• 대한기계학회논문집B
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• 제21권9호
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• pp.1185-1197
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• 1997

Three-dimensional flow within a film-cooling hole, which is normally oriented to the main flow, has been measured by using a straight five-hole probe for the blowing ratios of 1.0 and 2.0. The length-to-diameter ratio of the injection hole is fixed to be 1.0 throughout the whole experiments. The result shows that the secondary flow within the hole is strongly affected by the main flow and flow separation at the hole inlet. The higher blowing ratio provides less influence of the main flow on the injectant flow. The three-dimensional flow at the hole exit is considerably altered due to the strong interaction between the injectant and main flow. The aerodynamic loss produced inside the injection hole is mainly attributed to the inlet flow separation.

• 한국분무공학회지
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• 제16권1호
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• pp.44-50
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• 2011

An object of this study is to understand the correlation of injection characteristics and injector dimensions according to biodiesel mixture. The Injection characteristics of different types of common-rail injectors are the number of nozzle holes (5~8), jet cone angle ($146^{\circ}{\sim}153^{\circ}$), hydraulic flow rate (830~900 ml/min) injection quantity and response time. Prior to characteristic experiment, the reference injector has been selected in 6 candidates injectors under the investigation of injected quantity according to the biodiesel mixture so that injector type can be determined. The injector is used for the characteristic experiment which varied the various operating conditions including pressure 23 MPa, 80 MPa, 160 MPa, changing in injection duration 0.16 ms~1.2 ms and even mixture ratio. The result shows that the nozzle hole number and cone angle influence the injection quantity much more than nozzle hole diameter at low injection pressure and the nozzle hole diameter at high injection pressure, post injection duration.

• 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.

• 대한전자공학회논문지SD
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• 제45권5호
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• pp.19-25
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• 2008

본 연구에서는 유기반도체인 펜타센과 소스-드레인 금속전극사이에 $C_{60}$을 홀주입층으로 적용한 유기박막트랜지스터를 제작하여 $C_{60}$을 삽입하지 않은 소자와의 전기적특성을 비교하였다. $C_{60}/Au$ 이중전극을 사용한 소자의 경우 Au단일전극을 사용한 소자와 비교하였을 때 전하이동도는 0.298 $cm^2/V{\cdot}s$에서 0.452 $cm^2/V{\cdot}s$ 문턱전압의 경우 -13.3V에서 -10.8V로 향상되었으며, contact resistance를 추출하여 비교하였을 경우 감소함을 확인할 수 있었다. 이러한 성능의 향상은 $C_{60}$을 Au와 pentacene 사이에 삽입하였을 경우 Au-pentacene 간의 원하지 않는 화학적 반응을 막아줌으로써 홀 주입장벽를 감소시켜 홀 주입이 향상되었기 때문이다. 또한 Al을 전극으로 적용한 OTFT도 제작하였다. 기존에 Al은 OTFT에 단일전극으로 사용하였을 경우 둘간의 높은 홀 주입장벽으로 인해 채널이 거의 형성되지 않았으나, $C_{60}/Al$ 이중전극을 사용한 소자의 경우 전하이동도와 전류점멸비은 0.165 $cm^2/V{\cdot}s$, $1.4{\times}10^4$ 으로써 Al를 단일전극으로 사용하는 소자의 전기적 특성에 비해 크게 향상되어진 소자를 제작할 수 있었다. 이는 $C_{60}$과 Al이 접합시에 interface dipole의 형성으로 Al의 vacuum energy level이 변화로 인한 Al의 work function이 증가되어 pentacene과 Al간의 hole injection barrier가 감소되었기 때문이다.

• 한국CDE학회논문집
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• 제5권2호
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• pp.196-205
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• 2000

This paper proposes a topology-based algorithm for recognizing the passage features using a concept of multi-face hole loop. The Multi-face hole loop is a concetpual hole loop that is formed over several connected faces. A passage feature is recognized in the proposed approach by two multi-face hole loops that constitute its enterance and exit. The algorithm proposed in this paper checks the connectivity of the two multi-face hole loops to recognize passage features. The total number of passage features in a part is calculated from Euler equation and is compared with the number of found passage features to decide when to terminate. To find all multi-face hole loops in a part, this paper proposes an algorithm for finding all combinations of connected faces. The edge convexity is used to judge the validity of multi-face hole loops. By using the algorithm proposed in this paper, the passage features could be recognized effectively. The approach proposed in this paper is illustrated with several example parts.

