• Toxicological Research
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• v.29 no.2
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• pp.107-114
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• 2013

Mass spectrometry (MS) is a very powerful instrument that can be used to analyze a wide range of materials such as proteins, peptides, DNA, drugs, and polymers. The process typically involves either chemical or electron (impact) ionization of the analyte. The resulting charged species or fragment is subsequently identified by the detector. Usually, single mass uses source-induced dissociation (SID), whereas mass/mass uses collision-induced dissociation (CID) to analyze the chemical fragmentations Each technique has its own advantages and disadvantages. While CID is most effective for the analysis of pure substances, multiple-step MS is a powerful technique to get structural data. Analysis of veterinary drugs ampicillin, chloramphenicol, ciprofloxacin, and oxytetracycline serves to highlight the slight differences between SID and CID. For example, minor differences were observed between ciprofloxacin and oxytetracycline via SID or CID. However, distinct fragmentation patterns were observed for ampicllin depending on the analysis method. Both SID and CID showed similar fragmentation spectra but different signal intensities for chloramphenicol. There are several factors that can influence the fragmentation spectra, such as the collision energy, major precursor ion, electrospray mode (positive or negative), and sample homogeneity. Therefore, one must select a fragmentation method on an empirical and case-by-case basis.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.66-74
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• 2016

Environmental pollution from abandoned metal mines has been awarded as serious problem and many techniques have been applied to remediate pollutants. Main objective of this research was to evaluate efficiency of heavy metal sorption capacity of spent mushroom media (SMM) in aqueous and soil matrix. Laboratory batch experiment was conducted and 4 different heavy metals (Cd, Pb, Cu, Zn) were evaluated. In aqueous phase, all 4 heavy metals showed high reduction efficiency ranged from 60-99% and Pb showed the highest sorption efficiency. In case of soil phase, much lower sorption efficiency was observed compared to aqueous phase. The highest reduction efficiency was observed in Cd (average of 38%). With scanning electron microscopy energy dispersive detector (SED-EDS) analysis, we confirmed sorption of heavy metals at the surface of SMM. Overall, SMM can be used as sorption materials for heavy metals in both aqueous and soil matrix and more research should be conducted to increase sorption efficiency of SMM in soil.

• Analytical Science and Technology
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• v.15 no.1
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• pp.67-71
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• 2002

The residual analysis and half-life time of imidazole fungicide prochloraz in soils (silty clay) were investigated by gas chromatography equipped electron capture detector (GC-ECD). The soil samples were extracted acetone/hexane(1:1) solvent and analyzed after separated by $LC-NH_2$ Sep-Pak solid column. Linear sensitivity of standard calibration curve was Y = 268.8600X + 0.0664, $R^2=0.9998$ between 0.05~1.00 ng. The detection limit was 0.02 mg/L and the average recoveries were 94.5~97.3% from the standard additional experiments with 0.10 and 0.40 mg/L. The half-life time was 24.4 days in room laboratory and 7.6 days in the field test soil.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.639-642
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• 2013

In this paper, proposed NED(nuclear event detectors) for detection of a transient radiation. Nuclear event detector was blocked of power temporary for defence of critical damage at a electric device when a induced transient radiation. Conventional NED consist of BJT, resistors and capacitors. The NED supply voltage of 5V and MCM(Multi Chip Module) structures. The proposed NED were designed for low supply voltage using 0.18um CMOS process. The response time of proposed NED was 34.8ns. In addition, pulse radiation experiments using a electron beam accelerator, the output signal has occurred.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.985-989
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• 1998

In this study, removal efficiencies of pesticides on apples and peppers with water, dishwashing detergent, and alcoholic disinfectant were investigated by Gas Chromatography. Different conditions of pretreatment for increase of pesticide recovery were investigated for optimum condition. In our experiment, the supelco-STB-608 column and electron capture detector(ECD) were used to analyze pesticides residue. Removal efficiency of pesticide was in the order of alcoholic disinfectant>dishwashing detergent>water.

• Atmosphere
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• v.18 no.3
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• pp.225-235
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• 2008

Sulfur hexafluoride ($SF_6$), man-made compound, has been paid attention as a potent greenhouse gas. After Kyoto Pototcol on Climate Change in 1997, nations established the policy aimed at minimizing release of $SF_6$ to atmosphere. We have developed and operated an automatic analytical system for monitoring atmospheric $SF_6$ using gas chromatography with electron capture detector (GC-ECD) and packed separate-column. Here, we report and discuss 4-month record of atmospheric $SF_6$ concentrations monitored at Seoul National University (SNU) pilot station near the Kwanak Mountain, Seoul. Most of observed $SF_6$ concentrations were excessively high compared with Northern Hemisphere (NH) background trend obtained from National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) monitoring stations. And the observed $SF_6$ showed extremely wide variability ranging from 4.6 pptv to $1.1{\times}10^3$ pptv, which may be affected by local sources placed nearby. Simultaneous wind data with $SF_6$ measurements show that relatively high values of $SF_6$ correspond to weak wind as well as southerly. There are many engineering installations to the south of the station. The regional value of the atmospheric $SF_6$ estimated from the data selection by wind conditions is about 6.8 pptv. This value, which is similar to concentrations of urban areas, is higher than NH background concentration.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.171-171
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• 1999

