arXiv subjects

Arturo C. Martí

Publications and source records attributed to Arturo C. Martí.

12 recordsLinked to original sources

arXiv2026

Stable levitation of ring magnets: A low-cost, 3D-printed experiment on the magnetic force-distance law

Magnetic levitation is one of the most captivating phenomena in physics, combining a striking visual appeal with the rich underlying physics of forces and interactions in equilibrium. Bringing it into undergraduate laboratories in a quantitative way is nevertheless often hindered by the intrinsic instability of static magnetic systems and by the high cost of active control systems. Here we present a simple, safe, and very low-cost experiment that uses ring-shaped ferrite magnets together with a mechanical stabilization system fabricated by 3D printing in a male--female configuration. The apparatus lets undergraduate students explore directly and quantitatively the relationship between the magnitude of the magnetic force and the separation distance. We assess the robustness of the device through experimental tests, whose results show excellent quantitative agreement with the equivalent current-loop model. Furthermore, we validate this model through a complementary, independent first-principles-based methodology based on axial magnetic field profiling. To support reproducibility, the 3D design files are made available in a public, open-access repository.

physics.ed-ph↗

arXiv2026

Uniform and Accelerated Circular Motion with a Smartphone: A No-Code, AI-Generated Browser Laboratory

Smartphones have become a standard measurement instrument in the physics laboratory. Their built-in accelerometers, gyroscopes, magnetometers, and cameras have been used to investigate a wide range of phenomena in mechanics, and rotational motion in particular has proven especially well-suited to smartphone-based experiments. A recurring limitation, however, is that most experiments rely on precompiled sensor apps whose interfaces cannot be tailored to a specific activity, and until recently creating customized smartphone laboratories required programming knowledge beyond what most physics teachers possess. This paper makes two connected contributions. First, we present a validated smartphone experiment for uniform circular motion (UCM) and uniformly accelerated circular motion (UACM), in which the angular velocity and the angular acceleration are obtained from two independent smartphone channels and checked against independent video analysis with Tracker.10,14 Second, we show that generative AI can serve as a no-code development tool for the physics laboratory: the browser-based application used here was produced entirely through natural-language prompting, with no manual coding, extending to rotational motion the approach we recently introduced for acoustic experiments. The emphasis is therefore not only on what is measured, but also on how the measuring instrument itself was built.

physics.ed-ph↗

arXiv2025

Displacement current: examples that go beyond the beaten path

The Ampere-Maxwell's law and the displacement current constitute one of the most difficult aspects of electromagnetic theory for students in introductory electromagnetics courses. Here we present a set of examples that go beyond the classical ones usually discussed in introductory textbooks. In-depth analysis of these examples allows students to develop a deeper understanding of electromagnetic theory even in students who have not acquired the full mathematical toolkit of the more advanced courses.

physics.ed-ph↗

arXiv2024

Effectiveness of Turbulent Fountains in Frost Mitigation and Pollution Control

We investigate the efficacy of turbulent fountains as a tool for frost mitigation and pollution control in stratified ambient fluids. By examining the interaction between the ejected fountain fluid and the lower atmospheric layers, we develop predictive models to assess their impact on temperature distribution and the return of polluted ejected fluid to the ground. This analysis covers a range of fountain parameters, including $Fr^{-2}$ and $u^{\prime}/U$, where $Fr$ is the Froude number and $u^{\prime}/U$ represents the turbulent intensity at the inlet. Notably, we identify an optimal set of parameter values where the temperature rise is maximised, independent of the fountain's turbulence intensity. This optimal condition occurs in the so-called semi-collapse regime, as described by Sarasúa et al. [Flow, Turbulence and Combustion, 112(4), 1009-1025 (2024)], where the returning fluid, mixed with warmer upper ambient layers, significantly increases local temperature. Our findings underscore the importance of carefully tuning fountain parameters to balance their effects on the surrounding environment, offering valuable insights for the practical use of turbulent fountains in environmental management.

physics.flu-dyn↗

arXiv2023

RLC series circuit made simple and portable with smartphones

This article presents a novel method for studying RLC series circuits using two smartphones, one used as a signal generator and the other as an oscilloscope. We measure the voltage at the external resistor as a function of frequency when subjected to a sinusoidal electromotive force. The experimental results demonstrate a remarkable agreement with the theoretical curve for the voltage at the resistor and the resonance frequency, validating the accuracy of the smartphone-based setup. The experiment fills the gap in educational materials related to electrical circuits and provides a portable alternative to traditional, expensive laboratory equipment.

physics.ed-ph↗

arXiv2021

What are the attitudes and beliefs about Science of the Physics teachers and future Physics teachers in Uruguay?

