scholarly journals Nanocellular Polymers: The Challenge of Creating Cells in the Nanoscale

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 797 ◽  
Author(s):  
Judith Martín-de León ◽  
Victoria Bernardo ◽  
Miguel Rodríguez-Pérez
Keyword(s):  
Production Process ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Topical Issue ◽  
Nanostructured Polymers ◽  
Foaming Process ◽  
Process Gas ◽  
Evolution Of Technology ◽  
Future Work ◽  
Better Than

The evolution of technology means that increasingly better materials are needed. It is well known that as a result of their interesting properties, nanocellular polymers perform better than microcellular ones. For this reason, the investigation on nanocellular materials is nowadays a very topical issue. In this paper, the different approaches for the production of these materials in our laboratory are explained, and results obtained by using polymethylmethacrylate (PMMA) are shown. Homogeneous nucleation has been studied by using raw PMMA, while two different systems were used for heterogeneous nucleation; adding nanoparticles to the system and using nanostructured polymers as solid precursors for foaming. The effects of the different parameters of the production process (gas dissolution foaming process) have been evaluated for all systems being possible to establish a comparison between the materials produced by different approaches. Moreover, the limitations and future work to optimise the materials produced are also discussed.

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

scholarly journals The Effectiveness of Multi-Label Classification and Multi-Output Regression in Social Trait Recognition

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4127
Author(s):  
Will Farlessyost ◽  
Kelsey-Ryan Grant ◽  
Sara R. Davis ◽  
David Feil-Seifer ◽  
Emily M. Hand
Keyword(s):  
Social Interactions ◽  
First Impressions ◽  
Social Traits ◽  
Judicial Proceedings ◽  
Facial Attributes ◽  
Future Work ◽  
Automated Methods ◽  
Insight Into ◽  
Social Trait ◽  
Better Than

First impressions make up an integral part of our interactions with other humans by providing an instantaneous judgment of the trustworthiness, dominance and attractiveness of an individual prior to engaging in any other form of interaction. Unfortunately, this can lead to unintentional bias in situations that have serious consequences, whether it be in judicial proceedings, career advancement, or politics. The ability to automatically recognize social traits presents a number of highly useful applications: from minimizing bias in social interactions to providing insight into how our own facial attributes are interpreted by others. However, while first impressions are well-studied in the field of psychology, automated methods for predicting social traits are largely non-existent. In this work, we demonstrate the feasibility of two automated approaches—multi-label classification (MLC) and multi-output regression (MOR)—for first impression recognition from faces. We demonstrate that both approaches are able to predict social traits with better than chance accuracy, but there is still significant room for improvement. We evaluate ethical concerns and detail application areas for future work in this direction.

Direct Nucleation of Crystalline SiGe on Substrates by Reactive Thermal CVD with Si2H6 and GeF4

1997 ◽  
Vol 467 ◽  
Author(s):  
Fumio Yoshizawa ◽  
Kunihiro Shiota ◽  
Daisuke Inoue ◽  
Jun-ichi Hanna
Keyword(s):  
Growth Rate ◽  
Gas Phase ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Film Growth ◽  
Early Stage ◽  
Gaseous Mixture ◽  
The Other ◽  
Thermal Cvd ◽  
Initial Deposition

ABSTRACTPolycrystalline SiGe (poly-SiGe) film growth by reactive thermal CVD with a gaseous mixture of Si2H6 and GeF4 was investigated on various substrates such as Al,Cr, Pt, Si, ITO, ZnO and thermally grown SiO2.In Ge-rich film growth, SEM observation in the early stage of the film growth revealed that direct nucleation of crystallites took place on the substrates. The nucleation was governed by two different mechanisms: one was a heterogeneous nucleation on the surface and the other was a homogeneous nucleation in the gas phase. In the former case, the selective nucleation was observed at temperatures lower than 400°C on metal substrates and Si, where the activation of adsorbed GeF4 on the surface played a major role for the nuclei formation, leading to the selective film growth.On the other hand, the direct nucleation did not always take place in Si-rich film growth irrespective of the substrates and depended on the growth rate. In a growth rate of 3.6nm/min, the high crystallinity of poly-Si0.95Ge0.05in a 220nm-thick film was achieved at 450°C due to the no initial deposition of amorphous tissue on SiO2 substrates.

