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- 저자 : Hubner, David (검색결과 11 건)
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Hubner, David,Verhoeven, Thibault,Muller, Klaus-Robert,Kindermans, Pieter-Jan,Tangermann, Michael IEEE 2018 IEEE computational intelligence magazine Vol.13 No.2
<P>One of the fundamental challenges in brain-computer interfaces (BCIs) is to tune a brain signal decoder to reliably detect a user's intention. While information about the decoder can partially be transferred between subjects or sessions, optimal decoding performance can only be reached with novel data from the current session. Thus, it is preferable to learn from unlabeled data gained from the actual usage of the BCI application instead of conducting a calibration recording prior to BCI usage. We review such unsupervised machine learning methods for BCIs based on event-related potentials of the electroencephalogram. We present results of an online study with twelve healthy participants controlling a visual speller. Online performance is reported for three completely unsupervised learning methods: (1) learning from label proportions, (2) an expectation-maximization approach and (3) MIX, which combines the strengths of the two other methods. After a short ramp-up, we observed that the MIX method not only defeats its two unsupervised competitors but even performs on par with a state-of-the-art regularized linear discriminant analysis trained on the same number of data points and with full label access. With this online study, we deliver the best possible proof in BCI that an unsupervised decoding method can in practice render a supervised method unnecessary. This is possible despite skipping the calibration, without losing much performance and with the prospect of continuous improvement over a session. Thus, our findings pave the way for a transition from supervised to unsupervised learning methods in BCIs based on eventrelated potentials.</P>
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Implementing Internet-Assisted Distance Learning in Tonga : Educational and Social Issues
Ronald Mellado Miller,Clayton Hubner APEC국제교육협력원 2006 Asia-Pacific Cybereducation Journal Vol.2 No.1
Tonga, a geographically isolated developing nation in the South Pacific was chosen as the site for a pilot implementation of Internet-assisted distance learning. As a high context, traditional society, and the last kingdom in the Pacific, with a monarchy and social traditions stretching back more than a millennium, distance learning in Tonga could only be implemented by taking into account its history and culture as well as technical and educational issues. Educational issues encountered were computer literacy, teaching-learning styles, delivery mode, availability of off-the shelf courses, language barriers, curriculum alignment, remote and onsite functions, virtual office hours, and evaluation/assessment. Social-cultural issues included social protocols at a distance, conflict between new and traditional teaching-learning patterns, access to resources, security, and tribal mentality. The issues addressed appear to be some of those that will arise in other places pursuing the goal of ubiquitous education through distance learning, whether in geographically remote nations such as Tonga or in isolated locations within a larger high-context nation, such as China.
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Weiland, U.,Pietsch, J.,Hubner, M. Korean Society of Environmental Impact Assessment 1993 환경영향평가 Vol.2 No.2
Aims of the EXCEPT project and tasks and characteristics of the EXCEPT system are presented based on an analysis of urban planning EIAs. The methodology of evaluation in EIAs, which had to be developed in order to program the system, is based on a model of evaluation processes. Evaluation principles, evaluation rates, an environmental model and a model of the projects being planned are presented. The evaluation concern re-unifies the different components of evaluation again.
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Compressible Simulation of Rotor-Stator Interaction in Pump-Turbines
Yan, Jianping,Koutnik, Jiri,Seidel, Ulrich,Hubner, Bjorn Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.4
This work investigates the influence of water compressibility on pressure pulsations induced by rotor-stator interaction (RSI) in hydraulic machinery, using the commercial CFD solver ANSYS-CFX. A pipe flow example with harmonic velocity excitation at the inlet plane is simulated using different grid densities and time step sizes. Results are compared with a validated code for hydraulic networks (SIMSEN). Subsequently, the solution procedure is applied to a simplified 2.5-dimensional pump-turbine configuration in prototype with different speeds of sound as well as in model scale with an adapted speed of sound. Pressure fluctuations are compared with numerical and experimental data based on prototype scale. The good agreement indicates that the scaling of acoustic effects with an adapted speed of sound works well. With respect to pressure fluctuation amplitudes along the centerline of runner channels, incompressible solutions exhibit a linear decrease while compressible solutions exhibit sinusoidal distributions with maximum values at half the channel length, coinciding with analytical solutions of one-dimensional acoustics. Furthermore, in compressible simulation the amplification of pressure fluctuations is observed from the inlet of stay vane channels to the spiral case wall. Finally, the procedure is applied to a three-dimensional pump configuration in model scale with adapted speed of sound. Normalized Pressure fluctuations are compared with results from prototype measurements. Compared to incompressible computations, compressible simulations provide similar pressure fluctuations in vaneless space, but pressure fluctuations in spiral case and penstock may be much higher.
