Catálogo de publicaciones - revistas

<jats:p>A daily quiz on Newtonian biomechanics has previously been shown to improve student self-confidence, enthusiasm, and test results in biomechanics courses. This study investigated whether such a quiz could also improve retention of knowledge over a longer term. Our study found that students who participated very actively in daily quizzes scored significantly better on a retention test compared to those who participated less actively or not at all. From these results, we can conclude that very active participation in a daily quiz resulted in a slight gain in the long-term retention of biomechanics knowledge.</jats:p>

<jats:p>The pendulum wave apparatus exhibits cyclic pendulum patterns, including wave-like motion and pendulums alignments. This work presents a complete analytical solution to the times and numbers of pendulum alignment, which is shown to be a subset of Thomae's function. Based on the properties of this function and basic number theory, a comprehensive analysis of pendulum patterns is presented.</jats:p>

<jats:p>Angular momentum is traditionally taught as a (pseudo)vector quantity, tied closely to the cross product. This approach is familiar to experts but challenging for students, and full of subtleties. Here, we present an alternative pedagogical approach: angular momentum is described using bivectors which can be visualized as “tiles” with area and orientation, and whose components form an antisymmetric matrix. Although bivectors have historically been studied in specialized contexts like spacetime classification or geometric algebra, they are no more complicated to understand than cross products. The bivector language provides a more fundamental definition for rotational physics and opens the door to understanding rotations in relativity and in extra dimensions.</jats:p>

<jats:p>A classic nonlinear spring mass oscillator, the nonlinearity of which could be varied by changing the initial stretching of the spring, was used to investigate how the amplitude dependence of the period and the harmonic content depended on the nonlinearity. The oscillations were measured with a photogate and a MEMS accelerometer, allowing both the oscillation period and the Fourier components of the motion to be precisely determined. The results were in good agreement with theory.</jats:p>

<jats:p>Providing students of introductory thermal physics with a plot of the heat capacities of many low density gases as a function of temperature allows them to look for systematic trends. Specifically, large amounts of heat capacity data not only allow students to discover the equipartition theorem but also point to its limited applicability. Computer code to download and plot the temperature-dependent heat capacity data is provided.</jats:p>

<jats:p>One-dimensional (1D) systems in which metastable states exist are physically important, but they are usually not discussed quantitatively in textbooks. This paper presents a relatively simple 1D system involving a piecewise-constant potential for which metastable states can be easily calculated using a computer algebraic system. The metastable-state wave functions are computed and plotted for various particle energies. The Breit–Wigner approximation is used to fit the resulting resonant structure in the transmission coefficient. Connections are made between the initial analysis and poles of the scattering matrix that corresponds to the potential.</jats:p>

<jats:p>A mirage or fatamorgana is typically an upside-down “mirror” image of a scenery in deserts, over sun-heated roads, or above bodies of water. When the temperature gradient of air is large, as can happen near a surface, it results in a large gradient of the density and the refractive index as a function of height. Mirages appear when light travels through a medium with a gradient in its refractive index and, therefore, get bent towards the higher values, generating reflected images. A computer program that simulates mirages above water using the method of ray tracing has been developed and is presented here in detail for educational purposes. Results on the effect are shown by simulated images for various water-air temperature-difference cases with values ranging from 5 to 0 °C. Comparison of the simulations to a real-life scenario at Lake Balaton, Hungary has also been provided.</jats:p>

<jats:p>The generalized semi-classical game of life (gSCGOL) is a cellular automaton in which qubits evolve through repeated applications of birth, death, and survival operators. gSCGOL is used to model human–virus interactions during the COVID-19 pandemic by using cell “liveness” to be equivalent to the human population that is vulnerable to the disease. A match to the United Kingdom (UK) daily 7-day average COVID-19 deaths was achieved by daily changes to a parameter V representing the vulnerability of the population to the virus. The model predicts that the first COVID-19 virus entered the UK on December 22, 2019 with an uncertainty of ±1 days. The changes in the vulnerability V elucidate the human response to the unfolding pandemic during 2020, quantifying the impact of the lockdown, the relaxation of restrictions, and the opening and closing of schools. The model predicts that starting the first UK national lockdown one week earlier would have led to 40% fewer COVID-19-related deaths, equivalent to 17 000 lives.</jats:p>

<jats:p>We present an inexpensive sodium molecular spectroscopy experiment for use in an advanced undergraduate laboratory course in physics or chemistry. The molecules were excited predominantly from the ground X1Σg+(v″ = 15) state to the B1Πu(v′ = 6) state using a commercially available 532-nm broadband diode laser. The laser-induced molecular fluorescence was measured using a miniature fiber-coupled spectrometer at a resolution of 0.5 nm. The spectral peak assignments were done by comparing the observed spectrum with the calculated Franck–Condon values. Important molecular constants such as fundamental frequency, anharmonicity, bond strength, and dissociation energy of the ground electronic state were determined by using the Birge–Sponer extrapolation method. The presence of highly visible blue glowing molecules along the green laser beam creates an engaging laboratory experience. Emphasis is placed on students developing their understanding of the molecular structure, practicing molecular spectroscopic techniques, and applying knowledge of light–matter interactions to a physical system.</jats:p>

<jats:p>Lock-in detection is a widely used experimental technique in which a weak signal is measured by modulating it at a particular frequency. Then, by detecting an experimental output at that frequency, the desired signal can be isolated from much larger-amplitude noise. Here, we report on the implementation and optimization of a homemade laser barcode scanner based on the lock-in technique. Our setup is comprised of components that are readily available in an undergraduate instructional laboratory. The successful transcription of the barcode into a digital signal was achieved, and this digital signal was collected with a simple computer and processed to reveal the encoded number.</jats:p>