• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.21-27
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• 2001

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression, principle of virtual work is adapted The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants and stresses can be predicted by input of few factors.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.702-710
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• 1999

U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

• Journal of the Korea Convergence Society
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• v.2 no.3
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• pp.15-23
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• 2011

This paper deals with the analysis for the operation characteristic of PV 3 phase inverter, considering the state equation through d-q coordinates transformation, and proposes an algorithm of controlling current using PI(Proportional Integral) controller to control the output and the theory algorithm of sinusoidal PWM method to design inverter. And also this paper performs PV modelling using PSCAD/EMTDC S/W which is commonly used in analysis of distribution system and confirms effectiveness of the modelling proposed in this paper by analyzing and comparing the EMTDC/PSCAD simulation result with the theoretical method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.9
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• pp.869-876
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• 2017

Analysis of actuating forces and joint reaction forces are essential to determine the capacity of actuators, to control the mechanical system and to design its components. This paper presents an algorithm that calculates actuating forces(or torques), depending on the various types of driving constraints, in order to produce a given system motion in the joint coordinate space. The joint coordinates are used as the generalized coordinates of a kinematic system. System equations of motion and constraint acceleration equations are transformed from the Cartesian coordinate space to the joint coordinate space using the velocity transformation method. A numerical example is carried out to verify the algorithm proposed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.2
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• pp.213-223
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• 1998

This paper deals with the geoid modelling in and around Korean peninsula referred to Bessel ellipsoid. Several useful data were used to compute precise geoidal heights referred to GRS80 by remove and restore technique and FFT technique was used to evaluate Stokes' integral. All grid point elevations extracted from GTOPO 30 and Bessel coordinates of all grid point were computed through coordinates transformation by applying three transformation parameters. Finally, geoidal heights referred to Bessel ellipsoid were calculated by geometric method. As the results of this study, a precise gravimetric geoid model referred to GRS80 (KOGGDM33) and geoid model referred to Bessel ellipsoid(KOBGDM33) in and around Korean peninsula were developed. KOBGDM33 shows the gradual distribution of geoidal heights from -91.8 m in Yongampo to -39.0 m in the straits of Korea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.4
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• pp.125-132
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• 1987

The bundle adjustment used in photogrammetric data reduction is based on the collinearity condition. Photogrammetry has been used in many non-topographic applications. Due to the necessities of having fiducial marks and knowing initial approximations for interior and exterior orientation elements in bundle adjustment, it cannot be applied when non-metric cameras are used. Marzan and Karara develop the DLT(Direct Linear Transformation) program which directly transforms comparator coordinates into object space coordinates without approximate values. In this paper, several modifications of original DLT program have been made for accuracy improvement in close-range photogrammetry using non-metric cameras. In modified program, gross error detection method and computation of exterior orientation elements are incorporated, and more iterations are introdued.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.950-954
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• 2004

According to the rapid advance of computer and communication techniques, the request of mobile internet services is highly increasing. However, the main obstacles for mobile vector map service environments, are large data volume and narrow wireless bandwidth. Among the many possible solutions, spatial data compression technique may contribute to reduce the load of bandwidth and client response time. This thesis proposes two methods for spatial data compression. The one is relative coordinates transformation method, and the other is client coordinates transformation method. And, this thesis also proposes the system architecture for experiments. The two compression methods could be evaluated the compression effect and the response time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.358-362
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• 2004

According to the rapid advance of computer and communication techniques, the request of mobile internet services is highly increasing. However, the main obstacles for mobile vector map service environments, are large data volume and narrow wireless bandwidth. Among the many possible solutions, spatial data compression technique may contribute to reduce the load of bandwidth and client response time. This thesis proposes two methods for spatial data compression. The one is relative coordinates transformation method, and the other is client coordinates transformation method. And, this thesis also proposes the system architecture for experiments. The two compression methods could be evaluated the compression effect and the response time.

• International Journal of Computer Science & Network Security
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• v.22 no.11
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• pp.373-380
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• 2022

The field of land surveying is changing dramatically due to the way data is processed, analyzed and presented. Also, there is a growing demand for digital spatial information, coming primarily from the GIS (Geographical Information System) user community. Such a demand has created a strong development potential for a new land surveying software. An overview of the development and capabilities of a land surveying software platform based on the Windows system, SurveyingMap, is presented. Among its many features, SurveyingMap provides a lot of adaptability for networks adjustment, geodetic and plane coordinates transformation, contouring, sectioning, DTM (Digital Terrain Model) generation, and large scale mapping applications. The system output is compatible with well known computer aided drafting (CAD) /GIS packages to expand its scope of applications. SurveyingMap is also suitable for non-technical users due to the user-friendly graphic user interface. The system could be used in engineering, architecture, GIS, and academic teaching and research, among other fields. Two applications of SurveyingMap, extension of field control and large scale mapping, for the case study area are established. The results demonstrate that the system is adaptable and reasonably priced for use by college and university students.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.669-675
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• 2005

This paper proposes coordinates transformation and calibration algorithm using 3D parabolic coordinate transformation and delta-bar-delta neural algorithm for the omni-directional image captured by catadioptric camera. Experimental results shows that the proposed algorithm has accuracy and confidence in coordinate transformation which is sensitive to environmental variables.