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The field modulation effect has been proposed and investigated in various electric machine topologies. Among them, permanent magnet vernier machines (PMVMs) have attained intensive research due to the high torque density and simple structure. However, the performance of PMVMs in terms of fault tolerance is seldom mentioned. This article proposes a novel dual 3-phase fault-tolerant PMVM with segregated concentric windings. Benefiting from the field modulation effect, the PMVM can generate high torque with low PM flux. The low PM flux also implies small fault currents in the short-circuit case. Therefore, the PMVM exhibits inherent good fault-tolerant capability without sacrificing torque performance. Two independent 3-phase modular winding sets are adopted to improve redundancy. To realize the physical and electrical isolation, each winding set is controlled by a standard 3-phase inverter. The healthy performance and fault tolerance of the proposed machine are evaluated by finite element analysis and verified by experimental tests. The results infer its advantages in healthy conditions and various fault scenarios, including open-circuit, short-circuit, and interturn short-circuit conditions.

In this article, five different triple three-phase windings are presented for fault-tolerant permanent magnet (PM) machine drive to achieve advanced turn short circuit fault (TSCF) current reduction effect. First, the five different winding configurations are briefly introduced and the reasons for the TSCF reduction effect are explained. Then, the healthy performance and fault-tolerant capabilities of several fault modes are investigated by detailed finite element prediction and test verification. They exhibit almost the same healthy performance. It is demonstrated that the zero sequence (ZS) flux linkages in Y-connected winding are the fundamental factor of the huge TSCF current since the Y winding does not contain ZS current path. Thus, the Y-Δ winding exhibits the best TSCF current suppression capability which creates the ZS current path to nullify the ZS flux linkages, and the delta winding ranks as the second which contains a larger ZS circuit. The investigation provides effective approaches and solutions to obtain enhanced fault-tolerant capability on the worst TSCF for safety-critical applications.

The clarification of the critical operating conditions and the failure mechanism of superlubricity systems is of great significance for seeking appropriate applications in industry. In this work, the superlubricity region of 1,3-diketone oil EPND (1-(4-ethyl phenyl) nonane-1,3-dione) on steel surfaces was identified by performing a series of ball-on-disk rotation friction tests under various normal loads (3.5–64 N) and sliding velocities (100–600 mm/s). The result shows that beyond certain loads or velocities superlubricity failed to be reached due to the following negative effects: (1) Under low load (≤ 3.5 N), insufficient running-in could not ensure good asperity level conformity between the upper and lower surfaces; (2) the high load (≥ 64 N) produced excessive wear and big debris; (3) at low velocity (≤ 100 mm/s), the weak hydrodynamic effect and the generated debris deteriorated the lubrication performance; (4) at high velocity (≥ 500 mm/s), oil migration occurred and resulted in oil starvation. In order to expand the load and velocity boundaries of the superlubricity region, an optimized running-in method was proposed to avoid the above negative effects. By initially operating a running-in process under a suitable combination of load and velocity (e.g. 16 N and 300 mm/s) and then switching to the target certain higher or lower load/velocity (e.g. 100 N), the superlubricity region could break through its original boundaries. The result of this work suggests that oil-based superlubricity of 1,3-diketone is a promising solution to friction reduction under suitable operating conditions especially using a well-designed running-in strategy.

AbstractTo explore the effect of design parameters on the mechanical performance of the proposed all-steel buckling-restrained brace (BRB), the finite element software ABAQUS is adopted. The brace consists of an inner round steel tube and an outer square steel tube to restrain its inner core, designed with both the cruciform-section core and the H-section steel core. Quasi-static tests are performed on the all-steel BRB to explore its energy dissipation capacity. The cyclic behavior of the specimen models is evaluated. The validity of the numerical model is verified by comparing the predicted results with the experimental results. Next, the effects of three parameters on the mechanical properties of the brace—the width-thickness ratio of the inner core, the clearance between the inner core and the inner round steel tube c1, and the constraint ratio—are investigated by the validated numerical model. The width-thickness ratio varies from 6 to 20, the gap value ranges from 1 to 7 mm, and the constraint ratio ranges from 0.43 to 1.03. Results show that the hysteresis curves of the two braces are full, with stable hysteretic performance and good energy dissipation capacity, which justifies the construction. Based on the parameters analysis results, the optimum values of the width-thickness ratio, gap, and constraint ratio have been recommended for steel BRBs.

