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Summary: This paper proposes the gated recurrent unit (GRU)‐recurrent neural network (RNN), a deep learning approach to predict the remaining useful life (RUL) of lithium‐ion batteries (LIBs), accurately. The GRU‐RNN structure can self‐learn the network parameters utilizing adaptive gradient descent algorithms, leading to a reduced computational cost. Unlike the long short‐term memory (LSTM) model, GRU‐RNN allows time‐series dependencies to be tracked between degraded capacities without using any memory cell. This enables the method to predict non‐linear capacity degradations and build an explicitly capacity‐oriented RUL predictor. Additionally, feature selection based on the random forest technique was used to enhance the prediction precision. The analyses were conducted based on four separate cycling life testing datasets of a lithium‐ion battery. The experimental results indicate that the average percentage of root mean square error for the proposed method is about 2% which respectively is 1.34 times and 8.32 times superior to the LSTM and support vector machine methods. The outcome of this work can be used for managing the Li‐ion battery's improvement and optimization. [ABSTRACT FROM AUTHOR]

Charging stations not only provide charging service to electric vehicles (EVs), but also integrate distributed energy sources. This integration requires an appropriate planning to achieve the future sustainable distribution network. Real EV charging demand is stochastic and affected by many uncertainties, which pose challenges to the planning of a charging station. This study presents a stochastic planning model of the EV charging station with photovoltaic (PV), battery and transformer, mainly considering the uncertainties from charging demand and PV power generation. Firstly, a comprehensive EV charging demand model is established through reflecting the coupling among the EV stochastic charging behaviour, charger specifications and EV charging assignment model. Then, the planning model is formulated to minimise the total cost of the charging station, where the uncertainties arising from EV charging are addressed in various constraints. Using this model, the optimal sizing of the charging station is determined, together with the associated optimal operation strategy. Finally, the effectiveness of the proposed model is validated by multiple case studies. [ABSTRACT FROM AUTHOR]

Background: The aim of this study is to find the potential miRNA expression signature capable of predicting survival time for cervical squamous cell carcinoma (CSCC) patients. Methods: The expression of 332 miRNAs was measured in 131 (Training cohort) and 130 (Validation cohort) patients with CSCC in the Cancer Genome Atlas (TCGA) data portal. The miRNA expression signature was identified by Cox Proportion Hazard regression model to the Training data set, and subsequently validated in an independent Validation set. Kaplan-Meier curves and the receiver operating characteristic analyses of 5 years were used to access the overall survival of miRNA signature. MiRNA signature-gene target analysis was performed, followed by the construction of the regulatory network. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis were used to explore the function of target genes of miRNA signature. Results: A 2-miRNA expression signature of hsa-mir-642a and hsa-mir-378c associated with survivability was identified in CSCC. Both of them had a significant diagnostic and prognostic value of patients with CSCC. A total of 345 miRNA signature-target pairs were obtained in the miRNA signature-gene target regulatory network, in which 316 genes were targets of has-mir-378c and has-mir-642a. Functional analysis of target genes showed that MAPK signaling pathway, VEGF signaling pathway and endocytosis were the significantly enriched signal pathways that covered most genes. Conclusions: The 2-miRNA signature adds to the prognostic value of CSCC. In-depth interrogation of the 2-miRNAs will provide important biological insights that finding and developing novel molecularly prediction to improve prognosis for CSCC patients. [ABSTRACT FROM AUTHOR]

The charging coordination of electric vehicle (EV) fleets in both temporal domain and spatial domain has attracted growing attention in recent years. Meanwhile, the uncertainties in EV arrival time and total available charging power from charging stations make the coordination problem highly dynamic and challenging. This paper develops a new temporal–spatial EV charging coordination scheme that jointly considers the above two major uncertainties. Firstly, EV charging scheduling (i.e., temporal coordination) is treated as a generalized Nash equilibrium game, in which each EV (including an upcoming EV) prefers to meet its own charging demand with minimized charging cost. The probability of EV charging availability is especially proposed to incorporate the charging demands of the upcoming EVs into the coordination scheme. In order to provide flexibility and private information protection, a distributed receding horizon optimization-based solution is developed, through which the Lagrange multipliers to reach the social equilibrium are determined via an iterative manner. The charging station selection is then recommended that minimizes the objective function over the entire optimization horizon. Finally, simulations under both small-scale and large-scale scenarios effectively demonstrate improved service quality of the EV charging, both in temporal and spatial domains, and avoidance of overload in charging stations. Results in a 150-EV scenario show that, averagely, the proposed method reduces battery SoC mismatch by 43% and increases degree of consistency by 5.9%. • Temporal uncertainty and spatial uncertainty are jointly addressed. • EV charging power fluctuations and shortage are considered. • Upcoming EVs are incorporated in the charging coordination scheme. • Battery SoC mismatch is reduced by 43% in a 150-EV simulation scenario. [ABSTRACT FROM AUTHOR]

Objective: To identify differentially expressed genes (DEGs) in endometriosis and further analyze molecular mechanisms implicated in disease pathogenesis.Materials and Methods: Gene expression data (ID: GSE7846) of human endometrial endothelial cells (HEECs) collected from eutopic endometria tissue of patients with and without endometriosis were downloaded from Gene Expression Omnibus. DEGs were screened using Limma package, followed by enrichment analysis using clusterProfiler package in R. Thereafter, protein-protein interactions (PPIs) were analyzed using STRING (Search Tool for the Retrieval of Interacting Genes) database and visualized by Cytoscape software. Meanwhile, transcription factors were screened from the DEGs based on TRANSFA database, followed by construction of regulatory network using Cytoscape.Results: A total of 2255 up- and 408 down-regulated genes were identified in endometriosis patients as compared with control patients. Those DEGs were predominantly enriched in focal adhesion (e.g., FN1, EGF, FYN, EGFR, RAC1, CCND1 and JUN), regulation of actin cytoskeleton (e.g., FN1, EGF, EGFR, RAC1 and JUN) and MAPK signaling pathway (e.g., EGF, EGFR, RAC1, JUN, TGFB1 and MYC). Importantly, EGF, EGFR, JUN, FN1, RAC1, TGFB1, CCND1 and FYN were hub nodes in the PPI network. Additionally, TGFB1, SMAD1 and SMAD4 showed up-regulation in TGFB signaling pathway. Transcription factor MYC had a regulatory effect on the most DEGs, including TGFB1, RAC1 and CCND1.Conclusions: Focal adhesion, regulation of actin cytoskeleton, MAPK and TGFB/SMAD signaling pathway may be important molecular mechanism underlying the pathogenesis of endometriosis. [ABSTRACT FROM AUTHOR]

