• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.178-184
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• 2010

The aim of this work is the fabrication of polyelectrolyte microcapsules composed of biocompatible polymers such as chitosan, heparin and alginate, to encapsulate the fluorescein isothiocyanate(FITC)-albumin, and to investigate the protein release behavior therefrom. Polyelectrolyte capsules with 4-layer structures could be prepared with biocompatible materials by oppositely charged adsorption using melamin-foramide as a template. Transmission electron microscope(TEM), scanning electron microscope(SEM) and optical microscope confirmed hollow capsule structures. Protein release before and after encapsulation was monitored with a UV-Vis spectrometer. Microcapsules have different behaviors depending on the kind of polyelectrolyte polymers, chitosan-heparin capsules or chitosan-alginate capsules. In conclusion, the polyelectrolyte multilayer shells can be switched between an open and closed state by means of tuning the pH value.

• Journal of Surface Science and Engineering
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• v.37 no.6
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• pp.307-312
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• 2004

Extensive efforts have been made in an attempt to utilize photocatalytic properties of $TiO_2$ in visible range. $TiO_2$ and TiO-N thin films were made by the DC reactive magnetron sputtering method at $300^{\circ}C$. Various gases (Ar, $O_2$ and $N_2$) were used and Ti target was impressed by 0.6 kW-5.8 kW power range. The hysteresis phenomenon of the $TiO_2$ thin film as a function of the discharge voltage characteristic was observed to be higher as applied power increases. That of TiO-N thin film was occurred at the 5.8 kW power. The cross section and surface roughness of thin films were observed by FE-SEM and AFM. Average surface roughness of TiO-N thin film was observed as $15.9\AA$ and that of $TiO_2$ as $13.2\AA$. The crystal phases of both $TiO_2$ and TiO-N thin films were found to be anatase structure. The atomic $\beta$-N (396 eV peak in N 1s XPS) was shown in the rutile crystal of TiO-N and was considered acting as the origin of wavelength shift to the visible light.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.40-47
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• 2024

The anatomy and histology of the olfactory organ of Monopterus albus was investigated using stereo microscopy, light microscopy, and scanning electron microscopy. The external structure of the olfactory organ exhibited closed anterior and posterior nostrils parallel to the skin surface. The interior structure consisted of a pipe-like chamber, and lower and upper accessory nasal sacs. The olfactory chamber was composed of the sensory and non-sensory epithelium, and an unidentified organ. The sensory epithelium of the pseudostratified epithelial layer was composed of olfactory receptor neurons, supporting cells, basal cells, and lymphatic cells; and the non-sensory epithelium of the stratified squamous layer contained stratified epithelial cells and mucous cells with acidic mucopolysaccharides. The presence of intraepithelial blood capillaries and abundant dermal vascularization in the sensory epithelium of the olfactory chamber may provide strong histological evidence that respiration occurs through the olfactory epithelium.

• Journal of the Economic Geographical Society of Korea
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• v.1 no.1
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• pp.151-172
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• 1998

Over the past two decades, the process of globalization of multinational corporations has increased at a rapid rate. One manifestation of this process is the establishment of corporate head offices in a variety of international centers to administer and coordinate, the day-to-day operations in the host countries. In establishing a subsidiary overseas a firm creates a direct link between the operations of the domestic corporate center and the foreign host center This paper investigates elements of stability and change in the international linkage patterns among domestic parent corporations and host subsidiaries over the past several decades. In particular, it seeks answers to a number of question related to stability and change in linkages among foreign centers of control and those Canadian centers selected to administer the subsidiary operations from 1970 to 1991 over the four primary sectors, namely, resources, manufacturing, services, and finance. By confirming the core stability and dispersed linkages hypotheses, the papar offers some generalizations with respect to the location and stability of subsidiary headquarters centers in Canada and their respective subsector specialties. Finally, it addresses further research avenues fer the quaternary place study.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.12-16
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• 2012

In the paper, we fabricated a Ni master with $45^{\circ}$-mirror structures for flexible waveguide fabrication. The flexible waveguide films with embedded $45^{\circ}$-angled mirrors at the waveguide ends were successfully fabricated using a UV-imprint process. Next, in order to enhance the reflectivity of the mirrors, Ni(3 nm)-Au(200 nm) bilayers were evaporated on the $45^{\circ}$-angled facets through a locally opened thin mask using an electron beam evaporator. We measured propagation loss, bending loss, mirror loss and bending reliability of the fabricated waveguide.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.131-135
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• 2020

Single crystal phased CaZrO₃ : Eu³⁺ phosphor have been synthesized by skull melting method. The crystal structure, morphology and optical properties of synthesized phosphor were investigated XRD (X-ray diffraction), SEM (scanning electron microscopy), UV (ultraviolet) fluorescence reaction and PL (photo luminescence). The starting materials having chemical composition of CaO: ZrO₂ : Eu₂O₃= 0.962 : 1.013 : 0.025 mol% were charged into a cold crucible. The cold crucible was 120 mm in inner diameter and 150 mm in inner height, and 3 kg of mixed powder (CaO, ZrO₂ and Eu₂O₃) was completely melted within 1 hour at an oscillation frequency of 3.4 MHz, maintained in the molten state for 2 hours, and finally air-cooled. The XRD results show that synthesized phosphor is stabilized in orthorhombic perovskite structure without any impurity phases. The synthesized phosphor could be excited by UV light (254 or 365 nm) and the emission spectra results indicated that bright red luminescence of CaZrO₃ : Eu³⁺ due to magnetic dipole transition ⁵D₀→⁷F₂ at 615 nm was dominant.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.127-131
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• 2008

