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The dual active bridge (DAB) converter is a power electronic device commonly used for DC voltage regulation and stabilization. However, during its control process, external disturbances, load variations, input voltage variations, switching tube voltage drops, dead time, etc. lead to errors in the control output, thus reducing the control accuracy of the system. Therefore, this article propose a robust control scheme for the output voltage based on uncertainty and disturbance estimator. In this article, an average small-signal model of the dual active bridge converter was established in terms of the basic principles and operation mechanisms, simplifying the controller's design. Then, the basic principles of the uncertainty and disturbance estimator (UDE) are introduced. The small-signal model of the dual active bridge (DAB) converter is applied to the UDE to minimize output voltage error by enabling the controller to directly regulate the shift ratio. Finally, this article discusses the application and effectiveness of the uncertainty and disturbance estimator (UDE) in the simulation and control of dual active bridge (DAB) converters. A series of experimental comparative studies are conducted, demonstrating that this scheme offers significant advantages in suppressing system uncertainties and disturbances.

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Direct AC-AC converters are strong candidates in the power converting system to regulate grid voltage against the perturbation in the line voltage and to acquire frequency regulation at discrete step levels in variable speed drivers for industrial systems. All such applications require the inverted and non-inverted form of the input voltage across the output with voltage-regulating capabilities. The required value of the output frequency is gained with the proper arrangement of the number of positive and negative pulses of the input voltage across the output terminals. The period of each such pulse for low-frequency operation is almost the same as the half period of the input grid or utility voltage. These output pulses are generated by converting the positive and negative input half cycles in noninverting and inverting forms as per requirement. There is no control complication to generate control signals used to adjust the load frequency as the operating period of the switching devices is normally greater than the period of the source voltage. However, high-frequency pulse width modulated (PWM) control signals are used to regulate the output voltage. The size of the inductor and capacitor is inversely related to the value of the switching frequency. Similarly, the ripple contents of voltage and currents in these filtering components are also inversely linked with PWM frequency. These constraints motivate the circuit designer to select high PWM frequency. However, the alignment of the high-frequency control input with the variation in the input source voltage is a big challenge for a design engineer as the switching period of a high-frequency signal normally lies in the microsecond. It is also required to operate some high-frequency devices for various half cycles of the source voltage, creating control complications as the polarities of the half cycles are continuously changing. This requires at least the generation of two high-frequency signals for different intervals. The interruption of the filtering inductor current is a big source of high voltage surges in circuits where the high-frequency transistors operate in a complementary way. This may be due to internal defects in the switching transistors or some unnecessary inherent delay in their control signals. In this research work, a simplified AC-AC converter is developed that does not need alignment of high-frequency control with the polarity of the source voltage. With this approach, high-frequency signals can be generated with the help of any analog or digital control system. By applying this technique, only one high-frequency control signal is generated and applied in AC circuits, as in a DC converter, without applying a highly sensitive polarity sensing circuit. So, controlling complications is drastically simplified. The circuit and configuration always avoid the current interruption problem of filtering the inductor. The proposed control and circuit topology are tested both in computer-based simulation and practically developed circuits. The results obtained from these platforms endorse the effectiveness and validation of the proposed work.

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H+ co-intercalation chemistry of the cathode is perceived to have damaging consequences on the low-rate and long-term cycling of aqueous zinc batteries, which is a critical hindrance to their promise for stationary storage applications. Herein, the thermodynamically competitive H+ storage chemistry of an attractive high-voltage cathode LiMn2O4 is revealed by employing operando and ex-situ analytical techniques together with density functional theory-based calculations. The H+ electrochemistry leads to the previously unforeseen voltage decay with cycling, impacting the available energy density, particularly at lower currents. Based on an in-depth investigation of the effect of the Li+ to Zn2+ ratio in the electrolyte on the charge storage mechanism, a purely aqueous and low-salt concentration electrolyte with a tuned Li+/Zn2+ ratio is introduced to subdue the H+-mediated charge storage kinetically, resulting in a stable voltage output and improved cycling stability at both low and high cathode loadings. Synchrotron X-ray diffraction analysis reveals that repeated H+ intercalation triggers an irreversible phase transformation leading to voltage decay, which is averted by shutting down H+ storage. These findings unveiling the origin and impact of the deleterious H+-storage, coupled with the practical strategy for its inhibition, will inspire further work toward this under-explored realm of aqueous battery chemistry.

