scholarly journals Simulation of Full-Scale Rockfall Tests with a Fragmentation Model

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 168 ◽  
Author(s):  
Gerard Matas ◽  
Nieves Lantada ◽  
Jordi Corominas ◽  
Josep Gili ◽  
Roger Ruiz-Carulla ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Spatial Distribution ◽  
Parametric Analysis ◽  
Fractal Model ◽  
Stochastic Program ◽  
Fragmentation Model ◽  
Volume Distribution ◽  
Fractal Fragmentation ◽  
The Impact ◽  
Real Scale

In this paper, we present the upgraded version of RockGIS, a stochastic program for the numerical simulation of rockfalls and their fragmentation, based on a fractal model. The code has been improved to account for a range of fragmentation scenarios, depending on the impact conditions. In the simulation, the parameters of the fractal fragmentation model that define the sizes of the generated fragments were computed at each impact according to the kinematic conditions. The performance of the upgraded code was verified and validated by real-scale rockfall tests performed in a quarry. The tests consisted of the release of 21 limestone blocks. For each release, the size and spatial distribution of the fragments generated by the impacts were measured by hand and from orthophotos taken via drone flights. The trajectories of the blocks and the resulting fragments were simulated with the code and calibrated with both the volume distribution and the runout distances of the fragments. Finally, as all the relevant rockfall parameters involved were affected by strong uncertainty and spatial variability, a parametric analysis was carried out and is discussed.

Rockfall fragmentation simulations of real scale tests

2020 ◽  
Author(s):  
Gerard Matas ◽  
Nieves Lantada ◽  
Jordi Corominas ◽  
Josep Antoni Gili ◽  
Roger Ruiz-Carulla ◽  
...  
Keyword(s):  
Size Distribution ◽  
Block Size ◽  
Energy Conditions ◽  
Fragmentation Model ◽  
Model Parameters ◽  
Size Distributions ◽  
Lumped Mass ◽  
Fractal Fragmentation ◽  
The Impact ◽  
Real Scale

<p>Consideration of fragmentation during rockfalls is relevant for the assessment of hazard since it affects the number of generated blocks, their trajectories and impact energies, which also depends on the topography. Recently many scholars have paid attention to these phenomena since there are still many uncertainties around fragmentation regarding how mass and energy are distributed after fragmentation and how trajectory dispersion affects risk analysis. We developed a specific fragmentation model (Rockfall Fractal Fragmentation Model), as well as a 3D trajectory simulator called RockGIS with the fragmentation module implemented. In this contribution, we present the calibration of our rockfall trajectory simulator, based on real scale fragmentation tests performed on a quarry.</p><p>The RockGIS model considers a lumped mass approach and accounts block fragmentation upon impact with the terrain. Some improvements have been made on the simulator code regarding the consideration of rotation inside the kinematics of the model and restitution factors. The block size distributions obtained from natural rockfall events inventoried, as well as from the real scale fragmentation tests in a quarry, shows a fractal behaviour. On this way, the fractal fragmentation model implemented in the RockGIS simulator is able to reproduce the observed block size distributions.</p><p>To calibrate the model we used data gathered from a real scale rockfall test performed in a quarry. We calibrate the relations between the impact energy conditions and the fragmentation model parameters to generate the measured fragments size distribution. The initial volume of the tested blocks were measured manually using a tape and the release positions of the blocks were obtained with terrestrial photogrammetry. Both, the volume and spatial distribution of the fragments after each release were measured on the orthophotos obtained from UAV flights. Three calibration criteria were considered: runout distribution, volume distribution and cumulative volume as a function of the runout. Finally, the degree of fragmentation can be adjusted in the simulations allowing the comparison between different possible hazard scenarios (null, moderate, or severe fragmentation).</p><p>Finally, the results of the calibration shows that the RockGIS is able to reproduce the fragmentation behaviour in terms of block size distribution after breakage, as well as the spatial propagation, being a new tool with capabilities to assess the hazard related with fragmental rockfalls and the consequently risk associated.</p><p><span>The RockGIS tool and the fragmentation model based on the data collected from recent rockfall events have been developed within the RockRisk (2014-2016, BIA2013-42582-P) and RockModels (2016-2019, BIA2016-75668-P, AEI/FEDER, UE) projects. Both projects were funded by the Spanish Ministerio de Economía y Competitividad.</span></p>

Real Scale Simulation of Ballistic Tests for Multi-Layer Fabric Body Armors

2014 ◽  
Author(s):  
Mario Dippolito ◽  
Youqi Wang ◽  
Ying Ma ◽  
Chian-Fong Yen ◽  
James Q. Zheng ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Design Process ◽  
Ballistic Impact ◽  
Element Mesh ◽  
Hybrid Mesh ◽  
Hybrid Element ◽  
Element Approach ◽  
Ballistic Tests ◽  
The Impact ◽  
Real Scale

