Changes In Tension Research Articles

Dynamic response of a transmission conductor following delayed ice shedding by reduced-scale model test

Ice shedding on conductors of transmission lines can induce severe vertical vibrations and abrupt tension changes, potentially causing structural damage and power outages. Prior experiments and numerical simulations assumed that ice sheds instantaneously from transmission lines, neglecting the practical delays in the ice shedding process, which resulted in unrealistic conductor dynamic responses. This study introduces a reduced-scale modeling system designed to simulate delayed ice shedding on conductors. The jump height and dynamic tension of an isolated-span transmission line following delayed ice shedding are analyzed, and various factors such as the two-dimensional delay duration, shedding sequence, and weight of ice accretion are examined through reduced-scale model tests. Based on the experimental data, simplified formulas are proposed to calculate the conductor's jump height and maximum tension after ice shedding by taking the time delay of the shedding process into account.

Properties of Chemically Stabilized Methanol–HVO Blends

Approximately 25% of global carbon emissions come from food production. Renewable fuels are crucial for curbing greenhouse gas (GHG) emissions from vehicles, non-road machines, and agricultural machinery. Tractors, key to modern farming, are central to these efforts. As agriculture strives for sustainability, alternative fuels like methanol and hydrotreated vegetable oil (HVO) are arousing interest because they are renewable and offer potential for blending for use in diesel engines. Methanol and HVO have limited solubility in direct mixing, so the addition of a co-solvent is essential. This study addresses the research gap regarding the properties of HVO and methanol blends with co-solvents. It investigated the impact of three co-solvents, 1-dodecanol, 1-octanol, and methyl butyrate, on the miscibility of HVO and methanol. The experimental measurements cross-varied the co-solvent type with different blending ratios (MeOH5 and MeOH10). Investigated parameters include fuel density, kinematic viscosity, distillation properties, and surface tension. The co-solvents enabled the formation of a singular, clear, and homogeneous phase in methanol-HVO blends. The co-solvent 1-dodecanol demonstrated the highest solubilizing capacity for MeOH5 and MeOH10 blends, followed by 1-octanol. Adding co-solvents led to increased fuel density, decreased kinematic viscosity, and small changes in surface tension. These findings contribute to the optimization of methanol–HVO fuel blends for efficient and environmentally friendly use in vehicles, non-road machinery, and agricultural machinery.

Develop Tandem Tension Sensor to Gauge Integrin-Transmitted Molecular Forces.

DNA-based tension sensors have innovated the imaging and calibration of mechanosensitive receptor-transmitted molecular forces, such as integrin tensions. However, these sensors mainly serve as binary reporters, only indicating if molecular forces exceed one predefined threshold. Here, we have developed tandem tension sensor (TTS), which comprises two consecutive force-sensing units, each with unique force detection thresholds and distinct fluorescence spectra, thereby enabling the quantification of molecular forces with dual reference levels. With TTS, we revealed that vinculin is not required for transmitting integrin tensions at approximately 10 pN (piconewtons) but is essential for elevating integrin tensions beyond 20 pN in focal adhesions (FAs). Such high tensions have emerged during the early stage of FA formation. TTS also successfully detected changes in integrin tensions in response to disrupted actin formation, inhibited myosin activity, and tuned substrate elasticity. We also applied TTS to examine integrin tensions in platelets and revealed two force regimes, with integrin tensions surpassing 20 pN at cell central regions and 13-20 pN integrin tensions at the cell edge. Overall, TTS, especially the construct consisting of a hairpin DNA (13 pN opening force) and a shearing DNA (20 pN opening force), stands as a valuable tool for the quantification of receptor-transmitted molecular forces within living cells.

