• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2014-2021
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• 1999

The present investigation is concerned with the degradation characteristics of cast stainless steel(CF8M), exposed to the $\sigma$-phase degradation at $700^{\circ}C$. In the present paper, the degradation of CF8 M at $700^{\circ}C$ is evaluated by a non-destructive test, DL-EPR(double loop electrochemical potentiokinetic reactivation). The surface of specimens is observed by using scanning electron microscopy after DL-EPR test. Also. chromium contents of matrix, grain boundary and ferrite phase are analyzed by electron probe X-ray micro analyzer. Through the experiments, the following results are obtained 1) The degree of sensitization(DOS) of CF8M aged up to 15hr at $700^{\circ}C$ is increased with acing time while that is decreased with aging time from 15hr to 150hr. 2) The impact energy decreases with increase of $\sigma$-phase while DOS increases with $\sigma$-phase until aging time reaches to 15hr. After the aging time. 15hr, the $\sigma$-phase and the rate of impact energy with respect to aging time decreases. Therefore the degradation behavior of the CF8M can be evaluated by comparing SEM micrographs and the value of DOS.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.33-40
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• 2006

Since early 1990's, several Quaternary faults have been found in the southeastern part of the Korean peninsula with reference to fault activity. Because some of these faults could be considered a capable fault, it is a very delicate matter, which need to be deal with carefully in assessing the seismic hazard. In determining whether or not a faults are capable, because of the low rate of seismicity and insufficient relationship between instrumental macro-seismicity and fault, there has been considerable debate among geologists and geophysicists in Korea. In this study, we discuss the criteria and probabilistic approaches that are used to assess whether or not a fault is seismogenic. And, we preliminarily also suggest the probability of fault activity from the spatial association between faults and earthquake epicenters, fault slip and tectonic stress, and geological evidence for multiple episodes of reactivation.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.670-691
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• 2018

This study presents the research results of the BMT(Benchmark Model Test) simulations of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to predict fault reactivation and the coupled hydro-mechanical behavior of fault. BMT scenario simulations of Task B were conducted to improve each numerical model of participating group by demonstrating the feasibility of reproducing the fault behavior induced by water injection. The BMT simulations consist of seven different conditions depending on injection pressure, fault properties and the hydro-mechanical coupling relations. TOUGH-FLAC simulator was used to reproduce the coupled hydro-mechanical process of fault slip. A coupling module to update the changes in hydrological properties and geometric features of the numerical mesh in the present study. We made modifications to the numerical model developed in Task B Step 1 to consider the changes in compressibility, Permeability and geometric features with hydraulic aperture of fault due to mechanical deformation. The effects of the storativity and transmissivity of the fault on the hydro-mechanical behavior such as the pressure distribution, injection rate, displacement and stress of the fault were examined, and the results of the previous step 1 simulation were updated using the modified numerical model. The simulation results indicate that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing interaction and collaboration with other research teams of DECOVALEX-2019 Task B and validated using the field experiment data in a further study.

• Corrosion Science and Technology
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• v.21 no.3
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• pp.230-241
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• 2022

Austenitic stainless steel has been widely used because of its good corrosion resistance and mechanical properties. However, intergranular corrosion can occur if the alloy is welded or aged. The objective of this study was to determine intergranular corrosion behaviors of austenitic medium carbon (0.05 wt%) and low carbon (0.02 wt%) stainless steel aged at several conditions. Alloys were evaluated according to ASTM A262 Practice A, ISO 12732 DL-EPR (double loop-electrochemical potentiokinetic reactivation) test, and ASTM A262 Practice C. The degree of sensitization and intergranular corrosion rate were obtained. The relationship between the degree of sensitization and the intergranular corrosion rate showed a very large fluctuation. Such behavior might be related to whether two-dimension tests or three-dimension tests were performed. On the other hand, regardless of carbon content of alloys, when the intergranular corrosion rate increased, the degree of sensitization also increased. However, the DL-EPR test showed a higher sensitivity than the Huey test for differentiating the intergranular corrosion property at a low intergranular corrosion rate, while the Huey test had a higher sensitivity than the DL-EPR test for distinguishing the intergranular corrosion property at a high intergranular corrosion rate.

