• 대한교통학회지
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• 제18권6호
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• pp.89-99
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• 2000

전통적인 OD조사에 의한 OD추정방법의 여러 문제점들로 인해 링크에서 관측된 교통량과 기존OD를 결합해 새로운 OD를 추정하고자 하는 연구들이 지속되고 있으며, 그 필요성도 증대되고 있다. 그러한 기법중의 하나가 Yang(1995)이 제시한 바이레벨 모형으로, 그는 일반화최소자승법을 풀기위한 Sensitivity Analysis Based (SAB)을 제시하였다. 그러나 SAB 알고리즘은 두가지 중요한 문제점을 가지고 있다. 첫 번째 문제는 실제 OD를 알기가 어렵기 때문에, 기존 OD 조사시의 통행패턴이 현재의 통행패턴과 큰 변화가 없다는 가정 하에, 기존 OD를 추정시 중요한 추정기준으로 설정한다는 점이다. 그러나 이러한 기존 OD에 대한 추정의 종속성으로 인해, SAB는 기존 OD와 실제 OD의 차이가 큰 경우 정확한 해를 도출하지 못하고 추정결과가 일관적(robust)이지 않게 도출된다. 두 번째 문제는 SAB는 통행패턴 추정시 선형근사화를 가정하기 때문에 게임이론적 측면에서 전제로 설정한 완전한 Stackelberg 상황을 구현하지 못한다는 점이다. 이러한 문제점을 피하기 위해서는 기존 OD의 오차나 관측교통량의 오차에 대해 일관적이고 안정적인 해도출 기법이 필요하다. 본 연구의 목적은 SAB를 비롯한 기존 바이레벨 OD추정기법의 문제점을 지적하고 이에 대한 대안기법을 제시하는 것이다. OD추정의 문제는 본질적으로 비선형이고 비볼록하기 때문에, 다중해를 도출하게 된다. 따라서 전역해 탐색기법이 필요한데, 본 연구에서는 전역최적화가 가능한 유전알고리즘(Genetic Algorithm)을 이용한 OD추정모형(GA-Model:GAM)을 제시하였다. 사례네트워크에 대한 비교분석결과, GAM은 기존 OD의 오타에 대해 크게 종속적이지 않으며 OD구조가 변하는 경우에도 추정이 가능하여, 일반적으로 실제 OD를 알 수 없는 (기존OD의 오차가 어느 정도인지를 알 수 없는) 도시부 네트워크에서 신뢰성있는 추정력을 보였다.

• 한국정보통신학회논문지
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• 제11권5호
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• pp.997-1003
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• 2007

이 논문에서는 LCD에 사용되는 편광필름 영상에서 결함을 검출하는 방법을 제안하였다. 제안한 방법은 결함의 지엽적인 특징을 이용하는 것이 아니라 특이값 분해를 이용하여 영상의 전역적인 정보를 반영하는 방법이다. 편광필름 영상을 특이값 분해하고 특이값 중에서 첫 번째 특이값만을 사용하여 영상을 재구성하면 재구성한 영상에서 정상 부분의 화소값과 결함 부분의 화소값들은 서로 다른 특성을 나타낸다. 입력 영상과 재구성한 영상의 화소값 비를 구하고 확률론적 방법을 사용하여 결함을 검출하였다. 제안한 방법을 이용하여 여러 가지 결함을 갖는 편광필름 영상에서 결함을 검출한 결과 검출력이 매우 우수한 것으로 나타났다.

• Journal of Positioning, Navigation, and Timing
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• 제11권3호
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• pp.181-189
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• 2022

The public open signals from Global Navigation Satellite System (GNSS) including Global positioning system (GPS) are used widely by many peoples in the world except for the public regulated restriction signals which are encrypted. Nowadays there are growing concerns about GNSS signal spoofing which can deceive the GNSS receivers by abusing these open services. To counter these spoofing threats, many researches have been studied including array antenna techniques which can detect the direction of arrival by means of Multiple Signal Classification (MUSIC) algorithm. Originally the array antenna techniques were developed to countermeasure the jamming signal in electronic warfare by using the nulling or beamforming algorithm toward a certain direction. In this paper, we study the anti-spoofing techniques using array antenna to overcome the jamming and spoofing issues simultaneously. First, we will present the theoretical analysis results of spoofing signal response of Minimum Variance Distortionless Response (MVDR) algorithm in array antenna. Then the eigenvector algorithm of covariance matrix is suggested and verified to work with the existing anti-jamming method. The modeling and simulation are used to verify the effectiveness of the anti-spoofing algorithm. Also, the field test results show that the array antenna system with the proposed algorithms can perform the anti-spoofing function. This anti-spoofing method using array antenna is very effective in the view point of solving both the jamming and spoofing problems using the same array antenna hardware.

