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Sungwoo Jang,Sung Il Jin,Chan Ryang Park* 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.12
We report the application of time-dependent density functional theory (TDDFT) to the calculation of potential energy profile relevant to the excited state intramolecular proton transfer (ESIPT) processes in title molecules. The TDDFT single point energy calculations along the reaction path have been performed using the CIS optimized structure in the excited state. In addition to the Stokes shifts, the transition energies including absorption, fluorescence, and 0-0 transition are estimated from the TDDFT potential energy profiles along the proton transfer coordinate. The excited state TDDFT potential energy profile of SA and 3ASA resulted in very flat function of the OH distance in the range ROH = 1.0-1.6 , in contrast to the relatively deep single minimum function in the ground state. Furthermore, we obtained very shallow double minima in the excited state potential energy profile of SA and 3ASA in contrast to the single minimum observed in the previous work. The change of potential energy profile along the reaction path induced by the substitution of electron donating groups (-NH2 and -OCH3) at different sites has been investigated. Substitution at para position with respect to the phenolic OH group showed strong suppression of excited state proton dislocation compared with unsubstitued SA, while substitution at ortho position hardly affected the shape of the ESIPT curve. The TDDFT results are discussed in comparison with those of CASPT2 method.
Enhancement of interfacial adhesion based on nanostructured alumina/aluminum laminates
Jang, Sungwoo,Chung, Jihoon,Seo, Seokhoon,Lee, Sukyung,Lee, Yoonha,Lee, Sangmin,Choi, Hae-Jin Elsevier 2017 Composites Part B, Engineering Vol.129 No.-
<P><B>Abstract</B></P> <P>Adhesive methods can enhance the dynamic impact resistance of composite armor systems. We employed nanostructured interfacial adhesion to improve the bonding strength of alumina/aluminum laminates. ZnO nanowires and anodized aluminum oxide nanoholes were fabricated on alumina and aluminum surfaces, respectively, to increase the surface area and roughness of adhered surfaces. These substrates were bonded to form an alumina/aluminum laminated armor. Effects of nanostructured interfacial adhesion were evaluated by performing drop-weight impact tests. Permanent deformations of the aluminum back plate bonded with nanostructured interfacial adhesion were smaller than in laminates without such adhesion. In addition, nanohole-structured bonding was more effective than nanowire-structured bonding.</P>
Experimental and numerical study on jet properties and penetration of doublelayered shaped charge
Sungwoo Jang,Kimin Yoo,Hyungnam Lim,Hae-Jin Choi,Jungsu Park,Keundeuk Lee 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12
Double-layered shaped charge (DLSC) is a special type of shaped charge which has been recently attracted to enhance the penetration performance. The DLSC consists of a co-axial double-layered charge composed of outer high-velocity explosive and inner lowvelocity explosive. In this paper, numerical simulations and experiments are carried out to investigate the usefulness of the DLSC compare to an ordinary shaped charge (OSC) at different stand-off distances. Jet properties of shaped charges are measured by simulation models and compared with the experimental penetration depths. It was found that the penetration performance strongly depends on the existence of jet breakup and the DLSCs performed better than the OSC only when no jet breakup occurs before reaching the target. The comparison study between the simulations and experiments also revealed that the jet properties such as kinetic energy, cumulative jet mass, and the initial jet breakup distance are highly related to the penetration performance.
Dynamics of OH Production in the Reaction of O(<sup>1</sup>D<sub>2</sub>) with Cyclopropane
Jang, Sungwoo,Jin, Sung Il,Kim, Hong Lae,Kim, Hyung Min,Park, Chan Ryang Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.6
The OH($X^2{\Pi}$, ${\upsilon}^{\prime\prime}=0,1$) internal state distribution following the reaction of electronically excited oxygen atom ($O(^1D_2)$) with cyclo-$C_3H_6$ has been measured using laser-induced fluorescence, and compared with that following the reaction of $O(^1D_2)$ with $C_3H_8$. The overall characteristics of the OH internal energy distributions for both reactions were qualitatively similar. The population propensity of the ${\Pi}(A^{\prime})$ ${\Lambda}$-doublet sub-level suggested that both reactions proceeded via an insertion/elimination mechanism. Bimodal rotational population distributions supported the existence of two parallel mechanisms for OH production, i.e., statistical insertion and nonstatistical insertion. However, detailed analysis revealed that, despite the higher exoergicity of the reaction, the rotational distribution of the OH following the reaction of $O(^1D_2)$ with $C_3H_8$ was significantly cooler than that with cyclo-$C_3H_6$, especially in the vibrational ground state. This observation was interpreted as the effect of the flexibility of the insertion complex and faster intramolecular vibrational relaxation (IVR).
크리깅 근사모델기반 복합충격 저항 샌드위치 패널 최적설계
장성우(Sungwoo Jang),백운경(Woon-Kyoung Baik),최해진(Hae-Jin Choi),박순석(Soon Suk Park) (사)한국CDE학회 2015 한국CDE학회 논문집 Vol.21 No.2
Sandwich panels consisting of various materials have widely been applied for mitigating dynamic impacts such as ballistic and blast impacts. Especially, the selection of materials for different core set-ups can directly influence its performance. In this study, we design the sandwich panels for alleviating ballistic and blast impacts by controlling the stacking sequence of core materials and their thicknesses. FEM studies are performed to simulate the dynamic behavior of sandwich panels subjected to ballistic and blast impacts. Delamination between the core layers is also considered in the FEM studies for feasible design. Based on the FEM data, kriging models are generated for approximating design space and quickly predicting the FEM outputs. Finally, design optimizations are implemented to find the optimum stacking sequence of core materials and thicknesses with given impact situations.