• Transactions of the Korean Society of Mechanical Engineers
• /
• v.7 no.4
• /
• pp.386-391
• /
• 1983

Two-dimensional slow viscous flow due to a stokeslet near a slit is investigated on the basis of Stokes approximation. Velocity fields and stream function are obtained in closed forms by finding two sectionally holomorphic functions which are determined by reducing the problem to Riemann-Hilbert problems. The force exerted on a small cylinder is calculated for the arbitrary position of the cylinder translating in an arbitrary direction. The features of fluid flow are also investigated.

• International Journal of Safety
• /
• v.6 no.2
• /
• pp.13-16
• /
• 2007

This study focuses on the trends and issues of improving safety management of elevators in Korea. Frequency and severity of accidents in relation to conditional pass in periodic inspection, maintenance, market surveillance are analyzed based on the statistical data and social cost due to a variety of related fields in managing elevator safety was estimated first. The results of statistical analysis performed in this study will provide logical basis and future direction for improving the safety management system. The role of certification and supervision is particularly addressed to reduce the related accidents and the social cost. The effectiveness of such procedures can be found from the results of simple statistical analysis.

• Proceedings of the Korea Inteligent Information System Society Conference
• /
• 2000.04a
• /
• pp.365-373
• /
• 2000

Data Envelopment Analysis (DEA), a non-parametric productivity analysis tool, has become an accepted approach for assessing efficiency in a wide range of fields. Despite of its extensive applications and merits, some features of DEA remain bothersome. DEA offers no guideline about to which direction relatively inefficient DMUs improve since a reference set of an inefficient DMU, several efficient DMUs, hardly provides a stepwise path for improving the efficiency of the inefficient DMU.In this paper, we aim to show that DEA can be used to evaluate the efficiency of life insurance companies while overcoming its limitation with the aids of machine learning methods.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.5-6
• /
• 2010

In this study, assuming that there is a diagonal uniaxial compression field in combination with triangular homogeneous stress fields in the cracked concrete wall and a tensile stress of a steel plate occurs in the perpendicular to the direction of the diagonal compression field, an ultimate shear strength of a slender composite shear wall is estimated.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.643-645
• /
• 2008

To obtain weight reduction and high performance, level set based topology optimization in magnetic fields is promising for the design of magnetic devices where the precise boundary shape and topological chanages are required. Level set function is introduced to represent ferromagnetic material boundaries and material properties of the magnetic reluctivity are determined. The optimization problem is formulated for maximizing the actuating force in a prescribed direction under limited usage of ferromagnetic material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.730-734
• /
• 2003

A beamforming method is a kind of spatial filter that focus the amy's signal capturing abilities in a desired direction. In this paper, we detect the location of a source under reflective condition using the multi-dimensional MUSIC algorithm then, we can iud the image source locations from the experimental geometry, and we reconstruct the partial fields for direct wave and reflected wave by using Adaptive nulling algorithm. Numerical simulations are performed to verify its performance under various conditions.

• Journal of Technology Innovation
• /
• v.10 no.1
• /
• pp.83-97
• /
• 2002

With the limited resources the proper distribution of the national R&D investment is very crucial to improving the national competence. This crucial decision should be based on the priorities which are driven with the consideration about the relative importance among the scientific technology fields. Such priorities can be useful in planning the national R&D investment and in determining the direction of the national R&D investment policy. In this paper, we used the AHP in order to drive systematically and scientifically the priorities of the major science and technology areas in the national R&D investment, and also analyzed the evaluation differences among the expert groups.

• Journal of Educational Research in Mathematics
• /
• v.9 no.1
• /
• pp.239-244
• /
• 1999

This study aims to present the necessity of 'mathematics for teacher' and advices for enhancing professionalism of mathematics teacher. Many mathematics teachers don't know formula giving roots of cubic and quartic equation which is presented as a example of mathematics for teacher, but they feel the necessity of professional knowledge like mathematics for teacher. As the role of mathematics teachers changes, professionalism in various fields is required. That is, they must be equipped with the belief and attitude as a professional and understand the content of mathematics for teacher and mathematics education theory. After all, loaming mathematics depends on the quality of mathematics teacher.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.10
• /
• pp.1166-1172
• /
• 2012

In this paper, by using a commercial EM simulator, we could obtain the array manifold which are phase responses of an array antenna for the incident plane wave and then verified the effectiveness of methodology after comparing with the measurement. The result shows that the array manifold can be calculated including not only the phase response of the ideal point sources but also the influences of the mutual coupling between antennas and the installed platform. Also it can exclude the interference of strong broadcasting signal and the disturbance of the multipath in the calibration process. Finally, to predict the performances of direction finding systems, a novel method using both the EM simulation-based receiving signal and the sparsely sampled array manifold with the parabolic estimation is proposed. This method can be utilized in the various fields of direction-finding since it shows the superior predictive performance even in low SNR conditions.

• Journal of Korea Water Resources Association
• /
• v.54 no.11
• /
• pp.933-942
• /
• 2021

The surface image velocimetry was developed to measure river flow velocity safely and effectively in flood season. There are a couple of methods in the surface image velocimetry. Among them the spatio-temporal image velocimetry is in the spotlight, since it can estimate mean velocity for a period of time. For the spatio-temporal image velocimetry analyzes a series of images all at once, it can reduce analyzing time so much. It, however, has a little drawback to find out the main flow direction. If the direction of spatio-temporal image does not coincide to the main flow direction, it may cause singnificant error in velocity. The present study aims to propose a new method to find out the main flow direction by using a fast Fourier transform(FFT) to a spatio-temporal (image) volume, which were constructed by accumulating the river surface images along the time direction. The method consists of two steps; the first step for finding main flow direction in space image and the second step for calculating the velocity magnitude in main flow direction in spatio-temporal image. In the first step a time-accumulated image was made from the spatio-temporal volume along the time direction. We analyzed this time-accumulated image by using FFT and figured out the main flow direction from the transformed image. Then a spatio-temporal image in main flow direction was extracted from the spatio-temporal volume. Once again, the spatio-temporal image was analyzed by FFT and velocity magnitudes were calculated from the transformed image. The proposed method was applied to a series of artificial images for error analysis. It was shown that the proposed method could analyze two-dimensional flow field with fairly good accuracy.