Physics

21 pages, 7965 KiB

Open AccessArticle

Investigation of the Impact of an Electric Field on Polymer Electrolyte Membranes for Fuel Cell Applications

by Hamdy F. M. Mohamed, Esam E. Abdel-Hady, Mohamed H. M. Hassanien and Wael M. Mohammed

Physics 2024, 6(4), 1345-1365; https://doi.org/10.3390/physics6040083 - 17 Dec 2024

Viewed by 638

A systematic study was carried out on Nafion^® 112 membranes to evaluate the effects of different electric field strengths on the structural and electrical properties of the membranes. The membranes were subjected to different electric field strengths (0, 40, 80, and 140 [...] Read more.

A systematic study was carried out on Nafion^® 112 membranes to evaluate the effects of different electric field strengths on the structural and electrical properties of the membranes. The membranes were subjected to different electric field strengths (0, 40, 80, and 140 MV/m) at a temperature of 90 °C. Proton conductivity was measured using an LCR meter, revealing that conductivity values varied with the electric field strengths, with the optimal conductivity observed at 40 MV/m. Positron annihilation lifetime (PAL) spectroscopy provided insights into the free volume structure of the membranes, showing an exponential increase in the hole volume size as the electric field strength increased. It was also found that the positronium intensity of the Nafion^® 112 membranes was influenced by their degree of crystallinity, which decreased with higher electric field strengths. This indicates complex interactions between structural changes and the effects of the electric field. Dielectric studies of the membranes were characterized over a frequency range of 50 Hz to 5 MHz, demonstrating adherence to Jonscher’s law. The Jonscher’s power law’s s-parameter values increased with the electric field strength, suggesting a transition from a hopping conduction mechanism to more organized ionic transport. Overall, the study emphasizes the relationship between the free volume, crystallinity, and macroscopic characteristics, such as ionic conductivity. The study highlights the potential to adjust membrane performance by varying the electric field. Full article

(This article belongs to the Section Applied Physics)

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30 pages, 10922 KiB

Open AccessArticle

Chemically Reactive Micropolar Hybrid Nanofluid Flow over a Porous Surface in the Presence of an Inclined Magnetic Field and Radiation with Entropy Generation

by Sudha Mahanthesh Sachhin, Parashurampura Karibasavanaika Ankitha, Gadhigeppa Myacher Sachin, Ulavathi Shettar Mahabaleshwar, Igor Vladimirovich Shevchuk, Sunnapagutta Narasimhappa Ravichandra Nayakar and Rachappa Kadli

Physics 2024, 6(4), 1315-1344; https://doi.org/10.3390/physics6040082 - 13 Dec 2024

Viewed by 838

Abstract

The present study investigates the entropy generation of chemically reactive micropolar hybrid nanoparticle motion with mass transfer. Magnetic oxide (Fe₃O₄) and copper oxide (CuO) nanoparticles were mixed in water to form a hybrid nanofluid. The governing equations for velocity, [...] Read more.

The present study investigates the entropy generation of chemically reactive micropolar hybrid nanoparticle motion with mass transfer. Magnetic oxide (Fe₃O₄) and copper oxide (CuO) nanoparticles were mixed in water to form a hybrid nanofluid. The governing equations for velocity, concentration, and temperature are transformed into ordinary differential equations along with the boundary conditions. In the fluid region, the heat balance is kept conservative with a source/sink that relies on the temperature. In the case of radiation, there is a differential equation along with several characteristic coefficients that transform hypergeometric and Kummer’s differential equations by a new variable. Furthermore, the results of the current problem can be discussed by implementing a graphical representation with different factors, namely the Brinkman number, porosity parameter, magnetic field, micropolar parameter, thermal radiation, Schmidt number, heat source/sink parameter, and mass transpiration. The results of this study are presented through graphical representations that depict various factors influencing the flow profiles and physical characteristics. The results reveal that an increase in the magnetic field leads to a reduction in velocity and entropy production. Furthermore, temperature and entropy generation rise with a stronger radiation parameter, whereas the Nusselt number experiences a decline. This study has several industrial applications in technology and manufacturing processes, including paper production, polymer extrusion, and the development of specialized materials. Full article

(This article belongs to the Section Applied Physics)

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9 pages, 292 KiB

Open AccessArticle

Interaction Between Gravitational Waves and Trapped Bose–Einstein Condensates

by Alessio Perodi and Luca Salasnich

Physics 2024, 6(4), 1306-1314; https://doi.org/10.3390/physics6040081 - 5 Dec 2024

Viewed by 1089

Abstract

Inspired by recent proposals for detecting gravitational waves by using Bose–Einstein condensates (BECs), we investigated the interplay between these two phenomena. A gravitational wave induces a phase shift in the fidelity amplitude of the many-body quantum state. We investigated the enhancement of the [...] Read more.

