• 대한조선학회논문집
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• 제59권2호
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• pp.96-108
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• 2022

In this paper, we propose a systematic hull form variation technique which automatically satisfies the displacement constraint and guarantees a high level of fairness. This method is possible through multiple parameter correction curves. The present method is to improve the hull form variation method based on parametric modification function and consists of two sub-categories: SAC variation and section lines modification. For SAC variation, the utilization of two B-Spline curves satisfying GC¹ condition led to the satisfaction of displacement constraint and high level of fairness at the same time. Section lines modification methods involves in using two fuctions: the first is the waterplane modification function combining two cubic splines. the other function is the sectional area modification function consisting of 2nd order polynomial over the DLWL(Design Load Waterline) and 3rd order polynomial below the DLWL, This function enables not only the fundamental U-V section shape variation but also systematically modified section lines. The present method is expected to be more useful in the hull form optimization process using CFD compared to the existing method.

• Wind and Structures
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• 제14권2호
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• pp.85-112
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• 2011

Wind turbine structures are long slender columns with a rotor and blade assembly placed on the top. These slender structures vibrate due to dynamic environmental forces and its own dynamics. Analysis of the dynamic behavior of wind turbines is fundamental to the stability, performance, operation and safety of these systems. In this paper a simplied approach is outlined for free vibration analysis of these long, slender structures taking the soil-structure interaction into account. The analytical method is based on an Euler-Bernoulli beam-column with elastic end supports. The elastic end-supports are considered to model the flexible nature of the interaction of these systems with soil. A closed-form approximate expression has been derived for the first natural frequency of the system. This new expression is a function of geometric and elastic properties of wind turbine tower and properties of the foundation including soil. The proposed simple expression has been independently validated using an exact numerical method, laboratory based experimental measurement and field measurement of a real wind turbine structure. The results obtained in the paper shows that the proposed expression can be used for a quick assessment of the fundamental frequency of a wind turbine taking the soil-structure interaction into account.

• Earthquakes and Structures
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• 제10권1호
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• pp.25-51
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• 2016

In this study, graph product rules are applied to the dynamic analysis of regular skeletal structures. Graph product rules have recently been utilized in structural mechanics as a powerful tool for eigensolution of symmetric and regular skeletal structures. A structure is called regular if its model is a graph product. In the first part of this paper, the formulation of time history dynamic analysis of regular structures under seismic excitation is derived using graph product rules. This formulation can generally be utilized for efficient linear elastic dynamic analysis using vibration modes. The second part comprises of random vibration analysis of regular skeletal structures via canonical forms and closed-form eigensolution of matrices containing special patterns for symmetric structures. In this part, the formulations are developed for dynamic analysis of structures subjected to random seismic excitation in frequency domain. In all the proposed methods, eigensolution of the problems is achieved with less computational effort due to incorporating graph product rules and canonical forms for symmetric and cyclically symmetric structures.

• 한국초등수학교육학회지
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• 제17권2호
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• pp.185-205
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• 2013

본 연구에서는 덧셈, 뺄셈, 곱셈, 나눗셈과 직접적으로 연관이 있는 초등학교용 사칙계산 관련 어휘를 획정하기 위하여, 먼저 사칙계산 어휘를 수집하고 그것의 종별, 군별 분류에 관해 논의하였다. 다음으로 기본적인 사칙계산 관련 어휘에 관해 논의하였다. 이때 덧셈, 뺄셈, 곱셈, 나눗셈 관련 어휘가 기본적으로 각각 더하다, 빼다, 곱하다, 나누다의 네 동사에서 비롯된다고 보고, 각각의 어간(즉, 더, 빼, 곱, 나누)을 포함하는 어휘를 기본적인 사칙계산 관련 어휘로 삼았다. 이어 연산을 보조하는 어휘와 연산의 결과를 나타내는 어휘를 그것에 포함시키고, 다음 준거에 맞추어 초등학교용 사칙계산 관련 어휘를 획정하였다. 첫째, 동사의 명사형을 어근으로 한 새로운 동사나 파생어를 사용하지 않는다. 둘째, 편수자료 또는 표준국어대사전에 등재되어 있지만, 교과서/익힘책에 용례가 없거나 드문 어휘는 사용하지 않는다. 셋째, 대체가 불가능한 어휘와 교수학적 이유가 있는 어휘는 사용한다.

