• International Journal of Highway Engineering
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• v.14 no.5
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• pp.1-9
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• 2012

PURPOSES: A viscoelastic axisymmetric finite element analysis code has been developed for stress analysis of asphalt pavement structures. METHODS: Generalized Maxwell Model (GMM) and 4-node isoparametric element were employed for finite element formulation. The code was developed using $C^{+}^{+}$ computer program language and named as KICTPAVE. For the verification of the developed code, a structural model of a pavement system was constructed. The structural model was composed of three layers: asphalt layer, crushed stone layer, and soil subgrade. Two types of analysis were considered for the verification: (1)elastic static analysis, (2)viscoelastic time-dependent analysis. For the elastic static analysis, linear elastic material model was assigned to all the layers, and a static load was applied to the structural model. For the viscoelastic time-dependent analysis, GMM and linear elastic material model were assigned to the asphalt layer and all the other layers respectively, and a cyclic loading condition was applied to the structural model. RESULTS: The stresses and deformations from KICTPAVE were compared with those from ABAQUS. The analysis results obtained from the two codes showed good agreement in time-dependent response of the element under the loading area as well as the surface deformation of asphalt layer, and horizontal and vertical stresses along the axisymmetric axis. CONCLUSIONS: The validity of KICTPAVE was confirmed by showing the agreement of the analysis results from the two codes.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.23-30
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• 2009

The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Furthermore, numerical simulations for supersonic shock boundary layer interaction with a bleed region were performed and their results were compared with the existing computational results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.162-163
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• 2023

As the development of the 4^th industiral revolution in the maritime industry has progressed, the technical development of autonomous ships, and the development of international regulations have been accelerated. In particular, the IMO Maritime Safety Committee(MSC) has established a road-map for the development of the non-mandatory goal-based MASS instrument(MASS Code) and started developing a non-mandatory MASS Code at MSC 105^th meeting. Many countries are actively participating in the Correspondence Group on the development of MASS Code, and the development of detailed requirements for MASS functions in the MASS Code is underway. Especially, the concept of "Mode of Operation" for MASS functions was mentioned in the Correspondence Group for the first time, and it is expected that discussions on these modes will be conducted from the IMO MASS JWG meeting to held in April 2023. The concept of "Mode of Operation" will be useful in explaining MASS and MASS functions and will be discussed in the future for the development of MASS Code. This paper reviews the contents of the IMCA M 220 document, which provides guidelines on operating modes, to conduct research on the benchmark for setting the operating modes of MASS.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.179-183
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• 2006

Surface roughness is present in most of the microfluidic devices due to the microfabrication techniques. This paper presents lattice Boltzmann method (LBM) results for laminar flow in a microchannel with surface roughness. The surface roughness is modeled by an array of rectangular modules placed on top and bottom side of a parallel-plate channel. In this study, LBGK D2Q9 code in lattice Boltzmann Method is used to simulate flow field for low Reynolds number in a micro-channel. The effects of relative surface roughness, roughness distribution, roughness size and the results are presented in the form of the product of friction factor and Reynolds number. Finally, a significant increase in Poiseuille number is detected as the surface roughness is considered, while the effect of roughness on the microflow field depends on the surface roughness.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.70-77
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• 2016

In this paper, the structural design and integrity evaluations for a reactor vessel of PGSFR sodium-cooled fast reactor(150MWe) are carried out in compliance with ASME BPV III, Division 5 Subsection HB. The reactor vessel is designed with a direct contact of primary sodium coolant to its inner surface and has a double vessel concept enclosing by containment vessel. To assure the structural integrity for 60 years design lifetime and elevated operating temperature of $545^{\circ}C$, which can invoke creep and creep-fatigue damage, the structural integrity evaluations are carried out in compliance with the ASME code rules. The design loads considered in this evaluations are primary loads and operation thermal cycling loads of normal heat-up and cool-down. From the evaluations, the PGSFR reactor vessel satisfies the ASME code limits but it was found that there is a little design margin of creep damage for inner surface at the region of cold pool free surface.

• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.32-36
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• 2012

This paper presents a comparison of potential and viscous computational codes for the water entry problem. A po-tential code was developed which adopted the boundary element method to solve the problem. A nonlinear free surface boundary condition was integrated to find new locations of free surface. The dynamic boundary condition was simplified by taking constant potential values for every time steps. The simplified dynamic boundary condition was applied in the new position of the free surface not at the mean level, which is the usual practice for linearized theory. The commercial code FLUENT was used to solve the water entry problem from the viscosity point of view. The movement of the air-liquid interface is traced by distribution of the volume fraction of water in a computational cell. The pressure coefficients were compared with each other, while experimental results published by other researchers were also examined. The characteristics of each method were discussed to clarify merits and limitations when they were applied to the water entry problems.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.11-19
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• 2010

A code is developed to simulate incompressible free surface flows using the Roe's flux-difference splitting scheme. An interface of two fluids is considered as a moving contact discontinuity. The continuities of pressure and normal velocity across the interface are enforced by the conservation law in the integral sense. The fluxes are computed using the Roe's flux-difference splitting scheme for two incompressible fluids. The interface can be identified based on the computed density distribution. However, no additional treatment is required along the interface during the whole computations. Complicated time evolution of the interface including topological change can be captured without any difficulties. The developed code is applied to simulate the Rayleigh-Taylor instability of two incompressible fluids in the density ratio of 7.2:1 and the broken dam problem of water-air. The present results are compared with other available results and good agreements are achieved for the both cases.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.417-423
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• 2012

Radar Cross Section(RCS) is a measure of how detectable an object is with a radar. A larger RCS indicates that an object is more easily detected. Informally, the RCS of an object is the cross-sectional area of a perfectly reflecting sphere that would produce the same amount of reflection strength as the object in question would. In order to estimate RCS of aircraft weapons the external surface is modeled as a collection of simple shape elements. And the overall RCS is estimated as a vector sum of configuring elements' cross-sections which are well known given by analytic formulae. A RCS estimation code is developed for a typical shape of Air-To-Surface bombs and missiles. Size of weapons and location of fins are implemented in the code in addition to the presence of canards. The ability to predict radar return from flying vehicles becomes a critical technology issue in the development of stealth configurations. This simplified method of RCS estimation is known to be fast and accurate enough in an optical region of high frequency incident radio wave.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.2
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• pp.47-54
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• 1987

Linear and nonlinear hydrodynamic force, which acts on submerged circular and eilliptic cylinders in oscillations as well as in advancing motion, are investigated as an initial-boundary value problem using a numerical method, which makes use of the source distribution on the body surface and the spectral method for treating the free surface waves. In the numerical code developed here, the boundary condition at the body surface is linearized. Using the numerical code so attained, nonlinear effects for different forward speeds and of the large-amplitude motion are computed. One of the major findings is that, when the forward speed is large, the added mass has its minimum and the damping force change rapidly around the frequency corresponding to the speed-frequency parameter, $\tau$=0.25, Compared to the result of Grue's [10], who used linear theory to get abrupt changes in values of the added mass and the damping force at the frequency corresponding to $\tau$=0.25, the present study, which takes nonlinear effects into account, shows much smoother variations near the frequency.

• The Korean Journal of Food & Health Convergence
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• v.5 no.3
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• pp.35-40
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• 2019

In this study, general bacterial counts and coliform counts, which are hygienic indicator microorganisms, were tested for candy, chocolate, and jelly which are easily available and enjoyed around. After dropping each sample on the desk, indoors, and outdoors, it is immediately collected, or washed and collected to confirm the myth of the 3-second rule. Immediately after removing the wrapping paper, each sample was dropped on the desk, indoors, and outdoors, and after 3 seconds from the moment of contact with the surface, and then collected in a sample bag using sterilized sanitary gloves. After the same operation, each sample was rinsed for 5 seconds using sterilized sanitary gloves and sterilized distilled water, and then collected in a sample bag. The number of bacteria detected in non-washing candies was 41 CFU/g at outdoor and the number of bacteria detected in non-washing chocolate was 76 CFU/g at outdoor. The number of bacteria detected in non-washing jellies was 79 CFU/g at outdoor. Coliform group was not detected in all samples. This showed good results at the level of m = 10,000 or less, which is an allowable value suggested in the Food Code. Also, effect of washing on contaminated food was confirmed. This result is remarkably low compared with the microorganism specimens shown in Food Code, and it is confirmed that contamination occurs but not high value. Therefore, the myth of the 3-second rule is true compared to the figures based on Food Code. However, it showed the characteristics of bacteria that could survive and cross-contaminate on dry food surfaces and emphasized the importance of hygiene through food contact to unsanitary surfaces to minimize the risk of food poisoning.