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1.
Toshiki Aikawa 《Astrophysics and Space Science》1986,125(2):325-330
The short-period limiting pulsation found by Fadeyev and Fokin (1985) in a short-period, Population II Cepheid model is examined by means of the Baker-von Sengbush-Stellingwerf (BSS) algorithm of limit cycles.It is shown that the model has a stable limit cycle of the fundamental mode and an unstable limit cycle of the first overtone mode. When the method is applied for pulsations spanning the time interval of twice the period of the fundamental mode, we find only the fundamental cycle repeated doubly or the first overtone limit cycle repeated three times, depending on initial conditions of the integration.We thus conclude that the period-doubling limiting pulsation found by Fadeyev and Fokin (1985) is a transient feature of the model. 相似文献
2.
The Banda Sea earthquake of November 4, 1963 (h = 100 km, mB = 7.8) is probably one of the largest intermediate-depth shocks to have occurred worldwide this century. The mechanism of this earthquake is studied in detail on the basis of P-wave first motion, surface wave and aftershock data. From the analysis of long-period multiple surface waves, a seismic moment of 3.1 × 1028 dyn-cm is obtained, which is the largest reported so far for any intermediate or deep focus shock. This value, together with the estimated fault area of 90 × 70 km2, gives an average dislocation of 7.0 m and a stress drop of 120 bar. This event represents an oblique thrust movement on a plane with dip direction N170°E, dip 48° and rake 52°. A geometrical consideration for the fault plane and the configuration of the inclined seismic zone beneath the Banda arc suggests, almost definitely, that the large-scale faulting took place within the subducted plate and offset it. Further repetition of such large-scale faulting might eventually break the subducted plate. The 1963 Banda Sea earthquake thus represents a seismological manifestation of the large-scale deformation of the subducted plate in the mantle. 相似文献
3.
Toshiki Aikawa 《Astrophysics and Space Science》1984,104(2):405-408
It is shown that the coincidence between the pulsation periods and the critical frequencies found by Fadeyev (1982) results from strong effects of non-adiabaticity on the linear pulsation periods in low surface gravity models. If we apply the boundary condition of running waves for super-critical pulsations, it is found that the linear growth-rates are considerably affected by the boundary condition. 相似文献
4.
We found a hydrodynamic pulsation model of yellow supergiants under subharmonic resonance. It is confirmed that the feature of pulsation by the resonance is long-lived in the model by performing the hydrodynamical simulation for a long time. 相似文献
5.
Mixing states of cloud interstitial particles between water-soluble and insoluble materials apparently differ under various cloud-forming conditions. To study the mixing states of cloud interstitial particles, we made observations at Mt. Tateyama, Japan (2300 m a.s.l.) during June 2007 using fog (> 10 μm)-cut inlets. Number concentrations of dried particles (0.3–0.5 μm diameter) selected for less-grown (LG) particles (particles smaller than 0.56 μm diameter at 88% relative humidity) were used to quantify tendencies of the growth characteristics of cloud interstitial particles. Size-segregated soot mass concentrations (< 0.4 and < 1.1 μm) were also measured for cloud interstitial particles. Three samples of cloud interstitial LG particles at 88% RH were investigated for water-soluble and insoluble components using dialysis (extraction) of water-soluble materials with transmission electron microscopy (TEM). For one TEM sample with high fractions of the LG particles and high soot mass concentrations under high precipitation (2–6 mm/h), most particles (0.1–0.5 μm) were found to be water insoluble. More than half of the water-insoluble particles were considered to be soot particles showing chain aggregations of electron-opaque spherules. Regarding the other two TEM samples with low fractions of the LG particles under less intense precipitation (ca. 1 mm/h), most particles were partly water soluble. The scavenging process in the precipitating cloud can change the population of particles left behind, preferentially leaving insoluble particles according to cloud formation conditions. 相似文献
6.
Sato Minoru Oba Takashi Hosokawa Takao Yamaguchi Toshiyasu Nakano Toshiki Saito Tadao Muramoto Koji Kahara T akashi Funayama Katsura Kobayashi Akio Nakano Takahisa 《中国海洋大学学报(英文版)》2005,4(3):209-213
Brown alga （ Undaria pinnatifida） was treated with alginate lyase and hydrolyzed using 17 kinds of proteases and the inhibitory activity of the hydrolysates for the angiotensin-I-converting enzyme （ACE） was measured. Four hydrolysates with potent ACE-inhibitory activity were administered singly and orally to spontaneously hypertensive rats （SHRs）. The systolic blood pressure of SHRs decreases significantly after single oral administration of the brown alga hydrolysates by pro- tease S ＇ Amano＇ （from Bacillus stearothermophilus） at the concentration of 10 （mg protein） （kg body weight）^ - 1. In the 17 weeks of feeding experiment, 7-week-old SHRs were fed standard diet supplemented with the brown alga hydrolysates for 10 weeks. In SHRs fed 1.0 and 0.1% brown alga hydrolysates, elevating of systolic bloodpressure was significantly suppressed for 7 weeks. To elucidate the active components, the brown alga hydrolysates were fractionated by 1-butanol extraction and HPLC on a reverse-phase column. Seven kinds of ACE-inhibitory peptides were isolated and identified by amino acid composition analysis, sequence analysis, and LC-MS with the results Val-Tyr, Ile-Tyr, Ala-Trp, Phe-Tyr, Val-Trp, Ile-Trp, and Leu-Trp. Each peptide was determined to have an antihypertensive effect after a single oral administration in SHRs. The brown alga hydrolysates were also confirmed to decrease the blood pressure in humans. 相似文献
7.
