Advanced Materials Research Vols. 403-408

Abstract: Using a modified Lattice Boltzmann Method (LBM), pressure driven flow through micro and nano channels has been modeled. Based on the improving of the dynamic viscosity, an effective relaxation time formulation is proposed which is able to simulate wide range of Knudsen number, Kn, covering the slip, transition and to some extend the free molecular regimes. The results agree very well with exiting empirical and numerical data.

Abstract: Considering the dependency of viscosity on Kn, a unified flow model for all flow regimes with different Kn was obtained. Applying the Dary Brinkman – Forchheimer flow model with the slip boundary condition, finite difference solutions for fully developed velocity distribution in a nanochannel of circular cross section, filled with porous media was presented. Convection heat transfer of the system, reflected in Nu was analyzed using the temperature jump boundary condition. It is shown that despite of the fact that in most of previous researches, Kn was assumed constant along the channel, the variations of Kn due to the pressure variations, have considerable effects on heat transfer and temperature distribution across the channel cross section.

Abstract: As the requirement for the low loss phase shifter increases, so does the development of RF MEMS as a solution. This paper presents the design & simulation of Switched line MEMS phase shifter for Ku band using GaAs substrate. The phase shift can be achieved by varying the lengths in delay path to the reference path for the same phase velocity. The electromagnetic & electromechanical simulations were carried out with various structural parameters to optimize the design. The novelties like low insertion loss, low actuation voltage with distributed actuation pads for DC and RF are used to make the design unique. The EM simulations are carried out using 3D simulator HFSS and a phase shift of 172.6 deg./dB for a total Phase shift of 348.75deg was achieved with return loss of 15.5dB over a frequency band from 16-18 GHz and a phase shift error less than ±2 degree in the 32 states. The electromechanical simulations are carried to achieve the low actuation voltage of 15.3V. These parameters make these suitable for the Phased array applications [1, 2].

Abstract: Metal injection molding (MIM) technology is known for its ability of producing near net shape components. This study presents the results of flow behavior of multi-walled carbon nanotubes (MWCNTs) reinforced copper composites mixes. The solid loadings in the copper mixes were investigated in the ranges of 55-61 V% using a binder. Copper mixes and copper/MWCNTs were compounded using a Z-blade mixer for homogenous dispersion of solids in the binder. Results identified a mix containing 59 V% copper suitable for substitution of MWCNTs. The flow properties were measured using a capillary rheometer in the shear rate range expected to occur during metal injection molding. An increasing trend in viscosity of the copper mixes with powder loading was noted. Copper/MWCNTs composite mixes showed viscosity more than 1000 Pa.s perhaps due to addition of MWCNTs and increasing trend in viscosity of copper/MWECNTs was recorded. The results of flow data showed that all copper composite mix containing up to 10 Vol.% MWCNTs were successfully injection molding and test samples were produced.