• Journal of applied mathematics & informatics
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• 제34권5_6호
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• pp.495-508
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• 2016

A singularly perturbed reaction-diffusion fourth-order ordinary differential equation(ODE) with discontinuous source term is considered. Due to the discontinuity, interior layers also exist. The considered problem is converted into a system of weakly coupled system of two second-order ODEs, one without parameter and another with parameter ε multiplying highest derivatives and suitable boundary conditions. In this paper a computational method for solving this system is presented. A zero-order asymptotic approximation expansion is applied in the second equation. Then, the resulting equation is solved by the numerical method which is constructed. This involves non-overlapping Schwarz method using Shishkin mesh. The computation shows quick convergence and results presented numerically support the theoretical results.

• Korean Journal of Mathematics
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• 제31권2호
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• pp.189-201
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• 2023

In this article, we establish Hilbert-type integral inequalities with the help of a non-homogeneous kernel of hyperbolic function with best constant factor. We also study the obtained inequalities's equivalent form. Additionaly, several specific Hilbert's type inequalities with constant factors in the term of the rational fraction expansion of higher order derivatives of cotangent and cosine functions are presented.

• 한국해양공학회지
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• 제31권3호
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• pp.189-195
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• 2017

A three-dimensional higher order boundary element method based on the B-spline is presented. The method accurately models piecewise continuous bodies and induced velocity potentials using B-spline tensor product representations, and it is capable of obtaining accurate pointwise values for the potential and its derivatives, especially in the trailing edge and tip region of the lift generating body, which may be difficult or impossible to evaluate with constant panel methods. In addition, we implement a wake roll-up and examine the tip vortex formation in the near wake region. The results are compared with existing numerical results and the results of experiments performed out at the cavitation tunnel of Chungnam National University.

• Interaction and multiscale mechanics
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• 제2권4호
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• pp.333-352
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• 2009

We introduce a radial basis collocation method to solve axially moving beam problems which involve $2^{nd}$ order differentiation in time and $4^{th}$ order differentiation in space. The discrete equation is constructed based on the strong form of the governing equation. The employment of multiquadrics radial basis function allows approximation of higher order derivatives in the strong form. Unlike the other approximation functions used in the meshfree methods, such as the moving least-squares approximation, $4^{th}$ order derivative of multiquadrics radial basis function is straightforward. We also show that the standard weighted boundary collocation approach for imposition of boundary conditions in static problems yields significant errors in the transient problems. This inaccuracy in dynamic problems can be corrected by a statically condensed semi-discrete equation resulting from an exact imposition of boundary conditions. The effectiveness of this approach is examined in the numerical examples.

• 한국건설관리학회논문집
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• 제11권2호
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• pp.54-63
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• 2010

국내 외 경기 침체의 영향으로 국내 건설업체들은 자금조달의 어려움을 겪고 있다. 이러한 경기 침체기에 자금의 유동화와 건설경기의 활성화를 촉진할 수 있는 리츠 제도가 2001년에 도입되어 점차 확대되고 있지만, 비슷한 시기에 도입한 다른 나라에 비해 성장속도 및 시장규모가 작은 편이다. 본 연구에서는 리츠의 활성화를 위하여 보다 높은 수익률 확보를 위한 포트폴리오 구성 방법으로, 마코위츠 포트폴리오 선정 모형을 적용한 리츠 투자 포트폴리오 구성 방법에 대해 제안하고자 한다. 주요 내용은 다음과 같다. 첫째, 2007년 7월 3일부터 2008년 7월 21일까지의 투자분석기간 동안 마코위츠 모형을 적용한 리츠의 투자결과와 비교대상 리츠들의 평균 수익률을 비교하여 수익률 향상정도를 분석하였다. 그 결과 마코위츠 모형을 적용한 수익률이 비교대상 리츠들의 평균 수익률보다 약 10% 높게 나타났다. 둘째, 기존 수익률의 자료 수집기간과 포트폴리오 교체주기에 대한 민감도 분석을 하여, 최적의 수익률을 나타낼 수 있는 자료 수집기간과 포트폴리오 교체주기를 도출하였다. 수익률 자료 수집기간이 6개월 일 때 비교대상 리츠들의 평균 수익률보다 마코위츠 모형을 적용한 수익률이 약 16% 높게 나타났으며, 포트폴리오 교체주기를 2주 간격으로 설정하였을 때는 약 11% 높게 나타났다.

• Steel and Composite Structures
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• 제23권1호
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• pp.41-51
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• 2017

A $C^0$ FE model developed based on an efficient higher order zigzag theory is used for hygrothermal analysis of laminated composite plates. The $C^0$ FE model satisfies the inter-laminar shear stress continuity at the interfaces and zero transverse shear stress conditions at plate top and bottom. In this model the first derivatives of transverse displacement have been treated as independent variables to circumvent the problem of $C^1$ continuity associated with the above plate theory. In the present theory the above mentioned $C^0$ continuity of the present element is compensated in the stiffness matrix formulation by using penalty parameter approach. In order to avoid stress oscillations observed in the displacement based finite element, the stress field derived from temperature/moisture fields (initial strains) must be consistent with total strain field. Special steps are introduced by field consistent approach (e.g., sampling at gauss points) to compensate this problem. A nine noded $C^0$ continuous isoparametric element is used in the proposed FE model. Comparison of present numerical results with other existing solutions shows that the proposed FE model is efficient, accurate and free of locking.

