• East Asian Economic Review
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• v.26 no.2
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• pp.143-169
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• 2022

This study investigates the effect of economic factors on immigration using the gravity model of immigration. Cross-sectional regression and panel data analyses are conducted from 2000 to 2019 using the OECD International Migration Database, which consists of 36 destination countries and 201 countries of origin. The Poisson pseudo-maximum-likelihood method, which can effectively correct potential biased estimates caused by zeros in the immigration data, is used for estimation. The results indicate that the economic factors strengthened after the global financial crisis. Additionally, this effect varies depending on the type of immigration (the income level of origin country). The gravity model applied to immigration performs reasonably well, but it is necessary to consider the country-specific and time-varying characteristics.

• Journal of the Korean earth science society
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• v.30 no.1
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• pp.49-57
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• 2009

We studied a structure of the Kunsan basin in the Yellow Sea using ship-borne magnetic data and altimetry satellite-derived gravity data provided from the Scripps institution of oceanography in 2006. The gravity data was analyzed via power spectrum analysis and gravity inversion, and the magnetic data via analytic signal technique, pseudo-gravity transformation, and its inversion. The results showed that the depth of bedrock tended to increase as we approached the center of the South Central Sag in Kunsan basin and that the maximum and minimum of its depth were estimated to be about 6-8 km and 2 km, respectively. Inaddition, the observed high anomaly of gravity and magnetism was attributed to the intrusion of igneous rock of higher density than the surrounding basement rock in the center of South Central Sag, which was consistent with the interpretation of seismic data obtained in the same region.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.33-41
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• 2002

Recently, the seismic safety evaluation of concrete gravity dams is raised due to the damage or the failure of dams occurred by the 1995 Kobe earthquake, the 1999 Taiwan earthquake, etc. Failre of dam may incur loss of life and properties around the dam as well as damage to dam structure itself. Recently, there has been growing much concerns about 'earthquake-resistance' or 'seismic safety'of existing concrete gravity dams designed before current seismic design provisions were implemented. This research develops three evaluation levels for seismic safety of concrete gravity dams on the basis of the evaluation method of seismic safety of concrete gravity dams in U.S.A., Japan, Canada, and etc. level 1 is a preliminary evaluation which is for purpose f screening. Level 2 is a pseudo-static evaluation on the basis of the seismic intensity method. Finally, level 3 is a detail evaluation by the dynamic analysis. Evaluation results on existing concrete gravity dam on operation showed good seismic performance under the designed artificial earthquake.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.1
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• pp.15-22
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• 2018

Pseudo-static approach has been conventionally applied for the design of gravity type quay walls. In this method, seismic coefficient ($k_h$), expressed in terms of acceleration due to gravity, is used to convert the real dynamic behavior to an equivalent pseudo-static inertial force for seismic analysis and design. Therefore, the calculation of an appropriate $k_h$ considering frequency characteristics of input earthquake is critical for representing the real dynamic behavior. However, the definitions of $k_h$, which is used for simplified analysis in Korea, focuses only on convenience that is easy to use, and the frequency characteristics of input earthquake are not reflected in the $k_h$ definitions. This paper evaluates the influences of the frequency characteristics of input earthquake on $k_h$ by initially reviewing the $k_h$ definitions in the existing codes of Japan for port structures and then by performing a series of dynamic centrifuge tests on caisson gravity quay walls of different earthquake input motions (Ofunato, Hachinohe). A review of the existing codes and guidelines has shown that the $k_h$ values are differently estimated according to the frequency characteristics of input earthquake. On the other hand, based on the centrifuge tests, it was found that the permanent displacements of wall are more induced when long-period-dominant earthquake is applied.

• Earthquakes and Structures
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• v.8 no.1
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• pp.19-35
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• 2015

This study compares the seismic performances of two reinforced concrete frame specimens tested by the pseudo-dynamic procedure. The pair of 3-storey, 3-bay frames specimens are constructed with typical characteristics of older construction which is lacking seismic design. One of the specimens is a bare frame while the other is infilled with low-strength autoclave aerated concrete (AAC) block masonry. The focus of this study is to investigate the influence of low strength masonry infill walls on the seismic response of older RC frames designed for gravity loads. It is found that the presence of weak infill walls considerably reduce deformations and damage in the upper stories while their influence at the critical ground story is not all that positive. Infill walls tend to localize damage at the critical story due to a peculiar frame-infill interaction, and impose larger internal force and deformation demands on the columns and beams bounding the infills. Therefore the general belief in earthquake engineering that infills develop a second line of defence against lateral forces in seismically deficient frames is nullified in case of low-strength infill walls in the presented experimental research.

