Due to the novel applications of flexible pipes conveying fluid in the field of soft robotics and biomedicine,the investigations on the mechanical responses of the pipes have attracted considerable attention.The fluid...Due to the novel applications of flexible pipes conveying fluid in the field of soft robotics and biomedicine,the investigations on the mechanical responses of the pipes have attracted considerable attention.The fluid-structure interaction(FSI)between the pipe with a curved shape and the time-varying internal fluid flow brings a great challenge to the revelation of the dynamical behaviors of flexible pipes,especially when the pipe is highly flexible and usually undergoes large deformations.In this work,the geometrically exact model(GEM)for a curved cantilevered pipe conveying pulsating fluid is developed based on the extended Hamilton's principle.The stability of the curved pipe with three different subtended angles is examined with the consideration of steady fluid flow.Specific attention is concentrated on the large-deformation resonance of circular pipes conveying pulsating fluid,which is often encountered in practical engineering.By constructing bifurcation diagrams,oscillating shapes,phase portraits,time traces,and Poincarémaps,the dynamic responses of the curved pipe under various system parameters are revealed.The mean flow velocity of the pulsating fluid is chosen to be either subcritical or supercritical.The numerical results show that the curved pipe conveying pulsating fluid can exhibit rich dynamical behaviors,including periodic and quasi-periodic motions.It is also found that the preferred instability type of a cantilevered curved pipe conveying steady fluid is mainly in the flutter of the second mode.For a moderate value of the mass ratio,however,a third-mode flutter may occur,which is quite different from that of a straight pipe system.展开更多
Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functiona...Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functionalgrading (FG). However, the procedure is usually complex and often is time-consuming. We thus put forward adeep learning method to model the geometrically nonlinear bending behavior of FG plates, bypassing the complexIGA simulation process. A long bidirectional short-term memory (BLSTM) recurrent neural network is trainedusing the load and gradient index as inputs and the displacement responses as outputs. The nonlinear relationshipbetween the outputs and the inputs is constructed usingmachine learning so that the displacements can be directlyestimated by the deep learning network. To provide enough training data, we use S-FSDT Von-Karman IGA andobtain the displacement responses for different loads and gradient indexes. Results show that the recognition erroris low, and demonstrate the feasibility of deep learning technique as a fast and accurate alternative to IGA formodeling the geometrically nonlinear bending behavior of FG plates.展开更多
Auxetic materials are cellular materials with a unique property of negative Poisson’s ratio.The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction.For...Auxetic materials are cellular materials with a unique property of negative Poisson’s ratio.The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction.For the first time,the quasi-static uniaxial compression performance of fused filament fabricated re-entrant diamond auxetic metamaterial is evaluated in the x-direction(in-plane)and z-direction(out-of-plane).The most commonly used thermoplastic feedstock,Acrylonitrile butadiene styrene,is considered a material of choice.The effect of influential geometrical parameters of the re-entrant diamond structure and printing parameter is systematically studied using Taguchi’s design of experiments.Grey-based multi-objective optimisation technique has been adopted to arrive at the optimal structure.Efforts are made to improve the stiffness and strength of the structure with fibre reinforcements.Micro glass fibre reinforcements have enhanced specific strength and stiffness in both in-plane and out-ofplane directions.A sevenfold and thirteen times increase in specific strength and energy absorption is evident for glass fibre-reinforced structures in out-of-plane directions compared to in-plane ones.Proper tuning of geometrical parameters of the re-entrant diamond structure can result in a Poisson’s ratio of up to-3.49 when tested in the x-direction.The parametric study has illustrated the tailorability of the structure according to the application requirements.The statistical study has signified each considered parameter’s contribution to the compression performance characteristics of the 3D printed re-entrant diamond auxetic metamaterial.展开更多
The perturbed Riemann problem for a hyperbolic system of conservation laws arising in geometrical optics with three constant initial states is solved.By studying the interactions among of the delta-shock,vacuum,and co...The perturbed Riemann problem for a hyperbolic system of conservation laws arising in geometrical optics with three constant initial states is solved.By studying the interactions among of the delta-shock,vacuum,and contact discontinuity,fourteen kinds of structures of Riemann solutions are obtained.The compound wave solutions consisting of delta-shocks,vacuums,and contact discontinuities are found.The single and double closed vacuum cavitations develop in solutions.Furthermore,it is shown that the solutions of the Riemann problem for the geometrical optics system are stable under certain perturbation of the initial data.Finally,the numerical results completely coinciding with theoretical analysis are presented.展开更多