• Journal of Korean Society of Forest Science
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• v.49 no.1
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• pp.1-5
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• 1980

In this study, enzymatic saccharification of substrates from Alnus hirsuta Ruper (8-14 years). Quercus acutissima Carruthers, Betula platyphylla var. japonica Nera, Populus euramericana Guiner and Platanus orientalis L. were investigated using crude cellulase preparations of Trichoderma viride Pers. ex. Fr. SANK 16374, and conduced on the optimum treated conditions of the cellulase sacchrification and reactivation of residue of digested substrates. The Trichoderma viride cellulase was produced by the submerged culture process and produced in the culture fluid was salted out quantitatively by the use of ammonium sulfate. The method of dilignification from wood (5 species) was treated by the peracetic acid(PA) method. The reducing sugar was determined by the dinitrosalicylic acid (DNS) method. 1. The results of tests carried out for 96 hr. (Figure 1), show conclusively the initial substrates from 5 species ($S_3$) which has been rendered highly reactive form and the mean rate of reducing sugar was 28.3 %. 2. The results of tests carried out for 96 hr., the reactivation of residue of digested substrates (improvement in the quality of the substrate through preheating in air at $190^{\circ}C$. for 45 min. followed by milling was (60 mesh size) at the same substrate level, increased concentrations of cellulase at the same substrate level, and increased concentrations of cellulase increases the rate of hydrolysis considerably. 3. Figure 1. shows conclusively that the residue of digested substrates ($S_1$ dried at $60^{\circ}C$) which has been rendered extremly resistant to cellulase action can be reactivated into a highly reactive form ($S_2$), almost comparable to that of the initial substrates ($S_3$). And the reducing sugar formation did not show statistically significent differences at 5% levels by initial substrates and the residue of digested substrates (preheating in air at $190^{\circ}C$. for 45 min. fallowed by milling was (60 mesh size).

• Health Policy and Management
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• v.5 no.2
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• pp.104-126
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• 1995

This study was carried out to assess the utilization of urban health center and its related factors among the urban residents. The survey was carried out for 2,394 households in Taegu and Kyongju by the structured questionnaire from 28 March to 4 April and from 2 July to 9 July, 1994. Well trained interviewers visited 2,630 households in Taegu and Kyongju, and interviewed with housewives. Of the target households, 91.0%(2,394 households) were responded through three-time visiting. The major results were summarized as follows : The fourth and fifth decad utilized the health center more frequently than any other age groups.. The lower income group showed higher rate of health center utilization than those in higher income group in Taegu City. The mean length of residence among residents of Kyongju City is longer than those of Taegu City, and the longer length of residence, the higher rate of the health center utilization. Those who are living together with neonate and infant or elderly people showed higher rate of health center utilization than those who are living without neonate and infant or elderly people in both Taegu and Kyongju. The most common reason for visiting the health center was 'low cost'. The major reasons for not visiting the health center were 'not regular customer', 'poor health center facility', and 'low quality of care'. Vaccination, communicable disease control, outpatient care, public hygiene, maternal and child health program were well recognized as health center activities. In logistic regression for the utilization of health center, the significant independent variables were length of residence and recognize the site of health center in both Taegu and Kyongju. The improvement of quality of health service, physical environment of health center and public relations on health center's activities shoulod be considered for reactivation and reingorcement of health center functions.

• Journal of Acupuncture Research
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• v.40 no.1
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• pp.16-34
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• 2023

Herpes zoster (HZ) results from the reactivation of a varicella-zoster virus infection and is accompanied by moderate-to-severe pain in most patients. The most common treatment is medication; however, there are still limitations. Acupuncture reportedly has meaningful therapeutic effects and is a possible alternative option in HZ. However, no systematic reviews examining the use of acupuncture and electro-acupuncture (EA) alone have been published; in this study, we therefore aimed to systematically review those techniques. We searched for clinical trials of acupuncture and EA treatment for HZ up to October 2022. Trials that used acupuncture were included. Outcomes were visual analog scale (VAS) and effective rate. Secondary outcomes were time to pain relief, time to pain elimination, incrustation, decrustation, lastly incidence of post-herpetic neuralgia (PHN). In total, 22 randomized controlled trials were included in this research. Compared with conventional medication therapy, acupuncture was associated with a significant improvement in VAS, effective rate, and times to pain relief and elimination. Times to new blister cessation, incrustation, and decrustation (days) were significantly improved. Furthermore, the incidence rate of PHN was lower in acupuncture groups. The results suggest that acupuncture could be a reasonable treatment option for patients with HZ who suffer from pain and accompanying symptoms.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.280-285
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• 1987

