Distributed consensus control for multi‐agent systems using terminal sliding mode and Chebyshev neural networks

This paper investigates the problem of consensus tracking control for second‐order multi‐agent systems in the presence of uncertain dynamics and bounded external disturbances. The communication ?ow among neighbor agents is described by an undirected connected graph. A fast terminal sliding manifold based on lumped state errors that include absolute and relative state errors is proposed, and then a distributed finite‐time consensus tracking controller is developed by using terminal sliding mode and Chebyshev neural networks. In the proposed control scheme, Chebyshev neural networks are used as universal approximators to learn unknown nonlinear functions in the agent dynamics online, and a robust control term using the hyperbolic tangent function is applied to counteract neural‐network approximation errors and external disturbances, which makes the proposed controller be continuous and hence chattering‐free. Meanwhile, a smooth projection algorithm is employed to guarantee that estimated parameters remain within some known bounded sets. Furthermore, the proposed control scheme for each agent only employs the information of its neighbor agents and guarantees a group of agents to track a time‐varying reference trajectory even when the reference signals are available to only a subset of the group members. Most importantly, finite‐time stability in both the reaching phase and the sliding phase is guaranteed by a Lyapunov‐based approach. Finally, numerical simulations are presented to demonstrate the performance of the proposed controller and show that the proposed controller exceeds to a linear hyperplane‐based sliding mode controller. Copyright © 2011 John Wiley & Sons, Ltd.     

Artificial intelligence solution to transmission loss allocation problem

The problem of transmission loss allocation of deregulated power system has been solved through the application of artificial neural network (ANN). Two network structures namely Levenberg–Marquardt back propagation (LMBP) and Bayesian regularization back propagation (BRBP) have been trained and their performance compared. It has been found that LMBP network gives faster solution for same accuracy level. As the working range of power flow transaction is quite vast, a huge volume of data need to be stored and processed for the training of neural network. The time needed for training of neural network against such huge data is prohibitive for real time application of the ANN based solution tool where raw data are used for training. A simple filtering technique has been found to be very effective to improve the solution time and training data volume requirement and make the proposed technique suitable for real time applications. With the use of filtered data for training both the training network have shown comparable performance.     

Measurements of absolute x-ray generation efficiency for selected K,L, and M-lines

The absolute efficiency of generation of a selection of K, L, and M- x-ray lines has been measured as a function of the incident electron beam energy. At an overvoltage U=2 this efficiency falls within the range 1E-4 to 1E-7, with K-lines being highest and L-Lines usually being the lowest. It is shown that for all three families of lines the efficiency has a functional variation which has the form A. (U- 1)n, as first suggested by Compton and Allison, where A and n are constants. Values of A and n for the K, L, and M shells are tabulated. The smoothly varying behavior of the efficiency makes it well suited for analytical use and spectrum simulation purposes.     

A comparative study to evaluate the corrosion performance of Zr incorporated Cr3C2-(NiCr) coating at 900 °C

In this study zirconium incorporated Cr₃C₂-(NiCr) coating has been sprayed on three superalloys viz. Superni 718, Superni 600 and Superco 605 using D-gun technique. A comparative study has been carried out to check the cyclic oxidation in air and hot corrosion in simulated incinerator environment (40%Na₂SO₄-40%K₂SO₄-10%NaCl-10%KCl) for the coated specimens at 900 °C for 100 cycles. Oxidation kinetics has been established for all the specimens using weight change measurements. Corrosion products have been characterized using X-ray diffractometer (XRD) and scanning electron microscopy/energy-dispersive analysis (SEM/EDAX). Cr₃C₂-(NiCr) + 0.2%wtZr coating provides very good corrosion resistance in air oxidation for all the three coated superalloys. As all the three coated superalloys shows parabolic behaviour with parabolic rate constant as 0.07 × 10^?10 (g² cm^?4 s^?1) for Superni 718, 0.43 × 10^?10 (g² cm^?4 s^?1) for Superni 600 and 0.3 × 10^?10 (g² cm^?4 s^?1) for Superco 605 This coating is also effective in the molten salt environment but coating on Co-based superalloy Superco 605 did not perform satisfactorily. The parabolic rate constants for coated Superni 718 is 0.61 × 10^?10 (g² cm^?4 s^?1), for coated Superni 600 is 6.72 × 10^?10 (g² cm^?4 s^?1) and for coated Superco 605 is 17.5 × 10^?10 (g² cm^?4 s^?1).     

An investigation on microstructures and mechanical properties of explosive cladded C103 niobium alloy over C263 nimonic alloy

Futuristic aerospace applications such as advanced turbojet and scramjet engines used in subsonic, supersonic, and trans-atmospheric flights require materials with ever-increasing temperature and load bearing capabilities for improved performance. The materials C103 niobium alloy and C263 nimonic alloy are widely employed in the manufacturing of scramjet engine components. Efforts to join these two materials by fusion welding process have revealed that they are metallurgically incompatible due to the extreme propensity to form brittle intermetallics. The possibility of interdicting interlayer is explored to overcome the formulation of intermetallics and the attempts have not yielded fruitful results. Explosive welding/cladding is one of the possible ways to join these materials, as it is a solid state joining process.     

A Comparative Study on the Effect of Chemical,Microwave, and Pulsed Electric Pretreatments on Convective Drying and Quality of Raisins

In order to discourage the use of chemicals in raisin processing, the effect of microwave and pulsed electric field (PEF) pretreatments on the drying rate and other quality parameters like color, total soluble solids, bulk density, appearance, and market quality were compared with that of chemically pretreated raisins dried at 65°C. The untreated and pretreated samples had a statistically significant difference in drying rate (P < 0.05). The drying rate of chemically pretreated raisins was the highest when compared to others. The results showed that the PEF and microwave-treated samples had a significantly high Total Soluble Solids (TSS), along with good appearance and market quality.