Gas Turbines are among the most important energy systems for aviation and thermal-based power generation.The performance of gas turbine intakes with S-shaped diffusers is vulnerable to flow separation,reversal flow,an...Gas Turbines are among the most important energy systems for aviation and thermal-based power generation.The performance of gas turbine intakes with S-shaped diffusers is vulnerable to flow separation,reversal flow,and pressure distortion,mainly in aggressive S-shaped diffusers.Severalmethods,including vortex generators and energy promoters,have been proposed and investigated both experimentally and numerically.This paper compiles a review of experimental investigations that have been performed and reported to mitigate flow separation and restore system performance.The operational principles,classifications,design geometries,and performance parameters of Sshaped diffusers are presented to facilitate the analysis and understanding of the influence of each mitigation method on flowenhancement in S-shaped diffusers.Theinfluencing design parameters on the performance of the S-shaped diffuser and the findings achieved by various experimental investigations are discussed and compared.The review concludes that reducing the intake length reduces the size and weight of the gas turbine,leading to a higher power-to-weight ratio.However,the main challenge in shortening the S-shaped diffusers is the flow separation in the high-curvature section,which must be prevented to maintain high performance.Prevention can be achieved through flow control methods,which are categorized into passive and aggressive methods.The static pressure recovery coefficient,total pressure loss coefficient,ideal static pressure coefficient,distortion coefficient,and skin friction coefficient are the primary performance evaluation and comparison parameters between the experimentally investigated mitigation methods.The new trend in S-shaped diffuser studies includes the integration of computational and data-driven methods.展开更多
Conversion of ammonia into hydrogen,a crucial pathway for the hydrogen economy,is severely constrained by the intricacy of the required equipment and the low efficiency.Herein,Pd@Pt Ni Co Ru Ir coreshell mesoporous bi...Conversion of ammonia into hydrogen,a crucial pathway for the hydrogen economy,is severely constrained by the intricacy of the required equipment and the low efficiency.Herein,Pd@Pt Ni Co Ru Ir coreshell mesoporous bifunctional electrocatalysts were fabricated via a one-step wet-chemical reduction approach.By utilizing the limiting effect of triblock copolymers,gradient distribution control of six metal elements(Pd core and Pt/Ni/Co/Ru/Ir high-entropy alloys shell) was achieved,where the high-entropy alloy shell forms high-density active sites through lattice distortion effect.With the help of lattice distortion and mesoporous-confinement-enabled interfacial coupling effects,Pd@Pt Ni Co Ru Ir catalyst exhibited exceptional bifunctional performance in alkaline media:A low hydrogen evolution reaction(HER) overpotential of 30.5 m V at 10 m A/cm^(2) and a high ammonia oxidation reaction(AOR) peak current density of 19.6 m A/cm^(2) at 0.7 V vs.RHE,representing a 3.83-fold enhancement over commercial Pt/C.Moreover,a rechargeable Zn-NH_(3) battery system was constructed and achieved 92.3 % Faradaic efficiency(FE) for NH_(3)-to-H_(2) conversion with outstanding stability at 16 m A/cm^(2),thereby providing an innovative solution for efficient ammonia decomposition-based hydrogen production.展开更多
Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressi...Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressing these shortcomings,thiswork presents a robust 15-level PackedUCell(PUC)inverter topology designed for renewable energy and grid-connected applications.The proposed systemintegrates a sensor less proportional-resonant(PR)controller with an advanced carrier-based pulse width modulation scheme.This approach efficiently balances capacitor voltage,minimizes steady-state error,and strongly suppresses both zero and third-order harmonics resulting in reduced total harmonic distortion and enhanced voltage regulation.Additionally,a novel switching algorithm simplifies the design and implementation,further lowering voltage stress across switches.Extensive simulation results validate the performance under various resistive and resistive-inductive load conditions,demonstrating compliance with IEEE-519 THD standards and robust operation under dynamic changes.The proposed sensorless PR-controlled 15-PUC inverter thus offers a compelling,cost-effective solution for efficient power conversion in next-generation renewable energy systems.展开更多
As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding...As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.展开更多
Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length...Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length reduction of a bare S-shaped diffuser to an aggressive S-shaped diffuser would risk flow separation and performance reduction of the diffuser and the air intake of the GT.The objective of this research is to propose and assess fitted energy promoters(EPs)to enhance the S-shaped diffuser performance by controlling and modifying the flow in the high bending zone of the diffuser.After experimental assessment,the work has been extended to cover more cases by numerical investigations on bare,bare aggressive,and aggressive with energy promoters S-shaped diffusers.Three types of EPs,namely co-rotating low-profile,co-rotating streamline sheet,and trapezoidal submerged EPs were tested with various combinations over a range of Reynolds numbers from 40,000 to 75,000.The respective S-shaped diffusers were simulated by computational fluid dynamics(CFD)using ANSYS software adopting a steady,3D,standard k-εturbulence model to acquire the details of the flow structure,which cannot be visualized in the experiment.The diffuser performance has been evaluated by the performance indicators of static pressure recovery coefficient,total pressure loss coefficient,and distortion coefficient(DC(45°)).The enhancements in the static pressure recovery of the S-shaped aggressive diffuser with energy promoters are 19.5%,22.2%,and 24.5%with EPs at planes 3,4 and 5,respectively,compared to the aggressive bare diffuser.In addition,the installation of the EPs resulted in a DC(45°)reduction at the outlet plane of the diffuser of about 43%at Re=40,000.The enhancements in the performance parameters confirm that aggravating the internal flow eliminates the flow separation and enhances the GT intake efficiency.展开更多
Improvements in surgical techniques have led to 90% success in the surgical repair of rhegmatogenous retinal detachment(RRD).However,anatomical reattachment of the retina does not ensure complete recovery of visual fu...Improvements in surgical techniques have led to 90% success in the surgical repair of rhegmatogenous retinal detachment(RRD).However,anatomical reattachment of the retina does not ensure complete recovery of visual function.The incidence of metamorphopsia remains the most common postoperative complaint,from 24% to 88.6%.Currently,the risk factors of metamorphopsia are categorized into macular involvement,retinal shift,outer retinal folds,subretinal fluid,secondary epiretinal membrane,outer retinal layer damage,and surgical approach.The associations of metamorphopsia with postoperative best-corrected visual acuity and postoperative vision-related quality of life were still controversial.The most popular methods for assessment of metamorphopsia remain the Amsler grid and M-Charts.Most treatments cannot progress beyond the management of negative visual sensations,through methods such as occlusion therapy and aniseikonia-correcting spectacles.The main treatment approach involves RRD prevention and the management of risk factors that can lead to postoperative metamorphopsia after RRD repair.Additional research concerning metamorphopsia treatment,further upgrades of auxiliary inspection methods,and more accurate microstructural assessments are needed to address this common complication.展开更多
