Leibniz University Hannover
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Enhanced mechanical and tribological performance of additively manufactured 316L steel by MoS2-reinforcement
Get PDF316L stainless steel is commonly used in industrial and biomedical applications due to its corrosion resistance and biocompatibility, though its wear resistance is limited. This study aims to enhance the wear performance of 316L using additive manufacturing (AM) via laser powder bed fusion (LPBF), reinforcing it with MoS2 particles. Metal matrix composites (MMCs) were fabricated with MoS2 particles of different combinations in size (1.5, 4.5, 12.5 µm) and concentration (1, 3, 5 wt-%). Increasing MoS2 content reduced the density across all particle sizes due to MoS2′s lower intrinsic density, with smaller particles increasing surface roughness and larger particles reducing roughness variation while enhancing hardness. Notable variations in the coefficient of friction and wear coefficients were observed across different composites and temperatures in a steel ball-on-three-MMC plate setup under dry conditions. At 25 °C, 4.5 µm MoS2 at 5 wt-% reduced MMC plates’ wear by 96.3 % and counter body (steel ball) wear by 85.5 %. At 37 °C, 12.5 µm MoS2 at 1 wt-% reduced plate wear by 97.1 % and ball wear by 91 %. These improvements were attributed to enhanced solid lubrication and load distribution, particularly with optimal MoS2 size and concentration. This research highlights the potential of LPBF-AM in producing high-performance 316L MMCs for applications requiring improved wear resistance
Explaining media coverage of Constitutional Court decisions in Germany: The role of case characteristics
Get PDFResearch on the media coverage of decisions by the U.S. Supreme Court has revealed that the newsworthiness of a court decision – as determined by specific case characteristics – influences the likelihood that the decision will be covered by the media. However, in the context of European constitutional courts, media coverage of court decisions can be understood to be a form of justice reporting that focuses on general public interest and is operationalized by case characteristics that indicate the newsworthiness of the decisions. Using the case of the German Federal Constitutional Court, the determining factors behind whether court decisions are featured in the German media (i.e., that they receive media coverage in at least one newspaper article) are expounded. A local text alignment measurement of court decisions and newspaper articles enables media coverage to be identified based on original data on 3,404 decisions and 9,436 newspaper articles from between 2008 and 2018. The results demonstrate that media coverage of the German Court is not affected by declarations of unconstitutionality, though coverage is more likely when a decision is accompanied by a press release, an oral hearing, a dissenting opinion, or a combination of all three items. As these decisional aspects are the prerogative of the FCC, the results demonstrate that the German Constitutional Court has the necessary instruments to independently influence media coverage
On select problems for univariate, multivariate and spatial stochastic processes
Get PDFThis cumulative habilitation thesis consists of four publications which cover different
regimes within the mathematical analysis of time series. In the first two articles,
novel bootstrap methods in frequency domain for time series are developed. As I
point out in the Introduction – even after four decades of active research – the
range of validity of bootstrap methods for dependent data, and in particular in frequency
domain, remained limited. Previously established approaches were in general
valid only under a double restriction in terms of the dependence structure (linear
time series) and the statistics covered (ratio statistics). Towards this end, me and
my co-authors introduce the concept of the Hybrid Periodogram Bootstrap (HPB)
for univariate time series and the Multivariate Frequency domain Hybrid Bootstrap
(MFHB) for multivariate time series, to close this long-standing gap. The key for
these procedures to succeed is that they are able to properly imitate the finite-sample
dependence structure of periodogram ordinates at different frequencies. The MFHB
for multivariate time series has to take a number of obstacles into account that are
not present in the univariate situation and that have to be solved in a novel way. In
particular, the limiting distribution of most relevant statistics is a complex normal
distribution where both covariance and relation matrix depend on the fourth-order
moment structure of the underlying process. Therefore, the MFHB construction is
designed to simultaneously imitate both of these quantities in a proper way.
