Revista Mexicana de Física

Un modelo térmico para la estimación de la temperatura interior en viviendas rurales de Michoacán, México

David Espinosa Gómez — 2026-07-01

En la actualidad existe un interés creciente en mejorar la eficiencia térmica de las viviendas y edificios, siendo importante el desarrollo de modelos que analicen el comportamiento térmico de estos inmuebles y sugieran mejoras para optimizar el confort en la infraestructura habitacional. En este trabajo se desarrolló un modelo térmico que permite la estimación de la temperatura interior en viviendas rurales del estado de Michoacán mediante el método de analogías eléctricas. La metodología propuesta se basa en tres etapas: (a) la formulación de un modelo a partir de un sistema de circuito eléctrico que se fundamenta en principios físicos a través de la transferencia de calor y el balance de energía de un sistema de vivienda cúbica simple, donde se han utilizado las propiedades térmicas del techo, como la conductividad, el área, el espesor y la densidad; (b) el análisis del comportamiento térmico de tres tipos de viviendas con piso de cemento, muros de ladrillo de arcilla cocida y techos variables de cemento, lámina de asbesto y láminas de cartón negro, en cuyo caso se han registrado las temperaturas internas mediante termómetros ambientales, y externa mediante termopares y termografía aérea; y (c) la validación del modelo a través de la comparación de las temperaturas máximas y mínimas por día en las viviendas analizadas, contrastando las predicciones del modelo con los datos experimentales. Los resultados muestran que el modelo térmico es funcional. Se probó en distintas viviendas durante los meses de marzo y abril de 2024, obteniendo un error relativo absoluto medio porcentual del 4% respecto a la temperatura real de la vivienda. En los casos con mayores fluctuaciones climatológicas y de variación de temperaturas en los techos de las viviendas estudiadas, se observaron errores menores al 10%. Las temperaturas exteriores de los techos de las viviendas, como condición de frontera del modelo, pueden estimarse mediante tomografía aérea, lo que permite predecir, mediante técnicas de medición no invasivas, las temperaturas interiores de los tipos de viviendas analizadas con errores aceptables. Se espera que esta herramienta pueda utilizarse en el diagnóstico de materiales y la formulación de estrategias que promuevan la mejora de habitaciones para incentivar el confort térmico en comunidades rurales.

Currently, there is growing interest in improving the thermal efficiency of homes and buildings. It is important to develop models that analyze the thermal behavior of these buildings and suggest improvements to optimize comfort in housing infrastructure. In this work, a thermal model was developed that allows for the estimation of indoor temperatures in rural homes in the state of Michoacán using the electrical analogy method. The proposed methodology is based on three stages: (a) the formulation of a model from an electrical circuit system that is based on physical principles through the heat transfer and energy balance of a simple cubic housing system, where the thermal properties of the roof have been used, such as conductivity, area, thickness and density (b) the analysis of the thermal behavior of three types of houses with cement floors, baked clay brick walls and variable roofs of cement, asbestos sheets and black cardboard sheets, in which case internal temperatures have been recorded using ambient thermometers, and external temperatures using thermocouples and aerial thermography, and (c) the validation of the model through the comparison of the maximum and minimum temperatures per day in the analyzed houses, contrasting the predictions of the model with the experimental data. The results show that the thermal model is functional. It was tested in different homes during March and April 2024, obtaining an average absolute relative error of 4% with respect to the actual temperature of the home. In cases with greater climatic fluctuations and temperature variations on the roofs of the homes studied, errors were less than 10%. The exterior temperatures of the roofs of the homes, as a boundary condition of the model, can be estimated using aerial tomography, which allows the interior temperatures of the types of homes analyzed to be predicted with acceptable errors through non-invasive measurement techniques. It is expected that this tool can be used in the diagnosis of materials and the formulation of strategies that promote room improvements to encourage thermal comfort in rural communities.

