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Behavior of near-field dilution of thermal buoyant jet discharged horizontally in compound open-channel 被引量:2
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作者 槐文信 肖庆华 +2 位作者 曾玉红 杨中华 钱忠东 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2008年第2期263-271,共9页
The RNG κ-ε model considering the buoyancy effect, which is solved by the hybrid finite analytic method, is used to simulate the mixture of the horizontal round thermal buoyant jet in compound open channel flow. The... The RNG κ-ε model considering the buoyancy effect, which is solved by the hybrid finite analytic method, is used to simulate the mixture of the horizontal round thermal buoyant jet in compound open channel flow. The mixing features near the spout and flowing characteristic of the secondary currents are studied by numerical simulation. Meanwhile, (1) the distribution of the measured isovels for stream-wise velocity, (2) secondary currents, (3) the distribution of the measured isovels for temperature of typical cross-section near the spout, were obtained by the three-dimensional Micro ADV and the temperature measuring device. Compared with experimental data, the RNG κ-ε model based on buoyancy effect can preferably simulate the jet which performs the bifurcation phenomenon, jet reattachment (Conada effect) and beach secondary currents phenomenon with the effect of ambient flow, buoyancy, and secondary currents of compound section and so on. 展开更多
关键词 turbulence model compound channel buoyant jets hybrid finite analytic method secondary currents
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Characteristics of a radio-frequency cold atmospheric plasma jet produced with a hybrid cross-linear-field electrode configuration 被引量:1
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作者 Jing LI Heping LI 《Plasma Science and Technology》 SCIE EI CAS CSCD 2019年第5期102-112,共11页
Cold atmospheric plasma(CAP)jet has wide applications in various fields including advanced materials synthesis and modifications,biomedicine,environmental protection and energy saving,etc.Appropriate control on the vo... Cold atmospheric plasma(CAP)jet has wide applications in various fields including advanced materials synthesis and modifications,biomedicine,environmental protection and energy saving,etc.Appropriate control on the volume,temperature and chemically reactive species concentratio ns of the CAP jet is of great importance in actual applications.In this paper,an radio-frequency atmospheric-pressure glow discharge(RF-APGD)plasma generator with a hybrid cross-linear-field electrode configuration is proposed.The experimental results show that,with the aid of the copper mesh located at the downstream of the traditional co-axial-type plasma generator with a cross-field electrode configuration,a linear field between the inner powered electrode of the traditional plasma generator and the copper mesh can be established.This linerfield can,to some extent,enhance the discharges at the upstream of the copper mesh,resulting in small increments(all less than 12.5%)of the species emission intensities,electron excitation temperatures and gas temperatures by keeping other parameters being unchanged.And due to the intrinsic transparent and conducting features of the grounded copper mesh to the gas flowing,electric current and heat flux of the plasma plumes,a plasma region with higher concentrations of chemically reactive species and larger plasma plume diameters is obtained at the downstream of the grounded copper mesh on the same level of the gas temperature and electron excitation temperature compared to those of the plasma free jet.In addition,the charged particle number densities at the same downstream axial location of the grounded copper mesh decrease significantly compared to those of the plasma free jet.This means that the copper mesh is also,to some extent,helpful for separating the chemically reactive neutral species from the charged particles in side a plasma environment.The preceding results indicate that the cross-linear-field electrode configuration of the plasma generator is an effective approach for tuning the characteristics of the RF-APGD plasma jet in order to obtain an appropriate combination of the plasma jet properties with higher chemically reactive species concentrations,especially relative higher number densities of neutral species,larger plasma volumes and lower gas temperatures. 展开更多
关键词 COLD ATMOSPHERIC PLASMA hybrid-cross-linear-field electrode configuration grounded copper mesh PLASMA jet CHARACTERISTICS modulation
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Controllable and switchable chiral near-fields in symmetric graphene metasurfaces