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Proton Exchange Membrane Fuel Cells (PEMFCs) are promising sources of clean and renewable energy, but their performance and efficiency depend on an accurate modeling and identification of their system parameters. However, existing methods for PEMFC modeling suffer from drawbacks, such as slow convergence, high computational cost, and low accuracy. To address these challenges, this research work proposes an enhanced approach that combines a modified version of the SqueezeNet model, a deep learning architecture that reduces the number of parameters and computations, and a new optimization algorithm called the Modified Transient Search Optimization (MTSO) Algorithm, which improves the exploration and exploitation abilities of the search process. The proposed approach is applied to model the output voltage of the PEMFC under different operating conditions, and the results are compared with empirical data and two other state-of-the-art methods: Gated Recurrent Unit and Improved Manta Ray Foraging Optimization (GRU/IMRFO) and Grey Neural Network Model integrated with Particle Swarm Optimization (GNNM/PSO). The comparison shows that the proposed approach achieves the lowest Sum of Squared Errors (SSE) and the highest accuracy, demonstrating its superiority and effectiveness in PEMFC modeling. The proposed approach can facilitate the optimal design, control, and monitoring of PEMFC systems in various applications.

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Sliding grating-structured triboelectric nanogenerators (SG-TENGs) can multiply transferred charge, reduce open-circuit voltage, and increase short-circuit current, which have wide application prospects in self-powered systems. However, conventional SG-TENGs have an ultrahigh internal equivalent impedance, which reduces the output voltage and energy under low load resistances (<10 MΩ). The Pulsed SG-TENGs can reduce the equivalent impedance to near zero by introducing a synchronously triggered mechanical switch (STMS), but its limited output time causes the incomplete charge transfer under high load resistances (>1 GΩ). In this paper, a conventional and pulsed hybrid SG-TENG (CPH-SG-TENG) is developed through rational designing STMS with tunable width and output time. The matching relationship among grid electrode width, contactor width of STMS, sliding speed, and load resistance has been studied, which provides a feasible solution for simultaneous realization of high output energy under small load resistances and high output voltage under high load resistances. The impedance matching range is extended from zero to at least 10 GΩ. The output performance of CPH-SG-TENG under low and high load resistances are demonstrated by passive power management circuit and arc discharge, respectively. The general strategy using tunable STMS combines the advantages of conventional and pulsed TENGs, which has broad application prospects in the fields of TENGs and self-powered systems.

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Monolithic integrated micro-supercapacitors (MIMSCs) with high systemic performance and cell-number density are important for miniaturized electronics to empower the Internet of Things. However, fabrication of customizable MIMSCs in an extremely small space remains a huge challenge considering key factors such as materials selection, electrolyte confinement, microfabrication and device-performance uniformity. Here, we develop a universal and large-throughput microfabrication strategy to address all these issues by combining multistep lithographic patterning, spray printing of MXene microelectrodes and controllable 3D printing of gel electrolytes. We achieve the monolithic integration of electrochemically isolated micro-supercapacitors in close proximity by leveraging high-resolution micropatterning techniques for microelectrode deposition and 3D printing for precise electrolyte deposition. Notably, the MIMSCs obtained demonstrate a high areal-number density of 28 cells cm-2 (340 cells on 3.5 × 3.5 cm2), a record areal output voltage of 75.6 V cm-2, an acceptable systemic volumetric energy density of 9.8 mWh cm-3 and an unprecedentedly high capacitance retention of 92% after 4000 cycles at an extremely high output voltage of 162 V. This work paves the way for monolithic integrated and microscopic energy-storage assemblies for powering future microelectronics.

