• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3205-3214
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• 1996

In this paper, the microstrip phased array antennas with coupling-slots for the base station of mobile communication is proposed and anlyzed with accurate analysis method which is based on both reciprocity principle and full-wave analysis. The basis functions used for the numerical analysis are determined depending upon the accuracy, convergence properties of the solution, and the computation time. The patch uses 3 EB mode and the slot uses IPWS mode. The designed phased array antenna has 8 slot-coupled microstrip patch array elements and the beam scanning capability is obtained by using the 4-bit PIN-diode phase shifters as switching devices which are consisted of the loaded line phase shifters for 30.deg. and 60.deg. and the reflection type phase shifters for 90.deg. and 180.deg. repectively. The 4-bits phase shifters which aremade by connecting each phase shifter have about 2.deg.-3.deg. phase errors and their insertion loss are about 3dB for each phase state. The fabricated 8-element phased array antenna with 4-bits phase shifters provides 12.deg.-14.deg. beamwidths depending on the scanning angle and is capable of scanning its beam to .+-.45.deg. with 9.deg. intervals, and the gain 12dBi. The overall results show that the slot-coupled phased array antenna has great advantages of wideband, high gain and reduced spurious radiation. Also, the antenna can be made small and thin. Furthermore, the scanning property of this antenna allows for its application in several areas, such as mobile communication system and PCS.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.263-267
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• 2008

$(Bi_{1/2}Na_{1/2})TiO_3$-based ceramics have been intensively studied as lead-free piezoelectric ceramics. In this study, the piezoelectric properties and phase transition behaviors of BNT based solid solution $(Bi_{0.5}Na_{0.5})_{1-x}Ca_xTiO_3$ ($X=0.01{\sim}0.25$) were investigated. The morphotropic phase boundary(MPB) zone which BNT is transformed from rhombohedral to cubic structure was appeared by adding $CaTiO_3$ with 0.12 mol by the measurement of permittivity and X-ray diffraction. The behavior which ferroelectric BNT with adding $CaTiO_3$ was changed to antiferroelectric and paraelectric state was confirmed by the measurement ofhysterisis loop and depolarization temperature as a function of temperature. As $CaTiO_3$ concentration was increased, the phase transition temperature was decreased. The piezoelectric properties were highest at 0.01 mol of $CaTiO_3$ concentration. The electromechanical coupling factor($K_t$) and mechanical quality factor($Q_m$) were 42% and 254, respectively.

• Journal of Korea Foundry Society
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• v.40 no.2
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• pp.16-24
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• 2020

The effect of a heat treatment on the microstructure and mechanical properties of Inconel 713C alloy vacuum investment castings were investigated. The microstructure of the as-cast state was observed, showing well-developed dendrite structures and distributed carbide particles and solidified massive precipitates in the grain or grain boundary during solidification, in this case the γ′ phase and MC particles. During a heat treatment, the γ phase matrix was reinforced by solid solution elements, carbide particles from the film morphology precipitated along the grain boundary, and many micro-precipitates of second γ′ phases 0.2 ㎛~2 ㎛ in size were newly formed in the γ phase matrix according to SEM-EDS analysis results. The tensile strength at a high temperature (850℃) decreased slightly becoming comparable with the room-temperature result, while the hardness value of the specimen after the vacuum heat treatment increased by approximately 19%, becoming similar to that of the as-cast condition. However, the impact values at room temperature and low temperature (-196℃) were approximated; this alloy was mostly not affected by an impact at a low temperature. In the observations of the fracture surface morphologies of the specimens after the tensile tests, the fractures at room temperature were a mix of brittle and ductile fractures, and an intergranular fracture in the inter-dendrite structure and some dimples in the matrix were observed, whereas the fractures at high temperatures were ductile fractures, with many dimples arising due to precipitation. It was found that a reinforced matrix and precipitates of carbide and the γ′ phase due to the heat treatment had significant effects, contributing greatly to the excellent mechanical properties.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.375-381
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• 1987

