Simulation and Control for Load Change Process on a Solid Oxide Fuel Cell

This paper addresses the dynamic characteristics of SOFC with an emphasis on control strategy development for optimized temperature control during load change. A methodology on regulating fuel utilization (Uf) and air excess ratio (λ) is investigated to validate alleviation of temperature fluctuation. An integrated dynamic model of SOFC, composed of mass balance, temperature balance, and electrochemistry, collaborates with Model Predictive Controller (MPC) in MATLAB/Simulink to verify the dynamic characteristic during load change process in the paper. A variable λ strategy is proposed and compared with traditional fixed λ strategy. Simulation results show the variable λ strategy can reduce the temperature variation for a safe operation, in comparison with that by the fixed λ strategy.

ON THE LOG-CONCAVITY OF THE DEGENERATE BERNOULLI NUMBERS

The degenerate Bernoulli numbers βn(λ) are polynomials with rational coefficients of degree n in the variable λ, which arise in several combinatorial settings. An appropriate change of variable transforms βn(λ) into a polynomial whose coefficients are all positive. Here, we prove that this transformed polynomial is log-concave, and therefore unimodal. As a consequence, we deduce bounds on the absolute values of the roots of βn(λ).

RP-HPLC Analysis and Antidiabetic Activity of Swertia paniculata

1,2,6,8-Tetrahydroxyxanthone (SR1) and 2,8-dihydroxy-1,6-dimethoxyxanthone (SR2) have been qualitatively and quantitatively determined in leaves and rhizomes of Swertia paniculata. The methanol extracts were analyzed on a C18 column using MeOH and H2O as mobile phase at a flow rate of 1 mL/min. Identification was achieved using an UV variable Λ detector set at 260 nm. Variation in the bioactive compounds with respect to season and altitude was determined, along with the examination of the antidiabetic activity of the plant. The maximum concentration of SR1 and SR2 was found in leaves collected from Tungnath (3600 m), Uttarakhand, India, in October. The blood sugar level in alloxan induced rats was decreased by 51.0% by the methanol extract of the leaves. Overall, results showed that the concentration of bioactive compounds increased with altitude. October was the period of prime potency and should be the time of harvest for S. paniculata.