Equatorial field-aligned irregularities deduced from the echo-train and hybrid whistlers     

Masashi Hayakawa  Yoshihito Tanaka 《Pure and Applied Geophysics》1973,111(1):2336-2340

Summary Equatorial field-aligned irregularities have been studied by using low-latitude echotrain and hybrid whistlers observed at Sakushima Station (geomag. lat. 24°). The structure is discussed in relation to the propagation mode trapped by field-aligned irregularities. We then find that the field-aligned irregularities responsible for the trapping of low latitude whistlers are of such small dimension as the HF ducts.  相似文献   

Analysis of tubular steel bridge piers     

Toshiki Ishizawa  Masashi Iura 《地震工程与结构动力学》2005,34(8):985-1004

A one‐dimensional model is proposed for the static and dynamic analysis of tubular steel bridge piers subjected to strong ground motions. The present formulation does not require experimental results nor shell analysis to obtain the constitutive equation of the model, which shows strength deterioration. The material properties and dimensions of bridge piers are required for static and dynamic analysis of the present model. The present analysis consists of two steps. The first step is to obtain the stress and strain relationship of the base plastic‐hinge region, where local inelastic buckling is observed. The modified Shanley's model and fiber elements are used to establish the compressive skeleton curve. The strength deterioration is taken into account in the resulting constitutive model. The second step is to analyze static and dynamic responses of tubular steel bridge piers. For overall analysis, the base plastic‐hinge region is discretized in the circumferential direction by using fiber elements whose constitutive equation was obtained in the first step. The validity of the present model has been confirmed through comparisons with existing experimental results. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Incorporation of Be isotopes and other trace metals into marine ferromanganese deposits     

Masashi Kusakabe  Teh-Lung Ku 《Geochimica et cosmochimica acta》1984,48(11):2187-2193

Two-to threefold inward increase of ¹⁰Be, ⁹Be, Cu and Ni have been found in surface layers of marine ferromanganese deposits. We interpret this phenomenon as reflecting the manner in which the Be isotopes and probably other trace metals (e.g. Cu and Ni) are incorporated. On reaching the sea floor exchangeable Be is released from its carrier phase to the pore water of the ferromanganese deposits, diffuses inward and gets fixed into the deposits. The fixation process may be related to the mineralogical reorganizations suggested by previous studies. We have modeled this concept and applied it to a Mn crust on which detailed analyses of Cu, Ni and natural decay-series nuclides, as well as Be isotopes are made. Post-depositional fixation of Th isotopes may also occur. The redistributions of Be and Th isotopes are confined to regions very close to the surface of the deposits. For all practical purposes, they will not affect growth rate determinations conventionally done using these isotopes. The “linearly” extrapolated ${}^{10}\text{Be}{}^9\text{Be}$ ratio to the surface from deep layers of a Mn deposit does not necessarily represent that ratio in sea water.  相似文献   

冲绳海槽海底热液喷出口附近海水中~(210)Pb和~(210)Po的行为     

杨永亮  日下部正志  山本惠幸 《海洋学报》2001,(6)

讨论了在冲绳海槽伊平屋海岭和南奄西海丘两处海底热液喷出口附近海水中的铀系子体放射性核素2 10 Pb和2 10 Po浓度的垂直分布剖面 .在伊平屋海岭 ,甲烷及2 2 2 Rn的数据表明海底热液活动不强 ,总2 10 Pb和2 10 Po放射性均低于它们各自母体的放射性 ,2 10 Pb和2 10 Po在海水中的平均停留时间分别为 2 0和 2～ 5a ,而在以“黑色烟雾”为特征的海底热液活动强烈的南奄西海丘 ,在”烟雾”中的总2 10 Pb含量 ( 0 1 6 7× 1 0 -3～ 2 50× 1 0 -3Bq/kg)相对其母体2 2 6Ra贫乏 ,而总2 10 Po含量 ( 1 83× 1 0 -3～ 2 83×1 0 -3Bq/kg)则相对其母体2 10 Pb过剩 .该处海水中的2 10 Po的放射性高于东海陆架区及冲绳海槽其他海区 ,并且显示了2 10 Po过剩 .2 10 Pb/ 2 2 6Ra以及2 10 Po/ 2 10 Pb放射性比值的范围分别为 0 1～ 0 4和 1 1～ 7 8.在热液扩散带中2 10 Pb被优先从海水中清除 .控制南奄西海丘海水中2 10 Pb浓度的可能机制涉及到2 10 Pb通过扩散作用的横向输送 .在热液扩散带中高2 10 Po/ 2 10 Pb放射性比值表明2 10 Pb的耗尽及2 10 Po从海底热液喷出口的加入 .  相似文献   

Sedimentation flux from mariculture of oyster (Crassostrea Gigas) in Ofunato estuary, Japan   总被引：1，自引：0，他引：1  

Hayakawa  Y.; Kobayashi  M.; Izawa  M. 《ICES Journal of Marine Science》2001,58(2):435-444

