Creep evaluation and temperature dependence in self-sensing micro carbon polymer-based composites for further development as an Internet of Things Sensor device

This article investigates the dependency of temperature on electrical resistance (R) change in micro carbon fiber polymer composites (MCFPC), for further development as an Internet of Things sensor from previous research works. Three mixtures were prepared using Dow Corning’s Silastic 145 as base polymer and made vary fiber content weight percentages: fiber diameter to length ratio ∅⁄l 0.13 and carbon fiber content of 13%; ∅⁄l:0.66 and carbon fiber contents of 40% and 50%. Composites tested were submitted to temperature loading, with a constant strain of 0.0%, for assessment of R when a change in the composite’s temperature occurs. The composite response was observed to follow an Arrhenius function, for temperatures ranging from −10°C to 40°C. The apparent activation energy was calculated to evaluate further differences between carbon fiber contents and the sensitivity factor, [Formula: see text] due to temperature is determined. The specimens were also tested with a constant strain of 2.86% to assess creep. It was found that creep and R, over the period of time in the analysis, best fit a discrete latent variable model. The sensitivity factor change is determined in regard to stress relaxation, [Formula: see text]. The properties of MCFPC investigated here can be used to establish relationships between electrical resistance outputs and environmental loading conditions for this type of composites, enabling the possibility of deployment as part of a management system network for structural monitoring with real-time data acquisition.

Equivalent method for obtaining concrete age on the basis of electrical resistivity

Concrete age is the time since the moment water is added to the cement, and the age of concrete comprehensively reflects the physical properties of the concrete when curing under standard conditions. For concrete under nonstandard conditions, its physical properties are directly related to both its age and temperature history. The equivalent age of concrete is the time at which concrete under nonstandard conditions reaches the same state as concrete under standard conditions. Most equivalent methods, such as the Nurse-Saul function and the Arrhenius function, are based on a maturity index. However, the accuracy of these methods breaks down when the curing temperature range is wide. In this paper, the electrical resistivity of concrete is used as the index to determine the equivalent age of concrete. This method is based on the assumption that concrete with the same mixture proportions has the same electrical resistivity when the maturity of the concrete is the same, regardless of the curing history. The proposed method is advantageous because it can be performed in real time and is nondestructive. To constantly measure the electrical resistivity of concrete, an automatic data acquisition system is developed to monitor the electrical resistivity of concrete and reduce the error caused by polarization as much as possible. Then, a model for predicting the electrical resistivity of concrete under different curing temperatures is proposed to conveniently calculate the equivalent coefficient. Finally, the results calculated by the proposed equivalent method are compared with those of the standard method (Nurse-Saul equation), and the results of the proposed model are found to be more reasonable.

Effect of Temperature and Time on Oxygen Consumption by Olive Fruit: Empirical Study and Simulation in a Non-Ventilated Container

Fermentation processes within olive fruit jeopardize the quality of the extracted oil. Aeration, temperature, and time play a crucial role in attaining the critical threshold at which an aerobic respiration shifts towards anaerobic. In this work, the O2 consumption and CO2 production of olive fruit kept in a closed container at different temperatures (5–45 °C) were measured over 7 h. The data allowed us to describe the relationship between the temperature and the respiration rate as an Arrhenius function and simulate the oxygen consumption in the inner part of a container full of fruit with low aeration, considering the generated respiration heat over time. The simulation revealed that olives risk shifting to anaerobic respiration after 3 h at 25 °C and less than 2 h at 35 °C when kept in a non-ventilated environment. The results underline the irreversible damage that high day temperatures can produce during the time before fruit processing, especially during transport. Lowering, as soon as possible, the field temperature thus comes to the fore as a necessary strategy to guarantee the quality of the olives before their processing, like most of the fruit that is harvested at excessive temperatures.

Mixed Convection and Thermally Radiative Flow of MHD Williamson Nanofluid with Arrhenius Activation Energy and Cattaneo–Christov Heat-Mass Flux

In this paper, we explored the impact of thermally radiative MHD flow of Williamson nanofluid over a stretchy plate. The flow in a stretchy plate is saturated via Darcy–Forchheimer relation. Cattaneo–Christov heat-mass flux theory is adopted to frame the energy and nanoparticle concentration equations. Additionally, the mass transfer analysis is made by activation energy and binary chemical reaction. Activation energy is invoked through the modified Arrhenius function. The intention of the current investigation is to enhance the heat transfer rate in industrial processes. The non-Newtonian nanofluids have more prominent thermal characteristics compared to ordinary working fluids. The governing models are altered into ODE models, and these models are numerically solved by applying the MATLAB bvp4c algorithm. The graphical and tabular interpretations have scrutinized the impact of sundry distinct parameters. The fluid speed escalates for enhancing the Richardson number, and it falls off for higher values of the Weissenberg number. It is noticed that the fluid temperature declines for higher values of the Brownian motion parameter and it grows for larger values of the thermophoresis parameter. The activation energy enriches the heat transfer gradient and suppresses the local Sherwood number. Additionally, the more significant heat transfer gradient occurs in heat-absorbing nonradiative viscous nanofluid and a smaller heat transfer gradient occurs in heat-generating radiative Williamson nanofluid. Also, we noticed that a higher heat transfer gradient appears in the Fourier model than in the Catteneo–Christov model. In addition, the comparative results are confirmed and reached an outstanding accord.

