1,722,343 research outputs found
Characterizing the hysteretic response of extended endplate connections based on deformation mode classification
No full textExtended endplate connections (EEPCs) response ranges from full strength to partial strength. In the former, beam buckling is the primary deformation mode, while in the latter, a multitude of deformation modes can occur individually or simultaneously, including endplate bending, column flange bending, and column web-panel zone shear deformation. The deformation mode controls the connection's hysteretic response under cyclic drift demands, and particularly the magnitude of the pinching behavior. To that end, a data-driven study was conducted to first classify the primary deformation mode in EEPCs, out of six prescribed modes, given their geometric layout and material parameters. This is done using decision tree-based approaches that were trained using a large experimental/simulation dataset of more than 1200 data points. The new model constitutes a faster and more accurate alternative to existing analytical and mechanical models. Second, recommendations are provided for the numerical modeling of the connection hysteretic response as part of phenomenological deterioration models. Specifically, empirical values are provided for the pinching, stiffness degradation, and strength degradation parameters. The developed classification model and empirical hysteretic parameters aim to assist in achieving targeted designs and in conducting accurate system-level dynamic simulations
Estimation of Site Effects in Beijing City
No full textFor the realistic modeling of the seismic ground motion in lateral heterogeneous anelastic media, the database of 3-D geophysical structures for Beijing City has been built up to model the seismic ground motion in the City, caused by the 1976 Tangshan and the 1998 Zhangbei earthquakes. The hybrid method, which combines the modal summation and the finite-difference algorithms, is used in the simulation. The modeling of the seismic ground motion, for both the Tangshan and the Zhangbei earthquakes, shows that the thick Quaternary sedimentary cover amplifies the peak values and increases the duration of the seismic ground motion in the northwestern part of the City. Therefore the thickness of the Quaternary sediments in Beijing City is the key factor controling the local ground effects. Four zones are defined on the base of the different thickness of the Quaternary sediments. The response spectra for each zone are computed, indicating that peak spectral values as high as 0.1 g are compatible with past seismicity and can be well exceeded if an event similar to the 1697 Sanhe-Pinggu occurs
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
High resolution Rayleigh wave group velocity tomography in North China from ambient seismic noise
No full textThis study presents the results of the Rayleigh wave group velocity tomography in North
China performed using ambient seismic noise observed at 190 broadband and 10 very broadband
stations of the North China Seismic Array. All available vertical component time-series
for the 14 months between 2007 January and 2008 February are cross-correlated to obtain
empirical Rayleigh wave Green’s functions that are subsequently processed, with the multiple
filter method, to isolate the group velocity dispersion curves of the fundamental mode of the
Rayleigh wave. Tomographic maps, with a grid spacing of 0.25◦ × 0.25◦, are computed at
periods of 4.5, 12, 20 and 28 s. The maps at short periods reveal lateral heterogeneity in the
crust of North China, in good agreement with known geological and tectonic features. The
North China Basin is imaged as a broad low velocity area, while the Taihangshan and Yanshan
uplifts and Ordos block are imaged as high velocity zones, and the Quaternary intermountain
basins show up as small low-velocity anomalies. A well-defined low velocity zone in the
Beijing–Tianjin–Tangshan region is observed at 28 s period. The low velocity zone may be
associated with the upwelling of hot mantle material. The group velocity maps at 4.5, 12 and
20 s are consistent with Bouguer gravity anomalies measured in the area of the Taihangshan
fault, that cuts through the lower crust at least
Simultaneous Fault Diagnosis and Size Estimation Using Multitask Federated Incremental Learning
No full textFederated learning (FL)-based fault diagnosis is being widely developed. However, most of the existing FL methods may suffer from two drawbacks: 1) they are limited to a single diagnosis task, and this may be insufficient when comprehensive health status information is needed and 2) most of them work offline, thus neglecting the useful information contained in newly collected operation data. For this end, this article proposes a multitask federated incremental learning (multitask-FIL) framework. First of all, a multitask feature sharing network is established by assigning the extracted general features to different downstream tasks, so that the joint loss function is obtained for subsequent collaborative training. Then, Q-learning algorithm is used to select the incremental sequences for all the parties from real-time running data, which can facilitate the model performance by involving additional data information and preferred parties. After that, the incremental weight of each party is dynamically adjusted according to the loss depth and sample size in each round of communication, so that the effects of different parties can be quantified throughout the model iteration and aggregation process. Finally, experiments on three challenging cases are performed to show that the proposed method has strong multitask collaboration capability
Fillunger-Heinrich's Theory of Porodynamics: Predictive Power and Analytical Solution
No full textThe first articulation of the second type of dilatational wave propagating through fluid-saturated geomaterials has been traced to Heinrich's formulation built on Fillunger's framework of the mixture theory and Terzaghi's principle of effective stress. Although this Fillunger-Heinrich theory (FHT) precedes the celebrated Biot's wave theory and Frenkel's theory, research has yet to systematically investigate the FHT's predictive ability. To value the scientific heritage, the original formulation of FHT was first revisited with minor corrections and then reformulated in a dimensionless form. Using the method of separation of variables, an analytical solution was developed for the dimensionless FHT in the context of consolidation under instantaneously applied surcharge and with one-way drainage at the top boundary of the consolidating stratum. The predictive power of FHT was validated against available wave measurements; the proposed solution was verified against the finite-difference method with nonclassical Newmark's integration schemes. The parametric analysis conducted herein further suggests that FHT can qualitatively interpret observed complex phenomena, including the consolidation delay effect, the top-down progressive pattern, and the initial settlement overestimation. FHT significantly fills the knowledge gap between Terzaghi's classic theory and Biot's theory, thus enabling engineers to analyze the one-dimensional dynamic behavior of saturated geo-/poro-materials with incompressible constituents
Improving the Split-Spectrum Method for Sentinel-1 Differential TOPSAR Interferometry
No full textDifferential SAR interferometry (DInSAR) is a useful technique used to measure small movements and surface deformation. However, ionospheric phase screens are a major error source in multipass terrain observation by progressive scans sar (TOPSAR) interferograms. In this letter, an improved split-spectrum method is proposed. First, the burst used for ionospheric phase estimation is selected through coherence, and then, the ionospheric phase of the burst is estimated based on the split-spectrum method. Finally, the TOPSAR ionospheric space-variable phase in a large scene is obtained through 2-D space-variable fitting, which avoids the complicated processing of splicing between bursts of different periods and reduces the number of unwrapping calculations for large scenes after splicing. The method can ensure that the number of calculations is reduced without loss of accuracy. Sentinel-1 TOPSAR real data processing verifies the correctness of the proposed method
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