• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1061-1070
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• 2003

A triple flame in a mixing layer was studied experimentally with concentration gradient and mean velocity by using a multi-slot burner, which can stabilize the lift-off flame. Flame stabilization condition, lift-off heights, and some other characteristics were examined for methane and propane flame within a range of very low concentration gradient. Pitot-tube and LDV(Laser Doppler Velocimetry) were used for velocity. Mass spectroscopy and Rayleigh scattering signal were used for concentration gradients. Thermo-couples and SiC TFP(Thin Filament Pyrometer) were used for temperature. It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity and this means that the propagation velocity has a maximum value. The scales of flame to the burner nozzle and intensity variation of the diffusion flame were suspected as the cause.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.328-334
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• 2018

The paper reviews an improved continuous-wave (CW) terahertz (THz) imaging system developed for nondestructive inspection, such as CW-THz quasi-time-domain spectroscopy (QTDS) and interferometry. First, a comparison between CW and pulsed THz imaging systems is reported. The CW-THz imaging system is a simple, fast, compact, and relatively low-cost system. However, it only provides intensity data, without depth and frequency- or time-domain information. The pulsed THz imaging system yields a broader range of information, but it is expensive because of the femtosecond laser. Recently, to overcome the drawbacks of CW-THz imaging systems, many studies have been conducted, including a study on the QTDS system. In this system, an optical delay line is added to the optical arm leading to the detector. Another system studied is a CW-THz interferometric imaging system, which combines the CW-THz imaging system and far-infrared interferometer system. These systems commonly obtain depth information despite the CW-THz system. Reportedly, these systems can be successfully applied to fields where pulsed THz is used. Lastly, the applicability of these systems for nondestructive inspection was confirmed.

• Atmosphere
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• v.29 no.3
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• pp.269-282
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• 2019

While it is important to obtain the accurate information on snowfall data due to the increase in damage caused by the heavy snowfall in the winter season, it is not easy to observe the snowfall quantitatively. Recently, snow measurements using a weighing precipitation gauge have been carried out, but there is a problem that high snowfall intensity results in low accuracy. Also, the observed snowfall data are sensitive depending on wind speed, temperature, and humidity. In this study, a new process of quality control for snow water equivalent (SWE) data of the weighing precipitation gauge were proposed to cover the low accuracy of snow data and maximize the data utilization. Snowfall data (SWE) observed by Pluvio, Parsivel, snow-depth meter using laser or ultrasonic, and rainfall gauge in Cloud Physics Observation Site (CPOS) were compared and analyzed. Applying the QC algorithm including the use of number of hydrometeor particles as reference, the increased SWE per the unit time was determined and the data noise was removed and marked by flag. The SWE data converted by the number concentration of hydrometeor particles are tested as a method to restore the QC-removed data, and show good agreement with those of the weighing precipitation gauge, though requiring more case studies. The three events data for heavy snowfall disaster in Pyeongchang area was analyzed. The SWE data with improved quality was showed a good correlation with the eye-measured data ($R^2$ > 0.73).

• Environmental Analysis Health and Toxicology
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• v.15 no.3
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• pp.69-80
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• 2000

