uni bremen dissertation

Dissertations

• Ji Joint PHY and MAC Layer Perspective for Compressed Sensing in Wireless Communications BibT E X Y. Ji Ph.D. Thesis, Shaker Verlag , Bremen, Germany, May 2022 , ISBN 978-3-8440-8595-2
• Compressive Sensing based Dynamic Spectrum Access for Interference-Networks BibT E X D. Wieruch Ph.D. Thesis, Shaker Verlag , Bremen, Germany, September 2021 , ISBN 978-3-8440-8208-1
• Signal Processing for Distributed Kernel-based Estimation BibT E X B.-S. Shin Ph.D. Thesis, Shaker Verlag , Bremen, Germany, April 2020 , ISBN 978-3-8440-7311-9
• In-Network Processing Algorithms for Cooperative Networks BibT E X G. Xu Ph.D. Thesis, Shaker Verlag , Bremen, Germany, March 2020 , ISBN 978-3-8440-7270-9
• Factor Graph-based Receivers for Multi-Carrier Transmission in Two-Way Relaying and Massive Machine Type Communications BibT E X M. Woltering Ph.D. Thesis, Shaker Verlag , Bremen, Germany, December 2019 , ISBN 978-3-8440-7050-7
• Efficient Globally Optimal Resource Allocation in Wireless Interference Networks BibT E X B. Matthiesen Ph.D. Thesis, TU Dresden , Dresden, Germany, November 2019
• Acquisition and Reconstruction of Compressed Signals with Applications in Wireless Neural Systems BibT E X T. Schnier Ph.D. Thesis, Shaker Verlag , Bremen, Germany, April 2019 , ISBN 978-3-8440-6593-0
• Physical-Layer Cooperation in Coded OFDM Relaying Systems BibT E X M. Wu Ph.D. Thesis, Shaker Verlag , Bremen, Germany, December 2017 , ISBN 978-3-8440-5625-9
• Signal Processing for Compressed Sensing Multiuser Detection BibT E X F. Monsees Ph.D. Thesis, Staats- und Universitätsbibliothek Bremen , Bremen, Germany, November 2017
• IDMA-based Relaying for Future Mobile Communication Systems BibT E X F. Lenkeit Ph.D. Thesis, Shaker Verlag , Bremen, Germany, March 2017 , ISBN 978-3-8440-5137-7
• Energy Savings in Phantom Cell Concept Heterogeneous Networks BibT E X E. Ternon Ph.D. Thesis, Shaker Verlag , Bremen, Germany, January 2017 , ISBN 978-3-8440-5005-9
• Compressive Sensing Multi-User Detection Approaches for Sporadic Communication BibT E X H. Schepker Ph.D. Thesis, University of Bremen, Germany, Schaker Verlag , Bremen, Germany, December 2015 , ISBN 978-3-8440-4111-8
• Efficient Detection and Adaptive Transmission for MIMO-OFDM Systems BibT E X R. Böhnke Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, March 2015 , ISBN 978-3-8440-3449-3
• Signalverarbeitung für die Relay-gestützte Datenübertragung BibT E X P. Weitkemper Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, June 2013 , ISBN 978-3-8440-2020-5

• Robuste Vorentzerrung in TDD-Systemen mit nicht perfekter Kanalreziprozität BibT E X M. Petermann Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, September 2012 , ISBN 978-3-8440-1244-6
• Robust Link Adaptation in Coded OFDM Systems BibT E X C. Bockelmann Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, April 2012 , ISBN 978-3-8440-0913-2
• Digitale Signalverarbeitung für die faseroptische OFDM-Übertragung BibT E X H. Paul Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, January 2012 , ISBN 978-3-8440-0669-8
• Multiple Antenna Doppler-Compensation for OFDM Systems BibT E X P. Klenner Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, May 2011 , ISBN 978-3-8440-0108-2
• Effiziente Konzepte für die UMTS-Abwärtsstrecke BibT E X R. Seeger Ph.D. Thesis, University of Bremen, Germany, Shaker Verlag , Bremen, Germany, July 2010 , ISBN 978-3-8322-9226-3

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Dissertationen

Das BIBA steht für eine anwendungsorientierte, differenzierte akademische Ausbildung auf hohem Niveau. Das zeigt sich auch an den abgeschlossenen Doktorarbeiten, die an dem mit dem BIBA verknüpften Fachgebieten des Uni-Fachbereiches Produktionstechnik erfolgten. Am BIBA forschen und promovieren Wissenschaftlerinnen und Wissenschaftler aus aller Welt.

Automation of inflight services

The dissertation investigates the automation of inflight catering services in the aviation industry. The complex nature of this field necessitates improvements to systems both within and outside the aircraft. In close collaboration with the industry, experiences and requirements were gathered, and a passenger survey involving 1000 participants was conducted to specify the needs. The trend towards individualization served as an example of the transformation impacting new developments. The developed method allows for the consistent development and evaluation of automation concepts for inflight catering services. The work not only sheds light on a little-explored area but also presents a new approach that integrates product design, process analysis, and decision-making, thus opening up new possibilities for the early development of automation concepts with a consistent comparison.

