• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.97-101
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• 2005

ZnO thin films were grown at different plume-substrate (P-S) angles of 90$^{\circ}$ (on-axis PLD), 45$^{\circ}$ and 0$^{\circ}$ (off-axis PLD) using pulsed laser deposition. The x-ray diffraction pattern exhibiting a dominant (002) and a minor (101) peak of ZnO indicates all films were strongly c-axis oriented. By observing of (002) peak, the FWHMs of ZnO (002) peaks decreased and c-axis lattice constant approached the value of bulk ZnO as P-S angle decreased. Whereas the carrier concentration of ZnO thin film deposited at P-S angle of 90$^{\circ}$ was ~ 10$^{19}$ /cm$^{3}$, the Hall measurement of ZnO thin films deposited at P-S angles of 0$^{\circ}$ and 45$^{\circ}$ was impossible due to the decrease of the carrier concentration by the improvement of stoichiometry and crystalline quality. By decreasing P-S angle, the grain size of the films and the UV intensity investigated by photoluminescence (PL) increased and UV peak position showed red shift. The improvement of properties in ZnO thin films deposited by off-axis technique was due to the decrease of repulsive force between a substrate and the particle in plume and the relaxation of supersaturation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.9
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• pp.81-87
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• 2019

The automatic tool changer of a machining center consists of a tool magazine and a cam box, and the core components of the cam box are a roller gear cam and a turret. Recently, the roller gear cam of a cam box has been replaced by a ball gear cam. In this study, the design and machining method of ball gear cam for an automatic tool changer was studied. Additionally, an algorithm for a 4-axis post processing method was established from an instrumental formula by designing a ball gear cam, thus preventing machining at the bottom of ball end mill and enabling the ball on the turret to be driven at the entrance and exit of a curve without collision due to machining errors. In conclusion, machining using only the 4-axis method including the C-axis on a BC -Type 5-axis machine produced the desired ball gear cam.

• The Korean Journal of Ecology
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• v.21 no.4
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• pp.321-328
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• 1998

To describe the major environmental factors operating in coastal wetland and to characterize the distribution of the plant species over the wetland in relation to the major environmental gradients, 12 soil physical and chemical properties were determined. The gradient of water and osmotic potential of soil, electrical conductivity, sodium and chloride content and soil texture alsong the three habitat types of salt marshes, salt swamp and sand dune were occurred. The 24 coastal plant communities from principal component analysis (PCA) on the 12 variables were at designated as a gradient for soil texture and water potential related with salinity by Axis I and as a gradient for soil moisture and total nitrogen gradient by Axis II On Axis I were divided into 3 groups (1) 9 salt marsh communities including Salicornia herbacea communities (2) 5 salt swamp communities including Scirpus fluviatilis communities and (3) 10 sand dune communities including Jmperata cylindrica communities on Axis II were divided into 2 groups (1) salt marsh and sand dune communities, and (2) 3 salt swamp communities. The results could account for the zonation of plant communities on coastal wetland observed alsong envionmental gradients.

• Journal of Computational Design and Engineering
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• v.2 no.4
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• pp.268-275
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• 2015

Blisk is an essential component in aero engines. To maintain good aero-dynamic performance, one critical machining requirement for blades on blisk is that the generated five-axis tool path should be boundary-conformed. For a blade discretely modeled as a point cloud or mesh, most existing popular tool path generation methods are unable to meet this requirement. To address this issue, a novel five-axis tool path generation method for a discretized blade on blisk is presented in this paper. An idea called Linear Morphing Cone (LMC) is first proposed, which sets the boundary of the blade as the constraint. Based on this LMC, a CC curve generation and expansion method is then proposed with the specified machining accuracy upheld. Using the proposed tool path generation method, experiments on discretized blades are carried out, whose results show that the generated tool paths are both uniform and boundary-conformed.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.811-817
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• 2020

This study aims to evaluate the Modulation Transfer Function (MTF) according to the change in the number of channels of the CT examination device by changing the posture of the patient to the X-axis and Y-axis in the wrist joint CT examination. Using a CT device and a wrist phantom, the test was performed by moving 0 (matched), 5, 10, and 15 cm in the X-axis around the isocenter, and the Z-axis was rotated by -20° and -40°. For the test, 16, -40 and 64 channels were used to check whether there was a difference for each number of channels. The examined images were compared by measuring the MTF values of the ulna and left and right sides of the radius. In the experiment where the isocenter was moved along the X-axis, the MTF value decreased with an increase in the moving distance, and the MTF value was found to be unaffected by the number of channels. In the experiment in which the wrist joint was rotated by -20° and -40° on the Z-axis, the degree of deviation and MTF were found to be irrelevant. It was not related to the number of channels either. In conclusion, the movement of the wrist along the X-axis should be restrained as much as possible for a wrist joint CT scan, whereas deviation around the Z-axis depending on the environment for the patient would not affect the MTF of the image.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.399-404
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• 2002

