NOPR Collection:

Effect of annealing on optical, dielectric and ac conduction properties of Bi₂Se₃ thin films

2016-07-20T04:37:05Z

Title: Effect of annealing on optical, dielectric and ac conduction properties of Bi₂Se₃ thin films Authors: Nataraj, D; Senthil, K; Narayandass, Sa K; Mangalaraj, D Abstract: Bi₂Se₃ thin films, prepared by thermal evaporation onto well-cleaned glass and freshly cleaved KBr substrates, have been annealed for 30 min under a vacuum pressure of 2.7x10^-3 Pa at different temperatures (373-473 K). The variation in optical constants with annealing temperature for these films has been studied in detail. Large changes in transmittance (ΔT= 13% at 633 nm), reflectance (ΔR =8% at 633 nm) and high absorption coefficient (α>10⁴cm^-1) are noticed for these annealed films. Thin film capacitors (Al –Bi₂Se₃-Al) have also been fabricated and studies on capacitance and dielectric constant as a function of temperature and frequency carried out. Loss minimum (tanδ_min) has been observed and found to shift towards high frequency side as the temperature increases. The frequency and temperature dependence of their ac conductivity reveal that the conduction in these films proceeds via electron hopping. Page(s): 164-169

Microstructure and properties of high strength aluminium alloys subjected to rapid solidification processing

2016-07-20T04:37:50Z

Title: Microstructure and properties of high strength aluminium alloys subjected to rapid solidification processing Authors: Rao, V Venkateswara Abstract: High strength aluminium alloys of 7075 type, modified by the addition of 1.0 wt% Fe, Mn, or Ni were rapidly solidified (RS) by centrifugal atomization and substrate quenching. The product was in the form of circular platelets of 3-5 mm diameter and 20-50 μm thick and solidified at a cooling rate of ≥10⁴ °C/s. Microstructural study of the RS alloys revealed some novel features like bimodal morphology and spiral morphology. The RS platelets were consolidated by compacting, vacuum heat treatment and hot extrusion. The consolidated alloys had good surface finish and exhibited moderate improvement in properties. Page(s): 158-163

Shovel-truck optimization study in an opencast min-A queueing approach

2016-07-20T04:37:04Z

Title: Shovel-truck optimization study in an opencast min-A queueing approach Authors: Trivedi, Ratnesh; Rai, P; Nath, R Abstract: The shovel-truck combination is the versatile work horse in small as well as large opencast mining projects. The optimization of shovel-truck combination is imperative in order to increase productivity from this system. The optimization studies aim at eliminating the excess shovel or excess truck capacity in order to minimise the shovel and/or truck idling period. The present case-study is the approach of queueing theory to the optimization of shovel-truck combination in an Indian open cast mine. The formulation of appropriate queueing model has been undertaken and the (M/M/C); (FIFO/K/K) model has been adjudged to be the best model to suit the shovel-truck optimization problem. Relationships between the length of queues, waiting time in queue, utilisation of shover, approximate output from the shovel-truck combination and the costs involved in the system are critically analysed with respect to variation in the number of trucks. The optimum total cost and the optimum number of trucks in the case-study are deduced from the proposed queueing model. Page(s): 153-157

Synthesis and electrical behaviour of poly(chlorotrifluoroethylene)

2016-07-20T04:38:36Z

Title: Synthesis and electrical behaviour of poly(chlorotrifluoroethylene) Authors: H Chohan, M H; Siddiqui, Masood A; Hussain, Rizwan; Munir, Arshad Abstract: The synthesis of poly (chlorotrifluoroethylene) [PCTFE) and its electrical measurements are reported here. A linear increase in current with voltage up to 400 V, and an exponential increase thereafter, is observed at all the studied temperatures. This is an indication of the Schottky or Poole Frankel conduction mechanisms to be operative. The variation of dielectric constant and dielectric loss with frequency at the studied temperatures suggests the contribution of electronic and ionic polarization to this effect. Page(s): 170-172

NOPR Collection:

Effect of annealing on optical, dielectric and ac conduction properties of Bi2Se3 thin films

Microstructure and properties of high strength aluminium alloys subjected to rapid solidification processing

Shovel-truck optimization study in an opencast min-A queueing approach

Synthesis and electrical behaviour of poly(chlorotrifluoroethylene)

Effect of annealing on optical, dielectric and ac conduction properties of Bi₂Se₃ thin films