Localization for hybrid sensor networks in unknown environments using received signal strength indicator

An algorithm of localization for hybrid sensor networks is proposed in this paper. It is designed to be used in the unknown indoor environments. Received signal strength indicator is used to evaluate the distance between mobile node and static nodes. Mobile node takes a random walk and emits signal packets including its positional information. The static nodes can improve its positional precision via running Bayesian filters. The proposed approach does not require any navigation equipments like GPS or IMU in the nodes\u27 hardware. The real experimental results show that the localization of static nodes is approximately accurate and the distribution of static nodes\u27 location become further precise after using Bayesian filters. © 2008 IEEE

Nonfragile Finite-Time Extended Dissipative Control for a Class of Uncertain Switched Neutral Systems

This paper is concerned with finite-time extended dissipative analysis and nonfragile control for a class of uncertain switched neutral systems with time delay, and the controller is assumed to have either additive or multiplicative form. By employing the average dwell-time and linear matrix inequality technique, sufficient conditions for finite-time boundedness of the switched neutral system are provided. Then finite-time extended dissipative performance for the switched neutral system is addressed, where we can solve H∞, L2-L∞, Passivity, and (Q,S,R)-dissipativity performance in a unified framework based on the concept of extended dissipative. Furthermore, nonfragile state feedback controllers are proposed to guarantee that the closed-loop system is finite-time bounded with extended dissipative performance. Finally, numerical examples are given to demonstrate the effectiveness of the proposed method

Photoluminescence of Colloids of Pristine ZnAl Layered Double Hydroxides

Colloids of pristine ZnAl layered double hydroxides (LDHs) were found to display an unexpected photoluminescence (PL) phenomenon disparate from the corresponding LDH solids. First, ZnAl LDHs with nitrate in the interlayer were prepared by a hexamethylenetetramine hydrolysis method. Their colloids were obtained by subsequent delamination in formamide at room temperature. Interestingly, an unexpected PL phenomenon was observed for the colloids, different from that of the relevant solid powder. The Zn/Al ratio and concentration did not change the Stokes shift. However, they were found to be the major factors in the emission intensity. Numerous surface defect sites and interaction of LDH with formamide were believed to be the main reasons

Comparative Morphology of the Lungs and Skin of two Anura, Pelophylax nigromaculatus and Bufo gargarizans

Abstract The lungs and skin are important respiratory organs in Anura, but the pulmonary structure of amphibians remains unclear due to the lack of a suitable procedure. This study improved the procedure used for fixing lungs tissues and used light microscopy, transmission electron microscopy and scanning electron microscopy to reveal the differences in the lung and skin morphologies between Pelophylax nigromaculatus (P. nigromaculatus) and Bufo gargarizans (B. gargarizans). In P. nigromaculatus and B. gargarizans, the cystic lungs comprise a continuous outer pulmonary wall on which primary, secondary, and tertiary septa attach, and a number of regular lattices form from raised capillaries and the pulmonary epithelium on the surfaces of the pulmonary wall and septa. Each lattice in P. nigromaculatus consists of several elliptical sheets and flat bottom, and the septa are distributed with denser sheets and have a larger stretching range than the pulmonary wall. The lattice in B. gargarizans consists of thick folds and an uneven bottom with several thin folds, and the septa have more developed thick and thin folds than the pulmonary wall. However, the density of the pulmonary microvilli, the area of a single capillary, the thicknesses of the blood-air barrier, pulmonary wall and septum, and the lung/body weight percentage obtained for B. gargarizans were higher than those found for P. nigromaculatus. In P. nigromaculatus, the dorsal skin has dense capillaries and a ring surface structure with mucus layer on the stratum corneum, and the ventral skin is slightly keratinized. In B. gargarizans, the stratum corneum in both the dorsal and ventral skins is completely keratinized. A fine ultrastructure analysis of P. nigromaculatus and B. gargarizans revealed that the pulmonary septa are more developed than the pulmonary walls, which means that the septa have a stronger respiratory function. The more developed lungs are helpful for the adaptation of B. gargarizans to drought environments, whereas P. nigromaculatus has to rely on more vigorous skin respiration to adapt to a humid environment

An Improved Gas Leakage Model and Research on the Leakage Field Strength Characteristics of R290 in Limited Space

Some alternative refrigerants with excellent environmental performance often have different flammable limits. When refrigerant leaks, the external space may have a certain explosion risk if the refrigerant is not diffused timely. To understand the leakage and diffusion characteristics of the refrigerant, an improved gas leakage model was proposed in this paper, and the accuracy verification of the improved model was developed. Based on the above works, taking R290 as the research object, the variation law of the field strength between the leaked gas and external space and the influence of different initial leakage pressures on the field strength characteristics were analyzed. The simulation results showed that when the initial leakage pressure was 2 MPa, the R290 gas entered the external space as a supersonic jet, the gas underwent continuous expansion and compression processes in the near-field area and a Mach disk was formed within the flow area. During this process, parameters, such as the temperature, pressure, velocity and density of the leaked R290 gas, changed dramatically, and then the gas gradually returned to room temperature and normal pressure through interaction with the external space. The flammable area formed by the leaked R290 was mainly concentrated in the local flow area below the leak hole, and the existence of the Mach disk caused the R290 high concentration area to increase. With the increase in the initial leakage pressure, the distance from the Mach disk to the leak hole and the circumferential diameter of the Mach disk increased, and the flammable area increased slightly in the horizontal direction, whereas the flammable area increased significantly in the vertical direction