• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.367-374
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• 2019

We investigate the effect of soil-structure interaction (SSI) on the response of LNG storage tanks to vertical seismic excitation depending on the type of foundation. An LNG storage tank with a diameter of 71 m on a clay layer with a thickness of 30 m upon bedrock, was selected as an example. The nonlinear behavior of the soil was considered in an equivalent linear method. Four types of foundation were considered, including shallow, piled raft, and pile foundations (surface and floating types). In addition, the effect of soil compaction within the group pile on the seismic response of the tank was investigated. KIESSI-3D, an analysis package in the frequency domain, was used to study the SSI and the stress in the outer tank was calculated. Based on an analysis of the numerical results, we arrived at three main conclusions: (1) for a shallow foundation, the vertical stress in the outer tank is less than the fixed base response due to the SSI effect; (2) for foundations supported by piles, the vertical stress can be greater than the fixed base stress due to the increase in the vertical impedance due to the piles and the decrease in radiation damping; and (3) soil compaction had a miniscule impact on the seismic response of the outer tank.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.365-372
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• 2017

The rolling motion of a floating body makes crews and passengers exhausted and/or applies forces to the structure to cause damage; it might even upset the body. Therefore, almost all ships are equipped with bilge keels for anti-rolling; in special cases, an anti-rolling tank(ART) or fin stabilizer or gyroscope could be installed. But an ART requires a large capacity to install it, and a fin stabilizer and gyroscope need great costs to install and also many expenses to operate. The authors suggest the use of an anti-rolling pendulum(ARP), and they showed that the ARP is effective to reduce rolling by experiments and via a Runge-Kutta analysis. This paper introduces the linearized 2 degrees of freedom with a viscous damping system for a ship equipped with ARP; it also shows the validation of the linearized analysis for the ship's roll motion. The paper proposes an optimum ARP on the basis of the justified model. The case of the 7.7kg model with ship 20g ARP of a mass ratio of 0.26%, is the most effective for reducing roll motion. The paper shows the ARPs with various mass ratios are effective for reducing the roll motion of a ship by free decaying roll experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.310-318
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• 2016

This study examined the correlation between microscopic factors and pedestrian volume in an urban environment, focusing on the microscopic factors that stimulate the pedestrian volume, such as density, diversity, network structure, accessibility, and the form of lots and buildings. In particular, factors already known to boost the pedestrian volume include density, diversity and accessibility, which are three variables strongly related to the concept of the 3Ds (Density, Diversity, Design) proposed by Cervero and Kockelman (1997) and the additional 2Ds (Distance to Transit, Destination Accessibility) suggested by Ewing et al. (2008). The analysis in this study was based on the 2010 survey of the floating population in Seoul, particularly on the data from Jongro-gu and Jung-gu in Gangbuk area. Data were established by analyzing the microscopic factors within a 500m radius around each of the 1,028 spots from which the pedestrian volume in Jongro-gu and Jung-gu was measured. The analysis showed that density, diversity and accessibility, three factors that were already known to be effective in increasing pedestrian volume, also have the same effect in Jongro-gu and Jung-gu.

• Journal of Ecology and Environment
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• v.45 no.3
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• pp.105-116
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• 2021

