The near crack line analysis method was used to investigate a crack loaded by a pair of point shear forces in an infinite plate in an elastic-perfectly plastic solid. The analytical solution was obtained, that is the ...The near crack line analysis method was used to investigate a crack loaded by a pair of point shear forces in an infinite plate in an elastic-perfectly plastic solid. The analytical solution was obtained, that is the elastic-plastic fields near crack line and law that the length of the plastic zone along the crack line is varied with external loads. The results are sufficiently precise near the crack line and are not confined by small scale yielding conditions.展开更多
BACKGROUND Few systematic comparative studies of the different methods of physical elastography of the spleen are currently available.AIM To compare point shear wave and two-dimensional elastography of the spleen cons...BACKGROUND Few systematic comparative studies of the different methods of physical elastography of the spleen are currently available.AIM To compare point shear wave and two-dimensional elastography of the spleen considering the anatomical location(upper,hilar,and lower pole).METHODS As part of a prospective clinical study,healthy volunteers were examined for splenic elasticity using four different ultrasound devices between May 2015 and April 2017.The devices used for point shear wave elastography were from Siemens(S 3000)and Philips(Epiq 7),and those used for two-dimensional shear wave elastography were from GE(Logiq E9)and Toshiba(Aplio 500).In addition,two different software versions(5.0 and 6.0)were evaluated for the Toshiba ultrasound device(Aplio 500).The study consisted of three arms:A,B,and C.RESULTS In study arm A,200 subjects were evaluated(78 males and 122 females,mean age 27.9±8.1 years).In study arm B,113 subjects were evaluated(38 men and 75 women,mean age 26.0±6.3 years).In study arm C,44 subjects were enrolled.A significant correlation of the shear wave velocities at the upper third of the spleen(r=0.33088,P<0.0001)was demonstrated only for the Philips Epiq 7 device compared to the Siemens Acuson S 3000.In comparisons of the other ultrasound devices(GE,Siemens,Toshiba),no comparable results could be obtained for any anatomical position of the spleen.The influencing factors age,gender,and body mass index did not show a clear correlation with the measured shear wave velocities.CONCLUSION The absolute values of the shear wave elastography measurements of the spleen and the two different elastography methods are not comparable between different manufacturers or models.展开更多
The near crack line analysis method was used to investigate a centric crack loaded by two pairs of point shear forces in a finite plate, and the analytical solution was obtained. The solution includes the unit normal ...The near crack line analysis method was used to investigate a centric crack loaded by two pairs of point shear forces in a finite plate, and the analytical solution was obtained. The solution includes the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near the crack line, the variations of the length of the plastic zone along the crack line with an external load, and the bearing capacity of a finite plate with a centric crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of small scale yielding theory have not been made and no other assumptions are taken.展开更多
An analytical solution of the governing equations of the interacting shear flows for unsteady oblique stagnation point flow is obtained. It has the same form as that of the exact solution obtained from the complete NS...An analytical solution of the governing equations of the interacting shear flows for unsteady oblique stagnation point flow is obtained. It has the same form as that of the exact solution obtained from the complete NS equations and physical analysis and relevant discussions are then presented.展开更多
Asymmetric plate impact experiments are conducted on LY12 aluminium alloy in a pressure range of 85-131 GPa. The longitudinal sound speeds axe obtained from the time-resolved particle speed profiles of the specimen me...Asymmetric plate impact experiments are conducted on LY12 aluminium alloy in a pressure range of 85-131 GPa. The longitudinal sound speeds axe obtained from the time-resolved particle speed profiles of the specimen measured with Velocity Interferometer System for Any Reflector （VISAR） technique, and they are shown to be good agreement with our previously reported data of this alloy in a pressure range of 20-70 GPa, and also with those of 2024 aluminium reported by McQueen. Using all of the longitudinal speeds and the corresponding bulk speeds calculated from the Gruneisen