• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.413-414
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• 2008

Abstract should be in English. The leaning angle optimization of turbine blade using the genetic algorithm was conducted in this paper. The calculation CFD technique was based upon the Diagonalized Alternating Directional Implicit scheme(DADI) with algebraic turbulencemodeling. The leaning angle of VKI turbine blade was represented using B-spline curve. The control points are the design variable. Genetic algorithm was taken into account as an optimization tool. The objective was to minimize the total pressure loss. The optimized final geometry shows the better aerodynamic performance compared with the initial turbine blade.

• 한국철도학회논문집
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• 제6권4호
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• pp.294-299
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• 2003

Using a conventional railway, a tilting train was applied as a means of improving vehicle speed during curve negotiation without any modification of infrastructure. As a study for the optimum design of the tilting mechanism of a tilting vehicle, the kinematics sensitivity of the tilting mechanism was analyzed. Using the geometric relationship of the linkage-type tilting mechanism, the relationship of the parameters and the performance index was defined using nonlinear algebraic equations. With the defined relation, the effect of change in the parameters on the performance was analyzed. The analysis result can be used in the optimum design of a tilting mechanism that considers the track environment, vehicle and operational condition in which the tilting vehicle is applied.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제24권3호
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• pp.305-320
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• 2020

This study aims to generalize MINRES-N2 method [1]. It means that we tend to obtain an algorithm to transfer each normal matrix - that its eigenvalues belong to an algebraic curve of low degree k- to its condensed form through using a unitary similarity transformation. Then, we aim to obtain a method to solve a system of linear equations that its coefficient matrix is equal to such a matrix by utilizing it. Finally this method is compared to the well-known GMRES method through using numerical examples. The results obtained through examples show that the given method is more efficient than GMRES.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.686-689
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• 2008

The leaning angle optimization of turbine blade using the genetic algorithm was conducted in this paper. The calculation CFD technique was based upon the Diagonalized Alternating Directional Implicit scheme(DADI) with algebraic turbulence modeling. The leaning angle of VKI turbine blade was represented using B-spline curve. The control points are the design variable. Genetic algorithm was taken into account as an optimization tool. The objective was to minimize the total pressure loss. The optimized final geometry shows the better aerodynamic performance compared with the initial turbine blade.

• 수산해양기술연구
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• 제27권1호
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• pp.75-82
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• 1991

어선의 초기 설계 단계에서 필요한 초기선형의 선수미부 생성을 위하여 B-spline 곡선과 형상계수를 결합한 방법을 적용하였다. 선수미부의 각부분에 대하여 선형별로 형상계수를 선정한 뒤 이를 이용하여 B-spline 곡선의 정점을 구하도록 하였다. 선수부분의 경우 bulbous bow를 가지는 경우와 그렇지 않는 것으로 크게 분류한 뒤 bulbous bow를 가지는 경우는 수선면 근처의 형상에 따라 2가지로 분류하였다. 수선면보다 윗부분에 대해서는 bulbuos bow와는 무관하므로 이의 유무에 상관없이 직선으로 갑판까지 가는 경우와 곡선을 가지는 경우로 분류하여 다루었다. 선미부분의 경우는 수선면 윗부분은 transom stern과 cruiser stern으로 분류하였으며 수선면이하의 부분은 선미 bulb를 가진 선형과 shoe piece를 가진 선형으로 분류하여 다루었다. 형상계수는 각 경우에 따라 반드시 지켜야 할 점의 좌표와 기울기 등이 우선 선정되었으며 곡선부의 볼록한 정도를 조절해 주는 계수들이 선정되었다. 형상계수를 이용하여 곡선을 생성시킬 기법으로는 다항식, cubic spline, parabolic blending, bezier curve, non-algebraic function 등이 있으나 연속성이 충분히 보장되고, 국부적으로 변형이 가능하며, 불연속점이 정의 및 직선의 표현이 가능한 B-spline을 선택하였다

• 호남수학학술지
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• 제36권3호
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• pp.695-706
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• 2014

Various properties of digital covering spaces have been substantially used in studying digital homotopic properties of digital images. In particular, these are so related to the study of a digital fundamental group, a classification of digital images, an automorphism group of a digital covering space and so forth. The goal of the present paper, as a survey article, to speak out utility of digital covering theory. Besides, the present paper recalls that the papers [1, 4, 30] took their own approaches into the study of a digital fundamental group. For instance, they consider the digital fundamental group of the special digital image (X, 4), where X := $SC^{2,8}_4$ which is a simple closed 4-curve with eight elements in $Z^2$, as a group which is isomorphic to an infinite cyclic group such as (Z, +). In spite of this approach, they could not propose any digital topological tools to get the result. Namely, the papers [4, 30] consider a simple closed 4 or 8-curve to be a kind of simple closed curve from the viewpoint of a Hausdorff topological structure, i.e. a continuous analogue induced by an algebraic topological approach. However, in digital topology we need to develop a digital topological tool to calculate a digital fundamental group of a given digital space. Finally, the paper [9] firstly developed the notion of a digital covering space and further, the advanced and simplified version was proposed in [21]. Thus the present paper refers the history and the process of calculating a digital fundamental group by using various tools and some utilities of digital covering spaces. Furthermore, we deal with some parts of the preprint [11] which were not published in a journal (see Theorems 4.3 and 4.4). Finally, the paper suggests an efficient process of the calculation of digital fundamental groups of digital images.

