• Journal of Conservation Science
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• v.37 no.6
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• pp.767-777
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• 2021

This study analyzed the microstructures and chemical composition of three samples of bronze mirrors excavated in the Jeollanam-do region, particularly Goheung and Damyang. Under x-ray irradiation, the analysis results confirmed the broken parts and pores caused by cracks, casting, and corrosion. Major and minor elemental analysis were performed on three mirrors by Scanning electron microscopy (SEM) with Energy dispersive x-ray spectrometry (EDS) and Inductively coupled plasma mass spe ctrome try (ICP-MS). The re sult shows that the bronze mirrors containe d Cu-Sn-Pb alloys. Alpha phase and eutectic phase were observed in the microstructure, confirming that the casting was performed without additional heat treatment. Notably, Three bronze mirrors were made early Three Kingdoms period in Korea.

• Imaging Science in Dentistry
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• v.50 no.1
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• pp.15-22
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• 2020

Purpose: This study was conducted to objectively and subjectively compare the accuracy and reliability of 2-dimensional(2D) photography and 3-dimensional(3D) soft tissue imaging. Materials and Methods: Facial images of 50 volunteers(25 males, 25 females) were captured with a Nikon D800 2D camera (Nikon Corporation, Tokyo, Japan), 3D stereophotogrammetry (SPG), and laser scanning (LS). All subjects were imaged in a relaxed, closed-mouth position with a normal smile. The 2D images were then exported to Mirror^® Software (Canfield Scientific, Inc, NJ, USA) and the 3D images into Proplan CMF^® software (version 2.1, Materialise HQ, Leuven, Belgium) for further evaluation. For an objective evaluation, 2 observers identified soft tissue landmarks and performed linear measurements on subjects' faces (direct measurements) and both linear and angular measurements on all images(indirect measurements). For a qualitative analysis, 10 dental observers and an expert in facial imaging (subjective gold standard) completed a questionnaire regarding facial characteristics. The reliability of the quantitative data was evaluated using intraclass correlation coefficients, whereas the Fleiss kappa was calculated for qualitative data. Results: Linear and angular measurements carried out on 2D and 3D images showed excellent inter-observer and intra-observer reliability. The 2D photographs displayed the highest combined total error for linear measurements. SPG performed better than LS, with borderline significance (P=0.052). The qualitative assessment showed no significant differences among the 2D and 3D imaging modalities. Conclusion: SPG was found to a reliable and accurate tool for the morphological evaluation of soft tissue in comparison to 2D imaging and laser scanning.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.575-579
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• 2001

GaN buffer layer and epilayer have been grown on sapphire (0001) by metal organic chemical vapor deposition (MOCVD). GaN buffer layer ranging from 26 nm to 130 nm in thickness was grown at 55$0^{\circ}C$ prior to the 4 $\mu\textrm{m}$ thick GaN epitaxial deposition at 110$0^{\circ}C$. After GaN buffer layer growth, buffer layer surface was examined by atomic force microscopy (AFM). As the thickness of GaN buffer layer was increased, surface morphology of GaN epilayer was investigated by scanning electron microscopy (SEM). Double crystal X-ray diffraction (DCXRD) and Raman spectroscopy were employed to study crystallinity of GaN epilayers. Optical properties of GaN epilayers were measured by photoluminescence (PL). The epilayer grown with a thin buffer layer had rough surface, and the epilayer grown with a thick buffer layer had mirror-like surface of epilayer. Although the stress on the latter was larger than on the former, its crystallinity was much better. These results imply that the internal free energy is decreased in case of the thick buffer layer. Decrease in internal free energy promotes the lateral growth of the GaN film, which results in the smoother surface and better crystallinity.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.633-638
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• 2011

Mn substituted La, Sr or Ba-hexaaluminate were prepared by $(NH_4)_2CO_3$ co-precipitate method and calcined at $1,200^{\circ}C$ for 5 h. Catalysts were characterized by X-ray diffraction and $N_2$ physisorption and scanning electron microscope (SEM). Compared to $SrMnAl_{11}O_{19}$ and $BaMnAl_{11}O_{19}$, $LaMnAl_{11}O_{19}$ in which La located at mirror plane showed better crystallinity and high surface area, 13 $m^2/g$. $LaMnAl_{11}O_{19}$ revealed well developed plate-like structure which is characteristic structure of hexaaluminate. The catalytic activity of methane combustion increased in the following order: $LaMnAl_{11}O_{19}$ > $SrMnAl_{11}O_{19}$ > $BaMnAl_{11}O_{19}$ and was dependent on surface area of catalysts. 60 wt% $CeO_2/LaMnAl_{11}O_{19}$ calcined at $700^{\circ}C$ showed enhanced methane activity and methane was oxidized completely at low temperature ($700^{\circ}C$). It was confirmed that addition of ceria seems to be effective for the low and middle temperature combustion of methane. But, after calcination at high temperature of $1,200^{\circ}C$, it lost the promoting effect of ceria due to increase of ceria particle size and it had a limit to applying to the high temperature catalytic combustion.

