A Tractable Line-of-Sight Product Channel Model: Application to Wireless Powered Communications

We here present a general and tractable fading model for line-of-sight (LOS) scenarios, which is based on the product of two independent and non-identically distributed κ- μ shadowed random variables. Simple closed-form expressions for the probability density function and cumulative distribution function are derived, which are as tractable as the corresponding expressions derived from a product of Nakagami-m random variables. This newly proposed model simplifies the challenging characterization of LOS product channels, as well as combinations of LOS channels with non-LOS ones. Results are used to analyze performance measures of interest in the context of wireless powered communications.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Turbulent Erosion of Magnetic Flux Tubes

Results from a numerical and analytical investigation of the solution of a nonlinear axially symmetric diffusion equation for the magnetic field are presented for the case when the nonlinear dependence of the diffusivity nu(B) on the magnetic field satisfies basic physical requirements. We find that for sufficiently strong nonlinearity (i.e. for sufficiently strong reduction of nu inside the tube) a current sheet is spontaneously formed around the tube within one diffusion timescale. This sheet propagates inwards with a velocity inversely proportional to the ratio of the field strength just inside the current sheet to the equipartition field strength B0/Be, so the lifetime of a tube with constant internal flux density is increased approximately by a factor not exceeding B0/Be, even for infinitely effective inhibition of turbulence inside the tube. Among the applications of these results we point out that toroidal flux tubes in the solar convective zone are subject to significant flux loss owing to turbulent erosion on a timescale of about 1 month, and that turbulent erosion may be responsible for the formation of a current sheet around a sunspot. It is further proposed that, despite the simplifying assumptions involved, our solutions correctly reflect the essential features of the sunspot decay process.Comment: 17 pages, 11 figure

Small-scale magnetic flux emergence in the quiet Sun

Small bipolar magnetic features are observed to appear in the interior of individual granules in the quiet Sun, signaling the emergence of tiny magnetic loops from the solar interior. We study the origin of those features as part of the magnetoconvection process in the top layers of the convection zone. Two quiet-Sun magnetoconvection models, calculated with the radiation-magnetohydrodynamic (MHD) Bifrost code and with domain stretching from the top layers of the convection zone to the corona, are analyzed. Using 3D visualization as well as a posteriori spectral synthesis of Stokes parameters, we detect the repeated emergence of small magnetic elements in the interior of granules, as in the observations. Additionally, we identify the formation of organized horizontal magnetic sheets covering whole granules. Our approach is twofold, calculating statistical properties of the system, like joint probability density functions (JPDFs), and pursuing individual events via visualization tools. We conclude that the small magnetic loops surfacing within individual granules in the observations may originate from sites at or near the downflows in the granular and mesogranular levels, probably in the first 1 or 1.5 Mm below the surface. We also document the creation of granule-covering magnetic sheet-like structures through the sideways expansion of a small subphotospheric magnetic concentration picked up, and pulled out of the interior, by a nascent granule. The sheet-like structures we found in the models may match the recent observations of Centeno et al. (2017).Comment: 9 pages, 5 figures, Published in The Astrophysical Journal Letter

Proposal of a Novel Setup for Linac Monitoring Using a Specifically Designed Plastic Scintillator and a Spectrophotometer

In this work we report the design, implementation and results of an alternative monitoring system for a linear accelerator (LINAC) used in medical therapy. The system proposed consist in aslab of scintillator plastic with awavelength shifter fiberoptically coupled to collect the light generated,and a Spectrophotometer Ocean Optics USB4000 as analyzer. The control was made with two computers, one into the therapy room and another, using a VNC (Virtual Network Computer) and Ethernet wire, outside of the room in order to avoid radiation exposure. The LINAC dose range covered was 1, 2, 3, 4, 5, 10, 20, 30 and 40 Monitor Units (MU) with 6 and 18 MeV energy photons. The spectrum obtained was compared with the measures of the LINAC ionization camera used to calibrate it. The results obtained allowus to propose this device as an alternative method to monitor the LINAC performance

Effect of fructose-containing feedstocks on the microstructure of multicomponent coatings deposited by suspension plasma spraying

