In high-altitude cold areas,freeze-thaw(F-T)cycles induced by day-night and seasonal temperature changes cause numerous rock mass slope engineering disasters.To investigate the dynamic properties of rock in the natura...In high-altitude cold areas,freeze-thaw(F-T)cycles induced by day-night and seasonal temperature changes cause numerous rock mass slope engineering disasters.To investigate the dynamic properties of rock in the natural environment of a high-altitude cold area,standard specimens were drilled from the slope of the Jiama copper mine in Xizang,and dynamic compression tests were performed on watersaturated and frozen sandstone with different numbers of F-T cycles(0,10,20,30,and 40)by the split Hopkinson pressure bar(SHPB)system with a cryogenic control system.The influence of water-saturated and frozen conditions on the dynamic performance of sandstone was investigated.The following conclusions are drawn:(1)With increasing strain rate,the attenuation factor(la)of water-saturated sandstone and the intensifying factor(li)of frozen sandstone linearly increase.As the number of F-T cycles increases,the dependence factor(ld)of water-saturated sandstone linearly decreases,whereas the ld of frozen sandstone linearly increases.(2)The prediction equation of the dynamic compressive strength of water-saturated and frozen sandstone is obtained,which can be used to predict the dynamic compressive strength of sandstone after various F-T cycles based on the strain rate.(3)The mesoscopic mechanism of water-saturated and frozen sandstone’s dynamic compressive strength evolution is investigated.The water softening effect causes the dynamic compressive strength of water-saturated sandstone to decrease,whereas the strengthening effect of pore ice causes it to increase.(4)The decrease in the relative dynamic compressive strength of water-saturated sandstone and the increase in the relative dynamic compressive strength of frozen sandstone can be attributed to the increased porosity.展开更多
Defects in kinematic joints can sometimes highly influence the simulation response of the whole multibody system within which these joints are included. For instance, the clearance, the friction, the lubrication and t...Defects in kinematic joints can sometimes highly influence the simulation response of the whole multibody system within which these joints are included. For instance, the clearance, the friction, the lubrication and the flexibility affect the transient behaviour, reduce the component life and produce noise and vibration for classical joints such as prismatics, cylindrics or universal joints.In this work, a new 3D cylindrical joint model which accounts for the clearance, the misalignment and the friction is presented. This formulation has been used to represent the link between the planet gears and the planet carrier in an automotive differential model. C 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi：10.1063/2.1301303]展开更多
Microfluidic device with patterned microstructures on the substrate surface was used to regulate cell adhesion,morphology,and functions in tissue engineering.We developed a microfluidic device which employing microsca...Microfluidic device with patterned microstructures on the substrate surface was used to regulate cell adhesion,morphology,and functions in tissue engineering.We developed a microfluidic device which employing microscale patterned microstructures to achieve enhanced cell adhesion and migration.Biocompatible hydrogel substrates with micro-wavy and lattice-patterned microstructures were fabricated using standing surface acoustic waves and ultraviolet solidification.After seeding the L929 mouse fibroblast cells onto the patterned substrate of the microfluidic device,we determined that the viability and proliferation rate of cell migration can be greatly enhanced.Furthermore,L929 cells showed two types of gathering modes after 48 h of culturing.Cell growth was guided by the patterned substrate used in the microfluidic device and showed differences in the location distribution.Therefore,the developed microfluidic device with patterned microstructures can extend the application of in vitro cell culturing for future drug development and disease diagnosis.展开更多
The bicuspid aortic valve (BAV) is a major congenital valvular abnormality and is associated with a high prevalence of aortic dilation, whose expression depends on the type of leaflet fusion. Although BAV hemodynamics...The bicuspid aortic valve (BAV) is a major congenital valvular abnormality and is associated with a high prevalence of aortic dilation, whose expression depends on the type of leaflet fusion. Although BAV hemodynamics is considered a potential pathogenic contributor, the impact of BAV fusion on ascending aorta (AA) wall shear stress (WSS) remains largely unknown. A fluid-structure interaction approach was implemented to predict the hemodynamics and WSS characteristics in realistic AA models subjected to the flow of a normal tricuspid aortic valve (TAV) and three BAV morphotypes (left-right coronary cusp fusion (LR), right-non coronary cusp fusion (RN) and non-left coronary cusp fusion (NL)). TAV flow conditions subjected the proximal and middle AA to a streamlined flow typical of flows in bends, while BAV flow conditions generated increased flow helicity. The LR-BAV orifice jet generated flow abnormalities primarily in the proximal AA, which were marked by a uniform WSS overload along the wall circumference and contrasted WSS directionalities on the wall convexity and concavity. Flow abnormalities generated by the RN-BAV and NL-BAV inlet flow conditions were more diffuse and consisted of WSS overloads in the convexity of the proximal and middle AA and contrasted WSS directionalities in the anterior and posterior wall regions. This study demonstrates the impact of the BAV morphotype on AA hemodynamics and provides quantitative evidence for the existence of WSS abnormalities in aortic wall regions prone to dilation.展开更多
A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing...A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the accuracy of the method and even more, allows us to validate the nu- merical analysis. Therefore, two important results are obtained： a simplified analytical solution for the buckling problem and validation of the numerical results. Another important and novel finding is related to the influence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90~ oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the ma- terial reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under cer- tainply orientation angles.展开更多
This paper presents a straightforward model studying the performance of a solid oxide electrolysis cell at less computational effort while is still comprehensive accounting for details of all physics involved. The mod...This paper presents a straightforward model studying the performance of a solid oxide electrolysis cell at less computational effort while is still comprehensive accounting for details of all physics involved. The model is one dimensional and can be used to optimize SOECs that have composite electrodes. It includes an average mass transfer analysis used to simulate concentration polarization, activation polarization, as well as ohmic loss. The electrochemical reaction that occurs within the electrode functional layers has been accounted for in the calculation of the concentration polarization. This is believed to give a more realistic view of the mass transfer that occurs in SOECs with composite electrodes via a simple and straightforward one dimensional model. Experimental work with SOECs also has been done and some results are reported. The simulation results are compared with experimental data and the agreement is satisfactory. The model can be conveniently used for optimization of the SOEC electrodes and operational conditions.展开更多
