Spectral separation of evoked and spontaneous cortical activity, Part 2: Somatosensory high frequency oscillations. - In: Biomedical signal processing and control, ISSN 1746-8108, Volume 95, part A (2024), article 106456, S. 1-8
N-Interval Fourier Analysis (N-FTA) allows for simultaneous spectral assessment of evoked and spontaneous activity in the frequency domain. We applied this method to signals following peripheral electrical nerve stimulation and performed analysis of cortical somatosensory evoked potentials within the 400 to 750 Hz band. For median nerve stimulation, data from eleven volunteers were analyzed. For tibial nerve stimulation, three subjects were investigated. For both stimulation sites, evoked high frequency oscillations (HFOs) components were identified. Furthermore, two kinds of background HFO activity were detected in sham stimulation trials. Spectral component models were applied for quantifying signal properties. Evoked spectral components reflected HFOs being time-locked to the stimulus. The detected spectral components were distributed over the entire investigated spectral band. Their spectral amplitude was close to the limit of the resolution of N-FTA. The experimentally observed spectral amplitude were in quantitative agreement with a model using a Morlet morphology. Within the HFO band, a flat noise floor was observed. Spontaneous physiological background activity contributes significantly to the spectral amplitude. This random activity is the dominant source of interference when extracting evoked HFOs. Within the HFO band, narrow spectral peaks in background activity were detected – both for real and sham stimulation. In the data sampled at 9.6 kHz, such peaks were observed in all recordings. For the 5.0 kHz sampling rate, these peaks were visible in about half of the recordings, and their amplitude was reduced. Based on a mathematical model, these peaks may be generated by organized spontaneous HFO activity producing a stable background wave.
https://doi.org/10.1016/j.bspc.2024.106456
A deep learning approach to explore the association of age-related macular degeneration polygenic risk score with retinal optical coherence tomography: a preliminary study. - In: Acta ophthalmologica, ISSN 1755-3768, Bd. 0 (2024), 0, S. 1-11
Purpose: Age-related macular degeneration (AMD) is a complex eye disorder affecting millions worldwide. This article uses deep learning techniques to investigate the relationship between AMD, genetics and optical coherence tomography (OCT) scans. Methods: The cohort consisted of 332 patients, of which 235 were diagnosed with AMD and 97 were controls with no signs of AMD. The genome-wide association studies summary statistics utilized to establish the polygenic risk score (PRS) in relation to AMD were derived from the GERA European study. A PRS estimation based on OCT volumes for both eyes was performed using a proprietary convolutional neural network (CNN) model supported by machine learning models. The method's performance was assessed using numerical evaluation metrics, and the Grad-CAM technique was used to evaluate the results by visualizing the features learned by the model. Results: The best results were obtained with the CNN and the Extra Tree regressor (MAE = 0.55, MSE = 0.49, RMSE = 0.70, R2 = 0.34). Extending the feature vector with additional information on AMD diagnosis, age and smoking history improved the results slightly, with mainly AMD diagnosis used by the model (MAE = 0.54, MSE = 0.44, RMSE = 0.66, R2 = 0.42). Grad-CAM heatmap evaluation showed that the model decisions rely on retinal morphology factors relevant to AMD diagnosis. Conclusion: The developed method allows an efficient PRS estimation from OCT images. A new technique for analysing the association of OCT images with PRS of AMD, using a deep learning approach, may provide an opportunity to discover new associations between genotype-based AMD risk and retinal morphology.
https://doi.org/10.1111/aos.16710
Hierarchical model-based cybersecurity risk assessment during system design. - In: ICT systems security and privacy protection, (2024), S. 30-44
Cybersecurity risk assessment has become a critical priority in systems development and the operation of complex networked systems. However, current state-of-the-art approaches for detecting vulnerabilities, such as automated security testing or penetration testing, often result in late detections. Thus, there is a growing need for security by design, which involves conducting security-related analyses as early as possible in the system development life cycle. This paper proposes a novel hierarchical model-based security risk assessment approach that enables the early assessment of security risks during the system design process. The approach uses different OMG UML-based models, supplemented by a lightweight extension using profiles and stereotypes. Various security attributes, including vulnerability information and asset values, are then used by algorithms to compute relevant properties including threat space, possible attack paths, and selected network-based security metrics. A real-life industrial example is then used to demonstrate the approach.
GOLDi labs as fully integrated learning environment. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), insges. 6 S.