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作者 Li Hu Hongxia Dai +1 位作者 Fayin Cheng Yuxia Tang 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第12期563-570,共8页
A strong chiral near-field plays significant roles in the detection,separation and sensing of chiral molecules.In this paper,a simple and symmetric metasurface is proposed to generate strong chiral near-fields with bo... A strong chiral near-field plays significant roles in the detection,separation and sensing of chiral molecules.In this paper,a simple and symmetric metasurface is proposed to generate strong chiral near-fields with both circularly polarized light and linearly polarized light illuminations in the mid-infrared region.Owing to the near-field interaction between plasmonic resonant modes of two nanosheets excited by circularly polarized light,there is a strong single-handed chiral near-field in the gap between the two graphene nanosheets and the maximum enhancement of the optical chirality could reach two orders of magnitude.As expected,the intensity and the response wavelength of the chiral near-fields could be controlled by the Fermi level and geometrical parameters of the graphene nanosheets,as well as the permittivity of the substrate.Meanwhile,based on the interaction between the incident field and scattered field,the one-handed chiral nearfield in the gap also could be generated by the linearly polarized light excitation.For the two cases,the handedness of the chiral near-field could be switched by the polarized direction of the incident light.These results have potential opportunities for applications in molecular detection and sensing. 展开更多
关键词 plasmonic resonance chiral near-field GRAPHENE metasurface
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Assessment of compressive strength of jet grouting by machine learning 被引量:1
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作者 Esteban Diaz Edgar Leonardo Salamanca-Medina Roberto Tomas 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第1期102-111,共10页
Jet grouting is one of the most popular soil improvement techniques,but its design usually involves great uncertainties that can lead to economic cost overruns in construction projects.The high dispersion in the prope... Jet grouting is one of the most popular soil improvement techniques,but its design usually involves great uncertainties that can lead to economic cost overruns in construction projects.The high dispersion in the properties of the improved material leads to designers assuming a conservative,arbitrary and unjustified strength,which is even sometimes subjected to the results of the test fields.The present paper presents an approach for prediction of the uniaxial compressive strength(UCS)of jet grouting columns based on the analysis of several machine learning algorithms on a database of 854 results mainly collected from different research papers.The selected machine learning model(extremely randomized trees)relates the soil type and various parameters of the technique to the value of the compressive strength.Despite the complex mechanism that surrounds the jet grouting process,evidenced by the high dispersion and low correlation of the variables studied,the trained model allows to optimally predict the values of compressive strength with a significant improvement with respect to the existing works.Consequently,this work proposes for the first time a reliable and easily applicable approach for estimation of the compressive strength of jet grouting columns. 展开更多
关键词 jet grouting Ground improvement Compressive strength Machine learning
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Investigation of hydroxyl-terminated polybutadiene propellant breaking characteristics and mechanism impacted by submerged cavitation water jet 被引量:1
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作者 Wenjun Zhou Meng Zhao +3 位作者 Bo Liu Youzhi Ma Youzhi Zhang Xuanjun Wang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第3期559-572,共14页
A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impac... A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms. 展开更多
关键词 Submerged cavitation water jet Hydroxyl-terminated polybutadiene propellant Breaking characteristics Failure modes
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Interdecadal variability of summer precipitation in the Three River Source Region: Influences of SST and zonal shifts of the East Asian subtropical westerly jet 被引量:1
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作者 Yumeng Liu Xianhong Meng +5 位作者 Lin Zhao S-Y.Simon Wang Lixia Zhang Zhaoguo Li Chan Wang Yingying An 《Atmospheric and Oceanic Science Letters》 CSCD 2024年第5期47-53,共7页
