Microwave-absorbing polymeric composites based on single-walled carbon nanotubes （SWNTs） are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption...Microwave-absorbing polymeric composites based on single-walled carbon nanotubes （SWNTs） are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption perfor- mances in a range of 2 GHz-18 GHz. For instance, a maximum absorbing value as high as 28 dB can be achieved for each of these SWNT-epoxy composites （1.3-mm thickness） with only 1 wt% loading of SWNTs, and about 4.8 GHz bandwidth, corresponding to a microwave absorption performance higher than 10 dB, is obtained. Furthermore, such low and appro- priate loadings of SWNTs also enhance the mechanical strength of the composite. It is suggested that these remarkable results are mainly attributable to the excellent intrinsic properties of SWNTs and their homogeneous dispersion state in the polymer matrix.展开更多
目的探讨不同追踪触发监测频率对冠状动脉CTA图像质量及辐射剂量的影响。方法选择2016年1月至2018年12月佛山市禅城区中心医院诊治的144例冠心病患者为研究对象,按随机数表法将其分为A (54例)、B (46例)、C (44例)三组,均接受冠状动脉CT...目的探讨不同追踪触发监测频率对冠状动脉CTA图像质量及辐射剂量的影响。方法选择2016年1月至2018年12月佛山市禅城区中心医院诊治的144例冠心病患者为研究对象,按随机数表法将其分为A (54例)、B (46例)、C (44例)三组,均接受冠状动脉CTA检查,A、B、C三组追踪触发监测频率分别为1.14 s、1.17 s、2.00 s,观察并比较三组冠状动脉CTA图像质量及辐射剂量的差异。结果 A组、B组和C组患者的反折现象比率分别为22.22%、17.39%和6.82%,差异有统计学意义(P<0.05);A组、B组和C组患者主动脉根部(AO)的CT值[(486.23±5.02) Hu vs (464.22±6.57) Hu vs (494.17±5.91) Hu]、噪声[(34.25±5.26) vs (32.11±4.25) vs (33.47±4.23)]、信噪比(SNR)[(14.455±3.20) vs (15.23±2.15) vs (14.28±1.32)]和对比信噪比(CNR)[(23.45±10.23) vs (20.23±8.78) vs (25.47±5.56)]比较差异均无统计学意义(P>0.05);A组、B组和C组患者右冠状动脉近段(RCA)和左主干(LM)中的CT值[(472.44±64.11) Hu vs (455.27±95.21) Hu vs (455.78±62.44) Hu]和CNR [(25.44±7.23) vs (28.47±23.01) vs (28.47±5.26)]以及主观评分[(1.89±0.06)分vs (1.86±0.04)分vs (1.88±0.05)分]等指标比较差异均无统计学意义(P>0.05);A组监测次数为(4.77±2.23)次,高于B组的(3.72±1.44)次和C组的(2.71±0.95)次,而B组又高于C组,差异均有统计学意义(P<0.05);A组、B组和C组患者辐射剂量中的剂量长度乘积(DLP)[(4.10±2.23) mSv vs (2.15±0.82) mSv vs (1.51±0.53) m Sv]和有效剂量(ED)[(0.057±0.031) mSv vs (0.034±0.015) mSv vs (0.023±0.008) mSv]比较,A组均高于B、C两组,B组又高于C组,差异均有统计学意义(P<0.05)。结论不同追踪触发监测频率获得图像质量均较高,但监测频率为2.00 s时能显著降低监测次数及辐射剂量。展开更多
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB933401 and 2014CB643502)the National Natural Science Foundation of China(Grant Nos.21374050,51273093,and 51373078)
文摘Microwave-absorbing polymeric composites based on single-walled carbon nanotubes （SWNTs） are fabricated via a simple yet versatile method, and these SWNT-epoxy composites exhibit very impressive microwave absorption perfor- mances in a range of 2 GHz-18 GHz. For instance, a maximum absorbing value as high as 28 dB can be achieved for each of these SWNT-epoxy composites （1.3-mm thickness） with only 1 wt% loading of SWNTs, and about 4.8 GHz bandwidth, corresponding to a microwave absorption performance higher than 10 dB, is obtained. Furthermore, such low and appro- priate loadings of SWNTs also enhance the mechanical strength of the composite. It is suggested that these remarkable results are mainly attributable to the excellent intrinsic properties of SWNTs and their homogeneous dispersion state in the polymer matrix.
文摘目的探讨不同追踪触发监测频率对冠状动脉CTA图像质量及辐射剂量的影响。方法选择2016年1月至2018年12月佛山市禅城区中心医院诊治的144例冠心病患者为研究对象,按随机数表法将其分为A (54例)、B (46例)、C (44例)三组,均接受冠状动脉CTA检查,A、B、C三组追踪触发监测频率分别为1.14 s、1.17 s、2.00 s,观察并比较三组冠状动脉CTA图像质量及辐射剂量的差异。结果 A组、B组和C组患者的反折现象比率分别为22.22%、17.39%和6.82%,差异有统计学意义(P<0.05);A组、B组和C组患者主动脉根部(AO)的CT值[(486.23±5.02) Hu vs (464.22±6.57) Hu vs (494.17±5.91) Hu]、噪声[(34.25±5.26) vs (32.11±4.25) vs (33.47±4.23)]、信噪比(SNR)[(14.455±3.20) vs (15.23±2.15) vs (14.28±1.32)]和对比信噪比(CNR)[(23.45±10.23) vs (20.23±8.78) vs (25.47±5.56)]比较差异均无统计学意义(P>0.05);A组、B组和C组患者右冠状动脉近段(RCA)和左主干(LM)中的CT值[(472.44±64.11) Hu vs (455.27±95.21) Hu vs (455.78±62.44) Hu]和CNR [(25.44±7.23) vs (28.47±23.01) vs (28.47±5.26)]以及主观评分[(1.89±0.06)分vs (1.86±0.04)分vs (1.88±0.05)分]等指标比较差异均无统计学意义(P>0.05);A组监测次数为(4.77±2.23)次,高于B组的(3.72±1.44)次和C组的(2.71±0.95)次,而B组又高于C组,差异均有统计学意义(P<0.05);A组、B组和C组患者辐射剂量中的剂量长度乘积(DLP)[(4.10±2.23) mSv vs (2.15±0.82) mSv vs (1.51±0.53) m Sv]和有效剂量(ED)[(0.057±0.031) mSv vs (0.034±0.015) mSv vs (0.023±0.008) mSv]比较,A组均高于B、C两组,B组又高于C组,差异均有统计学意义(P<0.05)。结论不同追踪触发监测频率获得图像质量均较高,但监测频率为2.00 s时能显著降低监测次数及辐射剂量。