Motion Response of the Submersible Underwater Towed System as Cable Length Changes

Submersible underwater towed systems usually need to transition from steady-state motion to maneuvering motion during operation while dynamically adjusting the length of the towed cable. The lumped mass approach was employed to convert the dragged cable into a model with a concentrated mass. Analyzed utilizing a computational simulation tool, the motion response of the towed system was examined for both simple and composite maneuvering motions. By comparing the changes in tension at the end of the towed cable and the depth of the towed body motion under different motion states and cable retraction and deployment speeds, the motion response law of the system when the length of the towed cable changes during the submarine maneuver motion is obtained. The maximum tension value occurred at 1.0 m/s during the acceleration maneuver when the velocity change of the submersible ended at the same time as the cable length change. After the deployment maneuver in a circular rotating motion, the range of tension fluctuations decreased by 93%, greatly improving the stability of the towed system. An analysis was conducted to examine the impact of various motion and structural parameters on the motion response. The study revealed that the buoyancy-to-gravity ratio of the towed body, the acceleration time of the accelerated motion, and the rotational speed of the circular rotational motion had a notable influence on the outcomes. When the buoyancy-to-gravity ratio of the towed body is 1.0, the maximum tension value of the towed cable is minimized, and the depth change of the towed body is closer to 0 m.

Individual and collective manipulation of multifunctional bimodal droplets in three dimensions.

Spatiotemporally controllable droplet manipulation is vital across numerous applications, particularly in miniature droplet robots known for their exceptional deformability. Despite notable advancements, current droplet control methods are predominantly limited to two-dimensional (2D) deformation and motion of an individual droplet, with minimal exploration of 3D manipulation and collective droplet behaviors. Here, we introduce a bimodal actuation strategy, merging magnetic and optical fields, for remote and programmable 3D guidance of individual ferrofluidic droplets and droplet collectives. The magnetic field induces a magnetic dipole force, prompting the formation of droplet collectives. Simultaneously, the optical field triggers isothermal changes in interfacial tension through Marangoni flows, enhancing buoyancy and facilitating 3D movements of individual and collective droplets. Moreover, these droplets can function autonomously as soft robots, capable of transporting objects. Alternatively, when combined with a hydrogel shell, they assemble into jellyfish-like robots, driven by sunlight. These findings present an efficient strategy for droplet manipulation, broadening the capabilities of droplet-based robotics.

Yttrium induced formation of new pores in an as-cast nickel-based single crystal superalloy

Pores are the most fatal defects in single crystal superalloys, which severely deteriorates the mechanical properties. Yttrium (Y) has been applied in commercial superalloys, but its effect on the morphology change of casting pores is not clear. This work focuses on the effect of Y on the evolution of pores formed after directional solidification in a second-generation superalloy. SEM, TEM and XRT were used to characterize the pores, and Thermo-Calc was used to calculate the surface tension change during the solidification process. Results show that, besides the formation of two types of conventional shrinkage pores during solidification, new types of pores, i.e., Type III and Type IV, due to the addition of Y element to 0.5 wt% in superalloy, were also observed. The formation of Type III pore could be ascribed to the surface tension drop in the liquid phase, which enhances the wettability at the solid/liquid interface, and promotes the mobility of liquid phase, due to the incorporation of Y element. The formation of Type IV pore is due to the simultaneous formation and growth of M23C6 and Ni3Al in the Ni5Y phase, triggering the formation of closed zone with a small but irregular shape at the multi-phase interface.

Recent Advances in Geochemical and Mineralogical Studies on CO2–Brine–Rock Interaction for CO2 Sequestration: Laboratory and Simulation Studies