Summer precipitation in the Three Rivers Source Region(TRSR)of China is vital for the headwaters of the Yellow,Yangtze,and Lancang rivers and exhibits significant interdecadal variability.This study investigates the i... Summer precipitation in the Three Rivers Source Region(TRSR)of China is vital for the headwaters of the Yellow,Yangtze,and Lancang rivers and exhibits significant interdecadal variability.This study investigates the influence of the East Asian westerly jet(EAWJ)on TRSR rainfall.A strong correlation is found between TRSR summer precipitation and the Jet Zonal Position Index(JZPI)of the EAWJ from 1961 to 2019(R=0.619,p<0.01).During periods when a positive JZPI indicates a westward shift in the EAWJ,enhanced water vapor anomalies,warmer air,and low-level convergence anomalies contribute to increased TRSR summer precipitation.Using empirical orthogonal function and regression analyses,this research identifies the influence of large-scale circulation anomalies associated with the Atlantic–Eurasian teleconnection(AEA)from the North Atlantic(NA).The interdecadal variability between the NA and central tropical Pacific(CTP)significantly affects TRSR precipitation.This influence is mediated through the AEA via a Rossby wave train extending eastward along the EAWJ,and another south of 45°N.Moreover,the NA–CTP Opposite Phase Index(OPI),which quantifies the difference between the summer mean sea surface temperatures of the NA and the CTP,is identified as a critical factor in modulating the strength of this teleconnection and influencing the zonal position of the EAWJ. 展开更多
关键词 Summer precipitation East Asian subtropical westerly jet Three River Source Region Atlantic-Eurasian teleconnection
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A historical overview of nano-optics:From near-field optics to plasmonics
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作者 邓妙怡 朱星 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第5期134-145,共12页
Nano-optics is an emergent research field in physics that appeared in the 1980s,which deals with light–matter optical interactions at the nanometer scale.In early studies of nano-optics,the main concern focus is to o... Nano-optics is an emergent research field in physics that appeared in the 1980s,which deals with light–matter optical interactions at the nanometer scale.In early studies of nano-optics,the main concern focus is to obtain higher optical resolution over the diffraction limit.The researches of near-field imaging and spectroscopy based on scanning near-field optical microscopy(SNOM)are developed.The exploration of improving SNOM probe for near-field detection leads to the emergence of surface plasmons.In the sense of resolution and wider application,there has been a significant transition from seeking higher resolution microscopy to plasmonic near-field modulations in the nano-optics community during the nano-optic development.Nowadays,studies of nano-optics prefer the investigation of plasmonics in different material systems.In this article,the history of the development of near-field optics is briefly reviewed.The difficulties of conventional SNOM to achieve higher resolution are discussed.As an alternative solution,surface plasmons have shown the advantages of higher resolution,wider application,and flexible nano-optical modulation for new devices.The typical studies in different periods are introduced and characteristics of nano-optics in each stage are analyzed.In this way,the evolution progress from near-field optics to plasmonics of nano-optics research is presented.The future development of nano-optics is discussed then. 展开更多
关键词 NANO-OPTICS near-field optics surface plasmon plasmonic modulation
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Modeling Near-Field Impulsive Waves Generated by Deformable Landslide Using the HBP Model Based on the SPH Method
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作者 WANG Wei WEI Weicheng +4 位作者 CHAI Bo XIA Hao WANG Yang DU Juan LIU Jizhixian 《Journal of Ocean University of China》 CAS CSCD 2024年第2期328-344,共17页