This paper discusses the assignment of generalized time constant for a non-all-pole system. The generalized time constant is found to be important because it simultaneously influences the speed of response, damping (i.e., overshoot), and robustness. For the ease of explanation, a general two-mass system is introduced as a case study, which has one pair of $j\omega$-axis zeroes. Under an ideal two-parameter control configuration, the exact lower bound of the generalized time constant is determined that results in monotonic step responses, while a moderate generalized time constant is shown to be desirable for robustness purposes. A modified-Integral–Proportional–Derivative control configuration is then adopted for the implementation of the ideal two-parameter controller. It is found that, in real applications, a specific control configuration and signal delay may also impose limits on the assignment of the generalized time constant and characteristic ratios. Due to the clear physical meaning of the polynomial method, the tradeoff relationship among the speed of response, damping, and robustness can be explicitly represented. This unique advantage leads to a straightforward controller design procedure. Finally, the theoretical analysis is validated by experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, low-order integral–proportional (IP), modified IP (m-IP), and modified integral–proportional–derivative (m-IPD) controllers are designed for the speed control of a two-mass system based on a normalized model and polynomial method. In order to have sufficient damping, the parameters of the controllers are determined through characteristic-ratio assignment under the principle that all the characteristic ratios should be larger than two. It is found that for an inertia ratio smaller than one-third, an IP controller can effectively suppress the vibrations with proper damping, while for a relatively larger inertia ratio, an m-IP controller (i.e., IP controller with an additional low-pass filter) is effective. m-IPD control is theoretically effective for a large inertia ratio. However, the necessity of a negative derivative gain leads to a very poor robustness. Both simulation and experimental results verified the effectiveness of the designed IP and m-IP controllers when the inertia ratio is relatively small. For the m-IPD controller, its poor robustness is demonstrated by introducing a large gear backlash in experiments, while the IP and m-IP controllers show promising results of a much better robustness against the gear backlash nonlinearity. [ABSTRACT FROM PUBLISHER]

Current research on electric vehicles (EVs) is focusing on the environment and energy aspects. However, electric motors also have much better control performance than conventional internal combustion engines. EVs could not only be 'cleaner' and 'more energy efficient', but also become 'safer' with 'better driving performance'. In this paper, a discrete elasto-plastic friction model is proposed for a dynamic emulation of road/tyre friction in order to validate the control design of EV control systems in laboratory facilities. Experimental results show the dynamic emulation is able to capture the transient behaviour of the road/tyre friction force during braking and acceleration, therefore enabling a more reliable validation of various EV control methods. And the computation of inverse dynamics, which usually needs to be considered in conventional emulation approaches, can be avoided using the proposed dynamic friction model. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the various technological options for the future development of China's electric power sector taking into consideration its environmental impact. A baseline case, four sulfur control cases, and two carbon control cases were simulated in the least-cost optimization energy model. The calculated results show that with no environmental constraints coal-fired power plants would remain China's least-cost option to satisfy its rapidly growing electricity demand in the future. Sulfur control alone in China's electric power sector would have a limited impact on the improvement of its overall generation efficiency and carbon emissions, and carbon control would bring not only significant sulfur and carbon emission mitigation but also an improvement in the overall generation efficiency and fuel switching from coal to natural gas. The low marginal costs of carbon mitigation in China's electric power sector show that future possible international cooperation with the sector on climate change issues such as the Clean Development Mechanism under the Kyoto Protocol would be cost-effective. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the various technological options for the future development of China's electric power sector taking into consideration its environmental impact. A baseline case, four sulfur control cases, and two carbon control cases were simulated in the least-cost optimization energy model. The calculated results show that with no environmental constraints coal-fired power plants would remain China's least-cost option to satisfy its rapidly growing electricity demand in the future. Sulfur control alone in China's electric power sector would have a limited impact on the improvement of its overall generation efficiency and carbon emissions, and carbon control would bring not only significant sulfur and carbon emission mitigation but also an improvement in the overall generation efficiency and fuel switching from coal to natural gas. The low marginal costs of carbon mitigation in China's electric power sector show that future possible international cooperation with the sector on climate change issues such as the Clean Development Mechanism under the Kyoto Protocol would be cost-effective. [ABSTRACT FROM AUTHOR]

Objective To approach the protective effects of different-dose rosuvastatin at the perioperative period on percutaneous coronary intervention (PCI) on patients with coronary heart disease (CHD). Methods A total of 173 patients with PCI from Octoer 2012 to February 2014 were selected and divided into group A (10 mg rosuvastatin, n=58), group B(20 mg rosuvastatin, n=59), and group C(40 mg rosuvastatin, n=56) according to the doses of rosuvastatin. The three groups were examined in liver and renal functions, serum lipid parameters as well as times of balloon dilatation and quantity of bailout-stenting. The level of high-sensitive c-reactive protein (hs-CRP), interleukin-18 (IL-18), creatine kinase isoenzyme (CK-MB)and troponin-T (cTn-T) were determined before the operation, after postoperative 24 h and 7 d respectively. Automatic biochemical analyzer was used to detected to the parameters of liver and renal functions, blood fat, CK-MB and cTn-T as well as IL-8 by enzyme-linked immunosor-bent assay and hs-CRP by immunoturbidimetry. Results The liver and renal function, serum lipid parameters as well as times of balloon dilatation and quantity of bailout-stenting before the treatment among the three groups were compared, whose difference has no statistic significance(P>0.05). The level of hs-CRP, IL-18, CK-MB, cTn-T before operation compared and showed no statistic significance in difference(P>0.05);The levels of hs-CRP, IL-18, CK-MB, cTn-I after postoperative 24 h were higher than those before operation; The levels of hs-CRP, IL-18, CK-MB, cTn-I after postoperative 7 d were higher than those before operation and after postoperative 24 h (P<0.05);Comparing these parameters after postoperative 7 d among the three groups , group C is super visor than those of group B(P<0.05). The cardiovascular events and incidences of adverse effects after the operation among the three groups were compared[8.62%(5/58), 5.08%(3/59), 7.14%(4/56)], which was no difference in statistic significance (P>0.05). Conclusion The rosuvastatin with doses at 20 mg, 40 mg against myocardial injury at the preoperative period with PCI after operation is better in than the dose at 10 mg, further, the effect of 40 mg-dose is supervisor than the dose at 20 mg. [ABSTRACT FROM AUTHOR]