Sulfide-based all-solid-state lithium batteries suffer from electrochemo-mechanical damage to Ni-rich oxide-based cathode active materials(CAMs),primarily caused by severe volume changes,results in significant stress ...Sulfide-based all-solid-state lithium batteries suffer from electrochemo-mechanical damage to Ni-rich oxide-based cathode active materials(CAMs),primarily caused by severe volume changes,results in significant stress and strain,causes micro-cracks and interfacial contact loss at potentials>4.3 V(vs.Li/Li^(+)).Quantifying micro-cracks and voids in CAMs can reveal the degradation mechanisms of Ni-rich oxidebased cathodes during electrochemical cycling.Nonetheless,the origin of electrochemical-mechanical damage remains unclear.Herein,We have developed a multifunctional PEG-based soft buffer layer(SBL)on the surface of carbon black(CB).This layer functions as a percolation network in the single crystal LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)and Li_(6)PS_(5)Cl composite cathode layer,ensuring superior ionic conductivity,reducing void formation and particle cracking,and promoting uniform utilization of the cathode active material in all-solid-state lithium batteries(ASSLBs).High-angle annular dark-field STEM combined with nanoscale X-ray holo-tomography and plasma-focused ion beam scanning electron microscopy confirmed that the PEG-based SBL mitigated strain induced by reaction heterogeneity in the cathode.This strain produces lattice stretches,distortions,and curved transition metal oxide layers near the surface,contributing to structural degradation at elevated voltages.Consequently,ASSLBs with a LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)cathode containing LCCB-10(CB/PEG mass ratio:100/10)demonstrate a high areal capacity(2.53 mAh g^(-1)/0.32 mA g^(-1))and remarkable rate capability(0.58 mAh g^(-1)at 1.4 mA g^(-1)),with88%capacity retention over 1000 cycles.展开更多
Intergrowth ferroelectric semiconductors with excellent spontaneous polarization field are highly promising piezo-photocatalytic candidate materials.In addition,developing structural design and revealing polarization ...Intergrowth ferroelectric semiconductors with excellent spontaneous polarization field are highly promising piezo-photocatalytic candidate materials.In addition,developing structural design and revealing polarization enhancement in-depth mechanism are top priorities.Herein,we introduce the intergrowth ferroelectrics Bi_(7)Ti_(4)NbO_(21)thin-layer nanosheets for piezo-photocatalytic CO_(2)reduction.Density functional theory(DFT)calculations indicate that interlayer lattice mismatch leads to increased tilting and rotation angle of Ti/NbO_(6)octahedra on perovskite-like layers,serving as the main reason for increased polarization.Furthermore,the tilting and rotation angle of the interlayer octahedron further increase under stress,suggesting a stronger driving force generated to facilitate charge carrier separation efficiency.Meanwhile,Bi_(7)Ti_(4)NbO_(21)nanosheets provide abundant active sites to effectively adsorb CO_(2)and acquire sensitive stress response,thereby presenting synergistically advanced piezo-photocatalytic CO_(2)reduction activity with a high CO generation rate of 426.97μmol g^(-1)h^(-1).Our work offers new perspectives and directions for initiating and investigating the mechanisms of high-performance intergrowth piezo-photocatalysts.展开更多
1.C.Li,"Holding‘China Inc.’Together:The CCP and The Rise of China’s Yangqi",The China Quarterly,Vol.228,2016,pp.927-949.2.J.Gao,"‘Bypass the Lying Mouths’:How Does the CCP Tackle Information Distor...1.C.Li,"Holding‘China Inc.’Together:The CCP and The Rise of China’s Yangqi",The China Quarterly,Vol.228,2016,pp.927-949.2.J.Gao,"‘Bypass the Lying Mouths’:How Does the CCP Tackle Information Distortion at Local Levels?",The China Quarterly,Vol.228,2016,pp.950-969.3.C.Sorace,"Party Spirit Made Flesh:The Production of Legitimacy in the Aftermath of the 2008Sichuan Earthquake",The China Journal,Vol.76,2016,pp.41-62.4.Y.Yeo,"Complementing the Local Discipline Inspection Commissions of the CCP:Empowerment of the Central Inspection Groups",Journal of Contemporary China,Vol.25,No.97,2016,pp.59-74.展开更多
The conversion of CO_(2)to dimethyl carbonate(DMC)offers a promising route for CO_(2)utilization.In this study,four CeO2 catalysts with distinct nanostructures were synthesized via a template-free hydrothermal method ...The conversion of CO_(2)to dimethyl carbonate(DMC)offers a promising route for CO_(2)utilization.In this study,four CeO2 catalysts with distinct nanostructures were synthesized via a template-free hydrothermal method by systematically varying the types and concentrations of precipitants as well as the hydrothermal reaction conditions,and they were employed for DMC synthesis from CO_(2)and methanol.The atomic arrangements of CeO_(2)varied significantly with its morphology,leading to differences in lattice distortion,which directly influenced the concentration of oxygen vacancies.Notably,the CeO_(2)nanospheres,which exhibited the highest lattice distortion and oxygen vacancy concentration,achieved a DMC yield(11.12 mmol/g)48 times greater than that of the nanocubes(0.23 mmol/g).The results indicated that oxygen vacancies played a pivotal role in the catalytic process by facilitating the adsorption and activation of CO_(2)to form bidentate carbonates,as well as activating methanol to generate methoxy species.These processes collectively promoted the formation of the key intermediate(*CH3OCOO).This study proposes a strategy to enhance the oxygen vacancy concentration by increasing lattice distortion,providing valuable insights for designing high-performance CeO_(2)catalysts for DMC synthesis.展开更多
Collecting amounts of distorted/clean image pairs in the real world is non-trivial,which severely limits the practical application of these supervised learning-based methods to real-world image super-resolution(RealSR...Collecting amounts of distorted/clean image pairs in the real world is non-trivial,which severely limits the practical application of these supervised learning-based methods to real-world image super-resolution(RealSR).Previous works usually address this problem by leveraging unsupervised learning-based technologies to alleviate the dependency on paired training samples.However,these methods typically suffer from unsatisfactory texture synthesis due to the lack of supervision of clean images.To overcome this problem,we are the first to take a close look at the under-explored direction for RealSR,i.e.,few-shot real-world image super-resolution,which aims to tackle the challenging RealSR problem with few-shot distorted/clean image pairs.Under this brand-new scenario,we propose distortion relation guided transfer learning(DRTL)for the few-shot RealSR by transferring the rich restoration knowledge from auxiliary distortions(i.e.,synthetic distortions)to the target RealSR under the guidance of the distortion relation.Concretely,DRTL builds a knowledge graph to capture the distortion relation between auxiliary distortions and target distortion(i.e.,real distortions in RealSR).Based on the distortion relation,DRTL adopts a gradient reweighting strategy to guide the knowledge transfer process between auxiliary distortions and target distortions.In this way,DRTL is able to quickly learn the most relevant knowledge from the synthetic distortions for the target distortion.We instantiate DRTL with two commonly-used transfer learning paradigms,including pretraining and meta-learning pipelines,to realize a distortion relation-aware few-shot RealSR.Extensive experiments on multiple benchmarks and thorough ablation studies demonstrate the effectiveness of our DRTL.展开更多
