• Journal of Astronomy and Space Sciences
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• v.6 no.2
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• pp.119-125
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• 1989

UBV observations of the primary eclipse of Algol-type long period eclipsing binary AY Persei have been successfully made using the 61-cm reflector at the Ilsan Station of Yonsei University Observatory in September and October, 1989. These light curves furnish ones to deduce following results; (1) the total duration of the eclipse lasted for about 0.066(0.78 days) with no clear evidence of the existence of the totality, (2) the depths of mid-eclipse of $0^m.91$ and $1^m.07$ for V and B, respectively, (3) two times of minimum light, JD2447820.203 and JD 2447820.200 for V and B, respectively, and (4) no period variation with the improved light elements, Min I =JD2427152.237+$11^d.776620e$, $pm$10 $pm$4 are made.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.711-716
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• 2010

New electroluminescent polymers with fluoro groups in vinylene units, poly(m-silylphenyl-p-phenylene-difluorovinylene) (m-SiP-PPDFV) have been synthesized by GILCH polymerization. These polymers have been used as the electroluminescent (EL) layers in single layer light-emitting diodes (LEDs) (ITO/PEDOT/polymer/Ca:Al). m-SiP-PPDFV shows PL around $\lambda_{max}$ = 452 nm and green EL around $\lambda_{max}$ = 497 nm. The current-voltage-luminance (I-V-L) characteristics of the polymers show turn-on voltages of 4.0 V approximately. Two fluoro groups were introduced on every vinylene units of m-SiP-PPV to give m-SiP-PPDFV in an attempt to increase the electron affinity of the parent polymer, and the devices show an increased color stability even with vinylene units. The color stability is attributed to the electron-withdrawing effect of the fluoro groups, which protect vinylene units from oxidation in PPV derivatives. We believe that fluoro groups can be introduced in vinylene units in order to attain excellent stability of PPV derivatives.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.842-848
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• 1998

The stability of paraseodymium-based zinc oxide varistor consisting of Zn-Pr-Co-Cr-Y oxide was investigated according to yttria additives under different stress conditons, such as 0.8V\ulcorner\ulcorner/373K/12h and 0.85V\ulcorner\ulcorner/393K/12h. Wholly, all varistor after the stress showed nearly symmetric and stable I-V characteristics. Particularly, in the case of 2.0mol% and 4.0mol% yttria-added varistor showing a good I-V characteristics, the varation rate of varistor voltage were less 1% and that of nonlinear coefficient were about degree of 5%, and what is remarkable, leakage current with increasing stress time during the applied stress was almost constant. It the light of these facts, it is estimated that varistor constituents having 2.0mol% and 4.0mol% yittria, respectively, will be utilized to various application fields.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.323-325
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• 2002

Because of the progress of civilization, outdoor electricity facilities as a street light, signal light and standing signboard etc. have being increased rapidly. Therefore the application of underground distributing wires is largely expended. In this paper, capacitance for the kinds of 600V CV cable is measured and leakage current for underground cable is calculated. The measurement of capacitance is done which there are defects of cable sheath or not Calculated leakage current is applied to choose the circuit breaker and the like.

• Journal of IKEEE
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• v.17 no.3
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• pp.221-228
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• 2013

About functional parameters of a LED/UVLED (Light Emitting Diode/Ultra Violet LED), one of the most important parameters is the I-V characteristic. By researching factors affect to the I-V characteristic of uvled, we found that beside of the structure of the device itself, there is the influence of the electrode materials, electrode shapes, the process of wiring and packaging. In this work, we want to improve the performance of UVLED to find out the optimal mask design principles. The study is based on theoretical mathematical models, as well as the use of simulation software tool Comsol. From all results obtained, the team has improved mask design to manufacture electrodes for GaN-based UVLED. Electrode masks are designed by three softwares, which are Intellisuite, Klayout and AutoCad. Intellisuite masks would be used in fabrication simulation while Klayout and AutoCad are used to fabricate electrodes in experiments. As well as, we silmulated the structure of an uvled 355nm emission wavelength by TCAD software, in order to compare with uvled sample that has the same emission wavelength.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.150-155
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• 2013

Textured surface has been fabricated to reduce the light reflectance from the solar cells. The textured surface is very suitable for the multi-junction III-V solar cells because it can decrease the light reflectance over a large wavelength range. In this study, we have generated a textured structure on InAlP which is used for the window layer of the multi-junction III-V solar cells. Ultra-thin Pt layer (0.7 nm) has been used for wet etching mask. An array of nanosized pyramid shape formed on InAlP surface dramatically reduces the light reflectance up to 13.7% over a large wavelength range (i.e., $0.3{\sim}1.5{\mu}m$).

• Korean Journal of Crystallography
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• v.11 no.3
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• pp.137-146
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• 2000

The stoichiometric mix of evaporating materials for he CuInS₂ single crystal thin films was prepared. To obtain the single crystal thin films, CuINS₂ mixed crystal was deposited on etched semi-insulator GaAs(100) substrate by the hot wall epitaxy(HWE) system. The source and substrate temperature were 640℃ and 430℃, respectively and the thickness of the single crystal thin films was 2 ㎛. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility deduced from Hall data are 9.64x10/sup 22//㎥ and 2.95x10/sup -2/ ㎡/V·s, respectively at 293 K. he optical energy gap was found to be 1.53 eV at room temperature. From the photocurrent spectrum obtained by illuminating perpendicular light on the c-axis of the thin film, we have found that the values of spin orbit coupling splitting ΔSo and the crystal field splitting ΔCr were 0.0211 eV and 0.0045 eV at 10K, respectively. From PL peaks measured at 10K, were can assign the 807.7 nm (1.5350 eV) peak to E/sub x/ peak of the free exciton emission, the 810.3 nm(1.5301 eV) peak to I₂ peak of donar-bound exciton emission and the 815.6 nm(1.5201 eV) peak to I₁ peak of acceptor-bound excition emission. In addition, the peak observed at 862.0 nm(1.4383 eV) was analyzed to be PL peak due to donor-acceptor pair(DAP).

