Tension Coefficient Research Articles

Surface tension of Coulomb balls

Herein, we have calculated plasma parameters corresponding to those of a dc discharge in neon at 77 K temperature at self-organization of dense Coulomb balls with a dust particle number density of more than 4×1011m−3. To calculate the plasma parameters, we employed the fluid model of the positive column of the glow discharge with dust particles. The potential energy of the dust particle and the analogue of the surface tension coefficient of the Coulomb ball at neon pressures from 20 to 160 Pa have been obtained. For the obtained values of the surface tension coefficient analogue, a comparison with data obtained by other authors has been carried out.

An Experimental Study of the Effect of the Addition of Silicon Oxide Nanoparticles on the Wettability Characteristics of Rocks with Respect to Oil

The results of an experimental study of the interfacial tension and surface wettability in the nanosuspension/oil/rock system are given. The effect of the concentration and size of silicon oxide nanoparticles on the coefficient of interfacial tension and the contact angle of wetting has been systematically studied for the first time. A wide range of weight concentrations of nanoparticles (from 0 to 1 wt %) and their average sizes (from 5 to 50 nm) are considered. It is established that the use of nanosuspensions makes it possible to radically change the wettability of rocks with respect to oil. In this case, this effect depends substantially on the concentration and size of nanoparticles.

Influence of the curvature correction to the surface tension on nuclear fragmentation at intermediate energy head-on heavy ion collisions

Hydrodynamic model of the ”doughnut”-like structures formation in the head-on heavy ion collisions at intermediate energies is analyzed. Modification of the model is suggested to include the curvature correction to the surface tension coefficient. It is shown that accounting for the curvature correction changes the overall reaction time, maximum size of the system and the number of fragments. The results obtained show good correspondence with the results of the transport theory calculations and experimental data for the number of fragments and spreading size. The conducted analysis suggests that accounting for the curvature correction to the surface tension coefficient is essential when studying the dynamics of the system in the heavy ion collisions.

Experimental study of nanoparticle size and material effect on the oil wettability characteristics of various rock types

The paper presents the results of systematic experimental studies of interfacial tension (IFT) and oil wettability of three different types of rock (dolomite, metabasalt, and sandstone) in nanosuspensions. Nanoparticles of silicon and aluminum oxides were used at the concentration ranged from 0.01 to 1 wt%. It is shown that with increasing NP concentration, the contact angle of an oil droplet resting on a rock in a nanosuspension increases quite essentially (from 33 to 153°). The nanoparticle size and compositional effects on interfacial tension coefficient and contact angle (CA) within a wide range of particle concentrations were systematically studied for the first time. The contact angle oil/dolomite/nanofluid increased from 92 to 151° with decrease in the SiO2 nanoparticle size 50 nm to 5 nm. With an increase in the NP size from 5 to 50 nm, there was a decrease in interfacial tension of about 30%. The first-ever experiments were conducted to study the influence of nanoparticles in water on the oil wettability of various types of hydrophilic and hydrophobic rocks. It is shown that the wettability characteristics of various types of rocks can be controlled by adding minor amounts of nanoparticles of different sizes and compositions to influence the parameters that play a key role in the problems related to oil recovery enhancement during reservoir flooding.

Passing Lecture On The Topic" Fluid Flow And Biophysical Properties " In The Online System

This article is devoted to the transition of"fluid flow and biophysical properties" in the module system. It is stated that it is possible to find the coefficient of viscosity in the Stox method, the coefficient of viscometric methods, to find the coefficient of viscosity in the axiom of Medicine, in diagnosis and in medical and forensic expertise. It is also described to find the coefficient of processes and surface tension on the surface of liquids by drip method.

Surface Thermodynamics, Viscosity, Activation Energy of N-Methyldiethanolamine Aqueous Solutions Promoted by Tetramethylammonium Arginate

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated.

Pumping of electrolyte with mobile liquid metal droplets driven by continuous electrowetting: A full-scaled simulation study considering surface-coupled electrocapillary two-phase flow.

