Dispersion and attenuation of elastic waves due to multiple scattering from inclusions     

Masayuki Kikuchi 《Physics of the Earth and Planetary Interiors》1981,25(2):159-162

The propagation of elastic waves in a medium containing many inclusions is considered. Under the assumption that the spatial distribution of inclusions is uniform, a general equation is derived for the determination of the velocity dispersion and attenuation coefficient of the effective waves. A simple example is presented where scatterers are infinitesimally thin cracks. The calculated results show that the attenuation coefficient Q^?1 takes a peak value for the wavelength nearly equal to twice the crack length.  相似文献   

A numerical method for estimation of impulse response and its application to laboratory data     

Masayuki Kikuchi 《Physics of the Earth and Planetary Interiors》1979,19(3):255-262

Following Burg's algorithm, we develop a new mathematical method of estimating the impulse response of a linear system. Since no data-invariant time window is used in this method, the estimated impulse response gives us reliable information on both the amplitude and the phase spectra of the system.The method is applied to laboratory data to investigate the dynamical response of rock specimens. The experimental results show that the waveform distortion with travel distance may well be described by a standard viscoelastic solid model. However, they also show that there is an additional factor of attenuation which is independent of the frequency and therefore not accompanied by any velocity dispersion.  相似文献   

Dependence of the build-up of the colour–magnitude relation on cluster richness at z∼ 0.8     

Yusei Koyama  Tadayuki Kodama  Masayuki Tanaka  Kazuhiro Shimasaku  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2007,382(4):1719-1728

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Synthesis of highly dense and fine-grained aggregates of mantle composites by vacuum sintering of nano-sized mineral powders     

Sanae Koizumi  Takehiko Hiraga  Chihiro Tachibana  Miki Tasaka  Tomonori Miyazaki  Tamio Kobayashi  Asako Takamasa  Naoki Ohashi  Satoru Sano 《Physics and Chemistry of Minerals》2010,37(8):505-518

Synthesized mineral powders with particle size of <100 nm are vacuum sintered to obtain highly dense and fine-grained polycrystalline mantle composites: single phase aggregates of forsterite (iron-free), olivine (iron containing), enstatite and diopside; two-phase composites of forsterite + spinel and forsterite + periclase; and, three-phase composites of forsterite + enstatite + diopside. Nano-sized powders of colloidal SiO₂ and highly dispersed Mg(OH)₂ with particle size of ≤50 nm are used as chemical sources for MgO and SiO₂, which are common components for all of the aggregates. These powders are mixed with powders of CaCO₃, MgAl₂O_4, and Fe(CO₂CH₃)₂ to introduce mineral phases of diopside, spinel, and olivine to the aggregates, respectively. To synthesize highly dense composites through pressureless sintering, we find that calcined powders should be composed of particles that have: (1) fully or partially reacted to the desired minerals, (2) a size of <100 nm and (3) less propensity to coalesce. Such calcined powders are cold isostatically pressed and then vacuum sintered. The temperature and duration of the sintering process are tuned to achieve a balance between high density and fine grain size. Highly dense (i.e., porosity ≤1 vol%) polycrystalline mantle mineral composites with grain size of 0.3–1.1 μm are successfully synthesized with this method.  相似文献   

Numerical forecasting of the time interval between successive M8 earthquakes along the Nankai Trough,southwest Japan,using ocean bottom cable network data     

Takane Hori  Mamoru Hyodo  Shin’ichi Miyazaki  Yoshiyuki Kaneda 《Marine Geophysical Researches》2014,35(3):285-294

One possible approach to estimating the time interval between large-scale Tōnankai (Tōkai) and Nankai earthquakes on the Japan arc is sequential assimilation of crustal deformation data. We conducted numerical modeling of sequential assimilation using surface deformation calculated from earthquake generation cycle simulations along the Nankai Trough. To account for observation noise, we used measured ocean bottom pressure gauge data, excluding tidal modulation, from a station on the ocean bottom cable network Dense Oceanfloor Network System for Earthquakes and Tsunamis in the Kumano basin. We used sequential importance sampling as our data assimilation method. We found that as the amount of data increased, the estimated time interval between the Tōnankai and Nankai earthquakes approached the “true” observed interval. In addition, the noise in the pressure gauge data was sufficiently small that simulated crustal deformation patterns could be distinguished for different time intervals.  相似文献   

