The authors regret<to remove Prof.Jien-Wei Yeh from the authorship for some reason.The removal is agreed by Prof.Jien-Wei Yeh>.The authors would like to apologise for any inconvenience caused.
Microstructure and mechanical properties of non-equiatomic(CuNi)_(100-x)Co_(x)(x=15,20,25 and 30,at.%)medium-entropy alloys(MEAs)prepared by vacuum arc-melting were investigated.Results show that all the as-cast MEAs ...Microstructure and mechanical properties of non-equiatomic(CuNi)_(100-x)Co_(x)(x=15,20,25 and 30,at.%)medium-entropy alloys(MEAs)prepared by vacuum arc-melting were investigated.Results show that all the as-cast MEAs exhibit dual face-centered cubic(fcc)solid-solution phases with identical lattice constant,showing typical dendrite structure consisting of(Ni,Co)-rich phase in dendrites and Cu-rich phase in inter-dendrites.The positive enthalpy of mixing among Cu and Ni-Co elements is responsible for the segregation of Cu.With the increase of Co content,the volume fraction of(Ni,Co)-rich phase increases while the Cu-rich phase decreases,resulting in an increment of yield strength and a decrement of elongation for the(CuNi)_(100-x)Co_(x) MEAs.Nano-indentation test results show a great difference of microhardness between the two fcc phases of the MEAs.The measured microhardness value of the(Ni,Co)-rich phase is almost twofold as compared to that of the Cu-rich phase in all the(CuNi)_(100-x)Co_(x) MEAs.During the deformation of the MEAs,the Cu-rich phase bears the main plastic strain,whereas the(Ni,Co)-rich phase provides more pronounced strengthening.展开更多
The phase equilibria of the Cu−Zr−Si system at 600°C were experimentally studied by means of X-ray diffraction(XRD)and scanning electron microscopy with energy dispersive X-ray spectroscopy(SEM−EDS).A comprehensi...The phase equilibria of the Cu−Zr−Si system at 600°C were experimentally studied by means of X-ray diffraction(XRD)and scanning electron microscopy with energy dispersive X-ray spectroscopy(SEM−EDS).A comprehensive set of thermodynamic parameters for the Cu−Zr−Si system were obtained through detailed analysis using the CALPHAD(CALculation of PHAse Diagrams)approach.Based on the CALPHAD calculations,five as-cast alloys were designed,and the Scheil−Gulliver model was used to simulate their solidification paths.By testing hardness,friction and wear properties,the wear resistance of the Cu−Zr−Si alloys was investigated.Wear morphologies were analyzed using SEM and 3D profiling techniques.It was found that the alloy Cu80Zr19Si1 exhibits a good performance with a hardness of HV 342,frictional coefficient of 0.23 and wear rate of 2.19×10^(−7)mm^(3)/(N·m).The wear surfaces are mainly characterized by grooves,spalling pits and oxide particles.The wear mechanism of the alloys is adhesive wear and oxidative wear under dry sliding condition.This study provides a theoretical basis for the design of the wear-resistant Cu−Zr−Si alloys.展开更多
The concept of local shock strength and a quantitative measure index str of local shock strength are proposed,derived from the oblique shock relation and the monotonic relationship between total pressure loss ratio an...The concept of local shock strength and a quantitative measure index str of local shock strength are proposed,derived from the oblique shock relation and the monotonic relationship between total pressure loss ratio and normal Mach number.Utilizing the high density gradient characteristic of shock waves and the oblique shock relation,a post-processing algorithm for two-dimensional flow field data is developed.The objective of the post-processing algorithm is to obtain specific shock wave location coordinates and calculate the corresponding str from flow filed data under the calibration of the oblique shock relation.Valida-tion of this post-processing algorithm is conducted using a standard model example that can be solved analytically.Combining the concept of local shock strength with the post-processing algorithm,a local shock strength quantitative mapping approach is established for the first time.This approach enables a quantitative measure and visualization of local shock strength at distinct locations,represented by color mapping on the shock structures.The approach can be applied to post-processing numerical sim-ulation data of two-dimensional flows.Applications to the intersection of two left-running oblique shock waves(straight shock waves),the bow shock in front of a cylinder(curved shock wave),and Mach reflection(mixed straight and curved shock waves)demonstrate the accuracy,and effectiveness of the mapping approach in investigating diverse shock wave phenomena.The quan-titative mapping approach of str may be a valuable tool in the design of supersonic/hypersonic vehicles and the exploration of shock wave evolution.展开更多
Achieving optimal mechanical performance in high-pressure die-cast(HPDC)Mg-based alloys through experimental methods is both costly and time-intensive due to significant variations in composition.This study leverages ...Achieving optimal mechanical performance in high-pressure die-cast(HPDC)Mg-based alloys through experimental methods is both costly and time-intensive due to significant variations in composition.This study leverages machine learning(ML)techniques to accelerate the development of high-performance Mg-based alloys.Data on alloy composition and mechanical properties were collected from literature sources,focusing on HPDC Mg-based alloys.Six ML models—extra trees,CatBoost,k-nearest neighbors,random forest,gradient boosting,and decision tree—were trained to predict mechanical behavior.Cat Boost yielded the highest prediction accuracy with R^(2) scores of 0.95 for ultimate tensile strength(UTS)and 0.92 for yield strength(YS).Further validation using published datasets reaffirmed its reliability,demonstrating R^(2) values of 0.956(UTS)and 0.936(YS),MAE of 1%and 2.8%,and RMSE of 1%and 3.5%,respectively.Among these,the CatBoost model demonstrated the highest predictive accuracy,outperforming other ML techniques across multiple optimization metrics.展开更多
Viscoelasticity and poroelasticity commonly coexist as time-dependent behaviors in polymer gels. Engineering applications often require knowledge of both behaviors separated; however, few methods exist to decouple vis...Viscoelasticity and poroelasticity commonly coexist as time-dependent behaviors in polymer gels. Engineering applications often require knowledge of both behaviors separated; however, few methods exist to decouple viscoelastic and poroelastic properties of gels. We propose a method capable of separating viscoelasticity and poroelasticity of gels in various mechanical tests. The viscoelastic char- acteristic time and the poroelastic diffusivity of a gel define an intrinsic material length scale of the gel. The experimen- tal setup gives a sample length scale, over which the solvent migrates in the gel. By setting the sample length to be much larger or smaller than the material length, the viscoelasticity and poroelasticity of the gel will dominate at different time scales in a test. Therefore, the viscoelastic and poroelastic properties of the gel can be probed separately at different time scales of the test. We further validate the method by finite-element models and stress-relaxation experiments.展开更多