Structural and optical analysis of amorphous TiO2 films pbtained by sol-gel process and deposited by spin coating on PET/ITO at room temperature

CARLOS MONTERO-TAVERA — 2026-07-01

In this work, we proposed a methodology based on the spin coating technique for the deposition of amorphous TiO₂ layers obtained by the sol-gel method onto flexible PET/ITO substrates intended for application in flexible organic solar cells (FOSCs). Spin-coated TiO₂ layers were used to investigate the influence of their optical and structural properties on the light absorption behavior of the P3HT:PCBM active layer, to integrate the photovoltaic system PET/ITO/TiO₂/P3HT:PCBM. Raman spectroscopy confirmed the amorphous nature of TiO₂. The average particle size was 216 nm according to SEM results. UV-Vis measurements of TiO₂ layers showed a transmittance greater than 65% and a bandgap of 3.77 eV, which corresponds to the bandgap of amorphous TiO₂, making them a novel material for electromagnetic radiation to reach the P3HT:PCBM absorber layer and generate excitons within it. A high light absorbance zone (300-550 nm) and a weak light zone (650-900 nm) were found. FT-IR spectra revealed the characteristic absorbance bands of Ti−O at 523 cm^-1 and Ti−O−Ti at 434 cm^-1. AFM images revealed a uniform distribution of TiO₂ onto PET/ITO, and the typical P3HT:PCBM microstructure. This methodology enables the deposition of TiO₂ layers at room temperature without the use of any additional chemical bonding agents, which is a key factor for low - temperature fabrication of FOSCs.

Estudio por medio de cálculos de primeros principios de las propiedades cristalográficas y electrónicas del dicalcogenuro KTMS₂ (TM = Nb y Ta)

Yaneth Stefania Florez Sirocama — 2026-07-01

Debido a sus excepcionales propiedades estructurales y electrónicas, los dicalcogenuros de metales de transición (TMDs) se han consolidado recientemente como candidatos prometedores para su integración en electrónica avanzada y sistemas de almacenamiento de energía. En este trabajo, presentamos un estudio sistemático y predictivo de las propiedades estructurales, la estabilidad termodinámica y la estructura electrónica de los dicalcogenuros de potasio y metal de transición KTMS$_2$ (TM = Nb y Ta). Los cálculos se realizaron a partir de primeros principios dentro del marco de la Teoría de los Funcionales de la Densidad (DFT). El funcional de intercambio y correlación se trató mediante la Aproximación del Gradiente Generalizado (GGA) en su parametrización optimizada para sólidos, PBEsol. La estructura del estado fundamental para cuatro fases distintas ($\alpha$ y $\eta$ para KNbS$_2$, y $\zeta_1$ y $\zeta_2$ para KTaS$_2$) fue determinada ajustando la energía total en función del volumen a la Ecuación de Estado de Birch-Murnaghan de cuarto orden. Nuestros resultados energéticos indican que la fase $\eta$ es termodinámicamente más estable que la fase $\alpha$ en el sistema KNbS$_2$. Por otro lado, para el sistema KTaS$_2$, se determinó que las fases$\zeta_1$ y $\zeta_2$ son energéticamente degeneradas en el estado fundamental. El análisis de la estructura electrónica reveló un ancho de banda prohibida indirecto para las cuatro fases, donde el máximo de la banda de valencia (VBM) se localiza consistentemente en el punto $\Gamma$ del espacio $k$, mientras que el mínimo de la banda de conducción (CBM) se ubica a lo largo de la dirección $\Gamma-K$ en el punto $(u, u, 0)$. Los valores del gap fundamental calculados fueron de 0.80 eV, 0.75 eV y 0.68 eV para las fases $\alpha$, $\eta$ y $\zeta_1$ ($\zeta_2$), respectivamente. Estos estrechos gaps sugieren una fuerte absorción de fotones en la región del infrarrojo cercano (NIR), posicionando a estos materiales como candidatos prometedores para su aplicación en dispositivos fotovoltaicos de baja energía.

