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111.
C. Kaito Y. Ojima K. Kamitsuji O. Kido Y. Kimura H. Suzuki T. Sato T. Nakada Y. Saito C. Koike 《Meteoritics & planetary science》2003,38(1):49-57
Abstract— Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain‐grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain‐rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain‐rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite. 相似文献
112.
The production of Fe2SiO4 (fayalite) crystalline grains was performed by two processes, namely, grain formation in a plasma field by evaporating a mixture powder of Fe and SiO and heat treatment of the product collected on the radio-frequency (RF) electrode side. Fe grains <20 nm in size covered with an amorphous SiO layer selectively formed Fe2SiO4 grains by heating at 800 °C. By heating at 600 °C, in addition to the formation of Fe2SiO4 crystal grains, the FeO phase appeared. The doping effect of excited oxygen in a plasma field into the Fe small grains may be the trigger on the formation of fayalite through the FeO phase formation. The present experimental result suggests that the probability of Fe2SiO4 grain formation in space is low. 相似文献
113.
The bulk flow of the solar wind plasma in the flank-side of the magnetospheric boundary layer, where the magnetic field lines are closed, has a component transverse to the ambient field. There is quite a strong velocity shear. The theoretical model ignores inhomogeneities in the ambient field and the mass density which occur at the magnetopause on about the same length scale as that of the velocity shear.Consideration is restricted to hydromagnetic waves which have a k-vector nearly normal to the Bo-Vo plane, i.e., approximately the magnetopause surface (kx >kz ~ ky′kxLB > 1 and LB = 0.1 ~ 1.0 RE where LB is a characteristic length of the boundary layer). It is found that a long-period (T ? 40 sec) hydromagnetic wave [the Alfvén-like wave ()] driven by velocity shear instability can be excited in the shear plasma. It is also found that the group velocity of the HM-wave is directed almost along the magnetic field line and that the magnetic variance in the shear plasma tends to be parallel to the Bo-Vo plane. The velocity shear instability in the magnetospheric boundary layer is judged to be a likely source of long-period magnetic pulsations. 相似文献
114.
As a major type of soil internal erosion, suffusion is causative for many geotechnical problems of earth structures and foundations. Although full laboratory tests are laborious, it is inevitable for susceptible soils. However, a good quick assessment can define those susceptible soils by eliminating quickly very stable and unstable soils from consideration. Traditional assessment methods often correlate and combine some predefined fixed particle sizes representing coarse and fine fractions of soils. This paper presents a novel, simple assessment method for identifying susceptibility to suffusion based on the general curvature of particle size distribution of soils. The further down a particle size distribution departs from its mean line, the more likely it behaves suffusive. The new assessment method has been tested against experimental data, and the results show some good correlation. 相似文献
115.
Gui-Chen Ma Kazuhide Sawada Atsushi Yashima Hideki Saito 《Rock Mechanics and Rock Engineering》2015,48(2):787-802
This paper examines a new method for evaluating the stability of rock blocks on slopes using a remotely positioned Laser Doppler Vibrometer (LDV). A series of experiments using physical models were conducted to evaluate the validity of this new method. Based on the experimental studies, the applicability of LDV was examined by comparing results with a conventional seismometer measurement. To examine the quantitative correlations between vibration properties and the stability of a rock block, the effects on the vibration properties of the size of the rock block, the initial block position, the slope incline, and the type of ground surface were studied. The experimental results showed that LDV measurements agreed with conventional seismometer measurements. There was also a good correlation between vibration properties and rock-block stability. On the other hand, it was found that for a boulder on tightly compacted ground, the application of block stability assessment by tonometry was difficult when measuring microtremors or sloppy vibration due to nearby vehicle traffic. Furthermore, numerical analysis of the slope model was carried out to examine the validity of the model experiment and application of the suggested technique. The results of the analysis demonstrated that the suggested technique was effective for application to stability monitoring of a block and evaluation of the effect of stability measures. 相似文献
116.
Laurel Saito Bill Christian Jennifer Diffley Holly Richter Melissa M. Rohde Scott A. Morrison 《Ground water》2021,59(3):322-333
Groundwater is a critical resource not only for human communities but also for many terrestrial, riparian, and aquatic ecosystems and species. Yet groundwater planning and management decisions frequently ignore or inadequately address the needs of these natural systems. As a consequence, ecosystems dependent on groundwater have been threatened, degraded, or eliminated, especially in arid regions. There is growing acknowledgment that governmental protections for these ecological resources are necessary, but current legal, regulatory and voluntary provisions are often inadequate. Groundwater management premised on “safe yield,” which aims to balance human withdrawals with natural recharge rates, typically provides little to no consideration for water needed by ecosystems. Alternatively, the “sustainable yield” concept aims to integrate social, economic and environmental needs for groundwater, but the complexity of groundwater systems creates substantial uncertainty about the impact that current or future groundwater withdrawals will have on ecosystems. Regardless of the legal or regulatory framework, guidance is needed to help ensure environmental water needs will be met, especially in the face of pressure to increase human uses of groundwater resources. In this paper, we describe minimum provisions for planning, managing, and monitoring groundwater that collectively can lower the risk of harm to groundwater-dependent ecosystems and species, with a special emphasis on arid systems, where ecosystems and species may be especially reliant upon and sensitive to groundwater dynamics. 相似文献
117.