• Wind and Structures
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• 제27권3호
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• pp.175-186
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• 2018

With the continuous increase of span lengths, modern bridges are becoming much more flexible and more prone to flutter under wind excitations. A reasonable probabilistic flutter analysis of long-span bridges involving random and uncertain variables may have to be taken into consideration. This paper presents a method for estimating the reliability index and failure probability due to flutter, which considers the very important variables including the extreme wind velocity at bridge site, damping ratio, mathematical modeling, and flutter derivatives. The Aizhai Bridge in China is selected as an example to demonstrate the numerical procedure for the flutter reliability analysis. In the presented method, the joint probability density function of wind speed and wind direction at the deck level of the bridge is first established. Then, based on the fundamental theories of structural reliability, the reliability index and failure probability due to flutter of the Aizhai Bridge is investigated by applying the Monte Carlo method and the first order reliability method (FORM). The probabilistic flutter analysis can provide a guideline in the design of long-span bridges and the results show that the structural damping and flutter derivatives have significant effects on the flutter reliability, more accurate and reliable data of which is needed.

• 한국실내디자인학회논문집
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• 제20권6호
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• pp.291-299
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• 2011

As our lifestyles have changed due to rapid industrialization and urbanization, new social and communication problems have been caused and there have been lots of discussion on regional communication. For communities to become alternatives with realistic meanings in this changed society, considerations on social and spatial conditions are needed. Therefore, public space which works as a device of physical environment for activation of communities needs more active changes which encourages social communication. In respect to the activation of communities, the following suggestions are given: First, physical devices of a urban plaza should be arranged to support various programs presented along with consideration of human behaviors as users. Second, fundamental facilities of the plaza should accommodate various activities through connections with programs and commercial space. Third, when cultural and historical characteristics of the community are understood, the plaza can form regionality and symbolism through artistic representation. And users can form the identity of community. Fourth, transportation facilities should be separated from or coexist with areas of passengers and the plaza should have its own identity through symbolic sculptures.

• 호남수학학술지
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• 제39권3호
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• pp.363-377
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• 2017

In the present study we consider the generalized rotational surfaces in Euclidean spaces. Firstly, we consider generalized spherical curves in Euclidean (n + 1)-space ${\mathbb{E}}^{n+1}$. Further, we introduce some kind of generalized spherical surfaces in Euclidean spaces ${\mathbb{E}}^3$ and ${\mathbb{E}}^4$ respectively. We have shown that the generalized spherical surfaces of first kind in ${\mathbb{E}}^4$ are known as rotational surfaces, and the second kind generalized spherical surfaces are known as meridian surfaces in ${\mathbb{E}}^4$. We have also calculated the Gaussian, normal and mean curvatures of these kind of surfaces. Finally, we give some examples.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.617-622
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• 2001

This paper presents the effectiveness of cold weather concreting by applying both anti-freeze agent and insulating forms developed through previous study investigating insulating effects on the concrete and the strength gain. According to test results, in $-10^{\circ}C$ of air temperature, when euroforms are applied, the temperature of plain concrete drops below $0^{\circ}C$ and maintains its temperature during early 24 hours. However, when insulating forms are applied, the temperature of concrete keeps 8~$13^{\circ}C$ during first 24 hours. Insulating forms has better performance on insulating effects than existing euroforms. Concrete containing anti-freeze agent shows temperature rising effects about $1^{\circ}C$ compared to plain concrete. Strength gain of core concrete shows higher when insulating forms is applied.

• 대한조선학회지
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• 제22권3호
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• pp.19-26
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• 1985

This paper deals with the representation and fairing of ship hull using a B-spline surface which is known as a 3-D model in computer aided free-form design. The first part of this paper is devoted to the fundamental concepts of B-spline theory and its geometrical characteristics. In its second part are described the facillities for efficient application, fast rendering of B-spline surface, and intersection of B-spline surfaces. The examples are presented with actual application to a real ship in the last part. And also a new concept of evaluating the surface fairness by the Gaussian curvature isolines is briefly discussed and its examples are presented.

• 산업기술연구
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• 제24권A호
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• pp.47-57
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• 2004

Industrial efforts for increased market sales have directed towards the development and implementation of on-line marketing systems under recent e-business environment. Internet-based shopping mall is one of the most popular system. A business process model for an intermediary type shopping mall using IDEF0 has been presented in this study. Specific efforts have been focused on defining and analyzing a diversity of business processes embedded in practical B2B and B2C mall system operations. We first briefly examined the considered system with IDEF0 design. We then defined fundamental business processes within shopping mall systems. Upon careful examination and analysis of them, a detailed business process model based on IDEF methodology has been designed. The results in this study may well form a conceptual framework for shopping mall development and operations.