Background: The aim of this study is to examine miRNA profiling and miR-369-3p participates in endometrioid adenocarcinoma (EEC) via the regulation of autophagy. Methods: EEC and its adjacent normal tissues were obtained from 20 clinical patients after surgery. MiRNA profiling was performed using next generation sequencing (NGS) and was validated with quantitative real time PCR (qRT-PCR). qRT-PCR was also employed to measure miR-369-3p and autophagy-related protein 10 (ATG10) expression levels. Western blotting assay was performed to measure the expressions of ATG10 and LC3B. Luciferase reporter assay was conducted to confirm the direct targeting of ATG10 by miR-369-3p. Cell proliferation and migration assays were utilized to analyze the role of miR-369-3p in HEC-1-A cells. Results: We found that miR-369-3p expression levels were down-regulated in EEC compared to the control tissues. The overexpression of miR-369-3p inhibited cell proliferation and migration in EEC; furthermore, ATG10 expression increased in EEC tissues. ATG10 was found to be a potential target of miR-369-3p via a dual-luciferase reporter assay, and ATG10 was shown to be down-regulated by miR-369-3p in protein levels. Conclusions: This study revealed that miR-369-3p inhibited cell proliferation and migration by targeting ATG10 via autophagy in EEC. [ABSTRACT FROM AUTHOR]

In this study, a decentralized power dispatch in a charging station serving electric vehicles (EVs) is discussed. The power dispatch problem is solved through a Stackelberg game in real time. In this game, the leader is the EV charging station (EVCS) while the followers are EVs. The preferences of the EVCS are designed as being self‐sufficient, providing charging services to the EVs, and maintaining the energy level of the battery energy storage system (BESS), which are described through different utility functions. In addition, the preferences of followers are to maximize their EV charging powers. The learning algorithm utilizes the consensus network to reach the generalized Stackelberg equilibrium as the power dispatch among EVs in an iterative decentralized manner. Both the static and dynamic case studies in the simulation verify the successful implementation of the proposed strategy, the flexibility to uncertainties and the re‐configurability to the number of EVs. It also has an excellent performance compared with the centralized benchmark strategy with criteria, that is, the average EV charging time, the number of charge and discharge rate of the BESS and energy exchange to the grid. Finally, a down‐scaled experiment implementation is set up to validate the functionality and the effectiveness of the game theory‐based strategy. [ABSTRACT FROM AUTHOR]

For multiple-receiver wireless power transfer (WPT), a scalable solution is desired that functions with changing number of receivers. Meanwhile, challenges lie in differences in load characteristics, power level, and cross coupling between the receivers. This article employs Class E2 dc–dc converter topology for the multiple-receiver WPT systems working at megahertz (MHz). The shunt capacitor capacitances of the Class E rectifiers and magnitude of constant output current of the current-mode Class E power amplifier are chosen as design parameters aiming at decoupling the received power of each receiver. Design procedures are developed to simultaneously achieve high efficiency and desired individual load powers over a target variation range of the cross coupling. An experimental 6.78-MHz three-receiver WPT system is optimally designed. The system is shown to be capable of providing different target load powers (10, 8, and 6 W) and maintaining a high system efficiency (above 70%) with different combinations and positions of the receivers. [ABSTRACT FROM AUTHOR]

In real applications, it is usually desirable to have a regulated dc output voltage from a wireless power transfer (WPT) system. This voltage regulation is especially necessary because of possible variation in coupling coil relative position and thus a changing mutual inductance. For WPT systems working at megahertz (MHz), Class E rectifiers are known to be advantageous, thanks to their simple configuration and soft-switching operation. In this paper, we propose a new Class-E-based active rectifier. This rectifier is capable to simultaneously perform high-efficiency rectification and output voltage regulation, but without the need to have an additional regulating circuit. Analytical derivations and analysis are provided to explain the operation principle in detail. Guidance is also developed for a balanced design of parameters, which compromises among different criteria. Final experiments validate the analytical analysis and dc output voltage regulation via the active rectifier. With the duty cycle control of the rectifier, a constant output voltage (10 V) can be maintained under a varying mutual inductance coefficient and with more than 92% rectifying efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes an equivalent series resistance (ESR)-based control, namely a circuit-level approach, to efficiently distribute load in battery-ultracapacitors (UC) hybrid energy storage systems (HESSs). The ESR circuit model of an example capacitor semiactive HESS is first built representing the energy losses at both circuit and system levels. The analytical derivations show that the overall energy loss of the HESS solely depends on the ratio of the dynamic load provided by the battery pack to the entire dynamic load. This energy loss is minimized following the load distribution determined by the ratio of the ESR of the battery pack to those of the UC pack and dc–dc converter. An ESR-based real-time control strategy is then developed to minimize the energy loss and regulate UC state-of-charge (SOC) to avoid overcharge/overdischarge. Both the simulation and experimental results verify the effectiveness of the proposed ESR-based control in terms of improvements in energy efficiency, usage of UC pack, and temperature rise reduction in batteries. The ESR-based control achieves a performance close to that using the ideal dynamic programming method. Compared with the battery-alone system, the total energy loss and battery temperature rise in the example HESS are averagely reduced by 44.9% and 51.9%, respectively, under the proposed ESR-based control. [ABSTRACT FROM AUTHOR]

This study proposes distributed energy management approach for charging multi‐class electric vehicles (EVs) in community microgrids. The energy management problem is implemented in real‐time and represented by a non‐cooperative Stackelberg game for the power distribution inside the microgrid. In this game, a battery energy storage system is chosen as a leader and the EVs are designated as followers. The charging power distribution among EVs is tackled in the two cases of 'plenty of power' and 'lack of power'. The challenging case of 'lack of power' occurs when the total charging power is insufficient to meet the need of each EV, such as when weather conditions are unfavourable. A priority factor is included in the EV utility functions to address charging priorities of different classes of EVs in practical scenarios. A consensus‐based distributed algorithm is developed later to iteratively reach the Nash equilibrium, i.e. final charging power distribution, among EVs with different charging priorities. Both simulation and experimental results show that the charging power is properly distributed when the predefined charging priorities are followed, particularly in the case of a 'lack of power'. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) systems working at several megahertz (MHz) are widely considered as a promising solution for a mid-range transfer of a medium amount of power. The soft-switching-based Class E power amplifier (PA) and rectifier are known to be suitable for high-frequency applications, which may potentially improve the performance of the MHz WPT systems. Meanwhile, the efficiency and output power of the Class E PA are sensitive to its loading condition, particularly when there is variation in the relative position of the coupling coils, namely a changed mutual inductance between the coils. Thus the purpose of this paper is to propose and discuss circuit and design improvements that maintain a high efficiency and output power of the MHz WPT systems over a wide range of mutual inductance, when the Class E PA and the Class E rectifier are employed. Besides, the suppression of the harmonic contents, i.e., the electromagnetic interference problem, is also considered in the circuit design. Both the simulation and experimental results show that the newly added and optimally designed $\pi $ matching network obviously improves the drops of the efficiency and output power of the Class E PA and the overall WPT system when the mutual inductance varies. The reduction of the total harmonic distortion in the input voltage of the coupling coils is also significant, from the original 52.9% to 9.6%. The circuit and design improvements discussed in this paper could serve as a general and practical solution for building high-performance MHz WPT systems. [ABSTRACT FROM PUBLISHER]

