1,720,955 research outputs found
Performance Analysis and Application of Superconducting Magnetic Energy Storage in a Power System
No full textDelivering an adequate amount of power to electrical equipment is being a tough job due to the continuous upgradation and technological advancement in the equipment. One of such familiar challenging technology adapted nowadays in power system for some specific applications is termed as pulsed power technology. The electrical grid with pulsed power loads is of the significant interest in aerospace and marine applications. Keeping in the mind of pulsed power applications, especially in defence sectors, the Superconducting Magnetic Energy Storage (SMES) system is proposed for a smooth and reliable power flow in the grid. In SMES system, the PCU interfaces the SMES magnet and the AC system in order to give an efficient power exchange and high quality power flow. Power Converter Unit (PCU) of the SMES system consists of a bidirectional DC-DC converter and a three-phase Voltage Source Inverter (VSI) coupled with a common DC-link capacitor. The control schemes employed for both the VSI and DC-DC converter is intended to maintain a constant DC-link voltage. Particularly, the voltage across the DC-link capacitor is tightly regulated using a Dynamic Evolution Control (DEC) strategy instead of a PI controller for the DC-DC converter. Consequently, the DC-link voltage is maintained almost constant with a voltage regulation well below ±10% during a Pulsed Power Load (PPL) condition.
Initially, the performance of the SMES system using a Leaky Least Mean Square (LLMS) control algorithm is compared with that using a Synchronous Reference Frame (SRF) control technique. The comparison is presented to show the effectiveness of the SMES system for power quality improvement. Henceforth, the control scheme for the VSI is proposed based on the Modified SRF (MSRF). Similarly, DEC or PI control strategy is employed to generate appropriate switching pulses for the DC-DC converter. It has been observed that the PI in the inner loop of MSRF is found sluggish during the PPL. Thus, PI is replaced by the DEC scheme to provide a fast response to the PPL. Also, the DC-DC converter employs the DEC instead of a PI in order to achieve a less rippled coil current and uniform voltage distribution across the SMES coil irrespective of load profile. Consequently, it ensures a reduced and acceptable AC loss across the SMES system, and a symmetric voltage distribution across the coil. Moreover, the control performance of the DEC scheme is compared with that of the Proportional-Integral (PI) control technique.
A uniform source current and power with minimum variations is maintained irrespective of the pulsed power load. A detrimental high rating stress on the system due to the load is substantially reduced by the proposed system. The DEC scheme is implemented for tight error regulation of the controlling parameters. The system supply current is found almost balanced, and its Total Harmonic Distortion (THD) is found well below 5%. An effective PPL compensation and a symmetric and uniform voltage distribution across the SMES coil, are achieved due to the precise solid-state control. Nevertheless, it has been seen that the SAPF is incompetent under high PPL demands whereas the SMES system has shown excellent performance under such load conditions. Moreover, a comparative analysis has been made between the conventional SAPF and the SMES system under PPL and Nonlinear Load (NL) conditions, to check the effectiveness of the SMES system. The performance of the proposed system is presented by using Sim Power System (SPS)/MATLAB Simulink, and real-time digital simulator (i.e. Opal RT-Lab/ dSPACE-1104)
Design and modelling of vacuum experimental set-ups
Get PDFThis thesis deals with study, modelling and designing of some laboratory apparatus in Cryogenics Engineering and Vacuum Technology field. The project is totally educational oriented. Project's aim is to give a clear idea about vacuum technology and modelling of such vacuum experimental set-ups which can serve as the laboratory experiments for both undergraduate and post graduate students. This project work is broadly classified into three parts:-- (i) Study, selection techniques and designing of some vacuum components. (ii) Modelling and operation of vacuum experimental set-ups. (iii) Making bills of materials for the proposed experimental se-ups. The experiments to be done are namely; (i) Study & Calculation of pumping speed of diffusion pump. (ii) Study & Calculation of pumping speed of roots pump. (iii) Study & Calculation of pumping speed of vacuum ejector pump. (iv) Study & Calculation of pumping speed of cryopump. (v) Calibration of vacuum gauges using primary gauges. (vi) Study and calculation of boil-off rate & heat transfer characteristics of vacuum insulation. Design of various components is done like vacuum chambers, thickness and length of pipe lines etc. So many calculations are done like calculation of pumping speed & flow rate of rotary pump, diffusion pump, roots pump and cryopump. Also calculation of boil-off rate of LN2 in vacuum insulation experiments is carried out. Constant volume method and constant pressure methods are used for pumping speed calculation. Vacuum insulation is studied in three ways one is with plain vacuum, second is with powder vacuum and the third one is with multilayer insulation
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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