Introduction: In humans, it has not been established that the use of elastic tourniquet (ET) during myomectomies, whose delivery times do not exceed 90 minutes, which is responsible for ischemia reperfusion (I/R) syst...Introduction: In humans, it has not been established that the use of elastic tourniquet (ET) during myomectomies, whose delivery times do not exceed 90 minutes, which is responsible for ischemia reperfusion (I/R) systemic. Objectives: To study the plasma variations of markers of I/R during myomectomies performed with ET, whose exposure time does not exceed 90 minutes. Population and methods: Plasma créatinin phosphokinase kinase (CPK) and gluthatione peroxydase (GPX) levels of patients with ET myoma (M + G +, n = 19), taken before, during and after exposure, were compared to those of women operated on myoma without tourniquet (M + G -, n = 15), carriers of unoperated myomas (M + G0, n = 20) and controls (M0G0, n = 18). The duration of exposure of the ET was determined, and perioperative variations of GPX, Ca2+, K+ and CPK between M + G + and others groups were analyzed (p Results: The average duration of exposure of the ET was 51.56 ± 14.12 [30 - 88] min. In M + G +, prior to insertion, CPK was 71.64, GPX 3.537, Ca2+ 3.000, K+ 3.934, and did not vary from those of M + G - (CPK = 59.354, GPX = 3.205, Ca2+ = 2.525, K+ = 3.788), M + G0 (CPK = 71.640, GPX = 2.759, Ca2+ = 3.004, K+ = 3.934) and M0G0 (CPK = 57.2, GPX = 2.306, Ca2+ = 2.879, K+ = 3.705). Conversely, during the posture (CPK = 95.665, GPX = 3.645, Ca2+ = 3.642, K+ = 4.757) and after the release of the ET (CPK = 135.443, GPX = 3.694, Ca2+ = 3.892, K+ = 5.322), these rates were higher among the M + G + compared to the M + G0 and M0G0, but did not differ from those of the M + G - during (CPK = 91.270, GPX = 3.413, Ca2+ = 3.068, K+ = 4.257) and after release (CPK = 137.776, GPX = 3.632, Ca2+ = 3.148, K+ = 5.075). Conclusion: The plasmatic concentration of ischemia (CPK, K+) and reperfusion (GPX, Ca2+) biomarkers does not differ between M + G + and M + G -, but is elevated relatively to controls (M0G0), but also to M + G0’s group. These results show that, for exposure times not exceeding 90 minutes, the elastic tourniquet is probably not the cause of the in展开更多
The behavior of the stress intensity factor at the tips of cracks subjected to uniaxial tension σχ^∞= p with traction-free boundary condition in half-plane elasticity is investigated. The problem is formulated into...The behavior of the stress intensity factor at the tips of cracks subjected to uniaxial tension σχ^∞= p with traction-free boundary condition in half-plane elasticity is investigated. The problem is formulated into singular integral equations with the distribution dislocation function as unknown. In the formulation, we make used of a modified complex potential. Based on the appropriate quadrature formulas together with a suitable choice of collocation points, the singular integral equations are reduced to a system of linear equations for the unknown coefficients. Numerical examples show that the values of the stress intensity factor are influenced by the distance from the cracks to the boundary of the half-plane and the configuration of the cracks.展开更多
The objective of this study is to determine the time-dependent strengths of salt mine pillars in the Maha Sarakham formation,northeast of Thailand.Strain rate-controlled triaxial compression tests have been performed ...The objective of this study is to determine the time-dependent strengths of salt mine pillars in the Maha Sarakham formation,northeast of Thailand.Strain rate-controlled triaxial compression tests have been performed on salt specimens under confining pressures from 0 MPa to 12 MPa.The strain rates are from 10^-7 s^-1 to 10^-4 s^-1.The axial stresses and lateral strains are monitored through the strain-softening region.The results indicate that the strengths and elastic moduli increase exponentially with the strain rates.The power creep law parameters are calibrated with the test results,and hence allows constructing series of strain-time curves for the salt pillars under different depths and extraction ratios.The strain energy density principle is applied to develop a strength criterion for the salt pillars.Combining this criterion with the series of the strain-time curves the time-dependent strengths of the salt pillars for different extraction ratios can be predicted.展开更多