equation of state （EOS）, shear moduli of LY12 aluminium alloy are obtained. A comparison of the shear moduli in the solid phase region with those estimated from the Steinberg model demonstrate that the latter are systematically lower than the measurements. By re-analysing the pressure effect on the shear modulus, a modified equation is proposed, in which the pressure term of P/η^1/3 in the Steinberg model is replaced by a linear term. Good agreement between experiments and the modified equation is obtained, which implies that the shear modulus of LY12 aluminium varies linearly both with pressure and with temperature throughout the whole solid phase region. On the other hand, shear modulus of aluminium in a solid-liquid mixed phrase region decreases gradually and smoothly, a feature that is very different from the drastic dropping at the melting point under static conditions.展开更多
A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the ba...A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the basic motion law of the shear ram,combined its structural and operating parameters comprehensively,a model for solving the stress on the cutting edge was established corresponding to three stages(i.e.,shear point contact,cutting and penetrating the drill pipe)according to the wedge stress theory.Then,based on the novel shear ram,the numerical simulation and indoor shear experiment were carried out on CT90 coiled tubing to understand the variation laws of ram stress and shear point stress in the shearing process.And the following research results were obtained.First,when the shear point doesn't contact with the CT90 coiled tubing,the stress at the V-shaped angular center of the ram is the largest,and that at the shear point is extremely small.Second,when the shear point just touches the CT90 coiled tubing,the phenomenon of stress concentration occurs in the vicinity of the shear point of the ram cutting edge.Third,when the shear point cuts into the CT90 coiled tubing,the stress on the shear point and on both wedge edges is the largest,reaching the strength limit of the ram(1050MPa).Fourth,when the shear point enters the annulus after penetrating the CT90 coiled tubing,the ram stress on both sides of the junction between the cutting edge chamfer and the vertical plane is the largest.Fifth,After the CT90 coiled tubing is cut,crack damage occurs in the vicinity of the shear point of the ram cutting edge.In conclusion,the research results can better reflect the stress state of the ram cutting edge and its interaction with the drill pipe in the shearing process,and can provide an important reference for the design,manufacturing and the correct field application of shear rams.展开更多
The objective of the present study is to explore the relation between the near-wall vortices and the shear stress on the wall in two-dimensional channel flows. A direct numerical simulation of an incompressible two-di...The objective of the present study is to explore the relation between the near-wall vortices and the shear stress on the wall in two-dimensional channel flows. A direct numerical simulation of an incompressible two-dimensional turbulent channel flow is performed with spectral method and the results are used to examine the relation between wall shear stress and near-wall vortices. The two-point correlation results indicate that the wall shear stress is associated with the vortices near the wall and the maximum correlation-value location of the near-wall vortices is obtained. The analysis of the instantaneous diagrams of fluctuation velocity vectors provides a further expression for the above conclusions. The results of this research provide a useful supplement for the control of turbulent boundary layers.展开更多
Pour point depressants （PPD） are used to improve the theology of waxy crude. The affect of various factors on the theological properties, and the thermal characteristics of waxy crude treated by PPD have been invest...Pour point depressants （PPD） are used to improve the theology of waxy crude. The affect of various factors on the theological properties, and the thermal characteristics of waxy crude treated by PPD have been investigated. The conclusions are as follows： PPD can reduce the pour point and abnormal point of waxy crude, broaden the temperature range of Newtonian fluid of waxy crude, and lower greatly the viscosity of non-Newtonian fluid of waxy crude. The influence of reheating and high-rate shear on the effect of PPD mainly depends on their temperature. When the reheating temperature is more than the abnormal point of crude by 10℃, the reheating process has little effect on the modification effect of PPD. However, when the reheating temperature is below the abnormal point of crude, the reheating process will reduce the modification effect of PPD. When temperature is above the abnormal point of crude, the high-rate shear has little effect on the modification effect of PPD. At a temperature range where a lot of wax is precipitating, high-rate shear will greatly reduce the modification effect of PPD.展开更多
