Abele, 2003; Evers & Sieverding, 2014). Manuscripts 2, 3, and 4 address the (in)accuracy of speech stereotypes regarding stereotypic content and suggested within-group homogeneity. This is carried out by the application of different methodological approaches. On the one hand, relevant acoustic parameters of lesbian/gay and straight women and men were averaged for each group. On the other hand, voice morphing was applied in order to create prototypical and naturally sounding voice averages (Kawahara et al., 2008). Lesbians and straight women differed in none, gay and straight men in one of the analyzed acoustic parameters only. In contrast, a fine-grained psychological analysis yielded various evidence for acoustic within-group heterogeneity. In particular, the exclusivity of sexual orientation and gender-role self-concept have been acoustically indexicalized which suggests that speech stereotypes are inaccurate. However, voice averages do carry perceivable sexual orientation information. Hence, speech stereotypes can be considered as exaggerations of tiny kernels of truth. In Manuscript 5, previous literature on the interpersonal construction of sexual orientation is integrated in a model: The Expression and Perception of Sexual Orientation Model (EPSOM). This model postulates an indirect route and describes how sexual orientation information is transmitted from producer to perceiver by proposing three mediating components. Thereby, the model is able to offer an explanation why sexual orientation can be perceived with above-chance but far-away-from-perfect accuracy.
Overall, the present thesis provides meaningful impulses for enhancements of research on social markers of sexual orientation and gender. This thesis offers a model on how sexual orientation is expressed and perceived, shows the benefits of combining sociophonetic and social psychological approaches, and points out the value of applying novel methods and technologies. Beyond that, the present thesis offers useful implications for practice. Speech stereotypes in the context of sexual orientation can be rejected as inaccurate – for example, native German straight men do not nasalize more or less than gay men. Thereby, the present thesis contributes to an erosion of stereotypes and a potential reduction of homonegative discrimination.
Social entrepreneurship is a form of entrepreneurship that marries a social mission to a competitive value proposition. Notably, social entrepreneurship fosters a more equitable society by addressing social issues and trying to achieve an ongoing sustainable impact through a social mission rather than purely profit maximization. The topic of social entrepreneurship has appealed considerably to many different streams of research. The focus on understanding how and why entrepreneurs think and act is a significant justification for future research. Nevertheless, the theoretical examination of this phenomenon is in its infancy. Social entrepreneurship research is still largely phenomenon-driven. Specifically, Social Entrepreneurial Intention is in an early stage and lacks quantitative research. Therefore, this thesis proposes to address this need. The thesis’ objectives are twofold: (1) develop a formation model for Social Entrepreneurial Intentions in general and (2) test the model by conducting an empirical study. Based on these objectives, the two research questions guiding the thesis are (1) what factors influence the intention of a person to become a social entrepreneur and (2) what relationships exist among these factors.
In order to answer these two research questions, this thesis uses purposeful research design, which is a combination of literature review and empirical study. The literature review is based on a comprehensive range of books, articles, and research papers published in leading academic journals and conference proceedings in different disciplines such as entrepreneurship, social entrepreneurship, entrepreneurship education, management, social psychology, and social economics. The empirical study is conducted via a survey of 600 last-year students from four universities in three regions in Vietnam: Hanoi, Da Nang, and Ho Chi Minh. The data are analyzed with SPSS-AMOS version 24, using screening data, scale development, exploratory factor analysis, and confirmation factor analysis. The thesis ascertains that Entrepreneurship Experience/Extra-curricular Activity, Role Model, Social Entrepreneurial Self-Efficacy, and Social Entrepreneurial Outcome Expectation directly and positively affect the intention of the Vietnamese students to be social entrepreneurs. Entrepreneurship Education also influences the Social Entrepreneurial Intention, but not directly, otherwise indirectly via Social Entrepreneurial Self-Efficacy and Social Entrepreneurial Outcome Expectation. Similarly, Perceived Support has no direct relationship to Social Entrepreneurial Intention; however, it shows an indirect link via the mediator ‘Social Entrepreneurial Outcome Expectation’. Furthermore, the dissertation brings new insights to the social entrepreneurship literature and provides important implications for practice. Limitations and future directions are also provided in the thesis.
Social Business Documents: An Investigation of their Nature, Structure and Long-term Management
(2018)
Business documents contain valuable information. In order to comply with legal requirements, to serve as organisational knowledge and to prevent risks they need to be managed. However, changes in technology with which documents are being produced introduced new kinds of documents and new ways of interacting with documents. Thereby, the web 2.0 led to the development of Enterprise Collaboration Systems (ECS), which enable employees to use wiki, blog or forum applications for conducting their business. Part of the content produced in ECS can be called Social Business Documents (SBD). Compared to traditional digital documents SBD are different in their nature and structure as they are, for example, less well-structured and do not follow a strict lifecycle. These characteristics bring along new management challenges. However, currently research literature lacks investigations on the characteristics of SBD, their peculiarities and management.
