• 대한수학회지
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• 제44권3호
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• pp.627-645
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• 2007

We investigate the eigenvalues of the semi-circulant preconditioned matrix for the finite difference scheme corresponding to the second-order elliptic operator with the variable coefficients given by $L_vu\;:=-{\Delta}u+a(x,\;y)u_x+b(x,\;y)u_y+d(x,\;y)u$, where a and b are continuously differentiable functions and d is a positive bounded function. The semi-circulant preconditioning operator $L_cu$ is constructed by using the leading term of $L_vu$ plus the constant reaction term such that $L_cu\;:=-{\Delta}u+d_cu$. Using the field of values arguments, we show that the eigenvalues of the preconditioned matrix are clustered at some number. Some numerical evidences are also provided.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.696-699
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. There systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.173-180
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• 1999

When Automobile runs high velocity, it causes sleepy velocity profile then that generates lift force and drag force. Lift force reduce tire friction force. Drag force increase consumed power. For improve automobile performance, reduction of Lift force and Drag force was seriously considered. It measured experimently using wind tunnel, numerically using numerical analysis. Finite difference method is using difference equation and simplifed mesh. This method require less calculation time and computer power than other method.

• 한국광학회지
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• 제4권4호
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• pp.493-495
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• 1993

횡자장하에서 Zeeman 분리된 두 편광성분의 맥놀이 주파수와 출력 차를 이용하여 내부 반사경형 633nm He-Ne 레이저의 주파수를 각각 안정화시켰다. 맥놀이 주파수를 이용할 경우 주파수안정도(square root Allan variance)와 주파수 온도계수는 $7.0{\times}10^{-11}$과 $170 kHz/^{\circ}C$였으며, 출력차이를 이용할 경우에는 $1.1{\times}10^{-9}$과 $1.8 MHz/^{\circ}C$였다. 이 결과로부터 두 편광성분의 맥놀이 주파수를 이용한 안정화 방법이 출력차의 방법보다 10배 이상의 우수한 주파수 안정화 특성을 갖고 있음을 알 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.956-959
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the common system is required. The common systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system solve these problem. In this paper the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave get orators are performed. The effect of transporting speed according to the change of weight and amplification voltage are verified. In addition, the system performance for actual use is evaluated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.34-36
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• 1998

In these days the hybrid interrupters are widely used for medium voltage class circuit breakers. In the design of the hybrid interrupter, the shape of the short-circuit ring is one of the most important design parameters. Recently the investigation into the phase difference between arc current and magnetic field due to the shape variation of the short circuit ring has been conducted. In this paper, the results of eddy current analyses in the hybrid interrupter and test result are presented.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.515-521
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• 1998

In this study the mixing process of two-phase flow which makes two jets existing vlocity difference are analyzed. The primary jet is jetted on the condition of the state mixed pulverized solid pariticle with air and the velocity in the secondary jet is changed into three kinds velocities(0.60, 75m/s) The velocity vector field concentration field and turbulent properties of solid particles are measured by using 3-Dimensional Particles Dynamics Analyzer. As the velocity of secondary jet increases the solid particle recirculation zone becomes larger. Also solid particle concentration gets dense due to velocity decrement of particles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.177-180
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• 1999

In this paper, we studied Surface Discharge Type Flat Fluorescent Lamp(FFL) with High Luminance for LCD Backlighting. This lamp is Surface Discharge Type structure with a pair of Sodalime glass, insulator layer, phosphor layer, and Xe gas gap. There are two influences of Electric field on different dielectric thickness. The Electric field difference at the dielectric layer itself enhances minimum value of firing voltage and luminance uniformity. So, we measured the Electric filed at 0.5mm, 1mm gap length and discharge voltage for difference dielectric layer thickness. In experiment result, the thicker dielectric layer has higher firing voltage and lower current.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.227-228
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• 2023

This study is tocompare and analyze the results of hydration heat analysis and on-field measurements using the method with hydration heat difference and insulation curing method for controlling hydration heat in mass concrete. As a result of the analysis, the temperature difference between the center and the surface was predicted very similarly, and the mass concrete surface was controlled to a safe level when evaluating with a temperature crack index, and after being finished, it was confirmed that there was no hydration crack.

• 대한가정학회지
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• 제43권4호
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• pp.161-172
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• 2005

The present study investigation the effect of a project approach program on children's cognitive styles. It examined closely the characteristics and processes of the project approach program to determine its impact on children's individual cognitive styles such as divergent thinking, field independence, and reflection. The subjects were 384-year-old children. Eighteen children were assigned to the experimental group and twenty to the control group. Pretest-treatment-posttest design was adopted for this study. Collected data were analyzed with SPSS Win 10.0 and processed statistically using average, standard deviation, and ANCOVA. For the children's divergent thinking, the children with the project approach program showed significant difference in fluency and flexibility, but no difference in originality and elaboration, compared to the children in the control group. Children with the project approach program showed more field independence than those in the control group. Children with the project approach program showed no difference in reflection. These results showed that the project approach pro!3ram partly influenced the children's cognitive styles.