This study presents a high-speed geometrically nonlinear flutter analysis calculation method based on the highprecision computational fluid dynamics/computational structural dynamics methods.In the proposed method,the...This study presents a high-speed geometrically nonlinear flutter analysis calculation method based on the highprecision computational fluid dynamics/computational structural dynamics methods.In the proposed method,the aerodynamic simulation was conducted based on computational fluid dynamics,and the structural model was established using the nonlinear finite element model and tangential stiffness matrix.First,the equilibrium position was obtained using the nonlinear static aeroelastic iteration.Second,the structural modal under a steady aerodynamic load was extracted.Finally,the generalized displacement time curve was obtained by coupling the unsteady aerodynamics and linearized structure motion equations.Moreover,if the flutter is not at a critical state,the incoming flow dynamic pressure needs to be changed,and the above steps must be repeated until the vibration amplitude are equal.Furthermore,the high-speed geometrically nonlinear flutter of the wing-body assemblymodel with a high-aspect ratio was investigated,and the correctness of the method was verified using high-speed wind tunnel experiments.The results showed that the geometric nonlinearity of the large deformation of the wing caused in-plane bending to become a key factor in flutter characteristics and significantly decreased the dynamic pressure and frequency of the nonlinear flutter compared to those of the linear flutter.展开更多
Wear and mileage performance are the foremost performances for truck bus radial (TBR) tires. There are a lot of researches about the tire wear performance as well as the contact patch phenomenon by using finite elemen...Wear and mileage performance are the foremost performances for truck bus radial (TBR) tires. There are a lot of researches about the tire wear performance as well as the contact patch phenomenon by using finite element analysis (FEA) method or testing. But there is little published data on the correlations between the footprint geometry and the tread wear performance of tires. In this paper, an experiment on tire-ground performance of TBR tires is carried out by using Tekscan. The real-time changes of contact-area pressure distribution that occurred during the process of continuous load and unload are recorded. Three types of tires that act differently in behavior under normal usage are analyzed. A new method of researching in tire tread wear, which focuses on the geometrical characters of the footprint, is put forward. The experimental results of the three tires are described by using footprint geometrical characters. On the basis of studying the changing laws of footprint geometrical characters during the loading process and considering consumer survey and factory feedback information, the correlations between the geometrical character of footprints and tread destruction form are built. The analyzed results show that a greater contact area coefficient and a steady coefficient of contact result in a better wear performance for TBR tires. The footprint-shape coefficient changing laws in the process of loading are found to have a very good coincidence with the tread wear of the three types of tires. Tires with a smaller footprint-shape coefficient are likely to have an average tread wear while avoiding the shoulder wear first. The proposed research provides a new solution to predict tire-ground performance at the point of footprint and several useful references for improving tire design.展开更多
Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes ...Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes which are subjected to stress-induced failure.The probability of failure(POF)depends on many factors,of which the geometry of an open stope is especially important.In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF,using numerical modelling.Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines.A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D,to generate model realizations containing stopes with different geometrical features.The probability of failure(POF)for different categories of stope geometry,is calculated by considering two modes of failure;relaxation-related gravity driven(tensile)failure and rock mass brittle failure.The individual and interactive effects of stope geometrical parameters on the POF,are analyzed using a general multi-level factorial design.Finally,mathematical optimization techniques are employed to estimate the most stable stope conditions,by determining the optimal ranges for each stope’s geometrical parameter.展开更多
The present work is an analytical study of the influence of geometrical parameters, such as length, thickness and immersion of the plate, on the reflection coefficient of a regular wave for an immersed horizontal plat...The present work is an analytical study of the influence of geometrical parameters, such as length, thickness and immersion of the plate, on the reflection coefficient of a regular wave for an immersed horizontal plate in the presence of a uniform current with the same direction as the propagation of the incident regular wave. This study was performed using the linearized potential theory with the evanescent modes while searching for complex roots to the dispersion equation that are neither pure real nor pure imaginary. The results show that the effects of the immersion and the relative length on the reflection coefficient of the plate are accentuated by the presence of the current, whereas the plate thickness practically does not have an effect if it is relatively small.展开更多
