• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.810-816
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• 2001

In this paper, we theoretically analyzed the NRRO(the non-repeatable run-out) of a ball bearing with geometric imperfection. The quasi-static and dynamic analysis of a ball bearing was performed to calculate the displacement of shaft center caused by the form errors while the shaft is rotating. From consideration of the generating mechanism of NRRO, it is found that the waviness of one ball generates vibrations with nf$\sub$b/${\pm}$f$\sub$c/(where n is odd) components. Also it is confirmed that the outer race waviness of the order n = jZ${\pm}$1 generates vibration with jZf$\sub$c/ components. The form errors of ball bearing elements were precisely measured and NRRO of a ball bearing was calculated using the measured data. It is concluded that the ball bearings must has large ball number and small ball diameter to obtain low NRRO.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.55-59
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• 2008

For effective mobility control of UGV(unmanned ground vehicle), the terrain cover classification is an important component as well as terrain geometry recognition and obstacle detection. The vision based terrain cover classification algorithm consists of pre-processing, feature extraction, classification and post-processing. In this paper, we present a method to classify terrain covers based on the color and texture information. The color space conversion is performed for the pre-processing, the wavelet transform is applied for feature extraction, and the SVM(support vector machine) is applied for the classifier. Experimental results show that the proposed algorithm has a promising classification performance.

• Journal of KIISE:Software and Applications
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• v.36 no.11
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• pp.947-954
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• 2009

This paper proposes a novel method that reconstructs a surfel-based object by using visual hull from multiple images. The surfel is a point primitive that effectively approximates point-set surface. We create the surfel representation of an object from images by combining the LDC(Layered Depth Cube) surfel sampling with the concept of visual hull that represents the approximated shape from input images. Because the surfel representation requires relatively smaller memory resources than the polygonal one and its LDC resolution is freely changed, we can control the reconstruction quality of the target object and acquire the maximal quality on the given memory resource.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.739-742
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• 2007

For the mass evaluation on the earth cutting volume, Geographic information system(GIS) based on digital topographical map executed on the ground condition in presents states and after installing utilities, and making visual decision. This study presents that the general reviews considering economical, technological efficiency as well as natural factors was carried. To the rational examines about plan and procedure of development was approved, the geographical analysis was performed that was based on the topographical shape before construction and the field states after construction, which will be utilized more useful data for mass curve calculation.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.2
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• pp.154-159
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• 2007

Wake distribution data of stem flow fields have been accumulated systematically by model tests. If the correlation between geometrical hull information and wake distribution is grasped through the accumulated data, this correlation can be helpful to designing similar ships. In this paper, Neuro-Fuzzy system that is emerging as a new knowledge over a wide range of fields nowadays is tried to estimate the wake distribution on the propeller plan. Neuro-Fuzzy system is well known as one of prospective and representative analysis method for prediction, classification, diagnosis of real complicated world problem, and it is widely applied even in the engineering fields. For this study three-dimensional stern hull forms and nominal wake values from a model test ate structured as processing elements of input and output layer, respectively. The proposed method is proved as an useful technique in ship design by comparing measured wake distribution with predicted wake distribution.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.2
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• pp.113-121
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• 2011

In this paper, we proposed the method automatically to match areal feature based on similarity using spatial information. For this, we extracted candidate matching pairs intersected between two different spatial datasets, and then measured a shape similarity, which is calculated by an weight sum method of each matching criterion automatically derived from CRITIC method. In this time, matching pairs were selected when similarity is more than a threshold determined by outliers detection of adjusted boxplot from training data. After applying this method to two distinct spatial datasets: a digital topographic map and street-name address base map, we conformed that buildings were matched, that shape is similar and a large area is overlaid in visual evaluation, and F-Measure is highly 0.932 in statistical evaluation.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.358-365
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• 2014

When a ship propeller having wing type sections rotates at high speed underwater, local pressure on the blade decreases and various types of the cavitation inevitably occur where the local pressure falls below the vapor pressure. Fundamentally characteristics of the cavitation are determined by the shapes of the blade section and their operating conditions. Underwater noise radiated from a ship propeller is directly connected to the occurrence of the cavitation. In order to design low noise propeller, it is preferentially demanded to figure out key features: how the cavity is generated, developed and collapsed and how the effect of viscosity works in the process. In this study, we first perform inviscid analysis of the partial cavity generated on two dimensional hydrofoil. Secondly, viscous analysis using FLUENT with different turbulence and cavitation models are presented. Results from both approaches are also compared and estimated.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.73-83
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• 1998

Considering dynamic behaviors according to initial tension forces, geometric nonlinearity and the effect of higher eigen modes to participate in dynamic behaviors increase as initial tension forces decrease, and from phase portrait we can realize that period attractors are produced in many area with complexity. If initial tension forxes increase, difference between linear and nonlinear solutions will decrease and the first eigen mode dominate the dynamic behaviors and observing phase portrait, period attractors appear in certain area regularly. These results may offer meaningful informations to nonlinear dynamic analysis using modal reduction methods such as Lanczos modal analysis. And actually nonlinear dynamic analysis needs very large computational efforts. So, if we determine the number of eigen modes to take part in modal analysis corresponding to initial tension forces we will get more accurate data close to exact nonlinear dynamic solutions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.236-242
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• 2019

Recently, scanning projects have been carried out in various construction and construction fields for maintenance purposes. The point cloud generated by the scan results is composed of a number of points representing the object to be scanned. The process of extracting the necessary information, including dimensions, from such scan data is called paradox. The reverse engineering process of modeling a point cloud as BIM involves considerable manual work. Owing to the time-consuming reverse engineering nature of the work, the costs increase exponentially when rework requests are made, such as design changes. Reverse engineering automation technology can help improve these problems. On the other hand, the reverse design product is variable depending on the use, and the kind and detail level of the product may be different. This paper proposes the G2BM (Geometry-to-BIM mapping) rule definition method that automatically maps a BIM object from a primitive geometry to a BIM object. G2BM proposes a process definition and a customization method for reverse engineering BIM objects that consider the use case variability.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.329-335
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• 2011

The finite element method (FEM) has been used for various fields like mathematics and engineering. However, the FEM has a difficulty in describing the geometric shape exactly due to its property of piecewise linear discretization. Recently, however, a so-called isogeometric analysis method that uses the non-uniform rational B-spline(NURBS) basis function has been developed. The NURBS can be used to describe the geometry exactly and play a role of basis functions for the response analysis. Nevertheless, constructing the NURBS basis functions in analysis is as costly as a meshing process in the FEM. Since the isogeometric method shares geometric data with CAD, it is possible to intactly import the model data from commercial CAD tools. In this paper, we use the Rhinoceros 3D software to create CAD models and export in the form of STEP file. The information of knot vectors and control points in the NURBS is utilized in the isogeometric analysis. Through some numerical examples, the accuracy of isogeometric method is compared with that of FEM. Also, the efficiency of the isogeometric method that includes the CAD and CAE in a unified framework is verified.