检索结果-南通市图书馆

science China(Technological sciences) 2024年第6期67卷 1923-1932页

作者： ZHAO Tao SHI Yan LU Kun XI Xiang WU XueZhong XIAO DingBang College of Intelligence science and Engineering National University of Defense TechnologyChangsha410073China

The quality factor(Q factor)is a crucial performance parameter for *** this paper,a novel release method for highquality micro fused silica shell resonators with teeth-like tines with good surface morphology is *** method is based on femtosecond laser-assisted chemical ***,the optimal energy range of femtosecond laser modification is obtained through mechanism ***,the optimal parameters for a straight line and arc pattern are determined by optimizing the average output power,processing speed,and processing *** results demonstrate why edge breakage in rounded corners is easy under different ***,according to these conclusions,the processing is performed on a micro fused silica shell resonator with a Q factor exceeding 6 *** addition,subsurface damage is rare throughout the fabrication process,and the surface roughness of the released cross section reaches the nanometer *** improved Q factor helps suppress mechanical thermal noise and reduce zero bias and zero bias drift,constituting the primary method for enhancing the performance of the resonant gyroscope.

关键词： micro hemispherical resonator fused silica laser-assisted chemical etching quality factor

Large eddy simulation study on drag reduction performance of array-based plasma synthetic jet actuators

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第10期37卷 118-135页

作者： Yunan WANG Zhenbing LUO Wei XIE Yan ZHOU Qiang LIU Wenqiang PENG Yinxin ZHU College of Aerospace science and Engineering National University of Defense TechnologyChangsha 410073China

Large Eddy Simulation(LES)is first used to investigate the drag reduction effect of an array-based configuration of Plasma Synthetic Jet Actuators(PSJAs)on a hemisphere in supersonic inflow,and analyze the effect of energy allocation and array angle on the drag reduction performance of opposing Plasma Synthetic Jet(PSJ)in this *** simulation results have been compared with experimental data,confirming the validity of the simulation *** results show that different energy allocations have a significant effect on the drag of the ***,the effect of the change in array angle on the drag of the hemisphere is not as noticeable as the effect caused by energy *** regions between the two PSJAs occur,which undermine the effectiveness of drag *** Turbulent Kinetic Energy(TKE)regions primarily concentrate on the core region of the jet and downstream of the bow *** influence of the array angle on TKE is most evident in the downstream region of the exits of the PSJs on both *** evolution of the coherent structures reveals that as the PSJ intensity decreases,the largescale vortices progressively break up into smaller-scale vortices,and energy is also transferred from large-scale structures to small-scale structures.

关键词： Plasma synthetic jet Shock wave Large eddy simulation Drag reduction Flow control

Minimal Context-Switching Data Race Detection with Dataflow Tracking

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Computer science & technology 2024年第1期39卷 211-226页

作者：郑龙李洋辛杰刘海峰郑然廖小飞金海 national Engineering Research Center for Big Data technology and System School of Computer Science and Technology Huazhong University of Science and TechnologyWuhan 430074China Services Computing technology and System Laboratory School of Computer Science and TechnologyHuazhong University of Science and TechnologyWuhan 430074China Cluster and Grid Computing Laboratory School of Computer Science and TechnologyHuazhong University of Science and TechnologyWuhan 430074China

Data race is one of the most important concurrent anomalies in multi-threaded *** con-straint-based techniques are leveraged into race detection,which is able to find all the races that can be found by any oth-er sound race ***,this constraint-based approach has serious limitations on helping programmers analyze and understand data ***,it may report a large number of false positives due to the unrecognized dataflow propa-gation of the ***,it recommends a wide range of thread context switches to schedule the reported race(in-cluding the false one)whenever this race is exposed during the constraint-solving *** ad hoc recommendation imposes too many context switches,which complicates the data race *** address these two limitations in the state-of-the-art constraint-based race detection,this paper proposes DFTracker,an improved constraint-based race detec-tor to recommend each data race with minimal thread context ***,we reduce the false positives by ana-lyzing and tracking the dataflow in the *** this means,DFTracker thus reduces the unnecessary analysis of false race *** further propose a novel algorithm to recommend an effective race schedule with minimal thread con-text switches for each data *** experimental results on the real applications demonstrate that 1)without removing any true data race,DFTracker effectively prunes false positives by 68%in comparison with the state-of-the-art constraint-based race detector;2)DFTracker recommends as low as 2.6-8.3(4.7 on average)thread context switches per data race in the real world,which is 81.6%fewer context switches per data race than the state-of-the-art constraint based race ***,DFTracker can be used as an effective tool to understand the data race for programmers.

