• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.4
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• pp.202-209
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• 2002

The stochiometric mix of evaporating materials for the $CuInSe_2$single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CuInSe_2$compound crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuInSe_2$single crystal thin films measured from Hall effect by van der Pauw method. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$single crystal thin film, we have found that the values of spin orbit splitting $\Delta$So and the crystal field splitting $\Delta$Cr. From the photoluminescence measurement on $CuInSe_2$single crystal thin film, we observed free exciton ($E_x$) existing only high quality crystal and neutral bound exciton ($A^{\circ}$, X) having very strong peak intensity. Then, the full-width-at-half-maximum (FWHM) and binding energy of neutral donor bound exciton were 7 meV and 5.9 meV, respectivity. By haynes rule, an activation energy of impurity was 59 meV.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.255-264
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• 2013

Cobalt aluminate ($CoAl_2O_4$) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, $CoAl_2O_4$ is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, $CoAl_2O_4$ pigments were synthesized by polymerized complex method and solid state reaction. Then $CoAl_2O_4$ pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE $L^*a^*b^*$. The XRD patterns of $CoAl_2O_4$ show single phase spinel structure. The particle size of $CoAl_2O_4$ measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained $CoAl_2O_4$ pigments could be confirmed through CIE $L^*a^*b^*$ measurement.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.147-159
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• 2000

The purpose of this study was the evaluation of spectral transmission of the commercial three shade guides and the relationship of hue, value, and chroma according to the transmission rate. The spectral transmittance of three shade guides - Vita Lumin Shade Guide, Vintage and Unibond Shade Guide, and Vitapan 3D-Master Shade Guide - were measured. For direct transmission measurements, each shade tabs were placed at the entrance port of the 1mm diameter intergrating sphere. The intensity of the light source passing through the shade tabs to the right angle was continuously recorded for wavelength from 400 to 700 nm. A transmission spectrum and digital data were obtained for each measurement and they were evaluated using Microcal Origin program. The obtained results of this study were as follows : 1. In Vita Lumin Shade Guide, sum of the transmission rate of the shade tabs at the wavelength 400-700nm was decreased in agreement with the arrangement order at each A, B, C, D group, except D4 shade tab. However, there were no relationships between the transmission rate of the shade tabs and the value-oriented. 2. In Vintage and Unibond Shade Guide, sum of the total transmission rate of the shade tabs was decreased in agreement with the arrangement order at each A, B, C, B group. When all shade tabs arranged in value-oriented, transmission rate was accord with the order, except D4 shade tab. 3. When shade tabs of the Vitapan 3D-Master Shade Guide have the same value and hue, sum of their total transmission rate decreased in accordance with the chroma-oriented. When the shade tabs have the same value and chroma, there were no differences from the order of the transmission rate to the various hue type. However, in the 'R' tabs of reddish hue type, the transmission rate increased at the long wavelength range area. In conclusion, we need the quantitative analyzing instruments in transmission determination. Vitapan 3D-Master Shade Guide covers the tooth color space taking into account the parameters of the systematic value, chroma, hue oriented, and the transmission rate relatively accorded with that sequence.

• Journal of Radiation Protection and Research
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• v.37 no.1
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• pp.10-15
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• 2012

Design and performance test results of a newly developed optically stimulated luminescence (OSL) measurement system are presented in this paper. Generally, different types of optical filters are used in OSL reader system to minimize the interference of the stimulation light in the OSL signal. For optically stimulation of $Al_2O_3:C$, we have arrived at an optimal combination of the filters, i.e., GG420 filter for filtering the stimulating light source, and a combined UG11 and BG39 filter at the detecting window (PMT). By using a high luminance blue LED (Luxeon V), sufficient luminous intensity could be obtained for optically stimulation. By using various control boards, the OSL reader device was successfully interfaced with a personal computer. A software was developed to deliver required commands to operate the OSL reader by using the LabView program (National Instruments, Inc.). In order to evaluate the reliability and the reproducibility of newly designed-OSL reader. Performance testing of the OSL reader was carried out for OSL efficiency, OSL decay curve and signal to noise ratio of the standard $Al_2O_3:C$ OSL material. It was found to be comparable with that of commercial Riso reader system.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.6
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• pp.21-27
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• 1998

Electrical and optical characteristics of ZnS:Mn/ZnS:Tb multilayer TFEL devices were investigated for multi-color electroluminescent display applications. Emission spectra of M $n^{2+}$ and T $b^{3+}$ ions were observed from ZnS:Mn/ZnS:Tb multi-layer TFEL devices, and were very broad from 540 nm to 640 nm. Saturation luminance measured at 155 V was 1025 Cd/$m^2$. C-V, $Q_{t}$ - $V_{p}$ curves showed that the phosphor capacitance ( $C_{p}$ ) and the insulator capacitance ( $C_{i}$ ) were 13.5nF/$\textrm{cm}^2$ and 60 nF/$\textrm{cm}^2$, respectively. Threshold voltage( $V_{thl}$) was shown to decrease from 126 V to 93 V due to the increase of the applied voltage from 155 V to 185 V, which was attributed to the increase of the polarization charge. The equation for the calculation of the threshold voltage as a function of the applied voltage was proposed for the first time. The calculated threshold voltage agreed well with the data obtained from the measurement.t.t.t.

