• Proceedings of the Materials Research Society of Korea Conference
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• 2008.05a
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• pp.23.2-23.2
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• 2008

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.400.1-400.1
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• 2016

Interfacial engineering approaches as an efficient strategy for improving the power conversion efficiencies (PCEs) of inverted polymer solar cells (iPSCs) has attracted considerable attention. Recently, polymer surface modifiers, such as poly(ethyleneimine) (PEI) and polyethylenimine ethoxylated (PEIE), were introduced to produce low WF electrodes and were reported to have good electron selectivity for inverted polymer solar cells (iPSCs) without an n-type metal oxide layer. To obtain more efficient solar cells, quantum dots (QDs) are used as effective sensitizers across a broad spectral range from visible to near IR. Additionally, they have the ability to efficiently generate multiple excitons from a single photon via a process called carrier multiplication (CM) or multiple exciton generation (MEG). However, in general, it is very difficult to prepare a bilayer structure with an organic layer and a QD interlayer through a solution process, because most solvents can dissolve and destroy the organic layer and QD interlayer. To present a more effective strategy for surpassing the limitations of traditional methods, we studied and fabricated the highly efficient iPSCs with mono-layered QDs as an effective multi-functional layer, to enhance the quantum yield caused by various effects of QDs monolayer. The mono-layered QDs play the multi-functional role as surface modifier, sub-photosensitizer and electron transport layer. Using this effective approach, we achieve the highest conversion efficiency of ~10.3% resulting from improved interfacial properties and efficient charge transfer, which is verified by various analysis tools.

• Archives of Plastic Surgery
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• v.45 no.2
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• pp.111-117
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• 2018

Background Fat grafting, or lipofilling, represent frequent clinically used entities. The fate of these transplants is still not predictable, whereas only few animal models are available for further research. Quantum dots (QDs) are semiconductor nanocrystals which can be conveniently tracked in vivo due to photoluminescence. Methods Fat grafts in cluster form were labeled with cadmium-telluride (CdTe)-QD 770 and transplanted subcutaneously in a murine in vivo model. Photoluminescence levels were serially followed in vivo. Results Tracing of fat grafts was possible for 50 days with CdTe-QD 770. The remaining photoluminescence was $4.9%{\pm}2.5%$ for the QDs marked fat grafts after 30 days and $4.2%{\pm}1.7%$ after 50 days. There was no significant correlation in the relative course of the tracking signal, when vital fat transplants were compared to non-vital graft controls. Conclusions For the first-time fat grafts were tracked in vivo with CdTe-QDs. CdTe-QDs could offer a new option for in vivo tracking of fat grafts for at least 50 days, but do not document vitality of the grafts.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.148-148
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• 2015

Over the past several years, Colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been developed for the future of optoelectronic applications. An inverted-type quantum-dot light-emitting-diode (QDLED), employing low work function organic material polyethylenimine ethoxylated(PEIE) (<10 nm)[1] modified ZnO nanoparticles (NPs) as electron injection and transport layer, was fabricated by all solution processing method, instead of electrode in the device. The PEIE surface modifier incorporated on the top of the ZnO NPs film, facilitates the enhancement of both electorn injection into the CdSe-ZnS QD emissive layer by lowering the workfunction of ZnO from 3.58eV to 2.87eV and charge balance on the QD emitter. In this inverted QDLEDs, blend of poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo) and poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] are used as hole transporting layer (HTL) to improve hole transporting property. At the operating voltage of 7.5 V, the QDLED device emitted spectrally orange color lights with high luminance up to 11110 cd/m2, and showed current efficiency of 2.27 cd/A.[2]

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.374-379
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• 2001

We have investigated the annealing effects on the optical properties of InAs quantum dots(QDs) capped with InGaAs(sample QDl), where InGaAs layer was deposited by opening Gallium, Arsenic, Indium and Arsenic shutters alternately with 3 periods, grown by molecular beam epitaxy. The emission wavelength of the sample of InAs QDs capped by GaAs barriers was observed to be blue-shifted as the annealing temperature was increased. On the other hand, the photoluminescence(PL) peak position of sample QD1 was observed to be red-shifted at the annealing temperature of up to $600^{\circ}C$ and, then, it was found to be blue-shifted at temperatures ranging from 700 to $800^{\circ}C$. The full width at half maximum values of sample QD1 subjected to annealing treatments show different behavior compared to typical InAs quantum dot structures.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.186-193
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• 2006

In this study, we analyzed the electrical and optical properties of metalorganic chemical vapor deposition grown InGaAs/InGaAsP/InP quantum dot(QD) molecules by using photoluminescence and deep-level transient spectroscopy. From these resulte, the energy levels of the large QDs are located at deeper region from the conduction band edge of the barrier than that of the small QDs, The large QDs seem to have the energy states more than two, and these energy levels of the QD molecules are located at 0.35, 0.42, and 0.45 eV from conduction band edge under -4 V reverse bias conditions. The energy levels are closely coupled under low reverse bias, and then decoupled as the bias voltage is increased.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.6
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• pp.29-51
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• 2001

