An Algorithm for Short-Circuit Current Interval in Distribution Networks with Inverter Type Distributed Generation Based on Affine Arithmetic

During faults in a distribution network,the output power of a distributed generation(DG)may be uncertain.Moreover,the output currents of distributed power sources are also affected by the output power,resulting in uncertainties in the calculation of the short-circuit current at the time of a fault.Additionally,the impacts of such uncertainties around short-circuit currents will increase with the increase of distributed power sources.Thus,it is very important to develop a method for calculating the short-circuit current while considering the uncertainties in a distribution network.In this study,an affine arithmetic algorithm for calculating short-circuit current intervals in distribution networks with distributed power sources while considering power fluctuations is presented.The proposed algorithm includes two stages.In the first stage,normal operations are considered to establish a conservative interval affine optimization model of injection currents in distributed power sources.Constrained by the fluctuation range of distributed generation power at the moment of fault occurrence,the model can then be used to solve for the fluctuation range of injected current amplitudes in distributed power sources.The second stage is implemented after a malfunction occurs.In this stage,an affine optimization model is first established.This model is developed to characterizes the short-circuit current interval of a transmission line,and is constrained by the fluctuation range of the injected current amplitude of DG during normal operations.Finally,the range of the short-circuit current amplitudes of distribution network lines after a short-circuit fault occurs is predicted.The algorithm proposed in this article obtains an interval range containing accurate results through interval operation.Compared with traditional point value calculation methods,interval calculation methods can provide more reliable analysis and calculation results.The range of short-circuit current amplitude obtained by this algorithm is slightly larger than those obtained using the Monte Carlo algorithm and the Latin hypercube sampling algorithm.Therefore,the proposed algorithm has good suitability and does not require iterative calculations,resulting in a significant improvement in computational speed compared to the Monte Carlo algorithm and the Latin hypercube sampling algorithm.Furthermore,the proposed algorithm can provide more reliable analysis and calculation results,improving the safety and stability of power systems.

Mutagenesis reveals that the rice OsMPT3 gene is an important osmotic regulatory factor

Plant mitochondrial phosphate transporters regulate phosphate transport and ATP synthesis. Determining whether they function in abiotic stress response process would shed light on their response to salt stress. We used the CRISPR/Cas9 gene-editing system to mutagenize two mitochondrial phosphate transporters, OsMPT3;1 and OsMPT3;2, to investigate their regulatory roles under salt stress. Two cas9(CRISPR-associated protein9)-free homozygous mutants, mpt33 and mpt30, were confirmed to be stable. Both OsMPT3;1 and OsMPT3;2 were markedly induced by salt stress, and their mutagenesis strongly inhibited growth and development, especially under salt stress. Mutagenesis sharply reduced the accumulation of ATP, phosphate, calcium, soluble sugar, and proline and increased osmotic potential, malondialdehyde, and Na^+ /K^+ ratio under salt stress. Both mutants demonstrate normal growth and development in the presence of ATP, revealing high sensitivity to exogenous ATP under salt stress. The mutants showed lowered rates of Na^+ efflux but also of K^+ and Ca^(2+) influx under salt stress. Mutagenesis of OsMPT3;2 altered the enrichment profiles of differentially expressed genes involved mainly in synthesis of secondary metabolites, metabolism of glycolysis, pyruvate, tricarboxylic acid cycle, in response to salt stress. The mutant displayed significant accumulation differences in 14 metabolites involved in 17 metabolic pathways, and strongly up-regulated the accumulation of glutamine, a precursor in proline synthesis, under salt stress. These findings suggest that the OsMPT3 gene modulates phosphate transport and energy supply for ATP synthesis and triggers changes in accumulation of ions and metabolites participating in osmotic regulation in rice under salt stress, thus increasing rice salt tolerance. This study demonstrates the effective application of CRISPR/Cas9 gene-editing to the investigation of plant functional genes.

