1,720,967 research outputs found
DC/AC converter prototype design.
No full textIn this project I will be making modified sine wave power inverter. Power inverters are devices which can convert electrical energy of DC form into that of AC. In this work there were made converter electrical principal and structural scheme. Was made converter. Investigated converter's efficiency. And were made conclusions
The modernization of feather and down cleaning machine.
No full textDown and feathers are an important by-product of the poultry industry which is usually destroyed or used as an additive for the production of low nutrition value animal food. The projected global growth of poultry consumption is determining the need of finding more efficient ways for down and feather usage. However, in order to be used, first of all, the feathers must be properly treated, that is cleaned and dried from dirt, blood or fat residues. Special feather cleaning machines are used for this purpose. The topic of this final bachelor's work is actual as it is looking for ways to optimize a specific feather and down cleaning machine. The aim of the work is to analyze the operation principle and the process of cleaning process and to propose a modernization plan of the down and feather cleaning machine ASTRA К-49IА УХЛ4 produced by the Lithuanian company Astra. The current state of the machine and the overall quality of the equipment has been rated as poor due to equipment’s age and many consequences of poor quality repair. The electric drives and devices examined require in many cases repair or replacement of parts, such as: repair of electromechanical controller and a steam generator; replacement of punch card, main fan bearing and rubber bush, cutter blade grinding and general machine cleaning. According to the tasks set, new control and power circuit diagrams were designed and a programmable logic controller was chosen instead of an electromechanical controller. The results of this final work will be used by the company, for the renovation and upgrading of existing down and feathers cleaning machine, and for the academic community to familiarize themselves with the operating principles of such equipment and schemes for optimizing the specific cleaning machine
Modernization laboratory kit of voltage inverter.
No full textJuška G. perform modernization of voltage converter laboratory kit. Electrical engineering Bachelor’s Thesis / scientific advisor assoc. E. Bielskis; Šiauliai University, the faculty of technology and natural science, electronic and electrical Department. – Šiauliai, 2015. 40p. Relevance. The usage of renewable energy sources are increasingly expanding not only in industry, but also in households. Everyone wants to meet the electricity needs without purchasing it from the grid. The produced electricity by renewable energy sources are stored in battery packs, a problem arise when need to use stored electricity to household applications, because household appliances use 230 V, 50 Hz supply. So stored electricity need to be converted. In that case, students of electrical engineering have to know how voltage converter works and what for is it. The existing voltage converter laboratory kit is outdated and has limited possibilities. So it was decided to modernize a training stand of voltage converter. In this Bachelor’s thesis I have described operation principles of voltage inverter, and it design process. Also there are described all the selected components, and presented their characteristics. The inverter was designed so that it would be clearly what components it contains. Conclusions: The voltage inverter training stand was updated and extended it capabilities. The price of this stand is much lower in comparison with similar stands offered by other manufacturers. Students will learn about this power electronics device while performing laboratory task
Development of energy efficient photovoltaic microinverter
No full textDarbe siūlomi sprendimai ir atliekami tyrimai skirti fotovoltinio mikroinverterio naudingumo koeficiento didinimui bei jo tiekiamos srovės į elektros tinklą netiesinių iškraipymų mažinimui. Sukurtas ir eksperimentiškai ištirtas energetiškai efektyvus vienos pakopos fotovoltinis tinklo mikroinverteris. Sukurtas valdymo algoritmas ir jį įgyvendinantis valdiklis tiekiamos į elektros tinklą mikroinverterio srovės valdymui.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra.
Pirmajame skyriuje atlikta fotovoltinių inverterių savybių mokslinių tyrimų analizė. Išanalizuoti fotovoltinių mikroinverterių veikimo principai, aptarti jų privalumai ir trūkumai, išanalizuotos mikroinverterio išėjimo srovės valdymo sistemos. Apžvelgti mikroinverteriuse naudojami nuolatinės įtampos keitikliai. Suformuluoti disertacijoje uždaviniai.
Antrajame skyriuje pateikti sukurtų nuolatinės įtampos grįžtamojo (angl. Flyback) keitiklio su alternatyvia aktyviąja viršįtampio gesinimo grandine ir dviejų raktų grįžtamojo keitiklio eksperimentiniai naudingumo koeficiento tyrimų rezultatai. Jie palyginti su klasikinio nuolatinės įtampos grįžtamojo keitiklio tyrimų rezultatais. Pasiūlytas naujas vienos pakopos fotovoltinis mikroinverteris, sukurtas naudojant du dviejų raktų grįžtamuosius nuolatinės įtampos keitiklius. Atlikti mikroinverterio naudingumo koeficiento ir išėjimo įtampos bei srovės tyrimai.
Trečiajame skyriuje pasiūlytas naujas proporcinis integralinis (PI) valdiklis su keičiamu laike proporciniu koeficientu, ištirta mikroinverterio srovės valdymo sistema su sukurtu valdikliu. Gauti mikroinverterio išėjimo srovės spektrai, įvertinti ir palyginti srovės netiesiniai iškraipymai. Ištirta mikroinverterio elementų parametrų įtaka naudingumo koeficientui. Tyrimai atlikti eksperimentiškai bei modeliuojant. Sukurto mikroinverterio naudingumo koeficiento padidinimui, patobulintas jame naudojamas grįžtamasis transformatorius.
Pagrindiniai disertacijos rezultatai paskelbti 7 mokslinėse publikacijose – 5 iš jų atspausdinti recenzuojamuose mokslo žurnaluose, 2 konferencijų leidiniuose. Rezultatai viešinti 10 mokslinių konferencijų.Daktaro disertacij
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
