Understanding how the Internet is used by HEP is critical to optimizing the performance of the inter-lab computing environment.Typically use requirements have been defined by discussions between collaborators.However,...Understanding how the Internet is used by HEP is critical to optimizing the performance of the inter-lab computing environment.Typically use requirements have been defined by discussions between collaborators.However,later analysis of the actual traffic has shown this is often misunderstood and actual use is significantly different to that predicted.Passive monitoring of the real traffic provides insight into the true communications requirements and the performance of a large number of a large number of inter-communicating nodes.It may be useful in identifying performance problems that are due to factors other than Internet congestion especially when compared to other methods such as active monitoring where traffic is generated specifically to measure its performance.Controlled active monitoring between dedicated servers often gives an indication of what can be achieved on a network,Passive monitoring of the real traffic gives a picture of the true performance.This paper will discuss the method and results of collecting and analyzing flows of data obtained from the SLAC Internet border,The unique nature of HEP traffic and the needs of the HEP community will be highlighted.The insights this has brought to understanding the network will be reviewed and the benefit is can bring to engineering networks will be discussed.展开更多
We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chi...We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.展开更多
Scalar fields should have no spin angular momentum according to conventional textbook understandings inclassical field theory.Yet,recent studies demonstrate the undoubted existence of wave spin endowed by acousticand ...Scalar fields should have no spin angular momentum according to conventional textbook understandings inclassical field theory.Yet,recent studies demonstrate the undoubted existence of wave spin endowed by acousticand elastic longitudinal waves,which are of irrotational curl-free nature without vorticity and can be describedby scalar fields.Moreover,the conventional theory cannot even answer the question of whether wave spin existsin dissipative fields,given the ubiquitous dissipation in reality.Here,to resolve the seeming paradox and answerthe challenging question,we uncover the origin of wave spin in scalar fields beyond traditional formalism byclarifying that the presence of higher-order derivatives in scalar field Lagrangians can give rise to non-vanishingwave spin.For“spinless”scalar fields of only first-order derivatives,we can make the hidden wave spin emergeby revealing a latent field that leads to the original field through a time derivative,thus giving higher-order termsin Lagrangian.Based on the standard Noether theorem approach,we exemplify the wave spin for unconventionaldrifted acoustic fields,and even for dissipative media,in scalar fields with higher-order derivative Lagrangian.The results would prompt people to build more comprehensive and fundamental understandings of structuralwave spin in classical fields.展开更多
We demonstrate for the first time the critical influence of binder molecular weight on the performance of slurry-cast lithium nickel manganese cobalt oxide(NMC)cathodes in sulfide-based all-solid-state batteries(SSBs)...We demonstrate for the first time the critical influence of binder molecular weight on the performance of slurry-cast lithium nickel manganese cobalt oxide(NMC)cathodes in sulfide-based all-solid-state batteries(SSBs).SSBs are increasingly recognized as a safer and potentially more efficient alternative to traditional Li-ion batteries,owing to the superior ionic conductivities and inherent safety features of sulfide solid electrolytes.However,the integration of high-voltage NMC cathodes with sheet-type sulfide solid electrolytes presents significant fabrication challenges.Our findings reveal that higher molecular weight binders not only enhance the discharge capacity and cycle life of these cathodes but also ensure robust adhesion and structural integrity.By optimizing binder molecular weights,we effectively shield the active materials from degradation and mechanical stress,significantly boosting the functionality and longevity of SSBs.These results underscore the paramount importance of binder properties in advancing the practical application of high-performance all-solid-state batteries.展开更多
Recent progress in the accelerator structure studies at SLAC is reported. This paper covers the room temperature accelerator structures for the ILC e+/e- sources; RF structures for some photon science projects includi...Recent progress in the accelerator structure studies at SLAC is reported. This paper covers the room temperature accelerator structures for the ILC e+/e- sources; RF structures for some photon science projects including RF deffectors and the LCLS RF gun; the high gradient accelerator R&D in a global CLIC collaboration for the future multi-TeV linear colliders.展开更多
Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properti...Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properties of materials.But as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material synthesis.The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena.In pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization.In this regard,it would be very interesting to explore the electronic structure in doped LHPs.Here,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry directions.DFT calculations are performed and directly compared with the ARPES data.Our results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) compound.Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength.These results will help understand the physical properties of LHPs as a function of doping.展开更多
Axions are hypothetical particles proposed to solve the strong CP problem in QCD and may constitute a significant fraction of the dark matter in the universe. Axions are expected to be produced in superfluid neutron s...Axions are hypothetical particles proposed to solve the strong CP problem in QCD and may constitute a significant fraction of the dark matter in the universe. Axions are expected to be produced in superfluid neutron stars and subsequently decay, producing gamma-rays detectable by the Fermi Large Area Telescope (Fermi-LAT). Considering that light QCD axions, as opposed to axions > 1 eV, may travel a long range before they decay into gamma rays, neutron stars may appear as a spatially extended source of gamma rays. We extend our previous search for gamma rays from axions, based on a point source model, to consider the neutron star as an extended source of gamma rays. The extended consideration of neutron stars leads to higher sensitivity to searches for axions, as it will be shown. We investigate the spatial emission of gamma rays using phenomenological models of neutron star axion emission. We present models including the fundamental astrophysics and relativistic, extended gamma-ray emission from axions around neutron stars. A Monte Carlo simulation of the LAT gives us an expectation for the extended angular profile and spectrum. For a source of ≃100 pc, we predict a mean angular spread of ≃2˚ with gamma-ray energies in the range 10 - 200 MeV, due to the cutoff of the spin-structure function Sσ(ω). We demonstrate the feasibility of setting more stringent limits for axions in this mass range, excluding a range not probed by observations before. We consider projected sensitivities for mass limits on axions from RX J1856-3754, a neutron star at a distance of 130 pc. The limit based on 7.9 years of Fermi-LAT data is 3.9 meV for an inner temperature of the neutron star of 20 MeV.展开更多
Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy.By improving control over the heat dissipating from the human body,personal thermal...Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy.By improving control over the heat dissipating from the human body,personal thermal management can provide effective personal cooling and warming.Here,we propose a facile surface modification approach to tailor the thermal conduction and radiation properties based on commercially available fabrics,to realize better management of the whole heat transport pathway from the human body to the ambient.A bifunctional asymmetric fabric(BAF)offering both a cooling and a warming effect is demonstrated.Due to the advantages of roughness asymmetry and surface modification,the BAF demonstrates an effective cooling effect through enhanced heat conduction and radiation in the cooling mode;in the warming mode,heat dissipation along both routes is reduced for personal warming.As a result,a 4.6℃ skin temperature difference is measured between the cooling and warming BAF modes,indicating that the thermal comfort zone of the human body can be enlarged with one piece of BAF clothing.We expect this work to present new insights for the design of personal thermal management textiles as well as a novel solution for the facile modification of available fabrics for both personal cooling and warming.展开更多
Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at∼1800 km depth.The inner zone is governed by pressure-induced...Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at∼1800 km depth.The inner zone is governed by pressure-induced physics and chemistry dramatically different from the conventional behavior in the outer zone.These differences generate large physical and chemical potentials between the two zones that provide fundamental driving forces for triggering major events in Earth’s history.One of the main chemical carriers between the two zones isH_(2)Oin hydrous minerals that subducts into the inner zone,releases hydrogen,and leaves oxygen to create superoxides and form oxygen-rich piles at the core–mantle boundary,resulting in localized net oxygen gain in the inner zone.Accumulation of oxygen-rich piles at the base of the mantle could eventually reach a supercritical level that triggers eruptions,injecting materials that cause chemical mantle convection,superplumes,large igneous provinces,extreme climate changes,atmospheric oxygen fluctuations,and mass extinctions.Interdisciplinary research will be the key for advancing a unified theory of the four-dimensional Earth system.展开更多
