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421.
422.
423.
A marine magnetic survey was carried out in and around the northern part of Socotra Basin, offshore Korea (31°42′32″–32°46′29″N
and 123°56′26″–125°49′16″E), in order to better delineate its northern and eastern boundaries. Analyses of the observed magnetic
field and estimation of the basement depth were used to assess these boundaries. The power spectrum and the three-dimensional
analytical signal methods were used for depth estimation and to reconstruct basement configuration. Estimated depths resulting
from the power spectrum method range from 1.5 to 6.0 km for deep sources (basement troughs), and from 0.3 to 1.7 km for shallower
sources (basement peaks). An isopach map shows that the sedimentary sequence varies from 1.4 to 6.0 km in thickness. Estimated
depths from the analytic signal method fluctuate in the range 1.2–6 km. The results of the observed field analysis and depth
estimation indicate good agreement with the formerly proposed eastern boundary but disagreement with the northern boundary.
The findings suggest either an extension of the Socotra Basin or the existence of other sub-basins possibly interconnected
with the study area. 相似文献
424.
Won Je Lee 《Ocean Science Journal》2006,41(2):75-95
The diversity of heterotrophic flagellates was examined at marine sediments around Cape Tribulation, Australia. The species
described belong to the Alveolates, Apusomonadidae, Cercomonadida, Choanoflagellida, Cry ptomonadida, Diplomonadida, Euglenozoaincertae sedis, Kathablepharidae, Kinetoplastida, Pedinellids, Stephanopogonidae, Stramenopiles, Stramenopilesincertae sedis, Thaumatomonadidae and Protistaincertae sedis. Among the 51 species from 38 genera encountered in this study is one new taxon:Glissandra similis n. sp., and two new names are introduced:Goniomonas abrupta (Skvortzov 1924) nomen nodum andCercomonas skvortzovi (Skvortzov 1977) nomen nodum. There was little evidence for endemism because most flagellates including one new taxon described
here have been reported. 相似文献
425.
Clay minerals of the surface sediments of Bransfield Strait, Antarctica, exhibit distinctive geographical distributions: kaolinite has the highest concentration near the shore of the South Shetland Islands in the northern strait (20%); chlorite, near Smith Island in the northwestern strait; illite, on the continental shelf off the Antarctic Peninsula in the southern strait (80%); and smectite, close to the Penguin and Bridgeman islands in the northeastern strait (25%). This distribution pattern, combined with hydrographic and climatic data for the strait, are used to infer clay mineral provenance and dispersal patterns. 相似文献
426.
Summary The East Asian (China, Korea and Japan) summer monsoon precipitation and its variability are examined from the outputs of
the coupled climate models performing coordinated experiments leading to the Intergovernmental Panel on Climate Change Fourth
Assessment Report (IPCC AR4). Out of the 22 models examined, 14 reproduce the observed shape of the annual cycle well with
peak during the boreal summer (June through August), but with varying magnitude. Three models simulate the maximum a month
later and with lower magnitudes. Only one model considerably underestimates the magnitude of the annual cycle. The remaining
4 models show some deviations from the observed. Models are unable to simulate the minimum in July with peaks in June and
August associated with northward shifts of the Meiyu-Changma-Baiu precipitation band. The realistic simulation of the annual cycle does not appear to depend on the model resolution. The inter-model
variation is slightly larger during summer, implying larger diversity of the models in simulating summer monsoon precipitation.
The spatial rainfall patterns are reasonably well simulated by most of the models, with several models able to simulate the
precipitation associated with the Meiyu-Changma-Baiu frontal zone and that associated with the location of the subtropical high over the north Pacific. Simulated spatial distribution
could be sensitive to model resolution as evidenced by two versions of MIROC3.2 model. The multi-model ensemble (MME) pattern
reveals an underestimation of seasonal precipitation over the east coast of China, Korea-Japan peninsular and the adjoining
oceanic regions. This may be related with the mass-flux based scheme employed for convective parameterization by majority
of the models. Further the inter-model variation of precipitation is about 2 times stronger south of 30° N, than north of
this latitude, indicating larger diversity of the coupled models in simulating low latitude precipitation. The simulated inter-annual
variability is estimated by computing the mean summer monsoon seasonal rainfall and the coefficient of variability (CV). In
general the mean observed seasonal precipitation of 542 mm and CV of 6.7% is very well simulated by most of the models. Except
for one model mean seasonal precipitation varies from 400 to 650 mm. However the CV varies from 2 to 9%.
