• 제목/요약/키워드: Near AC/A

검색결과 147건 처리시간 0.026초

DyCoO3 세라믹스의 교류전도특성 (Alternating-Current Electrical Conduction Properties of DyCoO3 Ceramics)

  • 정우환
    • 한국재료학회지
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    • 제20권3호
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    • pp.161-166
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    • 2010
  • The ac, dc conductivity and dielectric properties of $DyCoO_3$ were reported in the temperature range of 77 - 300K and in the frequency range of 20 Hz - 100 kHz. It was observed that at low temperature, ac conductivity is much higher than dc conductivity and the hopping carrier between localized states near the Fermi level was the dominant loss mechanism. A comparison of the measured ac conductivity $\sigma(\omega)$ was made with some of the models of hopping conductivity of the proposed earlier in the literature. It was observed that in $DyCoO_3$ the measured ac conductivity, over the entire frequency and temperature region, can be explained reasonably well by assuming two contributions $\sigma_1(\omega)$ and $\sigma_2(\omega)$ to the measured $\sigma(\omega)$. The first, $\sigma_1(\omega)$, which dominates at low temperature, may be due to impurity conduction in a small polaron; the second, $\sigma_2(\omega)$, which dominates at higher temperatures, depending on the frequency of measurements, may be due to the hopping of a small polaron and is reasonable for the dielectric relaxation peak.

3D 영상 시청에 대한 시각적 피로도의 임상적 고찰 (Clinical Consideration of Visual Fatigue on 3D Images)

  • 김정호;손정식;박성진;권순철
    • 한국통신학회논문지
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    • 제38C권11호
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    • pp.990-999
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    • 2013
  • 기존의 연구들에서 이론적 근거를 바탕으로 3D 영상 시청에 대해 시각피로도와 연관이 있는 요소와 영향을 주는 요소들에 대해 경험적 데이터를 기반하여 지속적으로 밝혀내고 있다. 하지만, 이러한 영향을 미치는 요소와 맞물려 실제로 시청자가 느끼는 피로감과 연계하여 측정된 자료는 미비한 상태이다. 본 연구에서는 시청자가 느끼는 자각적 피로도에 따른 시기능적 데이터인 IPD, AC/A비, 그리고 사위도와 그 변화량에 미치는 영향 및 상관관계를 알아보고자 하였다. 자각적 피로도의 기술통계량 점수 $6.00{\pm}3.88$점에 기초하여 피로도 점수 합계 0 ~ 6점을 피로 미호소 그룹, 7 ~ 16점을 피로 호소 그룹으로 분류하였다. 실험 결과 자각적 피로도별 영상 만족도, IPD, 원거리 사위도에서는 차이를 나타내지 않았다. 피로 미호소 그룹에서 AC/A비가 높게 나타났고, 피로 호소 그룹에서는 근거리 사위도가 높게 나타났다. 3D 영상 시청 이후에서는 피로 미호소 그룹에서 더 높은 외사위도 증가 경향을 나타냈다. 본 실험에서 나타난 상관관계에서 AC/A비와 근거리 사위도가 3D 영상 시청 시 느끼는 자각적 피로도와 밀접한 관련이 있는 것으로 나타났다. 3D 영상 시청 시 두 데이터에 기반하여 피로도를 예측할 수 있을 것으로 보이며 콘텐츠 제작 시에도 피로도 경감 차원의 주요한 근거 데이터로 사용될 것으로 판단된다.

단일 스위칭소자를 이용한 전류연속형 PWM AC/DC 부스터 콘버어터의 고역율 구현에 관한 연구 (The study on the high performance continuous input current type PWM AC/DC boost converter using one semiconduction switch)

  • 박성준;변영복;김광태;권순재;김철우
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1995년도 하계학술대회 논문집 A
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    • pp.379-381
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    • 1995
  • Many new electronic products are required to have a near unity power factor and a distortion free input current waveform. In this paper, a high performance single phase PWM AC/DC converter with input power factor correction is proposed. This proposed control strategy has many advantages which include one semiconduction switch, simplified control circuit, high performance features and continuous input current. The experimental results are included to verify the validity of this approach.

