1,720,966 research outputs found
Failure analysis of a transmission tower by non-Newtonian debris flow impact with user-defined SPH particles and finite elements
No full textWe present numerical methodologies for simulating transmission tower failure under debris flow impacts. To accurately represent the shear-thinning behavior of debris flows, a user-defined Cross rheology model is implemented within the LS-DYNA SPH framework, overcoming limitations of existing built-in materials. The coupled SPH-FEM model captures strain-rate-dependent viscosity and reproduces large deformation and fluid-structure interactions. Structural failure is explicitly modeled through plasticity, energy dissipation, and element erosion, enabling detailed analysis of collapse initiation and progression. Simulations with varying debris flow volumes identify three damage limits (DL1-DL3), corresponding to initial failure, partial member failure, and total collapse of the tower, with critical flow volumes of 2,400, 3,600, and 4,500 m3, respectively. These findings offer practical insights for structural risk assessment in debris flow-prone mountainous regions.
Multiscale numerical approach to assess impact forces on cylindrical barriers by debris flows
No full textDebris flow is a flow-like landslide involving a mixture of water and earth materials that rapidly moves downslope. Conducting real-scale experiments is costly and resource-intensive, making numerical analysis an efficient alternative for evaluating the performance of countermeasures. This study investigates impact forces on barriers caused by debris flows using a multiscale numerical approach. First, a 3D depth-averaged model simulates debris flow characteristics at a channel-length scale. Then, a 3D Smoothed Particle Hydrodynamics (SPH) model examines debris-barrier interactions at a channel-width scale. Two real-scale debris flow experiments conducted in Pyeongchang, Korea, were used for validation: one without barriers for flow calibration and another with cylindrical baffle-type countermeasures for impact force validation. The depth-averaged model was calibrated to replicate observed runout distances and velocities, while the SPH model simulated interactions with cylindrical baffles. Due to the curved terrain near the first baffle array, debris primarily impacts outer baffles, resulting in higher dynamic impact coefficients. The parametric study reveals that the initial velocity has a negative correlation with the dynamic impact coefficient but a positive correlation with the Froude number. Increased density reduces both the dynamic impact coefficient and pressure gradient. In addition, previously proposed semi-empirical models effectively reproduce the summed impact forces across all baffles upon calibration against the numerical results, but capturing individual baffle's responses and estimating localized impact forces in open-type barriers still remain challenging. These findings highlight the critical influence of local terrain and flow dynamics on impact force distribution. demonstrating the values of combining numerical simulations and real-scale experiments in geohazard risk assessment and mitigation strategy development.
Physics-based landslide susceptibility machine learning model for mountainous solar power plants
No full textBetween 2018 and 2020, several landslides occurred on solar power plants constructed on hillsides after extreme rainfall in South Korea. This study presents a physics-informed machine-learning model to conduct real-time physically-based landslide susceptibility assessment on solar panels installed on mountains. Through a statistical filtering process, fourteen landslide triggering factors related to the topography, soil geotechnical properties, soil hydrological properties, meteorological effects, and solar panels model were selected. While accounting for the presence of solar panels, 136,262 numerical simulations of rainfall infiltration transient seepage and slope stability analyses were performed. Among three machine learning models (random forest, support vector regression, and multi-layer perceptron) developed from numerical simulation data points, the multi-layer perceptron (MLP) model showed the highest prediction accuracy (R2 = 96% and mean square error = 0.001) without indicating overfitting. The sensitivity analysis on the developed MLP model indicated that the soil strength properties strongly influenced the factors of safety (FOS), but hydraulic properties showed a relatively small impact. The developed MLP model was applied to a solar power plant in Jangsu-gun, Jeonbuk-do, South Korea, to verify the model’s predictability and showed the applicability of the developed MLP model for physically-based landslide susceptibility assessment. Furthermore, the Jangsu-gun example demonstrated the potentiality of the MLP model for a landslide early warning system (LEWS) for mountainous solar power plants thanks to its fast computational speed at predicting real-time FOS.
토석류 사방구조물 최적 위치선정 및 성능평가 모델
No full text학위논문(박사) - 한국과학기술원 : 건설및환경공학과, 2022.8,[viii, 127 p. :]To mitigate the risk of debris-flow hazards through barriers, efficient methods for designing optimal barriers and debris-flow analysis methods that can evaluate barrier performance are essential. The newly-developed SPEC-debris-barrier platform is multi-purpose analysis software capable of analyzing debris-flow propagation, designing optimal barriers, and evaluating closed and open-type barrier performance. The developed platform can model various barriers and utilize CPU multiprocessing to enhance computational speed. Furthermore, the platform generates 2D and 3D web-based interactive plots and animations to visualize the analysis results. The SPEC-debris simulation is a numerical analysis method incorporated into the SPEC-debris-barrier platform. The method is a meshless numerical method that follows the “equivalent fluid” principle. The following equations govern the SPEC-debris model: (a) smoothing particle hydrodynamic interpolation, (b) pathway algorithm adopted from shallow-water equations, (c) energy conservation model, and (d) collision mechanism. The SPEC-debris simulation utilizes coefficient of restitution and conservation of linear momentum to simulate the loss of kinetic energy after collision with a barrier. The optimal barrier design framework incorporated in the SPEC-debris-barrier platform is used to determine optimal barrier locations. The framework compiles the particles from the SPEC-debris method into clusters through cluster analysis, then stores the debris-flow cluster data into a network data structure. The network data structure and stochastic tabu search heuristic optimization algorithm search optimal closed and open-type barrier locations that satisfy multiple optimization criteria. The capability and applicability of the SPEC-debris-barrier platform for assessing debris-flow and designing barriers were tested and verified through back-analyses of flume test and the 2011 debris-flow incident at Mt. Umyeon, Seoul. In addition, the sensitivity analysis demonstrated the application of selecting optimal closed and open-type barrier locations. With continuous back-analyses and accurate prediction of material properties, the SPEC-debris-barrier platform should be the ideal software suite for runout simulation and mitigation design.한국과학기술원 :건설및환경공학과
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
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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