Design of Buoys for Mounting Wind Turbines at Exposed Sites     

ERDO?AN Beytullah  ?EL?KKOL Barbaros  SWIFT Robinson 《中国海洋大学学报(英文版)》2018,17(2):257-266

In this study, two designs for a buoy capable of supporting a 10 kW wind turbine and its tower were developed to operate at the University of New Hampshire’s Center of Ocean Renewable Energy testing site located off the Isles of Shoals, New Hampshire. The buoys are to be moored by a catenary chain system. To evaluate wave response, two Froude-scaled models were constructed, tested, and compared at the Ocean Engineering wave tank at the University of New Hampshire. These buoys have been implemented and compared with wave tank measurements of the spar displacement at a reference elevation 2.44 m above the mean water level.  相似文献   

Drought events in Southern Portugal from the 12th to the 19th centuries: integrated research from descriptive sources     

Afonso Do Ó  Maria J. Roxo 《Natural Hazards》2008,47(1):55-63

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Robust adaptive control of underactuated ships on a linear course with comfort     

K. D. Do  J. Pan  Z. P. Jiang   《Ocean Engineering》2003,30(17):2201-2225

This paper addresses an important problem in ship control application—the robust stabilization of underactuated ships on a linear course with comfort. Specifically, we develop a multivariable controller to stabilize ocean surface ships without a sway actuator on a linear course and to reduce roll and pitch simultaneously. The controller adapts to unknown parameters of the ship and constant environmental disturbances induced by wave, ocean current and wind. It is also robust to time-varying environmental disturbances, time-varying change in ship parameters and other motions of the ship such as surge and heave. The roll and pitch can be made arbitrarily small while the heading angle and sway are kept to be in reasonably small bounds. The controller development is based on Lyapunov’s direct method and backstepping technique. A Lipschitz continuous projection algorithm is used to update the estimate of the unknown parameters to avoid the parameters’ drift due to time-varying environmental disturbances. Simulations on a full-scale catamaran illustrate the effectiveness of our proposed controller.  相似文献   

Quaternary evolution of the Gulf of İzmit (NW Turkey): a sedimentary basin under control of the North Anatolian Fault Zone     

Erdal Dolu  Erkan Gökaşan  Engin Meriç  Mustafa Ergin  Tolga Görüm  Hüseyin Tur  Berkan Ecevitoğlu  Niyazi Avşar  Muhittin Görmüş  Fatmagül Batuk  Buğser Tok  Oktay Çetin 《Geo-Marine Letters》2007,27(6):355-381

The Quaternary evolution of the Gulf of İzmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence of the Gulf of İzmit. According to these data, Plio-Quaternary deposits supplied from the northern terrestrial area started to accumulate during a progradational phase, in a south-facing half-graben. A coarse-grained sedimentary unit prograding into the gulf from the south since 200 ka b.p. indicates a dramatic variation in the evolution of the gulf, with the initiation of a new strike-slip fault of the NAFZ and a corresponding uplift of the Armutlu Peninsula in the south of the gulf. During the evolution of this fault from a wide shear zone consisting of right-stepped strike-slip faults and pull-apart basins to a localized principal fault zone, sediments were deposited under the influence of northerly prograding terrestrial and shallow-marine conditions due to relative sea-level fluctuations in the Marmara Sea. During this period, the Gulf of İzmit was invaded mainly by Mediterranean and partly by Black Sea waters. In the latest glacial period, shallow areas in the gulf became subaerially exposed, whereas the central and western sub-basins of the gulf turned into lakes. The present evolution of the Gulf of İzmit is controlled by the after effects of the new rupture of the NAFZ and the estuarine nature of the gulf environment.  相似文献   

Robust and adaptive path following for underactuated autonomous underwater vehicles   总被引：1，自引：0，他引：1  

K. D. Do  J. Pan  Z. P. Jiang 《Ocean Engineering》2004,31(16):1967-1997

This paper proposes a nonlinear robust adaptive control strategy to force a six degrees of freedom underactuated underwater vehicle with only four actuators to follow a predefined path at a desired speed despite of the presence of environmental disturbances and vehicle’s unknown physical parameters. The proposed controller is designed using Lyapunov’s direct method, the popular backstepping and parameter projection techniques. The closed loop path following errors can be made arbitrarily small. Interestingly, it is shown that our developed control strategy is easily extendible to situations of practical importance such as parking and point-to-point navigation. Numerical simulations are provided to illustrate the effectiveness of the proposed methodology.  相似文献   

Stratigraphy of the sediment infill in Bosphorus Strait: water exchange between the Black and Mediterranean Seas during the last glacial Holocene     

