A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped C...A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.展开更多
Polypropylene(PP) accounts for approximately 28.0% of the global polyolefin market,valued at $243.4 billion in 2022.Known for its lightweight,chemical resistance,costeffectiveness,high strength and melting point,PP is...Polypropylene(PP) accounts for approximately 28.0% of the global polyolefin market,valued at $243.4 billion in 2022.Known for its lightweight,chemical resistance,costeffectiveness,high strength and melting point,PP is widely used in various applications.Its properties and applications are closely tied to its tacticity.One-dimensional(1D) conventional 13C NMR has been extensively utilized to analyze PP tacticity,but its low sensitivity and longer relaxation time remain drawbacks.Typically,analyzing a single PP sample requires around 9 h of NMR time.Using of a cryogenically cooled 10 mm NMR probe can significantly reduce this measurement time;however,its high cost makes it inaccessible for most NMR laboratories.While the refocused insensitive nuclei enhanced by polarization transfer(RINEPT) technique is well-known for enhancing NMR sensitivity,there are no published studies using 1D 13C RINEPT to quantify PP tacticity.Relaxation agents like chromium(Ⅲ) acetylacetonate(Cr(acac)_(3)) have also been used to reduce relaxation times in polyolefin NMR analyses.Here we introduce a straightforward and easily implementable 1D 13C NMR method for rapid PP tacticity quantification.This method combines Cr(acac)_(3),Bruker's existing RINEPT pulse sequence(ineptrd),and our recently published ~1H decoupling sequence(bi_waltz65_256 pl) to eliminate ~1H decoupling artifacts.It is worth noting that decoupling artifacts are always present.When the signal-to-noise ratio(SNR) is low,these artifacts are obscured by noise.For example,in some two-dimensional(2D) or three-dimensional(3D) NMR spectra,decoupling artifacts are barely visible because of the low SNR.However,when attempting to observe weak signals in ~1D spectra,increasing the sample concentration or the number of scans enhances the SNR,revealing the decoupling artifacts.The decoupling artifacts appeared superimpose with some other weak signals,affecting the measurements of signal intensities.Therefore,improved ~1H-decoupling methods are crucial for such data acquisitio n.This synergy results in a 9.4-to 9.7-fold sensitivity enhancement,equating to an 88-to 94-fold reduction(9.4^(2)≈88,9.7^(2)≈94) in NMR acquisition time compared to conventional 1D 13C NMR experiment with Cr(acac)_3.The time savings are even more substantial compared to experiments without Cr(acac)_3.The faster and quantitative approach is accessible to researchers with or without cryoprobes.Beyond PP,this method can be applied to tacticity measurements of other polyolefins,such as polybutene,polyhexene and polyoctene.展开更多
This study focuses on empirical modeling of the strength characteristics of urban soils contaminated with heavy metals using machine learning tools and their subsequent stabilization with ordinary Portland cement(OPC)...This study focuses on empirical modeling of the strength characteristics of urban soils contaminated with heavy metals using machine learning tools and their subsequent stabilization with ordinary Portland cement(OPC).For dataset collection,an extensive experimental program was designed to estimate the unconfined compressive strength(Qu)of heavy metal-contaminated soils collected from awide range of land use pattern,i.e.residential,industrial and roadside soils.Accordingly,a robust comparison of predictive performances of four data-driven models including extreme learning machines(ELMs),gene expression programming(GEP),random forests(RFs),and multiple linear regression(MLR)has been presented.For completeness,a comprehensive experimental database has been established and partitioned into 80%for training and 20%for testing the developed models.Inputs included varying levels of heavy metals like Cd,Cu,Cr,Pb and Zn,along with OPC.The results revealed that the GEP model outperformed its counterparts:explaining approximately 96%of the variability in both training(R2=0.964)and testing phases(R^(2)=0.961),and thus achieving the lowest RMSE and MAE values.ELM performed commendably but was slightly less accurate than GEP whereas MLR had the lowest performance metrics.GEP also provided the benefit of traceable mathematical equation,enhancing its applicability not just as a predictive but also as an explanatory tool.Despite its insights,the study is limited by its focus on a specific set of heavy metals and urban soil samples of a particular region,which may affect the generalizability of the findings to different contamination profiles or environmental conditions.The study recommends GEP for predicting Qu in heavy metal-contaminated soils,and suggests further research to adapt these models to different environmental conditions.展开更多
The undercurrent research survey explores the roles of nonlocality and strain gradient size dependencies in nonlinear asymmetric buckling of shallow nanoscale arches having dissimilar end conditions through a numerica...The undercurrent research survey explores the roles of nonlocality and strain gradient size dependencies in nonlinear asymmetric buckling of shallow nanoscale arches having dissimilar end conditions through a numerical analysis.The arches,made from a functionally graded graphene nanofiller reinforced composite(FG-GNRC),are subjected to discretional radial concentrated loads along with converting of temperature.To account for the size dependencies,the exploration is carried out stemming from the nonlocal strain gradient theory(NSGT)in the sense of a quasi-2D parabolic shear flexible concept of curved beam.The material properties of the contemplated FG-GNRC sandwich are determined using the modified Halpin-Tsai micromechanics model.Subsequently,an extended isogeometric analysis(XIGA)is manipulated comprising insertion plus multiplication of knots to achieve the demanded lower continuity allocated to the integration between flexural and tangential reflexes.It is perceived that the both softening and stiffening concomitants assigned to the salient concentrated radial loads obtained by the developed NSGT-based XIGA diminish from the first upper limit to the second one,and then likewise from the first lower limit to the second one.Although,by becoming the upsurge in temperature higher,these softening and stiffening concomitants get more remarkable.展开更多
