OPUS Online Publikationen der Universität Stuttgart
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Compact modeling of modern power MOSFETs based on industry-standard CMOS models
No full textThis work presents a modeling approach adopting the industry-standard models for circuit simulation with necessary extensions to describe vertical power MOSFETs. Standard models, which are developed for CMOS logic devices, are adopted with their proven robustness and fidelity to describe the voltage-controlled channel behavior of power MOSFETs. Considering the vertical MOSFET structure, the extended components including the nonlinear drift region, body-diode and the parasitic capacitance are defined as model extensions. The specific requirements for SiC MOSFETs different from the Si devices are also analyzed. The static and dynamic characteristics considering the thermal effects are measured as the reference for the model parameter extraction.
Some attempts to create high voltage MOSFET models by adding elements to a standard MOSFET model are already reported, but these models are still not developed aiming at high current level power MOSFETs, or some crucial effects like the asymmetric reverse conducting current, reverse recovery of the body-diode etc. are not defined. This work provides a particular approach to characterize commercially available vertical power MOSFETs and proposes the modeling method describing the critical effects of power MOSFETs which enable the model to precisely describe the performance of the devices in switching mode simulations.
Moreover, the model extension approach discussed in this work is not limited to a certain standard model.
The physics based standard models can be categorized into three groups: threshold voltage based, inversion charge based, and surface potential based. The properties of three standard models from each group are analyzed and compared. The appropriate extension strategy is developed for each standard model and the specific parameter extraction flow is also provided for each proposed model.
Compared with the vendor model, the modeling method proposed in this work can increase the accuracy of the simulation of the transient switching loss by around 20%, which can contribute to improve the power MOSFET compact modeling of the semiconductor community in view of improving the design of switched-mode power converters
Nanoscale mapping of magnetic auto-oscillations with a single spin sensor
No full textSpin Hall nano-oscillators convert DC to magnetic auto-oscillations in the microwave regime. Current research on these devices is dedicated to creating next-generation energy-efficient hardware for communication technologies. Despite intensive research on magnetic auto-oscillations within the past decade, the nanoscale mapping of those dynamics remained a challenge. We image the distribution of free-running magnetic auto-oscillations by driving the electron spin resonance transition of a single spin quantum sensor, enabling fast acquisition (100 ms/pixel). With quantitative magnetometry, we experimentally demonstrate for the first time that the auto-oscillation spots are localized at magnetic field minima acting as local potential wells for confining spin-waves. By comparing the magnitudes of the magnetic stray field at these spots, we decipher the different frequencies of the auto-oscillation modes. The insights gained regarding the interaction between auto-oscillation modes and spin-wave potential wells enable advanced engineering of real devices.Carl-Zeiss-StiftungEUDeutsche ForschungsgemeinschaftBundesministerium für Bildung und ForschungCenter for Integrated Quantum Science and Technolog
VR maze with omnidirectional treadmill
No full textDiese Ausarbeitung beschäftigt sich mit der Entwicklung eines Labyrinthspiels für die virtuelle Realität (VR), das speziell für das omnidirektionale Laufband Omnideck konzipiert wurde und auf der Unity Engine basiert. Durch die Integration von physischer Bewegung in das Gameplay wird ein immersives Erlebnis geschaffen, das den Spieler aktiv in die digitale Welt eintauchen lässt. Ein zentrales Element dieses Projekts ist die Entwicklung eines Tools zur Generierung von 3D-Modellen aus Vektoren, das die Erstellung und Anpassung von Labyrinthstrukturen vereinfacht. Das Tool wird zudem um eine Funktion erweitert, die es ermöglicht, 3D-Modelle aus Bildern zu generieren. Dabei kann ein 2D-Labyrinth-Modell als Eingabe verwendet werden, welches das Tool pixelweise analysiert und vektorisiert. Diese Vektordaten dienen dann als Grundlage für die Erstellung eines 3D-Modells. Durch die pixelgenaue Analyse des Bildes können Strukturen und Konturen des Labyrinths präzise erfasst und in die dritte Dimension übertragen werden. Des Weiteren wird der gesamte Entwicklungsprozess von der Konzeptualisierung über die technische Implementierung bis zur abschließenden Integration des Omnidecks erläutert. Herausforderungen und Lösungen, die sich aus der Zusammenführung von Hardware- und Softwareelementen ergeben, werden ebenfalls behandelt
Rubble Works: Leveraging digital technologies for design and construction with mixed mineral construction and demolition waste
No full textThis report presents the results of the research project Robots//Reuse, funded by the Research Initiative Zukunft Bau. In this research project, David Chipperfield Architects Berlin and the Institute for Computational Design and Construction at the University of Stuttgart explored the reuse of rubble by looking at how material, techniques, and digital technologies can be combined to make construction and demolition waste relevant to contemporary architecture.
