• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.176.2-176.2
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• 2013

Property of optical diagnostics for pulse-discharged plasma in liquid and its biological applications to proteins are investigated by making use of high voltage Marx generator. The Marx generator has been consisted of 5 stages, where each charging capacitor is 0.5 ${\mu}F$, to generate a high voltage pulse with rising time of $1{\mu}s$. We have applied an input voltage of 6 kV to the each capacitor of 0.5 ${\mu}F$. High voltage pulsed plasma has been generated inside a polycarbonate tube by a single-shot operation, where the breakdown voltage is measured to be 7 kV, current of 1.2 kA, and pulse width of ~ 1 ${\mu}s$ between the two electrodes of anode-cathode whose material is made of tungsten pin, which are immersed into the liquids. We have investigated the emitted hydrogen lines for optical diagnostics of high voltage pulsed plasma. The emission line of 656.3 nm from $H-{\alpha}$ and 486.1 nm from $H-{\beta}$ have been measured by a monochromator. If we assumed that the focused plasma regions satisfy the local thermodynamic equilibrium conditions, the electron temperature and density of the high voltage pulsed plasma in liquid could be obtained by the Stark broadening of optical emission spectroscopy. For the investigation of the influence of pulsed plasma on biological proteins, we have exposed it onto the proteins such as hemoglobin and myoglobin. The structural changes in these proteins and their analysis have also been obtained by circular dichroism (CD) and ultraviolet (UV) visible spectroscopy.

• Journal of The Korean Astronomical Society
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• v.36 no.spc1
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• pp.55-61
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• 2003

There are at least three effects of the non-thermal particle bombardment on the solar atmosphere: (1) non-thermal ionization and excitation; (2) proton-hydrogen charge exchange; (3) impact line polarization. Due to the non-thermal ionization and excitation effects of electron bombardments in flares, H$\alpha$ line is widely broadened and shows a strong central reversal. Significant enhancements at the line wings of Ly$\alpha$ and Ly$\beta$ are also predicted. In the case of proton bombardment, less strong broadening and no large central reversal are expected. However, due to proton-hydrogen charge exchange, the enhancements at the red wings of Ly$\alpha$ and especially of Ly$\beta$ lines at the early impulsive phase of flares are significant. Electron beam can also in some cases generates visible and UV continuum emission in white-light flares. However, at the onset phase, a negative 'black' flare may appear in several seconds, due to the increase of the $H^-$ opacity. The impact polarization of atomic lines can provide complementary information on the energetic particles, the energy transport and deposit in the solar chromosphere. New results of spectropolarimetric analysis for the major flare on July 23, 2002 are also given in the paper.

• YAKHAK HOEJI
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• v.40 no.2
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• pp.193-201
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• 1996

In order to study the role of C-terminal aromatic region of T4 endonuclease V in the interaction with substrate DNA, NMR and Fluorescence spectrum were recorded. Analysis of flu orescence emission spectra showed that C-terminal region of T4 endonuclease V is in or very near the binding site. In the HSQC spectrum of $^{15}N$-Tyr-labeled T4 endonuclease V*DNA complex, the broadening of a peak was observed. It is presumed that this peak corresponds to one among three tyrosine residues which belong to the WYKYY segment of C-terminal region of T4 endonuclease V. Interactions of peptide fragments consisting of C-terminal residues of T4 endonuclease V with DNAs(TT-, T^T-DNA) were investigated by NMR and Fluorescence experiment. The results suggest that two peptide fragments themselves bind to DNAs and their binding pattern is not an intercalation mode.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.3
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• pp.255-271
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• 2011

