Accurate conductor Q-factor of dielectric resonator placed in anMIC environment

The unloaded Q-factor of a dielectric resonator is degraded due to conductor loss when it is placed in an MIC environment. The authors report approximate but quite accurate closed form expressions for the Q-factor due to conductor loss. The results obtained are in good agreement with those of rigorous numerical methods. The effect of geometrical parameters on the useful tuning range of the structure is studied. Finally, an explicit relationship between the resonant frequency sensitivity factors and the conductor Q-factor is derived     

The role of particle size distribution of suspended solids in defining the flow properties of milk chocolate

The flow characteristics of molten milk chocolate, like most dense suspensions, are a function of the maximum packing fraction ((_m) of the suspended solids. Milk chocolates were prepared from mixtures of two relatively narrow coarse (d_4,3 = 17 μm) and fine (d₄,₃ = 8.5 μm) size distributions of non‐fat solids to contain 0, 25, 50, 75, and 100% of the coarse component. Solids bed density (a measure of maximum packing fraction) correlated with the apparent viscosity of milk chocolates (r = ‐0.98). The highest value for solids bed density and lowest value for apparent viscosity were measured for size distributions with 75% of solids from the coarse fraction. Casson yield value correlated with d_4,3 (r = ‐0.98) and specific surface area (r = 0.93). The maximum packing fraction of binary mixtures of two distinct sizes of non‐fat chocolate solids attained a maximum value for a specific volume ratio of the components. The maximum in _m corresponded with the minimum viscosity in molten chocolate at a given solids volume concentration.     

Half-split dielectric resonator placed on metallic plane for antenna applications

A practical dielectric resonator antenna structure has been proposed for use at microwave and millimetre-wave frequencies. The radiator can be designed to have a low radiation Q-factor resulting in a relatively wider bandwidth of operation. The scheme used for feeding the antenna shields the feeding arrangement and the associated circuitry from the radiation zone.<>     

Mixing strategies for zinc oxide nanoparticle synthesis via a polyol process

We report on the effect of mixing on the morphology of ultrafine zinc oxide nanoparticles synthesized via a polyol process using zinc acetate and water in a diethylene glycol medium. Three mixing strategies were considered: stirred batch, T‐mixer, and impinging free jets. The particle granulometry was accessed using the transmission electron microscopy and x‐ray diffraction methods. The nanoparticle size and polydispersity decreased with an increase in the local dissipated energy. In particular, the polyol process conducted in the same chemical environment at 353 K did not lead to the observation of nanoparticles in the stirred batch reactor but resulted in unconventionally small 6‐nm particles in the T‐mixer and impinging jet configurations. This result is apparently related to the micromixing eddy geometry described by the Kolmogorov length. The hydrodynamic flow patterns and energy dissipation were obtained from computational ?uid dynamics simulations, which are essential in the design, optimization, and scale‐up of the polyol process. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1708–1721, 2015     

Equivalent circuit parameters of an aperture coupled open resonatorcavity

In this paper, we use modified form of Bethe's small hole coupling theory to compute equivalent circuit parameters of an aperture coupled open resonator cavity. The open resonator cavity is composed of spherical mirrors of circular cross section. The cavity is coupled to a rectangular waveguide by means of a common hole in the mirror and the shorted end wall of the rectangular waveguide. Closed form expressions have been obtained for the equivalent circuit parameters. Experiments conducted in the W-band frequency range show good agreement with theory when an experimentally estimated correction to the transmission coefficient is applied for the thickness of the coupling holes     

Dielectric resonator antennas—a review and general design relations for resonant frequency and bandwidth

Open dielectric resonators (DRs) offer attractive features as antenna elements. These include their small size, mechanical simplicity, high radiation efficiency due to no inherent conductor loss, relatively large bandwidth, simple coupling schemes to nearly all commonly used transmission lines, and the advantage of obtaining different radiation characteristics using different modes of the resonator. In this article, we give a comprehensive review of the modes and the radiation characteristics of DRs of different shapes, such as cylindrical, cylindrical ring, spherical, and rectangular. Further, accurate closed form expressions are derived for the resonant frequencies, radiation Q-factors, and the inside fields of a cylindrical DR. These design expressions are valid over a wide range of DR parameters. Finally, the techniques used to feed DR antennas are discussed. © 1994 John Wiley & Sons, Inc.     

Cost of reducing CO2 emissions from India: Imperatives for international transfer of resources and technologies

This paper evaluates the cost, capital and foreign exchange requirements associated with restraining the growth of CO₂ emissions in India through a range of technological alternatives. The different options include higher-cost efficiency improvements, fuel switching from coal to oil to gas and increasing the use of renewables. The paper also examines the types of actions required at both the national and international levels to effectively curtail India's CO₂ growth. The development of a coupon system, which would allow carbon-restraining technologies to be transferred from the industrialized to the developing world, is one of the novel mechanisms suggested in this analysis.     

AN ADVANCED SPRAY MODEL FOR APPLICATION TO THE PREDICTION OF GAS TURBINE COMBUSTOR FLOW FIELDS

It is well known that fuel preparation, its method of injection into a combustor, and its atomization characteristics have a significant impact on emissions. A simple dilute spray model, which assumes that droplet heating and vaporization occur in sequence, has been implemented in the past within computational fluid dynamics (CFD) codes at General Electric (GE) and has been used extensively for combustion applications. This spray model coupled with an appropriate combustion model makes reasonable predictions of the combustor pattern factor and emissions. To improve upon this predictive ability, a more advanced quasi-steady droplet vaporization model has been considered. This article describes the evaluation of this advanced model. In this new approach, droplet heating and vaporization take place simultaneously (which is more realistic). In addition, the transport properties of both the liquid and vapor phases are allowed to vary as a function of pressure, gas phase temperature, and droplet temperature. These transport properties, which are most up to date, have been compiled from various sources and appropriately curve-fit in the form of polynomials. Validation of this new approach for a single droplet was initially performed. Subsequently calculations of the flow and temperature field were conducted and emissions (NOx, CO, and UHC) were predicted for a modern single annular turbofan engine combustor using both the standard spray model and the advanced spray model. The effect of the number of droplet size ranges as well as the effect of stochastic treatment of the droplets were both investigated.