Dynamic Viscosity Research Articles

ANALYSIS OF PHYSICOCHEMICAL PROPERTIES AND SPECTROPHOTOMETRIC CHARACTERISTICS OF SELECTED VEGETABLE OILS

Introduction. Vegetable oils are a known source of mono- and polyunsaturated fatty acids (MUFA and PUFA). The growing demand for vegetable oils, rich in unsaturated fatty acids, increases the use of new oil plants to obtain them. In this study, the physicochemical properties (density, pH, refractive index, dynamic viscosity, contact angle, surface tension, color) were examined, a spectroscopic analysis was carried out and antioxidant properties were determined. In order to determine the indicated parameters, simple and easily accessible analytical methods were used, which provide key information about the prop erties of oils and serve as indicators for assessing their quality. Six commercially available oils were se lected for the study: evening primrose seeds (Oenothera paradoxa), milk thistle seeds (Silybum maria num), pumpkin seeds (Cucurbita oleo), linseed (Linum usitaissimum L.), winter camelina seeds (Camelina silvestris) and black cumin seeds (Nigella sativa). Results and conclusions. The conducted research provided significant insights into the relationship between the determined parameters of vegetable oils. The positive correlation between density and refrac tive index also highlights the influence of fatty acid composition on these properties. The observed diversi ty of colors of the oils tested highlights the unique composition of dyes characteristic of each oil. It was found that the pH of vegetable oils is a key indicator reflecting the level of acidity in the oil. The correla tion between contact angle and surface tension revealed complex surface interactions.

ВЛИЯНИЕ ЭКСТРАКТИВНЫХ АГЕНТОВ НА ПЛОТНОСТЬ И ВЯЗКОСТЬ ЖИДКОЙ ФАЗЫ ПРИ РЕКТИФИКАЦИИ СМЕСИ ИЗОПРОПАНОЛ-ВОДА

In this work, the dynamic viscosity and density of three-component mixtures consisting of a binary azeotropic mixture of isopropanol-water and an extractive agent were investigated. Three points of the profile of concentrations in the liquid phase in the extractive separation column of isopropanol-water mixture in recalculation on the pseudobinary mixture were selected for research: the first point - 95/5 % wt. %; the second point - 5/95 % wt. %; the third azeotrope point - 88/12 % wt. %. For the selected points model mixtures were prepared to which 13 % wt. % of the extractive agent was added. The extractants used in this work were monoethylene glycol (EG), which is used in industrial processes, 1-ethyl-3-methyl imidazolium chloride ([Emim][Cl]) and triethylene glycol-based boronic acid amino ester (AEBA). Experimental data on concentration and temperature dependences of dynamic viscosity and density were obtained for these mixtures. The results showed that the viscosity of the system increases in the series of EG, AEBA, [Emim][Cl]. To carry out calculations of the investigated thermophysical properties in the work we used known expressions: for density - through the sum of volumes; for viscosity - the Kendall-Manroe model. For a three-component mixture with EG, the results of calculations of properties performed in the AspenPlus V12 package are presented. The studies carried out in this work have shown that the density modeling of the studied mixtures is quite accurate, the discrepancy between experimental and calculated data does not exceed 1%. Modeling of the dynamic viscosity coefficient of the system by the Kendall-Manroe model for isopropanol-water mixture in the presence of the studied extractive agents can lead to significant errors, the maximum value reaches 52%. The calculated values of the dynamic viscosity coefficient are underestimated, which in turn can lead to errors in modeling (on the basis of these properties) of heat and mass transfer processes occurring in the apparatus.

Lipid composition and physicochemical parameters of unrefined sunflower oil

Unrefined sunflower oil is obtained by pressing of the sunflower seeds and subsequent fine filtration. It contains more biologically active substances compared to the refined one, it is more stable to oxidation processes, for that reason it is widely used in the composition of the various food products. The main acids in the oil are oleic (56.5%), linoleic (31.7%), palmitic (6.4%), and stearic acid (3.2%). Total sterol content is 0.7%, with ß-sitosterol as a main component (84.0%). The quantity of tocopherol is 188 mg/kg and it consists of one compound α-tocopherol (100%). Different physicochemical parameters were obtained at temperature ranges (from 20 to 80°C). The values of these parameters decrease with an increase in temperature, density (from 0.938 to 0.901 g/ml), surface tension (from 44.124 to 31.787 mN/m), dynamic viscosity (from 29.195 to 14.913 mPa.s), and kinematic viscosity (from 31.125 to 16.552 mm2/s). All these changes are in confirmation of the data from the literature and are relevant in our next studies.