The data-driven machine learning paradigm typically requires high-quality,large-scale datasets for training neural networks,which are often unavailable in many scientific and engineering applications.Integrating physi...The data-driven machine learning paradigm typically requires high-quality,large-scale datasets for training neural networks,which are often unavailable in many scientific and engineering applications.Integrating physics equations into machine learning models,either fully or partially,can mitigate these data requirements and improve generalizability;however,such approaches frequently rely on differentiable programming frameworks.This ability poses significant challenges when legacy or commercial numerical solvers,which are often nondifferentiable and difficult to modify without introducing code changes,are integrated.This work addresses these challenges by leveraging the mini-batching iterative ensemble Kalman inversion(EKI)algorithm as a gradientfree training framework for hybrid neural models.The use of stochastic mini-batching significantly enhances the computational efficiency and convergence of EKI,making it well-suited for high-dimensional learning problems.The proposed method is demonstrated for modeling a fiber-reinforced composite plate,where heterogeneous local constitutive laws are parameterized by a trainable neural network embedded within the FEniCS finite element solver.Using the displacement field as indirect data,the hybrid neural FEM solver successfully predicts deformations by learning the local constitutive laws,even for unseen fiber volume fraction distributions and varying test loading conditions.These results demonstrate the effectiveness of iterative EKI in training hybrid neural models with non-differentiable components,paving the way for broader adoption of hybrid neural models in scientific and engineering applications.展开更多
In many applications,flow measurements are usually sparse and possibly noisy.The reconstruction of a high-resolution flow field from limited and imperfect flow information is significant yet challenging.In this work,w...In many applications,flow measurements are usually sparse and possibly noisy.The reconstruction of a high-resolution flow field from limited and imperfect flow information is significant yet challenging.In this work,we propose an innovative physics-constrained Bayesian deep learning approach to reconstruct flow fields from sparse,noisy velocity data,where equationbased constraints are imposed through the likelihood function and uncertainty of the reconstructed flow can be estimated.Specifically,a Bayesian deep neural network is trained on sparse measurement data to capture the flow field.In the meantime,the violation of physical laws will be penalized on a large number of spatiotemporal points where measurements are not available.A non-parametric variational inference approach is applied to enable efficient physicsconstrained Bayesian learning.Several test cases on idealized vascular flows with synthetic measurement data are studied to demonstrate the merit of the proposed method.展开更多
This paper focuses on a method to solve structural optimization problems using particle swarm optimization （PSO）, surrogate models and Bayesian statistics. PSO is a random/stochastic search algorithm designed to fin...This paper focuses on a method to solve structural optimization problems using particle swarm optimization （PSO）, surrogate models and Bayesian statistics. PSO is a random/stochastic search algorithm designed to find the global optimum. However, PSO needs many evaluations compared to gradient-based optimization. This means PSO increases the analysis costs of structural optimization. One of the methods to reduce computing costs in stochastic optimization is to use approximation techniques. In this work, surrogate models are used, including the response surface method （RSM） and Kriging. When surrogate models are used, there are some errors between exact values and approximated values. These errors decrease the reliability of the optimum values and discard the realistic approximation of using surrogate models. In this paper, Bayesian statistics is used to obtain more reliable results. To verify and confirm the efficiency of the proposed method using surrogate models and Bayesian statistics for stochastic structural optimization, two numerical examples are optimized, and the optimization of a hub sleeve is demonstrated as a practical problem.展开更多
Over millions of years of evolution,nature has created organisms with overwhelming performances due to their unique materials and structures,providing us with valuable inspirations for the development of next-generati...Over millions of years of evolution,nature has created organisms with overwhelming performances due to their unique materials and structures,providing us with valuable inspirations for the development of next-generation biomedical devices.As a promising new technology,3D printing enables the fabrication of multiscale,multi-material,and multi-functional threedimensional(3D)biomimetic materials and structures with high precision and great flexibility.The manufacturing challenges of biomedical devices with advanced biomimetic materials and structures for various applications were overcome with the flourishing development of 3D printing technologies.In this paper,the state-of-the-art additive manufacturing of biomimetic materials and structures in the field of biomedical engineering were overviewed.Various kinds of biomedical applications,including implants,lab-on-chip,medicine,microvascular network,and artificial organs and tissues,were respectively discussed.The technical challenges and limitations of biomimetic additive manufacturing in biomedical applications were further investigated,and the potential solutions and intriguing future technological developments of biomimetic 3D printing of biomedical devices were highlighted.展开更多