  相似文献   

冲绳海槽海底热液喷出口附近海水中210Pb和210Po的行为   总被引：1，自引：0，他引：1  

杨永亮  日下部正志  山本惠幸 《海洋学报》2001,23(6):59-75

讨论了在冲绳海槽伊平屋海岭和南奄西海丘两处海底热液喷出口附近海水中的铀系子体放射性核素210Pb和210Po浓度的垂直分布剖面.在伊平屋海岭,甲烷及222Rn的数据表明海底热液活动不强,总210Pb和210Po放射性均低于它们各自母体的放射性,210Pb和210Po在海水中的平均停留时间分别为20和2～5a,而在以“黑色烟雾”为特征的海底热液活动强烈的南奄西海丘,在”烟雾”中的总210Pb含量(0.167×10-3～2.50×10-3Bq/kg)相对其母体226Ra贫乏,而总210Po含量(1.83×10-3～2.83×10-3Bq/kg)则相对其母体210Pb过剩.该处海水中的210Po的放射性高于东海陆架区及冲绳海槽其他海区,并且显示了210Po过剩.210Pb/226Ra以及210Po/210Pb放射性比值的范围分别为0.1～0.4和1.1～7.8.在热液扩散带中210Pb被优先从海水中清除.控制南奄西海丘海水中210Pb浓度的可能机制涉及到210Pb通过扩散作用的横向输送.在热液扩散带中高210Po/210Pb放射性比值表明210Pb的耗尽及210Po从海底热液喷出口的加入.  相似文献   

Iron K-emission line from Cygnus X-2     

T. Hirano  S. Hayakawa  F. Nagase  Y. Tawara 《Astrophysics and Space Science》1986,119(1):77-80

The iron K-emission line of Cyg X-2 was detected from the TENMA observation. The centre energy, the equivalent width and the intrinsic line width are 6.7 keV, 30 eV, and less than 0.6 keV, respectively. These properties indicate that the observed line is mostly due to helium-like iron and the electron scattering depth of the line emitting region is smaller than three.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Astronomy in Japan     

Satio Hayakawa  Mamoru Saito 《Astrophysics and Space Science》1984,99(1-2):393-402

The research activity in Japanese astronomy is described, taking into account the social and historical background. A trend in the last two decades is shown by the numbers of papers in 13 branches of astronomy. Major research facilities and international collaboration programs are summerized. Future programs under consideration are briefly discussed.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.  相似文献   

Comparison of time delays of sprites induced by winter lightning flashes in the Japan Sea with those in the Pacific Ocean     

Y. Matsudo  T. Suzuki  K. Michimoto  K. Myokei  M. Hayakawa 《Journal of Atmospheric and Solar》2009,71(1):101-111

The measurement of unusual winter sprites in the Hokuriku area (Japan Sea side) was performed as a primary target of the 2006/2007 winter campaign by means of coordinated optical and extremely low frequency (ELF)/very high-frequency (VHF) electromagnetic observations. We have also added the same observations for the sprites in the Pacific Ocean, to be compared with the characteristics of Hokuriku sprites. The following results have emerged from this campaign: (i) the predominance of column sprites in winter has been confirmed not only for the Hokuriku area but also in the Pacific Ocean (with the probability just above 60%), (ii) carrots are much more frequently observed in the Pacific Ocean (with a probability of ～28%) than in the Hokuriku area (～16%), (iii) a very unique property of Hokuriku sprites is the surprisingly long delay (average ～90 ms) of sprites from their parent lightning flashes and the delays for carrots and columns exhibit some significant difference (80 ms for columns and 100 ms for carrots) and (iv) the time delay of Pacific Ocean sprites is much shorter (～43 ms average) than that at Hokuriku, but there is no remarkable difference in delay between carrots and columns. Finally we discussed the importance of time delay studies to understand sprite generations and their parent lightning discharges, because the difference of time delays on the Japan Sea side and in the Pacific Ocean are thought to be causally related to the parameters of parent thunderstorms.  相似文献   

Development of Long-period Ground Motions from the Nankai Trough, Japan, Earthquakes: Observations and Computer Simulation of the 1944 Tonankai (Mw 8.1) and the 2004 SE Off-Kii Peninsula (Mw 7.4) Earthquakes     

Takashi Furumura  Toshihiko Hayakawa  Misao Nakamura  Kazuki Koketsu  Toshitaka Baba 《Pure and Applied Geophysics》2008,165(3-4):585-607

Strong ground motions recorded in central Tokyo during the 1944 Tonankai Mw8.1 earthquake occurring in the Nankai Trough demonstrate significant developments of very large (>10 cm) and prolonged (>10 min) shaking of long-period (T > 10–12 s) ground motions in the basin of Tokyo located over 400 km from the epicenter. In order to understand the process by which such long-period ground motions developed in central Tokyo and to mitigate possible future disasters arising from large earthquakes in the Nankai Trough, we analyzed waveform data from a dense nation wide strong-motion network (K-NET and KiK-net) deployed across Japan for the recent SE Off-Kii Peninsula (Mw 7.4) earthquake of 5 September 2004 that occurred in the Nankai Trough. The observational data and a corresponding computer simulation for the earthquake clearly demonstrate that such long-period ground motion is primarily developed as the wave propagating along the Nankai Trough due to the amplification and directional guidance of long-period surface waves within a thick sedimentary layer overlaid upon the shallowly descending Philippine Sea Plate below the Japanese Island. Then the significant resonance of the seismic waves within the thick cover of sedimentary rocks of the Kanto Basin developed large and prolonged long-period motions in the center of Tokyo. The simulation results and observed seismograms are in good agreement in terms of the main features of the long-period ground motions. Accordingly, we consider that the simulation model is capable of predicting the long-period ground motions that are expected to occur during future Nankai Trough M 8 earthquakes.  相似文献