Future projections under the radiative forcing of doubled CO2 scenario are examined for individual models and by the MME technique. Changes in mean precipitation and variability are tested
by the t-test and F-ratio respectively to evaluate their statistical significance. The changes in mean precipitation vary from −0.6% (CNRM-CM3)
to about 14% (ECHO-G; UKMO-HadCM3). The MME technique reveals an increase varying from 5 to 10%, with an average of 7.8% (greater
than the observed CV of 6.7%) over the East Asian region. However the increases are significant over the Korea-Japan peninsula
and the adjoining north China region only. The increases may be attributed to the projected intensification of the subtropical
high, Meiyu-Changma-Baiu frontal zone and the associated influx of moist air from the Pacific inland. The projected changes in the amount of precipitation
are directly proportional to the projected changes in the strength of the subtropical high. Further the MME suggests a possible
increase in the length of the summer monsoon precipitation period from late spring through early autumn. The changes in precipitation
could be stabilized by controlling the CO2 emissions. 相似文献
427.
On Nov. 9, 1996 at 21h56min (Beijing Time), an earthquake of MS=6.1 occurred in offshore outside the Yangtze River Mouth (31o43¢N, 123o04¢E). The shock affected Shanghai City and both Jiangsu and Zhejiang Provinces in China mainly. The shock was felt more strongly in the Yangtze River Mouth and Hangzhou Bay area than in the rest of them, particularly in high buildings of Shanghai City. In addition, the earthquake was felt in South Korea and also stronger in apartments or high buildings. LIU, JIN (1998) and LIU, et al (1999) described effect of the shock on the eastern China. The paper describes the effect of the earthquake on South Korea and the whole intensity distribution in South Korea and eastern China. 相似文献
428.
This paper presents an active control algorithm using the probability density function of structural energy. It is assumed that structural energy under excitation has a Rayleigh probability distribution. This assumption is based on the fact that the Rayleigh distribution satisfies the condition that the structural energy is always positive and the occurrence probability of minimum energy is zero. The magnitude of the control force is determined by the probability that the structural energy exceeds the specified target critical energy, and the sign of the control force is determined by the Lyapunov controller design method. The proposed control algorithm shows much reduction of peak responses under seismic excitation compared with the LQR controller, and it can consider the control force limit in the controller design. Also, the chattering problem which sometimes occurs in the Lyapunov controller can be avoided. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
429.
Gyesoon Park Seokhoon Oh Heuisoon Lee Jung-Ho Kim Byung-Doo Kwon 《Journal of Applied Geophysics》2011,73(3):232-242
To enhance the spatial resolution, two types of complementary integration methods were developed using gravity and magnetotelluric (MT) data. The first method involves the enhancement processing of gravity vertical resolution using MT data. This is called a layer density correction (LDC) process which makes the density distribution more sensitive to geologic structure. The second method involves the spatial expansion processing of MT data using the enhanced gravity data. In this process, non-linear indicator transformation (NLIT) and simple kriging with varying local means (SKlm) methods were employed. The assumptions are that while the results are analyzed by different physical properties, each method senses the same underlying geologic structure and thus there is a relationship among the physical properties. The proposed geostatistical integration methods were tested using synthetic models and field data. The experiment illustrates that the integration method proposed in this study can provide improved structures. The method integrates constructively the gravity information having a wider spatial distribution and the MT information having higher vertical resolution. 相似文献
430.
Forecasting space weather more accurately from solar observations requires an understanding of the variations in physical
properties of interplanetary (IP) shocks as solar activity changes. We examined the characteristics (occurrence rate, physical
parameters, and types of shock driver) of IP shocks. During the period of 1995 – 2001, a total of 249 forward IP shocks were
observed. In calculating the shock parameters, we used the solar wind data from Wind at the solar minimum period (1995 – 1997) and from ACE since 1998 including the solar maximum period (1999 – 2001). Most
of IP shocks (68%) are concentrated in the solar maximum period. The values of physical quantities of IP shocks, such as the
shock speed, the sonic Mach number, and the ratio of plasma density compression, are larger at solar maximum than at solar
minimum. However, the ratio of IMF compression is larger at solar minimum. The IP shock drivers are classified into four groups:
magnetic clouds (MCs), ejecta, high speed streams (HSSs), and unidentified drivers. The MC is the most dominant and strong
shock driver and 150 out of total 249 IP shocks are driven by MCs. The MC is a principal and very effective shock driver not
only at solar maximum but also at solar minimum, in contrast to results from previous studies, where the HSS is considered
as the dominant IP shock driver. 相似文献