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51.
本文介绍了长江口区水文泥沙概况,举例说明了SSA1-1型声水位计在崇头潮位站比测试验和投产应用情况,结果表明该水位计是收集长江口区潮位资料较理想的仪器。 相似文献
52.
Marco Ortiz 《Marine Ecology》2002,23(1):1-9
Abstract. The current article describes statistical power analysis as an efficient strategy for the estimation of the optimum sample size. The principle aim is constructively to criticise and enrich the results presented by Mouillot et al. (1999) , who estimate the optimum sample size for evaluating possible perturbations. The authors did not make any reference to statistical power analysis, even though their objective clearly went beyond a simple stock evaluation to assess management strategies in a particular marine ecosystem. Surprisingly, they proposed (a priori) an ANOVA design to test a hypothesis considering both space and temporal scales. However, the authors did not cover important topics related with power analysis and the precautionary principle, both used into environment impact assessment programmes for marine ecosystems. Based on their results and on statistical power analysis, it is demonstrated that the variability (dispersion statistics), a key factor they used to estimate the sample size, is less relevant than the magnitude of perturbation (effect size). Therefore, a greater effort must be devoted to estimate the effect size of a particular phenomenon rather than a desired variability. 相似文献
53.
Moo Hee Kang Hyun-Chul Han Hyesu Yun Gee Soo Kong Kyong O. Kim Youn Soo Lee 《Marine Geophysical Researches》2007,28(3):257-269
A seamount chain with an approximately WNW trend is observed in the northeastern Ulleung Basin. It has been argued that these
seamounts, including two islands called Ulleung and Dok islands, were formed by a hotspot process or by ridge related volcanism.
Many geological and geophysical studies have been done for all the seamounts and islands in the chain except Anyongbok Seamount,
which is close to the proposed spreading ridge. We first report morphological characteristics, sediment distribution patterns,
and the crustal thickness of Anyongbok Seamount using multibeam bathymetry data, seismic reflection profiles, and 3D gravity
modeling. The morphology of Anyongbok Seamount shows a cone shaped feature and is characterized by the development of many
flank cones and flank rift zones. The estimated surface volume is about 60 km3, and implies that the seamount is smaller than the other seamounts in the chain. No sediments have been observed on the seamount
except the lower slope, which is covered by more than 1,000 m of strata. The crustal structure obtained from a 3D gravity
modeling (GFR = 3.11, SD 3.82 = mGal) suggests that the seamount was formed around the boundary of the Ulleung Plateau and
the Ulleung Basin, and the estimated crustal thickness is about 20 km, which is a little thicker than other nearby seamounts
distributed along the northeastern boundary of the Ulleung Basin. This significant crustal thickness also implies that Anyongbok
Seamount might not be related to ridge volcanism. 相似文献
54.
How are large western hemisphere warm pools formed? 总被引:1,自引:0,他引:1
During the boreal summer the Western Hemisphere warm pool (WHWP) stretches from the eastern North Pacific to the tropical North Atlantic and is a key feature of the climate of the Americas and Africa. In the summers following nine El Niño events during 1950–2000, there have been five instances of extraordinarily large warm pools averaging about twice the climatological annual size. These large warm pools have induced a strengthened divergent circulation aloft and have been associated with rainfall anomalies throughout the western hemisphere tropics and subtropics and with more frequent hurricanes. However, following four other El Niño events large warm pools did not develop, such that the mere existence of El Niño during the boreal winter does not provide the basis for predicting an anomalously large warm pool the following summer.In this paper, we find consistency with the hypothesis that large warm pools result from an anomalous divergent circulation forced by sea surface temperature (SST) anomalies in the Pacific, the so-called atmospheric bridge. We also find significant explanations for why large warm pools do not always develop. If the El Niño event ends early in the eastern Pacific, the Pacific warm anomaly lacks the persistence needed to force the atmospheric bridge and the Atlantic portion of the warm pool remains normal. If SST anomalies in the eastern Pacific do not last much beyond February of the following year, then the eastern North Pacific portion of the warm pool remains normal. The overall strength of the Pacific El Niño does not appear to be a critical factor. We also find that when conditions favor a developing atmospheric bridge and the winter atmosphere over the North Atlantic conforms to a negative North Atlantic Oscillation (NAO) pattern (as in 1957–58 and 1968–69), the forcing is reinforced and the warm pool is stronger. On the other hand, if a positive NAO pattern develops the warm pool may remain normal even if other circumstances favor the atmospheric bridge, as in 1991–92. Finally, we could find little evidence that interactions internal to the tropical Atlantic are likely to mitigate for or against the formation of the largest warm pools, although they may affect smaller warm pool fluctuations or the warm pool persistence. 相似文献
55.
56.
