Micro-Tomography to Characterize Size Distribution of Fragments Created by Laser Shock-Induced Micro-Spallation of Metallic Sample

2014 ◽  
Vol 566 ◽  
pp. 225-231 ◽  
Author(s):  
D. Loison ◽  
T. de Resseguier ◽  
A. Dragon
Keyword(s):  
Size Distribution ◽  
High Energy ◽  
Size Distributions ◽  
Laser Shock ◽  
Synchrotron Facility ◽  
Theoretical Predictions ◽  
Ballistic Properties ◽  
Molten Droplets ◽  
Micro Tomography ◽  
Metallic Sample

Dynamic fragmentation in the liquid state after shock-induced melting, usually referred to as micro-spallation, is an issue of great interest for both basic and applied science. Recent efforts have been devoted to the characterization of the resulting ejecta, which consist in a cloud of fine molten droplets. We present laser shock experiments on tin and aluminium, to pressure ranging from about 50 to 300 GPa, with complementary diagnostics including a Photonic Doppler Velocimeter (PDV) set at a small tilt angle from the normal to the free surface, which enables probing the whole cloud of ejecta1, and a soft recovery device consisting of a low density gel to collect debris. Optical microscopy of these gel collectors reveals the presence of droplets which confirm shock-induced melting prior to fragmentation. To quantify size distribution of the collected debris, 3D micro-tomography has been performed, using the consistent and high-energy X-ray irradiation available at the ESRF synchrotron facility in France (similar to Japan SPRING-8), where sub-micrometer spatial resolution could be achieved. In this paper, the resulting size distributions are presented and compared with theoretical predictions based on a one-dimensional description accounting for laser shock loading, wave propagation, phase transformations, and fragmentation. Discrepancies between measured and calculated size distributions are discussed. Finally, combining size and velocity data provides access to the ballistic properties of debris and their kinetic energy, which are key issues for anticipating the damage produced by their impacts on nearly equipments.

Electrochemical feedback on strain dynamics in noble metal nanocatalysts

2021 ◽  
Author(s):  
Raphael Chattot ◽  
Isaac Martens ◽  
Marta Mirolo ◽  
Michal Ronovsky ◽  
Florian Russello ◽  
...  
Keyword(s):  
Structural Integrity ◽  
High Energy ◽  
Liquid Electrolyte ◽  
Model Description ◽  
Reactivity Descriptors ◽  
Storage Devices ◽  
Electrochemical Processes ◽  
Synchrotron Facility ◽  
Energy Conversion And Storage ◽  
Theoretical Predictions

Abstract The theoretical design of effective metal electrocatalysts for energy conversion and storage devices relies on the structure sensitivity of electrochemical processes to their catalyst materials, assuming the structural integrity during operation. However, theoretical predictions do not necessarily match practical performance. Here, by using high-energy X-ray diffraction from the new Extremely Brilliant Source of the European Radiation Synchrotron Facility (ESRF-EBS) on device-relevant Pd and Pt nanocatalysts during cyclic voltammetry experiments in liquid electrolyte, we quantitatively reveal how different electrochemical processes permanently affect the bulk microstructure of nanocatalysts in a distinctive fashion. The reported structural insights provide experimental access to reactivity descriptors such as adsorption and absorption trends operando. The ease and power of such an experimental approach at new and future beamlines is foreseen to guide computational model description of practical nanomaterials in electrochemical environment while providing a discovery platform toward the study of nanocatalysts encompassing a large variety of applications.

scholarly journals Automated iceberg detection using Landsat: method and example application in Disko Bay, west Greenland

2018 ◽  
Author(s):  
Jessica Scheick ◽  
Ellyn M. Enderlin ◽  
Gordon Hamilton
Keyword(s):  
Time Series ◽  
Size Distribution ◽  
Automated Analysis ◽  
High Energy ◽  
Direct Result ◽  
Freshwater Flux ◽  
Ecosystem Structure ◽  
Size Distributions ◽  
Negative Power ◽  
West Greenland

