High-precision RCS measurement of aircraft's weak scattering source

The radar cross section （RCS） of weak scattering source on the surface of an aircraft is usually less than -40 dBsm. How to accurately measure the RCS characteristics of weak scattering source is a technical challenge for the aircraft＇s RCS measurement. This paper proposes separating and extracting the two-dimensional （2D） reflectivity distribution of the weak scattering source with the microwave imaging algorithm and spectral transform so as to enhance its measurement preci- sion. Firstly, we performed the 2D microwave imaging of the target and then used the 2D gating function to separate and extract the reflectivity distribution of the weak scattering source. Secondly, we carried out the spectral transform of the reflectivity distribution and eventually obtained the RCS of the weak scattering source through calibration. The prototype experimental results and their analysis show that the measurement method is effective. The experiments on an aircraft＇s low-scattering conformal antenna verify that the measurement method can eliminate the clutter on the surface of aircraft. The precision of measuring a -40 dBsm target is 3 5 dB better than the existing RCS measurement methods. The measurement method can more accurately obtain the weak scattering source＇s RCS characteristics.

Estimation of relations among hysteretic response measures and design parameters for RC rectangular shear walls

Seismic design of RC structures requires estimation of structural member behavioral measures as functions of design parameters. In this study, the relations among cyclic behavioral measures and design parameters have been investigated for rectangular RC shear walls using numerical simulations calibrated based on the published laboratory tests. The OpenSEES numerical simulations modeling of plastic hinge hysteretic behavior of RC shear walls and estimation of empirical relations among wall hysteretic indices and design parameters are presented. The principal design parameters considered were wall dimensions, axial force, reinforcement ratios, and end-element design parameters. The estimated hysteretic response measures are wall effective stiffness, yield and ultimate curvatures, plastic moment capacity, yield and ultimate displacements, flexural shear capacity, and dissipated energy. Using results of numerous analyses, the empirical relations among wall cyclic behavioral measures and design parameters are developed and their accuracy is investigated.