To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the stre...To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the strength and elastic modulus of mortar and concrete prepared with mechanism aggregates of the corresponding lithology,and the stress-strain curves of concrete were investigated.In this paper,a coarse aggregate and mortar matrix bonding assumption is proposed,and a prediction model for the elastic modulus of mortar is established by considering the lithology of the mechanism sand and the slurry components.An equivalent coarse aggregate elastic modulus model was established by considering factors such as coarse aggregate particle size,volume fraction,and mortar thickness between coarse aggregates.Based on the elastic modulus of the equivalent coarse aggregate and the remaining mortar,a prediction model for the elastic modulus of the two and three components of concrete in series and then in parallel was established,and the predicted values differed from the measured values within 10%.It is proposed that the coarse aggregate elastic modulus in highstrength concrete is the most critical factor affecting the elastic modulus of concrete,and as the coarse aggregate elastic modulus increases by 27.7%,the concrete elastic modulus increases by 19.5%.展开更多
Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes...Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes with SiO_(2)and Al_(2)O_(3)ratios were investigated using various techniques.It is found that when SiO_(2)is replaced by Al_(2)O_(3),the Q^(4) to Q^(3) transition of silicon-oxygen network decreases while the aluminum-oxygen network increases,which result in the transformation of Si-O-Si bonds to Si-O-Al bonds and an increase in glass network connectivity even though the intermolecular bond strength decreases.The glass transition temperature(T_(g))increases continuously,while the thermal expansion coefficient increases and high-temperature viscosity first decreases and then increases.Meanwhile,the elastic modulus values increase from 93 to 102 GPa.This indicates that the elastic modulus is mainly affected by packing factor and dissociation energy,and elements with higher packing factors and dissociation energies supplant those with lower values,resulting in increased rigidity within the glass.展开更多
AIM： To compare dgid proctoscope and flexible endoscope for elastic band ligation of internal hemorrhoids. METHODS： Patients between 18 and 80 years old, with chronic complaints （blood loss, pain, itching or prola...AIM： To compare dgid proctoscope and flexible endoscope for elastic band ligation of internal hemorrhoids. METHODS： Patients between 18 and 80 years old, with chronic complaints （blood loss, pain, itching or prolapse） of internal hemorrhoids of grade 1-91, were randomized to elastic band ligation by rigid proctoscope or flexible endoscope （preloaded with 7 bands）. Patients were retreated every 6 wk until the cessation of complaints. Evaluation by three-dimensional anal endosonography was performed. RESULTS： Forty-one patients were included （median age 52.0, range 27-79 years, 20 men）. Nineteen patients were treated with a rigid proctoscope and twenty two with a flexible endoscope. Twenty-nine patients had grade I hemorrhoids, 9 patients had grade 11 hemorrhoids and 3 patients had grade 91 hemorrhoids. All patients needed a minimum of 1 treatment and a maximum of 3 treatments. A median of 4.0 bands was used in the rigid proctoscope group and a median of 6.0 bands was used in the flexible endoscope group （P 〈 0.05）. Pain after ligation tended to be more frequent in patients treated with the flexible endoscope （first treatment： 3 vs 20 patients, P 〈 0.05）. Three- dimensional endosonography showed no sphincter defects or alterations in submucosal thickness. CONCLUSION： Both techniques are easy to perform, well tolerated and have a good and fast effect. It is easier to perform more ligations with the flexible endoscope. Additional advantages of the flexible scope are the maneuverability and photographic documentation. However, treatment with the flexible endoscope might be more painful and is more expensive.展开更多
Dynamic contact stiffness at the interface between a vibrating rigid sphere and a semi-infinite transversely isotropic viscoelastic solid is investigated. An oscillating force superimposed onto a static compressive fo...Dynamic contact stiffness at the interface between a vibrating rigid sphere and a semi-infinite transversely isotropic viscoelastic solid is investigated. An oscillating force superimposed onto a static compressive force in the vertical direction excites the vibration of a rigid sphere, which causes variable contact radius and contact pressure distribution in the contact region. The assumption of a sufficiently small oscillating force yields a dynamic contact-pressure distribution of a constant contact radius, which gives dynamic contact stiffness at the interface between the rigid sphere and the semi-infinite solid. Numerical calculations show the influence of vibration frequency of the sphere, and elastic constants of the transversely isotropic solid on dynamic contact stiffness, which benefits quantitative evaluation of elastic constants and orientation of single hexagonal grains by resonance-frequency shifts of the oscillator in resonance ultrasound microscopy.展开更多
The new method proposed herc will subsitute for the traditional means of hanging weight in rigidity measurement of precision elastic elements. This system which utilizes a single chip processor as the control unit an...The new method proposed herc will subsitute for the traditional means of hanging weight in rigidity measurement of precision elastic elements. This system which utilizes a single chip processor as the control unit and the precision force and submicron displacement transducers as the measuring elements, has performed effectively the automatic measuring process from data collection to rigidity computation. Accordingly a series of measuring instrurments have been made and successfully applied to production process. Application results shows that this new measuring method is superior to the traditional means both in technique and in economy.展开更多
