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Interaction tonal noise generated by contra-rotating open rotors

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Chinese Journal of Aeronautics 2023年第4期36卷 134-147页

作者： Wangjian SHU Congcong CheN Lin DU Xiang He Xiaofeng SUN School of Energy and Power Engineering Beihang UniversityBeijing 100191China Research Institute of Aero-Engine Beihang UniversityBeijing 100191China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412002China

Fast and accurate prediction of sound radiation of Contra-Rotating Open Rotors(CRORs)is an essential element of design methods of low-noise open rotor propulsion systems.In the present work,a previous frequency-domain model is extended to predict CROR noise.It builds explicitly the relationship between harmonic loadings and corresponding tonal noise,by which the influential parameters to noise generation can be clearly understood.The real distribu-tions of steady and unsteady blade loadings are calculated by the Nonlinear Harmonic(NLH)method.In the present hybrid approach,both the CFD and acoustic modules are solved in the fre-quency domain.To assess the accuracy of the developed method,the loading noise of a CROR is calculated and compared against results by using the time-domain FW-H module of NUMECA.The predicted sound directivities by the two methods are in good agreements.The present acoustic model in the frequency domain is proven to be accurate and have high efficiency in far-field noise prediction and data processing.Furthermore,the characteristics of the CROR interaction tonal noise are analyzed and discussed.

关键词： Contra-Rotating Open Rotors(CRORs) Interaction tonal noise Nonlinear Harmonic(NLH) Frequency domain Acoustic analogy

In-situ growth of porous Cu_(3)(BTC)_(2) on cellulose nanofibrils for ultra-low dielectric films with high flexibility

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Journal of Materials Science & Technology 2022年第17期112卷 202-211页

作者： Rui Liu Xiang He Miao Miao Shaomei Cao Xin Feng Department of Chemistry College of SciencesShanghai UniversityShanghai 200444China Research Center of Nano Science and Technology College of SciencesShanghai UniversityShanghai 200444China

The design of flexible polymeric films with internal porous structures has received increasing attention in low dielectric applications.The highly porous metal-organic frameworks(MOFs)of[Cu_(3)(BTC)_(2)]_(n)(BTC=benzene-1,3,5-tricarboxylate)were introduced into aramid nanofibers(ANF)matrix by using carboxylated cellulose nanofibrils(CNF)as carriers to obtain strong,flexible,and ultra-low dielectric films.The well-dispersed“flowers-branch”like CNF@CuBTC through in-situ growth of CuBTC on CNF surface endowed the ANF/CNF@Cu BTC films with excellent thermal stability,mechanical integrity and low dielectric properties.Besides,the flexible dielectric films exhibited superior ultraviolet(UV)resistance,lower coefficient of thermal expansion(4.28×10^(-5)℃^(-1))and increased water contact angle(83.81°).More interestingly,the removal of guest molecules from the ANF/CNF@CuBTC films according to the vacuum heat treatment(VHT)process significantly improved their dielectric response.The specific surface areas of the composite films after VHT increased obviously,and the dielectric constant and dielectric loss tangent decreased to the expected 1.8-2.2 and 0.001-0.03 at 100 MHz,respectively.Consequently,such designable ultra-low dielectric films with high flexibility play an incredible significance in applications of microelectronics under large deformation conditions,especially in flexible/wearable devices at the arrival of 5 G era.

关键词： Aramid nanofibers Carboxylated cellulose nanofibrils Vacuum heat treatment Dielectric properties Metal-organic frameworks

Hydrophobic long alkyl chain organic cations induced 2D/3D heterojunction for efficient and stable perovskite solar cells

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Journal of Materials Science & Technology 2022年第29期124卷 243-251页

作者： Xiang He Min Wang Fengren Cao Wei Tian Liang Li School of Physical Science and Technology Center for Energy Conversion Materials and PhysicsJiangsu Key Laboratory of Thin FilmsSoochow UniversitySuzhou 215006China

Designing post-formed two-dimensional(2D)perovskite on the surface of three-dimensional(3D)perovskite with matched energy levels and high stability is crucial for improving the performance and stability of perovskite solar cells(PSCs).herein,a long alkyl chain dodecylammonium bromide(DABr)was applied to react with excessive lead iodide(PbI_(2))on the grain boundary of metal halide perovskite preferentially,forming DA_(2)PbI_(4)(n=1)to constitute a clear 2D/3D heterojunction.The existence of heterojunction increases the intensity of the built-in electric field of the device to enhance carrier separation and extraction,and the amino group of dodecylammonium cation passivates defects,which jointly contribute to the improvement of the power conversion efficiency(PCE)from 20.35 to 21.81%.The long alkyl chain endows the 2D perovskite with good hydrophobic properties,improving the humidity and thermal stability of the device.The unencapsulated device can maintain 64%of its initial efficiency after 1065 h storage in ambient air.

