Effect of surface area of nanosilica particles on the cure kinetics parameters of an epoxy resin system

Knowing of thermoset curing kinetics is essential for process development, quality control, and achieving desirable products. Hence, in this article, cure kinetics of an EPON 828 epoxy resin/dicyandiamide curing agent/diuron accelerator system is investigated. This resin system is usually used for the production of epoxy/glass fiber prepregs used in wind turbine blades. For this, differential scanning calorimetry analysis is used and the effect of temperature, weight percentage, and size of nanosilica is studied by conducting isothermal tests at several temperatures for samples with and without nanoparticles. An autocatalytic curing model is applied to describe the cure kinetic of system and then the variations in model parameters calculated by curve fitting using the MATLAB software. The results show that the increase in temperature, weight percentage of nanosilica from 0 to 6%, and surface area of nanosilica particles lead to the increase in curing rate, whereas the increase in the percentage and surface area of nanosilica particles significantly decreases total heat of reaction. At the end, the relation between each of model parameters and the total surface area of nanosilica particles, calculated by mathematical equations, is obtained. The allowable maximum surface area of nanosilica used in the mathematical equations is 12 m² g⁻¹. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47958.     

Nonlinear elastoplastic analysis of pressure sensitive materials

When structures undergo extreme loading conditions, the materials pass the elastic limits. Therefore, to preserve economy as well as safety, it is essential to perform a realistic elastoplastic analysis using the constitutive equations in plasticity. On the other hand, computing the stress alongside its associated variables on Gauss points is a delicate process and virtually the most important part of these analyses. In this study, an efficient stress-updating technique is presented for the constitutive rate equations of the pressure sensitive materials such as concrete, rock, soil and some kind of metals. Accordingly, the Drucker–Prager plasticity is utilized to consider the hydrostatic pressure in addition to the J ₂-invariant of the deviatoric stress. Moreover, the isotropic and kinematic hardenings are used to take into account more realistic behavior of the materials. Finally, a wide range of numerical tests is carried out to show the performance of the presented method together with the application of the suggested formulations in elastoplastic analysis of a gravity dam.     

Entanglement dynamics of a two-qutrit system under DM interaction and the relevance of the initial state

Using concurrence as a measure of entanglement, we present analytical and numerical study of entanglement dynamics in a two-qutrit system in the presence of the Dzyaloshinskii–Moriya interaction, as a function of the parameters involved. Three distinct initial states: a superposition of the ground and the first excited state, the Bell-type state and a superposition of qutrit coherent states will be considered in this investigation.     

Critical assessment of arterial transport models

Works pertinent to arterial transport models are analyzed and a critical assessment of the models utilized in the study of fluid flow and mass transfer within the arteries is presented with an emphasis on the role of porous media. Arterial transport models are assessed and classified based on their ability to physically prescribe the arterial anatomy as well as the related transport processes. Pertinent models such as wall-free, homogeneous-wall, and multi-layer models as well as the governing equations and different types of boundary conditions utilized in each model are analyzed.     

Thermophysical and rheological behavior of polystyrene/silica nanocomposites: Investigation of nanoparticle content

In this work, solvent blending in combination with extruding are applied to provide polystyrene/silica nanocomposite specimens. Transmission electron microscope (TEM) and scanning electron microscope (SEM) show same nanoparticle dispersion in PS matrix in low to high filler loadings. Differential scanning calorimetry (DSC), dynamic mechanical thermal analyzer (DMTA) and thermogravimetric analyzer (TGA) were used to study the thermophysical characteristic of the nanocomposites in solid state. In addition, the melt state rheological behavior of the samples was investigated under constant and zero shear rates. Interestingly, different behaviors were detected in nanocomposites in low and high nanoparticle loadings. In addition, rheological characteristics of molten polymer are dramatically affected in samples with low nanosilica concentration while stabilized in high filler loadings.     