Rates for the aquation of trans-[Cr(tn)$_2Cl_2]^+$ and trans-[Cr(en)(tn)Cl$_2$]^+$ ions in aqueous acidic solution have been measured by spectrophotometric method at various temperatures and pressures. Activation volumes are negative and lie in the limited range -1.7 ∼ -2.9cm$^3$mol$^{-1}$ or the complex ions. Activation entropies and activation compressibility coefficients are small negative values. From the results of thermodynamic parameters, it can be inferred that the aquation of the complex ions proceed through an associative interchange(Ia) mechanism. Furthermore, the information on possible transition state structure and reaction paths can be obtained by considering total stabilization energy of the hypothetical intermediates within the framework of angular overlap model. It is found that the theoretically predicted mechanism is consistent with the experimentally observed results.

• Korean Security Journal
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• no.1
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• pp.123-134
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• 1997

Our conuntry have come out to the phenomenon to the atrocity crimes, make into a intellecture crims and specialization with them due to various change to the expension of economy growth, drift of population to cities and sense of value is plunged in confution, Now that things have come to this day, since foundation of the security guard law it first begin, ten years, civilian securities guard law was include to the civil service securities law due to amendment fo the civility secuties law newly on Dec. 30, 1995. According to the amendment, the part of the public peace of peoples livelihood were slough of the visual angle in knowledge which function of the civilies security were only be in under the government dimension were put in order to be tointly according to the such state of affairs, should found the consider a counterplan fundamentally regarding to the what to doing efforts foster the civilities securitylaw and qualitalive elevation of presidential guards. To make a long story short by few words, the question resolves itself into the following five points. The first, peoples arrengements for the attitude fo public duty service with devotedly Sustaining publicity work activities for the thire divert of the understanding of civilian security guard. The secondly, Existing security traders and security association should to support to the civilian security works. The third, The government office concerned should strengthen the licensing system in order to improve the quality of existings in order to may establishment newly systems of license and technical institute of regarding to them. The fourth, Should be newly organixed the exclusive organization of personal protective works in the police buroau for the sustaining development of civirity guard works and soundness of the upbringing. The fifth, It is necessary to found the reserch institute for the study on oretical, scholarly, study for the technical reserch and enlargement of effeciveness And try to find a solution to the Universitys function and duty, activity plan, support plan to the Department of security specialist for the come forward in succession it under the national assistance. The finally, I am sure that the Korean security association could be transiormed into the organization which reliable and receive a love from the peoples when doing best utmost to do pursuit of the structure to be a securitys legalism, specialization and total security systems.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.139-139
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• 2010

Ionic Transition Metal Complex based (iTMC) Light-emitting electrochemical cells (LEECs) have been drawn attention for cheap and easy-to-fabricate light-emitting device. LEEC is one of the promising candidate for next generation display and solid-state lighting applications which can cover the defects of current commercial OLEDs like complicated fabrication process and strong work-function dependent sturucture. We have investigated the performance characteristics of LEECs based on poly (3, 4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-incorporated transition metal complex, which is tris(2, 2'-bipyridyl)ruthenium(II) hexafluorophosphate in this study. There are advantages using conductive polymer-incorporated luminous layer to prevent light disturbance and absorbance while light-emitting process between light-emitting layer and transparent electrode like ITO. The devices were fabricated as sandwiched structure and light-emitting layer was deposited approximately 40nm thickness by spin coating and aluminum electrode was deposited using thermal evaporation process under the vacuum condition (10-3Pa). Current density and light intensity were measured using optical spectrometer, and surface morphology changes of the luminous layer were observed using XRD and AFM varying contents of PEDOT:PSS in the Ruthenium(II) complex solution. To observe enhanced ionic conductivity of PEDOT:PSS and luminous layer, space-charge-limited-currents model was introduced and it showed that the performances and stability of LEECs were improved. Main discussions are the followings. First, relationship between film thickness and performance characteristics of device was considered. Secondly, light-emitting behavior when PEDOT:PSS layer on the ITO, as a buffer, was introduced to iTMC LEECs. Finally, electrical properties including carrier mobility, current density-voltage, light intensity-voltage, response time and turn-on voltages were investigated.