Landslide-generated impulsive waves(LGWs)in reservoir areas can seriously threaten waterway safety as well as hu-man life and properties around the two side slopes.The risk reduction and mitigation of such a hazard re... Landslide-generated impulsive waves(LGWs)in reservoir areas can seriously threaten waterway safety as well as hu-man life and properties around the two side slopes.The risk reduction and mitigation of such a hazard require the accurate prediction of near-field wave characteristics,such as wave amplitude and run-up.However,near-field LGW involves complicated fluid-solid interactions.Furthermore,the wave characteristics are closely related to various aspects,including the geometry and physical features of the slide,river,and body of water.However,the empirical or analytical methods used for rough estimation cannot derive accurate results,especially for deformable landslides,due to their significant geometry changes during the sliding process.In this study,the near-field waves generated by deformable landslides were simulated by smoothed particle hydrodynamics(SPH)based on multi-phase flow.The deformable landslides were generalized as a kind of viscous flow by adopting the Herschel-Bulkley-Papanastasiou(HBP)-based nonNewtonian rheology model.The HBP model is capable of producing deformable landslide dynamics even though the high-speed sliding process is involved.In this study,an idealized experiment case originating from Lituya LGW and a practical case of Gongjiafang LGW were reproduced for verification and demonstration.The simulation results of both cases show satisfactory consistency with the experiment/investigation data in terms of landslide movement and near-field impulsive wave characteristics,thus indicating the applicability and accuracy of the proposed method.Finally,the effects of the HBP model’s rheological parameters on the landslide dynamics and near-field wave characteristics are discussed,providing a parameter calibration method along with sug-gestions for further applications. 展开更多
关键词 deformable landslide impulsive waves near-field SPH nonNewtonian fluids
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The medium-temperature dependence of jet transport coefficient in high-energy nucleus-nucleus collisions
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作者 Man Xie Qing-Fei Han +2 位作者 En-Ke Wang Ben-Wei Zhang Han-Zhong Zhang 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2024年第7期173-191,共19页
The medium-temperature T dependence of the jet transport coefficient̂q was studied via the nuclear modification factor RAA(p_(T))and elliptical flow parameter v_(2)(p_(T))for large transverse momentum p_(T) hadrons in... The medium-temperature T dependence of the jet transport coefficient̂q was studied via the nuclear modification factor RAA(p_(T))and elliptical flow parameter v_(2)(p_(T))for large transverse momentum p_(T) hadrons in high-energy nucleus-nucleus collisions.Within a next-to-leading-order perturbative QCD parton model for hard scatterings with modified fragmentation functions due to jet quenching controlled by q,we check the suppression and azimuthal anisotropy for large p_(T) hadrons,and extract q by global fits to RAA(pT)and v_(2)(pT)data in A+A collisions at RHIC and LHC,respectively.The numerical results from the best fits show that q∕T^(3) goes down with local medium-temperature T in the parton jet trajectory.Compared with the case of a constant q∕T^(3),the going-down T dependence of q∕T^(3) makes a hard parton jet to lose more energy near T_(c) and therefore strengthens the azimuthal anisotropy for large pT hadrons.As a result,v_(2)(p_(T))for large pT hadrons was enhanced by approximately 10%to better fit the data at RHIC/LHC.Considering the first-order phase transition from QGP to the hadron phase and the additional energy loss in the hadron phase,v_(2)(p_(T))is again enhanced by 5-10%at RHIC/LHC. 展开更多
关键词 jet quenching jet transport parameter Hadron suppression Elliptic flow coefficient Energy loss asymmetry
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Jets,Accretion and Spin in Supermassive Black Holes
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作者 Yongyun Chen Qiusheng Gu +5 位作者 Jianghe Yang Junhui Fan Xiaoling Yu Dingrong Xiong Nan Ding Xiaotong Guo 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第11期112-118,共7页
The theoretical model suggests that relativistic jets of active galactic nuclei(AGNs)rely on the black hole spin and/or accretion.We study the relationship between jet,accretion,and spin using supermassive black hole ... The theoretical model suggests that relativistic jets of active galactic nuclei(AGNs)rely on the black hole spin and/or accretion.We study the relationship between jet,accretion,and spin using supermassive black hole samples with reliable spin of black holes.Our results are as follows:(1)There is a weak correlation between radio luminosity and the spin of the black hole for our sample,which may imply that the jet of the supermassive black hole in our sample depends on the other physical parameters besides black hole spins,such as accretion disk luminosity.(2)The jet power of a supermassive black hole can be explained by the hybrid model with magnetic field of corona.(3)There is a significant correlation between radio-loudness and black hole spin for our sample.These sources with high radio-loudness tend to have high black hole spins.These results provide observational evidence that the black hole spin may explain the bimodal phenomena of radio-loud and radio-quiet AGNs. 展开更多
