• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.96-99
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• 1998

In this study, a novel long term stabilization method of optical feedback for the resonant cavity coupled semiconductor lasers is proposed, and its utility was shown experimentally. The proposed method is realized by using the pahse discriminator of optical feedback with high gain. The phase discriminating signal was obtained by the polarization spectroscopic technique using reflection light from the external reflector, which is a confocal Fabry-Perot cavity. Experimental result shows that stable control state can be maintained up to 20 hours. The period can be increased by reducing size of the system and/or fixing position stably of optical parts used, which were arranged on an optical table by using magnetic bases in this experiment. The proposed long-term stabilization method of optical feedack of a resonant external cavity coupled semiconductor laser is very useful for the field of high sensitivity measurement, and for the use in the laboratory level in particular.

• Applied Microscopy
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• v.46 no.1
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• pp.6-13
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• 2016

Fluorescence lifetime imaging microscopy (FLIM) has been considered an effective technique to investigate chemical properties of the specimens, especially of biological samples. Despite of this advantageous trait, researchers in this field have had difficulties applying FLIM to their systems because acquiring an image using FLIM consumes too much time. Although analog mean-delay (AMD) method was introduced to enhance the imaging speed of commonly used FLIM based on time-correlated single photon counting (TCSPC), a real-time image reconstruction using AMD method has not been implemented due to its data processing obstacles. In this paper, we introduce a real-time image restoration of AMD-FLIM through fast parallel data processing by using Threading Building Blocks (TBB; Intel) and octa-core processor (i7-5960x; Intel). Frame rate of 3.8 frames per second was achieved in $1,024{\times}1,024$ resolution with over 4 million lifetime determinations per second and measurement error within 10%. This image acquisition speed is 184 times faster than that of single-channel TCSPC and 9.2 times faster than that of 8-channel TCSPC (state-of-art photon counting rate of 80 million counts per second) with the same lifetime accuracy of 10% and the same pixel resolution.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.1935-1946
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• 2022

The investigations of the coated-particles of nuclear fuel samples are carried out in three stages: front-end, irradiation in the reactor core, and post-irradiation examination. The front-end stage is the initial analysis of the failures rates of produced samples before they are placed in the reactor core. The purpose of the verification is to prepare the particles for an experiment that will determine the degree of damage to the coated particles at each stage. Before starting experiments with the samples, they must be properly prepared. Polishing the samples in order to uncover the inner layers is an important, initial experimental step. The authors of this paper used a novel way to prepare samples for testing - by applying an ion polisher. Mechanical polishing used frequently for sample preparations generates additional mechanical damages in the studied fuel particle, thus directly affecting the experimental results. The polishing methods were compared for three different coated particles using diagnostic methods such as Raman spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy. Based on the obtained results, it was concluded that the ion polishing method is better because the level of interference with the structures of the individual layers of the tested samples is much lower than with the mechanical method. The same technique is used for the fuel particles undergone ion implantation simulating radiation damage that can occur in the reactor core.

• Journal of the Korean institute of surface engineering
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• v.57 no.2
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• pp.71-85
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• 2024

This article provides an overview of Raman spectroscopy and its practical applications for surface analysis of semiconductor processes including real-time monitoring. Raman spectroscopy is a technique that uses the inelastic scattering of light to provide information on molecular structure and vibrations. Since its inception in 1928, Raman spectroscopy has undergone continuous development, and with the advent of SERS(Surface Enhanced Raman Spectroscopy), TERS(Tip Enhanced Raman Spectroscopy), and confocal Raman spectroscopy, it has proven to be highly advantageous in nano-scale analysis due to its high resolution, high sensitivity, and non-destructive nature. In the field of semiconductor processing, Raman spectroscopy is particularly useful for substrate stress and interface characterization, quality analysis of thin films, elucidation of etching process mechanisms, and detection of residues.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.303-309
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• 2007