This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not ...This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not necessarily for real-time testing, but rather for models that involve large-scale physical sub-structures and highly nonlinear numerical models. Four case studies are presented and discussed. In the first case study, the accuracy of integration schemes including two widely used methods, namely, modified version of the implicit Newmark with fixed-number of iteration （iterative） and the operator-splitting （non-iterative） is examined through pure numerical simulations. The second case study presents the results of 10 hybrid simulations repeated with the two aforementioned integration methods considering various time steps and fixed-number of iterations for the iterative integration method. The physical sub-structure in these tests consists of a single-degree-of-freedom （SDOF） cantilever column with replaceable steel coupons that provides repeatable highly- nonlinear behavior including fracture-type strength and stiffness degradations. In case study three, the implicit Newmark with fixed-number of iterations is applied for hybrid simulations of a 1：2 scale steel moment frame that includes a relatively complex nonlinear numerical substructure. Lastly, a more complex numerical substructure is considered by constructing a nonlinear computational model of a moment frame coupled to a hybrid model ofa 1：2 scale steel gravity frame. The last two case studies are conducted on the same porotype structure and the selection of time steps and fixed number of iterations are closely examined in pre-test simulations. The generated unbalance forces is used as an index to track the equilibrium error and predict the accuracy and stability of the simulations.展开更多
Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer ...Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.展开更多
An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties ...An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology.Especially,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work.Applying Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is obtained.The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass.The GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium.The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature.The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail.These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium.Thereby,they offer appropriate operational approaches for the structure when employed in various mediums.展开更多
The prediction of liquefaction-induced lateral spreading/displacement(Dh)is a challenging task for civil/geotechnical engineers.In this study,a new approach is proposed to predict Dh using gene expression programming(...The prediction of liquefaction-induced lateral spreading/displacement(Dh)is a challenging task for civil/geotechnical engineers.In this study,a new approach is proposed to predict Dh using gene expression programming(GEP).Based on statistical reasoning,individual models were developed for two topographies:free-face and gently sloping ground.Along with a comparison with conventional approaches for predicting the Dh,four additional regression-based soft computing models,i.e.Gaussian process regression(GPR),relevance vector machine(RVM),sequential minimal optimization regression(SMOR),and M5-tree,were developed and compared with the GEP model.The results indicate that the GEP models predict Dh with less bias,as evidenced by the root mean square error(RMSE)and mean absolute error(MAE)for training(i.e.1.092 and 0.815;and 0.643 and 0.526)and for testing(i.e.0.89 and 0.705;and 0.773 and 0.573)in free-face and gently sloping ground topographies,respectively.The overall performance for the free-face topology was ranked as follows:GEP>RVM>M5-tree>GPR>SMOR,with a total score of 40,32,24,15,and 10,respectively.For the gently sloping condition,the performance was ranked as follows:GEP>RVM>GPR>M5-tree>SMOR with a total score of 40,32,21,19,and 8,respectively.Finally,the results of the sensitivity analysis showed that for both free-face and gently sloping ground,the liquefiable layer thickness(T_(15))was the major parameter with percentage deterioration(%D)value of 99.15 and 90.72,respectively.展开更多
Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional cali...Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional calibration of material parameters often relies on a trial-and-error approach,in which the parameters are manually adjusted until the corresponding finite element model results in a response matching the experimental global response.The parameter estimates are often subjective.To address this issue,in this paper we treat the identification of material parameters as an optimization problem and introduce the particle swarm optimization(PSO)algorithm as the optimization approach.We provide material parameters of two uncoupled ductile fracture models—the Rice and Tracey void growth model(RT-VGM)and the micro-mechanical void growth model(MM-VGM),and a coupled model—the gurson-Tvergaard-Needleman(GTN)model for ASTM A36,A572 Gr.50,and A992 structural steels using an automated PSO method.By minimizing the difference between the experimental results and finite element simulations of the load-displacement curves for a set of tests of circumferentially notched tensile(CNT)bars,the calibration procedure automatically determines the parameters of the strain hardening law as well as the uncoupled models and the coupled GTN constitutive model.Validation studies show accurate prediction of the load-displacement response and ductile fracture initiation in V-notch specimens,and confirm the PSO algorithm as an effective and robust algorithm for seeking ductile fracture model parameters.PSO has excellent potential for identifying other fracture models(e.g.,shear modified GTN)with many parameters that can give rise to more accurate predictions of ductile fracture.Limitations of the PSO algorithm and the current calibrated ductile fracture models are also discussed in this paper.展开更多
