Action Of Forces Research Articles

Optimal Solutions for a Class of Impulsive Differential Problems with Feedback Controls and Volterra-Type Distributed Delay: A Topological Approach

In this paper, the existence of optimal solutions for problems governed by differential equations involving feedback controls is established for when the problem must account for a Volterra-type distributed delay and is subject to the action of impulsive external forces. The problem is reformulated within the class of impulsive semilinear integro-differential inclusions in Banach spaces and is studied by using topological methods and multivalued analysis. The paper concludes with an application to a population dynamics model.

Aloe vera Miller extract as a plasticizer agent to polymeric films: A structural and functional component

The pharmaceutical and cosmetic industries have found natural polysaccharides-based polymeric films helpful for the topical application of drugs. Plasticizers, such as glycerol, are added to achieve films' desired mechanical, elastic, and flexible properties. Aloe vera Miller mucilage is known for healing burns and wounds, relieving pain, and moisturizing, suggesting its great potential for managing multiple topical issues. Herein, we exploited the plasticizing potentialities of A. vera extract when combined with gellan or carrageenan polysaccharides to produce films. The extract of A. vera mucilage was prepared in propane-1,2-diol, and its composition was comparatively evaluated with a commercial extract using a chemometric method. Next, it was added to the films obtained using the solvent-casting method. The formulations were investigated regarding the mechanical properties, swelling, water loss, porosity, water vapor transmission rate, degree of occlusion, adhesion force, and antioxidant action. Fourier transform infrared spectroscopy assessed the films stability and homogeneity with an exploratory chemometric method to classify the samples. The results showed that carrageenan and gellan polysaccharides-based polymeric films have great potential for including A. vera extract. The extract acts as a plasticizer and promotes desirable properties and swelling behavior for films intending wound management. Comparatively, films prepared with glycerol beyond the extract presented higher thickness, lower swelling, and higher occlusion and antioxidant activity. Despite this, glycerol seems to negatively influence the homogeneity of the extract on the film surface. In addition, regarding polysaccharides, carrageenan showed higher bioadhesion. Therefore, the films produced exhibited favorable properties, highlighting their potential for further research regarding wound management.

Purcell-modified Doppler cooling of quantum emitters inside optical cavities

Standard cavity cooling of atoms or dielectric particles is based on the action of dispersive optical forces in high-finesse cavities. We investigate here a complementary regime characterized by large cavity losses, resembling the standard Doppler cooling technique. For a single two-level emitter a modification of the cooling rate is obtained from the Purcell enhancement of spontaneous emission in the large cooperativity limit. This mechanism is aimed at cooling quantum emitters without closed transitions, which is the case for molecular systems, where the Purcell effect can mitigate the loss of population from the cooling cycle. We extend our analytical formulation to the many-particle case governed by small individual coupling, but exhibiting large collective coupling. Published by the American Physical Society 2024

The first principle study on the hydrogen storage properties of monolayer and bilayer α-graphyne decorated by alkali metal atoms

Using the first-principles density functional theory, the hydrogen storage properties of monolayer and bilayer α-graphyne systems decorated by alkali metal are investigated. The results of band structure and density of state analysis indicate that alkali metal decoration enhances the chemical activity of the adsorption substrate, leading to increased H2 adsorption capacities for Li, Na and K decorated monolayer systems (15.0 wt.%, 14.5 wt.%, 10.7 wt.%, respectively). The combined action of interlayer force and decorated metal atoms results in higher H2 adsorption capacities for Li, Na and K decorated bilayer systems (17.7 wt.%, 16.9 wt.%, 13.0 wt.%, respectively), which means the bilayer graphyne structures enhance the storage capacities for decorated structures. Additionally, the Na decorated rhombus bilayer system demonstrates the highest adsorption density of H2 molecules between α-graphyne layers. Overall, alkali metal decorated monolayer and bilayer systems exhibit promising H2 adsorption potentials.