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In this study, two constructed wetland-microbial fuel cells (CW-MFC), including a closed-circuit system (CCW-MFC) and an open-circuit system (OCW-MFC) with petroleum coke as electrode and substrate, were constructed to explore the effect of multiple key factors on their operation performances. Compared to a traditional CW, the CCW-MFC system showed better performance, achieving an average removal efficiency of COD, NH4+-N, and TN of 94.49 ± 1.81%, 94.99 ± 4.81%, and 84.67 ± 5.6%, respectively, when the aeration rate, COD concentration, and hydraulic retention time were 0.4 L/min, 300 mg/L, and 3 days. The maximum output voltage (425.2 mV) of the CCW-MFC system was achieved when the aeration rate was 0.2 L/min. In addition, the CCW-MFC system showed a greater denitrification ability due to the higher abundance of Thiothrix that might attract other denitrifying bacteria, such as Methylotenera and Hyphomicrobium, to participate in the denitrifying process, indicating the quorum sensing could be stimulated within the denitrifying microbial community.

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The severe acute respiratory syndrome coronavirus (SARS-CoV-2) has spread rapidly around the world. In order to prevent the spread of infection, city blockades and immigration restrictions have been introduced in each country, but these measures have a severe serious impact on the economy. This paper examines the possibility of both harvesting vibration energy and detecting mass by using a magnetostrictive alloy. Few efforts have been made to develop new magnetostrictive biosensor materials. Therefore, we propose magnetostrictive Fe-Co/Ni clad steel vibration energy harvesters with mass detection, and we numerically and experimentally discuss the effect of the proof mass weight on the frequency shift and output voltage induced by bending vibration. The results reveal that the frequency and output voltage decrease significantly as the mass increases, indicating that the energy harvesting device is capable of mass detection. In the future, device miniaturization and the possibility of virus detection will be considered.

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Facing the increasingly serious problem of environmental pollution and energy waste, the thermoelectric generator has been attracting more and more attention owing to its advantages including low cost, no pollution, and good stability. The family of thermoelectric material is constantly extended with enhanced performance. Note that nanostructuring can enhance thermoelectric performance. However, the most recent excellent material with effective thermoelectric transformation reported from bulk materials has definite benefits to the practical application compared to nanomaterials. In this work, a nanostructure integrated macroscale thermoelectric chip, that is an alloyed band gap gradient macroscale chip (1.0 cm × 2.0 cm) composed of CdSSe nanowires, has been proven as an excellent thermoelectric generator for the first time. A high Seebeck coefficient of -152.4 µV/K and the average output voltage of 10.8 mV are obtained after optimizing the electrode patterns and distance between electrodes. More interestingly, upon illumination by white light from a xenon lamp, a photo-thermoelectric output voltage is greatly elevated to 45 mV due to the high concentration of photogenerated carriers. The CdSSe thermoelectric chip also shows good repeatability and high stability with a relative error of <6%. No study on the thermoelectric performance of such an alloyed band gap gradient macroscale chip is mentioned before. The results illustrate a bright avenue to realize a type of light-modulated macroscale thermoelectric chips by nanostructure, allowing such kinds of CdSSe chips to be used to generate electric energy in the near future.

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Self-powered devices have great potential in daily applications ranging from portable electronics to wearable body sensors, yet their working lifetime and performance are normally limited by the low energy density of the power unit as well as additional resistive losses induced by connections between electronic and power moieties. Herein, we report an effective programmable laser-assisted fabrication of facilely integrated microphotocapacitors (integrated devices of solar cells and microsupercapacitors, mPCs) exhibiting high output voltage and energy density (32.3 µWh cm-2). An mPC pack (8 mPCs in series within a size of 3 × 3 cm2) delivers an excellent Voc of 7.3 V, and an output voltage of 90 V can be obtained with an array of 14 mPC packs when tested outdoors under solar illumination (63 mW cm-2), setting a new benchmark for integrated self-charging power packs. These devices have also shown good stability (stable operation over 2000 cycles, 2.1 × 104 s) and performance under low- or intermittent-intensity light illuminations, highlighting their abilities to work indoors or under cloudy weather.

