• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.349-350
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• 2007

Polyethylene is widely used as the insulator for power cable. To investigate the conduction mechanism for power cable insulation under ac high field, it is very important to acquire the dissipation current under actual running field. Recently, we have developed the unique system, which make possible to observe the nonlinear dissipation current waveform. In this system, to observe the nonlinear properties with high accuracy, capacitive current component is canceled by using inverse capacitive current signal instead of using the bridge circuit for canceling it. As the results of these estimations, it was found that the dissipation current will depend on not only the instantaneous value of electric field but also the time differential of applied electric field due to taking a balance between applied field and internal field. Furthermore, two large peaks of dissipation current for each half cycle were observed under certain condition. In this paper, to clarify the reason why it shows two peaks for each half cycle, the film thickness dependences of dissipation current waveforms were observed by using the three different thickness LDPE films.

• 한국세라믹학회지
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• 제24권5호
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• pp.477-483
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• 1987

Cr2O3 doped Pb(Zr0.525 Ti0.475)O3 piezoelectric ceramics were prepared from reagent grade oxide mixture, PbO, ZrO2, TiO2 and Cr2O3. Piezoelectric and aging properties of specimens were measured for various additions of Cr2O3. Generally, it has been known that aging rate decreased with Cr2O3 addition by stabilizing the domain wall. But hysteresis loops showed that the domain destabilization was occurred at high electric field (larger than 10KV/cm). In smaller additions of Cr2O3 (0-0.2mol%), aging rate increased and microcracks were created with increasing poling filed due to increasing internal stress. In larger additions of Cr2O3(0.4∼0.6mol%), aging rate decreased with increasing poling field.

• 한국염색가공학회지
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• 제9권1호
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• pp.23-32
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• 1997

Composite membranes having different mixing ratio of Wool(SCMK) and poly(ethylene terephthalate) (PET) were prepared by dissolving wool/PET in hexafluoro-2-propanol(HFIP), casting the obtained solution on a glass plate and evaporation the solvent in the presence and absence of an electric field. The internal structure of the prepared membrane was investigated using polarise microscope dyeing and dye permeation method. In the composite membrane prepared under electric field, both components were micro mixing, while in the membranes prepared under nonelectric field, the two components formed a random sea/island structure according to different mixing ratio. Such characteristic membrane structure was influenced the permeation behavior of C.I. Acid Red 118 through the membranes from an aqueous solution.

• Journal of Information Display
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• 제10권4호
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• pp.143-148
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• 2009

The theoretical current density equations for organic semiconductors was derived according to the internal carrier emission equation based on the diffusion model at the Schottky barrier contact and the mobility equation based on the field dependence model, the so-called "Poole-Frenkel mobility model." The electric field becomes constant because of the absence of a space charge effect in the case of a higher injection barrier height and a lower sample thickness, but there is distribution in the electric field because of the space charge effect in the case of a lower injection barrier height and a higher sample thickness. The transition between the injection- and bulk-limited currents was presented according to the Schottky barrier height and the sample thickness change.

• 한국세라믹학회지
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• 제29권10호
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• pp.806-814
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• 1992

The aim of this study was to investigate the change in compressive strength, freacture behavior and degradation of piezoelectric properties with compressive cyclic loading in Pb(Zr, Ti)O3 of tetragonal, morphotropic phase boundary and rhombohedral composition. The highest compressive strength was found in rhombohedral composition. After poling treatment the strength increased by 8.4% and 6.5% in tetragonal and morphotropic phase boundary compositions respectively while changed little in rhombohedral. The increase of compressive strength after poling treatment is believed to be due to the internal stress around grain boundary by domain alginment toward electric field direction in the microstructures having tetragonality and the occurrence of domain switching to the direction perpendicular to electrical field during fracture. Fracture mode relatively change from transgranular to intergranular was observed in the large grain sized tetragonal and morphotropic phase boundary compositions before and after poling but the transgranular fracture mode always remained in the rhombohedral composition. From the X-ray diffractometer analysis the domains parallel to the electric field direction is known to undergo rearrangement during the cyclic loading into random direction that is responsible for the degradation of piezoelectric property.

