• International Journal of Aeronautical and Space Sciences
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• 제4권2호
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• pp.1-8
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• 2003

Satellite formation flying is the placing micro-satellites with the same mission into nearby orbits to form a cluster. Clohessy-Wiltshire equations are used to describe the relative motion and control strategies between satellites within a cluster, which are known as Hill's equations. Even though Hill's equations are powerful in determining initial conditions for the satellite formation flying, they can not accurately express the relative motion under J2 perturbation. Some methods have been developed for the determination of initial conditions to avoid limits of Hill's equation. This paper gives a new method of determining initial conditions using mean elements. For this research mean elements were transformed to osculating elements using Brouwer's theory and the orbit was propaeated with the consideration of J2-J8 to get a relative position. The results show that satellites within a cluster are maintained in the desired boundary for long period and the method is effective on a fuel saving for satellite formation flying.

• 대한조선학회지
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• 제24권1호
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• pp.51-66
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• 1987

In this paper, the authors investigate theoretically the motion and longitudinal strength of ships among waves talking account of the effects of nonlinearities such as the hull shape, bottom emergence, and hydrodynamic impact. Incidentally the ship is treated as an elastic beam in heading wave condition regarding characteristics of slamming and whipping-according to the variation in the range of a quarter length of the ship forward and the increase of the elastic modes up to 4-th vibration mode were investigated by the present theory. Calculations are performed for 97m container ship and its validity is confirmed by a series of model tests. Conclusions obtained are as follows; 1) Acceleration and pressure estimated by the present theory are in good accordance with experiments. 2) The present non-linear theory may be applied for estimating longitudinal bending moment of ships in slamming and whipping conditions. 3) In investigation of the characteristic in response according to shape variation for parts under draft and vow-flare in the range of a quarter length of the ship forward, dynamic responses due to the former were much more conspicuous than those due to the later. 4) In the maximum bending moment, the considering case up to 2-the mode are larger, about $10{\sim}15%$, than that up to 4-th mode.

• 디자인학연구
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• 제12권2호
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• pp.185-196
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• 1999

문학, 건축 순수미술, 영화 산업디자인 등 다양한 분야에서 영향을 마치고 있는 해체주의(Deconstruction)는 디자인 분야에도 다양한 양상으로 나타나고 있고 그 보여지는 모습도 매우 광범위하며 표현에 있어서도 많은 잠재성을 가지고 있다. 해체주의 디자인은 포스트 모던한 상황과 다원화된 후기 산업사회, 데리다(J. Derrida)의 해체 이론과의 관계성을 통해 접근하고 있다. 특히 기호와 텍스트로 커뮤니케이션 하는 타이포그래피와 시각 디자인 분야는 해체 철학의 영향을 받을 수밖에 없다. 본 연구는 이러한 철학적 영향을 받고 있는 해체 타이포그래피 스타일의 변화를 분석하고 그 특성을 도출함으로써 해체 철학이 타이포그래피에 실제적으로 어떻게 적용되고 있는지 고찰하고자 한다.

• 대한조선학회지
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• 제18권3호
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• pp.29-38
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• 1981

In general the drift result in ship heeling, thus it seems to be necessary to analyze the ship motion by considering both the drifting and heeling phenomena. In this paper, a drift velocity and a heeling angle are given as prior conditions, and then within the linear potential theory the hydrodynamic coefficients and wave exciting forces and moments are derived for a ship advancing and drifting with constant speeds. And numerical calculations are preformed for a cylindrical body of shiplike cross section at zerp forward velocity. The 2-D hydrodynamic forces and moments of a heeled cylinder are calculated by using the Frank Close-Fit method. These numerical results for the oscillating cylinder without drift velocity have shown better agreements with experimental data than the numerical results of Kobayashi[2]. The motion responses for a drifting cylinder are calculated ignoring the drift velocity effect in the free surface condition. The accuracy of these calculations can not be verified, because the experimental data are not available. Through these numerical calculations to so concluded that drift velocity effects on the body motion are signiffcant.

• 소성∙가공
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• 제16권2호
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• pp.138-143
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• 2007

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a 3-D rigid visco-plastic finite element method. A constant-triangular element based on membrane approximation and an incremental theory of plasticity are employed for the formulation. The coulomb friction law is used for interface friction between tool and material. Pressure-time relationship for a given optimal strain rate is calculated by stress and pressure values at the previous iteration step. In order to improve the contact searching, hierarchical search algorithm has been applied and implemented into the code. Various geometries including sandwich panel and 3 sheet shape for 3-D SPF/DB model are analyzed using the developed program. The validity fer the analysis is verified by comparison between analysis and results in the literature.