Applied scenario simulation

Spatial concentrations of interlinked companies and institutions along a value chain represent a considerable competitive advantage for companies and regions and are known as industrial clusters. Certain networks in such clusters, particularly the cluster initiative, are responsible for strategic planning for the cluster. The family of scenario techniques in particular offers very good approaches for strategy search and development. In this thesis, an extended version of dynamic-causal cross-impact analysis, implemented as a software system by the author, was used for the simulative generation and structuring of scenarios in the context of a case study in an aviation cluster.

Nutzungsdaten in der Produktentwicklung

Obwohl die zunehmende Menge an Produktnutzungsinformationen (PUI), wie z.B. Kundenrezensionen und Wartungsdaten, für die Entwicklung neuer Produktgenerationen immer wertvoller werden, gibt es bisher nur wenige Ansätze, diese systematisch für die Entscheidungsfindung in der Produktentwicklung zu nutzen. Das Ziel dieser Dissertation ist die Entwicklung eines umfassenden Ansatzes, um Produktentwicklern die für ihre aktuellen Aufgaben relevanten PUI zur Verfügung zu stellen. Der Ansatz besteht aus einer Methodik und einem Metamodell. Kern des Ansatzes ist die systematische Berücksichtigung des Kontextes der zu bearbeitenden Aufgabenstellung in der Produktentwicklung. Durch die Berücksichtigung des Kontextes werden dem Produktentwickler geeignete PUI zur Verfügung gestellt.

Training Simulators for Manufacturing

Training simulators are an integral part of training in medicine, aviation, the military and other fields. However, they are rarely used in manufacturing. Existing frameworks for training simulator design stem from areas with a long history of simulation-based training and do not question its applicability. Therefore, a task analysis method was developed in the dissertation to determine the achievable benefit of a training simulation for specific manufacturing tasks. The evaluation in the use cases of welding, milling, gluing and additive manufacturing has shown that the method is also suitable to identify challenges regarding human-machine interface (HMI) technologies.

Extreme loads for offshore wind turbines

This thesis addresses the design process of offshore structures and focuses on offshore wind turbines. Wind turbines are typically designed for a design life of 20 or 25 years and therefore must withstand all environmental conditions that can reasonably be expected during this time. This work addresses three design process steps where current methods to describe the environment and calculate structural loads can lead to problems: (1) Modeling the probability distribution of significant wave height; (2) modeling the joint distribution of wind speed and wave height; and (3) determining 50-year joint environmental extremes. New methods to deal with these three steps are proposed and evaluated. Finally, a case study on a 5 MW wind turbine is conducted.

Automatic Selection of Forecasting Methods

To conduct their production planning, manufacturing companies use demand forecasts based on past customer orders within time series. In this context, either an individual forecasting model has to be selected for each time series or the forecasts of several models are combined. To harness the advantages of both approaches, this thesis developed a hybrid approach that selects a single model or combines multiple models depending on time series characteristics. Referred to as a selbination approach, this achieved a significantly higher forecast accuracy and a better trade-off between service level and required safety stock than standard methods from the state of the art, according to a comprehensive empirical study on a real industrial dataset.

The Intelligent Container

Cyber-physical systems can contribute to the improvement of logistical quality as well as to the optimization of logistical processes. If the planning or optimization of logistics processes is already an interdisciplinary task, the use of cyber-physical systems expands it to include additional disciplines. Existing modeling concepts take into account the known disciplines, while the "new" disciplines of systems engineering or electrical engineering are given little or no consideration. The interaction of this multitude of disciplines can lead to inefficiencies in the design and development of cyber-physical logistics systems. For this reason, this thesis develops a modeling concept that improves the communication between the disciplines involved and thus leads to more efficient processes in the design and development. https://media.suub.uni-bremen.de/handle/elib/5997

Optimal Supplier Development for Original Equipment Manufacturers

Original Equipment Manufacturers (OEM) face procurement costs of raw materials and com ponents of more than half of the manufacturers’ total profit. Therefore, OEMs depend on their suppliers, and the supplier’s performance has a noticeable effect on many product as pects, such as cost, quality, and on-time delivery. Consequently, OEMs place increasing concentration on a more efficient supply chain utilizing supplier development. Like other types of investments, investment in supplier development contains the risk whether it pays off the proposed revenue or not. Therefore OEMs need to be aware of the profitability of their supplier development investments in advance. Regarding this topic, many researchers conducted quantitive and qualitative supplier development studies. They tried to address different aspects of this concept, like supplier development outcomes, applications, or its importance. They provided in-depth knowledge of suppler development investment in both theory and practice. The presented studies considered supplier development in a static mar ket situation. Additionally, they did not offer any suggestions toward the profitability of supplier development regarding the period of investment in a dynamic market.

Efficient Distributed Control Systems

Distributed systems are present in all areas today, e.g. in the form of machines in production plants, collaborative robots or autonomously driving networked vehicles. The entities in such distributed systems require efficient coordination as well as communication exchange in order to make do with as few resources of wireless technologies as possible. In this thesis, a quantisation of the communication between the systems with the reduction of the communication overhead was developed and, in addition, proofs of convergence and admissibility of solutions were provided. Furthermore, dynamic priority rules were also considered and various criteria for accelerating the convergence of the overall system were investigated.

Using social media data for decision making

Fashion and apparel supply chains are highly complex and dynamic. Forecasting demand is difficult, but fashion is an important topic on so-cial media. This is where the dissertation starts – it provides a methodology for the exploitation of data from social media. The research ap-proach strictly follows the method of design sci-ence research. As an artifact, a process model was developed that uses text mining to extract information from fashion blogs. The realisation of the process model is based on the modelling language BPMN 2.0. Experimental results have shown the time lag between blog and real sales data across different supply chain levels in a real-world scenario.

