• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.42-50
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• 2017

A cerebral aneurysm is a ballooning arising from a weakened area in the wall of a blood vessel in the brain. In this study, the flow analysis of the blood vessel, including the cerebral aneurysm and the stent, was conducted to investigate the effect of the stent shape on reduction of blood flowing into the cerebral aneurysm. We used the Carreau model to describe Non-Newtonian behaviors of blood flow. Two kinds of stents, which had different cross angles were modelled by the commercial CAD program and the geometries of those stents were reflected in the analysis domain of the blood vessel. From the results of the flow analysis, we found that the blood flowing into the cerebral aneurysm was decreased as the cross angle of the stent was decreased.

• Journal of the Korean Mathematical Society
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• v.57 no.3
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• pp.721-745
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• 2020

In this paper we study fractional Sobolev spaces characterized by a norm based on eigenfunction expansions. The goal of this paper is twofold. The first one is to define fractional Sobolev spaces of order -1 ≤ s ≤ 2 equipped with a norm defined in terms of Neumann eigenfunction expansions. Due to the zero Neumann trace of Neumann eigenfunctions on a boundary, fractional Sobolev spaces of order 3/2 ≤ s ≤ 2 characterized by the norm are the spaces of functions with zero Neumann trace on a boundary. The spaces equipped with the norm are useful for studying cross-sectional traces of solutions to the Helmholtz equation in waveguides with a homogeneous Neumann boundary condition. The second one is to define fractional Sobolev spaces of order -1 ≤ s ≤ 1 for vector-valued functions in a simply-connected, bounded and smooth domain in ℝ². These spaces are defined by a norm based on series expansions in terms of eigenfunctions of the vector Laplacian with boundary conditions of zero tangential component or zero normal component. The spaces defined by the norm are important for analyzing cross-sectional traces of time-harmonic electromagnetic fields in perfectly conducting waveguides.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.23 no.4
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• pp.367-380
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• 2019

A 1kW-class horizontal axis wind turbine (HAWT) rotor blade is taken into account to investigate elastic characteristics in 2-D. The elastic blade field is composed of symmetric cross-ply laminated composite material. Blade element momentum theory is applied to obtain the boundary conditions pressuring the blade, and the plane stress elasticity problem is formulated in terms of two displacement parameters with mixed boundary conditions. For the elastic characteristics a fair of differential equations are derived based on the elastic theory. The domain is divided by triangular and rectangular elements due to the complexity of the blade configuration, and a finite element method is developed for the governing equations to search approximate solutions. The results describe that the elastic behavior is deeply influenced by the layered angle of the middle laminate and the stability of the blade can be improved by controlling the layered angle of laminates, which can be evaluated by the mathematical approach.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.5
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• pp.282-290
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• 2009

A ceramic monolith heat exchanger is studied to find the performance of heat transfer and pressure drop by numerical computation and $\xi$-NTU method. The numerical computation was performed throughout the domain including fluid region in exhaust gas-side rectangular ducts, ceramic core and fluid region in air-side rectangular duct with the air and exhaust in cross flow direction. In addition, the heat exchanger was also analyzed to estimate the performance by conventional $\xi$-NTU method with several Nusselt number correlations for flow in rectangular duct from literature. By comparisons of both performances by the numerical computation and the $\xi$-NTU method, the effectiveness by $\xi$-NTU method was closest to the result by numerical computation within a relative error of 2.14% when Stephan's Nusselt number correlation was adopted to the $\xi$-NTU method among the several correlations.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.4
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• pp.551-559
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• 2014

The influence of the battle damage hole on the velocity and vorticity flow field have been studied by using particle image velocimetry. Time averaged velocity and vorticity vector fields in the vicinity of jet are presented. The perforated damage hole on a wing created from a hit by anti-air artillery was modeled as a 10% chord size hole which positioned at quarter chord. At low angles of attack, the vorticity in the forward side of the jet is cancelled due to mixing with the wing surface boundary layer. Stretching of vorticity in the backside of the jet generates a semi-cylindrical vortical layer that enclosing a domain with slow moving reverse flow. Conversely, at higher the angles of attack, the jet vorticity advected away from the wing surface and remains mostly confined to the jet. The mean flow behind the jet has a wake-like structure.

