Gibberellins(GAs)and auxin play central regulatory roles in seed germination and root system development,respectively,so that the application of these phytohormones to crops would be worthwhile,with an increasing pote...Gibberellins(GAs)and auxin play central regulatory roles in seed germination and root system development,respectively,so that the application of these phytohormones to crops would be worthwhile,with an increasing potential demand in agriculture.However,there are few effective chemicals that simultaneously enhance both GA and auxin signaling.Here,we report on an artificial thiourea derivative chemical,Y21,that serves as both a GA-signaling agonist and an auxin analog,promoting seed germination and root development,as well as low-phosphorus tolerance.Phenotypic,biochemical,and genetic evidence demonstrated that Y21 enhances the interaction between GA and its receptor GID1C via the Val239 amino acid residue and consequently promotes degradation of the DELLA proteins REPRESSOR OF ga1-3(RGA)and RGA-LIKE 2.Furthermore,we found that Y21 interacts with the auxin receptor TIR1 via the Cys405 residue and thus promotes the turnover of the auxinresponsive Aux/IAA proteins.Consequently,Y21significantly increases low-phosphorus tolerance of treated plants by positively regulating lateral root development.To our knowledge,Y21 is the first GA-signaling agonist to be identified,and our results also demonstrate that this potent synthetic chemical,identified by chemical genetic screening,is effective at modulating plant development and stress tolerance.展开更多
The emergence of precision electronic devices and wearable electronic products urgently requires high-performance multifunctional electromagnetic wave(EMW)absorbers to meet the applicability and versatility in various...The emergence of precision electronic devices and wearable electronic products urgently requires high-performance multifunctional electromagnetic wave(EMW)absorbers to meet the applicability and versatility in various applications.Herein,a dual-network(DN)gel was successfully prepared using acrylamide and sodium lignosulphonate as the basic units by simple chemical cross-linking and physical cross-linking methods.Specifically,the hydrogel forms two types of cross-linking networks through metal coordination and hydrogen bonding.Benefiting from the combined effects of dipole polarization and conductivity loss,the gel achieves an effective absorption bandwidth(EAB)of 6.74 GHz at a thickness of only 1.89 mm,demonstrating excellent EMW absorption performance.In addition,this unique structural configuration endows the EMW absorber with multifunctional features,such as remarkable tensile strength,good environmental compatibility,ultraviolet(UV)resistance,and excellent adhesion.Integrating multiple functional features into the EMW gels displays a broad application prospect in a variety of application scenarios.This research reveals the significance of DN structure design in the electromagnetic wave absorption(EWA)performance of gel-based materials,providing a substantial foundation for the multifunctional design of gel-based absorbers.展开更多
The lack of autonomous take-off and landing capabilities of bird-like flapping-wing aerial vehicles(BFAVs)seriously restricts their further development and application.Thus,combined with the current research results o...The lack of autonomous take-off and landing capabilities of bird-like flapping-wing aerial vehicles(BFAVs)seriously restricts their further development and application.Thus,combined with the current research results on the autonomous take-off and landing technology of unmanned aerial vehicles,four types of technologies are studied,including jumping take-off and landing technology,taxiing take-off and landing technology,gliding take-off and landing technology,and vertical take-off and landing(VTOL)technology.Based on the analytic hierarchy process(AHP)-comprehensive evaluation method,a fuzzy comprehensive evaluation model for the autonomous take-off and landing scheme of a BFAV is established,and four schemes are evaluated concretely.The results show that under the existing technical conditions,the hybrid layout VTOL scheme is the best.Furthermore,the detailed design and development of the prototype of a BFAV with a four-rotor hybrid layout are carried out,and the vehicle performance is tested.The results prove that through the four-rotor hybrid layout design,the BFAV has good autonomous take-off and landing abilities.The power consumption analysis shows that for a fixed-point reconnaissance mission,when the mission radius is less than 3.38 km,the VTOL type exhibits longer mission duration than the hand-launched type.展开更多
Wingtip slots,where the outer primary feathers of birds split and spread vertically,are regarded as an evolved favorable feature that could effectively improve their aerodynamic performance.They have inspired many to ...Wingtip slots,where the outer primary feathers of birds split and spread vertically,are regarded as an evolved favorable feature that could effectively improve their aerodynamic performance.They have inspired many to perform experiments and simulations as well as to relate their results to aircraft design.This paper aims to provide guidance for the research on the aerodynamic mechanism of wingtip slots.Following a review of previous wingtip slot research,four imperfections are put forward:vacancies in research content,inconsistencies in research conclusions,limitations of early research methods,and shortage of the aerodynamic mechanism analysis.On this basis,further explorations and expansion of the influence factors for steady state are needed;more attention should be poured into the application of flow field integration method to decompose drag,and evaluation of variation in induced drag seems a more rational choice.Geometric and kinematic parameters of wingtip slot structure in the unsteady state,as well as the flexibility of wingtips,should be taken into account.As for the aerodynamic mechanism of wingtip slots,the emphasis can be placed on the study of the formation,development,and evolution of wingtip vortices on slotted wings.Besides,some research strategies and feasibility analyses are proposed for each part of the research.展开更多
The slotted wingtip structure of birds is considered to be the product of improving flight efficiency in the process of evolution. It can change the vortex structure of wingtip and improve aerodynamic efficiency. This...The slotted wingtip structure of birds is considered to be the product of improving flight efficiency in the process of evolution. It can change the vortex structure of wingtip and improve aerodynamic efficiency. This paper reports a numerical investigation of slotted wing configuration undergoing bio-inspired flapping kinematics(consisting of plunging and in-line movement)extracted from a free-flying bald eagle wing. The aim is to eluci-date the collective mechanism of the flow generated by slotted tips and the lift contribution of each tip. Specifi-cally, the objective of the study is to determine how changes in the wing spacing affect the resulting aerodynamic interaction between the slotted tips and how that affects the force generation and efficiency. Changes in the phase angle between the flapping motions of slotted tips, as well as the spacings among them,can affect the resulting vortex inter-actions. The rear tips often operates in the wake of the frontal tips and, meanwhile, the vortex generated by the movement of the rear tips promote the frontal tips.The interaction of vortices in time and space leads to wing-wing interference and the flow around slotted tips becomes complicated and unstable. The innovative study of wingtip slot in unsteady state leads us to find that the aerodynamic interaction among slotted tips makes the overall lift characteristic better than that of the unslotted wings. The slotted wing configuration can efficiently convert more energy into lift. As the flapping frequency increases, the collective feature of slotted wing with constantly changing gaps can be more advantageous to enhance lift-generation performance.展开更多
Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtain...Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.展开更多
As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancin...As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.展开更多
Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction...Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.展开更多
CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties,suggesting its potential as a structural material.Nevertheless,the challenge lies in achieving an elusive combination of high hardness and ...CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties,suggesting its potential as a structural material.Nevertheless,the challenge lies in achieving an elusive combination of high hardness and inherent self-lubrication on the worn surface,which is crucial for attaining exceptional tribological performance in medium-entropy alloy(MEA).This study reports the preparation of a novel CoCrNi-based self-lubricating composite by powder metallurgy,which is reinforced simultaneously with Ag solid lubricating phase and SiC ceramic particles.During the sintering process,SiC decomposes to form high hardness in situ Cr_(23)C_(6),enabling the composite to achieve high load-bearing capacity.During the sliding process,thick and dense Ag self-lubricating film is successfully achieved due to the mechanical and thermal effects.The protective tribo-layer effectively mitigates surface stress concentration induced by wear,thereby inhibiting surface coarsening and substantially enhancing the tribological performance.The results showed that compared with CoCrNi MEA,the wear rate and friction coefficient of CoCrNi/SiC/Ag composite are reduced by 88.1%and 32.8%,respectively,showing superior tribological properties over most MEA-based self-lubrication composites.This study further elucidates the wear mechanism of CoCrNi/SiC/Ag composite,providing a new strategy for developing self-lubricating materials with excellent comprehensive performance,which overcomes the inherent trade-off between wear resistance and lubrication.展开更多
Highly developed electronic information technology has undoubtedly resulted in numerous benefits to the military and public life.However,the resulting electromagnetic wave(EW)pollution cannot be ignored.Therefore,the ...Highly developed electronic information technology has undoubtedly resulted in numerous benefits to the military and public life.However,the resulting electromagnetic wave(EW)pollution cannot be ignored.Therefore,the application of highly efficient EW materials is becoming an important requirement.In this study,magnetic-dielectric heterointerface strategy was applied to construct absorbers with desirable electromagnetic wave properties.A novel CoO/Co nanoparticle anchored to N-doped mesoporous carbon(CoO/Co/N-CMK-3)composites was fabricated by facile precipitation reaction and the electromagnetic characteristics have been well optimized by adjusting pyrolysis temperature.The CoO/Co/N-CMK-3 yielded its highest performance at an annealing temperature of 800℃,with an extended effective absorption bandwidth of 5.83 GHz and unusually low minimum reflection loss of−63.82 dB,even at a thickness of just 1.8 mm and low filler loading(10%).For the excellent microwave absorption property,the advantages of the CoO/Co/N-CMK-3 can be summed up as follows.Firstly,the incorporation of heterointerfaces among N-CMK-3,CoO,and Co introduces abundant polarization centers,triggering various polarization effects and increasing dielectric losses.Secondly,the CoO/Co magnetic component introduced the strong magnetic loss and improved the impedance matching capability of CoO/Co/N-CMK-3.Thirdly,the extraordinary magnetic-dielectric behavior is supported by multiple magnetic coupling networks and enriched air-material heterointerfaces,boosted the magnetoelectric cooperative loss for further optimizing the electromagnetic dissipation and broadening the effective absorption frequency band.Moreover,the CST simulation results validate the impressive operational bandwidth and reflection loss characteristics of the obtained absorbers.This study demonstrates a novel heterointerface engineering strategy for designing lightweight,wide-band,and high-performance EW absorbers.展开更多
The paper presents a two-layer,disturbance-resistant,and fault-tolerant affine formation maneuver control scheme that accomplishes the surrounding of a dynamic target with multiple underactuated Quadrotor Unmanned Aer...The paper presents a two-layer,disturbance-resistant,and fault-tolerant affine formation maneuver control scheme that accomplishes the surrounding of a dynamic target with multiple underactuated Quadrotor Unmanned Aerial Vehicles(QUAVs).This scheme mainly consists of predefinedtime estimators and fixed-time tracking controllers,with a hybrid Laplacian matrix describing the communication among these QUAVs.At the first layer,we devise predefined time estimators for leading and following QUAVs,enabling accurate estimation of desired information.In the second layer,we initially devise a fixed-time hybrid observer to estimate unknown disturbances and actuator faults.Fixedtime translational tracking controllers are then proposed,and the intermediary control input from these controllers is used to extract the desired attitude and angular velocities for the fixed-time rotational tracking controllers.We employ an exact tracking differentiator to handle variables that are challenging to differentiate directly.The paper includes a demonstration of the control system stability through mathematical proof,as well as the presentation of simulation results and comparative simulations.展开更多
The development of lithium-ion batteries with high-energy densities is substantially hampered by the graphite anode's low theoretical capacity(372 mAh g^(-1)).There is an urgent need to explore novel anode materia...The development of lithium-ion batteries with high-energy densities is substantially hampered by the graphite anode's low theoretical capacity(372 mAh g^(-1)).There is an urgent need to explore novel anode materials for lithium-ion batteries.Silicon(Si),the second-largest element outside of Earth,has an exceptionally high specific capacity(3579 mAh g^(-1)),regarded as an excellent choice for the anode material in high-capacity lithium-ion batteries.However,it is low intrinsic conductivity and volume amplification during service status,prevented it from developing further.These difficulties can be successfully overcome by incorporating carbon into pure Si systems to form a composite anode and constructing a buffer structure.This review looks at the diffusion mechanism,various silicon-based anode material configurations(including sandwich,core-shell,yolk-shell,and other 3D mesh/porous structures),as well as the appropriate binders and electrolytes.Finally,a summary and viewpoints are offered on the characteristics and structural layout of various structures,metal/non-metal doping,and the compatibility and application of various binders and electrolytes for silicon-based anodes.This review aims to provide valuable insights into the research and development of silicon-based carbon anodes for high-performance lithium-ion batteries,as well as their integration with binders and electrolyte.展开更多