This paper presents systematic analysis and design of a megahertz multiple-receiver (RX) wireless power transfer (WPT) system driven by a Class E power amplifier. Both circuit-level and system-level analyses are conducted to discuss the characteristics of the WPT system. In order to simultaneously manage the power flow and maximize the overall system efficiency, a new control scheme is proposed that combines maximum efficiency point tracking and time-division multiplexing. Through the proposed scheme, RXs with different loading and coupling conditions can be charged by the same transmitter with simplified design and control strategy. Finally, the proposed control scheme is validated using an example 6.78-MHz three-RX WPT system. The experimental results show that various power requirements can be quickly and stably satisfied, and the overall average system efficiency can reach as high as 71.7%. [ABSTRACT FROM PUBLISHER]

Wireless power transfer (WPT) working at megahertz (MHz) is now being widely considered a promising candidate for the midrange transfer of a medium amount of power. Efforts have been made to build high-efficiency MHz WPT systems via both component- and system-level approaches. However, so far there have been few discussions on high-frequency rectifier for MHz WPT applications. The soft-switching-based rectifiers, such as the Class E rectifiers, are one of the promising candidates for MHz rectification. This paper investigates the application of a Class E full-wave current-driven rectifier, for the first time, in WPT systems. A procedure is also developed to optimize the design of the rectifier and the MHz WPT system. For comparison purposes, the performances of both the Class E rectifier and the conventional full-bridge rectifier are investigated in terms of total harmonic distortion (THD), efficiency, power factor, voltage/current stresses, and voltage/current transfer functions, when being applied in an example 6.78-MHz WPT system. The simulation and experimental results show that the input voltage THD of the Class E full-wave rectifier is reduced to one-fourth of the THD of the full-bridge rectifier. In the optimally designed MHz WPT system, efficiencies of both the rectification (over 91%) and the overall system (around 80%) are obviously improved compared to the system using the conventional full-bridge rectifier. [ABSTRACT FROM PUBLISHER]

Prognostics and health management (PHM) will ensure the safe and reliable operation of the battery systems. The remaining useful life (RUL) prediction as one of the major PHM strategies gives early warning of faults, which can be applied to recognize the necessary battery maintenance and replacement in advance. This study investigates a novel deep learning method for predicting lithium-ion battery RUL, which can learn the long-term dependency of degradation trend of batteries. This is the first time which a stacked bidirectional long short-term memory (SBLSTM) based on extreme gradient boosting (XGBoost) is applied to predict the battery capacity degradation trajectories. Using the XGBoost technique, important time-domain features are selected as multivariate inputs to feed the deep learning model for predicting. To improve the trained model, Bayesian optimization (BO) is also performed to tune the hyper-parameters. The findings show that the SBLSTM model achieves a low root mean square percentage error of 1.94%, which is lower than the state-of-the-art methods due to two-way learning. The suggested model will provide excellent support for the maintenance strategy development and health management of the battery systems. • Remaining useful life prediction using feature engineering through XGBoost. • SBLSTM performs well with multivariate time series input data. • Bayesian optimization performs to tune the hyper-parameters. • Precise and robust lifetime prediction for battery degradation with error low to 1.94%. [ABSTRACT FROM AUTHOR]

This article develops explicit design of an impedance matching network (IMN) to enhance the robustness of megahertz (MHz) wireless power transfer (WPT) systems against variations in their final load and coil coupling. Unlike the existing trial-and-error-based solutions, analytical derivations are conducted to calculate the parameters of a two-port T- or $\bf \Pi$ -IMN. The load-pull technique is first applied to determine a target impedance ray that represents a desired loading condition of the power amplifier. Based on the analytical derivations, the three degrees of the design freedom of the IMN are then fully utilized to accurately match the starting point and direction of the target impedance ray. Different features of a final MHz WPT system, such as load-independent output voltage and high tolerance to coil misalignment, are further achieved by having different target impedance rays. Performance enhancement of an experimental 6.78-MHz WPT system is investigated under largely varied final load (10–50 $\mathbf{\Omega }$) and coil coupling (0–53%). With an explicitly designed IMN, the maximum efficiency drops are reduced from 18% to 6% under the changing final load and 21% to 3.9% under the changing coil coupling (0–40%), respectively. An actual application of wireless drone charging is also included to demonstrate the practicability of the proposed IMN design [ABSTRACT FROM AUTHOR]

This letter develops a systematic approach to quantitatively evaluate and compare LiFePO $_4$ battery cycle life improvement using ultracapacitors (UCs). The impact of UC sizing on temperature rise, capacity loss, and power fade under a real dynamic load profile is included for a comprehensive discussion and evaluation. It is found that the cycle-related battery capacity losses are reduced by 28.6% (C/3) and 29.0% (1C) using the optimized number of UCs, while the reductions are 36.3% (C/3) and 39.3% (1C) assuming an infinite number of UCs. The reductions on the power fade are 23.6% and 57.3% for the cases with optimized and infinite numbers of UCs, respectively. The reductions on temperature rise, 1.38 $^\circ$C and 1.93  $^\circ$C, in the two cases are also observed when discharging from 80% to 30% state of charge in one test cycle. The developed approach in the letter could serve as a general procedure to evaluate the cycle life improvement for other types of batteries when combined with UCs. [ABSTRACT FROM AUTHOR]

Magnetic resonance coupling working at megahertz (MHz) is widely considered as a promising technology for the mid-range transfer of a medium amount of power. It is known that the soft-switching-based Class E rectifiers are suitable for high-frequency rectification, and thus potentially improve the overall efficiency of MHz wireless power transfer (WPT) systems. This paper reports new results on optimized parameter design of a MHz WPT system based on the analytical derivation of a Class E current-driven rectifier. The input impedance of the Class E rectifier is accurately derived, for the first time, considering the on-resistance of the diode and the equivalent series resistance of the filter inductor. This derived input impedance is then used to develop and guide design procedures that determine the optimal parameters of the rectifier, coupling coils, and a Class E PA in an example 6.78-MHz WPT system. Furthermore, the efficiencies of these three components and the overall WPT system are also analytically derived for design and evaluation purposes. In the final experiments, the analytical results are found to well match the experimental results. With loosely coupled coils (mutual inductance coefficient $k$ =0.1327), the experimental 6.78-MHz WPT system can achieve 84% efficiency at a power level of 20 Watts. [ABSTRACT FROM AUTHOR]

