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Dynamic flight stability of hovering model insects:theory versus simulation using equations of motion coupled with Navier-Stokes equations

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Acta Mechanica Sinica 2010年第4期26卷 509-520页

作者： Yan-lai zhang Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Institute of Fluid Mechanics Beihang University 100191 Beijing China

In the present paper, the longitudinal dynamic flight stability properties of two model insects are predicted by an approximate theory and computed by numerical sim- ulation. The theory is based on the averaged model （which assumes that the frequency of wingbeat is sufficiently higher than that of the body motion, so that the flapping wings＇ degrees of freedom relative to the body can be dropped and the wings can be replaced by wingbeat-cycle-average forces and moments）; the simulation solves the complete equations of motion coupled with the Navier-Stokes equations. Comparison between the theory and the simulation provides a test to the validity of the assumptions in the theory. One of the insects is a model dronefly which has relatively high wingbeat frequency （164 Hz） and the other is a model hawkmoth which has relatively low wingbeat frequency （26 Hz）. The results show that the averaged model is valid for the hawkmoth as well as for the dronefly. Since the wingbeat frequency of the hawkmoth is relatively low （the characteristic times of the natural modes of motion of the body divided by wingbeat period are relatively large） compared with many other insects, that the theory based on the averaged model is valid for the hawkmoth means that it could be valid for many insects.

关键词： Insect Hovering Dynamic flight stability Averaged model Equations-of-motion Navier-Stokes simulation

Stabilization control of a hovering model insect:lateral motion

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Acta Mechanica Sinica 2011年第5期27卷 823-832页

作者： Yan-lai zhang Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Beihang University 100191 Beijing China

Our previous study shows that the lateral disturbance motion of a model drone fly does not have inherent stability （passive stability）,because of the existence of an unstable divergence *** drone flies are observed to fly *** active control must be applied to stabilize the *** this study,we investigate the lateral stabilization control of the model drone *** method of computational fluid dynamics is used to compute the lateral control derivatives and the techniques of eigenvalue and eigenvector analysis and modal decomposition are used for solving the equations of *** analysis shows that although inherently unstable,the lateral disturbance motion is *** feeding back the state variables （*** translation velocity,yaw rate,roll rate and roll angle,which can be measured by the sensory system of the insect） to produce anti-symmetrical changes in stroke amplitude and/or in angle of attack between the left and right wings,the motion can be stabilized,explaining why the drone flies can fly stably even if the flight is passively unstable.

关键词： Hovering drone fly Lateral motion Flight stability Stabilization control Modal analysis

New Agegraphic Dark Energy in Brans-Dicke Theory

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Communications in Theoretical Physics 2009年第10期52卷 761-768页

作者： LIU Xiang-lai zhang Xin Department of Physics Northeastern University Shenyang 110004 China

In this paper, we investigate the new agegraphic dark energy model in the framework of Brans-Dicke theory, which is a natural extension of the Einstein＇s general relativity. In this framework the form of the new agegraphic dark energy density takes as pq = 3n^2Ф（t）η^-2, where η is the conformal age of the universe and Ф（t） is the Brans-Dicke scalar field representing the inverse of the time-variable Newton＇s constant. We derive the equation of state of the new agegraphic dark energy and the deceleration parameter of the universe in the Brans-Dicke theory. It is very interesting to find that in the Brans-Dicke theory the agegraphic dark energy realizes quintom-like behavior, i.e., its equation of state crosses the phantom divide ω= -1 during the evolution. We also compare the situation of the agegraphic dark energy model in the Brans-Dicke theory with that in the Einstein＇s theory. In addition, we discuss the new agegraphic dark energy model with interaction in the framework of the Brans-Dicke theory.

