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   

Remote sensing parameterization of the processes of energy and water cycle over desertification areas     

Yaoming Ma  Osamu Tsukamoto  Hirohiko Ishikawa 《中国科学D辑(英文版)》2002,45(1):47-53

In order to understand the processes of land surface-atmosphere interaction over desertification area, it is indispensable to utilize of satellite remote sensing. Two scenes of Landsat TM were used to produce a set of maps of surface reflectance, MSAVI, vegetation coverage, surface temperature, net radiation, soil heat flux, sensible heat flux and latent heat flux. Statistical analysis based on these maps revealed some quantitative significant land surface characteristics. Future developments of the method are also discussed.  相似文献   

GPS-measured land subsidence in Ojiya City, Niigata Prefecture, Japan   总被引：1，自引：0，他引：1  

Hiroshi P. Sato  Kaoru Abe  Osamu Ootaki 《Engineering Geology》2003,67(3-4):379-390

Land subsidence caused by compression of clay layers in Ojiya City, Japan was measured by global positioning system (GPS) between 1 April 1996 and 31 December 1998.

Three baselines were selected in and around the city, and height difference on a WGS-84 ellipsoid was measured by GPS on each baseline. The ground at the GPS station in the city subsides and rebounds 7 cm every winter and spring, respectively. Measurement accuracy was 9.5 mm standard deviation. Ground water level was observed at a well near the GPS station. Regression analysis between total strain, calculated as ratio of the height difference displacement to the total thickness of the clay layers, and the layers' effective stress change with ground water level change gave good correlation. The slope of regression line 7.0×10⁻¹¹ m²/N was obtained as an average apparent coefficient of volume compressibility of the layers.  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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Internal Microanatomy and Zoological Affinity of the Early Cambrian Olivooides     

HAN Jian  LI Guoxiang  Kubota Shin  Ou Qiang  Toshino Sho  Wang Xing  Yang Xiaoguang  Uesugi Kentaro  Masato Hoshino  Sasaki Osamu  Kano Harumas  Sato Tomohiko  Komiya Tsuyoshi 《《地质学报》英文版》2016,90(1):38-65

The early Cambrian pentamerous microfossil Olivooides/Punctatus in South China, which is characterized by a diagnostic stellate tubular apex, has been well-known for its almost complete development sequence that can be confidently traced from embryos and hatched juveniles, to conical adults. However, its zoological affinity remains highly controversial. Here we describe the internal microanatomic structures of the soft-body inside the peridermal theca of Olivooides multisulcatus Qian, 1977, including interradial pairs of tentacles, adradial and perradial frenula, perradial oral marginal lappets and twins of perradial gastric saccule-like humps as well as a circular velarium with striated coronal muscles. Particularly, one specimen shows bifurcated velarial canals along the bell aperture. Both the components of the soft-body and the external theca (or cyst) are arranged in perfect pentaradial symmetry. These characteristics are more compatible with those of living cubomedusans and co-occurring Cambrian athecate embryonic cubozoans. Concerning the presence of peridermal theca, Olivooides most likely represents an extinct thecate stem-group cubomedusae but devoid of both perradial eyes and specialized pedalia. The well-grown soft body inside the peridermal tube displays a set of mixed features of both polyp and medusa.  相似文献   

Seasonal variations in the nitrogen isotopic composition of settling particles at station K2 in the western subarctic North Pacific     

Yoshihisa?MinoEmail author  Chiho?Sukigara  Makio?C.?Honda  Hajime?Kawakami  Kazuhiko?Matsumoto  Masahide?Wakita  Minoru?Kitamura  Tetsuichi?Fujiki  Kosei?Sasaoka  Osamu?Abe  Jan?Kaiser  Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836

Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ ¹⁵N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ ¹⁵N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ ¹⁵N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ ¹⁵N(SUS) signature was reflected by δ ¹⁵N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ ¹⁵N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ ¹⁵N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ ¹⁵N(DST) vs. PP regression to δ ¹⁵N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully.  相似文献   

Depth-dependent and seasonal variability in archaeal community structure in the subarctic and subtropical western North Pacific     

Ryo Kaneko  Toshi Nagata  Shotaro Suzuki  Koji Hamasaki 《Journal of Oceanography》2016,72(3):427-438

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Traveling wave effects on a tall and narrow building: Observation and analysis     

T. Sugiyama  K. Maeda  M. Kaneko 《Computers and Geotechnics》1990,9(4):307-324

The purpose of this paper is to investigate the seismic response of a tall and narrow building, for example, a turbine building of thermal power plant, due to a traveling shear wave. It is considered that the dynamic response of the building can be affected by the spatial variance of seismic ground motion, because the building has a long-shaped foundation (43 meters wide by 343 meters long by 4 meters thick). First, analytical study was conducted using obliquely incident harmonic motion. And comparing the earthquake response observed at different points of foundation slab, it was found that the response at the end point where input wave reaches later is larger than that at the other end. From these studies, it was assured that the antisymmetric mode, which can be neglected in ordinary analysis, is excited by phase difference of input motion.  相似文献   

Hypocenter distribution and focal mechanism of AE events during two stress stage creep in Yugawara andesite     

Osamu Nishizawa  Kaoru Onai  Kinichro Kusunose 《Pure and Applied Geophysics》1984,122(1):36-52

More than a thousand acoustic-emission (AE) hypocenters were determined in a cylindrical andesite specimen under two-stage uniaxial creep at stresses of 204 and 214 MPa. Strains were monitored for 6 peripheral points at the middle part of the cylindrical specimen's wall. The strain data indicate gradual increase of nonuniform deformation during steady creep and strong intensification of the nonuniformity during acceleration creep and, therefore, biased stress distribution within the specimen. The correlation between dilatant strain and AE hypocenters was investigated for whether or not tensile cracks emit AE. The region with high AE activity shows only a small dilatant strain. This negative correlation between AE and the dilatant region may eliminate tensile cracks as possible AE sources. A composite focal-mechanism solution of local AE events, covering a wide solid angle of the focal hemisphere, indicates that shear fractures emit AE waves. The direction of the compressional axis in this solution shows a significant deviation from that inferred from the applied external force, suggesting that the local stress field is governed by preexisting weak zones that are, presumably, produced by tensile cracks within the specimen. AE hypocenters tended to form clusters during steady creep under the constant compressional stress. During acceleration creep caused by a small step increase of the external stress, the preceding clusters disappeared while a new cluster appeared in an incipient fault plane. This suggests that changes in seismicity pattern such as migrations or quiescences of swarm—important clues for earthquake predictions—may be caused by an instantaneous change in the tectonic-stress levels.  相似文献   

Antiferromagnetic transition of fayalite under high pressure studied by Mössbauer spectroscopy     

Mitsuhiko Hayashi  Ichiro Tamura  Osamu Shimomura  Hiroshi Sawamoto  Haruki Kawamura 《Physics and Chemistry of Minerals》1987,14(4):341-344

Néel temperature (Tm _N of α-Fe₂SiO₄ (fayalite) was measured as a function of pressure by means of Mössbauer spectroscopy in the pressure range 0–16 Gpa. High pressure was generated using a clamp-type miniature diamond anvil cell which was inserted into a cryostat. The Néel temperature increased linearly with increasing pressure at a rate of dT _N /dp=2.2±0.2 K/GPa. The result is discussed on the basis of the model proposed for the magnetic structure of fayalite by Santoro et al. (1966). The observed dT _N /dp suggests that the superexchange interactions vary as the ?10/3 power of the volume while the volume dependence of the direct exchange interactions is positive and small.  相似文献