Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology a...Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology as renal cancer were collected and were randomly divided into experimental group and control group with 50 cases respectively. The two groups of patients were treated with iodine concentration of 300 mg/ml and 350 mg/ml non-ionic contrast agent, with a dosage of 1.5 ml/kg and an injection rate of 4 ml/s. The contrast agent intelligently tracking method was adopted bolus. The control group used the conventional CTA scanning, with a reference tube voltage/tube current of 100 kv/ref150 mas. The experimental group adopted the double energy scanning, with ball tube A and ball tube B. The reference tube voltage/tube current was 100 kv/ref250 mas and sn150 kv/ref125 mas respectively. The images of the experimental group were non-linear fused to obtain the Mono+ 55 kev single-energy images. The CT value, SNR contrast ratio of the abdominal aorta, renal artery and tumor tissue of the experimental group images and the 100 KV images and the Mono+ 55 kev images of the control group were compared. The objective evaluation and subjective evaluation of the image quality of the three groups of images was performed. Results: The results showed that the 100 kV images of the experimental group were statistically different from those of the control group (P05) in CT value, SNR and CNR (P 0.05). And there was no statistically significant difference between the non-linear fusion single-energy Mono+ 55 kev images and the control group images in CT value, SNR and CNR (P > 0.05). The subjective evaluation of image quality showed that there was no significant difference between Mono+ 55 kev images and control group images, and the quality of Mono+ 55 kev images was higher than that of experimental group 100 kV images. Conclusion: The dual-energy CT non-linear fusion technique can improve the quality of CTA image in patients with renal cancer, and it is possible to obtain high quality CTA images with low iodine concentration contrast agent.展开更多
当前高压电容式电压互感器(capacitor voltage transformer,CVT)缺少有效的在线监测数据,辨识不足。利用在线监测多数据源存在线性相关的数据特性,提出了基于分析数据相关系数进行有效数据辨识的方法。针对目前高压CVT故障诊断普遍存在...当前高压电容式电压互感器(capacitor voltage transformer,CVT)缺少有效的在线监测数据,辨识不足。利用在线监测多数据源存在线性相关的数据特性,提出了基于分析数据相关系数进行有效数据辨识的方法。针对目前高压CVT故障诊断普遍存在信息单一、精度不高、局部放电在线监测装置故障信号检测受干扰因素影响较大、准确性差等问题,提出了基于多维信息融合的故障诊断方法。首先,利用因子分析对CVT的诊断指标进行数据层信息融合,提取各故障类型对应的公共因子方差贡献值,作为反映故障类型差异的特征值;然后,利用模糊理论进行特征层信息融合,将公共因子方差贡献值作为隶属函数的输入参数,识别CVT的故障类型,准确诊断高压CVT故障。案例验证了所提方法的有效性,为CVT故障诊断提供了理论参考和实践经验。展开更多
针对电力机车牵引变流器中故障率最高的单相脉宽调制(pulse width modulation,PWM)整流器,提出一种流形学习算法融合多域特征的故障诊断方法。根据整流器在不同工作状态下的时域、频域和时频域特征构建多域特征向量;采用Hessian局部线...针对电力机车牵引变流器中故障率最高的单相脉宽调制(pulse width modulation,PWM)整流器,提出一种流形学习算法融合多域特征的故障诊断方法。根据整流器在不同工作状态下的时域、频域和时频域特征构建多域特征向量;采用Hessian局部线性嵌入(Hessian local linear embedding,HLLE)算法融合多域特征,根据故障样本数和聚类结果,解决高维数据中固有维数和最近邻数选取困难的问题,得到用于描述故障特征的最优低维特征向量,减少特征之间的冲突和冗余;采用支持向量机进行模式识别,实现对整流器的故障诊断。结果表明:对不同的输出电压,不同的训练和测试比,15种故障模式均具有较高的诊断率。与其他方法相比,本文方法具有较好的融合效果和较强的鲁棒性。展开更多
时空融合技术通过输出高时空分辨率的遥感图像,为持续监测研究地球系统动态变化提供了经济高效的解决方案。尽管该技术已发展出STARFM、ESTARFM等多种时空融合方法,但对于复杂地表区域仍存在空间细节和纹理难以准确模拟和预测的问题。...时空融合技术通过输出高时空分辨率的遥感图像,为持续监测研究地球系统动态变化提供了经济高效的解决方案。尽管该技术已发展出STARFM、ESTARFM等多种时空融合方法,但对于复杂地表区域仍存在空间细节和纹理难以准确模拟和预测的问题。文章提出一种适用于复杂地表的时空数据融合方法(Adapted Complex Land Spatiotemporal Data Fusion,ACLSDF),该方法通过线性回归和引导滤波分别计算时间和空间变化量,再通过变化指数为发生地表覆盖类型变化的像元赋予不同的时间空间权重,最后结合时间空间变化和变化指数计算最终预测值。为了评估ACLSDF方法在异质性区域的性能,文章进行了ACLSDF融合结果与地面实测光谱数据的对比分析试验,结果表明:ACLSDF方法在复杂地表区域融合结果相关系数高于0.93,均方根误差低于0.07,结构相似性均在0.98以上,与地面实测光谱数据的均方根误差均小于0.04,仅次于“高分一号”宽幅相机(GF-1 WFV)原始影像,证实了该方法的可行性和有效性。展开更多
