• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.9
• /
• pp.819-825
• /
• 2007

Vibration characteristics of an duel-cooling cylindrical fuel rod, which was proposed as a candidate design of fuel's cross section for the ultra-high burnup nuclear fuel, according to the cross-sectional dimensions and the number of supports or the span length were analytically studied. Finite element(FE) modeling for the annular cross sectional fuel was based on the methodology, that have been proven by the test verification, for the conventional PWR nuclear fuel rod. A commercial FEA code, ABAQUS, was used for the FE modeling and analysis. A planar beam element (B21) that uses a linear interpolation was used for the fuel rod and a linear spring element for the spring and dimple of the SG. Natural frequencies and mode shape were calculated according to the preliminary design candidates for the fuel's cross sectional dimension and the number of span. From the analysis results, the design scheme of the annular fuel compatible to the present PWR nuclear reactor core was discussed in terms of the number of supports and fuel's cross section.

• International Journal of Precision Engineering and Manufacturing
• /
• v.5 no.1
• /
• pp.36-41
• /
• 2004

The blanking of thin sheet metal using progressive dies is an important process on production of precision electronic machine parts such as IC leadframe. This paper summarizes the results of simulating the progressive blanking process by means of LS/DYNA. In order to verify the influence of blanking order on the final lead profile and deformed configuration, simulation technique has been proposed and analyzed using a commercial FEM code, LS/DYNA. The results of FE-simulations are in good agreement with the experimental result. After then, to construct rule base in progressive blanking process, FE-simulation has been performed using a simple model. Based on this result rule base is set up and then the blanking order of inner lead is rearranged. Consequently, from the results of FE-simulation using suggested method in this paper, it is possible to predict the shift of lead to manufacture high precision lead frame in progressive blanking process. The proposed method can give more systematic and economically feasible means for designing progressive blanking process.

• Transactions of Materials Processing
• /
• v.16 no.3 s.93
• /
• pp.172-177
• /
• 2007

The process design for large-scale ring rolling of Ti-6Al-4V alloy was performed by calculation method, processing map approach and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was used to make geometry design such as initial billet and blank sizes, and final rolled ring shape. A commercial FEM code, SHAPE-RR was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling and the formation of over-heating above $\beta$-transus temperature due to deformation heating, the process-map approach based on Ziegler's instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler's instability map and FEM simulation results.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.08a
• /
• pp.144-151
• /
• 2003

Computations of the mean and turbulence flows over three-dimensional hill of conical shape have implemented. Beside the standard $\kappa-\epsilon$, two other modifications proposed by Detering & Etling and Duynkerke for atmospheric applications were also considered. These predictions were compared with the data of a wind tunnel experiment. From the comparison, it was concluded that all three models predict the mean flow velocities equally well while only the Duynkerke's model accurately predicts the turbulence data statistics. It also concluded that there are large discrepancies between model predictions and the measurements near the ground surface. The flow field, which was obtained by using the Duynkerke's modification, was used to simulate gas dispersion from an upwind source. The calculation results are verified based on the measurement data. Modifications of the turbulent Schmidt number were carried out in order to match the measured results. The code was used to investigate the influence of the recirculation zone behind a building of cubical shape on the transport and dispersion of pollutant. For a stack behind and near the obstacle, some conclusions about the effect of the stack height and stack location were derive

• Journal of Korean Medical classics
• /
• v.32 no.1
• /
• pp.105-116
• /
• 2019

Objectives : There are many secluded Chinese characters - so called Byeokja (僻字) in ancient classic literature, and Chinese characters that are not registered in Unicode and Variant characters (heterogeneous characters) that cannot be found in the current font sets often appear. In order to register all possible Chinese characters including such characters as units of information exchange, this study attempts to propose a method to encode the morphological information of Chinese characters according to certain rules. Methods : This study suggests the methods to encode the connection between the nodules constituting the Chinese character and the coordinates of the nodules. In addition to that, rules for expressing information about curves, expressions of aspect ratios of characters, rules for minimizing coordinate lines, and rules for expressing aggregation status of character components are added. Results : Through the proposed method, it is possible to generate codes of a certain length by extracting only information expressing the morphological configuration of characters. Conclusions : The method of character encoding proposed in this study can be used to distinguish variant characters with small variations in Byeokja, new Chinese characters and character strokes and to store and search them.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.291-293
• /
• 2002

Accurate dose calculation in radiation treatment planning is most important for successful treatment. Since human body is composed of various materials and not an ideal shape, it is not easy to calculate the accurate effective dose in the patients. Many methods have been proposed to solve the inhomogeneity and surface contour problems. Monte Carlo simulations are regarded as the most accurate method, but it is not appropriate for routine planning because it takes so much time. Pencil beam kernel based convolution/superposition methods were also proposed to correct those effects. Nowadays, many commercial treatment planning systems, including Pinnacle and Helax-TMS, have adopted this algorithm as a dose calculation engine. The purpose of this study is to verify the accuracy of the dose calculated from pencil beam kernel based treatment planning system Helax-TMS comparing to Monte Carlo simulations and measurements especially in inhomogeneous region. Home-made inhomogeneous phantom, Helax-TMS ver. 6.0 and Monte Carlo code BEAMnrc and DOSXYZnrc were used in this study. Dose calculation results from TPS and Monte Carlo simulation were verified by measurements. In homogeneous media, the accuracy was acceptable but in inhomogeneous media, the errors were more significant.