Bioinspired stiff–soft gradient network structure for high-performance impact-resistant elastomers

Traditional impact-resistance materials relying on the combination of supporting materials and energy-dissipation elastomers can effectively reduce shock load, yet the sharp interface between two types of materials causes discontinuous stress transfer and cracking. Here, inspired by the squid beak, we report a type of high impact-resistance gradient elastomers with large-scale modulus gradient with about three orders of magnitude (modulus range of 7 × 103 ∼ 7 × 106 Pa) and high energy dissipation (loss factor > 0.6) over a wide temperature range by diffusively introducing stiff polymers in a highly damping elastomer with controlled mechanical properties. Under the action of an external force, our gradient elastomers exhibit soft-while-stiff attributes, combining cushioning and support. In drop hammer impact tests, our gradient materials can reduce impact strength by 80 %, significantly better than commercial protective gear. It is worth mentioning that the modulus of the bottom layer matches that of the tissues for better protection.

Numerical Simulation of Electromagnetic-Thermal-Fluid Coupling for the Deformation Behavior of Titanium-Aluminum Alloy under Electromagnetic Levitation.

Electromagnetic levitation (EML) is a good method for high-temperature processing of reactive materials such as titanium-aluminum (Ti-Al) alloys. In this study, the oscillation and deformation processes of Ti-48Al-2Cr alloy specimens at different high-frequency currents during the EML process were simulated using the Finite Element Method and Arbitrary Lagrangian-Eulerian (ALE) methods. The data of oscillation, stabilization time, deformation, and distribution of electromagnetic-thermal-fluid fields were finally obtained. The accuracy of the simulation results was verified by EML experiments. The results show the following: the strength and distribution of the induced magnetic field inside the molten droplet are determined by the high-frequency current; under the coupling effect of the electromagnetic field, thermal field, and fluid field, the temperature rise of electromagnetic heating is rapid, and accompanied by strong stirring, resulting in a uniform distribution of the internal temperature and a small temperature difference. Under the joint action of gravity and Lorentz force, the molten droplets are first within a damped oscillation and then tend to stabilize with time, and finally maintain the "near rhombus" shape.

COMPUTATIONAL AND EXPERIMENTAL STUDY OF THE STRESS-STRAIN STATE OF A PIPE UNDER EXTERNAL RADIAL LOAD, INTERNAL PRESSURE AND TEMPERATURE DIFFERENCE

Oil and gas pipelines are subjected to complex of loads and impacts during operation. The purpose of this article is an experimental assessment of the stress-strain state of a pipe under the action of external radial force on a laboratory bench by the strain gauge method, as well as a computational and experimental assessment of the stress-strain state under the combined action of radial force, internal pressure and temperature difference. Accounting for internal pressure and temperature difference (other factors affecting the pipeline) is carried out using well-known theoretical formulas which are confirmed by practice. The total stresses from the effects of several factors of influence are determined due to the principle of superposition.Experimental and computational studies of the stress-strain state of the pipe cross section under the influence of external radial force corresponding to the pipe deflection from 0 to 8 mm; internal pressure from 0 to 14 MPa; temperature difference from minus 60 C to 60 C have been carried out. Graphs of the dependence of maximum stresses on the factors of influence are constructed. Empirical formulas have been obtained for calculating the maximum equivalent von Mises stress of the cross-section of the pipe with a diameter of 325 mm under various loading options, they are necessary to assess the strength of the pipeline structure.

O-114 Instructions for assembly of early mammalian embryos

Abstract The Plachta lab has pioneered the use of live-imaging approaches to discover how the preimplantation embryo forms in real time. Our recent findings help to transform the field of preimplantation development by showing how diverse processes occurring at the level of transcription dynamics, cytoskeletal organization, and the action of mechanical forces are integrated in real time to ensure proper embryo development. We extend our studies from mouse to human embryos, which enabled us to discover differences in embryo patterning between species and some of the events causing developmental errors, such as aneuploidy within the intact-developing system.

