Annual variation of the angular distribution of the UV beneath public shade structures

Local governments provide many shade structures at parks and sporting ovals for public use. However, the question remains of how effective are public shade structures at reducing biologically effective UV radiation throughout the year? Broadband measurements of the angular distribution of scattered UV beneath three specific public shade structures was conducted for relatively clear skies and for a solar zenith angle (SZA) ranging from 13 degrees to 76 degrees. The ultraviolet protection factors (UPF) for the shade structures ranged from 18.3 to 1.5 for an increasing SZA. Measurements showed that the horizontal plane received the highest SUV levels from the SZA of 28 degrees to 75 degrees, 42 degrees to 76 degrees, and 50 degrees to 76 degrees for the small, medium and large structures, respectively. This was due to the angle of the sun causing the shade created by the shade structure to be outside the structure. For the small shade structure, the measurements directed to the west were the highest levels in the shade after approximately 28 degrees. For the medium and large shade structures, the measurements directed to the west and south were the highest levels in the shade after roughly 42 degrees and 50 degrees, respectively.     

Spectral shade ratios on horizontal and sun normal surfaces for single trees and relatively cloud free sky.

Spectral shade ratios, defined as the ratios of the spectral irradiances on horizontal and sun normal planes in the tree shade to those on a horizontal plane in sunlight, were calculated. These planes were in the shade of an isolated medium canopy density tree and a sparse canopy density tree at the tree shade sites of the centre, edge and trunk. The sun normal plane was employed as there are some activities that have exposures to parts of the body that are orientated in a sun normal plane. The horizontal plane shade ratios for the medium density canopy dropped by 47-56% from the ratios in the range 301 to 310 nm to the ratios in the range 391 to 400 nm. In absolute terms, the largest change in the shade ratio of 0.28 was for the centre and edge sites compared to 0.07 for the trunk. Similarly, for the sun normal plane, the ratio dropped by 40-49% with an absolute reduction of 0.19 for the edge and 0.04 for the trunk. For the sparse density canopy, the decrease in the shade ratios over the same wavelength range was a drop by 37-42% on a horizontal plane or, in absolute terms, a reduction by 0.22 for the edge and 0.13 for the trunk. Similarly, the decrease was 34-39% on the sun normal plane or, in absolute terms, a reduction by 0.19 for the edge and 0.12 for the trunk.     

Indium and tin oxide polycrystalline thin films as NO gas sensors produced by reactive pulsed laser ablation and deposition

Pulsed laser ablation is a very interesting method of depositing thin films of several materials and compounds, such as oxides, nitrides, insulators, semiconductors, and superconductors. Indium and tin oxide polycrystalline thin films have been grown on silicon (100) substrates by reactive PLD from two metallic targets of indium and tin by multilayered deposition, in the presence of oxygen, using a frequency-doubled Nd-YAG laser (5=532 nm). The films produced have been studied to evaluate their use as NO gas sensors, and the best performance has been found by varying some important parameters, such as the substrate temperature and the pressure of oxygen in the deposition chamber. X-ray diffraction analysis of the deposited films shows that they are polycrystalline with a preferential (400) orientation. Electrical resistivity measurements, performed by using a four-point probe technique, show a sharp increase in resistivity when the films are exposed to NO. The electrical responses of tin oxide-indium oxide multilayered thin films are reported.     

Tunability range of 245 nm in a diode-pumped Tm:BaY2F8 laser at 1.9 μm: a theoretical and experimental investigation

Extremely wide wavelength tuning ranges of up to ∼300 nm around 1.9 μm are theoretically predicted in a Tm-doped BaY₂F₈ crystal, on the basis of near-infrared measurements of emission and absorption cross sections. A tunability interval of 245 nm, from 1849 nm to 2059 nm, has been demonstrated by room-temperature laser experiments using a 8% Tm-doped crystal. PACS 42.55.Xi; 42.55.Rz; 42.60.Pk; 42.70.Hj; 42.60.Lh     

Morphological and dynamical aspects of the room evacuation process

We study the evacuation of a set of 200 pedestrians from a room under a state of panic. The dynamics of the pedestrians is given by the Social Force Model. The degree of panic is controlled by a parameter v_d which represents the velocity at which pedestrians wish to move. We show that the “faster is slower effect” can be understood in terms of the works performed by the different forces present in the system and the role played by dissipative terms in the model. Beyond the maximum flow rate the “granular cluster” mass distribution displays a transition from exponentially decaying to “U-shaped” as this value of v_d evacuation efficiency begins to decrease rapidly.     

Numerical study of metastable States in ising spin glasses

We study numerically the structure of metastable states in the Sherrington-Kirkpatrick spin glass. We find that all nonparamagnetic stationary points of the free energy are organized into pairs, consisting of a minimum and an order 1 saddle, which coalesce in the thermodynamic limit. Within the annealed approximation, the entropic contribution of these states, that is the complexity, is compatible with the supersymmetry-breaking calculation performed by Bray and Moore [J. Phys. C 13, L469 (1980)]]. This result indicates that the supersymmetry is spontaneously broken in the Sherrington-Kirkpatrick model.