Kinetics of Crystal Growth of Calcium Tungstate from Solutions in Sodium Tungstate Melts by Continuous Cooling

Crystallization kinetics of calcium tungstate from unstirred supersaturated solutions in sodium tungstate melts was studied by continuous cooling from initial crystallization temperature T _O=1000° to 800°C to room temperature at cooling rates R_T =0.67° to 3.3°C min⁻¹. Crystals were examined by optical microscopy and analyzed by various methods. The main crystal growth was diffusion-rate-controlled. The final crystal growth was rate-controlled by the development rate of excess solute concentration. Diffusion rate constant ( k_D ) values were estimated. These values increased with cooling rate and initial crystallization temperatures but they are very much smaller than the rate constants for diffusion-controlled growth of calcium tungstate from lithium chloride melts.     

Elemental micro-segregation characteristic of fiber laser welded Hastelloy C-276 sheet

The elemental micro-segregation characteristic within the weld zone for ytterbium fiber laser welded Hastelloy C-276 sheet was investigated. The analysis of segregation ratio and equilibrium distribution coefficient of elements, determined through EDS data, indicate the reduction in micro-segregation of elements compared with the previous reported literatures for laser welded Hastelloy C-276. High melting efficiency of ytterbium fiber laser, reduction in the amount of linear heat input, and high cooling rate of the mushy zone lead to the reduction in micro-segregation. The melting efficiency of ytterbium fiber laser for welding of Hastelloy C-276 of 64% is higher than that (48%) of conventional welding methods. High melting efficiency leads to the reduction in the linear heat input required for welding. Hence, in the present investigation, the same was found to substantially reduce as compared to the previous reported literature. The cooling rate from liquidus temperature to solidus temperature at the weld centerline was found to be in the order of 10³ °C/s. Cellular dendritic substructure that constituted for lower micro-segregation was formed at the weld centerline.     

Mapping geological features of the Jharia coalfield from Landsat-5 TM data

False Colour Composite 754, the principal component imagery and edge enhanced imagery of Landsat-5 TM data have been found useful in delineating the regional geological features, viz, the curvilinear coal bands and sandstone ridges, faults, fractures and dolerite dykes of the Jharia Coalfield of Bihar, India, covering an area of about 480 km², where many parts are inaccessible to direct field mapping due to extensive opencast mining operations. The features, their occurrences and spatial dispositions, as deciphered from satellite data, are found to match significantly well with selective field maps.     

Effect of Treatment, Ice Storage and Freezing on Residual Sulfite in Shrimp

When fresh shell-on tails of penaeid shrimp were treated with sodium bisulfite according to current good manufacturing practices, residual sulfite (SO₂) on the edible portion varied from a high of 92.7 to a low of 60.9 ppm with an average of 80.2 ppm. During freezing and a short period of frozen storage, there was an average loss of 17% in residual sulfite. For shrimp held on ice storage, on the other hand, there was a rapid decrease in residual sulfite to below 10 ppm after six days of storage. The residual levels found on treated shrimp were consistent with action levels set by USFDA for shrimp treated according to good manufacturing practices.     

An expert system for the design and analysis of composite structures

A prototype expert system is described for concurrent design and analysis of composite structures. This system integrates symbolic, numerical and knowledge-based tools in an object-oriented programming environment for design synthesis, evaluation and modification. The system determines structural behavior utilizing a combination of analytical and numerical tools. Design modifications and structural optimization are performed using heuristic and experientially derived knowledge bases. The different domain-specific programs and commercial packages utilized by the system are integrated using a generic interfacing mechanism. The utility of the system is demonstrated by means of a design case study for a typical aircraft or rotorcraft structural component.     

Synthesis, characterization and in vitro cytotoxicity assessment of hydroxyapatite from different bioresources for tissue engineering application

In the present study, hydroxyapatite (HAp) is synthesized from different biosources like eggshell, fish scale and bovine bone in a cost effective and ecofriendly way. HAp materials were synthesized from eggshell by wet precipitation method whereas thermal decomposition method was applied in case of fish scale and bovine bone. The phase purity and crystallinity of different calcined HAp powder were determined by XRD and FTIR analyses. The thermogravimetric analysis was carried out to show thermal stability of HAp powder. Average grain sizes of sintered samples were in submicron range. The morphology of the powders were observed under scanning electron microscopy (SEM). The dried powders were wet ball milled for several hours and surfactants like Triton-X small fillers (2 / 4 mm long rod-shaped) were made for in vitro testing. In order to verify the biocompatibility of HAp powders, cytotoxicity evaluation was carried out in RAW macrophage like cell line media for an incubation period of 72 h. The cell attachment studies on HAp compacts show an excellent affinity between cells and compact surface. These results proved high biocompatibility of HAp powders obtained from different biosources for tissue engineering applications.     

Cyclic fracture behaviour of 304LN stainless steel under load and displacement control modes

Attempts have been made to understand cyclic fracture behaviour of AISI 304LN stainless steel used for nuclear piping materials under load vis‐à‐vis displacement controlled fracture tests; the former closely simulate the seismic loading conditions. The load controlled tests indicate that a material fails in a limited number of cycles even when the load amplitudes are sufficiently below the maximum load in a monotonic J–R test. The displacement controlled tests, on the other hand, show that the energy absorbing ability of a material gets severely reduced under cyclic loading conditions. The obtained results on standard laboratory specimens have been compared with similar available results on components in order to provide guidelines for maximum load bearing capability of engineering components under cyclic loading.