Abstract: The grand challenge of “net-zero carbon” emission calls for technological breakthroughs in energy production. The traveling wave reactor (TWR) is designed to provide economical and safe nuclear power and solve imminent problems, including limited uranium resources and radiotoxicity burdens from back-end fuel reprocessing/disposal. However, qualification of fuels and materials for TWR remains challenging and it sets an “end of the road” mark on the route of R&D of this technology. In this article, a novel approach is proposed to maneuver reactor operations and utilize high-temperature transients to mitigate the challenges raised by envisioned TWR service environment. Annular U-50Zr fuel and oxidation dispersion strengthened (ODS) steels are proposed to be used instead of the current U-10Zr and HT-9 ferritic/martensitic steels. In addition, irradiation-accelerated transport of Mn and Cr to the cladding surface to form a protective oxide layer as a self-repairing mechanism was discovered and is believed capable of mitigating long-term corrosion. This work represents an attempt to disruptively overcome current technological limits in the TWR fuels. Impact statement: After the Fukushima accident in 2011, the entire nuclear industry calls for a major technological breakthrough that addresses the following three fundamental issues: (1) Reducing spent nuclear fuel reprocessing demands, (2) reducing the probability of a severe accident, and (3) reducing the energy production cost per kilowatt-hour. An inherently safe and ultralong life fast neutron reactor fuel form can be such one stone that kills the three birds. In light of the recent development findings on U-50Zr fuels, we hereby propose a disruptive, conceptual metallic fuel design that can serve the following purposes at the same time: (1) Reaching ultrahigh burnup of above 40% FIMA, (2) possessing strong inherent safety features, and (3) extending current limits on fast neutron irradiation dose to be far beyond 200 dpa. We believe that this technology will be able to bring about revolutionary changes to the nuclear industry by significantly lowering the operational costs as well as improving the reactor system safety to a large extent. Graphical abstract:

We demonstrate a multifunctional optical spectral shaper on a silicon photonic chip. The proposed structure is composed of a tunable microring resonator (MRR) and three tunable Sagnac loop mirrors (SLMs), which can be regarded as a large SLM incorporating an MRR-coupled Fabry–Perot (FP) cavity. To realize flexible tuning, thermo-optically tunable Mach-Zehnder interferometer (MZI) couplers are used to replace conventional directional couplers with fixed coupling coefficients. By controlling the tunable MZI couplers, the proposed structure can be reconfigured as various functional structures including an all-pass MRR with tunable coupling regime, a tunable FP cavity, an SLM incorporating FP cavity, and an MRR-coupled FP cavity. This flexible reconfiguration allows for multifunctional optical spectral shaping including tunable comb filtering, Fano and EIT-like resonances. In particular, the complementary flat-top comb filtering responses can be theoretically obtained in the two ports of this device with same free spectral range (FSR) value, which enable the (de)interleaver operation. The experimental results show that the implemented all-pass MRR has a maximum extinction ratio (ER) of 38.9 dB and the corresponding quality factor is 6.5×104. The comb filter based on configured FP cavity can be switched from narrowband response (0.06 nm) to wideband flat-top response (0.23 nm), with ERs up to 10.6 dB and 22 dB, respectively. Moreover, a dynamic conversion between Lorentz, EIT, and Fano resonance line shapes based on the coupled resonant system can be realized. The demonstrated integrated device holds great potential for various applications such as filtering and switching in optical wavelength-division multiplexing (WDM) communication networks.

This study proposes a new type of all-steel buckling restrained brace with double steel tubes composed of an inner round steel tube and an outer square steel tube, the inner core adopting a cruciform section and an H-section. These two types of cross-sectional inner cores have larger cross-sectional stiffness than round bars and better meet the requirement that inner core should be easy to yield but not easy to buckle. In this study, a theoretical design method for designing the proposed BRB in a simplified and optimal way is presented. The assembly scheme, constraint system, and overall structure are defined. The quasi-static tests of two brace specimens under a cyclic load are carried out to verify the brace's mechanical performance, axial strain distribution, and energy dissipation capacity. These results show that, relying on these two types of cross-sections, the hysteresis curves of all-steel buckling restrained braces with double-steel tubes are overall in good shape and stable. In addition, its energy dissipation performance is stable without any widespread instability phenomena. Also, the inner core has a stable plastic deformation capacity even after yielding, based on the comparative analysis of axial strain response of each components. Both specimens can meet the requirements of seismic design.

