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51.
Resonance occupation of trans-neptunian objects (TNOs) in the scattered disk (>48 AU) was investigated by integrating the orbits of 85 observed members for 4 Gyr. Twenty seven TNOs were locked in the 9:4, 16:7, 7:3, 12:5, 5:2, 8:3, 3:1, 4:1, 11:2, and 27:4 resonances. We then explored mechanisms for the origin of the resonant structure in the scattered disk, in particular the long-term 9:4, 5:2, and 8:3 resonant TNOs (median 4 Gyr), by performing large scale simulations involving Neptune scattering and planetary migration over an initially excited planetesimals disk (wide range of eccentricities and inclinations). To explain the formation of Gyr-resident populations in such distant resonances, our results suggest the existence of a primordial planetesimal disk of at least 45-50 AU radius that suffered a dynamical perturbation leading to 0.1-0.3 or greater eccentricities and a range of inclinations up to ∼20° during early stages of the Solar System history, before planetary migration. 相似文献
52.
Masayuki Ehiro Satoru Kojima Tadashi Sato Talat Ahmad Tomoyuki Ohtani 《Island Arc》2007,16(1):124-132
Abstract Callovian (late Middle Jurassic) ammonoids Macrocephalites and Jeanneticeras were recovered from the Shyok suture zone, northeast of Chang La Pass, Ladakh, northwest India. They are the first reliable Jurassic fossils and the oldest chronologic data from the Shyok suture zone. The ammonoid-bearing Jurassic strata, newly defined as the Tsoltak Formation, consist largely of terrigenous mudstone with thin sandstone beds and were probably a part of the continental basement to the Cretaceous Ladakh Arc. 相似文献
53.
Ken Yanagisawa Fumihiko Imamura Tsutomu Sakakiyama Tadashi Annaka Tomoyoshi Takeda Nobuo Shuto 《Pure and Applied Geophysics》2007,164(2-3):565-576
The present study focuses on evaluation of the maximum and minimum water levels caused by tsunamis as risk factors for operation
and management at nuclear power facilities along the coastal area of Japan. Tsunamis generated by submarine earthquakes are
examined, basing literature reviews and databases of information on historical tsunami events and run-up heights. For simulation
of water level along the coast, a numerical calculation system should be designed with computational regions covering a particular
site. Also the calculation system should be verified by comparison of historical and calculated tsunami heights. At the beginning
of the tsunami assessment, the standard faults, their locations, mechanisms and maximum magnitudes should be carefully estimated
by considering historical earthquake-induced tsunamis and seismo-tectonics at each area. Secondly, the range of errors in
the model parameters should be considered since earthquakes and tsunamis are natural phenomena that involve natural variability
as well as errors in estimating parameters. For these reasons, uncertainty-induced errors should be taken into account in
the process of tsunami assessment with parametric study of the tsunami source model. The element tsunamis calculated by the
standard fault models with the errors would be given for the design. Then, the design tsunami can be selected among the element
tsunamis with the most significant impact, maximum and minimum water levels, on the site, bearing in mind the possible errors
in the numerical calculation system. Finally, the design tsunami is verified by comparison with the run-up heights of historical
tsunamis, ensuring that the design tsunami is selected as the highest of all historical and possible future tsunamis at the
site. 相似文献
54.
