• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.403-404
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• 2010

This paper introduces new impact apparatus using elastic strain energy for Fiber Reinforced Cementitious Composites [HPFRCC] which requires larger size of specimen and higher impact load and energy to fail the specimens. New impact apparatus utilize elastic strain energy to generate high rate impact stress wave and it is much smaller, cheaper and safer than current other impact devices.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.11
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• pp.112-119
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• 1996

Impact ionization model in GaAs has been presented by modified keldysh formula with two sets of power exponent of 7.8 and 5.6 in study. Impact ionization rate is derived from fermil's golden rule and ful lenergy band stucture based on empirical pseudopotential method. Impact ionization rates show anisotropic property in low energy region (<3eV), but isotropic in high energy region (3>eV). Full band monte calo simulator is coded for investigating the validity of the GaAs impact ionization model, and validity is checked by comparing impact ionization coefficients with experimental values and ones in anisotropic model. Valley transitions to energy alteration are explained by investigating electron motion in brillouin zone for full band model to electric field variation.

• International Journal of Safety
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• v.4 no.1
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• pp.1-7
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• 2005

The direction of the applied load and displacement rate on the femur during falls may be an important factors in the etiology of hip fractures. Nonetheless, previous studies did not consider these two factors simultaneously for falling condition. Therefore, in the present study, an impact test system is developed to simulate the falling condition and the influence of impact angle on the deformation pattern changes of proximal femur is investigated. The results showed that a slight variation in impact angle quite affects deformation pattern of the proximal femur. Along with bone mineral density and trabaecular morphology, the impact angle can be another important factor affecting the structural capacity of the proximal femur.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.3
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• pp.271-287
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• 2015

In this article, a more generalized form of the impact time and angle control guidance law is proposed based on the linear quadratic optimal control methodology. For the purpose on controlling an additional constraint such as the impact time, we introduce an additional state variable that is defined to be the jerk (acceleration rate). Additionally, in order to provide an additional degree of freedom in choosing the guidance gains, the performance index that minimizes the control energy weighted by an arbitrary order of time-to-go is considered in this work. First, the generalized form of the impact angle control guidance law with an additional term which is used for the impact time control is derived. And then, we also determine the additional term in order to achieve the desired impact time. Through numbers of numerical simulations, we investigate the superiority of the proposed guidance law compared to previous guidance laws. In addition, a salvo attack scenario with multiple missile systems is also demonstrated.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.3
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• pp.241-247
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• 2013

Yellow clay dispersion has been applied to minimize fisheries impact by the red tide Cochlodinium polykrikoides blooms in Korean coasts since 1995. The present preliminary study documents the effect of yellow clay on Korean rockfish, Sebastes schlegelii, in terms of oxygen consumption rate (OCR). The OCR in the low clay suspension (0.05 and 0.23 %, w/w) showed normal level compared to the control. In contrast, the OCR for each one of three replicates in the high clay suspension (1.16 and 5.58 %, w/w) was not returned to the previous level that clay was not treated, indicating that high clay suspension (${\geq}1.16%$, w/w) might give negative effect on Korean rockfish. Overall, this result suggests that field application of clay to control Harmful Algal Blooms (HABs) may not give impact on Korean rockfish once the clay is dispersed in a low concentration (${\leq}0.23%$). In order to understand the changes of OCR in the repeated exposure to clay, it is required to do further studies on the changes of OCR when the fish is exposed to clay repeatedly after recovery in the normal seawater.

• Proceedings of the Korean Society of Crop Science Conference
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• 2000.11a
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• pp.12-27
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• 2000

During the recent decades, he problem of climate variability and change has been in the forefront of scientific problems. The objective of this study was to assess the impact of climate variability on crop growth and yield. The growth duration was the main impact of climate variability on crop yield. Phyllochronterval was shortened in the global worming situations. A simple model to describe developmental traits was provided from heading data of directly seeded rice cultivars and temperature data. Daily mean development rate could be explained by the average temperature during the growth stage. Simple regression equation between daily mean development rate(x) and the average temperature(y) during the growth period as y = ax + b. It can be simply modified as x = 1/a $\ast$ (y-b). The parameters of the model could depict the thermo sensitivity of the cultivars. On the base of this model, the three doubled CO2 GCM scenarios were assessed. The average of these would suggest a decline in rice production of about 11% if we maintained the current cultivars. Future cultivar's developmental traits could be suggested by the two model parameters.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.29-35
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• 2020

To manage the non-point source pollution and restore the water circulation, many technologies including infiltration or reservoir systems were installed in the urban area. These facilities have many problems regarding maintenance as their operation period becomes lengthier. The purpose of this study was to estimate the optimal maintenance timing through a long-term load test on the infiltration trench as one of the low impact development techniques. An infiltration trench was installed in the demonstration test facility, and stormwater was manufactured by Manual on installation and operation of non-point pollution management facilities from the Ministry of Environment, Korea and entered into the infiltration trench. Particle size distribution (PSD), suspended solids (SS) removal efficiency, and infiltration rate change tests were performed on inflow and outflow water. In case of the PSD, the maximum particulate size in the outflow decreased from 64 ㎛ to 33 ㎛ as the operating duration elapsed. The SS removal efficiency improved from 97 % to 99 %. The infiltration rate changed from 0.113 L/sec to 0.015 L/sec during the operation duration. The maintenance timing was determined based on the stormwater runoff requirements with these changes in water quality and infiltration rate. The methodologies in this study could be used to estimate the timing of maintenance of other low impact development techniques.

• Journal of Environmental Impact Assessment
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• v.22 no.1
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• pp.79-87
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• 2013

The purpose of this study is to establish PM-10 management manual for developing large scale sites by assessing the status of PM-10 reduction at ongoing large scale development sites. After analyzing the meteorological conditions and air quality characteristics of Sihwa MTV development site, ISCST3 (Industrial Source Complex Short Term Model 3) was implemented to predict PM-10 generation. The outcomes of ISCST3 modelling were utilized for verification of site survey data. As a result of applying air pollution modeling, the diffusion rate of PM-10 decreases according as the wind speed decreases. And the emission rate of PM-10 increase is linear to the concentration of PM-10. The reduction target of PM-10 can be derived quantitatively from the difference between the forecasted emission rate and the permissible emission limit of PM-10. The assessment of PM-10 characteristics which is deduced from ISCST3 and site survey can be practically applied to accomplish environmentally acceptable air quality manual for large scale development sites.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.6
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• pp.611-621
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• 2009

This paper first reviews the physical meanings and the expressions of two representative strain rate models: CSM (Cowper-Symonds Model) and JCM (Johnson-Cook Model). Since it is known that the CSM and the JCM are suitable for low-intermediate and intermediate-high rate ranges, many studies regarding marine accidents such as ship collision/grounding and explosion in FPSO have employed the CSM. A formula to predict the material constant of the CSM is introduced from literature survey. Numerical simulations with two different material constitutive equations, classical metal plasticity model based on von Mises yield function and micromechanical porous plasticity model based on Gurson yield function, have been carried out for the stiffened plates under impact loading. Simulation results coincide with experimental results better when using the porous plasticity model.