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1,655 results on '"Nakahara, H"'

7. Separating Rayleigh and Love waves based on the SPAC method

Author

Nakahara, H. and Haney, M.

Abstract

The spatial autocorrelation (SPAC) method was developed by Aki (1957) to estimate subsurface velocity structure from the coherence of ambient seismic noise. The SPAC method has been widely used and extended to various cases. Separation of Rayleigh and Love waves is essential to obtain reliable phase velocity dispersion curves. Three-component displacement data is necessary (e.g., Okada and Matsushima, 1989; Chouet et al., 1998). Cross-correlation between the vertical-radial components helps isolate Rayleigh waves (Haney et al., 2012). Recently, the formulation of the SPAC method was extended to strain, rotation, and tilts by Nakahara et al. (2021) and to the mixed correlations between displacement and strain by Nakahara and Haney (2022). Here, we revisit the separation of Rayleigh and Love waves based on these recent developments of the SPAC theory. Isolation of Rayleigh waves is possible using the following components: vertical displacement, areal strain, and tilts. On the other hand, isolation of Love waves is possible using only the vertical-component rotation. Both Rayleigh and Love waves contribute to most auto- and cross-correlation pairs. Therefore, a reasonable method is to isolate Rayleigh waves first and then estimate the contribution of Love waves. Recently, measurements of strain and rotation are becoming possible thanks to the developments of distributed acoustic sensing (DAS) and rotational seismometers. These technical developments, along with the extended SPAC theory, will clearly distinguish Rayleigh and Love waves from ambient noise, which makes it possible to measure radial anisotropy by virtue of the difference between SV and SH velocities.&nbsp, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023
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26. Adsorption of sodium iodine at air/water interface

Author

Nguyen, C.V., Nakahara, H., Shibata, O., Phan, Chi, Nguyen, C.V., Nakahara, H., Shibata, O., and Phan, Chi

Abstract

© 2019 Elsevier B.V. The change in surface potential was measured for NaI solutions. The modelled surface charge was then calculated and compared with molecular simulations. It was found that I− was enhanced at the air/water interface more than Na+. The result, which was confirmed by simulations, was opposite to the previous observation with NaCl. The trend is also consistent with anionic effects: larger and more polar anions adsorbed stronger at the air/water interface. The theoretical model was applied successfully to describe the changes for both systems, which are positive for NaCl and negative for NaI, respectively. The combined results of the two systems also revealed that the self-ionization of pure water induced a positive surface charge at 16.9 mV.

Published
2020

27. Surface potential of the air/water interface

Author

Nguyen, C.V., Nakahara, H., Phan, Chi, Nguyen, C.V., Nakahara, H., and Phan, Chi

Abstract

© 2020 by Japan Oil Chemists’ Society. The surface charge/surface potential of the air/water interface plays a key role in many natural and industrial processes. Since the first decade of the 20th century, there are many theoretical proposals to describe the surface charge in the presence of different moieties. However, a complete and consistent description of the interfacial layer remains elusive. More recently, the theoretical frameworks and experimental data get complementary support from the simulation at a molecular level. This paper reviews the recent developments from the theoretical, experimental and simulation aspects. The combined results indicated that the interaction between hydration shells of adsorbed ions and the H-bonds network of surface water plays a critical role in the ionic adsorption. The factor should be incorporated into the conventional theories to correctly predict the ion distribution near the air/water surface.

Published
2020

31. EC and α decays of 235Am

Author

Asai, M., Sakama, M., Tsukada, K., Ichikawa, S., Haba, H., Nishinaka, I., Nagame, Y., Goto, S., Kojima, Y., Oura, Y., Nakahara, H., Shibata, M., and Kawade, K.

Published
2004
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32. Perinatal anoxia degrades auditory system function in rats

Author

Strata, F., Deipolyi, A.R., Bonham, B.H., Chang, E.F., Liu, R.C., Nakahara, H., and Merzenich, M.M.

Subjects
Hypoxia -- Research, Auditory cortex -- Research, Learning disabilities -- Research, Science and technology
Abstract

Little is known about the neural bases of the reduced auditory and cortical processing speeds that have been recorded in language-impaired, autistic, schizophrenic, and other disabled human populations. Although there is strong evidence for genetic contributions to etiologies, epigenetic factors such as perinatal anoxia (PA) have been argued to be contributors, or causal, in a significant proportion of cases. In this article, we explored the consequences of PA on this elementary aspect of auditory behavior and on auditory system function in rats that were briefly perinatally anoxic. PA rats had increased acoustic thresholds and reduced processing efficiencies recorded in an auditory behavioral task. These rats had modestly increased interpeak intervals in their auditory brainstem responses, and substantially longer latencies in poststimulus time histogram responses recorded in the primary auditory cortex. The latter were associated with degraded primary auditory cortex receptive fields and a disrupted tonotopy. These processing deficits are consistent with the parallel behavioral and physiological deficits recorded in children and adults with a history of language-learning impairment and autism. auditory behavior | auditory brainstem responses | auditory cortex | autism | language learning impairment

Published
2005

38. Transactinide nuclear chemistry at JAERI

Author

Nagame, Y., Haba, H., Tsukada, K., Asai, M., Akiyama, K., Hirata, M., Nishinaka, I., Ichikawa, S., Nakahara, H., Goto, S., Kaneko, T., Kudo, H., Toyoshima, A., Shinohara, A., Schädel, M., Kratz, J. V., Gäggeler, H. W., and Türler, A.

Published
2003
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