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Impact of Nanocellulose Loading on the Crystal Structure, Morphology and Properties of PVDF/Magnetite@NC/BaTiO3 Multi-component Hybrid Ceramic/Polymer Composite Material
No full textThe hybrid multifunctional magnetic organic/inorganic composite materials, with addition of optimal filler type and quantities are attractive due to wide range of potential application, from various pressure sensors, through smart packaging, to tissue engineering and medicine. The structural, morphological and magnetic properties of polyvinylidene fluoride/nanocellulose/magnetite@BaTiO3 hybrid films were investigated. The presented study revealed significant impact of nanocellulose (NC) content on formation of the polymorphs of PVDF, responsible for ferro-, piezo- and pyroelectric properties. The structural characterization, XRD and Raman measurements confirmed enhancement of the β and γ phases when the loading of NC higher then 4 wt% in multi-component hybrid films. The saturation magnetization value gradually raises with increasing amount of NC and reaches its maximum value of 41.2 emu/g at content of 4 wt% NC. Further, addition of NC decreases saturation magnetization value regardless of constant amount of magnetite, indicating optimal content of NC substrate for co-precipitation of Fe3O4 onto NC matrix.This is the peer reviewed version of the paper: Janićijević, Aleksandra, Pavlović, Vera P., Kovačević, Danijela, Đorđević, Nenad, Marinković, Aleksandar, Vlahović, Branislav, Karoui, Abdennaceur, Pavlović, Vladimir B., Filipović, Suzana, "Impact of Nanocellulose Loading on the Crystal Structure, Morphology and Properties of PVDF/Magnetite@NC/BaTiO3 Multi-component Hybrid Ceramic/Polymer Composite Material". Journal of Inorganic and Organometallic Polymers and Materials (2024), https://doi.org/10.1007/s10904-023-02953-
WAVES IN BEAM METASTRUCTURES WITH RIGID BODIES ON INERTER-BASED FOUNDATIONS
No full textThis research explores the dynamic behavior of structures encountered in various engineering
fields by modeling them as a series of elastic beams interconnected with rigid bodies and supported on an inerter-based elastic foundation. The analytical framework employed enables the derivation of a continuous-mass transfer matrix for arbitrary unit cells, which are tessellated to form a periodic structure (metastructure). Emphasizing the core design of a rigid body suspended
between two elastic beams, the study employs Timoshenko beam theory to model the beam
segments and performs a thorough analysis of rigid body motion. Dynamical properties of such
structures are evaluated by creating band diagrams and analyzing their dispersion properties. The
dispersion properties of a supported unit cell are compared to those of a unit cell with free-free
boundary conditions, not resting on any foundation. The presence of an elastic foundation increases the system's stiffness, causing the dispersion curves to shift to lower frequencies. This effect is more pronounced with an inerter-based foundation due to inertia amplification
Variational Approach to Heat Conduction Modeling
Get PDFIt is known that Fourier’s heat equation, which is parabolic, implies an infinite
velocity propagation, or, in other words, that the mechanism of heat
conduction is established instantaneously under all conditions. This is unacceptable
on physical grounds in spite of the fact that Fourier’s law agrees well
with experiment. However, discrepancies are likely to occur when extremely
short distances or extremely short time intervals are considered, as they must
in some modern problems of aero-thermodynamics. Cattaneo and independently
Vernotte proved that such process can be described by Heaviside’s telegraph
equation. This paper shows that this fact can be derived using calculus of
variations, by application of the Euler-Lagrange equation. So, we proved that
the equation of heat conduction with finite velocity propagation of the thermal
disturbance can be obtained as a solution to one variational proble
The safety climate, hierarchical levels and resilience assessment in transport and mining companies
No full textTransport and mining companies are vulnerable to a variety of hazards, and this paper offers a novel conceptual framework for organisational resilience assessment at different organisational levels. It is based on a safety climate and performances assessment in companies in the transport and mining sector. The framework contains factor and reliability analysis and continues by applying the SMART method from the perspective of resilience corners: anticipate, monitor, react and learn. The highest resilience coefficients at all organisational levels are obtained regarding safety awareness, safety training and safety communication areas, while the lowest values are observed for risk assessment and the organisational environment. The obtained results indicate that the ‘monitor’ resilience corner must be improved at all organisational levels, employees trained and procedures changed, since employees do not sufficiently use experience from previous events. The very high values at all organisational levels of the coefficients regarding the ‘anticipate’ and ‘learn’ resilience corners indicate organisational adaptation to changes through corrective activities, rather than planned preventive ones. All hierarchical levels have good resilience indicators, except for middle management, which expressed an adequate resilience index, due to the lower ratings of the safety training, organisational commitment, risk assessment and management support areas
The Possibility of Applying a Universal Testing Machine for Evaluating Food Textures
No full textThe evaluation of food texture is an essential aspect of food quality control, directly influencing consumer acceptance and preference. Various methods have been developed to assess food texture, including sensory evaluation, rheological measurements, and instrumental analysis. Among the versatile instruments used for measuring the mechanical properties of food, the universal testing machine (UTM) stands out. Traditionally used in the field of materials science
and engineering, the possibility of applying UTM for evaluating food textures has gained significant attention in recent years. The UTM can perform compression, tension, bending, and shear tests on food samples, providing objective and quantifiable data on their mechanical properties. Compression testing involves measuring the force required to compress a food sample between two plates, shear testing measures the force required to cut through a food sample, while puncture testing measures the force required to puncture a food sample with a probe. This paper reviews the current state-of-the-art of UTM in the evaluation of food textures, including the types of tests that can be performed, the parameters that can be measured, and the challenges and limitations associated with the technique. The potential of utilizing UTMs in the food industry for quality control
