Eddy-resolving Simulation of CAS-LICOM3 for Phase 2 of the Ocean Model Intercomparison Project

A 61-year(1958–2018)global eddy-resolving dataset for phase 2 of the Ocean Model Intercomparison Project has been produced by the version 3 of Chinese Academy of Science,the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics(LASG/IAP)Climate system Ocean Model(CAS-LICOM3).The monthly and a part of the surface daily data in this study can be accessed on the Earth System Grid Federation(ESGF)node.Besides the details of the model and experiments,the evolutions and spatial patterns of large-scale and mesoscale features are also presented.The mesoscale features are reproduced well in the high-resolution simulation,as the mesoscale activities can contribute up to 50%of the total SST variability in eddy-rich regions.Also,the large-scale circulations are remarkably improved compared with the low-resolution simulation,such as the climatological annual mean SST(the RMSE is reduced from 0.59°C to 0.47°C,globally)and the evolution of Atlantic Meridional Overturning Circulation.The preliminary evaluation also indicates that there are systematic biases in the salinity,the separation location of the western boundary currents,and the magnitude of eddy kinetic energy.All these biases are worthy of further investigation.

Density functional theory study of formaldehyde adsorption and decomposition on Co-doped defective CeO_(2) (110) surface

Formaldehyde as an air pollutant to adverse health effects for humanity has been getting attention.The adsorption and dissociation of formaldehyde(HCHO)on the CoxCe1−xO_(2)−δ(110)surface were investigated by the density functional theory(DFT)calculations.We calculated the oxygen vacancy formation energy as the function of its site around dopant Co in detail.The results showed that Co doping was accompanied by compensating oxygen hole spontaneous formation.The adsorption configurations and bindings of HCHO at different locations on the CoxCe1−xO_(2)(110)were presented.Four possible pathways of oxidation of formaldehyde on the catalytic surface were explored.The results suggested that formaldehyde dissociation at different adsorption sites on the doped CeO_(2)(110)—first forming dioxymethylene(CH2O_(2))intermediate,and then decomposing into H2O,H2,CO_(2),and CO molecules.It was found that the presence of cobalt and oxygen vacancy significantly prompted the surface activity of CeO_(2).

AquaSee: Predict Load and Cooling System Faults of Supercomputers Using Chilled Water Data

An analysis of real-world operational data of Tianhe-1A(TH-1A)supercomputer system shows that chilled water data not only can reflect the status of a chiller system but also are related to supercomputer load.This study proposes AquaSee,a method that can predict the load and cooling system faults of supercomputers by using chilled water pressure and temperature data.This method is validated on the basis of real-world operational data of the TH-1A supercomputer system at the National Supercomputer Center in Tianjin.Datasets with various compositions are used to construct the prediction model,which is also established using different prediction sequence lengths.Experimental results show that the method that uses a combination of pressure and temperature data performs more effectively than that only consisting of either pressure or temperature data.The best inference sequence length is two points.Furthermore,an anomaly monitoring system is set up by using chilled water data to help engineers detect chiller system anomalies.

Storage wall for exascale supercomputing

The mismatch between compute performance and I/O performance has long been a stumbling block as supercomputers evolve from petaflops to exaflops. Currently, many parallel applications are I/O intensive,and their overall running times are typically limited by I/O performance. To quantify the I/O performance bottleneck and highlight the significance of achieving scalable performance in peta/exascale supercomputing, in this paper, we introduce for the first time a formal definition of the ‘storage wall' from the perspective of parallel application scalability. We quantify the effects of the storage bottleneck by providing a storage-bounded speedup,defining the storage wall quantitatively, presenting existence theorems for the storage wall, and classifying the system architectures depending on I/O performance variation. We analyze and extrapolate the existence of the storage wall by experiments on Tianhe-1A and case studies on Jaguar. These results provide insights on how to alleviate the storage wall bottleneck in system design and achieve hardware/software optimizations in peta/exascale supercomputing.

