Papers by gustavo castillo
American Journal of Public Health, 1945
We present measurements of tribocharged, chemically identical grains falling from a hopper. Tribo... more We present measurements of tribocharged, chemically identical grains falling from a hopper. Tribocharging is the transfer of electrical charge between contacting surfaces. Granular interactions are governed by contacts, and not-surprisingly tribocharging can have important effects on bulk granular behavior. What is surprising is that this occurs even in grains of the same material. Typically same chemistry tribocharging (SCT) correlates with the particle size distribution: larger particles charge positively and smaller particles negatively. However, the detailed mechanism of SCT remains elusive. We have developed an experimental technique to make in situ measurements of the particle size and charge on small (˜100-500 μm) grains. With high speed videography of freely-falling grains we resolve particle sizes down to a few microns, charges as small as a few thousand electrons, and forces as small as a few picoNewtons. Our results confirm the qualitative charge segregation observed in previous SCT experiments and provide quantitative measurement for theoretical comparison.
This study aims to quantify density fluctuations in a fluidized quasi-two-dimensional granular sy... more This study aims to quantify density fluctuations in a fluidized quasi-two-dimensional granular system close to a solid-liquid-like transition. This transition is reached above an acceleration threshold and at sufficiently high density. The system is a shallow square cell built with two square ITO coated glass plates. The cell is filled with approximately 10000 spherical 1 mm stainless steel particles and the filling density is about 85%. Due to the dissipative nature of grain contacts, energy is injected in the system by vertical vibrations. To characterize the system we measure its Static Structure Factor as well as dynamical correlation functions.
TEMÁTICA EDUCACIÓN AMBIENTAL ETAPA EI, EP, ESO,…
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Papers by gustavo castillo