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The deployer uses a voice coil actuator (VCA) to control precisely the separation velocity of CubeSats with different masses. This article proposes a novel VCA with a new structure of double magnetic circuits featuring high thrust density. Unlike the conventional design, the new design achieves high thrust density by using a new structure of double magnetic circuits to concentrate the magnetic flux in the airgap and alleviate the magnetic saturation in the yoke. An improved equivalent magnetic circuit is developed to reveal the performance improvement of the novel VCA. The electromagnetic characteristics of the new VCA are investigated and compared with the conventional counterparts by finite element analysis and experimental tests. One VCA deployer prototype has been fabricated and testedexperimentally to validate the thrust density and separation characteristics. [ABSTRACT FROM AUTHOR]

Due to a short-time gap breakdown in electrical discharge machining (EDM), a high dynamic response and flexible discharge current control ability are required for a pulse power generator. Therefore, a one-cycle control(OCC) of output current for a buck-type EDM pulse power generator is proposed. Considering the inductor current operating state, a full-range OCC current control is presented, and the Taylor expansion method is used for the duty cycle calculation. A duty cycle optimization strategy is proposed for transient states. Based on the small signal modeling, the dynamic response ability of the system is analyzed. The discharge current can switch from many transient states to a steady state in a few switching cycles without a current overshoot, and follow the average current reference well in the steady state. [ABSTRACT FROM AUTHOR]

The vacuum interrupter-based DC circuit breaker is one of the most important equipments in the DC power system. The dielectric recovery (DR) of vacuum interrupter (VI) is essential for breaking reliability, especially on some occasions with ultra-large fault current such as the outlet of generator. To measure the DR of VI under high arcing current, an experiment circuit is designed and the DR under arcing current from 20 kA to 60 kA is presented in this paper. The influence of arcing current, contact separation, di/dt before current zero and arcing time on the DR is investigated. Particularly, it's found that under a specific arcing current, there exists an optimal arcing time for DR, and it shows a negative correlation with the arcing current. [ABSTRACT FROM AUTHOR]

In Industry 4.0, medical data present a trend of multisource development. However, in complex information networks, an information gap often exists in data exchange between doctors and patients. In the case of diseases with complex manifestations, doctors often perform qualitative analysis, which is macroscopic and fuzzy, to present treatment recommendations for patients. Improving the reliability of data acquisition and maximizing the potential of data, require attention. To solve these problems, a multimodal data-driven rehabilitation strategy auxiliary feedback method is proposed. In this study, depth sensor and functional near-infrared spectroscopy (fNIRS) were used to obtain ethology and brain function data, and skeleton tracking analysis and ethology discrete statistics were performed to assist the diagnostic feedback of rehabilitation strategies. This study takes rhythm rehabilitation training of autistic children as a case, and results show that the multimodal data-driven rehabilitation strategy auxiliary feedback method can provide effective feedback for individuals or groups. The proposed auxiliary decision method increases the dimension of data analysis and improves the reliability of analysis. Through discrete statistical results, the potential of data are maximized, thereby assisting the proposed rehabilitation strategy diagnostic feedback. [ABSTRACT FROM AUTHOR]

This article evaluates silicon carbide (SiC) mosfet’s reliability and ruggedness comprehensively between two widely employed device package types: common source and Kelvin source. Multiple accelerated lifetime tests are conducted to comprehensively investigate SiC mosfet’s reliability at both package and die levels. Specifically, a conventional high electric field test is applied to induce gate oxide degradation, whereas package degradation is investigated by the widely adopted power cycling test. To mimic gate oxide degradation patterns closer to realistic cases, an active channel gate bias test is proposed in this study, and a fair comparison is made regarding the device's degradation pattern in the conventional high electric field test. Throughout accelerated lifetime tests, devices’ electrical parameters, consumable lifetime, and end-of-life failure modes are comprehensively evaluated. For ruggedness comparison, a single-shot short-circuit test is conducted on both common-source and Kelvin-source packaged devices with the same die technique and configuration. Other than analytical discussions with experimental waveforms, failure analysis is also conducted to investigate the device's failure mode and root cause. In respect of experimental results in accelerated lifetime tests and short-circuit tests, the existence of the common-source inductance and resistance may mitigate the electrothermal stress applied on the chip with lower gate–source voltage under load current and results in mitigated device instability and longer consumable lifetime. [ABSTRACT FROM AUTHOR]

The hybrid dc circuit breaker (HDCCB) is one of the most promising solutions for the dc interruption. But the power electronics-based load commutation switch (LCS) in the main current path causes the high on-state loss and cost, which inhibits the application of the HDCCB. In this paper, a novel hybrid dc circuit breaker is proposed, in which the vacuum interrupter with the external transverse magnetic field (ETMF) is designed to improve the arc voltage and thus enhance the current commutation to power electronics. The ETMF-based vacuum interrupter achieves the fast current commutation instead of the LCS, which realizes the low on-state loss and cost while preserving the short commutation and interruption time. The arc voltage characteristic with ETMF is analyzed, and the influence of the different factors on the commutation time and di/dt before current zero are investigated in detail. Based on the calculation results, a 10 kV dc breaker prototype based on the proposed topology is developed with the breaking current of 15.5 kA. Finally, the application of the proposed scheme in HVdc grids is discussed. [ABSTRACT FROM AUTHOR]

