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Influence of Vanes and Blades on Ingress in Axial Rim seal for Turbine stages

Journal of Thermal science 2024年第3期33卷 833-846页

作者： ren Ran DU Qiang LIU Guang ZENG Yanlian XIE Lei Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing100190China National Key Laboratory of science and Technology on Advanced Light-duty Gas-turbine Beijing100190China school of Aeronautics and Astronautics University of Chinese Academy of SciencesBeijing100190China

Hot gas ingestion refers to the phenomenon of mainstream hot gas flowing into the space cavity of a turbine wheel.Previous studies have found that mainstream annulus pressure distribution plays an important role in hot gas ingestion,but due to its complexity,the mechanism of the interaction between mainstream flow and hot gas ingestion remains unclear.This paper adopts the URANs method,and three sealing flow rates are considered,named C_(w)=0,C_(w)=500,and C_(w)=5000.The time-averaged annulus pressure distribution shows that an increase in the sealing flow decreases the pressure value,and the effects of the sealing flow on the pressure distribution of the leading edge of the blade are much more influential than that of the trailing edge of the vane.The unsteady pressure time-space distribution in the annulus indicates that a time-space tilted distribution of pressure at the rim exits when the sealing flow exists.This phenomenon is mainly due to the strong feedback mechanism of the sealing flow to the annulus pressure field.A comparison of the pressure and mean radial velocity distribution of the mainstream shows that the ingestion mainly occurs on the blade side,where the pressure is lower than on the vane side.The flow characteristics at the wheel rim are analyzed with a sealing flow rate C_(w)=5000,and under these conditions,both pressure-induced ingestion and ingestion caused by a passage vortex can be inferred.The three-dimensional and inertial effects of the mainstream at the wheel rim lead to the generation of separation vortices on the blade side,and the presence of separation vortices leads to ingestion along the blade side.At the same time,pressure on the blade side will cause the fluid to have a radial inward flow tendency,which will promote the formation of separation vortices,leading to more serious ingestion in the high-pressure region on the blade side.The blade pressure field can be more significant than the vane trailing pressure field in the rim seal ingestion,and it contributes some explanations

关键词： separation vortex unsteady rim seal the effect of blade on ingestion

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surfactant-assisted crystallization of lysozyme and its mechanism

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Particuology 2024年第7期90卷 199-208页

作者： Yujie song Rongfei ren Min su Zhihan Liang Qi Hao school of Chemical Engineering Hebei University of TechnologyTianjin 300130China

surfactants were used to assist in the crystallization of lysozyme.Three types of surfactants with different structures(sodium dodecyl sulfate,cetyltrimethylammonium bromide,or betaine hydrochloride[BH])were used.The study indicated that three surfactants were all capable of shortening the crystallization induction time of lysozyme,with BH inducing the shortest crystallization induction time(t=1 min)and the largest crystal size(37μm).The molecular interactions among each of the three surfactants aforementioned and lysozyme were also investigated by simulations.It was found that hydrogen bonding dominantly acted between the carboxyl structure of the surfactant BH and the lysozyme,which produced the most favorable conformation for the self-assembly of lysozyme(promote lysozyme orderly aggregation and shorten the crystallization induction time).On this basis,the mechanism of surfactant-promoted lysozyme crystallization was proposed.

关键词： Protein Crystallization surfactant Lysozyme Molecular interaction Mechanism

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Visible Light Indoor Positioning system Based on Pisarenko Harmonic Decomposition and Neural Network

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Chinese Journal of Electronics 2024年第1期33卷 195-203页

作者： Li ZHAO Yi ren Qi WANG Lange DENG Feng ZHANG school of Electronic Information Engineering Xi’an Technological University

Visible-light indoor positioning is a new generation of positioning technology that can be integrated into smart lighting and optical communications. The current received signal strength(Rss)-based visible-light positioning systems struggle to overcome the interferences of background and indoor-reflected noise. Meanwhile, when ensuring the lighting, it is impossible to use the superposition of each light source to accurately distinguish light source information; furthermore, it is difficult to achieve accurate positioning in complex indoor environments. This study proposes an indoor positioning method based on a combination of power spectral density detection and a neural network. The system integrates the mechanism for visible-light radiation detection with Rss theory, to build a back propagation neural network model fitting for multiple reflection channels. Different frequency signals are loaded to different light sources at the beacon end, and the characteristic frequency and power vectors are obtained at the location end using the Pisarenko harmonic decomposition method. Then, a complete fingerprint database is established to train the neural network model and conduct location tests. Finally, the location effectiveness of the proposed algorithm is verified via actual positioning experiments. The simulation results show that, when four groups of sinusoidal waves with different frequencies are superimposed with white noise, the maximum frequency error is 0.104 Hz and the maximum power error is 0.0362 W. For the measured positioning stage, a 0.8 m × 0.8 m × 0.8 m solid wood stereoscopic positioning model is constructed, and the average error is 4.28 cm. This study provides an effective method for separating multi-source signal energies, overcoming background noise, and improving indoor visible-light positioning accuracies.

