Results 1 - 10 of 42
Results 1 - 10 of 42. Search took: 0.015 seconds
|Sort by: date | relevance|
[en] The caustic of a two-dimensional parabola illuminated off-axis is the Tschirnhausen cubic and does not contain any singular points. The caustic of a three-dimensional paraboloid of revolution similarly illuminated consists of two cusped sheets containing a hyperbolic umbilic singularity. We relate these two situations by considering a suitable sequence of illuminated elliptic paraboloids
[en] Highlights: → A combined domed Fresnel lens - CPC PVT system is designed and characterized. → Electrical and thermal experiments have been performed. → CFD analysis has been used to determine thermal characteristic dimensionless numbers. - Abstract: An advanced solar unit is designed to match the needs of building integration and concentrating photovoltaic/thermal generation. The unit proposed accurately combines three elements: a domed linear Fresnel lens as primary concentrator, a compound parabolic reflector as secondary concentrator and a photovoltaic-thermal module. In this work the photovoltaic-thermal generator is built, analysed and characterized. Models for the electrical and thermal behaviour of the module are developed and validated experimentally. Applying a thermal resistances approach the results from both models are combined. Finally, efficiency electrical and thermal curves are derived from theoretical analysis showing good agreement with experimental measurements.
[en] To enhance the coordinates measuring accuracy of the multi-beam laser tracking 3D coordinates measuring system, measurement for the optical error of the cat's eye retro-reflector is necessary. For this purpose, measurement method for the optical error of the cat's eye retroreflector is proposed. The main sources of the optical error of cat's eye retro-reflector are analysed first, and associated experiment setup and measuring data processing method are described. Experiment results show that the maximum optical error of the measured cat's eye retro-reflector is approximately 4μm
[en] We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided by means of ray tracing simulations. It turns out that the usual misalignment approximations fail under these extreme conditions
[en] Full text: Focusing SANS using advanced reflective optics. We propose a new concept of neutron focusing on SANS spectrometers using a combination of curved super mirrors (SM). The aim is to design a focusing system which is achromatic and has no absorption. The proposed design combines advanced neutron optical element such as parabolic and elliptic SM. Some simulation results will be presented and discussed. (author)
[en] MIDAS (MIcrowave Detector of Air Showers) is a prototype of a microwave telescope to detect extensive air showers: it images a 20°×10° region of the sky with a 4.5 m parabolic reflector and 53 feeds in the focal plane. It has been commissioned in March 2010 and is currently taking data. We present the design, performance and first results of MIDAS.
[en] Taking into account a plasma layer on a long metallic cylindrical parabolic reflector the deviation in distribution of energy on its focal axis are simulated. By introducing a criterion for width of energy distribution the effects of thickness of plasma layer and its particle density, the focal of parabolic and wave frequency on width of energy distribution are investigated. Investigations have done for S-polarized electromagnetic beam.
[en] Parabolic refractive x-ray lenses with short focal distance can generate intensive hard x-ray microbeams with lateral extensions in the 100 nm range even at a short distance from a synchrotron radiation source. We have fabricated planar parabolic lenses made of silicon that have a focal distance in the range of a few millimeters at hard x-ray energies. In a crossed geometry, two lenses were used to generate a microbeam with a lateral size of 380 nm by 210 nm at 25 keV in a distance of 42 m from the synchrotron radiation source. Using diamond as the lens material, microbeams with a lateral size down to 20 nm and below are conceivable in the energy range from 10 to 100 keV
[en] A 350 mK helium-4 coated mirror was used to increase the intensity of an ultra-cold electron-spin-polarized atomic hydrogen beam. The mirror uses the observed specular reflection of atomic hydrogen from a superfluid-helium-covered surface. A quasi-parabolic polished copper mirror was installed with its focus at the 5 mm diameter exit aperture of an atomic hydrogen stabilization cell in the gradient of an 8 T solenoid. The four-coned mirror shape, which was designed specifically for operation in the gradient, increased the beam intensity focused by a sextupole magnet into a compression tube detector more than seven-fold