The stability limit of coplanar hierarchical triple systems is numerically studied. Systems we investigated consist of two equal mass bodies initially on a circular orbit and third body with various masses, which at the maximum are equal to the mass of the binary. In order to estimate the stability limit, we use an empirically-found fact that the system is quasi-periodic if the initial eccentricity of the outer binary is less than some critical value, otherwise the third body eventually escapes. We make an analytical expression for the stability limit in terms of the ratio of the orbital radii and find that the expression improves the previous criteria. The resultant expression also suggests that the ratio of the orbital radii rapidly approaches to a certain value (e.g. $\sim $ 2, in an initially circular outer binary) as the mass of the third-body tends to zero. 相似文献
118.
M. M. Saito K. Tanikawa V. V. Orlov 《Celestial Mechanics and Dynamical Astronomy》2012,112(3):235-251
The stability of hierarchical triple system is studied in the case of an extrasolar planet or a brown dwarf orbiting a pair
of main sequence stars. The evolution of triple system is well modelled by random walk (RW) diffusion, particularly in the
cases where the third body is small and tracing an orbit with a large eccentricity. A RW model neglects the fact that there
are many periodic orbits accompanied by stability islands, and hence inherently overestimates the instability of the system.
The present work is motivated by the hope to clarify how far the RW model is applicable. Escape time and the surface section
technique are used to analyse the outcome of numerical integrations. The analysis shows that the RW-like model explains escape
of the third body if the initial configuration is directly outside of the KAM tori. A small gap exists in (q
2/a
1, e
2)-plane between locations of the stability limit curves based on our numerical study and on RW-model (the former is shifted
by –1.4 in q
2/a
1 direction from the latter). 相似文献
119.
Satoshi Saito Makoto Arima Takashi Nakajima Kenichiro Tani Takashi Miyazaki Ryoko Senda Qing Chang Toshiro Takahashi Yuka Hirahara Jun-Ichi Kimura 《Contributions to Mineralogy and Petrology》2012,163(4):611-629
The Miocene Kaikomagatake pluton is one of the Neogene granitoid plutons exposed in the Izu Collision Zone, which is where
the juvenile Izu-Bonin oceanic arc is colliding against the mature Honshu arc. The pluton intrudes into the Cretaceous to
Paleogene Shimanto accretionary complex of the Honshu arc along the Itoigawa-Shizuoka Tectonic Line, which is the collisional
boundary between the two arcs. The pluton consists of hornblende–biotite granodiorite and biotite monzogranite, and has SiO2 contents of 68–75 wt%. It has high-K series compositions, and its incompatible element abundances are comparable to the average
upper continental crust. Major and trace element compositions of the pluton show well-defined chemical trends. The trends
can be interpreted with a crystal fractionation model involving the removal of plagioclase, biotite, hornblende, quartz, apatite,
and zircon from a potential parent magma with a composition of ~68 wt% SiO2. The Sr isotopic compositions, together with the partial melting modeling results, suggest that the parent magma is derived
by ~53% melting of a hybrid lower crustal source comprising ~30% Shimanto metasedimentary rocks of the Honshu arc and ~70%
K-enriched basaltic rocks of the Izu-Bonin rear-arc region. Together with previous studies on the Izu Collision Zone granitoid
plutons, the results of this study suggest that the chemical diversity within the parental magmas of the granitoid plutons
reflects the chemical variation of basaltic sources (i.e., across-arc chemical variation in the Izu-Bonin arc), as well as
a variable contribution of the metasedimentary component in the lower crustal source regions. In addition, the petrogenetic
models of the Izu Collision Zone granitoid plutons collectively suggest that the contribution of the metasedimentary component
is required to produce granitoid magma with compositions comparable to the average upper continental crust. The Izu Collision
Zone plutons provide an exceptional example of the transformation of a juvenile oceanic arc into mature continental crust. 相似文献
120.
Daniel Brown Keiko Saito Meng Liu Robin Spence Emily So Michael Ramage 《Bulletin of Earthquake Engineering》2012,10(3):741-764
The M7.9 Wenchuan earthquake on May 12th, 2008 was the most destructive in China since 1976. The event caused huge damage and loss of life and exposed weaknesses both in the formulation and implementation of the regulations governing building in the affected provinces. Following the earthquake a massive relief and recovery operation was mounted by the Chinese government. The authors took part in field studies in the affected area which took place 5 and 11?months after the event, at which time recovery operations were well-advanced. The aims of the study were to assess the effects caused by the earthquake to the built environment and society, to collect information on the ongoing recovery efforts and future plans, and to demonstrate the use of tools that allow the collection of spatially referenced damage and recovery data. Based on available satellite imagery supplemented by ground observation, geodatabases were constructed containing information on damage and recovery in several parts of the affected area. The paper gives an overview of the recovery process, describes the methods used to construct these geodatabases, and offers some analysis of the data obtained. It is argued that such databases have great potential for the management of post-disaster recovery and for creating a permanent record of the recovery process. 相似文献