Statement of problem. The effect of gold electroforming on gold alloy was not studied. Purpose. This in vitro study investigate the effect of gold electroforming on gold-silver-palladium alloy. Material and methods. Three pieces of gold strips had undergone the electroforming procedures on one side and then half of the side again electroformed. The set mode for this study was program 1 ($200{\mu}m$). And the processing time was 15min (1/20 time to form $200{\mu}m$ coping). The confocal laser scanning microscope (PASCAL 5, Carl Zeiss, Bernried, Germany) was used to measure the thickness of the pure gold layer electroformed on the gold strips. Half of the gold strip was coated two times with electroformed gold, and the other half one time. The data from the cone focal laser system was processed to get the vertical profile of the strips and the difference of the vertical height between the double coated and single coated layer was regarded as the thickness of the gold coating. The layer thickness value to built 3D image of the cone-focal laser was set $0.5{\mu}m$. Next to the measurement of the thickness of the coating, the Vicker's hardness test was done. It was performed on the double coated surface, single coated surface and non-coated surface (back side) three times each. Results. The mean thickness value gained from gold electroforming technique was measured to be $22{\mu}m$ for sample 1, $23{\mu}m$ for sample 2, $21{\mu}m$ for sample 3. In the same condition of time, power and the amount of electrolyte, the data showed no difference between samples. According to the results of variance analysis, the differences among the variations in number of coating were statistically insignificant (p>0.05), meaning that the two times of gold electroforming coating did not change the hardness of gold-silver-palladium alloy. Conclusion. The test of thickness of gold coating proved the coherency of the gold electroforming procedure, in other words, when the power, the exposed surface area, processing time and the amount of electrolytes were set same, the same thickness of gold would be coated on. The hardness test showed that the electroformed gold coating did not change the hardness of the gold-silver-palladium alloy when it is coated not more than $45{\mu}m$.

• Journal of Conservation Science
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• v.30 no.2
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• pp.123-136
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• 2014

Considering that decision in conservation treatment for damaged objects should consider not only various options of methodology of intervention but also possible consequences of different types of intervention, it is a difficult task to decide and propose clear and safest solution of preserving an object. In addition, it should be constantly challenged by conservators even if it is proved technique or methodology in a past treatment. Therefore, there is no absolute solution which can be applied to all practice but each decision can be different case by case. It is not possible to estimate the way how the present condition of material and environmental aspects would affect to the condition of an object in future. However if conservators keep trying to set out various ways of analysing pro and against effect of past treatments, it would be able to provide useful logics of proving efficiency and appropriateness of a certain treatment. Understanding that the advantage of laser technique is to adopt a way of cleaning an object without making a direct contact, which is different from other techniques, this paper aims at securing stability of laser techniques, although it remains a limitation in the compatibility to all other materials. This study has examined reacting process on the painted pigments against laser beam by using CLSM in order for it to display both the problems from such reacting process and the efficiency of it as a cleaning methodology. It has intended to estimate the result of laser techniques and propose the range of applicability.

• Journal of Preventive Medicine and Public Health
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• v.32 no.4
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• pp.459-466
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• 1999

Objectives:eurotoxicity is mediated by nitric oxide(NO) in the rat primary neuronal cultures and assess the effect of $Mn^{2+}$ on the N-methyl-D aspartate(NMDA) receptors. Methods: We have used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)assay to examine the effect of cytotoxicity of $MnCl_2$ in neuronal cells , NO production was determined by measuring nirites, a stable oxidation product of NO. The neurons in the rat that contains neuronal nitric oxide synthase(nNOS) were examined by immunofluorescence and confocal microscopy. The effects of $Mn^{2+}$ on the NMDA receptors was assesed by the whole cell voltage clamp technique. Results: We showed that the NO release and NOS expression was increased with 500uM $MnCl_2$ treatment and an NOS inhibitors, $N^G-nitro-L-arginine$, prevented neurotoxicity elicited by manganese. In the electrophysiological study, $Mn^{2+}$ does not block or activate the NMDA receptors and not pass through the NMDA receptors in a neurons of basal ganglia. Conclusions: It is concluded that manganese neurotoxicity in basal ganglia was partially mediated by nitric oxide in the cell culture model.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.5
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• pp.49-55
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• 2013

