Application of homogenization heat treatments to improve continuous-annealing furnace roller fractures

In this work, several cycles of homogenization heat treatments were employed to improve continuous-annealing furnace roller fractures at Mobarakeh Steel Company. Previous studies revealed that roller fractures were caused by sigma phase embrittlement and an increase of precipitations in the microstructure. Therefore, impact samples were prepared from failed rollers and homogenization treatments were carried out at temperatures ranging from 950 to 1100 °C in increments of 50 °C for 2 h. After cooling the samples in different mediums (furnace, air, oil and water), the impact energy was experimentally determined. In order to investigate the microstructures, the sigma phase and precipitation contents, and fractured surfaces, optical microscopy metallography, X-ray and SEM examinations were performed respectively on fractured samples. The results of these investigations indicate that homogenization treatment at 1100 °C for 2 h, followed by cooling in air, resulted in a significant increase in impact energy, a decrease in sigma phase and other precipitation contents, and produced a ductile fracture surface.     

An algorithmic approach to the optimization of process cogeneration

In most industrial processes, there is a significant need for electric power and for heating. Process cogeneration is aimed at the simultaneous provision of combined heat and power. The net result is usually a reduction in the overall cost and emissions of greenhouse gases. Therefore, there is a significant need for the optimal design of process cogeneration systems. This objective of this paper is to introduce an algorithmic approach to the optimal design of process cogeneration systems. Focus is given to the interaction of the power cycle with the process heat requirements. Because of the need for explicit thermodynamic expressions, a new set of thermodynamic correlations of steam properties is developed for proper inclusion within a mathematical-programming approach. An optimization formulation is developed to provide a generally applicable tool for integrating the process and the power cycle and for identifying the optimum equipment size, operating parameters (such as boiler pressure, superheat temperature and steam load). The objective can be chosen as minimizing the cost, satisfying the heat requirement of the process, or producing the maximum possible of power. A case study is solved to illustrate the applicability of the devised approach and associated thermodynamic correlations.     

Coupled thermoelasticity and second sound in finite length functionally graded thick hollow cylinders (without energy dissipation)

In this article, the coupled thermoelasticity behavior of functionally graded thick hollow cylinders is studied. The governing coupled thermoelasticity and the energy equations are solved for a finite length functionally graded cylinder subjected to thermal shock load. The coupled thermoelastic equations are considered based on Green–Naghdi theory. The mechanical properties of cylinder are graded across the thickness as a power law function of radius. The cylinder is assumed to be made of many isotropic sub-cylinders (layers) across the thickness. Functionally graded properties are created by suitable arrangement of layers and governing equations are expanded in longitudinal direction by means of trigonometric function expansion. The Galerkin Finite Element and Newmark Methods are used to analyze the cylinder. The dynamic behavior of temperature distribution, mechanical displacement and thermal stresses is obtained and discussed. The second sound and elastic wave propagation are determined for various kinds of variation in the mechanical properties. The comparison of present results with published data shows the excellent agreement.     

Linear parameter-varying discrete time-delay systems: Stability and l 2-gain controllers

In this paper, we investigate a class of linear parameter-varying discrete time-delay (LPVDTD) systems where the state-space matrices depend on time-varying parameters and the delay is unknown but bounded. We treat both notions of quadratic stability based on a single quadratic Lyapunov function and affine quadratic stability using parameter-dependent Lyapunov functions. In both cases, we develop LMI-based results of stability testing for time-delay as well as delayless discrete-time systems. Then, we design state-feedback controllers which guarantee quadratic stability and an induced l ₂-norm bound. For the case of dynamic output feedback control, we use a parameter-independent quadratic Lyapunov-Krasovskii function to develop LMI-based solvability conditions which are evaluated at the extreme points of the admissible parameter set. Throughout the paper, complementary results for linear parameter-varying discrete (LPVD) systems without delay are presented.     

Removal of Heavy Metals and COD by SRB in UAFF Reactor

Sulfate-reducing bacteria, under anaerobic conditions, reduce sulfate, SO4?2, to sulfide, S?2, which in turn can effectively precipitate heavy metals. In this research project, sulfate-reducing bacteria were grown in an upflow anaerobic fixed-film (UAFF) reactor using optimum growth conditions obtained in previous studies. These reactors were then fed with different heavy metals at increasing loading rates until complete failure occurred as metal removal reached zero and residual sulfide dropped to zero. The metal concentrations were measured as total, dissolved, and free ions both in the influent and in the effluent streams. The results of this research showed that 100% removal efficiencies could be obtained with individual concentrations up to 200 mg∕L for Cu, 150 mg∕L for Ni and Zn, 75 mg∕L for Cr, 50 mg∕L for Cd, and 40 mg∕L for Pb. Also, the corresponding organic matter removal as total organic carbon was found to be about 50% of the influent total organic carbon. A set of mathematical equations were derived to express the mass balance inside the UAFF reactor, with respect to metal influent concentrations and sulfide production. These equations were corrected by incorporating a correction product, α?β, to represent the toxicity effect of the increasing metal concentrations.     