FMN-dependent glycolate oxidase from spinach is inactivated by diethyl pyrocarbonate at pH 7.0. Inactivation of both apo- and holoenzyme by diethyl pyrocarbonate follows pseudo-first-order kinetics and first order with respect to the reagent. A series of difference spectra of inactivated and native enzymes show a single peak at 240 nm, indicating the modification of histidyl residues. No decrease in absorbance at around 280 nm due to formation of O-carbethoxytyrosine is observed. The rate of inactivation is dependent on pH, and the data for pH dependent rates implicate the involvement of a group with a pKa of 6.9. The activity lost by treatment with diethyl pyrocarbonate could be almost fully restored by incubation with 0.75M hydroxylamine. The reactivation by hydroxylamine and the pH dependence of inactivation are also consistent with that the inactivation is due to modification of histidyl residues. Although coenzyme FMN is without protective effect, the substrate glycolate, the product glyoxylate, and two competitive inhibitors, oxalate and oxalacetate, provide marked protection against the inactivation of the holoenzyme. These results suggest that the inactivation of the oxidase by diethyl pyrocarbonate occurs by modification of essential histidyl residue(s) at the active site.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.400-425
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• 2018

This study presents the research results and current status of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to simulate the coupled hydro-mechanical behavior of fault, including slip or reactivation, induced by water injection. The first research step of Task B is a benchmark simulation which is designed for the modelling teams to familiarize themselves with the problem and to set up their own codes to reproduce the hydro-mechanical coupling between the fault hydraulic transmissivity and the mechanically-induced displacement. We reproduced the coupled hydro-mechanical process of fault slip using TOUGH-FLAC simulator. The fluid flow along a fault was modelled with solid elements and governed by Darcy's law with the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by creating interface elements between two separating rock blocks in FLAC3D. A methodology to formulate the hydro-mechanical coupling relations of two different hydraulic aperture models and link the solid element of TOUGH2 and the interface element of FLAC3D was suggested. In addition, we developed a coupling module to update the changes in geometric features (mesh) and hydrological properties of fault caused by water injection at every calculation step for TOUGH-FLAC simulator. Then, the transient responses of the fault, including elastic deformation, reactivation, progressive evolutions of pathway, pressure distribution and water injection rate, to stepwise pressurization were examined during the simulations. The results of the simulations suggest that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing collaboration and interaction with other research teams of DECOLVAEX-2019 Task B and validated using the field data from fault activation experiments in a further study.

• KSBB Journal
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• v.14 no.4
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• pp.452-459
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• 1999

A two-stage continuous stirred tank reactor (CSTR)/trickling biofilter reactor (TBR) system was developed for the degradation of gas-phase trichloroethlene (TCE) using Methylosinus trichoporium OB3b. Mrthylosinus trichosporium OB3b was immobilized on activated carbons in TBR and the microbial growth reactor of a CSTR was coupled for the reactivation of the deactivated cells during TCE degradation. The effect of operation variables on TCE conversion and degradation rate were studied. At inlet TCE concentrations ranging from 10 to 80 $\mu$mol/L, TCE degradation rate was increased up to 525 mg TCE/Lㆍday with 75% conversion. The TCE degradation rates were also increased with increse in broth recycle flow rate, gas flow rate and dilution rate. When the temperature of TBR was changed from 3$0^{\circ}C$ to 15$^{\circ}C$, TCE degradation rate and TCE conversion were increased due to the enhanced TCE transfer from gas-phase. The two-stage reactor system was found to be stable and has been operated for more than 270 days.