• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.98-99
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• 2003

PIN photodiode has been used in solid-state detector for x-ray detection as a photosensor of visible light from scintillator. Since the light from CWO is short wavelength having peak at 490nm, the light is absorbed within a very shallow layer near the surface of the photodiode before arriving at the depletion layer and does not contribute to the signal. In designing the PIN photodiode, it is important to make the p-layer as shallow as possible. (omitted)

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.232-233
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• 2002

Nanostructed high energy Nd-Fe-B based bulk magnet can be prepared by hot-working process (hot press and die-upset) from melt-spun amorphous or nanocrystalline powder.[1] Recently, we have investigated a modified method, current-applied pressure-assisted (CAPA) process, to produce nanocrystalline isotropic and anisotropic NdFeB magnets. The process consists of current-applied pressing the melt-spun powders to obtain isotropic precursor subsequent current-applied deforming the precursor to obtain textured magnet.[2-3] (omitted)

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.354-354
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• 2012

실리콘 양자점 태양전지는 실리콘이 nm 크기의 양자점으로 될 경우 밴드갭이 증가하여 태양광 중의 가시광선을 광전변환에 활용함으로써 효율을 향상시키는 차세대 태양전지이다. 그러나 실리콘 양자점이 SiO2 매질 내에 분포하므로 양자점층의 두께가 증가할 경우 박막의 직렬저항이 증가하여 일정 두께 이상이 되면 효율이 감소하는 결과를 가져온다. 본 연구에서는 두께증가에 따른 효율저하 문제를 해결하기 위해 다결정 실리콘으로 이루어진 완충층을 도입 하였다. 이를 위해 본 연구에서는 두 가지 형태의 실리콘 양자점 태양전지를 제작하여 광전변환 특성을 비교하였다. 첫 번재 구조는 B이 도핑된 단일 실리콘 양자점층 태양전지이다. 양자점층은 2 nm SiOx 층과 2 nm SiO2 층을 적층한 후 $1,100^{\circ}C$에서 20분간 질소 분위기에서 급속 열처리하여 제작하였다. 실리콘 양자점 층의 두께를 40 nm에서 200 nm까지 변화시키면서 효율을 측정한 결과 100 nm 정도에서 효율이 감소하기 시작하였다. 이러한 효율감소는 양자점층의 저항 증가에 따른 전류감소에 의함이 확인되었다. 이와는 대조적으로 실리콘 양자점 층의 저항을 줄이기 위해 실리콘 양자점층 내에 50 nm 간격으로 10 nm 두께의 B이 도핑된 다결정 실리콘층을 배치하는 실리콘 양자점 태양전지를 개발하였다. 이러한 실리콘 양자점 층의 두께를 증가시킬 경우 효율이 지속적으로 증가함을 관찰하였다. 이러한 두 가지 형태의 양자점층을 이차이온질량분석법으로 분석한 결과 단일 실리콘 양자점층의 경우 두께가 약 70 nm 정도부터 이온빔 스퍼터링에 의한 저항증가에 따른 대전현상 (charging)이 관찰되었으나 다결정 실리콘 층이 배치된 실리콘 양자점층에서는 전혀 대전현상이 발생하지 않았다. 이는 다결정 실리콘 층이 캐리어를 이동시키는 매개체 역할을 하는 것으로 해석될 수 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.51.2-51.2
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• 2015

Understanding interfacial phenomena has been one of the main research issues not only in semiconductors but only in life sciences. I have been trying to meet the atomic scale surface and interface analysis challenges from semiconductor industries and furthermore to extend the application scope to biomedical areas. Optical imaing has been most widely and successfully used for biomedical imaging but complementary ion beam imaging techniques based on mass spectrometry and ion scattering can provide more detailed molecular specific and nanoscale information In this presentation, I will review the 27 years history of medium energy ion scattering (MEIS) development at KRISS and DGIST for nanoanalysis. A electrostatic MEIS system constructed at KRISS after the FOM, Netherland design had been successfully applied for the gate oxide analysis and quantitative surface analysis. Recenlty, we developed time-of-flight (TOF) MEIS system, for the first time in the world. With TOF-MEIS, we reported quantitative compositional profiling with single atomic layer resolution for 0.5~3 nm CdSe/ZnS conjugated QDs and ultra shallow junctions and FINFET's of As implanted Si. With this new TOF-MEIS nano analysis technique, details of nano-structured materials could be measured quantitatively. Progresses in TOF-MEIS analysis in various nano & bio technology will be discussed. For last 10 years, I have been trying to develop multimodal nanobio imaging techniques for cardiovascular and brain tissues. Firstly, in atherosclerotic plaque imaging, using, coherent anti-stokes raman scattering (CARS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) multimodal analysis showed that increased cholesterol palmitate may contribute to the formation of a necrotic core by increasing cell death. Secondly, surface plasmon resonance imaging ellipsometry (SPRIE) was developed for cell biointerface imaging of cell adhesion, migration, and infiltration dynamics for HUVEC, CASMC, and T cells. Thirdly, we developed an ambient mass spectrometric imaging system for live cells and tissues. Preliminary results on mouse brain hippocampus and hypotahlamus will be presented. In conclusions, multimodal optical and mass spectrometric imaging privides overall structural and morphological information with complementary molecular specific information, which can be a useful methodology for biomedical studies. Future challenges in optical and mass spectrometric imaging for new biomedical applications will be discussed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.7
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• pp.22-27
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• 2001

In this paper, the complex permittivity of various dielectrics such as powder(sugar and flour) and solid(teflon and acrvl) are measured by using an open ended coaxial-line probe, which is self designed and manufactured, The probe is connected to a vector network analyzer(VNA) through a coaxial cable, The end of the cable is corrected by using an OSL(open, short, and load) calibration kit, The phase difference, which is produced by inserting the probe at the end of the line. is compensated by using the numerically calculated reflection coefficient of distilled water, The complex permittivity is reconstructed by inserting the measured reflection coefficient, which is produced at the interface between the probe and measuring material, into ,an virtual conical cable conversion model. Over a wide frequency range from 30 MHz to 3 GHz, the measured complex permittivitis of various powder and solid using the our method are compared with the results, which are measured by using an transmission-line method of the Korea Research Institute of Standards and Science(KRISS).

