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

Sustainable Corporate Governance
(2026) Seeck, Björn; Pott, Christiane; Pflitsch, Max
Diese kumulative Dissertation untersucht, wie Sustainable Corporate Governance als integratives Steuerungskonzept in unterschiedlichen organisationalen Kontexten verstanden, implementiert und wirksam wird. Angesichts wachsender regulatorischer Anforderungen und gesellschaftlicher Erwartungen adressiert sie die Forschungslücke, wie Nachhaltigkeitsanforderungen in organisationale Entscheidungs- und Steuerungsprozesse integriert werden. Konzeptionell verbindet die Arbeit Ansätze der Corporate Governance, Nonprofit Governance und Nachhaltigkeitsberichterstattung und versteht (Sustainable Corporate) Governance als Zusammenspiel von Berichterstattung, Selbstregulierung sowie strukturellen und akteursbezogenen Mechanismen. Die Arbeit besteht aus drei Beiträgen: Erstens zeigen qualitative Experteninterviews, dass Governance Kodizes im öffentlichen Sektor ein hohes Potenzial zur Strukturierung der Nachhaltigkeitsberichterstattung besitzen, während ihre Wirkung im NPO-Sektor stärker kontextabhängig ist. Zweitens erweitert eine theoretische Analyse die Funktionen von Nonprofit Governance-Kodizes über Kontrolle und Transparenz hinaus um Lern, Koordinations- und Kulturmechanismen. Drittens weist eine Panelanalyse börsennotierter Unternehmen einen robust positiven Zusammenhang zwischen Geschlechterdiversität in Leitungsgremien und der Umsetzung regulatorischer Nachhaltigkeitsanforderungen nach. Insgesamt verdeutlicht die Dissertation, dass nachhaltigkeitsbezogene Governance aus dem Zusammenspiel von Regulierung, Transparenz, Selbstregulierung, organisationaler Einbettung und der Zusammensetzung zentraler Akteure entsteht.
Computational modelling of quenching and grinding processes for bearing steels
(2026) Furlan, Tim; Menzel, Andreas; Denzer, Ralf; Biermann, Dirk
The manufacturing of roller bearing components from bearing steels such as 100Cr6 requires the processing of the workpieces in several successive production steps. Each of these processes modifies the initial state of the product at the beginning of the subsequent process. As a result, complex interdependencies arise between the process parameters of the individual processes and the properties of the finished product. In this work, approaches for the numerical modelling of the quenching and grinding processes in such production chains are developed. For quenching after austenitisation, a fully thermomechanically coupled model is developed which accounts for the occurring phase transformations to martensite and bainite. The athermal transformation of austenite to martensite is modelled by a variant of the classical Koistinen–Marburger ansatz, while the diffusive transformation of austenite to bainite is modelled using a JMAK approach. It is taken into account that the resulting bainite may exhibit a different carbon content than the austenite by solving the mass balance for carbon. To this end, the parameters of the transformation models are parametrised based on the current carbon content of the austenite. The coupling to the mechanical and thermal problems arises from transformation strains and the release of latent heat during the transformations. Due to the process forces in internal traverse grinding with electroplated cBN tools, elastic deflection occurs between the tool and the workpiece, which can lead to dimensional errors and shape deviations. In this work, a geometric simulation of the grinding process is used, where the grain geometries on the digital grinding wheel are based on measurements of real grains. To account for elastic deflection during the grinding process, two surrogate models are developed: a model for the process force contribution of a single grinding grain engaged in mesoscopic cutting, and a model for the total compliance between the tool and the workpiece. The force model is calibrated using finite element simulations of an idealised single-grain cutting process, while a static analogy test is used to calibrate the compliance model. For the simulation of single-grain engagement, a new thermodynamically consistent material model is also developed. This model is inspired by the widely used Johnson–Cook model for cutting simulations but is adapted in several aspects to the behaviour of 100Cr6. To account for the large deformations occurring during mesoscopic material removal, a new simulation framework in the finite element software Abaqus, based on the Coupled Eulerian Lagrangian method, is presented and compared with an existing framework based on periodic remeshing. The developed models improve the simulation capabilities for the manufacturing of roller bearing components from 100Cr6 and thereby contribute to better coordination of the process parameters across different manufacturing steps.
