Brazilian Journal of Physics最新文献

{"title":"Spectroscopic Analysis in GdSr3(PO4)3:Tb3+/Eu3+ Phosphor for Optical Applications","authors":"Esarat Ansari,&nbsp;Shruti Patle,&nbsp;Ashvini Pusdekar,&nbsp;Nilesh Ugemuge","doi":"10.1007/s13538-025-01862-2","DOIUrl":"10.1007/s13538-025-01862-2","url":null,"abstract":"<div><p>A series of Tb³⁺/Eu³⁺ co-activated GdSr₃(PO₄)₃ commonly known as GSP phosphors with tunable luminescence properties were successfully synthesized using conventional solid-state reaction (SSR) method. The structural analysis of GdSr₃(PO₄)₃:Tb³⁺, Eu³⁺ confirms the cubic crystal system with I <span>(overline{4 })</span> 3d (220) space-group. Also, the scanning electron microscopy (SEM), X-ray energy dispersive spectra (EDS), and photoluminescence (PL) spectroscopy were employed to characterize the samples. The luminescent behavior of synthesized compound was examined at various excitation as well as at different doping concentration, confirming high intensity emission near white light. The emission spectra for GSP:Tb³⁺ recorded at 337 nm give the dominant peak of green color at 546 nm, with highest intensity noted for 3 mol% of doping. Whereas, emission spectra plotted for GSP:Eu³⁺ at excitation 394 nm emit intense red color emission at 615 nm for 4 mol% doping concentration. The co-activated GSP:Tb³⁺, Eu³⁺ phosphor excited at 337 nm, 377 nm, and 393 nm gives tunable properties. When excited at 337 nm, the characteristics emission of only Tb³⁺ ion is recorded in emission spectra, while for 377 nm excitation, both Tb³⁺ and Eu³⁺ ions emission are observed, and for 393 nm excitation, only Eu³⁺ ion emissions are recorded. The energy transfer from Tb³⁺  → Eu³⁺ is observed. The variation in lifetime, color rendering index (CRI), and correlated color temperature (CCT) is observed due to varied doping concentration of Eu³⁺, Tb³⁺ ions indicating vibrant and intense light. This phosphor has potential applications in the field of optoelectronics specifically as a wLED.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145142405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aerva lanata-Derived Reduced Graphene Oxide: Synthesis, Microstructural, Thermal and Antibacterial Studies","authors":"Shibi Krishnan,&nbsp;Arun S. Prasad","doi":"10.1007/s13538-025-01857-z","DOIUrl":"10.1007/s13538-025-01857-z","url":null,"abstract":"<div><p>The graphene oxide prepared through the modified Hummers method was subsequently reduced using methanolic extract of <i>Aerva lanata</i> (L.) to obtain the reduced graphene oxide. The formation of <i>A. lanata</i>-derived reduced graphene oxide and the total phenols were assessed. To evaluate the efficiency, the antioxidant potential of the <i>A. lanata</i> extract was also tested using a 2,2-diphenyl-1-picrylhydrazyl assay; its IC50 value was then calculated. The <i>A. lanata</i>-derived reduced graphene oxide was characterized using X-ray diffraction, UV–Vis spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The micro structural and morphological investigations of the samples were performed using high-resolution transmission electron microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopic measurements. Furthermore, the thermal properties were investigated through thermogravimetric analysis and thermal conductivity measurements that indicated improved thermal stability and enhanced thermal conductivity for the synthesized reduced graphene oxide over graphene oxide. The study revealed remarkable enhancement in antibacterial activity for the synthesized reduced graphene oxide against both Gram-negative and Gram-positive bacteria.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145142058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unsteady MHD Flow Over a Stretching Sheet in a Darcy-Forchheimer Porous Medium: Influence of Joule Heating, Soret Effect, and Chemical Reaction","authors":"Saleem Jabed Al Khayer,&nbsp;Shyamanta Chakraborty","doi":"10.1007/s13538-025-01870-2","DOIUrl":"10.1007/s13538-025-01870-2","url":null,"abstract":"<div><p>This study explores the combined effects of a chemical reaction, heat source, and Joule heating on the unsteady, two-dimensional flow of an incompressible, viscous, magnetohydrodynamic (MHD) fluid over a vertically stretched surface within a Darcy-Forchheimer porous medium. The system of coupled partial differential equations governing the flow is simplified into a set of nonlinear ordinary differential equations using similarity