• Journal of Korean Port Research
• /
• v.12 no.1
• /
• pp.145-154
• /
• 1998

Protection characteristics of the corroded steel pile which was served as a pier structure over 8 years in seawater have been examined in terms of corrosion potential, electrochemical impedance spectroscopy(EIS) and anodic/cathodic polarization curves. The steel structure was sectioned into two parts, waterline(splash zone, just above the seawater surface) and in-water(underwater), and protection characteristics for the two parts were investigated with the application of cathodic protection(CP) by sacrificial anodes using Zn and Al alloys. The main results obtained were as follows; (1) The corrosion potential of waterline zone was higher than that of in-water, which implied that the corrosion of waterline was more severe than that of in-water, (2) As a result of EIS examination, the transition period from the apparent CP to the substantial CP took about twenty to thirty days according to the corrosion condition.

• Ocean Systems Engineering
• /
• v.8 no.4
• /
• pp.381-407
• /
• 2018

This paper presents a hybrid numerical approach, which combines a two-phase Navier-Stokes model (NS) and the fully nonlinear potential theory (FNPT), for modelling wave-structure interaction. The former governs the computational domain near the structure, where the viscous and turbulent effects are significant, and is solved by OpenFOAM/InterDyMFoam which utilising the finite volume method (FVM) with a Volume of Fluid (VOF) for the phase identification. The latter covers the rest of the domain, where the fluid may be considered as incompressible, inviscid and irrotational, and solved by using the Quasi Arbitrary Lagrangian-Eulerian finite element method (QALE-FEM). These two models are weakly coupled using a zonal (spatially hierarchical) approach. Considering the inconsistence of the solutions at the boundaries between two different sub-domains governed by two fundamentally different models, a relaxation (transitional) zone is introduced, where the velocity, pressure and surface elevations are taken as the weighted summation of the solutions by two models. In order to tackle the challenges associated and maximise the computational efficiency, further developments of the QALE-FEM have been made. These include the derivation of an arbitrary Lagrangian-Eulerian FNPT and application of a robust gradient calculation scheme for estimating the velocity. The present hybrid model is applied to the numerical simulation of a fixed horizontal cylinder subjected to a unidirectional wave with or without following current. The convergence property, the optimisation of the relaxation zone, the accuracy and the computational efficiency are discussed. Although the idea of the weakly coupling using the zonal approach is not new, the present hybrid model is the first one to couple the QALE-FEM with OpenFOAM solver and/or to be applied to numerical simulate the wave-structure interaction with presence of current.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.1
• /
• pp.99-114
• /
• 2000

In the secure DNS the amount of information that should be managed greatly increased and the interdependency in the information became very complex. Therefore, it became necessary to develop a mechanism which can manage zone information efficiently. Moreover, a consistent interface became also necessary so that a secure DNS may be efficiently interconnected with other Internet application services. In this paper we explain the design and implementation of a secure DNS extended with two functions : (1) a dynamic update function which enables to add and remove zone information dynamically and (2) a zone transfer function that efficiently transfers update zone information among DNS servers. We developed a method which integrates two zone transfer mechanisms, full zone transfer and incremental zone transfer, and also proposed a method to compress data in the zone transfer message. We also introduced a data structure called a delta file to integrate the zone transfer function and the dynamic update function.

• Journal of the Korean Society of Safety
• /
• v.31 no.2
• /
• pp.76-82
• /
• 2016

A 2-D hydrodynamic model for predicting the movement of debris flow was developed. The developed model was validated against a dam break flow problem conducted in EU CADAM project, and the performance of the model was shown to be satisfactory. In order to suggest structural alternative for hazardous zone vulnerable to debris flow disaster, two types of initial mass distribution and two shapes of defensive structure were considered. It was found that 1) the collapse of debris mass initiated with square pyramid shape induced more damage compared with that of cubic shape; and 2) a defensive structure with semi-circular shape was vulnerable to debris flow disaster in terms of debris control or primary defense compared with that of rectangular-shaped structure.

• Journal of Korean Society of Rural Planning
• /
• v.17 no.4
• /
• pp.61-74
• /
• 2011

Based on the critical review of previous new village planning proposals in Saemangeum Farming Zone, this study tried to derive rational and realistic planning/design criteria for new villages firstly through home-and-abroad case studies analysis, interview works on farmers in two villages located in the existing reclaimed farming areas and influential zone analysis from neighborhood villages in old land. By applying these criteria(population structure, farming size, maximum distance between farmland and home, village site size, number of new villages planned) on Saemangeum Farming Zone, basic new village planning framework was proposed finally.