The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions.This study reports an epoxy resin coating fi...The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions.This study reports an epoxy resin coating filled with benzotriazole loaded metal-organic frameworks(BTA-MOFs)functionalized graphene oxide nanoribbons(GONR)that exhibit active anti-corrosion,act as a barrier to corrosive ion,and enhance wear resistance.The GONR@BTA-MOFs composite is synthesized through chemically etching multi-walled carbon nanotubes and subsequent electrostatic self-assembly corrosion inhibitors loaded MOFs onto the GONR.The composite demonstrates improved compatibility with epoxy resins compared to carbon nanotubes.The anti-corrosion performance of the composite coating is investigated using electrochemical impedance spectroscopy.After immersing in a 3.5 wt.%NaCl solution for 25 d,the alternating current impedance of the composite coating is three orders of magnitude higher than that of pure epoxy resin.Simultaneously,the controlled release of the corrosion inhibitor retards the deterioration of the coating after localized damage occurrence,which functions as active corrosion protection.The GONR@BTA-MOFs/EP composite coating exhibits the highest corrosion potential of-0.188 V and the lowest corrosion current of 3.162×10^(−9)A cm^(−2)in the Tafel test.Tribological studies reveal a reduction in the friction coefficient from 0.62 to 0.08 after incorporating GONR@BTA-MOFs in the coating,with the wear volume being seven times lower than that of pure epoxy resin.The excellent lubrication effect of the nanomaterials reduces the coefficient of friction of the coating,thereby improving the abrasion resistance of the coating.The synergy between the self-lubrication of the two-dimensional layered fillers and the corrosion resistance of the smart inhibitor containers suggests a promising strategy for enhancing the performance of epoxy resins under complex working conditions.展开更多
Fiber-reinforced composites are an ideal material for the lightweight design of aerospace structures. Especially in recent years, with the rapid development of composite additive manufacturing technology, the design o...Fiber-reinforced composites are an ideal material for the lightweight design of aerospace structures. Especially in recent years, with the rapid development of composite additive manufacturing technology, the design optimization of variable stiffness of fiber-reinforced composite laminates has attracted widespread attention from scholars and industry. In these aerospace composite structures, numerous cutout panels and shells serve as access points for maintaining electrical, fuel, and hydraulic systems. The traditional fiber-reinforced composite laminate subtractive drilling manufacturing inevitably faces the problems of interlayer delamination, fiber fracture, and burr of the laminate. Continuous fiber additive manufacturing technology offers the potential for integrated design optimization and manufacturing with high structural performance. Considering the integration of design and manufacturability in continuous fiber additive manufacturing, the paper proposes linear and nonlinear filtering strategies based on the Normal Distribution Fiber Optimization (NDFO) material interpolation scheme to overcome the challenge of discrete fiber optimization results, which are difficult to apply directly to continuous fiber additive manufacturing. With minimizing structural compliance as the objective function, the proposed approach provides a strategy to achieve continuity of discrete fiber paths in the variable stiffness design optimization of composite laminates with regular and irregular holes. In the variable stiffness design optimization model, the number of candidate fiber laying angles in the NDFO material interpolation scheme is considered as design variable. The sensitivity information of structural compliance with respect to the number of candidate fiber laying angles is obtained using the analytical sensitivity analysis method. Based on the proposed variable stiffness design optimization method for complex perforated composite laminates, the numerical examples consider the variable stiffness design optimization of typical non-perforated and perforated composite laminates with circular, square, and irregular holes, and systematically discuss the number of candidate discrete fiber laying angles, discrete fiber continuous filtering strategies, and filter radius on structural compliance, continuity, and manufacturability. The optimized discrete fiber angles of variable stiffness laminates are converted into continuous fiber laying paths using a streamlined process for continuous fiber additive manufacturing. Meanwhile, the optimized non-perforated and perforated MBB beams after discrete fiber continuous treatment, are manufactured using continuous fiber co-extrusion additive manufacturing technology to verify the effectiveness of the variable stiffness fiber optimization framework proposed in this paper.展开更多
DNA2,a multifunctional enzyme with structure-specific nuclease,5'-to-3'helicase,and DNA-dependent ATPase activities,plays a pivotal role in the cellular response to DNA damage.However,its involvement in cerebr...DNA2,a multifunctional enzyme with structure-specific nuclease,5'-to-3'helicase,and DNA-dependent ATPase activities,plays a pivotal role in the cellular response to DNA damage.However,its involvement in cerebral ischemia/reperfusion(I/R)injury remains to be elucidated.This study investigated the involvement of DNA2 in cerebral I/R injury using conditional knockout(cKO)mice(Nestin-Cre)subjected to middle cerebral artery occlusion(MCAO),an established model of cerebral I/R.Results demonstrated a gradual up-regulation of DNA2 expression,peaking at 72 h post-MCAO.Notably,DNA2 cKO mice exhibited more pronounced brain injury,neurological deficits,and neuronal apoptosis within the penumbra following MCAO.Additionally,DNA2 expression was elevated in an oxygen-glucose deprivation/reoxygenation(OGD/R)cell culture model,and DNA2 knockdown(KD)exacerbated neuronal apoptosis and oxidative stress.Transcriptome analysis of ischemic penumbra tissues via RNA sequencing revealed significant down-regulation of Homer1 in DNA2 cKO mice.Furthermore,in vitro experiments demonstrated that overexpression of Homer1a ameliorated DNA2 KD-induced neuronal apoptosis.Collectively,these findings demonstrate that DNA2 deficiency exacerbates cerebral I/R injury through the down-regulation of Homer1a,highlighting a novel regulatory axis in ischemic neuroprotection.展开更多
The modular design pattern revolutionizes the monolithic morphology of traditional spacecraft into the reconfigurable combination of modular units.However,due to the morphological changes,the effective takeover contro...The modular design pattern revolutionizes the monolithic morphology of traditional spacecraft into the reconfigurable combination of modular units.However,due to the morphological changes,the effective takeover control of the combination through multiple independent modules,including the controller and actuator modules,remains a challenge.In this paper,a robust takeover control scheme with high allocation accuracy,independent of precise inertia,is proposed for the reconfigurable combination in the presence of the inertia uncertainty,model parameters uncertainty,communication delay,and external disturbance.By reregulating the conditions for performance synthesis into a symmetric form with similar structure,a hybrid non-fragile H_(2)/H_(∞)controller is designed for handling two types of controller gain perturbations,achieving superior performance with less energy consumption through simultaneous perturbation suppression.Moreover,through temporarily storing the allocation signals in the initial stage to cover the upper bound of the communication delay,the proposed distributed dynamic allocation scheme enables the actuator modules to implement the control signals jointly to stabilize the combination.Distinguished from general allocators,the proposed high-precision allocation scheme under communication delay can not only ensure full exploitation of controller performance,but also dynamically adjust allocation coefficients based on energy consumption index of controller modules to prevent actuator saturation.Numerical simulations demonstrate the superiority of the proposed hybrid non-fragile controller and the allocation scheme.展开更多
