针对复合材料电池包下箱体的树脂传递模塑(Resin Transfer Molding,RTM)成型进行了方案设计,基于PAM-RTM软件对其充模过程进行仿真分析及孔隙缺陷预测。首先,对比了两种方案在三种出胶口状态下充模时间,分析了注胶压力及树脂黏度对RTM...针对复合材料电池包下箱体的树脂传递模塑(Resin Transfer Molding,RTM)成型进行了方案设计,基于PAM-RTM软件对其充模过程进行仿真分析及孔隙缺陷预测。首先,对比了两种方案在三种出胶口状态下充模时间,分析了注胶压力及树脂黏度对RTM成型时间的影响规律;其次,分析了充模过程中注胶口附近位置的压力变化情况;最后,预测了宏观/微观两种尺度孔隙缺陷在构件中分布及注胶压力对孔隙含量的影响规律,并结合流速优化理论控制树脂前沿流速以降低孔隙含量。结果表明,模腔内注胶与出胶口压力差越大,成型用时越少,且受到注胶位置影响。注胶压力与充模时间呈线性关系,压力越低,充模时间缩短效果越明显,且黏度越大,充模时间越长。孔隙含量与前沿流速有关,注胶压力越大导致流速越快,宏观孔隙随之减少,微观孔隙相应增多;且流速优化方式注胶能够显著降低总体孔隙率水平,但会延长成型周期。展开更多
Objectives: Patients undergoing 18F-FDG PET/CT imaging are considered external radiation sources. Accurate dose rate estimates are important for conducting realistic risk assessments and performing dose reconstruction...Objectives: Patients undergoing 18F-FDG PET/CT imaging are considered external radiation sources. Accurate dose rate estimates are important for conducting realistic risk assessments and performing dose reconstruction in cases of accidental exposures. The patient radiation self-attenuation factor is assumed to be a function of the patient’s body size metrics, but we can use these metrics to predict the dose rate around the patients with accuracy. The objective of this work was first to measure the patient attenuation factor by performing direct dose rate measurements from patients undergoing PET/CT imaging studies using 18F-FDG. The second objective was to study the possible correlation between the measured dose rate constant per unit activity from the patients and their body size metrics;five metrics were tested in this work. The last objective was to measure the patients’ voiding factor. Methods: We have measured dose rates at one meter from 57 patients and noted the patient’s height (H), weight (W) and calculated patient size metrics namely: Equivalent Cylindrical Diameter (ECD), Equivalent Spherical Diameter (ESD) and the Body Mass Index (BMI). Results: The measured average dose rate was 92.2 ± 14 μSv·h-1·GBq-1 measured at one meter. Therefore, the dose rate constant of 92 μSv·h-1·GBq-1 proposed by the AAPM, TG-108 report is adequate for radiation protection purposes. There was no statistically significant correlation between the dose rate constant per unit activity and the patient body size metrics. We have measured a patient voiding factor of 0.89 ± 0.06 in comparison with 0.85 recommended by the AAPM. Conclusions: The presented data can be used by medical physicist working in nuclear medicine in formulating more accurate risk estimations resulting from radiation exposure from patients undergoing 18F-FDG PET/CT imaging.展开更多
文摘针对复合材料电池包下箱体的树脂传递模塑(Resin Transfer Molding,RTM)成型进行了方案设计,基于PAM-RTM软件对其充模过程进行仿真分析及孔隙缺陷预测。首先,对比了两种方案在三种出胶口状态下充模时间,分析了注胶压力及树脂黏度对RTM成型时间的影响规律;其次,分析了充模过程中注胶口附近位置的压力变化情况;最后,预测了宏观/微观两种尺度孔隙缺陷在构件中分布及注胶压力对孔隙含量的影响规律,并结合流速优化理论控制树脂前沿流速以降低孔隙含量。结果表明,模腔内注胶与出胶口压力差越大,成型用时越少,且受到注胶位置影响。注胶压力与充模时间呈线性关系,压力越低,充模时间缩短效果越明显,且黏度越大,充模时间越长。孔隙含量与前沿流速有关,注胶压力越大导致流速越快,宏观孔隙随之减少,微观孔隙相应增多;且流速优化方式注胶能够显著降低总体孔隙率水平,但会延长成型周期。
文摘Objectives: Patients undergoing 18F-FDG PET/CT imaging are considered external radiation sources. Accurate dose rate estimates are important for conducting realistic risk assessments and performing dose reconstruction in cases of accidental exposures. The patient radiation self-attenuation factor is assumed to be a function of the patient’s body size metrics, but we can use these metrics to predict the dose rate around the patients with accuracy. The objective of this work was first to measure the patient attenuation factor by performing direct dose rate measurements from patients undergoing PET/CT imaging studies using 18F-FDG. The second objective was to study the possible correlation between the measured dose rate constant per unit activity from the patients and their body size metrics;five metrics were tested in this work. The last objective was to measure the patients’ voiding factor. Methods: We have measured dose rates at one meter from 57 patients and noted the patient’s height (H), weight (W) and calculated patient size metrics namely: Equivalent Cylindrical Diameter (ECD), Equivalent Spherical Diameter (ESD) and the Body Mass Index (BMI). Results: The measured average dose rate was 92.2 ± 14 μSv·h-1·GBq-1 measured at one meter. Therefore, the dose rate constant of 92 μSv·h-1·GBq-1 proposed by the AAPM, TG-108 report is adequate for radiation protection purposes. There was no statistically significant correlation between the dose rate constant per unit activity and the patient body size metrics. We have measured a patient voiding factor of 0.89 ± 0.06 in comparison with 0.85 recommended by the AAPM. Conclusions: The presented data can be used by medical physicist working in nuclear medicine in formulating more accurate risk estimations resulting from radiation exposure from patients undergoing 18F-FDG PET/CT imaging.
