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Coherence Gated Three-dimensional Imaging System using Organic Photorefractive Holography
Hwang, Ui-Jung,Choi, Jongwan,Kim, Chuntae,Kim, Won-Guen,Oh, Jin-Woo,Kim, Nakjoong Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.3
This paper discusses a coherence-gated three-dimensional imaging system based on photorefractive holography, which was applied to imaging through turbid media with a view to developing biomedical instrumentation. A rapid response photorefractive device doped with 2,4,7-trinitro-9-fluorenylidene malononitrile was used to generate the hologram grating. The estimated depth resolution was $20{\mu}m$, which corresponds to the coherence length of the light source. In this coherence imaging system, tomographic imaging of a 3-dimensional object composed of a $50{\mu}m$ thick cylindrical layer was achieved. The proposed coherence imaging system using an organic photorefractive material can be used as an optical tomography system for biological applications.
N-p-Nitrophenyl Poly(m-Phenylene Isophthalamide)의 합성
김홍범,김동현,이재웅,송상엽,김낙중,Hongbum Kim,Donghyun Kim,Jaewung Lee,Sangyeop Song,Nakjoong Kim 대한화학회 1993 대한화학회지 Vol.37 No.2
N-p-nitrophenyl poly(m-phenylene isophthalamide)는 poly(m-phenylene isophthalamide)를 디메틸술폭사이드(DMSO) 용매속에서 수소화나트륨(NaH)과 반응시킨 후, 1-fluoro-4-nitrobenzene을 첨가하여 43 wt%를 얻었다. 고유점성도는 폴리머를 98% 황산에 녹여 $30^{\circ}C$에서 측정하였으며 그 값은 0.606g/cm${\cdot}$sec(0.125g/25ml)였다. Poly(m-phenylene isophthalamide) 합성에 있어서, 1,3-페닐디아민은 트리에틸아민과 트리에틸아민·염화수소가 있는 클로로포름 용매속에서 클로로이소프탈산과 반응에 의해 얻어졌다. 고유 점성도 값은 같은 조건에서 0.560g/cm${\cdot}$sec 였다. N-p-nitrophenyl poly(m-phenylene isophthalamide)의 치환비율은 $^1H-NMR$ integration에 의해 16.7~47.0%였다. 고유점성도가 큰 poly(m-phenylene isophthalamide)를 사용했을 때는 치환비율이 낮았다. N-p-nitrophenyl poly(m-phenylene isophthalamide) was obtained from treatment of poly(m-phenylene isophthalamide) with sodium hydride in dimethyl sulfoxide followed by the addition of 1-fluoro-4-nitrobenzene in 43 wt% yield. Its inherent viscosity was 0.606 g/cm${\cdot}$sec determined from a solution of 0.125 g of the above polymer dissolved in 25 ml of 98% sulfuric acid at $30^{\circ}C.$ In order to synthesize poly(m-phenylene isophthalamide), 1,3-phenylenediamine is allowed to react with isophthaloyl chloride in chloroform in the presence of triethylamine and added triethylamine hydrochloride. The value of inherent viscosity is 0.560 g/cm${\cdot}$sec measured at the same condition. The substitution ratio of N-p-nitrophenyl poly(m-phenylene isophthalamide) was to be 16.7∼47.0% by using the $^1H-NMR$ integration. When the higher inherent viscosity of poly(m-phenylene isophthalamide) was used, lower substitution ratio would be calculated.
오진우,Nakjoong Kim 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.1
In this work, we report on the characterization of six low-Tg poly[methyl-3-(9-carbazolyl) propylsiloxane] based photorefractive (PR) composites sensitized with poly(3-hexylthiophene) (P3HT) in different concentrations,ranging from 0.2 to 1 wt %. At 632.8 nm, photoconductivity, space charge field, refractive index modulation, and grating buildup time were measured versus external electric field. The photoconductivity was strongly dependent on the visible light absorption and mobility. The magnitude of space charge field was affected by the conductivity contrast σph/(σph + σd). The refractive index modulation increased with the magnitude of space charge field and the PR grating buildup speed increased with the photoconductivity.
CFD Analysis of a Counter-rotating Tubular Type Micro-Turbine with Diffuser
이낙중(Lee, Nakjoong),박지훈(Park, Jihoon),황영호(Hwang, Young-Ho),김유택(Kim, Youtaek),이영호(Lee, Youngho) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.05
Micro hydraulic turbines take a growing interest because of its small and simple structure as well as high possibility of applying to micro and small hydropower resources. The differential pressure exiting within the city water pipelines can be used efficiently to generate electricity like the energy generated through gravitational potential energy in dams. In order to reduce water pressure at the inlet of water cleaning centers, pressure reducing valves are used widely. Therefore, pressure energy is wasted. Instead of using the pressure reduction valve, a micro counter-rotating hydraulic turbine can be replaced to get energy caused by the large differential pressure found in the city water pipelines. In this study, in order to acquire design data of counter-rotating tubular type micro-turbine, output power, head, and efficiency characteristics due to the diffuser.
Bandgap engineering of nanosized carbon dots through electron-accepting functionalization
Choi, Jongwan,Kim, Nakjoong,Oh, Jin-Woo,Kim, Felix Sunjoo THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.65 No.-
<P><B>Abstract</B></P> <P>We report tuning of energy bandgap of nanosized carbon dots by chemical modification with electron-accepting moieties. The carbon dot derivatives were synthesized by oxidation and hydrothermal reaction, followed by addition/substitution reactions, resulting in uniform-sized carbon dots. Structural characterization and photophysical investigation were performed by applying various microscopic and spectroscopic techniques. The bandgap of the carbon dots was controlled by chemical functionalization with nitro and nitrile groups, as evidenced by the red-shift in the absorption and photoluminescence emission spectra. Calculations based on density functional theory were employed to support the observed bandgap tuning via functionalization of the carbon dots.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Choi, Jongwan,Kim, Nakjoong,Oh, Jin-Woo,Song, Heeseok,Choi, Moonhyun,Hong, Jinkee,Kim, Felix Sunjoo Korean Physical Society 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.11
<P>We studied a series of fullerene derivatives, which had been functionalized by an electron-donating group (triphenylamine) or an electron-accepting group (cyanobenzene), for use as photosensitizers in photoconducting polymer composites. The functionalized fullerenes were synthesized via the Prato reaction. The electronic energy levels of the fullerene derivatives and photo-charge-generation efficiencies of charge-transfer complex between the photoconducting polymer and the dopant were investigated by using density functional theory calculations, optical absorption spectroscopy, and xerographic discharge methods.</P>