This work addressed to investigate the use of fructose as an additive in the water-based suspension feedstock of a Y-TZP/Al2O3/SiC multicomponent coating manufactured by suspension plasma spraying. The effect of fructose on suspension rheology and surface tension and on the microstructure and thermal conductivity of the resulting coatings was assessed. It was observed that addition of fructose slightly affected the rheological behaviour of the suspensions while a strong decrease in the surface tension of water occurred. The fructose addition led to the development of columnar-like structures, probably associated with its effect on surface tension. X-ray diffraction patterns in the final coating displayed that crystallinity of tetragonal zirconia formed when fructose was added whereas silicon carbide crystalline phase was practically preserved. The determination of thermal conductivity showed that the formation of a controlled columnar structure along with inter-columnar porosity can be beneficial for thermal insulation

Good and bad practices in pv plants

The PVCROPS project (PhotoVolta ic Cost r€duction, Reliability, Operational performance, Prediction and Simulation), cofinanced by European Commission in the frame of Seventh Framework Programme, has compiled in the “Good and bad practices: Manual to improve the quality and reduce the cost of PV systems” a collection of good and bad practices in actual PV plants . All the situations it collects represent the state-of-the-art of existing PV installations all around Europe. They show how the different parts of an installation can be implem ented properly or not. The aim of this manual is to represent a reference text which can help any PV actor (installers, electricians, maintenance operators, owners, etc.) not only to check and improve an already existing installation but will also, and mainly, avoid the previously known bad practices for the construction of a new PV installation. Thus, solving a priori the known errors, new PV installations will be more reliable, efficient and cost-effective and can recover the initial investment in a shorter time. The manual is going to be free available in the PVCROPS website in several languages

Evaluation of physical and chemical soil properties under different management types in the south-western Colombian Andes

Aim of study: Evaluating the variability of physical and chemical soil properties under different soil uses in an experimental farmland of the southwestern Colombian Andes.Area of study: This research was conducted at the Botana Experimental Farm in the mountainous area of Nariño, at the south-western Colombia.Material and methods: nine soil variables were measured under six soil uses which included traditional agriculture, agroforestry systems, and a 67-year-old secondary forest that was used as a reference for comparisons with other soil uses. Data was analyzed through Principal Component Analysis and Duncan’s tests.Main results: organic carbon, cation exchange capacity, clay contents and base saturation were the variables with higher variability among soil uses. The secondary forest and an agroforestry system with alley-cropped wax laurel showed the best soil conditions, whilst pastures and monoculture potato crop plots showed the least desirable conditions for all variables.Research highlights: We found that soils under alley-crop with wax laurel presented the characteristics most similar to the secondary forest. Conversely, soils under alley-crop with alder resembled the soils under intensive management (pasture and potato monocrop); which is related to the inadequate management of this agroforestry systems, provoking that the woody component does not accomplish its goal when implemented.Keywords: soil; agroforestry systems; Andes; forest.Abbreviations used: ACAL, Alley cropping of Alder Trees, ACWL; Alley cropping of Wax Laurel; AFS, agroforestry systems; AWC, available water capacity; BD, Bulk Density; BS, Base saturation; CEC, Cation Exchange Capacity; CLA, Clay; CI, Confidence Intervals, INF, Infiltration; ANOVA, Analysis of Variance; OC, Soil Organic Carbon;  PAST, Pasture; PCA, Principal Component Analysis; PC, Principal Component; POCR, Potato Crop; POR, Soil Porosity; SCAL, Scattered Alder Trees; SEFO, Secondary Forest; SU, soil uses; AU, Animal unit

Essential oils from Argentinean native species reduce in vitro methane production

