读者来信摘登

安康学院的方小兵老师来信指出：在《物理实验》2006年第2期上，关于“超声波波型转换与表面波的检测”一文中，出现波形与波型混用．波形和波型，虽然都是用来描述波的性质，但两者没有任何因果关系，波形由波源的振动决定，由示波器来显示，波型则是通过测量声速来判定，它的类型由波源和介质共同决定且在介面上能发生波型转换．     

Microwave-promoted Palladium Catalyzed Suzuki Cross-coupling Reaction in WaterI

A simple, rapid and environmental friendly method for the synthesis of biaryl compounds under microwave irradiation is reported.     

荧光X射线分析装置

本发明的课题在于提供一种进行氮置换的荧光X射线分析装置，容易更换试样室和照射室之间的隔壁膜，在分析时，试样室的空气不流入照射室。第1支架（21）按照其窗（21a）与试样室（3）和照射室（8）之间的壁部（4）的窗（如）重合的方式气密地安装于壁部（4）上，按照覆盖第1支架的窗（21a）的方式设置隔壁膜（9）。第2支架（23）按照其窗（23a）夹持隔壁膜（9），与第1支架的窗（21a）重合的方式设置。     

高能闪光照相对电子束参数的要求

对高能闪光机光源性能用Monte-Carlo方法模拟研究发现：并非击靶电子束半径越小、发射度越低, 闪光机的照相性能就会越好. 研究结果表明：为了使闪光照相图像视面上照射量分布比较均匀, 对束半径与电子束归一发射度有一个联合限制, 对于20MeV闪光机, 如果击靶电子束有效半径是0.12cm, 那么仅当束归一发射度≥550cm.mrad时,在2°内的照射量不均匀性才小于5%.     

Detecting emboli from Doppler ultrasound signals with the wavelet packet analysis method

A Doppler ultrasound analysis method based on wavelet package transform was proposed for embolic detection. The embolic Doppler signal was firstly decomposed using the wavelet packet. Then the sensitive characteristics were calculated from each sub-band signal and used in the emboli classification. This method was applied to analyze 300 cases simulated and 163 cases clinical Doppler signals. The minimum error ratio of embolic detection using this method was 13 percents lower than that using the traditional spectrogram analysis method.It was shown that this method overcame the limit between the time and frequency resolution in the short time Fourier transform, improved the accuracy of embolic detection greatly and extracted more reliable parameters for the clinical diagnosis.     

超声波在有机合成方面的新进展

超声波作为一种新型的技术应用于有机合成,开始时只不过是“试试看”,并没有引起足够的重视。实验结果表明超声波不仅可以改善反应条件,加快反应速度和提高反应产率,还可以使一些难以进行的化学反应得以实现,从而引起了化学家的极大兴趣。近年来超声波在有机合成中的应用研究发展非常迅速,形成了一个     

超声波作用下5, 5-二取代乙内酰脲的合成

本文以氰化钠水溶液、碳酸铵和相应的醛或酮为原料, 于25℃~45℃超声波作用3~4h合成八种5, 5-二取代乙内酰脲, 收率30.1~100%。与传统方法比较, 反应时间缩短, 产品收率提高。     

Decomposition of Transformer Oil Under Ultrasonic Irradiation During Degassing Process

In the degassing process of transformer oil with ultrasonic waves ,decompostition of the oil was observed.Light hydrocarbons,including methane,ethane,ethylene ,aceylene,propane etc,were found to be released continuously from the oil into headspace within a closed vial placed in an ultrasonic field ,The gases came from decomposition of hydrocarbon molecules under cavitation effect.