Background:Stretching has wide appeal,but there seems to exist some mismatch between its purported applications and what the evidence shows.There is compelling evidence for some stretching applications,but for others,...Background:Stretching has wide appeal,but there seems to exist some mismatch between its purported applications and what the evidence shows.There is compelling evidence for some stretching applications,but for others,the evidence seems heterogeneous or unsupportive.The discrepancies even affect some systematic reviews,possibly due to heterogeneous eligibility criteria and search strategies.This consensus paper seeks to unify the divergent findings on stretching and its implications for both athletic performance and clinical practices by delivering evidence-based recommendations.Methods:A panel of 20 experts with a blend of practical experience and scholarly knowledge was assembled.The panel meticulously reviewed existing systematic reviews,defined key terminologies(e.g.,consensus definitions for different stretching modes),and crafted guidelines using a Delphi consensus approach(minimum required agreement:80%).The analysis focused on 8 topics,including stretching's acute and chronic(long-term)effects on range of motion,strength performance,muscle hypertrophy,stiffness,injury prevention,muscle recovery,posture correction,and cardiovascular health.Results:There was consensus that chronic and acute stretching(a)improves range of motion(although alternatives exist)and(b)reduces muscle stiffness(which may not always be desirable);the panel also agreed that chronic stretching(c)may promote vascular health,but more research is warranted.In contrast,consensus was found that stretch training does not(a)contribute substantively to muscle growth,(b)serve as an allencompassing injury prevention strategy,(c)improve posture,or(d)acutely enhance post-exercise recovery.Conclusion:These recommendations provide guidance for athletes and practitioners,highlighting research gaps that should be addressed to more comprehensively understand the full scope of stretching effects.展开更多
This study involved the development of an interpretable prediction framework to access the stretch formability of AZ31 magnesium alloys through the combination of the extreme gradient boosting(XGBoost)model with the s...This study involved the development of an interpretable prediction framework to access the stretch formability of AZ31 magnesium alloys through the combination of the extreme gradient boosting(XGBoost)model with the sparrow search algorithm(SSA).Eleven features were extracted from the microstructures(e.g.,grain size(GS),maximum pole intensity(I_(max)),degree of texture dispersion(μ),radius of maximum pole position(r),and angle of maximum pole position(A)),mechanical properties(e.g.,tensile yield strength(TYS),ultimate tensile strength(UTS),elongation-to-failure(EL),and strength difference(∆S))and test conditions(e.g.,sheet thickness(t)and punch speed(v))in the data collected from the literature and experiments.Pearson correlation coefficient and exhaustive screening methods identified ten key features(not including UTS)as the final inputs,and they enhanced the prediction accuracy of Index Erichsen(IE),which served as the model’s output.The newly developed SSA-XGBoost model exhibited an improved prediction performance,with a goodness of fit(R^(2))of 0.91 compared with traditional machine learning models.A new dataset(four samples)was prepared to validate the reliability and generalization capacity of this model,and below 5%errors were observed between predicted and experimental IE values.Based on this result,the quantitative relationship between the key features and IE values was established via Shapley additive explanation method and XGBoost feature importance analysis.I_(max),TYS,EL,r,GS,andΔS showed a crucial influence on the IE of 10 input features.This work offers a reliable and accurate tool for the prediction of the stretch formability of AZ31 magnesium alloys and provides insights into the development of high-formable magnesium alloys.展开更多
Tissue expansion is a widely utilized technique in plastic and reconstructive surgery;however,the biological mechanisms underlying the skin response remain poorly understood.We propose that tissue fluidity,the transit...Tissue expansion is a widely utilized technique in plastic and reconstructive surgery;however,the biological mechanisms underlying the skin response remain poorly understood.We propose that tissue fluidity,the transition of tissue from a solid-like state to a fluid-like state,plays a pivotal role in enabling the reorganization of the epidermal structure and cellular spatial order,which is essential for effective tissue expansion.Drawing parallels between fluidity in materials science and biological systems,we suggest that the fluid-like behavior in the skin may be critical for mechanical adaptability.Understanding the influence of tissue fluidity may open pathways for modulating this process,potentially enhancing tissue expansion efficiency,reducing procedural duration,and improving clinical outcomes.This perspective highlights the importance of investigating the biological dynamics of tissue fluidity and exploring the potential for targeted manipulation of fluidity-related pathways to optimize tissue expansion.Such advancements could profoundly affect regenerative and reconstructive surgical practices.展开更多
