Meta-heuristics for real time routing selection in Flexible Manufacturing Systems (FMS)

Abstract Most studies in real-time Flexible Manufacturing System (FMS) scheduling and control area do not consider the effect of routing flexibility; their focus is typically on use of scheduling (i.e., dispatching) rules based on routing selection carried out prior to production. Such an approach is not applicable to random-type FMS, in which no knowledge about incoming part types is available prior to production. For such a scenario, parts can have alternative routings, even for parts of the same type. Thus, the control system of a random-type FMS requires the capability to adapt to the randomness in arrivals and other unexpected events in the system by effectively using operation and routing flexibility in real-time. In this chapter, the objective is to present a comparative study of a group of meta-heuristics, including tabu search (TS), ant colony optimization (ACO), genetic algorithms (GA), particle swarm optimization (PSO), electromagnetic meta-heuristic (EM), and simulated annealing (SA), against the Modified Dissimilarity Maximization Method (Modified DMM). DMM (Saygin and Kilic 1999) is an alternative process plan selection method originally proposed for the routing selection in off-line scheduling of an FMS. In subsequent studies (Saygin, Chen, and Singh, 2001) and (Saygin, Chen, and Singh, 2004) DMM has been: (i) used as a real-time decision-making tool to select routings for the parts that are in the system, (ii) tested and benchmarked against First-in-First-out/First Available (FIFO/FA) and Equal Probability Loading (EPL). Based on the DMM model, a modified DMM (Hassam and Sari 2007) is developed for selection of alternative routings in real time in an FMS. Modified DMM method improves the performances of the FMS in terms of higher production rate, higher utilization rate of the machines and the material handling system

Synthesis, characterization and photocatalytic behavior of Ag doped TiO2 thin film

Superlattices and Microstructures 85 (2015) 255–265In this study, structure, microstructure, optical properties and photocatalytic degradation of Rhodamine B (RhB) have been investigated in an aqueous heterogeneous media containing pure and Ag doped TiO2 nanostructures thin films which were prepared by a simple sol–gel route. Thermal analysis demonstrated that Ag content decreased the temperature of anatase-to-rutile phase transformation. X-ray diffraction analysis confirmed that the prepared nanostructures crystallize within anatase-type structure and that the dopant Ag ions were not fully incorporated within TiO2 host lattice, meanwhile both the refractive index and optical band gap were affected by Ag concentration. The photodegradation of Rhodamine B under UV-C radiation by using pure and Ag-doped TiO2 nanostructures showed that Ag played an important role in a significant improvement of the photodegradation efficiency and that the optimum content of Ag ions was found to be 0.5% molar rati

Structure, microstructure and determination of optical constants from transmittance data of co-doped Zn0.90Co0.05M0.05O (M@Al, Cu, Cd, Na) films

ZnO, Zn0.95Co0.05O and Zn0.90Co0.05M0.05O (M@Al, Cd, Na, Cu) single phase films have been successfully synthesized by ultrasonic spray pyrolysis technique. Structural analysis by X-ray diffraction show that all the films have hexagonal wurtzite structure with an average crystallite size in the range of 19–25 nm. SEM analysis revealed that Cd and Na preserve the shape of nanopetals observed with ZnO or CoAZnO films, while the doping with Al or Cu promote the formation of dense films constituted of nanorods. By the application of Levenberg–Marquardt least square method, the experimental transmittance data were fitted perfectly with the transmittance data calculated via a combination of Wemple– DiDomenico model, absorption coefficient of an electronic transition and Tauc–Urbach model. The concentration of absorbing centres NCo and oscillator strength f of d–d transition of Co2+ ions are calculated from Smakula’s formula

pH Controlled Nanostructure and Optical Properties of ZnO and Al-Doped ZnO Nanorod Arrays Grown by Microwave-Assisted Hydrothermal Method

The low-temperature microwave-assisted hydrothermal method was used to successfully grow pure and Al-doped ZnO (AZO) nanorod (NR) arrays on glass substrates. The combined effects of doping and pH on the structural properties, surface chemistry, and optical properties of all samples were investigated. Thermodynamic-based simulations of the growth solution were performed and a growth mechanism, that considers the effects of both the pH and Al-doping, is proposed, and discussed. Tuning the solution pH is key parameter to grow well-aligned, single crystal, highly packed, and high aspect ratio nanorod arrays. Moreover, the optical absorption in the visible range is enhanced by controlling the pH value. The PL spectra reveal a shift of the main radiative emission from the band-to-band into a transition involving deep defect levels of Zinc interstitial Zni. This shift is caused by an enhancement of the non-radiative components (phonon relaxation) at high pH values. The production of well-ordered ZnO and AZO nanorod arrays with visible-active absorption/emission centers would increase their potential use in various applications

Investigation of nanoscale interactions by means of subharmonic excitation

Multifrequency atomic force microscopy holds promise as a method to provide qualitative and quantitative information about samples with high spatial resolution. Here, we provide experimental evidence of the excitation of subharmonics in ambient conditions in the regions where capillary interactions are predicted to be the mechanism of excitation. We also experimentally decouple a second mechanism for subharmonic excitation that is highly independent of environmental conditions such as relative humidity. This implies that material properties could be mapped. Subharmonic excitation could lead to experimental determination of surface water affinity in the nanoscale whenever water interactions are the mechanism of excitation