• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1253-1258
• /
• 2007

The media transport systems, such as printers, copy machines, facsimiles, ATMs, cameras, etc. have been widely used and being developed rapidly. In the development of those sheet-handling machineries, it is important to predict the static and dynamic behavior of the sheet with a high degree of reliability because the sheets are fed and stacked at such a high speed. Flexible media are very thin, light and flexible, so they behave in geometric nonlinearity with large displacement and large rotation but small strain. In the flexible media analysis, aerodynamic effect from the surrounding air must be included because any small force can make large deformation. In this paper, only the flexible media analysis is performed as early stage of analysis including aerodynamic effect. Through formulations and simulations for total Lagrangian(TL), updated Lagrangian (UL) and co-rotational(CR) method which are widely used for geometric nonlinear analysis, usefulness and reliability of each methods are investigated.

• Tunnel and Underground Space
• /
• v.16 no.4 s.63
• /
• pp.288-295
• /
• 2006

In this study, dynamic behavior of the vehicles is analyzed, while the track is subjected to lateral vibrations due to earthquake and blasting load. A computer program(WERIA, Wheel Rail Interaction Analysis) is used, which can simulate dynamic responses of vehicles subjected to lateral vibrations. The analysis considers two types of vehicles: I.e. power cars of KTX and Busan subway train. It can also consider the interaction with sub-structures such as tracks and soil. The creep force module is considered, and the running safety of railway vehicles subjected to earthquake and blasting loading is studied. Based on the results of this study, the running safety of the vehicles can be confirmed against lateral vibration.

• Proceedings of the Korea Contents Association Conference
• /
• 2004.11a
• /
• pp.265-268
• /
• 2004

Keyword matching technique which is used in most information retrieval systems is unfit for efficient processing of geometrically increasing information. The problem can be solved by using semantic information and an efficient method of semantic processing is introduced in this paper. The technique uses conceptual graph to represent the semantic information and apply it for information retrieval. The implemented system can perform exact matching and partial matching. Partial matching has two different types. One is syntactic partial matching and the other is semantic partial matching. The semantic semilaries are measured by the subclass relations in the ontology. The introduced technique can be used not only information retrieval but also in various applications such as an implementation of dynamic hyperlinks.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.4 no.1 s.12
• /
• pp.1-14
• /
• 2004

The objective of this study is firstly to frame up the seismic safety of concrete gravity dams. It is necessary to analyze seismic response and evaluate seismic performance of concrete gravity dams during earthquake. In this study, seismic damage and dynamic analysis of concrete gravity dams using structural analysis package such as SAP2000 and MIDAS were performed. Additional dynamic water pressure due to earthquake considered as additional mass for numerical seismic analysis. According detailed analysis, the vibration through the dam structure (transverse to water flow) seems to be very critical depending on the shape of the dam. For more precise evaluation of seismic fragility of concrete gravity dams, further research is still needed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.05a
• /
• pp.141-144
• /
• 2008

Atomization characteristics and spatial distribution of the spray emanating from an injector of liquid-propellant thruster are investigated by using dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters such as the mean velocity, Sauter mean diameter (SMD), and velocity fluctuation are measured at various locations along the spray axis as well as on the radial direction. Those data are quantified in radial profile and also used to scrutinize the correlation between diameter and turbulence intensity of spray droplets. For the better visual grasp, dynamic behavior of spray droplets along the spray stream is presented through the velocity vectors projected on the plane of geometric axis of nozzle orifice and radial coordinate.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.2
• /
• pp.183-189
• /
• 2010

This paper deals with the comparison of analysis methodologies by applying both Euler angle and quaternion to observe the kinematical behavior of the universal joint system used as an automotive drive-shaft. At first, conventional approaches are applied to predict a kinematical behavior by introducing only Euler angles into the universal joint system, but turns out to be lack in consistency and reliability of the analysis. Then to overcome this deficiency in numerical analysis a different methodology is proposed by using quaternion in this system. Its corresponding advantage is discussed in terms of kinetic energy, rotational velocity and rotational displacement. The application of quaternions in the numerical experiment is shown to be a more useful and valid way of establishing the ideal analytical model of the universal joint system.