关键词 GALAXIES active-galaxies general-galaxies jets
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Experimental and Three-Dimensional Numerical Simulation of Phenomena Induced by Submerged Oblique Jet Scouring
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作者 Hao Chen Xianbin Teng +2 位作者 Faxin Zhu Zhibin Zhang Jie Wang 《Fluid Dynamics & Materials Processing》 EI 2024年第8期1799-1821,共23页
Scouring experiments were conducted using a three-dimensional laser scanning technology for angles of the jet spanning the interval from 0°to 30°,and the characteristics of the scour hole in equilibrium cond... Scouring experiments were conducted using a three-dimensional laser scanning technology for angles of the jet spanning the interval from 0°to 30°,and the characteristics of the scour hole in equilibrium conditions were investigated accordingly.The results indicate that the optimal scouring effects occur when the jet angle is in the ranges between 15°and 20°.Moreover,the dimensionless profiles of the scour hole exhibit a high degree of similarity at different jet angles.Numerical simulations conducted using the Flow-3D software to investigate the bed shear stress along the jet impingement surface have shown that this stress is influenced by both the resultant force and the jet impingement surface area.It reaches its maximum value when the jet is vertical,decreases rapidly as the jet starts to tilt,then increases slightly,and decreases again significantly when the angle exceeds 20°. 展开更多
关键词 Submerged jet jet angle experimental study numerical simulation bed shear stress
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A novel approach of jet polishing for interior surface of small-grooved components using three developed setups
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作者 Qinming Gu Zhenyu Zhang +6 位作者 Hongxiu Zhou Jiaxin Yu Dong Wang Junyuan Feng Chunjing Shi Jianjun Yang Junfeng Qi 《International Journal of Extreme Manufacturing》 SCIE EI CAS CSCD 2024年第2期428-447,共20页
It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanw... It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken. 展开更多
关键词 abrasive air jet polishing multi-phase jet polishing interior curved surface small-grooved component aluminum alloy
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Influence of substrate effect on near-field radiative modulator based on biaxial hyperbolic materials
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作者 刘睿一 刘皓佗 +2 位作者 胡杨 崔峥 吴小虎 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第4期56-64,共9页
Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer(NFRHT)in anisotropic media.Due to the strong in-plane anisotropy,natural hyperbolic materials can be... Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer(NFRHT)in anisotropic media.Due to the strong in-plane anisotropy,natural hyperbolic materials can be used to construct near-field radiative modulators with excellent modulation effects.However,in practical applications,natural hyperbolic materials need to be deposited on the substrate,and the influence of substrate on modulation effect has not been studied yet.In this work,we investigate the influence of substrate effect on near-field radiative modulator based onα-MoO_(3).The results show that compared to the situation without a substrate,the presence of both lossless and lossy substrate will reduce the modulation contrast(MC)for different film thicknesses.When the real or imaginary component of the substrate permittivity increases,the mismatch of hyperbolic phonon polaritons(HPPs)weakens,resulting in a reduction in MC.By reducing the real and imaginary components of substrate permittivity,the MC can be significantly improved,reaching 4.64 forε_(s)=3 at t=10 nm.This work indicates that choosing a substrate with a smaller permittivity helps to achieve a better modulation effect,and provides guidance for the application of natural hyperbolic materials in the near-field radiative modulator. 展开更多
关键词 near-field radiative modulator substrate effect hyperbolic material modulation contrast
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Fast synthesis of gold nanoparticles by cold atmospheric pressure plasma jet in the presence of Au^(+) ions and a capping agent
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作者 Tatiana HABIB José Mauricio A.CAIUT Bruno CAILLIER 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第7期108-115,共8页
