• Journal of Advanced Navigation Technology
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• v.25 no.4
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• pp.267-272
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• 2021

The end of the ROK-U.S. missile guidelines opened up the possibility of developing space launch vehicles for various platforms based on air and sea. In particular, the air-based space launch vehicle is an essential space power projection capability compared to the ground-based space launch vehicle in consideration of the geographical location of the Korean Peninsula, such as the deployment of various satellite orbits and the timely launch of satellite. In addition, compared to the ground-based launch vehicle, the cost reduction effect is large, and it has the merit of energy gain because it can be launched with the advantage of the aircraft's altitude and speed. Therefore, in this paper, the necessity of air-based space launch vehicle in the strategic environment of the Korean Peninsula is clearly presented, and through technology trend analysis of various air launch vehicle, the three methods are proposed to have the most efficient air-based space launch vehicle capability in the Korean situation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.3
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• pp.422-429
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• 2022

In this paper, the intermediate frequency transmission signal level between the network system-based baseband and RF unit consisting of multi-channel airborne relay devices and a lot of mission devices, which are currently undergoing technology development tasks, is kept constant at the reference signal level. Considering the other party's receiving input range, despite changes in the short-range long-range wireless communication environment, it presents a multi-link protection and MLP-A algorithm that allows signals to be transmitted stably and reliably through signal detection automatic gain control, and experiments and analysis considering short-distance and long-distance wireless environments were performed by designing, manufacturing, and implementing RF units to which MLP-A algorithms were applied, and applying distance calculation equations to the configuration of multiple air movements and verification networks. Through this, it was confirmed that a stable and reliable RF communication system can be operated.

• Korean journal of communication and information
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• v.41
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• pp.41-74
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• 2008

Based on the theory of news media's agenda-setting function, this study analyzed Korean public's most important problems (MIP) and the degree of public consensus on the importance of those MIP's. The analysis was done in terms of both time and social strata. According to the findings, economy, social welfare, and political issues were in the for tier of the MIP list. The analysis of issue diversity (H-statistic) also demonstrated a relatively high degree of agenda consensus among Korean public despite some fluctuation in the consensus level, which appears to be higher than that among the American public. A decrease in the degree of agenda consensus with the passage of time appealed to be a general phenomenon across diverse social strata. However, the degrees of consensus-building were different in light of education, socioeconomic status, and the size of residential area. Those who are more educated, have more economic power, and live in a larger city had more chances to experience agenda consensus. These results seem to be basically attributable to the presumed positive relationship between these demographic variables and media exposure. The different degrees of public consensus according to the different levels of those demographic variables suggest that a closer investigation into the various influences on the importance of public issues among the respondents should be done in future studies.

• The Journal of the Korea Contents Association
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• v.20 no.6
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• pp.326-341
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• 2020

Based on theoretical background of Situational Theory of Problem Solving(STOPS), we have examined the role of STOPS variables on a group of online public in their issue recognition and communicative behavior on Korea's nationwide civil boycott movement of Japanese goods. Results from 524 survey cases from a Korea's major online community show that two independent variables(Problem Recognition, Referent Criterion) revealed positive in their effect on mediating variable(Situational Motivation in Problem Solving). Situational Motivation also revealed positive in its effect on six dependent variables(Information Forefending, Information Permitting, Information Forwarding, Information Sharing, Information Seeking, Information Attending) of Communicative Behavior. Involvement Recognition and Constraint Recognition revealed positive without proper statistical significance. As a result, study on the case of online public in Korea supports STOPS theory as high-level of Problem Recognition and Referent Criterion effects on Communicative Behavior in positive way via Situational Motivation. Implications from the findings have discussed and proposed suggestions for government public relations and further studies.

• KSBB Journal
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• v.23 no.3
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• pp.226-230
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• 2008

In this study we have studied adhesive properties of various microorganisms onto surfaces of phosphorylcholine-based copolymer for the application of optical biosensors. Three microorganisms, E.coli JM109, B.cereus 318, P.pastoris X-33 were cultivated in confocal cultivation dishes with glass surface, respectively. The glass surface was coated with copolymer containing 0% 5% and 10% MPC (2-methacryloxyethyl phosphorylcholine). After cultivation, culture medium was discarded and adhered microorganisms were dyed by gram staining method. Adhered microorganisms were analyzed using an optical microscope and scanning electronic microscope (SEM). A great number of microorganisms, $2-3{\times}10^3/mm^2$ were adhered on the surfaces of glass and copolymer membrane without MPC. But the antifouling effects of copolymer containing 5% and 10% phosphorylcholine were large, that microorganisms of less than $50-100/mm^2$ were attached on the copolymer membranes. Thus, the copolymer containing phosphorylcholine is very useful as an antifouling coating material for optical biosensor.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.970-976
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• 1996

An ester-carbonate copolymer was synthesized, in which carbonate was inserted into a biodegradable aliphatic polyester, poly(butylene succinate) (PBS), to modify its mechanical properties. The synthesis was carried out by condensation reactions in two steps. In the first step, oligo(butylene succinate) was prepared by the reaction of succinic acid with 1,4-butanediol (BD). In the second step, it was reacted with oligohexamethylenecarbonate diol (OHMCG) to prepare the ester-carbonate copolymer. Titanium(IV) isopropoxide (TIP) was used as a catalyst for the reaction. The structure of the copolymer was confirmed by FT-IR and $^1H$-NMR and the thermal behavior and mechanical properties were investigated by differential scanning calorimetry (DSC) and universal testing machine (UTM), respectively. It was found that optimum amount of the catalyst for the formation of high molecular weight copolymer was 1wt% for succinic acid. When the BD:OHMCG is in the range 149:1~249:1, the copolymer with high viscosity was obtained. As the OHMCG content was increased, melting temperature ($T_m$) of the copolymer was decreased. When BD:OHMCG is 149:1, the copolymer showed a increase in ultimate strain by two times and the slight decrease in modulus compared to those of PBS.

