High-throughput studies and machine learning for design of β titanium alloys with optimum properties

Based on experimental data,machine learning(ML) models for Young's modulus,hardness,and hot-working ability of Ti-based alloys were constructed.In the models,the interdiffusion and mechanical property data were high-throughput re-evaluated from composition variations and nanoindentation data of diffusion couples.Then,the Ti-(22±0.5)at.%Nb-(30±0.5)at.%Zr-(4±0.5)at.%Cr(TNZC) alloy with a single body-centered cubic(BCC) phase was screened in an interactive loop.The experimental results exhibited a relatively low Young's modulus of(58±4) GPa,high nanohardness of(3.4±0.2) GPa,high microhardness of HV(520±5),high compressive yield strength of(1220±18) MPa,large plastic strain greater than 30%,and superior dry-and wet-wear resistance.This work demonstrates that ML combined with high-throughput analytic approaches can offer a powerful tool to accelerate the design of multicomponent Ti alloys with desired properties.Moreover,it is indicated that TNZC alloy is an attractive candidate for biomedical applications.

Online Optimization in Power Systems With High Penetration of Renewable Generation:Advances and Prospects

Traditionally,offline optimization of power systems is acceptable due to the largely predictable loads and reliable generation.The increasing penetration of fluctuating renewable generation and internet-of-things devices allowing for fine-grained controllability of loads have led to the diminishing applicability of offline optimization in the power systems domain,and have redirected attention to online optimization methods.However,online optimization is a broad topic that can be applied in and motivated by different settings,operated on different time scales,and built on different theoretical foundations.This paper reviews the various types of online optimization techniques used in the power systems domain and aims to make clear the distinction between the most common techniques used.In particular,we introduce and compare four distinct techniques used covering the breadth of online optimization techniques used in the power systems domain,i.e.,optimization-guided dynamic control,feedback optimization for single-period problems,Lyapunov-based optimization,and online convex optimization techniques for multi-period problems.Lastly,we recommend some potential future directions for online optimization in the power systems domain.

Mg/MgO interfaces as efficient hydrogen evolution cathodes causing accelerated corrosion of additive manufactured Mg alloys:A DFT analysis

The corrosion rates of additive-manufactured Mg alloys are higher than their as-cast counterparts,possibly due to increased kinetics for the hydrogen evolution reaction on secondary phases,which may include oxide inclusions.Scanning Kelvin Probe Force Microscopy demonstrated that MgO inclusions could act as cathodes for Mg corrosion,but their low conductivity likely precludes this.However,the density of state calculations through density functional theory using hybrid HSE06 functional revealed overlapping electronic states at the Mg/MgO interface,which facilitates electron transfers and participates in redox reactions.Subsequent determination of the hydrogen absorption energy at the Mg/MgO interface reveals it to be an excellent catalytic site,with HER being found to be a factor of 23x more efficient at the interface than on metallic Mg.The results not only support the plausibility of the Mg/MgO interface being an effective cathode to the adjacent anodic Mg matrix during corrosion but also contribute to the understanding of the enhanced cathodic activities observed during the anodic dissolution of magnesium.

Recent Advances in In-Memory Computing:Exploring Memristor and Memtransistor Arrays with 2D Materials

The conventional computing architecture faces substantial chal-lenges,including high latency and energy consumption between memory and processing units.In response,in-memory computing has emerged as a promising alternative architecture,enabling computing operations within memory arrays to overcome these limitations.Memristive devices have gained significant attention as key components for in-memory computing due to their high-density arrays,rapid response times,and ability to emulate biological synapses.Among these devices,two-dimensional(2D)material-based memristor and memtransistor arrays have emerged as particularly promising candidates for next-generation in-memory computing,thanks to their exceptional performance driven by the unique properties of 2D materials,such as layered structures,mechanical flexibility,and the capability to form heterojunctions.This review delves into the state-of-the-art research on 2D material-based memristive arrays,encompassing critical aspects such as material selection,device perfor-mance metrics,array structures,and potential applications.Furthermore,it provides a comprehensive overview of the current challenges and limitations associated with these arrays,along with potential solutions.The primary objective of this review is to serve as a significant milestone in realizing next-generation in-memory computing utilizing 2D materials and bridge the gap from single-device characterization to array-level and system-level implementations of neuromorphic computing,leveraging the potential of 2D material-based memristive devices.

