国内外中短波调幅广播技术20年来的回顾和展望

文章回顾２０年来国内外调幅广播在调制制式，射频放大系统以及包括单边带，浮动载波和调幅多工等多种功能的发展状况。同时对今后调幅广播技术发展方向发表了几点看法。     

介绍一种并机网络

本文介绍ＤＸ－６００型机使用的一种较有新意的并机设备，且与国内现用的并机网络加以比较。     

Compton scattering in a large-aperture positron imaging system

Compton scattering of gamma rays within the image volume has been assessed for a large-aperture positron-emission-tomography imaging system. The Compton scattered attenuation and the Compton scattered background were both modeled and measured for point sources centered in scattering spheres up to 10 cm in diameter. Good agreement was obtained between simulations and measurements. The attenuation problem is independent of the detector system, but its correction is more difficult in a large-aperture system. The scattered coincidence background is large in this system (43% for a 10-cm-diameter scattering sphere), but the background overlap is reduced with 3D imaging.     

Effect of a direct magnetic field on the interfacial microstructure between molten aluminium and solid iron

Many processing techniques, such as hot dip aluminizing, bimetal formation, liquid metal corrosion, cementing, welding and diffusion bonding, are basically dependent on interfacial reactions [1-3]. It is therefore important to investigate the formation and growth of intermetallic layers at the interface. There have been several studies carried out to examine chemical compositions and growth kinetics of intermetallic layers in the Al-Fe system [4-9]. Most authors have come to an agreement that…