FEATURES OF CALCULATING LONGITUDINAL DISPLACEMENTS OF PIPELINES LAID IN HETEROGENEOUS SOILS

Achieving and maintaining the required reliability of the linear part of the main gas pipelines is of particular importance. Emergency destruction usually leads to large gas leaks into the atmosphere and undersupply to consumers, significant costs for the restoration of main gas pipelines. The difficulty and cost of carrying out repairs of main gas pipelines directly depends on the difficult conditions of the route and special technical solutions are needed to achieve the stability and reliability of pipelines on low-bearing soils. Thus, on existing gas pipelines, their longitudinal movements occur under the action of longitudinal forces, which leads to an increase in the stress state of gas pipelines and even the destruction of pipes. The significant time duration of the increase in gas pipeline movements indicates that these movements occur due to the rheological properties of soils. An analysis of the stress state of such sections of gas pipelines is necessary to assess their reliability, timing and methods of repair.

Forced Bending Vibrations of a Plane Rod Fixed on a Rigid Support Element of Finite Length Under the Action of an External Transverse Force Aplied to Its Free End

Forced Bending Vibrations of a Plane Rod Fixed on a Rigid Support Element of Finite Length Under the Action of an External Transverse Force Aplied to Its Free End

RESISTANCE OF FERRITE-PERLITE STEEL TUBING BRANCH PIPE METAL TO DESTRUCTION IN HYDROGEN SULFIDE MEDIUM

This paper discusses the problems of resistance of the metal of the tubing branch pipe (tubing) to the process of its destruction in a medium containing hydrogen sulfide and when exposed to external forces. A 73х73 tubing nozzle made of 38G2SFA steel was selected as the material for research. The tubing fragment was destroyed during production well operation. To establish the reasons for the failure of the tubing nozzle, a visual inspection was carried out, tests were performed to assess the hardness and mechanical properties, the microstructure and microtexture of the metal were analyzed using scanning electron microscopy (SEM) methods. To analyze the nature of the distribution of introduced defects, the mutual orientation of structural components and crystallographic texture, studies were carried out by the method electron backscatter diffraction (EBSD). Studies of the suspended branch pipe, which does not have chemical protection, showed that the cause of its destruction was hydrogen sulfide stress corrosion cracking (SSCC) as a result of hydrogen embrittlement and the action of external tensile forces exceeding the yield strength of the metal. It was established that as a result of the interaction of hydrogen sulfide of the distilled product with the metal of the branch pipe, hydrogen embrittlement of the material of the branch pipe occurred. The process of hydrogen embrittlement of the fragment was proved by detecting hydrogen blisters in the metal microstructure and establishing the process of coalescence of neighboring inclusions. In addition, the results of the test to measure the hardness of the metal along the wall thickness further supported the hypothesis of hydrogen embrittlement of the tubing. EBSD analysis showed that the threaded part of the branch pipe is characterized by a small size of structural elements and an increased density of introduced defects (geometrically necessary dislocations), which are a promising site for the deposition of molecular hydrogen. It is concluded that reaching the limit concentration of molecular hydrogen reduces the binding energy of metal atoms and this process initiates the formation of pores. It has been established that the development of cracks along large-angle grain boundaries is facilitated, and small-angle and coincidence site lattice (Σ3, Σ5, Σ11 and Σ13b) grain boundaries are active barriers to crack propagation. It has been shown that by optimizing the elemental composition of steel, controlling the microstructure, crystallographic texture, as well as the type and state of grain boundaries, new pipeline steels can be produced that are more resistant to SSCC.

Tunable plasmonic tweezers based on nanocavity array structure for multi-site nanoscale particles trapping

The ability of plasmonic optical tweezers based on metal nanostructure to stably trap and dynamically manipulate nanoscale objects at low laser power has been widely used in the fields of nanotechnology and life sciences. In particular, their plasmonic nanocavity structure can improve the local field intensity and trap depth by confining electromagnetic fields to subwavelength volumes. In this paper, the R6G dye molecules with 10−6 M were successfully trapped by using the Ag@Polydimethylsiloxane nanocavity array structure, and a R6G micro-ring was formed under the combined action of plasmonic optical force and thermophoresis. Subsequently, the theoretical investigation revealed that the trapping performance can be flexibly adjusted by changing the structural parameters of the conical nanocavity unit, and it can provide a stable potential well for polystyrene particles of RNP = 14 nm when the cavity depth is 140 nm. In addition, it is found that multiple trapping sites can be activated simultaneously in the laser irradiation area by investigating the trapping properties of the hexagonal conical nanocavity array structure. This multi-site stable trapping platform makes it possible to analyze multiple target particles contemporaneously.

