• KSBB Journal
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• v.22 no.3
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• pp.157-161
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• 2007

This study is to investigate the biological degradation and the characteristics of MEA, a pH regulator to be put in the cooling water circulation system for power plants, loading to elevate concentrations of COD and N when eluted into the water environment. MEA, $NH_4^+$ and CODcr were monitored in flask cultures and in a batch aerator. MEA was found to be biologically degradable, producing substantial amount of ammonia (max. 78.1%) in a form of $NH_4^+$ and other carboneous intermediates. The degradation reaction rates were similar one another over all MEA concentrations tested as the activated sludge (microbial consortium) was acclimated to MEA with the gradual and stepwise increase in MEA input into the batch aerator. Also, MLVSS kept increasing with increasing MEA input. The COD-based degradation reaction order was determined to be 1.

• Earthquakes and Structures
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• v.20 no.4
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• pp.431-444
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• 2021

T-shaped column is usually used as side column in buildings, which is one of the weak members in structural system. This paper presented a quasi-static cyclic loading experiment of six specimens of reinforced concrete (RC) T-shaped columns under compression-flexure-shear-torsion combined loadings to investigate the effect in the ratio of torsion to moment (T/M) and axial compression ratio (n) and height-thickness ratio of flange plate (φ) on their seismic performance. Based on the test results, the failure characteristics, hysteretic curves, ductility, energy dissipation, stiffness degradation and strength degradation were analyzed. The results show that the failure characteristics of RC T-shaped columns mainly depend on the ratio of torsion to moment, which can be divided into bending failure, bending-torsion failure and shear-torsion failure. With the increase of T/M ratio, the torsion ductility coefficient increased, and in a suitable range, the torsion and horizontal displacement ductility coefficient of RC T-shaped columns could be effectively improved with the increase of axial compression ratio and the decrease of height-thickness ratio of flange plate. Besides, the energy dissipation capacity of the specimens mainly depended on the bending and shear energy dissipation capacity. On the other hand, the increase of axial compression ratio and the ratio of torsion to moment could accelerate the torsional and bending stiffness degradation of RC T-shaped columns. Moreover, the degradation coefficient of torsion strength was between 0.80 and 0.98, and that of bending strength was between 0.75 and 1.00.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.67-78
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• 2012

An electric double-layer capacitor(EDLC) is an electrochemical capacitor with relatively high energy density, typically hundreds of times greater than conventional electrolytic capacitors. EDLCs are widely used for energy storage rather than as general-purpose circuit components. They have a variety of commercial applications, notably in energy smoothing and momentary-load devices, and energy-storage and kinetic energy recovery system devices used in vehicles, etc. This paper presents an accelerated degradation test of an EDLC with rated voltage 2.7V, capacitance 100F, and usage temperature $-40^{\circ}C{\sim}65^{\circ}C$. The EDLCs are tested at $50^{\circ}C$, $60^{\circ}C$, and $70^{\circ}C$, respectively for 1,750hours, and their capacitances are measured at predetermined times by constant current discharge method. The failure times are predicted from their capacitance deterioration patterns, where the failure is defined as 30% capacitance decrease from the initial one. It is assumed that the lifetime distribution of EDLC follows Weibull and Arrhenius life-stress relationship holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.1
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• pp.17-22
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• 2016

The activation energy of a material is an important factor that significantly affects the lifetime and can be used to develop a degradation model. In this study, a thermal analysis was carried out to evaluate and collect quantitative data on the degradation of insulation materials like EPR and CSP used for nuclear power plant cables. The activation energy was determined from the relationship between log ${\beta}$ and 1/T based on the Flynn.Wall.Ozawa method, by a TGA test. The activation energy was also derived from the relationship between ln(t) and 1/T based on isothermal analysis, by an OIT test. The activation energy of EPR derived from thermal analysis was used to calculate the accelerated aging time corresponding to the number of years of use, employing the Arrhenius equation, and determine the elongation corresponding to the accelerated aging time.

• Earthquakes and Structures
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• v.13 no.2
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• pp.177-191
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• 2017

In the present study, exterior beam column sub-assemblages are designed in accordance with the codal stipulations prevailed at different times prior to the introduction of modern seismic provisions, viz., i) Gravity load designed with straight bar anchorage (SP1), ii) Gravity load designed with compression anchorage (SP1-D), iii) designed for seismic load but not detailed for ductility (SP2), and iv) designed for seismic load and detailed for ductility (SP3). Comparative seismic performance of these exterior beam-column sub-assemblages are evaluated through experimental investigations carried out under repeated reverse cyclic loading. Seismic performance parameters like load-displacement hysteresis behavior, energy dissipation, strength and stiffness degradation, and joint shear deformation of the specimens are evaluated. It is found from the experimental studies that with the evolution of the design methods, from gravity load designed to non-ductile and then to ductile detailed specimens, a marked improvement in damage resilience is observed. The gravity load designed specimens SP1 and SP1-D respectively dissipated only one-tenth and one-sixth of the energy dissipated by SP3. The specimen SP3 showcased tremendous improvement in the energy dissipation capacity of nearly 2.56 times that of SP2. Irrespective of the level of design and detailing, energy dissipation is finally manifested through the damage in the joint region. The present study underlines the seismic deficiency of beam-column sub-assemblages of different design evolutions and highlights the need for their strengthening/retrofit to make them fit for seismic event.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.931-932
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• 2005

