In recent years, the two-stage control valve has been used more and more in the quantitative loading control system, and its advantages such as fast control response, high quantitative accuracy and low maintenance cos...In recent years, the two-stage control valve has been used more and more in the quantitative loading control system, and its advantages such as fast control response, high quantitative accuracy and low maintenance cost have been widely recognized. Not only can it meet the needs of quantitative loading control, but it can also be used as interlocking cut-off, and its action time and response speed are unmatched by analog control valves. It can still be competent in control scenarios with high response speed requirements.展开更多
New principles of work and energy as well as power and energy rate with cross terms for polar and nonlocal polar continuum field theories were presented and from them all corresponding equations of motion and boundary...New principles of work and energy as well as power and energy rate with cross terms for polar and nonlocal polar continuum field theories were presented and from them all corresponding equations of motion and boundary conditions as well as complete equations of energy and energy rate with the help of generalized Piola's theorems were naturally derived in all and without any additional requirement. Finally, some new balance laws of energy and energy rate for generalized continuum mechanics were established. The new principles of work and energy as well as power and energy rate with cross terms presented in this paper are believed to be new and they have corrected the incompleteness of all existing corresponding principles and laws without cross terms in literatures of generalized continuum field theories.展开更多
A systematic methodology for solving the inverse dynamics of the Delta robot is presented.First,the inverse kinematics is solved based on the vector method.A new form of the Jacobi matrix formulized by the vectors is ...A systematic methodology for solving the inverse dynamics of the Delta robot is presented.First,the inverse kinematics is solved based on the vector method.A new form of the Jacobi matrix formulized by the vectors is obtained so the three types kinematics singularities namely inverse, direct and combined types, can be identified with the physical meaning.Then based on the principle of virtual work, a methodology for driving the dynamical equations of motion is developed.Meanwhile the whole actuating torques, the torques caused by the gravity, the velocity and the acceleration are computed respectively in the numerical example. Results show that torque caused by the acceleration term is much bigger than the other two terms.This approach leads to efficient algorithms since the constraint forces and moments of the robot system have been eliminated from the equations of motion and there is no differential equation for the whole procedure when the principle of virtual work is applied to solving the inverse dynamical problem.展开更多
This paper presents an energy principle, zero different principle of coupledsystems in photoelasticity, from which the potential energy, the complementary energy,generalized potential energy and generalized complemen...This paper presents an energy principle, zero different principle of coupledsystems in photoelasticity, from which the potential energy, the complementary energy,generalized potential energy and generalized complementary energy variationalprinciples of the coupled systems in photoelasticity are derived What is called the coupled systems means that two deformational bodies, forwhich figures, sizes,loads and boundary conditions are the same and they are all inactual states but they are made of different materials.Prototype body and model body in photoelasticity are essentially the coupledsystems, therefore the above principles become the theoretical basis of defining theinflunce of Poissons ratio v on accuracy of the frozen-stress method.展开更多
According to the basic idea of dual-complementarity,in a simple and unified way proposed by the author,some basic principles in dynamic theory of elastic materials with voids can be established sys- tematically.In thi...According to the basic idea of dual-complementarity,in a simple and unified way proposed by the author,some basic principles in dynamic theory of elastic materials with voids can be established sys- tematically.In this paper, an important integral relation in terms of convolutions is given,which can be con- sidered as the generalized principle of virtual work in mechanics.Based on this relation,it is possible not on- ly to obtain the principle of virtual work and the reciprocal theorem in dynamic theory of elastic materials with voids,but also to derive systematically the complementary functionals for the eight-field,six-field, four-field and two-field simplified Gurtin-type variational principles.Furthermore,with this approach,the in- trinsic relationship among various principles can be explained clearly.展开更多
Various steady models for interaction between heart and arterial system have been given in liter- ature,In our recent study,a dynamic principle,i.e.the principle of least cardiac work is proposed,and a dy- namic model...Various steady models for interaction between heart and arterial system have been given in liter- ature,In our recent study,a dynamic principle,i.e.the principle of least cardiac work is proposed,and a dy- namic model for interaction of heart and arterial system is established.Preliminary results of our experiments show that both the principle and the model are consistent with the physiological phenomena.It reveals that the pres- ent analysis may offer a new measure for the study of dynamic process of interaction between heart and arterial system.展开更多