transformations. These equations are then solved using the bvp4c numerical method. Graphs are used to illustrate and analyze how various physical parameters namely, Hartmann number, Forchheimer number, Joule heating parameter, Prandtl number, heat source parameter, Soret number, Schmidt number, and chemical reaction parameter etc. affect the fluid’s velocity, temperature, and concentration. Numerical values for skin friction, the Sherwood number, and the Nusselt number are presented in tables. To verify the accuracy of the method, the results are compared with previously published studies and show strong agreement. The results indicate that increasing the Forchheimer number leads to a decrease in fluid velocity, while the temperature increases. Moreover, higher Hartmann numbers and unsteadiness parameters result in reduced skin friction.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145142161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neuro-Fuzzy Systems Applied to Structural Health Monitoring by Electromechanical Impedance","authors":"Fellipe A. D. Prudente,&nbsp;Rosana S. M. Jafelice,&nbsp;José W. Silva,&nbsp;Diogo S. Rabelo,&nbsp;José R. V. Moura Jr.,&nbsp;Roberto M. Finzi Neto","doi":"10.1007/s13538-025-01864-0","DOIUrl":"10.1007/s13538-025-01864-0","url":null,"abstract":"<div><p>This study investigates structural health monitoring (SHM) to identify potential damage in structures. This work focuses on applying SHM in oil and gas facilities. The main objective is to perform temperature compensation for electromechanical impedance data using two distinct neuro-fuzzy systems: the adaptive neuro-fuzzy inference system (ANFIS) and the hybrid neural fuzzy inference system (HyFIS). Both techniques combine neural networks with fuzzy sets, considering the uncertainties of the problem variables. The data was collected using PZT (lead zirconate titanate) patches installed on a steel plate subjected to five types of damage. The experiments took place in the field under varying environmental conditions. Part of the data was used to train the neuro-fuzzy networks that build the FRBS, with temperature and frequency as inputs and the real part of the impedance as output. A comparative analysis was performed by calculating the correlation coefficient deviation (CCD) between the results of the fuzzy rule-based systems (FRBS) generated by ANFIS and HyFIS and the experimental data. The results were promising, with HyFIS achieving over 90% accuracy in the experiment. The HyFIS FRBS enabled the measurement of impedance differences between baseline values and those observed under the five types of damage using three defined metrics. HyFIS was chosen due to its higher precision in validation compared to ANFIS. In summary, neuro-fuzzy networks applied to SHM have shown promising results in optimizing the training process for damage diagnosis, suggesting that the technique can be effectively used in the context of petroleum product storage tanks, which is the focus of this work.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multifunctional Co2+-Substituted SnO2: Insights from Soft Magnetism, Optical Tuning, and MEM-Based Electronic Structure","authors":"K. KaviyaPandimeena,&nbsp;M. Charles Robert","doi":"10.1007/s13538-025-01856-0","DOIUrl":"10.1007/s13538-025-01856-0","url":null,"abstract":"<div><p>Multifunctional and single-phase Co²⁺-substituted SnO₂ dilute magnetic semiconductors (DMS) were synthesized via a simple co-precipitation method. Electron paramagnetic resonance (EPR) analysis confirms the successful incorporation of divalent cobalt ions into the SnO₂ host lattice, both at substitutional and interstitial sites. Optical studies reveal a reduction in the energy band gap and an enhancement in ultraviolet (UV) absorption with increasing Co²⁺doping, with an absorption edge observed at 282 nm. Photoluminescence (PL) measurements indicate a strong red emission at 639 nm, which remains relatively unchanged with varying Co²⁺concentrations. The material’s transparency and conductivity render it suitable for optoelectronic and magneto-optical applications. Among the investigated compositions, the 5% Co²⁺-doped sample exhibits the highest ferromagnetic saturation (2.798 emu/g) and coercivity (206.17 Oe) at room temperature, attributed to the exchange interactions between Co²⁺ ions mediated by oxygen vacancies. The low coercivity suggests facile magnetic switching with minimal hysteresis loss and weak domain wall pinning, making