Despite the global attention towards pollution,it remains a significant global threat and challenge for both developed and developing countries.Urbanization and economic development influence different types of pollut...Despite the global attention towards pollution,it remains a significant global threat and challenge for both developed and developing countries.Urbanization and economic development influence different types of pollution.Visual pollution is considered a new phenomenon referring to the impact of existing and growing mainstream pollution which impairs an individual’s ability to enjoy visits or views.Recently,Jordanian cities have expanded in response to urbanization and ongoing development.Irbid City has the second largest population in Jordan after the capital Amman City highest population density in Jordan.In the modern era,Irbid City dramatically increased in population and dimension.The growth of the demographic population has been significant and has led to overpopulation,rapid urbanization,and unresolved problems associated with spatial planning and infrastructures leading to different types of pollution including visual pollution.The study area focuses on the city center with the most crowded population through field visits and actual observations.The study technique is descriptive and analytical,with a focus on meticulous monitoring and a follow-up-based questionnaire which is a tool for the study,involving data collection,classification,presentation,analysis,interpretation,and exploration to identify new facts and generalizations that can help solve current issues of visual pollution.The study provides recommendations for Irbid Municipal to eliminate visual pollution,in parallel with stricter supervision from the municipality during the building process to ensure proper implementation of the new rules,adopting an integrated policy for the city with the rest of the social,political,sensory,cultural,economic,and functional aspects,so that this policy is in the short and long term.展开更多
Indian Railways have been the largest people moving transport infrastructure in India.Over the years the systems and trains have been upgraded resulting in both better passenger amenities and reduction in travel time....Indian Railways have been the largest people moving transport infrastructure in India.Over the years the systems and trains have been upgraded resulting in both better passenger amenities and reduction in travel time.The newest addition is the Vande Bharat Express,a semi-high-speed train that was introduced in India in 2019.The train currently runs between 10 routes and has brought significant changes to India’s railway network.This article explores the introduction of Vande Bharat Express trains in India and its effects on the country’s interstation time-space shrinkage using cartographic techniques.The cartographic techniques like stepwise multidimensional scaling and interpolation using the distance cartogram plugin in QGIS are mainly used for generating the time-space maps for various speeds.The limitations of these techniques and the methods to overcome those limitations are also explored in this article.展开更多
Images with complementary spectral information can be recorded using image sensors that can identify visible and near-infrared spectrum.The fusion of visible and nearinfrared(NIR)aims to enhance the quality of images ...Images with complementary spectral information can be recorded using image sensors that can identify visible and near-infrared spectrum.The fusion of visible and nearinfrared(NIR)aims to enhance the quality of images acquired by video monitoring systems for the ease of user observation and data processing.Unfortunately,current fusion algorithms produce artefacts and colour distortion since they cannot make use of spectrum properties and are lacking in information complementarity.Therefore,an information complementarity fusion(ICF)model is designed based on physical signals.In order to separate high-frequency noise from important information in distinct frequency layers,the authors first extracted texture-scale and edge-scale layers using a two-scale filter.Second,the difference map between visible and near-infrared was filtered using the extended-DoG filter to produce the initial visible-NIR complementary weight map.Then,to generate a guide map,the near-infrared image with night adjustment was processed as well.The final complementarity weight map was subsequently derived via an arctanI function mapping using the guide map and the initial weight maps.Finally,fusion images were generated with the complementarity weight maps.The experimental results demonstrate that the proposed approach outperforms the state-of-the-art in both avoiding artificial colours as well as effectively utilising information complementarity.展开更多
Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challe...Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challenge for cutting-edge applications. Here, a high-entropy strategy is proposed to construct multiple local distortions, including various types of oxygen octahedral tilts, highly dynamic polar nanoregions, and lattice distortions. This approach effectively delays polarization saturation, reduces energy loss, and, in conjunction with the ultrafine grains induced by the high-entropy effect, enhances mechanical properties and breakdown field. Therefore, a remarkable recoverable energy density of 9.1 J cm-3, a high conversion efficiency of 82.7 %, and a large Vickers hardness of 8.77 GPa are simultaneously achieved in 0.73Bi_(0.47)Na_(0.47)Ba_(0.06)TiO_(3)-0.27Ca_(0.7)La_(0.2)Zr_(0.15)Ti_(0.85)O_(3) lead-free high-entropy relaxors. Additionally, superior frequency and temperature stability, as well as excellent charge/discharge performance, are also obtained. These findings demonstrate that the high-entropy strategy is a promising method for designing high-performance dielectric ceramics.展开更多
5-Hydroxymethylfurfural electrooxidation reaction(HMFOR)provides a promising route for producing highvalue-added compounds.It is generally believed that NiOOH is the active species in HMFOR process,but its inherently ...5-Hydroxymethylfurfural electrooxidation reaction(HMFOR)provides a promising route for producing highvalue-added compounds.It is generally believed that NiOOH is the active species in HMFOR process,but its inherently poor electron transfer ability leads to limited catalytic activity.In this work,a W doping strategy is adopted to regulate the electron transfer between NiOOH and reaction molecules.Electrochemical results show that W-doped Ni_(5)P_(4)-R exhibits excellent electrochemical performance for the oxidation of HMF to FDCA with the conversion of HMF and yield of FDCA both close to~100%.Density functional theory and in-situ characterization reveal that the introduction of W causes the distortion of NiOOH lattice,resulting in the Jahn-Teller distortion and the elimination of orbital degeneracy,thereby broadening the e_(g)^(*)band of NiOOH.This feature is beneficial for the electron transfer between W-doped NiOOH and HMF(1.31 e^(-)),thereby promoting the C–H bond activation of the aldehyde group in HMF and effectively reducing the energy barrier of rate-determining step(RDS).展开更多