We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axi...We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles.Results of the analyses revealed significant along-trench variations in plate flexural bending:the trench relief(W0)of 1.9 to 5.1 km;trench-axis vertical loading(V0)of-0.5×10^12 to 2.2×10^12 N/m;axial bending moment(M0)of 0.1×10^17 to 2.2×10^17 N;effective elastic plate thickness seaward of the outer-rise region(Te^M)of 20 to 65 km,trench-ward of the outer-rise(Te^M)of 11 to 33 km,and the transition distance(Xr)of 20 to 95 km.The Horizon Deep,the second greatest trench depth in the world,has the greatest trench relief(W0 of 5.1km)and trench-axis loading(V0 of 2.2×10^12N/m);these values are only slightly smaller than that of the Challenger Deep(W0 of 5.7km and V0 of 2.9×10^12N/m)and similar to that of the Sirena Deep(W0 of 5.2 km and V0 of 2.0×10^12 N/m)of the Mariana Trench,suggesting that these deeps are linked to great flexural bending of the subducting plates.Analyses using three independent methods,i.e.,the/inversion,the flexural curvature/yield strength envelope analysis,and the elasto-plastic bending model with normal faults,all yielded similar average Te reduction of 28%-36% and average Te reduction area of 1195-1402 km^2 near the trench axis.The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes.Comparisons of the Manila,Philippine,Tonga-Kermadec,Japan,and Mariana Trenches revealed that the average values Te^M of Te^M and both in general increase with the subducting plate age.展开更多
To improve on the mechanical properties of polymers in general, the concept of hybrid composites was developed by using two or more different reinforcements in the same matrix, or by using two or more different sizes ...To improve on the mechanical properties of polymers in general, the concept of hybrid composites was developed by using two or more different reinforcements in the same matrix, or by using two or more different sizes of the same reinforcement (auto-hybrid composites). In this case, most of the literature results showed that the resulting elastic modulus can be well approximated by the simple rule of mixture (linear additive law) from the tensile modulus of each reinforcement used alone. But is some cases, a positive deviation from this linear approximation was reported up to a point where an optimum composition can give a modulus above the value of both reinforcements used separately. In this work, a simple model is presented to show that positive deviations are possible and the optimum reinforcement ratio is around 25/75 in terms of the lowest/highest reinforcing particle. The model is also compared with literature data where good qualitative agreements are obtained as a first approximation.展开更多
We define two nonlinear shell models whereby the deformation of an elastic shell with small thickness minimizes ad hoc functionals over sets of admissible deformations of Kirchhoff-Love type. We establish that both mo...We define two nonlinear shell models whereby the deformation of an elastic shell with small thickness minimizes ad hoc functionals over sets of admissible deformations of Kirchhoff-Love type. We establish that both models are close in a specific sense to the well-known nonlinear shell model of W.T. Koiter and that one of them has a solution, by contrast with Koiter’s model for which such an existence theorem is yet to be proven.展开更多
A series of self-designed and woven compression stockings were used in this pressure comparison experiment. In order to compare the differences of the garment pressure values exerted by the compression stockings with ...A series of self-designed and woven compression stockings were used in this pressure comparison experiment. In order to compare the differences of the garment pressure values exerted by the compression stockings with different structure parameters among three methods. The experiments were carried out with Flexi force sensors. The pressure value of nine pairs of compression stockings on five subjects and the model leg was collected, and the tensile force of the every section of these stockings was collected to calculate the pressure according to Laplace’s equation. The data analysis results show that the pressure values of the compression stockings obtained by comparing the three methods have great differences in various testing methods. There is a significant correlation between processing parameters and stitch density(SD). The pressure design of the compression stockings should be based on the actual wearing of the pressure.展开更多
This paper presents the design and manufacture process of a wheel-less,modular snake robot with series elastic actuators to reliably measure motor torque signal and investigate the effectiveness of active stiffness co...This paper presents the design and manufacture process of a wheel-less,modular snake robot with series elastic actuators to reliably measure motor torque signal and investigate the effectiveness of active stiffness control for achieving adaptive snake-like locomotion.A polyurethane based elastic element to be attached between the motor and the links at each joint was designed and manufactured using water jet cutter,which makes the final design easier to develop and more cost-effective,compared to existing snake robots with torque measurement capabilities.The reliability of such torque measurement mechanism was examined using simulated dynamical model of pedal wave motion,which proves the efficacy of the design.A distributed control system was also designed,which with the help of an admittance controller,enables active control of the joint stiffness to achieve adaptive snake robot pedal wave locomotion to climb over obstacles,which unlike existing methods does not require prior information about the location of the obstacle.The effectiveness of the proposed controller in comparison to open-loop control strategy was verified by the number of experiments.The results show the capability of the robot to successfully climb over obstacles with the height of more than 55%of the diameter of the snake robot modules.展开更多
