• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.43-49
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• 2008

The evaporation heat transfer coefficient and pressure drop of R-22 and R-407C in horizontal copper tubes were investigated experimentally. The main components of therefrigerant loop are a receiver, a compressor, a mass flow meter, a condenser and a double pipe type evaporator (test section). The test section consists of a smooth copper tube of 4.3 mm and 6.4 mm inner diameter. The refrigerant mass fluxes were varied from 100 to $300[kg/m^2s]$ and the saturation temperature of evaporator were 5 [$^{\circ}C$]. The evaporation heat transfer coefficients of R-22 and R-407C rise with the increase in mass flux and vapor quality. The evaporation heat transfer coefficient of R-22 for inner diameter tube of 4.3 mm and 6.4 mm is about $7.3{\sim}47.1%$ and $5.68{\sim}46.6%$ higher than that of R-407C, respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.3
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• pp.267-275
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• 2007

This paper presents about energy input and output modeling for a flywheel energy storage system that can store and supply mechanical energy, which is emerging as one of clean energy sources, and the analysis and control of a PWM inverter system. Moreover, this paper describes flywheel's characteristics related to variations of mechanical and electrical parameters like as voltage and current versus speed characteristics formed as numerical formula and thus simulate behaviour-status of flywheel energy. Also for comparison and analysis between PI control and PDFF control, the modeling, design and analysis to the single-phase full bridge inverter with double loop feedback control is accomplished through numerical description and simulation. Finally, under load condition 0.1[pu], 1[pu]. it is validated that harmonic characteristics for voltage and current wave is controlled within 5% below even dynamics condition.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.109-116
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• 2006

An incremental approach to predict the time dependent flexural behavior of composite girder is presented in the framework of incremental finite element method. Age dependent nature of creep, shrinkage, and maturing of elastic modulus of concrete is prescribed in the incremental tangent description of constitutive relation derived based on the first order Taylor series expansion applying to the total from of stress-strain relation. The loop phenomenon in which age dependent nature of concrete causes stress redistribution and it causes creep in turn is taken into account in the formulation through the incremental representation of constitutive relation. The developed algorithm predicts the time dependent deflections of 4.8m long two span double composite box girder subjected to shrinkage, maturing of elastic modulus, and creep initially induced by self weight. Comparison shows a good agreement between the predicted and measured results.

• The KIPS Transactions:PartA
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• v.11A no.3
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• pp.189-198
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• 2004

We consider the fault hamiltonian properties of m ${\times}$ n meshes with two wraparound links on the first row and the last row, denoted by M$_2$(m,n), (m$\geq$2, n$\geq$3). M$_2$(m,n), which is bipartite, with a single faulty link has a fault-free path of length mn-l(mn-2) between arbitrary two nodes if they both belong to the different(same) partite set. Compared with the previous works of P$_{m}$ ${\times}$C$_{n}$ , it also has these hamiltonian properties. Our result show that two additional wraparound links are sufficient for an m${\times}$n mesh to have such properties rather than m wraparound links. Also, M$_2$(m,n) is a spanning subgraph of many interconnection networks such as multidimensional meshes, recursive circulants, hypercubes, double loop networks, and k-ary n-cubcs. Thus, our results can be applied to discover fault-hamiltonicity of such interconnection networks. By applying hamiltonian properties of M$_2$(m,n) to 3-dimensional meshes, recursive circulants, and hypercubes, we obtain fault hamiltonian properties of these networks.

• Journal of Digital Convergence
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• v.12 no.6
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• pp.13-22
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• 2014

This study analyzed the globalization policy of ICT SMEs and ventures using cognitive map analysis and derived the priority to importance about action plans using AHP model, while the globalization paradigm has been rapidly changing in the ICT industry. Empirical results showed that policy tool variables should be needed to develop because policy goal variables are generally presented more than policy tool variables. In addition, this cognitive map could be characterized by a scarcity of feedback loops which means policy landscape for ICT SMEs and ventures' globalization is unilateral rather than cyclical to reach policy goal from policy tools. Another finding is that creative economy policy variable was not observed as policy tool variable but as policy goal variable. This means creative economy can be implemented through support for ICT SMEs and ventures' globalization. Finally, for detailed policy measures, installation of global start-up center, recruiting and utilization of global specialists, revitalization of ICT R&D international collaboration study, enlargement of global investment network, accompanied overseas advance of large enterprises and SMEs are presented in order in terms of the importance of policy priority.