The urgent need to find mitigating pathways for limiting world CO2 emissions to net zero by 2050 has led to intense research on CO2 sequestration in deep saline reservoirs. This paper reviews key advancements in lab- and simulation-scale research on petrophysical, geochemical, and mineralogical changes during CO2–brine–rock interactions performed in the last 25 years. It delves into CO2 MPD (mineralization, precipitation, and dissolution) and explores alterations in petrophysical properties during core flooding and in static batch reactors. These properties include changes in wettability, CO2 and brine interfacial tension, diffusion, dispersion, CO2 storage capacity, and CO2 leakage in caprock and sedimentary rocks under reservoir conditions. The injection of supercritical CO2 into deep saline aquifers can lead to unforeseen geochemical and mineralogical changes, possibly jeopardizing the CCS (carbon capture and storage) process. There is a general lack of understanding of the reservoir’s interaction with the CO2 phase at the pore/grain scale. This research addresses the gap in predicting the long-term changes of the CO2–brine–rock interaction using various geochemical reactive transport simulators. Péclet and Damköhler numbers can contribute to a better understanding of geochemical interactions and reactive transport processes. Additionally, the dielectric constant requires further investigation, particularly for pre- and post-CO2–brine–rock interactions. For comprehensive modeling of CO2 storage over various timescales, the geochemical modeling software called the Geochemist’s Workbench was found to outperform others. Wettability alteration is another crucial aspect affecting CO2–brine–rock interactions under varying temperature, pressure, and salinity conditions, which is essential for ensuring long-term CO2 storage security and monitoring. Moreover, dual-energy CT scanning can provide deeper insights into geochemical interactions and their complexities.

Insights in caveolae protein structure arrangements and their local lipid environment.

Caveolae are 50-80 nm sized plasma membrane invaginations found in adipocytes, endothelial cells or fibroblasts. They are involved in endocytosis, lipid uptake and the regulation of the cellular lipid metabolism as well as sensing and adapting to changes in plasma membrane tension. Caveolae are characterized by their unique lipid composition and their specific protein coat consisting of caveolin and cavin proteins. Recently, detailed structural information was obtained for the major caveolae protein caveolin1 showing the formation of a disc-like 11-mer proteincomplex. Furthermore, the importance of the cavindisordered regions in the generation of cavin trimers and caveolae at the plasma membrane were revealed. Thus,finally, structural insights about the assembly of the caveolar coat can be elucidated. Here, we review recent developments in caveolae structural biology with regard to caveolae coat formation and caveolae curvature generation. Secondly, we discuss the importance of specific lipid speciesnecessary for caveolae curvature and formation. Inthe last years, it was shown that specifically sphingolipids, cholesterol and fatty acids can accumulate in caveolae invaginations and may drive caveolae endocytosis. Throughout, we summarize recent studies in the field and highlight future research directions.

Importance of Fluid/Fluid Interactions in Enhancing Oil Recovery by Optimizing Low-Salinity Waterflooding in Sandstones

Low-salinity waterflooding/smart waterflooding (LSWF/SWF) is a technique involving the injection of water with a modified composition to alter the equilibrium between rock and fluids within porous media to enhance oil recovery. This approach offers significant advantages, including environmental friendliness and economic efficiency. Rock/fluid mechanisms such as wettability alteration and fines migration and fluid/fluid mechanisms such as a change in interfacial tension and viscoelasticity are considered active mechanisms during LSWF/SWF. In this study, we evaluated the effect of these mechanisms, by LSWF/SWF, on sandstones. To investigate the dominant mechanisms, coreflooding studies were performed using different injected fluid composition/salinity and wettability states. A comparative analysis of the recovery and mobility reduction factor was performed to clarify the conditions at which fluid/fluid mechanisms are also effective. Our studies showed that wettability alteration is the most dominant mechanism during LSWF/SWF, but, for weak oil-wet cases, optimizing brine compositions may activate fluid/fluid mechanisms. Brine composition significantly influences interface stability and performance, with sulfate content playing a crucial role in enhancing interface properties. This was observed via mobility behavior. A comparative analysis of pressure differentials showed that fines migration may act as a secondary mechanism and not a dominant one. This study highlights the importance of tailored brine compositions in maximizing oil recovery and emphasizes the complex interplay between rock and fluid properties in enhanced oil recovery strategies.

The breath shape controls intonation of mouse vocalizations.