This dissertation uses document theory and documentary practice as theoretical lenses to investigate the new challenges of the long-term management of SBD in ECS. By using an interpretative, exploratory, mixed methods approach the study includes two major research parts. First, the nature and structure of Social Business Documents is addressed by analysing them within four different systems using four different modelling techniques each. The findings are used to develop general SBD information models, outlining the basic underlying components, structure, functions and included metadata, as well as a broad range of SBD characteristics. The second phase comprises a focus group, a case study including in-depth interviews and a questionnaire, all conducted with industry representatives. The focus group identified that the kind of SBD used for specific content and the actual place of storage differ between organisations as well as that there are currently nearly no management practices for SBD at hand. The case study provided deep insights into general document management activities and investigated requirements, challenges and actions for managing SBD. Finally, the questionnaire consolidated and deepened the previous findings. It provides insights about the value of SBD, their current management practices as well as management challenges and needs. Despite all participating organisations storing information worth managing in SBD most are not addressing them with management activities and many challenges remain.
Together, the investigations enable a contribution to practice and theory. The progress in practice is summarised through a framework, addressing the long-term management of Social Business Documents. The framework identifies and outlines the requirements and challenges of and the actions for SBD management. It also indicates the dependencies of the different aspects. Furthermore, the findings enable the progress in theory within documentary practice by discussing the extension of document types to include SBD. Existing problems are outlined along the definitions of records and the newly possible characteristics of documents emerging through Social Business Documents are taken into account.
The physical-biological interactions that affect the temporal variability of benthic oxygen fluxes were investigated to gain improved understanding of the factors that control these processes. This study, for the first time is able to resolve benthic diffusive boundary layer (DBL) dynamics using the newly developed lifetime-based laser induced fluorescence (τLIF) oxygen imaging system, which enables study of the role of small-scale fluid mechanics generated by benthic organism activity, and hence a more detailed analysis of oxygen transport mechanisms across the sediment-water interface (SWI).
The net benthic oxygen flux across the sediment-water interface is controlled by sediment oxygen uptake and oxygen transport. While the oxygen transport is largely influenced by turbulence driven by large-scale flows, sediment oxygen uptake is mainly affected by oxygen production and biological- and chemical-oxygen degradation of organic matter. Both processes can be enhanced by the presence of fauna and are intimately coupled. The benthic oxygen flux can be influenced by fauna in two ways, i.e. by modulating the availability of oxygen, which enhances the sediment oxygen uptake, and by enhancing the transport of oxygen.
In-situ and a series of laboratory measurements were conducted to estimate the short- and seasonal variability of benthic fluxes including the effects of burrow ventilation activity by tube-dwelling animals using eddy correlation (EC) and τLIF oxygen imaging techniques, respectively.
The in-situ benthic oxygen fluxes showed high variability at hourly and seasonal timescales, where statistical analysis indicated that current velocity and water depth were the most significant predictors of benthic oxygen flux at the waterside, which co-varied with the discharge, temperature, and oxygen concentration. The range of variability of seasonal fluxes corresponded to the friction velocities which were driven by large-scale flows. Application of a simplified analytical model that couples the effect of hydrodynamic forcing of the diffusive boundary layer with a temperature-dependent oxygen consumption rate within the sediment showed that friction velocity and temperature cause similar variability of the steady-state benthic oxygen flux.
The application of τLIF oxygen imaging system in bioturbation experiments enabled the investigation and discovery of insights into oxygen transport mechanisms across the sediment-water interface. Distinct oxygen structures above burrow openings were revealed, these were associated with burrow ventilation. The DBL was degraded in the presence of burrow ventilation. Advective transport generated by the energetic plumes released at burrow outlets was the dominant transport driving mechanism. The contribution of diffusive flux to the total estimated decreased with increasing larval density. For a range of larvae densities, commonly observed in ponds and lakes, sediment oxygen uptake rates increased up to 2.5-fold in the presence of tube-dwelling animals, and the oxygen transport rate exceeded chironomid respiration by up to a factor of 4.
The coupled physical-biological factors affecting net benthic oxygen flux can be represented by temperature, which is a prominent factor that accounts for both oxygen transport and sediment oxygen uptake. Low oxygen transport by flow coincided with high summer temperatures, amplified by a reduction of benthic population density and pupation. It can also, however, be offset by increased ventilation activity. In contrast, low temperature coincided with high oxygen concentrations, an abundance of larvae, and higher flow is offset by less burrow ventilation activity. Investigation of the effect of hydrodynamics on oxygen transport alone suggested that the expected increase of benthic oxygen flux under global warming can be offset by a reduction in flow velocity, which could ultimately lead to increasing carbon burial rates, and in a growing importance of anaerobic mineralization pathways with increasing emission rates of methane.
This study suggests a significant contribution of biological induced benthic oxygen flux to physical transport driven by large-scale flow-fields contributing to bottom-boundary layer turbulence.
