• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.2
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• pp.116-127
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• 2002

Most of finite difference numerical models for the simulation of tsunami propagation developed so for are based on the shallow-water equations which are frequently solved by the leap-frog scheme. If the grid size is properly selected, this numerical scheme gives a correct dispersion effect fur constant water depth. However, if the water depth changes, the dispersion effect of tsunamis can not be accurately considered at every grid point in the whole computational domain. In this study we improved the existing two-dimensional dispersion-correction finite difference numerical scheme. The present scheme satisfies the local dispersion relationships of tsunamis propagating over a slowly varying topography while using uniform grid size and time step. To verify the applicability of the improved numerical model, a tsunami due to 1983 East Sea central earthquake is simulated for Korean harbors with the tide gage records such as Sokcho, Mukho, Pohang and Ulsan in the East Sea. Numerical results of the 1983 tsunami are compared with the measured data and the accuracy of the present numerical model is evaluated.

• Journal of the Korea Convergence Society
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• v.10 no.11
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• pp.111-116
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• 2019

With recent rapid development of computer capabilities, various technologies that can facilitate the interaction between humans and computers are being studied. The paradigm tends to change to NUI using the body such as 3D motion, haptics, and multi-touch with GUI using traditional input devices. Various studies have been conducted on transferring human movements to computers using sensors. In addition to the development of optical sensors that can acquire 3D objects, the range of applications in the industrial, medical, and user interface fields has been expanded. In this paper, I provide a model that can execute other programs through gestures instead of the mouse, which is the default input device, and control Windows based on the lip motion. To propose a model which converges with an Android application and can be controlled by various media and voice instruction functions using voice recognition and buttons through connection with a main client. It is expected that Internet media such as video and music can be controlled not only by a client computer but also by an application at a long distance and that convenient media viewing can be performed through the proposal model.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.159-164
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• 2008

This study simulated the flood inundations of the Nakdong River catchment running through Yangsan, a small city located in the south eastern area of Korea by using the depth averaged two-dimensional hydrodynamic numerical model. The numerical model employs the staggered grid system including moving boundary and a finite different method to solve the Saint-Venant equations. A second order upwind scheme is used to discretize the nonlinear convection terms of the momentum equations, whereas linear terms are discretized by a second order Leap-frog scheme(Cho and Yoon, 1998). The numerical model was applied to a real topography to simulate the flood inundation of the Yangsan basin in Yangsan. The numerical result for urban district was visualization for three dimension. These results can be essentially utilized to construct the three dimensional inundation map after building the GIS-based database in local public organizations in order to protect the life and property safely.

• Korea Trade Review
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• v.48 no.1
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• pp.263-285
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• 2023

The purpose of this study is to examine the business model, growth process, and success factors of the successful super app Gojek in the Southeast Asian and Indonesian markets. Gojek's business model analysis focused on the business canvas (9 blocks) that many companies have used to establish business models. Gojek's growth process was analyzed based on timeline. Gojek 1.0 is from the start of the ride hailing service. Gojek 2.0 is a leap forward into a life-friendly platform. Gojek 3.0 is a process of expanding and diversifying domestic and foreign businesses. Gojek 4.0 is a stage of changing to GoTo through mergers with Tokopedia, and setting a higher leap forward. Based on this, the success factors of Gojek are ① Hyperlocalization ② First mobile ③ A company that is loved through mission execution ④ Provide financial inclusion ⑤ Business expansion and diversification through mergers and acquisitions and partnerships ⑥ Entry into overseas markets ⑦ Attracting various partners and investment ⑧ Lock-in effect and hyperpersonalization. The implications obtained through this study and the limitations and direction of the study were discussed.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.179-182
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• 2008

This study simulated the flood inundations of the Nakdong River catchment running through Yangsan, a small city located in the south eastern area of Korea by using the depth averaged two-dimensional hydrodynamic numerical model. The numerical model employs the staggered grid system including moving boundary and a finite different method to solve the Saint-Venant equations. A second order upwind scheme is used to discretize the nonlinear convection terms of the momentum equations, whereas linear terms are discretized by a first order leap-frog scheme(Cho and Yoon, 1998). The numerical model was applied to a real topography to simulate the flood inundation of the Yangsan basin. The numerical results for urban district are visualized in three dimension. These results can be essentially utilized to construct the three dimensional inundation map after building the GIS-based database in local public organizations in order to protect the life and property safely.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.431-434
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• 2008

