• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.238-241
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• 2010

The purpose of this study is to solve the problems of radio frequency bandwidth frequency depletion, confusion possibilities, and security that are in current wireless communications systems, and to confirm the possibility of applying those solutions for the next generation network. To solve the problems of the current wireless communications system, a visible light communications system for power line communication (PLC) via 8-bit microcontroller is created and the capacity is analyzed. The exclusive PLC chip APLC-485MA, an 8-bit ATmega16 microcontroller, high brightness 5pi light emitting diodes (LEDs), and the LLS08-A1 visible light-receiving sensor were used for the transmitter and receiver. The performance was analyzed using a designed program and an oscilloscope. The voltage change was measured as a function of distance from 10-50 cm. Blue LEDs showed the best performance among the measured LED types, with 0.47 V of voltage loss, but for a distance over 50 cm, precise data was not easy to obtain due to the weak light. To overcome these types of problems, specific values such as the changing conditions and efficiency value relevant to the light emitting parts and the visible light-receiving sensor should be calculated, and continuous study and improvements should also be realized for better communication conditions.

• Biomedical Science Letters
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• v.12 no.3
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• pp.139-143
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• 2006

Jopock (Jpk) has previously been ascertained that induces both bacterial and mammalian cell death. The Escherichia coli cells expressing Glutathion S-transferase (GST) fused Jpk showed elongated phenotype and inhibited cell growth which led eventual cell death. In an attempt to search the genetic suppressor of the lethal protein Jpk in bacterial cells, we constructed a unidirectional protein expression vector inserting tac promoter next to the C-terminus Jpk in pGEX-Jpk. The function of additional tac promoter was confirmed by substituting lac promoter in Plac-TOPO plasmid. The cells harboring plac- TOPO, which regulates $lacZ{\alpha}$ gene expression under lac promoter, formed blue colonies in 5-bromo-4-3 $indolyo-{\beta}-D-galactoside$ (X-gal) plate. When lac promoter was changed to tac promoter, same results were observed. Since the addition of tac promoter did not affect the toxic effect of Jpk, the pGEX-Jpk-ptac could be a useful vector for the screening of suppressor(s) for Jpk, in which GST-Jpk and a putative Jpk-suppressing protein are coexpressing from two unidirectional tac promoters, which response to the same inducer, $isopropyl-{\beta}-D-thiogalactopyranoside (IPTG)$.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.63-67
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• 2016

Divalent europium-activated $Ca_2PO_4Cl$ phosphor powders were prepared by a chemical synthetic method followed by heat treatment in reduced atmosphere, and the crystal structures, morphologies and photoluminescence properties of the powders were investigated by x-ray powder diffraction, scanning electron microscope and spectrometer. The effect of Ca/P mole ratio at the starting materials on the final products was evaluated. The optimized synthesis condition obtained in this study was Ca/P mole ratio of 2.0. The present phosphor materials had higher photoluminescence intensity and better color purity than the commercial blue phosphor powders, $(Ca,Ba,Sr)_{10}(PO_4)_6Cl_2:Eu^{2+}$. The result of excitation spectrum measurement indicated that the excitation efficiency of the synthesized powders was higher for the long-wavelength UV region than that of the commercial phosphor. It was thus concluded that the samples prepared in this study can be successfully applied for the light-emitting devices such as LED excited with long-wavelength UV light sources.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.119-119
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• 1999