With the development of More Electric Aircraft(MEA),the Permanent Magnet Synchronous Motor(PMSM)is widely used in the MEA field.The PMSM control system of MEA needs to consider the system reliability,and the inverter ...With the development of More Electric Aircraft(MEA),the Permanent Magnet Synchronous Motor(PMSM)is widely used in the MEA field.The PMSM control system of MEA needs to consider the system reliability,and the inverter switching frequency of the inverter is one of the impacting factors.At the same time,the control accuracy of the system also needs to be considered,and the torque ripple and flux ripple are usually considered to be its important indexes.This paper proposes a three-stage series Model Predictive Torque and Flux Control system(three-stage series MPTFC)based on fast optimal voltage vector selection to reduce switching frequency and suppress torque ripple and flux ripple.Firstly,the analytical model of the PMSM is established and the multi-stage series control method is used to reduce the switching frequency.Secondly,selectable voltage vectors are extended from 8 to 26 and a fast selection method for optimal voltage vector sectors is designed based on the hysteresis comparator,which can suppress the torque ripple and flux ripple to improve the control accuracy.Thirdly,a three-stage series control is obtained by expanding the two-stage series control using the P-Q torque decomposition theory.Finally,a model predictive torque and flux control experimental platform is built,and the feasibility and effectiveness of this method are verified through comparison experiments.展开更多
This paper presents a predefined-time controller for Multiple Space transportation Robots System (MSRS), which can be applied in on-orbit assembly tasks to transport modules to pre-assembly configuration quickly. Firs...This paper presents a predefined-time controller for Multiple Space transportation Robots System (MSRS), which can be applied in on-orbit assembly tasks to transport modules to pre-assembly configuration quickly. Firstly, to simplify the analysis and design of predefined-time controller, a Predefined-time Stability Criterion is proposed in the form of Composite Lyapunov Function (CLF-PSC). Besides simplicity, the CLF-PSC also has the advantage of less conservativeness due to utilization of initial state information. Secondly, a concept of Lp-Norm-Normalized Sign Function (LPNNSF) is proposed based on the CLF-PSC. Different from traditional norm-normalized sign function, the Lp-norm of LPNNSF can be selected arbitrarily according to practical control task requirements, which means that the proposed LPNNSF is more generalized and more convenient for calculation. Thirdly, a predefined-time disturbance observer and predefined-time controller are designed based on the LPNNSF. The observer has the property of predefined-time convergence to achieve quicker and more accurate estimation of the lumped disturbance. The controller has less control input and chattering phenomenon than traditional predefined-time controller. In addition, by introducing the observer into the controller, the closed-loop system enjoys high precision and strong robustness. Finally, the effectiveness of the proposed controller is verified by numerical simulations. By employing the controller, the MSRS can carry assembly modules to the desired pre-assembly configuration accurately within predefined time.展开更多
Ensuring the long-term and stable operation of mechanical equipment has been a research emphasis with the development of aerospace and polar exploration,which necessitates the prepared materials with high mechanical s...Ensuring the long-term and stable operation of mechanical equipment has been a research emphasis with the development of aerospace and polar exploration,which necessitates the prepared materials with high mechanical strength as well as excellent wear resistance[1].The traditional lubricant is widely acknowledged to be susceptible to evaporation or decomposition under extreme conditions,necessitating the deposition of a protective thin film on critical mechanical parts’surfaces to enhance their mechanical and tribological properties[2,3].展开更多
A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state ...A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state of the medium and low speed maglev coupled system by the additional deformation of the maglev track.This study investigated the dynamic properties of the coupled vibration system affected by the subgrade settlement.First,a theoretical coupled vibration model of a maglev train-track-ground girder system with uneven subgrade settlement was proposed and verified.Then,the effect mechanism of the coupled system caused by the uneven subgrade settlement was explored.Finally,settlement types and subgrade support voiding were examined.The analysis showed that the uneven subgrade settlement considerably increased the dynamic responses of the levitation control system and maglev vehicle while having a minor influence on those of the track-ground girder.The influence of a single ground girder settling was the strongest,and adjacent sides’settling of two ground girders was the weakest for the vibration of a maglev train.An extremely large uneven settlement exceeding 6 mm led to active levitation control system instability.The subgrade support voiding enlarged the vehicle-induced vibration of the track ground girder.展开更多
基金supported by grants from the National Natural Science Foundation of China(32470364,31872850,and 31872804)the Natural Science Basic Research Program of Shaanxi(2025JC-JCQN-056 and 2024JC-YBMS-151)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(2025A1515012749)the China Postdoctoral Science Foundation(2025M774348)the Shaanxi Fundamental Science Research Project for Chemistry&Biology(22JHZ007and 22JHQ054)。
文摘Gibberellins(GAs)and auxin play central regulatory roles in seed germination and root system development,respectively,so that the application of these phytohormones to crops would be worthwhile,with an increasing potential demand in agriculture.However,there are few effective chemicals that simultaneously enhance both GA and auxin signaling.Here,we report on an artificial thiourea derivative chemical,Y21,that serves as both a GA-signaling agonist and an auxin analog,promoting seed germination and root development,as well as low-phosphorus tolerance.Phenotypic,biochemical,and genetic evidence demonstrated that Y21 enhances the interaction between GA and its receptor GID1C via the Val239 amino acid residue and consequently promotes degradation of the DELLA proteins REPRESSOR OF ga1-3(RGA)and RGA-LIKE 2.Furthermore,we found that Y21 interacts with the auxin receptor TIR1 via the Cys405 residue and thus promotes the turnover of the auxinresponsive Aux/IAA proteins.Consequently,Y21significantly increases low-phosphorus tolerance of treated plants by positively regulating lateral root development.To our knowledge,Y21 is the first GA-signaling agonist to be identified,and our results also demonstrate that this potent synthetic chemical,identified by chemical genetic screening,is effective at modulating plant development and stress tolerance.
基金supported by the National Natural Science Foundation of China(Nos.52231007,51872238,52074227,and 21806129)the Fundamental Research Funds for the Central Universities(Nos.3102018zy045,3102019AX11,and 5000220455)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118).
文摘The emergence of precision electronic devices and wearable electronic products urgently requires high-performance multifunctional electromagnetic wave(EMW)absorbers to meet the applicability and versatility in various applications.Herein,a dual-network(DN)gel was successfully prepared using acrylamide and sodium lignosulphonate as the basic units by simple chemical cross-linking and physical cross-linking methods.Specifically,the hydrogel forms two types of cross-linking networks through metal coordination and hydrogen bonding.Benefiting from the combined effects of dipole polarization and conductivity loss,the gel achieves an effective absorption bandwidth(EAB)of 6.74 GHz at a thickness of only 1.89 mm,demonstrating excellent EMW absorption performance.In addition,this unique structural configuration endows the EMW absorber with multifunctional features,such as remarkable tensile strength,good environmental compatibility,ultraviolet(UV)resistance,and excellent adhesion.Integrating multiple functional features into the EMW gels displays a broad application prospect in a variety of application scenarios.This research reveals the significance of DN structure design in the electromagnetic wave absorption(EWA)performance of gel-based materials,providing a substantial foundation for the multifunctional design of gel-based absorbers.