The traditional orbit determination method based on pulsar profile distortion can determine the six elements of the orbit.However,the estimation accuracies of these methods are limited and the computational load of a ...The traditional orbit determination method based on pulsar profile distortion can determine the six elements of the orbit.However,the estimation accuracies of these methods are limited and the computational load of a six-dimensional search is huge.To solve this problem,the differential-geometry-based Multi-dimensional Joint Position-Velocity Estimation(MJPVE)using Crab pulsar profile distortion is proposed in this paper.Firstly,through theoretical analysis,it is found that the pulsar profile distortion caused by the initial state error in some joint positionvelocity directions is very small.In other words,the accuracies of estimation in these directions are very low.Namely,the search dimension can be reduced,which in turn greatly reduces the computational load.Then,we construct the chi-squared function of the pulsar profile with respect to the estimation error in joint position-velocity direction and use differential geometry to find the joint position-velocity directions corresponding to different degrees of distortion.Finally,we utilize the grid search based on directory folding in these joint position-velocity directions corresponding to large degrees of distortion to obtain the joint position-velocity estimation.The experimental results show that compared with the grouping bi-chi-squared inversion method,MJPVE has high precision and extensive navigation information.展开更多
In response to the complex working conditions of the power grid caused by the high proportion of new energy access,which leads to insufficient output accuracy of the second-order generalized integrator(SOGI)phaselocke...In response to the complex working conditions of the power grid caused by the high proportion of new energy access,which leads to insufficient output accuracy of the second-order generalized integrator(SOGI)phaselocked loop,this article proposes an improved frequency adaptive phase-locked loop structure for SOGI.Firstly,an amplitude compensation branch is introduced to compensate for the SOGI tracking fundamental frequency signal,ensuring the accuracy of the SOGI output orthogonal signal under frequency fluctuation conditions.Secondly,by cascading two adaptive SOGI modules,the suppression capability of low-order harmonics and Direct Current(DC)components has been improved.Finally,the positive and negative sequence separation method of orthogonal signals is introduced to eliminate the influence of unbalanced components on the phase-locked loop.The comparative experiment with the classic SOGI-PLL method shows that the proposed phase-locked loop structure effectively improves the accuracy of power grid synchronization detection under complex working conditions such as harmonic components,unbalanced components,and frequency fluctuations.It can complete frequency detection within 1.5 power frequency cycles,and the detected fundamental frequency positive sequence voltage has a higher sinuosity and harmonic distortion rate within 0.5%.展开更多
The Vienna rectifier is a widely adopted solution for high-power rectification due to its efficiency and straightforward design.However,its performance can degrade under unbalanced three phase voltage conditions,leadi...The Vienna rectifier is a widely adopted solution for high-power rectification due to its efficiency and straightforward design.However,its performance can degrade under unbalanced three phase voltage conditions,leading to current zero-crossing distortion and compromised dynamic response.This paper investigates the causes of these distortions,identifying a phase shift between the input current and the grid voltage as a primary factor,and proposes an effective distortion phase identification strategy.Furthermore,the dynamic performance is enhanced through improved current reference calculations and a refined power feedforward strategy.This approach optimizes the system's response to load changes and maintains output voltage stability under unbalanced conditions.Simulation results validate the effectiveness of the proposed methods in reducing current distortion and improving overall performance.展开更多
This study designs and synthesizes highly dense Li2 Mg_(6)ZnTi_(6)O_(20)microwave dielectric ceramics based on a high-entropy strategy,focusing on achieving stable structures,low sintering temperatures,and excellent c...This study designs and synthesizes highly dense Li2 Mg_(6)ZnTi_(6)O_(20)microwave dielectric ceramics based on a high-entropy strategy,focusing on achieving stable structures,low sintering temperatures,and excellent comprehensive performance.The ceramics exhibit a predominant face-centered cubic disordered phase(Fd-3 m)sintered at 1200-1280℃,alongside an increased presence of the second phase MgTiO_(3) at higher temperatures.Remarkably,these ceramics demonstrate excellent microwave dielectric properties(ε_(r)=16.69,Q×f=88,230 GHz,and τ_(f)=−36.5 ppm/℃).Additionally,we have explored the addition of x wt%LiF(1≤x≤5)to the Li2 Mg_(6)ZnTi_(6)O_(20)ceramics to enhance their applicability.The ceramics feature a spinel structure for LiF contents up to 3 wt%,while higher LiF concentrations induce the formation of a secondary phase,LiTiO2,characterized by a rock salt structure.Notably,the lattice distortion induced by LiF leads to a constant decrease in ε_(r).A moderate degree of lattice distortion serves to enhance the lattice stability of ceramics,which is reflected in increased lattice energy.Excellent microwave dielectric properties(ε_(r)=16.23,Q×f=89,728 GHz,τ_(f)=−43.5 ppm/℃)were obtained for x=3 ceramic sintered at 1140℃.Even at x=5,the ceramic retains excellent microwave dielectric properties(ε_(r)=16.02,Q×f=63,079 GHz,τ_(f)=−26 ppm/°C)at a low sintering temperature of 900°C.This work realizes the multiple effects of LiF and confirms good chemical compatibility with silver for LTCC(low-temperature co-fired ceramics)applications.展开更多
文摘Gas Turbines are among the most important energy systems for aviation and thermal-based power generation.The performance of gas turbine intakes with S-shaped diffusers is vulnerable to flow separation,reversal flow,and pressure distortion,mainly in aggressive S-shaped diffusers.Severalmethods,including vortex generators and energy promoters,have been proposed and investigated both experimentally and numerically.This paper compiles a review of experimental investigations that have been performed and reported to mitigate flow separation and restore system performance.The operational principles,classifications,design geometries,and performance parameters of Sshaped diffusers are presented to facilitate the analysis and understanding of the influence of each mitigation method on flowenhancement in S-shaped diffusers.Theinfluencing design parameters on the performance of the S-shaped diffuser and the findings achieved by various experimental investigations are discussed and compared.The review concludes that reducing the intake length reduces the size and weight of the gas turbine,leading to a higher power-to-weight ratio.However,the main challenge in shortening the S-shaped diffusers is the flow separation in the high-curvature section,which must be prevented to maintain high performance.Prevention can be achieved through flow control methods,which are categorized into passive and aggressive methods.The static pressure recovery coefficient,total pressure loss coefficient,ideal static pressure coefficient,distortion coefficient,and skin friction coefficient are the primary performance evaluation and comparison parameters between the experimentally investigated mitigation methods.The new trend in S-shaped diffuser studies includes the integration of computational and data-driven methods.
