Laser annealing of silicon

In recent years laser processing has attracted much attention in view of its potential use in basic solid-state and material science research as well as in new processing technologies. The dominant feature of laser processing being the deposition of large amounts of energy (a few J/cm²) over very short time scales (a few tens of nanoseconds), it leads to melting of surface layers of solid followed by rapid resolidification. In this article, a few basic consequences of such laser-induced phenomena in silicon are reviewed.     

Surface properties of magnesium oxide obtained from basic magnesium carbonate: Influence of preparation conditions of magnesium carbonate

Surface area, total basicity and base strength distribution (weak, strong and intermediate strength basic sites) of magnesium oxide obtained from basic magnesium carbonate (by its decomposition at 873 K) prepared by precipitation using different magnesium slats, precipitating agents and precipitating conditions (viz. concentration of magnesium salt. pH, temperature, mode of mixing and ageing period) have been thoroughly investigated. The total basicity and base strength distribution of the different magnesium oxide samples have been determined by step-wise thermal desorption of carbon dioxide from 323 to 1253 K. The chemical composition of basic magnesium carbonate and the surface properties and carbon dioxide content of magnesium oxide are found to be strongly influenced by the aforementioned preparation conditions of basic magnesium carbonate.     

Selective etching of habit faces of ferroelectric Ca2Sr(C2H5CO2)6 crystals

Crystallographically oriented etch traces produced by selective etchant on (111) and (110) habit faces of dicalcium strontium propionate [Ca₂Sr(C₂H₅CO₂)₆] crystals are attributed to the growth traces nucleated during the superficial growth of crystal. This view is supported by the absence of such etch traces on seized habit faces and from the observations of layer structure on the bottom faces. Mother liquid acting as an etchant produces circular terraced depressions on habit faces. These depressions originate at the sites of isolated impurity centres. Identical features such as circular etch structures bounded by cylindrical outer periphery produced on cooled faces are attributed to isolated domains.     

Melting treatment of waste asbestos using mixture of hydrogen and oxygen produced from water electrolysis

In this study, we melted four types of waste asbestos containing material such as spread asbestos, plasterboard asbestos, slate asbestos and asbestos 99 wt%, in a melting furnace at 1,450–1,550 that uses a mixture of hydrogen and oxygen (Brown’s gas) as a fuel. More volatile components (CaO, K₂O) are enriched in spread asbestos, plasterboard asbestos, and slate asbestos, while less volatile compounds (SiO₂, Fe₂O₃, MgO) remain in asbestos 99%. Through basicity of raw materials, spread asbestos, plasterboard asbestos, and slate asbestos were found to have more alkalinity, and asbestos 99% was found more acidic. SEM and EDX results revealed that all raw materials had various kinds of asbestos fiber. Spread asbestos, plasterboard asbestos, and slate asbestos were considered as tremolite asbestos, whereas asbestos 99% was considered as chrysotile asbestos. It was further confirmed by SEM and XRD studies that all waste materials contained some crystalline structures which transformed into amorphous glassy structure on melting. Also, in case of added glass cullet during the melting of spread asbestos, it transformed the raw material into a perfect vitrified product having more glassy surface and amorphous in nature     

Simultaneous absorption of two gases which react between themselves in a liquid medium: An approximate solution

An approximate solution for the simultaneous absorption and reaction of two gases in a liquid has been presented based on the film theory, assuming a nonlinear (exponential) profile for the concentration of each of the gaseous species in the film. The solution obtained has been compared with the numerical solution of Roper, Hatch and Pigford and found to be in good agreement, thus proving the validity of the approximations.     

Can multiple subchannels improve the delay performance of RTS/CTS-based MAC schemes?

We analyze the delay performance of RTS/CTS-based (Request-To-Send/Clear-To-Send) multi-channel MAC (Medium Access Control) schemes for wireless networks. These schemes usually employ multiple data subchannels for data transmission and one control subchannel to send the RTS/CTS dialogue for channel reservation. Through theoretical analysis and simulations, we show that, in fully-connected networks, such multi-channel MAC schemes suffer longer delays than the corresponding single channel MAC scheme, that puts the RTS/CTS dialogue on the same channel as data packet transmissions. This conclusion holds even when data packets have different priorities and higher priority traffic is sent ahead of lower priority traffic.     

High Power Factor Operation of a Three-Phase Rectifier for an Adjustable-Speed Drive

This paper presents a novel approach to improve the power factor (PF) and reduce the harmonics generated by an adjustable-speed drive (ASD). A high-frequency (HF) current injection technique is used to improve the PF and harmonic performance. The HF current at the same switching frequency (33 kHz) is injected into the input of a front-end rectifier from the output of an HF inverter. The main feature of the circuit is that it does not require any additional active devices for current injection. The inverter driving the induction motor is operated using a sinusoidal pulsewidth-modulation technique. The circuit simulation and experimental prototype results are presented for 67-hp (50 kW) and 3-hp three-phase induction motors, respectively.     

Transient heat flux measurement analysis from coaxial thermocouples at convective based step heat load

The measurement of surface heating rate is an imperative parameter in the force convection ground-based facility for short duration investigation due to the heat transfer rate is changing rapidly. The coaxial thermocouples are suitable to measure the transient heat flux in fast varying heat transfer application because of having fast response time in the range microseconds or less. In this addition, the K-type, E-type, and J-type of coaxial thermocouples are contrived as well as the thermal coefficient resistance (TCR) and sensitivity (S) has been calculated from oil-bath based technique. These handmade coaxial thermocouples are exposed in a forced convection flow facility having three different input step heat loads as well as their transient heat fluxes are estimated using one-dimensional heat conduction modeling for the semi-infinite body. The numerical simulation has also been carried out with the analogous experimental parameters using ANSYS-FLUENT v.15.0 and compared with the outcome of the experimental approach and it is found that the average value of the transient temperatures having 0.3% error and surface heat flux recovered from this temperature is 10%. This study reveals the measuring ability of these handmade coaxial thermocouples at low temperature and low velocity on short duration transient measurements.     

Ultra-Thin High-K Dielectric Profile Based NBTI Compact Model for Nanoscale Bulk MOSFET

Silicon - Negative Bias Temperature Instability (NBTI) is a key reliability and consistency issue for ultra-scaled Silicon IC technology with substantial consequences on both analog and digital...