The aim of this study was to evaluate the effect of Argentinean essential oils (EO) on methane production during in vitro fermentation compared to EO with proven effects as rumen fermentation modifiers. A complete randomized block design was used and the treatments included EO from Aloysia gratissima (50, 100, 150 and 300 mg/L), Eucalyptus globulus (5, 50, 150 and 300 mg/L), Lippia turbinata (30, 60, 120 and 240 mg/L), Mentha x piperita var. vulgaris (50, 100, 200 and 400 mg/L), Origanum vulgare ssp. hirtum cv. Compacto (0.5, 5, 50 and 250 mg/L) and cv. Mendocino (50, 150, 250 and 350 mg/L), Rosmarinus officinalis (100, 300, 500 and 700 mg/L), Schinus molle (75, 150, 300 and 600 mg/L), Tagetes minuta (5, 50, 125 and 250 mg/L), and Thymus vulgaris (5, 50, 150 and 300 mg/L). Two controls were included: control (not containing EO) and monensin (1.87 mg/L). Variables measured were: digestibility of neutral detergent fiber, gas and methane production. Compared to the control, monensin reduced methane production by 44%, but with a 15% reduction in fiber digestibility. Except for E. globulus and L. turbinata, each variable measured was significantly reduced with the higher level of inclusion compared to the control, representing that overall microbial activity was affected. L. turbinata (60.8% limonene) reduced methane by half compared to control, and by 35 to 85% when compared to monensin, without affecting digestibility of the fiber. Some essential oils from native Argentinean plants exhibited great potential to reduce enteric methane production without affecting digestibility, of which L. turbinata was the most promising alternative.El objetivo de este estudio fue evaluar el efecto de aceites esenciales (AE) de plantas nativas de Argentina en la producción de metano durante la fermentación in vitro, en comparación con AE con efectos comprobados como modificadores de la fermentación ruminal. Se realizó un diseño en bloque completos al azar y los AE y dosis evaluados fueron: Aloysia gratissima (0,5, 5, 50 y 250 mg/L) , Eucalyptus globulus (5, 50, 150 y 300 mg/L), Lippia turbinata (30, 60, 120 y 240 mg/L), Mentha x piperita var. vulgaris (50, 100, 200 y 400 mg/L), Origanum vulgare ssp. hirtum cv. Compacto (0,5, 5, 50 y 250 mg/L) y cv. Mendocino (50, 150, 250 y 350 mg/L), Rosmarinus officinalis (100, 300, 500 y 700 mg/L), Schinus molle (75, 150, 300 y 600 mg/L), Tagetes minuta (5, 50, 125 y 250 mg/L), y Thymus vulgaris (5, 50, 150 y 300 mg/L). Se incluyeron dos controles: control (sin AE) y monensina (1,87 mg/L). Las variables evaluadas fueron: digestibilidad in vitro de la fibra en detergente neutro, producción de gas y metano. En comparación al control, la monensina redujo la producción de metano en un 44%, pero con una reducción de un 15% en la digestibilidad de la fibra. Con excepción a E. globulus y L. turbinata, todas las variables fueron reducidas significativamente con el mayor nivel de inclusión comparado con el control, lo cual representa que la actividad microbiana se vio afectada. L. turbinata (60,8% limoneno) redujo la producción de metano a la mitad comparado al control, y entre un 35 y 85% en comparación a la monensina, sin que la digestibilidad de la fibra se vea afectada. Algunos aceites esenciales de plantas nativas de Argentina demostraron gran potencial para reducir la producción de metano entérico sin afectar la digestibilidad, de los cuales L. turbinata fue la alternativa más promisoria.EEA ManfrediFil: García, F. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Brunetti, Maria Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Lucini, Enrique I. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias,; ArgentinaFil: Scorcione Turcato, M.C. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Moreno, Maria Valeria. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Frossasco, Georgina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Colombatto, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomia; Argentina.Fil: Martinez, Maria Jose. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Martinez Ferrer, Jorge. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; Argentin

Flow Field Evolution of a Decaying Sunspot

We study the evolution of the flows and horizontal proper motions in and around a decaying follower sunspot based on time sequences of two-dimensional spectroscopic observations in the visible and white light imaging data obtained over six days from June~7 to~12, 2005. During this time period the sunspot decayed gradually to a pore. The spectroscopic observations were obtained with the Fabry-P\'{e}rot based Visible-Light Imaging Magnetograph (VIM) in conjunction with the high-order adaptive optics (AO) system operated at the 65 cm vacuum reflector of the Big Bear Solar Observatory (BBSO). We apply local correlation tracking (LCT) to the speckle reconstructed time sequences of white-light images around 600 nm to infer horizontal proper motions while the Doppler shifts of the scanned \FeI line at 630.15 nm are used to calculate line-of-sight (LOS) velocities with sub-arcsecond resolution. We find that the dividing line between radial inward and outward proper motions in the inner and outer penumbra, respectively, survives the decay phase. In particular the moat flow is still detectable after the penumbra disappeared. Based on our observations three major processes removed flux from the sunspot: (a) fragmentation of the umbra, (b) flux cancelation of moving magnetic features (MMFs; of the same polarity as the sunspot) that encounter the leading opposite polarity network and plages areas, and (c) flux transport by MMFs (of the same polarity as the sunspot) to the surrounding network and plage regions that have the same polarity as the sunspot.Comment: 9 pages, 7 figures, The Astrophysical Journal, accepted September, 200