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Institute
Ray Tracing als Bildsyntheseverfahren ist relevant für viele Anwendungsbereiche, da es Aspekte des Lichttransports physikalisch korrekt simulieren kann. Aufgrund des hohen Berechnungsaufwands sind der Einsatz von Datenstrukturen zur Beschleunigung und die parallele Verarbeitung notwendig. GPUs sind inzwischen hoch parallele, programmierbare Prozessoren mit zahlreichen Kernen und eignen sich aufgrund ihrer hohen Leistungsfähigkeit dazu, aufwändige, parallelisierbare Probleme zu lösen. In dieser Arbeit geht es um GPU Ray Tracing, beschleunigt durch Bounding Volume Hierarchien (BVH). Auf Basis relevanter Veröffentlichungen zu Aufbau und Traversierung von BVHs und der Abbildung des Ray Tracing Prozesses auf die GPU Architektur wird ein GPU Ray Tracer konzeptioniert und entwickelt. Während der BVH Aufbau vorab auf dem Host stattfindet, wird der gesamte Ray Tracing Prozess durch mehrere Kernel komplett auf der GPU ausgeführt. Die Implementierung der Kernel erfolgt in Form von OpenGL Compute Shader Programmen, und die Aufteilung des Ray Tracers auf mehrere Kernel ist durch die GPU Achitektur und das SIMT Ausführungsmodell motiviert. Für die Speicherorganisation der binären BVHs werden zwei Varianten betrachtet, klassisch und als MBVH, wobei sich die MBVH Organisation als effizienter erweist. Zudem werden verschiedene Varianten für die Traversierung ohne Stack und für die Stack-basierte Traversierung umgesetzt und bewertet. Der in mehrere Kernel strukturierte GPU Ray Tracer wird zudem mit einer Einzelkernel Version verglichen. Die besten Ergebnisse erreicht die Traversierung ohne Stack mit einem while-while Ablauf und MBVH im Rahmen des aufgeteilten GPU Ray Tracers.
One of the main goals of the artificial intelligence community is to create machines able to reason with dynamically changing knowledge. To achieve this goal, a multitude of different problems have to be solved, of which many have been addressed in the various sub-disciplines of artificial intelligence, like automated reasoning and machine learning. The thesis at hand focuses on the automated reasoning aspects of these problems and address two of the problems which have to be overcome to reach the afore-mentioned goal, namely 1. the fact that reasoning in logical knowledge bases is intractable and 2. the fact that applying changes to formalized knowledge can easily introduce inconsistencies, which leads to unwanted results in most scenarios.
To ease the intractability of logical reasoning, I suggest to adapt a technique called knowledge compilation, known from propositional logic, to description logic knowledge bases. The basic idea of this technique is to compile the given knowledge base into a normal form which allows to answer queries efficiently. This compilation step is very expensive but has to be performed only once and as soon as the result of this step is used to answer many queries, the expensive compilation step gets worthwhile. In the thesis at hand, I develop a normal form, called linkless normal form, suitable for knowledge compilation for description logic knowledge bases. From a computational point of view, the linkless normal form has very nice properties which are introduced in this thesis.
For the second problem, I focus on changes occurring on the instance level of description logic knowledge bases. I introduce three change operators interesting for these knowledge bases, namely deletion and insertion of assertions as well as repair of inconsistent instance bases. These change operators are defined such that in all three cases, the resulting knowledge base is ensured to be consistent and changes performed to the knowledge base are minimal. This allows us to preserve as much of the original knowledge base as possible. Furthermore, I show how these changes can be applied by using a transformation of the knowledge base.
For both issues I suggest to adapt techniques successfully used in other logics to get promising methods for description logic knowledge bases.
The publication of open source software aims to support the reuse, the distribution and the general utilization of software. This can only be enabled by the correct usage of open source software licenses. Therefore associations provide a multitude of open source software licenses with different features, of which a developer can choose, to regulate the interaction with his software. Those licenses are the core theme of this thesis.
After an extensive literature research, two general research questions are elaborated in detail. First, a license usage analysis of licenses in the open source sector is applied, to identify current trends and statistics. This includes questions concerning the distribution of licenses, the consistency in their usage, their association over a period of time and their publication.
