A General Mathematical Formulation for the Determination of Differential Leakage Factors in Electrical Machines with Symmetrical and Asymmetrical Full or Dead-Coil Multiphase Windings

This paper presents a simple and general mathematical formulation for the determination of the differential leakage factor for both symmetrical and asymmetrical full and dead-coil windings of electrical machines. The method can be applied to all multiphase windings and considers Görges polygons in conjunction with masses geometry in order to find an easy and affordable way to compute the differential leakage factor, avoiding the adoption of traditional methods that refer to the Ossanna's infinite series, which has to be obviously truncated under the bound of a predetermined accuracy. Moreover, the method described in this paper allows the easy determination of both the minimum and maximum values of the differential leakage factor, as well as its average value and the time trend. The proposed method, which does not require infinite series, is validated by means of several examples in order to practically demonstrate the effectiveness and the easiness of application of this procedure

Mitral Valve Repair Techniques With Neochords: When Sizing Matters

Mitral valve (MV) repair procedures have evolved over time and multiple approaches have been proposed also for the repair with neochords implantation. This article compiles the currently available approaches for implanting and sizing neochords, to restore a proper coaptation of the MV leaflets and a good systo-dyastolic movement. The described techniques are aimed at standardizing chordal measurement, in order to reduce variability in chordal length. The placement of annuloplasty ring before chordae implantation should be avoided. Regardless of the technique chosen, it is important that the implanted chordae do not interfere with normal native chordae, to avoid the risk that neochordae may heal together or get damaged. This article aims to give an overview of the most common sizing techniques available

Minimally invasive aortic valve surgery

Since their introduction, it has been demonstrated that minimally invasive aortic valve replacement (MIAVR) approaches are safe and effective for the treatment of aortic valve diseases. To date, the main advantage of these approaches is represented by the reduced surgical trauma, with a subsequent reduced complication rate and faster recovery. This makes such approaches an appealing choice also for frail patients [obese, aged, chronic obstructive pulmonary disease (COPD)]. The standardization of the minimally invasive techniques, together with the implementation of preoperative workup and anesthesiological intraand post-operative care, led to an amelioration of surgical results and reduction of surgical times. Moreover, the improvement of surgical technology and the introduction of new devices such as sutureless and rapid deployment (SURD) valves, has helped the achievement of comparable results to traditional surgery. However, transcatheter technologies are nowadays more and more important in the treatment of aortic valve disease, also in low risk patients. For this reason surgeons should put new efforts for further reducing the surgical trauma in the future, even taking inspiration from other disciplines. In this review, we aim to present a review of literature evidences regarding minimally invasive treatment of aortic diseases, also reflecting our personal experience with MIAVR techniques. This review could represent a tool for a well-structured patient assessment and preoperative planning, in order to safely carrying out an MIAVR procedure with satisfactory outcomes

Sutureless and rapid deployment valves: Implantation technique from A to Z-the perceval valve

In the last two decades, sutureless (Perceval, Livallova PLC, London, UK) and rapid deployment valves (RD) (Intuity, Edwards Lifesciences, Irvine, CA, USA) were introduced to the market as an innovative alternative to traditional valves for patients requiring an aortic valve replacement (AVR). These devices have been studied extensively and in use across the last fifteen years. They have proven to not only demonstrate comparable results with conventional sutured biological valves-particularly helpful in minimally invasive cardiac surgery-but also provide an almost curative treatment to patients with intermediate-to-high surgical risk, filling the gap between transcatheter aortic valve implantation (TAVI) and traditional AVR. However, both sutureless and RD valves require special steps for implantation, resulting in a learning curve. Specific training for all surgical team members is mandatory, as recommended by the manufacturers. The aim of this review article is therefore to provide cardiac surgeons with a thorough guide on the implantation technique for each of these two prosthetic devices, from A to Z. In this first article, we will start by focusing on Perceval

Sutureless and rapid deployment valves: implantation technique from A to Z-the INTUITY Elite valve

In the last two decades, sutureless (Perceval, Livanova PLC, London, UK) and rapid deployment (INTUITY Elite, Edwards Lifesciences, Irvine, CA, USA) valves were introduced to the market as an innovative alternative to traditional valves for patients needing aortic valve replacement (AVR). These devices have been used and studied extensively across these fifteen years, and have proven to be a valid alternative treatment option compared to sutured biological valves, particularly helpful in minimally invasive cardiac surgery, and an almost curative treatment to patients with intermediate to high surgical risk, filling the gap between transcatheter and traditional AVR. However, both sutureless and rapid deployment valves require special steps for implantation, and also a learning curve. Proper specific training to all surgical team members is required as mandatory by the manufacturers. The aim of this review article is to provide cardiac surgeons with a thorough guide on the implantation technique from A to Z, for each of these two prosthetic devices. In this second part of our review article, we will focus on the INTUITY Elite valve

Rotor bar pre-fault detection in the squirrel cage induction motors

The paper deals with a diagnosis technique to detect and monitor incipient faults in the rotor bars of squirrel gage induction motors. The failure mode analysis is performed monitoring the motor axial vibrations. To accomplish the task, the authors present a mathematical model that allows relating the occurrence and the severity of the faults to the presence and the magnitude of some frequency components of the axial vibration spectrum. To validate the proposed approach, the results obtained by applying the mathematical model are compared with the ones obtained by experimental tests done on both healthy and faulty motors