1,721,336 research outputs found
Evolution of symmetrical microvortices in a generating microdroplet during neck breakage stage in an altered T-shaped microchannel
No full textVortices are a fascinating flow phenomenon and an important research topic in fluid mechanics. In this study, the evolution of symmetrical vortices within a generating droplet in an altered T-shaped microchannel was investigated using microparticle image velocimetry (micro-PIV) and high-speed imaging microscopy. Transient flow patterns within the microdroplet were visualized in the focal plane, revealing a high-speed jet flow and two counter-rotating symmetric vortex pairs. These findings suggest that the internal flow field of the microdroplet exhibits intricate three-dimensional structures. The vortical flow behaviors were quantitatively characterized in detail by calculating the vorticity, rotation, shear deformation, and tensile deformation. These results are crucial for comprehending the initial flow dynamics and mixing processes occurring within generating microdroplets
Scattering Characteristics In Heterogeneous Fractured Reservoirs From Waveform Estimation
Full text linkOffset-dependent characteristics of seismic scattering are useful in the interpretation of fractured reservoirs. Synthetic seismograms generated by a 3-D finite difference modeling are used to study elastic wave propagation and scattering in heterogeneous fractured reservoirs. We use two models having different background medium properties and different azimuthal AVO responses and build heterogeneous fracture density realizations through stochastic modeling. Gas-saturated fractured reservoirs and waveforms ill fracture normal and strike directions are considered in this paper. The multiple signal classification (MUSIC) frequency estimator is used in waveform estimation to provide frequency domain attributes related to seismic wave scattering by fractures. Our results indicate that the strength of the scattered field increases with increasing fracture scatter density and decreasing correlation length of spatial variations of fracture density. It is also a function of the background medium. The strength of the scattering field is stronger in model 1 which has smaller property contrasts in the background medium than model 2. The scattering characteristics for both models are different at the top and the base of the fractured reservoir. Our results show that the scattered field is weak at the top of a fractured reservoir. The first order results are dominated by velocity anisotropy of a mean crack density field. However, the base of the fractured reservoir corresponds to a strong scattered field on which fracture heterogeneity has a larger effect.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation
ConsortiumUnited States. Dept. of Energy (Grant DE-82066-223II-1
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
Effects Of Fractured Reservoir Elastic Properties On Azimuthal Avo
Full text linkAligned vertical fractures introduce velocity anisotropy which is directly related to
parameters, such as fracture density, fracture shape and fracture contents. Effective
medium models allow us to study qP- and qS-wave velocity anisotropy in rocks with
aligned vertical fractures, intersecting fracture sets and aligned fractures with smallscale porosity. Spatially varying fracture density distributions result in velocity spatial variations. Stochastic modeling is used to quantify velocity heterogeneity in a fractured reservoir, where the fracture density field is modeled as a stationary Gaussian random field specified by a covariance function describing the amplitude, orientation, characteristic wavenumbers, and roughness of a fracture density field. The goal of the modeling is to relate the stochastic forward model to the statistics of the velocity and seismic reflectivity fields.
Three-dimensional finite difference modeling has been used to investigate the seismic
response of fractured reservoirs in P-wave seismic data, and the effects of background
Vs/Vp contrasts and anisotropic overburden. The numerical results indicate that background Vs/Vp contrasts across the reflecting boundary, and the presence of anisotropy
above the reservoir, have significant effects on azimuthal AVO response at the top of
fractured reservoirs. Although a larger Vs/Vp contrast gives rise to a strong AVO response in isotropic media, it is not necessary to give rise to a strong azimuth AVO
response. Our numerical modeling shows that the smaller Vs/Vp contrast model gives
rise to a strong azimuthal AVO response. Anisotropic overburden always modifies the
azimuthal AVO response.Massachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation
Consortiu
P and SV waves 3-D Numerical Modeling of AVOA from Heterogeneous Fractured Reservoirs
Full text linkWe study the effects of fracture-induced anisotropy and lateral fracture density heterogeneity on the reflected P and SV wave amplitude variation with offset and azimuth (AVOA), using 3-D finite-difference simulations. The models show that for an isotropic layer overlying on a fractured reservoir, the anisotropic behavior of AVOA depends on fracture density as well as the contrast in elastic properties between the reservoir layer and the overlying material. It is also verified that the SV wave is more sensitive to fractures than the P wave. The sensitivity of AVOA to spatial variations of fracture density is also investigated
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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