Two New Species of Placolecis (Lichenized Ascomycota) from China

( An Cheng Yin ),( Xin Yu Wang ),( Dong Liu ),( Yan Yun Zhang ),( Mei Xia Yang ),( Li Juan Li ),( Li Song Wang ) 한국균학회 2019 Mycobiology Vol.47 No.4

Two new species of the lichen genus Placolecis are discovered in China, namely P. kunmingensis An. C. Yin & Li S. Wang and P. sublaevis An. C. Yin & Li S. Wang. The new combination P. loekoesiana (S.Y. Kondr., Farkas, J.J. Woo & Hur) An. C. Yin is proposed. Placolecis kunmingensis is characterized by having simple, spherical or ellipsoid, hyaline spores, and pear-shaped pycnidia; while P. sublaevis can be distinguished by its thallus forming larger aggregations with slightly flattened lobes at the thallus margin, and urn-shaped pycnidia. Descriptions, a phylogenetic tree and a key are provided for all the known Placolecis species in China.

Ultrasonic Evaluation of Creep Damage in 316LN Stainless Steel

Song-Nan Yin,Yeong-Tak Hwang,Won Yi 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.4

Creep failure of 316LN stainless steel (SS) occurs due to the nucleation and growth of cracks. An investigation was performed to correlate the creep damage with ultrasonic wave speeds and angular frequencies using creep-tested 316LN SS specimens. Ultrasonic wave measurements were made in the direction of and perpendicular to the loading using contact probes with central frequencies of 10. 15. and 20 MHz. We found that the angular frequency and wave speed decreased with increasing creep time to rupture by analyzing the ultrasonic signals from the 15 and 20 MHz probes. Therefore, the creep damage was sensitive to the angular frequency and wave speed of ultrasonic waves.

Analysis of Undrained Shear Characteristics and Structural Damage of Granite Residual Soil

Song Yin,Pengfei Liu,Pan Yan,Xianwei Zhang,Xinming Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

Three-dimensional consolidation testing, scanning electron microscopy, and undrained triaxial testing of granite residual soil (GRS) in Shenzhen, China, were conducted. The effect of the structural strength of GRS was quantitatively analyzed using the method of comprehensive structure potential parameter description. The failure strength ratio of the soil decreases with increasing confining pressure, and it is approximately 1 when the confining pressure is higher than the yield stress (σs). The undrained shear strength (Su) of the undisturbed soil varies in stages with confining pressure σ3. The relationship between Su and σ3 for the reconstituted soil is approximated as a straight line through the origin. The soil’s comprehensive structure potential parameters (the structural contribution rates of the tangential shear modulus, mE, and the deviatoric stress, md) decrease linearly with increasing σ3. The mE and md sample values are similar under the same confining pressure. It is reasonable to use structure potential parameters to quantitatively evaluate the structure contribution rate of GRS. The microstructure is constantly adjusted, and the soil microstructure form for different confining pressures strongly correlates with its shear characteristics.

전산 해석을 통한 안전밸브 구조 최적화 연구

Yin Song,곽시영(S.Y. Kwak),황호영(H.Y. Hwang) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3

The safety valve is an essential device for high-pressure equipment; because high-pressure equipment is used in many fields, the use of safety valves is also increasing. Safety valves are used in various fields such as the petroleum industry, power plants, and nuclear power industries. In the 19th century, many boiler explosion accidents occurred due to improper boiler design or the failure of safety valves used in boilers. These incidents drew the attention of the US government, and the American Society of Mechanical Engineers (ASME) enacted the first ASME code for safety valves in response to government requirements. A safety valve is a device used to protect high-pressure systems and people from accidents, and because of its importance, many related studies have been conducted, and related standards are continuously being updated. In actual safety valve experiments, it is difficult to observe the characteristics of fluid flow. In this study, the opening process of a safety valve under high pressure was studied using a simulation method. Analysis was conducted using the commercial software COMSOL Multiphysics and the fluid–structure interaction (FSI) technique. The FSI is calculated by reflecting the interaction between a structure and fluid and is a suitable method for analyzing the safety valve operation process. Two shapes that can reduce flow resistance were designed by analyzing the simulation results and the same flow analysis was performed on these shapes. By comparing the proposed shape’s simulation results with those of existing shapes, it was confirmed that the pressure loss was reduced in the improved method, and the flow rate was further increased due to a relatively low pressure loss. This means that the fluid inside the pressure vessel can be discharged faster and the pressure can be lowered faster, so it was determined that the improved shape safety valve showed better performance.

