Search Results (12)

Density and viscosity are fundamental properties necessary for processing of red palm oil (RPO). The main fatty acid constituents of RPO were determined to be palmitic acid (C_16:0), oleic acid (C_18:1), and linoleic acid (C_18:2). Rheology measurements confirmed that RPO behaved as a Newtonian fluid. Viscosities and atmospheric densities of RPO were measured at 0.1 MPa and (293 K to 413) K and correlated with the Rodenbush model (0.05% deviation). Dynamic viscosities of RPO were correlated with the Vogel–Fulcher–Tammann model (0.06% deviation) and Doolittle free volume model (0.04% deviation). High-pressure densities of RPO were measured at (10 to 150) MPa and (312 to 352) K. The Tait equation could correlate the high-pressure densities of RPO to within 0.021% deviation and was used to estimate the thermal expansion as 5.1 × 10⁻⁴ K⁻¹ (at 312 K, 150 MPa) to 4.8 × 10⁻⁴ K⁻¹ (at 352 K, 150 MPa) and isothermal compressibility as 7.3 × 10⁻⁴ MPa⁻¹ (at 352 K, 0.1 MPa) to 3.5 × 10⁻⁴ MPa⁻¹ (at 352 K, 150 MPa). Parameters for the perturbed-chain statistical associating fluid theory equation of state were determined and gave an average of 0.143% deviation in density. The data and equations developed should be useful in high-pressure food processing as well as in applications considering vegetable oils as heat transfer fluids or as lubricants. Full article

Particle breakage is a common phenomenon during the processes of production, storage, and transportation. Because of the requirements for pellet integrity in poultry farming, research on the breakage characteristics of feed pellets is necessary. In this paper, repeated compression tests under different loading forces and repeated impact tests under different air pressures were carried out with feed pellets as the research object. The breakage behaviors were described, and the particle size distribution of feed pellets was analyzed quantitatively. The results revealed a positive correlation between crack density in feed particle beds and loading force. The compression process was divided into three stages based on force–displacement curves. The size of the feed pellets during repeated impacts decreased continuously and was negatively correlated with air pressure. The Weibull function accurately described the particle size distribution, with R² values exceeding 0.97 and 0.96. The Weibull parameters showed a steady breakage degree in compression tests and a growing breakage degree in impact tests. The variation in energy and pulverization rate under different loading conditions was examined as the number of loading cycles increased. The relationship between energy and pulverization rates was fitted, showing that both parameters increased with loading cycles in different loading methods. The model of Vogel and Peukert could describe the relationship between energy and pulverization rate well, with R² values exceeding 0.94. The minimum energy required for pellet breakage was higher in compression than in impact due to the compaction of the feed particle bed during repeated compression. The results can provide basic theory and data support for breakage characteristics and quality evaluation of feed pellets. Full article

The study investigated the effect of the molecular weight of three difunctional poly(propylene glycol) diacrylates on the temperature-dependent ionic conductivity of these monomers and their blends with an eutectic nematic liquid crystal mixture (E7). The results revealed two distinct regions. At low temperatures, ionic conduction can be described by the Vogel–Tamman–Fulcher (VTF) equation, while at high temperatures, the conductivity data follow the prediction of the Arrhenius model. The Arrhenius and VTF parameters and their corresponding activation energies were determined using the least squares method. In addition, a conductivity analysis based on an ionic hopping model is proposed. Estimates of ion concentrations and diffusion constants were calculated. It was found that both the ionic concentration and the diffusion constant decrease with the increase in the molecular weight of the monomers. The static dielectric permittivity decreases in the following order: TPGDA, PPGDA540, and PPGDA900. This can be explained by the higher dipole moment of TPGDA, which is caused by an enhanced volume density of carbonyl groups. Full article

Crystallization often occurs in the laser welding of amorphous alloys, reducing the properties of amorphous alloys. Therefore, the research in this thesis focuses on the experimental selection of suitable welding parameters to prevent crystallization of Zr-based amorphous alloys during the laser welding process. As such, it is necessary to simulate the temperature field curve of the welding area by computer and then determine the power and laser moving speed of laser welding. In this paper, the temperature field curve of the Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 (Vit1) amorphous alloy in laser welding is obtained by finite element analysis. The continuous heating curve (CHT) of Vit1 is fitted by the Vogel–Fulcher–Tammann (VFT) equation and the Kissinger equation. If the temperature field curve intersects with the CHT curve, crystallization occurs. The experiment results show that the VFT equation can be used to predict the crystallization of Vit1 better in laser welding. The temperature and welding time are increased by using a low welding speed. Therefore, the temperature of the weld zone cannot fall in time, resulting in the intersection of the temperature field curve and the CHT curve. Thus, crystallization can be avoided if the welding speed is controlled within a reasonable range, and the highest temperature is kept under the CHT curve. The combination of the CHT curve and the temperature field curve shows that the samples at 300 W-3 mm/s and 300 W-6 mm/s welding parameters all undergo crystallization, while the samples at 300 W-9 mm/s and 300 W-12 mm/s welding parameters do not undergo crystallization. Through the flexural test, it is found that the flexural strength of the welded interface is at its the maximum under 300 W-9 mm/s. Full article

