• Proceedings of the KSME Conference
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• 2001.06a
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• pp.274-279
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• 2001

Creep-fatigue crack growth behavior was experimentally measured particularly when a crack was located in the heat affected region of 1Cr-0.5Mo steel. Load hold times of the tests for trapezoidal fatigue waveshapes were varied among 0, 30, 300 and 3,600 seconds. Time-dependent crack growth rates were characterized by the $C_t$-parameter. It was found that the crack growth rates were the highest when the crack path was located along the fine-grained heat affected zone(FGHAZ). Cracks located in other heat affected regions had a tendency to change the crack path eventually to FGHAZ. Creep-fatigue crack growth law of the studied case is suggested in terms of $(da/dt)_{avg}$ vs. $(C_t)_{avg}$ for residual life assessment.

• The Korean Journal of Pesticide Science
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• v.21 no.1
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• pp.97-105
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• 2017

This study was carried out to determine residual characteristics and to evaluate safety of bifenthrin, carbendazim and metconazole in minor crop, Angelica gigas Nakai. The test pesticides were sprayed onto the crop according to the combinations of spray days before harvest and frequency and then sampling was performed at the harvest day. Non-systemic pesticide bifenthrin was not detected in all samples, whereas systemic pesticides, carbendazim and metconazole, were detected from the crop in the range of from 0.14 to 0.49 and from 0.19 to 0.26, respectively. These results indicated that residual characteristics of the test pesticides in Angelica gigas Nakai were affected by their systemic properties. Also, residual concentration of carbendazim and metconazole in the crop was increased as more spraying frequency and spraying more closer to harvest day. And residual concentration of carbendazim in the crop on the last spraying day was 2.1 times higher than that of metconazole because nominal spraying dose of carbendazim was higher than that of metconazole by 1.9 times. The residue levels of the test pesticides in the crop were evaluated to be safe, considering their %ADIs were less than 0.9%.

• Structural Engineering and Mechanics
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• v.16 no.6
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• pp.749-769
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• 2003

The structural deterioration of concrete structures due to reinforcement corrosion is a major worldwide problem. Service life of the age-degraded concrete structures is governed by the protective action provided by the cover concrete against the susceptibility of the reinforcement to the corrosive environment. The corrosion of steel would result in the various corrosion products, which depending on the level of the oxidation may have much greater volume than the original iron that gets consumed by the process of corrosion. This volume expansion would be responsible for exerting the expansive radial pressure at the steel-concrete interface resulting in the development of hoop tensile stresses in the surrounding cover concrete. Once the maximum hoop tensile stress exceeds the tensile strength of the concrete, cracking of cover concrete would take place. The cracking begins at the steel-concrete interface and propagates outwards and eventually resulting in the through cracking of the cover concrete. The cover cracking would indicate the loss of the service life for the corrosion-affected structures. In the present paper, analytical models have been developed considering the residual strength of the cracked concrete and the stiffness provided by the combination of the reinforcement and expansive corrosion products. The problem is modeled as a boundary value problem and the governing equations are expressed in terms of the radial displacement. The analytical solutions are presented considering a simple 2-zone model for the cover concrete viz. cracked or uncracked. A sensitivity analysis has also been carried out to show the influence of the various parameters of the proposed models. The time to cover cracking is found to be function of initial material properties of the cover concrete and reinforcement plus corrosion products combine, type of rust products, rate of corrosion and the residual strength of the cover concrete. The calculated cracking times are correlated against the published experimental and analytical reference data.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.4
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• pp.111-116
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• 2001

As part of the recycling methods, residual food through the anaerobic fermentation process was decomposed into methane gas and fermentation liquid. The research was conducted to measure the effect of application of fermentation liquid on chemical properties of soil and plant growth according to application rate and separate manure at the base of nitrogen in fermentation liquid. The fermentation liquid contained 0.52% nitrogen was applied in treatments by standard fertilizer. The treatments were composed of the control only with chemical fertilizer and N-50, N-100-4, N-100-8 were each of applied with 50, 100(6 times), 100(3 times)% of fermentation liquid contrast to standard fertilizer. Properties of fermentation liquid was high EC because of waster soluble organic compounds as well as much of salts and also contained a lot of suspended solid. The changes of soil chemical properties little occurred in before and after of experiment but EC and content of ex. Ca in soil were increased. Fresh weigh in treatments applied with fermentation is high than that of control but the difference between treatments little showed. The above result means if fermentation liquid be used instead of chemical fertilizer the volume of used fermentation liquid will be reduced by 50% of present standard fertilizer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.10a
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• pp.36-39
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• 2000

This paper presents the technology of condition diagnosis & life estimation on insulation system of the traction motor. In the non-destructive methods for diagnosis of coil insulation state, residual dielectric strength is estimated by the D-map which consist of the partial discharge quantity Q and average degradation degree $\Delta$. In the operating history of machine, the N-Y life estimation method is based on the stop-starting numbers and operating times with considering each degradation factor by the thermal, electrical and heat-cycle stress. With the on-line conditioning monitoring on the currents of traction motors, detecting the abnormal operating state due to bearing faults, stator or armature faults, eccentricity related faults and broken rotor bars can be performed.

