Synthesis and characterization of ethylene-xylene-based polysulfide block-copolymers using the interfacial polymerization method

Copolymers of linear and aromatic polysulfide blocks are synthesized using interfacial polymerization of dichloro-xylene-based aromatic and ethylene-dichloride-based non-aromatic organic monomers. Synthesized copolymers consist of poly(ethylene sulfide) as well as ploy (xylene sulfide) blocks. Fascinating properties of linear and aromatic polysulfide species are gathered in the structure of synthesized polysulfide copolymers. Ethylene dichloride and α,α′-dichloro-p-xylene are used as the non-aromatic and aromatic organic monomers, respectively. To investigate the influences of sulfur contents in the backbone of the polymer on the thermal stability of synthesized copolymers, poly(ethylene-xylene disulfide) (PEXDS), poly(ethylene-xylene trisulfide) (PEXTRS) and poly(ethylene-xylene tetrasulfide) (PEXTS) copolymers are synthesized using, respectively, sodium disulfide, sodium trisulfide and sodium tetrasulfide, as aqueous monomers. Compared to both linear and nonlinear homopolymers, synthesized copolymers exhibit improved thermal stability. Moreover, the thermal degradation temperatures of synthesized copolymers improve by decreasing the number of sulfur atoms in the backbone of copolymers. These results reveal that thermal degradation of polysulfide copolymers can be tailored by controlling the polysulfide chain’s sulfur contents. Structural characteristics of synthesized polysulfide copolymers are also investigated using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and X-ray diffraction analysis.     

Synthetic and physical characterization of phase change materials microencapsulated by complex coacervation for thermal energy storage applications

This paper presents a comprehensive study of encapsulated phase change materials (PCMs). In order to investigate some synthesis parameters, microencapsulated paraffin with gelatin/gum Arabic wall system was prepared by the complex coacervation method and the performance of these microcapsules was evaluated by optical microscopy and differential scanning calorimetry. Further investigations were carried out on the impact of physical parameters on the melting time by studying the constrained melting transformation of an encapsulated PCM in a spherical shell subjected to a constant temperature media. Results indicate successful production of PCM microcapsules with high melting enthalpy (116 kJ/kg), and the effects of diameter and thermal conductivity on melting time of PCMs were demonstrated. Copyright © 2014 John Wiley & Sons, Ltd.     

Stream processing coalgebraically

We study various operations for splitting, partitioning, projecting and merging streams of data. These operations are motivated by their use in dataflow programming and stream processing languages. We use the framework of stream calculus and stream circuits for defining and proving properties of such operations using behavioural differential equations and coinduction proof principles. As a featured example we give proofs of results, observed by Moessner, from elementary number theory using our framework. We study the invariance of certain well patterned classes of streams, namely rational and algebraic streams, under splitting and merging. Finally we show that stream circuits extended with gates for dyadic split and merge are expressive enough to realise some non-rational algebraic streams, thereby going beyond ordinary stream circuits.     

Genetic-based modeling of uplift capacity of suction caissons

In this study, classical tree-based genetic programming (TGP) and its recent variants, namely linear genetic programming (LGP) and gene expression programming (GEP) are utilized to develop new prediction equations for the uplift capacity of suction caissons. The uplift capacity is formulated in terms of several inflecting variables. An experimental database obtained from the literature is employed to develop the models. Further, a conventional statistical analysis is performed to benchmark the proposed models. Sensitivity and parametric analyses are conducted to verify the results. TGP, LGP and GEP are found to be effective methods for evaluating the horizontal, vertical and inclined uplift capacity of suction caissons. The TGP, LGP and GEP models reach a prediction performance better than or comparable with the models found in the literature.     

Experimental study of the punching behavior of GFRP reinforced lightweight concrete footing

This paper presents the results of an experimental study of structural lightweight concrete with glass fiber reinforcement (GFRP) bar for prefabricated single footing. In this study, seven full scale concrete single footings specimens, which were reinforced by GFRP bar located on a bed of soil, were tested. One of the specimens was made of normal weight concrete and the others were made of structural lightweight concrete. Four of the lightweight footing specimens contained polymer fibers. Also, two of the lightweight footing specimens contained shear reinforcement. Results indicated that the maximum GFRP strain on normal weight and lightweight concrete footing with polypropylene fibers are about 55 and 23% of the ultimate strain, respectively. Furthermore, adding polypropylene fiber and shear reinforcement enhanced the structural behavior of footings and limited the extent width of cracks which was wider in lightweight footings than that of normal weight concrete.     

Effective Thermal Conductivity Modeling of Sandstones: SVM Framework Analysis

Among the most significant physical characteristics of porous media, the effective thermal conductivity (ETC) is used for estimating the thermal enhanced oil recovery process efficiency, hydrocarbon reservoir thermal design, and numerical simulation. This paper reports the implementation of an innovative least square support vector machine (LS-SVM) algorithm for the development of enhanced model capable of predicting the ETCs of dry sandstones. By means of several statistical parameters, the validity of the presented model was evaluated. The prediction of the developed model for determining the ETCs of dry sandstones was in excellent agreement with the reported data with a coefficient of determination value (\({R}^{2})\) of 0.983 and an average absolute relative deviation of 0.35 %. Results from present research show that the proposed LS-SVM model is robust, reliable, and efficient in calculating the ETCs of sandstones.     

Preparation of epoxy-based insulator and optimization of its thermal property by Taguchi robust design method in double base propellant grain application

Taguchi method (orthogonal array, OA₉) was used to design an epoxy insulator by evaluating its glass transition temperature (T _g) for using in a double base (DB) propellant grain. In this design method, three epoxy resins based on diglycidylether bisphenol A (DGEBA), three polyamine curing agents and a DGEBA-based reactive diluent agent were used. The curing process of epoxy resins with polyamines was studied by Fourier transform infrared spectroscopy. The results showed that the curing process was completed at room temperature. The effects of four parameters including resin type, curing agent type, curing agent concentration and diluent quantity were investigated to design a resin formulation with a highest T _g after curing. The obtained results were quantitatively evaluated by the analysis of variance (ANOVA). The results of ANOVA showed that the highest T _g of 86.0 ± 9.0 °C was obtained for the optimum formulation of MANA POX-95 as epoxy resin, H-30 as curing agent and 52 phr H-30. The T _g measured by the experiment was 78.0 ± 0.9 °C. In addition, the single lap shear strength (adhesion strength) of the optimized insulator was measured at 13.66 ± 1.02 MPa. Pull-off test performed on the surface of DB propellant resulted a 1.935 ± 0.003 MPa adhesion strength.     

Performance improvement of an active vibration absorber subsystem for an aircraft model using a bees algorithm based on multi-objective intelligent optimization

This study develops a mathematical model to investigate the behaviour of adaptable shock absorber dynamics for the six-degree-of-freedom aircraft model in the taxiing phase. The purpose of this research is to design a proportional-integral-derivative technique for control of an active vibration absorber system using a hydraulic nonlinear actuator based on the bees algorithm. This optimization algorithm is inspired by the natural intelligent foraging behaviour of honey bees. The neighbourhood search strategy is used to find better solutions around the previous one. The parameters of the controller are adjusted by minimizing the aircraft’s acceleration and impact force as the multi-objective function. The major advantages of this algorithm over other optimization algorithms are its simplicity, flexibility and robustness. The results of the numerical simulation indicate that the active suspension increases the comfort of the ride for passengers and the fatigue life of the structure. This is achieved by decreasing the impact force, displacement and acceleration significantly.