Inspired by recent proposals for detecting gravitational waves by using Bose–Einstein condensates (BECs), we investigated the interplay between these two phenomena. A gravitational wave induces a phase shift in the fidelity amplitude of the many-body quantum state. We investigated the enhancement of the phase shift in the case of Bose condensates confined by an anisotropic harmonic potential, considering both ideal and interacting BECs. Full article

(This article belongs to the Special Issue Complexity in High Energy and Statistical Physics)

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12 pages, 747 KiB

Open AccessArticle

Optical Medium Approach: Simplifying General Relativity and Nonlinear Electrodynamics for Educational Purposes

by Saken Toktarbay, Nurzada Beissen, Manas Khassanov, Temirbolat Aitassov and Amina Sadu

Physics 2024, 6(4), 1294-1305; https://doi.org/10.3390/physics6040080 - 5 Dec 2024

Viewed by 905

Abstract

This paper explores the optical approach to simplifying complex concepts in general relativity (GR) and nonlinear vacuum electrodynamics. The focus is on using optical analogies to simplify the understanding of spacetime curvature and interactions in strong gravitational and magnetic fields. We demonstrate how [...] Read more.

This paper explores the optical approach to simplifying complex concepts in general relativity (GR) and nonlinear vacuum electrodynamics. The focus is on using optical analogies to simplify the understanding of spacetime curvature and interactions in strong gravitational and magnetic fields. We demonstrate how applying concepts of effective refractive index can facilitate the teaching and comprehension of GR optical effects, such as gravitational lensing and the behavior of light around massive objects. Additionally, the paper covers the application of optical analogies in the context of nonlinear vacuum electrodynamics, showing how strong magnetic fields affect light propagation. This interdisciplinary approach provides a more natural understanding and modeling of complex physical phenomena, making them better accessible for study and teaching. Full article

(This article belongs to the Section Physics Education)

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13 pages, 3609 KiB

Open AccessArticle

Dynamics of Neutron Transfer in the Reaction ³He + ⁹Be

by Aidos K. Azhibekov, Englik K. Almanbetova, Mikhail A. Naumenko, Kairat O. Mendibayev, Sergey M. Lukyanov, Talgat G. Issatayev, Bakhytzhan A. Urazbekov, Asset M. Kabyshev, Kuralay Dyussebayeva and Timur K. Zholdybayev

Physics 2024, 6(4), 1281-1293; https://doi.org/10.3390/physics6040079 - 21 Nov 2024

Viewed by 1162

Abstract

The paper presents the results of experiments on measuring cross-sections for the neutron transfer channels ⁹Be(³He, α)⁸Be_gs,3.03 in the reaction of the ³He (30 MeV) ions with the ⁹Be target. To describe the angular distributions, [...] Read more.

The paper presents the results of experiments on measuring cross-sections for the neutron transfer channels ⁹Be(³He, α)⁸Be_gs,3.03 in the reaction of the ³He (30 MeV) ions with the ⁹Be target. To describe the angular distributions, we use the Distorted Wave Born Approximation (DWBA) applying the FRESCO code. The results of the theoretical analysis are in agreement with the experimental data. In addition, we perform calculations based on the solution of the time-dependent Schrödinger equation (TDSE) for the weakly bound neutron of the ⁹Be nucleus. The TDSE approach allows us to determine the dynamics of the neutron transfer process and calculate the probabilities for the transfer and removal of the neutron of the ⁹Be nucleus in the ³He + ⁹Be reaction. Full article

(This article belongs to the Section Atomic Physics)

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17 pages, 356 KiB

Open AccessArticle

Accelerating Charge: Add-Ons to Rest Mass and Field Energy

by Elizabeth P. Tito and Vadim I. Pavlov

Physics 2024, 6(4), 1264-1280; https://doi.org/10.3390/physics6040078 - 19 Nov 2024

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Abstract

We present—in the framework of classical theory—a self-consistent derivation scheme which produces equations for the calculation of add-ons to the full field energy and to the effective mass of a charge moving with acceleration, which may be practically used for analyses in various [...] Read more.

