• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.185-193
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• 2010

In the present study, wave deformation and wave-induced current were calculated under the regular wave conditions using the Boussinesq model. The model results of the wave deformation showed good agreements with the preceeding laboratory experiments of others. The wave-induced current of the fully developed sea state was calculated. For field application of model, the preceeding field data by others in the real scale of the water area were compared, the numerical result of wave deformation showed a relatively good agreement with the field data. Although the numerical result of wave-induced current was underestimated over the longshore bar developed area, the Boussinesq model is generally suitable to predict the wave-induced current.

• Atmosphere
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• v.29 no.2
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• pp.131-147
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• 2019

On the urban scale, Micro-climate analysis models for urban scale have been developed to investigate the atmospheric characteristics in urban surface in detail and to predict the micro-climate change due to the changes in urban structure. BioCAS (Biometeorological Climate Impact Assessment System) is a system that combines such analysis models and has been implemented internally in the Korea Meteorological Administration. One of role in this system is the analysis of the health impact by heat waves in urban area. In this study, the vegetation cooling models A and B were developed and linked with BioCAS and evaluated by the temperature drop at the vegetation areas during ten selected heat-wave days. Smaller prediction errors were found as a result of applying the vegetation cooling models to the heat-wave days. In addition, it was found that the effects of the vegetation cooling models produced different results according to the distribution of vegetation area in land cover near each observation site - the improvement of the model performance on temperature analysis was different according to land use at each location. The model A was better fitted where the surrounding vegetation ratio was 50% or more, whereas the model B was better where the vegetation ratio was less than 50% (higher building and impervious areas). Through this study, it should be possible to select an appropriate vegetation cooling model according to its fraction coverage so that the temperature analysis around built-up areas would be improved.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.1
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• pp.37-49
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• 2004

Four different data reduction methods for the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two heat and mass transfer models and two fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the reduced heat transfer coefficients revealed that the single potential heat and mass transfer model yielded the humidity-independent heat transfer coefficients. Two fin efficiency models-enthalpy model and humidity model-yielded approximately the same fin efficiencies, and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.355-358
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• 2008

This study deals with a substantial problems with SEA modeling methods in shipboard noise predictions. As a first problems with respect to modeling, fineness of model that represents a real structure is numerically investigated by comparison among 3 models, Fine, Coarse and Simplified models. Comparison reveals that Fine model shows the lowest noise level among them since this model involve more energy transfer paths than the other models. Influence of in-plane wave is also examined by numerical comparison. It is clear that inclusion of in-plane wave affects the high frequency and the cabin far from a source.

• Journal of the Korean Institute of Navigation
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• v.13 no.1
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• pp.77-106
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• 1989

Two numerical models of the shoreline change and sediment transport rates, explicit and implicit, are simulated with shore structures such as breakwaters, a jetty, groins and a seawall. The applied study area is songdo Beach, Youngil bay, Korea since it has all the shore structures mentinoed above. The two models investigate the beach line changes and sedimen transport rates for the beach before design of three groins with and without an offshore breakwater. In order to estimate the shoreline changes after three groins were built, the beach response inside the three groin compartiments and the offshore barrier are also investigated. The simulation based on the initial shoreline conditions surveyed by the Hydrographic office, Koreai 1979 and 1984. The breaking wave characteristics are introduced into the models by calculation from the empirical equations and modification from the numerical and hydraulic model test results developed for waves behind an offshore breakwater. The numerical simulation describes well the tendencies of the sand transport and shoreline changes affected by wave diffraction behind a detached breakwater and by interruption of sand transport at three groins.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.4
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• pp.353-363
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• 1994

In order to give a useful guide for engineering applications on numerical models based on nonlinear stream function wave theory. collocation method and least squares method are directly compared input parameters of the revised Dean's Table (Chaplin, 1980). Two models ive both accurate and almost same results for all the cases except very long or nearly breaking waves. Overall comparison seems to favor the least squares method for general use.

• Journal of Navigation and Port Research
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• v.29 no.4
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• pp.299-304
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• 2005

A simulation system is needed to train students and mariners in order that they can take suitable actions to evade typhoon's strike promptly and sufficiently. In order to make such kind of system, three kinds of models about the typhoon are necessary, typhoon prediction model to generate typhoon's track, wind & wave-field model to make sea conditions around the typhoon and evaluation model of trainee's action whether their actions were suitable or not during simulation. We have developed the prediction and wind & wave-field models of typhoon, but the evaluation model has not been developed yet. In this paper, after making a method for evaluating trainee's actions by seakeeping performance, we propose an typhoon avoidance simulation system for training mariners so that they can promote their abilities to evade the typhoons at sea.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2006.09a
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• pp.61-64
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• 2006

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.2
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• pp.37-49
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• 2024

To date, numerous empirical formulas have been proposed through hydraulic model experiments to predict the wave breaker index, including wave height and depth of wave breaking, due to the inherent complexity of generation mechanisms. Unfortunately, research on the characteristics of wave breaking and the prediction of the wave breaker index for gravel beaches has been limited. This study aims to forecast the wave breaker index for gravel beaches using representative linear-based machine learning techniques known for their high predictive performance in regression or classification problems across various research fields. Initially, the applicability of existing empirical formulas for wave breaker indices to gravel seabeds was assessed. Various linear-based machine learning algorithms were then employed to build prediction models, aiming to overcome the limitations of existing empirical formulas in predicting wave breaker indices for gravel seabeds. Among the developed machine learning models, a new calculation formula for easily computable wave breaker indices based on the model was proposed, demonstrating high predictive performance for wave height and depth of wave breaking on gravel beaches. The study validated the predictive capabilities of the proposed wave breaker indices through hydraulic model experiments and compared them with existing empirical formulas. Despite its simplicity as a polynomial, the newly proposed empirical formula for wave breaking indices in this study exhibited exceptional predictive performance for gravel beaches.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.53.2-53.2
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• 2017

Stochasitc gravitational wave background (SGWB) is expected to be contributed by primordial sources (e.g. inflation signature) and astrophysical sources (e.g., incoherent superposition of a large numbers of compact binary inspirals throughout in the Universe). Theoretically, SGWB is predicted to span in a broad frequency range between less than nHz up to kHz. Many gravitational-wave (GW) detectors such as LIGO or LISA aim to detect or constrain SGWB in different frequency band that is most sensitive for each detector. In this talk, we focus on the prospectives of constraining the energy density of SGWB between 0.1-10 Hz. We introduce the characteristics of SGWB and representative models for primordial and astrophysical sources. Then, we propose a signal extraction scheme to detect SGWB using one or several omni-directional GW detectors such as SLGT(Superconducting Low-frequency Gravitational-wave Telescope). Considering SLGT sensitivity, we discuss how to observe SGWB in 0.1-10 Hz if we have SLGT network. Finally, we highlight interesting SGWB models that can be constrained in 0.1-10 Hz with SLGT.