Construction and demolition waste (CDW) is Europe’s largest waste stream and a major global problem. Despite an emergent interest and focus in the material group, it does not find its way back into architecture to a sufficient extent as the most widely currently applied recycling practice for CDW is crushing to secondary aggregates. Achieving a circular use of building materials requires both the development of cost-effective and time-efficient technologies that enable the reuse, and an architectural aesthetic that attracts users, investors, and architects to choose to build with it.
In the past, the reuse of building materials was common practice, and many renowned architectural projects were built from, for example, reused wood, stones, and brick. These projects showcase both the large and varied aes-thetic potential of reuse. Yet, common for all of them is the dependence on manual labor. Skilled craftspeople would select, adapt and carefully implement found or taken building components and elements into new architecture. Today, the scale of both the mass manufacturing industry and the CDW problem overgoes the scale at which a craftsperson works. The high costs associated with the processing of non-standardized and irregular materials are, next to barri-ers relating to material quality, building code and logistics, one of the greatest barriers to the reuse of CDW in architecture.
However, recent advances in robotics and scanning allow us to disassociate the technique from the manual effort and open up new design possibilities. The evolution of manufacturing—from traditional craft production to mass production and then to mass customization—points towards a future of flexible automation. Here, complex fabrication and assembly processes involving non-standardized materials are as efficient in terms of time, cost, and energy-consumption as the production of new materials. Beyond automating existing techniques, digital technologies also offer the chance to develop entirely new ones.
While the potential of matching CDW with new building technology has already been explored in other research projects, there seems to be little research compared to the large amount of this type of waste and the research project tend to focus on larger pieces.
The aim of the project is through a combined expertise from both practice and academia to explore how a synergy between material, tools and aesthetics can be achieved in the light of four overarching research questions:
What are the current limitations of computer-based design and digital fabrication processes used to process and assemble non-standardized building materials?
Which digital design processes could be suitable for building with reused building materials?
How can the use of computer-based design and digital fabrication methods make the reuse of building materials attractive to architects, companies and users in terms of aesthetics, scalability and efficiency?
How can we bridge the gap between architectural design practice and current academic research on the reuse of building materials?
Inspired by both traditional crafts and new technologies, these research questions and new potentials for designing with reclaimed materials were explored on a both theoretical and practical level. The project was split into a historical pre-study of reuse in architecture, and a case study focused specifically on rubble. Through methods ranging from an analysis of traditional and contemporary reuse and masonry-related techniques, to material classification and prototyping, we developed different approaches to how to think about, handle and design with rubble. One direction, jammed rubble, was explored in depth along with concepts for robotic rubble placement and pouring.
The project is a conceptual, basic research project and although it is out of the project’s scope to develop finished solutions, certifiable building systems, or complete robotic workflows, it provides a starting point for rediscovering the potential of reuse of reclaimed materials through digital tools. The overall outcome of the project is a series of rubble works that, rather than offering a definitive solution to rubble’s challenges, provide a starting point for rediscovering its potential
Material availability in fluid assembly systems
No full textAusgangspunkt der vorliegenden Arbeit ist die aus den Defiziten starr verketteter Fließmontagelinien resultierende Forderung nach veränderungsfähigen Systemen für die zukünftige Automobilmontage. Als Ausprägungsform eines veränderungsfähigen Systems grenzt die fluide Montage, die im Kontext des Forschungscampus ARENA2036 erarbeitet wird und über eine spezifische Anzahl an Freiheitsgraden verfügt, den Untersuchungsbereich dieser Arbeit ab. Es zeigt sich, dass in dieser Umgebung die Gewährleistung der kurzfristigen Materialverfügbarkeit infolge dynamischer Materialflussstrukturen eine besondere Herausforderung darstellt. Aus diesem Grund beschäftigt sich die vorliegende Arbeit mit der übergeordneten Forschungsfrage, wie sich die Materialverfügbarkeit während des Betriebs eines fluiden Montagesystems sicherstellen lässt. Als konkreter Handlungsbedarf wird die Entwicklung und Untersuchung einer Methodik zur Überprüfung und Sicherstellung der Materialverfügbarkeit in fluiden Montagesystemen identifiziert. Die entwickelte Methodik setzt sich aus vier aufeinanderfolgenden Prozessschritten zusammen. Hierbei handelt es sich um die Schritte Initialisierung, Zielsuche und Aufgabenableitung, Lösungssuche sowie Lösungsauswahl. Die Methodik ist als Bestandteil des Materialbereitstellungssystems dem Aufgabenfeld der Logistik zugeordnet und trägt zur Koordination des Montage- und Materialbereitstellungssystems bei, da sie an der Schnittstelle dieser beiden Systeme eingesetzt wird. Die simulationsbasierte Untersuchung der Methodik erfolgt am Beispiel einer Cockpit-Vormontage. Verschiedene Experimente werden durchgeführt, um die Funktionsweise der Methodik zu erproben und den Einfluss verschiedener Größen auf die Materialverfügbarkeit zu analysieren. Wie die Simulationsergebnisse zeigen, gelingt es durch den Einsatz der Methodik, die Materialverfügbarkeit in fluiden Montagesystemen während des laufenden Betriebs sicherzustellen. Hierbei hat sich insbesondere die Verwendung des Ansatzes zur logistik- und montageinduzierten Materialverfügbarkeit als förderlich erwiesen. Dadurch leistet die vorliegende Arbeit einen Beitrag zur Ausgestaltung der Materialbereitstellung in fluiden Montagesystemen