关键词： Hydrophobic 2D/3D perovskite heterojunction Solar cell Stability

Microstructure and mechanical properties of a cast TRIP-assisted multiphase stainless steel

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China Foundry 2024年第3期21卷 221-228页

作者： Meng-xin Wang Zi-xiang Wu Jing-yu he xiang Chen School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

Stainless steels are used in a wide range of complex environments due to their excellent corrosion resistance.Multiphase stainless steels can offer an excellent combination of strength,toughness and corrosion resistance due to the coexistence of different microstructures.The microstructure and mechanical properties of a novel cast multiphase stainless steel,composed of martensite,ferrite,and austenite,were investigated following appropriate heat treatment processes:solution treatment at 1,050℃ for 0.5 h followed by water quenching to room temperature,and aging treatment at 500℃ for 4 h followed by water quenching to room temperature.Results show reversed austenite is formed by diffusion of Ni element during aging process,and the enrichment of Ni atoms directly determines the mechanical stability of austenite.The austenite with a lower Ni content undergoes a martensitic transformation during plastic deformation.The tensile strength of the specimen exceeds 1,100 MPa and the elongation exceeds 24%after solid solution,and further increases to 1,247 MPa and 25%after aging treatment.This enhancement is due to the TRIP effect of austenite and the precipitation of the nanoscale G-phase pinning dislocations in ferrite and martensite.

关键词： multiphase stainless steel mechanical properties TRIP effect reversed austenite G-phase

pH Induced Self-assembly of AIE Fluorescent Probe for Tumor Imaging

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Chinese Journal of Polymer Science 2024年第1期42卷 7-13,I0005页

作者： Jing-Yuan xiang Wen-Long Zhang he-Ting Li Ya-Ning he Department of Chemical Engineering Key Laboratory of Advanced Materials(MOE)Tsinghua UniversityBejing 100084China

This work reported an AIE fluorescent probe for tumor imaging based on the p H induced self-assembly strategy. The fluorescent probe was composed of an acid-responsive soluble copolymer PEG-b-PAMA-DMMA with a maleic acid amide group and an anionic soluble aggregation-induced emission fluorogen(AIEgen) TPE-2SO_(3)^(-). The polymer could be transformed into a protonated amine-containing polymer after the hydrolysis of maleic acid amide in acidic tumor microenvironment, which would be further self-assembled with TPE-2SO_(3)^(-)to form aggregated nanoparticles. The transition of TPE-2SO_(3)^(-)from dispersed state to aggregated state led to an obvious increase in fluorescence intensity due to its AIE characteristics.

关键词： p H-responsive Self-assembly Fluorescent probe AIE Tumor imaging

Meditator and Doer： On the Socialist New Man in Liu Qing＇s Novel The Builders

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Frontiers of Literary Studies in China-Selected Publications from Chinese Universities 2012年第2期6卷 232-254页

作者： Xiang He Department of Comparative Literature New York University New York NY 10003 USA

This article examines Liu Qing＇s 1959 novel The Builders, an epical work on the Agricultural Cooperation Movement, from the perspective of configuration of the Socialist New Man. Illuminated by the works of the May Fourth generation, especially Lu Xun, the author argues that the figure of the Socialist New Man usually differentiates itself into two literary prototypes--meditator and doer. Liu Qing attempts to maintain a productive and dialectic tension between meditations and deeds, instead of mere discrepancy or incompatibility. The article demonstrates that in literature, while the meditator can be depicted thoroughly through psychological dynamics and unconscious dreams, it is more problematic to represent the doer. Such a formal and philosophical problem is central to literature, as well as corresponds to the socio-historical paradox of the 1950s China.

