A selective review of the finite element-ABC and the finite element-boundary integral methods for electromagnetic scattering

Annals of Telecommunications - This paper reviews two hybrid (frequency domain) finite element methods for electromagnetic scattering applications. Specifically, the progress over the last five...     

Race of new inorganic materials towards an ultra neolithic age

Three generally accepted generic groups of competitive engineering materials—metals, inorganic ceramics, as well as plastics and polymers belonging to the organic family—have been comparatively reviewed in the context of raw materials availability, energy requirements in production, engineering properties, combustibility and environmental friendliness. The intrinsic advantages of inorganic materials have been discussed. The shortcomings of engineering properties of inorganic materials and the new technologies of making chemically bonded ceramics or biomimic compounds from inorganic materials with improved toughness have been dealt with. The expanding application horizons of inorganic materials have been illustrated with the help of several novel products.     

Heat transfer between a fluidized bed and an immersed vertical U-tube

The design details of a 0.254 m stainless steel cylindrical fluidized bed pilot plant facility, whose fabrication, installation and testing have been recently completed, are described. It primarily consists of a fluidized-bed reactor, fluidizing air-supply system, solids feeder, off-gas cleaning and exhaust system, and cooling water-supply system for heat-transfer tubes provided in the bed and in the freeboard sections. The plant is operated at ambient pressure in the temperature range 300–600 K, both in the batch and continuous modes for solids feed. Bed-pressure drop measurements as a function of fluidizing velocity for two different bed heights reveal that the quality of fluidization is good. Similar experiments have been conducted with the continuous solids feed. The heat-transfer coefficient between the bed and an immersed stainless steel U-tube is measured as a function of fluidizing air velocity at five different temperatures. The effects on bed-to-tube heat-transfer rate of solids feed rate, bed height, air-flow rate, and bed temperature are examined. All of these observed variations are interpreted in terms of the solids mixing and bubble mechanics in the bed.     

The join calcium monoaluminate-calcium fluoride

The system CaO-Al₂O₃-CaF₂ is important in cement and slag technology and in metallurgy. A section of this system, the pseudo-binary join CaO·Al₂O₃-CaF₂, has been studied and the phase diagram established. This join is of particular interest since CaO·Al₂O₃ is one of the main constituents of high alumina cement.Quenching in sealed platinum capsules followed by microscopic and X-ray examination was the principal method used. The only compound on the join is 3CaO·3Al₂O₃·CaF₂ which melts congruently at 1507±1.5° C and forms one eutectic with CaO·Al₂O₃ at 11% CaF₂ and 1498±5° C and another with CaF₂ at 97.5% CaF₂ and 1405±10° C. There is a wide zone of liquid immiscibility. The m.p. of CaF₂ was determined to be 1422±1° C.Attempts to use high temperature microscopy to study this system are described.     

On the nature and structure of ‘niobic acid’ and its pyrolytic products: 1H NMR,I.R., conductivity and Ion exchange studies

Niobic acid of composition H₈Nb₆O₁₉ has been prepared by thorough drying of the hydrated oxide at 150°C. The mass was heated in stages up to 1200°C and the intermediate products were subjected to ¹H NMR measurements for determining their proton content. Infra red spectra indicate the presence of protons which are highly delocalised among different oxygen sites. The electrical conductivity of niobic acid has been interpreted as due to proton-hopping. The ion exchange capacity of the material has also been studied. The data have been used to formulate the structure of niobic acid and to obtain the correct procedure for the gravimetric determination of niobium as oxide.     

The phase equilibrium diagram of the system CaO-Al2O3-CaF2

The phase equilibria of the system CaO-Al₂O₃-CaF₂ have been studied by quenching in sealed platinum capsules followed by microscopic and X-ray examination of quenched products. The established phase diagram contains five ternary eutectics, two ternary peritectics and two invariant points of four-phase monotectic transformations. The system Al₂O₃-CaF₂ has been established to be the stable diagonal of the reversible reciprocal system Al₂O₃ + 3CaF₂ = 3CaO + 2AlF₃. In the high-fluoride region a wide zone of liquid immiscibility has been found. The system also shows such rarely noticed but theoretically possible phenomena as the transformation of peritecticals into eutecticals and occurrence of three different primary fields under single continuous zone of liquid immiscibility.     

Inhibition of pyrite oxidation by a phospholipid in the presence of silicate

The influence of sodium silicate on the ability of a diacetylene-containing phospholipid (23:2 diyne PC) to inhibit the oxidation of pyrite at pH 2 and pH 6 was investigated. The phospholipid used has previously been reported to show up to 80% suppression of pyrite oxidation and to show excellent stability down to at least pH 2. Pyrite was leached with a solution containing Fe3+ but no coating agent and three different solutions or treatments: a lipid treatment, a silicate treatment, and a lipid + silicate treatment. Pyrite oxidation was based on iron (Fe3+, Fe2+) leached out of a continuous-flow porous-bed reactor system. The results show that at pH 6 the silicate and lipid both bind strongly to the pyrite surfaces, providing a barrier that inhibits the production and subsequent release of oxidation products. The lipid is superior to the silicate in suppressing pyrite oxidation at both pH 2 and pH 6. Also, the presence of silicates decreased the ability for the lipid to suppress pyrite oxidation, both at pH 2 and pH 6. The reaction mechanism for pyrite oxidation at pH 2 is first order for pyrite leached by solutions containing only ferric, ferric together with silicate, and ferric combined with silicate and lipid. The only treatment that effectively prevented pyrite oxidation at pH 2 was the lipid treatment. The Fe speciation results are supported by both SEM images and EDS calculations.     

Flow of materials in rotary kilns used for sponge iron manufacture: Part II. Effect of kiln geometry

The present work identifies the basic features of burden movement in a rotary kiln. The cold model study was conducted with iron ore as the feed material to determine the influence of length to diameter ratio (L/D) of a rotary kiln on the filling degree, hold-up, and residence time of the charge. An empirical equation correlating different operating variables has been derived on the basis of the experimental results. The influence of individual parameters under different conditions on the residence time and back spillage has also been evaluated. Formerly Joint Director, Research and Development, TISCO