<div style="text-align:justify;"> Arches are employed for bridges. This particular type of structures, characterized by a very old use tradition, is nowadays, widely exploited because of its strength, ...<div style="text-align:justify;"> Arches are employed for bridges. This particular type of structures, characterized by a very old use tradition, is nowadays, widely exploited because of its strength, resilience, cost-effectiveness and charm. In recent years, a more conscious design approach that focuses on a more proper use of the building materials combined with the increasing of the computational capability of the modern computers, has led the research in the civil engineering field to the study of optimization algorithms applications aimed at the definition of the best design parameters. In this paper, a differential formulation and a MATLAB code for the calculation of the internal stresses in the arch structure are proposed. Then, the application of a machine learning algorithm, the genetic algorithm, for the calculation of the geometrical parameters, that allows to minimize the quantity of material that constitute the arch structures, is implemented. In this phase, the method used to calculate the stresses has been considered as a constraint function to reduce the range of the solutions to the only ones able to bear the design loads with the smallest volume. In particular, some case studies with different cross-sections are reported to prove the validity of the method and to compare the obtained results in terms of optimization effectiveness. </div>展开更多
There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates...There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates the incorporation of sisal fibers of 20 mm and 40 mm in length and volume fraction of 0.5% and 1% for concrete masonry structural blocks, and determines the use of these units to build prisms and mini-walls. Laboratory tests were carried out to characterize the physical of blocks and mortar, in addition to the axial compression tests of the units, prisms, and mini-walls. The sisal had low apparent density and high water absorption, which is a common feature of such material due to the high incidence of permeable pores. The physical properties of the blocks with and without addition complied with the standard requirements established to validate their use. The obtained results showed that the fiber-reinforced mini-walls obtained values very close to or even higher than those obtained for the mini-walls without fibers, demonstrating better performance than the blocks and prisms.展开更多
Isogeometric analysis(IGA),which aims at integrating CAD and CAE models,is one of the most active research topics in both computational mechanics and computer-aided geometric design.The rapidly growing interests in IG...Isogeometric analysis(IGA),which aims at integrating CAD and CAE models,is one of the most active research topics in both computational mechanics and computer-aided geometric design.The rapidly growing interests in IGA has led to profound developments of relevant theories and applications,one of which being structural optimization.With the rapid growth of researches in IGA,this special issue contributes to highlight recent developments,challenges and opportunities of IGA and IGA-based structural design optimization,with focuses on theory development,numerical implementations and potential applications.展开更多
The main goal of this study is analysis the mechanical behavior, failure mode and deflections of masonry beams lintels when subjected to concentrated loading. Walls were built using hollow clay blocks, using horizonta...The main goal of this study is analysis the mechanical behavior, failure mode and deflections of masonry beams lintels when subjected to concentrated loading. Walls were built using hollow clay blocks, using horizontal reinforcement on bed joint, and using of Murfor steel reinforcement. The conclusions of this work was： at middle of span, the load and displacement results present a linear behavior until failure; there two regions of failure, the region ＂A＂ presents the association of crushing and the region ＂B＂ shows the shear stress between block and mortar; the visual analysis of experimental tests shows the lost of adhesion between the mortar joint and blocks. It was not observed cracks on the mid-span produced by bending; it is possible to detach that the use of plane truss in Brazil as technological alternative is feasible and makes the masonry walls execution more rational, increasing the velocity of production.展开更多
Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,howev...Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,however,are complicated and computationally challenging,and hence impractical for application to individual projects.To address this issue,design guidance proposes target reliability indices for normal design conditions,but no target reliability indices are defined for structural fire design.We revisit the background of the cost-optimization based approach underlying normal design target reliability indices then we extend this approach for the case of fire design of structures.We also propose a modified objective function for cost-optimization which simplifies the evaluation of target reliability indices and reduces the number of assumptions.The optimum safety level is expressed as a function of a new dimensionless variable named“Damage-to-investment indicator”(DII).The cost optimization approach is validated for the target reliability indices for normal design condition.The method is then applied for evaluating DII and the associated optimum reliability indices for fire-exposed structures.Two case studies are presented:(i)a one-way loaded reinforced concrete slab and(ii)a steel column under axial loading.This study thus provides a framework for deriving optimum(target)reliability index for structural fire design which can support the development of rational provisions in codes and standards.展开更多
Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many metals.Despite the global research effort,the underlying hydrogen-GB interactions in polyc...Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many metals.Despite the global research effort,the underlying hydrogen-GB interactions in polycrystals remain inadequately understood.In this study,using Voronoi tessellations and atomistic simulations,we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation sites.Three distinct peaks in the energy spectrum are identified,corresponding to different structural fingerprints.The first peak(-0.205 eV)represents the most favorable segregation sites at GB core,while the second and third peaks account for the sites at GB surface.By incorporating a thermodynamic model,the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs,unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental studies.The identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion,with the low-barrier channels inside GB core contributing to short-circuit diffusion,while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion barriers.Mean square displacement analysis further confirms the findings,and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of lattice.The present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.展开更多