• Journal of Oral Medicine and Pain
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• v.32 no.1
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• pp.45-55
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• 2007

Plant extract has attracted considerable interest in oral disease therapy. The present study was performed to observe the antibacterial effect on cariogenic Streptococcus mutans GS5 and Streptococcus sobrinus 6715, and periodontopathic Actinobacillus actinomycetemcomitans Y4 of phytoncide from Chamaecyparis obtusa Sieb. et Zucc employing the measurement of optical density, viable cell counts, and antibiotic sensitivity. The results were as follows: 1. Minimum inhibitory concentration of the phytoncide for S. mutans, S. sobrinus, and A. actinomycetemcomitans was observed to be 0.5%, 1%, and 0.2%, respectively. 2. Minimum bactericidal concentration of the phytoncide for S. mutans, S. sobrinus, and A. actinomycetemcomitans was determined to be 0.5%, 2%, and 0.2%, respectively. 3. The bacteria exposed to the phytoncide become more sensitive to antibiotics. The phytoncide enhanced significantly antibacterial activity of ampicillin against S. mutans and S. sobrinus. It also increased significantly the activity of penicillin and amoxicillin against S. sobrinus. In contrast, the phytoncide augmented the activity of amoxicillin and cefotaxime against A. actinomycetemcomitans but the increase was not statistically significant. The overall results indicate that phytoncide from Chamaecyparis obtusa Sieb. et Zucc used for this study has a strong antibacterial activity against cariogenic and periodontopathic bacteria and that it also has permeabilizing effect on certain antibiotics against these bacteria. Therefore, the phytoncide may be used as a candidate for prevention and therapeutic agent against oral infectious disease including dental caries and periodontal disease.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.87-103
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• 2008

In recent years, the field of THz photonics based on THz pulse technology has gained tremendous, world-wide interest as a new exciting research subject. With a possibility of many commercial applications as well as fundamental scientific achievements in the field, many advanced nations are stepping up their effort in advancing the field of THz photonics. This fact is supported by the observation of the significant increase in the number of papers on THz pulse technology presented in renowned international journals and conferences. The subject that is interesting for the THz application is the development of THz pulse sources and detectors, and other passive devices. In this paper, we present a brief review on some of the key devices and their relavant measurement techniques such as THz photoconductive antennas, optical rectification, difference frequency geneneration with quasi-phase matching structures, electro-optic sampling, high speed real time measurements, THz transmission lines, and other various waveguide structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.589-598
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• 2000

A pilot-scale Spray Drying Sorber (SDS) system was set up to evaluate the effect of spray characteristics on the desulfurization yield. The size distribution and the Sauter Mean Diameters of slurry droplets were measured in advance using the optical size measurement system, Malvern 2600. The desulfurization yield of the drying chamber by size was measured for the conditions of inlet gas and spray injection. As a reagent, 10% limestone slurry of $Ca(OH)_2$ was treated with flue gas containing $SO_2$, and the combustion gas analyzer and gas detectors were attached to measure the $SO_2$ concentration. With a flow rate of 144 Nm3/h and a temperature range of $200{\sim}300^{\circ}C$, the experiments were performed for the Stoichiometric Ratio (SR) of 1.0 to 3.0 and droplet mean diameter of 6.5 to $34.3{\mu}m$. In case of smaller spray droplets, the desulfurization efficiency improved due to the increase of total droplet surface area, while the reduction in evaporation time reduced the contact time between the droplets and $SO_2$ gas. In some typical region of droplet diameter, this negative effect, reduction of contact time, became dominant and the desulfurization yield decreases the desulfurization yield in spite of the expansion in absorption area. These results revealed that there exists the optimal size of spray droplets for a given state, which is determined by the compromise between the total surface area of slurry droplets and the evaporation time of droplets. The measurements also indicated that the inlet temperature of flue gas changes the optimal injection condition by varying the driving force for evaporation. The results confirm that the effect of the evaporation time of slurry droplets should be considered in analyzing the desulfurization yield as well as the total surface area, for it is a significant aspect of the correlation with the capabilities of $SO_2$ absorption in wet droplets. In conclusion, the optimal condition of spray can be determined based on these results, which might be applied to design or scale-up of SDS system.

• Korean Journal of Food Science and Technology
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• v.28 no.4
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• pp.786-789
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• 1996

An image processing system was built to evaluate the color properties of apple and meat. The system consisted of video camera, video card, 32 bit microcomputer and an optical illuminator. The operating software was developed to carry out capturing, analyzing, displaying and storing of the 8 bit digitized images of food. The images of apples at various maturing stages were investigated to obtain the color histogram of R, G, B and Hunter value. RGB histogram showed a major difference in G value, 35.01, the minor change in R value, 6.16, and the negligible difference in B value. The image of beef cut was separated into two parts, fat and lean tissue, by applying threshold value method based on the digital value of color. The threshold value for fat was over 240 and for lean under 230 in R value, respectively. The resulting non fat image showed 2% decreased color difference value, ${\Delta}E$, than whole meat cut.

• Journal of the Korean Chemical Society
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• v.57 no.4
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• pp.432-438
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• 2013

We report a contact angle goniometer that can be easily assembled and used in high school and general chemistry experiments. It consists of an LED flash, a sample stand, and a camera fixed on an optical bread board, and the sample area is covered to block light from outside with a box with holes on both sides. ImageJ, free image analyzing software and a JAVA plugin (Drop_analysis) were used to determine the contact angle of liquid drop resting on solid surface. The contact angles of various liquids were successfully measured on various surfaces. The solid surface energies have also been determined using the Owen-Wendt method from the contact angles of $H_2O$ and $CH_2I_2$. The results reasonably agree with the previously reported values, showing the surface characteristics and modification as well as the dispersive and polar contributions. These contact angle goniometer and method for determination of the contact angle and surface energy can be applied to observation of various surface properties including wettability, hydrophilicity, and water repelling. Students can learn how the surface properties are related to the intermolecular interactions and gain experience about the equilibrium between the related forces, optics, and mathematical derivations.