目前,传统雷达成像方法的发展日渐完善,但在前视成像场景下,雷达难以获取方位向上的多普勒信息,从而限制了其方位向分辨率。为了解决这一问题,国内提出了微波关联成像方法。微波关联成像方法利用关联成像原理进行雷达成像,无需利用目标...目前,传统雷达成像方法的发展日渐完善,但在前视成像场景下,雷达难以获取方位向上的多普勒信息,从而限制了其方位向分辨率。为了解决这一问题,国内提出了微波关联成像方法。微波关联成像方法利用关联成像原理进行雷达成像,无需利用目标的多普勒信息即可实现高分辨率成像。这一新型雷达成像方法突破了传统雷达成像方法中受限于雷达孔径的分辨率,具有极高的前视成像发展潜力。目前,国内外对微波关联成像的研究主要集中在产生随机波前、解决模型失配问题和研制超材料孔径等方面,但对关键的关联过程的优化主要集中在压缩感知和深度学习方面,而在伪逆算法方面的研究相对较少。因此,为了进一步完善微波关联成像体系,本文提出了一种新的针对伪逆算法优化的微波关联前视成像方法。本文结合截断奇异值分解(Truncated Singular Value Decomposition,TSVD)处理和吉洪诺夫正则化(Tikhonov)提出了奇异值分解和吉洪诺夫正则化的联合处理方法(TSVD-Tikhonov,TSVDT),通过TSVDT方法对时空随机辐射阵进行处理,然后进行压缩关联成像。同时,本文比较了广义交叉验证(Generalized Cross-Validation,GCV)和L曲线法,并证明了在微波关联成像方法中,利用GCV法选择截断参数的运算耗时更短且更稳定。最后,利用微波暗室实验验证了该方法在低信噪比条件下提高了成像的抗干扰能力,并且仍能保持较快的运算速度。展开更多
The morphology and microstructure of flow pattern defects （FPDs） in lightly boron-doped Czochralski-grown silicon （Cz-Si） crystals were investigated using optical microscopy and atomic force microscopy. The experi...The morphology and microstructure of flow pattern defects （FPDs） in lightly boron-doped Czochralski-grown silicon （Cz-Si） crystals were investigated using optical microscopy and atomic force microscopy. The experimental results showed that the morphology of FPDs was parabola-like with several steps. Single-type and dual-type voids were found on the tip of FPDs and two heaves exist on the left and right sides of the void. All the results have proved that FPDs were void-type defects. These results are very useful to investigate FPDs in Cz-Si wafers further and explain the annihilation of FPDs during high-temperature annealing.展开更多
The morphology and microstructure of flow pattern defects (FPDs) in lightly boron-doped Czochralski-grown silicon (Cz-Si) crystals were investigated using optical microscopy and atomic force microscopy. The experiment...The morphology and microstructure of flow pattern defects (FPDs) in lightly boron-doped Czochralski-grown silicon (Cz-Si) crystals were investigated using optical microscopy and atomic force microscopy. The experimental results showed that the morphology of FPDs was parabola-like with several steps. Single-type and dual-type voids were found on the tip of FPDs and two heaves exist on the left and right sides of the void. All the results have proved that FPDs were void-type defects. These results are very useful to investigate FPDs in Cz-Si wafers further and explain the annihilation of FPDs during high-temperature annealing.展开更多
比较分析国产重离子加速器均匀扫描与光子调强放疗(IMRT)治疗计划在颅底恶性肿瘤治疗中的剂量学差异。回顾分析国产重离子设备(Heavy Ion Medical Machine,HIMM)采用均匀扫描方式治疗8例颅底恶性肿瘤的患者治疗计划,包括7例脊索瘤、1例...比较分析国产重离子加速器均匀扫描与光子调强放疗(IMRT)治疗计划在颅底恶性肿瘤治疗中的剂量学差异。回顾分析国产重离子设备(Heavy Ion Medical Machine,HIMM)采用均匀扫描方式治疗8例颅底恶性肿瘤的患者治疗计划,包括7例脊索瘤、1例软骨肉瘤。碳离子治疗(Carbon Ion Radiotherapy,CIRT)计划采用兰州科近泰基公司的ciPlan计划系统(V1.0)进行计划设计,处方剂量为计划靶区57.6~60.8 Gy(RBE),16分次,单次3.6~3.8 Gy(RBE)。治疗使用多叶准直器(Multi Leaf Collimator,MLC)调节射束横向适形度,脊形过滤器(Ridge Filter,RF)展宽Bragg峰,补偿器(Bolus)调节射束远端的适形度。使用90°固定水平治疗头,采取床角为0°,及转床90°或180°实现两野交角照射或对穿照射。光子IMRT计划采用美国Varian公司的Eclipse计划系统(V13.5)设计5野固定野调强计划,处方剂量和CIRT计划一致。所有计划在满足危及器官(Organ At Risk,OAR)限量的基础上进行剂量评估,相关剂量学参数包括:靶区覆盖、适形度指数(CI)、均匀性指数(HI)、以及危及器官受量。PTV的V95两者之间比较无统计学差异(P=0.106),Dmean、CI、HI均有统计学差异,IMRT计划优于CIRT计划(P值分别为0.048,0.031和0.024)。OAR受量方面,大部分OAR的CIRT计划比IMRT计划的小,但没有统计学差异,而视交叉、左晶体、右晶体的最大剂量及脑干、右侧视神经的平均剂量有统计学差异(P值分别为0.034,0.000,0.047,0.008和0.030)。OAR与靶区的距离,使用最小hausdorff距离(HD_(min))来描述,当HD_(min)>7.1 mm时,CIRT计划明显优于IMRT计划。均匀扫描方式的碳离子治疗计划在靶区均匀度及适形度方面劣于光子IMRT计划,但在OAR受量方面,均匀扫描碳离子治疗计划优于IMRT计划。剂量学优势能否转化为临床获益有待于通过临床研究进一步验证。展开更多