Contemporary industrial parks are challenged by the growing concerns about high cost and low efficiency of energy supply. Moreover, in the case of uncertain supply/demand, how to mobilize delay-tolerant elastic loads and compensate real-time inelastic loads to match multi-energy generation/storage and minimize energy cost is a key issue. Since energy management is hardly to be implemented offline without knowing statistical information of random variables, this paper presents a systematic online energy cost minimization framework to fulfill the complementary utilization of multi-energy with time-varying generation, demand and price. Specifically to achieve charging/discharging constraints due to storage and short-term energy balancing, a fast distributed algorithm based on stochastic gradient with two-timescale implementation is proposed to ensure online implementation. To reduce the peak loads, an incentive mechanism is implemented by estimating users' willingness to shift. Analytical results on parameter setting are also given to guarantee feasibility and optimality of the proposed design. Numerical results show that when the bid–ask spread of electricity is small enough, the proposed algorithm can achieve the close-to-optimal cost asymptotically. • A systematic online optimization framework ensuring provable performance for multi-energy system management is presented. • A method is proposed for estimating users' willingness to shift inelastic loads via public data. • The energy storage balance and real-time supply–demand balance can be achieved by two-timescale optimization. • Fast distributed method is proposed to deal with temporally-coupled constraints. [ABSTRACT FROM AUTHOR]

Emerging evidence suggests that physiological distress is highly correlated with cancer incidence and mortality. However, the mechanisms underlying psychological challenges‐mediated tumor immune evasion are not systematically explored. Here, it is demonstrated that acute restraint (AR) increases the level of the plasma neuropeptide hormones, kisspeptin, and the expression levels of its receptor, Gpr54, in the hypothalamus, splenic and tumor‐infiltrating T cells, suggesting a correlation between the neuroendocrine system and tumor microenvironment. Accordingly, administration of kisspeptin‐10 significantly impairs T cell function, whereas knockout of Gpr54 in T cells inhibits lung tumor progression by suppressing T cell dysfunction and exhaustion with or without AR. In addition, Gpr54 defective OT‐1 T cells show superior antitumor activity against OVA peptide‐positive tumors. Mechanistically, ERK5‐mediated NR4A1 activation is found to be essential for kisspeptin/GPR54‐facilitated T cell dysfunction. Meanwhile, pharmacological inhibition of ERK5 signaling by XMD8‐92 significantly reduces the tumor growth by enhancing CD8+ T cell antitumor function. Furthermore, depletion of GPR54 or ERK5 by CRISPR/Cas9 in CAR T cells intensifies the antitumor responses to both PSMA+ and CD19+ tumor cells, while eliminating T cell exhaustion. Taken together, these results indicate that kisspeptin/GPR54 signaling plays a nonredundant role in the stress‐induced tumor immune evasion. [ABSTRACT FROM AUTHOR]

Wireless power transfer has shown revolutionary potential in challenging the conventional charging method for consumer electronic devices. Through magnetic resonance coupling, it is possible to supply power from one transmitter to multiple receivers simultaneously. In a multiple-receiver system, the overall system efficiency highly depends on the loads’ and receivers' positions. This paper extends the conventional circuit-model-based analysis for the one-receiver system to investigate a general one-transmitter multiple-receiver system. It discusses the influence of the loads and mutual inductance on the system efficiency. The optimal loads, the input impedance, and power distribution are analyzed and used to discuss the proper system design and control methods. Finally, systems with a different number of receivers are designed, fabricated, and measured to validate the proposed method. Under the optimal loading conditions, an efficiency above 80% can be achieved for a system with three different receivers working at 13.56 MHz. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Multiple miRNAs are dysregulated in Endometrial Carcinoma. [•] Let-7 MicroRNAs are downregulated in Endometrial Carcinoma. [•] Aurora-B is a target for miR-let-7a. [•] Let-7a suppresses the growth of HeLa cells by targeting Aurora-B. [ABSTRACT FROM AUTHOR]

Long non-coding RNA HOTAIR has been revealed to participate in the tumorigenesis of various cancers. However, the mechanism of HOTAIR involvement in cervical cancer has not been identified. Hence, this study aimed to explore the oncogenic and chemoresistant roles of HOTAIR in cervical cancer, and its underlying mechanism. RT-PCR, Western blot, and Luciferase assay were employed to determine the relationship of HOTAIR with miR-29b and PTEN and to study the role of HOTAIR in cervical cancer. CCK8 assay, cell migration, and invasion assay were used to reveal the role of HOTAIR in cervical cancer cell proliferation and metastasis. The inhibitory dose of chemotherapeutics was determined by CCK8 assay using probit analysis. HOTAIR was found to bind with miR-29b, and a negative correlation existed between HOTAIR and miR-29b expression in cervical cancer cells. In addition, HOTAIR promoted the migration and proliferation of cervical cancer cell lines HeLa and Siha, showing effects opposite to miR-29b. Further, HOTAIR facilitated the resistance of both HeLa and Siha cells against cisplatin, paclitaxel and docetaxel, whereas miR-29 suppressed the resistance of both cervical cancer cells against the 3chemotherapeutics. In addition, HOTAIR enhanced epithelial-to-mesenchymal transition (EMT), while miR-29b exerted an inhibitory effect on EMT. In cervical cancer cells, miR-29b did not affect promoter methylation of PTEN but regulated PTEN expression by targeting SP1. Transfection of miR-29b mimics led to a significant downregulation of PI3K. HOTAIR promotes chemoresistance by facilitating EMT through the miR-29b/PTEN/PI3K axis in cervical cancer. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) systems operating at several MHz are known to be advantageous for realizing high spatial freedom of power transfer and compact and lightweight designs. The combined use of multiple transmitting (Tx) coils for magnetic field shaping is expected to further increase the spatial freedom. This article studies an extendable planar Tx-coil array architecture. This architecture provides new conveniences for the MHz WPT systems to efficiently charge devices in 3D space. Time-domain and phasor-domain modelings are carried out in turn to analyze the magnetic field shaping effect under the current phase shift modulation of the Tx coils. An overlap design of the Tx-coil layout is also developed to minimize the cross coupling between the coils, which reduces the interference between Tx coils. Finally, the above concepts are experimentally implemented. The results clearly demonstrate the new advantages of the planar Tx-coil array-based magnetic field shaping, in terms of spatial freedom of the power transfer, efficiency, and output power capability, when charging receivers with six-degrees-of-freedom positions and orientations in 3D space. For instance, a perpendicular receiver in the center of the Tx-coil array can be charged with 82% dc–dc efficiency and 45 W, which is difficult for a conventional single Tx-coil solution. [ABSTRACT FROM AUTHOR]