Afterwards the recommendation of licenses for specific projects is investigated. Therefore, a recommendation logic is presented, which includes several influences on a suitable license choice, to generate an at most applicable recommendation. Besides the exact features of a license of which a user can choose, different methods of ranking the recommendation results are proposed. This is based on the examination of the current situation of open source licensing and license suggestion. Finally, the logic is evaluated on the exemplary use-case of the 101companies project.
The provision of electronic participation services (e-participation) is a complex socio-technical undertaking that needs comprehensive design and implementation strategies. E-participation service providers, in the most cases administrations and governments, struggle with changing requirements that demand more transparency, better connectivity and increased collaboration among different actors. At the same time, less staff are available. As a result, recent research assesses only a minority of e-participation services as successful. The challenge is that the e-participation domain lacks comprehensive approaches to design and implement (e-)participation services. Enterprise Architecture (EA) frameworks have evolved in information systems research as an approach to guide the development of complex socio-technical systems. This approach can guide the design and implementation services, if the collection of organisations with the commonly held goal to provide participation services is understood as an E Participation Enterprise (EE). However, research & practice in the e participation domain has not yet exploited EA frameworks. Consequently, the problem scope that motivates this dissertation is the existing gap in research to deploy EA frameworks in e participation design and implementation. The research question that drives this research is: What methodical and technical guides do architecture frameworks provide that can be used to design and implement better and successful e participation?
This dissertation presents a literature study showing that existing approaches have not covered yet the challenges of comprehensive e participation design and implementation. Accordingly, the research moves on to investigate established EA frameworks such as the Zachman Framework, TOGAF, the DoDAF, the FEA, the ARIS, and the ArchiMate for their use. While the application of these frameworks in e participation design and implementation is possible, an integrated approach is lacking so far. The synthesis of literature review and practical insights in design and implementation of e participation services from four projects show the challenges of adapting architecture frameworks for this domain. However, the research shows also the potential of a combination of the different approaches. Consequently, the research moves on to develop the E-Participation Architecture Framework (EPART-Framework). Therefore, the dissertation applies design science research including literature review and action research. Two independent settings test an initial EPART-Framework version. The results yield into the EPART-Framework presented in this dissertation.
The EPART-Framework comprises of the EPART-Metamodel with six EPART-Viewpoints, which frame the stakeholder concerns: the Participation Scope, the Participant Viewpoint, the Participation Viewpoint, the Data & Information Viewpoint, the E-participation Viewpoint, and Implementation & Governance Viewpoint. The EPART-Method supports the stakeholders to design the EE and implement e participation and stores its output in an architecture description and a solution repository. It consists of five consecutive phases accompanied by requirements management: Initiation, Design, Implementation and Preparation, Participation, and Evaluation. The EPART-Framework fills the gap between the e participation domain and the enterprise architecture framework domain. The evaluation gives reasonable evidence that the framework is a valuable addition in academia and in practice to improve e-participation design and implementation. The same time, it shows opportunities for future research to extend and advance the framework.
“Did I say something wrong?” A word-level analysis of Wikipedia articles for deletion discussions
(2016)
This thesis focuses on gaining linguistic insights into textual discussions on a word level. It was of special interest to distinguish messages that constructively contribute to a discussion from those that are detrimental to them. Thereby, we wanted to determine whether “I”- and “You”-messages are indicators for either of the two discussion styles. These messages are nowadays often used in guidelines for successful communication. Although their effects have been successfully evaluated multiple times, a large-scale analysis has never been conducted. Thus, we used Wikipedia Articles for Deletion (short: AfD) discussions together with the records of blocked users and developed a fully automated creation of an annotated data set. In this data set, messages were labelled either constructive or disruptive. We applied binary classifiers to the data to determine characteristic words for both discussion styles. Thereby, we also investigated whether function words like pronouns and conjunctions play an important role in distinguishing the two. We found that “You”-messages were a strong indicator for disruptive messages which matches their attributed effects on communication. However, we found “I”-messages to be indicative for disruptive messages as well which is contrary to their attributed effects. The importance of function words could neither be confirmed nor refuted. Other characteristic words for either communication style were not found. Yet, the results suggest that a different model might represent disruptive and constructive messages in textual discussions better.
