In this paper, a flatly broadened and highly coherent supercontinuum generation by induced modulation instability in ANDi-PCF is proposed. The numerical results show that the bandwidth of supercontinuun can be increas...In this paper, a flatly broadened and highly coherent supercontinuum generation by induced modulation instability in ANDi-PCF is proposed. The numerical results show that the bandwidth of supercontinuun can be increased by increasing the modulation depth and the coherence property of supercontinuum can be improved with the optimal modulation frequency. A highly coherent supercontinuum with the 10 dB bandwidth of 1305 nm and the flatness of less than 10 dB can be obtained when seeding at the modulation depth of 0.3 and modulation frequency of 24 THz.展开更多
The commercialization of solid oxide fuel cells depends on the cathode,which possesses both high catalytic activity and a thermal-expansion coefficient(TEC)that aligns with the electrolyte.Although the cobalt-based ca...The commercialization of solid oxide fuel cells depends on the cathode,which possesses both high catalytic activity and a thermal-expansion coefficient(TEC)that aligns with the electrolyte.Although the cobalt-based cathode La_(0.6)Sr_(0.4)CoO_(3)(LSC)offers excellent catalytic performance,its TEC is significantly larger than that of the electrolyte.In this study,we mechanically mix Sm_(0.2)Ce_(0.8)O_(2−δ)(SDC)with LSC to create a composite cathode.By incorporating 50wt%SDC,the TEC decreases significantly from 18.29×10^(−6) to 13.90×10^(−6) K^(−1).Under thermal-shock conditions ranging from room temperature to 800℃,the growth rate of polarization resistance is only 0.658%per cycle,i.e.,merely 49%that of pure LSC.The button cell comprising the LSC-SDC composite cathode operates stably for over 900 h without Sr segregation,with a voltage growth rate of 1.11%/kh.A commercial flat-tube cell(active area:70 cm^(2))compris-ing the LSC-SDC composite cathode delivers 54.8 W at 750℃.The distribution of relaxation-time shows that the non-electrode portion is the main rate-limiting step.This study demonstrates that the LSC-SDC mixture strategy effectively improves the compatibility with the electrolyte while maintaining a high output,thus rendering it a promising commercial cathode material.展开更多
Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-ze...Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.展开更多
With the most advanced and sophisticated technologies and equipment,NYBELT is one of the largest manufacturers of flat transmission belts in the world.Under the Certified Quality,Environment,Occupational Health&Sa...With the most advanced and sophisticated technologies and equipment,NYBELT is one of the largest manufacturers of flat transmission belts in the world.Under the Certified Quality,Environment,Occupational Health&Safety,and Energy Standardized ISO Management System,NYBELT can produce all kinds of flat transmission belts,roller coverings and conveyor belts applicable to textile,printing&packaging,electronics and other industries.Due to the superior quality and the reasonable prices,we have become well known in providing high quality belting products and excellent service to customers all over the world.Our success in the past gives us the confidence to look into the future with great expectations.展开更多
In a peach orchard in Lyuxiang Town,Jinshan District,Shanghai,youth delegates from 13 countries,officials from the Food and Agriculture Organization of the United Nations(FAO),and agricultural heritage experts were im...In a peach orchard in Lyuxiang Town,Jinshan District,Shanghai,youth delegates from 13 countries,officials from the Food and Agriculture Organization of the United Nations(FAO),and agricultural heritage experts were impressed by sweet and juicy Jinshan flat peaches.Jinshan has a history of flat peach cultivation that spans hundreds of years dating back to the Yuan Dynasty(1271-1368).展开更多
Shaoxing Shuifu Reeds is professional on producing all kinds of Air Jet Reeds and Flat Reeds,which has an annual output of 90,000 meters air-jet reeds,300,000,000 pcs of profile dents and 60,000 meters of Flat Reeds,W...Shaoxing Shuifu Reeds is professional on producing all kinds of Air Jet Reeds and Flat Reeds,which has an annual output of 90,000 meters air-jet reeds,300,000,000 pcs of profile dents and 60,000 meters of Flat Reeds,Which has been honored with China Air Jet Profile Reeds Research Center by China Textile Machinery Association in 2015.In order to reach the demands of high quality fabric and industrial textile products,the yarn is developing to high count,multicolor,various fibers,and the fabric is developing to high count,high density,environment protection.So we have researched out high density,multicolor,multinozzle,double energy saving type profile reeds to let you choose.展开更多
The Lieb lattice, characterized by its distinctive Dirac cone and flat-band electronic structures, hosts a variety of exotic physical phenomena. However, its realization remains largely confined to artificial lattices...The Lieb lattice, characterized by its distinctive Dirac cone and flat-band electronic structures, hosts a variety of exotic physical phenomena. However, its realization remains largely confined to artificial lattices. In this work, we propose the concept of a Lieb electride, where the non-bound electrons gather at the middle edges,behaving as the quasi-atoms of a Lieb lattice, enabling the emergence of flat bands. Using crystal structure prediction method MAGUS and first-principles calculations, we predict a stable candidate, Ca_(2)I, at ambient pressure. Distinct from conventional electrides with localized electrons at cavity centers, Ca_(2)I features interstitial electrons situated at cavity edges. The resultant flat bands lie close to the Fermi level, giving rise to a pronounced peak in the density of states and leading to Stoner-type ferromagnetism. With increasing pressures, we observe quantum phase transitions from ferromagnetic to non-magnetic and finally to antiferromagnetic orders in Ca_(2)I.Intriguingly, superconductivity emerges in the antiferromagnetic region, suggesting potential competition between these correlated states. Our study not only extends the concepts of electrides but also provides a novel strategy for realizing Lieb lattices through non-bound electrons. This work establishes Ca_(2)I as a promising platform for exploring flat-band physics and correlated electronic states, opening avenues for novel quantum phenomena in electride-based materials.展开更多
