Showing papers by "Bauhaus University, Weimar published in 2022"

Machine-learning-driven on-demand design of phononic beams

Abstract: The development of phononic crystals, especially their interaction with topological insulators, allows exploration of the anomalous properties of acoustic/elastic waves for various applications. However, rapidly and inversely exploring the geometry of specific targets remains a major challenge. In this work, we show how machine learning can address this challenge by studying phononic crystal beams using two different inverse design schemes. We first develop the theory of phononic beams using the transfer matrix method. Then, we use the reinforcement learning algorithm to effectively and inversely design the structural parameters to maximize the bandgap width. Furthermore, we employ the tandem-architecture neural network to solve the training-difficulty problem caused by inconsistent data and complete the task of inverse structure design with the targeted topological properties. The two inverse-design schemes have different adaptabilities, and both are characterized by high efficiency and stability. This work provides deep insights into the combination of machine learning, topological property, and phononic crystals and offers a reliable platform for rapidly and inversely designing complex material and structure properties.

A 3D nano scale IGA for free vibration and buckling analyses of multi-directional FGM nanoshells.

Abstract: This article explores a three-dimensional solid isogeometric analysis (3D-IGA) approach based on a nonlocal elasticity theory to investigate size effects on natural frequency and critical buckling load for multi-directional functionally graded (FG) nanoshells. The multi-directional FG material uses a power law rule with three power exponent indexes concerning three parametric coordinates. Nanoshell's geometries include the square plate, cylindrical and spherical panels with the side length considered in a nanoscale with various thickness ratios. Because 3D-IGA utilizes an approximation of NURBS basic functions to integrate from geometry modeling to discretized domain, it does not require any hypotheses for deformations distribution and stress component through the plate's thickness. Therefore, the results from the 3D solution are obtained accurately with any thickness ratio of the shells. The numerical solutions are verified by those published in several pieces of literature to determine the current approach's accuracy and reliability. After a convergence solution is examined, a quartic NURBS basic function can yield ultra-converged and high-accurate results with a low computational cost. The findings show the size effect parameters which significantly impact the frequencies and the critical buckling factors of the multi-directional FG nanoshells. Generally, increases in the size effect parameters will cause declines in the frequencies and the critical buckling factors of the nanoshells.

Business ecosystems in digital journalism: cross-border collaborative investigations as a novel organizational form

Abstract: This chapter focuses on cross-border collaborative investigations in digital journalism through the lens of digital business ecosystems research. By summarizing the state of research on objectives and motivations, actors and their positions (particularly the role of keystone organizations) and the activities and links in such ecosystems, it opens up an innovative perspective on a novel organizational form of digital journalism. Given journalism's crucial role in society and the enormous struggles the industry is facing economically in the wake of digitization, digital journalistic ecosystems can be considered specific contrasting cases amongst conventional business ecosystems. The chapter therefore asks what research on digital business ecosystems can learn from the case of journalism, emphasizing the need for empirical follow-up research.

Datenmodelle für digitale Zwillinge von Brücken und bildbasierte Zustandsaufnahmen

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Pholkos – Efficient Large-State Tweakable Block Ciphers from the AES Round Function

Abstract: This paper proposes Pholkos, a family of heavyweight tweakable block ciphers with state and key sizes of $${\ge }256$$ and tweaks of either 128 or 256 bits. When encrypting large chunks of data under the same key, modes with Pholkos do not require “beyond-birthday security” since it provides “bigger birthday security”. This also makes it a good choice for quantum-secure authenticated encryption modes like QCB. Pholkos runs at 1–2 cycles per byte on Intel 6-th generation and more recent, following design principles from Haraka, AESQ, and the TWEAKEY framework. Building on the AES round function not only boosts software performance but also improves security, employing knowledge from two decades of cryptanalysis of the AES.