• Journal of Conservation Science
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• v.22
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• pp.87-98
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• 2008

Microstructures and chemical compositions of 24 bronze mirrors recovered from the Korean peninsula were examined using the scanning electron microscope equipped with the energy dispersive spectrometer in an effort to characterize the treatments applied on their surface. Their provenance and chronology are mostly unspecified except for two objects from a Koryo burial site. In antiquity the surface of bronze mirrors was frequently finished by mere polishing when their tin content was high enough to guarantee the required reflectivity. In many cases, however, their surface was given a special treatment. The most typical treatment was to coat the surface with tin in two different processes referred to as wipe-tinning and amalgam-tinning. In wipe-tinning only tin was used, but in amalgam-tinning tin and mercury were used together. The surface was often coated with mercury in a process known as mercury-polishing. The present mirrors showed that all these techniques were in fact practiced, not only on the reflective surface but, in some cases, on the decorative surface. The detection of mercury played a crucial role in the assessment of a specific technique applied in each mirror. Mercury often remained in the substrate in the form of sulfide and thereby allowed the method of surface treatment to be estimated even when the coated layer was completely lost. The future study is expected to uncover the regional and temporal variation of the surface treatments to the better understanding of bronze mirrors with respect to provenance and chronology.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.34-40
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• 2004

In this paper, we have studied the OCT(Optical Coherence Tomography) system which has been advantages of high resolution, 2-D cross-sectional images, low cost and small size configuration. The characteristics of light source determine the resolution and coherence length. The light source has a commercial SLD with a central wavelength of 1,285 ill11, 35.3 nm(FWHM). The optical delay line is necessary to make equal with the optical path length to scattered light or reflected light from a sample. In order to make equal the optical path length, the stage that is attached to a reference mirror is controled by a step motor. And the interferometer is configured with the Michelson interferometer by using a single mode fiber, and the scanner can be focused on the sample by using a reference ann Also, the 2-dimension cross-sectional images were measured with scanning the transverse direction of the sample by using a step motor. After detecting the internal signal of lateral direction, a scanner is moved to obtain the cross-sectional image of 2-dimension by using step motor. A photodiode, which has high detection sensitivity and excellent noise characteristics has been used. The detected small signal has a noise and interference. After filtering and amplifying the signal, the output signal is demodulated the waveform And then, a cross-sectional image is seen through converting this signal into a digitalized signal by using an AID converter. The resolution of the sample is about 30${\mu}{\textrm}{m}$, which corresponds to the theoretical resolution. Also, the cross-sectional images of onion cells were measured in real time scheme.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.5-9
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• 2004

In this paper, we studied the OCT(Optical Coherence Tomography) system which it has been extensively studied because of having some advantages such as high resolution cross-sectional images, low cost, and small size configuration. A basic principle of OCT system is Michelson interferometer. The characteristics of light source determine the resolution and the transmission depth. As a results, the light source have a commercial SLD with a central wavelength of 1,285 nm and FWHM(Full Width at Half Maximum) of 35.3 nm. The optical delay line part is necessary to equal of the optical path length with scattered light or reflected light from sample. In order to equal the optical path length, the stage which is attached to reference mirror is moved linearly by step motor And the interferometer is configured with the Michelson interferometer using single mod fiber, the scanner can be focused of the sample by using the reference arm. Also, the 2-dimensional cross-sectional images were measured with scanning the transverse direction of the sample by using step motor. After detecting the internal signal of lateral direction at a paint of sample, scanner is moved to obtain the cross-sectional image of 2-demensional by using step motor. Photodiode has been used which has high detection sensitivity, excellent noise characteristic, and dynamic range from 800 nm to 1,700 nm. It is detected mixed small signal between noise and interference signal with high frequency After filtering and amplifying this signal, only envelope curve of interference signal is detected. And then, cross-sectional image is shown through converting this signal into digitalized signal using A／D converter. The resolution of the OCT system is about 30$\mu\textrm{m}$ which corresponds to the theoretical resolution. Also, the cross-sectional image of ping-pong ball is measured. The OCT system is configured with Michelson interferometer which has a low contrast because of reducing the power of feedback interference light. Such a problem is overcomed by using the improved inteferometer. Also, in order to obtain the cross-sectional image within a short time, it is necessary to reduce the measurement time for improving the optical delay line.