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A high-order full-discretization method using Hermite interpolation for periodic time-delayed differential equations

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Acta Mechanica Sinica 2015年第3期31卷 406-415页

作者： Yilong Liu Achim Fischer Peter Eberhard Baohai wu Key Laboratory of Contemporary Design and Integrated Manufacturing Technology Northwestern Polytechnical University Institute of Engineering and Computational Mechanics University of Stuttgart

A high-order full-discretization method （FDM） using Hermite interpolation （HFDM） is proposed and implemented for periodic systems with time delay. Both Lagrange interpolation and Hermite interpolation are used to approximate state values and delayed state values in each discretization step. The transition matrix over a single period is determined and used for stability analysis. The proposed method increases the approximation order of the semidiscretization method and the FDM without increasing the computational time. The convergence, precision, and efficiency of the proposed method are investigated using several Mathieu equations and a complex turning model as examples. Comparison shows that the proposed HFDM converges faster and uses less computational time than existing methods.

关键词： Full-discretization method Time delay -Stability Chatter

Duality in interaction potentials for curved surface bodies and inside particles

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Applied Mathematics and Mechanics(English Edition) 2017年第8期38卷 1071-1090页

作者： Dan WANG Yajun YIN Jiye wu Zheng ZHONG Department of Engineering Mechanics Tsinghua University Department of Civil Engineering Nanjing Tech University Department of Engineering Mechanics Tongji University

Based on the viewpoint of duality, this paper studies the interaction between a curved surface body and an inside particle. By convex/concave bodies with geometric duality, interaction potentials of particles located outside and inside the curved surface bodies are shown to have duality. With duality, the curvature-based potential between a curved surface body and an inside particle is derived. Furthermore, the normal and tangential driving forces exerted on the particle are studied and expressed as a function of curvatures and curvature gradients. Numerical experiments are designed to test accuracy of the curvature-based potential.

关键词： curved duality curvature concave tangential viewpoint convex intersection body radius

Experimental investigations on cavity-actuated under-expanded supersonic oscillating jet

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Chinese Journal of Aeronautics 2015年第5期28卷 1372-1380页

作者： Sun Bo Luo Xiaochen Feng Feng wu Xiaosong Department of Aerospace Engineering Nanjing University of Science and Technology

As one type of potential flow control actuators, cavity-actuated supersonic jet oscillators, which consist of a 2-D convergent nozzle and two face to face cavities, need to be investigated dee- ply to get the knowledge of their oscillating feature and underlying mechanism. Wind tunnel testing are conducted under different back pressures in a vacuum-type wind tunnel for two supersonic jet oscillators, to obtain their characteristics and the conditions for jet oscillating. The experimental results show that the continuous, nearly symmetric or asymmetric flipping between the two cavities appears over certain nozzle pressure ratio （NPR） range for both oscillators according to schlieren visualizations. Compared to the free jet, the oscillating jet with large exit achieves larger mixing; the oscillating jet with small exit has less mixing, based on the analysis of jet axial peak velocity and the entrainment. The cross-junction mode for estimating the resonance frequency in a pipe with two closed side branches is modified and obtained comparable estimations of the frequency of jet flipping with experimental data, but further investigations are needed to discover the underlying mechanism for the jet flipping.

关键词： Jet cavity interactions Jet flipping Oscillating jet Supersonic jet Wind-tunnel testing

Recent advances in post-chiroptical manipulation of supramolecular aggregates assembled with molecular modules

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Science China Chemistry 2024年第9期67卷 2842-2863页

作者： Yanling Shen Wanhua wu Zhipeng Yu Cheng Yang Key Laboratory of Green Chemistry&Technology of Ministry of Education College of Chemistry InstitutionSichuan UniversityChengdu 610064China

Recently,various supramolecular assembly systems have been identified where the pre-existing chiral supramolecular structure can be manipulated through environmental adjustments,such as temperature,solvent,and *** changes result in diverse microscopic morphologies during the assembly process and induce chiroptical variations,particularly in circular dichroism(CD)and circularly polarized luminescence(CPL)*** chiroptical properties serve as direct indicators of the chiral supramolecular structure and hold promise for applications in sensing,molecular recognition,asymmetric synthesis,and material *** review focuses on research published in the last five years,highlighting instances where assembled structures aggregated by small organic molecular modules demonstrate in-situ chiroptical changes through external condition *** categorizes and discusses different modes of regulation,aiming to offer insights and guidelines for exploring dynamic changes in assembly processes and designing in-situ adjustable structures of assembly modules.

关键词： supramolecular assemblies post-chiroptical manipulation in-situ structural changes

The ANOVA-Type Inference in Linear Mixed Model with Skew-Normal Error

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Journal of Systems Science & Complexity 2017年第3期30卷 710-720页

作者： wu Mixia ZHAO Jing WANG Tonghui ZHAO Yan College of Applied Sciences Beijing University of Technology Department of Mathematical Sciences New Mexico State University

Linear mixed effect models with skew-normal errors and distribution-free random effects are considered. The ANOVA-type F-tests are proposed to test the significance of random effects and the hypothesis on fixed effects of interest, respectively. Both tests are proved to be exact F-tests under this model, and the exact confidence interval for fixed effects of interest is derived. Simulation results are given to study the powers of ANOVA-type tests.

关键词： ANOVA-type estimator ANOVA-type F-test skew-normal error.

