• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.23.1-23.1
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• 2010

Alkanethiol (CH3(CH2)nSH) 자기 조립 박막은 금, 은, 팔라듐 그리고 구리와 같은 금속 물질과 결합하여 산화 방지 보호막, 생화학적 멤브레인 그리고 케미컬 센서로 널리 이용되었다. 전도성을 가진 많은 금속 분말 중에서, 구리는 뛰어난 열, 전기 전도성과 풍부한 양으로 다른 귀금속에 비교하여 경제성까지 갖춘 물질이다. 그러나 이러한 구리 나노 분말은 대기에 노출된 구리 분말이 쉽게 산화된다는 결정적인 단점 때문에 그동안 널리 이용되지 못하였다. 이러한 구리의 단점을 극복하고 뛰어난 전도성의 특징을 이용하고자, Langmuir-Blodgett (LB), layer by layer (LbL), electrophoretic deposition (EPD), self-assembled monolayer (SAM)과 같은 구리 나노 분말 위에 유기 박막을 형성하고자 하는 많은 방법이 시도되어왔다. 이러한 방법들 대부분은 습식 방법으로 진행되었으며, 약 2-nm 두께의 SAM 구조를 형성할 수 있음이 많은 연구를 통하여 확인되었다. 그러나 습식 기반의 SAM 구조는 단지 수일 동안만 유효하며, 이는 코팅을 수행하면서 점차 떨어지는 source solvent의 순도와 적합하지 않은 코팅 조건, 그리고 이러한 원인으로 형성된 부실한 막질 구조 때문으로 추측된다. 게다가 이러한 습식 기반 공정은 코팅 막의 두께 조절과 코팅 시 solvent의 순도를 일정하게 유지하는 것이 매우 복잡하고 어려운 작업으로 알려져 왔다. 본 실험에서는 고 진공 챔버 (< $4.0{\times}10-6$ torr) 시스템을 이용하여 습식 기반 공정의 문제점을 극복하고 구리 나노 분말의 산화를 막기 위한 실험을 진행하였다. 1-octanethiol (CH3(CH2)7SH)은 중간 길이의 hydrocarbon (n=7) 구조를 가진 특징 때문에 코팅 물질로 사용되었다. 게다가, alkanethiol 족 특유의 물질인 황(sulfur)은 구리와 결합하여 산화방지 보호막의 역할을 수행할 수 있다. 저 진공 조건에서는 10-nm의 multilayer가 일괄적으로 코팅됨을 확인할 수 있었다. 본 실험에서는 약 10-nm 두께의 자기 조립 박막(self assembled monolayers: SAMs)이 고 진공 조건에서 구리 나노 분말 표면 위에 코팅 조건의 변경을 통해서 5-nm에서 10-nm 두께의 1-octanethiol SAMs 구조를 얻어낼 수 있었다. 이는 고 진공 조건에서 1-octanethiol SAMs의 코팅 두께를 조절함으로 다양한 크기의 분말에 코팅 물질로 쓰일 수 있음을 알 수 있다.

• Journal of Powder Materials
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• v.23 no.2
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• pp.108-111
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• 2016

$Y_2O_3-H_3BO_3:Eu^{3+}$ powders are synthesized using a mechanical alloying method, and their photoluminescence (PL) properties are investigated through luminescence spectrophotometry. For samples milled for 300 min, some $Y_2O_3$ peaks ([222], [440], and [622]) and amorphous formations are observed. The 300-min-milled mixture annealed at $800^{\circ}C$ for 1 h with Eu = 8 mol% has the strongest PL intensity at every temperature increase of $100^{\circ}C$ (increasing from 700 to $1200^{\circ}C$ in $100^{\circ}C$ increments). PL peaks of the powder mixture, as excited by a xenon discharge lamp (20 kW) at 240 nm, are detected at approximately 592 nm (orange light, $^5D_o{\rightarrow}^7F_1$), 613 nm, 628 nm (red light, $^5D_o{\rightarrow}^7F_2$), and 650 nm. The PL intensity of powder mixtures milled for 120 min is generally lower than that of powder mixtures milled for 300 min under the same conditions. PL peaks due to $YBO_3$ and $Y_2O_3$ are observed for 300-min-milled $Y_2O_3-H_3BO_3$ with Eu = 8 mol% after annealing at $800^{\circ}C$ for 1 h.

• Journal of Biosystems Engineering
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• v.23 no.1
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• pp.49-56
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• 1998

The objectives of this study were to develop models to predict the contents of moisture and protein of single kernel of brown rice based on visible/NIR (near-infrared) spectroscopic technique. The reflectance spectra of rice were obtained in the range of the wavelength 400 to 2,500 nm with 2 nm intervals. Multiple linear regression(MLR) and partial least squares (PLS) were used to develop the models. The MLR model using the first derivative spectra(10 nm of gap) with Standard Normal Variate and Detrending (SNV and Drt.) preprocessing showed the best results to predict moisture content of the sin린e kernel brown rice. To predict the protein content of a single kernel of brown ricer the PLS model used the raw spectra with multiplicative scatter correction(MSC) preprocessing over the wavelength of 1,100~1,500 nm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.4
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• pp.18-23
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• 2007

This paper presents a transmissive dispersion compensator based on tilted chirped fiber Bragg grating pairs which happen mode coupling between core mode and cladding mode. And, as a result of simulation, the phase matching condition and optimum tilted angle to maximize the mode-coupling in the dispersion compensator are shown and the dispersion slope and bandwidth in the proposed dispersion compensator is respectively 3,068ps/nm and 0.45nm.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1325-1326
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• 2006