Previous studies of microarrays have produced mass data that are far from fully applied. To make full use of the available mass data and to avoid redundancy and unnecessary waste, we employed bioinformatics tools GeneSifter and Ingenuity Pathway Analysis (IPA) to mine and annotate 45 microarrays related to endometrium receptivity from GEO (Gene Expression Omnibus) database. In total, 1543 gene sets were found to express differentially, of which 148 highly regulated genes were listed as potential biomarkers of the receptive endometrium. The function and pathway analysis identified the differentially expressed genes primarily involved in immune response and cell cycle. Two networks related to the cardiovascular system and cancers were generated within the genes which changed more than 10-fold. Nine genes were validated by real-time polymerase chain reaction. It was a meaningful exploration of the existing data to acquire useful and reliable information, and our results undoubtedly provided valuable clues for further studies. [ABSTRACT FROM AUTHOR]

In megahertz (MHz) wireless power transfer (WPT) systems, a varying reflected reactance due to a changing final load deteriorates the overall system performance, such as efficiency and output voltage stability. This article aims to achieve a compact and robust MHz WPT system working over a wide range of load. A novel concept of reactance compression design is proposed to compress the variation of the reflected reactance through positioning of a “reactance window.” Efficient receiving-side parameter design procedures are then developed to best compress the reactance variation and satisfy maximum output power requirement in a wide load range but without adding any other hardware. This makes it possible to directly apply the existing voltage-source design using a modified Class E power amplifier (PA) and current-source design using an LCC transformation network. An edge inductor also becomes worthy to replace the bulky air-core infinite inductor required by the modified Class E PA, thereby further improving circuit compactness. Finally, the receiving-side design concept and the edge inductor are experimentally implemented to verify their performance over a 5–50- $\Omega$ load and with the maximum final output power of 20 W. The results well validate the improved reactance compression, output voltage stability, efficiency, and harmonic distortions over the wide load range. [ABSTRACT FROM AUTHOR]

Cervical cancer stem cells contribute respond to considerable recurrence and metastasis of patients with cervical cancer. The stemness properties were partly regulated by the interaction of lncRNAs and miRNAs. HOTAIR functions as an oncogenic lncRNA. Previous research studies revealed its role in regulating stemness properties in various cancers. However, the role of HOTAIR in cervical cancer stem cells is still unknown. Here, cisplatin-resistant and serum-free cultured cells exhibited stem cells properties. Cervical cancer stem cells exhibited greater invasion and migration compared with their parental cells, which was similar to cells overexpressing HOTAIR. HOTAIR was significantly overexpressed in cervical cancer stem cells, and knockdown of HOTAIR generated statistical downregulation of stemness markers. Additionally, HOTAIR expression was negatively correlated with the level of miR-203, which was found to be an inhibitory miRNA in regulating the expressions of stemness markers. Also, miR-203 expression was negatively correlated with ZEB1. These findings suggested that HOTAIR should be a positive contributor in stemness acquisition of cervical cancer cells, and this effect should correlate with the interaction with miR-203, which can be suppressed by ZEB1. [ABSTRACT FROM AUTHOR]

For wireless power transfer (WPT) in mobile applications, the receiving side is usually embedded inside the devices, which makes the heating issue quite challenging, especially at high operating frequency (such as 6.78 MHz) and high power levels. High-frequency synchronous resonant rectification is expected to significantly reduce the power loss on the receiving side and thus improve the rectifier power density. This article proposes a universal optimal drain–source voltage (ODSV) tracking scheme for synchronous resonant rectifier in megahertz (MHz) WPT applications. The ODSV tracking enables the switches in the synchronous rectifiers work at the same switching operation with that of the diodes in the passive rectifiers. Thus, the soft-switching operation can be maintained with minimized body-diode conduction. A tracking algorithm is then developed to adaptively achieve the optimal operation of the synchronous rectifier under varying loading conditions. Finally, the proposed ODSV tracking scheme is implemented in a GaN-based Class E full-wave synchronous rectifier and tested in an experimental 6.78-MHz WPT system. A dc–dc efficiency of 91.6% is achieved under the output power of 120 W. The efficiency of the synchronous rectifier is 97.0% and the rectifier power density can be as high as 1212 W/in $^{3}$. [ABSTRACT FROM AUTHOR]

Purpose: Cervical squamous cell carcinoma (CSCC) seriously affects women's health worldwide, and it is of great significance to illuminate the specific role of circRNAs in CSCC. Materials and Methods: Three mRNA datasets, two miRNA datasets and one circRNA dataset of CSCC, downloaded from GEO, were utilized in this study. Differentially expressed mRNAs (DEmRNAs), miRNAs (DEmiRNAs) and circRNAs (DEcircRNAs) were identified, and a ceRNA (DEcircRNA-DEmiRNA-DEmRNA) regulatory network was constructed. GO and pathway analyses of DEcircRNAs and DEmRNAs in the ceRNA regulatory network were performed. Quantitative real-time polymerase chain reaction (qRT-PCR) validation of the expression of the selected DEmRNAs, DEmiRNAs and DEcircRNAs was performed. Results: A total of 1356 DEmRNAs, 13 DEmiRNAs and 77 DEcircRNAs were obtained. The ceRNA network contained 3 circRNA-miRNA pairs and 158 miRNA-mRNA pairs, including 3 circRNAs, 3 miRNAs, and 138 mRNAs. Functional annotation of DEmRNAs in the ceRNA regulatory network revealed that these DEmRNAs were significantly enriched in cell cycle, p53 signalling pathway and DNA replication. The qRT-PCR results were generally consistent with those of our integrated analysis. Conclusion: In conclusion, we speculate that the regulation of the hsa_circ_0000069/hsa-miR-125b-5p/CDKN2A and hsa_circ_0020594/hsa-let-7c-5p/CCNB2 axes may be involved in CSCC. [ABSTRACT FROM AUTHOR]