The relationship between wall shear stresses and near-wall streamwise vortices is investigated via a direct numerical simulation(DNS) of turbulent flows over a wavy boundary with traveling-wave motion. The results ind...The relationship between wall shear stresses and near-wall streamwise vortices is investigated via a direct numerical simulation(DNS) of turbulent flows over a wavy boundary with traveling-wave motion. The results indicate that the wall shear stresses are still closely related to the near-wall streamwise vortices in the presence of a wave. The wave age and wave phase significantly affect the distribution of a two-point correlation coefficient between the wall shear stresses and streamwise vorticity. For the slow wave case of c/Um = 0.14, the correlation is attenuated above the leeward side while the distribution of correlation function is more elongated and also exhibits a larger vertical extent above the crest. With respect to the fast wave case of c/U_m=1.4, the distribution of the correlation function is recovered in a manner similar to that in the flat-wall case. In this case, the maximum correlation coefficient exhibits only slight differences at different wave phases while the vertical distribution of the correlation function depends on the wave phase.展开更多
In this study, a point source mathematical model is proposed to describe the diffusion of adenosine di-phosphate (ADP) from either damaged red blood cell (RBC) or activated platelet. The convective diffusion equation ...In this study, a point source mathematical model is proposed to describe the diffusion of adenosine di-phosphate (ADP) from either damaged red blood cell (RBC) or activated platelet. The convective diffusion equation is reduced to describe the suggested problem. The final differential equation is solved using Laplace transforms and ADP concentration profiles around the source are obtained. Thrombi of 5 to 20 μm<sup>3</sup> containing platelets and a range of red blood cells (RBCs) (0%, 25%, 50%, 75%, 100%) concentrations are used to apply the model. Reported ADP concentrations in the literature are used and its dynamic release from the point source is calculated. Results suggest that RBC chemical contribution to platelet aggregation in the bulk is much less than that of platelet (almost) negligible. However, the physical effect of RBCs is dominant in the bulk through augmentation of released ADP and platelets diffusivities. Moreover, the chemical contribution reported in previous studies is suggested to be as a result of interaction of RBC with the surface under the influence of shear stresses in the boundary region.展开更多
This paper focuses on the high intensity filaments (dye patches) embedded in dye plumes in a wall-bounded shear flow, to investigate the shear effect on the dye patch distribution. Motivated by the widely concerned in...This paper focuses on the high intensity filaments (dye patches) embedded in dye plumes in a wall-bounded shear flow, to investigate the shear effect on the dye patch distribution. Motivated by the widely concerned inverse estimation of the source location, we try extracting useful information to know the source location from down-stream dye patches. Accordingly, we changed the dye injection location at different distances from the wall and made observations at different downstream (diffusion) distances from the source. The orientation angle and roundness of dye patches were concerned to examine the shear effect and dye patch characteristics. To capture the dye plume images, a planar laser induced fluorescence (PLIF) technique was used. The orientation and roundness of each dye patch were calculated by least-square fitting. The statistics of both the orientation angle and the roundness were compared with those in homogeneous turbulent cases to reveal the shear effect. Different from uniformly-orientated dye patches in the homogeneous flow, larger occurrence probabilities with positive orientation angles of dye patches are observed in wall-bounded shear flow, in particular, when the injection location is near the wall. As with information extraction for the inverse estimation of source location, it is found that the orientation distribution of dye patches is independent of the diffusion distance, but related with the injection location from the wall. While for the homogeneous flow cases, a strong dependence on the diffusion distance is observed in the orientation distribution profiles. As for the roundness, similar aspects are found regarding the dependencies on the injection location in shear flow and on diffusion distance in homogeneous flow.展开更多