In 2023,pivotal advancements in artificial intelligence(AI)have significantly experienced.With that in mind,traditional methodologies,notably the p-y approach,have struggled to accurately model the complex,nonlinear s...In 2023,pivotal advancements in artificial intelligence(AI)have significantly experienced.With that in mind,traditional methodologies,notably the p-y approach,have struggled to accurately model the complex,nonlinear soil-structure interactions of laterally loaded large-diameter drilled shafts.This study undertakes a rigorous evaluation of machine learning(ML)and deep learning(DL)techniques,offering a comprehensive review of their application in addressing this geotechnical challenge.A thorough review and comparative analysis have been carried out to investigate various AI models such as artificial neural networks(ANNs),relevance vector machines(RVMs),and least squares support vector machines(LSSVMs).It was found that despite ML approaches outperforming classic methods in predicting the lateral behavior of piles,their‘black box'nature and reliance only on a data-driven approach made their results showcase statistical robustness rather than clear geotechnical insights,a fact underscored by the mathematical equations derived from these studies.Furthermore,the research identified a gap in the availability of drilled shaft datasets,limiting the extendibility of current findings to large-diameter piles.An extensive dataset,compiled from a series of lateral loading tests on free-head drilled shaft with varying properties and geometries,was introduced to bridge this gap.The paper concluded with a direction for future research,proposes the integration of physics-informed neural networks(PINNs),combining data-driven models with fundamental geotechnical principles to improve both the interpretability and predictive accuracy of AI applications in geotechnical engineering,marking a novel contribution to the field.展开更多
The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement co...The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement concrete facing panels,and gravity-type earth-retaining walls.The finite element(FE)simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses.The seismic performance of differentmodels,which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls,was simulated and examined using the FE approach.It also displays comparative studies such as stress distribution,deflection of the wall,acceleration across the wall height,lateral wall displacement,lateral wall pressure,and backfill plastic strain.Three components of the created ER walls were found throughout this research procedure.One is a granular reinforcement backfill,while the other is a wall-facing panel and base foundation.The dynamic response effects of varied earth-retaining walls have also been studied.It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls.The proposed analytical model’s validity has been evaluated and compared with the reinforcement concrete facing panels,gravity-type ER wall,scientifically available data,and American Association of State Highway and Transportation Officials(AASHTO)guidelines results based on FE simulation.The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types.The methodology and results of this study establish standards for future analogous investigations and professionals,particularly in light of the increasing computational capabilities of desktop computers.展开更多
In the article“Influence of Various Earth-Retaining Walls on the Dynamic Response Comparison Based on 3D Modeling”by Muhammad Akba,Huali Pan,Jiangcheng Huang,Bilal Ahmed,Guoqiang Ou(Computer Modeling in Engineering&...In the article“Influence of Various Earth-Retaining Walls on the Dynamic Response Comparison Based on 3D Modeling”by Muhammad Akba,Huali Pan,Jiangcheng Huang,Bilal Ahmed,Guoqiang Ou(Computer Modeling in Engineering&Sciences,2024,Vol.139,No.3,2835–2863.DOI:10.32604/cmes.2024.046993,URL:https://www.techscience.com/CMES/v139n3/55652),one author’s affiliation was not included in the original article.展开更多
Background The incidence of cryptogenic stroke(CS)accounts for about 25%of ischemic stroke.Current studies have shown that cryptogenic stroke is closely related to patent foramen ovale(PFO).Evaluating the correlation ...Background The incidence of cryptogenic stroke(CS)accounts for about 25%of ischemic stroke.Current studies have shown that cryptogenic stroke is closely related to patent foramen ovale(PFO).Evaluating the correlation between PFO and CS needs to be combined with multidisciplinary evaluation.Many clinical studies have shown that drug therapy can reduce the risk of ischemic stroke in elderly PFO patients(>60 years old).However,whether elderly PFO patients(>60 years old)can benefit from PFO closure is still controversial.This article reviewed the research progress of drug therapy and PFO closure therapy for cryptogenic stroke associated with PFO in the elderly.[S Chin J Cardiol 2024;25(1):50-56].展开更多
This article presents a study on the structural behavior of transversely prestressed laminated timber slabs,focusing on an innovative approach:vertically misaligned lamellae.This misalignment,achieved by sliding verti...This article presents a study on the structural behavior of transversely prestressed laminated timber slabs,focusing on an innovative approach:vertically misaligned lamellae.This misalignment,achieved by sliding vertically the wooden lamellae rather than aligning them,enhances the slab’s cross-section moment of inertia,thereby improving load-bearing capacity and stiffness.Testing involved two groups of structural size specimens:one with vertically aligned lamellae(control group)and the other with misaligned lamellae(study group).Results showed the study group exhibited 42%superior stiffness and 10%less load capacity compared to the control.Failures typically occurred individually in the lamellae,particularly in those with defects or lower modulus of elasticity,concentrated in the middle third of the slabs’free span where tensile stresses peak.Despite a higher number of failed lamellae,the study group demonstrated promising performance.Analysis of prestressing bar indicated no damage at all in the thread,suggesting potential for reducing bar diameter.These findings offer crucial insights into applying these slabs in timber construction as well as to any kind of construction.展开更多
基金supported by the National Key R&D Program of China(No.2019YFA0209902)the Natural Science Foundation of China(Nos.52071326,52192593,51601204)+1 种基金the NSFC Basic Science Center Program for Multiscale Problems in Nonlinear Mechanics(No.11988102)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040503).
文摘A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.