• The Journal of Fisheries Business Administration
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• v.51 no.4
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• pp.85-96
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• 2020

The purpose of this study is to find out the determinants of export in Korean fishery products. For the analysis, laver and tuna, which account for almost half of seafood exports, were selected, and a gravity model widely used in trade analysis was applied. As explanatory variables, GDP, number of overseas Koreans, exchange rate, FTA, and WTO were applied, and fixed effect terms were included to take into account multilateral resistance that hinders trade. The analysis period is from 2000 to 2018, and the Poisson Pseudo Maximum Likelihood (PPML) method was applied to solve the problem of zero observation and heteroscedasticity inherent in trade data. As a result of the analysis, GDP was found to have a significant positive effect on both laver and tuna. The number of overseas Koreans was significant in canned tuna exports, but not in laver and the other tuna products. As the exchange rate increased, the export of laver and tuna for sashimi increased. The impacts of the FTA were confirmed in the exports of dried laver and raw tuna, which supports the results of the previous study. WTO was not significant for laver and tuna. Based on these results, it is necessary to find a way to make good use of the FTA to expand exports of seafood.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.5 no.1
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• pp.32-42
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• 1987

Global change and local fluctuation of earth's gravity field play important roles in accurate vertical positioning as well as in accurate horizontal positioning. Regarding the impotance, in this study, the concept of gravity potential theory connected with the influence of gravity field and every kind of height were discussed. Various kind of heights using the observed gravity and leveling data were computed and analysed to study the influence of earth's gravity field in accurate vertical positioning. Taking the route from Busan to Kyongju and investigating the ratios ($\Delta$H/dH) of height defferences (dH) between calculated heights considering gravity field and leveling height to relative heights (dH) between adjacent stations, we get the result that the values by correction formula increase linearly according to latitude, and the values by gravity potential ere strongly influenced by pseudo topography.

• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.64-74
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• 2016

Recently, the seismic stability evaluation of concrete gravity dams is raised due to the failure of dams occurred by the Izmit, Turkey and JiJi, Taiwan earthquake in 1999. Dams failure may incur loss of life and properties around the dam as well as damage to dam structure itself. Recently, there has been growing much concerns about "earthquake - resistance" or "seismic safety" of existing concrete gravity dams designed before current seismic design provisions were implemented. This research develops three evaluation levels for seismic stability of concrete gravity dams on the basis of the evaluation method of seismic stability of concrete gravity dams in U.S.A., Japan, Canada, and etc. Level 1 is a preliminary evaluation which is for purpose of screening. Level 2 is a pseudo-static evaluation on the basis of the seismic intensity method. And level 3 is a detail evaluation by the dynamic analysis. Evaluation results on existing concrete gravity dams on operation showed good seismic performance under designed artificial earthquake(KHC earthquake).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.16 no.3
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• pp.181-192
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• 2012

Here in this paper, the steady paint film flow on a vertical wall of a non-Newtonian pseudo plastic fluid for drainage problem has been investigated. The exact solution of the nonlinear problem is obtained for the velocity profile. Also the average velocity, volume flux, shear stress on the wall, force to hold the wall in position and normal stress difference have been derived. We retrieve Newtonian case, when material constant ${\mu}_1$ and relaxation time ${\lambda}_1$ equal zero. The results for co-rotational Maxwell fluid is also obtained by taking material constant ${\mu}_1$ = 0. The effect of the zero shear viscosity ${\eta}_0$, the material constant ${\mu}_1$, the relaxation time ${\lambda}_1$ and gravitational force on the velocity profile for drainage problem are discussed and plotted.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.513-516
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• 2006

This study tested gravity separation with pseudo heavy liquid to produce structural recycled aggregates and recycled aggregates for road construction.