abstract angstrom-prescott equation is one of the most commonly used methods for the estimation of global solar radiation (rs) based on sunshine hours. the critical step in the application of this method's is the calibration of its coefficients for each region. although the coefficients of the equation have been calibrated in different parts of the world, the effect of different time scales has...

The concept of canopy spectral invariants states that simple algebraic combinations of leaf and canopy spectral transmittance and reflectance become wavelength independent and determine a small set of canopy structure specific variables. This set of structural variables specify the spectral response of a vegetation canopy to the incident solar radiation and allow for a simple and accurate param...

We used a natural experiment to test whether wildfire smoke induced changes in the vertical distribution of zooplankton in Lake Tahoe by decreasing incident ultraviolet radiation (UV). Fires have a variety of effects on aquatic ecosystems, but these impacts are poorly understood and have rarely been observed directly. UV is an important driver of zooplankton vertical migration, and wildfires ma...

The dependence of radiation damage to protein crystals at cryogenic temperatures upon the X-ray absorption cross-section of the crystal has been examined. Lysozyme crystals containing varying heavy-atom concentrations were irradiated and diffraction patterns were recorded as a function of the total number of incident photons. An experimental protocol and a coefficient of sensitivity to absorbed...

We address 2D arrays of metallic nano-particles arranged in a honeycomb lattice in the proximity of a hetero-interface of two media with high dielectric contrast. These systems can function as antennas in the visible range of the spectrum. We demonstrate that their radiation patterns can be made very directional by appropriate choice of the system geometry and materials. We show also that if su...

Scattering of electromagnetic radiation by an object of arbitrary shape or a structured surface, infinite in extent, is considered. When radiation is incident on an interface separating vacuum from a material medium, a current density is induced in the bulk and a surface current density may appear on the boundary surface. The electromagnetic field is then the sum of the incident field and the f...

In this paper, after a brief overview on laser warning system (LWS), a new structure for an optical array that is used in its optical subsystem is introduced. According to the laser threats’ wavelengths (0.5 – 1.6 µm) and our desirable field of view (FOV), we used 6 lenses for gathering the incident radiation and then optimized the optical array. Lenses’ radius, their se...

We demonstrate a terahertz (THz) beam steering method using difference frequency generation that is based on the principle of phased array antennas. A strip-line photoconductive antenna was illuminated by two spatially dispersed beams produced from an ultrafast laser. THz radiation with a bandwidth of 65 GHz was generated from the overlapping area of the two beams, between which the frequency d...

An anomalous achromatic mirror operating in the near-IR and visible frequency ranges was designed using an array of metal−insulator−metal (MIM) resonators. An incident wave interacting with the MIM resonator experiences phase shift that is equal to the optical path traveled by the gap plasmon excited by the wave. A phase gradient along the mirror surface is created through the difference in pla...