Recently, the non-centrosymmetric WC-type materials(i.e., MoP, ZrTe, TaN, etc) have attracted extensive interest due to the discovery of their topological properties.By means of the first-principles calculations, here...Recently, the non-centrosymmetric WC-type materials(i.e., MoP, ZrTe, TaN, etc) have attracted extensive interest due to the discovery of their topological properties.By means of the first-principles calculations, here we have investigated the structural, thermodynamic, elastic, and electronic properties of the WC-type MX compounds(TiS, TiSe, TiTe, ZrS, ZrSe,ZrTe, HfS, HfSe, and HfTe).Among these nine compounds, five of them(TiS, ZrS, ZrSe0.9, ZrTe, and Hf0.92 Se) have been experimentally synthesized to crystallize in the WC-type structure and other four members have never been reported.Our calculations demonstrated that they are all structurally, thermodynamically, and dynamically stable, indicating that all of them should be possibly synthesized.We have also derived their elastic constants of single crystalline and their bulk and shear moduli in terms of the R.Hill approximations.Furthermore, in similarity to ZrTe, all these compounds have been theoretically derived to be topological semimetals.Whereas TiS is unique because of the coexistence of the Dirac nodal lines(DNLs) and sixfold degenerate nodal points(sixfold DNPs), the other eight members are revealed to exhibit coexisted Weyl nodes(WPs) and triply degenerate nodal points(TDNPs).Their electronic and topological properties have been further discussed.展开更多
Soft materials with semi-linear strain energy function can be used as smart transformation media to manipulate elastic waves via finite pre-deformation. However, the intrinsic cons train ts involved in such materials ...Soft materials with semi-linear strain energy function can be used as smart transformation media to manipulate elastic waves via finite pre-deformation. However, the intrinsic cons train ts involved in such materials limit the shapes of t ransformation devices to very sim - pie cases. In this work, combining theoretical and numerical analyses, we report an approach of achieving the in-plane elastodynamic cloak with arbitrary shape. We demonstrate that with the appropriate out-of^plane st retch applied on the semi-linear material, cloaking effec t can be achieved for both P- and SV-waves in the symmetrie plane of a 3D domain, and the performance of the cloak with arbitrary cross section can be guaranteed for relatively small in-plane rot at ion. In addition, we propose an empirical formula to predic t the deformation limit of the cloaks with semi-linear materials. This work may stimulate the experimental research on softmatter- based transformation devices. Potential applications can be anticipated in nondestructive testing, structure impact protection, biomedical imaging and soft robotics.展开更多
Elastic scattering angular distributions and total reaction cross-sections of 7,10,11,12Be projectiles are predicted by the systematic 9Be global phenomenological optical model potential for target mass numbers rangin...Elastic scattering angular distributions and total reaction cross-sections of 7,10,11,12Be projectiles are predicted by the systematic 9Be global phenomenological optical model potential for target mass numbers ranging from 24 to 209.These predictions provide a detailed analysis by their comparison with the available experimental data.Furthermore,these elastic scattering observables are also predicted for some targets out of the mass number range.The results are in reasonable agreement with the existing experimental data,and they are presented in this study.展开更多
Two austenitic Mn steels(Fe-17Mn and Fe-17Mn-3Al(wt%,so as the follows))were subjected to thermomechanical processing(TMP)consisting of forging followed by solutionization and hot rolling.The rolled samples were annea...Two austenitic Mn steels(Fe-17Mn and Fe-17Mn-3Al(wt%,so as the follows))were subjected to thermomechanical processing(TMP)consisting of forging followed by solutionization and hot rolling.The rolled samples were annealed at 650 and 800℃to relieve the internal stress and to induce recrystallization.The application of TMP and heat treatment to the Fe-17Mn/Fe-17Mn-3Al steels refined the austenite grain size from 169μm in the as-solutionized state to 9–13μm,resulting in a substantial increase in hardness from HV 213 to HV 410 for the Fe-17Mn steel and from HV 210 to HV 387 for the Fe-17Mn-3Al steel.The elastic modulus values,as evaluated by the nanoindentation technique,increased from(175±11)to(220±12)GPa and from(163±15)to(205±13)GPa for the Fe-17Mn and Fe-17Mn-3Al steels,respectively.The impact energy of the thermomechanically processed austenitic Mn steels was lower than that of the steels in their as-solutionized state.The addition of Al to the Fe-17Mn steel decreased the hardness and elastic modulus but increased the impact energy.展开更多