We used dc magnetization and ac susceptibility to investigate the magnetic relaxation of ferrofluids made of 8 nm average-diameter Fe₃O₄ nanoparticles dispersed in hexane. Samples of different concentrations (δ) spanning two orders of magnitude ranging from 0.66 to 0.005 mg (Fe₃O₄)/mL (hexane) were used to vary the interparticle interaction strength. Our data reveal a critical concentration, δ_c = 0.02 mg/mL, below which the ferrofluid behaves like an ideal nanoparticle ensemble where the superspins relax individually according to a Néel–Brown activation law $\mathsf{\tau }(\mathrm{T})={\mathsf{\tau }}_0\exp \left(\frac{{\mathrm{E}}_{\mathrm{B}}}{{\mathrm{k}}_{\mathrm{B}}\mathrm{T}}\right)$ with a characteristic time τ_o ~10⁻⁹ s. That is further confirmed by the observed invariance of the relative peak temperature variation per frequency decade $∆=\frac{∆\mathrm{T}}{\mathrm{T}·∆\mathrm{l}\mathrm{o}\mathrm{g}\left(\mathrm{f}\right)}$, which stays constant at ~0.185 when δ < δ_c. At higher concentrations, between 0.02 and 0.66 mg/mL, we found that Δ exhibits a monotonic increase with the inverse concentration, $\frac{1}{\delta }$, and the collective superspin dynamics is described by a Vogel–Fulcher law, $\mathsf{\tau }(\mathrm{T})={\mathsf{\tau }}_0\exp \left[\frac{{\mathrm{E}}_{\mathrm{B}}}{{\mathrm{k}}_{\mathrm{B}}\left(\mathrm{T}-{\mathrm{T}}_0\right)}\right]$. Within this regime, the dipolar interaction strength parameter T₀ increases from T₀ = 0 K at δ_c = 0.02 mg/mL to T₀ = 14.7 K at δ = 0.66 mg/mL. Full article

Due to globalization in this modern age of technology and other uncontrollable influences, transportation parameters can differ within a certain range of a given period. In this situation, a managerial position’s objective is to make appropriate decisions for the decision-makers. However, in general, the determination of an exact solution to the interval data-based transportation problem (IDTP) becomes an NP-hard problem as the number of choices within their respective ranges increases enormously when the number of suppliers and buyers increases. So, in practice, it is difficult for an exact method to find the exact solution to the IDTP in a reasonable time, specifically the large-sized problems with large interval sizes. This paper introduces solutions to the IDTP where supply, demand, and cost are all in interval numbers. One of the best interval approximations, namely the closed interval approximation of pentagonal fuzzy number, is proposed for solving the IDTP. First, in the proposed closed interval approximation method (Method-1), the pentagonal fuzzification method converts the IDTP to a fuzzy transportation problem (FTP). Subsequently, two new ranking methods based on centroid and in-center triangle concepts are presented to transfer the pentagonal fuzzy number into the corresponding crisp (non-fuzzy) value. Thereafter, the optimal solution was obtained using Vogel’s approximation method coupled with the modified distribution method. The proposed Method-1 is reported against a recent method and shows superior performance over the aforementioned and a proposed Method-2 via benchmark instances and new instances. Full article

The diffusion of small molecules or ions within polymeric materials is critical for their applications, such as polymer electrolytes. Cross-linking has been one of the common strategies to modulate solute diffusivity and a polymer’s mechanical properties. However, various studies have shown different effects of cross-linking on altering the solute transports. Here, we utilized coarse-grained molecular dynamics simulation to systematically analyze the effects of cross-linking and polymer rigidity of solute diffusive behaviors. Above the glass transition temperature ${\mathrm{T}}_{\mathrm{g}}$, the solute diffusion followed the Vogel–Tammann–Fulcher (VTF) equation, D = D${}_0$ e${}^{-{\mathrm{E}}_{\mathrm{a}}/\mathrm{R}(\mathrm{T}-{\mathrm{T}}_0)}$. Other than the conventional compensation relation between the activation energy ${\mathrm{E}}_{\mathrm{a}}$ and the pre-exponential factor D${}_0$, we also identified a correlation between ${\mathrm{E}}_{\mathrm{a}}$ and Vogel temperature T${}_0$. We further characterized an empirical relation between T${}_0$ and cross-linking density. Integrating the newly identified correlations among the VTF parameters, we formulated a relation between solute diffusion and the cross-linking density. The combined results proposed the criteria for the optimal solute diffusivity in cross-linked polymers, providing generic guidance for novel polymer electrolyte design. Full article

We construct characteristic identities for the split (polarized) Casimir operators of the simple Lie algebras in adjoint representation. By means of these characteristic identities, for all simple Lie algebras we derive explicit formulae for invariant projectors onto irreducible subrepresentations in $T^{\otimes 2}$ in the case when T is the adjoint representation. These projectors and characteristic identities are considered from the viewpoint of the universal description of the simple Lie algebras in terms of the Vogel parameters. Full article

