Wall slip and melt fracture of poly(lactides)

The wall slip and melt fracture behaviour of several commercial polylactides (PLAs) as well as their rheological properties under shear and extensional have been investigated. The PLAs have had weight-average molecular weights in the range of 10⁴–10⁵ g/mol and studied in the temperature range of 160–200°C. The solution properties and linear viscoelastic behaviour of melts indicate linear microstructure behaviour. PLAs with molecular weights greater than a certain value were found to slip, with the slip velocity to increase with decrease of molecular weight. The capillary data were found to agree well with linear viscoelastic envelope once correction for slip effects was applied. The onset of melt fracture for the high molecular weight PLAs was found to occur at about 0.2 to 0.3 MPa, depending on the geometrical characteristics of the dies and independent of temperature. Addition of 0.5 wt.% of a polycaprolactone (PCL) into the PLA that exhibits melt fracture was found to be effective in eliminating and delaying the onset of melt fracture to higher shear rates. This is due to significant interfacial slip that occurs in the presence of PCL.     

A numerical scheme based on Bernoulli wavelets and collocation method for solving fractional partial differential equations with Dirichlet boundary conditions

In this paper, an efficient and accurate numerical method is presented for solving two types of fractional partial differential equations. The fractional derivative is described in the Caputo sense. Our approach is based on Bernoulli wavelets collocation techniques together with the fractional integral operator, described in the Riemann‐Liouville sense. The main characteristic behind this approach is to reduce such problems to those of solving systems of algebraic equations, which greatly simplifies the problem. By using Newton's iterative method, this system is solved and the solution of fractional partial differential equations is achieved. Some results concerning the error analysis are obtained. The validity and applicability of the method are demonstrated by solving four numerical examples. Numerical examples are presented in the form of tables and graphs to make comparisons with the results obtained by other methods and with the exact solutions much easier.     

On strongly (<Emphasis Type="Italic">P</Emphasis>)-cyclic acts

By a regular act we mean an act such that all its cyclic subacts are projective. In this paper we introduce strong (P)-cyclic property of acts over monoids which is an extension of regularity and give a classification of monoids by this property of their right (Rees factor) acts.     

(Homo) Flatness of posets on poideal extensions

We consider pomonoids , where G is a pogroup and I is a poideal of S and show that if an S-poset is principally weakly flat, (weakly) flat, po-flat, (principally) weakly po-flat, (po-) torsion free or satisfies Conditions (P), (P _E ), (P _w ), (PWP), (PWP) _w , (WP) or (WP) _w as an I ¹-poset, then it has these properties as an S-poset. We also show that an S-poset which is free, projective or strongly flat as an I ¹-poset may not generally have these properties as an S-poset.     

Investigation of the effect of cobalt on the Ni–Al2O3 catalyst prepared by the mechanochemical method for CO2 methanation

Research on Chemical Intermediates - Various Ni–Co catalysts supported on alumina were produced by the mechanochemical technique and applied to CO2 Methanation. X-ray diffraction,...     

Spectromicroscopic determinations of chemical environments of Ni in MoS2-Ag-Ni ternary systems

Using heterogeneous photocatalysts for harvesting sunlight and converting it for water remediation and splitting are promising to mitigate the possible crisis of environment and energy. Among various composites, the MoS₂-based heterostructures and Ni-based systems exhibit unique electronic, optical properties and redox capabilities, enabling their roles as photocatalysts. Herein, the impacts of chemical environments on the Ni electronic structures within the MoS₂-Ag-Ni ternary systems are studied via X-ray photoemission electron spectroscopy (X-PEEM). Ni nanoparticles with two different sizes of 70 and 200 nm were loaded to MoS₂ flakes with silver buffers as bridges. Heterostructures with a nominal mol percentage of (MoS₂)₇₇Ag_3.7Ni_19.3 were synthesized through an ultrasound-assisted wet method. The oxidation states and various interfacial interactions of Ni with MoS₂ in MoS₂-Ag-Ni ternary composite are spectromicroscopically determined, combining the X-ray absorption spectroscopy near Ni L-edges and the imaging capability of the X-PEEM. Results showed that Ni mainly retrains its chemical states of metal and native oxidizations without observable electronic features subjected to bonding with the sulfur from the MoS₂ flakes. The charge migration channel set up by the Ag buffer thus contributes to electron–hole migrations that facilitate the photocatalytic performance of the ternary system eventually.     

Transient thermal stress analysis for a short thick hollow FGM cylinder with nonlinear temperature-dependent material properties

Journal of Thermal Analysis and Calorimetry - In this study, nonlinear transient thermo-elastic analysis for a thick hollow 1D-FGM (functionally graded material) axisymmetric cylinder with finite...     

Salting‐out homogeneous liquid–liquid extraction in narrow‐bore tube: Extraction and preconcentration of phthalate esters from water

In this study a simple and rapid sample preparation technique, homogeneous liquid–liquid extraction based on phase separation in the presence of a salt performed in a narrow‐bore tube, followed by GC‐flame ionization detection has been developed. In this work, sodium chloride and ACN were used as the salting‐out agent and water‐soluble extraction solvent, respectively. The homogeneous solution of water and ACN was broken by addition of the salt. Small volume of ACN was collected on top of the tube and the extracted analytes in the collected phase were determined. It has been successfully used for the analysis of five phthalate esters as model compounds in aqueous sample. Experimental parameters affecting the extraction efficiency such as kind and volume of the water‐soluble organic solvent, length and diameter of the tube, and pH of the sample solution were investigated. Under the optimal conditions, the LODs were between 0.02 and 0.7 μg/L and enrichment factors were in the range of 172–309. In addition, good linearity (between 1 and 5000 μg/L) and high precision on the base of RSD (<8%, C = 600 μg/L, n = 6) were achieved.