1,721,747 research outputs found
Tregouboviopsis Guo, Xu & Huang 2017, gen. nov
No full textGenus Tregouboviopsis Guo, Xu & Huang, gen. nov. Type species: Tregoubovia perradialis Xu, Huang & Du, 2012. Diagnosis. Ptilocodiidae medusae spherical; without tentacles; bell margin with nematocyst ring from which originate didermic centripetal tracks running meridionally on exumbrella; manubrium large, mouth quadratic with simple and long, unbranched oral tentacles, arising above mouth rim, unarmed terminal nematocyst clusters, and with ring nematocysts along the whole length of the oral tentacles; gonads very large, covering perradial on manubrium well, with mescenteries; without ocelli. Hydroid. Unknown. Remarks. The species Tregoubovia perradialis Xu, Huang & Du, 2012 is originally described under the genus Tregoubovia by the distinctness of simple unbranched oral tentacles, without marginal tentacles and exumbrella with didermic centripetal tracks. By reexamining the type specimens, its positions of oral tentacles and gonads are different from Tregoubovia atentaculata Picard, 1958, the type species of the genus. T. atentaculata has 4 oral arms extending directly from the perradial corners of mouth margin, with one terminal nematocyst clusters; gonads on interradial manubrium (Fig. 5), while T. perradialis has 4 oral tentacles arising above mouth rim, unarmed terminal nematocyst clusters, and with ring nematocysts along the whole oral tentacles; gonads on perradial manubrium (Figs 6–7). Therefore, the species T. perradialis is removed from the genus Tregoubovia and a new genus Tregouboviopsis Guo, Xu & Huang, gen. nov. is erected to accommodate it. Etymology. The genus name is derived from the Latin tregouboviopsis, meaning Tregoubovi-opsis, referring to external characters of both genera are nearly resemble.Published as part of Wang, Lianggen, Du, Feiyan, Xu, Zhenzu, Huang, Jiaqi & Guo, Donghui, 2017, Taxonomical notes on the family Ptilocodiidae (Anthomedusae) from the central and southern of South China Sea, with a new genus and a new species, pp. 236-242 in Zoological Systematics 42 (2) on pages 239-240, DOI: 10.11865/zs.201713, http://zenodo.org/record/461701
Simulations on perturbation growth and mixing of a shocked light fluid layer with two different interfaces
No full textThe Richtmyer-Meshkov instability of a light fluid layer with two different interface modes is studied numerically. By fixing the wavelength of the second interface (I2) while varying that of the first interface (I1), we examine distinct cases with identical wavelengths at both interfaces, as well as smaller or larger wavelengths at I1, to explore the effects of initial layer configurations on instability development. The larger wavelength interface significantly transmits modes to the smaller wavelength interface, whereas mode transmission in the reverse direction is limited. This results in two primary consequences: (i) the smaller wavelength interface and the overall mixing layer evolve periodically with the larger wavelength; (ii) compared to the identical wavelength case, the linear amplitude growth duration of I2 is slightly extended for the smaller I1 wavelength case, but significantly prolonged for the larger I1 wavelength case. The linear amplitude growth rate of I2 for all cases can be predicted by the model of Jacobs et al. [ J. Fluid Mech., vol. 195, 23-42 (1995)]. For cases with identical wavelengths and larger I1 wavelengths, the collisions of finger structures at both interfaces occur earlier, suppressing the growth of mixing width at early times while enhancing the mixed mass. In the later stages, the overall mixing efficiency in these cases significantly declines, despite continuous increases in both mixing width and mixed mass. This decline is attributed to severe deformation of the mixing layer due to interactions between finger structures, confining intense mixing to localized regions
Interfacial instabilities driven by co-directional rarefaction and shock waves
No full textWe report the first experiments on hydrodynamic instabilities of a single-mode light/heavy interface driven by codirectional rarefaction and shock waves. The experiments are conducted in a specially designed rarefaction-shock tube that enables the decoupling of interfacial instabilities caused by these co-directional waves. After the impacts of rarefaction and shock waves, the interface evolution transitions into Richtmyer-Meshkov unstable states from Rayleigh-Taylor (RT) stable states, which is different from the finding in the previous case with counter-directional rarefaction and shock waves. A scaling method is proposed, which effectively collapses the RT stable perturbation growths. An analytical theory for predicting the time-dependent acceleration and density induced by rarefaction waves is established. Based on the analytical theory, the model proposed by Mikaelian (Phys. Fluids, vol. 21, 2009, p. 024103) is revised to provide a good description of the dimensionless RT stable behaviour. Before the shock arrival, the unequal interface velocities, caused by rarefaction-induced uneven vorticity, result in a V-shape-like interface. The linear growth rate of the amplitude is insensitive to the pre-shock interface shape, and can be well predicted by the linear superposition of growth rates induced by rarefaction and shock waves. The nonlinear growth rate is higher than that of a pure single-mode case, which can be predicted by the nonlinear models (Sadot et al., Phys. Rev. Lett., vol. 80, 1998, pp. 1654-1657; Dimonte & Ramaprabhu, Phys. Fluids, vol. 22, 2010, p. 014104)
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
Machine learning powered sketch aided design via topology optimization
No full textStructural topology optimization is an important design tool in the conceptual design phase of a product. However, the current topology optimization design is mostly driven strictly based on mathematical and mechanical models. Although the innovative design can be automated, it mostly lacks effective manual experience guidance. To improve the efficiency of computer-aided structural design models, this work proposes a sketch-guided topology optimization approach based on machine learning. Using neural network-based style transfer techniques, computer-digitized/handdrawn sketches are explicitly incorporated into topology optimization in the form of constraint functions. The obtained optimization results not only satisfy the requirements of optimal mechanical properties, but also fully demonstrate the design intention and requirements of designers. Numerical examples show that the proposed approach can effectively compensate for the lack of manual experience guidance for topology optimization.
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
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