| 1. |
- Ly, Duy Nam, et al.
(författare)
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360TourGuiding: Towards Virtual Reality Training for Tour Guiding
- 2022
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Ingår i: MobileHCI 2022 Adjunct - Publication of the 24th ACM International Conference on Human-Computer Interaction with Mobile Devices and Services. - New York, NY, USA : ACM.
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Konferensbidrag (refereegranskat)abstract
- Tour guiding plays an important role in turning sightseeing tours into memorable experiences. Tour guides, especially inexperienced ones, must practice intensively to perfect their craft. It is key that guides acquire knowledge about sights, in-situ presentation skills, and perfection ability to interact with and engage tourists. Therefore, tour-guide education requires on-site training at the place of interest including live tourist audiences. However, for modest budgets, such setups are costly and tourism students have to practice tour guiding at home or in simulated class-room setups. It has become a challenge for students to adequately prepare themselves for jobs in terms of relevant knowledge and skills. To tackle this problem, we propose 360TourGuiding, a VR system enabling its users to practice tour guiding with 360 travel videos plus the attendance of remote audiences participating through their mobile and personal device. This paper reports on the concept, on our design, current implementation, and on a pilot study with the current 360TourGuiding prototype. Based on qualitative feedback gained through the pilot study, we discuss possible system improvements, future system updates, and plans for empirical evaluation.
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| 2. |
- Armakavicius, Nerijus, 1989-, et al.
(författare)
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Electron effective mass in GaN revisited: New insights from terahertz and mid-infrared optical Hall effect
- 2024
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Ingår i: APL Materials. - : AIP Publishing. - 2166-532X. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Electron effective mass is a fundamental material parameter defining the free charge carrier transport properties, but it is very challenging to be experimentally determined at high temperatures relevant to device operation. In this work, we obtain the electron effective mass parameters in a Si-doped GaN bulk substrate and epitaxial layers from terahertz (THz) and mid-infrared (MIR) optical Hall effect (OHE) measurements in the temperature range of 38-340 K. The OHE data are analyzed using the well-accepted Drude model to account for the free charge carrier contributions. A strong temperature dependence of the electron effective mass parameter in both bulk and epitaxial GaN with values ranging from (0.18 +/- 0.02) m(0) to (0.34 +/- 0.01) m(0) at a low temperature (38 K) and room temperature, respectively, is obtained from the THz OHE analysis. The observed effective mass enhancement with temperature is evaluated and discussed in view of conduction band nonparabolicity, polaron effect, strain, and deviations from the classical Drude behavior. On the other hand, the electron effective mass parameter determined by MIR OHE is found to be temperature independent with a value of (0.200 +/- 0.002) m(0). A possible explanation for the different findings from THz OHE and MIR OHE is proposed. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
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| 3. |
- Delgado Carrascon, Rosalia, et al.
(författare)
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Optimization of GaN Nanowires Reformation Process by Metalorganic Chemical Vapor Deposition for Device-Quality GaN Templates
- 2020
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Ingår i: Physica Status Solidi (B) Basic Research. - : Wiley. - 0370-1972 .- 1521-3951. ; 257:4
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Tidskriftsartikel (refereegranskat)abstract
- Herein, the potential of reformed GaN nanowires (NWs) fabricated by metalorganic chemical vapor deposition (MOCVD) for device-quality low-defect density templates and low-cost alternative to bulk GaN substrates is demonstrated. The effects of epilayer thickness and NW reformation conditions on the crystalline quality and thermal conductivity of the subsequent GaN epilayers are investigated. Smooth surfaces with atomically step-like morphologies with no spirals are achieved for GaN epilayers on the reformed NW templates, indicating step-flow growth mode. It is further found that annealing of the NWs at a temperature of 1030 °C in the presence of NH3 and H2, followed by a coalescence done at the same temperature under planar growth conditions, leads to the most efficient screw dislocation density reduction by nearly an order of magnitude. At these optimized conditions, the growth takes place in a layer-by-layer fashion, producing a smooth surface with a root mean square (RMS) roughness of 0.12 nm. The highest thermal conductivity of k = 206 W m−1 K−1, approaching the respective value of bulk GaN, is obtained for the optimized 2 μm-thick GaN layer. The thermal conductivity results are further discussed in terms of the phonon-dislocation and the phonon-boundary scattering.
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| 4. |
- Duyen, Nguyen Thi, et al.
(författare)
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Steroid glycosides isolated from Paris polyphylla var. chinensis aerial parts and paris saponin II induces G1/S-phase MCF-7 cell cycle arrest
- 2022
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215. ; 519
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Tidskriftsartikel (refereegranskat)abstract
- In our previous research on Vietnamese medicinal plants, we found that the ethanolic extract of the aerial parts of Paris polyphylla var. chinensis exhibited cytotoxic effects in vitro in the MCF-7 human cancer cell line. Here, we used combined chromatographic separations to isolate six compounds including a new steroid glycoside, paripoloside A (3), and five known compounds, from the butanol extract of the aerial parts of P. polyphylla. We unambiguously elucidated their structures based on spectroscopic data (proton and carbon-13 nuclear magnetic resonance, heteronuclear single quantum coherence, heteronuclear multiple bond correlation, correlation spectroscopy, and high-resolution electrospray ionization mass spectroscopy data), and chemical reactions. Among the isolated compounds, paris saponin II (PSII) had the strongest cytotoxic effects against MCF-7 breast cancer cells. Interestingly, PSII significantly increased the expression of p53, p21, p27, and Bax protein levels and significantly suppressed the expression of cyclin D1 and retinoblastoma protein. These data suggest that PSII may induce G1/S phase cell cycle arrest and apoptosis pathway development in MCF-7 cells. Furthermore, the MCF-7 breast cancer cells mechanism of PSII was also investigated using molecular docking. Together, our results demonstrate that isolated compounds from P. polyphylla are promising candidates as breast cancer inhibitors.
