• Coupled systems mechanics
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• v.7 no.3
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• pp.353-371
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• 2018

The Wavenumber or more accurately Wavenumber-FD approach was initially introduced for two-dimensional dynamic analysis of concrete gravity dam-reservoir systems. The technique was formulated in the context of pure finite element programming in frequency domain. Later on, a variation of the method was proposed which was referred to as Wavenumber-TD approach suitable for time domain type of analysis. Recently, it is also shown that Wavenumber-FD approach may be applied for three-dimensional dynamic analysis of concrete arch dam-reservoir systems. In the present study, application of its variation (i.e., Wavenumber-TD approach) is investigated for three-dimensional problems. The method is initially described. Subsequently, the response of idealized Morrow Point arch dam-reservoir system is obtained by this method and its special cases (i.e., two other well-known absorbing conditions) for time harmonic excitation in stream direction. All results for various considered cases are compared against the exact response for models with different values of normalized reservoir length and reservoir base/sidewalls absorptive conditions.

• International Journal of Contents
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• v.3 no.2
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• pp.25-29
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• 2007

In this paper, we discuss the mesh segmentation problem which divides a given 3D mesh into several disjoint sets. To solve the problem, we propose a greedy method based on the merging priority metric defined for representing the geometric properties of meaningful parts. The proposed priority metric is a weighted function using five geometric parameters, those are, a distribution of Gaussian map, boundary path concavity, boundary path length, cardinality, and segmentation resolution. In special, we can control by setting up the weight values of the proposed geometric parameters to obtain visually better mesh segmentation. Finally, we carry out an experiment on several 3D mesh models using the proposed methods and visualize the results.

• Proceedings of the Korean Society of Rural Planning Conference
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• 1998.03a
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• pp.17-20
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• 1998

For efficient development of rural facilities, 4 step optimum locational decision model was developed using agricultural-cum-industrial complex as a representative one ; formulation of locational goal system, ranking tabulation on components, determination of their significance values, calculation of their scores. The application results of the model to 3 typical case study areas(peri-urban flat, mountainous, coastal areas) showed relatively good representation of their areal characteristics.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.11
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• pp.1752-1758
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• 1989

For many different types of apertures the diffraction phenomenon on the electromagnetic wave is analyzed by unsing Kirchhoff and Fresnel's diffraction theory. The signal intensity in variation of aperture's parameters is numerically calculated by a computer. To obtain the experimental data many types of apertures were made on an acryl board on which a special materical Elecoat was painted for preventing some reflections on the board surface and transmissions through it. Two Yagi antennas were used for a transmitting and receiving antenna and the frequency was 820MHz. The theoretichal values agreed reasonably with experimental data and these results will be used for a system design in the mobile communication between many buildings in the middle of a city.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.80.4-80
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• 2002

Performance of the previously proposed 2D-image reconstruction method for soft tissues in x-ray computed tomography is evaluated thoroughly through numerical experiments with 4 assumed absorption rates of different symmetries under practical conditions, and the following special features are made clear: It is quite precise, especially at points where the object taking larger values; about two orders less magnitude errors than the conventional most precise method when no noise existing, without any 1D- or 2D-interpolation. In spite of its high sensitivity to the noises, it is even more precise by about 8dB than the latter, to relative pojection data noise power of 5%.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.389-392
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• 2000

Gouge-free tool-path generation is an important issue in mold & die machining and researches on cutter interference avoidance can be found in many articles. One of the various methods is construction of tool-offlet surface or cutter-location (CL) surface on which the cutter-center point (CL-point) locates. Provided that the CL surface is represented in a suitable form, cutter-interference avoidance can be performed without the burden of computing CL data for every cutter-contact (CC) point. In the paper, various methods of constructing a CL surface in the z-map form are presented, where z-map is a special form of discrete nonparametric representation in which the height values at grid points on the xy-plane are stored as a 2D array z［i,j］.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.3
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• pp.59-69
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• 1985

The purpose of this paper is to investigate the variations of out-of- roundness due to its assessment methods for the practical workpieces. Experiments were carried out with the test specimens having the typical roundness profile. The roundness measuring system which has the autocentripetal functions and the automatic centering table unit was used. From the experimental results, it was found that the ratio of LSC to MZC values varied with the shape of roundness profiles, and the rate of variation for out-of-roundness was increased logarithmically with the increment of undulations by the effect of filter. Therefore, it is suggested that the least squares center method should be useful with the sufficient accuracy except for some special cases in the roundness profiles, and the condition of filter has considerable influence upon the out-of-roundness to be measured.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.193-196
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• 2002

The relativistic theory has not been properly taken up by the marine hydrodynamicists. To take on a relativistic view, we confine ourselves to a simple vector case of a wave train in spacetime, to be shown to represent a sound wave or a surface wave, and bring in an observer who is travelling on another platform. We are interested in relative position of each event on these two worldlines. It, then, will be shown that the velocity, the acceleration, the encounter frequency, the group velocity, and the time and the space distance between the wave and the observer on the worldlines should all be derivable in principle. This is interpreted to mean that we really have the relativistic events taking place with different values of time dilation in the sense of 'spacetime', and that the well-known ${\lceil}special Theory of Relativity{\rfloor}$ applies just as well in hydrodynamic waves.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.741-745
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• 2001

The necessity of a Z-shape heat pipe may occur in a special application such as a cooling module for an electronic equipment having a limited accessible space. Either of the two end part works as evaporator or condenser and the length of the middle part is 200mm. The heat pipe was made of 3/8 inch copper tube having 60 spiral groove with screw angle of 10 degrees. Water and acetone were used as working fluids. The fill charge ratio of the working fluid was varied for different values of thermal loads. The thermal resistance was calculated based on the temperature measurements along the heat pipe axis. The maximum thermal loads were 80W for water and 100W for acetone heat pipe. The optimum fill charge ratio was identified through a series of experiments.

• Steel and Composite Structures
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• v.7 no.3
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• pp.185-200
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• 2007

Tubular construction is widely used in a range of civil and structural engineering applications. To date, the principal product range has comprised square, rectangular and circular hollow sections. However, hot-rolled structural steel elliptical hollow sections have been recently introduced and offer further choice to engineers and architects. Currently though, a lack of fundamental structural performance data and verified structural design guidance is inhibiting uptake. Of fundamental importance to structural metallic design is the concept of cross-section classification. This paper proposes slenderness parameters and a system of cross-section classification limits for elliptical hollow sections, developed on the basis of laboratory tests and numerical simulations. Four classes of cross-sections, namely Class 1 to 4 have been defined with limiting slenderness values. For the special case of elliptical hollow sections with an aspect ratio of unity, consistency with the slenderness limits for circular hollow sections in Eurocode 3 has been achieved. The proposed system of cross-section classification underpins the development of further design guidance for elliptical hollow sections.