In vitro cell loading experiments are used to investigate stimulation of strain to cellular proliferation. As the flowing conditions of culture fluid in loading systems has been little known, strictly people can not d...In vitro cell loading experiments are used to investigate stimulation of strain to cellular proliferation. As the flowing conditions of culture fluid in loading systems has been little known, strictly people can not detect the influence of strain to cellular proliferation exactly because shear flow can enhance cell proliferation either. Based on the working principle and cyclic loading parameters, we simplify Navier-Stokes equation to describe the flow of culture fluid on substrates of uniaxial and equi-biaxial flat tensile loading systems and four point bending system. With approximate solutions, the distributions of velocity field and wall shear flow to cells are gained. Results show: shear flows are zero in the middle (or fixed point or line) of substrate for all systems, and they get larger proportionally to distance from middle and substrate elongate; the shear flow on the substrate of four point bending system is much greater than those of others. This shear flow in four point bending system, confirmed by Owan, I., et al with OPN mRNA increase in their experiment, could cause more influence to osteoblast-like cells than that caused by strain. We estimate the average magnitude of shear stress in Owan’s device, the results are consistent with other experimental data about shear flow. In conclusion our study makes it possible to differentiate the influence of strain on cellular proliferation to that of shear flow in loading experiments with the devices mentioned above quantitatively.展开更多
研究薄壁型钢-轻质混凝土组合剪力墙的承压性能,旨在充分发挥这两种材料的优势,提高剪力墙结构的整体性能。利用薄壁型钢轻质混凝土两种材料制备组合剪力墙构件,并分别采用腹板拼接、高强螺杆对拉连接和L件连接3种装配方式完成材料试件...研究薄壁型钢-轻质混凝土组合剪力墙的承压性能,旨在充分发挥这两种材料的优势,提高剪力墙结构的整体性能。利用薄壁型钢轻质混凝土两种材料制备组合剪力墙构件,并分别采用腹板拼接、高强螺杆对拉连接和L件连接3种装配方式完成材料试件设计,得到3种类型试件(J-1、J-2、J-3)。并通过冷弯薄壁型钢骨架和轻质混凝土填充增强墙体的承载能力和稳定性。对每一试件的承压性能进行测试,试验结果表明:在3种试件中,J-3试件的承压性能最优,其峰值荷载最高可达到344.63 k N,且在开裂点荷载方面同样表现出较高的承压能力,其次是J-2试件,而J-1试件的承压性能相对较差;同时其刚度退化幅度较小,耗能能力较强,在不同荷载等级下均能够保持较小的侧向变形情况。因此,L件这一材料连接方式在提高装配式建筑薄壁型钢-轻质混凝土组合剪力墙的承压性能方面具有一定优势。展开更多
基金National Natural Science Foundation ofChina( No.5 98790 12 )
文摘The near crack line analysis method was used to investigate a crack loaded by a pair of point shear forces in an infinite plate in an elastic-perfectly plastic solid. The analytical solution was obtained, that is the elastic-plastic fields near crack line and law that the length of the plastic zone along the crack line is varied with external loads. The results are sufficiently precise near the crack line and are not confined by small scale yielding conditions.
文摘BACKGROUND Few systematic comparative studies of the different methods of physical elastography of the spleen are currently available.AIM To compare point shear wave and two-dimensional elastography of the spleen considering the anatomical location(upper,hilar,and lower pole).METHODS As part of a prospective clinical study,healthy volunteers were examined for splenic elasticity using four different ultrasound devices between May 2015 and April 2017.The devices used for point shear wave elastography were from Siemens(S 3000)and Philips(Epiq 7),and those used for two-dimensional shear wave elastography were from GE(Logiq E9)and Toshiba(Aplio 500).In addition,two different software versions(5.0 and 6.0)were evaluated for the Toshiba ultrasound device(Aplio 500).The study consisted of three arms:A,B,and C.RESULTS In study arm A,200 subjects were evaluated(78 males and 122 females,mean age 27.9±8.1 years).In study arm B,113 subjects were evaluated(38 men and 75 women,mean age 26.0±6.3 years).In study arm C,44 subjects were enrolled.A significant correlation of the shear wave velocities at the upper third of the spleen(r=0.33088,P<0.0001)was demonstrated only for the Philips Epiq 7 device compared to the Siemens Acuson S 3000.In comparisons of the other ultrasound devices(GE,Siemens,Toshiba),no comparable results could be obtained for any anatomical position of the spleen.The influencing factors age,gender,and body mass index did not show a clear correlation with the measured shear wave velocities.CONCLUSION The absolute values of the shear wave elastography measurements of the spleen and the two different elastography methods are not comparable between different manufacturers or models.