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| 5. |
- Gogova, Daniela, et al.
(författare)
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Epitaxial growth of β -Ga 2 O 3 by hot-wall MOCVD
- 2022
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 12:5, s. 055022-055022
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Tidskriftsartikel (refereegranskat)abstract
- The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and highperformance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth ofβ-Ga2O3. Epitaxial β-Ga2O3 layers at high growth rates (above 1 μm/h), at low reagent flows, and at reduced growth temperatures(740 ○C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. Thehot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial β-Ga2O3 layers are demonstrated with a 201 ¯rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) ¯ β-Ga2O3 substrates, indicative ofsimilar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be furtherexplored for the fabrication of β-Ga2O3
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| 6. |
- Gogova, Daniela, 1967-, et al.
(författare)
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Epitaxial growth of β-Ga2O3 by hot-wall MOCVD
- 2022
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of beta-Ga2O3. Epitaxial beta-Ga2O3 layers at high growth rates (above 1 mu m/h), at low reagent flows, and at reduced growth temperatures (740 degrees C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial beta-Ga2O3 layers are demonstrated with a 201 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) beta-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of beta-Ga2O3.
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| 7. |
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| 8. |
- Kuhne, Philipp, et al.
(författare)
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Enhancement of 2DEG effective mass in AlN/Al0.78Ga0.22N high electron mobility transistor structure determined by THz optical Hall effect
- 2022
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 120:25
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Tidskriftsartikel (refereegranskat)abstract
- We report on the free charge carrier properties of a two-dimensional electron gas (2DEG) in an AlN/AlxGa1-xN high electron mobility transistor structure with a high aluminum content (x = 0.78). The 2DEG sheet density N s = ( 7.3 +/- 0.7 ) x 10 12 cm(-2), sheet mobility mu s = ( 270 +/- 40 ) cm(2)/(Vs), sheet resistance R- s = ( 3200 +/- 500 ) omega/ ?, and effective mass m( eff) = ( 0.63 +/- 0.04 ) m( 0) at low temperatures ( T = 5 K ) are determined by terahertz (THz) optical Hall effect measurements. The experimental 2DEG mobility in the channel is found within the expected range, and the sheet carrier density is in good agreement with self-consistent Poisson-Schrodinger calculations. However, a significant increase in the effective mass of 2DEG electrons at low temperatures is found in comparison with the respective value in bulk Al0.78Ga22N ( m( eff) = 0.334 m( 0)). Possible mechanisms for the enhanced 2DEG effective mass parameter are discussed and quantified using self-consistent Poisson-Schrodinger calculations .Published under an exclusive license by AIP Publishing.
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| 9. |
- Pham, Tuan D, et al.
(författare)
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Fuzzy information fusion of classification models for high-throughput image screening of cancer cells in time-lapse microscopy
- 2007
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Ingår i: Journal of Knowledge-based & Intelligent Engineering Systems. - : IOS Press. - 1327-2314 .- 1875-8827. ; 11:4, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- Bioimaging at molecular and cellular levels requires specific image analysis methods to help life scientists develop methodologies and hypotheses in biology and biomedicine. In particular, this is true when dealing with microscopic images of cells and vessels. To facilitate the automation of cell screening, we have developed methods based on vector quantization and Markov model for classification of cellular phases using time-lapse fluorescence microscopic image sequences. Because of ambiguity inherently existing in the labeling of cell-phase feature vectors, we proposed to use relaxation labeling technique to reduce uncertainty among cell-phase models having overlapping properties. To further improve the classification rate we applied a fuzzy fusion strategy for combining individual results obtained from multiple classifiers. Our proposed image-classification methods can be useful for the task of high-content cell-cycle screening which is essential for biomedical research in the study of structures and functions of cells and molecules.
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| 10. |
- Quach, Kha Gia, et al.
(författare)
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Dyglip: A dynamic graph model with link prediction for accurate multi-camera multiple object tracking
- 2021
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Ingår i: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. ; , s. 13779-13788
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Konferensbidrag (refereegranskat)abstract
- Multi-Camera Multiple Object Tracking (MC-MOT) is a significant computer vision problem due to its emerging applicability in several real-world applications. Despite a large number of existing works, solving the data association problem in any MC-MOT pipeline is arguably one of the most challenging tasks. Developing a robust MC-MOT system, however, is still highly challenging due to many practical issues such as inconsistent lighting conditions, varying object movement patterns, or the trajectory occlusions of the objects between the cameras. To address these problems, this work, therefore, proposes a new Dynamic Graph Model with Link Prediction (DyGLIP) approach to solve the data association task. Compared to existing methods, our new model offers several advantages, including better feature representations and the ability to recover from lost tracks during camera transitions. Moreover, our model works gracefully regardless of the overlapping ratios between the cameras. Experimental results show that we outperform existing MC-MOT algorithms by a large margin on several practical datasets. Notably, our model works favorably on online settings but can be extended to an incremental approach for large-scale datasets.
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