With the excellent merits of both solid conductors and rheological fluids, liquid metal (LM) provides new opportunities to serve as flexible building blocks of miniaturized electronic and fluidic devices. The phenomenon of continuous electrowetting (CEW) has been long utilized for actuating LM contents in buffer medium, wherein an externally imposed voltage difference is responsible of manipulating the interfacial tension of deformable LM droplets. CEW effectively lowers the surface tension at the LM/electrolyte interface by driving bipolar counterions to the surface of conducting droplet. Since surface tension coefficient relies sensitively on the local voltage drop across the induced double layer, an electric-analogy Marangoni effect occurs even under a rather weak electric field in the presence of a surface gradient of the interfacial tension. CEW of LM routinely induces unidirectional pumping of electrolyte in the direction of applied electric field, with LM droplet translating oppositely within the device channel. Although this subject has received great attention from the microfluidic society in the past decade, previous reports concerned either the individual delivery of the suspension medium or the transport of LM droplet. Starting from this point, we offer herein a fully coupled physical description of two-phase flow dynamics occurring in CEW. The proposed simulation model successfully incorporates the synergy of the interfacial electrokinetic momentum transfer, surface tension on a curved surface, contact angle at the three-phase contact line as well as the gravity force density. The spatial-temporal motion of the contact interface is traced instantly with a moving mesh approach. By direct numerical simulation, the importance of the direct-current bias, additional alternating-current forcing, droplet size, initial ion adsorption in the process of CEW is addressed. Additionally, it is discovered that increasing the number of LM droplet is more cost-effective than enhancing the volume of a single drop in terms of achieving an improvement of the resulted electrocapillary pump performance, while the translational speed of the discrete droplet carrier does not make an observable change in response to a variation in the drop number. These results prove invaluable in terms of an elaborate design of smart on-chip electrokinetic frameworks embedding flexible LM contents in modern micro-total-analytical systems.

Numerical simulation of the influence of oxygen content on the weld pool depth during activated TIG welding

The required amount of surface-active element dissolved in the weld pool remarkably influences the depth of penetration during activated tungsten inert gas (A-TIG) welding process. This is mainly attributed to the changes in the surface tension coefficient sign by oxygen content, which in turn controls the reversal of fluid flow and the nature of heat transfer. It emphasizes that there is a strong correlation between the surface-active element oxygen content and the development of the weld pool. This research intends to find out the critical oxygen content required in the weld pool to cause complete reversal of Marangoni flow and its influence on the weld bead dimensions by numerical simulation during A-TIG welding. Three-dimensional evolution of thermal and velocity fields in the weld pool is simulated using ANSYS Fluent for 200 A and 300 A welding currents respectively by altering the dissolved oxygen levels in a 0.01 m thick 316 LN stainless steel (SS) plate. The simulated weld bead profile for varying dissolved oxygen levels is validated for 300 A current by carrying out A-TIG welding experiments in a 0.01-m–thick plate with different fluxes in order to achieve the diverse amounts of oxygen content in the weld pool. The simulated and experimentally obtained weld bead dimensions exhibited good agreement for various dissolved oxygen contents in the weld. The complete reversal of fluid flow has been found to occur in the weld pool when the dissolved oxygen in the weld pool is 335 ppm at 300 A and 200 ppm at 200 A current.

