• 한국정밀공학회지
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• 제21권1호
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• pp.181-188
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• 2004

Structural analysis for materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. For the homogenization process, a unit cell is defined and loaded somehow, and its response is investigated to evaluate the properties. The imposed loading conditions should accord to the behavior of unit cell immersed in the macroscopic structure in order to guarantee the accuracy of the effective properties. Each unit cell shows periodic variation of strain if the material is loaded uniformly, and in this study, direct implementation of this characteristic behavior is attempted on FE models of unit cell. Conventional finite element analysis tool can be used without any modification, and the boundary of unit cell is constrained in a way that the periodicity is satisfied. The proposed method is applicable to skew arrayed in-homogeneity problems. The flexibility matrix relating tonsorial stress and strain components in skewed rectilinear coordinate system is transformed so that the required engineering constants can be evaluated. Effective properties are computed for the materials with square and skew arrayed circular holes, and its accuracy is examined.

• 한국수학교육학회지시리즈A:수학교육
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• 제50권3호
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• pp.355-365
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• 2011

The purpose of this study is to provide mathematical knowledge for supporting the didactical knowledge on circular measure and radian in the high school curriculum. We show that circular measure related to arcs can be mathematically justified as an angular measure and radian is a well defined concept to be able to reconcile the values of trigonometric functions and ones of circular functions, which are real variable functions. Radian has two-fold intrinsic attributes of angular measure and arc measure on the unit circle, in particular, the latter property plays a very important role in simplifying the trigonometric derivatives. To improve students's low academic achievement in trigonometry section, the useful advantage and the background over the introduction of radian should be preferentially taught and recognized to students. We suggest some teaching plans to practice in the class of elementary and middle school for enhancing teachers' and students' understanding of radian.

• 한국전자파학회논문지
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• 제26권8호
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• pp.730-739
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• 2015

본 논문에서는 6~18 GHz 주파수 범위의 미앤더선로로 구성된 다층 구조의 광대역 원편파 편파기를 설계 및 제작하였다. 미앤더선로-유전체-스페이서의 단위 구성요소에 대한 전송행렬을 경계값 해를 적용하여 제시하였다. 또한, 도파관 모델이 적용되도록 미앤더선로의 배열 구조와 함께 미앤더선로의 등가 서셉턴스를 HFSS 전자기장 해석방법으로 계산하는 방법을 제안하였다. 전자기장 해석방법과 전송행렬을 연동한 하이브리드 방법과 반복 수행법을 이용하여 광대역, 낮은 삽입손실, 낮은 축비 특성을 갖는 다층 구조의 미앤더선로 원편파 편파기를 설계하였다. 제작된 편파기는 동작주파수의 92 % 대역에서 -10 dB 이하의 반사손실과 평균 -0.24 dB의 삽입손실 및 평균 2.6 dB 이하의 축비 특성으로 설계값과 잘 일치함을 확인하였다.

• 한국공작기계학회논문집
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• 제13권5호
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• pp.1-6
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• 2004

Measurements of circular motion accuracy of NC lathe have achieved with ball bar systems proposed by Bryan, but the ball bar systems have ifluenced on the measuring data by way of the accuracy of the balls and the contacts of balls and bar seats. Therefore in this study, error data during of circular motion of ATC(Automatic Tool Changer) of NC lathe will be acquired by reading zx plane coordinates using two optical linear scales. Two optical linear scales of measuring unit are fixed on z-x plane of NC lathe, and the moving part is fixed to ATC and then is made to receive data of coordinates of the ATC at constant time intervals using tick pulses comming out from computer. And then, error data files of radial direction of circular motion are calculated with the data read, and the aspect of circular motion are modeled to plots, and are analysed by means of statistical treatments of circularity, means, standard deviations etc.

• 한국전자파학회논문지
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• 제22권10호
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• pp.999-1004
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• 2011

본 논문에서는 무선 전력 전송 시스템에서 널리 사용되는 원형 코일 사이의 상호 인덕턴스 계산 방법과 이를 이용한 해석 결과를 제시한다. 두 원형 코일은 수직으로 배열되었다. 상호 인덕턴스 계산을 위해 수직 배열된 수전부 원형 코일의 면적을 일정한 높이의 단위 셀로 나누고, 각 단위 셀에 쇄교하는 자속 밀도를 구하여 상호인덕턴스를 계산하였다. 이를 위해 두 원형 코일을 필라멘트 코일로 모델링하였고, 각 코일에서의 전류는 균일 하다고 하였다. 검증을 위해 헬리컬, 스파이럴 형태로 두 원형 코일을 제작하였고, z 방향의 간격이 50~100 cm인 구간에서 상호 인덕턴스를 측정한 결과, 본 논문에서 제시한 이론값과 일치하였다.