Coupling nanoscale transmission X-ray microscopy (nanoTXM) with a diamond anvil cell (DAC) has exciting potential as a powerful three-dimensional probe for non-destructive imaging at high spatial resolution of materia...Coupling nanoscale transmission X-ray microscopy (nanoTXM) with a diamond anvil cell (DAC) has exciting potential as a powerful three-dimensional probe for non-destructive imaging at high spatial resolution of materials under extreme conditions. In this article, we discuss current developments in high-resolution X-ray imaging and its application in high-pressure nanoTXM experiments in a DAC with third-generation synchrotron X-ray sources, including technical considerations for preparing successful measurements. We then present results from a number of recent in situ high-pressure measurements investigating equations of state (EOS) in amorphous or poorly crystalline materials and in pressureinduced phase transitions and electronic changes. These results illustrate the potential this technique holds for addressing a wide range of research areas, ranging from condensed matter physics and solidstate chemistry to materials science and planetary interiors. Future directions for this exciting technique and opportunities to improve its capabilities for broader application in high-pressure science are discussed.展开更多
Carbon materials have been playing important roles in advancing energyrelated technologies and offering great promise to addressing the rising global energy demands and environmental issues.Nanodiamonds,an exciting cl...Carbon materials have been playing important roles in advancing energyrelated technologies and offering great promise to addressing the rising global energy demands and environmental issues.Nanodiamonds,an exciting class of carbon materials,with excellent mechanical,chemical,electronic,and optical properties,have great potentials in energy-related applications.In this contribution,we summarized some of the recent progress on nanodiamonds for energy storage,conversion,and other related applications in sustainable energy research.We discussed the promising opportunities and outlooks for nanodiamonds in energy-related fields.展开更多
Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials,such asCHplastic at extreme pressures,up to 800 Mbar.The“Gbar”design employs a strong sp...Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials,such asCHplastic at extreme pressures,up to 800 Mbar.The“Gbar”design employs a strong spherically converging shock launched through a solid ball of material using a hohlraum radiation drive.The shock front conditions are characterized using x-ray radiography.In this paper we examine the role of radiation in heating the unshocked material in front of the shock to understand the impact it has on equation of state measurements and how it drives the measured data off the theoretical Hugoniot curve.In particular,the two main sources of radiation heating are the preheating of the unshocked material by the high-energy kilo-electron-volt x-rays in the hohlraum and the heating of the material in front of the shock,as the shocked material becomes hot enough to radiate significantly.Using our model,we estimate that preheating can reach 4 eV in unshocked material,and that radiation heating can begin to drive data off the Hugoniot significantly,as pressures reach above 400 Mb.展开更多
Ni-Ti-based shape memory alloys(SMAs)have found widespread use in the last 70 years,but improving their functional stability remains a key quest for more robust and advanced applications.Named for their ability to ret...Ni-Ti-based shape memory alloys(SMAs)have found widespread use in the last 70 years,but improving their functional stability remains a key quest for more robust and advanced applications.Named for their ability to retain their processed shape as a result of a reversible martensitic transformation,SMAs are highly sensitive to compositional variations.Alloying with ternary and quaternary elements to finetune the lattice parameters and the thermal hysteresis of an SMA,therefore,becomes a challenge in materials exploration.Combinatorial materials science allows streamlining of the synthesis process and data management from multiple characterization techniques.In this study,a composition spread of Ni-Ti-Cu-V thin-film library was synthesized by magnetron co-sputtering on a thermally oxidized Si wafer.Composition-dependent phase transformation temperature and microstructure were investigated and determined using high-throughput wavelength dispersive spectroscopy,synchrotron X-ray diffraction,and temperature-dependent resistance measurements.Of the 177 compositions in the materials library,32 were observed to have shape memory effect,of which five had zero or near-zero thermal hysteresis.These compositions provide flexibility in the operating temperature regimes that they can be used in.A phase map for the quaternary system and correlations of functional properties are discussed w让h respect to the local microstructure and composition of the thin-film library.展开更多
