• Korean Journal of Mathematics
• /
• 제23권4호
• /
• pp.503-519
• /
• 2015

In this work, certain classes of admissible functions are considered. Some strong dierential subordination and superordination properties of analytic functions associated with new generalized derivative operator $B^{{\mu},q,s}_{{\lambda}_1,{\lambda}_2,{\ell},d}$ are investigated. New strong dierential sandwich-type results associated with the generalized derivative operator are also given.

• 대한수학회보
• /
• 제40권1호
• /
• pp.77-83
• /
• 2003

In this paper, we study the strong Perron integral, and show that the strong Perron integral is equivalent to the McShane integral.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제5권4호
• /
• pp.310-315
• /
• 2005

This paper proposes a fast optimization method by combining queen-bee evolution and derivative evaluation in genetic algorithms. These two operations make it possible for genetic algorithms to focus on highly fitted individuals and rapidly evolved individuals, respectively. Even though the two operations can also increase the probability that genetic algorithms fall into premature convergence phenomenon, that can be controlled by strong mutation rates. That is, the two operations and the strong mutation strengthen exploitation and exploration of the genetic algorithms, respectively. As a result, the genetic algorithm employing queen-bee evolution and derivative evaluation finds optimum solutions more quickly than those employing one of them. This was proved by experiments with one pattern matching problem and two function optimization problems.

• 한국전산구조공학회논문집
• /
• 제29권3호
• /
• pp.237-244
• /
• 2016

본 연구는 재료비선형 문제를 다루기 위한 비선형 MLS 차분법의 정식화 과정을 제시한다. MLS 차분법은 절점모델을 기반으로 고속 미분근사식을 활용하여 지배 미분방정식을 직접 이산화 하는데, 변수를 변위로 일원화한 Navier 방정식을 사용하여 탄성재료 문제를 다룬 기존의 MLS 차분법은 재료의 구성방정식을 별도로 고려할 수 없다. 본 연구에서는 비선형 재료의 구성방정식을 반영할 수 있는 강정식화를 위해 1차 미분근사를 반복 사용하는 겹미분근사를 고안했다. 응력의 발산으로 표현되는 평형방정식을 그대로 이산화하고 Newton 방법을 적용하여 반복계산을 통해 수렴해를 찾는 비선형 알고리즘을 제시했다. 응력 계산과 내부변수의 갱신은 return mapping 알고리즘을 활용하였고, 알고리즘 접선계수(algorithmic tangent modulus)의 적용을 통해 빠르고 안정적인 반복계산이 가능하도록 하였다. 재생성 시험을 통해 겹미분근사의 정당성을 검증했고, 비선형재료에 대한 인장문제의 해석을 통해 개발된 비선형 MLS 차분 알고리즘의 정확성과 안정성을 확인하였다.

• 한국기계가공학회지
• /
• 제10권2호
• /
• pp.104-109
• /
• 2011

I present a method of aspheric surface profile measurement using 2nd derivative of local area profile. This method is based on the principle of curvature sensor which measures the local 2nd derivative under test along a line. The profile is then reconstructed from the data on the each point. Unlike subaperture-stiching method and slope detection method, 2nd derivative method has strong points from a geometric point of view in measuring the aspheric surface profile. The second derivative terms of surface profile is an intrinsic property of the test piece, which is independent of its position and tip-tilt motion. The curvature is measured at every local area with high accuracy and high lateral resolution by using White-light scanning interferometry.

• 약학회지
• /
• 제43권1호
• /
• pp.28-32
• /
• 1999

Four derivatives of kojic acid were synthesized and their inhibitory activities against tyrosinase were evaluated. The C-2 hydroxymethyl and C-7 hydroxyl of kojic acid were replaced by carboxylate and amine, respectively. These derivatives were coupled to L-phenylalanine, producing two amide compounds. The carboxylate derivative (3), its amide compound (5), and the amine derivative (7) were weak inhibitors. The amide compound (9) where amine derivative (7) coupled to L-phenylalanine showed strong inhibitory activity ($IC_{50}=24.6{\;}{\mu}M$) comparable to kojic acid.

• 대한수학회논문집
• /
• 제20권2호
• /
• pp.291-297
• /
• 2005

In this paper, we introduce the SP-integral and the $SP_\alpha-integral$ defined on an interval in the n-dimensional Euclidean space $\mathbb{R}^n$. We also investigate the relationship between these two integrals.

• Steel and Composite Structures
• /
• 제21권6호
• /
• pp.1389-1410
• /
• 2016

This paper proposes a hybrid of topological derivative-based level set method (LSM) and isogeometric analysis (IGA) for structural topology optimization. In topology optimization a significant drawback of the conventional LSM is that it cannot create new holes in the design domain. In this study, the topological derivative approach is used to create new holes in appropriate places of the design domain, and alleviate the strong dependency of the optimal topology on the initial design. Furthermore, the values of the gradient vector in Hamilton-Jacobi equation in the conventional LSM are replaced with a Delta function. In the topology optimization procedure IGA based on Non-Uniform Rational B-Spline (NURBS) functions is utilized to overcome the drawbacks in the conventional finite element method (FEM) based topology optimization approaches. Several numerical examples are provided to confirm the computational efficiency and robustness of the proposed method in comparison with derivative-based LSM and FEM.

• 충청수학회지
• /
• 제15권2호
• /
• pp.41-46
• /
• 2003

In this paper, we investigate the $SP_{\alpha}$-integral and the $M_{\alpha}$-integral defined on an interval of the n-dimensional Euclidean space $\mathbb{R}^n$. In particular, we show that these two integrals are equivalent.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
• /
• pp.583-590
• /
• 2002

Point collocation method based on the fast derivatives approximation of meshfree shape function is applied to solid mechanics in this study. Enhanced meshfree approximation with approximated derivative of shape function is reviewed, and formulation of linear elastic solid mechanics by point collocation method is presented. It implies that governing equation of solid mechanics with strong form is directly formulated without no numerical integration cells or grid. The regularity of weight function is not required due to a use of approximated derivative, so we propose the exponential type weight function that is discontinuous in first derivative. The convergence and stability of the proposed method is verified by passing the generalized patch test. Also, the efficiency and applicability of the proposed method in solid mechanics is verified by solving types of solid problems. Numerical results show that not only a use of proposed weight function leads lower error and higher convergence rate than that of the conventional weight functions, but also the improved collocation method with derivative approximation enables to compute the derivatives of shape function very fast and accurately enough to replace the classical direct derivative calculation.