Enhanced bifunctional catalytic activities of N-doped graphene by Ni in a 3D trimodal nanoporous nanotubular network and its ultralong cycling performance in Zn-air batteries

Free-standing and fexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER)are crucial to the development of wearable Zn-air rechargeable batteries.In this work,we synthesize a fexible air electrode consisting of 3D nanoporous N-doped graphene with trimodal shells and Ni particles through repeated chemical vapor deposition(CVD)and acidic etching processes.Our results indicate that such trimodal graphene morphology significantly enhances the active N-dopant sites and graphene-coated Ni surface,which consequentially boosts both the ORR and OER activities,as well as catalytic durability.First-principles density functional theory(DFT)calculations reveal the synergetic effects between the Ni and the N-doped graphene;namely,the Ni nanoparticles boost the bifunctional activities of the coated N-doped graphene,and in turn the graphene-covering layers enhance the stability of Ni.Thanks to the better protection from the triple graphene shells,our trimodal N-doped graphene/Ni-based Zn-air battery can be stably discharged/recharged beyond 2500 h with low overpotentials.It is reasonable to expect that such freestanding trimodal graphene/Ni would be promising in many fexible energy conversion/storage devices.

Ultrasonic Fatigue of Ti₄₀Zr₁₀Cu₃₄Pd₁₄Sn₂Glassy Alloy

In this work, ultrasonic fatigue behavior of the Ti40Zr10Cu34Pd14Sn2 glassy alloy was investigated at 20 kHz at a stress ratio of R = -1. The number of cycles to failure in the S-N curve obtained in this work did not decrease again even after 107 - 108 cycles unlike previous findings for some steels. The fatigue endurance limit and the fatigue rate were σW = 762 MPa and σW/σB = 0.37, respectively. Fish-eye type inertial crack initiation, reported in many papers on giga-cycle fatigue testing, was not observed. A tendency for the fatigue strength of the Ti40Zr10Cu34Pd14Sn2 glassy alloy specimens to be divided into two groups was observed, that is, specimens with a short fatigue lifetime (6 cycles) with distinct cast defects as crack initiation sites and the other specimens with a long fatigue lifetime (>106 cycles). This may have been caused by accidental nucleation of micro-defects such as impurities, voids and precipitates in the glassy rod specimens during the casting.

Optical modification of nonlinear crystals for quasi-parametric chirped-pulse amplification

Quasi-parametric chirped-pulse amplification(QPCPA),which features a theoretical peak power much higher than those obtained with Ti:sapphire laser or optical parametric chirped-pulse amplification,is promising for future ultra-intense lasers.The doped rare-earth ion used for idler dissipation is critical for effective QPCPA,but is usually not compatible with traditional crystals.Thus far,only one dissipative crystal of Sm^(3+)-doped yttrium calcium oxyborate has been grown and applied.Here we introduce optical means to modify traditional crystals for QPCPA applications.We theoretically demonstrate two dissipation schemes by idler frequency doubling and sum-frequency generation with an additional laser.In contrast to absorption dissipation,the proposed nonlinear dissipations ensure not only high signal efficiency but also high small-signal gain.The demonstrated ability to optically modify crystals will facilitate the wide application of QPCPA.

Optimization of mechanical properties and corrosion resistance of Zn-0.4Mn-0.8Li alloy using the hot rolling process

