Rate-dependent serrated flow and plastic deformation in Ti45Zr16Be20Cu10Ni9 bulk amorphous alloy during nanoindentation

The plastic deformation of Ti₄₅Zr₁₆Be₂₀Cu₁₀Ni₉ bulk metallic glass has been investigated by nanoindentation performed with loads ranging from 10 to 200 mN in a wide range of loading rates. The plastic flow in the alloy exhibited conspicuous serrations at low loading rates. The serrations, however, became less prominent as the rate of indentation increased. Atomic force microscopy showed a significant pile-up of materials around the indents, indicating that a highly localized plastic deformation occurred under nanoindentation. The possible mechanism governing the plastic deformation in bulk metallic glass specimens is tentatively discussed in terms of strain-induced free volume.     

Stochastic analysis and maintenance planning of the ash handling system in the thermal power plant

This paper discusses stochastic analysis of the ash handling system in a thermal power plant. The system consists of four subsystems A_i, B_j, C and D_k in series, with three possible states: good, reduced and failed. Failure and repair rates for each subsystem are taken to be constants. Using a probabilistic approach, the differential equations are generated and the expression for steady state availability is computed. Taking data from the thermal power plant, situated in North India, the behaviour of each working unit is analysed. Problems and remedies with appropriate maintenance schedules have been discussed. The results are discussed with the plant personnel and are helpful to the management in predicting the behaviour of each operating unit, so that timely decisions can be taken for maintaining the system in upstate for a long duration.     

An indigenously developed electronic control system for Langmuir-Blodgett film deposition set-up

An indigenous and simple electronic control system for Langmuir-Blodgett (LB) film deposition set-up has been developed. This set-up consists of a microstepping circuit to drive the stepper motors with precision and smooth motion, essential for controlled movement of the barriers and substrate in the LB set-up. Linear variable differential transformer (LVDT)-based displacement measuring device has been developed and used to measure the surface pressure of the monolayer material spread on the water surface. A control program is written which incorporates all operational modes required to drive the set-up and to acquire the datain situ using a set of user-friendly commands. This control set-up has been successfully used to plot the pressure-area isotherm of various amphiphilic compounds such as ferric stearate, zinc arachidate etc. and for deposition of ordered LB films of ferric stearate.     

A new energy efficient, environment friendly and high productive texturization process of industrial multicrystalline silicon solar cells

A new texturization process based on a uniform, isotropic and slow removal of silicon, using a composition of sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) solution at an elevated temperature is developed recently for multicrystalline silicon solar cells. This process is applied in optimized condition in regular industrial production line and it immediately replaces the old popular industrial process of texturization using a combination of NaOH solution, alcoholic NaOH solution and hydrochloric acid solution in different steps at a higher temperature. Also the gain in solar cell efficiency at global AM1.5 spectrum, 1 SUN intensity condition is nearly 10% in final value. In addition, it has become finally an energy efficient and environment friendly texturization process for large area multicrystalline silicon solar cells for commercial use. In this paper the cost effectiveness and environment friendly aspects of the proposed process have been studied in detail along with the surface texture analysis of wafers with SEM and AFM micrographs to substantiate the reasons behind the above facts.     

Antibacterial Activity of the Sponge Ircinia Ramosa: Importance of its Surface-Associated Bacteria

Variations in the antibacterial activity of the sponge Ircinia ramosa were evaluated during two collection periods (January and May) against vicinity fouling bacteria (VFB) and sponge surface-associated bacteria (SAB). The density of fouling bacteria in the water column, as well as epibacterial abundance on the sponge surface, was enumerated during both collections, and both increased in the warmer month of May. The extracts obtained from SAB were also tested for their role in antibacterial activity of the host. Sponge-associated bacteria are capable of producing antibacterial metabolites. The antibacterial activity that originated from polar fractions in the cooler month of January shifted towards the nonpolar fractions in May. Nonpolar fractions were more useful for the sponge when threatened with increased bacterial density. Thus, the chemical nature and production of antibacterial compounds produced by sponge or its associated bacteria appears to be governed by the environment. An inverse relationship was observed between the epibacterial abundance over the sponge surface in nature and the antibacterial activity displayed by the sponge extracts in laboratory bioassays. This investigation reveals the importance of collection period as well as the role of associated bacteria in the evaluation of antibacterial activity.     

Characterization of influence zones of simulated droughts and floods of water bodies in a floodplain

During flooding processes, randomly situated water bodies of varying sizes and shapes in a floodplain tend to self-organize. At high degrees of flooding intensity, water bodies contact together to form influence zones, which indicate the self-organized criticality of the flooding of water bodies. The characterization of water bodies and their influence zones provides useful insight into the geomorphic properties of floodplain terrains. In this paper, characterization of the influence zones of simulated droughts and floods of water bodies in a floodplain is performed. First, drought and flood simulations are implemented by performing morphological erosion and dilation, respectively, on water bodies using square kernels of increasing sizes. The level of droughting/flooding is indicated by the kernel size. The average areas of the influence zones of the generated simulated droughts and floods of water bodies are computed. It is observed that as the droughting level increases from 1 to 5, the average area of the influence zones of water bodies reduces due to the shrinking of water bodies. As the droughting level increases from 5 to 15, the average area of the influence zones of water bodies increases due the vanishing of small water bodies. Flooding causes an increase in the average area of the influence zones of water bodies due to the merging of adjacent water bodies. A power law relationship is observed between the average area of the influence zones of the simulated droughts/floods and the level of droughting/flooding. The scaling exponent of this power law, which is named as a fractal dimension, indicates the rate of change of average area of the influence zones of simulated droughts/floods of water bodies in a floodplain over varying levels of droughting/flooding.     

