1,721,032 research outputs found
The effect of voids on the flexural fatigue properties of carbon/epoxy composites
No full textThe role of voids in composite failures has not been well understood or been characterized. This study presents the result of an investigation aimed at examining the mechanical behaviour of unidirectional carbon fibre-reinforced polymer matrix materials as used by the wind turbine industry. The experimental program investigates the effect of the void content, different manufacturing methods, type of loading (the three-point bending vs. the four-point bending) on the static strength and fatigue life under a flexural load.The four ply unidirectional carbon/epoxy composites were manufactured using the SPRINT and prepreg manufacturing methods. Manufacturing by these methods has successfully produced the composite materials with varied void contents and the voids are found to concentrate primarily in the area where the adjacent plies meet. The SPRINT materials contain voids in the range of 1.63- 2.89% while the prepreg laminates have an average void content of 3.6% for thedebaulked laminates and 6.8% for the non-debaulked laminates. The voids in the SPRINT laminate are small and they are distributed inhomogeneously. The majority of the voids are less than 0.04 mm2 in size with a shape between a circle and an ellipse.The three point bending tests show that the flexural strength exponentially decrease as much as 6.4% for the SPRINT and 6% for the prepreg for every 1% increase of the void content. The similar void effect for both materials may be due to their similar microstructures. There is a similar effect on the increase in the void content for the flexural strength and the flexural fatigue sensitivity for both the three and four point bending tests. This means that the voids do not play any large role in the three-point bending as compared to the four point bending.The mechanism of failure is observed using the optical microscopy and the X-ray tomography of the polished edge and cross section of the area near the failure. The voids are found to interact with the cracks in both the static and fatigue failures. The image of the cross section near the failure area of the static test samples seem to suggest that the voids coalesce to each other under loading. By using the acoustic emission, it can be confirmed that a major failure occurs due to the fibre breakage. In addition, the acoustic emission results also show that the failure behaviour of the low and high void content specimens is significantly different
Chemical constituents from pericarp of garcinia mangostana linn / Siti Aisyah Mohamed Azlan
Get PDFGarcinia mangostana L. is a tropical tree from Southeast Asia and its fruit pericarp is
a well-known traditional medicine. Extraction and isolation were carried out by
chromatographic and spectroscopic technique respectively. A hexane extract of
Garcinia mangostana L. pericarp shows abundant of xanthones compounds and three
xanthones that being identified and elucidated their structure were a-mangostin (4),
p-mangostin (12) and garcinone D (39). Their structures were elucidated on the basis
of IR, UV, NMR and MS spectroscopic data, in addition to comparison with
literature data
Design of band pass filter for wireless surveillance system application at 2.4GHZ operating frequency / Mohamed Azlan Mohamed Noor
Get PDFThis paper deals with design of band pass filter for Wireless Surveillance System application. The specification for this filter included an operating frequency (center frequency) of 2.4GHz, bandwidth of 500MHz and pass band ripple of 0.5dB. The design process including creating a lumped element prototype, which was then transformed into Microwave Office 2004 for schematic circuit design and output verification by simulation results. One comparison circuit was construct according to the result was published by other paper for comparison of design circuit performance. The insertion losses and return losses graphs were used in all odd order number N for verification and comparison of performance of the filter specification. The resulting result filter had an operating frequency of 2.4GHz, a 500MHz bandwidth and 0.5 dB ripple
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
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