Compton rocket effect due to the action of radiation reaction force in degenerate plasma

A closed set of fluid equations with radiation reaction force (RRF) are constructed from the moments of the appropriate single particle kinetic equation describing a relativistic degenerate (high density) electron plasma. The closure, in analogy with the Maxwellian closure for non-degenerate plasmas, is affected via a parametrized Fermi-Dirac distribution. It is shown that the degeneracy increases RRF just as will be predicted from the so-called “Compton Rocket” effect.

Researching the accounting-state-market dynamic in China: A literature review and research agenda

Accounting has long been studied as a social and institutional practice structured by the actions of state agencies and market forces. Such studies are increasingly conducted in non-Western jurisdictions. This paper presents a review of extant studies investigating the dynamic connections among accounting, state agencies, and markets in modern China. Our aim is to critically evaluate extant literature, synthesize its insights, and open up new research avenues. We examine 92 accounting studies, which have been inductively classified into three distinctive thematic clusters. In so doing, three major features of current research are identified: first, an emphasis on the inexorable power of Chinese state agencies; second, a focus on national relations among accounting, state, and market; and third, a lack of attention to how accounting functions in specific local settings. Consequently, key research opportunities lie in (a) deeper theorization of the hybridity of China's state-market mix, (b) analysis of the local-global networks in which hybridity circulates and is manifested, and (c) contemporary studies of accounting in action in a Chinese context.

О влиянии «гидрофобности» газовой фазы на образование флотокомплексов в процессах флотации

Introduction. A model of a three-phase system in which, as a result of hetero coagulation from a bulk liquid, its thin layer has formed, the surfaces of which separate the gas and condensed phases with different potentials, is a wetting film. The study of wetting films adds to the knowledge of the nature of the structure-induced surface forces acting in them, which serves to develop the theory of hetero coagulation and is of interest for solving various topical problems of the theory and practice of flotation. The purpose of the work is to study the influence of “hydrophobic” properties of the gas phase on the separation of minerals by flotation with a vapor-air mixture in flotation schemes with jet countercurrent flow of feed and rough concentrate. Materials and Methods. Methods and installations have been developed to investigate the temperature dependence of the equilibrium thickness of wetting films and wetting edge angles. Studies of wetting films are supplemented by measurements of induction time at adhesion of minerals to each other and to an air bubble on a specially designed installation. In-situ flotation experiments were performed on a sample of apatite-nepheline ores. Results. The temperature dependence of the equilibrium thickness of the wetting film has been revealed, which does not contradict the experimentally established decrease of the exponentially decreasing (non-oscillating) part of the cleavage pressure with increasing temperature. It is shown that the temperature dependence of the boundary angles formed by the wetting film on the hydrophobic and hydrophilic surface is multidirectional. The connection between the temperature dependence of the boundary angle and the temperature dependence of the spreading coefficient obtained from Young’s law and determined by multiplication of parameters characterizing the magnitude and long-range action of forces caused by the difference between the structure and properties of the liquid in the boundary layers and their values in the volume is shown. “Hydrophobicity” of the bubble is associated with a smaller range effect of structural repulsion forces compared to hydrophobic attraction forces. By measuring the induction time, it is shown that the “hydrophobicity” of air manifests itself in the difference in the stability of wetting (when hydrophobic and hydrophilic particles adhere to the air bubble) and symmetric (when particles of the same hydrophobicity/hydrophilicity adhere to each other) films as the temperature increases. Discussion. In the framework of the phonon mechanism of surface forces, the dynamic structure of the liquid in the boundary layers (the sign and magnitude of the phonon component of the bowing pressure) determines the selectivity of aggregation and completeness of particle extraction, as well as the stability of symmetric and wetting films from temperature. Conclusion. When discussing the stability of disperse systems, the concepts of additional (to dispersive (van der Waals) and ionic-electrostatic interactions) forces associated with the overlap of boundary layers of liquids with structure parameters changed compared to their bulk values are fruitfully used. Such differences are understood as static deviations of the structure and properties of the liquid induced by the surface. However, the main reason for changes in the stability of wetting films at increasing temperature may be the high sensitivity to temperature of the entire set of rotational and vibrational motions of atoms and molecules of the liquid, i. e., its dynamic structure and the associated phonon component of the wedging pressure. Resume. The results of the study can be used to improve the technological performance of ores enriched by flotation. Consideration of the influence of linear tension on the system with the line of threephase contact will be useful for revealing the peculiarities of flotation of micro-dispersions of minerals by the developed technology.

