• 충청수학회지
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• 제21권1호
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• pp.61-69
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• 2008

For a real subextension of some cyclotomic function field with a non-cyclic Galois group order $l^2$, l being a prime different from the characteristic of function field, we compute the index of the Sinnott group of circular units.

• 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.

• 호남수학학술지
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• 제27권3호
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• pp.389-397
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• 2005

Let K be an absolutely real abelian number field with $G=Gal(K/{\mathbb{Q}})$. Let E be a subfield of K and ${\Delta}=Gal(K/E)$. Let $C_K$ and $C_E$ be the group of circular units of K and E respectively. In [G], Greither has shown that if G is cyclic then $C_K^{\Delta}=C_E$. In this paper we show that the same result holds in function field case.

• Structural Engineering and Mechanics
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• 제61권6호
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• pp.747-754
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• 2017

Exact solutions for stresses for an infinite rectangular plate perforated by two circular holes of different radii subjected to uni-axial or bi-axial uniform loads are investigated using the Airy stress function. The hoop stresses occurring at the edge of the circular hole are computed and plotted. Comparisons are made for the stress concentration factors for several types of loading conditions.

• 전자공학회논문지S
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• 제34S권2호
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• pp.94-103
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• 1997

The WCHF-FSJTC (wavelet circular harmonic function frequency selective joint transform correlator) using th wavelet transformed CHF as the reference image in FSJTC is proposed for rotation invariant pattern recognition. Since the wavelet transform has the property of feature extraction, the proposed system can have the better DC (discrimination cpability) and the higher SNR(signal to noise ratio) compared with the conventional CHF-CJTC(circular harmonic function conventional joint transform correlator). And since the structure of the proposed system is FSJTC which can eliminate auto-correlation and cross-correlation between input images, it can eliminate false alarm caused by the overlapping among correlation peaks. The used wavelet functio is the morlet function, which is proper for the reference image used in this paper. the optimal dialation parameter and oscillation frequency of the wavelet function are also achieved with varying the parameters of the wavelet function. The computer simulation shows that the proposed system has the best performance when the dilation parameter is 0.8 and the oscillation frequency is 0.48.

• 제어로봇시스템학회논문지
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• 제6권12호
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• pp.1053-1060
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• 2000

In this paper, a discrete-time variable structure control method using recursively defined switching function and a decoupled variable structure disturbance compensator is used to achieve high performance circular motion control of a CNC machining center. The discrete-time variable structure control with the decoupled disturbance compensator method developed in this paper uses a recursive switching function defined as the sum of the current tracking error vector and the previous value of the switching function multiplied by a positive constant less than one. This recursive switching function provides much improved performance compared to the method that uses a switching function defined only as a linear combination of the current tracking error. Enhancements in tracking performance are demonstrated in the circular motion control using a CNC milling machine.

• 대한기계학회논문집
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• 제14권6호
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• pp.1382-1390
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• 1990

본 연구에서는 Yang의 이론을 바탕으로 여러가지 원형집중하중을 받는 원형평 판에 관한 최대하계해를 구하고자 한다.앞서 열거한 문헌에서는 여러가지 해석법이 제시되었으나, 문제의 성격에 비하여 그 해법이 매우 복잡하였다. 본 논문에서는 원 형평판에 관한 해법으로서 전산기를 응용하여 가능한 한 단순한 해법으로 최대화기법 에 의한 완전한 해를 얻기 위한 시도를 제시하고자 한다.

• International Journal of Aeronautical and Space Sciences
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• 제2권2호
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• pp.46-55
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• 2001

A Green's function approach based on the laminate theory is adopted to obtain the unsteady temperature distributions in a semi-infinite hollow circular cylinder made of functionally graded materials (FGMs). The transient heat conduction equation based on the laminate theory is formulated into an eigenvalue problem for each layer by using the eigenfunction expansion theory and the separation of variables. The eigenvalues and the corresponding eigenfunctions obtained by solving an eigenvalue problem for each layer constitute the Green's function solution for analyzing the unsteady temperature distributions. Numerical calculations are carried out for the semi-infinite hollow circular FGM cylinder subjected to partially heated loads, and the numerical results are shown in figures.

• 대한조선학회지
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• 제22권1호
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• pp.1-8
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• 1985

The buckling characteristics of cylindrical shells with a circular hole, under axially compressed loads, have been analyzed and the results have been compared with existed experimental results. Deflection function with decay factor is assumed, and stress distribution around a circular hole in tensioned infinite plate is used for formulating buckling energy function. Applying Rayleigh Ritz procedure to this energy function, characteristic equation of eigenvalue problem is determined. Buckling load is defined by the minimum value of eigenvalues calculated according to several decay factors, and as the radius ratios of a circular hole (a/R) and shell thickness ratios (R/t) are varied, the reducing characteristics of buckling load are studied. As a result, buckling loads are reduced by about 50% according to some radius ratios ($a/R{\geq}0.15$) of circular hole and are not nearly affected by shell thickness ratio(R/t).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제25권1호
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• pp.1-15
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• 2021

A Green's function approach is adopted to solve the two-dimensional thermoelastic problem of a thin hollow circular disk. Initially, the disk is kept at temperature T0(r, z). For times t > 0, the inner and outer circular edges are thermally insulated and the upper and lower surfaces of the disk are subjected to convection heat transfer with convection coefficient hc and fluid temperature T∞, while the disk is also subjected to the axisymmetric heat source. As a special case, different metallic disks have been considered. The results for temperature and thermal deflection has been computed numerically and illustrated graphically.