• East Asian mathematical journal
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• v.27 no.1
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• pp.23-33
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• 2011

Due to underutilization of spectrum under current inefficient and static spectrum management policy, various kinds of opportunistic spectrum access (OSA) strategies have appeared. Myopic policy is a simple and robust OSA strategy with reduced complexity that maximizes immediate throughput. In this paper, we propose mathematical models to evaluate the throughput and the MAC delay of a myopic policy under saturation tra c conditions. Using the MAC delay distribution, we evaluate the packet delay of secondary users under nonsaturation conditions. Numerical results are given to show the performance of the myopic policy in cognitive radio networks.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.505-508
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• 1999

To evaluate the strength of square reinforced concrete shot columns, thirty specimens were manufactured and tested under monotonically increasing concentric compression. The test parameters included the volumetric ratio of transverse reinforcement($\rho$h = 0.49~2.65), and concrete compressive strength (234, 437, 704 kgf/$\textrm{cm}^2$). Test results are shown that : (1) Behavior of high -strength concrete column is improved by providing increased volumetric ratio; and (2) ACI, Eq. is not proper to evaluate HSC short column strength.

• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1295-1302
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• 2011

We present an analytic model of an unslotted opportunistic spectrum access (OSA) network and evaluate its performance such as interruption probability, service completion time, and throughput of secondary users. Numerical examples are given to show the performance of secondary users in cognitive networks. The developed modeling and analysis method can be used to evaluate the performance of various OSA networks.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.2
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• pp.87-93
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• 2009

In this paper, we propose and evaluate the availability of single sensor node using a hierarchial modeling approach. We divides a sensor node into a software and hardware and analyze failures of each component. We construct Markov chains to represent the components of a sensor node, and then we construct a hierarchical model which use fault tree in upper level and Markov chains in lower level. We evaluate the availability and down of single sensor node.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.370-375
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• 1998

The objectives of this study are to evaluate the applicability of SCS TR-20 model for small ungauged watershed, to show the behavior of the model with variation of topography in watershed, and to evaluate the storage effect of paddy field for flood flow. For this purpose, simulated data from the model were compared with the observed flood data at two sites (HS#3, HS#4) in Balan watershed. From the comparison between simulated and observed data, it was found that the model is applicable to this watershed.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.04a
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• pp.81-85
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• 1991

The object of this study is to propose the bending moment-curvature relationships based on the bond properties between concrete and steel for noncraking zone, and evaluate the flexural displacement of reinforced concrete members. The bond-slip relationship and the strain hardening effect of steel were taken into account in order to evaluate the spacing of the cracks and the curvature distribution. Calculated curvature distribution along the longitudinal axis was transformed into equivalent curvature distribution. The flexural displacement was calculated by means of double intergral of the equivalent curvature. Calculated values are in good agreement with the experimental data.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.431-436
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• 2002

The purpose of this study is to evaluate resistance capacity of the damaged wall structural system against earthquake ground accelerations. Two lumped damage models(5 story, 12 story) are investigated by nonlinear time history analysis. As a result of analyses, the effect of stiffness degradation due to structural damages might change the interstorydrift of the structure. Therefore the increasing interstorydrift of damaged structures might be applied to evaluate the seismic performance of damaged structures.

• Journal of Ecology and Environment
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• v.36 no.1
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• pp.85-88
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• 2013

Bioassessment is the use of biosurvey data, most commonly for benthic macroinvertebrates and fish, to obtain information about the health of waters in a region. In rivers, bioassessment results are used to evaluate biological condition and trends, to establish relationships between stressors and impairments, and to guide and evaluate management actions.

• Proceedings of the Korean Society for Quality Management Conference
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• 2006.11a
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• pp.333-338
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• 2006

A simple but practical approach to evaluate the reliability of electronic ballasts for the low wattage fluorescent lamp has been presented in this study. We briefly reviewed the basic concepts of the electronic ballast. We then proposed a simple model and evaluated the reliability of the ballast using computer simulation.

• Bulletin of the Korean Mathematical Society
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• v.36 no.3
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• pp.441-450
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• 1999

In this paper we first evaluate the conditional Wiener integral of certain functionals using a Park and Skoug's formula. and we also evaluate the conditional wiener integral E(F│$X_\alpha$) of functional F on C[0, T] given by $F(x)=exp\{{\int_0}^T s^kx(s)ds\}$ for a general conditioning function $X_\alpha$ on C[0,T].