The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr,which can assist in forming an inert film on the corroding surface.To maximize the corrosion-resistant ability of ...The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr,which can assist in forming an inert film on the corroding surface.To maximize the corrosion-resistant ability of Cr,a thorough study dealing with the passivation behaviors of this metal,including the structure and composition of the passive film as well as related reaction mechanisms,is required.Here,continuous electrochemical adsorptions of OH-groups of water molecules onto Cr terraces in acid solutions are investigated using DFT methods.Different models with various surface conditions are applied.Passivation is found to begin in the active region,and a fully coated surface mainly with oxide is likely to be the starting point of the passive region.The calculated limiting potentials are in reasonable agreement with passivation potentials observed via experiment.展开更多
In this work,we explore the suitability of several density functionals with the generalized gradient approximation(GGA)and beyond for describing the dissociative chemisorption of methane on the reconstructed Pt(110)-(...In this work,we explore the suitability of several density functionals with the generalized gradient approximation(GGA)and beyond for describing the dissociative chemisorption of methane on the reconstructed Pt(110)-(2×1)surface.The bulk and surface structures of the metal,methane adsorption energy,and dissociation barrier are used to assess the functionals.A van der Waals corrected GGA functional(optPBE-vdW)and a metaGGA functional with van der Waals correction(MS PBEl-rVV10)are selected for ab initio molecular dynamics calculations of the sticking probability.Our results suggest that the use of these two functionals may lead to a better agreement with existing experimental results,thus serving as a good starting point for future development of reliable machine-learned potential energy surfaces for the dissociation of methane on the Pt(110)-(2×1)surface.展开更多
文摘Understanding how the Internet is used by HEP is critical to optimizing the performance of the inter-lab computing environment.Typically use requirements have been defined by discussions between collaborators.However,later analysis of the actual traffic has shown this is often misunderstood and actual use is significantly different to that predicted.Passive monitoring of the real traffic provides insight into the true communications requirements and the performance of a large number of a large number of inter-communicating nodes.It may be useful in identifying performance problems that are due to factors other than Internet congestion especially when compared to other methods such as active monitoring where traffic is generated specifically to measure its performance.Controlled active monitoring between dedicated servers often gives an indication of what can be achieved on a network,Passive monitoring of the real traffic gives a picture of the true performance.This paper will discuss the method and results of collecting and analyzing flows of data obtained from the SLAC Internet border,The unique nature of HEP traffic and the needs of the HEP community will be highlighted.The insights this has brought to understanding the network will be reviewed and the benefit is can bring to engineering networks will be discussed.
文摘We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1404400 and 2023YFA1406900)the Natural Science Foundation of Shanghai(Grant No.23ZR1481200)the Program of Shanghai Academic Research Leader(Grant No.23XD1423800)。
文摘Scalar fields should have no spin angular momentum according to conventional textbook understandings inclassical field theory.Yet,recent studies demonstrate the undoubted existence of wave spin endowed by acousticand elastic longitudinal waves,which are of irrotational curl-free nature without vorticity and can be describedby scalar fields.Moreover,the conventional theory cannot even answer the question of whether wave spin existsin dissipative fields,given the ubiquitous dissipation in reality.Here,to resolve the seeming paradox and answerthe challenging question,we uncover the origin of wave spin in scalar fields beyond traditional formalism byclarifying that the presence of higher-order derivatives in scalar field Lagrangians can give rise to non-vanishingwave spin.For“spinless”scalar fields of only first-order derivatives,we can make the hidden wave spin emergeby revealing a latent field that leads to the original field through a time derivative,thus giving higher-order termsin Lagrangian.Based on the standard Noether theorem approach,we exemplify the wave spin for unconventionaldrifted acoustic fields,and even for dissipative media,in scalar fields with higher-order derivative Lagrangian.The results would prompt people to build more comprehensive and fundamental understandings of structuralwave spin in classical fields.
基金partially sponsored by the Office of Energy Efficiency and Renewable Energy(EERE)in the Vehicle Technologies Office(VTO)through the Advanced Battery Materials Research(BMR)Program,managed by DrsThe Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan(http://energy.gov/downloads/doe-public-access-plan).