• Structural Engineering and Mechanics
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• 제23권6호
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• pp.691-711
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• 2006

This paper uses the finite element method to simultaneously consider the coupled cable-deck vibrations and the parametric vibrations of stay cables in dynamic analysis of a cable-stayed bridge. The stay cables are represented by some cable finite elements, which can consider the parametric vibration of the cables. In addition to modeling stay cables using multiple link cable elements, a procedure for removing the self-weight term of cable element is proposed. A eigenvalue analysis process using dynamic condensation method for sorting out the natural modes of the girder-tower vibrations and the Rayleigh damping considering element damping for damping matrix are also proposed for dynamic analyses of cable-stayed bridges. The possibilities of using cable elements and of using global and local vibrations to evaluate the parametric vibrations of stay cables in a cable-stayed bridge are confirmed, respectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.571-577
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• 2003

This research proposes a finite element method to determine the natural vibration characteristics of the spinning disk-spindle system in a HDD including the flexibility of supporting structure. Finite element equations of each substructure are derived with the introduction of consistent variables to satisfy the geometric compatibility at the internal boundaries. The natural frequencies and modes from the global asymmetric matrix equations of motion are determined by using the implicit restarted Arnoldi iteration method. The validity of the proposed method is verified by the experimental modal testing. It also shows that the flexibility of base plate plays an important role to determine the natural frequencies of the spinning disk-spindle system in a HDD.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.859-865
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• 2007

This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered bearing and flexible supporting structures by using the finite element method and the mode superposition method. The appropriate finite element equations for polygon mirror are described by rotating annular sector element using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. The rotating components except for the polygon mirror are modeled by Timoshenko beam element including the gyroscopic effect. The flexible supporting structures are modeled by using a 4-node tetrahedron element and 4-node shell element with rotational degrees of freedom. Finite element equations of each component of the polygon mirror scanner motor and the flexible supporting structures are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between sleeve and sintered bearing to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. Unbalance responses in time and frequency domain are performed by superposing the eigenvalues and eigenvectors from the free vibration analysis. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results. This research also shows that the flexibility of supporting structures plays an important role in determining the unbalance response of the polygon mirror scanner motor.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.557-568
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• 2002

For the evaluation of the capability of a tubular member of an offshore structure to absorb the collision energy, a simple method can be employed for the collision analysis without performing the detailed analysis. The most common simple method is the rigid-plastic method. However, in this method any characteristics for horizontal movement and rotation at the ends of the corresponding tubular member are not included. In a real structural system of an offshore structure, tubular members sustain a certain degree of elastic support from the adjacent structure. End fixity has influences in the behaviors of a tubular member. Three-dimensional FEM analysis can include the effect of end fixity fully, however in viewpoints of the inherent computational complexities of the 3-D approach, this is not the recommendable analysis at the initial design stage. In this paper, influence of end fixity on the behaviors of a tubular member is investigated, through a new approach and other approaches. A new analysis approach that includes the flexibility of the boundary points of the member is developed here. The flexibility at the ends of a tubular element is extracted using the rational reduction of the modeling characteristics. The property reduction is based on the static condensation of the related global stiffness matrix of a model to end nodal points of the tubular element. The load-displacement relation at the collision point of the tubular member with and without the end flexibility is obtained and compared. The new method lies between the rigid-plastic method and the 3-demensional analysis. It is self-evident that the rigid-plastic method gives high strengthening membrane effect of the member during global deformation, resulting in a steeper slope than the present method. On the while, full 3-D analysis gives less strengthening membrane effect on the member, resulting in a slow going load-displacement curve. Comparison of the load-displacement curves by the new approach with those by conventional methods gives the figures of the influence of end fixity on post-yielding behaviors of the relevant tubular member. One of the main contributions of this investigation is the development of an analytical rational procedure to figure out the post-yielding behaviors of a tubular member in offshore structures.