Introduction: Middle ear volume(MEV) is a clinically relevant parameter across middle ear diseases. MEV values between these techniques have never before been tested for agreement in ears with perforated tympanic memb...Introduction: Middle ear volume(MEV) is a clinically relevant parameter across middle ear diseases. MEV values between these techniques have never before been tested for agreement in ears with perforated tympanic membranes(TMs).Methods: Middle ears were identified from 36 patients ranging 18-89 years of age with TM perforations who underwent tympanometry and temporal bone computed tomography(CT) between 2005 and 2015. MEVs calculated by both tympanometry and three-dimensional volume reconstruction(3DVR) were analyzed for agreement using Bland Altman plots. The differences between tympanometric and 3DVR MEV values for each given middle ear were characterized across MEV quartiles(1= smallest; 4= largest) and across increasing states of middle ear disease using Kruskale Wallis and Wilcoxon testing with Bonferroni correction.Results: Bland Altman plots demonstrated significant disagreement between MEV measurement techniques. Differences between tympanometric(T) and 3DVR MEV values were significantly greater with increasing average(i.e.(Tt3DVR)/2)) MEV per linear regression(p < 0.0001). Significance was demonstrated between fourth and first average MEV quartiles(p= 0.0024), fourth and second quartiles(p= 0.0024), third and first quartiles(p= 0.0048), and third and second quartiles(p= 0.048). Absolute MEV difference was not significantly different across varying states of middle ear disease(p= 0.44).Conclusion: Statistically and clinically significant disagreement was demonstrated between tympanometric and 3DVR MEV values. Studies that vary in MEV estimation techniques may be expected to demonstrate significantly different results. These preliminary results suggest that clinicians should endeavor to seek further confirmation when interpreting high tympanometric MEV values.展开更多
Previous studies showed that an axisymmetric hub-initiated disturbance defined as partial surge may initiate the stall of a transonic compressor; to reveal the instability evolution under full-span incompressible flow...Previous studies showed that an axisymmetric hub-initiated disturbance defined as partial surge may initiate the stall of a transonic compressor; to reveal the instability evolution under full-span incompressible flow for different levels of hub loading and B parameter, an experimental investigation is conducted on a single-stage low-speed compressor. Experimental results show that under a uniform inflow condition without inlet flow distortion, a modal-type stall inception dominates in this low-speed compressor. When an inlet screen introducing hub distortion is used to increase the hub loading, a compressor stall is initiated by a modal wave, but large disturbances are present in the hub region before the compressor stall, which become stronger as the hub loading increases. Under high hub loading and large B parameter（implemented by adding hub distortion through an inlet screen and enlarging the outlet plenum volume, respectively）, a compressor stall is triggered by an axisymmetric hub-initiated disturbance, which is much different from the modal-like disturbances. The beginning of this axisymmetric disturbance may be captured over 800 rotor revolutions prior to the onset of stall, and the amplitude grows with time. The disturbance is hub-initiated because the disturbance signal at the hub is detected much earlier than that at the tip; meanwhile, the frequency of this axisymmetric disturbance changes with the length of the inlet duct. The characteristics of instability evolution in the low-speed compressor are also compared with those in a transonic compressor.展开更多
Magnesium phosphate cements have come under investigation in recent years for use as an alternative to calcium phosphate cements for bone void repair applications.Evidence indicates that magnesium phosphate cements ob...Magnesium phosphate cements have come under investigation in recent years for use as an alternative to calcium phosphate cements for bone void repair applications.Evidence indicates that magnesium phosphate cements obtain higher initial strengths after cement reaction and resorption in more clinically appropriate time frames than commercially available calcium phosphate cements.In this study,amorphous,partially amorphous and crystalline tri-magnesium phosphate powders were synthesized via an aqueous precipitation reaction with subsequent thermal treatment,and characterized using techniques such as X-ray diffraction and Fourier transform infrared spectroscopy.These materials were assessed for their functionality in cementing reaction with a 3.0 mol/L,pH 7.0 ammonium phosphate solution,including setting time and pH evolution in phosphate buffered saline solution.Results indicated that the amorphous and semi-crystalline tri-magnesium phosphate powders were highly reactive with the setting solution but resulted in mechanically weak cements,while the crystalline tri-magnesium phosphate powder reacted efficiently with the cement solution and were mechanically strong following the cement reaction.X-ray diffraction and scanning electron microscopy analyses indicated significant changes in the phase composition and morphology of the cements following incubation in phosphate buffered saline.These were perceived to be detrimental to the integrity of the amorphous and semi-crystalline tri-magnesium phosphate derived cements but not to those created with fully crystalline tri-magnesium phosphate.The crystalline tri-magnesium phosphate material resulted in the most functional cement as this embodiment displayed the most clinically relevant setting time as well as the highest mechanical resilience and neutral pH during incubation in saline solution rendering them potentially viable as bone void fillers.展开更多
