Switchable Quantized Signal between Longitudinal Conductance and Hall Conductance in Dual Quantum Spin Hall Insulator TaIrTe4.

Topological insulating states in 2-dimensional (2D) materials are ideal systems to study different types of quantized response signals due to their in gap metallic states. Very recently, the quantum spin Hall effect was discovered in monolayer TaIrTe4 via the observation of quantized longitudinal conductance that rarely exists in other 2D topological insulators. The nontrivial Z 2 topological charges can exist at both charge neutrality point and the van Hove singularity point with correlation-effect-induced bandgap. On the basis of this model 2D material, we studied the switch of quantized signals between longitudinal conductance and transversal Hall conductance via tuning external magnetic field. In Z 2 topological phase of monolayer TaIrTe4, the zero Chern number can be understood as 1 - 1 = 0 from the double band inversion from spin-up and spin-down channels. After applying a magnetic field perpendicular to the plane, the Zeeman split changes the band order for one branch of the band inversion from spin-up and spin-down channels, along with a sign charge of the Berry phase. Then, the net Chern number of 1 - 1 = 0 is tuned to 1 + 1 = 2 or -1 - 1 = -2 depending on the orientation of the magnetic field. The quantized signal not only provides another effective method for the verification of topological state in monolayer TaIrTe4 but also offers a strategy for the utilization of the new quantum topological states based on switchable quantized responses.

Experimental study on the heat transfer characteristics of waste printed circuit boards pyrolysis.

In order to study the appropriate and advanced technology for recycling waste printed circuit boards (PCBs), a fixed bed pyrolysis device with stirring function has been designed and developed. The effect of rotating speed on the temperature distribution and mass change in the pyrolysis process of FR-4 PCB has been analyzed. The heat transfer and pyrolysis characteristics of different granular layers with and without stirring have been investigated. The results indicate that the stirring can change the main way of heat transfer from conduction to convection in the PCB layers. As the increase of rotating speed, the temperature rising rate of material at the bottom of the pyrolysis furnace gradually decreases, while the heating rate is increasing at the upper layer, and the temperature difference between the upper and bottom layers is gradually reduced. When the rotating speed varies from 0r/min to 18r/min, the weight loss of the material increases from 3.97% to 6.76%, and the overall pyrolysis degree is improved. During the pyrolysis process, the material layer can be divided into three zones along the vertical direction, namely complete pyrolysis zone, partial pyrolysis zone and non-pyrolysis zone. As the rotating speed is 0r/min, the thickness of each zones is 6cm, 6cm and 3cm, respectively. However, when the rotating speed is increased to 18r/min, the non-pyrolysis zone disappears, and the thickness of complete pyrolysis zone and partial pyrolysis zone increase to 9cm and 6cm, respectively.