Body-of-revolution finite-difference time-domain modeling of hybrid-plasmonic ring resonators.

Development of a computational technique for the analysis of quasi-normal modes in hybrid-plasmonic resonators is the main goal of this research. Because of the significant computational costs of this analysis, one has to take various symmetries of these resonators into account. In this research, we consider cylindrical symmetry of hybrid-plasmonic ring resonators and implement a body-of-revolution finite-difference time-domain (BOR-FDTD) technique to analyze these resonators. We extend the BOR-FDTD method by proposing two different sets of auxiliary fields to implement multi-term Drude-Lorentz and multi-term Lorentz models in BOR-FDTD. Moreover, we utilize the filter-diagonalization method to accurately compute the complex resonant frequencies of the resonators. This approach improves numerical accuracy and computational time compared to the Fourier transform method used in previous BOR-FDTD methods. Our numerical analysis is verified by a 2D axisymmetric solver in COMSOL Multiphysics.

Effect of process parameters on greenhouse gas generation by wastewater treatment plants.

The effect of key process parameters on greenhouse gas (GHG) emission by wastewater treatment plants was evaluated, and the governing parameters that exhibited major effects on the overall on- and off-site GHG emissions were identified. This evaluation used aerobic, anaerobic, and hybrid anaerobic/aerobic treatment systems with food processing industry wastewater. The operating temperature of anaerobic sludge digester was identified to have the highest effect on GHG generation in the aerobic treatment system. The total GHG emissions of 2694 kg CO2e/d were increased by 72.5% with the increase of anaerobic sludge digester temperature from 20 to 40 degrees C. The operating temperature of the anaerobic reactor was the dominant controlling parameter in the anaerobic and hybrid treatment systems. Raising the anaerobic reactor's temperature from 25 to 40 degrees C increased the total GHG emissions from 5822 and 6617 kg CO2e/d by 105.6 and 96.5% in the anaerobic and hybrid treatment systems, respectively.

Estimation of greenhouse gas generation in wastewater treatment plants--model development and application.

A comprehensive mathematical model has been developed to estimate greenhouse gas (GHG) emissions by wastewater treatment plants (WWTP) resulting from on-site and off-site activities. The contribution of individual processes to the production of GHGs in a typical hybrid treatment system for food processing wastewaters has been determined. The results show that the recovery of biogas and its reuse as fuel have a remarkable impact on GHG emissions and reduce the overall emissions by 1023 kg CO(2)e d(-1) from a total of 7640 kg CO(2)e d(-1) when treating a wastewater at 2000 kg BOD d(-1). Furthermore, the recovery of biogas and its combustion may be used to cover the entire energy needs of the treatment plant for aeration, heating and electricity generation while creating emissions credit equal to 34 kg CO(2)e d(-1). The off-site GHG emissions resulting from the manufacturing of material for on-site usage were identified as the major source of GHG generation in hybrid treatment systems. These emissions account for the generation of 4138 kg CO(2)e d(-1), or 62% of the overall GHG emissions when biogas recovery is carried out. The inclusion of GHG emissions from nutrient removal as well as off-site processes in the overall GHG emissions of WWTPs increased the accuracy and completeness of this estimation, lending support to the novelty of the present study.

Impact of process design on greenhouse gas (GHG) generation by wastewater treatment plants.

The overall on-site and off-site greenhouse gas emissions by wastewater treatment plants (WWTPs) of food processing industry were estimated by using an elaborate mathematical model. Three different types of treatment processes including aerobic, anaerobic and hybrid anaerobic/aerobic processes were examined in this study. The overall on-site emissions were 1952, 1992, and 2435 kg CO2e/d while the off-site emissions were 1313, 4631, and 5205 kg CO2e/d for the aerobic, anaerobic and hybrid treatment systems, respectively, when treating a wastewater at 2000 kg BOD/d. The on-site biological processes made the highest contribution to GHG emissions in the aerobic treatment system while the highest emissions in anaerobic and hybrid treatment systems were obtained by off-site GHG emissions, mainly due to on-site material usage. Biogas recovery and reuse as fuel cover the total energy needs of the treatment plants for aeration, heating and electricity for all three types of operations, and considerably reduce GHG emissions by 512, 673, and 988 kg CO2e/d from a total of 3265, 6625, and 7640 kg CO2e/d for aerobic, anaerobic, and hybrid treatment systems, respectively. Considering the off-site GHG emissions, aerobic treatment is the least GHG producing type of treatment contrary to what has been reported in the literature.

Coupling of free space sub-terahertz waves into dielectric slabs using PC waveguides.

The paper presents theoretical and experimental results on photonic crystal structures which work under the self-collimation condition to couple free space waves into dielectric slabs in the sub-terahertz range. Using a standard machining process, two-dimensional photonic crystal structures consisting of a square array of air holes in the dielectric medium are fabricated. One of the structures has two adjacent parallel line-defects that improve the coupling efficiency. This leads to a combination of self-collimation and directional emission of electromagnetic waves. The experimental results are in good agreement with those of the Finite- Element-Method calculations. Experimentally we achieve a coupling efficiency of 63%.

A Novel open-ended intravascular MRI loop probe.

Recently, intravascular catheter probes have been developed to increase SNR for MR imaging of coronary arteries. Miniaturization of these catheter probes without degrading their performances is very essential in imaging small arteries. Since both signal and noise received by intravascular loop probes are of low level, the noise generated by the cable connecting the probe to the matching circuit may reduce SNR significantly. Therefore, the tuning and matching circuit must be placed very close to the loop probe, which restricts its miniaturization and flexibility. We propose a novel open-ended loop probe for 64 MHz with an input impedance of 20 Ohm and a length of only 4 cm in the bare case. This has two advantages. Firstly, the matching and tuning circuits of the proposed probe can be located outside the vessel. Secondly, its signal level and uniformity is superior to that of the conventional loop antennas.