An elastic and plastic mechanical model is proposed to characterize the normal contact of rough surfaces. The contact process is considered as three separated contact regimes, i.e., the fully elastic, mixed elastic一p...An elastic and plastic mechanical model is proposed to characterize the normal contact of rough surfaces. The contact process is considered as three separated contact regimes, i.e., the fully elastic, mixed elastic一plastic and fully plastic ones. The Hertzian elastic contact solutions and the classical fully plastic contact model of Abbott and Fires tone are used to model the contact behaviors of fully elastically deformed asperities and fully plastically deformed ones, respectively. For the mixed elastic-plastic regime, an improved Hermit interpolation method is applied to enforce the continuity and smoothness at the critical contact interference, and to decrease the interpolation waving effect by transforming the physical quantities of contact load into logarithmic coordinates. The contac t model of rough surfaces is formula ted by using the Greenwood and Williamson^ statistics analysis. Comparisons with the CEB, ZMC and KE models are then performed to examine the effects of plasticity index and mean separation. Agreeing well with the ZMC model, our results show that the total contact load of rough surfaces decreases with the increase in mean separation, and the difference between the prediction results of elastic models and the plastic ones also decreases, indicating that the contact behaviors mainly dominated by plastically deformed asperities have been changed to be controlled by elastically deformed ones. Larger plasticity index represents more plastically deformed asperities, inducing normal contact behaviors mainly dominated by plastic solutions.展开更多
The three main components of the media layer of the aorta are elastic fibers,collagen fibers and smooth muscle cells(SMC).[1]This layer’s elastic properties are major determinants of its biomechanics in health and di...The three main components of the media layer of the aorta are elastic fibers,collagen fibers and smooth muscle cells(SMC).[1]This layer’s elastic properties are major determinants of its biomechanics in health and disease states.[2,3]Age-related changes in such elastic properties are associated with altered hemodynamic parameters,such as systolic hypertension,[4,5]and end-organ damage,[6,7]and are thought to result from changes of its main components.展开更多
In continuation of our recent report on molybdates [Appl. Phys. A 124, 44(2018)], the structural, electronic, elastic,and optical properties of ZMoO3(Z = Ba and Sr) molybdates are investigated under pressure(10 GPa–5...In continuation of our recent report on molybdates [Appl. Phys. A 124, 44(2018)], the structural, electronic, elastic,and optical properties of ZMoO3(Z = Ba and Sr) molybdates are investigated under pressure(10 GPa–50 GPa) comprehensively by deploying the density functional theory. Our investigations show that the studied compounds exhibit stable cubic phase with metallic attributes. The thermodynamic parameters such as enthalpy of formation, Debye, and melting temperatures of the compounds are observed to increase with pressure. While the Gr¨uninsen parameter and the coefficient of super-plastic deformation decrease as the pressure increases. Mechanical properties elucidate an increase in measured values of hardness, bulk, shear, and young’s moduli with pressure. Our results suggest that the studied compounds are useful in high pressure optoelectronic devices. The optical properties of BaMoO3(BMO) and SrMoO3(SMO) are computed for the radiation of up to 35 eV. The present compounds show beneficial optical applications in the anti-reflection coating,lenses, and the high avoiding solar heating applications in the variant applied pressure.展开更多
