The aims of this work turn towards the valorization of the underutilized Raw Sugar Beet Pulp by-product to produce white Cellulose Microfibers(CMFs),and its potential effect as a reinforcement for the development of H...The aims of this work turn towards the valorization of the underutilized Raw Sugar Beet Pulp by-product to produce white Cellulose Microfibers(CMFs),and its potential effect as a reinforcement for the development of High-Density Polyethylene(HDPE)composites.Pure CMFs were first obtained by subjecting raw SBP to alkali and bleaching treatments.Several characterization techniques were performed to confirm the successful removal of the amorphous compounds from the surface of individual fibers,including SEM,XRD,TGA,and FT-IR analysis.Various CMF loadings(5–10 wt%)were incorporated as bio-fillers into HDPE polymer to evaluate their reinforcing ability in comparison to raw and alkali-treated SBP using twin-screw extrusion followed by injection molding.Styrene–(Ethylene–Butene)–Styrene Three-Block Co-Polymer Grafted with Maleic Anhydride was used as a compatibilizer to improve the interfacial adhesion between fibers and the matrix.Thermal,mechanical,and rheological properties of the produced composite samples were investigated.It was found that the Young’s modulus were gradually increased with increasing of fibers loadings,with a maximum increase of 30%and 26%observed for composite containing 10 wt%of CMFs and raw SBP,respectively,over neat HDPE.While,the use of coupling agent enhances the ductile behavior of the composites.It was also found that all fiber improves the hardness and toughness behavior of all reinforced composites as well as the complex modulus particularly at 10 wt%.The thermal stability slightly increases with the addition of fibers.This study demonstrates a new route for the valorization of SBP by-products.These fibers can be considered as a valuable bio-fillers candidate for the development of composite materials with enhanced properties.展开更多
Hybrid metaheuristic algorithms play a prominent role in improving algorithms' searchability by combining each algorithm's advantages and minimizing any substantial shortcomings. The Quantum-based Avian Naviga...Hybrid metaheuristic algorithms play a prominent role in improving algorithms' searchability by combining each algorithm's advantages and minimizing any substantial shortcomings. The Quantum-based Avian Navigation Optimizer Algorithm (QANA) is a recent metaheuristic algorithm inspired by the navigation behavior of migratory birds. Different experimental results show that QANA is a competitive and applicable algorithm in different optimization fields. However, it suffers from shortcomings such as low solution quality and premature convergence when tackling some complex problems. Therefore, instead of proposing a new algorithm to solve these weaknesses, we use the advantages of the bonobo optimizer to improve global search capability and mitigate premature convergence of the original QANA. The effectiveness of the proposed Hybrid Quantum-based Avian Navigation Optimizer Algorithm (HQANA) is assessed on 29 test functions of the CEC 2018 benchmark test suite with different dimensions, 30, 50, and 100. The results are then statistically investigated by the Friedman test and compared with the results of eight well-known optimization algorithms, including PSO, KH, GWO, WOA, CSA, HOA, BO, and QANA. Ultimately, five constrained engineering optimization problems from the latest test suite, CEC 2020 are used to assess the applicability of HQANA to solve complex real-world engineering optimization problems. The experimental and statistical findings prove that the proposed HQANA algorithm is superior to the comparative algorithms.展开更多
The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,co...The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,contact electrification and its relationship with adhesion are systematically studied using the first-principles calculation.Charge transfers from CNT or its special form,graphene,to the metal surface during the contact,and the transferred charge linearly correlates with the work function difference.Meanwhile,the adhesion energy is linearly related to the transferred charge for both CNT and graphene.More charge transfers from the flat graphene to metal surfaces than the curved CNT,leading to higher adhesion between graphene and metal surfaces.The curved structure of the CNT causes an irregular change of charge at the interface and hinders the charge transfer.Moreover,the curved structure induces electronic localization,which also decreases the interfacial charge transfer.The structure affects contact electrification,and hence adhesion is further demonstrated by the CNT with different deformation when contacting different surfaces.This study advances our understanding of contact electrification and its relationship with adhesion at the interface for bio-inspired carbon adhesive materials and sheds light on the control of them for engineering applications.展开更多
Inspired by the self-healing function of biological organisms,Bionic Laser Alloying(BLA)process was adopted to fabricate the bionic self-healing Thermal Barrier Coatings(TBCs).The BLA with different fractions of TiAl3...Inspired by the self-healing function of biological organisms,Bionic Laser Alloying(BLA)process was adopted to fabricate the bionic self-healing Thermal Barrier Coatings(TBCs).The BLA with different fractions of TiAl3 self-healing agent and Ceria and Yttria-Stabilized Zirconia(CYSZ)on the plasma-sprayed 7YSZ TBCs was carried out by a pulsed Nd:YAG laser.The effect of TiAl3 content on the microstructure,phase composition,and thermal shock behaviors of the bionic self-healing TBCs were investigated.Results indicated that the bionic self-healing TBCs had better thermal shock resistance than that of the as-sprayed TBCs.The thermal shock resistance increased first and then decreased with increasing TiAl3 fraction.The thermal shock resistance of the bionic self-healing TBCs with 15%TiAl3 is triple that of the as-sprayed TBCs.On one hand,the columnar crystals and vertical cracks could improve strain compatibility of TBCs during the thermal shock process;on the other hand,the TiAl3 as a self-healing agent reacted with oxygen in air at high temperature to seal the microcracks,thereby delaying the crack connection.展开更多
