Energy and exergy analysis of a novel turbo-compounding system for supercharging and mild hybridization of a gasoline engine

Journal of Thermal Analysis and Calorimetry - Number of hybrid vehicles has increased around the world significantly. Automotive industry is utilizing the hybridization of the powertrain system to...     

Promising new catalytic properties of a Co (II)-carboxamide complex and its derived Co3O4 nanoparticles for the Mizoroki-Heck and the Epoxidation reactions

The new Co(II) - carboxamide complex ( 1 ) and Co₃O₄ nanoparticles ( 2 ), by way of thermal decomposition of ( 1 ) have been efficiently synthesised in the environment-friendly. X-ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in ( 1 ) and regular octahedral or tetrahedral ones (oxygens only) in ( 2 ). The investigation of ( 1 ) and ( 2 ) in the Mizoroki-Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts.     

Investigation of a novel serpentine micromixer based on Dean flow and separation vortices

Meccanica - Passive micromixers, due to their relatively high mixing efficiency and simple fabrication, have wide applications in biological, medical, and chemical processes. Serpentine and...     

Combined electroosmotically and pressure driven flow of power-law fluids in a slit microchannel

Electroosmotic flow of power-law fluids in the presence of pressure gradient through a slit is analyzed. After numerically solving the Poisson–Boltzmann equation, the momentum equation with electroosmotic body force is solved through an iterative numerical procedure for both favorable and adverse pressure gradients. The results reveal that, in case of pressure assisted flow, shear-thinning fluids reach higher velocity magnitudes compared with shear-thickening fluids, whereas the opposite is true when an adverse pressure gradient is applied. The Poiseuille number is found to be an increasing function of the dimensionless Debye–Hückel parameter, the wall zeta potential, and the flow behavior index. Comparison between the exact and the results based on the Debye–Hückel linearization reveals that the simplified solution leads to large errors in evaluating the velocity profile for zeta potentials higher than 25 mV, except for shear-thickening fluids in the presence of favorable pressure gradient.     

An improved heuristic for the far from most strings problem

The Far From Most Strings Problem (FFMSP) asks for a string that is far from as many as possible of a given set of strings. All the input and the output strings are of the same length, and two strings are far if their Hamming distance is greater than or equal to a given threshold. FFMSP belongs to the class of sequence consensus problems which have applications in molecular biology, amongst others. FFMSP is NP-hard. It does not admit a constant-ratio approximation either, unless P=NP. In the last few years, heuristic and metaheuristic algorithms have been proposed for the problem, which use local search and require a heuristic, also called an evaluation function, to evaluate candidate solutions during local search. The heuristic function used, for this purpose, in these algorithms is the problem’s objective function. However, since many candidate solutions can be of the same objective value, the resulting search landscape includes many points which correspond to local maxima. In this paper, we devise a new heuristic function to evaluate candidate solutions. We then incorporate the proposed heuristic function within a Greedy Randomized Adaptive Search Procedure (GRASP), a metaheuristic originally proposed for the problem by Festa. The resulting algorithm outperforms state-of-the-art with respect to solution quality, in some cases by orders of magnitude, on both random and real data in our experiments. The results indicate that the number of local optima is considerably reduced using the proposed heuristic.     

Effects of graphene quantum dot (GQD) on photoluminescence,mechanical, thermal and shape memory properties of thermoplastic polyurethane nanocomposites

A group of shape memory polyurethane‐based nanocomposites containing graphene quantum dot nanoparticles (GQDs) were prepared via in‐situ polymerization method. GQD nanoparticles were synthesized by a facile and rapid microwave‐assisted method and characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction pattern, field emission scanning microscopy, transmission electron microscopy, and fluorescence analysis. Chemical structure and hydrogen bonding index (HBI_[C=O]) of the nanocomposites were analyzed via FTIR spectra. The results show that the incorporation of GQDs in PU matrix reduces HBI_(C=O) of nanocomposites. Crystalline structure and thermal properties of the nanocomposites were investigated by differential scanning calorimetry. As results indicate, nucleation effect of GQDs raises crystallinity content of the samples. Mechanical examinations indicate that incorporation of GQDs improves Young's modulus of the nanocomposites, while their elongation at break values are reduced. In addition, shape memory analyses reveal that the presence of GQDs in PU matrix increases the shape fixity ratios in nanocomposites.     

Preparation of electrospun shape memory polyurethane fibers in optimized electrospinning conditions via response surface methodology

Herein, the electrospinning method, as an effective approach, was utilized to fabricate poly (ε‐caprolactone)‐based polyurethane (PCL‐based PU) fibers. PCL was synthesized by ring‐opening polymerization, and characterized by proton nuclear magnetic resonance (¹H NMR) and Fourier‐transform infrared (FTIR) spectroscopies. Afterward, PU was prepared by step‐growth polymerization. The effects of solution concentration and solvent type on fibers' diameter were investigated. Scanning electron microscopy (SEM) images revealed that the optimum solution was N, N‐dimethylformamide(DMF): chloroform with a ratio of 60:40. In addition, results showed that bead‐less nanofibers could be achieved by a concentration of 5 w/v% (polymer to solvent). Various optimum practical parameters, such as applied voltage, feeding rate, and needle‐to‐collector distance, were obtained and compared with the results of response surface methodology (RSM). On the other hand, the mechanical evaluations indicated that the porous structure of scaffolds caused them to possess lower mechanical properties, as well as shape fixity ratios than those of bulk samples.     

Three-component synthesis of 4-amino-2-aryl-2H-pyrimido-[1,2-b][1,3]benzazole-3-carbonitriles and 4H-pyrimido-[2,1-b][1,3]benzazoles in the presence of magnesium oxide and 12-tungstophosphoric acid as catalysts

A simple and convenient approach was suggested for the synthesis of 4-amino-2-aryl-2H-pyrimido[1,2-b][1,3]benzimidazole-3-carbonitriles or -benzothiazole-3-carbonitriles through a three-component reaction of 2-aminobenzimidazole or 2-aminobenzothiazole, aldehyde, and malononitrile in the presence of magnesium oxide (MgO) and 12-tungstophosphoric acid as catalysts. Three-component reactions of aldehyde, β-ketoester, and 2-aminobenzimidazole or 2-aminobenzothiazole with the formation of 4H-pyrimido[2,1-b]benzimidazole or 4H-py-rimido[2,1-b]benzothiazole derivatives, respectively, were also studied. These approaches have the advantage of high yields, rapid and pure course of the reactions, as well as the use of cheap and available catalysts.     

An Optimal Extension of the Polak–Ribière–Polyak Conjugate Gradient Method

Based on a singular value analysis on an extension of the Polak–Ribière–Polyak method, a nonlinear conjugate gradient method with the following two optimal features is proposed: the condition number of its search direction matrix is minimum and also, the distance of its search direction from the search direction of a descent nonlinear conjugate gradient method proposed by Zhang et al. is minimum. Under proper conditions, global convergence of the method can be achieved. To enhance e?ciency of the proposed method, Powell’s truncation of the conjugate gradient parameters is used. The method is computationally compared with the nonlinear conjugate gradient method proposed by Zhang et al. and a modified Polak–Ribière–Polyak method proposed by Yuan. Results of numerical comparisons show e?ciency of the proposed method in the sense of the Dolan–Moré performance profile.     

Two–parameter scaled memoryless BFGS methods with a nonmonotone choice for the initial step length

Numerical Algorithms - A class of two–parameter scaled memoryless BFGS methods is developed for solving unconstrained optimization problems. Then, the scaling parameters are determined in a...