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A “Sequential Design of Simulations” approach for exploiting and calibrating discrete element simulations

《化学科学与工程前沿(英文)》 2022年 第16卷 第6期   页码 874-885 doi: 10.1007/s11705-021-2131-1

摘要: The flow behaviours of cohesive particles in the ring shear test were simulated and examined using discrete element method guided by a design of experiments methodology. A full factorial design was used as a screening design to reveal the effects of material properties of partcles. An augmented design extending the screening design to a response surface design was constructed to establish the relations between macroscopic shear stresses and particle properties. It is found that the powder flow in the shear cell can be classified into four regimes. Shear stress is found to be sensitive to particle friction coefficient, surface energy and Young’s modulus. A considerable fluctuation of shear stress is observed in high friction and low cohesion regime. In high cohesion regime, Young’s modulus appears to have a more significant effect on the shear stress at the point of incipient flow than the shear stress during the pre-shear process. The predictions from response surface designs were validated and compared with shear stresses measured from the Schulze ring shear test. It is found that simulations and experiments showed excellent agreement under a variety of consolidation conditions, which verifies the advantages and feasibility of using the proposed “Sequential Design of Simulations” approach.

关键词: discrete element method     cohesive materials     parameter calibration     ring shear cell     design of experiments    

Mean wind load induced incompatibility in nonlinear aeroelastic simulations of bridge spans

Zhitian ZHANG

《结构与土木工程前沿(英文)》 2019年 第13卷 第3期   页码 605-617 doi: 10.1007/s11709-018-0499-x

摘要: Mean wind response induced incompatibility and nonlinearity in bridge aerodynamics is discussed, where the mean wind and aeroelastic loads are applied simultaneously in time domain. A kind of incompatibility is found during the simultaneous simulation of the mean wind and aeroelastic loads, which leads to incorrect mean wind structural responses. It is found that the mathematic expectations (or limiting characteristics) of the aeroelastic models are fundamental to this kind of incompatibility. In this paper, two aeroelastic models are presented and discussed, one of indicial-function-denoted (IF-denoted) and another of rational-function-denoted (RF-denoted). It is shown that, in cases of low wind speeds, the IF-denoted model reflects correctly the mean wind load properties, and results in correct mean structural responses; in contrast, the RF-denoted model leads to incorrect mean responses due to its nonphysical mean properties. At very high wind speeds, however, even the IF-denoted model can lead to significant deviation from the correct response due to steady aerodynamic nonlinearity. To solve the incompatibility at high wind speeds, a methodology of subtraction of pseudo-steady effects from the aeroelastic model is put forward in this work. Finally, with the method presented, aeroelastic nonlinearity resulted from the mean wind response is investigated at both moderate and high wind speeds.

关键词: bridge     aerodynamics     nonlinear     aeroelastic model     Pseudo-steady     mean wind loads    

Molecular level simulations on multi-component systems —a morphology prediction method

C. SCHMIDT, J. ULRICH

《化学科学与工程前沿(英文)》 2013年 第7卷 第1期   页码 49-54 doi: 10.1007/s11705-013-1307-8

摘要: The crystal morphology grown from a solution composed of an organic solvent, solute and additive can be predicted reliably by a computational method. Modeling the supersaturated solution as liquid phase is achieved by employing commercial software. The molecular composition of this solution is a required input parameter. The face specific diffusion coefficient of the solid (crystal surface) and liquid (solution) system is determined using the molecular dynamics procedure. The obtained diffusion coefficient is related to the specific face growth rate via the attachment energy of the pure morphology. The significant improvements are achieved in the morphology prediction because the investigation on the face growth rates in a complex growth environment (as multi-component solutions with additives) can be carried out based on the diffusion coefficients.

关键词: crystallization     morphology     molecular dynamics     solution    

machine learning models to explore the solution space of large nonlinear systems underlying flowsheet simulations

《化学科学与工程前沿(英文)》 2022年 第16卷 第2期   页码 183-197 doi: 10.1007/s11705-021-2073-7

摘要: Flowsheet simulations of chemical processes on an industrial scale require the solution of large systems of nonlinear equations, so that solvability becomes a practical issue. Additional constraints from technical, economic, environmental, and safety considerations may further limit the feasible solution space beyond the convergence requirement. A priori, the design variable domains for which a simulation converges and fulfills the imposed constraints are usually unknown and it can become very time-consuming to distinguish feasible from infeasible design variable choices by simply running the simulation for each choice. To support the exploration of the design variable space for such scenarios, an adaptive sampling technique based on machine learning models has recently been proposed. However, that approach only considers the exploration of the convergent domain and ignores additional constraints. In this paper, we present an improvement which particularly takes the fulfillment of constraints into account. We successfully apply the proposed algorithm to a toy example in up to 20 dimensions and to an industrially relevant flowsheet simulation.