An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompress...An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompressible solid grain. Using Fourier-Bessel series, the problem of multiple scattering is solved by imposing continuity conditions and equilibrium conditions at the soil-pile interfaces with the translational addition theorem. A parametric analysis is conducted to investigate the influence of the permeability of poroelastic soil, separation between piles, number of piles and frequency of incident waves on screening effectiveness of the barrier, and the results are compared with those in an elastic soil medium. Computed results show that the intrinsic permeability of the soil medium displays an apparent effect on the screening of plane S waves.展开更多
In this paper, a mathematical model for Love wave propagation in a porous elastic layer under a rigid boundary resting over a poro-elastic half-space has been developed. The study shows that such a medium transmits tw...In this paper, a mathematical model for Love wave propagation in a porous elastic layer under a rigid boundary resting over a poro-elastic half-space has been developed. The study shows that such a medium transmits two types of Love waves. The first front depends on the change in volume fraction of the pores whereas the second front depends upon the modulus of rigidity of the elastic matrix of the medium and is the same as the Love wave in an elastic layer over an elastic half-space. It is observed that the first front is many times faster than the shear wave in the medium with void pores due to the change in the volume fraction of the pores and is significant.展开更多
The dynamic analysis of a generalized linear elastic body undergoing large rigid rotations is investigated. The generalized linear elastic body is described in kine- matics through translational and rotational deforma...The dynamic analysis of a generalized linear elastic body undergoing large rigid rotations is investigated. The generalized linear elastic body is described in kine- matics through translational and rotational deformations, and a modified constitutive relation for the rotational deformation is proposed between the couple stress and the curvature tensor. Thus, the balance equations of momentum and moment are used for the motion equations of the body. The floating frame of reference formulation is applied to the elastic body that conducts rotations about a fixed axis. The motion-deformation coupled model is developed in which three types of inertia forces along with their incre- ments are elucidated. The finite element governing equations for the dynamic analysis of the elastic body under large rotations are subsequently formulated with the aid of the constrained variational principle. A penalty parameter is introduced, and the rotational angles at element nodes are treated as independent variables to meet the requirement of C1 continuity. The elastic body is discretized through the isoparametric element with 8 nodes and 48 degrees-of-freedom. As an example with an application of the motion- deformation coupled model, the dynamic analysis on a rotating cantilever with two spatial layouts relative to the rotational axis is numerically implemented. Dynamic frequencies of the rotating cantilever are presented at prescribed constant spin velocities. The maximal rigid rotational velocity is extended for ensuring the applicability of the linear model. A complete set of dynamical response of the rotating cantilever in the case of spin-up maneuver is examined, it is shown that, under the ultimate rigid rotational velocities less than the maximal rigid rotational velocity, the stress strength may exceed the material strength tolerance even though the displacement and rotational angle responses are both convergent. The influence of the cantilever layouts on their responses and the multiple displacement trajectories observed in the floating frame is simultaneously investigated. The motion-deformation coupled model is surely expected to be applicable for a broad range of practical applications.展开更多
Micromechanical theory is applied to study the nonlinear elastic and viscoelastic constitutive relations of polymeric matrix filled with high rigidity solid particles. It is shown that Eshelby's method can be exte...Micromechanical theory is applied to study the nonlinear elastic and viscoelastic constitutive relations of polymeric matrix filled with high rigidity solid particles. It is shown that Eshelby's method can be extended to the case of nonlinear matrix and Eshelby's tensor still exists provided that Poisson's ratio of the nonlinear matrix assumes constant value in deforming process and the rigidity of elastic filling particles is much higher than that of the matrix. A new method for averaging process is proposed to overcome the difficulty that occured in applying the ordinary equivalent inclusion method or the seff-consistant method to nonlinear matrices. A rather simple constitutive equation is obtained finally and the strengthening effect of solid particles to composites is investigated.展开更多
