Propiedades ópticas de peliculas Ldep con diferentes mezclas de aditivos.

In this article, different formulations of linear low density polyethylene (PEBD) mixed with 5 different types of additives were processed, the objective of which is to analyze the effect of the additives on the optical properties of PEBD films for crop protection directed primarily for constructions of greenhouses suitable for performance in tropical environments. The results of the ultra violet and visible region transmission show that the light transmission of the reference films is greater in the visible area than in films made with additive mixtures, due to the diffusive effect of some elements and the synergistic action of the additives decreasing the transmission of light in the ultra violet and visible area.En el presente artículo se procesaron diferentes formulaciones de polietileno lineal de baja densidad (PEBD) mezclado con 5 tipos de aditivos diferentes, cuyo objetivo es analizar el efecto de los aditivos en las propiedades ópticas de películas de PEBD de protección de cultivo dirigida fundamentalmente para construcciones de invernaderos adecuados para el desempeño en medios tropicales. Los resultados de la transmisión de la región ultra violeta y visible muestran que la transmisión de luz de las películas de referencia es mayor en la zona visible que en las películas fabricadas con mezclas de aditivos, debido al efecto difusivo de algunos elementos y a la acción sinérgica de los aditivos disminuyendo la transmisión de luz en la zona ultra violeta y visible

Propiedades ópticas de peliculas Ldep con diferentes mezclas de aditivos.

In this paper were processed dierent linear low density polyethylene (LDPE)formulations, mixed it with ve kind of dierent additives whose objectivewas analyzing the additives eects in the optical properties of LDPE lms ongreenhouse cover structure in protected cultivation for tropical environments.The results of ultra violet and visible region showed that the light transmissionfrom the reference lm was higher than additives lms mixtures in thevisible region, eect of some elements and synergistic action from additivescontributing to decrease the light transmission in the ultra violet and visibleregion.PACS: 78.66.BzEn el presente artículo se procesaron diferentes formulaciones de polietileno lineal de baja densidad (PEBD) mezclado con 5 tipos de aditivos diferentes, cuyo objetivo es analizar el efecto de los aditivos en las propiedades ópticas de películas de PEBD de protección de cultivo dirigida fundamentalmente para construcciones de invernaderos adecuados para el desempeño en medios tropicales. Los resultados de la transmisión de la región ultra violeta y visible muestran que la transmisión de luz de las películas de referencia es mayor en la zona visible que en las películas fabricadas con mezclas de aditivos, debido al efecto difusivo de algunos elementos y a la acción sinérgica de los aditivos disminuyendo la transmisión de luz en la zona ultra violeta y visible.PACS: 78.66.B

Evaluación de la corrosión de la aleación de aluminio 6063 protegida mediante el proceso de anodizado duro

The purpose of this work is show the propertiesagainst the corrosion of the aluminum alloy 6063by means of the process of hard anodizing. In theobtaining of the coating they are had as variablethe time of immersion in the sulfuric acid bath15% in weight to a temperature of 0±3 ºC (20, 50and 80 minutes) and the density of current (2.7, 4and 5 A/dm2). The rank of obtained thicknessesgoes from 23.3 to 125.5 micrometers. The microhardnessto the alloy and the hard anodizing wereobtaining that with the process of hard anodizing,El propósito de este trabajo es presentar laspropiedades frente a la corrosión de la aleación dealuminio 6063 mediante el proceso de anodizadoduro. En la obtención del recubrimiento se tienencomo variables el tiempo de inmersión en el bañode ácido sulfúrico al 15% en peso a una temperaturade 0±3 ºC (20, 50 y 80 minutos) y la densidad decorriente (2,7; 4 y 5 A/dm2). El rango de espesoresobtenidos va desde 23,3 hasta 125,5 micrómetros.Se midieron las microdurezas a la aleación y alos anodizados, obteniendo que con el procesode anodizado duro, se alcanza una microdurezade hasta cinco veces el valor de la aleación sinrecubrir. Para evaluar el comportamiento a lacorrosión, se realizaron las pruebas de curvasde polarización (Tafel) y Espectroscopia deImpedancia Electroquímica (EIS) sobre probeta

Evaluación de la corrosión del acero embebido en concreto AAS, expuesto a carbonatación mediante un experimento factorial con medidas repetidas.

This article presents various techniques for assessing corrosion, the linear polarization resistance and galvanostatic pulse, the analysis was performed using analysis of variance models using a factorial experiment with three factors, one repeated measure, because on the same experimental unit (reinforced concrete), it experienced several samples to be measured in time (0 h=1, 350 h=2, 700 h=3, 1050 h=4, 1700 h=5 y 2600 h=6). This makes the observations are not independent, the other two factors relate to, the binder (ce: 1 = activated slag [AAS] and 2 = ordinary Portland concrete [OPC]) and the exposure condition (ca: 1 = y 2 = environmental exposure accelerated carbonation). These factors were discussed according to the results of the electrochemical properties. Initially performed the statistical processing of each of the variables in relation to the properties and analyzed the interaction between them. Where they established the differences in materials used as coating steel, concrete, OPC and AAS. OPC concrete specimens, exhibited a resting potential, polarization resistance and ohmic (CO2 condition) than those obtained for reinforced concrete in AAS.Este artículo presenta varias técnicas para evaluar la corrosión, la resistencia a la polarización lineal y el pulso galvanostático, el análisis se realizó utilizando análisis de modelos de varianza utilizando un experimento factorial con tres factores, una medida repetida, porque en la misma unidad experimental (hormigón armado), experimentó varias muestras para medir a tiempo (0 h = 1, 350 h = 2, 700 h = 3, 1050 h = 4, 1700 h = 5 y 2600 h = 6). Esto hace que las observaciones no sean independientes, los otros dos factores se relacionan con el aglutinante (ce: 1 = escoria activada [AAS] y 2 = concreto Portland ordinario [OPC]) y la condición de exposición (ca: 1 = y 2 = ambiental exposición a la carbonatación acelerada). Estos factores fueron discutidos de acuerdo con los resultados de las propiedades electroquímicas. Inicialmente realizó el procesamiento estadístico de cada una de las variables en relación con las propiedades y analizó la interacción entre ellas. Donde establecieron las diferencias en los materiales utilizados como revestimiento de acero, hormigón, OPC y AAS. Las muestras de hormigón OPC exhibieron un potencial de reposo, resistencia a la polarización y óhmica (condición de CO2) que las obtenidas para el hormigón armado en AAS

Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory

The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been used for the past 25 years as a reference source in TeV astronomy, for calibration and verification of new TeV instruments. The High Altitude Water Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe the Crab Nebula at high significance across nearly the full spectrum of energies to which HAWC is sensitive. HAWC is unique for its wide field-of-view, nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC's sensitivity improves with the gamma-ray energy. Above $\sim$1 TeV the sensitivity is driven by the best background rejection and angular resolution ever achieved for a wide-field ground array. We present a time-integrated analysis of the Crab using 507 live days of HAWC data from 2014 November to 2016 June. The spectrum of the Crab is fit to a function of the form $\phi(E) = \phi_0 (E/E_{0})^{-\alpha -\beta\cdot{\rm{ln}}(E/E_{0})}$. The data is well-fit with values of $\alpha=2.63\pm0.03$, $\beta=0.15\pm0.03$, and log$_{10}(\phi_0~{\rm{cm}^2}~{\rm{s}}~{\rm{TeV}})=-12.60\pm0.02$ when $E_{0}$ is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the systematic errors in this HAWC measurement is discussed and estimated to be $\pm$50\% in the photon flux between 1 and 37 TeV. Confirmation of the Crab flux serves to establish the HAWC instrument's sensitivity for surveys of the sky. The HAWC survey will exceed sensitivity of current-generation observatories and open a new view of 2/3 of the sky above 10 TeV.Comment: Submitted 2017/01/06 to the Astrophysical Journa

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth

The unexpectedly high flux of cosmic ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the HighAltitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera-electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.Comment: 16 pages (including supplementary material), 5 figure

The 2HWC HAWC Observatory Gamma Ray Catalog

We present the first catalog of TeV gamma-ray sources realized with the recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the most sensitive wide field-of-view TeV telescope currently in operation, with a 1-year survey sensitivity of ~5-10% of the flux of the Crab Nebula. With an instantaneous field of view >1.5 sr and >90% duty cycle, it continuously surveys and monitors the sky for gamma ray energies between hundreds GeV and tens of TeV. HAWC is located in Mexico at a latitude of 19 degree North and was completed in March 2015. Here, we present the 2HWC catalog, which is the result of the first source search realized with the complete HAWC detector. Realized with 507 days of data and represents the most sensitive TeV survey to date for such a large fraction of the sky. A total of 39 sources were detected, with an expected contamination of 0.5 due to background fluctuation. Out of these sources, 16 are more than one degree away from any previously reported TeV source. The source list, including the position measurement, spectrum measurement, and uncertainties, is reported. Seven of the detected sources may be associated with pulsar wind nebulae, two with supernova remnants, two with blazars, and the remaining 23 have no firm identification yet.Comment: Submitted 2017/02/09 to the Astrophysical Journa

Search for very-high-energy emission from Gamma-ray Bursts using the first 18 months of data from the HAWC Gamma-ray Observatory

The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory is an extensive air shower detector operating in central Mexico, which has recently completed its first two years of full operations. If for a burst like GRB 130427A at a redshift of 0.34 and a high-energy component following a power law with index -1.66, the high-energy component is extended to higher energies with no cut-off other than from extragalactic background light attenuation, HAWC would observe gamma rays with a peak energy of $\sim$300 GeV. This paper reports the results of HAWC observations of 64 gamma-ray bursts (GRBs) detected by $\mathit{Swift}$ and $\mathit{Fermi}$, including three GRBs that were also detected by the Large Area Telescope ($\mathit{Fermi}$-LAT). An ON/OFF analysis method is employed, searching on the time scale given by the observed light curve at keV-MeV energies and also on extended time scales. For all GRBs and time scales, no statistically significant excess of counts is found and upper limits on the number of gamma rays and the gamma-ray flux are calculated. GRB 170206A, the third brightest short GRB detected by the Gamma-ray Burst Monitor on board the $\mathit{Fermi}$ satellite ($\mathit{Fermi}$-GBM) and also detected by the LAT, occurred very close to zenith. The LAT measurements can neither exclude the presence of a synchrotron self-Compton (SSC) component nor constrain its spectrum. Instead, the HAWC upper limits constrain the expected cut-off in an additional high-energy component to be less than $100~\rm{GeV}$ for reasonable assumptions about the energetics and redshift of the burst.Comment: 19 pages, 6 figures, published in Ap