We investigated the epistemological conceptions of the uruguayan Physics teachers and future Physics teachers through the application of the CLASS test (Colorado Learning Attitudes about Science Survey), one of the most accepted instruments in the research community in Physics education. The results obtained allow us to compare the attitudes and beliefs about science of both groups and quantitatively evaluate the agreement or not with the conceptions of experts in the field. First, we present a general screenshot of the responses and then we identify categories in which there are significant similarities or differences between the two groups studied and in turn with the reference of the experts. The categories that show significant positive or negative variations between the opinions of future teachers and teachers indicate the areas where training is favorable or unfavorable. On the other hand, the areas where the differences with the opinions of the experts are globally notorious suggest that they should be strengthened. To get a more global perspective, we also compare our results with those published in the literature. Finally, we raise several questions that we think may favor further inquiries.

physics.ed-ph↗

arXiv2019

Small-worldness favours network inference

A main goal in the analysis of a complex system is to infer its underlying network structure from time-series observations of its behaviour. The inference process is often done by using bi-variate similarity measures, such as the cross-correlation (CC), however, the main factors favouring or hindering its success are still puzzling. Here, we use synthetic neuron models in order to reveal the main topological properties that frustrate or facilitate inferring the underlying network from CC measurements. Specifically, we use pulse-coupled Izhikevich neurons connected as in the Caenorhabditis elegans neural networks as well as in networks with similar randomness and small-worldness. We analyse the effectiveness and robustness of the inference process under different observations and collective dynamics, contrasting the results obtained from using membrane potentials and inter-spike interval time-series. We find that overall, small-worldness favours network inference and degree heterogeneity hinders it. In particular, success rates in C. elegans networks -- that combine small-world properties with degree heterogeneity -- are closer to success rates in Erdös-Rényi network models rather than those in Watts-Strogatz network models. These results are relevant to understand better the relationship between topological properties and function in different neural networks.

cond-mat.dis-nn↗

arXiv2019

Going back to the roots: how to create stroboscopic photos from digital videos

We show here how to create from digital films using the well-known software Tracker stroboscopic photos in order to analyze different types of movements. The advantage of this procedure is that it is possible to analyze the printed photo or on a computer screen in an intuitive way for the students. After presenting a historical perspective of the use of stroboscopic photos in secondary education we discuss several examples: the movement of a remote control car, an elastic planar collision, the movement of a projectile and also an experiment in electromagnetism, more specifically, the discharge of a capacitor measured using an analog multimeter.

physics.ed-ph↗

arXiv2014

Exact detection of direct links in networks of interacting dynamical units

The inference of an underlying network topology from local observations of a complex system composed of interacting units is usually attempted by using statistical similarity measures, such as Cross-Correlation (CC) and Mutual Information (MI). The possible existence of a direct link between different units is, however, hindered within the time-series measurements. Here we show that, for the class of systems studied, when an abrupt change in the ordered set of CC or MI values exists, it is possible to infer, without errors, the underlying network topology from the time-series measurements, even in the presence of observational noise, non-identical units, and coupling heterogeneity. We find that a necessary condition for the discontinuity to occur is that the dynamics of the coupled units is partially coherent, i.e., neither complete disorder nor globally synchronous patterns are present. We critically compare the inference methods based on CC and MI, in terms of how effective, robust, and reliable they are, and conclude that, in general, MI outperforms CC in robustness and reliability. Our findings could be relevant for the construction and interpretation of functional networks, such as those constructed from brain or climate data.

physics.data-an↗

arXiv2014

Electronic Implementation of the Mackey-Glass Delayed Model

The celebrated Mackey-Glass model describes the dynamics of physiological \textit{delayed} systems in which the actual evolution depends on the values of the variables at some \textit{previous} times. This kind of systems are usually expressed by delayed differential equations which turn out to be infinite-dimensional. In this contribution, an electronic implementation mimicking the Mackey-Glass model is proposed. New approaches for both the nonlinear function and the delay block are made. Explicit equations for the actual evolution of the implementation are derived. Simulations of the original equation, the circuit equation, and experimental data show great concordance.

nlin.CD↗

arXiv2014

Acceleration Measurements Using Smartphone Sensors: Dealing with the Equivalence Principle

Acceleration sensors built into smartphones, i-pads or tablets can conveniently be used in the Physics laboratory. By virtue of the equivalence principle, a sensor fixed in a non-inertial reference frame cannot discern between a gravitational field and an accelerated system. Accordingly, acceleration values read by these sensors must be corrected for the gravitational component. A physical pendulum was studied by way of example, and absolute acceleration and rotation angle values were derived from the measurements made by the accelerometer and gyroscope. Results were corroborated by comparison with those obtained by video analysis. The limitations of different smartphone sensors are discussed.

physics.ed-ph↗

arXiv2007

Dynamics of delayed-coupled chaotic logistic maps: influence of network topology, connectivity and delay times

We review our recent work on the synchronization of a network of delay-coupled maps, focusing on the interplay of the network topology and the delay times that take into account the finite velocity of propagation of interactions. We assume that the elements of the network are identical ($N$ logistic maps in the regime where the individual maps, without coupling, evolve in a chaotic orbit) and that the coupling strengths are uniform throughout the network. We show that if the delay times are sufficiently heterogeneous, for adequate coupling strength the network synchronizes in a spatially homogeneous steady-state, which is unstable for the individual maps without coupling. This synchronization behavior is referred to as ``suppression of chaos by random delays'' and is in contrast with the synchronization when all the interaction delay times are homogeneous, because with homogeneous delays the network synchronizes in a state where the elements display in-phase time-periodic or chaotic oscillations. We analyze the influence of the network topology considering four different types of networks: two regular (a ring-type and a ring-type with a central node) and two random (free-scale Barabasi-Albert and small-world Newman-Watts). We find that when the delay times are sufficiently heterogeneous the synchronization behavior is largely independent of the network topology but depends on the networks connectivity, i.e., on the average number of neighbors per node.

nlin.CD↗