Publications Search Results

Now showing 1 - 10 of 681
  • Publication
    An optimization approach for a milling dynamics simulation based on Quantum Computing
    ( 2024-02-01) ;
    Danz, Sven
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    Kienast, Pascal
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    König, Valentina
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    Since the machining of complex aerospace components, like integral compressor-rotors (blade integrated disks), is very cost-intensive, optimizing the process by means of process simulations is an active field of research. With the rise of Quantum Computing, a new instrument with high optimization potential is moving into focus. In this paper, a possible application of Quantum Computing for the machining simulation of multi-axis milling of thin-walled aerospace components is discussed. For this reason, a simulation framework used for the milling simulation is analyzed and each component is evaluated separately in relation to Quantum Computing. Parts of the Harrow, Hassidim, and Lloyd algorithm are proposed to enhance the Finite-Element simulation-based component, like the modal analysis for dynamics simulation. This algorithm can solve linear system problems with exponential speed-up over the classical method. The paper presents a roadmap on how the classical steps of a modal analysis for dynamics simulation could be replaced by quantum algorithms based on quantum phase estimation. The implementation of the first working steps is presented to validate this approach. The linear system problem, arising from the dynamics simulation, is analyzed in detail and a minimal value problem of linear coupled oscillators is derived.
  • Publication
    Disentangling Morphed Identities for Face Morphing Detection
    ( 2024)
    Caldeira, Eduarda
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    Neto, Pedro C.
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    Gonçalves, Tiago
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    Sequeira, Ana F.
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    Cardoso, Jaime S.
    Morphing attacks keep threatening biometric systems, especially face recognition systems. Over time they have become simpler to perform and more realistic, as such, the usage of deep learning systems to detect these attacks has grown. At the same time, there is a constant concern regarding the lack of interpretability of deep learning models. Balancing performance and interpretability has been a difficult task for scientists. However, by leveraging domain information and proving some constraints, we have been able to develop IDistill, an interpretable method with state-of-the-art performance that provides information on both the identity separation on morph samples and their contribution to the final prediction. The domain information is learnt by an autoencoder and distilled to a classifier system in order to teach it to separate identity information. When compared to other methods in the literature it outperforms them in three out of five databases and is competitive in the remaining.
  • Publication
    Multispectral Imaging for Differential Face Morphing Attack Detection: A Preliminary Study
    ( 2024)
    Ramachandra, Raghavendra
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    Venkatesh, Sushma
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    Vetrekar, Narayan
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    Gad, R.S.
    Face morphing attack detection is emerging as an increasingly challenging problem owing to advancements in high-quality and realistic morphing attack generation. Reliable detection of morphing attacks is essential because these attacks are targeted for border control applications. This paper presents a multispectral framework for differential morphing-attack detection (D-MAD). The D-MAD methods are based on using two facial images that are captured from the ePassport (also called the reference image) and the trusted device (for example, Automatic Border Control (ABC) gates) to detect whether the face image presented in ePassport is morphed. The proposed multi-spectral D-MAD framework introduce a multispectral image captured as a trusted capture to acquire seven different spectral bands to detect morphing attacks. Extensive experiments were conducted on the newly created Multispectral Morphed Datasets (MSMD) with 143 unique data subjects that were captured using both visible and multispectral cameras in multiple sessions. The results indicate the superior performance of the proposed multispectral framework compared to visible images.
  • Publication
    SFace2: Synthetic-Based Face Recognition with w-Space Identity-Driven Sampling
    The use of synthetic data for training neural networks has recently received increased attention, especially in the area of face recognition. This was mainly motivated by the increase of privacy, ethical, and legal concerns of using privacy-sensitive authentic data to train face recognition models. Many authentic datasets such as MS-Celeb-1M or VGGFace2 that have been widely used to train state-of-the-art deep face recognition models are retracted and officially no longer maintained or provided by official sources as they often have been collected without explicit consent. Toward this end, we first propose a synthetic face generation approach, SFace which utilizes a class-conditional generative adversarial network to generate class-labeled synthetic face images. To evaluate the privacy aspect of using such synthetic data in face recognition development, we provide an extensive evaluation of the identity relation between the generated synthetic dataset and the original authentic dataset used to train the generative model. The investigation proved that the associated identity of the authentic dataset to the one with the same class label in the synthetic dataset is hardly possible, strengthening the possibility for privacy-aware face recognition training. We then propose three different learning strategies to train the face recognition model on our privacy-friendly dataset, SFace, and report the results on five authentic benchmarks, demonstrating its high potential. Noticing the relatively low (in comparison to authentic data) identity discrimination in SFace, we started by analysing the w-space of the class-conditional generator, finding identity information that is highly correlated to that in the embedding space. Based on this finding, we proposed an approach that performs the sampling in the w-space driven to generate data with higher identity discrimination, the SFace2. Our experiments showed the disentanglement of the latent w-space and the benefit of training face recognition models on the more identity-discriminated synthetic dataset SFace2.
