Wave enhancement due to blockage in semi-submersible and TLP structures

An exact analytical method is described to solve the diffraction problem of a group of truncated vertical cylinders. In order to account for the interaction between the cylinders, Kagemoto and Yue's exact algebraic method is utilised (Kagemoto, H., Yue, D.K.P., 1986. Interactions among multiple three-dimensional bodies in water waves: an exact algebraic method. J Fluid Mech, 46, 129–139). The isolated cylinder diffraction potential is obtained using Garret's solution and evanescent mode solutions are derived in a similar manner (Garret, C.J.R., 1971. Wave forces on a circular dock. J Fluid Mech, 46, 129–139).Free surface elevations are calculated for an array of four cylinders and compared with experiments. Comparisons show good agreement.     

Modelling phytoplankton succession on the Bering Sea shelf: role of climate influences and trophic interactions in generating Emiliania huxleyi blooms 1997–2000

Several years of continuous physical and biological anomalies have been affecting the Bering Sea shelf ecosystem starting from 1997. Such anomalies reached their peak in a striking visual phenomenon: the first appearance in the area of bright waters caused by massive blooms of the coccolithophore Emiliania huxleyi (E. huxleyi). This study is intended to provide an insight into the mechanisms of phytoplankton succession in the south-eastern part of the shelf during such years and addresses the causes of E. huxleyi success by means of a 2-layer ecosystem model, field data and satellite-derived information. A number of potential hypotheses are delineated based on observations conducted in the area and on previous knowledge of E. huxleyi general ecology. Some of these hypotheses are then considered as causative factors and explored with the model. The unusual climatic conditions of 1997 resulted most notably in a particularly shallow mixed layer depth and high sea surface temperature (about 4 °C above climatological mean). Despite the fact that the model could not reproduce for E. huxleyi a clear non-bloom to bloom transition (pre- vs. post-1997), several tests suggest that this species was favoured by the shallow mixed layer depth in conjunction with a lack of photoinhibition. A top-down control by microzooplankton selectively grazing phytoplankton other than E. huxleyi appears to be responsible for the long persistence of the blooms. Interestingly, observations reveal that the high N:P ratio hypothesis, regarded as crucial in the formation of blooms of this species in previous studies, does not hold on the Bering Sea shelf.     

Geochemistry of the Pliocene basalts erupted along the Malatya-Ovacik fault zone (MOFZ), eastern Anatolia, Turkey: Implications for source characteristics and partial melting processes

The study area is located on the middle sector of the Malatya-Ovacık Fault Zone (MOFZ) in the eastern Anatolia. Four basaltic flows from bottom to top, which are tholeiitic in character and intercalated with Pliocene sedimentary rocks, were erupted along this fault zone. Chemical compositions of these flows reveal some differences between the first flow and others in terms of high-field strength elements (HFSEs) (e.g. Ti, Zr, Nb). Limited variations in compositions within the first flow and upper flows suggest a limited fractionation range. Trace-element patterns exhibit that all the flows have similar and OIB-like patterns without positive peak at Pb and a trough at Nb—Ta, indicating minimal or no crustal contribution. Rare-earth element (REE) patterns indicate that the first flow has flat patterns with negative Eu anomaly, whereas the upper flows have variable enrichments in LREE and depletions in HREE. La/Sm_N, Dy/Yb_N and Zr/Y ratios exhibit that the degree of partial melting decreases from the first flow to upper flows. Higher values of La/Yb_N ratio for the upper flows and depletions at Y and Yb on the trace-element patterns suggest the presence of garnet as a residual phase, which imply that the depth of partial melting took place solely in the garnet-stability field. OIB-like trace-element patterns and trace-element ratios (e.g. La/Nb, Ce/Y and Zr/Nb) emphasize that the melts forming the Arguvan basalt were originated from the asthenospheric mantle rather than the lithospheric mantle.     

Comparison of Static,Kinematic and Dynamic Geodetic Deformation Models for Kutlugün Landslide in Northeastern Turkey

Being the cause of the loss of life and damaging property, landslide is an important natural hazard. Therefore, landslides have to be monitored and preventive measures taken accordingly. In Geodesy, landslides can be determined with static, kinematic and dynamic geodetic models. The aim of this study is to develop a dynamic geodetic model for landslides and compare it with static and kinematic geodetic models. A study area was selected in the Northeastern Black Sea Region of Turkey where landslides are the most effective natural hazard. Movements were determined with static, kinematic and dynamic geodetic models using geodetic, geologic and geophysical measurements made in the study area. Groundwater levels changes were regarded as causative forces in the formulation of the dynamic model. The dynamic model delivered more detailed information (direction, values, velocity, acceleration of movements) about landslide movements. It is possible to formulate more realistic strategies about prevention of landslides by using this information. As a result, it can be suggested that dynamic geodetic models are more useful in landslide studies.     