Experimental research of reinforced concrete elements under the action of transverse forces

Almost all reinforced concrete structures to one degree or another work on the perception of shear forces, and the corresponding calculations are decisive when determining the dimensions of the cross section and shear reinforcement ofstructures. At the same time, strength calculations under the action of shear forces are based on specific types of destruction and depend, first of all, onthe scheme (type) of loading. One of these types of failure is the failure due to shearing of concrete in the compressed zone, which occurs along a diagonalcrack that runs from the support to the concentrated force, which is located at a distance of 1...2.5d (d -the working height of the section).Due to the lack of a sufficient number of experimental studies of this type of failure, sufficiently approximate calculation methods are used in practice,which do not take into account the stress-strain state during failure in the zone of action of shear forces due to shearing of concrete in the compressed zone.The article presents the methodology, composition and results of experimental studies of reinforced concrete beams of two series (with transverse and without transverse reinforcement) on the effect of transverse loading.Within the framework of this work, experimental studies of the nature of crack formation, stress-strain state and strength of elements during failure due toshearing of concrete in the compressed zone above an inclined crack and the connection with other possible types of failure - along an inclined strip anddue to crushing of the concrete of the compressed zone above the inclined crack.The main regularities of the development of cracks, the stress-strain state and the strength of the elements destroyed due to the shearing of concrete in the compressed zone above the inclined crack have been established.Conclusions and prospects for further research of reinforced concrete structures, which are destroyed in the area of action of transverse forces, are presented.

ОБЩИЙ ПОДХОД К РЕШЕНИЮ ЗАДАЧИ ИЗГИБА ПРЯМОУГОЛЬНОЙ ПЛАСТИНКИ С ЛЮБЫМИ ГРАНИЧНЫМИ УСЛОВИЯМИ

In the work under consideration, an approach is proposed that makes it possible to calculate rectangular plates with any continuous types of boundary conditions from a unified position. The solution for plate deflections is constructed as a product of two functions, each of which represents its own function of the differential equation of bending vibrations of the rod with boundary conditions corresponding to the support of the rectangular plate. The problem reduces to an infinite system of linear algebraic equations for the coefficients of the eigenfunctions, which can be solved by the truncation method. Two examples of the calculation of rectangular plates with rigidly clamped and hingedly supported sides under the action of a concentrated force and with two clamped and two hingedly supported sides under the action of a uniformly distributed load are given.

DETERMINATION OF THE CALCULATED LENGTH OF THE COLUMNS TAKING INTO ACCOUNT THEIR FORM OF DEFORMATION AND UNEQUAL LOADING IN THE FRAME COMPOSITIOND

