A B-spline based higher order panel method for analysis of steady flow around marine propellers

A higher order panel method based on B-spline representation for both the geometry and the solution is developed for the analysis of steady flow around marine propellers. The self-influence functions due to the normal dipole and the source are desingularized through the quadratic transformation, and then shown to be evaluated using conventional numerical quadrature. By selecting a proper order for numerical quadrature, the accuracy of the present method can be increased to the machine limit. The far- and near-field influences are shown to be evaluated based on the same far-field approximation, but the near-field solution requires subdividing the panels into smaller subpanels continuously, which can be effectively implemented due to the B-spline representation of the geometry. A null pressure jump Kutta condition at the trailing edge is found to be effective in stabilizing the solution process and in predicting the correct solution. Numerical experiments indicate that the present method is robust and predicts the pressure distribution on the blade surface, including very close to the tip and trailing edge regions, with far fewer panels than existing low-order panel methods.     

Identification of Pb sources in Yellow Sea sediments using stable Pb isotope ratios

Rapid economic developments in East Asian countries have inevitably resulted in environmental degradation in the surrounding seas, and concern for both the environment and protection from pollutants is increasing. Identification of sources of contaminants is essential to environmental pollution management. In this study, the provenance of anthropogenic lead (Pb), a major pollutant of Yellow Sea sediments, was determined for river mouth sediments, including those of the Changjiang, Huanghe, Han, and Geum Rivers, and for age-determined shelf core sediments through the measurement of Pb isotope ratios in the HCl-leached fraction using multi-collector inductively coupled plasma-mass spectrometry (MC ICP/MS). Anthropogenic Pb has accumulated in shelf core sediments since 1910, and its isotope ratios were estimated as 0.863–0.866 and 2.119–2.125 for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively, from the mixing relationships of the two endmembers. River mouth sediments exhibited enough distinction in anthropogenic Pb isotope ratios to be discriminated: 0.874 (2.144) in the Huanghe, 0.856 (2.129) in the Han, 0.857 (2.122) in the Geum, and 0.854 (2.101) in the Changjiang for ²⁰⁷Pb/²⁰⁶Pb (²⁰⁸Pb/²⁰⁶Pb), respectively. Although isotope ratios of geogenic Pb in sediments dating before 1910 showed narrow ranges (0.842–0.845 and 2.088–2.100 for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively), distinct isotope ratios in each core permitted source identification of sediments in the Yellow Sea based on geographic locations and the geogenic Pb of each river. By comparing the isotope ratios of the estimated anthropogenic Pb to source-related materials, the provenances of anthropogenic Pb in Chinese river sediments were presumed to be Chinese coal or ore, which is also a major source of atmospheric particulate Pb. The anthropogenic Pb in the shelf core sediments in the northern Yellow Sea originated from northern Chinese cities such as Beijing and Tianjin through atmospheric pathways. Pb isotope ratios indicated that Pb in Korean river sediments was characteristic of local Korean ores.     

Peptide decomposition by extracellular hydrolysis in coastal seawater and salt marsh sediment

Extracellular peptide hydrolysis rates were measured in seawater and sediment from Flax Pond salt marsh using peptide analogs (LYA-peptides) as substrates. This technique allows the direct measurement of specific hydrolysis products and thus provides insights into enzymatic hydrolysis pathways. In sediments, hydrolysis rate constants of LYA-peptides varied seasonally and with depth. Highest activity was found in spring and summer, and most cores exhibited a subsurface maximum. Calculations using the concentrations of chemically-measured peptides suggested that extracellular hydrolysis of peptides is faster than the rate of free amino acids uptake. However, not all peptides may be available for enzymatic hydrolysis. In both seawater and sediment, extracellular hydrolysis of peptides of up to 8 amino acids yielded smaller peptides and free amino acids. Hydrolysis rates depended on size of the peptide substrate, although a clear relationship with number of amino acid constituents was not evident. Peptides containing >2 amino acids were hydrolyzed 10–400 times faster than dipeptides or the fluorogenic substrate Leucine-MCA. Thus, dipeptidases are either uncommon in nature, or hydrolysis is carried out by nonspecific hydrolases that with a low affinity for dipeptides. This is also suggested by the presence of a lag time before dipeptide hydrolysis begins, and the absence of dipeptide hydrolysis in 0.2-μm-filtered. One implication of this finding is that measurements of hydrolysis rates using substrates like Leu-MCA may not accurately predict the magnitude of hydrolysis rates of macromolecules in the marine environment. Even though dipeptide hydrolysis is slow compared to that of larger peptides, LYA-dipeptides are preferentially produced from the hydrolysis of larger substrates. LYA-dipeptides do not penetrate cell membranes of microorganisms because of their size, but natural dipeptides are smaller and can be transported across the cell membrane. Since dipeptides do not appear to accumulate in natural waters, they must be rapidly removed by microorganisms.     

