arXiv subjects

A. J. Batista-Leyva

Publications and source records attributed to A. J. Batista-Leyva.

9 recordsLinked to original sources

arXiv2022

Continuous to intermittent flows in growing granular heaps

If a granular material is poured from above on a horizontal surface between two parallel, vertical plates, a sand heap grows in time. For small piles, the grains flow smoothly downhill, but after a critical pile size $X_c$, the flow becomes intermittent: sudden avalanches slide downhill from the apex to the base, followed by an "uphill front" that slowly climbs up, until a new downhill avalanche interrupts the process. By means of experiments controlling the distance between the apex of the sandpile and the container feeding it from above, we show that $X_c$ grows linearly with the input flux, but scales as the square root of the feeding height. We explain these facts based on a phenomenological model based on the experimental observation that the flowing granular phase forms a "wedge" on top of the static one, differently from the case of stationary heaps. Moreover, we demonstrate that our controlled experiments allow to predict the value of $X_c$ for the common situation in which the feeding height decreases as the pile increases in size.

cond-mat.soft↗

arXiv2021

Protecting others vs. protecting yourself against ballistic droplets: Quantification by stain patterns

It is often accepted a priori that a face mask worn by an infected subject is effective to avoid the spreading of a respiratory disease, while a healthy person is not necessarily well protected when wearing the mask. Using a frugal stain technique, we quantify the ballistic droplets reaching a receptor from a jet-emitting source which mimics a coughing, sneezing or talking human: in real life, such droplets may host active SARS-CoV-2 virus able to replicate in the nasopharynx. We demonstrate that materials often used in home-made face masks block most of the droplets. We also show quantitatively that less liquid carried by ballistic droplets reaches a receptor when a blocking material is deployed near the source than when located near the receptor, which supports the paradigm that your face mask does protect you, but protects others even better than you.

physics.med-ph↗

arXiv2018

Optics undergraduate experiments using smart (and not so smart) phones

Smartphones may be seen as miniature toolboxs to perform Physics experiments. In this paper, we present three different "optics workbenches" mainly based on the light meter of a smartphone. One is aimed at the precise study of Malus law and other effects associated to linearly polarized light, the second allows quantifying the light intensity distribution of diffraction or interference patterns projected on a screen, and the third demonstrates the so-called inverse square law obeyed by the light from a pointlike source. These experiments allow to quantitatively demonstrate three fundamental laws of optics using quite inexpensive equipment.

physics.ed-ph↗

arXiv2016

Intruder penetration into granular matter studied by Lock-in Accelerometry

Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. In this work, we use Lock-in accelerometry to study the penetration of intruders into quasi-2D granular matter fluidized by lateral shaking. We observed that there are two well-defined stages in the penetration dynamics as the intruder sinks into the granular material.

cond-mat.soft↗

arXiv2016

Sink vs. tilt penetration into shaken dry granular matter: the role of foundation

We study the behavior of cylindrical objects as they sink into a dry granular bed fluidized due to lateral oscillations, in order to shed light on human constructions and other objects. Somewhat unexpectedly, we have found that, within a large range of lateral shaking powers, cylinders with flat bottoms sink vertically, while those with a "foundation" consisting in a shallow ring attached to their bottom, tilt besides sinking. The latter scenario seems to dominate independently from the nature of the foundation when strong enough lateral vibrations are applied. We are able to reproduce the observed behavior by quasi-2D numerical simulations, and the vertical sink dynamics with the help of a Newtonian equation of motion for the intruder.

cond-mat.soft↗

arXiv2015

Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter

Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental Physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. While the penetration of intruders in two dimensional (2D) laboratory granular beds can be followed using video recording, it is useless in three dimensional (3D) beds of non-transparent materials such as common sand. Here we propose a method to quantify the sink dynamics of an intruder into laterally shaken granular beds based on the temporal correlations between the signals from a reference accelerometer fixed to the shaken granular bed, and a probe accelerometer deployed inside the intruder. Due to its analogy with the working principle of a lock in amplifier, we call this technique Lock in accelerometry (LIA). During Earthquakes, some soils can lose their ability to sustain shear and deform, causing subsidence and sometimes substantial building damage due to deformation or tumbling

cond-mat.soft↗

arXiv2005

Local transport measurements in laser patterned BSCCO-Ag tapes

The determination of inter- and intra-filament transport characteristics in superconducting composites such as BSCCO-Ag tapes is of great importance for material evaluation towards applications. Most attempts to separate the two contributions have relied on indirect methods based on magnetic measurements such as SQUID or magneto-optic imaging techniques. Here we show that laser patterning of superconducting BSCCO-Ag tapes constitutes a simple approach to measure local transport properties in a direct way, even able to separate inter- and intra-filament contributions to the overall transport behavior of the sample. Our technique is potentially useful for sub-millimeter devices based on superconducting tapes.

cond-mat.supr-con↗

arXiv2004

On the interpretation of "off the edge" avalanches

We establish both experimentally and theoretically the relation between off the edge and internal avalanches in a sandpile model, a central issue in the interpretation of most experiments in these systems. In BTW simulations and also in the experiments the size distributions of internal avalanches show power laws and critical exponents related with the dimension of the system. We show that, in a SOC scenario, the distributions of off the edge avalanches do not show power laws but follow scaling relations with critical exponents different from their analogous for the internal avalanche distributions.

cond-mat.stat-mech↗

arXiv2002

Sandpile formation by revolving rivers

Experimental observation of a new mechanism of sandpile formation is reported. As a steady stream of dry sand is poured onto a horizontal surface, a pile forms which has a thin river of sand on one side flowing from the apex of the pile to the edge of its base. The river rotates about the pile, depositing a new layer of sand with each revolution, thereby growing the pile. For small piles the river is steady and the pile formed is smooth. For larger piles, the river becomes intermittent and the surface of the pile becomes undulating. The frequency of revolution of the river is measured as the pile grows and the results are explained with a simple scaling argument. The essential features of the system that produce the phenomena are discussed.

cond-mat.soft↗