Hochschule Bonn-Rhein-Sieg
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Entwicklung, Verifikation und Validierung einer Time-of-Flight Beleuchtungsbaugruppe mit HF-modulierten, individuell aktivierbaren VCSEL-Arrays
No full textDiese Arbeit stellt die Entwicklung eines modularen, leistungsstarken Laserbeleuchtungssystems für Time-of-Flight (ToF)-Kameras vor, das bestehende Beleuchtungslösungen ersetzen soll. Durch die Erhöhung der optischen Ausgangsleistung und die Verkürzung der Anstiegszeiten wird die Leistungsfähigkeit einer modernen ToF-Kamera signifikant verbessert. Im Vergleich zu einer Referenzbeleuchtung konnte die Gesamtleistung verfünffacht werden. Die notwendigen Schritte zur Erreichung einer optischen Spitzenleistung von 10 W je Lichtquelle bei Modulationsfrequenzen bis zu 100 MHz werden beschrieben, was zu einer 1,2-fach höheren Leistung pro Lichtquelle im Vergleich zur Referenz führt. Die neue Beleuchtung ermöglicht zudem den Einsatz höherer Modulationsfrequenzen. An einem diffusen, weißen Referenztarget getestet, sank das Entfernungsrauschen bei 3 Metern von über 35 mm bei der Referenzbeleuchtung auf unter 5 mm bei der neuen Beleuchtung.
Durch das elektronische Zuschalten von bis zu vier Lichtquellen wird eine optische Spitzenleistung von 40 W bei einer Wellenlänge von 940 nm und einer Modulationsfrequenz von 100 MHz erreicht. Das individuelle Zuschalten der Lichtquellen bietet zukünftig die Möglichkeit, durch kombinierte Distanzmessverfahren die Zuverlässigkeit zu erhöhen. Die Entwicklung erfolgte in zwei Iterationen, wobei Voruntersuchungen Optimierungspunkte identifizierten. Basierend auf diesen Erkenntnissen wurde die Beleuchtungsplatine weiterentwickelt und der Einfluss auf das Phasenrauschen einer ToF-Kamera untersucht. Die erzielten Ergebnisse wurden mit den theoretischen Vorhersagen der Tiefenreproduzierbarkeit basierend auf dem Signal-Rausch-Verhältnis des empfangenen Signals verglichen. Die Ergebnisse bestätigten die theoretischen Vorhersagen und zeigten, in welchen Betriebssituationen das Tiefenrauschen vom Sensor- oder vom aktiven Schrotrauschen dominiert wird.
Ferner wurden Untersuchungen zur optischen Signalform der Lichtquellen und zum Einfluss unterschiedlicher Einschaltpunkte durchgeführt. Die geforderten optischen Anstiegs- und Abfallzeiten von 2 ns wurden unabhängig von der Modulationsfrequenz erreicht. Die optischen Signale der jeweiligen Lichtquellen überschritten die im Lastenheft geforderte maximale Asynchronität von 200 ps. Untersuchungen der elektrischen Signale zeigten, dass Verzögerungen durch den verwendeten Lasertreiber entstehen. Durch die unterschiedlichen Einschaltpunkte verringerte sich der Modulationskontrast auf 91%.This paper presents the development of a modular, high-performance laser illumination system for Time-of-Flight (ToF) cameras, designed to replace existing illumination solutions. By increasing the optical output power and reducing rise times, the performance of a state-of-the-art ToF camera is significantly enhanced. Compared to a reference illumination system, the new design quintupled the total optical power. Necessary steps to achieve an optical peak power of 10 W per light source at modulation frequencies up to 100 MHz are outlined, resulting in a 1.2-fold increase in power per light source over the reference. The new illumination also supports higher modulation frequencies. When tested on a diffuse white target, distance noise at 3 meters was reduced from over 35 mm with the reference illumination to less than 5 mm with the new system.
The system allows the electronic selection of up to four light sources, achieving a peak optical power of 40 W at a wavelength of 940 nm and a modulation frequency of 100 MHz. This individual light source activation provides future options for combined distance measurement techniques to improve reliability. The development proceeded in two iterations, with preliminary studies identifying optimization points. Based on these insights, the illumination board was further developed and validated by examining its impact on the phase noise of a ToF camera. The results were compared with theoretical predictions of depth reproducibility from the signal-to-noise ratio of the received signal. The findings confirmed the theoretical predictions, highlighting scenarios where depth noise is dominated by either sensor noise or active shot noise.