The third publication in this thesis deals with a structural question for spatial processes
on grids Z^d, d ≥ 1. For the time series case, i.e. d = 1, Akaike’s identity
provides an insightful link between the Yule-Walker matrix and finite predictor coefficients.
We prove that this result in general no longer holds true for d > 1. We
provide a complete characterization of the cases in which an Akaike-type identity is
valid. As it turns out, this is only the case in trivial situations. Thus, we clarify a
misunderstanding that appears to be present in previous spatial process literature.
The fourth publication covers locally stationary time series. We provide a nonparametric
estimator for the characteristic functions of such time series. Consistency,
asymptotic normality and process convergence are shown for this estimator. Moreover,
these results are used for statistical applications: We investigate two different
ways to estimate local parameters based on our estimator. Also, we generalize the
powerful concept of distance correlation to locally stationary processes
Wo der Name Programm ist: Innovation – Technologie & Entrepreneurship aus erster Hand
Get PDFEntrepreneurship steht für mutiges Innovieren, kraftvolles Gestalten und die Durchdringung von bestehenden oder neuen Märkten mit neuen Produkten/ Prozessen oder Dienstleistungen. Angesichts globaler Herausforderungen befasst sich das Institut für Innovations-Forschung, Technologie-Management & Entrepreneurship (ITE) insbesondere mit nachhaltigen Innovationen für eine Gesellschaft im Wandel, um die Bedarfe transformierter Gesellschaften von morgen zu bedienen. Dabei setzt es auf Kooperationen mit Wissenschaft, Wirtschaft, Politik und Gesellschaft
Review of climate-resilient agriculture for ensuring food security: Sustainability opportunities and challenges of India
Get PDFClimate Resilient Agriculture (CRA) effectively responds to climate change while contributing to sustainable productivity adapted to local hydro-meteorological conditions. CRA provides resilience to climate variability by enhancing agricultural viability through water exchange between surface and groundwater systems. In water-stressed countries such as India, where demand for water from agriculture, industry, and domestic use is increasing, CRA offers ways to address current and future food security challenges. This review examines the role of the CRA in agricultural sustainability and community participation in India. It assesses critical CRA projects and policies in India and explores how CRA can improve water policy by integrating farmers' perspectives in groundwater-based agriculture. The study also shows that collaboration between government agencies, NGOs, and local groups is important to sustaining CRA initiatives. Discussions indicated that empirical studies, clear sustainability indicators, and integration of advanced technology such as artificial intelligence and geo-spatial tools are needed to improve India's adaptation strategies to climate change. This study highlighted how CRA aligns with key SDGs by addressing poverty, hunger, climate action, and community wellbeing. GRACE data indicated that northwestern India emerged as a critical water scarcity hotspot, displaying negative trends of around −7.413 cm per year. Furthermore, the analysis clearly showed that the Western Dry Region, Western Himalayan, and Gangetic Plain agro-ecological zone (AEZ) experienced the sharpest declines in equivalent water thickness (EWT) compared to other AEZ regions in India. The review also highlighted the value of knowledge-sharing platforms and tailored CRA strategies that increase agricultural productivity and enable farmers to make informed decisions in the face of climate uncertainty
An Approach To Develop A Vision For Sustainable Tool and Die Manufacturing
Get PDFIn the contemporary manufacturing industry, there is an increasing emphasis on ecological sustainability. The development of an effective key performance indicator system is paramount for the assessment and promotion of this sustainability. To this end, the development of a methodology that aims to link sustainable tool manufacturing with relevant success factors is imperative. To this end, an analysis of extant sustainability guidelines within and outside the tool and die industry is conducted for the purpose of defining the target vision and success factors. Following this analysis, stakeholders and their respective requirements are identified, and specific goals and success factors are developed. The culmination of this process is the compilation of results into a comprehensive catalog. The systematic involvement of stakeholders fosters the identification of pragmatic sustainability goals and success factors. These goals and factors facilitate a comprehensive evaluation of