Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenie...Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.展开更多
As a newly proposed two-terminal mechanical element, there are many realizations of inerter such as ball-screw, rack and pinion,hydraulic, fluid and mechatronic inerter. This paper concerns about a novel mechatronic i...As a newly proposed two-terminal mechanical element, there are many realizations of inerter such as ball-screw, rack and pinion,hydraulic, fluid and mechatronic inerter. This paper concerns about a novel mechatronic inerter, which is consisted of a hydraulic piston inerter and linear motor, called hydraulic electric inerter(HEI). Firstly, the structural components and the working principles of two types HEI device are introduced, and the dynamic model of the HEI is established. Then, three classifications of mechatronic inerter, namely, the single motor type, the linear inerter-motor type and the rotary inerter-motor type are presented,and in the meanwhile, some comparisons among the three types mechatronic inerter are analyzed. Subsequently, a methodology of designing and experimental tests of the HEI device is proposed by considering the rated working conditions of the linear motor and the electric elements. At last, the HEI device is conducted, and the force tests of the non-loaded HEI and loaded HEI are tested in order to validate their properties. The experimental results are analyzed, and the discrepancies are also further discussed.展开更多
The paper deals with the design and experimental validation of the actuation mechanism control system for a morphing wing model.The experimental morphable wing model manufactured in this project is a full-size scale w...The paper deals with the design and experimental validation of the actuation mechanism control system for a morphing wing model.The experimental morphable wing model manufactured in this project is a full-size scale wing tip for a real aircraft equipped with an aileron.The morphing actuation of the model is based on a mechanism with four similar in house designed and manufactured actuators,positioned inside the wing on two parallel lines.Each of the four actuators used a BrushLess Direct Current(BLDC)electric motor integrated with a mechanical part performing the conversion of the angular displacements into linear displacements.The following have been chosen as successive steps in the design of the actuator control system:(A)Mathematical and software modelling of the actuator;(B)Design of the control system architecture and tuning using Internal Model Control(IMC)methodology;(C)Numerical simulation of the controlled actuator and its testing on bench and wind tunnel.The morphing wing experimental model is tested both at the laboratory level,with no airflow,to evaluate the components integration and the whole system functioning,but also in the wind tunnel,in the presence of airflow,to evaluate its behavior and the aerodynamic gain.展开更多
Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to det...Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation coefficient.Eight mooring cables are symmetrically arranged on both sides of the model.The floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and gravity.The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response.Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model.The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs.The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types.These results may provide a reference to facilitate the mooring design of VLFS.展开更多
This article will introduce a new version of the metal deck for building residential flooring with a newly designed cold form U section. This flooring will allow residential structures to be built more quickly while a...This article will introduce a new version of the metal deck for building residential flooring with a newly designed cold form U section. This flooring will allow residential structures to be built more quickly while also reducing the necessary thickness of the floor. The level of strength and deflection of this floor will be determined via analysis of a floor bed comprised of cold-formed inverted U sections (IUS) covered by sheathing that is subjected to different loading scenarios. The necessary computational quantities associated with the experiment have been compared to established laboratory values by performing all related and applicable tests. Then, these quantities are compared to different existing flooring techniques to determine the efficacy of this technique. The results show that this flooring technique can be effective and cost-efficient in residential applications.展开更多
Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around 10<sup>-35</sup> m, empty space may behave as a crystal, si...Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around 10<sup>-35</sup> m, empty space may behave as a crystal, singly or doubly refractive. This hypothesis, however, remains uncheckable for any direct measurement since the smallest distance accessible in experiment is about 10<sup>-19</sup> m at the LHC. Here we propose a laboratory test to measure space birefringence or refractivity induced by gravity. A sensitivity 10<sup>-31</sup> m for doubly and 10<sup>-28</sup> m for singly refractive vacuum could be reached with PETRA 6 GeV beam exploring UV laser Compton scattering.展开更多
A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dis...A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dismantling and reinstallation.An FB composed of twin pontoons and multi-porous vertical plates is proposed to improve the wave attenuation performance.The wave attenuation performance is investigated for different FB structures and vertical plate types under different incident wave heights and periods using 2D wave physical model tests in a wave flume.The results demonstrate that the proposed FB has a better performance than that of the conventional single pontoon-type FB.It reduces the wave transmission due to its enhanced wave reflection and energy loss.The wave transmission coefficient of the proposed FB decreases with an increase in the number of layers and relative draft depth of the vertical plates.However,a further decrease in the wave transmission coefficient is not observed when the number of porous vertical plates is increased from 4 to 5 layers.An equation has been derived to predict the wave transmission of the proposed FB based on the experimental results.展开更多
