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Convection of Maxwell fluid over stretching porous surface with heat source/sink in presence of nanoparticles:Lie group analysis

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Applied Mathematics and Mechanics(English Edition) 2016年第4期37卷 433-442页

作者： Limei CAO Xinhui si Liancun ZHENG Department of Applied Mathematics School of Mathematics and PhysicsUniversity of Science and Technology Beijing

The convection of a Maxwell fluid over a stretching porous surface with a heat source/sink in the presence of nanoparticles is investigated. The Lie symmetry group transformations are used to convert the boundary layer equations into coupled nonlinear ordinary differential equations. The ordinary differential equations are solved numerically by the Bvp4c with MATLAB, which is a collocation method equivalent to the fourth-order mono-implicit Runge-Kutta method. Furthermore, more attention is paid to the effects of the physical parameters, especially the parameters related to nanoparticles, on the temperature and concentration distributions with consideration of permeability and the heat source/sink.

关键词： Lie group Maxwell fluid porous stretching surface heat sink or source

Recursive super-convergence computation for multi-dimensional problems via one-dimensional element energy pro jection technique

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Applied Mathematics and Mechanics(English Edition) 2018年第7期39卷 1031-1044页

作者： si YUAN Yue WU Qinyan XING Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry Department of Civil Engineering Tsinghua University

This paper presents a strategy for computation of super-convergent solutions of multi-dimensional problems in the finite element method （FEM） by recursive application of the one-dimensional （1D） element energy projection （EEP） technique. The main idea is to conceptually treat multi-dimensional problems as generalized 1D problems, based on which the concepts of generalized 1D FEM and its consequent EEP formulae have been developed in a unified manner. Equipped with these concepts, multi-dimensional problems can be recursively discretized in one dimension at each step, until a fully discretized standard finite element （FE） model is reached. This conceptual dimension-by- dimension （D-by-D） discretization procedure is entirely equivalent to a full FE discretization. As a reverse D-by-D recovery procedure, by using the unified EEP formulae together with proper extraction of the generalized nodal solutions, super-convergent displacements and first derivatives for two-dimensional （2D） and three-dimensional （3D） problems can be obtained over the domain. Numerical examples of 3D Poisson＇s equation and elasticity problem are given to verify the feasibility and effectiveness of the proposed strategy.

关键词： three-dimensional(3D)problem generalized one-dimensional(1D)finiteelement method (FEM) dimension-by-dimension(D-by-D) super-convergence elementenergy projection(EEP)

Formulations of a hydromechanical interface element

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Acta Mechanica sinica 2011年第5期27卷 697-705页

作者： Zhong-Zhi Fu si-Hong Liu College of Water Conservancy and Hydropower Engineering Hohai University 210098 Nanjing China

A hydromechanical interface element is proposed for the consideration of the hydraulic-mechanical coupling effect along the *** fully coupled governing equations and the relevant finite element formulations are derived in detail for the interface *** the involved matrices are of the same form as those of a solid element,which makes the incorporation of the model into a finite element program *** examples are then numerically simulated using the interface *** results confirm the correctness of the proposed model and motivate its application in hydromechanical contact problems in the future.

关键词： Hydromechanical interface element · Coupling effect · Finite element · Contact problem

RMAC： A Reliable MAC Protocol Supporting Multicast for Wireless Ad Hoc Networks

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Journal of Computer Science & Technology 2005年第5期20卷 702-712页

作者： Wei-Sheng si Cheng-Zhi Li School of Software Dalian University of Technology P.R. China Department of Computer Science and Engineering University of Texas at Arlington U.S.A.