文摘Polypropylene(PP) accounts for approximately 28.0% of the global polyolefin market,valued at $243.4 billion in 2022.Known for its lightweight,chemical resistance,costeffectiveness,high strength and melting point,PP is widely used in various applications.Its properties and applications are closely tied to its tacticity.One-dimensional(1D) conventional 13C NMR has been extensively utilized to analyze PP tacticity,but its low sensitivity and longer relaxation time remain drawbacks.Typically,analyzing a single PP sample requires around 9 h of NMR time.Using of a cryogenically cooled 10 mm NMR probe can significantly reduce this measurement time;however,its high cost makes it inaccessible for most NMR laboratories.While the refocused insensitive nuclei enhanced by polarization transfer(RINEPT) technique is well-known for enhancing NMR sensitivity,there are no published studies using 1D 13C RINEPT to quantify PP tacticity.Relaxation agents like chromium(Ⅲ) acetylacetonate(Cr(acac)_(3)) have also been used to reduce relaxation times in polyolefin NMR analyses.Here we introduce a straightforward and easily implementable 1D 13C NMR method for rapid PP tacticity quantification.This method combines Cr(acac)_(3),Bruker's existing RINEPT pulse sequence(ineptrd),and our recently published ~1H decoupling sequence(bi_waltz65_256 pl) to eliminate ~1H decoupling artifacts.It is worth noting that decoupling artifacts are always present.When the signal-to-noise ratio(SNR) is low,these artifacts are obscured by noise.For example,in some two-dimensional(2D) or three-dimensional(3D) NMR spectra,decoupling artifacts are barely visible because of the low SNR.However,when attempting to observe weak signals in ~1D spectra,increasing the sample concentration or the number of scans enhances the SNR,revealing the decoupling artifacts.The decoupling artifacts appeared superimpose with some other weak signals,affecting the measurements of signal intensities.Therefore,improved ~1H-decoupling methods are crucial for such data acquisitio n.This synergy results in a 9.4-to 9.7-fold sensitivity enhancement,equating to an 88-to 94-fold reduction(9.4^(2)≈88,9.7^(2)≈94) in NMR acquisition time compared to conventional 1D 13C NMR experiment with Cr(acac)_3.The time savings are even more substantial compared to experiments without Cr(acac)_3.The faster and quantitative approach is accessible to researchers with or without cryoprobes.Beyond PP,this method can be applied to tacticity measurements of other polyolefins,such as polybutene,polyhexene and polyoctene.
基金funded by the Natural Science Foundation of China(Grant No.52090084)was partially supported by the Sand Hazards and Opportunities for Resilience,Energy,and Sustainability(SHORES)Center,funded by Tamkeen under the NYUAD Research Institute Award CG013.
文摘This study focuses on empirical modeling of the strength characteristics of urban soils contaminated with heavy metals using machine learning tools and their subsequent stabilization with ordinary Portland cement(OPC).For dataset collection,an extensive experimental program was designed to estimate the unconfined compressive strength(Qu)of heavy metal-contaminated soils collected from awide range of land use pattern,i.e.residential,industrial and roadside soils.Accordingly,a robust comparison of predictive performances of four data-driven models including extreme learning machines(ELMs),gene expression programming(GEP),random forests(RFs),and multiple linear regression(MLR)has been presented.For completeness,a comprehensive experimental database has been established and partitioned into 80%for training and 20%for testing the developed models.Inputs included varying levels of heavy metals like Cd,Cu,Cr,Pb and Zn,along with OPC.The results revealed that the GEP model outperformed its counterparts:explaining approximately 96%of the variability in both training(R2=0.964)and testing phases(R^(2)=0.961),and thus achieving the lowest RMSE and MAE values.ELM performed commendably but was slightly less accurate than GEP whereas MLR had the lowest performance metrics.GEP also provided the benefit of traceable mathematical equation,enhancing its applicability not just as a predictive but also as an explanatory tool.Despite its insights,the study is limited by its focus on a specific set of heavy metals and urban soil samples of a particular region,which may affect the generalizability of the findings to different contamination profiles or environmental conditions.The study recommends GEP for predicting Qu in heavy metal-contaminated soils,and suggests further research to adapt these models to different environmental conditions.
基金supported by projects VEGA 1/0307/23 and APVV-23-0204 of Scientific Grant Agency of the Ministry of Education,Research,Development and Youth of the Slovak Republic.
文摘The undercurrent research survey explores the roles of nonlocality and strain gradient size dependencies in nonlinear asymmetric buckling of shallow nanoscale arches having dissimilar end conditions through a numerical analysis.The arches,made from a functionally graded graphene nanofiller reinforced composite(FG-GNRC),are subjected to discretional radial concentrated loads along with converting of temperature.To account for the size dependencies,the exploration is carried out stemming from the nonlocal strain gradient theory(NSGT)in the sense of a quasi-2D parabolic shear flexible concept of curved beam.The material properties of the contemplated FG-GNRC sandwich are determined using the modified Halpin-Tsai micromechanics model.Subsequently,an extended isogeometric analysis(XIGA)is manipulated comprising insertion plus multiplication of knots to achieve the demanded lower continuity allocated to the integration between flexural and tangential reflexes.It is perceived that the both softening and stiffening concomitants assigned to the salient concentrated radial loads obtained by the developed NSGT-based XIGA diminish from the first upper limit to the second one,and then likewise from the first lower limit to the second one.Although,by becoming the upsurge in temperature higher,these softening and stiffening concomitants get more remarkable.