Perforation of tympanic membrane is one of the main reasons for both deafness and dyssaudia.We could improve and restore audition by restoring or replacing the tympanic membrane.So,whether you can make the spurious ty...Perforation of tympanic membrane is one of the main reasons for both deafness and dyssaudia.We could improve and restore audition by restoring or replacing the tympanic membrane.So,whether you can make the spurious tympanic membrane successfully is one of the keys to a successful operation.Utilizing CMM (Coordinate Measuring Machine) measurement equipment, we measured tympanic membrane model precisely and digitally.We also analysed the measured data by point to surface and we have successfully reconstructed the CAD model of the spurious tympanic membrane.Using the model we have got,we schemed out the mold of spurious tympanic membrane.In addition,we utilized MasterCAM compiling CNC (Computerized Numerical Con- trol) code and simulating the course of working.Ultimately,we obtained the mold of spurious tympanic membrane.Our research in this article has great significance to the success of spurious tympanic membrane grafting operation.展开更多
We studied quantum correlation and quantum entanglement of a quantum system in which a coherent state light field interacts with two qubits that are initially prepared in a separable and mixed state.The influence of m...We studied quantum correlation and quantum entanglement of a quantum system in which a coherent state light field interacts with two qubits that are initially prepared in a separable and mixed state.The influence of mean photon number of the coherent field and distribution probability of the atom on the geometrical quantum discord and the negativity are discussed.Our results show that the mean photon number of light field and distribution function of the atom can regulate and control the quantum correlation and quantum entanglement.展开更多
The aim is to compute all sources of geometrical uncertainty in prostate radiotherapy using fiducial markers and determine the safety treatment margins. Based on the markers position, correlations between prostate rot...The aim is to compute all sources of geometrical uncertainty in prostate radiotherapy using fiducial markers and determine the safety treatment margins. Based on the markers position, correlations between prostate rotation/deformation and rectal and bladder fillings as well as changes in prostate volume during the treatment course are analyzed. The study includes 375 pre-treatment CBCT images from 15 prostate cancer patients treated with hypofractionated radiotherapy. The position coordinates of the markers were obtained from each image acquisition. In addition, rectum and bladder were outlined on CBCTs. The intrafractional error was estimated by an additional post-treatment CBCT acquired on alternate days. Tau-Kendall analysis was performed to correlate organ fillings with prostate rotation/deformation. Delineation uncertainty was assessed from contours of 10 patients performed by two radiation oncologists and repeated twice. The CT contouring was assisted by a multiparametric MR approach combining a T2-weighted with diffusion-weighted imaging, and a gradient recalled echo for fiducial marker identification. Uncertainty associated to treatment unit was estimated from phantom measurements. The obtained clinical margins were 4.4, 7.3, 5.1 mm in the Left-Right, Superior-Inferior, and Anterior-Posterior directions, respectively, being the contouring the most important contribution. The mechanical limitations of the beam delivery system and the associated imaging device entailed errors of the same order as prostate motion, rotation or deformation. Weak correlations between variation of the rectal volume and the presence of rotations/deformations were found (correlation coefficient 0.182, p = 0.001 for rotations around lateral axis;correlation coefficients 0.1, p < 0.05 for deformations). The distance between markers decreased with session number, becoming more pronounced from fraction 13 and reaching 1 - 1.8 mm at the end of the treatment. In summary we have determined the optimal treatment margins based on geometrical uncertainty assessment using van Herk formalism. An appropriate preparation of rectum and bladder involves minimizing the effect of prostate rotations/deformations. The prostate tends to decrease in size during the treatment which could influence treatment re-planning strategies.展开更多
Optical surface scattering analyses based on diffractive optics (DO) are typically applied to one surface;however, there is a need for simulating surface scattering losses for devices having many surface interactions ...Optical surface scattering analyses based on diffractive optics (DO) are typically applied to one surface;however, there is a need for simulating surface scattering losses for devices having many surface interactions such as light pipes. Light pipes are often simulated with geometric optics (GO) using ray tracing, where surface scattering is driven by the surface slope distribution. In the DO case, surface scattering analyses depend on the spatial frequency distribution and amplitude as well as wavelength, with the sinusoidal grating as a fundamental basis. A better understanding of the link, or transition, between DO and GO scattering domains would be helpful for efficiently incorporating scattering loss analyses into ray trace simulations. A formula for the root-mean-square (rms) scattered angle width of a sinusoidal reflection grating that depends only on the surface rms slope is derived from the nonparaxial scalar diffraction theory, thereby linking it to GO. The scatter angle’s mean and rms width are evaluated over a range of grating amplitudes and periods using scalar theory and full vector simulations from the COMSOL® wave optic module for a sinusoidal reflection grating. The conditions under which the diffraction-based solution closely approximates the GO solution, as predicted by the rms slope, are identified. Close agreement is shown between the DO and GO solutions for the same surface rms slope scattering loss due to angular filtering near the critical angle of a total internal reflection (TIR) glass-to-air interface.展开更多