• 대한수학회지
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• 제38권3호
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• pp.623-631
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• 2001

Let $\kappa$ be a real abelian field of conductor f and $\kappa$(sub)$\infty$ = ∪(sub)n$\geq$0$\kappa$(sub)n be its Z(sub)p-extension for an odd prime p such that płf$\phi$(f). he aim of this paper is ot compute the cohomology groups of circular units. For m>n$\geq$0, let G(sub)m,n be the Galois group Gal($\kappa$(sub)m/$\kappa$(sub)n) and C(sub)m be the group of circular units of $\kappa$(sub)m. Let l be the number of prime ideals of $\kappa$ above p. Then, for mm>n$\geq$0, we have (1) C(sub)m(sup)G(sub)m,n = C(sub)n, (2) H(sup)i(G(sub)m,n, C(sub)m) = (Z/p(sup)m-n Z)(sup)l-1 if i is even, (3) H(sup)i(G(sub)m,n, C(sub)m) = (Z/P(sup)m-n Z)(sup l) if i is odd (※Equations, See Full-text).

• 소음진동
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• 제4권3호
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• pp.337-343
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• 1994

A method of the leak detection from the pipe system by using accelerometer is proposed. The signal detected from accelerometer is proved experimentally to be a dispersive wave. Based on the experiments, a method using the narrow band pass filter and the unit impulse response function is analyzed. The method uses the characteristics of the unit impulse response function, that the function is available evenin the narrow band signal because, unlike the cross correlation, it is normalized by the auto spectrum. The accelerometer is quite easier to use than the hydrophone in adapting to the pipe system.

• 연구논문집
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• 통권24호
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• pp.49-61
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• 1994

In this paper, the experimental unit of the cross inductive radio line and two linear induction motors driven by IGBT inverter for train control was made. In actual condition, the track has straight line, but so as to be able to achieve in small space, the unit prepared was shaped into two circular plates. Then by detecting inductive signal, the position data could be obtained. Also the equipment representing speed and thrust of LIM and train position by means of the experimantal unit could be composed.

• 대한기계학회논문집A
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• 제27권7호
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• pp.1071-1075
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• 2003

In this paper, we present a DNA manipulation device in the reaction chamber, which consists of a center electrode and circular outer electrodes of a reaction unit. The charged bio-molecules, DNA, are manipulated by the charge of the electrode in reaction unit. Controlling the induced dynamic electric field between the center electrode and the outer electrodes, concentration / repulsion / manipulation of bio-molecules are enabled at a periphery of electrode. Concentration of the fluorescent DNA at the center electrode is observed by applying ＋2V. Subsequently, applying －2V, the concentrated DNA is repelled rapidly from the center electrode, which makes dispersion completely in 0.5second. Furthermore, repeated applying ＋1V/－1V every 5 seconds at each outer electrode, we can circulate the DNA. We also investigate a micro-heater and sensor for DNA manipulation and reaction temperature. The coefficient of heat-resistance and heater temperature characteristic is 0.0043 and 100$^{\circ}C$/sec, respectively.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.650-654
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• 1995

In this study, in order to measure energy-absorbing charactistics in collapse test of CFRP thin-walled laminates and interpretate the cause of decreasing age when collapse test is carried out under the environments of high temperatures and hygrothermals, the moisture absorbing behavior according to the variety of orientation angel is observed and collapse characteristics is compared with the influence of high temperatures and hygrothermals. Especially, we supposed to clearly understand reationship between collapse characteristics in proportion to the variety of orientation angel and moisture absorbing. The value of the maximum loading, mean loading,rate of energy absorption energy per unit volume and mass in CFRP thin-walled laminates on the high temperatures and hygrothermals is measured lower than under no moisture absorbing. The maximum collapse loading in dynamic impact test is taken measurement lower than in static collapse test regarding compared with collapse characteristics conformity with the variety of the CFRP circular laminates in high temperatures and hygrothermals. But the absorbed energy per unit mass and volume is almost same and the biggest amount of energy is shown in the CFRP circular laminates with orientation angel of 15 .deg.. Therefore, in the case of use to CFRP circular laminates with axisymmetric mode, CFRP thin-walled structal members with orientation angel of 10 .deg. , 15 . deg. are generally useful.