• Earthquakes and Structures
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• 제17권4호
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• pp.387-398
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• 2019

On the basis that ground motions may arrive at a structure from any horizontal direction and that different directions of seismic incidence would result in different structural dynamic responses, this paper focuses on orienting the crucial seismic incidence of transmission tower-line systems based on the wavelet energy method. A typical transmission tower-line system is chosen as the case study, and two finite element (FE) models are established in ABAQUS, with and without consideration of the interaction between the transmission towers and the transmission lines. The mode combination frequency is defined by considering the influence of the higher-order modes of the structure. Subsequently, wavelet transformation is performed to obtain the total effective energy input and the effective energy input rate corresponding to the mode combination frequency to further judge the critical angle of seismic incidence by comparing these two performance indexes under different seismic incidence angles. To validate this approach, finite element history analysis (FEHA) is imposed on both FE models to generate comparative data, and good agreement is found. The results demonstrate that the wavelet energy method can forecast the critical angle of seismic incidence of a transmission tower-line system with adequate accuracy, avoiding time-consuming and cumbersome computer analysis. The proposed approach can be used in future seismic design of transmission tower-line systems.

• 한국통신학회논문지
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• 제28권12C호
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• pp.1225-1238
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• 2003

본 논문에서는 PDA에 장착된 카메라를 사용하여 획득한 명함 영상에 대한 회전 보정 알고리듬을 제안한다. 제안된 방법은 크게 블록적응 이진화부, 스트라이프 생성부, 회전각 계산부, 그리고 영상 회전부로 구성된다. 블록적응 이진화부에서는 입력 영상의 불균일한 조명이나 그림자의 영향을 감소시키기 위하여 입력 영상을 블록별로 이진화한다. 스트라이프 생성부에서는 인접한 문자와 이들로 이루어진 문자열들을 병합하여 문자열 클러스터를 생성하고, 생성된 클러스터 중에서 회전각 계산에 유용한 것들을 스트라이프로 분류한다. 회전각 계산부에서는 스트라이프들의 방향각을 중심 모멘트를 이용하여 계산하고 이들 방향각을 평균하여 입력 영상의 회전각으로 결정한다. 영상 회전부에서는 입력 영상을 계산된 회전각 만큼 회전시킨다. 실험결과 제안된 방법은 여러 종류의 명함을 다양한 주변 여건에서 PDA로 획득한 시험 영상에 대하여 약 93%의 회전 보정률을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1233-1235
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• 2000

A new control method of three phase converter without measuring input phase-voltage and DC-link voltage is proposed. Input phase-voltage of these required voltages is estimated using EKF(Extended Kalman Filter) and DC-link voltage is estimated from the measured line currents and the estimated input phase-voltage. This control method is achieved without PLL(Phase Locked Loop) which senses the angle of input phase-voltage and DC-link voltage sensor. In addition, the proposed method controls high power factor and DC-link voltage utilizing the estimated phase angle. This paper describes the effectiveness of the proposed estimated algorithm through simulations.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.227-230
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• 2001

A new control method of three phase converter without measuring input Phase-voltage and DC-link voltage is Proposed. Input Phase-voltage of these required voltages is estimated using EKF(Extended Kalman Filter) and DC-link voltage is estimated from the measured line currents and the estimated input phase-voltage. This control method is achieved without PLL(Phase Locked Loop) which senses the angle of input phase-voltage and DC-link voltage sensor. In additon, the proposed method controls high power factor and DC-link voltage utilizing the estimated phase angle. This paper describes the effectiveness of the proposed estimated algorithm through simulations.

• Journal of Power Electronics
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• 제10권4호
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• pp.428-433
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• 2010

This paper proposes a harmonics reduction technique for the input currents of three phase PWM converters. The quality of the phase angle information on the utility voltage connected to the PWM converters affects their control performance. Under a distorted utility voltage, the extracted phase angle based on the synchronous reference frame PLL method is distorted. This causes large harmonics in the input currents of a PWM converter. In this paper, a harmonics reduction method that makes the input currents in the PWM converter sinusoidal even under distorted utility conditions is proposed. By the proposed method, without additional hardware, the THD (Total Harmonic Distortion) of the input currents can be readily limited to below 5% which is the harmonic current requirements of IEEE std. 519. Its validity is verified by simulations and experimental results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.275-281
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• 2001

While basic input parameters for the performance and noise of axial fan are flow rate, pressure rise, rotating speed, and fan diameter, the geometric parameters of blade are sweep angle, solidity, and camber angle. The sweep angle does not affect fan performance much, but on fan noise significantly. Solidity and camber angle are very critical design parameters acting on the fan performance directly. The solidity and camber angle are closely related, therefore they have to be carefully determined for the low-noise and high-performance fan. In This paper, different design points are selceted and also geometric parameters are deliberately changed for the comparison of fan noise. As a result, at the same performance, the input rotational speed affects radiated noise more significantly than others. When solidity and camber angle are increased more than those by iDesignFan／sup TM／ program, more noise is experienced. The blade sweep method and blade numbers at same solidity are observed to results in different levels of performance and noise.