Crystal Nucleation in Submicron Droplets of Pure Elements

1993 ◽  
Vol 321 ◽  
Author(s):  
Louis M. Holzman ◽  
Thomas F. Kelly ◽  
W. N. G. Hitchon
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Crystal Nucleation ◽  
Droplet Radius ◽  
Electrohydrodynamic Atomization ◽  
Submicron Droplets ◽  
Diffraction Patterns

ABSTRACTLiquid-to-crystal nucleation has been studied extensively through droplet experiments to locate examples of homogeneous nucleation. However, prior to this work very few examples have been found, which implies that the experiments have not been able to isolate heterogeneous nucleants in a small percentage of the droplets as is required. In this research, electrohydrodynamic atomization (EHD) is used to produce sub-Micron droplets of pure elements that are largely free of heterogeneous nucleants.Diffraction patterns of individual EHD-produced droplets are viewed to determine the fraction of crystalline droplets produced as a function of droplet radius. These results are compared to theories for surface and volume heterogeneous nucleation and for homophase nucleation. It is found that Si and Ge nucleate through either homogeneous nucleation or nucleation by homophase impurities. Nucleation results for vanadium and iron were not conclusive.

Bubbles and element clusters in rock melts: A chicken and egg problem

2021 ◽  
Author(s):  
Renelle Dubosq ◽  
Pia Pleše ◽  
Brian Langelier ◽  
Baptiste Gault ◽  
David Schneider
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Growth Dynamics ◽  
Gas Bubbles ◽  
Atom Probe ◽  
Bubble Nucleation ◽  
Interface Element ◽  
Rich Cluster ◽  
Heterogeneous Distribution ◽  
Rapid Decompression

<p>The nucleation and growth dynamics of gas bubbles and crystals play a vital function in determining the eruptive behaviour of a magma. Their rate and relative timing, among other factors, are controlled by the magma’s ascent rate. Investigating the kinetics of decompression-induced degassing and crystallization processes can thus give us insight into the rheology of magmas. For example, the rapid decompression of magmas inhibits microlite crystallization and bubble nucleation during ascent leading to crystallization and degassing at shallow levels. This results in a drastic increase in viscosity and an over pressured system, which can lead to violent eruptions. Although many experiments and numerical simulations of magma decompression have been carried out, nascent and initial bubble nucleation remain poorly understood. It is widely accepted that there are two ways bubbles can nucleate within a melt: heterogeneous (on a pre-existing surface) and homogeneous nucleation (within the melt), where homogeneous nucleation requires a higher volatile supersaturation. It has since been tentatively suggested that homogeneous nucleation is simply a variety of heterogeneous nucleation where nucleation occurs on the surface of submicroscopic crystals. However, evidence of these crystals is equivocal. Thus, we have combined novel 2D and 3D structural and chemical microscopy techniques including scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS) mapping, and atom probe tomography (APT) to investigate the presence of sub-nanometer scale chemical heterogeneities in the vicinity of gas bubbles within an experimental andesitic melt. The combined STEM and EELS data reveal a heterogeneous distribution of bubbles within the melt ranging between 20-100 nm in diameter, some of which have Fe and/or Ca element clusters at the bubble-melt interface. Element clusters enriched in Fe, Ca, and Na are also observed heterogeneously distributed within the melt. The reconstructed APT data reveals bubbles as low ionic density regions overlain by a Na-, Ca-, and K-rich cluster and heterogeneously distributed Fe clusters within the bulk of the melt. Based on these observations, our data demonstrate the existence of nano-scale chemical heterogeneities within the melt and at the bubble-melt interface of bubbles that were previously interpreted to be nucleated homogeneously within the melt, therefore contributing to the proposed hypothesis that homogeneous nucleation could in fact be a variety of heterogeneous nucleation. These results highlight the need to redefine homogeneous nucleation and revisit whether bubbles or crystals occur first within volcanic melts. </p>

Desequilibres entre phases solides et fluides mineraux dans la petrogenese

1962 ◽  
Vol S7-IV (2) ◽  
pp. 157-164 ◽  
Author(s):  
Georges Deicha
Keyword(s):  
Crystal Growth ◽  
Solid Solutions ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Fluid Solution ◽  
Secondary Intervention ◽  
The Moment

Abstract The importance of phenomena conditioned by the disequilibrium between gases, liquids, or magmas, and solid minerals is discussed. Four modes of crystal growth are capable of causing the precipitation of a crystalline species in a supersaturated or supercooled fluid solution. In homogeneous nucleation crystallization occurs at the moment when saturation is reached and only in the presence of preformed crystals of the same species. Germinal nucleation occurs when crystallization develops in conditions of disequilibrium causing the formation of minerals of the same composition but of different structure. Crystals of this mode are twinned. Metastable nucleation involves the formation of a species different in structure from the stable crystal which developed after twinning. In heterogeneous nucleation crystallization of a species has its beginning on the surface of another crystal. This introduces impurities which inhibit nucleation and crystal growth. Secondary intervention of liquid or solid solutions in the rocks also produces phenomena equally effected by disequilibrium.

scholarly journals Heterogeneous Nucleation of Calcium Oxalate on Native Oxide Surfaces