Objective: Condition-oriented maintenance

Within the scope of the dissertation, a Condition Monitoring System (CMS) was developed which uses the Complex Event Processing (CEP) approach to achieve real-time monitoring of a system status, identify causes of faults and evaluate the status of technical components. This requires new information landscapes based on event-driven architectures. The work investigates on the one hand by means of a reference model how the CMS structure has to be designed for the successful application of the CEP approach and on the other hand the methodology for configuring the CMS so that sensor data of different components can be related to each other in real time for the correct assessment of global conditions.

Evaluation of floor-free container transport technologies

The dissertation describes a procedure for the scenario-specific evaluation of overhead container transportation technologies. Trends in global maritime traffic, such as an increase in international container traffic, larger vessels and harbour consolidation, have made it necessary to develop transport technologies with an infrastructure level that differs from the conventional one (overhead container transportation). The dissertation describes technologies (such as container cableways) that can be used for overhead container transportation and develops a procedure for their scenario-specific evaluation. This is integrated into a data-based analytics tool and evaluated for every scenario.

Proactive Design of Supply Chain Robustness

Supply chains operate in an uncertain context, in which the future evolution of the customer demand as well as the available production ca-pacity may deviate from past observations. This may prohibit the satisfaction of future customer demand. This thesis addresses this kind of un-certainty by the development of a decision sup-port methodology for the design of robust sup-ply chains by the strategic allocation of produc-tion capacity. In contrast to the well-established planning techniques the infinite number of fu-ture scenarios of the uncertain parameters is divided into two sets. In this context the proac-tive design of the set for which the satisfaction of the future customer demand can be guaran-teed is of interest.

Human Factors in Production Systems

The introduction of cyber-physical systems is shifting human work in manufacturing towards mainly cognitive tasks. Thus, to design this changed work in a human-oriented way, there is a need for adequate interfaces between humans and machines. These can be designed using a novel method which was developed in this the-sis. By conducting extensive human factors studies with the aid of an experimental platform, the method was validated and was able to pro-duce a set of possible design principles for hu-man-machine interfaces. Overall, the thesis facil-itated a better understanding of the mecha-nisms between human factors and human work.

Prediction & Analysis of Material Flows

The field of complex networks has developed concepts and methods to analyse and predict networks, such as friendship networks or protein interactions. However, although these examples have equivalents in the form of company net-works and interactions within manufacturing processes, more sophisticated methods have not yet been transferred to manufacturing and logistics. We propose to apply methods from clustering and graph embedding on machine in-teractions to analyze the structural stability of manufacturing systems and to predict structural changes of such systems. Overall, we successful-ly transferred clustering with stochastic block models to manufacturing systems and contri-buted to graph machine learning with our statis-tical manifold embedding of directed graphs.

Effizient vom Automobilwerk zum Händler

Der schnelle und kostengünstige Transport neuer Fahrzeuge vom Werk zum Händler, die sogenannte Fahrzeugdistribution, ist für Automobilhersteller ein wichtiger Wettbewerbsfaktor. Innerhalb der Dissertation wird untersucht, welchen Beitrag die automatische Identifikation von Fahrzeugen mit RFID-Technik hierzu leisten kann. Darauf aufbauend wird der Frage nachgegangen, ob der XML-basierte EPCIS-Standard geeignet ist, die so erzeugten Daten effizient den beteiligten Unternehmen zur Verfügung zu stellen. Die Ergebnisse der Arbeit weisen darauf hin, dass durch den Einsatz der beiden genannten Technologien die Transparenz in Distributionsprozessen gesteigert und somit deren Wirtschaftlichkeit verbessert werden kann.

A Method for Predicting the Delivery Time

Particularly in multimodal freight transport chains, a suitable prediction method is required to reliably predict the delivery time without using planning data. According to the literature, only machine learning algorithms can ade-quately deal with the complex and dynamic behaviour during transportation. This thesis develops such a prediction method using ma-chine learning and evaluates the findings based on data from a real transport chain from Germa-ny to the USA. Taking into account an average transport time between 22 and 31 days, this thesis obtained an average error of 15 hours or 5 percent, based on the actual delivery time.

Permissible Stressing of Preforms

Semi-finished products are stressed by numer-ous handling manipulations during the produc-tion of rotor blades for wind energy turbines. The knowledge of the relation between this stress and its effect on the quality of the subse-quent composite product is of great importance for the process optimisation. In this thesis, the process chain for the production of textile pre-forms was analysed. Followed by the measure-ment of permeability of imperfect textile sam-ples the relation between handling effects and the quality of preforms were shown.

Machinery-oriented capacity control

Nowadays, manufacturers are confronted with various challenges arising from customer requirements concerning different types of products, quantities and delivery dates. Reconfigurable machine tools and operator-based robust right coprime factorisation (RRCF) provide an opportunity for a new capacity control strategy to be established. The main objective of the dissertation was to develop a machinery-oriented control strategy and compare it with the classic proportional-integral-derivative (PID) control method. A decentralised control structure was adopted, and simulation results show that the RRCF control method is able to handle rush orders and delays within a shorter settling time and exhibits less overshoots than PID.