Though the Butterfly Bptimization Algorithm(BOA)has already proved its effectiveness as a robust optimization algorithm,it has certain disadvantages.So,a new variant of BOA,namely mLBOA,is proposed here to improve its...Though the Butterfly Bptimization Algorithm(BOA)has already proved its effectiveness as a robust optimization algorithm,it has certain disadvantages.So,a new variant of BOA,namely mLBOA,is proposed here to improve its performance.The proposed algorithm employs a self-adaptive parameter setting,Lagrange interpolation formula,and a new local search strategy embedded with Levy flight search to enhance its searching ability to make a better trade-off between exploration and exploitation.Also,the fragrance generation scheme of BOA is modified,which leads for exploring the domain effectively for better searching.To evaluate the performance,it has been applied to solve the IEEE CEC 2017 benchmark suite.The results have been compared to that of six state-of-the-art algorithms and five BOA variants.Moreover,various statistical tests,such as the Friedman rank test,Wilcoxon rank test,convergence analysis,and complexity analysis,have been conducted to justify the rank,significance,and complexity of the proposed mLBOA.Finally,the mLBOA has been applied to solve three real-world engineering design problems.From all the analyses,it has been found that the proposed mLBOA is a competitive algorithm compared to other popular state-of-the-art algorithms and BOA variants.展开更多
Water-lubricated bearing has become the development trend in the future because of its economy and environmental friendliness.The poor friction performance under low speed and heavy load seriously limits the populariz...Water-lubricated bearing has become the development trend in the future because of its economy and environmental friendliness.The poor friction performance under low speed and heavy load seriously limits the popularization and application of water-lubricated bearings.Learning from nature,the phenomenon of low friction and wear in nature has aroused great interest of scientists,and a lot of research has been carried out from mechanism analysis to bionic application.In this review,our purpose is to provide guiding methods and analysis basis for the bionic design and theoretical research of anti-friction and anti-wear of water-lubricated bearings.The development of water-lubricated bearing materials are described.Some typical examples of natural friction reduction and drag reduction are introduced in detail,and several representative preparation methods are listed.Finally,the application status of bionic tribology in water-lubricated bearings is summarized,and the future development direction of water-lubricated bearings is prospected.展开更多
In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated.Inspired by periodically beating cilia the loop part of a punched ...In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated.Inspired by periodically beating cilia the loop part of a punched metallic hook-and-loop tape with tilted protruding loops was used as a waveguide for plate waves in water.Such waves were excited in the frequency range of 110 Hz to 220 Hz by directly coupling the tape to a loudspeaker membrane.A flow generated in the tilt direction of the loops with velocities up to 60 mm s 1 was visualized by ink droplets deposited on the tape.The phenomenon persisted,when the protruding length of the loops was reduced by decreasing the protrusion angle.However,after closing the punch holes near the loops with sticking tape streaming could not be observed any longer.The same happened with open punch holes when the ink was replaced by glycerol.Low-frequency acoustic streaming around vibrating sharp edges is proposed as an explanation for the observed phenomena.Applications are expected with respect to the modification of flow profiles and the enhancement of transport processes along and across liquid-solid boundaries.展开更多
The pitching-down flapping is a new type of bionic flapping,which was invented by the author based on previous studieson the aerodynamic mechanisms of fruit fly(pitching-up)flapping.The motivation of this invention is...The pitching-down flapping is a new type of bionic flapping,which was invented by the author based on previous studieson the aerodynamic mechanisms of fruit fly(pitching-up)flapping.The motivation of this invention is to improve the aerodynamiccharacteristics of flapping Micro Air Vehicles(MAVs).In this paper the pitching-down flapping is briefly introduced.Themajor works include:(1)Computing the power requirements of pitching-down flapping in three modes(advanced,symmetrical,delayed),which were compared with those of pitching-up flapping;(2)Investigating the effects of translational accelerationtime,Δτ_t,and rotational time,Δτ_r,at the end of a stroke,and the angle of attack,α,in the middle of a stroke on the aerodynamiccharacteristics in symmetrical mode;(3)Investigating the effect of camber on pitching-down flapping.From the above works,conclusions can be drawn that:(1)Compared with the pitching-up flapping,the pitching-down flapping can greatly reduce thetime-averaged power requirements;(2)The increase in Δτt and the decrease in Δτ_r can increase both the lift and drag coefficients,but the time-averaged ratio of lift to drag changes a little.And α has significant effect on the aerodynamic characteristicsof the pitching-down flapping;(3)The positive camber can effectively increase the lift coefficient and the ratio of lift to drag.展开更多
Common displays such as CRT or LCD screens have limited capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed a...Common displays such as CRT or LCD screens have limited capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed are the mixture of these three colours. Consequently these devices can be confusing in testing human color identification, because the spectral distribution of the colors displayed is the combined spectrum of the three primaries. We have developed a new instrument for spectrally correct color vision measurement. This instrument uses light emitting diodes (LEDs) and is capable of producing all spectra of perceivable colors, thus with appropriate test methods this instrument can be a reliable and useful tool in test^ing human color vision and in verifying color vision correction.展开更多
Some living organisms with hierarchical structures in nature have received extensive attention in various fields.The hierarchical structure with multiple pores,a large number of solid-gas interfaces and tortuous condu...Some living organisms with hierarchical structures in nature have received extensive attention in various fields.The hierarchical structure with multiple pores,a large number of solid-gas interfaces and tortuous conduction paths provide a new direction for the development of thermal insulation materials,making the living creatures under these extreme conditions become the bionic objects of scientific researchers.In this review,the research progress of bionic hierarchical structure in the field of heat insulation is highlighted.Polar bears,cocoons,penguin feathers and wool are typical examples of heat preservation hierarchy in nature to introduce their morphological characteristics.At the same time,the thermal insulation mechanism,fractal model and several preparation methods of bionic hierarchical structures are emphatically discussed.The application of hierarchical structures in various fields,especially in thermal insulation and infrared thermal stealth,is summarised.Finally,the hierarchical structure is prospected.展开更多
