Experimental study on the rheological properties of polycrystalline solid nitrogen and methane: Implications for tectonic processes on Triton     

Yasuyuki Yamashita  Manabu Kato 《Icarus》2010,207(2):972-977

To investigate the evolution of any processes on planetary surfaces in the outer Solar System, the rheological properties of non-water ices were studied by means of a sound velocity measurement system and a uniaxial deformation apparatus. A pulse transmission method was used to obtain longitudinal (V_p) and transverse (V_s) wave velocities through solid nitrogen and methane at temperatures ranging from 5 to 64 K and from 5 to 90 K, respectively. The measured velocities confirmed that the solid methane and solid nitrogen samples were non-porous polycrystalline samples without any cracks and bubbles inside. Compression tests at constant strain-rate were performed for solid nitrogen and methane at temperatures of 5-56 K and 5-77 K, respectively, at strain-rates of 10⁻⁴-10⁻² s⁻¹. Both brittle and ductile behavior was observed for solid nitrogen and methane under these conditions. The maximum strength of solid nitrogen was observed to be 9 MPa in the brittle failure mode, and that of solid methane was 10 MPa. These low strengths cannot support cantaloupe structures with the topographic undulation larger than several kilometers found on Triton’s surface, suggesting that other materials such as H₂O ice could underlay solid methane and nitrogen and support these structures.  相似文献   

Regional seismic responses of shallow basins incorporating site‐city interaction analyses on high‐rise building clusters     

Bence Kato  Gang Wang 《地震工程与结构动力学》2021,50(1):214-236

This study assesses the 3D amplification effects in shallow basins and quantifies the effects of site‐city interaction (SCI) on high‐rise buildings. A regional‐scale 3D spectral element simulation is conducted on the Tuen Mun‐Yuen Long basin, which contains multiple subbasins with heterogeneous and nonlinear soil profiles, while 3D city models with various building layouts are fully integrated into the basin model for our SCI study. We found a good correlation between spectral amplification factors and soil depths. Site response is significantly amplified at basin edges and centers due to surface waves generated at basin edges and the focusing effects stemming from 3D basin geometry. Transfer functions of 3D basins can be up to fourfold at fundamental frequencies as compared to 1D response, and further amplifications occur at high frequencies due to surface waves. In the SCI simulations, we observe wave trapping in the open space amid buildings resulting in energy concentration and up to twofold PGA amplifications. The wave trapping effect diminishes as the space between buildings increase beyond their range of influence (～100 m). The SCI analyses show that destructive kinetic energy in superstructures increases 28% in one horizontal direction but decreases 22% in the other. Our study concluded that, 1D site response analysis can significantly underestimate the seismic demand in shallow basins. Site‐city interaction of high‐rise buildings increases the short‐period spectra of ground motions, leading to an increase in their story accelerations by up to 50% and to a substantial decrease in the seismic safety of short structures in their vicinity.  相似文献   

Features of the orbital variability in the brightness of the WZ Sge type dwarf nova V1108 Her     

E. P. Pavlenko  T. Kato  O. I. Antonyuk  A. Imada  R. Ishioka  H. Maehara 《Astrophysics》2011,54(4):483-495

Results are presented from photometric studies of the dwarf nova V1108 Her conducted at the primary focus of the 2.6-m G. A. Shajn Telescope at the Crimean Astrophysical Observatory during June-July 2008, 4 years after the 2004 outburst. An orbital period of 0.05672(4) days is found for the system. An analysis of observations made earlier during the 2004 outburst reveals an orbital signal which indicates that V1108 Her is an eclipsing system. The mass ratio of the secondary component to the white dwarf is estimated to be q = 0.068, which makes it highly likely that the secondary component of this system is a brown dwarf. The orbital light curves indicate a complex structure for the accretion disk whose radius has reached a 2:1 resonance. An explanation is suggested for a quasi-periodic modulation in the brightness at 1/4 of the orbital period observed in V1108 Her and other WZ Sge systems.  相似文献   

Hydrodynamic equations of differentially rotating stellar systems and the velocity ellipsoid     

Shoji Kato 《Astrophysics and Space Science》1968,2(1):37-47

Anisotropic hydrodynamic equations for differentially rotating collisionless stellar systems are derived. These equations can describe the evolution of the systems in a time span longer than their rotation periods.As a by-product of derivation of hydrodynamic equations, the well-known relation that the ratio of the principal axes of the velocity ellipse in a differentially rotating stellar disk is [B/(B-A)]^1/2 is re-found if the system is in a purely circular rotation, whereA andB are the Oort's constants. In addition, we find a systematic mean motion superposed on a purely circular differential rotation makes the directions of axes of the velocity ellipse deviate from the radial and the transverse direction. The observed deviation of directions of axes in our neighbourhood in the Galaxy can be explained if in the mean motion superposed on a purely circular differential rotatin the gas of stars near us is compressed in the radial direction or rarefied in the transverse directions, with irregularities of the order of 5 km/sec in amplitude of velocity and 1 kpc in size. These magnitudes of irregularities agree with those actually observed or with those anticipated from other theoretical considerations.  相似文献   

Possible Mechanism of Precursory Seismic Quiescence: Regional Stress Relaxation due to Preseismic Sliding   总被引：3，自引：0，他引：3  