Within the framework of the Navier–Stokes equations,the Weissenberg effect of turbulence is investigated.We begin with our investigation on the elastic effect of homogeneous turbulent shear flow.First,in the sense of...Within the framework of the Navier–Stokes equations,the Weissenberg effect of turbulence is investigated.We begin with our investigation on the elastic effect of homogeneous turbulent shear flow.First,in the sense of Truesdell(Physics of Fluids,1964)on the natural time of materials,we derive the natural time of turbulence,and use it together with the natural viscosity of turbulence derived in the article of Huang et al.(Journal of Turbulence,2003)to define the natural Weissenberg number of turbulence as a measure of the elastic effect of homogeneous turbulence.Second,we define a primary Weissenberg number of turbulence,which in laminar flow reduces to the Weissenberg number widely applied in rheology to characterize the elasticity of visco-elastic fluids.Our analysis based on the experimental results of Tavoularis and Karnik(Journal of Fluid Mechanics,1989)indicates that the larger is the Weissenberg number of turbulence,the more elastic becomes the turbulent flow concerned.Furthermore,we put forth a general Weissenberg number of turbulence,which includes the primary Weissenberg number of turbulence as a special case,to measure the overall elastic effects of turbulence.Besides,it is shown that the general Weissenberg number can also be used to characterize the elastic effects of non-Newtonian fluids in laminar flow.展开更多
文摘Introduction: In humans, it has not been established that the use of elastic tourniquet (ET) during myomectomies, whose delivery times do not exceed 90 minutes, which is responsible for ischemia reperfusion (I/R) systemic. Objectives: To study the plasma variations of markers of I/R during myomectomies performed with ET, whose exposure time does not exceed 90 minutes. Population and methods: Plasma créatinin phosphokinase kinase (CPK) and gluthatione peroxydase (GPX) levels of patients with ET myoma (M + G +, n = 19), taken before, during and after exposure, were compared to those of women operated on myoma without tourniquet (M + G -, n = 15), carriers of unoperated myomas (M + G0, n = 20) and controls (M0G0, n = 18). The duration of exposure of the ET was determined, and perioperative variations of GPX, Ca2+, K+ and CPK between M + G + and others groups were analyzed (p Results: The average duration of exposure of the ET was 51.56 ± 14.12 [30 - 88] min. In M + G +, prior to insertion, CPK was 71.64, GPX 3.537, Ca2+ 3.000, K+ 3.934, and did not vary from those of M + G - (CPK = 59.354, GPX = 3.205, Ca2+ = 2.525, K+ = 3.788), M + G0 (CPK = 71.640, GPX = 2.759, Ca2+ = 3.004, K+ = 3.934) and M0G0 (CPK = 57.2, GPX = 2.306, Ca2+ = 2.879, K+ = 3.705). Conversely, during the posture (CPK = 95.665, GPX = 3.645, Ca2+ = 3.642, K+ = 4.757) and after the release of the ET (CPK = 135.443, GPX = 3.694, Ca2+ = 3.892, K+ = 5.322), these rates were higher among the M + G + compared to the M + G0 and M0G0, but did not differ from those of the M + G - during (CPK = 91.270, GPX = 3.413, Ca2+ = 3.068, K+ = 4.257) and after release (CPK = 137.776, GPX = 3.632, Ca2+ = 3.148, K+ = 5.075). Conclusion: The plasmatic concentration of ischemia (CPK, K+) and reperfusion (GPX, Ca2+) biomarkers does not differ between M + G + and M + G -, but is elevated relatively to controls (M0G0), but also to M + G0’s group. These results show that, for exposure times not exceeding 90 minutes, the elastic tourniquet is probably not the cause of the in
基金University Putra Malaysia for Putra Grant(9442300).
文摘The behavior of the stress intensity factor at the tips of cracks subjected to uniaxial tension σχ^∞= p with traction-free boundary condition in half-plane elasticity is investigated. The problem is formulated into singular integral equations with the distribution dislocation function as unknown. In the formulation, we make used of a modified complex potential. Based on the appropriate quadrature formulas together with a suitable choice of collocation points, the singular integral equations are reduced to a system of linear equations for the unknown coefficients. Numerical examples show that the values of the stress intensity factor are influenced by the distance from the cracks to the boundary of the half-plane and the configuration of the cracks.
基金funded by Suranaree University of Technology and by the Higher Education Promotion and National Research University of Thailand.
文摘The objective of this study is to determine the time-dependent strengths of salt mine pillars in the Maha Sarakham formation,northeast of Thailand.Strain rate-controlled triaxial compression tests have been performed on salt specimens under confining pressures from 0 MPa to 12 MPa.The strain rates are from 10^-7 s^-1 to 10^-4 s^-1.The axial stresses and lateral strains are monitored through the strain-softening region.The results indicate that the strengths and elastic moduli increase exponentially with the strain rates.The power creep law parameters are calibrated with the test results,and hence allows constructing series of strain-time curves for the salt pillars under different depths and extraction ratios.The strain energy density principle is applied to develop a strength criterion for the salt pillars.Combining this criterion with the series of the strain-time curves the time-dependent strengths of the salt pillars for different extraction ratios can be predicted.
