Small-Amplitude Disturbances in a Radiating and Scattering Grey MediumIII. Gravitational Effects on the Solutions of Given Real Wave Number k     

Noboru Kaneko  Kazuhiko Morita 《Astrophysics and Space Science》2006,305(4):349-376

We study the fundamental modes of radiation hydrodynamic linear waves that arise from one-dimensional small-amplitude initial fluctuations with wave number k in a radiating and scattering grey medium by taking into account the gravitational effects. The equation of radiative acoustics is derived from three hydrodynamic equations, Poisson’s equation, and two moment equations of radiation, by assuming a spherical symmetry for the matter and radiation and by using the Eddington approximation. We solve the dispersion relation as a quintic function of angular frequency ω, the wave number k being a real parameter. Numerical results reveal that wave patterns of five solutions are distinguished into three types: the radiation-dominated, type 1, and type 2 matter-dominated cases. In the case of no gravitaional effects (Kaneko et al., 2005), the following wave modes appear: radiation wave, conservative radiation wave, entropy wave, Newtonian-cooling wave, opacity-damped and cooling-damped waves, constant-volume and constant-pressure diffusions, adiabatic sound wave, cooling-damped and drag-force-damped isothermal sound waves, isentropic radiation-acoustic wave, and gap mode. Meanwhile, the gravitaional effects being taken into account, the growing gravo-diffusion mode newly arises from the constant-pressure diffusion at the point that k agrees with Jeans’ wave number specified by the isothermal sound speed. This mode changes to the growing radiation-acoustic gravity mode near the point that k becomes Jeans’ wave number specified by the isentropic radiation-acoustic speed. In step with a transition between them, the isentropic radiation-acoustic wave splits into the damping radiation-acoustic gravity mode and constant-volume diffusion. The constant-volume diffusion emerges twice if the gravitational effects are taken into account. Since analytic solutions are derived for all wave modes, we discuss their physical significance. The critical conditions are given which distinguish between radiation-dominated and type 1 matter-dominated cases, and between type 1 and type 2 matter-dominated cases. Waves in a self-gravitating scattering grey medium are also analyzed, which provides us some hints for the effects of energy and momentum exchange between matter and radiation.  相似文献   

Estimation of variation of mercury concentration in the oceans during the last several decades     

Katsuhiko Matsunaga 《Journal of Oceanography》1976,32(1):48-50

Variation of mercury concentration in the oceans during the last several decades has been investigated by determining the mercury concentration in rock fishes caught recently andca. 20 years ago. From this result, it is concluded that there has been no variation of mercury concentration in the oceans during the last several decades.  相似文献   

Relationship between cadmium and phosphate in the northwest Pacific Ocean     

Katsuhiko Matsunaga  Kazuo Abe 《Journal of Oceanography》1985,41(3):193-197

The relationship between Cd and PO₄ in the Kuroshio and Oyashio regions and the Okhotsk Sea was examined. The resultant equations are as follows: Cd (ng l^–1)=37.0 PO₄ (M)+2.6; Cd(ng l^–1)=32.1 PO₄ (M)+1.2 and Cd (ng l^–1)=34.1 PO₄ (M)+7.9, respectively. These results are in good agreement with previously reported studies, and indicate that during removal from surface waters to deeper waters by biological assimilation and regeneration in deeper waters Cd and PO₄ maintain the same ratio in the open ocean. The relationship between Cd and PO₄ in coastal waters, however, differed from that in the open ocean.  相似文献   

Archeological evidence of Pacific salmon distribution in northern Japan and implications for future global warming     

Yukimasa Ishida  Tsutomu Hariu  Junichi Yamashiro  Skip McKinnell  Takeshi Matsuda  Hiromasa Kaneko 《Progress in Oceanography》2001,49(1-4)

Archeological evidence of Pacific salmon in Hokkaido is reviewed and compared with results from western North America. Salmon remains have been found at 24 sites in Hokkaido from the Early Jomon Period to the Ainu Period (6000–100 years ago). Fish remains at three archeological sites in the Kushiro River basin indicated that Pacific salmon (Oncorhynchus spp.) were distributed and utilized from 6000 years ago. The present Kushiro Wetland was formerly covered with seawater and called the Paleo Kushiro Bay 5000–6000 years ago. Based on the molluscan fossil fauna, seawater temperature at Paleo Kushiro Bay was about 5°C warmer than at present. Warmer conditions for salmon in Kushiro 5000–6000 years ago corresponded with the poor conditions for salmon in the Columbia River basin 6000–7000 years ago. If the future global warming is similar to the conditions that prevailed 5000–6000 years ago, the southern limit of salmon distribution will shift northwards and the salmon production will decrease. However, they will not disappear from either Hokkaido or southwestern North America.  相似文献   

