检索结果-南通市图书馆

Towards a unified nonlocal, peridynamics framework for the coarse-graining of molecular dynamics data with fractures

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2023年第7期44卷 1125-1150页

作者： H.Q.you X.XU Y.YU s.sILLING M.D'ELIA j.FOsTER Department of Mathematics Lehigh UniversityBethlehemPA 18015U.S.A Department of Petroleum and Geosystems Engineering The University of Texas at AustinTX 78712-1139U.S.A. Center for Computing Research Sandia National LaboratoriesCA 94551-0969U.S.A.

Molecular dynamics(MD)has served as a powerful tool for designing materials with reduced reliance on laboratory ***,the use of MD directly to treat the deformation and failure of materials at the mesoscale is still largely beyond *** this work,we propose a learning framework to extract a peridynamics model as a mesoscale continuum surrogate from MD simulated material fracture data ***,we develop a novel coarse-graining method,to automatically handle the material fracture and its corresponding discontinuities in the MD displacement data *** by the weighted essentially non-oscillatory(WENO)scheme,the key idea lies at an adaptive procedure to automatically choose the locally smoothest stencil,then reconstruct the coarse-grained material displacement field as the piecewise smooth solutions containing ***,based on the coarse-grained MD data,a two-phase optimizationbased learning approach is proposed to infer the optimal peridynamics model with damage *** the first phase,we identify the optimal nonlocal kernel function from the data sets without material damage to capture the material stiffness ***,in the second phase,the material damage criterion is learnt as a smoothed step function from the data with *** a result,a peridynamics surrogate is *** a continuum model,our peridynamics surrogate model can be employed in further prediction tasks with different grid resolutions from training,and hence allows for substantial reductions in computational cost compared with *** illustrate the efficacy of the proposed approach with several numerical tests for the dynamic crack propagation problem in a single-layer *** tests show that the proposed data-driven model is robust and generalizable,in the sense that it is capable of modeling the initialization and growth of fractures under discretization and loading settings that are different from the ones used during training.

关键词： nonlocal model machine learning homogenization peridynamics material fracture

Experimental Investigation of the secondary Flow in a Rotating smooth Channel subjected to Thermal Boundary Conditions

在线全文

学校读者我要写书评

暂无评论

journal of Thermal science 2020年第6期29卷 1463-1474页

作者： LI Haiwang you Haoliang you Ruquan TAO Zhi National Key Laboratory of science and Technology on Aero-Engines Aero-thermodynamics Beihang UniversityBeijing 100191China

In the current study,thermal boundary conditions are considered in a rotating smooth channel with a square cross-section to investigate the secondary flow and compare it to that of the same channel without *** measurement is conducted at three streamwise planes(X=445 mm,525 mm,605 mm).The flow parameters are the Reynolds number(Re=4750,which was based on the average longitudinal or primary velocity U and the hydraulic diameter D of the channel cross-section),the rotation number(Ro=?D/U,where?is the rotational velocity,ranging from 0 to 0.26),and the aspect ratio of the channel cross-section(AR=1,which is calculated by dividing the channel height by the channel width).The leading and trailing walls are heated under a constant heat flux qw=380 W/m^2,and the top and bottom walls are isothermal at room *** work is in a series with our previous work without thermal boundary *** on the experimental data,we obtained a four-vortex *** is a counter-rotating vortex pair near the leading side and the trailing *** the leading and trailing walls are heated,the buoyancy force increases the relative vertical position of the vortex pair near the trailing side from 5%to 12.5%of the hydraulic *** moving upstream along the streamwise direction,the upper vortex near the trailing wall becomes weaker,whereas the lower vortex becomes *** the rotational speed increases,the vortex pair near the trailing side is inhibited by the Coriolis *** heated thermal boundary conditions,the vortex pair near the trailing side reappears due to the effect of buoyancy *** results indicate that the buoyancy force has a substantial effect on the secondary flow regime under thermal boundary conditions.

关键词： flow dynamic rotating smooth channel secondary flow buoyancy force

On the Rates of the Other Law of the Logarithm

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica sinica,English series 2012年第4期28卷 781-792页

作者： Li-Xin ZHANG you-you CHEN Department of Mathematics Zhejiang University

Let X, X1, X2,… be i.i.d, random variables, and set sn =X1＋…＋Xn,Mn=maxk≤n｜sk｜,n≥*** an=o（√log n）.By using the strong approximation, we prove that, if EX = 0,

关键词： Complete convergence tail probabilities of sums of i.i.d random variables the other lawof the logarithm strong approximation

Theoretical study on the synergistic mechanism of Fe–Mn in sodium-ion batteries

在线全文

学校读者我要写书评

暂无评论

Particuology 2024年第10期93卷 284-290页

作者： Yang you Mingliang Yuan school of Mineral Processing and Bioengineering Central South UniversityChangsha410083China