关键词： meditations deeds the Socialist New Man selflessness

A micro–macro constitutive model for rock considering breakage effects

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International Journal of Mining Science and Technology 2023年第2期33卷 173-184页

作者： Di Yu Enlong Liu Bo xiang Yunyong he Fei Luo Chuan he State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu 610065China b Institute for Disaster Management and Reconstruction Sichuan UniversityChengdu 610207China Highway Planning Survey and Design Research InstituteSichuan Provincial Transport DepartmentChengdu 610041China College of Civil Engineering Sichuan Agricultural UniversityChengdu 611830China

The paper proposes a three-scale binary medium-based constitutive model on the basis of the meso structures and micro components to describe the elasto-plastic mechanical behavior of mudstone samples.Based on the breakage mechanism of geomaterials,mudstone samples are considered as two different materials(bonded and frictional elements)at mesoscales.From micro to meso scales,given the similar but different mineralogy composition and porosity of the bonded and frictional elements at microscale,as well as their separate mechanical characteristics,different homogenization methods are adopted to obtain their respective meso mechanical properties.At the mesoscale,in view of the unique meso structures and the continuous material transformation,the extended self-consistent scheme(SCS)is improved to be adaptable to elasto-plastic composites with varying meso components.With the consideration of the evolution form of the breakage ratio under the external loading being given based on the assumed strength distribution of the meso bonded elements,the mechanical relations between meso and macro scales are established.Finally,on the basis of the mean-field method and combined with the critical mechanical connections between different scales,the micro-meso-macro constitutive model for mudstone samples are proposed.The model validation shows that,with a few model parameters,the proposed model can well reflect the stress and deformation features of mudstone samples with complex micro-components.

关键词： Micromechanics Binary-medium model Multiscale model Breakage mechanism Mudstone

Numerical study on flow control of ship airwake and rotor airload during helicopter shipboard landing

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Chinese Journal of Aeronautics 2019年第2期32卷 324-336页

作者： Yongjie SHI Xiang He Yi XU Guohua XU National Key Laboratory of Rotorcraft Aeromechanics Nanjing University of Aeronautics and Astronautics Shanghai Institute of Electro-Mechanical Engineering

A numerical study on flow control of ship airwake during shipboard landing is carried out to address the effect of flow control devices on helicopter rotor airload. The in-house Reynolds Averaged Navier-Stokes(RANS) based solver Rotorcraft AeroDynamics and Aeroacoustics Solver(RADAS), with combination of momentum source approach is employed to conduct the helicopter shipboard landing simulation. The control effects of three aerodynamic modifications of ship superstructure, i.e. ramp, notch and flap, in different Wind-Over-Deck(WOD) conditions are discussed.From the steady simulation results, the effect of spatial variation of ship airwake on rotor airloads is concluded. The aerodynamic modifications reduce the strength of shedding vortex and increase rotor normal force through delaying and relieving flow separation, and therefore are beneficial to alleviate the limitation of control inputs. By contrast, the perturbation of unsteady ship airwake can cause the serious oscillation of rotor forces during shipboard landing. The unsteady simulations show that the turbulence intensity of ship airwake and oscillatory rotor airloading, represented by Root-Mean-Square(RMS) loading, can be remarkably reduced by the ramp and notch modifications, while the flap modification has adverse effect. It means that flow control devices have large potential benefits to alleviate the pilot's workload and improve the shipboard landing safety, but they should be well designed to avoid the introduction of more vortex, which leads to increase in disturbance of flow field.

关键词： Flow control helicopter Rotor airload Ship airwake Shipboard landing

Aerodynamic impact of train-induced wind on a moving motor-van

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Frontiers of Structural and Civil Engineering 2022年第7期16卷 909-927页

作者： Jiajun he Huoyue xiang Yongle LI Bin HAN Southwest Municipal Engineering Design and Research Institute of China Chengdu 610299China Department of Bridge Engineering Southwest Jiaotong UniversityChengdu 610031China Wind Engineering Key Laboratory of Sichuan Province Southwest Jiaotong UniversityChengdu 610031China Sichuan Railway Investment Group Co. Ltd.Chengdu 610093China

The newly-built single-level rail-cum-road bridge brings the issue of the aerodynamic impact of train-induced wind on road automobiles.This research introduced a validated computational fluid dynamics(CFD)model regarding this concern.Such an aerodynamic impact mechanism was explored;a relationship between the transverse distance between train and motor-van(hereinfafter referred to as van)and the aerodynamic effects on the van was explored to help the optimization of bridge decks,and the relationship between the automobile speed and aerodynamic variations of a van was fitted to help traffic control.The fitting results are accurate enough for further research.It is noted that the relative speed of the two automobiles is not the only factor that influences the aerodynamic variations of the van,even at a confirmed relative velocity,the aerodynamic variations of the van vary a lot as the velocity proportion changes,and the most unfavorable case shows an increase of over 40%on the aerodynamic variations compared to the standard case.The decay of the aerodynamic effects shows that not all the velocity terms would enhance the aerodynamic variations;the coupled velocity term constrains the variation amplitude of moments and decreases the total amplitude by 20%–40%.

关键词： rail-cum-road bridge aerodynamic impact train-induced wind CFD aerodynamic force quantitative analysis fitting