To explore the paper materials for restoration of the Annals of the Joseon Dyansty, durability of the three type of the traditional Korean Papers were estimated in this study, through moist heat artificial aging test. Three types(D, F, and G) which showed the best preservation performance in dry heat and UV treatment in the previous study were selected and artificial accelerated aging treatment with moist-heat process was conducted; the viscosity change rate was D>G>F; folding endurance G>D>F; $L^*$ value F>D>G; $a^*$ and $b^*$ change rate D>G>F; brightness decrease rate D>G>F, suggesting paper F showed the least change rate in physical/optical properties. Also the CLSM image observation showed fair coherence among fibers and confirmed paper mulberry. And in FDI extraction from each sample, paper F showed the highest value. Overall, paper F (traditional glossy paper) showed the highest stability against thermal treatment. It confirms that paper F is suitable as restoration paper for tributary remains including the annals of the Joseon Dynasty for its steady strength/viscosity decrease rate and color change rate.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.583-589
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• 2011

Fluorescence correlation spectroscopy (FCS) is a sophisticated and an accurate analytical technique used to study the diffusion of molecules in a solution at the single-molecule level. FCS is strongly affected by many factors such as the stability of the excitation power, photochemical processes, mismatch between the refractive indices, and variations in the cover glass thickness. We have studied FCS near the surface of a cover glass by using rhodamine 123 as a fluorescent probe and have observed that the surface has a strong influence on the measurements. The temporal autocorrelation of FCS decays with two characteristic times when the confocal detection volume is positioned near the surface of the cover glass. As the position of the detection volume is moved away from the surface, the FCS autocorrelation becomes one-component decaying; the characteristic time of the decay is the same as the faster-decaying component in the FCS autocorrelation near the surface. This observation suggests that the faster component can be attributed to the free diffusion of the probe molecules in the solution, while the slow component has its origin from the interaction between the probe molecules and the surface. We have characterized the surface contribution to the FCS measurements near the surface by changing the position of the detection volume relative to the surface. The influence of the surface on the diffusion of the probe molecules was monitored by changing the chemical properties of the surface. The surface contribution to the temporal autocorrelation of the FCS strongly depends on the chemical nature of the surface. The hydrophobicity of the surface is a major factor determining the surface influence on the free diffusion of the probe molecules near the surface.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.39-45
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• 1999

Refining in papermaking plays an important role in changing fiber properties as well as paper properties. The major effects of refining on pulp fibers are internal and external fibrillation, fiber shortening, and fines formation. Many workers showed that internal fibrillation of the primary refining effects was most influential in improving paper properties. In particular, refining produces separation of fiber walls into several lamellae, thus causing fiber wall swelling with water penetration. This leads to the increase of fiber flexibility and of fiber-to-fiber contact during drying. If the fibers are very flexible, they will be drawn into close contact with each other by the force of surface tension as the water is removed during the drainage process and drying stages. In order to study the effect of fiber wall delamination on paper properties, cross-sectional image of fibers in a natural condition had to be generated without distortion. Finally, it was well recognized that confocal laser scanning microscope (CLSM) could be one of the most efficient tool for creating and quantifying fiber wall delamination in combination with image analysis technique. In this study, the CLSM could be used not only to observe morphological features of transverse views of swollen fibers refined under low and high intensity, but also to investigate the sequence of fiber wall delamination and fiber wall breakage. From the CLSM images, increasing the specific energy or refining decreased the degree of fiber collapse, fiber cross-sectional area, fiber wall thickness and lumen area. High intensity refining produced more external fibrillation.