关键词： Visible-light communication Indoor positioning Frequency estimation Pisarenko harmonic decomposition Back propagation neural network

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Integral precession calibration method of PIGA on linear vibration table

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Chinese Journal of Aeronautics 2024年第3期37卷 219-236页

作者： Chuang sUN shun-qing ren Jun-wei CAO Ru HUO Department of Automation Tsinghua UniversityBeijing 100084China school of Astronautics Harbin Institute of TechnologyHarbin 150001China Beijing National Research Center for Information science and Technology Tsinghua UniversityBeijing 100084China Faculty of Information technology Beijing University of TechnologyBeijing 100124China

Linear vibration table can provide harmonic accelerations to excite the nonlinear error terms of Pendulous Integrating Gyro Accelerometer(PIGA).Integral precession calibration method is proposed to calibrate PIGA on a linear vibration table in this paper.Based on the precise expressions of PIGA’s inputs,the error calibration model of PIGA is established.Precession angular velocity errors of PIGA are suppressed by integer periodic precession and the errors caused by non-integer periods vibrating are compensated.The complete calibration process,including planning,preparation,PIGA testing,and coefficient identification,is designed to optimize the test operations and evaluate the calibration results.The effect of the main errors on calibration uncertainty is analyzed and the relative sensitivity function is proposed to further optimize the test positions.Experimental and simulation results verify that the proposed 10-position calibration method can improve calibration uncertainties after compensating for the related errors.The order of calibration uncertainties of the second-and third-order coefficients are decreased to 10^(-8)(rad.s^(-1))/g^(2)and 10^(-8)(rad.s^(-1))/g3,respectively.Compared with the other two classical calibration methods,the calibration uncertainties of PIGA’s nonlinear error coefficients can be effectively reduced and the proportional residual errors are decreased less than 3×10-6(rad.s^(-1))/g by using the proposed calibration method.

关键词： PIGA Linear vibration table Vibration measurement Calibration Error analysis Uncertainty analysis

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Copper-Free Resin-Based Braking Materials:A New Approach for substituting Copper with Fly-Ash Cenospheres in Composites

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Chinese Journal of Mechanical Engineering 2024年第2期37卷 401-412页

作者： Kaikui Zheng Youxi Lin shanmin You Zhiying ren Jianmeng Huang school of Mechanical Engineering and Automation Fuzhou UniversityFuzhou 350108China National United Engineering Laboratory for Advanced Bearing Tribology Henan University of Science and TechnologyLuoyang 471023China

Copper particles emitted from braking have become a significant source of environmental pollution.However,copper plays a crucial role in resin-based braking materials.Developing high-performance braking materials without copper has become a significant challenge.In this paper,the resin-based braking materials were filled with flyash cenospheres to develop copper-free braking materials.The effects of fly-ash cenospheres on the physical properties,mechanical and friction and wear properties of braking materials were studied.Furthermore,the wear mechanism of copper-free resin-based braking materials filled with fly-ash cenospheres was discussed.The results indicate that the inclusion of fly-ash cenospheres in the braking materials improved their thermal stability,hardness and impact strength,reduced their density,effectively increased the friction coefficient at medium and high temperatures,and enhanced the heat-fade resistance of the braking materials.The inclusion of fly-ash cenospheres contributed to the formation of surface friction film during the friction process of the braking materials,and facilitated the transition of form from abrasive wear to adhesive wear.At 100-350℃,the friction coefficient of the optimal formulation is in the range of 0.57-0.61,and the wear rate is in the range(0.29-0.65)×10^(-7) cm^(3)·N^(-1)·m^(-1),demonstrating excellent resistance to heat-fade and stability in friction coefficient.This research proposes the use of fly-ash cenospheres as a substitute for environmentally harmful and expensive copper in brake materials,which not only improves the performance of braking materials but also reduces their costs.

