1,720,975 research outputs found
Combined effect of fiber hybridization and matrix modification on mechanical properties of polymer composites
No full textPROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART L-JOURNAL OF MATERIALS-DESIGN AND APPLICATIONSGlass/carbon fiber reinforced hybrid composites are great candidates for wind turbine blade manufacturers to make larger blades. Variation of stacking sequences ensures design freedom to the composite engineers to optimize the composite structure's mechanical performance. On the other hand, matrix modification of polymer composites with nanoparticles is also of interest to introduce multifunctional properties. This research aims to scrutinize the influence of simultaneous fiber hybridization and matrix modification on polymer composites' tensile, flexural, and low-velocity impact properties. Hybrid glass/carbon epoxy composites and hybrid glass/carbon/multi-walled carbon nanotube (MWCNT) multiscale polymer composites of stacking sequences [GCGCGC](S), [CGCGCG](S), and [G(6)C(6)] were manufactured. Fiber hybridization dramatically improved tensile strength between 51 and 76 compared to glass fiber composite. Depending on the stacking sequence, the flexural strength of the hybrid composites was improved between 10 and 16 concerning carbon fiber composite. With the introduction of MWCNTs, a slight increase in the tensile strength for unsymmetrical hybrid composites by around 5 and decreases by 7 for symmetrical ones were observed. Similar behavior was seen for bending characteristics. Additionally, low-velocity impact tests showed that it is achievable to bring greater impact peak forces up to 70 for hybrid composites than carbon fiber epoxy composites. MWCNTs modification of the matrix restrained the impact damage propagation, as proved by C-scan analysis
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
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
Effect of swcnt and TiO2 layer addition on the performance of P3Ht: PCBM organic solar cells
No full textBu çalışmada tek cidarlı karbon nanotüp ve polimer P3HT:PCBM'den oluşan kompozit karışımın fotovoltaik özellikleri incelenmiştir. SWNT:P3HT:PCBM kompozit karışımı spin-coating tekniği kullanılarak kaplanmış ve daha sonra tavlanmıştır. Polimer ile SWNT arasındaki yapıyı ve yük transferini anlamak için, yapılan güneş pilleri AFM, SEM, absorbans ile karakterize edilmiştir. Düşük (% 0.025) karbon nanotüp konsantrasyonlu güneş pillerinin fotovoltaik karakteristiği incelenmiş olup kısa devre akımı 0.89 mA/cm2, açık devre gerilimi 500 mV, dolum faktörü 0.34 olarak belirlenmiş ve verimin % 0.61 olmasına yol açmıştır. SWNT'nin ilave edilmesi hem kısa devre akım yoğunluğunun hem de dolum faktörünün artmasına neden olmuştur. Kısa devre akım yoğunluğunun ve dolum faktörünün artması, verimin artmasını sağlamıştır. TiO2 tabakası boşluk bloke edici ve elektron seçici olmasına rağmen açık devre gerilimini, kısa devre akımını ve dolum faktörünü azalttığından dolayı güneş pilinin verimini düşürmüştür.In this study, photovoltaic proporties of single-walled carbon nanotubes (SWCNT) ? conjugated polymers, P3HT:PCBM, blend composites are investigated. The SWNT:P3HT:PCBM composites are deposited using a spin-coating technique and, then annealed. Devices characterized by atomic force microscopy (AFM) , absorbance and scanning electron microscope (SEM) to underline the structure and the charge transfer between the SWCNT and P3HT. Diodes with low nanotube concentration (0.025 %) show photovoltaic behaviour, with a short circuit current of 0.89 mA/cm2, an open circuit voltage of 500 mV and a fill factor of 0.34, which leads to a power conversion efficiency of 0.61 %. The addition of SWCNTs resulted in an improvement of both the short circuit current density and the fill factor. Enhancement of fill factor and short circuit current density of cells result in increase of efficiency. Although TiO2 layer act as hole blocking and electron selective, device performance was lessened with the TiO2 layer due to significant the decrease open circuit voltage, short circuit current and fill factor