In this work, analysis of ion transport parameters of polymer blend electrolytes incorporated with magnesium trifluoromethanesulfonate (Mg(CF₃SO₃)₂) was carried out by employing the Trukhan model. A solution cast technique was used to obtain the polymer blend electrolytes composed of chitosan (CS) and poly (2-ethyl-2-oxazoline) (POZ). From X-ray diffraction (XRD) patterns, improvement in amorphous phase for the blend samples has been observed in comparison to the pure state of CS. From impedance plot, bulk resistance (R_b) was found to decrease with increasing temperature. Based on direct current (DC) conductivity (σ_dc) patterns, considerations on the ion transport models of Arrhenius and Vogel–Tammann–Fulcher (VTF) were given. Analysis of the dielectric properties was carried out at different temperatures and the obtained results were linked to the ion transport mechanism. It is demonstrated in the real part of electrical modulus that chitosan-salt systems are extremely capacitive. The asymmetric peak of the imaginary part (M_i) of electric modulus indicated that there is non-Debye type of relaxation for ions. From frequency dependence of dielectric loss (ε″) and the imaginary part (M_i) of electric modulus, suitable coupling among polymer segmental and ionic motions was identified. Two techniques were used to analyze the viscoelastic relaxation dynamic of ions. The Trukhan model was used to determine the diffusion coefficient (D) by using the frequency related to peak frequencies and loss tangent maximum heights (tanδ_max). The Einstein–Nernst equation was applied to determine the carrier number density (n) and mobility. The ion transport parameters, such as D, n and mobility (μ), at room temperature, were found to be 4 × 10⁻⁵ cm²/s, 3.4 × 10¹⁵ cm⁻³, and 1.2 × 10⁻⁴ cm²/Vs, respectively. Finally, it was shown that an increase in temperature can also cause these parameters to increase. Full article

Wire coatings are necessary to provide protection from the aggressive environment and to add mechanical strength to wires and cables. In this study, we investigated the effect of radiative linear as well as non-linear heat transfer on the wire coating in response to joule heating, using a third grade fluid as the coating material. For the temperature dependent viscosity, two models namely—Reynolds’ and Vogel’s—were used. The non-linear ordinary differential equations were solved analytically by the Homotropy Analysis Method (HAM). Numerical technique was also applied for comparison and good agreement was found. It is interesting to note that the temperature parameter had a remarkable effect on the temperature distribution and heat transfer characteristics in the flow region within the die. It was observed that the velocity of the fluid within the die decreased as the magnetic parameter increased, while the magnetic field had an accelerating effect on the temperature distribution. Near the surface of the wire, the velocity of the coating material accelerated as the temperature parameter and radiation parameter increased. Analysis also showed that the temperature of the coating material decreased with increasing radiation and temperature parameters. Full article

Multiarm star polymers, denoted PEIx-PLAy and containing a hyperbranched poly(ethyleneimine) (PEI) core of different molecular weights x and poly(lactide) (PLA) arms with y ratio of lactide repeat units to N links were used in this work. Samples were preconditioned to remove the moisture content and then characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). The glass transition temperature, T_g, is between 48 and 50 °C for all the PEIx-PLAy samples. The dielectric curves show four dipolar relaxations: γ, β, α, and α′ in order of increasing temperature. The temperatures at which these relaxations appear, together with their dependence on the frequency, allows relaxation maps to be drawn, from which the activation energies of the sub-T_g γ- and β-relaxations and the Vogel–Fulcher–Tammann parameters of the α-relaxation glass transition are obtained. The dependence of the characteristic features of these relaxations on the molecular weight of the PEI core and on the ratio of lactide repeat units to N links permits the assignation of molecular motions to each relaxation. The γ-relaxation is associated with local motions of the –OH groups of the poly(lactide) chains, the β-relaxation with motions of the main chain of poly(lactide), the α-relaxation with global motions of the complete assembly of PEI core and PLA arms, and the α′-relaxation is related to the normal mode relaxation due to fluctuations of the end-to-end vector in the PLA arms, without excluding the possibility that it could be a Maxwell–Wagner–Sillars type ionic peak because the material may have nano-regions of different conductivity. Full article

The Vogel-Fulcher-Tammann (VFT) equation has been used extensively in the analysis of the experimental data of temperature dependence of the viscosity or of the relaxation time in various types of supercooled liquids including metallic glass forming materials. In this article, it is shown that our model of viscosity, the Bond Strength—Coordination Number Fluctuation (BSCNF) model, can be used as an alternative model for the VFT equation. Using the BSCNF model, it was found that when the normalized bond strength and coordination number fluctuations of the structural units are equal, the viscosity behaviors described by both become identical. From this finding, an analytical expression that connects the parameters of the BSCNF model to the ideal glass transition temperature T₀ of the VFT equation is obtained. The physical picture of the Kohlrausch-Williams-Watts relaxation function in the glass forming liquids is also discussed in terms of the cooperativity of the structural units that form the melt. An example of the application of the model is shown for metallic glass forming liquids. Full article