ADP-rubosylation may be involved in the process of macrophage activation. Nitric oxide (NO) has emerged as an important intracellular and interacellular regulatory molecule with function as diverse as vasodilation, neural communication or host defense. NO is derived from the oxidation of the terminal guanidino nitrogen atom of L-arginine by the NADPH -dependent enzyme, nitric oxide synthase (NOS) which is one of the three different isomers in mammalian tissues. Since NO can exert protective or regulatory functions in the cell at a low concentration while toxic effects at higher concentrations, its role may be tightly regulated in the cell. Therefore, this paper was focused on signal transduction pathway of NO synthesis, role of endogenous TGF-$\beta$ in NO production. effect of NO on superoxide formation. Costimulation of murine peritoneal macrophages with interferon-gamma (IFN-γ) and phorbol 12-myristate 13-acetate (PMA) increased both NO secretion and mRNA expression of inducible nitric oxide synthase (iNOS) when PMA abolished costimulation. Pretreatmnet of the cells with PMA abolished costimuation effects due to the depletion of protein kinase C (PKC) activities . The involvement of PKC in NO secretion could be further confirmed by PKC inhibitor, stauroprine, and phorbol ester derivative, phorbol 12,13-didecanoate. Addition of actinomycine D in IFN-γ plus PMA stimulated cells inhibited both NO secretion and mRNA expression of iNOS indication that PMA stabilizes mRNA of iNOS . Exogenous TGF-$\beta$ reduced NO secretion in IFN -γ stimulated murine macrophages. However addition of antisense oligodeoxynucleotide (ODN) to TGF-$\beta$ to this system recovered the ability of NO production and inhibited mRNA expression of TGF-$\beta$. ACAS interactive laser cytometry analysis showed that transportation of FITC -labeled antisense ODN complementary to TGF-$\beta$ mRNA could be observed within 5 min and reached maximal intensity in 30 min in the murine macrophage cells. NO released by activated macrophages inhibits superoxide formation in the same cells . This inhibition nay be related on NO-induced auto -adenosine diphosphate (ADP) -ribosylation . In addition, ADP-ribosylation may be involved in the process of macrophage activation .

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.512-513
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• 2008

The study examined what effects 100kHz PWM LED light irradiation causes to bone marrow cells of SD-Rat when LED characterized cheap and safe is used onto the light therapy by replacing the low 1evel laser. We developed the equipment palpating cell proliferation using a high brightness LED. This equipment was fabricated using a micro-controller and a high brightness LED, and designed to enable us to control light irradiation time, intensity, frequency and so on. Especially, to control the light irradiation frequency, FPGA was used, and to control the change of output value, TLC5941 was used. Consequent1y, the current value could be controlled by the change of 1eve1 in Continue Wave(CW) and Pulse Width Modulation(PWM), and the output of a high brightness LED could be controlled stage by stage. MTT assay method was chosen to verify the cell increase of two groups and the effect of irradiation on cell proliferation was examined by measuring 590nm transmittance of ELISA reader. As a result, the cell increase of Rat bone marrow cells was verified in 100kHz PWM LED light irradiation group as compared to non-irradiation group.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.4
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• pp.311-316
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• 2008

In this study, we have investigated the effects of ultraviolet (UV) irradiation on the external and internal structure of human hair. For changes in morphological and chemical structure of UV-exposed hair, we utilized several microscopic techniques such as scanning electron microscope (SEM), transmission electron microscope (TEM), confocal laser scanning microscope (CLSM), and etc. The SEM showed the scales of UV-exposed hair appeared to be rough and bulkier because of chemical oxidation during UV irradiation. Small bulgy area of UV_exposed hair surface was appeared as a result of the decomposition in cysteic acid. In the TEM picture the UV-exposed hair showed the cleaved aperture of hair and destruction of melanin granules. Three dimensional topographical images were obtained by using CLSM. In the optical single section, high fluorescent intensity appeared in virgin hair. In the case of UV-exposed hair, low fluorescence intensity appeared. This means the aromatic amino acids in virgin hair were more abundant than UV-exposed hair.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1034-1037
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• 2005

The variation of shapes and related properties of ZnO nanostructures grown on the metal pattern and Si substrate have been investigated. Ni, Cr metal patterns were formed on Si (111) substrates by e-beam evaporation, and ZnO nanostructures were fabricated on it by using thermal evaporation of Zn powder in air. Growth temperature was controlled from 500 $^{\circ}$C to 700 $^{\circ}$C. When the growth temperature was relatively low, no considerable effect was found. However, UV emission intensity decreased, and Green-emission intensity, which is regarded as originated from the defect state in the ZnO nanostructure, increased as growth temperature increase. Also, the variation of nanostructure shape at high temperature (700 $^{\circ}$C) is understood in terms of the enhanced incorporation of metal vapor during the nanostructure formation.

