• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.139-145
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• 2008

In this paper, a microstrip surface wave antenna(SWA) with a frequency selective surface structure(FSS) is designed and measured. A microstrip SWA has many advantages such as low profile, low weight, easy fabrication, and compatibility with monolithic microwave integrated circuits(MMIC). In addition, it has demonstrated monopole like beam patterns. The microstrip SWA consists of two parts : a center-fed modified microstrip patch to excite surface wave, and a periodic patches to support the propagation of the surface waves. To obtain wide bandwidth, the ring type parasitic element is inserted and the circular patch is selected for the unit element in FSS structure. Experimental results show that the microstrip SWA has monopole like beam patterns at 5.9GHz. Impedance bandwidth and gain is 12% and 5.6dBi.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.269-275
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• 2017

The aeroelastic stability of a fighter type aircraft can be severly affected by the store mass, aerodynamic characteristics, and store combinations. Hence, the stability for the all store configurations must be substantiated before the aircraft in service. For the aeroelastic analysis, the design data and information for the aircraft structure, mass distribution, control surface characteristics, and external shape etc. are required. This is the reason that the store compatibility substantiations by a third party are restricted. However, according to the change of operational environment or the improvement of avionic technology, a new external store is developed and it should be installed on an aircraft without the support from the original supplier. This paper describe the process to substantiate the aeroelastic compatibility between a new external store and an imported aircraft whose design data is not available to a third party operating the aircraft.

• Journal of the Korean Geographical Society
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• v.49 no.1
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• pp.45-56
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• 2014

Data composite methods have been typically applied to satellite-based vegetation index(VI) data to continuously acquire vegetation greenness over the land surface. Data composites are useful for construction of long-term archives of vegetation indices by minimizing missing data or contamination from noise. In addition, if multi-sensor vegetation indices that are acquired during the same composite periods are used interchangeably, data stability and continuity may be significantly enhanced. This study evaluated the influences of sensor geometry on MODIS vegetation indices and investigated data compatibility of two difference vegetation indices, the Normalized Difference Vegetation Index(NDVI) and the Enhanced Vegetation Index(EVI), for potential improvement of long-term data construction. Relationships between NDVI and EVI turned out statistically significant with variations among vegetation covers. Due to their curvilinear relationships, NDVI became saturated and leveled off as EVI reached high ranges. Correlation coefficients between Terra- and Aqua-based vegetation indices ranged from 0.747 to 0.963 for EVI, and from 0.641 to 0.880 for NDVI, showing better compatibility for EVI compared to NDVI. In-depth analyses of VI outliers that deviated from regression equations constructed from the two different sensors remain as a future study to improve their compatibility.

• Macromolecular Research
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• v.8 no.6
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• pp.276-284
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• 2000

A wettability chemogradient on poly(L-lactide-co-glycolide) (PLGA) films was prepared by treating the films in air with corona from a knife-type electrode whose power increases gradually along the sample length. The PLGA surfaces oxidized gradually with the increasing corona power, and the wettability chemogradient was created on the surfaces as evidenced by the measurement of water contact angles and electron spectroscopy for chemical analysis. The wettability chemogradient PLGA surfaces were used to investigate the interaction of four different types of cells such as hepatoma (Hep G2), osteoblast (MG 63), bovine aortic endothelial (CPAE), and fibroblast (NIH/3T3) cells in terms of the surface hydrophilicity/hydrophobicity of PLGA. The cells adhered and grown on the chemogradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability chemogradient PLGA surface than the more hydrophobic or hydrophillic positions, regardless of the cell types used. The maximum adhesion and growth of the cells appeared at around water contact angles of 53～55°. This result seems closely related with the serum protein adsorption on the surface; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability chemogradient surface. It seems that the wettability plays important roles for cell adhesion, spreading and growth on the PLGA surface. The surface modification technique used in this study may be applicable tothe area of tissue engineering for the improvement of tissue compatibility of films- or scaffold-type substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.33-33
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• 2009

Silicon nano-structures have great potential in bionic sensor applications. Atomic force microscopy (AFM) anodic oxidation have many advantages for the nanostructure fabrication, such as simple process in atmosphere at room temperature, compatibility with conventional Si process. In this work, we fabricated simple FET structures with channel width W~ 10nm (nanowire) and $1{\mu}m$ (nano-ribbon) on ~10, 20 and 100nm-thinned silicon-on-insulator (SOI) wafers in order to investigate the surface effect on the transport characteristics of nano-channel. For further quantitative analysis, we carried out the 2D numerical simulations to investigate the effect of channel surface states on the carrier distribution behavior inside the channel. The simulated 2D cross-sectional structures of fabricated devices had channel heights of H ~ 10, 20, and 100nm, widths of L ~ $1{\mu}m$ and 10nm respectively, where we simultaneously varied the channel surface charge density from $1{\times}10^{-9}$ to $1{\times}10^{-7}C/cm2$. It has been shown that the side-wall charge of nanowire channel mainly affect the I-V characteristics and this was confirmed by the 2D numerical simulations.

