• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.446-451
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• 2007

An Improved finite element model updating method to address the numerical difficulty associated with ill-conditioning and rank-deficiency. These difficulties frequently occur in model updating problems, when the identification of a larger number of physical parameters is attempted than that warranted by the information content of the experimental data. Based on the standard Bounded Variables Least-squares (BVLS) method, which incorporates the usual upper/lower-bound constraints, the proposed method is equipped with new constraints based on the correlation coefficients between the sensitivity vectors of updating parameters. The effectiveness of the proposed method is investigated through the numerical simulation of a simple framed structure by comparing the results of the proposed method with those obtained via pure BVLS and the regularization method. The comparison indicated that the proposed method and the regularization method yield approximate solutions with similar accuracy.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.698-707
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• 2003

A new quadratic response surface modeling method is presented. In this method, the incomplete small composite design (ISCD) is newly proposed to .educe the number of experimental runs than that of the SCD. Unlike the SCD, the proposed ISCD always gives a unique design assessed on the number of factors, although it may induce the rank-deficiency in the normal equation. Thus, the singular value decomposition (SVD) is employed to solve the normal equation. Then, the duality theory is used to newly develop the conservative least squares fitting (CONFIT) method. This can directly control the ever- or the under-estimation behavior of the approximate functions. Finally, the performance of CONFIT is numerically shown by comparing its'conservativeness with that of conventional fitting method. Also, optimizing one practical design problem numerically shows the effectiveness of the sequential approximate optimization (SAO) combined with the proposed ISCD and CONFIT.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.5
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• pp.489-496
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• 2006

The random-based cleaning algorithm is a simple algorithm widely used in commercial vacuum cleaning robots. This algorithm has two limitations, that is, cleaning takes a long time and there is no guarantee that the cleaning will cover the whole cleaning area. This has lead to customer dissatisfaction. Thus, in recent years, many intelligent cleaning algorithms that takes into consideration information gathered from the cleaning area environment have been proposed. The plowing-based algorithm, which is the most efficient algorithm known to date when there are no obstacles in the cleaning area, has a deficiency that when obstacle prevail, its performance is not guaranteed. In this paper, we propose the Group-k algorithm that is efficient for that situation, that is, when obstacle prevail. The goal is not to complete the cleaning as soon as possible, but to clean the majority of the cleaning area as fast as possible. The motivation behind this is that areas close to obstacles are usually difficult for robots to handle, and hence, many require human assistance anyway In our approach, obstacles are grouped by the complexity of the obstacles, which we refer to as 'complex rank', and then decide the cleaning route based on this complex rank. Results from our simulation-based experiments show that although the cleaning completion time takes longer than the plowing-based algorithm, the Group-k algorithm cleans the majority of the cleaning area faster than the plowing algorithm.

• The korean journal of orthodontics
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• v.47 no.2
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• pp.77-86
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• 2017

Objective: The aim of this study was to evaluate the skeletal and dentoalveolar changes after miniscrew-assisted rapid palatal expansion (MARPE) in young adults by cone-beam computed tomography (CBCT). Methods: This retrospective study included 14 patients (mean age, 20.1 years; range, 16-26 years) with maxillary transverse deficiency treated with MARPE. Skeletal and dentoalveolar changes were evaluated using CBCT images acquired before and after expansion. Statistical analyses were performed using paired t-test or Wilcoxon signed-rank test according to normality of the data. Results: The midpalatal suture was separated, and the maxilla exhibited statistically significant lateral movement (p < 0.05) after MARPE. Some of the landmarks had shifted forwards or upwards by a clinically irrelevant distance of less than 1 mm. The amount of expansion decreased in the superior direction, with values of 5.5, 3.2, 2.0, and 0.8 mm at the crown, cementoenamel junction, maxillary basal bone, and zygomatic arch levels, respectively (p < 0.05). The buccal bone thickness and height of the alveolar crest had decreased by 0.6-1.1 mm and 1.7-2.2 mm, respectively, with the premolars and molars exhibiting buccal tipping of $1.1^{\circ}-2.9^{\circ}$. Conclusions: Our results indicate that MARPE is an effective method for the correction of maxillary transverse deficiency without surgery in young adults.

• Structural Engineering and Mechanics
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• v.42 no.2
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• pp.229-245
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• 2012

Bridge vibration displacements have been directly measured by LVDTs (Linear Variable Differential Transformers) or laser equipment and have also been indirectly estimated by an algorithm of integrating measured acceleration. However, LVDT measurement cannot be applied for a bridge crossing over a river or channel and the laser technique cannot be applied when the weather condition is poor. Also, double integration of accelerations may cause serious numerical deviation if the initial condition or a regression process is not carefully controlled. This paper presents an algorithm of estimating bridge vibration displacements using vibration strains measured by FBG (Fiber Bragg Grating) sensors and theoretical mode shapes of a simply supported beam. Since theoretically defined mode shapes are applied, even high modes can be used regardless of the quality of the measured data. In the proposed algorithm, the number of theoretical modes is limited by the number of sensors used for a field test to prevent a mathematical rank deficiency from occurring in computing vibration displacements.89The proposed algorithm has been applied to various types of bridges and its efficacy has been verified. The closeness of the estimated vibration displacements to measured ones has been evaluated by computing the correlation coefficient and by comparing FRFs (Frequency Response Functions) and the maximum displacements.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.445-454
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• 1991

