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An extended unresolved CFD-DEM coupling method for simulation of fluid and non-spherical particles

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Particuology 2022年第9期20卷 1-12页

作者： Liping He Zhengxian liu Yongzhi Zhao Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin 300350China Institute of Process Equipment College of Energy EngineeringZhejiang UniversityHangzhou 310027China

This study develops an extended unresolved CFD-DEM coupling method for simulation of the fluid-solid flow with non-spherical *** limitation of fluid grid size is discussed,by simulating the settling of a cylinder in a Newtonian fluid based on the resolved and unresolved CFD-DEM coupling ***,the calculation of porosity and the fluid-particle relative velocity based on the particle shape enlarge-ment method for simulation of non-spherical particles is *** availability of the particle shape enlargement method for the simulation of non-spherical particles with different sphericity is discussed in this work,by comparing it with the results from the equivalent diameter enlargement *** lim-itation of the equivalent diameter enlargement method for non-spherical particles is revealed from the simulation *** typical cases are employed to elaborate and verify the extended unresolved CFD-DEM method based on particle shape enlargement method,by presenting a good consistency with the experimental *** proves that the extended unresolved CFD-DEM method is suitable for differ-ent CFD grid size ratios,and consolidates that it is a universal calculation method for CFD-DEM coupling simulation.

关键词： CFD-DEM Unresolved method Fluid-solid flow Non-spherical particle Rod

Remote sensing image encryption algorithm utilizing 2D Logistic memristive hyperchaotic map and SHA-512

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Science China(Technological Sciences) 2024年第5期67卷 1553-1566页

作者： LAI Qiang liu Yuan YANG Liang School of Electrical and Automation Engineering East China Jiaotong UniversityNanchang330013China

The two-dimensional Logistic memristive hyperchaotic map(2D-LMHM)and the secure hash SHA-512 are the foundations of the unique remote sensing image encryption algorithm(RS-IEA)suggested in this *** proposed map is formed from the improved Logistic map and the memristor,which has wide phase space and hyperchaotic range and is exceptionally excellent to be utilized in specific *** proposed image algorithm uses the permutation-assignment-diffusion *** generates two position matrices in a progressive manner to achieve an efficient random exchange of pixel positions,assignment is carried through on the image pixels of the permutated image to entirely remove the original image information,strengthening the relationship between permutation and diffusion,and loop diffusion in two different directions can use subtle changes of pixels to affect the whole *** random key and plain-image SHA-512 hash values are used to produce an additional key,which is then utilized to figure out the permutation parameters and the initial value of a chaotic *** experimental results with the average NPCR=99.6094%(NPCR:number of pixels change rate),average UACI=33.4638%(UACI:unified average changing intensity),100%pass rate of the targets in the test set,the average correlation coefficient is 0.00075,and the local information entropy is 7.9025,which shows that the algorithm is able to defend against a variety of illegal attacks and provide more trustworthy protection than some of the existing state-of-the-art algorithms.

关键词： chaos memristive hyperchaotic map remote sensing SHA-512 image encryption RS-IEA

Chiroluminophores based on non-conjugated benzenes

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Science China Chemistry 2023年第7期66卷 2130-2140页

作者： Yiping liu Aiyou Hao Pengyao Xing School of Chemistry and Chemical Engineering Shandong UniversityJinan 250100China

Point-chiral groups as pendants conjugated to the aromatic luminophore generate weak chiroptical signals without self-assembly,showing the dependence on the flexibility of tethers,which hinders the development of point-chiral molecular materials with chiroptical properties such as the circularly polarized luminescence(CPL).Herein we introduce the molecular chiroptical materials based on the point chirality on a single benzene luminophore *** were stepwise conjugated to single benzene luminophores to boost the steric hindrance and tension,whereby the chirality transfer efficiency from point-chiral substituents to luminophores was *** intramolecular CH-πinteractions anchor the whole asymmetric geometry with ultra-high rotation energy barriers and excellent *** g-factors of circular dichroism and CPL spectra up to 10^(-3)order of magnitude were realized in solutions,which are comparable to the inherent-chiral luminophores such as helicene and binaphthyl *** acridine-appended single benzene system shows the emergence of thermally activated delayed fluorescence(TADF),which extends the potentials of the single benzene chiral system in the TADF-based chiroptical devices.