The bottle-neck issues to resolve for numerical simulation of real scale ballistic tests of fabric body armors are computer capacity limitation and prohibitive computational cost. It is not realistic to use micro-level computer simulations for an open end design process. Most numerical simulations are only applicable for small scale parametric analyses, which could facilitate apprehension of fabric failure mechanisms during ballistic impact, but not applicable for the design process. In this paper, a sub-yarn model, the digital element approach, is applied to simulate real scale ballistic tests for soft body armors. In this approach, a yarn is discretized into multiple digital fibers and each fiber is discretized into many digital elements. In order to improve efficiency, two hybrid element mesh concepts are investigated: area based hybrid mesh and yarn based hybrid mesh. The area based hybrid mesh procedure is similar to one utilized in the conventional finite element approach. A fine element mesh is adopted in the area near the impact center; a course element mesh in the area far away. However, numerical simulation results show that the stress wave travels along the principal yarns at the speed of sound immediately after ballistic impact. High yarn stress develops quickly from the impact center to a distance along the principal yarn. As such, the area based hybrid mesh approach fails to obtain improved computer efficiency without loss of accuracy. Because the high stress only develops within principal yarns after a ballistic impact, a yarn based hybrid element mesh procedure is adopted. In this procedure, only principal yarns and yarns near principal yarns are discretized into fine digital fibers; other yarns are discretized into coarse digital fibers. Because only a few principal yarns resist load in a typical ballistic impact, the yarn based hybrid technique could improve simulation efficiency up to 90–95% without sacrificing accuracy. A numerical tool is then developed to generate fabric with a yarn based hybrid mesh. Accuracy of the approach is analyzed. The hybrid mesh technique is applied to simulate real scale ballistic tests of ballistic armors made of 4 to 20 piles of 2-D plain woven fabrics. Numerical results are compared to real scale standard ballistic results.

Modelling Agricultural Controls for Flooding and Soil Erosion

2018 ◽  
pp. 776-796
Author(s):  
Roger Moussa ◽  
Bruno Cheviron
Keyword(s):  
Spatial Distribution ◽  
Model Structure ◽  
Land Uses ◽  
Research Challenges ◽  
Water And Sediment ◽  
Flow Processes ◽  
Cultivation Practices ◽  
Modelling Strategies ◽  
The Impact ◽  
Significant Factors

Floods are the highest-impact natural disasters. In agricultural basins, anthropogenic features are significant factors in controlling flood and erosion. A hydrological-hydraulic-erosion diagnosis is necessary in order to choose the most relevant action zones and to make recommendations for alternative land uses and cultivation practices in order to control and reduce floods and erosion. This chapter first aims to provide an overview of the flow processes represented in the various possible choices of model structure and refinement. It then focuses on the impact of the spatial distribution and temporal variation of hydrological soil properties in farmed basins, representing their effects on the modelled water and sediment flows. Research challenges and leads are then tackled, trying to identify the conditions in which sufficient adequacy exists between site data and modelling strategies.

scholarly journals Measuring spatial allocative efficiency in basketball

2020 ◽  
Vol 16 (4) ◽  
pp. 271-289
Author(s):  
Nathan Sandholtz ◽  
Jacob Mortensen ◽  
Luke Bornn
Keyword(s):  
Spatial Distribution ◽  
Hierarchical Model ◽  
Opportunity Cost ◽  
Allocative Efficiency ◽  
Bayesian Hierarchical Model ◽  
National Basketball Association ◽  
Spatial Context ◽  
Bayesian Hierarchical ◽  
The Impact

AbstractEvery shot in basketball has an opportunity cost; one player’s shot eliminates all potential opportunities from their teammates for that play. For this reason, player-shot efficiency should ultimately be considered relative to the lineup. This aspect of efficiency—the optimal way to allocate shots within a lineup—is the focus of our paper. Allocative efficiency should be considered in a spatial context since the distribution of shot attempts within a lineup is highly dependent on court location. We propose a new metric for spatial allocative efficiency by comparing a player’s field goal percentage (FG%) to their field goal attempt (FGA) rate in context of both their four teammates on the court and the spatial distribution of their shots. Leveraging publicly available data provided by the National Basketball Association (NBA), we estimate player FG% at every location in the offensive half court using a Bayesian hierarchical model. Then, by ordering a lineup’s estimated FG%s and pairing these rankings with the lineup’s empirical FGA rate rankings, we detect areas where the lineup exhibits inefficient shot allocation. Lastly, we analyze the impact that sub-optimal shot allocation has on a team’s overall offensive potential, demonstrating that inefficient shot allocation correlates with reduced scoring.

