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Valve core shapes analysis on flux through control valves in nuclear power plants
Jin-yuan Qian,Cong-wei Hou,Juan Mu,Zhi-xin Gao,Zhi-jiang Jin 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10
Control valves are widely used to regulate fluid flux in nuclear power plants, and there are more than1500 control valves in the primary circuit of one nuclear power plant. With their help, the flux can beregulated to a specific level of water or steam to guarantee the energy efficiency and safety of the nuclearpower plant. The flux characteristics of the control valve mainly depend on the valve core shape. In orderto analyze the effects of valve core shapes on flux characteristics of control valves, this paper focuses onthe valve core shapes. To begin with, numerical models of different valve core shapes are established, andresults are compared with the ideal flux characteristics curve for the purpose of validation. Meanwhile,the flow fields corresponding to different valve core shapes are investigated. Moreover, relationshipsbetween the valve core opening and the outlet flux under different valve core shapes are carried out. Theflux characteristics curve and equation are proposed to predict the outlet flux under different valve coreopenings. This work can benefit the further rese
Wei-hua Yin,Yan Zhang,Xiang-nan Li,Hong-yue Wang,Yun-qiang An,Yang Sun,Zhi-hui Hou,Yang Gao,Bin Lu,Zhe Zheng 대한영상의학회 2020 Korean Journal of Radiology Vol.21 No.2
Objective: We sought to distinguish lipid plaques using a CT quantitative pixel density histogram, based on the pathological diagnosis of lipid cores as the gold standard. Materials and Methods: Eight patients awaiting heart transplantation due to end-stage coronary heart disease underwent coronary CT angiography (CCTA) spectroscopy prior to heart transplantation; coronary artery pathological analysis was performed for all patients. Lipid-core plaques were defined pathologically as manifesting a lipid core diameter > 200 μm, a circumference > 60 degrees, and a cap thickness < 450 μm. The percentage distributions of CT pixel attenuation ≤ 20, 30, 40, and 50 HU were calculated using quantitative histogram analysis. Results: A total of 271 transverse sections were co-registered between CCTA and pathological analysis. Overall, 26 lipid cores and 16 fibrous plaques were identified by pathological analysis. There was no significant difference in median CT attenuation between the lipid and fibrous plaques (51 HU [interquartile range, 46–63] vs. 57 HU [interquartile range, 50–64], p = 0.659). The median percentage of CT pixel attenuation ≤ 30 HU accounted for 11% (5–17) of lipid-core plaques and 0% (0–2) of fibrous plaques (p < 0.001). The sensitivity and specificity of the method for diagnosing lipid plaques by the average CT pixel attenuation ≤ 30 HU were 80.8% and 87.5%, respectively. The area under the receiver operator characteristics curve was 0.898 (95% confidence interval: 0.765–0.970; 3.0% was the best cut-off value). The diagnostic performance was significantly higher than those of the average pixel CT attenuation percentages ≤ 20, 40, and 50 HU and the mean CT attenuation (p < 0.05). Conclusion: In in vivo conditions, with the pathological lipid core as the gold standard, quantification of the percentage of average CT pixel attenuation ≤ 30 HU in the histogram can be useful for accurate identification of lipid plaques.