Hydroelastic response of a very large floating structure over a variable bottom topography

An influence of sea-bottom topography on the hydroelastic response of a Very Large Floating Structure (VLFS) is considered. When the floating structure is constructed near the shore, the sea-bottom topographical effect should be considered. In this study, the effect of sea-bottom topography is investigated for four different bottom cases. To calculate the sea-bottom effects rigorously, the finite-element method based on the variational formulation is used in the fluid domain. The pontoon-type floating structure is modeled as the Kirchhoff plate. The mode superposition method is adopted for the hydroelastic behavior of the floating structure.     

Comparative study on the fauna composition of intertidal invertebrates between natural and artificial substrata in the northeastern coast of Jeju Island

This study was carried out to learn about differences in the sessile macrobenthic fauna communities between the artificial and natural habitats. There were some differences in terms of species composition and dominant species and community structure between two habitat types. The dominant species include Pollicipes mitella and Granuilittorina exigua in natural rocky intertidal zones; Monodonta labio confusa, Ligia exotica, Tetraclita japonica in the artificial rocky intertidal zones. Among all the species, L. exotica and T. japonica occurred only in the artificial rocky intertidal zone. The results of cluster analysis and nMDS analysis showed a distinct difference in community structure between artificial and natural rocky intertidal zones. The fauna in the natural rocky intertidal zones were similar to each other and the fauna in the artificial rocky intertidal zones were divided depending on the slope of the substratum. In the case of a sloping tetrapod, M. labio confusa and P. mitella were dominant, but at the vertical artificial seawall, Cellana nigrolineata, L. exotica T. japonica were dominant. The analysis of the species presented in natural and artificial rocky intertidal areas showed the exclusive presence of 10 species on natural rocks and 12 species on artificial rocks. The species in the natural rocky intertidal area included mobile gastropods and cnidarians (i.e. rock anemones), and the species in the artificial rocky intertidal area mostly included non-mobile attached animals. The artificial novel structure seems to contribute to increasing the heterogeneity of habitats for marine invertebrate species and an increase the species diversity in rocky coastal areas.     

Assessment of pollution and ecological risk of heavy metals in the surface sediments of Ulsan Bay,Korea

Heavy metal concentrations in the surface sediments of specially managed Ulsan Bay were investigated to determine metal distribution, pollution status and its ecological risk using pollution indices (enrichment factor and geo-accumulation index), potential ecological risk index and sediment quality guidelines (SQGs). The order of mean concentration (mg/kg) of metals was Zn (361.9) > Cu (95.6) > Pb (90.7) > Cr (64.7) > Ni (32.2) > Co (16.6) > As (15.8) > Cd (0.40) > Hg (0.16) in sediments of Ulsan Bay. Spatial distribution of metals in sediments showed a significantly higher concentration near industrial complexes, indicating that metal pollution is caused by anthropogenic sources. The results of enrichment factor (EF) and geo-accumulation index (I_geo) showed that sediments were significantly accumulated with Cu, Zn, As, Cd, Pb and Hg, indicating moderate to very severe enrichment (pollution) by these metals. Based on the potential ecological risk index, Hg and Cd posed a very high and a considerable potential ecological risk. Cu and As posed a moderate potential ecological risk, while, other metals (Cr, Co, Ni, Zn and Pb) rarely posed any potential ecological risk to the coastal environments. The sediments in Ulsan Bay showed a very high level of ecological risk, dominated by Hg and Cd. Metal concentrations in sediments were 80% for Cu, 96.7% for Zn, 50% for As, 70% for Pb and 50% for Hg above the threshold effects level (TEL), respectively.     

Effects of surfactants and electrolyte solutions on the properties of soil

Biosurfactants are frequently used in petroleum hydrocarbon and dense non-aqueous phase liquids (DNAPLs) remediation. The applicability of biosurfactant use in clayey soils requires an understanding and characterization of their interaction. Comprehensive effects of surfactants and electrolyte solutions on kaolinite clay soil were investigated for index properties, compaction, strength characteristics, hydraulic conductivities, and adsorption characteristics. Sodium dodecyl sulfate (SDS) and NaPO₃ decreased the liquid limit and plasticity index of the test soil. Maximum dry unit weights were increased and optimum moisture contents were decreased as SDS and biosurfactant were added for the compaction tests for mixtures of 30% kaolinite and 70% sand. The addition of non-ionic surfactant, biosurfactant, and CaCl₂ increased the initial elastic modulus and undrained shear strength of the kaolinite–sand mixture soils. Hydraulic conductivities were measured by fixed-wall double-ring permeameters. Results showed that the hydraulic conductivity was not significantly affected, but slightly decreased from 1×10⁻⁷ cm/s (water) to 0.3×10⁻⁷ cm/s for Triton X-100 and SDS. The adsorption characteristics of the chemicals onto kaolinite were also investigated by developing isotherm curves. SDS adsorbed onto soil particles with the strongest bonding strength of the fluids tested. Correlations among parameters were developed for surfactants, electrolyte solutions, and clayey soils.     

