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Thesis An Exact Bienstock-Zuckerberg-based algorithm for solving the Convex Hull Pricing problem with ramps constraint An Exact Bienstock-Zuckerberg-based algorithm for solving the Convex Hull Pricing problem with ramps constraint(Universidad Técnica Federico Santa María, 2026-05-29)This thesis addresses the problem of price distortions and uplift payments in non convex electricity markets by proposing an efficient methodology for Convex Hull Pricing computation. An extended network-flow–based Unit Commitment formulation is developed, explicitly incorporating intertemporal ramping constraints and warm-up periods, and solved through an adaptation of the Bienstock–Zuckerberg algorithm. This column-generation and partition-refinement framework enables an accurate representation of generator operational flexibility and the computation of prices that minimize unrecovered costs, while progressively tightening the feasible solution space across iterations. Computational experiments on real-world systems from California, FERC, RTS-GMLC and Belgium demonstrate that the proposed approach outperforms traditional methods such as Dantzig–Wolfe decomposition and the Level Method in terms of robustness and convergence speed. Moreover, the results show that omitting ramp constraints leads to an underestimation of equilibrium prices, and that preprocessing techniques are critical for the computational viability of the model. - Some of the metrics are blocked by yourconsent settings
Publication Probability of Rock Block Fracturing Upon Impacting a Rock Bed(Springer Science and Business Media LLC, 2025-04-10)This study investigates the mechanical response of rockfall-induced fragmentation by implementing a novel numerical breakage model within a discrete-element framework. The model evaluates the size distribution and breakage probability of rock blocks upon impact, considering key variables such as impact height and initial rock size. The system consists of a rock buffer layer and a freely falling rock block, with irregular geometries incorporated for greater computational realism. Results highlight the strong influence of impact height and rock size ratio on fragmentation, increasing the breakage probability as energy dissipates through the medium. Notably, rock fracture does not always occur instantaneously upon impact but may be delayed by milliseconds as stress propagates through the granular bed. A simple probability model is proposed to estimate the survival rate of rock blocks based on impact height and rock size, demonstrating strong agreement with reported rockfall cases in caving mines. This approach enables back-analysis of rockfall conditions prior to secondary fragmentation, aiding in the understanding of fragment behaviour within the mineral column before extraction. Additionally, the findings contribute to geomechanical risk mitigation by offering insights into rock mass dynamics and energy dissipation mechanisms during impact. - Some of the metrics are blocked by yourconsent settings
Publication The cumulative vehicle routing problem with time windows: models and algorithm(Springer Science and Business Media LLC, 2023-01-31)The cumulative vehicle routing problem with time windows (CumVRP-TW) is a vehicle routing variant that aims at minimizing a cumulative cost function while respecting customers' time windows constraints. Mathematical formulations are proposed for soft and hard time windows constraints, where for the soft case, violations are permitted subject to penalization. By means of the cumulative objective and the time windows consideration, routing decisions incorporate the environmental impact related to CO2 emissions and permit obtaining a tradeoff between emissions and time windows fulfillment. To solve this problem, we propose a matheuristic approach that combines the features of the Greedy Randomized Adaptive Search Procedure (GRASP) with the exact solution of the optimization model. The solution approaches are tested on instances proposed in the literature as well as on a new benchmark suite proposed for assessing the soft time windows variant. The computational results show that the mathematical formulations provide optimal solutions for scenarios of 10, 20, and several of 50 customers within suitable computational times. Nevertheless, the same performance is not observed for several medium as well as for all large scenarios. In those cases, the proposed matheuristic algorithm is able to report feasible and improved routes for those instances where the exact solver does not report good results. Finally, we verify that the fuel consumption and carbon emissions are reduced when the violation of the time windows is allowed in the case of soft time windows. - Some of the metrics are blocked by yourconsent settings
Publication Advantages of the Adoption of a Generalized Flame Displacement Velocity as a Central Element of Flamelet Theory(Springer Science and Business Media LLC, 2024-12-11)In combustion theory, flames are usually described in terms of the dynamics of iso-surfaces of a specific scalar. The flame displacement speed is then introduced as a local variable quantifying the progression of these iso-surfaces relative to the flow field. While formally defined as a scalar, the physical meaning of this quantity allows relating it with a vector pointing along the normal direction of the scalar iso-surface. In this work, this one-dimensional concept is extended by the introduction of a generalized flame displacement velocity vector, which is associated with the dynamics of iso-surfaces of two generic scalars, α and β. It is then shown how a new flamelet paradigm can be built around this velocity vector, which leads to (i) an alternative procedure for the derivation of general flamelet equations, which is much simpler and more direct than the ones currently available in the literature, (ii) a very compact set of two-dimensional flamelet equations for the conditioning scalar gradients, gα = |∇α| and gβ = |∇β|, which comprise several effects in few terms directly related to the projections of the generalized flame displacement velocity, and (iii) the possibility of characterizing different composition space coordinate systems through the same generalized flame displacement velocity. The proposed framework is discussed in the context of partially premixed combustion, emphasizing how its adoption can contribute to both the further development of 2D flamelet theory and its coupling with CFD codes. - Some of the metrics are blocked by yourconsent settings