• Fashion & Textile Research Journal
• /
• v.22 no.5
• /
• pp.617-627
• /
• 2020

This study investigates the apparel sizing communication presented in online retail websites focusing on women's ready-to-wear tailored jackets and to analyze the meaning of these information as the actual product size guide factor. A total of 34 retail websites were selected based on the highest growth fashion companies list and the best fashion brands list. We collected size information in two types: size specifications including sizing code, body measurements, garment measurements, and size references including customized size guide tools, size information in customer reviews, model size information, and others. Most websites prefer to present garment measurements rather than body measurements that are recommended notations under Korean standards and related regulations. In addition, there was the absence of consistency in presenting measurements list and terms that can confuse consumers in size communication. This study found that the stature measurement was a key factor in size reference despite that it did not represent a proper garment size. The obsolete Korean numbering sizing code such as '55 and '66 was still used in many ways such as idiomatic expressions for body shape. It also implied that we can take advantage of the old sizing code for accessible size information. The finding of this study gives an in-depth diagnosis of current online sizing information problems and suggests useful basic data for developing online apparel size standards and marketing strategies.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.1
• /
• pp.15-23
• /
• 2008

In this study, modeling shear characteristics of a coarse material mainly containing crushed stones were implemented using PFC2D, a commercially available code based on DEM(Discrete Element Method). Using the DEM code, this study provides the methodology considering the shear characteristics due to a irregular grain shape, GSD(Grain Size Distribution) and porosity of coarse material which are not effectively incorporated in conventional continuum numerical codes. Direct shear test was simulated for the GSD and porosity generated sample using the code and the simulated results showed very good agreement with the laboratory test results. The current modeling approach can be applied to other coarse materials having various GSD and porosities. Using such application, prediction of the strength characteristics of coarse material in field scale would be possible, which is limited in laboratory scale so far.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.75.2-76
• /
• 2021

MESSIER is a science satellite project to observe the Low Surface Brightness (LSB) sky at UV and optical wavelengths. The wide-field, optical system of MESSIER is optimized minimizing optical aberrations through the use of a Linear Astigmatism Free - Three Mirror System (LAF-TMS) combined with freeform mirrors. One of the key factors in observations of the LSB is the shape and spatial variability of the Point Spread Function (PSF) produced by scatterings and diffraction effects within the optical system and beyond (baffle). To assess the various factors affecting the PSF in this design, we use PhoSim, the Photon simulator, which is a fast photon Monte Carlo code designed to include all these effects, and also atmospheric effects (for ground-based telescopes) and phenomena occurring inside of the sensor. PhoSim provides very realistic simulations results and is suitable for simulations of very weak signals. Before the application to the MESSIER optics system, PhoSim had not been validated for confocal off-axis reflective optics (LAF-TMS). As a verification study for the LAF-TMS design, we apply Phosim sequentially. First, we use a single parabolic mirror system and compare the PSF results of the central field with the results from Zemax, CODE V, and the theoretical Airy pattern. We then test a confocal off-axis Cassegrain system and check PhoSim through cross-validation with CODE V. At the same time, we describe the shapes of the freeform mirrors with XY and Zernike polynomials. Finally, we will analyze the LAF-TMS design for the MESSIER optical system.

• Journal of Engineering Education Research
• /
• v.19 no.2
• /
• pp.60-69
• /
• 2016

This paper deals with the selection method of effective engineering design problem based on LEGO Mindstorm NXT for basic design education. By YouTube case study of various LEGO-based engineering designs for olympic sports, performance criteria have been developed including programming complexity, structural complexity, sensor/actuator complexity and variety of game operation. Programming complexity includes range of programming code length and possible program variety. Structural complexity includes variety of structural elements such as length, shape, weight, and volume to overcome design restrictions. Sensor/actuator complexity includes variety of sensor used and number of possible actuator assemblies. Variety of game operation includes game complexity and required creativity to make LEGO robots. Based on these performance criteria, four representative sports were selected as the candidates for effective engineering design problem. Finally, feasibility and attributes of each candidate were verified by real implementation examples.