Electrical and thermal transport properties of icosahedral Al70Pd22.5(Re1−xMnx)7.5 quasicrystals
This work presents measurements of the electrical resistivity (ρ), Seebeck coefficient, and thermal conductivity (κ) of icosahedral Al70Pd22.5(Re1−xMnx)7.5 quasicrystals from 10to300K. A series of quasicrystals was prepared with x=0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, and 1.0 to systematically study the effect of substitution. The electrical resistivity increases as the temperature decreases, suggesting a semiconductinglike behavior in these alloys. The room-temperature values of the Seebeck coefficient vary from −5μV∕K to +65μV∕K, showing a significant dependence on the value of x. However, κ exhibits a rather weak composition dependence in the temperature range investigated. The room-temperature dimensionless thermoelectric figure of merit (ZT) of this system is optimized at x=0.1. With further appropriate heat treatments, high ZT is presumably available at elevated temperatures in the Al70Pd22.5(Re0.9Mn0.1)7.5 sample.
Anomalous Hall effect in the hopping regime of the insulating Al70Pd22.5Re7.5 quasicrystal
Abstract The Hall coefficient RH is seen to rise rapidly with decreasing temperature in the hopping regime of the insulating Al70Pd22.5Re7.5 quasicrystal with a resistivity ratio r= ρ(4.2 K ) ρ(300 K ) equal to 24 and to exhibit the variable-range hopping behavior i.e. R H =R 0 T 0H T 1/4 . The obtained value of T0H is much larger than the Mott’s temperature T0 extracted from the conductivity in the hopping regime. This is contrary to the prediction of Gruenewald et al. [Solid State Commum. 64 (1987) 11] for disordered systems. No existing theories can account for this anomalous effect.
"Flying Triangulation" - a new optical 3D sensor enabling the acquisition of surfaces by freehand motion
In order to obtain complete 3D surface information of an object it is often necessary to acquire many partial 3D views. For this purpose, the sensor has to be moved (e.g. for the acquisition of sculptures or rooms). Further, in many cases a motion of the object relative to the sensor is unintended but inevitable (e.g. for medical applications such as intraoral measurements of teeth). Nearly all existing optical 3D sensors either lack an easy handling or require a standstill during the acquisition of a single partial 3D view, since usually multiple camera shots have to be taken for this purpose. This makes such measurements elaborate or even impossible.