基金The National Natural Science Foundation of China under contract Nos 41976064,91958211,41890813,91858207,91628301,U1606401,41976066 and 41706056the Programs of the Chinese Academy of Sciences under contract Nos Y4SL021001,QYZDY-SSW-DQC005 and 133244KYSB20180029+1 种基金the National Key Research and Development Program of China under contract Nos 2018YFC0309800 and 2018YFC0310100the China Ocean Mineral Resources R&D Association under contract No.DY135-S2-1-04.
文摘We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench.Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles.Results of the analyses revealed significant along-trench variations in plate flexural bending:the trench relief(W0)of 1.9 to 5.1 km;trench-axis vertical loading(V0)of-0.5×10^12 to 2.2×10^12 N/m;axial bending moment(M0)of 0.1×10^17 to 2.2×10^17 N;effective elastic plate thickness seaward of the outer-rise region(Te^M)of 20 to 65 km,trench-ward of the outer-rise(Te^M)of 11 to 33 km,and the transition distance(Xr)of 20 to 95 km.The Horizon Deep,the second greatest trench depth in the world,has the greatest trench relief(W0 of 5.1km)and trench-axis loading(V0 of 2.2×10^12N/m);these values are only slightly smaller than that of the Challenger Deep(W0 of 5.7km and V0 of 2.9×10^12N/m)and similar to that of the Sirena Deep(W0 of 5.2 km and V0 of 2.0×10^12 N/m)of the Mariana Trench,suggesting that these deeps are linked to great flexural bending of the subducting plates.Analyses using three independent methods,i.e.,the/inversion,the flexural curvature/yield strength envelope analysis,and the elasto-plastic bending model with normal faults,all yielded similar average Te reduction of 28%-36% and average Te reduction area of 1195-1402 km^2 near the trench axis.The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes.Comparisons of the Manila,Philippine,Tonga-Kermadec,Japan,and Mariana Trenches revealed that the average values Te^M of Te^M and both in general increase with the subducting plate age.
文摘To improve on the mechanical properties of polymers in general, the concept of hybrid composites was developed by using two or more different reinforcements in the same matrix, or by using two or more different sizes of the same reinforcement (auto-hybrid composites). In this case, most of the literature results showed that the resulting elastic modulus can be well approximated by the simple rule of mixture (linear additive law) from the tensile modulus of each reinforcement used alone. But is some cases, a positive deviation from this linear approximation was reported up to a point where an optimum composition can give a modulus above the value of both reinforcements used separately. In this work, a simple model is presented to show that positive deviations are possible and the optimum reinforcement ratio is around 25/75 in terms of the lowest/highest reinforcing particle. The model is also compared with literature data where good qualitative agreements are obtained as a first approximation.
文摘We define two nonlinear shell models whereby the deformation of an elastic shell with small thickness minimizes ad hoc functionals over sets of admissible deformations of Kirchhoff-Love type. We establish that both models are close in a specific sense to the well-known nonlinear shell model of W.T. Koiter and that one of them has a solution, by contrast with Koiter’s model for which such an existence theorem is yet to be proven.
基金National Key Research and Development Program of China(No.2018YFC2000900).
文摘A series of self-designed and woven compression stockings were used in this pressure comparison experiment. In order to compare the differences of the garment pressure values exerted by the compression stockings with different structure parameters among three methods. The experiments were carried out with Flexi force sensors. The pressure value of nine pairs of compression stockings on five subjects and the model leg was collected, and the tensile force of the every section of these stockings was collected to calculate the pressure according to Laplace’s equation. The data analysis results show that the pressure values of the compression stockings obtained by comparing the three methods have great differences in various testing methods. There is a significant correlation between processing parameters and stitch density(SD). The pressure design of the compression stockings should be based on the actual wearing of the pressure.
文摘This paper presents the design and manufacture process of a wheel-less,modular snake robot with series elastic actuators to reliably measure motor torque signal and investigate the effectiveness of active stiffness control for achieving adaptive snake-like locomotion.A polyurethane based elastic element to be attached between the motor and the links at each joint was designed and manufactured using water jet cutter,which makes the final design easier to develop and more cost-effective,compared to existing snake robots with torque measurement capabilities.The reliability of such torque measurement mechanism was examined using simulated dynamical model of pedal wave motion,which proves the efficacy of the design.A distributed control system was also designed,which with the help of an admittance controller,enables active control of the joint stiffness to achieve adaptive snake robot pedal wave locomotion to climb over obstacles,which unlike existing methods does not require prior information about the location of the obstacle.The effectiveness of the proposed controller in comparison to open-loop control strategy was verified by the number of experiments.The results show the capability of the robot to successfully climb over obstacles with the height of more than 55%of the diameter of the snake robot modules.