Water vapor transmission properties of acrylic organic coatings

In this work, we evaluate the water vapor transmission rate (WVTR), the permeability (P), solubility (S), and diffusion (D) coefficients of Paraloid B44, Paraloid B72, and Incralac coatings in the temperature range of 5–35°C. The Arrhenius function—diffusion activation energy and preexponential factor—has also been determined from the data: $$D_{B44} = 35.2\;{\text{cm}}^{2} \;{\text{s}}^{ - 1} \exp \left( { - 25\;{\text{kJ mol}}^{ - 1} /{\text{RT}}} \right)$$ D B 44 = 35.2 cm 2 s - 1 exp - 25 kJ mol - 1 / RT ; $$D_{B72} = 9.5\;{\text{cm}}^{2} \;{\text{s}}^{ - 1} \exp \left( { - 23\;{\text{kJ mol}}^{ - 1} /{\text{RT}}} \right)$$ D B 72 = 9.5 cm 2 s - 1 exp - 23 kJ mol - 1 / RT ; $$D_{\text{Incralac}} = 622.8\;{\text{cm}}^{2} \;{\text{s}}^{ - 1} { \exp }\left( { - 28\;{\text{kJ mol}}^{ - 1} /{\text{RT}}} \right)$$ D Incralac = 622.8 cm 2 s - 1 exp - 28 kJ mol - 1 / RT . These resins are important coating materials, for example, for conservators to protect metallic artifacts, such as statues, against corrosion. Despite Paraloid B44 and B72 resins being considered as reference materials in conservation practice, that is, new coating materials (either water vapor retarders or transmitters) are often compared to them, there are no comprehensive data for the quantities describing the vapor permeability (P, S, D) of these materials. The measurements are based on the ISO cup-method using substrate/coating composite samples. The strength of this technique is that it can also be used when the coating is non-self-supporting; nevertheless, P, S, and D can be deduced for the coating layer itself, and it seems to be a standardizable procedure for comparative performance testing of coating materials. Paraloid B72 layers exhibited higher WVTRs—from 39 to 315 g m−2 day−1 as the temperature increased from 5 to 35°C—compared to Paraloid B44 and Incralac coatings—from 17 to 190 g m−2 day−1, respectively. The transmission rate parameters were also compared to the results of corrosion tests. Incralac was the most effective corrosion inhibitor, and the performance of the B44 was better than the B72, which is in good agreement with the transmission rate tests.

The Effects of Activation Energy and Thermophoretic Diffusion of Nanoparticles on Steady Micropolar Fluid along with Brownian Motion

The present study is related to the effects of activation energy and thermophoretic diffusion on steady micropolar fluid along with Brownian motion. The activation energy and thermal conductivity of steady micropolar fluid are also discussed. The equation of motion, angular momentum, temperature, concentration, and their boundary conditions are presented for the micropolar fluid. The detail of geometry reveals the effects of several parameters on the parts of the system. The nonlinear partial differential equations are converted into nonlinear ordinary differential equations, and a famous shooting scheme is used to present the numerical solutions. The comparison of the obtained results by the shooting technique and the numerical bvp4c technique is presented. The behavior of local skin friction numbers and couple stress number is tabulated for different parameters, and some figures are plotted to present the different parameters. For uplifting the values of AE for parameter λA, the concentration profile is increased because of the Arrhenius function, and AE increases with the reduction of this function. The increasing values of the parameter of rotation G show the decrement in velocity because of the rotation of the particle of the fluid, so the linear motion decreases. Thermophoresis is responsible for shifting the molecules within the fluid, and due to this, an increment in boundary layer thickness is found, so by a greater value of Nt, the concentration profile decreases and temperature profile goes down.

Hot Deformation Behavior and Strain-Compensated Constitutive Equation of Nano-Sized SiC Particle-Reinforced Al-Si Matrix Composites

The hot deformation behavior of nano-SiCp/Al-Si composites was studied by isothermal compression tests at 470–530 °C and strain rates of 0.01–5 s−1. A strain-compensation constitutive model was developed with a Z parameter and an Arrhenius function, and its accuracy was verified by error analysis. The results show that the flow stress of the composites decreased with the increase in deformation temperature and the decrease in strain rate. The average activation energy for nano-SiC particle-reinforced Al-Si matrix composites was 277 kJ/mol, which was larger than the activation energy for self-diffusion of pure aluminum. The average relative error was calculated as 2.88%, indicating the strain-compensated constitutive equation could accurately predict the hot deformation behavior of nano-SiCp/Al-Si composites.