1,720,974 research outputs found
Dynamic tension control of cardboard packing machnine
No full textTyössä tutkitaan PI-säätimen käyttöä dynaamisessa kireydensäädössä ilman varsinaista kireyden takaisinkytkentää. Kireyttä säädetään epäsuorasti käyttämällä takaisinkytkentätietona kahden telan välistä paikkaeroa. Kireyssäädin toteutetaan nopeussäätimen rinnalle. Rinnakkaisrakenteella pyritään kireyden muutoksiin nopeasti reagoivaan säätöratkaisuun. Rakenne toteutetaan osaksi taajuusmuuttajan säätöketjua.
Työssä esitetään telasysteemin simulointimalli, jonka toimivuus varmistetaan käytännön mittauksin. Lisäksi työssä arvioidaan kireyssäädön toimintaa dynaamisessa kireydensäädössä simulointien ja testilaitteistolla suoritettavien mittausten perusteella.In this thesis use of PI-controller is studied in dynamical web tension control without tension feedback. The web tension is controlled indirectly based on feedback information of position difference between two rollers. The tension controller is implemented in parallel with the speed controller. With the parallel control structure the dynamic reaction to the changes in the web tension is tried to be improved. The tension controller is implemented as part of the frequency converter control structure.
In this thesis a simulation model for the web handling system is introduced. The performances of the model and the controller designed are tested with experimental tests. Also the effectiveness of the tension control in dynamical web handling is studied with simulations and by experimental tests
Online Time and Frequency Domain Identification of a Resonating Mechanical System in Electric Drives
Full text linkIn modern machinery, the dynamic performance of electric drives is often limited by the
mechanical characteristics of the system such as flexibilities. With the growing demand
for high-performance machinery, there is an increasing need for techniques to estimate
mathematical models in real time that describe these mechanical systems and the possible
changes in order to obtain a high-performance control. At the same time, requirements
for high reliability are continuously increasing, which significantly motivates to improve
system identification methods for the diagnostics and condition monitoring of mechanical
parts in electric drives.
A proper real-time system identification method is of great importance in order to obtain
an analytical model that sufficiently represents the most important characteristics of the
identified system. Even though many identification methods have been proposed in the
system identification literature, there is a strong motivation to develop computationally
efficient algorithms for online frequency response estimation. Especially, online
nonparametric identification could provide several opportunities for fault diagnostics and
robust controller design. In this doctoral dissertation, the online system identification of
a resonating mechanical system in an electrical drive is studied. The discussion covers
closed-loop identification approaches, which are based on both time and frequency
domain observations. The time domain identification approach employs a closed-loop
output error-based identification routine. In addition, two different types of frequency
domain identification approaches are proposed that are based on a time-frequency
representation of signals by applying sliding-DFT and Kalman filters. It is shown that the
proposed online frequency domain methods provide a good alternative to the
conventional time domain online identification solutions.
Theoretical approaches are tested with experimental mechanical test setups that can be
regarded as resonating two-mass systems. The experimental results confirm the feasibility
of the identification methods by verifying the obtained models according to a given
validation criterion, thereby showing that the system dynamics can be identified with an
accuracy that makes it possible to apply the proposed approaches for online frequency
response analysis.ei tietoa saavutettavuudest
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Energy efficiency of conveyor drives in refrigerating rooms
No full textWe study how conveyor drives in refrigerating rooms affect total energy costs. Studied conveyor drives are different types of gear motor drives. Energy efficiencies of the conveyor drives are determined by using direct torque measurement and energy costs of the conveyor drives are approximated from these results.
From the measurement results and the approximated total costs it can be seen how the energy efficiency of a conveyor drive has a considerable influence on the total costs, especially, with large operating hours. An energy efficient conveyor drive can minimize the total energy costs by reducing the energy consumption of the conveyor motor while cooling costs in refrigerated rooms are also reduced.Työssä tutkitaan kylmätiloihin sijoitettavien kuljetinkäyttöjen vaikutusta kokonaisenergiakustannuksiin. Tutkittavina kuljetinkäyttöinä ovat erityyppiset vaihdemoottorikäytöt. Kuljetinkäytöille suoritetaan hyötysuhdemittauksia käyttäen suoraa mittausmenetelmää ja saatujen tulosten perusteella arvioidaan käyttöjen aiheuttamia energiakustannuksia kylmätilassa.
Mittaustulosten ja kustannusarvioiden pohjalta saadaan selkeä näkemys siitä, kuinka kuljetinkäytön hyötysuhteella on suuri merkitys muodostuviin kokonaiskustannuksiin erityisesti suurilla käyttötuntimäärillä. Energiatehokkaalla kuljetinkäytöllä vähennetään moottorin sähkökulutuksen lisäksi myös kylmätilan jäähdytysenergian tarvetta
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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