• 대한물리치료과학회지
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• 제22권1호
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• pp.11-17
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• 2015

Purpose : The current study examines changes of static uprighting balance in the visual input characteristics. Method : Total 50 person(male 16, female 34) were participated in this study. They were tested with 'hole in the card' for identification of dominant eye's side, then they were divided 3 groups(both visual input group, dominant visual input group, and non-dominant visual input group). 3 groups were measured with Romberg test on the force platform device to compare the static uprighting balance characteristics ; moving distance, mean velocity, and sway area of the CoM(center of mass), during 20 seconds. Results : The results by one-way repeated measure ANOVA were as follows. In moving distance and mean velocity of CoM, non-dominant visual input group was unstable than dominant visual group and both visual input group(p<0.05). But, in sway area of CoM, significant difference was not existed statistically. Conclusion : These result can be applied to design the static uprighting balance program using visual input mediation.

• 한국군사과학기술학회지
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• 제11권2호
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• pp.144-151
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• 2008

An experimental study has been conducted to investigate the effects of circular damage hole on the characteristics of airfoil performance. The damage on a wing created from a hit by anti-air artillery was modeled as a circular hole. Force balance measurements and static pressure measurements on the wing surface were carried out for the cases of having damage holes of 10% chord size at quarter chord and/or half chord positions. All experiments were conducted at Reynolds number of $2.85\times10^5$ based on the chord length. The surface pressure data show big pressure alterations near the circular damage holes. This abnormal surface pressure distribution produces shear stress that could lead to the acceleration of the structural degradation of the wing around the circular damage hole. However, in spite of the existence of circular damage holes, the measured force data indicated the only a slight decrease in lift accompanied by increase in drag compared to the results of undamaged one. The influence of damage hole on the aerodynamic performance was increased as the location of damage moved to the leading edge. The effect on the control force was insignificant when the damaged size was not large.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.146-146
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• 2015

We report the enhanced performance of poly(N-vinylcarbozole) (PVK)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based quantum-dot light-emitting diodes by inserting the polyaniline:poly (p-styrenesulfonic acid) (PANI:PSS) interlayer. The QD-LED with PANI:PSS interlayer exhibited a higher luminance and luminous current efficiency than that without PANI:PSS. Ultraviolet photoelectron spectroscopy results exhibited different electronic energy alignments of QD-LEDs with/without the PANI:PSS interlayer. By inserting the PANI:PSS interlayer, the hole-injection barrier at the QD layer/PVK interface was reduced from 1.45 to 1.23 eV via the energy level down-shift of the PVK layer. The reduced barrier height alleviated the interface carrier charging responsible for the deterioration of the current and luminance efficiency. This suggests that the insertion of PANI:PSS interlayer in QD-LEDs contributed to (i) increase the p-type conductivity and (ii) reduce the hole barrier height of QDs/PVK, which are critical factors leading to improve the efficiency of QD-LEDs.

• 지질공학
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• 제13권3호
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• pp.281-292
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• 2003

모형시추공 내에서 공내수 전기전도도의 자동 측정시스템을 구축하고 이로부터 수리상수 결정과 관련된 제반 기초 환경을 검증하였다. 실험은 상대적으로 높은 염도를 공내수로 하고 증류수를 지층수로 사용하여 지층수의 유입과 유출되는 유량을 일정하게 유지한 상태에서 공내수의 전기전도도 프로파일을 구하는 방식으로 이루어졌다. 관찰의 주 대상은 공내수와 지층수 사이의 염도차. 온도차 및 지층수의 유입량. 유입 ·유출구에 따른 모형시추공 내에서의 전기전도도 변화 양상 파악에 있었다. 실헌결과, 이들 요인이 미치는 영향범위와 적정 측정 환경이 제시되어 향후 모델 실험 및 원위치시험에서 적용될 기초실험 여건이 마련되었다.

• 전기전자학회논문지
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• 제24권3호
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• pp.706-712
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• 2020

유기전기발광소자(Organic light diodes, OLEDs)의 전기발광특성을 향상시키기 위해, 본 논문에서는 용액 공정 정공주입층으로 신규 hexaazatrinaphthylene(HATNA) 유도체들을 도입한 고효율 녹색인광 OLED소자의 특성을 연구하였다. HATNA 유도체는 Indium Tin Oxide(ITO)의 일함수와 비슷한 낮은 the lowest unoccupied molecular orbital(LUMO) 에너지 준위를 가져 다른 개념의 정공주입 메커니즘을 보여주었다. HATNA 유도체를 hole injection layer(HIL)로 사용한 OLED소자들은 HTL로의 정공주입장벽을 효과적으로 감소시키고 발광층 내에 전자와 정공의 균형을 최적화 시켜 외부양자효율이 10.8%에서 15.6%로, 전류 효율은 34.3 cd/A에서 42.7 cd/A로 소자 효율이 크게 향상 되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.250-250
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• 2012