• Journal of Astronomy and Space Sciences
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• v.6 no.2
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• pp.109-117
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• 1989

A total of 266 photoelectric observations(91 in V, 93 in B, and 82 in U) for an eclipsing binary, ZZ Cnc, has been secured by using the 61-cm reflector and an uncooled iP21 photomultiplier phototube of Yonsei University Observatory during 4 years from March 1984 to May 1988. One time of minimum light, JD 2446887.534 is obtained. Although Kim et al.(1988) suggested the possibility of the period change, the present study shows that the orbital period of ZZ Cnc should be constant. According in a reasonable interpretation of the eclipse light curves. Min I = JD Hel 2446887.574+25d.5944E $pm$2 $pm$2 may be useflul as new light elements for future observations.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.230-232
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• 2019

Light Triggerd Thyristor (LTT)는 HVDC 및 산업용 스위치 등에 사용되는 대전력 반도체소자이다. 일반적인 Thyristor가 전기적 신호에 의해 trigger 되는 것과는 다르게 LTT는 광신호에 의해 동작하는 소자이다. 본 논문에서는 5,000V, 2,200A 급의 4인치 LTT 소자의 제작 및 전기적인 특성평가 결과를 기술하였다. 4인치 LTT의 구조적인 특징은 전면부 중앙에 광신호가 주입되는 수광부가 위치해 있으며 입력 전류 증폭을 위한 4-단계 증폭 게이트 (gate) 구조를 가지도록 설계하였다. $400{\Omega}{\cdot}cm$ 비저항을 갖는 1mm 두께의 n-형 실리콘 웨이퍼에 boron 이온주입과 열처리 공정으로 약 $30{\mu}m$ 깊이의 p-base를 형성하였으며, 고내압 저지를 위한 edge termination은 VLD (variable lateral doping) 기술을 적용하였다. 제작된 4인치 LTT는 6,500 V의 순방향 항복전압 ($V_{DRM}$) 특성을 나타내었으며, 100V의 어노드전압 ($V_A$)과 20 mA의 게이트전류 ($I_G$)에 의하여 thyristor가 trigger 됨을 확인하였다. 제작한 LTT 소자는 disk형 press-pack 패키지를 진행한 후, LTT의 수광부에 $10{\mu}s$, 50 mW의 900 nm 광 펄스를 조사하여 전류 특성을 평가하였다. LTT 패키지 샘플에 60 Hz 주파수의 광 펄스를 조사한 경우 2,460 A의 순방향 평균전류 ($I_T$)와 $336A/{\mu}s$의 반복전류상승기울기 (repetitive di/dt)에 안정적으로 동작함을 확인하였다. 또한, 펄스 전류 시험의 경우 61.6 kA의 최대 통전 전류 (ITSM, surge current)와 $1,050A/{\mu}s$의 펄스전류 상승 기울기 (di/dt of on-state pulse current)에도 LTT의 손상 없이 동작함을 확인하였다.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2743-2750
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• 2011

Lanthanide(III)-cored complex as a wavelength conversion material has been successfully designed and synthesized for highly efficient dye-sensitized solar cells, for the first time, since light with a short wavelength has not been effectively used for generating electric power owing to the limited absorption of these DSSCs in the UV region. A black dye (BD) was chosen and used as a sensitizer, because BD has a relatively weak light absorption at shorter wavelengths. The overall conversion efficiency of the BD/WCM device was remarkably increased, even with the relatively small amount of WCM added to the device. The enhancement in $V_{oc}$ by WCM, like DCA, could be correlated with the suppression of electron recombination between the injected electrons and $I_3{^-}$ ions. Furthermore, the short-circuit current density was significantly increased by WCM with a strong UV light-harvesting effect. The energy transfer from the Eu(III)-cored complex to the $TiO_2$ film occurred via the dye, so the number of electrons injected into the $TiO_2$ surface increased, i.e., the short-circuit current density was increased. As a result, BD/WCM-sensitized solar cells exhibit superior device performance with the enhanced conversion efficiency by a factor of 1.22 under AM 1.5 sunlight: The photovoltaic performance of the BD/WCM-based DSSC exhibited remarkably high values, $J_{sc}$ of 17.72 mA/$cm^2$, $V_{oc}$ of 720 mV, and a conversion efficiency of 9.28% at 100 mW $cm^{-2}$, compared to a standard DSSC with $J_{sc}$ of 15.53 mA/$cm^2$, $V_{oc}$ of 689 mV, and a conversion efficiency of 7.58% at 100 mW $cm^{-2}$. Therefore, the Eu(III)-cored complex is a promising candidate as a new wavelength conversion coadsorbent for highly efficient dye-sensitized solar cells to improve UV light harvesting through energy transfer processes. The abstract should be a single paragraph which summaries the content of the article.