N. Kato  M. Ohtake  T. Hirasawa 《Pure and Applied Geophysics》1997,150(2):249-267

—We propose a new model to physically explain the seismic quiescence precursory to a large interplate earthquake. A numerical simulation is performed to quantitatively examine possible stress changes prior to a great interplate earthquake in a subduction zone. In the present study, the frictional force following a laboratory-derived friction law, in which the friction coefficient is dependent on slip rate and slip history, is assumed to act on a dip-slip fault plane of infinite width in a uniform elastic half-space. The values of friction parameters are determined so that the result of numerical simulation may explain some properties of great interplate earthquakes in subduction zones, such as the recurrence interval and the seismic coupling coefficient. The result of simulation reveals that significant quasi-stable sliding occurs prior to a great earthquake and, accordingly, stresses are changed on and around the plate boundary. In a relatively wide area of the overriding continental plate, the compres sional horizontal-stress perpendicular to the trench axis is decreased for a few years before the occurrence of a great earthquake. This decrease in regional compressional stress may account for the appearance of seismic quiescence prior to a great interplate earthquake.  相似文献   

Steady mass-loss from supermassive stars     

Mariko Kato 《Astrophysics and Space Science》1986,119(1):57-59

Structures of Newtonian super-massive stars are calculated with the opacity for Comptor effectK ₀/(1 + T), whereK ₀=0.21(1 +X and =2.2×10^–9K^–1. The track of the Main-Sequence is turned right in the upper part of the HR diagram. Mass loss will occur in a Main-Sequence stage for a star with mass larger than a critical mass. The cause of mass loss and the expansion of the radius is continuum radiation pressure. The critical mass for mass loss is 1.02×10⁶ M for a Population I star, and 1.23×10⁵ M for Population III star. Mass loss rates expected in these stars are 3.3×10^–3 and 4.0×10^–3 M yr^–1, respectively.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

V-2 Study on the system simulation for an O.W.C. type wave energy absorber     

Takeshi Kinoshita  Koichi Masuda  Shogo Miyajima  Wataru Kato 《Ocean Engineering》1985,12(6):580-581

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Vertical distribution of various elements in sediment cores from the Japan Sea     

Toyoaki Kato  Masami Endo  Michio Kato 《Marine Geology》1983,53(4):277-290

Deep-sea sediment cores ranging up to 30,000–80,000 yrs in age were taken from a southern region of the Japan Sea and subjected to analyses for 5 major and 11 trace elements by means of instrumental photon activation analysis with 30 MeV bremsstrahlung. These elements were Ca, Fe, Mg, Na, Ti, Ba, Ce, Co, Cr, Mn, Nb, Ni, Rb, Sr, Y and Zr. Additionally, Al was determined spectrophotometrically. Distribution patterns of these elements with depth in the sediment columns were derived. Enrichments of Ca and Sr by biogenous process were observed; these Ca maxima are well correlated with Mn maxima. Below the Holocene—Pleistocene boundary, continuous transportation of poorly degraded continental debris, which was low in metallic constituents, was noted. A distinct enrichment of the top layer of the sediments in Mn was observed. This is the result of post-depositional upward migration of Mn. Fe, Co and Ni were also enriched in the top layers. In the central part of the basin, the oxidized post-glacial zone appears to be a typical pelagic sediment.  相似文献   

Influence ofNoctiluca's predation on theAcartia population in Ise Bay,central Japan     

Hideo Sekiguchi  Takashi Kato 《Journal of Oceanography》1976,32(5):195-198

The influence ofNoctiluca's predation on theAcartia population in Ise Bay was examined by taking samples at 27 stations once a month from May to December, 1974.The copepod eggs were found inNoctiluca mainly in May and June. Considering from various spawning types of copepods, the eggs were presumed to beAcartia, the most numerous species of all copepods in the bay.Noctiluca was dominant plankton in May and June whenAcartia was abundantly distributed.Acartia eggs were found in 33.2–39.3% of individuals ofNoctiluca in May and June.Noctiluca was more frequently observed to contain one egg ofAcartia per individual. It was suggested that 55.0 eggs perAcartia female per day were eaten by theNoctiluca population in May wherease 3.5 eggs in June. It was deduced that 74% of the eggs produced byAcartia was preyed on byNoctiluca (about 5% in June). The predation byNoctiluca as well as that by the sand-eel must influence greatly to the production ofAcartia in the bay.  相似文献   

A case study of the application of a microcomputer-based favorability evaluation system: Uranium exploration in the Alligator Rivers Uranium Field, Northern Territory, Australia     

T. Kobayashi  T. Semba  Y. Yamada  S. Williams  Y. Kato 《Mathematical Geology》1994,26(8):937-960

We have attempted to develop an expert system to evaluate the favorability of uranium exploration projects using the Data-directed Numerical Method (DdM). We developed the system for the Macintosh personal computer, so as to facilitate the iterative processes of trial and error inherent in the DdM. In a detailed case study, we use the above system to evaluate the favorability of the Alligator Rivers Uranium Field, Northern Territory, Australia. The favorability of the target area is evaluated by considering several exploration parameters related to the geological factors controlling ore formation. The selection of appropriate exploration parameters is important to the success of the method. We then selected 15 model cells to validate each exploration parameter and also to design the exploration model by the application of the chi-square test. The result of the favorability evaluation, as displayed by the developed system, indicates that our designed exploration model is acceptable. By employing the above processes we conclude that the system using the DdM is applicable as an exploration tool and is useful in establishing an exploration model.  相似文献