Review of High-frequency PWM Acoustic Noise Suppression Methods for PMSMs

Permanent magnet synchronous motors(PMSMs)driven by voltage source inverters(VSIs)with pulse width modulation(PWM)are widely used.Given the impact of acoustic noise on the environment and human ears,the comfort level of the high-frequency vibration noise emitted by PMSMs has become an important factor.This study introduces the current mainstream high-frequency vibration noise suppression strategies for PMSMs by reducing the high-frequency current harmonics of stator windings,including spread spectrum technology,vector position exchange technology,and interleaved parallel technology.Furthermore,this study analyzed and compared the advantages and disadvantages of various suppression strategies.

RankXGB-Based Enterprise Credit Scoring by Electricity Consumption in Edge Computing Environment

With the rapid development of the internet of things(IoT),electricity consumption data can be captured and recorded in the IoT cloud center.This provides a credible data source for enterprise credit scoring,which is one of the most vital elements during the financial decision-making process.Accordingly,this paper proposes to use deep learning to train an enterprise credit scoring model by inputting the electricity consumption data.Instead of predicting the credit rating,our method can generate an absolute credit score by a novel deep ranking model–ranking extreme gradient boosting net(rankXGB).To boost the performance,the rankXGB model combines several weak ranking models into a strong model.Due to the high computational cost and the vast amounts of data,we design an edge computing framework to reduce the latency of enterprise credit evaluation.Specially,we design a two-stage deep learning task architecture,including a cloud-based weak credit ranking and an edge-based credit score calculation.In the first stage,we send the electricity consumption data of the evaluated enterprise to the computing cloud server,where multiple weak-ranking networks are executed in parallel to produce multiple weak-ranking results.In the second stage,the edge device fuses multiple ranking results generated in the cloud server to produce a more reliable ranking result,which is used to calculate an absolute credit score by score normalization.The experiments demonstrate that our method can achieve accurate enterprise credit evaluation quickly.

泥石流防治工程损毁度评价——以汶川地区为例

泥石流岩土防治工程被广泛应用于泥石流灾害的治理,而工程的损毁程度会对工程的功能性产生一定的影响,并影响效益的持续发挥。文章以汶川为研究区域,选取18条泥石流沟的岩土防治工程作为研究对象,结合现场考察,对防治工程的损毁程度进行评价。评价指标体系总体上分为拦挡工程因子和排导工程因子2项,细化二级评价指标包括坝基损毁度、坝肩损毁度、坝体损毁度、基础冲刷度、结构冲击度、斜坡推力度等6项。运用模糊综合评价方法构建判断矩阵和隶属度函数,将损毁度等级划分为优、良、中、差四个等级。评价结果显示,除板子沟和登溪沟的防治工程损毁等级为差和中以外,其余泥石流沟内防治工程损毁等级均为良或优,且评价结果与现场考察一致。

Electrically triggered dual-band tunable terahertz metamaterial band-pass filter based on Si_3N_4–VO_2–Si_3N_4 sandwich

We experimentally demonstrate an electrically triggered terahertz(THz) dual-band tunable band-pass filter based on Si_3 N_4–VO_2–Si_3 N_4 sandwich-structured hybrid metamaterials. The insulator–metal phase transition of VO_2 film is induced by the Joule thermal effect of the top metal layer. The finite-integration-time-domain(FITD) method and finite element method(FEM) are used for numerical simulations. The sample is fabricated using a surface micromachining process,and characterized by a THz time-domain-spectrometer(TDS). When the bias current is 0.225 A, the intensity modulation depths at two central frequencies of 0.56 THz and 0.91 THz are about 81.7% and 81.3%, respectively. This novel design can achieve dynamically electric–thermo–optic modulation in the THz region, and has potential applications in the fields of THz communications, imaging, sensing, and astronomy exploration.

