Holographic View of Cosmological Perturbations     

Jiro Soda  Sugumi Kanno 《Astrophysics and Space Science》2003,283(4):639-644

The cosmological perturbation theory is revisited from the holographic point of view. In the case of the single brane model, it turns out that the AdS/CFT correspondence plays an important role. In the case of the two-brane model, it is shown that the effective equations of motion becomes the quasi-scalar-tensor gravity. It is also demonstrated that the radion anisotropy gives the CMB fluctuations through the Sachs-Wolfe effect. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Possible Density Change of the Origin of North Pacific Intermediate Water Due to Double Diffusion in the Mixed Water Region     

Ryuichiro?InoueEmail author  Jiro?Yoshida 《Journal of Oceanography》2005,61(5):871-883

In this study we test Talley's hypothesis that Oyashio winter mixed-layer water (26.5–26.6σ _θ) increases its density to produce the North Pacific Intermediate Water (NPIW) salinity minimum (26.7– 26.8σ_θ) in the Mixed Water Region, assuming a combination of cabbeling and double diffusion. The possible density change of Oyashio winter mixed-layer water is discussed using an instantaneous ratio of the change of temperature and salinity along any particular intrusion (R _l ). We estimate the range of R _l ^DD required to convert Oyashio winter mixed-layer water to the NPIW salinity minimum due to double diffusion, and then assume double-diffusive intrusions as this conversion mechanism. A double-diffusive intrusion model is used to estimate R _l ^DD in a situation where salt fingering dominates vertical mixing, as well as to determine whether Oyashio winter mixed-layer water can become the NPIW salinity minimum. Possible density changes are estimated from the model R _l ^DD by assuming the amount of density change due to cabbeling. From these results, we conclude that Oyashio winter mixed-layer water contributes to a freshening of the lighter layer of the NPIW salinity minimum (around 26.70σ_θ) in the MWR.  相似文献   

Japan-equator XBT sections in late November 1989 and in early December 1991     

Jiro Yoshida  Hideo Sudo  Masaji Matsuyama  Yoshihiro Kurita  Yuji Mine 《Journal of Oceanography》1993,49(1):121-129

A comparison between Japan-equator XBT sections along 150°E in late November 1989 and along 140°E in early December 1991 is made. The warmest surface water above 29°C diminished to the south of 2–4°N and the surface mixed layer noticeably decreased in thickness in the equatorial region in December 1991; besides, the North Equatorial Countercurrent was intensified. This is considered to be a manifestation of changes in the surface layer of the western equatorial Pacific in the mature phase of El Niño.  相似文献   

Phytoplankton communities in the Bering Sea and adjacent seas     

Akira Taniguchi  Kazutoshi Saito  Akio Koyama  Mitsuo Fukuchi 《Journal of Oceanography》1976,32(3):99-106

Vertical distribution of phytoplankton in early warming season in the eastern Bering Sea and adjacent sea areas was investigated. In the surface layer which was under the influence of newly melted sea ice in the shelf water region of the Bering Sea in May, remarkably dense populations ofThalassiosira hyalina andT. nordenskiöldii and relatively large populations ofFragilaria andNavicula occupied large part of phytoplankton community. In June, although theThalassiosira populations sunk into the bottom layer and withered, a certain part of theFragilaria-Navicula populations was still suspended in subsurface layer. Thus,Fragilaria-Navicula were the leading components of the June community in the shelf region.In the Bering Basin region, no dense phytoplankton populations were developed until a shallow thermocline was established. In June when the shallow thermocline developed near shelf edge,Thalassiosira decipiens burst out. As the shallow thermocline extended from near shelf to central part of the Basin region with surface warming, the areas of blooming also shifted from near shelf to the central part.Contribution No. 73 from the Research Institute of North Pacific Fisheries, Hokkaido University.  相似文献   

Positioning accuracy of the Data Collection Platform through the translocation and orbit correction method     

Toshiharu Kakihara  Jiro Segawa 《Journal of Oceanography》1989,45(1):1-10

A new algorithm has been developed to determine the position of a Data Collection Platform (DCP) that is used for the ARGOS Localization and Data Collection System. The algorithm uses an estimation scheme to correct the orbital parameters to achieve accurate positioning of the NOAA meteorological satellite. It is proved that the positioning accuracy of a DCP by the method of orbital Paramater correction is superior to the translocation method.Positioning of a moving DCP was also attempted by installing a DCP on board a vessel.  相似文献   