基金Key Project(2004BA901A02) supported by the Ministry of Science and Technology of China
文摘The near crack line analysis method was used to investigate a centric crack loaded by two pairs of point shear forces in a finite plate, and the analytical solution was obtained. The solution includes the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near the crack line, the variations of the length of the plastic zone along the crack line with an external load, and the bearing capacity of a finite plate with a centric crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of small scale yielding theory have not been made and no other assumptions are taken.
文摘An analytical solution of the governing equations of the interacting shear flows for unsteady oblique stagnation point flow is obtained. It has the same form as that of the exact solution obtained from the complete NS equations and physical analysis and relevant discussions are then presented.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10232040 and 10672149)the foundation of Laboratory for Shock Wave and Detonation Physics Research, China Academy of Engineering Physics (Grant No 9140C6702020603)
文摘Asymmetric plate impact experiments are conducted on LY12 aluminium alloy in a pressure range of 85-131 GPa. The longitudinal sound speeds axe obtained from the time-resolved particle speed profiles of the specimen measured with Velocity Interferometer System for Any Reflector （VISAR） technique, and they are shown to be good agreement with our previously reported data of this alloy in a pressure range of 20-70 GPa, and also with those of 2024 aluminium reported by McQueen. Using all of the longitudinal speeds and the corresponding bulk speeds calculated from the Gruneisen equation of state （EOS）, shear moduli of LY12 aluminium alloy are obtained. A comparison of the shear moduli in the solid phase region with those estimated from the Steinberg model demonstrate that the latter are systematically lower than the measurements. By re-analysing the pressure effect on the shear modulus, a modified equation is proposed, in which the pressure term of P/η^1/3 in the Steinberg model is replaced by a linear term. Good agreement between experiments and the modified equation is obtained, which implies that the shear modulus of LY12 aluminium varies linearly both with pressure and with temperature throughout the whole solid phase region. On the other hand, shear modulus of aluminium in a solid-liquid mixed phrase region decreases gradually and smoothly, a feature that is very different from the drastic dropping at the melting point under static conditions.
基金supported by the National Major Special Project of Oil and Gas(No.2016ZX05042003-001,2016ZX05066004-002)the Scientific and Technological Research Guidance Project(No.MTKJ2016-279)by the China National Coal Association,and the Jiangsu Provincial Postdoctoral Scientific and Technological Funding Program(No.1601053C).
文摘A shear ram is of great significance to ensuring the safe operation of oil/gas well drilling and production,but the mechanical properties of the ram itself in the shearing process are rarely researched.Based on the basic motion law of the shear ram,combined its structural and operating parameters comprehensively,a model for solving the stress on the cutting edge was established corresponding to three stages(i.e.,shear point contact,cutting and penetrating the drill pipe)according to the wedge stress theory.Then,based on the novel shear ram,the numerical simulation and indoor shear experiment were carried out on CT90 coiled tubing to understand the variation laws of ram stress and shear point stress in the shearing process.And the following research results were obtained.First,when the shear point doesn't contact with the CT90 coiled tubing,the stress at the V-shaped angular center of the ram is the largest,and that at the shear point is extremely small.Second,when the shear point just touches the CT90 coiled tubing,the phenomenon of stress concentration occurs in the vicinity of the shear point of the ram cutting edge.Third,when the shear point cuts into the CT90 coiled tubing,the stress on the shear point and on both wedge edges is the largest,reaching the strength limit of the ram(1050MPa).Fourth,when the shear point enters the annulus after penetrating the CT90 coiled tubing,the ram stress on both sides of the junction between the cutting edge chamfer and the vertical plane is the largest.Fifth,After the CT90 coiled tubing is cut,crack damage occurs in the vicinity of the shear point of the ram cutting edge.In conclusion,the research results can better reflect the stress state of the ram cutting edge and its interaction with the drill pipe in the shearing process,and can provide an important reference for the design,manufacturing and the correct field application of shear rams.