Conductive Polyaniline/Cellulose/Graphite Composite Films with High Thermal Stability and Antibacterial Activity

Functional composite films were successfully prepared from cellulose, graphite(GP), and polyaniline(PANI) using a combination of physical and chemical processes. Cellulosewasdissolved in N-methylmorpholine-N-oxide monohydrate(NMMO) and regenerated in water to form the matrix. GP was dispersed in the NMMO solvent prior to the dissolution of the cellulose, and PANI was deposited on the surfaces of the cellulose/GP films by in situ chemical polymerization. The structures of the PANI/cellusose/GP composite films were investigated using X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy(SEM), and SEM/energy-dispersive X-ray spectroscopy. The mechanical strengths, thermal stabilities, conductivities, and antibacterial activities of the films were studied in detail. The results showed that GP formed a multilayered structure in the cellulose matrix and that the PANI nanoparticles were tightly wrapped on the film surface. The film thickness increased from 40 mm to 100 mm after the addition of GP and PANI. The tensile strength of the composite films was 80~107 MPa, with the elongation at break being 3%~10%. The final residual weight of the composite films was as high as 65%, and the conductivity of the composite films reached 14.36 S/m. The cellulose matrix ensured that the films were flexible and exhibited desirable mechanical properties, while the GP filler significantly improved the thermal stability of the films. The PANI coating acted as a protective layer during burning and provided good electrical conductivity and antibacterial activity against Escherichia coli; both of these characteristics were slightly enhanced by the incorporation of GP. These PANI/cellulose/GP composite films should be suitable for use in electronics, antistatic packing, and numerous other applications.

桥梁伸缩缝破坏机理与修补措施探讨

伸缩缝是桥梁上部主体结构的一个重要组成部分,对于保证桥梁结构稳定、行车安全等具有重要意义。然而,在自然环境和道路交通运行荷载的共同作用下,伸缩缝装置会出现不同程度的破坏,导致桥梁使用寿命降低。本文以介绍桥梁伸缩缝的类型为出发m,总结桥梁伸缩缝的主要破坏形式和破坏机理,从设计施工、材料和养护管理等方面对伸缩缝损坏的原因进行探讨,并从结构和材料两个方面提出修复措施,旨在为桥梁伸缩缝的深入研究提供借鉴和参考。

三分量光纤地震计

提出并实验论证了一种全金属三分量光纤地震计。基于机电理论给出了理论分析。标定结果表明:在5~400Hz频带,轴向灵敏度约41dB(0dB=1rad/g),波动±2dB。横向灵敏度约-40dB。地震计中的3个加速度计的加速度灵敏度波动在±2.5dB之内。相位产生载波的最小相位解调检测准度为10^(-5)rad/Hz^(1/2),最小可检测加速度值经计算可达到90ng/Hz^(1/2)。

Insights into high-efficient removal of tetracycline by a codoped mesoporous carbon adsorbent

Adsorbents with simple preparation and high surface area have become increasingly prevalent for the removal of organic contaminants.Herein,a carbon nanoplate codoped by Co and N elements with abundant ordered mesoporous(Co/N-MCs)was applied as an adsorbent for tetracycline removal.Taking integrated advantages of ordered mesopores on carbon-based structures and N-doping inducing the strengthenedπ–πdispersion and generation of pyridinic N,as well as cobaltic nanoparticles embedded in carbon nanoplates,the Co/N-MCs was tailored for high efficiently absorbing tetracycline viaπ-πinteraction,Lewis acid-base interaction,metal complexation and electrostatic attraction.The Co/N-MCs had the advantages of high surface area,porous structure,plenty adsorption sites,and easy separation.As such,the as-prepared Co/N-MCs adsorbents significantly enhanced tetracycline removal performance with a maximum adsorption capacity of 344.83 mg·g^(-1) at pH 6 and good reusability,which was finally applied to removal tetracycline from tap water sample.Furthermore,the adsorption process towards tetracycline hydrochloride could be well attributed to the pseudo-second-order kinetic and Langmuir isotherm models.Compared with traditional carbon-based adsorbents,it owns a simpler synthesis method and a higher adsorption capacity,as well as it is a promising candidate for water purification.

