1,720,972 research outputs found
Formulation of photovoltaic inverter weighted conversion efficiency for equatorial climate
Full text linkThe system energy yield (Esys) is a performance indicator used by the installer to predict the energy output generated by a photovoltaic (PV) system. From the Esys estimation, the return of investment (ROI) for the installation can be approximated. The Esys equation consists of several elements, in which one of them is the PV inverter efficiency. The peak or maximum efficiency (ηmax) value from the inverter data sheet is usually used, but this practice is inaccurate because the PV inverters rarely operate at the peak power. Alternatively, the weighted efficiency is more preferable as it essentially considers the power conversion characteristics of the inverter when subjected to varying solar irradiance. Currently, the European weighted efficiency (ηEURO) is the most recognized and widely accepted. This is because, historically, European countries (particularly Germany) used to be the largest exporter and consumer of PV inverters throughout the world. Since ηEURO is developed based on a specific European irradiance profile, it is suspected that its value may not be suitable for inverters installed in different climatic conditions, particularly the equatorial region. Thus, the first objective of this work is carried out to prove this hypothesis. A one-year dataset from a weather station located at Universiti Teknikal Malaysia Melaka is collected with adherence to the IEC 61724 Standard. This irradiance profile is injected into a PV array simulator (PVAS) and tested on four PV inverters with different sizes and technologies. It is found that the recalculated ηEURO does not conform to the value stated in the respective inverter’s datasheet, thus confirming the above hypothesis. This finding inspires the formulation of a new weighted efficiency formula for the equatorial climate (ηEQUA). Three methods have been utilized, namely the IEC 61683 Standard, Response Surface Methodology (RSM) and Equatorial Irradiance-Duration Curve. The outcomes revealed that the last approach is the most practical solution to formulate ηEQUA. The newly developed formula is validated by the measured data from the field. It is demonstrated that the prediction of Esys using ηEQUA closely matched the Esys of a real 3 kW PV system, with only 0.16% difference between the two. It is envisaged that the usage of ηEQUA instead of ηmax (or ηEURO) will results in more accurate Esys and ROI predictions for PV system installed in the equatorial region
Performance analysis on the effect of stoichiometric air fuel ratio and ignition strength for spark ignition engine / Azhan Ab Rahman
No full textAn approach for control of the spark ignition on the advance / retard and also the
spark voltage with air fuel ratio for a model of carburetor engine is proposed. The
amount of air to fuel ratio is one of the well-known problems in an engine
management system design. It is one of the most critical parameter to the analysis of
engine performance, torque and fuel consumption. It is common in the production
plant as well as in the market use a greater diameter of high-tension cable that is
expected to provide a proportional power with the increase amount of spark intensity
to achieve the desired engine performance with stoichiometric air fuel ratio. A
manually voltage control coils before the high tension cable is used to vary the spark
strength in the combustion chamber in order to measure the power, torque and fuel
consumption. Sets of experiments were conducted and results obtained were
presented in term of graphs
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
Thruster Modelling for Underwater Vehicle Using System Identification Method
Full text linkThis paper describes a study of thruster modelling for a remotely operated underwater vehicle (ROV) by system identification using Microbox 2000/2000C. Microbox 2000/2000C is an XPC target machine device to interface between an ROV thrusters with the MATLAB 2009 software. In this project, a model of the thruster will be developed first so that the system identification toolbox in MATLAB can be used. This project also presents a comparison of mathematical and empirical modelling. The experiments were carried out by using a mini compressor as a dummy depth pressure applied to a pressure sensor. The thruster model will thrust and submerge until it reaches a set point and maintain the set point depth. The depth was based on pressure sensor measurement. A conventional proportional controller was used in this project and the results gathered justified its selection
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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