文摘The objective of the present study is to explore the relation between the near-wall vortices and the shear stress on the wall in two-dimensional channel flows. A direct numerical simulation of an incompressible two-dimensional turbulent channel flow is performed with spectral method and the results are used to examine the relation between wall shear stress and near-wall vortices. The two-point correlation results indicate that the wall shear stress is associated with the vortices near the wall and the maximum correlation-value location of the near-wall vortices is obtained. The analysis of the instantaneous diagrams of fluctuation velocity vectors provides a further expression for the above conclusions. The results of this research provide a useful supplement for the control of turbulent boundary layers.
文摘Pour point depressants （PPD） are used to improve the theology of waxy crude. The affect of various factors on the theological properties, and the thermal characteristics of waxy crude treated by PPD have been investigated. The conclusions are as follows： PPD can reduce the pour point and abnormal point of waxy crude, broaden the temperature range of Newtonian fluid of waxy crude, and lower greatly the viscosity of non-Newtonian fluid of waxy crude. The influence of reheating and high-rate shear on the effect of PPD mainly depends on their temperature. When the reheating temperature is more than the abnormal point of crude by 10℃, the reheating process has little effect on the modification effect of PPD. However, when the reheating temperature is below the abnormal point of crude, the reheating process will reduce the modification effect of PPD. When temperature is above the abnormal point of crude, the high-rate shear has little effect on the modification effect of PPD. At a temperature range where a lot of wax is precipitating, high-rate shear will greatly reduce the modification effect of PPD.
基金Project supported by the the National Natural Science Foundation of China(Nos.91752205 and 11772172)the "13th Five-Year Plan" Equipment Development Common Technology Pre-research(No.41407020501)
文摘The relationship between wall shear stresses and near-wall streamwise vortices is investigated via a direct numerical simulation(DNS) of turbulent flows over a wavy boundary with traveling-wave motion. The results indicate that the wall shear stresses are still closely related to the near-wall streamwise vortices in the presence of a wave. The wave age and wave phase significantly affect the distribution of a two-point correlation coefficient between the wall shear stresses and streamwise vorticity. For the slow wave case of c/Um = 0.14, the correlation is attenuated above the leeward side while the distribution of correlation function is more elongated and also exhibits a larger vertical extent above the crest. With respect to the fast wave case of c/U_m=1.4, the distribution of the correlation function is recovered in a manner similar to that in the flat-wall case. In this case, the maximum correlation coefficient exhibits only slight differences at different wave phases while the vertical distribution of the correlation function depends on the wave phase.
文摘In this study, a point source mathematical model is proposed to describe the diffusion of adenosine di-phosphate (ADP) from either damaged red blood cell (RBC) or activated platelet. The convective diffusion equation is reduced to describe the suggested problem. The final differential equation is solved using Laplace transforms and ADP concentration profiles around the source are obtained. Thrombi of 5 to 20 μm<sup>3</sup> containing platelets and a range of red blood cells (RBCs) (0%, 25%, 50%, 75%, 100%) concentrations are used to apply the model. Reported ADP concentrations in the literature are used and its dynamic release from the point source is calculated. Results suggest that RBC chemical contribution to platelet aggregation in the bulk is much less than that of platelet (almost) negligible. However, the physical effect of RBCs is dominant in the bulk through augmentation of released ADP and platelets diffusivities. Moreover, the chemical contribution reported in previous studies is suggested to be as a result of interaction of RBC with the surface under the influence of shear stresses in the boundary region.
