• Structural Engineering and Mechanics
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• 제35권1호
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• pp.53-65
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• 2010

The rigid body inertia properties of a structure including the mass, the center of gravity location, the mass moments and principal axes of inertia are required for structural dynamic analysis, modeling of mechanical systems, design of mechanisms and optimization. The analytical approaches such as solid or finite element modeling can not be used efficiently for estimating the rigid body inertia properties of complex structures. Several experimental approaches have been developed to determine the rigid body inertia properties of a structure via Frequency Response Functions (FRFs). In the present work two experimental methods are used to estimate the rigid body inertia properties of a frame. The first approach consists of using the amount of mass as input to estimate the other inertia properties of frame. In the second approach, the property of orthogonality of modes is used to derive the inertia properties of a frame. The accuracy of the estimated parameters is evaluated through the comparison of the experimental results with those of the theoretical Solid Work model of frame. Moreover, a thorough discussion about the effect of accuracy of measured FRFs on the estimation of inertia properties is presented.

• Structural Engineering and Mechanics
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• 제21권2호
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• pp.205-220
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• 2005

This paper presents the possibilities of adapting artificial neural networks (ANNs) to predict the dimensionless parameters related to the maximum contact pressures of an elasticity problem. The plane symmetric double receding contact problem for a rigid stamp and two elastic strips having different elastic constants and heights is considered. The external load is applied to the upper elastic strip by means of a rigid stamp and the lower elastic strip is bonded to a rigid support. The problem is solved under the assumptions that the contact between two elastic strips also between the rigid stamp and the upper elastic strip are frictionless, the effect of gravity force is neglected and only compressive normal tractions can be transmitted through the interfaces. A three layered ANN with backpropagation (BP) algorithm is utilized for prediction of the dimensionless parameters related to the maximum contact pressures. Training and testing patterns are formed by using the theory of elasticity with integral transformation technique. ANN predictions and theoretical solutions are compared and seen that ANN predictions are quite close to the theoretical solutions. It is demonstrated that ANNs is a suitable numerical tool and if properly used, can reduce time consumed.

• Structural Engineering and Mechanics
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• 제47권6호
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• pp.757-771
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• 2013

We present a semi-rigid connection estimation method by using cross modal strain energy method. While rigid or pinned assumptions are adopted for steel frames in traditional modeling via finite element method, the actual behavior of the connections is usually neither. Semi-rigid joints enable connections to be modeled as partially restrained, which improves the quality of the model. To identify the connection stiffness and update the FE model, a newly-developed cross modal strain energy (CMSE) method is extended to incorporate the connection stiffness estimation. Meanwhile, the relations between the correction coefficients for the CMSE method are derived, which enables less modal information to be used in the estimation procedure. To illustrate the capability of the proposed parameter estimation algorithm, a four-story frame structure is demonstrated in the numerical studies. Several cases, including Semi-rigid joint(s) on single connection and on multi-connections, without and with measurement noise, are investigated. Numerical results indicate that an excellent updating is achievable and the connection stiffness can be estimated by CMSE method.

• 대한수학회보
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• 제48권1호
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• pp.157-167
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• 2011

For a ring endomorphism of a ring R, Krempa called $\alpha$ rigid endomorphism if $a{\alpha}(a)$ = 0 implies a = 0 for a $\in$ R, and Hong et al. called R an $\alpha$-rigid ring if there exists a rigid endomorphism $\alpha$. Due to Rege and Chhawchharia, a ring R is called Armendariz if whenever the product of any two polynomials in R[x] over R is zero, then so is the product of any pair of coefficients from the two polynomials. The Armendariz property of polynomials was extended to one of skew polynomials (i.e., $\alpha$-Armendariz rings and $\alpha$-skew Armendariz rings) by Hong et al. In this paper, we study the relationship between $\alpha$-rigid rings and extended Armendariz rings, and so we get various conditions on the rings which are equivalent to the condition of being an $\alpha$-rigid ring. Several known results relating to extended Armendariz rings can be obtained as corollaries of our results.

• 한국안광학회지
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• 제12권4호
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• pp.71-76
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• 2007

본 연구의 목적은 RGP콘택트렌즈 착용 시 나타날 수 있는 증상에 관한 안경사의 이해도를 조사하는 것인데, RGP 콘택트렌즈 착용 시의 나타날 수 있는 증상에 대한 이해도가 높다면 적응증상과 이상증상을 구분하고 해결하여 RGP콘택트렌즈의 착용성공률을 보다 높여 줄 것이기 때문이다. 96명의 안경사를 대상으로 설문지를 통해 RGP콘택트렌즈 처방에 사용되는 기기 사용방법 및 경험, RGP콘택트렌즈 착용 시 나타날 수 있는 증상 등에 대한 이해수준을 조사하였다. 결과는 RGP콘택트렌즈 착용 시 증상에 대한 정확한 이해력이 상당히 낮은 수준으로 조사되었고, 정확한 처방을 위해 이론교육 및 실습교육 등이 더 강화되어야 한다.