Strengthening-softening transition and maximum strength in Schwarz nanocrystals

Recently,a Schwarz crystal structure with curved grain boundaries(GBs)constrained by twin-boundary(TB)networks was discovered in nanocrystalline Cu through experiments and atomistic simulations.Nanocrystalline Cu with nanosized Schwarz crystals exhibited high strength and excellent thermal stability.However,the grainsize effect and associated deformation mechanisms of Schwarz nanocrystals remain unknown.Here,we performed large-scale atomistic simulations to investigate the deformation behaviors and grain-size effect of nanocrystalline Cu with Schwarz crystals.Our simulations showed that similar to regular nanocrystals,Schwarz nanocrystals exhibit a strengthening-softening transition with decreasing grain size.The critical grain size in Schwarz nanocrystals is smaller than that in regular nanocrystals,leading to a maximum strength higher than that of regular nanocrystals.Our simulations revealed that the softening in Schwarz nanocrystals mainly originates from TB migration(or detwinning)and annihilation of GBs,rather than GB-mediated processes(including GB migration,sliding and diffusion)dominating the softening in regular nanocrystals.Quantitative analyses of simulation data further showed that compared with those in regular nanocrystals,the GB-mediated processes in Schwarz nanocrystals are suppressed,which is related to the low volume fraction of amorphous-like GBs and constraints of TB networks.The smaller critical grain size arises from the suppression of GB-mediated processes.

Thermal conductivity of GeTe crystals based on machine learning potentials

GeTe has attracted extensive research interest for thermoelectric applications.In this paper,we first train a neuroevolution potential(NEP)based on a dataset constructed by ab initio molecular dynamics,with the Gaussian approximation potential(GAP)as a reference.The phonon density of states is then calculated by two machine learning potentials and compared with density functional theory results,with the GAP potential having higher accuracy.Next,the thermal conductivity of a GeTe crystal at 300 K is calculated by the equilibrium molecular dynamics method using both machine learning potentials,and both of them are in good agreement with the experimental results;however,the calculation speed when using the NEP potential is about 500 times faster than when using the GAP potential.Finally,the lattice thermal conductivity in the range of 300 K-600 K is calculated using the NEP potential.The lattice thermal conductivity decreases as the temperature increases due to the phonon anharmonic effect.This study provides a theoretical tool for the study of the thermal conductivity of GeTe.

3D-Printed Monolith Metallic Ni-Mo Electrodes for Ultrahigh Current Hydrogen Evolution

In this work,we reported a series of monolithic 3D-printed Ni-Mo alloy electrodes for highly efficient water splitting at high current density(1500 mA cm^(-2))with excellent stability,which provides a solution to scale up Ni-Mo catalysts for HER to industry use.All possible Ni-Mo metal/alloy phases were achieved by tuning the atomic composition and heat treatment procedure,and they were investigated through both experiment and simulation,and the optimal NiMo phase shows the best performance.Density functional theory(DFT)calculations elucidate that the NiMo phase has the lowest H2O dissociation energy,which further explains the exceptional performance of NiMo.In addition,the microporosity was modulated via controlled thermal treatment,indicating that the 1100℃sintered sample has the best catalytic performance,which is attributed to the high electrochemically active surface area(ECSA).Finally,the four different macrostructures were achieved by 3D printing,and they further improved the catalytic performance.The gyroid structure exhibits the best catalytic performance of driving 500 mA cm^(-2)at a low overpotential of 228 mV and 1500 mA cm^(-2)at 325 mV,as it maximizes the efficient bubble removal from the electrode surface,which offers the great potential for high current density water splitting.