Zinc-based degradable metals are considered one of the most promising biodegradable materials due to their moderate corrosion rate,excellent mechanical properties,and good biocompatibility.In this work,biodegradable Zn-0.4Mn-0.8Li alloy was fabricated and rolled in multiple passes at different tem peratures.As the hot rolling temperature increases,the grain size of Zn-0.4Mn-0.8Li alloy was found to increase cor-respondingly.Further,a multi-scale structure with the coexistence of coarse grains and fine grains was obtained.The results demonstrated that the mechanical strength and corrosion resistance were improved by increasing the rolled temperature.It was observed that Zn-0.4Mn-0.8Li alloy with a total reduction of 90%after hot rolling at 325℃ exhibited excellent mechanical and corrosion properties.The cooperation of multi-scale microstructure and twinning was found to improve the strength and guarantee the duc-tility of Zn-0.4Mn-0.8Li alloy significantly so that the 325℃ hot-rolled Zn-0.4Mn-0.8Li alloy has optimal comprehensive properties.Further,yield strength,ultimate tensile strength,and elongation were found to be 449.7±5.3 MPa,505.1±6.5 MPa,and 40.5%±7.5%,respectively.Meanwhile,Zn-0.4Mn-0.8Li al-loy via 325℃ hot-rolled processes also exhibited excellent corrosion resistance.The corrosion current density and corrosion potential were found to be 8.8×10-5 mA cm^(-2)and−0.929 V,respectively.The preliminary study indicates that Zn-0.4Mn-0.8Li alloy is a promising candidate material for medical de-vice applications.

Fabrication of porous TiZrNbTa high-entropy alloys/Ti composite with high strength and low Young’s modulus using a novel MgO space holder

Stress shielding is caused by the mismatch of stiffness between bone and implant materials,which may give rise to bone resorption and loosening,thereby causing implantation failure.There is a huge gap between Young’s modulus of human bone and low Young’s modulusβTi alloys.A porous structure design can achieve the target of low Young’s modulus,and thus achieve the matching between human bone and implant materials.However,a suitable space holder(SH)that can be applied at high temperatures and sintering pressure has not been reported.In this study,the TiZrNbTa/Ti titanium matrix composite(TMC)with high strength and large ductility was used as scaffold materials and combined the SH technique with the spark plasma sintering(SPS)technique to obtain a porous structure.A novel space holder,i.e.,MgO particles was adopted,which can withstand high-temperature sintering accompanied by a sintering pressure.The porous TiZrNbTa/Ti with 40 vol.%MgO added exhibits a maximum strength of 345.9±10.4 MPa and Young’s modulus of 24.72±0.20 GPa,respectively.It possesses higher strength compared with human bone and matches Young’s modulus of human bone,which exhibits great potential for clinical application.

Spatiotemporally mode-locked soliton fiber laser at 2.8µm

Spatiotemporal mode-locking creates great opportunity for pulse energy scaling and nonlinear optics research in fiber.Until now,spatiotemporal mode-locking has only been realized in normal-dispersion dissipative soliton and similariton fiber lasers.In this paper,we demonstrated the first experimental realization of a spatiotemporally mode-locked soliton laser in mid-infrared fluoride fiber with anomalous dispersion.The mode-locked fluoride fiber oscillator directly generated a record pulse energy of 16.1 nJ and peak power of 74.6 kW at 2.8µm wavelength.This work extends the spatiotemporal mode-locking to soliton fiber lasers and should have a wide interest for the laser community.

Generation of 131 fs mode-locked pulses from 2.8μm Er:ZBLAN fiber laser

We demonstrated a femtosecond mode-locked Er:Zr F4-Ba F2-La F3-Al F3-Na F(Er:ZBLAN)fiber laser at 2.8μm based on the nonlinear polarization rotation technique.The laser generated an average output power of 317 m W with a repetition rate of 107 MHz and pulse duration as short as 131 fs.To the best of our knowledge,this is the shortest pulse generated directly from a mid-infrared mode-locked Er:ZBLAN fiber laser to date.Numerical simulation and experimental results confirm that reducing the gain fiber length is an effective way to shorten the mode-locked pulse duration in the Er:ZBLAN fiber laser.The work takes an important step towards sub-100-fs mid-infrared pulse generation from mode-locked Er:ZBLAN fiber lasers.

2.8 μm all-fiber Q-switched and mode-locked lasers with black phosphorus

In past years, rare-earth-doped fluoride fiber lasers(FFLs) have developed rapidly in the mid-infrared(mid-IR)region. However, due to the lack of fiber optic devices and challenge of fluoride fiber splicing, most mid-IR FFLs have been demonstrated with free-space optic elements, limiting the advantages of all-fiber lasers for flexible delivery, stability, and compactness. Here, we report, to the best of our knowledge, the first pulsed all-fiber FFL in the mid-IR region. By taking advantage of the integration of black phosphorus flake, stable Q-switched and mode-locked pulses were obtained at 2.8 μm wavelength. We believe that this all-fiber design will promote the application of pulsed FFL in the mid-IR region.

