Mondragon University

Phase discrepancy is a major source of error in the measurements of core losses, so reactive cancellation techniques are used to improve the measurement accuracy. To do so, an air core transformer is introduced in the measurement setups. In this work, an alternative methodology for correction of the phase discrepancy is presented, which makes use of the air core transformer introduced in previous techniques. Unlike reactive cancellation techniques, whose objective is to reduce the reactive voltage in the core under test, the proposed method directly addresses the phase discrepancy based on the fundamental assumption that there are no core losses on an air core transformer. The proposed methodology does not rely on Fast Fourier Transform algorithms, which minimizes the required computational resources for the post-processing of the measured waveforms.

A discrete-time small-signal modelling strategy is developed for the dual active bridge converter operating under modulation strategies for transient dc-bias inductor current suppression. Most of these techniques consist on changing the phase-shift in a two-step manner, which is modelled by expanding the matrices that form the difference equation. The dynamics of two different current offset mitigation strategies are compared with the basic single-step single-side modulation. The obtained control-to- output voltage and input current transfer functions are validated in simulations, which demonstrate the model effectively accounts for the high frequency dynamics of the different modulation strategies. Finally, by integrating an averaging filter of the measured variables into the model, the additional delay caused by the two-step phase-shift transition is observed in the results, which causes a higher phase decay at high frequencies than in the case of the single-step modulation.

High-power-density converters concentrate heat in smaller areas of printed circuit boards (PCBs), a challenge exacerbated by Gallium Nitride (GaN)-based components in surface-mount device (SMD) packages. While these components reduce parasitic inductance and electromagnetic interference (EMI), they also transfer heat directly to the PCB, increasing local temperatures. Traditionally, PCB thermal design relies on computational fluid dynamics (CFD), which is computationally expensive and requires multiple iterations. This paper presents an analytical thermal model to evaluate and optimise PCB thermal resistance with significantly reduced simulation time. The model examines the influence of design parameters on thermal resistance for through-hole and blind vias, identifying optimal via diameters and spacing to minimise thermal resistance while limiting impacts on copper pouring areas (and parasitic inductance). By addressing both the area beneath the heat source and its surroundings, the model provides a comprehensive understanding of PCB thermal behaviour. Validation against CFD simulations shows a deviation of only 7%, with substantially lower computational time.

We present an experimental investigation of mass transport phenomena in aqueous lithium bromide (LiBr-H2O) solutions, focusing on both molecular diffusion and thermodiffusion (Soret effect). Our results show a non-monotonic trend in the diffusion coefficient D with a pronounced maximum at w ≈ 0.3 kg/kg (LiBr), a feature that is consistently observed in multiple independent studies and likely reflects microstructural transitions within the solution. Using a Soret cell with porous media, we measured Soret coefficients ST over a range of mass fractions relevant for practical applications. The Soret coefficient revealed consistently negative values, indicating thermophilic behavior in which LiBr migrates toward warmer regions under a temperature gradient. Interestingly, while the absolute value of thermodiffusion coefficient |DT| decreases with concentration, the Soret ST = |DT/D| increases in magnitude due to the stronger suppression of molecular diffusion. These results highlight the importance of considering both molecular mobility and solution structure when analyzing transport behavior.

To prolong battery lifetime and maximize performance, battery management systems (BMSs) need to estimate internal variables that are related to battery aging. For that, accurate battery models that can represent internal variables that are not directly measurable are required. However, most present BMSs use equivalent-circuit models (ECMs or EQMs) for state of charge (SOC) and state of health (SOH) estimation. These models are not able to predict these aging-related variables, and therefore, they cannot be used to limit battery degradation. In this paper, we propose a method for electrode-level SOC (eSOC) and electrode-level SOH (eSOH) estimation using an electrode-level ECM (eECM), which can describe both electrodes’ potentials, giving valuable information for aging prevention. The method produces state of lithiation (SOL) and potential estimates of both electrodes, and updates the eSOH parameters to maintain estimation accuracy through the lifetime of the battery. Furthermore, the eSOH parameter estimates are used to obtain degradation mode information, which could be used to improve state estimation, health diagnosis and prognosis.

