• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.33-44
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• 1999

An energy balance procedure is developed to incorporate the effects of earthquake duration which involves the effect of cyclic loading and the corresponding cumulative plastic deformation. Particular emphasis is given to the flexural failure of non-seismically designed columns of reinforced concrete frames. For this, conceptual strength deterioration models for columns, governed by concrete, anchorage failure and longitudinal steel fracture due to low-cycle fatigue, are proposed. It is evident that the energy-based method has good agreement with the experimental data and is able to predict the failure mode.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.153-160
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• 2000

Occupational cumulative traumas (CTDs) are becoming one of leading ailments in industrialized worl $d^{(1.2)}$. The degree of muscle fatigue is important parameter to understand cause of occupational cumulative trauma disorders. To quantify degree of muscle fatigue, muscle EMG activity was measured during isometric and dynamic contractions(repetitive concentric/eccentric muscle contraction) and its analyzed data, such as RMS, median frequency, and median power were compared when the muscle was fresh and exhausted. When muscle become fatigue, it was observed that median frequency decreased and median power and RMS increased However, based on overall prolonged observation, median frequency increased and median power and RMS decreased. Therefore it was concluded that shifting patterns of RMS, median frequency, and median power values can be used as parameter to evaluate degree of muscle fatigue even in dynamic muscle contraction.

• Journal of Biomedical Engineering Research
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• v.9 no.1
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• pp.73-78
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• 1988

The polymer electrolyte complex hydrogels consisting of poly (methacrylic acid) and poly (4-vinylpyrridine) were formed and 5-flurouracil and pilocarpine drugs were loaded on their hydrogels. Cumulative 5-FU released from PEC hydrogel was affected by the degree of loading and release rate of 5-FU was followed by the monolithic type. Cumulative pilocarpine released from PEC hydrogel increased by ionic interaction between cationic pilocarpine and anionic PMA. Release rate showed the zero order after burst effect.

• East Asian Economic Review
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• v.25 no.2
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• pp.205-230
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• 2021

This study examines the impact of the number of coronavirus cases on regime-switching in stock return volatility. This study documents the empirical evidence that the COVID-19 cases had an asymmetric effect on the regime of stock return volatility. When the stock return is in the low volatility regime, the probability of switching to the high volatility regime in the next trading day increases as the number of cumulative cases increases. In contrast, in the high volatility regime, the effect of cumulative cases on the transition probability is not statistically significant. This study also documents the evidence that the government measures against the pandemic contribute to promoting the high volatility regime of the KOSPI during the pandemic. Besides, this study projects future stock prices through the Monte Carlo simulation based on the estimated parameters and the predicted number of the COVID-19 new cases. Under a scenario where the number of new cases rapidly increases, stock price indices in Korea are expected to be in a downward trend over the next three months. On the other hand, under the moderate scenario and the best scenario, the stock indices are likely to continue to rise.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.594-599
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• 2011

In this paper, the effect of the boundary conditions on the reliability and the cumulative distribution characteristics of the fatigue failure life is analyzed in a magnesium alloy AZ31. The boundary conditions are specimen thickness, stress ratio, and maximum fatigue load. The statistical data of the fatigue failure life are obtained by fatigue crack propagation tests under the detail conditions for each boundary condition. The 3-parameter Weibull distribution is used to analyze a statistical characteristics of the fatigue failure life in magnesium alloy AZ31. It is found that the statistical fatigue failure life is long in the case of a thicker specimen, a larger stress ratio, and a smaller maximum fatigue load. Under the opposite cases, the reliability on the fatigue failure life is rapidly dropped.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.116-121
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• 2004

Simulation of proton irradiation in space is undertaken with a cyclotron accelerator. The cyclotron is capable of accelerating protons up to 200MeV with nominal fluxes near $10^6-10^8\;protons/cm^2/s$. Accelerated protons are irradiated onto a MPC860 for space application. Both the transient and cumulative responses of the device are found due to the proton irradiation. The primary transient response of the device is modification of the stored data in the circuit, whereas intermittent functional interrupts are also found. The cumulative response of the device is the increase of current consumption by the device.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.48-52
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• 2011

The effect of soil water content on the transformation potential of N compounds derived from hydrolysis of urea applied in a reclaimed tidal soils which was saline-sodic was observed to evaluate nitrification rates of urea. Soil samples were collected from Moonpo series at the newly reclaimed area in Saemanguem. For the transformation potential of N compounds from urea (46% N), newly reclaimed tidal soils (RS) were amended with urea at the rates of 0, 10, and 20 kg $10a^{-1}$. With leachate obtained from the incubated RS in a leaching tube at $25^{\circ}C$, urea hydrolysis and nitrification were measured for a total of 30days. The cumulative amounts of $NO_3{^-}$-N in each of the four soils treated with urea was linear with time of incubation. Results showed that increase in pH occurred with increasing application rate of urea and volumetric water content due to hydrolysis of urea. The total N in the RS was decreased with incubation time, indicating that rates of urea hydrolysis was influenced by soil moisture conditions. Also, the cumulative amount of nitrate in RS gradually increased with increase in time of incubation.