关键词： point chirality single-benzene based luminophores chirality transfer circularly polarized luminescence thermally activated delayed fluorescence

A new progressive open-set recognition method with adaptive probability threshold

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Chinese Journal of Aeronautics 2023年第11期36卷 297-310页

作者： Zhunga liu Xuemeng HUI Yimin FU Department of Automation Northwestern Polytechnical UniversityXi’an 710072China

In the traditional pattern classification method,it usually assumes that the object to be classified must lie in one of given(known)classes of the training data ***,the training data set may not contain the class of some objects in practice,and this is considered as an Open-Set Recognition(OSR)*** this paper,we propose a new progressive open-set recognition method with adaptive probability *** the labeled training data and the test data(objects to be classified)are put into a common data set,and the k-Nearest Neighbors(k-NNs)of each object are sought in this common ***,we can determine the probability of object lying in the given *** the majority of k-NNs of the object are from labeled training data,this object quite likely belongs to one of the given classes,and the density of the object and its neighbors is taken into account ***,when most of k-NNs are from the unlabeled test data set,the class of object is considered very uncertain because the class of test data is unknown,and this object cannot be classified in this *** the objects belonging to known classes with high probability are all found,we re-calculate the probability of the other uncertain objects belonging to known classes based on the labeled training data and the objects marked with the estimated *** iteration will stop when the probabilities of all the objects belonging to known classes are not ***,a modified Otsu’s method is employed to adaptively seek the probability threshold for the final *** the probability of object belonging to known classes is smaller than this threshold,it will be assigned to the ignorant(unknown)class that is not included in training data *** other objects will be committed to a specific *** effectiveness of the proposed method has been validated using some experiments.

关键词： Data mining k-nearest neighbors Open-set recognition Object recognition The Otsu’s method

Facile electrodepositing coral-/urchin-like polyaniline on carbon cloth in salty media as electrode for high-performance flexible supercapacitors

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Progress in Natural Science:Materials International 2023年第5期33卷 668-673页

作者： Jinmei Li Lining Zhao Peng liu College of Chemistry and Chemical Engineering State Key Laboratory of Applied Organic Chemistry Lanzhou University

The electrochemical performance of the carbon cloth(CC)-based flexible electrodes is determined by the kind,micro-structure, and morphology of the deposited pseudocapacitive materials. In the present work, the coral-/urchin-like polyaniline(PANI) was designed to boost the electrochemical property of CC, by integrating the microstructure advantages of coral-like and nanowire arrays, via the facile electrochemical polymerization of aniline on the functionalized carbon cloth(FCC) in salty media. The corresponding electrode delivered a high specific capacitance of 3376 m F cm-2at 1 m A cm-2and 151 F g-1at 1 A g-1, with an ultrahigh boosting in specific capacitance of 246 % and superior cycling stability of 149.8 % after 10,000 cycles, in comparison with the reported PANI/CC ones via electrodeposition. This work provided a new idea for the construction of conductive polymers with unique nano-architectures on CC for high-performance electrodes for flexible supercapacitors.

关键词： Flexible solid-state supercapacitors Coral-/urchin-like polyaniline Electrodeposition Salty media Carbon cloth

A New DGM(1,1)Model with a Grey Parameter and Its Application

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Journal of Systems Science and Information 2022年第3期10卷 297-308页

作者： Xin ZENG Jun liu Fuxiang liu Hongmei liu School of Science China Three Gorges UniversityYichang 443002China Three Gorges Mathematical Research Center Yichang 443002China

In the DGM(1, 1) model modeling process, the influencing factors are uncertain. But the solution of DGM(1, 1) model with uncertain information is unique, which conflicts with the nonuniqueness principle of solution in grey theory. In view of this situation, this paper makes an in-depth analysis of the meaning of grey action quantity β_(2) in DGM(1, 1) model and regards β_(2) as an interval grey number. The maximum possibility whitenization value is given to estimate the kernel of grey number,and the typical possibility function is constructed to describe the possibility of grey number taking different values. A new DGM(1, 1) model with a grey parameter is then proposed, whose simulation results are interval grey numbers. The proposed model is compatible with the DGM(1, 1) model in model structure and simulation results. Finally, the practical example results show the applicability and effectiveness of the proposed model.