基金supported in part by the National Key Research and Development Program of China(No.2017YFB1300102)the Key R&D Program in Shaanxi Province of China(No.2020ZDLGY06-05,No 2021ZDLGY09-10)the National Natural Science Foundation of China(No.11902103,No.11872314).
文摘The lack of autonomous take-off and landing capabilities of bird-like flapping-wing aerial vehicles(BFAVs)seriously restricts their further development and application.Thus,combined with the current research results on the autonomous take-off and landing technology of unmanned aerial vehicles,four types of technologies are studied,including jumping take-off and landing technology,taxiing take-off and landing technology,gliding take-off and landing technology,and vertical take-off and landing(VTOL)technology.Based on the analytic hierarchy process(AHP)-comprehensive evaluation method,a fuzzy comprehensive evaluation model for the autonomous take-off and landing scheme of a BFAV is established,and four schemes are evaluated concretely.The results show that under the existing technical conditions,the hybrid layout VTOL scheme is the best.Furthermore,the detailed design and development of the prototype of a BFAV with a four-rotor hybrid layout are carried out,and the vehicle performance is tested.The results prove that through the four-rotor hybrid layout design,the BFAV has good autonomous take-off and landing abilities.The power consumption analysis shows that for a fixed-point reconnaissance mission,when the mission radius is less than 3.38 km,the VTOL type exhibits longer mission duration than the hand-launched type.
基金support from National Natural Science Foundation of China(Grant 11872314 and U1613227)Youth Program of Natural Science Basic Research Plan in Shaanxi Province of China(Grant 2019JQ-394)Key R&D Program in Shaanxi Province of China(Grant 2020GY-154).
文摘Wingtip slots,where the outer primary feathers of birds split and spread vertically,are regarded as an evolved favorable feature that could effectively improve their aerodynamic performance.They have inspired many to perform experiments and simulations as well as to relate their results to aircraft design.This paper aims to provide guidance for the research on the aerodynamic mechanism of wingtip slots.Following a review of previous wingtip slot research,four imperfections are put forward:vacancies in research content,inconsistencies in research conclusions,limitations of early research methods,and shortage of the aerodynamic mechanism analysis.On this basis,further explorations and expansion of the influence factors for steady state are needed;more attention should be poured into the application of flow field integration method to decompose drag,and evaluation of variation in induced drag seems a more rational choice.Geometric and kinematic parameters of wingtip slot structure in the unsteady state,as well as the flexibility of wingtips,should be taken into account.As for the aerodynamic mechanism of wingtip slots,the emphasis can be placed on the study of the formation,development,and evolution of wingtip vortices on slotted wings.Besides,some research strategies and feasibility analyses are proposed for each part of the research.
基金the support from the National Natural Science Foundation of China(Nos.11872314 and U1613227)the Key R&D Program in Shaanxi Province of China(No.2020GY-154)。
文摘The slotted wingtip structure of birds is considered to be the product of improving flight efficiency in the process of evolution. It can change the vortex structure of wingtip and improve aerodynamic efficiency. This paper reports a numerical investigation of slotted wing configuration undergoing bio-inspired flapping kinematics(consisting of plunging and in-line movement)extracted from a free-flying bald eagle wing. The aim is to eluci-date the collective mechanism of the flow generated by slotted tips and the lift contribution of each tip. Specifi-cally, the objective of the study is to determine how changes in the wing spacing affect the resulting aerodynamic interaction between the slotted tips and how that affects the force generation and efficiency. Changes in the phase angle between the flapping motions of slotted tips, as well as the spacings among them,can affect the resulting vortex inter-actions. The rear tips often operates in the wake of the frontal tips and, meanwhile, the vortex generated by the movement of the rear tips promote the frontal tips.The interaction of vortices in time and space leads to wing-wing interference and the flow around slotted tips becomes complicated and unstable. The innovative study of wingtip slot in unsteady state leads us to find that the aerodynamic interaction among slotted tips makes the overall lift characteristic better than that of the unslotted wings. The slotted wing configuration can efficiently convert more energy into lift. As the flapping frequency increases, the collective feature of slotted wing with constantly changing gaps can be more advantageous to enhance lift-generation performance.
基金supported by National Natural Science Foundation of China(12374358,91950207)Guangdong Basic and Applied Basic Research Foundation(2024A1515010420).
文摘Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.
基金supported by the National Natural Science Foundation of China(Nos.52130204,52174376,52202070,51822405)Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120028)+6 种基金TQ Innovation Foundation(No.23-TQ09-02-ZT-01-005)Aeronautical Science Foundation of China(No.20220042053001)Science and Technology Innovation Team Plan of Shaanxi Province(No.2021TD-17)Key R&D Project of Shaanxi Province(No.2024GX-YBXM-220)Thousands Person Plan of Jiangxi Province(JXSQ2020102131)Fundamental Research Funds for the Central Universities(Nos.D5000230348,D5000220057)China Scholarship Council(Nos.202206290133,202306290190).
文摘As a 3D printing method,laser powder bed fusion(LPBF)technology has been extensively proven to offer significant advantages in fabricating complex structured specimens,achieving ultra-fine microstructures,and enhancing performances.In the domain of manufacturing melt-grown oxide ceramics,it encounters substantial challenges in suppressing crack defects during the rapid solidification process.The strategic integration of high entropy alloys(HEA),leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles.The ingenious doping of HEA parti-cles preserves the eutectic microstructures of the Al_(2)O_(3)/GdAlO_(3)(GAP)/ZrO_(2)ceramic composite.The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF,effectively reducing crack initiation and growth.Due to in-creased curvature forces and intense Marangoni convection at the top of the molt pool,particle collision intensifies,leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool.However,this phenomenon can be effectively alleviated in the remelting process of subsequent layer de-position.Furthermore,a portion of the HEA particles partially dissolves and sinks into the molten pool,acting as heterogeneous nucleation particles,inducing the formation of equiaxed eutectic and leading pri-mary phase nucleation.Some HEA particles diffuse into the lamellar ternary eutectic structures,further promoting the refinement of eutectic microstructures due to increased undercooling.The innovative dop-ing of HEA particles has effectively facilitated the fabrication of turbine-structured,conical,and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm,demonstrating significant developmental potential in the field of ceramic composite manufacturing.