Exploration of structured data using AI-enabled magic lenses
No full textIn the era of increasingly complex and high-dimensional datasets, enabling intuitive and effective data exploration remains a significant challenge. This thesis presents a novel AI-enabled magic lens system designed to support rapid and insightful exploration of structured data through natural language interaction and dynamic visualization. The system projects the provided data onto a 2D canvas based on the prior dimensionality reduction. It leverages large language models (LLMs) to interpret user queries and generate contextually appropriate visualizations or textual responses. Beyond visual exploration, the system supports iterative dialogue with the AI, allowing users to refine visualizations and request explanations. Furthermore, users can document their findings through a notes panel. These notes can be evaluated using an LLM to provide feedback, contextual insights, and suggestions for further exploration. Additional key features include the ability to annotate clusters using LLM-generated labels, compare data subsets using multiple adjustable lenses, and view global visualizations for comparative analysis. To evaluate the system, an expert evaluation was conducted. Results indicate strong support for the system’s effectiveness and usability, highlighting the potential of LLM-enhanced data exploration tools. This work proves that the concept of integrating natural language interfaces and generative AI into interactive visualization systems can significantly enhance data analysis workflows, paving the way for future advancements in human-AI collaborative data exploration
Crystal structure of trichloro(3,3’)-trimethylene- 2,2’-biquinoline)gold(III) chloroform hemisolvate, [(C9H5N)(CH3)][(C9H6N)(CH3)]AuCl3 · 0.5 CHCl3 and of tribromo(3,3’)-trimethylene-2,2’-biquinoline)gold(III) chloroform hemisolvate, [(C9H5N)(CH3)] [(C9H6N)(CH3)]AuBr3 · 0.5CHCl3
No full textC21.5H16.5AuCl4.5N2, monoclinic, P12i/nl (No. 14), a = 9.777(2) Å, b = 18.734(4) Å, c = 12.339(2) Å, β = 101.87(3)°, V= 2211.7 Å3, Z = 4, Rgt(F) = 0.034, wR(F) = 0.031, T = 293 Κ
Zwei Dichter und ihre Katastrophensucht - Lukas Bärfuss und Heinrich von Kleist
No full textAusgehend von der Kleistrede, die Lukas Bärfuss 2011 in Thun gehalten hat, wird literaturwissenschaftlich untersucht, welche Bezugspunkte es in seinem Werk zu demjenigen von Heinrich von Kleist gibt
Sensoren zur lokusspezifischen Visualisierung epigenetischer Modifikationen
No full textDynamic changes of the epigenome at specific gene loci, including alterations of chemical modifications on the DNA or histone proteins, are critical in development and disease. Bimolecular Anchor Detector (BiAD) sensors can be used to visualize these modifications in living cells with locus resolution. Recently, we improved the BiAD technology by enhancing the sensor sensitivity and expanded the range of detectable modifications, enabling a broad application of the BiAD sensors in various contexts.Projekt DEA
The lakehouse : state of the art on concepts and technologies
No full textIn the context of data analytics, so-called lakehouses refer to novel variants of data platforms that attempt to combine characteristics of data warehouses and data lakes. In this way, lakehouses promise to simplify enterprise analytics architectures, which often suffer from high operational costs, slow analytical processes and further shortcomings resulting from data replication. However, different views and notions on the lakehouse paradigm exist, which are commonly driven by individual technologies and varying analytical use cases. Therefore, it remains unclear what challenges lakehouses address, how they can be characterized and which technologies can be leveraged to implement them. This paper addresses these issues by providing an extensive overview of concepts and technologies that are related to the lakehouse paradigm and by outlining lakehouses as a distinct architectural approach for data platforms. Concepts and technologies from literature with regard to lakehouses are discussed, based on which a conceptual foundation for lakehouses is established. In addition, several popular technologies are evaluated regarding their suitability for the building of lakehouses. All findings are supported and demonstrated with the help of a representative analytics scenario. Typical challenges of conventional data platforms are identified, a new, sharper definition for lakehouses is proposed and technical requirements for lakehouses are derived. As part of an evaluation, these requirements are applied to several popular technologies, of which frameworks for data lakes turn out to be particularly helpful for the construction of lakehouses. Our work provides an overview of the state of the art and a conceptual foundation for the lakehouse paradigm, which can support future research.Projekt DEALUniversität Stuttgar