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.     

Crystal morphology of calcium aluminates hydrated for 14 days

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

EFFECT OF DIFFERENT PREMILLING TREATMENTS ON DEHULLING OF BLACK GRAM (PHASEOLUS MUNGO L.)

Black gram is mainly used after dehulling. Various types of premilling treatments are applied for proper dehulling. In this study, premilling treatments such as the dry method, chemical and hydrothermal treatments were carried out. It was found that premilling treatments with certain chemicals such as sodium bicarbonate, acetic acid and alcohol were found effective in dehulling black gram. Several vegetable oils at varying concentrations (0.2, 0.4, 0.6, 0.8 and 1.0%) were used; it was found that 0.6% was optimal, except that sesame oil was effective even at 0.2%. Oil treatment gave dhal suitable for use in many traditional products. Although chemicals were effective, they had to be used at relatively high concentrations of approximately 5%. It was also found that a steaming time of 10–15 min was adequate to loosen the hull, resulting in easy dehulling. It was concluded that hydrothermal treatment could be used for dehulling black gram. However, hydrothermally pretreated dhal was not suitable for fermented products, in which case a conventional oil pretreatment method should be used with sesame oil preferred.

PRACTICAL APPLICATIONS

This study shows the effects of different premilling treatments on dehulling black gram. Black gram dehulling efficiency can be enhanced by premilling treatments such as dry method, chemical method or hydrothermal treatment. For practical application, it is important to give due consideration to the end product use of dehulled black gram. Hydrothermal treatment for 10 min is suitable for dehulling black gram if the finished product is used for nonfermented products, and dry method with sesame oil concentration of 0.4% w/w would suit both fermented as well as nonfermented products. This study could be used by black gram processors for optimizing process conditions and premilling treatment.     

Effect of high pressure on the dielectric properties of relaxor compositions [Pb(Fe1/2Nb1/2)O3]1-x-y-[Pb(Zn1/3Nb2/3)O3]x- [BaTiO3]y

Abstracts are not published in this journal     

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.     

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.     

Preparation and properties of acrylonitrile–butadiene rubber–graphene nanocomposites

The graphene oxide (GO) was prepared by sonication‐induced exfoliation from graphite oxide, which was produced by oxidation from graphite flakes with a modified Hummer's method. The GO was then treated by hydrazine to obtain reduced graphene oxide (rGO). On the basis of the characterization results, the GO was successfully reduced to rGO. Acrylonitrile–butadiene rubber (NBR)–GO and NBR–rGO composites were prepared via a solution‐mixing method, and their various physical properties were investigated. The NBR–rGO nanocomposite demonstrated a higher curing efficiency and a change in torque compared to the gum and NBR–GO compounds. This agreed well with the crosslinking density measured by swelling. The results manifested in the high hardness (Shore A) and high tensile modulus of the NBR–rGO compounds. For instance, the tensile modulus at a 0.1‐phr rGO loading greatly increased above 83, 114, and 116% at strain levels of 50, 100, and 200%, respectively, compared to the 0.1‐phr GO loaded sample. The observed enhancement was highly attributed to a homogeneous dispersion of rGO within the NBR matrix; this was confirmed by scanning electron microscopy and transmission electron microscopy analysis. However, in view of the high ultimate tensile strength, the NBR–GO compounds exhibited an advantage; this was presumably due to strong hydrogen bonding or polar–polar interactions between the NBR and GO sheets. This interfacial interaction between GO and NBR was supported by the marginal increase in the glass‐transition temperatures of the NBR compounds containing fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42457.