Due to their exceptional structural and electronic properties, transition metal dichalcogenides (TMDs) have recently emerged as promising candidates for integration into advanced electronics and energy storage systems. In this work, we present a systematic and predictive study of the structural properties, thermodynamic stability, and electronic structure of potassium transition-metal dichalcogenides KTMS$_2$ (TM = Nb and Ta). The calculations were performed from first principles within the framework of Density Functional Theory (DFT). The exchange–correlation functional was treated using the Generalized Gradient Approximation (GGA) in its optimized parametrization for solids, PBEsol. The ground-state structure for four distinct phases ($\alpha$ and $\eta$ for KNbS$_2$, and $\zeta_1$ and $\zeta_2$ for KTaS$_2$) was determined by fitting the total energy as a function of volume to the fourth-order Birch–Murnaghan Equation of State. Our energetic results indicate that the η phase is thermodynamically more stable than the α phase in the KNbS$_2$ system. On the other hand, for the KTaS$_2$ system, the $\zeta_1$ and $\zeta_2$ phases were found to be energetically degenerate in the ground state. The electronic structure analysis revealed an indirect band gap for all four phases, where the valence band maximum (VBM) is consistently located at the $\Gamma$ point of the $k$-space, while the conduction band minimum (CBM) is positioned along the $\Gamma–K$ direction at the $(u, u, 0)$ point. The calculated fundamental gap values were 0.80 eV, 0.75 eV, and 0.68 eV for the $\alpha$, $\eta$, and $\zeta_1$ ($\zeta_2$) phases, respectively. These narrow gaps suggest strong photon absorption in the near-infrared (NIR) region, positioning these materials as promising candidates for application in low-energy photovoltaic devices.

Appearance of half-metallicity and study of the electronic, elastics and thermodynamics properties in the Full-Heusler alloys

Youcef GUERMIT — 2026-07-01

This study investigates the full-Heusler (FH) ferromagnetic compound, Ir₂MnZ (Z=Sn, Si) half-metallic (HM) characteristics through first-principal calculations within the density functional theory (DFT) framework. Utilizing spin-polarized calculations and employing the full-potential linearized augmented plane-wave (FP-LAPW) method, with the Generalized Gradient Approximation (GGA) and the modified Becke-Johnson (mBJ) potential. Both ferromagnetic (FM) and non-magnetic (NM) phases of Cu₂MnAl-type and Hg₂CuTi-type structures were analyzed. The results indicate that the FM phase in the Cu₂MnAl-type structure is the most stable for both alloys. Electronic analysis reveals half-metallic ferromagnetism with integer magnetic moments of 5.0μ_B. Mechanical parameters such as bulk modulus, shear modulus, and Poisson’s ratio confirm the mechanical stability of both alloys. The half-metallic bandgaps are calculated as 0.644 eV for Ir₂MnSi and 0.23 eV for Ir₂MnSn. Thermodynamic properties, including heat capacity and Debye temperature, were evaluated using the quasi-harmonic Debye model, offering insights into the thermal stability of Ir₂MnZ. The robust HM characteristics of these compounds make them interesting candidates for spintronic devices

Synthesis of colloidal suspensions of CoOx/C nanomaterials using laser ablation of solids in liquids

Noé Enríquez-Sánchez — 2026-07-01

In this work, colloidal suspensions of CoOx/ nanomaterials were synthesized using laser ablation of solids in liquids. In the first stage, experiments were carried out using a cobalt target and deionized water as the liquid medium in order to establish the conditions for the synthesis of the nanomaterials. Subsequently, the cobalt target was irradiated in two liquid media containing carbon nanomaterials: a colloidal suspension of carbon nanoparticles (CNPs) and another of graphene oxide nanosheets (GONs). The effect of the liquid medium was studied as an important parameter, which determines the composition and structure of the final products. The resulting CoOx/C nanomaterials were characterized morphologically and structurally using infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy. In addition, the optical properties of the colloidal suspensions were evaluated using fluorescence spectroscopy. The results show that ablation in deionized water produces Co₃O₄ nanoparticles with an average diameter of 10.43 nm, while ablation in colloidal suspensions of carbon nanomaterials led to the formation of two types of structures: carbon-coated CoOx nanoparticles and spherical CoOx nanoparticles embedded in a carbon matrix. These cobalt oxide and carbon-based nanomaterials have broad potential in biomedical applications and energy storage devices.

