• 대한수학회보
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• 제50권3호
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• pp.747-752
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• 2013

It's known that one could use a fixed loxodromic or parabolic element in $M(\bar{\mathbb{R}}^n)$ as a test map to test the discreteness of a non-elementary M$\ddot{o}$bius group G. In this paper, we discuss the discreteness of G by using a fixed elliptic element.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.110-114
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• 1987

A method for synthesizing low-pass elliptic filters in a microstrip configuration is presented. The realization consists of the cascade connection of proper rectangular elements, each one corresponding to four reactive elements of the lumped-constant prototype. This allows an effictive control of parasitics and unwanted reactances. Which results in the possibility of realizing higher order filters with cutoff frequencies UP to X-band. Fifth and seventh order filters were fabricated on allumina substrates.

• Journal of applied mathematics & informatics
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• 제31권3_4호
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• pp.425-441
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• 2013

In literature, several strong designated verifier signature (SDVS) schemes have been devised using elliptic curve bilinear pairing and map-topoint (MTP) hash function. The bilinear pairing requires a super-singular elliptic curve group having large number of elements and the relative computation cost of it is approximately two to three times higher than that of elliptic curve point multiplication, which indicates that bilinear pairing is an expensive operation. Moreover, the MTP function, which maps a user identity into an elliptic curve point, is more expensive than an elliptic curve scalar point multiplication. Hence, the SDVS schemes from bilinear pairing and MTP hash function are not efficient in real environments. Thus, a cost-efficient SDVS scheme using elliptic curve cryptography with pairingfree operation is proposed in this paper that instead of MTP hash function uses a general cryptographic hash function. The security analysis shows that our scheme is secure in the random oracle model with the hardness assumption of CDH problem. In addition, the formal security validation of the proposed scheme is done using AVISPA tool (Automated Validation of Internet Security Protocols and Applications) that demonstrated that our scheme is unforgeable against passive and active attacks. Our scheme also satisfies the different properties of an SDVS scheme including strongness, source hiding, non-transferability and unforgeability. The comparison of our scheme with others are given, which shows that it outperforms in terms of security, computation cost and bandwidth requirement.

• 소성∙가공
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• 제9권3호
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• pp.313-319
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• 2000

Finite element analysis is carried out for simulation of the multi-stage elliptic cup drawing process with the large aspect ratio. The analysis incorporates with shell elements for an elasto-plastic finite element method with the explicit time integration scheme. For the simulation, LS-DYNA3D is utilized for its wide capability of solving forming problems. The simulation result shows that the non-uniform drawing ratio at the elliptic cross section ad the small shoulder radius cause failure such as tearing and wrinkling. The result suggests the guideline to modify the tool shape for prevention of the failure during the drawing process.

• Composites Research
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• 제17권4호
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• pp.25-31
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• 2004

본 연구에서는 다중세포로 구성된 타원형 단면 복합재료 블레이드의 정밀 1차원 보 해석모델을 개발하였다. 보의 정식화를 위하여 Reissner의 반보족에너지 함수를 이용하였으며, 고전적인 강성도 및 유연도법을 결합한 혼합보 이론 체계를 구축하였다. 타원단면의 특성계수들을 구하기 위해 단면의 외곽선을 유한개의 선분으로 분할하고 여기에 Gauss 적분을 수행하였다. 또한, 단면을 구성하는 각 세포에 대해 4개의 연속방정식이 충족되도록 구성하였다. 개발된 보 이론을 단일 및 이중세포로 구성된 타원형 복합재료 블레이드에 적용하였으며, 다차원 정밀 유한요소 해석 결과와 비교하여 그 타당성을 확보하였다.

• 대한수학회지
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• 제53권6호
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• pp.1411-1429
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• 2016

We consider the nite volume element method for elliptic problems using isoparametric bilinear elements on quadrilateral meshes. A gradient recovery method is presented by using the patch interpolation technique. Based on some superclose estimates, we prove that the recovered gradient $R({\nabla}u_h)$ possesses the superconvergence: ${\parallel}{\nabla}u-R({\nabla}u_h){\parallel}=O(h^2){\parallel}u{\parallel}_3$. Finally, some numerical examples are provided to illustrate our theoretical analysis.

• 한국전자파학회지:전자파기술
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• 제2권3호
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• pp.26-31
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• 1991

The scattering property of TMz illuminated a elliptic dielectric cylinders with arbitrary cross section are analyzed by the boundary element techniques. The boundary element equations are for- mulated via Maxwell's equations, weighted residual of Green's theorem, and the boundary conditions. The unknown surface fields on the boundaries are then calculated by the boundary element integral equations. Once the surface fields are found, the scattered fields in far-zone and scattering widths (SW) are readily determined. To show the validity and usefulness of this formulation, computations are compared with those obtained using analytical method and one layer circular cylinder. As exten- sion to arbitrary cross-sectioned cylinders, plane wave scattering from a elliptic dielectric cylinders are numerically analyzed. A general computer program has been developed using the quadratic ele- ments(Higher order borndary elements) and the Gaussian quadrature.

• 대한전기학회논문지
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• 제43권4호
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• pp.672-678
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• 1994

A design of 5th-order Elliptic OTA-C filter for operation at 4.2MHz is presented. the filter structure is composed entirely of five OTAs(Operational transoonductance Amplifiers), one buffer and seven capacitors. To prevent decreasing of frequency charaoteristios due to the parasitic effeots of OTA and buffer, the design considering of parasitic capacitance and finite resistane of OTA and fuffer is pertormed. As the result of the simulation using SPICE with $2{\mu}m$ CMOS parameters, The performances were found to be essentially within the specifications` less than 0.25dB passband attenuation, 30dB stopband attenuation and 4.2MHz cut-off frequency were satisfactorily obtained. The number of elements is also considerably reduced than other design methods.

• 한국통신학회논문지
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• 제31권12C호
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• pp.1297-1308
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• 2006

유한체상의 곱셈은 타원곡선 암호시스템의 구현에 있어 가장 중요한 연산 중 하나이다. 본 논문에서는 가우시안 정규기저를 이용하여, $GF(2^m)$상의 새로운 곱셈 알고리즘 및 VLSI 구조를 제안한다. 제안된 곱셈 알고리즘은 정규기저 원소의 대칭성이용과 계수의 인덱스 변형에 기반하며, 타원곡선 암호 시스템을 위해 NIST(National Institute of Standards and Technology) 및 IEEE 1363에서 권고하는 다섯 가지 $GF(2^m)$, $m\in${163, 233, 283, 409, 571}, 모두에 적용 할 수 있다. 제안된 곱셈알고리즘에 기만한 VLSI 구조는 기존의 $GF(2^m)$상의 정규기저 곱셈기에 비해 속도 혹은 하드웨어 면적에 있어 향상된 성능을 보인다. 또한 본 논문에서는 정규기저 원소의 기본 곱셈 행렬을 쉽게 찾을 수 있는 방법을 제시한다.

• Korean Journal of Mathematics
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• 제13권2호
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• pp.127-137
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• 2005

The objective of numerical analysis is to devise and analyze efficient algorithms or numerical methods for equations arising in mathematical modeling for science and engineering. In this article, we present some recent topics in computational mathematics, specially in the finite element method and overview the development of the mixed finite element method in the context of second order elliptic and parabolic problems. Multiscale methods such as MsFEM, HMM, and VMsM are included.