Intonation in speech is the control of vocal pitch to layer expressive meaning to communication, like increasing pitch to indicate a question. Also, stereotyped patterns of pitch are used to create distinct sounds with different denotations, like in tonal languages and, perhaps, the 10 sounds in the murine lexicon. A basic tone is created by exhalation through a constricted laryngeal voice box, and it is thought that more complex utterances are produced solely by dynamic changes in laryngeal tension. But perhaps, the shifting pitch also results from altering the swiftness of exhalation. Consistent with the latter model, we describe that intonation in most vocalization types follows deviations in exhalation that appear to be generated by the re-activation of the cardinal breathing muscle for inspiration. We also show that the brainstem vocalization central pattern generator, the iRO, can create this breath pattern. Consequently, ectopic activation of the iRO not only induces phonation, but also the pitch patterns that compose most of the vocalizations in the murine lexicon. These results reveal a novel brainstem mechanism for intonation.

Structural design and control strategy of a cable-driven robot under high-altitude facade conditions with large span and multiple constraints

Purpose This paper explores the challenges of using cable-driven parallel robots on high-altitude, large-span facades, where redundancy in multicable systems and the elastic deformation of the cables are significant issues. This study aims to improve the accuracy and stability of the work platform through enhanced control strategies. These strategies address the redundancy in multicable systems and reduce the risks associated with cable deformation and mechanical failures during large-span movements. Design/methodology/approach The paper proposes a dynamic model for a four-rope parallel robot designed explicitly for large-span applications. The study introduces a position–force control strategy incorporating kinematic inverse solutions and a rope dynamics model to account for rope elasticity and its effects. This approach increases the number of system equations to match the unknowns, effectively solving the redundancy problem inherent in multicable systems. In addition, the tension changes of ropes and the stability of the working platform are examined under different motion distances (X = 50 m and X = 100 m) and varying Young’s modulus values (K = 5000 MPa and K = 8000 MPa). Findings This study’s large-span rope force–position control strategy successfully resolves the typical nonlinear characteristics and external disturbances in multicable parallel systems. By continuously monitoring and adjusting cable tension and end positions, this strategy ensures precise control over each cable’s tension, optimizes the distribution of cable tensions and maintains the system’s stability and response speed. The analysis in this paper indicates that this control strategy significantly improves the motion accuracy of robots operating on large-span high-altitude facades. Practical implications Industry adoption: The design and control strategies developed for the four-cable-driven parallel robot can be adopted by companies specializing in facade maintenance, construction or inspection. This could lead to safer, more efficient and cost-effective operations, especially in challenging environments like high-rise buildings. Innovation in robotic solutions: The research can inspire innovation within the field of robotics, particularly in developing robots for specific applications such as large surface maintenance. It showcases how adaptive control and stability can be achieved in complex operational scenarios. Safety improvements: By demonstrating a more stable and precise control mechanism for navigating large facades, the study could contribute to significant safety improvements, reducing the risk of accidents associated with manual facade maintenance and inspection tasks. Originality/value This paper combines the force/position hybrid control method with actual robotic applications, offering a novel solution to the complex issue of controlling cable-driven parallel robots in challenging environments. Thus, it contributes to the field. The proposed method significantly enhances the precision and stability of such systems and provides robust technical support for high-precision tasks in complex mechanical settings.

Activation of hTREK-1 by polyunsaturated fatty acids involves direct interaction

TREK-1 is a mechanosensitive channel activated by polyunsaturated fatty acids (PUFAs). Its activation is supposed to be linked to changes in membrane tension following PUFAs insertion. Here, we compared the effect of 11 fatty acids and ML402 on TREK-1 channel activation using the whole cell and the inside-out configurations of the patch-clamp technique. Firstly, TREK-1 activation by PUFAs is variable and related to the variable constitutive activity of TREK-1. We observed no correlation between TREK-1 activation and acyl chain length or number of double bonds suggesting that the bilayer-couple hypothesis cannot explain by itself the activation of TREK-1 by PUFAs. The membrane fluidity measurement is not modified by PUFAs at 10 µM. The spectral shift analysis in TREK-1-enriched microsomes indicates a KD,TREK1 at 44 µM of C22:6 n-3. PUFAs display the same activation and reversible kinetics than the direct activator ML402 and activate TREK-1 in both whole-cell and inside-out configurations of patch-clamp suggesting that the binding site of PUFAs is accessible from both sides of the membrane, as for ML402. Finally, we proposed a two steps mechanism: first, insertion into the membrane, with no fluidity or curvature modifications at 10 µM, and then interaction with TREK-1 channel to open it.