Rubble mound breakwaters with a crown wall are a common coastal engineering structure.The wave force on crown walls is an important parameter for the practice engineering design.Particularly,the wave force on crown wa...Rubble mound breakwaters with a crown wall are a common coastal engineering structure.The wave force on crown walls is an important parameter for the practice engineering design.Particularly,the wave force on crown walls under intermediate depths has been studied through physical model tests and numerical simulations.In this study,a three-dimensional numerical wave flume was developed to investigate monochromatic wave interactions in a rubble mound breakwater with a crown wall.Armor blocks were modeled in detail.The Navier-Stokes equations for two-phase incompressible flows,combined with shear stress transport k-ωturbulence model and volume of fluid method for tracking the free surface,were solved.A set of laboratory experiments were performed to validate the adopted model.Subsequently,a series of numerical simulations were implemented to examine the impacts of different hydrodynamic parameters(including wave height,incident wave period,and water depth)and the berm width on the wave force of the crown wall.Finally,a comparison of the experimental results and Martin method shows that the latter method is not suitable for this experimental scope.New empirical formulas are proposed to predict the wave force on crown walls under intermediate depth.The results can provide a basis for the design of crown wall of rubble mound breakwaters at intermediate depths.展开更多
Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure.In the present work,numerical analysis of square and circle short column...Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure.In the present work,numerical analysis of square and circle short columns,and reinforced concrete(RC)beams reinforced with fiber reinforced polymer composites are carried out.This work is divided into two parts.In the first part,numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer(GFRP)and Basalt Fiber Reinforced Polymer(BFRP)bars and spiral,and Carbon Fiber Reinforced Polymer(CFRP)wraps is conducted.The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio.In addition,the results of the numerical analysis showed good correlation with the experimental ones.An interaction diagram for BFRP RC columns is also developed with considering various eccentricities.The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column.For the cases considered in this study,column with two middle closely spaced CFRP wraps demonstrated the best performance.In the second part of this research,flexural behavior of RC beams reinforced with BFRP,GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests.The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams.It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.展开更多
The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental dama...The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental damages. In the present study, a series of experimental tests are performed to investigate the sloshing phenomenon in a baffled rectangular storage tank. In addition, the sloshing phenomenon is also modeled by using Open Foam. Based on the experimental and numerical studies, optimization of the geometric parameters of the tank is performed based on some criteria such as tank area, entropy generation, and the horizontal force exerted on the tank area due to the sloshing phenomenon.The optimization is also carried out based on the entropy generation minimization analysis. It is noted that the optimum baffle height is in the range of h_b/h_w=0.5-0.75 in the present study(where h_b and h_w are the baffle height and water depth, respectively). Based on the results, the optimal design of the tank is achieved with R_A= 0.9-1.0(where R_A=L/W, L and W are the length and width of the tank, respectively). The results also show that the increase of h_b can lead to a decrease of the maximum pressure and horizontal force exerted on the tank. It is also noted that the horizontal force exerted on the tank firstly continues to increase as the sway motion amplitude increases.However, as the normalized motion amplitude parameter, a/L(The parameter a is the motion amplitude), exceeds0.067, the effect of motion amplitude on the force is not obvious. The same optimization is also performed in the multiple-variable-baffled tank and prismatic storage tank.展开更多
Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instru...Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instruments that underlie the assessment of their production and handling safety have been described.Studies of a large number of compounds have revealed relationships between their sensitivity parameters and structure of individual compounds and compositions.The range of change of physical and chemical characteristics for the compounds we examined covers the entire region of their existence.Theoretical methodology and equations have been formulated to estimate the impact and friction sensitivity parameters of energetic materials and to evaluate the technological safety in use.The developed methodology is characterized by high-accuracy calculations and prediction of sensitivity parameters.展开更多
A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are perform...A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are performed using theδ-SPH model and experimental tests are conducted to validate the numerical model.The numerical results of both the free surface elevations and motions of the floating breakwater are in good agreement with the experimental results.Numerical results show that when the pontoon drafts are larger,the double pontoon floating breakwater performs better in wave attenuations compared with the single pontoon floating breakwater,and for all the drafts,the amplitudes of motions including sway,heave and roll of the double pontoon floating breakwater is always smaller.In addition,increasing the spacing between the two pontoons can further reduce the amplitudes of pontoon motions and improve the wave attenuation ability of the double pontoon floating breakwater.展开更多