3-D modelling and analysis of Dst C-responses in the North Pacific Ocean region, revisited     

Alexei Kuvshinov  Hisashi Utada  Dmitry Avdeev  Takao Koyama 《Geophysical Journal International》2005,160(2):505-526

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Temporal variations in the current structure and volume transport of the Coastal Oyashio revealed by direct current measurement     

Akira Kusaka  Yugo Shimizu  Toru Sato  Jiro Yoshida 《Journal of Oceanography》2016,72(4):601-615

Direct current measurements by a shipboard and bottom-mounted acoustic Doppler current profiler and concurrent hydrographic observations with a CTD were conducted off southeastern Hokkaido, Japan, between January and May 2005 to reveal temporal variations in the current structure and volume transport of the Coastal Oyashio (CO). The CO, which has a baroclinic jet structure with southwestward speeds exceeding 90 cm s^?1 and a width of 7–8 km, was associated with a surface-to-bottom density front and was formed on the offshore side of the shelf break. The volume transport of CO (T _CO) was estimated by integrating the fluxes of lower-density water that was trapped against the coast along the density front represented by the 26.2 σ _θ isopycnal line. This transport decreased monotonously from 0.79 Sv (1 Sv = 10⁶ m³ s^?1) in January to 0.21 Sv in March and subsequently to 0.12 Sv in May, possibly due to the decay of the East Sakhalin Current Water in the Okhotsk Sea. Accompanied by a decrease in T _CO, the location of the jet structure associated with the density front moved toward the coast while the maximum speed of the jet decreased and the tilt of the front became more horizontal. Consequently, more saline offshore Oyashio water flowed into the deep part of the shelf area, and the current structure altered from relatively barotropic in winter to baroclinic in spring. This study is the first to estimate the observed volume transport of the CO from direct current measurements.  相似文献   

Rockfall hazard in the Daisekkei Valley, the northern Japanese Alps, on 11 August 2005     

Yoshihiko Kariya  Go Sato  Kuniyasu Mokudai  Jiro Komori  Masaki Ishii  Ryoko Nishii  Yosuke Miyazawa  Noriko Tsumura 《Landslides》2007,4(1):91-94

This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps. The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of ≥8,000 m³. Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints. Seasonal and diurnal freeze–thaw activities and snow avalanches and wash appear to be important factors responsible for the retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards, is required.  相似文献   

ACTIVE system for monitoring volcanic activity: A case study of the Izu-Oshima Volcano,Central Japan     

Hisashi Utada  Yuji Takahashi  Yuichi Morita  Takao Koyama  Tsuneomi Kagiyama 《Journal of Volcanology and Geothermal Research》2007

A system is proposed for the monitoring of changes in the underground structure of an active volcano over time by applying a transient electromagnetic method. The monitoring system is named ACTIVE, which stands for Array of Controlled Transient-electromagnetics for Imaging Volcano Edifice. The system consists of a transmitter dipole used to generate a controlled transient electromagnetic (EM) field and an array of receivers used to measure the vertical component of the transient magnetic field at various distances, with automatic operation of both units. In order to verify the performance of the proposed system, numerical and field experiments were carried out by application of the system to the Izu-Oshima volcano, where a remarkable change in the apparent DC resistivity over time had been detected in association with the eruption in 1986.  相似文献   

GIS-based spatial and temporal prediction system development for regional land subsidence hazard mitigation   总被引：3，自引：0，他引：3  

Guoyun?ZhouEmail author  Tetsuro?Esaki  Jiro?Mori 《Environmental Geology》2003,44(6):665-678

An integrated GIS-based approach for establishing a spatial and temporal prediction system for groundwater flow and land subsidence is proposed and applied to a subsidence-progressed Japanese coastal plain. Various kinds of fundamental data relating to groundwater flow and land subsidence are digitized and entered into a GIS database. A surface water hydrological cycle simulation is performed using a GIS spatial data operation for the entire plain, and the spatial and temporal groundwater infiltration quantity is hereby obtained. Through the data transformation from the GIS database to a groundwater flow code (MODFLOW), a 3D groundwater flow model is established and unsteady groundwater flow simulation for the past 21 years is conducted with results which compare satisfactorily with observed results. Finally, a Visual Basic code is developed for land subsidence calculations considering aquifer and aquitard deformation. Future land subsidence in the plain is predicted assuming different water pumping scenarios, and the results provide important information for land subsidence mitigation decision-making.  相似文献