A refractometric glucose biosensor incorporating a vertically coupled microring resonator in polymers was proposed and realized. The ring was covered with a target analyte of glucose solution with a certain concentration, so that its effective refractive index could be altered and, as a result, the resonance wavelength of the sensor was shifted. Therefore the concentration of the glucose solution can be estimated by observing the shift in the resonance wavelength. Two schemes were exploited for enhancing the sensitivity of the sensor. First, the effective refractive index of the polymeric waveguide used for the resonator sensor was adjusted to approach that of the target analyte as best as possible. Second, the ring waveguide, which serves as a crucial sensing part, was appropriately over-etched to enlarge its contact area with the analyte. The proposed resonator sensor was designed with the beam propagation method. The refractive indices of the core and cladding polymer involved were 1.430 and 1.375 respectively, leading to the waveguide's effective refractive index of ${\sim}1.390$, which is faiirly close to that of the glucose solution of ${\sim}1.333$. The prepared ring resonator with the $400-{\mu}m$ radius exhibited the free spectral range of 0.66 nm, the bandwidth of 0.15 nm, and the quality factor of 10,000. For the sensor operating at 1,550 nm wavelength, the achieved sensitivity was as great as 0.28 pm/(mg/dL), which is equivalent to 200 nm/RIU.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.961-968
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• 1998

In order to investigate the effects of substrate bias voltage on the formation of$ZnS-SiO_2$ protective film in phase change optical disk by R.F. magnetron sputtering method, thin dielectric film was formed on Si wafer and Corning glass by using ZnS(80mol%)-$SiO_2$(20mol%)t arget under argon gas. In this study, the Taguchi experimental method was applied in order to obtain optimum conditions with reduced number of experiments and to control numerous variables effectively. At the same time this method can assure the reproducibility of experiments. Optimum conditions for film formation obtained by above method were target RF power of 200 W. substrate RF power of 20 W, Ar pressure of 5 mTorr. sputtering time of 20 min.. respectively. The phase of specimen was determined by using XRD and TEM. The compositional analysis of specimen was performed by XPS test. In order to measure the thermal resistivity of deposited specimen, annealing test was carried out at $300^{\circ}C$ and $600^{\circ}C$. For the account of void fraction in thin film, the Bruggeman EMA(Effective Medium Approximation) method was applied using the optical data obtained by Spectroscopic Ellipsometry. According to the results of this work, the existence of strong interaction between bias voltage and sputtering time was confirmed for refractive index value. According to XRD and TEM analysis of specimen, the film structure formed in bias voltage resulted in more refined structures than that formed without bias voltage. But excess bias voltage resulted in grain growth in thin film. It was confirmed that the application of optimum bias voltage increased film density by reduction of void fraction of about 3.7%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.230-234
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• 2013

IR cut-off thin films consisted of ATO nanoparticles were successfully fabricated by sol-gel method. The coating solution was synthesized with organic/inorganic hybrid binder and ATO colloidal solution and ATO thin films were coated on a slide glass with the withdrawal speed of 5~40 mm/s. As the withdrawal speed increased from 5 mm/s to 40 mm/s, the thickness of coating thin films also increased from $1.05{\mu}m$ to $4.25{\mu}m$ and the IR cut-off in wavelength of 780~2500 nm increased from 49.5 % to 66.7 %. In addition, the pencil hardness of ATO thin films dried at $80^{\circ}C$ was ca. 5H and the coating films were not removed after a cross cutter tape test because of the hybrid binder synthesized with tetraethylorthosilicate and methyltrimethoxysilane. The surface morphologies, optical properties and film thickness of prepared thin films with a different withdrawal speed were measured by field emission scanning electron microscope (FE-SEM), UV-Vis spectrophotometer, and Dektak.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.159-163
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• 2016

Up-conversion (UC) luminescence properties of polycrystalline $Er^{3+}/Yb^{3+}$ doped $NaGd(MoO_4)_2$ phosphors synthesized by a simple solid-state reaction method were investigated in detail. Used to 980 nm excitation (InfraRed area), $Er^{3+}/Yb^{3+}$ co-doped $NaGd(MoO_4)_2$ exhibited very weak red emissions near 650 and 670 nm, and very strong green UC emissions at 540 and 550 nm corresponding to the infra 4f transitions of $Er^{3+}(^4F_{9/2},\;^2H_{11/2},\;^4S_{3/2}){\rightarrow}Er^{3+}(^4I_{15/2})$. The optimum doping concentration of $Er^{3+}$, $Yb^{3+}$ for highest emission intensity was determined by XRD and PL analysis. The $Er^{3+}/Yb^{3+}$ (10.0/10.0 mol%) co-doped $NaGd(MoO_4)_2$ phosphor sample exhibited very strong shiny green emission. A possible UC mechanism for $Er^{3+}/Yb^{3+}$ co-doped $NaGd(MoO_4)_2$ depending on the pump power dependence was discussed.