Hydrophobic nanocellulose aerogels with high loading of metal-organic framework particles as floating and reusable oil absorbents

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Frontiers of Chemical Science and Engineering 2021年第5期15卷 1158-1168页

作者： Jiajia Li Shengcheng Zhai Weibing wu Zhaoyang Xu Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forestry Resources College of Materials Science and EngineeringNanjing Forestry UniversityNanjing210037China College of Light Industry and Food Engineering Nanjing Forestry UniversityNanjing210037China

In this paper,we employed a facile approach to prepare flexible and porous metal-organic frameworks(MOFs)containing cellulose nanofiber(CNF)aerogels(MNCAs)through freeze-drying MOF-containing cellulose nanofiber *** coating with methyltrimethoxysilane(MTMS)by chemical vapor deposition,recycled and hydrophobic MTMS-coated MNCAs(MMNCAs)were *** to the low density(0.009 g/cm^(3)),high porosity(97%)and good mechanical properties of the aerogel,the adsorption capacity of MMNCAs reached up to 210 g/g,which was nearly 3–5 times that of pure CNF *** prepared aerogels showed excellent oil/water selectivity and high capacity to adsorb oil and organic *** kind of cellulose-based aerogel may be applicable in the field of environmental protection.

关键词： cellulose nanofibers aerogels metal-organic framework oil-adsorption

Aerodynamic Performance of a Flapping Foil with Asymmetric Heaving Motion near a Wall

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Journal of Bionic Engineering 2018年第4期15卷 636-646页

作者： Xingjian Lin Shuhao Guo Jie wu Jingwen Nan Department of Aerodynamics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The effect of asymmetric heaving motion on the aerodynamic performance of a two-dimensional flapping foil near a wall is studied numerically. The foil executes the heaving and pitching motion simultaneously. When the heaving motion is symmetric, the mean thrust coefficient monotonically increases with the decrease in mean distance between foil and wall. Meanwhile, the mean lift coefficient first increases and then decreases sharply. In addition, the negative mean lift coefficient appears when the foil is very close to the wall. After the introduction of asymmetric heaving motion, the influence of wall effect on the force behavior becomes complicated. The mean thrust coefficient is enhanced when the duration of upstroke is reduced. Moreover, more and more enhancement can be achieved when the foil approaches the wall gradually. On the other hand, the positive mean lift coefficient can be observed when the duration of downstroke is shortened. By checking the flow patterns around the foil, it is shown that the interaction between the vortex shed from the foil and the wall can greatly modify the pressure distribution along the foil surface. The results obtained here might be utilized to optimize the kinematics of the Micro Aerial Vehicles （MAVs） flying near a solid wall.

关键词： asymmetric heaving motion wall effect thrust enhancement positive mean lift

A RANKING METHOD FOR DMUS WITH INTERVAL DATA BASED ON DEA CROSS-EFFICIENCY EVALUATION AND TOPSIS

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Journal of Systems Science and Systems Engineering 2013年第2期22卷 191-201页

作者： Jie wu Jiasen SUN Malin SONG Liang LIANG School of Management University of Science & Technology of China

The traditional data envelopment analysis （DEA） model can evaluate the relative efficiencies of a set of decision making units （DMUs） with exact values of inputs and outputs, but it cannot handle imprecise data. Imprecise data, for example, can be expressed in the form of the interval data or mixtures of interval data and ordinal data. In this study, a cross-efficiency method is introduced into the DEA model to calculate the interval of cross-efficiency values, based on which a new TOPSIS method is proposed to rank the DMUs. Two examples are presented to illustrate and validate the proposed method.

关键词： Data envelopment analysis (DEA) cross-efficiency TOPSIS

Integrating Variable Reduction Strategy With Evolutionary Algorithms for Solving Nonlinear Equations Systems

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IEEE/CAA Journal of Automatica Sinica 2022年第1期9卷 75-89页

作者： Aijuan Song Guohua wu Witold Pedrycz Ling Wang School of Traffic and Transportation Engineering Central South UniversityChangsha 410075China Department of Electrical and Computer Engineering University of AlbertaEdmontonAB T6G 2V4Canada Department of Electrical and Computer Engineering Faculty of EngineeringKing Abdulaziz UniversityJeddah 21589Saudi Arabia Systems Research Institute Polish Academy of SciencesWarsaw 01447Poland Department of Automation Tsinghua UniversityBeijing 100084China

Nonlinear equations systems(NESs)are widely used in real-world problems and they are difficult to solve due to their nonlinearity and multiple *** algorithms(EAs)are one of the methods for solving NESs,given their global search capabilities and ability to locate multiple roots of a NES simultaneously within one ***,the majority of research on using EAs to solve NESs focuses on transformation techniques and improving the performance of the used *** contrast,problem domain knowledge of NESs is investigated in this study,where we propose the incorporation of a variable reduction strategy(VRS)into EAs to solve *** VRS makes full use of the systems of expressing a NES and uses some variables(i.e.,core variable)to represent other variables(i.e.,reduced variables)through variable relationships that exist in the equation *** enables the reduction of partial variables and equations and shrinks the decision space,thereby reducing the complexity of the problem and improving the search efficiency of the *** test the effectiveness of VRS in dealing with NESs,this paper mainly integrates the VRS into two existing state-of-the-art EA methods(i.e.,MONES and DR-JADE)according to the integration framework of the VRS and EA,*** results show that,with the assistance of the VRS,the EA methods can produce better results than the original methods and other compared ***,extensive experiments regarding the influence of different reduction schemes and EAs substantiate that a better EA for solving a NES with more reduced variables tends to provide better performance.

关键词： Evolutionary algorithm(EA) nonlinear equations systems(ENSs) problem domain knowledge variable reduction strategy(VRS)