Homogeneous gold nanoparticles were synthesized under atmospheric pressure using a nonthermal helium plasma jet in a single-step process.A current power supply was used to generate the plasma discharge rich in diverse... Homogeneous gold nanoparticles were synthesized under atmospheric pressure using a nonthermal helium plasma jet in a single-step process.A current power supply was used to generate the plasma discharge rich in diverse reactive species.These species induce rapid chemical reactions responsible for the reduction of the gold salts upon contact with the liquid solution.In this study,spherical and monodispersed gold nanoparticles were obtained within 5 min of plasma exposure using a solution containing gold(Ⅲ)chloride hydrate(HAuCl_(4))as a precursor and polyvinylpyrrolidone(PVP)as a capping agent to inhibit agglomerations.The formation of these metal nanoparticles was initially perceptible through a visible change in the sample's color,transitioning from light yellow to a red/pink color.This was subsequently corroborated by UVvis spectroscopy,which revealed an optical absorption in the 520-550 nm range for Au NPs,corresponding to the surface plasmon resonance(SPR)band.An investigation into the impact of various parameters,including plasma discharge duration,precursor and capping agent concentrations,was carried out to optimize conditions for the formation of well-separated,spherical gold nanoparticles.Dynamic light scattering(DLS)was used to measure the size of these nanoparticles,transmission electron microscopy(TEM)was used to observe their morphology and X-ray diffraction(XRD)was also employed to determine their crystallographic structure.The results confirm that homogeneous spherical gold nanoparticles with an average diameter of 13 nm can be easily synthesized through a rapid,straightforward,and environmentally friendly approach utilizing a helium atmospheric pressure plasma. 展开更多
关键词 gold nanoparticles NON-THERMAL plasma jet HELIUM DBD
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Near-field radiative heat transfer between nanoporous GaN films
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作者 韩晓政 张纪红 +2 位作者 刘皓佗 吴小虎 冷惠文 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第4期109-120,共12页
Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional path... Photon tunneling effects give rise to surface waves,amplifying radiative heat transfer in the near-field regime.Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer,leading to a substantial enhancement of near-field radiative heat transfer(NFRHT).Being a direct bandgap semiconductor,GaN has high thermal conductivity and stable resistance at high temperatures,and holds significant potential for applications in optoelectronic devices.Indeed,study of NFRHT between nanoporous GaN films is currently lacking,hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT.In this work,we delve into the NFRHT of GaN nanoporous films in terms of gap distance,GaN film thickness and the vacuum filling ratio.The results demonstrate a 27.2%increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5.Moreover,the spectral heat flux exhibits redshift with increase in the vacuum filling ratio.To be more precise,the peak of spectral heat flux moves fromω=1.31×10^(14)rad·s^(-1)toω=1.23×10^(14)rad·s^(-1)when the vacuum filling ratio changes from f=0.1 to f=0.5;this can be attributed to the excitation of surface phonon polaritons.The introduction of graphene into these configurations can highly enhance the NFRHT,and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio,which can be explained by the excitation of surface plasmon polaritons.These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control,management and thermal modulation. 展开更多
关键词 near-field radiative heat transfer nanoporous GaN film surface phonon polaritons surface plasmon polaritons
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Cavitation cloud impingement and scattering motion of jet in rock breaking process
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作者 Qi-Heng Zhu Fei Ma +2 位作者 Bo-Shen Liu Tian-Xu Luo Yan Pan 《Petroleum Science》 SCIE EI CAS CSCD 2024年第5期3535-3546,共12页
