A fast algorithm and practical considerations for passive macromodeling of measured/simulated data

Passive macromodeling of high-speed package and interconnect modules characterized by measured/simulated data has generated immense interest during the recent years. This paper presents an efficient algorithm for transient simulation of interconnect networks characterized by measured/simulated data in the presence of other linear and nonlinear devices. A new set of linear constraints are proposed, which help in preserving the passivity of resulting macromodels. Examples are presented to demonstrate the validity and efficiency of the proposed algorithm.     

Sensitivity analysis of lossy coupled transmission lines

An analysis method, based on the numerical inversion of the Laplace transform, is described for the evaluation of the time domain sensitivity of networks that include lossy coupled transmission lines. The sensitivity can be calculated with respect to network components and parameters of the transmission lines. Sensitivity analysis is useful for waveform shaping and optimization. Examples and comparisons with sensitivity determined by perturbation are presented     

An integrated system for hydrogen and methane production during landfill leachate treatment

The patent-pending integrated waste-to-energy system comprises both a novel biohydrogen reactor with a gravity settler (Biohydrogenator), followed by a second stage conventional anaerobic digester for the production of methane gas. This chemical-free process has been tested with a synthetic wastewater/leachate solution, and was operated at 37 °C for 45 d. The biohydrogenator (system (A), stage 1) steadily produced hydrogen with no methane during the experimental period. The maximum hydrogen yield was 400 mL H₂/g glucose with an average of 345 mL H₂/g glucose, as compared to 141 and 118 mL H₂/g glucose for two consecutive runs done in parallel using a conventional continuously stirred tank reactor (CSTR, System (B)). Decoupling of the solids retention time (SRT) from the hydraulic retention time (HRT) using the gravity settler showed a marked improvement in performance, with the maximum and average hydrogen production rates in system (A) of 22 and 19 L H₂/d, as compared with 2–7 L H₂/d in the CSTR resulting in a maximum yield of 2.8 mol H₂/mol glucose much higher than the 1.1–1.3 mol H₂/mol glucose observed in the CSTR. Furthermore, while the CSTR collapsed in 10–15 d due to biomass washout, the biohydrogenator continued stable operation for the 45 d reported here and beyond. The methane yield for the second stage in system (A) approached a maximum value of 426 mL CH₄/gCOD removed, while an overall chemical oxygen demand (COD) removal efficiency of 94% was achieved in system (A).     

Effect of organic loading on a novel hydrogen bioreactor

This study investigated the impact of six organic loading rates (OLR) ranging from 6.5 gCOD/L-d to 206 gCOD/L-d on the performance of a novel integrated biohydrogen reactor clarifier systems (IBRCSs) comprised a continuously stirred reactor (CSTR) for biological hydrogen production, followed by an uncovered gravity settler for decoupling of solids retention time (SRT) from hydraulic retention time (HRT). The system was able to maintain a high molar hydrogen yield of 2.8 mol H₂/mol glucose at OLR ranging from 6.5 to 103 gCOD/L-d, but dropped precipitously to approximately 1.2 and 1.1 mol H₂/mol glucose for the OLRs of 154 and 206 gCOD/L-d, respectively. The optimum OLR at HRT of 8 h for maximizing both hydrogen molar yield and volumetric hydrogen production was 103 gCOD/L-d. A positive statistical correlation was observed between the molar hydrogen production and the molar acetate-to-butyrate ratio. Biomass yield correlated negatively with hydrogen yield, although not linearly. Analyzing the food-to-microorganisms (F/M) data in this study and others revealed that, both molar hydrogen yields and biomass specific hydrogen rates peaked at 2.8 mol H₂/mol glucose and 2.3 L/gVSS-d at F/M ratios ranging from 4.4 to 6.4 gCOD/gVSS-d. Microbial community analysis for OLRs of 6.5 and 25.7 gCOD/L-d showed the predominance of hydrogen producers such as Clostridium acetobutyricum, Klebsiella pneumonia, Clostridium butyricum, Clostridium pasteurianum. While at extremely high OLRs of 154 and 206 gCOD/L-d, a microbial shift was clearly evident due to the coexistence of the non-hydrogen producers such as Lactococcus sp. and Pseudomonas sp.     