Nonlinear model predictive control

Despite risks relating to high work in process (WIP), long lead times and poor delivery time reliability – particularly when faced with unpredictable events – highly flexible job shop organisation continues to play an important role in today’s manufacturing systems. Adjustments are typically achieved by labour-oriented approaches. In his thesis, Qiang considers machinery-based capacity adjustment via reconfigurable machine tools (RMTs) and proposes to control the WIP level directly. To include RMTs effectively at the operational and tactical layer, he suggests a complementing feedback approach using nonlinear model predictive control (NMPC). Based on numerical simulations, he shows that the WIP can be asymptotically stabilised to the greatest extent possible by using RMTs.

Wind energy: Cooperation & Collaboration

The thesis considers the topic of planning and control in the network of the construction phase of offshore wind energy. Due to the need for change and optimisation within the industry, a scientific discourse which goes beyond the existing framework is required. The result of this work includes the demonstration of efficiency improvement potentials as well as approaches for the implementation of resource and information sharing in the construction phase of offshore wind energy. For this purpose, approaches of cooperative logistics and a combination of supply chain-wide and cross-project collaborative logistics design were developed and the necessary success factors for implementation were elaborated.

eMobility in city logistics

The use of electric commercial vehicles (ECVs) can support the achievement of sustainable urban freight transport (UFT). However, their commercial use in urban freight transport has so far remained relatively low. Combining the characteristics of ECVs and UFT preferences and evaluating them quantitatively may provide a way of increasing market penetration. With this in mind, a sustainable ECV-UFT matching concept was developed as part of the dissertation and implemented by means of a simulation platform. The core elements of the concept are the methodology of assessment and the methodology of determination. The first evaluates the possible combinations quantitatively with respect to economic, social and ecological perspectives, while the second helps decision-makers to select the right combinations.

Improving robustness and solution quality

The factor uncertainty distinguishes today's decision problems from traditional mathematical optimization problems. Robust solutions often result in a deterioration of the solution quality, e.g. in route planning. Experiments in the context of the dissertation showed significant improvements over a deterministic approach by refinement of the wellknown Vehicle Routing Problem to a Static and Stochastic Capacitated Vehicle Routing Problem with Stochastic Demands. The newly developed mathematical decision model is based on a Mean Absolute Deviation Aim Function (MAD). It combines the minimization of the expected planned transport costs (optimality) and the mean absolute deviation of the second stage transport costs (robustness).

Vehicular ad hoc networks

The dissertation addresses the challenges of a vehicular ad hoc network (VANET), which arise from the high mobility of the vehicles, their short contact duration and traffic congestion on the road. An adaptive protocol is proposed by combining the functionality of topology and position-based routing. The MAC-based adaptive link layer considers the reorientation of routing at the data link layer. In addition to the theoretical analysis of applications for a vehicular environment as well as flooding and routing procedures for the dissemination of safety alerts and messages in the network, this study also deals with experiments to validate the use of a VANET with the latest technologies.

Flexible network design model

Nowadays, the design of a supply chain network must allow operations to take place at the lowest possible cost, while providing the best possible customer service and complying with environmental protection standards. With industrial players under pressure to take back used products, the dissertation attempts to incorporate this reverse flow through the integrated design of a flexible forward/reverse supply chain network. A cyclic, seven-stage, logistics network problem was formulated as an NP-hard mixed integer linear programming model. This integrated, multistage model is enriched by using a complete delivery graph in forward flow. To find a near optimal solution, a memetic algorithm with a neighbourhood search mechanism and a novel chromosome representation has been applied.

Trust in Sharing Logistics Resources

Efficient resource sharing in logistics requires trust to support partners to collaborate. However, trust uncertainties resulting from partner behavior and collaborative processes impede needed sharing. Such uncertainties hinder efforts to reduce: logistics costs; underutilization of physical assets, and; harms to the environments. Thus, this dissertation developed a Trust Mechanism (TrustMech) concept to help partners to forecast trustworthiness of prospective resource sharing networks. The TrustMech unveils how partner behavior under the influence of collaborative logistics processes reinforces trusting outcomes. The TrustMech stands on a conceptual paradigm of socio-cognition, and; its validation and application build on experimentation in Multi-Agent Systems.

Integrated cyber-physical manufacturing control

The development towards cyber-physical production systems (CPPS) in the context of "IoT" causes a shift in the task structure of production planning and manufacturing control in favour of the latter. Besides order release, also the traditional planning tasks of dispatching, scheduling and capacity control are meanwhile tasks of manufacturing control. This thesis presents a method of manufacturing control, which considers the broadened task structure of manufacturing control in CPPS. The method is evaluated in flexible flow shop and job shop scenarios and benchmarked with traditional methods of manufacturing control.

Batches Green Logistics

Within the globalized environment, the flow of these batches is raising dramatically to satisfy the recurrent demands of the increasing population. This research develops a green logistics oriented framework in the case of the batch process industry in which we integrate the tactical and operational levels of planning and scheduling. The analysis results provide insightful results on supply chain costs and emissions. Based on the results, savings of about 43 percent of the total related economic and environmental costs are proved comparing to the actual situation at the tested cases. Building such a framework provides a practical tool which links being green and being economically successful.

