• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.895-903
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• 2004

In this paper are presented the blade vibration characteristics at the starting conditions of the low pressure multistage axial compressor of heavy-duty 100 MW gas turbine. Vibration data have been collected through strain gauges during aerodynamic tests of the model compressor. The influences of operating modes at the starting conditions are investigated upon the compressor blade vibrations. The exciting mechanisms and features of blade vibrations are investigated at the surge, rotating stall, and buffeting flutter. The influences of operating modes upon blade dynamic stresses are investigated for the first and second stages. It is shown that a high dynamic stress peak of 120 MPa can occur in the first stage blades due to resonances with stall cell excitations or with inlet strut wake excitations at the stalled conditions.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.9
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• pp.857-862
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• 2011

This paper studies the output consensus problem for a class of heterogeneous linear multi-agent systems under a fixed directed communication network. The dynamics, as well as its dimension, of each agent can widely differ from the others, but all the agents are assumed to have the same transfer matrix. In addition, only the system outputs are constrained to be delivered through the network. Under these conditions, we show that the output consensus is reached by a group of identical controllers, which is designed to achieve the state consensus for the homogeneous multi-agent system obtained from the minimal realization of the transfer matrix. Finally, an example is given to demonstrate the proposed result.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.59.1-59.1
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• 2016

Blue Straggler Stars(BSS) affect their host star cluster in various parameters like color, dynamics, etc. For this reason, it is important to know how to relate BSS frequency and evolution of their host stellar system. To statistical study about global properties of open clusters as the environments of BSS formation, we use three catalogues - (1) two galactic open clusters catalogues including BSS candidate, (2) Milky Way Star Cluster (MWSC) survey data. Then, we compare with the data of two BSS catalogues for test of the result of Marchi et al. 2006. We also investigate the radial mass distribution in open cluster, because it is possible that changing the gradient of radial mass distribution cause increasing the BSS frequency. When we group the open cluster into having BSS or not and other criteria, the groups show slight discrepancies, but we show some important results.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.431-436
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• 2010

Recently, several open source codes for computational fluid dynamics (CFD) have been emerged and are spreading fast. Our group has chosen OpenFOAM as a platform to develop our own in-house code. In this paper, we would like to share the information on the codes and what we have experienced so far. We introduce several features of OpenFOAM, which include the performance compared with commercial packages, estimation for current user population and our own prospect for future improvement in performance and growth in user population. In addition, we briefly introduce our experience gained in embedding the level set method into the OpenFOAM.

• Journal of computational fluids engineering
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• v.15 no.3
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• pp.46-53
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• 2010

Recently, several open source codes for computational fluid dynamics (CFD) have been introduced and are spreading fast. Our group has chosen the OpenFOAM as a platform to develop our own in-house code. In this brief review, we would like to share the information on the codes and what we have experienced so far. We introduce several features of OpenFOAM, which include the performance compared with commercial packages, estimation for current user population, and our own prospect for future improvement in performance and growth in user population. In addition, we briefly introduce our experience gained in embedding the level set method into the OpenFOAM.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.152-159
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• 2001

In this paper it is intended to set-up a sound model of the 60,000rpm 100kW prototype APU gas turbine rotor-bearing system, and particularly to investigate the influences of the tie shaft on the rotordynamic characteristics of the entire APU gas turbine rotor-bearing system, employing the dual shaft model. Firstly, a mock-up APU rotor has been constructed to test and verify the model. Analytical natural frequency results have agreed with the corresponding modal test ones to within 5% difference. Then, the rotordynamic characteristics of the prototype APU rotorbearing system have been investigated. Natural vibration and unbalance response analyses results have shown that the inner tie shaft resonance can cause high enough vibration of the outer main rotor shaft. This could be a concern as the rotor journals operate on very thin air film at high speed. It is concluded as a conservative design practice that the inner tie shaft should be explicitly modeled in the rotordynamic analysis of the APU rotor-bearing system.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.6
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• pp.501-507
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• 2013

This paper presents the development and balancing control of GYROBO, a one wheeled mobile robot system. GYROBO is a disc type one wheel mobile robot that has three actuators, a drive motor, a spin motor, and a tilt motor. The dynamics and kinematics of GYROBO are analyzed, and simulation studies conducted. A one-wheeled robot, GYROBO is built and its balancing control is performed. Experimental studies of GYROBO's balancing abilities are conducted to demonstrate the gyroscopic effects generated by the spin and tilt angles of a flywheel.

• Journal of Contemporary Eastern Asia
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• v.14 no.2
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• pp.87-96
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• 2015

Social media comprises a vast and consequential landscape that has been poorly mapped and understood. Hundreds of millions of people have eagerly moved many of the conversations and discussions that compose civil society into these services and platforms. There is a need to document and analyze these social spaces for many academic and commercial purposes. The Social Media Research Foundation has engaged a strategy to cultivate better research into the structure and dynamics of social media. The foundation is dedicated to the creation of open tools, open data, and open scholarship related to social media. It has implemented a free and open network collection, analysis, and visualization tool called NodeXL to facilitate social media network research. Using NodeXL a group of researchers has collectively authored a publicly available archive, called the NodeXL Graph Gallery, composed of network data sets and visualizations from users around the world. This site has enabled the aggregation of tens of thousands of network datasets and images. Use of the archive has led to scholarly research results that are based on the wide range and scope of social media data sets available.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.223-235
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• 1993

VTR(Video Tape Recorder) has very complicated mechanisms composed of various cams, links, gears and so on. To satisfy kinematic requirements of VTR components, various geometric constraints between rigid bodies and a translational cam design program are developed. Mechanisms of VTR are divided into functional groups like a control part, a loading part and a tape guide part. Each group is modeled for kinematic and dynamic analysis. Finally, all groups are combined together for a complete VTR model and loads required for each function of VTR controls are studied. Detailed description of developed programs are presented and result are discussed.

• Macromolecular Research
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• v.8 no.3
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• pp.125-130
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• 2000

Resorcinol formaldehyde resins are synthesized by polycondensation of resorcinol with formal-dehyde and have various structures by the condensation type. The influence of polycondensation type on the stability and structure of the resorcinol formaldehyde resin was studied by molecular mechanics and molecular dynamics. The resins formed by 2,6-polycondensation and 4,6-polycondensationwith head-to-tail orientations have structures of intramolecular hydrogen bonds between 1-hydroxyl groups and between outer hydroxyl groups of the adjacent resorcinols, respectively. The resin formed by 2,6-polycon-densation with head-to-head orientation has a structure that inner hydroxyl groups cluster in the center of the molecule. Energetical stability of the resin is affected by both the intramolecular hydrogen bonds and the steric' hindrance by phenyl group.