This paper presents a new reliable MAC protocol called “RMAC”supporting reliable multicast for wireless ad hoc networks. By utilizing the busy tones to realize the multicast reliability, RMAC has three novelties：（1） it uses a variablelength control frame to stipulate an order for the receivers to respond, thus solving the feedback collision problem; （2） it extends the usage of busy tone for preventing data frame collisions into the multicast scenario; and （3） it introduces a new usage of busy tone for acknowledging data frames positively. In addition, RMAC is generalized into a comprehensive MAC protocol that provides both reliable and unreliable services for all the three modes of communications： unicast, multicast, and broadcast, making it capable of supporting various upper-layer protocols. The evaluation shows that RMAC achieves high reliability with very limited overhead. RMAC is also compared with other reliable MAC protocols, showing that RMAC not only provides higher reliability but also involves lower cost.

关键词： wireless ad hoc network medium access control reliable multicast busy tone

Prediction of cutting forces in flank milling of parts with non-developable ruled surfaces

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Chinese Journal of Aeronautics 2019年第7期32卷 1788-1796页

作者： Liping WANG Hao si Liheng GU Department of Mechanical Engineering Tsinghua UniversityBeijing100084China Beijing Beiyi Machine Tool Co.Ltd. Beijing101300China

Predicting the cutting forces required for five-axis flank milling is a challenging task due to the difficulties involved in determining the Undeformed Chip Thickness(UCT) and CutterWorkpiece Engagement(CWE). To solve these problems, this paper presents a new mechanistic cutting force model based on the geometrical analysis of a flank milling process. In the model,the part feature and corresponding cutting location data are taken as input information. The UCT considering cutter runout is calculated according to the instantaneous feed rate of the element cutting edges. A solid-discrete-based method is used to precisely and efficiently identify the CWE between the end mill and the surface being machined. Then, after calibrating the specific force coef-ficients, the mechanistic milling force can be obtained. During the validation process, two practical operations, three-axis flank milling of a vertical surface and five-axis flank milling of a nondevelopable ruled surface, are conducted. Comparisons between predicted and measured cutting forces demonstrate the reliability of the proposed cutting force model.

关键词： Chip thickness Cutting force Five-axis flank milling Machining Ruled surface

A measurement-driven adaptive probability hypothesis density filter for multitarget tracking

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Chinese Journal of Aeronautics 2015年第6期28卷 1689-1698页

作者： si Weijian Wang Liwei Qu Zhiyu College of Information and Communication Engineering Harbin Engineering University

This paper studies the dynamic estimation problem for multitarget tracking. A novel gat- ing strategy that is based on the measurement likelihood of the target state space is proposed to improve the overall effectiveness of the probability hypothesis density （PHD） filter. Firstly, a measurement-driven mechanism based on this gating technique is designed to classify the measure- ments. In this mechanism, only the measurements for the existing targets are considered in the update step of the existing targets while the measurements of newborn targets are used for exploring newborn targets. Secondly, the gating strategy enables the development of a heuristic state estima- tion algorithm when sequential Monte Carlo （SMC） implementation of the PHD filter is investi- gated, where the measurements are used to drive the particle clustering within the space gate. The resulting PHD filter can achieve a more robust and accurate estimation of the existing targets by reducing the interference from clutter. Moreover, the target birth intensity can be adaptive to detect newborn targets, which is in accordance with the birth measurements. simulation results demonstrate the computational efficiency and tracking performance of the proposed algorithm.

关键词： Adaptive Measurement-driven Multitarget trackin Probability hypothesis density Sequential Monte Carlo

Controlled growth of Au/Ni bimetallic nanocrystals with different nanostructures

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Rare Metals 2017年第4期36卷 229-235页

作者： si-Bin Duan Rong-Ming Wang School of Mathematics and Physics University of Science and Technology Beijing Beijing 100083 China

Bimetallic nanomaterials are of great signifi- cance to both fundamental research and industrial appli- cations. Their physicochemical performances are critically dependent on their architectures and electronic structures. Here, it was reported a controlled synthesis of Au/Ni bimetallic nanocrystals with different nanostructures, i.e., dumbbell, core@shell and alloyed nanostructures in a one- pot synthesis procedure. Detailed structural characteriza- tions were conducted with the combination of transmission electron microscopy （TEM） and X-ray diffraction （XRD）. Even there is a large lattice mismatch between Au and Ni, Au@Ni core@shell nanocrystals are obtained with the seeded growth method. The growth mechanism was deeply investigated. Triphenylphosphine is demonstrated to be an effective capping agent to modify the interfacial energy to form core@shell nanocrystals, and the higher temperature is proved to be a key role in obtaining alloyed nanocrystals.