GERON Card Clothing(Jiangsu)Co.,Ltd.was founded in 1987 and is a professional textile carding equipment enterprise integrating research,production and sales.The production and sales of carding equipment have been lead...GERON Card Clothing(Jiangsu)Co.,Ltd.was founded in 1987 and is a professional textile carding equipment enterprise integrating research,production and sales.The production and sales of carding equipment have been leading the industry for many years.Our products include metallic card clothing,flat-top,stationary flat,circular comb and combing roller.Our brands include TYRION,Blue Diamond,Diamond,Pioneer and Lance.We provide customers with the most advanced carding solutions.展开更多
Understanding the characteristics of windsand flow field in the curve section of desert highway under different wind directions is helpful for reducing the wind-sand damage in the curve section.Therefore,taking the de...Understanding the characteristics of windsand flow field in the curve section of desert highway under different wind directions is helpful for reducing the wind-sand damage in the curve section.Therefore,taking the desert section of Wuma Expressway in Zhongwei city,Ningxia,China as the research background,the wind-sand flow field and sand accumulation phenomenon of concave surface plane curve embankment under different wind directions is calculated and analyzed by computational fluid dynamics(CFD)numerical simulation method.The results show that:(1)Under different wind directions,along the direction of the route,at the starting point of the route,the windward slope of the embankment is a circular arc section,which reduces the resistance of wind-sand flow and promotes the acceleration of sand particles.In the middle of the route,the low-speed area of the windward slope toe and the leeward slope toe is small;at the end of the route,the high-speed area on the shoulder side of the leeward road rises upward.(2)Under different wind directions,the smaller the angle between the wind direction and the route,the stronger the lateral transport effect on the wind-blown sand flow,and the more sand particles transported along the route direction.(3)Under different wind directions,in the concave windward horizontal curve,with the increase of the angle,the sand area on the top of the embankment shows an increasing trend.Whenα=30°,45°,60°,75°,the percentage of the sand area on the top of the embankment to the total embankment area is 0%,33.3%,64.4%,71.0%,respectively.(4)Under different wind directions,along the route direction,the sand transport efficiency of the concave surface upwind plane curve embankment shows a decreasing trend.In the case of a certain radius of the horizontal curve,the angle range between the wind direction and the concave horizontal curve route is recommended to be 30°-45°.展开更多
This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Div...This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Diverse volume fractions(1%, 2%, and 3%) of Al_(2)O_(3)-water nanofluids are meticulously prepared and analyzed. The essential physical properties of these nanofluids, critical for evaluating their thermal and flow characteristics, have been comprehensively assessed. From a quantitative perspective, numerical simulations are employed to predict the Nusselt number(Nu) and friction factor(f). The empirical findings reveal intriguing trends: the friction factor experiences an upward trend with diminishing velocity, attributed to heightened molecular cohesion. Conversely, the friction factor demonstrates a decline with diminishing volume fractions, a consequence of reduced particle size. Both the nanofluid's viscosity and heat transfer coefficient exhibit a rise in tandem with augmented volume flow rate and concentration gradient. Notably, the simulation results harmonize remarkably well with experimental data. Rigorous validation against prior studies underscores the robust consistency of these outcomes. In the pursuit of augmenting heat transfer, a volume fraction of 3% emerges as particularly influential, yielding an impressive 53.8% enhancement. Minor increments in the friction factor, while present, prove negligible and can be safely overlooked.展开更多
This study analyzes the energy impact of applying green roofs on flat roofs of existing buildings,assessing their potential to reduce the demand for non-renewable primary energy for heating and cooling.Through dynamic...This study analyzes the energy impact of applying green roofs on flat roofs of existing buildings,assessing their potential to reduce the demand for non-renewable primary energy for heating and cooling.Through dynamic numerical simulations conducted on two real buildings located near Florence,Italy,and modeled in 130 different European locations,with a particular focus on the Mediterranean climate,it was possible to quantify the energy benefits derived from the application of green roofs on existing structures.The results show that,while the effect on heating is limited,with an average reduction in energy demand of only a few percentage points,the impact on cooling is significantly more pronounced,with average savings of 20%in non-renewable primary energy,particularly in Mediterranean climates with high CDD(cooling degree days)values.The study confirms that green roofs can be an effective solution to improve the energy efficiency of existing buildings with flat roofs in the Mediterranean climate,in line with European goals for reducing CO_(2) emissions and promoting renewable energy.展开更多