基金supported by the National Nat-ural Science Foundation of China(Nos.51872238,52074227,and 21806129)the Fundamental Research Funds for the Central Universities,China(Nos.3102018zy045 and 3102019AX11)+2 种基金the Guangdong Basic and Applied Basic Research Foundation,China(No.2024A1515010298)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118)the Key Laboratory of Icing and Anti/De-icing of CARDC(No.IADL20220401).
文摘Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.
基金supported by the Natural Science Foundation of China(Nos.52175188 and 52274367)the Key Research and Development Program of Shaanxi Province(No.2023-YBGY-434)+2 种基金he Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(No.LKLAMTF202301)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012378)the Science and Technology on Reactor System Design Technology Laboratory.
文摘CoCrNi medium-entropy alloy has demonstrated remarkable mechanical properties,suggesting its potential as a structural material.Nevertheless,the challenge lies in achieving an elusive combination of high hardness and inherent self-lubrication on the worn surface,which is crucial for attaining exceptional tribological performance in medium-entropy alloy(MEA).This study reports the preparation of a novel CoCrNi-based self-lubricating composite by powder metallurgy,which is reinforced simultaneously with Ag solid lubricating phase and SiC ceramic particles.During the sintering process,SiC decomposes to form high hardness in situ Cr_(23)C_(6),enabling the composite to achieve high load-bearing capacity.During the sliding process,thick and dense Ag self-lubricating film is successfully achieved due to the mechanical and thermal effects.The protective tribo-layer effectively mitigates surface stress concentration induced by wear,thereby inhibiting surface coarsening and substantially enhancing the tribological performance.The results showed that compared with CoCrNi MEA,the wear rate and friction coefficient of CoCrNi/SiC/Ag composite are reduced by 88.1%and 32.8%,respectively,showing superior tribological properties over most MEA-based self-lubrication composites.This study further elucidates the wear mechanism of CoCrNi/SiC/Ag composite,providing a new strategy for developing self-lubricating materials with excellent comprehensive performance,which overcomes the inherent trade-off between wear resistance and lubrication.
基金financially supported by National Key Research and Development Program of China(Nos.2022YFB3807100 and 2022YFB3807101)National Science Fund for Distinguished Young Scholars(No.52025034)+3 种基金National Natural Science Foundation of China(No.22205182)Guangdong Basic and Applied Basic Re-search Foundation(No.2024A1515011516)China Postdoctoral Science Foundation(Nos.2022M722594 and 2024T171710)financially supported by Innovation Team of Shaanxi Sanqin Scholars.
文摘Highly developed electronic information technology has undoubtedly resulted in numerous benefits to the military and public life.However,the resulting electromagnetic wave(EW)pollution cannot be ignored.Therefore,the application of highly efficient EW materials is becoming an important requirement.In this study,magnetic-dielectric heterointerface strategy was applied to construct absorbers with desirable electromagnetic wave properties.A novel CoO/Co nanoparticle anchored to N-doped mesoporous carbon(CoO/Co/N-CMK-3)composites was fabricated by facile precipitation reaction and the electromagnetic characteristics have been well optimized by adjusting pyrolysis temperature.The CoO/Co/N-CMK-3 yielded its highest performance at an annealing temperature of 800℃,with an extended effective absorption bandwidth of 5.83 GHz and unusually low minimum reflection loss of−63.82 dB,even at a thickness of just 1.8 mm and low filler loading(10%).For the excellent microwave absorption property,the advantages of the CoO/Co/N-CMK-3 can be summed up as follows.Firstly,the incorporation of heterointerfaces among N-CMK-3,CoO,and Co introduces abundant polarization centers,triggering various polarization effects and increasing dielectric losses.Secondly,the CoO/Co magnetic component introduced the strong magnetic loss and improved the impedance matching capability of CoO/Co/N-CMK-3.Thirdly,the extraordinary magnetic-dielectric behavior is supported by multiple magnetic coupling networks and enriched air-material heterointerfaces,boosted the magnetoelectric cooperative loss for further optimizing the electromagnetic dissipation and broadening the effective absorption frequency band.Moreover,the CST simulation results validate the impressive operational bandwidth and reflection loss characteristics of the obtained absorbers.This study demonstrates a novel heterointerface engineering strategy for designing lightweight,wide-band,and high-performance EW absorbers.
基金supported by Natural Science Basic Research Plan in Shaanxi Province of China(No.2023-JC-QN-0733)Guangdong Basic and Applied Basic Research Foundation,China(No.2022A1515110753)+2 种基金China Postdoctoral Science Foundation(No.2022M722583)China Industry-UniversityResearch Innovation Foundation(No.2022IT188)National Key Laboratory of Air-based Information Perception and Fusion and the Aeronautic Science Foundation of China(No.20220001068001)。
文摘The paper presents a two-layer,disturbance-resistant,and fault-tolerant affine formation maneuver control scheme that accomplishes the surrounding of a dynamic target with multiple underactuated Quadrotor Unmanned Aerial Vehicles(QUAVs).This scheme mainly consists of predefinedtime estimators and fixed-time tracking controllers,with a hybrid Laplacian matrix describing the communication among these QUAVs.At the first layer,we devise predefined time estimators for leading and following QUAVs,enabling accurate estimation of desired information.In the second layer,we initially devise a fixed-time hybrid observer to estimate unknown disturbances and actuator faults.Fixedtime translational tracking controllers are then proposed,and the intermediary control input from these controllers is used to extract the desired attitude and angular velocities for the fixed-time rotational tracking controllers.We employ an exact tracking differentiator to handle variables that are challenging to differentiate directly.The paper includes a demonstration of the control system stability through mathematical proof,as well as the presentation of simulation results and comparative simulations.
基金supported by National Natural Science Foundation of China(No.22205182)National Science Fund for Distinguished Young Scholars(No.52025034)+2 种基金China Postdoctoral Science Foundation(Nos.2022M722594/2024T171170)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515011516)financially supported by Innovation Team of Shaanxi Sanqin Scholars。
文摘The development of lithium-ion batteries with high-energy densities is substantially hampered by the graphite anode's low theoretical capacity(372 mAh g^(-1)).There is an urgent need to explore novel anode materials for lithium-ion batteries.Silicon(Si),the second-largest element outside of Earth,has an exceptionally high specific capacity(3579 mAh g^(-1)),regarded as an excellent choice for the anode material in high-capacity lithium-ion batteries.However,it is low intrinsic conductivity and volume amplification during service status,prevented it from developing further.These difficulties can be successfully overcome by incorporating carbon into pure Si systems to form a composite anode and constructing a buffer structure.This review looks at the diffusion mechanism,various silicon-based anode material configurations(including sandwich,core-shell,yolk-shell,and other 3D mesh/porous structures),as well as the appropriate binders and electrolytes.Finally,a summary and viewpoints are offered on the characteristics and structural layout of various structures,metal/non-metal doping,and the compatibility and application of various binders and electrolytes for silicon-based anodes.This review aims to provide valuable insights into the research and development of silicon-based carbon anodes for high-performance lithium-ion batteries,as well as their integration with binders and electrolyte.