文摘We demonstrate for the first time the critical influence of binder molecular weight on the performance of slurry-cast lithium nickel manganese cobalt oxide(NMC)cathodes in sulfide-based all-solid-state batteries(SSBs).SSBs are increasingly recognized as a safer and potentially more efficient alternative to traditional Li-ion batteries,owing to the superior ionic conductivities and inherent safety features of sulfide solid electrolytes.However,the integration of high-voltage NMC cathodes with sheet-type sulfide solid electrolytes presents significant fabrication challenges.Our findings reveal that higher molecular weight binders not only enhance the discharge capacity and cycle life of these cathodes but also ensure robust adhesion and structural integrity.By optimizing binder molecular weights,we effectively shield the active materials from degradation and mechanical stress,significantly boosting the functionality and longevity of SSBs.These results underscore the paramount importance of binder properties in advancing the practical application of high-performance all-solid-state batteries.
基金Supported by the US Department of Energy (DE-AC02-76SF00515)
文摘Recent progress in the accelerator structure studies at SLAC is reported. This paper covers the room temperature accelerator structures for the ILC e+/e- sources; RF structures for some photon science projects including RF deffectors and the LCLS RF gun; the high gradient accelerator R&D in a global CLIC collaboration for the future multi-TeV linear colliders.
基金Project supported by the International Partnership Program of the Chinese Academy of Sciences(Grant No.123GJHZ2022035MI)the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000015 and WK3510000012)。
文摘Organic–inorganic lead halide perovskites(LHPs) have attracted great interest owing to their outstanding optoelectronic properties.Typically,the underlying electronic structure would determinate the physical properties of materials.But as for now,limited studies have been done to reveal the underlying electronic structure of this material system,comparing to the huge amount of investigations on the material synthesis.The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena.In pristine CsPbBr_(3),the Fr?hlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization.In this regard,it would be very interesting to explore the electronic structure in doped LHPs.Here,we report high-resolution angle-resolved photoemission spectroscopy(ARPES) studies on both pristine and Cl-doped CsPbBr_(3).The experimental band dispersions are extracted from ARPES spectra along both ■ and ■ high symmetry directions.DFT calculations are performed and directly compared with the ARPES data.Our results have revealed the band structure of Cl-doped CsPbBr_(3) for the first time,which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr_(3) compound.Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength.These results will help understand the physical properties of LHPs as a function of doping.
文摘Axions are hypothetical particles proposed to solve the strong CP problem in QCD and may constitute a significant fraction of the dark matter in the universe. Axions are expected to be produced in superfluid neutron stars and subsequently decay, producing gamma-rays detectable by the Fermi Large Area Telescope (Fermi-LAT). Considering that light QCD axions, as opposed to axions > 1 eV, may travel a long range before they decay into gamma rays, neutron stars may appear as a spatially extended source of gamma rays. We extend our previous search for gamma rays from axions, based on a point source model, to consider the neutron star as an extended source of gamma rays. The extended consideration of neutron stars leads to higher sensitivity to searches for axions, as it will be shown. We investigate the spatial emission of gamma rays using phenomenological models of neutron star axion emission. We present models including the fundamental astrophysics and relativistic, extended gamma-ray emission from axions around neutron stars. A Monte Carlo simulation of the LAT gives us an expectation for the extended angular profile and spectrum. For a source of ≃100 pc, we predict a mean angular spread of ≃2˚ with gamma-ray energies in the range 10 - 200 MeV, due to the cutoff of the spin-structure function Sσ(ω). We demonstrate the feasibility of setting more stringent limits for axions in this mass range, excluding a range not probed by observations before. We consider projected sensitivities for mass limits on axions from RX J1856-3754, a neutron star at a distance of 130 pc. The limit based on 7.9 years of Fermi-LAT data is 3.9 meV for an inner temperature of the neutron star of 20 MeV.
