Bond graph model of a vertical U-tube steam condenser coupled with a heat exchanger

A simulation model for a vertical U-tube steam condenser in which the condensate is stored at the bottom well is developed in this paper. The U-tubes carrying the coolant are partially submerged in the stored condensate and thus the bottom well acts as a heat exchanger. The storage of hydraulic and thermal energies is represented using a coupled pseudo-bond graph model. Advection effects are modelled by considering reticulated segments of the tubes carrying coolant, over which condensation takes place. The developed model is of intermediate complexity and it is intended for use in observer based real time process supervision, which works by comparing the process behaviour to the reference model outputs. The simulation results obtained from the bond graph model are validated with experimental data from a laboratory set-up.     

Three-dimensional analysis of round-to-angle section extrusion through straight converging die

The increasing interest in the modeling of metal-forming processes in recent years has brought the development of different analytical and/or numerical technique. However, due to the complexity nature of the problem, most of the attempts are made with plain strain assumptions. Among the different techniques used, the upper bound method is a convenient tool for evaluating the rate of work in processes involving predominantly plastic deformation of rigid/perfectly plastic material. The present study is an endeavor to remodel and apply the spatial elementary rigid region technique for analyzing extrusion of angle-section bars from round billets through the linearly converging die. Optimized values of the nondimensional average extrusion pressure at various area reductions have been computed and compared with experimental results. It is observed that the proposed technique can be used effectively with adequate accuracy to predict the optimal die geometry which requires a minimal forming stress at different reduction of areas and friction conditions.     

Letter to the Editor: Smart Grid Initiatives in India

Abstract

The Indian power industry is one of the fastest growing sectors and needs a paradigm shift through next-generation automation to handle the operational challenges. Presently, the Indian power sector possesses a number of issues, such as minimizing transmission and distribution losses, power theft, inadequate grid infrastructure, low metering efficiency, and lack of awareness etc. This gap can only be bridged by bringing smart grid initiatives into the Indian power industry.     

Role of Prandtl number in the interaction phenomenon of surface radiation with an opposing mixed convection within a differential heated cavity

A numerical analysis has been done for opposing mixed convection resulting due to wall movement and buoyancy induced by a clockwise fluid motion in a differentially heated cavity. The effect of Prandtl number (Pr) and wall surface emissivity (?) has been investigated for different values of Richardson number. The net radiation method has been employed to simulate the effect of surface radiation. The energy equation along with its nonlinear boundary condition is treated with the Newton‐Raphson scheme. As momentum and energy equations are coupled with each other through their source terms, an iterative solution procedure is employed. A vorticity‐stream function formulation of the momentum equation has been adopted and solved by using an underrelaxation parameter of 0.45. The effect of Prandtl number with respect to the transformation of a multi‐cellular structure of streamline into a unicellular structure has been analyzed. For the same Richardson number (Ri) with an increase in Prandtl number, the flow and heat transfer phenomena changes from a buoyancy‐induced dominated flow to a shear‐induced dominated flow, which leads to some exciting results with respect to wall movement as well. Furthermore, the role of surface radiation in this respect has been emphasized. Nusselt number variation with the Prandtl number and surface emissivity has also been presented. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21003     

Joint strength prediction in a pulsed MIG welding process using hybrid neuro ant colony-optimized model

In this work, a pulsed metal inert gas welding (PMIGW) process is modeled by using a hybrid soft computing technique. Ant colony optimization (ACO) and back-propagation neural network (BPNN) models are combined to predict the ultimate tensile strength of butt-welded joints. A large number of experiments have been conducted, and comparative study shows that the hybrid neuro ant colony-optimized model produces faster and also better weld-joint strength prediction than the conventional back propagation model.     

Trichuris vulpis infection in an Indian tribal population

Stools from 28 of the 82 inhabitants on remote Little Andaman Island in India were examined for parasite eggs and cysts. Trichuris trichiura eggs were found in 27, Trichuris vulpis eggs in 5, Strongyloides stercoralis larvae in 3, hookworm eggs in 15, Entamoeba histolytica and Entamoeba coli cysts each in 9, Giardia lamblia in 6, Retortamonas sp. in 3, Iodoamoeba sp. in 2, and Chilomastix sp. in 2 stools. Ascaris lumbricoides eggs were not seen. The occurrence of T. vulpis eggs in 5 stools and the absence of A. lumbricoides eggs were considered unusual findings.     

Microstructural features of Cd0·8Zn0·2Te thin films studied by X-ray diffraction and electron microscopy

Thin films of synthesized Cd_0·8Zn_0·2Te have been deposited on glass substrate at different substrate temperatures. Different microstructural parameters like crystallite size, rms strain, dislocation density, stacking fault probability and stacking fault energy are determined by XRD, SEM, TEM and TED. XRD and XPS have been used to determine the composition. Variations of the microstructural parameters with film thickness and substrate temperature have been studied in order to obtain optimum growth condition for maximum particle size and least microstructural defects. An effort has been made to correlate the experimental results.     

Characterization of deformation instability in modified 9Cr–1Mo steel during thermo-mechanical processing

In this study, various existing instability criteria were employed to delineate the unstable flow regions in modified 9Cr–1Mo steel during hot deformation. Experimental stress–strain data obtained from isothermal hot compression tests, in a wide range of temperatures (1123–1373 K) and strain rates (10⁻³–10 s⁻¹), were employed to develop instability maps. The domains of these instability maps were validated through detailed microstructural study. It has been observed that Hart’s stability criterion, Jonas’s criterion and Semiatin’s criterion under-predicts the instability regions in the studied temperatures and strain rates regime. Gegel’s and Alexander’s criteria as well as Murty’s metallurgical instability criterion, on the other hand, found to over-predict the instability domains. The instability map developed based on Dynamic Materials Model criterion has been found to precisely predict the instability domains. This instability map revealed four major unstable domains. Microscopic examination in these domains revealed that the instability is manifested in the specimens either as localized deformation band primarily along one of the diagonal or inhomogeneous distribution of martensite lath in the prior austenite grains.     

Physicochemical characterization and catalytic applications of MoO3–ZrO2 composite oxides towards one pot synthesis of amidoalkyl naphthols

A series of MoO₃–ZrO₂ composite oxide catalysts were prepared by coprecipitation and impregnation methods and characterized by XRD, Raman, UV–Vis, TEM and sorptometric techniques. Characterization studies indicated the presence of tetragonal zirconia phase and well dispersed MoO₃ species as isolated and polymolybdate clusters in the composite oxide. The MoO₃(20 mol%)–ZrO₂ material was used as efficient catalyst for synthesis of amidoalkyl naphthols under solvent free conditions using conventional as well as microwave heating. The results obtained clearly showed that the composite oxide catalyst was recyclable and highly efficient for the reaction giving good yield and purity of the products.