Loss-cone instabilities are studied for linear fusion devices. The gyro-kinetic equation for such a configuration is rigorously constructed in terms of action-angle variables by making use of canonical transformation....Loss-cone instabilities are studied for linear fusion devices. The gyro-kinetic equation for such a configuration is rigorously constructed in terms of action-angle variables by making use of canonical transformation. The dispersion relation, including for the first time, finite bounce frequency is obtained and numerically solved. The loss-cone modes are found near ion-cyclotron frequency. The growth rates are greatly reduced and approaching zero with increasing beta value. The results suggest that loss-cone instabilities are unlikely to be threatening to linear fusion devices since a new longitudinal invariant is found and gives a constraint which helps confinement.展开更多
文摘Objective: To explore the significance of dual-energy CT non-linear fusion technique in improving the quality of CTA image of renal cancer. Methods: The CTA images of 100 patients who had been confirmed by pathology as renal cancer were collected and were randomly divided into experimental group and control group with 50 cases respectively. The two groups of patients were treated with iodine concentration of 300 mg/ml and 350 mg/ml non-ionic contrast agent, with a dosage of 1.5 ml/kg and an injection rate of 4 ml/s. The contrast agent intelligently tracking method was adopted bolus. The control group used the conventional CTA scanning, with a reference tube voltage/tube current of 100 kv/ref150 mas. The experimental group adopted the double energy scanning, with ball tube A and ball tube B. The reference tube voltage/tube current was 100 kv/ref250 mas and sn150 kv/ref125 mas respectively. The images of the experimental group were non-linear fused to obtain the Mono+ 55 kev single-energy images. The CT value, SNR contrast ratio of the abdominal aorta, renal artery and tumor tissue of the experimental group images and the 100 KV images and the Mono+ 55 kev images of the control group were compared. The objective evaluation and subjective evaluation of the image quality of the three groups of images was performed. Results: The results showed that the 100 kV images of the experimental group were statistically different from those of the control group (P05) in CT value, SNR and CNR (P 0.05). And there was no statistically significant difference between the non-linear fusion single-energy Mono+ 55 kev images and the control group images in CT value, SNR and CNR (P > 0.05). The subjective evaluation of image quality showed that there was no significant difference between Mono+ 55 kev images and control group images, and the quality of Mono+ 55 kev images was higher than that of experimental group 100 kV images. Conclusion: The dual-energy CT non-linear fusion technique can improve the quality of CTA image in patients with renal cancer, and it is possible to obtain high quality CTA images with low iodine concentration contrast agent.