National market of diagnostic tests and test systems

The aim of the work was to analyze the market of diagnostic tests and test systems that are in circulation in Ukraine. Materials and methods . To achieve this goal, electronic and paper official sources of information were used, as well as pharmacy websites. The search, analytical, systematic, comparative and statistical methods and methods of mathematical and logical analysis were used in the work. Results. Analysis of the modern market of diagnostic tests and test systems were allowed to establish the range and brand structure (90 manufacturers). The vast majority of them are outside Ukraine (85.5 %). Among foreign producers, the largest importer is China (19.5 %). In the course of work to determine the level of competition between manufacturers of similar groups of tests and test systems set the coefficient of tension. To determine the level of availability, price liquidity and solvency adequacy ratios were calculated. Conclusion . The Ukrainian market of diagnostic tests and test systems was studied. It was established that the company structure consists of 90 manufacturers and 20 countries. The vast majority of products come from importing countries (85.5 %), where the leader is China (19.5 %). Analysis of competitiveness showed that the greatest competition was observed among companies that produce tests to determine pregnancy, glucose, ketones, nitrites and protein in the blood and urine (K vi = 0.96), and there was no test manufacturers for sperm testing (K vi = 0). The calculated price liquidity and adequacy of solvency ratios indicate high price competition and low availability for some groups of diagnostic tests and test systems.

Густина та поверхневий натяг розплавів Sn1–xBix

Методом лежачої краплi дослiджено поверхневий натяг та густину системи Sn1−xBix iз вмiстом 5, 10 та 15 ат.% Bi в температурному iнтервалi 470–800 K у вакуумi 10 Па. Для отримання експериментальних значень дослiджуваних фiзичних характеристик використовувалась програма DROP. Виявлено, що додавання вiсмуту до олова приводить до зменшення поверхневої енергiї розплавiв системи Sn1−xBix. Також показано, що iснують лiнiйнi температурнi залежностi для коефiцiєнта поверхневого натягу та густини.

Bose–Einstein Condensation as a Deposition Phase Transition of Quantum Hard Spheres and New Relations between Bosonic and Fermionic Pressures

We investigate the phase transition of Bose–Einstein particles with the hard-core repulsion in the grand canonical ensemble within the Van der Waals approximation. It is shown that the pressure of non-relativistic Bose–Einstein particles is mathematically equivalent to the pressure of simplified version of the statistical multifragmentation model of nuclei with the vanishing surface tension coefficient and the Fisher exponent тF = 5/2 , which for such parameters has the 1-st order phase transition. The found similarity of these equations of state allows us to show that within the present approach the high density phase of Bose-Einstein particles is a classical macro-cluster with vanishing entropy at any temperature which, similarly to the system of classical hard spheres, is a kind of solid state. To show this we establish new relations which allow us to identically represent the pressure of Fermi–Dirac particles in terms of pressures of Bose–Einstein particles of two sorts.

Enhanced melting flow and vaporization model and its applications in pulsed laser polishing on mold steel.

A developed three-dimensional finite element model to describe surface profiles and root mean square (RMS) roughness by pulsed laser polishing based on the melting flow and vaporization removal mechanism is innovatively presented. In this paper, we indicate that the melting flow and vaporization removal are the primary mechanisms in the laser polishing process and successfully simulated the S316 mold steel pulsed laser polishing via the finite element method. Notably, vaporization removal, vaporization expansion, and plasma impact pressure, which is based on the Navier-Stokes equation, continuity equation, and Marangoni effects, are crucial factors, which are creatively taken into account in this model. Besides, due to the physical parameters changing with temperature, it is critical to considering the temperature-dependent density, specific heat capacity, thermal conductivity coefficient, dynamic viscosity, and tension coefficient to make the simulation results and model accurately. In addition, the tailored model can predict the theoretical polishing surface profiles and RMS roughness based on the melting flow and vaporization removal mechanism. Regarding the single pulse laser polishing, we investigated the surface profiles and RMS roughness on different single pulse energy and pulse width. In summary, it is expected that this study could provide a theoretical reference regarding the laser polishing metals and pave the way for laser manufacturing in various industrial applications.

Induced surface and curvature tensions equation of state of hard spheres and its virial coefficients

Here, we present new results obtained for the equation of state with induced surface and curvature tensions. The explicit formulas for the first five virial coefficients of system pressure and for the induced surface and curvature tension coefficients are derived and their possible applications are briefly discussed.

Dripping, Jetting and Regime Transition of Droplet Formation in a Buoyancy-Assisted Microfluidic Device.