The cavitation cloud impingement of the jet in the rock breaking process was experimentally investigated to reveal the jet erosion mechanism in drilling of petroleum exploitation. Serial erosion tests and flow visuali... The cavitation cloud impingement of the jet in the rock breaking process was experimentally investigated to reveal the jet erosion mechanism in drilling of petroleum exploitation. Serial erosion tests and flow visualization were performed, where the cavitation cloud motion in the erosion crater was obtained with the designed transparent specimen. Various erosion patterns were identified in the whole erosion process based on the eroded specimen topography. The shallow eroded crater with a shrinking erosion area is generated by the combination of impinging and scattering cavitation clouds. The increase of l_(d) promotes the development of cavitation cloud σ_(c) but reduces the impingement frequency f_(d), suggesting that the jet aggressive ability is enhanced when the balance between σ_(c) and f_(d) is reached. The cavitation cloud motion in the erosion crater was investigated with the transparent specimen. The erosion in the crater at shorter exposure periods T_(e) is generated by the combination of impingement and restricted scattering of cavitation clouds. With the continuous development of the erosion damage, the jet's aggressive ability is diminished due to the erosion expansion on sandstone, where the cavitation clouds impinge on the target and then collapse and vanish without restricted scattering. 展开更多
关键词 EROSION Cavitating jet Rock breaking Flow visualzation 3D-printing
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CONVEXITY OF THE FREE BOUNDARY FOR AN AXISYMMETRIC INCOMPRESSIBLE IMPINGING JET
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作者 王晓慧 《Acta Mathematica Scientia》 SCIE CSCD 2024年第1期234-246,共13页
This paper is devoted to the study of the shape of the free boundary for a threedimensional axisymmetric incompressible impinging jet.To be more precise,we will show that the free boundary is convex to the fluid,provi... This paper is devoted to the study of the shape of the free boundary for a threedimensional axisymmetric incompressible impinging jet.To be more precise,we will show that the free boundary is convex to the fluid,provided that the uneven ground is concave to the fluid. 展开更多
关键词 Euler system axisymmetric impinging jet INCOMPRESSIBLE free boundary CONVEXITY
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The interaction between a shaped charge jet and a single moving plate
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作者 Andreas Helte Jonas Lundgren Jonas Candle 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第1期1-13,共13页
Reactive armour is a very efficient add-on armour against shaped charge threats.Explosive reactive armour consists of one or several plates that are accelerated by an explosive.Similar but less violent acceleration of... Reactive armour is a very efficient add-on armour against shaped charge threats.Explosive reactive armour consists of one or several plates that are accelerated by an explosive.Similar but less violent acceleration of plates can also be achieved in a completely inert reactive armour.To be efficient against elongated jets,the motion of the plates needs to be inclined against the jet such that a sliding contact between the jet and the plates is established.This sliding contact causes a deflection and thinning of the jet.Under certain circumstances,the contact will become unstable,leading to severe disturbances on the jet.These disturbances will drastically reduce the jet penetration performance and it is therefore of interest to study the conditions that leads to an unstable contact.Previous studies on the interaction between shaped charge jets and flyer plates have shown that it is mainly the forward moving plate in an explosive reactive armour that is effective in disturbing the jet.This is usually attributed to the higher plate-to-jet mass flux ratio involved in the collision of the forward moving plate compared to the backward moving plate.For slow moving plates,as occurs in inert reactive armour,the difference in mass flux for the forward and backward moving plate is much lesser,and it is therefore of interest to study if other factors than the mass flux influences on the protection capability.In this work,experiments have been performed where a plate is accelerated along its length,interacting with a shaped charge jet that is fired at an oblique angle to the plate’s normal,either against or along the plate’s velocity.The arrangement corresponds to a jet interacting with a flyer plate from a reactive armour,with the exception that the collision velocity is the same for both types of obliquities in these experiments.The experiments show that disturbances on the jet are different in the two cases even though the collision velocities are the same.Numerical simulations of the interaction support the observation.The difference is attributed to the character of the contact pressure in the interaction region.For a backward moving plate,the maximum contact pressure is obtained at the beginning of the interaction zone and the contact pressure is therefore higher upstream than downstream of the jet while the opposite is true for a forward moving plate.A negative interface pressure gradient with respect to the jet motion results in a more stable flow than a positive,which means that the jet-plate contact is more stable for a backward moving plate than for a forward moving plate.A forward moving plate is thus more effective in disturbing the jet than a backward moving plate,not only because of the higher jet to plate mass flux ratio but also because of the character of the contact with the jet. 展开更多
