• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.704-711
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• 2000

This study is carried out using a circuit model approach. First, the self and shunt impedances of all the conductors in the rail system and the mutual impedances between different conductors are computed. Then, a circuit representing the both rail systems at interfaces including the rails, feeders, protection wires, contact wires, ground wires is built. Auto-transformers in the system are also represented in the circuit model. The circuit model is then 1]recessed using a circuit solver based on a double-elimination method. Several different scenarios are analyzed, including the load conditions and a few fault conditions with different fault locations. The effect of the buried ground wires is also analyzed by comparing the results with and without the presence of the ground wires. The analysis procedure presented in the paper demonstrated an accurate way of computing fault current distribution and EMC at interfaces between both systems. The results presented in the paper can be used as a reference for estimating interference levels in similar rail systems.

• 한국정보통신학회논문지
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• 제6권6호
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• pp.897-903
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• 2002

본 논문에서는 Inset-fed 안테나의 급전구조를 변형하여 기존의 Inset-fed 안테나 보다 그 성능을 향상시킨 안테나를 설계 및 제작하였다. Patch 안테나에서 gap 결합에 의한 급전 방식을 기초로 하여 변형된 급전 방식을 Inset-fed 안테나에 적용하였다. 설계된 안테나는 FDTD에 의한 simulation을 수행하여 최적치를 얻었으며 제작된 안테나는 공진 주파수에서 511은 -l4dB이고 cross polarization level은 -20dB의 특성을 보였다.

• Tribology and Lubricants
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• 제33권5호
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• pp.187-201
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• 2017

This paper presents the impact of couple stress lubricant on performance of slot-entry hydrostatic/hybrid journal symmetric/asymmetric bearings. Reynolds Equation using Finite Element Technique has been solved for the flow of couple stress and Newtonian lubricants in bearings. The results have been computed for concentric design pressure ratio(${\beta}^{\ast}=0.5$), slot width ratio (SWR = 0.25) and chosen parameters of couple stress lubricant ${\bar{l}}=5$, 10, 15. It is observed that numerically simulated outcomes for slot-entry journal bearings, considering the influence of couple stress lubricant indicate a substantial improvement in the performance of the bearing.

• 소성∙가공
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• 제8권6호
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• pp.604-611
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• 1999

This paper is concerned with the family of parts that generally feature a central hub with radial protrusions. As opposed to conventional forward and backward extrusion, in which the material flows in a direction parallel to that of the punch or die motion, the material flows perpendicular to the punch motion in radial extrusion. Three variants of radial extrusion of a collar or flange are investigated. Case I involves forcing a cylindrical billet against a flat die, Case II involves deformation against a stationary punch recessed in the lower die, and Case III involves both the upper and lower punches moving together toward the center of the billet. Extensive simulational work is performed with each case to see the process conditions in terms of forging load, balanced and symmetrical flow in the flange. Also, the effect of the gap size and die corner radii to the material flow are investigated. In this study, the forming characteristics of radial extrusion will be considered by comparing the forces, shapes etc. The design factors during radial extrusion are investigated by the rigid-plastic FEM simulation.

• 한국항공운항학회지
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• 제14권2호
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• pp.71-78
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• 2006

In this paper, it is described on the exportation trend and future development paradigm of the localized small aircraft which was recently developed four seated canard type aircraft for exportation purpose. Presently, even though the development of small aircraft is recessed, if we start development of the proper airplane models by integrating domestic power of industry-university-institute on the base of research experience from now on, we can go into the global market and take up the level of world top 10 makers without doubt. For successful operation of exportation system of small aircraft, it is needed to set up development strategy paradigm by forming consortium centering around the medium and small enterprises.

• ETRI Journal
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• 제32권3호
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• pp.406-413
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• 2010

In order to guarantee the proper operation of a recessed channel array transistor (RCAT) pseudo SRAM, the back-bias voltage must be changed in response to changes in temperature. Due to cell drivability and leakage current, the obtainable back-bias range also changes with temperature. This paper presents a pseudo SRAM for mobile applications with an adaptive back-bias voltage generator with a negative temperature dependency (NTD) using an NTD VBB detector. The proposed scheme is implemented using the Samsung 100 nm RCAT pseudo SRAM process technology. Experimental results show that the proposed VBB generator has a negative temperature dependency of -0.85 $mV/^{\circ}C$, and its static current consumption is found to be only 0.83 ${\mu}A$@2.0 V.

