• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.1 no.1
• /
• pp.5-14
• /
• 2002

Hemisphere shapes were machined for different tool paths and machining conditions with ball endmill cutters. It was also found out how feedrate affect the precision of the machining and also tried to study the most suitable feedrate in specific cutting condition. Tool deflection, cutting forces and shape accuracy were measured according to the inclination position of the sculptured surface. As the decreasing of inclination position angle, the tool deflection was increased due to the decreased cutting speed when the cutting edge is approaching toward the center. Tool deflection when upward cutting IS obtained less than that of downward cutting and down-milling in upward cutting showed the least tool deflection for the sculptured surface. For down-milling, the cutting resistance of the side wall direction is larger than that of feed direction. It was found that the tool deflection is getting better as tool path is going to far from the center for convex surface.

• Journal of Korean Institute of Industrial Engineers
• /
• v.28 no.2
• /
• pp.128-138
• /
• 2002

In this paper, we address how to reduce the length of tool retraction in a zigzag pocket machining. Tool retraction, in a zigzag pocket machining, is a non-cutting operation in which the tool moves to any remaining regions for machining. We developed an algorithm of generating tool retraction length in convex or concave polygonal shapes including islands. In the algorithm, we consider concave areas of cutting direction in the polygonal shape. Considering concave areas of cutting direction, the polygonal shape is decomposed to subregions which do not need any tool retraction. Using the proposed algorithm, we calculated the shortest length of tool retraction in cutting direction. Examples are shown to verify the validity of the algorithm.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.1
• /
• pp.58-66
• /
• 2007

Genetic Algorithms (GA) have some difficulties in practical applications because of too many function evaluations. To overcome these limitations, an approximated modeling method such as Response Surface Modeling(RSM) is coupled to GAs. Original RSM method predicts linear or convex problems well but it is not good for highly nonlinear problems cause of the average effect of the least square method(LSM). So the locally approximated methods. so called as moving least squares method(MLSM) have been used to reduce the error of LSM. In this study, the efficient evolutionary GAs tightly coupled with RSM with MLSM are constructed and then a 2-dimensional inviscid airfoil shape optimization is performed to show its efficiency.

• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.2
• /
• pp.61-69
• /
• 2004

In this study, flow around rudder is analyzed by utilizing the numerical calculation, and the rudder open water test is performed to validate the calculation. The aim of this study is to design the new rudder shape to improve manoeuvring performance. In first, flow around two-dimensional rudder section is analyzed to understand the characteristics of section profile. And the calculation for all-movable rudders is performed and compared with results of rudder open water test. It is hard to numerically predict the drag force because the value is sensitive to the turbulence modeling and grid spacing near the wall. However, the lift force is predicted well. And we can prove that concave profile of the rudder section produce more lift and torque than convex one as a experiment. However PANEL method that ignore viscous effect cannot distinguish the difference of them. So, we can look for the numerical tool to be developed the new rudder shape.

• Structural Engineering and Mechanics
• /
• v.52 no.3
• /
• pp.445-468
• /
• 2014

In this paper a new particle swarm ray optimization algorithm is proposed for truss shape and size optimization with natural frequency constraints. These problems are believed to represent nonlinear and non-convex search spaces with several local optima and therefore are suitable for examining the capabilities of new algorithms. The proposed algorithm can be viewed as a hybridization of Particle Swarm Optimization (PSO) and the recently proposed Ray Optimization (RO) algorithms. In fact the exploration capabilities of the PSO are tried to be promoted using some concepts of the RO. Five numerical examples are examined in order to inspect the viability of the proposed algorithm. The results are compared with those of the PSO and some other existing algorithms. It is shown that the proposed algorithm obtains lighter structures in comparison to other methods most of the time. As will be discussed, the algorithm's performance can be attributed to its appropriate exploration/exploitation balance.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.572-575
• /
• 2005

A microlens connected to microfluidic channel is fabricated. The microlens is sealed with an elastomeric membrane which deforms by pressure of fluid driven by a syringe pump resulting in the shape change of the microlens. The optical properties of the microlens could be controlled by changing the microlens shape. The microlens system were made of an elastomer, PDMS, using molding from a photoplastic master patterned by UV photolithography. The test results show the optical property of the lens could be made into convex and concave type by applying the fluidic pressure positive and negative.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.48 no.2
• /
• pp.9-15
• /
• 2011

In this paper, we propose a method to extract the external oblique muscle of abdomen images that is often excluded by previous method due to image distortion. In the preprocessing phase of the proposed method, we emphasize the brightness contrast with Ends-in search stretching algorithm after removing noise from the initial ultrasonic images. Then we apply average binarization in vertical direction to extract candidate fascia areas. After removing other areas than fascia with morphological characteristics, the lost part in the fascia during the process is restored with such characteristic information and location information. Then the skin area is also removed with information from the arc appearing in convex filming and the candidate muscle areas are extracted by overlapping two results two way up-down search algorithm. Another noise removing process is done to determine the muscle area. In case of obtaining obscure result, after restoring the muscle area by smearing method, the thickness of the muscle is measured by min square method. The experiment verifies that the proposed method is sufficiently effective to analyze the size and shape of muscles in abdomen in ultrasonography than previously used methods.

• Journal of the Korean Geosynthetics Society
• /
• v.17 no.1
• /
• pp.95-109
• /
• 2018

Recently, GRS (Geosynthetic Retaining Segmental) wall has been widely used as a method to replace concrete retaining wall because of its excellent structural stability and economic efficiency. It has been variously applied for foundation, slope, road as well as retaining wall. The GRS wall system, however, has a weak point that is serious crack of wall due to stress concentration at curved part of it. In this study, therefore, behaviour of GRS wall according to shape of it, shich has convex and concave, are analysed and compared using Finite Element analysis as the fundamental study for design optimization. Results including lateral deflection, settlements of ground surface and wall obtained from 2D FE analysis are compared between straight and curved parts from 3D FE analysis.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.10
• /
• pp.1155-1162
• /
• 2012

The purpose of this study is to investigate the effects of the bead shape on the crash performance of an aluminum crash box under a low-velocity impact condition. The initial peak load and impact energy absorption of a crash box with three types of bead shapes-edge concave, surface convex, and surface concave type-were studied through an FE analysis and an experiment. In addition, the effects of the bead shapes on the crash performance of the crash box were verified through a low-velocity-impact test with a front side member assembled with an aluminum crash box. The initial peak load of the surface-concave-type crash box was reduced by the bead, and therefore, deformation of the front side member at initial contact could be prevented. Furthermore, there was no deformation of the front side member after the impact test because the crash box with a surface-concave-type bead absorbed all the impact energy.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.8
• /
• pp.1998-2009
• /
• 1998

An effective algorithm for tracking rigid or non-rigid moving object(s) which segments local moving parts from image sequence in the presence of backgraound motion by camera movenment, predicts the direction of it, and tracks the object is proposed. It requires no camera calibration and no knowledge of the installed position of camera. In order to segment the moving object, feature points configuring the shape of moving object are firstly selected, feature flow field composed of motion vectors of the feature points is computed, and moving object(s) is (are) segmented by clustering the feature flow field in the multi-dimensional feature space. Also, we propose IRMAS, an efficient algorithm that finds the convex hull in order to cinstruct the shape of moving object(s) from clustered feature points. And, for the purpose of robjst tracking the objects whose movement characteristics bring about the abrupt change of moving trajectory, an improved order adaptive lattice structured linear predictor is used.