关键词: machine learning     flowsheet simulations     constraints     exploration    

Kinetic Monte Carlo simulations of plasma-surface reactions on heterogeneous surfaces

Daniil Marinov

《化学科学与工程前沿(英文)》 2019年 第13卷 第4期   页码 815-822 doi: 10.1007/s11705-019-1837-9

摘要: Reactions of atoms and molecules on chamber walls in contact with low temperature plasmas are important in various technological applications. Plasma-surface interactions are complex and relatively poorly understood. Experiments performed over the last decade by several groups prove that interactions of reactive species with relevant plasma-facing materials are characterized by distributions of adsorption energy and reactivity. In this paper, we develop a kinetic Monte Carlo (KMC) model that can effectively handle chemical kinetics on such heterogenous surfaces. Using this model, we analyse published adsorption-desorption kinetics of chlorine molecules and recombination of oxygen atoms on rotating substrates as a test case for the KMC model.

关键词: plasma-surface interaction     kinetic Monte Carlo     plasma nano technology    

Atomistic simulations of plasma catalytic processes

Erik C. Neyts

《化学科学与工程前沿(英文)》 2018年 第12卷 第1期   页码 145-154 doi: 10.1007/s11705-017-1674-7

摘要: There is currently a growing interest in the realisation and optimization of hybrid plasma/catalyst systems for a multitude of applications, ranging from nanotechnology to environmental chemistry. In spite of this interest, there is, however, a lack in fundamental understanding of the underlying processes in such systems. While a lot of experimental research is already being carried out to gain this understanding, only recently the first simulations have appeared in the literature. In this contribution, an overview is presented on atomic scale simulations of plasma catalytic processes as carried out in our group. In particular, this contribution focusses on plasma-assisted catalyzed carbon nanostructure growth, and plasma catalysis for greenhouse gas conversion. Attention is paid to what can routinely be done, and where challenges persist.

关键词: atomic scale simulation     plasma-catalyst    

Latest progress in numerical simulations on multiphase flow and thermodynamics in production of natural

Lin ZUO, Lixia SUN, Changfu YOU

《能源前沿(英文)》 2009年 第3卷 第2期   页码 152-159 doi: 10.1007/s11708-009-0017-x

摘要: Natural gas hydrates are promising potential alternative energy resources. Some studies on the multiphase flow and thermodynamics have been conducted to investigate the feasibility of gas production from hydrate dissociation. The methods for natural gas production are analyzed and several models describing the dissociation process are listed and compared. Two prevailing models, one for depressurization and the other for thermal stimulation, are discussed in detail. A comprehensive numerical method considering the multiphase flow and thermodynamics of gas production from various hydrate-bearing reservoirs is required to better understand the dissociation process of natural gas hydrate, which would be of great benefit to its future exploration and exploitation.

关键词: numerical simulation     natural gas hydrate     dissociation     thermodynamics     multiphase flow    

Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

《机械工程前沿(英文)》 2007年 第2卷 第4期   页码 399-403 doi: 10.1007/s11465-007-0069-8

摘要: Fracture is a common defect in sheet metal forming and it is essentially caused by tensile instability. This paper analyzes some experiments and theories for building forming limit diagrams of sheet metal and points out the advantages and disadvantages of current experiments and theories. According to this, a method that integrates the finite element simulation and experiment was used to research the forming limit diagrams of the sheet metal under complex strain paths. Taking the rear hanger that undergoes twice stamping as an example, the strain paths of the dangerous point of the rear hanger is investigated. Finally, the forming method of the rear hanger is confirmed. Results indicate that finite element method (FEM) can achieve the complex strain paths and different strain paths will have great impacts on the result of the sheet metal forming.

