Medfazna reologija: Pregled merilnih tehnik in njen pomen v disperzijah in elekrostatskemu sukanju

Interfacial rheological properties have yet to be thoroughly explored. Only recently, methods have been introduced that provide sufficient sensitivity to reliably determine viscoelastic interfacial properties. In general, interfacial rheology describes the relationship between the deformation of an interface and the stresses exerted on it. Due to the variety in deformations of the interfacial layer (shear and expansions or compressions), the field of interfacial rheology is divided into the subcategories of shear and dilatational rheology. While shear rheology is primarily linked to the long-term stability of dispersions, dilatational rheology provides information regarding short-term stability. Interfacial rheological characteristics become relevant in systems with large interfacial areas, such as emulsions and foams, and in processes that lead to a large increase in the interfacial area such as electrospinning of nanofibers.Medfazne reološke lastnosti so še dokaj neraziskane. Šele pred kratkim so razvili metode, s katerimi je mogoče z zadostno občutljivostjo in natančnostjo določiti viskoelastične lastnosti medfaze. Medfazna reologija opisuje odnos med deformacijo medfaze in silo, ki to deformacijo povzroči. Zaradi različnih deformacij medfazne plasti (strig in raztezanje, oziroma krčenje) se tudi medfazna reologija deli na strižno in dilatacijsko. Strižne reološke lastnosti medfaze se odražajo v dolgotrajni stabilnosti disperzij, medtem ko sedilatacijske predvsem v kratkotrajni stabilnosti. Poznavanje medfaznih reoloških lastnosti je pomembno v sistemih z velikimi medfaznimi površinami, kot so emulzije in pene ter pri procesih, kjer pride do velikega povečanja medfazne površine, kot je elektrostatsko sukanje nanovlaken

Nanofibers and their biomedical use

The idea of creating replacement for damaged or diseased tissue, which will mimic the physiological conditions and simultaneously promote regeneration by patients\u27 own cells, has been a major challenge in the biomedicine for more than a decade. Therefore, nanofibers are a promising solution to address these challenges. These are solid polymer fibers with nanosized diameter, which show improved properties compared to the materials of larger dimensions or forms and therefore cause different biological responses. On the nanometric level, nanofibers provide a biomimetic environment, on the micrometric scale three-dimensional architecture with the desired surface properties regarding the intended application within the body, while on the macrometric scale mechanical strength and physiological acceptability. In the review, the development of nanofibers as tissue scaffolds, modern wound dressings for chronic wound therapy and drug delivery systems is highlighted. Research substantiates the effectiveness of nanofibers for enhanced tissue regeneration, but ascertains that evidences from clinical studies are currently lacking. Nevertheless, due to the development of nano- and bio-sciences, products on the market can be expected in the near future

Processing of a large-sized cement kiln bandage by a robotic machine

In this paper, we describe the concept of setting the base of large-sized parts with a diameter of up to 8300 mm and a mass of up to 120 tons, such as a bandage of a rotating cement kiln during machining using a mobile robotic machine. The issue of controlled cutting to ensure accurate shaping of a large-sized part with a thickness of the removed metal layer up to 6 mm is considere

Modeling and calculation of the technological process of testing piston hydraulic cylinders with energy recovery

One of the most important problems of modern mechanical engineering is the energy efficiency of technological equipment and manufactured products. A separate issue in this series is the technology and means of testing finished product samples, including hydraulic machines. In this article, an original scheme of a test bench for piston hydraulic cylinders and a method of mathematical modeling of the process of its functioning, based on the application of the theory of volumetric rigidity of hydraulic systems, is proposed, which makes it possible to describe with high accuracy and reliability the processes occurring in the test system during its operation. The test efficiency coefficient is proposed, which makes it possible to evaluate and compare various test processes by the criterion of their energy efficiency. An example of a preliminary calculation of the functioning of the proposed stand is given

Properties, Engineering and Applications of PolymericNanofibers: Current Research and Future Advances

