• 한국전자파학회논문지
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• 제16권8호
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• pp.803-809
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• 2005

본 논문은 평면 배열 안테나의 성능 향상을 위한 안테나 소자간의 새로운 상호 결합 억제 방법을 제안하고 있다. 연구에 사용된 IEEE 802.1la($5.15\~5.35 GHz,\;5.75\~5.85\;GHz$)를 만족하는 두 개의 안테나 소자가 반파장 간격으로 배열되어 있을 때, 안테나 소자간의 상호 결합은 -20 dB 정도였으나 본 논문에서 제안된 뒤집힌 U자형 구조물을 안테나 단 사이에 삽입한 경우, 5 GHz전 대역에서 상호 결합이 -30 dB 이하로 현저히 억압되는 특성을 나타내었다. 본 논문에서 제안한 역 U자형 구조물은 안테나간 상호 결합을 개선할 뿐 아니라, 기생 안테나 성분으로 동작하여 안테나 이득도 2 dBi 이상 개선되는 특성을 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.73-78
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• 1990

Large panel building systems are composed of vertical wall panels which support horizontal roof and floor panels to form a box like structure. The simplecity of the connections, which makes precast concrete economically viable, causes a lack of continuity in stiffness, strength and ductility. This precast concrete large panel systems typically have weak connection regions. Three types of 2-story full-scale precast concrete subassemblages were tested under reversed cyclic loading. The seismic resistance capacity and failure mode of each system are compared in connection with the characteristics of joint connection details.

• 보건행정학회지
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• 제16권4호
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• pp.24-47
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• 2006

Based on the findings of a study focused on medical institutions(Fama & French, 2002), this study determined possible causality between determinants of capital structure and liability level, while estimating targeted debt ratio. Moreover, it also examined hypotheses about the adjustment of targeted debt ratio and the of fundraising patterns, so that it verified the relative priority of trade-off theory and pecking order theory. First, profitability had positive(+) relationships with liability level, while investment opportunities had negative(-) relationships with liability level. This finding supported pecking order theory, and non-liability tax shield effects had negative(-) relationships with liability level as estimated in both trade-off theory and pecking order theory. Next, this study verified trade-off and pecking order theory at once by means of regression analysis about the variation of liability level in associations with disparity from targeted debt ratio and short-term fluctuation of profit and investment. As a result, it was noted that liability level became mean-reversed to targeted liability ratio but slowly, SO it was difficult to assert that such mean reverse may support trade-off theory. However, the finding that most of short-term fluctuations of profit and investment are absorbed into liabilities supported pecking order theory. On the other hand, it was found that the larger scale of medical institutions is more supportive of pecking order theory in the associations between liability level and profitability and the fundraising patterns than trade-off theory.

• Bulletin of the Korean Chemical Society
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• 제10권6호
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• pp.504-509
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• 1989

The effect of oxygen-deficiency on the charge distributions and orbital energies for small copper oxide clusters representing the superconducting materials $YBa_2Cu_3O_x (6{\leq}x{\leq}7)$ were investigated by the extended Huckel molecular orbital (EHMO) method with the tight-binding model. Our calculations show +3 oxidation state of Cu(1) in the $CuO_3$ chain and +2 or +1 of Cu(2) in the $CuO_2$ layers for $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 (or +5), while for $YBa_2Cu_3O_6$ +1 oxidation state of Cu(1) and +3 (or +2) of Cu(2) in the $CuO_2$ layers with the nominal charge of $Cu_3$ = +7 (or +5). For $Cu_3O_{12}$ cluster representing $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 the Cu(2) $d_{{x^2}-{y^2}}$ orbitals in the $CuO_2$ layers is a typical Jahn-Teller $d^9$ system with the partial hole and the Cu(1) $d_{{_z2}-{_y2}}$ orbital in the $CuO_3$ chain contains hole occupancy. For $Cu_3O_{10}$ cluster representing $YBa_2Cu_3O_6$ with the nominal charge of Cu = +5 the orbital character of the highest partially occupied MO (HPOMO) and the lowest completely unoccupied MO (LCUMO) of $Cu_3O_{12}$ representing $YBa_2Cu_3O_7$ with the nominal charge of $Cu_3$ = +7 is reversed, and the character of Cu(1) $d{{x^2}-{y^2}}$ orbital of LCUMO of the $Cu_3O_{12} $cluster is vanished. It is suggested that the local crystal field environment of Cu(1) by the oxygens in the Cu(1) chain may play a vital role in conductivity and superconductivity, either alone or through cooperative electronic coupling with the Cu(2) layers in $YBa_2Cu_3O_7.$.