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Antiarthritic Activity and Inflammatory Mediators Modulation Effect of Traditional Ajmodadi Churna on Arthritis Experimental Model

  • Vikash Sharma;Shiv Shankar Shukla;Bina Gidwani;Ravindra Kumar Pandey
    • 대한약침학회지
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    • 제26권3호
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    • pp.257-264
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    • 2023
  • Objectives: The study was designed to evaluate anti-arthritic activity of Ajmodadi Churna (AC) and its effect on Complete freund's adjuvant (CFA)-induced arthritis in Wistar rats. Methods: Arthritis was induced by injecting 0.2 mL CFA into sub plantar surface of left hind paw. Test sample AC-1 and AC-2, 200 and 400 mg/kg, respectively was given to the animals for 21 consecutive days. The increase in swelling was observed after induction of arthritis. The paw edema was measured on 0, 3, 7, 14 and 21 day using Vernier caliper after the induction of arthritis. The collected blood samples further used for the estimation of red blood cells (RBC), white blood cells (WBC), erythrocytes sedimentation rate (ESR), and hemoglobin (Hb), using hematology analyzer. Serum concentration of IL-6 and TNF-α were also measured using rat ELISA kits. Results: Results showed that a significant reduction in paw edema was observed in AC-2 treated rats. The paw edema was restored on day 21 was 4.48 mm for AC-2, which is near to the control group. The arthritis score in treated rats was found to be considerably lower than in the control group i.e. 0.83 for AC-2 and 1.50 for AC-1. A decrease in levels of RBC and hemoglobin were observed in arthritic rats. Inflammation was significantly reduced and serum levels of IL-6 and TNF-α were lowered after treatment with the test drug. Conclusion: It can be concluded from the study that AC possess significant anti-arthritic activity. Furthermore, this condition was linked to a reduction in abnormal humoral immune responses.

사위를 가진 정시안의 안정피로에 영향을 미치는 요인 (The Factors Influencing the Asthenopia of Emmetropia with Phoria)

  • 김정희;이동희
    • 한국안광학회지
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    • 제10권1호
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    • pp.71-82
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    • 2005
  • 사위를 가진 정시안의 안정피로에 영향을 미치는 요인을 조사하고 양안 시생활에서 느낄 수 있는 안정피로 완화를 위한 기초 자료를 제공하고자, 사시안, 안질환 또는 전신질환을 가지고 있는 자를 제외하고, 무작위로 근거리 시작업을 지속적으로 하고 있는 19세에서 30세 미만의 327명을 검사대상으로 하여 사위량, 폭주기능, 조절기능, AC/A를 측정하고 설문지를 통해 양안시에서의 안정피로 여부를 조사하였다. 또한, 안정피로에 영향을 미치는 요인들을 분석하고, 안정피로를 느끼는 사람들에게 프리즘을 장용하여 안정피로 증상이 완화되는지를 확인하였다. 자료 분석은 Chi-Square 단별량 검정과 다변량 Logistic 회귀분석으로 하였고, 다음과 같은 결과를 얻을 수 있었다. 정시안의 양안시에 영향을 미치는 특성별 단별량 분석에서는 조절력과 폭주력이 낮을 때 안정피로 호소가 매우 유의하게 높았으며(p<0.001), AC/A는 낮을수록 안정피로 호소가 높은 경향을 보였고, 근거리 사위량은 크게 영향을 미치지 않았다. 다변량 로지스틱 분석을 한 결과에서는 조절력과 폭주력이 낮을 때 안정피로 호소율이 매우 높았고 통계학적으로 유의한 상관관계가 있는 것으로 조사되었다. 근거리에서 사위는 내사위를 가지고 있거나 기준치보다 많은 외사위량을 가지고 있을 때 안정피로 호소율이 높았고, AC/A는 정상에 비해 낮을 때가 안정피로 호소율이 높은 것으로 나타났으나, 근거리 사위량과 AC/A는 안정피로와 상관관계가 없는 것으로 조사되었다. 근거리 양안시에서 안정피로를 호소하는 사위를 가진 정시안에 프리즘을 처방하였더니 정시에서는 74.2%가 안정피로 증상이 완화되었다.

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광전극으로서 TiO2 부동태 피막의 반도체 성질에 대한 연구 (Semiconductive Properties of Passivating TiO2 Film as Photoanode)

  • 김창하;변수일
    • 한국수소및신에너지학회논문집
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    • 제1권1호
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    • pp.48-54
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    • 1989
  • Semiconductive property of the passivating $TiO_2$ film was investigated by measuring the impedance of passivated titanium electrode in a 0.1 N NaOH solution. The passive film was prepared galvanostatically with $10mA/cm^2$ at formation potential of 50 V in a 1 N $H_2SO_4$ solution. The impedance measurement was conducted by superimposing an ac voltage of 5 m V amplitude with the frequency ranging from 5 to 10000 Hz on a dc bias (applied potential). The donor distribution in the film was depicted from the analysis of the non-linear slope of Mott-Schottky plot. The region with nearly constant concentration of donors near the electrolyte/film interface amounts at about 60 percent of the total film thickness and donor concentration increases largely with distance from the surface in an inner region near the film/metal interface. In a region of the film/metal interface the donor concentration showed a frequency dependence greater than in a region of the electrolyte/film interface. The result of donor concentration against frequency suggests a transition from crystalline to amorphous state with distance from the electrolyte/film interface in the passivating $TiO_2$ films. This is also confirmed by the ac conductivity measurement.