Structural changes in macrozoobenthic communities due to summer hypoxia in Gamak Bay,Korea

The purpose of this study was to examine the structural changes that macrozoobenthic communities underwent as a result of the annual summer hypoxia at the northern part of Gamak Bay, Korea. During this study period, summer hypoxia occurred at the northern part of Gamak Bay in July. Under hypoxic conditions, both the number of species and population density decreased rapidly. Species diversity also manifested lower values during this hypoxic period. Faunal composition changed seasonally with Capitella capitata dominant at the hypoxic sites in spring but disappearing in summer. The health condition of the benthic faunal community assessed by the composition of functional groups within community also changed due to the summer hypoxia from a slightly polluted condition to a highly polluted condition. From these results it has been shown that the recent macrozoobenthic community structure in Gamak Bay has returned to a state similar to what it was before dredging works commenced.     

Day-Night and Gastrointestinal Changes in Winter Feeding Intensity and Prey Composition of Apogon lineatus Inhabiting the Southeastern Waters of Korea

Ocean Science Journal - Diel and gastrointestinal changes in relation to the feeding intensity and prey composition of Apogon lineatus were investigated through the analysis of the diet contents of...     

A review of sediment dynamical processes in the west coast of Korea,eastern Yellow Sea

Sediment dynamical processes began to be systematically monitored in the west coast of Korea facing the eastern Yellow Sea in the 1990s. The early investigations were largely conducted aboard vessels that provided results where the resolution was highly restricted in both temporal and spatial aspects. However, full-fledged autonomous instruments introduced early in the 2000s allowed for a quantum leap in the level of this sub-field of sedimentology. The investigated sites include various environments such as estuaries, bays, tidal flats, beaches, and offshore deposits. Among them, a total of seven sites were selected for the review: Han estuary, Daeho tidal flats, Garolim Bay, Saemangeum Region, Byunsan Beach, Gomso Bay, and Huksan Mud Belt. The major results from each site were briefly summarized. The summary clearly demonstrates that wind-generated currents and waves particularly during winter should be carefully considered in interpreting sedimentary environments. This is because winter-season processes interrupt or actively displace much of the sediments worked by tidal currents in the remaining seasons. The summary hence suggests that seasonal investigations of sediment dynamics are necessary to understand shallow-water sedimentation in the west coast of Korea that is governed complicatedly by two major forcing agents: waves and tidal currents.     

Applicability of Individual Transferable Quotas (ITQs) in Japanese fisheries: A comparison of rights-based fisheries management in Iceland, Japan, and United States

ITQs have not yet been introduced by the Government of Japan. In coastal areas, fishery cooperative associations have traditionally played an important role in managing fisheries through self-imposed rules and peer-monitoring systems. Recently, however, the economic competitiveness of Japanese fisheries in the international market is being questioned. In this paper, a detailed examination of the pros and cons of the current system in Japan is compared to the current fishery management measures of Iceland and the United States, where attaining economically or biologically efficient outcomes may be prioritized in making fisheries management decisions. For many coastal fisheries in Japan, maintaining a management scheme in which stakeholders play an active role in determining fisheries measures seems more relevant if their priority is to maintain the stability of coastal communities and equity of stakeholders. Intensive dialog among stakeholders would be necessary to identify shared objectives of their fishery operations and to make decisions to establish specific steps toward the goal of increasing economic efficiency, environmental sustainability, or stability of communities and equity of stakeholders.     

Assessment of Dynamic Characteristics for Compaction Piles with Geophysical Logging in Soft Ground

In this paper, a case study was performed on a sand compaction pile (SCP) and a gravel compaction pile (GCP) to estimate the dynamic characteristics and the improvement effect of soft ground. The dynamic elastic modulus, shear modulus, bulk modulus, and Poisson's ratio were estimated and the dynamic characteristics were analyzed using the compression and shear wave velocity of the improved ground based on the results of suspension P- and S-wave (PS) logging. The results revealed that the dynamic properties were increased in the order of unimproved subsoil and improved subsoil using SCP and GCP. The increase in the effects of dynamic properties with each replacement ratio of SCP was not large, whereas a good increase in the effects was observed in the case of the improved subsoil with GCP. Consequently, it was presented that the resistance characteristics against the seismic loading of GCP are excellent. As a result of analyzing the density distribution of the improved subsoil through density field logging, the overall density distribution gradually exhibits increasing trends in the order of unimproved subsoil and improved subsoil with SCP and GCP. Thus, the improvement effect of GCP was relatively high in comparison with the same replacement ratio of SCP.     

Static bay beach concept for scientists and engineers: A review

Headland-bay beach (HBB) is one of the most prominent physiographic features on the oceanic margin of many countries in the world. Under the influence of a predominant swell, its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and/or a riverain source within its own embayment. Coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s. As the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time, some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management. Nowadays, many useful applications have emerged since the publication of the parabolic bay shape equation (PBSE) developed for static equilibrium planform (SEP) in late 1980s. The advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept (SBBC).