Determination of the surface states from the ultrafast electronic states in a thermoelectric material

We reveal the electronic structure in Yb Cd_(2)Sb_(2),a thermoelectric material,by angle-resolved photoemission spectroscopy(ARPES)and time-resolved ARPES(tr ARPES).Specifically,three bulk bands at the vicinity of the Fermi level are evidenced near the Brillouin zone center,consistent with the density functional theory(DFT)calculation.It is interesting that the spin-unpolarized bulk bands respond unexpectedly to right-and left-handed circularly polarized probe.In addition,a hole band of surface states,which is not sensitive to the polarization of the probe beam and is not expected from the DFT calculation,is identified.We find that the non-equilibrium quasiparticle recovery rate is much smaller in the surface states than that of the bulk states.Our results demonstrate that the surface states can be distinguished from the bulk ones from a view of time scale in the nonequilibrium physics.

Topological Dirac surface states in ternary compounds GeBi_(2)Te_(4),SnBi_(2)Te_(4) and Sn_(0.571)Bi_(2.286)Se_(4)

Using high-resolution angle-resolved and time-resolved photoemission spectroscopy,we have studied the low-energy band structures in occupied and unoccupied states of three ternary compounds GeBi_(2)Te_(4),SnBi_(2)Te_(4) and Sn_(0.571)Bi_(2.286)Se_(4) near the Fermi level.In previously confirmed topological insulator GeBi_(2)Te_(4) compounds,we confirmed the existence of the Dirac surface state and found that the bulk energy gap is much larger than that in the first-principles calculations.In SnBi_(2)Te_(4) compounds,the Dirac surface state was observed,consistent with the first-principles calculations,indicating that it is a topological insulator.The experimental detected bulk gap is a little bit larger than that in calculations.In Sn_(0.571)Bi_(2.286)Se_(4) compounds,our measurements suggest that this nonstoichiometric compound is a topological insulator although the stoichiometric SnBi_(2)Se_(4) compound was proposed to be topological trivial.

Plasmon-induced transparency effect in hybrid terahertz metamaterials with active control and multi-dark modes

We numerically demonstrate a photo-excited plasmon-induced transparency(PIT)effect in hybrid terahertz(THz)metamaterials.The proposed metamaterials are regular arrays of hybrid unit cells composed of a metallic cut wire and four metallic split-ring resonators(SRRs)whose gaps are filled with photosensitive semiconductor gallium arsenide(GaAs)patches.We simulate the PIT effect controlled by external infrared light intensity to change the conductivity of GaAs.In the absence of photo excitation,the conductivity of Ga As is 0,thus the SRR gaps are disconnected,and the PIT effect is not observed since the dark resonator(supported by the hybrid SRRs)cannot be stimulated.When the conductivity of GaAs is increased via photo excitation,the conductivity of Ga As can increase rapidly from 0 S/m to 1×10^(6)S/m and GaAs can connect the metal aluminum SRR gaps,and the dark resonator is excited through coupling with the bright resonator(supported by the cut wire),which leads to the PIT effect.Therefore,the PIT effect can be dynamically tuned between the on and off states by controlling the intensity of the external infrared light.We also discuss couplings between one bright mode(CW)and several dark modes(SRRs)with different sizes.The interference analytically described by the coupled Lorentz oscillator model elucidates the coupling mechanism between one bright mode and two dark modes.The phenomenon can be considered the result of linear superposition of the coupling between the bright mode and each dark mode.The proposed metamaterials are promising for application in the fields of THz communications,optical storage,optical display,and imaging.