We studied the charge redistribution in the Pt-M (M=Cu, Co) alloys by X-ray Absorption Near Edge Spectroscopy(XANES) and X-ray Photoelectron Spectroscopy(XPS). These analysis tools provide us information about the charge transfer in the valence band of intermetallic bonding. The samples were prepared by arc-melting method. After annealing this samples in vacuum for several hours, we cold get the ordered samples, which were confirmed with XRD analysis. the core and valence level energy shift in these system were investigated by Mg $K\alpha$(1253.6eV) x-ray source for Pt-Co alloys and monochromatized Al $K\alpha$ (1486.6eV) for Pt-Cu alloys. Pt L2, L3-edge, and Cu, Co K-edge XANES spectra were measured with the total electron-yield mode detector at the 3Cl beam line of the PLS (Pohang light source0. from the changes of White line (WL) area and the core level shifts of the each metal sites, we can obtain the information about the electrons participating in the intermetallic bonding of the Pt-Cu and Pt-Co alloys.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.324-326
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• 2006

CCD형 영상소자는 방사선 피폭 시 표면과 격자내부에 모두 손상을 받게 되며, 감마방사선이나 X선과 같은 고에너지의 이온화 방사선에 노출될 경우 격자 실리콘 내부에 전자-전공쌍(Electron-hole pair, EHP)이 발생된다. 이러한 EHP는 CCD의 순간 출력 광전류로 변환되어 백색 화소 형태의 영상잡음으로 가시화되며, 이 화소 수는 피폭 방사선량에 비례하여 증가하는 특성을 지니고 있다. 따라서 출력 영상정보를 분석하면 조사된 방사선의 양과 특성을 측정할 수 있다. 본 연구에서는 CCD를 이용하여 가상의 방사능 물질 누출 공간에서 방사선원의 방향과 거리정보를 고속으로 탐지하기 위한 장치와 고속 측정 알고리즘을 구현하고 실제 방사선장에서 실증시험을 수행하였다. 방사선 탐지기는 콘형 납 콜리메이터(Collimator)와 가시광 변환용 신틸레이터(CsITl) 및 차폐체로 구성된 센서부와 제어 및 방사광 신호처리를 수행하는 PC부로 구성된다. 감마방사선($^{60}Co$) 방사선장 실증시험에서 방사선원간 거리 83cm에서 측정된 거리 탐지는 5.3%의 오차로 확인되었다. 이 방사선 탐지기는 임의의 고방사선 누출사고에 대한 초기대응 작업을 수행하기 위한 무인 이동로봇용 방사선 탐지기로 활용이 가능하다.

• Particle and aerosol research
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• v.8 no.1
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• pp.29-35
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• 2012

The Faraday cup electrode of different size has been developed and evaluated to investigate the diffusion effect of particles by Brownian motion in a particle beam mass spectrometer(PBMS). Particles which focused and accelerated by aerodynamic lens are charged to saturation in an electron beam, and then deflected electrostatically into a Faraday cup detector for measurement of the particle current. The concentration of particles is converted from currents detected by Faraday cup. Measurements of particle current as a function of deflection voltage are combined with measured relationships between particle velocity and diameter, charge and diameter, and mass and diameter, to determine the particle size distribution. The particle currents were measured using 5, 10, 20, 40 mm sized Faraday cup that can be move to one direction by motion shaft. The current difference for each sizes as a function of position was compared to figure out diffusion effect during transport. Polystyrene latex(PSL) 100, 200 nm sized standard particles were used for evaluation. The measurement using 5 mm sized Faraday cup has the highest resolution in a diffusion distance and the smaller particles had widely diffused.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.603-606
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• 2007

Gas chromatograph equipped with ECD (Electron Ionization Detector) was used to investigate the adsorption characteristics of 1,2-dichlorobenzene, which has a similar structure with dioxin, on graphite. Equilibrium adsorption constants of 1,2-dichlorobenzene on graphite were measured as 10.333, 6.167 and $4.270m^3/kg$ at 220, 240, $260^{\circ}C$, respectively. The isosteric heat of adsorption of 1,2-dichlorobenzene on graphite was 11.554 kcal/mol. This was because specific surface area was low and the amount of surface functional groups was small.