• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.240-244
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• 2007

We investigated the diffraction grating efficiency by the Diode Pumped Solid State(DPSS 532 nm) laser beam wavelength to improve the diffraction efficiency on $As_{40}Ge_{10}Se_{15}S_{35},\;Ag/As_{40}Ge_{10}Se_{15}S_{35}$ and $As_{40}Ge_{10}Se_{15}S_{35}/Ag/As_{40}Ge_{10}Se_{15}S_{35}$ thin film. Diffraction efficiency was obtained from DPSS laser, used (P:P)polarized laser beam on each thin films. As a result, for the laser beam intensity in $0.24mW/cm^2$, single $As_{40}Ge_{10}Se_{15}S_{35}$ thin film shows the highest value of 0.161% diffraction efficiency at 300 s and for laser beam intensity in $2.4mW/cm^2$, it was recorded with the fastest speed of 50 s(0.013%), which the diffraction grating forming speed is faster than that of $0.24mW/cm^2$ beam. $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ double layer and $As_{40}Ge_{10}Se_{15}S_{35}/Ag/As_{40}Ge_{10}Se_{15}S_{35}$ multi-layered thin film also show the faster grating forming speed at $2.4mW/cm^2$ and higher value of diffraction efficiency at $0.24mW/cm^2$.

• Asian Journal of Atmospheric Environment
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• v.6 no.4
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• pp.288-303
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• 2012

In this study, real time measurements of particle number size distribution in urban Gwangju, coastal Taean, and industrial Yeosu in Korea were conducted in 2008 to understand the occurrence of ultrafine particle (UFP) (<100 nm) events, the variation of its concentration among different sampling sites, and UFP formation pathways. Also, to investigate seasonal and long-term variation of the UFP number concentration, data were collected for the period of 5 years (2007, 2008, 2010, 2011, and 2012) in urban Gwangju. Photochemical and combustion events were found to be responsible for the formation of UFP in the urban Gwangju site, whereas only photochemical event led to the formation of UFP in the coastal Taean site. The highest UFP concentration was found in industrial Yeosu (the average UFP number fractions were 79, 59 and 58% in Yeosu, Gwangju, and Taean, respectively), suggesting that high amount of gas pollutants (e.g., $NO_2$, $SO_2$, and volatile organic carbon (VOC)) emitted from industries and their photochemical reaction contributed for the elevated UFP concentration in the industrial Yeosu site. The UFP fraction also showed a seasonal variation with the peak value in spring (61.5, 54.5, 50.5, and 40.7% in spring, fall, summer, and winter, respectively) at urban Gwangju. Annual average UFP number concentrations in urban Gwangju were $5.53{\times}10^3\;cm^{-3}$, $4.68{\times}10^3\;cm^{-3}$, $5.32{\times}10^3\;cm^{-3}$, $3.99{\times}10^3\;cm^{-3}$, and $2.16{\times}10^3\;cm^{-3}$ in the year 2007, 2008, 2010, 2011, and 2012, respectively. Comparison of the annual average UFP number concentration with urban sites in other countries showed that the UFP concentrations of the Korean sites were lower than those in other urban cities, probably due to lower source strength in the current site. TEM/EDS analysis for the size-selected UFPs showed that the UFPs were classified into various types having different chemical species. Carbonaceous particles were observed in both combustion (soot and organics) and photochemical events (sulfate and organics). In the photochemical event, an internal mixture of organic species and ammonium sulfate/bisulfate was identified. Also, internal mixtures of aged Na-rich and organic species, aged Ca-rich particles, and doughnut shaped K-containing particles with elemental composition of a strong C with minor O, S, and K-likely to be originated from biomass burning nearby agricultural area, were observed. In addition, fly ash particles were also observed in the combustion event, not in the photochemical event.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.296-296
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• 2014

