Capella Education Company

About: Capella Education Company is a based out in . It is known for research contribution in the topics: Radar cross-section & Osteoblast. The organization has 720 authors who have published 393 publications receiving 4943 citations.

RCS Reduction of Waveguide Slot Antenna With Metamaterial Absorber

Abstract: This communication investigates the application of metamaterial absorber (MA) to waveguide slot antenna to reduce its radar cross section (RCS). A novel ultra-thin MA is presented, and its absorbing characteristics and mechanism are analyzed. The PEC ground plane of waveguide slot antenna is covered by this MA. As compared with the slot antenna with a PEC ground plane, the simulation and experiment results demonstrate that the monostatic and bistatic RCS of waveguide slot antenna are reduced significantly, and the performance of antenna is preserved simultaneously.

Wideband RCS Reduction of a Microstrip Antenna Using Artificial Magnetic Conductor Structures

Abstract: A design approach aimed at reducing the radar cross section (RCS) of microstrip antenna in wide frequency band is proposed. First, two different artificial magnetic conductor (AMC) unit cells are designed to obtain 180 $^\circ $ ( $ \pm 30^\circ $ ) reflection phase difference over broadband frequency range. Then, chessboard configuration is structured with the two AMC unit cells and is applied to a microstrip antenna for RCS reduction. The simulated results indicate that the proposed antenna possesses remarkable RCS reduction from 8.0 GHz to 20.0 GHz for both polarizations, covering the working band of the original antenna. The maximum reduction is 31.9 dB. Moreover, the radiation performance of the antenna has been well kept. Measured results of the fabricated prototype are in good agreement with the simulations.

A Coding Diffuse Metasurface for RCS Reduction

Abstract: In this letter, a coding diffuse metasurface for radar cross section (RCS) reduction is designed, simulated, and measured. First, two kinds of artificial magnetic conductor (AMC) unit cell are analyzed, and 5 × 5 AMC unit cells construct metamaterials block. A linear array factor is optimized by the ergodic algorithm, and the sequence is expanded from one-dimension code to two-dimension code. Then, the diffuse metasurface is constructed through the metamaterials blocks arrangement. Simulation results show that the bandwidth of RCS reduction is expanded compared to the classical chessboard arrangement. The diffuse characteristic of the metasurface is achieved under normal and oblique incidence wave. Experiment results verify the validity of the theoretical design and simulation. This letter provides a rapid design method to obtain diffuse metasurface, and this metasurface may achieve potential applications on low-scattering vehicle.

Icariin is more potent than genistein in promoting osteoblast differentiation and mineralization in vitro.

Abstract: There has been a strong interest in searching for natural therapies for osteoporosis. Genistein, an isoflavone abundant in soy, and icariin, a prenylated flavonol glycoside isolated from Epimedium Herb, have both been identified to exert beneficial effects in preventing postmenopausal bone loss. However, the relative potency in osteogenesis between the individual phytoestrogen flavonoids remains unknown. The present study compared ability of genistein and icariin in enhancing differentiation and mineralization of cultured rat calvarial osteoblasts in vitro. Dose-dependent studies in osteoblast differentiation measuring alkaline phosphatase (ALP) activity revealed optimal concentrations of genistein and icarrin for stimulating osteogenesis to be both at 10(-5) M. Time course studies comparing the two compounds both at 10(-5) M demonstrated that icariin treatment always produced higher ALP activity, more and larger areas of CFU-F(ALP) colonies and mineralized nodules, more osteocalcin secretion, and calcium deposition, and a higher level of mRNA expression of osteogenesis-related genes COL1α2, BMP-2, OSX, and RUNX-2. However, they inhibited the proliferation of osteoblasts to a similar degree. In conclusion, although future in vivo studies are required to investigate whether icariin is more efficient in improving bone mass and/or preventing bone loss, our in vitro studies have demonstrated that icariin has a stronger osteogenic activity than genistein. In addition, while the prenyl group on C-8 of icariin could be the active group that takes part in osteoblastic differentiation and explains its greater potency in osteogenesis, mechanisms of action, and reasons for the relative potency of icariin versus genistein need to be further studied.