关键词： Bimetallic nanomaterials Au/Ni nanocrystals Interfacial energy Core@shell structure

Laser ablation of block copolymers with hydrogen-bonded azobenzene derivatives

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Frontiers of Chemical Science and Engineering 2018年第3期12卷 450-456页

作者： Jintang Huang Youju Huang si Wu Max Planck Institute for Polymer Research Aekermannweg 10 55128 Mainz Germany Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Soft Matter ChemistrY/ Anhui Key Laboratory ofOptoelcctronic Science and Technology Innovation Centre of Chemistry for Energy Materials Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China

Supramolecular assemblies （PS-b-P4VP （AzoR）） are fabricated by hydrogen-bonding azobenzene derivatives （AzoR） to poly（4-vinyl pyridine） blocks of polystyrene-block-poly（4-vinyl pyridine）（PS-b-P4VP）. PS-b-P4VP（AzoR） forms phase separated nanostructures with a period of-75-105 nm. A second length scale structure with a period of 2μm is fabricated on phase separated PS-b-P4VP（AzoR） by laser interference abla- tion. Both the concentration and the substituent of AzoR in PS-b-P4VP（AzoR） affect the laser ablation process. The laser ablation threshold of PS-b-P4VP（AzoR） decreases as the concentration of AzoR increases. In PS-b-P4VP（AzoR） with different substituents （R = CN, H, and CH3）, ablation thresholds follow the trend： PS-b-P4VP（AzoCN）〈 PS-b- P4VP（AzoCH3）〈PS-b-P4VP（AzoH）. This result indicates that the electron donor group （CH3） and the electron acceptor group （CN） can lower the ablation threshold of PS-b-P4VP（AzoR）.

关键词： laser ablation block copolymers hydrogen-bond azobenzene derivatives supramolecular assembly

Redox-active nanoparticles for inflammatory bowel disease

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Nano Research 2021年第8期14卷 2535-2557页

作者： Qinjuan Ren si Sun Xiao-Dong Zhang Department of Physics and Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology School of SciencesTianjin UniversityTianjin 300350China Tianjin Key Laboratory of Brain Science and Neural Engineering Academy of Medical Engineering and Translational MedicineTianjin UniversityTianjin 300072China

Homeostasis of gut microbiota is extremely essential for maintaining nutrient metabolism and regulating immunological *** increasing evidence suggests that inflammatory bowel disease(IBD)is strongly associated with dysregulation of gut *** activated inflammation,excessive reactive oxygen species(ROS)and reactive nitrogen species(RNS)produced by inflammatory cells play a detrimental role in regulating IBD and gut ***/RNS cause damage to the surrounding tissues,including nutrient absorption disorders,intestinal dysmotility and barrier ***,ROS/RNS provide terminal electron receptors for anaerobic respiration and support the bloom of facultative anaerobes,eventually causing gut microbiota ***-active nanoparticles(NPs)with catalytic properties or enzyme-like activities can effectively scavenge ROS/RNS,and selectively target inflamed sites via ultrasmall size-mediated enhanced permeation and retention(EPR)effect,showing great potential to regulate IBD and maintain the homeostasis of gut *** addition,the widespread application of NPs in commercial products 1 has increased their accumulation in healthy organisms,and the biological effects on normal microbiota resulting from long-term exposure of NPs to gastrointestinal tract also need attention.

关键词： gut microbiota IBD ROS/RNS redox-active NPs