Biotechnology for the development of a functional fermented milk product using vegetable raw materials

This article discusses the possibility of using flour from pomegranate waste and persimmon waste as a biologically active additive in yogurt formulations. To assess the effect of the additive used, the dynamics of titrated acidity during sample storage was studied, and dynamic viscosity was considered. Since the main indicators of product quality for the consumer are its organoleptic properties, the taste, smell, color and consistency of the developed samples of low-fat yogurt were evaluated. It was determined that in the formulation of low-fat yogurt, the optimal use of flour from pomegranate waste in an amount of 2.0%. The introduction of a fruit additive from persimmon flour into the prototypes was 1, 3, 6, 9% by weight. The results of the degree of syneresis and viscosity indicate a positive effect of the additive on the formation of a milk clot. In low-fat yogurt without the addition of flour from pomegranate waste, the texture of the milk clot was not oily, loose and less viscous, and with an increase in the mass of the added additive, the smell and taste became more pronounced, the color of the yogurt turned pink. Studies show that adding persimmons to yogurt can increase the content of antioxidants, in particular lycopene, which exhibits the strongest antioxidant properties among carotenoids, vitamins and minerals. The nutrients contained in persimmons, combined with probiotics from yogurt, can have beneficial effects on digestion, strengthen the immune system and promote overall health.

СИСТЕМА УПРАВЛЕНИЯ БЕЗОПАСНОСТЬЮ ПОЛЁТОВ ЛЕТАТЕЛЬНЫХ АППАРАТОВ С БАЗОВОЙ ВСТРОЕННОЙ СИСТЕМОЙ АВТОМАТИЧЕСКОГО ДОПУСКОВОГО КОНТРОЛЯ ГИДРАВЛИЧЕСКОЙ СИСТЕМЫ И СИСТЕМ МОНИТОРИНГА И ПРОГНОЗИРОВАНИЯ ОТКАЗОВ

This paper considers an integrated tolerance control system with failure monitoring and prediction subsystems for aircraft safety management system (ASMS), which is relevant nowadays. The paper deals with the operational component of hydraulic system (HS) tolerance zones. The internal measured parameter is pressure, so it was necessary to find an algorithm that reflects its dependence on operating conditions, its coefficient of kinematic viscosity of the fluid, its temperature, operating time, ambient temperature and flight stage. The operational component of the tolerance zone can be derived from the obtained expression for the pressure by substituting the boundary values of the parameters included in this dependence. While polling the sensors of the automatic control system it is necessary each time to calculate the range of variation of the parameter for the given stage of flight and other conditions with the help of algorithms for calculating the tolerance zone obtained in the paper. Moreover, the control system has to process a large amount of information using artificial intelligence (AI) methods which allows the safety of aircraft flight (SAF) to be managed.

Dynamic framework for large-scale modeling of membranes and peripheral proteins.

In this chapter, we present a novel computational framework to study the dynamic behavior of extensive membrane systems, potentially in interaction with peripheral proteins, as an alternative to conventional simulation methods. The framework effectively describes the complex dynamics in protein-membrane systems in a mesoscopic particle-based setup. Furthermore, leveraging the hydrodynamic coupling between the membrane and its surrounding solvent, the coarse-grained model grounds its dynamics in macroscopic kinetic properties such as viscosity and diffusion coefficients, marrying the advantages of continuum- and particle-based approaches. We introduce the theoretical background and the parameter-space optimization method in a step-by-step fashion, present the hydrodynamic coupling method in detail, and demonstrate the application of the model at each stage through illuminating examples. We believe this modeling framework to hold great potential for simulating membrane and protein systems at biological spatiotemporal scales, and offer substantial flexibility for further development and parametrization.

A Monte Carlo simulation of tracer diffusion in amorphous polymers.