• Macromolecular Research
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• v.15 no.1
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• pp.51-58
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• 2007

The approach studied in the present work produced an exfoliated state of clay layers via confinement of the charged nano-sized polystyrene (PS) beads within the gallery of swollen pristine clay. It was demonstrated that adsorption of the polymer nanobeads dramatically promotes expansion of the clay gallery. A comparative study of incorporation was conducted by employing organo-modified clay along with two different colloid polymer systems: electrostatically stabilized PS nanobeads and cationic monomer-grafted PS nanobeads. The mechanism of adsorption of the monomer-grafted polymer beads onto clay via cationic exchange between the alkyl ammonium group of the polymer nanobeads and the interlayer sodium cation of the layered silicate was verified by using several techniques. As distinct from the polymer nanobeads formed using conventional miniemulsion polymerization method, competitive adsorption of stabilizing surfactant molecules was be prevented by grafting the surface functional groups into the polymer chain, thereby supporting the observed effective adsorption of the polymer beads. The presence of surface functional groups that support the establishment of strong polymer-clay interactions was suggested to improve the compatibility of the clay with the polymer matrix and eventually play a crucial role in the performance of the final nanocomposites.

• Polymer(Korea)
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• v.34 no.3
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• pp.198-201
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• 2010

We have worked a surface modification to release a strong agglomeration of multi-walled carbon nanotube(MWCNT) and a incorporation of hydrophilic polymer to improve compatibility between MWCNT and polymers. Carboxylated MWCNT was easily obtained by acid treatment and the carboxylate was converted to acylchloride by thionyl chloride. Then, we tried one more synthesizing routes to achieve covalent bonds with poly(ethylene oxide) having amine end groups of low molecular weight. We measured the polymer content on the surface of MWCNT by TGA and observed increased diameter of MWCNT by SEM and TEM analysis.

• Macromolecular Research
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• v.11 no.2
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• pp.115-121
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• 2003

In this research, the in vitro anti-thrombogenecity of artificial materials was evaluated using hydrophilic/hydrophobic copolymers containing oiligosaccharide as hydrophilic moiety and phospholipid as hydrophobic moiety respectively. N-(p-vinylbenzyl)-[O-$\alpha$-D-glucopyranosyl-(1longrightarrow4)]$_{n-1}$-D-glucoamide(VM7A) was (VM7 A) was adopted as hydrophilic oligosaccharide and 2-acryloxybutyl-2-(triethylammonium)ethyl phosphoric acid (HBA-choline) was adopted as hydrophobic phospholipid. Copolymers having various monomer feeding molar ratios were synthesized through radical polymerization. The synthesized copolymers were identified using FT-IR, $^1$H-NMR, XPS, and DSC. The surface energy of the copolymers were evaluated by dynamic contact angle (DCA) method and checked different roles of VM7A as hydrophilic moiety and HBA-choline as hydrophobic moiety on surface. The surface morphological differences between hydrated and unhydrated surfaces of copolymers were observed and evaluated using Am. The platelets were separated from canine whole blood by centrifugation and adopted to the anti-thromobogenecity test of the copolymers. From the results, we find out that as VM7A ratio increases, so did anti-thrombogenecity. Such results show the possibility of using these copolymers as blood compatible materials in living body.y.

• Polymer(Korea)
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• v.32 no.1
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• pp.7-12
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• 2008

We confirmed that poly (ethylene terephthalate) (PET) fiber had the possibility to improve the mechanical properties of polypropylene (PP) by fabricating PP/PET fiber composites because PET enhanced mechanical properties and higher melting temperature than PP. But lower compatibility of between PP and PET fibers induced poor mechanical properties of PP/PET fiber composites in spite of incorporating PP-g-MAH as compatibilizer. To solve these problems of PP/PET fiber composites, we carried out a surface treatment on PET fiber using NaOH solution and Prepared PP/PET fiber composites with good mechanical properties by adding PP-g-MAH as a compatibilizer Then the behavior of the mechanical properties was correlated with the results obtained from SEM and IR spectroscopy.

• Journal of the Korean institute of surface engineering
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• v.40 no.4
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• pp.197-202
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• 2007

Fit of the restoration and its cementation procedure is crucial to both its short and long term prognosis. Marginal fit is affected by many variables during the fabrication process. These variables, being intrinsic properties of the materials or the clinical technique used, can cause changes in the size and shape of the definitive restoration. Even if all variables are controlled carefully, the seating of a restoration can still be affected due to insufficient space for the luting agent. The use of die spacer can reduce the elevation of a cast restoration of a prepared tooth, decreased seating time, improve the outflow of excess cement, and lower the seating forces. The purpose of this study was to evaluate the marginal fidelity according to die spacer application times and measurement site. Casting alloys were prepared and fabricated using non-precious metal at $950^{\circ}C$. Specimens are divided into four groups: I(die spacer painted casting for wax pattern), II(die spacer non painted casting for wax pattern). The specimens were cut and polished for marginal gap observation. The marginal gap was observed using scanning electron microscopy (SEM).