• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.380-386
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• 2006

In this study, we had designed and fabricated the plasma focus device which can generate the light source for EUV(Extreme Ultra Violet) lithography. And we also have investigated the basic electrical characteristics of currents, voltages, resistance and inductance of this system. Voltage and current signals were measured by C-dot and B-dot probe, respectively. We applied various voltages of 1.5, 2, 2.5 and 3 kV to the anode electrode and observed voltages and current signals in accordance with various Ar pressures of 1 mTorr to 100 Torr in diode chamber. It is observed that the peak values of voltage and current signals were measured at 300 mTorr, where the inductance and impedance were also estimated to be 73 nH and $35 m{\Omega}$ respectively. The electron temperature has been shown to be 13000 K at the diode voltage of 2.5 kV and this gas pressure of 300 mTorr. It is also found that the ion density Ni and ionization rate 0 have been shown to be $N_i = 8.25{\times}10^{15}/cc$ and ${\delta}$= 77.8%, respectively by optical emission spectroscopy from assumption of local thermodynamic equilibrium(LTE) plasma.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.233-241
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• 1994

Purpose : This study was performed to verify dose distribution with the tissue compensator which is used for uniform dose distribution in total body irradiation(TBI). Materials and methods : The compensators were made of lead(0.8mm thickness) and aluminum(1mm or 5mm thickness) plates. The humanoid phantom of adult size was made of paraffin as a real treatment position for bilateral total body technique. The humanoid phantom was set at 360cm of source-axis distance(SAD) and irradiated with geographical field size(FS) $144{\times}144cm^2(40{\times}40cm^2$ at SAD 100cm) which covered the entire phantom. Irradiation was done with 10MV X-ray(CLINAC 1800, Varian Co., USA) of linear accelerator set at Department of Therapeutic Radiology, Chonnam University Hospital. The midline absorbed dose was checked at the various regions such as head, mouth, mid-neck, sternal notch, mid-mediastinum, xiphoid, umbilicus, pelvis, knee and ankle with or without compensator, respectively. We used exposure/exposure rate meter(model 192, Capintec Inc., USA) with ionization chamber(PR 05) for dosimetry, For the dosimetry of thorax region TLD rods of $1x1x6mm^3$ in volume(LiF, Harshaw Co., Netherland) was used at the commercially available humanoid phantom. Results : The absorbed dose of each point without tissue compensator revealed significant difference(from $-11.8\%\;to\;21.1\%$) compared with the umbilicus dose which is a dose prescription point in TBI. The absorbed dose without compensator at sternal notch including shoulder was $11.8\%$ less than the dose of umbilicus. With lead compensator the absorbed doses ranged from $+1.3\%\;to\;-5.3\%$ except mid-neck which revealed over-compensation($-7.9\%$). In case of aluminum compensator the absorbed doses were measured with less difference(from $-2.6{\%}\;to\;5.3\%$) compared with umbilicus dose. Conclusion : Both of lead and aluminum compensators applied to the skull or lower leg revealed a good compensation effect. It was recognized that boost irradiation or choosing reference point of dose prescription at sternal notch according to the lateral thickness of patient in TBI should be considered.

• Mass Spectrometry Letters
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• v.5 no.2
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• pp.42-48
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• 2014

A specific and sensitive liquid chromatography-electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed and validated for the simultaneous quantification of porphyrins (coproporphyrin, pentacarboxylporphyrin, hexacarboxylporphyrin, heptacarboxylporphyrin, and uroporphyrin) in human plasma and urine. Acidified plasma samples and urine samples were prepared by using liquid-liquid extraction using ethyl acetate and protein precipitation with acetonitrile, respectively. The separation was achieved onto a Synergi Fusion RP column ($150mm{\times}2.0mm$, $4{\mu}m$) with a gradient elution of mobile phase A (0.1% formic acid in 2 mmol/L ammonium acetate, v/v) and mobile phase B (20% methanol in acetonitrile, v/v) at a flow rate of $450{\mu}L$/min. Porphyrins and the internal standard (IS), coproporphyrin I-$^{15}N_4$, were detected by a tandem mass spectrometer equipped with an electrospray ion source operating in positive ion mode. Multiple reaction monitoring (MRM) transitions of the protonated precursor ions and the related product ions were optimized to increase selectivity and sensitivity. The proposed method was validated by assessing selectivity, linearity, limit of quantification (LOQ), precision, accuracy, recovery, and stability. The calibration curves were obtained in the range of 0.1-100 nmol/L and the LOQs were estimated as 0.1 nmol/L for all porphyrins. Results obtained from the validation study of porphyrins showed good accuracy, precision, recovery, and stability. Finally, the proposed method was successfully applied to clinical studies on the autism spectrum disorder (ASD) diagnosis of 203 Korean children.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.467-474
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• 2014