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In this paper, based on the principles of general operational amplifiers, a high-voltage operational amplifier is developed. Considering the influences of piezoelectric stack actuators on the circuit, a novel structure using the high-voltage operational amplifier as a noninverting amplifier is proposed. Because of the simple circuit principles and the voltage feedback control structure, the proposed power amplifier has the advantages of low noise and small size, and it can be realized by discrete electric elements easily. In the application of precision positioning, a power amplifier using the proposed circuit principles for driving piezoelectric stack actuators is designed, simulated, and tested. The simulated results show that the proposed power amplifier could conform to the theory of the circuit. The experimental results show that the designed power amplifier conforms to the simulation, the bandwidth of the power amplifier is about 57 kHz, and the ripple of the power amplifier is less than 2 mV. Furthermore, the output of the proposed power amplifier maintains the same type of wave within in a large range of frequency, while the input is the sinusoidal or square wave, and the resolution of the mechanism which the power amplifier is applied in is about 4.5 nm. By selecting the critical electronic elements and using feedback control, the proposed circuit structure is able to realize a low-cost and high-performance power amplifier to drive piezoelectric stack actuators flexibly, which is the novel work of the paper.

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Piezoelectric transducers are triggered by the output voltage signal of a transmit voltage amplifier (TVA). In mobile ultrasound instruments, the sensitivity of piezoelectric transducers is a critical parameter under limited power supply from portable batteries. Therefore, the enhancement of the output voltage amplitude of the amplifier under limited power supply could increase the sensitivity of the piezoelectric transducer. Several-stage TVAs are used to increase the voltage amplitude. However, inter-stage design issues between each TVA block may reduce the voltage amplitude and bandwidth because the electronic components of the amplifier are nonlinearly operated at the desired frequency ranges. To compensate for this effect, we propose a novel inter-stage output voltage amplitude improvement (OVAI) circuit integrated with a class-B TVA circuit. We performed fundamental A-mode pulse-echo tests using a 15-MHz immersion-type piezoelectric transducer to verify the design. The echo amplitude and bandwidth when using an inter-stage OVAI circuit integrated with a class-B TVA circuit (696 mVPP and 29.91%, respectively) were higher than those obtained when using only the class-B TVA circuit (576 mVPP and 24.21%, respectively). Therefore, the proposed OVAI circuit could be beneficial for increasing the output amplitude of the class-B TVA circuit for mobile ultrasound machines.

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The storage of solar energy in battery systems is pivotal for a sustainable society, which faces many challenges. Herein, a Zn-air battery is constructed with two cathodes of poly(1,4-di(2-thienyl))benzene (PDTB) and TiO2 grown on carbon papers to sandwich a Zn anode. The PDTB cathode is illuminated in a discharging process, in which photoelectrons are excited into the conduction band of PDTB to promote oxygen reduction reaction (ORR) and raise the output voltage. In a reverse process, holes in the valence band of the illuminated TiO2 cathode are driven for the oxygen evolution reaction (OER) by an applied voltage. A record-high discharge voltage of 1.90 V and an unprecedented low charge voltage of 0.59 V are achieved in the photo-involved Zn-air battery, regardless of the equilibrium voltage. This work offers an innovative pathway for photo-energy utilization in rechargeable batteries.

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A comparative study of the electrical performance of triboelectric nanogenerators (TENGs) with plain- and 2/1 twill-woven cotton textiles was conducted. Furthermore, the microstructures of the cotton fiber surfaces were examined to understand the fundamental mechanical interaction among the cotton fibers in the TENGs. The TENG with 2/1 twill-woven cotton textiles exhibited higher output voltages compared to that with plain-woven cotton textiles. The difference in the output voltage between the two types of TENGs resulted from the difference in triboelectric charge generation between the constituent cotton textiles. The higher output voltage of the TENG with 2/1 twill-woven cotton textiles was attributed to the higher density in triboelectric interactions among the cotton fiber molecules.