In this paper,the optical efficiency and output thermal power of the heliostat mirror field are analyzed and optimized by constructing a geometric model and an optimization algorithm for the optimal design of the heli...In this paper,the optical efficiency and output thermal power of the heliostat mirror field are analyzed and optimized by constructing a geometric model and an optimization algorithm for the optimal design of the heliostat mirror field of a tower-type solar photovoltaic power plant.First,based on the solar position model and the optical efficiency model of the heliostat mirror field,the annual average optical efficiency,the annual average output thermal power,and the annual average output thermal power per unit mirror area of the heliostat mirror field are calculated.Secondly,the EB layout was used to optimize the heliostat field,and the parameters of heliostat size and mounting height were optimized by genetic algorithm and particle swarm algorithm to maximize the annual average output thermal power per unit mirror surface area.The results show that the optimized heliostat mirror field significantly increases the annual average output thermal power per unit mirror area under the condition of achieving the rated power,which provides theoretical basis and technical support for the design and operation of the tower solar thermal power plant.展开更多
Phase change heat transfer devices like heat pipes are widely utilized in temperature control and heat transfer.However,the traditional single uniform wick makes it hard to meet the requirements of capillary pressure ...Phase change heat transfer devices like heat pipes are widely utilized in temperature control and heat transfer.However,the traditional single uniform wick makes it hard to meet the requirements of capillary pressure and permeability for high-performance heat pipes,thus limiting the improvement of heat transfer performance.In this paper,a gradient structure wick sintered by 316 L stainless steel powder is designed.The capillary performance is tested and characterized through permeability test experiments and capillary rise infrared test experiments.Moreover,the influence of different particle sizes of sintered powder on the capillary performance of the wick structure is studied.The experimental results indicate that the capillary pressure and permeability of the gradient structure wick are significantly improved compared with the traditional single structure wick.Its capillary performance parameter S(K·Pcap)is enhanced by more than 30%,providing an effective alternative for the wick of two-phase heat exchange devices.展开更多
The present review explores the promising role of nanofluids and related hybrid variants in enhancing the efficiencyof flat tube car radiators.As vehicles become more advanced and demand better thermal performance,tra...The present review explores the promising role of nanofluids and related hybrid variants in enhancing the efficiencyof flat tube car radiators.As vehicles become more advanced and demand better thermal performance,traditional coolants are starting to fall short.Nanofluids,which involve tiny nanoparticles dispersed into standardcooling liquids,offer a new solution by significantly improving heat transfer capabilities.The article categorizesthe different types of nanofluids(ranging from those based on metals and metal oxides to carbon materials andhybrid combinations)and examines their effects on the improvement of radiator performance.General consensusexists in the literature that nanofluids can support better heat dissipation and enable accordingly the developmentof smaller and lighter radiators,which require less coolant and allow more compact vehicle designs.However,thisreview demonstrates that the use of nanofluids does not come without challenges.These include the long-termstability of these fluids and material compatibility issues.A critical discussion is therefore elaborated about thegaps to be filled and the steps to be undertaken to promote and standardize the use of these fluids in the industry.展开更多
Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electri...Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electric field of the incident light parallel to its crystalline ab-plane. The ab-plane optical conductivity spectra of Nb_(3)SiTe_(6) single crystals exhibit a remarkable peak-like feature around 1.20 eV, which is mainly contributed by the direct optical transitions between the two ab-initio-calculation-derived flat bands along the momentum direction Z–U. Our results pave the way for investigating exotic quantum phenomena based on the flat bands in topological hourglass semimetals.展开更多
The accurate photoneutron cross section of the^(27)Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for^(26)A...The accurate photoneutron cross section of the^(27)Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for^(26)Al in nuclear astrophysics.The photoneutron cross sections for the^(27)Al(γ,n)^(26)Al reaction,within the neutron separation energy range of 13.2-21.7 MeV,were meticulously measured using a new flat efficiency detector array at the Shanghai Laser-Electron Gamma Source.The uncertainty of the data was controlled to below 4%throughout the process,and inconsistencies between the present data and existing data from different gamma sources,as well as the TENDL-2021 data,are discussed in detail.These discussions provide a valuable reference for addressing discrepancies in the^(27)Al(γ,n)^(26)Al cross-section data and improving related theoretical calculations.展开更多