Double Generalized Linear Models for spatio-temporal data
(2026) Maletz, Steffen; Fried, Roland; Groll, Andreas
Spatio-temporal data arises when a variable is measured at multiple locations over time. Modeling such data poses several challenges: In addition to spatial factors, such as the position of sensors or regions, and temporal trends, the data may also be subject to autoregressive dynamics, as is the case with infectious diseases. Furthermore, additional data characteristics, such as integer values or non-negativity, must be taken into account in the modeling process. This dissertation contributes to the state of research on the modeling of spatio-temporal data on a fixed spatial grid, with a particular focus on non-normal data. We adapt multivariate count data time series models for the spatio-temporal domain. Assuming marginal Poisson distributions for observations conditional on the past, the models describe the conditional expected value by past observations of the same and neighboring locations, a latent feedback process, and optional covariates. Building on this foundation, we investigate an approach to detect persistent level shifts within this framework. Such level shifts may be caused by political measures, campaigns, or other extraordinary events. Methods from univariate intervention analysis in count time series models are further developed to test for level shifts at unknown times or unknown locations. We propose an iterative procedure to detect multiple intervention effects simultaneously. Subsequently, the modeling framework is extended by using the idea of double generalized linear models (DGLMs), relaxing the assumption of a marginal Poisson distribution for the conditional observations in favor of arbitrary distributions from the exponential dispersion family. In addition to the conditional expectation, this allows the dispersion parameter to be described by a spatio-temporal model, thereby accommodating overdispersion and other data characteristics. The full framework is implemented in the R package glmSTARMA. The theoretical properties and usefulness of the models are studied in simulations. We illustrate the application using data examples.
On a lack of stability of parametrized BV solutions to rate‐independent systems with nonconvex energies and discontinuous loads
(Wiley, 2024-04-26) Andreia, Merlin; Meyer, Christian
We consider a rate-independent system with nonconvex energy under discontinuous external loading. The underlying space is finite-dimensional and the loads are functions in 𝐵⁢𝑉⁡([0,𝑇];ℝ𝑑). We investigate the stability of various solution concepts w.r.t. a sequence of loads converging weakly* in 𝐵⁢𝑉⁡([0,𝑇];ℝ𝑑) with a particular emphasis on the so-called normalized, 𝔭-parametrized balanced viscosity solutions. By means of three counterexamples, it is shown that common solution concepts are not stable w.r.t. weak* and even intermediate (or strict) convergence of loads in the sense that a limit of a sequence of solutions associated with these loads need not be a solution corresponding to the load in the limit. We moreover introduce a new solution concept, which is stable in this sense, but our examples show that this concept necessarily allows “solutions” that are physically meaningless.
N‐Cyanopiperazines as specific covalent inhibitors of the deubiquitinating enzyme UCHL1
(Wiley, 2024-01-19) Schmidt, Mirko; Grethe, Christian; Recknagel, Sarah; Kipka, Gian‐Marvin; Klink, Nikolas; Gersch, Malte
Cyanamides have emerged as privileged scaffolds in covalent inhibitors of deubiquitinating enzymes (DUBs). However, many compounds with a cyanopyrrolidine warhead show cross-reactivity toward small subsets of DUBs or toward the protein deglycase PARK7/DJ-1, hampering their use for the selective perturbation of a single DUB in living cells. Here, we disclose N’-alkyl,N-cyanopiperazines as structures for covalent enzyme inhibition with exceptional specificity for the DUB UCHL1 among 55 human deubiquitinases and with effective target engagement in cells. Notably, transitioning from 5-membered pyrrolidines to 6-membered heterocycles eliminated PARK7 binding and introduced context-dependent reversibility of the isothiourea linkage to the catalytic cysteine of UCHL1. Compound potency and specificity were analysed by a range of biochemical assays and with a crystal structure of a cyanopiperazine in covalent complex with UCHL1. The structure revealed a compound-induced conformational restriction of the cross-over loop, which underlies the observed inhibitory potencies. Through the rationalization of specificities of different cyanamides, we introduce a framework for the investigation of protein reactivity of bioactive nitriles of this compound class. Our results represent an encouraging case study for the refining of electrophilic compounds into chemical probes, emphasizing the potential to engineer specificity through subtle chemical modifications around the warhead.