Unusual Band Splitting and Superconducting Gap Evolution with Sulfur Substitution in FeSe

High-resolution angle-resolved photoemission measurements were taken on FeSe;S;(x=0,0.04,and 0.08)superconductors.With an ultrahigh energy resolution of 0.4 meV,unusual two hole bands near the Brillouin-zone center,which was possibly a result of additional symmetry breaking,were identified in all the sulfur-substituted samples.In addition,in both of the hole bands highly anisotropic superconducting gaps with resolution limited nodes were evidenced.We find that the larger superconducting gap on the outer hole band is reduced linearly to the nematic transition temperature while the gap on the inner hole is nearly S-substitution independent.Our observations strongly suggest that the superconducting gap increases with enhanced nematicity although the superconducting transition temperature is not only governed by the pairing strength,demonstrating strong constraints on theories in the FeSe family.

三参数冰相云微物理方案在CIESM模式中的应用

由于云的时空尺度非常宽广,云微物理参数化方案一直是气候模式中的薄弱环节.本文借鉴中尺度模式云微物理方案从双参数向三参数扩展的思路方法,发展了联合地球系统模式(Community Integrated Earth System Model,CIESM)三参数冰相云微物理方案,弥补了默认双参数方案不能预报冰晶粒径分布谱形参数(μ)的不足,进而分析了双、三参数方案对气候模拟的影响.模拟结果表明,相较于双参数方案(μ为0),三参数方案预报得出的μ更为合理,其在垂直分布上整体呈现出“高层小低层大”的特点,高层的低值主要是由于冰晶核化以及较大的冰晶粒子沉降后粒子之间相互混合导致的,而低层的高值主要是由于冰晶粒子在沉降过程中的粒子分选机制导致的.与双、三参数方案中μ的差异相呼应,模式模拟的气候平均态出现明显差异,其中三参数方案模拟的总云云量、低云云量、中云云量和总降水相较于双参数方案更接近观测结果,高云云量的误差增大.其中总降水的改进主要是由于高云云量的增加,大气稳定度增加,对流性降水减少.此外,还调整了相关参数,以改善模式对辐射的模拟能力.总之,本文在全球气候模式中评估了双、三参数方案对于模拟气候平均态的不同影响,为气候模式中云微物理方案的发展改进提供了一定的参考意义.

Visible light-driven oxidation of non-native substrate by laccase attached on Ru-based metal-organic frameworks

Light-induced electron transfer can broaden the substrate range of metalloenzyme.However,the efficiency of photo-enzyme coupling is limited by the poor combination of photosensitizer or photocatalyst with enzyme.Herein,we prepared the nano-photocatalyst MIL-125-NH_(2)@Ru(bpy)by in site embedding ruthenium pyridine-diimine complex[Ru(bpy)_(3)^(2+)into metal organic frameworks MIL-125-NH_(2)and associated it with multicopper oxidase(MCO)laccase.Compared to[Ru(bpy)_(3)]^(2+),the coupling efficiency of MIL-125-NH_(2)@Ru(bpy)_(3)for enzymatic oxygen reduction increased by 35.7%.A series of characterizations confirmed that the amino group of laccase formed chemical bonds with the surface defects or hydrophobic groups of MIL-125-NH_(2)@Ru(bpy)_(3).Consequently,the tight binding accelerated the quenching process and electron transfer between laccase and the immobilized ruthenium pyridine-diimine complex.This work would open an avenue for the synthesis of MOFs photocatalyst towards photo-enzyme coupling.

Design principle of single-atom catalysts for sulfur reduction reaction—interplay between coordination patterns and transition metals

The polysulfide shuttling effect is the primary bottleneck restricting the industrial application of Li-S batteries,and the electrocatalytic sulfur reduction reaction(SRR)has emerged as an effective solution.Carbon-based singleatom catalysts(SACs),which promotes SRR,show great potential in inhibiting the shuttling effect of polysulfides.Meanwhile,the optimization and rational design of such catalysts requires a deep understanding to the fundamental SRR mechanism and remains highly nontrivial.In this work,we construct a comprehensive database of carbon-based SACs,covering different coordination patterns,heteroatoms,and transition metals.The SRR activities are determined using density functional theory calculations,revealing a synergistic effect between the p orbital of the heteroatom and the d orbital of the transition metal.This interplay underscores the critical importance of the coordination environment for SRR under the ortho-P_(2)C_(2)structure.Regardless of the transition metal type,the ortho-P_(2)C_(2)coordination pattern significantly enhances the SRR performance of SACs,surpassing the widely reported N_(3)C_(1)and N_(4)coordinated graphene-based SACs.Furthermore,heteroatoms with ortho-P_(2)C_(2)may exhibit SRR activity.In a word,by using this comprehensive dataset and data-driven framework,we propose a promising novel class of coordination structure(ortho-P_(2)C_(2)structure)and neglected design principle.

