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소형 위성 SAR용 Deep Reflector 안테나의 초크 급전기 설계
조승주,임정환,이택경,이재욱 한국전자파학회 2020 한국전자파학회논문지 Vol.31 No.1
본 논문에서는 소형 위성 SAR에 적합한 전개형 반사형 안테나의 급전 안테나로서 초크 안테나를 설계 및 제작하였다. 전개형 안테나의 수납효율에 유리하도록 deep reflector 안테나를 선정하였고, 개구면의 가장자리 테이퍼를 고려하여 급전안테나가 넓은 빔폭을 갖도록 설계하기 위해서 초크 링의 개수와 부착 위치의 최적화를 수행하였다. 설계한 초크 안테나를 반사판 안테나의 급전으로 사용하였을 때의 반사판 안테나 성능을 분석하였으며, 이때의 반사판 안테나 패턴으로부터 SAR 시스템 성능을 분석하여 설계한 초크 안테나가 전개형 안테나의 급전으로써 적합함을 확인하였다.
전개형 반사판 안테나의 패널 불완전 전개에 의한 편파특성 영향
조승주,이시아,이택경,이재욱 한국전자파학회 2020 한국전자파학회논문지 Vol.31 No.5
본 논문에서는 전개형 반사판 안테나의 불완전 전개가 안테나의 편파 성능에 미치는 영향에 대해 분석하였다. 포물면의 성질을 이용하는 전개형 반사판 안테나에 불완전 전개가 발생하면 안테나의 형상이 온전한 포물면의 형상을 이루지못하여 안테나의 동일편파 패턴뿐만 아니라, 교차편파 패턴 또한 악화시켰다. 안테나의 불완전 전개가 대칭으로 발생한경우와 비대칭으로 발생한 경우에 대한 안테나 성능 저하의 차이를 조사하였다. 불완전 전개 형상이 대칭인 경우에는교차편파 성능에 미치는 영향이 미약하지만, 비대칭 형상의 경우에는 교차편파가 68 dB 정도 높으며, 교차편파 성능은안테나의 비대칭 형상에 의해 주로 발생하는 것을 확인하였다.
Toward Proper 3D-QSAR Datasets for Parameter Evaluation
조승주 조선대학교 기초과학연구원 2011 조선자연과학논문집 Vol.4 No.3
3D-QSAR techniques including CoMFA have been used a lot for more than two decades now. For now, the perspective of 3D-QSAR has been changed. The realization of gorge activity cliffs and higher chance correlation with many independent variables (IVs) has changed the requirements. Some suggested the benchmarking datasets for 3D-QSAR. However, were they still useful for right reasons? Here, we propose the requirement of any general purpose 3D-QSAR benchmarking datasets for lead optimization, especially for feasibility test of any IVs. Specifically, we summarize the conceptual requirements for an ideal settings for 3D-QSAR especially CoMFA.
조승주 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.9
Recently we have reported a novel class of anion receptors which are based on 2n-crown-n topology. Trioxane derivatives are capable of anion sensing through pure aliphatic C-H hydrogen bonding. In this work, we highlight another interesting property, i.e., they can also recognize cations as normal crown ethers (3n-crownn topology). Since the same functional moiety can recognize anions and cations, these coronands are predicted to be amphi-ionophores. However, we could not detect cations even in the gas phase. Considering trioxane is analogous to [16]starand, this was rather counter-intuitive. The calculation results show that these coronands can detect alkali metals with very low affinity. The low affinity toward cations should be responsible for this failure of experimental detection. With careful theoretical study, we found that this low affinity toward cations could be explained by the unfavorable charge-dipolar moiety orientations as proposed by Cui et al. As in the case of [16]starand, this is an example that underscores the importance of charge-dipolar moiety orientation in supramolecular interactions.
Docking and Quantum Mechanics-Guided CoMFA Analysis of b-RAF Inhibitors
조승주,M. Muddassar,F. A. Pasha,유경호,이소하 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.8
Pyrazine derivatives bind to b-RAF receptor which is important in cancer therapy. The ligand-receptor interactions have been studied by comparative molecular field analysis (CoMFA) and molecular docking methods. Applying conventional ligand-based alignment schemes for the whole set was not successful. However, QM and DFT results suggested that some ligands have electrostatic interaction while others have steric interactions. On the basis of these results, we divided the dataset into two subsets. Electrostatic effect was found to be important in one set while steric effect for the other. Best docking modes were obtained for each subset based on the available crystal structure. These receptor-guided CoMFA models propose an interesting possibility which is difficult to obtain otherwise. i.e., in one binding mode the electrostatic interaction plays a key role for one subset (q2 = 0.46, r2 = 0.98), while in another binding mode steric effect is important with another subset (q2 = 0.43, r2 = 0.74).
The Importance of Halogen Bonding: A Tutorial
조승주 조선대학교 기초과학연구원 2012 조선자연과학논문집 Vol.5 No.3
Halogen atoms in a molecule are traditionally considered as electron donors, since they have unshared electrons. Normally when they are bonded, there are three lone pair electrons. These lone pairs can function as Lewis bases. However, when they are bound to electron withdrawing groups, they can act as Lewis acids. Since the situation is similar hydrogen bonding (HB), this type of interaction is named as halogen bonding (XB). This mainly comes from the uneven distribution of electron density around the halogen atoms. Since the electron density around halogen atom opposite to σ-bond is depleted, its electropositive region is called σ-hole. This σ-hole can attract halogen bond acceptors, requiring more stringent directionality compared to HB. Since this interaction mainly comes from electrostatic origin, the geometry tends to be linear. Since the XB energy is comparable to corresponding HB. Still in its infancy, XB shows a broad range of applicability, with potentially more useful properties, compared to corresponding HB.