关键词： agegraphic dark energy quantum gravity cosmic acceleration Brans--Dicke theory

Lateral dynamic flight stability of hovering insects: theory vs. numerical simulation

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Acta Mechanica Sinica 2012年第1期28卷 221-231页

作者： Yan-lai zhang Jiang-Hao Wu Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Beihang University100191 BeijingChina

In the present paper, the lateral dynamic flight stability properties of two hovering model insects are predicted by an approximate theory based on the averaged model, and computed by numerical simulation that solves the complete equations of motion coupled with the Naviertokes equations. Comparison between the theoretical and simulational results provides a test to the validity of the assumptions made in the theory. One of the insects is a model dronefly which has relatively high wingbeat frequency （164Hz） and the other is a model hawkmoth which has relatively low wingbeat frequency （26 Hz）. The following conclusion has been drawn. The theory based on the averaged model works well for the lateral motion of the dronefly. For the hawkmoth, relatively large quantitative differences exist between theory and simulation. This is because the lateral non-dimensional eigenvalues of the hawkmoth are not very small compared with the non-dimensional flapping frequency （the largest lateral non-dimensional eigenvalue is only about 10% smaller than the non-dimensional flapping frequency）. Nevertheless, the theory can still correctly predict variational trends of the dynamic properties of the hawkmoth＇s lateral motion.

关键词： Insect - Hovering Lateral dynamic flight stabil- ity Averaged model Equations-of-motion Navier-Stokes simulation

Laser Powder Bed Fusion of Beta-Type Titanium Alloys for Biomedical Application:A Review

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 17-28页

作者： Xuan Luo Chao Yang Dongdong Li lai-Chang zhang State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan430074China National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials Guangdong Provincial Key Laboratory for Processing and Forming of Advanced Metallic MaterialsSouth China University of TechnologyGuangzhou510640China Centre for Advanced Materials and Manufacturing School of EngineeringEdith Cowan University270 Joondalup DriveJoondalupPerthWA6027Australia

Additive manufacturing ofβ-type titanium alloy is expected to replace Ti-6Al-4V alloy in the field of orthopedic implantation because of their low elastic modulus,excellent corrosion resistance,and *** briefly introducing the laser powder bed fusion(LPBF)process and physical phenomena,this paper reviews the recent progresses in LPBF-edβ-type Ti *** strategies to strengthening and tougheningβ-type Ti alloys are critically *** is followed by the processing routes employed to achieve to low modulus for orthopedic applications,especially a new methodology for tailoring crystallographic orientation called multi-track coupled directional *** effect of processing and compositions on performance metrics ofβ-type Ti alloys included corrosion behavior,and biocompatibility is *** the end,challenges in additive manufacturing ofβ-type Ti alloys in future are highlighted,with the aim to ensue clinical application of LPBF-edβ-type Ti alloys.

关键词： β-type Ti alloys Laser powder bed fusion Mechanical properties Elastic modulus Biocompatibility

Efficient nanostructured heterogeneous catalysts by electrochemical etching of partially crystallized Fe-based metallic glass ribbons

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Journal of Materials Science & Technology 2021年第2期61卷 159-168页

作者： Qiaoyue zhang Shun-Xing Liang Zhe Jia Wenchang zhang Weimin Wang lai-Chang zhang School of Engineering Edith Cowan University270Joondalup DriveJoondalupPerthWA 6027Australia Technical Chemistry I and Center for Nanointegration Duisburg-Essen(CENIDE) University of Duisburg-EssenUniversitaetsstrasse 7Essen 45141Germany School of Mechanical and Manufacturing Engineering.UNSW Sydney SydneyNSW 2052Australia Ji'an Ecological Environment Monitoring Center of Jiangxi Province Ji'anJiangxi Province 343000China School of Materials Science and Engineering.Shandong University JinanShandong Province 250061China

Although an increasing interest has been attracted to further develop heterostructured catalysts from metallic glasses(MGs) by heat treatment, overcoming surface oxidation effect is still a critical problem for such environmental catalysts. Herein, a short-time electrochemical etching of partially crystallized Febased ribbons in 0.3 M H3 PO4 electrolyte enables the formation of honeycomb-like nanoporous structure as effective catalytic active sites in Fenton-like process. Studies of structure and surface morphologies reveal that the formation of nanoporous structure by potentiostatic etching originates from electrochemical potential difference of nanocrystals(a-Fe(Si) and Fe2 B) and residual amorphous phase in partially crystallized ribbons, where Fe2 B having a lower open circuit potential tends to be selectively ***, thin oxide layer after electrochemical etching exposes more active sites for H2 O2 activation and provides an effective protection of nanocrystals from massive loss during etching. Investigation of optimal processing conditions suggests that the selection of electrolyte plays an important role;dye degradation rates of etched ribbons in HNO3 and Na2 SO4 electrolytes can also achieve at least 2 times higher than that of as-annealed ribbons. This work holds the promise to develop novel environmental catalysts by effective electrochemical etching of partially crystallized ribbons.

