1,720,989 research outputs found
He et al. Reply:
No full textMax-Planck-Gesellschaft http://dx.doi.org/10.13039/501100004189National Natural Science Foundation of China http://dx.doi.org/10.13039/50110000180
Limitations of accuracy in PIV due to individual variations of particle image intensities
No full textThe effect of independent variations of the intensity of individual tracer particles between consecutive images on the accuracy of common displacement estimation methods in particle image velocimetry (PIV) is investigated. Such variations can be observed, e.g., in flows with components perpendicular to the illumination sheet, leading to out-of-plane displacements of the tracer particles. The achievable accuracy of PIV measurements is shown to be limited by this effect alone to be of the order of 0.1 pixel, yielding a basic limitation of the PIV technique
Comment on "Effect of Boundary Layers Asymmetry on Heat Transfer Efficiency in Turbulent Rayleigh-Bénard Convection at Very High Rayleigh Numbers"
No full textA Comment on the Letter by P. Urban, P. Hanzelka, T. Kralik, V. Musilova, A. Srnka, and L. Skrbek, Phys. Rev. Lett. 109, 154301 (2012). The authors of the Letter offer a Reply
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
On Turbulent Rayleigh-Bénard Convection in a Two-Phase Binary Gas Mixture
Get PDFIn this thesis an attempt is made to generate cloud patterns in a laboratory scale experiment. A two-phase binary gas mixture is employed as a physical model system. The fluid mixture is composed of a condensable gas which forms a liquid and a vapor phase and a noncondensable gas which serves as a background or carrier gas. The fluid mixture is confined between a bottom and a top plate. If the fluid mixture is exposed to a constant temperature difference, two intriguing phenomena can be observed.
First a film condensation sets in at the cold top plate that results in the formation of a very regular hexagonal droplet pattern. The temporal evolution of the droplet pattern is quantified and it is shown that a stable mass flux is essential in order to the maintain the hexagonal symmetry of the droplet patten. Second cloud-like patterns occur in a thin layer above the liquid-vapor interface. The dynamics of the cloud-like patterns reveal the turbulent flow inside the gaseous phase. An area-perimeter analysis of the cloud-like patterns results in a fractal dimension that is similar to the one obtained by the fractal analysis of two-dimensional cloud and rain areas in satellite and radar data.
This thesis is meant as a proof of concept which is why most of the results are still qualitative. However, a physical model system is presented that is appropriate in order to study the dynamics of cloud-like patterns in a turbulent Rayleigh-Bénard convection experiment. The origin of the cloud-like patterns is still a matter of debate. Therefore further experiments that could reveal the nature of these patterns must be performed
Variations on the Author
Get PDF“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
Pseudo-random generators using linear feedback shift registers with output extraction
Get PDFThe use of three extractors, fed by linear feedback shift registers (LFSR)
for generating pseudo-random bit streams is investigated. Specifically, a
standard LFSR is combined with a von Neumann extractor, a modified LFSR,
extended by the all-zero state, is combined with an output logic, which
translates every three bits from the LFSR into up to two output bits and a run
extraction of the input bit stream into single output bits are investigated.
The latter two achieve better efficiency in using bits from the primary bit
stream, the last one reaches 50\%. Compared to other generator logics, the
three extractors investigated are less performant in terms of their
cryptographic strength. However, the focus of this report is on the quality of
the pseudo-random bit stream in comparison to really random bits and on the
efficiency of using the bits of the primary stream from the LFSR and generating
valid output bits, while fulfilling a minimum cryptographic strength only,
beyond that of the pure LFSR.Comment: 18 pages, 13 figure
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