Sylvie Labroue Philippe Gaspar Joel Dorandeu Oz Zanif F. Mertz Patrick Vincent Denis Choquet 《Marine Geodesy》2004,27(3):453-481
The Jason-1 sea state bias (SSB) is analyzed in depth from the first year of GDR products. Compared to previous missions, this work benefits from two aspects of the empirical determination of the SSB from the altimetric data themselves. First, from a methodological point of view, a nonparametric technique (NP) has been developed and largely tested on TOPEX/Poseidon 1, GFO and Envisat data. The NP estimator has proven to be a useful tool in the SSB estimation, and it is now mature enough to be used for a refined analysis. On the other hand, the SSB can be extracted from three different data sets (crossovers, collinear data, and residuals) with different characteristics. It is then possible to cross calibrate various estimations of the SSB models and to determine the most accurate one. A systematic comparison is made between these different estimates for the Jason-1 altimeter. The collinear and crossover data sets yield very similar estimates despite their difference of spatial and temporal distributions. These SSB models assure consistency with the TOPEX mission when comparing Jason-1 and TOPEX residuals during the tandem phase. Thanks to the present work, the impact of the short wavelengths filtering on the SSB estimation is evidenced. More generally, our understanding of potential errors affecting the sea surface height and their impact onto the SSB estimation is also improved. 相似文献
57.
Jonathan M. Bull Martin Gutowski Justin K. Dix Timothy J. Henstock Peter Hogarth Timothy G. Leighton Paul R. White 《Marine Geophysical Researches》2005,26(2-4):157-169
Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable source signature (1–24 kHz) to produce
decimetre vertical resolution cross-sections of the sub-seabed. Here the design and development of the first true 3D Chirp
system is described. When developing the design, critical factors that had to be considered included spatial aliasing, and
precise positioning of sources and receivers. Full 3D numerical modelling of the combined source and receiver directivity
was completed to determine optimal source and receiver geometries. The design incorporates four source transducers (1.5–13 kHz)
that can be arranged into different configurations, including Maltese Cross, a square and two separated pairs. The receive
array comprises 240 hydrophones in 60 groups whose group-centres are separated by 25 cm in both horizontal directions, with
each hydrophone group containing four individual elements and a pre-amplifier.
After careful consideration, it was concluded that the only way to determine with sufficient accuracy the source–receiver
geometry, was to fix the sources and receivers within a rigid array. Positional information for the array is given by a Real
Time Kinematic GPS and attitude system incorporating four antennas to give position, heading, pitch and roll. It is shown
that this system offers vertical positioning accuracy with a root-mean-square (rms) error less than 2.6 cm, while the horizontal
positioning rms error was less than 2.0 cm. The system is configured so that the Chirp source signature can be chosen by software
aboard the acquisition vessel.
The complete system is described and initial navigational and seismic data results are presented. These data demonstrate that
the approach of using fixed source-receiver geometry combined with RTK navigation can provide complete 3D imaging of the sub-surface. 相似文献
58.
59.
LAPP对中国对虾(Penaeus chinensis)生长、缺氧耐受力及免疫抵抗力的影响 总被引:11,自引:0,他引:11
实验研究维生素C多聚磷酸酯(LAPP)添加在对虾饲料中,对中国对虾的生长、缺氧耐受力及免疫抵抗力的影响;实验进一步证明了中国对虾饲料中LAPP的最适添加量为400mg/100g饲料;本文还提出饲料中的LAPP能够提高中国对虾的缺氧耐受力,在溶氧超过3.1mg/kg海水的情况下,效果显著,在降低到2.3mg/kg海水时,作用减弱;用副溶血弧菌(Vibroparahaemolyticus)注射入虾体内,12小时内记录发现,饲料中不含LAPP的一组中国对虾,死亡率高于其它组,并且,LAPP含量最高的一组,死亡率明显低,死亡时间也出现较晚,这证明LAPP能够提高中国对虾的免疫抵抗力;本实验用注射金黄色葡萄球菌后细胞的吞噬百分率作指标,研究对虾细胞的吞噬作用,发现饲料中不含LAPP的对虾的吞噬百分率较低,随着饲料中LAPP浓度的提高,对虾血细胞的吞噬百分率逐渐升高,说明中国对虾细胞的吞噬作用逐步增强。 相似文献
60.
Sequence variation of the first internal transcribed spacer of ribosomal DNA ( ITS - 1 ) was examined and its application to the study of genetic variation was explored in four populations of farter' s scallop Chlamys farreri. ITS - 1 fragments, with a length of about 300 bp,of 78 individuals collected from Dalian, Qingdao, Yantai in China and Korea respectively were amplified via PCR, cloned and sequenced. Intra-genomic variation was examined by sequencing several clones of single individuals. Alignment and polymorphism analysis detected 44 haplotypes and 50 polymorphic sites which consist of 30 substitutions and 20 indels, indicating a high level of polymorphisms. Sequence analysis also showed a very low level of intra-individual variation. All these features validated the feasibility of application of ITS - 1 fragment to population analysis. Polymorphism analysis showed that the Korea sample has the richest genetic variation, followed by Yantai and Qingdao samples. AMOVA (analysis of molecular variance) showed that the majority (96.26%) of genetic variation was distributed within populations and 3.74% resulted from among populations, but with P 〈 0.05 ( = 0.042), indicating that the populations in this study have significant divergence. This output was basically concordant with the result arising from RAPD data and different from that from mitochondrial 16S rDNA sequence data. Discussion on this inconsistency was made accordingly. 相似文献