• Journal of the Korean Wood Science and Technology
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• 제28권4호
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• pp.72-82
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• 2000

Attempts were made to analyze the behavior of single and multiple-bolted connections through theoretical methods such as European yield theory, empirical approaching method, and semi-rigid theory instead of many experimental methods that have been actually inefficient and non-economical. In the case of a single-bolted connection, if accurate characteristic values of a material could be guaranteed, it would be more convenient and economical to perform the behavior analysis using a model based on the semi-rigid theory, instead of the existing complex yield model, or the empirical formula which produces errors, giving different results from the actual ones. If the variables of equation determining the load and deformation could be appropriately controlled, the analytical method in conjunction with a semi-rigid theory could be effectively applied to obtain the desirably predicted value, considering that the appropriate solution could be derived through a simpler equation using a less difficult method compared to the existing yield model. It is concluded that analytical method with semi-rigid theory can be used in the behavior analysis of bolted connection because our developed method showed excellent analysis ability of behavior until number of bolt is two. Although our analytical method has the disadvantage that the number of bolt is limited to two, it is concluded that it has the advantage than numerical method which complicated and time-consuming.

• 정보처리학회논문지B
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• 제16B권2호
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• pp.109-116
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• 2009

본 논문에서는 스테레오 영상 기반에서 능동 특징점 모델(active feature model)과 광류(optical flow)를 이용한 객체 추적 기술을 제안한다. 스테레오의 기하학적 정보와 변위를 이용하여 관심 객체와 특징점의 2.5차원 이동 정보(translation information)를 계산한다. 이 정보를 이용하여 폐색 객체의 특징점의 이동 정보를 예측하여 추적 성능을 개선하였다. 정형(rigid) 및 비정형(non-rigid) 객체에 실험을 하였다. 실험 결과 복잡한 배경 속에서의 실시간 객체 추적이 가능하였다. 또한 정형, 비정형 객체에 관계없이 추적이 가능 하였으며 폐색 상황에 향상된 결과를 보였다.

• Ocean Systems Engineering
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• 제8권1호
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• pp.57-77
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• 2018

The present paper deals with the finite element analysis of water tanks with rigid baffle. Fluid is discretized by two dimensional eight-node isoparametric elements and the governing equation is simulated by pressure based formulation to reduce the degrees of freedom in the domain. Both free vibration and force vibration analysis are carried out for different sizes and positions of block at tank bottom. The fundamental frequency depends on block height and it reduces with the increase of block height. The variation of hydrodynamic pressure on tank walls not only depends of the exciting frequency but also on the size and position of rigid block at tank bottom. The hydrodynamic pressure has higher value when the exciting frequency is equal and lower than the fundamental frequency of the water in the tank. Similarly, the hydrodynamic pressure increases with the increase of width of the block for all exciting frequencies when the block is at the centre of tank. The left and right walls of tank have experienced different hydrodynamic pressure when the block is placed at off-centre. However, the increase in hydrodynamic pressure on nearest tank wall becomes insignificant after a certain value of the distance between the wall and the rigid block.

• Structural Engineering and Mechanics
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• 제43권1호
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• pp.31-51
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• 2012

This paper presents a computational study that explores the design of rigid steel frames by considering construction related costs. More specifically, two different aspects are investigated in this study focusing on the effects of (a) reducing the number of labor intensive rigid connections within a frame of given geometric layout, and (b) reducing the number of different member section types used in the frame. A genetic algorithm based optimization framework searches design space for these objectives. Unlike some studies that express connection cost as a factor of the entire frame weight, here connections and their associated cost factors are explicitly represented at the member level to evaluate the cost of connections associated with each beam. In addition, because variety in member section types can drive up construction related costs, its effects are evaluated implicitly by generating curves that show the trade off between cost and different numbers of section types used within the frame. Our results show that designs in which all connections are considered to be rigid can be excessively conservative: rigid connections can often be eliminated without any appreciable increase in frame weight, resulting in a reduction in overall cost. Eliminating additional rigid connections leads to further reductions in cost, even as frame weight increases, up to a certain point. These complex relationships between overall cost, rigid connections, and member section types are presented for a representative five-story steel frame.

• 한국산학기술학회논문지
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• 제12권11호
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• pp.5300-5305
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• 2011

Winkler 지반과 2변수 Winkler 지반상에 놓인 강성보에 집중하중과 모멘트가 작용하는 경우에 대해 강성보에 발생하는 변위, 접촉압력, 모멘트를 유도하여 보았다. Winkler 지반상의 강성보에 발생하는 모멘트의 유도결과로 부터 강성보를 따르는 모멘트분포는 스프링 상수와 무관하게 나타남을 알 수 있었고 스프링 상수가 선형인 경우가 일정한 경우에 비해 모멘트값이 크게 계산되었다. 간단한 계산을 통해 볼 때 2변수 Winkler 지반에 놓인 강성보에 발생하는 최대 휨모멘트가 Winkler 지반에 놓인 강성보에 발생하는 그것에 비해 크게 계산되었다.