Ultrasonic Evaluation of Creep Damage in 316LN Stainless Steel

Yin, Song-Nan,Hwang, Yeong-Tak,Yi, Won Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.4

Creep failure of 316LN stainless steel (SS) occurs due to the nucleation and growth of cracks. An investigation was performed to correlate the creep damage with ultrasonic wave speeds and angular frequencies using creep-tested 316LN SS specimens. Ultrasonic wave measurements were made in the direction of and perpendicular to the loading using contact probes with central frequencies of 10, 15, and 20 MHz. We found that the angular frequency and wave speed decreased with increasing creep time to rupture by analyzing the ultrasonic signals from the 15 and 20 MHz probes. Therefore, the creep damage was sensitive to the angular frequency and wave speed of ultrasonic waves.

시간-온도 파라미터법과 최소구속법에 의한 크리프 수명예측과 오차 분석

윤송남(Song-Nan Yin),김우곤(Woo-Gon Kim),류우석(Woo-Seog Ryu),이원(Won Yi) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3

To predict long-term creep lifetime from short-term creep data, various parametric methods such as Larson-Miller (L-M), Orr-Sherby-Dorn (O-S-D), Manson-Haferd (M-H) parameters, and Minimum Commitment Method (MCM) were suggested. A number of the creep data were collected through literature surveys and experimental data produced in KAERI for predicting the creep life of type 316LN SS. The polynomial equations for predicting the creep life were obtained by the time-temperature parameters (TTP) and the MCM. Standard error (SE) and standard error of mean (SEM) values were compared for the each method with temperatures. The TTP methods were good in the creep-life prediction, but the MCM was much superior to the TTP ones at 700℃ and 750℃. It was found that the MCM were lower in the SE values when compared to the TTP methods.

Experimental and numerical investigation on the pressure pulsation in reactor coolant pumps under different inflow conditions

Huang Song,Song Yu,Yin Junlian,Xu Rui,Wang Dezhong 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.4

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78–128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.

Taylor 급수를 이용한 Alloy 617 의 장시간 크리프 수명 예측 모델의 적용성

윤송남(Song-Nan Yin),김우곤(Woo-Gon Kim),박재영(Jea-Yeong Park),김용완(Yong-Wan Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Creep life prediction has been commonly used by a time-temperature parameter (TTP) which is correlated to a rupture time and temperature, such as Larson-Miller (LM), Orr-Sherby-Dorn (OSD), Manson-Haferd (MH) and Manson-Succop (MS) parameters. A Taylor series model(T-SM) based on Arrhenius, McVetty and Monkman-Grant equations was newly proposed through a mathematical procedure and in order to reduce the fitting errors the McVetty’s equation was transformed by taking the first three-terms of Taylor series equation. The model parameters were properly determined by means of a technique of maximum likelihood estimation of statistical method, and this model was applied to the creep data of Alloy 617. The T-SM results revealed better agreement than the Eno’s model and the LM parameter one. Especially, it was identified that the T-SM showed a good estimation in predicting the long-term creep life of Alloy 617.

Hastalloy-X 합금의 초고온 크리프 거동 예측

윤송남(Song-Nan Yin),김우곤(Woo-Gon Kim),정익희(Ik-Hee Jung),김용완(Yong-Wan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

The nickel-based Hastelloy X alloy is one of the candidate materials for structural components of the high temperature gas-cooled reactor (HTGR). Its creep data was obtained from the creep tests under several stress levels at 950℃, and using this data, the creep behavior was investigated by the θ-projection model. The proper fitting range was determined from the creep curves at any stress level because the θ<SUB>i</SUB>-parameters are dependent on a fitting strain range. A stress dependency for the B-parameters was established to accurately predict the creep curve of a low stress level. The time to 1%-low strains was predicted for various stress levels, and the ratios between the time to 1%-low strain and time to rupture were lower than 15%. Also, a predicted minimum creep rate revealed a good agreement with the experimental data.

Alloy 617 의 장시간 크리프 수명 예측을 위한 다중회귀 선형 모델의 제안 및 평가

윤송남(Song-Nan Yin),김우곤(Woo-Gon Kim),정익희(Ik-Hee Jung),김용완(Yong-Wan Kim) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.4

Creep life prediction has been commonly used by a time-temperature parameter (TTP) which is correlated to an applied stress and temperature, such as Larson-Miller (LM), Orr-Sherby-Dorn (OSD), Manson-Haferd (MH) and Manson-Succop (MS) parameters. A stress-temperature linear model (STLM) based on Arrhenius, Dorn and Monkman-Grant equations was newly proposed through a mathematical procedure. For this model, the logarithm time to rupture was linearly dependent on both an applied stress and temperature. The model parameters were properly determined by using a technique of maximum likelihood estimation of a statistical method, and this model was applied to the creep data of Alloy 617. From the results, it is found that the STLM results showed better agreement than the Eno’s model and the LM parameter ones. Especially, the STLM revealed a good estimation in predicting the long-term creep life of Alloy 617.