Dynamic soaring,inspired by the wind-riding flight of birds such as albatrosses,is a biomimetic technique which leverages wind fields to enhance the endurance of unmanned aerial vehicles(UAVs).Achieving a precise soar...Dynamic soaring,inspired by the wind-riding flight of birds such as albatrosses,is a biomimetic technique which leverages wind fields to enhance the endurance of unmanned aerial vehicles(UAVs).Achieving a precise soaring trajectory is crucial for maximizing energy efficiency during flight.Existing nonlinear programming methods are heavily dependent on the choice of initial values which is hard to determine.Therefore,this paper introduces a deep reinforcement learning method based on a differentially flat model for dynamic soaring trajectory planning and optimization.Initially,the gliding trajectory is parameterized using Fourier basis functions,achieving a flexible trajectory representation with a minimal number of hyperparameters.Subsequently,the trajectory optimization problem is formulated as a dynamic interactive process of Markov decision-making.The hyperparameters of the trajectory are optimized using the Proximal Policy Optimization(PPO2)algorithm from deep reinforcement learning(DRL),reducing the strong reliance on initial value settings in the optimization process.Finally,a comparison between the proposed method and the nonlinear programming method reveals that the trajectory generated by the proposed approach is smoother while meeting the same performance requirements.Specifically,the proposed method achieves a 34%reduction in maximum thrust,a 39.4%decrease in maximum thrust difference,and a 33%reduction in maximum airspeed difference.展开更多
We propose a method to measure the flatness of an object with a petal-like pattern generated by the interference of the measured orbital angular momentum(OAM)beam and the reference OAM beam which carries the opposite ...We propose a method to measure the flatness of an object with a petal-like pattern generated by the interference of the measured orbital angular momentum(OAM)beam and the reference OAM beam which carries the opposite OAM state.By calculating the difference between the petal rotation angle without/with the object,the thickness information of the object,and then the flatness information,can be evaluated.Furthermore,the direction of the object’s flatness can be determined by the petal’s clockwise/counterclockwise rotation.We theoretically analyze the relationship between the object’s thickness and petal rotation angle,and verify the proposed method by experiment.The experimental results show that the proposed method is a high precision flatness measurement and can obtain the convex/concave property of the flatness.For the 1.02 mm glass sample,the mean deviation of the flatness is 1.357×10^(-8) and the variance is 0.242×10^(-16).For the 0.50 mm glass sample,the mean deviation of the flatness is 1.931×10^(-8) and the variance is 2.405×10^(-16).Two different topological charges are adopted for the 2.00 mm glass sample,and their flatness deviations are 0.239×10^(-8)(ℓ=1)and 0.246×10^(-8)(ℓ=2),where their variances are 0.799×10^(-18)(ℓ=1)and 0.775×10^(-18)(ℓ=2),respectively.It is shown that the flatness measured by the proposed method is the same for the same sample when different topological charges are used.All results indicate that the proposed method may provide a high flatness measurement,and will be a promising way to measure the flatness.展开更多
Moiré superlattices have revolutionized the study of two-dimensional materials, enabling unprecedented control over their electronic, magnetic, optical, and mechanical properties. This review provides a comprehen...Moiré superlattices have revolutionized the study of two-dimensional materials, enabling unprecedented control over their electronic, magnetic, optical, and mechanical properties. This review provides a comprehensive analysis of the latest advancements in moiré physics, focusing on the formation of moiré superlattices due to rotational misalignment or lattice mismatch in two-dimensional materials. These superlattices induce flat band structures and strong correlation effects,leading to the emergence of exotic quantum phases, such as unconventional superconductivity, correlated insulating states,and fractional quantum anomalous Hall effects. The review also explores the underlying mechanisms of these phenomena and discusses the potential technological applications of moiré physics, offering insights into future research directions in this rapidly evolving field.展开更多
In this paper,we will discuss the almost global existence result for d-dimensional fractional nonlinear Schrodinger equation on flat torus,which is based on BNF technique,the tame property and the analysis of the spec...In this paper,we will discuss the almost global existence result for d-dimensional fractional nonlinear Schrodinger equation on flat torus,which is based on BNF technique,the tame property and the analysis of the spectrum of(-Δ)^(s).展开更多
文摘In this paper, a flatly broadened and highly coherent supercontinuum generation by induced modulation instability in ANDi-PCF is proposed. The numerical results show that the bandwidth of supercontinuun can be increased by increasing the modulation depth and the coherence property of supercontinuum can be improved with the optimal modulation frequency. A highly coherent supercontinuum with the 10 dB bandwidth of 1305 nm and the flatness of less than 10 dB can be obtained when seeding at the modulation depth of 0.3 and modulation frequency of 24 THz.