Implementing Distributed Solutions: Which Strategy to Choose?

This article examines the information infrastructure and business operations of a small IS firm. Due to environmental conditions such as advanced IT applications and pressure from customers, the company was forced to improve its IT infrastructure and rethink its ways of doing business. the company moved away from a central processing computing strategy to an Internet-based strategy. Through this, the company learned that the Internet-based solution has been more effective than a client/server-based solution.     

Granular Properties of Different Starch Phosphate Monoesters

Different starch types (corn, rice, and potato starch, corn amylose and corn amylopectin) were phosphorylated by reaction with a mixture of mono and disodium phosphate at different molar ratios (mol phosphate/mol anhydrous glucose) under heat and vacuum. The starch granules of the modified and the native starches were microscopically examined for their sizes and morphology. The correlation between the variation in granular size of the modified starches with the extent of phosphorylation and some other physicochemical properties was studied. The granular size was generally increased while the iodine absorption capacity was decreased by phosphorylation. There were strong correlations between the variation in the starch granular size in dependence on phosphorylation and the corresponding changes in some physicochemical parameter of starch, e.g. solubility, swelling and paste clarity. This relationship was most evident in the case of phosphorylated corn amylopectin. Starch granular size can be taken as a quick indicator of the physicochemical properties of the native and modified starches.     

XPS studies of radiation grafted PTFE‐g‐polystyrene sulfonic acid membranes

Structural investigations of PTFE‐g‐polystyrene sulfonic acid membranes prepared by radiation grafting of styrene onto PTFE were conducted by X‐ray photoelectron spectroscopy (XPS). The analyzed materials included original PTFE film as a reference material, grafted film, and sulfonated membrane samples having various degrees of grafting. Interest is focused on C1s, F1s, O1s, and S2p of narrow XPS spectra as the basic elemental components of the membrane. The original PTFE film was found to undergo structural changes in terms of chemical composition and shifting in binding energy induced by incorporation of sulfonated polystyrene grafts, and the amount of such changes depends on the degree of grafting. The atomic ratio of F/C was found to decrease with the increase in the degree of grafting, while that for S/C and O/C were found to increase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 336–349, 2000     

A blind equalization algorithm for biological signals transmission

Direct transmission of biological signals such as electrocardiogram (ECG) and electroencephalogram (EEG) through mobile network provides practically unlimited movement of the patients and unlimited coverage area. However, transmission of such signals over a bandlimited channel or through a multipath propagation is subject to inter symbol interference (ISI), whereby adjacent symbols on the output of the channel smear and overlap each other causing degradation of error performance. Mitigation of such kind of distortion can be achieved through equalization filter. Recently an adaptive blind channel equalization using sinusoidally-distributed dithered signed-error constant modulus algorithm (DSE-CMA) has been proposed. In this paper we investigate the performance and the feasibility of this scheme for wireless ECG and EEG transmission. Also, this paper discusses the importance of adaptive blind equalizer for biological signals transmission over existing wireless networks such as Global System for Mobile Communications (GSM) and the Enhanced Data rates for GSM Evolution (EDGE). The geometrical-based hyperbolically distributed scatterers (GBHDS) channel model for macrocell environments was simulated with angular spreads (AS) taken from measurement data. Simulation results show that the low complexity of implementation and the fast convergence rate are the major advantages of deploying this scheme for telemedicine applications. It is also shown that the equalizer output signal is highly correlated with the original transmitted signal in time and joint time-frequency domains.     

Microbial and physiochemical changes in yoghurts containing different Lactobacillus delbrueckii subsp. bulgaricus strains in association with Lactobacillus plantarum as an adjunct culture

Two strains of slow and normal acid‐producing Lactobacillus delbrueckii subsp. bulgaricus, mixed separately with Streptococcus thermophilus, were used in the preparation of yoghurt with or without Lactobacillus plantarum A7. Viable cell counts of lactic bacteria, pH, lactic acid and acetic acid concentrations, soluble nitrogen content, spontaneous syneresis, viscosity and firmness were studied at selected points during the refrigerated storage period. Results showed that survival of L. plantarum A7 in yoghurt was independent of the acidification capability of L. delbrueckii subsp. bulgaricus strains which had already been characterised in their pure culture. Thus, in the preparation of probiotic yoghurt, using slow acid‐producing L. delbrueckii subsp. bulgaricus strain in combination with nondairy lactobacilli postfermentation acidification is not restricted but instability in other physicochemical properties of the yoghurt may be expected.