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本文论述用于激光荧光肺癌诊断图象处理系统滤光片的膜系设计,制备这套滤光片所采取的工艺措施,最后给出研制的结果。 相似文献
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《Indagationes Mathematicae》2017,28(1):38-54
To extend a natural concept of equivalence of sequences to two-sided infinite sequences, the notion of permutation transducer is introduced. Requiring the underlying automaton to be deterministic in two directions, it provides the means to rewrite bi-infinite sequences. The first steps in studying the ensuing hierarchy of equivalence classes of bi-infinite sequences are taken, by describing the classes of ultimately periodic two-sided infinite sequences. It is important to make a distinction between unpointed and pointed sequences, that is, whether or not sequences are considered equivalent up to shifts. While one-sided ultimately periodic sequences form a single equivalence class under ordinary transductions, which is shown to split into two under permutation transductions, in the two-sided case there are three unpointed and seven pointed equivalence classes under permutation transduction. 相似文献
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Acoustic emission (AE) is a widely used technique that has been employed for the integrity testing of a range of vessels and structures for many years. The last decade has seen advances in signal processing, such that the reliability of AE technology is now being recognised by a wider range of industries. Furthermore, the need for quality control at the manufacturing stage, and requirements of in-service testing, is encouraging the issue of traceable measurements to be addressed. Currently, no independent calibration service for acoustic emission transducers is available within Europe. The UKs National Physical Laboratory (NPL) is undertaking work to develop a measurement facility for the traceable calibration of AE sensors. Such calibrations can contribute to greater acceptance of AE techniques in general, by meeting quality system and other traceability requirements. In this paper the key issues surrounding the development of such a facility are reviewed, including the need to establish repeatable AE sources, select suitable test blocks and to understand the limitations imposed by AE sensors themselves. To provide an absolute measurement of the displacement on the surface of a test block, laser interferometry is employed. In this way the output voltage of an AE sensor can be directly related to the displacement detected at the block surface. A possible calibration methodology is discussed and preliminary calibration results are presented for a commercially available AE sensor, showing its response to longitudinal wave modes. 相似文献
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In this paper an alternative approach to estimate the sound field of an elliptically shaped transducer in an infinite baffle is described. The method is based on a singular value decomposition of a propagating matrix which is computed through a division of the vibrating surface into a finite number of small circular piston sources flush-mounted on the elliptical surface. This decomposition is combined with the volume velocity vector on the discretized surface to obtain the sound pressure field. Numerical examples for both on-axis sound pressure and directivity are presented for the uniform elliptical piston transducer and they are in good agreement with the results given by other methods. 相似文献
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为提高用于水下成像的电容式微机械超声换能器的指向性,文中用ANSYS力电耦合分析法设计了工作频率为400 k Hz的收发一体传感器的结构参数并完成了实验验证。同时研究了阵列设计方法,分析了电容式微机械超声换能器阵列各参数对指向性的影响,完成了从微小敏感单元到阵列的设计,实现了阵列指向性的优化设计。该阵列为16阵元的线阵,阵元间距为1.925 mm,阵元宽度为1.82 mm。进行了水下指向性测试,实验表明该线阵的-3 dB主瓣宽度为5?,最大旁瓣级为-13.5 dB,对称性好。该设计是实现较远距离的探测,提高成像分辨率的前提。 相似文献
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Compliance effects on the torsional flow of a viscoelastic fluid 总被引:1,自引:0,他引:1
The effects of transducer compliance on transient stress measurements in torsional flows of a viscoelastic fluid are investigated theoretically. The analysis is based on the torsional flow of an upper-convected Maxwell fluid between a rotating and ‘stationary’ disk, which is allowed to twist and displace axially as a result of the stresses exerted on the disk by the fluid. An approximate analytical solution to the governing equations is obtained using a standard perturbation method. Results of the analysis are used to examine how the fluid velocity is altered by the motion of the stationary disk and to gain insight on how transient stress measurements are affected by transducer compliance. The analysis shows that compliance effects increase with applied shear rate and that the effects of torsional and axial compliance are coupled in measurements of the shear stress and first normal stress difference. 相似文献
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