The relative dose calculated by MCNPX and the relative dose measured by ionization chamber and solid phantoms evaluated the accuracy comparing with Monte Carlo simulation. In order to apply Monte Carlo simulation the intraluminal brachytherapy of extrahepatic bile duct cancer, 192Ir sealed radioactive source replicate, Bile duct and surrounding organs were made using KMIRD phantom based on a South Korea standard man. To check the absorbed dose of normal organs around bile duct, we set the specific effective energy and initial radioactivity to 1 Ci using MCNPX. Evaluation of the accuracy of the Monte Carlo simulation, the difference of the relative dose is the most 1.96% that satisfy the criteria that is the relative error less than 2% suggested by MCNPX code. In addition, The specific effective energy and absorbed dose of normal organs that were relatively adjacent to bile duct such as right side of kidney, liver, pancreas, transverse colon, spinal cord, stomach and small intestine were relatively high. on the contrary, the organs that were relatively distant to bile duct such as left side of kidney, spleen, ascending colon, descending colon and sigmoid colon were relatively low.

• Analytical Science and Technology
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• v.24 no.2
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• pp.78-84
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• 2011

The fragmentation patterns of a serine protease inhibitor, camostat, and its degradation product, 4-(4-guanidinobenzoyloxy)phenylacetic acid (GBPA), were for the first time investigated by a triple quadrupole tandem mass spectrometry equipped with an electrospray source (ESI-MS/MS) in positive and/or negative ion mode under collision-induced dissociation (CID). The positive CID spectrum of camostat showed distinctly that the single bond (C-O) cleavage between carbonyl group and oxygen atom of the ester bonds of the compound favorably occurred and then the loss of N,N-dimethylcarbamoylmethyl group was more susceptible than that of guanidine moiety. In the positive ion CID spectrum of GBPA, the initial cleavage between the carbonyl group and oxygen atom of 4-guanidinobenzoyloxy group also occurred, yielding the most abundant fragment ion at m/z 145. On the other hand, the negative CID spectrum of GBPA characteristically showed the occurrence of the most abundant peak at m/z 226 resulting from the sequential neutral losses of $CO_2$ and HN=C=NH from the parent ion at m/z 312.

• Journal of The Korean Astronomical Society
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• v.49 no.1
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• pp.25-35
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• 2016

Multiple color selection techniques are successful in identifying quasars from wide-field broadband imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at 5 ≲ z ≲ 5.7 due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R ~ 15. By conducting medium-band observations of high redshift quasars at 4.7 ≤ z ≤ 6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color section in separating high redshift quasars from brown dwarfs. In addition, we show that redshifts of high redshift quasars can be determined to an accuracy of Δz/(1 + z) = 0.002 - 0.026. The selection technique can be extended to z ~ 7, suggesting that the medium-band observation can be powerful in identifying quasars even at the re-ionization epoch.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.470-478
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• 2015