Energy methods and the principle of virtual work are commonly used for obtaining solutions of boundary value problems (BVPs) and initial value problems (IVPs) associated with homogeneous, isotropic and non-homogeneous...Energy methods and the principle of virtual work are commonly used for obtaining solutions of boundary value problems (BVPs) and initial value problems (IVPs) associated with homogeneous, isotropic and non-homogeneous, non-isotropic matter without using (or in the absence of) the mathematical models of the BVPs and the IVPs. These methods are also used for deriving mathematical models for BVPs and IVPs associated with isotropic, homogeneous as well as non-homogeneous, non-isotropic continuous matter. In energy methods when applied to IVPs, one constructs energy functional (<i>I</i>) consisting of kinetic energy, strain energy and the potential energy of loads. The first variation of this energy functional (<em>δI</em>) set to zero is a necessary condition for an extremum of <i>I</i>. In this approach one could use <i>δI</i> = 0 directly in constructing computational processes such as the finite element method or could derive Euler’s equations (differential or partial differential equations) from <i>δI</i> = 0, which is also satisfied by a solution obtained from <i>δI</i> = 0. The Euler’s equations obtained from <i>δI</i> = 0 indeed are the mathematical model associated with the energy functional <i>I</i>. In case of BVPs we follow the same approach except in this case, the energy functional <i>I</i> consists of strain energy and the potential energy of loads. In using the principle of virtual work for BVPs and the IVPs, we can also accomplish the same as described above using energy methods. In this paper we investigate consistency and validity of the mathematical models for isotropic, homogeneous and non-isotropic, non-homogeneous continuous matter for BVPs that are derived using energy functional consisting of strain energy and the potential energy of loads. Similar investigation is also presented for IVPs using energy functional consisting of kinetic energy, strain energy and the potential energy of loads. The computational approaches for BVPs and the IVPs designed using energy functional and principle of virtual work, their consistency and validity are also investigated. Classical continuum mechanics (CCM) principles <i>i.e.</i> conservation and balance laws of CCM with consistent constitutive theories and the elements of calculus of variations are employed in the investigations presented in this paper.展开更多
The virtual displacement principle of elasto-plastic damage mechanics is presented. A linear complementary method for elasto-plastic damage problem is proposed by using FEM technique. This method is applicable to solv...The virtual displacement principle of elasto-plastic damage mechanics is presented. A linear complementary method for elasto-plastic damage problem is proposed by using FEM technique. This method is applicable to solving the damage structure analysis of hardened and softened nonlinear material.展开更多
By expanding the yielding function according toTaylor series and neglecting the high order terms, the elastoplastic constitutive equation is written in a linear complementary form. Based on this linear complementary f...By expanding the yielding function according toTaylor series and neglecting the high order terms, the elastoplastic constitutive equation is written in a linear complementary form. Based on this linear complementary form and the principle of virtual work, a finite element-complementary method is derived for elastoplastic problem. This method is available for materials which satisfy either associated or nonassociated flow rule. In addition, the existence and uniqueness oj solution for the method are also discussed and some useful conclusions are given.展开更多
Soft grippers are favored for handling delicate objects due to their compliance but often have lower load capacities compared to rigid ones.Variable Stiffness Module(VSM)offer a solution,balancing flexibility and load...Soft grippers are favored for handling delicate objects due to their compliance but often have lower load capacities compared to rigid ones.Variable Stiffness Module(VSM)offer a solution,balancing flexibility and load capacity,for which particle jamming is an effective technology for stiffness-tunable robots requiring safe interaction and load capacity.Specific applica-tions,such as rescue scenarios,require quantitative analysis to optimize VSM design parameters,which previous analytical models cannot effectively handle.To address this,a Grey-box model is proposed to analyze the mechanical response of the particle-jamming-based VSM by combining a White-box approach based on the virtual work principle with a Black-box approach that uses a shallow neural network method.The Grey-box model demonstrates a high level of accuracy in predict-ing the VSM force-height mechanical response curves,with errors below 15%in almost 90%of the cases and a maximum error of less than 25%.The model is used to optimize VSM design parameters,particularly those unexplored combinations.Our results from the load capacity and force distribution comparison tests indicate that the VSM,optimized through our methods,quantitatively meets the practical engineering requirements.展开更多
