• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.569-579
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• 2013

A steel-type breakwater that uses a submerged dual horizontal porous plate was originally proposed by Kweon et al. (2005), and its hydrodynamic characteristics and design methodology were investigated in a series of subsequent researches. In particular, Kweon et al. (2011) proposed a method of estimating the vertical uplift force that acts on the horizontal plate, applicable to the design of the pile uplift drag force. However, the difference between the method proposed by Kweon et al. (2011), and the wave force measured at a different time without a phase difference, have not yet been clearly analyzed. In this study, such difference according to the method of estimating the wave force was analyzed, by measuring the wave pressure acting on a breakwater model. The hydraulic model test was conducted in a two-dimensional wave flume of 60.0 m length, 1.5 m height and 1.0 m width. The steepness range of the selected waves is 0.01~0.03, with regular and random signals. 20 pressure gauges were used for the measurement. The analysis results showed that the wave force estimate in the method of Kweon et al. (2011) was smaller than the wave force calculated from the maximum pressure at individual points, under a random wave action. Meanwhile, the method of Goda (1974) that was applied to the horizontal plate produced a smaller wave force, than the method of Kweon et al. (2011). The method of Kweon (2011) was already verified in the real sea test of Kweon et al. (2012), where the safety factor of the pile uplift force was found to be greater than 2.0. Based on these results, it was concluded that the method of estimating the wave force by Kweon et al. (2011) can be satisfactorily used for estimating the uplift force of a pile.

• Fashion & Textile Research Journal
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• v.19 no.1
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• pp.40-48
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• 2017

In this study, the impact of the fashion design education on the brain wave and the psychological change of the senior females and its change was intended to analyze. 16 senior females were selected as a subject and the brain wave and the psychology were analyzed before and after the educational program of 4 hours a day for total 3 weeks. Out of the brain wave, the increase of alpha wave represents the mental stability and the comfortable state and its decrease represents the tension and stress. On the contrary, the increase of beta wave represents the tension and the excitation. In the brain wave analysis results, the alpha wave was increased and the beta wave was decreased after the design education program, through which it is deemed that the design education would help to increase the psychological stability and to decrease the tension and the stress in the senior females. In the results of analyzing the psychological test, while the test results for 4 senior females were shown as anxious out of 16 senior females, the BAI score was decreased to 'minor anxiety' after the education and the BAI score was decreased except 2 subjects, through it is deemed that the fashion design education would help to reduce the anxiety in the senior females and it seems that it is coincided with the beta wave analysis results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.700-711
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• 2022

In this study, deepwater design waves were estimated for 16 wave directions and various return periods based on statistical analysis of extreme waves observed for more than 20 years at three stations (Chilbal-do, Geomun-do, Donghae). These values were compared with design waves estimated based on the omni-directional wave data. The Weibull distribution was used as the probability distribution function whose parameters were determined by the least square method. The Kolmogorov-Smirnov test was applied for the goodness of fit test. Notably, the directional design waves were smaller than the omni-directional design wave for every wave direction. The maximum 50-year wave heights for directional sectors were 7.46 m (NNE), 12.05 m (S), and 9,59 m (SSW) at Chilbal-do, Geomun-do and Donghae whereas those for uni-directional wave data were 7.91 m, 13.82 m and 10.38 m, respectively. This implied possible under-estimation of the deepwater design waves for 16 wave directions being currently used in the design of offshore and coastal structures.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.212-217
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• 2020

Recently, with the interest in the 4th industrial revolution, the demand for autonomous driving technology is increasing. V2X communication technology is a core technology for autonomous vehicles that exchanges information with objects such as vehicles, infrastructure, networks, and pedestrians through wired and wireless networks. In this paper, we present the results of the hybrid V2X communication system, which is a hybrid design of WAVE and LTE, and the coverage test to confirm the performance of the system. Through coverage measurement, we show that the hybrid V2X communication performance is superior to the existing LTE or WAVE single communication system in communication coverage, so it can be effectively applied to autonomous driving services.

• Land and Housing Review
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• v.2 no.4
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• pp.387-395
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• 2011

According to the seismic design criteria for structural buildings in Korea, the ground is classified into 5 types based on the average shear wave velocity measured from elastic wave tests on site and seismic load applied to the structure is estimated. However, elastic wave tests in site, however, on the engineering fill, cannot be performed during the construction period. Therefore, to evaluate shear wave velocity considering field conditions, resonant column (RC) and torsional shear (TS) tests are performed and compared with various elastic wave test results. As a result, if confining pressure for the tests using engineering fill are considered properly, we can obtain similar results comparing with those of elastic wave tests. In addition, by considering the effect of maximum shear modulus and confining pressure by RC/TS tests, n values shows typical values ranging from 0.434 to 0.561 so that utilization of RC/TS tests can be useful to infer shear modulus in field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5D
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• pp.483-492
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• 2012

The early setting time of concrete is an important factor determining the slip up velocity of the slip-form system. Accordingly, need is for a technique evaluating the early setting time in order to secure the safety of the slip-form system and the construction quality of concrete. This paper intends to estimate the early setting time by evaluating the setting degree of concrete using surface wave velocity so as to determine the slip up time of the slip-form system. Penetration resistance test and compressive strength test are performed first to clarify the relationship between the early setting time of concrete and the compressive strength. Then, compressive strength test and ultrasonic wave test are conducted to examine the relation between the compressive strength and the surface wave velocity. Continuous wavelet transform is adopted to measure the surface wave velocity. Numerical analysis is carried out to demonstrate the appropriateness of the application of continuous wavelet transform. Based on these results, the propagation velocity of the surface wave required for the slip up of slip-form system is suggested. Finally, a reduced model test of the slip-form system is conducted to verify the feasibility of the proposed surface wave velocity for the determination of th slip up velocity.

