• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.615-624
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• 2014

It has been well known the sloshing pressure has complex shape and various patterns. The pattern of sloshing pressure is variously characterized by the pressure amplitude, duration time and skewness. The structural response induced by the sloshing pressure is also affected by the pattern of sloshing pressure and the type of structural members. In order to understand the structural response by the perspective view of categorized pattern, it is more efficient to make simple sloshing pressure pattern than to reflect the complex pressure history. In this study, the sloshing pressures obtained by the small scale model test are simplified with respect to their duration and skewness. Dynamic analyses of Mark-III LNG CCS are then parametrically performed with the consideration of various types of sloshing impact. Meanwhile, the failure pressures given the duration and skewness are investigated after parametric calculations are conducted to investigate the effect of pressure parameters on the structural response.

• Wind and Structures
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• v.30 no.4
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• pp.433-450
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• 2020

The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon "Megi". Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.373-379
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• 2006

We investigated the relationship of the organic pollutant index in wastewater where the high percentages of an organic load to a water body was found. Measuring of TOC was to identify the relationship with COD and BOD which were used already. The correlation coefficient (r) of TOC/COD, BOD/COD and TOC/BOD were effected by the types of industry such as paper, textile, chemical, food and metal industries. In food industry it was found that the highest correlation coefficient (r) of TOC/COD, BOD/COD and TOC/BOD as 0.967, 0.969 and 0.990, respectively. There is low correlation coefficient in many cases. Hence it was impossible that the use of TOC for the water standard or monitoring instead of COD and BOD directly. However it can be used as alternative index to management a water process in the case of waste water where there was found high correlation coefficient of TOC/ COD, BOD/COD and TOC/BOD. It was sure that the water quality of river body can be protected if we use these the relationship among organic index.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.128-135
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• 2021

Thin-walled tubes have been widely used as energy absorbing devices because they are light and have high energy-absorption efficiency. However, the downside is that conventional thin-walled tubes usually exhibit an excessive initial peak crushing force (IPCF) and a large fluctuation in the load-displacement curve, and thus lack stability as energy absorbing devices. Corrugated tubes were introduced to reduce IPCF and to increase the stability of collision energy-absorbing devices. Since the performance of corrugated tubes is highly influence by geometry, design optimization methods can be utilized to optimize the performance of corrugated tubes. In this paper, we utilize shape design optimization based on an adaptive surrogate model for crashworthiness analysis. The amplitude and wavelength of the corrugation, as well as curvature changes in the features, are the design variables. A morphing methodology is adopted to perform shape design parameterization. Through numerical examples, we compare optimal design results based on the adaptive surrogate model, with optimal results based on conventional surrogate models, and we show that direct optimal design methods produce more efficient results.

• Composites Research
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• v.32 no.2
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• pp.90-95
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• 2019

Sloshing impact loads on liquefied natural gas (LNG) carr iers are the main issue of damage to the insulation system in LNG cargo containment system (LNG CCS). The damage to the insulation system would be fatal in maintaining a temperature-savings environment in LNG CCS. The typical method is to enhance the insulation materials that can maintain a constant cryogenic temperature. Insulation materials consist of polyurethane foam and plywood, an adhesive for bonding these two materials. This study intends to improve the absorption energy of the material when the impact load is applied by creating a glass bubble/epoxy composite resin as part of the insulation. The experimental scenarios consider the effect of temperature ($20^{\circ}C$, $-163^{\circ}C$), glass bubble weight fraction in epoxy resin through free fall experiments. Experiments have shown that if the glass bubble additive reaches 20 wt.%, the cryogenic absorption energy is a maximum performance and that 0 wt.% has a maximum ambient absorption energy. However, the agglomeration has been occurred due to deterioration of the stirring performance if weight fraction was 20 wt.% and the result of 0 wt.% have been revealed that ambient absorption energy is significantly lower.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.78-86
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• 2019

This paper describes the stiffness optimization of the torsion spring hinge of the large SAR antenna considering the deployment performance. A large SAR antenna is folded in a launch environment and then unfolded when performing a mission in orbit. Under these conditions, it is very important to find the proper stiffness of the torsion spring hinge so that the antenna panels can be deployed with minimal impact in a given time. If the torsion spring stiffness is high, a large impact load at the time of full deployment damages the structure. If it is weak, it cannot guarantee full deployment due to the deployment resistance. A multi-body dynamics analysis model was developed to solve this problem using RecurDyn and the development performance were predicted in terms of: development time, latching force, and torque margin through deployment analysis. In order to find the optimum torsion spring stiffness, the deployment performance was approximated by the response surface method (RSM) and the optimal design was performed to derive the appropriate stiffness value of the rotating springs.