Influence of Rheological Behavior of Purely Viscous Fluids on Analytical Residence Time Distribution in Straight Tubes

In an effort to better understand the homogeneity of heat treatment of foodstuffs in holding tubes, the cumulative residence time distribution function is derived for a Herschel‐Bulkley fluid from fully developed laminar flow in a straight circular tube under isothermal conditions when diffusional effects are negligible. The proposed analytical solution can be reduced to solutions for Newtonian, shear‐thinning, dilatant, Bingham fluids by setting particular rheological parameters, and consequently, it is possible to successfully explain the dependence of residence time distribution on fluid properties for almost all of the rheological models used for time‐independent purely viscous fluids.     

Bacteriological Evaluation of Gingival Crevicular Fluid in Teeth Restored Using Fixed Dental Prostheses: An In Vivo Study

The present in vivo study determined the microbiological counts of the gingival crevicular fluid (GCF) among patients with fixed dental prostheses fabricated using three different techniques. A total of 129 subjects were divided into three study groups: first, cobalt-chrome-based, metal-ceramic prostheses fabricated by the conventional method (MC, n = 35); the second group consisted of cobalt-chrome-based, metal-ceramic prostheses fabricated by the computer-aided design and computer-aided manufacturing (CAD/CAM) technique (CC-MC, n = 35); the third group comprised zirconia-based ceramic prostheses fabricated using the CAD/CAM technique (CC-Zr, n = 35). The control consisted of 24 patients using prostheses fabricated with either MC, CC-MC, or CC-Zr. The GCF was obtained from the subjects before treatment, and 6 and 12 months after the prosthetic treatment. Bacteriological and bacterioscopic analysis of the GCF was performed to analyze the patients’ GCF. The data were analyzed using SPSS V20 (IBM Company, Chicago, IL, USA). The number of microorganisms of the gingival crevicular fluid in all groups at 12 months of prosthetic treatment reduced dramatically compared with the data obtained before prosthetic treatment. Inflammatory processes in the periodontium occurred slowly in the case of zirconium oxide-based ceramic constructions due to their biocompatibility with the mucous membranes and tissues of the oral cavity as well as a reduced risk of dental biofilm formation. This should be considered by dentists and prosthodontists when choosing restoration materials for subjects with periodontal pathology.     

Phases and Microstructures in Zirconia-Calcia-Titania Multiphase Ceramics

Two cubic phases of differing compositions and lattice parameters and a monoclinic phase are found in samples of zirconia with 8 mol% calcia and 4 to 10 mol% titania. Increasing amounts of titania reduce the amounts of the cubic phases. The monoclinic phase dissolves small amounts (∼1 mol%) of calcia and up to 4.7 mol% titania; these amounts for the cubic phases are much larger. The cubic lattices contract linearly with increasing amounts of titaia and a contraction in the monoclinic lattice is also evident.     

Synthesis of pyrazolo[4′,3′:5,6]pyrazino[2,3-c]pyrazoles and pyrazolo[4′,3′:5,6]pyrazino[2,3-d]pyrimidines and their application to polyester fibres

4-Nitroso-1-phenyl-3-methyl-5-aminopyrazole ( 1 ) was condensed with ethylcyanoacetate ( 2 ), malononitrile ( 4a ) and 2-cyanomethylbenzimidazole ( 4b ) to yield 6-hydroxy-5-cyano, 6-amino-5-cyano and 6-amino-5-(benzimidazol-2-yl)-3-methylpyrazolo [3,4-b]pyrazines 3, 5a and 5b , respectively. 5-Cyano-6-chloro derivative 6 obtained from 3 was converted to 3-aminopyrazolo[4′,3′:5,6]pyrazino[2,3-c]pyrazoles 8a and 8b by the treatment with hydrazin hydrate ( 7a ) and phenylhydrazine ( 7b ), respectively. Compound 5a was treated with formamide ( 9a ), urea ( 9b ) and thiourea ( 9c ) to give 4-aminopyrazolo[4′,3′:5,6]pyrazino[2′3′-d]pyrimidines 10a–10c. With refluxing acetic anhydride compounds 8a, 8b and 10a gave corresponding acetamido derivatives 8c, 8d and 10d. Compound 5a was treated with ethylorthoformate ( 11 ), acetic anhydride ( 12 ) or benzoylchloride ( 13 ) to give fused benzimidazopyrazolo[4′,3′:5,6]pyrazino[2′,3′-d]pyrimidines, viz., benzimidazol[1,2-c]pyrazolo[4,3-g]pteridines ( 14a–14c ). Some of the compounds 8, 10 and 14 were applied to polyester as disperse dyes and their fastness properties were studied.