Data-driven self-organization with implicit self-coordination for coverage and capacity optimization in cellular networks. - In: IEEE transactions on network and service management, ISSN 1932-4537, Bd. 20 (2023), 2, S. 1153-1169
Coverage and Capacity Optimization (CCO) and Inter-Cell Interference Coordination (ICIC) are two tightly coupled and conflicting Self-Organizing Network (SON) functions that are responsible for ensuring optimal coverage and capacity in any cellular network. While executing currently, these functions may modify the same RF and antenna parameters, resulting in severe performance deteriorations. In this context, a centralized optimization and coordination approach may be impractical considering the large sizes of network clusters and the dynamics involved between the several other defined SON use cases. In this work, an implicitly coordinated and scalable self-organizing architecture is followed such that when a carefully defined multi-objective utility function for CCO-ICIC joint optimization is optimized locally by each RAN node, a desired balance between the two conflicting network targets of coverage and capacity is ensured globally. Pareto analysis of three variants of the proposed Local Multi-Objective KPI (LMO KPI) has been conducted to implicitly coordinate the two SON functions in a distributed self-organized manner. In order to recommend appropriate network configurations dynamically to quickly adapt to altering network environments, two collaborative filtering-based Recommender Systems (RecSys), one using a Deep Autoencoder and another based on Singular Value Decomposition, have been employed along with a neural network regressor to improve recommendations for cold-start scenarios. The two proposed hybrid-RecSys-based SON coordination solutions, while adopting an appropriate Local Multi-Objective KPI (LMO KPI), outperform previous work in coverage by 36% and in capacity by around 2% while reducing power consumption by more than 50%. The study demonstrates that the definition of the LMO KPI is crucial to the performance of this approach. Altogether, the work shows that the adopted self-organization and implicit SON-coordination approach is not only feasible and performant but also scales well if implemented meticulously.
https://doi.org/10.1109/TNSM.2023.3262401
Linearly modulated multi-focal diffractive lens for multi-sheet excitation of flow driven samples in a light-sheet fluorescence microscope. - In: Journal of the European Optical Society, ISSN 1990-2573, Bd. 19 (2023), 1, 26, S. 1-8
Light sheet fluorescence microscope with single light sheet illumination enables rapid 3D imaging of living cells. In this paper we show the design, fabrication and characterization of a diffractive optical element producing several light sheets along a 45˚ inclined tube. The element, which is based on a multi-focal diffractive lens and a linear grating, generates five thin light sheets with equal intensities when combined with a refractive cylindrical lens. The generated uniform light sheets can be applied for the scanning of samples in tubes enabling flow-driven 3-dimensional imaging.
https://doi.org/10.1051/jeos/2023022
2.5D+ plasma etching for a continuously adjustable sidewall angle in SiO2. - In: Optical materials express, ISSN 2159-3930, Bd. 13 (2023), 6, S. 1780-1796
We present a systematic investigation of an SiO2 etching process using a standard fluorocarbon chemistry ICP-RIE etch tool with a cryogenically cooled electrode. Our goal is to enable the control of the SiO2 feature morphology, i.e., the sidewall angle, in order to add a degree of freedom for the design of resonant micro-/nanooptical elements. For such elements as e.g., whispering gallery mode resonators with specific mode profiles, it is essential to maintain low surface roughness. To this end, we investigate a variety of gas compositions. For statistical evaluation, we use a surface response methodology for several parameters and investigate the influence of the substrate temperature on the sidewall angle. Different hypotheses from the literature for the cause of non-anisotropic etch behavior are discussed for our specific case. Various investigations based on the prior hypothesis are presented, which provide more information about the pseudo-isotropic etch profile. Finally, we present two use cases: firstly, a classical anisotropic etch with a high aspect ratio and very low roughness (<1 nm), and secondly, an etch process for the fabrication of whispering gallery mode resonators that confine the light at the bottom of the resonator.
