• Korean Journal of Computational Design and Engineering
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• v.4 no.3
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• pp.173-179
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• 1999

In reverse engineering, when a shape containing multi-patched surfaces is digitized, the boundaries of these surfaces should be detected. The objective of this paper is to introduce a computationally efficient segmentation technique for extracting edges, ad partitioning the 3D measuring point data based on the location of the boundaries. The procedure begins with the identification of the edge points. An automatic edge-based approach is developed on the basis of local geometry. A parametric quadric surface approximation method is used to estimate the local surface curvature properties. the least-square approximation scheme minimizes the sum of the squares of the actual euclidean distance between the neighborhood data points and the parametric quadric surface. The surface curvatures and the principal directions are computed from the locally approximated surfaces. Edge points are identified as the curvature extremes, and zero-crossing, which are found from the estimated surface curvatures. After edge points are identified, edge-neighborhood chain-coding algorithm is used for forming boundary curves. The original point set is then broke down into subsets, which meet along the boundaries, by scan line algorithm. All point data are applied to each boundary loops to partition the points to different regions. Experimental results are presented to verify the developed method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.5
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• pp.15-21
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• 2009

Deformity detection in a Light Emitting Diode (LED) is an important aspect for improving its quality. These LED deformities can be checked through several methods. This paper details the automatic deformity detection inspection system of a LED using the LabVIEW Builder 3.6 software. This software has a graphical user interface which makes it easy to observe and modify the behavior of its element. The LabVIEWs essential elements are also presented and explained aside from its image acquisition system. Details on how to build an inspection system and how to implement vision inspection algorithm which mainly consists of edge detection, geometry point location, and distance measurement are included in this paper.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1107-1116
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• 2006

The droplet ejection process driven by an evaporating bubble in a thermal inkjet printhead is investigated by numerically solving the conservation equations for mass, momentum and energy. The phase interfaces are tracked by a level set method which is modified to include the effect of phase change at the interface and extended for multiphase flows with irregular solid boundaries. The compressibility effect of a bubble is also included in the analysis to appropriately describe the bubble expansion behaviour associated with the high pressure caused by bubble nucleation. The whole process of bubble growth and collapse as well as droplet ejection during thermal inkjet printing is simulated without employing a simplified semi-empirical bubble growth model. Based on the numerical results, the jet breaking and droplet formation behaviour is observed to depend strongly on the bubble growth and collapse pattern. Also, the effects of liquid viscosity, surface tension and nozzle geometry are quantified from the calculated bubble growth rate and ink droplet ejection distance.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1097-1107
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• 2001

In this paper, the wall following navigation algorithm of the mobile robot using a mono vision system is described. The key points of the mobile robot navigation system are effective acquisition of the environmental information and fast recognition of the robot position. Also, from this information, the mobile robot should be appropriately controlled to follow a desired path. For the recognition of the relative position and orientation of the robot to the wall, the features of the corridor structure are extracted using the mono vision system, then the relative position, the offset distance and steering angle of the robot from the wall, is derived for a simple corridor geometry. For the alleviation of the computation burden of the image processing, the Kalman filter is used to reduce search region in the image space for line detection. Next, the robot is controlled by this information to follow the desired path. The wall following control scheme by the PD control scheme is composed of two control parts, the approaching control and the orientation control, and each control is performed by steering and forward-driving motion of the robot. To verify the effectiveness of the proposed algorithm, the real time navigation experiments are performed. Through the result of the experiments, the effectiveness and flexibility of the suggested algorithm are verified in comparison with a pure encoder-guided mobile robot navigation system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.5
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• pp.568-575
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• 2015