Abstract. Over the last two decades, the flux of icebergs into Greenland's fjords and coastal waters has increased, concurrent with changes in mass loss and dynamics of Greenland's marine-terminating outlet glaciers. Icebergs impact fjord circulation and stratification, freshwater flux, and ecosystem structure and pose a hazard to marine navigation and infrastructure, yet they remain a relatively understudied component of the ice-ocean system. Icebergs are easily detected in optical satellite imagery, but manual analysis to derive an iceberg size distribution time series is time prohibitive and partially cloudy scenes pose a challenge to automated analysis. Here we present a novel, computationally simple machine learning-based cloud mask for Landsat 7 and 8. This mask is incorporated into a larger iceberg delineation algorithm that allows us to extract iceberg size distributions, including outlines of individual icebergs, for cloud-free and partially cloud-covered Landsat scenes. We applied the algorithm to the Landsat archive covering Disko Bay, west Greenland, to derive a time series of iceberg size distributions from 2000–2002 and 2013–2015. The time series captures the seasonal signal in ice cover resulting from the annual cycles of sea ice formation and breakup and calving of Jakobshavn Isbrae, the dominant source of icebergs in Disko Bay. We note a change in this annual signal during the latter time period, likely a direct result of changes in the calving regime of Jakobshavn Isbrae. During 2000–2002, Jakobshavn Isbrae's floating ice tongue disintegrated and disappeared, transitioning the glacier from low energy, tabular iceberg calving to high energy, full thickness calving and the production of more small icebergs. This transition is also evident in the change in the number of small (~ 225 m2) icebergs found on the bay, which increased during the latter period. The change in the number of small icebergs also led to increasingly negative power law slopes fit to the iceberg size distribution time series. This work suggests that iceberg size distribution time series may provide useful insights into changes in calving dynamics and the physics of iceberg decay, while aiding marine and navigation safety in iceberg laden waters.

scholarly journals Effect of Strain-Induced Precipitation on the Recrystallization Kinetics in a Model Alloy

2021 ◽  
Author(s):  
Mo Ji ◽  
Martin Strangwood ◽  
Claire Davis
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Avrami Exponent ◽  
Model Alloy ◽  
Size Distributions ◽  
Recrystallization Kinetics ◽  
Grain Size Distributions ◽  
Recrystallized Grain Size ◽  
Nb Addition

AbstractThe effects of Nb addition on the recrystallization kinetics and the recrystallized grain size distribution after cold deformation were investigated by using Fe-30Ni and Fe-30Ni-0.044 wt pct Nb steel with comparable starting grain size distributions. The samples were deformed to 0.3 strain at room temperature followed by annealing at 950 °C to 850 °C for various times; the microstructural evolution and the grain size distribution of non- and fully recrystallized samples were characterized, along with the strain-induced precipitates (SIPs) and their size and volume fraction evolution. It was found that Nb addition has little effect on recrystallized grain size distribution, whereas Nb precipitation kinetics (SIP size and number density) affects the recrystallization Avrami exponent depending on the annealing temperature. Faster precipitation coarsening rates at high temperature (950 °C to 900 °C) led to slower recrystallization kinetics but no change on Avrami exponent, despite precipitation occurring before recrystallization. Whereas a slower precipitation coarsening rate at 850 °C gave fine-sized strain-induced precipitates that were effective in reducing the recrystallization Avrami exponent after 50 pct of recrystallization. Both solute drag and precipitation pinning effects have been added onto the JMAK model to account the effect of Nb content on recrystallization Avrami exponent for samples with large grain size distributions.

scholarly journals Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study

2004 ◽  
Vol 4 (5) ◽  
pp. 1255-1263 ◽  
Author(s):  
B. Mayer ◽  
M. Schröder ◽  
R. Preusker ◽  
L. Schüller
Keyword(s):  
Remote Sensing ◽  
Size Distribution ◽  
Droplet Size ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Single Scattering ◽  
Effective Radius ◽  
Radiative Properties ◽  
High Angular Resolution ◽  
Size Distributions