https://doi.org/10.1364/OME.484157
Contraception on YouTube, Instagram, and TikTok : a content and quality analysis
Verhütung auf YouTube, Instagram und TikTok : eine Inhalts- und Qualitätsanalyse. - In: Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz, ISSN 1437-1588, Bd. 66 (2023), 9, S. 990-999
Hintergrund: Jugendliche und Erwachsene beziehen Informationen über Verhütung zunehmend über soziale Medien. Ziel der Arbeit: Vor diesem Hintergrund ist es Ziel der vorliegenden Studie, erstmals Inhalte und Qualität deutschsprachiger Verhütungsbeiträge auf YouTube, Instagram und TikTok zu untersuchen. Beantwortet werden sollen Forschungsfragen zu Anbieter*innen (F1), Inhalten (F2) und Qualität der Verhütungsbeiträge (F3) sowie zu Publikumsreaktionen (F4). Material und Methoden: Es wurde eine Stichprobe von N= 1000 Verhütungsbeiträgen von YouTube (500), Instagram (250) und TikTok (250) gezogen. Pro Beitrag gingen maximal 20 verhütungsbezogene Kommentare in das Kommentar-Sample ein (N= 12.454). Die Beiträge und Kommentare wurden mittels reliabilitätsgeprüfter Codebücher analysiert. Die Datenanalyse erfolgte mit SPSS. Die Studie ist präregistriert und alle Daten, Materialien und Analyseskripte sind öffentlich verfügbar. Ergebnisse: Es zeigte sich, dass die Verhütungsbeiträge mehrheitlich von Gesundheitslaien stammten (52%), gefolgt von Medienprofis und Gesundheitsprofis (F1). Inhaltlich deckten die Verhütungsbeiträge alle verfügbaren Verhütungsmethoden ab, wobei Pille (69%) und Kondom (40%) dominierten (F2). Nach gängigen Qualitätskriterien zeigten sich deutliche Defizite, wobei im Vergleich YouTube-Videos am besten abschnitten (F3). TikTok-Videos dagegen waren Spitzenreiter bei den Publikumsreaktionen, sie verzeichneten die meisten Views, Likes und Kommentare. Die Kommentarspalten wurden vom Publikum oft genutzt, um eigene Verhütungserfahrungen zu teilen oder Nachfragen zu stellen (F4). Diskussion: Weitere Forschung sowie Praxismaßnahmen sind notwendig, um die Qualität von Verhütungsinformationen in sozialen Medien besser einschätzen und optimieren zu können.
https://doi.org/10.1007/s00103-023-03698-0
Phase formation of cubic silicon carbide from reactive silicon-carbon multilayers. - In: MRS advances, ISSN 2059-8521, Bd. 8 (2023), 9, S. 494-498
Silicon carbide layers were fabricated using self-propagating high-temperature synthesis of binary silicon-carbon based reactive multilayers. The silicon and carbon bilayers were fabricated with two different bilayer thicknesses. They are deposited by magnetron sputtering in an alternating layer system with a total thickness of 1 μm. The entire system is annealed by rapid thermal annealing at different temperatures ranging from 500 to 1100 ˚C. From XRD analysis we could find that the formation of the silicon carbide phase was initiated from 700 ˚C. With increasing bilayer thickness the silicon carbide phase formation was partially suppressed by the silicon recrystallization due to resulting lower carbon diffusion into silicon. The transformation process proceeds in a four-step process: densification/recrystallization, interdiffusion, nucleation and transformation. From this, it was noted that when compared to low bilayer thickness samples, the formation of the silicon carbide phase is delayed with increasing bilayer thickness and needs higher reaction initiation temperatures.