The coefficient of expansion of the columns, which are used in the warehouse of one-span frames with crane attachments, must depend on the shape of their deformation and the unequal attachment of the columns. At this time, the peculiarity of the current development of the frame is the fact that the most likely objectives can be achieved by only one column in the warehouse. If one of the columns (which has a heavy tap with a vantage) is subject to the maximum influx of constant force at the moment, then the longitudinal column of the same cut allows for the influx of significantly less force. The overall rigidity of the columns in the warehouse frame plays a vital role in the stability of the columns. In a transverse direction, two columns of one span of the workshop are connected by a crossbar into a frame system. The development of significant plastic deformations in one of the columns does not cause a loss of the column’s strength. The protruding column is becoming increasingly important. The regulation of the efficient operation of columns in warehouses allows for more rational design in accordance with current standards. The arrangement of the crazy work of unequally attractive columns in the warehouse can be characterized as a refinement of the first form of deformation. Meanwhile, under active pressure, the frame is deformed according to a mixed shape, which in addition to the first appears in the form of warehouses and other types of normative, effective form of deformation in action. The form of deformation of the frame is stimulated by the following main factors, and, as a rule, does not coincide with the first moisture form and does not predict it. Essentially, the structured combination includes a vantage that stimulates different moisture forms, and a vantage that fits on a similar frame that can be laid out in warehouses that stimulates a variety of moisture forms. The resulting form, due to the resistance of permanent forces in the plastic elements and the elasticity of the material, is a linear combination of warehouse forms and this form can be called mixed. The established principle of independence of action of forces can be distributed on the rod or rod system of storage in the warehouse, where the skin storage force is stimulated by those and other moisture forms. A method has been developed for assessing the durability of steel-curved columns of steel frames with crane attachments, which ensures the effective operation of differently attached columns in the warehouse and the shape of deformation under the action of active forces. The calculated lengths of the columns, determined for cross-sections with crane loads according to the proposed method, are smaller than the calculated lengths determined according to the standard method by 8-20%. Keywords: squeezed columns, gauge length, deformed form, making a column in a frame.

Effect of bismuth on the mechanical properties and microstructure evolution of iron matrix during drawing: a molecular dynamics study

This paper investigates the effects of bismuth nanoparticles on the mechanical properties and microstructure evolution of single-crystal iron matrix materials during the drawing process using molecular dynamics methods, and also explores the effects of different drawing speeds and loading methods on the drawing process. The results show that the incorporation of bismuth nanoparticles has a significant effect on the axial drawing force, dislocation, shear strain and crystal evolution during the drawing process. When the bismuth nanoparticles started to deform under the action of drawing force, the atomic shear strain and crystal evolution were concentrated around them, which hindered the generation of dislocations and led to the reduction of their axial drawing force. In addition, the degree of atomic shear strain and crystal evolution increases with the increase of drawing speed, leading to work hardening of the material, and thus increasing the axial drawing force. Finally, when the loading mode is positioned at the rear end, shear strain becomes more concentrated around the bismuth nanoparticles, hindering dislocation generation and increasing the material’s hardness and axial drawing force. This study is important for understanding the mechanism of bismuth nanoparticles on the iron matrix of single-crystal during the drawing process.

Progressive Collapse Behavior of a Precast Reinforced Concrete Frame System with Layered Beams

A possible way to improve the structural safety and robustness of precast building structures is to develop effective precast frame systems with layered beams, which combine prefabricated parts with cast-in situ ordinary concrete, high-performance concrete, fiber concrete, or FRP. The paper provides a new type of precast reinforced concrete frame system with layered beams for rapidly erected multi-story buildings resistant to accidental actions. Using a combination of the variational method and two-level design schemes, a simplified analytical model has been developed for structural analysis of the precast reinforced concrete frame system, both for serviceable and ultimate limit states as well as for accidental actions. The proposed model allows for determining shear deformations and the formation and opening of longitudinal cracks in the intermediate contact zone between precast and monolithic parts of reinforced concrete structural elements of the frame, as well as the formation and opening of normal cracks because of the action of axial tensile force or bending moment in these elements. The design model was validated by comparing the calculated and experimental data obtained from testing scaled models of the precast reinforced concrete frame system with layered beams. The paper investigates and thoroughly analyzes the factors affecting the stiffness and bearing capacity of the intermediate contact zone, discusses the criteria for the formation of shear cracks along the contact zone of precast and monolithic concrete, and examines the change in the stiffness and dissipative properties of layered elements at different stages of their static–dynamic loading. The robustness of the experimental models of the structural system was not ensured under the specified load, section dimensions, and reinforcement scheme. Following an accidental action, longitudinal cracks were observed in the contact joint between the monolithic and prefabricated parts in the layered beams. This occurred almost simultaneously with the opening of normal cracks in adjacent sections. A comprehensive analysis of the results indicated a satisfactory degree of agreement between the proposed semi-analytical model and the test data.