Background: Cancer stem cell (CSC) is identified in osteosarcoma (OS) and considered resistant to chemotherapeutic agents. However, the mechanism of osteosarcoma stem cell (OSC) resistant to chemotherapy remains debatable and vague, and the metabolomics feature of OSC is not clarified. Materials and methods: OSC was isolated by using sphere forming assay and identified. Untargeted LC–MS/MS analysis was performed to reveal the metabolomics feature of OSC and underlying mechanisms of OSC resistant to methotrexate (MTX). Results: OSC was efficiently isolated and identified from human OS 143B and MG63 cell lines with enhanced chemo-resistance to MTX. The untargeted LC–MS analysis revealed that OSC showed differential metabolites and perturbed signaling pathways, mainly involved in metabolisms of fatty acid, amino acid, carbohydrate metabolism and nucleic acid. After treated with MTX, metabolomics feature of OSC was mainly involved metabolisms of amino acid, fatty acid, energy and nucleic acid. Moreover, compared with their parental OS cells response to MTX, the differential metabolites and perturbed signaling pathways were mainly involved in metabolism of amino acid, fatty acid and nucleic acid. What's more, Rap1 signaling pathway and Ras signaling pathway were involved in OS cells and their SCs response to MTX. Conclusion: Sphere-forming assay was able to efficiently isolate OSC from human OS cell lines and the untargeted LC–MS/MS analysis was suggested a sufficient methodology to investigate metabolomics features of OS cells and OSCs. Moreover, the metabolomics features of OSCs response to MTX might reveal a further understanding of chemotherapeutic resistance in OS. [ABSTRACT FROM AUTHOR]

Polo-like kinase 1 (PLK1) is a ubiquitous serine/threonine protein kinase. It is reported to be involved in the occurrence and progression of various human cancers. In the present study, we explored the role and molecular mechanism of PLK1 in the proliferation of osteosarcoma (OS) cells. We found that PLK1 expression was higher in MG63/Dox cells than in MG63 cells, while inhibiting or interfering with the level of PLK1 suppressed cell proliferation of MG63/Dox cells. TargetScan analysis predicted that miR-4779 would interact with the 3′-UTR of PLK1 mRNAs and also inhibit cell autophagy of MG63/Dox cells. The data demonstrated that miR-4779 negatively regulates the expression of PLK1, and both miR-4779 and PLK1 regulate cell proliferation and cell apoptosis of MG63/Dox cells, processes that are involved in the drug resistance of OS cells. [ABSTRACT FROM AUTHOR]

Purpose/aim of the study: To investigate high-risk human papillomavirus (HPV) infection clearance following thin loop electrosurgical excision procedure (t-LEEP) among patients with cervical benign lesion. Materials and Methods: This retrospective study analyzed clinical data from patients with cervical benign lesion and HPV infection, who had undergone t-LEEP (T-Group), compared with patients with HPV infection undergone no treatment (NT-Group). Both groups attended regular follow-up between January 2008 and January 2012. Kaplan–Meier analysis was used to compare the HPV clearance time. Results: The average clearance time was 7.7 months (M) (95% confidence interval [CI]: 6.5–8.9 M) in T-Group, and 10.4 M (95%CI: 9.4–11.3 M) in NT-Group, with significant difference between groups (p = 0.003). Among patients with low viral load, the HPV clearance times were 7.6 M (95%CI: 6.3–9.0 M) in T-Group and 9.7 M (95%CI: 8.6–10.8 M) in NT-Group (p = 0.042). Among patients with high viral load, the HPV clearance times were 8.0 M (95%CI: 5.3–10.6 M) in T-Group and 11.4 M (95%CI: 9.7–13.1 M) in NT-Group (p = 0.041). The average time of HPV clearance in T-Group was shorter than NT-Group in all age groups, with significant differences in ≤29Y-group (p = 0.008) and 30–39Y-group (p = 0.005). The accumulated clearance rate of HPV infection at sixth month and 12th month were 24.5% and 67.9% in T-Group, 7.8% and 43.1% in NT-Group, with significant differences (p = 0.001 at 6th month, p = 0.032 at 12th month). Conclusions: T-LEEP accelerates the clearance of high-risk HPV infection and make the HPV infection rates dropped rapidly in the first year. [ABSTRACT FROM AUTHOR]

This paper proposes and implements autonomous control of a multiple-receiver wireless charging system. The charging control problem is challenging due to the decentralized nature of the system, possible changing numbers and types of energy storage devices as loads of the receivers, and complexity in wireless power distribution mechanism. The game-theory-based control is developed that fully respects the unique characteristics of the transmitter (i.e., charger) and receivers. The preferences of the individual devices are first quantified using utility functions. Then, the charging control problem is formulated as a generalized Stackelberg game considering the leader–follower relationship between the transmitter and receivers, and the limited total charging power. At each control instant, the generalized Nash equilibrium among the receivers, i.e., charging power distribution here, is reached by searching the Lagrange multiplier while the total charging power from the transmitter is updated in a step-by-step manner. Both simulation and experimental results show that the proposed charging control autonomously manages and updates the power distribution in the cases where the receivers with different energy storage devices quit or join the wireless charging. [ABSTRACT FROM PUBLISHER]

Class $E^2$ DC–DC converter composed of Class $E$ power amplifier (PA) and rectifier is a promising candidate for MHz wireless power transfer. It is soft-switching based and able to achieve high efficiency at MHz frequency. However, the converter implemented through traditional static design is sensitive to the variations of operation condition. Its performance gets deteriorated when DC load and coil coupling deviate from their respective optimum values. This paper demonstrates that the degradation of system efficiency is mostly due to the mismatch of PA load, and the efficiency drop can be efficiently improved by adding an L-type impedance matching network (IMN) after PA. A fixed IMN is sufficient to maintain a high efficiency, while a tunable IMN is required to ensure stable output power when operation condition dramatically changes. Key techniques, particularly system-level optimization, are discussed in this paper that ensure high efficiency over a wide range of variation in operation condition and also with reduced capacitor/inductor tuning ranges in the IMN. The 6.78-MHz Class $E^2$ DC–DC converters with and without the fixed/tunable IMN are fabricated and measured for validation purposes. The experimental results show that both high efficiency ( $>$66%) and stable output power (around 9 W) are maintained for the tunable converter when there are variations in the DC load and coil coupling. [ABSTRACT FROM AUTHOR]

This paper develops a novel voltage equalizer by combining wireless power transfer (WPT) and a voltage multiplier (VM) for series-connected energy storage cells. The physical isolation achieved by WPT can offer several unique benefits that traditional equalizers can hardly provide. In this paper, the characteristics of a multiple-output VM are analytically discussed and used to develop an equivalent one-output VM model. Based on this model, parameters of the WPT system are properly designed. The proposed design methodology can achieve a single-switch voltage equalizer without feedback control, which dramatically decreases the circuit complexity and cost. Moreover, this methodology can naturally ensure a robust system under small coil misalignment. In the experiment, the proposed system is built to balance four series-connected ultracapacitor modules. The system efficiency is 72.8% at a load power level of 10 W. [ABSTRACT FROM PUBLISHER]

