Characterisation of the mixing of non‐newtonian fluids with a scaba 6SRGT impeller through ert and CFD

An attempt has been made to study the mixing of yield‐pseudoplastic fluids with a Scaba 6SRGT impeller using electrical resistance tomography (ERT) and computational fluid dynamics (CFD). The ERT system with four sensor planes, each containing 16 equispaced stainless steel electrodes, was used to measure the mixing time. The multiple reference frames (MRF) technique and the modified Herschel–Bulkley model were applied to simulate the impeller rotation and the rheological behaviour of the non‐Newtonian fluids, respectively. To validate the model, the CFD results for the power consumption were compared to the experimental data. The validated model was then employed to obtain further information regarding the averaged impeller shear rate, impeller circulation, and pumping capacities. The CFD and ERT data were utilised to investigate the effect of the impeller power, fluid rheology, and impeller size on the mixing time. The mixing time results obtained in this study were in good agreement with those reported in the literature. © 2011 Canadian Society for Chemical Engineering     

Preparation and colorimetric characterization of polymeric nanophotonic structures

A spin‐casting machine was designed and fabricated for preparation of multilayer polymer films from parent polymer solutions together with a polymeric dispersion of nanoparticles. The dispersion consists of polystyrene (PS)‐based core coated with a poly(methyl methacrylate‐co‐butyl acrylate) shell. Multilayer structure of such films was confirmed using a scanning electron microscope A sandwiched dispersed nanoparticles cast from the spin‐casting machine assumed a near to hexagonal arrangement. This structure affected the optical properties of the cast films. The films were characterized using colorimetric methods such as spectrophotometric and goniospectrophotometric techniques. Moreover, a dispersion of styrene‐based nanoparticles is sandwiched between PS and poly(methyl methacrylate) layers. The multilayer sandwiched films illustrated a greenish color shift attributed to the formation of hexagonal structures. The dispersion of styrene‐based nanoparticles within this sandwich restricts the observation of some wavelengths, which could be attributed to changes in the refractive indices of such samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Incidence of Shiga toxin-producing Escherichia coli serogroups in ruminant's meat

To assess the presences of Escherichia coli, its serogroups, virulence factors and antibiotic resistance properties in ruminant's meat, a total of 820 raw meat samples were collected and then evaluated using culture, PCR and disk diffusion methods. Totally, 238 (29.02%) samples were positive for presence of Escherichia coli. All of the isolates had more than one virulence gene including Stx1, Stx2, eaeA and ehly. All investigated serogroups were found in beef and sheep and all except O145, O121 and O128 were found in goat. The O91, O113, O111, O103, O26 and O157 serogroups were found in camel. Totally, aadA1–blaSHV combination was the most predominant antibiotic resistance gene. The highest resistance of STEC strains was seen against penicillin while resistance to nitrofurantoin and ciprofloxacin was minimal. These findings showed that health care and meat inspection should be reconsidered in Iranian slaughterhouses and butchers.     

A Novel Energy-Efficient Ternary Successor and Predecessor Using CNTFET

This paper presents a novel design for a ternary successor and predecessor using carbon nanotube field-effect transistors (CNTFETs). The chirality of the CNTFETs is utilized for threshold voltage control. The proposed designs are simulated and examined, using Synopsys HSPICE with Standard 32 nm CNTFET technology in various situations. Simulation results demonstrate the correct and high-performance operation of the proposed circuits even in the presence of process variations. It is shown that the proposed ternary circuits achieve a significant saving in energy consumption (95.18 % for successor and 91 % for predecessor) compared with previously presented designs.     

Calculation of time dependent mesh stiffness of helical planetary gear system using analytical approach

Time-dependent mesh stiffness is a most important reason of vibration and dynamic excitation in gear sets. In this research, analytical formulas of the helical gear set and the planetary gear system are combined to calculate the time-dependent mesh stiffness of the helical planetary gear system. For this purpose, at the first step, the analytical equations are derived for the spur gear pair. Then by dividing a helical tooth into the several independent thin spur tooth slices, the helical gear pair mesh stiffness is extracted. Finally, these equations are extended to the helical planetary gear system. The suggested analytical results and those which obtained by the finite element method (FEM) are compared and are in good agreement when the helix angle is less than 15 degrees. Also, the helical planetary gear system mesh stiffness in different cases such as fixed carrier, fixed sun gear and fixed ring gears is calculated. These results show that the value of mesh frequency ratio in each case scales the mesh stiffness shapes in the rotation angle direction. In other words, mesh frequency ratio parameter determines the number of meshing period in each rotation of planets.     

A GA/TS algorithm for the stage shop scheduling problem

This paper presents a special case of the general shop called stage shop problem. The stage shop is a more realistic generalization of the mixed shop problem. In the stage shop problem, each job has several stages of operations. In order to solve the stage shop problem with makespan objective function, an existing neighborhood of job shop is used. In this neighborhood, few enhanced conditions are proposed to prevent cycle generation. In addition, a new neighborhood for operations that belong to the same job is presented. These neighborhoods are applied to the stage shop problem in a tabu search framework. A genetic algorithm is used to obtain good initial solutions. An existing lower bound of the job shop is adapted to our problem and the computational results have been compared to it. Our algorithm has reached the optimal solutions for more than half of the problem instances.     

A practical R&D selection model using fuzzy pay-off method

The aim of this paper is to develop a practical R&D portfolio selection model that addresses effective R&D project valuation issue, while it tackles R&D uncertainty in portfolio optimization. Fuzzy sets theory is employed to capture and model the inaccuracy in project information. To avoid the well-known complications of fuzzy real option valuation, the fuzzy pay-off method is used to more effectively value R&D projects. The resulting problem is formulated as a fuzzy zero–one integer programming model which is later transformed into a crisp mathematical formulation to solve the problem for various degrees of risk. A numerical example is used to illustrate the proposed approach.     

A simple quantitative approach for post earthquake damage assessment of flexure dominant reinforced concrete bridges

Conventional methods for displacement based condition assessment of bridges solely rely on the maximum level of displacements experienced by the piers, and do not take into account the accumulated damage that result from cyclic loading. More advanced approaches take this into account by considering the structural damage as a linear combination of the normalized maximum displacements and hysteretic energy. Computation of the dissipated hysteretic energy requires monitoring of the lateral forces during the seismic events, which are not as practical as monitoring bridge pier deformations. This article reports on the development of a simple damage assessment method that considers the effect of cyclic loading on the state of damage and it is merely based on monitoring the bridge pier deformations. A fiber optic displacement serial array was designed for measuring the crack opening displacement reversals at the plastic hinge areas.