• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.1
• /
• pp.1-12
• /
• 1995

Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.27 no.5
• /
• pp.578-586
• /
• 2013

The objective of this study was to investigate the diagnosis and treatment of Sjogren's syndrome(SS) such as syndrome differentiation and herbal medicine by reviewing Chinese traditional medicine's journals. The journal search was carried out using China National Knowledge Infrastructure(CNKI) and PubMed from January 2007 to July 2012. Searching key words were the various combination of "Sjogren's syndrome", "Traditional Chinese Medicine", "herbal medicine", and "syndrome differentiation". The final selection of 57 studies were extracted and summarized by two researchers independently. The syndrome differentiation was classified as yin deficiency with fluid depletion, yin deficiency with dryness heat, dryness toxin with yin damage, internal obstruction of static blood, dual deficiency of qi and yang, dampness-heat obstructing, wind with external contraction, liver qi depression, blood deficiency and wind-dryness, dual deficiency of yin and yang, and internal obstruction of phlegm-blood stasis. Liriope platyphylla(麥門冬), Rehmania glutinosa(生地黃), and Scrophularia buergeriana(玄蔘) were primarily prescribed to tonify yin, engender fluid and moisten dryness.

• The Journal of Korean Medicine
• /
• v.16 no.1 s.29
• /
• pp.251-270
• /
• 1995

In the Literatual Study on the Dysphonia, the results were as follows. 1. The causes of dysphonia are exogenous pathogenic factors,(specially cold evil)internal damage and meridian in The Yellow Emperor's Canon of Interal Medicine, since then endogenous pathogenic factors are lung-asthenia and deficiency of lung-yin etc. The main causes are disease caused by exogenous evils, general body weakness, emotional stimulation and excess of high voice rescently. 2. The pathogenesis of dysphonia originated from two factors; The first internal damages are consumption of body fluid with the formation of dryness evil resulting from the insufficienty of lung-yin and lung-collaterals damaged by heat-evil caused by deficiency of lung and kidney-yin. The second disease caused by exogenous evils is sluggishness of lung-energy caused by exogenous pathogenic factors. 3. The main relative organ are heart, lung and kidney etc. 4. The prescriptions of wind-cold symptoms are Samyoutang(三拗湯) and Hangsosan(杏蘇散), in the prescriptions of phlegm-heat symptom is Chenginyongphetang(淸咽寧肺湯), in the prescriptions of depressive syndrome due to disorder of vital energy are Sogangkitang(小降氣湯) and Shihochenggantang(柴胡淸肝湯加減), in the prescriptions of consumption of body fluid with the formation of dryness evil resulting from the insufficiency of lung-yin symptoms are Sanghangtang(桑杏湯) and Chenginguphetang(淸咽救肺湯, in the prescriptions of deficiency of lung and kidney-yin are Baekhabgokumtang(百合固金湯) and Maekmigiwhangtang(麥味地黃湯). 5. The treatment of acupunctures are used by LI-4(合谷), H-7(湧泉), Liv-3(太衝), K-3(太谿), Sp-6(三陰交), H-5(通里), GV-15(아門), CV-23(廉泉), S-40(農隆), K-6(照海), L-7(列缺), S-36(足三里) etc.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.3
• /
• pp.66-72
• /
• 2016

An LED lighting control system was developed to combine information technology and LED lights for efficient management and energy savings. The system can monitor and control the status of an LED luminaire using Bluetooth wireless communication, sensor technology, and smart phones. An LED lighting control circuit was designed using a temperature sensor, illumination sensor, and Bluetooth module with a fuzzy constant-current control circuit. We extended the lifetime and prevented damage to the LED by optimizing the supply current of the LED luminaire based on the heat-generation temperature of $70^{\circ}C$ of an LED heat sink. We also automatically adjusted the ON/OFF time depending on the ambient illumination of the LED luminaire. By allowing easy control of the LED luminaires on a smartphone, we improved the efficiency and achieved energy savings. The control system was validated through experiments for normal operation.

• Journal of the Korean Institute of Gas
• /
• v.3 no.2 s.7
• /
• pp.77-84
• /
• 1999

The XX company that is handling the class IV hazardous materials, located in Bu-Chon City and the LPG station in front of the XX company which is about 20 meters apart, was chosen as the standard model for this study In carrying out the consequence analysis, PHAST and Super-Chems were used for the study and utilizing the output of the simulation, we have evaluated the consequences throughout the probit analysis and explosion overpressure analysis. In case of Acetone, the effect distance of the damage on facilities-that is the result of radiation heat flux of $37.5kW/m^2$ by TNO model-is 68.51m by PHAST model and 40.93m by Super-Chem model. The risk assessment of the LPG station which is based on the explosion resulted as the analysis of the fire ball showed the diameter 125.2m, the height 206.2m and the duration 11.28sec and the effect distance for the radiant heat flux $37.5kW/m^2$ was 137.0m.