While reading this sentence, you probably gave (more or less deliberately) instructions to approximately 100 to 200 muscles of your body. A sceptical face or a smile, your fingers scrolling through the text or holding a printed version of this work, holding your head, sitting, and much more.
All these processes take place almost automatically, so they seem to be no real achievement. In the age of digitalization it is a defined goal to transfer human (psychological and physiological) behavior to machines (robots). However, it turns out that it is indeed laborious to obtain human facial expression or walking from robots. To optimize this transfer, a deeper understanding of a muscle's operating principle is needed (and of course an understanding of the human brain, which will, however, not be part of this thesis).
A human skeletal muscle can be shortened willingly, but not lengthened, thereto it takes an antagonist. The muscle's change in length is dependent on the incoming stimulus from the central nervous system, the current length of the muscle itself, and certain muscle--specific quantities (parameters) such as the maximum force. Hence, a muscle can be mathematically described by a differential equation (or more exactly a coupled differential--algebraic system, DAE), whose structure will be revealed in the following chapters. The theory of differential equations is well-elaborated. A multitude of applicable methods exist that may not be known by muscle modelers. The purpose of this work is to link the methods from applied mathematics to the actual application in biomechanics.
The first part of this thesis addresses stability theory. Let us remember the prominent example from middle school physics, in which the resting position of a ball was obviously less susceptible towards shoves when lying in a bowl rather than balancing at the tip of a hill. Similarly, a dynamical (musculo-skeletal) system can attain equilibrium states that react differently towards perturbations.
We are going to compute and classify these equilibria.
In the second part, we investigate the influence of individual parameters on model equations or more exactly their solutions. This method is known as sensitivity analysis.
Take for example the system "car" containing a value for the quantity "pressure on the break pedal while approaching a traffic light". A minor deviation of this quantity upward or downward may lead to an uncomfortable, abrupt stop or even to a collision, instead of a smooth stop with a sufficient gap.
The considered muscle model contains over 20 parameters that, if changed slightly, have varying effects on the model equation solutions at different instants of time. We will investigate the sensitivity of those parameters regarding different sub--models, as well as the whole model among different dynamical boundary conditions.
The third and final part addresses the \textit{optimal control} problem (OCP).
The muscle turns a nerve impulse (input or control) into a length change and therefore a force response (output). This forward process is computable by solving the respective DAE. The reverse direction is more difficult to manage. As an everyday example, the OCP is present regarding self-parking cars, where a given path is targeted and the controls are the position of the
steering wheel as well as the gas pedal.
We present two methods of solving OCPs in muscle modeling: the first is a conjunction of variational calculus and optimization in function spaces, the second is a surrogate-based optimization.
Externe Repräsentationen spielen eine wichtige Rolle für die Lösung von mathematischen Textaufgaben. Die vorliegende Studie untersucht die Effekte bereitgestellter Repräsentationen beim Lösen problemhaltiger Textaufgaben in der Grundschule. Insbesondere problemhaltige Textaufgaben sind für Schüler anspruchsvoll, da sie nicht direkt mit den eingeübten und routinierten Rechenoperationen gelöst werden können. Sie zeichnen sich dadurch aus, dass sich der Lösungsweg nicht auf einen Blick erschließt, die mathematische Grundstruktur daher zunächst erkannt, entfaltet und verstanden werden muss und häufig mehrere Aufgabenbedingungen bei der Planung und Beschreitung des Lösungswegs bedacht und verarbeitet werden müssen. Um diesen komplexen Anforderungen begegnen zu können, benötigen Schüler die Fähigkeit, das Problem adäquat zu repräsentieren. Dabei können verschiedene Darstellungsformen wie Zeichnungen und Tabellen verwendet werden, die dann als Werkzeuge für die kognitiven Lösungsprozesse dienen. Da Grundschüler von sich aus häufig keine externen Repräsentationen erstellen, geht die vorliegende Studie den Fragen nach, (1) ob vorgefertigte Repräsentationen das Problemlösen verbessern und erleichtern, (2) ob sich eine Auseinandersetzung mit vorgefertigten Tabellen und Zeichnungen auch auf späteres Problemlösen ohne bereitgestellte Hilfsmittel auswirkt, (3) welche Repräsentationsform (Zeichnung oder Tabelle) und (4) wie viel Vorstrukturierung