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Impact of welding equipment on power quality

China Welding 2024年第3期33卷 44-51页

作者： kovács attila Molnár Judit Jármai Károly Institute of Physics and Electrical Engineering Department of Electrical and Electronic Engineering Institutional DepartmentUniversity of MiskolcMiskolc H3515Hungary Institute of Energy and Chemical Engineering University of MiskolcMiskolc H3515Hungary

In an industrial facility,many electrical consumers can affect the quality of ***,the freedom from interference sources of these devices and equipment can be crucial for quality and uninterrupted electricity *** welding equipment is also a possible source of *** electrical harmonic injections created by welding equipment into the electrical network can affect the operation of other consumers connected to the given distribution points and cause unjustified overheating and shutdowns of some network *** aim of the research is to analyse the current harmonic injection of welding equipment of different types and modes of operation connected to the internal distribution network of the industrial *** effectiveness of the active harmonic filter built into the welding equipment was also examined in the *** results showed that the built-in active harmonic filter of the DC045 laser welding equipment was ineffective because the total harmonic distortion(THD)was about three times the 8%allowed by IEEE 519−2022 *** current harmonic injection of MIG 320 and MM403 type welding equipment was more than five times the permissible value of 5%.The current harmonic distortion of the PLAS140 type plasma-jet cutter equipment was below the 5% value allowed in the standard,thus it complied with *** on the measurement results,it can be concluded that the use of protection against harmonics is also necessary for welding ***,proposals were made in the paper to reduce the effect of harmonics.

关键词： electrical transients harmonic distortion electrical network disturbances voltage breaks total harmonic distortion(THD)

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Harmonics in the Squirrel Cage Induction Motor Analytic Calculation Part III: Influence on the Torque-speed Characteristic

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CES Transactions on Electrical Machines and Systems 2024年第1期8卷 86-102页

作者： G.kovács the Ganz Electric Works BudapestHungary

The harmonics that appear in the squirrel cage asynchronous machine have been discussed in great detail in the literature for a long time. However, the systematization of the phenomenon is still pending, so we made an attempt to fill this gap in the previous parts of our study by elaborating formulas for calculation of parasitic torques. It was a general demand among those who work in this field towards the author to verify his formulas with measurements. In the literature, it seems,only one detailed, purposeful series of measurements has been published so far, the purpose of which was to investigate the effect of the number of rotor slots on the torque-speed characteristic curve of the machine. The main goal of this study is to verify the correctness of the formulas by comparing them with the referred series of measurements. Relying on this, the expected synchronous parasitic torques were developed for the frequently used rotor slot numbers-as a design guide for the ***, together with our complete table for radial magnetic pull published in our previous work, the designer has all the principles, data and formulas available for the right number of rotor slots for his given machine and for the drive system. This brings this series of papers to an end.

关键词： Asynchronous parasitic torques Induction motor Squirrel cage rotor Space harmonics Synchronous parasitic torques

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Harmonics in the Squirrel Cage Induction Motor Analytic Calculation-Part Ⅰ: Differential Leakage, Attenuation, Asynchronous Parasitic Torques

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CES Transactions on Electrical Machines and Systems 2023年第4期7卷 320-329页

作者： G.kovács Ganz Electric Works 1095 BudapestHungary

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.

关键词： Asynchronous parasitic torque Attenuation Differential leakage Squirrel cage induction motor Winding harmonics

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The application of traditional transmission electron microscopy for autophagy research in Caenorhabditis elegans

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Biophysics Reports 2015年第2期1卷 99-105页

作者： attila L.kovács Department of Anatomy Cell and Developmental Biology Eotvos Lorand University

Traditional ultrastructural characterization of autophagic processes remains an important approach to be used in parallel with molecular genetics,light microscopy,and other *** special nature of Caenorhabditis elegans as an object for transmission electron microscopy makes its introduction into autophagy research a challenging *** basis of the protocol to prepare *** samples for autophagy studies was worked out around the turn of the millennium and has been used since then in my laboratory with some *** method described here enables the user to prepare samples for systematic morphologic as well as morphometric investigations to characterize autophagy with a high but still realistic investment of effort.

关键词： Dehydration Embedding Fixation Sample preparation Staining

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On Non-normal Arc-Transitive 4-Valent Dihedrants

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Acta Mathematica Sinica,English Series 2010年第8期26卷 1485-1498页

作者： István kovcs Botjan KUZMAN Aleksander MALNI FAMNIT University of Primorska PeF University of Ljubljana IMFM University of Ljubljana

Let X be a connected non-normal 4-valent arc-transitive Cayley graph on a dihedral group Dn such that X is bipartite, with the two bipartition sets being the two orbits of the cyclic subgroup within Dn. It is shown that X is isomorphic either to the lexicographic product Cn[2K1] with n 〉 4 even, or to one of the five sporadic graphs on 10, 14, 26, 28 and 30 vertices, respectively.

