Energy balance in a mango orchard in Northeast of Brazil.

The main objective of this research was the determination of the energy balance in a mango orchard

Modelling of photonic wire Bragg Gratings

Some important properties of photonic wire Bragg grating structures have been investigate. The design, obtained as a generalisation of the full-width gap grating, has been modelled using 3D finite-difference time-domain simulations. Different types of stop-band have been observed. The impact of the grating geometry on the lowest order (longest wavelength) stop-band has been investigated - and has identified deeply indented configurations where reduction of the stop-bandwidth and of the reflectivity occurred. Our computational results have been substantially validated by an experimental demonstration of the fundamental stop-band of photonic wire Bragg gratings fabricated on silicon-on-insulator material. The accuracy of two distinct 2D computational models based on the effective index method has also been studied - because of their inherently much greater rapidity and consequent utility for approximate initial designs. A 2D plan-view model has been found to reproduce a large part of the essential features of the spectral response of full 3D models

Componentes do balanco de energia em pomar irrigado no Nordeste.

Results of an energy balance based on the Bowen ratio method are presented. Two field experiments were carriedout in 1998 and 1999, with a mango orchard in Petrolina, PE. The mango trees were irrigated by a drip irrigationsystem. A micrometeorology tower was set up for installation of the instruments used for the energy balance,which are: net radiation, two psychrometers and two anemometers installed in two levels above the canopy of theculture, and more two radiometers (global solar radiation and the radiation reflected by the culture). Two plates formeasuring the soil heat flux in a depth of 5 cm were installed. The analog signals of all instruments were scannedonce every five seconds and averaged every 10 minutes using a micrologger. It was verified that didn't happengreat differences among the components of the energy balance in relation to the two experiments. In general, thelatent heat flux was of the order of 80% of Rn, while H and G represented around 15% and 5% of Rn, respectively.Such relationships were analyzed in different phenological phases, as well as the seasonal behavior of the energybalance component

Coeficiente de cultura e produtividade da mangueira irrigada.

Data of solar radiation, soil heat flux and dry and wet bulbs air temperature were used in the elaboration of theabove canopy energy balance based on Bowen ratio. Also, data soil humidity profiles were used in thedetermination of the soil water balance of a dripping irrigated seven years old mango orchard, cv. ?Tommy Atkins’.The field experiment was conducted in the irrigated perimeter of Bebedouro, in Petrolina-PE, Brazil (Latitude:09009`S, Longitude: 40022`W; altitude: 365.5m), in the years of 1998 and 1999. The obtained results indicatedthat, in the submedian San Francisco river region soil and climate conditions, the mango orchard waterconsumption, represented by the corp coefficient (Kc), doesn't stay constant throughout the productive cycle, but itvaries as a function of the days after flowering(DAF) according to the following equation: Kc = 0.36 + 0.009(DAF) – 4.0 x 10-5 (DAF)2, with r2 = 0.79

Balanco hidrico no solo cultivado com mangueiras.

The experimental part of the present research was conducted in the irrigated perimeter of Bebedouro, Petrolina, PE,Brazil (Latitude: 09009`S, Longitude: 40022`W; altitude: 365.5m) in the years of 1998 and 1999, in a drippingirrigated plot area of 9,880 m2 seven years old mango orchard, cv. ?Tommy Atkins`, planted in a spacing of 5mbetween plants by 8m between arrays. This work evaluated the efficiency of the soil water balance for determiningthe evapotranspiraration throughout the mango orchard productive cycle. The errors analysis indicated that, for thesubmedian San Francisco river region soil and climate conditions, the soil water balance method for estimatingevapotranspiration should not be applied for periods lower than a week. Also, according to the obtained results, thesoil water balance method is only efficient in the estimates of the evapotranspiration of mango orchard whenconsidering the term regarding to the deep drainage or water ascent

Alguns aspectos fisiologicos da mangueira em condicoes irrigada e de estresse hidrico.

Este estudo analisou medidas porométricas feitas em um pomar de manga, variedade Tommy Atkins, plantado em Fevereiro de 1993, e irrigado por gotejamento no campo experimental da Embrapa Semi-Árido em Petrolina, PE, Brasil (Latitude: 090 09`S, Longitude: 400 22`W; altitude: 365,5m), usando um porômetro de difusão, LI - 1600 (Licor, EUA)

Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides

All-optical signal processing is envisioned as an approach to dramatically decrease power consumption and speed up performance of next-generation optical telecommunications networks. Nonlinear optical effects, such as four-wave mixing (FWM) and parametric gain, have long been explored to realize all-optical functions in glass fibers. An alternative approach is to employ nanoscale engineering of silicon waveguides to enhance the optical nonlinearities by up to five orders of magnitude, enabling integrated chip-scale all-optical signal processing. Previously, strong two-photon absorption (TPA) of the telecom-band pump has been a fundamental and unavoidable obstacle, limiting parametric gain to values on the order of a few dB. Here we demonstrate a silicon nanophotonic optical parametric amplifier exhibiting gain as large as 25.4 dB, by operating the pump in the mid-IR near one-half the band-gap energy (E~0.55eV, lambda~2200nm), at which parasitic TPA-related absorption vanishes. This gain is high enough to compensate all insertion losses, resulting in 13 dB net off-chip amplification. Furthermore, dispersion engineering dramatically increases the gain bandwidth to more than 220 nm, all realized using an ultra-compact 4 mm silicon chip. Beyond its significant relevance to all-optical signal processing, the broadband parametric gain also facilitates the simultaneous generation of multiple on-chip mid-IR sources through cascaded FWM, covering a 500 nm spectral range. Together, these results provide a foundation for the construction of silicon-based room-temperature mid-IR light sources including tunable chip-scale parametric oscillators, optical frequency combs, and supercontinuum generators

Avaliação do comportamento dos coeficientes de transferência turbulenta de calor sensivel e calor latente num pomar de mangueiras.

O presente trabalho objetiva avaliar a magnitude e o comportamento diurno dos coeficientes de transferência turbulenta de calor sensível e calor latente num pomar de mangueira em condições irrigadas

Componentes do balanco de energia num pomar de mangueiras em condicoes especificas de nebulosidade.

O presente trabalho tem como objetivo analisar o comportamento médio dos componentes do balanço de energia, ao longo do ciclo produtivo da mangueira, em condições específicas de energia, e a eficiência dos modelos de estimativa do fluxo de calor latente em função do saldo de radiação