• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.437-439
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• 2000

The internal quantum efficiency of EL devices using fluorescent organic materials is limited within 25% because of the triplet excitons which can hardly emit light. So there has been considerable interest in finding ways to obtain light emission from triplet excitons. One approach has been to add phosphorescent compounds to one of the layers in an EL device. Then triplet excitons can transfer to these phosphorescent molecules and emit light. In this study, multilayer organic light-emitting devices with phosphorescent emitter, tris (2-phenylpyridine)iridium ($Ir(ppy)_3$) were prepared. The device exhibited power luminous efficiency of 1.07 1m/W at the luminance of $61.6\;cd/m^2$ diriven at the voltage of 9 V and current density of $1.9mA/cm^2$. At the luminance of $100\;cd/m^2$, the luminous efficiency was obtained 1.05 lm/W with the voltage of 9.5 V and the corrent density of $2.8\;mA/cm^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.1
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• pp.57-63
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• 2015

Recently, LED is widely used in the kinds of display devices or lighting. In this paper, we fabricated LED chamber light for naval vessels to replace to conventional chamber light using incandescent lamp. The LED package of chamber light was designed with luminous intensity of 5.5 cd, color temperature of $6,000{\pm}500K$, forward voltage of 3~3.2 V and input current of 60 mA. A LED module was composed of 36 LED packages and metal PCB. The VF and luminous intensity of LED package were getting down when temperature increased. The temperature of LED chamber light was measured by changing the number of LED package and applied current for one hour when an electric current flow. The heat transfer capability have been improved by using metal PCB. The power consumption of LED chamber light reduced by 86% compared to the conventional chamber light using incandescent lamp.

• Journal of the Korean Society for Railway
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• v.14 no.5
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• pp.411-415
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• 2011

DC/DC switching power converters are commonly used to generate a regulated DC output voltages with high efficiencies from different DC input sources. The voltage mode DC/DC converter utilizes MOSFET (metal-oxide semiconductor field effect transistor), inductor, and a PWM (pulse-width modulation) controller with oscillator, amplifier, and comparator, etc. to efficiently transfer energy from the input to the output at periodic intervals. The fundamental boost converter and a buck converter containing a switched-mode power supply are studied. In this paper, the electrical characteristics of DC/DC power converters are simulated by program of SPICE, and the PWM controller is implemented to check the operation. In addition, power efficiency is analyzed based on the specification of each component.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.2
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• pp.39-45
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• 2004

This paper describes the design and implementation of Serial ATA physical layer and performance measurement. It is composed of tranceiver circuit that has the NRZ data stream with +/-250㎷ voltage level and 1.5Gbps data rate, transmission PLL circuit, clock ＆ data recovery circuit, serializer/deserializer circuit and OOB(Out Of Band) generation/detection circuit. We implement the verification of the silicon chip with 0.18${\mu}{\textrm}{m}$ Standard CMOS process. It can be seen that all of the blocks operate with no errors but the data transfer rate is limited to the 1.28Gbps even this should support 1.5Gbps data transfer rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.11
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• pp.963-971
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• 2000

In order to investigate the effects of an electric field on EHD(Electro-hydrodynamic) nucleate boiling hat transfer characteristics in a nonuniform electric field under saturated pool boiling, the basic study has been performed experimentally. In the present study, the working fluid is R-113 and the plate-wire electrode system is used to generate a steep electric field gradient. Boiling parameters are investigated by using a high speed camera. The electric field distribution around a wire is obtained to understand the effect of an electric field on bubble departure/movement. The experimental results show EHD effects are much more considerable when the applied voltage increases. Bubbles depart away from the heated wire in radial direction. It is confirmed that the mechanisms of EHD nucleate boiling are closely connected with the dynamic behavior of bubbles. The boiling parameters are significantly changed by the electric field strength. With increasing applied voltages, the bubble size decreases and the nucleation site density, bubble velocity and bubble frequency increase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.170-173
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• 2000

