104,816 research outputs found
Eclipsing binaries observed with the WIRE satellite. II, β Aurigae and non-linear limb darkening in light curves
No full textAims. We present the most precise light curve ever obtained of a detached eclipsing binary star and use it investigate the inclusion of non-linear limb darkening laws in light curve models of eclipsing binaries. This light curve, of the bright eclipsing system β Aurigae, was obtained using the star tracker aboard the wire satellite and contains 30 000 datapoints with a point-to-point scatter of 0.3mmag.
Methods. We analyse the wire light curve using a version of the ebop code modified to include non-linear limb darkening laws and to directly incorporate observed times of minimum light and spectroscopic light ratios into the photometric solution as individual observations. We also analyse the dataset with the Wilson-Devinney code to ensure that the two models give consistent results.
Results. ebop is able to provide an excellent fit to the high-precision wire data.Whilst the fractional radii of the stars are only defined to a precision of 5% by this light curve, including an accurate published spectroscopic light ratio improves this dramatically to 0.5%. Using non-linear limb darkening improves the quality of the fit significantly compared to the linear law and causes the measured radii to increase by 0.4%. It is possible to derive all of the limb darkening coefficients from the light curve, although they are strongly correlated with each other. The fitted coefficients agree with theoretical predictions to within their fairly large error estimates. We
were able to obtain a reasonably good fit to the data using the Wilson-Devinney code, but only using the highest available integration accuracy and by iterating for a long time. Bolometric albedos of 0.6 were found, which are appropriate to convective rather than radiative envelopes.
Conclusions. The radii and masses of the components of β Aur are RA = 2.762 ± 0.017 R, RB = 2.568 ± 0.017 R, MA = 2.376 ±0.027 M and MB = 2.291 ± 0.027 M, where A and B denote the primary and secondary star, respectively. Theoretical stellar evolutionary models can match these parameters for a solarmetal abundance and an age of 450−500 Myr. The Hipparcos trigonometric parallax and an interferometrically-derived orbital parallax give distances to β Aur which are in excellent agreement with each other
and with distances derived using surface brightness relations and several sets of empirical and theoretical bolometric corrections
Variability Among B Stars Observed with WIRE
No full textItem does not contain fulltextFollowing the failure of the main experiment on board the Wide-Field Infrared Explorer satellite (WIRE), the on-board star camera was used as the first space-based asteroseismology experiment. From May 1999 through November 2006, well over 200 targets were observed for periods ranging up to 40+ days. The typical noise level (measured at a frequency of 10 mHz) of these observations was <5 ppm for a 3rd magnitude star. More than 35 Beta Cep and SPB stars have been observed with WIRE, and analysis has been ongoing for some time. New oscillation modes have been observed for targets such as Beta Cru (Cuypers et al. 2002), Kappa Sco (Cuypers et al. 2004), and Lambda Sco (Bruntt & Buzasi 2006). Lambda Sco in particular comprises two B type stars in a wide orbit (P = 1083 d), and one of these components has a low mass companion (P = 5.95 d). After subtracting the Beta Cep pulsation Bruntt & Buzasi (2006) could clearly see the primary and secondary eclipses in the close system. From their preliminary light curve analysis they constrained the mass and radius of the component stars. Until now, however, the majority of the B stars observed with WIRE have not been analyzed. Here we begin this process, presenting light curves and power spectra, and reporting frequencies and amplitudes for the B stars in the WIRE collection
H&M and The Coolest Monkey in the Jungle: A case study of H&M's online Crisis Communication
