• International Journal of Naval Architecture and Ocean Engineering
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• 제9권4호
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• pp.439-445
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• 2017

Plunging breaker slamming pressures on vertical or sloping sea dikes are one of the most severe and dangerous loads that sea dike structures can suffer. Many studies have investigated the impact forces caused by breaking waves for maritime structures including sea dikes and most predictions of the breaker forces are based on empirical or semi-empirical formulae calibrated from laboratory experiments. However, the wave breaking mechanism is complex and more research efforts are still needed to improve the accuracy in predicting breaker forces. This study proposes a semi-empirical formula, which is based on impulse-momentum relation, to calculate the slamming pressure due to plunging wave breaking on a sloping sea dike. Compared with some measured slamming pressure data in two literature, the calculation results by the new formula show reasonable agreements. Also, by analysing probability distribution function of wave heights, the proposed formula can be converted into a probabilistic expression form for convenience only.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1043-1046
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• 2013

Prediction of physicochemical properties of organic molecules is an important process in chemistry and chemical engineering. The MSEP approach developed in our lab calculates the molecular surface electrostatic potential (ESP) on van der Waals (vdW) surfaces of molecules. This approach includes geometry optimization and frequency calculation using hybrid density functional theory, B3LYP, at the 6-31G(d) basis set to find minima on the potential energy surface, and is known to give satisfactory QSPR results for various properties of organic molecules. However, this MSEP method is not applicable to screen large database because geometry optimization and frequency calculation require considerable computing time. To develop a fast but yet reliable approach, we have re-examined our previous work on organic molecules using two semi-empirical methods, AM1 and PM3. This new approach can be an efficient protocol in designing new molecules with improved properties.

• Journal of the Korean Physical Society
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• 제80권
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• pp.953-963
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• 2022

Post-neutron emission fission product mass distributions are calculated by using pre-neutron emission fission product yields (FPYs) and neutron multiplicity. A semi-empirical model is used to calculate the pre-neutron FPY, first. Then the neutron multiplicity for each fission fragment mass is used to convert the pre-neutron FPY to the post-neutron FPY. In doing so, assumptions are made for the probability for a pre-emission fission fragment with a mass number A^* to decay to a post-emission fragment with a mass number A. The resulting post-neutron FPYs are compared with the data available. The systems where the experimental data of not only the pre- and post-neutron FPY but also neutron multiplicity are available are the thermal neutron-induced fission of ²³³U, ²³⁵U and ²³⁹Pu. Thus, we applied the model calculations to these systems and compared the calculation results with those from the GEF and the data from the ENDF and the EXFOR libraries. Both the pre- and post-neutron fission product mass distributions calculated by using the semi-empirical model and the neutron multiplicity reproduce the overall features of the experimental data.

• Bulletin of the Korean Chemical Society
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• 제27권1호
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• pp.33-34
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• 2006

• 한국항공우주학회지
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• 제36권3호
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• pp.220-228
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• 2008

반실험적 기법과 CFD 코드를 이용하여 자유회전 테일핀을 갖는 커나드 조종 미사일의 공력특성을 연구하였다. 반실험적 기법에서는 테일핀의 회전각에 따른 공력계수의 평균을 구한 후 자유회전 테일핀의 공력계수를 계산하였다. 또한 테일핀의 평균 롤링 및 롤 댐핑 모멘트계수를 이용하여 자유회전 테일핀의 회전율을 예측하였다. CFD 계산의 경우 중첩격자를 이용한 6-자유도 해석을 통해 테일핀의 회전율을 계산하였다. 미사일의 공력계수 예측 값들은 풍동실험 결과와 유사하게 나타났고, 커나드 롤 조종 및 요 조종시의 테일핀 회전율 또한 풍동실험결과와 근접하게 나타났다. 본 연구를 통해 자유회전 테일핀을 갖는 커나드 조종 미사일에 관한 공력해석에 반실험적 기법을 적용할 수 있음을 확인하였다.