  • Publication
    Constrained Optimal Experimental Design: Theory, Algorithm and Applications
    (Fraunhofer Verlag, 2024)
    While the literature on optimal experimental design (OED) is primarily concerned with unconstrained problems, it is also of interest to restrict individual experiments, certain design quantities, or even the entire experimental plan. A classic approach to OED models the problem as an unconstrained optimization problem over the infinite dimensional space of probability measures. This thesis introduces a general framework for constrained OED problems and discusses optimality criteria in form of saddle point conditions. Particular attention is paid to the required constraint qualifications. For the numerical solution of such constrained infinite-dimensional nonlinear OED problems this thesis proposes an adaptive discretization scheme, utilizing the derivative of the Lagrangian function. Furthermore, this thesis discusses the multi-criteria OED problem and presents algorithmic schemes for convex and non-convex objective functions. Finally, the algorithms are illustrated on an application example from chemical process engineering.
  • Publication
    Bias and Diversity in Synthetic-based Face Recognition
    Synthetic data is emerging as a substitute for authentic data to solve ethical and legal challenges in handling authentic face data. The current models can create real-looking face images of people who do not exist. However, it is a known and sensitive problem that face recognition systems are susceptible to bias, i.e. performance differences between different demographic and non-demographics attributes, which can lead to unfair decisions. In this work, we investigate how the diversity of synthetic face recognition datasets compares to authentic datasets, and how the distribution of the training data of the generative models affects the distribution of the synthetic data. To do this, we looked at the distribution of gender, ethnicity, age, and head position. Furthermore, we investigated the concrete bias of three recent synthetic-based face recognition models on the studied attributes in comparison to a baseline model trained on authentic data. Our results show that the generator generate a similar distribution as the used training data in terms of the different attributes. With regard to bias, it can be seen that the synthetic-based models share a similar bias behavior with the authentic-based models. However, with the uncovered lower intra-identity attribute consistency seems to be beneficial in reducing bias.
  • Publication
    Automatic Segmentation and Scoring of 3D In Vitro Skin Models Using Deep Learning Methods
    Cell-based in vitro skin models are an effective method for testing new medical compounds without any animal harming in the process. Histology serves as a cornerstone for evaluating in vitro models, providing critical insights into their structural integrity and functionality. The recently published BSGC score is a method to assess the quality of in vitro epidermal models, based on visual examination of histopathological images. However, this is very time-consuming and requires a high level of expertise. Therefore, this paper presents a method for automatic evaluation of three-dimensional in vitro epidermal models that involves segmentation and classification of epidermal layers in cross-sectional histopathological images. The input images are first pre-processed and in an initial classification step low-quality skin models are filtered. Subsequently, the individual epidermal strata are segmented and a masked image is generated for each stratum. The strata are scored individually using the masked images with a classification network per stratum. Finally the individual scores are merged into an overall weighted score per image. With an accuracy of 81% for the overall scoring the method provides promising results and allows for significant time savings and less subjectivity compared to the manual scoring process.
  • Publication
    Towards scalability for resource reconfiguration in robotic assembly line balancing problems using a modified genetic algorithm
    ( 2024) ;
    Hornek, Timothée
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    Assembly lines are still one of the most used manufacturing systems in modern-day production. Most research affects the building of new lines and, less frequently, the reconfiguration of existing lines. However, the first is insufficient to meet the reconfigurable production paradigm required by volatile market demands. Consequent reconfiguration of resources by production requests affects companies’ competitiveness. This paper introduces a problem-specific genetic algorithm for optimizing the reconfiguration of a Robotic Assembly Line Balancing Problem with Task Types, including additional company constraints. First, we present the greenfield and brownfield optimization objectives, then a mathematical problem formulation and the composition of the genetic algorithm. We evaluate our model against an Integer Programming baseline on a reconfiguration dataset with multiple equipment alternatives. The results demonstrate the capabilities of the genetic algorithm for the greenfield case and showcase the possibilities in the brownfield case. With a scalability improvement through computation time decrease of up to ∼ 2.75 × , reduced number of equipment and workstations, but worse objective values, the genetic algorithm holds the potential for reconfiguring assembly lines. However, the genetic algorithm has to be further optimized for the reconfiguration to leverage its full potential.