Wood and wood-based composite materials have gained increasing attention in the sustainable building industry because of their renewability and environmental friendliness.Oriented oblique strand lumber(Eucalyptus Stra...Wood and wood-based composite materials have gained increasing attention in the sustainable building industry because of their renewability and environmental friendliness.Oriented oblique strand lumber(Eucalyptus Strand Wood,ESWood),which is manufactured from fast-growing small diameter eucalyptus wood(Eucalyptus urophylla×E.grandis),is introduced in this paper.Small clear specimen tests were conducted to determine the mechanical properties of ESWood material while full-scale component tests were performed to observe the structural performance of ESWood beams.A comparison of mechanical properties of ESWood with other wood/bamboo-based materials is then reported.From the results presented herein,it appears that the strength and stiffness properties of ESWood are affected by grain directionality and glued layers.However,it still has preferable mechanical properties as a building material,which is comparable or superior to those of other engineered wood/bamboo-based products(e.g.,Sitka spruce,LVL,OSL,Glulam,and Glubam).Furthermore,results from full-scale component tests show the stable mechanical performance of beams made by ESWood.This study makes a significant contribution to a potential utilization of fast-growing eucalyptus for general use in construction,and the presented mechanical tests results can serve as a fundamental data for more applications of ESWood in practical engineering.展开更多
The study endeavors to provide statistical inference for a (1 + 1) cascade system for exponential distribution under joint effect of stress-strength attenuation factors. Estimators of reliability function are obtained...The study endeavors to provide statistical inference for a (1 + 1) cascade system for exponential distribution under joint effect of stress-strength attenuation factors. Estimators of reliability function are obtained using Maximum Likelihood Estimator (MLE) and Uniformly Minimum Variance Unbiased Estimator (UMVUE) of the parameters. Asymptotic distribution of the parameters is also obtained. Comparison between estimators is made using data obtained through simulation experiment.展开更多
Aircraft icing has long been a plague to aviation for its serious threat to flight safety.Recently,researches about a newly proposed deicing method based on Plasma Synthetic Jet Actuator(PSJA)have just started.To meet...Aircraft icing has long been a plague to aviation for its serious threat to flight safety.Recently,researches about a newly proposed deicing method based on Plasma Synthetic Jet Actuator(PSJA)have just started.To meet the requirements of in-flight deicing,structure of PSJA needs to be adjusted.This paper completed the detailed design and experimental validation of a novel plasma striker,which was a modified version of PSJA.Influences of mass of the moving part and rod shapes on the ice-breaking performances were also studied.Besides,a“conical-nosed rod configuration”was proposed.Its purpose was to ensure a good ice-breaking performance of the plasma striker on long ice,by generating a splitting failure.Results show that,though mass of the moving part was just several grams,ice-breaking performance was better when the mass was lighter.The rectangular rod could generate an elliptical circumferential crack,whose major axis was parallel to the direction of the long side of the rectangular rod.And the“conical-nosed rod”concept was verified to be able to generate a splitting crack which can spread completely to the far end of long ice,and the crack direction was parallel to edge line of the cone.In general,the plasma striker has the advantages of simple structure,low energy consumption,little harm to the flow field and the aircraft skin.Simulations will be carried out in future works to study in detail the working process of the plasma striker.展开更多
Background:The eye globe exhibits significant regional variation of mechanical behaviour.The aim of this present study is to develop a new experimental technique for testing intact eye globes in a form that is represe...Background:The eye globe exhibits significant regional variation of mechanical behaviour.The aim of this present study is to develop a new experimental technique for testing intact eye globes in a form that is representative of in vivo conditions,and therefore suitable for determining the material properties of the complete outer ocular tunic.Methods:A test rig has been developed to provide closed-loop control of either applied intra-ocular pressure or resulting apical displacement;measurement of displacements across the external surface of the eye globe using high-resolution digital cameras and digital image correlation software;prevention of rigid-body motion and protection of the ocular surface from environmental drying.The method has been demonstrated on one human and one porcine eye globe,which were cyclically loaded.Finite element models based on specimen specific tomography,free from rotational symmetry,were used along with experimental pressure-displacement data in an inverse analysis process to derive the mechanical properties of tissue in different regions of the eye’s outer tunic.Results:The test method enabled monitoring of mechanical response to intraocular pressure variation across the surface of the eye globe.For the two eyes tested,the method showed a gradual change in the sclera’s stiffness from a maximum at the limbus to a minimum at the posterior pole,while in the cornea the stiffness was highest at the centre and lowest in the peripheral zone.Further,for both the sclera and cornea,the load–displacement behaviour did not vary significantly between loading cycles.Conclusions:The first methodology capable of mechanically testing intact eye globes,with applied loads and boundary conditions that closely represent in vivo conditions is introduced.The method enables determination of the regional variation in mechanical behaviour across the ocular surface.展开更多