This article conducts first-principles calculations to initially explore the construction of two configurations,NaFeO_(2)(NFO)and NaMnO_(2)(NMO),and studies the mixing enthalpies under different Fe–Mn *** results indicate that NaFe_(3/8)Mn_(5/8)O_(2)(NFMO)exhibits the most thermodynamically stable *** calculations on the mixing enthalpies and volume changes during the sodium extraction process for NFO,NMO,and NFMO configurations are presented,along with the partial density of states(PDOs)and Bader charges of transition metals(TM)and *** calculations reveal the synergistic mechanism of Fe and *** and Mn can engage in more complex electron exchanges during sodium extraction,optimizing the internal electron density distribution and overall charge balance,thereby stabilizing the crystal structure and reducing the migration of Fe^(3+)to the sodium layers during deep sodium *** interaction between Fe’s 3d electrons and Mn’s 3d electrons through the shared oxygen atoms’2p orbitals occurs in the Fe–Mn–O *** interaction can lead to a rebalancing of the electron density around Mn³⁺atoms,mitigating the asymmetric electron density distribution caused by the d4 configuration of the lone Mn³⁺and suppressing the jahn-Teller effect of Mn^(3+).Moreover,the synergistic effects between Fe and Mn can provide a more balanced charge distribution,reducing extreme changes to the charge state of oxygen atoms and decreasing the irreversible oxygen release caused by anionic redox reactions during deep sodium extraction,thereby enhancing the material’s *** in-depth study of the interaction mechanism at the microscopic level when co-doping Fe and Mn offers valuable insights for the rational design and development of high-performance cathode materials.

关键词： First-principles calculations sodium-ionbatteries Layered oxides NaFe_(3/8)Mn_(5/8)O_(2)

A copula-based approach to accommodate intra-household interaction in workers' daily maintenance activity stop generation modeling

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

journal of Traffic and Transportation Engineering(English Edition) 2022年第1期9卷 59-68页

作者： you-Lian Chu Parsons Transportation Group New YorkNY 10005USA

A new stop frequency model was developed to predict the daily number of maintenance activity stops made by individual household heads during a typical weekday. This new model was based on the modification of a conventional multivariate ordered probit(MOP) model by maintaining the probit assumption for the marginal distributions while introducing nonnormal dependence among the error terms using copula functions. Therefore, the copulabased MOP model would relieve the restriction of imposing joint normality on the error terms in the conventional MOP model. The new MOP model would not only account for the intrahousehold interactions in stop-making decisions, but also allow the best functional form to be determined for representing dependencies among household heads. Using the New York Metropolitan Transportation Council’s 2010/2011 regional household travel survey data, the copula-based MOP model was employed to examine stop-making behavior for individual household heads residing in New York City and its adjacent counties in Mid-Hudson Valley and New jersey. Empirical results provided useful insights into the observed effects of sociodemographics, land use density, transportation service, and work schedule together with potential unobserved common effects on the inter-relatedness of spousal stop-making decisions at the household level. The results show that the MOP model with a Clayton copula structure provides the best data fits and there is a very strong positive dependence among error terms of stop-making equations. Furthermore, the dependence among the maintenance activity propensities of household heads is asymmetric, with a stronger tendency of household heads to simultaneously have low maintenance activity levels than to simultaneously have high maintenance activity levels.

关键词： stop-making propensity Maintenance activity episodes Multivariate ordered probit model Copula-based approach Intra-household interaction

Characterization of geological uncertainties from limited boreholes using copula-based coupled Markov chains for underground construction

在线全文

学校读者我要写书评

暂无评论

Underground space 2024年第3期16卷 94-105页

作者： Fan Wang Heng Li Gang Li Zheng-jun you Elton j.Chen National Center of Technology Innovation for Digital Construction Huazhong University of Science and TechnologyWuhan 430074China Department of Civil and Hydraulic Engineering Huazhong University of Science and TechnologyWuhan 430074China Department of Building and Real Estate The Hong Kong Polytechnic UniversityKowloon 999077Hong KongChina shanghai Tunnel Engineering Co. Ltd.Shanghai 200032China Wuhan Metro Group Co.Ltd. Wuhan 430070China

This paper proposes an efficient method for quantifying the stratigraphic uncertainties and modeling the geological formations based on *** Markov chains are used to describe the soil transitions along different directions,and the transition probability matrices(TPMs)of the Markov chains are analytically expressed by *** copula expression is efficient since it can represent a large TPM by a few unknown *** to the analytical expression of the TPMs,the likelihood function of the Markov chain model is given in an explicit *** estimation of the TPMs is then re-casted as a multi-objective constrained optimization problem that aims to maximize the likelihoods of two independent Markov chains subject to a set of parameter *** the method which determines the TPMs by counting the number of transitions between soil types,the proposed method is more statistically ***,a random path sampling method is presented to avoid the directional effect problem in *** soil type at a location is inferred from its nearest known neighbors along the cardinal directions.A general form of the conditional probability,based on Pickard’s theorem and Bayes rule,is presented for the soil type *** proposed stratigraphic characterization and simulation method is applied to real borehole data collected from a construction site in Wuhan,*** is illustrated that the proposed method is accurate in prediction and does not show an inclination during simulation.