• International Journal of Control, Automation, and Systems
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• 제2권4호
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• pp.494-500
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• 2004

The wing rock phenomenon is a high angle of attack aerodynamic motion manifested by limit cycle roll oscillations. Experimental studies reveal that direct control and manipulation of leading edge vortices, through the use of 'blowing' techniques is effective in the suppression of wing rock. This paper presents the design of a robust controller for the experimental implementation of one such 'blowing' technique - recessed angle spanwise blowing (RASB), to achieve wing rock suppression over a range of operating conditions. The robust controller employs Takagi - Sugeno fuzzy system, which is fine-tuned by experimental simulations. Performance of the controller is assessed by real-time wind tunnel experiments with an 80 degree swept back delta wing. Robustness is demonstrated by the suppression of wing rock at a range of angles of attack and free stream velocities. Numerical simulation results are used to further substantiate the experimental findings.

• Wind and Structures
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• 제21권5호
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• pp.505-521
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• 2015

A general approach of aerodynamic optimization of tall buildings is presented in this paper, focusing on how to best compromise wind issues with other design aspects in the most efficient manner. The given approach is reinforced by establishing an empirical method that can quickly assess the across-wind loads and accelerations as a function of building frequencies, building dimensions, aspect ratios, depth-to-width ratios, and site exposures. Effects of corner modifications, including chamfered corner and recessed corner, can also be assessed in early design stages. Further, to assess the effectiveness of optimization by tapering, stepping or twisting building elevations, the authors introduce a method that takes use of sectional aerodynamic data derived from a simple wind tunnel pressure testing to estimate reductions on overall wind loads and accelerations for various optimization options, including tapering, stepping, twisting and/or their combinations. The advantage of the method is to considerably reduce the amount of wind tunnel testing efforts and speed up the process in finding the optimized building configurations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.361-364
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• 2004

Surface doped SOI RESURF LDMOSFET with recessed source region is proposed to improve the on- and off-state characteristics. Surface region of the proposed LDMOS structure is doped like step. The characteristics of the proposed LDMOS is verified by two-dimensional process simulator ATHENA and device simulator ATLAS[1]. The numerically calculated on-resistance($R_{ON}$) of the proposed LDMOS is $10.36\Omega-cm$ and breakdown voltage is 205V when $L_{dr}=7{\mu}m$ with step doped surface.

• 한국결정학회지
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• 제4권2호
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• pp.54-62
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• 1993

Cd2+ 이온으로 이온교환된 제올라이트 A를 650℃에서 2 ×10-6 T orr의 진공하에서 탈수한 구조 (a:l2.189(2)A)와 이 결정에 요오드가 흡착된 구조 (a:l2.168(2) A)를 21℃에서 입방공간군 Pm3m를 사용하여 단결정 X-선회절법으로 해석하고 정밀화하였다. 탈수한 가In-A의 구조 는 Full-rmoix 최소자승법 정밀화 계산에서 I > 3σ(I)인 186개의 독립반사를 사용하여 최종오차인자를 Rl:0.057, Ra:0.003 까지 정밀화 계산하였고, 이 결정을 요오드로 흡착시킨 구조는 181 개의 독립 반사를 사용하려 Rl = 0.082, R2 : 0.085가지 정밀화시켰다. 두 결정에서 단위세포당 6개의 Cd2+ 이온은 서로 다른 2개의 3회 회전축상에 위치 하고 있었다. 요오드가 흡착된 구조에서 4개의 Cd2+ 이온 은 0(3)의 (111) 평면에서 큰 동공쪽으로 약 0.68(1) A 들어간 I3- 이온이 결합하고 있고 나머지 2개의 Cd2+ 이온은 0(3)의 (111) 평면에서 소다라이트 동공 깊숙히 약 0.68(1) A 들어간 자리에 위치 하고 있다. 단위세포당 약 4개의 I이온이 큰 동공내에 흡착되었다. 각각의 I-는 6-링 Cd2+와 골조의 8-링 산소에 다리를 놓고 있으며 0(1)-I(1)-I(2) 각도는 172(1)˚로써 거의 선형이고 약한 전 하이동 착물을 골조의 8-링 산소와 이루고 있다. 큰 동공 내에 존재하는 I이온은 부분적으로 탈수된 효In-A에서 요오드 증기와 물분자가 반응하여 H+이온과 I-이온이 생성된 후 다시 I이온과 l2 분자와 반응하여 생성되었을 것이다.