Abstract. Cloud single scattering properties are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI) in 180° backscatter geometry, we found that high angular resolution aircraft observations of the glory provide unique new information which is not available from traditional remote sensing techniques: Using only one single wavelength, 753nm, we were able to determine not only optical thickness and effective radius, but also the width of the size distribution at cloud top. Applying this novel technique to the ACE-2 CLOUDYCOLUMN experiment, we found that the size distributions were much narrower than usually assumed in radiation calculations which is in agreement with in-situ observations during this campaign. While the shape of the size distribution has only little relevance for the radiative properties of clouds, it is extremely important for understanding their formation and evolution.

Factors Influencing the Particle Size Distribution in an Abrasive Waterjet

1991 ◽  
Vol 113 (4) ◽  
pp. 402-411 ◽  
Author(s):  
T. J. Labus ◽  
K. F. Neusen ◽  
D. G. Alberts ◽  
T. J. Gores
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Cutting Speed ◽  
Target Material ◽  
Abrasive Waterjet ◽  
Sieve Analysis ◽  
Size Distributions ◽  
Mixing Process ◽  
Jet Mixing

A basic investigation of the factors which influence the abrasive jet mixing process was conducted. Particle size analysis was performed on abrasive samples for the “as-received” condition, at the exit of the mixing tube, and after cutting a target material. Grit size distributions were obtained through sieve analysis for both water and air collectors. Two different mixing chamber geometries were evaluated, as well as the effects of pressure, abrasive feed rate, cutting speed, and target material properties on particle size distributions. An analysis of the particle size distribution shows that the main particle breakdown is from 180 microns directly to 63 microns or less, for a nominal 80 grit garnet. This selective breakdown occurs during the cutting process, but not during the mixing process.

scholarly journals Universal opening of four-loop scattering amplitudes to trees

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Selomit Ramírez-Uribe ◽  
Roger J. Hernández-Pinto ◽  
Germán Rodrigo ◽  
German F. R. Sborlini ◽  
William J. Torres Bobadilla
Keyword(s):  
Scattering Amplitudes ◽  
General Expression ◽  
High Energy Physics ◽  
Scattering Amplitude ◽  
Causal Structure ◽  
High Energy ◽  
Quantum Field Theories ◽  
Efficient Computation ◽  
Perturbative Approach ◽  
Theoretical Predictions

Abstract The perturbative approach to quantum field theories has made it possible to obtain incredibly accurate theoretical predictions in high-energy physics. Although various techniques have been developed to boost the efficiency of these calculations, some ingredients remain specially challenging. This is the case of multiloop scattering amplitudes that constitute a hard bottleneck to solve. In this paper, we delve into the application of a disruptive technique based on the loop-tree duality theorem, which is aimed at an efficient computation of such objects by opening the loops to nondisjoint trees. We study the multiloop topologies that first appear at four loops and assemble them in a clever and general expression, the N4MLT universal topology. This general expression enables to open any scattering amplitude of up to four loops, and also describes a subset of higher order configurations to all orders. These results confirm the conjecture of a factorized opening in terms of simpler known subtopologies, which also determines how the causal structure of the entire loop amplitude is characterized by the causal structure of its subtopologies. In addition, we confirm that the loop-tree duality representation of the N4MLT universal topology is manifestly free of noncausal thresholds, thus pointing towards a remarkably more stable numerical implementation of multiloop scattering amplitudes.

scholarly journals On the Shape–Slope Relation of Drop Size Distributions in Convective Rain

2005 ◽  
Vol 44 (7) ◽  
pp. 1146-1151 ◽  
Author(s):  
Axel Seifert
Keyword(s):  
Size Distribution ◽  
Gamma Distribution ◽  
Drop Size ◽  
Empirical Relation ◽  
Size Distributions ◽  
Shape Parameters ◽  
Raindrop Size Distribution ◽  
Raindrop Size ◽  
Drop Size Distributions ◽  
Good Agreement

Abstract The relation between the slope and shape parameters of the raindrop size distribution parameterized by a gamma distribution is examined. The comparison of results of a simple rain shaft model with an empirical relation based on disdrometer measurements at the surface shows very good agreement, but a more detailed discussion reveals some difficulties—for example, deviations from the gamma shape and the overestimation of collisional breakup.

