A new method for the generation of second-order random waves     

Peter Jan van Leeuwen  Gert Klopman 《Ocean Engineering》1996,23(2):167-192

In order to prevent the generation of spurious free sub- and superharmonics of random waves in a laboratory channel, the control signal for the wave board has to be derived according to a higher-order wave theory. An expression for this control signal has been derived with the perturbation method of multiple scales. It is much less complex and requires less computation time than the expressions obtained from the full second-order theory. The new method for second-order subharmonics was verified experimentally for waves with bichromatic and continuous first-order spectra. The data were analysed with the complex-harmonic principal-component analysis to reduce the influence of noise.  相似文献   

Tropical Marine Fungi*     

Jan Kohlmeyer 《Marine Ecology》1984,5(4):329-378

Abstract. Marine Ascomycetes, Basidiomycetes and Deuteromycetes were collected in tropical and subtropical regions (Australia, Belize, Fiji, Hawaii, Marshall Islands, Mexico, New Zealand, Palau, Thailand), and the known range of distribution for these fungi was extended. Exclusively tropical are 27 taxa, 9 are probably restricted to the tropics also, and 11 are cosmopolitan. Distribution maps are given for 5 taxa. New species (4), varieties (3), and combinations (2) of Ascomycetes are proposed, and keys to the taxa of Halosarpheia and Lulworthia are presented. Most of the species are decomposers of mangrove parts or of detritus in sandy beaches. Nine new host plants were found. Marine Ascomycetes were discovered for the first time living in shells of foraminifera.  相似文献   

Validating management simulation models and implications for communicating results to stakeholders     

Pastoors  Martin A.; Poos  Jan Jaap; Kraak  Sarah B. M.; Machiels  Marcel A. M. 《ICES Journal of Marine Science》2007,64(4):818-824

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Circulation and Brackish Water Dispersal in a Coastal Lagoon of Southwest Taiwan     

Sen Jan  Shenn-Yu Chao  Jia-Jang Hung 《Journal of Oceanography》2001,57(6):647-661

Modest observations and numerical experiments were conducted to investigate circulation and brackish water dispersal in a coastal lagoon southwest of Taiwan. The Chi-Ku Lagoon, partially shielded from the sea by a string of sandbar barriers with two entrances among them, receives modest and episodic runoff from Chi-Ku Stream. Flood and ebb tidal streams entering and leaving the two entrances are found to converge and diverge in a flow stagnation area inside the lagoon. Under weak wind conditions, brackish water is preferentially retained in the flow stagnation area. Besides the observations, scenario runs using a three-dimensional numerical model also indicate strong modulation by monsoon winds. Both summer southwest monsoon and winter northeast monsoon reduce brackish water retention; the latter is found to be more effective. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Gaussian wave packets — a new approach to seakeeping testsof ocean structures     

Günther F. Clauss  Jan Bergmann 《Applied Ocean Research》1986,8(4):190-206

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Modelling infection of Baltic herring (Clupea harengus membras) by larval Anisakis simplex     

Horbowy  Jan; Podolska  Magdalena 《ICES Journal of Marine Science》2001,58(1):321-330

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Population dynamics of two marine polychaetes: the relative role of density dependence, predation, and winter conditions     

van der Meer  Jaap; Beukema  Jan J; Dekker  Rob 《ICES Journal of Marine Science》2000,57(5):1488-1494

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Glacial-interglacial relationship between carbonate components and sediment reflectance in the North Atlantic   总被引：2，自引：0，他引：2  

Jan P. Helmke  Henning A. Bauch 《Geo-Marine Letters》2001,21(1):16-22

A high-resolution composite sediment record from intermediate water depths in the North Atlantic, dating back to marine isotope stage (MIS) 13, was investigated in order to determine the relationship between sediment reflectance (gray level%) and carbonate content (weight%). For this purpose, a detailed analysis of the coarse (>20 µm) and fine (<20 µm) carbonate components was carried out to assess which of the two carbonate components drives glacial-interglacial changes in sediment gray level. The results indicate that the bulk carbonate component is clearly dominated by the fine carbonate fraction, regardless of glacial or interglacial climatic mode, suggesting that the sediment gray level is usually controlled by fluctuations of the fine carbonate content. However, a comparison of MIS 1 and 5.5 indicates that, besides this difference in the contents of the two carbonate size fractions, changing modes in carbonate preservation, i.e., the preservational state of planktonic Foraminifera, may also have a profound influence on total sediment reflectance.  相似文献   

A GIS-based step-wise procedure for assessing physical exposure in fragmented archipelagos     

Jan Ekebom  Pasi Laihonen  Tapio Suominen 《Estuarine, Coastal and Shelf Science》2003,57(5-6):887-898

Wind and waves are major forces affecting the geomorphology and biota in coastal areas. We present a generally applicable method for measuring and calculating fetch length, fetch direction and wave exposure. Fetch length and direction, measured by geographic information system-based methods, are used along with wind direction and wind speed data to estimate wave height and period by applying forecasting curves. The apparent power of waves approaching the shore, used as a proxy for wave exposure, is then calculated by a linear wave model. We demonstrate our method by calculating fetch lengths and wave exposure indices for five areas with varying exposure levels and types of meteorological conditions in the Finnish Archipelago Sea, situated in the northern Baltic Sea. This method is a rapid and accurate means of estimating exposure, and is especially applicable in areas with geomorphologically varying and complicated shorelines. We expect that our method will be useful in several fields, such as basic biogeographical and biodiversity research, as well as coastal land-use planning and management.  相似文献   

Meadow fragmentation and reproductive output of the SE Asian seagrass Enhalus acoroides     

Jan E. Vermaat  Rene N. Rollon  Cristina Day A. Lacap  Claire Billot  Filipe Alberto  Hildie M.E. Nacorda  Frank Wiegman  Jorge Terrados 《Journal of Sea Research》2004,52(4):201

Flower and fruit production of the abundant, tall, long-lived, dioecious, surface-pollinating seagrass species Enhalus acoroides (L.) Royle were estimated at seven sites in the reef flats off Bolinao (NW Luzon, The Philippines) featuring different fragmentation of the seagrass meadows. Fragmentation of the seagrass meadow was quantified as cover of E. acoroides and all seagrass species present in 20×20 m plots. E. acoroides and overall seagrass cover were correlated positively. The proportion of female flowers of E. acoroides that developed a fruit increased sharply as overall seagrass cover was around 50%. Apparent sex ratio bore no relationship with overall seagrass cover. This threshold-type of relationship suggests that fragmentation of seagrass meadows can have a major effect on the reproductive output of this species. A possible mechanism underlying these results would be a non-linear increase of the efficiency of trapping the surface-dispersed pollen with increasing seagrass canopy density. This provides the first evidence based on real data that fragmentation can affect the population dynamics of seagrass species.  相似文献