In this study,the effects of geometrical and physical factors on light particles dispersion in stirred tank were investigated by agitation characteristic curve.The experiments and CFD simulations with discrete phase m...In this study,the effects of geometrical and physical factors on light particles dispersion in stirred tank were investigated by agitation characteristic curve.The experiments and CFD simulations with discrete phase model(DPM)and volume of fluid model(VOF)were conducted in this paper.Five factors,which include four geometrical factors(submergence,impeller-to-tank ratio,number of impeller blades and baffling mode)and a physical factor(liquid viscosity)were considered.For each factor,the power consumption curve and agitation characteristic curve were drawn to compare the power consumption and mixing results in the stirred tank.Characteristics of the agitation characteristic curves were compared with the previous published literatures and theories.It is found that the agitation characteristic curves reflect the tendency of power consumption and particles distribution well in stirred tank.The good agreement indicates the applicability of the agitation characteristic curves for the study of light particles distribution in stirred tank.展开更多
Boundary conditions constructed by two typical geometrical configurations related to themanufacturing methods of bronze process and tin-rich Nb tube method have been consideredin a diffusion model in which the diffusi...Boundary conditions constructed by two typical geometrical configurations related to themanufacturing methods of bronze process and tin-rich Nb tube method have been consideredin a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as-sumed.The dependence of thickness of Nb<sub>3</sub>Sn layer on reaction time has been derived.It isshown that the growth rate of Nb<sub>3</sub>Sn relates to the configuration of the superconductor,thegeometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con-sistent with the experimental results.展开更多
The parity operator P and time reversal operator T are two important operators in the quantum theory, in particular, in the PT -symmetric quantum theory. By using the concrete forms of P and T , we discuss their geome...The parity operator P and time reversal operator T are two important operators in the quantum theory, in particular, in the PT -symmetric quantum theory. By using the concrete forms of P and T , we discuss their geometrical properties in two dimensional spaces. It is showed that if T is given, then all P links with the quadric surfaces;if P is given, then all T links with the quadric curves. Moreover, we give out the generalized unbroken PT -symmetric condition of an operator. The unbroken PT -symmetry of a Hermitian operator is also showed in this way.展开更多
A six-variable geometrical nonlinear shear deformation laminated theory is presented bywhich normal stress and strain distribution can be calculated.By considering some affective factorsthat were neglected under the f...A six-variable geometrical nonlinear shear deformation laminated theory is presented bywhich normal stress and strain distribution can be calculated.By considering some affective factorsthat were neglected under the finite deformation condition,an improved yon Karman geometrical non-linear deformation-strain relation is used for large deformation analysis.After analyzing the bendingproblem of laminated plates,and comparing it with 3-D elasticity solutions and J.N.Reddy five-vari-able simple higher-order shear deformation laminated theory,we can conclude that a satisfactory cal-culation precision has been achieved,which shows that it is especially suitable for the calculation in thecondition of large deformation and the laminated thick plate analysis.展开更多
This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the s...This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design.The TPFGS plate is analyzed considering linearly,bi-linearly,and exponentially varying thicknesses.The plate’s effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate.Incorporating the non-linear finite element formulation to develop the kinematic equation’s displacement model for the TPFGS plate is based on the first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinearity.The nonlinear governing equations are established by Hamilton’s principle.The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies.The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters.The influence of taper ratio,variable thickness,skewness,porosity distributions,gradation,and boundary conditions on the plate’s nonlinear vibration is demonstrated.The nonlinear frequency analysis reveals that the geometrical nonuniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness.Besides,exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.展开更多