Organic light-emitting diodes (OLED) and polymer light emitting diodes (PLED) have been regarded as the candidate for the next generation light source and flat panel display. Currently, the most common OLED industrial fabrication technology used in producing real products utilizes a fine shadow mask during the thermal evaporation of small molecule materials. However, due to high potential including low cost, easy process and scalability, various researches about solution process are progressed. Since polymer has some disadvantages such as short lifetime and difficulty of purifying, small molecule OLED (SMOLED) can be a good alternative. In this work, we have demonstrated high efficient solution-processed OLED with small molecule. We use CBP (4,4'-N,N'-dicarbazolebiphenyl) as a host doped with green dye (Ir(ppy)3 (fac-tris(2-phenyl pyridine) iridium)). PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) and TPD (N,N'diphenyl-N,N'-Bis (3-methylphenyl)-[1,1-biphenyl]-4,4'-diamine) are employed as an electron transport material and a hole transport material. And TPBi (2,2',2''-(1,3,5-phenylene) tris (1-phenyl-1H-benzimidazole)) is used as an hole blocking layer for proper hole and electron balance. With adding evaporated TPBi layer, the current efficiency was very improved. Among various parameters, we observed the property of OLED device by changing the thickness of hole transporting layer and solvent which can dissolve organic material. We could make small molecule OLED device with finding proper conditions.

• 공업화학
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• 제26권6호
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• pp.725-729
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• 2015

유기발광다이오드(organic light emitting diodes, OLEDs)는 높은 효율, 안정성, 신물질 개발과 같은 연구들을 바탕으로 차세대 디스플레이 및 조명으로써의 높은 기술력과 학문적 발전을 달성하였다. 본 논문에서는 hexaazatrinaphthylene (HAT) 유도체들을 OLEDs 소자의 정공주입층으로 사용하여 제작된 고효율의 녹색 인광 OLEDs 소자의 특성을 연구하였다. Indium Tin Oxide (ITO)전극과 정공수송층 사이에 삽입된 박막의 HAT 유도체층은 $1,000cd/m^2$의 구동 조건에서 OLEDs 소자의 외부양자효율을 기존의 8.8%에서 13.6%로, 전류효율을 30.8 cd/A에서 47.7 cd/A로 각각 향상시켰다. 삽입된 HAT 유도체층은 발광층 내부에서 최적화된 전자-정공의 균형을 이루게 하여 소자의 효율 향상에 기여하였다.

• 한국산업정보학회논문지
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• 제10권2호
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• pp.76-81
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• 2005

본 연구에서는 차세대 디스플레이 소자로 각광을 받고 있는 유기발광 소자의 전기적인 특성을 해석적으로 접근하였다. 기본적인 OLED의 동작 메카니즘은 일함수(work function)가 낮은 음극(cathode) 전극으로부터 주입된 전자(electron)와 양극(anode) 전극으로 주입된 정공(hole)이 수송층을 지나 발광층으로 유입되어 여기상태(exciton state)를 거치며 재결합함으로써 발광되는 것으로 알려져 있다. 따라서 음극과 양극을 통해 들어오는 수송자(carrier)들이 원활한 전자-정공 쌍(electron - hole pair)을 이루기 위해 다층 박막 구조로 소자를 제작하여 높은 에너지 장벽을 완만하게 만들고 또한 박막의 두께를 조절하여 정공과 전자의 이동도 밸런스(balance)를 맞추어 수송자-전자와 정공-들이 수송층(CTL : carrier transport layer)을 통해 발광층(EML : emitting material layer)으로 주입을 용이하게 만든다 따라서 본 논문에서는 유기 발광소자의 최적의 발광특성을 얻기 위해서는 수치 해석을 통한 가장 높은 발광 효율을 가지게되는 박막의 두께를 예측하고 예측된 유기발광소자의 수치해석 값이 실제 제작된 소자의 특성 값과 일치하여 타당성이 있음을 증명하고자 한다.

• 한국전기전자재료학회논문지
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• 제23권7호
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• pp.539-544
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• 2010

We have synthesized new blue electroluminescent polyalkylfluorene-based copolymers [poly(F-co-Py)x:y, where x:y = 99:1 or 95:5 mole ratios] containing the hole-injecting pyrazole derivative [3,3'-(4,6-bis(octyloxy)-1,3-phenylene)bis(1,5-diphenyl-4,5-dihydro-1H-pyrazole] through Ni(0) mediated polymerization, and their electroluminescent properties were investigated. Electroluminescent (EL) devices were fabricated with ITO / PEDOT:PSS (110 nm) / copolymers or PF homopolymer (80 nm) / Ca (50 nm) / Al (200 nm) configuration. Each EL device constructed from the copolymer exhibited significantly enhanced brightness and efficiency compared with a device constructed from the PF homopolymer. The EL device constructed with poly(F-co-Py)99:1 exhibited the highest luminous efficiency and brightness (0.95 cd/A and $2,907\;cd/m^2$, respectively). The achieved luminous efficiency was an excellent result, providing almost a 4-fold improvement on the efficiency obtainable with the a PF homopolymer device. This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arises from the HOMO level (~5.83 eV) of the poly(F-co-Py)99:1 copolymer, which is higher than that of the PF homopolyme (~5.90 eV).

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.632-635
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• 2004

We have studied the effect of $TiO_2$ layer deposited by RF magnetron sputtering which is used as an ultra thin hole-injection buffer layer in organic light-emitting diode (OLED). The $TiO_2$ thin film layer prevents metallic ions from diffusing from the ITO layer to the organic layers and improves the balance of hole and electron injections and the interface characteristics between the electrode and the organic layer. With 2 nm thickness of $TiO_2$, the quantum efficiency was improved by 45 % compared to the device fabricated without the $TiO_2$ layer.