• 대한기계학회논문집A
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• 제37권7호
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• pp.921-927
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• 2013

본 연구는 운용 파라미터의 불확실성을 고려한 착륙장치 완충성능 해석 기법을 제시한다. 실제 운용 환경에서 완충성능에 영향을 미치는 많은 파라미터는 어느 정도의 불확실성을 가지게 되는데, 완충장치 가스 압력과 오일 체적, 타이어 압력, 외부 온도 등을 예로 들 수 있다. 본 연구에서는 Convex Modeling 과 Interval Analysis 기법을 적용하여, 이러한 불확실성이 착륙 시의 지면 반력에 미치는 효과를 해석하였다. 불확실한 파라미터를 고려할 경우, 완충효율 및 구조 건전성에 중요한 영향을 주는 Peak load 가 Deterministic analysis 의 결과보다 크게 증가하였다. 안전성과 신뢰성의 확보를 위해서는 이러한 불확실성을 반영하는 것이 필요하며, 제시한 방법은 이를 효율적으로 처리할 수 있음을 보여준다.

• 대한수학회지
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• 제55권4호
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• pp.833-848
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• 2018

In this paper we study the existence of conditional expectation for closed and convex valued Pettis-integrable random sets without assuming the Radon Nikodym property of the Banach space. New version of multivalued dominated convergence theorem of conditional expectation and multivalued $L{\acute{e}}vy^{\prime}s$ martingale convergence theorem for integrable and Pettis integrable random sets are proved.

• 한국정보통신학회논문지
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• 제12권8호
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• pp.1377-1383
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• 2008

3차원 메쉬 매개변수화는 기하학적 모델링과 컴퓨터그래픽스의 여러 응용분야에서 핵심적인 문제이다. 메쉬 매개변수화 방법에는 크게 두 가지의 패러다임, 에너지 최소화 방법과 볼록 조합법이 있다. 일반적으로 볼록 조합법은 간단한 개념과 일대일 대응 때문에 널리 이용되고 있다. 그러나 이 방법은 경계선 근처의 높은 왜곡이 생긴다는 문제와 선형 시스템 구성에 있어 다소 많은 시간이 소요되는 문제를 가지고 있다. 또한 이 방법은 다루는 메쉬 의 기하학 정보에 따라 선형시스템의 안정성이 해손 될 수도 있다. 본 논문에서는 볼록 조합법이 갖고 있는 선형시스템 안정성 문제와 시간 복잡도 문제를 중간값 좌표계를 이용하여 해결한다. 빠른 시간에 안정적으로 처리가 가능하기 때문에 보다 실용적이라 할 수 있다.

• 대한기계학회논문집A
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• 제25권3호
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• pp.369-380
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• 2001

Although extensive efforts have been devoted to the optimal design of composite laminated plates in recent years, some practical issues still need further research. Two of them are: the handling of the ply angle as either continuous or discrete; and that of the uncertainties in material properties, which were treated as continuous and ignored respectively in most researches in the past. In this paper, an algorithm for stacking sequence optimization which deals with discrete ply angles and that for thickness optimization which considers uncertainties in material properties are used for a two step optimization of composite laminated plates. In the stacking sequence optimization, the branch and bound method is modified to handle discrete variables; and in the thickness optimization, the convex modeling is used in calculating the failure criterion, given as constraint, to consider the uncertain material properties. Numerical results show that the optimal stacking sequence is found with fewer evaluations of objective function than expected with the size of feasible region taken into consideration; and the optimal thickness increases when the uncertainties of elastic moduli considered, which shows such uncertainties should not be ignored for safe and reliable designs.

• International Journal of CAD/CAM
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• 제8권1호
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• pp.29-36
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• 2009

Domain mapping is a bijective transformation of one domain to another, usually from a complicated general domain to a chosen convex domain. This is directly useful in many application problems like shape modeling, morphing, texture mapping, shape matching, remeshing, path planning etc. A new approach considering the domain as made up of structural elements, like membranes or trusses, is developed and implemented using the nonlinear finite element formulation. The mapping is performed in two stages, boundary mapping and inside mapping. The boundary of the 3-D domain is mapped to the surface of a convex domain (in this case, a sphere) in the first stage and then the displacement/distortion of this boundary is used as boundary conditions for mapping the interior of the domain in the second stage. This is a general method and it develops a bijective mapping in all cases with judicious choice of material properties and finite element analysis. The consistent global parameterization produced by this method for an arbitrary genus zero closed surface is useful in shape modeling. Results are convincing to accept this finite element structural approach for domain mapping as a good method for many purposes.

• 한국생산제조학회지
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• 제5권2호
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• pp.20-28
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• 1996

Compound surface modeling is widely used for die cavities and punches. A compound surface is defined in 3-D space by specifying the topological relationship of several anlytic surface elements and a sculptured surface. A constructive solid gemonetry scheme is employed to model the analytic compound surface. the desired compound surface can be accomplished by specifying topological reationship in terms of boolean relations between pimitives and the sculptured surfaces. Additionally, a method is presented for checking and avoiding the tool interference occuued in machining the compound surface. Using this method. the interference of concave, convex, and side region can be checked easily and avoided rpapidly.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.575-580
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• 1992

Mixed H$_{2}$/H$_{\infty}$ robust control synthesis is considered for finite dimensional linear time-invariant systems under the presence of diagonal structured uncertainties. Such uncertainties arise for instance when there is real perturbation in the nominal model of the state space system or when modeling multiple (unstructured) uncertainty at different locations in the feedback loop. This synthesis problem is reduced to convex optimization problem over a bounded subset of matrices as well as diagonal matrix having certain structure. For computational purpose, this convex optimization problem is further reduced into Generalized Eigenvalue Minimization Problem where a powerful algorithm based on interior point method has been recently developed..

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.240-242
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• 2007

The game theoretic analysis in wireless networks can be classified into the jamming game of the physical layer, the multiple access game of the medium access layer, the forwarder's dilemma and joint packet forwarding game of the network layer, and etc. In this paper, the game theoretic analysis about the multiple access game that selfish nodes exist in the IEEE 802.11 DCF(Distributed Coordination Function) wireless networks is addressed. In this' wireless networks, the modeling of the CSMA/CA protocol based DCF, the utility or payoff function calculation of the game, the system optimization (using optimization theory or convex optimization), and selection of Pareto-optimality and Nash Equilibrium in game strategies are the important elements for analyzing how nodes are operated in the steady state of system. Finally, the main issues about the game theory in the wireless network are introduced.

• 한국통신학회논문지
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• 제38A권12호
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• pp.998-1012
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• 2013

The article is concerned with a mathematical modeling which can improve performances of PDE-based restoration models. Most PDE-based restoration models tend to lose fine structures due to certain degrees of nonphysical dissipation. Sources of such an undesirable dissipation are analyzed for total variation-based restoration models. Based on the analysis, the so-called equalized net diffusion (END) modeling is suggested in order for PDE-based restoration models to significantly reduce nonphysical dissipation. It has been numerically verified that the END-incorporated models can preserve and recover fine structures satisfactorily, outperforming the basic models for both quality and efficiency. Various numerical examples are shown to demonstrate effectiveness of the END modeling.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.323-324
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• 2006

This study is described the modeling of aspheric lens, manufacturing and inspection. The aspheric lens is different from a convex lens and concave lens in that is useful to aspherical, but modeling mettled of this isn't open to the public. Therefore, This study is designed to the aspheric lens of geometric form, manufactured a sample by CAM which is applied to Euler method. So, we have verified modeling and CAM process for aspheric lens through a experiment.