Three-dimensional(3D)-printed scaffolds have attracted considerable attention in recent years as they provide a suitable environment for bone cell tissue regeneration and can be customized in shape.Among many other ch...Three-dimensional(3D)-printed scaffolds have attracted considerable attention in recent years as they provide a suitable environment for bone cell tissue regeneration and can be customized in shape.Among many other challenges,the material composition and geometric structure have major impacts on the performance of scaffolds.Hydroxyapatite and tricalcium phosphate(HA/TCP),as the major constituents of natural bone and teeth,possess attractive biological properties and are widely used in bone scaffold fabrication.Many fabrication methods have been investigated in attempts to achieve HA/TCP scaffolds with microporous structure enabling cell growth and nutrient transport.However,current 3D printing methods can only achieve the fabrication of HA/TCP scaffolds with certain range of microporous structure.To overcome this challenge,we developed a slurry-based microscale mask image projection stereolithography,allowing us to form a HA/TCP-based photocurable suspension with complex geometry including biomimetic features and hierarchical porosity.Here,the curing performance and physical properties of the HA/TCP suspension were investigated,and a circular movement process for the fabrication of highly viscous HA/TCP suspension was developed.Based on these investigations,the scaffold composition was optimized.We determined that a 30 wt%HA/TCP scaffold with biomimetic hierarchical structure exhibited superior mechanical properties and porosity.Cell proliferation was investigated in vitro,and the surgery was conducted in a nude mouse in vivo model of long bone with cranial neural crest cells and bone marrow mesenchymal stem cells.The results showed our 3D-printed HA/TCP scaffold with biomimetic hierarchical structure is biocompatible and has sufficient mechanical strength for surgery.展开更多
To improve the industrialization of the process,the study of a thixoforming line stability was proposed.The thixoforming line is fully automated to optimize the repeatability of the experiments.Parameters of the heati...To improve the industrialization of the process,the study of a thixoforming line stability was proposed.The thixoforming line is fully automated to optimize the repeatability of the experiments.Parameters of the heating cycle,the slug temperature,the tool temperature and the forming speed were studied.For each of them,a range of the expected variations in a steady-state process as well as the effects of these variations on the process itself(forming load and parts quality) were given.These variations are shown to be acceptable.Three different tools were used in the experiments.Some mathematical simulations were realized on the finite elements code Forge2008with a semi-solid constitutive law.The capacity of the model to represent the process stability was discussed.The simulation results are in agreement with the experiment results.展开更多
During the electrochemical machining (ECM), the cathodes designed by the existing methods are mainly unitary cathodes, which can be only used to produce the workpieces with the same shapes. However, there are few rese...During the electrochemical machining (ECM), the cathodes designed by the existing methods are mainly unitary cathodes, which can be only used to produce the workpieces with the same shapes. However, there are few researches on designing cathodes for machining the different workpieces with the different surfaces. This paper presents the grid cathode composed of the square cells to produce the workpieces with different shapes. Three types of the square cells, 2.5 mm′2.5 mm, 3 mm′3 mm, and 4 mm′4 mm, are utilized to construct the plane, the slant, and the blade cathode. The material of the cathode and the anode is CrNi 18 Ti 9 , and the ingredient of electrolyte is 15% NaCl and 15% NaNO 3 . The machining equilibrium machining current and time are acquired and analyzed, the machining process and the workpiece quality are compared between using the grid cathode and the unitary cathode. Moreover, the machining errors on the workpiece surface are measured and analyzed, and the error reasons are traced and discussed to obtain the better surface quality of the workpiece. The experiment and analysis results show that the grid cathode can be used to manufacture the workpieces with complex shapes in certain range of the error. The workpiece quality improves with the size of the square cell being reduced, and if the square element is small enough, the workpiece quality is almost equal to the one machined by the unitary cathode. The proposed research realizes a single cathode machining the different workpieces with the different surfaces.展开更多
Zr-doped-TiO2 loaded glass fiber（ZT/GF） composite photocatalysts with different Zr/Ti ratios were prepared with a sol–gel process. Zr4＋can replace Ti4＋in the TiO2 lattice, which is conducive to forming the anatas...Zr-doped-TiO2 loaded glass fiber（ZT/GF） composite photocatalysts with different Zr/Ti ratios were prepared with a sol–gel process. Zr4＋can replace Ti4＋in the TiO2 lattice, which is conducive to forming the anatase phase and reducing the calcination temperature. The glass fiber carrier was responsible for better dispersion and loading of Zr-doped-TiO2 particles, improving the applicability of the Zr-doped-TiO2. The ZT/GF photocatalysts were characterized by X-ray diffraction（XRD）, scanning electron microscope（SEM）, Fourier transform infrared spectroscopy（FT-IR）, ultraviolet–visible spectroscopy（UV–vis） and Barrett–Joyner–Halenda（BJH）. The performance of photocatalysts with different loading was evaluated in formaldehyde degradation under visible light at room temperature. ZT/GF0.2exhibited the highest activity, with a formaldehyde removal rate as high as 95.14% being observed, which is better than that of the photocatalyst particles alone. The stability of the catalyst was also tested, and ZT/GF exhibited excellent catalytic performance with 94.38%removal efficiency, even after seven uses.展开更多
AIM:To explore ex vivo the role of bone morphogenetic protein-4(BMP-4) and transforming growth factorbeta1(TGF-β1) in acute valvular response to fluid shear stress(FSS) abnormalities.METHODS:Porcine valve leaflets we...AIM:To explore ex vivo the role of bone morphogenetic protein-4(BMP-4) and transforming growth factorbeta1(TGF-β1) in acute valvular response to fluid shear stress(FSS) abnormalities.METHODS:Porcine valve leaflets were subjected ex vivo to physiologic FSS,supra-physiologic FSS magnitude at normal frequency and supra-physiologic FSS frequency at normal magnitude for 48 h in a double-sided cone-and-plate bioreactor filled with standard culture medium. The role of BMP-4 and TGF-β1 in the valvular response was investigated by promoting or inhibiting the downstream action of those cytokines via culture medium supplementation with BMP-4 or the BMP antagonist noggin,and TGF-β1 or the TGF-β1 inhibitor SB-431542,respectively. Fresh porcine leaflets were used as controls. Each experimental group consisted of six leaflet samples. Immunostaining and immunoblotting were performed to assess endothelial activation in terms of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expressions,paracrine signaling in terms of BMP-4 and TGF-β1 expressions and extracellular matrix(ECM) remodeling in terms of cathepsin L,cathepsin S,metalloproteinases(MMP)-2 and MMP-9 expressions. Immunostained images were quantified by normalizing the intensities of positively stained regions by the number of cells in each image while immunoblots were quantified by densitometry. R E S U LT S :Regardless of the culture medium,physiologic FSS maintained valvular homeostasis. Tissue exposure to supra-physiologic FSS magnitude in standard medium stimulated paracrine signaling(TGF-β1:467% ± 22% vs 100% ± 6% in freshcontrols,BMP-4:258% ± 22% vs 100% ± 4% in fresh controls; P < 0.05) and ECM degradation(MMP-2:941% ± 90% vs 100% ± 19% in fresh controls,MMP-9:1219% ± 190% vs 100% ± 16% in fresh controls,cathepsin L:1187% ± 175% vs 100% ± 12% in fresh controls,cathepsin S:603% ± 88% vs 100% ± 13% in fresh controls; P < 0.05),while BMP-4 supplementation also promoted fibrosa activation and TGF-β1 inhibition reduced MMP-9 expression to the native tissue level(MMP-9:308% ± 153% with TGF-β1 inhibition vs 100% ± 16% in fresh control; P > 0.05). Supra-physiologic FSS frequency had no effect on endothelial activation and paracrine signaling regardless of the culture medium but TGF-β1 silencing attenuated FSS-induced ECM degradation via MMP-9 downregulation(MMP-9:302% ± 182% vs 100% ± 42% in fresh controls; P > 0.05).CONCLUSION:Valvular tissue is sensitive to FSS abnormalities. The TGF-β1 inhibitor SB-431542 is a potential candidate molecule for attenuating the effects of FSS abnormalities on valvular remodeling.展开更多