Buoyancy-assisted droplet formation in a quiescent continuous phase is an effective technique to produce highly monodispersed droplets, especially millimetric droplets. A comprehensive study combining visualization experiment and numerical simulation was carried out to explore the underlying physics of single droplet generation in a buoyancy-assisted microfluidic device. Typical regimes, including dripping and jetting, were examined to gain a deep insight into the hydrodynamic difference between the regimes. Particularly, the transition from dripping regime to jetting regime was investigated to give an in-depth understanding of the transitional behaviors. The effects of interfacial tension coefficient on the droplet size and formation regimes are discussed, and a regime diagram is summarized. The results show that oscillation of the interface in dripping regimes after detachment is caused by the locally accelerated fluid during the neck pinching process. Droplet formation patterns with the characteristics of both dripping regime and jetting regime are observed and recognized as the transitional regime, and the interface oscillation lasts longer than that in dripping regime, implying intensive competition between interfacial tension and inertial force. Reducing interfacial tension coefficient results in the dripping-to-jetting transition occurring at a lower flow rate of the dispersed phase. The regime diagram indicates that only the inertial force is the indispensable condition of triggering the transition from dripping to jetting.

Surface tension and heat of the surface formation of liquids

By the potential method, it was determined that regardless of the nature of the liquid, the surface tension coefficient is determined by [Formula: see text]. In this expression, [Formula: see text] is the specific heat of the surface formation, [Formula: see text] is the critical temperature. According to our approach, the specific heat of the surface formation (SHS) also depends on temperature: [Formula: see text] ([Formula: see text] — the specific heat of the surface formation at the mealting temperature, [Formula: see text] — thermal coefficent of SHS). In this research work, the temperature dependence of the surface tension coefficient was calculated for seven dissimilar liquids. It was revealed that the calculated values of [Formula: see text] are in satisfactory agreement with the available experimental values.

Association of Lennard-Jones particles in nanoconfined aqueous solution: Theory and molecular dynamics simulations

We develop a new Gibbs free energy-based association model and perform series of molecular dynamics (MD) simulations to study the association behavior of Lennard-Jones (LJ) particles in nanoconfined aqueous solution. In the association model, the total Gibbs free energy is the sum of free energy cost in the nucleation of a densely packed cluster with an isotropic shape and a radius dependent interfacial tension coefficient, and the translation entropy of dispersed particles outside the cluster. Two key theoretical expressions – total Gibbs free energy formula and the thermodynamic equilibrium equation – are obtained to estimate the cluster aggregation number for a given LJ particle number and the corresponding total Gibbs free energy. Using MD simulations, we observe that the association state transforms from the stable dispersion state, through the reversible state, finally to the stable aggregation state as the LJ particle number increases. In the reversible state, the system reversibly switch in between the dispersion and aggregation states. The existence of three types of association states is also found for LJ particles with the varied well depth. According to our model, the Gibbs free energy curve shows from a single minimum, through two minima, finally to a single minimum, leading to the transformation of association states. The occurrence of reversible state transition is attributed to the free energy barrier of the order of thermal fluctuation in water between the dispersion and aggregation states. These findings deepen the understanding of nucleation/aggregation of hydrophobic gas molecules or particles in solution under nanoconfinement.

Determination of the surface tension coefficient of ferrites 600NN upon sintering

The manufacturing process of ferrite production consists in a chain of structural and phase transformations resulted in formation of ferrite ceramics from disperse systems (their solid phase is represented by metal oxides). The forces of surface tension play a crucial role at all stages of the technological process. A decrease in surface tension forces during grinding due to the use of surfactants (surface active substances) leads to better disaggregation of the components (both original and ferritized). The use of surfactants reduces interparticle friction and provides manufacturing of more dense workpieces at the stage of pressing. Microadditives promote faster formation of contact isthmuses. The goal of the study is to develop a method for determining the surface tension coefficient of 600NN ferrite material during sintering. The proposed approach is based on measurements of the shrinkage of various fragments of a vertically sintered ferrite rod, which are used to determine the values of the coefficient. It is shown that the surface tension coefficient of the studied ferrite material during sintering was σ = 65.2 ± 13.0 N/m with a confidence probability of 95%. The results obtained can be used to study the effect of the sintering temperature, the size of sintered particles, the amount and quality of alloying additives on the forces of surface tension. Moreover, the data can be used in the study of the relationship between the value of the surface tension coefficient and the parameters of the microstructure.