Maximizing the efficiency of thermal engineering equipment involves minimizing entropy generation,which arises from irreversible processes.This study examines thermal transport and entropy generation in viscous flow o...Maximizing the efficiency of thermal engineering equipment involves minimizing entropy generation,which arises from irreversible processes.This study examines thermal transport and entropy generation in viscous flow over a radially stretching disk,incorporating the effects of magnetohydrodynamics(MHD),viscous dissipation,Joule heating,and radiation.Similarity transformations are used to obtain dimensionless nonlinear ordinary differential equations(ODEs)from the governing coupled partial differential equations(PDEs).The converted equations are then solved by using the BVP4C solver in MATLAB.To validate the findings,the results are compared with previously published studies under fixed parameter conditions,demonstrating strong agreement.Various key parameters are analyzed graphically to assess their impact on velocity and temperature distributions.Additionally,Bejan number and entropy generation variations are presented for different physical parameters.The injection parameter(S<0)increases the heat transfer rate,while the suction parameter(S>0)reduces it,exhibiting similar effects on fluid velocity.The magnetic parameter(M)effectively decreases entropy generation within the range of approximately 0≤η≤0.6.Beyond this interval,its influence diminishes as entropy generation values converge,with similar trends observed for the Bejan number.Furthermore,increased thermal radiation intensity is identified as a critical factor in enhancing entropy generation and the Bejan number.展开更多
In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers ...In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers from small spherulites to a mixture of transcrystalline and enlarged spherulites,and finally to pure transcrystalline;meanwhile,the lamellae making up the transcrystalline or spherulite were fragmented into smaller ones;spatial scan by wide-angle X-ray scattering(WAXS)and small angle X-ray scattering(SAXS)revealed that the crystallinity is increased from 25.3%to 30.1%and the crystal orientation was enhanced greatly,but the lamellae orientation was quite weak.The rise of enlarged spherulites or a mixture of transcrystalline and spherulites can also be found in UHMWPE stretched at 140 and 148℃,whereas absent in UHMWPE stretched at 30℃.In situ WAXS/SAXS measurements suggest that during stretching at 30℃,the crystallinity is reduced drastically,and a few voids are formed as the size increases from 50 nm to 210 nm;during stretching at 120℃,the crystallinity is reduced only slightly,and the kinking of lamellae occurs at large Hencky strain;during stretching at 140 and 148℃,an increase in crystallinity with stretching strain can be found,and the lamellae are also kinked.Taking the microstructure and morphology transition into consideration,a mesoscale morphology transition mode is proposed,in the stretching-induced crystallization the fragmented lamellae can be rearranged into new supra-structures such as spherulite or transcrystalline during hot stretching.展开更多
The study of stretching surfaces has garnered significant attention due to its importance in a wide range of industrial and engineering functions,including the drawing of wires and plastic films,shrink film production...The study of stretching surfaces has garnered significant attention due to its importance in a wide range of industrial and engineering functions,including the drawing of wires and plastic films,shrink film production,polymer sheet extrusion,the manufacturing of glass fibers,and the manufacturing of polyester heat-shrink tubing.This research incorporates a Darcy-Forchheimer porous medium to account for the effects of porosity.The governing equations are transformed into a boundary value problem and solved semi-analytically using the Taylor wavelet method.The effects of various parameters are depicted through graphical analyses.The results show that for both converging and diverging stretching surfaces,an increase in the porosity parameter causes a decrease in the velocity field.Additionally,higher Reynolds numbers enhance inertial effects,leading to more pronounced velocity fluctuations.Stretching causes a consistent drop in velocity toward the center and an increase close to the walls in both types of channels,indicating that the volume percentage of nanoparticles influences the heat distribution.Notably,stretching induces a marked temperature drop at the channel's center.展开更多
