• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.711-717
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• 2006

In order to study gas hydrate, potential future energy resources, Korea Institute of Geoscience and Mineral Resources has conducted seismic reflection survey in the East Sea since 1997. one of evidence for presence of gas hydrate in seismic reflection data is a bottom simulating reflector (BSR). The BSR occurs at the interface between overlaying higher velocity, hydrate-bearing sediment and underlying lower velocity, free gas-bearing sediment. That is often characterized by large reflection coefficient and reflection polarity reverse to that of seafloor reflection. In order to apply depth migration to seismic reflection data. we need high performance computers and a parallelizing technique because of huge data volume and computation. Phase shift plus interpolation (PSPI) is a useful method for migration due to less computing time and computational efficiency. PSPI is intrinsically parallelizing characteristic in the frequency domain. We conducted conventional data processing for the gas hydrate data of the Ease Sea and then applied prestack depth migration using message-passing-interface PSPI (MPI_PSPI) that was parallelized by MPI local-area-multi-computer (MPI_LAM). Velocity model was made using the stack velocities after we had picked horizons on the stack image with in-house processing tool, Geobit. We could find the BSRs on the migrated stack section were about at SP 3555-4162 and two way travel time around 2,950 ms in time domain. In depth domain such BSRs appear at 6-17 km distance and 2.1 km depth from the seafloor. Since energy concentrated subsurface was well imaged we have to choose acquisition parameters suited for transmitting seismic energy to target area.

• Communications for Statistical Applications and Methods
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• v.29 no.1
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• pp.103-125
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• 2022

In this paper, we analyze the time series data of the case and death counts of COVID-19 that broke out in China in December, 2019. The study period is during the lockdown of Wuhan. We exploit functional data analysis methods to analyze the collected time series data. The analysis is divided into three parts. First, the functional principal component analysis is conducted to investigate the modes of variation. Second, we carry out the functional canonical correlation analysis to explore the relationship between confirmed and death cases. Finally, we utilize a clustering method based on the Expectation-Maximization (EM) algorithm to run the cluster analysis on the counts of confirmed cases, where the number of clusters is determined via a cross-validation approach. Besides, we compare the clustering results with some migration data available to the public.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.758-771
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• 2005

Information systems in current corporations are managing and storing large data officially happened on individual and various databases. Corporations for migrating the stored data from these individual databases are adopting with technologies of EAI, MDR, DW etc.. However these technologies are not only required to expenses introduction charge and maintenance cost but also have problems of heterogeneous environment required per each vender In this paper, to solve problems of these current existing technologies, we propose to design our data migration system to migrate source data and semantic constraint condition between heterogeneous relation databases based on web service. As corporations use web services, they can reduce introduction expense and maintenance cost because of using current existent web environment. Each system can independently migrate XML based data against any platform, system environment, and Implementation language.

• Geophysics and Geophysical Exploration
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• v.5 no.3
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• pp.185-192
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• 2002

We made a study of 3-D migration which could precisely image data of GPR (Ground Penetrating Radar) applied to NDT (Non-Destructive Test) field for the inspection of structural safety. In this study, we obtained 3-D migrated images of important targets in structuresurvey (e.g. steel pipes, cracks) by using 3-D Kirchhoff prestack depth migration scheme developed for seismic data processing. For a concrete model consisting of steel pipe and void, the targets have been well defined with opposite amplitude according to the parameters of the targets. And migrated images using Parallel-Broadside array (XX configuration) have shown higher resolution than those using Perpendicular-Broadside array (YY configuration) when steel pipes had different sizes. Therefore, it is required to analyze the migrated image of XX configuration as well as that of general YY configuration in order to get more accurate information. As the last stage, we chose a model including two steel pipes which cross each other. The upper pipe has been resolved clearly but the lower has been imaged bigger than the model size due to the high conductivity of the upper steel.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.97-104
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• 2016

Because of rapid growth of data size, the number of data storage has been increased. When using multiple data storages, a distribute file system is essential to insure the availability of data files. The power consumption is a major problem when using a distributed file system with many data storages. Previous works have aimed at reducing the energy consumption with efficient file block layout by changing some data servers into stand-by mode. The file block migration has not been seriously considered because migration causes large cost. But when we consider addition of a new data server or file, file block migration is needed. This paper formulates the minimization of data block migration as an ILP optimization problem and solves it using branch-and-bound method. Using this technique, we can maximize the number of stand-by data servers with the minimum number of file block movement. However, computation time of branch-and-bound method of an ILP optimization problem increases exponentially as the problem size grows. Therefore this paper also proposes a data block and data server grouping method to solve many small ILP problems.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.315-322
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• 2010

