• 한국초전도ㆍ저온공학회논문지
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• 제15권1호
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• pp.19-24
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• 2013

In this paper, the Superconductor flywheel energy storage system (SFESS) was used for the load frequency control (LFC) of an interconnected 2 area power system. The robust SFESS controller using quantitative feedback theory (QFT) was designed to improve control performance in spite of parameter uncertainty and unexpected disturbances. An overlapping decomposition method was applied to simplify SFESS controller design for the interconnected 2 area power system. The model for simulation of the interconnected 2 area power system included the reheat steam turbine, governor, boiler dynamics and nonlinearity such as governor deadband and generation rate constraint (GRC). To verify robust performance of proposed SFESS controller, dynamic simulation was performed under various disturbances and parameters variation of power system. The results showed that the proposed SFESS controller was more robust than the conventional method.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권1호
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• pp.51-58
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• 2011

Extensible processors provide an efficient mechanism to boost the performance of the whole system without losing much flexibility. However, due to the intense demand of low cost and power consumption, customizing an embedded system has been more difficult than ever. In this paper, we present a framework for custom instruction generation considering both area constraints and resource sharing. We also present how we can speed up the process through pruning and library-based design space exploration.

• 전자공학회논문지
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• 제52권8호
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• pp.89-96
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• 2015

인간의 시각은 색순응을 통해서 사물의 색을 광원의 색에 영향 없이 인지 할 수 있다. 반면에, 카메라는 입력 값을 그대로 기록하기 때문에, 광원에 따라 물체의 색이 다르게 나타난다. 최근에 희박성 제약조건의 비음수 행렬 분해(nonnegative matrix factorization with sparseness constraint; NMFsc)를 이용한 광원추정 방법이 제안되었다. 이 방법은 낮은 희박성 제약조건을 사용해서 광원을 추정하고, 높은 희박성 제약조건을 사용해서 반사율을 추정한다. 하지만, 희박성 제약조건의 비음수 행렬분해를 이용한 광원 추정 방법은, 영상의 전역적인 정보를 사용하므로, 영상에서 동일한 색이 넓은 영역에 존재하는 경우, 추정된 광원이 큰 오차를 가진다. 이러한 단점을 보완하기 위해, 영상에서 주색도 분석과 희박성 제약조건의 비음수 행렬 분해를 이용한 광원 추정 방법을 제안하였다. 먼저 주색도를 분석하기 위해 영상을 색도 좌표계로 옮기고 색도 히스토그램을 이용하여 유사한 색도를 가지는 영역들로 영상을 분할한다. 다음으로 영상의 주색도는 분할된 영상들 중 색도의 표준편차가 가장 적은 영상의 색도로 선택한다. 마지막으로 주색도 분석 결과와 희박성 제약조건의 비음수 행렬 분해를 이용해 입력 영상에서 주색도 성분을 제거하고 최종적인 광원을 추정한다. 실제 촬영 영상에 대한 평균 각오차를 사용하여 기존의 방법과의 성능을 비교하였고, 그 결과 제안하는 방법의 평균 각 오차는 5.5를 나타내어 영상의 주 색도를 포함하여 광원을 추정한 기존 방법의 평균 각 오차 5.7 보다 우수한 성능을 나타내었다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.219-224
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• 2002

This paper aims to derive a mathematical model of the dynamics of handling tasks in robot finger which stable grasping and manipulates a rigid object with some dexterity. Firstly, a set of differential equation describing dynamics of the manipulators and object together with geometric constraint of tight area-contacts is formulated by Lagrange's equation. Secondly, problems of controlling both the internal force and the rotation angle of the grasped object under the constraints of area-contacts of tight area-contacts are discussed. The effect of geometric constraints of area-contacts on motion of the overall system is analyzed and a method of computer simulation for overall system of differential-algebraic equations is presented. Thirdly, simulation results are shown and the effects of geometric constraints of area-contact is discussed. Finally, it is shown that even in the simplest case of dual single D.O.F manipulators there exists a sensory feedback from sensing data of the rotational angle of the object to command inputs to joint actuators and this feedback connection from sensing to action eventually realizes secure grasping of the object, provided that the object is of rectangular shape and motion is confined to a horizontal plane.