Ratiometric Fluorescence Probes for In Situ Imaging of Membrane Tension in Live Cells.

Membrane tension is an important physical parameter of describing cellular homeostasis, and it is widely used in the study of cellular processes involving membrane deformation and reorganization, such as cell migration, cell spreading, and cell division. Despite the importance of membrane tension, direct measurement remains difficult. In this work, we developed a ratiometric fluorescent probe sensitive to membrane tension by adjusting the carbon chain structure based on polarity-sensitive fluorophores. The probe is sensitive to changes in membrane tension after cells were subjected to physical or chemical stimuli, such as osmotic shock, lipid peroxidation, and mechanical stress. When the polarity of the plasma membrane increases (the green/red ratio decreases) and the membrane tension increases, the relative magnitude of the membrane tension can be quantitatively calculated by fluorescence ratio imaging. Thus, the probe proved to be an efficient and sensitive membrane tension probe.

Experimental Investigation on the Interfacial Characteristics of Tight Oil Rocks Induced by Tuning Brine Chemistry.

Currently, research on enhancing imbibition oil recovery in tight oil reservoirs through the ion-tuning technique remains limited. Two critical parameters for capillary imbibition are the wettability and interfacial tension between oil and water. In this investigation, we manipulate the properties of two types of formation water for both aged and unaged samples by diluting brine and altering ion composition. Subsequently, we employ captive and pendant-drop methods to assess rock wettability and interfacial tension under varied brine conditions. Additionally, we elucidate the primary mechanisms underlying changes in rock wettability and interfacial tension. Meanwhile, we analyze capillarity characteristics and assess the relative significance of wettability and interfacial tension. Results indicate that there is a critical interfacial tension with progressive dilution of two types of formation water. However, modifying ion composition leads to a complex trend in interfacial tension, which can be explained qualitatively through the Gibbs adsorption isotherm. For unaged samples, the contact angle demonstrates a pronounced water-wet characteristic, showing a nonmonotonic trend with respect to dilution times. Remarkably, the rock surface exhibits the strongest water-wet, particularly evident in the case of FW-10, largely influenced by variations in interfacial tension. Conversely, aged samples demonstrate strong oil-wet, with a critical salinity resulting in the lowest contact angle, while altering brine ion types can alter rock wettability from strongly oil-wet to intermediate-wet, which is not sufficient to result in the wettability alteration. The removal of multivalent cations is proposed as the most effective method for wettability modification. Furthermore, capillarity variations among different brine cases are primarily contingent upon contact angle changes, and interfacial tension does not have a significant change when regulating the brine properties. Consequently, we emphasize the significance of wettability in the adoption of ion-tuned brine techniques for tight oil reservoirs. Overall, our study underscores the potential of reasonably regulating brine properties to enhance capillarity and, thereby, improve imbibition oil recovery.

A Hexagonal Aim as a Driver of Change for Health Care and Health Insurance Systems.