Restitution coefficient(RC)of garlic bulb is an important mechanical property that is required to establish the kinematics model of bulb collision and research the damage mechanism of bulb collision.In this study,kine...Restitution coefficient(RC)of garlic bulb is an important mechanical property that is required to establish the kinematics model of bulb collision and research the damage mechanism of bulb collision.In this study,kinetic equations of bulb collision were established based on Hertz's contact theory.The kinematics characteristics,elastoplastic deformation and contact damage during bulb collision were analyzed by using high-speed photography.The effects of bulb mass,moisture content,collision material,material thickness and release height on the RC were investigated by mixed orthogonal experiments and single-factor experiments.The results showed that the movement of bulb in the compression stage was translation,and the movement in the rebound stage was translation and rotation.During collision,the larger the rotational angular velocity of the bulb was,the smaller the measured RC would be.The contact damage of bulb included internal damage of the tissue,epidermis stretch and tear.The significance of effects of factors on RC decreased with the following sequence:collision material,release height,material thickness,bulb mass,and moisture content.Collision material,release height,material thickness,and bulb mass were significant factors.The RC between the bulb and Q235,nylon,and rubber decreased sequentially.The RC decreased with the increase of release height and bulb mass.The RC increased with the increase of material thickness of Q235,while it decreased with the increase of material thickness of rubber or Nylon.The determination coefficients of the regression equations between the significant factors and the RC were all greater than 0.96.The results will be helpful for damage mechanism analysis and design of garlic production equipment.展开更多
Due to assembly,wear and manufacturing errors and clearance in the joints are inevitable.When the clearance is introduced into a mechanical system,the impact force in the clearance joint will cause undesirable vibrati...Due to assembly,wear and manufacturing errors and clearance in the joints are inevitable.When the clearance is introduced into a mechanical system,the impact force in the clearance joint will cause undesirable vibration of the system.In this paper,the dynamic responses of the mechanical system with two revolute clearance joints are studied using computational and experimental methodology.The clearance joint is considered as force constraint.The normal contact force and tangential friction force between the journal and bearing in a clearance joint are modeled using a nonlinear contact force model considering energy loss and a modified Coulomb friction model considering a dynamic friction coefficient,respectively.A planar slider-crank mechanism with two revolute clearance joints is used to implement the study.The dynamic responses obtained from numerical simulation are compared with the experimental test.Numerical simulations and experimental tests for different clearance sizes and crank speeds are presented and discussed,respectively.The simulation results agree quite well with those of the experiment for different cases,which proves the accuracy and efficiency of the computational method for dynamics analysis of the mechanical system with two revolute clearance joints in this study.The investigation indicates that the clearances in revolute joints significantly affect the dynamic characteristics of mechanical systems,which must be considered in the precision analysis,design,and control of multibody systems,especially for high-speed machinery.展开更多
The estimated parameters accuracy of poly-phase induction motors is crucial for effective performance prediction and/or control in various manufacturing applications.This study investigates hybrid algorithm between pa...The estimated parameters accuracy of poly-phase induction motors is crucial for effective performance prediction and/or control in various manufacturing applications.This study investigates hybrid algorithm between particle swarm optimization and Jaya optimization algorithms for finding the optimal parameters estimation of poly-phase induction motors.It is carried out using the manufacturer’s operation characteristics on two poly-phase induction motors.Numerical results show the capability of the proposed hybrid optimization algorithm.The proposed algorithm has competitive performance compared with conventional algorithms as well as with differ-ential evolution and genetic algorithms.Experimental verifications are carried out on three-phase and six-phase induction motors.Also,it emulates the closeness between experimental and estimated parameters with fast con-vergence compared to other algorithms.Also,the results reflect the high robustness of the proposed algorithm compared with other algorithms for varied iteration numbers,population size and convergence.展开更多
Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This st...Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas,and analyze its influence on reflector surface accuracy.Firstly,the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted.Secondly,a non-button connecting method is proposed and analyzed to reduce manufacturing errors.Thirdly,two physical experiment models based on 2.62-meter mesh reflector antenna are made.Finally,numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method.Compared with the traditional method,the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy.Moreover,the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process,and thereby improves the deployment reliability.展开更多
文摘Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.
