桑叶提取物对DPPH自由基的清除能力研究

以超声波法对桑叶有效成分进行提取,得到Ⅰ、Ⅱ、Ⅲ共3个提取物,然后采用二苯代苦味酰肼自由基（DPPH·）法对提取物进行了自由基清除试验。结果表明：3个桑叶提取物对DPPH自由基均具有较好的自由基清除能力,这说明了桑叶可作为自由基清除物质资源开发利用。     

A new coding scheme in coded ultrasound using staggering repetition interval

The increase of frame rate, though with the potential in a coded ultrasound system, is generally concomitant with the simultaneous transmission of a number of apertures, and in consequence leads to increased cross-talks between different apertures. In view of this, a new coding scheme using staggering repetition interval was proposed. The transmitting signals were constructed by repeating the two （or more） modulated codes using staggering repetition interval, and then allocated to and transmitted simultaneously among different apertures. The decoding process was based on the subsection-matched filter under the assistance of different matched filters for different apertures. At last the outputs of subsection-matched filtering were added together. Staggering changed the positions of cross-correlation （CC） peaks from coinciding, which resulted in an effective reduction of CC. Our theoretical analysis and simulations showed that, the coding scheme can be used to reduce cross-talk, and a good cross-talk reduction will be achieved if the staggering delay is kept in an appropriate range.     

病毒性肝炎213例胆囊声像图变化的临床分析

本文对病毒性肝炎２１３例胆囊声像图变化进行分析，初步探讨了病毒性肝炎胆囊改变发生机制。     

便携式超声波测距仪设计

以AT89S52单片机为核心,本文设计了低成本、便携式、可数字显示的测距仪,利用超声波测距原理,实现距离数据的测量。该测距仪适应一般的工业测量,具有灵敏度高、测量准确的特点。     

超声提取-高效液相色谱测定滁菊中的木犀草素

为建立超声波提取-高效液相色谱法测定滁菊中木犀草素的方法。采用purospher star RP-18(250 mm×4.6 mm,5μm)色谱柱;以0.1%磷酸溶液(pH=2.6)-甲醇(40:60)为流动相;流速为1 mL/min;检测波长为327 nm。结果表明,木犀草素在10 min内实现快速基线分离,且在0.002~0.05 mg/mL范围内线性关系良好,r=0.9999,平均回收率为99.22%,RSD为1.7%(n=3)。该方法简便快速,可作为滁菊原药材的质量标准。     

基于相关法的超声波流量测量的发射设计

针对传统相关法的超声波流量测量过程中计算结果不能准确的反映信号时间差的缺点,采用改进的相关法,使用FPGA(现场可编程门阵列)发出占空比调制的驱动脉冲,使超声波探头在需要的一定周期内发射出幅度调制的波形,克服等振幅周期信号在做相关后时间差判断不准的情况。通过实验可以证明,控制激励探头的脉冲信号的占空比,可以改变发射波形的幅值特性,从而得到适合相关运算的波形,达到预期的测量效果。     

Historical plasters on light thin vaults: State of conservation assessment by a Hybrid ultrasonic method

Historical plasters on light thin vaults, usually made by mats of reeds nailed to an upper wooden framework, were used in several historical and monumental Italian buildings and churches built between the 16th and the 19th century and almost all of the historical Italian theatres built between the 18th and the 19th century to cover the theatre-hall and to improve its acoustic properties. The non-destructive inspection of these structures is very important, but traditional inspection techniques are usually limited in resolution, which may be a problem for detection of defects at a very early stage. The paper presents the development and application of a high-resolution inspection technique based on a hybrid ultrasonic method, where a contact emitter probe and a non-contact air-coupled receiver probe are used. Results show the effectiveness of the method on laboratory samples and propose an inspection procedure for in-field application.     

Modelling of ultrasonic motor with dead-zone based on Hammerstein model structure

The ultrasonic motor （USM） possesses heavy nonlinearities which vary with driving conditions and load-dependent characteristics such as the dead-zone. In this paper, an identification method for the rotary travelling-wave type ultrasonic motor （RTWUSM） with dead-zone is proposed based on a modified Hammerstein model structure. The driving voltage contributing effect on the nonlinearities of the RTWUSM was transformed to the change of dynamic parameters against the driving voltage. The dead-zone of the RTWUSM is identified based upon the above transformation. Experiment results showed good agreement between the output of the proposed model and actual measured output.     

小麦中提取尿囊素工艺的研究

采用超声波法从小麦中提取尿囊素,通过正交实验研究了最佳提取条件为:提取试剂60%的乙醇,料液比1∶15,超声温度40℃,超声时间20 min,提取次数为2次.采用高效液相色谱法对小麦中尿囊素含量进行测定.     

改进型小波阈值超声图像去噪方法

在D.L.Donoho提出的小波软、硬阈值去噪方法的基础上,提出了一种新的改进型半-软阈值方法,克服了经典小波阈值方法的缺点,能有效地改善图像的质量.通过Matlab对斑点超声图像进行去噪仿真,结果表明该方法优于软、硬阈值法,具有一定的应用价值.