A novel design for an electrostriction appliance derived from the theory and application of electromagnetics is presented. The working principle, that is the application of gravitation and elasticity together to reali...A novel design for an electrostriction appliance derived from the theory and application of electromagnetics is presented. The working principle, that is the application of gravitation and elasticity together to realize the ＂shrinking＂ and ＂extending＂ effect from the distortion and transforming power into mechanical energy, is briefly explained. The characteristic parameter relationships are established and the experimental research is performed. Experimental results show that this sort of electrostriction appliance can perform well as regards driving force and beeline displacement, and furthermore, its self-weight is smaller. This makes it suitable for beeline drivers with a high application value, especially for the driver of the bionic appliance. In the application of the electrostriction appliance to a bionics-flapping aircraft, the wings can work with a flapping angle in the range of a certain value by controlling the ＂shrinking＂ and ＂extending＂ of the electrostriction appliance. It can reduce the startup power and the impact load of the driver. The flapping extent of the wings will change when the voltage which is put into the electrostriction appliance varies. This makes it more flexible as the bionics-flapping aircraft realizes different actions of flying.展开更多
Understanding the relationship between normal stiffness and permeability in rock fractures under high and true-triaxial in situ stress conditions is critical to assess hydro-mechanical coupling in the Earth's crus...Understanding the relationship between normal stiffness and permeability in rock fractures under high and true-triaxial in situ stress conditions is critical to assess hydro-mechanical coupling in the Earth's crust.Previous data on stiffness–permeability relations are measured under uniaxial stress states as well as under normal stress.However,many projects involve faulted formations with complex three-dimensional(3D)stress states or significant changes to the original stress state.We rectified this by following the permeability evolution using a true-triaxial stress-permeability apparatus as well as independently applying a spectrum of triaxial stresses from low to high.The relationship between permeability and fracture normal stiffness was quantified using constraints based on the principle of virtual work.The impacts of fracture-lateral and fracture-normal stresses on permeability and normal stiffness evolution were measured.It was found that permeability decreases with increasing fracture-lateral and fracture-normal stresses as a result of Poisson confinement,independent of the orientation of the fracture relative to the stresses.The lateral stresses dominated the evolution of normal stiffness at lower normal stresses(σ_(3)=10 MPa)and played a supplementary role at higher normal stresses(σ_(3)>10 MPa).Moreover,correlations between the evolution of permeability and normal stiffness were extended beyond the low-stiffness,high-permeability region to the high-stiffness,low-permeability region under high fracture-lateral stresses(10–80 MPa)with fracture-normal stress(10–50 MPa)conditions.Again,high lateral stresses further confined the fracture and therefore reduced permeability and increased normal stiffness,which exceeded the previous reported stiffness under no lateral stress conditions.This process enabled us to identify a fundamental change in the flow regime from multi-channel to isolated channelized flow.These results provide important characterizations of fracture permeability in the deep crust,including recovery from deep shale-gas reservoirs.展开更多
Proportional direction valve is one of the most fundamental elements in electronic-hydraulic control technique.Its function is to control the operating speed,direction,position,and strength of output force of the hydr...Proportional direction valve is one of the most fundamental elements in electronic-hydraulic control technique.Its function is to control the operating speed,direction,position,and strength of output force of the hydraulic actuator continuously.Considering the different application and the cost,the existing technique mainly includes the internal feedback valve used in open loop system,and the electronic closed loop controlled valve used in closed loop system.Because of their different mechanical structure and the gre at different in performance,it brings inconvenience for customer to select,also inconvenience for enterprise to produce.Aiming at this problem,the idea of combining the above two kinds of valves into one body is proposed first,and then the new valve's structure to realize this target is designed.The idea intends to apply the displacement pilot flow feedback control principle in present 2-position 2-way valve system to the proportional direction valve of 3-position 4-way system.Newly designed feed forward controller can decouple the interference between the internal feedback and the electronic closed loop.Redundant conversion is designed to electronic switch mode.Experiment on dynamic and static characteristic of new proportional direction valve in internal feedback control mode and electronic closed loop control mode is discussed to prove the new theory is correct.Although the new valve is of excellent dynamic response characteristic,its steady control characteristic in open loop control mode needs to be improved further.The research results prepare one new fundamental element for electronic-hydraulic control technology.展开更多
Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were appli...Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were applied in the derivation. Results and Conclusion The principle of virtual work, Betti's reciprocal theorem and the uniqueness theorem of quasicrystal elasticity theory are proud, and some conservative integrals in quasicrystal elasticty theory are obtained.展开更多
China's first Mars exploration mission will carry out comprehensive global surveys of the planet from data collected by instruments carried in orbit and roving on the planet itself.Goals of the mission include det...China's first Mars exploration mission will carry out comprehensive global surveys of the planet from data collected by instruments carried in orbit and roving on the planet itself.Goals of the mission include detailed inspections and surveys of key areas on the surface of Mars.One of the main scientific payloads installed on the orbiter is the moderate resolution camera.Its mission is to image the surface of Mars sufficiently to produce a global remote sensing image map of the planet,and to explore and record changes to the topography of Mars,including major geological structures,and to advance research on topography and geomorphology in general.The moderate resolution camera uses a lightweight and compact integrated design;its primary components are an optical module,a focal plane module,a camera control module,a power and interface module,a camera support module,a thermal control module,and a reference module.Radiometric calibration,color calibration,and geometric calibration have been carried out to ensure that the camera can acquire sufficient accurate data to complete mission goals.This paper introduces the camera's detection mission,its system composition,and its working principle;it also describes the camera's ground calibration tests and their results,and provides a reference for processing the camera's scientific data and for future applications.展开更多
The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and sca...The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and scavenge processes based on the open thermodynamic systems were presented. A simulation was executed at given geometric parameters and initial conditions. The results manifest that the working principle of MFPSE is feasible.展开更多
Based on a comprehensive analysis of the structure and existing problems ofthe gear pump, provided a structure principle of a synchronous gear pump.The discussionsfocused on the working principle, construction feature...Based on a comprehensive analysis of the structure and existing problems ofthe gear pump, provided a structure principle of a synchronous gear pump.The discussionsfocused on the working principle, construction features and finite element analysis ofthe hydraulic gear.The research indicates that the new pump has such advantages aslower noise, better distributed flow and a high work pressure, and it can be widely used inhydraulic systems.展开更多
Over the last 50 years,the explosive adoption of modern agricultural practices has led to an enormous increase in the emission of non-biodegradable and highly biotoxic ions into the hydrosphere.Excess intake of such i...Over the last 50 years,the explosive adoption of modern agricultural practices has led to an enormous increase in the emission of non-biodegradable and highly biotoxic ions into the hydrosphere.Excess intake of such ions,even essential trace elements such as Cu^(2+)and F^(-),can have serious consequences on human health.Therefore,to ensure safe drinking water and regulate wastewater discharge,photoelectrochemical(PEC)online sensors were developed,with advantages such as low energy consumption,inherent miniaturization,simple instrumentation,and fast response.However,there is no publicly available systematic review of the recent advances in PEC ion sensors available in the literature since January 2017.Thus,this review covers the various strategies that have been used to enhance the sensitivity,selectivity,and limit of detection for PEC ion sensors.The photoelectrochemically active materials,conductive substrates,electronic transfer,and performance of various PEC sensors are discussed in detail and divided into sections based on the measurement principle and detected ion species.We conclude this review by highlighting the challenges and potential future avenues of research associated with the development of novel high-performance PEC sensors.展开更多
This paper introduces a set of electrical energy-saving system for commercial office buildings,aiming at making better use of solar energy and photovoltaic power generation.Solar energy is a renewable energy source,wh...This paper introduces a set of electrical energy-saving system for commercial office buildings,aiming at making better use of solar energy and photovoltaic power generation.Solar energy is a renewable energy source,which is inexhaustible clean energy and has great commercial application value.Based on this fact,we plan to design a unique and novel solar shutter in combination with the daily observation and the shape of solar panels.The shutter blades are equipped with an automatic light tracking system,and the angle of the blades can be adjusted in time through photoresistor induction,that is,as much solar energy as possible can be converted into electric energy for load use,and at the same time,comfortable light can be provided for the house.In essence,the system is a small photovoltaic power generation system,which runs all day with high-efficiency based on automatic sun tracking.Among them,the basic operation route includes:solar position detection,computer data processing,photovoltaic and electric volt energy conversion,circuit connection,etc.From the current debugging results,the shutter has the characteristics of humanization,high efficiency,cleanliness and so on.Through this energy-saving system,we hope to maximize the use of solar energy in the premise of low cost,so as to achieve the purpose of energy saving.展开更多
