• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.3
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• pp.101-110
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• 2002

Most of the agricultural structures are in shortage of feasible facility management because these structures are small in size and spacially distributed in rural area. Inspection tools based on visual inspections are generally used for agricultural structures in most of the countries, including Korea. It is necessary to survey data of the irrigation structures to maintain records, and to develop the interface program by constructing database of inspection data. This study was conducted to develop a system for safe appraisal and repair works on agricultural irrigation structures. Repair and rehabilitation method can be chosen from an optimum viewpoint if the information between the method and life-cycle management cost of agricultural structures is constructed in the database. In this study, the system assisting onsite field investigation and determining the typical rehabilitation method of typical agricultural structural problems such as fractures and cracks of members was developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.933-941
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• 1997

In the analysis of thin elastic structures such as plate and shell-like structures, classical lower-order theories like Kirchhoff and Reissner-Mindin theories are insufficient to describe the behavior of such structures in the region where the state of stresses is complex. On the other hand, the fully three dimensional theory of linear elasticity can provide desired analysis accuracy, but requires expensive computational implementation compared to the classical theories. This paper is concerned with the development of hierarchical models for elastic structures which can be used for hierarchical modeling for the analysis of such structures. Derivation and limit model analysis (when the thickness of structures tends to zero) of hierarchical models are presented together with a introduction of modeling error estimation. Also, numerical results supporting theoretical results are given.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.62-70
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• 2005

In this paper, we present an architecture for supporting QoS multicast routing in mobile ad-hoc networks. The proposed architecture consists of three parts as follows. The first part is a mobility-based clustering as underlying structure for supporting stable multicast services. In the second part, a framework which can support and evaluate the stability of route and network for supporting QoS routing is presented. In the third part, we describe a method which uses two structures of the first and second parts for supporting QoS multicast routing services. The performance evaluation of our proposed architecture is accomplished via modeling and simulation using the Optimized Network Engineering tool(OPNET).

• Journal of the Korean Society for Aviation and Aeronautics
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• v.15 no.4
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• pp.24-32
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• 2007

In this study, computational structural vibration analyses of a smart unmanned aerial vehicle (SUAV) with tilt-rotors due to dynamic hub loads have been conducted considering detailed supporting structures of installed equipments. Three-dimensional dynamic finite element model has been constructed for different fuel conditions and tilting angles corresponding to helicopter, transition and airplane flight modes. Practical computational procedure for modal transient response analysis is successfully established. Also, dynamic loads generated by rotating blades and wakes in the transient and forward flight conditions are calculated by unsteady computational fluid dynamics technique with sliding mesh concept. As the results of present study, transient structural displacements and accelerations of the vibration sensitive equipments are presented in detail. In addition, vibration characteristics of structures and installed equipments of which safe operation is normally limited by the vibration environment specifications are physically investigated for different flight conditions.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.63-74
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• 2007

Large spatial structures consist of roof structure and its supporting structure. Authors simply call the supporting structure "lower parts" and roof structure "upper parts". To study the influence of an lower part on the seismic response of the upper part of a structure as a first step, authors substitute the upper part and the lower part of the structure to a single degree of freedom system individually, and set up a new 2 DOF structural model connected by them. It is clarified that the mass ratio and the period ratio of an upper part to a lower part are important parameters to find the amplification or reduction of the seismic response of an upper part.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.251-258
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• 2005

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.572-578
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• 2003

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Journal of the Korean Society for Railway
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• v.9 no.5 s.36
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• pp.582-587
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• 2006

Since Kyung-Bu High Speed Line has been introduced, a railway electrification has been proceeded rapidly. Therefore, in this study, a specification and application standard for an overhead catenary supporting thin walled steel pole using STKT590 material are proposed in order to improve an economical efficiency. To decide the specification, strength analysis, deflection analysis, deflection test and fracture test are performed. If the supporting structures using high strength materials such as STKT590 are installed, the advantages of cost by the materials price reduction and demand and supply are expected.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.4
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• pp.199-204
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• 2003

This paper proposes reconfigurable hardware structures for spreading and scrambling of multi-mode CDMA systems. The proposed reconfigurable structures supporting IS-95, cdma2000 and WCDMA, include a pseudo noise code generator, a channelization code generator and a control circuit for signal flow control. The proposed reconfigurable structures provide an efficient hardware usage for multi-mode CDMA systems. The synthesis results show the area reduction about 24.7% compared with the original code generators. The proposed structures can provide efficient reconfigurability and high speed operations for future SDR systems.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.179-194
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• 1991

This paper explains outline of a behavior analysis program for underground structures, and its application to a tunnel problem. The program can deal with elasto-plastic behavior of medium and supporting structures, discontinuous behavior due to existing joint, creation and propagation of cracks. in-situ loading condition, and incremental behavior due to stepwise excavation, etc. The program also has additional capabilities such as graphic output of mesh, displacement pattern, stress condition, and safety factor contour, and automatic mesh generation during the excavation steps.