Selective laser melting(SLM)has been applied to manufacture various alloy components with excellent properties,but its further application is restricted by the intrinsic defects.In this work,the internal defect distri...Selective laser melting(SLM)has been applied to manufacture various alloy components with excellent properties,but its further application is restricted by the intrinsic defects.In this work,the internal defect distributions in samples of three alloys(316L stainless steel,AlSi10Mg and Inconel 718)were investigated respectively,considering the effects of geometrical characteristics of the samples.The defects in the 316L stainless steel sample tend to be formed densely in the central part with large wall thickness,indicating a strong sensitivity to heat accumulation.Contrarily,the Inconel 718 sample shows a higher relative density with homogeneous defect distribution,indicating better formability for the SLM process.For the AlSi10Mg sample,the defect density keeps increasing as the deposition goes on.Typically,the defect density located at sample edges shows an abnormally high level comparing with the inner part,especially in the top sections of AlSi10Mg and Inconel 718 samples.The results are helpful for the geometrical design,the adjustment of building orientation and the further optimization of process parameters in the SLM process.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos.12072119,12325201,and 52205594)the China National Postdoctoral Program for Innovative Talents (No.BX20220118)。
文摘Due to the novel applications of flexible pipes conveying fluid in the field of soft robotics and biomedicine,the investigations on the mechanical responses of the pipes have attracted considerable attention.The fluid-structure interaction(FSI)between the pipe with a curved shape and the time-varying internal fluid flow brings a great challenge to the revelation of the dynamical behaviors of flexible pipes,especially when the pipe is highly flexible and usually undergoes large deformations.In this work,the geometrically exact model(GEM)for a curved cantilevered pipe conveying pulsating fluid is developed based on the extended Hamilton's principle.The stability of the curved pipe with three different subtended angles is examined with the consideration of steady fluid flow.Specific attention is concentrated on the large-deformation resonance of circular pipes conveying pulsating fluid,which is often encountered in practical engineering.By constructing bifurcation diagrams,oscillating shapes,phase portraits,time traces,and Poincarémaps,the dynamic responses of the curved pipe under various system parameters are revealed.The mean flow velocity of the pulsating fluid is chosen to be either subcritical or supercritical.The numerical results show that the curved pipe conveying pulsating fluid can exhibit rich dynamical behaviors,including periodic and quasi-periodic motions.It is also found that the preferred instability type of a cantilevered curved pipe conveying steady fluid is mainly in the flutter of the second mode.For a moderate value of the mass ratio,however,a third-mode flutter may occur,which is quite different from that of a straight pipe system.
基金the National Natural Science Foundation of China(NSFC)under Grant Nos.12272124 and 11972146.
文摘Isogeometric analysis (IGA) is known to showadvanced features compared to traditional finite element approaches.Using IGA one may accurately obtain the geometrically nonlinear bending behavior of plates with functionalgrading (FG). However, the procedure is usually complex and often is time-consuming. We thus put forward adeep learning method to model the geometrically nonlinear bending behavior of FG plates, bypassing the complexIGA simulation process. A long bidirectional short-term memory (BLSTM) recurrent neural network is trainedusing the load and gradient index as inputs and the displacement responses as outputs. The nonlinear relationshipbetween the outputs and the inputs is constructed usingmachine learning so that the displacements can be directlyestimated by the deep learning network. To provide enough training data, we use S-FSDT Von-Karman IGA andobtain the displacement responses for different loads and gradient indexes. Results show that the recognition erroris low, and demonstrate the feasibility of deep learning technique as a fast and accurate alternative to IGA formodeling the geometrically nonlinear bending behavior of FG plates.
文摘Auxetic materials are cellular materials with a unique property of negative Poisson’s ratio.The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction.For the first time,the quasi-static uniaxial compression performance of fused filament fabricated re-entrant diamond auxetic metamaterial is evaluated in the x-direction(in-plane)and z-direction(out-of-plane).The most commonly used thermoplastic feedstock,Acrylonitrile butadiene styrene,is considered a material of choice.The effect of influential geometrical parameters of the re-entrant diamond structure and printing parameter is systematically studied using Taguchi’s design of experiments.Grey-based multi-objective optimisation technique has been adopted to arrive at the optimal structure.Efforts are made to improve the stiffness and strength of the structure with fibre reinforcements.Micro glass fibre reinforcements have enhanced specific strength and stiffness in both in-plane and out-ofplane directions.A sevenfold and thirteen times increase in specific strength and energy absorption is evident for glass fibre-reinforced structures in out-of-plane directions compared to in-plane ones.Proper tuning of geometrical parameters of the re-entrant diamond structure can result in a Poisson’s ratio of up to-3.49 when tested in the x-direction.The parametric study has illustrated the tailorability of the structure according to the application requirements.The statistical study has signified each considered parameter’s contribution to the compression performance characteristics of the 3D printed re-entrant diamond auxetic metamaterial.
基金supported by the National Natural Science Foundation of China(12061084)the Natural Science Foundation of Yunnan Province(2019FY003007).