ecological, economic, and social sustainability in the context of tool manufacturing. To ensure continuous adaptation and improvement, the resulting methodology emphasizes the importance of stakeholder involvement and regular reviews. The developed methodology provides a structured approach to define a vision and associated success factors for sustainable tool manufacturing. Regular reviews of the goals are crucial to ensure sustainable development. The incorporation of stakeholders in the review process, facilitated through workshops, is instrumental in this regard. Future research endeavors should prioritize the validation and further development of the prototype to optimize its practical application and promote sustainable transformation in the tool and die industry. Subsequent steps may include the implementation of the developed methodology to establish a sustainability metrics system for the tool and die industry
Adaptable Control System for Electrode Wet Coating in Lithium-Ion Battery Cell Production: A Systematic Literature Review
Get PDFThe production of lithium-ion batteries faces significant challenges in scaling up, particularly in maintaining quality and reducing costs. The electrode wet coating process, crucial for battery cell manufacturing, often suffers from inconsistencies that affect battery performance and longevity. Manufacturers adopt various strategies to address the main challenge of coating - the scrap rate. Traditional coating machine control systems usually focus on basic parameters like web speed, often neglecting critical aspects such as thickness and uniformity. While some progress has been made using machine learning (ML) to create feedback loops between cell performance and coating parameters, these models struggle to adapt to dynamic changes in the coating process. The industry's experience in setting machine setpoints or evaluating sensor signals typically relies on a large feedback loop to control coating parameters based on cell performance. However, this approach often overlooks subsequent process steps, like calendaring, and their impact on coating or cell performance. Efficient control requires a model that approximates reality (e.g. drying rate) to translate sensor feedback into appropriately adjusted actuator values. A more accurate control model that considers extended factors would be beneficial but requires sufficient data points for training. Empirical trials combined with statistical experimental design can provide the necessary data, but a full factorial design is almost inevitable in the absence of domain knowledge and data. Consequently, empirical data collection for model design demands significant effort and expertise. This research will review existing literature on control systems for continuous production processes applicable to electrode wet coating. The goal is to relate intermediate product properties to process parameters. The underlying research question is: How can a controller for electrode wet coating in battery cell production be empirically designed and implemented with significantly less effort than a statistical experimental design
Concept For Enabling Intralogistics Considering R-Strategies Related Processes In Circular Manufacturing Systems
Get PDFThis study proposes a novel concept for facilitating intralogistics within circular manufacturing systems and supply networks to optimize production systems taking into account circular product strategies (R-strategies) in real-time. Central to this concept is the integration of highly flexible and reconfigurable factories with end-to-end digitalization techniques. By leveraging these technologies, the necessary processes for the realization of R-strategies can be dynamically determined, ensuring performance optimization within circular supply networks. Key components of this concept include the implementation of versatile intralogistics systems capable of adapting to changing production requirements and seamlessly integrating with circular economy principles. Through a comprehensive review of existing literature and theoretical frameworks, this paper elucidates the potential benefits and challenges associated with the proposed concept. Moreover, practical implications and future research directions are discussed, highlighting the transformative potential of this approach in advancing circular economy practices within academics and industrial contexts
Towards Modelling Flexibility Limits In Cyber-Physical Production Systems
