CFD modelling of air flow and fine powder deposition in the respiratory tract

This project was to investigate and observe characteristics of micro particles suspended in the ambient air or pharmaceutical aerosols with respect to the mechanisms of deposition in human airways under different inspiratory conditions. Such determination includes pattern observations of inspiratory flow-field of the air, particle trajectory during inspiratory conditions and particle deposition. Computational fluid dynamic (CFD) was employed to simulate above problems, aiming to observe flow-field of the inspiratory air and characteristic of flow turbulence in the respiratory tract as well as particle behaviour in the respiratory tract regarding to the particle deposition. In order to do so, three different airway models were employed for the simulations: two realistic airway models introduced by Kitaoka and Weibel airways model. The motion of micro-sized particles between 1~20 μm were simulated under the steady state two inlet-inspiratory conditions – inhalation condition (60 L/min) and breathing condition (18 L/min); to evaluate deposition efficiency. Inertial impaction was dominantly caused high density deposition of particles in upper tracheobronchial region, particularly in regions where daughter airways bifurcate. Results also showed that the velocity in the first bifurcation of airway was higher than the inlet velocity. Back pressures were been observed in lower generations, and high pressures were been observed at every bifurcation regions. The increase of velocity was observed where the fluid directions rapidly changed. Turbulence kinetic energy was the least in main bronchus of respiratory tract and fluctuated from generation to generation. In Kitaoka’s generation 0-7 model, deposition fractions of 2 μm, 6 μm and 10 μm particles were 6.6%, 60.7% and 91.5% respectively under inhalation condition whereas deposition fractions of such particles were 2.9%, 9.0% and 44.9% under breathing condition. In Kitaoka’s generation 0-11 model, deposition fractions of 2 μm, 6 μm and 10 μm particles were 30.9%, 80.1% and 99.8% respectively under inhalation condition whereas deposition fractions of such particles were 16.2%, 24.4% and 62.6% under breathing condition. Furthermore in Weibel’s generation 3-6 model, deposition fractions of 2 μm, 6 μm and 10 μm particles were 9.7%, 38.3% and 97.4% respectively under inhalation condition whereas deposition fractions of such particles were 3.2%, 15.6% and 56.2% under breathing condition

SPANet: Frequency-balancing Token Mixer using Spectral Pooling Aggregation Modulation

Recent studies show that self-attentions behave like low-pass filters (as opposed to convolutions) and enhancing their high-pass filtering capability improves model performance. Contrary to this idea, we investigate existing convolution-based models with spectral analysis and observe that improving the low-pass filtering in convolution operations also leads to performance improvement. To account for this observation, we hypothesize that utilizing optimal token mixers that capture balanced representations of both high- and low-frequency components can enhance the performance of models. We verify this by decomposing visual features into the frequency domain and combining them in a balanced manner. To handle this, we replace the balancing problem with a mask filtering problem in the frequency domain. Then, we introduce a novel token-mixer named SPAM and leverage it to derive a MetaFormer model termed as SPANet. Experimental results show that the proposed method provides a way to achieve this balance, and the balanced representations of both high- and low-frequency components can improve the performance of models on multiple computer vision tasks. Our code is available at $\href{https://doranlyong.github.io/projects/spanet/}{\text{https://doranlyong.github.io/projects/spanet/}}$.Comment: Accepted paper at ICCV 202

A new species of torrent catfish, Liobagrus geumgangensis (Teleostei, Siluriformes, Amblycipitidae), from Korea

In a recent survey of populations of the Korean torrent catfish Liobagrus, a distinctive species was discovered from the Geum River and its tributaries flowing into the western coast of Korea, and here described as a new species, L. geumgangensis sp. nov. It is distinguishable from other congeners by a combination of the following characters: I, 8 pectoral fin-rays; 52–56 caudal-fin rays; a relatively short occiput to dorsal-fin origin distance (6.9–9.8% SL); a short pelvic-fin insertion to anal-fin origin distance (11.9–17.3% SL); a long dorsal-fin base (10.6–13.5% SL); 8–9 gill rakers; 5–8 serrations on the pectoral fin; the body and fins are dark yellow, the margins of the dorsal, anal, and caudal fins are dark brown, but the outermost rim is faintly yellow. Analysis of the cytb gene also confirmed that L. geumgangensis is a monophyletic lineage distinct from other congeners