der bereitgestellten Repräsentation dabei hilfreicher ist. In einem experimentellen Studiendesign arbeiteten 199 Viertklässler an unterschiedlichen problemhaltigen Textaufgaben. Das Design bestand aus drei Tests: (1) Vor-, (2) Treatment- und (3) Transfertest. Im Vortest wurde die Ausgangsleistung der Probanden bei problemhaltigen Textaufgaben gemessen. Im Treatment-Test wurde die Performance beim Problemlösen mit vorgegebenen Repräsentationen erhoben: Probanden der Experimentalgruppe erhielten Zeichnungen und Tabellen in unterschiedlichen Vorstrukturierungsgraden zu den Aufgaben (Intervention), eine Kontrollgruppe erhielt keine Repräsentationen. Im Transfertest bearbeiteten die Teilnehmer vergleichbare Aufgaben wiederum ohne vorgegebene Repräsentationen, um die Problemlöse-Performance nach der Intervention zu messen. Die Ergebnisse zeigten erstens, dass die bereitgestellten Repräsenta-tionen entgegen der Annahme die Problemlöseprozesse insgesamt nicht verbessert und erleichtert haben. Zweitens: Wurde eine Repräsentation bereitgestellt, war eine Zeichnung wie angenommen hilfreicher als eine Tabelle. Jedoch war dieser Effekt abhängig vom Problemtyp und vom Grad der Vorstrukturierung. Offensichtlich genügte es nicht, Zeichnungen und Tabellen einfach nur bereitzustellen, da die Probanden vielfach Schwierigkeiten bei der Interpretation und adäquaten Verwendung der Repräsentationen hatten. Dies spricht für die Notwendigkeit eines Trainings zur Ausbildung und Förderung einer frühen „diagram literacy“ bereits bei Grundschülern.
The goal of this thesis is to create and develop a concept for a mobile city guide combined with game-based contents.
The application is intented to support flexible and independent exploration of the city of Koblenz.
Based on the geographical data, historical information for and interesting stories of various places were provided in this application. These informations are combined with playful elements in order to create a motivating concept.
Therefore, related approaches were examined and, combined with own ideas, a new concept has been developed. This concept has been prototypically implemented as an Android application and afterwards evaluated by 15 test persons. A questionnaire was used to examine the operability, the motivation of game patterns and the additional value of the application.
While Virtual Reality has been around for decades it gained new life in recent years. The release of the first consumer hardware devices allows fully immersive and affordable VR for the user at home. This availability lead to a new focus of research on technical problems as well as psychological effects. The concepts of presence, describing the feeling of being in the virtual place, body ownership and their impact are central topics in research for a long time and still not fully understood.
To enable further research in the area of Mixed Reality, we want to introduce a framework that integrates the users body and surroundings inside a visual coherent virtual environment. As one of two main aspects we want to merge real and virtual objects to a shared environment in a way such that they are no longer visually distinguishable. To achieve this the main focus is not supposed to be on a high graphical fidelity but on a simplified representation of reality. The essential question is, what level of visual realism is necessary to create a believable mixed reality environment that induces a sense of presence in the user? The second aspect considers the integration of virtual persons. Can characters be recorded and replayed in a way such that they are perceived as believable entities of the world and therefore act as a part of the users environment?
The purpose of this thesis was the development of a framework called Mixed Reality Embodiment Platform. This inital system implements fundamental functionalities to be used as a basis for future extensions to the framework. We also provide a first application that enables user studies to evaluate the framework and contribute to aforementioned research questions.
Science education has been facing important challenges in the recent years: the decline in student’s interest in scientific topics, and moreover, the decrease of students pursuing science beyond their compulsory studies (Bennett, Hogarth, Lubben, 2003). As a result, research has focus on examining different approaches that could attempt to improve the situation. One of these approaches has been the use of context-based problem-solving tasks (Kölbach & Sumfleth, 2011; Bennett, Hogarth, Lubben, 2003). While research into context-based problem-solving tasks suggest that they are very motivating for students, it is still unclear how they influence motivation. Following an experimental pretest-postest design, two studies examined the effects of context-based task characteristics of contextualization, complexity, and transparency, on students’ motivational variables, performance, and metacognitive experiences.