文摘目前,传统雷达成像方法的发展日渐完善,但在前视成像场景下,雷达难以获取方位向上的多普勒信息,从而限制了其方位向分辨率。为了解决这一问题,国内提出了微波关联成像方法。微波关联成像方法利用关联成像原理进行雷达成像,无需利用目标的多普勒信息即可实现高分辨率成像。这一新型雷达成像方法突破了传统雷达成像方法中受限于雷达孔径的分辨率,具有极高的前视成像发展潜力。目前,国内外对微波关联成像的研究主要集中在产生随机波前、解决模型失配问题和研制超材料孔径等方面,但对关键的关联过程的优化主要集中在压缩感知和深度学习方面,而在伪逆算法方面的研究相对较少。因此,为了进一步完善微波关联成像体系,本文提出了一种新的针对伪逆算法优化的微波关联前视成像方法。本文结合截断奇异值分解(Truncated Singular Value Decomposition,TSVD)处理和吉洪诺夫正则化(Tikhonov)提出了奇异值分解和吉洪诺夫正则化的联合处理方法(TSVD-Tikhonov,TSVDT),通过TSVDT方法对时空随机辐射阵进行处理,然后进行压缩关联成像。同时,本文比较了广义交叉验证(Generalized Cross-Validation,GCV)和L曲线法,并证明了在微波关联成像方法中,利用GCV法选择截断参数的运算耗时更短且更稳定。最后,利用微波暗室实验验证了该方法在低信噪比条件下提高了成像的抗干扰能力,并且仍能保持较快的运算速度。
基金This work was financially supported by the National Natural Science Foundation of China (No. 60076001 and No.50032010), the Natural Science Foundation of Tianjin (No. 043602511) and the Natural Science Foundation of Hebei Province of China (No. E2005000057).
文摘The morphology and microstructure of flow pattern defects （FPDs） in lightly boron-doped Czochralski-grown silicon （Cz-Si） crystals were investigated using optical microscopy and atomic force microscopy. The experimental results showed that the morphology of FPDs was parabola-like with several steps. Single-type and dual-type voids were found on the tip of FPDs and two heaves exist on the left and right sides of the void. All the results have proved that FPDs were void-type defects. These results are very useful to investigate FPDs in Cz-Si wafers further and explain the annihilation of FPDs during high-temperature annealing.
文摘The morphology and microstructure of flow pattern defects (FPDs) in lightly boron-doped Czochralski-grown silicon (Cz-Si) crystals were investigated using optical microscopy and atomic force microscopy. The experimental results showed that the morphology of FPDs was parabola-like with several steps. Single-type and dual-type voids were found on the tip of FPDs and two heaves exist on the left and right sides of the void. All the results have proved that FPDs were void-type defects. These results are very useful to investigate FPDs in Cz-Si wafers further and explain the annihilation of FPDs during high-temperature annealing.
文摘比较分析国产重离子加速器均匀扫描与光子调强放疗(IMRT)治疗计划在颅底恶性肿瘤治疗中的剂量学差异。回顾分析国产重离子设备(Heavy Ion Medical Machine,HIMM)采用均匀扫描方式治疗8例颅底恶性肿瘤的患者治疗计划,包括7例脊索瘤、1例软骨肉瘤。碳离子治疗(Carbon Ion Radiotherapy,CIRT)计划采用兰州科近泰基公司的ciPlan计划系统(V1.0)进行计划设计,处方剂量为计划靶区57.6~60.8 Gy(RBE),16分次,单次3.6~3.8 Gy(RBE)。治疗使用多叶准直器(Multi Leaf Collimator,MLC)调节射束横向适形度,脊形过滤器(Ridge Filter,RF)展宽Bragg峰,补偿器(Bolus)调节射束远端的适形度。使用90°固定水平治疗头,采取床角为0°,及转床90°或180°实现两野交角照射或对穿照射。光子IMRT计划采用美国Varian公司的Eclipse计划系统(V13.5)设计5野固定野调强计划,处方剂量和CIRT计划一致。所有计划在满足危及器官(Organ At Risk,OAR)限量的基础上进行剂量评估,相关剂量学参数包括:靶区覆盖、适形度指数(CI)、均匀性指数(HI)、以及危及器官受量。PTV的V95两者之间比较无统计学差异(P=0.106),Dmean、CI、HI均有统计学差异,IMRT计划优于CIRT计划(P值分别为0.048,0.031和0.024)。OAR受量方面,大部分OAR的CIRT计划比IMRT计划的小,但没有统计学差异,而视交叉、左晶体、右晶体的最大剂量及脑干、右侧视神经的平均剂量有统计学差异(P值分别为0.034,0.000,0.047,0.008和0.030)。OAR与靶区的距离,使用最小hausdorff距离(HD_(min))来描述,当HD_(min)>7.1 mm时,CIRT计划明显优于IMRT计划。均匀扫描方式的碳离子治疗计划在靶区均匀度及适形度方面劣于光子IMRT计划,但在OAR受量方面,均匀扫描碳离子治疗计划优于IMRT计划。剂量学优势能否转化为临床获益有待于通过临床研究进一步验证。
