Real-time difference imaging analysis of MOA Galactic bulge observations during 2000     

I.A. Bond  F. Abe  R.J. Dodd  J.B. Hearnshaw  M. Honda  J. Jugaku  P.M. Kilmartin  A. Marles  K. Masuda  Y. Matsubara  Y. Muraki  T. Nakamura  G. Nankivell  S. Noda  C. Noguchi  K. Ohnishi  N.J. Rattenbury  M. Reid  To. Saito  H. Sato  M. Sekiguchi  J. Skuljan  D.J. Sullivan  T. Sumi  M. Takeuti  Y. Watase  S. Wilkinson  R. Yamada  T. Yanagisawa  P.C.M. Yock 《Monthly notices of the Royal Astronomical Society》2001,327(3):868-880

We describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification is high and/or of short duration. These events are particularly useful for studies of extrasolar planets and faint stars. Approximately 17 deg² were monitored at a sampling rate of up to six times per night. The images were analysed in real time using a difference imaging technique. 20 microlensing candidates were detected, of which eight were alerted to the microlensing community whilst in progress. Approximately half of the candidates had high magnifications (≳10), at least one had very high magnification (≳50), and one exhibited a clear parallax effect. The details of these events are reported here, together with details of the on-line difference imaging technique. Some nova-like events were also observed and these are described, together with one asteroid.  相似文献   

Microboudin structures of piemontite along the Sambagawa metamorphic belt, Japan: implications for lateral variation of differential stress during regional metamorphism     

T. Masuda  T. Shibutani  T. Ochiai  S. Akagi  H. Yamaguchi  Y. Kugimiya  N. Kimura  T. Miyake 《Journal of Metamorphic Geology》2004,22(3):199-205

Evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains (p) in a quartz matrix in metacherts. It is proposed that p is a practical indicator of relative differential stress. Analysis of 123 metacherts from the 800 km long Sambagawa metamorphic belt, Japan, reveals that p‐values range from < 0.01 to 0.7 in this region. Most samples from Wakayama in the mid‐belt area have p‐values of 0.4–0.6, whereas those from western Shikoku have p‐values of < 0.1. This difference cannot be explained by variations in metamorphic temperature, and is instead attributed to a regional, lateral variation in differential stress during metamorphism.  相似文献   

Magnitude of σ₁, σ₂, and σ₃ at mid-crustal levels in an orogenic belt: Microboudin method applied to an impure metachert from Turkey     

Toshiaki Masuda  Shotaro Nakayama  Nozomi Kimura  Atsushi Okamoto   《Tectonophysics》2008,460(1-4):230-236

We revised an equation for estimating palaeostress magnitude using the microboudin technique by incorporating the influence of time on the fracture strength of minerals. The equation was used to estimate triaxial palaeostresses from a rare sample of metachert from Turkey that contains microboudinaged, columnar tourmaline grains in a wide range of orientations within the foliation plane. The estimated principal palaeostresses are σ₁ = 605 MPa, σ₂ = 598 MPa, and σ₃ = 597 MPa. As the microboudinage is considered to have occurred immediately before the rock encountered the brittle-plastic transition during exhumation, these stress values correspond to conditions at approximately 18 km depth and 300 °C within a Cretaceous orogenic belt.  相似文献   

Relationship between Salinity and Nutrients in the Subsurface Layer in the Suruga Bay     

Tatsuya?IwataEmail author  Yoshiko?Shinomura  Yuta?Natori  Yasumasa?Igarashi  Rumi?Sohrin  Yoshimi?Suzuki 《Journal of Oceanography》2005,61(4):721-732

We investigated the water structure and nutrient distribution in the Suruga Bay from April 2000 to July 2002, especially the Offshore Water, which occupies a large part of the bay. The maximum salinity in the upper 200 m varied between 34.49 and 34.71, indicating a temporal change in the influence of Kuroshio Water on the Offshore Water. Seasonal variation in nutrient concentrations was largest from surface to 50 m. On the other hand, the variance in nutrient concentrations within each season was largest in the subsurface layer of 100–300 m in spring, summer and fall. In the Offshore Water, the change of nutrients was negatively correlated with that of salinity in each season. This suggests that an increasing intrusion of saline water brings about a lower nutrient concentration in the Offshore Water. Likewise, negative correlations were observed between the change of the maximum salinity and chlorophyll a (Δ [chl.a-int])/nutrients integrated in the upper 200 m. Δ[chl.a-int] was significantly correlated with the changes of nitrate and phosphorus, but there were no significant correlations between Δ[chl.a-int] and the change of silicate. These results suggest that the concentrations of chlorophyll a and nutrients in the Offshore Water were decreased due to the increasing intrusion of Kuroshio Water. The Offshore Water is likely to be related to the regulation of primary production by nitrate.  相似文献   

II-3 Full-scale performance tests on tandem wells turbine     

Yukihisa Washio  Hitoshi Hotta  Takeaki Miyazaki  Yoshio Masuda 《Ocean Engineering》1985,12(6):564

  相似文献   

State Estimation of the North Pacific Ocean by a Four-Dimensional Variational Data Assimilation Experiment   总被引：1，自引：0，他引：1  