Results from both studies suggest that the task characteristic of contextualization directly influences how students’ interest is triggered and maintained throughout the task. On the other hand, the task characteristics of complexity and transparency had different effects for the other dependent variables of effort, difficulty, and solution correctness.
Moreover, data shows that other motivational variables such as anxiety and success expectancies are strongly influenced by the interaction of the parameters under study. The dissertation concludes that appropriate design and use of context-based task characteristics can benefit students’ learning processes and outcomes.
The aim of this thesis was to develop and to evaluate a method, which enables the utilization of traditional dialog marketing tools through the web. For this purpose, a prototype of a website with "extended real-time interaction (eEI)" capabilities has been implemented and tested. The prototype was evaluated by a methodology based on the five-dimensional "e-service quality" measure after Gwo-Guang Lee und Hsiu-Fen Lin. The Foundation of the "e-service quality" measure is the SERVQUAL-Model. A statistical analysis of the user study results showed a significant correlation between eEI and user satisfaction. Before the actual realization of eEI, the "Technology Acceptance Model" after Fred D. Davis was used to investigate currently used real-time interaction systems.
Augmented Reality has many areas of application. It can be used to simplify everyday life as well as working processes. However, since there are
many manufacturers that offer greatly varying systems, choosing the correct system according to application as well as cross-platform development are dfficult. This thesis attempts to develop an application which can be used to simulate Augmented Reality devices on Virtual Reality systems. This should simplify the processes of choosing a system as well as cross-platform
development.
Since the simulation will be designed to run on mobile devices, it should be possible to render high quality, realistic environments in advance, using a panoramic image. On a Virtual Reality device, they need to be displayed as a stereoscopic image. To achieve this, several methods are presented that can be used to perform this conversion. An editor will be created which will allow the creation of scenes, configuration of Augmented Reality devices and displaying them on a Virtual Reality system. For closing this thesis a test will be performed, to check the quality of the simulation as well as improvements that can be made.
The (un-)controlled application of olive oil mill wastewater (OMW) has positive and negative effects on soil quality. On the one hand it can be used as fertilizer, on the other hand especially the occurrence of soil water repellency is problematic. Due to this fact the objective of this study was to characterize the effects of OMW application on soil and to investigate the mechanisms that are in combination with changes of soil organic matter quality responsible for soil water repellency depending on the climatic conditions.
At first several locations of uncontrolled OMW disposal were screened for positive and negative im-pacts. Then, laboratory incubation experiments and finally a field experiment in Israel were conducted in order to determine the influence of climatic conditions. Besides standard soil parameters (pH, elec-tric conductivity, total carbon, dissolved organic carbon , specific UV-Absorption) it was focused on the determination of phenolic compounds, the carbon isotope ratio, the water drop penetration time and the contact angle as well as the thermal analysis.
This thesis shows that soil water repellency of OMW-polluted soils depends on the climatic conditions, i.e. the application season. In the laboratory as well as in the field the wettability of the soil was strongly reduced under hot and dry conditions. It was observed, that the stable carbon fraction characterized by a high calorific value is responsible for soil water repellency. In particular, amphiphilic substances, e.g. fatty acids, may interact with soil particles as a consequence of drying. On the contrary, no reduc-tion of the wettability of the soil was determined under moist conditions and degradation of organic matter of the OMW was enhanced. Nevertheless, too strong irrigation or rainfall, e.g. in winter, may leach phenolic ingredients of the OMW into the groundwater.
At the same time the application led to an increase of organic and inorganic nutrients, which should be emphasized as a positive effect. Due to these results, a controlled application of olive oil mill wastewater as alternative, low-cost and sustainable treatment option is recommended. But, instead of the current application season winter, the olive mill wastewater should be stored and not be spread before spring in order to avoid negative impacts on the soil.
Ein zentrales Problem der stationären Behandlung psychischer und psychosomatischer Störungen ist die Nachhaltigkeit von Therapieerfolgen. Im Rahmen einer Pilotstudie wurde ein SMS-basiertes Nachsorgeprogramm zur Modifikation Perfektionismus-bezogener Kognitionen im Anschluss an eine stationäre Behandlung von Burnout-Patienten evaluiert.
