Design Of Hybrid Filter Research Articles

Multiple hydrogen bonding self-assembly tailored electrospun polyimide hybrid filter for efficient air pollution control

Air pollutions are extremely serious threats to human health and the functional hybrid filter is able to remove complicated pollutants with great potential. However, the stable structure design of hybrid filter to provide efficient filtration and adsorption performance for high temperature applications still remains a challenge. In this study, electrospun polyimide (PI) based hybrid filter was fabricated via multiple hydrogen bonding self-assembly for high-temperature air purification. In particular, Octa(amino-propylsilsesquioxane) (POSS-NH2) was utilized as “bridge” for the surface activation of PI fiber, and then amino-functionalized Zeolitic Imidazolate Framework-8 (NH2-ZIF-8) nanocrystals were anchored on the fiber surface through hydrogen bonding. On account of the synergistic effect of the interception effect of fibers and the electrostatic interaction of NH2-ZIF-8 nanocrystals, the as-obtained PI-POSS@ZIF hybrid filter possessed excellent filtration performance with a high PM0.3 removal efficiency of 99.28% and a low pressure drop of 49.21 Pa at high temperature of 280 °C. Moreover, due to the massive micropore structure, rich open metal sites and functional groups of NH2-ZIF-8, the hybrid filter exhibited prominent VOCs adsorption performance with adsorption capability of 89.95 mg/g for formaldehyde.

Distributed Power Quality Conditioning System for Three-Phase Four-Wire Low Voltage Networks

This paper presents distributed power quality conditioning system to compensate current and voltage distortions in three-phase four-wire networks caused by unbalanced non-linear single-phase loads. The proposed conditioning system consists of several hybrid filter units installed in various nodes for compensation of excessive neutral currents and voltage distortions in a selected area of the distribution network. The system is open and it can be easily modified by installation of new filter units. A novel hybrid filter design procedure based on filter frequency characteristics optimization in the parameters of passive and active parts is presented. A digital system of control signal computation for active filters based on the use of modern methods of spectral analysis is considered. The proposed digital control system enables selective compensation of fundamental and harmonic components. The mathematical model of the proposed power quality conditioning system is developed in the MatLab software. The simulated results show that the presented conditioning system reduces the level of neutral conductor currents and the voltage unbalance as well ensures harmonic compensation in three-phase four-wire networks.

Hybrid filter design of fault detection for networked linear systems with variable packet dropout rate

The study focuses on the fault detection filter design problem for a class of networked systems with intermittent measurements. The fault detection filter, which is used as residual generator, is formulated as an $\mathcal {H} _{\infty }$H ∞ filtering form. The random packet dropouts are governed by a Bernoulli distributed sequence, and the packet dropout rate is uncertain and variable, which is described by a semi-Markov stochastic process. A more general class of Lyapunov functions that not only depend on the system modes, but also on the staying time during the current system mode is utilised. Afterwards, numerically testable sufficient conditions on the existence of a desired fault detection filter are established such that the filtering error system is $\sigma $σ-error mean square stable with a prescribed $\mathcal {H}_{\infty }$H ∞ disturbance attenuation level. Finally, an illustrative example is provided not only to demonstrate the effectiveness of the designed filter and the superiority of the utilisation of semi-Markov chain, but also the necessity of considering the variation of packet dropout rate in the design phase.