Get PDFIn the context of cyber-physical production systems, the term "flexibility" is typically employed in an intuitive and implicit manner. It is uncommon for proposals that quantify the flexibility of production systems, and even then, only by measuring certain general aspects top-down. However, as flexibility is becoming increasingly crucial for contemporary and future systems in both production and logistics, it must be regarded as a value- and data-driven resource for comprehensive system analysis. This paper presents a generic model for quantifying the flexibility of entities within a production system, comprising processes, products, and resources. These three entities represent the fundamental elements of any production system, which is therefore conceptualised and presented as a multi-agent system. The flexibility model of an entity is defined in terms of two sets of constraints. Firstly, the inherent limits of the solution space of any singular entity must be considered. These limits are formed by factors such as the limitations of the software or hardware in use. Secondly, the boundaries of the flexibility space are defined by the interactions between entities. Such constraints may be formed, for example, by entity interdependencies or preparatory measures for the interaction. By employing these types of constraints, which are both rule- and data-driven, this generic methodology can describe the resulting numerical flexibility space of individual entities. This paper focuses on temporal flexibility models, which are the most universally applicable flexibility dimension, and considers their implementation for products, processes, and resources
Wissenstransfer als Ausgangslage für eine Translation der Forschung in die Praxis für mehr Tierwohl und Tiergesundheit in der Geflügelwirtschaft : Eine explorative Studie zu dem Potential qualitativer empirischer soziologischer Forschungsmethoden für die Life Sciences vor dem Hintergrund des One-Health-Ansatzes
No full textDas Forschungsprojekt an der Klinik für Geflügel der Tierärztlichen Hochschule Hannover (TiHo) untersucht den Wissenstransfer zwischen Forschung und Praxis, um Tierwohl und Tiergesundheit in der Geflügelwirtschaft zu fördern. Im Rahmen des One-Health-Ansatzes werden die Wechselbeziehungen zwischen Mensch, Tier und Umwelt analysiert, unter Berücksichtigung gesellschaftlicher Rahmenbedingungen und des landwirtschaftlichen Transformationsprozesses in Deutschland. Mithilfe narrativer Interviews wird erforscht, wie Landwirt:innen Wissen erwerben, weitergeben und anwenden. Biografische und sozio-kulturelle Prägungen spielen dabei eine zentrale Rolle. Wissenstransfer wird als wechselseitiger Prozess verstanden, der an die Biografien und den „Wissenshabitus“ der Landwirt:innen angepasst werden muss, um effektiv zu sein. Fachtierärzt:innen und Berater:innen werden als Schlüsselakteure für praxisrelevantes Wissen identifiziert. Face-to-face-Formate, wie Fachveranstaltungen, fördern die Wissensvermittlung und schaffen Vertrauen sowie Reflexionsräume. Die Eigenständigkeit von Landwirt:innen als Entrepreneure in einem komplexen Umfeld wird hervorgehoben. Die biografischen Methoden ergänzen quantitative Ansätze und bieten Einblicke in soziale Dynamiken des Wissenstransfers, um Strategien für die Translation von Forschung in die Praxis zu optimieren.The explorative research project at the Clinic for Poultry at the University of Veterinary Medicine Hannover (TiHo) examines knowledge transfer between research and practice to improve animal welfare and health in poultry farming. Using the One Health framework, it analyzes the interrelations between humans, animals, and the environment, considering societal structures shaping human actions. The transformation of agriculture in Germany serves as a key context, requiring farmers to navigate sustainability challenges, regulatory demands, and cultural shifts. Using qualitative sociological methods, particularly narrative interviews, the study explores how farmers acquire, transmit, and apply knowledge in practice. Biographical and socio-cultural factors significantly influence this process. Knowledge transfer is defined as a reciprocal process between research and practice, requiring alignment with farmers' individual biographies and “knowledge habitus” for effectiveness. Specialist veterinarians and agricultural advisors are identified as key agents in transferring practical knowledge. Regular face-to-face formats, such as professional events, are crucial for successful knowledge exchange, fostering trust and creating reflective spaces. Farmers and researchers view these exchanges positively, as they enhance collaboration and mutual understanding. The study emphasizes the autonomy of farmers, who increasingly see themselves as entrepreneurs operating within complex socio-regulatory contexts. Biographical methods offer valuable insights into the social dynamics of knowledge transfer, complementing quantitative life sciences approaches. These findings inform strategies for translating research into practice and provide a deeper understanding of human-animal-environment interactions