High-voltage DC (HVDC) circuit breaker is the necessary equipment for multiterminal HVDC grids, which is a prospective power transmission method in the future. Therefore, the research about HVDC interruption ushered in an explosive development in recent years. The mechanical DC circuit breaker based on the precharged capacitor for current commutation and interruption is considered to be one of the most promising HVDC interruption solution. However, the commutation capacitor requires a complicated precharging circuit, especially in high-voltage applications, which brings a great challenge to the promotion of mechanical interruption solution. In this article, a novel self-charging mechanical HVDC circuit breaker is proposed. It utilizes the induced voltage generated by part of current limiting reactor to adaptively charge the commutation capacitor under different fault current conditions without extra auxiliary charging circuit. By investigating the influence of capacitance and inductance on the charging time and current commutation process, the optimized parameters are determined. Then, the breaking performance of proposed HVDC breaker under different rising rates of fault current is evaluated in a two-terminal HVDC system. Finally, a low-power prototype is developed to verify the feasibility of the proposed topology and an improved scheme for rated current breaking is discussed. [ABSTRACT FROM AUTHOR]

This article presents a novel unequal power divider based on an inverted microstrip gap waveguide. This new geometry can achieve a large power ratio of the two output ports and a small phase difference less than 5°. Based on this novel geometry, a few distinctive unequal power dividers with different output power ratios were proposed for designing a low sidelobe array antenna at 39 GHz. To verify the design, a $16\times 16$ antenna array was designed and measured. The measurement results indicate that the entire array antenna achieves a −10 dB impedance bandwidth of 18.5% (in the range of 35.9–43.2 GHz), a gain greater than 29 dBi from 37.5 to 41.8 GHz, and an antenna efficiency greater than 50% over the entire operating frequency band. Based on the application of the newly invented distribution network, the proposed array antenna is below −23 dB on both the E- and H-planes at 37–42 GHz. Furthermore, the radiation pattern of the entire array complies with the European Telecommunications Standards Institute (ETSI)-Class II standard for all azimuth angles. [ABSTRACT FROM AUTHOR]

Objective: Limited by spherical focused ultrasound transducer (SUT) with a high acoustic numerical aperture, photoacoustic microscopy (PAM) suffers a rapidly degrading sensitivity and lateral resolution as increased depth. In this study, an ellipsoidal focused ultrasound transducer (EUT) was developed to address the above restriction via providing high sensitivity and lateral resolution over a large depth of field (DOF). Methods: To fabricate the EUT, the piezoelectric element was laminated onto a curved steel surface for self-focusing (the ellipsoidal continuous-focus geometry was employed instead of the spherical single-focus one). Additionally, phantoms and in vivo animal experiments were performed by an extend-focus PAM equipped with EUT to characterize its performance. Results: The EUT involved over 30 MHz center frequency and -6 dB bandwidth of 124% with a resolution-invariant focal depth of 1.39 mm, more than 3 times the DOF of the SUT. Conclusion: The in vivo imaging results demonstrated that the EUT was capable of extending the focal depth to get rid of the restriction of the visual field, while the DOF of the SUT was limited by the nature of spherical geometry. Significance: The EUT markedly enhances the image quality at different imaging depths, which has great potential for promoting the biomedical development of in vivo rapid-noninvasive PAM. [ABSTRACT FROM AUTHOR]

Medium-voltage dc (MVdc) distribution systems have the advantages of high power density, low line loss and fast system response. However, the high rise rate and large peak value of short circuit current make the fault current interruption a critical problem in MVdc systems. To solve this problem, a novel circuit breaker scheme based on integrated gate-commutated thyristor (IGCTs) current sharing integrated with freewheeling is proposed in this article, which not only can ensure a high breaking capacity and short interruption time in the full current range, but also have superior vacuum interrupter recovery performance and high breaking reliability. The analysis of key factors, including stray parameters, inductance-capacitance (LC) parameters and arcing time, on the current commutation characteristics is presented, and the optimal design principle of the circuit breaker parameters is obtained. Finally, the proposed MVdc circuit breaker is verified with a 64.2 kA/10 kV fault current interruption experiment. [ABSTRACT FROM AUTHOR]

We demonstrate a hybrid solution for simultaneous transfer of ultra-stable optical frequency, RF frequency and time signal on a 100 km fiber spool with the same wavelength based on coherent demodulation and optical phase-lock-loop (OPLL). The one pulse per second (1PPS) is encoded by phase and RF frequency is encoded with an intensity modulator. The noise caused by fiber link is compensated by the round-trip method. And the bad effect on optical frequency caused by optical phase modulation (PM) can be cleaned using OPLL. When the fiber link is stabilized, the transferred time deviation (TDEV) can be 2.4E-11@1s and 1.9E-12@104s, RF frequency stability can achieve 8.0E-14@1s and 2.5E-17@104s, the modified Allan deviation (MDEV) of cleaned optical frequency can be 1.4E-16@1s and 1.6E-19@104s. [ABSTRACT FROM AUTHOR]