关键词： data race satisfiability modulo theory multi-threaded program dynamic detection

Influence of tungsten particle size on microstructure and mechanical properties of high strength and tough tungsten particle-reinforced nickel-based composites by laser-direct energy deposition

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials science & technology 2024年第5期172卷 213-227页

作者： Wenji Song Dengzhi Wang Congwen Tang Pengfei Sun Jiaxing Yang Zhidong Xu Tao Lai Jianqiang Gong Qianwu Hu Xiaoyan Zeng Wuhan national Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430000China

Tungsten(W)particle-reinforced nickel(Ni)-based composites were fabricated via laser-direct energy de-position(L-DED).The influence of the W particle size on the microstructure and mechanical properties of the deposited samples was systematically *** results indicate that refining the W particle size could refine theγ-Ni grains and subgrains,thin the(Ni,Cr)_(4)W interface layer,and increase the disloca-tion density of the intergranular matrix,thus improving the tensile strength and elongation of the L-DED *** W particle size decreased from 75 to 150μm to 6.5-12μm,the tensile strength and elonga-tion of the deposited samples increased by 150 MPa and 2.9 times to 1347.6±15.7 MPa and 17.5±0.4%,*** on the properties of the interface(Ni,Cr)_(4)W,a load-transfer efficiency factor suitable for this composite was proposed and the load-transfer strengthening formula was optimized.A quanti-tative analysis of the strengthening mechanisms was established considering load-transfer strengthening,Hall-Petch strengthening,thermal-mismatch strengthening,and solid-solution *** calcu-lated contribution of each strengthening mechanism to the yield strength and theoretical calculations were in good agreement with the experimental *** article breaks the bottleneck of poor plasticity of W particle-reinforced Ni-based composites prepared by L-DED and provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites with excellent mechanical properties.

关键词： Laser-direct energy deposition(L-DED) Tungsten particle reinforcements Mechanical property Strengthening mechanism

Room-temperature ferrimagnetism and size-modulated electronic structures in two-dimensional cluster-based metal-organic frameworks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

science China Chemistry 2024年第4期67卷 1334-1340页

作者： Jing Cheng Xingxing Li Jinlong Yang Key Laboratory of Precision and Intelligent Chemistry University of Science and Technology of ChinaHefei 230026China Department of Chemical Physics University of Science and Technology of ChinaHefei 230026China Hefei national Research Center for Physical sciences at the Microscale University of Science and Technology of ChinaHefei 230026China Hefei national Laboratory University of Science and Technology of ChinaHefei 230088China

Cluster-assembled materials have attracted particular attention for their complex hierarchical structures and unique ***,the majority of cluster-based assemblies developed so far are either non-magnetic or only exhibit magnetic ordering with a relatively low Curie temperature,limiting their applications in ***,two-dimensional(2D)cluster-assembled materials with room-temperature magnetism remain highly *** this purpose,based on first principles calculations,we design a series of thermodynamically stable 2D cluster-based metal-organic frameworks(MOFs)Fe_(n)-(pyz)(n=1-6)by utilizing Fenmetal clusters as nodes and nitrogen-containing pyrazine ligands as organic *** 2D cluster-based MOFs exhibit robust ferrimagnetic ordering due to the strong d-p direct exchange interaction between d-electron spin of Fe_(n)(n=1-6)clusters and charge transfer-induced p-electron spin of pyrazine *** particular,the ferrimagnetic Curie temperatures are well above room temperature(up to 836 K).Additionally,altering the size of Fe_(n)clusters in Fe_(n)-(pyz)(n=1-6)MOFs results in diverse functional spintronic properties,including bipolar magnetic semiconductors,half semiconductors and Dirac half ***,these 2D assembled MOFs possess sizable magnetic anisotropy energies,up to 9.16 me V per formula.