A Pandemic of Violence? The Impact of COVID-19 on Conflict

2020 ◽  
Vol 26 (3) ◽  
Author(s):  
Sara M.T. Polo
Keyword(s):  
Spatial Distribution ◽  
Real Time ◽  
Case Studies ◽  
Armed Conflict ◽  
Event Data ◽  
Social Unrest ◽  
Johns Hopkins University ◽  
The World ◽  
Political Advantage ◽  
The Impact

AbstractThis article examines the impact and repercussions of the COVID-19 pandemic on patterns of armed conflict around the world. It argues that there are two main ways in which the pandemic is likely to fuel, rather than mitigate, conflict and engender further violence in conflict-prone countries: (1) the exacerbating effect of COVID-19 on the underlying root causes of conflict and (2) the exploitation of the crisis by governments and non-state actors who have used the coronavirus to gain political advantage and territorial control. The article uses data collected in real-time by the Armed Conflict Location & Event Data Project (ACLED) and the Johns Hopkins University to illustrate the unfolding and spatial distribution of conflict events before and during the pandemic and combine this with three brief case studies of Afghanistan, Nigeria, and Libya. Descriptive evidence shows how levels of violence have remained unabated or even escalated during the first five months of the pandemic and how COVID-19-related social unrest has spread beyond conflict-affected countries.

scholarly journals Spatial distribution patterns of soil total phosphorus influenced by climatic factors in China’s forest ecosystems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jie Zhu ◽  
Anchi Wu ◽  
Guoyi Zhou
Keyword(s):  
Spatial Distribution ◽  
Forest Ecosystems ◽  
Climatic Factors ◽  
Critical Role ◽  
Effect Of Temperature ◽  
P Concentration ◽  
Single Effect ◽  
The Impact ◽  
P Distribution ◽  
Total P

AbstractPhosphorus (P) is an important element in terrestrial ecosystems and plays a critical role in soil quality and ecosystem productivity. Soil total P distributions have undergone large spatial changes as a result of centuries of climate change. It is necessary to study the characteristics of the horizontal and vertical distributions of soil total P and its influencing factors. In particular, the influence of climatic factors on the spatial distribution of soil total P in China’s forest ecosystems remain relatively unknown. Here, we conducted an intensive field investigation in different forest ecosystems in China to assess the effect of climatic factors on soil total P concentration and distribution. The results showed that soil total P concentration significantly decreased with increasing soil depth. The spatial distribution of soil total P increased with increasing latitude and elevation gradient but decreased with increasing longitude gradient. Random forest models and linear regression analyses showed that the explanation rate of bioclimatic factors and their relationship with soil total P concentration gradually decreased with increasing soil depths. Variance partitioning analysis demonstrated that the most important factor affecting soil total P distribution was the combined effect of temperature and precipitation factor, and the single effect of temperature factors had a higher explanation rate compare with the single effect of precipitation factors. This work provides a new farmework for the geographic distribution pattern of soil total P and the impact of climate variability on P distribution in forest ecosystems.

scholarly journals Spatial Dependence Evaluation of Agricultural Technical Efficiency—Based on the Stochastic Frontier and Spatial Econometric Model

2021 ◽  
Vol 13 (5) ◽  
pp. 2708
Author(s):  
Ziqi Yin ◽  
Jianzhai Wu
Keyword(s):  
Spatial Distribution ◽  
Technical Efficiency ◽  
Spatial Dependence ◽  
Stochastic Frontier ◽  
Hebei Province ◽  
Agricultural Technology ◽  
Agricultural Product ◽  
Spatial Econometric ◽  
Frontier Analysis ◽  
The Impact

In recent years, through the implementation of a series of policies, such as the delimitation of major grain producing areas and the construction of advantageous and characteristic agricultural product areas, the spatial distribution of agriculture in China has changed significantly; however, research on the impact of such changes on the efficiency of agricultural technology is still lacking. Taking 11 cities in Hebei Province as the research object, this study examines the spatial dependence of regional agricultural technical efficiency using the stochastic frontier analysis and spatial econometric analysis. The results show that the improvement in agricultural technical efficiency is evident in all cities in Hebei Province from 2008 to 2017, but there is scope for further improvement. Industrial agglomeration has statistical significance in improving the efficiency of agricultural technology. Further, there is an obvious spatial correlation and difference in agricultural technical efficiency. Optimizing the spatial distribution of agricultural production, promoting the innovation, development, and application of agricultural technology, and promoting the expansion of regional elements can contribute to improving agricultural technical efficiency.

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