Characterization of ThO2-UO2 pellets made by co-precipitation process

The co-precipitation technique renders an excellent route to obtain a homogeneous mixture of ThO₂ and UO₂ powders. In this process, after the nitrate solutions of Th and U are mixed in the intended ratio, oxalic acid is added for co-precipitation. The precipitate is then dried and calcined to get a solid solution of ThO₂ and UO₂. In this study, ThO₂-30%UO₂ and ThO₂-50%UO₂ (% in weight) powders were characterized in terms of particle size, particle shape, surface area, phase content, O/M ratio etc. The pellets obtained by sintering these powders were characterized with the help of optical microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The XRD data for ThO₂-30%UO₂ and ThO₂-50%UO₂ pellets showed the presence of a small amount of U₃O₈ phase besides fluorite phase. The grain size of ThO₂-30%UO₂ and ThO₂-50%UO₂ was found to be 5.7 and 4.5 μm, respectively.     

10Be annual fallout in rains in India

The ¹⁰Be concentrations of annual rainfall collections during 1979–1981, at eight stations in India, ranged from 0.43 × 10⁷ to 8.48 × 10⁷ atoms/l and the corresponding ¹⁰Be fallouts are in the range of 0.31 × 10 ⁶ to 2.73 × 10⁶ atoms cm^?2 a^?1. The estimated ¹⁰Be global fallout based on the presently available data is 1.55 × 10⁷ atoms^?2 a^?1 or 5 × 10^?2 atoms cm^?2 s^?1. Most of the measured rates of fallout and deep sea deposition of ¹⁰Be are a factor of 2–3 lower than the present estimate.     

Persuasive Strategies for Encouraging Social Interaction for Older Adults

Social isolation among older adults represents a significant societal challenge in which persuasion offers a potential solution. To develop a persuasive interactive system for this purpose, we conducted a modeling study with carers to discover how persuasion is used to encourage social interaction among older adults. From an analysis of the results, we identified and defined effective persuasive strategies grounded in theories of persuasion and developed a computational model for applying them. This article reports the findings from an evaluation of the generalizability of this model and presents a revised version based on these results. The article concludes with a discussion on possible domain-specific conceptual features between the model evaluated and the revised model developed.     

New equations for enthalpy of vaporization from the triple point to the critical point

Two new equations are proposed for the enthalpy of vaporization from the triple point to the critical point. One of these equations containing four parameters is exceptionally good for fitting the data. The other equation containing three parameters is quite adequate for fitting the data but it is exceptionally suited for interpolation when the data do not cover the entire range. These equations have been tested using the enthalpy of vaporization of water from the triple point to the critical point and are compared with other equations.Nomenclature T _c Critical temperature, K - T _t Triple point, K - T _x Any particular temperature, K - T _r Reduced temperature - P _r Reduced pressure - R Gas constant - P Vapor pressure - X (T _c–T)/T _c - Y (T _c–T)/T - X _x (T _c–T)/(T _c–T _x) - X _t (T _c–T)/(T _c–T _t) - H _vt Enthalpy of vaporization at the triple point, kJ · mol^–1 - H _vx Enthalpy of vaporization at any temperature x, kJ · mol^–1 - Z _v Compressibilty factor of the saturated vapor - Z ₁ Compressibilty factor of the saturated liquid Relative deviation = 100[H_v(obs)–H_v(cal)]/H_v(obsd) Standard deviation = { [H _v(obs)–H _v(cal)]²/(No. points — No. parameters)}^0.5     

Wax and Fatty Acids from Rice Bran Oil Sludges

Sludges obtained as tank settlings from solvent-extracted rice bran oil have been shown to be rich sources of wax and fatty acids. The wax content is variable, being about 18% in one sample and about 39% in a second sample of sludge. The wax was bleached to light colour. The crude wax shows good compatibility with other types of waxes. The oil fraction of sludges is high in free fatty acids (over 70%), about three fourth of which could be vacuum-distilled directly to yield light-coloured fatty acids.     

Influence of carbon on combustion characteristics of Magnesium-Sodium Nitrate Propellant

Effect of addition of carbon in the form of graphite and carbolac on the combustion characteristics of Magnesium-Sodium nitrate propellant has been studied. Results indicated that the burning rate of the propellant increased significantly by the addition of graphite upto 2%. Thermal decomposition studies revealed that the graphite particles in addition to its absorption of thermal energy being an inert material react with the decomposed products of the sodium nitrate just above the burning surface of the propellant for the exothermic heat release. This heat release which is high at low concentration of graphite is seen causing high burning rate. Any further increase in graphite concentration beyound 2% reduces the burning rate as the thermal energy absorption exceeds the heat release at the burning surface. When carbon in the form of carbolac was used in the composition reactive species diffuse out prior to the sample ignition without participating in the combustion thus reduces the burning rate. The heat of reaction data supported the suggested mechanism.     

Selection of an igniter system for magnesium-based solid fuel rich propellant

Suitability of a number of metal based igniter compositions have been studied for magnesium based fuel rich propellant. Igniter compositions have been tested in closed vessel for evaluation of ignition pressure output and impetus. Heat energy values were determined calorimetrically in a closed bomb. Vented vessel study was carried out in a test motor for assessing relative behaviour and to select a suitable composition. Compositions containing magnesium powder and potassium nitrate were found to give satisfactory ignition to the propellant.     

Mössbauer studies of iron doped poly(methyl methacrylate) before and after ion beam modification

High-energy MeV ions from accelerators are known to produce drastic modifications in polymers. The typical effects include chain scissions, crosslinks, molecular emission and double bond formation. Poly(methyl methacrylate) was doped with Fe(III) and irradiated with 95 MeV O⁷⁺ ions.⁵⁷Fe-Mössbauer studies were done on the doped samples before and after irradiation. Before irradiation, no Mössbauer absorption was observed. The irradiated samples showed a good Mössbauer absorption, which seems to indicate that there is a significant interaction between the metal ion and the polymer matrix. Two possibilities exist at these doses (～ 22 × 10¹² ions/cm): Fe(III) ions may be bridging the various polymer segments through crosslinking or amorphization of the sample leading to Fe-C bonding. Studies of FTIR, conductivity and glass transition temperatures on these samples support these observations.