NEW METHOD OF REFLECTOR SURFACE SHAPING TO PRODUCE A PRESCRIBED CONTOUR BEAM

A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of the shaped subreflector is expressed using a new set of equations employing differential geometry. The proposed equations require only a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO) based method is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed method, a shaped Cassegrain dual reflector system is designed. The field scattered from the subreflector is calculated using uniform geometrical theory of diffraction (UTD). Finally, a numerical example is provided showing how a shaped subreflector produces more uniform illumination over the main reflector aperture compared to an unshaped subreflector.

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Numerical investigations of shape of the reflecting surface made of knitted mesh fabric being pulled on the curvilinear frame

EPJ Web of Conferences ◽

10.1051/epjconf/201922101031 ◽

2019 ◽

Vol 221 ◽

pp. 01031

Author(s):

Vitaly Meshkovsky ◽

Anatoly Sdobnikov ◽

Sergey Churilin ◽

Yuri Kisanov

Keyword(s):

Surface Shape ◽

Equilibrium Equations ◽

Scaled Model ◽

Linear Elasticity Theory ◽

Antenna Structure ◽

Numerical Investigations ◽

Surface Shaping ◽

Reflector Surface ◽

Type Boundary ◽

Flexible Cables

This paper presents the surface shaping numerical investigations results of truss space constructions mesh reflectors, such as antennas and calibration and adjustment satellites. Shape-generating structure of mentioned constructions adds up to set of triangular facets, made in the form of spatio-curvilinear bar frames, bearing reflecting knitted mesh fabric pulled on it. This work proposes the algorithm of calculation of step-by-step reflecting mesh pulling on the bearing frame’s bars process, using finite elements method. Numerical execution of the developed algorithm involves for resolving the linear elasticity theory first-type boundary value problem, which implies integration of elastic body equilibrium equations without taking into account mass forces when kinematic boundary conditions are given. Analyzing when having done numerical calculations, it's possible to determine what grade obtained shapes of reflecting surfaces are precise with, and to find possible for developing variants of the antenna structure, which would allow to obtain the reflector surface shape with required accuracy by using flexible cables as a part of shape-generating structure. Comparing results of numerical investigations with experimental data received using full-scaled model of spherical calibration and adjustment satellite shows satisfactory qualitative and quantitative matching of both results.

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Selective Sampling and Orientation of Non-Homogeneous Tissues

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100238 ◽

1968 ◽

Vol 26 ◽

pp. 98-99

Author(s):

C. C. Clawson ◽

L. W. Anderson ◽

R. A. Good

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Light Microscopy ◽

Random Sampling ◽

New Method ◽

Microscope Examination ◽

Small Areas ◽

Selective Sampling ◽

Large Numbers ◽

Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

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