Comparison of various settling velocity functions and non-Newtonian fluid models in circular secondary clarifiers

An axisymmetric single-phase model that predicts the sedimentation of activated sludge in a circular secondaryclarifier is developed. The k-ɛ turbulence model is used on a two-dimensional, orthogonal and stepwise grid. The concentration equation, which is extended to incorporate the sedimentation of activated sludge in the field of gravity, governs the mass transfer in the clarifier. The computational domain includes the sludge blanket where the viscosity is affected by the rheological behavior of the sludge. Results in case of non-Newtonian fluid model are compared with another numerical approach provided by Lakehal et al. Non-Newtonian fluid models—Bingham, Casson, and Herschel-Bulkley—are used. The influence of settling velocity functions and non-Newtonian models on the flow behavior isinvestigated. Finally, the best models are introduced and the ways that the non-Newtonian model introduces the plastic viscosity are discussed.     

NUMERICAL SIMULATION OF SPHERICAL, CYLINDRICAL AND AXIAL BUBBLE CLOUDS COLLAPSE

The nonlinear dynamics of a spherical,cylindrical and axial cloud of cavitation bubbles were numerically simulated in order to learn more about the physical phenomena occurring in the cloud cavitation....     

Agent Models and Different User Ontologies for an Electronic Market Place

In this paper the agent-based electronic market architecture GEMS is described. The market incorporates different user perspectives: consumers, retailers, and producers. Ontologies for the different user perspectives are included. Knowledge is included to relate information from the different perspectives; for example, evaluation knowledge that can be used to derive product evaluations in terms of user ontology from product information based on producer ontology. Agent models are used as a high-level design structure for the architecture. It is shown how this combination of agent models, ontologies and knowledge provides an adequate approach to the distributed and knowledge-intensive character of the application.     

Viability of milk neutrophils and severity of bovine coliform mastitis

To study the host-pathogen interactions during Escherichia coli mastitis, we first determined whether E. coli infection would change blood and milk polymorphonuclear neutrophil (PMN) chemiluminescence (CL) and viability. We then hypothesized that when E. coli invade the mammary gland, the viable PMN in milk would efficiently phagocytose and destroy E. coli before establishment of infection. We observed that the phagocytosis-dependent and independent CL were closely linked to PMN viability and were crucial to the outcome of mastitis. Maximal PMN influx and colony-forming units in infected quarters appeared at postinfection hours (PIH) 6 to 24. This further boosted PMN recruitment through bone marrow-blood barrier as well as blood-milk barrier. The survival of recruited PMN in the E. coli-infected quarters was much higher than that of noninfected quarters. Chemiluminescence activity of PMN from the infected quarters significantly increased following E. coli infection, even exceeding that of blood at PIH 6, 12, and 18 to 24; no such increase was observed in noninfected quarters, suggesting that the various responses of milk PMN to stimuli resulted largely from PMN viability. The highest CL intensity and durability was observed in milk PMN from infected quarters at PIH 12. Whereas an increased viability of PMN in the noninfected quarters was only significant at PIH 6, the viability of PMN in infected quarters was long lasting and significantly higher at PIH 6 to 72. Importantly, higher preinfection milk PMN viability correlated with bacterial clearance, which was accompanied by faster recovery. Our study strongly supports the hypothesis that boosting milk PMN viability could be a strategy with which to prevent or reduce the severity of coliform mastitis in dairy cows. This strategy might be achieved through strengthening bone marrow functionality.     

Energy consumption and economic activities in Iran

The causal relationship between overall GDP, industrial and agricultural value added and consumption of different kinds of energy are investigated using vector error correction model for the case of Iran within 1967–2003. A long-run unidirectional relationship from GDP to total energy and bidirectional relationship between GDP and gas as well as GDP and petroleum products consumption for the whole economy was discovered. Causality is running from value added to total energy, electricity, gas and petroleum products consumption and from gas consumption to value added in industrial sector. The long-run bidirectional relations hold between value added and total energy, electricity and petroleum products consumption in the agricultural sector. The short-run causality runs from GDP to total energy and petroleum products consumption, and also industrial value added to total energy and petroleum products consumption in this sector.