Thermal analysis of graphite intercalation compounds with FeCl3

The behaviour of graphite intercalation compounds with FeCl₃ (1st and 2nd stages) was characterized by a number of thermal analysis methods up to 800 K. The compounds were shown to undergo reversible solid phase transformations and were subjected to thermal destruction. Temperature, kinetic, and energy characteristics of thermally stimulated processes in the compounds under different ambient conditions are given. An assumption is made about a pyrolysis mechanism for different temperature ranges. A conclusion is drawn about the slightly higher thermal stability of the 2nd stage as compared with the 1st stage graphite intercalation compounds with FeCl₃.     

GA and Lyapunov theory-based hybrid adaptive fuzzy controller for non-linear systems

In this present article, a new hybrid methodology for designing stable adaptive fuzzy logic controllers (AFLCs) for a class of non-linear system is proposed. The proposed design strategy exploits the features of genetic algorithm (GA)-based stochastic evolutionary global search technique and Lyapunov theory-based local adaptation scheme. The objective is to develop a methodology for designing AFLCs with optimised free parameters and guaranteed closed-loop stability. Simultaneously, the proposed method introduces automation in the design process. The stand-alone Lyapunov theory-based design, GA-based design and proposed hybrid GA–Lyapunov design methodologies are implemented for two benchmark non-linear plants in simulation case studies with different reference signals and one experimental case study. The results demonstrate that the hybrid design methodology outperforms the other control strategies on the whole.     

Electron Microscopic Study on the Suction Cast In Situ Ti-Fe-Sn Ultrafine Composites

The current investigation reports detailed study on the microstructural evolution in the suction cast hypereutectic Ti₇₁Fe_29?x Sn _x alloys during Sn addition with x = 0, 2, 2.5, 3, 3.85, 4.5, 6, and 10 at. pct and the solidification of these ternary alloys using SEM and TEM. These alloys have been prepared by melting high-purity elements using vacuum arc melting furnace under high-purity argon atmosphere. This was followed by suction casting these alloys in the water-cooled split Cu molds of diameters, ? = 1 and 3 mm, under argon atmosphere. The results indicate the formation of binary eutectic between bcc solid solution ??-Ti and B2 FeTi in all alloys. ??-Ti undergoes eutectoid transformation, ??-Ti ?? ??-Ti + FeTi, during subsequent solid-state cooling, leading to formation of hcp ??-Ti and FeTi. For alloys x < 2, the primary FeTi forms from the liquid before the formation of eutectic with minute scale Ti₃Sn phase. For alloys with 2 ?? x ?? 10, the liquid is found to undergo ternary quasi-peritectic reaction with primary Ti₃Sn, L+Ti₃Sn ?? ??-Ti+FeTi, leading to formation of another kind of FeTi. In all the other alloy compositions (3.85 ?? x ?? 10), Ti₃Sn and FeTi dendrites are observed in the suction cast alloys with profuse amount of Ti₃Sn being formed for alloys with x ?? 4.5. The current study conclusively proves that the liquid undergoes ternary quasi-peritectic reaction involving four phases, L + Ti₃Sn ?? ??-Ti + FeTi, which lies at the invariant point Ti_69.2±0.8Fe_27.4±0.7Sn_3.4±0.2 (denoted by P). Below P, there is one univariant reaction, i.e., L ?? ??-Ti + FeTi for all alloy compositions, whereas above P, liquid undergoes one of the univariant reactions, i.e., L + ??-Ti ?? Ti₃Sn (Sn = 2, 2.5, 3, and 4.5 at. pct) or L + FeTi ?? Ti₃Sn for alloys (Sn = 6, 10 at. pct). For alloy with Sn = 3.85 at. pct, the ternary quasi-peritectic reaction is co-operated by two monovariant eutectic reactions, i.e., L ?? ??-Ti + FeTi below P and L ?? FeTi + Ti₃Sn above P. Detailed microstructural information allows us to construct liquidus projection of the investigated alloys. The results are critically discussed in the light of available literature data.     

Hybrid A–B–A type nanowires through cation exchange

Hybrid A–B–A type nanowires (NWs) with Ag5Te3–HgTe–Ag5Te3 composition have been created by the reaction of Hg2+ with Ag2Te NWs. The NW morphology of Ag2Te is preserved upon reaction with minor changes and the two separate phases formed are spatially separated within the same NW. The reaction of Hg2+ with Ag2Te NWs was monitored at different concentrations and the reactivity was attributed to cationic exchange depending on solubility products. Hybrid NWs were formed by partial cation exchange only at low concentrations (below 50 ppm) resulting in Ag5Te3 and HgTe within the same NW. However, at high concentrations (above 100 ppm), the HgTe phase alone was formed. These studies have been extended to other metal ions such as Pb2+, Cd2+, and Zn2+ whose reactivity towards Ag2Te NWs is different from that of Hg2+. These ions form a passivating Te oxide layer upon reaction with other metal ions. The mechanism of reactivity of Hg2+ is explained on the basis of free energy of formation of the ionic solid. Phase transition of Hg2+-reacted NWs occurs at a lower temperature than the parent (Ag2Te NWs) and other metal ions-reacted Ag2Te NWs. Details of the process were elucidated using microscopic and spectroscopic investigations. The physical and chemical properties of the individual components within a NW are expected to provide a novel functionality to the metal chalcogenide systems.     

