Subjects: Other Disciplines submitted time 2025-04-03
Abstract： Abstract [Background] Molten salt reactors generate large amounts of xenon, krypton, and tritium during operation, and these airborne radionuclides adversely affect neutron economy, heat transfer characteristics, and material lifetime, respectively. In order to ensure the stability and safety of the reactor during long-term operation, it is planned to remove these airborne radionuclides online by means of bubble degassing, which requires confirmation of bubble size compliance. Considering the complexity of the research object, X-ray imaging is the more feasible one among many two-phase flow parameter measurement methods. However, the method is less effective in the face of light substances, so it is necessary to optimize the imaging system to improve the image quality.[Purpose] The purpose of this study is to investigate the influence laws of four parameters, namely, pipe inner diameter, pipe wall thickness, tube voltage, and exposure, on the performance of the imaging system, so as to provide a reference for the subsequent optimization of the imaging system. [Methods] Firstly, the calculation formula of FoM is proposed with reference to the existing studies and imaging objects.Secondly, based on the four factors of pipe inner diameter, pipe wall thickness, tube voltage and exposure, each factor is set to six levels to design the orthogonal table. Orthogonal experiments were carried out using the model built by monte carlo method, and the FoM under different combinations was calculated and analyzed by polar analysis and analysis of variance .Subsequently, the orthogonal experiments were repeated by changing the bubble position, pixel size, and geometric magnification to ensure the generalizability of the study.Finally, the machine learning algorithm is used to output the influence weights of each factor.[ Results] The experimental results show that the pipe wall thickness and exposure have a significant effect on the FoM, with influence weights of 42.2% and 40.3%, respectively, while the pipe inner diameter and tube voltage have a lesser effect on the FoM, with influence weights of 11.2% and 5.3%. The same conclusion can still be obtained after changing the detector pixel size and geometric magnification. Reducing the pixel size or geometrical magnification greater than 2 showed a decreasing trend in FoM. [Conclusions] A set of models was constructed that can be used to study the optimization of X-ray imaging system parameters. When using a conventional cesium iodide flat-panel detector and a suitable layout of the imaging system, the performance of the imaging system mainly depends on the pipe wall thickness and the exposure .The performance of the imaging system decreases when the pixel size is reduced or the geometric magnification is greater than 2 without changing other parameters.
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. submitted time 2023-08-29 Cooperative journals: 《中国全科医学》
Abstract： Background Cardiovascular disease is a major chronic disease that seriously endangers human health，and remains a public health problem to be solved in China and even globally. Objective To explore the epidemic characteristics and disease burden of cardiovascular diseases in China from 1990 to 2019，forecast the incidence of cardiovascular diseases in China from 2020 to 2050，and provide a reference for the formulation of relevant prevention and treatment strategies of cardiovascular diseases. Methods The 2019 Global Burden of Disease Study （GBD 2019） database was searched to extract and analyze relevant data on cardiovascular disease burden and risk factors in China and globally from 1990 to 2019. The prevalence of cardiovascular diseases was quantified by using the publicly available incidence，prevalence，mortality， and corresponding age-standardized rate（referred to as standardized rate） based on GBD 2019 database，and the burden of diseases was quantified by years lived with disability（YLD），years of life lost（YLL） and disability adjusted life year（DALY），and the ARIMA model was constructed to predict the incidence of cardiovascular diseases in China from 2020 to 2050. Results Compared with 1990，the incidence，prevalence and mortality of cardiovascular diseases in China showed an increasing trend by year up to 2019，in which the incidence，prevalence and mortality increased by 93.75%，99.75% and 57.39%，respectively. The standardized incidence and prevalence of females were higher than those of males，while the standardized mortality was lower than that of males. According to the data in 2019，the overall incidence of cardiovascular diseases in China showed an increasing trend with age，reaching its highest value in the age group of 95 years and above. Incidence trends for both men and women were similar to the overall trend，with slight differences. The overall prevalence also increases with age and is higher in women than men. There is an increasing trend in cardiovascular disease mortality after the age of 45，with males having a higher mortality rate than females at all ages. Compared with 1990，the rates of YLL，YLD and DALY in Chinese men increased by 36.99%，102.42% and 40.78%，respectively，and increased by 2.79%，107.13% and 11.50% in women. According to the data in 2019，the YLL rate，YLD rate and DALY rate of cardiovascular diseases in Chinese population showed an upward trend with the increase of age，with no inflection point. YLL rate and DALY rate of males gradually increased with the progress of population aging and were much higher than females，YLD rate gradually increased in the the age group of 55-59 years and was much higher than males. From 1990 to 2019，the global standardized incidence，standardized prevalence and standardized mortality of cardiovascular diseases showed a downward trend by year，while the standardized morbidity and standardized morbidity still increased in China，the standardized incidence and prevalence decreased，but that was still higher than the global scale. From the global level，the standardized YLL rate and DALY rate of cardiovascular diseases in China showed a downward trend along with the global level，but the disease burden of cardiovascular diseases in China was higher than the global level after 2000，and the standardized YLD rate increased by year. Risk factors associated with death from cardiovascular diseases mainly included smoking，second-hand smoke，alcohol consumption，low physical activity，high fasting blood glucose，high systolic blood pressure，high BMI，high low density lipoprotein cholesterol and renal insufficiency. From the relevant data in China and globally，high systolic blood pressure （hypertension） was still the primary risk factor for death from cardiovascular diseases，and the number of deaths was increasing by year. High density lipoprotein cholesterol （hyperlipidemia） was the second cause of death from cardiovascular diseases globally and in China in recent years. From 2020 to 2050，the standardized incidence of cardiovascular diseases in China is still on the rise，and it is expected that the standardized incidence of cardiovascular diseases will reach 663.618 per 100 000 by 2050. Conclusion The incidence，prevalence and mortality of cardiovascular diseases in China from 1990 to 2019 have shown an increasing trend by year. The disease burden caused by cardiovascular diseases is more severely，and there is no inflection point in the next 50 years. The prevalence and burden of diseases are higher than those of the world. It is expected that the standardized incidence of cardiovascular diseases will reach 663.618 per 100 000 by 2050.
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