GaN-based 물질들은 blue와 UV 영역의 LED, LD와 같은 광소자가 상용화되었을 뿐만아니라 HBT, FET와 같은 전기소자로도 널리 응용될 시점이지만 아직까지 해결되지 않은 문제점들이 있다. 그 중에 하나가 바로 GaN의 격자상수와 일치하는 기판이 없어 발생하는 dislocation인데, 이를 해결하기 위한 방법으로 새로운 기판이나, buffer, 또는 새로운 성장방법(ELOG) 등을 시도하고 있으나 dislocation density는 아직 높은 (107~1010cm-2) 상태이다. 이에 본 연구에서는 dislocation을 줄이기 위한 방책으로 InxGa1-xN를 새로운 buffer층으로 사용하여 GaN 박막을 MBE 방법으로 성장하였다. InxGa1-xN를 선택한 이유는 GaN와의 격자상수차이가 In0.12Ga0.88N일 경우 거의 일치한다는 보고가 있으며, 특히 InGaN의 melting point는 GaN의 성장온도 보다는 약간 높기 때문에 GaN 박막을 성장할 때와 식힐 때의 InGaN 원자결합은 약하게 작용되며, 결국 이는 열적인 stress를 줄여주게 된다. 이와 같이 성장된 GaN 박막은 그 결정성을 XRD로 분석하였고, 표면과 계면을 SEM으로 관찰하였다. 그리고 그 광학적 특성을 저온 PL로서 조사하였다. 그 결과를 살펴보면 35$^{\circ}$ 근방에서 GaN(0002) peak가 나온 것으로 보아 wurtzite 구조가 성장됨을 XRD로부터 확인하였다. 그리고 저온 (12K) PL에서는 3.470eV의 D$^{\circ}$X peak뿐만 아니라 3.258eV에 해당하는 peak를 얻었는데, 이는 InxGa1-xN buffer layer의 vapour pressure가 높은 (<50$0^{\circ}C$)에 도달하게 됨으로써 dissociation이 일어나면서 초기 성장이 이루어졌고 이는 다시 계면에서의 inter-diffusion을 발생시킨 것으로 보여진다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_4
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• pp.189-196
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• 2001

The blue green alga, Microcystis aeruginosa, was found to accumulate proline under the stressful concentration of cupric ions. The changes of proline level in Microcystis aeruginosa in response to copper(Cu) have been monitored and the function of the accumulated proline was studied with respect to its effect on Cu uptake. Exposure of Microcystis aeruginosa elevated concentrations of Cu led to accumulation of fee proline depending on the concentrations of the metal in the external medium. The greater the toxicity or accumulation of the metal, the higher the amount of proline in algal cells were found. When proline was exogenously supplied prior to Cu treatment, the absorption of Cu was markedly reduced. When exogenous proline was supplied after Cu treatment, it resulted in a remarkable desorption of the adsorbed Cu immediately after the addition of proline. Pretreatment of Microcystis aeruginosa with proline counteracted with metal-induced lipid peroxidation. The results of the present study showed a protective elect of proline on metal toxicity through inhibition of lipid peroxidation and suggested that the accumulation of proline may be related to the tolerance mechanism for dealing with Cu stress.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.114-114
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• 2000

III-nitride 게 물질들은 blue와 UV 영역의 LED, LD와 같은 광소자뿐만 아니라 HBT, FET와 같은 전자소자로도 널리 응용되고 있다. 이와 같은 물질을 이용한 소자를 제작할 경우 낮은 저항의 ohmic contact은 필수적이다. p-GaN의 ohmic contact은 아직까지 많은 문제점을 내포하고 있다. 그 중의 하나는 높은 doping 농도(>1018cm-3)의 p-GaN 박막을 성장하기가 어렵다는 것이며, 또 하나는 낮은 접촉 비저항을 얻기 위해선 7.5eV 이상의 큰 재가 function을 지닌 금속을 선택해야 한다. 그러나 5.5eV 이상의 재가 function을 갖는 금속은 존재하지 않는다. 위와 같은 문제점들은 p-GaN의 접촉 비저항이 10-2$\Omega$cm2이상의 높은 값을 갖게 만들고 있으며 이에 대한 해결방안으로는 고온의 열처리를 통하여 p-GaN와 금속사이에서 화학적 반응을 일으킴으로써 표면근처에서 캐리어농도를 증가시키고, 캐리어 수송의 형태가 tunneling 형태로 일어날 수 있도록 하는 tunneling current mechaism을 이용하는 것이다. 이에 본 연구에서는 MOCVD로 성장된 p-GaN 박막을 Mg의 activation을 증가시키기 위해 N2 분위기에서 4분간 80$0^{\circ}C$에서 RTA로 annealing을 하였으며, ohmic 접촉을 위한 금속으로 높은 재가 function과 좋은 adhesion 그리고 낮은 자체저항을 가지고 있는 Ni/ZSi/Ni/Au를 ohmic metal로 하여 contact한 후에 $700^{\circ}C$에서 1분간 rapid thermal annealing (RTA) 처리를 했다. contact resistance를 계산하기 위해 circular-TLM method를 이용하여 I-V 특성을 조사하였고, interface interaction을 알아보기 위해 SEM과 EDX, 그리고 XRD로 분석하였다. 또한 추가적으로 Si 계열의 compound metal인 PdSi와 PtSi에 대한 I-V 특성도 조사하여 비교하여 보았다.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.441-445
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• 2017

