@misc{StrobelAlvaradoChavarinVoelkeletal., author = {Strobel, Carsten and Alvarado Chavarin, Carlos and V{\"o}lkel, Sandra and Jahn, Andreas and Hiess, Andre and Knaut, Martin and Albert, Matthias and Wenger, Christian and Steinke, Olaff and Stephan, Ulf and R{\"o}hlecke, S{\"o}ren and Mikolajick, Thomas}, title = {Enhanced Electrical Properties of Optimized Vertical Graphene-Base Hot Electron Transistors}, series = {ACS Applied Electronic Materials}, volume = {5}, journal = {ACS Applied Electronic Materials}, number = {3}, issn = {2637-6113}, doi = {10.1021/acsaelm.2c01725}, pages = {1670 -- 1675}, abstract = {The arrival of high-mobility two-dimensional materials like graphene leads to the renaissance of former vertical semiconductor-metal-semiconductor (SMS) hot electron transistors. Because of the monolayer thickness of graphene, improved SMS transistors with a semimetallic graphene-base electrode are now feasible for high-frequency applications. In this study we report about a device that consists of amorphous silicon, graphene, and crystalline silicon. For the first time, this device is fabricated by a four-mask lithography process which leads to significant improvements in the device performance. A strongly increased common-emitter current gain of 2\% could be achieved while the on-off ratio improved to 1.6 × 105, which is already higher than predicted theoretically. This could be mainly attributed to better interface characteristics and decreased lateral dimensions of the devices. A cutoff frequency of approximately 26 MHz could be forecasted based on the DC measurements of the device.}, language = {en} } @misc{HenkSchymuraXue, author = {Henk, Martin and Schymura, Matthias and Xue, Fei}, title = {Packing minima and lattice points in convex bodies}, series = {Moscow Journal of Combinatorics and Number Theory}, volume = {10}, journal = {Moscow Journal of Combinatorics and Number Theory}, number = {1}, publisher = {Mathematical Sciences Publishers}, issn = {2640-7361}, doi = {10.2140/moscow.2021.10.25}, pages = {25 -- 48}, abstract = {Motivated by long-standing conjectures on the discretization of classical inequalities in the geometry of numbers, we investigate a new set of parameters, which we call packing minima, associated to a convex body K and a lattice Λ. These numbers interpolate between the successive minima of K and the inverse of the successive minima of the polar body of K and can be understood as packing counterparts to the covering minima of Kannan \& Lov{\´a}sz (1988). As our main results, we prove sharp inequalities that relate the volume and the number of lattice points in K to the sequence of packing minima. Moreover, we extend classical transference bounds and discuss a natural class of examples in detail.}, language = {en} } @misc{RichterKarnapkeWerner, author = {Richter, Martin and Karnapke, Reinhardt and Werner, Matthias}, title = {Utilizing sensor and actuator virtualization to achieve a systemic view of mobile heterogeneous cyber-physical systems}, series = {Proceedings of the 14th International Conference on Simulation and Modeling Methodologies, Technologies and Applications}, journal = {Proceedings of the 14th International Conference on Simulation and Modeling Methodologies, Technologies and Applications}, publisher = {SCITEPRESS - Science and Technology Publications}, isbn = {978-989-758-708-5}, doi = {10.5220/0012715800003758}, pages = {207 -- 214}, abstract = {When programming cyber-physical systems, application developers currently utilize physical sensors and actuators individually to achieve the desired observations and impacts within the physical world. This is an error-prone and complex task given the size, heterogeneity, and mobility of prevailing cyber-physical systems. We introduce an application model that allows the application developers to take a physical perspective. By means of this model, the programmers describe desired observations and influences with respect to the physical world without directly referencing physical devices. We present an additional model for a runtime environment that transparently utilizes the available physical devices to reach the application developers' targets. We show that an implementation of our models is functional via simulation.}, language = {en} } @misc{KraljevskiDuckhornBarthetal., author = {Kraljevski, Ivan and Duckhorn, Frank and Barth, Martin and Tsch{\"o}pe, Constanze and Schubert, Frank and Wolff, Matthias}, title = {Autoencoder-based Ultrasonic NDT of Adhesive Bonds}, series = {IEEE SENSORS 2021, Conference Proceedings, Oct 31- Nov 4, Sydney, Australia}, journal = {IEEE SENSORS 2021, Conference Proceedings, Oct 31- Nov 4, Sydney, Australia}, publisher = {IEEE}, isbn = {978-1-7281-9501-8}, doi = {10.1109/SENSORS47087.2021.9639864}, pages = {4}, abstract = {We present an approach for ultrasonic non-destructive testing of adhesive bonding employing unsupervised machine learning with autoencoders.The models are trained exclusively on the features derived from pulse-echo ultrasonic signals on a specimen with good adhesive bonding and tested on another specimen with artificially added defects.The resulting pseudo-probabilities indicating anomalies are visualized and presented along to the C-scan of the same specimen. As a result, we achieved improved representation of the defects, allowing their automatic and reliable detection.