Anion-derived solid electrolyte interphase realized in usualconcentration electrolyte for Li metal batteries

Constructing anion-derived solid electrolyte interphase(SEI)by recruiting anions into the solvation sheath of Li+is extremely conducive to restrain the dendrite growth of Li metal anode.However,the presence of anions in the solvation sheath of Li+is severely hindered by the solvents with strong coordinating ability in conventional electrolyte.Herein,we boost the content of anions in the primary solvation sheath of Li+by employing a solvent with low donor number,2-methyltetrahydrofuran,inducing an anion-derived SEI.As a result,the Li||Cu cells show a high average Coulombic efficiency(>99%)over 500 cycles and the Li||LiFePO4 cells under a low negative/positive capacity ratio of 2:1 exhibit an impressive capacity retention of 90%after 100 cycles.This work provides insights on constructing stable anion-derived SEI and offers guidance in designing electrolytes for stable Li metal batteries.

Fast Ion Conductor Nanofibers and Aramid Nanofibers with Hydrogen Bonds Synergistically Enhanced Composite Solid Electrolytes

The low ionic conductivities,poor high-voltage stabilities,and lithium dendrite formation of polymer solid electrolytes preclude their use in all-solid-state lithium metal batteries(ASSLMBs).This work provides a simple and scalable technique for constructing fast ion conductor nanofibers(FICNFs)and poly-m-phenyleneisophthalamide(PMIA)nanofibers synergistically enhanced polyethylene oxide(PEO)-based composite solid electrolytes(CSEs)for ASSLMBs.The FICNFs,which were mainly composed of high loadings of ZrO_(2)or Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)nanoparticles,had a percolated ceramic phase inside the nanofibers,while the exposed nanoparticles formed continuous organic–inorganic interfaces with the PEO matrix to enable Li+transport.The interfacial transport rate between ZrO_(2)and PEO was calculated as 4.78×10^(–5)cm^(2)s^(−1)with ab initio molecular dynamics(AIMD)simulations.Besides,the PMIA nanofibers provided strong skeletal support for the CSEs,ensuring excellent mechanical strength and safety for thin CSEs even at high temperatures.More importantly,the amide groups in PMIA provided abundant hydrogen bonds with TFSI−,which lowered the lowest unoccupied molecular orbital(LUMO)level of lithium salts,thus promoting the generation of lithium fluoride-rich solid electrolyte interphase.Consequently,the modified CSEs exhibited satisfactory ionic conductivities(5.38×10^(–4)S cm^(−1)at 50°C)and notable Li dendrite suppression(>1500 h at 0.3 mAh cm^(−2)).The assembled LiFePO4||Li full cells display ultra-long cycles(>2000 cycles)at 50°C and 40°C.More strikingly,the LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811)||Li cell also can stably run for 500 cycles,and the LiFePO_(4)||Li flexible pouch cells also cycled normally,demonstrating tremendous potential for practical application.

FTRP:a new fault tolerance framework using process replication and prefetching for high-performance computing

As the scale of supercomputers rapidly grows, the reliability problem dominates the system availability. Existing fault tolerance mechanisms, such as periodic checkpointing and process redundancy, cannot effectively fix this problem. To address this issue, we present a new fault tolerance framework using process replication and prefetching （FTRP）, combining the benefits of proactive and reactive mechanisms. FTRP incorporates a novel cost model and a new proactive fault tolerance mechanism to improve the application execution efficiency. The novel cost model, called the ＇work-most＇ （WM） model, makes runtime decisions to adaptively choose an action from a set of fault tolerance mechanisms based on failure prediction results and application status. Similar to program locality, we observe the failure locality phenomenon in supercomputers for the first time. In the new proactive fault tolerance mechanism, process replication with process prefetching is proposed based on the failure locality, significantly avoiding losses caused by the failures regardless of whether they have been predicted. Simulations with real failure traces demonstrate that the FTRP framework outperforms existing fault tolerance mechanisms with up to 10% improvement in application efficiency for common failure prediction accuracy, and is effective for petascale systems and beyond.