Multiscale engineering of molecular electrocatalysts for the rapid hydrogen evolution reaction

Molecular electrocatalysts have demonstrated potential for the hydrogen evolution reaction(HER)due to their well-defined structures and high intrinsic activities.Achieving rapid production of hydrogen requires molecular electrocatalysts to operate at high current densities,which still presents a challenge.In this work,we demonstrate that molecularly dispersed electrocatalysts of cobalt phthalocyanine anchored on carbon nanotubes(CoPc MDEs)are superior candidates due to the efficient charge transport between the substrate and the active site.The intrinsic activity can be enhanced by introducing functional groups on phthalocyanine.To facilitate mass transport,di(ethylene glycol)substituted CoPc molecules are further anchored on a threedimensional self-supported electrode(CoPc-DEG MDE@CC),enabling continuous operation for 25 h at−1000 mA/cm^(2)in 1.0 M KOH.Our study demonstrates the potential of molecular electrocatalysts for HER and emphasizes the importance of adjusting intrinsic activity,and charge and mass transport capacity for practical molecular electrocatalysts.

三参数冰相云微物理方案的构建及在单柱大气模式中的应用

云微物理的参数化对天气及气候的准确模拟至关重要,其中云粒子谱分布特征通过改变云演化发展和云辐射效应,必然进一步影响气候模拟.目前广泛使用的双参数云微物理方案,无法预报云粒子谱分布的谱形参数,阻碍了气候模式对云物理过程的准确描述.鉴于此,本文在单柱大气模式SCAM5.3(Single Column Atmosphere Model,Version 5.3)中增加雷达反射率因子的预报方程,构建了三参数冰相云微物理方案,实现了冰晶粒子谱分布谱形参数的预报.利用该模式,模拟了大气辐射观测计划在1997年夏季实施的为期29 d的观测个例(ARM97),分析了双、三参数方案对云量和辐射的模拟差异.结果表明:首先,三参数方案预报的冰晶粒子谱的谱形参数主要集中在0~4,峰值在2左右,至少有85%的μ都大于默认的0.其次,与双参数方案相比,三参数方案对云量的模拟更接近观测;利用辐射通量密度的观测值进行评估,发现无论是短波还是长波辐射通量密度,三参数方案的误差都比双参数方案小.最后,揭示了三参数方案对云量和辐射模拟效果的改进机理:主要是因为三参数方案减弱了冰晶到雪的自动转化过程,增强了冰晶凝华增长过程,从而增大了冰晶浓度和冰云云量.本文构建的三参数冰相云微物理方案,将有利于增强模式对云-气候反馈等过程的模拟能力.

Effects of main active components of rosemary on growth performance,meat quality and lipid metabolism in finishing pigs