• 한국항공우주학회지
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• 제47권4호
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• pp.300-308
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• 2019

드론이 농업 및 산업 운송 분야에 이용되기 위해서는 큰 탑재 하중과 긴 운용시간이 필요하다. 현재의 배터리 기술로는 탑재 하중과 체공 시간을 늘리는 데에 한계가 있고, 특히 현장에서 지속적인 운용이 필요할 때에 배터리의 충전 또는 교환이 번거로운 문제가 있다. 본 연구에서는 내연기관과 발전기, 그리고 배터리와 전기모터가 결합된 복합적인 추진기관을 사용하는 드론의 동력시스템을 최적화하는 과정을 제시한다. 운반과 운용의 제약을 고려하여 이륙중량 200kg 급의 기체를 선정하였다. 내연기관과 직접 연결된 2개의 주 로터가 기체 중량의 대부분을 담당하고, 내연기관으로 구동되는 발전기의 전력을 사용하는 4개의 모터가 자세제어를 담당하도록 시스템을 구성하였다. 드론의 에너지 흐름을 파악하여, 기존의 상용품 중 최적의 모터와 프로펠러를 선정하는 기법을 제시하고, 내연기관의 측정 데이터를 이용하여 최적의 운용 점과 기어비를 도출하는 기법을 제시한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.588-593
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• 2014

Current crowding problem can worsen the internal quantum efficiency and the negative-voltage ESD of InGaN-based LEDs. In this paper, by using photon emission microscope and thermal emission microscope measurement, we confirmed that the electric field and the current of the InGaN-based LED sample are crowded in specific regions where the distance between p-type metal contact and n-type metal contact is shorter than other regions. To improve this crowding problem of electric field and current, modified metal contact geometry having uniform distance between the two contacts is proposed and verified by a numerical simulation. It is confirmed that the proposed structure shows better current spreading, resulting in higher internal quantum efficiency and reduced reverse leakage current.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.415-415
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• 2013

We have investigated the optical and electrical properties of the CIGS thin film solar cells by the electroreflectance (ER), photoreflectance (PR), photoluminescence (PL), and photocurrent (PC) spectroscopies at room temperature. The ER spectrum had two narrow signal regions and one broad signal region. We measured PL and PC to confirm the signals at low energy region (1.02~1.35 eV), so these signals are related to the CIGS thin film, and the high energy region (2.10~2.52 eV) is related to the CdS bandgap energy. The broad signal region (1.35~2.09 eV) is due to the internal electric field by the p-n junction from the comparison between PR and ER spectra, and we calculated the internal electric field by the p-n junction. In the high efficiency solar cell, the CdS signal of ER spectrum is narrower than the lower efficiency solar cells.

• 풍력에너지저널
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• 제15권2호
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• pp.5-9
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• 2024

This paper describes the insulation breakdown characteristics of 72.5 kV dry-air insulated switchgear under development for installation in a wind power generator when a lightning impulse voltage is applied. For this study, the weak point of insulation due to the electric field concentration of the switchgear's internal shape was identified by finite element method (FEM) analysis, and the shape was actually simulated to measure and analyze the polarity of the lightning impulse voltage and the insulation breakdown characteristics according to the gas pressure at dry-air pressures of 0.1 Mpa to 0.45 Mpa. This study derives the maximum electric field with a 50 % discharge probability for each switchgear internal insulation vulnerable point based on the actual test and electrical simulation, which will be useful as reference data for supplementing and changing insulation design in the future.

• 공업화학
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• 제28권3호
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• pp.290-293
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• 2017

블록공중합체와 나노입자로 이루어진 박막은 많은 관심을 불러 일으켜 왔다. 그리고, 이 혼성체들의 물성과 거동을 조절하기 위해서 다양한 방법이 접근되어 왔다. 본 연구에서는, 블록 공중합체와 나노입자로 이루어진 복합체를 박막 형태로 제조한 후, 이를 전기장에 조사하여 박막 내부 구조의 변화와 거동을 살펴보고자 한다. 본 실험에서는 폴리스티렌과 폴리(2-비닐피리딘)으로 구성된 블록공중합체를 사용하였고, 영구 쌍극자를 포함하는 CdSe 나노 입자를 그 속에 도입하였다. 이를 스핀코팅을 통해 박막 형태로 제조하였고, 전기장을 조사하여 전자현미경 방법으로 내부의 구조변화를 고찰하였다. 결과적으로 도입된 나노입자는 전기장에 의해 부여된 힘에 영향을 거의 받지 않고 블록공중합체의 내부에 존재하였으며, 공중합체의 내부 미세상은 전기장의 영향을 받아 전기장 방향으로 배향하였다. 이는 향후 이종으로 구성된 나노복합체의 전기장 하에서의 거동을 파악하는 데 도움이 될 것이다.