Cd-rich portion of the pseudo-binary system Cd3B2O6-Zn3B2O6 was investigated. A new cadmium zinc borate, Cd2.42Zn0.58B2O6, was synthesized successfully by a traditional solid-state reaction method. The compound crysta...Cd-rich portion of the pseudo-binary system Cd3B2O6-Zn3B2O6 was investigated. A new cadmium zinc borate, Cd2.42Zn0.58B2O6, was synthesized successfully by a traditional solid-state reaction method. The compound crystallizes in the monoclinic space group C2/c with a = 17.3048, b = 8.4356, c = 10.2962 A^°, β = 93.157°, V = 1500.7（2） A^°3, Dc = 5.683 g/cm^3, F（000） = 2301, Z = 24, R = 0.0351 and wR = 0.0741. In its structure, BO3 triangle, CdO6 and CdO5 （or ZnO5） polyhedra are joined together by sharing bridging O atoms to form an intricate three-dimensional framework. A comparison of the structures of Cd2.42Zn0.58B2O6, α-Cd3B2O6 and β-Cd3B2O6 is presented. The IR spectrum confirms the presence of BO3 unit. The UV cut-off wavelength of Cd2.42Zn0.58B2O6 is 313 nm. The differential thermal analysis （DTA） suggests that Cd2.42Zn0.58B2O6 is an incongruent melting compound.展开更多
Body-centred cubic(BCC) metals are known to have unstable intrinsic stacking faults and high resistance to deformation twinning, which can strongly influence their twinning behaviour. Though twinning mechanisms of BCC...Body-centred cubic(BCC) metals are known to have unstable intrinsic stacking faults and high resistance to deformation twinning, which can strongly influence their twinning behaviour. Though twinning mechanisms of BCC metals have been investigated for more than 60 years, the atomistic level dynamics of twinning remains under debate, especially regarding its impact on competition between twinning and slip. Here, we investigate the atomistic level dynamics of twinning in BCC tungsten(W) nanowires using in situ nanomechanical testing. Quantitative experimental studies directly visualize that deformation twins in W nanowires have a minimum size of six-layers and grow in increments of approximately three-layers at a time, in contrast to the layer-by-layer growth of deformation twins in face-centred cubic metals. These unique twinning dynamics induces a strong competition with ordinary dislocation slip,as exhibited by a size-dependent dislocation-to-twin transition in W nanowires, with a transition size of ~40 nm. Our work provides physical insight into the dynamics of twinning at the atomic level, as well as a size-dependent dislocation-twinning competition, which have important implications for the plastic deformation in a broad class of BCC metals and alloys.展开更多
Soft robots complement the existing efforts of miniaturizing conventional,rigid robots,and have the potential to revolutionize areas such as military equipment and biomedical devices.This type of system can accomplish...Soft robots complement the existing efforts of miniaturizing conventional,rigid robots,and have the potential to revolutionize areas such as military equipment and biomedical devices.This type of system can accomplish tasks in complex and time-varying environments through geometric reconfiguration induced by diverse external stimuli,such as heat,solvent,light,electric field,magnetic field,and mechanical field.Approaches to achieve reconfigurable mesostructures are essential to the design and fabrication of soft robots.Existing studies mainly focus on four key aspects:reconfiguration mechanisms,fabrication schemes,deformation control principles,and practical applications.This review presents a detailed survey of methodologies for morphable mesostructures triggered by a wide range of stimuli,with a number of impressive examples,demonstrating high degrees of deformation complexities and varied multi-functionalities.The latest progress based on the development of new materials and unique design concepts is highlighted.An outlook on the remaining challenges and open opportunities is provided.展开更多
A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)sys...A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inhomogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.展开更多
As-cast alloys often require complex thermomechanical processing to obtain a hierarchical structure to achieve a good combination of strength and ductility.Here in this work,a novel hierarchical Fe_(27)Ni_(35)Cr_(18.2...As-cast alloys often require complex thermomechanical processing to obtain a hierarchical structure to achieve a good combination of strength and ductility.Here in this work,a novel hierarchical Fe_(27)Ni_(35)Cr_(18.25)Al_(13.75)Co_(2)Ti_(2)Mo_(2) high-entropy alloy(HEA)with ultra-high tensile strength and excellent ductility was fabricated by direct casting.The as-cast alloy exhibits hierarchical structure with an ul-trafine lamellar microstructure(ULM),ultrafine rhombus microstructure(URM),ultrafine vermicular mi-crostructure(UVM),nanosized precipitates and spinodal decomposition(SP)that develops during casting and cooling.The incompatibility of face-centered cubic(FCC)and body-centered cubic(BCC)phases in the deformation process leads to heterogeneous deformation-induced(HDI)hardening,which brings the alloy a tensile yield strength(YS)of~1056 MPa,an ultimate tensile strength(UTS)of~1526 MPa and a total elongation(El)of~15.6%.Additionally,the numerous interfaces generated by the hierarchical structure absorb the energy during deformation,effectively retarding the dislocation motion and causing strong work-hardening.展开更多
Environmental and compositional factors often influence the hot-corrosion behavior of alloys and coatings used in gas turbine engine applications.This presentation examines the effects of environmental factors such as...Environmental and compositional factors often influence the hot-corrosion behavior of alloys and coatings used in gas turbine engine applications.This presentation examines the effects of environmental factors such as salt deposition rate,gas composition,and extent of oxidation on the hot-corrosion resistance(TypeⅠ-900℃and TypeⅡ-704℃) of Ni-based alloys and coatings.It also evaluates the effects of Pt-modified b-NiAl alloy composition on hot-corrosion resistance.Both types of hot corrosion conditions were simulated by depositing Na_2SO_4 salt on the test samples and then exposing those samples to a catalyzed O_2:SO_2 atmosphere.It will be shown that TypeⅠhot corrosion resistance tends to decrease with increase in salt deposition rate up to 8 mg/cm^2;however,no measurable hot corrosion was observed when the sample was completely buried in a salt.It will also be shown that the TypeⅡhot corrosion resistance of Pt-modified Ni-based alloys is very sensitive to both alloy and gas composition.展开更多
We report on a first-principles study of a novel band modulation in zigzag double-walled boron nitride nan- otubes （DBNNTs） by applying radial strain and coupled ex- ternal electric field. We show that the band alig...We report on a first-principles study of a novel band modulation in zigzag double-walled boron nitride nan- otubes （DBNNTs） by applying radial strain and coupled ex- ternal electric field. We show that the band alignment be- tween the inner and outer walls of the DBNNTs can be tuned from type I to type II with increasing radial strain, accompa- nied with a direct to indirect band gap transition and a sub- stantial gap reduction. The band gap can be further signifi- cantly reduced by applying a transverse electric field. The coupling of electric field with the radial strain makes the field-induced gap reduction being anisotropic and more re- markable than that in undeformed DBNNTs. In particular, the gap variation induced by electric field perpendicular to the radial strain is the most remarkable among all the modu-lations. These tunable properties by electromechanical cou- pling in DBNNTs will greatly enrich their versatile applica- tions in future nanoelectronics.展开更多