Standard solutions provided by modular robots

This dissertation describes a concept for an overarching module and configuration management system, designed for industrial robotics systems in logistics processes. Due to their dynamic nature, these processes are difficult to manage from a technical point of view, meaning that numerous technical components are used. This results in cost-intensive isolated solutions rather than economically beneficial standard products. Based on the principles underpinning mass customisation, a system for modularising and configuring robot systems is being developed in a way that is specifically tailored to individual processes. The main approach for this is based on ontologies. This overarching concept enables modules to be developed and used in an integrative and comprehensive manner, thus reducing the number of isolated solutions.

Optimal coordination of production and transport operations

In industry, nowadays, production planning and transport planning are done separately, while the related physical processes within a supply chain are closely linked with each other. This leads to the assumption that current planning methods do not generate the best possible schedules. This assumption is the topic of the dissertation, which investigates the differences in the results of a separate or an integrated planning of production and transport processes. The work also includes the development and evaluation of a new solution algorithm for the computation of integrated schedules.

Integration of production and transport

The developed integrated planning method for production and distribution scheduling is based on a framework with a multi-stage decomposition and integration procedure of the sub-problems. The integrated planning method applies this new multi-stage structure for the problem solving process and uses already known solution methods to solve the sub-problems. The evaluation shows that the overall costs of planning results generated by solution methods compared with are up to 26% higher than the overall costs of the planning results generated by the integrated solution method developed. Furthermore, it was proved in a sensitivity analysis that there is a positive impact on overall costs applying the integrated solution method developed within a wide range of cost parameters.

Modern Maintenance Systems in the Spotlight

From an operational perspective, maintaining complex technical systems is a huge challenge. Status-based maintenance improves the planning and management of maintenance activities, and the use of technical equipment for status detection purposes in particular is increasingly gaining in importance. This paper investigates the extent to which the development of an integration model for status detection and optimisation of maintenance for complex technical systems is required. The result is the development of a comprehensive procedure for the successful integration of status-based maintenance methods in complex operational environments, which is tested in a case study using port handling equipment as an example.

Transparency in transport logistics

The demand for what are known as intelligent, innovative and efficient transport systems is constantly on the increase in the logistics sector. To meet this demand, concepts are needed that can sustainably cut down on freight traffic. This project aims to design and develop a system that supports the planning and control of load carriers in logistics in order to meet the aforementioned demand. In order to do this, the basic principles of all the areas relevant to this topic are discussed in detail. By integrating and implementing examples, the defined objectives can be checked in terms of their performance in order to verify the effectiveness of the system. A final discussion aims to show the need for further research on this subject.

Autonomously controlled disposition

Global markets for customer oriented individual products challenge companies due to the resulting complex and dynamic production and logistic networks. Innovative production control methods constitute a possibility to manage the correspondingly complex processes, both within individual companies and global networks. This doctoral thesis evaluates the application of the autonomous control paradigm in the sector of event logistics, especially in relation to the disposition of rental articles. At this, methods for route planning and order disposition from this field are adapted to the practical example. The result is an autonomously controlled disposition system for event logistics.

Process model for developing simulation games

In SMEs, the success of company cooperation is determined by its employees' ability to cooperate. Employees who previously had no direct connection with collaborative processes are faced with new tasks that they are not always able to overcome. Simulation games have been proven to be a successful method of imparting the skills necessary for this. This thesis develops a process model that identifies key design elements for a company-specific simulation game template by analysing the current business situation. Employees can use the simulation game developed to train their skills using authentic cooperation scenarios.

Short lead times for large batches

The dilemma of operations scheduling is a familiar challenge when it comes to planning in the manufacturing industry and describes the trade-off between minimum lead times and maximum capacity utilisation. This research illustrates that the influence that these two factors have on each other is in no way linear. It develops planning and control methods for multi-stage, simultaneous batch productions with stage-specific order families. Adapting them to an application scenario from the automotive industry dramatically reduces downtimes while keeping batch sizes economical at the same time. This result shows that competing targets do not follow a general trade-off function and that specific planning approaches can generate solutions that make sense in both regards.

Intelligent and robust object detection

Rapid progress in the field of 3D sensor technology and artificial intelligence has made it possible to develop cognitive and flexible robotic systems that do not require predefined and constant environmental conditions, therefore enabling robots to react to unforeseen events. Developing a flexible robot for unloading different types of goods from containers requires an object recognition method that is able to detect and locate individual goods from several classes of forms and unknown sizes correctly. The method analyses 3D sensor data from a laser scanner. As part of this thesis, an object recognition method was developed and evaluated using realistic test scenarios in a demonstrator and simulated sensor data.

Increased flexibility in production

Capacity control in manufacturing is tasked with fulfilling a high achievement of the logistic objectives. This requires a certain degree of flexibility in terms of capacity which is typically achieved through the flexible deployment of the available employees and adaptations to working hours. In addition to this, the development of reconfigurable machine tools can increase capacity flexibility in the future. Against this background this thesis discusses the potentials and limitations of such machines when it comes to controlling capacity in a job shop production. Thus, the thesis emphasizes the positive impact of reconfigurable machine tools on economically relevant objectives such as inventory, lead time, adherence to delivery dates and utilization.

