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Machine learning potentials for metal-organic frameworks using an incremental learning approach

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npj Computational Materials 2023年第1期9卷 2147-2154页

作者： Sander Vandenhaute Maarten Cools-Ceuppens Simon DeKeyser Toon Verstraelen Veronique Van Speybroeck center for Molecular modeling Ghent UniversityTechnologiepark 469052 ZwijnaardeBelgium

Computational modeling of physical processes in metal-organic frameworks(MOFs)is highly challenging due to the presence of spatial heterogeneities and complex operating conditions which affect their *** functional theory(DFT)may describe interatomic interactions at the quantum mechanical level,but is computationally too expensive for systems beyond the nanometer and picosecond ***,we propose an incremental learning scheme to construct accurate and data-efficient machine learning potentials for *** scheme builds on the power of equivariant neural network potentials in combination with parallelized enhanced sampling and on-the-fly training to simultaneously explore and learn the phase space in an iterative *** only a few hundred single-point DFT evaluations per material,accurate and transferable potentials are obtained,even for flexible frameworks with multiple structurally different *** incremental learning scheme is universally applicable and may pave the way to model framework materials in larger spatiotemporal windows with higher accuracy.

关键词： framework incremental neural

Ensemble Forecast: A New Approach to Uncertainty and Predictability

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Advances in Atmospheric Sciences 2005年第6期22卷 781-788页

作者： Yuejian ZHU Environmental modeling center NCEP/NWS/NOAA Washington DC USA

Ensemble techniques have been used to generate daily numerical weather forecasts since the 1990s in numerical centers around the world due to the increase in computation ability. One of the main purposes of numerical ensemble forecasts is to try to assimilate the initial uncertainty （initial error） and the forecast uncertainty （forecast error） by applying either the initial perturbation method or the multi-model/multiphysics method. In fact, the mean of an ensemble forecast offers a better forecast than a deterministic （or control） forecast after a short lead time （3-5 days） for global modelling applications. There is about a 1-2-day improvement in the forecast skill when using an ensemble mean instead of a single forecast for longer lead-time. The skillful forecast （65% and above of an anomaly correlation） could be extended to 8 days （or longer） by present-day ensemble forecast systems. Furthermore, ensemble forecasts can deliver a probabilistic forecast to the users, which is based on the probability density function （PDF） instead of a single-value forecast from a traditional deterministic system. It has long been recognized that the ensemble forecast not only improves our weather forecast predictability but also offers a remarkable forecast for the future uncertainty, such as the relative measure of predictability （RMOP） and probabilistic quantitative precipitation forecast （PQPF）. Not surprisingly, the success of the ensemble forecast and its wide application greatly increase the confidence of model developers and research communities.

关键词： ensemble forecast predictability uncertainty

Progress of MJO Prediction at CMA from Phase I to Phase II of the Sub-Seasonal to Seasonal Prediction Project

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Advances in Atmospheric Sciences 2023年第10期40卷 1799-1815页

作者： Junchen YAO Xiangwen LIU Tongwen WU Jinghui YAN Qiaoping LI Weihua JIE center for Earth System modeling and Prediction of China Meteorological Administration Beijing 100081China

As one of the participants in the Subseasonal to Seasonal(S2S)Prediction Project,the China Meteorological Administration(CMA)has adopted several model versions to participate in the S2S *** study evaluates the models’capability to simulate and predict the Madden-Julian Oscillation(MJO).Three versions of the Beijing Climate center Climate System Model(BCC-CSM)are used to conduct historical simulations and re-forecast experiments(referred to as EXP1,EXP1-M,and EXP2,respectively).In simulating MJO characteristics,the newly-developed high-resolution BCC-CSM outperforms its *** terms of MJO prediction,the useful prediction skill of the MJO index is enhanced from 15 days in EXP1 to 22 days in EXP1-M,and further to 24 days in *** the first forecast week,the better initial condition in EXP2 largely contributes to the enhancement of MJO prediction ***,during forecast weeks 2–3,EXP2 shows little advantage compared with EXP1-M because the increased skill at MJO initial phases 6–7 is largely offset by the degraded skill at MJO initial phases 2–*** at initial phases 2–3,EXP1-M skillfully captures the wind field and Kelvin-wave response to MJO convection,leading to the highest prediction skill of the *** results reveal that,during the participation of the CMA models in the S2S Project,both the improved model initialization and updated model physics played positive roles in improving MJO *** efforts should focus on improving the model physics to better simulate MJO convection over the Maritime Continent and further improve MJO prediction at long lead times.

