Optimization of bead geometry of submerged arc weld using fuzzy based desirability function approach

The present study highlights application of Taguchi’s robust design coupled with fuzzy based desirability function approach for optimizing multiple bead geometry parameters of submerged arc weldment. Fuzzy inference system has been adapted to avoid uncertainly, imprecision and vagueness in experimentation as well as in data analysis by traditional Taguchi based optimization approach. Detailed methodology and unique features of the proposed method has been highlighted through a case study. The said approach can efficiently be used in off-line quality control of any production process as well as automation of the process.     

Broadcast stochastic receding horizon control of multi-agent systems

Optimal regulation of stochastically behaving agents is essential to achieve a robust aggregate behavior in a swarm of agents. How optimally these behaviors are controlled leads to the problem of designing optimal control architectures. In this paper, we propose a novel broadcast stochastic receding horizon control architecture as an optimal strategy for stabilizing a swarm of stochastically behaving agents. The goal is to design, at each time step, an optimal control law in the receding horizon control framework using collective system behavior as the only available feedback information and broadcast it to all agents to achieve the desired system behavior. Using probabilistic tools, a conditional expectation based predictive model is derived to represent the ensemble behavior of a swarm of independently behaving agents with multi-state transitions. A stochastic finite receding horizon control problem is formulated to stabilize the aggregate behavior of agents. Analytical and simulation results are presented for a two-state multi-agent system. Stability of the closed-loop system is guaranteed using the supermartingale theory. Almost sure (with probability 1) convergence of the closed-loop system to the desired target is ensured. Finally, conclusions are presented.     

Obtaining expert advice [filter synthesis]

Unlike other filter-synthesis design tools, EXSHOF employs knowledge-based synthesis of a high-order active filter. The package is completely menu driven and extremely user friendly. At the various stages of filter design it asks questions of the user and provides guidelines to these questions; i.e., it gives expert help in making decisions. It assumes that the user has little knowledge of computers and filters. Users have the option of using any of the five approximation functions or directly inputting the transfer function. It can design four types of different high-order filter structures and nine different biquad circuits. The detailed diagram of the designed circuit is presented to the user in a modular form using graphics. The frequency response of the circuit has been simulated using PSpice and it has been found that the response exactly matches the input specifications     

Economic and energy efficiency of salvaging biomass from wildfire burnt areas for bioenergy production in northwestern Ontario: A case study

Wildfire burnt forest biomass can be salvaged as feedstock for bioenergy power generating stations. Despite availability of such forest biomass in northwestern Ontario, its procurement has generally been considered uneconomic and no studies have looked into the cost of harvesting, processing, and transporting the burnt material for bioenergy production. In order to meet the demand of biomass for proposed and existing power generating stations using renewable fuels, a standard costing model is used to determine the feasibility of procuring biomass from burnt areas using a full-tree to roadside, roadside grinder to mill system. The case-study was conducted at the Hogarth Plantations near Thunder Bay, Ontario, Canada. The total cost incurred for processing and delivery of biomass from wildfire burnt area with a hauling distance of 7 km and total trip cycle time of 2.55 h was found to be $29.65 gt^?1, with net energy content of 11.4 GJ gt^?1. The total procurement cost depends on the hauling distance and a linear relationship between the two was established. The energy analysis found a net energy output to input ratio of 35:1 for the operation.     

Test for linear trend in 2 x K ordered tables with open-ended categories

A method of evaluating trend (positive or negative) in 2 x K ordered tables is suggested for cases in which the scores for the first (K-1) categories are known a priori but the score for the last category is not known. Such a category is termed as open-ended category in this paper. Ordered tables with an open-ended category are often encountered while evaluating the Cochran-Armitage-Mantel (CAM) trend. In the present paper, the distribution of the test statistic is presented and simulations are carried out to check the asymptotics. The method is then exemplified by an existing data set.     

Stochastic shape functions and stochastic strain–displacement matrix for a stochastic finite element stiffness matrix

Summary For conventional finite element problems, element geometry is adequate to determine shape functions. However, to account for secondary effects due to material randomness, conventional shape functions need to be modified according to the spatial fluctuation of constitutive variables in each Monte Carlo sample. This paper develops a method to compute stochastic shape functions based on local equilibrium criteria when each simulated sample complies with the same order of accuracy as designated for the associated deterministic problem. The resulting stochastic stiffness matrix is then calculated via the stochastic strain–displacement matrix based on those stochastic shape functions. In order to attain high accuracy, which is the characteristic of the boundary element method, rational polynomial shape functions are used in this paper. The proposed formulation is indispensable when secondary effects (due to nano size and time scale in modern technology, fiber randomness in composites, thermodynamic interactions in biological tissues, to name a few) demand a high accuracy finite element formulation. The elasto-plastic deformation that introduces concavity motivated the numerical example elaborated here. An example of a concave quadrilateral element with spatial randomness for the modulus of elasticity is illustrated. Since isoparametric shape functions for concave quadrilaterals do not exist, the Wachspress rational polynomial shape functions with irrational terms are used. The computer algebra environment Mathematica is employed here. Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday     

Electrical,mechanical, and thermal properties of exfoliated graphite/phenolic resin composite bipolar plate for polymer electrolyte membrane fuel cell

Exfoliated graphite (EG) was synthesized from natural flake graphite by acid treatment followed by microwave irradiation. A maximum expanded volume of 560 mL/g was achieved for this exfoliation of graphite. EG/phenolic resin composite bipolar plates for polymer electrolyte membrane fuel cell were fabricated with a high loading of EG by compression molding. The composites possess low density, high electrical conductivity, high thermal stability, and high compressive strength. The composite bipolar plates were also characterized by X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and so on. The composite prepared with 50 wt% of EG has shown the desired properties for bipolar plate as per the US Department of Energy (DOE‐2015) targets. As a result, the EG–resin composites can be used as bipolar plates for polymer electrolyte membrane fuel cell applications. POLYM. ENG. SCI., 55:917–923, 2015. © 2014 Society of Plastics Engineers     

Investigation on jet stability,fiber diameter,and tensile properties of electrospun polyacrylonitrile nanofibrous yarns

Electrospinning is a flexible and efficient method for producing nanofibers by using relatively dilute polymer solution. However, there are many parameters related to material and processing that influence the morphology and property of the nanofibers. This study investigates the influence of electric field and flow rate on diameter and tensile properties of nanofibers produced using polyacrylonitrile (PAN)‐dimethylformamide (DMF) solution. Stability of the spinning jet is investigated via fiber current measurement and an image system at different electric fields and solution flow rates. It is observed that a set of electric field and flow rate conditions favor producing thinnest, strongest, and toughest nanofibers during electrospinning process. Other conditions may lead to instability of the Taylor cone, discontinuous jet, larger diameter fiber, and lower mechanical properties. Finally, a simple dynamic whipping model is adopted to correlate the nanofiber diameter with volumetric charge density and is found to be excellent validating our experimental results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41918.