O. Algan  N. Çağatay  A. Tchepalyga  D. Ongan  C. Eastoe  E. Gökaşan 《Geo-Marine Letters》2001,20(4):209-218

The sediment infill over the Paleozoic bedrock in the Bosphorus Strait consists of four sedimentary units which were deposited in the last 26,000 ¹⁴C years B.P. The stratigraphy of these units suggests that this part of the Bosphorus was a freshwater lake between 26,000 and 5,300 ¹⁴C years B.P., depositing sands with a freshwater mollusc fauna of Black Sea neo-euxinian affinity (Dreissena rostriformis, Dreissena polymorpha, and Monodacna pontica). The first appearance of euryhaline Mediterranean molluscs (e.g., Ostrea edulis, Mytilus edulis) was observed at 5,300 ¹⁴C years B.P. in this part of the Bosphorus. Deposition of coarse Mytilus-bank and Ostrea-bank units suggests that the establishment of the present dual-flow regime in the Bosphorus took place at about 4,400 ¹⁴C years B.P.  相似文献   

Effects of pulsed nutrient inputs on phytoplankton assemblage structure and blooms in an enclosed coastal area   总被引：6，自引：0，他引：6  

Sofie Spatharis  George Tsirtsis  Daniel B. Danielidis  Thang Do Chi  David Mouillot   《Estuarine, Coastal and Shelf Science》2007,73(3-4):807-815

The response of phytoplankton assemblage structure to terrestrial nutrient inputs was examined for the Gulf of Kalloni in the Northern Aegean Sea, a productive semi-enclosed coastal marine ecosystem. The study was focused on a typical annual cycle, and emphasis was placed on the comparative analysis between blooms developing after significant nutrient inputs from the watershed, and naturally occurring blooms. Baseline information was collected on a monthly basis from a network of stations located in the oligotrophic open sea and the interior and more productive part of the embayment. Intensive sampling was also carried out along a gradient in the vicinity of a river which was the most important source of freshwater and nutrient input for the Gulf. Phytoplankton assemblage structure was analyzed from 188 samples using diversity indices (Shannon and Average Taxonomic Distinctness), multivariate plotting methods (NMDS), multivariate statistics (PERMANOVA), and canonical correspondence analysis (CCA). Three characteristic assemblages were recognized: (1) an autumn assemblage developed under nutrient depleted conditions, having low diversity due to the dominance of two small diatoms, (2) a winter bloom of the potentially toxic species Pseudo-nitzschia calliantha occurring immediately after a nutrient peak and characterized by very low diversity, and (3) a naturally occurring early summer bloom of centric diatoms with relatively high diversity. The results of the study support the view that moderate nutrient inputs may have a beneficial effect on the functioning of coastal ecosystems, stimulating the taxonomic diversity through the growth of different taxonomic groups and taxa. On the other hand, a sudden pulse of high nutrient concentrations may greatly affect the natural succession of organisms, have a negative effect on the diversity through the dominance of a single species, and can increase the possibility of a harmful algal bloom development.  相似文献   

Phosphorus removal in low alkalinity secondary effluent using alum     

R. J. Banu Ph.D.  K. U. Do Ph.D.  I. T. Yeom M.Sc. 《International Journal of Environmental Science and Technology》2008,5(1):93-98

The alkalinity plays an important role in phosphorus removal using coagulant. The dosage of coagulant in the low alkalinity wastewater is limited due to rapid pH changes. In the present study, a series of jar test was conducted using low alkalinity wastewater (50 mg/L) to evaluate the optimum pH, dosage and performance parameters (slow mixing and settling time) for the common coagulant alum. From the experiment, it was found that the dosage of coagulant and removal of phosphorus depend upon the pH of the wastewater after adding coagulant. The final optimum pH for efficient P removal was found to be within the range of 5.7–5.9. This range acts as an indicator and it is the maximum tolerable pH range for phosphorus removal for low alkalinity wastewater. The optimum time for slow mix and settling was found to be 20 min. The optimum mole ratio of alum to remove one mole of phosphorous was found to be 2.3. The alum coagulation at pH 7 produced effluent with the total residual phosphorus and reactive phosphorus content of 0.3 and 0.9 mg/L, respectively.  相似文献   

Low frequency flickering of TT arietis: Hard and soft X-ray emission region     

Altan Baykal  Ümit Kiziloğlu 《Astrophysics and Space Science》1996,246(1):29-38

Using archival ASCA observations of TT Arietis, X-ray energy spectra and power spectra of the intensity time series are presented for the first time. The energy spectra are well-fitted by a two continuum plasma emission model with temperatures 1 keV and 10 keV. A coherent feature at 0.643 mHz appeared in the power spectra during the observation.  相似文献   

The contact binary system YY Eri     

E. Budding  C-H. Kim  O. Demircan  Z. Müyesseroğlu  K. Saijo  T. Banks 《Astrophysics and Space Science》1996,246(2):229-242

Relatively new and unanalysed photometric data-sets of the contact binary system YY Eri are presented. The light curves have been analysed using information limit optimization techniques, and the Binary Maker program of Bradstreet (1992).Comparison of the results allows insight into determinacy questions affecting the W UMa type of light curve, which relates to our general understanding of contact binaries. A limiting contact configuration cannot be ruled out on the basis of empirical data-analysis alone.Very careful analysis of the photospheric flux distribution over the surface of the Sun may help establish appropriate values of the gravity brightening parameter for cool dwarf stars. At present, however, empirical photometric information on contact binaries is non-discriminatory: i.e. alternative cosmogonies can find alternative support from available evidence. The implication is then for more and better observational data to allow better real independent parameter determination.  相似文献