We present—in the framework of classical theory—a self-consistent derivation scheme which produces equations for the calculation of add-ons to the full field energy and to the effective mass of a charge moving with acceleration, which may be practically used for analyses in various scenarios. The charge is treated as a quasi-point-like charge; this helps to resolve the complications of the “infinite” electromagnetic energy, which are avoided by the procedure of slightly “spreading” the charge. As a result, the concept of the size of the particle takes a straightforward physical interpretation. Indeed, it is within the charge spread, at scales smaller than Compton’s length, where the quantum-field-mechanics approach to be applied. Beyond this region, no “infinite” tails of quantities accumulate. The seeming divergences of the integrals at the upper limits are not physical if one takes into account that the charge moves with acceleration only for a finite duration of time; every real physical process has its beginning and its end. The key focus of this paper is on the methodological aspects of the calculations. Full article

(This article belongs to the Section Classical Physics)

13 pages, 344 KiB

Open AccessArticle

The Two-Thirds Power Law Derived from a Higher-Derivative Action

by Nicolas Boulanger, Fabien Buisseret, Frédéric Dierick and Olivier White

Physics 2024, 6(4), 1251-1263; https://doi.org/10.3390/physics6040077 - 11 Nov 2024

Viewed by 1178

Abstract

The two-thirds power law is a link between angular speed

ω

and curvature

κ

observed in voluntary human movements:

ω

is proportional to

κ^{2 / 3}

. Squared jerk is known to be a Lagrangian leading to the latter law. However, it [...] Read more.

The two-thirds power law is a link between angular speed

ω

and curvature

κ

observed in voluntary human movements:

ω

is proportional to

κ^{2 / 3}

. Squared jerk is known to be a Lagrangian leading to the latter law. However, it leads to unbounded movements and is therefore incompatible with quasi-periodic dynamics, such as the movement of the tip of a pen drawing ellipses. To solve this drawback, we give a class of higher-derivative Lagrangians that allow for both quasi-periodic and unbounded movements, and at the same time lead to the two-thirds power law. The current study extends this framework and investigates a wider class of Lagrangians admitting generalised conservation laws. Full article

(This article belongs to the Section Classical Physics)

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11 pages, 2309 KiB

Open AccessArticle

Impacts of Am Aggregation on the Bulk Properties of Mixed Oxides (U, Am)O₂ from First Principles

by Tao Liu, Ziyi Yang, Xiaoyan Yu and Tao Gao

Physics 2024, 6(4), 1240-1250; https://doi.org/10.3390/physics6040076 - 7 Nov 2024

Viewed by 680

Abstract

We present a first-principles density functional theory with the Coulomb interaction U (DFT + U) investigation of the bulk properties, including structural, energetic, electronic, and mechanical properties for uranium–americium mixed oxides (U, Am)O₂. The various Am aggregation contents were investigated [...] Read more.

We present a first-principles density functional theory with the Coulomb interaction U (DFT + U) investigation of the bulk properties, including structural, energetic, electronic, and mechanical properties for uranium–americium mixed oxides (U, Am)O₂. The various Am aggregation contents were investigated to better understand the impact of Am on the nuclear fuel UO₂. The supercell defect models at different scales were used to describe the solid solution (U, Am)O₂. The obtained results show that different contents of Am aggregation have a significant impact on the volume and energy of the formation of mixed oxide systems. The results of the electronic structure calculations exhibit no bandgap owing to the mixing of UO₂ and AmO₂. The mixing enthalpy of the Am aggregation systems is used to describe the phase stability of the solid solution. In particular, the mixing enthalpy of (U, Am)O₂ is significantly reduced as the Am content increases. The elastic properties of the (U, Am)O₂ mixed oxides have also been compared as a function of the Am content. Moreover, the impacts of the whole Pu aggregation content range on the bulk properties for the (U, Pu)O₂ mixed oxides are also discussed. Full article

(This article belongs to the Section Applied Physics)

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18 pages, 323 KiB

Open AccessReview

Entropy Considerations in Stochastic Electrodynamics

by Daniel C. Cole

Physics 2024, 6(4), 1222-1239; https://doi.org/10.3390/physics6040075 - 28 Oct 2024

Viewed by 1238

Abstract

The use of entropy concepts in the field of stochastic electrodynamics is briefly reviewed here. Entropy calculations that have been fully carried out to date are discussed in two main cases: first, where electric dipole oscillators interact with zero-point, or zero-point plus Planckian, [...] Read more.