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Utilization of solar energy is of great interest for a sustainable society, and its conversion into electricity in a compact battery is challenging. Herein, a zinc-air battery with the polymer semiconductor polytrithiophene (pTTh) as the cathode is reported for direct conversion of photoenergy into electric energy. Upon irradiation, photoelectrons are generated in the conduction band (CB) of pTTh and then injected into the π2p * orbitals of O2 for its reduction to HO2 - , which is disproportionated to OH- and drives the oxidation of Zn to ZnO at the anode. The discharge voltage was significantly increased to 1.78 V without decay during discharge-charge cycles over 64 h, which corresponds to an energy density increase of 29.0 % as compared to 1.38 V for a zinc-air battery with state-of-the-art Pt/C. The zinc-air battery with an intrinsically different reaction scheme for simultaneous conversion of chemical and photoenergy into electric energy opens a new pathway for utilization of solar energy.

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The micro-supercapacitors are of great value for portable, flexible, and integrated electronic equipments. Here, the large-scale and integrated asymmetrical micro-supercapacitor (AMSC) array is fabricated in virtue of the laser direct writing and electrodeposition technology. The AMSC shows the ideal flexibility, high areal specific capacitance (21.8 mF cm-2 ), and good rate capability. Moreover, its energy density reaches 12.16 µW h cm-2 , outperforming most micro-supercapacitors reported previously. Meanwhile, large-scale series-connected AMSCs are integrated on the flexible substrates (e.g., indium tin oxide-polyethylene terephthalate film), which can power a veriety of the commercial electronics. The combination of AMSCs array, solar cell, and electronic device proves the feasibility for practical application in the portable, flexible, and integrated electronic equipments.

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Energy-harvesting utilizing piezoelectric materials has recently attracted extensive attention due to the strong demand of self-powered electronics. Unfortunately, low power density and poor long-term stability seriously hinder the implementation of lead-free piezoelectrics as high-efficiency energy harvesters. For the first time, we demonstrate that tailoring grain orientations of lead-free ceramics via templated grain growth can effectively produce ultrahigh power generation performance and excellent endurance against electrical/mechanical fatigues. Significantly improved fatigue resistance was observed in (Ba0.94Ca0.06)(Ti0.95Zr0.05)O3 grain-oriented piezoceramics (with ∼99% [001]c texture) up to 106 bipolar cycles, attributed to the enhanced domain mobility, less defect accumulation, and thus suppressed crack generation/propagation. Interestingly, the novel energy harvesters, which were developed based on the textured ceramics with high electromechanical properties, possessed ∼9.8 times enhancement in output power density compared to the nontextured counterpart while maintaining stable output features up to 106 vibration cycles. The power densities, which increased from 6.4 to 93.6 µW/mm3 with increasing acceleration excitation from 10 to 50 m/s2, are much higher than those reported previously on lead-free energy harvesters. This work represents a significant advancement in piezoelectric energy-harvesting field and can provide guidelines for future efforts in this direction.

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E-cigarettes are used by millions of people despite the fact that the harmful effect of aerosol emitted from these products to the human organism is still not clear. In this paper, toxicity of vapor generated using different solutions and battery output voltage on A549 cells viability is presented. The obtained EC50 values for commercially available propylene glycol/glycerol solution 1:1 e-liquids based on 3.2 V (0.127%), 4.0 V (0.112%) and 4.8 V (0.038%) were about 1.5-4.5 times higher than in tobacco smoke (0.0086%). Furthermore, it was shown that the increase of battery output voltage decreased A549 cell viability. In addition, commercially available extracts were more cytotoxic than laboratory made extracts. Owing to the expansiveness of e-cigarettes, it is very important to estimate their impact on public health. Our results not only confirm less cytotoxicity of e-liquid aerosol than cigarette smoke, but also demonstrate that solutions used in e-liquids and, for the first time, battery output voltage have a significant impact on cytotoxicity of e-cigarette vapor. Thus, the results of this study are very important for the current and future legal regulations on e-cigarettes.

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