This study was investigated the anthocyanin composition of 'Gaeryangmeoru', 'Kyoho', and 'Hongisul' grapes cultivated in Korea using ultra-performance liquid chromatography (UPLC) coupled to a mass spectrometer (MS) equipped with an ESI (electrospray ionization) source. 'Gaeryangmeoru' is a dark-blue grape used for winemaking that can reach its coloring in unfavorable weather. The 'Kyoho' and 'Hongisul' varieties are hybrid grapes that feature black and pink skin, respectively. The anthocyanins extracted from the peels of grapes were analyzed using UPLC-ESI-MS/MS. Twenty-five anthocyanins were identified in the 'Gaeryangmeoru' and 'Kyoho' varieties, and 21 were identified in the 'Hongisul' variety. Eight, 14 and five predominant anthocyanins were identified in 'Gaeryangmeoru', 'Kyoho' and 'Hongisul' grape respectively. In all three varieties, mono-glucosides were 2.3-5.9 times more abundant than di-glucoside. Malvidin was the predominant anthocyanidin in 'Gaeryangmeoru' (44.1%) and 'Kyoho' (56.5%), but cyanidin (96.8%) was in 'Hongisul'. The acylated anthocyanins in 'Gaeryangmeoru' (2.0%) were rare, whereas acylated anthocyanins with p-coumaric acid were predominant in 'Kyoho' (40.9%) and 'Hongisul' (70.7%). In particular, cyanidin feruloyl glucoside was found only in the 'Hongisul' cultivar and considered to be useful as a criterion for identification of the variety. As a result, the grape varieties were demonstrated to have variety-specific anthocyanin characteristics, enabling classification based on anthocyanin composition in terms of anthocyanidins, glucosylation and acylation. The taxonomical application of anthocyanin composition confirmed the possibility that 'Gaeryangmeoru' originated from Vitis amurensis or its hybrids, and the 'Hongisul' grape was distinguished from other grapes by cyanidin feruloyl glucoside.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.34-37
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• 2017

In recent emerging industry, Display field becomes bigger and bigger, and also semiconductor technology becomes high density integration. In Flat Panel Display, there is an issue that electrostatic phenomenon results in fine dust adsorption as electrostatic capacity increases due to bigger size. Destruction of high integrated circuit and pattern deterioration occur in semiconductor and this causes the problem of weakening of thermal resistance. In order to solve this sort of electrostatic failure in this process, Soft X-ray ionizer is mainly used. Soft X-ray Ionizer does not only generate electrical noise and minute particle but also is efficient to remove electrostatic as it has a wide range of ionization. X-ray Generating efficiency has an effect on soft X-ray Ionizer affects neutralizing performance. There exist variable factors such as type of anode, thickness, tube voltage etc., and it takes a lot of time and financial resource to find optimal performance by manufacturing with actual X-ray tube source. MCNPX (Monte Carlo N-Particle Extended) is used for simulation to solve this kind of problem, and optimum efficiency of X-ray generation is anticipated. In this study, X-ray generation efficiency was measured according to target material thickness using MCNPX under the conditions that tube voltage is 5 keV, 10 keV, 15 keV and the target Material is Tungsten(W), Gold(Au), Silver(Ag). At the result, Gold(Au) shows optimum efficiency. In Tube voltage 5 keV, optimal target thickness is $0.05{\mu}m$ and Largest energy of Light flux appears $2.22{\times}10^8$ x-ray flux. In Tube voltage 10 keV, optimal target Thickness is $0.18{\mu}m$ and Largest energy of Light flux appears $1.97{\times}10^9$ x-ray flux. In Tube voltage 15 keV, optimal target Thickness is $0.29{\mu}m$ and Largest energy of Light flux appears $4.59{\times}10^9$ x-ray flux.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.422.2-422.2
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• 2014