关键词： DGM(1,1)model non-uniqueness principle of solution interval grey number maximum possibility whitenization value

Simulation Study on Flow and Heat Transfer of Cross-Arrangement Tube Bundle

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Journal of Thermal Science 2023年第4期32卷 1435-1444页

作者： LI Shuangfei LI Jinjing liu Zhenhua School of Mechanical Engineering Shanghai Jiaotong UniversityShanghai200240China

The air precooler of SABRE engine(Synergetic Air-Breathing Rocket Engine)is a tube bundle type of heat exchanger consisting of thousands of small *** cold helium gas flows in the small tube bundle,and the high-speed hot air circulates outside the tubes and exchanges heat with the helium in the *** this study,the cross-arrangement tube bundle consisting of small tubes with outer diameter of 1mm was taken as the research *** system simulation calculation and data sorting were carried *** is found that the empirical correlation of the conventional tube bundle is no longer applicable to the small tube and the reasons for inapplicability are explained by analysis of flow *** addition,the results show that the average heat transfer coefficient of cross small/micro tube bundle isn’t affected by heat flux,but increases with the increase of Reynolds number,increases with the increase of transverse spacing,and decreases with the increase of longitudinal *** flow resistance coefficient isn’t affected by heat flux and longitudinal spacing,but decreases with the increase of Reynolds number,and decreases with the increase of transverse spacing.

关键词： staggered arrangement small tube fitting formulas air cooler SABRE engine

Residual stress indentation model based on material equivalence

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Chinese Journal of Aeronautics 2022年第8期35卷 304-313页

作者： Xiaokun liu Lixun CAI Hui CHEN Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu 610031China School of Civil Engineering Changsha University of Science&TechnologyChangsha 410114China

A novel residual stress indentation model for conical indentation loading is proposed to describe the relationship between the residual stress,material constitutive parameters,load,and displacement for materials with a uniaxial constitutive relationship that obeys Hollomon’s power law(H-law).The novel model was established based on the principle that the equivalent material without residual stress corresponds to the original material with residual stress,conical indentation theoretical model based on energy density equivalence,and an assumed power-law relationship between the dimensionless residual stress and relative difference of the yield stresses of the equivalent material and original *** imaginary H-law materials with ten equibiaxial and ten uniaxial residual stresses were investigated by Finite Element Analysis(FEA).The residual stresses predicted by the novel model from the indentation load–displacement curves simulated for the imaginary materials are in close agreement with those applied by the ***,indentation tests for Cr12Mo V steel,45 steel,and 6061-T6511 aluminum alloy were carried out on their specimens without residual stress and their bending specimens with equibiaxial and uniaxial residual *** residual stresses predicted by the novel model according to the indentation load–displacement test curves are in good agreement with those applied by the tests.

关键词： Conical indentation Equivalent material Finite element analysis Residual stress Theoretical model

Numerical simulation of rime ice accretion on a threedimensional wind turbine blade using a Lagrangian approach

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Frontiers of Structural and Civil Engineering 2023年第12期17卷 1895-1906页

作者： Tiange ZHANG Xuanyi ZHOU Zhenbiao liu State Key Laboratory of Disaster Reduction in Civil Engineering Tongji UniversityShanghai 200092China State Key Laboratory of Photovoltaic Science and Technology Trina SolarChangzhou 213031China

The accreted ice on wind turbine blades significantly deteriorates the blade aerodynamic performance and consequently the power *** existing numerical simulations of blade icing have mostly been performed with the Eulerian approach for two-dimensional(2D)blade profiles,neglecting the possible three-dimensional(3D)rotating *** paper conducts a numerical simulation of rime ice accretion on a 3D wind turbine blade using the Lagrangian *** simulation results are validated through previously published experimental *** icing characteristics along the blade radial direction are then investigated in *** radial airflow along the blade is observed,which demonstrates the necessity of 3D *** addition,more droplets are found to impinge on the blade surface near the tip region,thereby producing severer ice accretion *** accreted ice increases almost linearly along the blade radial direction in terms of both ice mass and maximum ice thickness.

关键词： ice accretion wind turbine numerical simulation Lagrangian approach