基金National Science Foundation(NSF)under grant No.CMMI-0748111
文摘This study examines the performance of integration methods for hybrid simulation of large and complex structural systems in the context of structural collapse due to seismic excitations. The target application is not necessarily for real-time testing, but rather for models that involve large-scale physical sub-structures and highly nonlinear numerical models. Four case studies are presented and discussed. In the first case study, the accuracy of integration schemes including two widely used methods, namely, modified version of the implicit Newmark with fixed-number of iteration （iterative） and the operator-splitting （non-iterative） is examined through pure numerical simulations. The second case study presents the results of 10 hybrid simulations repeated with the two aforementioned integration methods considering various time steps and fixed-number of iterations for the iterative integration method. The physical sub-structure in these tests consists of a single-degree-of-freedom （SDOF） cantilever column with replaceable steel coupons that provides repeatable highly- nonlinear behavior including fracture-type strength and stiffness degradations. In case study three, the implicit Newmark with fixed-number of iterations is applied for hybrid simulations of a 1：2 scale steel moment frame that includes a relatively complex nonlinear numerical substructure. Lastly, a more complex numerical substructure is considered by constructing a nonlinear computational model of a moment frame coupled to a hybrid model ofa 1：2 scale steel gravity frame. The last two case studies are conducted on the same porotype structure and the selection of time steps and fixed number of iterations are closely examined in pre-test simulations. The generated unbalance forces is used as an index to track the equilibrium error and predict the accuracy and stability of the simulations.
基金National Natural Science Foundation of China under Grant No.51878508。
文摘Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.
文摘An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology.Especially,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work.Applying Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is obtained.The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass.The GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium.The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature.The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail.These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium.Thereby,they offer appropriate operational approaches for the structure when employed in various mediums.
文摘The prediction of liquefaction-induced lateral spreading/displacement(Dh)is a challenging task for civil/geotechnical engineers.In this study,a new approach is proposed to predict Dh using gene expression programming(GEP).Based on statistical reasoning,individual models were developed for two topographies:free-face and gently sloping ground.Along with a comparison with conventional approaches for predicting the Dh,four additional regression-based soft computing models,i.e.Gaussian process regression(GPR),relevance vector machine(RVM),sequential minimal optimization regression(SMOR),and M5-tree,were developed and compared with the GEP model.The results indicate that the GEP models predict Dh with less bias,as evidenced by the root mean square error(RMSE)and mean absolute error(MAE)for training(i.e.1.092 and 0.815;and 0.643 and 0.526)and for testing(i.e.0.89 and 0.705;and 0.773 and 0.573)in free-face and gently sloping ground topographies,respectively.The overall performance for the free-face topology was ranked as follows:GEP>RVM>M5-tree>GPR>SMOR,with a total score of 40,32,24,15,and 10,respectively.For the gently sloping condition,the performance was ranked as follows:GEP>RVM>GPR>M5-tree>SMOR with a total score of 40,32,21,19,and 8,respectively.Finally,the results of the sensitivity analysis showed that for both free-face and gently sloping ground,the liquefiable layer thickness(T_(15))was the major parameter with percentage deterioration(%D)value of 99.15 and 90.72,respectively.
基金the National Natural Science Foundation of China(No.51908416)the Shanghai Pujiang Program(No.19PJ1409500)the Fundamental Research Funds for the Central Universities,China。
文摘Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional calibration of material parameters often relies on a trial-and-error approach,in which the parameters are manually adjusted until the corresponding finite element model results in a response matching the experimental global response.The parameter estimates are often subjective.To address this issue,in this paper we treat the identification of material parameters as an optimization problem and introduce the particle swarm optimization(PSO)algorithm as the optimization approach.We provide material parameters of two uncoupled ductile fracture models—the Rice and Tracey void growth model(RT-VGM)and the micro-mechanical void growth model(MM-VGM),and a coupled model—the gurson-Tvergaard-Needleman(GTN)model for ASTM A36,A572 Gr.50,and A992 structural steels using an automated PSO method.By minimizing the difference between the experimental results and finite element simulations of the load-displacement curves for a set of tests of circumferentially notched tensile(CNT)bars,the calibration procedure automatically determines the parameters of the strain hardening law as well as the uncoupled models and the coupled GTN constitutive model.Validation studies show accurate prediction of the load-displacement response and ductile fracture initiation in V-notch specimens,and confirm the PSO algorithm as an effective and robust algorithm for seeking ductile fracture model parameters.PSO has excellent potential for identifying other fracture models(e.g.,shear modified GTN)with many parameters that can give rise to more accurate predictions of ductile fracture.Limitations of the PSO algorithm and the current calibrated ductile fracture models are also discussed in this paper.
