Investigation of pump installation effects in outboard dynamic-inlet waterjet

openModern marine propulsion systems are primarily based on traditional screw propellers, but waterjet propulsion has gained attention as an innovative alternative due to its superior efficiency at high speeds and reduced cavitation effects. This thesis aims to investigate the hydrodynamic performance of a novel axial engine designed for zero-impact naval propulsion. The study, carried out as part of the university research project "Impronta Zero", utilises Computational Fluid Dynamics (CFD) simulations performed with Ansys Fluent software to analyse the turbomachinery's flow characteristics. The analysis focuses on evaluating propulsive performance and flow dynamics for various configurations, including isolated pump geometry and installed systems with a dynamic inlet to optimize flow guidance. The results reveal an overall efficiency of approximately 70% under design conditions, with hydraulic efficiencies exceeding 85%. These findings highlight the potential for further optimization of the design to minimise losses and enhance the adaptation of waterjet propulsion systems to real-world marine operational scenarios.Modern marine propulsion systems are primarily based on traditional screw propellers, but waterjet propulsion has gained attention as an innovative alternative due to its superior efficiency at high speeds and reduced cavitation effects. This thesis aims to investigate the hydrodynamic performance of a novel axial engine designed for zero-impact naval propulsion. The study, carried out as part of the university research project "Impronta Zero", utilises Computational Fluid Dynamics (CFD) simulations performed with Ansys Fluent software to analyse the turbomachinery's flow characteristics. The analysis focuses on evaluating propulsive performance and flow dynamics for various configurations, including isolated pump geometry and installed systems with a dynamic inlet to optimize flow guidance. The results reveal an overall efficiency of approximately 70% under design conditions, with hydraulic efficiencies exceeding 85%. These findings highlight the potential for further optimization of the design to minimise losses and enhance the adaptation of waterjet propulsion systems to real-world marine operational scenarios

Redex2Coq: Towards a Theory of Decidability of Redex’s Reduction Semantics

We propose the first step in the development of a tool to automate the translation of Redex models into a semantically equivalent model in Coq, and to provide tactics to help in the certification of fundamental properties of such models. The work is based on a model of Redex’s semantics developed by Klein et al. In this iteration, we were able to code in Coq a primitive recursive definition of the matching algorithm of Redex, and prove its correctness with respect to the original specification. The main challenge was to find the right generalization of the original algorithm (and its specification), and to find the proper well-founded relation to prove its termination. Additionally, we also adequate some parts of our mechanization to prepare it for the future inclusion of Redex features absent in Klein et al., such as the Kleene’s closure operator

Gain scheduling for hybrid force/velocity control in contour tracking task

In this paper a gain scheduling approach is proposed for the hybrid force/velocity control of an industrial manipulator employed for the contour tracking of objects of unknown shape. The methodology allows to cope with the configuration dependent dynamics of the manipulator during a constrained motion and therefore a significant improvement of the performance results. Experimental results obtained with an industrial SCARA manipulator demonstrate the effectiveness of the technique

Understanding complaint channel usage in multichannel retailing

This study aims to understand customer patterns of channel usage to voice complaints to multichannel retailers. Data were collected from multichannel shoppers for apparel in Spain by means of an online survey. Latent Class Analysis on complaint channel (store, website, mobile app and social media) usage was performed. The analysis identifies four customer segments that use complaint channels differently. Channel dependencies emerged, particularly related to mobile app usage. The study then explores how the identified patterns are related to channel usage for information search and purchase and to the quality of the relationship with the retailer. Results provide theoretical and managerial contributions to the retailing field

Novel missense variant in SPTBN2 possibly associated with spinocerebellar ataxia type 5 presenting as Parkinson´s disease

Spinocerebellar ataxias are a heterogeneous group of neurodegenerative diseases. There are more than 40 subtypes described so far, being spinocerebellar ataxia type 5 (SCA5) a rare autosomal-dominant ataxia with pure cerebellum involvement.  The gene responsible is the non-erythrocyte beta 2 spectrin gene (SPTBN2), encoding β-III spectrin, highly expressed in Purkinje cells. Onset is usually before 30 years, although it ranges from infancy to 70 years. The main clinical manifestations are limb and gait ataxia (> 90%); however, some patients also show trunk ataxia, sensory deficits, abnormal eye movements, dysarthria, and hyperactive deep tendon reflexes (25–90%)