Onset of thermal instability in a horizontal layer of fluid with modulated boundary temperatures

Thermal instability in a horizontal layer of fluid, with the boundary temperatures modulated sinusoidally in time, is studied. The amplitude of modulation is assumed small and is used as an expansion parameter. It is shown that an exact solution can be obtained, even when the boundaries are considered to be rigid. When only the lower boundary temperature is modulated, for small values of the Prandtl number modulation is always stabilizing, while for large values it can be stabilizing or destabilizing depending on the modulation frequency. When both boundary temperatures are modulated in phase, modulation is destabilizing for low modulation frequency, but for higher modulation frequency stabilization occurs for low values of the Prandtl number. When the two boundary temperatures are modulated out of phase the modulation always has a stabilizing effect.     

Integrating ABM/TOC approaches for performance improvement: A framework and application

During the last 20 years, new philosophies such as the Theory of Constraints (TOC) and Activity-Based Management (ABM) have emerged as viable, distinct alternatives for measuring and improving the performance of world-class manufacturing companies. In the early phase of their evolution, these philosophies differed fundamentally in their approaches; but there is increasing evidence that both philosophies have now evolved to a stage where an integrated framework can be developed for enhancing cross-functional coordination, thereby improving organizational performance. In this paper, a general framework is presented that integrates the basic concepts, as well as recent advances of TOC and ABM philosophies, into a cohesive framework that can be used to guide performance improvement initiatives . A successful implementation in a world-class manufacturing company is described to validate the framework and to demonstrate that these philosophies can indeed work together in positive ways. Insights are provided into the reasons for implementing such an integrative framework, e.g. identifying the most profitable mix of products, allocating scarce resources optimally, establishing priorities for process improvements, analysing the strategic investment (or expansion) alternatives, and exploiting new market segments.     

Stress-intensity factors for a wide range of semi-elliptical surface cracks in finite-thickness plates

Surface cracks are among the more common flaws in aircraft and pressure vessel components. Accurate stress analyses of surface-cracked components are needed for reliable prediction of their crack growth rates and fracture strengths. Several calculations of stress-intensity factors for semi-elliptical surface cracks subjected to tension have appeared in the literature. However, some of these solutions are in disagreement by 50–100%.

In this paper stress-intensity factors for shallow and deep semi-elliptical surface cracks in plates subjected to tension are presented. To verify the accuracy of the three-dimensional finite-element models employed, convergence was studied by varying the number of degrees of freedom in the models from 1500 to 6900. The 6900 degrees of freedom used here were more than twice the number used in previously reported solutions. Also, the stress-intensity variations in the boundary-layer region at the intersection of the crack with the free surface were investigated.     

Lanthanum samarium oxalate — its growth and structural characterization

Lanthanum samarium oxalate (LSO) single crystals are grown in silica gels by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and samarium nitrate into the test tube having the set gel impregnated with oxalic acid. Tabular crystals of LSO having well defined hexagonal basal planes are observed at different depths inside the gel. LSO crystals grown by this method are colourless and transparent. Laue transmission X-ray diffraction pattern of LSO reveals well defined spots with two-fold symmetry along the horizontal axis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) support that LSO loses water around 120°C, and CO and CO₂ around 350–450°C. The infrared (IR) absorption spectrum of LSO establishes the presence of oxalate (C₂ O₄)²⁻ ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Sm in the sample. X-ray photoelectron spectroscopic (XPS) studies of LSO confirm the presence of La and Sm in their respective oxide states. An empirical structure for LSO has been proposed on the basis of these findings.     

Electrochemical recovery of silver from waste aqueous Ag(I)/Ag(II) redox mediator solution used in mediated electro oxidation process

The paper presents a process for the electrochemical recovery of silver(Ag) by electro deposition on the electrode surface from the waste solutions of Ag(I)/Ag(II) redox system in nitric acid medium used for the mediated electrochemical process. Electrochemical recovery was carried out in an undivided cell with DSA-O₂ electrodes at room temperature condition. At an optimized current density of 12 A/dm², 99% of Ag recovery efficiency was achieved with high yield and low energy consumption. Experimental runs were made in order to observe the performance of the Ag recovery process. The operating conditions like current density, temperature and Ag(I) concentration of the electrolyte, the acid concentrations, agitation rate and inter-electrode distance were optimized.     

