• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.358-360
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• 2007

In this paper, an auto-diagnosis method of the stator winding fault for small induction motor is suggested. 3-phase stator currents are sampled, filtered, and transformed with Park's vector transformation. After then Park's vector patterns are obtained. To detect the stator winding fault automatically, a distortion ratio (id/iq) is newly defined and compared with the one of healthy motor, and the threshold levels are suggested. The 2-turn, 4-turn, 8-turn winding fault are tested with no load, 25%, 50%, 75%, and 100% rated load. The distortion ratio of the Park's vector patterns are increased as the increase of the faulted turns, but are same as the increase of the load.

• Macromolecular Research
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• 제17권10호
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• pp.797-806
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• 2009

The mechanical and thermal behaviors of polyamide-6/clay nanocomposites were studied using the continuum-based, micromechanical models such as Mori-Tanaka, Halpin-Tsai and shear lag. Mechanic-based model prediction provides a better understanding regarding the dependence of the nanocomposites' reinforcement efficiency on conventional filler structural parameters such as filler aspect ratio ($\alpha$), filler orientation (S), filler weight fraction (${\Psi}_f$), and filler/matrix stiffness ratio ($E_f/E_m$). For an intercalated and exfoliated nanocomposite, an effective, filler-based, micromechanical model that includes effective filler structural parameters, the number of platelets per stack (n) and the silicate inter-layer spacing ($d_{001}$), is proposed to describe the mesoscopic intercalated filler and the nanoscopic exfoliated filler. The proposed model nicely captures the experimental modulus behaviors for both intercalated and exfoliated nanocomposites. In addition, the model prediction of the heat distortion temperature is examined for nanocomposites with different filler aspect ratio. The predicted heat distortion temperature appears to be reasonable compared to the heat distortion temperature obtained by experimental tests. Based on both the experimental results and model prediction, the reinforcement efficiency and heat resistance of the polyamide-6/clay nanocomposites definitely depend on both conventional (${\alpha},\;S,\;{\Psi}_f,\;E_f/E_m$) and effective (n, $d_{001}$) filler structural parameters.

• The Journal of Asian Finance, Economics and Business
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• 제6권4호
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• pp.19-26
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• 2019

The study investigates the impact of accrual anomaly on stock return ratio of listed firms in Vietnam. Data were collected from listed firms for the period from 2008 to 2018. To learn about the causes of accrual anomaly in returns and future rate of returns on the Vietnamese stock market, this research is based on accrual analysis of Richardson, Sloan, Soliman, and Tuna (2006) on growth and effective components. We employ GLS regression model for examining the impact of accrual anomaly on stock return ratio and T-test for checking the difference between the lowest and the highest portfolio. The results show that accounting distortion is the main factor impacting the stock return, not growth determinant. Both two determinants of accounting distortion and growth contribute the explanation of the impact of accrual anomaly on profit and future stock return ratio. Experimental evidence confirms an abnormal existence of accrual in the Vietnam stock market. Aggregate accrual is negatively correlated with future operating profit and future stock return. However, after considering the factors contributing to the impact of future profitability and return on stock returns, the study results show that accounting distortion can account for low sustainability of income that is not growth.

• Journal of Power Electronics
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• 제18권6호
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• pp.1642-1649
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• 2018

A single-stage flyback LED AC-DC converter based on primary-side control under constant current mode is proposed in this study. The proposed converter features low total harmonic distortion (THD) and high power factor (PF). It also consists of a zero-crossing distortion compensation circuit and a variable duty ratio control compensation circuit to deal with the line current distortions caused by fixed duty ratio control. The system model and layout are built in Simplis and Cadence, respectively. The feasibility and performance of the proposed circuit is verified by designing and fabricating an IC controller in the HHNEC $0.35{\mu}m$ 5 V/40 V HVCMOS process. Experimental results show that the PF can reach a level in the range of 0.985-0.9965. Moreover, the average THD of the entire system is approximately 10%, with the minimum being 6.305%, as the input line voltage changes from 85 VAC to 265 VAC.

• 대한전자공학회논문지
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• 제3권2호
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• pp.18-23
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• 1966

본청문에서는 후리에 변환을 이용하여 단봉형복, 동조형형, Foster-Seely 형 및 Ratio 변별기의 동적해석을 하였다. 변별기의 출력파형의 디스토오숀과 FM 입력신호정수 및 변별기회로정수와의 제관계를 명시하였다. 복동조형, Foster-Seely 및 Ratio 형변별기에는 우수고조파는 존재하지 않으며 단봉형변별기에는 우수 및 기수고조파가 존재한다. 복동조형 변별기가 변별할 수 있는 주파수대역은 단봉형변별기의 주파수대역보다 10배이상 넓으며 Foster-Seely 및 Ratio 변별기의 것의 약 2배이다.