On the base of controllable variable stiffness property,variable stiffness composites were the main components of functional materials in aerospace.However,the relatively low mechanical strength,stiffness range,and re...On the base of controllable variable stiffness property,variable stiffness composites were the main components of functional materials in aerospace.However,the relatively low mechanical strength,stiffness range,and response rate restricted the application of variable stiffness composite.In this work,the novel variable stiffness composite system with characteristics of repeatable high load bearing and response rate was successfully prepared via the double-layer anisotropic structure to solve the bottlenecks of variable stiffness composites.The novel variable stiffness composite systems were composed of variable stiffness layer of polycaprolactone(PCL)and the driven layer of silicone elastomer with alcohol,which continuously changed Young’s modulus from 0.1 to 7.263 MPa(72.63 times variation)in 200 s and maintained maximum weight of 11.52 times its own weight(8.5 g).Attributed to the relatively high variable stiffness range and load bearing value of variable stiffness composite system,the repeatable response process led to the efficient high load driven as“muscle”and diversified precise grab of objects with different shapes as“gripper”,owning widespread application prospects in the field of bionics.展开更多
The goat’s hind limbs play an important role in dampening vibrations caused by ground impact during movement.Inspired by the unique structure of their hind limbs,a novel bionic limb vibration isolator has been develo...The goat’s hind limbs play an important role in dampening vibrations caused by ground impact during movement.Inspired by the unique structure of their hind limbs,a novel bionic limb vibration isolator has been developed to suppress low-frequency vibrations.It consists of the base,the carrying platform,four bionic legs and so on.The bionic legs are made up of rods of varying lengths and springs in different directions to imitate the various shapes of bones such as the femur and patella of the hind limbs of goats and developed muscles such as the biceps and quadriceps.The bionic device was found to have excellent nonlinear stiffness through statics analysis,and could be flexibly adjusted to the work range and load capacity.The bionic vibration isolator offers lower natural frequencies(2.3 Hz),better vibration isolation effect and a wider vibration isolation band than conventional linear vibration isolator.The bionic device can effectively suppress vibrations above 3.2 Hz and reduce the amplitude of random vibrations to more than 90%.In addition,compared to similar bionic vibration isolation devices,the bionic isolator achieves excellent load-bearing capacity in a smaller size,which facilitates its application in practical production.展开更多
Emerging 5G communication solutions utilize the millimeter wave(mmWave)band to alleviate the spectrum deficit.In the mmWave range,Multiple Input Multiple Output(MIMO)technologies support a large number of simultaneous...Emerging 5G communication solutions utilize the millimeter wave(mmWave)band to alleviate the spectrum deficit.In the mmWave range,Multiple Input Multiple Output(MIMO)technologies support a large number of simultaneous users.In mmWave MIMO wireless systems,hybrid analog/digital precoding topologies provide a reduced complexity substitute for digital precoding.Bit Error Rate(BER)and Spectral efficiency performances can be improved by hybrid Minimum Mean Square Error(MMSE)precoding,but the computation involves matrix inversion process.The number of antennas at the broadcasting and receiving ends is quite large for mm-wave MIMO systems,thus computing the inverse of a matrix of such high dimension may not be practically feasible.Due to the need for matrix inversion and known candidate matrices,the classic Orthogonal Matching Pursuit(OMP)approach will be more complicated.The novelty of research presented in this manuscript is to create a hybrid precoder for mmWave communication systems using metaheuristic algorithms that do not require matrix inversion processing.The metaheuristic approach has not employed much in the formulation of a precoder in wireless systems.Five distinct evolutionary algorithms,such as Harris–Hawks Optimization(HHO),Runge–Kutta Optimization(RUN),Slime Mould Algorithm(SMA),Hunger Game Search(HGS)Algorithm and Aquila Optimizer(AO)are considered to design optimal hybrid precoder for downlink transmission and their performances are tested under similar practical conditions.According to simulation studies,the RUN-based precoder performs better than the conventional algorithms and other nature-inspired algorithms based precoding in terms of spectral efficiency and BER.展开更多
Ladder climbing is a relatively new but practical locomotion style for robots. Unfortunately, due to their size and weight, ladder climbing by human-sized robots developed so far is struggling with the speedup of ladd...Ladder climbing is a relatively new but practical locomotion style for robots. Unfortunately, due to their size and weight, ladder climbing by human-sized robots developed so far is struggling with the speedup of ladder climbing motion itself. Therefore, in this paper, a new ladder climbing gait for the robot WAREC-1R is proposed by the authors, which is both faster than the former ones and stable. However, to realize such a gait, a point that has to be taken into consideration is the deformation caused by the self-weight of the robot. To deal with this issue, extra hardware (sensor) and software (position and force control) systems and extra time for sensing and calculation were required. For a complete solution without any complicated systems and time only for deformation compensation, limb stiffness improvement plan by the minimal design change of mechanical parts of the robot is also proposed by the authors, with a thorough study about deformation distribution in the robot. With redesigned parts, ladder climbing experiments by WAREC-1R proved that both the new ladder climbing gait and the limb stiffness improvement are successful, and the reduced deformation is very close to the estimated value as well.展开更多