Background:Mechanical ventilation(MV)provides life support for patients with severe respiratory distress but can simultaneously cause ventilator-induced lung injury(VILI).However,due to a poor understanding of its mec...Background:Mechanical ventilation(MV)provides life support for patients with severe respiratory distress but can simultaneously cause ventilator-induced lung injury(VILI).However,due to a poor understanding of its mechanism,there is still a lack of effective remedies for the often-deadly VILI.Recent studies indicate that the stretch associated with MV can enhance the secretion of extracellular vesicles(EVs)and induce endoplasmic reticulum(ER)stress in airway smoothmuscle cells(ASMCs),both of which can contribute to VILI.But whetherMVassociated stretch enhances the secretion of EVs via ER stress in ASMCs as an underlying mechanism of VILI remains unknown.Methods:In this study,we exposed cultured human ASMCs to stretch(13%strain)and mouse models to MV at tidal volume(18 mL/kg).Subsequently,the amount of secreted EVs in the culture medium of ASMCs and the bronchoalveolar lavage fluid(BALF)of mousemodels was quantitatively evaluated by ultracentrifugation,transmission electron microscopy,Western blot,flow cytometry,and nanoparticle tracking analysis.The cultured ASMCs and the lung tissues of mouse models were assessed for expression of biomarkers of EVs(cluster of differentiation antigen 63,CD63),ER stress(heat shock protein family A member 5,HSPA5),and EVs regulating molecule Rab27a by immunofluorescence microscopy,immunohistochemistry(IHC)and enzyme-linked immunosorbent assay(ELISA),respectively.MicroRNAs(miRNAs)in EVs from ASMCs were measured with miRNA whole genome sequencing(miRNA-Seq).Results:We found that stretch enhanced EV secretion from cultured ASMCs.In addition,the cultured ASMCs and the mouse models were either or not pretreated with ER stress inhibitor(tauroursodeoxycholic acid,TUDCA)/EV secretion inhibitor(GW4869)prior to stretch or MV.We found that MV-associated stretch enhanced the expression of CD63,HSPA5,and Rab27a in cultured ASMCs and BALF/lung tissues of mousemodels,which could all be attenuated with TUDCA/GW4869 pretreatment.miRNA-Seq data show that differentially expressed miRNAs in EVsmainlymodulate gene transcription.Furthermore,the EVs fromcultured ASMCs under stretch tended to enhance detachment and expression of inflammatory cytokines,i.e.,transforming growth factor-β1(TGF-β1),interleukin-10(IL-10)in cultured airway epithelial cells.The expression of TGF-β1 and IL-10 in BALF of the mouse models also increased in response to MV,which was attenuated together with partial improvement of lung injury by pretreatment with TUDCA,GW4869/Rab27a siRNAs.Conclusion:Taken together,our data indicate thatMV-associated stretch can enhance the secretion of EVs from ASMCs via ER stress signaling to mediate airway inflammation and VILI,which provides new insight for further exploring EVs for the diagnosis and treatment of VILI.展开更多
This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity a...This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity and thermal slip boundary conditions are also examined.The considered hybrid nano-fluid contains silver(Ag)and iron oxide(Fe_(3)O_(4))nanoparticles dispersed in the water to prepare the Ag-Fe_(3)O_(4)/water-based hybrid nanofluid.The requisite posited partial differential equations model is converted to ordinary differential equations using similarity transformations.For a numerical solution,the shooting method in Maple is employed.Moreover,the duality in solutions is achieved for both cases of the disk(stretching(λ>0)and shrinking(λ<0)).At the same time,a unique solution is observed for λ=0.No solution is found for them at λ<λ_(c),whereas the solutions are split at the λ=λ_(c).Besides,the value of the λ_(c) is dependent on the φ_(hnf).Meanwhile,the values of f″(0)and -θ′(0)intensified with increasing φ_(hnf).Stability analysis has been applied using bvp4c in MATLAB software due to a dual solution.Furthermore,analysis shows that the first solution is stable and feasible physically.For the slip parameters,an increase in the velocity slip parameter increases the velocity and shear stress profiles while increasing the temperature profile in the first solutions.While the rise in thermal slip parameter reduces the temperature profile nanoparticle volume fractions increase it.展开更多
Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ult...Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ultrathin films induced by stretching was investigated using transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The results show that stretching can enhance the crystallinity and increase the average thickness of the lamellae.A fullα-βphase transition can be achieved for PVDF ultrathin films of 20.6%βphase stretched to aλ(stretching ratio)of 1.5,while fewαphases still exist for ultrathin films of 35.0%βphase,together with bent and tilted lamellae.Compared to thicker PVDF films undergoing stretching-inducedα-βphase transition,the higherα-βphase transition efficiency of the PVDF ultrathin films can be attributed to the parallel aligned lamellar structure.Moreover,a higherβ-phase content can suppressα-βphase transition because of the stress concentration effect ofβ-phase.Ultimately,these results provide valuable insights into the stretching-inducedα-βphase transition of PVDF ultrathin films.展开更多