Mechanosensation is an important process in biological fluid-structure interaction. To understand the biophysics underlying mechanosensation, it is essential to quantify the correlation between membrane deformation, m...Mechanosensation is an important process in biological fluid-structure interaction. To understand the biophysics underlying mechanosensation, it is essential to quantify the correlation between membrane deformation, membrane tension, external fluid shear stress, and conformation of mechanosensitive (MS) channels. Smoothed dissipative particle dynamics (SDPD) simulations of vesicle/cell in three types of flow configurations are conducted to calculate the tension in lipid membrane due to fluid shear stress from the surrounding viscous flow. In combination with a simple continuum model for an MS channel, SDPD simulation results suggest that shearing adhered vesicles/cells is more effective to induce membrane tension sufficient to stretch MS channels open than a free shear flow or a constrictive channel flow. In addition, we incorporate the bilayer-cytoskeletal interaction in a two-component model to probe the effects of a cytoskeletal network on the gating of MS channels.展开更多
Future unconstrained and science-driven missions to Mars will require advanced guidance algorithms that are able to adapt to more demanding mission requirements, e.g. landing on selected locales with pinpoint accuracy...Future unconstrained and science-driven missions to Mars will require advanced guidance algorithms that are able to adapt to more demanding mission requirements, e.g. landing on selected locales with pinpoint accuracy while autonomously flying fuel-efficient trajectories. In this paper, a novel guidance algorithm designed by applying the principles of reinforcement learning(RL) theory is presented. The goal is to devise an adaptive guidance algorithm that enables robust, fuel efficient,and accurate landing without the need for off line trajectory generation and real-time tracking. Results from a Monte Carlo simulation campaign show that the algorithm is capable of autonomously following trajectories that are close to the optimal minimum-fuel solutions with an accuracy that surpasses that of past and future Mars missions. The proposed RL-based guidance algorithm exhibits a high degree of flexibility and can easily accommodate autonomous retargeting while maintaining accuracy and fuel efficiency. Although reinforcement learning and other similar machine learning techniques have been previously applied to aerospace guidance and control problems(e.g., autonomous helicopter control), this appears, to the best of the authors knowledge, to be the first application of reinforcement learning to the problem of autonomous planetary landing.展开更多
Deep-tissue solid cancer treatment has a poor prognosis,resulting in a very low 5-year patient survival rate.The primary challenges facing solid tumor therapies are accessibility,incomplete surgical removal of tumor t...Deep-tissue solid cancer treatment has a poor prognosis,resulting in a very low 5-year patient survival rate.The primary challenges facing solid tumor therapies are accessibility,incomplete surgical removal of tumor tissue,the resistance of the hypoxic and heterogeneous tumor microenvironment to chemotherapy and radiation,and suffering caused by off-target toxicities.Here,sonodynamic therapy(SDT)is an evolving therapeutic approach that uses low-intensity ultrasound to target deep-tissue solid tumors.The ability of ultrasound to deliver energy safely and precisely into small deep-tissue(>10 cm)volumes makes SDT more effective than conventional photodynamic therapy.While SDT is currently in phase 1/2 clinical trials for glioblastoma multiforme,its use for other solid cancer treatments,such as breast,pancreatic,liver,and prostate cancer,is still in the preclinical stage,with further investigation required to improve its therapeutic efficacy.This review,therefore,focuses on recent advances in SDT cancer treatments.We describe the interaction between ultrasound and sonosensitizer molecules and the associated energy transfer mechanism to malignant cells,which plays a central role in SDT-mediated cell death.Different sensitizers used in clinical and preclinical trials of various cancer treatments are listed,and the critical ultrasound parameters for SDT are reviewed.We also discuss approaches to improve the efficacies of these sonosensitizers,the role of the 3-dimensional spheroid in vitro investigations,ultrasound-controlled CAR-T cell and SDT-based multimodal therapy,and machine learning for sonosensitizer optimization,which could facilitate clinical translation of SDT.展开更多
This paper studies a master-slave type of synchronization systems for a general form of two discrete Lur＇e systems. Some simple necessary and/or sufficient conditions for synchronization are derived. They are basical...This paper studies a master-slave type of synchronization systems for a general form of two discrete Lur＇e systems. Some simple necessary and/or sufficient conditions for synchronization are derived. They are basically algebraic conditions, and are convement to be applied in engineering applications.展开更多
A longitudinal magnetic field was introduced to submerged arc cladding （SAC）. Electromagnetic stirring was caused by the interaction between arc plasma and external magnetic field. The grain size was refined and the...A longitudinal magnetic field was introduced to submerged arc cladding （SAC）. Electromagnetic stirring was caused by the interaction between arc plasma and external magnetic field. The grain size was refined and the average hardness was improved. On the base of a group of optimized parameters calculated by orthogonal optimization, some tests were made to study the effects of electromagnetic stirring on hardness and grain size of surfacing layers. It was confirmed that the solidification made of liquid metal could be improved by electromagnetic stirring and hardness and grain size of surfacing layers could be improved.展开更多
基金supported by the Hunan Provincial Natural Science Foundation of China(Grant No.2020JJ4704)the Fundamental Research Funds for the Central Universities of Central South University,China(Grant Nos.2021zzts0881 and 2021zzts0279).