Applicability and evaluation of an implicit self-starting unconditionally stable methodology for the dynamics of structures

The applicability and evaluation of a new self-starting, unconditionally stable, implicit methodology of computation for the dynamics of structures is described. The methodology offers different perspectives and architecture for structural dynamics compared with the tranditional (widely advocated and commonly used) time integration methods. It is based on velocity representations and architecture and uses finite elements as the principal analysis tool for structural dynamic modeling/analysis. In particular, the dynamics of beam-type flexural models are considered, and comparative results validate and support the proposed use of the self-starting methodology of computation for the dynamics of linear/nonlinear structures. The overall effectiveness and elegance strongly support its use in most existing commercial codes.     

Dielectric relaxation of conductive carbon black reinforced ethylene‐octene copolymer vulcanizates

The dielectric relaxation behavior of different conducting carbon black‐filled ethylene‐octene copolymer (EOC) vulcanizates prepared by melt‐mixing method has been studied as a function of frequency (100 Hz–5 MHz) over a wide range of temperatures (25–100°C). The effect of filler loading and frequency on AC conductivity, dielectric permittivity, impedance, and dielectric loss tangent (tanδ) has been studied. The nature of variation of the dielectric permittivity with the filler loadings was explained on the basis of interfacial polarization of the filler in the polymer matrix. The effect of filler loading on the real and complex part of the impedance was explained by the relaxation dynamics of the polymer chains in the vicinity of the fillers. The effect of filler and temperature on dielectric loss tangent, dielectric permittivity, AC conductivity, and Nyquist plot was also reported. The bound rubber (BR) value increases with increase in filler loading suggesting the formation of strong interphase, which is correlated with dielectric loss. Thermal activation energy (E_a) was found to be decreasing with the temperature, which follows the Arrhenius relation: τ_b = τ₀ exp(−E_a/K_BT) where τ_b is the relaxation time for the bulk material. From the plot of lnτ_b versus inverse of absolute temperature (1/T), the activation energies (E_a) were found to be 0.37 and 0.44eV, respectively. The percolation threshold was observed with 40 phr carbon black loading. POLYM. COMPOS., 37:342–352, 2016. © 2014 Society of Plastics Engineers     

Analyzing CT images for detecting lung cancer by applying the computational intelligence-based optimization techniques

Lung cancer is the most critical disease because it affects both men and women. Most of the time, lung cancer leads to death due to less health care and medical attention. In addition, lung cancer is difficult to identify in earlier stages due to the low-level symptoms and risk factors. To overcome the complexity, effective techniques must predict lung cancer earlier. To attain the problem statement, an lung cancer identification system is developed with the help of a meta-heuristic algorithm. The CT imageries obtained from the CIA database are analyzed step by step. The gathered image noise is removed by applying the mean filter, and the affected regions are segmented with the help of the Butterfly Optimization Algorithm-based K-Means Clustering (BOAKMC) algorithm. Afterward, various statistical features are derived, and the Supervised Jaya Optimized Rough Set related Feature Selection (SJORSFS) process is used to select the lung features. Finally, the lung cancer is identified using Autoencoder based Recurrent Neural Network (ARNN) classification algorithm, successfully recognizing the lung cancer features. Then the system's efficiency is evaluated using a MATLAB setup; here, 3000 are treated as training images and 2043 for testing images. The effective training enhances overall lung cancer prediction accuracy by up to 99.15%.     

Fe-Zn Alloy Coating on Galvannealed (GA) Steel Sheet to Improve Product Qualities

Galvannealed steel sheets (GA) have become the mainstream steel sheet for automobile applications because of their superior corrosion resistance, paintability, and weldability. To impart specific properties, different coatings on GA steel sheet were reported to improve properties further. In this context, we have developed an electroplating process (flash coating) for bright and adherent Fe-Zn alloy coating on GA steel sheet to enhance performances such as weldability, frictional behavior, phosphatability, and defect coverage. A comparative study with bare GA steel sheet was carried out for better elastration. The electroplating time was reduced below 10 s for practical applicability in an industrial coating line by modulating the bath composition. Electroplating was performed at current density of 200-500 A/m² which yielded with higher cathode current efficiency of 85-95%. The performance results show that Fe-10 wt.% Zn-coated GA steel sheet (coating time 7 s) has better spot weldability, lower dynamic coefficient of friction (0.06-0.07 in lubrication), and better corrosion resistance compared to bare GA steel sheet. Uniform phosphate coating with globular crystal size of 2-5 µm was obtained on Fe-Zn flash-coated GA steel sheet. Hopeite was the main phosphate compound (77.9 wt.%) identified along with spencerite (13.6 wt.%) and phosphophyllite (8.5 wt.%).