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Insect pollinators play a vital role in global crop pollination. Due to climate change, agricultural intensification, and urbanization in recent decades, insect pollinator abundance and species richness have declined rapidly at global and regional scales. Insufficient pollination on croplands is becoming a significant challenge worldwide. In recent years, planting of field-side companion plants that flower concurrently in the vacant space on croplands has been proposed as an effective measure in developed countries to improve pollinator abundance and diversity. These companion plants can provide stable food sources (such as nectar and pollen) and nesting sites for pollinators. Related studies in China are still limited. We reviewed the global research status on the effects of field-side companion plants on crop pollination services, focused on the factors influencing the impacts of co-flowering plants on crop pollination, optimal selection principles for companion plants, and put forward perspectives for application in Chinese agriculture. [ABSTRACT FROM AUTHOR]

Hydroquinone (HQ), one of the metabolites of benzene in humans, has significant hepatotoxic properties. Chronic exposure to HQ can lead to leukemia. In a previous study by this group, we constructed a model of malignant transformation of human lymphoblastoid cells (TK6) induced by chronic exposure to HQ with significant subcutaneous tumorigenic capacity in nude mice. miR‐92a‐3p is a tumor factor whose role in HQ‐induced malignant transformation is not yet clear. In the present study, raw signal analysis and dual‐luciferase reporter gene results suggested that miR‐92a‐3p could target and regulate TOB1, and the expression level of miR‐92a‐3p was significantly upregulated in the long‐term HQ‐induced TK6 malignant transformation model, while the anti‐proliferative factor TOB1 was significantly downregulated. To investigate the mechanism behind this, we inhibited miR‐92a‐3p in a malignant transformation model and found a decrease in cell viability, a decrease in MMP‐9 protein levels, a G2/M phase block in the cell cycle, and an upregulation of the expression of G2/M phase‐related proteins cyclinB1 and CDK1. Inhibition of miR‐92a‐3p in combination with si‐TOB1 restored cell viability, inhibited cyclin B1 and CDK1 protein levels, and attenuated the G2/M phase block. Taken together, miR‐92a‐3p reduced the cell proliferation rate of HQ19 and caused cell cycle arrest by targeting TOB1, which in turn contributed to the altered malignant phenotype of the cells. This study suggests that miR‐92a‐3p is likely to be a biomarker for long‐term HQ‐induced malignant transformation of TK6 and could be a potential therapeutic target for leukemia caused by long‐term exposure to HQ. [ABSTRACT FROM AUTHOR]

The circuit modeling and analysis of resonant inverters is complex because the state variables such as inductor currents and capacitor voltages are ac dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonic of interest. Correspondingly, the circuit is decomposed into two dc subcircuits, the state variables of which are the time-varying Fourier coefficients of the original ac variables. A small-signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A phasor-domain modeling method is used to investigate the resonant inverters in high-frequency ac power distribution systems. A resonant inverter system with five energy storage elements is modeled and simulated, and compared with switch simulation for both steady state and transients. The phasor model simulation matches the switch model simulation in both steady state and transients, but takes much less computing time. In addition, this model closely relates to the power converter topology in time domain, and therefore, keeps the physical meaning of the state variables. It can be used for high accuracy of modeling, simulation, and circuit analysis and control design. It can be extended to a higher order of resonant topologies including parasitic components. A high-frequency ac system with two pulse-phase-modulation-controlled resonant inverters is modeled and simulated, and the current distribution control is investigated with the phasor model. The model simulation is compared with switch-level simulation and experimental results. Index Terms--High-frequency ac power distribution system, modeling, phasor-domain, pulse phase modulation (PPM), resonant converter, resonant inverter system.

Resonant inverters are connected to a high-frequency ac (HFAC) bus, where power is delivered to different locations for points-of-use power management. Such a power distribution system subjects to more perturbations and load uncertainties than inverters operating with single load. A novel voltage control method is proposed in this paper for a high-frequency full-bridge resonant inverter with series-parallel resonant tank. A modified one-cycle controlled phase-shift modulation is proposed to effectively compensate the input line variations. The uncertainty model of the high frequency resonant inverter is developed and analyzed with the resonant circuit component tolerance, input line and load variations taken into design considerations. The voltage feedback controller is designed based on the H[infinity] robust control theory and is implemented with analog discrete devices. The proposed control scheme has the advantages of fast response for both input line and load perturbations. It also ensures a wide range of system stability and guarantees robustness of the power converter. Both simulations and experimental results are provided to verify with the theoretical analysis through an experimental prototype of a full-bridge resonant inverter with an output power of 150-W operating at 1 MHz and an output voltage of 28 V (rms). Index Terms--Full bridge, high frequency, one-cycle control, phase-shift modulation, resonant inverter, robust control.

