• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.451-451
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• 2012

Instead of a highly toxic CdSe and ZnScore-shell,InP/ZnSecore-shell quantum dots [1,2] were investigated as an active material for quantum dot light emitting diode (QD-LED). In this paper, aquantum dot light-emitting diode (QDLED), consisting of a InP/ZnS core-shell type materials, with the device structure of glass/indium-tin-oxide (ITO)/PEDOT:PSS/Poly-TPD/InP-ZnS core-shell quantum dot/Cesium carbonate(CsCO3)/Al was fabricated through a simple spin coating technique. The resulting InP/ZnS core-shell QDs, emitting near blue green wavelength, were more efficient than the above CdSe QDs, and their luminescent properties were comparable to those of CdSe QDs.Thebrightness ofInP/ZnS QDLED was maximumof 179cd/m2.

• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.35-39
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• 2011

The PSPICE equivalent circuit elements of a 1550 nm InGaAsP laser diode were derived by using multi-level rate equations. The device parameters were extracted by using a self-consistent numerical method for the optical gain properties of the MQW active regions. The resulting equivalent circuit model is also applied to an actual optical transmitter, and its PSPICE simulation results show good agreement with the measured results once the parasitic capacitance due to the packaging is taken into account.

• Journal of the Korea Safety Management & Science
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• v.12 no.4
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• pp.61-66
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• 2010

Organic light emitting diode(OLED) has been developed fast from 1963 when electric light emitting phenomenon was discovered. PMOLED(passive matrix OLED) is producted earlier than AMOLED(active matrix OLED). PMOLED is mainly mounted at sub display, but AMOLED is mounted at main display. Nowadays AMOLED is expanded to PMP(portable multimedia players), navigation and TV market. Even thought OLED's market is opening to many applications, OLED's life is worried until now. If we know about OLED's real life, we need time to test so much time over 20,000hrs. Realistically, there is difficult to test such as long time with products from the information-technology sector having a short life cycle. In this paper, we study about OLED's accelerated test to reduce life test by current. We can design OLED's accelerated life model by the result of test. The model consists of design variables like ratio of light emitting, organic material structure, condition of aging, etc. In conclusion, this model can be applied to study about organic material, machine and manufacturing process etc, and also it's possible to develop a method of manufacturing process & materials, so we need to study on the subject of this paper continuously.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.84-84
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• 2008

A multidimensional ZnO light-emitting diode LEDstructure comprising film/nanorods/substrate was fabricated on a p-type Si substrate using metal organic chemical vapor deposition at relatively low growth temperature. The filmlike top layer used for the metal contact was continuously formed on the ZnO nanorods by varying the growth conditions and the resulting structure allowed us to utilize the nanorods with intense emission as an active layer. We investigated the performance of the resulting multidimensional LED. An extremely high breakdown voltage and low reverse leakage current as well as typical rectification behavior were observed in the I-V characteristics.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.2
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• pp.140-149
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• 2017

This study proposes a new type of active-clamp forward-flyback converter with two transformers that operate in forward and flyback modes during on and off times, respectively, instead of not using an output inductor. The main switch can be turned on with zero-voltage switching (ZVS) using the leakage inductance of the transformer and the output capacitor of the main switch. The leakage inductance should be increased to ZVS. However, the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches results in a serious voltage spike. A forward-flyback converter employing auxiliary inductor and auxiliary diode is proposed to overcome the problem. The operational principles are analyzed in detail and validated through experiments with a 385 V-to-53 V/37 A prototype.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.518-523
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• 1999

In thi, study, we made experiments to fonn a mesa shape by meltback method with various concentration of solutions and found that unsaturated (20%) InGaAsP (1.55 !-tm) solution at a growth temperature was the most suitable for the formation of a mesa ,hape on the wafer which has an InGaAsP active layer and an InP cap layer on an n-InP substrate. It was difficult to form a proper mesa shape for the fabrication of PBH-LDs only by the meltback method; therefore, we fabricated PBH-LDs by forming the mesa shape with the meltback method after wet etching and by growing a current-blocking layer successively. As the electrical and optical charaleri,tiecs of MQW-PBH-LDs fabricated by above methods, when the cavity length was $300{\mu}m$, the threshold current was about 10 mA, internal quantum efficiency 82%, internal loss $9.2cm^{-1}$, and characteristic temperature was 65 K at $25~45^{\circ}C$ and 42 K at $45~65^{\circ}C$. /TEX>.

• Journal of Radiation Protection and Research
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• v.25 no.4
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• pp.197-205
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• 2000

A prototype electronic dosimeter(PED) adopting a silicon PIN diode detector as a radiation detector has been developed, manufactured and test-evaluated. A radiation signal processing circuit has been electronically tested and then the radiation detection characteristics of this PED has been performance-tested by using a reference photon radiation field. As a result in a electronic performance test, radiation signals from a detector were well observed in the signal processing circuit. The radiation detection sensitivity of this PED after several test-irradiations to $^{137}Cs$ gamma radiation source appeared to be 1.85 cps/$Gy{\cdot}h^{-1}$ with 19.3% of the coefficient of variation, which satisfied the performance criteria for the active personnel radiation monitor. Further improvement of the electronic circuit and operating program will enable the PED to be used in personal monitoring purpose.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.473-477
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• 2015

In this paper, a commercial phosphorescent white light-emitting diode (WLED) visible light communication (VLC) system with an equalization circuit to achieve the high modulation bandwidth was designed and demonstrated. An analytical method to examine the performance of the equalizer was carried out using a general circuit-simulator, PSpice. The equalization circuit was composed of two passive filters with resisters and a capacitor and an active filter with an op-amp. Utilizing our post-equalization technology, the ~3.5 MHz bandwidth of phosphor WLED could be extended to ~25 MHz without using an optical blue-filter. In this VLC system with a single round-type WLED and a single PIN photo-diode, ASK data transmission up to 35 Mbps at a 1m free space distance was obtained. The resulting bit-error-rate was $7.6{\times}10^{-4}$, which is less than the forward error correction (FEC) limit of $3.8{\times}10^{-3}$.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.74-81
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• 2010

A modeling methodology for the analysis of injection-locked Fabry-Perot laser diodes (FP-LDs), promising for cost-effective WDM-PON sources, is proposed. The time-domain large-signal model that is used is found to provide quite similar results to some experimental ones. With our methodology, we model characteristics of FP-LDs, such as influence of reflectivity at a facet and detuning on injection-locking. The eye diagram characteristics are also investigated. It is observed that the facet reflectivity at the injection side should be lower than 1% to provide stable operation in terms of good side-mode suppression ratio and independence from detuning between narrow-band injection noise and LD modes. It is also observed that good eye opening can be obtained for 155 Mbps modulation while the parameters such as the active region thickness should be properly optimized to obtain reasonable eye opening at 1.25 Gbps.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.311-317
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• 1999

Unidirectional single-mode operation of a diode-pumped Nd:YAG laser with a planar semimonolithic ring cavity has been demostrated at 1064 nm. The semimonolithic cavity consists of a laser active medium placed in a magnetic field, a crystal quartz plate, and an output coupling mirror. They form an optical diode by acting each part as a Faraday rotator, a reciprocal polarization rotator and a partial polarizer, respectively. An eigenpolarization theory for the cavity configuration was presented and losses for the eigenmodes were calculated. A pump-limited single-mode output power of 155 mW and a slope efficiency of 17% were obtained when the laser was pumped by a 1.2 W, 809 nm diode-laser. A laser linewidth of less than 100 kHz is inferred from a beat note frequency spectrum between two identical laser systems and continous single-mode tuning range was more than 2 GHz.