The morphologies of ceria nanocrystals play an essential role in determining their redox and catalytic performances in many applications, yet the effects of synthesis variables on the formation of ceria nanoparticles of different morphologies and their related growth mechanisms have not been systematised. The design of these morphologies is underpinned by a range of fundamental parameters, including crystallography, optical mineralogy, the stabilities of exposed crystallographic planes, CeO2−xstoichiometry, phase equilibria, thermodynamics, defect equilibria, and the crystal growth mechanisms. These features are formalised and the key analytical methods used for analysing defects, particularly the critical oxygen vacancies, are surveyed, with the aim of providing a source of design parameters for the synthesis of nanocrystals, specifically CeO2−x. However, the most important aspect in the design of CeO2−xnanocrystals is an understanding of the roles of the main variables used for synthesis. While there is a substantial body of data on CeO2−xmorphologies fabricated using low cerium concentrations ([Ce]) under different experimental conditions, the present work fully maps the effects of the relevant variables on the resultant CeO2−xmorphologies in terms of the commonly used raw materials [Ce] (and [NO3−] in Ce(NO3)3·6H2O) as feedstock, [NaOH] as precipitating agent, temperature, and time (as well as the complementary vapour pressure). Through the combination of consideration of the published literature and the generation of key experimental data to fill in the gaps, a complete mechanistic description of the development of the main CeO2−xmorphologies is illustrated. Further, the mechanisms of the conversion of nanochains into the two variants of nanorods, square and hexagonal, have been elucidated through crystallographic reasoning. Other key conclusions for the crystal growth process are the critical roles of (1) the formation of Ce(OH)4crystallite nanochains as the precursors of nanorods and (2) the disassembly of the nanorods into Ce(OH)4crystallites and NO3−-assisted reassembly into nanocubes (and nanospheres) as an unrecognised intermediate stage of crystal growth.

Currently, no effective and safe medicines are available to treat diabetic nephropathy (DN). Bardoxolone methyl (CDDO-Me) has displayed promising anti-DN activity as well as serious side effects in clinical trials, probably because the highly reactive α-cyano-α,β-unsaturated ketone (CUK) in ring A of CDDO-Me can covalently bind to thiol functionalities in many biomacromolecules. In this study, we designed and synthesized a γ-glutamyl transpeptidase (GGT)-based and CUK-modified derivative of CDDO-Me (2) to address this issue. 2can be specifically cleaved by GGT, which is highly expressed in the kidney, to liberate CDDO-Me in situ. It should be noted that 2exhibited anti-DN efficacy comparable to that of CDDO-Me with much less toxicity in cells and db/dbmice, suggesting that its safety is better than CDDO-Me. Our findings not only reveal the therapeutic potential of 2but also provide a strategy to optimize other synthetic molecules or natural products bearing a pharmacophore like CUK to achieve safer pharmaceutical drugs.

Kenyon SL, Taylor DJ, Tarnow-Mordi W, et al. Broad-spectrum antibiotics for preterm, prelabour rupture of fetal membranes: the ORACLE I randomised trial. Lancet 2001; 357: 979-88. * BACKGROUND PPROM is [...]

Multidrug-resistant Gram-negative bacteria present an urgent and formidable threat to the global public health. Polymyxins have emerged as a last-resort therapy against these ‘superbugs’; however, their efficacy against pulmonary infection is poor. In this study, we integrated chemical biology and molecular dynamics simulations to examine how the alveolar lung surfactant significantly reduces polymyxin antibacterial activity. We discovered that lung surfactant is a phospholipid-based permeability barrier against polymyxins, compromising their efficacy against target bacteria. Next, we unraveled the structure–interaction relationship between polymyxins and lung surfactant, elucidating the thermodynamics that govern the penetration of polymyxins through this critical surfactant layer. Moreover, we developed a novel analog, FADDI-235, which exhibited potent activity against Gram-negative bacteria, both in the presence and absence of lung surfactant. These findings shed new light on the sequestration mechanism of lung surfactant on polymyxins and importantly pave the way for the rational design of new-generation lipopeptide antibiotics to effectively treat Gram-negative bacterial pneumonia.