Tracer diffusion in amorphous polymers is a sought-after quantity for a range of technological applications. In this regard, a quantitative description of the so-called decoupling from the reverse proportionality between viscosity and diffusion coefficient into a fractional one remains a challenge requiring a deeper insight. This work employs a Monte Carlo simulation framework in 3 dimensions to investigate the consequences of different scenarios for estimating this fractional exponent on the diffusion coefficient of tracers in polymers near glass transition. To this end, we adopted a continuous-time random walk model for tracer diffusion in the supercooled liquid state. The waiting time distribution of the diffusants was computed based on the rotational correlation times of the polymer. This proposed procedure is of particular interest because it brings the quantity of waiting time (and its statistics) in connection with the measurable observable of rotational times. In the framework of our simulations the aforementioned fractional exponent appears in the relation between the diffusant's waiting time and the rotational time of the diffusion medium. A limited comparison with experimental diffusivities from the literature revealed a reasonable agreement with a fractional exponent on the basis of the molar volumes of the diffusant and the monomeric unit. Finally, an analysis of time-averaged mean squared displacement pointed to normal Brownian dynamics for tracer diffusion in polymers above the glass transition temperature.

Preparation and Antifiltration Performance of Organic Zirconium Crosslinker for Guar Gum‐Fracturing Fluid

Aiming at the characteristics of low shear resistance and high filtration loss of guar gum‐fracturing fluid, a high‐efficiency organic zirconium crosslinker was prepared. In addition, the effects of different factors on the filtration coefficient and apparent viscosity of fracturing fluid were studied, and this study explores the micro mechanisms of various factors affecting the filtration coefficient from a molecular dynamics perspective. The results show that the antifiltration ability of guar gum‐fracturing fluid is inversely proportional to the fluid viscosity. The increase of crosslinker content and reservoir pressure is beneficial to improve the viscosity and antishear ability of guar gum‐fracturing fluid. When the crosslinker content is 0.25% and pressure is 30 MPa, the fracturing fluid parameters are 145 mPa·s and 2.1 × 10−2 m3 · min1/2, respectively, while the increase of reservoir temperature and the shear rate reduces the rheology and shear resistance of guar gum‐fracturing fluid, so that the viscosity and filtration coefficient of fracturing fluid at 180°C and 200 s-1 are 123 mPa·s and 2.3 × 10-2 m3·min1/2, respectively. This work not only paves a new avenue for synthesizing organic zirconium as a crosslinker but also provides an efficient measure to reduce the filtration of guar gum‐fracturing fluid on the oil and gas reservoirs.

PES and transport properties of the He⋯HBr complex from kinetic theory and molecular dynamics simulations.

The ab initio intermolecular potential of the He⋯HBr van der Waals (vdW) complex was calculated at the CCSD(T)/a5zBF level of theory and expanded in terms of the orthogonal Legendre polynomials. The PES then was implemented to calculate the interaction viscosity (η12) and diffusion (D12) coefficients through classical Mason-Monchick approximation (MMA), quantum mechanical close-coupling (CC), and molecular dynamics (MD) simulations. Energy-dependent Senftleben-Beenakker (SB) cross-sections were calculated using rotationally averaged cross-sections, and Boltzmann averaging was used to reveal the temperature dependence of the SB cross-sections over the temperature range of T = 50-1000 K. The calculated transport properties from MMA are in close agreement with the CC results, especially for temperatures lower than T = 900 K. The ab initio potential data then were used to derive LJ (12,6) and Vashishta MD force fields, and the equilibrium MD simulation methods were implemented to extract η12 and D12 coefficients using Einstein formulas. It was found that the Vashishta 3-body interaction potential model shows better accuracy than the LJ (12,6) model in MD simulations of D12. For η12, however, both MD potential models are successful, and an average absolute deviation of lower than 1% was obtained when compared to the quantum mechanical CC method.

Convergence analysis of Euler and BDF2 grad-div stabilization methods for the time-dependent penetrative convection model

<abstract><p>Based on the grad-div stabilization method, the first-order backward Euler and second-order BDF2 finite element schemes were studied for the approximations of the time-dependent penetrative convection equations. The proposed schemes are both unconditionally stable. We proved the error bounds of the velocity and temperature in which the constants are independent of inverse powers of the viscosity and thermal conductivity coefficients when the Taylor-Hood element and $ P_2 $ element are used in finite element discretizations. Finally, numerical experiments with high Reynolds numbers were shown to confirm the theoretical results.</p></abstract>

Viscosity, surface energies and surface heat capacities of three essential oils

In these study three essential oils were investigated in temperature range between 10 and 40°C. The surface energy and surface heat capacity were determined for them. Dynamic and kinematic viscosity were found in same temperature range. According investigations the best results are obtained for the Pinus sylvestris essential oil, after that for the Junipperus communis essential oil and Oreganum herachoticum, essential oil, respectively.