The high thermal conductivity of the nanoparticles in hybrid nanofluids results in enhanced thermal conductivity associated with their base fluids.Enhanced heat transfer is a result of this high thermal conductivity,w...The high thermal conductivity of the nanoparticles in hybrid nanofluids results in enhanced thermal conductivity associated with their base fluids.Enhanced heat transfer is a result of this high thermal conductivity,which has significant applications in heat exchangers and engineering devices.To optimize heat transfer,a liquid film of Cu and TiO_(2)hybrid nanofluid behind a stretching sheet in a variable porous medium is being considered due to its importance.The nature of the fluid is considered time-dependent and the thickness of the liquid film is measured variable adjustable with the variable porous space and favorable for the uniform flow of the liquid film.The solution of the problem is acquired using the homotopy analysis method HAM,and the artificial neural network ANN is applied to obtain detailed information in the form of error estimation and validations using the fitting curve analysis.HAM data is utilized to train the ANN in this study,which uses Cu and TiO_(2)hybrid nanofluids in a variable porous space for unsteady thin film flow,and it is used to train the ANN.The results indicate that Cu and TiO_(2)play a greater role in boosting the rate.展开更多
The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and ...The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and strain distributions in the cross-section of the part. With the proposed model, analysis of the effect of pre-stretch force and post-stretch force on springback angle shows that springback decreases as the pre-stretch force or post-stretch force increases. Comparative study with experiments clearly demonstrates that the prediction of springback can resort to the current model without the loss of accuracy.展开更多
CuCrZr alloys were treated with the thermal stretch process at various temperatures from 100 to 300℃.The results reveal that the thermal stretch process is successfully developed to manufacture the precipitation hard...CuCrZr alloys were treated with the thermal stretch process at various temperatures from 100 to 300℃.The results reveal that the thermal stretch process is successfully developed to manufacture the precipitation hardening CuCrZr alloys with a good combination of microhardness and electrical conductivity.By increasing the tensile elongations at each temperature from 100 to 300℃,the microhardness increases whereas the electrical conductivity decreases slightly.Cr-containing precipitate phases with a Nishiyama-Wasserman orientation relationship to the copper matrix were observed by TEM.The achievement of high micro-hardness and acceptable electrical conductivity in the thermal stretch treated alloys is ascribed to the interactions of the heteroatom solution,dislocation increment,grain refinement and dispersive precipitation effect.展开更多
To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identi...To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method （FEM）, Latin hypercube sampling （LHS）, Kriging model and multi-island genetic algorithm （MIGA）. The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill’90 is discussed. The results show that the Hill’90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.展开更多
In this work,the lamellar structural evolution and microvoids variations of βpolypropylene(β-PP)during the processing of two different stretching methods,sequential biaxial stretching and simultaneous biaxial stretc...In this work,the lamellar structural evolution and microvoids variations of βpolypropylene(β-PP)during the processing of two different stretching methods,sequential biaxial stretching and simultaneous biaxial stretching,were investigated in detail.It was found that different stretching methods led to significantly different lamellae deformation modes,and the microporous membranes obtained from the simultaneous biaxial stretching exhibited better mechanical properties.For the sequential biaxial stretching,abundant coarse fibers originated from the tight accumulation of the lamellae parallel to the longitudinal stretching direction,whereas the lamellae perpendicular to the stretching direction were easily deformed and separated.Those coarse fibers were difficult to be separated to form micropores during the subsequent transverse stretching process,resulting in a poor micropores distribution.However,for the simultaneous biaxial stretching,theβcrystal had the same deformation mode,that is,the lamellae distributed in different directions were all destroyed,forming abundant microvoids and little coarse fibers.展开更多
