Adaptive output feedback stabilization for nonlinear systems with unknown polynomial-of-output growth rate and sensor uncertainty

summary:In this paper, the problem of adaptive output feedback stabilization is investigated for a class of nonlinear systems with sensor uncertainty in measured output and a growth rate of polynomial-of-output multiplying an unknown constant in the nonlinear terms. By developing a dual-domination approach, an adaptive observer and an output feedback controller are designed to stabilize the nonlinear system by directly utilizing the measured output with uncertainty. Besides, two types of extension are made such that the proposed methods of adaptive output feedback stabilization can be applied for nonlinear systems with a large range of sensor uncertainty. Finally, numerical simulations are provided to illustrate the correctness of the theoretical results

Performance Limits and Geometric Properties of Array Localization

Location-aware networks are of great importance and interest in both civil and military applications. This paper determines the localization accuracy of an agent, which is equipped with an antenna array and localizes itself using wireless measurements with anchor nodes, in a far-field environment. In view of the Cram\'er-Rao bound, we first derive the localization information for static scenarios and demonstrate that such information is a weighed sum of Fisher information matrices from each anchor-antenna measurement pair. Each matrix can be further decomposed into two parts: a distance part with intensity proportional to the squared baseband effective bandwidth of the transmitted signal and a direction part with intensity associated with the normalized anchor-antenna visual angle. Moreover, in dynamic scenarios, we show that the Doppler shift contributes additional direction information, with intensity determined by the agent velocity and the root mean squared time duration of the transmitted signal. In addition, two measures are proposed to evaluate the localization performance of wireless networks with different anchor-agent and array-antenna geometries, and both formulae and simulations are provided for typical anchor deployments and antenna arrays.Comment: to appear in IEEE Transactions on Information Theor

Leader-following consensus for lower-triangular nonlinear multi-agent systems with unknown controller and measurement sensitivities

summary:In this paper, a novel consensus algorithm is presented to handle with the leader-following consensus problem for lower-triangular nonlinear MASs (multi-agent systems) with unknown controller and measurement sensitivities under a given undirected topology. As distinguished from the existing results, the proposed consensus algorithm can tolerate to a relative wide range of controller and measurement sensitivities. We present some important matrix inequalities, especially a class of matrix inequalities with multiplicative noises. Based on these results and a dual-domination gain method, the output consensus error with unknown measurement noises can be used to construct the compensator for each follower directly. Then, a new distributed output feedback control is designed to enable the MASs to reach consensus in the presence of large controller perturbations. In view of a Lyapunov function, sufficient conditions are presented to guarantee that the states of the leader and followers can achieve consensus asymptotically. In the end, the proposed consensus algorithm is tested and verified by an illustrative example

Modelling hydrological responses to climate change in a data-scarce semiarid basin in the Tianshan Mountains

The Tianshan Mountains, known as the Water tower of Central Asia, are an essential freshwater source for downstream rivers, residents, irrigation agriculture and ecosystems in Central Asia. Climate in this semiarid region has changed from warm-dry to warm-wet in the last decades. Water resources are highly sensitive to climate change, and their availability is expected to become more unstable in the future. However, hydrological processes in glacierized basins are poorly known due to data scarcity and complex snow and glacier melt dynamics. It is therefore particularly important to improve our understanding of climate change and its impacts on hydrological regimes in dry, glacierized mountain regions such as the Tianshan Mountains. Emphasizing the research gaps related to the scarcity of observational data and lack of understanding of climate variability and hydrological regimes, the aim of this thesis is to model hydrological responses to climate change in a data-scarce glacierized basin in the Tianshan Mountains to better understand mountain hydrology. Spatio-temporal changes of climate change, climate extremes, hydrological and cryosphere were summarized based on data analysis and literature review. ..

DNA barcoding for the identification of common economic aquatic products in Central China and its application for the supervision of the market trade

Common economic aquatic products are important contributors to the human food supply. However, with the rapid globalization of the aquatic products industry, aquatic products market has become increasingly disordered. Therefore, an accurate and convenient method for identifying common economic aquatic products is important and necessary in many areas. DNA barcoding, which constitutes the analysis of a short fragment of the mitochondrial cytochrome c oxidase subunit I (COI) sequence, has been widely used in species identification. To discriminate common economic aquatic species using DNA barcoding, we collected 534 COI barcode sequences of 66 common species consisting of 39 fish, 9 crustaceans and 18 mollusks. The intraspecific genetic distances based on the Kimura 2-parameter (K2P) model were less than 1.37% for fish, 7.32% for crustaceans and 3.40% for mollusks, whereas the intragenus distances ranged from 3.91% to 13.82% for fish, 14.99%-16.17% for crustaceans and 14.82%-1636% for mollusks. The average intraspecific K2P distance was also compared with the average intragenus distance. The taxonomic resolution ratio values obtained for fish, crustaceans and mollusks were 58.50, 21.59 and 27.63 respectively, which are higher than the threshold of (10 x). A neighbor-joining (NJ) tree based on the K2P distance, and a maximum likelihood (ML) tree, based on the GTR + I + G model, were constructed, and all of the species could be identified unambiguously in the trees with several branches exhibiting high bootstrap values. Our results demonstrated high efficiency of DNA barcoding as an efficient molecular tool for the identification of common economic aquatic products, and 8 substitute species were successfully detected in 66 species. Our analyses also indicated that the common aquatic products trade industry could be effectively monitored and managed by DNA barcoding. Therefore, a simple identification database of common economic aquatic products was constructed. (C) 2015 Published by Elsevier Ltd