Mapping grasps from human to anthropomorphic robotic hands is an open issue in research,because the master hand and the slave hand have dissimilar kinematics.This paper proposes a hybrid mapping method to solve this p...Mapping grasps from human to anthropomorphic robotic hands is an open issue in research,because the master hand and the slave hand have dissimilar kinematics.This paper proposes a hybrid mapping method to solve this problem.In the proposed method,fingers in the master and the slave hands are divided into vital and synergic fingers according to their contribution to the grasping task.The tip of the vital finger of the master hand is first mapped to that of the slave hand while ensuring that both are in simultaneous contact with the object to be grasped.Following postural synergy theory,joints of the other synergic fingers of the slave hand are then used to generate an anthropomorphic grasping configuration according to the shape of the object to be grasped.Following this,a human-guided impedance controller is used to reduce the pre-grasping error and realize compliant interaction with the environment.The proposed hybrid mapping method can not only generate the posture of the humanoid envelope but can also carry out impedance-adaptive matching.It was evaluated using simulations and an experiment involving an anthropomorphic robotic slave hand.展开更多
Both thermochromic and photochromic coating have attracted many attentions due to their widely applications,but the low stability is a big obstacle.Inspired by the lotus leaf,to endow the chromic coating with superhyd...Both thermochromic and photochromic coating have attracted many attentions due to their widely applications,but the low stability is a big obstacle.Inspired by the lotus leaf,to endow the chromic coating with superhydrophobicity is a possible solution.In this research,a dual response coating was prepared by adding photochromic and thermochromic particles simultaneously.The prepared sample demonstrated at least four-state color switching,which can be successfully used in tactile imaging,multi-color fabric,erasable record,and security labels.The superhydrophobicity was achieved by introducing vinyl-terminated polydimethylsiloxane,which not only offers low surface energy but also can cross-link with the particles to increase the adhesion.Thus,the prepared sample maintained superhydrophobicity after various kinds of destruction(such as sandpaper abrasion,corrosive liquid attack,ultrasonic treatment,UV irradiation,and high-speed drops/turbulent jets impact).Even though the superhydrophobicity can be destroyed by plasma etching,it can be recovered after 12 h at room temperature.展开更多
Microstructures and corrosion of TiNbTaZrMo(Ti_(20)Nb_(20)Ta_(20)Zr_(20)Mo_(20))High-Entropy Alloy(HEA)were investigated in the Simu-lated Body Fluid(SBF).Microstructure of this alloy was investigated by X-Ray Difirac...Microstructures and corrosion of TiNbTaZrMo(Ti_(20)Nb_(20)Ta_(20)Zr_(20)Mo_(20))High-Entropy Alloy(HEA)were investigated in the Simu-lated Body Fluid(SBF).Microstructure of this alloy was investigated by X-Ray Difiraction(XRD)and Scanning Electron Microscopy(SEM)techniques.Our observations confirmed the presence of two bcc phases as the major matrix as well as another minor phase in themicrostructure of the alloy.Concentration of some elements,such as tantalum,niobium,and molybdenum in the dendritic branches and thepresence of zirconium and titanium in the inter-dendritic branches were clearly evidenced by Energy Dispersive X-ray(EDX)analysis.Given importance of corrosion of implant alloys in the human's body,elctrochemical impedance and cyclic polarization tests werepcerformed on the alloy in SBF.Through the corrosion tests,corrosion potential,current,and resistance were obtained as E_(corr)=-0.42 V,i_(corr)=0.34μA·cm^(-2),and R_(p)=27.44 k ohm·cm^(2),respectively.The results revealed that the rate of corrosion in TiNbTaZrMo HEA is about 26 times better than that of Ti_(6)Al_(4)V alloy.Also,both alloys had no pitting corrosion in the SBF solution.展开更多
Polyvinyl alcohol(PVA)hydrogels with excellent characteristics are considered as promising cartilage replacement materials.However,there are still some main issues to be solved for PVA hydrogel,such as poor mechanical...Polyvinyl alcohol(PVA)hydrogels with excellent characteristics are considered as promising cartilage replacement materials.However,there are still some main issues to be solved for PVA hydrogel,such as poor mechanical strength and disordered structure.Inspired by the highly ordered structure of biological soft tissues such as articular cartilage,here,we prepared a high-strength but anisotropic polyvinyl alcohol-nanohydroxyapatite-polyacrylic acid(PVA-HA-PAA)composite hydrogel by directional stretching,freezing–thawing,and annealing method.Stretching of an as-prepared isotropic PVA-HA-PAA composite hydrogel leads to the orientation of PVA crystallites and PVA chains,which enables the formation of ordered structure and more hydrogen bonds via freezing under stretching.The microstructure,water content,swelling and creep performance,tensile and bio-tribology properties of the composite hydrogel are studied,the results indicated that the properties of the hydrogel are aff ected by stretching due to the formation of ordered structure in the anisotropic hydrogel.For instance,the elastic modulus and tensile strength of the anisotropic hydrogel reach 5.703 MPa and 18.958 MPa,respectively,which is significantly enhanced by comparing with isotropic hydrogel.Moreover,the friction property is anisotropic,and the Coefficient Of Friction(COF)reduced in the parallel direction.Thus,this work provides a simple and practicable strategy to design strong and anisotropic hydrogels for potential applications in biomedical materials such as cartilage substitute.展开更多
This paper presents a new Pulse Width Modulation (PWM) controller for Unmanned Aerial Vehicle (UAV) precisionsprayer for agriculture using a TL494 fixed-frequency pulse width modulator together with a data acquisition...This paper presents a new Pulse Width Modulation (PWM) controller for Unmanned Aerial Vehicle (UAV) precisionsprayer for agriculture using a TL494 fixed-frequency pulse width modulator together with a data acquisition board and developedsoftware. An UAV can be remotely controlled or flown autonomously by pre-programmed flight plans. The PWMcontroller was implemented through the guidance system on the UAV with control commands sent between the UAV helicopterand the ground control station via a wireless telemetry system. The PWM controller was tested and validated using LabVIEW8.2. Several analyses were performed in a laboratory to test different control signals. The results show that the PWM controllerhas promise as a higher precision technique for spray applications, which will improve efficiency of pesticide application,especially in crop production areas.展开更多
基金financial assistance of the Moroccan National Center for Scientific and Technical Research(CNRST)toward this research is hereby acknowledgedThanks to Abou El Kacem QAISS from Moroccan Foundation for Advanced Science,Innovation and Research(MAScIR)for his help to elaborate and characterize all our composites.