关键词： Fly-ash cenospheres Braking materials Friction and wear Heat-fade resistance Wear form

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Graphene enables equiatomic FeNiCrCoCu high-entropy alloy with improved TWIP and TRIP effects under shock compression

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Journal of Materials science & Technology 2024年第3期170卷 186-199页

作者： Hongcai Xie Zhichao Ma Wei Zhang Hongwei Zhao Luquan ren school of Mechanical and Aerospace Engineering Jilin UniversityChangchun 130025China Key Laboratory of CNC Equipment Reliability Ministry of Education Jilin UniversityChangchun 130025China Key Laboratory of Bionic Engineering Ministry of Education Jilin UniversityChangchun 130025China Weihai Institute for Bionics-Jilin University Weihai 264400China Institute of structured and Architected Materials Liaoning Academy of MaterialsShenyang 110167China

Graphene(Gr)reinforced high-entropy alloy(HEA)matrix composites are expected as potential candidates for next-generation structural applications in light of outstanding mechanical properties.A deep comprehension of the underlying deformation mechanisms under extreme shock loading is of paramount importance,however,remains lacking due to experimentally technical limitations in existence.In the present study,by means of nonequilibrium molecular dynamics simulations,dynamic deformation behaviors and corresponding mechanisms in equiatomic FeNiCrCoCu HEA/Gr composite systems were investigated in terms of various shock velocities.The resistance to dislocation propagation imparted by Gr was corroborated to encourage the elevated local stress level by increasing the likelihood of dislocation interplays,which facilitated the onset of twins and hexagonal close-packed(HCP)martensite laths.Meanwhile,the advent of Gr was demonstrated to endow the HEA with an additional twinning pathway that induced a structural conversion from HCP to parent face-centered cubic(FCC)inside HCP martensite laths,different from the classical one that necessitated undergoing the intermediate procedure of extrinsic stacking fault(EsF)evolution.More than that,by virtue of an increase in flow stress,the transformation-induced plasticity(TRIP)effect was validated to be additionally evoked as the predominant strain accommodation mechanism at higher strains on the one hand,but which only assisted plasticity in pure systems,and on the other hand,can also act as an auxiliary regulation mode together with the twinning-induced plasticity(TWIP)effect under intermediate strains,but with enhanced contributions relative to pure systems.One may expect that TRIP and TWIP effects promoted by introducing Gr would considerably inspire a synergistic effect between strength and ductility,contributing to the exceptional shock-resistant performance of FeNiCrCoCu HEAs under extreme regimes.

关键词： Molecular dynamics High-entropy alloy Graphene TRIP TWIP shock

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Can soil organic carbon sequestration and the carbon management index be improved by changing the film mulching methods in the semiarid region?

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Journal of Integrative Agriculture 2024年第5期23卷 1541-1556页

作者： Jialin Yang Liangqi ren Nanhai Zhang Enke Liu shikun sun Xiaolong ren Zhikuan Jia Ting Wei Peng Zhang College of Agronomy Northwest A&F UniversityYangling 712100China Key Laboratory of Crop Physi-Ecology and Tillage science in Northwestern Loess Plateau Ministry of Agriculture and Rural AfairsNorthwest A&FUniversityYangling 712100China Institute of Environment and sustainable Development in Agriculture Chinese Academy of Agricultural SciencesBeijing 100081China College of Water Resources and Architectural Engineering Northwest A&F UniversityYangling 712100China

Plastic film mulching has been widely used to increase maize yield in the semiarid area of China.However, whether long-term plastic film mulching is conducive to agricultural sustainability in this region remains controversial.A field experiment was initiated in 2013 with five different film mulching methods:(i) control method, flat planting without mulching (CK),(ii) flat planting with half film mulching (P),(iii) film mulching on ridges and planting in narrow furrows(s),(iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R).The effects on soil organic carbon (sOC) content, storage, and fractions, and on the carbon management index (CMI)were evaluated after nine consecutive years of plastic film mulching.The results showed that long-term plastic film mulching generally maintained the initial sOC level.Compared with no mulching, plastic film mulching increased the average crop yield, biomass yield, and root biomass by 48.38, 35.06, and 37.32%, respectively, which led to the improvement of sOC sequestration.specifically, plastic film mulching significantly improved CMI, and increased the sOC content by 13.59%, sOC storage by 7.47%and easily oxidizable organic carbon (EOC) by 13.78%on average,but it reduced the other labile fractions.sOC sequestration and CMI were improved by refining the plastic film mulching methods.The s treatment had the best effect among the four mulching methods, so it can be used as a reasonable film mulching method for sustainable agricultural development in the semiarid area.

