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排序方式: 共有207条查询结果,搜索用时 281 毫秒
121.
This paper presents the application of system identification (SI) to long‐span cable‐supported bridges using seismic records. The SI method is based on the System Realization using Information Matrix (SRIM) that utilizes correlations between base motions and bridge accelerations to identify coefficient matrices of a state‐space model. Numerical simulations using a benchmark cable‐stayed bridge demonstrate the advantages of this method in dealing with multiple‐input multiple‐output (MIMO) data from relatively short seismic records. Important issues related to the effects of sensor arrangement, measurement noise, input inclusion, and the types of input with respect to identification results are also investigated. The method is applied to identify modal parameters of the Yokohama Bay Bridge, Rainbow Bridge, and Tsurumi Fairway Bridge using the records from the 2004 Chuetsu‐Niigata earthquake. Comparison of modal parameters with the results of ambient vibration tests, forced vibration tests, and analytical models are presented together with discussions regarding the effects of earthquake excitation amplitude on global and local structural modes. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
122.
Kiyoshi Tanaka Yutaka Michida Teruhisa Komatsu Kenji Ishigami 《Journal of Oceanography》2009,65(2):165-177
We have investigated the spreading of river water in Suruga Bay by performing numerical experiments and conducting field surveys
with drifting buoys. There are clear seasonal variations in the large river discharges into the bay: increased discharge in
the rainy summer season and decreased discharge in the dry winter season. The numerical model reproduces the main feature
that has been observed in the actual sea: the river water extends gradually from the northwestern to the southeastern regions
in the bay, especially in summer. The river water spreading is greatly influenced by the bottom topography of the bay: the
Fuji River water spreads over a deep continental slope as a surface-advected plume and extends well offshore, since a large
bulge (anticyclonic eddy at the river mouth) extends well offshore and effectively transports the river water offshore. On
the other hand, the Oi River water tends to flow parallel to isobaths (along a coastline) on a shallow continental shelf as
a bottomadvected plume. Moreover, the influences of seasonal variations in the stratification and a bay-scale, wind-driven
circulation are also investigated. Trajectories of the drifting buoys, which were released around the Fuji River mouth, certainly
suggest that the bulge exists there. 相似文献
123.
The dynamics of the wind-driven circulations and surface transport processes in Suruga Bay have been examined by performing
numerical experiments. While strong winds exist outside the bay, the winds inside the bays are greatly reduced, which generates
a strong wind stress curl in winter and autumn. In particular, in winter, a strong positive curl region is located across
the bay mouth, and a strong surface circulation with counterclockwise rotation is generated beneath it. The circulation is
nearly geostrophic, but is not affected by the bottom topography in the deep bay. It is suggested that intense surface water
exchange through the bay mouth occurs in winter, whereas it is not active in the other seasons when no significant vorticity
is supplied on the bay mouth from the atmosphere. Moreover, we propose a hypothesis that the atmospheric wind stress curl
will cause the frequent appearance of the counterclockwise circulation in winter in the real ocean. 相似文献
124.
Ian A. Navarrete Kiyoshi Tsutsuki Victor B. Asio Renzo Kondo 《Environmental Geology》2009,58(6):1257-1268
This study was conducted to evaluate the physical, chemical, and mineralogical characteristics of rain forest soils derived
from late Quaternary basaltic rocks in Leyte, Philippines. Four sites along a catena were selected at an elevation of 75–112 m
above sea level with an average annual rainfall of 3,000 mm and an average temperature of 28°C. Results indicate that the
soils are deep, clayey, and reddish in color, which is indicative of the advanced stage of soil development. They also posses
excellent physical condition (friable and highly porous) although they are plastic and sticky when wet as is usual for clayey
soils. In terms of chemical characteristics, the soils are acidic with low CEC values and generally low in organic matter
and nutrient contents. The clay mineralogy of the soils is dominated by halloysite and kaolinite with minor amounts of goethite
and hematite, and they also have generally high dithionite-extractable Fe contents confirming the advanced stage of their
development. The soils in the more stable slope positions (PL-1, PL-2, and PL-4) have generally similar characteristics and
appeared more developed than the one in the less stable position (PL-3). The most important pedogenic processes that formed
the soils appear to be weathering, loss of bases and acidification, desilification, ferrugination, clay formation and translocation,
and structure formation. The nature of the parent rock and climatic conditions prevailing in the area as well as slope position
appear to have dominant effects on the development of the soils. 相似文献
125.
126.