BACKGROUND A total of 100 patients diagnosed with mixed hemorrhoids from October 2022 to September 2023 in our hospital were randomly divided into groups by dice rolling and compared with the efficacy of different tre...BACKGROUND A total of 100 patients diagnosed with mixed hemorrhoids from October 2022 to September 2023 in our hospital were randomly divided into groups by dice rolling and compared with the efficacy of different treatment options.AIM To analyze the clinical effect and prognosis of mixed hemorrhoids treated with polidocanol injection combined with automatic elastic thread ligation operation(RPH).METHODS A total of 100 patients with mixed hemorrhoids who visited our hospital from October 2022 to September 2023 were selected and randomly divided into the control group(n=50)and the treatment group(n=50)by rolling the dice.The procedure for prolapse and hemorrhoids(PPH)was adopted in the control group,while polidocanol foam injection+RPH was adopted in the treatment group.The therapeutic effects,operation time,wound healing time,hospital stay,pain situation(24 hours post-operative pain score,first defecation pain score),quality of life(QOL),incidence of complications(post-operative hemorrhage,edema,infection),incidence of anal stenosis 3 months post-operatively and recurrence rate 1 year post-operatively of the two groups were compared.RESULTS Compared with the control group,the total effective rate of treatment group was higher,and the difference was significant(P<0.05).The operation time/wound healing time/hospital stay in the treatment group were shorter than those in the control group(P<0.05).The pain scores at 24 hours after operation/first defecation pain score of the treatment group was significantly lower than those in the control group(P<0.05).After surgery,the QOL scores of the two groups decreased,with the treatment group having higher scores than that of the control group(P<0.05).Compared with the control group,the incidence of postoperative complications in the treatment group was lower,and the difference was significant(P<0.05);However,there was no significant difference in the incidence of postoperative bleeding between the two groups(P>0.05);There was no significant difference in the incidence of anal stenosis 3 months after operation and the recurrence rate 1 year after operation between the two groups(P>0.05).CONCLUSION For patients with mixed hemorrhoids,the therapeutic effect achieved by using polidocanol injection combined with RPH was better.The wounds of the patients healed faster,the postoperative pain was milder,QOL improved,and the incidence of complications was lower,and the short-term and long-term prognosis was good.展开更多
Conductor materials with good mechanical performance as well as high electrical and thermal conductivities are particularly important to break through the current bottle-neck limit(~ 100 T) of pulsed magnets. Here, we...Conductor materials with good mechanical performance as well as high electrical and thermal conductivities are particularly important to break through the current bottle-neck limit(~ 100 T) of pulsed magnets. Here, we perform systematic studies on the elastic properties of the Cu–6wt% Ag alloy wire, which is a promising candidate material for the new-generation pulsed magnets, by employing two independent ultrasonic techniques, i.e., resonant ultrasound spectroscopy(RUS) and ultrasound pulse-echo experiments. Our RUS measurements manifest that the elastic properties of the Cu–6wt% Ag alloy wires can be improved by an electroplastic drawing procedure as compared with the conventional cold drawing. We also take this opportunity to test the availability of our newly-built ultrasound pulse-echo facility at the Wuhan National High Magnetic Field Center(WHMFC, China), and the results suggest that the elastic performance of the electroplastically-drawn Cu–6wt% Ag alloy wire remains excellent without anomalous softening under extreme conditions,e.g., in ultra-high magnetic field up to 50 T and nitrogen or helium cryogenic liquids.展开更多
The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elast...The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elastic perfectly plastic. Analysis is carried out to study the effect of varying modulus of elasticity and sphere radius in wide range of dimensionless interference until the inception of plasticity as well as in plastic range. Results are compared with previous elastic-plastic models. It is found that materials with Young’s modulus to yield strength (E/Y) ratio less than and greater than 300 show strikingly different contact phenomena. The dependency of E on dimensionless interference at which the plastic region fully covers the surface is observed. However with different radius, finite element study exhibits similar elastic-plastic phenomena.展开更多
A contact problem for an infinitely long hollow cylinder is considered. The cylinder is compressed by an outer rigid ring with a circular profile. The material of the cylinder is linearly elastic and isotropic. The ex...A contact problem for an infinitely long hollow cylinder is considered. The cylinder is compressed by an outer rigid ring with a circular profile. The material of the cylinder is linearly elastic and isotropic. The extent of the contact region and the pressure distribution are sought. Governing equations of the elasticity theory for the axisymmetric problem in cylindrical coordinates are solved by Fourier transforms and general expressions for the displacements are obtained. Using the boundary conditions, the formulation is reduced to a singular integral equation. This equation is solved by using the Gaussian quadrature. Then the pressure distribution on the contact region is determined. Numerical results for the contact pressure and the distance characterizing the contact area are given in graphical form.展开更多
Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loa...Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.展开更多
