Thermal Response of Symmetric Cross-Ply Laminated Plates Subjected to Linear and Non-Linear Thermo-Mechanical Loads

The flexural response of symmetric cross-ply laminated plates subjected to uniformly distributed linear and non-linear thermo-mechanical loads is presented using trigonometric shear deformation theory. The in-plane displacement field uses sinusoidal function in terms of thickness coordinate to include the shear deformation effect. The theory satisfies the shear stress-free boundary conditions on the top and bottom surfaces of the plate. The present theory obviates the need of shear correction factor. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. Thermal stresses and displacements for three-layer symmetric square cross-ply laminated plates subjected to uniform linear and nonlinear and thermo-mechanical loads are obtained. The results of present theory are compared with those of classical plate theory, first-order shear deformation theory and higher-order shear deformation theory.     

Switchover Control Strategies for Improving Performance of Refrigeration Systems under Off-Design Conditions

A typical 3-ton vapor compression refrigeration system using R-22 as the refrigerant is addressed. Two models are developed: a design model and a hierarchical control model. The design model is operated to observe the response of a typical system under various off-design operating conditions. In lieu of laboratory experiments, the normalized responses from the design model (normalized with respect to the design conditions) are compared to the normalized values based on the experimental data reported in the literature. This is done to validate the design model to the extent possible, limited by the reported experimental data in the literature. From this design model a hierarchical control model is developed, in which different control techniques for system capacity regulation and for operation over a range of ambient temperature are employed. By varying corresponding control parameters in each technique, information is developed regarding the refrigerant conditions within the system and system performance under different operating conditions. From the results of these simulations, hierarchical or switchover control strategy for an integrated refrigeration system is postulated to achieve the specific operational requirements with the highest feasible system efficiency over a wide range of off-design operating conditions. A similar approach can be used to postulate different hierarchical control based on other performance measures and considerations.     

Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2

Nanocrystalline TiO₂ was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N₂ adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO₂ for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO₂ for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO₂ for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO₂ is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst.     

Assessing manufacturing strategy definitions utilising text-mining

The variations in Manufacturing Strategy (MS) definitions create confusion and lead to lack of shared understanding between academic researchers and practitioners on its scope. The purpose of this study is to provide an empirical analysis of the paradox in the difference between academic and industry definitions of MS. Natural Language Processing (NLP) based text mining is used to extract primary elements from the various academic, and industry definitions of MS. Co-word and Principal Component Analysis (PCA) provide empirical support for the grouping into nine primary elements. We posit from the terms evolution analysis that there is a stasis currently faced in academic literature towards MS definition while the industry with its emphasis on ‘context’ has been dynamic. We believe that the proposed approach and results of the present empirical analysis can contribute to overcoming the current challenges to MS design and deployment – imprecise definition leading to its inadequate operationalisation.     

Effect of Small Amount of Manganese on the Interdiffusivities in Fe-Al Alloys

The ability to weld aluminum and steel sheets depends strongly on the formation of intermetallic phases; a process that is, in turn, controlled by the interdiffusion of iron and aluminum across the welded interface. Understanding the interdiffusion behavior, and how it is influenced by tertiary elements such as manganese, will allow for better prediction of the properties of the spot weld. Hence, interdiffusion coefficients and activation energies for interdiffusion were determined in the α solid solution and B2 intermetallic phases of Fe-Al alloys in the presence of 1.5-2 at.% manganese with pseudo-binary diffusion couples investigated at 900-1095 °C. The interdiffusion coefficients in α were found to increase in the presence of Mn at all temperatures compared with those reported in the binary Fe-Al alloys. The activation energies for interdiffusion in α are correspondingly lower than those in the binary Fe-Al alloys. The increase in the main interdiffusion coefficients in the presence of Mn indicates that diffusional interactions between Fe and Al are increased in the presence of Mn. The expected increase in diffusional interactions of Fe and Al are found to be consistent with the thermodynamic interactions between Fe and Al in the binary Fe-Al and ternary Fe-Al-Mn system as estimated from the literature. The presence of Mn is found to decrease the solubility of Al in the α solid solution, which, in turn, is expected to decrease the growth rate of the intermetallic at the interface between steel and aluminum.     