No full textThe purpose of this thesis is to examine the crisis, which H&M experienced in January 2018 after the ‘Coolest Monkey in the Jungle’ incident. The crisis emerged after a photo on H&M’s web shop featuring an African-American boy in a hoodie with the writing ‘Coolest Monkey in the Jungle’, sparked racist accusations on social media towards H&M. H&M’s social media accounts overflowed with comments calling H&M racist and condemning the behavior and decisions, which led to this sweatshirt being put on an African-American boy, focusing on the subliminal messaging this induced. H&M therefore issued a public apology across social media channels, taking full responsibility for the crisis. This thesis therefore deals with the uprising on social media against H&M, and how the crisis communication was constructed, leading to the following problem formulation with sub-questions: How may this thesis’ choice of theory and methodological framework enrich the field of Crisis Communication on Social Media? - How was H&M’s ‘Coolest Monkey in the Jungle’ crisis perceived by consumers on social media? - Which rhetorical aspects did H&M apply in the apology issued? This is analyzed using a thematic analysis conducted through coding, which establishes the consumer perspective, both on H&M and the crisis, but also the perception of the crisis communication. The apology issued via a Press Release was analyzed using the Appraisal Framework, which considers the evaluative stance of the writer, and how the text establishes feelings, and lets the reader adopt a similar stance. Additionally, an analysis of rhetorical appeals was conducted, as this in combination with an Appraisal analysis helped to establish how rhetorical aspects aid crisis communication and its adoption. Henceforth, H&M’s Press Release was analyzed using the Situational Crisis Communication Theory by Timothy Coombs, to establish whether H&M adopted the best suited approach in the aftermath. The findings concluded that 15% of consumers viewed H&M and its crisis communication in a positive light and 26% in a negative light, despite the rhetorical analysis revealing that H&M followed the best suited approach for this given crisis. The Appraisal analysis revealed a high level of Judgment markers towards H&M itself, and graduation markers enforcing the unequivocal admittance of guilt. Simultaneously, the analysis of persuasive appeals revealed a higher level of Ethos and Pathos, hence focusing on feelings rather than logical and rational reasoning. This finding is also in accordance to the ethical nature of the crisis. Conclusively, the thesis found that despite H&M’s best intentions and practices, the ethical nature of the crisis acted as a natural hedge to the results of crisis communication
The Small IRAIT telescope. Photometric time-series during the polar night
No full textThe Small IRAIT is a 25 cm telescope which was deployed and installed at Dome C, on the high antarctic plateau, in 2007. During the polar night an intensive photometric program was carried out: despite the harshness of the polar winter, the telescope worked in a semi-robotic way giving us a large amount of photometric data and precious informations about technology and procedures for polar missions
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
No full textWe 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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Contribution of Information and Communication Technology (ICT) in Country’S H-Index
No full textThe aim of this study is to examine the effect of Information and Communication Technology (ICT) development on country’s scientific ranking as measured by H-index. Moreover, this study applies ICT development sub-indices including ICT Use, ICT Access and ICT skill to find the distinct effect of these sub-indices on country’s H-index. To this purpose, required data for the panel of 14 Middle East countries over the period 1995 to 2009 is collected. Findings of the current study show that ICT development increases the H-index of the sample countries. The results also indicate that ICT Use and ICT Skill sub-indices positively contribute to higher H-index but the effect of ICT access on country’s H-index is not clear
Fully Turbulent Mean Velocity Profile for Purely Viscous non-Newtonian Fluids
No full textThe characteristic near wall behavior of turbulent flow of purely-viscous non-Newtonian fluids is discussed for both power-law (P.-L.) and Herschel-Bulkley (H.-B.) rheological models. A proper scaling is presented for H.-B. fluids to establish an analogy with power-law fluids with same flow index. To provide reference data for turbulent flow of non-Newtonian fluids, DNS simulations of power-law fluids are conducted in a rectangular channel for a large range of power-law indices ( = 0.5, 0.69, 0.75, 0.9, 1, 1.2). The DNS data show that the mean velocity profile in the viscous and logarithmic layers follow expressions of the form and respectively, where shows a logarithmic dependency on the flow index.Comparison with some experimental data shows the above formulation to be valid for Reynolds numbers (based on shear velocity) as high as 1000
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