Comportamento reológico, hidratação e propriedades mecânicas de sistemas LC3 com a incorporação de nanotubos de carbono de paredes múltiplas funcionalizados

Abstract Alternatives to conventional Portland cement with a more sustainable appeal are increasingly recurrent. Among these are the Limestone Calcined Clay (LC3) systems, characterized by high replacement percentages of Portland clinker by calcined clay and limestone, materials widely available worldwide. A complete understanding of the rheological behavior of LC3 systems is necessary for the practical application of this type of cement to be consolidated. Furthermore, although not yet investigated, the incorporation of nanomaterials stands out as a promising alternative for accelerating reactions and enhancing the mechanical performance of these systems at early ages. This study investigated the incorporation of carbon nanotubes (CNT) contents from 0.05 to 0.125% in an LC3 system through rotational rheometry, isothermal calorimetry, compressive strength at 7 and 28 days, and X-ray diffraction. Although the CNT incorporation increased the dynamic yield stress and equivalent viscosity of the LC3 pastes, the content of 0.1 wt.% slightly increased and anticipated the occurrence of the main peak of the aluminates. Increases of up to 13.5% in compressive strength at 7 and 28 days of hydration were observed for a CNT content of 0.1 wt.%.

Knee Joint Assist in Seated Motion Focusing on Variable Viscosity Property in Exoskeleton Assistive Device -Comparison of Variable and Constant Viscosity Coefficients-

Knee Joint Assist in Seated Motion Focusing on Variable Viscosity Property in Exoskeleton Assistive Device -Comparison of Variable and Constant Viscosity Coefficients-

Pore-pressure and stress-coupled creep behavior in deep coal: Insights from real-time NMR analysis

Understanding the variations in microscopic pore-fracture structures (MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance (NMR) detection was conducted. Full-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging (NMRI) techniques. The results revealed that seepage pores and microfractures (SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores (AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damage-state adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics (size and degree of difficulty) of coal.

Improving crystallization and photoelectric performance of CsPbI<sub>2</sub>Br perovskite under ambient air via dynamic hot-air assisted recrystallization strategy

CsPbI<sub>2</sub>Br thin films prepared in ambient air are susceptible to humidity, resulting in low coverage, poor crystallization quality, numerous pinholes, and easy transformation into non perovskite phases. To overcome the troubles of pervoksite fabrication in ambient air, a feasible way is to reduce the moisture around the films as much as possible according to dynamic hot-air assisted strategy. However, the hot air accelerates the evaporation rate of solvent, resulting in the decrease of grain size. In order to improve the crystal growth and long-term stability in dynamic hot-air assisted strategy, in this work, we present a dynamic hot-air assisted recrystallization (DHR) strategy to prepare high-quality CsPbI<sub>2</sub>Br thin films in ambient air (i.e. the CsPbI<sub>2</sub>Br thin films prepared via dynamic hot-air strategy are recrystallized by using a green solvent (methylamine acetate) with high viscosity coefficient). Under ambient air with high humidity (RH＞60%), the CsPbI<sub>2</sub>Br thin film with high coverage, (100) preferred orientation, large average grain size, and stable structure is prepared via DHR strategy. The dynamic hot-air process can effectively reduce the moisture around the film and increase the nucleation sites in the precursor solution, thereby improving the coverage of the film. However, this process inevitably results in the significant decrease of grain size (<i>R</i><sub>ave</sub>= 0.32 μm) (i.e. more grain boundaries), exacerbating non-radiative recombination of carriers associated with trap states at these boundaries. The high coverage increases the grain-to-grain contact area, facilitating complete recrystallization. Thus, the recrystallization process can significantly increase the grain size (<i>R</i><sub>ave</sub> = 2.63 μm) and obtain a (100) preferred orientation (<i>I</i><sub>(110)</sub>/<i>I</i><sub>(200)</sub> = 0.006), resulting in high photoluminescence intensity and long fluorescence lifetime (118 ns). The unencapsulated CsPbI<sub>2</sub>Br perovskite solar cell (PSC) optimized via DHR strategy with low hysterescence factor (2.34%) and high repeatability exhibits a high power conversion efficiency (PCE = 17.55%), which is higher than those of most CsPbI<sub>2</sub>Br PSCs prepared in ambient air and gloveboxes previously reported. Moreover, the unencapsulated CsPbI<sub>2</sub>Br PSC possesses an excellent storage stability under ambient air with high humidity (RH > 60%), remaining 96% of the original PCE after aging 40 days. This provides a promising approach for achieving high-performance and long-term stable CsPbI<sub>2</sub>Br films under ambient air with high humidity, which is expected to promote the commercialization process of perovskite/silicon tandem cells and semi-transparent devices.