• 대한기계학회논문집
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• 제18권3호
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• pp.645-652
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• 1994

The leading edge of a turbine blade was simulated as a circular cylindrical surface. The effect of free-stream turbulence on the mass transfer upstream of the injectionhole has been investigated experimentally. The effects of injection location, blowing ratio on the Sherwood number distribution were examined as well. The mass transfer coefficients were measured by a naphthalene sublimation technique. The free-stream Reynolds number based on the cylinder diameter is 53,000. Other conditions investigated are: free-stream turbulence intensities of 3.9% and 8.0%, injection locations of $40^{\circ}$, $50^{\circ}$, and $60^{\circ}$ from the front stagnation point of the cylinder, and blowing ratios of 0.5 and 1.0. The role of the horseshoe vortex formed upstream edge of the injected jet is dicussed in detail. When the blowing ratio is unity, and the coolant jet is injected at $40^{\circ}$, the mass transfer upstream of the jet is not affected by the coolant jet at all. On the other hand, when the injection hole is located beyond $50^{\circ}$, the mass transfer upstream edge of the injection hole suddenly increases due to the formation of the horseshoe vortex, but it dereases as the free-stream turbulence intensity increases because the strength of the horseshoe vortex structure becomes weakened. The role of the horseshoe vortex is clearly evidenced by placing a rigid rod at the injection hole instead of issuing the jet. In the case of the rigid rod, the spanwise Sherwood number upstream of the injection hole is much larger due to the intense influence of the horseshoe vortex.

• Transactions on Electrical and Electronic Materials
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• 제8권6호
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• pp.260-264
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• 2007

We have studied stability in organic light-emitting diode depending on buffer layer and cathode. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. An electron injection energy barrier into organic material is different depending on a work function of cathodes. Theoretically, the energy barriers for the electron injection are 1.2 eV, -0.1 eV, and 0.0 eV for Al, LiAl, and LiF/Al at 300 K, respectively. We considered the cases that holes are injected to organic light-emitting diode. The hole injection energy barrier is about 0.7 eV between ITO and TPD without buffer layer. For hole-injection buffer layers of CuPc and PEDOT:PSS, the hole injection energy barriers are 0.4 eV and 0.5 eV, respectively. When the buffer layer of CuPc and PEDOT:PSS is existed, we observed the effects of hole injection energy barrier, and a reduction of operating-voltage. However, in case of PVK buffer layer, the hole injection energy barrier becomes high(1.0 eV). Even though the operating voltage becomes high, the efficiency is improved. A device structure for optimal lifetime condition is ITO/PEDOT:PSS/TPD/$Alq_3$/LiAl at an initial luminance of $300cd/m^2$.

• Journal of Information Display
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• 제4권1호
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• pp.29-33
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• 2003

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of $ITO/bufferr/TPD/Alq_3/Al$. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.310-310
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• 2009

In the two structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/R-H : R-D/Al device, ITO/Amorphous Fluoropolymers/TPD/R-H : R-D/LiF/Al device. we studied the effect of organic materials defending on the electrical characteristics of red OLEDs. The thickness of TPD and R-H : R-D was manufactured 40 nm, 60 nm, respectively under a base pressure of $5\times10^{-6}$Torr using a thermal evaporation. The AF used for an hole-injection is the thickness of 0.5 [nm] and the LiF used for an electron-injection is the thickness of 0.5 [nm]. Compared to the two from the devices made with the hole injection and without hole injection We found that the luminous efficiency and the external quantum efficiency are improved a fact of one- hundred, two, respectively.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.80-86
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• 2002

A fuel injection system has an important role in the performance and emission gas in a diesel engine. In this paper, an experimental study has been performed to verify the effect of the performance and the emission gas with the factors such as diameters of an injection nozzle hole, diameters of an injection pipe, and injection timing in the fuel injection system. We have obtained the results that the fuel consumption ratio is reduced and NOx concentration is increased as the smaller diameter of injection nozz1e hole, the smaller diameter of injection pipe, and more advanced injection timing. They show that optimizing the factors of fuel injection system is significant to enhance the performance of the engine system and consumption ratio of fuel, smoke, and NOx.