Bounding algorithms for two-terminal network reliability

Determining the exact reliability of a complex network involves extremely large amount of computation. Consequently, it is appropriate to discuss method for approximating network reliability. This paper develops methods for obtaining upper and lower bounds for two-terminal network reliability. Construction of different layers for a network is used to develop an algorithm to compute an upper bound for the reliability of a network. The nodes of this network are completely reliable and arcs fail statistically independently with known probabilities. A simple approach, to obtain a lower bound for the reliability of the network is also presented. Examples illustrate the use of the algorithms and show that the proposed bounds fare better than the well-known Esary and Proschan bounds.     

Anaerobic co-digestion of hazardous tannery solid waste and primary sludge: biodegradation kinetics and metabolite analysis

Generation of solid waste is inherent to manufacture of leather from skin and hide. Solid wastes generated at various unit operations of the tanning process considerably vary in quantity and composition. Fleshing is a type of animal tissue waste generated during the preparatory leather processing stage in relatively larger quantities as compared to other types of solid waste in the tanning industry. Fleshing mainly contains fat and protein and residual chemicals such as lime and sulphide used in the ‘unhairing’ process of beam house operation. Another type of solid waste in tanning industry which requires safe disposal is the primary sludge from tannery wastewater treatment plant. This study shows that both fleshing and primary sludge contains a significant quantity of volatile solids amenable for biodegradation. Different proportions of waste fleshing and primary sludge were subjected to anaerobic digestion. The studies were carried out in a laboratory scale reactor with an aim of developing an appropriate technology for recovery of bioenergy from the waste and subsequently ensure their safe disposal. Volatile solid destruction between 41 and 52%, specific gas production between 0.419 and 0.635 l/g volatile solids feed and methane yield between 71 and 77% were achieved. Further, the biomethanation potential of animal fleshing and substrate specific kinetics of the reaction process were also examined.     

A Lightweight Cryptography Technique with Random Pattern Generation

Wireless Personal Communications - The lightweight cryptography (LWC) is an interesting research area in the field of information security. So, different lightweight mechanisms have been developed...     

Low-Temperature High-Pressure Consolidation of Amorphous Al2O3–15 mol% Y2O3

This study examined pressure consolidation of amorphous Al₂O₃–15 mol% Y₂O₃ powders prepared by co-precipitation and spray pyrolysis. The two amorphous powders had similar true densities and crystallization sequences. Uniaxial hot pressing was carried out at 450°–600°C with a moderate pressure of 750 MPa. The co-precipitated powder could be hot pressed to a maximum relative density of 98% and remained amorphous. Pressure adversely affected the densification of the spray-pyrolyzed powder by favoring an early crystallization of γ-Al₂O₃ phase at 580°C. Plastic deformation of the amorphous phase is believed to be responsible for the large densification of the amorphous powders.     

Evaluation of elastic properties of reduced NiO-8YSZ anode-supported bi-layer SOFC structures at elevated temperatures in ambient air and reducing environments

Elastic properties of Ni-8YSZ anode-supported bi-layer SOFC structures were studied at elevated temperatures up to 1,000 °C in both ambient air and H₂ environments. The anode samples with desired porosity and microstructure were fabricated by reducing a NiO-8YSZ anode precursor structure in a gas mixture of 5% H₂–95% Ar at 800 °C for selected time periods up to 8 h. The development of the essential porous microstructure in forming the Ni-8YSZ cermet phase was analyzed with SEM. It was observed that the room temperature elastic moduli and hardness of the anode samples decrease significantly with increasing fraction of reduced NiO. Since the elastic properties of fully dense Ni, NiO, and 8YSZ are comparable to each other, the decrease in the magnitude in elastic moduli and hardness is evidently due to the colossal increase in porosity in the reduced Ni-8YSZ cermet anodes because of the reduction of NiO to Ni. At elevated temperatures, the Ni-8YSZ anodes show a complex profile of Young’s modulus as a function of temperature, which is significantly different from the unreduced NiO-8YSZ samples. When studied in ambient air, the Young’s modulus of the Ni-8YSZ samples decrease slowly up to ~250 °C, then more rapidly from 250 to 550 °C, and finally it increases monotonically with the increase in temperature. However, in reducing environment, the Young’s moduli values decrease continuously throughout the temperature range. Two sets of samples of different thicknesses were studied simultaneously to highlight the effects of the sample thickness on the elastic properties of the anodes.     