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Changes of hemodynamic and cerebral oxygenation after exercise in normobaric and hypobaric hypoxia
Tobias Kammerer,Valentina Faihs,Nikolai Hulde,Andreas Bayer,Max Hubner,Florian Brettner,Walter Karlen,Julia Maria Kropfl,Markus Rehm,Christina Spengler,Simon Thomas Schafer 대한직업환경의학회 2018 대한직업환경의학회지 Vol.30 No.-
Objective: Normobaric (NH) and hypobaric hypoxia (HH) are associated with acute mountain sickness (AMS) and cognitive dysfunction. Only few variables, like heart-rate-variability, are correlated with AMS. However, prediction of AMS remains difficult. We therefore designed an expedition-study with healthy volunteers in NH/HH to investigate additional non-invasive hemodynamic variables associated with AMS. Methods: Eleven healthy subjects were examined in NH (FiO₂ 13.1%; equivalent of 3.883 m a.s.l; duration 4 h) and HH (3.883 m a.s.l.; duration 24 h) before and after an exercise of 120 min. Changes in parameters of electrical cardiometry (cardiac index (CI), left-ventricular ejection time (LVET), stroke volume (SV), index of contractility (ICON)), near-infrared spectroscopy (cerebral oxygenation, rScO₂), Lake-Louise-Score (LLS) and cognitive function tests were assessed. One-Way-ANOVA, Wilcoxon matched-pairs test, Spearman’s-correlation-analysis and Student’s t-test were performed. Results: HH increased heart rate (HR), mean arterial pressure (MAP) and CI and decreased LVET, SV and ICON, whereas NH increased HR and decreased LVET. In both NH and HH cerebral oxygenation decreased and LLS increased significantly. After 24 h in HH, 6 of 11 subjects (54.6%) developed AMS. LLS remained increased until 24 h in HH, whereas cognitive function remained unaltered. In HH, HR and LLS were inversely correlated (r = − 0.692; p < 0.05). More importantly, the rScO2-decrease after exercise in NH significantly correlated with LLS after 24 h in HH (r = − 0.971; p < 0.01) and rScO2 correlated significantly with HR (r = 0.802; p < 0.01), CI (r = 0.682; p < 0.05) and SV (r = 0.709; p < 0.05) after exercise in HH. Conclusions: Both acute NH and HH altered hemodynamic and cerebral oxygenation and induced AMS. Subjects, who adapted their CI had higher rScO2 and lower LLS. Furthermore, rScO2 after exercise under normobaric conditions was associated with AMS at high altitudes.
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Hartmann, Thomas,Shrestha, Tej B.,Bossmann, Stefan H.,Hubner, Christian,Renn, Alois,Durr, Heinz Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.8
We have synthesized a prototype of a photochromic styrylquinolyl-dihydroindolizine (DHI), which forms a highly coloured and fluorescent betaine upon irradiation with $\lambda$ < 400 nm. Embedding this photochromic DHI in a thin polymethyl methacrylate (PMMA) film permits the non-destructive readout via fluorescence at low temperature (77 K). Thus, either a non-destructive photoswitch or an information recording system becomes available. Both possibilities have been explored: image recording and read-out, as well as information storage (at 77 K) have been demonstrated. Cluster- and single molecule-fluorescence upon laser excitation ($\lambda$ = 355 nm) of the styrylquinolyl-dihydroindolizine in a PMMA matrix, and the effect of fluorescence blinking has been observed.
