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SUMRAY: R and Python Codes for Calculating Cancer Risk Due to Radiation Exposure of a Population
Sasaki Michiya,Furukawa Kyoji,Satoh Daiki,Shimada Kazumasa,Kudo Shin’ichi,Takagi Shunji,Takahara Shogo,Kai Michiaki 대한방사선방어학회 2023 방사선방어학회지 Vol.48 No.2
Background : Quantitative risk assessments should be accompanied by uncertainty analyses of the risk models employed in the calculations . In this study, we aim to develop a computational code named SUMRAY for use in cancer risk projections from radiation exposure taking into ac- count uncertainties . We also aim to make SUMRAY publicly available as a resource for further improvement of risk projection . Materials and Methods : SUMRAY has two versions of code written in R and Python . The risk models used in SUMRAY for all-solid-cancer mortality and incidence were those published in the Life Span Study of a cohort of the atomic bomb survivors in Hiroshima and Nagasaki . The confidence intervals associated with the evaluated risks were derived by propagating the statisti- cal uncertainties in the risk model parameter estimates by the Monte Carlo method . JRPR Results and Discussion : SUMRAY was used to calculate the lifetime or time-integrated attrib- utable risks of cancer under an exposure scenario (baseline rates , dose[s] , age[s] at exposure , age at the end of follow-up, sex) specified by the user. The results were compared with those calculated using another well-known web-based tool , Radiation Risk Assessment Tool (Rad- RAT; National Institutes of Health) , and showed a reasonable agreement within the estimated confidential interval . Compared with RadRAT, SUMRAY can be used for a wide range of ap- plications , as it allows the risk projection with arbitrarily specified risk models and/or popula- tion reference data . Conclusion : The reliabilities of SUMRAY with the present risk-model parameters and their variance-covariance matrices were verified by comparing them with those of the other codes . The SUMRAY code is distributed to the public as an open-source code under the Massachusetts Institute of Technology license .
Numerical Study on Loss Mechanism in Rear Rotor of Contra-Rotating Axial Flow Pump
De Zhang,Yusuke Katayama,Satoshi Watanabe,Shin-Ichi Tsuda,Akinori Furukawa 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1
It is known that higher efficiency can be achieved with reduced specific speed design of rear rotor in contra-rotating axial flow pump. To investigate the mechanism of increased efficiency with the reduced specific speed of rear rotor, three models with different specific-speed rear rotors are designed with the conventional method, and the flow fields are simulated by unsteady RANS simulation. To analyze the loss generation mechanism, two loss evaluation methods based on the entropy production rate and the material-derivative of rothalpy are employed. It is found that, although the both methods qualitatively estimate the total loss through the rear rotor, the derivative of rothalpy can give much better quantitative prediction of the losses. Two distinct flow features are observed in the rear rotor, the corner separation at the hub corner of blades and the tip leakage vortex, both of which are responsible for the loss generation. With the evaluation of local loss generation based on the material derivative of rothalpy, the loss contribution of corner separation is found to be very small compared with that due to the tip leakage vortex. The tip leakage vortex structure in high specific speed rear rotor shows the strong interaction with the leading edge of adjacent blade, which seems to strengthen the blockage effect in the tip region. This is relieved in the lower specific speed rear rotor, resulting in the achievement of higher efficiency with it.