Thermal rectification in bulk materials with asymmetric shape
  We investigate thermal rectification in a bulk material with a pyramid shape to elucidate shape dependence of the thermal rectification, and find that rectifying coefficient R is 1.35 for this shape, which is smaller than R=1.43 for a rectangular shape. This result is fully duplicated by our numerical calculation based on Fourier's law. We also apply this calculation to a given shape, and show a possible way to increase R depending on the shape. 
D. Sawaki, W. Kobayashi, Y. Moritomo, and I. Terasaki
cond-mat.mtrl-sci