• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.776-780
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• 2009

In this study, the opto-electric properties of EL devices with PMN dielectric layer with variation of firing tempereature were investigated. For the PMN dielectric layer process, the paste was prepared by optimization of quantitative mixing of PMN powder, $BaTiO_3$, Glass Frit, $\alpha$-Terpineol and ethyl cellulose. The EL device stack consists of Alumina substrate ($Al_2O_3$), metallic electrode (Au), insulating layer (manufactured PMN paste), phosphor layer (ELPP- 030, ELK) and transparent electrode (ITO), which is well structure as a thick film EL device. The phase transformation properties of PMN dielectric with various firing temperatures of $150^{\circ}C$ to $850^{\circ}C$ was characterized by XRD. Also the opto-electric properties of EL devices with different firing temperature were investigated by LCR meter and spectrometer. We found the best opto-electric property was obtained at the condition of $550^{\circ}C$ firing which is 3432.96 $cd/m^2$ at 1948.3 pF Capacitance, 40 kHz Frequency, 40% Duty, Vth+330 V voltage.

• Advances in aircraft and spacecraft science
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• v.2 no.3
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• pp.329-343
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• 2015

This study aimed to observe the effect of a novel concept (referred to as the flap extension) implemented on the leading edge of the flap of a three element high lift device. The high lift device, consisting of a flap, main element and slat is designed around an Airbus research profile for sufficient take off and landing performance of a large commercial aircraft. The concept is realised on the profile and numerically optimised to achieve an optimum geometry. Two different optimisation approaches based on Genetic Algorithm optimisations are used: a zero order approach which makes simplifying assumptions to achieve an optimised solution: as well as a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. Both methods converge to different optimised solutions due to simplifying assumptions. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. The concept was seen to increase lift locally at the flap for both optimisation methods.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.7
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• pp.66-79
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• 1999

We investigate the effects of high input power on the performance of optical bistable symmetric self-electooptic effect devices (S-SEEDs) using extremely shallow quantum wells (ESQWs). In this study, we consider the four ESQWs SEEDs; anti-reflection (AR)-coated ESQWs S-SEED, back-to-back AR coated ESQWs S-SEED, asymmetric F뮤교-Perot (AFP) ESQWs S-SEED, and back-to-back AFP-ESQWs S-SEED. As the input power increases, device performances such as on/off contrast ratio, on/off reflectivity difference are seriously degraded because of ohmic heating and exciton saturation. On the other hand, switching speed of the device increases up to certain value and then begins to decrease. With reasonable optimization of the input power for the best switching speed operation of the devices in a cascading optical interconnection system, we simulate and analyze the system bit-rate of the various ESQWs S-SEEDs, for a mesa of $5{\times}5{\mu}m^2$ size, changing the namber of quantum wells for the external bias of 0 V and -5V.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.49-53
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• 2008

The yellow base polymer light emitting diodes(PLEDs) with double emission and hole blocking layers were prepared to improve the light efficiency. ITO(indium tin oxide) and PEDOT : PSS[poly(3,4-ethylenedioxythiophene) : poly(styrene sulfolnate)] were used as cathode and hole transport materials. The PFO[poly(9,9-dioctylfluorene)] and MEH-PPV[poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and guest materials, respectively. TPBI[Tpbi1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene] was used as hole blocking layer. To investigate the optimization of device structure, we prepared four kinds of PLED devices with different structures such as single emission layer(PFO : MEH-PPV), two double emission layer(PFO/PFO : MEH-PPV, PFO : MEH-PPV/PFO) and double emission layer with hole blocking layer(PFO/PFO : MEH-PPV/TPBI). The electrical and optical properties of prepared devices were compared. The prepared PLED showed yellow emission color with CIE color coordinates of x = 0.48, y = 0.48 at the applied voltage of 14V. The maximum luminance and current density were found to be about 3920 cd/$m^2$ and 130 mA/$cm^2$ at 14V, respectively for the PLED device with the structure of ITO/PEDOT : PSS/PFO/PFO : MEH-PPV/TPBI/LiF/Al.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.12-16
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• 2009