Primary melt from Sannome-gata volcano,NE Japan arc: constraints on generation conditions of rear-arc magmas     

Takeshi?KuritaniEmail author  Takeyoshi?Yoshida  Jun-Ichi?Kimura  Toshiro?Takahashi  Yuka?Hirahara  Takashi?Miyazaki  Ryoko?Senda  Qing?Chang  Yoshinori?Ito 《Contributions to Mineralogy and Petrology》2014,167(2):969

The conditions under which rear-arc magmas are generated were estimated using primary basalts from the Sannome-gata volcano, located in the rear of the NE Japan arc. Scoriae from the volcano occur with abundant crustal and mantle xenoliths, suggesting that the magma ascended rapidly from the upper mantle. The scoriae show significant variations in their whole-rock compositions (7.9–11.1 wt% MgO). High-MgO scoriae (MgO > ~9.5 wt%) have mostly homogeneous ⁸⁷Sr/⁸⁶Sr ratios (0.70318–0.70320), whereas low-MgO scoriae (MgO < ~9 wt%) have higher ⁸⁷Sr/⁸⁶Sr ratios (>0.70327); ratios tend to increase with decreasing MgO content. The high-MgO scoriae are aphyric, containing ~5 vol% olivine microphenocrysts with Mg# [100 × Mg/(Mg + Fe²⁺)] of up to 90. In contrast, the low-MgO scoriae have crustal xenocrysts of plagioclase, alkali feldspar, and quartz, and the mineralogic modes correlate negatively with whole-rock MgO content. On the basis of these observations, it is inferred that the high-MgO scoriae represent primary or near-primary melts, while the low-MgO scoriae underwent considerable interaction with the crust. Using thermodynamic analysis of the observed petrological features of the high-MgO scoriae, the eruption temperature of the magmas was constrained to 1,160–1,220 °C. Given that the source mantle was depleted MORB-source mantle, the primary magma was plausibly generated by ~7 % melting of a garnet-bearing spinel peridotite; taking this into consideration, and considering the constraints of multi-component thermodynamics, we estimated that the primary Sannome-gata magma was generated in the source mantle with 0.5–0.6 wt% H₂O at 1,220–1,230 °C and at ~1.8 GPa, and that the H₂O content of the primary magma was 6–7 wt%. The rear-arc Sannome-gata magma was generated by a lower degree of melting of the mantle at greater depths and lower temperatures than the frontal-arc magma from the Iwate volcano, which was also estimated to be generated by ~15 % melting of the source mantle with 0.6–0.7 wt% H₂O at ~1,250 °C and at ~1.3 GPa.  相似文献   

Instruments, Detectors and the Future of Astronomy with Large Ground Based Telescopes     

Douglas A. Simons  Paola Amico  Dietrich Baade  Sam Barden  Randall Campbell  Gert Finger  Kirk Gilmore  Roland Gredel  Paul Hickson  Steve Howell  Norbert Hubin  Andreas Kaufer  Ralf Kohley  Philip MacQueen  Sergej Markelov  Mike Merrill  Satoshi Miyazaki  Hidehiko Nakaya  Darragh O'Donoghue  Tino Oliva  Andrea Richichi  Derrick Salmon  Ricardo Schmidt  Hongjun Su  Simon Tulloch  Maria Luisa García Vargas  R. Mark Wagner  Olivier Wiecha  Binxun Ye 《Experimental Astronomy》2005,19(1-3):15-44