关键词： Cayley graph arc transitivity dihedral group

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Complications in children with percutaneous endoscopic gastrostomy (PEG) placement

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World Journal of Pediatrics 2019年第1期15卷 12-16页

作者： Brigitta Balogh Tamás kovács Amulya Kumar Saxena Division of Pediatric Surgery Department of PediatricsUniversity of SzegedKorányi fasor 14-15Szeged 6725Hungary Department of Pediatric Surgery Chelsea Children's HospitalChelsea and Westminster NHS Fdn TrustImperial College LondonLondonUK

Introduction The aim of this study was to analyze the complication rates and mortality in association with different operative techniques of percutaneous endoscopic gastrostomy (PEG),age,underlying diseases and other risk ***,analysis of the indications of PEG insertion and the underlying comorbidities was also *** This study performs a literature analysis of PEG-related complications in *** was searched on PubMed(R) (1994-2017) using terms 'percutaneous endoscopic gastrostomy','complications','mortality' and 'children'.Results Eighteen articles with 4631 patients were *** mean age was 3 years (0-26 years).Operative techniques were:pull technique in 3507 (75.7%),1 stage PEG insertion in 449 (9.7%),introducer technique in 435 (9.4%),image-guided technique in 195 (4.2%) and laparoscopic-assisted PEG in 45 (1.6%).Most frequent indications for PEG insertion were dysphagia (n =859,32.6%),failure to thrive (n =723,27.5%) and feeding difficulties (n =459,17.4%).Minor complications developed in n 1518 patients (33%),including granulation (n =478,10.3%),local infection (n =384,8.3%) and leakage (n =279,6%).In 464 (10%) patients,major complications occurred;the most common were systemic infection (n =163,3.5%)and cellulitis (n =47,1%).Severe complication like perforation occurred in less than 0.3%.Patients with lethal outcomes (n =7,0.15%) had severe comorbidities;and the cause of mortality was sepsis in all *** or young age did not affect complication *** with ventriculoperitoneal (VP) shunt had higher risk of major *** high-risk patients,laparoscopic-assisted PEG insertion had less major and severe complication than traditional pull *** PEG is a safe operative technique;although minor complications are relatively common and occur in up to 1/3 of patients,there is a fairly low rate of severe ***-thirds of PEG patients have at least one ***

关键词： Children Complications Percutaneous endoscopic gastrostomy

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Isomorphisms of Cubic Cayley Graphs on Dihedral Groups and Sparse Circulant Matrices

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Acta Mathematica Sinica,English Series 2023年第4期39卷 618-632页

作者： Istvan kovAcs UP IAM&FAMNIT University of PrimorskaMuzejski trg 26000 KoperSlovenia

We show that,up to isomorphism,there is a unique non-CI connected cubic Cayley graph on the dihedral group of order 2n for each even number n≥*** answers in the negative the question of Li whether all connected cubic Cayley graphs are CI-graphs(Discrete Math.,256,301-334(2002)).As an application,a formula is derived for the number of isomorphism classes of connected cubic Cayley graphs on dihedral groups,which generalises the earlier formula of Huang et *** with the particular case when n is a prime(Acta ***.,***.,33,996-1011(2017)).As another application,a short proof is also given for a result on sparse circulant matrices obtained by Wiedemann and Zieve(arXiv preprint,(2007)).

关键词： Cayley graph graph isomorphism dihedral group circulant matrix

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Hyperactive learning for data-driven interatomic potentials

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npj Computational Materials 2023年第1期9卷 599-612页

作者： Cas van der Oord Matthias Sachs Dávid Péter kovács Christoph Ortner Gábor csányi University of Cambridge Cambridge CB21PZUK University of Birmingham Birmingham B152TTUK University of British Columbia VancouverBC V6T 1Z2Canada

Data-driven interatomic potentials have emerged as a powerful tool for approximating ab initio potential energy *** most time-consuming step in creating these interatomic potentials is typically the generation of a suitable training *** aid this process hyperactive learning(HAL),an accelerated active learning scheme,is presented as a method for rapid automated training database *** adds a biasing term to a physically motivated sampler(*** dynamics)driving atomic structures towards uncertainty in turn generating unseen or valuable training *** proposed HAL framework is used to develop atomic cluster expansion(ACE)interatomic potentials for the AlSi10 alloy and polyethylene glycol(PEG)polymer starting from roughly a dozen initial *** HAL generated ACE potentials are shown to be able to determine macroscopic properties,such as melting temperature and density,with close to experimental accuracy.

关键词： starting generating consuming

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On the neutrality of two symmetric TSP solvers toward instance specification

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Science China(Information Sciences) 2019年第11期62卷 198-200页

作者： Gloria Cerasela CRI?AN László Barna IANTOVIcs László kovács Faculty of Sciences Vasile Alecsandri University Faculty of Sciences and Letters University of MedicinePharmacy Sciences and Technology Faculty of Mechanical Engineering and Informatics University of Miskolc

Dear editor,Currently, many computationally difficult problems can be solved using very efficient *** of these state-of-the-art methods have online implementations. The research question addressed herein is how sensit... 详细信息

关键词： On the neutrality of two symmetric TSP solvers toward instance specification

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Efficiency of local minima and GLM techniques in sinkhole extraction from a LiDAR-based terrain model

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International Journal of Digital Earth 2019年第9期12卷 1067-1082页

作者： Péter Enyedi Melinda Pap Zoltán kovács László Takács-Szilágyi Szilárd Szabó a Department of Physical Geography and Geoinformatics University of DebrecenDebrecenHungary Internet of Things Research Institute Eszterházy Károly University of Applied SciencesEgerHungary

The aim of this paper was to study reliable automated delineationpossibilities of karst sinkholes using a LiDAR-based digital terrain model(DTM) with pixel-based classifications. We applied two approaches toextract sinkholes: (1) general linear modeling (GLM) with morphometricindices derived from DTM;(2) and a local minima-based delineationusing only LiDAR DTM as the input layer. The outcome of the localminima was significantly different from the reference ones but found allthe sinkholes without previous knowledge of the area. The GLM-basedoutcome did not differ statistically from the reference. Results showedthat these approaches were efficient in detecting sinkholes based onLIDAR derivatives, and can be used for risk assessment and hazardpreparedness in karst areas: GLM had an overall accuracy of 89.5% andlocal minima had an accuracy of 92.3%;both methods identifiedsinkholes but also had commission errors, identifying depressions assinkholes.

关键词： Karst mapping sinkhole identification general linear model statistical evaluation sink fill

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