The current energy demand increases every day and the deficit of electricity generation in Colombia due to technical aspects such as the lack of generation infrastructure, cost overruns in the construction projects of new plants and environmental variability as a consequence of climate change, entail a high risk of energy rationing; for this reason some of the users, whether industrial or residential, have decided to seek multiple alternatives to reduce the costs of their billing in interconnected areas and even supply their energy needs. Among these alternatives is found solar energy in its thermal and photovoltaic use, a resource that must be characterized in order to determine the technical and budgetary aspects involved in the implementation of profitable energy generation projects. This article seeks to provide technical tools for the design and implementation of generation projects based on solar energy, providing physical-mathematical approach based in the classical Angström-Prescott model that allow engineers and researchers to model the global solar radiation on the Earth’s surface in order to maximize the use of this resource in a specific geographical location. Although there are different ways to characterize the solar resource on the earth’s surface, this paper presents a review study focused on the most important global solar radiation estimation models present in the literature.
Objective: To design and build an instrument capable of measuring long-wave infrared radiation with elements of the national market that offers an excellent performance in measuring energy in this spectral band. Methodology: The best design was determined based on other existing instruments, innovating its development by using materials that are easily accessible in the country, and its operation was verified by characterizing an incandescent light bulb used as an infrared radiation pattern. Then, the radiation measured by the instrument was compared to that emitted by the source by means of an experimental setup that involved measuring the temperature at several distances. Results: A functional prototype was obtained, and its operation could be verified through a series of irradiance measurements according to the Stefan-Boltzmann law, through a calibration process with a known radiation source. Conclusions: A radiometric instrument for the thermal infrared band was designed and built. Raw materials and electronic components were used which were available in the local market, thus noticeably reducing the equipment’s production costs. Funding: This research was funded by the authors.
En las labores docentes de los profesores universitarios, no es un secreto la existencia de un bajo desempeño y alta mortalidad académica de los estudiantes de física de las diversas carreras (ciencias naturales, ingenierías, ciencias de la educación, tecnologías, etc.) que cuentan en sus programas curriculares con esta disciplina como base de su formación. En el trabajo desarrollado a continuación se exponen algunos de los problemas más sobresalientes de la enseñanza de la física y se propone el desarrollo de la física computacional como estrategia útil para el desarrollo de aprendizaje significativo de esta ciencia en estudiantes de primeros semestres del nivel universitario.
Se describe el efecto de un campo magnético uniforme en materiales conductores, y cómo estos apantallan el campo que los atraviesa. Con el fin de crear dicho campo,se energiza una bobina que encierra el material apantallador y la bobina sensor de campo magnético, mediante una señal sinusoidal producida por un generador de señales con una tensión de 10 [Vp]. La medida del campo magnético se realiza de manera indirecta ubicando una bobina como sensor en el centro de una bobina de diámetro mayor, realizando la medida de tensión en el sensor, de tal manera que al colocar un material apantallador que encierre la bobina se reduzca el campo magnético en su interior y, por ende, la tensión inducida en la bobina. Los materiales apantalladores que se emplearon fueron: acero, aluminio, hierro y cobre, la eficiencia de estos materiales fue estudiada en un rango de frecuencias de 60-100.000 Hz, obteniendo como resultado que el material más eficiente desde 60- 12.000 Hz es el hierro, y para 32.000-100.000 es el cobre.
Objective: To determine the behavior of dielectric permittivity of class II ceramic capacitor in function of frequency up to 10MHz. Context: in telecommunications and high frequency circuits is necessary to take into account the diminishing of permittivity on dielectrics of ceramic capacitors with the frequency growth, two quantitative methods are proposed to determine this behavior. Method: First, the impedance meter bridge FLUKE PM5306 was used in the frequency range from 10^2 Hz to 10^5 Hz; and second, a novel low-cost electronic circuit for the frequency range between 10^4 Hz to 10^7. Results: The results from the circuit were validated using the impedance meter bridge RLC FLUKE PM 6306. The measure of the complex capacitance from three capacitors and their loss tangent were obtained. Conclusions: The capacitance decreasing with the increment of the frequency was observed in the impedance meter bridge and the implemented circuit, finding a convergence between both methods in the common frequency region.
Objective: This paper aims to conduct a study of the speed of sound in Colombia for heights below the troposphere, taking into account the temperature as a function of altitude for a tropical zone, in order to determine the distance of lightning strike. Methodology: A speed of sound profile for Colombia was determined by analyzing data on altitude, temperature, and relative humidity in the country. The temperature equation as a function of altitude presented by NASA and the International Standard Atmosphere was taken into account to compare with the data obtained from meteorological stations located in different parts of the country (this stations measure information of temperature and other physical variables). Additionally, a sound profile map of Colombia was obtained using the interpolation in ArcGIS software. Results: A map of the speed of sound in Colombia was obtained, thus finding the speed range in the country. Likewise, the temperature was determined as function of the altitude for Colombia (a country in the tropical zone), with which it is possible to have data closer to the real speed of sound in the place and determinate the distance of impact of a lighting in land. Conclusions: The study of variables such as temperature, relative humidity, and altitude helped determine the speed of sound for Colombia. It was also possible to define a temperature equation as a function of altitude for a tropical country; with the speed of sound, the radius of impact of a lightning can be found.
ResumenEn este artículo se presenta una nueva metodología para el estudio del comportamiento en condensadoresasimétricos del fenómeno de levitación electromagnética, sometido a altas tensiones (AC y DC).Se realizaron modelos experimentales para un análisis cinemático, simulaciones para observar el campo eléctrico y magnético, y por último se hicieron estudios de termografía de los condensadores asimétricos, con el fin de realizar un análisis cuantitativo y cualitativo del fenómeno de levitación electromagnética, comparando el comportamiento que se presenta con cada tipo de señal (AC y DC). Como resultado el condensador asimétrico sometido a 30 kV en corriente directa, presentó una levitación Estable en comparación con la señal en corriente alterna.
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