Vol. 62 No. 2 Jul-Dec (2016): Revista Mexicana de Física E
Published:
2016-01-01
Artículos
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Análisis del coeficiente de amortiguamiento viscoso en un sistema masa-resorte-amortiguador utilizando PPLANE y GEOGEBRA
Abstract:In this article a mass-spring-damper system is studied. The influence of the viscosity of the fluid and the damping coefficient is analyzed by using three fluids, water, edible oil and gasoline engine oil SAE 10W-40. Numerical simulations using PPLANE and GeoGebra shown under the paradigm of problem-based learning (PBL) are performed. Comparing the three dampers it is made.⬇️ Scroll down to see the full summary -
Desigualdades de Bell: un experimento sencillo para licenciatura
Abstract:This paper presents an experiment suitable for advanced undergraduate students. We use polarization-entangled photon pairs in order to demonstrate quantum nonlocality. The entangled state is created by spontaneous parametric downconversion using a violet laser diode and nonlinear BBO-II crystals. The idea behind Bell's inequality is commented, and finally a test of the Clauser, Horne, Shimony, and Holt version of the Bell inequality is performed, finding $S=-2.32\pm 0.045$ contradicting the hidden variables theories prediction. This experimental setup takes less than a few hours to be ready, while the data collection takes no more than ten minutes.⬇️ Scroll down to see the full summary -
Comment to the article ``On thermal waves velocity: some open questions in thermal waves physics'', Rev. Mex. Fis. E {62} (2016) 1-4
Abstract:It is showed here that an upper limit must exist for the speed of thermal waves because Fourier's laws of heat conduction cannot be used at very short length scales, but only over a length larger than the mean free path of the heat carriers.⬇️ Scroll down to see the full summary -
Chua's circuit from the linear system perspective
Abstract:This paper analyzes the Chua's circuit, considering it linear by parts in its internal representation model. This approach allows graduate students to develop skills in matrix algebra and linear systems, using physics as a fundamental tool to model and simulate dynamic systems. Through this approach, the student will understand the importance of the knowledge of state equations to form the matrices that represent the circuit, where the main matrix dictates its values and eigenvectors, as well as its similar matrix. A physical simulation of the Chua's circuit is carried out, along with the corresponding experiments. The electric circuit is composed by resistors, capacitors, inductance, diodes and an operational amplifier.⬇️ Scroll down to see the full summary -
Simetrías en la naturaleza y efecto túnel: breve estudio de pozos cuánticos dobles
Abstract:It is interesting to understand the mechanism by which some materials in nature, with an asymmetrical appearance, are formed and to relate it with a quantum problem. For this reason, we analyze with full details the behavior of a quantum particle in a finite double well potential and in a similar one, a double Dirac delta function well in order to explain, how and when, the symmetry breakup takes place in these cases. For simplicity we consider both potentials in one dimension ($x$) and we focus our attention on the symmetry $V(x)=V(-x)$ of the potentials. We find, and illustrate in detail, the eigenstates (and energies) of the Hamiltonian $\hat{H}$ and of the parity symmetry $\hat{\pi}$ operator. We determine the time evolution of the parity-eigenstates, we find that the parity symmetry is broken when they are combined in a special way and we set out the consequences of this breaking. We emphasize the relevance of the tunnel effect which arises in the quantum treatment of the problems and we relate the obtained results with naturally occurring situations and materials (NH$_3$), its possible influence on our environment and particularly, with the physics involved in the operation of the Maser.⬇️ Scroll down to see the full summary -
Solving Schrödinger equation by meshless methods
Abstract:In this paper we apply a numerical meshless scheme for solving one and two dimensional time independent Schrödinger equation by means of collocation method with Radial Basis Functions interpolants. In particular we approximate the solutions using multiquadrics. The method is tested with some of the well-known configurations of Schrödinger equation and compared with analytical solutions, showing a great accuracy and stability. We also provide some insight on how to use meshless algorithms for obtaining the eigenenergies and wavefunctions of one- and two-dimensional Schrodinger problems.⬇️ Scroll down to see the full summary -
Simulación computacional de una fibra óptica con índice escalonado y propagación multimodal
Abstract:In this paper the computational simulation of electromagnetic propagation multimodal inside an optical fiber with step index is performed. A sinusoidal source placed at the left end feeds an electromagnetic field to the optical fiber; fiber layers are modeled staggered to achieve total internal reflection of the incident light according to the wave theory of light. The simulation is performed using tools of computational electromagnetics such as Method Finite Difference Time Domain (FDTD) and the method of perfectly matched layers (PML) as boundary condition absorption to prevent electromagnetic propagation continue to infinity. The operating frequency is 187 THz used and the wavelength of 1600nm is, this simulation is achieved by developing a computational algorithm in Matlab. electromagnetic parameters propagated in the core of the optical fiber such as magnetic field components $Hx$ and $Hy$ and $Ez$ electric field are obtained. We want students to achieve understanding of the behavior of light as an electromagnetic wave inside the optical fiber, it may be something that might be perceived as simple, however, we are sure to see the electromagnetic propagation according to the results allowing clearly interpret these optical phenomena.⬇️ Scroll down to see the full summary -
One-dimensional point interactions and bound states
Abstract:We analyze various representative examples of nonrelativistic (Schrödinger) point interactions in one dimension, with boundary conditions and with singular potentials, and study their corresponding bound states.⬇️ Scroll down to see the full summary -
Interferometria speckle para evaluar la flexión de una barra de aluminio
Abstract:In a Digital Speckle Pattern Interferometry, DSPI, a two light coherent wavefront superposition from two surfaces is produced; the first one from the object under study, the aluminum bar, and the other from the reference ground glass. Here, we study the aluminum bar deformation with dimensions of 15.20 mm $\times$ 158.00 mm $\times$ 0.72 mm, with an extreme fixed in a base and the other extreme subjected to a container in which diferent mechanical charges are applied generating a serie of flexion stresses. The correlograms are digitally acquired by a vision system, before and after, different loads to bar extreme are applied, these correlograms represent the phase differences of the beams from the two surfaces, that permit us to determine the bar deformations produced by applied mechanical stresses. Algorithms are applied to determine the bar deformation and the Young modulus.⬇️ Scroll down to see the full summary -
Geodesic time travel in Gödel's universe
Abstract:This work is an introduction at a beginning graduate or advanced undergraduate level to Kurt Gödel's foray into cosmology. After an elementary introduction to the basics of Einstein's theory of gravitation, we simply present the Gödel's solution and the geodesic equations associated with it. This equations are then explicitly solved obtaining its full set of temporal geodesics. Armed with such explicit expressions, the geodesic time-travelling possibilities of Gödel's universe are discussed. We search for their time-like closed geodesics that, following Gödel's analysis, other people has imagined as possible routes for time-travel. We next exhibit that such time-travelling possibility do not exist in his model universe. This is done in the most straightforward way possible, framing the discussion as to serve as a simple example for students of General Relativity.⬇️ Scroll down to see the full summary