文摘The aims of this work turn towards the valorization of the underutilized Raw Sugar Beet Pulp by-product to produce white Cellulose Microfibers(CMFs),and its potential effect as a reinforcement for the development of High-Density Polyethylene(HDPE)composites.Pure CMFs were first obtained by subjecting raw SBP to alkali and bleaching treatments.Several characterization techniques were performed to confirm the successful removal of the amorphous compounds from the surface of individual fibers,including SEM,XRD,TGA,and FT-IR analysis.Various CMF loadings(5–10 wt%)were incorporated as bio-fillers into HDPE polymer to evaluate their reinforcing ability in comparison to raw and alkali-treated SBP using twin-screw extrusion followed by injection molding.Styrene–(Ethylene–Butene)–Styrene Three-Block Co-Polymer Grafted with Maleic Anhydride was used as a compatibilizer to improve the interfacial adhesion between fibers and the matrix.Thermal,mechanical,and rheological properties of the produced composite samples were investigated.It was found that the Young’s modulus were gradually increased with increasing of fibers loadings,with a maximum increase of 30%and 26%observed for composite containing 10 wt%of CMFs and raw SBP,respectively,over neat HDPE.While,the use of coupling agent enhances the ductile behavior of the composites.It was also found that all fiber improves the hardness and toughness behavior of all reinforced composites as well as the complex modulus particularly at 10 wt%.The thermal stability slightly increases with the addition of fibers.This study demonstrates a new route for the valorization of SBP by-products.These fibers can be considered as a valuable bio-fillers candidate for the development of composite materials with enhanced properties.
文摘Hybrid metaheuristic algorithms play a prominent role in improving algorithms' searchability by combining each algorithm's advantages and minimizing any substantial shortcomings. The Quantum-based Avian Navigation Optimizer Algorithm (QANA) is a recent metaheuristic algorithm inspired by the navigation behavior of migratory birds. Different experimental results show that QANA is a competitive and applicable algorithm in different optimization fields. However, it suffers from shortcomings such as low solution quality and premature convergence when tackling some complex problems. Therefore, instead of proposing a new algorithm to solve these weaknesses, we use the advantages of the bonobo optimizer to improve global search capability and mitigate premature convergence of the original QANA. The effectiveness of the proposed Hybrid Quantum-based Avian Navigation Optimizer Algorithm (HQANA) is assessed on 29 test functions of the CEC 2018 benchmark test suite with different dimensions, 30, 50, and 100. The results are then statistically investigated by the Friedman test and compared with the results of eight well-known optimization algorithms, including PSO, KH, GWO, WOA, CSA, HOA, BO, and QANA. Ultimately, five constrained engineering optimization problems from the latest test suite, CEC 2020 are used to assess the applicability of HQANA to solve complex real-world engineering optimization problems. The experimental and statistical findings prove that the proposed HQANA algorithm is superior to the comparative algorithms.
基金supported by the National Natural Science Foundation of China(Grant Nos.51505217,51435008,and 51705247)the Fundamental Research Funds for the Central Universities(Grant No.1011/56XAA19014).
文摘The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,contact electrification and its relationship with adhesion are systematically studied using the first-principles calculation.Charge transfers from CNT or its special form,graphene,to the metal surface during the contact,and the transferred charge linearly correlates with the work function difference.Meanwhile,the adhesion energy is linearly related to the transferred charge for both CNT and graphene.More charge transfers from the flat graphene to metal surfaces than the curved CNT,leading to higher adhesion between graphene and metal surfaces.The curved structure of the CNT causes an irregular change of charge at the interface and hinders the charge transfer.Moreover,the curved structure induces electronic localization,which also decreases the interfacial charge transfer.The structure affects contact electrification,and hence adhesion is further demonstrated by the CNT with different deformation when contacting different surfaces.This study advances our understanding of contact electrification and its relationship with adhesion at the interface for bio-inspired carbon adhesive materials and sheds light on the control of them for engineering applications.
基金supported by National Natural Science Foundation of China(Grant No.52105311)Natural Science Foundation of Zhejiang Province(Grant No.LQ21E010002)Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-A2020009).
文摘Inspired by the self-healing function of biological organisms,Bionic Laser Alloying(BLA)process was adopted to fabricate the bionic self-healing Thermal Barrier Coatings(TBCs).The BLA with different fractions of TiAl3 self-healing agent and Ceria and Yttria-Stabilized Zirconia(CYSZ)on the plasma-sprayed 7YSZ TBCs was carried out by a pulsed Nd:YAG laser.The effect of TiAl3 content on the microstructure,phase composition,and thermal shock behaviors of the bionic self-healing TBCs were investigated.Results indicated that the bionic self-healing TBCs had better thermal shock resistance than that of the as-sprayed TBCs.The thermal shock resistance increased first and then decreased with increasing TiAl3 fraction.The thermal shock resistance of the bionic self-healing TBCs with 15%TiAl3 is triple that of the as-sprayed TBCs.On one hand,the columnar crystals and vertical cracks could improve strain compatibility of TBCs during the thermal shock process;on the other hand,the TiAl3 as a self-healing agent reacted with oxygen in air at high temperature to seal the microcracks,thereby delaying the crack connection.