Explainable Artificial Intelligence to Advance Structural Health Monitoring

Abstract: In recent years, structural health monitoring (SHM) applications have significantly been enhanced, driven by advancements in artificial intelligence (AI) and machine learning (ML), a subcategory of AI. Although ML algorithms allow detecting patterns and features in sensor data that would otherwise remain undetected, the generally opaque inner processes and black-box character of ML algorithms are limiting the application of ML to SHM. Incomprehensible decision-making processes often result in doubts and mistrust in ML algorithms, expressed by engineers and stakeholders. In an attempt to increase trust in ML algorithms, explainable artificial intelligence (XAI) aims to provide explanations of decisions made by black-box ML algorithms. However, there is a lack of XAI approaches that meet all requirements of SHM applications. This chapter provides a review of ML and XAI approaches relevant to SHM and proposes a conceptual XAI framework pertinent to SHM applications. First, ML algorithms relevant to SHM are categorized. Next, XAI approaches, such as transparent models and model-specific explanations, are presented and categorized to identify XAI approaches appropriate for being implemented in SHM applications. Finally, based on the categorization of ML algorithms and the presentation of XAI approaches, the conceptual XAI framework is introduced. It is expected that the proposed conceptual XAI framework will provide a basis for improving ML acceptance and transparency and therefore increase trust in ML algorithms implemented in SHM applications.

Fault Diagnosis in Structural Health Monitoring Systems Using Signal Processing and Machine Learning Techniques

Abstract: Smart structures leverage intelligent structural health monitoring (SHM) systems, which comprise sensors and processing units deployed to transform sensor data into decisions. Faulty sensors may compromise the reliability of SHM systems, causing data corruption, data loss, and erroneous judgment of structural conditions. Fault diagnosis (FD) of SHM systems encompasses the detection, isolation, identification, and accommodation of sensor faults, aiming to ensure the reliability of SHM systems. Typically, FD is based on “analytical redundancy,” utilizing correlated sensor data inherent to the SHM system. However, most analytical redundancy FD approaches neglect the fault identification step and are tailored to specific types of sensor data. In this chapter, an analytical redundancy FD approach for SHM systems is presented, coupling methods for processing any type of sensor data and two machine learning (ML) techniques, (i) an ML regression algorithm used for fault detection, fault isolation, and fault accommodation, and (ii) an ML classification algorithm used for fault identification. The FD approach is validated using an artificial neural network as ML regression algorithm and a convolutional neural network as ML classification algorithm. Validation is performed through a real-world SHM system in operation at a railway bridge. The results demonstrate the suitability of the FD approach for ensuring reliable SHM systems.

Maker-Literacy

Abstract: Der Aufsatz führt in das Konzept der Maker-Literacy ein. Damit soll das Verständnis digitaler Bildung um die Dimension des Machen-Könnens im Sinne eigenmächtiger Eingriffsmöglichkeiten in digitale Kultur erweitert werden. Making, verstanden als digitales Basteln, stellt in dieser Perspektive produktive Einübungsweisen in digitale Kultur in Aussicht, die durch eine spezifische Komplexitätskompetenz gekennzeichnet werden können. Um diese These argumentativ nachvollziehbar zu gestalten, verfolgt der Text einen Dreischritt: Ausgehend von einer Positionierung in der digitalen Kultur (1) entwickelt er einerseits eine Perspektive auf Making als digitales Basteln und stellt andererseits das genutzte Literacy-Konzept vor (2). Anhand einer Kontrastierung mit der Literalität des Schreibens und Lesens wird eine spezifische Maker-Literalität entwickelt und präsentiert, die Making als wichtige Komponente des Umgangs mit und der Einübung in digitale(r) Kultur beschreibt (3).

