Parameter Deviation Effect Study of the Power Generation Unit on a Doubly-Fed Induction Machine-based Shipboard Propulsion System

To lower the difficulty of fault protection,a doubly-fed induction machine based shipboard propulsion system(DFIM-SPS)that is partially power decoupled is presented.In such an intrinsically safe SPS architecture,a synchronous generator(SG)is employed for power generation,and the accuracy of the parameters of power generation unit(PGU)plays an important role in SPS stable operation.In this paper,the PGU parameter deviations are studied to evaluate the effects on system performance.The models of salient-pole SG,type DC1A excitation system(EXS)and DFIM are illustrated first.Besides,the corresponding control scheme is explained.For the 16 important parameters of PGU,up to 40%of parameter deviations are applied to implement parameter sensitivity analysis.Then,simulation studies are carried out to evaluate the parameter deviation effects on system performance in detail.By defining three parameter deviation effect indicators(PDEIs),the effects on the PGU output variables,which are the terminal voltage and output active power,are studied.Moreover,the increasing rates of PDEIs with different degrees of parameter deviations for the key parameters are analyzed.Furthermore,the overall system performance is investigated for the two most influential PGU parameters.This paper provides some vital clues on SG and EXS parameter identification for DFIM-SPS.

Toward an optimized strategy of using various airway mucus clearance techniques to treat critically ill COVID-19 patients

Coronavirus disease 2019(COVID-19)caused by acute respiratory syndrome coronavirus 2(SARS-Cov-2)is still threatening the human life and society throughout the world.For those critically ill patients,mechanical ventilation(MV)is essential to provide life support during treatment.However,both the virus infection and MV disrupt the balance between secretion and elimination of airway mucus and lead to mucus accumulation in the lung.Postmortem examination verified that the lungs in patients died of COVID-19 are indeed filled with sticky mucus,suggesting a great need to improve airway mucus clearance in critically ill COVID-19 patients.Therefore,it may be helpful to comprehensively review the current understanding regarding the changes of biochemical and rheological features of airway mucus associated with the disease,as well as the physiological principles and algorithm to decide airway clearance techniques suitable for the critically ill COVID-19 patients.Based on these considerations,optimized strategies may be developed to eliminate the airway mucus accumulated in the airways of critically ill COVID-19 patients.

Safety Evaluation of Tongchui Baihua Capsule

[Objectives]The study aimed to evaluate the safety of Tongchui Baihua capsule.[Methods]Long-term toxicology experiment was adopted,the rats were randomly divided into control group and administration group according to the gender of male and female;the drug administration group was given different doses of Tongchui Baihua capsules,and the drug was administered by continuous gavage for 13 weeks;the general conditions,haematological indexes,blood biochemical indexes and visceral coefficients of the rats were detected at the 13th week and 4 weeks after the drug withdrawal respectively,and the toxic symptoms were observed.[Results]The rats were given Tongchui Baihua capsule in different doses by gavage for 13 weeks,and no obvious toxicity was observed in weight,haematological indexes,blood biochemical indexes and histopathology.[Conclusions]Under the condition of long-term toxicity experiment,Tongchui Baihua capsule was safe for rats.

Polarized holographic lithography system for high-uniformity microscale patterning with periodic tunability

Periodic microscale array structures play an important role in diverse applications involving photonic crystals and diffraction gratings.A polarized holographic lithography system is proposed for patterning high-uniformity microscale two-dimensional crossed-grating structures with periodic tunability.Orthogonal two-axis Lloyd’s mirror interference and polarization modulation produce three sub-beams,enabling the formation of two-dimensional crossed-grating patterns with wavelength-comparable periods by a single exposure.The two-dimensional-pattern period can also be flexibly tuned by adjusting the interferometer spatial positioning.Polarization states of three sub-beams,defining the uniformity of the interference fringes,are modulated at their initial-polarization states based on a strict full polarization tracing model in a three-dimensional space.A polarization modulation model is established considering two conditions of eliminating the unexpected interference and providing the desired identical interference intensities.The proposed system is a promising approach for fabricating high-uniformity two-dimensional crossed gratings with a relatively large grating period range of 500–1500 nm.Moreover,our rapid and stable approach for patterning period-tunable two-dimensional-array microstructures with high uniformity could be applicable to other multibeam interference lithography techniques.

Dual-comb spectroscopy resolved three-degreeof-freedom sensing

Precise and fast determination of position and orientation, which is normally achieved by distance and angle measurements, has broad applications in academia and industry. We propose a dynamic three-degree-of-freedom measurement technique based on dual-comb interferometry and a self-designed grating-corner-cube(GCC) combined sensor. Benefiting from its unique combination of diffraction and reflection characteristics, the absolute distance, pitch, and yaw of the GCC sensor can be determined simultaneously by resolving the phase spectra of the corresponding diffracted beams. We experimentally demonstrate that the method exhibits a ranging precision(Allan deviation) of 13.7 nm and an angular precision of 0.088 arcsec, alongside a 1 ms reaction time. The proposed technique is capable of precise and fast measurement of distances and two-dimensional angles over long stand-off distances. A system with such an overall performance may be potentially applied to space missions,including in tight formation-flying satellites, for spacecraft rendezvous and docking, and for antenna measurement as well as the precise manufacture of components including lithography machines and aircraftmanufacturing devices.

Three-Probe Error Separation with Chromatic Confocal Sensors for Roundness Measurement

In this study,three-probe error separation was developed with three chromatic confocal displacement sensors for roundness measurement.Here,the harmonic suppression is discussed first to set suitable orientation angles among three sensors.Monte Carlo simulation is utilized to test the error separation and optimize the orientation angles and off-axial distance.The experimental setup is established using chromatic confocal sensors with a precise rotary platform.The experimental results show that the measured roundness with an orientation-angle combination of(0°,90.1°,and 178.6°)is much better than that of another nonoptimal selection(0°,90.4°,and 177.4°).The roundness error is only 0.7%between the proposed measurement system and an expensive ultraprecision roundness meter.Furthermore,it is proven that the eccentricity distance should be decreased as small as possible to improve the measurement accuracy.In sum,this paper proposes a feasible method for roundness measurement with reliable simulations,easily integrated sensors,and an ordinary precision rotary platform.

Overview on Fault-Tolerant Four-Switch Three-Phase Voltage Source Converters

With the rapid development and widespread applications of power electronic converters,strong fault-tolerant capability of power electronic converters is required since they play important roles in power systems.In this paper,a review of one of the most promising fault-tolerant topologies for semiconductor open-circuit fault,called four-switch three-phase(FSTP)topology,is presented in terms of modeling analysis,modulation techniques,and control strategies.The configuration of FSTP voltage source converter(VSC)is illustrated.To minimize the negative effects caused by the innate drawbacks of this fault-tolerant converter topology,considerable research has been carried out regarding modulation techniques and control strategies.The modulation principle for FSTP topology is explained in detail,since the performance of FSTP VSCs relies on it.This paper aims to illustrate current research progress on this fault-tolerant FSTP VSC topology.