Background: The creation of the National Institute of Ecology began as a national alternative project to preserve mudflats instead of constructing the industrial complexes by reclamation, and achieve regional development. On the other hand, at the national level, the research institute for ecology was needed to cope with the worsening conditions for maintaining biodiversity due to accelerated climate change such as global warming and increased demand for development. In order to meet these needs, the National Institute of Ecology has the following objectives: (1) carries out studies for ecosystem change due to climate change and biodiversity conservation, (2) performs ecological education to the public through exhibition of various ecosystem models, and (3) promotes regional development through the ecological industry. Furthermore, to achieve these objectives, the National Institute of Ecology thoroughly followed the basic principles of ecology, especially restoration ecology, in the process of its construction. We introduce the principles and cases of ecological restoration applied in the process. Results: We minimized the impact on the ecosystem in order to harmonize with the surrounding environment in all the processes of construction. We pursued passive restoration following the principle of ecological restoration as a process of assisting the recovery of an ecosystem degraded for all the space except in land where artificial facilities were introduced. Reference information was applied thoroughly in the process of active restoration to create biome around the world, Korean peninsula forests, and wetland ecosystems. In order to realize true restoration, we pursued the ecological restoration in a landscape level as the follows. We moved the local road 6 and high-voltage power lines to underground to ensure ecological connectivity within the National Institute of Ecology campus. To enhance ecological diversity, we introduced perch poles and islands as well as floating leaved, emerged, wetland, and riparian plants in wetlands and mantle communities around the forests of the Korean Peninsula in the terrestrial ecosystem. Furthermore, in order to make the public aware of the importance of the intact nature, the low-lying landscape elements, which have disappeared due to excessive land use in most areas of Korea, was created by imitating demilitarized zone (DMZ) landscape that has these landscape elements. Conclusions: The National Institute of Ecology was created in an eco-friendly way by thoroughly reflecting the principles of ecology to suit its status and thus the impact on the existing ecosystem was minimized. This concept was also designed to be reflected in the process of operation. The results have become real, and a result of analysis on carbon budget analysis is approaching the carbon neutrality.

• Journal of the Korean Regional Science Association
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• v.37 no.2
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• pp.3-16
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• 2021

This study analyzed various indicators of new stores targeting urban regeneration areas and compared them with the control group to evaluate the possibility of revitalization of areas where urban regeneration projects are taking place. The results of the study are divided into three categories. First, the density of new start-ups in urban regeneration areas was higher than that of the control group. Through this, urban regeneration areas will bring about an influx of new floating populations and will act as a positive factor in local revitalization. Second, the urban regeneration areas and the control group were compared based on the business type of new start-up stores. As a result of the analysis, urban regeneration areas have a high proportion of industries targeting the active population, not residents. This will promote local activation by attracting the daytime population. Third, the urban regeneration areas and the control group were compared based on the diversity of the business types of newly established stores. As a result of the analysis, urban regeneration areas in metropolitan cities will induce multipurpose shopping for consumers as stores selling different products are concentrated. On the other hand, urban regeneration areas in small cities will induce consumers to compare shopping as stores selling similar products are concentrated.

• Applied Chemistry for Engineering
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• v.33 no.4
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• pp.386-393
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• 2022

In this study, the surface modification of calcium carbonate (CaCO₃) nanoparticles by a silane coupling agent, octyltrimethoxysilane (OTMS), was investigated and characterized using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) analysis. Both floating tests and contact angle measurements were also conducted to study the effect of OTMS concentration on the hydrophobicity of CaCO₃ nanoparticles. It was found that the active ratio for the CaCO₃ nanoparticles modified by 1 wt% of OTMS was 97.0 ± 0.5%, indicating that OTMS is a very effective silane coupling agent in enhancing the hydrophobicity of the CaCO₃ nanoparticle surface. The most stable foam was generated with 1 wt% of CaCO₃ nanoparticles in aqueous solutions at 1 wt% of OTMS, where the contact angle of water was found to be 91.8 ± 0.7°. It was also found that the most stable emulsion drops were formed at the same OTMS concentration. These results suggest that CaCO₃ nanoparticles modified by a silane coupling agent OTMS are a powerful candidate for a foam stabilizer or an emulsifier in many industrial applications.

