Liquid Crystal Droplet-Embedded Biopolymer Hydrogel Sheets For Biosensor Applications

The development of simple, portable, and low-cost biosensing platforms is of great interest in the clinical diagnosis of disease. Here, we report liquid crystal (LC) droplet-embedded chitosan (CHI) hydrogel films formed by the Ag+ ion-triggered fast gelation of the CHI/surfactant complex-stabilized LC emulsion which is cast on substrates. The small sheets cut from the LC droplet-embedded hydrogel films combine the advantages of both hydrogels and LC droplets, offering a portable and label-free sensing platform for the real-time detection of bile acids in a small amount of solution. We find that the response time and detection limit of LC droplet-embedded hydrogel sheets for bile acids depend on their chemical structures

Matrix converter based virtual synchronous generation technology

Energy is an important driving force for social development. The shortage of natural resources urgently promotes the research of energy and the development of related technologies. Meanwhile, the distributed generation is one of the most important approaches. Virtual synchronous generator (VSG) technology, as a kind of control strategy that can participate actively in grid power regulation, has drawn much attention. Traditional VSG technology uses the two-level inverter as the main circuit. Based on the theory of VSG and the matrix converter (MC) as the main circuit of the VSG, the control system can imitate synchronous generator's characteristics such as inertial characteristics, frequency response characteristics and frequency modulation. The method provides a feasible solution for the power conversion of the distributed generation, which is the AC output, omitting the procedure of AC–DC–AC. Through the simulation, it is verified that the VSG technology can be applied to the MC, which provides a new idea for the exchange transformation in distributed generation

Surface Modified Liquid Crystal Droplets As An Optical Probe For The Detection Of Bile Acids In Microfluidic Channels

We report the surface modification of 4-n-pentyl-4’-cyanobiphenyl (5CB) droplets in aqueous solution by the adsorption of sulfated β-CD/tetradecyl sulfate sodium (SC14S) complexes at the 5CB-aqueous interface, followed by the coating of poly(diallyldimethylammonium chloride) (PDADMAC) through electrostatic interaction. The PDADMAC/sulfate β-CD/SC14S complex-coated 5CB droplets are highly stable in aqueous solution. We show that bile acids are able to penetrate into the PDADMAC coating and displace the SC14S from the cavity of the β-CD immobilized at the surface of the 5CB droplets through the competitive host-guest recognition, consequently inducing the radial-to-bipolar configuration transition of the 5CB droplets. The integration of PDADMAC/sulfate β-CD/SC14S complex-coated 5CB droplets in microfluidic channels allows the selective detection of bile acids in a small sample volume (1 μL) in the presence of ascorbic acid, uric acid, creatinine and urea by observing the configuration transition of the 5CB droplets. The detection limit of the miniaturized 5CB droplet-based sensor platform for bile acids can be tuned by the number density of 5CB droplets

Modeling and Control of Grid Side Converter in Wind Power Generation System Based on Synchronous VFDPC with PLL

Virtual flux oriented direct power control (VFDPC) is combined space vector modulation (SVM) with PI of DC-link voltage, active power and reactive power to control the grid side converter in wind power generation system in this paper. VFDPC has reached good performances with PLL (phase lock loop). First the mathematical models of grid side converter, LCL filter and phase lock loop are given. Then the control strategy of grid side converter-based wind power generation system is given in detail. Finally the simulation model is modeled consisting of power circuits, such as the grid side converter, LCL filter, transformer grid, and control parts, such as PI controllers of DC-link voltage, active power, reactive power, and SVM, and so on. The simulation results have verified that the control strategy is feasible to fit for control of gird currents, active power, reactive power and DC-link voltage in wind power generation system.</jats:p

Modeling and Simulation of Single-Phase Full Bridge Two-Level PV H6 Inverter Connected to Grid

PLECS is used to model the PV H6 inverter connected to grid and good results are obtained. First, several common topologies of PV inverters are introduced. Then the unipolar PWM control strategy is described for PV H6 inverter. Third, PLECS is briefly introduced. Fourth, the modeling of PV H6 inverter is presented with PLECS. Finally, a series of simulations are carried out. The simulation results tell us PLECS is very powerful tool to real power circuits and it is very easy to simulate LCL filter. They have also verified that the unipolar PWM control strategy is feasible to control the PV H6 inverter.</jats:p