No abstract

No abstract

Electrical and optical properties of p-type CuFe1-xSnxO2 (x = 0.03, 0.05) delafossite-oxide

It is essential to carry out real-time position and speed monitoring of trains to ensure the safety of railway operation. In this letter, the phase-sensitive optical-time-domain reflectometry ( -OTDR) is demonstrated to overcome the drawbacks of the track circuit, which is widely used and has the risk to be damaged by lightening, for the first time. A long sensing cable, buried nearby to two parallel railways, is used to detect the vibration signals generated by trains with -OTDR and the realtime vibration signals of the trains are extracted/quantified by wavelet denoising. With the edge detection by normalized sliding variance, the operation status of two nearby trains, including their relative position and speed, are obtained over a 10.2-km measurement length in real time. This letter offers a new passive way for safety monitoring of railway operation.Index Terms-Optical fiber sensor, optical time-domain reflectometry (OTDR), railway safety, vibration measurement.

The ZrW 2 O 8 family of materials has been shown to display the unusual property of an isotropic bulk contraction in volume as a function of temperature. We report here on negative thermal expansion properties and oxygen migration at very low temperatures in ZrW 2-x Mo x O 8 phases. ZrWMoO 8 shows significant negative thermal expansion (R l ) -8.7 × 10 -6 K -1 ) and oxygen migration at temperatures as low as 200 K with an activation energy of 0.23 eV. We are unaware of oxygen migration at such low temperatures in other electronic insulators. The low-temperature migration is associated with an order-disorder transition between the R and β forms of the material with ∆V disorder ) -0.24%. A negative volume change for an order-disorder transition is unusual.