• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1058-1063
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• 2004

This paper presents a new approach regarding thermal characteristics associated with a design of the high efficiency motor. Electrical conduction materials, such as coil and aluminum embedded in the core generate high heat exerting negative influence on both lifetime and performance of machine. Thus, it is necessary to design high efficiency motor considering heat transfer in order to improve motor performance and to be protected against overheating. In this paper, firstly, numerical analysis of electromagnetic field is carried out by the nonlinear transient finite element method (FEM). Secondly, the linear static FEA of magneto-thermal field is implemented by applying source current computed by the nonlinear transient analysis. FE results are validated in terms of electromagnetics and heat transfer by experiments. And then, the pseudo-transient topology optimization using a multi-objective function is performed. The proposed method is applied to a squirrel cage single-phase induction motor of the scroll compressor.

• Journal of the Korean Vacuum Society
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• v.21 no.2
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• pp.69-77
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• 2012

Visualization of the electromagnetic vector fields are presented and examined with Mathematica. Vector fields may be used to represent a great of many physical quantities in various area of physics, including electromagnetism with vector differential operators. Because they deal with abstract, three-dimensional fields that are some times very difficult to visualize, electromagnetism can be conceptually rather difficult. Visual representation of such an abstract vector fields is invaluable to student or researchers working in this field and also helps teaching electromagnetism to physics or engineering students. Mathematica provides a wider range of graphical tools including plot of vector fields and vector analysis, which can be applied to visualization of electromagnetic system. We have visualized the most fundamental concepts of the electromagnetic vector $\vec{E}=-\vec{\nabla}_{\varphi}$, $\vec{D}={\epsilon}\vec{E}$, $\vec{\nabla}{\times}\vec{A}$, $\vec{B}={\mu}\vec{H}$, $\vec{B}={\mu}_0(\vec{H}+\vec{M})$, which are confirmed with vector calculations and valid graphically with some presentations.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.78-82
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• 2010

An integrated multi-disciplinary design system plays a critical role in the preliminary design of an aircraft. In this paper such system is developed for the multi-disciplinary computation and design; aerodynamics elasticity, and radio frequency stealth. Common data base of geometry and structured grids is generated and used for aerodynamic, structural and eletromagnetics analysis. The Navier-Stokes CFD, FEM, and CEM technique are used for aerodynamic, structural, and RF stealth computations respectively.

• The Korean Journal of Quaternary Research
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• v.9 no.1
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• pp.61-86
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• 1995

칠레 북부해안에는 여러개의 해안 단구들이 발견되는데 이는 지구조 운동과 하께 해수면 변동과 밀접한 관련이 있다, 단구의 형성시기는 전부 밝혀지지는 않았으며 여전히 논란이 되고 있다,. 안토파가스타에서 이끼케까지 9개지역에서 발견되는 여러단구에 대한 탄 소 연대측정 전자스핀 공명법, 우라늄측정, 아미노산 연대측정 방법들을 이용하여 그 형성시 기를 측정하였다, 그결과들은 기본적으로 3∼4개의 뚜렷한 단구를 선정하여 지역간에 서로 대비하였다, 대부분의 단구들은 산소 동위연소 연대(Oxygen Isotope State) 3에서 11범주에 들어가는데 이것은 계단식 단구들이 단지 지구조 운동만으로 형성된 것이 아니라 전지구 기 후 변동과 밀접하게 관련된 전세계 해수면 변동에 의해 강한 영향을 받았음을 시사한다. 특 히 플라이스토세에 형성된 일련의 해빈 사구들은 플라이스토세 초기에서 중기사이 반복된 간빙기를 나타낸다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.4
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• pp.1-6
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• 2005

The ability to predict radar return from flying vehicles becomes a critical technology issue in the development of stealth configurations. Toward developing a CEM code based on Maxwell's equations for analysis of RCS reduction schemes, an explicit upwind scheme suitable for multidisciplinary design is presented. The DFFT algorithm is utilized to convert the time-domain field values to the frequency-domain. A Green's function based on near field-to-far field transformation is also employed to calculate the bistatic RCS. To verify the numerical calculation the two-dimensional field around a perfectly conducting cylinder is considered. Finally results are obtained for the scattering electromagnetic field around an airfoil in order to illustrate the feasibility of applying CFD based methods to CEM.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.1
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• pp.70-78
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• 2000