基金provided by the National Natural Science Foundation of China (No.52573275)Taishan Scholars Program of Shandong Province (No.tsqn202507205)+4 种基金Youth Innovation Team of Higher Education Institutions in Shandong Province (No.2023KJ105)Collaborative Innovation Center of Yellow River Basin Pharmaceutical Green Manufacturing and Engineering Equipment,University of Jinan,Jinan 250022,ChinaJinan City University Integration Development Strategy Project (No.JNSX2023021)supported by Talents’ plan Foundation of Guangdong Second Provincial General Hospital (No.2024D003)Science and Technology Projects in Guangzhou (No.2025A04J4629)。
文摘Conversion of ammonia into hydrogen,a crucial pathway for the hydrogen economy,is severely constrained by the intricacy of the required equipment and the low efficiency.Herein,Pd@Pt Ni Co Ru Ir coreshell mesoporous bifunctional electrocatalysts were fabricated via a one-step wet-chemical reduction approach.By utilizing the limiting effect of triblock copolymers,gradient distribution control of six metal elements(Pd core and Pt/Ni/Co/Ru/Ir high-entropy alloys shell) was achieved,where the high-entropy alloy shell forms high-density active sites through lattice distortion effect.With the help of lattice distortion and mesoporous-confinement-enabled interfacial coupling effects,Pd@Pt Ni Co Ru Ir catalyst exhibited exceptional bifunctional performance in alkaline media:A low hydrogen evolution reaction(HER) overpotential of 30.5 m V at 10 m A/cm^(2) and a high ammonia oxidation reaction(AOR) peak current density of 19.6 m A/cm^(2) at 0.7 V vs.RHE,representing a 3.83-fold enhancement over commercial Pt/C.Moreover,a rechargeable Zn-NH_(3) battery system was constructed and achieved 92.3 % Faradaic efficiency(FE) for NH_(3)-to-H_(2) conversion with outstanding stability at 16 m A/cm^(2),thereby providing an innovative solution for efficient ammonia decomposition-based hydrogen production.
文摘Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressing these shortcomings,thiswork presents a robust 15-level PackedUCell(PUC)inverter topology designed for renewable energy and grid-connected applications.The proposed systemintegrates a sensor less proportional-resonant(PR)controller with an advanced carrier-based pulse width modulation scheme.This approach efficiently balances capacitor voltage,minimizes steady-state error,and strongly suppresses both zero and third-order harmonics resulting in reduced total harmonic distortion and enhanced voltage regulation.Additionally,a novel switching algorithm simplifies the design and implementation,further lowering voltage stress across switches.Extensive simulation results validate the performance under various resistive and resistive-inductive load conditions,demonstrating compliance with IEEE-519 THD standards and robust operation under dynamic changes.The proposed sensorless PR-controlled 15-PUC inverter thus offers a compelling,cost-effective solution for efficient power conversion in next-generation renewable energy systems.
文摘As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.
文摘Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length reduction of a bare S-shaped diffuser to an aggressive S-shaped diffuser would risk flow separation and performance reduction of the diffuser and the air intake of the GT.The objective of this research is to propose and assess fitted energy promoters(EPs)to enhance the S-shaped diffuser performance by controlling and modifying the flow in the high bending zone of the diffuser.After experimental assessment,the work has been extended to cover more cases by numerical investigations on bare,bare aggressive,and aggressive with energy promoters S-shaped diffusers.Three types of EPs,namely co-rotating low-profile,co-rotating streamline sheet,and trapezoidal submerged EPs were tested with various combinations over a range of Reynolds numbers from 40,000 to 75,000.The respective S-shaped diffusers were simulated by computational fluid dynamics(CFD)using ANSYS software adopting a steady,3D,standard k-εturbulence model to acquire the details of the flow structure,which cannot be visualized in the experiment.The diffuser performance has been evaluated by the performance indicators of static pressure recovery coefficient,total pressure loss coefficient,and distortion coefficient(DC(45°)).The enhancements in the static pressure recovery of the S-shaped aggressive diffuser with energy promoters are 19.5%,22.2%,and 24.5%with EPs at planes 3,4 and 5,respectively,compared to the aggressive bare diffuser.In addition,the installation of the EPs resulted in a DC(45°)reduction at the outlet plane of the diffuser of about 43%at Re=40,000.The enhancements in the performance parameters confirm that aggravating the internal flow eliminates the flow separation and enhances the GT intake efficiency.