ACE-Asia (Asian Pacific Regional Aerosol Characterization Experiment) in spring 2001 was a turning point to trigger international research interest on Asian dust (AD). This basically arose from the lack of research on AD, the important natural phenomenon to characterize the Northeast Asia. In contrast, health risk related to AD has been the primary concern in Korea. Although due in part to severe AD events of 2001~2002, research and mitigation measures on AD in Korea are typically based on the assumption that AD events are increasing in frequency and severity. However, contrary to the trend in Korea, the number of AD days and emission amounts of AD in China have decreased since 1980s. This paper reviews the impacts of AD on ambient air quality and variations in toxic substances during the AD event, reflecting the concern in Korea. While a great amount of dust particles flow into Korea during the AD event, a considerable amount of dust particles are locally generated as well. Since dust particles are mixed with toxic substances as they pass over polluted areas, the levels of toxic substances become lower in dust particles that do not pass over polluted areas. Broadening the research scope on AD is warranted to understand the AD as an important natural phenomenon, irrespective of its associated health risk.

• Journal of the Korean earth science society
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• v.36 no.5
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• pp.419-426
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• 2015

We investigated the high dispersion spectra that had been secured at the center of the planetary nebula NGC 7027 with the Bohyunsan Optical Echelle Spectrograph (BOES) on October, 20, 2009. We analyzed the forbidden lines of [OI], [SII], [OII], [NII], [ClIII], [ArIII], [OIII], [ArIV], [NeIII], [ArV], and [CaV] in the $3770-9225{\AA}$ wavelength region. The expansion velocities were derived from double Gaussian line profiles of the emission lines, after eliminating the subsidiary line broadening effects. The radial variations of the expansion velocities were obtained by projecting the derived expansion velocities: $19.56-31.93kms^{-1}$ onto the equatorial shell elements of the inner and the outer boundaries of the main shell of 2.5(2.1)" and 3.8(3.6)", according to the ionization potential of each ion. Analysis of equatorial shell spectra indicated that the equatorial shell generally expands in an accelerated velocity mode, but the expansion pattern deviates from a linear velocity growth with radial distance. NGC 7027, of which age is about 1000 years or less, might be still at its early stage. During the first few hundred years, plausibly in its early stage, the main shell of PN expands very slowly and, later, it gradually gain its normal expansion speed.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.5-10
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• 2003

This paper explores not only emerging scientific problems but also the difficulties communicating air quality issues into an increasingly sensitive the public and policy arena. The public understanding and trust in air pollution information and indices may be very different to the notions of validity or accuracy that are important for a scientist. We operate in a world where openness requires us to reveal both the difficulties and disagreements in our understanding of the polluted atmosphere. Yet this can be confusing and increase complexity in situations where clear political and social decisions are required. I am going to examine these issues, starting with questions of what substances we regard as pollutants and the difficulties of getting the correct balance of concern given the broadening the base of chemicals emitted to the environment. There are also questions of exposure particularly in terms of vulnerable populations, who may spend large amounts of time indoors, where air is rarely monitored. In contemporary society there are pollution problems that extend far beyond urban areas and we have to consider regional issues such as windblown dusts, smoke from forest fires along with issues of the emission of green house gases and ozone depleting substances. Finally I will discuss the issues of communicating with a concerned public and sceptical politicians and the troubling interface between technological and sociological control. Such complexity is often missed in a maze of seemingly stronger political and social needs.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.489-492
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• 2007

Temperature and injection current dependence of elctroluminescence(EL) spectral intensity of the $In_{0.27}Ga_{0.73}N/GaN$ multi-quantum-well(MQW) have been studied over a wide temperature and as a function of injection current level. EL peaks also show significant broadening into higher photon energy region with the increase of injection current. This is explained by the band-filling effect. When temperature is slightly increased to 300 from 15 K, the EL emission peak showed red-blue-red shift. It can be explained by the carrier localization by potential fluctuation of multiple quantum well and band-gap shrinkage as temperature increase. It is found that a temperature-dependent variation pattern of the EL efficiency under very low and high injection currents show a drastic difference. This unique EL efficiency variation pattern with temperature and current is explained field effects due to the driving forward bias in presence of internal(piezo and spontaneous polarization) fields.