Our vision is that an online lab will no longer be seen as a collection of monolithically constructed experiments but as a collection of laboratory devices communicating with each other. Nowadays, many interested learners have their own hardware at home. Therefore, an extension to the GOLDi remote lab, we provide learners with an interface unit, which in turn means they can easily connect to this interface with their control units and thus have the possibility to control these complex hardware models (from home). The availability of learning management systems and their LTI (Learning Tools Interoperability) extensibility ultimately leads to a fully integrated learning environment.
https://doi.org/10.1109/EDUNINE60625.2024.10500662
MagneticPillars: efficient point cloud registration through hierarchized Birds-Eye-View cell correspondence refinement. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), S. 7371-7380
Recent point cloud registration approaches often deal with a consecutive determination of coarse and fine feature correspondences for hierarchical pose refinement. Due to the unordered nature of point clouds, a common way to generate a subsampled representation for the coarse matching step is by applying 3D-sensitive convolution approaches. However, expensive grouping mechanisms such as nearest neighbour search have to be used to determine the associated fine features, generating individual associations for each point cloud and leading to an increased overall run-time. Furthermore current methods often tend to predict deficient point correspondences and rely on additional filtering by expensive registration backends like RANSAC impeding their application in time critical systems.To overcome these challenges, we present MagneticPillars utilizing a Birds-Eye-View (BEV) grid representation, entailing fixed affiliations between coarse and fine feature cells. We show that by extracting correspondences in this manner, a small amount of key points is already sufficient to achieve an accurate pose estimation without external optimization methods like RANSAC. We evaluate our approach on two autonomous driving datasets for the task of point cloud registration by applying SVD as the backend, where we outperform recent state-of-the-art methods, reducing the rotation and translation error by 12% and 40%, respectively, and to top it all off, cutting runtime in half.
https://doi.org/10.1109/WACV57701.2024.00722
Chance-constrained optimal design of PV-based microgrids under grid blackout uncertainties. - In: Energies, ISSN 1996-1073, Bd. 17 (2024), 8, 1892, S. 1-15
A grid blackout is an intractable problem with serious economic consequences in many developing countries. Although it has been proven that microgrids (MGs) are capable of solving this problem, the uncertainties regarding when and for how long blackouts occur lead to extreme difficulties in the design and operation of the related MGs. This paper addresses the optimal design problem of the MGs considering the uncertainties of the blackout starting time and duration utilizing the kernel density estimator method. Additionally, uncertainties in solar irradiance and ambient temperature are also considered. For that, chance-constrained optimization is employed to design residential and industrial PV-based MGs. The proposed approach aims to minimize the expected value of the levelized cost of energy (LCOE), where the restriction of the annual total loss of power supply (TLPS) is addressed as a chance constraint. The results show that blackout uncertainties have a considerable effect on calculating the size of the MG’s components, especially the battery bank size. Additionally, it is proven that considering the uncertainties of the input parameters leads to an accurate estimation for the LCOE and increases the MG reliability level.
https://doi.org/10.3390/en17081892
Are hemodynamics responsible for inflammatory changes in venous vessel walls? : a quantitative study of wall-enhancing intracranial arteriovenous malformation draining veins. - In: Journal of neurosurgery, ISSN 1933-0693, Bd. 0 (2024), 0, S. 1-10
Objective: Signal enhancement of vascular walls on vessel wall MRI might be a biomarker for inflammation. It has been theorized that contrast enhancement on vessel wall imaging (VWI) in draining veins of intracranial arteriovenous malformations (AVMs) may be associated with disease progression and development of venous stenosis. The aim of this study was to investigate the relationship between vessel wall enhancement and hemodynamic stressors along AVM draining veins. Methods: Eight AVM patients with 15 draining veins visualized on VWI were included. Based on MR venography data, patient-specific 3D surface models of the venous anatomy distal to the nidus were segmented. The enhanced vascular wall regions were manually extracted and mapped onto the venous surface models after registration of image data. Using image-based blood flow simulations applying patient-specific boundary conditions based on phase-contrast quantitative MR angiography, hemodynamics were investigated in the enhanced vasculature. For the shear-related parameters, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) were calculated. Velocity, oscillatory velocity index (OVI), and vorticity were extracted for the intraluminal flow-related hemodynamics. Results: Visual observations demonstrated overlap of enhancement with local lower shear stresses resulting from decreased velocities. Thus, higher RRT values were measured in the enhanced areas. Furthermore, nonenhancing draining veins showed on average slightly higher flow velocities and TAWSS. Significant decreases of 55% (p = 0.03) for TAWSS and of 24% (p = 0.03) for vorticity were identified in enhanced areas compared with near distal and proximal domains. Velocity magnitude in the enhanced region showed a nonsignificant decrease of 14% (p = 0.06). Furthermore, increases were present in the OSI (32%, p = 0.3), RRT (25%, p = 0.15), and OVI (26%, p = 0.3) in enhanced vessel sections, although the differences were not significant. Conclusions: This novel multimodal investigation of hemodynamics in AVM draining veins allows for precise prediction of occurring shear- and flow-related phenomena in enhanced vessel walls. These findings may suggest low shear to be a local predisposing factor for venous stenosis in AVMs.