Tadashi Hirayama 《Solar physics》1971,19(2):384-400
The abundance of helium relative to hydrogen is spectroscopically determined in prominences and in the chromosphere by using 1952, 1958, 1962 and 1966 eclipse data. Care is taken in the intensity calibration of emission lines, the self-absorption, and the departure from local thermodynamic equilibrium. We find from the line profiles and intensities of prominences and the chromosphere that the neutral helium lines are emitted in the metal-hydrogen emitting region where the kinetic temperature is low enough, 6000 8000 K, so that only the ionization due to UV radiation from the corona can explain the intensity of neutral helium emission. Also we find that the intensity ratio of Hei 3888.65 to H8 3889.05 increases towards the upper boundaries of prominences and of the chromosphere and that it approaches to a universal limiting value, both in various prominences or in the chromosphere, where it is considered that the ionization of neutral helium and hydrogen is nearly complete. From these facts the helium to hydrogen number ratio is found to be 6.5 ± 1.5%.A new schematic model of the chromosphere is presented where spicules have no hot region of emitting neutral helium lines. Here it is suggested that the kinetic temperature of spicules, 6000 8000 K, would be primarily determined by the radiation temperature of the corona and the transition region beyond the Lyman continuum of hydrogen which happens to be around those temperatures. 相似文献
55.
The position and shape of the Gegenschein’s maximum brightness provide information on the structure of the interplanetary dust cloud. We show that the asteroidal dust bands, extended near the anti-solar point, play an important role in determining both the position of the maximum brightness and the shape of the Gegenschein. After removing the asteroidal dust bands from an observation of the Gegenschein on November 2, 1997, it was found that the maximum brightness point shifted −0.4° in ecliptic latitude, i.e., to the south of the ecliptic plane, at an ecliptic longitude of 180°, in contrast to a latitude value of +0.1° when the dust bands were included. Furthermore, the part of the Gegenschein to the south of the ecliptic plane was brighter than the northern part at the time of observation. Referring to the cloud model of T. Kelsall et al. (1998, Astrophy. J. 508, 44-73), it can be estimated that the ascending node of the symmetry plane of the dust cloud is 57°−3°+7° when its inclination is 2.03° ? 0.50°. 相似文献
56.
Tadashi Yokoyama Massae Sato Masayoshi Tsuchida 《Celestial Mechanics and Dynamical Astronomy》1987,41(1-4):99-105
In a very simple way, it is possible to show the existence of small regions of instability, inside the observed 3/1 and 2/1 Kirkwood Gap, by using the classical Laplace-Lagrange secular theory. 相似文献
57.
Naoteru Gouda Takuji Tsujimoto Yukiyasu Kobayashi Tadashi Nakajima Naoki Yasuda Hideo Matsuhara 《Astrophysics and Space Science》2002,280(1-2):89-94
JASMINE is the name of a Japanese infrared (K-band) scanning astrometric satellite. JASMINE (I and/or II-project) is planned to be launched between 2013 and 2017 and will
measure parallaxes and proper motions with the precision of 10μas at K≃ 12 - 15 mag. JASMINE will observe a few hundred million stars belonging to the disk and the bulge components of our Galaxy,
which are hidden by the interstellar dust extinction in optical bands. Furthermore, JASMINE will also obtain photometry of
stars in K, J and H-bands. The main objective of JASMINE is to study the most fundamental structure and evolution of the disk and the bulge components
of the Milky Way Galaxy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
58.
Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit
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Keita Nagaki Toshihiko Kadono Tatsuhiro Sakaiya Tadashi Kondo Kosuke Kurosawa Yoichiro Hironaka Keisuke Shigemori Masahiko Arakawa 《Meteoritics & planetary science》2016,51(6):1153-1162
We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque), and III (transparent). Scanning electron microscopy combined with electron backscattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot elastic limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~10 GPa) to melting pressure (~100 GPa) in a hierarchical order. 相似文献
59.
In this work, the hydrochemical properties of the stratal water of several oil-gas fields of Western Siberia with normal and inverse vertical hydrochemical zonation are discussed. Maps of the injected water distribution, which were created on the basis of high bicarbonate ion concentration in the stratal water (to 30 eq wt %), as well as the computer modeling results of calcite precipitation in stratal water that results from the mixture of two water types: calcium chloride (injected) and sodium bicarbonate (stratal), are given. In addition, the need to consider the hydrochemical type of water when choosing the technique of hydrochemical data processing was established. 相似文献
60.