关键词 Reactive armour Flyer plate Shaped charge jet
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Characteristics and Formation Mechanisms of Low-Level Jets in Northeastern China
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作者 Hailong SHU Fan ZHANG +4 位作者 Yu DU Yue WANG Huichuang GUO Zhen SONG Qinghong ZHANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第12期2432-2445,共14页
This study examines low-level jets(LLJs)across Northeastern China during both warm(June-September)and cold seasons(December-March)from 1957 to 2021,using fifth generation of the European Centre for Medium-Range Weathe... This study examines low-level jets(LLJs)across Northeastern China during both warm(June-September)and cold seasons(December-March)from 1957 to 2021,using fifth generation of the European Centre for Medium-Range Weather Forecasts reanalysis data with 25-km resolution.LLJs manifest in two prominent regions,one along the leeward flank of the Da Hinggan Ling Mountains in the cold season and another at the center of Northeastern China in the warm season.The intricate interplay between ambient circulation and terrain shapes LLJ distribution,altitudes,wind directions,diurnal cycles,and seasonal diversities.During the warm season,prevailing southwesterly LLJs are found at 925 hPa,while the cold season features stronger and more frequent northwesterly LLJs at 875 hPa.Analysis of the diurnal patterns reveals distinctive behaviors of LLJs in the cold and warm seasons.During the warm season,the single peak in LLJ occurrence emerges around midnight;conversely,in the cold season,LLJs are most frequent shortly before midnight,with an additional sub-peak in the morning.A momentum budget analysis establishes mechanisms underlying these two distinct diurnal variations.In both seasons,the diurnal variation of LLJs is predominately driven by an inertial oscillation and mountain-valley circulations.However,the sub-peak observed in the cold-season morning arises from the thermodynamic and dynamic interaction between the low-level atmosphere and complex terrain. 展开更多
关键词 low-level jet seasonal disparities diurnal variation inertial oscillation terrain-flow interaction
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A large-scale cold plasma jet: generation mechanism and application effect
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作者 崔伟胜 张若兵 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第4期1-8,共8页
Atmospheric pressure cold plasma jets(APCPJs) typically exhibit a slender, conical structure,which imposes limitations on their application for surface modification due to the restricted treatment area. In this paper,... Atmospheric pressure cold plasma jets(APCPJs) typically exhibit a slender, conical structure,which imposes limitations on their application for surface modification due to the restricted treatment area. In this paper, we introduce a novel plasma jet morphology known as the large-scale cold plasma jet(LSCPJ), characterized by the presence of both a central conical plasma jet and a peripheral trumpet-like diffuse plasma jet. The experimental investigations have identified the factors influencing the conical and the trumpet-like diffuse plasma jet, and theoretical simulations have shed light on the role of the flow field and the electric field in shaping the formation of the LSCPJ. It is proved that, under conditions of elevated helium concentration, the distributions of impurity gas particles and the electric field jointly determine the plasma jet’s morphology. High-speed ICCD camera images confirm the dynamic behavior of plasma bullets in LSCPJ, which is consistent with the theoretical analysis. Finally, it is demonstrated that when applied to the surface treatment of silicone rubber, LSCPJ can achieve a treatment area over 28 times larger than that of APCPJ under equivalent conditions. This paper uncovers the crucial role of impurity gases and electric fields in shaping plasma jet morphology and opens up the possibility of efficiently diversifying plasma jet generation effects through external electromagnetic fields. These insights hold the promise of reducing the generation cost of plasma jets and expanding their applications across various industrial sectors. 展开更多
关键词 diffuse plasma jet flow field electric field surface treatment
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