and product development, instead of traditional sensory evaluation methods, is discussed, along with its advantages and disadvantages. Overall, UTM represents a promising tool for the objective evaluation of food textures, and further research is needed to optimize its application in this field
Determination of Compression Response for Various Dried Vegetables
No full textThe texture of food plays a vital role in its overall quality, affecting both sensory experience and functional aspects, such as processing and preservation. To study texture in the field of food science and technology, various analytical methods are used tomeasure mechanical properties such as hardness, cohesiveness, and viscosity. One widely utilized technique for evaluating the texture of solid foods, particularly those with high firmness or brittleness such as dried vegetables, is compression testing. Here, a force is applied to a food sample until it deforms or fractures. In this particular study, dried onions, carrots, and peppers were chosen as test samples to investigate their texture and compression properties. To perform the tests, the researchers employed a Shimadzu AGS-X universal testing machine equipped with a 1 kN load cell capacity. This machine allowed them to compress the samples and measure the force required to achieve a specific deformation. The obtained results revealed that the texture and compression properties of the
dried vegetables were significantly influenced by the specific part of the vegetable being tested. For instance, when examining the dried onions, a notable disparity was observed between the inner and outer parts. The basal plate of the onion, in particular, exhibited much greater hardness compared to the middle portion of the dried onion. Consequently, breaking the sample required a higher compression force. This discovery implies that the texture and compression properties of dried vegetables are closely tied to their inherent characteristics, internal structure, and
composition
О брахистохронных движениях твердых тел с различными ограничениями реакции связи
Get PDFPredavanje po pozivu na Seminaru "Išljinski" Katedre za primenjenu mehaniku i upravljanje Fakulteta za mehaniku i matematiku Moskovskog državnog univerziteta "Lomonosov
Filtering Efficiency of Pollutants in Heavy-Duty Vehicle Cabins
No full textQuality of air in the cabin of transportation vehicle is of high importance due to increase in globalization that hinders rise of transportation of goods worldwide. The largest source of streets pollution in urban areas is vehicular combustion, constituted mainly of gaseous pollutants such as CO2, CO, oxides of nitrogen (NOx), ozone, and particles such as ultra-fine particulate matter (UFP). Drivers of heavy-duty vehicles (HDV) are spending both their working and free time in vehicle cabins, making then highly exposed to toxic gases and hazardous aerosols. Intensive industrial development is more concentrated in metropolitan areas, and since it still relies on fossil fuels energy, it results in high pollution of air with traf- fic-related air pollutants (TRAPs). Primary sources of UFPs in the urban environment near road sites are caused by HDV, and they enter cabin air through windows, accumulating in the cabin air and on the surfaces, resulting of up to three times higher concentration of TRAPs in cabin than outdoor air. Exposures to high CO2, NOx and UFP can significantly reduce decision-making performance and is main cause of premature deaths of HDV drivers. Sedimentation of UFP onto filter surfaces, long filter exposure times, and high temperatures within cabins cause decrease of air-flow within the filter and drastic decrease of filtering efficiency. By combining experimental results obtained from in-filed measurements performed in the city of Belgrade, during peak traffic hours, for filtration systems (AFS) placed at different positions within the cabins, obtained master present role of air filtration systems. Using analytical approach of experimental results, we propose mathematical model that describes AFS efficiency on cabin pollution mitigation. Predicted results are in close agreement with the experimental data showing that outdoor to cabin pollutants concentration is possible to estimate as it depends on and terrain design, filtration time and thermodynamic parameters within cabin. We hope that this research rises organizational attention to the health and welfare of HDV drivers
Numerical and analytical modeling of a shaped charge penetration depth
Get PDFShaped charge effect have been successfully used in various fields, including defense (anti-armor projectiles and warheads) and non-military (explosive demolitions, oil and natural gas industry) applications. The shaped charge mechanism relies on conversion of explosive charge detonation energy into kinetic energy of a hypervelocity metal penetrator, known as a jet [1]. The focus of the present research is on the jet interaction with the target material and consequent target penetration.
Two approaches to the jet penetration depth determination are considered. The first is the well-known analytical model based on the virtual origin concept [2, 3]. The second approach is the numerical modeling of the penetration process. The commercial FEM based software Abaqus/Explicit has been used for simulations and the model formulation is described in detail. The complete process of the shaped charge jet formation and penetration is successfully simulated using the pure Eulerian approach with appropriate material models [4].
Comprehensive comparison between results obtained using various theoretical models (analytical and numerical) and experimental data has been made. The following process parameters are considered: jet tip velocity, jet diameter, target cavity diameter, penetration time and penetration depth (Fig. 1). The jet velocity gradient and jet evolution are carefully analyzed in order to provide evaluation of the position of the virtual origin in time-space coordinates (Fig. 2). Comparison of analytical and numerical model results in terms of the jet tip velocity, penetration velocity and penetration depth has been performed. In contrast to the theoretically constant ratio of penetration velocity to jet tip velocity, the simulation results show that this ratio is actually variable. Analytically determined penetration depth is about 10% higher than numerical evaluation. Generally, an acceptable correlation between analytical and numerical model results has been found, which nevertheless shows that an improvement of analytical models is needed
