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As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

The NUREG/CR-6909, which had provided the technical background for the Environmental Fatigue Evaluation (EFE), was revised in May 2018 to incorporate the Japan Nuclear Energy Safety organization (JNES)’s extensive fatigue ε-N data and to address concerns from interested stakeholders over the original NUREG/CR-6909. But the revised NUREG/CR-6909 sets limit of the temperature ranges to 325°C for the application of the environmental fatigue correction factor (Fen). Therefore, the revised NUREG/CR-6909-based EFE is not applicable to the materials whose temperatures are higher than 325°C. In this paper, Monte Carlo simulations have been performed to determine the transformed temperatures over 325°C for the materials which are not covered in the revised NUREG/CR-6909. To determine the distributions of fatigue lives in LWR environments, Monte Carlo simulations were performed using the fatigue life models in the LWR environments and transformed parameters provided in the revised NUREG/CR-6909 and JNES-SS-1005. The transformed parameters which affect the fatigue lives in the LWR environments were selected randomly using the uniform distribution. And a total of 100,000 simulations were performed for each material. The distributions of fatigue lives in LWR environments obtained from Monte Carlo simulations were fit to lognormal curves to estimate the cumulative distributions. The estimated cumulative distributions were individually determined in the temperature ranges of 100 ∼ 325°C and 325 ∼ 350°C to investigate the temperature effects (FT,effect) over 325°C. The temperature effect is defined as ratio of fatigue lives in the LWR environments in the temperature range of 100 ∼ 325°C to that in the temperature range of 325 ∼ 350°C in this paper. As a result of reviewing the temperature effects between the revised NUREG/CR-6909 and JNES-SS-1005, the transformed temperatures over 325°C for each material have been suggested for the application of the revised NUREG/CR-6909.

Thermal stratification-induced stresses could lead to a serious failure and fatigue crack on piping systems. U.S. NRC Bulletin 88-08 [1] requires to investigate which unisolable pipings are subjected to the thermal stratification and to demonstrate compliance with applicable code limits during the piping design stage by incorporating the thermal stratification-induced stresses into the fatigue evaluation. In this paper, the computational fluid dynamic (CFD) analyses considering both the out-leakage case by turbulent penetration and the in-leakage case by valve leakage were performed for the unisolable portion of the Direct Vessel Injection (DVI) piping between the reactor vessel nozzle and the first check valve to determine the change of temperature gradient on the pipe wall as a function of time due to the thermal stratification. And then the CFD-based temperature distributions on the pipe wall at each time interval were transformed as input data for the structural analysis to evaluate the stresses induced by the global bending moments and local stresses by the thermal stratification of the DVI piping. The localized thermal stratification stress intensities were directly extracted from the 3-D model using the ANSYS program and were categorized as the three stress terms induced by ΔT1, ΔT2, and Ta - Tb defined in NB-3600 of ASME B&PV Sec. III [2], but including thermal stratification effects herein for the fatigue analysis. To evaluate the air environment- and LWR environment-based fatigue damages for the DVI piping, the bending moments and three local stress terms due to the thermal stratification were incorporated into the fatigue analysis. NB-3200/-3600 of ASME B&PV Sec. III- and Regulatory Guide 1.207-based cumulative usage factors [3, 4] were compared with each other to investigate the effects of fatigue damages considering the thermal stratification in the air and light water reactor (LWR) environments.

Mineral oil has been widely used as an insulating oil for electrical transformers for a long time, but the necessity of employ- ing new insulation oil such as vegetable oil has been increased due to urgent needs for the biodegradability when it leaks and also for the thermal stability at a higher operation temperature. Although specific periods are required between the pro- duction and consumption, there are still short of the data to prove the insulation oils' storage stability depending upon various circumstances and their resources. Thus, this paper demonstrates the insulation oils' oxidation characteristics of both mineral and vegetable oils when each was exposed to different environments for 12 weeks. From this test, some properties including total acid number, water content and dielectric breakdown were changed under specific conditions and resources. Vegetable oils showed higher hydrophilicity and water saturation than those of mineral oils due to their molecular compositions. Under sunlight exposure condition, all insulation oils oxidized and changed their properties when exposing to the direct light, regard- less of the resource used.

This study evaluates the efficacy of titanium tetrachloride (TiCl 4 ) on phosphorus (P) removal in synthetic wastewater. Jar test experiments were performed at various TiCl 4 concentration (0.25-0.59 mM), and intensities of slow (30-60 rpm) and rapid (100-250 rpm) mixings to determine the conditions at which P removal was most efficient. The P-removal efficiency was highest (about 99%) at TiCl 4 concentration ([TiCl 4 ])=0.39 mM with rapid-mixing intensity=100 rpm and slow-mixing intensity=30 rpm. The slow-mixing intensity was more sensitive than the rapid-mixing intensity to the P removal efficiency when [TiCl 4 ] was low (0.25≤[TiCl 4 ]≤0.27 mM). Key Words : Coagulation, Mixing Intensity, pH, Phosphorus, Titanium Tetrachloride 요약: 본 연구는 TiCl 4 의 농도(0.25-0.59 mM)와 급속교반속도(100-250 rpm), 완속교반속도(30-60 rpm)의 변화가 인 제거효율에 미치는 영향을 알아보고자 하였다. 응집제 농도가 0.25≤[TiCl 4 ]≤0.39 mM 범위에서 인 제거 효율은 TiCl 4 의 농도가 증가할수록 증가하였으며 처리후 인의 농도는 0.2 mg/L 이하였다. 응집제 농도 0.39 mM, 급속교반속도 100 rpm, 완속교반속도 30 rpm에서 인 제거효율이 약 99%로 가장 높았다. TiCl