An efficient method of machining impeller is presented. In the roughing process, the cutting area is divided into two regions to reduce cutting time and select cutting tools. The regions are determined by characteristic point on the geometry of impeller blade. Then, the tool of the maximum radius is selected in each area. Tool interference in cutting areas is avoided by checking the intersection between cooing tool axis and ruling line on blade surface.

• Journal of Digital Convergence
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• v.13 no.12
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• pp.285-290
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• 2015

The purpose of this study is to compare the status of eyesight according to the change of astigmatism axis in myopic astigmatism and to minimize errors in making astigmatic glasses based on accurate optometry and prescription. The subjects were 93 males and females(186 eyes) who have myopic astigmatism without any ocular disease or systemic disease. We performed comparative analysis on the status of visual acuity according to the change of astigmatism axis to 5, 10 and 15 degree in corrected eyesight 1.0. The direct astigmatism was the most common astigmatism type among the 186 eyes. After all subjects were perfectly corrected into 1.0, the change of astigmatism axis affected eyesight; The results suggested that the more change was made in astigmatism axis, the worse their eyesight would become. The main astigmatism type was changed from direct astigmatism to inverse astigmatism as age increased. The change of the astigmatism axis resulted in failing of corrected eyesight. Therefore, the convergence of examination and correction for astigmatism strength and axis is necessary when conducting refraction inspection for astigmatism.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.411-416
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• 2019

In this paper, we describe a measurement system based on vision for detecting the rotation axis of dimpled golf ball. Some golf balls have wrong rotation axis owing to bad production and scratch. A flying golf ball makes sliced or curved motion mainly to owing the wrong rotation axis of golf ball. Dimples of golf ball make a golf ball higher and more straight flying. When we hit a golf ball by driver or iron club, the dimpled ball flies straight and rotates as well. While the ball flying, the rotating axis of the ball convergence. And this makes the ball motion curved. If we hit a golf ball in direction of the rotation axis, the flying ball makes straight motion. In this paper, we develop a control system to detect convergence axis and time of flying golf ball based on vision system. To show validity of the developed system, We experimented several case for dimpled golf balls.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.2
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• pp.113-117
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• 2014

Laser Assisted Machining (LAM) was often used in process of difficulty-to-cut materials. In previous study, Laser assisted machining was a straight path processing using 1-axis manipulator in laser module. But 1-axis manipulator in laser module was able to process only straight path. So, in this study, laser module in laser assisted machining equipped to 2-axis manipulator. 2-axis manipulator has two motors. First motor is machining direction motor and second motor is Vertical Motor. Machining direction motor rotates in the direction of machining and vertical motor rotates vertical direction in the direction of machining. Machining path of laser assisted machining was considered diagonal path and curved path of laser heat source. This study calculated the 2-axis manipulator's rotation angle in diagonal path and curved path.

• Korean Journal of Computational Design and Engineering
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• v.15 no.5
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• pp.354-361
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• 2010

The paper presents an efficient computation of optimal tool length for 5-axis mold & die machining. The implemented procedure processes an NC file as an initial input, where the NC data is generated by another commercial CAM system. A commercial CAM system generates 5-axis machining NC data which, in its own way, is optimal based on pre-defined machining condition such as tool-path pattern, tool-axis control via inclination angles, etc. The proper tool-length should also be provided. The tool-length should be as small as possible in order to enhance machinability as well as surface finish. A feasible tool-length at each NC block can be obtained by checking interference between workpiece and tool components, usually when the tool-axis is not modified at this stage for most CAM systems. Then the minimum feasible tool-length for an NC file consisting of N blocks is the maximum of N tool-length values. However, it can be noted that slight modification of tool-axis at each block may reduce the minimum feasible tool-length in mold & die machining. This approach can effectively be applied in machining feature regions such as steep wall or deep cavity. It has been implemented and is used at a molding die manufacturing company in Korea.