In applying high-${\underline{T_c}}$ superconducting material to microwave devices, Uncertainty of electromagnetics of high-${\underline{T_c}}$ superconductor(HTS) and the temperature dependence of the substrate fits with HTS thin film cause difficulty in realization of such antenna for industrial applications. It must be noted to characteristic the HTS antenna in contrast with normal conducting counterpart for this real application. In this paper, a comparative study between HTS microstrip antennas and gold antennas was reported in terms of the return loss, the characteristic impedance, efficiency, and other various characteristics. HTS thin films were $YBa_2Cu_3O_{7-x}$ (YBCO) on MgO substrates. Superconducting microstrip antennas used in this work were to directly inset a microstrip transmission line into the 50 ${\Omega}$ region of the radiating patch. Measurement results of HTS antennas and gold antennas showed that usable antennas can be made using this architecture.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.832-838
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• 2011

The shock absorber with magnetic effect is suggested for a lunar lander. The shock absorber consists of a metal tube, a piston rod, and several permanent magnets moved by a piston rod in the tube, and the shock energy can be dispersed and dissipated by magnetic effects such as the magnetic force existed between a metal and magnets and the eddy current effect generated by a relative motion with a conductor and magnets. Besides, the shock-absorbing effect similar to that of a coil spring can be obtained by arranging the magnets in line, which are facing the same polar each other. The device has a very simple structure and is usable in space due to the unnecessariness of any oil or gas. The shock absorber was designed and manufactured for experiments and its spring and damping characteristics were studied by the theoretical, analytical and experimental methods.

• The Korean Journal of Quaternary Research
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• v.11 no.1
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• pp.25-38
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• 1997

한국서남해안에 위치한 해남만의 조수 퇴적층(체)에 관한 층서 설정이 제4기후기 (late Quaternary)의 시간범위로 가능하였다. 즉 현재의 해남만에 분포하고 있는 조간대층은 지난 중기와 후기 현세(middle to late Holocene)동안에 형성된 퇴적지층단위(depositional sequence unit)이며 이 지층단위는 선현세(late Pleistocene)조간대 퇴적지층단위 disconformity 의 부정합 관계로 피복하고 있다 본연구에서는 전자를 Unit I(8-10m 내외의 두께)이라 칭하고 후자를 Unit II(10m 내외의 두께)라고 구분 명명하였다, 그런데 Unit II는 암상(lithofacies)의 특징에 근거하여 상부(upper part)와 하부(lower part)로 나누어진다. 상 부는 약 3-4m 의 두께를 가지고 있으며 황갈색을 분명히 나타내며 게 구멍 화석과 동토구 조(cryogenic structure)그리고 매우 높은 값의 전단응력을 나타낸다, 그러나 하부는 회색을 띄며 낮은 전단응력 값을 나타내 상부와 뚜렷이 구분된다 이러한 Unit II의 상부가 나타내 는 암상적 특징은 지난 간빙하기(Eemian interglacial time)에 형성된 오늘과 같은 조간대층 이 18,000년 전후의 최대 빙하기(last glacial maximum : LGM) 동안의 지배하에 노출되었 고 오랜동안 토양형성 과정이 풍화작용을 받은 증거를 나타내고 있다, 따라서 이지층의 층 서학적 단위 설정과 부정합 (disconformity) 적인 경계의미는 우리나라 제4기 층서(late Quaternary stratigraphy)를 규정하는데 매우 중요하다고 제안하는 바이다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.3
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• pp.68-74
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• 1995

In this paper, E-polarized electromagnetic scattering by a conducting strip grating with 2 dielectric layers is analyzed to calculate the geometrical reflected and transmitted power by applying the Fourier-Galerkin moment mothed. The induced current density is expanded in a Fourier series using a simple exponential func- tion, and we applied the boundary conditions to the electromagnetic fields at the boundary planes. The sca- ttered electromagnetic fields are expanded in a series of Floquet mode functions. To examine the accuracy of the present method, the geometrically reflected and transmitted power are evaluated and compared with those of the existing papers, and then the numerical results are found in good agreement with those of the existing paper.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.299-307
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• 2009

Emerging fiber optic sensor technologies have shown great potential to overcome the difficulties associated with conventional sensors. Fiber optic sensors are immune to EM noise and electric shock and thus can be used in explosion-prone areas. Several kinds of fiber optic sensors have been developed over the last two decades to take advantage of these merits. There have also been many field applications of fiber optic sensors for structural health monitoring as NDT/HDE. However, very few sensors, particularly a load cell have been successfully commercialized. This Paper Presents a load cell using fiber Bra99 gra1ing (FBG) sensors. The shape of the load cell is a link type, and three FBG sensors are used for measuring strains at three different points. Especially, these strains are processed with a differential method in order to exclude common mode noise such as temperature. Moreover, the sensitivity, the linearity and the resolution of the load cell were successfully verified from the experiment of tension test.