Es handelte sich um eine kontrollierte Verlaufsstudie mit vier Messzeitpunkten (Aufnahme, Entlassung, 6 und 10-Wochen-Katamnese). Die Patienten der Versuchsgruppe (n=31) erhielten zusätzlich zur Routine-Behandlung eine 6-wöchige kognitiv ausgerichtete individualisierte SMS-Nachsorge. Als Kontrollgruppe (n=30) diente eine Gruppe von Patienten mit einer stationären Routine-Behandlung. Zur Erfassung der Burnout-Symptomatik wurde das Maslach Burnout Inventory General Survey (MBI-GS-D) eingesetzt, die depressive Symptomatik wurde mit dem Beck-Depressions-Inventar-V (BDI-V) erhoben. Zur Erfassung der Facetten des Perfektionismus dienten Items aus der Multidimensional Perfectionism Scale (FMPS und HMPS) sowie der Almost Perfect Scale (APS-R).
Ein sehr hohes Interesse, eine hohe Inanspruchnahme sowie eine hohe Akzeptanz des Nachsorgeprogramms konnte anhand der Bereitschaft zur Teilnahme und der von den Teilnehmern bewertete Nutzen aufgezeigt werden.
Eine Wirksamkeit der SMS-Nachsorge bzgl. Burnout und depressiver Symptomatik sowie dysfunktionalen Facetten des Perfektionismus konnte mittels zweifaktoriellen Kovarianzanalysen (Gruppe, Zeit, Baseline als Kovariate) nicht nachgewiesen werden. Ein Grund hierfür könnte sein, dass der Interventionszeitraum von 10 Wochen nach der stationären Entlassung für eine effektive Nachsorge zu kurz bemessen wurde. Bzgl. einiger dysfunktionaler Perfektionismusskalen (Concern over Mistakes, Discrepancy, Socially Prescribed Perfectionism) zeigten sich kleinere Interaktionseffekte, die einen ersten Hinweis liefern, dass die eingesetzten SMS-Nachrichten Perfektionismus-bezogene Kognitionen verändern können. Da das vorgestellte Interventionsprogramm ein ökonomisches und niedrigschwelliges ambulantes Nachsorge-Konzept darstellt und sich erste Hinweise auf eine Wirksamkeit ergeben, wären für die Zukunft weitere Studien wünschenswert, die sich über einen längeren Interventionszeitraum erstrecken. Es sollten weitere Messinstrumente einbezogen und die Implementierung eines Feedbackprozesses erwogen werden.
Immer häufiger kommt es zum Einsatz von Servicepersonal in Krankenhäusern und anderen pflegerischen Einrichtungen um dem Fachkräftemangel in der Pflege zu kompensieren. Die vorliegende Arbeit zeigt eine Kompatibilität von Tätigkeiten von Servicepersonal und Professionstheorien der Pflege, sowie einen Lernbedarf für Servicepersonal im Setting der stationären Pflege im Krankenhaus.
Pflegeexperten sind der Meinung, dass ein Einsatz von Servicepersonal, das in der Lage ist, durch definierte Tätigkeiten und Anforderungen Pflegepersonal zu unterstützen, notwendig ist. Zur Entwicklung von Handlungskompetenz für ausgewählte Tätigkeiten bietet ein situatives, tätigkeitsbezogenes Anforderungsprofil, gegliedert nach dem Kompetenzmodell in persönliche, soziale, methodische und fachliche Kompetenz, eine Grundlage für eine Bildungsmaßnahme für Servicepersonal.
Die Erkenntnisse dieser Arbeit tragen einen Teil dazu bei, den gegenwärtigen und künftigen Herausforderungen der Pflege gewachsen zu sein.
Die folgende Arbeit zeigt eine Möglichkeit auf, Lokalisierung eines Objektes mittels Ultraschall zu realisieren. Dazu werden drei bis fünf im Raum verteilte Sensoren genutzt, um anhand von Distanzinformationen die Position eines Objekts relativ zu den Positionen der Sensoren zu bestimmen. Eine Besonderheit besteht dabei darin, dass die Sensoren nahezu beliebig in der Ebene verteilt sein können. Ihre Anordnung wird vom System in der Kalibrierungsphase mit Unterstützung des Anwenders ermittelt. Dabei dürften ein gleichseitiges Dreieck, ein Quadrat oder Pentagramm je nach Sensoranzahl die besten Ergebnisse liefern. Um die relative Bewegung in eine Absolute zu übertragen, findet eine Umrechnung in Meter anhand der Taktung der Mikrocontroller, des Prescalers des verwendeten Timers und der Schallgeschwindigkeit statt.