文摘Background:Stretching has wide appeal,but there seems to exist some mismatch between its purported applications and what the evidence shows.There is compelling evidence for some stretching applications,but for others,the evidence seems heterogeneous or unsupportive.The discrepancies even affect some systematic reviews,possibly due to heterogeneous eligibility criteria and search strategies.This consensus paper seeks to unify the divergent findings on stretching and its implications for both athletic performance and clinical practices by delivering evidence-based recommendations.Methods:A panel of 20 experts with a blend of practical experience and scholarly knowledge was assembled.The panel meticulously reviewed existing systematic reviews,defined key terminologies(e.g.,consensus definitions for different stretching modes),and crafted guidelines using a Delphi consensus approach(minimum required agreement:80%).The analysis focused on 8 topics,including stretching's acute and chronic(long-term)effects on range of motion,strength performance,muscle hypertrophy,stiffness,injury prevention,muscle recovery,posture correction,and cardiovascular health.Results:There was consensus that chronic and acute stretching(a)improves range of motion(although alternatives exist)and(b)reduces muscle stiffness(which may not always be desirable);the panel also agreed that chronic stretching(c)may promote vascular health,but more research is warranted.In contrast,consensus was found that stretch training does not(a)contribute substantively to muscle growth,(b)serve as an allencompassing injury prevention strategy,(c)improve posture,or(d)acutely enhance post-exercise recovery.Conclusion:These recommendations provide guidance for athletes and practitioners,highlighting research gaps that should be addressed to more comprehensively understand the full scope of stretching effects.
基金funded by the National Natural Science Foundation of China(No.52204407)the Natural Science Foundation of Jiangsu Province,China(No.BK20220595)+1 种基金the China Postdoctoral Science Foundation(No.2022M 723689)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.SJCX23_1913).
文摘This study involved the development of an interpretable prediction framework to access the stretch formability of AZ31 magnesium alloys through the combination of the extreme gradient boosting(XGBoost)model with the sparrow search algorithm(SSA).Eleven features were extracted from the microstructures(e.g.,grain size(GS),maximum pole intensity(I_(max)),degree of texture dispersion(μ),radius of maximum pole position(r),and angle of maximum pole position(A)),mechanical properties(e.g.,tensile yield strength(TYS),ultimate tensile strength(UTS),elongation-to-failure(EL),and strength difference(∆S))and test conditions(e.g.,sheet thickness(t)and punch speed(v))in the data collected from the literature and experiments.Pearson correlation coefficient and exhaustive screening methods identified ten key features(not including UTS)as the final inputs,and they enhanced the prediction accuracy of Index Erichsen(IE),which served as the model’s output.The newly developed SSA-XGBoost model exhibited an improved prediction performance,with a goodness of fit(R^(2))of 0.91 compared with traditional machine learning models.A new dataset(four samples)was prepared to validate the reliability and generalization capacity of this model,and below 5%errors were observed between predicted and experimental IE values.Based on this result,the quantitative relationship between the key features and IE values was established via Shapley additive explanation method and XGBoost feature importance analysis.I_(max),TYS,EL,r,GS,andΔS showed a crucial influence on the IE of 10 input features.This work offers a reliable and accurate tool for the prediction of the stretch formability of AZ31 magnesium alloys and provides insights into the development of high-formable magnesium alloys.
基金supported by the National Natural Science Foundation of China(grant nos.82102343 and 82372536)the Shanghai Municipal Health Commission Health Industry Clinical Research Special Program(grant no.20244Y0031)the Shanghai“Rising Stars of Medical Talents”Youth Development Program(Youth Medical Talents-Specialist Program).
文摘Tissue expansion is a widely utilized technique in plastic and reconstructive surgery;however,the biological mechanisms underlying the skin response remain poorly understood.We propose that tissue fluidity,the transition of tissue from a solid-like state to a fluid-like state,plays a pivotal role in enabling the reorganization of the epidermal structure and cellular spatial order,which is essential for effective tissue expansion.Drawing parallels between fluidity in materials science and biological systems,we suggest that the fluid-like behavior in the skin may be critical for mechanical adaptability.Understanding the influence of tissue fluidity may open pathways for modulating this process,potentially enhancing tissue expansion efficiency,reducing procedural duration,and improving clinical outcomes.This perspective highlights the importance of investigating the biological dynamics of tissue fluidity and exploring the potential for targeted manipulation of fluidity-related pathways to optimize tissue expansion.Such advancements could profoundly affect regenerative and reconstructive surgical practices.