基金the financial support from the National Natural Science Foundation of China(No.22209191)Ningbo Key R&D Project(No.2023Z155).
文摘The commercialization of solid oxide fuel cells depends on the cathode,which possesses both high catalytic activity and a thermal-expansion coefficient(TEC)that aligns with the electrolyte.Although the cobalt-based cathode La_(0.6)Sr_(0.4)CoO_(3)(LSC)offers excellent catalytic performance,its TEC is significantly larger than that of the electrolyte.In this study,we mechanically mix Sm_(0.2)Ce_(0.8)O_(2−δ)(SDC)with LSC to create a composite cathode.By incorporating 50wt%SDC,the TEC decreases significantly from 18.29×10^(−6) to 13.90×10^(−6) K^(−1).Under thermal-shock conditions ranging from room temperature to 800℃,the growth rate of polarization resistance is only 0.658%per cycle,i.e.,merely 49%that of pure LSC.The button cell comprising the LSC-SDC composite cathode operates stably for over 900 h without Sr segregation,with a voltage growth rate of 1.11%/kh.A commercial flat-tube cell(active area:70 cm^(2))compris-ing the LSC-SDC composite cathode delivers 54.8 W at 750℃.The distribution of relaxation-time shows that the non-electrode portion is the main rate-limiting step.This study demonstrates that the LSC-SDC mixture strategy effectively improves the compatibility with the electrolyte while maintaining a high output,thus rendering it a promising commercial cathode material.
基金supported by the Ministry of Science and Technology(Grant No.2022YFA1403901)the National Natural Science Foundation of China(Grant Nos.12494594,11888101,12174428,and 12504192)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB28000000)the New Cornerstone Investigator Program,the Chinese Academy of Sciences through the Youth Innovation Promotion Association(Grant No.2022YSBR-048)the Shanghai Science and Technology Innovation Action Plan(Grant No.24LZ1400800).
文摘Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.
文摘With the most advanced and sophisticated technologies and equipment,NYBELT is one of the largest manufacturers of flat transmission belts in the world.Under the Certified Quality,Environment,Occupational Health&Safety,and Energy Standardized ISO Management System,NYBELT can produce all kinds of flat transmission belts,roller coverings and conveyor belts applicable to textile,printing&packaging,electronics and other industries.Due to the superior quality and the reasonable prices,we have become well known in providing high quality belting products and excellent service to customers all over the world.Our success in the past gives us the confidence to look into the future with great expectations.
文摘In a peach orchard in Lyuxiang Town,Jinshan District,Shanghai,youth delegates from 13 countries,officials from the Food and Agriculture Organization of the United Nations(FAO),and agricultural heritage experts were impressed by sweet and juicy Jinshan flat peaches.Jinshan has a history of flat peach cultivation that spans hundreds of years dating back to the Yuan Dynasty(1271-1368).
文摘Shaoxing Shuifu Reeds is professional on producing all kinds of Air Jet Reeds and Flat Reeds,which has an annual output of 90,000 meters air-jet reeds,300,000,000 pcs of profile dents and 60,000 meters of Flat Reeds,Which has been honored with China Air Jet Profile Reeds Research Center by China Textile Machinery Association in 2015.In order to reach the demands of high quality fabric and industrial textile products,the yarn is developing to high count,multicolor,various fibers,and the fabric is developing to high count,high density,environment protection.So we have researched out high density,multicolor,multinozzle,double energy saving type profile reeds to let you choose.