Fresh water resources like rivers and reservoirs are exposed to a drastically changing world. In order to safeguard these lentic ecosystems, they need stronger protection in times of global change and population growth. In the last years, the exploitation pressure on drinking water reservoirs has increased steadily worldwide. Besides securing the demands of safe drinking water supply, international laws especially in Europe (EU Water Framework Directive) stipulate to minimize the impact of dams on downstream rivers. In this study we investigate the potential of a smart withdrawal strategy at Grosse Dhuenn Reservoir to improve the temperature and discharge regime downstream without jeopardizing drinking water production. Our aim is to improve the existing withdrawal strategy for operating the reservoir in a sustainable way in terms of water quality and quantity. First, we set-up and calibrated a 1D numerical model for Grosse Dhuenn Reservoir with the open-source community model “General Lake Model” (GLM) together with its water quality module “Aquatic Ecodynamics” library (AED2). The reservoir model reproduced water temperatures and hypolimnetic dissolved oxygen concentrations accurately over a 5 year period. Second, we extended the model source code with a selective withdrawal functionality (adaptive offtake) and added operational rules for a realistic reservoir management. Now the model is able to autonomously determine the best withdrawal height according to the temperature and flow requirements of the downstream river and the raw water quality objectives. Criteria for the determination of the withdrawal regime are selective withdrawal, development of stratification and oxygen content in the deep hypolimnion. This functionality is not available in current reservoir models, where withdrawal heights are generally provided a priori to the model and kept fixed during the simulation. Third, we ran scenario simulations identifying an improved reservoir withdrawal strategy to balance the demands for downstream river and raw water supply. Therefore we aimed at finding an optimal parallel withdrawal ratio between cold hypolimnetic water and warm epilimnetic or metalimnetic water in order to provide a pre-defined temperature in the downstream river. The reservoir model and the proposed withdrawal strategy provide a simple and efficient tool to optimize reservoir management in a multi-objective view for mastering future reservoir management challenges.
This thesis addresses the automated identification and localization of a time-varying number of objects in a stream of sensor data. The problem is challenging due to its combinatorial nature: If the number of objects is unknown, the number of possible object trajectories grows exponentially with the number of observations. Random finite sets are a relatively new theory that has been developed to derive at principled and efficient approximations. It is based around set-valued random variables that contain an unknown number of elements which appear in arbitrary order and are themselves random. While extensively studied in theory, random finite sets have not yet become a leading paradigm in practical computer vision and robotics applications. This thesis explores random finite sets in visual tracking applications. The first method developed in this thesis combines set-valued recursive filtering with global optimization. The problem is approached in a min-cost flow network formulation, which has become a standard inference framework for multiple object tracking due to its efficiency and optimality. A main limitation of this formulation is a restriction to unary and pairwise cost terms. This circumstance makes integration of higher-order motion models challenging. The method developed in this thesis approaches this limitation by application of a Probability Hypothesis Density filter. The Probability Hypothesis Density filter was the first practically implemented state estimator based on random finite sets. It circumvents the combinatorial nature of data association itself by propagation of an object density measure that can be computed efficiently, without maintaining explicit trajectory hypotheses. In this work, the filter recursion is used to augment measurements with an additional hidden kinematic state to be used for construction of more informed flow network cost terms, e.g., based on linear motion models. The method is evaluated on public benchmarks where a considerate improvement is achieved compared to network flow formulations that are based on static features alone, such as distance between detections and appearance similarity. A second part of this thesis focuses on the related task of detecting and tracking a single robot operator in crowded environments. Different from the conventional multiple object tracking scenario, the tracked individual can leave the scene and later reappear after a longer period of absence. Therefore, a re-identification component is required that picks up the track on reentrance. Based on random finite sets, the Bernoulli filter is an optimal Bayes filter that provides a natural representation for this type of problem. In this work, it is shown how the Bernoulli filter can be combined with a Probability Hypothesis Density filter to track operator and non-operators simultaneously. The method is evaluated on a publicly available multiple object tracking dataset as well as on custom sequences that are specific to the targeted application. Experiments show reliable tracking in crowded scenes and robust re-identification after long term occlusion. Finally, a third part of this thesis focuses on appearance modeling as an essential aspect of any method that is applied to visual object tracking scenarios. Therefore, a feature representation that is robust to pose variations and changing lighting conditions is learned offline, before the actual tracking application. This thesis proposes a joint classification and metric learning objective where a deep convolutional neural network is trained to identify the individuals in the training set. At test time, the final classification layer can be stripped from the network and appearance similarity can be queried using cosine distance in representation space. This framework represents an alternative to direct metric learning objectives that have required sophisticated pair or triplet sampling strategies in the past. The method is evaluated on two large scale person re-identification datasets where competitive results are achieved overall. In particular, the proposed method better generalizes to the test set compared to a network trained with the well-established triplet loss.