• Journal of Computing Science and Engineering
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• 제5권2호
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• pp.150-160
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• 2011

Automatic text classification has a long history and many studies have been conducted in this field. In particular, many machine learning algorithms and information retrieval techniques have been applied to text classification tasks. Even though much technical progress has been made in text classification, there is still room for improvement in text classification. In this paper, we will discuss remaining issues in improving text classification. In this paper, three improvement issues are presented including automatic training data generation, noisy data treatment and term weighting and indexing, and four actual studies and their empirical results for those issues are introduced. First, the semi-supervised learning technique is applied to text classification to efficiently create training data. For effective noisy data treatment, a noisy data reduction method and a robust text classifier from noisy data are developed as a solution. Finally, the term weighting and indexing technique is revised by reflecting the importance of sentences into term weight calculation using summarization techniques.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.415-418
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• 2009

Concerned with ambiguous stereochemistry assignment of natural (+)-glabridin, absolute configurations of (${\pm}$)-glabridin enantiomers were studied with synthetic glabridin. Synthetic glabridin enantiomers were separated by semi-preparative Sumi-chiral column chromatography, and characterized by UV-Vis and NMR spectroscopy. Three-dimensional molecular structure of glabridin was obtained as equatorial Ph-3 half chair chroman ring from semi-empirical PM3 calculation, and refined by coupling constants in $^1H$ NMR spectrum. Finally, absolute configurations of two enantiomers were determined by circular dichroism spectroscopy based on the empirical helicity rules. Absolute configuration of natural (+)-glabridin was confirmed as (R)-glabridin, as known.

• 대한화학회지
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• 제55권4호
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• pp.581-589
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• 2011

넓은 범위의 온도와 조성 하에 있는 벤젠-톨루엔, 벤젠- 페놀, 벤젠- p-자일렌의 이성분계 기체 혼합물에 대한 점도와 확산계수를 반실험적 반전 방법을 사용하여 예측하였다. 점도와 확산계수에 대한 정확도는 각각 3%와 4% 이내이다.

• 콘크리트학회논문집
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• 제11권3호
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• pp.69-80
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• 1999

The strengthening of reinforced concrete structures by externally bonded GFRP has become increasingly common in resent years. However the analysis and design method for GFRP plate strengthening of RC beams is not well established yet. The purpose of present paper is, therefore, to define the failure mechanism and failure behavior of strengthened RC beam using GFRP and then to propose a resonable method for the calculation of interface debonding load for those beams. From the experimental results of beams strengthened by GFRP, the influence of length and thickness, width of plate on the interfacial debonding failure behavior of beam is studied and, on the basis of test results, the semi-empirical equation to predict debonding load is developed. The proposed theory based on nonlinear analysis and critical flexural crack width, predicts relatively well the debonding failure load of test beams and may be efficiently used in the analysis and design of strengthened RC beams using GFRP.

• Bulletin of the Korean Chemical Society
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• 제21권5호
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• pp.465-470
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• 2000

The conformations and energies of p-tert-butylcalix[4] crown-6-ether (1) and its alkyl ammonium complexes have been simulated by AM1 semi-empirical quantum mechanics and molecular mechanics calculations using a variety of forcefields (MM2, MM+, CVFF). We performed molecular dynamics calculations to simulate the behavior of these coplexes primartily focusing on the three representative conformations (cone, partial cone, 1,3-alternate) of host molecule 1. When we performed AM1 semi-empirical and molecular mechanics calculations, the one conformation was generally found to be most stable for all the employed calculation methods. The primary binding site of host 1 for the recognition of alkyl ammonium guests was confirmed to be the central part of the crown moiety. The complexation enthalpy calculations revealed that the alkyl amonium cations having smaller and linear alkyl group showed the better complexation efficiencies when combined with p-tert-butylcalix[4]crown-6-ether, that is in satisfactory agreement with the experimental results.