中文摘要：

发展了二维梯度折射率介质热辐射传递的数值求解方法，研究了非线性折射率介质的表观方向发射率．研究结果表明，采用本文方法计算二维梯度折射率介质的表观方向发射率，最大相对误差小于1．6％．通过研究发现，二维非线性梯度折射率介质的热辐射能够呈现非常明显的定向辐射的特征，我们定义这种现象为类相干发射．

英文摘要：

The radiative transfer solution method of a two-dimensional graded index semitransparent medium was developed. The apparent directional emissivity of the medium with nonlinear refractive index distribution was also analyzed. The results show that the numerical technique of this method has a high numerical precision by which the maximum relative error of apparent directional emissivity is less than 1.6%. Results also show that apparent emission of the medium has an obvious directional pattern. This phenomenon is named as a quasi-coherent thermal emission.