The paper describes the working principle and structure of a newly designed high-precision （ inicrogal） gravimeter, which is basically a vertically suspending spring-weight system, using a highly sensitive capacitan...The paper describes the working principle and structure of a newly designed high-precision （ inicrogal） gravimeter, which is basically a vertically suspending spring-weight system, using a highly sensitive capacitance sensor of movement in a controlled temperature environment in a borehole and a multi-frequency output for both earth-tide and earthquake monitoring. The preliminary test indicated that, while in a stabilization process, it had met all the technical requirements for a relative gravimeter used for earth tide and earthquake monitoring.展开更多
文摘In recent years, the two-stage control valve has been used more and more in the quantitative loading control system, and its advantages such as fast control response, high quantitative accuracy and low maintenance cost have been widely recognized. Not only can it meet the needs of quantitative loading control, but it can also be used as interlocking cut-off, and its action time and response speed are unmatched by analog control valves. It can still be competent in control scenarios with high response speed requirements.
文摘New principles of work and energy as well as power and energy rate with cross terms for polar and nonlocal polar continuum field theories were presented and from them all corresponding equations of motion and boundary conditions as well as complete equations of energy and energy rate with the help of generalized Piola's theorems were naturally derived in all and without any additional requirement. Finally, some new balance laws of energy and energy rate for generalized continuum mechanics were established. The new principles of work and energy as well as power and energy rate with cross terms presented in this paper are believed to be new and they have corrected the incompleteness of all existing corresponding principles and laws without cross terms in literatures of generalized continuum field theories.
基金Supported by National Natural Science Foundation of China (No. 50375106) andKey Laboratory of Intelligent Manufacturing at Shantou University Grant (No. Imstu-2002-11).
文摘A systematic methodology for solving the inverse dynamics of the Delta robot is presented.First,the inverse kinematics is solved based on the vector method.A new form of the Jacobi matrix formulized by the vectors is obtained so the three types kinematics singularities namely inverse, direct and combined types, can be identified with the physical meaning.Then based on the principle of virtual work, a methodology for driving the dynamical equations of motion is developed.Meanwhile the whole actuating torques, the torques caused by the gravity, the velocity and the acceleration are computed respectively in the numerical example. Results show that torque caused by the acceleration term is much bigger than the other two terms.This approach leads to efficient algorithms since the constraint forces and moments of the robot system have been eliminated from the equations of motion and there is no differential equation for the whole procedure when the principle of virtual work is applied to solving the inverse dynamical problem.
文摘This paper presents an energy principle, zero different principle of coupledsystems in photoelasticity, from which the potential energy, the complementary energy,generalized potential energy and generalized complementary energy variationalprinciples of the coupled systems in photoelasticity are derived What is called the coupled systems means that two deformational bodies, forwhich figures, sizes,loads and boundary conditions are the same and they are all inactual states but they are made of different materials.Prototype body and model body in photoelasticity are essentially the coupledsystems, therefore the above principles become the theoretical basis of defining theinflunce of Poissons ratio v on accuracy of the frozen-stress method.
基金The project supported by the Foundation of Zhongshan University Advanced Research Center
文摘According to the basic idea of dual-complementarity,in a simple and unified way proposed by the author,some basic principles in dynamic theory of elastic materials with voids can be established sys- tematically.In this paper, an important integral relation in terms of convolutions is given,which can be con- sidered as the generalized principle of virtual work in mechanics.Based on this relation,it is possible not on- ly to obtain the principle of virtual work and the reciprocal theorem in dynamic theory of elastic materials with voids,but also to derive systematically the complementary functionals for the eight-field,six-field, four-field and two-field simplified Gurtin-type variational principles.Furthermore,with this approach,the in- trinsic relationship among various principles can be explained clearly.