At low temperature, Wax build-up and settling can affect adversely the cold weather performance of the diesel vehicle. In this study, we test the cold properties of diesel by blending ratio of biodiesel, kerosene and WAFI. Also, we test the cold weather performance for diesel vehicle by fuel cold properties. Cold properties of diesel are improved by adding the WAFI, kerosene and get worse by adding the biodiesel. WAFI is effective to improve a cold filter plugging point(CFPP) and Kerosene is effective to improve a cloud point(CP). CFPP and pour point(PP) are related to cold weather performance of diesel vehicle but CP is unrelated. CFPP indicate a limit temperature of vehicle driving possibility.

Bio diesel has advantages to reduce GHG(Greenhouse Gas) compare with the fossil fuel by using oil comes from plant/animal sources and even waste such as used cook oil. The diversity of energy feeds brings the positive effects to secure the national energy mix. In this circumstance, micro-algae is one of the prospective source, though some technical barriers. We analyzed the bio diesel which was derived from Dunaliella tertiolecta LB999 through the BD100 quality specifications designated by the law. From that result, it is revealed that the oxidation stability is one of the properties to be improved. In order to find the reason for low oxidation stability, we analyzed the oxidation tendency of each FAME components through some meth- ods(EN 14111, EN14112, EN16091). In this study, we could find the higher double bond FAME portion, the more oxidative property(C18:1

The cardiac conduction system is a complex network of cells that together orchestrate the rhythmic and coordinated depolarization of the heart. Dysfunction of the cardiac conduction system plays a central role in the pathogenesis of arrhythmia. While much progress has been made understanding cardiomyocyte differentiation, the molecular mechanisms regulating the specification and patterning of cells that form this conductive network is largely unknown. The LIM-homeodomain transcription factor ISL1 is highly expressed in the secondary heart field (SHF) progenitor population that makes a substantial contribution to the developing heart, comprising most cells in the right ventricle, both atria and pacemaker cells. Pacemaker cells comprise the most proximal component of the cardiac conduction system, which have been proposed as the source of most arrhythmogenic events. Their dominance on other spontaneous beating cell types makes them a suitable target for pharmacologic compounds, making access to this cell lineage necessary for the study of new therapeutic agents. To identify the signaling pathways that control the differentiation of human embryonic stem cell (hESC)-derived SHF cells into pacemaker cells, we performed RNA sequencing to compare the hESC-derived ISL1 + population, non-enriched population and undifferentiated hESCs. Furthermore, using a small molecule screen we identified compounds that can improve differentiation of hESCs toward pacemaker cells. Pathway analysis identified the Wnt pathway as the most significant regulator of SHF specification. Further differentiation of human pluripotent stem cells by stage-specific activation of BMP and WNT signaling pathways resulted in phenotypic pacemaker cells, which display morphological characteristics. More than 80% of these cells stained positively for HCN4, Contactin2(CNTN2) and GATA6, key markers of pacemaker cells. The differentiated cells express pacemaker markers, including CNTN2, TBX2, TBX3, HCN4, TBX18, GATA6 indicated by qRT-PCR. They show inward potassium currents through HCN channels in patch clamp experiments. Our data provides a new strategy to obtain human cardiac conduction cells in large scale for disease modeling, drug screening and cell therapy.

Protein of relevant evolutionary and lymphoid interest (PRELI) is known for preventing apoptosis by mediating intramitochondrial transport of phosphatidic acid. However, the role of PRELI remains unclear. This study has demonstrated functions of PRELI through PRELI-knockdown in hepatocellular carcinoma (HepG2) cells exposed to oxidative stress by hydrogen peroxide. Results show that PRELI has three functions in HepG2 cells with regard to oxidative stress. First, PRELI affects expressional regulation of SOD-1 and caspase-3 genes in HepG2 cells. PRELI knockdown HepG2 cells have shown up-regulation of caspase-3 and down-regulation of SOD-1. Second, PRELI suppresses mitochondrial apoptosis in HepG2 cells. Fluorescence intensity related to mitochondrial apoptosis in PRELI-knockdown HepG2 cells increased more than two-fold compared to normal HepG2 cells. Third, PRELI suppresses senescence of HepG2 cells with oxidative stress. PRELI knockdown HepG2 cells showed higher levels of senescence than normal HepG2 cells. These results suggest that PRELI is a crucial protein in the suppression of apoptosis in HepG2 cells in response to oxidative stress.