1,721,029 research outputs found
Physicochemical processes of frictional healing: Effects of water on stick-slip stress drop and friction of granular fault gouge
No full text
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
Experimental constraints on the relationship between clay abundance, clay fabric, and frictional behavior for the central deforming zone of the San Andreas fault
No full textThe presence of smectite (saponite) in fault gouge from the Central Deforming Zone of the San Andreas Fault at Parkfield, CA has been linked to low mechanical strength and aseismic slip. However, the precise relationship between clay mineral structure, fabric development, fault strength, and the stability of frictional sliding is not well understood. We address these questions through the integration of laboratory friction tests and FIB-SEM analysis of fault rock recovered from the San Andreas Fault Observatory at Depth (SAFOD) borehole. Intact fault rock was compared with experimentally sheared fault gouge and different proportions of either quartz clasts or SAFOD clasts extracted from the sample. Nano-textural measurements show the development of localized clay particle alignment along shear folia developed within synthetic gouges; such slip planes have multiples of random distribution (MRD) values of 3.0-4.9. The MRD values measured are higher than previous estimates (MRD 1.5) that show lower degrees of shear localization and clay alignment averaged over larger volumes. The intact fault rock exhibits less well-developed nano-clay fabrics than the experimentally sheared materials, and MRD values decrease with smectite content. We show that the abundance, strength, and shape of clasts all influence fabric evolution via strain localization: quartz clasts yield more strongly developed clay fabrics than serpentine-dominated SAFOD clasts. Our results suggest that (1) both clay abundance and the development of nano-scale fabrics play a role in fault zone weakening and (2) aseismic creep is promoted by slip along clay shears with >20 wt % smectite content and MRD values >= 2.7
Cold Diffusion Model for Seismic Denoising
Get PDFSeismic waves contain information about the earthquake source, the geologic structure they
traverse, and many forms of noise. Separating the noise from the earthquake is a difficult task because optimal
parameters for filtering noise typically vary with time and, if chosen inappropriately, may strongly alter the
original seismic waveform. Diffusion models based on Deep Learning have demonstrated remarkable
capabilities in restoring images and audio signals. However, those models assume a Gaussian distribution of
noise, which is not the case for typical seismic noise. Motivated by the effectiveness of “cold” diffusion models
in speech enhancement, medical anomaly detection, and image restoration, we present a cold variant for seismic
data restoration. We describe the first Cold Diffusion Model for Seismic Denoising (CDiffSD), including key
design aspects, model architecture, and noise handling. Using metrics to quantify the performance of CDiffSD
models compared to previous works, we demonstrate that it provides a new standard in performance. CDiffSD
significantly improved the Signal to Noise Ratio by about 18% compared to previous models. It also enhanced
Cross‐correlation by 6%, showing a better match between denoised and original signals. Moreover, testing
revealed a 50% increase in the recall of P‐wave picks for seismic picking. Our work show that CDiffSD
outperforms existing benchmarks, further underscoring its effectiveness in seismic data denoising and analysis.
Additionally, the versatility of this model suggests its potential applicability across a range of tasks and
domains, such as GNSS, Lab Acoustic Emission, and Distributed Acoustic Sensing data, offering promising
avenues for further utilization
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
Experimental Studies of Electrical Fields on a Breaking Rock Sample
No full textWhen a rock sample is pressed by a force, the pressure on the crystal lattice generates an electrical field around the quart grains due to the piezoelectric effect. If a rock is saturated by conductive fluid, the relative motion between the pore fluid and the matrix solid generates an electromagnetic field due to seismoelectric conversion, and the permeating of fluid into new microcracks made by the pressure changes the fluid distribution and the natural potential level.
In this paper, we measure the electrical fields on dry and water-saturated Westerly granite cylinder samples during their breaking. Experimental results show that there are two kinds of mechanisms that generate two kinds of electrical fields during rock breaking: (1) Pressure, or rock breaking, generates an electrical potential on the dry rock surface due to piezoelectric effect; and (2) the potential on a dry sample due to a piezoelectric effect is small, and its polarization depends on the characteristic and orientation of quartz grains around the measurement point. Experiments with water-saturated granite samples record two electrical fields: An electromagnetic wave due to seismoelectric conversion, and the dc or low-frequency electrical potential due to the piezoelectric effect, which is an important indicator of rock breaking
- …