Multiscale micro-patterned polymeric and carbon substrates derived from buckled photoresist films: fabrication and cytocompatibility

We report here a novel and simple buckling-based multiscale patterning of negative photoresist films which were subsequently pyrolyzed to yield complex micro-patterned carbon surfaces. Unlike other polymers, the use of a photoresist layer allows the overall pattern definition by photolithography on which the geometry and length scale of the buckling-instability are superimposed. The photoresist film swells anisotropically during developing and buckles after subsequent drying due to the difference in the shrinkage of the hard cross-linked layer on top of a softer native pre-polymer. We studied the conditions for the formation of a wide variety of complex, fractal buckling patterns as well as directionally aligned zigzag patterns over a large area. For example, the buckling diminished for the films below a critical thickness and after a prolonged UV exposure, both of which eliminate the softer under-layer. These patterned carbon substrates are also shown to be biocompatible for the cellular adhesion and viability by using L929 mouse fibroblast cells, thus indicating their potential use in bio-MEMS platforms with a conductive substrate. The buckled carbon patterns were found to be a better choice of a substrate for cell growth and viability as compared to flat and simply periodic patterned carbon surfaces.     

Mixed ionic electronic conducting perovskite anode for direct carbon fuel cells

The conversion of carbonaceous materials to electricity in a Direct Carbon Fuel Cell (DCFC) offers the most efficient process with theoretical electric efficiency close to 100%. One of the key issues for fuel cells is the continuous availability of the fuel at the triple phase boundaries between fuel, electrode and electrolyte. While this can be easily achieved with the use of a porous fuel electrode (anode) in the case of gaseous fuels, there are serious challenges for the delivery of solid fuels to the triple junctions. In this paper, a novel concept of using mixed ionic electronic conductors (MIEC) as anode materials for DCFCs has been discussed. The lanthanum strontium cobalt ferrite, La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) was chosen as the first generation anode material due to its well known high mixed ionic and electronic conductivities in air. This material has been investigated in detail with respect to its conductivity, phase and microstructural stability in DCFC operating environments. When used both as the anode and cathode in a DCFC, power densities in excess of 50 mW/cm² were obtained at 804 °C in electrolyte supported small button cells with solid carbon as the fuel. The concept of using the same anode and cathode material has also been evaluated in electrolyte supported thick wall tubular cells where power densities around 25 mW/cm² were obtained with carbon fuel at 820 °C in the presence of helium as the purging gas. The concept of using a mixed ionic electronic conducting anode for a solid fuel, to extend the reaction zone for carbon oxidation from anode/electrolyte interface to anode/solid fuel interface, has been demonstrated.     

Lightweight proactive queue management

The quest for better resource control has been the driving force behind Active Queue Management (AQM) research. Random Early Detection (RED), the defacto standard and its variants have been proposed as simple solutions to the AQM problem. These approaches, however, are known to suffer from problems like parameter sensitivity and inability to capture input traffic load fluctuations accurately, thereby resulting in instability. This paper presents a proactive queue management algorithm called PAQMAN that captures input traffic load fluctuations accurately and regulates the queue size around the desirable level. PAQMAN draws from the predictability in the underlying traffic by employing the Recursive Least Squares (RLS) algorithm to forecast the average queue size over the next prediction interval using the average queue size information of the past intervals. The packet drop probability is then computed as a function of this predicted average queue size. The performance of PAQMAN has been evaluated and compared against existing AQM schemes through ns-2 simulations that encompass varying network conditions for networks comprising of single as well as multiple bottleneck links. Simulation results demonstrate that PAQMAN maintains a relatively low queue size, while at the same time achieving high link utilization and low packet loss. Moreover, the computational overhead of PAQMAN is negligible (lightweight) which further justifies its use.     

A very large scale neighborhood search algorithm for the q-mode problem

The q-mode problem is a combinatorial optimization problem that arises in the context of partitioning a given collection of data vectors with categorical attributes. A neighborhood search algorithm is proposed for solving the q-mode problem. This algorithm is based on a very large scale neighborhood that is implicitly searched using network flow techniques. The algorithm is evaluated through a computational experiment using randomly generated instances. The results show that in general this algorithm obtains very-good-quality local optima, and that in instances with strong natural clusters the algorithm consistently finds optimal or near-optimal solutions.     

Improved FEM model for defect-shape construction from MFL signal by using genetic algorithm

In-line inspection of ferromagnetic gas or oil pipe lines having pipe wall defects is typically accomplished using magnetic flux leakage (MFL) technique. An efficient modelling and computational scheme for forward model, during the process of solving inverse problems in magnetostatic non-destructive evaluation using finite-element method is presented. The shape, size and place of defect are determined considering the nonlinearity of the pipe material using genetic algorithm as the optimisation technique. It is shown that the reduced model improves the FE computations significantly. The methodology for construction of defect shapes from particular MFL signals has been explained