Improving health systems, such as the U.S. or French, requires simultaneous pursuit of a patient centered approach aligned with the health professional: improving the experience of care, improving the health of populations, reducing per capita costs of care - Triple Aim - and improving the work life of the care providers, including clinicians and staff - Quadruple Aim -. While these aims are already ambitious, they may be insufficient when considering the economic, social and environmental challenges to the health of our communities in the near and long term. A conceptual framework to provide additional ethical guardrails for health systems. Recently, authors have articulated a Fifth Aim and we propose to add a Sixth Aim to the Quadruple Aim model. These additional aims are meant to account for our growing knowledge around the determinants of health and the challenging processes and structures of governance across a wide range of sectors in society including healthcare. We are strengthening the Fifth Aim defined as equity through "health democracy" to represent the wants, needs and responsibility of the population in taking care of their health and their healthcare. The Sixth Aim is to account for the increase in risk to population health due to climate change as well as the impact our health systems have on the environment. As social tension and environmental changes seem to continue to impact the structure of our society this "Hexagonal Aim" taken together might provide additional ethical guiderails as we set our healthcare goals.

Research on Optimization of Nonlinear Extended State Observer for the Upper-Limb Rehabilitation Robot Controller

Background: In recent years, patents have shown that upper-limb rehabilitation robots play a significant role in home-based rehabilitation training for stroke hemiplegia patients. Changes in muscle tension during the flaccid paralysis phase cause the rehabilitation robot to deviate from the predetermined motion trajectory. This poses a challenge to the mathematical modeling of the rehabilitation robot and the design of the nonlinear extended state observer (NESO). Objective: To address the problem of trajectory tracking errors caused by the rehabilitation robot when the patient's muscle tension changes, a method based on optimizing the nonlinear function within the NESO is proposed. Methods: First, a mathematical model of the upper-limb rehabilitation robot is established to obtain the dynamic relationship between the robot's velocity and the input voltage. Second, the nonlinear function of NESO is optimized by adjusting the gain values of the sine and tangent functions to effectively estimate the muscle tension and reduce the problem of accumulative error due to changes in muscle tension. Finally, comparative simulations of trajectory tracking including the optimized nonlinear function as well as the sine, tangent and power functions are performed on the MATLAB platform. Results: NESO is constructed to estimate changes in muscle tension based on sine, tangent, and power functions, as well as optimized nonlinear functions. The equivalent gain values of each function and the muscle tension estimation curves of NESO are compared. The simulation results show that the equivalent gain value of the optimized nonlinear function acting in NESO is increased to more than 8 and the convergence time is reduced by 11.9% accordingly. This conclusion is validated by simulations and practical tests. Conclusion: The optimized nonlinear function shortens the estimation time of the NESO for changes in muscle tension, which can provide a reference value for the design of observers for upper-limb rehabilitation robots of patients in the flaccid paralysis stage.

The metal release and transformation mechanisms of V–Ti magnetite tailings: Role of the alternate flooding and drying cycles and organic acids

V–Ti magnetite tailings (VTMTs) contain various heavy metals, such as Fe, Mn, V, Co, and Ni. The groundwater pollution caused by the tailing metal release has become a local environmental concern. Although studies have demonstrated the influence of alternate flooding and drying cycles (FDCs) on metal form and mobility in minerals, little was known about whether FDCs affect the metal release of VTMTs and the transformation of released metals. This study investigated the metal release kinetics of VTMTs and the metal transformation under FDCs in the absence and presence of acid rain (sulfuric and nitric acids) and bio-secreted organic acids (acetic, oxalic, and citric acids). The results showed that FDCs promoted metal release whether or not acids were present. The maximum released concentrations of V, Mn, Fe, Co, and Ni were as high as 78.63 mg L−1,1.47 mg L−1, 67.96 μg L−1, 1.34 mg L−1, and 0.80 mg L−1, respectively, under FDCs and citric acids. FDCs enhanced the tailing metal release by increasing the metal labile fraction proportion. However, the concentrations of released Fe, Mn, V, Co, and Ni all gradually decreased due to their (co-)precipitation. These precipitates conversely inhibited the subsequent mineral dissolution by covering the tailing surface. FDCs also enhanced the tailings’ porosities by 2.94%–9.94%. The mineral dissolution, expansion and shrinkage, and changes in tension destroyed the tailing microstructure during FDCs. This study demonstrated the low metal pollution risk of VTMTs under FDCs, either in acid rain or bio-secreted organic acids. However, the increase in tailing porosity should be seriously considered as it would affect the tailing pond safety.