The phase-screen and the split-step Fourier migrations, which are implemented in both the frequency-wavenumber and frequency-space domains by using one-way scalar wave equation, allow imaging in laterally heterogeneous media with less computing time and efficiency. The generalized-screen migration employs the series expansion of the exponential, unlike the phase-screen and the split-step Fourier migrations which assume the vertical propagation in frequency-wavenumber domain. In addition, since the generalized-screen migration generalizes the series expansion of the vertical slowness, it can utilize higher-order terms of that series expansion. As a result, the generalized-screen migration has higher accuracy in computing the propagation with wide angles than the phase-screen and split-step Fourier migrations for media with large and rapid lateral velocity variations. In this study, we developed a 2D prestack generalized-screen migration module for imaging a complex subsurface efficiently, which includes various dips and large lateral variations. We compared the generalized-screen propagator with the phase-screen propagator for a constant perturbation model and the SEG/EAGE salt dome model. The generalized-screen propagator was more accurate than the phase-screen propagator in computing the propagation with wide angles. Furthermore, the more the higher-order terms were added for the generalized-screen propagator, the more the accuracy was increased. Finally, we compared the results of the generalizedscreen migration with those of the phase-screen migration for a model which included various dips and large lateral velocity variations and the synthetic data of the SEG/EAGE salt dome model. In the generalized-screen migration section, reflectors were positioned more accurately than in the phase-screen migration section.

• Korea journal of population studies
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• v.31 no.3
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• pp.159-178
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• 2008

The main purpose of this paper is to examine selectivity and rasons for move of internal migrants in Korea. There have only been a few studies available on the issues of selectivity and reasons for move of internal migration in Korea, mainly due to the lack of appropriate data. The main source of data for this analysis come from the raw data set of the 1997 Special Migration Survey conducted by the National Statistical Office. Analysis of selectivity of those who moved across the provincial boundary revealed that females, young adults, singles in their marital status and more educated are more likely to move. Among various reasons for move, employment related reason is the most important for all migration streams. But with different migration streams, diverse patterns are emerged. For those who moved into the Capital Region, employment related reason is outstanding. But those who moved out from the Capital Region, moved for employment as well as family related reasons. For movement within the Capital Region, housing related reason is equally important together with employment and family reason. The analysis also found that among individual attributes, age and marital status affect most significantly to the reasons for move. Education level and housing ownership are also important for explaining for variations in reasons for move.

• Korea journal of population studies
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• v.31 no.2
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• pp.133-155
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• 2008

The purpose of this study is to examine the pattern and characteristics of population movement in Kangwon province. The data for this study were drawn from in- out- migration data established by Korea National Statistical Office(KNSO) between 2000 and 2007. Sample survey and depth interview were also used. The results showed that the population of all Si and Gun except Choonchun and Wonju declined. This decline of population in Kangwon province persisted during the last decades. The decline started with the industrialization in the 1960s and 1980s. The decline of population in Kangwon province continued in the 1990s and 2000s with the open agriculture policy rooted in UR and FTA. All Si and Gun can be classified into five groups in terms of population movement in Kangwon province between 2000 and 2007. The first group(Group B) is where in-migration from other Si and Gun and out-migration to Seoul and Kyunggi continues in the period. Choonchun, Wonju, and Sokcho belong to this category. The second group(Group C) is where out-migrarion to Seoul and Kyunggi is larger the in-migration. It includes Cholwon, Taebaek, Donghae, and Samchok. The third group(Group D) is where out-migration to Group B is larger than that of other places. Hwachun, Pyungchang, Hoegsung, Gosung, and Hongchun are included in this group. The fourth group(Group E) is where out-migration to both Group B and Seoul & Kyunggi is large. Youngwol, Gangnung, and Chungsun belong to this category. The fifth group(Group F) is where few population movement occurs. It includes Yangyang, Yanggu, and Injae. The findings also shows that the extent of population movement to Choonchun and Wonju is larger than that of Seoul and Kyunggi in recent period. This finding indicates that the effect of base city like Choonchun and Wonju has become in recent years.

• Korean Journal of Social Welfare
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• v.62 no.2
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• pp.135-159
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• 2010

This study is thing about marital adjustment of marriage migration females. This research inspected relational and influential factors that has consequences for the marital adjustment. The subjects of research are 172 marriage migration females lived in Busan. Data were analyzed by MANOVA, Multiple Regression. The results are following: First, this study found that marriage migration female's marital satisfaction are significantly influenced by spousal support, family stress, level of communication. And marriage migration female's divorce intention are significantly influenced by children number, family stress. And marriage migration female's couple loving are influenced by length of marriage, spousal support, level of communication. Second, family stress is the most powerful factor to predict marital adjustment. Therefore the lower family stress is the better marital adjustment. And through this study I found that marital adjustment is more important family stress than acculturative stress.

• Journal of Labour Economics
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• v.41 no.2
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• pp.61-88
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• 2018

This paper examines the impact of internal migration on wage growth among college graduates using Propensity Score Matching methods. We define migration as moving between Seoul Metropolitan Area (SMA) and non-SMA based on the locations of graduates' first and second jobs. We also take the direction of migration into account for examining the wage premium in SMA. In order to estimate the impact of migration on wage growth, we use the Graduate Occupational Mobility Survey (2010GOMS) coupled with other supplementary data such as College Scholastic Ability Test score and local characteristic variables. The results reveals that graduates moving from SMA to non-SMA do not experience significant wage growth. However, we find that graduates moving from non-SMA to SMA experience an increase in their monthly wage about 170,000~186,000 KRW on average (9.5~10.3% of their monthly wage on the first job).