}, language = {en} } @misc{BeirowNakosStecklinaetal., author = {Beirow, Bernd and Nakos, Alex and Stecklina, Caroline and Noack, Martin and Firl, Matthias and Sasakaros, Marios}, title = {Implementation of intentional mistuning by means of finite element based shape optimization}, series = {Journal of engineering for gas turbines and power}, journal = {Journal of engineering for gas turbines and power}, publisher = {ASME International}, address = {New York}, issn = {0742-4795}, doi = {10.1115/1.4069624}, pages = {1 -- 15}, abstract = {Intentional Mistuning has turned out to be an effective measure to alleviate the maximum forced response of bladed wheels in the framework of numerous studies in the past. In particular solutions based on two different blade designs, following e.g. alternating or AABB patterns, have proved to be promising in this regard and moreover robust against the impact of unavoidable random mistuning. Thus, for example, a 40 percent reduction of the first blade bending maximum forced response has been proved experimentally for a turbine impeller of a turbo charger application. Despite this success, the technical implementation of the frequency based mistuning pattern followed an academic solution based on locally removing material at the leading edge tip, which is not suited for the use in serial wheels since it may disturb the flow channel. In addition, the forced response of other blade modes may be affected in a negative manner. In order to overcome these problems, an alternative way of implementing Intentional Mistuning is suggested by applying a marginal geometric modification of the blade thickness distribution to adjust the natural frequency of the first bending mode. Finite element based shape optimization is utilized to this end. Secondary conditions are ensuring that only the target frequency of the first bending mode is adjusted whereas natural frequencies of other modes are kept almost unchanged.}, language = {en} } @misc{BeirowNakosStecklinaetal., author = {Beirow, Bernd and Nakos, Alex and Stecklina, Caroline and Noack, Martin and Firl, Matthias and Sasakaros, Marios}, title = {Implementation of intentional mistuning by means of finite element based shape optimization}, series = {Proceedings of the ASME Turbo Expo 2025, Memphis, June 16-20, 2025}, journal = {Proceedings of the ASME Turbo Expo 2025, Memphis, June 16-20, 2025}, publisher = {The American Society of Mechanical Engineers}, address = {New York, NY}, isbn = {978-0-7918-8885-8}, doi = {10.1115/GT2025-151617}, pages = {11}, abstract = {Intentional Mistuning has turned out to be an effective measure to alleviate the maximum forced response of bladed wheels in the framework of numerous studies in the past. In particular solutions based on two different blade designs, following e.g. alternating or AABB patterns, have proved to be promising in this regard and moreover robust against the impact of unavoidable random mistuning. Thus, for example, a 40 percent reduction of the first blade bending maximum forced response has been proved experimentally for a turbine impeller of a turbo charger application. Despite this success, the technical implementation of the frequency based mistuning pattern followed an academic solution based on locally removing material at the leading edge tip, which is not suited for the use in serial wheels since it may disturb the flow channel. In addition, the forced response of other blade modes may be affected in a negative manner. In order to overcome these problems, an alternative way of implementing Intentional Mistuning is suggested by applying a marginal geometric modification of the blade thickness distribution to adjust the natural frequency of the first bending mode. Finite element based shape optimization is utilized to this end. Secondary conditions are ensuring that only the target frequency of the first bending mode is adjusted whereas natural frequencies of other modes are kept almost unchanged.}, language = {en} } @techreport{KlattPfeifferBendigetal., author = {Klatt, Matthias and Pfeiffer, Klaus and Bendig, Martin and Platta, Kristian and Matzekat, David}, title = {Betrachtungen zur Mindesterzeugung von Braunkohlekraftwerken im Kontext des Netzbetriebs}, publisher = {Brandenburgische Technische Universit{\"a}t, Fachgebiet Dezentrale Energiesysteme [u.a.]}, address = {Cottbus ; Senftenberg}, language = {de} } @misc{SchmittSowoidnichGosswamietal., author = {Schmitt, Ingo and Sowoidnich, Kay and Gosswami, Tapashi and Sumpf, Bernd and Maiwald, Martin and Wolff, Matthias}, title = {PCA-based peak feature selection for classification of spectroscopic datasets}, series = {Journal of chemometrics}, volume = {39}, journal = {Journal of chemometrics}, number = {11}, publisher = {John Wiley \& Sons Ltd.}, address = {New York, NY}, issn = {0886-9383}, doi = {10.1002/cem.70074}, pages = {1 -- 14}, abstract = {Reducing feature dimensionality in spectroscopic data is crucial for efficient analysis and classification. Using all available features for classification typically results in an unacceptably high runtime and poor accuracy. Popular feature extraction methods, such as principal component analysis (PCA), linear discriminant analysis (LDA), and autoencoders, reduce feature dimensionality by extracting latent features that can be challenging to interpret. To enable better human interpretation of the classification model, we avoid extraction methods and instead propose applying feature selection methods. In this work, we develop an innovative PCA-based feature selection method for spectroscopic data, providing an essential subset of the original features. As an important advantage, no prior knowledge about the characteristic signals of the respective target substance is required. In this proof-of-concept study, the proposed method is initially characterized using simulated Raman and infrared absorption datasets. From the top five PCA eigenvectors of spectroscopic data, we identify a set of three top peaks each at specific wavenumbers (features). The compact set of selected features is then used for classification tasks applying a decision tree. Based on two well-defined spectroscopic datasets, our study demonstrates that our new method of PCA-based peak finding outperforms selected other approaches with regard to interpretability and accuracy. For both investigated datasets, accuracies greater than 97\% are achieved. Our approach shows large potential for accurate classification combined with interpretability in further scenarios involving spectroscopic datasets.}, language = {en} }