文摘Improvements in surgical techniques have led to 90% success in the surgical repair of rhegmatogenous retinal detachment(RRD).However,anatomical reattachment of the retina does not ensure complete recovery of visual function.The incidence of metamorphopsia remains the most common postoperative complaint,from 24% to 88.6%.Currently,the risk factors of metamorphopsia are categorized into macular involvement,retinal shift,outer retinal folds,subretinal fluid,secondary epiretinal membrane,outer retinal layer damage,and surgical approach.The associations of metamorphopsia with postoperative best-corrected visual acuity and postoperative vision-related quality of life were still controversial.The most popular methods for assessment of metamorphopsia remain the Amsler grid and M-Charts.Most treatments cannot progress beyond the management of negative visual sensations,through methods such as occlusion therapy and aniseikonia-correcting spectacles.The main treatment approach involves RRD prevention and the management of risk factors that can lead to postoperative metamorphopsia after RRD repair.Additional research concerning metamorphopsia treatment,further upgrades of auxiliary inspection methods,and more accurate microstructural assessments are needed to address this common complication.
基金supported by the Hainan Province Science and Technology Special Fund(ZDYF2021SHFZ232,ZDYF2023GXJS022)the Hainan Province Postdoctoral Science Foundation(300333)the National Natural Science Foundation of China(21203008,21975025,12274025,22372008)。
文摘Sulfide-based all-solid-state lithium batteries suffer from electrochemo-mechanical damage to Ni-rich oxide-based cathode active materials(CAMs),primarily caused by severe volume changes,results in significant stress and strain,causes micro-cracks and interfacial contact loss at potentials>4.3 V(vs.Li/Li^(+)).Quantifying micro-cracks and voids in CAMs can reveal the degradation mechanisms of Ni-rich oxidebased cathodes during electrochemical cycling.Nonetheless,the origin of electrochemical-mechanical damage remains unclear.Herein,We have developed a multifunctional PEG-based soft buffer layer(SBL)on the surface of carbon black(CB).This layer functions as a percolation network in the single crystal LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)and Li_(6)PS_(5)Cl composite cathode layer,ensuring superior ionic conductivity,reducing void formation and particle cracking,and promoting uniform utilization of the cathode active material in all-solid-state lithium batteries(ASSLBs).High-angle annular dark-field STEM combined with nanoscale X-ray holo-tomography and plasma-focused ion beam scanning electron microscopy confirmed that the PEG-based SBL mitigated strain induced by reaction heterogeneity in the cathode.This strain produces lattice stretches,distortions,and curved transition metal oxide layers near the surface,contributing to structural degradation at elevated voltages.Consequently,ASSLBs with a LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)cathode containing LCCB-10(CB/PEG mass ratio:100/10)demonstrate a high areal capacity(2.53 mAh g^(-1)/0.32 mA g^(-1))and remarkable rate capability(0.58 mAh g^(-1)at 1.4 mA g^(-1)),with88%capacity retention over 1000 cycles.
基金support from the Natural Science Foundation of Jiangsu Province(BK20220596)Innovative science and technology platform project of cooperation between Yangzhou City and Yangzhou University,China(No.YZ202026305)+1 种基金Natural Science Foundation of China(21922202,21673202 and 22272147)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Intergrowth ferroelectric semiconductors with excellent spontaneous polarization field are highly promising piezo-photocatalytic candidate materials.In addition,developing structural design and revealing polarization enhancement in-depth mechanism are top priorities.Herein,we introduce the intergrowth ferroelectrics Bi_(7)Ti_(4)NbO_(21)thin-layer nanosheets for piezo-photocatalytic CO_(2)reduction.Density functional theory(DFT)calculations indicate that interlayer lattice mismatch leads to increased tilting and rotation angle of Ti/NbO_(6)octahedra on perovskite-like layers,serving as the main reason for increased polarization.Furthermore,the tilting and rotation angle of the interlayer octahedron further increase under stress,suggesting a stronger driving force generated to facilitate charge carrier separation efficiency.Meanwhile,Bi_(7)Ti_(4)NbO_(21)nanosheets provide abundant active sites to effectively adsorb CO_(2)and acquire sensitive stress response,thereby presenting synergistically advanced piezo-photocatalytic CO_(2)reduction activity with a high CO generation rate of 426.97μmol g^(-1)h^(-1).Our work offers new perspectives and directions for initiating and investigating the mechanisms of high-performance intergrowth piezo-photocatalysts.
文摘1.C.Li,"Holding‘China Inc.’Together:The CCP and The Rise of China’s Yangqi",The China Quarterly,Vol.228,2016,pp.927-949.2.J.Gao,"‘Bypass the Lying Mouths’:How Does the CCP Tackle Information Distortion at Local Levels?",The China Quarterly,Vol.228,2016,pp.950-969.3.C.Sorace,"Party Spirit Made Flesh:The Production of Legitimacy in the Aftermath of the 2008Sichuan Earthquake",The China Journal,Vol.76,2016,pp.41-62.4.Y.Yeo,"Complementing the Local Discipline Inspection Commissions of the CCP:Empowerment of the Central Inspection Groups",Journal of Contemporary China,Vol.25,No.97,2016,pp.59-74.
基金National Natural Science Foundation of China(22008166)Fundamental Research Program of Shanxi Province(202403021211029,201901D211047).
文摘The conversion of CO_(2)to dimethyl carbonate(DMC)offers a promising route for CO_(2)utilization.In this study,four CeO2 catalysts with distinct nanostructures were synthesized via a template-free hydrothermal method by systematically varying the types and concentrations of precipitants as well as the hydrothermal reaction conditions,and they were employed for DMC synthesis from CO_(2)and methanol.The atomic arrangements of CeO_(2)varied significantly with its morphology,leading to differences in lattice distortion,which directly influenced the concentration of oxygen vacancies.Notably,the CeO_(2)nanospheres,which exhibited the highest lattice distortion and oxygen vacancy concentration,achieved a DMC yield(11.12 mmol/g)48 times greater than that of the nanocubes(0.23 mmol/g).The results indicated that oxygen vacancies played a pivotal role in the catalytic process by facilitating the adsorption and activation of CO_(2)to form bidentate carbonates,as well as activating methanol to generate methoxy species.These processes collectively promoted the formation of the key intermediate(*CH3OCOO).This study proposes a strategy to enhance the oxygen vacancy concentration by increasing lattice distortion,providing valuable insights for designing high-performance CeO_(2)catalysts for DMC synthesis.
基金supported by the National Natural Science Foundation of China(623B2098,62021001,62371434)the Postdoctoral Fellowship Program of CPSF(GZC20252293)+1 种基金the China Postdoctoral Science Foundation–Anhui Joint Support Program(2024T017AH)Anhui Postdoctoral Scientific Research Program Foundation(2025A1015).