• Journal of Computing Science and Engineering
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• 제2권3호
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• pp.221-248
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• 2008

Data provenance is the background knowledge that enables a piece of data to be interpreted and used correctly within context. The importance of tracking provenance is widely recognized, as witnessed by significant research in various areas including e-science, homeland security, and data warehousing and business intelligence. In order to further advance the research on data provenance, however, one must first understand the research that has been conducted to date and identify specific topics that merit further investigation. In this work, we develop a framework based on semiotics theory to assist in analyzing and comparing existing provenance research at the conceptual level. We provide a detailed review of data provenance research and compare and contrast the research based on d semiotics framework. We conclude with an identification of challenges that will drive future research in this field.

• 논리연구
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• 제19권2호
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• pp.185-232
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• 2016

선결문제 요구의 오류가 왜 오류라고 할 수 있는지를 설명하기 위해서는 몇 가지 과제가 해결되어야 한다. 우선 우리는 선결문제 요구의 오류가 무엇인지를 섬세한 방식으로 이해하고 규명할 필요가 있다. 또한 그렇게 이해된 선결문제 요구의 오류가 왜 오류인지에 대해 설명하기 위해서는 논증 자체의 본성과 목적에 대해 성찰해야 할 필요가 있다. 이 논문에서 필자는 우선 논증의 주된 목적이 무엇인가에 대해 일반적 제안을 한 후에, 선결문제 요구의 오류를 이해하고 규정하기 위해서 이전 논문에서 제시했었던 다층적 이론을 논증 자체의 주된 목적에 대한 이 논문의 제안의 맥락속에 자리 잡게 해서, 그로부터 선결문제 요구의 오류가 왜 잘못이고 오류인지에 대한 설명들을 이끌어내기 위한 논의를 전개한다. 그리고 선결문제 요구의 오류가 어떻게 이해되어야 하는가, 그리고 그것이 왜 오류인가의 문제에 대한 기존의 주요 이론들-잭슨(F. Jackson), 월튼(D. Walton), 샌포드(D. Sanford), 바이로(J. Biro)의 이론들-을 검토하고 그 기존 이론들이 어떤 문제점들을 지니는지에 대해 비판적 고찰을 한다.

• Structural Engineering and Mechanics
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• 제11권5호
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• pp.547-564
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• 2001

The numerical formulation of a two-phase interface element appropriate for porous lining system is presented. The formulation is isoparametric and can be applied both for 2-D and 3-D analysis. Biot's theory is utilized as the basis for the development of the element constitutive theory. In order to be capable of simulating the reinforcing characteristics of some geotextiles utilized as lining system, a reinforcement component has also been implemented into the formulation. By employing this specially developed interface finite element, the influence of soil consolidation on the stress distribution along the lining system of a reservoir and a landfill has been investigated.

• Journal of Ship and Ocean Technology
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• 제1권2호
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• pp.1-10
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• 1997

The prediction of the total resistance of a ship is generally based on considering it to be a simple sum of the viscous resistance and the wave resistance. An experimental approach for predicting full-size ship resistance on this basis is practical but obviously has the deficiency that a model has to be built for each prototype of interest and the resulting tank tests are time consuming. On the other hand, purely theoretical calculations of the wave resistance, using, for example, the Michell theory, require relatively little computer time and give an excellent portrayal of the overall variation of the vessel resistance as a function of forward speed. Unfortunately, there are sufficient differences between this theory and the measured results to make this method impractical for design purposes. The proposal examined here is to use a data bank of experimental resistance results to modify the theoretical predictions. It is demonstrated that the technique will produce remarkably accurate resistance predictions and can take into account the effects of the water depth, any restriction of canal or river width, as well as the prismatic coefficient, and other geometric parameters.

• Kyungpook Mathematical Journal
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• 제46권2호
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• pp.261-271
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• 2006

In this paper, we investigate and characterize the class of A-semirings. A characterization of the Thierrin radical of a proper ideal of an A-semiring is given. Moreover, when P is a Q-ideal in the semiring R, it is shown that P is primary if and only if R/P is nilpotent.