In-situ high-resolution transmission electron microscopy(HRTEM)is performed to investigate the de-formation behavior of hexagonal close-packed rhenium(Re)which is compressed along the{1-100}di-rection.Atomistic simula...In-situ high-resolution transmission electron microscopy(HRTEM)is performed to investigate the de-formation behavior of hexagonal close-packed rhenium(Re)which is compressed along the{1-100}di-rection.Atomistic simulations are also conducted to better understand the deformation mechanisms.Two types of lattice reorientation are observed during compression.The first type involves the reori-entation of one lattice by∼90°around{11-20},which is accomplished by the formation of an interme-diate face-center-cubic(FCC)phase at the interface.This transformation sequence can be described as{1-100}matrix→{111}FCC→(0001)twin.In the second type,a new grain is formed but does not satisfy any known twin relationship with the matrix,and an intermediate FCC phase is also formed.The transfor-mation sequence can be described as{1¯101}matrix→{111}FCC→(0001)grain.Mechanisms responsible for the observed lattice reorientation and sequential phase transitions are analyzed by conducting lattice correspondence analyses on the simulation results.Strain accommodation is also analyzed to explain the mechanisms for lattice reorientation and the intermediate phase transformations.The results provide new insight into the deformation behavior of HCP metals.展开更多
Controlled intracellular delivery of biomolecular cargo is critical for developing targeted therapeutics and cell reprogramming.Conventional delivery approaches(e.g.,endocytosis of nano-vectors,microinjection,and elec...Controlled intracellular delivery of biomolecular cargo is critical for developing targeted therapeutics and cell reprogramming.Conventional delivery approaches(e.g.,endocytosis of nano-vectors,microinjection,and electroporation)usually require time-consuming uptake processes,labor-intensive operations,and/or costly specialized equipment.Here,we present an acoustofluidics-based intracellular delivery approach capable of effectively delivering various functional nanomaterials to multiple cell types(e.g.,adherent and suspension cancer cells).By tuning the standing acoustic waves in a glass capillary,our approach can push cells in flow to the capillary wall and enhance membrane permeability by increasing membrane stress to deform cells via acoustic radiation forces.Moreover,by coating the capillary with cargo-encapsulated nanoparticles,our approach can achieve controllable cell-nanoparticle contact and facilitate nanomaterial delivery beyond Brownian movement.Based on these mechanisms,we have successfully delivered nanoparticles loaded with small molecules or protein-based cargo to U937 and HeLa cells.Our results demonstrate enhanced delivery efficiency compared to attempts made without the use of acoustofluidics.Moreover,compared to conventional sonoporation methods,our approach does not require special contrast agents with microbubbles.This acoustofluidics-based approach creates exciting opportunities to achieve controllable intracellular delivery of various biomolecular cargoes to diverse cell types for potential therapeutic applications and biophysical studies.展开更多
Object detection under high-speed motion remains challenging due to severe motion blur,which degrades spatial appearance and limits the effectiveness of single-frame detectors.While temporal modeling is widely explore...Object detection under high-speed motion remains challenging due to severe motion blur,which degrades spatial appearance and limits the effectiveness of single-frame detectors.While temporal modeling is widely explored to enhance performance,its specific behavior under extreme motion blur is not yet fully characterized.In this work,we conducted an experimental study comparing a single-frame YOLOv8n detector and a temporal-enhanced variant that incorporates multi-frame inputs and frame-difference cues within the backbone.Results on a highly blurred table tennis dataset show that although the temporal-enhanced model and single-frame baseline achieve similar average precision(AP~0.52),they exhibit markedly different failure modes.Quantitative analysis reveals a Jaccard index of only 0.43,demonstrating a pronounced complementarity between the detection outcomes of the two models.By exploiting this behavioral divergence through a simple ensemble strategy,we achieve a substantial aggregate performance gain,increasing AP50 from 0.52 to 0.73.These findings suggest that under extreme blur,temporal modeling can induce complementary detection behavior beyond improving individual detector accuracy,offering an alternative perspective for designing robust detection systems in highly degraded visual environments.展开更多
文摘The authors regret<to remove Prof.Jien-Wei Yeh from the authorship for some reason.The removal is agreed by Prof.Jien-Wei Yeh>.The authors would like to apologise for any inconvenience caused.
基金supported by the Key-Area Research and Development Program of Guangdong Province(Grant No.2018B090905002)the National Natural Science Foundation of China(Grant No.52103360)the Basic Research Foundation of Guangzhou City(Grant No.201804020071).
文摘Microstructure and mechanical properties of non-equiatomic(CuNi)_(100-x)Co_(x)(x=15,20,25 and 30,at.%)medium-entropy alloys(MEAs)prepared by vacuum arc-melting were investigated.Results show that all the as-cast MEAs exhibit dual face-centered cubic(fcc)solid-solution phases with identical lattice constant,showing typical dendrite structure consisting of(Ni,Co)-rich phase in dendrites and Cu-rich phase in inter-dendrites.The positive enthalpy of mixing among Cu and Ni-Co elements is responsible for the segregation of Cu.With the increase of Co content,the volume fraction of(Ni,Co)-rich phase increases while the Cu-rich phase decreases,resulting in an increment of yield strength and a decrement of elongation for the(CuNi)_(100-x)Co_(x) MEAs.Nano-indentation test results show a great difference of microhardness between the two fcc phases of the MEAs.The measured microhardness value of the(Ni,Co)-rich phase is almost twofold as compared to that of the Cu-rich phase in all the(CuNi)_(100-x)Co_(x) MEAs.During the deformation of the MEAs,the Cu-rich phase bears the main plastic strain,whereas the(Ni,Co)-rich phase provides more pronounced strengthening.