As the stiffness of the elastic support varies with the physical-chemical erosion and mechanical friction, model catastrophe of a single degree-of-freedom(DOF) isolation system may occur. A 3-DOF four-point-elastic-su...As the stiffness of the elastic support varies with the physical-chemical erosion and mechanical friction, model catastrophe of a single degree-of-freedom(DOF) isolation system may occur. A 3-DOF four-point-elastic-support rigid plate(FERP) structure is presented to describe the catastrophic isolation system. Based on the newly-established structure, theoretical derivation for stiffness matrix calculation by free response(SMCby FR) and the method of stiffness identification by stiffness matrix disassembly(SIby SMD)are proposed. By integrating the SMCby FR and the SIby SMD and defining the stiffness assurance criterion(SAC), the procedures for stiffness identification of a FERP structure(SIFERP) are summarized. Then, a numerical example is adopted for the SIFERP validation, in which the simulated tested free response data are generated by the numerical methods, and operation for filtering noise is conducted to imitate the practical application. Results in the numerical example demonstrate the feasibility and accuracy of the developed SIFERP for stiffness identification.展开更多
In this paper, the interaction problem of a rigid line inclusion and an elastic circular inclusion has been reduced to solve a normal Cauchy-type singular integral equation. The stress intensity, factors at the ends o...In this paper, the interaction problem of a rigid line inclusion and an elastic circular inclusion has been reduced to solve a normal Cauchy-type singular integral equation. The stress intensity, factors at the ends of the rigid line inclusion and the interface stresses of the inclusions are obtained.展开更多
Previous work examined the effect of the attached stiffness matrix terms on stability of an elastic beam undergoing prescribed large overall motion. The aim of the present work is to extend the nonlinear formulations ...Previous work examined the effect of the attached stiffness matrix terms on stability of an elastic beam undergoing prescribed large overall motion. The aim of the present work is to extend the nonlinear formulations to an elastic beam with free large overall motion. Based on initial stress method, the nonlinear coupling equations of elastic beams are obtained with free large overall motion and the attached stiffness matrix is derived by solving sub-static formulation. The angular velocity and the tip deformation of the elastic pendulum are calculated. The analytical results show that the simulation results of the present model are tabled and coincide with the one-order approximate model. It is shown that the simulation results accord with energy conservation principle.展开更多
In the present paper a vibrational differential equation governing on a rigid beam on viscoelastic foundation has been investigated. The nonlinear differential equation governing on this vibrating system is solved by ...In the present paper a vibrational differential equation governing on a rigid beam on viscoelastic foundation has been investigated. The nonlinear differential equation governing on this vibrating system is solved by a simple and innovative approach, which has been called Akbari-Ganji＇s method （AGM）. AGM is a very suitable computational process and is usable for solving various nonlinear differential equations. Moreover, using AGM which solving a set of algebraic equations, complicated nonlinear equations can easily be solved without any mathematical operations. Also, the damping ratio and energy lost per cycle for three cycles have been investigated. Furthermore, comparisons have been made between the obtained results by numerical method （Runk45） and AGM. Results showed the high accuracy of AGM. The results also showed that by increasing the amount of initial amplitude of vibration （A）, the value of damping ratio will be increased, and the energy lost per cycle decreases by increasing the number of cycle. It is concluded that AGM is a reliable and precise approach for solving differential equations. On the other hand, it is better to say that AGM is able to solve linear and nonlinear differential equations directly in most of the situations. This means that the final solution can be obtained without any dimensionless procedure Therefore, AGM can be considered as a significant progress in nonlinear sciences.展开更多
基金Funded by State Railway Administration Research Project(No.2023JS007)National Natural Science Foundation of China(No.52438002)+1 种基金Research and Development Programs for Science and Technology of China Railways Corporation(No.J2023G003)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the strength and elastic modulus of mortar and concrete prepared with mechanism aggregates of the corresponding lithology,and the stress-strain curves of concrete were investigated.In this paper,a coarse aggregate and mortar matrix bonding assumption is proposed,and a prediction model for the elastic modulus of mortar is established by considering the lithology of the mechanism sand and the slurry components.An equivalent coarse aggregate elastic modulus model was established by considering factors such as coarse aggregate particle size,volume fraction,and mortar thickness between coarse aggregates.Based on the elastic modulus of the equivalent coarse aggregate and the remaining mortar,a prediction model for the elastic modulus of the two and three components of concrete in series and then in parallel was established,and the predicted values differed from the measured values within 10%.It is proposed that the coarse aggregate elastic modulus in highstrength concrete is the most critical factor affecting the elastic modulus of concrete,and as the coarse aggregate elastic modulus increases by 27.7%,the concrete elastic modulus increases by 19.5%.