基金Project supported by the National Natural Science Foundation of China (Grant No. 51671193)All calculations have been performed on the high-performance computational cluster in the Shenyang National University Science and Technology Park.
文摘Recently, the non-centrosymmetric WC-type materials(i.e., MoP, ZrTe, TaN, etc) have attracted extensive interest due to the discovery of their topological properties.By means of the first-principles calculations, here we have investigated the structural, thermodynamic, elastic, and electronic properties of the WC-type MX compounds(TiS, TiSe, TiTe, ZrS, ZrSe,ZrTe, HfS, HfSe, and HfTe).Among these nine compounds, five of them(TiS, ZrS, ZrSe0.9, ZrTe, and Hf0.92 Se) have been experimentally synthesized to crystallize in the WC-type structure and other four members have never been reported.Our calculations demonstrated that they are all structurally, thermodynamically, and dynamically stable, indicating that all of them should be possibly synthesized.We have also derived their elastic constants of single crystalline and their bulk and shear moduli in terms of the R.Hill approximations.Furthermore, in similarity to ZrTe, all these compounds have been theoretically derived to be topological semimetals.Whereas TiS is unique because of the coexistence of the Dirac nodal lines(DNLs) and sixfold degenerate nodal points(sixfold DNPs), the other eight members are revealed to exhibit coexisted Weyl nodes(WPs) and triply degenerate nodal points(TDNPs).Their electronic and topological properties have been further discussed.
基金National Natural Science Foundation of China (Grant Nos. 11472044, 11521062, 11602294, 11632003)the Chinese Universities Scientific Fund (Grant No. 2019TC134).
文摘Soft materials with semi-linear strain energy function can be used as smart transformation media to manipulate elastic waves via finite pre-deformation. However, the intrinsic cons train ts involved in such materials limit the shapes of t ransformation devices to very sim - pie cases. In this work, combining theoretical and numerical analyses, we report an approach of achieving the in-plane elastodynamic cloak with arbitrary shape. We demonstrate that with the appropriate out-of^plane st retch applied on the semi-linear material, cloaking effec t can be achieved for both P- and SV-waves in the symmetrie plane of a 3D domain, and the performance of the cloak with arbitrary cross section can be guaranteed for relatively small in-plane rot at ion. In addition, we propose an empirical formula to predic t the deformation limit of the cloaks with semi-linear materials. This work may stimulate the experimental research on softmatter- based transformation devices. Potential applications can be anticipated in nondestructive testing, structure impact protection, biomedical imaging and soft robotics.
基金Supported by the National Natural Science Foundation of China(11405099,11575291)this work is also a part of IAEA Coordinated Research Projects(CRPs)on Recommended Input Parameter Library(RIPL)for Fission Cross Section Calculations(20464).
文摘Elastic scattering angular distributions and total reaction cross-sections of 7,10,11,12Be projectiles are predicted by the systematic 9Be global phenomenological optical model potential for target mass numbers ranging from 24 to 209.These predictions provide a detailed analysis by their comparison with the available experimental data.Furthermore,these elastic scattering observables are also predicted for some targets out of the mass number range.The results are in reasonable agreement with the existing experimental data,and they are presented in this study.
文摘Two austenitic Mn steels(Fe-17Mn and Fe-17Mn-3Al(wt%,so as the follows))were subjected to thermomechanical processing(TMP)consisting of forging followed by solutionization and hot rolling.The rolled samples were annealed at 650 and 800℃to relieve the internal stress and to induce recrystallization.The application of TMP and heat treatment to the Fe-17Mn/Fe-17Mn-3Al steels refined the austenite grain size from 169μm in the as-solutionized state to 9–13μm,resulting in a substantial increase in hardness from HV 213 to HV 410 for the Fe-17Mn steel and from HV 210 to HV 387 for the Fe-17Mn-3Al steel.The elastic modulus values,as evaluated by the nanoindentation technique,increased from(175±11)to(220±12)GPa and from(163±15)to(205±13)GPa for the Fe-17Mn and Fe-17Mn-3Al steels,respectively.The impact energy of the thermomechanically processed austenitic Mn steels was lower than that of the steels in their as-solutionized state.The addition of Al to the Fe-17Mn steel decreased the hardness and elastic modulus but increased the impact energy.