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An Electrical and Optical Characteristics of the Color ac Plasma Displays with a New Cell Structure

  • Lee, Woo-Geun;Lee, Jae-Young;Park, Jae-Moon;Park, Chung-Hoo
    • Journal of Information Display
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    • 제2권1호
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    • pp.5-9
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    • 2001
  • New types of ac plasma display panel (PDP) cells are designed and tested electro-optically. We proposed two types of sustaining electrode to improve the luminous efficiency. One is the meander electrode, which has longer discharge path length and smaller electrode area than conventional type. The other is the bridge-shaped electrode, which eliminates the transparent electrode near the barrier ribs. They show higher luminous efficiency and lower power consumption than conventional type.

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전원선용 SPD의 효과적인 설치기법 (An Effective Approach of Installation of Surge Protective Devices for AC Mains)

  • 이동문;정동철;이승칠;이복희
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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    • pp.2229-2231
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    • 2005
  • Recently, damages of electronic equipments due to lightning surges coming from AC power lines are increasing. In this work, to propose the effective installation methods of surge protective devices(SPDs), the protective performances of SPDs in actual-sized test circuits were experimentally investigated. In order to obtain the lowest limiting voltage and best protection, long leads of SPDs in installation practices are significantly undesirable. An effective installation method of SPDs for AC mains was proposed. The way of installing SPDs at every branch circuits is more effective than that of installing a SPD near the point of entry.

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A Single-Input Single-Output Approach by using Minor-Loop Voltage Feedback Compensation with Modified SPWM Technique for Three-Phase AC-DC Buck Converter

  • Alias, Azrita;Rahim, Nasrudin Abd.;Hussain, Mohamed Azlan
    • Journal of Power Electronics
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    • 제13권5호
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    • pp.829-840
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    • 2013
  • The modified sinusoidal pulse-width modulation (SPWM) is one of the PWM techniques used in three-phase AC-DC buck converters. The modified SPWM works without the current sensor (the converter is current sensorless), improves production of sinusoidal AC current, enables obtainment of near-unity power factor, and controls output voltage through modulation gain (ranging from 0 to 1). The main problem of the modified SPWM is the huge starting current and voltage (during transient) that results from a large step change from the reference voltage. When the load changes, the output voltage significantly drops (through switching losses and non-ideal converter elements). The single-input single-output (SISO) approach with minor-loop voltage feedback controller presented here overcomes this problem. This approach is created on a theoretical linear model and verified by discrete-model simulation on MATLAB/Simulink. The capability and effectiveness of the SISO approach in compensating start-up current/voltage and in achieving zero steady-state error were tested for transient cases with step-changed load and step-changed reference voltage for linear and non-linear loads. Tests were done to analyze the transient performance against various controller gains. An experiment prototype was also developed for verification.

자기센서용 Ni-PZT-Ni, Co, Fe 적층구조 소자의 ME 특성 (Magnetoelectric Characteristics on Layered Ni-PZT-Ni, Co, Fe Composites for Magnetic Field Sensor)

  • 류지구;전성즙
    • 한국전기전자재료학회논문지
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    • 제28권2호
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    • pp.92-98
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    • 2015
  • The magnetoelectric characteristics on layered Ni-PZT-Ni, Co, Fe composites by epoxy bonding for magnetic field sensor were investigated in the low-frequency range. The ME coefficient of Ni-PZT-Ni, Ni-PZT-Co and Ni-PZT-Fe composites reaches a maximum of $200mV/cm{\cdot}Oe$ at $H_{dc}=110$ Oe, $106mV/cm{\cdot}Oe$ at $H_{dc}=90$ Oe and $87mV/cm{\cdot}Oe$ at $H_{dc}=160$ Oe, respectively. A trend of ME charateristics on Ni-PZT-Co, Ni-PZT-Fe composites was similar to that of Ni-PZT-Ni composites. The ME output voltage shows linearly proportional to ac field $H_{ac}$ and is about 0~150 mV at $H_{ac}$=0~7 Oe and f=110 Hz in the typical Ni-PZT-Ni sample. The frequency shift effect due to the load resistance $R_L$ shows that the frequency range for magnetic field sensor application can be modulated with appropriate load resistance $R_L$. This sample will allow for a low-magnetic ac field sensor in the low-frequency (near f=110 Hz).