• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.2
• /
• pp.175-182
• /
• 2012

In this paper we are concerned with the performance of structural stability of torsion in square cross section of a beam with holes. The critical load is defined as the smallest load at which the equilibrium of the structure fails to be stable as the load is slowly increased from zero. The beams subjected to torsion are frequently encountered in general structures and these forces influence to the stability of structure. The boundary element method is found to be very efficient and accurate for the analysis of torsion problems including complex boundary conditions with respect to its simplicity and generality. In this paper, it is required to derive the boundary element formulation for torsion problem and integrate directly on the discrete boundary. To investigate the validity of the developed computer program, three distinctly solid cross-sections which are elliptical, rectangular and triangular one are analyzed, and comparisons are made with analytical approaches where these can also be used.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.09a
• /
• pp.156-160
• /
• 2002

실험적 베리오그램의 모델링에 SA(Simulated Annealing)기법을 이용하였다. 최소 자승법의 해를 구하기 위하여 기존의 상용 프로그램에서 많이 이용되고 있는 반복법에 근거한 방법에 비해서 SA 기법은 초기 가정값에 크게 영향을 받지 않고 일정한 모델 인자의 값을 제시하였다. 임의의 초기 가정값을 입력하여도 충분한 반복 계산을 통하여 목적함수의 값이 광역적 최소값으로 수렴하는 것을 확인할 수 있었다. 베리오그램 모델이 일반적으로 비선형 모델이기 때문에 목적함수의 지역적 최소값으로의 수렴이 문제가 되고 이로 인하여 구해지는 인자의 값이 정확하지 않을 수 있지만 SA 기법을 이용하여 최소 자승법의 해를 구하게 되면 정확한 인자의 값을 구할 수 있음을 확인하였다.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.948-949
• /
• 2015

일반적으로 IPMSM의 전압방정식은 d축과 q축이 90도의 위상차를 가지고 있기 때문에 d-q축 간의 상호 인덕턴스를 고려하지 않는다. 하지만 실제로는 d축의 인덕턴스는 q축 전류에 영향을 받으며, 반대로 q축의 인덕턴스도 d축 전류에 영향을 받는다. 따라서 비선형 모델링을 통해 실제 전동기의 형태에 더 가깝게 묘사 하였다. 또한 일반적인 수학식으로 계산하여 Ldq, Lqd를 구해 LPF 필터를 사용하였고 이산적인 최소자승법을 이용한 Gain값을 통해 과도상태에서 더 적합한 LPF와 최소자승법을 비교하는 논문이다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.189-193
• /
• 2005

기존의 회귀식을 사용하거나 새로 유도하여 사용하는 경우 모두 일반적으로 회귀분석의 특성을 간과하고 사용하는 경우가 종종 발생한다. 일반적으로 자료들에서 구해진 회귀식은 분명히 독립변수와 종속변수가 구분되어 유도되었음에도 불구하고 이 식을 사용함에 있어서는 간혹 그 구분을 무시하고 역으로 적용하는 경향이 있었다. 그러나, 독립$\cdot$종속변수가 서로 바뀌면, 연직거리의 잔차들로부터 유도되는 기존의 회귀분석에 의하여, 회귀식이 서로 달라지기 때문에 역으로 적용하여서는 안된다. 이를 해결하기 본 연구에서는 상호변수 최소자승 회귀분석법을 제안하였다. 이론적 내용을 검토를 위해 임진강 영평천의 영중수위표 지점의 2001-2003년의 유량측정자료와 수위-유량곡선을 비교 분석하였다. 결론적으로 상호변수 회귀분석을 사용하면, 기존의 잘못 사용해온 관행을 해소할 수 있을 것이다.

