In previous work we have proposed utilizing Photonic Band Gap (PBG) structures as a new class of high-energy, high-intensity accelerator cavities. We have completed extensive MAFIA numerical calculations of multicell PBG structures, with each cell consisting of a square array of metal cylinders terminated by conducting sheets and surrounded by microwave absorber on the periphery. We find that o...

Natural convection is an important mode of heat transfer in many fields. Convection coefficient, Nusselt number Nu, is usually modeled as a function of Rayleigh number Ra, which describes the conditions that affect convection. Inclination and spacing are important parameters of stacked cylinders. Of the latest models for two-cylinder array includes both inclination θ and spacing d as parameters...

We present a novel and simple method for forming hexagonal gold nanoparticle arrays that uses Coulombic interactions between negatively charged gold nanoparticles on positively charged vertically oriented poly(4-vinylpyridine) cylinders formed in a spin cast polystyrene-b-poly(4-vinylpyridine) block copolymer film. Exposure of the block copolymer film to dibromobutane vapor quaternizes and cros...

We employ a simple model to describe the phase behavior of 4He and Ar in a hypothetical porous material consisting of a regular array of infinitely long, solid, parallel cylinders. We find that high porosity geometries exhibit two transitions: from vapor to film and from film to capillary condensed liquid. At low porosity, the film is replaced by a "necking" configuration, and for a range of in...

In this work multiple scattering by an array of perforated cylindrical shells with a porous core has been investigated. A semi-analytical model to predict scattering from such cylindrical units is presented in the context of the multiple scattering theory (MST), and validated against laboratory experiments. The suggested semi-analytical multiple scattering model uses an impedance expression to ...

One of the important issues in many of array systems such as Radar, Sonar, Mobile, and satellite telecommunications is the estimation of DOA of narrowband received signal. CRB is very important in evaluation of parameter estimation. CRB is the lower bound estimation error variance for any unbiased estimation. In this paper, the array antenna with equal distance arrays is extended in two separat...

This paper reports the result of an analytical investigation of a steady, incompressible and viscous flow between two eccentric, rotating cylinders at high Reynolds number. A one dimensional case is far from reality because the gap between the cylinders is very small. Further, when their axes are displaced by a small distance, usually caused by bearing loads, two dimensional effects become obvi...

antenna structures with low side lobe levels are normally the main goal during antenna design. in this paper, a new method for reduction of radiation pattern side lobe level in phased array antenna with uniform and non-uniform weighting is presented. in this method, by changing the array elements weight or adding several elements, such as slc technique, the pattern with low side lobe level can ...

In the present study, the author’s previous experimental investigations on the vortex induced vibration of uniform and tapered circular cylinders are numerically simulated. The circular cylinders have medium mass ratios (5.93, 6.1), low mass-damping parameters (0.0275, 0.0279) a mean diameter of 0.028m and an aspect ratio of about 14. A fully coupled two-way fluid-structure interaction (FSI) an...