these materials promising candidates for spintronic applications such as magnetic sensors, memory devices, and spin-based transistors. A detailed electronic structure and bonding analysis using the maximum entropy method (MEM) indicates that at 5% Co²⁺ doping, the Co²⁺ ions are optimally diluted within the Sn⁴⁺ host lattice. A newly established empirical correlation highlights the relationship between saturation magnetization and the MEM-derived electronic structure. The findings suggest that achieving an appropriate Co²⁺ substitution within the Sn⁴⁺ host lattice and minimized interstitial charge accumulation while maintaining balanced apical and equatorial (Sn/Co)-O bonding is critical for maximizing magnetic saturation.\u0000</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coexistence of Arbitrary Amplitude Compressive and Rarefactive Positron-Acoustic Solitons in a Non-Maxwellian Unmagnetized Multicomponent Plasma","authors":"Samir A. El-Tantawy,&nbsp;Sahibzada I. H. Bacha,&nbsp;Muhammad Khalid,&nbsp;Hanan Al-Ghamdi,&nbsp;Amnah S. Al-Johani","doi":"10.1007/s13538-025-01861-3","DOIUrl":"10.1007/s13538-025-01861-3","url":null,"abstract":"<div><p>The present investigation concerns the study of large-amplitude positron-acoustic solitary waves (PASWs) in four-component unmagnetized plasma exhibiting non-Maxwellian characteristics. The plasma model comprises cold inertial positrons, electrons described by a Cairns distribution, hot positrons governed by a Maxwellian distribution, and stationary ions. Sagdeev’s method is employed to derive the energy integral equation, which demonstrates the existence of both positive and negative polarity PASWs under appropriate plasma conditions. A comprehensive analysis is performed to determine the effect of various plasma parameters, including hot positron concentration, electron concentration, hot positron and electron temperature ratios, the Mach number, and the nonthermal parameter—which significantly influence the formation, amplitude, and width of these PASWs, as well as their existence regions. The findings suggest a possible association of these nonlinear structures with electrostatic perturbations observed in various laboratory plasmas and astrophysical environments, including the interstellar medium, pulsar magnetospheres, active galactic nuclei, and auroral acceleration regions.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamical Quantumness Transition Induced by Reset Dynamics: The Jaynes-Cummings Model","authors":"Maria L. G. D. dos Santos,&nbsp;Adélcio C. Oliveira","doi":"10.1007/s13538-025-01855-1","DOIUrl":"10.1007/s13538-025-01855-1","url":null,"abstract":"<div><p>We have studied the dynamics of the Jaynes-Cummings model with dissipation subject to stochastic reset. The main dynamic variables were investigated, such as momentum, position, and energy, and we found stationary states distinct from the vacuum state for a zero-temperature reservoir. There is a strong direct correlation between the reset probability and the final energy of the state. For dynamics without a reservoir, we investigated the non-classicality of the steady state as a function of the reset probability. This relationship is non-linear and exhibits a non-classicality transition, manifested as an abrupt change in the quantumness indicator. The position of this transition, in terms of the reset parameter, depends on the quantifier used. As we include an action of a dissipating reservoir, the transition is attenuated but not completely eliminated. A linear relationship between linear entropy, visibility, and roughness was also entered for the model dynamics. This relationship can be interpreted as a kind of complementary relationship, although the coefficients are dependent on the model parameters.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic Exploration of Electronic, Optical, and Thermoelectric Properties of SrCuXF (X = S, Se) Materials: Employing First-Principles Calculations","authors":"Abdelhay Salah Mohamed,&nbsp;Banat Gul,&nbsp;Muhammad Salman Khan,&nbsp;Ghlamallah Benabdellah,&nbsp;Siti Maisarah Aziz,&nbsp;Faheem Abbas","doi":"10.1007/s13538-025-01853-3","DOIUrl":"10.1007/s13538-025-01853-3","url":null,"abstract":"<div><p>Copper-based chalcogenides have exceptional features, including regulating optoelectronic features and good thermal stability. The density functional theory is employed to describe the intricate association between the structural, electronic, optoelectrical, and