基金supported by the China Postdoctoral Science Foundation(Grant No.2019M651723)the National Natural Science Foundation of China(Grant No.51705209)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20160533)the Foundation for Jiangsu Key Laboratory of Traffic and Transportation Security(Grant No.TTS2018-01)
文摘As a newly proposed two-terminal mechanical element, there are many realizations of inerter such as ball-screw, rack and pinion,hydraulic, fluid and mechatronic inerter. This paper concerns about a novel mechatronic inerter, which is consisted of a hydraulic piston inerter and linear motor, called hydraulic electric inerter(HEI). Firstly, the structural components and the working principles of two types HEI device are introduced, and the dynamic model of the HEI is established. Then, three classifications of mechatronic inerter, namely, the single motor type, the linear inerter-motor type and the rotary inerter-motor type are presented,and in the meanwhile, some comparisons among the three types mechatronic inerter are analyzed. Subsequently, a methodology of designing and experimental tests of the HEI device is proposed by considering the rated working conditions of the linear motor and the electric elements. At last, the HEI device is conducted, and the force tests of the non-loaded HEI and loaded HEI are tested in order to validate their properties. The experimental results are analyzed, and the discrepancies are also further discussed.
基金Bombardier AerospaceThales+1 种基金the Consortium for Research and Innovation in Aerospace in Quebec(CRIAQ)the National Sciences and Engineering Research Council(NSERC)for the funding received in connection with the CRIAQ MDO 505 project。
文摘The paper deals with the design and experimental validation of the actuation mechanism control system for a morphing wing model.The experimental morphable wing model manufactured in this project is a full-size scale wing tip for a real aircraft equipped with an aileron.The morphing actuation of the model is based on a mechanism with four similar in house designed and manufactured actuators,positioned inside the wing on two parallel lines.Each of the four actuators used a BrushLess Direct Current(BLDC)electric motor integrated with a mechanical part performing the conversion of the angular displacements into linear displacements.The following have been chosen as successive steps in the design of the actuator control system:(A)Mathematical and software modelling of the actuator;(B)Design of the control system architecture and tuning using Internal Model Control(IMC)methodology;(C)Numerical simulation of the controlled actuator and its testing on bench and wind tunnel.The morphing wing experimental model is tested both at the laboratory level,with no airflow,to evaluate the components integration and the whole system functioning,but also in the wind tunnel,in the presence of airflow,to evaluate its behavior and the aerodynamic gain.
基金financially supported by the National Key R&D Program of China (Grant Nos. 2019YFC1407702 and 2019YFC1407705)
文摘Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation coefficient.Eight mooring cables are symmetrically arranged on both sides of the model.The floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and gravity.The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response.Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model.The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs.The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types.These results may provide a reference to facilitate the mooring design of VLFS.
文摘This article will introduce a new version of the metal deck for building residential flooring with a newly designed cold form U section. This flooring will allow residential structures to be built more quickly while also reducing the necessary thickness of the floor. The level of strength and deflection of this floor will be determined via analysis of a floor bed comprised of cold-formed inverted U sections (IUS) covered by sheathing that is subjected to different loading scenarios. The necessary computational quantities associated with the experiment have been compared to established laboratory values by performing all related and applicable tests. Then, these quantities are compared to different existing flooring techniques to determine the efficacy of this technique. The results show that this flooring technique can be effective and cost-efficient in residential applications.
文摘Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around 10<sup>-35</sup> m, empty space may behave as a crystal, singly or doubly refractive. This hypothesis, however, remains uncheckable for any direct measurement since the smallest distance accessible in experiment is about 10<sup>-19</sup> m at the LHC. Here we propose a laboratory test to measure space birefringence or refractivity induced by gravity. A sensitivity 10<sup>-31</sup> m for doubly and 10<sup>-28</sup> m for singly refractive vacuum could be reached with PETRA 6 GeV beam exploring UV laser Compton scattering.
基金This work was financially supported by the National Key R&D Program of China(Grant No.2017YFC1404200).
文摘A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dismantling and reinstallation.An FB composed of twin pontoons and multi-porous vertical plates is proposed to improve the wave attenuation performance.The wave attenuation performance is investigated for different FB structures and vertical plate types under different incident wave heights and periods using 2D wave physical model tests in a wave flume.The results demonstrate that the proposed FB has a better performance than that of the conventional single pontoon-type FB.It reduces the wave transmission due to its enhanced wave reflection and energy loss.The wave transmission coefficient of the proposed FB decreases with an increase in the number of layers and relative draft depth of the vertical plates.However,a further decrease in the wave transmission coefficient is not observed when the number of porous vertical plates is increased from 4 to 5 layers.An equation has been derived to predict the wave transmission of the proposed FB based on the experimental results.
