Abstract

We investigate the use of normalizing flows to approximate transport maps from tractable reference densities to complex Bayesian posterior distributions for Bayesian model updating. A Gaus sian process (GP) surrogate with active sampling is used to provide a differentiable target density for optimizing the transport map. While results show normalizing flows can capture multimodal behavior in a simple example, further work is needed to refine the active sampling strategy and enable mode identification in the GP surrogate for robust multimodal density approximation.

Abstract

La soldadura ultrasónica continua robótica (cUSW) es una técnica prometedora para unir termoplásticos reforzados con fibra de carbono (CFR-TP), que ofrece alta eficiencia y tiempos de procesamiento rápidos. Sin embargo, mantener la calidad de la soldadura y la robustez del proceso presenta desafíos significativos. Las características de la soldadura, como la resistencia de la unión y el rendimiento a largo plazo, se ven fuertemente influenciadas por parámetros clave durante las fases de generación de calor y consolidación. Comprender las interacciones entre el sistema robótico y el proceso de soldadura ultrasónica es esencial, ya que impactan directamente en la calidad y consistencia de la soldadura. El robot debe controlar con precisión el movimiento del sonotrodo durante la fase de generación de calor para mantener una fuerza constante, precisión de trayectoria y uniformidad de velocidad, asegurando una transferencia de energía eficiente y una fusión uniforme. Durante la consolidación, tanto la velocidad como la fuerza son cruciales, controlando la disipación de calor para reducir la temperatura de la interfaz por debajo del punto de cristalización y prevenir defectos. Para abordar estos desafíos, es esencial la monitorización en tiempo real de los parámetros clave del proceso. La integración avanzada de sensores y las estrategias de control basadas en datos permiten ajustes dinámicos para optimizar las condiciones de soldadura y prevenir defectos. Este artículo explora los desafíos asociados con la soldadura ultrasónica continua robótica de CFR-TP y analiza técnicas de monitoreo y estrategias de control para mejorar la consistencia de la soldadura y la confiabilidad del proceso.

Abstract

Esta investigación se centra en aprovechar los residuos de pregreg multicapa sin curar generados durante la producción de componentes aeronáuticos, con especial énfasis en los procesos de AFP (Automatic Fibre Placement) y ATL (Automatic Tape Laying). Estos residuos, que presentan características repetitivas en cuanto a tamaño, forma y apilado, se procesan mediante un sistema mecánico de calandrado para darle una segunda vida al material. Este método desarrollado por FIDAMC está basado en preparar los residuos de ATL de prepreg sin curar en tiras longitudinales orientadas en la dirección predominante. Posteriormente, estas tiras se procesan mediante calandrado en condiciones específicas de temperatura, velocidad y ratios de reducción de espesor en diferentes pasos. Como resultado, se obtiene un material reusado intermedio manipulable para la fabricación de nuevas piezas. Este material se ha caracterizado física-química y mecánicamente para optimizar sus propiedades mecánicas y asegurar su viabilidad como material reusado. Aunque las piezas aeroespaciales de material compuesto deben cumplir estrictos requisitos de seguridad, existen aplicaciones no críticas donde se pueden emplear materiales más ecológicos y económicos, como la fibra de carbono reusada. Esto permite una reducción significativa del impacto ambiental y de los costes asociados. Para estudiar la viabilidad de fabricación con este material, se ha fabricado un demostrador de costilla de borde de ataque del elevador (elevator) del estabilizador horizontal (HTP) mediante el proceso de termoconformado. Este estudio pretende demostrar el desarrollo y aplicación de nuevos materiales reusados, los cuales pueden ser utilizados en piezas semi-estructurales en el sector aeronáutico, o bien, en el sector transporte, en general. Se ha estudiado el material mediante una caracterización físico-química (micrografía, DSC, digestión y porosidad) y mecánica (tracción, compresión, ILSS, G1C, IPSS, CAI, OHC y FHC), así como otros métodos de caracterización avanzada. También se ha estudio su viabilidad de fabricación mediante la producción de un componente de geometría compleja. Además, se han propuesto diferentes alternativas para mejorar la calidad el material y ampliar el abanico de aplicación. Los resultados obtenidos confirmaron el potencial del material reusado para aplicaciones no críticas, demostrando que cumple con los requisitos funcionales de este tipo de componentes y recorriendo el camino hacia una mayor sostenibilidad en el sector.