文摘Maximizing the efficiency of thermal engineering equipment involves minimizing entropy generation,which arises from irreversible processes.This study examines thermal transport and entropy generation in viscous flow over a radially stretching disk,incorporating the effects of magnetohydrodynamics(MHD),viscous dissipation,Joule heating,and radiation.Similarity transformations are used to obtain dimensionless nonlinear ordinary differential equations(ODEs)from the governing coupled partial differential equations(PDEs).The converted equations are then solved by using the BVP4C solver in MATLAB.To validate the findings,the results are compared with previously published studies under fixed parameter conditions,demonstrating strong agreement.Various key parameters are analyzed graphically to assess their impact on velocity and temperature distributions.Additionally,Bejan number and entropy generation variations are presented for different physical parameters.The injection parameter(S<0)increases the heat transfer rate,while the suction parameter(S>0)reduces it,exhibiting similar effects on fluid velocity.The magnetic parameter(M)effectively decreases entropy generation within the range of approximately 0≤η≤0.6.Beyond this interval,its influence diminishes as entropy generation values converge,with similar trends observed for the Bejan number.Furthermore,increased thermal radiation intensity is identified as a critical factor in enhancing entropy generation and the Bejan number.
基金supported by the National Natural Science Foundation of China(Nos.52003249,12072325 and 52273027)the Natural Science Foundation of Henan(No.242300421236).
文摘In this work,a morphology transition mode is revealed in ultra-high molecular weight polyethylene(UHMWPE)when stretching at 120℃:moving from the slightly deformed region to the necked region,the morphology transfers from small spherulites to a mixture of transcrystalline and enlarged spherulites,and finally to pure transcrystalline;meanwhile,the lamellae making up the transcrystalline or spherulite were fragmented into smaller ones;spatial scan by wide-angle X-ray scattering(WAXS)and small angle X-ray scattering(SAXS)revealed that the crystallinity is increased from 25.3%to 30.1%and the crystal orientation was enhanced greatly,but the lamellae orientation was quite weak.The rise of enlarged spherulites or a mixture of transcrystalline and spherulites can also be found in UHMWPE stretched at 140 and 148℃,whereas absent in UHMWPE stretched at 30℃.In situ WAXS/SAXS measurements suggest that during stretching at 30℃,the crystallinity is reduced drastically,and a few voids are formed as the size increases from 50 nm to 210 nm;during stretching at 120℃,the crystallinity is reduced only slightly,and the kinking of lamellae occurs at large Hencky strain;during stretching at 140 and 148℃,an increase in crystallinity with stretching strain can be found,and the lamellae are also kinked.Taking the microstructure and morphology transition into consideration,a mesoscale morphology transition mode is proposed,in the stretching-induced crystallization the fragmented lamellae can be rearranged into new supra-structures such as spherulite or transcrystalline during hot stretching.
文摘The study of stretching surfaces has garnered significant attention due to its importance in a wide range of industrial and engineering functions,including the drawing of wires and plastic films,shrink film production,polymer sheet extrusion,the manufacturing of glass fibers,and the manufacturing of polyester heat-shrink tubing.This research incorporates a Darcy-Forchheimer porous medium to account for the effects of porosity.The governing equations are transformed into a boundary value problem and solved semi-analytically using the Taylor wavelet method.The effects of various parameters are depicted through graphical analyses.The results show that for both converging and diverging stretching surfaces,an increase in the porosity parameter causes a decrease in the velocity field.Additionally,higher Reynolds numbers enhance inertial effects,leading to more pronounced velocity fluctuations.Stretching causes a consistent drop in velocity toward the center and an increase close to the walls in both types of channels,indicating that the volume percentage of nanoparticles influences the heat distribution.Notably,stretching induces a marked temperature drop at the channel's center.
基金funded by the Natural Science Foundation of China(NSFC),Grants No.12072048 to M.L.,12272063,and 11532003 to L.D.partially supported by the Science and Technology Innovation Leading Plan of High-Tech Industry in Hunan Province,China,Grant No.2020SK2018 to L.D.