Effects of nano-mat layer produced via electrospinning method on the fracture behaviour and mechanical properties of carbon fabric/epoxy composites
No full textHali hazırdaki bu çalışma MWCNT takviyeli PAN nanofiberlerin tabakalı Karbon/epoksi kompozit malzemelere uygulanmasını göstermektedir. Öncelikle PAN/MWCNT esaslı nanofiberlerin sentezi elektrospinning tekniğiyle gerçekleştirildi. Daha sonra tabakalar arasında nanofiber bulunan dört farklı karbon/epoksi numuneler vakum yardımlı reçine transfer kalıplama metodu ile konfigürasyonu gerçekleştirilmiştir. PAN esaslı nanofiberler karbon/epoksi kompozitlerin her bir tabaka aralığına çekme ve eğilme numuneleri elde etmek için başarılı bir şekilde yerleştirildi. DCB numunelerinde ise PAN esaslı nanofiberler karbon/epoksi kompozitlerin yalnızca orta tabakasına yerleştirildi. Mekanik özelliklerin belirlenmesi için PAN ve MWCNT/PAN esaslı kompozit malzemelere çekme ve eğilme testleri uygulanmıştır. Aynı zamanda dört farklı karbon/epoksi kompozit malzemelerin DCB testleri de yapılmıştır. Bu testlerden sonra numunelerin kırılma yüzeyleri SEM ve AFM ile morfolojik yapıları incelenmiştir. Bu nedenle toklandırma mekanizmaları altındaki nedenleri elde etmek için dört farklı karbon/epoksi kompozit numuneler detaylı olarak incelenmiştir. PAN ve MWCNT/PAN esaslı kompozit numunelerin çekme ve eğilme dayanımları nanofiber yerleştirilmeyen referans numunelere göre artmıştır. MWCNT katkılı elektrospun keçeler referans kompozit malzemelere kıyaslandığında tabakalar arası kırılma tokluğunu artırdığı sonuçlarda anlaşılmaktadır. Nanofiber ve MWCNT'nin sinerjik etkisinin sonucu olarak kırılma tokluğundaki artış % 77 olarak belirlenmiştir, ancak PAN5'in kırılma tokluğu yapısal bir kusur olarak davranan MWCNT aglomerasyonundan dolayı PAN3'ten düşük çıkmıştır. Nanofiberlerin varlığından dolayı meydana gelen temel mekanizmalar çatlak tutulması, çatlak yön değiştirmesi, fiber köprüleme, fiber sıyrılması ve fiber kırılmasıdır. Bu nedenle tabakalar arasına yerleştirilmiş böyle bir nanofiber tabakalı kompozit malzemeler için yeni fırsatlar sunmaktadır.The current study present application of MWCNT reinforced PAN nanofiber interleaves for the laminated Carbon/epoxy. Initially, the synthesis of PAN/MWCNT based nanofibers was performed by electrospinning technique. Afterwards, four types of carbon fiber/epoxy specimen were constructed by Vacuum Assisted Resin Transfer Molding method to evaluate mechanical features. The PAN based nanofiber were successfully placed as interleaves of each adjacent plies of carbon/epoxy composites to obtain tensile and flexural samples. For DCB sample, PAN based nanofiber were placed in the middle of carbon/epoxy composites. Tensile and flexural experiments were applied on PAN and MWCNT/PAN based nanofiber composite to determine mechanical properties. Meanwhile, DCB test was carried out for four types of carbon fiber/epoxy specimens. After performing tests, the fracture surfaces of samples were investigated by SEM and AFM. Hence, four types of carbon fiber/epoxy specimen were investigated to obtain an underlying reason of the toughening mechanism. For PAN and MWCNT/PAN samples, the tensile and flexural strength increased with respect to non- interleaved control samples. Results reveal that MWCNT reinforced electrospun mat contribute to enhance interlaminar fracture toughness compared to Reference sample. The fracture toughness energy of MWCNT reinforced electrospun mat shows a 77% increase as a result of the synergetic effect between MWCNT and nanofiber but the fracture toughness energy of PAN5 is lower than PAN3 due to the agglomeration MWCNT which can act as structural defects. The main toughening mechanisms due to the presence of nanofibrous interleave layer in between adjacent plies are crack pinning, crack deflection, fiber bridging, fiber pull- out and fiber breakage. Thus, such an interleaved nanofiber offers new opportunities for the laminated composite materials
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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