Estimation of Sediment Properties during Benthic Impact Experiments     

Tetsuo Yamazaki  Rahul Sharma 《Marine Georesources & Geotechnology》2013,31(4):269-289

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.  相似文献   

Seismic response control using electromagnetic inertial mass dampers          下载免费PDF全文

Yutaka Nakamura  Akira Fukukita  Kazuo Tamura  Issei Yamazaki  Taichi Matsuoka  Kazuhiko Hiramoto  Katsuaki Sunakoda 《地震工程与结构动力学》2014,43(4):507-527

This paper presents a new type of electromagnetic damper with rotating inertial mass that has been developed to control the vibrations of structures subjected to earthquakes. The electromagnetic inertial mass damper (EIMD) consists of a ball screw that converts axial oscillation of the rod end into rotational motion of the internal flywheel and an electric generator that is turned by the rotation of the inner rod. The EIMD is able to generate a large inertial force created by the rotating flywheel and a variable damping force developed by the electric generator. Device performance tests of reduced‐scale and full‐scale EIMDs were undertaken to verify the basic characteristics of the damper and the validity of the derived theoretical formulae. Shaking table tests of a three‐story structure with EIMDs and earthquake response analyses of a building with EIMDs were conducted to demonstrate the seismic response control performance of the EIMD. The EIMD is able to reduce story drifts as well as accelerations and surpasses conventional types of dampers in reducing acceleration responses. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Assessing flood disaster impacts in agriculture under climate change in the river basins of Southeast Asia   总被引：1，自引：0，他引：1  

Shrestha  Badri Bhakta  Perera  Edangodage Duminda Pradeep  Kudo  Shun  Miyamoto  Mamoru  Yamazaki  Yusuke  Kuribayashi  Daisuke  Sawano  Hisaya  Sayama  Takahiro  Magome  Jun  Hasegawa  Akira  Ushiyama  Tomoki  Iwami  Yoichi  Tokunaga  Yoshio 《Natural Hazards》2019,97(1):157-192

Natural Hazards - This study focused on flood damage assessment for future floods under the impact of climate change. Four river basins of Southeast Asia were selected for the study. They included...  相似文献   

The interdecadal variation characteristics of arctic sea ice cover-Enso-East asian monsoon and their interrelationship at quasi-Four years time scale   总被引：2，自引：0，他引：2  

Zhu Congwen  Chen Longxun  Nobuo Yamazaki 《大气科学进展》1999,16(4):641-652

l.Introducti0nTheclimateformationandvariabilityisnotonlythereflectionofatmosphericinternalbe-havi0rbutalsotheinnuencefromtheinteractionexistSintheclimatesystem.Becausetherela-tivecooIingandheatingsourcesofatmospherearelocatedinthePOlarandtropicalregionrespectively,itiseasytounderstandthattheArcticseaicecoverandSSTanomalieswhichim-pocttheatmosphericheatingtosomeextentcanexerttheirinfluenceontheremotCatmosphericcirculation-Inthisregard,thefocusrelatedtheinflueneeofArcticseaicecoverandtropica…  相似文献   

Longitudinal variability of the equatorial counter electrojet during the solar cycle 24     

Soares  Gabriel  Yamazaki  Yosuke  Matzka  Jürgen  Pinheiro  Katia  Stolle  Claudia  Alken  Patrick  Yoshikawa  Akimasa  Uozumi  Teiji  Fujimoto  Akiko  Kulkarni  Atul 《Studia Geophysica et Geodaetica》2019,63(2):304-319

Studia Geophysica et Geodaetica - Ground and space-based geomagnetic data were used in the investigation of the longitudinal, seasonal and lunar phase dependence of the equatorial counter...  相似文献   

Forecast of Tsunamis from the Japan–Kuril–Kamchatka Source Region     

Yoshiki Yamazaki  Yong Wei  Kwok Fai Cheung  George D. Curtis 《Natural Hazards》2006,38(3):411-435

This paper describes an investigation of the subfault distribution along the Japan–Kuril–Kamchatka subduction zone for the implementation of a far-field tsunami forecast algorithm. Analyses of seismic data from 1900 to 2000 define the subduction zone, which in turn is divided into 222 subfaults based on the fault characteristics. For unit slip of the subfaults, a linear long-wave model generates a database of mareograms at water-level stations along the subduction zone and at warning points in the North Pacific. When a tsunami occurs, an inverse algorithm determines the slip distribution from near-source water-level records and predicts the waveforms at the warning points using the pre-computed mareograms. A jackknife resampling scheme uses combinations of input water-level records to provide a series of waveform predictions for the computation of the confidence-interval bounds. The inverse algorithm is applied to hindcast two major tsunamis generated from the Japan–Kuril–Kamchatka source and the computed tsunami heights show good agreement with recorded water-level data.  相似文献   

