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Density functional theory studies of hydrogen bonding vibrations in sI gas hydrates
Abstract
To analyze the vibrational modes of water and methane in structure I gas hydrates, we constructed a 178-atom supercell with two small cages of type 512 and six large cages of type 51262. We applied the density functional theory method to simulate the vibrational spectrum and normal modes of methane hydrates. In accord with our previous studies, we confirmed that two groups of hydrogen bond (H-bond) peaks (at around 291 and 210 cm−1) in the translational bands come from two kinds of intermolecular H-bond vibrational modes. This is the first investigation of H-bond vibrations in methane hydrates. The partial modes of CH4 were extracted. We found that the CH4 phonons in the translational region are below 180 cm−1 so that the influence of methane on the H-bond is insignificant. We proposed a new method to decompose gas hydrates via direct application of terahertz radiation to the H-bonds. Herein, we confirmed that CH4 molecules do not absorb this energy.</jats:p
视觉分散和视听分散对接受结肠镜检病人焦虑和接受性的影响
2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers
2016-2017 > Academic research: refereed > Publication in refereed journal201804_a bcmaVersion of RecordPublishe
The Exotic XYZ Charmonium-like Mesons
Charmonium, the spectroscopy of c\bar{c} mesons, has recently enjoyed a
renaissance with the discovery of several missing states and a number of
unexpected charmonium-like resonances. The discovery of these new states has
been made possible by the extremely large data samples made available by the
B-factories at the Stanford Linear Accelerator Center and at KEK in Japan, and
at the CESR e^+e^- collider at Cornell. Conventional c\bar{c} states are well
described by quark potential models. However, many of these newly discovered
charmonium-like mesons do not seem to fit into the conventional c\bar{c}
spectrum. There is growing evidence that at least some of these new states are
exotic, i.e. new forms of hadronic matter such as mesonic-molecules,
tetraquarks, and/or hybrid mesons. In this review we describe expectations for
the properties of conventional charmonium states and the predictions for
molecules, tetraquarks and hybrids and the various processes that can be used
to produce them. We examine the evidence for the new candidate exotic mesons,
possible explanations, and experimental measurements that might shed further
light on the nature these states.Comment: 28 pages, 7 figures. Review for Ann Rev Nucl & Part Sc
Quantitative study of atmospheric effects in spaceborne InSAR measurements
Author name used in this publication: 李志伟Author name used in this publication: 丁晓利, DING Xiao-liAuthor name used in this publication: 朱建军Author name used in this publication: 邹峥嵘Journal title in Traditional Chinese: 中南工業大學學報 (英文版)2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Extraordinary strain hardening by gradient structure
Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures.</p
Derivation of 3-D coseismic surface displacement fields for the 2011 Mw 9.0 Tohoku-Oki earthquake from InSAR and GPS measurements
2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
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