370 research outputs found
E-beam-enhanced solid-state mechanical amorphization of alpha-quartz: Reducing deformation barrier via localized excess electrons as mobile anions
Under hydrostatic pressure, alpha-quartz undergoes solid-state mechanical
amorphization wherein the interpenetration of SiO4 tetrahedra occurs and the
material loses crystallinity. This phase transformation requires a high
hydrostatic pressure of 14 GPa because the repulsive forces resulting from the
ionic nature of the Si-O bonds prevent the severe distortion of the atomic
configuration. Herein, we experimentally and computationally demonstrate that
e-beam irradiation changes the nature of the interatomic bonds in alpha-quartz
and enhances the solid-state mechanical amorphization at nanoscale.
Specifically, during in situ uniaxial compression, a larger permanent
deformation occurs in alpha-quartz micropillars compressed during e-beam
irradiation than in those without e-beam irradiation. Microstructural analysis
reveals that the large permanent deformation under e-beam irradiation
originates from the enhanced mechanical amorphization of alpha-quartz and the
subsequent viscoplastic deformation of the amorphized region. Further,
atomic-scale simulations suggest that the delocalized excess electrons
introduced by e-beam irradiation move to highly distorted atomic configurations
and alleviate the repulsive force, thus reducing the barrier to the solid-state
mechanical amorphization. These findings deepen our understanding of
electron-matter interactions and can be extended to new glass forming and
processing technologies at nano- and microscale.Comment: 24 pages, 6 figure
Monoclinic and Correlated Metal Phase in VO_2 as Evidence of the Mott Transition: Coherent Phonon Analysis
In femtosecond pump-probe measurements, the appearance of coherent phonon
oscillations at 4.5 THz and 6.0 THz indicating the rutile metal phase of VO_2
does not occur simultaneously with the first-order metal-insulator transition
(MIT) near 68^oC. The monoclinic and correlated metal(MCM) phase between the
MIT and the structural phase transition (SPT) is generated by a photo-assisted
hole excitation which is evidence of the Mott transition. The SPT between the
MCM phase and the rutile metal phase occurs due to subsequent Joule heating.
The MCM phase can be regarded as an intermediate non-equilibrium state.Comment: 4 pages, 2 figure
High-fidelity 3D Human Digitization from Single 2K Resolution Images
High-quality 3D human body reconstruction requires high-fidelity and
large-scale training data and appropriate network design that effectively
exploits the high-resolution input images. To tackle these problems, we propose
a simple yet effective 3D human digitization method called 2K2K, which
constructs a large-scale 2K human dataset and infers 3D human models from 2K
resolution images. The proposed method separately recovers the global shape of
a human and its details. The low-resolution depth network predicts the global
structure from a low-resolution image, and the part-wise image-to-normal
network predicts the details of the 3D human body structure. The
high-resolution depth network merges the global 3D shape and the detailed
structures to infer the high-resolution front and back side depth maps.
Finally, an off-the-shelf mesh generator reconstructs the full 3D human model,
which are available at https://github.com/SangHunHan92/2K2K. In addition, we
also provide 2,050 3D human models, including texture maps, 3D joints, and SMPL
parameters for research purposes. In experiments, we demonstrate competitive
performance over the recent works on various datasets.Comment: code page : https://github.com/SangHunHan92/2K2K, Accepted to CVPR
2023 (Highlight
The Differential Effects of Acute Right- vs. Left-Sided Vestibular Deafferentation on Spatial Cognition in Unilateral Labyrinthectomized Mice
This study aimed to investigate the disparity in locomotor and spatial memory deficits caused by left- or right-sided unilateral vestibular deafferentation (UVD) using a mouse model of unilateral labyrinthectomy (UL) and to examine the effects of galvanic vestibular stimulation (GVS) on the deficits over 14 days. Five experimental groups were established: the left-sided and right-sided UL (Lt.-UL and Rt.-UL) groups, left-sided and right-sided UL with bipolar GVS with the cathode on the lesion side (Lt.-GVS and Rt.-GVS) groups, and a control group with sham surgery. We assessed the locomotor and cognitive-behavioral functions using the open field (OF), Y maze, and Morris water maze (MWM) tests before (baseline) and 3, 7, and 14 days after surgical UL in each group. On postoperative day (POD) 3, locomotion and spatial working memory were more impaired in the Lt.-UL group compared with the Rt.-UL group (p < 0.01, Tamhane test). On POD 7, there was a substantial difference between the groups; the locomotion and spatial navigation of the Lt.-UL group recovered significantly more slowly compared with those of the Rt.-UL group. Although the differences in the short-term spatial cognition and motor coordination were resolved by POD 14, the long-term spatial navigation deficits assessed by the MWM were significantly worse in the Lt.-UL group compared with the Rt.-UL group. GVS intervention accelerated the vestibular compensation in both the Lt.-GVS and Rt.-GVS groups in terms of improvement of locomotion and spatial cognition. The current data imply that right- and left-sided UVD impair spatial cognition and locomotion differently and result in different compensatory patterns. Sequential bipolar GVS when the cathode (stimulating) was assigned to the lesion side accelerated recovery for UVD-induced spatial cognition, which may have implications for managing the patients with spatial cognitive impairment, especially that induced by unilateral peripheral vestibular damage on the dominant side
Methods and performance of a three-dimensional whole-core transport code DeCART
DeCART is a three-dimensional whole-core transport code capable of performing direct core calculations at power generating conditions without involving a priori homogenized few-group constant generation. In this paper, the methods of DeCART, which are characterized by the planar method of characteristics (MOC) solutions, the cell based coarse mesh finite difference (CMFD) formulation, the subgroup method for resonance treatment and subpin level thermal feedback, are presented as a whole. The performance of the code in the aspect of solution accuracy and computing speed is then examined using the applications to the C5G7MOX benchmark and its modified rodded variation problems and also to a three-dimensional core case involving thermal feedback. The examination indicates that accurate direct whole core calculations with subpin level thermal feedback for practical PWR problems are quite possible on affordable LINUX clusters within a time span of a few hours.This work was supported by the International Nuclear Energy Research Initiative (I-NERI) program jointly funded by the Ministry of Science and Technology of Korea and the Department of Energy of the United States
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