• 대한조선학회논문집
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• 제39권1호
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• pp.8-15
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• 2002

B-spline을 이용하여 물체의 형상과 포텐셜을 표현함으로써, 저차경계요소법의 단점들을 극복하고 수치계산의 정도를 높이기 위한 고차 패널법을 개발하였다. 물체표면과 자유표면에 법선 다이폴과 쏘스를 분포시켰으며, 자유표면 및 방사조건을 만족시키기 위해 상류차분식을 사용하는 대신 B-spline의 기저함수를 미분하여 선형화된 자유표면 경계조건에 직접 적용하였다. 이 방법을 적용함으로써 Dawson 방법에서 문제가 되었던 수치감쇠 문제를 피할 수 있었다. 수치계산 프로그램을 검증하기 위해 2차원 원주주위의 유동계산과 날개면 주위의 유동해석을 수행하였으며, B-spline 기저 고차패널법에 의한 수치계산 결과가 저차패널법에 비해 빠른 수렴성과 정확성을 보였고 계산에 필요한 패널 수가 현저히 줄어드는 대단히 만족스러운 결과를 얻었다.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1355-1360
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• 2010

In order to search new inhibitors against farnesyl protein transferase (FPTase), a series of 2,3-bis-benzylidenesuccinaldehyde derivatives (1-29) were synthesized and their inhibition activities ($pI_{50}$) against FPTase were measured. From based on the reported results that the inhibitory activities of dimers 2,3-bis-benzylidenesuccinaldehydes were higher than those of monomers cinnamaldehydes, 3D-QSARs on FPTase inhibitory activities of the dimers (1-29) were studied quantitatively using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods. The statistical qualities of the optimized CoMFA model II ($r^2{_{cv.}}$= 0.693 and $r^2{_{ncv.}}$= 0.974) was higher than those of the CoMSIA model II ($r^2{_{cv.}}$ = 0.484 and $r^2{_{ncv.}}$ = 0.928). The dependence of CoMFA models on chance correlations was evaluated with progressive scrambling analyses. And the inhibitory activity exhibited a strong correlation with steric factors of the substrate molecules. Therefore, from the results of graphical analyses on the contour maps and of predicted higher inhibitory active compounds, it is suggested that the structural distinctions and descriptors that contribute to inhibitory activities ($pI_{50}$) against FPTase will be able to applied new inhibitor design.

• Fisheries and Aquatic Sciences
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• 제4권4호
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• pp.229-237
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• 2001

In order to identify of volatile flavor compounds and polycyclic aromatic hydrocarbons (PAHs) in commercial liquid smokes, this study was conducted to analyze volatile flavor compounds by solvent extraction and/or Purge & Trap method/GC/MSD. A total of 156 volatile flavor compounds were detected in 6 commercial liquid smokes, and these compounds were composed mainly of 12 aldehydes, 60 ketones, 7 alcohols, 14 acids, 20 esters, 24 aromatic compounds, 7 furans and 12 miscellaneous compounds. Ketones $(806.6-7,573.9\mu g/mL)$ and aromatic compounds $(282.6-7,896.3 \mu g/mL)$ were more abundant than others. The PAHs known as carcinogen have not been detected in this study. The acids $(422.9-4,903.1\mu g/mL)$ was identified in relatively high concentration compared to other groups. Phenol and its derivatives among aromatic compounds were in relatively high concentration. Especially, the phenol and its derivatives including o-cresol, guaiacol, 4-ethylguaiacol and syringol were in higher concentration.

• 환경생물
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• 제23권4호
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• pp.379-382
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• 2005

The new cationic meso-substituted N-quarternized 4-pyridylporphyrins and their metal derivatives were synthesized as novel chemotherapeutics. The level of DNA damage induced by porphyrins TOBut4PyP, TOBut4PyP, TOEt4PyPMn and TOBut4PyPMn and its dependence on the chemical structure of compounds were analyzed by the Comet-assay. On the base of data obtained, the investigated porphyrins may be arranged by their genotoxic activity in the following order: TOEt4PyP>TOEt4PyPMn>TOBut4PyP>TOBut4PyPMn. Thus, i) the genotoxicity of the Mn-derivatives of TOEt4PyP and TOBut4PyP is higher than the original porphyrins and ii) the genotoxicity of TOEt4PyP and TOEt4PyPMn is increased after substitution of a butyl radical for ethyl one. The applied Comet-assay permits to reveal the dependence of DNA damage induction on the chemical structure of porphyrins.