In this study, we have investigated the light-emitting property of the EL device with the thickness ratio of the HTL/ETL, which was 500$\AA$:500$\AA$, 400$\AA$:600$\AA$, 600$\AA$:400$\AA$. The ALq$_3$ was used for the ETL. We have studied the relation of voltage, contrase, efficiency for current density. Emission was observed above 10mA/$\textrm{cm}^2$ and luminance was measured to be 1030cd/$m^2$ at a current density of 100mA/$\textrm{cm}^2$ in 500$\AA$/500$\AA$ sample. A luminance of over 2500cd/$m^2$ was also observed after the final fabrication process in 500$\AA$/500$\AA$ sample

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.447-448
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• 2007

Product development is consisting by trend that accommodate almost function digital cam in camera phone that can speak of Mobile appliance, and competition about number of elemental area of image sensor is consisting for market prior occupation between these. Propose in this research and small size camera phone self-focusing adjustment actuator that do city manufacture is similar with general storehouse pickup actuator drive way, but selected in cylindrical to reduce space that lens holder occupies because there is restriction loading of lens and space enemy. Target number of research established that execute drive displacement more than $600{\mu}m$ in 2.75V that is house voltage that is used in Mobile device that is general. Also, described about maximum transfer displacement characteristic, displacement response characteristic, hysteresis, response characteristic, smallest transfer step characteristic, actuator's drive characteristic that is manufactured to examination item of maximum consumption electric power by special quality estimation system that apply laser displacement sensor that produce itself to evaluate city manufactured actuator's special quality.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.8
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• pp.664-668
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• 2011

In this study, we have fabricated the red OLED (organic light emitting diode). The basic device structure is ITO/hole transporting layer, TPD(500 $\AA$)/red emitting layer, Alq3 doped with DCM2:rubrene(20 $\AA$)/electron transporting layer, Alq3(M) (500 $\AA$-M $\AA$)/LiF(15 $\AA$)/Al(1,000 $\AA$). The thickness of electron transporting layer(500 $\AA$-M $\AA$) changed 0, 20, 40, 60 $\AA$. Turn on voltage of the red OLED was 5 V, 6 V, 6.5 V and 7.5 V, respectively with electron transfer layer changed ratio. Luminance of red OLED was 4,504, 1,840, 1,490 and 1,130 cd/$m^2$, respectively. Optimized electron transfer layer position changed ratio of the red OLED was 0 $\AA$.

• Journal of IKEEE
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• v.23 no.2
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• pp.375-379
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• 2019

$ZnO-SnO_2(ZTO)$ was deposited by RF magnetron sputtering using a ceramic target whose Zn atomic ratio to Sn is 2:1 as a target, and the crystal structure variation with thermal treats was investigated. Transparent thin film transistors (TTFT) were fabricated using the ZTO films as active layers. About 100 nm-thick $Si_3N_4$ film grown on 100 nm-thick $SiO_2$ film was adopted as gate dielectrics. The mobility, threshold voltage, $I_{on}/I_{off}$, and interface trap density were obtained from the transfer characteristics of ZTO TTFTs. The effects of substrate temperature, and post-annealing on the property variation of ZTO TTFT were analyzed.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.2
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• pp.117-122
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• 2016

Recently, the detection of pH with real-time and in vivo has been focal pointed in the environmental or medical fields. In this work, we developed the pH sensor using graphene sheet. Graphene has high biocompatibility. We fabricated flexible solution-gated field-effect transistors (SGFETs) on graphene sheet transferred on the polyethylene terephthalate (PET) substrate to detect pH in electrolyte solution. The gate length was $500{\mu}m$ and the gate width was 8 mm. We evaluated the current-voltage (I-V) transfer characteristics of graphene SGFETs in pH solution. The drain-source current ($I_{DS}$) and the gate-source voltage ($V_{GS}$) curves of graphene SGFETs were depended on pH value. The Dirac point of graphene SGFETs linearly shifted to the positive direction about 19.32 mV/pH depending on the pH value in electrolyte solution.