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Accurate attenuation correction is required in dedicated breast PET imaging systems for image artifact removal and quantitative studies. In this study, a method using only emission data based on consistency conditions is proposed for attenuation correction in breast PET imaging systems. The consistency conditions are exploited to evaluate the accuracy of the estimated attenuation distribution and find the appropriate parameters that yield the most consistent attenuation distribution with the measured emission data. We have proved the validity of the method with experimental investigations and single-patient studies using a dedicated breast PET. The results show that the method is capable of accurately estimating the attenuation distribution of a uniform attenuator from the experimental data with various relatively low activities. The results also show that in single-patient studies, the method is robust for the irregular boundary of breast tissue and provides a distinct improvement in image quality. 相似文献
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A photon-counting-based iterative parallel interference cancellation (PIC) scheme for free-space optical communications in the presence of multiple-access interference,shot noise,background radiation,and turbulence fading is designed.An efficient chip-level iterative equivalent noise estimation algorithm is also derived.Simulation results show that the proposed scheme can achieve a single-user performance,bound with the fast convergence property.More importantly,it can eliminate the bit-error rate floor of the conventional optical code-division multiple-access system with the aid of a relatively short spreading code length. 相似文献
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庞文品邓云江周小林 《理化检验(化学分册)》2018,(5):559-562
高岭土是一种天然存在的铝硅酸盐矿物,白度高、质软且易分散悬浮于水中,具有良好的可塑性、黏结性、烧结性及较高的耐火度等[1],其广泛应用于造纸、陶瓷、耐火材料、涂料、橡胶、塑料、涂料、肥皂、农药、医药等领域[2]。高岭土中微量组分对产品的主体性能影响较大,因此,准确测定高岭土中微量组分对高岭土的利用和评价十分关键。 相似文献
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按文[1]模型,模拟计算汞/水溶液界面五个不同温度的内层微分电容随表面电荷变化曲线.结果表明,文[1]处理方法对此类体系仍可成立.指出在溶液的冰点附近,吸附层上的水分子有可能以氢键缔合的方式连结并构成局部有序排列.温度升高,即趋无规分布状态。 相似文献
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本文提出电极/溶液界面溶剂化层偶极取向分布模型,应用统计力学方法及热力学平衡条件导出普遍化的单层吸附等温方程,其电解质溶液的溶剂组成可以是纯态的或混合物(多组份)的.文中分别以甲酰胺、碳酸亚乙酯和甲醇等三种纯溶剂的汞/溶液界面为例,采用曲线拟合计算内层微分电容随表面电荷变化关系。预计本模型处理对汞/水溶液或汞/(混合溶剂)溶液界面仍可适用。 相似文献
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