Studies on viscosity of calcium soaps in aqueous methanol

Viscosity measurements of calcium soaps show that two kinds of micelles are formed in aqueous methanol mixtures. The change in the nature of micelles from hydrophilic oleomicelles to lipophilic hydromicelles occurs in solvents containing 40–50% (v/v) of methanol. The equations of Vand and Moulik are applicable only above the critical micelle concentration of the soaps. The parameters of the equations have been evaluated. These may be used to calculate the viscosity of soap solutions in the concentration range in which the equations hold good.     

Aqueous and vapor phase mercury sorption by inorganic oxide materials functionalized with thiols and poly-thiols

The objective of the study is the development of sorbents where the sorption sites are highly accessible for the capture of mercury from aqueous and vapor streams. Only a small fraction of the equilibrium capacity is utilized for a sorbent in applications involving short residence times (e.g., vapor phase capture of mercury from coal-fired power plant flue gases). So, dynamic capacity rather than equilibrium capacity is more relevant for these kinds of situations. Rapid sorption rates and higher dynamic capacity can be achieved by increasing the accessibility of active sites and decreasing the diffusional resistance to mass transport for the adsorbing species. This requires the use of open structured sorbent materials and attachment of functional groups on the external surface area of supports. The strong interaction of sulfur containing ligands (e.g., thiol) with mercury makes them suitable candidates for immobilization on these types of materials. In this study, inorganic oxide supports like alumina and silica are functionalized with thiol moieties like mercapto silane, cysteine and poly-cysteine for capturing mercury from aqueous and vapor phase. Aqueous phase Hg (II) sorption studies with cysteine/poly-cysteine functionalized silica showed that high dynamic capacity can be achieved by attaching active sites (thiol) on the external area of supports. Vapor phase Hg capture studies with thiol-functionalized mesoporous silica (Hg⁰ concentration = 3.37 mg/m³ with N₂ as the carrier, gas temperature = 70 ^°C) yielded a capacity of 143 g Hg/g for the sorbent. Although the sulfur content for the sorbent was low (0.80 wt. %) the molar ratio of Hg captured to sulfur was comparatively high (2.86×10^–3) pointing to the high accessibility of sulfur sites.     

Dispersion of photoelastic constants in doped KDP crystals

The photoelastic behaviour ofkdp crystals with additives like borax,adp, nickel phosphate, manganese phosphate and sodium dihydrogen orthophosphate has been studied as a variable birefringent compensator. The dispersion of the stress birefringence with wavelength was studied for a single orientation.     

Large wire drawing plastic deformation in aluminum and its dilute alloys

The microstructures and hardening characteristics of Al and Al with dilute additions of soluble and insoluble impurities were compared during wire drawing at room temperature to true strains (ε _w ) of 4.95. Three stages of microstructure change are observed: formation of a dislocation cell structure; cell boundary sharpening and cell size refinement; dynamic recrystallization. A minimum effective cell size is reached at an intermediate strain level corresponding approximately to the onset of dynamic recrystallization. The amounts and types of impurities at levels less than 1 pct have a great effect on the details of the microstructural changes as well as the hardening characteristics. 99.98 pct pure Al alternately saturates and hardens fromε _w = 0 to 4.95. Al-0.6 Fe (insoluble) work softens nearε _w = 3.5. Al-0.2 Mg (soluble) and EC Al (with 0.15 pct soluble and insoluble impurities) both work harden at a diminishing rate toε _w ≃1.25 then enter a linear hardening stage which persists toε _w ≃5. A linear relation between yield strength and inverse cell size is established for EC Al and Al-0.2 Mg in the cell refinement strain range; however, the Petch slope is much less than that of similar Al alloys subjected to elevated temperature dynamic or static recovery. Al-0.6 Fe does not exhibit a consistent linear relation between yield strength and inverse cell size. These differences can be attributed to the degree of recovery and the interrelation between cell size, cell boundary character and total dislocation density.     

Radiation-Induced graft copolymerization of methyl methacrylate on natural and modified wool. II. Sorption behavior

The water vapor sorption-desorption isotherms of graft copolymers of methyl methacrylate with natural and chemically modified wool (i.e., oxidized, reduced, methylated, and crosslinked) has been investigated. As a result of graft copolymerization a reduction in water absorption was observed. The results have also been analysed in the light of Hailwood–Horrobin equations.     

The application of low temperature infra-red spectroscopy to studies of iron substitution in tricalcium aluminate (C3A)

Low temperature IR spectroscopy has been used to study the extent of solid solution of Fe in C₃A. The intensity of the bands in the IR spectra obtained in sufficient to permit peak ratios to be used (for the first time) as an aid to determining the extent and nature of the solid solution.     

On shape normalization for non-uniformly active catalyst pellets

The possibility of shape normalization of catalyst pellets with non-uniform catalytic activity profiles is examined. A first order isothermal reaction occurring in slab or spherical catalyst pellets, with a variety of activity profiles, is considered. Analytic solutions for the effectiveness factor are reported in all cases. When the catalytic activity at the external surface of the pellet is non-zero, a physically significant normalization of the Thiele modulus is suggested which makes the asymptotic behavior of the effectiveness factor identical for all pellet shapes and all activity profiles. For an operational range intermediate between kinetic and diffusion control, however, the normalization can lead to significant errors. No such normalization exists when the surface catalytic activity is zero.     

Polypyromellitimides. Thermally stable materials

The effect of backbone flexibility on the thermal behaviour of the polyimides was investigated by synthesizing copolyimides based on pyromellitic dianhydride (PMDA) and benzidine (B), p-phenylene diamine (P), and p,p′-diamino diphenyl methane (D). Soluble polyamic acids were obtained by carrying the reaction in dimethyl formamide (DMF) at 0°C. The cyclodehydration of amic acid to polyimides was carried out by chemical means (acetic anhydride : pyridine). Several copolyimides were prepared by changing the molar ratios of diamines in initial monomer feed. These were characterized by evaluation of intrinsic viscosity of polyamic acid in DMF at 30°C. The presence of amic acid and imide structures in the backbone was confirmed by IR spectra. Thermal behaviour of the polymers in air and nitrogen atmosphere was evaluated by dynamic thermogravimetry. The integral procedural decomposition temperature and activation energy of thermal degradation has been evaluated.     

Distributed control schemes for fast arbitration in large crossbarnetworks

In a large nonblocking crossbar switch, the controller often becomes a bottleneck in terms of both performance and reliability. We present a number of schemes for distributing the setup function among multiple controllers, thus improving both the performance and the reliability of the switch. The controllers are symmetric and operate in parallel. We present four distributed control schemes that provide a range of tradeoffs in controller complexity, speed, and hardware overhead for nonblocking operation. We derive a lower bound of N(1-1/K) for the number of buses required for nonblocking operation of a crossbar switch with N ports and K controllers under certain constraints. We then describe a scheme that actually achieves this lower bound. Results from simulation indicate that the hardware overhead in terms of the extra buses needed is small for all the schemes if a small probability of blocking is acceptable     

Characterization of coprecipitated ferroelectric Bi2 VO5·5

Fine powders of orthorhombic bismuth vanadate (Bi₂ VO_5·5) have been synthesized by coprecipitation method. Powder X-ray diffraction and electron microscopic techniques have been used to characterize these samples. The formation of the monophasic Bi₂ VO_5·5 was confirmed. The compacted powders sintered at 1070K have been characterized for their dielectric properties as a function of both temperature (300–900 K) and frequency (100 Hz–10 MHz) and found to be superior to those obtained by the conventional solid-state reaction route.