文摘Various steady models for interaction between heart and arterial system have been given in liter- ature,In our recent study,a dynamic principle,i.e.the principle of least cardiac work is proposed,and a dy- namic model for interaction of heart and arterial system is established.Preliminary results of our experiments show that both the principle and the model are consistent with the physiological phenomena.It reveals that the pres- ent analysis may offer a new measure for the study of dynamic process of interaction between heart and arterial system.
文摘Energy methods and the principle of virtual work are commonly used for obtaining solutions of boundary value problems (BVPs) and initial value problems (IVPs) associated with homogeneous, isotropic and non-homogeneous, non-isotropic matter without using (or in the absence of) the mathematical models of the BVPs and the IVPs. These methods are also used for deriving mathematical models for BVPs and IVPs associated with isotropic, homogeneous as well as non-homogeneous, non-isotropic continuous matter. In energy methods when applied to IVPs, one constructs energy functional (<i>I</i>) consisting of kinetic energy, strain energy and the potential energy of loads. The first variation of this energy functional (<em>δI</em>) set to zero is a necessary condition for an extremum of <i>I</i>. In this approach one could use <i>δI</i> = 0 directly in constructing computational processes such as the finite element method or could derive Euler’s equations (differential or partial differential equations) from <i>δI</i> = 0, which is also satisfied by a solution obtained from <i>δI</i> = 0. The Euler’s equations obtained from <i>δI</i> = 0 indeed are the mathematical model associated with the energy functional <i>I</i>. In case of BVPs we follow the same approach except in this case, the energy functional <i>I</i> consists of strain energy and the potential energy of loads. In using the principle of virtual work for BVPs and the IVPs, we can also accomplish the same as described above using energy methods. In this paper we investigate consistency and validity of the mathematical models for isotropic, homogeneous and non-isotropic, non-homogeneous continuous matter for BVPs that are derived using energy functional consisting of strain energy and the potential energy of loads. Similar investigation is also presented for IVPs using energy functional consisting of kinetic energy, strain energy and the potential energy of loads. The computational approaches for BVPs and the IVPs designed using energy functional and principle of virtual work, their consistency and validity are also investigated. Classical continuum mechanics (CCM) principles <i>i.e.</i> conservation and balance laws of CCM with consistent constitutive theories and the elements of calculus of variations are employed in the investigations presented in this paper.
文摘The virtual displacement principle of elasto-plastic damage mechanics is presented. A linear complementary method for elasto-plastic damage problem is proposed by using FEM technique. This method is applicable to solving the damage structure analysis of hardened and softened nonlinear material.
文摘By expanding the yielding function according toTaylor series and neglecting the high order terms, the elastoplastic constitutive equation is written in a linear complementary form. Based on this linear complementary form and the principle of virtual work, a finite element-complementary method is derived for elastoplastic problem. This method is available for materials which satisfy either associated or nonassociated flow rule. In addition, the existence and uniqueness oj solution for the method are also discussed and some useful conclusions are given.
基金supported by the National Key R&D Program of China(Grant No.2019YFB1311200).
文摘Soft grippers are favored for handling delicate objects due to their compliance but often have lower load capacities compared to rigid ones.Variable Stiffness Module(VSM)offer a solution,balancing flexibility and load capacity,for which particle jamming is an effective technology for stiffness-tunable robots requiring safe interaction and load capacity.Specific applica-tions,such as rescue scenarios,require quantitative analysis to optimize VSM design parameters,which previous analytical models cannot effectively handle.To address this,a Grey-box model is proposed to analyze the mechanical response of the particle-jamming-based VSM by combining a White-box approach based on the virtual work principle with a Black-box approach that uses a shallow neural network method.The Grey-box model demonstrates a high level of accuracy in predict-ing the VSM force-height mechanical response curves,with errors below 15%in almost 90%of the cases and a maximum error of less than 25%.The model is used to optimize VSM design parameters,particularly those unexplored combinations.Our results from the load capacity and force distribution comparison tests indicate that the VSM,optimized through our methods,quantitatively meets the practical engineering requirements.
