Proportional resonant control of three-phase grid-connected inverter during abnormal grid conditions

PhD ThesisThe development of using grid-connected three-phase inverter has augmented the standing of realizing muted distortion along with high-quality current waveform. The standard three-phase grid-connected inverter is the full-bridge voltage source inverter. This inverter is usually controlled by proportional integral (PI) controller in order to ensure sinusoidal current injection to the grid. Although the PI controller is well established and easy to use under normal grid conditions, it leads to system instability under abnormal grid conditions. When abnormal grid conditions are likely to occur, the control system with PI controller can be configured to include two separate PI controllers for the positive and negative sequence components of the grid current. However, this increases control complexity and total harmonic distortion (THD). More recently, the proportional resonant (PR) controller started to replace PI controller in a different application including grid-connected current control. In this thesis, a comprehensive theoretical and experimental comparison between the PI and PR controllers is presented. The comparison shows that the PR controller offers lower total harmonic distortion (THD) in the current signal spectrum and is simpler to implement as it uses only the positive sequence component of the grid current and consequently only one PR controller is needed. For these reasons, the PR controller is adopted in this thesis. Despite the PR controller offering enhanced functioning under abnormal grid conditions compared to PI controller, a sudden change in the grid voltage could additionally raise the error between the reference signal and the controlled signal which results in causing significant divergence from its ostensible value. In this case, the performance of the conventional PR controller will not keep up with the increase in the error which weakens controller performance. To overcome this problem, a new design concept for controlling the current of the three-phase grid connected inverter during normal and abnormal conditions is presented in this thesis. The proposed technique replaces the static control parameters by adaptive control parameters based on a look-up table. This adaptive PR, controller has been investigated and demonstrated with different normal and abnormal grid conditions. The proposed control technique is capable of providing low THD in the injected current even during the occurrence of abnormal grid conditions compared with PI and PR controllers. It also achieves lower overshoot and settling time as well as smaller steady-state error. Proportional Resonance Control of Three-Phase Grid-Connected Inverter II Additionally, despite the fact that both PI and PR controllers are relatively straightforward to tune, and are sometimes capable of dealing with many time-varying grid conditions. This research also presented an adaptive controller tuned using advanced optimization techniques based on particle swarm optimisation (PSO). PSO is presented to optimize the control parameters of both PI and PR controllers for the three-phase grid-connected inverter. There are many advantages of using PSO, such as no additional hardware being required. Thus, it can be extended to other applications and control methods. In addition, the proposed method is a self-tuning method and can thus be suitable for industrial applications where manual tuning is not recommended for time and cost reasons. Simulation and experimental test were carried out to investigate the performance of the proposed techniques. In the simulation, the system was tested under 100 kW model using Matlab/Simulink environment. In addition, the system was also investigated through a practical implementation of the control system using a Digital Signal Processor (DSP) and grid-connected three-phase inverter. This practical system was demonstrated a 300 W scaled-down prototype. As a result, the comparisons between experimental and simulation results show the behaviour and performance of the control to be accurately evaluated

Analysis of Gabapentinoids Abuse-Reports in the Middle East and North Africa Region Utilizing the Food and Drug Administration Adverse Event Reporting System

Objectives: The purpose of this study was to identify abuse-related post-marketing reports associated with gabapentinoids use in the Middle East and North Africa (MENA) region countries. Methods: A retrospective cross-sectional analysis of abuse-related adverse drug event (ADE) reports from the Middle East and North Africa (MENA) region. It was performed using the Food and Drug Administration Adverse Event Reporting System (FAERS) database from January 2008 through June 2020. Abuserelated ADE reports for gabapentin and pregabalin were extracted from the FAERS database. Descriptive statistics were performed, and the proportional reporting ratio (PRR) was calculated to detect disproportional attribution of abuse-related ADEs for gabapentin versus pregabalin. Results: We identified 559 all-cause ADE reports for gabapentinoids, including 205 (36.7%) abuse-related ADE reports reported to FAERS in the period of analysis. FAERS included 139 (67.8%) pregabalin and 66 (32.2%) gabapentin abuse-related ADE reports. Among MENA region countries, Turkey (55, 39.6%) and Saudi Arabia (34, 23.7%) had the highest number of abuse-related ADE reports for pregabalin. The most pregabalin abuse-related ADE reports involved adult male patients. The PRR of pregabalin versus gabapentin abuse-related ADE reports was 1.11, indicating that the number of abuse-related events was higher for pregabalin compared to gabapentin. Conclusion: Over 200 cases of abuserelated gabapentinoids events were reported to FEARS from the MENA region in the study period. Further studies should assess risk factors and potential programs to reduce gabapentinoids abuse

Magnetic field evaluation around 400 kv underground power cable under harmonics effects

Power lines or underground power cables generate electromagnetic interaction with other objects near to them. This study evaluates the magnetic field emitted by underground extra high voltage cables. The presented work aims to show a numerical simulation of the magnetic field of a buried 400 kV underground power line, which is used as a novel prototype in several countries at a short distance. The underground power cable study, in the presence of the current harmonics at different positions, with time variation by finite element resolution, using Comsol Multiphysics with Matlab software in two dimensions. The simulation results illustrate the magnetic flux density variation-in terms of amplitude and distribution as a function of different actual harmonics rates. The underground cable performance and magnetic field have affected by the harmonics effects. The maximum magnetic induction levels generated by significant harmonics are superior to the limits recommended by the international standard norms. In this paper, shielding has been used as an appropriate remedy to attenuate the magnetic field