We investigate experimentally and theoretically the splitting of surface plasmon (SP) resonance peaks under TE- and TM-polarized illumination. The SP structure at infrared wavelength is fabricated with a 2-dimensional square periodic array of circular holes penetrating through Au (gold) film. In brief, the processing steps to fabricate the SP structure are as follows. (i) A standard optical lithography was performed to produce to a periodic array of photoresist (PR) circular cylinders. (ii) After the PR pattern, e-beam evaporation was used to deposit a 50-nm thick layer of Au. (iii) A lift-off processing with acetone to remove the PR layer, leading to final structure (pitch, $p=2.2{\mu}m$; aperture size, $d=1.1{\mu}m$) as shown in Fig. 1(a). The transmission is measured using a Nicolet Fourier-transform infrared spectroscopy (FTIR) at the incident angle from $0^{\circ}$ to $36^{\circ}$ with a step of $4^{\circ}$ both in TE and TM polarization. Measured first and second order SP resonances at interface between Au and GaAs exhibit the splitting into two branches under TM-polarized light as shown in Fig. 1(b). However, as the incidence angle under TE polarization is increased, the $1^{st}$ order SP resonance peak blue-shifts slightly while the splitting of $2^{nd}$ order SP resonance peak tends to be larger (not shown here). For the purpose of understanding our experimental results qualitatively, SP resonance peak wavelengths can be calculated from momentum matching condition (black circle depicted in Fig. 2(b)), $k_{sp}=k_{\parallel}{\pm}iG_x{\pm}jG_y$, where $k_{sp}$ is the SP wavevector, $k_{\parallel}$ is the in-plane component of incident light wavevector, i and j are SP coupling order, and G is the grating momentum wavevector. Moreover, for better understanding we performed 3D full field electromagnetic simulations of SP structure using a finite integration technique (CST Microwave Studio). Fig. 1(b) shows an excellent agreement between the experimental, calculated and CST-simulated splitting of SP resonance peaks with various incidence angles under TM-polarized illumination (TE results are not shown here). The simulated z-component electric field (Ez) distribution at incident angle, $4^{\circ}$ and $16^{\circ}$ under TM polarization and at the corresponding SP resonance wavelength is shown in Fig. 1(c). The analysis and comparison of theoretical results with experiment indicates a good agreement of the splitting behavior of the surface plasmon resonance modes at oblique incidence both in TE and TM polarization.

• Korean Journal of Microbiology
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• v.50 no.1
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• pp.46-52
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• 2014

This study was carried out to investigate the characteristics of fermented chinese yam and rice (Dioscorea japonica, Dioscorea batatas, Dioscorea opposita, Rice, FCYR) using Monascus sp. MK805. The extracts from FCYR were measured to examine pigments, antioxidant activities were investigated through DPPH radical scavenging activity, total polyphenol and flavonoid contents, reducing power. Also it was investigated monacolin K productivity by FCYR. Pigments productivity (yellow, orange and red) were 26.2, 13.9, 17.3 at Dioscorea japonica, 41.9, 22.6, 53.2 at Dioscorea batatas, 12.5, 7.5, 9.7 at Dioscorea opposita and 10.1, 7.7, 10.2 at rice, respectively. DPPH radical scavenging activity of FCYR was about 69.7, 79.6, 57.8, and 42.3%, total polyphenol contents of FCYR was about 480.6, 658.7, 379.3, and 212.9 mg/kg, total flavonoid contents of FCYR was about 342.5, 448.4, 235.2, and 168.7 mg/kg, reducing power of FCYR was about 1.57, 2.14, 1.14, and 0.35 (OD at 700 nm), respectively. And then monacolin K productivity of FCYR was about 453.8, 509.5, 332.2, and 263.2 mg/kg, respectively.

• Journal of Pharmaceutical Investigation
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• v.36 no.1
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• pp.45-51
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• 2006

A rapid, selective and sensitive reversed-phase HPLC method for the determination of dipyridamole in human serum was developed, validated, and applied to the pharmacokinetic study of dipyridamole. Dipyridamole and internal standard, loxapine, were extracted from human serum by liquid-liquid extraction with diethyl ether and analyzed on a Nova Pak $C_{I8}$ column with the mobile phase of 40 mM ammonium acetate:methanol:acetonitrile (35:35:30)(v/v/v, pH 7.8). Detection wavelength of 280 nm and flow rate of 1.0 mL/min were fixed for the study. The assay robustness for the changes of mobile phase pH, organic solvent content, and flow rate was confirmed by $3^3$ factorial design using a fixed dipyridamole concentration (50 ng/mL) with respect to its peak area and retention time. And also, the ruggedness of this method was investigated at three different laboratories using same quality control (QC) samples. This method showed linear response over the concentration range of 2-2000 ng/mL with correlation coefficients greater than 0.999. The lower limit of quantification using 0.5 mL of serum was 2 ng/mL, which was sensitive enough for pharmacokinetic studies of dipyridamole. The overall accuracy of the quality control samples ranged from 103.94 to 105.86% for dipyridamole with overall precision (% C.V.) being 4.60-11.49%. The relative mean recovery of dipyridamole for human serum was 97.64%. Stability studies showed that dipyridamole was stable during storage, or during the assay procedure in human serum. The peak area and retention time of dipyridamole were not significantly affected by the changes of mobile phase pH, organic solvent content, and flow rate under the conditions studied. This method showed good ruggedness (within 15% C.V.) and was successfully used for the analysis of dipyridamole in human serum samples for the pharmacokinetic studies of orally administered Dimor tablet (75 mg as dipyridamole) at three different laboratories, demonstrating the suitability of the method.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.211-212
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• 2010