关键词： Madden-Julian Oscillation(MJO) Subseasonal to Seasonal(S2S) prediction skill improvement initial phase

An upgraded scheme of surface physics for Antarctic ice sheet and its implementation in the WRF model

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Science Bulletin 2016年第7期61卷 576-584页

作者： Yao Yao Jianbin Huang Yong Luo Zongci Zhao Ministry of Education Key Laboratory for Earth System modeling Center for Earth System Science and Joint Center for Global Change Studies Tsinghua University

Regional climate models often lack detailed description of ice sheet surface and, as a result, are limited in their capability to provide useful information for Antarctic climate research and field campaigns. In this study, an upgraded scheme of surface physics for Antarctic ice sheet(IST) is developed to improve the surface temperature simulations in Antarctica. Through stand-alone simulations, IST shows advantages over the Noah glacial module, a commonly utilized scheme in the widely used Weather Research and Forecasting(WRF) model. These improvements are mainly attributed to the incorporation of detailed snow physics and optimized surface layer parameterization, which results in better simulations of both the surface albedo in summer and the turbulent sensible heat flux in winter. When coupled with IST instead of Noah,WRF models show improved simulation of surface temperatures throughout the year. The bias and root-meansquare-error of annual mean surface temperatures are reduced from 5.7 and 6.0 to 0.2 and 2.7 K.

关键词： Regional climate model Antarctica Surface temperature Ice sheet

UML-based combat effectiveness simulation system modeling within MDE

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Journal of Systems Engineering and Electronics 2018年第6期29卷 1180-1196页

作者： ZHU Zhi LEI Yonglin SARJOUGHIAN Hessam LI Xiaobo ZHU Yifan Department of Military modeling and Simulation School of Systems Engineering National University of Defense Technology Arizona center for Integrated modeling and Simulation School of Computing Informatics and Decision Systems EngineeringArizona State University

To reduce complexity, the combat effectiveness simulation system(CESS) is often decomposed into static structure,physical behavior, and cognitive behavior, and model abstraction is layered onto domain invariant knowledge(DIK) and application variant knowledge(AVK) levels. This study concentrates on the specification of CESS’s physical behaviors at the DIK level of abstraction, and proposes a model driven framework for efficiently developing simulation models within model-driven engineering(MDE). Technically, this framework integrates the four-layer metamodeling architecture and a set of model transformation techniques with the objective of reducing model heterogeneity and enhancing model continuity. As a proof of concept, a torpedo example is illustrated to explain how physical models are developed following the proposed framework. Finally, a combat scenario is constructed to demonstrate the availability, and a further verification is shown by a reasonable agreement between simulation results and field observations.

关键词： domain specific modeling model-driven development system engineering effectiveness simulation

Large shear rate behavior for the Hebraud-Lequeux model Dedicated to the NSFC-CNRS Chinese-French summer institute on fluid mechanics in 2010

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Science China Mathematics 2012年第2期55卷 435-452页

作者： OLIVIER Julien Archimedes center for modeling Analysis and Computation University of Crete Iraklio 71003 Greece

The H@braud-Lequeux model is a model describing the flow of soft glassy material in a simple shear flow configuration. It is given by a kinetic/Fokker-Planck-type equation whose coefficients depend on the shear rate of the experiment. In this paper we want to study what happens to the stationary solutions of this model when the shear rate is asymptotically large. In order to do that, we expand the solution of the equation using singular perturbation tools. In the end, we rigorously prove the estimate of Hebraud and Lequeux that the material asymptotically behaves as a Newtonian fluid.