基金supported by the National Natural Science Foundation of China(Grant Nos.12125404,T2495231,123B2049,and 12204138)the National Key R&D Program of China(Grant No.2022YFA1403201)+7 种基金the Advanced MaterialsNational Science and Technology Major Project (Grant No.2024ZD0607000)the Basic Research Program of Jiangsu (Grant Nos.BK20233001 and BK20241253)the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant Nos.2024ZB002,2024ZB075,2025ZB440 and2025ZB852)the China Postdoctoral Science Foundation (Grant No.2025M773331)the Postdoctoral Fellowship Program of CPSF (Grant No.GZC20240695 and GZC20252202)the AI&AI for Science Program of Nanjing UniversityArtificial Intelligence and Quantum physics (AIQ) program of Nanjing Universitythe Fundamental Research Funds for the Central Universities。
文摘The Lieb lattice, characterized by its distinctive Dirac cone and flat-band electronic structures, hosts a variety of exotic physical phenomena. However, its realization remains largely confined to artificial lattices. In this work, we propose the concept of a Lieb electride, where the non-bound electrons gather at the middle edges,behaving as the quasi-atoms of a Lieb lattice, enabling the emergence of flat bands. Using crystal structure prediction method MAGUS and first-principles calculations, we predict a stable candidate, Ca_(2)I, at ambient pressure. Distinct from conventional electrides with localized electrons at cavity centers, Ca_(2)I features interstitial electrons situated at cavity edges. The resultant flat bands lie close to the Fermi level, giving rise to a pronounced peak in the density of states and leading to Stoner-type ferromagnetism. With increasing pressures, we observe quantum phase transitions from ferromagnetic to non-magnetic and finally to antiferromagnetic orders in Ca_(2)I.Intriguingly, superconductivity emerges in the antiferromagnetic region, suggesting potential competition between these correlated states. Our study not only extends the concepts of electrides but also provides a novel strategy for realizing Lieb lattices through non-bound electrons. This work establishes Ca_(2)I as a promising platform for exploring flat-band physics and correlated electronic states, opening avenues for novel quantum phenomena in electride-based materials.
文摘GERON Card Clothing(Jiangsu)Co.,Ltd.was founded in 1987 and is a professional textile carding equipment enterprise integrating research,production and sales.The production and sales of carding equipment have been leading the industry for many years.Our products include metallic card clothing,flat-top,stationary flat,circular comb and combing roller.Our brands include TYRION,Blue Diamond,Diamond,Pioneer and Lance.We provide customers with the most advanced carding solutions.
基金supported by the National Natural Science Foundation of China“Study on the failure mechanism and evaluation method of sand control measures for railway machinery in sandy areas”(12302511)。
文摘Understanding the characteristics of windsand flow field in the curve section of desert highway under different wind directions is helpful for reducing the wind-sand damage in the curve section.Therefore,taking the desert section of Wuma Expressway in Zhongwei city,Ningxia,China as the research background,the wind-sand flow field and sand accumulation phenomenon of concave surface plane curve embankment under different wind directions is calculated and analyzed by computational fluid dynamics(CFD)numerical simulation method.The results show that:(1)Under different wind directions,along the direction of the route,at the starting point of the route,the windward slope of the embankment is a circular arc section,which reduces the resistance of wind-sand flow and promotes the acceleration of sand particles.In the middle of the route,the low-speed area of the windward slope toe and the leeward slope toe is small;at the end of the route,the high-speed area on the shoulder side of the leeward road rises upward.(2)Under different wind directions,the smaller the angle between the wind direction and the route,the stronger the lateral transport effect on the wind-blown sand flow,and the more sand particles transported along the route direction.(3)Under different wind directions,in the concave windward horizontal curve,with the increase of the angle,the sand area on the top of the embankment shows an increasing trend.Whenα=30°,45°,60°,75°,the percentage of the sand area on the top of the embankment to the total embankment area is 0%,33.3%,64.4%,71.0%,respectively.(4)Under different wind directions,along the route direction,the sand transport efficiency of the concave surface upwind plane curve embankment shows a decreasing trend.In the case of a certain radius of the horizontal curve,the angle range between the wind direction and the concave horizontal curve route is recommended to be 30°-45°.
文摘This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Diverse volume fractions(1%, 2%, and 3%) of Al_(2)O_(3)-water nanofluids are meticulously prepared and analyzed. The essential physical properties of these nanofluids, critical for evaluating their thermal and flow characteristics, have been comprehensively assessed. From a quantitative perspective, numerical simulations are employed to predict the Nusselt number(Nu) and friction factor(f). The empirical findings reveal intriguing trends: the friction factor experiences an upward trend with diminishing velocity, attributed to heightened molecular cohesion. Conversely, the friction factor demonstrates a decline with diminishing volume fractions, a consequence of reduced particle size. Both the nanofluid's viscosity and heat transfer coefficient exhibit a rise in tandem with augmented volume flow rate and concentration gradient. Notably, the simulation results harmonize remarkably well with experimental data. Rigorous validation against prior studies underscores the robust consistency of these outcomes. In the pursuit of augmenting heat transfer, a volume fraction of 3% emerges as particularly influential, yielding an impressive 53.8% enhancement. Minor increments in the friction factor, while present, prove negligible and can be safely overlooked.