文摘<div style="text-align:justify;"> Arches are employed for bridges. This particular type of structures, characterized by a very old use tradition, is nowadays, widely exploited because of its strength, resilience, cost-effectiveness and charm. In recent years, a more conscious design approach that focuses on a more proper use of the building materials combined with the increasing of the computational capability of the modern computers, has led the research in the civil engineering field to the study of optimization algorithms applications aimed at the definition of the best design parameters. In this paper, a differential formulation and a MATLAB code for the calculation of the internal stresses in the arch structure are proposed. Then, the application of a machine learning algorithm, the genetic algorithm, for the calculation of the geometrical parameters, that allows to minimize the quantity of material that constitute the arch structures, is implemented. In this phase, the method used to calculate the stresses has been considered as a constraint function to reduce the range of the solutions to the only ones able to bear the design loads with the smallest volume. In particular, some case studies with different cross-sections are reported to prove the validity of the method and to compare the obtained results in terms of optimization effectiveness. </div>
文摘There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates the incorporation of sisal fibers of 20 mm and 40 mm in length and volume fraction of 0.5% and 1% for concrete masonry structural blocks, and determines the use of these units to build prisms and mini-walls. Laboratory tests were carried out to characterize the physical of blocks and mortar, in addition to the axial compression tests of the units, prisms, and mini-walls. The sisal had low apparent density and high water absorption, which is a common feature of such material due to the high incidence of permeable pores. The physical properties of the blocks with and without addition complied with the standard requirements established to validate their use. The obtained results showed that the fiber-reinforced mini-walls obtained values very close to or even higher than those obtained for the mini-walls without fibers, demonstrating better performance than the blocks and prisms.
基金This work has been supported by National Natural Science Foundation of China(51705158),Guangdong Basic and Applied Basic Research Foundation(2019A1515011783)Guangdong Regular Institutions of Characteristic Innovation Project(2017KTSCX176)KEY Laboratory of Robotics and Intelligent Equipment of Guangdong Regular Institutions of Higher Education(2017KSYS009).These supports are gratefully acknowledged.
文摘Isogeometric analysis(IGA),which aims at integrating CAD and CAE models,is one of the most active research topics in both computational mechanics and computer-aided geometric design.The rapidly growing interests in IGA has led to profound developments of relevant theories and applications,one of which being structural optimization.With the rapid growth of researches in IGA,this special issue contributes to highlight recent developments,challenges and opportunities of IGA and IGA-based structural design optimization,with focuses on theory development,numerical implementations and potential applications.
文摘The main goal of this study is analysis the mechanical behavior, failure mode and deflections of masonry beams lintels when subjected to concentrated loading. Walls were built using hollow clay blocks, using horizontal reinforcement on bed joint, and using of Murfor steel reinforcement. The conclusions of this work was： at middle of span, the load and displacement results present a linear behavior until failure; there two regions of failure, the region ＂A＂ presents the association of crushing and the region ＂B＂ shows the shear stress between block and mortar; the visual analysis of experimental tests shows the lost of adhesion between the mortar joint and blocks. It was not observed cracks on the mid-span produced by bending; it is possible to detach that the use of plane truss in Brazil as technological alternative is feasible and makes the masonry walls execution more rational, increasing the velocity of production.
基金funded by the Ghent University Special Research Fund under grant 01N01219“Multi-objective societal optimization of structural fire safety investments for uncommon projects using advanced regression techniques”.
文摘Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment.Cost-benefit analyses,however,are complicated and computationally challenging,and hence impractical for application to individual projects.To address this issue,design guidance proposes target reliability indices for normal design conditions,but no target reliability indices are defined for structural fire design.We revisit the background of the cost-optimization based approach underlying normal design target reliability indices then we extend this approach for the case of fire design of structures.We also propose a modified objective function for cost-optimization which simplifies the evaluation of target reliability indices and reduces the number of assumptions.The optimum safety level is expressed as a function of a new dimensionless variable named“Damage-to-investment indicator”(DII).The cost optimization approach is validated for the target reliability indices for normal design condition.The method is then applied for evaluating DII and the associated optimum reliability indices for fire-exposed structures.Two case studies are presented:(i)a one-way loaded reinforced concrete slab and(ii)a steel column under axial loading.This study thus provides a framework for deriving optimum(target)reliability index for structural fire design which can support the development of rational provisions in codes and standards.
基金financially supported by the Research Council of Norway under the M-HEAT project(No.294689)the HyLINE Project(No.294739)All simulation resources are provided by the Norwegian Metacenter for Computational Science(Nos.NN9110K and NN9391K).
文摘Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many metals.Despite the global research effort,the underlying hydrogen-GB interactions in polycrystals remain inadequately understood.In this study,using Voronoi tessellations and atomistic simulations,we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation sites.Three distinct peaks in the energy spectrum are identified,corresponding to different structural fingerprints.The first peak(-0.205 eV)represents the most favorable segregation sites at GB core,while the second and third peaks account for the sites at GB surface.By incorporating a thermodynamic model,the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs,unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental studies.The identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion,with the low-barrier channels inside GB core contributing to short-circuit diffusion,while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion barriers.Mean square displacement analysis further confirms the findings,and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of lattice.The present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.
基金supported by Prince Sultan University(Grant No.PSU-CE-TECH-135,2023).