First-principles investigation of silicon-substituted hybrid halide perovskites for lead-free optoelectronic applications

imad salym — 2026-07-01

Organic–inorganic halide hybrid perovskites have been extensively investigated for a range of optoelectronic applications, including tandem solar cells. However, instability and lead toxicity in widely studied hybrid halide perovskites (HHPs) necessitate the exploration of non-toxic semiconductor alternatives.
Here, we investigate the structural and optoelectronic properties of formamidinium silicon iodide (FASiI₃) using two complementary computational frameworks: the GGA–PBE functional and TB-mBJ exchange-correlation potential. Our results show that FASiI₃ crystallizes in a cubic lattice (space group Pm3m) with an equilibrium lattice parameter a = 6.29 Å.
Electronic structure calculations reveal that the TB–mBJ approach provides a more reliable description of FASiI₃’s semiconducting behavior, yielding a direct band gap conducive to photovoltaic operation. Optical analyses indicate pronounced anisotropy in the reflectivity and absorption spectra along the (xx) and (zz) axes, with absorption coefficients exceeding 10⁵ cm⁻¹in the near-infrared (NIR) region of the solar spectrum. These findings underscore FASiI₃’s potential as a lead-free, environmentally benign perovskite with robust light-harvestingcapabilities for next-generation photovoltaic and optoelectronic devices.

Comparison between current-voltage measurements and energy band diagrams of metal/p-type cupric oxide contacts

Roberto López — 2026-07-01

The need to generate ohmic contact between a metal and a semiconductor is fundamental for the development of electronic devices or integrated circuits. The aim of this report is to study the electrical contact between platinum, silver and gold to p-type cupric oxide films. Thermal oxidation was carried out on copper sheets at 1000 °C for 24 h to grown cupric oxide films. The metal/cupric oxide contacts were fabricated by evaporation of the metals on the surface of the cupric oxide films by the direct-current sputtering method. Determination of the crystal structure of the cupric oxide films was determined by the X-ray diffraction technique. Electrical characterization of the metal/cupric oxide films was performed by current-voltage measurements, where, independently of the metal used for the contact, all graphs exhibited ohmic behavior. Energy band diagrams of the metal/cupric oxide contact were developed based on the Schottky-Mott model. Current-voltage measurements matched well with the energy band diagrams only for platinum, which was favored by the high value of the work function of platinum. Conversely, the energy band diagrams corresponding to the silver/cupric oxide and gold/cupric oxide contacts, exhibited rectifying behavior. It was suggested that the mismatch between the current-voltage measurements and the energy band diagrams was due to the presence of defects at the surface of cupric oxide films, which led to the pinning of the Fermi level through the metal/semiconductor junction, making the contact, independent of the work functions.

Experimental and optimization investigations of multi cycle interrupted borocarburizing process

Surya Raj G — 2026-07-01

Multi cycle interrupted borocarburizing, a modified pack boriding technique, enhances AISI 1015 steel by improving strength while maintaining surface microhardness. Using response surface methodology, the effects of temperature, time, and cycles on microhardness and tensile strength were optimized. A regression model based on central composite design showed strong experimental agreement. The Multi cycle interrupted borocarburized layers exhibited distinct iron boride and carburized zones, with microhardness values of 1410HV0.05 in the iron boride zone, 650HV0.05 in the carburized zone, and 210HV0.05 in the base metal. Unlike continuous boriding, multi cycle borocarburized layers showed no needle-like structure and had a gradual hardness gradient. The X ray diffraction analysis revealed Fe3C, Fe2B, and FeB phases. The multi cycle interrupted borocarburized process achieved a 1.23 times improvement in tensile strength (488 MPa vs. 395.8 MPa). This study demonstrates multi cycle borocarburized process superiority in balancing ultimate tensile strength and microhardness compared to continuous pack boriding.

