The influence of fluctuation fields on the force-free field .2. The local expansion

In Paper I (Hu, 1982), we discussed the the influence of fluctuation fields on the force-free field for the case of conventional turbulence and demonstrated the general relationships. In the present paper, by using the approach of local expansion, the equation of average force-free field is obtained as (1+b)×B 0=(#x002B;a)B 0#x002B;a (1)×B 0#x002B;K. The average coefficientsa,a (1),b, andK show the influence of the fluctuation fields in small scale on the configurations of magnetic field in large scale. As the average magnetic field is no longer parallel to the average electric current, the average configurations of force-free fields are more general and complex than the usual ones. From the view point of physics, the energy and momentum of the turbulent structures should have influence on the equilibrium of the average fields. Several examples are discussed, and they show the basic features of the fluctuation fields and the influence of fluctuation fields on the average configurations of magnetic fields. The astrophysical environments are often in the turbulent state, the results of the present paper may be applied to the turbulent plasma where the magnetic field is strong.

氢对锆基块体非晶合金形变和开裂的影响

通过充氢和未充氢缺口拉伸试样和三点弯曲试样在SEM下的原位加载,研究了氢对Zr65Al7.5Ni10Cu17．5块体非晶合金形变和开裂过程的影响．结果表明,无论是否有氢,块体非晶的剪切带发展到临界尺寸,剪切裂纹就沿剪切带形核、扩展,它一旦张开就导致快速的断裂．断口边缘观察到的无特征区是剪切带,而不是剪切裂纹断口;剪切断口形貌和拉伸断口形貌没有本质区别．只有当长时间充氢才能形成氢鼓泡,如鼓泡很小或尚未形成,则氢对剪切带以及裂纹的形核、扩展没有明显影响;如存在较大的氢鼓泡,则当剪切带尚未充分发展时微裂纹就形核,导致低应力脆断．