关键词： metal-organic framework two-dimensional material half metal bipolar magnetic semiconductor magnet

Optical detection method of discharge mode transition of inductively coupled plasma in an atmosphere-breathing electric propulsion system

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第10期37卷 172-183页

作者： Yuxuan ZHONG Yu ZHANG Jianjun WU Peng ZHENG College of Aerospace science and Engineering National University of Defense TechnologyChangsha 410073China

Plasma discharge stability is an important problem in atmosphere-breathing electric propulsion system when maintaining long-term missions at ultra-low earth *** paper designed an inductively coupled plasma source to imitate the ionization *** effect of inflow rate and Radio Frequency(RF)power on the plasma discharge mode transition is experimentally studied.A discharge mode detection method is proposed,which determines the discharge mode by identifying the morphology of the plasma *** using the method,the discharge mode transition is quantified and a control model based on the parameter sensitivity is *** verify the method,the spectra are measured and the electron temperature spatial distribution is *** the method has been proven *** results show that the inductively coupled discharge contains capacitive components affected by the mass flow rate and the radio frequency *** plasma characteristics can be maintained stably by controlling the radio frequency power when the mass flow rate randomly changes in a certain *** is demonstrated that the application of detection method effectively identifies the discharge mode,which is a promising active control method for the plasma discharge mode.

关键词： Atmosphere-breathing electric propulsion Inductively coupled plasma Discharge mode transition Optical diagnosis Ultra-low earth orbit

A physics-informed deep learning framework for spacecraft pursuit-evasion task assessment

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第5期37卷 363-376页

作者： Fuyunxiang YANG Leping YANG Yanwei ZHU College of Aerospace science and Engineering National University of Defense TechnologyChangsha 410073China

Qualitative spacecraft pursuit-evasion problem which focuses on feasibility is rarely studied because of high-dimensional dynamics,intractable terminal constraints and heavy computational *** this paper,A physics-informed framework is proposed for the problem,providing an intuitive method for spacecraft threat relationship determination,situation assessment,mission feasibility analysis and orbital game rules *** the first time,situation adjustment suggestions can be provided for the weak player in orbital ***,a dimension-reduction dynamics is derived in the line-of-sight rotation coordinate system and the qualitative model is determined,reducing complexity and avoiding the difficulty of target set presentation caused by individual ***,the Backwards Reachable Set(BRS)of the target set is used for state space partition and capture zone ***-time analysis can eliminate the influence of changeable initial state and enable the proposed framework to analyze plural situations ***,a time-dependent Hamilton-Jacobi-Isaacs(HJI)Partial Differential Equation(PDE)is established to describe BRS evolution driven by dimension-reduction dynamics,based on level set ***,Physics-Informed Neural Networks(PINNs)are extended to HJI PDE final value problem,supporting orbital game rules summarization through capture zone evolution ***,numerical results demonstrate the feasibility and efficiency of the proposed framework.

关键词： Spacecraft pursuit-evasion Qualitative differential game Physics-Informed Neural Networks(PINNs) Reachability analysis Hamilton-Jacobi-Isaacs(HJI) Partial Differential Equations(PDEs)

Self-powered UVC detectors based on α-Ga_(2)O_(3) with enchanted speed performance

在线全文

学校读者我要写书评

暂无评论

Journal of Semiconductors 2024年第8期45卷 74-80页

作者： Aleksei Almaev Alexander Tsymbalov Bogdan Kushnarev Vladimir Nikolaev Alexei Pechnikov Mikhail Scheglov Andrei Chikiryaka Laboratory of Metal Oxide Semiconductors Research and Development Center for Advanced Technologies in MicroelectronicsNational Research Tomsk State UniversityTomsk 634050Russia Fokon LLC Kaluga 248035Russia Department of Semiconductor Electronics and Physics of Semiconductors National University of Science and Technology MISISMoscow 119049Russia Perfect Crystals LLC Saint Petersburg 194223Russia