• International journal of advanced smart convergence
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• v.10 no.4
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• pp.84-97
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• 2021

Digital twins are one of the promising digital technologies used to facilitate digital transformation. Therefore, it needs to continually be developed remain relevant in industry and academia. Consolidation of research is required to create a common understanding of the topic and to ensure that future research is built upon a solid foundation. Based on a bibliometric review and a thematic analysis of 217 publications on digital twins from the past two decades, this paper creates and analyzes a visual knowledge map and proposes areas for further research. To comprehensively analyze the development trends and research trends of digital twins, we performed statistical analysis of the relevant literature on digital twins within the core collection database of Web of Science. Through our research, we have shown that the current situation, trends, and hotspots of digital twin research were analyzed via CiteSpace. This study demonstrates that research on digital twins is rapidly growing in popularity, that the output of the research depends largely on the core group of authors conducting it, and that digital twins warrant cross-domain and cross-disciplinary research pathways.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.2
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• pp.77-87
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• 2002

In the field of secure information systems including electronic commercials, public key infrastructure(PKI) is widely used for secure services. The more PKI domains are established, the more needs we required for cross-domain certifications. Furthermore, each country has many certificate authorities(CA) which requires more complex cross certification. We may need a fast algorithm in order to fad the possible certification paths. This will be more indispensible in the growing PKI systems. Thus, in this paper we design a high-speed certification path discovery algorithm and implement it. Also we investigate the feature of operation of the system.

• Earthquakes and Structures
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• v.24 no.1
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• pp.65-79
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• 2023

A simplified analytical solution for seismic response of tunnel cross section in horizontally layered ground subjected to oblique incidence of SH wave is deduced in this paper. The proposed analytical solution consists of two main steps: free-field response in layered field and tunnel response. The free field responses of the layered ground are obtained by one-dimensional finite element method in time domain. The tunnel lining is treated as a thick-wall cylinder to calculate the tunnel response, which subject to free field stress. The analytical solutions are verified by comparing with the dynamic numerical results of two-dimensional ground-lining interaction analysis under earthquake in some common situations, which have a good agreement. Then, the appropriate range of the proposed analytical solution is analyzed, considering the height of the layered ground, the wavelength and incident angle of SH wave. Finally, by using the analytical solutions, the effects of the ground material, burial depth of the tunnel, and lining thickness and the slippage effect at the ground-lining interface on the seismic response of tunnels are investigated. The proposed solution could serve as a useful tool for seismic analysis and design of tunnels in layered ground.

• Journal of Microbiology
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• v.42 no.4
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• pp.328-335
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• 2004

The human immunodeficiency virus type 1 (HIV-I) Tat protein transduction domain (PTD), which con­tains rich arginine and lysine residues, is responsible for the highly efficient transduction of protein through the plasma membrane. In addition, it can be secreted from infected cells and has the ability to enter neighboring cells. When the PTD of Tat is fused to proteins and exogenously added to cells, the fusion protein can cross plasma membranes. Recent reports indicate that the endogenously expressed Tat fusion protein can demonstrate biodistribution of several proteins. However, intercellular transport and protein transduction have not been observed in some studies. Therefore, this study exam­ined the intercellular transport and protein transduction of the Tat protein. The results showed no evi­dence of intercellular transport (biodistribution) in a cell culture. Instead, the Tat fusion peptides were found to have a significant effect on the transduction and intercellular localization properties. This sug­gests that the HIV-1 PTD passes through the plasma membrane in one direction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.15-16
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• 2014

As trade cross the world is increasing these days, safe and effective management of harbour system is becoming important issue. With this background, the development of automatic time-domain simulation programme for ship berthing operation has been being peformed and PD (Proportional Derivative) controller has been used to control the speed and the heading angle of ships. This paper provides feasibility study for developing the time-domain simulation programme for berthing operation of ships with analysing advantages and drawbacks of the two different mathematical models, one is for low advance speed of ships by Kose (1984) and the other is MMG model for normal advance speed, through the simulations with various initial heading angles and positions of the ship.