文摘In 2023,pivotal advancements in artificial intelligence(AI)have significantly experienced.With that in mind,traditional methodologies,notably the p-y approach,have struggled to accurately model the complex,nonlinear soil-structure interactions of laterally loaded large-diameter drilled shafts.This study undertakes a rigorous evaluation of machine learning(ML)and deep learning(DL)techniques,offering a comprehensive review of their application in addressing this geotechnical challenge.A thorough review and comparative analysis have been carried out to investigate various AI models such as artificial neural networks(ANNs),relevance vector machines(RVMs),and least squares support vector machines(LSSVMs).It was found that despite ML approaches outperforming classic methods in predicting the lateral behavior of piles,their‘black box'nature and reliance only on a data-driven approach made their results showcase statistical robustness rather than clear geotechnical insights,a fact underscored by the mathematical equations derived from these studies.Furthermore,the research identified a gap in the availability of drilled shaft datasets,limiting the extendibility of current findings to large-diameter piles.An extensive dataset,compiled from a series of lateral loading tests on free-head drilled shaft with varying properties and geometries,was introduced to bridge this gap.The paper concluded with a direction for future research,proposes the integration of physics-informed neural networks(PINNs),combining data-driven models with fundamental geotechnical principles to improve both the interpretability and predictive accuracy of AI applications in geotechnical engineering,marking a novel contribution to the field.
基金supported by Supported by the Science and Technology Research Program of the Institute of Mountain Hazards and Environment,CAS(IMHE-ZDRW-01)the National Natural Science Foundation of China,China(Grant Numbers:42077275&42271086)the Special Project of Basic Research-Key Project,Yunnan(Grant Number:202301AS070039).
文摘The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement concrete facing panels,and gravity-type earth-retaining walls.The finite element(FE)simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses.The seismic performance of differentmodels,which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls,was simulated and examined using the FE approach.It also displays comparative studies such as stress distribution,deflection of the wall,acceleration across the wall height,lateral wall displacement,lateral wall pressure,and backfill plastic strain.Three components of the created ER walls were found throughout this research procedure.One is a granular reinforcement backfill,while the other is a wall-facing panel and base foundation.The dynamic response effects of varied earth-retaining walls have also been studied.It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls.The proposed analytical model’s validity has been evaluated and compared with the reinforcement concrete facing panels,gravity-type ER wall,scientifically available data,and American Association of State Highway and Transportation Officials(AASHTO)guidelines results based on FE simulation.The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types.The methodology and results of this study establish standards for future analogous investigations and professionals,particularly in light of the increasing computational capabilities of desktop computers.
文摘In the article“Influence of Various Earth-Retaining Walls on the Dynamic Response Comparison Based on 3D Modeling”by Muhammad Akba,Huali Pan,Jiangcheng Huang,Bilal Ahmed,Guoqiang Ou(Computer Modeling in Engineering&Sciences,2024,Vol.139,No.3,2835–2863.DOI:10.32604/cmes.2024.046993,URL:https://www.techscience.com/CMES/v139n3/55652),one author’s affiliation was not included in the original article.
基金supported by the National Natural Science Foundation of China(No.81370242)the Guangdong Provincial College Students Innovation and Entrepreneurship Training Program in 2023(No.S202310571076)+3 种基金the Zhanjiang Science and Technology Program(No.2022A01166/No.2022A01183)the Non-funded Science and Technology Research Program of Zhanjiang(No.2021B01145)the Guangdong Medical University Youth Scientific Research Training Fund(No.GDMUQ2021011)the Universty-level Innovation and Entrepreneurship Training Program of Guangdong Medical University(No.GDMU2021163/No.GDMU2021207)。
文摘Background The incidence of cryptogenic stroke(CS)accounts for about 25%of ischemic stroke.Current studies have shown that cryptogenic stroke is closely related to patent foramen ovale(PFO).Evaluating the correlation between PFO and CS needs to be combined with multidisciplinary evaluation.Many clinical studies have shown that drug therapy can reduce the risk of ischemic stroke in elderly PFO patients(>60 years old).However,whether elderly PFO patients(>60 years old)can benefit from PFO closure is still controversial.This article reviewed the research progress of drug therapy and PFO closure therapy for cryptogenic stroke associated with PFO in the elderly.[S Chin J Cardiol 2024;25(1):50-56].
文摘This article presents a study on the structural behavior of transversely prestressed laminated timber slabs,focusing on an innovative approach:vertically misaligned lamellae.This misalignment,achieved by sliding vertically the wooden lamellae rather than aligning them,enhances the slab’s cross-section moment of inertia,thereby improving load-bearing capacity and stiffness.Testing involved two groups of structural size specimens:one with vertically aligned lamellae(control group)and the other with misaligned lamellae(study group).Results showed the study group exhibited 42%superior stiffness and 10%less load capacity compared to the control.Failures typically occurred individually in the lamellae,particularly in those with defects or lower modulus of elasticity,concentrated in the middle third of the slabs’free span where tensile stresses peak.Despite a higher number of failed lamellae,the study group demonstrated promising performance.Analysis of prestressing bar indicated no damage at all in the thread,suggesting potential for reducing bar diameter.These findings offer crucial insights into applying these slabs in timber construction as well as to any kind of construction.