A perturbed parameter ensemble of HadGEM3-GC3.05 coupled model projections: part 1: selecting the parameter combinations     

Sexton  David M. H.  McSweeney  Carol F.  Rostron  John W.  Yamazaki  Kuniko  Booth  Ben B. B.  Murphy  James M.  Regayre  Leighton  Johnson  Jill S.  Karmalkar  Ambarish V. 《Climate Dynamics》2021,56(11):3395-3436

This is the first of two papers that describe the generation of a 25-member perturbed parameter ensemble (PPE) of high-resolution, global coupled simulations for the period 1900–2100, using CMIP5 historical and RCP8.5 emissions. Fifteen of these 25 coupled simulations now form a subset of the global projections provided for the UK Climate Projections 2018 (UKCP18). This first paper describes the selection of 25 variants (combinations of 47 parameters) using a set of cheap, coarser-resolution atmosphere-only simulations from a large sample of nearly 3000 variants. Retrospective 5-day weather forecasts run at climate resolution, and simulations of 2004–2009 with prescribed SST and sea ice are evaluated to filter out poor performance. We opted for a single design choice and sensitivity tests were done after the PPE was generated to demonstrate the effect of design choices on the filtering. Given our choice, only 38 of the parameter combinations were found to have acceptable performance at this stage. Idealised atmosphere-only simulations were then used to select the subset of 25 members that were as diverse as possible in terms of their CO₂ and aerosol forcing, and their response to warmer SSTs. Using our parallel set of atmosphere-only and coupled PPEs (the latter from paper 2), we show that local biases in the atmosphere-only experiments are generally informative about the biases in the coupled PPE. Biases in radiative fluxes and cloud amounts are strongly informative for most regions, whereas this is only true for a smaller fraction of the globe for precipitation and dynamical variables. Therefore, the cheap experiments are an affordable way to search for promising parameter combinations but have limitations.

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Amplification of coastal-trapped waves resonantly generated by wind around Sado Island,Japan     

Yosuke Igeta  Keiichi Yamazaki  Tatsuro Watanabe 《Journal of Oceanography》2015,71(1):41-51

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South Asian monsoon variability during the past 800 kyr revealed by rock magnetic proxies     

Y. Suganuma  T. Yamazaki  T. Kanamatsu 《Quaternary Science Reviews》2009,28(9-10):926-938

A rock magnetic investigation was carried out on a sedimentary core taken from the distal portion of the Bengal Fan in order to reconstruct the South Asian monsoon variability during the past 800 kyr. The 10.2 m long piston core MR0503-PC3, recovered at a water depth of 4400 m, consists of clay to silty clay with minor amounts of nannofossils. An age model for the MR0503-PC3 core is established by correlating a relative paleointensity record of the core [Suganuma Y., Yamazaki, T., Kanamatsu, T., Hokanishi, N., 2008. Relative paleointensity record during the last 800 kyr from the equatorial Indian Ocean: implication for relationship between inclination and intensity variations. Geochemistry, Geophysics, Geosystems. 9, Q02011. doi:10.1029/2007GC001723.] to the global paleointensity stack “Sint-800” [Guyodo, Y., Valet, J.P., 1999. Global changes in intensity of the Earth's magnetic field during the past 800 kyr. Nature. 399, 249–252.]. The age model is consistent with the published ages of tephra layers intercalated in the core, and shows continuous sedimentation during the past 800 kyr.Temporal variations in rock magnetic proxies for the magnetic concentration (ARM, IRM, and HIRM), the grain size (Mrs/Ms), and the composition (S_?0.3T and S_?0.1T) show that the amount of fine-grained magnetite increased during interglacial stages, and then gradually decreased toward the following glacial maxima. This indicates that the supply of fine-grained magnetite probably originated from areal expansion and/or increased pedogenic activity in the Ganges and Brahmaputra Rivers catchment. Increases during warmer periods suggest intensification of the South Asian summer monsoon during interglacial stages. During marine isotope stages (MIS) 15–11, enhancement of fine-grained magnetite and increased hematite and maghemite contributions are observed. These suggest a significant intensification of the South Asian summer monsoon during this period. Our record and other paleoclimatic reconstructions mainly from the low and mid-latitudes suggest that a major climatic event possibly occurred prior to the mid-Brunhes event (MBE), but the timing is not synchronous.  相似文献   

Evaluation and forecast of human impacts based on land use changes using multi-temporal satellite imagery and GIS: A case study on Zanjan,Iran     

Mohsen Ahadnejad  Yoshihisa Maruyama  Fumio Yamazaki 《Journal of the Indian Society of Remote Sensing》2009,37(4):659-669

Land use and land cover changes due to human activities in a time sequence. Detection of such changes may help decision makers and planners to understand the factors in land use and land cover change in order to take effective and useful measures. Remote sensing and GIS techniques may be used as efficient tools to detect and assess land use change.  相似文献