关键词: dangerous     forming method     different     hanger     forming    

Improving simulations of sulfate aerosols during winter haze over Northern China: the impacts of heterogeneous

Meng Gao,Gregory R. Carmichael,Yuesi Wang,Dongsheng Ji,Zirui Liu,Zifa Wang

《环境科学与工程前沿(英文)》 2016年 第10卷 第5期 doi: 10.1007/s11783-016-0878-2

摘要: Incorporating the missing heterogeneous oxidation of S(IV) by NO into the WRF-Chem model. Sulfate production is not sensitive to increase in SO emission. The newly added reaction reproduces sulfate concentrations well during winter haze. We implemented the online coupled WRF-Chem model to reproduce the 2013 January haze event in North China, and evaluated simulated meteorological and chemical fields using multiple observations. The comparisons suggest that temperature and relative humidity (RH) were simulated well (mean biases are -0.2K and 2.7%, respectively), but wind speeds were overestimated (mean bias is 0.5 m?s ). At the Beijing station, sulfur dioxide (SO ) concentrations were overpredicted and sulfate concentrations were largely underpredicted, which may result from uncertainties in SO emissions and missing heterogeneous oxidation in current model. We conducted three parallel experiments to examine the impacts of doubling SO emissions and incorporating heterogeneous oxidation of dissolved SO by nitrogen dioxide (NO ) on sulfate formation during winter haze. The results suggest that doubling SO emissions do not significantly affect sulfate concentrations, but adding heterogeneous oxidation of dissolved SO by NO substantially improve simulations of sulfate and other inorganic aerosols. Although the enhanced SO to sulfate conversion in the HetS (heterogeneous oxidation by NO ) case reduces SO concentrations, it is still largely overestimated by the model, indicating the overestimations of SO concentrations in the North China Plain (NCP) are mostly due to errors in SO emission inventory.

关键词: Sulfate aerosols     Winter haze     WRF-Chem     Northern China    

Burnett simulations of gas flow and heat transfer in microchannels

Fubing BAO, Jianzhong LIN

《机械工程前沿(英文)》 2009年 第4卷 第3期   页码 252-263 doi: 10.1007/s11465-009-0037-6

摘要: In micro- and nanoscale gas flows, the flow falls into the transition flow regime. There are not enough molecule collisions and the gas deviates from the equilibrium. The Navier-Stokes equations fail to describe the gas flow in this regime. The direct simulation Monte Carlo method converges slowly and requires lots of computational time. As a result, the high-order Burnett equations are used to study the gas flow and heat transfer characteristics in micro- and nanoscale gas flows in this paper. The Burnett equations are first reviewed, and the augmented Burnett equations with high-order slip boundary conditions are then used to model the gas flow and heat transfer in Couette and Poiseuille flows in the transition regime.

关键词: micro- and nanoscale gas flow     slip-transition flow regime     Burnett equations     numerical simulation    

A metadata model for collaborative experiments and simulations in earthquake engineering

Jean-Pierre BARDET, Nazila MOKARRAM, Fang LIU

《结构与土木工程前沿(英文)》 2010年 第4卷 第2期   页码 133-153 doi: 10.1007/s11709-010-0036-z

摘要: Research projects in earthquake engineering yield a very large amount of complex data from experiments and computer simulations. Understanding and exchanging these complicated and voluminous data sets prompted the development of metadata models that document the processes of data generation, and facilitate the collaboration and exchange of information between researchers. The present metadata model was designed to document and exchange a large number of large data files in earthquake engineering, but is applicable to other fields of engineering and science. The model was conceived based on a series of former data models, which were unduly complicated and limited to few types of experiments. Simpler than its predecessors, the present metadata model applies to all kinds of earthquake engineering experiments. It was developed in the object-oriented framework using Protégé. Its applications are illustrated with examples from centrifuge experiments.

关键词: metadata     data     documentation     experiment     simulation    

Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

Himanshu PATHAK,Akhilendra SINGH,I.V. SINGH,S. K. YADAV

《结构与土木工程前沿(英文)》 2015年 第9卷 第4期   页码 359-382 doi: 10.1007/s11709-015-0304-z

摘要: This paper deals with the fatigue crack growth simulations of three-dimensional linear elastic cracks by XFEM under cyclic thermal load. Both temperature and displacement approximations are extrinsically enriched by Heaviside and crack front enrichment functions. Crack growth is modelled by successive linear extensions, and the end points of these linear extensions are joined by cubic spline segments to obtain a modified crack front. Different crack geometries such as planer, non-planer and arbitrary spline shape cracks are simulated under thermal shock, adiabatic and isothermal loads to reveal the sturdiness and versatility of the XFEM approach.

关键词: 3-D cracks     fatigue life     Paris law     thermal load     XFEM    

Effect of ambient polycyclic aromatic hydrocarbons and nicotine on the structure of Aβ protein

《环境科学与工程前沿(英文)》 2023年 第17卷 第2期 doi: 10.1007/s11783-023-1615-2

摘要:

● B[a]P, nicotine and phenanthrene molecules altered the secondary structure of Aβ42.