Pratical dispersion-correction scheme is applicated to simulate the distant propagation of tsunami. This scheme is based on the leap-frog finite difference scheme for the linear shallow-water equations. The new scheme has the advantage of using the constant spatial grid size and time step size even in area of variable depths. And this new model constructed by using the 2nd upwind scheme, dynamic linking method, and staggered grid system. This model is simulated to near Sokcho harbor about The Central East Sea Tsunami in 1983. And this result is compared to tide gage and result of former model.

• The Korean Journal of Applied Statistics
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• v.13 no.2
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• pp.321-328
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• 2000

Working day variations caused by trading days, holidays and leap year make it difficult to analyze monthly or quarterly economic time series. In this paper, we adjust working day variations from economic time series via RegARIMA model.

• Knowledge Management Research
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• v.16 no.4
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• pp.191-213
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• 2015

With the advancement of virtual reality technology, virtual reality contents and devices are being competitively released. This research deals with an early stage adoption model of a motion-sensing input device which enhances the user experience of these virtual reality contents and devices. In contrast to the previous research on the adoption or resistance of innovative products, this work compares and analyzes the antecedents in MIR(Model of Innovation Resistance) of resistance-perspective as well as those in UTAUT2(Extended Unified Theory of Acceptance and Use of Technology) and IDT(Innovation Diffusion Theory) of adoption-perspective, and suggests a resistance-incorporated adoption model from a new viewpoint. The analysis of questionnaire data indicates the following results: Performance expectancy, effort expectancy, price value, hedonic motivation in UTAUT2 and visibility in IDT have a significant negative influence on innovation resistance. Compatibility in IDT and MIR exerts a positive influence on perceived value. Social influence and hedonic motivation in UTAUT2 positively relates to perceived value. Higher innovation resistance results in lower perceived value, with innovation resistance and perceived value negatively and positively affecting intention to use, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.659-663
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• 2010

In recent, flood inundation damages by hydraulic structure failures have increased drastically and thus a variety of countermeasures were needed to minimize such damages. A real-time flood inundation prediction technique is essential to protect and mitigate flood inundation damages. In the context of real time flood inundation modeling, this study aims to develop a grid based two-dimensional numerical method for flood inundation modeling using globally-available DEM data: SRTM with $90m{\times}90m$ spatial resolution. The newly-developed model guarantees computational efficiency in terms of geometric data processing by direct application of DEM for flood inundation modeling and also have good compatibility with various types of raster data when compared to a commercial model such as FLUMEN. The model, which employed the leap-frog algorithm to solve shallow water and continuity equations, can simulate inundating flow from channel to lowland and also returning flow from lowland to channel by comparing water levels between channel and lowland in real time. We applied the model to simulate the BaekSan levee break in the Nam river during a flood period from August 10 to 13, 2002. The simulation results had good agreements with the field-surveyed data in terms of inundated area and also showed physically-acceptable velocity vector maps with respect to inundating and returning flows.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.26.2-26.2
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• 2009

The Solar and Space Weather Research Group (SOS) in Korea Astronomy and Space Science Institute (KASI) is constructing the Space Weather Prediction Center since 2007. As a part of the project, we are developing automatic real-time system of the global 3-D magnetohydrodynamics (MHD) simulation. The MHD simulation model of earth's magnetosphere is designed as modified leap-frog scheme by T. Ogino, and it was parallelized by using message passing interface (MPI). Our work focuses on the automatic processing about simulation of 3-D MHD model and visualization of the simulation results. We used PC cluster to compute, and virtual reality modeling language (VRML) file format to visualize the MHD simulation. The system can show the variation of earth's magnetosphere by the solar wind in quasi real time. For data assimilation we used four parameters from ACE data; density, pressure, velocity of solar wind, and z component of interplanetary magnetic field (IMF). In this paper, we performed some initial tests and made a animation. The automatic real-time system will be valuable tool to understand the configuration of the solar-terrestrial environment for space weather research.