• Journal of Magnetics
• /
• 제19권4호
• /
• pp.349-352
• /
• 2014

The system for producing magnetic field constitutes an important component of magnetic refrigerator. Many researchers have directed significant effort to increase the magnetic field intensity, because the magnetocaloric effect at the Curie temperature increases with the power of 2/3 of the magnetic field. In this study, we report the simulation of the magnetic field intensity at polar axis of a Halbach cylinder (HC) by i) changing the length and thickness of the HC, ii) having with or without gap of the HC, and iii) surrounding the HC with a soft magnet shell, acting as a shielding. We simulated the field distribution of a HC with a finite size. Furthermore, the detailed numerical results of the magnetic field distribution and its dependence on shielding are presented in this study.

• 전기학회논문지
• /
• 제57권2호
• /
• pp.314-319
• /
• 2008

In this paper, the electric field distribution induced inside the brain during Transcranial Magnetic Stimulation(TMS) has been thoroughly investigated in terms of tissue heterogeneity and anisotropy as well as different head models. To achieve this, first, an elaborate head model consisting of seven major parts of the head has been built based on the Magnetic Resonance(MR) image data. Then the Finite Element Method(FEM) has been used to evaluate the electric field distribution under different head models or three different conductivity conditions when the head model has been exposed to a time varying magnetic field achieved by utilizing the Figure-Of-Eight(FOE) stimulation coil. The results show that the magnitude as well as the distribution of the induced field is significantly affected by the degree of geometrical asymmetry of head models and conductivity conditions with respect to the center of the FOE coil.

• Earthquakes and Structures
• /
• 제6권5호
• /
• pp.457-472
• /
• 2014

The paper presents the field investigations and seismic analyses of a historical masonry brick minaret damaged during October 23 (Erciş) and November 9 (Edremit), 2011 Van earthquakes in Turkey. Ulu Mosque Minaret located on Tebriz Kap1 Street in the city centre of Van, Turkey is selected for investigation. Two earthquakes hit the minaret within seventeen days, causing progressive damage. It was seen from the field investigations that the minaret was heavily damaged. To validate the field investigations, three dimensional finite element model of the minaret is constituted by ANSYS software using relievo drawings. Finite element model of the minaret is analyzed under the Van earthquake records to determine the seismic behavior. The displacements, maximum and minimum principal stresses and strains are obtained from the analyses and compared with field observations.

• 한국정보전자통신기술학회논문지
• /
• 제7권3호
• /
• pp.137-141
• /
• 2014

RFID 시스템은 공정관리, 물류관리, 고객관리, 출입통제, 환경 센싱, 개체식별 등 다양한 산업에 적용되고 있다. 그러나 무선통신을 이용하기 때문에 보안성이 매우 취약하다. 본 논문에서는 태그와 리더기 사이의 기본 보안사항인 인증에 대한 프로토콜을 제안한다. 제안 프로토콜은 유한체 위의 이변수 다항식을 이용하여 도청공격, 재전송공격, 위치추적, 트래픽분석에 대해서 안전함을 보인다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제34권3호
• /
• pp.369-375
• /
• 2010

The two-dimensional finite element formulation for the basic field equations governing electrochemical responses of ionic conducting polymer-metal composite(IPMC) actuators is proposed in the present study. Biaxial deformation of a platinum plated Nafion actuator having 4 electrodes is dominated by electro-osmosis of hydrated ions and self-diffusion of free water molecules. Some numerical studies for IPMC actuators with electric field are carried out in order to show the validity of the proposed formulation and electric field analysis for the initial condition of total charge distribution are conducted using commercial code ANSYS/Emag.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
• /
• pp.845-849
• /
• 1987

Finite field arithmetic logic is central in the implementation of Reed-Solomon coders and in some cryptographic algorithms. There is a need for good multiplication and basis conversion algorithms. In this paper, a new multiplication circuit is developed for the finite field GF($2^m$) based on a conventional basis. It is composed of AND gates and EXCLUSIVE-OR gates and is regular, simple, expandable and therefore, naturally suitable for VLSI implementations.

• ETRI Journal
• /
• 제25권5호
• /
• pp.315-320
• /
• 2003

Elliptic curve cryptography (ECC) offers the highest security per bit among the known public key cryptosystems. The operation of ECC is based on the arithmetic of the finite field. This paper presents the design of a 193-bit finite field multiplier and an inversion unit based on a normal basis representation in which the inversion and the square operation units are easy to implement. This scalable multiplier can be constructed in a variable structure depending on the performance area trade-off. We implement it using Verilog HDL and a 0.35 ${\mu}m$ CMOS cell library and verify the operation by simulation.

• 한국통신학회논문지
• /
• 제21권11호
• /
• pp.2954-2965
• /
• 1996

In this paper, the electromagnetic field characteristics of leaky caxial cable are anlyzed by using the finite difference-time domain(FDTD) technique. Finite difference equations of Maxwell's equations are definedin cylindrical coordinate systems. To simulate the open boundary problem like a free space, the Mur's Absorbing Boundary condition(Mur-ABC) is also used. After modeling the leaky coaxial cable with the three dimensional grid structure, the transient response of the field distribution and the current distribution, the field pattern, the coupling effect are depicted in the time domain.

• 대한전기학회논문지
• /
• 제41권4호
• /
• pp.362-368
• /
• 1992

This paper presents a coupling scheme, which couples an analytical solution and the standard finite element, for analyzing the electromagnetic fields. The former is a solution of the magnetic field in free space, i.e., the outer region of boundary, and the latter represents the system with source currents and magnetic materials in the inner region of boundary. The proposed method retains the sparsity and symmetry of the final system matrix, the merits of the standard FEM. To verify the usefulness of the proposed algorithm, an example which can be solved analytically is chosen and analyzed. The results are compared with those of the standard FEM and the analytic solutions.

• 융합보안논문지
• /
• 제7권3호
• /
• pp.31-37
• /
• 2007

유비쿼터스 환경에서 개인 프라이버시를 보호하기 위한 RFID 시스템 보안에 대한 많은 연구가 이루어지고 있다. RFID 시스템 보안 중 상호인증 방법으로 XOR 기반, 해쉬기반, 그리고 재암호화 기반의 프로토콜을 사용한다. 그러나 인증과 프라이버시를 보호하기 위한 프로토콜은 좀 더 강화된 암호 시스템을 사용해야 한다. 공개키는 강력한 보안성을 제공하나, 비용이 많이 요구되어 RFID 시스템에서 사용하기에는 적합하지 않다. 따라서 본 논문에서는 상호 인증과 안전성을 위하여 유한체 GF($2^n$)을 이용한 인증 프로토콜을 제안하고 RFID 시스템에서의 여러 공격에 대하여 안전성 분석을 하였다.