• Journal of the Korean Institute of Gas
• /
• v.18 no.3
• /
• pp.67-74
• /
• 2014

Buried natural gas pipelines in densely populated urban areas have serious hazards of property damages and casualties generated by release, dispersion, fire and explosion of gas caused by outside or inside failures. So as to prevent any accident in advance, managers implement danger management based on quantitative risk analysis. In order to evaluate quantitative risk about buried natural gas pipelines, we need calculation for radiant heat and pressure wave caused by calculation for release rate of chemical material, dispersion analysis, fire or explosion modeling through consequence analysis in priority, in this paper, we carry out calculation for release rate of pressured natural gas, radiant heat of fireball based in accident scenario of actual "San Bruno" buried high pressured pipelines through models which CCPS, TNO provide and compare with an actual damage result.

• Biomolecules & Therapeutics
• /
• v.23 no.6
• /
• pp.582-589
• /
• 2015

Several theories emphasize that aging is closely related to oxidative stress and disease. The formation of excess ROS can lead to DNA damage and the acceleration of aging. Vigna angularis is one of the important medicinal plants in Korea. We isolated vitexin from V. angularis and elucidated the lifespan-extending effect of vitexin using the Caenorhabditis elegans model system. Vitexin showed potent lifespan extensive activity and it elevated the survival rates of nematodes against the stressful environments including heat and oxidative conditions. In addition, our results showed that vitexin was able to elevate antioxidant enzyme activities of worms and reduce intracellular ROS accumulation in a dose-dependent manner. These studies demonstrated that the increased stress tolerance of vitexin-mediated nematode could be attributed to increased expressions of stress resistance proteins such as superoxide dismutase (SOD-3) and heat shock protein (HSP-16.2). In this work, we also studied whether vitexin-mediated longevity activity was associated with aging-related factors such as progeny, food intake, growth and movement. The data revealed that these factors were not affected by vitexin treatment except movement. Vitexin treatment improved the body movement of aged nematode, suggesting vitexin affects healthspan as well as lifespan of nematode. These results suggest that vitexin might be a probable candidate which could extend the human lifespan.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.5
• /
• pp.417-425
• /
• 2007

The ferritic 9Cr-1Mo-V-Nb heat-resisting steel was experimentally studied in order to characterize its microstructural evolution during creep-fatigue by coercivity measurement. The creep-fatigue test was conducted at $550\;^{\circ}C$ with the tensile holding time of 60s and 600s, respectively. The coercivity decreased until the failure and the hardness monotonously decreased for the whole fatigue life. As the life fraction of creep-fatigue increased, the $M_{23}C_6$ carbide coarsened following the Ostwald ripening mechanism. However, the MX carbonitrides did not grow during creep-fatigue due to so stable at $550\;^{\circ}C$. The width of martensite lath increased because of the dislocation recovery at the lath boundaries. The magnetic coercivity has an influence on the microstructural properties such as dislocation, precipitates and martensite lath boundaries, which interpreted in relation to microstructural changes. Consequently, this study proposes a magnetic coercivity to quantify the level of damage and microstructural change during the creep-fatigue of ferritic 9Cr-1Mo-V-Nb steel.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.3
• /
• pp.241-247
• /
• 2014

This study presents the ultrasonic nonlinearity of AISI316 austenitic stainless steels subjected to longterm isothermal aging. These steels are attractive materials for use in industrial mechanical structures because of their strength at high-temperatures and their chemical stability. The test materials were subjected to accelerated heat-treatment in an electrical furnace for a predetermined aging duration. The variations in the ultrasonic nonlinearity and microstructural damage were carefully evaluated through observation of the microstructure. The ultrasonic nonlinearity stiffly dropped after aging for up to 1000 h and, then, monotonously decreased. The polygonal shape of the initial grain structures changed to circular, especially as the annealing twins in the grains dissolved and disappeared. The delta ferrite on the grain boundaries could not be observed at 1000 h of aging, and these continuously transformed into their sigma phases. Consequently, in the intial aging period, the rapid decrease in the ultrasonic nonlinearity was caused by voids, dislocations, and twin annihilation. The continuous monotonic decrease in the ultrasonic nonlinearity after the first drop resulted from the generation of $Cr_{23}C_6$ precipitates and ${\sigma}$ phases.

• Journal of the Korean Society for Heat Treatment
• /
• v.19 no.1
• /
• pp.30-36
• /
• 2006

Fretting fatigue behavior of SCM420 steel commonly used in the automotive industry for structural applications was investigated in this study. In addition, the effect of bridge pad on the fretting fatigue test was evaluated from different pad materials and following conclusions were drawn. Simple fatigue limit of SCM 420 steel was determined to be 350 MPa while this value was 225 MPa and 285.5 MPa with SCM420H and with SM45C pad, respectively. Reduction in fatigue limit was, thus found to be 35.7% and 17.9% with SCM 420H pad and SM45C pad, respectively. Results of fracture surface observation revealed that typical striation pattern of fatigue failure existed as well as dimpled and cleavage frature appearance was found in final fractured region. From the EDS compositional analysis, test sample and pad part all had high signals for oxygen and iron, suggesting that worn particles might be iron oxide, although exact chemical composition has to be confirmed. Considerable reduction in fatigue life was apparent in SCM 420 steel under fretting fatigue against simple fatigue. Such reduced fatigue life by fretting damage should be considered as an important factor not only in the viewpoint of repairing but also inevitably in the design stage of structural components.