Nanospindle and nanorhombohedron and nanocube structured
α-Fe2O3
was synthesized by the solvothermal method. An intermixing of ethylenediamine (EN)
either with ethanol (EtOH) or water in different volume ratios (either 15:85,
50:50 or 85:15 in particular) was used to generate the structural forms of
α-Fe2O3. The study showed that, during synthesis, EN functioned as a ligand and facilitated the
growth of nanostructured samples. The probable growth mechanism is discussed in this
paper. Field emission scanning electron microscope (FESEM) and transmission electron
microscope (TEM) investigations revealed that the nanostructures were formed through
oriented attachment of primary nanocrystals. Fourier transform infrared spectroscopy
(FTIR) results showed the presence of Fe–O or Fe–O–Fe vibrational bands whereas
UV–vis–NIR optical absorbance spectra showed two prominent absorption bands around
540–560 and 670–680 nm. The room temperature magnetization measurement
revealed that the remanence and coercivity depend on the morphological attributes
of the nanocrystals. The magnetic hysteresis measurement also revealed that
α-Fe2O3
nanostructures displayed weak ferromagnetic behaviour at room temperature.
The temperature dependence of saturation magnetization of ferrite nanoparticles has been studied to investigate the applicability of Bloch spin-wave theory to the finite-size systems. T 3/2 law is valid above ∼75 K for the smallest ferrite particles obtained in this experiment having size of ∼2.5 nm. The region of validity of Bloch law increases at the lower-temperature end with the increase in particle size and interparticle interactions. The anomaly from the spinwave theory has been observed with an upturn at low temperature, which can be explained by considering the quantization of spin-wave spectrum due to the finite size of the particles.
The Vehicle Routing Problem with Backhauling deals with the supply of finished goods from a depot to a number of delivery points, and picking up returnable items and bringing them back to the depot using a fleet of trucks. Traditionally, the objective of the problem has been to determine the truck routes such that the total number of trucks and/or the total distance traveled/total route cost are minimized. Most of the papers available in the literature in this connection deal with problems where the linehaul (having a demand for finished goods) and backhaul (having items to be returned to the depot) customers are different, and a customer may be visited by at most one truck limiting demand and returns at a location by the capacity of the truck. In this paper, we allow the linehaul and backhaul customers to be the same leading to simultaneous delivery and pickup at a customer location, and also there is no restriction on the quantity demanded at (to be returned from) a customer location. As such a customer may be visited by more than one truck and more than once by the same truck. We developed a Mixed Integer Linear programming (MILP) formulation of the problem and a route construction heuristic. The heuristic averaged 80 ms for 110 problems tested, and in 78 of them the heuristic costs were either equal to the optimal costs or at most equal to the upper bounds on the optimal costs obtained after running the optimization package for 30 min. Optimal solutions were obtained for 28 problems at an average time of 295 ms. The heuristic could match the optimal solutions for 22 of these problems at an average time of 71 ms.
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