Eldorado - Repositorium der TU Dortmund

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Bei diesem Service handelt es sich um das Institutionelle Repositorium der Technischen Universität Dortmund. Hier werden Ressourcen aus und für Lehre, Studium und Forschung gespeichert, erschlossen und der Öffentlichkeit zugänglich gemacht.

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Aktuellste Veröffentlichungen

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    A sensor concept for direction-selective monitoring of partial discharges in medium-voltage switchgears
    (2026-03-25) Zimmer, Bastian; Jenau, Frank; Ripka, David; Porath, Nils
    Knowledge about the condition of electrical equipment in energy networks is of great importance to network operators. Partial discharges are a key parameter for evaluating the health of the insulation. While a quantifiable PD measurement for offline tests is state of the art, it is costly and labour-intensive. It, therefore, makes sense to carry out permanent monitoring during operation. At the medium-voltage level in the European interconnected grid, comprehensive monitoring of PD is not implemented. This study presents a novel sensor concept that is used to detect PD in medium-voltage switchgear and cables: the so-called Magnetic Flux Concentrator Sensor (MFCS). It is an inductive sensor concept with high sensitivity in the frequency range of a few MHz, like well-established High-Frequency Current Transformers (HFCTs) but with better magnetic saturation properties in specific use cases. The highly permeable ferrite core of the MFCS is unconventionally shaped, resulting in a higher-saturation field strength. Therefore, this sensor is not driven into saturation by the operating currents of typical MV power cables. Using the MFCS and conventional HFCT in a suitable combination enables direction-selective PD detection. This work presents the sensor concept and the method for directional detection of the PD location, as analysed and evaluated theoretically and practically with laboratory experiments.
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    HM-DyadCap – capture and mapping of 5-hydroxymethylcytosine/5-methylcytosine CpG dyads in mammalian DNA
    (2026-05-08) Engelhard, Lena; Schiller, Damian; Zambrano-Mila, Marlon S.; Keliuotyte, Kotryna; Buchmuller, Benjamin; Tiwari, Shashank; Imig, Jochen; Simeone, Angela; Schröter, Christian; Becker, Sidney; Summerer, Daniel
    5-Methylcytosine (mC) and 5-hydroxymethylcytosine (hmC) are the main epigenetic modifications of mammalian DNA, and play crucial roles in cell differentiation, development, and tumorigenesis. Both modifications co-exist with unmodified cytosine in palindromic CpG dyads in different symmetric and asymmetric combinations across the two DNA strands, each having unique regulatory potential. To facilitate investigating the individual functions of such dyad modifications, we report HM-DyadCap. This method employs an evolved methyl-CpG-binding domain (MECP2 HM) for the direct capture and sequencing of DNA fragments containing the CpG dyad hmC/mC. Binding studies reveal a high discrimination of MECP2 HM against off-target dinucleotides. We conduct comparative mapping experiments for mESC genomes with HM-DyadCap, standard MethylCap employing wild-type MECP2, as well as MeDIP and hMeDIP protocols. We find that MECP2 HM is blocked by hmC glucosylation and conduct control enrichments with glucosylated genomes that indicate highly selective enrichment of hmC/mC dyads by MECP2 HM. Metagene profiles correlate hmC/mC marks with actively transcribed genes and reveal global enrichment in gene bodies as well as depletion at transcription start sites. We anticipate that HM-DyadCap will enable effective enrichment and mapping of hmC/mC marks with broad applicability for unraveling the function of this dyad in chromatin biology and cancer.
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    Projected Gradient stabilization for unfitted finite element methods with application to tumor growth
    (2026) Bäcker, Jan-Phillip; Kuzmin, Dmitri; Olshanskii, Maxim; Röger, Matthias
    Motivated by mathematical models for tumor growth, the work conducted in this thesis is focused on stabilization techniques for unfitted finite element methods (FEMs). In such models, appropriate transmission conditions are imposed on the possibly evolving sharp interface between the subdomains occupied by the tumor and surrounding tissue. To avoid frequent remeshing, an unfitted FEM may be employed that uses a fixed background mesh together with an implicit description of the geometry. However, the presence of small cut cells can lead to numerical instabilities, poor conditioning of the system matrix and loss of accuracy caused by small cut cells. To deal with this issue, we introduce a new ghost penalty based on the difference between two consistent discretizations of the Laplacian operator. The proposed projected-gradient stabilization is straightforward to implement and provides an implicit extension of the solution beyond the physical domain. We show that the bilinear form of the stabilization term is symmetric and establish second order convergence in $L^2$ for the solution of the discrete problem. To overcome difficulties associated with numerical integration over sharp embedded interfaces, a diffuse-interface description based on a level set representation is developed. Results of several numerical examples support the theoretical analysis and illustrate the performance of the proposed unfitted FEM. Since the lumped-mass $L^2$ projection that we use for gradient recovery is at most second-order accurate, we introduce nodal averaging as an alternative projection operator for the stabilization term to attain optimal-order accuracy for higher-order polynomial approximations. The stabilization concept is then extended to unfitted FEMs for elliptic interface problems with discontinuous coefficients, for which analogous stability and convergence results are obtained. Moreover, the proposed stabilization is incorporated into an unfitted FEM for a convection-diffusion problem with an embedded interface, and its effectiveness is demonstrated by a numerical example. The unfitted FEM with projected-gradient stabilization is applied to a mathematical model for tumor growth. Using formal asymptotic expansions, a thin-rim limit problem for a tumor growth model is derived. In the thin-rim limit, the pressure satisfies a Poisson equation with a Robin boundary condition in a time-dependent domain whose evolution is governed by a forced mean curvature flow. In the case of stationary, rotationally symmetric solutions, the weak-star convergence of the pressure solution in $L^\infty$ is proven. A generalized thin-rim limit problem is discretized using the proposed stabilized unfitted FEM. The obtained numerical results exhibit good qualitative agreement with results published in the literature and illustrate convergence properties of the proposed method.
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