Mode-locked 2.8-μm fluoride fiber laser:from soliton to breathing pulse

The mode-locked fluoride fiber laser(MLFFL)is an exciting platform for directly generating ultrashort pulses in the mid-infrared(mid-IR).However,owing to difficulty in managing the dispersion in fluoride fiber lasers,MLFFLs are restricted to the soliton regime,hindering pulse-energy scaling.We overcame the problem of dispersion management by utilizing the huge normal dispersion generated near the absorption edge of an infrared-bandgap semiconductor and promoted MLFFL from soliton to breathing-pulse mode-locking.In the breathing-pulse regime,the accumulated nonlinear phase shift can be significantly reduced in the cavity,and the pulse-energy-limitation effect is mitigated.The breathing-pulse MLFFL directly produced a pulse energy of 9.3 nJ and pulse duration of 215 fs,with a record peak power of 43.3 kW at 2.8μm.Our work paves the way for the pulse-energy and peak-power scaling of mid-IR fluoride fiber lasers,enabling a wide range of applications.

Formation and crystallization behavior of Fe-based amorphous precursors with pre-existingα-Fe nanoparticles-Structure and magnetic properties of high-Cu-content Fe-Si-B-Cu-Nb nanocrystalline alloys

Structure,crystallization behavior,and magnetic properties of as-quenched and annealed Fe_(81.3)Si_(4)O_(13)Cu_(1.7)(Cu1.7)alloy ribbons and effects of Nb alloying have been studied.Three-dimensional atom probe and transmission electron microscopy analyses reveal that high-number-density Cu-clusters and Pre-existing Nano-sized a-Fe Particles(PN-a-Fe)are coexistence in the melt-spun Cu1.7 amorphous matrix,and the PN-α-Fe form by manners of one-direction adjoining and enveloping the Cu-clusters.Two-step crystallization behavior associated with growth of the PN-a-Fe and subsequent nucleation and growth of newly-formedα-Fe is found in the primary crystallization stage of the Cu1.7 alloy.The number densities of the Cu-clusters and PN-a-Fe in melt-spun Fe8_(1.3-x)Si_(4)B_(13)Cu_(1.7)Nb_(x)alloys are gradually reduced with enriching of Nb,and a fully amorphous structure forms at 4 at.%Nb,although smaller Cu-clusters still exist.After annealing,2 at.%Nb coarsens the average size(D_(α-F)e)of theα-Fe grains from 14.0 nm of the Nb-free alloy to 21.6 nm,and 4 at.%Nb refines the D_(α-Fe)to 8.9 nm.The mechanisms of theα-Fe nucleation and growth during quenching and annealing for the alloys with large quantities of PN-α-Fe as well as after Nb alloying have been discussed,and an annealing-induced oc-Fe growth mechanism in term of the barrier co-contributed by competitive growth among the PN-a-Fe and diffusion-suppression effect of Nb atoms has been proposed.A coercivity(HC)αDα-Fe^(3)correlation has been found for the nanocrystalline alloys,and the permeability is inverse with the H_(C).

Balancing the anionic framework polarity for enhanced thermoelectric performance in YbMg_(2)Sb_(2) Zintl compounds

1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb.In this paper,we adjust the covalently bonded network of MgeSb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb.The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity.Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn,the maximum ZT value of ~0.8 at 773 K is achieved in YbMg_(0.9)Zn_(1.1)Sb_(2) which is~100% enhancement compared with that of YbMg_(2)Sb_(2).