基金supported from the Outstanding Youth Talents Fund in Anhui Provincial Colleges and Universities,China(No.2023AH020027)the National Natural Science Foundation of China(No.52071002)+1 种基金the University Synergy Innovation Program of Anhui Province,China(No.GXXT-2023-019)the National Innovative Training Program for College Students,China(No.202210361075)。
文摘The phase equilibria of the Cu−Zr−Si system at 600°C were experimentally studied by means of X-ray diffraction(XRD)and scanning electron microscopy with energy dispersive X-ray spectroscopy(SEM−EDS).A comprehensive set of thermodynamic parameters for the Cu−Zr−Si system were obtained through detailed analysis using the CALPHAD(CALculation of PHAse Diagrams)approach.Based on the CALPHAD calculations,five as-cast alloys were designed,and the Scheil−Gulliver model was used to simulate their solidification paths.By testing hardness,friction and wear properties,the wear resistance of the Cu−Zr−Si alloys was investigated.Wear morphologies were analyzed using SEM and 3D profiling techniques.It was found that the alloy Cu80Zr19Si1 exhibits a good performance with a hardness of HV 342,frictional coefficient of 0.23 and wear rate of 2.19×10^(−7)mm^(3)/(N·m).The wear surfaces are mainly characterized by grooves,spalling pits and oxide particles.The wear mechanism of the alloys is adhesive wear and oxidative wear under dry sliding condition.This study provides a theoretical basis for the design of the wear-resistant Cu−Zr−Si alloys.
基金supported by the National Natural Science Foundation of China(Grant No.12372233)the Fund of NPU-Duke China Seed Program(Grant No.119003067)the“111 Project”of China(Grant No.B17037-106).
文摘The concept of local shock strength and a quantitative measure index str of local shock strength are proposed,derived from the oblique shock relation and the monotonic relationship between total pressure loss ratio and normal Mach number.Utilizing the high density gradient characteristic of shock waves and the oblique shock relation,a post-processing algorithm for two-dimensional flow field data is developed.The objective of the post-processing algorithm is to obtain specific shock wave location coordinates and calculate the corresponding str from flow filed data under the calibration of the oblique shock relation.Valida-tion of this post-processing algorithm is conducted using a standard model example that can be solved analytically.Combining the concept of local shock strength with the post-processing algorithm,a local shock strength quantitative mapping approach is established for the first time.This approach enables a quantitative measure and visualization of local shock strength at distinct locations,represented by color mapping on the shock structures.The approach can be applied to post-processing numerical sim-ulation data of two-dimensional flows.Applications to the intersection of two left-running oblique shock waves(straight shock waves),the bow shock in front of a cylinder(curved shock wave),and Mach reflection(mixed straight and curved shock waves)demonstrate the accuracy,and effectiveness of the mapping approach in investigating diverse shock wave phenomena.The quan-titative mapping approach of str may be a valuable tool in the design of supersonic/hypersonic vehicles and the exploration of shock wave evolution.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1A6A1A10044950)。
文摘Achieving optimal mechanical performance in high-pressure die-cast(HPDC)Mg-based alloys through experimental methods is both costly and time-intensive due to significant variations in composition.This study leverages machine learning(ML)techniques to accelerate the development of high-performance Mg-based alloys.Data on alloy composition and mechanical properties were collected from literature sources,focusing on HPDC Mg-based alloys.Six ML models—extra trees,CatBoost,k-nearest neighbors,random forest,gradient boosting,and decision tree—were trained to predict mechanical behavior.Cat Boost yielded the highest prediction accuracy with R^(2) scores of 0.95 for ultimate tensile strength(UTS)and 0.92 for yield strength(YS).Further validation using published datasets reaffirmed its reliability,demonstrating R^(2) values of 0.956(UTS)and 0.936(YS),MAE of 1%and 2.8%,and RMSE of 1%and 3.5%,respectively.Among these,the CatBoost model demonstrated the highest predictive accuracy,outperforming other ML techniques across multiple optimization metrics.
基金supported by NSF CAREER Award (CMMI-1253495)NSF grants (CMMI-1200515 and DMR- 1121107)+1 种基金NIH grant (UH2 TR000505)the support of a fellowship from Duke Center for Bimolecular and Tissue Engineering (NIH-2032422)
文摘Viscoelasticity and poroelasticity commonly coexist as time-dependent behaviors in polymer gels. Engineering applications often require knowledge of both behaviors separated; however, few methods exist to decouple viscoelastic and poroelastic properties of gels. We propose a method capable of separating viscoelasticity and poroelasticity of gels in various mechanical tests. The viscoelastic char- acteristic time and the poroelastic diffusivity of a gel define an intrinsic material length scale of the gel. The experimen- tal setup gives a sample length scale, over which the solvent migrates in the gel. By setting the sample length to be much larger or smaller than the material length, the viscoelasticity and poroelasticity of the gel will dominate at different time scales in a test. Therefore, the viscoelastic and poroelastic properties of the gel can be probed separately at different time scales of the test. We further validate the method by finite-element models and stress-relaxation experiments.