文摘The perturbed Riemann problem for a hyperbolic system of conservation laws arising in geometrical optics with three constant initial states is solved.By studying the interactions among of the delta-shock,vacuum,and contact discontinuity,fourteen kinds of structures of Riemann solutions are obtained.The compound wave solutions consisting of delta-shocks,vacuums,and contact discontinuities are found.The single and double closed vacuum cavitations develop in solutions.Furthermore,it is shown that the solutions of the Riemann problem for the geometrical optics system are stable under certain perturbation of the initial data.Finally,the numerical results completely coinciding with theoretical analysis are presented.
文摘This study presents a high-speed geometrically nonlinear flutter analysis calculation method based on the highprecision computational fluid dynamics/computational structural dynamics methods.In the proposed method,the aerodynamic simulation was conducted based on computational fluid dynamics,and the structural model was established using the nonlinear finite element model and tangential stiffness matrix.First,the equilibrium position was obtained using the nonlinear static aeroelastic iteration.Second,the structural modal under a steady aerodynamic load was extracted.Finally,the generalized displacement time curve was obtained by coupling the unsteady aerodynamics and linearized structure motion equations.Moreover,if the flutter is not at a critical state,the incoming flow dynamic pressure needs to be changed,and the above steps must be repeated until the vibration amplitude are equal.Furthermore,the high-speed geometrically nonlinear flutter of the wing-body assemblymodel with a high-aspect ratio was investigated,and the correctness of the method was verified using high-speed wind tunnel experiments.The results showed that the geometric nonlinearity of the large deformation of the wing caused in-plane bending to become a key factor in flutter characteristics and significantly decreased the dynamic pressure and frequency of the nonlinear flutter compared to those of the linear flutter.
基金supported by Jiangsu Provincial Innovation Program of Graduate Student of China (Grant No. CXZZ11_0551 )
文摘Wear and mileage performance are the foremost performances for truck bus radial (TBR) tires. There are a lot of researches about the tire wear performance as well as the contact patch phenomenon by using finite element analysis (FEA) method or testing. But there is little published data on the correlations between the footprint geometry and the tread wear performance of tires. In this paper, an experiment on tire-ground performance of TBR tires is carried out by using Tekscan. The real-time changes of contact-area pressure distribution that occurred during the process of continuous load and unload are recorded. Three types of tires that act differently in behavior under normal usage are analyzed. A new method of researching in tire tread wear, which focuses on the geometrical characters of the footprint, is put forward. The experimental results of the three tires are described by using footprint geometrical characters. On the basis of studying the changing laws of footprint geometrical characters during the loading process and considering consumer survey and factory feedback information, the correlations between the geometrical character of footprints and tread destruction form are built. The analyzed results show that a greater contact area coefficient and a steady coefficient of contact result in a better wear performance for TBR tires. The footprint-shape coefficient changing laws in the process of loading are found to have a very good coincidence with the tread wear of the three types of tires. Tires with a smaller footprint-shape coefficient are likely to have an average tread wear while avoiding the shoulder wear first. The proposed research provides a new solution to predict tire-ground performance at the point of footprint and several useful references for improving tire design.
基金funded by a grant from Natural Sciences and Engineering Research Council of Canada (NSERC)the authors would like to acknowledge the Niobec mine (Saint-Honoré, QuébecQuébec)
文摘Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes which are subjected to stress-induced failure.The probability of failure(POF)depends on many factors,of which the geometry of an open stope is especially important.In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF,using numerical modelling.Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines.A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D,to generate model realizations containing stopes with different geometrical features.The probability of failure(POF)for different categories of stope geometry,is calculated by considering two modes of failure;relaxation-related gravity driven(tensile)failure and rock mass brittle failure.The individual and interactive effects of stope geometrical parameters on the POF,are analyzed using a general multi-level factorial design.Finally,mathematical optimization techniques are employed to estimate the most stable stope conditions,by determining the optimal ranges for each stope’s geometrical parameter.
文摘The present work is an analytical study of the influence of geometrical parameters, such as length, thickness and immersion of the plate, on the reflection coefficient of a regular wave for an immersed horizontal plate in the presence of a uniform current with the same direction as the propagation of the incident regular wave. This study was performed using the linearized potential theory with the evanescent modes while searching for complex roots to the dispersion equation that are neither pure real nor pure imaginary. The results show that the effects of the immersion and the relative length on the reflection coefficient of the plate are accentuated by the presence of the current, whereas the plate thickness practically does not have an effect if it is relatively small.