基金supported by the National Natural Science Foundation of China(No.52475216)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515240030)+2 种基金the Natural Science Foundation of Shaanxi Province(No.2024RSCXTD-62)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)(No.2022-QZ-04)We would like to thank the Analytical&Testing Center of Northwestern Polytechnical University and the Shaanxi Materials Analysis and Research Center.
文摘The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions.This study reports an epoxy resin coating filled with benzotriazole loaded metal-organic frameworks(BTA-MOFs)functionalized graphene oxide nanoribbons(GONR)that exhibit active anti-corrosion,act as a barrier to corrosive ion,and enhance wear resistance.The GONR@BTA-MOFs composite is synthesized through chemically etching multi-walled carbon nanotubes and subsequent electrostatic self-assembly corrosion inhibitors loaded MOFs onto the GONR.The composite demonstrates improved compatibility with epoxy resins compared to carbon nanotubes.The anti-corrosion performance of the composite coating is investigated using electrochemical impedance spectroscopy.After immersing in a 3.5 wt.%NaCl solution for 25 d,the alternating current impedance of the composite coating is three orders of magnitude higher than that of pure epoxy resin.Simultaneously,the controlled release of the corrosion inhibitor retards the deterioration of the coating after localized damage occurrence,which functions as active corrosion protection.The GONR@BTA-MOFs/EP composite coating exhibits the highest corrosion potential of-0.188 V and the lowest corrosion current of 3.162×10^(−9)A cm^(−2)in the Tafel test.Tribological studies reveal a reduction in the friction coefficient from 0.62 to 0.08 after incorporating GONR@BTA-MOFs in the coating,with the wear volume being seven times lower than that of pure epoxy resin.The excellent lubrication effect of the nanomaterials reduces the coefficient of friction of the coating,thereby improving the abrasion resistance of the coating.The synergy between the self-lubrication of the two-dimensional layered fillers and the corrosion resistance of the smart inhibitor containers suggests a promising strategy for enhancing the performance of epoxy resins under complex working conditions.
基金supports for this research were provided by the National Natural Science Foundation of China(No.12272301,12002278,U1906233)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2023A1515011970,2024A1515010256)+1 种基金the Dalian City Supports Innovation and Entrepreneurship Projects for High-Level Talents,China(2021RD16)the Key R&D Project of CSCEC,China(No.CSCEC-2020-Z-4).
文摘Fiber-reinforced composites are an ideal material for the lightweight design of aerospace structures. Especially in recent years, with the rapid development of composite additive manufacturing technology, the design optimization of variable stiffness of fiber-reinforced composite laminates has attracted widespread attention from scholars and industry. In these aerospace composite structures, numerous cutout panels and shells serve as access points for maintaining electrical, fuel, and hydraulic systems. The traditional fiber-reinforced composite laminate subtractive drilling manufacturing inevitably faces the problems of interlayer delamination, fiber fracture, and burr of the laminate. Continuous fiber additive manufacturing technology offers the potential for integrated design optimization and manufacturing with high structural performance. Considering the integration of design and manufacturability in continuous fiber additive manufacturing, the paper proposes linear and nonlinear filtering strategies based on the Normal Distribution Fiber Optimization (NDFO) material interpolation scheme to overcome the challenge of discrete fiber optimization results, which are difficult to apply directly to continuous fiber additive manufacturing. With minimizing structural compliance as the objective function, the proposed approach provides a strategy to achieve continuity of discrete fiber paths in the variable stiffness design optimization of composite laminates with regular and irregular holes. In the variable stiffness design optimization model, the number of candidate fiber laying angles in the NDFO material interpolation scheme is considered as design variable. The sensitivity information of structural compliance with respect to the number of candidate fiber laying angles is obtained using the analytical sensitivity analysis method. Based on the proposed variable stiffness design optimization method for complex perforated composite laminates, the numerical examples consider the variable stiffness design optimization of typical non-perforated and perforated composite laminates with circular, square, and irregular holes, and systematically discuss the number of candidate discrete fiber laying angles, discrete fiber continuous filtering strategies, and filter radius on structural compliance, continuity, and manufacturability. The optimized discrete fiber angles of variable stiffness laminates are converted into continuous fiber laying paths using a streamlined process for continuous fiber additive manufacturing. Meanwhile, the optimized non-perforated and perforated MBB beams after discrete fiber continuous treatment, are manufactured using continuous fiber co-extrusion additive manufacturing technology to verify the effectiveness of the variable stiffness fiber optimization framework proposed in this paper.
基金supported by the National Natural Science Foundation of China (32070979)Shenzhen Science and Technology Program (JCYJ20220530161604009,JCYJ20240813150734043)+3 种基金Key Research and Development Program of Shaanxi (2024SF,YBXM,050)Fundamental Research Funds for the Central Universities (31020190QD004,3102019YX01001)Double First-Class Project of China Pharmaceutical University (CPUQNJC22_02)Global Pharmaceutical Development Alliance Plan of China Pharmaceutical University (1302090024-05)。
文摘DNA2,a multifunctional enzyme with structure-specific nuclease,5'-to-3'helicase,and DNA-dependent ATPase activities,plays a pivotal role in the cellular response to DNA damage.However,its involvement in cerebral ischemia/reperfusion(I/R)injury remains to be elucidated.This study investigated the involvement of DNA2 in cerebral I/R injury using conditional knockout(cKO)mice(Nestin-Cre)subjected to middle cerebral artery occlusion(MCAO),an established model of cerebral I/R.Results demonstrated a gradual up-regulation of DNA2 expression,peaking at 72 h post-MCAO.Notably,DNA2 cKO mice exhibited more pronounced brain injury,neurological deficits,and neuronal apoptosis within the penumbra following MCAO.Additionally,DNA2 expression was elevated in an oxygen-glucose deprivation/reoxygenation(OGD/R)cell culture model,and DNA2 knockdown(KD)exacerbated neuronal apoptosis and oxidative stress.Transcriptome analysis of ischemic penumbra tissues via RNA sequencing revealed significant down-regulation of Homer1 in DNA2 cKO mice.Furthermore,in vitro experiments demonstrated that overexpression of Homer1a ameliorated DNA2 KD-induced neuronal apoptosis.Collectively,these findings demonstrate that DNA2 deficiency exacerbates cerebral I/R injury through the down-regulation of Homer1a,highlighting a novel regulatory axis in ischemic neuroprotection.