文摘A novel design for an electrostriction appliance derived from the theory and application of electromagnetics is presented. The working principle, that is the application of gravitation and elasticity together to realize the ＂shrinking＂ and ＂extending＂ effect from the distortion and transforming power into mechanical energy, is briefly explained. The characteristic parameter relationships are established and the experimental research is performed. Experimental results show that this sort of electrostriction appliance can perform well as regards driving force and beeline displacement, and furthermore, its self-weight is smaller. This makes it suitable for beeline drivers with a high application value, especially for the driver of the bionic appliance. In the application of the electrostriction appliance to a bionics-flapping aircraft, the wings can work with a flapping angle in the range of a certain value by controlling the ＂shrinking＂ and ＂extending＂ of the electrostriction appliance. It can reduce the startup power and the impact load of the driver. The flapping extent of the wings will change when the voltage which is put into the electrostriction appliance varies. This makes it more flexible as the bionics-flapping aircraft realizes different actions of flying.
基金funded by the joint fund of the National Key Research and Development Program of China(Grant No.2021YFC2902101)National Natural Science Foundation of China(Grant No.52374084)+1 种基金the 111 Project(Grant No.B17009)DE acknowledges support from the G.Albert Shoemaker endowment.
文摘Understanding the relationship between normal stiffness and permeability in rock fractures under high and true-triaxial in situ stress conditions is critical to assess hydro-mechanical coupling in the Earth's crust.Previous data on stiffness–permeability relations are measured under uniaxial stress states as well as under normal stress.However,many projects involve faulted formations with complex three-dimensional(3D)stress states or significant changes to the original stress state.We rectified this by following the permeability evolution using a true-triaxial stress-permeability apparatus as well as independently applying a spectrum of triaxial stresses from low to high.The relationship between permeability and fracture normal stiffness was quantified using constraints based on the principle of virtual work.The impacts of fracture-lateral and fracture-normal stresses on permeability and normal stiffness evolution were measured.It was found that permeability decreases with increasing fracture-lateral and fracture-normal stresses as a result of Poisson confinement,independent of the orientation of the fracture relative to the stresses.The lateral stresses dominated the evolution of normal stiffness at lower normal stresses(σ_(3)=10 MPa)and played a supplementary role at higher normal stresses(σ_(3)>10 MPa).Moreover,correlations between the evolution of permeability and normal stiffness were extended beyond the low-stiffness,high-permeability region to the high-stiffness,low-permeability region under high fracture-lateral stresses(10–80 MPa)with fracture-normal stress(10–50 MPa)conditions.Again,high lateral stresses further confined the fracture and therefore reduced permeability and increased normal stiffness,which exceeded the previous reported stiffness under no lateral stress conditions.This process enabled us to identify a fundamental change in the flow regime from multi-channel to isolated channelized flow.These results provide important characterizations of fracture permeability in the deep crust,including recovery from deep shale-gas reservoirs.
基金supported by National Natural Science Foundation of China(Grant No.50575156)Shanxi Provincial Natural Science Foundation of China(Grant No.2008011053)
文摘Proportional direction valve is one of the most fundamental elements in electronic-hydraulic control technique.Its function is to control the operating speed,direction,position,and strength of output force of the hydraulic actuator continuously.Considering the different application and the cost,the existing technique mainly includes the internal feedback valve used in open loop system,and the electronic closed loop controlled valve used in closed loop system.Because of their different mechanical structure and the gre at different in performance,it brings inconvenience for customer to select,also inconvenience for enterprise to produce.Aiming at this problem,the idea of combining the above two kinds of valves into one body is proposed first,and then the new valve's structure to realize this target is designed.The idea intends to apply the displacement pilot flow feedback control principle in present 2-position 2-way valve system to the proportional direction valve of 3-position 4-way system.Newly designed feed forward controller can decouple the interference between the internal feedback and the electronic closed loop.Redundant conversion is designed to electronic switch mode.Experiment on dynamic and static characteristic of new proportional direction valve in internal feedback control mode and electronic closed loop control mode is discussed to prove the new theory is correct.Although the new valve is of excellent dynamic response characteristic,its steady control characteristic in open loop control mode needs to be improved further.The research results prepare one new fundamental element for electronic-hydraulic control technology.
文摘Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were applied in the derivation. Results and Conclusion The principle of virtual work, Betti's reciprocal theorem and the uniqueness theorem of quasicrystal elasticity theory are proud, and some conservative integrals in quasicrystal elasticty theory are obtained.
