177,485 research outputs found
Investigation into the Strouhal numbers associated with vortex shedding from parallel-plate thermoacoustic stacks in oscillatory flow conditions
No full textThis paper investigates vortex shedding processes occurring at the end of a stack of parallel plates, due to an oscillating flow induced by an acoustic standing wave. Here the hot-wire anemometry measurement technique is applied to detect the velocity fluctuations due to vortex shedding near the end of the stack. The hot-wire fast time response enables detailed frequency spectra of the velocity signal to be obtained, which can be used for identifying the dominant frequencies associated with vortex shedding, and thus allow calculation of the corresponding Strouhal numbers. By varying the stack configuration (the plate thickness and spacing) and the acoustic excitation level (the so-called drive ratio), the impact of the stack blockage ratio and the Reynolds number on the Strouhal number has been studied in detail. Furthermore, in the range of Reynolds numbers between 200 and 5000 a correlation between the Strouhal number and Reynolds number has been obtained and compared with analogous relationships in the steady flow. Particle Image Velocimetry (PIV) is also used to visualize the vortex shedding processes within an acoustic cycle, phase-by-phase, in particular during the part of the cycle when the fluid flows out of the stack—selected cases are shown for comparisons with hot-wire measurements
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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Modela-r as a Froude and Strouhal dimensionless numbers combination for dynamic similarity in running
No full textInternational audienceThe aim of this study was to test the hypothesis t hat running at fixed fractions of Froude (Nfr) and Strouhal (Str) dimensionless numbe rs combinations induce dynamic similarity between humans of different sizes. Ninet een subjects ran in three experimental conditions, i) constant speed, ii) similar speed (N fr) and iii) similar speed and similar step frequency (Nfr and Str combination). In addition to anthropometric data, temporal, kinematic and kinetic parameters were assessed at each stage to measure dynamic similarity informed by dimensional scale factors and by the decrease of dimensionless mechanical parameter variability. Over a total of 54 dynamic parameters, dynamic similarity from scale factors was met for 16 (mean r = 0.51), 32 (mean r = 0.49) and 52 (mean r = 0.60) parameters in the first, the second and the third experimental conditions, r espectively. The variability of the dimensionless preceding parameters was lower in the third condition than in the others. This study shows that the combination of Nfr and Str, computed from the dimensionless energy ratio at the center of gravity (Modela-r) ensures d ynamic similarity between different-sized subjects. The relevance of using similar experiment al conditions to compare mechanical dimensionless parameters is also proved and will hi ghlight the study of running techniques, or equipment, and will allow the identification of abnormal and pathogenic running patterns. Modela-r may be adapted to study other abilities requiring b ounces in human or animal locomotion or to conduct investigations in comparat ive biomechanics
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
Strouhal number of naturally-oscillating triangular and circular jets
No full textA nozzle consisting of an abrupt expansion into a short open- ended tube can produce a naturally-excited oscillating-jet flow. The characteristics of the oscillating jet depend on jet-orifice to chamber expansion ratio (D/d1), chamber length-to-diameter ratio (L/D), and shape of the jet orifice. In experiments using water as a flow medium, air-bubble visualisation and signals from a pressure transducer show that a triangular-jet orifice produces aperiodic oscillation without a spectral peak. In contrast, oscillation of the circular jet has clearly visible periodicity and the spectrum has a broad peak. The circular and triangular orifices produce completely different dependence of Strouhal number on expansion ratio. For a circular orifice, Strouhal number is inversely proportional to (D/d1−1). For a triangular orifice, Strouhal number is directly proportional to (D/d1−1). The two curves intersect at an expansion ratio of 4.8, which is approximately the minimum possible expansion ratio for a circular oscillating jet.S. K. Lee, P. V. Lanspeary and G. J. Nathanhttp://espace.library.uq.edu.au/view.php?pid=UQ:12083
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
Financial Analysis of Company R - FIN s.r.o.
No full textBakalářská práce se zabývá finanční analýzou společnosti R-FIN s.r.o. v letech 2013 - 2017. Cílem práce je zhodnotit výkonnost podniku a navrhnout možnosti na zlepšení finanční situace. Bakalářskou práci člením na dvě části. V teoretické části uvedu nástroje finanční analýzy. V praktické části představím společnost R-FIN s.r.o. a následně budu aplikovat nástroje z teoretické části. Na závěr provedu celkové zhodnocení a návrh na zlepšení finanční situace podniku.The bachelor thesis deals with the financial analysis of R-FIN s.r.o. in the years 2013 - 2017. The aim of the thesis is to evaluate the performance of the company and propose options for improving the financial situation. Bachelors work in two parts. In the theoretical part I will introduce financial analysis tools. In the practical part I will introduce company R-FIN s.r.o. and then apply the tools from the theoretical part. Finally, I will make an overall assessment and a proposal to improve the financial situation of the company
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
High-Strouhal-number pulsatile flow in a curved pipe
No full textThe high-Strouhal-number pulsatile flow in a curved pipe is studied numerically. A general force analysis is developed for the bend force, where the new contribution from flow acceleration is identified and analysed. The mechanisms of secondary flow production are studied by extending Hawthorne's (Proc. R. Soc. Lond. A, vol. 206, issue 1086, 1951, pp. 374–387) model to account for viscous effects and applied to assess the distinct contributions from an inviscid stretching and no-slip condition. A detailed comparison is made between the numerical simulations and models for a pipe flow characterised by a volume flux Q=UbA|sinΩpt| (where Ub is the maximum bulk velocity, Ωp is the angular frequency and A is the pipe cross-sectional area). For high-Reynolds-number (Reb) and high-Strouhal-number (St), the bend force predictions are in good agreement with the numerical results over a wide range of bend curvature (Rc/D; where Rc is the bend radius of curvature and D is the pipe diameter) owing to the influence of the streamwise flow acceleration on the pressure field. At high-St, the streamwise vorticity (secondary flow) distribution is steady and close to the low-St case, which is explained using a linear secondary flow model
- …