文摘Background:Mechanical ventilation(MV)provides life support for patients with severe respiratory distress but can simultaneously cause ventilator-induced lung injury(VILI).However,due to a poor understanding of its mechanism,there is still a lack of effective remedies for the often-deadly VILI.Recent studies indicate that the stretch associated with MV can enhance the secretion of extracellular vesicles(EVs)and induce endoplasmic reticulum(ER)stress in airway smoothmuscle cells(ASMCs),both of which can contribute to VILI.But whetherMVassociated stretch enhances the secretion of EVs via ER stress in ASMCs as an underlying mechanism of VILI remains unknown.Methods:In this study,we exposed cultured human ASMCs to stretch(13%strain)and mouse models to MV at tidal volume(18 mL/kg).Subsequently,the amount of secreted EVs in the culture medium of ASMCs and the bronchoalveolar lavage fluid(BALF)of mousemodels was quantitatively evaluated by ultracentrifugation,transmission electron microscopy,Western blot,flow cytometry,and nanoparticle tracking analysis.The cultured ASMCs and the lung tissues of mouse models were assessed for expression of biomarkers of EVs(cluster of differentiation antigen 63,CD63),ER stress(heat shock protein family A member 5,HSPA5),and EVs regulating molecule Rab27a by immunofluorescence microscopy,immunohistochemistry(IHC)and enzyme-linked immunosorbent assay(ELISA),respectively.MicroRNAs(miRNAs)in EVs from ASMCs were measured with miRNA whole genome sequencing(miRNA-Seq).Results:We found that stretch enhanced EV secretion from cultured ASMCs.In addition,the cultured ASMCs and the mouse models were either or not pretreated with ER stress inhibitor(tauroursodeoxycholic acid,TUDCA)/EV secretion inhibitor(GW4869)prior to stretch or MV.We found that MV-associated stretch enhanced the expression of CD63,HSPA5,and Rab27a in cultured ASMCs and BALF/lung tissues of mousemodels,which could all be attenuated with TUDCA/GW4869 pretreatment.miRNA-Seq data show that differentially expressed miRNAs in EVsmainlymodulate gene transcription.Furthermore,the EVs fromcultured ASMCs under stretch tended to enhance detachment and expression of inflammatory cytokines,i.e.,transforming growth factor-β1(TGF-β1),interleukin-10(IL-10)in cultured airway epithelial cells.The expression of TGF-β1 and IL-10 in BALF of the mouse models also increased in response to MV,which was attenuated together with partial improvement of lung injury by pretreatment with TUDCA,GW4869/Rab27a siRNAs.Conclusion:Taken together,our data indicate thatMV-associated stretch can enhance the secretion of EVs from ASMCs via ER stress signaling to mediate airway inflammation and VILI,which provides new insight for further exploring EVs for the diagnosis and treatment of VILI.
基金the Researchers Supporting Project number(RSPD2025R997),King Saud University,Riyadh,Saudi Arabia.
文摘This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity and thermal slip boundary conditions are also examined.The considered hybrid nano-fluid contains silver(Ag)and iron oxide(Fe_(3)O_(4))nanoparticles dispersed in the water to prepare the Ag-Fe_(3)O_(4)/water-based hybrid nanofluid.The requisite posited partial differential equations model is converted to ordinary differential equations using similarity transformations.For a numerical solution,the shooting method in Maple is employed.Moreover,the duality in solutions is achieved for both cases of the disk(stretching(λ>0)and shrinking(λ<0)).At the same time,a unique solution is observed for λ=0.No solution is found for them at λ<λ_(c),whereas the solutions are split at the λ=λ_(c).Besides,the value of the λ_(c) is dependent on the φ_(hnf).Meanwhile,the values of f″(0)and -θ′(0)intensified with increasing φ_(hnf).Stability analysis has been applied using bvp4c in MATLAB software due to a dual solution.Furthermore,analysis shows that the first solution is stable and feasible physically.For the slip parameters,an increase in the velocity slip parameter increases the velocity and shear stress profiles while increasing the temperature profile in the first solutions.While the rise in thermal slip parameter reduces the temperature profile nanoparticle volume fractions increase it.
