• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.33-37
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• 1989

According to the Rayleigh-Ritz approximation method, a solution can be represented as a finite series consisting of space-dependent functions, which satisfy all the geometric boundary conditions of the problem and appropriate smoothness requirement in the interior of the domain. In this paper, an efficient formulation for solving structural dynamics systems in frequency domain is presented. A general procedure called Ritz modes (or vectors) generation algorithm is used to generate the admissible functions, i.e. Ritz modes, Then, the use of direct superposition of the Ritz modes is utilized to reduce the size of the problem in spatial dimension via geometric coordinates projection. For the reduced system, the frequency domain approach is applied. Finally, a numerical example is presented to illustrate the effectiveness of the proposed method.

• Information Display
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• v.5 no.5
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• pp.4-9
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• 2004

최근 비오이 하이디스에서는 무제한의 광시야각과 시야각에 따른 색변화가 최소화된 선명한 색 특성을 갖는 Advanced FFS(Fringe Field Switching) 기술을 개발하였다. 이 기술은 resin 기술적용(평탄화에 의한 고개구율)없이 종래의 FFS 기술에서 액정의 전기 광특성을 최적화하는 새로운 디자인 룰을 찾아내어 실현하였다. 진보된 화소 개념은 전극의 모서리 구조, 전극 간격/폭, 칼라 필터의 블랙 마트릭스(BM)와 전극 간격등의 key parameters들의 최적화에 의해 달성되었고 액정 셀 내의 모서리와 전기장등이 액정을 미세하게 조정할 수 있도록 있게 된 것이다. 이러한 진보된 설계 개념은 모든 FFS 제품에 반영되어 개발되었다. 뿐만 아니라 12.1" XGA 제품에서 투과율이 22% 증가하고 흑백 대비비(Contrast Ratio)는 33% 증가한 600 : 1의 세계 최고 사양을 갖는 제품을 개발하게 되었다. 특히 태블릿과 노트북용 TFT- LCD 모듈에서 단일 도메인(Single Domain) 모드로도 White상태에서 시야각에 따른 색변화가 0.02 이하의 특성을 갖고 180도/180도의 무제한 시야각을 갖고 있다. Advanced FFS 기술의 브랜드 이름과 슬로건으로 'Viewiz'와 'Vision Magic'을 정하여 마케팅 중이며 세계적인 Top Tier 고객에 제품을 판매 중이고, 2004년 3분기에는 태블릿 시장에서 점유율 70%로 1위를 차지하였다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.1
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• pp.33-39
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• 2005

In this paper, we propose a slider servo-mechanism driven by electro-magnetic actuator to improve straightness of linear motor stages. Based on axial-position dependent deterministic characteristics of the straightness error, a feedforward compensation control is appled to reduce the straightness error. In the consideration of uncertain properties of friction and its effects on positioning accuracy, a sliding mode control is applied. The effectiveness of the suggested mechanism and the control performances are illustrated along with some experimental results.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2016-2019
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• 1997

To solve the low efficiency problem of low-voltage power supplies, it has been studied to replace the schottky barrier diode with the MOSFET synchronous rectifier. In this paper, Phase Shift-Controlled Clamp Mode Zero Voltage Switching-Multi Resonant Converter with Synchronous Rectifier (PSC CM ZVS-MRC with SR) is presented to achieve high efficiency in low-voltage power supplies. The characteristics analysis of synchronous rectifier is established by using the MOSFET equivalent circuit and efficiency comparison is established between the Synchronous Rectifier and the schottky barrier diode. To verify the validity of the analysis, 33W(3.3V, 10A) PSC CM ZVS-MRC with self-driven synchronous rectifier at switching frequency of 1MHz is designed and tested. And it is confirmed that the experimental results are well consistent with the theoretical results. The maximum efficiency of the converter is 83.4% at full load, which is 3.3% higher than conventional schottky diode rectification.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.4
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• pp.52-62
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• 1996