基金the Science Challenge Project (Grant No. TZ2018007)The authors also thank the National Key Research and Development Program of China (Grant No. 2016YFB0201004)+1 种基金the Defense Industrial Technology Development Program (Grant No. C1520110002)the Presidential Foundation of CAEP (Grant No. YZ2015011) for providing the financial support for this project.
文摘An elastic and plastic mechanical model is proposed to characterize the normal contact of rough surfaces. The contact process is considered as three separated contact regimes, i.e., the fully elastic, mixed elastic一plastic and fully plastic ones. The Hertzian elastic contact solutions and the classical fully plastic contact model of Abbott and Fires tone are used to model the contact behaviors of fully elastically deformed asperities and fully plastically deformed ones, respectively. For the mixed elastic-plastic regime, an improved Hermit interpolation method is applied to enforce the continuity and smoothness at the critical contact interference, and to decrease the interpolation waving effect by transforming the physical quantities of contact load into logarithmic coordinates. The contac t model of rough surfaces is formula ted by using the Greenwood and Williamson^ statistics analysis. Comparisons with the CEB, ZMC and KE models are then performed to examine the effects of plasticity index and mean separation. Agreeing well with the ZMC model, our results show that the total contact load of rough surfaces decreases with the increase in mean separation, and the difference between the prediction results of elastic models and the plastic ones also decreases, indicating that the contact behaviors mainly dominated by plastically deformed asperities have been changed to be controlled by elastically deformed ones. Larger plasticity index represents more plastically deformed asperities, inducing normal contact behaviors mainly dominated by plastic solutions.
基金the Animal Facility Services of Angelina Caron Hospital and by the Biological Sciences Sector of Federal University of Paraná.
文摘The three main components of the media layer of the aorta are elastic fibers,collagen fibers and smooth muscle cells(SMC).[1]This layer’s elastic properties are major determinants of its biomechanics in health and disease states.[2,3]Age-related changes in such elastic properties are associated with altered hemodynamic parameters,such as systolic hypertension,[4,5]and end-organ damage,[6,7]and are thought to result from changes of its main components.
文摘In continuation of our recent report on molybdates [Appl. Phys. A 124, 44(2018)], the structural, electronic, elastic,and optical properties of ZMoO3(Z = Ba and Sr) molybdates are investigated under pressure(10 GPa–50 GPa) comprehensively by deploying the density functional theory. Our investigations show that the studied compounds exhibit stable cubic phase with metallic attributes. The thermodynamic parameters such as enthalpy of formation, Debye, and melting temperatures of the compounds are observed to increase with pressure. While the Gr¨uninsen parameter and the coefficient of super-plastic deformation decrease as the pressure increases. Mechanical properties elucidate an increase in measured values of hardness, bulk, shear, and young’s moduli with pressure. Our results suggest that the studied compounds are useful in high pressure optoelectronic devices. The optical properties of BaMoO3(BMO) and SrMoO3(SMO) are computed for the radiation of up to 35 eV. The present compounds show beneficial optical applications in the anti-reflection coating,lenses, and the high avoiding solar heating applications in the variant applied pressure.
文摘Within the framework of the Navier–Stokes equations,the Weissenberg effect of turbulence is investigated.We begin with our investigation on the elastic effect of homogeneous turbulent shear flow.First,in the sense of Truesdell(Physics of Fluids,1964)on the natural time of materials,we derive the natural time of turbulence,and use it together with the natural viscosity of turbulence derived in the article of Huang et al.(Journal of Turbulence,2003)to define the natural Weissenberg number of turbulence as a measure of the elastic effect of homogeneous turbulence.Second,we define a primary Weissenberg number of turbulence,which in laminar flow reduces to the Weissenberg number widely applied in rheology to characterize the elasticity of visco-elastic fluids.Our analysis based on the experimental results of Tavoularis and Karnik(Journal of Fluid Mechanics,1989)indicates that the larger is the Weissenberg number of turbulence,the more elastic becomes the turbulent flow concerned.Furthermore,we put forth a general Weissenberg number of turbulence,which includes the primary Weissenberg number of turbulence as a special case,to measure the overall elastic effects of turbulence.Besides,it is shown that the general Weissenberg number can also be used to characterize the elastic effects of non-Newtonian fluids in laminar flow.