Recent Additions

  • Publication
    Design Principles for Boundary Spanning in Transdisciplinary Design Science Research
    ( 2022) ;
    Kruse, L.C.
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    Schoormann, T.
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    Design principles capture prescriptive design knowledge to guide design science researchers and design professionals in their design works. In the context of a transdisciplinary team, design principles can also be a powerful vehicle to bridge knowledge barriers and facilitate collaboration among team members with different backgrounds and expertise. These heterogeneous actors use design principles as a boundary object which helps to mediate their diverse perspectives. The paper draws from boundary object theory to explore the goals and the mechanisms of boundary spanning through ‘design principles-in-use’ and ‘design principles-in-formulation’. We discuss the applicability of our findings using a case of formulation and application of design principles for data spaces in a transdisciplinary research consortium. Our results add the layers of transdisciplinary collaboration to the ongoing discourse on design principles and design knowledge accumulation and evolution.
  • Publication
    Dihedron Algebraic Embeddings for Spatio-Temporal Knowledge Graph Completion
    ( 2022)
    Nayyeri, M.
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    Vahdati, S.
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    Khan, M.T.
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    Alam, M.M.
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    Wenige, L.
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    Behrend, A.
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    Many knowledge graphs (KG) contain spatial and temporal information. Most KG embedding models follow triple-based representation and often neglect the simultaneous consideration of the spatial and temporal aspects. Encoding such higher dimensional knowledge necessitates the consideration of true algebraic and geometric aspects. Hypercomplex algebra provides the foundation of a well defined mathematical system among which the Dihedron algebra with its rich framework is suitable to handle multidimensional knowledge. In this paper, we propose an embedding model that uses Dihedron algebra for learning such spatial and temporal aspects. The evaluation results show that our model performs significantly better than other adapted models.
  • Publication
    Recent Developments in Open Source Simulation Software pandapower and pandapipes
    ( 2022) ;
    Banerjee, Gourab
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    ;
    Drauz, Simon Ruben
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    Liu, Zheng
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    Majidi, Maryam
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    ; ;
    We introduce recent developments in the open source Python libraries pandapower and pandapipes. The purpose of pandapower is to provide an easy to use tool for power system analysis and enable a high degree of workflow automation. We describe the recent developments that extend the functionality of pandapower, such as new elements and controllers, as well as the calculation methods for state estimation, distributed slack, short circuit, asymmetric power flow, as well as advanced optimization functions via a new interface to the PowerModels.jl library. Furthermore, we describe the recent progress in the library pandapipes, which provides functionality to simulate pipe networks, such as district heating or gas networks. We demonstrate the new features of pandapipes in an example for transient temperature calculation and showcase the combined application of pandapower and pandapipes to model sector coupling.
  • Publication
    Comparison of Three-Level Grid-Forming Inverter Topologies for Unbalanced and Nonlinear Load Conditions in Microgrids
    Energy production in microgrids is more and more driven by distributed energy sources like photovoltaic, wind or battery systems, replacing diesel generators. For this purpose, inverters are needed that can serve load balancing and reactive power provision. This paper investigates two three-level topologies for grid-forming inverters for such applications with regard to the DC link voltage dimensioning. For the dimensioning of the DC link capacitors, an analytical solution approach for operation at active power is presented. The dimensioning of the capacitors for reactive power operation is determined by a numerical solution in the form of a circuit simulation. The efficiency of the two topologies investigated is compared based on the simulated semiconductor losses. Finally the simulation results of the DC voltage link deviation are compared for one operating point with measurement results of an inverter prototype.
  • Publication
    Analysis of interventions to optimize a pumping process in food production
    ( 2022)
    Colombo, Michael
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    Jell, Philipp
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    Heim, Albert
    In this work in progress report we show the use of Causal Inference with a Double Machine Learning approach to derive recommendations to favorably intervene in a pumping process in food production. At this point the machine learning does not yield statistically significant results due to lack of sufficient data. We further look into strata we have built from the data to study treatment effects but are again limited by the amount of data available. An outline how we intend to proceed with the work is given.