• Polymer(Korea)
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• v.38 no.4
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• pp.535-543
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• 2014

This work, which was about the synthesis of naphthalimidopropyl acrylate and GMA copolymers and their physical properties, investigated the compositions of the copolymer, the reactivity ratios of the monomer, resonance effect (Q), polar effect (e) and fluorescence of naphthalene. Azobisisobutyronitronitryl (AIBN) as an initiator was employed at $60^{\circ}C$ with dimethylformamide (DMF) of solvent for the copolymerization of NIPA. $r_1$ was found to be higher than $r_2$ from the reactivity ratios of the monomer obtained from Fineman-Ross (F-R), Kelen-$T{\ddot{u}}d{\ddot{o}}s$(K-T) methods. NIPA was found to be more copolymerized than GMA. $r_1{\cdot}r_2$ product was lower than 1, copolymerization was maked random-alternating type. The fluorescence spectrum of these polymers showed a weak monomer fluorescence band at 380 nm and a strong excimer fluorescence band at about 460 nm. Fluorescence life time of NIPA monomer showed fluorescence cover with UV 355 nm at room temperature, and life time showed $5.1449{\times}10^{-7}s$.

• Membrane Journal
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• v.25 no.3
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• pp.231-238
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• 2015

Co-polyimide membranes were prepared by two-step polymerization using semi-alicyclic 5-(2,5-dioxotetrahydrofuryl)-3-methyl-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) with five diamines such as 2,5-dimethyl-1,4-phenylene diamine (2M), 2,4,6-trimethyl-1,3-phenylene diamine (3M), 1,5-naphthalene diamine (NDA), 4,4-diaminodiphenyl methane (MDA), 4,4'-diaminodiphenyl ether (ODA). Synthesized co-polyimides were characterized by FT-IR, viscosity, solubility, DSC, TGA and gas permeation properties, compared with 6FDA-based co-polyimides. All co-polyimides had the intrinsic viscosity of 0.32~0.58 and excellent solubility in various solvents. DOCDA-based co-polyimides had thermal stability over $400^{\circ}C$ although those were lower than 6FDA-based co-polyimides. Gas permeabilities of the copolyimide membranes were measured for $CO_2$ and $CH_4$ at room temperature and presented the trade-off relationship.

• Polymer(Korea)
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• v.25 no.2
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• pp.186-198
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• 2001

pH/Thermal sensitive copolymers with the various acidic comonomer compositions composed of N-isopropylacrylamide (NIPAAm) with acrylic acid (AAc), 2-acrylamido glycolic acid (AAmGAc), and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesized by free radial polymerization. In this study, to characterize the effect of different acidic comonomer composition and pH on the lower critical solution temperature (LCST) behaviors of their copolymers. phase transition experiments were performed with a thermo-optical analyzer (TOA). The phase transition temperature (T$^{p}$ ) of aqueous poly(NIPAAm-co-AAc) solution was lowered with increasing the ionization of the acid group in AAc, that is, the ionized state induced the electrostatic repulsion of ionized groups. In contrast, when AAmGAc was introduced into PNIPAAm, T$^{p}$ was little changed at pH 1-3, whereas climbed up significantly from pH 1 to pH 3. In the range of pH 6-10, Tp was lower than that of pH 3-5. This result was considered to be \"Ionic Screen Effect\" and this effect had been also observed in the case of poly(NIPAAm-co-AMPS).-co-AMPS).

• Polymer(Korea)
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• v.36 no.2
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• pp.223-228
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• 2012

Temperature and pH sensitive graft copolymers [Pluronic-$g$-poly(NIPAAm-$co$-MMA), Polymer A] and [Pluronic-$g$-poly( NIPAAm-$co$-MAA), Polymer C] were synthesized by macro radical graft polymerization with $N$-isopropylacrylamide (NIPAAM)/$N,N$-diethylaminoethylmethacrylate (DEAEMA) and $N$-isopropylacrylamide (NIPAAm)/methacrylic acid (MAA) based on Pluronic, respectively. The chemical structure and molecular weight of the graft copolymers was characterized by $^1H$ NMR and gel permeation chromatography. The aqueous solution properties of graft copolymers were measured using a UV-visible spectrophotometer, contact angle and dynamic light scattering equipment with different temperature and pH conditions. The obtained graft copolymers showed a very sensitive phase transition in response to temperature and pH in aqueous media which suggested that the amine group of DEAEMA segment and carboxylic group of MAA had a great influence on the lower critical solution temperatures (LCST) in Polymer A and C, respectively. The graft copolymers can be utilized for drug delivery system and molecular switching applications where responses to temperature and pH changes are relevant.