Stacking ensemble-based hybrid algorithms for discharge computation in sharp-crested labyrinth weirs

Abstract: Labyrinth weirs are utilized to transport a greater discharge during floods in contrast to conventional weirs due to their increased weir crest length. Nevertheless, due to the increased geometric complexity of labyrinth weirs, determination of accurate discharge coefficients and accordingly, head-discharge ratings are quite essential issues in practical application. Hence, as a first step the present study proposes the following eight standalone algorithms: decision table (DT), Kstar, least median square (LMS), M5 prime (M5P), M5 rule (M5R), pace regression (PR), random forest (RF) and sequential minimal optimization (SMO). Then, applying the stacking (ST) algorithm, these standalone models were hybridized to predict the discharge coefficient (Cd) for sharp-crested labyrinth weirs. Potential/effective variables were constructed in the form of several independent dimensionless parameters (i.e., θ, h/W, L/B, L/h, Froude number (Fr), B/W and L/W) to predict Cd as an output. The accuracy of the developed models was examined in terms of different statistical visually based and quantitative-based error measurement criteria. The results illustrate that h/W and B/W parameters have the highest and lowest effect on the Cd prediction, respectively. According to NSE, all developed algorithms provided accurate performances, while ST-Kstar had the highest prediction power.

Historiography Avant la Lettre?

Abstract: Since the close of the nineteenth century, diverse historical accounts have been put in circulation as integral parts of planning theory. With the establishment of an independent British town planning literature and the rise of English as lingua franca, exemplary models and historical narratives were increasingly discussed on an international level. The release of seminal books and journals as well as personal interactions at town planning conferences led this process culminate around 1909/1910. This remarkable knowledge exchange achieved a global impact and resulted in a canonization of historical narratives in the town planning literature. This chapter examines diverse historical accounts in early town planning literature with a particular focus on pioneering German and British manuals. It firstly discusses related methodological approaches of literature-based analysis in planning history and the value of handbooks as research subjects for such an inquiry. It then traces the emergence and increase of various uses of history before the decisive juncture of 1909/1910, compares these texts with coeval writings, and analyzes their perception in the contemporary town planning discourse. The chapter finally discusses as to what extent the debate on history mirrored or even informed the formation process of modern town planning as an academic subject and profession.

The Atmospheric Worlds of Cinema

Abstract: To further advance the notion of the diegesis-as-environment and its material-affective nature, this chapter advocates for the atmospheric in cinematic perception. Drawing primarily upon the contemporary interdisciplinary surge of “atmosphere research” (e.g., Schmitz, Böhme, Ingold, Thibaut, and Griffero), this chapter maintains that although the concept of atmosphere has been omnipresent in the literature on film, it has yet to be adequately theoretically addressed. Moreover, what for classical narratology was deemed its conceptual weakness, its intermediate position between the subject (spectator) and object (film), is exactly its media-anthropological strength given that it carves out the anthropomedial space of their coexistence. Abandoned in the textual models of the diegesis, filmic atmospheres resurrect as the quintessential component of the diegesis-as-environment. It is argued that for atmosphere to become a key concept in narratology it needs to challenge the basic internalist assumptions of the contemporary “turn to mood” in (cognitive) film studies. Whereas the concept of “mood” is understood metaphorically as a filter that colors the already constituted narrative world in particular feeling tones, an “atmosphere” is the necessary ground out of which all filmic worlds emerge. Herein lies a new premise for understanding the narrative film: the atmospheric co-constitutes a film’s textual, representational, and propositional dimension rather than being its surplus. In its conclusion, the chapter explores two narrative atmospheric strategies employed by Alice Rohrwacher’s Happy as Lazzaro (Lazzaro Felice, 2018).