GaN 기반의 상부발광형 LED는 동작되는 동안 생기는 전기적 단락, 그리고 칩 위의 p-형 전극과 n-형 전극 사이에 생기는 누설전류 및 신뢰성 확보를 위하여 칩 표면에 passivation 층을 형성하게 된다. SiO2, Si3N4와 같은 passivation layers는 일반적으로 PECVD (Plasma Enhanced Chemical Vapor Deposition)공정을 이용한다, 하지만 이는 공정 특성상 plasma로 인한 damage가 유발되기 때문에 표면 누설 전류가 증가 한다. 이로 인해 forward voltage와 reverse leakage current의 특성이 저하된다. 본 실험에서는 원자층 단위의 박막 증착으로 인해 PECVD보다 단차 피복성이 매우 우수한 PEALD(Plasma Enhanced Atomic Layer Deposition)공정을 이용하여 Al2O3 passivation layer를 증착한 후, 표면 누설전류와 빛의 출력 특성에 대해서 조사해 보았다. PSS (patterned sapphire substrate) 위에 성장된 LED 에피구조를 사용하였고, TCP(Trancformer Copled Plasma)장비를 사용하여 에칭 공정을 진행하였다. 이때 투명전극을 증착하기 위해 e-beam evaporator를 사용하여 Ni/Au를 각각 $50\;{\AA}$씩 증착한 후 오믹 특성을 향상시키기 위하여 $500^{\circ}C$에서 열처리를 해주었다. 그리고 Ti/Au($300/4000{\AA}$) 메탈을 사용하여 p-전극과 n-전극을 형성하였다. Passivation을 하지 않은 경우에는 reverse leakage current가 -5V 에서 $-1.9{\times}10-8$ A 로 측정되었고, SiO2와 Si3N4을 passivation으로 이용한 경우에는 각각 $8.7{\times}10-9$과 $-2.2{\times}10-9$로 측정되었다. Fig. 1 에서 보면 알 수 있듯이 5 nm의 Al2O3 film을 passivation layer로 이용할 경우 passivation을 하지 않은 경우를 제외한 다른 passivation 경우보다 reverse leakage current가 약 2 order ($-3.46{\times}10-11$ A) 정도 낮게 측정되었다. 그 이유는 CVD 공정보다 짧은 ALD의 공정시간과 더 낮은 RF Power로 인해 plasma damage를 덜 입게 되어 나타난 것으로 생각된다. Fig. 2 에서는 Al2O3로 passivation을 한 소자의 forward voltage가 SiO2와 Si3N4로 passivation을 한 소자보다 각각 0.07 V와 0.25 V씩 낮아지는 것을 확인할 수 있었다. 또한 Fig. 3 에서는 Al2O3로 passivation을 한 소자의 output power가 SiO2와 Si3N4로 passivation을 한 소자보다 각각 2.7%와 24.6%씩 증가한 것을 볼 수 있다. Output power가 증가된 원인으로는 향상된 forward voltage 및 reverse에서의 leakage 특성과 공기보다 높은 Al2O3의 굴절률이 광출력 효율을 증가시켰기 때문인 것으로 판단된다.

• Korean journal of food and cookery science
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• v.28 no.6
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• pp.805-811
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• 2012