文摘In high-altitude cold areas,freeze-thaw(F-T)cycles induced by day-night and seasonal temperature changes cause numerous rock mass slope engineering disasters.To investigate the dynamic properties of rock in the natural environment of a high-altitude cold area,standard specimens were drilled from the slope of the Jiama copper mine in Xizang,and dynamic compression tests were performed on watersaturated and frozen sandstone with different numbers of F-T cycles(0,10,20,30,and 40)by the split Hopkinson pressure bar(SHPB)system with a cryogenic control system.The influence of water-saturated and frozen conditions on the dynamic performance of sandstone was investigated.The following conclusions are drawn:(1)With increasing strain rate,the attenuation factor(la)of water-saturated sandstone and the intensifying factor(li)of frozen sandstone linearly increase.As the number of F-T cycles increases,the dependence factor(ld)of water-saturated sandstone linearly decreases,whereas the ld of frozen sandstone linearly increases.(2)The prediction equation of the dynamic compressive strength of water-saturated and frozen sandstone is obtained,which can be used to predict the dynamic compressive strength of sandstone after various F-T cycles based on the strain rate.(3)The mesoscopic mechanism of water-saturated and frozen sandstone’s dynamic compressive strength evolution is investigated.The water softening effect causes the dynamic compressive strength of water-saturated sandstone to decrease,whereas the strengthening effect of pore ice causes it to increase.(4)The decrease in the relative dynamic compressive strength of water-saturated sandstone and the increase in the relative dynamic compressive strength of frozen sandstone can be attributed to the increased porosity.
基金the Belgian National Fund for Scientific research (FRIA) for its financial support
文摘Defects in kinematic joints can sometimes highly influence the simulation response of the whole multibody system within which these joints are included. For instance, the clearance, the friction, the lubrication and the flexibility affect the transient behaviour, reduce the component life and produce noise and vibration for classical joints such as prismatics, cylindrics or universal joints.In this work, a new 3D cylindrical joint model which accounts for the clearance, the misalignment and the friction is presented. This formulation has been used to represent the link between the planet gears and the planet carrier in an automotive differential model. C 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi：10.1063/2.1301303]
基金The authors acknowledge the funding support from the National Natural Science Foundation of China(U1809220)Zhejiang Provincial Funds for Distinguished Young Scientists of China(LR19E050001)+1 种基金Open Fund Project of Zhijiang Laboratory(2019MC0AB02)Fund for Creative Research Groups of National Natural Science Foundation of China(51821093).
文摘Microfluidic device with patterned microstructures on the substrate surface was used to regulate cell adhesion,morphology,and functions in tissue engineering.We developed a microfluidic device which employing microscale patterned microstructures to achieve enhanced cell adhesion and migration.Biocompatible hydrogel substrates with micro-wavy and lattice-patterned microstructures were fabricated using standing surface acoustic waves and ultraviolet solidification.After seeding the L929 mouse fibroblast cells onto the patterned substrate of the microfluidic device,we determined that the viability and proliferation rate of cell migration can be greatly enhanced.Furthermore,L929 cells showed two types of gathering modes after 48 h of culturing.Cell growth was guided by the patterned substrate used in the microfluidic device and showed differences in the location distribution.Therefore,the developed microfluidic device with patterned microstructures can extend the application of in vitro cell culturing for future drug development and disease diagnosis.
文摘The bicuspid aortic valve (BAV) is a major congenital valvular abnormality and is associated with a high prevalence of aortic dilation, whose expression depends on the type of leaflet fusion. Although BAV hemodynamics is considered a potential pathogenic contributor, the impact of BAV fusion on ascending aorta (AA) wall shear stress (WSS) remains largely unknown. A fluid-structure interaction approach was implemented to predict the hemodynamics and WSS characteristics in realistic AA models subjected to the flow of a normal tricuspid aortic valve (TAV) and three BAV morphotypes (left-right coronary cusp fusion (LR), right-non coronary cusp fusion (RN) and non-left coronary cusp fusion (NL)). TAV flow conditions subjected the proximal and middle AA to a streamlined flow typical of flows in bends, while BAV flow conditions generated increased flow helicity. The LR-BAV orifice jet generated flow abnormalities primarily in the proximal AA, which were marked by a uniform WSS overload along the wall circumference and contrasted WSS directionalities on the wall convexity and concavity. Flow abnormalities generated by the RN-BAV and NL-BAV inlet flow conditions were more diffuse and consisted of WSS overloads in the convexity of the proximal and middle AA and contrasted WSS directionalities in the anterior and posterior wall regions. This study demonstrates the impact of the BAV morphotype on AA hemodynamics and provides quantitative evidence for the existence of WSS abnormalities in aortic wall regions prone to dilation.