基金Supported by the National Key Research Program(No.2024-1129-954-112)National Natural Science Foundation of China(No.52372033)Guangxi Science and Technology Major Program(No.AA24263054)。
文摘Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes with SiO_(2)and Al_(2)O_(3)ratios were investigated using various techniques.It is found that when SiO_(2)is replaced by Al_(2)O_(3),the Q^(4) to Q^(3) transition of silicon-oxygen network decreases while the aluminum-oxygen network increases,which result in the transformation of Si-O-Si bonds to Si-O-Al bonds and an increase in glass network connectivity even though the intermolecular bond strength decreases.The glass transition temperature(T_(g))increases continuously,while the thermal expansion coefficient increases and high-temperature viscosity first decreases and then increases.Meanwhile,the elastic modulus values increase from 93 to 102 GPa.This indicates that the elastic modulus is mainly affected by packing factor and dissociation energy,and elements with higher packing factors and dissociation energies supplant those with lower values,resulting in increased rigidity within the glass.
文摘AIM： To compare dgid proctoscope and flexible endoscope for elastic band ligation of internal hemorrhoids. METHODS： Patients between 18 and 80 years old, with chronic complaints （blood loss, pain, itching or prolapse） of internal hemorrhoids of grade 1-91, were randomized to elastic band ligation by rigid proctoscope or flexible endoscope （preloaded with 7 bands）. Patients were retreated every 6 wk until the cessation of complaints. Evaluation by three-dimensional anal endosonography was performed. RESULTS： Forty-one patients were included （median age 52.0, range 27-79 years, 20 men）. Nineteen patients were treated with a rigid proctoscope and twenty two with a flexible endoscope. Twenty-nine patients had grade I hemorrhoids, 9 patients had grade 11 hemorrhoids and 3 patients had grade 91 hemorrhoids. All patients needed a minimum of 1 treatment and a maximum of 3 treatments. A median of 4.0 bands was used in the rigid proctoscope group and a median of 6.0 bands was used in the flexible endoscope group （P 〈 0.05）. Pain after ligation tended to be more frequent in patients treated with the flexible endoscope （first treatment： 3 vs 20 patients, P 〈 0.05）. Three- dimensional endosonography showed no sphincter defects or alterations in submucosal thickness. CONCLUSION： Both techniques are easy to perform, well tolerated and have a good and fast effect. It is easier to perform more ligations with the flexible endoscope. Additional advantages of the flexible scope are the maneuverability and photographic documentation. However, treatment with the flexible endoscope might be more painful and is more expensive.
基金supported by the National Natural Science Foundation of China(No.10602053)the Research Grants from Institute of Crustal Dynamics(Nos.ZDJ2007-2 and ZDJ2007-28).
