• 대한전자공학회논문지
• /
• 제26권3호
• /
• pp.137-144
• /
• 1989

아나로그 승산기를 구현하기 위하여 OTA를 회로의 기본요소로 사용하였다. OTA에서 일반적으로 나타나는 이동도 감쇄등의 비이상적인 현상을 두개의 OTA를 크로스 커플 형태로 사용함으로써 최소화 할 수 있음을 보였다. 실험적으로 $90^{circ}C$의 고온에서도 3차 고조파왜곡이 상쇄됨을 확인함으로써 OTA를 기본으로 하는 접근방식이 아나로그 신호처리에 적합함을 입증하였다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.144-147
• /
• 2000

The effect of accelerated aging test on ethylene-propylene-diene monomer(EPDM) rubber used for outdoor insulation was studied by X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), FFT spectrum alalysis, and electrical pulse counts using PC by oscilloscope(300 MHz). In electrical alalysis, FFT spectrum analysis indicated arcing caused a significant increase in the third harmonic content of the leakage current of polluted insulator. Also, pulse counts increased as aging time. The surface oxygen and aluminum content were found to increase and that of carbon and nitrogen were found to decrease with time. The detailed XPS analysis indicated that the concentration of carbon in C-C decreased and concentration of highly oxidized carbons increased with time, which was due to the oxidation of EPDM rubber polymer SEM analysis indicated that crack and erosion of EPDM rubber occurred with time.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
• /
• pp.59-61
• /
• 2003

This paper demonstrates an analysis of harmonics at the high speed railway substation and proved on this countermeasure using the PSCAD/EMTDC simulation tool. First, high speed railway feeding system is composed using PSCAD/EMTDC electrical railway feeding system model in advance. Second, This paper applications line capacitance values as feeder-trolley, trolley-rail and feeder-rail to analysis harmonics more accuracy in advance did not application. This capacitance values calculate using the EMTP(Electro Magnetic Transient Program). Third, the tractions are arranged in the section that substation supplies power, and this paper take the simulation each case(fractions composition amount) to see harmonic propagation from traction to substation. As a result, generated harmonics at traction can confirmed that harmonics did not reduce at utility source. This harmonics have an influence on bulk power system. Finally, this paper introduces the methods of harmonics effect minimum. This paper proved harmonics reduce effect through the passive filters application.

• Bulletin of the Korean Chemical Society
• /
• 제17권7호
• /
• pp.607-612
• /
• 1996

A series of new NLO-active poly(4-nitrophenylallylamine) derivatives was synthesized by the nucleophilic substitution reaction of several substituted 4-nitrohalobenzenes and poly(allylamine hydrochloride). All polymers obtained were amorphous and their glass transition temperatures (Tg) were observed around 148-160 ℃. For each of these polymers, their specific Tg values were dependent on characteristic electronic structures. UV-visible absorption spectra showed maximum absorption intensity at 355-393 nm for π-π* transition of alkylaminonitrophenyl groups. The χ(2)value of poly(4-nitrophenylallylamine), as determined by the second harmonic generation at 1064 nm, for a thin polymer film poled at an elevated temperature, was 1.4x10-8esu. The third-order NLO properties of poly(4-nitrophenylallylamine) derivatives were evaluated through measurement of degenerate four-wave mixing technique and χ(3) coefficient in the range of 2.7~3.2x10-12 esu at 602 nm was found with 400 fs laser pulses.

• Advances in nano research
• /
• 제13권1호
• /
• pp.47-61
• /
• 2022

The present research investigates the dynamic behavior of a rotating functionally graded (FG) nonlocal cylindrical beam. The cylindrical beam is mathematically modeled via third-order beam theory linked with nonlocal strain gradient theory. The tube structure is made of functionally graded materials composed of Aluminum oxide coated on the Nickel, which the mechanical properties vary in the tube radius direction according to the power law. The bending harmonic force is applied in the tube length middle. The nonlocal spinning equations of the tube are derived via the energy method of the Hamilton principle, and they are solved via a robust numerical procedure for different boundary conditions. The main application of the rotating nanostructures is for the production of small-scale motors and devices and the drug-delivery application, the presented results can help the researcher have a better view regarding the different conditions.

• Bulletin of the Korean Chemical Society
• /
• 제32권5호
• /
• pp.1443-1454
• /
• 2011

Methods to prepare novel second-order nonlinear optical (2O-NLO) materials composed of all-silica zeolite (silicalite-1) and a series of 2O-NLO molecules having high second order hyperpolarizability constants (${\beta}$ values) are reviewed. These methods include the development of novel methods to incorporate a series of hemicyanine (HC) molecules into the channels of silicaite-1 films in uniform orientations. The first method is to incorporate HC molecules tethered with long alkyl chains (octadecyl or longer) into the silicalite-1 channels with the long alkyl chain side first through the hydrophobic-hydrophobic interaction between the long alky chains and the silicalite-1 channels. The second method is to incorporate the HC molecule tethered with a medium length alkyl chain (nonyl) into the silicalite-1 channels with the medium length alkyl chain side first through hydrophobic-hydrophobic interaction between the medium length alky chain in the photoexcited state and the silicalite-1 channels. The third method is to incorporate the HC molecule tethered with propionic acid into the silicalite-1 channels with the propionic acid side last mediated by a tetrabultylammonium cation ion-paired to the propionate unit. A method to prepare a novel third-order nonlinear optical (3O-NLO) material composed of zeolite-Y and PbS or PbSe quantum dots is also reviewed. This Account thus describes a promising new direction to which the search for highly sensitive 2O-NLO and 3O-NLO materials has to be conducted and a new direction to which zeolite research and applications have to be expanded.