https://doi.org/10.1557/s43580-023-00531-3
Energy-efficient operation conditions of MoS2-based memristors. - In: Physica status solidi, ISSN 1862-6319, Bd. 220 (2023), 13, 2200893, S. 1-12
Sufficient energy consumption for conventional information processing makes it necessary to look for new computational methods. One of the possible solutions to this problem is neuromorphic computations using memristive devices. Memristors based on molybdenum disulfide (MoS2) are a promising way to provide a sizeable amount of hysteresis at low energy costs. Herein, different configurations of MoS2 memristors as well as the mechanisms involved in hysteresis formation are shown. Bottom gated configuration is beneficial in terms of hysteresis area and energy efficiency. The impact of device channel dimensions on the hysteresis area and energy consumption is discussed. Different operation conditions with triangular, rectangular, sinusoidal, and sawtooth drain-to-source pulses are simulated, and rectangular pulses demonstrate the highest energy efficiency. The study shows the potential to realize low-power neuromorphic systems using MoS2 memristive devices.
https://doi.org/10.1002/pssa.202200893
Adaptive update handling for graph HTAP. - In: Distributed and parallel databases, ISSN 1573-7578, Bd. 41 (2023), 3, S. 331-357
Hybrid transactional/analytical processing (HTAP) workloads on graph data can significantly benefit from GPU accelerators. However, to exploit the full potential of GPU processing, dedicated graph representations are necessary, which mostly make in-place updates difficult. In this paper, we discuss an adaptive update handling approach in a graph database system for HTAP workloads. We discuss and evaluate strategies for propagating transactional updates from an update-friendly table storage to a GPU-optimized sparse matrix format for analytics.
https://doi.org/10.1007/s10619-023-07428-y
Changes in formal structure towards self-managing organization and their effects on the intra-organizational communication network. - In: Journal of organization design, ISSN 2245-408X, Bd. 12 (2023), 3, S. 83-98
Changes in organizational structure affect the intra-organizational communication network. However, despite an increasing relevance of less hierarchical and less bureaucratic forms of organizing, the question of how self-managing forms of organization influence employees’ communication behavior has received only scant attention yet. In our study, we analyze the case of a medium-sized firm that experiences organizational change from rigid bureaucratic structures to a more self-managing organization model and question how employees’ centrality in the communication network is affected by this reorganization. Following an explorative research approach informed by prior research on self-managing forms of organizations and communication networks, our findings show that after the change process communication generally is less dependent on formal hierarchy. However, while employees who held a higher rank before the change process loose in centrality, their centrality at the end of the change process is still higher than that of other employees. Moreover, employees who experience a promotion become more central in the communication network while demotions do not have an effect. By discussing these findings in the context of organizational change and the persistence of organizational structures, we contribute to a more comprehensive understanding of the implementation process of self-managing organizations.
https://link.springer.com/content/pdf/10.1007/s41469-023-00143-z.pdf?pdf=button
The fallacy in productivity decomposition. - In: Journal of evolutionary economics, ISSN 1432-1386, Bd. 33 (2023), 3, S. 797-835
https://link.springer.com/content/pdf/10.1007/s00191-023-00816-8.pdf
Neuromorphic acoustic sensing using an adaptive microelectromechanical cochlea with integrated feedback. - In: Nature electronics, ISSN 2520-1131, Bd. 6 (2023), 5, S. 370-380
Many speech processing systems struggle in conditions with low signal-to-noise ratios and in changing acoustic environments. Adaptation at the transduction level with integrated signal processing could help to address this; in human hearing, transduction and signal processing are integrated and can be adaptively tuned for noisy conditions. Here we report a microelectromechanical cochlea as a bio-inspired acoustic sensor with integrated signal processing functionality. Real-time feedback is used to tune the sensing and processing properties, and dynamic switching between linear and nonlinear characteristics improves the detection of signals in noisy conditions, increases the sensor dynamic range and enables adaptation to changing acoustic environments. The transition to nonlinear behaviour is attributed to a Hopf bifurcation and we experimentally validate its dependence on sensor and feedback parameters. We also show that output-signal coupling between two coupled sensors can increase the frequency coverage.
https://doi.org/10.1038/s41928-023-00957-5