• Journal of the Korean Society of Food Culture
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• v.9 no.2
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• pp.131-136
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• 1994

The ethylacetate extract of Lactuca dentata Makino showed 6 flavonoidal components as detected by ferric chloride solution. The flavonoidal constituent of Lactuca dentata Makino was isolated and purified by the series of column chromatography. The chemical structure of one of the flavonoidal component named as compound E was identified by UV, IR and NMR spectrometry. The melting point range of compound E was $249.5^{\circ}C-251^{\circ}C$. The UV and IR spectra of purified compound E, and its genin were measured with the various shifting agents. The results of UV analysis showed the free state of hydroxy group at 3rd and 4th carbon and binding of sugar at the 7th carbon of compound. The sugar bound to the compound E was identified as glucose by TLC. The IR spectrum showed the presense of hydroxy group, conjugated carbonyl group and aromatic group. The analysis of NMR spectrum was done to the purified compound and its derivatives. The chemical shifts against hydrogen atom, hydroxy group, and the moiety of luteolin were observed in the NMR spectrum along with their position and number as well as type of sugar bound. The isolated and purified compound was identified as $luteolin-7-0-{\beta}-D-glucoside$.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.97-103
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• 2010

In this study, a new, relatively simple fabrication method for forming a mesoporous $Al(OH)_3$ film on Al substrates was demonstrated. This method, i.e., alkali surface modification, was simply comprised of dipping the substrate in a $5\times10^{-3}$ M NaOH solution at $80^{\circ}C$ for one minute and then immersing it in boiling water for 30 minutes. After alkali surface modification, a mesoporous $Al(OH)_3$ film was formed on the Al substrate, and its chemical state and crystal structure were confirmed by XPS and TEM. According to the results of the XPS analysis, the flake-like morphology after the alkali surface modification was mainly composed of $Al(OH)_3$, with a small amount of $Al_2O_3$. The mesoporous $Al(OH)_3$ layer was composed of three regions: an amorphousrich region, a region of mixed amorphous and crystal domains, and a crystalline-rich region near the $Al(OH)_3$ layer surface. It was confirmed that the stabilization process in the alkali surface modification strongly influenced the crystallization of the mesoporous $Al(OH)_3$ layer.

• Journal of the Korean Chemical Society
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• v.25 no.1
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• pp.7-12
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• 1981

Solvolysis of $p-CH_3, p-H, p-Cl and p-NO_2$-benzenesulfonyl chlorides have heen studied in MeOH-MeCN mixtures. A nonlinear Hammett plot with a ratio order of p-NO_2 > p-CH_3 > p-H > p-Cl was obtained; the reaction was thought to proceed by an S_N1-S_N2 borderline mechanism. In all cases the reactivity was a maximum at 90∼95%(v) methanol, whereas methanol monomer selectivity defined as fi = \frac{k1}{ki}i (k1; observed pseudo-first order rate constant: ki; hypothetical rate constant for MeOH solution having the same polymer structure as in the pure MeOH) was a maximum at 80% methanol with a decreasing order of fi as p-NO_2 > p-Cl > p-H > p-CH_3.$ This was interpreted as the decrease in tightness of transition state; the larger the fi, the tighter is the MeOH attached to the substrate, and hence the more susceptible the substrate becomes to the approaching monomer methanol.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.44-50
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• 1992

The ability to account for magnetic and spectra properties of complexes was investigated for the splitting of the degenerate d-orbitals and with nonaqueous solution by UV/vis-spectrophotometric method. The correlation of the magnetitude of 10Dq obtained from the spectra, the pairing energy, and the spin state of the complexes. The electrochemical behavior of complexes were investigated by the use of cyclic voltammetry in aprotic media. These reduction peak of $[(C_6H_5)3_P]_2Pd(II)(CH_3COO)_2$ and $[(C_6H_5)_3Pd]_2Pd(II)Cl_2$ were irreversible one-electron processes at peak $E_{pc1} = -1.32 V,\;E_{pc2} = -1.56 V$ and $E_{pc1} = -1.74 V,\;E_{pc2} = -1.88 V$ of these complexes vs. Ag/AgCl, but nickel complexes were not to be reducible.