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이직열,김정기 대한전자공학회 1985 전자공학회지 Vol.22 No.5
Fredholm 제 2종 적분 방정식의 수치해법에 관한 새로운 기범을 제시하였다. 문제 영역의 절점에 데이터를 혼합 형태로 가함으로써 근사해를 구하였다. 수치 해법에서 오차를 줄이기 위하여 모든 절정에서 2번 연속 미분가능한 cubic B-spline 함수를 기저함수로 사용하였다. 기저함수로서 cubit B-spline 함수를 이용한 본 기법의 결과와 기저함수로 pulse 함수 test 함수로는 delta 함수를 이용한 모멘트법의 결과를 예제를 통하여 비교하였다. 또한 이 방법에 대한 수렴 조건을 기술 하였다. An alternative technique (or the numerical solution of Fredholm integral equations of second kind is presented. The approximate solution is obtained by fitting the data in mixed form at knots in the region of the problem. To decrease the error in the numerical solution, cubic B-spline functions which are twice continuously differentiable at knots are employed as basis function. For a given example, the results of this technique are compared with those of Moment method employing pulse functions for basis function and delta functions for test function and found to br in good agreement.
이직열,정구철 한국통신학회 1994 韓國通信學會論文誌 Vol.19 No.2
전자장 해석을 위한 많은 수식들이 전계형 적분방정식으로 수식화되어 여러 가지 수치적인 방법으로 해석되어진다. 일반적으로 이 식은 특이점을 갖는 Kernel로 표현되어지며, 주어진 문제에 따라 식이 간략화 되어지지 않으면 해석시 수직과 프로그램이 복잡하여진다. 본 논문에서는 BOR구조의 도체에 적용할 수 있는 새로운 적분방정식을유도하였으며, 이 식은 직선형 wire도체의 경우에 더욱 간략화 되어진다. 동축선로로 급전되어지는 monopole안테나와 임의의 각도로 입사하는 평면파에 의한 도체의 산란문제를 응용예로서 다루었다. EFIE`s(Electric Field Integral Equations) are widely used in formulation of electric field problems and these equations are analyzed by several numerical method. In formulation of EFIF by forcing the tangential component of electric field on the perfect conducting body be zero, we can obtain equation with a kernel that has a logarithmic singularities. In this paper, an integral equation is presented which can be used for perfect BOR(Body of Revolution) objects and this can be more simplified for straight wire problem. As examples, monopole antenna which is driven by coaxial cable and scattering problems are considered.
矩形導波管에 對한 Dyadic Green's Function의 正確한 解析
金正祺,李直烈 중앙대학교 기술과학연구소 1981 기술과학연구소 논문집 Vol.8 No.-
The solution which satisfies boundary conditions can be expressed by the superposition of eigenfunctions. When sources are excited, the solutions are obtained by the Green's function method. Sources can be excited in vector forms, then the solution can be expressed in dyadic Green's function which has singularities at the source points. In this paper, the dyadic Green's function for rectangular waveguides is obtained by using Hansen's vector wave functions on the basis of Helmholtz theorem. The results have the same forms obtained by the other authors previously.
沈壽輔,李直烈 중앙대학교 기술과학연구소 1980 기술과학연구소 논문집 Vol.7 No.-
In this paper, a novel compensation technique to eliminate the effect of parasitic capacitances which are distributed in the GIC (Generalized Immittance Converter) circuit elements, is proposed. By using the GIC circuit, a floating inductance and capacitance are converted into the simulated inductance and FDNR, respectively, which are important elements in the design of active filters. Assuming the ideal characteristics of each element, the Q-factors of a simulated inductance and FDNR become to infinite, but practical elements reduce them noticeably because of parasitic capacitances. For obtaining high Q-factors the compensation circuit, which is newly proposed, is established in GIC circuit and the validity of the compensation is verified by experiments.
金正祺,李直烈 중앙대학교 기술과학연구소 1982 기술과학연구소 논문집 Vol.9 No.-
Switched-capacitor networks, which are composed of capacitors interconnected by an array of periodically operated switches, have become very attractive for the MOS/LSI realization of analog sampled-data filters. This paper proposes a general design technigue for obtaining a switched-capacitor filter from a passive RLC prototype by using the z-transformations. Inductor and resistor are simulated respectively by switched capacitor circuits. In the termination circuits, resistors are approximated by three different voltage-charge relationships. Design examples are represented by using the Forward Euler integrators.