Additionally, the optical signal shape of the light sources and the impact of different activation points were investigated. The required optical rise and fall times of 2 ns were consistently achieved regardless of modulation frequency. The optical signals of each light source exceeded the specified maximum asynchrony of 200 ps. Electrical signal investigations revealed delays caused by the laser driver, with different activation points reducing the modulation contrast to 91%
Reisekostenordnung des Studierendenparlaments der Hochschule Bonn-Rhein-Sieg vom 11.01.2024
No full textEffizienter Datenmanagement-Workflow zur Analyse eines PtGtX-Systems basierend auf Open-Source-Software und Low-Cost-Hardware
No full textUm ein Power-to-Gas-to-X-System effizient zu optimieren, kann ein digitaler Zwilling als Simulationsmodell auf Basis experimenteller Daten für ein Laborsystem erstellt und entsprechend verändert werden. Darüber hinaus müssen für die Überwachung des realen Systems bzw. die Online-Simulation kontinuierlich Daten aus Experiment und Simulation erfasst und verarbeitet werden. Insgesamt ist ein effizienter Datenmanagement-Workflow erforderlich.
In dieser Arbeit wird ein Workflow aus freier, etablierter und skalierbarer Open-Source-Software für die vorliegende Anwendung skizziert und insbesondere ein geeignetes Datenmodell entwickelt, implementiert und seine ressourcensparende Realisierung auf kostengünstiger Hardware gezeigt. Abhängig von der Datenmodellierung kann preiswerte und alte Hardware für die geforderte Aufgabe ausreichend sein.
Mit Apache NiFi wird ein visueller Workflow zum Abrufen und Verarbeiten von Daten aus verschiedenen Quellen geschaffen. Die extrahierten Daten werden in Apache Cassandra aggregiert, einem Datensystem, das aufgrund seiner Leistung, Skalierbarkeit und Haltbarkeit häufig verwendet wird.
Grafana wird zur visuellen Überwachung des Systems eingesetzt. Das gesamte System wird mit Hilfe von Docker-Containern aufgebaut zum Zwecke der Reproduzierbarkeit und effizienten Bereitstellung.
Benchmarks und realistische Hardware- und Datenmodellierungskonfigurationen demonstrieren die Leistung der vorgeschlagenen Lösung.In order to efficiently optimize a power-to-gas-to‑X system, a digital twin can be created as a simulation model based on experimental data for a laboratory system and modified accordingly. In addition, data from experiment and simulation must be continuously recorded and processed for monitoring and online simulation. Overall, an efficient data management workflow is required.
In this paper, a workflow consisting of free, established and scalable open-source software is outlined for the application at hand and, in particular, a suitable data model is developed, implemented and its resource-saving realization on low-cost hardware is demonstrated. Depending on the data modeling, inexpensive and old hardware may be sufficient for the required task.
Apache NiFi is used to create a visual workflow for retrieving and processing data from various sources. The extracted data is aggregated in Apache Cassandra, a data system widely used for its performance, scalability and durability.
Grafana is used for visual monitoring of the system. The entire system is built using Docker containers for the purpose of reproducibility and efficient deployment.
Benchmarks and realistic hardware and data modeling configurations demonstrate the stated performance and sustainability of the proposed solution
Trueness and precision of digital light processing fabricated 3D printed monolithic zirconia crowns
No full textOBJECTIVES: The present study aimed to evaluate the trueness and precision of monolithic zirconia crowns (MZCs) fabricated by 3D printing and milling techniques. METHODS: A premolar crown was designed after scanning a prepared typodont. Twenty MZCs were fabricated using milling and 3D-printing techniques (n=10). All the specimens were scanned with an industrial scanner, and the scanned data were analyzed using 3D measurement software to evaluate the trueness and precision of each group. Root mean square (RMS) deviations were measured and statistically analyzed (One-way ANOVA, Tukey's, p≤0.05). RESULTS: The trueness of the printed MZC group (140 ± 14 μm) showed a significantly higher RMS value compared to the milled MZCs (96 ± 27 μm,p<0.001). At the same time, the precision of the milled MZCs (61±17 μm) showed a significantly higher RMS value compared to that of the printed MZCs (31±5 μm,p<0.001). CONCLUSIONS: The Fabrication techniques had a significant impact on the accuracy of the MZCs. Milled MZCs showed the highest trueness, while printed MZCs showed the highest precision. All the results were within the clinically acceptable error values. CLINICAL SIGNIFICANCE: Although the trueness of the milled MZCs is higher, the manufacturing accuracy of the 3D-printed MZCs showed clinically acceptable results in terms of trueness and precision. However, additional clinical studies are recommended. Furthermore, the volumetric changes of the material should be considered
Internet Users' Willingness to Disclose Biometric Data for Continuous Online Account Protection: An Empirical Investigation
No full textContinuous authentication has emerged as a promising approach to increase user account security for online services. Unlike traditional authentication methods, continuous authentication provides ongoing security throughout the session, protecting against session takeover attacks due to illegitimate access. The effectiveness of continuous authentication systems relies on the continuous processing of users' sensitive biometric data. To balance security and privacy trade-offs, it's crucial to understand when users are willing to disclose biometric data for enhanced account security, addressing inevitable privacy concerns and user acceptance. To address this knowledge gap, we conducted an online study with 830 participants from the U.S., aiming to investigate user perceptions towards continuous authentication across different classes of online services. Our analysis identified four groups of biometric traits that directly reflect users' willingness to disclose them. Our findings demonstrate that willingness to disclose is influenced by both the specific biometric traits and the type of online service involved. User perceptions are strongly shaped by factors such as response efficacy, perceived privacy risks associated with the biometric traits, and concerns about the service providers' handling of such data. Our results emphasize the inadequacy of one-size-fits-all solutions and provide valuable insights for the design and implementation of continuous authentication systems