Deep Learning in Optical Inspections

The main objective of the investigation is reliable defect detection from sensorial data. This thesis focuses on two strategies. The first strategy is based on existing state-of-the-art feature representations and classification methods. Specifically, multi-scale texture analysis in combination with statistical feature representation is used to describe defective areas. In traditional machine learning, features are hand-coded and therefore designed manually. In contrast, the second strategy implements Deep Learning, which introduces feature generation into the learning process. The focus of this investigation is different design choices and hyperparameters and their influence on the overall detection result.

Job Shop Production Scheduling

Production scheduling is a key part of intelligent production in the context of Industry 4.0. Furthermore, the demands of competition are forcing manufacturers to improve their adherence to deadlines when delivering customer orders. This thesis expands on the Shifting Bottleneck (SB) method by adding the Variable Neighbourhood Search (VNS) in order to solve the job shop scheduling problem which is used extensively to model make-to-order manufacturing processes. It also provides guidelines for configuring the method. After carrying out computational experiments on benchmark instances with up to 150 orders and 20 machines, and conducting comparisons with state-of-the-art approaches, the results indicate that the SB method that has been developed is currently the most promising approach for practical applications.

Standards for Greater Transparency

Very few production, transport and installation strategies can be transferred from onshore to offshore wind turbines due to the harsher conditions in offshore applications (weather, transportation by ship, etc.). The production and logistics networks – which vary from project to project – have to cope with significant logistical challenges and extremely dynamic circumstances. Standard IT systems are not able to meet requirements relating to planning, management, event simulation and statuses. As the basis for an IT system, this paper develops an information flow concept designed to increase transparency for offshore wind energy logistics networks, derives relevant installation and logistics concepts, tests them as prototypes and then incorporates them into standard processes.

Two planning aids to counteract errors

Repeating work costs money, and the later an error has to be rectified, the more expensive it becomes. Expenses are more likely to be incurred if an error is allowed to propagate. Planning for the future can therefore save a lot of money. The aim of this paper was to support work planning and, in particular, work plan creation in such a way that the internal workpiece condition can be described when planning high-tensile steel components of propulsion technology with regards to distortion. It should be possible to use this to anticipate and consider undesired changes in terms of dimensions and shape during the planning phase. Two planning tools (recommendations for planning and process chain comparison) have been proposed as a solution during research activities.

Lightweight design principles from nature

In the science of engineering there is knowledge about a well-established procedure for constructing lightweight designs. A critical step within this procedure is the search for a suitable concept. In the technical field, this critical step is usually solved through practical experience and by using existing constructions serving as models. In nature the evolution has created mature constructional principles which can serve as models for technical lightweight constructions. A corresponding expansion of the established approach to the knowledge of nature leads to a variety of innovative lightweight designs, expanding the potential for highly effective constructions.

Enhance Companies Performance through Entire Supply Chain Integration

Manufacturing industries are in dynamic changes in both developed and developing countries. The literature suggested that supply chains (SC) compete, not companies. The performance of firms in DC is expected to contribute to the improvement of the entire SC. It is critical to seek a process-oriented model that facilitates modeling efforts. The most promising is the SC operations reference model. However, this model is tailored to the needs of developed industries. Particularly, the early processes situated in the DC have different situations and are not considered in the model. This thesis investigates the characteristics of SC that support model adaptation. The main contribution of this thesis is an adapted business process with its building blocks.

Technology for container security

Electronic seals (E-Seals) are a technology that promises to improve security and safety during container transportation processes. However, not much research has been devoted to exploring systematically this technology's influence on the dynamics of container flows. This research aims to investigate the possible impacts of different types of E-Seal on container logistics and, in particular, on its dynamics. Several theoretical models have been developed to solve this task. The simulation outcome has been applied in cost-benefit-analyses for eight different business cases to approve the adoption of different types of E-Seal in container systems. In addition, the most feasible advantages of E-Seals and a framework for their applications have also been determined.

Harmonised throughput times in production

The ability to plan the estimated throughput time of individual orders precisely in advance is of key importance for manufacturing companies, as it allows them to accurately predict the earliest possible delivery date. In this context, shorter delivery times represent a significant competitive advantage compared to other companies. Due to complex material flow structures, external fluctuations in demand cause huge variations in throughput times as well as a high proportion of waiting times, particularly in job-shop systems. The presented concept of throughput time harmonising capacity control extends the state of the art. This capacity control aims to improve the predictability of throughput time by considering the potential of reconfigurable machine tools.

Process Modell in the mining industry

At present, existing solutions for supply chain models focus primarily on the manufacturing industry, rather than on the entire supply chain, as they do not incorporate the processes of the mining industry. In a comparison of processes of the mining industry with those of the manufacturing industry, the sourcing process was revealed as the area with the greatest disparity. The sourcing process in mining differs from the “source” process of the SCOR model. With respect to mining, modelling efforts focus on the processes of exploration, engineering design, construction and extraction. To develop the modelling techniques of these processes, each process was analysed in order to adapt SCOR and DCOR models to these processes by using mining language to guide the implementation of the developed model.

Integrating Eight Modeling Levels

The industrialization of CFRP production demands new engineering tools in order to develop more efficient production systems. This thesis presents a new concept for digital production system engineering in the context of Digital Factory, which is focused on the integrated planning and simulation of complex CFRP production scenarios. As an approach to model-driven engineering, a domain-specific modeling language and a factory data model were developed to generate material flow simulation models. Thereby, major challenges of CFRP production engineering were considered and an eight-level modeling concept called GRA MOSA was developed which allow the management of alternative production scenarios by supporting manufacturing as well as logistics planning.