This paper develops a 6.78 MHz multiple-receiver wireless power transfer system driven by a Class E power amplifier. Constant output voltage is achieved for each receiver with optimized overall efficiency. A novel one-receiver model is built to analyze the overall power-efficiency characteristics. The loads and input voltage are then designed as two control variables. Through tuning the loads, constant output voltage is achieved by independent controllers at the receiver side. Then, the efficiency is optimized by tuning the input voltage at the transmitter side. Finally, the theoretical analysis and control scheme are validated using a three-receiver system. It shows that different constant output voltages, 5, 9, and 12 V can be achieved independently for different receivers. When the load resistance, real coupling, and number of receivers change, the voltage can be quickly regulated, and the overall optimum system efficiency is 66.6%. [ABSTRACT FROM AUTHOR]

This paper proposes a new battery cell voltage equalization approach using multiple-receiver wireless power transfer (WPT) working at megahertz (MHz). Compared with existing multiwinding transformer, the MHz multiple-receiver WPT system is advantageous in terms of saved weight and space, ease of implementation, and improved safety. In this paper, the unique operating principle of the WPT-based equalization is first explained, through which equalization currents are naturally determined by the battery cell voltage distribution. The currents are also analytically derived. This facilitates the discussion on power amplifier (PA) design. Performance analysis is then provided to investigate the influences of system parameters on the efficiency and equalization ability of the proposed WPT-based equalization system, and thus guide following design and implementation. Considering the uncertainty in PA load due to the random cell voltage distribution, a current-model Class $E$ PA is designed that enables approximately constant PA output current. Experimental results show that the proposed multiple-receiver WPT-based battery cell equalization system can achieve high overall system efficiency (above 71%) when equalizing six lithium-ion battery cells under loosely coupling ( $k$ = 0.065). A good match between the experimental and calculation results also validates the correctness of the theoretical discussion. [ABSTRACT FROM PUBLISHER]

Wireless power transfer (WPT) working at several megahertz (MHz), 6.78 or 13.56 MHz, is widely considered to be a promising candidate for charging electronic devices. The so-called Class $E^2$ converters combining the soft-switching-based Class $E$ power amplifier (PA) and Class $E$ rectifier are known to be suitable for high-frequency applications with improved efficiency. However, the charging of batteries usually need to follow a specific profile, in which battery voltage and charging current vary over time. The input reactance of the Class $E$ rectifier also becomes obvious at megahertz. This nonneglectable and varying reactance significantly lowers system efficiency and complicates parameter design. In this paper, a systematic design approach is developed that minimizes the energy loss of a 6.78-MHz Class $E^2$ wireless charging system during the entire battery charging cycle. A $LC$ matching network is added to improve the loading conditions of the Class $E$ PA and coupling coils, and provides new degrees of freedom in the parameter design. Average power loss is defined based on analytically derived system efficiency and a discretized battery charging profile. It serves as an objective function that is minimized through the proposed battery charging profile-based parameter design. In final experiments, the proposed design achieves a 24.5% reduction of the average power loss when comparing with that through the conventional design. [ABSTRACT FROM PUBLISHER]

The high-efficiency current-mode (CM) and voltage-mode (VM) Class-E power amplifiers (PAs) for MHz wireless power transfer (WPT) systems are first proposed in this paper and the design methodology for them is presented. The CM/VM Class-E PA is able to deliver the increasing/decreasing power with the increasing load and the efficiency maintains high even when the load varies in a wide range. The high efficiency and certain operation mode are realized by introducing an impedance transformation network with fixed components. The efficiency, output power, circuit tolerance, and robustness are all taken into consideration in the design procedure, which makes the CM and the VM Class-E PAs especially practical and efficient to real WPT systems. 6.78-MHz WPT systems with the CM and the VM Class-E PAs are fabricated and compared to that with the classical Class-E PA. The measurement results show that the output power is proportional to the load for the CM Class-E PA and is inversely proportional to the load for the VM Class-E PA. The efficiency for them maintains high, over 83%, when the load of PA varies from 10 to 100  $\Omega$, while the efficiency of the classical Class-E is about 60% in the worst case. The experiment results validate the feasibility of the proposed design methodology and show that the CM and the VM Class-E PAs present superior performance in WPT systems compared to the traditional Class-E PA. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) working at megahertz (MHz) is widely considered a promising technology for midrange and low-power applications. A Class $ E^2$ dc–dc converter is composed of a Class E power amplifier (PA) and a Class E rectifier. It is attractive for applications in MHz WPT due to the soft-switching properties of both the PA and the rectifier. Using the existing design, the Class $E^2$ dc–dc converter can only achieve optimal performance such as a high efficiency under a fixed operating condition. Meanwhile, in real applications variations in the coil relative position and the final load are common. The purpose of this paper is to analyze and develop a general design methodology for a robust Class $E^2$ dc–dc converter in MHz WPT applications. Component and system efficiencies are analytically derived, which serve as the basis for the determination of the design parameters. The classical matching network of the Class E PA is also improved that provides the required impedance compression capability. Then, a robust parameter design procedure is developed. Both the experimental and calculated results show that proposed design approach can significantly improve the robustness of the efficiency of the Class $E^2$ dc–dc converter against variations in coil relative position and final load. Finally, the experiments show that the range of variation of the system efficiency is narrowed from 47.5%–85.0% to 73.3%–83.7% using the proposed robust design. [ABSTRACT FROM AUTHOR]

In this paper, the loading effect of a Class E power amplifier (PA) driven 6.78 megahertz (MHz) wireless power transfer (WPT) system is analyzed at both circuit and system levels. A buck converter is introduced and controlled to track an optimal equivalent load that maximizes the system efficiency under uncertainties in the relative position of coils and the final load. For power control, an additional degree of freedom is provided by adding an ultracapacitor bank. A control strategy is proposed to track the maximum efficiency and charge/discharge the ultracapacitor bank through the on/off control of the Class E PA. Thus, high system efficiency can be maintained under various uncertainties and load power demands. Finally, the theoretical analysis and the control scheme are validated in experiments. The results show that the proposed Class E PA-driven MHz WPT system can stably achieve a high efficiency under different coil distances and various constant/pulsed power profiles. The measured highest system efficiency can reach 72.1% at a load power level of 10 W. [ABSTRACT FROM AUTHOR]