文摘Introduction: Middle ear volume(MEV) is a clinically relevant parameter across middle ear diseases. MEV values between these techniques have never before been tested for agreement in ears with perforated tympanic membranes(TMs).Methods: Middle ears were identified from 36 patients ranging 18-89 years of age with TM perforations who underwent tympanometry and temporal bone computed tomography(CT) between 2005 and 2015. MEVs calculated by both tympanometry and three-dimensional volume reconstruction(3DVR) were analyzed for agreement using Bland Altman plots. The differences between tympanometric and 3DVR MEV values for each given middle ear were characterized across MEV quartiles(1= smallest; 4= largest) and across increasing states of middle ear disease using Kruskale Wallis and Wilcoxon testing with Bonferroni correction.Results: Bland Altman plots demonstrated significant disagreement between MEV measurement techniques. Differences between tympanometric(T) and 3DVR MEV values were significantly greater with increasing average(i.e.(Tt3DVR)/2)) MEV per linear regression(p < 0.0001). Significance was demonstrated between fourth and first average MEV quartiles(p= 0.0024), fourth and second quartiles(p= 0.0024), third and first quartiles(p= 0.0048), and third and second quartiles(p= 0.048). Absolute MEV difference was not significantly different across varying states of middle ear disease(p= 0.44).Conclusion: Statistically and clinically significant disagreement was demonstrated between tympanometric and 3DVR MEV values. Studies that vary in MEV estimation techniques may be expected to demonstrate significantly different results. These preliminary results suggest that clinicians should endeavor to seek further confirmation when interpreting high tympanometric MEV values.
基金the supports of the National Natural Science Foundation of China (Nos.51636001 and 51706008)Aeronautics Power Foundation of China (No.6141B090315)China Postdoctoral Science Foundation (No.2017M610742)
文摘Previous studies showed that an axisymmetric hub-initiated disturbance defined as partial surge may initiate the stall of a transonic compressor; to reveal the instability evolution under full-span incompressible flow for different levels of hub loading and B parameter, an experimental investigation is conducted on a single-stage low-speed compressor. Experimental results show that under a uniform inflow condition without inlet flow distortion, a modal-type stall inception dominates in this low-speed compressor. When an inlet screen introducing hub distortion is used to increase the hub loading, a compressor stall is initiated by a modal wave, but large disturbances are present in the hub region before the compressor stall, which become stronger as the hub loading increases. Under high hub loading and large B parameter（implemented by adding hub distortion through an inlet screen and enlarging the outlet plenum volume, respectively）, a compressor stall is triggered by an axisymmetric hub-initiated disturbance, which is much different from the modal-like disturbances. The beginning of this axisymmetric disturbance may be captured over 800 rotor revolutions prior to the onset of stall, and the amplitude grows with time. The disturbance is hub-initiated because the disturbance signal at the hub is detected much earlier than that at the tip; meanwhile, the frequency of this axisymmetric disturbance changes with the length of the inlet duct. The characteristics of instability evolution in the low-speed compressor are also compared with those in a transonic compressor.
基金the financial support of the National Science Foundation(Grant #0933153)Edward R.Weidlein Chair Professorship Funds,University of Pittsburgh,the Center for Complex Engineered Multifunctional Materials(CCEMM), University of PittsburghThe National Science Foundation Graduate Research Fellowship Program(DGE-1247842)
文摘Magnesium phosphate cements have come under investigation in recent years for use as an alternative to calcium phosphate cements for bone void repair applications.Evidence indicates that magnesium phosphate cements obtain higher initial strengths after cement reaction and resorption in more clinically appropriate time frames than commercially available calcium phosphate cements.In this study,amorphous,partially amorphous and crystalline tri-magnesium phosphate powders were synthesized via an aqueous precipitation reaction with subsequent thermal treatment,and characterized using techniques such as X-ray diffraction and Fourier transform infrared spectroscopy.These materials were assessed for their functionality in cementing reaction with a 3.0 mol/L,pH 7.0 ammonium phosphate solution,including setting time and pH evolution in phosphate buffered saline solution.Results indicated that the amorphous and semi-crystalline tri-magnesium phosphate powders were highly reactive with the setting solution but resulted in mechanically weak cements,while the crystalline tri-magnesium phosphate powder reacted efficiently with the cement solution and were mechanically strong following the cement reaction.X-ray diffraction and scanning electron microscopy analyses indicated significant changes in the phase composition and morphology of the cements following incubation in phosphate buffered saline.These were perceived to be detrimental to the integrity of the amorphous and semi-crystalline tri-magnesium phosphate derived cements but not to those created with fully crystalline tri-magnesium phosphate.The crystalline tri-magnesium phosphate material resulted in the most functional cement as this embodiment displayed the most clinically relevant setting time as well as the highest mechanical resilience and neutral pH during incubation in saline solution rendering them potentially viable as bone void fillers.
基金supported by the Special Foundation for Young Scientists of Beijing(No.2014000020124G009)
文摘Cd-rich portion of the pseudo-binary system Cd3B2O6-Zn3B2O6 was investigated. A new cadmium zinc borate, Cd2.42Zn0.58B2O6, was synthesized successfully by a traditional solid-state reaction method. The compound crystallizes in the monoclinic space group C2/c with a = 17.3048, b = 8.4356, c = 10.2962 A^°, β = 93.157°, V = 1500.7（2） A^°3, Dc = 5.683 g/cm^3, F（000） = 2301, Z = 24, R = 0.0351 and wR = 0.0741. In its structure, BO3 triangle, CdO6 and CdO5 （or ZnO5） polyhedra are joined together by sharing bridging O atoms to form an intricate three-dimensional framework. A comparison of the structures of Cd2.42Zn0.58B2O6, α-Cd3B2O6 and β-Cd3B2O6 is presented. The IR spectrum confirms the presence of BO3 unit. The UV cut-off wavelength of Cd2.42Zn0.58B2O6 is 313 nm. The differential thermal analysis （DTA） suggests that Cd2.42Zn0.58B2O6 is an incongruent melting compound.