文摘This paper focuses on the high intensity filaments (dye patches) embedded in dye plumes in a wall-bounded shear flow, to investigate the shear effect on the dye patch distribution. Motivated by the widely concerned inverse estimation of the source location, we try extracting useful information to know the source location from down-stream dye patches. Accordingly, we changed the dye injection location at different distances from the wall and made observations at different downstream (diffusion) distances from the source. The orientation angle and roundness of dye patches were concerned to examine the shear effect and dye patch characteristics. To capture the dye plume images, a planar laser induced fluorescence (PLIF) technique was used. The orientation and roundness of each dye patch were calculated by least-square fitting. The statistics of both the orientation angle and the roundness were compared with those in homogeneous turbulent cases to reveal the shear effect. Different from uniformly-orientated dye patches in the homogeneous flow, larger occurrence probabilities with positive orientation angles of dye patches are observed in wall-bounded shear flow, in particular, when the injection location is near the wall. As with information extraction for the inverse estimation of source location, it is found that the orientation distribution of dye patches is independent of the diffusion distance, but related with the injection location from the wall. While for the homogeneous flow cases, a strong dependence on the diffusion distance is observed in the orientation distribution profiles. As for the roundness, similar aspects are found regarding the dependencies on the injection location in shear flow and on diffusion distance in homogeneous flow.
文摘In vitro cell loading experiments are used to investigate stimulation of strain to cellular proliferation. As the flowing conditions of culture fluid in loading systems has been little known, strictly people can not detect the influence of strain to cellular proliferation exactly because shear flow can enhance cell proliferation either. Based on the working principle and cyclic loading parameters, we simplify Navier-Stokes equation to describe the flow of culture fluid on substrates of uniaxial and equi-biaxial flat tensile loading systems and four point bending system. With approximate solutions, the distributions of velocity field and wall shear flow to cells are gained. Results show: shear flows are zero in the middle (or fixed point or line) of substrate for all systems, and they get larger proportionally to distance from middle and substrate elongate; the shear flow on the substrate of four point bending system is much greater than those of others. This shear flow in four point bending system, confirmed by Owan, I., et al with OPN mRNA increase in their experiment, could cause more influence to osteoblast-like cells than that caused by strain. We estimate the average magnitude of shear stress in Owan’s device, the results are consistent with other experimental data about shear flow. In conclusion our study makes it possible to differentiate the influence of strain on cellular proliferation to that of shear flow in loading experiments with the devices mentioned above quantitatively.
文摘研究薄壁型钢-轻质混凝土组合剪力墙的承压性能,旨在充分发挥这两种材料的优势,提高剪力墙结构的整体性能。利用薄壁型钢轻质混凝土两种材料制备组合剪力墙构件,并分别采用腹板拼接、高强螺杆对拉连接和L件连接3种装配方式完成材料试件设计,得到3种类型试件(J-1、J-2、J-3)。并通过冷弯薄壁型钢骨架和轻质混凝土填充增强墙体的承载能力和稳定性。对每一试件的承压性能进行测试,试验结果表明:在3种试件中,J-3试件的承压性能最优,其峰值荷载最高可达到344.63 k N,且在开裂点荷载方面同样表现出较高的承压能力,其次是J-2试件,而J-1试件的承压性能相对较差;同时其刚度退化幅度较小,耗能能力较强,在不同荷载等级下均能够保持较小的侧向变形情况。因此,L件这一材料连接方式在提高装配式建筑薄壁型钢-轻质混凝土组合剪力墙的承压性能方面具有一定优势。