Fabrication of fluoropolymer-modified hydrophobic functionalization of cotton fabric by admicellar polymerization

Herein, a hydrophobic polyfluoroacrylate adhered cotton fabric having a smart affair with water under oil, is developed using a simple surfactant-assisted polymerization technique commonly known as admicellar polymerization of low surface energy trifluoroethyl acrylate monomer. The hydrophobicity of the treated substrates was determined by the contact angle. The results show that the cotton fabric became hydrophobic. The surface investigation conducted by scanning electron microscopy (SEM) provided distinctive features of the untreated and treated fabric samples. The elementary analysis was also carried out on the substrate through energy dispersive X-ray to confirm the presence of hydrophobic groups. In addition to this, the hydrophobic cotton fabric shows excellent durability against home laundering and simple adhesive peel testing.     

Prediction of bed pressure drop and top packed bed formation in gas-liquid-solid semi-fluidized bed with irregular homogeneous binary mixtures

We studied the hydrodynamics of a gas-liquid-solid semi-fluidized bed relating to packed bed formation and bed pressure drop with irregular homogeneous binary mixtures in a 0.05 m internal diameter Perspex column, with water and air (secondary) as fluidizing medium at constant static bed height of 0.08 m. A homogeneous binary mixture has been taken for easy formation of a semi-fluidized bed. Air is supplied centrally below the bottom grid in radial direction with a special design air sparger after the bed is first fluidized by the liquid. Experimental parameters studied included superficial gas and liquid velocities, average particle size and density and the bed expansion ratio. Empirical and semi-empirical models were developed. The calculated values from predicted models were compared with the experimental values and fairly good agreement was obtained.     

Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.     

Code Based Analysis for Object-Oriented Systems

Tile basic features of object-oriented software makes it difficult to apply traditional testing methods in objectoriented systems. Control Flow Graph （CFG） is a well-known model used for identification of independent paths in procedural software. This paper highlights the problem of constructing CFG in object-oriented systems and proposes a new model named Extended Control Flow Graph （ECFG） for code based analysis of Object-Oriented （OO） software. ECFG is a layered CFG where nodes refer to methods rather than statements. A new metrics Extended Cyclomatic Complexity （E-CC） is developed which is analogous to McCabe＇s Cyclomatic Complexity （CC） and refers to the number of independent execution paths within the OO software. The different ways in which CFG＇s of individual methods are connected in an ECFG are presented and formulas for E-CC for these different cases are proposed. Finally we have considered an example in Java and based on its ECFG, applied these cases to arrive at the E-CC of the total system as well as proposed a methodology for calculating the basis set, i.e., the set of independent paths for the OO system that will help in creation of test cases for code testing.     

Isolation and characterization of biosurfactant producing microorganisms from petroleum contaminated soil samples for EOR and bioremediation

Using of biosurfactant producing microorganisms for pipeline cleaning, bioremediation, enhanced oil recovery, etc. is a much soughed approach of petroleum industry. Although, many alternatives are available to serve these purposes, being ecofriendly and economic, microbial application is considered superior than most of the alternatives. This paper presents a comprehensive study on effectiveness of bacterial strain isolated from oil contaminated soil sample of Lakwa oilfield for required purposes. Its temperature sustainability and surfactant production capability was studied. Further characteristics of the produced biosurfactant were assessed through Emulsification Index measurement, Fourier Transform Infrared Spectra, Drop Collapse Test, Contact Angle and Viscosity measurement.     

Suitability of Miniature Tensile Specimens for Estimating the Mechanical Property Data of Pressure Tubes: An Assessment

The integrity assessment of nuclear reactor pressure tubes (PTs) used in pressurized heavy water reactors necessitates the determination of their tensile property data. This in turn will require the employment of appropriate specimens that can be fabricated from them. If this is to be done on the material in the irradiated condition it will be essential to resort to sub-size or miniature sized specimens which need to be designed and tested to prove its efficacy in providing the correct output. With this aim in view two different sheet type tensile specimens were designed for estimating the tensile property data of both axial and circumferential directions of the PT. As the raw material was in the form of tube, sheath type tensile specimens with 25 mm gauge length and having the full thickness of the tube were designed for axial direction of the PT as per the broad guidelines of ASTM Std. A370 and tested as per ASTM Std. E8. Thus the output generated from the axial sheath tensile specimens would serve the purpose of providing standard and reliable tensile property data of the material and that too at the component level. The data from the axial sheet tensile specimens were found to match very well when compared with those from the sheath specimens thus proving not only the veracity of the data but also the transferability of such data from miniature specimens to that at the component level. Hence, sheet tensile specimens prepared in the circumferential direction of the PT alone were utilized to obtain the transverse tensile property data of the PT. This approach was employed in the case of both Zr-2 and Zr-2.5 % Nb PTs in the un-irradiated condition.