Late Quaternary sediments on the outer shelf of the Korea Strait and their paleoceanographic implications

Sedimentological and micropaleontological characteristics of core sediments from the outer shelf of the Korea Strait, which connects the northern East China Sea and the East Sea (Sea of Japan), were investigated to elucidate the paleoceanographic environment, especially the timing of the Kuroshio inflow, since the last glacial maximum. The core sediments, containing continuous records of the last 15,000 years, are characterized by a relatively high mud content (more than 50%, on average) and well-developed tide-influenced sedimentary structures. Their mineralogy suggests that the material originated from the paleo-Nakdong River system, which extended across the shelf of the Korea Strait during low sea-level periods. Planktonic foraminifers reveal a series of well-defined changes in paleoceanographic conditions during the late Pleistocene–Holocene. Down-core variations in the abundance of four foraminiferal assemblages, i.e., cold, coastal, tropical–subtropical, and Kuroshio water groups comprising characteristic planktonic species, suggest the occurrence of a distinct paleoenvironmental change in the surface water at 7,000 years b.p., i.e., from 15,000 to 7,000 years b.p., the area was influenced by coastal waters whereas since ca. 7,000 years b.p., it has been under the influence of open-sea water related to the Kuroshio Current flow, associated with both higher temperature and higher salinity. In particular, Pulleniatina obliquiloculata increased markedly in abundance at this time, documenting the inflow of the Kuroshio into the study area. These data indicate that the coastal water stage terminated at ca. 7,000 years b.p. when the warm Kuroshio and its major branch, the Tsushima Current, began to flow into the East Sea, as is the case today. The intrusion of the Tsushima Current through the Korea Strait after ca. 7,000 years b.p. resulted in abrupt changes in sedimentation rates and a dramatic increase in abundance of the Kuroshio indicator species, P. obliquiloculata.     

Changes in the Brewer-Dobson circulation for 1980–2009 revealed in MERRA reanalysis data

Changes in the Brewer-Dobson circulation (BDC) during the 30 years 1980–2009 are investigated using Modern Era Retrospective-analysis for Research and Applications (MERRA) reanalysis data. The mass streamfunction that is induced by wave forcings in the transformed Eulerian-mean (TEM) equation through the downward-control principle is used as a proxy for the BDC. The changes in the BDC are investigated using two aspects: the wave propagation conditions in the stratosphere and the wave activity in the upper troposphere. They are compared in the first (P1) and second (P2) 15-year periods. The resolved wave forcing, expressed by the Eliassen-Palm (EP) flux divergence (EPD), is significantly enhanced during the December-January-February (DJF) season in P2 in both the Northern Hemisphere (NH) high latitudes and the Southern Hemisphere (SH) mid- and high latitudes. The increased zonal mean zonal wind at high latitudes in the SH, caused by ozone depletion, leads to an upward shift of the Rossby-wave critical layer and this allows more transient planetary waves to propagate into the stratosphere. In the NH, the enhanced EPD in DJF leads to an increase in the frequency of Sudden Stratospheric Warming (SSW) events. The gravity wave drag (GWD) is smaller than the EPD and the change in it between the two time periods is insignificant. The residual term in the TEM equation is similar to the GWD in the two periods, but its change between the two periods is as large as the change in the EPD. Among the four components of the EP flux at 250 hPa, the meridional heat flux played a dominant role in the enhancement of the BDC in P2.     