文摘Collecting amounts of distorted/clean image pairs in the real world is non-trivial,which severely limits the practical application of these supervised learning-based methods to real-world image super-resolution(RealSR).Previous works usually address this problem by leveraging unsupervised learning-based technologies to alleviate the dependency on paired training samples.However,these methods typically suffer from unsatisfactory texture synthesis due to the lack of supervision of clean images.To overcome this problem,we are the first to take a close look at the under-explored direction for RealSR,i.e.,few-shot real-world image super-resolution,which aims to tackle the challenging RealSR problem with few-shot distorted/clean image pairs.Under this brand-new scenario,we propose distortion relation guided transfer learning(DRTL)for the few-shot RealSR by transferring the rich restoration knowledge from auxiliary distortions(i.e.,synthetic distortions)to the target RealSR under the guidance of the distortion relation.Concretely,DRTL builds a knowledge graph to capture the distortion relation between auxiliary distortions and target distortion(i.e.,real distortions in RealSR).Based on the distortion relation,DRTL adopts a gradient reweighting strategy to guide the knowledge transfer process between auxiliary distortions and target distortions.In this way,DRTL is able to quickly learn the most relevant knowledge from the synthetic distortions for the target distortion.We instantiate DRTL with two commonly-used transfer learning paradigms,including pretraining and meta-learning pipelines,to realize a distortion relation-aware few-shot RealSR.Extensive experiments on multiple benchmarks and thorough ablation studies demonstrate the effectiveness of our DRTL.
文摘Despite the global attention towards pollution,it remains a significant global threat and challenge for both developed and developing countries.Urbanization and economic development influence different types of pollution.Visual pollution is considered a new phenomenon referring to the impact of existing and growing mainstream pollution which impairs an individual’s ability to enjoy visits or views.Recently,Jordanian cities have expanded in response to urbanization and ongoing development.Irbid City has the second largest population in Jordan after the capital Amman City highest population density in Jordan.In the modern era,Irbid City dramatically increased in population and dimension.The growth of the demographic population has been significant and has led to overpopulation,rapid urbanization,and unresolved problems associated with spatial planning and infrastructures leading to different types of pollution including visual pollution.The study area focuses on the city center with the most crowded population through field visits and actual observations.The study technique is descriptive and analytical,with a focus on meticulous monitoring and a follow-up-based questionnaire which is a tool for the study,involving data collection,classification,presentation,analysis,interpretation,and exploration to identify new facts and generalizations that can help solve current issues of visual pollution.The study provides recommendations for Irbid Municipal to eliminate visual pollution,in parallel with stricter supervision from the municipality during the building process to ensure proper implementation of the new rules,adopting an integrated policy for the city with the rest of the social,political,sensory,cultural,economic,and functional aspects,so that this policy is in the short and long term.
文摘Indian Railways have been the largest people moving transport infrastructure in India.Over the years the systems and trains have been upgraded resulting in both better passenger amenities and reduction in travel time.The newest addition is the Vande Bharat Express,a semi-high-speed train that was introduced in India in 2019.The train currently runs between 10 routes and has brought significant changes to India’s railway network.This article explores the introduction of Vande Bharat Express trains in India and its effects on the country’s interstation time-space shrinkage using cartographic techniques.The cartographic techniques like stepwise multidimensional scaling and interpolation using the distance cartogram plugin in QGIS are mainly used for generating the time-space maps for various speeds.The limitations of these techniques and the methods to overcome those limitations are also explored in this article.
基金supports in part by the Natural Science Foundation of China(NSFC)under contract No.62171253the Young Elite Scientists Sponsorship Program by CAST under program No.2022QNRC001,as well as the Fundamental Research Funds for the Central Universities.
文摘Images with complementary spectral information can be recorded using image sensors that can identify visible and near-infrared spectrum.The fusion of visible and nearinfrared(NIR)aims to enhance the quality of images acquired by video monitoring systems for the ease of user observation and data processing.Unfortunately,current fusion algorithms produce artefacts and colour distortion since they cannot make use of spectrum properties and are lacking in information complementarity.Therefore,an information complementarity fusion(ICF)model is designed based on physical signals.In order to separate high-frequency noise from important information in distinct frequency layers,the authors first extracted texture-scale and edge-scale layers using a two-scale filter.Second,the difference map between visible and near-infrared was filtered using the extended-DoG filter to produce the initial visible-NIR complementary weight map.Then,to generate a guide map,the near-infrared image with night adjustment was processed as well.The final complementarity weight map was subsequently derived via an arctanI function mapping using the guide map and the initial weight maps.Finally,fusion images were generated with the complementarity weight maps.The experimental results demonstrate that the proposed approach outperforms the state-of-the-art in both avoiding artificial colours as well as effectively utilising information complementarity.
基金supported by the National Natural Science Foundation of China(No.52102129)the Hunan Provin-cial Natural Science Foundation of China(No.2023JJ30138)the Science and Technology Innovation Program of Hunan Province(2023RC3094).
文摘Dielectric ceramics with ultrahigh power density and ultrafast charge/discharge rates are crucial components of advanced dielectric capacitors. However, enhancing their comprehensive performance remains a major challenge for cutting-edge applications. Here, a high-entropy strategy is proposed to construct multiple local distortions, including various types of oxygen octahedral tilts, highly dynamic polar nanoregions, and lattice distortions. This approach effectively delays polarization saturation, reduces energy loss, and, in conjunction with the ultrafine grains induced by the high-entropy effect, enhances mechanical properties and breakdown field. Therefore, a remarkable recoverable energy density of 9.1 J cm-3, a high conversion efficiency of 82.7 %, and a large Vickers hardness of 8.77 GPa are simultaneously achieved in 0.73Bi_(0.47)Na_(0.47)Ba_(0.06)TiO_(3)-0.27Ca_(0.7)La_(0.2)Zr_(0.15)Ti_(0.85)O_(3) lead-free high-entropy relaxors. Additionally, superior frequency and temperature stability, as well as excellent charge/discharge performance, are also obtained. These findings demonstrate that the high-entropy strategy is a promising method for designing high-performance dielectric ceramics.
基金supported by the National Natural Science Foundation of China(22479031,22162004)the Natural Science Foundation of Guangxi(2022JJD120011)the High-performance Computing Platform of Guangxi University.