• Mass Spectrometry Letters
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• v.3 no.2
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• pp.58-61
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• 2012

A method based on flow injection-isotope dilution-cold vapor-inductively coupled plasma mass spectrometry (FI-IDCV-ICP/MS) has been applied to determine trace level of mercury in fly ash. $^{200}Hg$ isotopic spike was added to 0.25 g of BCR176R fly ash and then decomposed by microwave digestion procedure with acid mixture A (8 mL $HNO_3$ + 2 mL HCl + 2 mL HF) and acid mixture B (8 mL $HNO_3$ + 2 mL $HClO_4$ + 2 mL HF) for applying IDMS. Mercury cold vapor was generated by using reductant solution of 0.2% (w/w) $NaBH_4$ and 0.05% (w/w) NaOH. The measurements of n($^{200}Hg$)/n($^{202}Hg$) isotope ratio was made using a quadrupole ICP/MS system. The accuracy in this method was verified by the analysis of certified reference material (CRM) of fly ash (BCR 176R). The indicative value of Hg in BCR 176R fly ash was $1.60{\pm}0.23$ mg/kg (k = 2). The determined values of Hg in BCR 176R fly ash by the method of FI-CV-ID-ICP/MS described in this paper were $1.60{\pm}0.24$ mg/kg (k = 3.18) and the analysis results were in well agreement with the indicative value within the range of uncertainty.

• Journal of Information Management
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• v.42 no.2
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• pp.85-102
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• 2011

Conventionally, scientific data visualization is thought of as one of activities performed by scientists during the scientific data analysis. However, recently, there exits a set of research papers which count scientific data visualization as a independent research area. They show the research subjects for studying the scientific data visualization technology and methods. In case, a scientist or group of scientists can not solve their own visualization problem due to the unskillfulness and inexperience on using visualization tool. Therefore, it needs to help them by the systematic way for solving the problem. In this study, we analyze and propose the national level scientific visualization support system for scientists. In particular, we first analyze the existing papers and find out the critical success factors. Then, by integrating the findings of the analysis, we propose the research areas which need to be focused, and the strategic direction and specific research topics for scientific data visualization support system in national level.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1214-1221
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• 2020

Esculetin 6-O-β-D-arabinofuranosyl-(1 → 6)-β-D-glucopyranoside (EAG) is a coumarin glycoside isolated from the stem bark of Fraxinus rhynchophylla. This study scrutinized the anti-proliferative activity of EAG on blood cancer-derived Jurkat leukemic cells. Cell viability assays in leukemic cancer cells determined that EAG possesses potent anti-proliferative effects. Moreover, treatment with EAG increased the proportion of apoptotic cells, resulted in cell cycle arrest being induced at the subG0/G1 phase, and reduced the proportion of cells present in the S phase. In addition, mitochondrial membrane potential was reduced by EAG in Jurkat cells. Additionally, EAG triggered apoptosis that was mediated by the downregulation of BCL-XL, p-IκBα, and p-p65 expressions in addition to the upregulation of cleaved Caspase 3 and BAX expressions. These findings revealed that the toxic effect of EAG was mediated by intracellular signal transduction pathways that involved a mechanism in which reactive oxygen species (ROS) were upregulated. Thus, this study concludes that EAG could potentially serve as a therapeutic agent for leukemia.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.123-127
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• 2002

We have measured the wavelengths of the absorption lines of the $^{13}$ C$_2$H$_2$molecule by using a wavelength meter calibrated against the national optical frequency standard (iodine Stabilized He-Ne Laser, KRISS-R701) in the visible wavelength region. To measure the absolute wavelengths of the absorption lines, the frequency of the laser has been stabilized in the peaks and the sides of the absorption lines of $^{13}$ C$_2$H$_2$. Also, we have proposed the development of a frequency standard source of ITU-T grid using stabilization in the sides of the absorption lines of $^{13}$ C$_2$H$_2$.

• Korean Journal of Optics and Photonics
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• v.29 no.2
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• pp.70-76
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• 2018

Comparison calibration equipment for infrared-radiation thermometers below $0^{\circ}C$ has been established, using a TRT2 (transfer radiation thermometer 2, HEITRONICS) as a transfer standard and an ME30 (Model: ME30, HEITRONICS) as a variabletemperature blackbody. The TRT2 was calibrated using three fixed points (Ice ($0.01^{\circ}C$), In ($156.5985^{\circ}C$), and Sn ($231.928^{\circ}C$)) and the Planckian Sakuma-Hattori equation, and including the interpolation and extrapolation errors at $-50^{\circ}C$ in the uncertainty. The pneumatic lid is installed upon opening of the ME30 and is opened for only 30 seconds for measuring the radiation temperature, which prevents formation of ice in the ME30 and also reduces the calibration time to half. The farther away from the $0{\sim}232^{\circ}C$ region, the larger the uncertainty of the comparison calibration equipment becomes. The expanded uncertainty of the comparison calibration equipment was estimated as 0.26 K at $-20^{\circ}C$.