Stable rank of Leavitt path algebras of arbitrary graphs

The stable rank of Leavitt path algebras of row-finite graphs was computed by Ara and Pardo. In this paper we extend this for an arbitrary directed graph. In some parts, we proceed our computation as the row-finite case while in some parts we use the knowledge about row-finite setting by applying the desingularizing method due to Drinen and Tomforde. In particular, we characterize purely infinite simple quotients of a Leavitt path algebra

Rheological properties of modified Bitumen: Comparison of waste polymers’ performance

In this investigation, rheological properties of three different polymer-modified bitumen compounds containing recycled polyethylene terephthalate (R-PET), crumb rubber (CR) and poly (styrene-butadiene-styrene) (SBS) are evaluated and compared. The modified samples were tested by a dynamic shear rheometer (DSR) where complex modulus (G*), phase angle (δ) and rutting resistance (G*/Sinδ) of specimens were measured at different temperatures. The obtained results show that the optimum rheological properties will be gained when 7% wt. of a modifier mixture containing R-PET/CR (90/10 weight ratio) is added to the bitumen. In comparison with un-modified bitumen, the one modified by the latter modifier shows phase angle shift 68.9 oC, complex modulus 2190 (Pa) and rutting resistance 2520 (Pa), at temperature 80 oC. Generally, addition of the polymeric modifier increases complex modulus, rutting resistance and rigidity of the bitumen while a little decrease in phase angle is also observed

Ti3C2 MXene–polymer nanocomposites and their applications

MXene/polymer nanocomposites simultaneously benefit from the attractive properties of MXenes and the flexibility and facile processability of polymers. These composites have shown superior properties such as high light-to-heat conversion, excellent electromagnetic interference shielding, and high charge storage, compared to other nanocomposites. They have applications in chemical, materials, electrical, environmental, mechanical, and biomedical engineering as well as medicine. This property-based review on MXene/polymer nanocomposites critically describes findings and achievements in these areas and puts future research directions into perspective. It surveys novel reported applications of MXene-based polymeric nanocomposites. It also covers surface modification approaches that expand the applications of MXenes in nanocomposites

Effective Parameters on the Phase Morphology and Mechanical Properties of PP/PET/SEBS Ternary Polymer Blends

In this work, ternary polymer blends based on polypropylene (PP)/ polyethylene terephthalate (PET) /poly(styrene-b (ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer and a reactive maleic anhydride grafted SEBS (SEBS-g-MAH) at various compositions were prepared by co-rotating twin screw extruder. The effects of PET, SEBS and SEBS-g-MAH compatibilizer on morphology of the blends were examined by scanning electron microscopy (SEM). The blends morphology was also estimated by some predicting methods, however, SEM results revealed some contrasts between results of predicting methods and the real morphology. Population of individual and core-shell particles as well as average diameter of the rubber-based cavities is extremely dependent on SEBS, SEBS-g-MA and PET content. Mechanical inspection tests showed that in comparison with the pure PP, addition of SEBS/SEBS-MA causes an increase in the impact strength of the system. Keeping other parameters constant, with increase in SEBS rubbery phase, the core-shell morphology was affected and the impact strength increased consequently. On the other hand, increase in PET content results in modulus increase and the impact strength decrease. Finally, the optimum processing conditions for compounding ternary PP/PET/SEBS blends were achieved

An approach for optimization of controllable drilling parameters for motorized bottom hole assembly in a specific formation