文摘5-Hydroxymethylfurfural electrooxidation reaction(HMFOR)provides a promising route for producing highvalue-added compounds.It is generally believed that NiOOH is the active species in HMFOR process,but its inherently poor electron transfer ability leads to limited catalytic activity.In this work,a W doping strategy is adopted to regulate the electron transfer between NiOOH and reaction molecules.Electrochemical results show that W-doped Ni_(5)P_(4)-R exhibits excellent electrochemical performance for the oxidation of HMF to FDCA with the conversion of HMF and yield of FDCA both close to~100%.Density functional theory and in-situ characterization reveal that the introduction of W causes the distortion of NiOOH lattice,resulting in the Jahn-Teller distortion and the elimination of orbital degeneracy,thereby broadening the e_(g)^(*)band of NiOOH.This feature is beneficial for the electron transfer between W-doped NiOOH and HMF(1.31 e^(-)),thereby promoting the C–H bond activation of the aldehyde group in HMF and effectively reducing the energy barrier of rate-determining step(RDS).
基金supported in part by the National Natural Science Foundation of China(Nos.61873196,62373030,61772187)the Innovation Program for Quantum Science and Technology(No.2021ZD0303400)。
文摘The traditional orbit determination method based on pulsar profile distortion can determine the six elements of the orbit.However,the estimation accuracies of these methods are limited and the computational load of a six-dimensional search is huge.To solve this problem,the differential-geometry-based Multi-dimensional Joint Position-Velocity Estimation(MJPVE)using Crab pulsar profile distortion is proposed in this paper.Firstly,through theoretical analysis,it is found that the pulsar profile distortion caused by the initial state error in some joint positionvelocity directions is very small.In other words,the accuracies of estimation in these directions are very low.Namely,the search dimension can be reduced,which in turn greatly reduces the computational load.Then,we construct the chi-squared function of the pulsar profile with respect to the estimation error in joint position-velocity direction and use differential geometry to find the joint position-velocity directions corresponding to different degrees of distortion.Finally,we utilize the grid search based on directory folding in these joint position-velocity directions corresponding to large degrees of distortion to obtain the joint position-velocity estimation.The experimental results show that compared with the grouping bi-chi-squared inversion method,MJPVE has high precision and extensive navigation information.
基金supported by the Science and Technology Project of China Southern Power Grid Co.,Ltd.(Grant No.ZBKJXM20232471)the National Key R&D Program of China(Grant No.2021YFB1600200)the Innovation Capability Support Program of Shaanxi(Grant No.2022KXJ-144)。
文摘In response to the complex working conditions of the power grid caused by the high proportion of new energy access,which leads to insufficient output accuracy of the second-order generalized integrator(SOGI)phaselocked loop,this article proposes an improved frequency adaptive phase-locked loop structure for SOGI.Firstly,an amplitude compensation branch is introduced to compensate for the SOGI tracking fundamental frequency signal,ensuring the accuracy of the SOGI output orthogonal signal under frequency fluctuation conditions.Secondly,by cascading two adaptive SOGI modules,the suppression capability of low-order harmonics and Direct Current(DC)components has been improved.Finally,the positive and negative sequence separation method of orthogonal signals is introduced to eliminate the influence of unbalanced components on the phase-locked loop.The comparative experiment with the classic SOGI-PLL method shows that the proposed phase-locked loop structure effectively improves the accuracy of power grid synchronization detection under complex working conditions such as harmonic components,unbalanced components,and frequency fluctuations.It can complete frequency detection within 1.5 power frequency cycles,and the detected fundamental frequency positive sequence voltage has a higher sinuosity and harmonic distortion rate within 0.5%.
文摘The Vienna rectifier is a widely adopted solution for high-power rectification due to its efficiency and straightforward design.However,its performance can degrade under unbalanced three phase voltage conditions,leading to current zero-crossing distortion and compromised dynamic response.This paper investigates the causes of these distortions,identifying a phase shift between the input current and the grid voltage as a primary factor,and proposes an effective distortion phase identification strategy.Furthermore,the dynamic performance is enhanced through improved current reference calculations and a refined power feedforward strategy.This approach optimizes the system's response to load changes and maintains output voltage stability under unbalanced conditions.Simulation results validate the effectiveness of the proposed methods in reducing current distortion and improving overall performance.
基金supported by the National Natural Science Foundation of China(No.52102129)the Hunan Provincial Natural Science Foundation of China(No.2023JJ30138)the Science and Technology Innovation Program of Hunan Province(No.2023RC3094).
文摘This study designs and synthesizes highly dense Li2 Mg_(6)ZnTi_(6)O_(20)microwave dielectric ceramics based on a high-entropy strategy,focusing on achieving stable structures,low sintering temperatures,and excellent comprehensive performance.The ceramics exhibit a predominant face-centered cubic disordered phase(Fd-3 m)sintered at 1200-1280℃,alongside an increased presence of the second phase MgTiO_(3) at higher temperatures.Remarkably,these ceramics demonstrate excellent microwave dielectric properties(ε_(r)=16.69,Q×f=88,230 GHz,and τ_(f)=−36.5 ppm/℃).Additionally,we have explored the addition of x wt%LiF(1≤x≤5)to the Li2 Mg_(6)ZnTi_(6)O_(20)ceramics to enhance their applicability.The ceramics feature a spinel structure for LiF contents up to 3 wt%,while higher LiF concentrations induce the formation of a secondary phase,LiTiO2,characterized by a rock salt structure.Notably,the lattice distortion induced by LiF leads to a constant decrease in ε_(r).A moderate degree of lattice distortion serves to enhance the lattice stability of ceramics,which is reflected in increased lattice energy.Excellent microwave dielectric properties(ε_(r)=16.23,Q×f=89,728 GHz,τ_(f)=−43.5 ppm/℃)were obtained for x=3 ceramic sintered at 1140℃.Even at x=5,the ceramic retains excellent microwave dielectric properties(ε_(r)=16.02,Q×f=63,079 GHz,τ_(f)=−26 ppm/°C)at a low sintering temperature of 900°C.This work realizes the multiple effects of LiF and confirms good chemical compatibility with silver for LTCC(low-temperature co-fired ceramics)applications.