Tungsten-molydiside $W_xMo_{1-x}Si_2$ was synthesized by self-propagating high temperature synthesis (SHS). The SHS product with the initial composition of (0.5Mo+0.5W+2Si) contains 23.9% $MoSi_2$, 40.89% $WSi_2$ with remaining 9.11% Mo, 9.16% Si and 16.94%W. Lattice parameters of the $MoSi_2$ and $WSi_2$ determined by Rietvelt analysis were a=0.3206 nm, c=0.7841 nm and a=0.3212 nm, c=0.7822 nm, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8A
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• pp.821-828
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• 2008

In this paper, we present an optimized design of RS(23,17) decoder for UWB, which uses the pipeline structured-modified Euclidean(PS-ME) algorithm. Firstly, the modified processing element(PE) block is presented in order to get rid of degree comparison circuits, registers and MUX at the final PE stage. Also, a degree computationless decoding algorithm is proposed, so that the hardware complexity of the decoder can be reduced and high-speed decoder can be implemented. Additionally, we optimize Chien search algorithm, Forney algorithm, and FIFO size for UWB specification. Using Verilog HDL, the proposed decoder is implemented and synthesized with Samsung 65nm library. From synthesis results, it can operate at clock frequency of 250MHz, and gate count is 17,628.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.1
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• pp.23-29
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• 1997

Effects of Co thickness on the formation of epitaxial $CoSi_2$ from the Co/Ti bilayer have been investigated. Ti and Co were sequentially deposited with the Ti thickness fixed at 5 or 10nm, while the Co thickness was varied from 5 to 30nm. The metal-deposited samples were then rapidly thermal-annealed in $N_2$ at $900^{\circ}C$ for 20 sec. Material properties of $CoSi_2$ thin films were analyzed by the 4-point probe, XRD, AES, andXTEM. When the as-deposited Co thickness was below 15nm, the $CoSi_2$ with high resistivity and rough interface was formed. On the other hand, when the Co thickness was above 15 nm, the epitaxial $CoSi_2$ with the resistivity of about 16 ~ 19 $\mu\Omega.cm$, uniform composition and thickness and flat interface was formed. Initial Ti thickness has sizable effect on the formation of $CoSi_2$, when the Co layer was very thin (~ 5 nm). But there was no significant effect of the Ti thickness for the initial Co thickness of above 15 nm.

• Molecular & Cellular Toxicology
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• v.5 no.1
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• pp.23-31
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• 2009

To compare the effects of nanometer-sized silver ions and support materials (nano-silver coating material, NM-silver) and silver ions, we exposed zebrafish embryos to both types of nano-silver ions and compared the acute responses during embryogenesis. The amount of silver in the NM-silver (17.16%) was greater than that in the silver ion (4.56%). Both of these materials have different atomic compositions. The silver ion-exposed groups (10 and 20 ppt) showed lower survival rates than the NM-silver-exposed groups (10 and 20 ppt). NM-silver penetrated the skin and blood tube of zebrafish larvae as aggregated particles, whereas, silver ions penetrated the organelles, nucleus and yolk in a spread-out pattern. Micro-array analysis of RNA from zebrafish larvae (72 hours post-fertilization) that were treated with either NM-silver or silver ions, showed alteration in expression of the BMP, activin, TGF-$\beta$, and $GSK3{\beta}$ genes pathway. Additionally, $GSK3{\beta}$ gene pathway for apoptosis that was related with left-right asymmetry. Gene expression changes in the NM-silver or silver ions-treated zebrafish embryo led to phenotypic changes in the hatched larvae, reflecting increased apoptosis and incomplete formation of an axis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.264-267
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• 2003

Pitch measurements of 150 nm pitch one-dimensional grating standards were carried out using an contact mode atomic force microscopy(C-AFM) with a high resolution three-axis laser interferometer. It was called as 'Nano-metrological AFM' In Nano-metrological AFM, Three laser interferometers were aligned well to the end of AFM tip. Laser sources of the three-axis laser interferometer in the nano-metrological AFM were calibrated with an I$_2$-stablilzed He-Ne laser at a wavelength of 633 nm. So, the Abbe error was minimized and the result of the pitch measurement using the nano-metrological AFM has a traceability to the length standard directly. The uncertainty in the pitch measurement was estimated in accordance with the Guide to the Expression of Uncertainty in Measurement(GUM). The Primary source of uncertainty in the pitch-measurements was derived from repeatability of pitch-measurement, and its value was approx 0.186 nm. Expanded uncertainty(k=2) of less than 5.23 nm was obtained. It is suggested that the metrological AFM is a useful tool for the nano-metrological standard calibration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.416-417
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• 2006

Organic light emitting diodes (OLEDs) show a lot of advantages for display purposes. Because OLEDs provide white light emission with a high efficiency and stability, it is desirable to apply OLEDs as an illumination light source and back light in LCD displays. We synthesized new emissive materials, namely [2-(2-hydroxyphenyl)benzoxazole] ($Zn(HPB)_2$) and [(2-(2-hydroxyphenyl)benzoxazole)(8-hydoxyquinoline)] (Zn(HPB)q), which have a low molecular compound and thermal stability. We studied white OLEDs using $Zn(HPB)_2$ and Zn(HPB)q. The fundamental structures of the white OLEDs were ITO/PEDOT:PSS (23 nm)/NPB (40 nm)/$Zn(HPB)_2$ (40 nm)/Zn(HPB)q (20 nm)/$Alq_3$ (10 nm)/LiAl (120 nm). As a result, we obtained a maximum luminance of $15325\;cd/m^2$ at a current density of $997\;mA/cm^2$. The CIE(Commission International de l'Eclairage) coordinates are (0.28, 0.35) at an applied voltage of 9.75 V.