• The Mathematical Education
• /
• v.53 no.4
• /
• pp.493-507
• /
• 2014

The purpose of this study is to analyze how high school students form and interpret the mental image in the process of solving regular polyhedron problems. For this purpose, a set of problems about the regular polyhedron's vertex is developed on the base of the regular polyhedron's duality and circulation. and applied to 2 students of the 12th graders in D high school. After 2 hours of teaching and learning and another 2 hours of mental image-analysis process, the following research findings are obtained. Fisrt, a student who recorded medium high-level grade in the national scholastic test can build the dynamic image or the patten image in the process of solving regular polyhedron's vertex problems by utilizing the 3D geometry program. However, the other student who recorded low-level grade can build the concrete-pictorial image. Second, pattern image or dynamic image can help students solve the regular polyhedron's vertex problems by proper transformation of informations and the mental images while the concrete-pictorial image does not help. Hence, it is recommended that the mathematics teachers should develop teaching and learning materials about the regular polyhedron's duality and circulation and also give students suitable questions to build the various mental images.

• Journal of the Korea Computer Graphics Society
• /
• v.24 no.1
• /
• pp.1-8
• /
• 2018

We propose a modified real-time marching cubes technique that extracts isosurfaces in the form of connected meshes instead of triangle soup. In this way, a various mesh-based isosurface rendering techniques can be implemented and additional information of the isosurfaces such as its topology can be extracted in real-time. In addition, we propose a real-time technique to extract adjacency-triangle structure for geometry shaders that can be used for various shading effects such as silhouette rendering. Compared with the previous technique that welds the output triangles of classical marching cubes, our technique shows up to 300% performance improvement.

• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.541-545
• /
• 1997

This paper presents a modified geometric active contour model or edge detection and segmentation of computed tomography(CT) scan images. The method is based on the level setup approach developed by Osher and Sethian and the modeling of propagation fronts with curvature dependent speeds by Malladi. Based on above algorithms, the geometric active contour is obtained through a particular level set of hypersurface lowing along its gradient force and curvature force. This technique retains the attractive feature which is topological and geometric flexibility of the contour in recovering objects with complex shapes and unknown topologies. But there are limitations in this algorithm which are being not able to separate the object with weak difference from neighbor object. So we use speed limitation filter to overcome those problems. We apply a 2D model to various synthetic cases and the three cases of real CT scan images in order to segment objects with complicated shapes and topologies. From the results, the presented model confirms that it attracts very naturally and efficiently to the desired feature of CT scan images.

• Proceedings of the KAIS Fall Conference
• /
• 2006.05a
• /
• pp.513-516
• /
• 2006

인터넷의 발달로 인터넷 사용자는 기하급수적으로 증가하게 되었으며, 인터넷을 기반으로 하는 수많은 응용프로그램들이 개발되고 있다. 인터넷상에는 수많은 사이트(site)들이 존재하며 방문자들의 주목을 받기 위하여 여러 가지 기법을 선보이고 있다. 그러나 컴퓨터상의 정적인 2차원 평면하에서는 현실감 및 입체감을 경험하는 것이 한계가 있다. 따라서 플래시(flash)와 같은 플러그인(plug-in) 및 동영상을 도입하여 동적인 컨텐츠를 제공하는 사례가 늘고 있으며 한편으로 최근 가상현실(Virtual Reality) 기법을 이용한 사이트들이 점차 증가하고 있는 추세이다. 가상현실은 컴퓨터가 제공하는 3차원의 컴퓨터 그래픽 기술을 이용하여 사용자와 온라인으로 상호대화를 하는 기법이라고 간단히 정의할 수 있다[2,3]. 가상현실을 이용하여 3차원 실시간 구현 기술을 웹에 적용시킴으로서 3차원 공간에서 현실감을 느낄 수 있게 함과 동시에 입체적인 정보를 사용자에게 제공할 수 있게 하는 기법들이 속속 선보이게 되었다. 현재 다양한 인터넷 기반 3차원 가상 현실 기술이 각각 서로 다른 기술 및 특징들을 가지고 나와 있다. 3차원 가상 공간을 구현한다. 선택한 물체에 사진 이미지기반 방식과 3차원 모델링 방식을 모두 적용하여 보다 현실감 있고 모든 방향으로의 접근이 가능하도록 하며. 또한 3차원 사운드 및 동영상도 함께 제공하며 가상 공간과 인간의 실질적 교감을 현실화 시키는 인터페이스를 제시하는 데에 연구의 목적이 있다.