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901.
目前,SAR图像船只检测只能在当前编程软件中实现,无法被其他软件调用,很难在后续开发的软件系统中得到广泛的应用。为此,本文基于C#和Matlab混合编程,开发出了一种可以被调用的SAR图像船只检测界面性应用窗体。该窗体运行后,生成K分布、G^0分布和直方图统计模型的概率密度函数曲线和相应的检测结果图像,通过比较,可判别出K分布更适合应用于SAR图像的船只检测中。 相似文献
902.
Anne Levasseur Lei Shi Neil C. Wells Duncan A. Purdie Boris A. Kelly-Gerreyn 《Estuarine, Coastal and Shelf Science》2007,73(3-4):753-767
A three-dimensional hydrodynamic model has been developed to simulate water mass circulation in estuarine systems. This model is based on the primitive equation in Cartesian coordinates with a terrain-following structure, coupled with a Mellor–Yamada 2.5 turbulence scheme. A fractional-step method is applied and the subset of equations is solved with finite volume and finite element methods. A dry–wet process simulates the presence of the tidal flat at low water. River inputs are introduced using a point-source method. The model was applied to a partially mixed, macrotidal, temperate estuary: Southampton Water, UK. The model is validated by comparisons with sea surface elevation, ADCP measurements and salinity data collected in 2001. The mean spring range 2(M2 + S2) and the mean neap range 2(M2 − S2) are modelled with an error relative to observation of 12 and 16%, respectively. The unique tidal regime of the system with the presence of the ‘young flood stand’ corresponding to the slackening conditions occurring at mid flood and ‘double high water’ corresponding to an extension of the slackening conditions at high tide is accurately reproduced in the model. The dynamics of the modelled mean surface and bottom velocity closely match the ADCP measurements during neap tides (rms of the difference is 0.09 and 0.01 m s−1 at the bottom and at the surface, respectively), whereas at spring the difference is greater (rms of the difference is 0.25 and 0.20 m s−1 at bottom and surface, respectively). The spatial and temporal variation of the degree of stratification as indicated by salinity distributions compares well with observations. 相似文献
903.
1 Introduction Ocean upper mixed layer, with nearly uniform temperature, salinity and density, is formed by sea sur- face forces such as wind stress, buoyancy flux and sur- face waves, etc. Under the mixed layer, thermocline and halocline often exist. Usually the depth of them is almost equal. But in the tropical ocean, the halocline is often shallower than the thermocline. Then between the layer of uniform salinity and the thermocline, there is a layer which has a rather strong density gradi… 相似文献
904.
905.
Alexis Chaigneau Rosemary A. Morrow Stephen R. Rintoul 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):377
Seasonal and interannual variations of the mixed layer properties in the Antarctic Zone (AZ) south of Tasmania are described using 7 WOCE/SR3 CTD sections and 8 years of summertime SURVOSTRAL XBT and thermosalinograph measurements between Tasmania and Antarctica. The AZ, which extends from the Polar Front (PF) to the Southern Antarctic Circumpolar Current Front (SACCF), is characterized by a 150 m deep layer of cold Winter Water (WW) overlayed in summer by warmer, fresher water mass known as Antarctic Surface Water (AASW). South of Tasmania, two branches of the PF divide the AZ into northern and southern zones with distinct water properties and variability. In the northern AZ (between the northern and southern branches of the PF), the mixed layer depth (MLD) is fairly constant in latitude, being 150 m deep in winter and around 40–60 m in summer. In the southern AZ, the winter MLD decreases from 150 m at the S-PF to 80 m at the SACCF and from 60 to 35 m in summer. Shallower mixed layers in the AZ-S are due to the decrease in the wind speed and stronger upwelling near the Antarctic Divergence. The WW MLD oscillates by ±15 m around its mean value and modest interannual changes are driven by winter wind stress anomalies.The mixed layer is on annual average 1.7 °C warmer, 0.06 fresher and 0.2 kg m−3 lighter in the northern AZ than in the southern AZ. The Levitus (1998) climatology is in agreement with the observed mean summer mixed layer temperature and salinity along the SURVOSTRAL line but underestimates the MLD by 10–20 m. The winter MLD in the climatology is also closed to that observed, but is 0.15 saltier than the observations along the AZ-N of the SR3 line. MLD, temperature and density show a strong seasonal cycle through the AZ while the mixed layer salinity is nearly constant throughout the year. During winter, the AZ MLD is associated with a halocline while during summer it coincides with a thermocline.Interannual variability of the AZ summer mixed layer is partly influenced by large scale processes such as the circumpolar wave which produces a warm anomaly during the summer 1996–1997, and partly by local mechanisms such as the retroflection of the S-PF which introduces cold water across the AZ-N. 相似文献
906.
A new type of pycnostad has been identified in the western subtropical-subarctic transition region of the North Pacific, based
on the intensive hydrographic survey carried out in July, 2002. The potential density, temperature and salinity of the pycnostad
were found to be 26.5–26.7 σ
θ
, 5°–7°C and 33.5–33.9 psu respectively. The pycnostad is denser, colder and fresher than those of the North Pacific Central
Mode Water and different from those of other known mode waters in the North Pacific. The thickness of the pycnostad is comparable
to that of other mode waters, spreading over an area of at least 650 × 500 km around 43°N and 160°E in the western transition
region. Hence, we refer to the pycnostad as Transition Region Mode Water (TRMW). Oxygen data, geostrophic current speed and
climatology of mixed layer depth in the winter suggest that the TRMW is formed regularly in the deep winter mixed layer near
the region where it was observed. Analysis of surface heat flux also supports the idea and suggests that there is significant
interannual variability in the property of the TRMW. The TRMW is consistently distributed between the Subarctic Boundary and
the Subarctic Front. It is also characterized by a wide T-S range with similar density, which is the characteristic of such
a transition region between subtropical and subarctic water masses, which forms a density-compensating temperature and salinity
front. The frontal nature also tends to cause isopycnal intrusions within the pycnostad of the TRMW. 相似文献
907.
908.
Naoto Iwasaka Fumiaki Kobashi Yosuke Kinoshita Yuko Ohno 《Journal of Oceanography》2006,62(4):481-492
A seasonal evolution of surface mixed layer in the western North Pacific around 24°N between 143°E and 150°E was observed
by using an Argo float for more than 9 months, from December 2001 through August 2002. The result showed that the mixed layer
deepened gradually in the first two months. It reached its maximum depth of about 130 m at the end of January, after which
the mixed layer varied largely and sometimes the pycnocline below the mixed layer was much weakened until the summer mixed
layer formed in late April. The thin surface mixed layer was maintained during the rest of the observation period. Heat budget
analysis suggests that the vertical and horizontal temperature advections are the two most dominant terms in the heat balance
in the upper layer on time scales from a few days to a month. The vertical motions that are possibly responsible for the vertical
temperature advection are discussed. 相似文献
909.
Young Ho Seung 《Ocean Science Journal》2005,40(2):101-107
A simple analytical model is considered in an attempt to demonstrate a formation mechanism of the abyssal current in the East
Sea. In this model, the abyssal currents are driven by wind through an outcrop region and flow along closed geostrophic contours.
A rough estimate of the abyssal currents, arrived at by applying this model to the region of deep mixing in the East Sea,
gives currents comparable to those observed, although there is an uncertainty in the surface area of the outcrop region. It
seems that the spin-up of deep water by wind forcing through the region of deep winter mixing is, at least partly, an important
contribution to the formation of the abyssal currents in the East Sea. 相似文献
910.