V. Sivasankar Kiyoshi Omine T. A. M. Msagati M. Senthil kumar A. Chandramohan 《Arabian Journal of Geosciences》2014,7(8):3093-3107
The present research is contributed on groundwater quality, its deterioration and evaluation based on drinking, irrigation, and construction standards. The study area chosen for investigation on water quality is the Tirunagar (TN) area, located in the south-west of Madurai City. The TN area was formerly an agricultural land but presently a residential area that is at a starvation of drinking water quality. A total of 49 bore well samples from TN and Amaithisolai (AS) were investigated for drinking, irrigation, and construction qualities based on various physicochemical parameters. The chemistry of groundwater samples was reflected from very hard and noncarbonate-dominating species. TN was recorded with higher inorganic species in groundwater sources than AS. The Water Quality Index values indicated that 75 % of the samples fall under excellent category and the positive Langelier Saturation Index values of the samples highlighted their tendency to deposit calcium carbonate. The Gibbs plot showed that AS samples were categorized under the domination of rock–water interaction whereas the TN samples under evaporation zone. The US Salinity Laboratory Staff plot depicted that all the groundwater sources at AS with C3S1 type whereas 88 % of the TN sources represented C4S1 type. The results from Wilcox diagram for irrigation inferred that the groundwater sources at AS were permissible, but 68 % of the samples at TN was registered under unfit type. The suitability of groundwater from the knowledge of residual sodium carbonate, sodium absorption ratio, and sodium percentage was also investigated. The perception based on standards recommended the groundwater sources for construction activities. The contribution of ionic species and inter-relationship among the ions were also interpreted from the knowledge of statistical studies. 相似文献
127.
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
128.
129.
Jagdev Singh Takashi Sakurai Kiyoshi Ichimoto S. Muneer 《Journal of Astrophysics and Astronomy》2006,27(2-3):115-124
We have obtained spectroscopic observations in coronal emission lines by choosing two lines simultaneously, one [Fe x] 6374 Å and the other [Fe xi] 7892 Å or [Fe xiii] 10747 Å or [Fe xiv] 5303 Å. We found that in 95 per cent of the coronal loops observed in 6374 Å, the FWHM of the emission line increases with height above the limb irrespective of the size, shape and orientation of the loop and that in case of 5303 Å line decreases with height in about 89 per cent of the coronal loops. The FWHM of 7892 Å and 10747 Å emission lines show intermediate behavior. The increase in the FWHM of 6374 Å line with height is the steepest among these four lines. We have also studied the intensity ratio and ratio of FWHM of these lines with respect to those of 6374 Å as a function height above the limb. We found that the intensity ratio of 7892 Å and 10747 Å lines with respect to 6374 Å line increases with height and that of 5303 Å to 6374 Å decreases with height above the limb. This implies that temperature in coronal loops will appear to increase with height in the intensity ratio plots of 7892 Å and 6374 Å; and 10747 Å and 6374 Å whereas it will appear to decrease with height in intensity ratio of 5303 Å to 6374 Å lineversus height plot. These findings are up to a height of about 200 arcsec above the limb. The varying ratios with height indicate that relatively hotter and colder plasma in coronal loops interact with each other. Therefore, the observed increase in FWHM with height above the limb of coronal emission lines associated with plasma at about 1 MK may not be due to increase in non-thermal motions caused by coronal waves but due to interaction with the relatively hotter plasma. These findings also do not support the existing coronal loop models, which predict an increase in temperature of the loop with height above the limb. 相似文献
130.
Kiyoshi Fujimoto Kumiko Kawase Shigehiro Ishizuka Koji Shichi Akio Ohira Hiroshi Adachi 《Quaternary Science Reviews》2009,28(15-16):1472-1480
We estimated stored sediment and carbon during the Holocene for each layer of the Yahagi River Delta, central Japan and discussed the provenance of stored carbon. To estimate the bulk density and the carbon content of each layer, we collected two 30 m deep undisturbed cores. The volume of each layer was calculated using ArcView 3D analyst. Although the volume ratio of each layer to the total volume was calculated to be 9.5% for the top mud layer, 34.9% for the upper sand layer, 32.8% for the middle mud layer and 22.9% for the lower sand layer, the mass ratio of each layer to the total mass was calculated to be 8.5, 40.9, 25.2 and 25.4%, respectively, and the stored carbon ratio in each layer to the total stored carbon was 20.4, 4.7, 55.9 and 18.9%, respectively. These results suggest that the top mud and middle mud layers have a significant role as a place for carbon sequestration during postglacial time. Total stored carbon in the study area of only 92.1 km2 was estimated at 26 Tg C, which is equivalent to 0.003% of atmospheric carbon. This suggests that deltas on the globe have accumulated a massive amount of carbon during the evolution. The inorganic carbon ratio to total carbon reached more than 45% around the boundary between the middle mud and lower sand layers. The increasing trend in the Corg/Ntotal ratio accompanied with a decrease in δ13C from the bottom to the top horizon in the middle mud layer indicates a gradual increase in terrestrial organic matter contribution. The relative proportion of terrestrially derived materials decreases with increasing distance seaward. 相似文献