• 한국CDE학회논문집
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• 제13권1호
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• pp.1-7
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• 2008

Data compression becomes increasingly an important issue for reducing data storage spaces as well as transmis-sion time in network environments. In 3D geometric models, the normal vectors of faces or meshes take a major portion of the data so that the compression of the vectors, which involves the trade off between the distortion of the images and compression ratios, plays a key role in reducing the size of the models. So, raising the compression ratio when the normal vector is compressed and minimizing the visual distortion of shape model's shading after compression are important. According to the recent papers, normal vector compression is useful to heighten com-pression ratio and to improve memory efficiency. But, the study about distortion of shading when the normal vector is compressed is rare relatively. In this paper, new normal vector compression method which is clustering normal vectors and assigning Representative Normal Vector (RNV) to each cluster and using the angular deviation from actual normal vector is proposed. And, using this new method, Visually Undistinguishable Lossy Compression (VULC) algorithm which distortion of shape model's shading by angular deviation of normal vector cannot be identified visually has been developed. And, being applied to the complicated shape models, this algorithm gave a good effectiveness.

• 한국결정학회지
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• 제12권1호
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• pp.14-19
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• 2001

Effects of electric-field-induced lattice distortion on the polarization and strain were investigated in Pb(Mg/sub 1/3/Nb/sub 2/3)O₃ relaxor ferroelectric ceramics in the temperature range of -50℃∼90℃. The ratio of residual strain and polarization (S/sub r//P/sub r/ rarely depends on the temperature. However, the ratio of the electric field included strain and polarization (S/sub induced//P/sub induced/) increased as the temperature decreases below phase transition temperature. To explain these experimental results, a simple rigid ion model concentrating on only Bo/sub 6/ octahedron was suggested.

• 한국통신학회논문지
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• 제35권1C호
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• pp.65-76
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• 2010

OFDM (Orthogonal Frequency Division Multiplexing) 시스템은 고속의 무선 데이터 전송이 가능한 기술이다. 하지만 OFDM과 같은 다중 반송파 시스템은 비선형 왜곡에 매우 민감하다. OFDM 시스템에서는 심볼들을 다중 반송파를 이용하여 변조 후 더하여 전송함으로써 전송 신호 진폭의 변화가 매우 심하다. 이러한 신호 진폭의 변화와 송신기 내에 사용되는 고출력 증폭기 (High Power Amplifier; HPA)의 비선형 특성으로 인해 심각한 비선형 왜곡을 겪게 된다. 본 논문에서는 OFDM 시스템의 높은 PAPR (Peak-to-Average Power Ratio)과 HPA에 의한 비선형 왜곡을 보상하기 위해 CPWL (Canonical Piecewise-Linear) 모델 기반의 새로운 디지털 사전왜곡기를 제안한다. 모의실험을 통하여 새로운 사전왜곡 기법의 성능을 TD (Total Degradation)와 비트오율 (Bit Error Ratio; BER) 측면에서 평가한 결과, HPA에 의해 발생하는 비선형 왜곡을 효과적으로 보상함으로써, 우수한 성능 향상이 있음을 확인하였다.

• 한국지리정보학회지
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• 제12권4호
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• pp.125-135
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• 2009

FIHS(Fast Intensity Hue Saturation) 융합은 빠른 계산 능력 때문에 널리 이용되고 있으나 IHS(Intensity Hue Saturation) 융합과 마찬가지로 분광정보 왜곡 현상이 나타난다. 본 논문에서는 각 분광 대역의 비율을 이용하여 분광정보 왜곡을 줄일 수 있는 융합법(FIHS-BR)과 공간정보 및 분광 대역의 비율을 활용한 적응 FIHS 융합법(FIHS-SABR)을 제안하였다. 제안한 FIHS-BR 융합은 각 분광 대역의 비율을 이용하여 구한 분광 대역별로 서로 다른 공간 해상도 개선 값을 더하여 분광정보 왜곡을 줄일 수 있도록 하였으며, FIHS-SABR 융합은 국부 영상의 공간정보 특성에 따라 적응적으로 결정된 공간 해상도 개선 값을 각 분광 대역의 비율에 따라 분광 대역별로 재조정하여 분광 정보 왜곡을 더 많이 줄일 수 있도록 하였다. 제안한 FIHS-BR 융합과 FIHS-SABR 융합의 성능을 확인하기 위하여 IKONOS 위성 영상에 대하여 컴퓨터 시뮬레이션을 수행하였으며, 실험 결과 제안 방법들이 기존 융합 영상에서 색상 왜곡이 심하게 나타나는 삼림지역 등에서 색상 왜곡 현상이 적게 나타남을 확인할 수 있었으며, 융합 영상의 분광정보 특성 평가 결과도 가장 우수함을 확인할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.565-567
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• 1994

This paper presents a software based NPC PWM inverter control technique to eliminate the harmonics in the output waveforms of inverter. The proposed control technique is able to keep down total harmonic distortion and significantly improve the performance of the inverter. In the control node where the frequency ratio is 36 and the modulation index is $1.2\sim2.0$, the proposed inverter has been operated wi thin 5% Total Harmonic Distortion.