Determining the optimum image fusion method for better interpretation of the surface of the Earth

Image fusion is the production of high-resolution images by combining the spatial details of a high-resolution image with the spectral features of a low-resolution one. Reports of various quality metrics to evaluate the spectral and spatial qualities of fused images have been published. However, metrics may lead to misinterpretation due to inherent limitations in their mathematical algorithms. Hence, the use of additional assessment techniques in quality evaluation is reasonable. The purpose of the study was to compare the performances of several advanced fusion algorithms in order to help users in their choice of an appropriate fusion algorithm. Four different datasets were fused using advanced fusion algorithms, namely UNB PanSharp, Hyperspherical Color Space, High-Pass Filtering, Ehlers, Subtractive, Wavelet Single Band, Gram-Schmidt, Flexible Pixel-Based, and Criteria-Based. The spectral and spatial qualities of the fused images were evaluated using various quantitative procedures to ensure comprehensive and reliable comparison. The results showed that the Flexible Pixel-Based and High-Pass Filtering algorithms were very successful with regard to spatial quality, whereas the Flexible Pixel-Based and Criteria-Based algorithms were very successful with regard to spectral quality. The authors conclude that the Flexible Pixel-Based algorithm can be used for applications that require high spectral and spatial quality.     

Analytical solutions of the diffraction problem of a group of truncated vertical cylinders

An exact analytical method is described to solve the diffraction problem of a group of truncated vertical cylinders. In order to account for the interaction between the cylinders, Kagemoto and Yue's exact algebraic method is utilised. The isolated cylinder diffraction potential due to incident waves is obtained using Garret's solution and evanescent mode solutions are derived in a similar manner.Numerical results are presented for arrays of two and four cylinders. Comparisons between the results obtained from the method presented here and those obtained from numerical methods show excellent agreement.     

Strength Behavior of Fine Grained Soil Reinforced with Randomly Distributed Polypropylene Fibers

Admixtures and reinforcement materials are frequently used in practice to stabilize coarse and fine grained soils and to improve their engineering properties. However, a limited number of studies have been carried out on fiber-reinforced fine grained soils. In this study, a series of unconfined compression tests, direct shear tests, and California Bearing Ratio tests were carried out to investigate the effect of randomly distributed polypropylene fiber on the strength behavior of a fine grained soil. The content of polypropylene fiber was varied between 0.25 and 1% by total dry weight of the reinforced samples. It was observed that unconfined compression strength, cohesion intercept and California Bearing Ratio increased with the addition of fibers. On the other hand, the results of the tests indicated that shear strength angle was not affected significantly by the fiber reinforcement.     

Water table fluctuation analyses and associated empirical approach to predict spatial distribution of water table at Yeşilköy/AgiosAndronikos aquifer

The groundwater of the deep Ye?ilköy aquifer is the only water resource for agricultural and domestic consumption at the Karpaz Peninsula of Cyprus, which stretches approximately 100 km from the northeast of capital Nicosia to the northern tip of Cyprus. During the last decade, over-pumping and following dry periods have depleted the groundwater resources and the water surface elevation of the aquifer has dropped. The aim of this study is to understand the behavior of the Ye?ilköy aquifer in the last decade for the proper management of groundwater resources. This has been achieved based on well survey and field survey studies, monitoring programs followed by pumping tests, and safe yield analysis. Most of the research effort has been focused on field and well survey studies to quantify agricultural water consumption and abstraction rates from the aquifer. A long-term groundwater level monitoring program, short-term continuous groundwater monitoring and pumping tests provided information for the regression analyses while deriving a sixth order polynomial relationship between the period parameter and the head parameter. The equation was helpful to predict the short-term behavior of the water level when the present hydrogeological conditions prevail. The pumping test results satisfied the hydraulic properties of calcarenite formation yielding T = 1,782 m²/day and S = 0.0012. The results of safe yield analysis show that the annual deficit of the aquifer is 0.496 million cubic meters (MCM), which is equivalent to a 0.6 m drop in groundwater levels per year. Finally, the resultant annual safe yield of the aquifer is estimated as 0.84 MCM.