Functional Agarose Hydrogels Obtained by Employing Homogeneous Synthesis Strategies
No full textThe goal of this study was to explore a route for introducing functionalities into agarose-based hydrogels to tune the physical, chemical, and biological properties. Several agarose derivatives were prepared by homogeneous synthesis, including anionic agarose sulfates (ASs), reactive azido agaroses (AZAs), and cationic agarose carbamates (ACs), as well as agarose tosylates (ATOSs) and agarose phenyl carbonates (APhCs). The products were characterized in terms of their molecular structure and solubility behavior. The results suggest that the native gel-forming ability of agarose is retained if the introduced functionalities are hydrophilic, and the overall degree of substitution is low (DS < 0.5). Thus, functional hydrogels from several agarose derivatives could be obtained. The mechanical stability of the functional hydrogels was decreased compared to native agarose gels but was still in a range that enables safe handling. An increase in mechanical strength could be achieved by blending functional agarose derivatives and agarose into composite hydrogels. Finally, it was demonstrated that the novel functional agarose hydrogels are biocompatible and can potentially stimulate interactions with cells and tissue
Adaptive Role of (Universal) Child Benefits in Emergency Responses in Turkey
No full textSocial Protection strategies aim to build resilience against various shocks and risks. Adaptive social protection incorporates shock responsiveness to foster adaptive capacity through preparedness, coping mechanisms, and adaptation strategies. Safety nets and universal child benefits are recommended as essential schemes within a crisis context. The Kızılaycard, compromising the Emergency Social Safety Net (ESSN) and conditional cash transfers for education (CCTE), emerged as national European Union-funded schemes expanded to accommodate refugees following the influx of the Syrian population into Turkey. These programs strive to achieve adaptive capacity outcomes for refugee children by addressing social, economic, physical, and institutional vulnerabilities.
A context-specified adaptive capacity outcome framework assesses how the Kızılaycard contributes adaptively to building resilience among children, informing policies on universal child benefits. The content analysis examines 50 policy documents, impact evaluations, 2 intersectoral vulnerability studies, and 4 expert interviews. In the development of multi-stakeholder cooperation, partners engage in policy dialogues, produce learning documents, and conduct evidence-based impact evaluations. While the programs demonstrate positive impacts on basic needs and education, their efficacy in fostering lasting positive coping strategies resilient to the economic crisis remains limited, with children’s outcomes inadequately specified. Policy discussions take place within Steering Committees consisting of international agencies, with recommendations from The World Bank and UNICEF advocating for Turkey's adoption of universal child benefits to enhance adaptive capacity in policy frameworks, transforming institutional vulnerability into effective support and capacity for children. However, institutional vulnerabilities persist in multi-crisis environments, hindering the adoption of adaptive, child-responsive benefits for vulnerable children
Social support and frailty progression in community-dwelling older adults
No full textObjectives: Despite the growing evidence regarding the influence of social factors on frailty in older adults, the effect of social support remains unclear. This study aims to assess the association between social support and frailty progression (transition and incidence) in a sample of community-dwelling older adults.
Methods: Using a cohort study design, 1,059 older adults from the Berlin Initiative Study were followed up for 2.1 years. Multinomial and logistic regression analyses were performed to assess the association of social support using Oslo Social Support Scale-3 with frailty transition and incidence, respectively. Gender differences were explored using stratified analyses.
Results: At baseline, frailty prevalence in the study population [mean (SD) age 84.3 (5.6) years; 55.8% women] reached 33.1% with 47.0, 29.4 and 23.6% of the participants reporting moderate, strong and poor social support, respectively. Over the follow-up period, social support was not significantly associated with the frailty transition categories in the adjusted model. Conversely, the adjusted logistic regression analysis showed that participants with poor social support had twice the odds of becoming frail compared to those with strong social support (OR 2.07; 95% CI 1.08–3.95). Gender-stratified analyses showed comparable estimates to the main analysis but were statistically non-significant.
Discussion: Our study results underpin the role of social factors in frailty incidence and highlight social support as a potential target for frailty-preventing interventions in older adults. Therefore, it is important to adopt a biopsychosocial model rather than a purely biomedical model to understand and holistically improve the health of community-dwelling older adults
Urothelkarzinom als Berufskrankheit/Einwirkungskausalität und Ursachenzusammenhang
No full textUrteil des 2. Senats des BSG vom 27.9.2023 – B 2 U 8/21 R – ECLI:DE:BSG:2023:270923UB2U821R
