The characters of practicable magnetic potentiometers have not been rigorously proved. This paper deduced a mathematical description of mutual inductance of the cylindricalmagneticpotentiometerwithfinite turns cross...The characters of practicable magnetic potentiometers have not been rigorously proved. This paper deduced a mathematical description of mutual inductance of the cylindricalmagneticpotentiometerwithfinite turns crosssection and verifies that M is independent of the position with respect to the primary circuit and is unaffected by stray fields of current not linked with them. Using these features, a novel device is designed to measure ACcurrent of the measuring range 0~4 000 A. The experimental result shows the measuring error is less than 1%.The device holds various advantages: such as the fixed number of turns of the primary winding, low cost, small size and weight. This paper pointed out that if the device is used to measure the nonsinusoidal signal, an integrator can increase the accuracy.展开更多
T1加权三维磁化强度预备梯度回波序列(T1WI 3D MP RAGE)属于快速容积扫描技术,具有较高的空间分辨率和时间分辨率,信噪比高,伪影小,对脑内结构(如白质、灰质和脑脊液)的对比度良好,能三维显示人脑内部精细解剖结构,有利于显示小病灶及...T1加权三维磁化强度预备梯度回波序列(T1WI 3D MP RAGE)属于快速容积扫描技术,具有较高的空间分辨率和时间分辨率,信噪比高,伪影小,对脑内结构(如白质、灰质和脑脊液)的对比度良好,能三维显示人脑内部精细解剖结构,有利于显示小病灶及其细节,对神经系统疾病的诊断具有重要价值,同时也是获取正常人脑的三维可视化图谱的重要方法,因此,对临床、科研和教学具有重要意义。展开更多
为了能够对磁共振功放的强分叉非线性进行精确建模,提出一种时间功率混合分段模型。时间功率混合分段模型是针对磁共振功放的激励为辛格脉冲信号时的精确非线性模型。所提出的模型基于辛格脉冲信号的特点进行时域和幅度域分段,从而能够...为了能够对磁共振功放的强分叉非线性进行精确建模,提出一种时间功率混合分段模型。时间功率混合分段模型是针对磁共振功放的激励为辛格脉冲信号时的精确非线性模型。所提出的模型基于辛格脉冲信号的特点进行时域和幅度域分段,从而能够对磁共振功放的分叉非线性进行精确建模。采用辛格脉冲信号作为测试信号,测试信号的占空比为5%,设计输出峰值为18 k W的1.5 T磁共振功放（工作频率63.89 MHz）作为测试功放进行模型的有效性验证。实测磁共振功放和模型的AM/AM和AM/PM曲线的比较结果表明,时间功率混合分段模型能够对磁共振功放的分叉非线性进行精确建模。同时,所提出模型的归一化均方误差（NMSE）比记忆多项式、广义记忆多项式模型和时分多项式模型分别提高10.7 d B,10.3 d B和14.7 d B。展开更多
文摘The characters of practicable magnetic potentiometers have not been rigorously proved. This paper deduced a mathematical description of mutual inductance of the cylindricalmagneticpotentiometerwithfinite turns crosssection and verifies that M is independent of the position with respect to the primary circuit and is unaffected by stray fields of current not linked with them. Using these features, a novel device is designed to measure ACcurrent of the measuring range 0~4 000 A. The experimental result shows the measuring error is less than 1%.The device holds various advantages: such as the fixed number of turns of the primary winding, low cost, small size and weight. This paper pointed out that if the device is used to measure the nonsinusoidal signal, an integrator can increase the accuracy.
文摘T1加权三维磁化强度预备梯度回波序列(T1WI 3D MP RAGE)属于快速容积扫描技术,具有较高的空间分辨率和时间分辨率,信噪比高,伪影小,对脑内结构(如白质、灰质和脑脊液)的对比度良好,能三维显示人脑内部精细解剖结构,有利于显示小病灶及其细节,对神经系统疾病的诊断具有重要价值,同时也是获取正常人脑的三维可视化图谱的重要方法,因此,对临床、科研和教学具有重要意义。
文摘为了能够对磁共振功放的强分叉非线性进行精确建模,提出一种时间功率混合分段模型。时间功率混合分段模型是针对磁共振功放的激励为辛格脉冲信号时的精确非线性模型。所提出的模型基于辛格脉冲信号的特点进行时域和幅度域分段,从而能够对磁共振功放的分叉非线性进行精确建模。采用辛格脉冲信号作为测试信号,测试信号的占空比为5%,设计输出峰值为18 k W的1.5 T磁共振功放（工作频率63.89 MHz）作为测试功放进行模型的有效性验证。实测磁共振功放和模型的AM/AM和AM/PM曲线的比较结果表明,时间功率混合分段模型能够对磁共振功放的分叉非线性进行精确建模。同时,所提出模型的归一化均方误差（NMSE）比记忆多项式、广义记忆多项式模型和时分多项式模型分别提高10.7 d B,10.3 d B和14.7 d B。