文摘Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy.By improving control over the heat dissipating from the human body,personal thermal management can provide effective personal cooling and warming.Here,we propose a facile surface modification approach to tailor the thermal conduction and radiation properties based on commercially available fabrics,to realize better management of the whole heat transport pathway from the human body to the ambient.A bifunctional asymmetric fabric(BAF)offering both a cooling and a warming effect is demonstrated.Due to the advantages of roughness asymmetry and surface modification,the BAF demonstrates an effective cooling effect through enhanced heat conduction and radiation in the cooling mode;in the warming mode,heat dissipation along both routes is reduced for personal warming.As a result,a 4.6℃ skin temperature difference is measured between the cooling and warming BAF modes,indicating that the thermal comfort zone of the human body can be enlarged with one piece of BAF clothing.We expect this work to present new insights for the design of personal thermal management textiles as well as a novel solution for the facile modification of available fabrics for both personal cooling and warming.
基金We thank Yu He,Qingyang Hu,Jin Liu,Duckyoung Kim,and Li Zhang for sharing preliminary information.W.L.Mao acknowledges support from NSF Geophysics Grant No.EAR 1446969H.-k.Mao acknowledges supports from NSF Geochemistry Grant No.EAR-1447438+1 种基金NSF Geophysics Grant No.EAR-1722515This work was also partially supported by the National Natural Science Foundation of China Grant No.U1530402 and U1930401.
文摘Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at∼1800 km depth.The inner zone is governed by pressure-induced physics and chemistry dramatically different from the conventional behavior in the outer zone.These differences generate large physical and chemical potentials between the two zones that provide fundamental driving forces for triggering major events in Earth’s history.One of the main chemical carriers between the two zones isH_(2)Oin hydrous minerals that subducts into the inner zone,releases hydrogen,and leaves oxygen to create superoxides and form oxygen-rich piles at the core–mantle boundary,resulting in localized net oxygen gain in the inner zone.Accumulation of oxygen-rich piles at the base of the mantle could eventually reach a supercritical level that triggers eruptions,injecting materials that cause chemical mantle convection,superplumes,large igneous provinces,extreme climate changes,atmospheric oxygen fluctuations,and mass extinctions.Interdisciplinary research will be the key for advancing a unified theory of the four-dimensional Earth system.
基金supported by the Department of Energy(DOE)through the Stanford Institute for Materials&Energy Sciences(DE-AC02-76SF00515)
文摘Coupling nanoscale transmission X-ray microscopy (nanoTXM) with a diamond anvil cell (DAC) has exciting potential as a powerful three-dimensional probe for non-destructive imaging at high spatial resolution of materials under extreme conditions. In this article, we discuss current developments in high-resolution X-ray imaging and its application in high-pressure nanoTXM experiments in a DAC with third-generation synchrotron X-ray sources, including technical considerations for preparing successful measurements. We then present results from a number of recent in situ high-pressure measurements investigating equations of state (EOS) in amorphous or poorly crystalline materials and in pressureinduced phase transitions and electronic changes. These results illustrate the potential this technique holds for addressing a wide range of research areas, ranging from condensed matter physics and solidstate chemistry to materials science and planetary interiors. Future directions for this exciting technique and opportunities to improve its capabilities for broader application in high-pressure science are discussed.
基金We acknowledge the support from the Department of Energy,Office of Basic Energy Sciences,Division of Materials Sciences and Engineering,under contract DE‐AC02-76SF00515.
文摘Carbon materials have been playing important roles in advancing energyrelated technologies and offering great promise to addressing the rising global energy demands and environmental issues.Nanodiamonds,an exciting class of carbon materials,with excellent mechanical,chemical,electronic,and optical properties,have great potentials in energy-related applications.In this contribution,we summarized some of the recent progress on nanodiamonds for energy storage,conversion,and other related applications in sustainable energy research.We discussed the promising opportunities and outlooks for nanodiamonds in energy-related fields.
基金This work was performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract No.DE-AC52-07NA27344.