The subject of nanomedicine has seen a surge in research activity over the past decade, with nanofibers being a particularly active field. Nanofibers are solid, dry fibers with nanometer diameters, made of various polymers, whereas electrospinning is a versatile, simple, elegant, reproducible, continuous and scalable technology for their preparation. Nanofibers are a unique class of materials in the biomedical field, since they provide a biomimetic environment on the nanometer scale, a three-dimensional architecture with the desired surface properties on the micrometer scale, combined with mechanical strength and physiological acceptability on the macro scale. In particular, their ability to imitate the fibrillar elements of a natural extracellular matrix in a very realistic way is crucial. In this paper we introduce the fundamental aspects of the electrospinning process and the properties of nanofibers, as well as highlighting the enormous potential of nanofibers as drug-delivery systems and tissue scaffolds

Simulation of a synchronous hydrodynamic system based on a throttle flow divider of a non-valve type

Hydraulic drives, which for the most part is multi-circuit and branched, are widely used in hydraulic drives of modern mobile equipment and technological equipment. To synchronize the operation of mechanisms driven by a single power mechanism, throttle flow dividers are used. The article discusses various options for the functioning of the hydrodynamic system, as well as the device of the throttle flow divider. The dynamics of the synchronous hydraulic system based on throttle dividers is presented and the design scheme is described. The time integration of pressure values at various points, the values of movement and position of the moving element in space, the speed of movement in space and the values of velocities in real time and scale is carried out. The conclusion is made about the influence of system parameters on the selection of parameters of a suitable throttle flow divider

Analysis of non-spool throttle flow dividers for synchronous hydromechanical drives

Relevance and goals. Hydraulic drives of modern mobile machines and technological equipment are, as a rule, branched and multi-circuit. At the same time, there is often a need to ensure synchronous (coordinated) movement of two or more independent hydraulic motors. The analysis of the conducted studies has shown that throttle flow dividers are the most suitable for providing automatic control of hydraulic drives. The use of spool flow dividers in general-purpose hydraulic drives, especially if they work in harsh conditions with high dustiness of the environment is impractical. Materials and methods. The article provides an overview of existing designs of non-spool throttle flow dividers for synchronous hydromechanical drives, their design schemes and operating principle are given. A comparative analysis of the functions performed by them and the quality of work is carried out. Suggestions are given on the principles of selecting a particular design of the flow divider, depending on the operating conditions. Results. A scheme of a test bench for piston hydraulic cylinders with energy recovery is proposed. A mathematical model of the stand has been developed and an example of a preliminary calculation of its functioning is given. Conclusions. The conclusion is made about the design features that make it possible to ensure the synchronous operation of hydraulic drives with high accuracy at minimal cost

Analysis of multithreaded choke dividers and flow dividers-adders

Hydraulic drives, which for the most part is multi-circuit and branched, are widely used in hydraulic drives of modern mobile equipment and technological equipment. The analysis of the conducted studies has shown that throttle flow dividers, as well as flow dividers-adders, are the most suitable for providing automatic control of multi-circuit systems. Dividers are used to separate one working fluid flow entering the divided into two independent streams with an arbitrary flow ratio independent of loads. If it is necessary to organize a larger number of threads, two-threaded DP and DSP are switched on sequentially, and then one additional thread divider must be installed to receive each subsequent stream. Thus, in order to obtain n threads, it is necessary to have (n-1) two-threaded thread dividers, which is quite expensive and technically unjustified. The article describes the designs of multithreaded choke dividers and flow dividers-adders and a comparative analysis of their basic properties is carried out

Mathematical modelling of the hydromechanical drive of the test bench for plunger hydraulic cylinders with energy recovery

Reliability is a significant parameter of machines, mechanisms, drives, technological equipment and its component parts, including hydraulic motors. Reliability is checked and confirmed by carrying out resource tests, the results of which reveal the characteristics and properties of materials, components and working fluids that are used in the production of hydraulic cylinders and during operation. One of the practical ways to determine reliability is testing. The aim of the work is to improve the theory and methods of calculation and design of the hydromechanical drive system of the service life test bench of plunger hydraulic cylinders through the use of an energy recovery scheme that provides an increase in the energy efficiency of the testing process. Developed on the basis of the application of the theory of volumetric rigidity, a mathematical model of the hydromechanical drive system of the plunger hydraulic cylinder service life test bench made it possible to compare the influence of various design and functional parameters of the elements of the hydromechanical system of the stand on the dynamic performance and energy efficiency of its drive