Target-strength measurements of Pacific hake (Merluccius productus) in Canadian waters using quasi-ideal and conventional beam transducers     

Hamano  Akira; Sasakura  Toyoki; Kieser  Robert; Cooke  Ken; Kubota  Katsuhiko; Clay  Allen 《ICES Journal of Marine Science》1996,53(2):273-279

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The characteristic distribution of silica over the East China Sea shelf slope     

Toshimichi Ito  Arata Kaneko  Hiroyuki Tsubota  Noriaki Gohda 《Journal of Oceanography》1994,50(4):465-477

The localized near-bottom water with silica content higher than that in the adjacent shelf water was observed to exist at the eastern margins of the East China Sea continental shelf. The core of the high silica water possessed the silica content corresponding to that in the Kuroshio at depths greater than on the shelf. The mixing analysis of water masses using temperature (T) and silica (Si) showed that the core water can be produced through the vertical mixing of intermediate water of the Kuroshio deeper than 100 m. This study provides us a conclusion that the intermediate water of the Kuroshio is strongly mixed on the shelf slope and then upwelled to form the ridge-like distribution of water masses with low temperature and high silica content at the shelf edge.  相似文献   

A note on internal wavetrains and the associated undulation of the sea surface observed upstream of seamounts     

Arata Kaneko  Hiroyuki Honji  Kazuo Kawatate  Shinjiro Mizuno  Akira Masuda  Tsunehiro Miita 《Journal of Oceanography》1986,42(1):75-82

An internal wavetrain, generated by a tidal current in superposition with the Tsushima Warm Current, has been observed by use of an acoustic echo-sounder upstream of the Shichiri-Ga-Sone Seamounts in the East Tsushima Strait of the Japan Sea. The sea surface above the internal wavetrain was simultaneously observed and was found to be undulated at the wavelength of the internal wave.  相似文献   

Controlled experiment in the ionosphere with a rocket-borne plasma gun     

Nobuki Kawashima  Susumu Sasaki  Osamu Kaneko  Akira Yamori  Ryo Okamura  Shoichi Okamura 《Planetary and Space Science》1978,26(4):367-373

A controlled active experiment was performed by a plasma gun on-board a rocket to study the plasma stream across the magnetic field in space. A mother and daughter system was employed. An 8 kV 0.8 μF (25 J) capacitor bank on the daughter rocket was discharged every 12 s and about 10¹⁶ ion and electron pairs were ejected. A plasma signal was detected on the electron temperature probe. The propagation speed of the plasma stream is estimated to be 10⁶ cm/s, considerably lower than that obtained in the prelaunch test. The amplitude of the plasma signal decays as the inverse square of the mutual distance between the mother and daughter rockets and this decay is much slower than the free streaming. The importance of the geomagnetic field on the plasma propagation in space is discussed.  相似文献   

Internal deformation of Sikhote Alin volcanic belt, far eastern Russia: Paleocene paleomagnetic results     

Yo-ichiro Otofuji  Takaaki Matsuda  Ryo Enami  Koji Uno  Katsuhiko Nishihama  Li Su  Ruslan G. Kulinich  Petr S. Zimin  Anatoly P. Matunin  Vladimir G. Sakhno 《Tectonophysics》2002,350(3)

We present paleomagnetic results of Paleocene welded tuffs of the 53–50 Ma Bogopol Group from the northern region (46°N, 137°E) of the Sikhote Alin volcanic belt. Characteristic paleomagnetic directions with high unblocking temperature components above 560 °C were isolated from all the sites. A tilt-corrected mean paleomagnetic direction from the northern region is D=345.8°, I=49.9°, α₉₅=14.6° (N=9). The reliability of the magnetization is ascertained through the presence of normal and reversed polarities. The mean paleomagnetic direction from the northern region of the Sikhote Alin volcanic belt reflects a counterclockwise rotation of 29° from the Paleocene mean paleomagnetic direction expected from its southern region. The counterclockwise rotation of 25° is suggested from the paleomagnetic data of the Kisin Group that underlies the Bogopol Group. These results establish that internal tectonic deformation occurred within the Sikhote Alin volcanic belt over the past 50 Ma. The northern region from 44.6° to 46.0°N in the Sikhote Alin volcanic belt was subjected to counterclockwise rotational motion through 29±17° with respect to the southern region. The tectonic rotation of the northern region is ascribable to relative motion between the Zhuravlevka terrane and the Olginsk–Taukhinsk terranes that compose the basements of the Sikhote Alin volcanic belt.  相似文献   

The Dynamic Fracture Process in Rocks Under High-Voltage Pulse Fragmentation     

Sang Ho Cho  Sang Sun Cheong  Mitsuhiro Yokota  Katsuhiko Kaneko 《Rock Mechanics and Rock Engineering》2016,49(10):3841-3853

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