关键词： Geological stratigraphy Markov chain Transition probability matrix statistical method Copula

A mild, configurable, flexible CoNi-LDH（v）/Zn battery based on H-vacancy-induced reversible Zn2+ intercalation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

journal of Energy Chemistry 2025年第1期100卷 498-508页

作者： Xinyue Cheng Dingsheng Wu Hao Gao Qingqing Wang Pengfei Lv sam s.Yoon Qufu Wei Key Laboratory of Eco-textiles Ministry of Education Jiangnan University school of Mechanical Engineering Korea University

Flexible Zn-based batteries have attracted increasing research interest as essential components of wearable energy storage ***,the advancement of flexible aqueous Zn-based batteries based on Co-Ni layered double hydroxide （CoNi-LDH） as the cathode material is hampered by their poor cycling stability and the corrosiveness of alkaline ***,CoNi-LDH nanosheets enriched with H vacancies (CoNi-LDH（v）) were constructed on a flexible carbon cloth （CC） substrate via electrochemical deposition and *** Zn-based battery comprising CoNi-LDH（v）@CC as the cathode exhibited highly reversible conversion reactions and stable operation in 3 M ZnsO4electrolyte （pH=4）.The battery delivered an excellent specific capacity (225 mA h g-1,0.26 mA h cm-2),acceptable cycling stability（53.9%,900 cycles）,and high discharging *** abundant H vacancies served as active sites for the reversible intercalation of Zn2+and the extravasation of NO3-generated channels and space for Zn2+transport and storage,together enabling an excellent Zn2+storage ***,a sandwich-structured solid-state CoNi-LDH（v）@CC//Zn@CC battery was fabricated and was found to exhibit a noteworthy electrochemical performance and mechanical *** a proof of concept,the unencapsulated battery powered a digital watch under various deformation conditions and operated stably for 80 ***,the flexible battery displayed outstanding customizability,maintaining an open-circuit voltage of 1.42 V even after being cut *** proposed engineering strategy contributes to the realization of textiles with truly wearable energy-storage devices.

关键词： CoNi/Zn battery H vacancies Mild aqueous electrolyte Tailorable battery Wearable energy storage device

THERMAL sTRUCTURAL DIsORDER AND MELTING TRANsITION IN HIGH-ANGLE GRAIN-BOUNDARY: A MOLECULAR-DYNAMICs sTUDY

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica sinica(English Letters) 1998年第5期11卷 365-375页

作者： s.j.Zhao Y.C.Wang j.Q.you Q.B.Yang L.G.Zhou H.Q.Ye Xiangtan Univ Xiangtan China

A structural transition in the fcc ∑=5 (120)/[001] high-angle tilt grain-boundary(GB)is investigated by molecular-dynamics simulation. The calculations have been performed at various temperutures and the thermodynamic melting point Tm of the model system is determined by using a many-body potential fitted to copper. A thermal disorder transition in the GB region occurs well below the melting point. Our results indicate that such a transition is a continuous process and there is no evidence of premelting, which is entirely in accord with experiment results and theoretical *** we also observed that melting initiated at the interface and then propagated into the bulk quickly at or above Tm.

关键词： moleculandynamics grainboundary structural transition

THE sECOND-ORDER HYDROELAsTIC ANALYsIs OF A sWATH sHIP MOVING IN LARGE-AMPLITUDE WAVEs

在线全文

学校读者我要写书评

暂无评论

journal of Hydrodynamics 2006年第6期18卷 631-639页

作者： TIAN Chao WU you-sheng school of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai 200030China China ship scientific Research Center Wuxi 214082 China

Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear hydrodynamic actions induced by the rigid body rotations and the variations of instantaneous wetted surface area were included in the second order analysis. The first order wave potentials and responses, which are sure to make the major contributions to the second order hydrodynamic actions, were obtained by employing the translating and pulsating source Green function and the Kelvin steady wave flow solution based on the linear three-dimensional hydroelasticity theory. The influences of the forward speed and the steady wave flow on the responses, and the differences of the predicted non-linear responses were illustrated by the numerical examples of a sWATH ship traveling with forward speed of 12 kn in irregular waves.

关键词： hydroelaticity, non-linear responses, second order forces, translating and pulsating source, sWATH (small Waterplane Area Twin Hull) ship