文摘Though the Butterfly Bptimization Algorithm(BOA)has already proved its effectiveness as a robust optimization algorithm,it has certain disadvantages.So,a new variant of BOA,namely mLBOA,is proposed here to improve its performance.The proposed algorithm employs a self-adaptive parameter setting,Lagrange interpolation formula,and a new local search strategy embedded with Levy flight search to enhance its searching ability to make a better trade-off between exploration and exploitation.Also,the fragrance generation scheme of BOA is modified,which leads for exploring the domain effectively for better searching.To evaluate the performance,it has been applied to solve the IEEE CEC 2017 benchmark suite.The results have been compared to that of six state-of-the-art algorithms and five BOA variants.Moreover,various statistical tests,such as the Friedman rank test,Wilcoxon rank test,convergence analysis,and complexity analysis,have been conducted to justify the rank,significance,and complexity of the proposed mLBOA.Finally,the mLBOA has been applied to solve three real-world engineering design problems.From all the analyses,it has been found that the proposed mLBOA is a competitive algorithm compared to other popular state-of-the-art algorithms and BOA variants.
基金the National Natural Science Foundation of China(Grant no.52171319).
文摘Water-lubricated bearing has become the development trend in the future because of its economy and environmental friendliness.The poor friction performance under low speed and heavy load seriously limits the popularization and application of water-lubricated bearings.Learning from nature,the phenomenon of low friction and wear in nature has aroused great interest of scientists,and a lot of research has been carried out from mechanism analysis to bionic application.In this review,our purpose is to provide guiding methods and analysis basis for the bionic design and theoretical research of anti-friction and anti-wear of water-lubricated bearings.The development of water-lubricated bearing materials are described.Some typical examples of natural friction reduction and drag reduction are introduced in detail,and several representative preparation methods are listed.Finally,the application status of bionic tribology in water-lubricated bearings is summarized,and the future development direction of water-lubricated bearings is prospected.
基金This research was supported by the European Fund of Regional Development(EFRE)within the project“InnoTerm”and from“Technologieallianz Oberfranken(TAO)”.
文摘In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated.Inspired by periodically beating cilia the loop part of a punched metallic hook-and-loop tape with tilted protruding loops was used as a waveguide for plate waves in water.Such waves were excited in the frequency range of 110 Hz to 220 Hz by directly coupling the tape to a loudspeaker membrane.A flow generated in the tilt direction of the loops with velocities up to 60 mm s 1 was visualized by ink droplets deposited on the tape.The phenomenon persisted,when the protruding length of the loops was reduced by decreasing the protrusion angle.However,after closing the punch holes near the loops with sticking tape streaming could not be observed any longer.The same happened with open punch holes when the ink was replaced by glycerol.Low-frequency acoustic streaming around vibrating sharp edges is proposed as an explanation for the observed phenomena.Applications are expected with respect to the modification of flow profiles and the enhancement of transport processes along and across liquid-solid boundaries.
文摘The pitching-down flapping is a new type of bionic flapping,which was invented by the author based on previous studieson the aerodynamic mechanisms of fruit fly(pitching-up)flapping.The motivation of this invention is to improve the aerodynamiccharacteristics of flapping Micro Air Vehicles(MAVs).In this paper the pitching-down flapping is briefly introduced.Themajor works include:(1)Computing the power requirements of pitching-down flapping in three modes(advanced,symmetrical,delayed),which were compared with those of pitching-up flapping;(2)Investigating the effects of translational accelerationtime,Δτ_t,and rotational time,Δτ_r,at the end of a stroke,and the angle of attack,α,in the middle of a stroke on the aerodynamiccharacteristics in symmetrical mode;(3)Investigating the effect of camber on pitching-down flapping.From the above works,conclusions can be drawn that:(1)Compared with the pitching-up flapping,the pitching-down flapping can greatly reduce thetime-averaged power requirements;(2)The increase in Δτt and the decrease in Δτ_r can increase both the lift and drag coefficients,but the time-averaged ratio of lift to drag changes a little.And α has significant effect on the aerodynamic characteristicsof the pitching-down flapping;(3)The positive camber can effectively increase the lift coefficient and the ratio of lift to drag.
文摘Common displays such as CRT or LCD screens have limited capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed are the mixture of these three colours. Consequently these devices can be confusing in testing human color identification, because the spectral distribution of the colors displayed is the combined spectrum of the three primaries. We have developed a new instrument for spectrally correct color vision measurement. This instrument uses light emitting diodes (LEDs) and is capable of producing all spectra of perceivable colors, thus with appropriate test methods this instrument can be a reliable and useful tool in test^ing human color vision and in verifying color vision correction.
文摘Some living organisms with hierarchical structures in nature have received extensive attention in various fields.The hierarchical structure with multiple pores,a large number of solid-gas interfaces and tortuous conduction paths provide a new direction for the development of thermal insulation materials,making the living creatures under these extreme conditions become the bionic objects of scientific researchers.In this review,the research progress of bionic hierarchical structure in the field of heat insulation is highlighted.Polar bears,cocoons,penguin feathers and wool are typical examples of heat preservation hierarchy in nature to introduce their morphological characteristics.At the same time,the thermal insulation mechanism,fractal model and several preparation methods of bionic hierarchical structures are emphatically discussed.The application of hierarchical structures in various fields,especially in thermal insulation and infrared thermal stealth,is summarised.Finally,the hierarchical structure is prospected.