Computationally predicting spin semiconductors and half metals from doped phosphorene monolayers

First-principles computations are performed to investigate phosphorene monolayers doped with 30 metal and nonmetal atoms. The binding energies indicate the stability of all doped configurations. Interestingly, the magnetic atom Co doping induces the absence of the magnetism while the magnetism is realized in phosphorene with substitutional doping of nonmagnetic atoms (O, S, Se, Si, Br, and Cl). The magnetic moment of transition metal (TM)-doped systems is suppressed in the range of 1.0-3.97μB.The electronic properties of the doped systems are modulated differently;O, S, Se, Ni, and Ti doped systems become spin semiconductors, while V doping makes the system a half metal. These results demonstrate potential applications of functionalized phosphorene with external atoms, in particular to spintronics and dilute magnetic semiconductors.

mSwap: a large-scale image-compositing method with optimal m-ary tree

With the increasing of computing ability,large-scale simulations have been generating massive amounts of data in aerodynamics.Sort-last parallel rendering is the most classical image compositing method for large-scale scientific visualization.However,in the stage of image compositing,the sort-last method may suffer from scalability problem on large-scale processors.Existing image compositing algorithms tend to perform well in certain situations.For instance,Direct Send is well on small and medium scale;Radix-k gets well performance only when the k-value is appropriate and so on.In this paper,we propose a novel method named mSwap for scientific visualization in aerodynamics,which uses the best scale of processors to make sure its performance at the best.mSwap groups the processors that we can use with a(m,k)table,which records the best combination of m(the number of processors in subgroup of each group)and k(the number of processors in each group).Then in each group,using a m-ary tree to composite the image for reducing the communication of processors.Finally,the image is composited between different groups to generate the final image.The performance and scalability of our mSwap method is demonstrated through experiments with thousands of processors.

Vector Meson Mass in Finite Density and Temperature Lattice QCD

Vector meson mass values are studied at finite chemical potential and temperature in lattice QCD with lattice size of 24 × 122× 6 using two flavors of staggered quarks. The investigation focuses on the change of the vector meson mass in the critical region close to T c with two different types of chemical potentials switched on: the isoscalar chemical potential μS and its isovector counterpart μV. It is found that the vector meson mass increases in the QGP phase with both chemical potentials and decreases with μS in the confinement phase.

Toward atomistic models of intact severe acute respiratory syndrome coronavirus 2 via Martini coarsegrained molecular dynamics simulations

The causative pathogen of coronavirus disease 2019(COVID-19),severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),is an enveloped virus assembled by a lipid envelope and multiple structural proteins.In this study,by integrating experimental data,structural modeling,as well as coarse-grained and all-atom molecular dynamics simulations,we constructed multiscale models of SARS-CoV-2.Our 500-ns coarse-grained simulation of the intact virion allowed us to investigate the dynamic behavior of the membrane-embedded proteins and the surrounding lipid molecules in situ.Our results indicated that the membrane-embedded proteins are highly dynamic,and certain types of lipids exhibit various binding preferences to specific sites of the membrane-embedded proteins.The equilibrated virion model was transformed into atomic resolution,which provided a 3D structure for scientific demonstration and can serve as a framework forfuture exascale allatom molecular dynamics(MD)simulations.A short all-atom molecular dynamics simulation of 255 ps was conducted as a preliminary test for largescale simulationsofthis complexsystem.

Phase transition in finite density and temperature lattice QCD

We investigate the behavior of the chiral condensate in lattice QCD at finite temperature and finite chemical potential. The study was done using two flavors of light quarks and with a series of β and ma at the lattice size 24×122×6. The calculation was done in the Taylor expansion formalism. We are able to calculate the first and second order derivatives of ψψ in both isoscalar and isovector channels. With the first derivatives being small, we find that the second derivatives are sizable close to the phase transition and that the magnitude of ψψ decreases under the influence of finite chemical potential in both channels.

简便的变电流沉积法制备高强度(110)择优取向梯度铜箔

导电铜箔是电子工业中一种重要的原材料,但是常规的铜箔抗拉强度低(约350 MPa),韧性差,在生产和使用过程中容易断裂,难以满足高密度印制电路板和高能电池发展的需求.本文采用一种简便的变电流沉积法制备了具有(110)晶面优势取向的梯度晶铜箔,并可在9–50μm范围内调控其厚度.铜箔具有微米级粗晶粒逐渐过渡到纳米级细晶粒的梯度结构,使抗拉强度(~840 MPa)大幅提高的同时保持良好的韧性(~3.6%).特别值得一提的是,梯度铜箔还展现出高达3.3×10^(7)S m^(-1)的电导率,表明其在锂离子电池负极集流体和印制电路板中具有广阔的应用前景.这种简便的变电流沉积法也可为其他金属材料的制备提供借鉴.