基金co-supported by the National Natural Science Foundation of China(No.12372048)the China Postdoctoral Science Foundation(No.2023M742835)+3 种基金the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515011421)the Aeronautical Science Foundation of China(No.2022Z004053001)the Fundamental Research Funds for the Central Universities,China(No.D5000210833)the Young Talent Fund of Association for Science and Technology in Shaanxi,China(No.20220509)。
文摘The modular design pattern revolutionizes the monolithic morphology of traditional spacecraft into the reconfigurable combination of modular units.However,due to the morphological changes,the effective takeover control of the combination through multiple independent modules,including the controller and actuator modules,remains a challenge.In this paper,a robust takeover control scheme with high allocation accuracy,independent of precise inertia,is proposed for the reconfigurable combination in the presence of the inertia uncertainty,model parameters uncertainty,communication delay,and external disturbance.By reregulating the conditions for performance synthesis into a symmetric form with similar structure,a hybrid non-fragile H_(2)/H_(∞)controller is designed for handling two types of controller gain perturbations,achieving superior performance with less energy consumption through simultaneous perturbation suppression.Moreover,through temporarily storing the allocation signals in the initial stage to cover the upper bound of the communication delay,the proposed distributed dynamic allocation scheme enables the actuator modules to implement the control signals jointly to stabilize the combination.Distinguished from general allocators,the proposed high-precision allocation scheme under communication delay can not only ensure full exploitation of controller performance,but also dynamically adjust allocation coefficients based on energy consumption index of controller modules to prevent actuator saturation.Numerical simulations demonstrate the superiority of the proposed hybrid non-fragile controller and the allocation scheme.
基金co-supported by the National Natural Science Foundation of China(No.52477063)the National Key Research and Development Program of China(No.2023YFF0719100)。
文摘With the development of More Electric Aircraft(MEA),the Permanent Magnet Synchronous Motor(PMSM)is widely used in the MEA field.The PMSM control system of MEA needs to consider the system reliability,and the inverter switching frequency of the inverter is one of the impacting factors.At the same time,the control accuracy of the system also needs to be considered,and the torque ripple and flux ripple are usually considered to be its important indexes.This paper proposes a three-stage series Model Predictive Torque and Flux Control system(three-stage series MPTFC)based on fast optimal voltage vector selection to reduce switching frequency and suppress torque ripple and flux ripple.Firstly,the analytical model of the PMSM is established and the multi-stage series control method is used to reduce the switching frequency.Secondly,selectable voltage vectors are extended from 8 to 26 and a fast selection method for optimal voltage vector sectors is designed based on the hysteresis comparator,which can suppress the torque ripple and flux ripple to improve the control accuracy.Thirdly,a three-stage series control is obtained by expanding the two-stage series control using the P-Q torque decomposition theory.Finally,a model predictive torque and flux control experimental platform is built,and the feasibility and effectiveness of this method are verified through comparison experiments.
基金co-supported by the National Natural Science Foundation of China(Nos.12372048,12102343)the Key Program of the National Natural Science Foundation of China(No.U2013206)+1 种基金the China Postdoctoral Science Foundation(No.2023M742835)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515011421).
文摘This paper presents a predefined-time controller for Multiple Space transportation Robots System (MSRS), which can be applied in on-orbit assembly tasks to transport modules to pre-assembly configuration quickly. Firstly, to simplify the analysis and design of predefined-time controller, a Predefined-time Stability Criterion is proposed in the form of Composite Lyapunov Function (CLF-PSC). Besides simplicity, the CLF-PSC also has the advantage of less conservativeness due to utilization of initial state information. Secondly, a concept of Lp-Norm-Normalized Sign Function (LPNNSF) is proposed based on the CLF-PSC. Different from traditional norm-normalized sign function, the Lp-norm of LPNNSF can be selected arbitrarily according to practical control task requirements, which means that the proposed LPNNSF is more generalized and more convenient for calculation. Thirdly, a predefined-time disturbance observer and predefined-time controller are designed based on the LPNNSF. The observer has the property of predefined-time convergence to achieve quicker and more accurate estimation of the lumped disturbance. The controller has less control input and chattering phenomenon than traditional predefined-time controller. In addition, by introducing the observer into the controller, the closed-loop system enjoys high precision and strong robustness. Finally, the effectiveness of the proposed controller is verified by numerical simulations. By employing the controller, the MSRS can carry assembly modules to the desired pre-assembly configuration accurately within predefined time.
基金the National Natural Science Foundation of China(No.52175188)the Key Research and De-velopment Program of Shaanxi Province(No.2023-YBGY-434)+2 种基金the Open Fund of Liaoning Provincial Key Laboratory of Aero-engine Materials Tribology(No.LKLAMTF202301)the Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012378)the Science and Technology on Reactor System Design Tech-nology Laboratory and the Fundamental Research Funds for the Central Universities.
文摘Ensuring the long-term and stable operation of mechanical equipment has been a research emphasis with the development of aerospace and polar exploration,which necessitates the prepared materials with high mechanical strength as well as excellent wear resistance[1].The traditional lubricant is widely acknowledged to be susceptible to evaporation or decomposition under extreme conditions,necessitating the deposition of a protective thin film on critical mechanical parts’surfaces to enhance their mechanical and tribological properties[2,3].
基金National Natural Science Foundation of China under Grant Nos.52478467and 52108417Guangdong Basic and Applied Basic Research Foundation under Grant No.2024A1515012569the Natural Science Basic Research Program of Shaanxi under Grant No.2021JQ-101。
文摘A ground girder is laid on the preprocessed subgrade by gravity compaction and integrally uniformly supported by subgrade in maglev transit.The settlement of the maglev subgrade inevitably affects the vibration state of the medium and low speed maglev coupled system by the additional deformation of the maglev track.This study investigated the dynamic properties of the coupled vibration system affected by the subgrade settlement.First,a theoretical coupled vibration model of a maglev train-track-ground girder system with uneven subgrade settlement was proposed and verified.Then,the effect mechanism of the coupled system caused by the uneven subgrade settlement was explored.Finally,settlement types and subgrade support voiding were examined.The analysis showed that the uneven subgrade settlement considerably increased the dynamic responses of the levitation control system and maglev vehicle while having a minor influence on those of the track-ground girder.The influence of a single ground girder settling was the strongest,and adjacent sides’settling of two ground girders was the weakest for the vibration of a maglev train.An extremely large uneven settlement exceeding 6 mm led to active levitation control system instability.The subgrade support voiding enlarged the vehicle-induced vibration of the track ground girder.