关键词： Metallic glass Nanoporous structure Crystallization Electrochemical etching Selective dissolution

Corrosion Behavior of Selective Laser Melted AISi10Mg Alloy in NaCl Solution and Its Dependence on Heat Treatment

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Acta Metallurgica Sinica(English Letters) 2020年第3期33卷 327-337页

作者： Xin-Hui Gu Jun-Xi zhang Xiao-Lei Fan lai-Chang zhang Shanghai Key Laboratory of Material Protection and Advanced Material in Electric Power Shanghai University of Electric PowerShanghai 200090China School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia

This work investigates the corrosion behavior of AlSilOMg alloy produced by selective laser melting(SLM) and the counterparts heat-treated at 450-550℃in 3.5 wt% NaCl *** measurements and weight loss tests together with microstructural characterizations were *** SLM-produced alloy displays a microstructure with a continuous network of Si particles,exhibiting superior corrosion *** heat treatment,the Si particles are coarsened and isolated and A1 matrix dissolves into their surrounding area,thereby degrading the corrosion resistance ***,the corrosion resistance of AlSilOMg alloy degrades with increasing the heat treatment temperature.

关键词： Aluminum Selective laser melting XRD Electrochemistry Pitting corrosion

Tensile behavior of Sn-0.7Cu with Zn addition at various deformation temperatures

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Acta Metallurgica Sinica(English Letters) 2011年第2期24卷 155-160页

作者： Zhongbing L UO Jie ZHAO Junshan zhang lai WANG School of Materials Science and Engineering Dalian University of Technology Dalian 116085 China

The tensile behavior of Sn-0.7Cu and Sn-0.7Cu-1Zn was compared at various deformation temperatures. Refined microstructure and γ-CuZn particles were discovered with Zn addition. The strengths of Zn-containing solder were higher than that of Sn-0.7Cu at room and subzero temperatures. With the elevation of deformation temperature, they both decreased and they were nearly the same at 80 ？ C. The works of fracture exhibited the similar evolution law. For Sn-0.7Cu solder, the elongation after fracture was smaller and the reduction of area was bigger than those of Sn-0.7Cu-1Zn. This shows that Zn addition improved the deformation stability, which is attributed to the modification of the microstructure. Dimples in fracture surface became smaller and shallower with the decreasing temperature. Ductile fracture was discovered in all the samples.

关键词： Sn-0.7Cu Zn Tensile Temperature Strength Ductility Fracture

CROSS-DIFFUSION INDUCED TURING PATTERNS IN A SEX-STRUCTURED PREDATOR-PREY MODEL

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International Journal of Biomathematics 2012年第4期5卷 39-61页

作者： JIA LIU HUA ZHOU lai zhang College of Mathematics and Physics Changzhou University Changzhou 213016 P. R. China Department of Mathematics The Technical University of Denmark DK 2800 Lyngby Denmark

In this paper, we consider a sex-structured predator prey model with strongly coupled nonlinear reaction diffusion. Using the Lyapunov functional and Leray Schauder degree theory, the existence and stability of both homogenous and heterogenous steady-states are investigated. Our results demonstrate that the unique homogenous steady-state is locally asymptotically stable for the associated ODE system and PDE system with self-diffusion. With the presence of the cross-diffusion, the homogeneous equilibrium is destabilized, and a heterogenous steady-state emerges as a consequence. In addition, the conditions guaranteeing the emergence of Turing patterns are derived.

关键词： Predator-prey model cross-diffusion turing pattern sex structure.