Spatial Waveform Analysis of Ultrasonically Excited Capillary Waves for Measurements of Interfacial Tension Coefficient in Microgravity

A simplified method for measurements of low interfacial tension coefficient which is applicable for binary mixtures is proposed. The technique is based on generating progressive capillary waves at a liquid interface by radiation pressure of a short ultrasound pulse in microgravity condition. The waveforms are then processed in the spatial domain. The method presents the advantage of strongly reducing data volume of necessary images for analysis and, consequently, significantly minimizing both data processing and time expenses thanks to the analysis in spatial domain instead of time domain as hitherto reported in the literature.

Geoinformation-Cartographic Methods in Research of the Ecological and Economic Balance of the Territory

Estimation of the ecological and economic balance of the territory is important for developing a strategy for its rational use. A comprehensive account of the types of anthropogenic impact, the determination of the corresponding anthropogenic load, and, ultimately, the natural protection of the land is a source for forming recommendations and conducting activities to maintain sustainable development. Currently, in domestic science there are examples of such an assessment for areas with different types of specialization: agricultural, agro-industrial, industrial, recreational, which indicates the relevance of such studies. The aim of this work is to assess the environmental and economic balance of the territory of Krasnoarmeysky district of Saratov region using geoinformation mapping methods. The article successively describes the stages of assessing the environmental and economic balance: collecting, processing, decoding satellite images of Sentinel and Landsat; compiling a database of vector objects by the type of economic use; calculating the coefficients of anthropogenic load and natural protection of the territory based on statistical data obtained in the geoinformation system. According to the absolute tension coefficient (Ka), 3 clusters are identified in the territory of Krasnoarmeysky district: a cluster of medium intensity ECB (from 0.5 to 1), low (from 0 to 0.3) and lowered (from 0.3 to 0.5). Clusters of high degrees of tension are not allocated. According to the coefficient of relative tension (Ko), 2 clusters of low (from 0 to 2.5) and lowered (2.5–5) tension were identified. Clusters of high degrees of tension, as in the previous case, were not identified. According to the coefficient of natural security of the territory, 2 clusters are identified. According to the Kez coefficient, the northwestern part of the district refers to territories with average protection (0.43–0.49). The northeastern, central, and southern parts of the region belong to territories with increased (more than 0.5) security. Low (0–0.35) and lowered (0.36–0.42) natural security in the region is absent. The obtained values of the coefficients allow us to assess the economic development of the region as balanced.

Fatigue Life Prediction of Rivet Joints

Strength reduction in structures like an aircraft could be resulted as cyclic loads over a period of time and is an important factor for structural life prediction. Service loads are emphasized at the regions of stress concentration, mostly at the connection of components. The initial flaw prompting the service life was expected by using the Equivalent Initial Flaw Size (EIFS) which has been recognized as a powerful design tool for life prediction of engineering structures. This method was introduced 30 years ago in an attempt to study the initial quality of structural details. In this paper, the prediction of life based on failure mechanics in a riveted joint has been addressed through the concept of EIFS. For estimation of initial crack length by EIFS, extrapolation method has been used. The EIFS value is estimated using the coefficient of cyclic intensity (ΔK) and using the cyclic integral (ΔJ), and the results are compared with each other. The simulation results show that the if the coefficient of tension been used in EIFS estimation, which based on the Paris law, the EIFS value will be dependent on the loading domain, while the use of the J-Cyclic integral in the EIFS decrease its dependence on the load domain dramatically.