A Bayesian machine learning method for sensor selection and fusion with application to on-board fault diagnostics

In applications like feature-level sensor fusion, the problem of selecting an optimal number of sensors can lead to reduced maintenance costs and the creation of compact online databases for future use. This problem of sensor selection can be reduced to the problem of selecting an optimal set of groups of features during model selection. This is a more complex problem than the problem of feature selection, which has been recognized as a key aspect of statistical model identification. This work proposes a new algorithm based on the use of a Bayesian framework for the purpose of selecting groups of features during regression and classification. The hierarchical Bayesian formulation introduces grouping for the parameters of a generalized linear model and the model hyper-parameters are estimated using an empirical Bayes procedure. A novel aspect of the algorithm is its ability to simultaneously perform feature selection within groups to reduce over-fitting of the data. Further, the parameters obtained from this algorithm can be used to obtain a rank order among the selected sensors. The performance of the algorithm is first tested on a synthetic regression example. Finally, it is applied to the problem of fault detection in diesel engines (30,000 data records from 43 sensors, 8 classes) and used to compare the misclassification rates with a varying number of sensors.     

Charge transport and ammonia sensing properties of flexible polypyrrole nanosheets grown at air–liquid interface

Flexible polypyrrole nanosheets (thickness ∼150 nm) grown at the air–liquid interface have been investigated for charge transport and NH₃ sensing application. Polypyrrole nanosheets films exhibited a uniform and dense morphology. Temperature dependent charge transport measurements revealed that the PPy films obey Mott's 3-D variable range hopping mechanism. The mobility values calculated using temperature dependent current voltage characteristics indicated them to obey Arrhenius behaviour. These films exhibited a reversible response towards NH₃ at room temperature. The sensor exhibited a sensitivity of ∼12% with a typical response and recovery times of 240 s and 50 min, respectively towards 50 ppm of NH₃. Raman studies indicated that there is an increase in the antisymmetrical C–N stretching upon exposure to higher concentration of NH₃ (500 ppm) and could be assigned to the interaction of NH₃ with the carbon backbone of PPy film. Our results clearly emphasize that these flexible PPy films could be used to realize flexible sensors.     

Thermal and mechanical characterization of poly(methyl methacrylate) nanocomposites filled with TiO2 nanorods

Thick films of nanocomposites made of poly(methyl methacrylate) matrix and colloidal anatase TiO₂ nanorods fillers were prepared by solvent mixing and solution drop casting. Different concentrations of nanorods were tested in order to examine the influence of the nanoscale fillers on the composites material properties and structure. The thermal properties of the samples were investigated through thermogravimetric analysis, which showed an increase in thermal stability of the nanocomposites on increasing nanorods concentration, for the range of concentrations used. The viscoelastic properties were investigated through dynamic mechanical analysis, which showed an increase in both the storage and loss modulus on increasing nanorods concentration. The in-depth distribution of the TiO₂ nanorods in the matrix was evaluated through cross-sectional transmission electron microscopy, which pointed out a uniform dispersion of mesoscale nanorods agglomerates with increasing diameter of 100–200 nm range on increasing nanorods concentration.     

Numerical Study and Experimental Validation of Effect of Varying Fiber Crack Density on Stiffness Reduction in CFRP Composites

Representative volume element (RVE) has commonly been used to predict the stiffness of undamaged composite materials using finite element analysis (FEA). However, never has been an independently measured true microstructural damage quantity used in FEA to predict composite stiffness. Hence, in this work, measured fiber crack density in unidirectional fiber composite (generated using controlled fatigue loading) was used to predict reduction in stiffness using a RVE. It was found that the stiffness changes with change in depth of the volume element along the fiber direction and asymptotically reaches a constant value beyond a critical length called representative depth. It was argued that this representative depth should be more than the minimum of two characteristic length scales, twice of ineffective length and average length of broken fibers. Effective stiffness obtained from FEA of the optimum-sized RVE was in excellent agreement with the experimental results for given microstructural damage state.     

Synthesis of Biopolymer‐Derived Zirconium Carbide Powder by Facile One‐Pot Reaction

Zirconium carbide (ZrC) was synthesized by polycondensation and carbothermal reduction reactions from an organic–inorganic hybrid complex. A natural biopolymer Gum Karaya (GK) and zirconyl oxychloride octahydrate (ZOO) were used as the sources of carbon and zirconium, respectively. FTIR of as‐synthesized dried complexes revealed formation of Zr–O. Pyrolysis of the complexes at 1200°C/1 h under argon resulted in tetragonal and monoclinic zirconia which after heat treatment at 1400°C–1550°C transformed to zirconium carbide. Thermal analysis shows that the GK–ZOO complexes lost less mass than the pristine GK to 600°C. The intensity of exothermic decomposition decreases and shifted to higher temperature for the hybrid complexes indicating that zirconia induced thermal stability. A maximum ZrC yield of ~60 wt% is obtained for the intermediate GK–ZOO ratio of 1:2. Particles pyrolyzed for 1 h at 1550°C were coarser (5–10 μm) with flakes for lower GK–ZOO weight ratio, but were spheroidal with narrow size distribution (~1 μm) with increasing GK–ZOO weight ratio.     