文摘Over the last six years many experiments have been done at the National Ignition Facility to measure the Hugoniot of materials,such asCHplastic at extreme pressures,up to 800 Mbar.The“Gbar”design employs a strong spherically converging shock launched through a solid ball of material using a hohlraum radiation drive.The shock front conditions are characterized using x-ray radiography.In this paper we examine the role of radiation in heating the unshocked material in front of the shock to understand the impact it has on equation of state measurements and how it drives the measured data off the theoretical Hugoniot curve.In particular,the two main sources of radiation heating are the preheating of the unshocked material by the high-energy kilo-electron-volt x-rays in the hohlraum and the heating of the material in front of the shock,as the shocked material becomes hot enough to radiate significantly.Using our model,we estimate that preheating can reach 4 eV in unshocked material,and that radiation heating can begin to drive data off the Hugoniot significantly,as pressures reach above 400 Mb.
基金The author thanks Tieren Gao,Peer Decker,Alan Savan,and Manfred Wuttig for fruitful discussions.The authors gratefully acknowledge funding support by the National Science Foundation Graduate Research Fellowship Program(DGE 1322106).
文摘Ni-Ti-based shape memory alloys(SMAs)have found widespread use in the last 70 years,but improving their functional stability remains a key quest for more robust and advanced applications.Named for their ability to retain their processed shape as a result of a reversible martensitic transformation,SMAs are highly sensitive to compositional variations.Alloying with ternary and quaternary elements to finetune the lattice parameters and the thermal hysteresis of an SMA,therefore,becomes a challenge in materials exploration.Combinatorial materials science allows streamlining of the synthesis process and data management from multiple characterization techniques.In this study,a composition spread of Ni-Ti-Cu-V thin-film library was synthesized by magnetron co-sputtering on a thermally oxidized Si wafer.Composition-dependent phase transformation temperature and microstructure were investigated and determined using high-throughput wavelength dispersive spectroscopy,synchrotron X-ray diffraction,and temperature-dependent resistance measurements.Of the 177 compositions in the materials library,32 were observed to have shape memory effect,of which five had zero or near-zero thermal hysteresis.These compositions provide flexibility in the operating temperature regimes that they can be used in.A phase map for the quaternary system and correlations of functional properties are discussed w让h respect to the local microstructure and composition of the thin-film library.
基金financially supported by the National Key Research and Development Program of China(No.2017YFB0702100)the National Natural Science Foundation of China(Nos.51571028,51431004,and U1706221)financial support from China Scholarship Council
文摘The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr,which can assist in forming an inert film on the corroding surface.To maximize the corrosion-resistant ability of Cr,a thorough study dealing with the passivation behaviors of this metal,including the structure and composition of the passive film as well as related reaction mechanisms,is required.Here,continuous electrochemical adsorptions of OH-groups of water molecules onto Cr terraces in acid solutions are investigated using DFT methods.Different models with various surface conditions are applied.Passivation is found to begin in the active region,and a fully coated surface mainly with oxide is likely to be the starting point of the passive region.The calculated limiting potentials are in reasonable agreement with passivation potentials observed via experiment.
基金financial support from the National Natural Science Foundation of China(No.21973013 and No.21673040)the National Natural Science Foundation of Fujian Province,China(No.2020J02025)+3 种基金the“Chuying Program”for the Top Young Talents of Fujian Provincesupported financially through a NWO/CW TOP grant(No.715.017.001)by a grant of supercomputer time from NWO Exacte en Natuurwetenschappen(NWO-ENW,No.2019.015)the National Science Foundation(No.CHE1951328)。
文摘In this work,we explore the suitability of several density functionals with the generalized gradient approximation(GGA)and beyond for describing the dissociative chemisorption of methane on the reconstructed Pt(110)-(2×1)surface.The bulk and surface structures of the metal,methane adsorption energy,and dissociation barrier are used to assess the functionals.A van der Waals corrected GGA functional(optPBE-vdW)and a metaGGA functional with van der Waals correction(MS PBEl-rVV10)are selected for ab initio molecular dynamics calculations of the sticking probability.Our results suggest that the use of these two functionals may lead to a better agreement with existing experimental results,thus serving as a good starting point for future development of reliable machine-learned potential energy surfaces for the dissociation of methane on the Pt(110)-(2×1)surface.