文摘This study analyzes the energy impact of applying green roofs on flat roofs of existing buildings,assessing their potential to reduce the demand for non-renewable primary energy for heating and cooling.Through dynamic numerical simulations conducted on two real buildings located near Florence,Italy,and modeled in 130 different European locations,with a particular focus on the Mediterranean climate,it was possible to quantify the energy benefits derived from the application of green roofs on existing structures.The results show that,while the effect on heating is limited,with an average reduction in energy demand of only a few percentage points,the impact on cooling is significantly more pronounced,with average savings of 20%in non-renewable primary energy,particularly in Mediterranean climates with high CDD(cooling degree days)values.The study confirms that green roofs can be an effective solution to improve the energy efficiency of existing buildings with flat roofs in the Mediterranean climate,in line with European goals for reducing CO_(2) emissions and promoting renewable energy.
基金supported in part by the University-Industry Collaborative Education Program under Grant 241006627080140.
文摘In this paper,the optical efficiency and output thermal power of the heliostat mirror field are analyzed and optimized by constructing a geometric model and an optimization algorithm for the optimal design of the heliostat mirror field of a tower-type solar photovoltaic power plant.First,based on the solar position model and the optical efficiency model of the heliostat mirror field,the annual average optical efficiency,the annual average output thermal power,and the annual average output thermal power per unit mirror area of the heliostat mirror field are calculated.Secondly,the EB layout was used to optimize the heliostat field,and the parameters of heliostat size and mounting height were optimized by genetic algorithm and particle swarm algorithm to maximize the annual average output thermal power per unit mirror surface area.The results show that the optimized heliostat mirror field significantly increases the annual average output thermal power per unit mirror area under the condition of achieving the rated power,which provides theoretical basis and technical support for the design and operation of the tower solar thermal power plant.
文摘Phase change heat transfer devices like heat pipes are widely utilized in temperature control and heat transfer.However,the traditional single uniform wick makes it hard to meet the requirements of capillary pressure and permeability for high-performance heat pipes,thus limiting the improvement of heat transfer performance.In this paper,a gradient structure wick sintered by 316 L stainless steel powder is designed.The capillary performance is tested and characterized through permeability test experiments and capillary rise infrared test experiments.Moreover,the influence of different particle sizes of sintered powder on the capillary performance of the wick structure is studied.The experimental results indicate that the capillary pressure and permeability of the gradient structure wick are significantly improved compared with the traditional single structure wick.Its capillary performance parameter S(K·Pcap)is enhanced by more than 30%,providing an effective alternative for the wick of two-phase heat exchange devices.
文摘The present review explores the promising role of nanofluids and related hybrid variants in enhancing the efficiencyof flat tube car radiators.As vehicles become more advanced and demand better thermal performance,traditional coolants are starting to fall short.Nanofluids,which involve tiny nanoparticles dispersed into standardcooling liquids,offer a new solution by significantly improving heat transfer capabilities.The article categorizesthe different types of nanofluids(ranging from those based on metals and metal oxides to carbon materials andhybrid combinations)and examines their effects on the improvement of radiator performance.General consensusexists in the literature that nanofluids can support better heat dissipation and enable accordingly the developmentof smaller and lighter radiators,which require less coolant and allow more compact vehicle designs.However,thisreview demonstrates that the use of nanofluids does not come without challenges.These include the long-termstability of these fluids and material compatibility issues.A critical discussion is therefore elaborated about thegaps to be filled and the steps to be undertaken to promote and standardize the use of these fluids in the industry.
基金Project supported by the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2021B1515130007)the National Natural Science Foundation of China (Grant Nos. U21A20432 and 52273077)+1 种基金the National Key Research and Development Program of China (Grant No. 2022YFA1403800)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB33000000)。
文摘Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electric field of the incident light parallel to its crystalline ab-plane. The ab-plane optical conductivity spectra of Nb_(3)SiTe_(6) single crystals exhibit a remarkable peak-like feature around 1.20 eV, which is mainly contributed by the direct optical transitions between the two ab-initio-calculation-derived flat bands along the momentum direction Z–U. Our results pave the way for investigating exotic quantum phenomena based on the flat bands in topological hourglass semimetals.
基金supported by the National key R&D program(Nos.2023YFA1606901 and 2022YFA1602404)the National Natural Science Foundation of China(Nos.12375123 and 12388102)the Natural Science Foundation of Henan Province(No.242300422048)。
文摘The accurate photoneutron cross section of the^(27)Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for^(26)Al in nuclear astrophysics.The photoneutron cross sections for the^(27)Al(γ,n)^(26)Al reaction,within the neutron separation energy range of 13.2-21.7 MeV,were meticulously measured using a new flat efficiency detector array at the Shanghai Laser-Electron Gamma Source.The uncertainty of the data was controlled to below 4%throughout the process,and inconsistencies between the present data and existing data from different gamma sources,as well as the TENDL-2021 data,are discussed in detail.These discussions provide a valuable reference for addressing discrepancies in the^(27)Al(γ,n)^(26)Al cross-section data and improving related theoretical calculations.