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Wilke, Annika,Brans, Richard,Nordheider, Kathrin,Braumann, Antje,Hubner, Anja,Sonsmann, Flora K.,John, Swen M.,Wulfhorst, Britta Occupational Safety and Health Research Institute 2018 Safety and health at work Vol.9 No.4
Background: Occupational skin diseases (OSDs) are frequent in professions with exposure to skin hazards. Thus, a health educational intervention for apprentices of high-risk professions was conducted. It was the aim of this study to gain insight into possible effects of this intervention. Methods: A one-time skin protection seminar was conducted in 140 apprentices of health-related and non-health-related professions [trained cohort (TC)]. In addition, 134 apprentices of the same occupations were monitored [untrained cohort (UTC)]. The OSD-specific knowledge and the skin condition of the hands were assessed at baseline (T0), after the seminar (T1), and after 6 (T2) and 12 months (T3). Results: The OSD-specific knowledge increased in all cohorts from T0 to T3, but we found a significantly higher knowledge in the TC at T2 (p < 0.001, t = 3.6, df = 196, 95% confidence interval = 0.9, 3.3) and T3 (p < 0.001, t = 3.8, df = 196, 95% confidence interval = 1.0, 3.2) compared to the UTC. Our results indicated a better skin condition of the hands in the TC of the health-related professions but not in the non-health-related professions. Conclusion: The study indicates that an educational intervention may positively influence the disease-specific knowledge and the prevalence of OSD in apprentices. However, definite conclusions cannot be drawn because of the heterogeneous study cohorts and the study design. Future research should aim at tailoring primary prevention to specific target groups, e.g., in view of the duration and frequency of skin protection education, different professions, and gender-specific prevention approaches.
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Changes of hemodynamic and cerebral oxygenation after exercise in normobaric and hypobaric hypoxia
Tobias Kammerer,Valentina Faihs,Nikolai Hulde,Andreas Bayer,Max Hubner,Florian Brettner,Walter Karlen,Julia Maria Kropfl,Markus Rehm,Christina Spengler,Simon Thomas Schafer 대한직업환경의학회 2019 대한직업환경의학회지 Vol.30 No.-
Objective: Normobaric (NH) and hypobaric hypoxia (HH) are associated with acute mountain sickness (AMS) and cognitive dysfunction. Only few variables, like heart-rate-variability, are correlated with AMS. However, prediction of AMS remains difficult. We therefore designed an expedition-study with healthy volunteers in NH/HH to investigate additional non-invasive hemodynamic variables associated with AMS. Methods: Eleven healthy subjects were examined in NH (FiO2 13.1%; equivalent of 3.883 m a.s.l; duration 4 h) and HH (3.883 m a.s.l.; duration 24 h) before and after an exercise of 120 min. Changes in parameters of electrical cardiometry (cardiac index (CI), left-ventricular ejection time (LVET), stroke volume (SV), index of contractility (ICON)), near-infrared spectroscopy (cerebral oxygenation, rScO2), Lake-Louise-Score (LLS) and cognitive function tests were assessed. One-Way-ANOVA, Wilcoxon matched-pairs test, Spearman’s-correlation-analysis and Student’s t-test were performed. Results: HH increased heart rate (HR), mean arterial pressure (MAP) and CI and decreased LVET, SV and ICON, whereas NH increased HR and decreased LVET. In both NH and HH cerebral oxygenation decreased and LLS increased significantly. After 24 h in HH, 6 of 11 subjects (54.6%) developed AMS. LLS remained increased until 24 h in HH, whereas cognitive function remained unaltered. In HH, HR and LLS were inversely correlated (r = − 0.692; p < 0.05). More importantly, the rScO2-decrease after exercise in NH significantly correlated with LLS after 24 h in HH (r = − 0.971; p < 0.01) and rScO2 correlated significantly with HR (r = 0.802; p < 0.01), CI (r = 0.682; p < 0.05) and SV (r = 0.709; p < 0.05) after exercise in HH. Conclusions: Both acute NH and HH altered hemodynamic and cerebral oxygenation and induced AMS. Subjects, who adapted their CI had higher rScO2 and lower LLS. Furthermore, rScO2 after exercise under normobaric conditions was associated with AMS at high altitudes.
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