文摘Dynamic contact stiffness at the interface between a vibrating rigid sphere and a semi-infinite transversely isotropic viscoelastic solid is investigated. An oscillating force superimposed onto a static compressive force in the vertical direction excites the vibration of a rigid sphere, which causes variable contact radius and contact pressure distribution in the contact region. The assumption of a sufficiently small oscillating force yields a dynamic contact-pressure distribution of a constant contact radius, which gives dynamic contact stiffness at the interface between the rigid sphere and the semi-infinite solid. Numerical calculations show the influence of vibration frequency of the sphere, and elastic constants of the transversely isotropic solid on dynamic contact stiffness, which benefits quantitative evaluation of elastic constants and orientation of single hexagonal grains by resonance-frequency shifts of the oscillator in resonance ultrasound microscopy.
文摘The new method proposed herc will subsitute for the traditional means of hanging weight in rigidity measurement of precision elastic elements. This system which utilizes a single chip processor as the control unit and the precision force and submicron displacement transducers as the measuring elements, has performed effectively the automatic measuring process from data collection to rigidity computation. Accordingly a series of measuring instrurments have been made and successfully applied to production process. Application results shows that this new measuring method is superior to the traditional means both in technique and in economy.
基金Project (No. 50778136) supported by the National Natural Science Foundation of China
文摘An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompressible solid grain. Using Fourier-Bessel series, the problem of multiple scattering is solved by imposing continuity conditions and equilibrium conditions at the soil-pile interfaces with the translational addition theorem. A parametric analysis is conducted to investigate the influence of the permeability of poroelastic soil, separation between piles, number of piles and frequency of incident waves on screening effectiveness of the barrier, and the results are compared with those in an elastic soil medium. Computed results show that the intrinsic permeability of the soil medium displays an apparent effect on the screening of plane S waves.
文摘In this paper, a mathematical model for Love wave propagation in a porous elastic layer under a rigid boundary resting over a poro-elastic half-space has been developed. The study shows that such a medium transmits two types of Love waves. The first front depends on the change in volume fraction of the pores whereas the second front depends upon the modulus of rigidity of the elastic matrix of the medium and is the same as the Love wave in an elastic layer over an elastic half-space. It is observed that the first front is many times faster than the shear wave in the medium with void pores due to the change in the volume fraction of the pores and is significant.
基金supported by the Joint Fund of the National Natural Science Foundation of Chinathe China Academy of Engineering Physics(No.11176035)+1 种基金the National Natural Science Foundation of China(No.11072276)the National Basic Research Program of China(No.2011CB612211)
文摘The dynamic analysis of a generalized linear elastic body undergoing large rigid rotations is investigated. The generalized linear elastic body is described in kine- matics through translational and rotational deformations, and a modified constitutive relation for the rotational deformation is proposed between the couple stress and the curvature tensor. Thus, the balance equations of momentum and moment are used for the motion equations of the body. The floating frame of reference formulation is applied to the elastic body that conducts rotations about a fixed axis. The motion-deformation coupled model is developed in which three types of inertia forces along with their incre- ments are elucidated. The finite element governing equations for the dynamic analysis of the elastic body under large rotations are subsequently formulated with the aid of the constrained variational principle. A penalty parameter is introduced, and the rotational angles at element nodes are treated as independent variables to meet the requirement of C1 continuity. The elastic body is discretized through the isoparametric element with 8 nodes and 48 degrees-of-freedom. As an example with an application of the motion- deformation coupled model, the dynamic analysis on a rotating cantilever with two spatial layouts relative to the rotational axis is numerically implemented. Dynamic frequencies of the rotating cantilever are presented at prescribed constant spin velocities. The maximal rigid rotational velocity is extended for ensuring the applicability of the linear model. A complete set of dynamical response of the rotating cantilever in the case of spin-up maneuver is examined, it is shown that, under the ultimate rigid rotational velocities less than the maximal rigid rotational velocity, the stress strength may exceed the material strength tolerance even though the displacement and rotational angle responses are both convergent. The influence of the cantilever layouts on their responses and the multiple displacement trajectories observed in the floating frame is simultaneously investigated. The motion-deformation coupled model is surely expected to be applicable for a broad range of practical applications.
基金The work supported by the LNM, Institute of Mechanics, Chinese Academy of Sciencesthe National Natural Science Foundation of China
文摘Micromechanical theory is applied to study the nonlinear elastic and viscoelastic constitutive relations of polymeric matrix filled with high rigidity solid particles. It is shown that Eshelby's method can be extended to the case of nonlinear matrix and Eshelby's tensor still exists provided that Poisson's ratio of the nonlinear matrix assumes constant value in deforming process and the rigidity of elastic filling particles is much higher than that of the matrix. A new method for averaging process is proposed to overcome the difficulty that occured in applying the ordinary equivalent inclusion method or the seff-consistant method to nonlinear matrices. A rather simple constitutive equation is obtained finally and the strengthening effect of solid particles to composites is investigated.