This study examines the integration of cooperativism within the just ecosocial transition paradigm, addressing the urgent need for sustainable and equitable economic development. It analyses the alignment of cooperative principles with multidimensional justice considerations, including environmental, social, climate, energy and labour, to identify a framework where cooperatives act as key agents in promoting a just ecosocial transition. A narrative literature review was employed to critically analyse the theoretical and practical interconnections between cooperativism and just ecosocial transition, revealing both opportunities and inherent contradictions. The results and discussion indicate that, although cooperatives inherently support the dimensions of justice crucial to a just ecosocial transition, practical implementation often reveals challenges, particularly in balancing these ideals with market dynamics. A proposal has been made to overcome those challenges based on impact assessment methodologies, such as the Theory of Change.

Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs), with their superior on-resistance and switching times, provide a promising alternative to Silicon (Si) and SiC devices. Commercially available normally <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>GaN transistors can be categorized into two main groups: hybrid transistors, which incorporate a Si <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small>, and e-mode transistors. The latter are the most promising GaN transistors, as they do not have the limitations of Si <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfets</small>. Currently, there are two commercial e-mode transistors: the Schottky Gate (SG) p-GaN and the HD-GIT (Hybrid-Drain-embedded Gate Injection Transistor) transistors. However, they differ from the gate terminal standards that have been defined for years by Silicon IGBTs and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfets</small> (lower threshold voltage, nonconstant Miller plateau, etc.), complicating their adoption in power electronics converters. This is particularly true for the HD-GIT transistor, which diverges from standard <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> gate operations due to its nonisolated gate terminal. To aid application engineers in understanding these devices and facilitating their adoption in real power applications, simulation models are useful tools. However, there are no simple HD-GIT transistor models that can be easily parameterized by application engineers. Therefore, in this work, an experimentally verified behavioral model of an HD-GIT transistor is presented and described.

Abstract Aluminium alloy components are gaining traction in the automotive industry due to their lightweight properties, contributing to improved fuel efficiency and reduced emissions. Many of these components demand specific surface roughness profiles achieved through milling operations. However, excess material from upstream processes—such as flash remaining after demoulding —presents challenges for the machining process. These irregularities, combined with stringent demands for specific roughness, burr-free edges, and flatness, require careful selection of tool microgeometry, tool grade, and cutting parameters. Nonetheless, research concerning the behaviour of PCD tools when machining aluminium alloys remains limited, and existing studies often fail to address the complexities of high-volume production. This study investigates polycrystalline diamond (PCD) tool performance in high-speed milling of aluminium components through an eight-month production analysis comparing PCD grades and tool microgeometries. The research reveals that medium-sized grains in PCD tools lead to superior surface quality and a 22% longer tool life. Tools with larger tip radii (0.09 mm versus 0.06 mm) demonstrated significantly higher performance, reducing burr formation by 20% while maintaining lower surface roughness values. Insert height positioning emerged as a critical factor, since reducing deviations between insert heights substantially extended tool life and ensured consistent surface roughness. The findings provide practical criteria for PCD tool selection and tool microgeometry, directly impacting cost-efficiency in high-volume automotive component manufacturing.

ABSTRACT The present study explores the developmental patterns of bilingual secondary education students in a disciplinary writing task in Basque, their language of instruction. A cross-sectional sample of 547 bilingual students (Years 7–10) enrolled in Basque Model D immersion programmes completed a source-based writing task requiring them to produce two cognitive discourse functions: argue and compare. Students reported to have either Basque, Spanish or both as their L1. The corpus was analysed with an analytical rubric that considered students’ performance in three dimensions: arguing, comparing and using sources. Linear mixed models were used to assess the effect of Year and L1 on the three dimensions. Findings showed positive developmental patterns from Y7 to Y10 in all measures for all L1 profiles, with varying turning points. Most measures reached statistical significance when comparing two-year cycles. Similar developmental patterns were found in learners’ writing, especially between Y7 and Y9, after which Basque L1 students improved and Spanish L1 students stagnated. Students having both as their L1 showed the most irregular patterns. In conclusion, results show developmental patterns in disciplinary cognitive discourse function production and source-based writing. Implications for the development of disciplinary literacies and bi/multilingual education are discussed.