• Journal of the Korea Computer Graphics Society
• /
• v.23 no.4
• /
• pp.1-9
• /
• 2017

We propose an efficient method to determine the position of blueprint by using a vector field with optimized MLS(Moving Least Squares). Typically, a professional architectural design office takes a long time to work as well as a high processing cost because the designer manually determines the location to place the buildings in a specific area. In order to solve this inefficient problem, we propose a method to automatically determine the location of the blueprint based on the optimized MLS method. In the proposed framework, the designer selects the desired region in the actual city data and calculates the flow of the vector based on the region. Use the optimized MLS method to extract the vector field and determine the amount of rotation of the drawing based on this field. The location of the blueprint determined by the proposed method is very similar to the flow seen when the actual building is located. As a result, the efficiency of the overall architectural design process is further improved by reducing the designer's inefficient workforce.

• The Journal of the Acoustical Society of Korea
• /
• v.14 no.3
• /
• pp.37-48
• /
• 1995

This paper presents an sstimation of ARMA coefficients of noisy ARMA system using generalized total least square (GTLS) method. GTLS problem for ARMA system is defined as minimizing the errors between the noisy output vectors and estimated noisy-free output. The GTLS problem is solved in closed form by eigen-problem and the perturbation analysis of GTLS is presented. Also its recursive solution (recursive GTLS) is proposed using the power method and the covariance formula of the projected output error vector into the input vector space. The simulation results show that GTLS ARMA coefficients estimator is an unbiased estimator and that recursive GTLS achieves fast convergence.

• Proceedings of the KIEE Conference
• /
• 2005.07d
• /
• pp.2867-2869
• /
• 2005

색역폭 사상은 디스플레이 장치간의 색재현성 차이를 보정하는 하나의 방법이다. 일반적으로 실시간 색역폭 사상은 3차원 Look-Up Table과 3차원 보간기로 구성되고 3차원 보간기의 성능은 3차원 Look-Up Table에 의해 결정된다. 본 논문에서는 실시간 색역 사상에 사용되는 3차원 Look-Up Table을 Least Square Method(최소자승법)를 이용하여 최적화하고자 한다. 시뮬레이션 결과 제안된 방법에 의해 생성된 Look-Up Table이 기존의 방법에 비해 우선된 색 재현 성능을 갖는다.

• Geophysics and Geophysical Exploration
• /
• v.8 no.2
• /
• pp.129-136
• /
• 2005

The damped least-squares inversion has become a most popular method in finding the solution in geophysical problems. Generally, the least-squares inversion is to minimize the object function which consists of data misfits and model constraints. Although both the data misfit and the model constraint take an important part in the least-squares inversion, most of the studies are concentrated on what kind of model constraint is imposed and how to select an optimum regularization parameter. Despite that each datum is recommended to be weighted according to its uncertainty or error in the data acquisition, the uncertainty is usually not available. Thus, the data weighting matrix is inevitably regarded as the identity matrix in the inversion. We present a new inversion scheme, in which the data weighting matrix is automatically obtained from the analysis of the data resolution matrix and its spread function. This approach, named 'extended active constraint balancing (EACB)', assigns a great weighting on the datum having a high resolution and vice versa. We demonstrate that by applying EACB to a two-dimensional resistivity tomography problem, the EACB approach helps to enhance both the resolution and the stability of the inversion process.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.6
• /
• pp.619-623
• /
• 2008

A lane detection system is one of the major components of intelligent vehicle systems. Difficulties in lane detection mainly come from not only various weather conditions but also a variety of special environment. This paper describes a simple and stable method for the broken lane tracking in various environments. Probabilistic Hough Transform (PHT) and the Least-square method (LSM) are used to track and correct the lane orientation. For the efficiency of the proposed method, two regions of interest (ROIs) are placed in the lower part of each image, where lane marking areas usually appear with less intervention in our system view. By testing in both a set of static images and video sequences, the experiments showed that the proposed approach yielded robust and reliable results.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.1 s.44
• /
• pp.83-91
• /
• 2000

The first Procedure to identify structural system by using measured data is transformation of data to frequency domain and try to recognize modal characteristics in graphical condition. Those methods are doubted about the reliability to the civil structures, especially bridges which has coupled and close modal characteristics. In this paper, feasibility of time domain modal Identification methods were examined and applied double least square method to overcome bias characteristics of the identification methods. To show the advantage of proposed method, simulation were carried out for mass-spring model. And to examine the usage of the method in realistic case, sensitivity of the methods to noise was performed.