• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.5
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• pp.58-64
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• 2000

This paper proposes a method for determining optimal EDM parameters based on discharge area from the physical model of a tool electrode. Main parameters, which affect the EDM performance, are peak value of currents, pulse-on time, and pulse-off time. Such parameters are closely dependent on the discharge area in EDM process. In this paper the discharge area is estimated from the CMM scanning data to the tool electrode. The method is very useful when any geometric information to the tool electrode is not provided from tool modeler or producer. The method consists of following four steps. First a triangulation mesh is constructed from the CMM data. Secondly, the z-map is modeled from the triangulated mesh. Thirdly, the discharge area is estimated from intersection between the z-map model and a z-height plane. Finally, the machining parameters are easily calculated by some known EDM equations to the discharge area. An example is introduced to show that the machining parameters are calculated from the CMM data to a tool electrode.

• Imaging Science in Dentistry
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• v.47 no.2
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• pp.75-86
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• 2017

Purpose: The purpose of this study was to apply a newly developed free software program, at low cost and with minimal time, to evaluate the quality of dental and maxillofacial cone-beam computed tomography (CBCT) images. Materials and Methods: A polymethyl methacrylate (PMMA) phantom, CQP-IFBA, was scanned in 3 CBCT units with 7 protocols. A macro program was developed, using the free software ImageJ, to automatically evaluate the image quality parameters. The image quality evaluation was based on 8 parameters: uniformity, the signal-to-noise ratio (SNR), noise, the contrast-to-noise ratio (CNR), spatial resolution, the artifact index, geometric accuracy, and low-contrast resolution. Results: The image uniformity and noise depended on the protocol that was applied. Regarding the CNR, high-density structures were more sensitive to the effect of scanning parameters. There were no significant differences between SNR and CNR in centered and peripheral objects. The geometric accuracy assessment showed that all the distance measurements were lower than the real values. Low-contrast resolution was influenced by the scanning parameters, and the 1-mm rod present in the phantom was not depicted in any of the 3 CBCT units. Smaller voxel sizes presented higher spatial resolution. There were no significant differences among the protocols regarding artifact presence. Conclusion: This software package provided a fast, low-cost, and feasible method for the evaluation of image quality parameters in CBCT.

• Journal of Korean Society for Geospatial Information Science
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• v.4 no.1 s.6
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• pp.115-119
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• 1996

odel). One of important tasks for hydrological analysis is the division of watershed. It can be an essential factor amThe main objective of this study is to extract of the geometric characteristics of the Pyongchang River basin, headwaters of the South Ran River. A GIS is capable of extracting various hydrological factors from DEM(digital elevation mong various geometric characteristics of watershed. In this study, watershed itself and other geometric factors of watershed are extracted from DEM by using a GIS technique. The manual process of tasks to obtain geometric characteristics of watershed is automated. by using the function of ARC/INFO software as a GIS package. Scanned data is used for this study and it is converted to DEM data Various forms of representation of spatial data are handled in main modules and a GRID module of ARC/INFO. A GRID module is used on a stream in order to define watershed boundary, so it would be possible to obtain the watersheds. Also, a flowdirection, stream networks and others are generated. The results show that GIS can aid watershed management and research and surveillance. Also the geometric characteristics as parameters of watershed can be quantified by a using GIS technique. Resonable results can be obtained as compared with conventional graphic methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.1055-1058
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• 2002

Drilling process is one of the most common, yet complex operations among manufacturing processes. The performance of a drill is largely dependent upon drilling forces. Many researches focused on the effects of drill parameters on drilling forces. In this paper, the stresses occurring in drilling process are analyzed by finite element method. The analytic drilling forces considering the drill parameters and drilling conditions are used. Also, with ANSYS, geometric modeling and mesh generation of drill is performed automatically. From the study, optimal drill design and drilling condition determination may be achieved.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.40-47
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• 2003

In this paper, we constructed the analytic model of control valve as a function of electric and geometric parameters, and analyzed the influence of the design parameters on the dynamic characteristics. For improving the dynamic characteristics, optimal design is conducted by applying sequential quadratic programming method to the analytic model. This optimal design aims to minimize the response time and maximize force efficiency. By this procedure, control valve can be designed to have fast response in motion.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.88-97
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• 1994

We persent a method for kinematic calibration of open chain mechanisms based on the product of exponentials (POE) formula. The POE formula represents the forward kinematics of an open chain as a product of matrix exponentials, and is based on a modern geometric interpretation of classical screw theory. Unlike the kinematic parameters in the POE formula vary smoothly with changes in the joint axes;ad hoc methods designed to address the inherent singularities in the D-H parameters are therefore are therefore unnecessary. After introducing the POE formula, we derive a least-squares kinematic calibration algorithm for general open chain mechanisms. Simulation results with a 6-axis open chain are presented.

• The Mathematical Education
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• v.25 no.3
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• pp.57-69
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• 1987

A geometric interpretation of t-designs, in the context of posets, is given in the association scheme, not isomorphic with the Hamming scheme H(2,4), but having the same parameters as H(2,4). It is also shown that there is no similar poset which characterizes the designs for ally of the three exceptional association schemes, not isomorphic with the Johnson scheme J(8,2), but having the same parameters as J(8,2).

• 연구논문집
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• s.24
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• pp.13-26
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• 1994

The choice of design parameters for a robot arm depends on the desired workspace, load lifting capacity, application requirements, and the performance of the robot. The inverse process, which is the determination of a single robot's workspace for a given specification is also a common practice and is as important to the designers as it is to the users. Based on the geometric influence coefficients, the workspace areas on the vertical Y-Z plane are investigated and calculated. Using these areas, the effects of link parameters, link length ratios and joint rotation angles, are investigated.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.163-167
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• 2003

A novel method for 3-dimensional dynamic analysis of marine slender structure gas been developed by using Euler parameters. The Euler parameter rotation, which is being widely used in aerospace vehicle dynamics and multi-body dynamics, has been applied to elastic structure analysis. Large deformation of flexible slender structures is described by means of Euler parameters. Euler parameter method is implemented effectively in incremental-iterative algorithm for 3D dynamic analysis. The normalization constraint of Euler parameters is efficiently satisfied by means of a sequential updating method.

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.8-8
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• 2003