关键词: Polycyclic aromatic hydrocarbons     Nicotine     toxicology     42 peptide     Alzheimer’s disease     Molecular dynamics simulations     Environmental pollution    

Molecular dynamics simulations of initial Pd and PdO nanocluster growth in a magnetron gas aggregation

Pascal Brault, William Chamorro-Coral, Sotheara Chuon, Amaël Caillard, Jean-Marc Bauchire, Stève Baranton, Christophe Coutanceau, Erik Neyts

《化学科学与工程前沿(英文)》 2019年 第13卷 第2期   页码 324-329 doi: 10.1007/s11705-019-1792-5

摘要: Molecular dynamics simulations are carried out for describing growth of Pd and PdO nanoclusters using the ReaxFF force field. The resulting nanocluster structures are successfully compared to those of nanoclusters experimentally grown in a gas aggregation source. The PdO structure is quasi-crystalline as revealed by high resolution transmission microscope analysis for experimental PdO nanoclusters. The role of the nanocluster temperature in the molecular dynamics simulated growth is highlighted.

关键词: molecular dynamics     cluster growth     plasma sputtering     nanocatalyst    

Numerical simulations of morphological changes in barrier islands induced by storm surges and waves using

Soumendra Nath KUIRY, Yan DING, Sam S Y WANG

《结构与土木工程前沿(英文)》 2014年 第8卷 第1期   页码 57-68 doi: 10.1007/s11709-014-0235-0

摘要: In this paper, an advanced explicit finite volume flow model in two-dimensions is presented for simulating supercritical coastal flows and morphological changes in a tidal/coastal inlet and barrier islands due to storm surges and waves. This flow model is coupled with existing wave-action model and sediment transport model. The resulting integrated coastal process model is capable of simulating flows induced by extreme conditions such as waves, surge tides, river flood flows, etc., and morphological changes induced by rapid coastal currents and waves. This developed supercritical flow model is based on the solution of the conservative form of the nonlinear shallow water equations with the effects of the Coriolis force, uneven bathymetry, wind stress, and wave radiation stresses. The forward Euler scheme is used for the unsteady term; and the convective term is discretized using the Godunov-type shock-capturing scheme along with the HLL Riemann solver on non-uniform rectilinear grids. The accuracy of the developed model is investigated by solving an experimental dam-break test case. Barrier island breaching, overflow and overwash due to severe storm attack are simulated and the predicted morphological changes associated to the events are analyzed to investigate the applicability of the model in a coast where all the physical forces are present.

关键词: coastal inlet     coastal process modeling     supercritical flow     sediment transport     barrier islands    

标题 作者 时间 类型 操作

A “Sequential Design of Simulations” approach for exploiting and calibrating discrete element simulations

期刊论文

Mean wind load induced incompatibility in nonlinear aeroelastic simulations of bridge spans

Zhitian ZHANG

期刊论文

Molecular level simulations on multi-component systems —a morphology prediction method

C. SCHMIDT, J. ULRICH

期刊论文

machine learning models to explore the solution space of large nonlinear systems underlying flowsheet simulations

期刊论文

Kinetic Monte Carlo simulations of plasma-surface reactions on heterogeneous surfaces

Daniil Marinov

期刊论文

Atomistic simulations of plasma catalytic processes

Erik C. Neyts

期刊论文

Latest progress in numerical simulations on multiphase flow and thermodynamics in production of natural

Lin ZUO, Lixia SUN, Changfu YOU

期刊论文

Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

期刊论文

Improving simulations of sulfate aerosols during winter haze over Northern China: the impacts of heterogeneous

Meng Gao,Gregory R. Carmichael,Yuesi Wang,Dongsheng Ji,Zirui Liu,Zifa Wang

期刊论文

Burnett simulations of gas flow and heat transfer in microchannels

Fubing BAO, Jianzhong LIN

期刊论文

A metadata model for collaborative experiments and simulations in earthquake engineering

Jean-Pierre BARDET, Nazila MOKARRAM, Fang LIU

期刊论文

Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

Himanshu PATHAK,Akhilendra SINGH,I.V. SINGH,S. K. YADAV

期刊论文

Effect of ambient polycyclic aromatic hydrocarbons and nicotine on the structure of Aβ protein

期刊论文

Molecular dynamics simulations of initial Pd and PdO nanocluster growth in a magnetron gas aggregation

Pascal Brault, William Chamorro-Coral, Sotheara Chuon, Amaël Caillard, Jean-Marc Bauchire, Stève Baranton, Christophe Coutanceau, Erik Neyts

期刊论文

Numerical simulations of morphological changes in barrier islands induced by storm surges and waves using

Soumendra Nath KUIRY, Yan DING, Sam S Y WANG

期刊论文