Shock-induced dual-layer evolution

Shock-induced fluid-layer evolution has attracted much attention but remains a challenge mainly because the coupling between layers remains unknown. Linear solutions are first derived to quantify the layer-coupling effect on the shocked dual-layer evolution. Next, the motions of the waves and interfaces of a dual layer are examined based on the one-dimensional gas dynamics theory. Shock-tube experiments on the dual-layer, single-layer and single-mode interface are then performed to validate the linear solutions and investigate the reverberating waves inside the layers. It is proved that the layer-coupling effect destabilises the dual layer, especially when the initial layers are thin, and the reverberating waves impose additional instabilities on all interfaces. Our findings suggest that a slow/fast configuration with a large thickness in a dual layer can facilitate the suppression of hydrodynamic instabilities.

Bottom-up and Layerwise Domain Adaptation for Pedestrian Detection in Thermal Images

Pedestrian detection is a canonical problem for safety and security applications, and it remains a challenging problem due to the highly variable lighting conditions in which pedestrians must be detected. This article investigates several domain adaptation approaches to adapt RGB-trained detectors to the thermal domain. Building on our earlier work on domain adaptation for privacy-preserving pedestrian detection, we conducted an extensive experimental evaluation comparing top-down and bottom-up domain adaptation and also propose two new bottom-up domain adaptation strategies. For top-down domain adaptation, we leverage a detector pre-trained on RGB imagery and efficiently adapt it to perform pedestrian detection in the thermal domain. Our bottom-up domain adaptation approaches include two steps: first, training an adapter segment corresponding to initial layers of the RGB-trained detector adapts to the new input distribution; then, we reconnect the adapter segment to the original RGB-trained detector for final adaptation with a top-down loss. To the best of our knowledge, our bottom-up domain adaptation approaches outperform the best-performing single-modality pedestrian detection results on KAIST and outperform the state of the art on FLIR.

Reduction of a model for sodium exchanges in kidney nephron

<p style='text-indent:20px;'>This work deals with a mathematical analysis of sodium's transport in a tubular architecture of a kidney nephron. The nephron is modelled by two counter-current tubules. Ionic exchange occurs at the interface between the tubules and the epithelium and between the epithelium and the surrounding environment (interstitium). From a mathematical point of view, this model consists of a 5<inline-formula><tex-math id="M1">\begin{document}$ \times $\end{document}</tex-math></inline-formula>5 semi-linear hyperbolic system. In literature similar models neglect the epithelial layers. In this paper, we show rigorously that such models may be obtained by assuming that the permeabilities between lumen and epithelium are large. We show that when these permeabilities grow, solutions of the 5<inline-formula><tex-math id="M2">\begin{document}$ \times $\end{document}</tex-math></inline-formula>5 system converge to those of a reduced 3<inline-formula><tex-math id="M3">\begin{document}$ \times $\end{document}</tex-math></inline-formula>3 system without epithelial layers. The problem is defined on a bounded spacial domain with initial and boundary data. In order to show convergence, we use <inline-formula><tex-math id="M4">\begin{document}$ {{{\rm{BV}}}} $\end{document}</tex-math></inline-formula> compactness, which leads to introduce initial layers and to handle carefully the presence of lateral boundaries. We then discretize both 5<inline-formula><tex-math id="M5">\begin{document}$ \times $\end{document}</tex-math></inline-formula>5 and 3<inline-formula><tex-math id="M6">\begin{document}$ \times $\end{document}</tex-math></inline-formula>3 systems, and show numerically the same asymptotic result, for a fixed meshsize.</p>

Formation Mechanism of Dilute Region and Microstructure Evolution in Laser Solid Forming TA15/Ti2AlNb Dual Alloy

TA15/Ti2AlNb multiple-layer samples and a dual-alloy sample were fabricated by laser solid forming (LSF) in this study. The formation mechanism of the dilute region and microstructure evolution of the dual alloy were analyzed. The results confirmed a “step” distribution of the composition among several initial layers in the multiple-layer samples, which can be explained by calculating the ratio of the remelted zone to the deposited Ti2AlNb zone in each deposited layer. However, the “step” compositional distribution disappears, and the compositional variation tends to be more continuous and smooth in the TA15/Ti2AlNb dual-alloy sample, which is attributed to alloy elements’ diffusion at the subsequent multiple re-melting and the longer thermal cycle. The macrostructure of the TA15/Ti2AlNb dual-alloy sample consists of epitaxially grown columnar prior β grains at the TA15 side and equiaxed grains at the Ti2AlNb side, while the microstructure shows a transition of α+β→α+α2+β/B2→α2+β/B2→α2+B2+O with increasing amounts of Ti2AlNb, leading to the microhardness also changing significantly.