基金supported by the National Natural Science Foundation of China–Shandong Joint Fund(No.U1706226)the National Natural Science Foundation of China(No.52171284).
文摘Rubble mound breakwaters with a crown wall are a common coastal engineering structure.The wave force on crown walls is an important parameter for the practice engineering design.Particularly,the wave force on crown walls under intermediate depths has been studied through physical model tests and numerical simulations.In this study,a three-dimensional numerical wave flume was developed to investigate monochromatic wave interactions in a rubble mound breakwater with a crown wall.Armor blocks were modeled in detail.The Navier-Stokes equations for two-phase incompressible flows,combined with shear stress transport k-ωturbulence model and volume of fluid method for tracking the free surface,were solved.A set of laboratory experiments were performed to validate the adopted model.Subsequently,a series of numerical simulations were implemented to examine the impacts of different hydrodynamic parameters(including wave height,incident wave period,and water depth)and the berm width on the wave force of the crown wall.Finally,a comparison of the experimental results and Martin method shows that the latter method is not suitable for this experimental scope.New empirical formulas are proposed to predict the wave force on crown walls under intermediate depth.The results can provide a basis for the design of crown wall of rubble mound breakwaters at intermediate depths.
文摘Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure.In the present work,numerical analysis of square and circle short columns,and reinforced concrete(RC)beams reinforced with fiber reinforced polymer composites are carried out.This work is divided into two parts.In the first part,numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer(GFRP)and Basalt Fiber Reinforced Polymer(BFRP)bars and spiral,and Carbon Fiber Reinforced Polymer(CFRP)wraps is conducted.The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio.In addition,the results of the numerical analysis showed good correlation with the experimental ones.An interaction diagram for BFRP RC columns is also developed with considering various eccentricities.The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column.For the cases considered in this study,column with two middle closely spaced CFRP wraps demonstrated the best performance.In the second part of this research,flexural behavior of RC beams reinforced with BFRP,GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests.The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams.It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.
基金inancially supported by the National Natural Science Foundation of China (Grant No. 51761135011)Joint supported by NSFC and Royal Society (Grant No. 52011530183)。
文摘The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental damages. In the present study, a series of experimental tests are performed to investigate the sloshing phenomenon in a baffled rectangular storage tank. In addition, the sloshing phenomenon is also modeled by using Open Foam. Based on the experimental and numerical studies, optimization of the geometric parameters of the tank is performed based on some criteria such as tank area, entropy generation, and the horizontal force exerted on the tank area due to the sloshing phenomenon.The optimization is also carried out based on the entropy generation minimization analysis. It is noted that the optimum baffle height is in the range of h_b/h_w=0.5-0.75 in the present study(where h_b and h_w are the baffle height and water depth, respectively). Based on the results, the optimal design of the tank is achieved with R_A= 0.9-1.0(where R_A=L/W, L and W are the length and width of the tank, respectively). The results also show that the increase of h_b can lead to a decrease of the maximum pressure and horizontal force exerted on the tank. It is also noted that the horizontal force exerted on the tank firstly continues to increase as the sway motion amplitude increases.However, as the normalized motion amplitude parameter, a/L(The parameter a is the motion amplitude), exceeds0.067, the effect of motion amplitude on the force is not obvious. The same optimization is also performed in the multiple-variable-baffled tank and prismatic storage tank.
文摘Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instruments that underlie the assessment of their production and handling safety have been described.Studies of a large number of compounds have revealed relationships between their sensitivity parameters and structure of individual compounds and compositions.The range of change of physical and chemical characteristics for the compounds we examined covers the entire region of their existence.Theoretical methodology and equations have been formulated to estimate the impact and friction sensitivity parameters of energetic materials and to evaluate the technological safety in use.The developed methodology is characterized by high-accuracy calculations and prediction of sensitivity parameters.
基金supported by the National Natural Science Foundation of China(Grant Nos.51725903 and 52088102).
文摘A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are performed using theδ-SPH model and experimental tests are conducted to validate the numerical model.The numerical results of both the free surface elevations and motions of the floating breakwater are in good agreement with the experimental results.Numerical results show that when the pontoon drafts are larger,the double pontoon floating breakwater performs better in wave attenuations compared with the single pontoon floating breakwater,and for all the drafts,the amplitudes of motions including sway,heave and roll of the double pontoon floating breakwater is always smaller.In addition,increasing the spacing between the two pontoons can further reduce the amplitudes of pontoon motions and improve the wave attenuation ability of the double pontoon floating breakwater.