This study was carried out in order to optimize the manufacturing condition of fried garlic flakes as well as to investigate the physicochemical properties of the flakes. Fried garlic flake samples were prepared as follows: garlic was sliced by a thickness of 1.5 mm, 2.0 mm, 2.5 mm, which were measured by a thickness gage. The samples were fried in vegetable oil under different temperatures of $140{\sim}150^{\circ}C$, $160{\sim}170^{\circ}C$ and $180{\sim}185^{\circ}C$. The compression strength depending on the height (h) was measured in order to find the thickness effect by the rheometer (force control: 50 N, h: 3.25 mm). Moreover, the sample with 1.5 mm thickness showed crisp phenomena of the split compared with the crush shape of the 2.0 mm and 2.5 mm thick samples. The result of strength for time dependence showed a sample with a thickness of 1.5 mm, which was measured 5~9 times more than the 2.0 mm and 2.5 mm thick samples. We thought the reason that the 1.5 mm sample had less response power equivalent to compression force than the other samples. Alliin has been found to affect the immune responses in the blood, it is a derivative of the amino acid cysteine and is also quite heat stable. The LC system with a UV detection at 210 nm consists of a separation on a Zorbax TMS column and isocratic elution with water and ACN as a mobile phase. The alliin contents of raw and fried garlic flake under $140{\sim}150^{\circ}C$, $160{\sim}170^{\circ}C$ and $180{\sim}185^{\circ}C$ were 18.10 mg/mL, 14.0 mg/mL, 11.6 mg/mL and 11.1 mg/mL, respectively. The decrement of alliin content under different temperature was a small quantity hence, we confirmed that the increasing manufacturing temperature was not affected by the alliin content. Examining for the particle structure of fried garlic flakes by a polarization microscope, the color of the sample treated at $160{\sim}170^{\circ}C$ was pure yellow. Furder, the fiber shaped particle, which has an effect on the tough texture, almost did not appear compared to the different temperature conditions. Finally, the sensory test for the preference of fried garlic flake under different conditions was carried out and the scores for various sensory characteristics were surveyed. According to the physicochemical measurements and sensory evaluation, we confirmed that the optimum manufacturing condition of fried garlic flake was 1.5 mm thick at a temperature of $160{\sim}170^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.67-67
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• 2011

Pulsed DC $BCl_3/SF_6$ 플라즈마를 사용하여 GaAs와 AlGaAs의 건식 식각을 연구하였다. 식각 공정 변수는 가스 유량 (50~100 % $BCl_3$ in $BCl_3/SF_6$), 펄스 파워 (450~600 V), 펄스 주파수 (100~250 KHz), 리버스 시간 (0.4~1.2 ${\mu}s$)이었다. 식각 공정 후 표면 단차 측정기 (Surface profiler)를 사용하여 표면의 단차와 거칠기를 분석하였다. 그 결과를 이용하여 식각률 (Etch rate), 표면거칠기 (Surface roughness), 식각 선택비 (Selectivity)와 같은 특성 평가를 하였다. 실험 후 주사 현미경 (FE-SEM, Field Emission Scanning Electron Microscopy)을 이용, 식각 후 시료의 단면과 표면을 관찰하였다. 실험 결과에 의하면 1) 18 sccm $BCl_3$ / 2 sccm $SF_6$, 500 V (Pulsed DC voltage), 0.7 ${\mu}s$ (Reverse time), 200 KHz (Pulsed DC frequency), 공정 압력이 100 mTorr인 조건에서 GaAs와 Al0.2Ga0.8As의 식각 선택비가 약 48:1로 우수한 결과를 나타내었다. 2) 펄스 파워 (Pulsed DC voltage), 리버스 시간(Reverse time), 펄스 주파수(Pulsed DC frequency)의 증가에 따라 각각 500~550 V, 0.7~1.0 ${\mu}s$, 그리고 200~250 KHz 구간에서 AlGaAs에 대한 GaAs의 선택비가 감소하게 되는 것을 알 수 있었다. 이는 척 (chuck)에 인가되는 전류와 파워를 증가시키고, 따라서 GaAs의 식각률이 크게 증가했지만 AlGaAs 또한 식각률이 증가하게 되면서 GaAs에 대한 식각 선택비가 감소한 것으로 생각된다. 3) 표면 단차 측정기와 주사전자현미경 사진 결과에서는 GaAs의 경우 10% $SF_6$ (18 sccm $BCl_3$ / 2 sccm $SF_6$)가 혼합된 조건에서 상당히 매끈한 표면 (RMS roughness < 1.0 nm)과 높은 식각률 (~0.35 ${\mu}m$/min), 수직의 식각 측벽 확보에서 매우 좋은 결과를 보여주었다. 또한 같은 공정 조건에서 AlGaAs는 식각이 거의 되지 않은 결과 (~0.03 ${\mu}m$/min)를 보여주었다. 위의 결과들을 종합해 볼 때 Pulsed DC $BCl_3/SF_6$ 플라즈마는 GaAs와 AlGaAs의 선택적 식각 공정에서 매우 우수한 공정 결과를 나타내었다.