The design of a resonant inverter for high-frequency ac (HFAC) power distribution systems is complicated by the following three factors: 1) A number of electronic loads located in different locations are connected to the resonant inverter, the impedance, and the power factor of the equivalent load of which varies over a wider range than a system with a certain load; 2) the resonant inverter is subject to an input-line voltage varying over a wide range; and 3) the characteristics of the resonant inverter depend on the load impedance. It is mandatory to operate the inverter with zero-voltage switching under various load conditions of different power factors and over wide input variations. It is further desirable that multiple resonant inverters can be paralleled with simple current-sharing control (CSC). A phase-shift-modulation (PSM)-controlled full-bridge series-parallel resonant inverter is proposed for the HFAC power distribution architectures. A new PSM method is proposed with which the phase angle of the inverter output voltage is independent of the modulation signal of the phase-shift modulator. Such a feature allows multiple resonant inverters to operate in parallel with a magnitude CSC. The resonant inverter is analyzed with a general nonresistive load model, and the design curves are developed. A prototype resonant inverter system is designed and implemented with an operation frequency of 1 MHz, a rated output power of 150 W, and a sinusoidal output voltage of 1-MHz 28-V rms. The proposed resonant inverter has the advantages of high efficiency over wide input/output line variations, high waveform quality of the output voltage, and phase-angle independence of the voltage-feedback/feed-forward control and CSC. Index Terms--Full bridge, phase-shift modulation (PSM), power distribution architecture, resonant inverter, soft switching.

A high-efficiency two-stage resonant inverter with effective control of both the magnitude and phase angle of the output voltage was proposed in this paper for high-frequency ac (HFAC) power-distribution applications, where a number of resonant inverters need to be paralleled. In order to parallel multiple resonant inverters of the same operation frequency, each inverter module needs independent control of the phase angle and magnitude of the output voltage. It is also desirable that the output voltage has very low total harmonics distortion, as well as high efficiency over wide input and load ranges. The proposed resonant inverter consists of two stages. The first stage is a two-switch dc/dc converter with zero-voltage transition, and the second stage is a half-bridge resonant dc/ac inverter with fixed duty ratio. A series-parallel resonant tank is used to achieve high waveform quality of the output voltage. The magnitude of the output voltage is regulated through the duty-ratio control of the first stage with pulsewidth modulation. The phase angle of the output voltage is regulated through a pulse-phase-modulation control of the second stage. The proposed resonant inverter has the advantages of better waveform quality, wide range of input and load variations for soft-switching, and independent control of the phase angle and magnitude of the output voltage, making it an attractive candidate for applications where a number of resonant inverters need to be placed in parallel to the HFAC bus and a number of distributed loads are connected to the HFAC bus. The performance is verified with both simulation and experiments. Index Terms--High-frequency ac (HFAC), power-distribution architecture, pulse-phase modulation (PPM), pulsewidth modulation (PWM), resonant inverter, zero-voltage switching (ZVS).

The control issue of multiple inverter modules operated in parallel is investigated for high-frequency alternative current (HFAC) power distribution architectures, where multiple high-frequency resonant inverters are connected in parallel to the high-frequency high-voltage low-current (HVLC) ac bus, to feed a number of point-of-use power supplies. The circulating current in the multiple inverter system is analyzed first. A novel control scheme is proposed based on the active and reactive current decomposition concept. In the proposed control, there are two loops: 1) the current sharing control loop and 2) the voltage feedback control loop. For the current sharing loop, the active current and reactive current are controlled separately. It is shown that the minimization of the circulating current can be achieved if both the active current and reactive current of the equivalent load are evenly distributed among activated inverter modules. This control method is superior to the scalar control where only the magnitudes of the currents are controlled. Performance is verified with both simulations and experiments on a prototype HFAC power distribution system where two two-stage resonant inverter modules of 500 kHz and 100 W are connected in parallel through small connection inductors to the 500-kHz 28-V rms HFAC bus. Index Terms--Circulating current minimization, current decomposition, current sharing, high-frequency ac (HFAC) power distribution system, resonant inverter.

This paper presents a novel approach to induction motor current signature analysis based on wavelet packet decomposition (WPD) of the stator current. The novelty of the proposed method lies in the fact that by using WPD method the inherent nonstationary nature of stator current can be accurately considered. The key characteristics of the proposed method are its ability to provide feature representations of multiple frequency resolutions for faulty modes, ability to clearly differentiate between healthy and faulty conditions, and its applicability to nonstationary signals. Successful implementation of the system for two types of faults, i.e., rotor bar breakage and air-gap eccentricity is demonstrated here. The results are validated based on both simulation and experiments of a 5-hp induction motor. Index Terms--Air-gap eccentricity, induction motor, mechanical fault, rotor bar, stator current signature analysis, wavelet packet decomposition (WPD).