• The Pure and Applied Mathematics
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• v.12 no.4 s.30
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• pp.275-287
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• 2005

Geometric invariants are basic tools for geometric processing and computer vision. In this paper, we give a linear approximation for the differentiation of the binormal vector field of a space curve by using the forward and backward differences of discrete binormal vectors. Two kind of discrete torsion, say, back-ward torsion $T_b$ and forward torsion $T_f$ can be defined by the dot product of the (backward and forward) discrete differentiation of binormal vectors that are linear approximations of torsion. Using Frenet formula and Taylor series expansion, we give error estimations for the discrete torsions. We also give numerical tests for a curve. Notably the average of $T_b$ and $T_f$ looks more stable in errors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.570-577
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• 2002

Charged liquid particle's behavior in electric and flow field was simulated to define the effect of electric field on the contact area and its dispersion. For the simulation of flow and electric field finite volume method was applied. To find out the particle's moving path in that field lagrangian equation of motion was solved by Runge-Kutta methods. We assumed that the particle was charged 10% of Rayleigh limit while the particle passing through the electrode and the particle does not have an effect on the electric field. In case of 30[Kv] of voltage charging the particles injected from the central 60% of the nozzle injection area adhere to the grounded moving plate and no dispersion occurred. Increasing the charged voltage to 40[Kv], it brought about the same phenomena as that of 30[Kv] charging except the dispersion. Voltage increasing from 30[Kv] to 40 [Kv] caused higher Coulomb force acts on the particle and it made the particle dispersion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1165-1174
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• 2001

The objective of this study is to understand the generation mechanism of sound and to develop a prediction method for the acoustic pressure field of a centrifugal fan. If the fan is operating at the free field without the casing, the acoustic analogy is a good method to predict the acoustic of the fan. But, the casing gives a dominant effect to the radiated sound field and the scattering effect of casing should be considered. So, in this paper the Kirchhoff-BEM is developed, which can consider the scattering effect of the rigid body. In order to consider the scattering and diffraction effects owing to the casing, BEM is introduced. The source of BEM is newly developed, so the sound field of the centrifugal fan can be obtained. In order to compare the predicted one with experimental data, a centrifugal impeller and a wedge are used in the numerical calculation and the results are compared with the experimental data. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal sound. The radiated acoustic field shows the diffraction and scattering effects of the wedge clearly.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.05a
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• pp.54-55
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• 2000

• Journal of the Korean Magnetics Society
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• v.8 no.1
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• pp.13-20
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• 1998

The crystallographic and high frequency characteristics of $Fe_{73.9}Cu_{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$ soft magnetic alloys were investigated under the magnetic field annealing. As-cast ribbon with which already imbedded nanocrystalline Fe-Si phase on the surface have a preferred orientation with (400) plane to surface and also with the [011] direction parallel to the ribbon length. The extra nanocrystalline Fe-Si phase appeared throughout at 45$0^{\circ}C$ in samples with or without the longitudinal magnetic field. However the formation of nanocrystalline phase does not appear on the suface layer until 50$0^{\circ}C$ annealing temperature under the transverse field. The cryststallization fraction of annealed samples with longitudinal magnetic field is higher than that of samples without magnetic field. When the transverse magnetic field is applied, the crystallization fraction does not increases but decreases until 50$0^{\circ}C$. However the crystallization of internal regions can be confirmed by X-ray diffraction measurement via tilting the sample. It was found that for all samples, the saturation induction were all same with 1.3 T. The coercive field of as-cast sample was 1.06 A/cm, but in annealed samples it decrease from 0.56 to 0.1 A/cm with increasing annealing temperature from 400 and 55$0^{\circ}C$, respectively. The squareness of annealed samples under transverse magnetic field has a small value than that of both without field and with longitudinal field annealing.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.79-88
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• 2008

In this study electromagnetic fields near electric power lines were derived by dipole antenna theory and electromagnetic fields near 3 phase power lines with vertical configurations were formulated and could be computed easily using these formula. It seems that those formula could be applicable to the consideration of electromagnetic fields during the design of transmission and distribution lines. Those formulated equations on elements of electromagnetic fields were applied to the model of a transmission-line system and were calculated by Matlab programs. The calculation results are follows. For variation of horizontal distance profiles of $E_y$ and $B_z$ are same each other, and also those of $B_y$ and $E_z$ are same each other. This means that coupled elements of E and B are perpendicular each other and have the propagation direction of the right-hand system such as $x{\rightarrow}E_y{\rightarrow}B_z$. Resultant electric field E is dominated by the element $E_y$ and resultant magnetic field B is dominated by the element $B_z$.