Post-consumer Recycled PET Packaging for Fresh Berries: A Comparative Study between Incorporating an Antifungal Agent Superficially and into the Main Body of the Packaging

This study proposes to incorporate an antifungal agent (potassium sorbate, KS) to post-consumer recycled polyethylene terephthalate (PCRPET), by adding KS to the dip solution through which PCRPET normally passes after extrusion, in order to acquire a non-stick silicone coating, which prevents individual packages from adhering to each other while stacked. This method of imparting antifungal activity to the packaging is far more advantageous than adding KS to the extruder feed because it results in virtually no alterations to the colour and mechanical properties of PCRPET, which is a major issue when KS is added to the extruder feed. The antifungal efficacy of the active packaging was demonstrated against Botrytis cinerea growth by a novel method which mimics the action of the antifungal agent under fruit contact conditions. A reduction by 2 log cycles was observed when the initial concentration of the mould was 10⁵ conidia/mL. The active packaging was effective over a test period lasting 6 months. The packaging microstructure was visualized by scanning electron microscopy (SEM); its thermal properties were characterized using a differential scanning calorimeter (DSC); its optical properties were characterized using CIE Lab colorimetry; and its mechanical properties were characterized by measuring resistance to dynamic compression. The mechanical properties showed no significant difference (P?>?0.05) with those of the control (PCRPET without KS), and despite a statistically significant difference (P?<?0.05) in the colour parameters (L*, a* and b*), the total colour difference (ΔE*) was found to be too small to be visually noticed. This study achieved the aim of adding antifungal activity to PCRPET packaging with little or no perceptible changes to its mechanical, thermal and optical properties and virtually no changes being made to the standard high-speed packaging production line.     

Mathematical aspects of Rietveld refinement and crystal structure studies on PbTiO3 ceramics

The core mathematics, goodness-of-fit parameters of Rietveld refinement technique is introduced for structural analysis of crystalline materials not available as single crystals. X-ray diffraction (XRD) patterns of PbTiO₃ compound prepared by following solid-state route, suggests it to be in single crystal form. All the observed peaks could be indexed to P4mm space group with tetragonal symmetry. XRD pattern is analysed by employing Rietveld method. The unit cell parameters are found to be a = b = 38987 (0.0008) Å and c = 4·1380 (0·0009) Å. The axial ratio c/a and unit cell volume are found to be 1·0614 and 62·896 (0.023) ų. Bond lengths and angles are calculated using the cell parameters. Using the Rietveld refinement parameters a stable PbTiO₃ structure is suggested.     

Indian thermal power plant challenges and remedies via application of modified data envelopment analysis

This paper evaluates the performance of coal‐fired thermal power plants in India for the year 2008–2009 using data envelopment analysis (DEA); subdividing the power plants into three categories depending on their scale—small, medium, and large. The classical DEA model is analyzed to identify the efficient ones from the whole gamut of plants run by various organizations of the central government, state government, and private sector. Slack analysis is carried out to explore the specific areas that need to be focused on, in quantitative terms, for the overall efficiency improvement. Further efficiency evaluation is extended from a single criterion‐based conventional approach to a multiple criteria oriented approach, and the resulting DEA models are more efficient and flexible in many aspects, particularly in discriminant and weight analysis. Results of multicriteria DEA (MCDEA) are substantiated with cross‐efficiency analysis by deploying the weights obtained by the MCDEA in the cross‐efficiency analysis. On the basis of the insights provided by the outcome of the analysis, both qualitative and quantitative measures are proposed for improvement of the plant performances. The result of this analysis may assist the management of the power plants to introspect and review their systems and processes for optimal use of resources. The methodology adopted in the present work can also be employed for deeper understanding of power plants in other parts of India as well as in other countries.     

Vegetable oil based highly branched polyester/clay silver nanocomposites as antimicrobial surface coating materials

The unison of nanotechnology and polymer science enables the development of novel silver-based polyester nanocomposite as an antimicrobial coating material. Highly branched polyester/clay silver nanocomposites based on vegetable oil with different loadings of silver were prepared via reduction of silver salt by employing dimethylformamide as solvent as well as reducing agent at room temperature. Organically modified montmorillonite clay of 2.5 wt% was used as the nanofiller for the property improvement of the pristine polymer. The highly branched polyester resin was synthesized by condensation of 2,2-bis(hydroxymethyl) propionic acid with Mesua ferrea L. seed oil based carboxyl terminated pre-polymer, as reported earlier. FTIR, UV–vis, XRD, SEM and TEM studies substantiate the formation of well-dispersed silver nanoparticles within the clay gallery with an average size of 15 nm. The thermostability of the silver nanocomposites obtained by thermogravimetric analysis was enhanced by 20 °C. The mechanical properties such as tensile strength and scratch hardness were improved 4.5 and 2.6 units respectively and impact resistance improved a little by nanocomposites formation. The antimicrobial efficacy of the as-prepared silver nanocomposites was also premeditated and highly antibacterial activity against Gram negative bacteria (Escherichia coli and Psuedomonas aeruginosa) was observed. Excellent chemical resistance in various chemical media except in alkali has also been noticed. The study reveals that the polyester/clay silver nanocomposites based on vegetable oil show the potential to be applicable as antibacterial surface coating materials.     

Catalytically Active Vegetable‐Oil‐Based Thermoplastic Hyperbranched Polyurethane/Silver Nanocomposites

Sunflower oil‐based HBTPU/Ag and LTPU/Ag nanocomposites have been prepared by in situ catalytic reduction of a silver salt. The virgin polymer and their nanocomposites are soluble in various polar organic solvents and amenable for both solution‐casting and hot pressing. XRD, TEM, and UV spectroscopic analyses ascertained well‐dispersed, narrow‐sized Ag nanoparticles. Tensile testing, dynamic mechanical, thermogravimetric, and DSC analyses showed desirable mechanical and thermal features with improvement upon incorporation of Ag nanoparticles and the presence of a hyperbranched component in the nanocomposites. RSM has been used to evaluate the catalytic efficacy of the nanocomposites.