A hand-made vehicle with a formula (VF-1) was designed and manufactured with the aim of realizing a lightweight and high-performance vehicle. The driver's body weight and stiffness of the frame were considered. The vehicle was equipped with a one-cylinder Exiv 250 engine with intake manifold potting for realizing weight reduction, high performance, and low cost. The suspension system for the formula was designed through the analyses and tests of vehicle motion and equipment. In a steering system, anti-Ackerman geometry was introduced to increase the transverse force during cornering. A full electric paddle shift system was adopted to decrease the braking distance. For protection against the distortion and warping of the frame, tungsten inert gas (TIG) welding technology was used.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.53-61
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• 1999

Impinging jets are observed when exhaust gases from missiles or V/STOL aircrafts impinge on the ground, flame deflector, ship deck, etc. The flow shows different patterns according to the nozzle geometry, nozzle-to-plate distance, and plate angle, for example. This paper describes experimental works on the phenomena (pressure distribution, occurrence of stagnation bubble, and so on.) when underexpanded supersonic jets impinge on a perpendicular flat plate using a supersonic cold-flow system, and compares the results with those obtained using a shock tunnel. The flow characteristics for the supersonic cold-flow system were also investigated. Surface pressure distribution of supersonic cold-flow system differed from that of shock tunnel because of water and temperature in the low-pressure chamber. Surface pressure distribution as to underexpanded ratio showed similar patterns together.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.6
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• pp.48-55
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• 2008

We have simulated the performance of a simple engine model with a gas turbine engine simulation program based on CFD. 2-dimensional Navier-Stokes code for the viscous flow was applied to simulate a compressor and a turbine, and the chemical equilibrium code with the lumped method was applied to simulate the combustor. Unsteady-flow phenomenon between rotor and stator of the compressor and the turbine was analyzed by steady mixing-plane method. In this way, the influence of the turbine blade pitch on the engine was investigated. It was shown that the compressor is operated at more higher pressure conditions as narrower the pitch distance of the turbine.

• Journal of Digital Contents Society
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• v.15 no.3
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• pp.347-355
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• 2014

The general octree structure is common for various applications including computer graphics, geometry information analysis and query. Unfortunately, the general octree approach causes duplicated sample data and discrepancy between sampling and representation positions when applied to sample continuous spatial information, for example, signed distance fields. To address these issues, some researchers introduced the dual octree. In this paper, the weakness of the dual octree approach will be illustrated by focusing on the fact that the dual octree cannot access some specific continuous zones asymptotically. This paper shows that the primal tree presented by Lefebvre and Hoppe can solve all the problems above. Also, this paper presents a three-dimensional primal tree traversal algorithm based the Morton codes which will help to parallelize the primal tree method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.922-927
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• 2009

The transducers used in active sonar on surface ships are packed in a specific geometry in the array drum in order to meet the requirements such as the source level, directional beam pattern, etc. This paper describes the acoustic characteristics of the cylindrical array which is based on a 64 vertical staves arrangement, each stave composed 5 independent transducers. Firstly, the single transducer on the rigid baffle in the water is analyzed with the Finite Element Method. From the result of the FE analysis nodal velocities on the radiation surface is calculated and used with the boundary conditions of the transducers mounted on the array drum. Then the acoustic pressure is calculated in the field points using the Boundary Element Method and the other acoustic informations, the source level, beam pattern, near field and far-field distance, were acquired.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.47-53
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• 2006

An Experiment was carried out to find the scheme far minimization of burr formation on inclined exit surface in drilling. Several drills with different geometry are used for drilling the workpiece with inclined exit surface. Step drills are specified with step angle and step size. The influence of the inclination angle of exit surface on burr formation was observed, which enables to analyze the burr formation mechanism on inclined exit surface. Along the edge on the inclined exit surface, burrs are formed by the bending deflection to feed direction and also burrs are formed in exit direction of cutting edge. To minimize the burr formed in feed direction, the corner angle which is formed by the inclination angle and step angle must be large enough not to be bent to burr. By decreasing step angle of drill and decreasing the distance between two axes of two holes, burr formation at the intersecting holes can be minimized. Burr formation mechanisms are analyzed according to the drill geometries and cutting conditions. Several schemes far burr minimization on inclined exit surface were proposed.