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Konferenzveröffentlichung
Propagation and branching strategies for job shop scheduling minimizing the weighted energy consumption
(2023)
We consider a job shop scheduling problem with time windows, flexible energy prices, and machines whose energy consumption depends on their operational state (offline, ramp-up, setup, processing, standby or ramp-down). The goal is to find a valid schedule that minimizes the overall energy cost. To solve this problem to optimality, we developed a branch-and-bound algorithm based on a time-indexed integer linear programming (ILP) formulation, which uses binary variables that describe blocks spanning multiple inactive ...
Konferenzveröffentlichung
Identifying critical demand periods in capacity planning for networks including storage
(2023)
We consider a capacity planning problem for networks including storage. Given a graph and a time series of demands and supplies, we seek for integer link and storage capacities that permit a single commodity flow with valid storage in- and outtakes over all time steps. This problem arises, for example, in power systems planning, where storage can be used to buffer peaks of varying supplies and demands. For typical time series spanning a full year at hourly resolution, this leads to huge optimization models. To reduce ...
Dissertation
Towards a Better Understanding of Entrepreneurial Teams: Investigating Temporal Dynamics on Multiple Levels
(2023)
This dissertation investigates entrepreneurial teams in the process of creating new ventures. The new venture creation process is complex. Different actors impact the new venture creation process in various ways, either facilitating or complicating it. The three studies at the heart of this thesis aim to cut through this complexity by examining the social context (i.e., entrepreneurial teams) and the temporal dynamics occurring in more detail. All studies address the conditions underpinning entrepreneurial teamwork ...
Dissertation
Learning through Self-Explanation
(2023)
In this dissertation, the effectiveness of learning through self-explanation was examined through a series of experiments. The primary focus was on the acquisition of factual knowledge. Learners' self-explanations were coded and categorized into correct inferences, correct paraphrases, and false utterances.
Dissertation
Process optimisation and non-destructive quality attributes monitoring during drying: A case study of celeriac slices and characterisation of its powder
(2023)
This study investigated strategies applied in drying technology to produce an optimised quality of plant-sourced food while considering environmental and sustainability aspects based on a case study of celeriac and powder, respectively. The I-optimal design of response surface methodology with 30 experiment runs was applied for process optimisation. Pre-drying treatments (blanching at 85 °C, 3 min; dipping in 1% citric acid solution, 3 min; no pre-drying treatment), drying temperatures (50, 60, and 70 °C), air ...
Aufsatz
A comparative study using water atomized and gas atomized powder in laser powder bed fusion process – Assessment of the fatigue performance
(2022)
Gas-atomized (GA, spherical) and water-atomized (WA, spattered) commercially pure iron (cp-Fe) powders were processed using laser-based powder bed fusion, resulting in a slightly higher porosity of the WA condition. In addition to characterization of quasi-static mechanical properties, fatigue tests, which are known to be detrimentally affected by porosity, were finally considered, revealing good properties even for the WA condition. In terms of microstructure stability, the GA and WA specimens significantly differ; ...
Aufsatz
Parameter recommendation for injection molding based on similarity analysis of injection molded parts
(2023)
Injection molding is a widespread manufacturing process for producing complex plastic shapes. The process is controlled by a large number of parameters, which show interactions with each other. Thereby the determination of an optimal operating point during sampling is a resource-consuming and demanding task. The data, which is generated during sampling, is usually not used for subsequent sampling processes. In the context of Industry 4.0, manufacturing companies attempt to optimize production efficiency to save time ...
Aufsatz
Baumwolle als Faserverstärkung
(2023)
Jedes Jahr landen große Mengen Textilen auf Deponien oder in der thermischen Verwertung. Ein Teil dieser Abfälle könnte allerdings auch als Rohstoffe für Verbundwerkstoffe dienen. Baumwollfasern eignen sich etwa als Verstärkungsfasern, die die mechanischen Eigenschaften von biobasierten Kunststoffen steigern. Durch die Nutzung solcher Abfallströme können in Zukunft kostengünstig und biobasiert Materialien verstärkt werden.
Dissertation
Analysis of agricultural landscape transformation and cropping system diversification in southern Myanmar
(2023)
Myanmar's forests are rich in biodiversity and have significant potential for carbon reduction. Kyunsu Township in southern Myanmar is still covered by biodiverse tropical evergreen rainforests on the highlands and mangroves on the coastline, conserving carbon stocks. However, the expansion of croplands into these forests to meet the growing demand for food and crop income is a major driver of deforestation and loss of carbon sinks. Thus, balancing agricultural land use and natural resource conservation is vital for ...