•Oregano essential oil can inhibit respiratory metabolism and energy metabolism of MRSA.•The main component of oregano essential oil can change the DNA structure of MRSA.•Oregano essential oil has a ...significant effect on the expression level of the PVL gene.
Meticillin-resistant Staphylococcus aureus (MRSA) is highly pathogenic and multi-drug resistant, so MRSA infection has become one of the important pathogens of nosocomial infections. Oregano essential oil is an effective natural antibacterial agent and has been found to be effective in inhibiting MRSA. In this experiment, the effects of oregano essential oil on respiratory metabolism, energy metabolism and genetic material of MRSA were studied with the metabolism as the starting point. At the same time, the effects of oregano essential oil on the relative expression of pvl in MRSA were further studied from the genetic level. The results indicate that oregano essential oil can cause irreversible damage to the MRSA cell membrane and cause leakage of biological macromolecules in the cell. Oregano essential oil inhibits the tricarboxylic acid cycle pathway and its key enzymes and affects the metabolites. In addition, the main component of oregano essential oil, carvacrol, can be chimeric with DNA, and oregano essential oil inhibits the relative expression of the pvl gene.
Due to the adjacent cell-to-cell equalization, the classical switched-capacitor equalizer (SCE) has seriously low balancing speed and efficiency for a long battery string. Therefore, a series of ...star-structured switched-capacitor equalizers are proposed to achieve high balancing speed and efficiency independent of the cell number and the cell voltage distribution without significant influences on the size, cost, control, and reliability compared with the classical SCE. The proposed topologies use the least mosfets and capacitors to achieve the most direct balancing paths between any two cells, being the optimal switched-capacitor structures. An analysis method for the slow switching limit and the fast switching limit impedances of the proposed equalizers is proposed to provide a theoretical guidance for the selection of the switching frequency. The inherent advantages of the proposed systems are the small size, low cost, simple control, high efficiency, fast speed, easy modularization, and high reliability. A prototype for four lithium-ion battery cells is set up. Experimental results show improved balancing performances with strong robustness. Moreover, the measured peak balancing efficiency is about 93.1% despite faster balancing speed.
An optimized automatic equalizer based on coupled half-bridge converters using a multi-winding transformer is proposed for series-connected battery packs. The proposed equalizer not only reduces the ...transformer windings by half, achieving a compact size and low cost, but also realizes the automatic any-cell-to-any-cell equalization, significantly speeding up the equalization process. The expressions of the equalization current and efficiency are derived and verified by experimental results. The design considerations of the switching frequency and the magnetic inductance are analyzed and discussed to optimize the equalization current and efficiency. The maximum balancing efficiency of 95% is realized at the switching frequency of 5 kHz and the balancing power of 0.85 W. Comparative experimental studies of the proposed equalizer with the forward-flyback solution are conducted to validate that the balancing performances of the proposed equalizer are unaffected by the reduced transformer windings.
This paper is concerned with the l1-gain performance analysis and positive filter design for a positive discrete-time Markov jump linear system (MJLS) by using a linear programming (LP) approach. ...First, by constructing a linear stochastic Lyapunov function and introducing an “equivalent” deterministic positive discrete-time linear system, necessary and sufficient conditions in the form of LP are derived for stochastic stability and l1-gain performance of the positive discrete-time MJLS. Then a sufficient condition on the existence of the desired positive l1-gain filter is provided. The desired positive l1-gain filter can be designed by solving a standard LP problem. The pest’s structured population dynamic model is employed to illustrate the effectiveness of the proposed method.
In conventional equalizers, the facts of bulky size and high cost are widespread. Particularly, the zero-switching loss and zero-voltage gap (ZVG) between cells are difficult to implement due to the ...high-frequency hard switching and the voltage drop across power devices. To overcome these difficulties, a direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost dc-dc converter (BDDC) is proposed. The QRLCC is employed to gain zero-current switching, leading to a reduction of power losses. The BDDC is employed to enhance the equalization voltage gap for large balancing current and ZVG between cells. Moreover, through controlling the duty cycle of the BDDC, the topology can online adaptively regulate the equalization current according to the voltage difference, which not only effectively prevents overequalization but also abridges the overall balancing time. Instead of a dedicated equalizer for each cell, only one balancing converter is employed and shared by all cells, reducing the size and implementation cost. Simulation and experimental results show the proposed scheme exhibits outstanding balancing performance, and the energy conversion efficiency is higher than 98%. The validity of the proposed equalizer is further verified by a quantitative and systematic comparison with the existing active balancing methods.