• Journal of Dental Anesthesia and Pain Medicine
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• v.22 no.5
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• pp.323-338
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• 2022

Burning mouth syndrome (BMS) is a chronic oral disorder of unknown etiology which presents therapeutic challenges. Alpha-lipoic acid (ALA) has been studied as a potential treatment for BMS. The objective of this systematic review and meta-analysis was to evaluate the effectiveness of ALA compared to that of placebo or other interventions in individuals with BMS. Randomized controlled trials (RCT) using ALA to treat BMS were identified from MEDLINE, Cochrane Library, EMBASE, and Web of Science up to February 3, 2021. The assessment of the risk of bias in the included studies was based on the Cochrane guidelines. The primary outcome evaluated was the visual analog scale (VAS) pain intensity. ALA was compared with placebo, clonazepam, gabapentin, pregabalin, ALA plus gabapentin, capsaicin, Biotène^®, and laser therapy. Altogether, 137 records were scanned for inclusion/exclusion, and nine RCTs (two unclear and seven at high risk of bias) were included in the qualitative and quantitative analyses, with a total of 594 patients with BMS included in this review. All studies reported an improvement in VAS pain scores ranging from -0.72 to -2.77. Meta-analysis results showed a non-significant reduction in pain intensity for ALA (P = 0.616) compared to that of placebo on a VAS of 0-10. Patients taking ALA were 1.923 times more likely to show an improvement in self-reported BMS symptoms (P = 0.031) than those in the placebo group. Clonazepam and pregabalin showed a significant VAS pain reduction of 4.08 and 4.68 (P < 0.001), respectively, compared to that with ALA. Although ALA intervention provided a non-significant improvement in the pain score and was more likely to produce a reduction in BMS symptoms, the evidence was of low quality. Further research is needed to establish clear guidelines for the use of ALA for BMS treatment.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.445-451
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• 2019

The fluorescence intensity and fluorescence lifetime of $Ba_2GdV_3O_{11}$, a vanadate compound based on $Ba^{2+}$ ion, were investigated by adding $Eu^{3+}$ as a rare earth ion which is an alkaline earth metal, which is distributed around active ions and has a large influence on fluorescent properties when used as a host in a phosphor. $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor was synthesized by solid state method and the crystallinity of the phosphor was confirmed by X - ray diffraction analysis. The fluorescence properties of the $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor were measured using optical and laser. The energy transfer and diffusion of the $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor are highly dependent on the concentration of $Eu^{3+}$. When the concentration of $Eu^{3+}$ is low, it shows strong fluorescence to the CT band. However, as the concentration of $Eu^{3+}$ increases, the fluorescence due to 4f - 4f transition is strong. The concentration of $Eu^{3+}$ ion increased and the energy between ions was diffused, and the lifetime of fluorescence decreased. Energy transfer occurs between two $Eu^{3+}$ ions at low $Eu^{3+}$ concentration and energy diffusion occurs at high $Eu^{3+}$ concentration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.23-23
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• 2009

GaN-based nitride semiconductors have attracted considerable attention in high-brightness light-emitting-diodes (LEDs) and laser diodes (LDs) covering from green to ultraviolet spectral range. LED and LD heterostructures are usually grown on (0001)-$Al_2O_3$. The large lattice mismatch between $Al_2O_3$ substrates and the GaN layers leads to a high density of defects(dislocations and stacking faults). Moreover, Ga and N atoms are arranged along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs heterostructures, stress applied along the same axis can also give rise to piezoelectric polarization. The total polarization, which is the sum of spontaneous and piezoelectric polarizations, is aligned along the [0001] direction of the wurtzite heterostructures. The change in the total polarization across the heterolayers results in high interface charge densities and spatial separation of the electron and hole wave functions, redshifting the photoluminescence peak and decreasing the peak intensity. The effect of polarization charges in the GaN-based heterostructures can be eliminated by growing along the non-polar [$11\bar{2}0$] (a-axis) or [$1\bar{1}00$] (m-axis) orientation instead of thecommonly used polar [0001] (c-axis). For non-polar GaN growth on non-polar substrates, the GaN films have high density of planar defects (basal stacking fault BSFs, prismatic stacking fault PSFs), because the SFs are formed on the basal plane (c-plane) due to their low formation energy. A significant reduction in defect density was recently achieved by applying blocking layer such as SiN, AlN, and AlGaN in non-polar GaN. In this work, we were performed systematic studies of the defects in the nonpolar GaN by conventional and high-resolution transmission electron microscopy.