关键词： singular limit non-Newtonian rheology kinetic equations

Comparisons of JOULE 1 rocket thermospheric wind observations in high latitudes with GITM simulations

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Science China(Technological Sciences) 2017年第3期60卷 412-418页

作者： DENG Yue LARSEN Miguel F RIDLEY Aaron J ZHAN TianYu Department of Physics University of Texas at Arlington Department of Physics Clemson University center for Space Environment modeling The University of Michigan

4 Summary and conclusion The JOULE sounding rocket 1 experiment was carried out at Poker Flat Research Range in Alaska around 1200 UT on March 27th,2003 with two instrumented rockets and one chemical tracer *** the released TMA trails,neutral wind measurements from approximately 85 to 160 km altitude showed a vertically propagating wave and a jet structure around 120 km *** shears appeared at the bottom side of the jet with Richardson numbers close to or smaller than the critical value of 0.25,which implies the possible existence of Kelvin-Helmholtz instabilities caused by the vertical shear in the fast flows.

关键词： target tracking parallel vision processor MRID skipping searching image processing

Observational Study of Surface Wind along a Sloping Surface over Mountainous Terrain during Winter

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Advances in Atmospheric Sciences 2018年第3期35卷 276-284页

作者： Young-Hee LEE Gyuwon LEE Sangwon JOO Kwang-Deuk AHN Department of Astronomy and Atmospheric Sciences Kyungpook National University Numerical Data Application Division Numerical Modeling Center

The 2018 Winter Olympic and Paralympic Games will be held in Pyeongchang, Korea, during February and March. We examined the near surface winds and wind gusts along the sloping surface at two outdoor venues in Pyeongchang during February and March using surface wind data. The outdoor venues are located in a complex, mountainous terrain, and hence the near-surface winds form intricate patterns due to the interplay between large-scale and locally forced winds. During February and March, the dominant wind at the ridge level is westerly; however, a significant wind direction change is ob- served along the sloping surface at the venues. The winds on the sloping surface are also influenced by thermal forcing, showing increased upslope flow during daytime. When neutral air flows over the hill, the windward and leeward flows show a significantly different behavior. A higher correlation of the wind speed between upper- and lower-level stations is shown in the windward region compared with the leeward region. The strong synoptic wind, small width of the ridge, and steep leeward ridge slope angle provide favorable conditions for flow separation at the leeward toot of the ridge. The gust factor increases with decreasing surface elevation and is larger during daytime than nighttime. A significantly large gust factor is also observed in the leeward region.

关键词： flow separation gust factor leeward region sloping surface

Variable and Robust East Asian Monsoon Rainfall Response to El Nio over the Past 60 Years(1957–2016)

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Advances in Atmospheric Sciences 2017年第10期34卷 1235-1248页

作者： Bin WANG Juan LI Qiong HE Earth System modeling center Nanjing University of Information Science and Technology Department of Atmospheric Sciences and International Pacific Research center University of Hawaii at Manoa

Severe flooding occurred in southern and northern China during the summer of 2016 when the 2015 super El Nio decayed to a normal condition. However, the mean precipitation during summer（June–July-August） 2016 does not show significant anomalies, suggesting that — over East Asia（EA） — seasonal mean anomalies have limited value in representing hydrological hazards. Scrutinizing season-evolving precipitation anomalies associated with 16 El Nio episodes during 1957–2016 reveals that, over EA, the spatiotemporal patterns among the four categories of El Nio events are quite variable, due to a large range of variability in the intensity and evolution of El Nio events and remarkable subseasonal migration of the rainfall anomalies. The only robust seasonal signal is the dry anomalies over central North China during the El Nio developing summer. Distinguishing strong and weak El Nio impacts is important. Only strong El Nio events can persistently enhance EA subtropical frontal precipitation from the peak season of El Nio to the ensuing summer, by stimulating intense interaction between the anomalous western Pacific anticyclone（WPAC） and underlying dipolar sea surface temperature anomalies in the Indo-Pacific warm pool, thereby maintaining the WPAC and leading to a prolonged El Nio impact on EA. A weak El Nio may also enhance the post-El Nio summer rainfall over EA, but through a different physical process： the WPAC re-emerges as a forced response to the rapid cooling in the eastern Pacific. The results suggest that the skillful prediction of rainfall over continental EA requires the accurate prediction of not only the strength and evolution of El Nio, but also the subseasonal migration of EA rainfall anomalies.

关键词： El Nio impact monsoon rainfall East Asian monsoon Asian monsoon precipitation variability monsoon– ocean interaction western Pacific subtropical high