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.139-148
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• 1993

Thermosyphons are simple devices that can passively transport thermal energy over relatively long distance with little temperature degradation. These attributes permit the use of low grade thermal energy for thermal control of structures including the snow melting and deicing to the pavement surface. The thermosyphon system requires no costly energy input and Is completely maintenance free. This paper presents the experimental results of the snow melting system in which thermosyphon was utilized to transfer the geothermal energy to the pavement to obviate slipping traffic accidents due to freezing of pavement in winter.

• Journal of the Korean Society of Safety
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• v.21 no.4 s.76
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• pp.33-41
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• 2006

Material degradation should be considered to assess integrity and residual life of high temperature equipments. However, the property data reflecting degradation are not sufficient for practical use. In this study measuring properties for 1Cr-1Mo-0.25V forging steel generally used for turbine rotor was carried out. Degradation was simulated by isothermal ageing. heat treatment and variation of microstructure was observed. Mechanical properties such as tensile strength, impact energy, hardness and fracture toughness were measured. Assuming a semi-elliptical surface crack at the bore hole in a turbine rotor, material risk was estimated by using the aged material property data obtained in this study. Safety margin was decreased and life of the rotor was exhausted. This procedure can be used in assessing the residual life of a turbine rotor due to material degradation.

• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.190-197
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• 2024

A commercial PbO₂ mesh cylinder electrode was utilized as the anode for the electrochemical degradation of the textile effluent after the biological treatment with the titanium cylinder as the cathode in a self-made tube electrolyzer. The electrochemical performances of the PbO₂ electrode in tube electrolyzer under different initial pH, electrolyte flow rates, current densities and times of the electrochemical degradation were investigated. The experimental results illustrated that the PbO₂ electrode can reduce the chemical oxygen demand (COD) of the textile effluent from 94.0 mg L^-1 to 65.0 mg L^-1 with the current efficiency of 88.3%, the energy consumption of 27.7 kWh kg^-1 (per kilogram of degraded COD) and the carbon emissions of 18.0 kg CO₂ kg^-1 (per kilogram of degraded COD) under the optimal operating conditions. In addition, the COD of the textile effluent could be reduced from 94.0 mg L^-1 to 22.0 mg L^-1 after the fifth electrochemical degradation. Therefore, PbO₂ mesh cylinder electrode in the tube cylinder was promising for the electrochemical degradation of the textile effluent.

• Environmental Engineering Research
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• v.18 no.1
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• pp.21-28
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• 2013

In this study, the applicability of visible light-emitting-diodes (LEDs) to the photocatalytic degradation of indoor-level trichloroethylene (TCE) and perchloroethylene (PCE) over N-doped $TiO_2$ (N-$TiO_2$) was examined under a range of operational conditions. The N-$TiO_2$ photocatalyst was calcined at $650^{\circ}C$ (labeled N-650) showed the lowest degradation efficiencies for TCE and PCE, while the N-$TiO_2$ photocatalysts calcined at $350^{\circ}C$, $450^{\circ}C$, and $550^{\circ}C$ (labeled as N-350, N-450, and N-550, respectively) exhibited similar or slightly different degradation efficiencies to those of TCE and PCE. These results were supported by the X-ray diffraction patterns of N-350, N-450, N-550, and N-650. The respective average degradation efficiencies for TCE and PCE were 96% and 77% for the 8-W lamp/N-$TiO_2$ system, 32% and 20% for the violet LED/N-$TiO_2$ system, and ~0% and 4% for the blue LED/N-$TiO_2$ system. However, the normalized photocatalytic degradation efficiencies for TCE and PCE for the violet LED-irradiated N-$TiO_2$ system were higher than those from the 8-W fluorescent daylight lamp-irradiated N-$TiO_2$ system. Although the difference was not substantial, the degradation efficiencies exhibited a decreasing trend with increasing input concentrations. The degradation efficiencies for TCE and PCE decreased with increasing air flow rates. In general, the degradation efficiencies for both target compounds decreased as relative humidity increased. Consequently, it was indicated that violet LEDs can be utilized as energy-efficient light sources for the photocatalytic degradation of TCE and PCE, if operational conditions of N-$TiO_2$ photocatalytic system are optimized.