A hybrid genetic algorithm for the discrete time–cost trade-off problem

In this paper we present a hybrid strategy developed using genetic algorithms (GAs), simulated annealing (SA), and quantum simulated annealing techniques (QSA) for the discrete time–cost trade-off problem (DTCTP). In the hybrid algorithm (HA), SA is used to improve hill-climbing ability of GA. In addition to SA, the hybrid strategy includes QSA to achieve enhanced local search capability. The HA and a sole GA have been coded in Visual C++ on a personal computer. Ten benchmark test problems with a range of 18 to 630 activities are used to evaluate performance of the HA. The benchmark problems are solved to optimality using mixed integer programming technique. The results of the performance analysis indicate that the hybrid strategy improves convergence of GA significantly and HA provides a powerful alternative for the DTCTP.     

A stability study on first-order neutral systems with three rationally independent time delays

First-order linear time invariant and time-delayed dynamics of neutral type is taken into account with three rationally independent delays. There are two main contributions of this study. (a) It is the first complete treatment in the literature on the stability analysis of systems with three delays. We use a recent procedure, the cluster treatment of characteristic roots (CTCR), for this purpose. This procedure results in an exact and exhaustive stability tableau in the domain of the three delays. (b) It provides a proof of a complex concept called the delay-stabilisability (also known as strong stability) as a by-product of CTCR. Furthermore, we deploy a numerical method (infinitesimal generator approach) to approximate the dominant characteristic roots of this class of systems, which concur with the stability outlook generated by CTCR.     

A holonic approach based integration methodology for transportation and warehousing functions of the supply network

The supply chain (SC) is often defined as a network that is composed of different functions, including suppliers, manufacturing plants, warehouses/distribution centers, retailers and customers. A supply network (SN) is a sequence of different and multiple numbers of functions and individual functional units that must satisfy all capacities and demand requirements imposed by customers with minimum cost to the network. The most important functions of a SN are warehousing and transportation functions. This paper addresses the warehousing and transportation network design problem that involves determining the best strategy for distributing the sub-products from the suppliers to the warehouse and from the warehouse to the manufacturers. Considering some similarities between holonic systems and SN systems, a holonic approach based modeling methodology is proposed in this study. A multiple supplier, single warehouse and multiple manufacturer system are considered to be an integrated warehousing and transportation network. Consequently, a linear programming model is presented to maximize the profit of both of the overall SN and the individual functional units of the SN functions.     

Complete stability robustness of third-order LTI multiple time-delay systems

A unique procedure is presented in this paper, for a complete stability robustness of the third-order LTI multiple time-delay systems (LTI-MTDS). The uniqueness of the treatment is simply due to the fact that there is no comparable methodology, presently, in the literature. The end result of this procedure is an exhaustive and precise determination of the stable regions in the domain of time delays. The backbone of the method is a novel framework called “the cluster treatment of characteristic roots, (CTCR)”. CTCR is constructed over two fundamental propositions. The first proposition claims the existence of a bounded number of so-called “kernel curves”, where the only imaginary characteristic roots occur. The second proposition is on an interesting directional invariance property of the crossing tendencies of these imaginary roots. For simplicity of conveyance and without loss of generality, the number of time delays is taken as two in this document. The new methodology is expandable to higher-order dynamics with more time delays than two, as the authors intend to demonstrate in future publications.     

Electrophoretic deposition of hydroxyapatite‐shrimp crusts nanocomposite thin films for bone implant studies

Hydroxyapatite‐shrimp crusts nanocomposite thin films were deposited on titanium substrates by electrophoretic technique, under different preparation conditions, for bone implant applications. Fourier transform infrared spectrometer, atomic force microscope, X‐ray diffraction (XRD), optical microscope, and scanning electron microscope were employed to characterise the synthesised films. Vickers’ micro‐hardness measurements revealed a value of 502 HV for the hydroxyapatite films and 314.55 HV for the nanocomposite films. XRD results confirmed the polycrystalline nature of the hydroxyapatite and hydroxyapatite‐shrimp nanocomposite films. The in‐vitro bioactivity test of the synthesised films in simulated body fluid showed very low dissolution rate. Antibacterial activity of synthesised films was investigated against E. coli bacteria.Inspec keywords: electrophoretic coating techniques, thin films, nanocomposites, antibacterial activity, bone, prosthetics, nanomedicine, calcium compounds, bioceramics, nanofabrication, Fourier transform infrared spectra, atomic force microscopy, X‐ray diffraction, optical microscopy, scanning electron microscopy, Vickers hardness, microhardness, microorganisms, dissolvingOther keywords: Ti, Ca₁₀ (PO₄)₆ (OH)₂ , E. coli bacteria, antibacterial activity, dissolution rate, simulated body fluid, in‐vitro bioactivity test, polycrystalline nature, Vickers microhardness measurements, XRD, scanning electron microscopy, optical microscopy, X‐ray diffraction, atomic force microscopy, Fourier transform infrared spectrometer, bone implant applications, titanium substrates, hydroxyapatite‐shrimp crust nanocomposite thin films, electrophoretic deposition     

Range estimation of construction costs using neural networks with bootstrap prediction intervals

Modeling of construction costs is a challenging task, as it requires representation of complex relations between factors and project costs with sparse and noisy data. In this paper, neural networks with bootstrap prediction intervals are presented for range estimation of construction costs. In the integrated approach, neural networks are used for modeling the mapping function between the factors and costs, and bootstrap method is used to quantify the level of variability included in the estimated costs. The integrated method is applied to range estimation of building projects. Two techniques; elimination of the input variables, and Bayesian regularization were implemented to improve generalization capabilities of the neural network models. The proposed modeling approach enables identification of parsimonious mapping function between the factors and cost and, provides a tool to quantify the prediction variability of the neural network models. Hence, the integrated approach presents a robust and pragmatic alternative for conceptual estimation of costs.     

A unique methodology for the stability robustness of multiple time delay systems

The stability robustness is considered for linear time invariant (LTI) systems with rationally independent multiple time delays against delay uncertainties. The problem is known to be notoriously complex, primarily because the systems are infinite dimensional due to delays. Multiplicity of the delays in this study complicates the analysis even further. And “rationally independent” feature of the delays makes the problem prohibitively challenging as opposed to the TDS with commensurate time delays (where time delays are rationally related). A unique framework is described for this broadly studied problem and the enabling propositions are proven. We show that this procedure analytically reveals all possible stability regions exclusively in the space of the delays. As an added strength, it does not require the delay-free system under consideration to be stable. Our methodology offers a resolution to this question, which has been studied from variety of directions in the past four decades. None of these respectable investigations can, however, deliver an exact and exhaustive robustness declaration. From this stand point the new method has a unique contribution.     

Synthesis and Characterization of Titanium-Substituted Large Pore SSZ-42 Zeolite

Titanium-substituted large pore SSZ-42 zeolite was synthesized for the first time using the corresponding borosilicate as starting material. Substitution of boron by titanium took place via either high temperature treatment with TiCl₄ vapor or by treatment with Ti(OiPr)₄ in dry toluene at 120°C. Both deboronated and boron-containing samples were found to be suitable for post-synthesis incorporation of titanium in the zeolite framework. The obtained materials were characterized by FTIR, UV-visible and XPS. Titanium-modified SSZ-42 was found to be active for phenol hydroxylation and cyclohexene epoxidation.