Investigation of an electrode-driven hydrogen plasma method for in situ cleaning of tin-based contamination

To prolong the service life of optics,the feasibility of in situ cleaning of the multilayer mirror(MLM)of tin and its oxidized contamination was investigated using hydrogen plasma at different power levels.Granular tin-based contamination consisting of micro-and macroparticles was deposited on silicon via physical vapor deposition(PVD).The electrodedriven hydrogen plasma at different power levels was systematically diagnosed using a Langmuir probe and a retarding field ion energy analyzer(RFEA).Moreover,the magnitude of the self-biasing voltage was measured at different power levels,and the peak ion energy was corrected for the difference between the RFEA measurements and the self-biasing voltage(E_(RFEA)-eV_(self)).XPS analysis of O 1s and Sn 3d peaks demonstrated the chemical reduction process after 1 W cleaning.Analysis of surface and cross-section morphology revealed that holes emerged on the upper part of the macroparticles while its bottom remained smooth.Hills and folds appeared on the upper part of the microparticles,confirming the top-down cleaning mode with hydrogen plasma.This study provides an in situ electrode-driven hydrogen plasma etching process for tin-based contamination and will provide meaningful guidance for understanding the chemical mechanism of reduction and etching.

Structural Intensity Characterization of Composite Laminates Subjected to Impact Load

Structural intensity (SI) characterization of composite laminates subjected to impact load was dis-cussed. The SI pattern of the laminates which have different fiber orientations and boundary conditions was analyzed. The resultant forces and velocities of the laminates were calculated, and the structural intensity was evaluated. The SI streamlines of carbon fiber reinforced epoxy composite laminates and the steel plates were discussed. The results show that the SI streamlines of the graphite/epoxy laminates are different from that of the steel plates, and the SI streamlines are influenced by the boundaries, the stacking sequence of the composite laminates. The change of the historical central displacement of the graphite/epoxy laminates is fasten than that of the steel plates.

Pulling out a peptide chain from β-sheet crystallite: Propagation of instability of H-bonds under shear force

Anti-parallel β-sheet crystallite as the main component of silk fibroin has attracted much attention due to its superior mechanical properties. In this study, we examine the processes of pulling a peptide chain from β-sheet crystallite using steered molecular dynamics simulations to investigate the rupture behavior of the crystallite. We show that the failure of β-sheet crystallite was accompanied by a propagation of instability of hydrogen-bonds （H-bonds） in the crystallite. In addition, we find that there is an optimum size of the crystallite at which the H-bonds can work cooperatively to achieve the highest shear strength. In addition, we find that the stiffness of loading device and the loading rates have significant effects on the rupture behavior of β-sheet crystallite. The stiff loading device facilitates the rebinding of the Hbond network in the stick-slip motion between the chains, while the soft one suppresses it. Moreover, the rupture force of β-sheet crystallites decreases with loading rate. Particularly, when the loading rate decreases to a critical value, the rupture force of the β-sheet crystallite becomes independent of the loading rates. This study provides atomistic details of rupture behaviors of β-sheet crystallite, and, therefore, sheds valuable light on the underlying mechanism of the superior mechanical properties of silk fibroin.

Thermal properties of two-dimensional materials

Two-dimensional （2D） materials, such as graphene, phosphorene, and transition metal dichalcogenides （e.g., MoS2 and WS2）, have attracted a great deal of attention recently due to their extraordinary structural, mechanical, and physical properties. In particular, 2D materials have shown great potential for thermal management and thermoelectric energy generation. In this article, we review the recent advances in the study of thermal properties of 2D materials. We first review some important aspects in thermal conductivity of graphene and discuss the possibility to enhance the ultra-high thermal conductivity of graphene. Next, we discuss thermal conductivity of MoS2 and the new strategy for thermal management of MoS2 device. Subsequently, we discuss the anisotropic thermal properties of phosphorene. Finally, we review the application of 2D materials in thermal devices, including thermal rectifier and thermal modulator.

