The size of reference radiation field of low-energy x-ray was measured by film in different position from the tube spot,the diameter of the radiation field and its were obtained in reference plane(1 000 mm from the radiation source) and were compared with the results through two-dimensional ion chamber.The results show that the diameter of the radiation field is 100 mm within 1.5%(1 000 mm from the radiation source).The diamerers of theradiation field are 130 mm and 145 mm within 5% and 50%.These results well meet the requirements of the value repetition of the low-energy X-ray air kerma value standard device,international intercomparison and transfer of quantity values.

X射线辐射场均匀野的测量能够实现x射线主射束、光阑、快门、过滤片、定位装置同轴的调整，在参考平面得到一个均匀场．从而保证基准电离室和传递电离室定位于辐射野中心。根据辐射野不同均匀度下的尺寸．可以对基准或者传递电离室的定位准确度提出要求．并给出不确定度。因此它是建立和研究X射线国家基（标）准的重要基础。

结合DSP快速处理能力和具有合适控制的事件管理器的特点,提出一种基于TMS320LF2407的三电平PWM开关功率放大器.实验表明:基于DSP的三电平PWM开关功放具有效率高、电流纹波小,动态响应快,频带宽等优点.达到了很好的性能指标,满足了磁悬浮轴承的需要,为实现磁悬浮轴承数字系统实际应用奠定了基础.

It intruduces the output one-port flyback type switch basing on the TOP261YN chip.It analyzes this switch's working principles and design scheme.By using the flyback circuit and combining the peripheral feedback and pulse width modulation circuitthe,the power supply achieves high output as well as multiplexing.Experimental results show that the switch power supply has good performance.

高温高压染色机温度系统是一种复杂的控制对象,很难获得精确的数学模型.因此本文在分析染色机系统结构和染色机温度对象特性的基础上,根据染色过程的温度偏差和实际温度,设计了一种参数可变的PID控制器.本文基于Simulink对这种染色过程中的温度智能控制进行了系统仿真研究.

The brushless DC motor(BLDCM) has both simple structure as AC motor and high operating efficiency as normal brush DC motor.It,as well,has an excellent high-speed performance,and other characteristics.BLDCM is also widely used in precise position control of the servo system.Especially,the code plate of photoelectric encoder plays a key role in BLDCM high-precision servo-positioning.However,the code plate is often damaged because of improper installation in product line.Certainly it increases the failure rate of motor in the assembly line.This article describes a detection system based on FPGA,and this system had been proved that it could quickly detect the damage of BLDCM photoelectric encoder code disk.