基金the support from the National Natural Science Foundation of China (Nos.51701179,51771172 and 52071284)the Innovation Fund of the Zhejiang Kechuang New Materials Research Institute (No.ZKN-18-Z02)support from the Office of Naval Research (Nos.N00014-17-1-2810 and N00014-20-1-2788)。
文摘Body-centred cubic(BCC) metals are known to have unstable intrinsic stacking faults and high resistance to deformation twinning, which can strongly influence their twinning behaviour. Though twinning mechanisms of BCC metals have been investigated for more than 60 years, the atomistic level dynamics of twinning remains under debate, especially regarding its impact on competition between twinning and slip. Here, we investigate the atomistic level dynamics of twinning in BCC tungsten(W) nanowires using in situ nanomechanical testing. Quantitative experimental studies directly visualize that deformation twins in W nanowires have a minimum size of six-layers and grow in increments of approximately three-layers at a time, in contrast to the layer-by-layer growth of deformation twins in face-centred cubic metals. These unique twinning dynamics induces a strong competition with ordinary dislocation slip,as exhibited by a size-dependent dislocation-to-twin transition in W nanowires, with a transition size of ~40 nm. Our work provides physical insight into the dynamics of twinning at the atomic level, as well as a size-dependent dislocation-twinning competition, which have important implications for the plastic deformation in a broad class of BCC metals and alloys.
文摘Soft robots complement the existing efforts of miniaturizing conventional,rigid robots,and have the potential to revolutionize areas such as military equipment and biomedical devices.This type of system can accomplish tasks in complex and time-varying environments through geometric reconfiguration induced by diverse external stimuli,such as heat,solvent,light,electric field,magnetic field,and mechanical field.Approaches to achieve reconfigurable mesostructures are essential to the design and fabrication of soft robots.Existing studies mainly focus on four key aspects:reconfiguration mechanisms,fabrication schemes,deformation control principles,and practical applications.This review presents a detailed survey of methodologies for morphable mesostructures triggered by a wide range of stimuli,with a number of impressive examples,demonstrating high degrees of deformation complexities and varied multi-functionalities.The latest progress based on the development of new materials and unique design concepts is highlighted.An outlook on the remaining challenges and open opportunities is provided.
基金financially supported by the National Natural Science Foundation of China(No.51975492)the Research Fund Supported by Sichuan Science and Technology Program(No.2018JY0245)+1 种基金the Natural Science Foundation of Southwest University of Science and Technology(No.19xz7163)supported by the National Science Foundation of the United States(No.NSF CMMI-1901959)。
文摘A high-throughput approach based on magnetron co-sputtering of alloy libraries is employed to investigate mechanical properties of crystalline and amorphous alloys in a ternary palladium(Pd)-tungsten(W)-silicon(Si)system with the aim to reveal the difference in plastic deformation response and extract the relevant structure-property relationships of the alloys in the system.It was found that in contrast to crystalline alloys,the amorphous ones,i.e.,metallic glasses,exhibited a much smaller fluctuation range in the plasticity parameters(Er2/H and Wp/Wt),indicating a significant difference in the plastic deformation mechanism controlling the mechanical properties for the respective alloys.We propose that the inhomogeneous deformation of amorphous alloys localized in thin shear bands is responsible for the weaker compositional dependence of both plasticity parameters,while dislocation gliding in crystalline materials is significantly more dependent on the exact structure,thus resulting in a larger scattering range.Based on the representative efficient cluster packing model,a set of composition-dependent atomic structural models is proposed to figure out the structure-property relationships of amorphous alloys in Pd-W-Si alloy system.
基金J.C.Niu and Z.Q.Fu acknowledge the financial support from the National Natural Science Foundation of China(No.52103360)from the Pearl River Talent Program(No.2021QN02C766)+1 种基金from the Basic and Applied Basic Research Foundation of Guangdong Province(No.2020A1515111104)W.P.Chen thanks the financial support from the Key-Area Research and Development Program of Guangdong Province(No.2018B090905002)。
文摘As-cast alloys often require complex thermomechanical processing to obtain a hierarchical structure to achieve a good combination of strength and ductility.Here in this work,a novel hierarchical Fe_(27)Ni_(35)Cr_(18.25)Al_(13.75)Co_(2)Ti_(2)Mo_(2) high-entropy alloy(HEA)with ultra-high tensile strength and excellent ductility was fabricated by direct casting.The as-cast alloy exhibits hierarchical structure with an ul-trafine lamellar microstructure(ULM),ultrafine rhombus microstructure(URM),ultrafine vermicular mi-crostructure(UVM),nanosized precipitates and spinodal decomposition(SP)that develops during casting and cooling.The incompatibility of face-centered cubic(FCC)and body-centered cubic(BCC)phases in the deformation process leads to heterogeneous deformation-induced(HDI)hardening,which brings the alloy a tensile yield strength(YS)of~1056 MPa,an ultimate tensile strength(UTS)of~1526 MPa and a total elongation(El)of~15.6%.Additionally,the numerous interfaces generated by the hierarchical structure absorb the energy during deformation,effectively retarding the dislocation motion and causing strong work-hardening.
文摘Environmental and compositional factors often influence the hot-corrosion behavior of alloys and coatings used in gas turbine engine applications.This presentation examines the effects of environmental factors such as salt deposition rate,gas composition,and extent of oxidation on the hot-corrosion resistance(TypeⅠ-900℃and TypeⅡ-704℃) of Ni-based alloys and coatings.It also evaluates the effects of Pt-modified b-NiAl alloy composition on hot-corrosion resistance.Both types of hot corrosion conditions were simulated by depositing Na_2SO_4 salt on the test samples and then exposing those samples to a catalyzed O_2:SO_2 atmosphere.It will be shown that TypeⅠhot corrosion resistance tends to decrease with increase in salt deposition rate up to 8 mg/cm^2;however,no measurable hot corrosion was observed when the sample was completely buried in a salt.It will also be shown that the TypeⅡhot corrosion resistance of Pt-modified Ni-based alloys is very sensitive to both alloy and gas composition.