This study aimed to investigate growth rate and nutrient consumption of Chlorella vulgaris according to different light irradiation interval. Applied light irradiation intervals were 12 hr, 4 hr, 1 hr, and 1 min. The light source was flexible LED(Blue:Red=1:1), light intensity was 200 PPFD and Light/Dark cycle was 1:1. As a result, growth rate and nutrient removal efficiencies showed no significant differences depending on the light irradiation interval. Considering the reproduction characteristics of applied microalgae cultures of this study, this is thought to be one of the possible reasons of above results. Because Chlorella vulgaris performs an asexual reproduction and it is known that there is no significant relationship between light irradiation interval and growth rate, including nutrient consumption in case of asexual reproduction.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.10
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• pp.1215-1227
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• 2011

The recent craze for so-called skinny jeans is illustrative of the restraint of the body through dress. This phenomenon is noteworthy when considering the internalization of the corset in contemporary fashion. Grown out of the garments of soundly practical use, blue jeans have led the stream of fashion for about 150 years and now they serve as the new corset idealizing the female body in the form of skinny jeans. This study intends to examine the idealization of the body in contemporary fashion and focus on skinny jeans as an externalized corset. The struggle with corsets continues in that the real body is overwhelmed by fashion items. In the aspect of idealizing the body by constraining the body parts, skinny jeans externalize the control of the body as contemporary corsets. This study conducts literature research and content analysis as the method of investigation and focuses on women's fashion from the 20th century. Exerting a harmful influence on health (as corsets have done) the body in skinny jeans is regarded as a modifiable entity. The thinness of the body achieved by skinny jeans suggests the controlling power over the body. Moreover, this gives access to the power presented by the contemporary ideal of thinness. Skinny jeans are modern day glass slippers.

• Korean Journal of Materials Research
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• v.12 no.3
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• pp.190-194
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• 2002

InN/GaN multi-layers were grown by metalorganic chemical vapor deposition(MOCVD) in order to get the appropriate structure for an high power blue-green light emitting diode(LED), and effects of growth conditions (growth temperature, pressure, and $trimethylindium(TMIn)-NH_3-N_2\; flow\; rare)$ on the integrated photoluminescence (PL) intensity and PL peak energy in InN/GaN multi-layers were investigated. The optimized growth conditions with the highest integrated PL intensity for InN/GaN multi-layers were obtained: the growth temperature at $780^{\circ}C$, the growth pressure at 325 Torr, the TMIn flow rate with 150 $m\ell$/min, the $NH_3$flow rate with 3.2 ι/min, and $N_2$ flow rate with 2 ι/min.

• Korean Journal of Materials Research
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• v.30 no.8
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• pp.413-420
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• 2020

Lu₃Al_5-xGa_xO₁₂:Ce³⁺,Cr³⁺ powders are prepared using a solid-state reaction method. To determine the crystal structure, Rietveld refinement is performed. The results indicate that Ga³⁺ ions preferentially occupied tetrahedral rather than octahedral sites. The lattice constant linearly increases, obeying Vegard's law, despite the strong preference of Ga³⁺ for the tetrahedral sites. Increasing x led to a blue-shift of the Ce³⁺ emission band in the green region and a change in the emission intensity. Persistent luminescence is observed from the powders prepared with x = 2-3, occurring through a trapping and detrapping process between Ce³⁺ and Cr³⁺ ions. The longest persistent luminescence is achieved for x = 2; its lifetime is at least 30 min. The findings are explained using crystal structure refinement, crystal field splitting, optical band gap, and electron trapping mechanism.