文摘A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the accuracy of the method and even more, allows us to validate the nu- merical analysis. Therefore, two important results are obtained： a simplified analytical solution for the buckling problem and validation of the numerical results. Another important and novel finding is related to the influence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90~ oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the ma- terial reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under cer- tainply orientation angles.
文摘This paper presents a straightforward model studying the performance of a solid oxide electrolysis cell at less computational effort while is still comprehensive accounting for details of all physics involved. The model is one dimensional and can be used to optimize SOECs that have composite electrodes. It includes an average mass transfer analysis used to simulate concentration polarization, activation polarization, as well as ohmic loss. The electrochemical reaction that occurs within the electrode functional layers has been accounted for in the calculation of the concentration polarization. This is believed to give a more realistic view of the mass transfer that occurs in SOECs with composite electrodes via a simple and straightforward one dimensional model. Experimental work with SOECs also has been done and some results are reported. The simulation results are compared with experimental data and the agreement is satisfactory. The model can be conveniently used for optimization of the SOEC electrodes and operational conditions.
基金supported by the Air Force Office of Scientific Research(AFOSR),United States of America(Grant No.FA9550-22-1-0065).
文摘The data-driven machine learning paradigm typically requires high-quality,large-scale datasets for training neural networks,which are often unavailable in many scientific and engineering applications.Integrating physics equations into machine learning models,either fully or partially,can mitigate these data requirements and improve generalizability;however,such approaches frequently rely on differentiable programming frameworks.This ability poses significant challenges when legacy or commercial numerical solvers,which are often nondifferentiable and difficult to modify without introducing code changes,are integrated.This work addresses these challenges by leveraging the mini-batching iterative ensemble Kalman inversion(EKI)algorithm as a gradientfree training framework for hybrid neural models.The use of stochastic mini-batching significantly enhances the computational efficiency and convergence of EKI,making it well-suited for high-dimensional learning problems.The proposed method is demonstrated for modeling a fiber-reinforced composite plate,where heterogeneous local constitutive laws are parameterized by a trainable neural network embedded within the FEniCS finite element solver.Using the displacement field as indirect data,the hybrid neural FEM solver successfully predicts deformations by learning the local constitutive laws,even for unseen fiber volume fraction distributions and varying test loading conditions.These results demonstrate the effectiveness of iterative EKI in training hybrid neural models with non-differentiable components,paving the way for broader adoption of hybrid neural models in scientific and engineering applications.
基金support from the National Science Foundation (Grant CMMI-1934300)Defense Advanced Research Projects Agency (DARPA) under the Physics of Artificial Intelligence (PAI) program (Grant HR00111890034)partial funding support by graduate fellowship from China Scholarship Council (CSC) in this effort
文摘In many applications,flow measurements are usually sparse and possibly noisy.The reconstruction of a high-resolution flow field from limited and imperfect flow information is significant yet challenging.In this work,we propose an innovative physics-constrained Bayesian deep learning approach to reconstruct flow fields from sparse,noisy velocity data,where equationbased constraints are imposed through the likelihood function and uncertainty of the reconstructed flow can be estimated.Specifically,a Bayesian deep neural network is trained on sparse measurement data to capture the flow field.In the meantime,the violation of physical laws will be penalized on a large number of spatiotemporal points where measurements are not available.A non-parametric variational inference approach is applied to enable efficient physicsconstrained Bayesian learning.Several test cases on idealized vascular flows with synthetic measurement data are studied to demonstrate the merit of the proposed method.
文摘This paper focuses on a method to solve structural optimization problems using particle swarm optimization （PSO）, surrogate models and Bayesian statistics. PSO is a random/stochastic search algorithm designed to find the global optimum. However, PSO needs many evaluations compared to gradient-based optimization. This means PSO increases the analysis costs of structural optimization. One of the methods to reduce computing costs in stochastic optimization is to use approximation techniques. In this work, surrogate models are used, including the response surface method （RSM） and Kriging. When surrogate models are used, there are some errors between exact values and approximated values. These errors decrease the reliability of the optimum values and discard the realistic approximation of using surrogate models. In this paper, Bayesian statistics is used to obtain more reliable results. To verify and confirm the efficiency of the proposed method using surrogate models and Bayesian statistics for stochastic structural optimization, two numerical examples are optimized, and the optimization of a hub sleeve is demonstrated as a practical problem.
基金The authors acknowledge Arizona State University for the start-up funding support.
文摘Over millions of years of evolution,nature has created organisms with overwhelming performances due to their unique materials and structures,providing us with valuable inspirations for the development of next-generation biomedical devices.As a promising new technology,3D printing enables the fabrication of multiscale,multi-material,and multi-functional threedimensional(3D)biomimetic materials and structures with high precision and great flexibility.The manufacturing challenges of biomedical devices with advanced biomimetic materials and structures for various applications were overcome with the flourishing development of 3D printing technologies.In this paper,the state-of-the-art additive manufacturing of biomimetic materials and structures in the field of biomedical engineering were overviewed.Various kinds of biomedical applications,including implants,lab-on-chip,medicine,microvascular network,and artificial organs and tissues,were respectively discussed.The technical challenges and limitations of biomimetic additive manufacturing in biomedical applications were further investigated,and the potential solutions and intriguing future technological developments of biomimetic 3D printing of biomedical devices were highlighted.
基金supported by the Alfred E.Mann Institute at University of Southern California as a grant to Yang Chai and Yong Chenthe support of National Science Foundation(NSF)grants 1151191 and 1335476the Core Center of Excellence in Nano Imaging(CNI)at USC for the use of microscopic measuring equipment.