This study focuses on optimizing drilling parameters when using Positive Displacement Motors (PDMs). In drilling operations involving mud motors, weight-on-bit (WOB) alterations lead to variations in the system's parasitic pressure drop. Consequently, this affects the optimum flow rate and the hydraulic power of the bit. Also, if the flow rate changes, the bit's rotations per minute (RPM) also change. In other words, using PDMs creates a link between the hydraulic system and the drilling speed, such that changing drilling parameters such as the WOB causes changes in the hydraulic system's performance. Therefore, one possible way to optimize the drilling parameters is to consider the drilling rate and hydraulic system simultaneously using a multi-objective approach. This study used an integrated approach encompassing data mining and mathematical modeling, employing a multi-objective framework to identify optimal parameters. The approach was applied to Dariyan Formation drilling data. The data mining approach revealed a well-distributed data set covering optimal and suboptimal zones suitable for optimization. In data mining, the identification of optimal conditions included a WOB of 11500 lb, a rotation speed of 105.8 rev/min, and a flow rate of 843 gpm, leading to an ROP of 44.23 ft/h. In multi-objective optimization, the optimal parameters consisted of a WOB of 14480 lb, a rotation speed of 115 rev/min, and a flow rate of 920.8 gpm, resulting in an ROP of 40.49 ft/h. Comparing optimal results with the drilling data shows a substantial MSE reduction of over 35 %. The results show the good performance of this approach in detecting the optimal and non-optimal drilling variables

Surface Modification of a MXene by an Aminosilane Coupling Agent

MXenes, two-dimensional (2D) transition metal carbides and/or nitrides, possess surface termination groups such as hydroxyl, oxygen, and fluorine, which are available for surface functionalization. Their surface chemistry is critical in many applications. This article reports amine functionalization of Ti3C2Tx MXene surface with [3-(2-aminoethylamino)-propyl]trimethoxysilane (AEAPTMS). Characterization techniques such as X-ray photoelectron spectroscopy verify the success of the surface functionalization and confirm that the silane coupling agent bonds to Ti3C2Tx surface both physically and chemically. The functionalization changes the MXene surface charge from −35 to +25 mV at neutral pH, which allows for in situ preparation of self-assembled films. Further, surface charge measurements of the functionalized MXene at different pH values show that the functionalized MXene has an isoelectric point at a pH around 10.7, and the highest reported positive surface charge of +62 mV at a pH of 2.58. Furthermore, the existence of a mixture of different orientations of AEAPTMS and the simultaneous presence of protonated and free amine groups on the surface of Ti3C2Tx are demonstrated. The availability of free amine groups on the surface potentially permits the fabrication of crosslinked electrically conductive MXene/epoxy composites, dye adsorbents, high-performance membranes, and drug carriers. Surface modifications of this type are applicable to many other MXenes

A Review of Manufacturing Process of Polyethylene Pipe and Connectors for Applying in High-Pressure Natural Gas Pipelines

In this article various pipes used for transporting of gas are introduced and pros and cons of each one are elucidated. The pipes are categorized in three different subgroups including metallic, polymeric and metallic-wire reinforced polymeric pipes. Metallic-wire reinforced polymeric pipes are nominated as the best option for usage in high pressure pipelines transporting natural gas. As a result, some information about major manufacturers of this kind of polymeric pipes, raw material, production process and metallic-wire orientation are presented. Finally, from economical point of view, some calculations are done to estimate required amount of polymer and metallic-wire to manufacture such pipes. It is also possible to compare their manufacturing cost with usual metallic and polymeric pipes

On the Thermal Self-Initiation Reaction of n-Butyl Acrylate in Free-Radical Polymerization

This experimental and theoretical study deals with the thermal spontaneous polymerization of n-butyl acrylate (n-BA). The polymerization was carried out in solution (n-heptane as the solvent) at 200 and 220 °C without adding any conventional initiators. It was studied with the five different n-BA/n-heptane volume ratios: 50/50, 70/30, 80/20, 90/10, and 100/0. Extensive experimental data presented here show significant monomer conversion at all temperatures and concentrations confirming the occurrence of the thermal self-initiation of the monomer. The order, frequency factor, and activation energy of the thermal self-initiation reaction of n-BA were estimated from n-BA conversion, using a macroscopic mechanistic model. The estimated reaction order agrees well with the order obtained via our quantum chemical calculations. Furthermore, the frequency factor and activation energy estimates agree well with the corresponding values that we already reported for bulk polymerization of n-BA