Experiences in the development of magnesium cell technology at Central Electrochemical Research Institute, Karaikudi

Research activities on the preparation of magnesium metal by molten salt electrolytic process were initiated in CECRI as early as in 1958. CECRI started its experiments on a bench scale level and further developed into pilot plant scale and finally to the scale of semicommercial unit. Various types of electrolytic cells were developed at CECRI which include externally heated cells with different design modifications, modular cells, bipolar/multipolar cells and new modified monopolar ceUs. The primary aim of each development was aimed at high current efficiencies energy efficiencies and space time yields. Various types of raw materials like magnesite, sea bitterns, and byproduct MgCl2 from ZrrTi plants etc. were utilised during the investigations. These studies were carried out with financial grants from Govt. of Tamil Nadu, CSIR, DRDO and Nuclear Fuel Complex. The paper illustrates the design and operational features of different electrolytic cells with consequent gradual decrease in specific energy consumption for magnesium production and increased space time yields with improvement in cell design and operational parameters

Spectroscopy, modeling, and performance of Erbium-Doped Ta₂O₅ waveguide amplifiers

The design, fabrication, spectroscopic characterization, and performance of an Er:Ta2O5 rib waveguide amplifier is described. Rib waveguides with low loss (< 0.65 dB/cm at 1600 nm) were obtained. Their absorption spectrum was measured and McCumber theory was employed to obtain the emission spectrum, leading to the absorption and emission cross sections. Numerical modeling for gain optimization in Er:Ta2O5 waveguide amplifiers is presented, employing the experimentally determined parameters. Finally, net optical gain of 2.1 dB/cm at 1531.5 nm is demonstrated in a 2.3 cm long Er:Ta2O5 rib waveguide when pumped with 977 nm laser diode, and compared with simulations to deduce the extent of upconversion

High index contrast Er:Ta₂O₅ waveguide amplifier on oxidised silicon

We report a high index contrast erbium doped tantalum pentoxide waveguide amplifier. 2.3 cm long waveguides with erbium concentration of 2.7 × 1020 cm-3 were fabricated by magnetron sputtering of Er-doped tantalum pentoxide on oxidised silicon substrates and Ar-ion milling with photolithographically defined mask. A net on-chip optical gain of ~2.25 dB/cm at 1531.5 nm was achieved with 20mW of pump power at 977 nm launched into the waveguide. The pump threshold for transparency was 4.5mW.<br/

Anticipating Future Capital: Regional Caste Contestations, Speculation and Silent Dispossession in Andhra Pradesh

In 2014, the state of Andhra Pradesh was bifurcated by the Indian government, leaving the truncated state without a capital city. A period of political uncertainty before bifurcation and the announcement of the new capital city created possibilities for land speculation and for the acceleration of the commodification of real estate in different parts of the state. Concentrating on Guntur-Vijayawada in the Coastal Andhra region and Donakonda town close to the Rayalaseema region, this article explores how speculative investments based on political calculations by members of regional elite castes translated into the emergence of competing regional investment zones as possible future choices of the capital city. Through an extended and largely ethnographic study, this article shows how caste politics and regional processes of land speculation led to land transfers without violent struggles between different groups. Rather, the cultural politics of regional differentiation and the economy of anticipation allowed a pragmatic convergence of interests to emerge, where acquisition of agricultural land was followed by silent dispossession