• Ocean Systems Engineering
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• v.13 no.1
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• pp.1-20
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• 2023

An iterative focused wave generation method is developed and implemented in a local analytic based Navier-Stokes solver. This wave generation method is designed to reproduce the target focused wave by matching the target amplitude spectrum and phase angle. A 4-waves decomposition scheme is utilized to obtain the linearised component of the output wave. A model test studying the interaction between different focused waves and a fixed cylinder is selected as the target for the wave generation approach. The numerical wave elevations and dynamic pressure on the cylinder are compared with the experimental measurement and other state-of-the-art numerical methods' results. The overall results prove that the iterative adjustment method is able to optimize the focused wave generated by a CFD approach.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.38-49
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• 2015

Past study of tsunami heavily relied on the numerical modelling using 2D Boussinesq Eq. and Solitary wave. Lately, based on the fact that numerically simulated run up heights based on solitary wave are somewhat smaller than the measured one, Leading Depression N (LDN) Wave has been elaborated, which can account the advancement of a shore line before tsunami strikes a shore. Thereafter it is reported that more accurate simulation can be possible once LDN is deployed. On the other hand, there were numerous reports indicating that stable LDN wave can't be sustained in the hydraulic model test. These conflicts between the hydraulic model tests and numerical results have their roots on the assumption made in the derivation of Boussinesq type wave model such as that wave nonlinearity is equally balanced with wave dispersiveness. Hence, in the numerical simulation based on the Boussinesq type wave model, wave dispersiveness is inevitably underestimated, especially in deep water. Based on this rationale, we developed the modified methodology for the generation of stable LDN wave in the 3D numerical wave flume, and proceeded to numerically analyze the depression effect of Hybrid Breaker on the run up height due to tsunami using the Navier Stoke Equation. The verification of newly proposed wave model in this study was carried out using the run up height from the hydraulic model test. It was shown that Hybrid Breaker consisting of three water chamber and slope at its front can reduce 13% of run up height for H = 5m, and 10% of run up height for H = 6m.

• 보존과학연구
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• s.31
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• pp.31-42
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• 2010

This study were performed thermal shock test for four kind of different rocks (Iksan granite, Namsan granite, Jeongseon marble, Yeongyang sandstone), and according to heating temperature($400^{\circ}C$, $600^{\circ}C$) on samples were investigated physical properties such as specify gravity, porosity, p-wave velocity. As a result, the tendency was appeared that porosity increased, and specific gravity and p-wave velocity decreased at a more higher temperature. But, the situation of change appeared characteristic according to temperature and rock types. In the case of Yeongyang sandstone, it appeared in especially porosity increasing at $400^{\circ}C$. The specific gravity was little change in the all the rock at $400^{\circ}C$ but the decreased at $600^{\circ}C$. Therefore the specific gravity in the temperature range is due to the relatively small impact on the change is expected. Porosity of the granite at $400^{\circ}C$ changes little. but marble in the rate of change is large. Conversely, the sandstone porosity decreased. At $600^{\circ}C$ increased porosity in all of rocks. particularly sandstone the smallest increase in porosity. Experiments showed that p-wave velocity measured through dry rocks was sensitive to quantify the thermal damage. The p-wave velocity of all rocks decreased with increasing temperature. In the relation between porosity and p-wave velocity, p-wave velocity decreased with increasing porosity. On the other hand, in case of Yeongyang sandstone p-wave velocity decreased with decreasing porosity. thus, development of microcracks more affects p-wave velocity than porosity. In this study, damage intensity was well explained with porosity and p-wave velocity values depending on temperature increase.

• Journal of Wetlands Research
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• v.18 no.1
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• pp.84-93
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• 2016

As a transition region between ocean and land, coastal wetlands are significant ecosystems that maintain water quality, provide natural habitat for a variety of species, and slow down erosion. The energy of coastal waves and storm surges are reduced by vegetation cover, which also helps to maintain wetlands through increased sediment deposition. Wave attenuation by vegetation is a highly dynamic process and its quantification is important for understanding shore protection and modeling coastal hydrodynamics. In this study, laboratory experiments were used to quantify wave attenuation as a function of vegetation type as well as wave conditions. Wave attenuation characteristics were investigated under regular waves for rigid model vegetation. Laboratory hydraulic test and numerical analysis were conducted to investigate regular wave attenuation through emergent vegetation with wave steepness ak and relative water depth kh. The normalized wave attenuation was analyzed to the decay equation of Dalrymple et al.(1984) to determine the vegetation transmission coefficients, damping factor and drag coefficients. It was found that drag coefficient was better correlated to Keulegan-Carpenter number than Reynolds number and that the damping increased as wave steepness increased.