Detectors were developed for detecting irradiation in the short-wavelength ultraviolet(UVC)interval using high-quality single-crystallineα-Ga_(2)O_(3) films with Pt interdigital *** films ofα-Ga_(2)O_(3) were grown on planar sapphire substrates with c-plane orientation using halide vapor phase *** spectral dependencies of the photo to dark current ratio,responsivity,external quantum efficiency and detectivity of the structures were investigated in the wavelength interval of 200−370 *** maximum of photo to dark current ratio,responsivity,external quantum efficiency,and detectivity of the structures were 1.16×10^(4) ***.,30.6 A/W,1.65×10^(4)%,and 6.95×10^(15) Hz^(0.5)·cm/W at a wavelength of 230 nm and an applied voltage of 1 *** high values of photoelectric properties were due to the internal enhancement of the photoresponse associated with strong hole ***α-Ga_(2)O_(3) film-based UVC detectors can function in self-powered operation mode due to the built-in electric field at the Pt/α-Ga_(2)O_(3) *** a wavelength of 254 nm and zero applied voltage,the structures exhibit a responsivity of 0.13 mA/W and an external quantum efficiency of 6.2×10^(−2)%.The UVC detectors based on theα-Ga_(2)O_(3) films demonstrate high-speed performance with a rise time of 18 ms in self-powered mode.

关键词： HVPE gallium oxide solar-blind ultraviolet detector self-powered mode

Semi-supervised remote sensing image scene classification with prototype-based consistency

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第2期37卷 459-470页

作者： Yang LI Zhang LI Zi WANG Kun WANG Qifeng YU College of Aerospace science and Engineering National University of Defense TechnologyChangsha 410073China

Deep learning significantly improves the accuracy of remote sensing image scene classification,benefiting from the large-scale ***,annotating the remote sensing images is time-consuming and even tough for *** neural networks trained using a few labeled samples usually generalize less to new unseen *** this paper,we propose a semi-supervised approach for remote sensing image scene classification based on the prototype-based consistency,by exploring massive unlabeled *** this end,we,first,propose a feature enhancement module to extract discriminative *** is achieved by focusing the model on the foreground ***,the prototype-based classifier is introduced to the framework,which is used to acquire consistent feature *** conduct a series of experiments on NWPU-RESISC45 and Aerial Image Dataset(AID).Our method improves the State-Of-The-Art(SOTA)method on NWPU-RESISC45 from 92.03%to 93.08%and on AID from 94.25%to 95.24%in terms of accuracy.

关键词： Semi-supervised learning Remote sensing Scene classification Prototype network Deep learning

Efficient synthesis of bottle-brush polymers enabled by selective photoactivation strategy in NIR-induced PET-RAFT polymerization

在线全文

学校读者我要写书评

暂无评论

science China Chemistry 2024年第7期67卷 2353-2361页

作者： Hao Zha Lin Cheng Zuowei Wang Chao Liu Chunyan Hong Department of Polymer science and Engineering University of Science and Technology of ChinaHefei 230026China Hefei national Laboratory for Physical sciences at the Microscale University of Science and Technology of ChinaHefei 230026China

Bottle-brush polymers possessing densely grafted side chains have special properties that are distinct from linear ***,an efficient method for preparing bottle-brush polymers based on a selective photoactivation strategy in the photoinduced electron/energy transfer reversible addition-fragmentation chain transfer(PET-RAFT)polymerization was developed.A methacrylate monomer 2-(2-(dodecylthiocarbonothioylthio)propionate)ethyl methacrylate(DTPEMA)containing a 2-(dodecylthiocarbonothioylthio)propionate(DTP)unit with a secondary R group was *** the unique selectivity of metal naphthalocyanine photocatalyst zinc 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine(ZnTtBNc)toward trithiocarbonate with tertiary R group,the PET-RAFT polymerization of DTPEMA catalyzed by ZnTtBNc was performed under near infrared(NIR)light(λ_(max)=760 nm)irradiation at room temperature,using 4-cyano-4-[(dodecylsulfanylthiocarbonyl)-sulfanyl]pentanoic acid(CDTPA)with a tertiary R group as a chain transfer agent(CTA).Proton nuclear magnetic resonance(1H NMR)and gel permeation chromatography(GPC)results demonstrated that the DTP units in the side chains were inert during the *** grafting poly(methyl acrylate)(PMA)from PDTPEMA via thermal-initiated RAFT polymerization,welldefined P(DTPEMA-g-PMA)bottle-brush polymers could be ***,the film prepared from the bottle-brush polymer exhibited excellent scratch self-healing property due to the interlocking of side chains.

关键词： bottle-brush polymers PET-RAFT polymerization selective photoactivation scratch self-healing