基金support received by the National Natural Science Foundation of China(Grant Nos.52372398&62003272).
文摘Dynamic soaring,inspired by the wind-riding flight of birds such as albatrosses,is a biomimetic technique which leverages wind fields to enhance the endurance of unmanned aerial vehicles(UAVs).Achieving a precise soaring trajectory is crucial for maximizing energy efficiency during flight.Existing nonlinear programming methods are heavily dependent on the choice of initial values which is hard to determine.Therefore,this paper introduces a deep reinforcement learning method based on a differentially flat model for dynamic soaring trajectory planning and optimization.Initially,the gliding trajectory is parameterized using Fourier basis functions,achieving a flexible trajectory representation with a minimal number of hyperparameters.Subsequently,the trajectory optimization problem is formulated as a dynamic interactive process of Markov decision-making.The hyperparameters of the trajectory are optimized using the Proximal Policy Optimization(PPO2)algorithm from deep reinforcement learning(DRL),reducing the strong reliance on initial value settings in the optimization process.Finally,a comparison between the proposed method and the nonlinear programming method reveals that the trajectory generated by the proposed approach is smoother while meeting the same performance requirements.Specifically,the proposed method achieves a 34%reduction in maximum thrust,a 39.4%decrease in maximum thrust difference,and a 33%reduction in maximum airspeed difference.
基金supported by the National Natural Science Foundation of China(Grant No.62375140)the Open Research Fund of National Laboratory of Solid State Microstructures(Grant No.M36055).
文摘We propose a method to measure the flatness of an object with a petal-like pattern generated by the interference of the measured orbital angular momentum(OAM)beam and the reference OAM beam which carries the opposite OAM state.By calculating the difference between the petal rotation angle without/with the object,the thickness information of the object,and then the flatness information,can be evaluated.Furthermore,the direction of the object’s flatness can be determined by the petal’s clockwise/counterclockwise rotation.We theoretically analyze the relationship between the object’s thickness and petal rotation angle,and verify the proposed method by experiment.The experimental results show that the proposed method is a high precision flatness measurement and can obtain the convex/concave property of the flatness.For the 1.02 mm glass sample,the mean deviation of the flatness is 1.357×10^(-8) and the variance is 0.242×10^(-16).For the 0.50 mm glass sample,the mean deviation of the flatness is 1.931×10^(-8) and the variance is 2.405×10^(-16).Two different topological charges are adopted for the 2.00 mm glass sample,and their flatness deviations are 0.239×10^(-8)(ℓ=1)and 0.246×10^(-8)(ℓ=2),where their variances are 0.799×10^(-18)(ℓ=1)and 0.775×10^(-18)(ℓ=2),respectively.It is shown that the flatness measured by the proposed method is the same for the same sample when different topological charges are used.All results indicate that the proposed method may provide a high flatness measurement,and will be a promising way to measure the flatness.
基金Project supported by the National Key R&D Program of China (Grant No. 2019YFA0307800)the National Natural Science Foundation of China (Grant No. 12074377)+2 种基金Fundamental Research Funds for the Central Universities,the International Partnership Program of Chinese Academy of Sciences (Grant No. 211211KYSB20210007)the China Postdoctoral Science Foundation (Grant No. 2024M753465)the Postdoctoral Fellowship Program (Grade C) of China Postdoctoral Science Foundation (Grant No. GZC20241893)。
文摘Moiré superlattices have revolutionized the study of two-dimensional materials, enabling unprecedented control over their electronic, magnetic, optical, and mechanical properties. This review provides a comprehensive analysis of the latest advancements in moiré physics, focusing on the formation of moiré superlattices due to rotational misalignment or lattice mismatch in two-dimensional materials. These superlattices induce flat band structures and strong correlation effects,leading to the emergence of exotic quantum phases, such as unconventional superconductivity, correlated insulating states,and fractional quantum anomalous Hall effects. The review also explores the underlying mechanisms of these phenomena and discusses the potential technological applications of moiré physics, offering insights into future research directions in this rapidly evolving field.
基金Supported by the National Natural Science Foundation of China(12101542,12371189,12371241).
文摘In this paper,we will discuss the almost global existence result for d-dimensional fractional nonlinear Schrodinger equation on flat torus,which is based on BNF technique,the tame property and the analysis of the spectrum of(-Δ)^(s).