• The Journal of Internal Korean Medicine
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• v.42 no.5
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• pp.1035-1044
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• 2021

Objective: This study investigated two cases of Korean medical treatment for visual field impairment after stroke: Case 1, a 56-year-old male with a posterior cerebral artery infarction and right homonymous hemianopsia, and Case 2, a 46-year-old male with an intracerebral hemorrhage in the left parietal lobe and right homonymous hemianopsia. Methods: Case 1 was treated with acupuncture, electroacupuncture, and herbal medicine (Mangeum-tang) for two months, and Case 2 was treated with acupuncture, electroacupuncture, and herbal medicine (Oryeong-san) for 40 days. Results: Following treatment, for Case 1, the Humphrey visual field test showed improvement. The visual field indexes (VFIs) for the left and right eyes improved from 44% to 55% and 49% to 64% respectively, and the mean deviations (MDs) for the left and right eyes improved from -21.11 dB to -19.91 dB and -17.45 dB to -13.89 dB, respectively. The mean visual sensitivities (MVSs) of the left and right eyes also improved from 8.67 dB to 11.33 dB and 1.67 dB to 9.67 dB, respectively, with no side effects. For Case 2, the VFI for the left eye improved from 36% to 64% and that for the right eye remained unchanged. The MDs for the left and right eyes also improved from -22.02 dB to -14.47dB and -22.11 dB to -21.34 dB, respectively, with no side effects. Conclusions: This study suggests that Korean medical treatment may improve visual impairment after stroke, but further research is needed.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2003.11a
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• pp.95-100
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• 2003

The purpose of this study is to evaluate the noise environment of one-room type multi-family housing around the campus. The field measurements on equivalent noise level of indoor and outdoor were carried out in 6 subject house units during the 26th${\sim}$28th of November 2002. The results are as follows. 1) Outdoor noise levels of 6 subject buildings were distributed 52.8${\sim}$65.3dB(A) and were inappropriate to the standard for environmental noise, 55dB(A). 2) Indoor noise level of 6 subject house units were measured 27.5${\sim}$63.5dB(A). These values were higher than the indoor noise standard (40dB(A)) except subject house D(average 37.6dB(A)). 3) It was found that the differences of indoor noise levels between subject house units were caused by resident's living factor, characteristics of window, and existence of balcony.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1879-1886
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• 2001

n a enclosed square cavity occurred B nard convection, the flow phenomena in the surrounding of the bubble attached at the upper cooled solid wall were studied by using a thermo-sensitive liquid-crystal tracer and image processing techniques. This method offers the advantage of measuring the entire flow field in a selected plane within the fluid at a given instant of time in contrast to point by point method like T/C. Quantitative data of the temperature were obtained by applying a colour-image-processing to the visualized image. As the flowing in a bubble, In a bubble size appears the flow phenomena which the direction of flow is reversed in the entire temperature and flow field. The observed phenomena are described with regard to the thermocapillary convection.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.10
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• pp.822-830
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• 1991

In this paper, we propose a new process for ultrasonic B-mode image considering the sound field effects of a concave circuit focused transducer, and aim to remove the speckle pattern which cause the blurring on boundary in ultrasonic B-mode image. We discuss in detail the conception of speckle pattern generation, and the frequency compounding method which is applied to the process for getting a speckle reduced B-mode image. Through the computer simulation, we define the meaning of speckle region, and show the results of reduced speckle pattern. It is discovered in the results that the frequency compounding method is very effective for boundary detection and that the application of the method is limited by various conditions.