Abstract

In recent times, polymer matrix composite material technologies have undergone a genuine revolution, driven by the surge in demand—particularly in the transportation and energy sectors. Composites are being increasingly incorporated due to the significant weight reduction they enable in structural components, which in turn leads to a decrease in energy consumption in transportation as a result of this weight savings. Ambitious EU sustainability policies (such as the EU Green Deal or the New Industrial Strategy) are further accelerating this shift toward efficient and sustainable solutions, with a significant impact on the transportation sector, especially the automotive industry—both in conventional and emerging propulsion systems (the use of lightweight materials is expected to increase from the current 30% to 70% by 2030, with composites accounting for approximately 20%). However, the automotive sector is one of the most demanding in terms of processing times. Therefore, the optimization and monitoring of processing parameters through embedded sensors in molds is presented as a valuable tool for adapting processing times and enabling continuous quality control of parts. This paper presents the results obtained within the framework of the COMPCERTO project, which aims to develop solutions that facilitate the optimized manufacturing of components with structural requirements through Sheet Molding Compound (SMC) thermoforming processes. To achieve this, the implementation of sensors for monitoring curing, pressure, and temperature in molds is proposed, enabling the acquisition of representative values at critical points and in real time for the phenomena occurring during the thermoforming of parts in the press. Preliminary tests are carried out to optimize the curing cycle in order to determine the most suitable manufacturing parameters, and based on the results, a Design of Experiments (DoE) is proposed. Finally, mechanical, thermal, and microstructural characterizations are performed on the tests defined in the DoE. This will generate a database that serves to correlate the real-time data obtained from the parts with potential defects in the SMC components.

Abstract

La teoría de la información cuántica del vacío (TICV) plantea que el vacío cuántico no constituye una ausencia, sino una red activa de información entrelazada cuyas correlaciones generan la estructura del espacio-tiempo, el campo gravitacional y los fenómenos cuánticos. En este trabajo se desarrolla formalmente este enfoque, mostrando cómo principios como el entrelazamiento cuántico y la holografía permiten reinterpretar la geometría y la dinámica del universo desde una perspectiva informacional. Se demuestra que la paradoja de la pérdida de información en agujeros negros puede resolverse mediante redistribución no local de entropía en el vacío, preservando la unitariedad del sistema. Asimismo, se derivan predicciones concretas: correcciones tipo Yukawa a la ley de gravedad a escala micrométrica, firmas angulares en correlaciones ópticas (C(θ) ∝ cos(2θ)), y una corrección logarítmica positiva a la entropía de Bekenstein–Hawking. Estas hipótesis, aunque especulativas, son contrastables mediante tecnologías actuales como sensores cuánticos, interferometría de átomos fríos y simulaciones cuánticas. Finalmente, se discuten posibles aplicaciones en computación cuántica topológica, metrología de precisión y simulaciones de geometría emergente, así como conexiones con teorías como LQG, cuerdas y gravedad entraronpica. La TICV ofrece así un marco unificador que vincula mecánica cuántica y relatividad general, posicionando al vacío como el “código fuente” que estructura la realidad física.  

