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This paper investigates the average tracking problem for a class of nonlinear multi-agent systems with switching topologies. The control design is developed for switching topologies without requiring the accurate mode with nonlinear dynamics. An adaptive neural-network-based control algorithm is proposed for a team of agents to track the average of multiple time-varying reference signals, of which the dynamics of each subsystem is assumed to be unknown and will be estimated by using adaptive neural network mechanism. Finally, a numerical simulation is given to illustrate the effectiveness of presented consensus protocol.

Lurgi fixed-bed pressurized gasifiers have attracted significant commercial interest in China because they are suitable for the production of substitute natural gas. However, trace elements present in coal could be emitted during the gasification process and transferred into gas, water, or solids in downstream processes if not properly removed, and this could then be greatly toxic to human health or lead to environmental pollution. In this study, simulation tests were performed using a laboratory-scale fixed-bed pressurized gasifier, and the distribution and fate of toxic elements including F, Hg, As, Se, Pb, U, and Be were investigated. The results indicate that during pressurized gasification, with increasing temperature from 800 to 1100 °C, the volatility of Pb increases, whereas As, U, and Be exhibit the opposite trend. It is obviously affected by pressure, such that increasing pressure leads to the enrichment of As in the ash. Elements As, U, and Be are found to be enriched in the ash in the form of ...

Underground coal gasification (UCG) is a promising option for the recovery of low-rank and inaccessible coal resources, during which coal permeability plays an important role in various aspects, in...

Underground coal gasification (UCG) is a promising option for the recovery of low-rank and inaccessible coal resources. Detailed mineralogical information is essential to understand underground reaction conditions far from the surface and optimize the operation parameters during the UCG process. It is also significant in identifying the environmental effects of UCG residue. In this paper, with regard to the underground gasification of lignite, UCG slag was prepared through simulation tests of oxygen-enriched gasification under different atmospheric conditions, and the minerals were identified by X-Ray diffraction (XRD) and a scanning electron microscope coupled to an energy-dispersive spectrometer (SEM-EDS). Thermodynamic calculations performed using FactSage 6.4 were used to help to understand the transformation of minerals. The results indicate that an increased oxygen concentration is beneficial to the reformation of mineral crystal after ash fusion and the resulting crystal structures of minerals also tend to be more orderly. The dominant minerals in 60%-O2 and 80%-O2 UCG slag include anorthite, pyroxene, and gehlenite, while amorphous substances almost disappear. In addition, with increasing oxygen content, mullite might react with the calcium oxide existed in the slag to generate anorthite, which could then serve as a calcium source for the formation of gehlenite. In 80%-O2 UCG slag, the iron-bearing mineral is transformed from sekaninaite to pyroxene.

Coalfield fires are hazardous to the environment and human health as a result of the release of polycyclic aromatic hydrocarbons (PAHs). The incomplete combustion processes of the Ulanqab lignite from Inner Mongolia of northern China during coalfield fires were simulated in a tubular furnace, and 16 US Environmental Protection Agency priority pollutant PAHs in the flue gas were absorbed and analyzed. The results indicate that incomplete combustion results in a clear increase in PAH emission compared with other combustion methods; this is attributed to the formation of species with two and three benzene rings, such as naphthalene, acenaphthylene, and acenaphthene. Benzo[ a ]pyrene, dibenz[ a , h ]anthracene, and benz[ a ]anthracene make a large contribution to the toxicity equivalent value (TEQ), although they make up a small proportion of the PAHs. With temperature increasing, the total PAH yield peak occurs at 800 °C with a yield of 923.41 mg/kg at an air/coal ratio of 1 m 3 /kg. As the air/coal ratio increases, the amount of PAHs varies with the addition of oxygen. At a ratio of 2 m 3 /kg, the minimum PAH yield of 486.07 mg/kg occurs at 800 °C and the maximum concentrations of the most toxic species, benzo[ a ]pyrene, and dibenz[ a , h ]anthracene, are found. Increasing the coal particle size from 0.25 to 20 mm results in a significant growth of both the yields and TEQs of the PAH species.

In the study of cardiac activity, manual determination of local activation times is a time-consuming process that precludes the application of cardiac activity during a clinical procedure or an electrophysiologic experiment. Based on former bipolar algorithm and unipolar algorithm, this paper presents a novel method. Using unipolar electrograms and bipolar electrograms simultaneously, this method determines the activation times with good accuracy.

The first thorny problem in the study of atrial fibrillation (AF) is the establishment of reliable animal models. This paper presents how to create a canine sterile pericarditis model. A new data analysis method, Fast Fourier Transform is introduced. The data from canine sterile pericarditis model was analyzed using FFT. The results demonstrate that canine sterile pericarditis model is a reliable animal model for studying AF and that FFT is a rapid and effective method for analyzing AF data.

This paper introduces the history and background of studies on the mechanism of atrial fibrillation. The necessary equipment to study atrial fibrillation--a high-resolution cardiac mapping system is presented. This equipment has provided a strong basis for the future study to acquire a precise understanding of the mechanism of atrial fibrillation.