A bi-objective mathematical model toward dynamic cell formation considering labor utilization

This paper addresses dynamic cell formation problem (DCFP) via a new bi-objective mathematical formulation. Although literature body of DCFP includes a vast number of research instances, human-related issues are mostly neglected as an important aspect of DCFP in the corresponding literature. In this paper, the first objective function seeks to minimize relevant costs of the problem including machine procurement and relocation costs, machine variable cost, inter-cell movement and intra-cell movement costs, overtime cost and labor shifting cost between cells, while labor utilization of the modeled DCFP is maximized through the second objective function. Due to NP-hardness of DCFP, an ant colony optimization (ACO) meta-heuristic is developed for the first time in the literature to tackle the problem. Also, authors enhance diversification of the developed algorithm is enhanced by hybridization of the proposed ACO algorithm with a genetic one. Finally, some numerical samples are generated randomly to validate the proposed model by which strengths of the developed algorithm is shown.     

Robust incomplete factorization for nonsymmetric matrices

In this paper, a new incomplete LU factorization preconditioner for nonsymmetric matrices is being considered which is also breakdown-free (no zero pivots occurs) for positive definite matrices. To construct this preconditioner, only the information of matrix A is used and just one of the factors of the AINV process is computed. The L factor is extracted as a by-product of the AINV process. The pivots of the AINV process are used as diagonal entries of U. The new preconditioner has left and right-looking versions. To improve the efficiency of the preconditioner, we have used the inverse-based dropping strategies for both L and U factors. Numerical experiments show that the left-looking version of the preconditioner is significantly faster than its right-looking version in terms of preconditioning time and both are equally effective to reduce the number of iterations. Comparisons of the new preconditioner with AINV and ILUT preconditioners are also presented.     

An analytical approach for calculating natural frequencies of finite one-dimensional acoustic metamaterials

In this paper, an analytical matrix method is presented to drive closed-form characteristic equations for natural frequencies of finite monoatomic and diatomic metamaterials with various boundary conditions. Here, we extend the matrix method introduced by Louck for monoatomic lattice chains. The proposed method is used to calculate the vibration frequencies of the monoatomic metamaterials with fixed–fixed, fixed-free and free-free boundary conditions. In addition, the natural frequencies of fixed–fixed diatomic metamaterials are calculated. The existence of band gaps in the frequencies of the metamaterials is numerically shown.

     

Analytical analysis of the static interaction of fluid and cylindrical membrane structures

The static behavior of an inflated cylindrical membrane is theoretically investigated under different conditions of internal pressures, upstream and downstream fluid parameters. The membrane is attached to a horizontal base along two generators and can be inflated with a compressible fluid (air), an incompressible fluid (water), or a combination of them. The base width, curved perimeter, internal pressure, upstream and downstream fluid properties are given. Large deformation of the membrane due to the internal and external pressures makes the governing equation of the problem to be non-linear. In the present study, an analytical approach for the non-linear analysis of the static interaction of the fluid and the cylindrical membrane with different load distributions and boundary conditions is developed. Both geometric and equilibrium relations of the membrane element are used to obtain the membrane profile in explicit closed form. The validity of the present analytical approach is confirmed by comparing the results with experimental and numerical results obtained from the literature. It is shown that the present formulation is an appropriate method and a new approach to predict the static non-linear interaction of the fluid and the membrane structures with a good accuracy and less numerical effort.     

New breakdown-free variant of AINV method for nonsymmetric positive definite matrices

This paper proposes a new breakdown-free preconditioning technique, called SAINV-NS, of the AINV method of Benzi and Tuma for nonsymmetric positive definite matrices. The resulting preconditioner which is an incomplete factorization of the inverse of a nonsymmetric matrix will be used as an explicit right preconditioner for QMR, BiCGSTAB and GMRES(m) methods. The preconditoner is reliable (pivot breakdown can not occur) and effective at reducing the number of iterations. Some numerical experiments on test matrices are presented to show the efficiency of the new method and comparing to the AINV-A algorithm.     

All-solid-state Cr(III)-selective potentiometric sensor based on Cr(III)-imprinted polymer nanomaterial/MWCNTs/carbon nanocomposite electrode

A novel potentiometric sensor, based on carbon paste electrode (CPE), modified with ion-imprinted polymer (IIP) and multi-walled carbon nanotubes (MWCNTs), is introduced for detection of chromium (III). The IIP nanomaterial was synthesised and characterised by using scanning electron microscopy and Fourier Transform Infrared. The modification of the CPE with the IIP (as a ionophore) resulted in an all-solid-state Cr(III)-selective sensor. However, the presence of appropriate amount of MWCNTs in the electrode composition was found to be necessary to observe Nernstian response. The optimised electrode composition was 76.7% graphite, 14.3% binder, 5% IIP, and 4% CNT. The proposed sensor exhibited Nernstian slope of 20.2 ± 0.2 mV decade^?1 in the working concentration range of 1.0 × 10^?6?1.0 × 10^?1 mol L^?1 (52 µg L^?1–5.2 g L^?1), with a detection limit of 5.9 × 10^?7 mol L^?1 (30.68 µg L^?1) and a fast response time of less than 40 s. It displayed a stable potential response in the pH range of 2–5. It exhibited also high selectivity over some interfering ions. The proposed sensor was successfully applied for the determination of Cr(III) in real samples (sea, river water and soil).