分析了机械谐振频率对经纬仪系统性能的影响,在传统双 T 网络的基础上,提出了一种改进的数字滤波器。该滤波器可以通过适当的参数修改达到控制机械谐振点陷波幅值的效果。实验表明,本文提出的改进的数字滤波器滤波效果好于传统的双 T ...分析了机械谐振频率对经纬仪系统性能的影响,在传统双 T 网络的基础上,提出了一种改进的数字滤波器。该滤波器可以通过适当的参数修改达到控制机械谐振点陷波幅值的效果。实验表明,本文提出的改进的数字滤波器滤波效果好于传统的双 T 网络滤波器。展开更多
为解决HID灯的老化及灯的伏安特性变化引起的功率漂移问题,基于Buck降压变换器的平均电流控制模式,设计并制作了一款具有恒功率控制能力的数字控制电子镇流器驱动电路,包含两个控制环路:内电流环路用于维持稳定驱动,外功率环路用于维持...为解决HID灯的老化及灯的伏安特性变化引起的功率漂移问题,基于Buck降压变换器的平均电流控制模式,设计并制作了一款具有恒功率控制能力的数字控制电子镇流器驱动电路,包含两个控制环路:内电流环路用于维持稳定驱动,外功率环路用于维持灯在其使用期间的功率恒定,并根据Buck降压变换器DCM模式下的小信号模型,以PI算法作为数字补偿器,完成补偿环路设计,保证电路输出稳定性。为抑制声共振,该电路结构采用三级式结构的电子镇流器,以低频方波驱动。设计和测试结果表明,该电子镇流器驱动电路可实现450 W的恒功率控制,误差值小于3%。该电子镇流器驱动电路结构简单,可靠性高,可适用于450 W HID灯驱动。展开更多
Objective: The aim of the study was to investigate the efficacy of digital radiography(DR), computed tomography(CT) and magnetic resonance imaging(MRI) in bone tumors. Methods: Fifty-five patients with histologically ...Objective: The aim of the study was to investigate the efficacy of digital radiography(DR), computed tomography(CT) and magnetic resonance imaging(MRI) in bone tumors. Methods: Fifty-five patients with histologically confirmed bone tumors underwent imaging examinations. Fifty-five patients were performed DR, 21 CT and 20 MRI. Results: DR of 51 patients clearly revealed bone changes. DR of 40 patients well showed marginal. Twenty tumors appeared periosteal reaction on DR and 19 calcification on DR. CT scan of 21 patients clearly depicted bone changes, marginal and calcification and CT scan of 8 revealed periosteal reaction. MRI scan of 20 patients all showed marginal and soft-tissue mass and bone marrow edema was prominent in 8 patients. Conclusion: DR is the first imaging approach for born tumors. CT well reveal the extent and minute structure of the bone tumors, the extent, soft-tissue mass and bone marrow edema are more dramatically demonstrated on MRI imaging. DR integrates with CT and MRI, is helpful in diagnosis of bone tumors.展开更多
文摘为解决HID灯的老化及灯的伏安特性变化引起的功率漂移问题,基于Buck降压变换器的平均电流控制模式,设计并制作了一款具有恒功率控制能力的数字控制电子镇流器驱动电路,包含两个控制环路:内电流环路用于维持稳定驱动,外功率环路用于维持灯在其使用期间的功率恒定,并根据Buck降压变换器DCM模式下的小信号模型,以PI算法作为数字补偿器,完成补偿环路设计,保证电路输出稳定性。为抑制声共振,该电路结构采用三级式结构的电子镇流器,以低频方波驱动。设计和测试结果表明,该电子镇流器驱动电路可实现450 W的恒功率控制,误差值小于3%。该电子镇流器驱动电路结构简单,可靠性高,可适用于450 W HID灯驱动。
文摘Objective: The aim of the study was to investigate the efficacy of digital radiography(DR), computed tomography(CT) and magnetic resonance imaging(MRI) in bone tumors. Methods: Fifty-five patients with histologically confirmed bone tumors underwent imaging examinations. Fifty-five patients were performed DR, 21 CT and 20 MRI. Results: DR of 51 patients clearly revealed bone changes. DR of 40 patients well showed marginal. Twenty tumors appeared periosteal reaction on DR and 19 calcification on DR. CT scan of 21 patients clearly depicted bone changes, marginal and calcification and CT scan of 8 revealed periosteal reaction. MRI scan of 20 patients all showed marginal and soft-tissue mass and bone marrow edema was prominent in 8 patients. Conclusion: DR is the first imaging approach for born tumors. CT well reveal the extent and minute structure of the bone tumors, the extent, soft-tissue mass and bone marrow edema are more dramatically demonstrated on MRI imaging. DR integrates with CT and MRI, is helpful in diagnosis of bone tumors.