• 전력전자학회논문지
• /
• 제9권3호
• /
• pp.213-221
• /
• 2004

최근에, 평활용 직류 커패시터가 설치된 다이오드 정류기가 가전제품 및 교류 운전 장치와 같은 전자 장치에 점점 많이 사용되고 있고, 이러한 부하에 의해서 발생하는 고조파 문제가 점차 중요한 문제로 부각되고 있다. 또한, 3상 4선식 전력 시스템은 상업용 빌딩이나 제조 플랜트 등에 전력을 공급하는 방법으로 많이 사용되고 있는데 이러한 시스템에서는 중성선에 과도한 전류가 흐르게 되고, 중성선 전류는 기본적으로 3고조파 성분으로 중성선 도체 사이즈 선정의 실패나 중성점의 전위를 상승시키거나 변압기의 과열 현상 등을 유발할 수 있다. 이러한 관점에서 본 논문에서는 직접 보상전압 추출기법으로 동작하는 직렬 형 능동 필터를 제안하며, 성능함수 알고리즘의 장점은 게인을 곱하지 않고 보상 전압을 직접 구함으로써, 어떠한 다른 알고리즘보다 보상 전압 계산 방법이 간단하다. 제안된 알고리즘의 타당성을 증명하기 위하여 프로토타입 능동 필터를 제작하여 실험을 수행하였다.

• 대한전자공학회논문지TC
• /
• 제43권1호
• /
• pp.127-132
• /
• 2006

본 논문은 입력되는 주파수 대역에 따라 증폭기 및 주파수 체배기로 동작하도록 설계하여, 무선 LAN의 다양한 표준인 802.11a/b/g의 주파수 대역을 만족하는 이중 모우드 증폭기를 설계하였다. 기존의 이중대역 무선 LAM의 경우 동작주파수에 따라 별도의 증폭기를 구성하는 형태였으나, 본 연구에서는 서로 다른 바이어스 조건에 따라 802.11b/g 신호에 대해서는 증폭기로서 동작하고, 802.11a 신호에 대해서는 주파수 체배기로 동작하여 하나의 능동회로를 이용하여 각기 다른 표준의 주파수 대역을 증폭할 수 있도록 하였다. 증폭기로 동작할 경우 약 13dB의 이득과 약 17dBm의 PldB을 얻었으며, 2차 고조파는 약 -37dBc 이하로 억압되었다. 주파수 체배기로 동작할 경우 약 3.3dB의 체배 이득과 약 7.3dBm의 최대 전력을 얻었으며, 3차 고조파는 약 -50dBr 이하로 억압되었다.

• 대한후두음성언어의학회지
• /
• 제13권1호
• /
• pp.28-32
• /
• 2002

Background and Objective : Classical singing students who have received in systematic voice training appeared distinctive voice characteristics compared to normal people who have not received in systematic voice training. The purpose of this study was to determine the correlation between acoustic parameters and Electroglottography(EGG) parameters in two groups(ordinary college students vs. classical singing students group). Materials and Methods : The 80 ordinary college students and 65 classical singing students participated in this study by utilizing Dr. speech program to obtain acoustic measurements and physiologic measurements simultaneously. The Pearson correlation coefficient was used to find the correlation between acoustic parameters and EGG parameters in two groups(ordinary college students group and classical singing students group). Results : The results of the study were as follows : First, there was no correlation between Jitter and EGG Jitter in ordinary college students group, but there was strong correlation between Jitter and EGG Jitter in classical singing students group. Second, there was no correlation between Shimmer and EGG Shimmer in ordinary college students group, but there was strong correlation between Shimmer and EGG Shimmer in classical singing students group. Third, there was no correlation between Harmonic to Noise Ratio(HNR) and EGG HNR in ordinary college students group, but there was strong correlation between HNR and EGG HNR in classical singing students group. Finally, there was no correlation between Normalized Noise Energy(NNE) and EGG NNE in two groups.

• 전자공학회논문지T
• /
• 제35T권3호
• /
• pp.128-133
• /
• 1998

본 논문은 클록 초기치 누적 방식의 직접 디지털 주파수 합성기를 이용한 변조기의 성능해석에 관하여 연구한 것이다. 기존에는 랜덤한 주파수 도약을 실현하기 위하여 PLL 방식이나 디지털 주파수 합성 방식이 사용되어 왔다. 븐 논문에서는 두 방식의 단점을 개선하기 위하여 클록 초기치 누적 방식의 DDFS를 이용한 변조기 시스템을 구성하여 순시적인 주파수 도약 상태와 위상제어의 가능성 등을 확인하였다. 실험 결과 합성된 출력 주파수는 주파수 Index에 따라 기준주파수에 정확히 정수배가 되며, 합성된 정현파형의 스펙트럼은 기본파와 여러 고조파의 크기가 50 [㏈] 이상의 차이가 남으로서 고조파 성분들이 상당히 감소되었고, PN 코드를 사용한 순시적인 주파수 도약 상태는 스위칭 시간이 빠르기 때문에 주파수 도약 특성이 뛰어남을 알 수 있었다. 또한, 누산기의 set/reset상태변화에 따라 위상이 변한다는 사실도 입증하였다.