• Journal of Pharmaceutical Investigation
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• v.40 no.2
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• pp.101-107
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• 2010

A rapid and sensitive reversed-phase high performance liquid chromatography (HPLC) method was developed for the determination of N-(-4-Chlorophenyl)-6-hydroxy-7-methoxy-2-chromanecarboxamide (KAL-1120), a novel anti-inflammation agent, in the rat plasma. The method was applied to analyze the compound in the biological fluids such as bile, urine and tissue homogenates. After liquid-liquid extraction, the compound was analyzed on an HPLC system with ultraviolet detection at 275 nm. HPLC was carried out using reversed-phase isocratic elution with a $C_{18}$ column, a mobile phase of a mixture of acetonitril (40 v/v%) at a flow rate of 1.0 mL/min. The chromatograms showed good resolution and sensitivity and no interference of plasma. The calibration curve for the drug in plasma was linear over the concentration range of 0.05-50 ${\mu}g$/mL. The intra- and inter-day assay accuracies of this method ranged from 0.06% to 9.33% of normal values and the precision did not exceed 6.28% of relative standard deviation. The plasma concentration of KAL-1120 decreased to below the quantifiable limit at 1.5 hr after the i.v. bolus administration of 2-10 mg/kg to rats ($t_{1/2,({\alpha})}$ and $t_{1/2,({\beta})$ of 2.15 and 26.7 min at a dose of 2 mg/kg, 3.91 and 33.0 min at a dose of 10 mg/kg, respectively). The steady-state volume of distribution ($V_{dss}$) and the total body clearance ($CL_t$) were not significantly altered in rats given doses from 2 to 10 mg/kg. Of the various tissues tested, KAL-1120 was mainly distributed in the lung and heart after i.v. bolus administration. KAL-1120 was detected in the bile by 30 min after its i.v. bolus administration. However, the concentration in the urine after i.v. bolus administration became too low to measure, suggesting that KAL-1120 is mostly excreted in the bile. In conclusion, this analytical method was suitable for the preclinical pharmacokinetic studies of KAL-1120 in rats.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.87-87
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• 2018

다이아몬드 상 탄소(diamond-like carbon, DLC)는 상당량의 $sp^3$ 결합을 가지는 비정질 탄소(a-C) 또는 수소화 비정질 탄소(a-C:H)로 이루어진 준안정 형태의 탄소이다. DLC는 전기 저항과 굴절률이 높고 화학적으로 다른 물질과 반응하지 않으며, 마찰계수가 낮고 경도가 높아 자기 디스크, 광학 소자 등의 다양한 분야에서 적용되고 있다[1,2]. 또한 다이아몬드에 비해 상온에서 성장이 가능할 정도로 합성온도가 낮아 적용 기판의 제한이 거의 없고, 증착 방법과 조건에 따라 탄소 결합의 다양성과 비정질성이 변화하기 때문에 넓은 범위의 특성을 얻을 수 있는 장점이 있다. 지금까지 DLC 박막의 광학적 특성, 특히 굴절률, 광학적인 에너지 밴드 갭, 자외선과 적외선 투과성에 대해서는 많은 연구가 진행되었으나 가시광선의 투과성에 대한 연구는 제한적이며[4], 가시광선 투과도 개선에 대한 연구는 전무하다. 본 연구에서는 ITO 기판 위에 DLC를 합성하고 기계적 특성과 가시광선 영역 투과도를 조사하였다. RF-PECVD(radio frequency plasma enhanced chemical vapor deposition) 방법에 의해서 $C_2H_2+Ar$ 혼합 가스 비율과 $C_2H_2+N_2$ 혼합 가스 비율을 변화시켜 ITO 기판 위에 DLC 박막을 합성하였다. 공정 압력과 rf-power, 증착시간, 기판온도는 0.2 torr, 40 W, 5 분, $50^{\circ}C$로 고정하고, 공정 가스는 $C_2H_2+Ar$과 $C_2H_2+N_2$가 200 sccm이 되도록 비율을 변화하였다. $C_2H_2:Ar$과 $C_2H_2:N_2$의 비율은 180 : 20, 160 : 40, 140 : 60, 120 : 80, 100 : 100이 되도록 가스의 유량을 조절하였다. 투과도는 가시광선(380 ~ 780 nm) 범위에서 측정하였고 두께와 표면조도는 AFM으로 측정하였다. 투과도는 $C_2H_2+Ar$의 Ar 가스 비율이 증가할수록 증가해 140 : 60일 때 최댓값을 나타낸 후 다시 감소하였다. $C_2H_2+N_2$ 투과도는 $N_2$ 가스 비율이 증가할수록 감소하는 경향을 나타내었다. 표면 거칠기는 $C_2H_2+Ar$ 혼합 가스를 사용한 경우의 Ar의 가스 비율이 증가할수록 증가하였다. 그러나 $C_2H_2+N_2$ 혼합 가스를 사용한 경우에는 $N_2$ 가스의 혼합 비율이 증가할수록 감소하였다.