1,721,087 research outputs found
Tilting Pad Journal Bearing Computational Fluid Dynamic Parametric Modeling for New Energy Transition Challenges
Full text linkThe necessity of increasing the efficiency and reducing the carbon foot-print of machines is pushing centrifugal compressor bearings design to higher and higher peripheral speed and lower oil consumptions especially in the new energy transition fields, resulting in an increase in the bearing temperatures. Therefore, the bearing thermal management starts to play a major role in extending the machine operability and reducing the maintenance frequency. A
full three-dimensional (3D) parametric conjugate heat transfer computational fluid dynamic (CFD) model for tilting pad journal bearings (TPJBs) is introduced in this paper to address the temperature aspects of oil-film bearings. The parametric geometry of the model and the automatic mesh update, allow the equilibrium position search to be obtained without adopting any dynamic mesh algorithms. The tilting pad and rotating shaft equilibrium
position are automatically calculated with a Newton–Raphson algorithm. The static performance of the TPJB is investigated for different journal diameters, bearing clearance, and operating conditions. The numerical results obtained are compared with experimental data from compressor mechanical running tests to demonstrate the reliability of the model presented. The 3D distributions of the oil pressure, velocity, and temperature given by the CFD model, can be locally optimized to face the new energy transition challenges
Tilting Pad Journal Bearing CFD Parametric Modeling for New Energy Transition Challenges
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SPECTRAL CHARACTERIZATION OF THE NEAR-EARTH ENVIRONMENT WITH THE RAPTORS II TELESCOPE
No full textNear-Earth objects (NEOs) and artificial satellites are both found in the space environment around us and offer scientific value as well as an inherent risk. With the continuous discovery of new NEOs and the exponential increase of satellites in orbit, ground-based telescopes are becoming increasingly crucial in helping characterize the near-Earth environment. The RAPTORS II telescope is a remote-accessed, 0.6 m telescope located at Biosphere II in Oracle, Arizona. Among its seven filters, RAPTORS II is most notably equipped with a transmission grating capable of conducting visible to short-wave infrared (0.425 – 0.85 micron) spectral observations with moderate (1.7 nm/pixel) resolution. First installed in the summer of 2021, the setup and wavelength calibration of RAPTORS II took place during the fall semester as part of my honors thesis work. In the spring, additional filters were installed, and preliminary spectral data of main-belt asteroids was gathered to assess its spectroscopic capabilities. Our initial results suggest that RAPTORS II is capable of characterizing and discriminating space objects. Future work with RAPTORS II will consist of the characterization and grouping of cislunar objects and will likely be the topic of my Ph.D. thesis as a graduate student at the Lunar and Planetary Laboratory
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ROTATIONALLY RESOLVED VISIBLE AND NEAR-INFRARED SPECTROSCOPIC CHARACTERIZATION OF ASTEROID (223) ROSA
No full textWe present the results of our April, 2023 spectroscopic observation campaign in the form of four quarter-phase visible and near-infrared rotationally resolved spectra of the asteroid (223) Rosa as well as a rotationally combined median spectrum. (223) Rosa was confirmed to be an X-type asteroid under the Bus-DeMeo taxonomic system with a ~7.7%/𠜇m hemispherical variation caused by potential grain size or topological differences. Rosa's closest meteorite analog was found to be a weighted linear spectral mixture between 2 primitive meteorite types: a <125 𠜇m, relatively fresh sample of the meteorite Tagish Lake (10 %), and a 45-90 𠜇m sample of the meteorite Tarda (90 %) through chi-squared analysis. Similarities were found with both spectra, but albedo and density measurements favor Tagish Lake
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
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