介绍一种新型的眼科超声生物显微镜系统．该系统利用长焦距(13mm)换能器和机械扇扫, 实现了宽景扫描,具有4．8 mm×6 mm 和9．6 mm×12 mm 两种扫描窗宽．使用长焦距换能器还使得检查时换能器远离角膜,极大地减小角膜损伤的风...介绍一种新型的眼科超声生物显微镜系统．该系统利用长焦距(13mm)换能器和机械扇扫, 实现了宽景扫描,具有4．8 mm×6 mm 和9．6 mm×12 mm 两种扫描窗宽．使用长焦距换能器还使得检查时换能器远离角膜,极大地减小角膜损伤的风险．用现场可编程门阵列器件(FPGA)实现了硬件动态帧平均从而增强了图像的信噪比．系统中心频率为50MHz,纵向和横向分辨力分别为50 μm 和100μm．一个专门设计的层状靶被用来测试系统的纵向分辨力,其独特的结构保证了高分辨力超声设备的测试精度．展开更多
工程应用中常通过超声相控阵检测技术的脉冲反射法对缺陷进行扇形扫描,并基于反射波幅度的6 d B法测量缺陷尺寸。然而,6 d B测长方法很难对缺陷尺寸进行精确测量。该研究提出利用超声相控扇扫图中的缺陷衍射波图像测量缺陷尺寸以获得较...工程应用中常通过超声相控阵检测技术的脉冲反射法对缺陷进行扇形扫描,并基于反射波幅度的6 d B法测量缺陷尺寸。然而,6 d B测长方法很难对缺陷尺寸进行精确测量。该研究提出利用超声相控扇扫图中的缺陷衍射波图像测量缺陷尺寸以获得较高的测量精度。首先,分析了扇扫图像中缺陷衍射波特征图像及其影响参数以获得清晰的缺陷衍射波扇型扫描图像;其次,提出了基于端部衍射波时差的缺陷尺寸测量方法,并与其他测量方法的测量精度相比较。研究结果显示:基于相控阵扇型扫描的缺陷衍射波测长精度较之反射波幅度法更高,而反射波法更适用于缺陷取向的测量。该研究经过对比分析,为缺陷定量检测提供了一种更为有效的解决方案。展开更多
Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and time...Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and timely forecast about water bursts. Based on the smoke ring effect of transient electromagnetic fields,the principle of transient electro-magnetic method used in detecting buried water-bearing structures in coal mines in advance,is discussed. Small multi-turn loop configurations used in coal mines are proposed and a field procedure of semicircular sector scanning is presented. The application of this method in one coal mine indicates that the technology has many advantages compared with others. The method is inexpensive,highly accurate and efficient. Suggestions are presented for future solutions to some remaining problems.展开更多
文摘介绍一种新型的眼科超声生物显微镜系统．该系统利用长焦距(13mm)换能器和机械扇扫, 实现了宽景扫描,具有4．8 mm×6 mm 和9．6 mm×12 mm 两种扫描窗宽．使用长焦距换能器还使得检查时换能器远离角膜,极大地减小角膜损伤的风险．用现场可编程门阵列器件(FPGA)实现了硬件动态帧平均从而增强了图像的信噪比．系统中心频率为50MHz,纵向和横向分辨力分别为50 μm 和100μm．一个专门设计的层状靶被用来测试系统的纵向分辨力,其独特的结构保证了高分辨力超声设备的测试精度．
文摘工程应用中常通过超声相控阵检测技术的脉冲反射法对缺陷进行扇形扫描,并基于反射波幅度的6 d B法测量缺陷尺寸。然而,6 d B测长方法很难对缺陷尺寸进行精确测量。该研究提出利用超声相控扇扫图中的缺陷衍射波图像测量缺陷尺寸以获得较高的测量精度。首先,分析了扇扫图像中缺陷衍射波特征图像及其影响参数以获得清晰的缺陷衍射波扇型扫描图像;其次,提出了基于端部衍射波时差的缺陷尺寸测量方法,并与其他测量方法的测量精度相比较。研究结果显示:基于相控阵扇型扫描的缺陷衍射波测长精度较之反射波幅度法更高,而反射波法更适用于缺陷取向的测量。该研究经过对比分析,为缺陷定量检测提供了一种更为有效的解决方案。
基金Project 40674074 supported by the National Natural Science Foundation of China20050290501 by the Specialized Research Fund for the Doctoral Programof Higher EducationD200409 by the Scientific Research Fund for Youth of China University of Mining & Technology
文摘Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and timely forecast about water bursts. Based on the smoke ring effect of transient electromagnetic fields,the principle of transient electro-magnetic method used in detecting buried water-bearing structures in coal mines in advance,is discussed. Small multi-turn loop configurations used in coal mines are proposed and a field procedure of semicircular sector scanning is presented. The application of this method in one coal mine indicates that the technology has many advantages compared with others. The method is inexpensive,highly accurate and efficient. Suggestions are presented for future solutions to some remaining problems.