A Thermochromic, Viscoelastic Nacre-like Nanocomposite for the Smart Thermal Management of Planar Electronics

Cutting-edge heat spreaders for soft and planar electronics require not only high thermal conductivity and a certain degree of flexibility but also remarkable self-adhesion without thermal interface materials, elasticity, arbitrary elongation along with soft devices, and smart properties involving thermal self-healing, thermochromism and so on. Nacre-like composites with excellent in-plane heat dissipation are ideal as heat spreaders for thin and planar electronics. However, the intrinsically poor viscoelasticity, i.e., adhesion and elasticity, prevents them from simultaneous self-adhesion and arbitrary elongation along with current flexible devices as well as incurring high interfacial thermal impedance. In this paper, we propose a soft thermochromic composite(STC) membrane with a layered structure, considerable stretchability, high in-plane thermal conductivity(~30 Wm^(-1) K^(-1)), low thermal contact resistance(~12 mm^2 KW^(-1), 4–5 times lower than that of silver paste), strong yet sustainable adhesion forces(~4607 Jm^(-2), 2220 Jm^(-2) greater than that of epoxy paste) and self-healing efficiency. As a self-adhesive heat spreader, it implements efficient cooling of various soft electronics with a temperature drop of 20℃ than the polyimide case. In addition to its self-healing function, the chameleon-like behavior of STC facilitates temperature monitoring by the naked eye, hence enabling smart thermal management.

Unusual thermal properties of graphene origami crease:A molecular dynamics study

Graphene is a two-dimensional material that can be folded into diverse and yet interesting nanostructures like macro-scale paper origami.Folding of graphene not only makes different morphological configurations but also modifies their mechanical and thermal properties.Inspired by paper origami,herein we studied systemically the effects of creases,where sp^(2)to sp^(3)bond transformation occurs,on the thermal properties of graphene origami using molecular dynamics(MD)simulations.Our MD simulation results show that tensile strain reduces(not increases)the interfacial thermal resistance owing to the presence of the crease.This unusual phenomenon is explained by the micro-heat flux migration and stress distribution.Our findings on the graphene origami enable the design of the next-generation thermal management devices and flexible electronics with tuneable properties.

Thermal properties of transition-metal dichalcogenide

Beyond graphene, the layered transition metal dichalcogenides （TMDs） have gained considerable attention due to their unique properties. Herein, we review the lattice dynamic and thermal properties of monolayer TMDs, including their phonon dispersion, relaxation time, mean free path （MFP）, and thermal conductivities. In particular, the experimental and theoretical studies reveal that the TMDs have relatively low thermal conductivities due to the short phonon group velocity and MFP, which poses a significant challenge for efficient thermal management of TMDs-based devices. Importantly, recent studies have shown that this issue could be largely addressed by connecting TMDs and other materials （such as metal electrode and graphene） with chemical bonds, and a relatively high interracial thermal conductance （ITC） could be achieved at the covalent bonded interface. The ITC of MoS2/Au interface with chemical edge contact is more than 10 times higher than that with physical side contact. In this article, we review recent advances in the study of TMD-related ITC. The effects of temperature, interfacial vacancy, contact orientation, and phonon modes on the edge-contacted interface are briefly discussed.

Controlled buckling of thin film on elastomeric substrate in large deformation

Electronic systems with large stretchability have many applications.A precisely controlled buckling strategy to increase the stretchability has been demonstrated by combining lithographically patterned surface bonding chemistry and a buckling process.The buckled geometry was assumed to have a sinusoidal form,which may result in errors to determine the strains in the film.A theoretical model is presented in this letter to study the mechanics of this type of thin film/substrate system by discarding the assumption of sinusoidal buckling geometry.It is shown that the previous model overestimates the deflection and curvature in the thin film.The results from the model agree well with finite element simulations and therefore provide design guidelines in many applications ranging from stretchable electronics to micro/nano scale surface patterning and precision metrology.

HOMOGENIZATION—BASED TOPOLOGY DESIGN FOR PURE TORSION OF COMPOSITE SHAFTS

In conjunction with the homogenization theory and the finite element method,the mathematical models for designing the cross-section of composite shafts by maximizing the torsion rigidity are developed in this paper.To obtain the extremal torsion rigidity,both the cross-section of the macro scale shaft and the representative microstructure of the composite material are optimized using the new models.The micro scale computational model addresses the problem of finding the periodic microstructures with extreme shear moduli.The optimal microstructure obtained with the new model and the homogenization method can be used to improve and optimize natural or artificial materials.In order to be more practical for engineering applications,cellular materials rather than ranked materials are used in the optimal process in the existence of optimal bounds for the elastic properties.Moreover,the macro scale model is proposed to optimize the cross-section of the torsional shaft based on the tailared composites.The validating optimal results show that the models are very effective in obtaining composites with extreme elastic properties,and the cross-section of the composite shaft with the extremal torsion rigidity.