文摘BACKGROUND A total of 100 patients diagnosed with mixed hemorrhoids from October 2022 to September 2023 in our hospital were randomly divided into groups by dice rolling and compared with the efficacy of different treatment options.AIM To analyze the clinical effect and prognosis of mixed hemorrhoids treated with polidocanol injection combined with automatic elastic thread ligation operation(RPH).METHODS A total of 100 patients with mixed hemorrhoids who visited our hospital from October 2022 to September 2023 were selected and randomly divided into the control group(n=50)and the treatment group(n=50)by rolling the dice.The procedure for prolapse and hemorrhoids(PPH)was adopted in the control group,while polidocanol foam injection+RPH was adopted in the treatment group.The therapeutic effects,operation time,wound healing time,hospital stay,pain situation(24 hours post-operative pain score,first defecation pain score),quality of life(QOL),incidence of complications(post-operative hemorrhage,edema,infection),incidence of anal stenosis 3 months post-operatively and recurrence rate 1 year post-operatively of the two groups were compared.RESULTS Compared with the control group,the total effective rate of treatment group was higher,and the difference was significant(P<0.05).The operation time/wound healing time/hospital stay in the treatment group were shorter than those in the control group(P<0.05).The pain scores at 24 hours after operation/first defecation pain score of the treatment group was significantly lower than those in the control group(P<0.05).After surgery,the QOL scores of the two groups decreased,with the treatment group having higher scores than that of the control group(P<0.05).Compared with the control group,the incidence of postoperative complications in the treatment group was lower,and the difference was significant(P<0.05);However,there was no significant difference in the incidence of postoperative bleeding between the two groups(P>0.05);There was no significant difference in the incidence of anal stenosis 3 months after operation and the recurrence rate 1 year after operation between the two groups(P>0.05).CONCLUSION For patients with mixed hemorrhoids,the therapeutic effect achieved by using polidocanol injection combined with RPH was better.The wounds of the patients healed faster,the postoperative pain was milder,QOL improved,and the incidence of complications was lower,and the short-term and long-term prognosis was good.
基金Project supported by the National Key R&D Program of China (Grant Nos. 2022YFA1602602 and 2023YFA1609600)the National Natural Science Foundation of China (Grant No. U23A20580)+3 种基金the open research fund of Songshan Lake Materials Laboratory (Grant No. 2022SLABFN27)Beijing National Laboratory for Condensed Matter Physics (Grant No. 2024BNLCMPKF004)Guangdong Basic and Applied Basic Research Foundation (Grant No. 2022B1515120020)the interdisciplinary program of Wuhan National High Magnetic Field Center at Huazhong University of Science and Technology (Grant No. WHMFC202132)。
文摘Conductor materials with good mechanical performance as well as high electrical and thermal conductivities are particularly important to break through the current bottle-neck limit(~ 100 T) of pulsed magnets. Here, we perform systematic studies on the elastic properties of the Cu–6wt% Ag alloy wire, which is a promising candidate material for the new-generation pulsed magnets, by employing two independent ultrasonic techniques, i.e., resonant ultrasound spectroscopy(RUS) and ultrasound pulse-echo experiments. Our RUS measurements manifest that the elastic properties of the Cu–6wt% Ag alloy wires can be improved by an electroplastic drawing procedure as compared with the conventional cold drawing. We also take this opportunity to test the availability of our newly-built ultrasound pulse-echo facility at the Wuhan National High Magnetic Field Center(WHMFC, China), and the results suggest that the elastic performance of the electroplastically-drawn Cu–6wt% Ag alloy wire remains excellent without anomalous softening under extreme conditions,e.g., in ultra-high magnetic field up to 50 T and nitrogen or helium cryogenic liquids.
