Modern radars systems for anti-air and anti-ship application naturally had born interest how to do the antidote against of it. Stealth or how to do the reduction of the radar cross section concerns mainly two decisions: a) The creation specially oriented surfaces which reflect radar radiation to the space or down – some kind as “in milk” (on technical language). b) Using special absorption coating on the surfaces and places which is impossible or very difficult to exclude from the reflection of the radar radiation. Absorption in this case means – sounding radar power will be absorbed by the material/s of such coating. Such coating works as black body or matched loading if to talk on microwave language. For the microwave radiometer such surfaces and coating are not antidote for the disclosing according to the physics of radiometer’s job. Nature produces radiation, which re-reflect from the various surfaces to an antenna of the radiometer from the appropriated directions from the sphere of sky or the earth with power depending on, so named, radio-brightness temperatures. And the coating if it the matched loading produces microwave radiation corresponding to her physical temperature. For the both cases a) and b), Stealth object can be disclosed by radiometer in some real cases. Keywords: stealth coating, microwave radiometer,
The specially designed and produced Stealth coating for the aircrafts and for the ships must be effective by their direct tasks against of the radar (by the way for the laser, optical and IR remote control too). But it is not antidote in some cases for the passive device as the microwave radiometers, because their job is to evaluate natural radiation of an object at the background of the environment/s (sky is cold, Earth is warm). More to say such specially calculated surfaces which avoids the vertical ones for the radar beams and reflect this radiation “to the milk” can promote and to be convenient for the remote radiometric detection, because the sky radiates from any direction. For the case of Stealth coating with full microwave absorption it was interesting to do simplest evaluation and background of such possible passive method of the remote sensing at the sample of using the microwave discriminator. <i>Short explanation and the simplest evaluation </i>were performed about possible real distances for the disclosing.
Updating the finite element models of structures with semi-rigid joints and boundary are studied. While most researches in this field are on updating semi-rigid joints with moment-rotation effect, in this paper a hybrid finite element to consider both the moment-rotation and shear-displacement effects of joint are proposed. The hybrid element is composed of a beam element with two connections at both ends, and the semi-rigidity of joints of both rotational and shear effects are simulated at the two ends. The stiffness matrix and mass matrix of the hybrid finite element are formulated. A hybrid optimization technique is applied to update structures with semi-rigid joints and boundary. The method proposed is experimentally studied by updating the finite element of a 14-bay beam. The results show that the method can produce an analytical model that better duplicates the dynamic property of actual structure while keep physical connectivity between them.