In this paper, a new continuous-time current-mode integrator as basic building block of the low-voltage analog current-mode active filters was proposed. Compared to the current-mode integrator which was proposed by Zele, the proposed current-mode integrator had higher unity gain frequency and output impedance in addition to lower power dissipation. And also, a current-mode third-order lowpass active filter was designed with the proposed current-mode integrator. The designed circuits were fabricated using the ORBIT's 1.2.mu.m double-poly double-metal CMOS n-well process. The experimental resutls of the active filter designed and fabricated for this research have shown that it has the performance of 44.5MHz cutoff frequency, 3.3mW power dissipation and the third-order active filter area was 0.12mm$^{2}$.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.2
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• pp.112-120
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• 1997

The clamp mode (CM) forward zero voltage switching multi resonant converter (ZVS-MPC) with self-driven synchronous rectifier is studied. The loss at the synchronous rectification stage of the converter is analyzed using MOSFET piecewise linear model and is compared with the loss at the conventional schottky diode rectification stage of th econverter. From the results of the analysis, it is known that the use fo MOSFETs as a synchronous rectifier reduces the loss at the rectification stage overthe whole load range comparing the use of schottky diodes as a conventional rectifier in the converter. In order to verify the validit of the analysis, we have built a 33W(3.3V/10A) CM forward ZVS-MRC with self-driven synchronous rectifier, in which switching frequency is 1MHz, and tested. FRom the experimental results, it is known that the synchronous rectification achieved about 1W improvement in the loss at the rectification stage and about 3% in the efficiency at the converter as compared with the conventional schottky diode rectification.

• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.33-40
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• 2003

기존 대부분의 진동제어법이 모드제어에 근거한 것인데 반면, 본 연구에서는 진동억제의 또다른 방법인 파동제어기법을 다루었다. 무반사조건을 만족하면서 진동에너지를 흡수하는 파동제어는 특히 1차원 구조계에 유용하게 사용될수 있으리라고 기대되는데, 현실적으론 제어알고리즘의 실현화에 그 어려움이 있다. 본 연구에서는 근사화된 무한구조계를 계산기내에 구축하여, 진동에너지가 근사 무한구조계에 흡수되는 조건을 제어기가 실현하는 제어수법을 개발하였다. 시뮬레이션과 실험을 통하여, 본 연구에서 제안한 파동제어기법에 의해 이동하는 현수체의 진동억제가 효율적으로 이루어짐을 확인할 수가 있었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.28-33
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• 2004

We developed a fiber-optic CT for large current monitoring in power systems. We used a FRG fiber sensor coil to suppress CT output degradation caused by linear birefringence, and different optical sources were used to compare their noise characteristics. From the experiments, we obtained output variation less than $\pm$0.4(%) when the sensor coil suffered mechanical perturbations, and the ASE source showed -23(㏈) less noise in the output than singlemode laser diode.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.1
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• pp.26-33
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• 2000

본 논문에서는 PWM ac-dc 컨버터의 출력직류전압 안정화를 위한 새로운 방식의 입력전류 제어기법에 대해 기술하였다. 제안한 방식의 전류제어 기법은 히스테리시스 전류제어기가 갖는 장점을 모드 갖고 있을 뿐 아니라 스위칭 손실도 최소화되는 특성을 갖는다. 기존의 히스테리시스 전류제어기와 다른 점은 PWM 컨버터 각 상 입력전류의 반주기 내에 1/3구간에서는 컨버터의 스위칭 소자가 PWM에 의한 스위칭이 이루어지지 않는다는 것이다. 더군다나 입력전류의 피크값 근처에서 스위칭이 발생하지 않으므로 한 주기 평균 스위칭 손실을 최소로 할 수 있다는 것이 특징이다. 이러한 동작 원리에 대한 설명과 제안한 방식의 특성을 해석하였으며 실험을 통하여 그 효용성을 입증하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.105-109
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• 2012

In this study, thickness vibration mode piezoelectric devices for AE sensor application were simulated using ATILA FEM program, and then fabricated. Trajectory resonant displacement and electro mechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electro mechanical coupling factor was obtained when the ratio of diameter/thickness($\Phi/T$) was 0.75. The piezoelectric device of $\Phi/T$=0.75 exhibited the optimum values of fr= 183 kHz, displacement= $4.44{\times}10^{-7}[m]$, $k_{33}$= 0.69, which were suitable for the application of AE sensor piezoelectric device.