The use of entropy concepts in the field of stochastic electrodynamics is briefly reviewed here. Entropy calculations that have been fully carried out to date are discussed in two main cases: first, where electric dipole oscillators interact with zero-point, or zero-point plus Planckian, or Rayleigh–Jeans radiation; and second, where only these radiation fields exist within a cavity. The emphasis here is on the first, more complicated, case, where both charged particles and radiation fields are present and interacting. Unlike the usual exposition on entropy in classical statistical mechanics, involving probabilistic notions of phase-space occupation, the calculations to date for both particles and fields, or for fields alone, follow the caloric entropy method, where the notions of heat flow, adiabatic surfaces, and isothermal conditions are utilized. Probability notions certainly still enter into the calculations, as the fields and charged particles interact stochastically together, following Maxwellian electrodynamics. Examples of phase-space calculations for harmonic oscillators and classical hydrogen atoms are carried out, emphasizing how much farther caloric entropy calculations have successfully gone. Full article

(This article belongs to the Section Statistical Physics and Nonlinear Phenomena)

18 pages, 1348 KiB

Open AccessArticle

Adhesion Energy for Nonideal Cantilever and Its Relation to Casimir–Lifshitz Forces

by Ivan A. Soldatenkov and Vitaly B. Svetovoy

Physics 2024, 6(4), 1204-1221; https://doi.org/10.3390/physics6040074 - 23 Oct 2024

Viewed by 990

Abstract

The method of the adhered cantilever, borrowed from microtechnology, can help in gaining fundamental knowledge about dispersion forces acting at distances of about 10 nm, which are problematic to access in the usual Casimir-type experiments. A recently presented setup measures the shape of [...] Read more.

The method of the adhered cantilever, borrowed from microtechnology, can help in gaining fundamental knowledge about dispersion forces acting at distances of about 10 nm, which are problematic to access in the usual Casimir-type experiments. A recently presented setup measures the shape of cantilevers with high precision, which is needed for analyzing the involved forces. The first measurements reveal several nonidealities crucial for the data analysis. In this paper, a generalized formula is deduced that relates the parameters of a cantilever to the adhesion energy. The application of the formula is demonstrated using the first test result from the setup, where a silicon cantilever adhered to a substrate sputters with ruthenium. Detailed information of the roughness of interacting surfaces, which deviates significantly from the normal distribution, is emphasized. Although not crucial, the electrostatic contribution can be significant due to the slight twisting of the cantilever. The theoretical prediction of the adhesion energy is based on Lifshitz theory. Comparing theory and experiment yields a contact distance of 45 nm and an adhesion energy of 1.3 µJ/m², resulting from the Casimir–Lifshitz forces. Significant uncertainties arise from the uncontrolled electrostatic contribution. Factors that need to be addressed to measure weak adhesion between rough surfaces are highlighted. Full article

(This article belongs to the Section Classical Physics)

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13 pages, 271 KiB

Open AccessReview

Classicalization of Quantum Mechanics: Classical Radiation Damping Without the Runaway Solution

by Tomio Petrosky, Yuki Goto and Savannah Garmon

Physics 2024, 6(4), 1191-1203; https://doi.org/10.3390/physics6040073 - 22 Oct 2024

Viewed by 1351

Abstract

In this paper, we review a new treatment of classical radiation damping, which resolves a known contradiction in the Abraham–Lorentz equation that has long been a concern. This radiation damping problem has already been solved in quantum mechanics by the method introduced by [...] Read more.

In this paper, we review a new treatment of classical radiation damping, which resolves a known contradiction in the Abraham–Lorentz equation that has long been a concern. This radiation damping problem has already been solved in quantum mechanics by the method introduced by Friedrichs. Based on Friedrichs’ treatment, we solved this long-standing problem by classicalizing quantum mechanics by replacing the canonical commutation relation from quantum mechanics with the Poisson bracket relation in classical mechanics. Full article

(This article belongs to the Special Issue Matter-Radiation Interactions—In Memory of Professor Francesco Saverio Persico)

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Physics, Volume 6, Issue 4 (December 2024) – 11 articles

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