• Journal of Welding and Joining
• /
• v.33 no.1
• /
• pp.41-48
• /
• 2015

In this study, the effect of heat input on weld metal microstructure and the effects of dissimilar weld heat affected zone in quenched and tempered ASTM A517 on the stainless steel AISI 316L is investigated through the optimization of welding parameters. For this purpose, two welding techniques are used, tungsten-conventional gas and pulsed gas with weld wire ER 309MoL with Diameter 2.4 mm. Research showed that the grain size of the heat affected zone in pulsed welding is less compared with conventional welding; weld metal structure is fully austenitic, it has a finer structure in the pulsed method. Additionally, the growth of weld metal adjacent steel A517 is different from steel 316L. Further, investigation showed that the rate of dilution is less in the pulsed method and the impact energy is increased in each three regions of the weld metal and heat affected zones in the pulsed method; the fracture in the weld metal and heat affected zone of steel 316L is quite soft and it is semi-crispy in the heat affected zone of steel A517.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.715-716
• /
• 2008

A dead zone prediction system for vehicles are implemented in this paper. To improve performance reliability and stability, we import two method to get a information between car and car, and car and road. One is traffic lane detection method, another is vecle recognition. In this paper, we explain the methods and whole structure about this system except for details.

• Journal of Ecology and Environment
• /
• v.43 no.2
• /
• pp.271-281
• /
• 2019

Background: The plant communities within reservoir drawdown zones are ecologically important as they provide a range of ecosystem services such as stabilizing the shoreline, improving water quality, enhancing biodiversity, and mitigating climate change. The aim of the study was therefore to identify the major environmental factors affecting these plant communities within the drawdown zone of the Soyangho Reservoir in South Korea, which experiences a monsoonal climate, and thereafter to (1) elucidate the plant species responses and (2) compare the soil seedbank composition along main environmental gradients. Results: Two main environmental gradients affecting the plant community structure were identified within the drawdown zone; these were a vertical and longitudinal gradient. On the vertical dimension, a hydrological gradient of flood/exposure, the annual-dominated plant community near the water edge changed to a perennial-dominated community at the highest elevation. On the longitudinal dimension from the dam to the upstream, plant species composition changed from an upland forest-edge community to a lowland riverine community, and this was correlated with slope degree, soil particle size, and soil moisture content. Simultaneously, the composition of the soil seedbank was separated along the vertical gradient of the drawdown zone, with mainly annuals near the water edge and some perennials at higher elevations. The species composition similarity between the seedbank and extant vegetation was greater in the annual communities at low elevation than in the perennial communities at higher elevation. Conclusions: The structures of plant community and soil seedbank in the drawdown zone of a monsoonal riverine reservoir were changed first along the vertical and secondly along the longitudinal gradients. The soil seedbank could play an important role on the vegetation regeneration after the disturbances of flood/exposure in the drawdown zone. These results indicate that it is important to understand the vertical and longitudinal environmental gradients affecting shoreline plant community structure and the role of soil seedbanks on the rapid vegetation regeneration for conserving and restoring the drawdown zone of a monsoonal reservoir.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.7
• /
• pp.1097-1105
• /
• 1997

Because of the existence of stress interaction field made by other defects and propagating cracks, the structure may be weakened. Therefore in this study, the crack behavior in the interaction field made by two different cracks is studied experimentally. In the experiment, vertical distance between two cracks and applied stress are varied to make different stress interacted field. In addition, the effect of plastic zone is used to examine crack propagation path and rate. Three types of crack propagation in the interacted field were found, and crack propagating path and rate of two cracks were significantly changed according to different applied stress as each crack propagates. And the results are attributed to the effect of the size and shape of the plastic zone.

• 한국연소학회:학술대회논문집
• /
• 2014.11a
• /
• pp.135-137
• /
• 2014

Excess enthalpy flame propagating an porous inert medium, which recirculate exhaust heat to the upstream cold mixture, is theoretically analyzed. Using the activation-energy asymptotics, the flame structure is divided into the thin reaction and the gas-phase preheat zone, as is traditionally done. Ahead and behind of the two, there exist an outer preheat zone, where heat is convectively transferred from solid to gas, and a downstream re-equilibrium zone, where thermal equilibrium between phases is established. Asymptotic solutions of species and energy equations in each zone are obtained and then matched to each other, and finally the mass burning rate is obtained as a function of the flame propagation velocity with respect to the solid phase and physical properties of gas and solid.