Showing papers by "Lin Jiang published in 2012"

Delay-Dependent Stability for Load Frequency Control With Constant and Time-Varying Delays

Abstract: Load frequency control (LFC) requires transmitting measurements from remote RTUs to control center and control signals from the control center to plant side. Constant delays exist in the conventional dedicated communication channels, while the future usage of open communication networks will introduce time-varying delays. Those delays would degrade the dynamic performance of LFC and in the worst case, cause instability. The maximal delay time which allows an LFC scheme embedded with controllers to retain stable is defined as the delay margin. This paper investigates the delay-dependent stability of the LFC scheme by using Lyaponuv-theory based delay-dependent criterion and linear matrix inequalities (LMIs) techniques. Case studies are carried out based on one-area and multi-area LFC schemes installed with proportional-integral (PI) controllers, respectively. Relationship between the gains of PI controller and the delay margin of the LFC scheme are investigated and results obtained can be used to tune the PI controllers to achieve a compromise between the dynamic performance and the delay margin. Both constant and time-varying delays are considered. The effectiveness of the criterion used is verified by simulation studies.

Opp-Dibenzoporphyrins as a Light-Harvester for Dye-Sensitized Solar Cells

Abstract: New opp-dibenzoporphyrins were prepared in a concise method that was based on a Pd(0)-catalyzed cascade reaction. These porphyrins, which contained carboxylic-acid linker groups on benzene rings that were fused to the porphyrin at their β,β'-positions, were examined as sensitizers for dye-sensitized solar cells for the first time. Whereas all of the porphyrins showed solar-energy-to-electricity conversion, an opp-dibenzoporphyrin with conjugated carboxylic-acid linkers displayed the highest conversion efficiency and an exceptionally high J(sc) value. Cyclic voltammetry of these porphyrins suggested that the fusion of two aromatic benzene rings onto the periphery of the porphyrin lowered the HOMO-LUMO energy gap; the incorporation of a conjugated carboxylic-acid linker group decreased the HOMO-LUMO gap even further. These CV data are consistent with DFT calculations for these porphyrins and agree well with the UV/Vis absorption- and fluorescence spectra of these porphyrins.

The Separation and Concentration of Titanium(IV) from Sulfuric Acid Solution with Trioctylamine

Abstract: This paper presents research on separating and concentrating titanium(IV) from aqueous sulfuric acid solution, using trioctylamine (TOA) as extractant and kerosene as a diluent. We investigated the effects of reaction time, temperature, sulfuric acid concentration, organic/aqueous phase ratio, TOA concentration, and titanium concentration on the removal efficiency of titanium(IV). The results show that it is possible to recover over 99% of titanium(IV) after 15 min reaction time by TOA from the sulfuric acid solution under the optimum operation conditions and the loading capacity of TOA for titanium(IV) is 30 g Ti(IV)/100 g TOA. We expect that results studied would be applicable to separate and concentrate titanium from secondary sources such as red mud produced in the aluminum/alumina industry.

Asymptotical synchronization of chaotic Lur'e systems equipped with sampling controller

Abstract: The global asymptotical master-slave synchronization problem of the identical chaotic Lur'e systems equipped with a sampling controller is studied. The discussed system is transformed into a system with a spacial time-varying delay at first. Then a novel Lyapunov-Krasovskii functional (LKF) is developed to obtain a less conservative synchronization criterion and thus the gains of the controller can be obtained based on the linear matrix inequality (LMI) technique. Finally, case studies based on a typical Chua's circuit are carried out to verify the effectiveness and benefit of the proposed method.