Publication Zn and Al vapour-phase metalation of polyamide-6 via ALD: structural, functional, and biomedical insights(Springer Science and Business Media LLC, 2025-10-25)This study reports the effect of diethylzinc (DEZ) and trimethylaluminium (TMA) functionalization on polyamide-6 (PA6) films using the vapour-phase metalation (VPM) process within an atomic layer deposition (ALD) chamber. The resulting zinc- and aluminium-functionalized films are referred to henceforth as PA6-Zn and PA6-Al, respectively. Biocompatibility was preliminarily assessed via C2C12 cytotoxicity testing. Reaction mechanisms were examined using density functional theory, electrostatic potential maps, Mulliken charge distribution, and X-ray photoelectron spectroscopy, revealing interactions between metal precursors and PA6 amide groups. DFT confirmed alpha-PA6 as the dominant structure and identified reactive sites influencing functionalization pathways. Structural and morphological changes were analysed via environmental scanning electron microscopy and X-ray diffraction. ESEM showed Zn-functionalized PA6 forming strand-like structures, while Al-functionalized PA6 developed pore-like cavities. XRD indicated increased crystallinity upon metalation, with the alpha/gamma crystallite size ratio following the trend: PA6-Al > PA6-Zn > PA6. Spectroscopic analysis using infrared and Raman microscopy, along with UV-visible spectroscopy, highlighted modifications in chemical bonding and polymorphism, aligning with DFT predictions. Al functionalization had a stronger influence on PA6's spectroscopic and some mechanical properties, whereas Zn functionalization notably enhanced failure strain. Barrier and mechanical properties were evaluated, showing that Zn-functionalized PA6 exhibited superior oxygen permeability, while both metal-modified films improved water vapour transmission rates compared to bare PA6. Cytotoxicity testing revealed enhanced C2C12 cell proliferation in the order PA6-Al > PA6-Zn > PA6, suggesting VPM-modified PA6 as a promising material for biomedical applications.
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Publication Bound states in the continuum in whispering gallery resonators with pointlike impurities(Springer Science and Business Media LLC, 2024-11-13)Whispering gallery resonators offer a versatile platform for manipulating the photonic transmission. Here, we study such a system, including periodically distributed pointlike impurities along the resonator with ring geometry. Based on an exact expression for the transmission probability we obtain here, we demonstrate that the bound states in the continuum (BICs) form from the whispering gallery modes at the high-symmetry momenta in the ring's Brillouin zone. Furthermore, the presence of the inversion symmetry allows for a selective decoupling of resonant states, favoring the BIC generation and, therefore, allowing extra tunability in the optical transmission of the system. - Some of the metrics are blocked by yourconsent settings
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Publication A frequency peak at 3.1 kHz obtained from the spectral analysis of the cochlear implant electrocochleography noise(Public Library of Science (PLOS), 2024)The functional evaluation of auditory-nerve activity in spontaneous conditions has remained elusive in humans. In animals, the frequency analysis of the round-window electrical noise recorded by means of electrocochleography yields a frequency peak at around 900 to 1000 Hz, which has been proposed to reflect auditory-nerve spontaneous activity. Here, we studied the spectral components of the electrical noise obtained from cochlear implant electrocochleography in humans. - Some of the metrics are blocked by yourconsent settings
Thesis Simulación de aneurismas aórticos abdominales con el método de elementos finitos(Universidad Técnica Federico Santa María, 2022-03)El sistema cardiovascular es cerrado: las venas llevan sangre al corazón y las arterias la transportan oxigenada desde el corazón al cuerpo. La aorta, la arteria más grande (2 [cm] de diámetro), puede dilatarse con el tiempo; si supera los 5 [cm] se denomina aneurisma aórtico. El tratamiento consiste en insertar una prótesis endovascular para restringir el flujo sanguíneo en la zona debilitada, siendo eficaz pero con posibles fallos, por lo que el paciente requiere controles médicos. Este trabajo presenta tres modelos de aneurismas aórticos abdominales, cada uno con simulación sin y con prótesis, para estudiar velocidad y presión. Las geometrías varían pero las condiciones de borde son iguales. Se utilizan las ecuaciones de la mecánica de fluidos: conservación de masa y Navier-Stokes (régimen laminar), considerando sangre como incompresible, homogénea y newtoniana. Se resuelven mediante el método de elementos finitos, pasando del espacio continuo a discreto, obteniendo matrices constantes en el tiempo, usadas luego en un código que recibe matriz de nodos, conectividad y condiciones de borde. El mallado es generado por un software de código abierto que permite modificar parámetros como tamaño de elemento o número de nodos. Luego se realiza la simulación, obteniendo velocidad y presión. Los tiempos de simulación son bajos considerando el número de elementos y pasos de tiempo. Los resultados muestran poca diferencia entre los tres modelos sin prótesis, por lo que la geometría influye poco. Con prótesis, la velocidad aumenta dentro de esta y disminuye fuera, cumpliendo el objetivo. La longitud de la prótesis influye significativamente, generando zonas de alta velocidad entre esta y la pared arterial. Se discute también la inestabilidad de la presión y su mejora con otros métodos. Finalmente, los resultados se validan mediante una ecuación analítica y estudios previos. Este trabajo busca servir de base para nuevas investigaciones científicas y desarrollo académico.
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