Yuko Suto Sosuke Saito Ken-ichi Osada Hiroshi Takahashi Hideaki Motoyama Yoshiyuki Fujii Yoichi Tanaka 《Polar Science》2008,2(1):15-26
A next-generation drilling system, equipped with a thermal drilling device, is proposed for glacier ice. The system is designed to penetrate glacier ice via melting of the ice and continuously analyze melt-water in a contamination-free sonde. This new type of drilling system is expected to provide analysis data in less time and at less cost than existing systems. Because of the limited number of parameters that can be measured, the proposed system will not take the place of conventional drilling systems that are used to obtain ice cores; however, it will provide a useful method for quickly and simply investigating glacier ice.An electro-thermal drilling device is one of the most important elements needed to develop the proposed system. To estimate the thermal supply required to reach a target depth in a reasonable time, laboratory experiments were conducted using ice blocks and a small sonde equipped solely with heaters. Thermal calculations were then performed under a limited range of conditions. The experiments were undertaken to investigate the effects of the shape and material of the drill head and heater temperature on the rate of penetration into the ice. Additional thermal calculations were then performed based on the experimental results.According to the simple thermal calculations, if the thermal loss that occurs while heat is transferred from the heater to ice (in melting the ice) is assumed to be 50%, the total thermal supply required for heaters in the sonde and cable is as follows: (i) 4.8 kW (sonde) plus 0 W (cable) to penetrate to 300 m depth over 10 days into temperate glacier ice for which the temperature is 0 °C at all depths and to maintain a water layer along 300 m of cable; (ii) 10 kW (sonde) plus 19–32 kW (cable) to penetrate to 1000 m depth over 1 month into cold glacier ice for which the temperature is −25 °C at the surface and 0 °C at 1000 m depth and to maintain a water layer along 1000 m of cable; and (iii) 19 kW (sonde) plus 140–235 kW (cable) to penetrate to 3000 m depth over 2 months into an ice sheet for which the temperature is −55 °C at the surface and 0 °C at 3000 m depth and to maintain a water layer along 3000 m of cable. The thermal supply required for the cable is strongly affected by the thickness of the water layer, cable diameter, and the horizontal distance from the ice wall at which the ice temperature was maintained at its initial temperature. A large thermal supply is required to heat 3000 m of cable in an ice sheet (scenario (iii) above), but penetration into glacier ice (scenarios (i) and (ii) above) could be realistic with the use of a currently employed generator. 相似文献
8.
Antidunes are fluvial bedforms that form in rivers with supercritical flows. The water surface over antidunes is strongly in phase with the bed surface, and the water surface is amplified to produce large surface waves. Many experimental studies have addressed antidunes; however, the shapes of three-dimensional antidunes in a wide channel with alternate bars have not yet been appropriately understood. In this study, we experimentally investigated the streamwise and transverse length scales of antidunes under conditions with a large width–depth ratio. Our experimental results provide evidence for the coevolution of antidunes and free alternate bars, and show for the first time that the development of free bars greatly alters the three-dimensional shape of water surface waves over antidunes. In the absence of free bars in a wide channel, multiple longitudinal wave trains form, and the number of wave trains counted in the transverse direction increases with increases in the width–depth ratio. However, the presence of free bars affects the local flow characteristics, resulting in a decrease of the number of wave trains in the transverse direction. Therefore, we propose a simple model for predicting the reduction in the number of wave trains by combining two previous theories for antidunes and free bars. Results obtained by the model were found to largely agree with experimental observations. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
9.
Toshiki Aikawa 《Astrophysics and Space Science》1987,139(2):281-293
Hydrodynamic simulations of nonlinear pulsation for less-massive cool supergiants have been performed by several authors. Outburst of large amplitude oscillations at times is one of common features of these models. To find out routes of the transition from the limit cycles to the irregular pulsations. We performed hydrodynamic simulation for a series of models of luminosity log(L/L
)=3.505, andT
e
=5300 K with the range of the mass 1.4M
M1.5M
. With decreasing the mass, we confirm a transition from limit cycles to irregular oscillations.The nature of the transition is finally specified by examining the dissipation of pulsational kinetic energies in limit cycle models, when pulsations start with larger amplitudes than their limiting pulsations. We find that the rates of dissipation are so small that they might be marginally stable. Furthermore, the oscillation starting with even larger amplitudes gets the kinetic energies until it reaches a limit where the oscillation induces strong shock waves and dissipates its kinetic energy. Thus, we conclude that the model which has the stable limit cycle near the transition has another unstable fixed point above the limit cycle. The transition, therefore, is induced by disappearance of these two fixed points, as the mass, the control parameter in our case, is varied, and is found exactly in aggreement with the intermittency proposed by Pomeau and Manneville as a route to chaos in dissipative systems. 相似文献
10.
Toshiki Aikawa 《Astrophysics and Space Science》1985,110(1):125-131
The conclusions of the present paper broadly are: (a) The galactic concentration of doubles by comparing the distributions in galactic latitudes 0°<20° and >40° is nearly twice as large as the galactic concentration of stars in general. (b) The astrographic catalogues are not complete in the fainter magnitudes. (c) The large value of the ratioT:O
k (observed to optical number of pairs) from Kreiken's formula shows that almost all stars in the group 0<d5 and quite a few in the other two groups, viz., 5<d10 and 10<d15 might be shown true binaries. Consequently, Aitken's working definition of a true binary should be extended if it were to include all true binaries. (d) The doubles are probably stars of Population I. (e) The logarithm to the base 10 of the cumulative counts can be represented by an empirical relationA+B(m–1.5)+C(m–1.5)2.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846) 相似文献