文摘China's first Mars exploration mission will carry out comprehensive global surveys of the planet from data collected by instruments carried in orbit and roving on the planet itself.Goals of the mission include detailed inspections and surveys of key areas on the surface of Mars.One of the main scientific payloads installed on the orbiter is the moderate resolution camera.Its mission is to image the surface of Mars sufficiently to produce a global remote sensing image map of the planet,and to explore and record changes to the topography of Mars,including major geological structures,and to advance research on topography and geomorphology in general.The moderate resolution camera uses a lightweight and compact integrated design;its primary components are an optical module,a focal plane module,a camera control module,a power and interface module,a camera support module,a thermal control module,and a reference module.Radiometric calibration,color calibration,and geometric calibration have been carried out to ensure that the camera can acquire sufficient accurate data to complete mission goals.This paper introduces the camera's detection mission,its system composition,and its working principle;it also describes the camera's ground calibration tests and their results,and provides a reference for processing the camera's scientific data and for future applications.
基金National Natural Science Foundation(50375078)Key Discipline Construction Program of Beijing.
文摘The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and scavenge processes based on the open thermodynamic systems were presented. A simulation was executed at given geometric parameters and initial conditions. The results manifest that the working principle of MFPSE is feasible.
文摘Based on a comprehensive analysis of the structure and existing problems ofthe gear pump, provided a structure principle of a synchronous gear pump.The discussionsfocused on the working principle, construction features and finite element analysis ofthe hydraulic gear.The research indicates that the new pump has such advantages aslower noise, better distributed flow and a high work pressure, and it can be widely used inhydraulic systems.
基金financial support from the National Natural Science Foundation of China(NSFC,Nos.52176178,51876018)Innovation Research Group of Universities in Chongqing(No.CXQT21035)+1 种基金Scientific and Technological Research Program of Chongqing Municipal Education Commission of China(No.KJZDM202201101)Chongqing Postgraduate Innovation Project(No.CYS22645)。
文摘Over the last 50 years,the explosive adoption of modern agricultural practices has led to an enormous increase in the emission of non-biodegradable and highly biotoxic ions into the hydrosphere.Excess intake of such ions,even essential trace elements such as Cu^(2+)and F^(-),can have serious consequences on human health.Therefore,to ensure safe drinking water and regulate wastewater discharge,photoelectrochemical(PEC)online sensors were developed,with advantages such as low energy consumption,inherent miniaturization,simple instrumentation,and fast response.However,there is no publicly available systematic review of the recent advances in PEC ion sensors available in the literature since January 2017.Thus,this review covers the various strategies that have been used to enhance the sensitivity,selectivity,and limit of detection for PEC ion sensors.The photoelectrochemically active materials,conductive substrates,electronic transfer,and performance of various PEC sensors are discussed in detail and divided into sections based on the measurement principle and detected ion species.We conclude this review by highlighting the challenges and potential future avenues of research associated with the development of novel high-performance PEC sensors.
文摘This paper introduces a set of electrical energy-saving system for commercial office buildings,aiming at making better use of solar energy and photovoltaic power generation.Solar energy is a renewable energy source,which is inexhaustible clean energy and has great commercial application value.Based on this fact,we plan to design a unique and novel solar shutter in combination with the daily observation and the shape of solar panels.The shutter blades are equipped with an automatic light tracking system,and the angle of the blades can be adjusted in time through photoresistor induction,that is,as much solar energy as possible can be converted into electric energy for load use,and at the same time,comfortable light can be provided for the house.In essence,the system is a small photovoltaic power generation system,which runs all day with high-efficiency based on automatic sun tracking.Among them,the basic operation route includes:solar position detection,computer data processing,photovoltaic and electric volt energy conversion,circuit connection,etc.From the current debugging results,the shutter has the characteristics of humanization,high efficiency,cleanliness and so on.Through this energy-saving system,we hope to maximize the use of solar energy in the premise of low cost,so as to achieve the purpose of energy saving.
基金supported by the National Nature Science Foundation of China(40774025)
文摘The paper describes the working principle and structure of a newly designed high-precision （ inicrogal） gravimeter, which is basically a vertically suspending spring-weight system, using a highly sensitive capacitance sensor of movement in a controlled temperature environment in a borehole and a multi-frequency output for both earth-tide and earthquake monitoring. The preliminary test indicated that, while in a stabilization process, it had met all the technical requirements for a relative gravimeter used for earth tide and earthquake monitoring.