文摘Perforation of tympanic membrane is one of the main reasons for both deafness and dyssaudia.We could improve and restore audition by restoring or replacing the tympanic membrane.So,whether you can make the spurious tympanic membrane successfully is one of the keys to a successful operation.Utilizing CMM (Coordinate Measuring Machine) measurement equipment, we measured tympanic membrane model precisely and digitally.We also analysed the measured data by point to surface and we have successfully reconstructed the CAD model of the spurious tympanic membrane.Using the model we have got,we schemed out the mold of spurious tympanic membrane.In addition,we utilized MasterCAM compiling CNC (Computerized Numerical Con- trol) code and simulating the course of working.Ultimately,we obtained the mold of spurious tympanic membrane.Our research in this article has great significance to the success of spurious tympanic membrane grafting operation.
基金Project supported by the National Natural Science Foundation of China(Grant No.11604090)
文摘We studied quantum correlation and quantum entanglement of a quantum system in which a coherent state light field interacts with two qubits that are initially prepared in a separable and mixed state.The influence of mean photon number of the coherent field and distribution probability of the atom on the geometrical quantum discord and the negativity are discussed.Our results show that the mean photon number of light field and distribution function of the atom can regulate and control the quantum correlation and quantum entanglement.
文摘The aim is to compute all sources of geometrical uncertainty in prostate radiotherapy using fiducial markers and determine the safety treatment margins. Based on the markers position, correlations between prostate rotation/deformation and rectal and bladder fillings as well as changes in prostate volume during the treatment course are analyzed. The study includes 375 pre-treatment CBCT images from 15 prostate cancer patients treated with hypofractionated radiotherapy. The position coordinates of the markers were obtained from each image acquisition. In addition, rectum and bladder were outlined on CBCTs. The intrafractional error was estimated by an additional post-treatment CBCT acquired on alternate days. Tau-Kendall analysis was performed to correlate organ fillings with prostate rotation/deformation. Delineation uncertainty was assessed from contours of 10 patients performed by two radiation oncologists and repeated twice. The CT contouring was assisted by a multiparametric MR approach combining a T2-weighted with diffusion-weighted imaging, and a gradient recalled echo for fiducial marker identification. Uncertainty associated to treatment unit was estimated from phantom measurements. The obtained clinical margins were 4.4, 7.3, 5.1 mm in the Left-Right, Superior-Inferior, and Anterior-Posterior directions, respectively, being the contouring the most important contribution. The mechanical limitations of the beam delivery system and the associated imaging device entailed errors of the same order as prostate motion, rotation or deformation. Weak correlations between variation of the rectal volume and the presence of rotations/deformations were found (correlation coefficient 0.182, p = 0.001 for rotations around lateral axis;correlation coefficients 0.1, p < 0.05 for deformations). The distance between markers decreased with session number, becoming more pronounced from fraction 13 and reaching 1 - 1.8 mm at the end of the treatment. In summary we have determined the optimal treatment margins based on geometrical uncertainty assessment using van Herk formalism. An appropriate preparation of rectum and bladder involves minimizing the effect of prostate rotations/deformations. The prostate tends to decrease in size during the treatment which could influence treatment re-planning strategies.
文摘Optical surface scattering analyses based on diffractive optics (DO) are typically applied to one surface;however, there is a need for simulating surface scattering losses for devices having many surface interactions such as light pipes. Light pipes are often simulated with geometric optics (GO) using ray tracing, where surface scattering is driven by the surface slope distribution. In the DO case, surface scattering analyses depend on the spatial frequency distribution and amplitude as well as wavelength, with the sinusoidal grating as a fundamental basis. A better understanding of the link, or transition, between DO and GO scattering domains would be helpful for efficiently incorporating scattering loss analyses into ray trace simulations. A formula for the root-mean-square (rms) scattered angle width of a sinusoidal reflection grating that depends only on the surface rms slope is derived from the nonparaxial scalar diffraction theory, thereby linking it to GO. The scatter angle’s mean and rms width are evaluated over a range of grating amplitudes and periods using scalar theory and full vector simulations from the COMSOL® wave optic module for a sinusoidal reflection grating. The conditions under which the diffraction-based solution closely approximates the GO solution, as predicted by the rms slope, are identified. Close agreement is shown between the DO and GO solutions for the same surface rms slope scattering loss due to angular filtering near the critical angle of a total internal reflection (TIR) glass-to-air interface.
基金Supported by the National Natural Science Foundation of China(51474109,51609090,51679097).