Results of a survey of instrumentation and detector systems, either currently deployed or planned for use at telescopes larger than 3.5 m, in ground based observatories world-wide, are presented. This survey revealed a number of instrumentation design trends at optical, near, and mid-infrared wavelengths. Some of the most prominent trends include the development of vastly larger optical detector systems (> 10⁹ pixels) than anything built to date, and the frequent use of mosaics of near-infrared detectors – something that was quite rare only a decade ago in astronomy. Some future science applications for detectors are then explored, in an attempt to build a bridge between current detectors and what will be needed to support the research ambitions of astronomers in the future.  相似文献   

Flapping motions of the tail plasma sheet induced by the interplanetary magnetic field variations     

Toichi Tsutomu  Miyazaki Teruki 《Planetary and Space Science》1976,24(2):147-159

Flapping motions of the magnetotail with an amplitude of several earth radii are studied by analysing the observations made in the near (x = ?25 ~ ?30 R_E and the distant (x? ?60 R_E) tail regions. It is found that the flapping motions result from fluctuations in the interplanetary magnetic field, especially Alfvénic fluctuations, when the magnitude of the interplanetary magnetic field is larger than ~10 γ and they propagate behind the Earth with the solar wind flow. Flappings tend to be observed in early phases of the magnetospheric substorm, and they have two fundamental modes with periods of ~200 and ~500 sec. In some limited cases a good correspondence with the long period micropulsations (Pc5) in the polar cap region is observed. These observational results are explained by the model in which the Alfvénic fluctuations in the solar wind penetrate into the magnetosphere along the connected interplanetary-magnetospheric field lines. The characteristics of the flapping reveal that the geomagnetic tail is a good resonator for the hydromagnetic disturbances in the solar wind.  相似文献   

Measurement of methane flux over an evergreen coniferous forest canopy using a relaxed eddy accumulation system with tuneable diode laser spectroscopy detection     

Ayaka Sakabe  Ken Hamotani  Yoshiko Kosugi  Masahito Ueyama  Kenshi Takahashi  Akito Kanazawa  Masayuki Itoh 《Theoretical and Applied Climatology》2012,109(1-2):39-49

Very few studies have conducted long-term observations of methane (CH₄) flux over forest canopies. In this study, we continuously measured CH₄ fluxes over an evergreen coniferous (Japanese cypress) forest canopy throughout 1?year, using a micrometeorological relaxed eddy accumulation (REA) system with tuneable diode laser spectroscopy (TDLS) detection. The Japanese cypress forest, which is a common forest type in warm-temperate Asian monsoon regions with a wet summer, switched seasonally between a sink and source of CH₄ probably because of competition by methanogens and methanotrophs, which are both influenced by soil conditions (e.g., soil temperature and soil moisture). At hourly to daily timescales, the CH₄ fluxes were sensitive to rainfall, probably because CH₄ emission increased and/or absorption decreased during and after rainfall. The observed canopy-scale fluxes showed complex behaviours beyond those expected from previous plot-scale measurements and the CH₄ fluxes changed from sink to source and vice versa.  相似文献   

Climate change, land use change, and China’s food security in the twenty-first century: an integrated perspective   总被引：5，自引：0，他引：5  

Fulu Tao  Masayuki Yokozawa  Jiyuan Liu  Zhao Zhang 《Climatic change》2009,93(3-4):433-445

Food security in China, the world’s most populous country, has long been a concern because of the challenges of population growth, water shortages, and loss of cropland through urbanization, soil degradation, and climate change. Here, we present an integrated analysis of China’s food demand and supply under IPCC Special Report on Emissions Scenarios A1, A2, B1, and B2 in 2020, 2050, and 2080, based on official statistics and future development scenarios. Our analysis accounts for future socioeconomic, technological, and resource developments, as well the impact of climate change. We present a covariant relationship between changes in cereal productivity due to climate change and the cereal harvest area required to satisfy China’s food demand. We also estimated the effects of changing harvested areas on the productivity required to satisfy the food demand; of productivity changes due to climate change on the harvest area required to satisfy food demand; and of productivity and land use changes on the population at risk of undernutrition. China could be able to feed herself without disturbing the global food market in the twenty-first century, but whether the government will choose self-sufficiency or increased food imports may depend on the cost of change, which remains unknown.  相似文献