The purpose of this research is to analyze of biotope structure focused on the evaluation for the species and biotope preservation in the case of Soosung District in Daegu metropolitan city. We analyzed the structure of urban biotope, and investigated the disposition of space and several characteristics through the material collection relating to the existing urban ecological material and the field investigation. The results of this study were as follows; 1) The result of biotope type classification was divided into 17 biotope type groups and 90 biotope types belonging to them. 2) The biotope type of mixed forest(QD) has the highest rate in occupation area, 1.764ha and the biotope type of cultivation areas by vinyle-hothouse(KC) has the lowest rate, 0.3ha. 3) In the result of the first evaluation for the species and biotope preservation, biotope types such as QB, QI, PA, PB, NB and NC etc. possess great value. Particulary, these biotope types come from forest areas and transition zone. They have not appeared in the inner of cities. 4) The biotope types such as CA, NA, NB, ND and PB are proved to possess high value in the result of rarity and riskiness evaluation. There appear EE, MA, NB, QC and QD in IV grade which is impossible to have them regenerative. They usually have appeared in forest areas. 5) There emerge 3a biotope type that has the highest value in the result of the second evaluation such as CC, EE, KF, LD, MB, NC, PB, QB and QI etc. Most of them were presented into the large area of site size and were distributed in the forest areas intensively. So, it is certain that the space for the species and biotope preservation connected with residential district is scarce. 6) The detailed biotope plan must be made out specially continuously. It is about biotope spaces that are especially important for the species and biotope preservation from the result of this research. Also, the study on the detailed index settlement of the urban landscape plan based on the biotope map must be continued.

• Molecular & Cellular Toxicology
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• v.5 no.1
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• pp.51-57
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• 2009

Quantum Dot (QD) nanoparticles are used in various industrial applications, such as diagnostic, drug delivery, and imaging agents of biomedicine. Although QDs are extensively used in many medical science, several studies have been demonstrated the potential toxicity of nanoparticles. The first objective of this study was to investigate the nanotoxicity of QDs in the HaCaT human keratinocyte cell line by focusing on gene expression pattern. In order to evaluate the effect of QDs on gene expression profile in HaCaT cells, we analyzed the differential genes which related to oxidative stress and antioxidant defense mechanisms by using human cDNA microarray and PCR array. A human cDNA microarray was clone set, which was sorted for a list of genes correlated with cell mechanisms. We tried to confirm results of cDNA microarray by using PCR array, which is pathway-focused gene expression profiling technology using Real-Time PCR. Although we could not find the exactly same genes in both methods, we have screened the effects of QDs on global gene expression profiles in human skin cells. In addition, our results show that QD treatment somehow regulates cellular pathways of oxidative stress and antioxidant defense mechanisms. Therefore, we suggest that this study can enlarge our knowledge of the transcriptional profile and identify new candidate biomarker genes to evaluate the toxicity of nanotoxicology.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.246.1-246.1
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• 2014

Over the past several years, colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been extensively studied and developed for the future of optoelectronic applications. In the work, we fabricate an inverted CdSe/ZnS quantum dot (QD) based light-emitting diodes (QDLED). In order to reduce work function of indium tin oxide (ITO) electrode for inverted structure, a very thin (<10 nm) polyethylenimine ethoxylated (PEIE) is used as surface modifier[1] instead of conventional metal oxide electron injection layer. The PEIE layer substantially reduces the work function of ITO electrodes which is estimated to be 3.08 eV by ultraviolet photoemission spectroscopy (UPS). From transmission electron microscopy (TEM) study, CdSe/ZnS QDs are uniformly distributed and formed by a monolayer on PEIE layer. In this inverted QDLEDs, blend of poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo) and poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] are used as hole transporting layer (HTL) to improve hole transporting property. At the operating voltage of 8 V, the QDLED device emitted spectrally orange color lights with high luminance up to 2450 cd/m2, and showed current efficacy of 0.6 cd/A, respectively.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.291-297
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• 2011

In this paper, the differential quantized method and the parallel method to reduce the size of ROM in the direct digital frequency synthesizer(DDFS) is proposed And we design the DDFS by FPGA The new ROM compression method can reduce the ROM size by using the two ROM. The quantized value of sine is saved by the quantized-ROM(Q-ROM) and the differential ROM(D-ROM). Also we design the phase-to-sine converter using the phase accumulator of parallel type for generating the high frequency. So the total size of the ROM in the proposed DDFS is significantly reduced compared to the original ROM The ROM compression ratio of 67.5% is achieved by this method. Also, the power consumption is decreased according to the ROM size reduction and we can design the DDFS generating the high frequency.