Prioritising Organisational Factors Impacting Cloud ERP Adoption and the Critical Issues Related to Security, Usability, and Vendors: A Systematic Literature Review

Abstract: Cloud ERP is a type of enterprise resource planning (ERP) system that runs on the vendor’s cloud platform instead of an on-premises network, enabling companies to connect through the Internet. The goal of this study was to rank and prioritise the factors driving cloud ERP adoption by organisations and to identify the critical issues in terms of security, usability, and vendors that impact adoption of cloud ERP systems. The assessment of critical success factors (CSFs) in on-premises ERP adoption and implementation has been well documented; however, no previous research has been carried out on CSFs in cloud ERP adoption. Therefore, the contribution of this research is to provide research and practice with the identification and analysis of 16 CSFs through a systematic literature review, where 73 publications on cloud ERP adoption were assessed from a range of different conferences and journals, using inclusion and exclusion criteria. Drawing from the literature, we found security, usability, and vendors were the top three most widely cited critical issues for the adoption of cloud-based ERP; hence, the second contribution of this study was an integrative model constructed with 12 drivers based on the security, usability, and vendor characteristics that may have greater influence as the top critical issues in the adoption of cloud ERP systems. We also identified critical gaps in current research, such as the inconclusiveness of findings related to security critical issues, usability critical issues, and vendor critical issues, by highlighting the most important drivers influencing those issues in cloud ERP adoption and the lack of discussion on the nature of the criticality of those CSFs. This research will aid in the development of new strategies or the revision of existing strategies and polices aimed at effectively integrating cloud ERP into cloud computing infrastructure. It will also allow cloud ERP suppliers to determine organisations’ and business owners’ expectations and implement appropriate tactics. A better understanding of the CSFs will narrow the field of failure and assist practitioners and managers in increasing their chances of success

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Evolving trends in the management of acute appendicitis during COVID-19 waves. The ACIE appy II study

Background: In 2020, ACIE Appy study showed that COVID-19 pandemic heavily affected the management of patients with acute appendicitis (AA) worldwide, with an increased rate of non-operative management (NOM) strategies and a trend toward open surgery due to concern of virus transmission by laparoscopy and controversial recommendations on this issue. The aim of this study was to survey again the same group of surgeons to assess if any difference in management attitudes of AA had occurred in the later stages of the outbreak. Methods: From August 15 to September 30, 2021, an online questionnaire was sent to all 709 participants of the ACIE Appy study. The questionnaire included questions on personal protective equipment (PPE), local policies and screening for SARS-CoV-2 infection, NOM, surgical approach and disease presentations in 2021. The results were compared with the results from the previous study. Results: A total of 476 answers were collected (response rate 67.1%). Screening policies were significatively improved with most patients screened regardless of symptoms (89.5% vs. 37.4%) with PCR and antigenic test as the preferred test (74.1% vs. 26.3%). More patients tested positive before surgery and commercial systems were the preferred ones to filter smoke plumes during laparoscopy. Laparoscopic appendicectomy was the first option in the treatment of AA, with a declined use of NOM. Conclusion: Management of AA has improved in the last waves of pandemic. Increased evidence regarding SARS-COV-2 infection along with a timely healthcare systems response has been translated into tailored attitudes and a better care for patients with AA worldwide

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Evaluating an Interactive Electronic Lecture System

Evaluation is an essential part of creating and applying an interactive electronic lecture system (IELS). IELS is designed to enhance lecturing process for undergraduate students at King Abdulaziz University. To evaluate the IELS there are three main issues covered in this paper, namely IELS features, experiment design and research methods. IELS is integrated application that offers rich interactive components for users. The first issue is IELS features such as user accessibility, usability, learnability, interactivity, communication, satisfaction. The second issue is experimented design for evaluation IELS. Third issue describes how the data has been gathered and how the results are analysis

Mass and Heat Transport Assessment and Nanomaterial Liquid Flowing on a Rotating Cone: A Numerical Computing Approach

In the present study, we explore the time-dependent convectional flow of a rheological nanofluid over a turning cone with the consolidated impacts of warmth and mass exchange. It has been shown that if the angular velocity at the free stream and the cone’s angular velocity differ inversely as a linear time function, a self-similar solution can be obtained. By applying sufficient approximation to the boundary layer, the managed conditions of movement, temperature, and nanoparticles are improved; afterward, the framework is changed to a non-dimensional framework utilizing proper comparability changes. A numerical solution for the obtained system of governing equations is achieved. The effect of different parameters on the velocity, temperature, and concentration profiles are discussed. Tangential velocity is observed to decrease with an increase in the Deborah number, whereas tangential velocity increases with increasing values of the angular velocity ratio, relaxation to the retardation time ratio, and buoyancy parameter. Expansion in the Prandtl number is noted to decrease the boundary layer temperature and thickness. The temperature is seen to decrease with an expansion in the parameters of lightness, thermophoresis parameter, and Brownian movement. It is discovered that the Nusselt number expands by expanding the lightness parameter and Prandtl number, whereas it increases by decreasing the Deborah number. We also noticed that the Sherwood number falls incrementally in Deborah and Prandtl numbers, but it upsurges with an increase in the buoyancy parameter