Risiko-Träger Controlling: Identifizierung und Bewältigungsoptionen im Kontext dialogischer Führung
(2016)
Management control seen as an element of the management process is assigned with a broad range of tasks and functions within organizations. Its role throughout risk- and goal-oriented management schemes is well established in both theory and organizational practice but its contribution to risks within the management cycle is scarcely discussed in scholarly literature. This blind spot is taken up by this research paper aiming to identify the institutionalized controlling as a risk-bearing actor within organizational management and outlining options to cover it.
In Part I: "The flow-decomposition problem", we introduce and discuss the flow-decomposition problem. Given a flow F, this problem consists of decomposing the flow into a set of paths optimizing specific properties of those paths. We introduce different types of decompositions, such as integer decompositions and alpha-decompositions, and provide two formulations of the set of feasible decompositions.
We show that the problem of minimizing the longest path in a decomposition is NP-hard, even for fractional solutions. Then we develop an algorithm based on column generation which is able to solve the problem.
Tight upper bounds on the optimal objective value help to improve the performance.
To find upper bounds on the optimal solution for the shortest longest path problem, we develop several heuristics and analyze their quality. On pearl graphs we prove a constant approximation ratio of 2 and 3 respectively for all heuristics. A numerical study on random pearl graphs shows that the solutions generated by the heuristics are usually much better than this worst-case bound.
In Part II: "Construction and analysis of evacuation models using flows over time", we consider two optimization models in the context of evacuation planning. The first model is a parameter-based quickest flow model with time-dependent supply values. We give a detailed description of the network construction and of how different scenarios are modeled by scenario parameters. In a second step we analyze the effect of the scenario parameters on the evacuation time. Understanding how the different parameters influence the evacuation time allows us to provide better advice for evacuation planning and allows us to predict evacuation times without solving additional optimization problems. To understand the effect of the time-dependent supply values, we consider the quickest path problem with time-dependent supply values and provide a solution algorithm. The results from this consideration are generalized to approximate the behavior of the evacuation times in the context of quickest flow problems.
The second model we consider is a path-based model for evacuation in the presence of a dynamic cost function. We discuss the challenges of this model and provide ideas for how to approach the problem from different angles. We relate the problem to the flow-decomposition problem and consider the computation of evacuation paths with dynamic costs for large capacities. For the latter method we provide heuristics to find paths and compare them to the optimal solutions by applying the methods to two evacuation scenarios. An analysis shows that the paths generated by the heuristic yield close to optimal solutions and in addition have several desirable properties for evacuation paths which are not given for the optimal solution.
A special challenge of the basic musical education of children is to give them an understanding of reading and writing musical scores. During the training of young choristers it is furthermore important to educate them in directly transforming the written scores into sounds.
Therefore it is an interesting idea to play the sounds to the children via piano or keyboard and simultaneously present them on a screen in musical notation.
The aim of this bachelor thesis is the implementation of such a system that allows to enter scores using a MIDI-compatible keyboard and then depicting these as musical notation. The prototype of the application operates in three steps. It receives the musical scores via keyboard in form of MIDIdatasets. These MIDI-information are converted to the MusicXML-format. Based on this MusicXML-notation the software finally generates and displays the visual output.
This thesis is providing an overview over the current topics and influences of mobile components on Enterprise Content Management (ECM). With a literature review the core topics of enterprise mobility and ECM have been identified and projected on the context of using mobile Apps within the environment of ECM. An analysis of three ECM systems and their mobile software lead to an understanding of the functionalities and capabilities mobile systems are providing in the ECM environment. These findings lead to a better un- derstanding for the usage of mobile Enterprise Content Management and is preparation. The thesis focuses the most important topics, which need to be considered for the usage and adoption of mobile Apps in ECM.