Evaluation of the bactericidal characteristics of nano-copper oxide or functionalized zeolite coating for bio-corrosion control in concrete sewer pipes

The bactericidal characteristics of nano-copper oxide or functionalized zeolite coated concrete pipes against Acidithiobacillus thiooxidans were studied by measuring the temporal variation of bacterial dry cell weight measurement, cellular Adenosine Triphosphate production, as well as oxygen uptake rate of the aforementioned bacterium. Uncorroded (UC), severely corroded (SC), and moderately corroded (MC) concrete pipes were electrochemically coated with a nano-copper oxide, while another uncorroded concrete pipe was used to apply functionalized zeolite coating (Z2). Specimens were characterized by field emission-scanning electron microscopy, and optical microscopy. Oxygen uptake rate of the bacterium was the highest in UC followed by the MC. Oxygen uptake rate and cellular Adenosine Triphosphate decreased progressively in Z2 and SC throughout the duration of the experiment due to decline in live bacterial cell. The maximum bacterial specific growth rate was 1.1 × 10⁻² day⁻¹ for both UC and MC, with a decay rates varying from 1.4 × 10⁻² to 2.6 × 10⁻² day⁻¹. The minimum concentration limits for the inhibition of the bacterium in the nano-copper oxide coated concrete pipes ranged from 2.3 mg to 2.6 mg Cu per mg dry cell weight.     

Scattering Domain Passivity Verification and Enforcement of Delayed Rational Functions

This letter introduces new algorithms for passivity verification and compensation of macromodels constructed from delayed rational functions in the scattering domain. For passivity verification, a frequency-dependent generalized eigenvalue is formulated, which is used to accurately determine the regions of passivity violation. For passivity compensation, first order perturbation theory is used to iteratively perturb the residues of the system until passivity is achieved. Numerical results validating the proposed algorithms are presented.     

Analysis of lossy multiconductor transmission lines using theasymptotic waveform evaluation technique

A method is described for the transient analysis of lossy coupled transmission line networks with nonlinear elements. The method combines the asymptotic waveform evaluation technique with a piecewise decomposition algorithm. Two to three orders of magnitude speedup can be achieved relative to previously published methods with comparable accuracy. The method is useful for delay and crosstalk simulation of high speed VLSI interconnects     

Biokinetic modeling of in situ bioremediation of BTX compounds-impact of process variables and scaleup implications

The impact of three process parameters, i.e. ground water velocity, oxygen-to-BTX mass ratio, and benzene, toluene and xylene (BTX) concentrations on first-order biodegradation kinetics in a pilot-scale in situ bioremediation system was assessed. Generally, first-order biodegradation coefficients decreased with ground water velocity, and increased with hydrogen peroxide dose and BTX concentration. First-order biodegradation rate coefficients for benzene, toluene, and o-xylene varied from 0.3 to 0.81, 0.24 to 0.72, and 0.21 to 0.63 d(-1), respectively. Biomass-specific first-order rate coefficients were insensitive to ground water velocity, and decreased with increasing BTX concentrations. At 10mg/l BTX concentration, the specific first-order coefficients increased with peroxide dose. However, at the 50mg/l BTX concentration and a peroxide dose of 1020 mg/l, a 30-70% reduction in specific first-order biodegradation coefficients was observed. BTX biodegradation kinetics in this pilot-scale system were approximately one-to-two orders of magnitude slower than in soil microcosms and mixed culture bioreactors, and about 200-300% higher than full-scale systems.     

Fast Passivity Verification and Enforcement via Reciprocal Systems for Interconnects With Large Order Macromodels

With the ever increasing signal speeds, signal integrity issues of high-speed VLSI designs are presenting increasingly difficult challenges for state-of-the-art modeling and simulation tools. Consequently, characterization and passive macromodeling of high-speed modules such as interconnects, vias, and packages based on tabulated data are becoming important. This paper presents a fast algorithm for passivity verification and enforcement of large order macromodels of scattering parameter based multiport subnetworks. Numerous examples tested on this algorithm demonstrate a significant speed-up compared to the existing algorithms in the literature     

Compact Macromodeling of High-Speed Circuits via Delayed Rational Functions

This letter introduces a new method for compact macromodeling of high-speed circuits with long delays, characterized by tabulated time-domain data. The algorithm is based on partitioning the response and subsequently approximating each partition with a low-order sum-of-exponentials, delayed in time-domain. This results in a compact low-order macromodel in the form of delayed-differential equations, which can be efficiently analyzed using SPICE like simulators.