• Journal of Environmental Impact Assessment
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• v.32 no.2
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• pp.72-82
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• 2023

The purpose of this study is to estimate the trend of ecosystem water quality regulating services in Odaesan National park of the last five years and the corresponding economic values. Recently the climate change makes increased the value of the water, it is more important to protect the source of the riverthan to purify the contaminated water. To evaluate the water quality regulating services, we calculated the difference between purification and pollution from national park and estimated the quantitative value of the water quality regulating services. As a results, the amount of the value of the water quality regulating services from 2017 to 2021 was increased from approximately BOD 128.21 kg/Day, T-P 12.11 kg/Day to BOD 161.38 kg/Day, T-P 13.24 kg/Day and the economic value also increased from 2,304 million won to 2,817 million won.

• Composites Research
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• v.21 no.5
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• pp.23-30
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• 2008

Stab threats using sharp edged or pointed Instruments could be easily encountered by police officers or soldiers. In this study, the shear thickening fluids (STF) was impregnated into Kevlar fabrics to improve the stab protection and the resistance of STF impregnated Kevlar fabrics was experimentally investigated. The puncture and cut resistance were tested using a drop test machine withspike and knife indenters fabricated based on the National Institute of Justice (NIJ) standard. The STF was filled with spherical $SiO_2$ particles having an average diameter of 100nm, 300nm, and 500nm. The effect of particle size on puncture and cut resistance of STF impregnated Kevlar fabrics was also investigated. The measured impact load histories showed that STF impregnation into fabric leads to withstand higher peak loads than that of neat fabrics under spike test. The test results showed that Kevlar impregnated with STF exhibit remarkable improvements in puncture resistance while it is slightly influential on the cut resistance. Specifically, particle size is the one of the dominant factors controlling fabric resistance to puncture under spike impact test.

• Journal of Wetlands Research
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• v.25 no.4
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• pp.315-325
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• 2023

This study analyzed the disturbance process of river wetlands based on modern and contemporary maps and aerial photographs, and analyzed land cover and NDVI changes in the hydro-ecological impact zone around the Wangjin District. A stable sandbar was formed near Wangjinnaru and was naturally connected to the agricultural land within inland, but after the sandbar and river wetland were destroyed due to heavy floods, embankment construction, land readjustment, and comprehensive river management, artificial replaced wetlands and ecological parks were created, and sandbars in the form of river island were restored again. The change in land cover in the hydro-ecological impact zone showed that rice paddies and fields in agricultural areas decreased from 36.3% in 2013 to 22.9% in 2022, with the largest change in area to 814,476m². It was confirmed that the land cover was undergoing vegetation over time. Since the vegetation condition is good, a healthy food chain is formed in the waterfront ecosystem, which can be expected to be biodiversity-positive. Summarizing seasonal changes in the vegetation index, the overall change in the vegetation index was the largest in spring (March), followed by summer (June), and the change in autumn (September) was the smallest except for water. By land use, the overall vegetation index (NDVI) increased, including 39.1% improvement in alternative wetlands, 38.2% improvement in load, 44.3% improvement in ecological parks, 35.6% improvement in agricultural areas, and -8.1% decrease in water.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.6
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• pp.138-145
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• 2023

A study using numerical analysis techniques was conducted to examine the scour effect of pier-type dolphin structures installed in the domestic marine environment, and the effect of scour on horizontal bearing capacity was examined. In this study, we designed the berthing structures, taking into account the environmental and ground conditions of the target maritime area, and after calculating the predicted scour area, stability evaluation was performed by removing the ground elements of the area. The increase in scour depth was found to induce a direct decrease in horizontal bearing capacity due to soil loss in contact with the foundation, establishing a relationship that increases horizontal displacement. However, in the foundation designed to withstand the design load by reflecting the safety rate, the increase in horizontal displacement formed by possible scour is not large, which did not have a dominant effect on the horizontal bearing capacity of the foundation. In the future, research is required to analyze the impact of each factor and formalize evaluation and design techniques to evaluate the scour safety of marine foundations and pier-type structures installed in various ground conditions and structural formats.