Fructose vs. glucose: modulating stem cell growth and function through sugar supplementation.

In multicellular organisms, stem cells are impacted by microenvironmental resources such as nutrient availability and oxygen tension for their survival, growth, and differentiation. However, the accessibility of these resources in the pericellular environment greatly varies from organ to organ. This divergence in resource availability leads to variations in the potency and differentiation potential of stem cells. This study aimed to explore the distinct effects of glucose and fructose, as well as different oxygen tensions, on the growth dynamics, cytokine production, and differentiation of stem cells. We showed that replacing glucose with fructose subjected stem cells to stress, resulting in increased Hif1α expression and stability, which in turn led to a reduction in cell proliferation, and alterations in cytokine production. However, fructose failed to induce differentiation of human mesenchymal stem cells (hMSCs) as well as mouse fibroblasts into mature adipocytes compared to glucose, despite the upregulation of key markers of adipogenesis, including C/EBPβ, and PPARγ. Conversely, we showed that fructose induced undifferentiated mouse fibroblasts to release cytokines associated with senescence, including IL1α1, IL6, IL8, MCP1, and TNF1α, suggesting that these cells were undergoing lipolysis. Taken together, our results suggest that altering the culture conditions through changes in hexose levels and oxygen tension places considerable stress on stem cells. Additional research is required to further characterize the mechanisms governing stem cell response to their microenvironments.

Some physicochemical properties of ethyl oleate mixtures with ethanol and n-hexane

Due to the wide use of ethyl oleate (EO) in agriculture, medicine and automotive fuels, measurements of the surface tension, density, viscosity and contact angle of a mixture of ethyl oleate with ethanol (ET) and/or n-hexane (HEX) were made. The contact angle was measured on polytetrafluoroethylene (PTFE), poly(methyl methacrylate) (PMMA), glass and steel. The measurement results for the mixtures of EO + ET and EO + HEX were analyzed based on the properties of individual components of the mixtures. When considering the changes in the surface tension and contact angle on PTFE for the EO + ET and EO + HEX mixtures as a function of the mixture composition there were taken into account, not only the values of the total surface tension of the mixture components, but also the components and parameters of this tension. Based on the surface tension components and parameters of EO, ET, HEX, PTFE, PMMA, glass and steel, it was possible to predict changes in the surface tension of tested mixtures and the contact angle as a function of the mixture composition.

INVESTIGATION OF SURFACE PROPERTIES OF MODIFIED BITUMEN COMPOSITIONS

One of the main reasons for premature destruction of road surfaces is the poor quality of road bitumen. An effective way to improve the quality of a bitumen binder is to modify it with polymer or surface-active additives. The goal is to determine the effect of the concentration of modifiers on surface tension in binary "bitumen-surfactant", "bitumen-polymer" and triple "bitumen-surfactant-polymer" systems. The methodology of the work included measuring the surface tension of modified bitumen systems depending on the quantitative content of additives in bitumen. Results and discussion: As follows from the analysis of the data obtained, in bitumen systems with a limited concentration of polymer AG-4I (C≤1 g/dm3), the effect of reducing surface energy at the interface with air is achieved by concentrating surfactants in the surface layer, which are part of the structure of the bitumen itself. The extreme nature of the change in surface tension was also recorded in AC-2 bitumen compositions. Conclusion: In the "bitumen-AG-4I-AS-2" triple systems, the change in the specific surface energy at the "liquid-gas" interface is not an additive value, taking into account the separate contribution of AG-4I and AS-2. The concentration threshold of additives to achieve a minimum surface tension varies in comparison with binary compositions. With the combined administration of AG-4I (C=1g/dm3) and AC-2 (C=1g/dm3), the surface tension decreased by 9.30 mN/m compared with unmodified bitumen.