Effects of a marine ridge to western boundary current in a three-dimensional source-sink flow model     

Masahiro Endoh 《Journal of Oceanography》1978,34(6):303-306

A numerical experiment is made with a three-dimensional source-sink flow model in order to study effects of a marine ridge to the western boundary current. The model represents the Kuroshio current crossing the Izu Ridge which has a submarine narrow passage. It is indicated that most of the surface water of the western boundary current crosses the ridge through the narrow passage. A part of the surface water circulates around a warm eddy formed in an upstream region of the ridge. A water below the thermocline makes a long detour around the ridge and forms a subsurface northward current along the eastern slope of the ridge.  相似文献   

Gram Stain Index (GSI) of Bacterial and Archaeal Cells in the Natural Microbial Communities of Slightly and Extremely Saline Environments     

Haruo Saida  Masahiro Kamekura  Wael S. M. El-Sayed  Mohamed Abu-Shady  Yukuo Abe  Tomoharu Yamaguchi  Peiling Yang  Takaaki Maekawa  Humitake Seki 《Journal of Oceanography》2001,57(1):109-113

The use of GSI (Gram Stain Index) was studied for natural microbial cells in slightly and extremely saline environments. The GSI spectra of archaeal cells in an extremely saline environment showed unique profiles, different from those of Bacteria. These profiles can be applied for structural analysis of the microbial communities in aquatic environments.  相似文献   

Partitioning of heavy metals into mineral and organic fractions in a sediment core sample from Osaka Bay     

Yasushi Kitano  Masahiro Sakata  Eiji Matsumoto 《Journal of Oceanography》1981,37(5):259-266

Partitioning of copper, zinc, iron and manganese into oxide, sulfide, organic and silicate fractions has been determined with a selective chemical leaching technique on sediment samples from a core collected in Osaka Bay. The samples have been dated by the²¹⁰Pb method. Most of the copper and zinc in the polluted surface sediment layer are contained in both oxide and sulfide fractions. This suggests that the transformation of oxides and hydroxides to sulfides under anoxic conditions within the sediment is significant for the fixation of copper and zinc discharged through human activities into the sediment. Manganese is apparently enriched in oxide and hydroxide fractions of the surface layer due to the post-depositional migration of manganese within the sediment. The copper, zinc and manganese contents of the 30 % H₂O₂ soluble fraction (mostly organic fraction) decrease with depth in the sediment core, and correlate significantly with the organic carbon content. The heavy metal (Cu, Zn, Fe and Mn) contents of the silicate fraction, without exchangeable sites, are almost constant with depth.  相似文献   

Western boundary current crossing a ridge     

Masahiro Endoh 《Journal of Oceanography》1973,29(4):140-147

Investigated is a possibility of two-dimensional model in the study of the dynamics of the western boundary current by a numerical experiment. Emphasis is laid on the effect of bottom barrier corresponding to the Izu Ridge.The western boundary current in the model is formed by source and sink of the water prescribed at an artificial eastern wall (600 km offshore). The bottom topographyconsists of a continental slope parallel to the straight western coast, and a ridge protruding from the western coast to 500 km offshore (1,500 m deep and 400 km wide). The grid size of 12 km× 25 km (offshore and longshore directions, respectively) resolves both the western boundary current and the bottom topography.The assumption of homogeneity of the water density makes the western boundary current detour along the isobath of the ridge.A steady state solution is obtained under the assumptions that the horizontal velocity does not change direction vertically (equivalent barotropic), and that the geostrophic relationship holds at the bottom. Homogeneity of the water density is not assumed. The solution shows that most of the volume transport of the western boundary current cross the ridge and the current has cyclonic vorticity near the summit of the ridge. It seems to suggest that the investigation by three-dimensional models is neccesary in order to study the complete dynamics of the western boundary current crossing the ridge.  相似文献   

Distribution of Trace Bioelements in the Subarctic North Pacific Ocean and the Bering Sea (the R/V Hakuho Maru Cruise KH-97-2)   总被引：2，自引：1，他引：2  

Yukiyo Fujishima  Kazumasa Ueda  Masahiro Maruo  Ehchiro Nakayama  Chikako Tokutome  Hiroshi Hasegawa  Masakazu Matsui  Yoshiki Sohrin 《Journal of Oceanography》2001,57(3):261-273

A column concentration-high resolution inductively coupled plasma mass spectrometry (ICP-MS) determination was applied to measure the total dissolved concentrations of Fe, Co, Ni, Cu and Zn in seawater collected from the subarctic North Pacific (~45°N) and the Bering Sea in July–September 1997. Total adsorbable Mn was determined on board by column electrolysis preconcentration and chemiluminescence detection. The vertical profiles for Fe, Ni and Zn were nutrient-like. The deep water concentration of Fe was ~0.5 nM in the northeast Pacific (18°-140°W) and increased to ~1 nM in the northwest Pacific (161°E) and ~2 nM in the Bering Sea (57°N, 180°E). The deep water concentrations for Ni and Zn in the Bering Sea were also 1.3–2 times higher than in the North Pacific. The profiles for Co and Cu were examined in the subarctic North Pacific, and results obtained were consistent with previous reports. There was a significant correlation between the concentrations of Co and Mn except for surface mixed layer. The profiles for total adsorbable Mn were similar to the reported profiles for total dissolvable Mn. The deep water concentration of Mn in the Bering Sea was also 4 times higher than in the North Pacific. Iron and zinc were depleted in surface water of the subarctic North Pacific. The relationship between these trace elements and nutrients suggests that these elements could be a limiting factor of phytoplankton productivity. In the Bering Sea, surface water contained ~0.3 nM of Fe. The Zn concentration, which was less than the detection limit in surface water, increased at shallower depths (~30 m) compared with the subarctic North Pacific. These results imply a higher flux of Fe and Zn to surface water in the Bering Sea. This in turn may cause the ecosystem in the Bering Sea characterized by a dominance of diatoms and high regenerated production.  相似文献   

