RESUMENLos productos que proveen estimaciones de lluvia derivadas de satélites son útiles para el monitoreo tanto ambiental como de sequías, y permiten además afrontar el problema de las observaciones derivadas de estaciones pluviométricas mal distribuidas, siempre y cuando su precisión sea conocida. Venezuela es altamente vulnerable a eventos climáticos extremos como sequías extensivas y crecientes rápidas, por lo tanto conocer las debilidades y fortalezas de las estimaciones de lluvias derivadas de satélites resulta útil para la planificación de los recursos hídricos. Las estimaciones mensuales de lluvia derivadas del producto Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS v.2) son contrastadas con los registros proveniente de estaciones climáticas , empleando métricas numéricas para evaluar su desempeño en la estimación de la cantidad de lluvia, y métricas categóricas para evaluar su capacidad de detección de eventos de lluvia. Los análisis aplicados consideran diferentes categorías de lluvia, la estacionalidad y el contexto espacial. Los resultados muestran que el producto CHIRPS v.2 sobreestima (subestima) los valores más bajos (altos) de lluvia, aunque en la mayoría de las métricas de habilidad muestra un buen desempeño. Este producto consigue un mejor desempeño durante la estación lluviosa (abril-septiembre), pero sobreestima significativamente la frecuencia de los eventos de lluvias. También muestra mejor desempeño global en regiones planas abiertas (p. ej., Los Llanos), donde la precipitación es influida por la actividad de la zona de convergencia intertropical y los sistemas convectivos locales.ABSTRACT Satellite-derived rainfall products are useful for both drought and environmental monitoring, and they also allow for tackling the problem of sparse, unevenly distributed and erratic rain gauge observations provided their accuracy is well known. Venezuela is a country highly vulnerable to extreme weather events such as extensive droughts and flash floods; therefore, an understanding of the strengths and weaknesses of satellite-based rainfall products is useful for the planning of water resources. Using numerical metrics in order to evaluate performance, monthly rainfall estimates, from the Climate Hazards Group InfraRed Precipitation and Stations (CHIRPS v.2) product, are compared to gauge data from the 1981-2007 interval and categorical metrics for assessing rain-detection skills. The analysis was performed considering different rainfall categories, seasonality, and spatial context. The results show that the satellite product CHIRPS v.2 overestimates (underestimates) low (high) monthly rainfall values; although on the majority of numerical metrics of skill shows a good performance. This product, on the other hand, achieves better performance during the rainy season (April-September), significantly overestimating, however, the rainfall-events frequency. The product also shows best overall performance over flat and open regions (e.g., Los Llanos), where precipitation is influenced by...

Synchrotron radiation was originally studied by classical methods using the Liénard–Wiechert potentials of electric currents. Subsequently, quantum corrections to the classical formulas were studied, considering the emission of photons arising from electronic transitions between spectral levels, described in terms of the Dirac equation. In this paper, an intermediate approach is considered, in which electric currents generating the radiation are considered classically while the quantum nature of the radiation is taken into account exactly. Such an approximate approach may be helpful in some cases; it allows one to study one-photon and multi-photon radiation without complicating calculations using corresponding solutions of the Dirac equation. Here, exact quantum states of an electromagnetic field interacting with classical currents are constructed and their properties studied. With their help, the probability of photon emission by classical currents is calculated and relatively simple formulas for one-photon and multi-photon radiation are obtained. Using the specific circular electric current, the corresponding synchrotron radiation is calculated. The relationship between the obtained results and those known before are discussed, for example with the Schott formula, with Schwinger calculations, with one-photon radiation of scalar particles due to transitions between Landau levels, and with some previous results of calculating two-photon synchrotron radiation.

ABSTRACT:In Brazil, the conventional center pivot is widely used for irrigation of agricultural crops and its use has grown continuously. However, when improperly managed, it facilitates the development of diseases in all parts of the plant, with a direct effect on productivity, besides favoring losses of water by evaporation. The drip may be an alternative, since it minimizes the losses and does not wet the aerial parts of the plants, thereby reducing the incidence of diseases. A new system called localized mobile drip irrigation (IRGMO) is being developed in an attempt to combine the practicality and rusticity of the center pivot with the efficiency and water savings of the dripping irrigation systems. This fusion system is the central pivot with drip irrigation system for water distribution in the soil surface. This study aims to present a calculation methodology for the design of IRGMO system and compare it with conventional systems. It is concluded that this methodology allows the design of the IRGMO and that this new technology allows a savings of approximately 99% in a number of drip tubes compared to the conventional system with fixed drip irrigation lines in the field.

In this paper, the effective potential approach in quantum field theory is used in order to investigate self-interaction loop correction to the Casimir energy density and generation of topological mass for both massless and massive real scalar fields. It is assumed that the scalar field obeys a helix boundary condition. In addition, it is also considered a CPT-even aether-type violation of the Lorentz symmetry. In the absence of the Lorentz violation, we obtain analytical expressions for the loop correction to the Casimir energy density and to the mass of the scalar field. The same expressions are also obtained assuming the Lorentz violation in each of the spacetime directions. We also show some graphs that exhibit how the loop correction and the Lorentz violation affect the Casimir energy density and the mass of the scalar field.