Topological issues in single-phase power factor correction

The equipment connected to an electricity distribution network usually needs some kind of power conditioning, typically rectification, which produces a nonsinusoidal line current due to the nonlinear input characteristic. With the steadily increasing use of such equipment, line current harmonics have become a significant problem. Their adverse effects on the power system are well recognized. They include increased magnitudes of neutral currents in three-phase systems, overheating in transformers and induction motors, as well as the degradation of system voltage waveforms. Several international standards now exist, which limit the harmonic content due to line currents of equipment connected to electricity distribution networks. As a result, there is the need for a reduction in line current harmonics, or Power Factor Correction - PFC. In this dissertation, we address several issues concerning the application to single-phase PFC of various high-frequency switching converter topologies. The inherent PFC properties of second-order switching converters operating in Discontinuous Inductor Current Mode - DICM are well known, and Boost converters are widely used. However, their output voltage is always higher than the amplitude of the rectified-sinusoid input voltage. In addition, it is expected that the level of the differential-mode EMI is much higher in DICM, as compared to the Continuous Inductor Current Mode - CICM. Therefore, we first investigated the requirements for the EMI filter for a PFC stage based on a Boost converter operating in DICM. The high-level of differential-mode EMI that is associated with DICM operation prompted our interest to investigate the application of two-switch fourth-order converters for PFC. The switching cell of these converters contains two inductors, which can operate in DICM or in CICM, and one capacitor, which can operate in Discontinuous Capacitor Voltage Mode - DCVM or in Continuous Capacitor Voltage Mode - CCVM. As a consequence, in these topologies several combinations of operating modes can be obtained, which have characteristics that otherwise cannot be obtained in second-order switching converters. We analyze three fourth-order topologies operating in DCVM and CICM, which have both an input current with reduced high-frequency content and an inherent PFC property. One of the converters, i.e. the Buck converter with an LC input filter, is then selected for a more detailed analysis. In addition, a fourth-order topology with galvanic isolation and operating in DCVM and CICM is presented and analyzed, as well. We also consider the operation in CCVM and CICM, which is analyzed for a fourth-order topology with step-down conversion ratio. The 'zero-ripple' technique is applied to obtain an input current having a very low high-frequency content, and average current mode control is used to shape the input current. Methods for improving the efficiency of the PFC stage are addressed, too. We compare several Boost-type topologies that have lower conduction losses than the combined diode bridge and Boost converter, as well as one fourth-order topology that is able to operate with bipolar input voltage, in other words it can perform direct AC/DC conversion. Finally, we propose a novel Zero Voltage Transition - ZVT topology, which reduces the switching losses by creating zero voltage switching conditions at the turn-on of the active switch. This topology can be used in a variety of converters, for DC/DC or PFC applications.reviewe

Predictive Adaptive Control of an Activated Sludge Wastewater Treatment Process

This paper presents an application regarding a model based predictive adaptive controller used to improve the effluent quality of a conventionalactivated sludge wastewater treatment process. The adaptive control scheme consists of two modules: a robust parameter estimator and a predictive controller. The controller design is based on the process model obtained by recursive estimation. The performances of the adaptive control algorithm are investigated and compared tothenon-adaptive one. Both the set point tracking and the regulatory performances have been tested. The results show that this control strategy will help overcome the challenge for maintaining the discharged water quality to meet the regulations

Revascularization impact: quality of life enhancement in chronic limb-threatening ischemia

Introduction. Globally, over 230 million people have peripheral artery disease, often undiagnosed, leading to chronic limb-threatening ischemia. Revascularization is vital for preventing amputation and improving quality of life. While specific questionnaires for severe ischemia are lacking, the SF-36 questionnaire is widely used to assess quality of life, with variations like SF-12 and SF-8 for larger cohorts. Objectives. Our aim was to assess how different lower limb revascularization methods affect the postoperative quality of life in patients with chronic limb-threatening ischemia. Methods. This study was conducted at the St. Pantelimon Emergency Hospital of Bucharest, Romania. It included 166 adult patients with chronic limb-threatening ischemia who were monitored for 12 months. Quality of life was assessed using the SF-36 questionnaire. The patients were categorized into two groups: 112 underwent conventional surgery, and 54 had hybrid procedures. Data analysis involved t-tests, Mann-Whitney U tests and assessment of data reliability. Results. In the Conventional Surgery group, the average age was 70.5 years, predominantly male, with similar risk factors as the second group. The Hybrid Surgery group had an average age of 73 and exhibited more extensive distal arterial lesions, higher rates of ulcer/gangrene, and a higher occurrence of postoperative minor amputations. The SF-36 questionnaire showed low data reliability for the General Health and Social Functioning domains. Additionally, the Hybrid Surgery group had poorer preoperative perception in the Body Pain category. However, significant postoperative improvements in quality of life were observed in all domains for both groups with similar results. Conclusions. Revascularization improves the quality of life for patients with chronic limb-threatening ischemia, including those that also require minor amputations. SF-36 has good assessment for most QoL aspects, but reliability declines in severe ischemia

Programming Language Aggregation with Applications in Equivalence Checking

International audienceWe show that, given the operational semantics of two programming languages L and R, it is possible to construct an aggregate language, in which programs consist of pairs of programs from L and respectively R. In the aggregate language, a program P = (PL, PR) takes a step from either PL or PR. The main difficulty is how to aggregate the two languages so that data such as integers or booleans that are common to both languages has the same representation in the aggregate language. The aggregation is based on the pushout theorem, which allows us to construct a model of the aggregate language from models of the initial languages, while making sure that the interpretation of common data such as integers is the same. A main application of the aggregation result is in equivalence checking. It is possible to check for example that two programs PL and PR (written in L and respectively R) compute the same result by checking the partial correctness of the pair (PL,PR) in the aggregate language.Nous montrons qu'à partir des sémantiques opérationnelles de deux langages de programmation L et R il est possible de construire leur agrégation, qui est un langage dont les programmes sont des paires de programmes de L et de R. Dans ce nouveau langage, les données ou expressions communes à L et R sont factorisés afin d'éviter d'en garder deux copies distinctes. Ceci est rendu possible grâce au théorème de "pushout" qui construit un modèle de l'agrégation à partir de modèles des composantes L et R. Nous appliquons ces résultats à la preuve d'équivalence de programmes