This paper is concerned with L 1 -stochastic stability and L 1 -gain performance analysis of a continuous-time positive Markov jump linear system with a time-delay. By constructing a novel linear ...co-positive stochastic Lyapunov functional based on the positivity of the system, and characterizing the system equation of the mathematical expectation of the markovianized states, some necessary and sufficient delay-dependent conditions for L 1 -stochastic stability and L 1 -gain performance are presented in terms of linear programming. A numerical example is provided for showing the effectiveness of the obtained conditions, especially for exploring and revealing both the negative effect and the positive effect of the time-delay on stochastic stability of the positive Markov jump linear system with a time-delay.
SiC MOSFET has low on-state resistance and can work on high switching frequency, high voltage, and some other tough conditions with less temperature drift, which could provide the significant ...improvement of power density in power converters. However, for the bridge circuit in an actual converter, high dv/dt during fast switching transient of one mosfet will amplify the negative influence of parasitic components and produce the significant negative voltage spikes on the complementary MOSFET, which will threaten its safe operation. This paper proposes a new gate driver circuit for SiC MOSFET to attenuate the negative voltage spikes in a bridge circuit. The proposed gate driver adopts a simple voltage dividing circuit to generate a negative gate-source voltage as traditional and a passive triggered transistor with a series-connected capacitor to suppress the negative voltage spikes, which could satisfy the stringent requirements of fast switching SiC MOSFETs under the high dc voltage condition with low cost and less complexity. An analysis is presented in this paper based on the simulation and experimental results with the performance comparison evaluated.
Abstract
The widespread use of proton exchange membrane water electrolysis requires the development of more efficient electrocatalysts containing reduced amounts of expensive iridium for the oxygen ...evolution reaction (OER). Here we present the identification of 6H-phase SrIrO
3
perovskite (6H-SrIrO
3
) as a highly active electrocatalyst with good structural and catalytic stability for OER in acid. 6H-SrIrO
3
contains 27.1 wt% less iridium than IrO
2
, but its iridium mass activity is about 7 times higher than IrO
2
, a benchmark electrocatalyst for the acidic OER. 6H-SrIrO
3
is the most active catalytic material for OER among the iridium-based oxides reported recently, based on its highest iridium mass activity. Theoretical calculations indicate that the existence of face-sharing octahedral dimers is mainly responsible for the superior activity of 6H-SrIrO
3
thanks to the weakened surface Ir-O binding that facilitates the potential-determining step involved in the OER (i.e., O* + H
2
O → HOO* + H
+
+
e
¯
).
Self-heating is of extreme importance for improving the available capacity and lifetime of lithium-ion batteries in cold climates. However, few attempts have been done to achieve effective onboard ...self-heating for the batteries in electric vehicles. This paper derives a high-frequency sine-wave (SW) heater based on resonant LC converters to self-heat the automotive batteries at low-temperatures without the need of external heaters. To be specific, an interleaved-parallel topology is introduced to double the heating speed without extra damages to batteries compared to the single heater. Further, a corresponding thermoelectric model is developed to provide guidance for the optimal design of the parameters in the proposed SW heater. Experimental results show that with a high-frequency sinusoidal current motivated by the proposed heater, lithium-ion batteries could be effectively self-heated by the ohmic-loss and electrochemical heat. Moreover, the heating time could be significantly shortened through decreasing the characteristic impedance √(L/C) or increasing the ac-heating frequency.
Using the semi-tensor product of matrices, this paper investigates the maximum (weight) stable set and vertex coloring problems of graphs with application to the group consensus of multi-agent ...systems, and presents a number of new results and algorithms. Firstly, by defining a characteristic logical vector and using the matrix expression of logical functions, an algebraic description is obtained for the internally stable set problem, based on which a new algorithm to find all the internally stable sets is established for any graph. Secondly, the maximum (weight) stable set problem is considered, and a necessary and sufficient condition is presented, by which an algorithm to find all the maximum (weight) stable sets is obtained. Thirdly, the vertex coloring problem is studied by using the semi-tensor product method, and two necessary and sufficient conditions are proposed for the colorability, based on which a new algorithm to find all the k-coloring schemes and minimum coloring partitions is put forward. Finally, the obtained results are applied to multi-agent systems, and a new protocol design procedure is presented for the group consensus problem. The study of illustrative examples shows that the results/algorithms presented in this paper are very effective.
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