• Journal of the Korean Geotechnical Society
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• v.39 no.3
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• pp.5-16
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• 2023

The effect of raft flexibility on piled raft foundations in sandy soil was investigated using a numerical analysis and an analytical study. The investigation's emphasis was the load sharing between piles and raft following the raft rigidity (K_R), end-bearing conditions. The case of individual piles and subsequently the response of groups of piles was analyzed using a 3D FEM. This study shows that the α_pr, load-sharing ratio of piled raft foundations, decreases as the vertical loading increases and as the K_R decreases. This tendency is more obvious when using friction piles compared to using end-bearing piles. The effect of raft rigidity is found to be more significant for the axial force distribution - each pile within the foundations has almost similar axial forces of the pile head with a flexible raft; however, each pile has different values with rigid rafts, especially with the end-bearing piles. The axial force of the pile base with floating piles shows similar point-bearing resistance for all the piles; however, it shows different values with end-bearing piles. The differential settlement ratio of rafts showed a larger value with lower K_R.

• Analyses & Alternatives
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• v.7 no.3
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• pp.181-230
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• 2023

Evaluating the empirical validity of Modern Monetary Theory, this study implements panel cointegration analysis on annual panel data (2000-2022) of OECD countries. Specifically, the sample countries are divided into groups based on the presence of their own sovereign currencies, and for each group, the long-run equilibrium relation (cointegration) between the ratio of public debt or fiscal deficit and government bond rates is tested and estimated. Main findings are as follows: applying the pooled mean-group estimation for panel cointegration, it is found that both the ratios of public debt and fiscal deficit have significantly positive long-run correlation with government bond rates in countries without sovereign currency such as the Euro-zone or fixed exchange rate regime countries. However, in countries with sovereign currency such as non-Euro-zone or floating exchange rate regime countries, the long-run correlation is either negative or not statistically significant. Particularly, in countries without sovereign currency, the ratio of public debt has significantly positive correlation with the real government bond rates in the short run as well as the long run. These results are consistent with the prediction of Modern Monetary Theory, thus providing a supporting evidence for the empirical validity of the theory.

• Journal of Platform Technology
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• v.12 no.3
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• pp.16-26
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• 2024

Videos shot underwater are known to have significant color distortion. Typical causes are backscattering by floating objects and attenuation of red colors in proportion to the depth of the water. In this paper, we aim to analyze color correction performance and color distortion patterns for images taken underwater. Backscattering and attenuation caused by suspended matter will be discussed in the next study. In this study, based on the DeepSeeColor model proposed by Jamieson et al., we verify color correction performance and analyze the pattern of color distortion according to changes in water depth. The input images were taken in the US Virgin Islands by Jamieson et al., and out of 1,190 images, 330 images including color charts were used. Color correction performance was expressed as angular error using the input image and the correction image using the DeepSeeColor model. Jamieson et al. calculated the angular error using only black and white patches among the color charts, so they were unable to provide an accurate analysis of overall color distortion. In this paper, the color correction error was calculated targeting the entire color chart patch, so an appropriate degree of color distortion can be suggested. Since the input image of the DeepSeeColor model has a depth of 1 to 8, color distortion patterns according to depth changes can be analyzed. In general, the deeper the depth, the greater the attenuation of red colors. Color distortion due to depth changes was modeled in the form of scale and offset movement to predict distortion due to depth changes. As the depth increases, the scale for color correction increases and the offset decreases. The color correction performance using the proposed method was improved by 41.5% compared to the conventional method.

• Journal of Gifted/Talented Education
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• v.23 no.2
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• pp.237-256
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• 2013

The purpose of this study is to develop program that take a genuine interest in science and motivate students to keep up their study for science gifted children of start period. In this study, we develop and apply the program about sinking and floating for elementary science gifted students, and analyse degree of conceptual change. Students' prior knowledge is analysed for developing the program, and each step is settled about concept of density and buoyancy. Conceptests are arranged into step by step, and we apply the program to 26 science gifted students of 6th grade elementary school. We compare a percentage of correct answers of pre-test and post-test and evaluate Hake gain for analysis of degree of conceptual change. As a result, science gifted students' concepts are changed effectively into scientific concepts by program based on peer instruction for gifted students of start period. And they evaluate the program is novel and useful, also they can be motivated by the program.