transport nature of SrCuXF (X = S, Se) quaternary semiconductors. The electronic band structure confirming direct band gaps. In these materials, the substitution of Se by S increases the band gap energy. The substantial optical constants including the components of dielectric function were studied to describe their probable usage in optoelectronic applications. The peaks in the <i>ε</i>₁(<i>ω</i>) decline and reach the negative energy region, representing metallicity in these materials. These quaternary materials under investigation exhibit remarkable and substantial thermoelectric capabilities, suggesting their potential utility in thermoelectric applications. The current study confirms their potential use in state-of-the-art optoelectronic devices and opens up new technical methods.\u0000</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Self-Compression of Femtosecond Super-Gaussian Laser Pulse in Relativistically Strong Plasma","authors":"Pratibha Jaiswal,&nbsp;Sintu Kumar,&nbsp;Km Shivani Bhardwaj,&nbsp;Preeti Gupta,&nbsp;Rajesh Kumar Rai","doi":"10.1007/s13538-025-01854-2","DOIUrl":"10.1007/s13538-025-01854-2","url":null,"abstract":"<div><p>The study of self-compression of laser pulse having super-Gaussian profile in relativistically guided plasma has been investigated. A nonlinear propagation equation of laser pulse in plasma using relativistic nonlinearity has been derived. Moreover, a semi-analytical method was used to solve the nonlinear equation for self-compression and self-focusing of the laser pulse in plasma. It has been seen that pulse broadening and relativistic nonlinearity are sole origin for self-compression of Super-Gaussian laser pulse inside the plasma. The pulse broadening accure due to effect of group velocity dispersion (GVD) and when, nonlinearity combined (balanced) with it pulse broadening, result in formation of compressed and amplified pulse in enhance manner. Numerical computation result shows that, a 50 fs laser pulse gets compressed into 17 fs laser pulse.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A First-Principles Study of the Structural, Optoelectronic and Thermoelectric Properties of Ba2XIO6 (X = Li, K and Rb) for Energy Harvesting","authors":"M. Awais Ahmed,&nbsp;Shoaib Ullah,&nbsp;Khalil Ur Rehman,&nbsp;G. Murtza,&nbsp;Ahmad Ayyaz,&nbsp;M. Irfan,&nbsp;Imen Kebaili,&nbsp;Ali El-Rayyes","doi":"10.1007/s13538-025-01847-1","DOIUrl":"10.1007/s13538-025-01847-1","url":null,"abstract":"<div><p>This study presents an investigation into the properties of Ba₂XIO₆ (X = Li, K, and Rb) double perovskites using the WIEN2k computational code within the density functional theory (DFT) framework. First-principles calculations were used to thoroughly analyse the structural stability, electrical properties, optical features and thermoelectric capabilities of Ba₂XIO₆. The findings indicate that Ba₂XIO₆ (X = Li, K, and Rb) is crystallized in a resilient cubic double perovskite structure. The tolerance factors for Ba₂LiIO₆, Ba₂KIO₆, and Ba₂RbIO₆ are calculated to be 0.95, 0.86, and 0.86, respectively, supporting their structural stability. Electronic structure calculations reveal that Ba₂XIO₆ compounds are direct bandgap semiconductors with bandgaps located at the Γ point of the Brillouin zone. The computed bandgap values are 2.027 eV for Ba₂LiIO₆, 2.016 eV for Ba₂KIO₆, and 1.85 eV for Ba₂RbIO₆. For the energy range of 0–13.5 eV, real and imaginary portions of the dielectric function, absorption coefficient, optical conductivity, refractive index, reflectivity and energy loss function were all examined in a thorough analysis of optical characteristics using the OPTIC code. First peak reflectivity values were found to be 12%, 15%, and 21% for Ba₂LiIO₆, Ba₂KIO₆, and Ba₂RbIO₆, respectively. Furthermore, the thermoelectric performance was assessed using the BoltzTraP code, calculating the Seebeck coefficient, electrical conductivity, and thermal conductivity. The results indicate promising thermoelectric performance with a figure of merit (ZT) of 0.794, 0.808, and 0.793 for Ba₂LiIO₆, Ba₂KIO₆, and Ba₂RbIO₆, respectively. In summary, this first-principles study highlights the potential applications of Ba₂XIO₆ (X = Li, K, and Rb) in thermoelectric generators and optoelectronic devices, offering valuable insights into their multifunctional properties.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 5","pages":""},"PeriodicalIF":1.7,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}