Optimal Excitation Controller Design for Wind Turbine Generator

An optimal excitation controller design based on multirate-output controllers (MROCs) having a multirate sampling mechanismwith different sampling period in each measured output of the system is presented. The proposed H∞ -control techniqueis applied to the discrete linear open-loop system model which represents a wind turbine generator supplying an infinite busthrough a transmission line

Learning episodes in an intercultural virtual exchange: The case of social high-immersion virtual reality

Computer-mediated communication tools facilitate international collaboration projects between foreign language learners and peers abroad (O’Dowd, 2018). Social Virtual Reality (VR) applications allow for synchronous interactions and task-based communication in which learners can experience telepresence and immersion and conversate in a foreign language. Based on previous pilot experiences (Jauregi-Ondarra, Gruber, & Canto, 2020, 2021), this Virtual Exchange (VE) project aims to investigate how the specific affordances of Social High-immersion VR (SHiVR) in conjunction with designed tasks influence interaction patterns, and learning episodes. The VE took place between two groups of university students in the Netherlands (N=15) and Cyprus (N=14) through SHiVR in March 2022. The main aims of the tasks were to raise student intercultural awareness, stimulate task-based communication processes using English as a lingua franca and digital pedagogical competences of language education students. Different sources of data were gathered and analysed. In this paper, we describe and present the pedagogical experience and the initial result

Discrete Optimal Multirate Techniques for Excitation Controller Design of a Synchronous Machine

An optimal control strategy based on Two-Point-Multirate Controllers (TPMRCs), is used to design a desirable excitation controller of a hydrogenerator system, in order to enhance its dynamic stability characteristics. In the TPMRCs based scheme, the control is constrained to a certain piecewise constant signal, while each of the controlled plant outputs is detected many times over a fundamental sampling period T0. On the basis on this strategy, the original problem is reduced to an associate discrete-time linear quadratic (LQ) regulation problem for the performance index with cross product terms, for which a fictitious static state feedback controller is needed to be computed. Simulation results for the actual 117 MVA synchronous generator with conventional exciter supplying line to an infinite grid show the effectiveness of the proposed method which has a quite satisfactory performance

Discrete optimal multirate techniques for excitation controller design of a synchronous machine

Summarization: An optimal control strategy based on Two-Point-Multirate Controllers (TPMRCs), is used to design a desirable excitation controller of a hydrogenerator system, in order to enhance its dynamic stability characteristics. In the TPMRCs based scheme, the control is constrained to a certain piecewise constant signal, while each of the controlled plant outputs is detected many times over a fundamental sampling period T0. On the basis on this strategy, the original problem is reduced to an associate discrete-time linear quadratic (LQ) regulation problem for the performance index with cross product terms, for which a fictitious static state feedback controller is needed to be computed. Simulation results for the actual 117 MVA synchronous generator with conventional exciter supplying line to an infinite grid show the effectiveness of the proposed method which has a quite satisfactory performance.Presented on: Journal of Engineering Science and Technology Revie

Fat embolism due to bilateral femoral fracture: a case report

Konstantinos Porpodis1, Michael Karanikas2, Paul Zarogoulidis1, Maria Konoglou3, Kalliopi Domvri1, Alexandros Mitrakas2, Panagiotis Boglou4, Stamatia Bakali5, Alkis Iordanidis6, Vasilis Zervas1, Nikolaos Courcoutsakis6, Nikolaos Katsikogiannis7, Konstantinos Zarogoulidis11Pulmonary Department, “G Papanikolaou” General Hospital, Aristotle University of Thessaloniki, Thessaloniki, 21st Surgery Department, University General Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, 31st Pulmonary Department, “G Papanikolaou” General Hospital, Thessaloniki, Greece; 4Pulmonary Department, 5Microbiology Department, 6Radiology Department, University General Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, Greece; 7Surgery Department (NHS), University General Hospital of Alexandroupolis, Alexandroupolis, GreeceAbstract: Fat embolism syndrome is usually associated with surgery for large bone fractures. Symptoms usually occur within 36 hours of hospitalization after traumatic injury. We present a case with fat embolism syndrome due to femur fracture. Prompt supportive treatment of the patient’s respiratory system and additional pharmaceutical treatment provided the positive clinical outcome. There is no specific therapy for fat embolism syndrome; prevention, early diagnosis, and adequate symptomatic treatment are very important. Most of the studies in the last 20 years have shown that the incidence of fat embolism syndrome is reduced by early stabilization of the fractures and the risk is even further decreased with surgical correction rather than conservative management.Keywords: fat embolism syndrome, trauma, femur fracture, ARD

Williams–Campbell syndrome: a case report

Maria Konoglou1, Konstantinos Porpodis2, Paul Zarogoulidis2, Nikolaos Loridas1, Nikolaos Katsikogiannis3, Alexandros Mitrakas2, Vasilis Zervas2, Theodoros Kontakiotis2, Despoina Papakosta2, Panagiotis Boglou4, Stamatia Bakali5, Nikolaos Courcoutsakis6, Konstantinos Zarogoulidis21First Pulmonary Clinic, "G. Papanikolaou" General Hospital, Thessaloniki, Greece; 2Pulmonary Department, "G. Papanikolaou" General Hospital, Aristotle University of Thessaloniki, Greece; 3Surgery Department (NHS), University General Hospital of Alexandroupolis, Greece; 4Pulmonary Department, University General Hospital of Alexandroupolis, Democritus University of Thrace, Greece; 5Microbiology Department, University General Hospital of Alexandroupolis, Democritus University of Thrace, Greece; 6Radiology Department, University General Hospital of Alexandroupolis, Democritus University of Thrace, GreeceIntroduction: Williams–Campbell syndrome, also known as bronchomalacia, is a rare disorder characterized by a deficiency of cartilage in subsegmental bronchi, leading to distal airway collapse and bronchiectasis. There have been few reports about patients affected by saccular bronchiectasis, paracicatricial emphysema, and diminished cartilage. These are all characteristic of Williams–Campbell syndrome.Case presentation: This report presents a 57-year-old woman with progressive dyspnea, cough, sputum production, and fever. The clinical and laboratory examination revealed that the patient had a respiratory infection due to bronchiectasis caused by Williams–Campbell syndrome, which was undiagnosed in the patient until then.Conclusion: Although a rare syndrome, when patients' signs and symptoms include recurrent respiratory infections, bronchiectasis, productive cough, and dyspnea, Williams–Campbell syndrome should be included in the differential diagnosis.Keywords: bronchietasis, Williams–Campbell syndrome, bronchomalaci