The Diegesis as Environment

Abstract: The concept of diegesis is essential to film studies and narratology. The first part of the chapter examines the historical trajectory to which the present concept of the diegesis owes its appropriation in film semiology, structuralist narratology, film musicology, and cognitive formalism into a “textual” model detached from narrative experientiality and affect. In reference to recent debates concerning the concept of diegesis, it is evidenced how textual assumptions continue to impede a field trying to move on to more embodied understandings of the filmic experience. This chapter develops the “enactive” and “media-anthropological” concept of the diegesis-as-environment as an alternative to the dominant conception of the diegesis-as-text. In doing so, it returns to the original filmological conception of the diegesis as more than “a series of events” but, rather, the world of the story, including its affective components such as the atmospheres that radiate from it. Consequently, the diegesis-as-environment rejects the semiological reduction of the diegesis to the sum of a film’s “literal” meanings, its denotations. Such a definition effectively identifies filmic signification with linguistic and verbal signification, thereby neglecting cinema’s material and affective modes of communicating their worlds through ambient noises, subtle colorations, editing rhythms, performative techniques, and camera movements that communicate through embodied affects. Proposed instead is an affective semiotics that replaces the Saussurean “sign” with Deleuze’s “signaletic material” as the main constituent of cinematic signification.

The Moving Camera and the Motor-Affective Arrangement of Films

Abstract: With outset of the moving camera, this chapter argues that more than audiovisual cues for inferential elaboration, an externalization of our embodied mechanisms, a mimicking of ecological perception, or the activation of our motor cortex or mirror neuron system, cinematic motion perception is a particularly illuminating case of the media–man entanglement at the heart of the filmic experience without which there would be no narrative, no diegesis. Among the most established tropes in the study of cinema, its reception, and its production is that the camera presents a point of view onto an independently existing narrative world. The camera thus replaces the human eye as the gateway to the filmic diegesis. However, this trope relies on the illusion of the diegesis-as-text of being a story without discourse, i.e., an objective world existing independently of the spectator whose experience it belongs to. Contrarily, this chapter argues that the affective-motor resonances that flow between the embodied spectator and the material film must be conceived as an integral component of the cinematic diegesis. In reference to the camera work in Kalatozov’s The Cranes Are Flying (1957), it is argued that the true potential of embodiment is not to be found in cinema’s simulation or externalization of human embodied perception but the challenges it poses to a priori determinations of the “human” and the way it gestures toward “human technogenesis,” the coevolution of the human with technics. Embodiment is not separate from technics; it never was.

Afterword

Abstract: Rather than being confined to representing the real, cinema produces it by altering and modulating our perceptions, affects, cognitions, and experiences. Cinema comes alive though our visceral and cerebral investments into the flow of its movements. It is vital that we understand its direct material-affective mode of address to understand how it orchestrates its worlds to regulate, reproduce, or create experiences that go far beyond its text. This chapter emphasizes the ethical imperative that comes with cinema’s affective powers. To achieve this, it refers to how in the fifth season of Homeland a series of street art activists “hijacked” the diegesis to protest against the show’s stereotypical and antagonistic depiction of the Arab world and Islam.

Aber das sind doch die Guten – oder? Wohnungsgenossenschaften in Hamburg

Abstract: Warum werden in aktuellen Diskussionen Wohnungsgenossenschaften immer wieder als zentrale Akteure einer gemeinwohlorientierten Wohnraumversorgung benannt – obwohl sie kaum zur Schaffung neuen bezahlbaren Wohnraums beitragen? Warum wehrt sich die Mehrzahl der Wohnungsgenossenschaften mit Händen und Füßen gegen die Wiedereinführung eines Gesetzes zur Wohnungsgemeinnützigkeit, obwohl es doch gerade dieses Gesetz war, dass sie im 20. Jahrhundert zu im internationalen Vergleich großen Unternehmen wachsen ließ? Sind Wohnungsgenossenschaften nun klientilistische, wenig demokratische und nur halb dekommodifizierte Marktteilnehmer oder wichtiger Teil der Wohnungsversorgung der unteren Mittelschicht? Wer Antworten auf diese und andere Fragen sucht und Differenziertheit in ihrer Beantwortung aushält, lese Joscha Metzers Dissertation „Genossenschaften und die Wohnungsfrage.