scholarly journals Predictive Capabilities of 2D and 3D Block Propagation Models Integrating Block Shape Assessed from Field Experiments

Author(s):  
Franck Bourrier ◽  
Vincent Acary
2021 ◽  
Author(s):  
Franck Bourrier ◽  

<p>A comparative analysis between block propagation experiments and predictive simulations of block trajectories was conducted to evaluate the predictive capacities of block propagation analyses. Approximately one hundred blocks were released on two propagation paths with topographical discontinuities and configurations promoting block rolling. The block propagation was analysed at specific locations of the paths, called evaluation screens. A significant variability of the block velocities was measured at the screens and bimodal distributions of the velocities were observed for the screens located downhill topographical discontinuities.</p><p>The comparative analysis between the experimental results and the predictive simulations shows a large variability of the simulations results, that illustrates the uncertainties related with these predictions, done without calibration data. Specific limitations of the block propagation models were shown as regards to the modelling of block propagation similar to rolling motion on soft soils. Finally, the simulations were shown more predictive for extreme velocities than for mean ones and for block passing probabilities.</p><div> <div> <div></div> <div>What do you want to do ?</div> New mail</div> </div><div> <div> <div></div> <div>What do you want to do ?</div> New mail</div> </div>


2021 ◽  
Author(s):  
Vincent Acary ◽  
Franck Bourrier ◽  
David Toe ◽  
Francois Kneib

<p><br>Block propagation models are routinely used for the quantitative assessment of rockfall hazard. In these models, one of the major difficulties is the development of physically consistent and field applicable approaches to model the interaction between the block and the natural terrain. For most of propagation models, a thorough calibration of the input parameters is not available over the wide range of configurations encountered in practice. Consequently, the parameters choice is strongly depending on expert knowledge. In addition, most of models exhibit substantial sensitivity to some parameters, i.e. small changes of these parameters entail large differences in the simulation results.</p><p>The trajectory analysis platform Platrock, freely available upon request (contact: [email protected]), allows performing 2D and 3D simulations using both material point rebound models and models, based on non-smooth mechanics, that explicitly account for block shape. This platform provides several simulation tools for detailed analyses of block propagation on study sites.</p><p>The possibilities of the predictive capabilities of different block propagation modelling approaches integrated into the Platrock platform have been assessed on a well-documented study site, where a benchmark of propagation models has been done in the context of C2ROP research project. This analysis emphasized the capacities of trajectory analyses to traduce block propagation but also demonstrated their substantial sensitivity to model parameters. The results from these simulations cannot be relevantly interpreted if they are not accompanied with calibration proofs, sensitivity analysis, and detailed interpretation of the results from the expert in charge of the study.</p>


Author(s):  
M. Jose Yacaman

In the Study of small metal particles the shape is a very Important parameter. Using electron microscopy Ino and Owaga(l) have studied the shape of twinned particles of gold. In that work electron diffraction and contrast (dark field) experiments were used to produce models of a crystal particle. In this work we report a method which can give direct information about the shape of an small metal particle in the amstrong- size range with high resolution. The diffraction pattern of a sample containing small metal particles contains in general several systematic and non- systematic reflections and a two-beam condition can not be used in practice. However a N-beam condition produces a reduced extinction distance. On the other hand if a beam is out of the bragg condition the effective extinction distance is even more reduced.


Author(s):  
P.M. Rice ◽  
MJ. Kim ◽  
R.W. Carpenter

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.


2021 ◽  
Author(s):  
Ruoyang Liu ◽  
Ke Tian Tan ◽  
Yifan Gong ◽  
Yongzhi Chen ◽  
Zhuoer Li ◽  
...  

Covalent organic frameworks offer a molecular platform for integrating organic units into periodically ordered yet extended 2D and 3D polymers to create topologically well-defined polygonal lattices and built-in discrete micropores and/or mesopores.


2010 ◽  
Author(s):  
Susan M. Kochanowski ◽  
Charles F. Seifert ◽  
Gary A. Yukl ◽  
Dov Eden ◽  
Gary P. Latham
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