가스장 이온원(GFIS: Gas Field Ionization Source)은 전자현미경보다 분해능이 향상된 이온현미경의 광원으로 사용하기 위하여 연구되고 있고, 큰 각전류 밀도, 작은 크기의 가상 이온원 그리고 좁은 에너지 퍼짐을 특징으로 한다. 여러 가지 장점을 가지고 있는 GFIS을 개발하기 위해서는 GFIS에서 발생된 이온빔의 형상을 관찰 것이 매우 중요하며, 이러한 관찰을 위한 시스템에는 주로 마이크로 채널 플레이트 (MCP: Micro Channel Plate)가 사용된다. MCP는 채널내부에 입사한 입자의 에너지에 의해서 생성된 이차전자를 수 천 배에서 수 백 만 배 이상 증폭시켜 형광판에 조사하고 발광시키는 방법으로 작은 신호를 영상으로 관찰 할 수 있도록 한다. MCP의 큰 증폭비는 작은 크기의 신호를 큰 신호로 증폭하여 관찰하는데 용이하여, GFIS 방법으로 생성된 이온빔(이온빔 전류 값은 pA 수준)을 관찰하기에 적합하다. 그러나 MCP를 이용하여도 증폭된 이온빔의 세기가 매우 작기때문에 생성된 이온빔 형상을 정확하게 관찰하기 위해서는 MCP의 형광판을 촬영하는 카메라 노출시간을 길게하여 데이터 수집 시간을 늘려야 하는 문제가 있다. 본 발표에서는 이온빔 형상 관찰에 소요되는 시간을 단축하기 위하여 MCP의 잡음이 GFIS의 이온빔 이미지 관찰에 미치는 영향을 분석하고 이를 제거 방법을 소개한다. 본 연구에서는 GFIS 방출 이온빔의 이미지에 포함된 MCP 잡음 특성을 장(전계)이온현미경 (Field Ion Microscope)실험을 통하여 분석하였고, 디지털 이미지 처리 방법을 이용하여 방출 이온빔 이미지에서 MCP 잡음을 제거하여 방출 이온빔 이미지만 추출할 수 있었다. 본 연구에서 제안한 방법을 GFIS 방출 이온빔 관찰시스템에 적용함으로써 기존 방법에 비해 노출시간을 단축하여 방출 이온빔을 관찰 할 수 있었으며, 노이즈 제거 효과로 향상된 이온빔 형상을 얻을 수 있었다. 본 연구결과의 관찰시간 단축과 향상된 이온빔 형상 획득은 이온현미경 개발에 필수적인 단원자 이온빔을 보다 효율적으로 개발할 수 있으며 디지털 이미지 처리로 GFIS 이온빔 생성을 자동화하는데 응용할 수 있다. 더불어 기존방법에 비해 이미지 획득을 위한 MCP의 노출시간을 단축할 수 있으므로 실험장비 수명 단축 방지 및 관리에 큰 장점이 있다.

• Journal of Preventive Medicine and Public Health
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• v.33 no.1
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• pp.45-50
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• 2000

Objectives : This study was undertaken to evaluate correlation between the levels of hippuric acid in blood plasma (HAP) and those of toluene concentration in the workplace air. Methods : Study subjects were composed of two groups; 21 workers who were occupationally exposed to toluene and 25 rural-area residents who were not exposed to any known occupational toluene source, as an exposed group and a reference group, respectively. Mean age and work duration of the exposed was 42 years and five years, respectively. Mean age of the reference was 42 years. To determine toluene concentrations in the workplace air, air sampling has been conducted for more than six hours using a personal sampler, and analyzed by a gas chromatography-flame ionization detector. Concentrations of hippuric acid in biological samples were determined by a high performance liquid chromatography-ultraviolet detector. Results : Geometric mean(geometric standard deviation) of HAP and hippuric acid in urine(HAU) for the exposed was 1.39(2.21) mg/L and 2.77(1.46) g/L, respectively, which were significantly different from those of the reference [HAP, 9.45(2.94); HAU, 0.37(0.45)]. Teluene concentration in the workplace air was 86.92(range: $45.18\sim151.23$)ppm. The level of HAP or HAU was significantly correlated (r=0.70 and r=0.63, respectively) with that of toluene in the workplace air. The estimated regression equation was logHAP(mg/L)=-3.60+1.93 log(toluene, ppm) or logHAU(g/L)=-0.85+0.67 log(toluene, ppm). The magnitude of correlation was further enhanced when analyzing relationship between toluene concentrations lower than 100 ppm and its corresponding HAP levels. Conclusion : Overall, plasma hippuric acid levels were well correlated with toluene concentrations in the workplace air, and a statistically significant correlation was observed for the samples with toluene concentration lower than 100 ppm.