Current sensing in power semiconductors involves sensing of over-current in order to protect the device from harsh conditions. This technique is one of the most important functions in stabilizing power semiconductor device modules. The sense FET is very efficient method with low power consumption, fast sensing speed and accuracy. In this paper, we have analyzed the characteristics of proposed sense FET and optimized its electrical characteristics to apply conventional 450 V power MOSFET by numerical and simulation analysis. The proposed sense FET has the n-drift doping concentration $1.5{\times}10^{14}cm^{-3}$, size of $600{\um}m^2$ with $4.5\;{\Omega}$, and off-state leakage current below $50{\mu}A$. We offer the layout of the proposed sense FET to process actually. The offerd design and optimization methods are meaningful, which the methods can be applied to the power devices having various breakdown voltages for protection.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.23-28
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• 2008

To improve the external quantum efficiency by means of the optimization of the polymer light emitting diodes(PLEDs) structure, the PLED with ITO/PEDOT:PSS/(PFO)/PFO:MEH-PPV/LiF/Al structure were fabricated and investigated the electrical and optical properties for the prepared devices. ITO(indium tin oxide) and PEDOT:PSS [poly (3,4-ethylenedioxythiophene): poly(styrene sulfolnate)] were used as transparent anode film and hole transport materials, respectively. PFO[poly(9,9-dioctylfluorene)] and MEHPPV[poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and dopant materials. The doping concentration of MEH-PPV was 9wt% with thickness of about $400{\AA}$. We investigated the dependence of the PFO thickness ranging from $200{\AA}$ to $300{\AA}$ on the electrical, optical properties of PLEDs. Among prepared PLED devices with different PFO thicknesses, the highest value of the luminance was obtained for the PLED device with $250{\AA}$ in thickness. As a result, the current density and luminance ware found to be about $400mA/cm^2$ and $1500cd/m^2$ at 13V, respectively. In addition, the luminance and current efficiency of PLED device with double emitting layer (PFO/PFO:MEH-PPV) were improved about 3 times compared with the one with single emitting layer (PFO:MEH-PPV).

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1750-1755
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• 2006

Nonoptimal placement of short-channel-length TFTs in large-grained polycrystalline Si films with a periodic microstructure, as for instance obtained via 2-shot SLS, can potentially lead to degradation in the overall uniformity of the resultant devices. In this paper, we explain and demonstrate that by simply introducing a well-defined misorientation between the devices and the periodic microstructure, it is possible to significantly reduce (and potentially entirely eliminate) the device nonuniformity problem that can arise from such a cause.

• Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.135-139
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• 2006

We optimized the biological and physical parameters for DNA delivery into thalli of the red alga Porphyra yezoensis using a particle bombardment device. The efficiency of transformation was determined using the ${\beta}-glucuronidase$ (GUS) assay. The optimal helium pressure, distance of tungsten particle flight, and ratio of DNA to tungsten particles were $23kgf/cm^2$, 8 cm, and $5{\mu}g/mg$ tungsten, respectively. During bombardment, osmotic treatment with a mixture of 0.6 M mannitol and sorbitol increased the efficiency of GUS transformation. After 2 days, the blue color indicating GUS activity was observed using a histochemical assay.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1051-1054
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• 2009

This paper investigates approaches for improving effective mobility of organic thin film transistors (OTFTs). We consider gate dielectric optimization, whereby we demonstrated >2x increase in mobility by using a silicon-rich silicon nitride ($SiN_x$) gate dielectric for polythiophene-based (PQT) OTFTs. We also engineer the dielectric-semiconductor ($SiN_x$-PQT) interface to attain a 27x increase in mobility (up to 0.22 $cm^2$/V-s) using an optimized combination of oxygen plasma and OTS SAM treatments. Augmentative material systems by combining 1-D nanomaterials (e.g., carbon nanotubes, zinc oxide nanowires) in an organic matrix for nanocomposite OTFTs provided a further boost in device performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.975-980
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• 2017

Overhead catenary system of electric railway has overlap sections which devide and tighten trolley wire supplying electric power to train, where current collection performances may become worse according to railway speed-up. Current collection tests conducted at 400 km/h test-bed section of Honam high-speed railway show that balanced line arrangement at overlap section is needed to secure current collection without arc generation between trolley wire and train current collection device. This paper proposes a design procedure of the overlap section to allow for tension increase and uplift of the trolley wires according to railway speed-up. By applying the proposed procedure to the overhead catenary system of Honam high-speed railway, it is suggested that the minimum span length should be 33.2 m for railway speed-up to 350 km/h and 43.7 m for speed-up to 400 km/h.