Неалкогольный стеатоз печени и трансплантация печени: противоречия, результаты и перспективы

Clinica Gastroenterologie, Departamentul Medicină Internă, USMF N. Testemiţanu, Clinica Chirurgie Biliopancreatică, Departamentul Chirurgie, USMF N. Testemiţanu, Chișinău, Republica Moldova, Clinica de Chirurgie și Transplant Hepatic, Institutul Clinic Fundeni, București, România, Conferinţa Naţională de Gastroenterologie și Hepatologie cu participare internaţională 20 iunie 2014 Chişinău, Republica MoldovaNonalcoholic fatty liver disease affects a substantial proportion of the general population worldwide. This high prevalence of nonalcoholic fatty liver disease has important consequences in the donor selection process for liver transplantation, and in the post transplant period given the high recurrence rate of disease. De novo NAFLD can also occur in the allograft of patients transplanted for nonNAFLD liver disease. Predictors for NAFLD post-transplant recurrence include obesity, hyperlipidemia and diabetes as well as steroid dose after liver transplantation. A polymorphism in PNPLA3 that mediates triglyceride hydrolysis is linked to pre-transplant risk of obesity and has also been linked to post transplant NAFLD risk. This paper reviews the implications of NAFLD in both the pre- and post-liver transplantation settingЗначительная часть населения в мире страдает неалкогольным стеатозом печени. Высокая распространенность неалкогольного стеатоза печени имеет важные последствия в процессе отбора доноров для трансплантации печени. Неалкогольный стеатоз поражает пересаженную печень реципиентов, которые не страдали этой патологией до пересадки. Факторы, влияющие на развитие неалкогольного стеатоза печени после трансплантации, включают ожирение, гиперлипидемию и диабет, а также использование высоких доз стероидов после трансплантации. Генетический полиморфизм PNPLA3, влияя на гидролиз триглицеридов, связан с риском ожирения перед трансплантацией и риском неалкогольного стеатоза печени после трансплантации. В настоящем обзоре литературы рассматривается влияние неалкогольного стеатоза печени на состояние пациентов перед и после трансплантации

Cum steatoza hepatică non-alcoolică a grefei influenţează securitatea donatorului după transplant hepatic de la donator viu

Introducere: Nu este bine determinată influenţa gradului de steatoză a grefei asupra securităţii donatorului viu după hepatectomie efectuată pentru donare. Gradul steatozei hepatice la donator viu ar putea infl uenţa, precum şi potenţial afecta recuperarea donatorului după hepatectomie parţială. Scopul acestui studiu a fost evaluarea impactului steatozei hepatice macroveziculare minimale asupra evoluţiei postoperatorii şi securităţii donatorului de ficat viu. Material şi metode: În studiul au fost incluşi 7 donatori de ficat vii care au fost divizaţi în două grupe în dependenţă de prezenţa steatozei hepatice minimale macroveziculare la examenul morfopatologic. Grupele au fost analizate prin prisma examenului pre operator demografi c, antropometric, evaluării intraoperatorii, postoperatorii şi prevalenţei complicaţiilor. Rezultate: au fost găsite diferenţe semnificative statistic privind indicele masei corporale, duratei intervenţiei chirurgicale, nivelului ALAT, duratei normalizării transaminazelor. Prezenţa steatozei hepatice nu a infl uenţat numărul complicaţiile postoperatorii şi volumul hemoragiei intraoperatorii. Concluzii: supravieţuirea grefei şi a donatorului nu este afectata de steatoza hepatică macroveziculară minimală (până la 30%). Evoluţia postoperatorie nu depinde de prezenţa steatozei hepatice macroveziculare minimale

Transforming growth factor β-mediated micromechanics modulates disease progression in primary myelofibrosis.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked DownloadPrimary myelofibrosis (PMF) is a Ph-negative myeloproliferative neoplasm (MPN), characterized by advanced bone marrow fibrosis and extramedullary haematopoiesis. The bone marrow fibrosis results from excessive proliferation of fibroblasts that are influenced by several cytokines in the microenvironment, of which transforming growth factor-β (TGF-β) is the most important. Micromechanics related to the niche has not yet been elucidated. In this study, we hypothesized that mechanical stress modulates TGF-β signalling leading to further activation and subsequent proliferation and invasion of bone marrow fibroblasts, thus showing the important role of micromechanics in the development and progression of PMF, both in the bone marrow and in extramedullary sites. Using three PMF-derived fibroblast cell lines and transforming growth factor-β receptor (TGFBR) 1 and 2 knock-down PMF-derived fibroblasts, we showed that mechanical stress does stimulate the collagen synthesis by the fibroblasts in patients with myelofibrosis, through the TGFBR1, which however seems to be activated through alternative pathways, other than TGFBR2. Keywords: TGF-β; fibroblast activation; invasion; micromechanics; myelofibrosis; proliferation.School of Doctoral Studies-Iuliu Hatieganu University Romanian Government Ion Chiricuta Oncology Institute Cluj Napoca international collaborative grant of the European Economic Space between Romania and Iceland 2020-2022 1