1994 ◽  
Vol 346 ◽  
Author(s):  
Lin Song ◽  
Michael J. Pattillo ◽  
Gordon L. Graff ◽  
Allison A. Campbell ◽  
Bruce C. Bunker
Keyword(s):  
Calcium Oxalate ◽  
Heterogeneous Nucleation ◽  
Biomimetic Synthesis ◽  
Native Oxide ◽  
Oxide Surfaces ◽  
Constant Composition ◽  
Ceramic Thin Films ◽  
Atomic Force ◽  
Induction Times ◽  
Better Than

ABSTRACTThe aqueous deposition of calcium oxalate onto colloidal oxides has been studied as a model system for understanding heterogeneous nucleation processes of importance in biomimetic synthesis of ceramic thin films. Calcium oxalate nucleation has been monitored by measuring induction times for nucleation using Constant Composition techniques and by measuring nucleation densities on extended oxide surfaces using an atomic force microscope. Results show that the dependence of calcium oxalate nucleation on solution supersaturation fits the functional form predicted by classical nucleation theories. Anionic surfaces appear to promote nucleation better than cationic surfaces, lowering the effective energy barrier to heterogeneous nucleation.

A model for the simultaneous heterogeneous and homogeneous nucleation of gas bubbles

1979 ◽  
Vol 368 (1734) ◽  
pp. 331-343 ◽  
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Bubble Nucleation ◽  
Rate Theory ◽  
Rare Gases ◽  
Bubble Density ◽  
Competitive Mechanism ◽  
The Matrix ◽  
Arrhenius Energy ◽  
First Time

Electron microscope observations of cavities in steels have shown that they are often associated with microstructural features as well as occurring randomly in the matrix. Previous theoretical studies of gas bubble nucleation have concentrated on either homogeneous or heterogeneous nucleation. In the present work we extend the homogeneous nucleation rate theory for rare gases in solids to include, for the first time, the competitive mechanism of heterogeneous nucleation. The model indicates that the temperature dependence of the bubble density varies as the binding energy between a trap and a single gas atom is changed, and provides an interpretation of the high Arrhenius energy found from observed cavity densities.

scholarly journals The Industrial Internet and the Future of Work

2015 ◽  
Vol 137 (09) ◽  
pp. 30-35 ◽  
Author(s):  
Marco Annunziata ◽  
Stephan Biller
Keyword(s):  
Production Process ◽  
Technological Progress ◽  
High Performance ◽  
Human Beings ◽  
Future Of Work ◽  
Industrial Internet ◽  
The Future ◽  
Production Techniques ◽  
Performance Computing ◽  
Better Than

This article focuses on the transformation and dimming lines between digital and physical worlds. Industrial Internet tools and applications also help people collaborate in a faster and smarter way – making jobs not just more efficient but more rewarding. Technological progress and economic growth are contributing to a seismic shift in the role that human beings play in the production process. Technological progress, notably in high-performance computing, robotics, and artificial intelligence, is extending the range of tasks that machines can perform better than humans can. The Future of Work is being shaped by a profound transformation, driven by the meshing of the digital and the physical worlds, the emergence of new design and production techniques, and a seismic shift in the role that human beings play in the production process. Technological progress is expected to push a growing share of the workforce toward creativity and entrepreneurship, where humans have a clear comparative advantage over machines.

scholarly journals PENERAPAN CRITICAL CONTROL POINT DAGING RENDANG DI RUMAH MAKAN PADANG TERHADAP NILAI pH DAN MUTU RASA ORGANOLEPTIK

2021 ◽  
Vol 1 (1) ◽  
pp. 16
Author(s):  
Anggoro Rizky Narastyawan ◽  
Yoyok Budi Pramono ◽  
Bambang Dwiloka
Keyword(s):  
Data Analysis ◽  
Production Process ◽  
Test Data ◽  
Ph Value ◽  
Control Point ◽  
Research Data ◽  
Test Results ◽  
Critical Control Point ◽  
Production Processes ◽  
Better Than

This study aims to compare the production process of rendang at Padang restaurants and the production of rendang itself, namely by observing CCP management in the running production process or not. Observation of the implementation of CCP management was carried out on the pH value and organoleptic values. This study conducted observations on the implementation of CCP management in the rendang production process in Padang restaurants then carried out the production of rendang itself by implementing CCP management and made improvements in the production process so that rendang was analyzed for pH value and organoleptic. The research data were analyzed using the Independent Sample T Test. Data analysis on the organoleptic test used the non-parametric Kruskal Wallis test and continued with the Mann Whitney test. The results of this study indicate that the rendang that is produced by CCP management is better than the rendang produced in Padang restaurants because it does not apply CCP management and has a significant effect (P <0.05) so it has poor test results. The results showed that padang restaurants needed to take corrective action on their tighter production processes so that their food products would be better.

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