In this thesis, Mindlin plate element with nine nodes and three degrees-of-freedom at each node is formulated and is employed in eigen-analysis of a rectangular plates in order to alleviate locking phenomenon of eigenvalues. Eigenvalues and their modes may be locked if conventional $C_{0}$-isoparametric element is used. In order to reduce stiffness locking phenomenon, two methods (1, the general reduced and selective integration, 2, the new element that use of modified shape function) are studied. Additionally in order to reduce the error due to mass matrix, two mass matrixes (1, Gauss-Legendre mass matrix, 2, Gauss-Lobatto mass matrix) are considered. The results of eigen-analysis for two models (the square plate with all edges simply-supported and all edges built-in), computed by two methods for stiffness matrix and by two mass matrixes are compared with theoretical solutions and conventional numerical solutions. These comparisons show that the performance of the two methods with Gauss-Lobatto mass matrix is better than that of the conventional plate element. But, by considering the spurious rigid body motions, the element which employs modified shape function with full integration and Gauss-Lobatto mass matrix can elevate the accuracy and convergence of numerical solutions.

• Smart Structures and Systems
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• v.4 no.5
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• pp.629-640
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• 2008

A new algorithm is proposed to determine optimal accelerometer locations (OAL) when a structure is identified by frequency domain system identification (SI) method. As a result, a guideline is presented for selecting OAL which can reflect modal response of a structure properly. The guideline is to provide a minimum number of necessary accelerometers with the variation in the number of measurable target modes. To determine OAL for SI applications effectively, the modal sensitivity effective independence distribution vector (MS-EIDV) is developed with the likelihood function of measurements. By maximizing the likelihood of the occurrence of the measurements relative to the predictions, Fisher Information Matrix (FIM) is derived as a function of mode shape sensitivity. This paper also proposes a statistical approach in determining the structural parameters with a presumed parameter error which reflects the epistemic paradox between the determination of OAL and the application of a SI scheme. Numerical simulations have been carried out to examine the proposed OAL algorithm. A two-span multi-girder bridge and a two-span truss bridge were used for the simulation studies. To overcome a rank deficiency frequently occurred in inverting a FIM, the singular value decomposition scheme has been applied.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.94-100
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• 2001

When using a sample covariance matrix data in paucity of snapshots, adaptive matched field processing will have problem in inverting covariance matrix due to the rank deficiency. The general solutions are diagonal loading and eigenanalysis methods, but there is a significant bias in the power output. This paper presents a quantitative study of bias of power output and the performance of source localization through the simulation and the measured data analysis in fixed source case using the diagonal loading method for the minimum variance processor. Results show that the bias in power output is reduced and the performance of source localization is improved when the number of snapshots is greater than the number of array sensors.

• Journal of the Korean Institute of Landscape Architecture
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• v.22 no.3
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• pp.121-135
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• 1994

The Purpose of this study was to obtain data about management of the landscape plants and facility in APT. complex. Because of be completed 2 years ago, landscape plants ware damaged by transplantation and lost the nature tree shape. As well, the management conditions of plants and facility were wholly bad. In details, tree-species consisted of 52 species arbors and 35 species shrubs in APT. complex. The high rank 5 species were planted as main plants. The rates were 45.6-62.8% in arbors and 81.8-97.0% in shrubs. In the degree of tree shape and damage by diseuse and pest, the bad level of 1-2points were ranked highly as 13.9% and 10.4%. In the degree of tree shape and damage by disease and pest, the bad level of 1-2points were showed as 5.1% and 4.7%. In the interview Survey, the main problems of management-maintenance were expressed deficiency of budget, specialist and concern of residents. In the future, methods for the intensive management of APT. complex; First, the management of landscape plants and facility should be attained by a expert and need to establishment of maintenance scheme thoroughly. Above all, for improvement of residential life, we should be lead to convert of a resident recognition in the management -maintenance of exterior space.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1458-1463
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• 2003

This paper presents an improved identification algorithm of active magnetic bearing rotor systems considering sensor and actuator dynamics. An AMB rotor system has both real and complex poles so that it is very hard to identify them together. In previous research, a linear transformation through a fictitious proportional feedback was used in order to shift the real poles close to the imaginary axis. However, the identification result highly depends on the fictitious feedback gain, and it is not easy to identify the additional dynamics including sensor and actuators at the same time. First, this paper discusses the necessity and a selection criterion of the fictitious feedback gain. An appropriate feedback gain minimizes dominant SVD(Singular Value Decomposition) error through maximizing rank deficiency. Second, more improvement in the identification is achieved through separating the common additional dynamics in all elements of frequency response matrix. The feasibility of the proposed identification algorithm is proved with two theoretical AMB rotor models. Finally, the proposed scheme is compared with previous identification methods using experimental data, and a great improvement in model quality and large amount of time saving can be achieved with the proposed method.