scholarly journals Angle of repose experiments with snow: role of grain shape and cohesion

2020 ◽  
Vol 66 (258) ◽  
pp. 658-666
Author(s):  
Carolin Willibald ◽  
Henning Löwe ◽  
Thiemo Theile ◽  
Jürg Dual ◽  
Martin Schneebeli
Keyword(s):  
Grain Shape ◽  
Angle Of Repose ◽  
Geometrical Shape ◽  
Micro Computed Tomography ◽  
Computed Tomography Images ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Particle Segmentation

AbstractSnow appears as a granular material in most engineering applications. We examined the role of grain shape and cohesion in angle of repose experiments, which are a common means for the characterization of granular materials. The role of shape was examined by investigating diverse snow types with discernable shape and spherical ice beads. Two geometrical shape parameters were calculated from X-ray micro-computed-tomography images after a particle segmentation was performed with a watershed algorithm. Cohesion was examined by conducting experiments at six different temperatures between −40 and −2°C, assuming sintering as its cause, which accelerates with increasing temperature. As a cohesionless reference, experiments with glass beads were performed. We found that both shape and cohesion exerted about equally strong influence on the angle of repose. We utilized our results for an empirical model that describes the influence of shape and cohesion as additive corrections of the angle of repose of cohesionless spheres and explains all experiments with a correlation coefficient r2 = 0.95. With temperature and the chosen shape parameter as fitting variables, previous experiments with another snow type could be consistently included. The experiments highlight the relevance of these parameters in granular snow mechanics and can be used for model calibration.

The Role of Temperature on Hydration of Binary System of Metakaolin/Portland Cement

2016 ◽  
Vol 851 ◽  
pp. 51-56 ◽  
Author(s):  
Martin Boháč ◽  
Radoslav Novotný ◽  
Jakub Tkacz ◽  
Miroslava Hajdúchová ◽  
Martin Palou ◽  
...  
Keyword(s):  
Binary System ◽  
Portland Cement ◽  
Isothermal Calorimetry ◽  
Chemical Characterization ◽  
Exothermic Peak ◽  
Early Hydration ◽  
Different Temperatures ◽  
C 50

The role of temperature of metakaolin/Portland cement binary system was studied by isothermal calorimetry. Sample with 50 % of metakaolin replacement were monitored at 30 °C, 40 °C, 50 °C and 60 °C. Structural and chemical characterization of hardened pastes was obtained by scanning electron and Raman microscopy. Paper deals with kinetics of main exothermal reactions during early hydration of the system. Activation energies were calculated for processes related to each exothermic peak. The nature of hydration products at different temperatures was revealed by microstructural studies.

Characterization of the mass transfer of lyophilized products based on X-ray micro-computed tomography images

2017 ◽  
Vol 35 (8) ◽  
pp. 933-938 ◽  
Author(s):  
Roberto Pisano ◽  
Antonello A. Barresi ◽  
Luigi C. Capozzi ◽  
Giorgia Novajra ◽  
Irene Oddone ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Mass Transfer ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Computed Tomography Images

Analysis of C-V Characteristics of InP(p)/InSb/Al2O3/Au MIS Structures in Wide Temperature Range

2013 ◽  
Vol 685 ◽  
pp. 179-184
Author(s):  
M.A. Benamara ◽  
A. Talbi ◽  
Z. Benamara ◽  
B. Akkal ◽  
N. Chabane Sari ◽  
...  
Keyword(s):  
High Speed ◽  
Room Temperature ◽  
Electrical Characterization ◽  
State Density ◽  
Capacitance Voltage ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Accumulation Region ◽  
Interface Study

Superscript textThe III-V semiconductors materials and in particularly Indium Phosphide are a promising candidates for the elaboration of high speed electronic compounds. The importance of the interface study is increasing considerably in the last years to understand, the mechanism of interface formations and to control perfectly the technology of the elaborated compounds. This study presents an electrical characterization of InP(p)/InSb/Al2O3/ Au structures in the range of temperature varying from the temperature of liquid nitrogen to the temperature of 400°K. In order to give the evolution of electrical parameters of these structures with temperature, we have realized Capacitance-Voltage measurements at high frequency for different temperatures. The found results show that there is dispersion in the accumulation region as function with temperature. The quantity of positive charges in the insulator is estimated to 1.37×1012 atm/cm2 at room temperature. This value decreases slightly with increasing temperature. It varies fromSuperscript text 1.57×1012 atm/cm2 at 77°K to 1.12×1012 atm/cm2 at 400°K. The interface insulator/semiconductor of our samples presents a good electronical quality, the state density is equal to 4.1011 eV-1.cm-2 at room temperature, this one increases from 4.7×1010 eV-1.cm-2 to 7.1011 eV-1.cm-2 when temperature increases from 77°K to 400°K.

scholarly journals Systematic functional analysis of rab GTPases reveals limits of neuronal robustness to environmental challenges in flies

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Friederike E Kohrs ◽  
Ilsa-Maria Daumann ◽  
Bojana Pavlovic ◽  
Eugene Jennifer Jin ◽  
F Ridvan Kiral ◽  
...  
Keyword(s):  
Nervous System ◽  
Membrane Trafficking ◽  
Rab Gtpases ◽  
Continuous Stimulation ◽  
Different Temperatures ◽  
Morphological Defects ◽  
And Function

Rab GTPases are molecular switches that regulate membrane trafficking in all cells. Neurons have particular demands on membrane trafficking and express numerous Rab GTPases of unknown function. Here, we report the generation and characterization of molecularly defined null mutants for all 26 rab genes in Drosophila. In flies, all rab genes are expressed in the nervous system where at least half exhibit particularly high levels compared to other tissues. Surprisingly, loss of any of these 13 nervous system-enriched Rabs yielded viable and fertile flies without obvious morphological defects. However, all 13 mutants differentially affected development when challenged with different temperatures, or neuronal function when challenged with continuous stimulation. We identified a synaptic maintenance defect following continuous stimulation for six mutants, including an autophagy-independent role of rab26. The complete mutant collection generated in this study provides a basis for further comprehensive studies of Rab GTPases during development and function in vivo.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Consideraciones en torno a la reducción solipsista

1970 ◽  
Vol 11 ◽  
Author(s):  
Natalia Carolina Petrillo

ResumenEn el presente trabajo se intentará mostrar que la fenomenología no conduce a una postura solipsista. Para ello, se caracterizará en qué consiste el solipsismo. Luego, se intentará refutar a lo que se ha de llamar “solipsismo metafísico” y “solipsismo gnoseológico”, con el objetivo principal de poner de manifiesto el fundamento de motivación para la salida de la ficción solipsista.Palabras claves:Phenomenology – solipsim – empatía - HusserlAbstractWith the aim of showing that phenomenology does not lead in solipsism, I will first attempt a characterization of it. Then, I will attempt a refutation of the so-called “metaphysical” and “epistemological” solipsisms. Finally, the nature and role of Husserl´s solipsistic fiction is examined, and the grounds that motivate the overcoming of this standpoint are disclosed.key wordsFenomenología – solipsismo - empathy – Husserl

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