• 대한토목학회논문집
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• 제29권4D호
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• pp.555-561
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• 2009

굴착된 터널 형상 재현에서 단면의 종단 데이터는 터널의 유지를 위해서는 아주 중요하다. 터널이 완성되기전에 설계된 모델을 고려한 완성된 터널의 변형이 고려되어져야 한다. 그리고 변형은 터널 단면 전체를 따라 연속적으로 나타날 수 있다. 본 연구에서는 먼저 수학적 분석으로 접근하였고, 그것을 관측된 터널단면 데이터에 실험 하였다. 그 다음 선추적 방법, 유전자 알고리즘, 패턴 추적 방법 등으로 3D 터널 형상 재현을 비교하였다. 수학적 방법론은 철도 터널과 같은 간단한 원통형은 쉽게 해결이 되었으나, 도로터널과 같은 더욱 복잡한 모델(복심 곡선형과 비원통형)은 구속된 상태하에서 소프트 컴퓨팅 툴을 가지고 해결할 수 있었다. 유전자 알고리즘과 직접탐색법은 많은 계산 시간이 걸렸으나 복잡한 상태하에서 더욱 유연함을 보였으며, 선추적 방법은 초기값들이 제한된 범위 하에서 가장 빠르게 계산되어졌다.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.92-105
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• 2004

A new algorithm for planning a collision-free path based on algebraic curve is developed and the concept of collision-free Path Space (PS) is introduced. This paper presents a Geometry Mapping (GM) based on two straight curves in which the intermediate connection point is organized in elliptic locus ($\delta$, $\theta$). The GM produces two-dimensional PS that is used to create the shortest collision-free path. The elliptic locus of intermediate connection point has a special property in that the total distance between the focus points through a point on ellipse is the same regardless of the location of the intermediate connection point on the ellipse. Since the radial distance, a, represents the total length of the path, the collision-free path can be found as the GM proceeds from $\delta$=0 (the direct path) to $\delta$=$\delta$$\_$max/(the longest path) resulting in the minimum time search. The GM of elliptic workspace (EWS) requires calculation of interference in circumferential direction only. The procedure for GM includes categorization of obstacles to .educe necessary calculation. A GM based on rectangular workspace (RWS) using Cartesian coordinate is also considered to show yet another possible GM. The transformations of PS among Circular Workspace Geometry Mapping (CWS GM) , Elliptic Workspace Geometry Mapping (EWS GM) , and Rectangular Workspace Geometry Mapping (RWS GM), are also considered. The simulations for the EWS GM on various computer systems are carried out to measure performance of algorithm and the results are presented.

• Advances in Energy Research
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• 제7권2호
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• pp.85-100
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• 2020

Distributed energy resources (DERs) are essential for coping with growing multiple energy demands. A microgrid (MG) is a small-scale version of the power system which makes possible the integration of DERs as well as achieving maximum demand-side management utilization. Hence, this study focuses on the analysis of optimal power dispatch considering economic aspects in a multi-carrier microgrid (MCMG) with price-responsive loads. This paper proposes a novel time-based demand-side management in order to reshape the load curve, as well as preventing the excessive use of energy in peak hours. In conventional studies, energy consumption is optimized from the perspective of each infrastructure user without considering the interactions. Here, the interaction of energy system infrastructures is considered in the presence of energy storage systems (ESSs), small-scale energy resources (SSERs), and responsive loads. Simulations are performed using GAMS (General Algebraic modeling system) to model MCMG, which are connected to the electricity, natural gas, and district heat networks for supplying multiple energy demands. Results show that the simultaneous operation of various energy carriers, as well as utilization of price-responsive loads, lead to better MCMG performance and decrease operating costs for smart distribution grids. This model is examined on a typical MCMG, and the effectiveness of the proposed model is proven.

• 한국통신학회논문지
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• 제30권5A
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• pp.426-435
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• 2005

본 논문에서는 기존의 무선 PKI(Public Key Infrastructure)에서 개선되어야 할 여러 가지 사항 중에서 핸드오버시 인증서 획득시간을 단축하기 위한 새로운 인증구조에서의 블러킹 확률 분석을 알아보고자 한다. 기존의 키 교환방식에서 키 교환 설정단계가 단순히 이산대수문제에 근거하여 수행되었지만 인증서 시간단축을 위한 무선 PKI 인증구조의 상호인증과정에서는 키 교환 설정단계에서 타원곡선을 적용하였다. 제안한 무선 PKI 구조 안에서의 핸드오버 방법과 블러킹 확률 분석에 대하여 알아보았다. 핸드오버 방법은 CRL(Certification Revocation List) 검색시간을 단축시킬 수 있으므로 기존의 방법에 비하여 단축된 핸드오버 처리시간을 보여준다. 기존 알고리즘과 제안한 인증구조를 비교하여 실험해 보았을 때 호 도착율, 큐의 서비스율, 큐 사이즈 변화에 관계없이 제안한 인증 기법이 모든 환경에서 기존 알고리즘보다 우수한 성능을 보였다.