文摘Three-dimensional(3D)-printed scaffolds have attracted considerable attention in recent years as they provide a suitable environment for bone cell tissue regeneration and can be customized in shape.Among many other challenges,the material composition and geometric structure have major impacts on the performance of scaffolds.Hydroxyapatite and tricalcium phosphate(HA/TCP),as the major constituents of natural bone and teeth,possess attractive biological properties and are widely used in bone scaffold fabrication.Many fabrication methods have been investigated in attempts to achieve HA/TCP scaffolds with microporous structure enabling cell growth and nutrient transport.However,current 3D printing methods can only achieve the fabrication of HA/TCP scaffolds with certain range of microporous structure.To overcome this challenge,we developed a slurry-based microscale mask image projection stereolithography,allowing us to form a HA/TCP-based photocurable suspension with complex geometry including biomimetic features and hierarchical porosity.Here,the curing performance and physical properties of the HA/TCP suspension were investigated,and a circular movement process for the fabrication of highly viscous HA/TCP suspension was developed.Based on these investigations,the scaffold composition was optimized.We determined that a 30 wt%HA/TCP scaffold with biomimetic hierarchical structure exhibited superior mechanical properties and porosity.Cell proliferation was investigated in vitro,and the surgery was conducted in a nude mouse in vivo model of long bone with cranial neural crest cells and bone marrow mesenchymal stem cells.The results showed our 3D-printed HA/TCP scaffold with biomimetic hierarchical structure is biocompatible and has sufficient mechanical strength for surgery.
基金Project (415814) supported by the FIRST Europe,THIXOFROR
文摘To improve the industrialization of the process,the study of a thixoforming line stability was proposed.The thixoforming line is fully automated to optimize the repeatability of the experiments.Parameters of the heating cycle,the slug temperature,the tool temperature and the forming speed were studied.For each of them,a range of the expected variations in a steady-state process as well as the effects of these variations on the process itself(forming load and parts quality) were given.These variations are shown to be acceptable.Three different tools were used in the experiments.Some mathematical simulations were realized on the finite elements code Forge2008with a semi-solid constitutive law.The capacity of the model to represent the process stability was discussed.The simulation results are in agreement with the experiment results.
基金supported by Aeronautics Science Foundation of China (Grant No. 2008ZE52049)National Natural Science Foundation of China (Grant No. 51005122)
文摘During the electrochemical machining (ECM), the cathodes designed by the existing methods are mainly unitary cathodes, which can be only used to produce the workpieces with the same shapes. However, there are few researches on designing cathodes for machining the different workpieces with the different surfaces. This paper presents the grid cathode composed of the square cells to produce the workpieces with different shapes. Three types of the square cells, 2.5 mm′2.5 mm, 3 mm′3 mm, and 4 mm′4 mm, are utilized to construct the plane, the slant, and the blade cathode. The material of the cathode and the anode is CrNi 18 Ti 9 , and the ingredient of electrolyte is 15% NaCl and 15% NaNO 3 . The machining equilibrium machining current and time are acquired and analyzed, the machining process and the workpiece quality are compared between using the grid cathode and the unitary cathode. Moreover, the machining errors on the workpiece surface are measured and analyzed, and the error reasons are traced and discussed to obtain the better surface quality of the workpiece. The experiment and analysis results show that the grid cathode can be used to manufacture the workpieces with complex shapes in certain range of the error. The workpiece quality improves with the size of the square cell being reduced, and if the square element is small enough, the workpiece quality is almost equal to the one machined by the unitary cathode. The proposed research realizes a single cathode machining the different workpieces with the different surfaces.
基金financially supported by the Project of Science and Technology Department of Jiangsu Province (BE2016769)the Natural Science Foundation of China (No. 51608261)+2 种基金Six talent peaks project in Jiangsu Province (2016)Open fund by Jiangsu Engineering Technology Research Center of Environmental Cleaning Materials (KFK1503)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Zr-doped-TiO2 loaded glass fiber（ZT/GF） composite photocatalysts with different Zr/Ti ratios were prepared with a sol–gel process. Zr4＋can replace Ti4＋in the TiO2 lattice, which is conducive to forming the anatase phase and reducing the calcination temperature. The glass fiber carrier was responsible for better dispersion and loading of Zr-doped-TiO2 particles, improving the applicability of the Zr-doped-TiO2. The ZT/GF photocatalysts were characterized by X-ray diffraction（XRD）, scanning electron microscope（SEM）, Fourier transform infrared spectroscopy（FT-IR）, ultraviolet–visible spectroscopy（UV–vis） and Barrett–Joyner–Halenda（BJH）. The performance of photocatalysts with different loading was evaluated in formaldehyde degradation under visible light at room temperature. ZT/GF0.2exhibited the highest activity, with a formaldehyde removal rate as high as 95.14% being observed, which is better than that of the photocatalyst particles alone. The stability of the catalyst was also tested, and ZT/GF exhibited excellent catalytic performance with 94.38%removal efficiency, even after seven uses.
