On Multiplication Groups of Quasigroups

Quasigroups are algebraic structures in which divisibility is always defined. In this thesis we investigate quasigroups using a group-theoretic approach. We first construct a family of quasigroups which behave in a group-like fashion. We then focus on the multiplication groups of quasigroups, which have first appeared in the work of A. A. Albert. These permutation groups allow us to study quasigroups using group theory. We also explore how certain natural operations on quasigroups affect the associated multiplication groups. Along the way we take the time and special care to pose specific questions that may lead to further work in the near future

High-Power Power Conditioning Systems for Medium-Voltage Applications

The purpose of this dissertation is to address the background, theoretical analyses, design methodologies, and evaluation techniques relevant to high-power power conditioning systems (PCSs) tailored for medium-voltage (MV) applications. Conventional PCSs, reliant on line-frequency transformers (LFTs), suffer from many problems including low power densities, inflexible designs, and scalability constraints. Employing multilevel converters (MLCs), particularly cascaded H-bridge topology, eliminates the need for these LFTs. A key focus lies in minimizing the number of cascaded building blocks by harnessing MV power switching modules. The dissertation makes two primary contributions: firstly, it offers a design methodology for MV-PCS, facilitating the selection of the most suitable design aligning with predefined figures of merit. Secondly, it introduces a novel MLC architecture based on cascading three-level active neutral point clamped (3L-ANPC) building blocks. Furthermore, the dissertation presents experimental testing results of two MV building block prototypes, which are analyzed to validate the theoretical analyses and design propositions put forth. Through these contributions, this dissertation aims to advance the understanding and practical implementation of high-power MV-PCSs

Optimising the structure of a cascaded modular battery system for enhancing the performance of battery packs

The overall performance of battery packs may be affected by imbalances between the series connected cells which is more likely in packs with high number of cells needed to provide a high voltage as needed for example in electric vehicles. In this case, the overall capacity and power capability of the pack is limited by the weakest cell in the stack which results in incomplete utilization of the pack’s capabilities. In traditional centralized battery systems (TCBS), this is addressed by implementing cell active/passive balancing circuitry/techniques which restore some of the pack’s energy capability. This paper proposes the use of cascaded modular battery systems (CMBS) to remove the need for extra balancing circuitry and maximises the performance and reliability of a battery system containing unequal matched/aged cells. The analysis is assessing the CMBS overall system efficiency, reliability and weight compared to the TCBS for a design of a 300V/3.6kW battery system as a case study

Sintering and Properties of Pb0.98Ca0.02 [(Zr0.52Ti0.48)0,98(Cr3+0.5, Ta5+0.5)0,02] O3 Ferroelectric Ceramics Doped with P2O5

AbstractThe effect of phosphorus additions on the structure, microstructure and dielectrics properties of the Pb0.98Ca0.02[(Zr0.52Ti0.48)0,98(Cr3+0.5, Ta5+0.5)0,02]1-xPx O3 (x ranged from 0.01 to 0.12) ceramics have been investigated. All of the samples were prepared by a high-temperature solid-state reaction technique. AFM analysis of the compounds suggests that the average grain size increases with increasing sintering temperature which is characteristic of a ceramic material. Until that it reaches maximum values for the simple doped with 4 Wt. % of P2O5 at a sintering temperature of 1050°C. Dielectric studies of the compounds as a function of frequency (from 1 to 200 KHz) sintered at different sintering temperatures (1000, 1050, 1100, 1150 and 1180° C) show that the compounds undergo a phase transition of diffuse type. The transition temperature shifts towards higher side with increase in frequency a typical characteristic of a relaxor material

Optimising the structure of a cascaded modular battery system for enhancing the performance of battery packs

The overall performance of battery packs may be affected by imbalances between the series connected cells which is more likely in packs with high number of cells needed to provide a high voltage as needed for example in electric vehicles. In this case, the overall capacity and power capability of the pack are limited by the weakest cell in the stack which results in incomplete utilisation of the pack's capabilities. In traditional centralised battery systems (TCBS), this is addressed by implementing cell active/passive balancing circuitry/techniques which restore some of the pack's energy capability. This paper proposes the use of cascaded modular battery systems (CMBS) to remove the need for extra balancing circuitry and maximises the performance and reliability of a battery system containing unequal matched/aged cells. The analysis is assessing the CMBS overall system efficiency, reliability and weight compared to the TCBS for a design of a 300 V/3.6 kW battery system as a case study

Deep learning based face beauty prediction via dynamic robust losses and ensemble regression

In the last decade, several studies have shown that facial attractiveness can be learned by machines. In this paper, we address Facial Beauty Prediction from static images. The paper contains three main contributions. First, we propose a two-branch architecture (REX-INCEP) based on merging the architecture of two already trained networks to deal with the complicated high-level features associated with the FBP problem. Second, we introduce the use of a dynamic law to control the behaviour of the following robust loss functions during training: ParamSmoothL1, Huber and Tukey. Third, we propose an ensemble regression based on Convolutional Neural Networks (CNNs). In this ensemble, we use both the basic networks and our proposed network (REX-INCEP). The proposed individual CNN regressors are trained with different loss functions, namely MSE, dynamic ParamSmoothL1, dynamic Huber and dynamic Tukey. Our approach is evaluated on the SCUT-FBP5500 database using the two evaluation scenarios provided by the database creators: 60%-40% split and five-fold cross-validation. In both evaluation scenarios, our approach outperforms the state of the art on several metrics. These comparisons highlight the effectiveness of the proposed solutions for FBP. They also show that the proposed dynamic robust losses lead to more flexible and accurate estimators.This work was partially funded by the University of the Basque Country , GUI19/027

Development of a battery energy loss observer based on improved equivalent circuit modelling

This paper proposes a new energy loss observer for batteries that has a good accuracy and low complexity. This observer can provide a support for battery management systems (BMS) in terms of predicting battery energy loss and/or battery internal temperature for given load profiles, and this enhances BMS capabilities for predictive and corrective actions. The typical observer requires an accurate battery model that represents accurately the internal resistance of the battery, and therefore battery modelling guidelines to produce a simplified equivalent circuit model (ECM) have been proposed. Experiments to validate the accuracy of the proposed model have been performed on a LiFePO4 (3.6V/8Ah) battery cell. The model parameter estimation has been achieved by fitting the model impedance to the battery impedance data obtained from electrochemical impedance spectroscopy. The energy loss estimation based on the proposed observer showed good accuracy with maximum error of ±2% under different load profiles operated within the targeted frequency range

Investigating the benefits and limitations of cascaded converter topologies used in modular battery systems

The Performance of battery packs is highly affected by imbalances between the series connected cells that provide the required string voltage. A modular battery implementation based on cascaded converters can have advantages over traditional centralized battery systems with add-ons active/passive balancing techniques. This paper investigates the use of a modular battery integrated within a cascaded converter and how the choice of the converter topology for the module influences the benefits and limitations of the modular battery system performance. Simulation results have been obtained using detailed battery model to validate the analysis