基金by the Application for Collaborative Research Project under International Joint Research Laboratory of Earthquake Engineering(TMGFXK-2015-002-2)Fundamental Research Funds for the Central University(22120180315,22120170521).
文摘Wood and wood-based composite materials have gained increasing attention in the sustainable building industry because of their renewability and environmental friendliness.Oriented oblique strand lumber(Eucalyptus Strand Wood,ESWood),which is manufactured from fast-growing small diameter eucalyptus wood(Eucalyptus urophylla×E.grandis),is introduced in this paper.Small clear specimen tests were conducted to determine the mechanical properties of ESWood material while full-scale component tests were performed to observe the structural performance of ESWood beams.A comparison of mechanical properties of ESWood with other wood/bamboo-based materials is then reported.From the results presented herein,it appears that the strength and stiffness properties of ESWood are affected by grain directionality and glued layers.However,it still has preferable mechanical properties as a building material,which is comparable or superior to those of other engineered wood/bamboo-based products(e.g.,Sitka spruce,LVL,OSL,Glulam,and Glubam).Furthermore,results from full-scale component tests show the stable mechanical performance of beams made by ESWood.This study makes a significant contribution to a potential utilization of fast-growing eucalyptus for general use in construction,and the presented mechanical tests results can serve as a fundamental data for more applications of ESWood in practical engineering.
文摘The study endeavors to provide statistical inference for a (1 + 1) cascade system for exponential distribution under joint effect of stress-strength attenuation factors. Estimators of reliability function are obtained using Maximum Likelihood Estimator (MLE) and Uniformly Minimum Variance Unbiased Estimator (UMVUE) of the parameters. Asymptotic distribution of the parameters is also obtained. Comparison between estimators is made using data obtained through simulation experiment.
基金co-supported by the National Natural Science Foundation of China(No.12002377,52075538,11872374),the Open Fund of the Key Laboratory of IcingAnti/De-Icing(No.1901IADL20190401)+1 种基金the Natural Science Foundation of Hunan Province(No.2020JJ5670,2020JJ2031)China Postdoctoral Science Foundation(No.2019M652754).
文摘Aircraft icing has long been a plague to aviation for its serious threat to flight safety.Recently,researches about a newly proposed deicing method based on Plasma Synthetic Jet Actuator(PSJA)have just started.To meet the requirements of in-flight deicing,structure of PSJA needs to be adjusted.This paper completed the detailed design and experimental validation of a novel plasma striker,which was a modified version of PSJA.Influences of mass of the moving part and rod shapes on the ice-breaking performances were also studied.Besides,a“conical-nosed rod configuration”was proposed.Its purpose was to ensure a good ice-breaking performance of the plasma striker on long ice,by generating a splitting failure.Results show that,though mass of the moving part was just several grams,ice-breaking performance was better when the mass was lighter.The rectangular rod could generate an elliptical circumferential crack,whose major axis was parallel to the direction of the long side of the rectangular rod.And the“conical-nosed rod”concept was verified to be able to generate a splitting crack which can spread completely to the far end of long ice,and the crack direction was parallel to edge line of the cone.In general,the plasma striker has the advantages of simple structure,low energy consumption,little harm to the flow field and the aircraft skin.Simulations will be carried out in future works to study in detail the working process of the plasma striker.
基金The research was partially supported by the Engineering and Physical Sciences Research Council of the UK.
文摘Background:The eye globe exhibits significant regional variation of mechanical behaviour.The aim of this present study is to develop a new experimental technique for testing intact eye globes in a form that is representative of in vivo conditions,and therefore suitable for determining the material properties of the complete outer ocular tunic.Methods:A test rig has been developed to provide closed-loop control of either applied intra-ocular pressure or resulting apical displacement;measurement of displacements across the external surface of the eye globe using high-resolution digital cameras and digital image correlation software;prevention of rigid-body motion and protection of the ocular surface from environmental drying.The method has been demonstrated on one human and one porcine eye globe,which were cyclically loaded.Finite element models based on specimen specific tomography,free from rotational symmetry,were used along with experimental pressure-displacement data in an inverse analysis process to derive the mechanical properties of tissue in different regions of the eye’s outer tunic.Results:The test method enabled monitoring of mechanical response to intraocular pressure variation across the surface of the eye globe.For the two eyes tested,the method showed a gradual change in the sclera’s stiffness from a maximum at the limbus to a minimum at the posterior pole,while in the cornea the stiffness was highest at the centre and lowest in the peripheral zone.Further,for both the sclera and cornea,the load–displacement behaviour did not vary significantly between loading cycles.Conclusions:The first methodology capable of mechanically testing intact eye globes,with applied loads and boundary conditions that closely represent in vivo conditions is introduced.The method enables determination of the regional variation in mechanical behaviour across the ocular surface.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51805282)Funds for Central Universities,China(XDJK2018AC001)National Key R&D Program of China(2017YFD0701305-02).