• Geomechanics and Engineering
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• 제17권3호
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• pp.287-294
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• 2019

The finite element method (FEM) is widely used to evaluate the seismic performance of pile-supported buildings. However, there are problems associated with modeling the pile end resistance using the FEM, such as the dependence on the mesh size. This paper proposes a new method of modeling around the pile tip to avoid the mesh size effect in two-dimensional (2D) analyses. Specifically, we consider the area of influence around the pile tip as an artificial constraint on the behavior of the soil. We explain the problems with existing methods of modeling the pile tip. We then conduct a three-dimensional (3D) analysis of a pile in various soil conditions to evaluate the area of influence of the soil around the pile tip. The analysis results show that the normalized area of influence extends approximately 2.5 times the diameter of the pile below the pile tip. Finally, we propose a new method for modeling pile foundations with artificial constraints on the nodal points within the area of influence. The proposed model is expected to be useful in the practical seismic design of pile-supported buildings via a 2D analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.144-146
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• 2004

Stereo image analysis has been an important tool for reconstructing 3D terrain. By In its nature, occlusion is one of difficulties we cannot avoid in stereo matching. This paper presents a study on occlusion detection by employing LRC(Left-Right Check) and OCC(Occlusion Constraint). Experimental results show that these method can effectively detect occluded regions and those regions are usually occurred around object contours and scene discontinuity.

• Korea-Australia Rheology Journal
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• 제14권2호
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• pp.77-86
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• 2002

A microscopic theoretical study is performed to predict the rheological properties of human blood in the low concentration limit. The shear thinning behavior of blood in the low shear limit is studied by considering the aggregate formation of red blood cells, which is called the rouleaux formation. Then the constitutive equations of blood in the high shear limit are derived for various flow situations by considering the unique features of deformation of blood cells. Specifically, the effects of the surface-area-preserving constraint and the lank-treading motion of blood cells on the rheological properties are studied.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.145-150
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• 2007

The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rods saftely. Therefore, the spacer gl1d set should have sufficient strength for the external impact forces. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to tile flow-induced vibration. The conceptual design of the spacer grid set is performed based on the Independence Axiom of axiomatic design. Two functional requirements are defined and corresponding design parameters are selected. The overall flow of the design is defined according to the application of axiomatic design. The design for the impact load is carried out by using nonlinear dynamic analysis to determine the length of the dimple. Topology optimization is carried out to determine a new configuration of the spring. The fretting wear is reduced by shape optimization using the homology theory. In the design to reduce the fretting wear, the deformed shape of the spring should be the same as that of the fuel rod. This condition is transformed to a function and considered as a constraint in the shape optimization process. The fretting wear is expected to be reduced due to the homology constraint. The objective function is minimizing the maximum stress to allow a slight plastic deformation. Shape optimization results are confirmed through nonlinear static analysis because the contact area becomes wider.

• 한국항공우주학회지
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• 제37권11호
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• pp.1112-1120
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• 2009

본 논문에서는 현재 궤도상에서 운용중인 위성들을 특정 임무수행을 하도록 각 위성들 을 허용된 추진제량을 초과하지 않는 범위 내에서 궤도기동을 통해 재배치함으로써 일시적인 위성군집궤도를 형성하기 위한 목적궤도 설계기법을 소개하였다. 설계기법의 응용성을 확인하기 위해 본 연구에서는 두 가지 문제, 즉 각각 위성들에 대한 허용 추진제량이 모두 다른 경우 지상의 특정 지역을 정찰하는 문제와 지상을 지속적으로 이동하는 이동 물체를 동일한 허용 추진제량을 가진 위성들을 이용하여 정찰하는 문제를 다루었다. 유전 알고리즘을 이용한 접근방법의 유효성을 검증하기 위해 시뮬레이션을 수행하였으며, 결과적으로 현재 궤도배치 상에서 획득할 수 있는 평균재방문주기에 비해 재배치된 궤도상에서의 평균재방문주기가 각각 41%, 42% 감소함을 알 수 있었다. 제안된 방법에 의한 결과는 궤도조정 방법, 궤도상황, 센서 특성, 허용 추진제량, 그리고 추력기의 성능에 따라 다소 달라질 수 있다.

• 산업공학
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• 제16권4호
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• pp.450-462
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• 2003

In this paper, we deal with a process and layout design for producing a planned amount of Sikhye in a given limited time period under a reasonable production schedule. We represent a Sikhye production line as a vector N, the element of which denotes the number of tanks required in each process and our objective is to find an appropriate vector which minimizes the total investment cost. We suggest a systematic method for finding an appropriate N and an appropriate layout to N. In detail, first, we decide the required sequence of processes and the required operations for each process and we estimate standard operating times. Second, constructing a precedence diagram, we find a critical path in order to reduce the total production lead time for a batch of Sikhye. Third, given a limited N space, we manage to construct manually each production schedule using both the processing times of the critical operations and transfer times. Finally, we find an optimal vector N which gives a minimum investment cost and meets both the time constraint and quantity constraint. In addition, with the estimated relative size of each tank, we suggest an appropriate conceptual layout design including an expansion area for future demands, based on the span technique used in the field of architectural design.