Stacking procedures with the objective of improvement of signal to noise ratio were in use before the introduction of Common reflection point stacking introduced by Mayne in 1962. But, these techniques were problematic, at times, because they used reflections from a portion of reflectors that were too large. Hence, stacking tends to obscure the very detail of reflector which is being sought. So...

we introduce the notions of t-dual rickart and strongly t-dual rickart modules. we provide several characterizations and investigate properties of each of these concepts. it is shown that every free (resp. finitely generated free) $r$-module is t-dual rickart if and only if $overline{z}^2(r)$ is a  direct summand of $r$ and end$(overline{z}^2(r))$ is a semisimple (resp. regular) ring. it is sho...

In this note we begin the development of two types of Impulse Radiating Antenna (IRA). o These two designs include a 23 cm diameter reflector IR4, with an F/D of0.38, and a solid dielectric-lens IIU4, or dielectric-immersed lens IIU. This latter design is a Transverse Electromagnetic (TEM) horn immersed in a dielectric, with a prolate spheroidal lens interface to air. The reflector IR4 consists...

With the deployment of advanced multicast routing protocols and transport protocols for real-time data, multicast services on the Internet experience renaissance. Together with the global improvements in the underlying network infrastructure, this opens possibilities for a wide range of exciting multimedia applications. However, many Internet hosts are not connected to MBone, the Internet multi...

All of NASA’s Deep Space Network (DSN) 70-m reflectors were measured using a Leica TDM-5000 theodolite. The main-reflector surface was measured at five elevation angles so that a gravity deformation model could be derived that described the main-reflector distortions over the entire range of elevation angles. The article describes the measurement equipment and accuracy and the results derived f...

Antenna reflector losses play an important role in the calibration budget for a microwave radiometer. If the losses are small, they are difficult to measure by traditional means. However, they can be assessed directly by radiometric means using the sky brightness temperature as incident radiation. This paper describes how such measurements are carried out as well as a suitable experimental setu...

A low-threshold-current distributed reflector laser consisting of phase-shifted distributed feedback (DFB) grating and quantumwire distributed Bragg reflector (DBR) sections was realized. The device with a DFB length of 150μm, a DBR length of 240μm and a stripe width of 1.5μm achieved a threshold current as low as 1.2mA and a differential quantum efficiency of 13% from the front facet under RT-...

A high performance dye-doped cholesteric liquid crystal (CLC) laser is demonstrated by incorporating a passive CLC reflector to the active cell. The polarization-conserved CLC reflector effectively increases the distributed feedback cavity length which, in turn, results in a significant enhancement in lasing efficiency and a dramatic reduction in beam divergence. The lasing characteristics are ...

Based on the VMS survey of the compact array antenna CA02, the effects of gravity deformation were examined in AT 39.3/115. The dominant cause of gain loss and beam distortion was identified to be the deformation of the main reflector surface with elevation. This report examines whether active displacements in the sub-reflector and/or feed might compensate for the aperture wavefront errors. All...

A design criterion that permits truly omnidirectional reflectivity for all polarizations of incident light over a wide selectable range of frequencies was used in fabricating an all-dielectric omnidirectional reflector consisting of multilayer films. The reflector was simply constructed as a stack of nine alternating micrometer-thick layers of polystyrene and tellurium and demonstrates omnidire...