The Neftegorsk, Sakhalin Island, earthquake of 27 May 1995

Abstract Past seismic catastrophes were unknown in Sakhalin Island before 1995 except those suggested from findings of paleoseismodislocations. The first time that dwellers have experienced such a catastrophe in the Sakhalin Island history was on 27 May 1995. The devastating Neftegorsk earthquake occurred in Northern Sakhalin (?= 52.8° north; δ= 143.2° east; H = 18 km; M_s= 7.2), killed almost 2000 people in the small city of Neftegorsk, caused damage and destruction of buildings, bridges, railways and roads, breakage of oil and gas pipelines, electric and communication lines, and was accompanied by large-scale surface phenomena within a source area. It was felt all over the Sakhalin Island, as well as over the closest part of the Eurasian continent. Surface fracturing was the most impressive effect of the Neftegorsk earthquake. The 37-km long, right-lateral strike-slip fault, with a strike of north 15° east and a horizontal displacement up to a maximum of 8 m, has been observed from Taxon Mountain at the south to the junction of the Cadylanye and Keniga Rivers at the north. According to the results of a detailed geological survey and study of the aftershocks, the total extent of the source area was - 80 km. Various secondary phenomena have been observed at the Earth's surface, such as landslides, falls, soil liquefaction, mud volcanoes etc. The earthquake was followed by hundreds of aftershocks within the following 1-2 months. Spatially, the earthquake fault coincides with the pre-existing Upper Piltun fault, known earlier from geological studies. Recent high activity of the latter fault has been recognized only after the Neftegorsk event because of findings of traces of significant past dislocations within the fault zone. From a tectonic viewpoint it can be suggested that the Upper Piltun fault is a Riedel-type shear fracture located between two main regional faults: the Gyrgylanye-Dagy fault at the west and the Piltun-Ekhaby fault at the east. Therefore, its present activity, expressed by the destructive Neftegorsk earthquake, seems to be explained by a long strain accumulation within a broad zone of regional right-lateral shear faulting.     

Water quality assessment at Jinhae Bay and Gwangyang Bay,South Korea

A new water quality index for evaluating the water quality of Jinhae Bay and Gwangyang Bay was developed. Four water quality parameters were selected as water quality indicators for the water quality index: dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), chlorophyll-a (Chl-a), and dissolved oxygen (DO). Reference levels of DIN, DIP, and Chl-a were determined as 6.22 μmol L^?1, 0.38 μmol L^?1, and 2.32 μmol L^?1, respectively, on the basis of a long-term dataset that was collected monthly in the Korea Strait over a period of seven years (2006–2012). The water quality index established for Jinhae Bay and Gwangyang Bay is (bottom DO grade × 0.33) + (surface Chl-a grade × 0.33) + (surface DIN grade × 0.17) + (surface DIP grade × 0.17). On the basis of a three-year observation, the water quality of Jinhae Bay was classified as “good” in winter and spring, “poor” in summer, and “fair” in autumn and exhibited large spatial variation, with the lowest-quality water observed in Masan Bay. The water quality of Gwangyang Bay was classified as “good” in winter, “fair” in spring, “poor” in summer, and “fair” in autumn. Unlike Jinhae Bay, the water quality of Gwangyang Bay exhibited minimal spatial variation. In both bays, water quality among the four seasons was worse during summer. It is essential that a survey for water quality evaluation be conducted during summer.     

Spitzer IRAC infrared colours of submillimetre-bright galaxies

High-redshift submillimetre-bright galaxies identified by blank field surveys at millimetre and submillimetre wavelengths appear in the region of the Infra Red Array Camera (IRAC) colour–colour diagrams previously identified as the domain of luminous active galactic nuclei (AGNs). Our analysis using a set of empirical and theoretical dusty starburst spectral energy distribution (SED) models shows that power-law continuum sources associated with hot dust heated by young (≲100 Myr old), extreme starbursts at z > 2 also occupy the same general area as AGNs in the IRAC colour–colour plots. A detailed comparison of the IRAC colours and SEDs demonstrates that the two populations are distinct from each other, with submillimetre-bright galaxies having a systematically flatter IRAC spectrum (≳1 mag bluer in the observed [4.5]–[8.0] colour). Only about 20 per cent of the objects overlap in the colour–colour plots, and this low fraction suggests that submillimetre galaxies powered by a dust-obscured AGN are not common. The red infrared colours of the submillimetre galaxies are distinct from those of the ubiquitous foreground IRAC sources, and we propose a set of infrared colour selection criteria for identifying SMG counterparts that can be used even in the absence of radio or Multiband Imaging Photometer for Spitzer (MIPS) 24 μm data.     

3-D Geovisualization of satellite images on smart devices by the integration of spatial DBMS,RESTful API and WebGL

Recent technological advancements in web-based geographic information systems have enabled access to satellite images on smart devices. The Representational State Transfer (REST) architecture overcomes difficulties that are associated with conventional data communications on the web, and the Web Graphics Library (WebGL) can be used as an alternative to web-based three-dimensional geographic visualization (3-D geovisualization) due to its efficient image processing capabilities. This paper describes a 3-D geovisualization system that was developed for satellite images on smart devices by integrating a spatial database management system (DBMS), a RESTful application programming interface (API), and WebGL. Spatiotemporal objects were constructed for time-series satellite images within a DBMS and a RESTful API was built for spatiotemporal queries to the time-series database so that the requested satellite data could be represented in 3-D on smart devices using WebGL. Satellite images that are represented in WebGL give a more realistic 3-D experience when they are combined with terrain data and provide for intuitive observations of the relationships between pixel values and associated geospatial conditions. This paper shows that a creative combination of existing technologies can be used to enhance and display satellite images on smart devices for 3-D geovisualization.