High Dense Compressive Residual Stress Produced in Laser Shock Processing on Ti6Al4V Alloys

2007 ◽  
Vol 353-358 ◽  
pp. 1617-1620 ◽  
Author(s):  
Xu Dong Ren ◽  
Yong Kang Zhang ◽  
Jian Zhong Zhou ◽  
Yong Yu Gu ◽  
Y.Y. Xu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Surface Stress ◽  
Compressive Residual Stress ◽  
High Energy ◽  
Laser Shock ◽  
Laser Shock Processing ◽  
Large Spot ◽  
Small Spot ◽  
Shock Processing

Laser shock processing (LSP) employs high-energy laser pulses from a solid-state laser system to create intense shock waves into a material, which can induce compressive residual stresses in the target surface and improve its mechanical property efficiency. Residual stress of Ti6Al4V alloy both before and after LSP with multishocks was analysised. The depth of compressive residual stress was found to have a dependence on the number of shocking layers and a slight dependence on the level of irradiance. Surface stress improvements of more than 50% increases are possible after laser shock processing with either large spot or small spot patterns. The large spot gave a surface stress of 432MPa and a depth of over 1mm. The low intensity small spot gave a surface stress of 285MPa with a depth comparable to the large spot. Laser shock processing induces a compressive residual stress field, which increases fatigue crack initiation life and reduces fatigue crack growth rate.

scholarly journals Methodology for determining rom size distribution

2014 ◽  
Vol 67 (4) ◽  
pp. 405-412
Author(s):  
Christiane Ribeiro da Silva ◽  
Vládia C. G. de Souza ◽  
Jair C. Koppe
Keyword(s):  
Size Distribution ◽  
Distribution Curve ◽  
Size Distributions ◽  
Sampling Protocol ◽  
Product Size ◽  
Operational Conditions ◽  
Specific Protocol ◽  
Open Side ◽  
Ore Dressing

A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented according to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

Experimental Study of the Mixing and Segregation Behavior in Binary Particle Fluidized Bed with Wide Size Distributions

2018 ◽  
Vol 16 (12) ◽  
Author(s):  
Runjia Liu ◽  
Yong Zang ◽  
Rui Xiao
Keyword(s):  
Image Processing ◽  
Pressure Drop ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Processing Method ◽  
Size Distributions ◽  
Mixing Index ◽  
Image Processing Method ◽  
Segregation Behavior ◽  
Wide Size Distribution

Abstract Detailed understanding the particle mixing and segregation dynamic is essential in successfully designing and reasonably operating multicomponent fluidized bed. In this work, a novel fluorescent tracer technique combining image processing method has been used to investigate the mixing and segregation behavior in a binary fluidized bed with wide size distributions. The particle number percentage in each layer for different gas velocities is obtained by an image processing method. Fluidization, mixing and segregation behavior has been discussed in terms of bed pressure drop, gas velocity and mixing index. Different types of binary particle systems, including the jetsam and the flotsam-rich system, are analyzed and compared. The mixing indexes at different minimum fluidization velocities are also analyzed and compared with other work. The results show that the theoretical minimum fluidization velocity calculated from the bed pressure drop cannot represent the whole fluidization for a wide size distribution binary particle system. The effect of a wide size distribution is an inflection point in the mixing index curve. There is also a dead region in the bottom of the bed that consists of particles with large size and a low degree of sphericity. The particles in the dead region are extraordinarily difficult to fluidize and should be considered in the design of fluidized beds in industrial applications.

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