The calibration of a system for measuring the transmission of the atmosphere for laser radiation

A method of calibrating a system for measuring the transmission of laser radiation through the atmosphere along paths about 1 km long is proposed and tested on a model “experiment.” Translated from Izmeritel'naya Tekhnika, No. 9, pp. 52–54, September, 2008.     

Numerical technique for solving the radiative transfer equation for a spherical shell atmosphere

A method for numerically solving the equation of radiative transfer in a spherical shell atmosphere is presented. The method uses a conical boundary and a Gauss-Seidel iteration scheme to solve for all orders of scattering along a single radial line in the atmosphere. Tests of the model indicate an accuracy better than 1% for most Earth-atmosphere situations. Results from this model are compared with flat-atmosphere model results for a scattering-only atmosphere. These comparisons indicate that excluding spherical effects for solar zenith angles greater than 85° leads to errors larger than 5% at optical depths as small as 0.10.     

Vibrating knife-edge technique for measuring the focal length of a microlens

A vibrating knife-edge technique is proposed for measuring the focal length of a microlens. The technique is based on the propagation properties of Gaussian beams. A laser beam with a Gaussian intensity profile is focused in front of the microlens under test. After being transmitted through the microlens, the beam propagates toward a detector, which consists of a photodiode that is half blocked by a knife-edge. The photodiode integrates approximately half the intensity of the transmitted beam. The knife-edge vibrates sinusoidally with small amplitude in a plane normal to the direction of propagation. Our analysis shows that the output signal at the photodiode consists of a dc component plus a temporal sinusoidal signal whose amplitude is proportional to the focal length of the microlens. After system calibration, the focal length is measured with an envelope detector or a lock-in amplifier.     

Automatic technique for measuring the Polder resonance in ferritespheres

An automatic technique for measuring the parameters of Polder resonance in polycrystalline ferrite spheres is proposed. The diagonal elements of the external susceptibility tensor versus DC magnetic field are calculated from the changes in resonance frequency and unloaded Q factor of a microwave cavity by perturbation theory. From these diagonal elements, all the elements of the intrinsic permeability tensor can be obtained. By fitting the theoretical curves to experimental data, the parameters of Polder resonance, ΔH M_s, and the g factor, are simultaneously calculated. The whole measurement procedure is controlled by a desktop computer. An accuracy of 5% is obtained in ΔH and M _s, and of 0.1% in the g factor     

A radiometer for measuring high-intensity heat flux density and a method of calibrating it

The construction of an instrument for measuring time-varying high-intensity heat fluxes with a density of up to 50 kW/m³ is described and a model of an absolutely black body for calibrating it is presented. The procedure for making the calibration is described.     

Open-structure resonant technique for measuring the dielectricproperties of materials

A newly developed resonant measurement technique is extended to include rotationally symmetric materials in general. The technique involves a full wave analysis of the fixture containing the material under test. Therefore, the measurement technique is not restricted by the dimensions of the material or its electrical properties. This work describes the measurement technique and provides a characterization of the TE₀₁₁ resonant mode. Also, a method to account for conduction loss due to the surface resistance of the metal walls of the fixture is presented. Experimental results are compared to previously reported values and are in excellent agreement     

Crystal growth of KCl in a reactive atmosphere II: The crystal growth technique

The crystal growth technique employed in the growth of large single crystals of KCl while the material is undergoing reactive-atmosphere processing is described in detail.     

Transverse loading of monofilament reinforced microcomposites: a novel fragmentation technique for measuring the fibre compressive strength

Carbon/J-polymer single fibre composite samples were tested under tensile conditions with the fibre direction perpendicular to the tensile loading axis. The Poisson ratio effect induced a compression strain field in the fibre, resulting in a fragmentation phenomenon similar to that observed in a fibre subjected to tensile loading. This observation introduces a novel technique for the measurement of the compressive strength of single fibres, calculated either from the stress at first break, or from the Weibull scale parameter obtained from the fragmentation data produced at various stress levels. The special sample loading configuration used here also provides the first measurement of the effect of the length of the fibre on its compressive strength value.