• Journal of Korean Society of Steel Construction
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• v.15 no.4 s.65
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• pp.369-378
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• 2003

This study proposed a damage index for steel members and examined a process where steel square tubular columns under cycle loading failed to meet the damage index. A nonlinear analysis was carried out and a damage process analyzed using a finite element program. Material properties and strain characteristics were obtained from material testing. The effect on the damage of members was analyzed according to varying kinds of steels and conditions of loading based on material testing results. According to strain characteristics and cumulative plastic strain of each variable, the effect of conditions of loading and kinds of steels on the damage could be estimated quantitatively.

• Journal of Nutrition and Health
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• v.29 no.1
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• pp.97-103
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• 1996

This study was performed to investigate the effects of lipid on cellular senescence, lipid peroxide production, and morphological changes. For this study we used primary skin fibroblasts from neonate rats grown in media various lipid contents. Fibroblasts were cultured until they lost their proliferation potential either in control medium (Dulbecco's modified Eagle's medium supplement with 10% fetal bovine serum) or in media supplemented with various concentrations of lipid-cholesterol rice component from bovine serum. Cumulative population doublings(CPD, as an index of cellular life span), and cellular thiobarbituric acid reactive substances (TBARS, as an index of lipid peroxide) concentrations were measured and morphological changes were observed. CPD were shortened with increasing lipid concentration in media ; 28.12 for cells grown in control medium and 13.42, 11.42, and 6.19 for those grown in 0.1%, 1% and 5% lipid rich components containing media, respectively. Cellular proliferation ratios were those grown in 5% lipid rich components containing media were delayed and they were degenerated soon. TBARS concentrations were increased with increasing concentration of lipid in media. Morphological changes were observed in cells grown in control medium by cellular senescence. Especially lipid droplets were observed in cells grown in 5% lipid rich components containing media. Therefore it seems that lipid contents in media had an effect on cellular proliferation and cellular life span, possibly via lipid peroxide production.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.2
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• pp.173-183
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• 2021

Objectives: This study evaluated the skin permeability of lawsone in henna hair dyes to understand the exposure characteristics of henna hair dyes in the human body. It examined the protective effects of protectants by applying protectants A, B, and C to test skin. Methods: Skin absorption tests were conducted using Franz diffusion cells according to OECD test guideline 428. After applying one kind of natural henna hair dye and chemical henna hair dye, respectively, to a standardized pig skin model, samples of receptor fluid were collected at 1h, 3h, 6h, and 24h. The skin permeation of lawsone was determined using HPLC. After the skin absorption experiment, the skin to which hair dye was applied was analyzed to determine the residual amount of lawsone in the skin. Results: The cumulative permeation of both natural and chemical henna hair dyes increased over time, and the natural henna hair dye had a flux value (t=3.194, p<.05) high both in the K_p value (t=3.207, p<.05) and the residual amount (t=22.701, p<.001). For skin treated with a protectant, the cumulative permeation of natural henna hair dye 24h control and the cumulative permeation of protectant A, B, and C increased over time. Flux and K_p values were in the order control > protectant A > protectant C > protectant B. The residual amount (F=4.469, p<.05) was in the order of protectant C > protectant A > protectant B > control. At 3h, the dye application time of natural henna hair dye, the lawsone flux value (F=4.454, p<.05) and K_p value (F=4.455, p<.05) were higher in the control group than in the protectant groups. The 24h cumulative permeation of the chemical henna hair dye increased with time in both the control and the protectant groups, and the flux and K_p values were in the order of protectant A > protectant C > protectant B > control. The residual amount (F=7.901, p<.01) was in the order of protectant B > protectant A> protectant C > control. Conclusions: Within the normal dyeing time for henna hair dye (three hours for natural henna hair dyes and 30 minutes for chemical henna hair dyes) lawsone skin penetration was not observed even when no protective agent was applied. After that time, however, evidence of skin penetration and retention of lawsone and the protective effect of protective agents were observed.