Improved Control, more Reliability

Complex networks of suppliers, manufacturers and distributors are characterized by uncertainty. In order to handle this hardly predictable factor, managers must be able to know, and, if possible, monitor and control, its causes, influences and effects. This is the starting point for this thesis. It addresses the main types of uncertainties in complex supply networks. Critical routes were defined in PERT networks, and the uncertainty of the compliance with a specific delivery date was calculated by means of a combination of stochastic and mathematical models. This solution provides a more reliable control tool, leads to more reliability and makes an increase in performance in dynamic networks possible.

Significantly Better Prediction Results

Scheduling presents a highly complex problem which is of great relevance to industrial enterprises. In dynamic job shop and flexible flow shop scheduling, priority rules are often appliedto this end. As there is no rule which satisfactorily fulfils the target criterion in every situation, a dynamic method of selection and/or adaptation has been developed in the scope of a doctoral thesis. Predictions were made by applying Gaussian process regression models, based on which the adequate rules were dynamically selected. Evaluations in job shop and flexible flow shop scheduling revealed that significantly better predictions can be obtained this way and that the newly developed control method accounts for an enhanced performance.

A Three-Component Evaluation System

The implementation of autonomous logistic processes in production systems is capable of improving logistic target achievement in connection with increasing complexity. To this end, a three-component evaluation system for autonomous production systems was developed in this study. The main task of the system is to measure the logistic target achievement in the conflicting field of autonomous control and complexity levels. The system is capable of displaying these relationships. Its validation proceeded with simulation models and real data derived from a shop floor manufacturer. Simulations were conducted with varying levels of autonomous control and complexity to study the system’s application potential.

Technical Design Recommendations

This thesis is concerned with the conception of a design method for modeling mobile interaction devices with a special focus upon intelligent production environments. Its main result represents a method which identifies and describes the necessary model-based tasks for designing mobile interaction devices (mobile input devices, output devices and communication devices). An essential part of the method consists of a modeling tool based on a context model for configuring work situations in intelligent production environments. This tool enables the generation of technical design recommendations to be followed by product developers creating mobile interaction devices in the early phases of product development.

Improvement of Logistic Parameters

A heterogeneous product range, varying numbers of pieces, and the highly interconnected structures of material flow make it difficult to coordinate all logistic processes in shop manufacturing. One solution consists in the synchronization of logistical processes. Synchronization theory offers applicable methods for this purpose. In order to benefit from this form of decentralized self-organization, physical theory was combined with logistic processes, making it possible to represent both status and progress of a process by applying the concept of phase display. Phase coupling led to strategies which were evaluated by means of a simulation study. This thesis shows that the logistic target parameters can be improved this way.

Creating more Efficient Production Systems

The specialization of companies has led to a stronger urge to synchronize processes in networks. Here, however, effects also occur which cannot be adequately addressed by applying common planning and control methods. One example is deterministic chaos, which may cause an only apparently random behavior. The use of methods of nonlinear dynamics is a promising approach to describe such phenomena as well as identify nonlinear dependencies and dynamic working relationships. The aim is to identify policies and strategies that will ensure an efficient operation of the production system, evenif there are high degrees of complexity and dynamic boundary conditions.

Particularly suited for PET

High-quality recycling of plastics requires very specific separation methods. To exploit the intrinsic material properties, various plastics were combined and built into a component. Currently available recycling processes are not able to identify and separate this mixture of plastics. However, the application of a new single-material approach revealed that components consisting of only one plastic species display identical properties, thus reducing the challenge of sortingconsiderably. In addition, the degradation behavior of plastics is an essential aspect. The effects of the “quality of substitution “ and the “proportion of substitution” on various material properties and it is revealed that PET is particularly suited for this approach.

Great Potential for Efficiency Enhancement

Competition in the automobile industry forces the tool and die shops into a continual optimization process. In their machining departments, both automated NC programming and continual optimization processes for cutting strategies promise a great potential for efficiency enhancement. It is shown that the two approaches have hitherto actually contradicted each other. The automation of NC-programming is founded upon comprehensive standardization of the manufacturing processes and thus prevents the optimization of manufacturing strategies through modifications made by the users. The self-optimizing processes explored in this dissertation combine the potentials for single piece production with similarities in the machining process.

For New Telecommunication Services

The telecommunications industry is undergoing rapid changes. However, the great complexity of the telecommunication networks (TC networks) hampers the development of new innovative TC services. The concept presented in this thesis makes it possible to provide TC services oriented to individual customer requirements, lower development and maintenance costs, and shorten product cycles. It applies the principle of modular design and approaches to knowledge modeling which have been adjusted and further developed to TC specifications. The standard architecture of future TC networks, i.e. the IP Multimedia Subsystem Architecture, serves as a platform. The concept was tested under real-life conditions and is now already being used to develop commercial TC services.

The realisation of efficient product ramp-ups represents an essential competitive factor for small and medium-sized enterprises. By methodical control of interference factors, companies are able to realise ramp-up goals in regard to time, cost, quality and quantity. Efficient utilisation of ramp-up supporting programs, classifications, methods and tools is a precondition to meet these goals. Therefore, structured knowledge has to be available in a coordinated way. Mr. Krohne developed in his thesis an evaluation method, which supports the structured identification of ramp-up specific knowledge in order to improve it. The method has been realised in a software demonstrator and was exemplarily used in an automotive supplier company.