Studies on phase formation,microstructure development and elastic properties of reduced NiO–8YSZ anode supported bi-layer half-cell structures of solid oxide fuel cells

Half-cell structures of solid oxide fuel cells (SOFCs) with a thin and dense electrolyte layer of 8YSZ supported by a thick and porous NiO–8YSZ anode precursor structure were reduced in a gas mixture of 5% H₂–95% Ar at 800 °C for selected time periods in order to fabricate cermets with desired microstructure and composition, and to study their effects on the elastic properties at ambient and reactive atmospheres. It appears that 2 h of exposure to the reducing conditions is enough to reduce ～80% of NiO with an enhanced porosity value of 35%. The Ni–8YSZ cermet phase formation in the anode was analyzed with X-ray diffraction (XRD) in correlation with its microstructure. The elastic properties were determined after the reduction, at room and elevated temperatures using the impulse excitation technique. At room temperature the decrease in the Young's modulus was about 44% (after 8 h of reduction) and can be attributed mainly to the changes in the microstructure, particularly the increase in porosity from ～12% to 37%. Young's moduli of the as-received precursor and reduced anodes were evaluated as a function of temperature in air and reducing atmosphere. The results were explained in correlation to the initial porosity, composition and oxidation of Ni at the elevated temperatures.     

Inhibition of proteases during fermentation improves xylanase production by alkali tolerant Aspergillus fumigatus ARl

An alkali-tolerant Aspergillus fumigatus ARl produced a high level of xylanase (228 U/ml) at 42 h of submerged fermentation at pH 9.0. During later culture periods, xylanase activity declined considerably and reached 45 U/ml at 90 h. This trend is because of proteolytic degradation of xylanases since A. fumigatus co-produced multiple proteases with high activity (120-159 U/ml) during submerged fermentation. Xylanase and protease were found to be active over a wide range of pH from 5.5 to 9.0. In contrast, protease lost its activity completely in the presence of CuSO4 (25 mM) while xylanase remained active. The selective inhibition of proteases by the addition of CuSO4 to the culture medium prevented proteolytic degradation of xylanase and improved the production of xylanase by 3-fold.     

Assessment of availability of a Fluid Catalytic Cracking Unit through simulation

This paper presents a systematic approach to estimate the availability of process plants. The study includes a live problem at a Fluid Catalytic Cracking Unit (FCCU) of a refinery requiring high levels of availability for cost-effective operation. The system is modelled as a fault tree which is often used in the analysis of chemical process industries. A numerical evaluation of the fault tree assesses the characertistic safety parameters such as reliability and availability of the system. However, for large and complex systems, such analysis will normally require enormous computational effort, involving the breakdown of the fault tree into minimal cut sets. An alternative approach is to simulate the system using the Monte Carlo method. This paper presents an availability analysis of the Reactor/Regenerator system of the Fluid Catalytic Cracking Unit using the Monte Carlo simulation. The results of the simulation are validated by a comparison with the actual system. The method promises to be a useful tool for assessing the availability of complex systems with alternative configurations.     

Advance electrochemical oxidation of fipronil contaminated wastewater by graphite anodes and sorbent nano hydroxyapatite

Degradation of C₁₂H₄Cl₂F₆N₄OS phenylpyrazole insecticide (Fipronil) by advance electrochemical oxidation in aqueous water solution was studied. The process efficiency was figured based on the COD, chloride, and fluoride reduction from fipronil. Further, we tried to highlight the importance of nano-hydroxyapatite (n-Hap) as a cost-effective nano sorbent for removal of fluoride from fipronil. From the advance electrochemical oxidation experiment, it was found that the COD removal was 79%, chloride 52%, and fluoride 80%. The intermediate of fipronil compounds was examined by GC-MS. The final results conclude that advance electrochemical oxidation process was effective for removal of fipronil synthetic wastewater.