• 한국안전학회지
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• 제23권2호
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• pp.7-13
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• 2008

In a long-span bridge which is constructed on soft soil, it is requested to make a plan considering soil-structure interaction, and soil-structure interaction is partially under consideration at the actual bridge plan. Many researches on dynamic behavior of a bridge affected by soil-structure interacting have been accomplished, but it is difficult to estimate dynamic behavior of a bridge on soft soil accurately because of many uncertainties. This paper presents the results about dynamic response of a long-span suspension bridge in the site composed of soft soil considering incident angle of input ground motion. The effect of soft soil was evaluated by the use o computer program SASSI and a long-span suspension bridge was modeled by finite element program MIDAS. The effect of incident angle of input ground motion was investigated on the dynamic response of a long-span bridge.

• 대한전자공학회논문지SD
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• 제41권12호
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• pp.75-81
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• 2004

AE-CORDIC은 CORDIC 연산의 회전 방향을 미리 계산하는 알고리즘을 이용해 CORDIC의 연산속도를 향상 시켜준다. 회전방향을 예측할 수 없는 부분은 Lookup-Table로 대체하고, 예측 가능 부분만을 CORDIC 으로 처리하였는데, 회전방향 예측은 별도의 추가 하드웨어 없이 간단하게 인코딩 할 수 있게 된다. 그리고, Unrolled CORDIC 구조에서는 Lookup-Table입력 비트 수가 크지 않으면 Lookup-Table의 하드웨어 증가보다 CORDIC 연산 단에서 감소되는 ADDER의 하드웨어가 더 크기 때문에 오히려 전체 하드웨어 크기가 줄어든다. 본 논문에서는 회전방향 예측 가능 구간 및 예측 방법을 제안하고, 최적화된 Lookup-Table의 크기를 결정하여 기존의 회전방향 예측 알고리즘인 P-CORDIC 과 비교하였다. 그리고, 입력 각이 16비트 경우를 삼성 0.18㎛ 공정을 이용해 논리 합성하여 하드웨어 크기, 성능, 정확성을 검증하였다.

• 전기학회논문지
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• 제66권9호
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• pp.1437-1443
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• 2017

Electric energy is consumed or regenerated according to an operation of electric rail cars in urban railway power substations. A thyristor dual converter system is used to deal with the electric energy. Since the AC input voltage of power substations is $22.9kV{\pm}10%$, the magnitude of the AC voltage fluctuates according to load conditions, so the secondary side voltage of the DDY transformer also fluctuates. In the thyristor dual converter, the response characteristics of the DC output voltage and the DC output current are changed based on an initial firing angle in the cross mode conversion between the forward mode and the reverse mode. Therefore, this paper proposes the initial firing angle tracking algorithm considering fluctuation of the AC input voltage. The effectiveness of the proposed algorithm is verified by a simulation compared with the conventional algorithm.

• 전자공학회논문지D
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• 제35D권2호
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• pp.101-109
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• 1998

In this paper, we implemented holographic optical memory systm which can store and reconstruct many images using new input and angular multiplexing method. In the new input method, phase infomation of input image is inputed in the recording material instead of brightness information. To do so, we represented the images, which captured with CCD camera or displayed on the computer monitor, on the liquid crystal television(LCTV) which removed polarizer/analyzer. Therefore, we can generate uniform input beam intensity regardless of the total brightness of input image, and apply the scheduled recording method. Also we can increase the intensity of input beam so reduce the recording time of input image. And reconstructedimage is acquired by transforming phase information into brightness information of image with analyzer. The incident angle of reference beam is acquired by Fourier transform of the binary phase hologram(BPH) which designed with SA algorithm on the LCTV. The proposed optical memory system is stable because the incident angle of the reference beam is controlled easy and electronically. We demonstreated optical experiment which store and reconstruct various type images in BaTiO$_{3}$ using proposed holographic memory system.