The effect of Sr modification on thermal diffusivity of Al–8Si alloy

Newtonian and Fourier analysis techniques were used to calculate the solid fraction and latent heat during the solidification of Al–8Si alloy and the subsequent results were used to study the effect of Sr modification on thermal diffusivity of the solidifying melt. The results indicate that the thermal diffusivity increased significantly with increase in Sr content. The increase in the thermal diffusivity was attributed to the increase in the electronic conduction of the modified alloy due to the decreased activity of the bifilm. The results also indicate that the latent heat evolved during solidification increased with increase in Sr concentration and was associated with the increase in the solidification range that occurred during the modification process.     

Multiple Performance Optimization in Wear Characteristics of Mg-SiC Nanocomposites Using Grey-Fuzzy Algorithm

Silicon - The present investigation attempts to evaluate the effect of the SiC nano particles on the wear characteristics of Mg matrix nano composites. The wear tests on Mg matrix composites...     

Synthesis, growth and characterization analysis of nickel mercury thiocyanate crystal (NMTC)

The nonlinear optical single crystal of NiHg(SCN)₄ has been successfully synthesized and good quality single crystal has been grown by slow cooling solution growth technique. The grown single crystals have been analyzed by different characterization analyses in order to know its suitability for various applications. The functional groups have been identified from the FTIR analysis. The TG/DTA analysis reveals the thermal behavior of NMTC. The optical behaviour was assessed by UV–Vis analysis and was found with no absorption in the entire visible region and it may be useful for second harmonic and other relevant applications. The relative second harmonic generation efficiency was evaluated by Kurtz powder technique and was found to be good in comparison with the standard inorganic potassium dihydrogen phosphate.     

Comparative investigation on nanocrystal structure,optical, and electrical properties of ZnO and Sr-doped ZnO thin films using chemical bath deposition method

This paper reports on the comparative investigation of structural and optical properties of nano thin films of ZnO and Sr-doped ZnO (SZO) onto glass substrates synthesized by a two-step chemical bath deposition (CBD) technique. The mode of crystallization, structural properties, and morphologies have been investigated. The films are polycrystalline in nature with hexagonal phase having (002) preferential orientation. The typical crystallite size is also estimated and found to be around 30–80 nm. The shifts in optical band gap of the SZO films are estimated to be ∼3.25–3.27 eV with respect to the ZnO film and the refractive index is 2.35. The room temperature resistivity is of the order of ∼2,000 Ωcm. Thermoemf measurements show that films are of n-type. The sensitivity of the films was studied as a function of their temperature 275–575 K for a fixed ethanol concentration (400 ppm). The films have been tested for cross sensitivity for different gases and it has been confirmed that these are highly sensitive and selective for ethanol vapors around 200 °C in air atmosphere.     

Conformation, protein-carbohydrate interactions and a novel subunit association in the refined structure of peanut lectin-lactose complex

The structure of the complex of the tetrameric peanut lectin with lactose has been refined to an R-value of 16.4% using 2.25 angstroms resolution X-ray diffraction data. The subunit conformation in the structure is similar to that in other legume lectins except in the loops. It has been shown that in the tertiary structure of legume lectins, the short five-stranded sheet plays a major role in connecting the larger flat six-stranded and curved seven-stranded sheets. Furthermore, the loops that connect the strands at the two ends of the seven-stranded sheet curve toward and interact with each other to produce a second hydrophobic core in addition to the one between the two large sheets. The protein-lactose interactions involve the invariant features observed in other legume lectins in addition to those characteristic of peanut lectin. The "open" quaternary association in peanut lectin is stabilised by hydrophobic, hydrogen-bonded and water-mediated interactions. Contrary to the earlier belief, the structure of peanut lectin demonstrates that the variability in quaternary association in legume lectins, despite all of them having nearly the same tertiary structure, is not necessarily caused by covalently bound carbohydrate. An attempt has been made to provide a structural rationale for this variability, on the basis of buried surface areas during dimerisation. A total of 45 water molecules remain invariant when the hydration shells of the four subunits are compared. A majority of them appear to be involved in stabilising loops.     

Flotation of uranium from uranium ores in canada: Part I-flotation results with elliot lake uranium ores using chelating agents as collectors

About 150 flotation tests were done on Elliot Lake ore with 15 reagents as collectors in order to screen and choose an attractive collector for uranium flotation. Several variables were studied including pH, conditioning time and mode of collector addition. The tests were done in a Denver or Agitair subacration cell. The particle size of the ore was kept at 85% below-325 mesh. Three reagents (Kelex 100, TOPO, and cupferron) were identified as having the most promise. The best results were obtained with cupferron, where 93-95% of the uranium was recovered in 25-30% of the mass of original ore. Radium in the tails varied between 15 and 30 pCi/g depending on the mass of uranium floated. Radium was recovered in proportion to uranium in the tests done at neutral pH. The preconcentration results obtained by flotation alone were comparable to those obtained by Raicevic of CANMET using pyrite flotation and wet high intensity magnetic separation of uranium. The consumption of cupferron was 4 kg/Mg ore for each flotation stage. This was 10-15 times larger than the collector usage in conventional oxide flotation. This scheme did not require other reagents as depressants, activators or modifiers. Reproducibility was good and similar recoveries were obtained with fresh or old ores, and with distilled or mine water. The selectivity of cupferron for uranium in the ore studied was outstanding.     

Axial mixing and mass transfer in a vibrating perforated plate extraction column

The axial mixing and countercurrent mass transfer characteristics of a 5 cm diameter extraction column agitated by vibrating perforated Teflon plates have been investigated. The dispersed phase was an organic liquid (usually kerosene) and the continuous phase was water. Axial mixing was measured in both phases using pulse tracer techniques; in the continuous phase the axial mixing was estimated to have a significant effect on mass transfer, but axial mixing in the dispersed phase had a negligible effect. Mass transfer was measured for several different solutes; n-butyric acid, benzoic acid and phenol. The overall heights of a transfer unit (cont. phase) were in the order of 10-20 cm for the organic-acids but higher for transfer of phenol from very dilute solutions. The characteristics of the vibrating plate column have been compared with those of other types of extractor and suggestions are made for further development.     

Knowledge-based approach to domain modeling: Application to nasa''s payload operations control centers

Several institutions in industry and academia are pursuing research efforts in domain modeling to address unresolved issues in software reuse. To demonstrate the concepts of domain modeling and software reuse, a prototype software engineering environment is being developed at George Mason University to support the creation of domain models and the generation of target system specifications. This prototype environment, which is application domain independent, consists of an integrated set of commercial off-the-shelf software tools and custom-developed software tools. This paper describes the knowledge-based tool that has been developed as part of the environment to generate target system specifications from a domain model. This knowledge-based approach to domain modeling has been applied to NASA's Payload Operations Control Center (POCC) domain.     

Centralized power control in cellular radio systems

This paper describes a centralized power control scheme for cellular mobile radio systems. The power for the mobiles in the proposed scheme is computed based on signal strength measurements. All the mobiles using the same channel in this scheme will attain a common carrier-to-interference ratio. The proposed scheme is analyzed and shown to have an optimal solution