Self-diffusion and shear viscosity of pure 1-alkanol unary system: molecular dynamics simulation and review of experimental data.

Self-diffusion coefficients and shear viscosity coefficients of pure 1-alkanol liquids from methanol to 1-hexanol were predicted using molecular dynamics (MD) simulations. These coefficients have been calculated using the Green-Kubo and Einstein methods at a range of temperatures of 200-330 K with increments of 10 K. Two force fields, TraPPE-UA and OPLS-AA were applied. The predicted results were compared to the experimental data, and the activation energies for self-diffusion and shear viscosity were calculated using the Arrhenius equation. The Stokes-Einstein equation was used to examine its capability in predicting the relationship between self-diffusion and shear viscosity, and the effective hydrodynamic radius was determined using both the experimental data and the results from MD simulations. The TraPPE-UA force field showed better results for the transport properties of methanol, while the OPLS-AA force field performed well for predicting shear viscosity but weakly for self-diffusion, particularly at low temperatures and for 1-alkanol with higher methylene numbers. Using the mean squared displacement method for self-diffusion was found to be more accurate than the Green-Kubo method, while the Green-Kubo method was slightly better for calculating shear viscosity. The Stokes-Einstein equation is valid for pure 1-alkanol liquids with temperature-dependent effective hydrodynamic radius.

Well-posedness for heat conducting non-Newtonian micropolar fluid equations

<abstract><p>In this paper, we consider the first boundary value problem for a class of steady non-Newtonian micropolar fluid equations with heat convection in the three-dimensional smooth and bounded domain $ \Omega $. By using the fixed-point theorem and introducing a family of penalized problems, under the condition that the external force term and the vortex viscosity coefficient are appropriately small, the existence and uniqueness of strong solutions of the problem are obtained.</p></abstract>

Numerical solution of the problem of thermal effects on high-viscosity oil through a horizontal well

In this paper, the problem of developing a high-viscosity oil reservoir due to the effect of paragravity based on heating the reservoir section between the injection and production wells is considered. The thermal effect on the formation reduces the viscosity coefficient of the oil and increases the mobility of the raw material. The heat transfer equation is solved by the PSSS method. The task is solved in three stages. At the first stage, the oil reservoir is heated, at the second – its exposure, at the third - filtration.

Existence of large-data global weak solutions to kinetic models of nonhomogeneous dilute polymeric fluids

We prove the existence of large-data global-in-time weak solutions to a general class of coupled bead-spring chain models with finitely extensible nonlinear elastic (FENE) type spring potentials for nonhomogeneous incompressible dilute polymeric fluids in a bounded domain in $ \mathbb{R}^d $, $ d = 2 $ or $ 3 $. The class of models under consideration involves the Navier–Stokes system with variable density, where the viscosity coefficient depends on both the density and the polymer number density, coupled to a Fokker–Planck equation with a density-dependent drag coefficient. The proof is based on combining a truncation of the probability density function with a two-stage Galerkin approximation and weak compactness and compensated compactness techniques to pass to the limits in the sequence of Galerkin approximations and in the truncation level.

Study of the dependence between the chemical structure and dynamic viscosity of amidoesters of alkenyl succinic acids

Study of the dependence between the chemical structure and dynamic viscosity of amidoesters of alkenyl succinic acids