基金Supported by American Heart Association Scientist Development Grant,No.11SDG7600103
文摘AIM:To explore ex vivo the role of bone morphogenetic protein-4(BMP-4) and transforming growth factorbeta1(TGF-β1) in acute valvular response to fluid shear stress(FSS) abnormalities.METHODS:Porcine valve leaflets were subjected ex vivo to physiologic FSS,supra-physiologic FSS magnitude at normal frequency and supra-physiologic FSS frequency at normal magnitude for 48 h in a double-sided cone-and-plate bioreactor filled with standard culture medium. The role of BMP-4 and TGF-β1 in the valvular response was investigated by promoting or inhibiting the downstream action of those cytokines via culture medium supplementation with BMP-4 or the BMP antagonist noggin,and TGF-β1 or the TGF-β1 inhibitor SB-431542,respectively. Fresh porcine leaflets were used as controls. Each experimental group consisted of six leaflet samples. Immunostaining and immunoblotting were performed to assess endothelial activation in terms of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expressions,paracrine signaling in terms of BMP-4 and TGF-β1 expressions and extracellular matrix(ECM) remodeling in terms of cathepsin L,cathepsin S,metalloproteinases(MMP)-2 and MMP-9 expressions. Immunostained images were quantified by normalizing the intensities of positively stained regions by the number of cells in each image while immunoblots were quantified by densitometry. R E S U LT S :Regardless of the culture medium,physiologic FSS maintained valvular homeostasis. Tissue exposure to supra-physiologic FSS magnitude in standard medium stimulated paracrine signaling(TGF-β1:467% ± 22% vs 100% ± 6% in freshcontrols,BMP-4:258% ± 22% vs 100% ± 4% in fresh controls; P < 0.05) and ECM degradation(MMP-2:941% ± 90% vs 100% ± 19% in fresh controls,MMP-9:1219% ± 190% vs 100% ± 16% in fresh controls,cathepsin L:1187% ± 175% vs 100% ± 12% in fresh controls,cathepsin S:603% ± 88% vs 100% ± 13% in fresh controls; P < 0.05),while BMP-4 supplementation also promoted fibrosa activation and TGF-β1 inhibition reduced MMP-9 expression to the native tissue level(MMP-9:308% ± 153% with TGF-β1 inhibition vs 100% ± 16% in fresh control; P > 0.05). Supra-physiologic FSS frequency had no effect on endothelial activation and paracrine signaling regardless of the culture medium but TGF-β1 silencing attenuated FSS-induced ECM degradation via MMP-9 downregulation(MMP-9:302% ± 182% vs 100% ± 42% in fresh controls; P > 0.05).CONCLUSION:Valvular tissue is sensitive to FSS abnormalities. The TGF-β1 inhibitor SB-431542 is a potential candidate molecule for attenuating the effects of FSS abnormalities on valvular remodeling.
文摘Mechanosensation is an important process in biological fluid-structure interaction. To understand the biophysics underlying mechanosensation, it is essential to quantify the correlation between membrane deformation, membrane tension, external fluid shear stress, and conformation of mechanosensitive (MS) channels. Smoothed dissipative particle dynamics (SDPD) simulations of vesicle/cell in three types of flow configurations are conducted to calculate the tension in lipid membrane due to fluid shear stress from the surrounding viscous flow. In combination with a simple continuum model for an MS channel, SDPD simulation results suggest that shearing adhered vesicles/cells is more effective to induce membrane tension sufficient to stretch MS channels open than a free shear flow or a constrictive channel flow. In addition, we incorporate the bilayer-cytoskeletal interaction in a two-component model to probe the effects of a cytoskeletal network on the gating of MS channels.
文摘Future unconstrained and science-driven missions to Mars will require advanced guidance algorithms that are able to adapt to more demanding mission requirements, e.g. landing on selected locales with pinpoint accuracy while autonomously flying fuel-efficient trajectories. In this paper, a novel guidance algorithm designed by applying the principles of reinforcement learning(RL) theory is presented. The goal is to devise an adaptive guidance algorithm that enables robust, fuel efficient,and accurate landing without the need for off line trajectory generation and real-time tracking. Results from a Monte Carlo simulation campaign show that the algorithm is capable of autonomously following trajectories that are close to the optimal minimum-fuel solutions with an accuracy that surpasses that of past and future Mars missions. The proposed RL-based guidance algorithm exhibits a high degree of flexibility and can easily accommodate autonomous retargeting while maintaining accuracy and fuel efficiency. Although reinforcement learning and other similar machine learning techniques have been previously applied to aerospace guidance and control problems(e.g., autonomous helicopter control), this appears, to the best of the authors knowledge, to be the first application of reinforcement learning to the problem of autonomous planetary landing.
文摘Deep-tissue solid cancer treatment has a poor prognosis,resulting in a very low 5-year patient survival rate.The primary challenges facing solid tumor therapies are accessibility,incomplete surgical removal of tumor tissue,the resistance of the hypoxic and heterogeneous tumor microenvironment to chemotherapy and radiation,and suffering caused by off-target toxicities.Here,sonodynamic therapy(SDT)is an evolving therapeutic approach that uses low-intensity ultrasound to target deep-tissue solid tumors.The ability of ultrasound to deliver energy safely and precisely into small deep-tissue(>10 cm)volumes makes SDT more effective than conventional photodynamic therapy.While SDT is currently in phase 1/2 clinical trials for glioblastoma multiforme,its use for other solid cancer treatments,such as breast,pancreatic,liver,and prostate cancer,is still in the preclinical stage,with further investigation required to improve its therapeutic efficacy.This review,therefore,focuses on recent advances in SDT cancer treatments.We describe the interaction between ultrasound and sonosensitizer molecules and the associated energy transfer mechanism to malignant cells,which plays a central role in SDT-mediated cell death.Different sensitizers used in clinical and preclinical trials of various cancer treatments are listed,and the critical ultrasound parameters for SDT are reviewed.We also discuss approaches to improve the efficacies of these sonosensitizers,the role of the 3-dimensional spheroid in vitro investigations,ultrasound-controlled CAR-T cell and SDT-based multimodal therapy,and machine learning for sonosensitizer optimization,which could facilitate clinical translation of SDT.
文摘This paper studies a master-slave type of synchronization systems for a general form of two discrete Lur＇e systems. Some simple necessary and/or sufficient conditions for synchronization are derived. They are basically algebraic conditions, and are convement to be applied in engineering applications.
文摘A longitudinal magnetic field was introduced to submerged arc cladding （SAC）. Electromagnetic stirring was caused by the interaction between arc plasma and external magnetic field. The grain size was refined and the average hardness was improved. On the base of a group of optimized parameters calculated by orthogonal optimization, some tests were made to study the effects of electromagnetic stirring on hardness and grain size of surfacing layers. It was confirmed that the solidification made of liquid metal could be improved by electromagnetic stirring and hardness and grain size of surfacing layers could be improved.