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Master Thesis

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We welcome master students who wish to write a thesis in English, can work well independently and have an interest in one of the topics in the research and teaching area of the IMG .

Requirements:

• You must have submitted an exposé (1-2 pages).
• The thesis should be written in English.
• The completion time is 15 weeks.

There is no accompanying seminar for master students, but you will be supervised through individual appointments.

For a comprehensive overview of our requirements and the writing process, please read our Thesis Guidelines . Further information on the application process can be found in the following documents.

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Aline Grünewald

Publications.

• Lectures and Presentations
• Teaching and Doctoral Training

• 12 Publications

Grünewald, Aline, 2021: The Authoritarian Welfare State and the Historical Emergence of Old-Age Pensions around the World. Dissertation , Universität Bremen, Universität Bremen, doi:10.26092/elib/552

Journal Article reviewed

Grünewald, Aline, 2021: From Benefits and Beneficiaries: The Historical Origins of Old-Age Pensions From a Political Regime Perspective , in: Comparative Political Studies, 54 (8), pp. 1424 - 1458, doi:10.1177/0010414021989763 , 31.01.2021

Grünewald, Aline, 2021: Power consolidation with welfare designs? The emergence of old-age pensions in nondemocratic regimes around the world , in: Democratization, 2021, doi:10.1080/13510347.2021.1961129 , 12.08.2021

Grünewald, Aline, 2020: The historical origins of old-age pension schemes: Mapping global patterns , in: Journal of International and Comparative Social Policy, 37 (2), pp. 93 - 111, doi:10.1017/ics.2020.23 , 12.10.2020

Grünewald, Aline; Seelkopf, Laura, 2016: Auslaufmodell oder Erfolgsgeschichte? Soziale Sicherung in globaler Perspektive , in: Zeitschrift für Sozialreform, 62 (2), pp. 111 - 140

Article in Edited Volume

Grünewald, Aline, 2021: Between Aspiration and Reality. The Effect of the French Colonial Legacy on Old-Age Pension Coverage in Africa , in: Nullmeier, Frank; González de Reufels, Delia; Obinger, Herbert (Ed.), International Impacts on Social Policy. Short Histories in a Global Perspective, International Impacts on Social Policy. Short Histories in a Global Perspective, Cham.: Palgrave Macmillan, (forthcoming)

Working Paper/Discussion Paper

Grünewald, Aline, 2014: Social Security around the World. A Review of Datasets , Arbeitspapiere des Zentrums für Sozialpolitik/3/2014, Bremen: Zentrum für Sozialpolitik, Download PDF

Grünewald, Aline, 2017: Same or different? Old Age Pensions in Democratic and Nondemocratic Regimes around the World , NoPSA’s XVIII Political Science Congress, Nordic Political Science Association (NoPSA); Department of Political Science and Public Management, University of Southern Denmark, Odense, Denmark, 08.08.2017

Grünewald, Aline, 2017: Sozialpolitik in Diktaturen , 11. Salon Fehrfeld, Salon Fehrfeld - Forum für Kunst und Kultur, Bremen, Germany, 28.10.2017

Grünewald, Aline, 2017: The Historical Roots of Old Age Pension Systems in Democratic and Nondemocratic Regimes around the World , 1st DaWS Young Researchers' Workshop, Danish Centre for Welfare Studies (DaWS), University of Southern Denmark, Odense, Denmark, 23.01.2017

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Master Program Applied Geosciences Master Thesis

Information on thesis.

You start to develop a topic for your master thesis after the second semester, usually in close collaboration with a working group at the Department of Geosciences or with one of the cooperating research institutes. The topic should deal with a current problem, which is not yet fully documented in literature. In the 3rd semester Research Seminar, the thesis` topic should be clarified at the latest. The fourth semester is dedicated to thesis` work. Under the guidance of a supervisor, each student conducts an independent scientific project. The thesis can be carried out on field studies, laboratory experiments or projects outside the university, for example in cooperation with the industry. Parts of the master thesis are literature research, data preparation and interpretation, modeling and simulation (optional), and finally writing the report. The master thesis is evaluated by two supervisors, whereupon the first one usually takes a closer look on the development. In a concluding colloquium, the student presents and defends his/her work. The colloquium lasts about 45-60 minutes.

• Find a topic and specify during the Research Seminar (3rd semester)
• Find a supervisor (external supervision possible, then usually a colleague from the Geosciences Department serves as the 1rst reviewer)
• Find 2 evaluating supervisors (only teachers of Dept. GEO, but from different research groups)
• 60 CP including the module "Research Seminar" required before starting
• Apply 2 weeks before starting at the examination office, s. downloads
• Duration: 24 weeks
• Extension: upon application only possible once for 6 weeks
• Submit 3 print copies with the declaration (s. downloads) attached in each and 1 digital version at the examination office
• Evaluation reports must be present after max. 8 weeks
• Arrange the colloquium date with your supervisors, reserve a room (consultancy for study affairs and career perspectives)
• 2 weeks before: register for the colloquium at the examination office (s. downloads)
• Colloquiums date: bring the minutes form from examination office
• Failed? The master thesis can be retried once with a different topic.

24 weeks / 30 CP