文摘当前高压电容式电压互感器(capacitor voltage transformer,CVT)缺少有效的在线监测数据,辨识不足。利用在线监测多数据源存在线性相关的数据特性,提出了基于分析数据相关系数进行有效数据辨识的方法。针对目前高压CVT故障诊断普遍存在信息单一、精度不高、局部放电在线监测装置故障信号检测受干扰因素影响较大、准确性差等问题,提出了基于多维信息融合的故障诊断方法。首先,利用因子分析对CVT的诊断指标进行数据层信息融合,提取各故障类型对应的公共因子方差贡献值,作为反映故障类型差异的特征值;然后,利用模糊理论进行特征层信息融合,将公共因子方差贡献值作为隶属函数的输入参数,识别CVT的故障类型,准确诊断高压CVT故障。案例验证了所提方法的有效性,为CVT故障诊断提供了理论参考和实践经验。
文摘针对电力机车牵引变流器中故障率最高的单相脉宽调制(pulse width modulation,PWM)整流器,提出一种流形学习算法融合多域特征的故障诊断方法。根据整流器在不同工作状态下的时域、频域和时频域特征构建多域特征向量;采用Hessian局部线性嵌入(Hessian local linear embedding,HLLE)算法融合多域特征,根据故障样本数和聚类结果,解决高维数据中固有维数和最近邻数选取困难的问题,得到用于描述故障特征的最优低维特征向量,减少特征之间的冲突和冗余;采用支持向量机进行模式识别,实现对整流器的故障诊断。结果表明:对不同的输出电压,不同的训练和测试比,15种故障模式均具有较高的诊断率。与其他方法相比,本文方法具有较好的融合效果和较强的鲁棒性。
文摘时空融合技术通过输出高时空分辨率的遥感图像,为持续监测研究地球系统动态变化提供了经济高效的解决方案。尽管该技术已发展出STARFM、ESTARFM等多种时空融合方法,但对于复杂地表区域仍存在空间细节和纹理难以准确模拟和预测的问题。文章提出一种适用于复杂地表的时空数据融合方法(Adapted Complex Land Spatiotemporal Data Fusion,ACLSDF),该方法通过线性回归和引导滤波分别计算时间和空间变化量,再通过变化指数为发生地表覆盖类型变化的像元赋予不同的时间空间权重,最后结合时间空间变化和变化指数计算最终预测值。为了评估ACLSDF方法在异质性区域的性能,文章进行了ACLSDF融合结果与地面实测光谱数据的对比分析试验,结果表明:ACLSDF方法在复杂地表区域融合结果相关系数高于0.93,均方根误差低于0.07,结构相似性均在0.98以上,与地面实测光谱数据的均方根误差均小于0.04,仅次于“高分一号”宽幅相机(GF-1 WFV)原始影像,证实了该方法的可行性和有效性。
基金supported by the Natural Science Foundation for Young Scientists of China (No. 11605143)National Natural Science Foundation of China (Nos. 11575055,11261140327,11005035,11205053)+3 种基金the project,Plasma Confinement in the Advanced Magnetic Mirror (WX-2015-01-01)the Open Research Subject of the Key Laboratory of Advanced Computation in Xihua University (Nos. szjj2017-011 and szjj2017-012)the Young Scholarship Plan of Xihua University (No. 0220170201)the National Key Research and Development Program of China (No. 2017YFE0300405)
文摘Loss-cone instabilities are studied for linear fusion devices. The gyro-kinetic equation for such a configuration is rigorously constructed in terms of action-angle variables by making use of canonical transformation. The dispersion relation, including for the first time, finite bounce frequency is obtained and numerically solved. The loss-cone modes are found near ion-cyclotron frequency. The growth rates are greatly reduced and approaching zero with increasing beta value. The results suggest that loss-cone instabilities are unlikely to be threatening to linear fusion devices since a new longitudinal invariant is found and gives a constraint which helps confinement.
