Synthesis and Irreversibility of Oxygen Weight Loss in 80 K YBa2Cu4O8 Superconductor

Synthesis of YBa₂Cu₄O₈ superconductor usually requires oxygen pressure greater than 20 MPa and very long heating schedules at high temperatures. Here we report synthesis of YBa₂Cu₄O₈ superconductor by the standard solid-state reaction between the precursors BaCu₂O₃ and Y₂O₃ in the presence of alkali nitrate. NaNO₃, under ambient O₂ pressure. The resulting sample showed zero resistance at 78 K. The presence of 124 was confirmed by high-resolution X-ray diffraction studies. Irreversibility of oxygen weight loss was studied by thermogravimetric analysis and differential thermal analysis.     

Technique for preprocessing of digital mammogram

Digital mammogram has emerged as the most popular screening technique for early detection of breast cancer and other abnormalities in human breast tissue. It provides us opportunities to develop algorithms for computer aided detection (CAD). In this paper we have proposed three distinct steps. The initial step involves contrast enhancement by using the contrast limited adaptive histogram equalization (CLAHE) technique. Then define the rectangle to isolate the pectoral muscle from the region of interest (ROI) and finally suppress the pectoral muscle using our proposed modified seeded region growing (SRG) algorithm. The proposed algorithms were extensively applied on all the 322 mammogram images in MIAS database resulting in complete pectoral muscle suppression in most of the images. Our proposed algorithm is compared with other segmentation methods showing superior results in comparison.     

Intelligent system for prediction and control: Application in plasma spray process

Parametric drifts and fluctuations occur during plasma spraying. These drifts and fluctuations originate primarily from electrode wear and intrinsic plasma jet instabilities. One challenge is to control the manufacturing process by identifying the parameter interdependencies, correlations and individual effects on the in-flight particle characteristics. Such control is needed through methods that (i) consider the interdependencies that influence process variability and that also (ii) quantify the processing parameter-process response relationships. Due to the large amplitudes of the drifts and fluctuations, the strategy to adopt would depend on the required corrections to apply to the in-flight particle characteristics. Artificial intelligence is a pertinent tool to reach this objective. The system is flexible in order to permit a full control based on pre-defined rules aiming at maintaining at constant values in-flight particle characteristics (average surface temperature and velocity) by adjusting in real time the arc current intensity, the total plasma gas flow and the hydrogen content whatever the fluctuations.     

Phase formation in selected surface-roughened plasma-nitrided 304 austenite stainless steel

Direct current (DC) glow discharge plasma nitriding was carried out on three selected surface-roughened AISI 304 stainless steel samples at 833 K under 4 mbar pressures for 24 h in the presence of N₂:H₂ gas mixtures of 50 : 50 ratios. After plasma nitriding, the phase formation, case depth, surface roughness, and microhardness of a plasma-nitrided layer were evaluated by glancing angle x-ray diffractogram, optical microscope, stylus profilometer, and Vickers microhardness tester techniques. The case depth, surface hardness, and phase formation variations were observed with a variation in initial surface roughness. The diffraction patterns of the plasma-nitrided samples showed the modified intensities of the α and γ phases along with those of the CrN, Fe₄N, and Fe₃N phases. Hardness and case depth variations were observed with a variation in surface roughness. A maximum hardness of 1058 Hv and a case depth of 95 μm were achieved in least surface-roughened samples.     

Novel Synthesis of Silica-Coated Ferrite Nanoparticles Prepared Using Water-in-Oil Microemulsion

Ferrite nanoparticles (magnetite (Fe₃O₄) and cobalt-ferrite (Co _x Fe_{3− x} O₄)) coated with silica (SiO₂) were prepared using water-in-oil microemulsion of a polyoxyethylen(15)cetylether/cyclohexene system. Observation via transmission electron microscopy revealed that the ferrite nanoparticles were located nearly at the center of spherical SiO₂ particles. The sizes of Fe₃O₄ and Co _x Fe_{3− x} O₄ nanoparticles were in the range of 8–12 nm and 10–14 nm, respectively, and the thickness of the SiO₂ layer was ∼14.0 nm. The solid solution of cobalt ions into Fe₃O₄ to form Co _x Fe_{3− x} O₄ nanoparticles led to an increase in the coercivity of the SiO₂-coated ferrite nanoparticles. The coercivity increased with increasing amounts of added cobalt, obtaining a maximum value of 780 Oe around a Co/Fe ratio of 0.3–0.4.     

Friction stir processing of Al6061-SiC-graphite hybrid surface composites

Friction stir processing (FSP) of Al6061-SiC-Graphite hybrid composites is studied in detail via force analysis, spectroscopic, microstructural and indentation studies. Effect of various tool rotational speeds was assessed, and the axial force variation was monitored. The presence of graphite as a reinforcement influences the axial force fluctuations due to its flaky nature and high thermal conductivity. Variation in microstructure at different tool rotational speed is studied using scanning electron microscope. The tool rotational speed has a significant influence on the area of FSP zone, fragmentation and depth of penetration of particles, dispersion of agglomerates and grain refinement of the matrix material. Spectroscopic characterization of the processed samples was done using Raman analysis and X-Ray diffraction studies. A noticeable change in intensity and shift in the respective Raman peak positions were observed, indicating residual stresses and various disorders in the crystal structure of the reinforced particles. Influence of tool rotational speed and existence of SiC and Graphite particles on the mechanical properties were further evaluated using nano indentation testing. The hybrid composite shows the combination of best and uniform mechanical properties at an optimum set of processing parameters.     

Hydrodesulfurization on MoS2/MgO

A series of Mo/MgO catalysts with loadings ranging from 2–12 wt% Mo were studied by oxygen chemisorption, X-ray diffraction and activity for thiophene hydrodesulfurization (HDS) reaction. The results obtained from the above measurements are compared with those on Mo/--Al₂O₃. These results indicated that molybdenum is better dispersed on MgO. Hydrodesulfurization activity per g. Mo is found to be higher in the case of Mo/MgO. The higher activities are attributed to the increase in dispersion of Mo on MgO. A linear correlation is obtained between oxygen chemisorption and HDS activity. The parallelism between HDS and oxygen chemisorption is explained.     

Role of Support and Promoter in the Selective Conversion of Isophorone to 3,5-Xylenol over Chromia Catalysts

A detailed study has been undertaken regarding the role of support and promoter towards 3,5-xylenol selectivity improvements in the vapor-phase aromatization of isophorone. The supports used in this study include A1₂O₃, SiO₂, ZrO₂, MgO and carbon-covered alumina for Cr₂O₃ catalysts. K₂O has been used as a promoter for these catalysts. Influence of solvent during Cr₂O₃/MgO catalyst preparation step has also been studied. The parameters governing the aromatization selectivity observed from this study are: moderate acidic sites, coordinatively unsaturated sites of Cr₂O₃ and smaller crystallites of Cr₂O₃.