基金supported by the 973 Program(2012CB933403 and 2013CB932604)the National Natural Science Foundation of China(11172124 and 91023026)+5 种基金Jiangsu Province Natural Science Foundation(BK2011722)MOE doctoral discipline Foundation(20113218120033)China and Jiangsu Province Postdoctoral Science Foundation(2012T50494,20110490132 and 1002015B)the Fundamental Research Funds for the Central Universities(NS2012067)supported by the National Science Foundation(CMMI and NIRT)the U.S.Army Research Office MURI(W911NF-11-1-0362)
文摘We report on a first-principles study of a novel band modulation in zigzag double-walled boron nitride nan- otubes （DBNNTs） by applying radial strain and coupled ex- ternal electric field. We show that the band alignment be- tween the inner and outer walls of the DBNNTs can be tuned from type I to type II with increasing radial strain, accompa- nied with a direct to indirect band gap transition and a sub- stantial gap reduction. The band gap can be further signifi- cantly reduced by applying a transverse electric field. The coupling of electric field with the radial strain makes the field-induced gap reduction being anisotropic and more re- markable than that in undeformed DBNNTs. In particular, the gap variation induced by electric field perpendicular to the radial strain is the most remarkable among all the modu-lations. These tunable properties by electromechanical cou- pling in DBNNTs will greatly enrich their versatile applica- tions in future nanoelectronics.
基金support from No.NSF CMMI 1536811 through the University of PittsburghC.M.W.was supported by the PNNL LDRD program.Bin Li thanks for the support from Nos.NSF CMMI 1635088,2016263,and 2032483+1 种基金This work was performed,in part,at the William R.Wiley Environmental Molecular Sciences Laboratory,a national scientific user facility sponsored by the U.S.Department of Energy,Office of Biological and Environmental Research,and located at PNNLPNNL is operated by Battelle for the U.S.Department of Energy under contract No.DE-AC05-76RLO1830.
文摘In-situ high-resolution transmission electron microscopy(HRTEM)is performed to investigate the de-formation behavior of hexagonal close-packed rhenium(Re)which is compressed along the{1-100}di-rection.Atomistic simulations are also conducted to better understand the deformation mechanisms.Two types of lattice reorientation are observed during compression.The first type involves the reori-entation of one lattice by∼90°around{11-20},which is accomplished by the formation of an interme-diate face-center-cubic(FCC)phase at the interface.This transformation sequence can be described as{1-100}matrix→{111}FCC→(0001)twin.In the second type,a new grain is formed but does not satisfy any known twin relationship with the matrix,and an intermediate FCC phase is also formed.The transfor-mation sequence can be described as{1¯101}matrix→{111}FCC→(0001)grain.Mechanisms responsible for the observed lattice reorientation and sequential phase transitions are analyzed by conducting lattice correspondence analyses on the simulation results.Strain accommodation is also analyzed to explain the mechanisms for lattice reorientation and the intermediate phase transformations.The results provide new insight into the deformation behavior of HCP metals.
基金the support from the National Institutes of Health(R01GM141055)the National Science Foundation(CMMI2104295)+7 种基金the China Scholarship Councilthe NIH/NCATS UCLA CTSI(UL1TR001881)through the UC Center for Accelerated Innovationsupported by the National Science Foundation Graduate Research Fellowship(1644868)support from the UCLA Innovation Fund MedTech Innovator Awardthe Challenge Initiative at UCLAseed funding provided through a UCLA David Geffen School of Medicine Regenerative Medicine Theme Awardthe support provided by the NIH Common Fund through an NIH Director's Early Independence Award co-funded by the National Institute of Dental and Craniofacial Research and Office of the Director,NIH under award number(DP50D028181)the NIH for a predoctoral fellowship supported by the National Heart,Lung,and Blood Institute of the National Institutes of Health under Award Number(F31HL149356)。
文摘Controlled intracellular delivery of biomolecular cargo is critical for developing targeted therapeutics and cell reprogramming.Conventional delivery approaches(e.g.,endocytosis of nano-vectors,microinjection,and electroporation)usually require time-consuming uptake processes,labor-intensive operations,and/or costly specialized equipment.Here,we present an acoustofluidics-based intracellular delivery approach capable of effectively delivering various functional nanomaterials to multiple cell types(e.g.,adherent and suspension cancer cells).By tuning the standing acoustic waves in a glass capillary,our approach can push cells in flow to the capillary wall and enhance membrane permeability by increasing membrane stress to deform cells via acoustic radiation forces.Moreover,by coating the capillary with cargo-encapsulated nanoparticles,our approach can achieve controllable cell-nanoparticle contact and facilitate nanomaterial delivery beyond Brownian movement.Based on these mechanisms,we have successfully delivered nanoparticles loaded with small molecules or protein-based cargo to U937 and HeLa cells.Our results demonstrate enhanced delivery efficiency compared to attempts made without the use of acoustofluidics.Moreover,compared to conventional sonoporation methods,our approach does not require special contrast agents with microbubbles.This acoustofluidics-based approach creates exciting opportunities to achieve controllable intracellular delivery of various biomolecular cargoes to diverse cell types for potential therapeutic applications and biophysical studies.
基金the financial supports from the National Natural Science Foundation of China (No. 52103360)the Basic and Applied Basic Research Foundation of Guangdong Province, China (No. 2020A1515111104)+1 种基金the Key-Area Research and Development Program of Guangdong Province (No. 2018B090905002)the technical support of Sinoma Institute of Materials Research (Guangzhou) Co., Ltd. (China)。
文摘Object detection under high-speed motion remains challenging due to severe motion blur,which degrades spatial appearance and limits the effectiveness of single-frame detectors.While temporal modeling is widely explored to enhance performance,its specific behavior under extreme motion blur is not yet fully characterized.In this work,we conducted an experimental study comparing a single-frame YOLOv8n detector and a temporal-enhanced variant that incorporates multi-frame inputs and frame-difference cues within the backbone.Results on a highly blurred table tennis dataset show that although the temporal-enhanced model and single-frame baseline achieve similar average precision(AP~0.52),they exhibit markedly different failure modes.Quantitative analysis reveals a Jaccard index of only 0.43,demonstrating a pronounced complementarity between the detection outcomes of the two models.By exploiting this behavioral divergence through a simple ensemble strategy,we achieve a substantial aggregate performance gain,increasing AP50 from 0.52 to 0.73.These findings suggest that under extreme blur,temporal modeling can induce complementary detection behavior beyond improving individual detector accuracy,offering an alternative perspective for designing robust detection systems in highly degraded visual environments.