Attribution of satellite-observed vegetation trends in a hyper-arid region of the Heihe River basin, Western China

Terrestrial vegetation dynamics are closely influenced by both climate and by both climate and by land use and/or land cover change (LULCC) caused by human activities. Both can change over time in a monotonic way and it can be difficult to separate the effects of climate change from LULCC on vegetation. Here we attempt to attribute trends in the fractional green vegetation cover to climate variability and to human activity in Ejina Region, a hyper-arid landlocked region in northwest China. This region is dominated by extensive deserts with relatively small areas of irrigation located along the major water courses as is typical throughout much of Central Asia. Variations of fractional vegetation cover from 2000 to 2012 were determined using Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation index data with 250 m spatial resolution over 16-day intervals. We found that the fractional vegetation cover in this hyper-arid region is very low but that the mean growing season vegetation cover has increased from 3.4 % in 2000 to 4.5 % in 2012. The largest contribution to the overall greening was due to changes in green vegetation cover of the extensive desert areas with a smaller contribution due to changes in the area of irrigated land. Comprehensive analysis with different precipitation data sources found that the greening of the desert was associated with increases in regional precipitation. We further report that the area of land irrigated each year can be predicted using the runoff gauged 1 year earlier. Taken together, water availability both from precipitation in the desert and runoff inflow for the irrigation agricultural lands can explain at least 52 % of the total variance in regional vegetation cover from 2000 to 2010. The results demonstrate that it is possible to separate the satellite-observed changes in green vegetation cover into components due to climate and human modifications. Such results inform management on the implications for water allocation between oases in the middle and lower reaches and for water management in the Ejina oasis

Adaptive parameter estimation for an energy model of belt conveyor with DC motor

In practice, design parameters of a belt conveyor are likely drifting away from their design values by maintenance, readjustment, retrofit, abrasion and circumstance change. For the purpose of energy optimization, these parameters should be estimated through experiments. In this paper, a new energy model of a DC motor driven belt conveyor is presented. Then, based on an adaptive observer, a parameter estimation algorithm is derived. In addition, under a persistent excitation condition, the convergence of the parameters to the desired values can also be concluded. Compared with the existing methods, our methods can be implemented by measuring only the feed rate of the belt conveyor and the angular velocity of the rotor of the DC motor.National Science Foundation of China (No. 61074091, 61174216, 61273183), the National Science Foundation of Hubei Province (2011CDB187), the Scientific Innovation Team Project of Hubei Provincial Department of Education (T201103).http://eu.wiley.comhb201

Influence of grain refiners on the wettability of Al2O3 substrate by aluminum melt

It is well known that grain refiner additions in aluminum melts significantly reduce the filtration efficiency of ceramic foam filters (CFF). However, the mechanism remains unclear. In this work, the influence of grain refiners on the wettability of alumina substrate by aluminum melt was studied by both conventional sessile drop and improved sessile drop methods at different temperatures and vacuums. Commercial purity aluminum (CP-Al) and grain refiner master alloys Al-3Ti-1B, Al-5Ti-1B, Al-3Ti-0.15C were used. It is found that master alloy melts wet alumina substrate better than CP-Al. Generally, a lower temperature or lower vacuum results in a higher contact angle. The roles of grain refiner particles in improving the wettability were studied by analyzing the solidification structure of post wetting-test droplets using SEM. Strong sedimentation of grain refiner particles at the metal-substrate interface was observed, which is attributed to the higher density of grain refiner particles compared to the Al melt. Meanwhile, a large fraction of grain refiner particles agglomerates at the oxide skin of the aluminum droplets, showing a strong adhesion between the particles and oxide skin. Such adhering of grain refiner particles is proposed to enhance the rupture of the original oxide skin of the droplets and slow down the reoxidation process at the surface layer. Both adherence of grain refiner particles to surface oxide skin and sedimentation of particles at the metal-substrate interface are responsible for the wetting improvement.publishedVersio