Dual phase equal-atomic NbTaTiZr high-entropy alloy with ultra-fine grain and excellent mechanical properties fabricated by spark plasma sintering

Super-high strength NbTaTiZr high-entropy alloys(NbTaTiZr HEAs)have been successfully fabricated by the mechanical alloying(MA)with spark plasma sintering(SPS)technology,which is 2-fold compared with that of NbTaTiZr HEAs prepared by vacuum arc melting(VAM).After the SPS process,the bulk NbTaTiZr alloy samples are provided with dual-phase body-centered cubic(BCC)structure and nanoscale grain size about 500 nm that is obviously smaller than that of NbTaTiZr HEA fabricated by VAM.When the sintering temperature is 800℃,the compressive fracture strength is the highest reaching at 2511±78 MPa.When the sintering temperature is 1000℃,the fracture strain is the highest reaching at 12.8%,and compressive fracture strength and yield strength also reach at 2274±91 MPa and 2172±47 MPa,respectively.The excellent mechanical properties of bulk NbTaTiZr alloy samples are attributed to the merits of MA and SPS,and the collaboration effect of ultra-fine grains strengthening,solid solution strengthening and interstitial solid solution strengthening.

Mechanical properties and corrosion resistance of powder metallurgical Mg-Zn-Ca/Fe bulk metal glass composites for biomedical application

Magnesium(Mg)alloys can be regarded as the most promising biodegradable implant materials for orthopedic and stent applications due to their good biocompatibility and low Young’s modulus which is near to that of natural bone.However,its applicability is hindered because it exhibits a high corrosion rate in the physiological environments.In this work,we fabricated Mg_(66)Zn_(30)Ca_(4)/Fe bulk metallic glass composites via spark plasma sintering(SPS).We studied the influence of different contents of Fe on the properties of the composites.The results indicated that Fe was uniformly distributed on the surface of Mg_(66)Zn_(30)Ca_(4) metallic glass(MG)as a second phase,which led to an improvement in the corrosion resistance and mechanical strength.The standard potential of Mg_(66)Zn_(30)Ca_(4)/Fe bulk metallic glass(BMG)composites increased as compared to Mg_(66)Zn_(30)Ca_(4),while their mechanical strength improved from 355 MPa to 616 MPa.Furthermore,cytotoxicity was investigated via the CCK-8 assay and calcein-AM staining,which revealed that the extraction mediums diluted 6 times(EM×6)of the Mg_(66)Zn_(30)Ca_(4) and Mg_(66)Zn_(30)Ca_(4)/Fe did not cause cell toxicity on day 3 and 5,while the EM×6 of the Mg_(66)Zn_(30)Ca_(4) showed cytotoxicity on day 1,3 and 5.Thus,Mg_(66)Zn_(30)Ca_(4)/Fe BMG composites exhibit significant potential for fabricating implants with good mechanical strength and corrosion resistance.

Optimized strength and conductivity of multi-scale copper alloy/metallic glass composites tuned by a one-step spark plasma sintering(SPS)process

A superiority in interfacial bonding is favorable to fabricate high-strength conductive composites for electrical contact applications.In the present work,high strength and high conductivity multi-scale metallic glass composites(including micron-scale Cu Zr Al metallic glass reinforcement,hundred-nanometer-scale Cu Cr Zr crystalline grain matrix,and nano-scale precipitated phase)were fabricated by a one-step spark plasma sintering(SPS).The strength and conductivity of the bulk copper matrix metallic glass composites(BCMGCs)were enhanced simultaneously with the increase in the sintering pressure of the SPS.The excellent performance is attributed to the improved interfacial bonding between the metallic glass reinforcement and the copper alloy matrix due to the high pressure assisted by temperature and pulsed current.In particular,the precipitation of nanoprecipitates at the interface further reduces the interfacial resistance and improves the mechanical properties of the composites.This work broadens the horizon for the selection and optimization of reinforcements and manufacturing processes for high-performance electrical contact materials(ECMs).

