在虚拟参考站(VRS)技术中,参考站与流动站间的高程差异会引起对流层误差改正数中存在系统偏差影响,使对流层改正精度降低。在常规网络内插改正模型的基础上,借助先验对流层模型,提出了一种能自主修正高程偏差的距离相关对流层网络内插模...在虚拟参考站(VRS)技术中,参考站与流动站间的高程差异会引起对流层误差改正数中存在系统偏差影响,使对流层改正精度降低。在常规网络内插改正模型的基础上,借助先验对流层模型,提出了一种能自主修正高程偏差的距离相关对流层网络内插模型(MHDIM)。基于四川GPS连续运行参考站网络(Sichuan GPS Reference Station Network-SGRSN)实际测试数据的分析表明,对于地形变化较大的中长距离稀疏GPS/VRS参考站网络(如流动站与参考站间高程差异大于500m),应用MHDIM模型可使对流层延迟误差改正精度提高到2到3cm并实现cm级网络RTK定位结果,适用于GPS/VRS参考站网络cm级实时动态定位要求。展开更多
目的磁共振成像（magnetic resonance imaging,MRI）是临床医学影像检查的重要手段,然而受限于检查时间,高客观质量的MRI图像难以获得,有效提高MRI图像分辨率成为研究热点。本文为高效地提高MRI图像分辨率,减少患者检查时间,提出图像域...目的磁共振成像（magnetic resonance imaging,MRI）是临床医学影像检查的重要手段,然而受限于检查时间,高客观质量的MRI图像难以获得,有效提高MRI图像分辨率成为研究热点。本文为高效地提高MRI图像分辨率,减少患者检查时间,提出图像域的基于线性自回归模型自适应客观质量提升算法。方法首先,创建基于距离权重的自回归模型获得插值系数;其次,利用自适应算法解决自回归算法中插值矩阵病态的问题;最后,通过对标准数据库中具有不同噪声水平的图像进行测试。结果本算法重建图像的峰值信噪比（peak signal to noise ratio,PSNR）平均值比经典算法提高1.8～4 d B,结构相似度（structural similarity index measurement,SSIM）指标平均提高0.02～0.06。结论图像域自适应线性自回归MRI图像客观质量提升算法在有效提高MRI图像分辨率的同时,保持了较高的客观质量。展开更多
Due to heavy energy consumption and low technical efficiency, China＇s iron and steel industry is trapped in the dilemma ＂large but not strong＂. This situation not only exerts enormous pressure on energy security bu...Due to heavy energy consumption and low technical efficiency, China＇s iron and steel industry is trapped in the dilemma ＂large but not strong＂. This situation not only exerts enormous pressure on energy security but also on increased carbon emission and environmental pollution. The contribution of this study is to calculate the energy and environment efficiency of China＇s iron and steel industry and to analyze the factors affecting this efficiency. An index of energy and environment efficiency is introduced based on Directional Slacks-based Distance Measure Model. This index is adopted to measure the energy and environment efficiency of China＇s iron and steel industry using 2,382 firm observations during 2001 to 2005. In addition, Hierarchy Linear Model （HLM） is applied to analyze the factors which can influence the efficiency with both firm-level and province-level data. The conclusions are as follows： The energy and environment efficiency of China＇s iron and steel industry did not have a significant change during the research period. A firm＇s age, size, ownership, product category and the economy of its province have significant influence on its energy and environment efficiency.展开更多
文摘在虚拟参考站(VRS)技术中,参考站与流动站间的高程差异会引起对流层误差改正数中存在系统偏差影响,使对流层改正精度降低。在常规网络内插改正模型的基础上,借助先验对流层模型,提出了一种能自主修正高程偏差的距离相关对流层网络内插模型(MHDIM)。基于四川GPS连续运行参考站网络(Sichuan GPS Reference Station Network-SGRSN)实际测试数据的分析表明,对于地形变化较大的中长距离稀疏GPS/VRS参考站网络(如流动站与参考站间高程差异大于500m),应用MHDIM模型可使对流层延迟误差改正精度提高到2到3cm并实现cm级网络RTK定位结果,适用于GPS/VRS参考站网络cm级实时动态定位要求。
文摘目的磁共振成像（magnetic resonance imaging,MRI）是临床医学影像检查的重要手段,然而受限于检查时间,高客观质量的MRI图像难以获得,有效提高MRI图像分辨率成为研究热点。本文为高效地提高MRI图像分辨率,减少患者检查时间,提出图像域的基于线性自回归模型自适应客观质量提升算法。方法首先,创建基于距离权重的自回归模型获得插值系数;其次,利用自适应算法解决自回归算法中插值矩阵病态的问题;最后,通过对标准数据库中具有不同噪声水平的图像进行测试。结果本算法重建图像的峰值信噪比（peak signal to noise ratio,PSNR）平均值比经典算法提高1.8～4 d B,结构相似度（structural similarity index measurement,SSIM）指标平均提高0.02～0.06。结论图像域自适应线性自回归MRI图像客观质量提升算法在有效提高MRI图像分辨率的同时,保持了较高的客观质量。
文摘Due to heavy energy consumption and low technical efficiency, China＇s iron and steel industry is trapped in the dilemma ＂large but not strong＂. This situation not only exerts enormous pressure on energy security but also on increased carbon emission and environmental pollution. The contribution of this study is to calculate the energy and environment efficiency of China＇s iron and steel industry and to analyze the factors affecting this efficiency. An index of energy and environment efficiency is introduced based on Directional Slacks-based Distance Measure Model. This index is adopted to measure the energy and environment efficiency of China＇s iron and steel industry using 2,382 firm observations during 2001 to 2005. In addition, Hierarchy Linear Model （HLM） is applied to analyze the factors which can influence the efficiency with both firm-level and province-level data. The conclusions are as follows： The energy and environment efficiency of China＇s iron and steel industry did not have a significant change during the research period. A firm＇s age, size, ownership, product category and the economy of its province have significant influence on its energy and environment efficiency.
