A Two-Stage Approach for Routing Multiple Unmanned Aerial Vehicles with Stochastic Fuel Consumption

The past decade has seen a substantial increase in the use of small unmanned aerial vehicles (UAVs) in both civil and military applications. This article addresses an important aspect of refueling in the context of routing multiple small UAVs to complete a surveillance or data collection mission. Specifically, this article formulates a multiple-UAV routing problem with the refueling constraint of minimizing the overall fuel consumption for all of the vehicles as a two-stage stochastic optimization problem with uncertainty associated with the fuel consumption of each vehicle. The two-stage model allows for the application of sample average approximation (SAA). Although the SAA solution asymptotically converges to the optimal solution for the two-stage model, the SAA run time can be prohibitive for medium- and large-scale test instances. Hence, we develop a tabu-search-based heuristic that exploits the model structure while considering the uncertainty in fuel consumption. Extensive computational experiments corroborate the benefits of the two-stage model compared to a deterministic model and the effectiveness of the heuristic for obtaining high-quality solutions.Comment: 18 page

Biosynthesis of Copper Oxide (CuO) Nanowires and Their Use for the Electrochemical Sensing of Dopamine

A facile one-step, eco-friendly, and cost-effective approach for the formation of copper oxide (CuO) nanowires by a green method using saponin-rich Sapindus mukorossi fruit extract (SMFE). The physio-chemical characteristics of the synthesized CuO nanowires have been characterized by X-ray Diffractometry (XRD), X-ray Photoelectron Spectroscopy (XPS), FT-IR (Fourier Transform Infrared Spectroscopy, FE-SEM (Scanning Electron Microscopy), and High-Resolution Transmission Electron Microscopy (HR-TEM). Further, the electrocatalytic activity of the CuO nanowires synthesized with SMFE has been investigated, and they have been used as dopamine (DA) sensors. Because of their unique properties, the CuO nanowires/GCE exhibited remarkable electrochemical response for the detection of DA with enhanced current response. The anodic current demonstrated that the CuO nanowires/GCE linearly detects the concentration of DA over the range of 0.1 µM to 0.105 mM of DA with a regression co-efficient of 0.9960. The obtained results illustrated that the synthesized CuO nanowires can easily stimulate the electron transfer reaction between DA and the nanowires modified electrode with the improvement of the conductivity and stability of the electrode. This remarkable electrocatalytic property of CuO nanowires makes it a unique electrochemical sensor for the detection of DA. Furthermore, the sensor is free from the interference of ascorbic acid, uric acid, and other interfering species. Moreover, the anti-interference performance also showed that the CuO nanowires/GCE could be employed for the determination of DA in real samples with good selectivity and sensitivity

Sol-Gel Mediated Greener Synthesis of γ-Fe₂O₃ Nanostructures for the Selective and Sensitive Determination of Uric Acid and Dopamine

Novel eco-freindly benign morphology-controlled biosynthesis of acicular iron oxide (γ-Fe2O3) nanostructures with various shapes and sizes have been synthesized through greener surfactant, Aloe vera (AV) extract assisted sol-gel method. By simply varying the experimental parameters, pure phase of cubic spinel superparamagnetic γ-Fe2O3 nanospherical aggregates, nanobelts and nanodots have been developed. The synthesized γ-Fe2O3 nanostructures are characterized through X-Ray Diffractommetry (XRD), X-Ray Photoelectron Spectroscopy (XPS), Fourier Transform-Infrared Spectrsocopy (FT-IR), Field Emission-Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM). Moreover, the electrochemical determination of uric acid (UA) and dopamine (DA) of the as obtained γ-Fe2O3 nanostructures are systematically demonstrated. The electrochemical properties of the γ-Fe2O3 nanostructures modified glassy carbon electrode (GCE) displayed an excellent sensing capability for the determination of DA and UA, simultaneously than the bare GCE. When compared with the other iron oxide nanostructures, γ-Fe2O3 nanobelts/GCE exhibited remarkable oxidation current response towards the biomolecules. This occurred due to the high surface area and the unique one-dimensional nanostructure of γ-Fe2O3 nanobelts. Ultimately, the greener synthesis protocol explored in this research work may also be expanded for the preparation of other morphology controlled magnetic and non-magnetic nanomaterials, which could easily open up innovative potential avenues for the development of practical biosensors

A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

New titanium (IV), zirconium (IV) and hafnium (IV) alkoxide complexes supported by the tridentate [O,N,N] salicylaldiminato ligands were synthesized in high yields and characterized by conventional spectroscopic techniques and single crystal X-ray analysis. The structural composition for some of these complexes was as a result of in situ intramolecular Meerwein–Ponndorf–Verley (MPV) type reduction of the imine moiety from the ligand, resulting in the formation of unexpected amido compounds. Theoretical calculations were performed at the DFT level to calculate the energy barrier for this reduction and rationalize the reactivity pattern. These complexes were found to be active towards the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA), l-lactide (l-LA) and ε-caprolactone (CL), resulting in polymers with good number average molecular weight (Mn) and controlled molecular weight distributions (MWDs). The poly(lactic acid) (PLA) resulting from rac-LA were predominately heterotactic. Interestingly, these compounds were found to catalyze the ROP of epoxides such as rac-cyclohexene oxide (rac-CHO), rac-styrene oxide (rac-SO) and rac-propylene oxide (rac-PO) under solvent free condition. The kinetic and mechanistic studies associated with the polymerization have been included. In addition, these compounds were found to be useful as precatalysts for the polymerization of ethylene