Temporal-filtering dissipative soliton in an optical parametric oscillator

Dissipative solitons have been realized in mode-locked fiber lasers in the theoretical framework of the Ginzburg±Landau equation and have significantly improved the pulse energy and peak power levels of such lasers.It is interesting to explore whether dissipative solitons exist in optical parametric oscillators in the framework of three-wave coupling equations in order to substantially increase the performance of optical parametric oscillators.Here,we demonstrate a temporalfiltering dissipative soliton in a synchronously pumped optical parametric oscillator.The temporal-gain filtering of the pump pulse combined with strong cascading nonlinearity and dispersion in the optical parametric oscillator enables the generation of a broad spectrum with a nearly linear chirp;consequently,a significantly compressed pulse and high peak power can be realized after dechirping outside the cavity.Furthermore,we realized,for the first time,dissipative solitons in an optical system with a negative nonlinear phase shift and anomalous dispersion,extending the parameter region of dissipative solitons.The findings may open a new research block for dissipative solitons and provide new opportunities for mid-infrared ultrafast science.

Grating-free 2.8μm Er:ZBLAN fiber chirped pulse amplifier

We report on a grating-free fiber chirped pulse amplifier(CPA)at 2.8μm for the first time.The CPA system adopted Er:ZBLAN fiber with large anomalous dispersion as the stretcher and germanium(Ge)rods as the compressor with a compact structure.High-energy picosecond pulses of 2.07μJ were generated at the repetition rate of 100 kHz.Using highly dispersive Ge rods,the amplified pulses were compressed to 408 fs with a pulse energy of 0.57μJ,resulting in a peak power of approximately 1.4 MW.A spectral broadening phenomenon in the main amplifier was observed,which was caused by the special gain shape of the Er:ZBLAN fiber amplifier in operation and confirmed by our numerical simulation.This compact fiber CPA system at 2.8μm will be practical and meaningful for application fields.

Toward 5.2μm terawatt few-cycle pulses via optical parametric chirped-pulse amplification with oxide La3Ga5.5Nb0.5O14crystals

High-power femtosecond lasers beyond 5μm are attractive for strong-field physics with mid-infrared(IR)fields but are difficult to scale up.In optical parametric chirped-pulse amplification(OPCPA)at mid-IR wavelengths,a nonlinear crystal is vital,and its transmittance,dispersion,nonlinear coefficient and size determine the achievable power and wavelength.OPCPA beyond 5μm routinely relies on semiconductor crystals because common oxide crystals are not transparent in this spectral range.However,the small size and low damage threshold of semiconductor crystals fundamentally limit the peak power to gigawatts.In this paper,we design a terawatt-class OPCPA system at 5.2μm based on a new kind of oxide crystal of La3Ga5.5Nb0.5O14(LGN).The extended transparent range,high damage threshold,superior phase-matching characteristics and large size of LGN enable the generation of 0.13 TW seven-cycle pulses at5.2μm.This design fully relies on the state-of-the-art OPCPA technology of an octave-spanning ultrafast Ti:sapphire laser and a thin-disk Yb:YAG laser,offering the performance characteristics of high power,a high repetition rate and a stable carrier-envelope phase.

Demonstration of 85%pump depletion and 10-6 noise content in quasi-parametric chirped-pulse amplification

Full pump depletion corresponds to the upper limit of the generated signal photons relative to the pump pulse;this allows the highest peak power to be produced in a unit area of ultraintense laser amplifiers.In practical systems based on optical parametric chirped-pulse amplification,however,the typical pump depletion is only~35%.Here,we report quasi-parametric chirped-pulse amplification(QPCPA)with a specially designed 8-cm-thick Sm∶YCOB crystal that highly dissipates the idler and hence improves pump depletion.We demonstrate 56%QPCPA energy efficiency for an 810-nm signal converted from a 532-nm pump,or equivalently 85%pump depletion.As another advantage,such a record high depletion greatly suppresses the parametric superfluorescence noise in QPCPA to only~1.5×10-6 relative to the amplified signal energy.These results pave the way to beyond the ten-petawatt peak power of the currently most intense lasers.