基金the project of the National Key Research and Development Program of China(2018YFA0703300)the National Natural Science Foundation of China(52105302,52175271,52021003,and 91848204)+1 种基金the team of Innovation and entrepreneurship of Jilin Province(20210509047RQ,20210508057RQ)the Program for JLU Science and Technology Innovative Research Team(2017TD-04).
文摘On the base of controllable variable stiffness property,variable stiffness composites were the main components of functional materials in aerospace.However,the relatively low mechanical strength,stiffness range,and response rate restricted the application of variable stiffness composite.In this work,the novel variable stiffness composite system with characteristics of repeatable high load bearing and response rate was successfully prepared via the double-layer anisotropic structure to solve the bottlenecks of variable stiffness composites.The novel variable stiffness composite systems were composed of variable stiffness layer of polycaprolactone(PCL)and the driven layer of silicone elastomer with alcohol,which continuously changed Young’s modulus from 0.1 to 7.263 MPa(72.63 times variation)in 200 s and maintained maximum weight of 11.52 times its own weight(8.5 g).Attributed to the relatively high variable stiffness range and load bearing value of variable stiffness composite system,the repeatable response process led to the efficient high load driven as“muscle”and diversified precise grab of objects with different shapes as“gripper”,owning widespread application prospects in the field of bionics.
基金This research was funded by the the Science and Technology Development Program of Jilin Province,China(Grant No.20230101117JC)National Natural Science Foundation of China(Grant No.51775234,91748211,51305157)the Science and Technology Development Program of Jilin Province,China(Grant No.20190302101GX,20180101090JC).
文摘The goat’s hind limbs play an important role in dampening vibrations caused by ground impact during movement.Inspired by the unique structure of their hind limbs,a novel bionic limb vibration isolator has been developed to suppress low-frequency vibrations.It consists of the base,the carrying platform,four bionic legs and so on.The bionic legs are made up of rods of varying lengths and springs in different directions to imitate the various shapes of bones such as the femur and patella of the hind limbs of goats and developed muscles such as the biceps and quadriceps.The bionic device was found to have excellent nonlinear stiffness through statics analysis,and could be flexibly adjusted to the work range and load capacity.The bionic vibration isolator offers lower natural frequencies(2.3 Hz),better vibration isolation effect and a wider vibration isolation band than conventional linear vibration isolator.The bionic device can effectively suppress vibrations above 3.2 Hz and reduce the amplitude of random vibrations to more than 90%.In addition,compared to similar bionic vibration isolation devices,the bionic isolator achieves excellent load-bearing capacity in a smaller size,which facilitates its application in practical production.
文摘Emerging 5G communication solutions utilize the millimeter wave(mmWave)band to alleviate the spectrum deficit.In the mmWave range,Multiple Input Multiple Output(MIMO)technologies support a large number of simultaneous users.In mmWave MIMO wireless systems,hybrid analog/digital precoding topologies provide a reduced complexity substitute for digital precoding.Bit Error Rate(BER)and Spectral efficiency performances can be improved by hybrid Minimum Mean Square Error(MMSE)precoding,but the computation involves matrix inversion process.The number of antennas at the broadcasting and receiving ends is quite large for mm-wave MIMO systems,thus computing the inverse of a matrix of such high dimension may not be practically feasible.Due to the need for matrix inversion and known candidate matrices,the classic Orthogonal Matching Pursuit(OMP)approach will be more complicated.The novelty of research presented in this manuscript is to create a hybrid precoder for mmWave communication systems using metaheuristic algorithms that do not require matrix inversion processing.The metaheuristic approach has not employed much in the formulation of a precoder in wireless systems.Five distinct evolutionary algorithms,such as Harris–Hawks Optimization(HHO),Runge–Kutta Optimization(RUN),Slime Mould Algorithm(SMA),Hunger Game Search(HGS)Algorithm and Aquila Optimizer(AO)are considered to design optimal hybrid precoder for downlink transmission and their performances are tested under similar practical conditions.According to simulation studies,the RUN-based precoder performs better than the conventional algorithms and other nature-inspired algorithms based precoding in terms of spectral efficiency and BER.
文摘Ladder climbing is a relatively new but practical locomotion style for robots. Unfortunately, due to their size and weight, ladder climbing by human-sized robots developed so far is struggling with the speedup of ladder climbing motion itself. Therefore, in this paper, a new ladder climbing gait for the robot WAREC-1R is proposed by the authors, which is both faster than the former ones and stable. However, to realize such a gait, a point that has to be taken into consideration is the deformation caused by the self-weight of the robot. To deal with this issue, extra hardware (sensor) and software (position and force control) systems and extra time for sensing and calculation were required. For a complete solution without any complicated systems and time only for deformation compensation, limb stiffness improvement plan by the minimal design change of mechanical parts of the robot is also proposed by the authors, with a thorough study about deformation distribution in the robot. With redesigned parts, ladder climbing experiments by WAREC-1R proved that both the new ladder climbing gait and the limb stiffness improvement are successful, and the reduced deformation is very close to the estimated value as well.
基金supported in part by the China National Key Research and Development Program under Grant no.2020YFC2007801in part by the National Natural Science Foundation of China under Grant no.U1813209.
