Mean residence time of gas in mechanically agitated gas–liquid contactors

In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature.     

Estimation of wood char size at the end of devolatilization in a bubbling fluidized bed combustor

Two processes, namely shrinkage and primary fragmentation are known to be the major causes of size reduction of wood during its devolatilization in a fluidized bed combustor. A simple phenomenological model incorporating these effects to compute the average char size at the end of devolatilization is proposed. Experiments are conducted in a bubbling fluidized bed combustor using wood having three different shapes namely, cylinder, cuboid and sphere, to measure the average char size at the end of devolatilization. The model prediction of average char size agrees with the measured values within a deviation of 15%. An experimental correlation is derived to determine the number of fragments and is used to estimate the mean char size.     

Amphiphilic Poly(p‐phenylene)s for Self‐Organized Porous Blue‐Light‐Emitting Thin Films

Micro‐ and nanostructuring of conjugated polymers are of critical importance in the fabrication of molecular electronic devices as well as photonic and bandgap materials. The present report delineates the single‐step self‐organization of highly ordered structures of functionalized poly(p‐phenylene)s without the aid of either a controlled environment or expensive fabrication methodologies. Microporous films of these polymers, with a honeycomb pattern, were prepared by direct spreading of the dilute polymer solution on various substrates, such as glass, quartz, silicon wafer, indium tin oxide, gold‐coated mica, and water, under ambient conditions. The polymeric film obtained from C₁₂PPPOH comprises highly periodic, defect‐free structures with blue‐light‐emitting properties. It is expected that such microstructured, conjugated polymeric films will have interesting applications in photonic and optoelectronic devices. The ability of the polymer to template the facile micropatterning of nanomaterials gives rise to hybrid films with very good spatial dispersion of the carbon nanotubes.     

Phase‐dependent radiation‐resistant behavior of BaTiO3: An in situ X‐ray diffraction study

The radiation‐resistant response of BaTiO₃ in the tetragonal and rhombohedral phases on exposure to 100 MeV Ag⁷⁺ ion irradiation was investigated by in situ X‐ray diffraction (XRD) at room temperature (300 K) and low temperature (25 K), respectively. This study revealed that the BaTiO₃ in rhombohedral phase retained crystallinity up to an ion fluence of 1×10¹⁴ ions/cm², whereas tetragonal phase amorphized at much lower fluence viz. 1×10¹³ ions/cm². The in situ XRD along with Raman spectroscopy studies revealed that BaTiO₃ in rhombohedral phase is more radiation resistant than that of tetragonal phase. The density functional theory (DFT) calculations confirmed higher bond strength of rhombohedral phase as compared to tetragonal phase, which supported the experimental result of higher radiation stability of rhombohedral phase. The theoretical predictions on high‐temperature phase will be of relevance to the nuclear waste applications.     

A Novel Low-Temperature Synthesis of Nanosized NiZn Ferrite

Nanosized NiZn ferrite powder is synthesized by a low-temperature method, using a unique combination of citric acid and glycine. An appropriate molar ratio of both citric acid and glycine offers a low-temperature synthetic route by incorporating the complexation behavior of citric acid and the combustion nature of glycine. Thermal decomposition/controlled autocatalytic combustion of the composite gel occurs at a low temperature of around 175°C, with the evolution of a large amount of gases. Transmission electron microscopic studies showed that the average particle size of the ferrite obtained is ∼2.5 nm, with a narrow size distribution. Uniformly distributed fine-grained microstructure with low porosity is obtained for a sample sintered at 1000°C.     

Formation of BaCrO4 NanoCrystallites within Thermally Evaporated Sodium Bis-2-Ethylhexyl-Sulfosuccinate and Stearic Acid Thin Films

This paper describes the growth of barium chromate (BaCrO₄) nanocrystallites within thermally evaporated thin films of stearic acid (StA) and sodium bis-2-ethylhexyl-sulfosuccinate by a process of Ba²⁺ ion entrapment followed by in situ reaction with CrO₄²⁻ ions. Dense spherical assemblies of BaCrO₄ nanocrystallites of very uniform size (∼50 nm) were obtained within the two different host matrices. The spherical assemblies were composed of smaller (ca. 5–10 nm size) BaCrO₄ crystals indicating that efficient size control over crystal size may be exercised by the matrix. Contact angle measurements of the BaCrO₄–StA and BaCrO₄–sodium bis-2-ethylhexyl-sulfosuccinate films indicated that they were hydrophobic, thus pointing to the possible role of hydrophobic interaction between the StA and sodium bis-2-ethylhexyl-sulfosuccinate monolayer-covered BaCrO₄ crystals in the assembly process.     

An overview on oxyfuel coal combustion—State of the art research and technology development

Oxyfuel combustion is seen as one of the major options for CO₂ capture for future clean coal technologies. The paper provides an overview on research activities and technology development through a fundamental research underpinning the Australia/Japan Oxyfuel Feasibility Project. Studies on oxyfuel combustion on a pilot-scale furnace and a laboratory scale drop tube furnace are presented and compared with computational fluid dynamics (CFD) predictions. The research has made several contributions to current knowledge, including; comprehensive assessment on oxyfuel combustion in a pilot-scale oxyfuel furnace, modifying the design criterion for an oxy retrofit by matching heat transfer, a new 4-grey gas model which accurately predicts emissivity of the gases in oxy-fired furnaces has been developed for furnace modelling, the first measurements of coal reactivity comparisons in air and oxyfuel at laboratory and pilot-scale; and predictions of observed delays in flame ignition in oxy-firing.     

Impact of Variable Packet Length on the Performance of Heterogeneous Multimedia Wireless Sensor Networks

Wireless Personal Communications - Performance valuation of wireless sensor network (WSN) routing protocols calls for realistic data traffic models because of their application specific nature....     

Phase diagram analysis of (U,Pu)O2−x sub-system

The high plutonium, hypo-stoichiometric fuel exists as two phase system at low temperatures. The partial phase diagram of (U,Pu)O_2−x with two coexisting cubic phases was extensively investigated in this work using theoretical models. The critical temperature of the miscibility gap varies with Pu/M and O/M of the system. Based on the similar miscibility gap behaviour observed in PuO_2−x system and the experimental data available on the phase boundaries of (U,Pu)O_2−x for various Pu/M, some semi-empirical relationships and solution models were developed. With the help of these relationships, ternary isothermal sections of the miscibility gap, O/M at different temperatures and the critical temperature of the miscibility gap of (U,Pu)_2−x for different Pu/M values were calculated. These calculated values were compared with the available literature data.     

Hierarchical Self‐Organization of Nanomaterials into Two‐Dimensional Arrays Using Functional Polymer Scaffold

Fabrication of two and three‐dimensional nanostructures requires the development of new methodologies for the assembly of molecular/macromolecular objects on substrates in predetermined arrangements. Templated self‐assembly approach is a powerful strategy for the creation of materials from assembly of molecular components or nanoparticles. The present study describes the development of a facile, template directed self‐assembly of (metal/organic) nanomaterials into periodic micro‐ and nanostructures. The positioning and the organization of nanomaterials into spatially well‐defined arrays were achieved using an amphiphilic conjugated polymer‐aided, self‐organization process. Arrays of honeycomb patterns formed from conjugated C₁₂PPPOH film with homogenous distribution of metal/organic nanomaterials. Our approach offers a straightforward and inexpensive method of preparation for hybrid thin films without environmentally controlled chambers or sophisticated instruments as compared to multistep micro‐fabrication techniques.