• Journal of Advanced Marine Engineering and Technology
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• 제26권3호
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• pp.344-352
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• 2002

In the analysis of the 3 dimensional plate structures by the finite element method, the triangular elements are generally used for the global stiffness matrix of the analyzed system. But the triangular elements of the plates have some problems in the process of formulation and in the precision of analysis. The formulation of the finite element method to analyze 3 dimensional plate structures using quadrilateral elements is presented in this paper. The degree of freedom off nodal point is 6, that is, the displacements in the direction off-y-z is and the rotations about x-y-z axis and then the degree of freedom off element is 24. For the comparison of the analysis using triangular elements and quadrilateral elements, the rectangular plates subjected to the uniform load and a concentrated load on the centroid of the plate, for which the theoretical solutions have been obtained, are analyzed. The calculated deflections of the rectangular plates using the finite element method by the triangular elements and the quadrilateral elements are also compared with the deflections of the plates calculated by theoretical solutions. The defections of the rectangular plates calculated by the finite element method using the quadrilateral elements are closer to the theoretical solutions than the defections calculated by the finite element method using the triangular elements. The deflection of the centroid of plate, calculated by the finite element method, converges to that of theoretical solution as the number of elements is increased. This convergence is much more rapid for the case of using the quakrilateral elements than fir the case of using triangular elements.

• 산업경영시스템학회지
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• 제40권1호
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• pp.114-123
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• 2017

The global small and mid-sized display market is changing from thin film transistor-liquid crystal display to organic light emitting diode (OLED). Reflecting these market conditions, the domestic and overseas display panel industry is making great effort to innovate OLED technology and incease productivity. However, current OLED production technology has not been able to satisfy the quality requirement levels by customers, as the market demand for OLED is becoming more and more diversified. In addition, as OLED panel production technology levels to satisfy customers' requirement become higher, product quality problems are persistently generated in OLED deposition process. These problems not only decrease the production yield but also cause a second problem of deteriorating productivity. Based on these observations, in this study, we suggest TRIZ-based improvement of defects caused by glass pixel position deformation, which is one of quality deterioration problems in small and medium OLED deposition process. Specifically, we derive various factors affecting the glass pixel position shift by using cause and effect diagram and identify radical reasons by using XY-matrix. As a result, it is confirmed that glass heat distortion due to the high temperature of the OLED deposition process is the most influential factor in the glass pixel position shift. In order to solve the identified factors, we analyzed the cause and mechanism of glass thermal deformation. We suggest an efficient method to minimize glass thermal deformation by applying the improvement plan of facilities using contradiction matrix in TRIZ. We show that the suggested method can decrease the glass temperature change by about 23% through an experiment.

• 한국공간구조학회논문집
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• 제12권2호
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• pp.89-98
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• 2012

본 연구는 공간 트러스의 전체 좌굴을 고려한 최적 구조설계에 대해 연구를 하였으며, 구조물의 최소중량을 구하는 것이 목적이다. 응력제약에 의한 부재 최적화를 위해서 수리 계획법이 사용되었으며, 뜀-좌굴을 고려하기 위해 동적 계획법을 적용하였다. 트러스 부재의 최적설계를 위한 수리 모형은 전체중량 목적함수와 인장 또는 압축 허용응력 및 세장비 제약식으로 구성하였다. 평형경로상의 임계점 즉 좌굴하중을 구하기 위해서 접선 강성행렬의 행렬식 변화를 조사하였으며, 설계하중에 대한 좌굴하중 비율이 동적계획법의 반복계산과정에서 공간 트러스의 강성을 조절하기위해 반영되었다. 제안된 최적설계 프로세서의 검증을 위해서 스타 돔 구조물 예제를 통해 조사하였으며, 수치 결과는 잘 수렴하고 모든 제약을 만족하였다. 제시된 최적설계 프로세스는 전체좌굴을 고려한 최적설계를 수행하기 위한 비교적 간단 방법이고, 실무 구조설계를 반영하는데 가능하다.