Abstract

Climate change demands innovative renewable energy solutions, with wind energy emerging as a key resource. Vertical-axis wind turbines (VAWTs) are particularly suited for low-speed, turbulent wind environments due to their ability to capture wind from all directions. However, VAWTs face aerodynamic difficulties, especially at the downwind, where problems like negative torque and decreased efficiency are frequent. This study explores a novel solution for enhancing VAWT performance by incorporating an inner cylindrical deflector aimed at optimizing airflow around the blades. Using computational fluid dynamics (CFD) simulations, the study focuses on a three-bladed H-type VAWT with an airfoil profile of NACA0018 at a turbine diameter of 1 m. The simulations begin by evaluating a bare turbine arrangement, which shows negative torque beginning at an azimuth angle of about 165 degrees onwards. When a cylindrical deflector of different diameters is introduced, the torque coefficient and overall performance are greatly enhanced by a 0.3-meter diameter. The cylindrical deflector’s effectiveness is demonstrated by the 15% increase in power coefficient C pthat results from its inclusion. These results highlight how an inner cylindrical deflector could be a useful addition to VAWTs, resolving significant inefficiencies while preserving a positive angle of attack. This strategy offers a way forward for more effective VAWT designs in renewable energy systems in addition to increasing energy output. To enhance the efficiency of vertical-axis wind turbines (VAWTs) for both urban and rural applications, future research could investigate different configurations and empirically confirm these findings.OPEN ACCESS Received: 21/01/2025 Accepted: 10/03/2025 Published: 20/04/2025

Abstract

Underwater images play a critical role in underwater exploration and related tasks. However, due to light attenuation and other underwater factors, underwater images often suffer from color distortion and low contrast, which to some extent limit the efficiency and safety of underwater exploration. To meticulously address these issues and enhance the accuracy and reliability of underwater exploration, this paper proposes a multi-task underwater image enhancement method based on Retinex theory. This method divides the underwater image enhancement task into several sub-tasks, including image decomposition, color correction, detail reconstruction, and illumination adjustment. Specialized sub-networks— DecomNet, DecolorNet, and DelightNet—are designed to specifically address these problems, thereby alleviating color distortion, enhancing image details, and improving contrast. Experiments conducted on several publicly underwater image datasets indicate that the quality of underwater images is significantly improved after enhancement with the proposed method, compared to other representative underwater image processing techniques. For example, on the real-world dataset Underwater Image Enhancement Benchmark, the MSE, Structural Similarity Index Measure, and Peak signal-to-noise ratio scores achieved were 453.480, 0.901, and 25.145, respectively. This study holds significant implications for underwater exploration, with potential applications in the fields of marine research and underwater archaeology.OPEN ACCESS Received: 03/11/2024 Accepted: 27/12/2024 Published: 20/04/2025

Abstract

This work investigates the existence, uniqueness, and stability in the sense of Hyers-Ulam for a class of proportional fractional Itô-Doob stochastic integral equations (PFIDSIE). To establish these properties, we employ the Banach fixed point theorem (BFPT) in combination with several fundamental mathematical inequalities that provide insight into the structure of PFIDSIEs. The approach is structured to demonstrate not only the theoretical foundation of the existence and uniqueness of solutions but also the stability of these solutions in the Hyers-Ulam sense, which ensures that approximate solutions remain close to the exact solution under small perturbations. The results contribute to the broader field of fractional stochastic differential equations, particularly in situations where fractional dynamics and stochastic processes intersect. Furthermore, the findings are illustrated through three examples, showcasing the applicability and utility of the developed theory in practical settings.OPEN ACCESS Received: 29/01/2025 Accepted: 14/03/2025 Published: 20/04/2025

Abstract

The COVID-19 pandemic has necessitated the development of robust mathematical models to understand and mitigate its impact. This study presents a compartmental model for the Indian pandemic COVID-19 dynamics, incorporating key compartments such as susceptible, exposed, infected, quarantined, and recovered populations. The positivity and boundedness of solutions are rigorously analyzed to ensure that the model remains biologically meaningful over time. A detailed exploration of the basic reproduction number R

Abstract

The present paper develops and makes efficient, a new, state-of-theart numerical technique for solving the FitzHugh-Nagumo Nonlinear Equation (FH-NNE) with initial and boundary conditions, which represents perhaps the simplest mathematical model for discussing biological systems, including nerve signals and cardiac behavior. Which consists of operational matrices and spectral techniques based on Jacobi and Romanovski-Jacobi polynomials. It is ensured that the nonlinear system is modeled so accurately that it can be effectively solved to ensure the best accuracy combined with computational economy. Comparing the results with the respective numerical results, it is seen that the proposed techniques outdo the standard ones as respects accuracy and efficiency of computation.OPEN ACCESS Received: 11/01/2025 Accepted: 25/02/2025 Published: 07/04/2025