• Korean Journal of Materials Research
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• v.16 no.12
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• pp.771-776
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• 2006

In this study, we report a method to synthesize the aluminum nitride (AlN) powders from aluminum oxyhydroxide (AlOOH). AlOOH powders were prepared from the aluminum hydroxide ($Al(OH)_3$) by heattreatment at the reaction temperature of $350^{\circ}C$. Simple heat treatment of AlOOH in the flow of $NH_3$ gas leads to the formation of hexagonal AlN powders through intermediate conversion of ${\delta}-,\;{\gamma}-$ and ${\alpha}-Al_2O_3$. The FTIR transmission spectra show a broad peak related to Al-N bonds centered around 690 $cm^{-1}$ confirming the presence of AlN. The major peaks in Raman spectra were observed in 250 $cm^{-1}$ and 659 $cm^{-1}$. From the results, synthesized powders from the AlOOH powders were confirmed AlN powders.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.4114-4114
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• 2001

For the quality control of tablets several parameters have to be checked. The most important one is the content of an active ingredient which has to match a narrow range around the designated content. The only useful measurement mode is transmission which provides information of the complete tablet. A measurement in diffuse reflectance would register only the surface which is useless especially in case of a coated tablet. In this work tablets for a clinical study (placebo/verum studies) with very low concentrations of the active ingredient were measured. The concentration range was 0 to 6 mg with a total weight of the tablets of 105 mg, leading to a highest concentration of the active component of 5.7% by weight. Especially the spectroscopic distinction between the placebo and the low dosage forms with 0.25 and 0.5 mg active agent requires an extraordinarily accurate sampling technique. Using the VECTOR 22/N-T in transmission mode allows the collection of the information from the complete tablets. A quantitative PLS-model with transmission spectra from the tablets described above shows that the active substance can be predicted with a RMSECV (root mean square error of cross validation) of 0.04% absolute for this special application. The results are compared with those of measurements in diffuse reflectance using different accessories.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.1
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• pp.23-28
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• 2002

In order to survey the radiation characteristics of pure line noise of unwanted noise from overhead high voltage AC transmission lines, a disk type gap noise generator was manufactured. Disk size which decides capacitance between the noise generator and earth was selected through preliminary indoor experiments and analysis by using surface charge method. The capacitance is one of principal parameters related to the injection of a proper noise current into lines. On the basis of the capacitance obtained from calculation, 5mm of space was given to the gap of the noise generator to be installed o test line and an aluminum disk of 60cm radius was made. The field experiments were performed with the noise generator hung on the Kochang 765 kV full scale test line. As the results, the useful data which can be used to analysis the radiation characteristics of noise from transmission lines were obtained. Those are the directivity of antenna toward the line, lateral profiles, frequency spectra, height pattern and so on.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.31-34
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• 2013

Trivalent cerium-ion-doped $Y_3(Al,\;Ga)_5O_{12}$ nanoparticle phosphor nanoparticles were synthesized using the reverse micelle process. The Ce doped $Y_3(Al,\;Ga)_5O_{12}$ particles were obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase and poly(oxyethylene) nonylphenyl ether (Igepal CO-520) as the non-ionic surfactant. The crystallinity, morphology, and thermal properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy. The crystallinity, morphology, and chemical states of the ions were characterized; the photo-physical properties were studied by taking absorption, excitation, and emission spectra for various concentrations of cerium. The photo physical properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were studied by taking the excitation and emission spectra for various concentrations of cerium. The average particle size of the synthesized YAG powders was below $1{\mu}m$. Excitation spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ samples were 485 nm and 475 nm, respectively. The emission spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ were around 560 nm and 545 nm, respectively. $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ is a red-emitting phosphor; it has a high efficiency for operation under near UV excitation, and may be a promising candidate for photonic applications.

• Applied Microscopy
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• v.50
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• pp.2.1-2.7
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• 2020

Electron energy loss spectroscopy (EELS) is an analytical technique that can provide the structural, physical and chemical information of materials. The EELS spectra can be obtained by combining with TEM at sub-nanometer spatial resolution. However, EELS spectral information can't be obtained easily because in order to interpret EELS spectra, we need to refer to and/or compare many reference data with each other. And in addition to that, we should consider the different experimental variables used to produce each data. Therefore, reliable and easily interpretable EELS standard reference data are needed. Our Electron Energy Loss Data Center (EELDC) has been designated as National Standard Electron Energy Loss Data Center No. 34 to develop EELS standard reference (SR) data and to play a role in dissemination and diffusion of the SR data to users. EELDC has developed and collected EEL SR data for the materials required by major industries and has a total of 82 EEL SR data. Also, we have created an online platform that provides a one-stop-place to help users interpret quickly EELS spectra and get various spectral information. In this paper, we introduce EEL SR data, the homepage of EELDC and how to use them.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.269-273
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• 1990

The proton conserving effect of diffusion with self-aligned SiO2-cladding is investigated by infrared transmission spectra. Based on the proton conserving effect, proton-diffused channel waveguides with self-aligned SiO2-cladding substrates. And an electro-optic cutoff modulator with self aligned electrode that utilizes a single-mode proton-diffused channel waveguide in a Y-cut XX-propagating LiNbO3 substrate is fabricated. Over 20 dB extinction has been achieved with applied voltage of 15V.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.443-448
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• 1988

Colored Cubic Zircona(CCZ) single crystals were grown by the skull melting method. The grown crystals were doped with up to 0.1wt% transition (Cu, Ni, Co, Ti, Fe, Mo, Cr, V, Mn) metal ions on ZrO2-Y2O3(9.5~10mol%) and their Optical transmission spectra(λ=300~800nm)data were obtained. Various colors were pronounced due to dopant effects in the grown Crystals.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.82-88
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• 1998

We propose and design a new type of anrrow band-pass optical filter based on two fiber gratings with different reflection wavelength. The ripples occur in the spectra of the filter with two uniform fiber gratings. Our simulation results also show that the ripples disappear with the fiber gratings apodized to both gaussian and hyperbolic tangent function. The hyperbolic tangent function seems to be a better apodization function for improving the filter's performance in terms of narrow pass bandwidth and high transmission.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.35-36
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• 2007

We report a probe using a single double clad fiber (DCF) for fluorescence spectroscopy. Bidirectional separate transmission for excitation and fluorescence light in a single fiber was implemented. A DCF coupler made by side-polished method could extract none but the collected fluorescence signals propagating in inner cladding mode, thereby diminishing the interference of silica background generated by the excitation in core mode. The experimental results show that the fluorescence spectra of biological tissues obtained using the DCF probes have much less silica background than using a standard multiple-mode fiber.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.115-130
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• 1995

In order to produce Cu nanocrystallite in silicon wafer, the implantation technique was used. The samples of silicon (100) wafers were implanted by $Cu^+$ ions at 100 keV and with varying the doses at room temperature. Post-annealing was performed at $800^{\circ}C$ with Ar environment. To investigate the formation of Cu nanocrystallite with ion doses and growth process by thermal annealing, SIMS and HRTEM(high resolution transmission electron microscopy)spectra were studied.