Embedded gallium oxide-silica composites in silica matrix via sol-gel process

Francisco Ramírez-González — 2026-07-01

This work reports the synthesis of a gallium oxide (Ga2O3)–silica composite within a silica matrix via a modified sol-gel process, with the novelty residing in the incorporation of Ga2O3 during the condensation stage. In conventional sol-gel synthesis of silica matrices or nanoparticles, ethanol and tetraethyl orthosilicate (TEOS) are mixed prior to hydrolysis, followed by a distinct condensation step. Typically, the incorporation of a second material into a silica matrix, such as micro-or nanoparticles, is carried out in a separate step using techniques like spray pyrolysis, chemical vapor deposition (CVD), or sputtering. In contrast, the present approach enables the formation of a Ga2O3–silica composite during the condensation step, thereby eliminating the need for post-synthesis deposition methods. This is achieved by introducing a Ga2O3 suspension into the TEOS solution prior to hydrolysis. Samples were fabricated by dropcasting both standard and modified sols onto glass substrates, with each layer formed by three successive drops. The functionalization and structural characteristics of the resulting materials were analyzed using X-ray diffraction (XRD), micro-Raman spectroscopy, scanning electron microscopy (SEM), and electrostatic force microscopy (EFM). These characterization techniques confirmed the successful integration of Ga2O3 within the silica matrix. In particular, EFM measurements distinguished between silica and Ga2O3 domains based on surface charge amplitude. The results demonstrate that both the Ga2O3 concentration in the colloidal suspension and the number of deposited layers significantly influence the crystalline structure and morphology of the silica matrix. This simple modification to the sol-gel method is proposed as a general and scalable strategy for the synthesis of metal oxide–silica composites and the functionalization of silica-based materials.

Comparative study for reaction dynamics of ⁶He projectiles scattered from ⁵⁸Ni, ⁶⁴Zn, and ¹²⁰Sn targets

D. Elbehari — 2026-07-01

We perform a comparative analysis of the elastic scattering of $^6$He projectiles from $^{58}$Ni, $^{64}$Zn, and $^{120}$Sn targets at near-barrier energies (9–21.7 MeV, 9–17.9 MeV, and 17.4–20.5 MeV, respectively). The exotic two-neutron halo structure of $^6$He strongly influences the scattering dynamics near the Coulomb barrier. Using a range of microscopic and cluster-based potentials—including the double-folding potential (DFP), São Paulo potential (SPP), Brazilian nuclear potential (BNP), and a cluster folding potential (CFP)—we analyze the angular distributions to explore the effects of $^6$He breakup and the resulting dynamic polarization. Our study systematically examines the emergence of breakup threshold anomalies, the behavior of the optical potential parameters, and the role of target mass and charge in modifying the effective interaction. The CFP, which explicitly incorporates the $\alpha + 2n$ cluster configuration, consistently yields larger reaction cross-sections, underscoring the importance of cluster degrees of freedom in describing halo-nucleus collisions.

Measuring the radioactivity of sediment samples from the Shatt Al-Arab river in basra and comparing it statistically

shaymaa kadhim — 2026-07-01

Given the economic and tourism importance of the Shatt al-Arab River in Basra Governorate, this study aimed to evaluate the radiation levels in 20 sediment samples from different areas of the river. A gamma-ray spectrometer system coupled with a NaI(Tl) detector was used to determine the specific activities of the radioactive isotopes, ²²⁶Ra, ²³²Th and ⁴⁰K in the sediments. The specific activity values ranged from 0–16.80 Bq /kg with a mean of 3.29 Bq /kg for ²²⁶Ra, 0–4.31 Bq /kg with a mean of 1.08 Bq/kg for ²³²Th, and 17.58–464.25 Bq /kg with a mean of 213.02 Bq /kg for ⁴⁰K. The internal and external doses, absorbed doses, and equivalent radioactivity (Raeq) were also calculated. The results showed that all radiological indicators and calculated doses were within the internationally permissible limits. The calculated annual testicular dose (AGED) was lower than the international limit (300 μSv·y⁻¹), and the excess lifetime cancer risk (ELCR) was lower than the internationally permissible value (2.9 × 10⁻³) according to the UNSCEAR 2000 report. The data were also statistically analyzed to compare sediments between four different areas of the Shatt al-Arab, and the results showed no statistically significant differences, with the highest radioactivity recorded in the riverbank sediments compared to the areas closer to the riverbed. This study represents an important first step towards developing an integrated radiological map of the Shatt al-Arab.

