• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.43-47
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• 2001

A program to design an axial flow fan, analyze the performance and predict the noise was developed. In order to develop the low noise fan, that program is compulsory. This software is composed of three parts : the geometric design module, the performance analysis module, the fan noise prediction module. In order to analyze the performance, three dimensional vortex panel method is used. The unsteady flow field was analyzed by time-marching free wake method. The unsteady force data is then used in predicting the noise. Farassat's equation is used to predict the noise of fan.

• Honam Mathematical Journal
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• v.30 no.4
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• pp.603-616
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• 2008

A generalized n-dimensional Riemannian manifold $X_n$ on which the differential geometric structure is imposed by the unified field tensor $^*g^{{\lambda}{\nu}}$, satisfying certain conditions, through the $^*g$-ME-connection which is both Einstein's equation and of the form(3.1) is called $^*g$-ME-manifold and we denote it by $^*g-MEX_n$. In this paper, we prove a necessary and sufficient condition for the existence of $^*g$-ME-connection and derive a surveyable tensorial representation of the $^*g$-ME-connection and the $^*g$-ME-vector in $^*g-MEX_n$.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.63-72
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• 2003

On the basis of sensor types, satellites can be classified by two types, which are optical observation satellite and radar observation satellite. A satellite type is selected according to the specific mission. Optical observation satellite is more appropriate for getting high geometric resolution images and radar observation satellite is more appropriate for getting images independent of weather condition the more a demand of satellite increases, the more an importance of information increases. Therefore, development trend and state of earth observation satellite are surveyed and described in this paper. In the future, domestic development of satellites will be planned considering trend of satellite technologies.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.20-23
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• 2002

In this paper, various tow parameters such as equivalent tow thickness, amplitude of longitudinal tow and tow intervals were investigated and compared with each other by using microscopic observation to find out the exact deformation patterns between both directions of the fabric structure (Longitudinal and Transverse Directions). Specimens for the observation were taken from draped helmet which is made of fabric composite (Five Harness Satin Weave). From the observation results, it was found that there are different deformation pattern between tow directions and effect of geometric condition on the deformation of the fabric materials during draping process was verified.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.339-343
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• 1992

For the analysis of dynamic behavior of dynamic behavior of multibody systems by cartesian coordinate method, maximal sets of generalized coordinates and maximum numbers of differential equation and constraints must be considered. Therefore the inefficiency of the increase of CPU time is occurred. This paper is to analyze the dynamic system by using the relative coordinate method without violating the geometric condition of systems. The graph theory and system topology were used for this study. The dynamic systems could be analyzed by the automatic generation of the informations like equation of motion, constraints, and external forces etc. And the results were compared and verified with dynamic commercial package DADS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.952-956
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• 1997

This paper describes the method that can expand the forming limit of T type forging products used in aircraft and automotive forged products. The forming limitis determined by the ratio of web thickness to rib width in T type and the reduction in height of workpiece and especially depends on the ratio of web thickness to rib width. For this method, the geometric condition that consists of triangle type was introduced and FEM simulations and model exoeriments were carried out and compared with each other. The objective of this paper is to give the method not only that sink mark and folding phenomenon are eliminated but also that the forming limit and the structural strength of rib and web is increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1426-1429
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• 2003

This paper describes screw tool design and machining method witch is able to design tool profile and 3-dimensional geometry for screws in self-wiping co-rotating twin screw extruder. The geometric features of screws for co-rotating twin screw extruders are developed from kinematic principles. Closely self-wiping screw segments are manufactured in universal milling machine by using designed screw tools. It is shown that experimental results verified the closely intermeshing condition in twin screw.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.56-63
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• 2004

The real-time NURBS interpolation method using 2-stage interpolation is studied. The 2-stage interpolation method that compensates for interpolation errors within machine BLU is proposed. The interpolation result was filtered by an Acceleration/Jerk limitation equation. Through this 2-stage interpolation, both the interpolation error condition and the motion kinematics could be satisfied. Using computer simulation in which interpolation results are evaluated by a numerical iteration method, it is shown that the 2-stage interpolation algerian could interpolate target curves precisely with geometric and dynamic contentment. The proposed algorithm was implemented in the CNC simulator system and an experimental un was conducted to identify the real-time adaptation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.41-47
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• 2004

This study is aimed to measure the deflection of loaded table on machine tool. The deflection rate is measured then the table is in a stationary state and is moved. In conclusion we have found that the more load increases, the more the table deflections. Also, we have found that the deflection rate increases in accordance with the speed of movement. Therefore, we have concluded that inspection of machine tool should be done considering the weight of load and the speed of movement. However, since the condition of accuracy test for domestic brand of machine tool is defined as unloaded case, measures should be explored only for loaded case.

• Journal of KSNVE
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• v.8 no.1
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• pp.187-194
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• 1998

In order to predict the train noise propagation from a level railroad, this paper presents the model of train noise source and the prediction model based on the results by using the sound intensity method. The prediction model gives the effects of geometric attenuation, ground attenuation, and barrier attenuation of noise. There are several principal assumption in developing model: (a) the train noise is primarily rolling noise; (b) the rail head and wheels are in good condition; (c) the height of source is 10cm above track; (d) the directivity pattern of train noise sources is a dipole source. Calculated results based on this model are compared with available field data and good agreement has been obtained.