基金financially supported from the National Natural Science Foundation of China(Nos.52203026 and 52027804)。
文摘Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ultrathin films induced by stretching was investigated using transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The results show that stretching can enhance the crystallinity and increase the average thickness of the lamellae.A fullα-βphase transition can be achieved for PVDF ultrathin films of 20.6%βphase stretched to aλ(stretching ratio)of 1.5,while fewαphases still exist for ultrathin films of 35.0%βphase,together with bent and tilted lamellae.Compared to thicker PVDF films undergoing stretching-inducedα-βphase transition,the higherα-βphase transition efficiency of the PVDF ultrathin films can be attributed to the parallel aligned lamellar structure.Moreover,a higherβ-phase content can suppressα-βphase transition because of the stress concentration effect ofβ-phase.Ultimately,these results provide valuable insights into the stretching-inducedα-βphase transition of PVDF ultrathin films.
文摘The high thermal conductivity of the nanoparticles in hybrid nanofluids results in enhanced thermal conductivity associated with their base fluids.Enhanced heat transfer is a result of this high thermal conductivity,which has significant applications in heat exchangers and engineering devices.To optimize heat transfer,a liquid film of Cu and TiO_(2)hybrid nanofluid behind a stretching sheet in a variable porous medium is being considered due to its importance.The nature of the fluid is considered time-dependent and the thickness of the liquid film is measured variable adjustable with the variable porous space and favorable for the uniform flow of the liquid film.The solution of the problem is acquired using the homotopy analysis method HAM,and the artificial neural network ANN is applied to obtain detailed information in the form of error estimation and validations using the fitting curve analysis.HAM data is utilized to train the ANN in this study,which uses Cu and TiO_(2)hybrid nanofluids in a variable porous space for unsteady thin film flow,and it is used to train the ANN.The results indicate that Cu and TiO_(2)play a greater role in boosting the rate.
基金Project (20090450276) supported by the China Postdoctoral Science FoundationProject (50905008) supported by the National Natural Science Foundation of China
文摘The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and strain distributions in the cross-section of the part. With the proposed model, analysis of the effect of pre-stretch force and post-stretch force on springback angle shows that springback decreases as the pre-stretch force or post-stretch force increases. Comparative study with experiments clearly demonstrates that the prediction of springback can resort to the current model without the loss of accuracy.
基金Project(U1034002)supported by the National Natural Science Foundation of China(NSFC)-Guangdong Natural Science Mutual Funds
文摘CuCrZr alloys were treated with the thermal stretch process at various temperatures from 100 to 300℃.The results reveal that the thermal stretch process is successfully developed to manufacture the precipitation hardening CuCrZr alloys with a good combination of microhardness and electrical conductivity.By increasing the tensile elongations at each temperature from 100 to 300℃,the microhardness increases whereas the electrical conductivity decreases slightly.Cr-containing precipitate phases with a Nishiyama-Wasserman orientation relationship to the copper matrix were observed by TEM.The achievement of high micro-hardness and acceptable electrical conductivity in the thermal stretch treated alloys is ascribed to the interactions of the heteroatom solution,dislocation increment,grain refinement and dispersive precipitation effect.
基金Project(2011YSKF01)supported by the Henan Key Laboratory of Advanced Non-ferrous Metals,ChinaProject(50905008)supported by the National Natural Science Foundation of China
文摘To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method （FEM）, Latin hypercube sampling （LHS）, Kriging model and multi-island genetic algorithm （MIGA）. The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill’90 is discussed. The results show that the Hill’90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.
基金supported by the National Natural Science Foundation of China(No.51721091).
文摘In this work,the lamellar structural evolution and microvoids variations of βpolypropylene(β-PP)during the processing of two different stretching methods,sequential biaxial stretching and simultaneous biaxial stretching,were investigated in detail.It was found that different stretching methods led to significantly different lamellae deformation modes,and the microporous membranes obtained from the simultaneous biaxial stretching exhibited better mechanical properties.For the sequential biaxial stretching,abundant coarse fibers originated from the tight accumulation of the lamellae parallel to the longitudinal stretching direction,whereas the lamellae perpendicular to the stretching direction were easily deformed and separated.Those coarse fibers were difficult to be separated to form micropores during the subsequent transverse stretching process,resulting in a poor micropores distribution.However,for the simultaneous biaxial stretching,theβcrystal had the same deformation mode,that is,the lamellae distributed in different directions were all destroyed,forming abundant microvoids and little coarse fibers.