Comparative of parallel modified B-Spline interpolation again classic interpolation methods in Particle-Mesh step for Non-Linear Electro-Ion dynamics

Gibran Jalil Garnica — 2026-07-01

This work presents a comparative study of interpolation schemes for the Particle-Mesh step in Particle-in-Cell (PIC) simulations of nonlinear electron-ion dynamics, emphasizing an OpenMP parallel implementation of a modified cubic B-Spline kernel. The modified B-spline introduces a small, zero-mean perturbation close to the standard cubic B-Spline to mimic microscale fluctuations and mitigate oscillations caused by superparticle clustering. We compare this approach against non-parallel modified B-spline, classical cubic B-Spline, and trilinear (cloud-in-cell) interpolation. We propose a three-dimensional cubic benchmark with controlled initial conditions (following Brieda) to ensure a fair comparison. The metrics include the number of electrons, the electric field, and the conservation of energy. The classical modified B-Spline consistently attenuates noise and suppresses oscillations relative to the CIC and the standard cubic kernel, while preserving force accuracy and not degrading energy conservation beyond baseline levels. The OpenMP implementation achieves substantial speedups; the per-thread, seedable randomization adds only marginal overhead and maintains parallel scalability. Sensitivity analyzes (perturbation amplitude and random seed) indicate stable behavior and reproducibility. Overall, the OpenMP-parallel randomized cubic B-Spline provides a favorable trade-off between accuracy, robustness, and performance, making it a practical option for high-fidelity PIC of nonlinear electron-ion plasmas.

Exact solvability of the Gross-Pitaevskii equation for general potentials with bound states

MISAEL MIRON — 2026-07-01

In this paper we present the analytic solution of the bound state problem for the Gross-Pitaevskii (GP) equation in 1D and its properties, in the presence of external potentials such as finite square wells and attractive Dirac deltas, as well as stable solitons for repulsive defects. We show that the GP equation can be mapped to a first-order non-autonomous dynamical system, whose solutions can sometimes be written in terms of known functions. The formal solutions of this non-conservative system can be written with the help of Glauber-Trotter formulas or a series of ordered exponentials in the coordinate x. With this we illustrate how to solve any nonlinear problem based on a construction due to Mello and Kumar for the linear case (layered potentials). For the benefit of the reader, we comment on the difference between the integrability of a quantum system and the solvability of the wave equation.

Gauge structure of Yang-Mills theories with extra dimensions

José Alfonso Ahuatzi Avendaño — 2026-07-01

An effective Lagrangian for Yang-Mills theories with an arbitrary number of extra dimensions is constructed. We start from a field theory governed by the extra-dimensional Poincare group ${\rm ISO}(1,3+n)$ and by the extended gauge group ${\rm SU}(N,{\cal M}^{4+n})$, which is characterized by an unknown energy scale $\Lambda$ and is assumed to be valid at energies far below this scale. Assuming that the size of the extra dimensions is much larger than the distance scale at which this theory is valid, an effective theory with symmetry groups ${\rm ISO}(1,3)$ and ${\rm SU}(N,{\cal M}^{4})$ is constructed. The transition between such theories is carried out via a canonical transformation that allows us to hide the extended symmetries ${\rm ISO}(1,3+n)\otimes {\rm SU}(N,{\cal M}^{4+n})$ into the standard symmetries ${\rm ISO}(1,3)\otimes {\rm SU}(N,{\cal M}^{4})$, and thus endow the Kaluza-Klein gauge fields with mass. Using a set of orthogonal functions $\{f^{(\underline{0})},f^{(\underline{m})}(\bar x)\}$, which is generated by the Casimir invariant $\bar {P}^2$ associated with the translations subgroup $T(n)\subset {\rm ISO}(n)$, the degrees of freedom of ${\rm ISO}(1,3+n)\otimes {\rm SU}(N,{\cal M}^{4+n})$ are expanded via a general Fourier series, whose coefficients are the degrees of freedom of ${\rm ISO}(1,3)\otimes {\rm SU}(N,{\cal M}^{4})$. It is shown that these functions, which correspond to the projection on the coordinates basis $\{|\bar{x} \big >\}$ of the discrete basis $\{|0\big >,|p^{(\underline{m})}\big >\}$ generated by $\bar {P}^2$, play a central role in defining the effective theory. It is shown that those components along the base state $f^{(\underline{0})}=\big <\bar x|0\big>$ do not receive mass at the compactification scale, so they are identified with the standard Yang-Mills fields; but components along excited states $f^{(\underline{m})}=\big <\bar x|p^{(\underline{m})}\big>$ do receive mass at this scale, so they correspond to Kaluza-Klein excitations. In particular, it is shown that associated with any direction $|p^{(\underline{m})}\neq0\big >$ there are a massive gauge field and a pseudo-Goldstone boson. Some resemblances of this mass-generating mechanism with the Brout-Englert-Higgs mechanism are stressed.