文摘Restitution coefficient(RC)of garlic bulb is an important mechanical property that is required to establish the kinematics model of bulb collision and research the damage mechanism of bulb collision.In this study,kinetic equations of bulb collision were established based on Hertz's contact theory.The kinematics characteristics,elastoplastic deformation and contact damage during bulb collision were analyzed by using high-speed photography.The effects of bulb mass,moisture content,collision material,material thickness and release height on the RC were investigated by mixed orthogonal experiments and single-factor experiments.The results showed that the movement of bulb in the compression stage was translation,and the movement in the rebound stage was translation and rotation.During collision,the larger the rotational angular velocity of the bulb was,the smaller the measured RC would be.The contact damage of bulb included internal damage of the tissue,epidermis stretch and tear.The significance of effects of factors on RC decreased with the following sequence:collision material,release height,material thickness,bulb mass,and moisture content.Collision material,release height,material thickness,and bulb mass were significant factors.The RC between the bulb and Q235,nylon,and rubber decreased sequentially.The RC decreased with the increase of release height and bulb mass.The RC increased with the increase of material thickness of Q235,while it decreased with the increase of material thickness of rubber or Nylon.The determination coefficients of the regression equations between the significant factors and the RC were all greater than 0.96.The results will be helpful for damage mechanism analysis and design of garlic production equipment.
基金This study was funded by the National Natural Science Foundation of China(Nos.51775128 and 51305093).
文摘Due to assembly,wear and manufacturing errors and clearance in the joints are inevitable.When the clearance is introduced into a mechanical system,the impact force in the clearance joint will cause undesirable vibration of the system.In this paper,the dynamic responses of the mechanical system with two revolute clearance joints are studied using computational and experimental methodology.The clearance joint is considered as force constraint.The normal contact force and tangential friction force between the journal and bearing in a clearance joint are modeled using a nonlinear contact force model considering energy loss and a modified Coulomb friction model considering a dynamic friction coefficient,respectively.A planar slider-crank mechanism with two revolute clearance joints is used to implement the study.The dynamic responses obtained from numerical simulation are compared with the experimental test.Numerical simulations and experimental tests for different clearance sizes and crank speeds are presented and discussed,respectively.The simulation results agree quite well with those of the experiment for different cases,which proves the accuracy and efficiency of the computational method for dynamics analysis of the mechanical system with two revolute clearance joints in this study.The investigation indicates that the clearances in revolute joints significantly affect the dynamic characteristics of mechanical systems,which must be considered in the precision analysis,design,and control of multibody systems,especially for high-speed machinery.
文摘The estimated parameters accuracy of poly-phase induction motors is crucial for effective performance prediction and/or control in various manufacturing applications.This study investigates hybrid algorithm between particle swarm optimization and Jaya optimization algorithms for finding the optimal parameters estimation of poly-phase induction motors.It is carried out using the manufacturer’s operation characteristics on two poly-phase induction motors.Numerical results show the capability of the proposed hybrid optimization algorithm.The proposed algorithm has competitive performance compared with conventional algorithms as well as with differ-ential evolution and genetic algorithms.Experimental verifications are carried out on three-phase and six-phase induction motors.Also,it emulates the closeness between experimental and estimated parameters with fast con-vergence compared to other algorithms.Also,the results reflect the high robustness of the proposed algorithm compared with other algorithms for varied iteration numbers,population size and convergence.
基金supported by the National Natural Science Foundations of China(Nos.52022075,U1937202,&52175246)the Fundamental Research Funds for the Central Universities(Nos.QTZX2188&QTZX2173)。
文摘Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas,and analyze its influence on reflector surface accuracy.Firstly,the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted.Secondly,a non-button connecting method is proposed and analyzed to reduce manufacturing errors.Thirdly,two physical experiment models based on 2.62-meter mesh reflector antenna are made.Finally,numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method.Compared with the traditional method,the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy.Moreover,the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process,and thereby improves the deployment reliability.
