• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.643-647
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• 2010

O-carboxymethyl water-soluble chitosan (OCMCh) prepared for enhance the application of chitosan was modified with mthoxy polyethyleneglycol (mPEG) by ion-complex for long circulation in the blood. OCMCh-PEG-PLLs was prepared by forming ion-complex with OCMCh-PEG and Poly(L-Lysine) (PLL) for drug and gene delivery system. The physicochemcal characterisitcs of OCMCh-PEG-PLLs were investigated by FT-IR, $^1H$-NMR. These results showed that CMCh-PEG-PLLs were successfully syntehsized by ion-complex. Particle size distribution and zeta potential of the OCMCh-PEG-PLLs were determined using dynamic light scattering technique. Transmission electron microscopy (TEM) was also used to observe the morphology of the OCMCh-PEG-PLLs. OCMCh-PEG-PLLs have spherical shapes with particle size 290∼390 nm. OCMCh-PEG-PLLs were showed when the feeding amount of mPEG ratio was increased, particle size and zeta potential were decreased. Based on these results, it is possible to introduction of the OCMCh-PEG-PLLs into various biomedical fields such as drug and gene delivery system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.3
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• pp.158-163
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• 2012

The purpose of this study is to improve recycling rate of the coal reject ash by investigating bloating mechanism for artificial lightweight aggregate of reject ash. In this study, we use reject ash (R/A) and dredged soil (D/S) as raw materials. The artificial lightweight aggregates were formed by plastic forming (${\phi}$ = 10 mm) and sintered by temperature raising method at different temperatures (between 1200 and $1275^{\circ}C$). The physical properties of the aggregates such as bulk specific gravity, adsorption and microstructure of surface and cross-section are investigated with the sintering temperature and rate of R/A-D/S contents. As the result of the bulk specific gravity graphs, we can found out the inflection point at content of R/A 80 wt.%. From the microstructure images, we considered the artificial lightweight aggregates content of R/A over 80 wt.% are distributed numerous uniform micro-pores by vitrification without Black Core and the artificial lightweight aggregates of R/A below 80wt.% are distributed macro-pores with Black Core.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.920-928
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• 2000

In this paper, using newly proposed size reduction technique, the aperture coupled microstrip patch antenna for a repeater system in a mobile communication cellular band (824~849 MHz) is developed with a wide bandwidth, small size, light weight, and low cost. The resonant frequency of microstrip antennas is related to the electric field distribution of the radiating patch. The field strength of $TM_{01}$ mode of a rectangular patch antenna is strongest at each of the extremities of the radiating patch, but negligible at center. Therefore, the size of a patch antenna can be effectively minimized by inserting the narrow rectangular dielectric into just under the edges of the resonant Patch. This Paper also proposes the bandwidth improvement technique by using under-coupling technique with a tuning stub. The VSWR is less than 1.5 : 1 for the whole cellular band. The simulation tool was HFSS, Agilent Technologies, Inc.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.470-480
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• 2011

Analog ferrite phase shifters based on rectangular waveguides which are used as component of passive phased array system have high power handling capability, but it is heavy and has high cost to fabricate. In this paper, we propose an analog ferrite phase shifter using substrate integrated waveguide(SIW), which has low cost and is easy to fabricate because it uses printed circuit board(PCB) process. The proposed structure is fabricated by using centeral dielectric material removal for inserting a ferrite bar. The measured results show that the proposed structure has not only $5.1^{\circ}$/mm phase variation but also return loss variation under 12.9 dB. Therefore, it is expected that the proposed phase shifter can plays an role to reduce weight and to has low cost on the phased array system.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.109-115
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• 2012

In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.614-622
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• 2006

A Study on the characteristics of $Ta/Ta_2O_5/MnO_2$ capacitor applied $MnO_2$ by means of pyrolysis of manganese nitrate solution was carried out. Single phase of $MnO_2$ was obtained in the pyrolysis temperature range of 230 to $250^{\circ}C$ by TG/DSC analysis on manganese nitrate solution. Temperature of pyrolysis, concentration of manganese nitrate solution and the number of pyrolysis were selected for the basic parameters of embodying $MnO_2$ solid electrolyte and then the effects of these parameters on the characteristics of capacitor were estimated. The characteristics of capacitor pyrolyzed radiationally was superior to that of capacitor pyrolyzed convectionally on the basis of these optimized parameter conditions. It was verified that radiational pyrolysis formed smaller spherical $MnO_2$ particles than those of convectional one relatively and these facts resulted in forming uniform and dense solid electrolyte layer into the microporous sintered body of capacitor.

• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1205-1210
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• 1999

Far infrared ceramic/aluminum composite powders for thermal spray were fabricated by spray drying method and investigated the characteristics of the plasma sprayed coating layers, I.e. microstructure, phases, thermal shock resistance and spectral emissivity. The shape of the spray dried composite powder was spherical and the particle size distribution was 34~105${\mu}m $. Aluminum was distributed homogeneously in the spray dried composite powder. Spectral emissivity of the plasma sprayed coating layer ranges from 3 to 14${\mu}m $ whereas spectral emissivity of the raw ceramic powder ranges from 8 to 14${\mu}m $. And then spectral emissivity of the coatings was better than that of the raw powder but spectral emissivity was decreased with increasing aluminum content. It was found that aluminum content ranging from 20 to 30wt% was suitable for fabricating far-infrared radiator by plasma spraying method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.6-11
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• 2019

Methylammonium lead halide ($MAPbX_3$, X = I, Br) thin films, used as the light absorber of perovskite solar cells, were prepared using the dual feed ultrasonic spray method. Going through a deposition at a substrate temperature of below $60^{\circ}C$ and then a final heat treatment at $75^{\circ}C$ for 5 minutes using dual feed ultrasonic spray method, $MAPbI_3$ single phase could be formed. Whereas undergoing a deposition at temperatures above $80^{\circ}C$, the spheroidal grains could be changed into rod-shaped fractal structures due to the decomposition of the perovskite phase. Furthermore, using the same method at a higher heat treatment temperature of $100^{\circ}C$, $MAPbI_{3-x}Br_x$ thin films could also be formed from $MAPbI_3$ and $MAPbIBr_2$ solution.

• Korea Science and Art Forum
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• v.26
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• pp.339-351
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• 2016

This study analyzes convention tourism destination brand slogans focusing on the international convention cities. Data were collected from official tourism web sites of 190 cities which hosts more than ten international meetings in 2013. One hundred and six destination brand slogans were identified. Specifically, the researchers attempt to carry out content analysis of the linguistic and visual expressions of the slogans. Results indicated that in terms of linguistic expressions, most of slogans adopted word or phrase patterns pursuing brevity. In the brand slogan spectrum, nearly half of slogans are common type which didn't express destinations' specific attributes and benefits properly. And the most frequently used key words in the slogans are 'visit' and 'city'. While in terms of visual expressions, about 70% of slogans adopted typography for explicitness and 60% of them utilized human and natural resources as visual signs for building up unique images. Based on the results, implications for creating effective convention tourism destination brand slogans were also discussed.

• Applied Microscopy
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• v.9 no.1
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• pp.57-69
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• 1979

The ultrastructural changes of embryo and endosperm cells were observed during the green fruit with embryo about $250{\mu}$ long to germination. 1. In the embryo cells of green fruit with embryo about $250{\mu}$ long, mitochondrial cristae and plastid are undifferentiated and dictyosome are occasionally observed. There are electron-opaque globoids in the vacuole and a lot of spherosomes in the outer layer of smooth endoplasmic reticulum. Endosperm is filled with spherosomes and electron-opaque protein bodies surrounded by spherosomes, and due to these, other organelle are not observed. 2. In the embryo cells of seeds with red seed coat, mitochondrial cristae are well developed, electron-opaque globoids increased, and vacuoles are enlarged. In the endosperm, however, spherosomes increased, protein bodies are enlarged, and electron-opaque globoidal crystals are dispersed within them. 3. In the procambium and epicotyl cells of dehiscent seed, Golgi vacuoles and vesicles are well developed, and mitochondrial cristae are also well differentiated. Spherosomes are numerously present and radicle cells, peripheral cells of hypocotyl, and vacuoles of cotyledon are well differentiated. Endosperm is filled with spherosomes containing electron-opaque granules and protein bodies are surrounded by a single membrane. There are acid phosphatase around globoids and spherosomes. 4. At the time of seeding, spherosomes markedly increased in the outer layer of cotyledon and protein bodies are also observed. Cell organelles are differentiated and plastids containing starch are also present. 5. In the outer $2{\sim}3$ layers of cotyledons, radicle cells, and peripheral cells of hypocotyl during post-seeding to germination, spherosomes and plastids with starch increased, and mitochondria and microbodies are also found around the nucleus of embryo cells. With approaching, the germination stage, in the endosperm contacting with embryo, vacuoles are well differentiated but spherosomes decreased. There increased electron-opaque materials within vacuoles. In other endosperm, with the decrease of spherosome, mitochondria increased and electro n-opaque globular bodies are formed and gradually increased. The outer layer of protein bodies are reduced while electron-transparent portions are enlarged and fused together to occupy the outer layer where small particles are formed. 6. In the endosperm of germination stage, spherosomes decreased while protein bodies, are fused together to form 2 or 3 within a cell.