Rosemary extracts have been widely used as feed additives in recent years.This study aimed to investigate the effects of rosmarinic acid(RA)and ursolic acid(UA),the main active components of rosemary,on growth performance,meat quality and lipid metabolism in finishing pigs.A total of 72 finishing pigs(Landrace;initial age of 150 d)were randomly divided into 3 treatments with 8 replicates of 3 pigs each,and fed a basal diet or diet containing 500 mg/kg of RA or UA.The results showed that dietary supplementation of RA or UA had no significant effect on the growth performance and carcass traits of finishing pigs(P>0.05).However,both RA and UA significantly increased the triglyceride(TG)level in soleus muscle(P<0.001).Supplementation of RA increased the expression of genes related to lipogenesis and transport including fatty acid synthase(FAS)(P<0.001),sterol regulatory element binding protein-1c(SREBP1c)(P<0.001)and peroxisome proliferator-activated receptorγ(PPARγ)(P<0.05),while UA increased the expression of fatty acid transport protein 1(FATP1),a gene related to lipid uptake(P<0.05).However,RA reduced the expression of adipogenesis-related gene acetyl-coenzyme A carboxylase a(ACCa)(P<0.01).Characterization of cecal microbiota indicated that RA increased the microbial richness(chao 1,P<0.001)and diversity(observed species,P<0.01).Further analysis of the genera revealed that RA increased the relative abundance of Bacteroides and g-UCG-005(P<0.05),and UA enriched Prevotella(P<0.001).Correlation analysis showed that g-UCG-005 was positively correlated with the expression of FAS,carnitine palmitoyl transferase 1B(CPT1B),SREBP1c and PPARγ(P<0.01).In conclusion,dietary supplementation of RA or UA may increase fat deposition in muscle of finishing pigs by regulating lipid metabolism and gut microbiota.

Synthesis optimization and adsorption modeling of biochar for pollutant removal via machine learning

Due to large specific surface area,abundant functional groups and low cost,biochar is widely used for pollutant removal.The adsorption performance of biochar is related to biochar synthesis and adsorption parameters.But the influence factor is numerous,the traditional experimental enumeration is powerless.In recent years,machine learning has been gradually employed for biochar,but there is no comprehensive review on the whole process regulation of biochar adsorbents,covering synthesis optimization and adsorption modeling.This review article systematically summarized the application of machine learning in biochar adsorbents from the perspective of all-round regulation for the first time,including the synthesis optimization and adsorption modeling of biochar adsorbents.Firstly,the overview of machine learning was introduced.Then,the latest advances of machine learning in biochar synthesis for pollutant removal were summarized,including prediction of biochar yield and physicochemical properties,optimal synthetic conditions and economic cost.And the application of machine learning in pollutant adsorption by biochar was reviewed,covering prediction of adsorption efficiency,optimization of experimental conditions and revelation of adsorption mechanism.General guidelines for the application of machine learning in whole-process optimization of biochar from synthesis to adsorption were presented.Finally,the existing problems and future perspectives of machine learning for biochar adsorbents were put forward.We hope that this review can promote the integration of machine learning and biochar,and thus light up the industrialization of biochar.

Medium-range order endows a bulk metallic glass with enhanced tensile ductility

Developing ductile bulk metallic glasses(BMGs)can benefit from an in-depth understanding of the structure-property relation during plastic deformation.However,endowing BMGs with tensile ductility in BMGs needs to reveal the response of critical structure units during deformation.Here,we report the experimental results of an in-situ synchrotron high-energy X-ray study of a Zr-based BMG under uniaxial tension after preprocessing by canning compression of the three-dimensional compressive stress state.It is revealed that the canning-compressed BMG(CC-BMG)sample has better tensile ductility and higher ultimate strength than the as-cast sample,which possesses heterogeneous and loosely packed local struc-tures on medium-range scales.The experimental results revealed two stages of plastic deformation in the CC-BMGs compared with one stage of plastic deformation in the as-cast BMG.Moreover,the shift in the first sharp diffraction peak along the tension direction for the canning-compressed sample is substan-tially more pronounced than that of the as-cast sample.Furthermore,the real-space analysis illustrates a competition mechanism between the 2-atom and 3-atom connection modes on medium-range order during the plastic deformation of the CC-BMG.Additionally,the ordering on the medium-range scale de-creases in the first plastic deformation stage but increases in the second plastic deformation stage.There-fore,a structural crossover phenomenon occurs in the CC-BMG during plastic deformation.Our results demonstrate a structure-property correlation for the CC-BMGs of heterogeneous medium-range ordered structures,which may be beneficial for endowing BMGs with ductility based on medium-range order engineering techniques.