• Advances in nano research
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• v.7 no.1
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• pp.13-24
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• 2019

Well-crystalline $SnO_2$ nanoparticles of 4-5 nm size with different In contents were synthesized by hydrothermal process at relatively low temperature and characterized by transmission electron microscopy (TEM), microRaman spectroscopy and photoluminescence (PL) spectroscopy. Indium incorporation in $SnO_2$ lattice is seen to cause a lattice expansion, increasing the average size of the nanoparticles. The fundamental phonon vibration modes of $SnO_2$ lattice suffer a broadening, and surface modes associated to particle size shift gradually with the increase of In content. Incorporation of In drastically enhances the PL emission of $SnO_2$ nanoparticles associated to deep electronic defect levels. Although In incorporation reduces the band gap energy of $SnO_2$ crystallites only marginally, it affects drastically their dye degradation behaviors under UV illumination. While the UV degradation of methylene blue (MB) by undoped $SnO_2$ nanoparticles occurs through the production of intermediate byproducts such as azure A, azure B, and azure C, direct mineralization of MB takes place for In-doped $SnO_2$ nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.259.1-259.1
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• 2014

Recently non-thermal plasma has been frequently applied to various research fields. The liquid plasma have received much attention lately because of interests in surgical and nanomaterial synthesis applications. Especially, intensive researches have been carried out for non-thermal plasma in liquid by using various electrode configurations and power supplies. We have developed a bioplasma source which could be used in a liquid, in which outer insulator has been covered onto the outer electrode. Also we have also put an insulator between the inner and outer electrode. Based on the surface discharge mode, the nonthermal bioplasma has been generated inside a liquid by using an alternating current voltage generator with peak voltage of 12 kV under driving frequency of 22 KHz. Here the discharge voltage and current have been measured for electrical characteristics. Especially, We have measured discharge and optical characteristics under various liquids of deionized (DI) water, tap water, and saline by using monochromator. We have also observed nitric oxide (NO), hydrogen peroxide (H2O2), and hydroxyl (OH) radical species by optical emission spectroscopy during the operation of bioplasma discharge inside various kinds of DI water, tap water, and saline. Here the temperature has been kept to be $40^{\circ}C$ or less when discharge in liquid has been operated in this experiment. Also we have measured plasma temperature by high speed camera image and density by using either H-alpha or H-beta Stark broadening method.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.16-16
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• 2011

Plasmas in saline solutions receive considerable attention in recent years. How the operating parameters influence the plasma characteristics and how the electrode erosion occurs have been topics that require further study. In the first part of this talk, the effect of the frequency on the plasmas characteristics in saline solution driven by 50~1000 Hz AC power will be presented. Two distinct modes, namely bubble and jetting modes, are identified. The bubble mode occurs under low frequencies. In this mode, one mm-sized bubble is tightly attached to the electrode tip and oscillates with the applied voltage. With an increase in the frequency, it shows the jetting mode, in which many smaller bubbles are continuous formed and jetted away from the electrode surface. Multiple mechanisms that are potentially responsible to such a change in bubble dynamics have been proposed and the dominant mechanism is identified. From the Stark broadening of the hydrogen optical emission line, electron densities in both modes are estimated. It shows clearly that the driving frequency greatly influences the bubble dynamics, which in turn alters the plasma behavior. In the second part, the study of the erosion of a tungsten electrode immersed in saline solution under conditions suitable for bio-medical applications is presented. The electrode is immersed in 0.1 M saline solution and is positively or negatively biased using a DC power source up to 600 V. It is identified that when the electrode is positively biased, erosion by the surface electrolytic oxidation is the dominant mechanism with an applied voltage below 150 V. An increase in the applied voltage leads to the formation of the plasma and the damage by the plasma and the thermal effect becomes more prominent. The formation of the gas film at the electrode surface leads to the formation of the plasma and hinders the electrolytic erosion. In the negatively-biased electrode, no electrolytic oxidation is seen and the damage is mostly likely due to the plasma erosion and the thermal effect.