Toshiyuki Awaji  Shuhei Masuda  Yoichi Ishikawa  Nozomi Sugiura  Takahiro Toyoda  Tomohiro Nakamura 《Journal of Oceanography》2003,59(6):931-943

A four-dimensional variational data assimilation system has been applied to an experiment to describe the dynamic state of the North Pacific Ocean. A synthesis of available observational records and a sophisticated ocean general circulation model produces a dynamically consistent dataset, which, in contrast to the nudging approach, provides realistic features of the seasonally-varying ocean circulation with no artificial sources/sinks for temperature and salinity fields. This new dataset enables us to estimate heat and water mass transports in addition to the qualification of water mass formation and movement processes. A sensitivity experiment on our assimilation system reveals that the origin of the North Pacific Intermediate Water can be traced back to the Sea of Okhotsk and the Bering Sea in the subarctic region and to the subtropical Kuroshio region further south. These results demonstrate that our data assimilation system is a very powerful tool for the identification and characterization of ocean variabilities and for our understanding of the dynamic state of ocean circulation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

III-5 Research on hydrodynamic characteristics of OWC type floating wave power absorber     

Koichi Masuda 《Ocean Engineering》1985,12(6):572

  相似文献   

Bachelor-modon type eddies and isolated eddies near the coast on anf-plane     

Akira Masuda  Kenji Marubayashi  Michiyoshi Ishibashi 《Journal of Oceanography》1987,43(6):383-394

The behavior of isolated meso-scale eddies near the coastal boundary is studied by numerical experiments based on the quasi-geostrophic equation in a basin on an f-plane. First, Bachelor-modon type eddies are investigated as an idealized model of isolated eddies close to the wall. The first-mode Bachelor-modon type eddy is found to be robust enough to recover its original form even after it turns a corner of the basin. In contrast, the second mode is unstable; it tends to move away from the wall and finally splits into two eddies proceeding in opposite directions along the wall. An initially Gaussian eddy a little distant from the boundary interacts with a Bachelor-modon type eddy translating along the boundary, sometimes resulting in vortex merging and pairing just as in the head-on collision of two modons on a beta-plane. It is found that an initially Gaussian eddy located moderately close to the coast rapidly settles down to a steadily translating eddy, which can be approximated remarkably well by a first-mode Bachelor-modon type eddy not only in appearance but also in translation velocity within an error of about 20%.  相似文献   

A note on internal wavetrains and the associated undulation of the sea surface observed upstream of seamounts     

Arata Kaneko  Hiroyuki Honji  Kazuo Kawatate  Shinjiro Mizuno  Akira Masuda  Tsunehiro Miita 《Journal of Oceanography》1986,42(1):75-82

An internal wavetrain, generated by a tidal current in superposition with the Tsushima Warm Current, has been observed by use of an acoustic echo-sounder upstream of the Shichiri-Ga-Sone Seamounts in the East Tsushima Strait of the Japan Sea. The sea surface above the internal wavetrain was simultaneously observed and was found to be undulated at the wavelength of the internal wave.  相似文献   

Ce and Nd isotope geochemistry on island arc volcanic rocks with negative Ce anomaly: existence of sources with concave REE patterns in the mantle beneath the Solomon and Bonin island arcs   总被引：5，自引：0，他引：5  

Hiroshi Shimizu  Hideyuki Sawatari  Yousuke Kawata  Peter N. Dunkley  Akimasa Masuda 《Contributions to Mineralogy and Petrology》1992,110(2-3):242-252

¹³⁸Ce/¹⁴²Ce isotope ratios in Cenozoic island arc volcanic rocks are reported for the first time, together with isotope ratios of Nd and Sr and abundances of REE, Ba and Sr. The island arc volcanics studies here are boninites from Chichijima, the Bonin Islands, and basalts and andesites from the Solomon Islands. REE patterns of the island arc volcanic rocks from the Solmon Islands and the Bonin Islands are confirmed to have negative Ce anomalies. It is also disclosed that the majority of these island arc volcanic rocks show mainly positive values for both _Ce and _Nd. It is shown that these _Ce and _Ce values can hardly be interpreted by simple mixing between MORB and oceanic or continental crustal rocks; the former have positive _Nd and negative _Ce and the latter have negative _Ce and positive or negative _Nd. Existence of sources having positive _Ce and _Nd values is strongly suggested. If the sources are assumed to have been fractionated from CHUR (chondritic uniform reservoir) at the early or middle Precambrian era, the sources from which the volcanics were derived are concluded to have kept concave REE patterns with larger (La/Ce)_N and smaller (Nd/Sm)_N ratios than chondritic values over a substantial period of time, until the time of Cenozoic magmatism forming island arc volcanic rocks in question. During the periods of the Cenozoic magmatic activities and their related events, Ce anomalies are considered to have been created. From Ce and Nd isotope ratios, however, it is difficult to determine which of the following processes was responsible for the Ce anomaly; the incorporation process of subducted oceanic crust into magma at the mantle or the slab dehydration and metasomatism process. Nevertheless, so far as Ce and Nd isotopic ratios are concerned, incorporation of oceanic sediments did not take place to any clearly detectable degree.  相似文献