1,721,234 research outputs found
The effect of large-scale interannual variations in the Gulf of Guinea
No full textThe Gulf of Guinea is an important region of tropical Atlantic variability, and embedded within it are the Atlantic Ni~no and the seasonal tropical instability waves. Although, the dynamics of this region are accepted to modulate the monsoon system by the scientific community, it is still debated what controls temperatures and the exact coupling mechanism with the atmosphere. Here, I present the results of temperature advection, variability of the Equatorial Undercurrent (EUC) in relation to atmospheric forcing, influence of Gulf of Guinea sea surface temperature (SST) to rainfall variability over West Africa and the Sahel, spatio-temporal variability of nonseasonal ocean-atmosphere processes and the coupling of winds and SST. The central aim is to understand how anomalous currents advect temperatures, and how anomalous oceanic temperatures respond to the atmosphere to cause coupled variability.In order to understand the enigmatic influence of temperature advection by tropical instability waves (TIW), I examined the influence of anomalous currents and temperatures associated with the waves. Results show that TIWs advect temperatures zonally and warm the Gulf of Guinea during the boreal summer, and at the central equatorial Atlantic, they advect temperatures to the north. The EUC, represented by salinity maximum is investigated from four regions to cover the northern, central and southern branches of the current. West of the Gulf of Guinea, anomalous northward currents associated with TIWs destabilise the vertical positioning of the EUC core during the boreal summer. In the Gulf of Guinea, where bathymetry, river discharge and winds vary seasonally, vertical fluctuations are apparent every three months and the shallowing of the EUC affects the upper layer temperatures.The Gulf of Guinea SST correlates well with variability of rainfall over West Africa and the Sahel, where cold (warm) temperatures in 2005 (2007) explained the causes of drought (flooding) that occurred in those years respectively. Strongest intraseasonal SST variability is observed at the Guinea Dome and the Gulf of Guinea region and both occur due to seasonally varying northeasterlies and southeasterlies. However, north of 18N, zonal tropospheric winds associated with Madden-Julian Oscillation appear to alter the changes on surface winds. This connection between surface and atmospheric winds explains the inability of the winds to covary interannually with SST at the TIWs frontal zones. Investigations presented in this thesis increase our understanding of tropical Atlantic variability and results therein are useful as background conditions for coupled ocean-atmosphere models
The dynamic analysis and control of cracked rotating beams
No full textThis thesis covers the dynamic modelling of un-cracked and cracked rotating beams. Accordingly, a new model of a rotating cracked beam is developed using the finite element and the Rayleigh-Ritz method to characterise and analyse its dynamic behaviour. The effect of various parameters are investigated, such as rotational speed, hub ratio and slenderness ratio. In addition, the critical speed, buckling speed and veering phenomena are identified. The numerical results produced are shown to be in good agreement with models based on finite element representations.In addition to the theoretical investigations, experimental validation is presented. A test rig was designed and manufactured with a changeable rotating hub mount for different test requirements. Moreover, the rig was conceived to incorporate capabilities such as applying variable rotational speed using a variable frequency driver and provide vertical base excitation input to the centre of rotation of the hub. The tests were performed using random excitation at the root of the rotating cantilever beam to excite the flapwise modes of the beam. The responses were then measured optically using a high-speed camera, and the images were post-processed using a digital image correlation (DIC) method. This non-invasive optical method was used to extract the temporal deflection of the beam. The frequency response functions are then obtained from the measured responses. The estimated modal frequencies were compared with numerical simulations to validate the Rayleigh-Ritz and FE numerical models at various rotational speeds. Furthermore, an experimental crack detection was implemented and the results showed a good match to the introduced actual crack location and depth. The crack detection approach on the rotating cracked beam uses the fundamental and second natural frequencies.For vibration control of the rotating beam, a real-time velocity feedback control was applied using a remote single optical high-speed camera. An electromagnetic actuator was designed and mounted on the rotating hub to apply a feedback force on the rotating beam. The results for vibration control of the rotating beam show significant active damping and reduction in the amplitude of the first resonance over a wide range of rotational speeds
Dyeing of cotton with thyme and pomegranate peel
Full text linkWOS: 000344802700067Application of natural dyes for textiles is increasing due to awareness of environment, ecology, and pollution control. The purpose of this study is to determine the color, antimicrobial, and fastness properties of cotton fabrics dyed with thyme and pomegranate peel without a mordanting process. In this way, it was planned to avoid use of metallic mordants (heavy-metal salts) and prevent heavy-metal pollution for ecological production. Additionally, a variety of the most commonly used mordants, namely potassium aluminum sulfate, copper(II) sulfate, iron(II) sulfate, and tin(II) chloride, were used for mordanting of cotton fabrics in order to compare the differently mordanted and unmordanted dyed fabrics' color efficiencies (K/S) and CIE L (*) a (*) b (*) color values. It was found that mordant type had an effect on color efficiency and the color coordinates of fabrics dyed with both thyme and pomegranate fruit peel. Moreover, the antimicrobial properties of the fabrics only dyed directly with thyme and pomegranate peel without any mordanting process were determined to demonstrate the usability of these natural dye sources without use of any mordanting agents. The obtained antimicrobial activities were compared with undyed samples. Undyed samples showed no antimicrobial activity, whereas significant antimicrobial activity was obtained after the dyeing procedure using thyme and pomegranate peel on unmordanted fabrics. Washing, rubbing, perspiration, and lightfastness properties of dyed fabrics were also evaluated. Thyme and pomegranate fruit peel as natural dye sources revealed sufficient results even for unmordanted samples
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
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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