Computational analysis of Stirnol Engine

Humayun Arif — 2026-07-01

Global energy requirement is accelerating on daily basis resulting in energy void which leads to human quest to find simple and cost-effective solutions. A promising resolution is the application of renewable energy with thermo-mechanical conversion systems such as Stirling engines. Considerable effort is in hand at industry and academia domains to stimulate the development of Stirling technology. An encouraging answer to this problem is the revival of Stirling engines with the modification of Shape Memory Alloy Nitinol in it. Efficiency of Stirling engine is lower than other Internal Combustion Engines of this class. Stirling engine is being used for power generation but no significant work has been reported on its efficiency improvement; so, the options were required to be explored in order to increase its efficiency. In this regard two dimensions of engineering i.e., Stirling Engine and Shape Memory Alloy were studied and combined. The study employed a two-prong approach, integrating computational modeling and experimental analysis. The results of this integration reveal that addition of Nitinol spring enhances the overall efficiency of engine, demonstrating positive impact of shape memory alloy towards performance output of Stirling engine. The name of newly modified engine is coined as STIRNOL ENGINE (combination of Stirling and Nitinol). This research focuses on modelling of both engines in ANSYS Software and subsequent conduct of computational analysis. The significance of the research is that the low energy wastage (exhausts of home appliances like air conditioners, automobiles, factory waste etc.) can be utilized to run Stirnol engines which can produce useful work.

DFT-based analysis of structural, electronic, optical, mechanical, and thermodynamic characteristics of Rb2YAuX6 (X = Br, Cl) double perovskites for energy conversion applications

Amel Merrad — 2026-07-01

We investigated the potential of the double perovskite halides Rb₂YAuX₆ (X = Br, Cl) for renewable energy applications using density functional theory (DFT) with the full-potential linearized augmented plane wave (FP-LAPW) method. These compounds are structurally stable in the cubic Fm-3m phase and demonstrate excellent mechanical strength. Electronic structure calculations revealed that the compounds are indirect band gap semiconductors, with energy gaps ranging from 1.58 to 2.01 eV when using the PBE-GGA approximation, and from 3.49 to 3.70 eV when using the TB-mBJ potential. Optical analysis shows strong ultraviolet (UV) absorption and low reflectivity in the visible range. We estimated the thermodynamic properties as a function of temperature using the quasi-harmonic Debye model. Key thermal parameters, including entropy, specific heat capacity, and the Debye temperature, were calculated to evaluate thermal stability at high temperatures. These results are crucial for evaluating the suitability of Rb₂YAuX₆ (X = Br, Cl) compounds for use in industrial and high-temperature environments. This work represents the first predictive theoretical investigation of these materials, as no prior experimental or computational studies have been conducted on them. Our findings suggest that these double perovskites could be ideal for next-generation photovoltaic and energy harvesting applications.

FrYBi (Y = Ca, Sr, Ba) Semiconductors for Visible-Light Harvesting: A multifunctional platform for energy conversion and optoelectronic applications

O. Hammadache — 2026-07-01

This study presents a comprehensive first-principles investigation of the structural, electronic, optical, elastic, and thermoelectric properties of the novel half-Heusler compounds FrYBi (Y = Ca, Sr, Ba). Employing density functional theory (DFT) with both the GGA-PBE and mBJ-GGA approximations, we determine that these compounds crystallise in the cubic Clb structure and exhibit indirect band gaps ranging from 0.97 to 1.35 eV, confirming their semiconducting nature. Detailed optical analyses reveal high absorption coefficients, pronounced reflectivity, and favourable dielectric responses within the visible spectrum, indicating potential for optoelectronic applications. Calculations of the elastic properties demonstrate that all compounds are mechanically stable and exhibit ductile behaviour. Thermoelectric analysis indicates high Seebeck coefficients alongside good electrical conductivity, particularly at low to moderate temperatures, suggesting promising performance for energy conversion applications. These findings position FrYBi alloys as compelling candidates for next-generation thermoelectric and optoelectronic devices.