文摘The present study considers a finite element analysis of elastic-plastic axi-symmetric hemispherical contact for a frictionless deformable sphere pressed by a rigid flat. The material of the sphere is modeled as elastic perfectly plastic. Analysis is carried out to study the effect of varying modulus of elasticity and sphere radius in wide range of dimensionless interference until the inception of plasticity as well as in plastic range. Results are compared with previous elastic-plastic models. It is found that materials with Young’s modulus to yield strength (E/Y) ratio less than and greater than 300 show strikingly different contact phenomena. The dependency of E on dimensionless interference at which the plastic region fully covers the surface is observed. However with different radius, finite element study exhibits similar elastic-plastic phenomena.
文摘A contact problem for an infinitely long hollow cylinder is considered. The cylinder is compressed by an outer rigid ring with a circular profile. The material of the cylinder is linearly elastic and isotropic. The extent of the contact region and the pressure distribution are sought. Governing equations of the elasticity theory for the axisymmetric problem in cylindrical coordinates are solved by Fourier transforms and general expressions for the displacements are obtained. Using the boundary conditions, the formulation is reduced to a singular integral equation. This equation is solved by using the Gaussian quadrature. Then the pressure distribution on the contact region is determined. Numerical results for the contact pressure and the distance characterizing the contact area are given in graphical form.
基金Project(50478075) supported by the National Natural Science Foundation of ChinaProject(YBJJ0817) supported by Scientific Research Foundation of Graduate School of Southeast University
文摘Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.
基金Project(51221462)supported by the National Natural Science Foundation of ChinaProject(20120095110001)supported by the PhD Programs Foundation of Ministry of Education of ChinaProject(CXZZ13_0927)supported by Research and Innovation Project for College Graduates of Jiangsu Province,China
文摘As the stiffness of the elastic support varies with the physical-chemical erosion and mechanical friction, model catastrophe of a single degree-of-freedom(DOF) isolation system may occur. A 3-DOF four-point-elastic-support rigid plate(FERP) structure is presented to describe the catastrophic isolation system. Based on the newly-established structure, theoretical derivation for stiffness matrix calculation by free response(SMCby FR) and the method of stiffness identification by stiffness matrix disassembly(SIby SMD)are proposed. By integrating the SMCby FR and the SIby SMD and defining the stiffness assurance criterion(SAC), the procedures for stiffness identification of a FERP structure(SIFERP) are summarized. Then, a numerical example is adopted for the SIFERP validation, in which the simulated tested free response data are generated by the numerical methods, and operation for filtering noise is conducted to imitate the practical application. Results in the numerical example demonstrate the feasibility and accuracy of the developed SIFERP for stiffness identification.
文摘In this paper, the interaction problem of a rigid line inclusion and an elastic circular inclusion has been reduced to solve a normal Cauchy-type singular integral equation. The stress intensity, factors at the ends of the rigid line inclusion and the interface stresses of the inclusions are obtained.
基金supported by the National Natural Science Foundation of China (11132007)
文摘Previous work examined the effect of the attached stiffness matrix terms on stability of an elastic beam undergoing prescribed large overall motion. The aim of the present work is to extend the nonlinear formulations to an elastic beam with free large overall motion. Based on initial stress method, the nonlinear coupling equations of elastic beams are obtained with free large overall motion and the attached stiffness matrix is derived by solving sub-static formulation. The angular velocity and the tip deformation of the elastic pendulum are calculated. The analytical results show that the simulation results of the present model are tabled and coincide with the one-order approximate model. It is shown that the simulation results accord with energy conservation principle.
文摘In the present paper a vibrational differential equation governing on a rigid beam on viscoelastic foundation has been investigated. The nonlinear differential equation governing on this vibrating system is solved by a simple and innovative approach, which has been called Akbari-Ganji＇s method （AGM）. AGM is a very suitable computational process and is usable for solving various nonlinear differential equations. Moreover, using AGM which solving a set of algebraic equations, complicated nonlinear equations can easily be solved without any mathematical operations. Also, the damping ratio and energy lost per cycle for three cycles have been investigated. Furthermore, comparisons have been made between the obtained results by numerical method （Runk45） and AGM. Results showed the high accuracy of AGM. The results also showed that by increasing the amount of initial amplitude of vibration （A）, the value of damping ratio will be increased, and the energy lost per cycle decreases by increasing the number of cycle. It is concluded that AGM is a reliable and precise approach for solving differential equations. On the other hand, it is better to say that AGM is able to solve linear and nonlinear differential equations directly in most of the situations. This means that the final solution can be obtained without any dimensionless procedure Therefore, AGM can be considered as a significant progress in nonlinear sciences.
