• Journal of Navigation and Port Research
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• v.28 no.10 s.96
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• pp.909-915
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• 2004

This paper suggests an evaluation of risk level for damage of marine accidents in SRRs. Qualitative analyses in words is sometimes priorior to quantative analyses in numeric symbols. This paper introduces a concept of fuzzy theory with the plenty of related literature riview and AHP in the Korean SRRs of RCC and RSC. The methodology of this paper is $max{\cdot}min$ composition of fuzzy extensive principle, defuzzifiation is centroid of gravity methods. At the result, the evaluation of risk level is especially over Serious for marine accident of Busan SRRs. This paper recommends that many Rescue Vessels and Equipments need to the reduction of risk level about those.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.807-815
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• 2013

A numerical study on soot formation in a laminar ethylene diffusion flame at atmospheric pressure was conducted to obtain a better understanding of the effects of buoyancy on sooting flames under 0g and 1g using a gas-phase reaction mechanism and thermal and transport properties. A simple model was employed to predict soot formation, growth and oxidation with interactions between the gas phase chemistry and the soot chemistry taken into account. Results showed that the flames in 0g are much wider than that of 1g because of the thicker diffusion layer and reduction in axial velocity. The reduction in the axial velocity in 0g results in longer residence times, and resulting in greatly enhanced soot volume fraction. And, under zero-gravity, due to the lack of a buoyancy-induced instability, flame instability disappears.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.10-17
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• 2003

Acoustic and pressure type seabed installed wave sensors have advantage in observing long period infra-gravity wave and tsunami, while buoy type wave gauges which measure acceleration of the moored buoy motion are not able to detect long period waves. That's why most of the Japanese coastal wave observation sensors are seabed installed typed ones. Nationwide Japanese coastal wave observation systems with seabed installed sensors are gradually clarifying long-period tsunami profiles and infra-gravity wave characteristics (Nagai.et.al., 1996, 1997,2000,2002a,2002b). (omitted)

• Economic and Environmental Geology
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• v.18 no.2
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• pp.159-166
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• 1985

The computation of gravity anomalies by multi pole expansion is derived and compared with exact calculation for right rectangular prisms and right circular cylinders. For sources near field points, the multipole expansion results in a better approximation in volume integrals than in surface integrals. Nonetheless two approximate methods are coincident in the far-field of the general geophyical prospecting.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.4
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• pp.426-434
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• 2014

The research developed twin keel yacht for everyone which is able to stand erectly on mud flat without list and intended to commercialize the development product for popularization of west coast's marine leisure industry. Yacht's linear was utilized by "Blue Water21" has superior performance among the existing sailing yachts and twin keel model has been tested by calculation of mono keel's extent and its center of gravity. The result was that only 4 % of difference have been identified between mono keel and twin keel's hydrodynamic resistance which was smaller difference than predicted.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.285-297
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• 2005

Seismic reflection profile analysis, potential field analysis, and potential field modeling using deep seismic reflection, gravity, magnetic, and geological data were performed to better understand the location and nature of the Grenville Front in Ohio, USA. The seismic reflection profile reveals a broad zone of east dipping basement reflectors associated with the Grenville Front in western Ohio and a broad region of west dipping reflectors cutting through the entire crust in eastern Ohio. Potential field analysis indicates that the Grenville Front is characterized by a gravity low, an associated gravity positive and a magnetic high. The results of the gravity and magnetic modeling using seismic data suggest that the lower crust is thickened at the interpreted position of the Grenville Front and high grade metamorphic rocks make up the Grenville Front Tectonic Zone (GFTZ). The gravity low at the Grenville Front is due to the thickened crust, while the magnetic high is due to high grade metamorphic rocks. The gravity high immediately east of the GFTZ in central Ohio is caused by thrusting of high density lower and middle crustal rocks into the upper crust. There is no compelling evidence that this gravity high is related to a Precambrian rift zone as has been suggested in previous studies.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.971-979
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• 2023

Small ships (<499 GT) constitute 46% of the existing ships, therefore, it can be concluded that they produce relatively high CO₂ gas emissions. Operating in optimal trim conditions can reduce the resistance of the ship, which results in fewer greenhouse gases. An affordable way for trim optimization is to adjust the weight distribution to obtain an optimum longitudinal center of gravity (LCG). Therefore, in this study, the effect of LCG changes on the resistance of a small planing ship is studied using empirical and numerical analyses. The Savitsky method employing Maxsurf resistance and the STAR-CCM+ commercial computational fluid dynamics (CFD) software is used for the empirical and numerical analyses, respectively. Finally, the total resistance from the ship design process is compared to obtain the optimum LCG. To summarize, using numerical analysis, optimum LCG is achieved at the 46.2% length overall (LoA) at Froude Number 0.56, and 43.4% LoA at Froude Number 0.63, which provides a significant resistance reduction of 41.12 - 45.16% compared to the reference point at 29.2% LoA.

• Korean Journal of Remote Sensing
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• v.33 no.4
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• pp.351-358
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• 2017

A new method to decompose the footprints of marine atmosphere boundary layer (MABL) on Synthetic Aperture Radar (SAR) imagery into characteristic spatial scales is proposed. Using two-dimensional Empirical Mode Decomposition (EMD) we obtain three Intrinsic Mode Functions (IMFs), which mainly present longitudinal rolls, three-dimensional cells and atmospheric gravity waves (AGW). The rolls and cells have spatial scales between 3.0 km and 3.8 km and between 5.3 km and 7.1 km, respectively. Based on previous observations and mixed-layer similarity theory, we estimated MABL's depths that vary from 0.95 km to 1.2 km over the rolls and from 3.0 km to 3.8 km over the cells. The AGW has maximum spectrum at 14.3 km wavelength. The method developed in this work can be used to decompose other satellite imageries into individual features through characteristic spatial scales.

• Ocean Systems Engineering
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• v.8 no.1
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• pp.21-32
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• 2018

Due to the escalation in hydrocarbon consumption, the offshore industry is now looking for advanced technology to be employed for deep sea exploration. Riser system is an integral part of floating structure used for such oil and gas extraction from deep water offering a system of drill twines and production tubing to spread the exploration well towards the ocean bed. Thus, the marine risers need to be precisely employed. The incorporation of the strengthening material, fiber reinforced polymer (FRP) for deep and ultra-deep water riser has drawn extensive curiosity in offshore engineering as it might offer potential weight savings and improved durability. The design for FRP strengthening involves the local design for critical loads along with the global analysis under all possible nonlinearities and imposed loadings such as platform motion, gravity, buoyancy, wave force, hydrostatic pressure, current etc. for computing and evaluating critical situations. Finite element package, ABAQUS/AQUA is the competent tool to analyze the static and dynamic responses under the offshore hydrodynamic loads. The necessities in design and operating conditions are studied. The study includes describing the methodology, procedure of analysis and the local design of composite riser. The responses and fatigue damage characteristics of the risers are explored for the effects of FRP strengthening. A detail assessment on the technical expansion of strengthening riser has been outlined comprising the inquiry on its behavior. The enquiry exemplifies the strengthening of riser as very potential idea and suitable in marine structures to explore oil and gas in deep sea.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.1
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• pp.25-31
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• 2017

Generally, underwater gliders do not have separate propellers for their forward movement. They derive a propulsive force due to the difference between their buoyancy and gravity. The attitude of an underwater glider is controlled by changing the relative position of the buoyancy center and mass center. In this study, we derived nonlinear 6-DOF dynamic and mathematical models for the motion controller and buoyancy controller. Using these equations, we performed dynamic underwater glider simulations and verified the suitability of the design and dynamic performance of the proposed underwater glider.