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강철형,송광순,편영식 啓明大學校 醫科大學 1990 계명의대학술지 Vol.9 No.3
Though the incidence of tuberculous spondylitis in Korea has been steadily reduced recently, it is not uncommon yet. But the incidence of appendiceal tuberculosis fo the spine that is involving the posterior element of the spine is very rate. The diagnosis of this entity is often delayed because involvement of posterior element is poorly visualized by conventional radiograph. The computed tomography is much more sensitive method in visualization of the lesion. Paraplegia is a common complication of this entity because of 1) vicinity of the lesion to the spinal cord; tuberculous products can directly compress the spinal cord and partly because of 2) missing the diagnosis or delayed diagnosis. So the diagnosis of the posterior element tuberculosis should be kept in mind when vague radiological change is noted in conventional radiograph in patient with clinical symptoms. The bone scan, computed tomography or MRI is highly recommended for visualization of the lesion in such a case, thus leading to early diagnosis. Authors have experienced a case of spinal tuberculosis iinvolving posterior elements which confirmed by surgical biopsy and we are reporting this case with a review of literatures.
Integration of 1/(x<sup>n</sup>+a) over the Real Line
( Bierng- Chearl Ahn ) 충북대학교 산업과학기술연구소 2016 산업과학기술연구 논문집 Vol.30 No.2
The integration of a function over a real line or over the interval [-∞,∞] has many scientific and engineering applications. Formulas of the integral of 1/(x<sup>n</sup>+a) over the real line are derived from the theory of the complex contour integration. Formulas of the definite integral of the function 1/(z<sup>n</sup>+a) are available in open literature like a book by Gradshteyen and Ryzhik, but they are too complicated to apply to the evaluation of the integral over the interval [-∞,∞]. Formulas given in this paper are compact and easy to use. They can also be used in the course of engineering mathematics.
Analytic Integration of the Free-Space Green's Function over a Rectangular Region
( Bierng-chearl Ahn ) 충북대학교 산업과학기술연구소 2018 산업과학기술연구 논문집 Vol.32 No.1
This paper presents the analytic integration of the free-space Green's function over rectangular regions arising in electromagnetic theory. Specifically, closed-form formulas are presented for the integration of 1/R and 1/R<sup>2</sup> functions over a linear segment, over a rectangular surface, and over a rectangular volume. Presented formulas can be used for the calculation of the electrostatic potential, the electric field strength, the magnetic vector potential, and the magnetic field strength due to source (charge or current) uniformly distributed over rectangular regions.
( Bierng-chearl Ahn ) 충북대학교 산업과학기술연구소 2019 산업과학기술연구 논문집 Vol.33 No.1
In this paper, the image method formulation is presented for the capacitance of two non-contacting metallic spheres. First, a point source in the presence of a grounded conducting sphere is analyzed and equations for the image source are derived. Next, the image theory of a spherical conductor is applied to solve the problem of two non-contacting metallic spheres where one sphere is held at potential V0 and the other at zero potential and vice versa. The two metallic spheres are represented by an equivalent problem with an infinite sequence of image charges inside each spherical conductor, from which the total charge on each sphere is obtained using the Gauss theorem. The capacitance coefficients are obtained from the total charge and potential on each sphere. The mutual capacitance or simply the capacitance between two spheres is obtained from the capacitance coefficients. The potential, electric field, and force on the sphere are calculated using image charges.
A 3‐20GHz Vivaldi Antenna with Modified Edge
Bieng-Chearl Ahn, Otgonbaatar Gombo 충북대학교 컴퓨터정보통신연구소 2013 컴퓨터정보통신연구 Vol.21 No.1
A wideband elliptically-tapered-aperture Vivaldi antenna is proposed in this paper. The tapered aperture improves the lowfrequency impedance matching. The antenna is printed on a Teflon substrate and fed by a microstrip line. The size of the antenna is 92.9mm x 100.4mm x 0.787mm. The design, fabrication and measurement of the proposed antenna are presented.