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  • Publication
    Laser structured nickel-iron electrodes for oxygen evolution in alkaline water electrolysis
    ( 2019)
    Koj, M.
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    Gimpel, T.
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    Schade, W.
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    Turek, T.
    In the present work, the ultra-short pulse laser ablation method is applied to create novel surface alloys on NiFe electrodes for the oxygen evolution reaction (OER) in alkaline water electrolysis. The nickel-to-iron ratio in the alloy can be controlled with the ultra-short pulse laser ablation method by varying the thickness of electrochemically deposited iron layers onto the nickel mesh substrate. Besides the application of the additional catalyst, the laser treatment enhances the surface area and a defined micro- and submicrometer structure is created in a single step. The laser structured nickel-iron electrodes show a significantly lower overpotential of 249 mV than an electrochemically deposited Ni-NiFe alloy with 292 mV at 10 mA cm−2, 298 K and 32.5 wt% KOH for the OER, although some loss of iron over time could not be prevented.
  • Publication
    Semantisch unterstützte interaktive Visualisierung von Finanzdaten
    ( 2007)
    Georgi, Matthias
    ;
    Tekusová, Tatiana
    Das Ziel dieser Arbeit ist die Entwicklung eines web-basierten Visualisierungssystems, welches das interaktive Erforschen und Analysieren von hierarchischen Finanzdaten ermöglicht. Hierzu werden verschiedene Darstellungstechniken untersucht und als konfigurierbare Komponenten implementiert, welche von einem Anwender ohne Programmierkenntnisse arrangiert werden können. Um eine effiziente Analyse multidimensionaler Daten zu ermöglichen, wurde ein OLAP-System entworfen, welches über eine multidimensionale Anfragesprache abgerufen werden kann. Wesentliche Kriterien dieser Verfahrensweise sind die einfache Konfigurierbarbeit auf der einen und die einer Vielzahl von Situationen gerecht werdende Anwendbarkeit auf der anderen Seite.
  • Publication
    A comparison study on the production and recovery of lactic acid by fermenting dairy by-products with P. acidilactici and Lb. delbrüeckii spp. bulgaricus
    ( 2019)
    Klupsaite, Dovile
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    Juodeikiene, Grazina
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    Arbones, Enrique
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    Pérez Quintáns, Alfonso
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    Zadeike, Daiva
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    Bartkiene, Elena
    ;
    ;
    Dikiy, Alexander
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    Shumilina, Elena
    This paper provides a comparative study on the fermentative production of lactic acid (LA) by the novel Pediococcus acidilactici KTU05-7, previously isolated from rye sourdough, and the common dairy Lactobacillus delbrüeckii spp. bulgaricus using dairy by-products as a substrate. Lactic acid bacteria growth in different fermentation medium, v-d-galactosidase activity, lactose consumption, distribution of l(+)/d(−)-lactic acid isomers and LA purification using a system of membranes were also examined. The highest LA yield (1.9 g/g) was obtained fermenting the whey permeate for 24 h with the novel P. acidilactici. This strain also showed a better growth in whey permeate, a higher tolerance to low pH conditions and tended to produce mainly l(+)-lactic acid, compared to the standard L. bulgaricus. Furthermore, the proteolytic action of P. acidilactici simplified the membrane filtration procedure, and hindered the formation of protein aggregate in fermented broth as compared to L. bulgaricus. The findings of this research suggest that the Pediococcus acidilactici strain has a potential to improve the biotechnological production of LA from dairy industry waste and its recovery by membrane processes.
  • Publication
    Wachstum durch intelligente Kooperation
    ( 2014)
    Jahn, Carlos
    Die Seeverkehrsprognosen 2030 zeigen, dass das Wachstum im Güterverkehr anhalten wird. Ein Hebel zur Bewältigung des Wachstums stellt die effizientere Nutzung von Infrastruktur und Ressourcen dar. Projekte wie HH62+, "Hilde" und der Masterplan 2014 der Logistikinitiative zeigen, dass intelligente Kooperationen die Vernetzung fördern und viele Vorteile bringen.
  • Publication
    Effects of defects in series production of hybrid CFRP lightweight components - detection and evaluation of quality critical characteristics
    ( 2017)
    Berger, Dietrich
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    Brabandt, Daniel
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    Bakir, Can
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    Hornung, Tim
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    Lanza, Gisela
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    Summa, Jannik
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    Schwarz, Michael
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    Herrmann, Hans-Georg
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    Pohl, Markus
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    Stommel, Markus
    The field of application of carbon fibre reinforced plastics (CFRP) is expanded successively by the insertion of additional components in manufactured parts. These inserts can be used as mechanical interfaces between CFRP and external forces, which is why it is necessary to ensure that the interface is free of defects. Especially the CFRP component is prone to defects due to process and material properties. Currently there are very limited possibilities to evaluate the quality of this type of innovative combination of components. Therefore this publication presents the optimized operation of both 3D and 2D measurement systems in series production, which are used to detect defects that appear in the production of hybrid metal components in the Resin Transfer Moulding Process. The severity of these defects is characterized in both destructive and non-destructive testing and helps to evaluate the necessity of in-line measurement systems and their allocation in the production process.

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Subject
621 48680
620 47169
670 39460
006 30200
004 28957
Has content in original bundle
false 224814
true 26544
Entity type
Patent 11228