17 Previous studies of this model were either restricted to ^ = 0.5 (#=0), N = 2048 sites (Ref. 3) or to concentration c B = 0.25, iV = 500 sites lL. D. Fosdick, Phys.Rev. 1_16, 565 (1959)3 . This lattice size clearly is too small to study the phase transitions, however.18 This estimate is in good agreement with Ref. 3, indicating that the inaccuracy due to finite lattice size is small. 19A significant change of interaction parameters with lattice spacing has recently been revealed even for Principal planes of the 4 He solid-superfluid interface are expected to undergo roughening transitions at temperatures of about 1 K. An experiment is described in which two such transitions were observed in the hep-superfluid interface: first for the basal plane at 1.08 K and second for an orthogonal face at 0.85 K.
The infrared emission properties of an electrically heated single resistive element produced by ion implantation of diamond is reported. It is found that good contrast can be obtained between the implanted and unimplanted regions of the diamond mainly because of the increased emissivity following implantation. The infrared output is stronger if the diamond is viewed with the implanted surface facing away from the detector. The possible utilization of diamond-based pixels in infrared scene generation is discussed.
Atmospheric turbulence may have a strong impact on the imaging quality of long range warning sensors and other electro-optical systems. Major effects are beam broadening, intensity fluctuations (or scintillation) and angle-ofarrival fluctuations. The structure constant of refractive index fluctuations, C n 2 , is the parameter most commonly used to describe the strength of atmospheric turbulence. FGAN-FOM measured C n2 values in two different climates, moderate climate in mid-Europe, Germany and arid climate in Israel. The measurements in arid climate were carried out in co-operation with the EORD (Electro-Optics Research & Development Foundation Ltd.), TECHNION, Haifa, Israel. The measurements were performed with identical laser scintillometers along a horizontal optical path of about 100 m, above grassland in mid-Europe, and above stony ground without vegetation in Israel. The data were collected continuously for a time period of at least one year at a time resolution of 5 minutes. For both climates examples of the diurnal cycle of C n2 are given. Since C n 2 usually changes as a function of time-ofday and of season its influence on electro-optical systems can only be expressed in a statistical way. Therefore the cumulative frequencies of occurrence of C n 2 were calculated for a time period of one month for both climates. These results were used to calculate the corresponding turbulence modulation transfer function (MTF) and point spread function (PSF) for a typical IR sensor with a Cadmium Mercury Telluride detector (CMT) and a UV sensor.
This paper will describe a novel approach ofgenerating radiometric scenes ofnatural backgrounds that will serve as an input for simulating E-O sensor scene outputs in the thermal.band. The methodology is based on segmentation of a measured scene (in any spectral band) into elements that have similar thermal behavior. The thermal radiance value for each thermal element is calculated using a set of four semi empirically determined coefficients that relate the surface temperature to the local meteorological parameters such as solar radiation, longwave sky radiation, air temperature and wind speed. The thermal coefficients are determined using a theoretical model and an experimental data base. The diurnal variations of the scene are thus easily predicted by knowing the meteorological parameters and the individual set of thermal coefficients for the various thermal elements of the scene. Since the approach is based on a real scene image and an experimental database the generated images have a realistic appearance including realistic clutter properties. The generated thermal scene will serve as the input to a sensor model that will calculate the expected image of a thermal camera viewing the scene The paper will describe the methodology ofthe scene generation ,the sensor model and will demonstrate the approach by giving some examples.
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