scholarly journals Speckle-Based Sensing of Microscopic Dynamics in Expanding Polymer Foams: Application of the Stacked Speckle History Technique

Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6701
Author(s):  
Dmitry Zimnyakov ◽  
Marina Alonova ◽  
Ekaterina Ushakova ◽  
Sergey Volchkov ◽  
Olga Ushakova ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Temporal Dynamics ◽  
Time Varying ◽  
Polymer Foams ◽  
Structural Rearrangements ◽  
Nucleation Effect ◽  
Cell Nucleation ◽  
Speckle Patterns ◽  
Joint Mapping ◽  
Dynamic Scattering

Microscopic structural rearrangements in expanding polylactide foams were probed using multiple dynamic scattering of laser radiation in the foam volume. Formation and subsequent expansion of polylactide foams was provided by a rapid or slow depressurization of the “plasticized polylactide–supercritical carbon dioxide” system. Dynamic speckles induced by a multiple scattering of laser radiation in the expanding foam were analyzed using the stacked speckle history technique, which is based on a joint mapping of spatial–temporal dynamics of evolving speckle patterns. A significant decrease in the depressurization rate in the case of transition from a rapid to slow foaming (from 0.03 MPa/s to 0.006 MPa/s) causes dramatic changes in the texture of the synthesized stacked speckle history maps. These changes are associated with transition from the boiling dynamics of time-varying speckles to their pronounced translational motions and are manifested as significant slopes of individual speckle traces on the recovered stacked speckle history maps. This feature is interpreted in terms of the actual absence of a new cell nucleation effect in the expanding foam upon slow depressurization on the dynamic scattering of laser radiation.

Quantification of the effects of time-varying speckle patterns on speckle images using a modified speckle influence degree method

2020 ◽  
Vol 463 ◽  
pp. 125368
Author(s):  
Yuan Yuan ◽  
Yong Bi ◽  
Min Yuan Sun ◽  
Dong Dong Wang ◽  
Wei Nan Gao ◽  
...  
Keyword(s):  
Time Varying ◽  
Speckle Patterns ◽  
Influence Degree

scholarly journals Spatio-temporal modelling of the first Chikungunya epidemic in an intra-urban setting: The role of socioeconomic status, environment and temperature

2021 ◽  
Vol 15 (6) ◽  
pp. e0009537
Author(s):  
Laís Picinini Freitas ◽  
Alexandra M. Schmidt ◽  
William Cossich ◽  
Oswaldo Gonçalves Cruz ◽  
Marilia Sá Carvalho
Keyword(s):  
Temperature Effect ◽  
Temporal Dynamics ◽  
Urban Setting ◽  
Time Varying ◽  
Varying Coefficients ◽  
Temporal Models ◽  
Green Areas ◽  
Spatio Temporal ◽  
Time Varying Coefficients

Three key elements are the drivers of Aedes-borne disease: mosquito infestation, virus circulating, and susceptible human population. However, information on these aspects is not easily available in low- and middle-income countries. We analysed data on factors that influence one or more of those elements to study the first chikungunya epidemic in Rio de Janeiro city in 2016. Using spatio-temporal models, under the Bayesian framework, we estimated the association of those factors with chikungunya reported cases by neighbourhood and week. To estimate the minimum temperature effect in a non-linear fashion, we used a transfer function considering an instantaneous effect and propagation of a proportion of such effect to future times. The sociodevelopment index and the proportion of green areas (areas with agriculture, swamps and shoals, tree and shrub cover, and woody-grass cover) were included in the model with time-varying coefficients, allowing us to explore how their associations with the number of cases change throughout the epidemic. There were 13627 chikungunya cases in the study period. The sociodevelopment index presented the strongest association, inversely related to the risk of cases. Such association was more pronounced in the first weeks, indicating that socioeconomically vulnerable neighbourhoods were affected first and hardest by the epidemic. The proportion of green areas effect was null for most weeks. The temperature was directly associated with the risk of chikungunya for most neighbourhoods, with different decaying patterns. The temperature effect persisted longer where the epidemic was concentrated. In such locations, interventions should be designed to be continuous and to work in the long term. We observed that the role of the covariates changes over time. Therefore, time-varying coefficients should be widely incorporated when modelling Aedes-borne diseases. Our model contributed to the understanding of the spatio-temporal dynamics of an urban Aedes-borne disease introduction in a tropical metropolitan city.

scholarly journals Active dynamics of colloidal particles in time-varying laser speckle patterns

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Silvio Bianchi ◽  
Riccardo Pruner ◽  
Gaszton Vizsnyiczai ◽  
Claudio Maggi ◽  
Roberto Di Leonardo
Keyword(s):  
Colloidal Particles ◽  
Laser Speckle ◽  
Time Varying ◽  
Speckle Patterns

Imaging through dynamic scattering media with stitched speckle patterns

2020 ◽  
Vol 18 (4) ◽  
pp. 042604
Author(s):  
Xin Wang ◽  
Honglin Liu ◽  
Meijun Chen ◽  
Zhentao Liu ◽  
Shensheng Han
Keyword(s):  
Scattering Media ◽  
Speckle Patterns ◽  
Dynamic Scattering

Identification of vulnerable atherosclerotic plaque by analysis of time-varying laser speckle patterns

2004 ◽  
Author(s):  
Seemantini K. Nadkarni ◽  
Brett E. Bouma ◽  
Tina Helg ◽  
Milan Singh Minsky ◽  
Raymond Chan ◽  
...  
Keyword(s):  
Atherosclerotic Plaque ◽  
Laser Speckle ◽  
Time Varying ◽  
Vulnerable Atherosclerotic Plaque ◽  
Speckle Patterns

Optical measurement of sound using time-varying laser speckle patterns

2011 ◽  
Author(s):  
Terence S. Leung ◽  
Shihong Jiang ◽  
Jeremy Hebden
Keyword(s):  
Optical Measurement ◽  
Laser Speckle ◽  
Time Varying ◽  
Speckle Patterns

Diffusion of CO2 in Polymer Nanocomposites Containing Different Types of Carbon Nanoparticles for Solid-State Microcellular Foaming Applications

2013 ◽  
Vol 26 ◽  
pp. 63-74 ◽  
Author(s):  
Marcelo Antunes ◽  
Vera Realinho ◽  
Gabriel Gedler ◽  
David Arencón ◽  
Jose Ignacio Velasco
Keyword(s):  
Carbon Nanoparticles ◽  
Polymer Nanocomposite ◽  
Amorphous Polymers ◽  
Carbon Nanofibres ◽  
Nucleation Effect ◽  
Microcellular Foaming ◽  
Cell Nucleation ◽  
Nanocomposite Foams ◽  
Electrical Conductivities ◽  
Different Types

This work considers the study of the diffusion of carbon dioxide in polypropylene and amorphous polymers containing carbon nanoparticles, particularly carbon nanofibres and graphene, as well as nanoclays, to be used in microcellular foaming. The diffusion of CO2 out and into the nanocomposites was studied during high pressure CO2 dissolution, as the amount of CO2 dissolved into the nanocomposite and CO2 desorption rate are crucial in order to have a proper control of foaming. Comparatively, platelet-like nanoparticles slowed down the desorption of CO2 out of the nanocomposites by means of a physical barrier effect, enabling a higher concentration of CO2 to remain in the polymer and be used in foaming. As a consequence of the higher amount of CO2 retained in the polymer and the cell nucleation effect promoted by the nanoparticles, polymer nanocomposite foams presented finer microcellular structures, in the case of PMMA even sub-microcellular, and higher specific moduli and electrical conductivities when compared to their pure counterparts.

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