Topographic and geologic controls on landslides induced by the 2015 Gorkha earthquake and its aftershocks: an example from the Trishuli Valley,central Nepal   总被引：1，自引：0，他引：1  

Ching-Ying Tsou  Masahiro Chigira  Daisuke Higaki  Go Sato  Hiroshi Yagi  Hiroshi P. Sato  Akihiko Wakai  Vishnu Dangol  Shanmukhesh C. Amatya  Akiyo Yatagai 《Landslides》2018,15(5):953-965

The devastating Gorkha earthquake (M _w 7.8) on April 25, 2015 and its aftershocks triggered numerous landslides across the Lesser and Higher Himalayas of central Nepal. This study aims to characterize these landslides, based on the local topography and geology, and to develop data for landslide hazard zoning. This study focused on a mountainous catchment of the Trishuli River, where a digital elevation model was used to examine hilllslope and river profiles, aerial photos were used to identify 155 coherent landslides, and satellite images were used to map 912 earthquake-induced landslides. The topography of this area is mainly characterized by incised V-shaped inner gorges and steep (> 35°) SW-facing scarp slopes. Although most of the coherent landslides were not reactivated by the earthquakes, the Gogane landslide was affected by the earthquake and partly failed. A majority of the earthquake-induced landslides (91%) were new landslides, while the others were enlarged old landslides. The earthquake-induced landslides occurred mainly on the steep slopes of V-shaped inner gorges and scarp slopes, in gneiss and quartzite strata of the Lesser Himalayas, and they were primarily associated with fractured rock masses. This analysis provides a framework for zoning areas vulnerable to earthquake-induced landslides.  相似文献   

Test,analysis, and design of ovally-perforated vertically-flexible steel plate shear wall (OVSPW)     

Shao-Dong Shen  Masahiro Kurata  Peng Pan  Zhi-Zhou He 《地震工程与结构动力学》2022,51(1):66-85

A new type of steel plate shear wall (SPSW) with oval-curved architectural openings and vertically flexible horizontal connection elements is proposed. The vertical flexibility of the wall accommodates the construction settlement introduced by column contraction under the dead loads of the upper stories and allows sequential installation from the lower stories. A quasi-static cyclic loading test and finite element (FE) analysis verified the stable seismic behaviors of the ovally-perforated vertically-flexible steel plate shear wall (OVSPW). The results of FE parametric analysis showed that an OVSPW with an appropriate thickness of boundary elements effectively accommodated the construction settlement that could lead to large in-plane compression for a conventional SPSW. The horizontal connection elements made of steel tubes realized the vertical stiffness of OVSPW to less than 2% of the original value without changing the lateral stiffness. New design equations of the OVSPW were derived through integral and extreme value solutions to predict the mechanical behavior of OVSPW.  相似文献   

Random network model of electrical conduction in two-phase rock     

Fuji-ta  Kiyoshi  Seki  Masayuki  Ichiki  Masahiro 《Mineralogy and Petrology》2018,112(6):857-864

Mineralogy and Petrology - We developed a cell-type lattice model to clarify the interconnected conductivity mechanism of two-phase rock. We quantified electrical conduction networks in rock and...  相似文献   

A basic study on the application of LRFD in “the technical standard for port and harbour facilities in Japan”: a case of gravity type quay wall in a persistent design situation     

Masahiro Takenobu  Masafumi Miyata  Yu Otake  Takehiko Sato 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3):195-204

ABSTRACT

The Partial Factor Method (PFM) based on the Level 1 reliability design method was introduced in 2007 to the Technical Standards for Port and Harbour Facilities (TSPHF-2007) in Japan. After nearly 10 years of practical use of TSPHF-2007, the design standard has been revised based on requests from the practitioners who recommend the transition from the PFM to the Load Resistance Factor Design (LRFD). In this paper, we discuss the setting method of the target failure probability to determine the partial factors based on code calibration. Furthermore, we examine the impacts of implementing the LRFD concept to the TSPHF by taking the sliding and overturning of a gravity type quay wall as an example to represent port and harbour facilities. We found no practical difference in caisson width derived using the LRFD and the PFM, whereas the degree of matching of the target failure probability was somewhat more precise for the PFM. This finding indicates that the LRFD is a more reasonable design method than the PFM in terms of the simplicity of the performance function itself and the ease of engineering interpretation during the design procedure.  相似文献   

New developments of performance-based design codes and practice,honouring Prof. Yusuke Honjo     

Makoto Suzuki  Masahiro Shirato 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3)

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