• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.480-490
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• 2016

As wind turbines become larger and lighter, they are likely to respond sensitively by dynamic loads applied on them. Since the responses at resonances are particularly interested, it is required to be able to predict natural frequencies of wind turbines reliably at early design stage. To achieve this, the foundation-soil analysis is needed to be carried out and a finite element approach is adopted in general. However, the finite element approach would not be appropriate in early design stage because it demands heavy efforts in pile-soil modelling and computing facilities. On the contrary, theoretical approaches adopting linear approximations for soils are relatively simple and easy to handle. Therefore, they would be a useful tool in predicting a pile-soil interaction, particularly in early design stage. In this study an analysis for a pile inserted in soil is performed. The pile and soil are modelled as a beam and continuum medium, respectively, within an elastic range. In this analysis, influence factors at the pile head for lateral loads are predicted by means of this continuum approach for various length-diameter ratios of the pile. The influence factors predicted are validated with those reported in literature, proposed from a finite element analysis.

• Atmosphere
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• v.31 no.1
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• pp.29-43
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• 2021

In this study, two-step statistical approach including Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) was employed, and main meteorological factors explaining the high-PM2.5 episodes were identified in two regions: Seoul and Busan. We first performed PCA to isolate the Principal Component (PC) that is linear combination of the meteorological variables observed at two levels: surface and 850 hPa level. The employed variables at surface are: temperature (T2m), wind speed, sea level pressure, south-north and west-east wind component and those at 850 hPa upper level variables are: south-north (v850) and west-east (u850) wind component and vertical stability. Secondly we carried out MLR analysis and verified the relationships between PM2.5 daily mean concentration and meteorological PCs. Our two-step statistical approach revealed that in Seoul, dominant factors for influencing the high PM2.5 days are mainly composed of upper wind characteristics in winter including positive u850 and negative v850, indicating that continental (or Siberian) anticyclone had a strong influence. In Busan, however, the dominant factors in explanaining in high PM2.5 concentrations were associated with high T2m and negative u850 in summer. This is suggesting that marine anticyclone had a considerable effect on Busan's high PM2.5 with high temperature which is relevant to the vigorous photochemical secondary generation. Our results of both differences and similarities between two regions derived from only statistical approaches imply the high-PM2.5 episodes in Korea show their own unique characteristics and seasonality which are mostly explainable by two layer (surface and upper) mesoscale meteorological variables.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2C
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• pp.61-68
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• 2012

In general, verticality error necessarily occurs in marine pile foundation due to construction error or marine environmental effects. In marine structure, design by vertical load rather than horizontal load is dominant, but in the offshore wind turbine foundation, horizontal load is dominant. As the structure type that has dynamic movement by blade rotation, verticality error may have structurally significant effects. In this study, structural response feature of foundation and ground were analyzed according to verticality error of monopile foundation of 5MW offshore wind turbine. Marine environmental load was calculated per ISO standard and the margin of verticality error was calculated to be $L/{\infty}$(=0), L/300, L/200 and L/100. As a result of analysis, it was found that the maximum value of member force of the foundation with L/100 error increased about 7.2% compared to the monopile without verticality error.

• Atmosphere
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• v.21 no.1
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• pp.45-55
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• 2011

A definition on the tropical cyclone (TC) that influenced the Korean Peninsula (KP), the KP-influence TC, is widely used in the TC communities, but its criterion is not clear mainly due to the ambiguity and subjectiveness of the term such as 'influence', which led to the inconsistent TC statistical analysis. This study suggests a definition and criterion on the TC approaching to the KP (KP-approach TC) additionally, which is more obvious and objective than the KP-influence TC. In this study, the criterion on the KP-approach TC is determined when the TC's center from the RSMC best track data encounters the box areas of $28^{\circ}N{\sim}40^{\circ}N$ and $120^{\circ}E{\sim}138^{\circ}E$. The range is chosen by finding a minimum area that includes all official KP-influence TCs except three TCs that affected the KP as a tropical depression (TD). Statistical analysis reveals that, among total 1,537 TCs that occur in the western North Pacific during 1951-2008, the KP-approach TC was 472, the KP-influence TC was 187, and the KP-landfall TC was 87. August was the month that the largest TCs approach and influence to the KP. Finally, this paper suggests to determine the KP-influence TC by the strong wind and heavy rain advisories in the KP based on the observation after the storm's passage.

• Journal of Ship and Ocean Technology
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• v.7 no.3
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• pp.1-12
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• 2003

The influence of nonlinear phenomena on the behavior of stationary forced flexural-gravity waves on the surface of deep water is investigated, when the perturbation of external pressure moves with near-resonant velocity. It is shown that there are three branches of bounded stationary solutions turning into asymptotic solutions of the linear problem with zero initial conditions. For the first time ice sheet destruction by turbulent fluctuations of atmosphere pressure in ice adjacent layer in wind conditions is studied.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.571-576
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• 2000

This paper summarized deformation properties of hydroelectric power concrete dam through the comparison between measured and analysed data. This is a part of the process to evaluate concrete dam safety, which has become a critical concern in the country. We analysed strain and angle deformation data by considering only the effect of atmosphere temperature to evaluate deformation properties of Gaisan hydroelectric power concrete dam. Analysis results are almost identical with measured data, and behavior of Gusian dam can be cleared up more reliably in case of acting the external loads (seismic, wind water pressure, etc.) except the influence of temperature.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.20-25
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• 1993

In coastal waters, more often than not, waves propagate on currents driven by tidal forces, earth’s gravity, or wind. There have been a number of studies for dealing with the change of wave spectrum due to tile presence of current. Based on the conservation of wave action, Hedges et al. (1985) have proposed an equation which describes the influence of current on the change of wave spectrum in water of finite depth. (omitted)

• Journal of Environmental Impact Assessment
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• v.14 no.3
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• pp.135-145
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• 2005

This study was conducted to investigate the characteristics of meteorological environment variation before and after construction of Nak-dong river estuary barrage. We used meteorological data(air temperature, precipitation, relative humidity, visibility, wind) at Gimhae airport meteorological station. The construction of river estuary barrage can change climate at the neighboring districts and influence human's health and vegetable. The construction of Nakdong river estuary barrage brought rise of temperature, decrease of relative humidity and increase of poor visibility frequency.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.05a
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• pp.185-190
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• 2003

산업체 등에서 사용되고 있는 가스들중에서 일반적인 가스들과는 달리 위험한 가스(heavy gas)들은 누출사고시에 이들 고유한 확산과 계층화(stratification)방식에 의해 높은 위험성을 유발시키고 있다. 이러한 가스의 누출확산사고들과 일반적인 가스누출사고들의 비교는 그 사실들을 증명해주고 있다. 이런 사실에 의해 위험한 가스확산에 대한 실험과 고유특성을 고려한 확산모델의 개발이 여러 관점에서 진행되고 있으며, 이들의 중요성은 이미 세계적으로 의미를 부여하고 있다.(중략)

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.156-161
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• 2002

21세기 해양시대를 앞두고 있는 시점에서 해양자원의 탐사 및 개발과 해양환경 보존 및 해 ㆍ기 상예측에 대한 기술의 확보는 매우 중요한 사항으로 대두되고 있다. 이를 위해서는 해양자원 및 환경 에 관련된 정보를 상시 관측할 수 있는 시설이 확보되어야만 한다. 이러한 관점에서 볼 때 이어도 해양과학기지가 가지는 위상은 매우 중요하다. (중략)