Breakup of spherical vesicles caused by spontaneous curvature change

We present our theoretical analysis and coarse- grained molecular dynamics （CGMD） simulation results to describe the mechanics of breakup of spherical vesi- cles driven by changes in spontaneous curvature. System- atic CGMD simulations reveal the phase diagrams for the breakup and show richness in breakup morphologies. A the- oretical model based on Griffith fracture mechanics is devel- oped and used to predict the breakup condition.

Identification of genetic factors modulating doxorubicin-associated cytotoxicity by calcium

OBJECTIVE To examine the effect of calcium on the response towards doxorubicin,a widely used chemotherapeutic agent in the clinic,using fission yeast(Schizosaccharomycespombe)and human cancer cells(MCF7)This project built on a previously performed genome-wide search of doxorubicin-resistance(DXR)genes in Schizosaccharomycespombefission yeast,which identified a host of genes that counteracted doxorubicin cytotoxicity.METHODS Growth fitness of Schizosaccharomycespombe knock-out mutants of doxorubicin-resistance genes were tested on varying concentrations of calcium,doxorubicin or calcium+doxorubicin.Similar growth fitness experiments were also performed on MCF7 breast cancer cells.RESULTS We found that a subset of null mutants of DXR genes show concurrent hypersensitivity to calcium and doxorubicin.Interestingly,their hypersensitivity towards doxorubicinwas suppressed by calcium.This phenotype was dependent on the integrity of the proton pump vacuolar-ATPase(V-ATPase)as the disruption of the V-ATPase-assembly factors(Rav1 and Vph2)abolished the suppressive effect of calcium.CONCLUSION Our findings uncovered an unexpected negative regulation of chemotherapeutic drug efficacy by dietary micronutrient that may caution against the concurrent consumption of calcium-rich dietary products alongside doxorubicin treatment.

General theories and features of interfacial thermal transport

A clear understanding and proper control of interfacial thermal transport is important in nanoscale devices. In this review, we first discuss the theoretical methods to handle the interfacial thermal transport problem, such as the macroscopic model, molecular dynamics, lattice dynamics, and quantum transport theories. Then we discuss various effects that can significantly affect the interfacial thermal transport, such as the formation of chemical bonds at interface, defects, interface roughness, strain, substrates, atomic species, mass ratios, and structural orientations. Then importantly, we analyze the role of inelastic scattering at the interface, and discuss its application in thermal rectifications. Finally, the challenges and promising directions are discussed.

Pressure-dependent electronic,optical,and mechanical properties of antiperovskite X_(3)NP(X=Ca,Mg):A first-principles study

Hydrostatic pressure provides an efficient way to tune and optimize the properties of solid materials without chang-ing their composition.In this work,we investigate the electronic,optical,and mechanical properties of antiperovskite X_(3)NP(X^(2+)=Ca,Mg)upon compression by first-principles calculations.Our results reveal that the system is anisotropic,and the lat-tice constant a of X_(3)NP exhibits the fastest rate of decrease upon compression among the three directions,which is different from the typical Pnma phase of halide and chalcogenide perovskites.Meanwhile,Ca_(3)NP has higher compressibility than Mg_(3)NP due to its small bulk modulus.The electronic and optical properties of Mg_(3)NP show small fluctuations upon compression,but those of Ca_(3)NP are more sensitive to pressure due to its higher compressibility and lower unoccupied 3d orbital energy.For example,the band gap,lattice dielectric constant,and exciton binding energy of Ca_(3)NP decrease rapidly as the pressure increases.In addition,the increase in pressure significantly improves the optical absorption and theoretical conversion effi-ciency of Ca_(3)NP.Finally,the mechanical properties of X_(3)NP are also increased upon compression due to the reduction in bond length,while inducing a brittle-to-ductile transition.Our research provides theoretical guidance and insights for future experi-mental tuning of the physical properties of antiperovskite semiconductors by pressure.