• Proceedings of the KWS Conference
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• 1996.05a
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• pp.115-118
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• 1996

1. The crack is inifiated at a toe notch and reptured for the skip and continuous welding. 2. Fatigue life of continuous welding is greater than that of skip welding and fatigue life of 2pad continuous welding appears 1.7 times more than that of pad continuous welding. 3. For the skip and continuous welding, fatigue than that of welding materials appears shorter than that of welding materials because of the effect of plastic strain and compressive residual stresses at the crack tip, which are generated by the over loading. 4. Inter-relationship between da/dN-ΔK and delayed phenomenon increases linearly at the state growth area of heat effect section for the skip and continuous welding.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.324-329
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• 2000

Microstructure, mechanical and fatigue behaviors of TiCN and TiN/TiCN thin films, deposited on quenched and tempered STD61 tool steel, were investigated by using XRD, XPS, hardness, adhesion and fatigue tests. The TiCN thin film is grown along the (100), (111) orientation, whereas the TiN/TiCN thin film is grown along the (111) orientation. The preferred orientation of TiN/TiCN thin film strongly depends on the TiN buffer layer whose orientation is (111), as is well-known. The TiN/TiCN thin film showed the higher adhesion compared with TiCN single layer because the TiN buffer layer, having good toughness, reduces the effects of the lower hardness of substrate. In the high cycle tension-tension fatigue test, the fatigue life of the TiCN and the TiN/TiCN coated steel increased approximately two to four times and five to nine times respectively compared with uncoated specimens. The TiN buffer layer in multilayer thin films plays an important role in reducing residual stress and fatigue crack initiation, and then in restraining the fatigue propagation.

• Korean Journal of Environmental Agriculture
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• v.34 no.3
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• pp.223-229
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• 2015

BACKGROUND: It is important to understand residual patterns of pesticides applied on crops for ensuring their safety in agricultural products. However, there are few studies on the residual patterns of pesticides in minor crops, which are small in cultivation area. In this study, residual amounts of bifenthrin and chlorfenapyr sprayed on perilla leaf as a minor crop were investigated to know their residual patterns. METHODS AND RESULTS: Bifenthrin and chlorfenapyr were sprayed 2 or 3 times on perilla leaves at a week interval prior to harvest, and the perilla leaves were collected at 0, 1, 3, 5 and 7 days after the final application of pesticides. Recoveries for residual analysis of pesticides spiked on perilla leaves with concentrations of 0.1 and 0.5 mg/kg were 81.9-104.8%. The residual amounts of pesticides interpreted using first order kinetics model show that dissipation constants of bifenthrin and chlorfenapyr in perilla leaves were 0.0724-0.0535 and $0.0948-0.0821day^{-1}$, respectively. In addition, the dissipation half-lives in perilla leaves were 9.6-12.9 days for bifenthrin and 7.3-8.4 days for chlorfenapyr. When pre-harvest residue limits (PHRL) of bifenthrin and chlorfenapyr at 10 days before harvest calculated on the basis of the dissipation constants and maximum residue limits of the pesticides were calculated as 17.1 for bifenthrin and 15.9 mg/kg for chlorfenapyr. CONCLUSION: Therefore, the PHRL calculated using the time-dependant residual patterns of pesticides in perilla leaves and their regression analysis may be used as experimental evidences in order to ensure the safety of pesticides in perilla leaves before harvest.

• The Korean Journal of Pesticide Science
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• v.15 no.3
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• pp.317-322
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• 2011

A comparative experiment was conducted to investigate the persistence of chlorfenapyr residue and its biological activity to two spotted spider mite, Tetranychus urticae, after treatment of chlorfenapyr suspension concentrate (10% SC) on paprika plants at recommended (2000 times dilution) and double dosage. Biological half-lives of chlorpfenapyr were estimated as 8 and 5 days in leaves and fruits of paprika plants, respectively. While initial deposits of chlorfenapyr residues in leaves at recommended and double dosages were 22.22 and 37.75 ${\mu}g\;g^{-1}$ at the time of application, its residue decreased to 1.56 ${\mu}g\;g^{-1}$ and 3.62 ${\mu}g\;g^{-1}$ at 29 days after treatment, respectively. Residual biological activity of chlorfenapyr SC to T. urticae at recommended dosage lasted for 7 or 15 days on the basis of 24 or 48-hrs mortality test assayed with feeding on excised leaf chlorfenapyr-treated. The control efficacy to the mite showed a good agreement with the persistence of chlorfenapyr residues in leaves.

• The Korean Journal of Pesticide Science
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• v.17 no.2
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• pp.84-93
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• 2013

Validated analytical methods for isopyrazam are meager or lacking. In the present study, a single residual analytical method was developed for isopyrazam in selected commodities. Isopyrazam was analyzed in brown rice, soybean, green pepper, mandarin, cucumber, and Korean melon. We tried different solvents and methods through extraction, partition and purification steps to obtain best analytical results. For isopyrazam samples were extracted with acetonitrile, concentrated and partitioned with n-hexane, clean-up using florisil with n-hexane/ethylacetate (70/30) and analyzed with HPLC/UVD. The limit of quantitation (LOQ) for isopyrazam was 1.0 ng (S/N > 10) and method LOQ (MLOQ) was 0.04 mg $kg^{-1}$. Recovery ranged through 81.0~105.3% (syn-isomer) and 80.8~105.6% (anti-isomer) at fortification level of 0.04 (MLOQ), 0.4 (10 ${\times}$ MLOQ), and 2.0 (50 ${\times}$ MLOQ). The coefficient of variation (CV) for isopyrazam was less than 10% regardless of sample types. These results were further confirmed with LC/MS, respectively. The proposed method is highly reproducible and sensitive and is suitable for routine analysis.