文摘Mapping grasps from human to anthropomorphic robotic hands is an open issue in research,because the master hand and the slave hand have dissimilar kinematics.This paper proposes a hybrid mapping method to solve this problem.In the proposed method,fingers in the master and the slave hands are divided into vital and synergic fingers according to their contribution to the grasping task.The tip of the vital finger of the master hand is first mapped to that of the slave hand while ensuring that both are in simultaneous contact with the object to be grasped.Following postural synergy theory,joints of the other synergic fingers of the slave hand are then used to generate an anthropomorphic grasping configuration according to the shape of the object to be grasped.Following this,a human-guided impedance controller is used to reduce the pre-grasping error and realize compliant interaction with the environment.The proposed hybrid mapping method can not only generate the posture of the humanoid envelope but can also carry out impedance-adaptive matching.It was evaluated using simulations and an experiment involving an anthropomorphic robotic slave hand.
基金supported by the National Nature Science Foundation of China(51977079,51607067)the Central Guid-ance on Local Science and Technology Development Fund of Hebei Province(226Z1204G)+2 种基金the Top Young Innovative Talents of Colleges and universities of Higher Learning Institutions of Hebei(BJ2021095)Youth Elite Scientists Sponsorship Program by the Chinese Society for Electrical Engineering(CSEE-YESS-2017002)the Funda-mental Research Funds for the Central Universities(2020MS115,2017MS149).
文摘Both thermochromic and photochromic coating have attracted many attentions due to their widely applications,but the low stability is a big obstacle.Inspired by the lotus leaf,to endow the chromic coating with superhydrophobicity is a possible solution.In this research,a dual response coating was prepared by adding photochromic and thermochromic particles simultaneously.The prepared sample demonstrated at least four-state color switching,which can be successfully used in tactile imaging,multi-color fabric,erasable record,and security labels.The superhydrophobicity was achieved by introducing vinyl-terminated polydimethylsiloxane,which not only offers low surface energy but also can cross-link with the particles to increase the adhesion.Thus,the prepared sample maintained superhydrophobicity after various kinds of destruction(such as sandpaper abrasion,corrosive liquid attack,ultrasonic treatment,UV irradiation,and high-speed drops/turbulent jets impact).Even though the superhydrophobicity can be destroyed by plasma etching,it can be recovered after 12 h at room temperature.
文摘Microstructures and corrosion of TiNbTaZrMo(Ti_(20)Nb_(20)Ta_(20)Zr_(20)Mo_(20))High-Entropy Alloy(HEA)were investigated in the Simu-lated Body Fluid(SBF).Microstructure of this alloy was investigated by X-Ray Difiraction(XRD)and Scanning Electron Microscopy(SEM)techniques.Our observations confirmed the presence of two bcc phases as the major matrix as well as another minor phase in themicrostructure of the alloy.Concentration of some elements,such as tantalum,niobium,and molybdenum in the dendritic branches and thepresence of zirconium and titanium in the inter-dendritic branches were clearly evidenced by Energy Dispersive X-ray(EDX)analysis.Given importance of corrosion of implant alloys in the human's body,elctrochemical impedance and cyclic polarization tests werepcerformed on the alloy in SBF.Through the corrosion tests,corrosion potential,current,and resistance were obtained as E_(corr)=-0.42 V,i_(corr)=0.34μA·cm^(-2),and R_(p)=27.44 k ohm·cm^(2),respectively.The results revealed that the rate of corrosion in TiNbTaZrMo HEA is about 26 times better than that of Ti_(6)Al_(4)V alloy.Also,both alloys had no pitting corrosion in the SBF solution.
基金supported by Natural Science Foundation of Jiangsu Province(Grant No.BK20211243)National Natural Science Foundation of China(Grant No.51705517,51875564,51875563)China Postdoctoral Science Found(Grant No.2018M630622).
文摘Polyvinyl alcohol(PVA)hydrogels with excellent characteristics are considered as promising cartilage replacement materials.However,there are still some main issues to be solved for PVA hydrogel,such as poor mechanical strength and disordered structure.Inspired by the highly ordered structure of biological soft tissues such as articular cartilage,here,we prepared a high-strength but anisotropic polyvinyl alcohol-nanohydroxyapatite-polyacrylic acid(PVA-HA-PAA)composite hydrogel by directional stretching,freezing–thawing,and annealing method.Stretching of an as-prepared isotropic PVA-HA-PAA composite hydrogel leads to the orientation of PVA crystallites and PVA chains,which enables the formation of ordered structure and more hydrogen bonds via freezing under stretching.The microstructure,water content,swelling and creep performance,tensile and bio-tribology properties of the composite hydrogel are studied,the results indicated that the properties of the hydrogel are aff ected by stretching due to the formation of ordered structure in the anisotropic hydrogel.For instance,the elastic modulus and tensile strength of the anisotropic hydrogel reach 5.703 MPa and 18.958 MPa,respectively,which is significantly enhanced by comparing with isotropic hydrogel.Moreover,the friction property is anisotropic,and the Coefficient Of Friction(COF)reduced in the parallel direction.Thus,this work provides a simple and practicable strategy to design strong and anisotropic hydrogels for potential applications in biomedical materials such as cartilage substitute.
文摘This paper presents a new Pulse Width Modulation (PWM) controller for Unmanned Aerial Vehicle (UAV) precisionsprayer for agriculture using a TL494 fixed-frequency pulse width modulator together with a data acquisition board and developedsoftware. An UAV can be remotely controlled or flown autonomously by pre-programmed flight plans. The PWMcontroller was implemented through the guidance system on the UAV with control commands sent between the UAV helicopterand the ground control station via a wireless telemetry system. The PWM controller was tested and validated using LabVIEW8.2. Several analyses were performed in a laboratory to test different control signals. The results show that the PWM controllerhas promise as a higher precision technique for spray applications, which will improve efficiency of pesticide application,especially in crop production areas.
