DEVOLATILIZATION STUDIES ON A BITUMINOUS COAL UNDER VARIOUS GAS ENVIRONMENTS

Devolatilization of a bituminous coal was studied in the temperature range 3 50°C to 550°C and at two pressures: 30 psig and 375 psig. Three separate particle sizes were investigated: (-2, +l),(-4, +3) and (-9, +6) mm. The runs, lasting up to 30 minutes, were carried out under two different types of flowing gas environments: a synthetic gas mixture of composition similar to that entering the devolatilization zone from the gasification zone below in a fixed bed gasifier, and containing 3% steam by volume; and, a helium-steam mixture, also containing 3% steam by volume.

The gas evolution rates from devolatilization show a peak at 5-10 minutes from the start of a run and then gradually taper off to zero as the run progresses. The concentration of methane in the off-gas stream is observed to be higher in the helium runs. There, however, is no significant effect of gas environment on the molecular weights of the tar, which show a maximum in the range 300-500. The tar yields, however, are higher for the helium runs; in all cases, the tar yields peak at 4 °C. The gas yield, however, is higher for the reactive gas environment. The total volatiles yield appears independent of particle size; however, it seems to increase with pressure, over the temperature range studied.     

Parametric study of EAA polymer thin film deposition on carbon substrates in a fluidized electrode bed reactor

Electrodeposition of ethylene-co-acrylic acid (EAA) polymer, as thin films on carbon particle substrates, was carried out in a fluidized electrode bed reactor. Feeder current, time of deposition, and flow rate of anolyte (i.e., bed expansion or bed porosity) were the key parameters investigated. The film characteristics were evaluated through SEM and FTIR analyses and the amounts determined by weighing. The effect of these parameters on the electrodeposition process is discussed, and optimum conditions for deposition are proposed. Also, a possible mechanism for electrodeposition, particularly for the EAA–carbon system, is discussed.     

Low complexity ordered successive interference cancelation detection algorithm for uplink MIMO SC-FDMA system

In mobile communication, the most exploratory technology of fifth generation is massive multiple input multiple output (MIMO). The minimum mean square error and zero forcing based linear detectors are used in multiuser detection for MIMO single-carrier frequency division multiple access (SC-FDMA). When the received signal is detected and regularization sequence is joined in the equalization of spectral null amplification, these schemes experience an error performance and the signal detection assesses an inversion of a matrix computation that grows into complexity. Ordered successive interference cancelation (OSIC) detection is considered for MIMO SC-FDMA, which uses a posteriori information to eradicate these problems in a realistic environment. To cancel the interference, sorting is preferred based on signal-to-noise ratio and log-likelihood ratio. The distinctiveness of the methodology is to predict the symbol with the lowest error probability. The proposed work is compared with the existing methods, and simulation results prove that the defined algorithm outperforms conventional detection methods and accomplishes better performance with lower complication.     

LIMITATION OF BOUNDARY LAYER ANALYSES FOR BUOYANT CONVECTION IN STABLY STRATIFIED FLUIDS

Vertical buoyant convection in stably stratified fluids is revisited. The limitation of boundary layer analyses for such flows is quantified. This is accomplished by comparing the results of the present boundary layer numerical study with the published experimental measurements, and full numerical simulations. It is shown that boundary layer analysis underpredicts the heat transfer rates. This is explained with reference to the flow and thermal fields. The boundary layer results are shown to be inadequate for such characteristics as flow reversal and temperature defects. The underlying physical mechanisms are discussed.     

Structural Phase Transitions and Thermoelectric Properties of AgPb<Subscript>18</Subscript>SbTe<Subscript>20</Subscript> Under Compression

The high-figure-of-merit thermoelectric material AgPb₁₈SbTe₂₀ has been investigated by in situ angular-dispersive x-ray diffraction (XRD) and x-ray absorption fine-structure (XAFS) measurements up to 30 GPa. Resistivity and thermopower were measured with Bridgman-type opposed metal anvil cells. The results show that the ambient cubic ( Fm[`3] m ) \left( {Fm\overline{3} m} \right) structure transforms to orthorhombic (Pnma) at 6.4 GPa and then to the CsCl-type ( Pm[`3] m ) \left( {Pm\overline{3} m} \right) structure at 15 GPa. The ambient cubic ( Fm[`3] m ) \left( {Fm\overline{3} m} \right) phase is found to be recoverable on releasing the pressure. The thermoelectric power is found to increase with pressure for the cubic phase. The XAFS studies performed at the Pb L ₃-edge and Ag K-edge along with resistivity studies complement the XRD findings.     

Template-assisted electrohydrodynamic atomization of polycaprolactone for orthopedic patterning applications

This paper presents the development of the novel deposition of biodegradable polycaprolactone (PCL) polymer patterns on a metallic substrate using a jet spraying technique, template-assisted electrohydrodynamic atomization (TAEA), at ambient temperature. The structure of patterns was controlled by systematically varying the polymer concentration (2–15 wt.%) and the flow rate (1–25 μl min^? 1). Polymer deposition was carried out in the stable cone-jet mode to precisely control the surface structure and morphology. The patterns were studied by optical microscopy, scanning electron microscopy and profilometry, and a high degree of control over the pattern geometry and thickness was achieved by varying the spraying time. The hardness and the effective elastic modulus of the polymer patterns were estimated using nanoindentation. The effect of load, loading rate and the holding time on the hardness and effective elastic modulus was derived. Optimal results were obtained with 5 wt.% PCL in DMAC solution sprayed within the stable cone-jet mode operating window at a flow rate of 15 μl min^? 1 for 300 s at 11.1 kV with a working distance of 60 mm. Hexagonal patterns were well-defined and repeatable with thickness of ~ 34 μm. The hardness is 1.6 MPa at a loading rate of 0.1 μN/s and nearly halved when the load rate was increased to 1 μN/s. The effective elastic modulus of ~ 12 MPa is obtained for a load rate of 0.1 μN/s.