M2 Tidal Current Estimation from One-day Observation Data off the Western and Southern Coasts of Korea

Ocean Science Journal - A practical method to estimate the M2 tidal current is proposed based on one-day current observations. In this method, the semi-diurnal constituent, composed of several...     

Biomarker-based Seawater Temperatures of Winter Sinking Particles and Core-top Sediment in the Ulleung Basin of the East Sea

Ocean Science Journal - This study evaluates the application of biomarkerbased temperature proxy data (alkenone with its resultant $$U_{37}^{K'}$$ index and glycerol dialkyl glycerol tetraether...     

Experimental investigation of three-dimensional earth pressure according to aspect ratio of retaining wall

The purpose of this study is to investigate the scale and load distribution of three-dimensional active earth pressure and the load transferred to the adjacent soil by changing the aspect ratio of a retaining wall through a series of model tests. In this research, 42 earth pressure plates of different heights and widths were installed to evaluate the earth pressures by considering the wall aspect ratio and the change of earth pressure. The test results showed that the active earth pressures were uniformly converged when the percentage of limit displacement against wall height was 0.12%. The distribution of active earth pressure on the wall showed a parabola shape for most aspect ratios while the wedge shape identified by the model test was similar to the shell-shaped model. In this paper, two diagrams were proposed regarding the active earth pressure according to the aspect ratio of a retaining wall; (1) a diagram of earth pressure conversion against the aspect ratio based on evaluated three-dimensional active earth pressures with traditional two-dimensional earth pressures, (2) a load transfer diagram based on the horizontal distance by analyzing the horizontal and vertical load transfer ranges with the relevant increasing rates.     

Phosphorites,glass ramps and carbonate factories: The evolution of an epicontinental sea and a late Palaeozoic upwelling system (Phosphoria Rock Complex)

The Permian Phosphoria Rock Complex of the western USA contains an enigmatic assemblage of bioelemental rocks (i.e. phosphorites and cherts) that accumulated in a depositional system with no modern analogue. This study utilizes detailed sedimentological, stratigraphic and petrographic examination to evaluate the genetic relations of phosphorites, spiculitic chert and carbonates of the Ervay cycle (depositional sequence) and propose a unified oceanographic model for their deposition. The Ervay cycle contains three marine and one terrestrial facies association, each of which composes the bulk of a single lithostratigraphic unit. The marine facies associations include: (i) granular phosphorites (Retort Member); (ii) spiculitic cherty dolostones (Tosi Member); and (iii) marine to peritidal carbonates (Ervay Member). Red beds and intercalated gypsum (Goose Egg Formation) accumulated in the vast desert adjacent to the sea. The three marine members are chronostratigraphically distinct, successive and conformably stacked. They are not coeval facies belts. They reflect the progressive evolution of the epicontinental sea from the location of: (i) authigenic phosphogenesis (lowstand to transgression); to (ii) a glass ramp with biosiliceous (sponge) deposition (transgression); to (iii) a carbonate ramp (regression). This succession of switching biochemical sediment factories records the evolution of sea-level, nutrient supply, upwelling, oxygenation and dissolved Si. Intense upwelling, potentially coupled with aeolian input, led to sedimentary condensation and phosphogenesis. Decreased upwelling intensity during transgression increased oxygenation sufficiently for a siliceous sponge benthos. Sponges were favoured over biocalcifiers due to elevated dissolved silica and a low carbonate saturation state. The cessation of sponge dominance and transition to a carbonate ramp occurred due to decreasing upwelling intensity, Si drawdown and an increased carbonate saturation state. These results provide insight into the role of Si loading in faunal turnover on glass ramps and highlight how differences in dissolved Si utilizers in pre-Cretaceous versus post-Cretaceous upwelling systems influence the resultant deposits.     

Floodplain construction by recent,rapid vertical accretion: Waipaoa River,New Zealand

The rate of vertical accretion (typically 14–18 mm h⁻¹) during eight floods in the Waipaoa River basin, with recurrence intervals of 5 to 60 years, was determined by relating the floodplain stratigraphy at McPhail's bend to the 1948–1995 flood history. Overbank deposits remaining after a flood that occurred in March 1996 suggest a rate of vertical accretion of 15 mm h⁻¹. By contrast, because the flow velocity across the floodplain was too high to permit deposition from suspension, during the record flood of March 1988 the rate of vertical accretion was only 6 mm h⁻¹. The sequence of deposition is highly discontinuous, and the rapid vertical accretion is a response to a late 19th to early 20th century phase of deforestation in the headwaters that probably initiated a far greater change in suspended sediment yield than in discharge. Cross-section surveys conducted since 1948 indicate that the high suspended sediment load of the Waipaoa River also promoted in-channel deposition, which effected a progressive reduction in bankfull channel width although, due to the overbank deposition, channel capacity remained constant. © 1998 John Wiley & Sons, Ltd.     

Fundamental yet simplified model for liquefaction instability

A fundamental procedure is proposed for the identification of liquefaction in saturated soils based on the instability in the material's microstructure. The disturbed state concept (DSC) provides a unified constitutive model for the characterization of entire stress–strain behaviour under cyclic loading, and the values of disturbance at threshold states in the deforming microstructure provides the basis for the identification of liquefaction. The procedure is verified with respect to laboratory behaviour of two sands, saturated Ottawa and Reid Bedford. A mathematical analysis of the DSC constitutive matrix is also performed. Procedures for the application of the DSC for simplified analysis and design, and in finite element procedures are presented. It is believed that the proposed model can provide a fundamental yet simplified procedure for liquefaction analysis, and as a result, it is considered to be an improvement over the available empirical and energy-based procedures. © 1998 John Wiley & Sons, Ltd.     

Relic permafrost structures in the Gobi of Mongolia: age and significance

Relict permafrost structures (ice-wedge casts and cryoturbation structures) are present in the Gobi of southern Mongolia. Luminescence dates of sediments are presented to constrain the age of formation of permafrost structures. These data show that there was a phase of permafrost development during the latter part of the Last Glacial (after about 22 to 15 ka) that resulted in cryoturbated sediments and ice-wedge casts. Furthermore, permafrost degradation occurred during late Pleistocene times (13–10 ka) and was absent during the early Holocene. These permafrost structures mark the southernmost evidence of permafrost in northern Asia during late Quaternary times and indicate that the mean annual air temperature was below approximately −6°C during their formation. © 1998 John Wiley & Sons, Ltd.     

Can One-Run-Fixed-Arrhenius Kerogen Analysis Provide Comparable Organofacies Results to Detailed Palynological Analysis? A Case Study from a Prospective Mississippian Source Rock Reservoir (Bowland Shale,UK)

Natural Resources Research - Organofacies analysis, a fundamental component within source rock appraisal based on the study of kerogen within a source rock, is typically produced from microscopy...     

Development of the AUV ‘ISiMI’ and a free running test in an Ocean Engineering Basin

The Korea Ocean Research and Development Institute (KORDI) has developed a small AUV named ISiMI. The mission of ISiMI is to work as a test-bed AUV for the development and validation of various algorithms and instruments required to enhance the AUV's functions. The design concept of ISiMI is that of a vehicle small enough to cruise the Ocean Engineering Basin (OEB) of KORDI and to be handled by one or two people. The downsized design and the cruising ability in its tank enable fast experimental feedback on AUV technologies and a shorter development period for new technologies. This paper presents a review of our research work on the development of ISiMI, with a performance evaluation by simulation and an experimental test. After the design and implementation of ISiMI, including its positioning system in the OEB, are presented, a series of test results in the OEB and discussions of the results are presented, with comparisons of the simulation and experimental outputs.