  • Publication
    Efficient Explainable Face Verification based on Similarity Score Argument Backpropagation
    Explainable Face Recognition is gaining growing attention as the use of the technology is gaining ground in security-critical applications. Understanding why two face images are matched or not matched by a given face recognition system is important to operators, users, and developers to increase trust, accountability, develop better systems, and highlight unfair behavior. In this work, we propose a similarity score argument backpropagation (xSSAB) approach that supports or opposes the face-matching decision to visualize spatial maps that indicate similar and dissimilar areas as interpreted by the underlying FR model. Furthermore, we present Patch-LFW, a new explainable face verification benchmark that enables along with a novel evaluation protocol, the first quantitative evaluation of the validity of similarity and dissimilarity maps in explainable face recognition approaches. We compare our efficient approach to state-of-the-art approaches demonstrating a superior trade-off between efficiency and performance. The code as well as the proposed Patch-LFW is publicly available at: https://github.com/marcohuber/xSSAB.
  • Publication
    Automatische Generierung von Tabellendrillingen unter Beibehaltung originärer Metadaten
    ( 2024)
    Möller, Simon
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    Die gesamte Welt ist voll von Informationen in Form von Daten. Eine Möglichkeit diese Daten zu erfassen ist, sie in Form von Tabellen zu speichern. Diese Art der Datenspeicherung ermöglicht eine strukturierte Gruppierung von Datensätzen, welche leichter zu betrachten sind und gut weiterverarbeitet werden können. Alle Tabellen besitzen einen strukturellen Aufbau von Informationen, welche in Zeilen und Spalten gegliedert sind. Sie unterscheiden sich nicht nur inhaltlich, sondern auch in ihrer Größe, dem Kontext, ihrer Beschriftung, sowie weiterer veränderbaren Faktoren wie der Anzahl an leeren, oder numerischen Feldern. Sind die Unterschiede gering, ergibt sich ein größeres Maß an Ähnlichkeit zwischen verschiedenen Tabellen. So nutzt unter anderem Google Tabellen mit ähnlichen Informationen zur Erweiterung der Suchergebnisse in ihrer Suchmaschine [3, 1]. Durch Finden eines solchen Ähnlichkeitsmaßes wird es möglich, Tabellen um Werte einer zu ihrer ähnlichen Tabelle zu erweitern (Tabellen Augmentation). Somit kann zum Beispiel eine Tabelle durch eine Wertvorhersage automatisch vervollständigt, oder gelöschte Einträge nachträglich wiederhergestellt werden. Aktuell existieren viele Verfahren zur Schätzung von Tabellenähnlichkeit, aber keine systematische Übersicht existiert. Geschweige denn eine akzeptierte "Best Practice", welches die Ähnlichkeit zwischen zwei oder mehreren Tabellen beschreibt [15]. Jedoch gibt es bereits mehrere verschiedene Ansätze wie Tabsim [6] um einen Ähnlichkeitswert zu errechnen, oder Tabbie [7] um Tabellen-Strukturen zu erkennen und Vorhersagen dazu treffen zu können. In den letzten Jahren wurde unter anderem der Einfluss von oben genannten Tabellenfeatures auf die Güte von Tabellenähnlichkeitsmaßen [12] am Fraunhofer Institut für Graphische Datenverarbeitung IGD weiter untersucht und verschiedene Modelle auf automatisch generierten Datensätzen durch Trainieren von einem Deep Learning Algorithmus auf ihre Genauigkeit evaluiert. Die Qualität der Ergebnisse dieser Evaluation hängen sehr stark von den generierten Datensätzen ab, so ist es nicht nur wichtig, dass die Datensätze korrekt sind, sondern auch, dass sie in einer ausreichenden Menge vorhanden sind. Ein pragmatischer Ansatz im maschinellen Lernen ist der, dass selbst ein schlechter Algorithmus einen sehr guten schlagen kann, wenn er genügend Daten zum Lernen bereitgestellt bekommt [4]. Dadurch gewinnt die automatische Generierung der Datensätze sehr an Relevanz, womit sich diese Arbeit genauer befasst. In der Vorgängerarbeit "Evaluation von Tabellenfeatures und ihr Einfluss auf die Güte von Tabellenähnlichkeitsmaßen" [12] wurde ein Verfahren entwickelt, um die Performance von Tabellenähnlichkeitsmodellen zu vergleichen. Dazu wurden Tabellen-Triplets (siehe Definition 3.4 über Triplets) automatisch generiert und ausgewertet, ob das zu untersuchende Modell die relativen Distanzen korrekt schätzt. Die automatische Generation von Triplets wurde durch wiederholte Anwendung verschiedener Manipulationsoperatoren realisiert. Im Zuge der Arbeit wurden bereits Operationen zur Permutation von Reihen und Spalten sowie dem Löschen von Reihen, Spalten und Zellen. Das Löschen von Zeilen oder Spalten verändert jedoch die Metadaten einer Tabelle, wodurch das Modell sich auf diese Änderung und weniger auf die weiteren unabhängigen Variablen der Tabellen beziehen kann und dadurch bestimmte Modelle besser bewertet werden als andere.