关键词： plastic film mulching soil organic carbon labile organic carbon fractions semiarid area

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Dynamic mechanical characteristics of deep Jinping marble in complex stress environments

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 630-644页

作者： Chendi Lou Heping Xie Ru Zhang Hai ren Hao Luo Kun Xiao Yuan Peng Qiang Tan Li ren Institute for Disaster Management and Reconstruction Sichuan UniversityChengdu610207China College of Water Resource&Hydropower Sichuan UniversityChengdu610065China MOE Key Laboratory of Deep Earth science&Engineering Sichuan UniversityChengdu610065China Yalong River Hydropower Development Company Ltd.Chengdu610051China (Chongqing)International Engineering Technology Company Ltd.Chongqing401121China

To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.

关键词： Rock mechanics split-Hopkinson pressure bar Coupled static‒dynamic loading Different depths Holmquist-Johnson-Cook(HJC)model

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Boosting Hydrogen storage Performance of MgH_(2) by Oxygen Vacancy-Rich H-V_(2)O_(5) Nanosheet as an Excited H-Pump

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Nano-Micro Letters 2024年第8期16卷 398-416页

作者： Li ren Yinghui Li Zi Li Xi Lin Chong Lu Wenjiang Ding Jianxin Zou National Engineering Research Center of Light Alloys Net Forming&state Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China shanghai Engineering Research Center of Mg Materials and Applications&school of Materials science and Engineering Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China Center of Hydrogen science Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China Instrumental Analysis Center of sJTU Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China

MgH_(2) is a promising high-capacity solid-state hydrogen storage material,while its application is greatly hindered by the high desorption temperature and sluggish kinetics.Herein,intertwined 2D oxygen vacancy-rich V_(2)O_(5) nanosheets(H-V_(2)O_(5))are specifically designed and used as catalysts to improve the hydrogen storage properties of MgH_(2).The as-prepared MgH_(2)-H-V_(2)O_(5) composites exhibit low desorption temperatures(Tonset=185℃)with a hydrogen capacity of 6.54 wt%,fast kinetics(Ea=84.55±1.37 kJ mol^(-1) H_(2) for desorption),and long cycling stability.Impressively,hydrogen absorption can be achieved at a temperature as low as 30℃ with a capacity of 2.38 wt%within 60 min.Moreover,the composites maintain a capacity retention rate of~99%after 100 cycles at 275℃.Experimental studies and theoretical calculations demonstrate that the in-situ formed VH_(2)/V catalysts,unique 2D structure of H-V_(2)O_(5) nanosheets,and abundant oxygen vacancies positively contribute to the improved hydrogen sorption properties.Notably,the existence of oxygen vacancies plays a double role,which could not only directly accelerate the hydrogen ab/de-sorption rate of MgH_(2),but also indirectly affect the activity of the catalytic phase VH_(2)/V,thereby further boosting the hydrogen storage performance of MgH_(2).This work highlights an oxygen vacancy excited“hydrogen pump”effect of VH_(2)/V on the hydrogen sorption of Mg/MgH_(2).The strategy developed here may pave a new way toward the development of oxygen vacancy-rich transition metal oxides catalyzed hydride systems.

关键词： Hydrogen storage MgH_(2) V_(2)O_(5)nanosheets Oxygen vacancies VH_(2)

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Green development and economic resilience:Evidence from Chinese resource-based cities

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Frontiers of Engineering Management 2024年第2期11卷 194-206页

作者： Zongrun WANG Xuxin CAO Xiaohang ren school of Business Central South UniversityChangsha 410083China

Resource-based cities are currently facing challenges due to ecological pollution and an unbalanced industrial structure,which hinders sustainable economic growth.The focus on green development as a strategy for economic growth and environmental protection is becoming increasingly popular.This study employs a spatial econometric model to explore the effect of green development on economic resilience in Chinese resource-based cities from 2011 to 2019,revealing a positive correlation between green development and economic resilience.For each 1 unit increase in green development,economic resilience increases by an average of 0.512 units.Furthermore,the analysis of heterogeneity reveals differences in the factors influencing various resource-based cities.In addition,provincial green policies bolster economic resilience by encouraging green development.This research aids in comprehending the balance between the economy and the environment.

关键词： economic resilience green development spatial econometric models resource-based cities

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