文摘In this study,the effects of geometrical and physical factors on light particles dispersion in stirred tank were investigated by agitation characteristic curve.The experiments and CFD simulations with discrete phase model(DPM)and volume of fluid model(VOF)were conducted in this paper.Five factors,which include four geometrical factors(submergence,impeller-to-tank ratio,number of impeller blades and baffling mode)and a physical factor(liquid viscosity)were considered.For each factor,the power consumption curve and agitation characteristic curve were drawn to compare the power consumption and mixing results in the stirred tank.Characteristics of the agitation characteristic curves were compared with the previous published literatures and theories.It is found that the agitation characteristic curves reflect the tendency of power consumption and particles distribution well in stirred tank.The good agreement indicates the applicability of the agitation characteristic curves for the study of light particles distribution in stirred tank.
文摘Boundary conditions constructed by two typical geometrical configurations related to themanufacturing methods of bronze process and tin-rich Nb tube method have been consideredin a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as-sumed.The dependence of thickness of Nb<sub>3</sub>Sn layer on reaction time has been derived.It isshown that the growth rate of Nb<sub>3</sub>Sn relates to the configuration of the superconductor,thegeometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con-sistent with the experimental results.
基金Supported by Research Fund,Kumoh National Institute of Technology
文摘The parity operator P and time reversal operator T are two important operators in the quantum theory, in particular, in the PT -symmetric quantum theory. By using the concrete forms of P and T , we discuss their geometrical properties in two dimensional spaces. It is showed that if T is given, then all P links with the quadric surfaces;if P is given, then all T links with the quadric curves. Moreover, we give out the generalized unbroken PT -symmetric condition of an operator. The unbroken PT -symmetry of a Hermitian operator is also showed in this way.
文摘A six-variable geometrical nonlinear shear deformation laminated theory is presented bywhich normal stress and strain distribution can be calculated.By considering some affective factorsthat were neglected under the finite deformation condition,an improved yon Karman geometrical non-linear deformation-strain relation is used for large deformation analysis.After analyzing the bendingproblem of laminated plates,and comparing it with 3-D elasticity solutions and J.N.Reddy five-vari-able simple higher-order shear deformation laminated theory,we can conclude that a satisfactory cal-culation precision has been achieved,which shows that it is especially suitable for the calculation in thecondition of large deformation and the laminated thick plate analysis.
文摘This article presents the investigation of nonlinear vibration analysis of tapered porous functionally graded skew(TPFGS)plate considering the effects of geometrical non-uniformities to optimize the thickness in the structural design.The TPFGS plate is analyzed considering linearly,bi-linearly,and exponentially varying thicknesses.The plate’s effective material properties are tailor-made using a modified power-law distribution in which gradation varies along the thickness direction of the TPFGS plate.Incorporating the non-linear finite element formulation to develop the kinematic equation’s displacement model for the TPFGS plate is based on the first-order shear deformation theory(FSDT)in conjunction with von Karman’s nonlinearity.The nonlinear governing equations are established by Hamilton’s principle.The direct iterative method is adopted to solve the nonlinear mathematical relations to obtain the nonlinear frequencies.The influence of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the TPFGS plate for different skew angles and variable thicknesses are studied for various geometrical parameters.The influence of taper ratio,variable thickness,skewness,porosity distributions,gradation,and boundary conditions on the plate’s nonlinear vibration is demonstrated.The nonlinear frequency analysis reveals that the geometrical nonuniformities and porosities significantly influence the porous functionally graded plates with varying thickness than the uniform thickness.Besides,exponentially and linearly variable thicknesses can be considered for the thickness optimizations of TPFGS plates in the structural design.
基金the National Key R&D Program of China(No.2018YFB1106100)Jiangsu Key Laboratory for Advanced Metallic Materials(No.BM2007204)。
文摘Selective laser melting(SLM)has been applied to manufacture various alloy components with excellent properties,but its further application is restricted by the intrinsic defects.In this work,the internal defect distributions in samples of three alloys(316L stainless steel,AlSi10Mg and Inconel 718)were investigated respectively,considering the effects of geometrical characteristics of the samples.The defects in the 316L stainless steel sample tend to be formed densely in the central part with large wall thickness,indicating a strong sensitivity to heat accumulation.Contrarily,the Inconel 718 sample shows a higher relative density with homogeneous defect distribution,indicating better formability for the SLM process.For the AlSi10Mg sample,the defect density keeps increasing as the deposition goes on.Typically,the defect density located at sample edges shows an abnormally high level comparing with the inner part,especially in the top sections of AlSi10Mg and Inconel 718 samples.The results are helpful for the geometrical design,the adjustment of building orientation and the further optimization of process parameters in the SLM process.