Establishment of local diagnostic reference levels in mammography: multicenter retrospective study in Trujillo, Peru

Cecilia Querebalu Garcia — 2026-07-01

Radiation exposure in mammography can vary considerably across centers, potentially affecting both diagnostic quality and patient safety. In Trujillo, Peru, no locally adjusted absorbed dose values were previously available. Therefore, the objective of this study was to establish local diagnostic reference levels (LDRLs) for digital mammography within the EsSalud hospital network (Social Health Insurance) in Trujillo. A retrospective, multicenter study was conducted in three hospitals, analyzing 133 digital mammograms acquired with Hologic Selenia Dimensions systems. Technical parameters such as kilovoltage, tube load, compression force, compressed breast thickness, and average glandular dose (AGD) were collected and processed using automated systems. The LDRLs, defined as the 75th percentile of the AGD distribution, were determined for the craniocaudal (CC) and mediolateral oblique (MLO) projections. Multiple linear regression analysis was performed to identify independent predictors of AGD. The proposed LDRLs were 1.78 mGy for CC and 2.12 mGy for MLO, values well below the reference level of 3 mGy recommended by the Basic Safety Standards of the International Atomic Energy Agency (IAEA), and 30 − 39% lower than the regional LDRLs previously reported for direct digital radiography (DDR) systems in Latin America. Tube load (β = 0.886, p < 0.001 for CC; β = 0.572, p < 0.001 for MLO) and compressed breast thickness (β = 0.193, p < 0.001 for CC; β = 0.297, p = 0.001 for MLO) were identified as the most significant technical predictors of AGD. The established LDRLs demonstrate optimized dosimetric practices within the EsSalud network in Trujillo, ensuring that patient doses are appropriate, consistent, and aligned with international standards. Their implementation will facilitate ongoing dose monitoring, protocol standardization, and the strengthening of radiation protection in breast cancer screening programs.

BaTi(O$_{1-x}$S$_x$)$_3$ chalcogenide perovskite thin films with band gap ideal for solar cell applications

Fátima Lizbeth González Gregorio — 2026-07-01

BaTi(O$_{1-x}$S$_x$)$_3$ chalcogenide perovskite thin films were deposited by the spin coating technique, using a solution formed by a powder of BaTi(O0.50S0.50)$_3$ perovskite compound previously synthesized and ethanol as a solvent. To obtain the powdered BaTi(O$_{1-x}$S$_x$)$_3$ perovskite compound used as precursor material, a sulfidization process to barium titanate (BaTiO$_3$) was carried out in a constant flow CS$_2$/Ar atmosphere at a temperature of 600 °C for four hours. After depositing, the films were annealed for one hour in a tube furnace at a temperature of 400 °C, in an Ar and CS$_2$ reactive atmosphere. EDX-RF, XRD, FTIR and Uv-Vis-NIR techniques were used to analyze the structural, vibrational, and optical properties of the films. All deposited and annealed films showed the hexagonal crystalline structure typical of BaTiS$_3$perovskite with an absorption coefficient greater than 4x10$^4$ cm$^{-1}$ in the range 600 to 950 nm. The band gap of the BaTi(O$_{1-x}$S$_x$)$_3$ chalcogenide perovskite thin films was narrowed as a function of the concentration of sulfur in the sample. The final band gap values obtained were 1.51, 1.45 and 1.35 eV for sulfur percentages of 24.3, 25.3 and 28.7, respectively. This results projected the BaTi(O$_{1-x}$S$_x$)$_3$ chalcogenide perovskites have the ideal band gap for they possible applications of perovskite solar cells.