• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.1-9
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• 2020

Chloride ion, which penetrates into the cement composites from the outside, generally diffuses by the concentration gradient. Chloride ions are adsorbed by the chemical reaction with cement hydrates. Recent studies have shown that anion exchange resin (AER) powder can effectively adsorb the chloride ion in the cement composites, and thus, the cement composites containing AER have a high chloride adsorption capacity and a good resistance for chloride penetration. In this study, the chloride adsorption ability of the AER powder was investigated under the conditions of distilled water and calcium hydroxide saturated solution to determine if the AER powder is less effective to increase the chloride adsorption ability after grinding process. The chloride adsorption ability of AER powder was compared with the previous research about the chloride adsorption of AER bead. In addition, the compressive strength, chloride diffusion coefficient (using NT Build 492 method), and the chloride profile of cement mortar substituted with AER powder were investigated. There was no decrease in the chloride adsorption capacity of AER powder but increase in the kinetic property for chloride adsorption after the grinding process. The AER powder could absorb the chloride ion in the mortar quickly, and showed better chloride ion adsorption ability than the cement hydrates.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2955-2960
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• 2012

Product ion yields in the in- and post-source decays of three peptide ions, $[Y_5X+H]^+$ (X = Y (tyrosine), K (lysine), and R (arginine)), generated by matrix-assisted laser desorption ionization (MALDI) were measured at six wavelengths, 307, 317, 327, 337, 347, and 357 nm, using ${\alpha}$-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) as the matrices. The temperatures of the early and late plumes generated by MALDI were estimated via kinetic analysis of the product ion yield data. For both matrices, the temperature drop (${\Delta}T$), i.e. the difference in the temperature between the early and late plumes, displayed negative correlation with the absorption coefficient. This was in agreement with the previous reasoning that deeper laser penetration and larger amount of material ablation arising from smaller absorption coefficient would result in larger extent of expansion cooling. The results support the postulation of the expansion cooling occurring in the plume presented previously.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.416-421
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• 2002

This paper dealt with an experimental study on the hydro-elastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based n the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plates in air. It was empirically found that the natural frequencies of the perforated plate in air increase with an increase of P/D, on the other hand, the natural frequencies of the perforated plate in contact with water decrease with an increase of P/D. Additionally, the effect of the submerged depth on the natural frequency was investigated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.95-99
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• 2004

This paper describe inner-collision-characteristics of the ship structural plates when the projectile collides with plate-material using LS-DYNA3D which is general and useful finite element analysis tool in collision problem fields. The series analyses were carried out from high speed(41.56m／s-118.9m／s) to ultrahigh speed(544.05m／s-800m／s). Through these analyses we can approach empirical formula to estimate penetration limit of the ship structural plates with which the projectile of various speed collides.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.533-538
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• 2016

In a power grid that has a high penetration of wind power, the highly-fluctuating output power of wind turbine generators (WTGs) adversely impacts the power quality in terms of the system frequency. This paper proposes a power smoothing scheme of a variable-speed WTG that can smooth its fluctuating output power caused by varying wind speeds, thereby improving system frequency regulation. To achieve this, an additional loop relying on the frequency deviation that operates in association with the maximum power point tracking control loop, is proposed; its control gain is modified with the rotor speed. For a low rotor speed, to ensure the stable operation of a WTG, the gain is set to be proportional to the square of the rotor speed. For a high rotor speed, to improve the power smoothing capability, the control gain is set to be proportional to the cube of the rotor speed. The performance of the proposed scheme is investigated under varying wind speeds for the IEEE 14-bus system using an EMTP-RV simulator. The simulation results indicate that the proposed scheme can mitigate the output power fluctuation of WTGs caused by varying wind speeds by adjusting the control gain depending on the rotor speed, thereby supporting system frequency regulation.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.181-182
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• 2015

In a power system with a high wind power penetration level, the output power of a wind power plant (WPP) might give negative impacts on the frequency control of a power system. This paper proposes a power smoothing scheme of a wind turbine generator (WTG) to reduce the frequency deviation. To do this, an additional control loop is used, the output of which depends on the frequency deviation. The gain of the additional loop is determined depending on the kinetic energy (KE) of a WTG; in the under frequency condition, the gain is set to be proportional to the releasable KE of a WTG; otherwise, it is set to the maximum value. The performance of the proposed scheme is investigated for 100-MW doubly-fed induction generator based WPP using an EMTP-RV simulator under various wind conditions. The results show that the proposed scheme successfully reduces the frequency deviation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.70-78
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• 2003

This paper dealt with an experimental study on the hydroelastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plates in air. It was empirically found that the natural frequencies of the perforated plate in air increase with an increase of P/D, on the other hand, the natural frequencies of the perforated plate in contact with water decrease with an increase of P/D. Additionally. the effect of the submerged depth on the natural frequency was investigated.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.720-725
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• 2011

W-Ni-Fe heavy alloys have been used in various fields, such as kinetic energy penetrators and radiation shielding materials, due to their high density and good mechanical properties. In this study, the sintering of W-Ni-Fe alloys with various Ni/Fe ratios was demonstrated to improve the mechanical properties and penetration capabilities of heavy alloys by formation of interfacial phase. The microstructural changes and the mechanical properties of the W-Ni-Fe alloys after liquid-phase sintering were investigated. The Vickers hardness and tensile strength of the 95W1.3Ni3.7Fe sample, which had coated W grains by $Fe_7W_6$ phase (${\mu}$-phase), were 450 Hv and 1560 MPa, respectively. As a result, enhancement of the mechanical properties was considered to have uniformly generated ${\mu}$-phase around W grains.

• Fire Science and Engineering
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• v.22 no.3
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• pp.221-227
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• 2008

In this study, the fire suppression characteristics of a water mist with natural wind in a road tunnel were calculated using the FDS(Fire Dynamic Simulation) code. In addition, the cooling and the chemical kinetic effects of water vapor on fire extinction ere investigated in a counterflow non-premixed flame using a detailed chemistry. As a result, the behavior of fire plume and the spray characteristics of water mist are modified remarkably with the increasing of wind velocity. In the case which is not the external natural wind, small droplets are more efficient in fire suppression than large droplets. However, the large droplets show better results on the fire suppression than the small droplets with the increasing of wind velocity. It can be estimated that the natural wind disturb the penetration of water droplets into the flame region and decrease the effect of oxygen dilution. Finally, it can be identified that the fire into the natural wind can be suppressed with smaller amount of $H_2O$ by flame stretching effect in the flame region than one in an enclosure, and the chemical kinetic effects of $H_2O$ on fire extinction are not affected significantly the velocity of natural wind.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1021-1028
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• 2013

The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.