https://doi.org/10.3171/2024.1.JNS232625
Deontic knowledge representation and reasoning in industrial accident prevention training by means of time travel prevention games. - In: International journal of advanced corporate learning, ISSN 1867-5565, Bd. 17 (2024), 2, S. 4-16
Industrial accident prevention is an issue of societal relevance to avoid loss of human lives, injuries, damage of installations, and financial losses. The authors deploy game-based training in virtual environments where trainees experience challenges of safe operation and disastrous self-induced accidents. Nothing is more affective and, thus, effective than a trainee’s own experience. Time travel prevention games are a game category particularly tailored to the needs of human players who look for opportunities to make good for a damage. Time travel pre-vention games for purposes such as accident prevention in the industries are ad-vantageous due to their conservation of resources including human health and lives. They are affective by allowing for unprecedented learner/player/trainee ex-periences and they are effective due to the fascination of application-oriented game play including opportunities to influence the fate, the latter being less close to reality, but the more attractive and worth telling. For optimal guidance to human trainees, the digital game system needs to learn about the trainees’ strength and weaknesses, about needs and desires. In terms of behavioral sciences, the system observing a human’s behavior hypothesizes theories of mind. In training games, modalities of events/actions are decisive. There are modalities of events/actions such as possibility, unavoidability, and the like as well as obliga-tions and oughts. Training aims at the emergence of cognitive states that are use-ful in practice. The system’s reasoning is deontic.
https://doi.org/10.3991/ijac.v17i2.42975
APP-CEP: adaptive pattern-level privacy protection in complex event processing systems. - In: Proceedings of the 10th International Conference on Information Systems Security and Privacy, Volume 1, (2024), S. 486-497
Although privacy-preserving mechanisms endeavor to safeguard sensitive information at the attribute level, detected event patterns can still disclose privacy-sensitive knowledge in distributed complex event processing systems (DCEP). Events might not be inherently sensitive, but their aggregation into a pattern could still breach privacy. In this paper, we study in the context of APP-CEP the problem of integrating pattern-level privacy in event-based systems by selective assignment of obfuscation techniques to conceal private information. Compared to state-of-the-art techniques, we seek to enforce privacy independent of the actual events in streams. To support this, we acquire queries and privacy requirements using CEP-like patterns. The protection of privacy is accomplished through generating pattern dependency graphs, leading to dynamically appointing those techniques that have no consequences on detecting other sensitive patterns, as well as non-sensitive patterns required to prov ide acceptable Quality of Service. Besides, we model the knowledge that might be possessed by potential adversaries to violate privacy and its impacts on the obfuscation procedure. We assessed the performance of APP-CEP in a real-world scenario involving an online retailer’s transactions. Our evaluation results demonstrate that APP-CEP successfully provides a privacy-utility trade-off. Modeling the background knowledge also effectively prevents adversaries from realizing the modifications in the input streams.
https://doi.org/10.5220/0012358700003648
Increasing resilience of SD-WAN by distributing the control plane [extended version]. - In: IEEE transactions on network and service management, ISSN 1932-4537, (2024), S. 1-13
Modern WAN interconnects utilize SD-WAN to automatically respond to network changes and improve link utilization, latency, and availability. Therefore, they incorporate controllers with a centralized view, which collect network state from managed gateways, calculate suitable forwarding actions, and distribute them accordingly. However, this limits the robustness and availability of the network control plane, especially in the event of node or partial network outages. In this paper, we propose a distributed and highly robust SD-WAN control plane without any central or regional controller. Our solution can handle arbitrary device failures as well as network partitioning. The distributed forwarding decisions are based on user-defined, dynamically evaluated path cost functions, and consider not only path quality but also quality fluctuations. The evaluation shows that our approach can handle several thousand SD-WAN gateways and hundreds of network policies in terms of computation. Further, the communication overhead introduced due to its distributed architecture is discussed and shown to be negligible compared to a central approach. This paper is an extended version of our work published in altheide2023. It describes the information transmitted between sites as well as a strategy for deploying policies, discusses approaches reducing communication bandwidth, introduces grouping of multiple flows without requiring explicit coordination, and provides a detailed analysis of the bandwidth required.
https://doi.org/10.1109/TNSM.2024.3386962