scholarly journals Visualization of Large-scale Atomic Interactions During the Melting and Crystallization Process

VLSI Design ◽  
2001 ◽  
Vol 13 (1-4) ◽  
pp. 269-271
Author(s):  
Roman Durikovic
Keyword(s):  
Large Scale ◽  
Defect Formation ◽  
Equations Of Motion ◽  
Material Model ◽  
Atomic Scale ◽  
Three Dimensions ◽  
Langevin Equations ◽  
Short Range Repulsion ◽  
Solid Liquid Interface ◽  
Behaviour Simulation

Atomic-scale material model capable of melting, crystallization and amorphization has been developed to examine the defect formation and crystal growth processes from melted silicon (Si) based on the ordinary Langevin equations of motion. The developed computer system consists of simulation and visualization part. Simulation supports the large-scale molecular-dynamics (MD) clusters with solid/liquid interface responding interactively to the control parameters such as the temperature gradient and pulling speed. Material behaviour simulation is limited to 104 particle objects representing different atoms. A particle in proposed dynamic system interacts through attractive covalent forces and short-range repulsion forces in all three dimensions. This research was conducted to understand the processes that can control the quality of single-crystal Si grown from the melt by Czochralski crystal puller.

An Efficient Numerical Method for Dynamic Interaction Analysis of Shinkansen Train and Railway Structure During an Earthquake

2007 ◽  
Author(s):  
M. Tanabe ◽  
N. Matsumoto ◽  
H. Wakui ◽  
M. Sogabe ◽  
H. Okuda ◽  
...  
Keyword(s):  
Numerical Method ◽  
High Speed ◽  
Large Scale ◽  
Interaction Analysis ◽  
Plastic Material ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Material Model ◽  
Dynamic Interaction ◽  
Contact Dynamics

In this paper, a simple and efficient numerical method to solve for the dynamic interaction of a Shinkansen train (high-speed train in Japan) and railway structure during an earthquake is given. The motion of the train is modeled in multibody dynamics with nonlinear springs and dampers used to connect components. An efficient mechanical model for contact dynamics between wheel and rail during an earthquake is presented. The railway structure is modeled with various finite elements. A three-dimensional nonlinear spring element based on a trilinear elastic-plastic material model is given for the concrete railway structure during an earthquake. A loop structure model has been devised to obtain an approximated combined motion of the train and railway structure during an earthquake. A modal method has been developed to solve large-scale nonlinear equations of motion of the train and railway structure effectively. Based on the present method, a computer program DIASTARS for the dynamic interaction of a Shinkansen train and railway structure during an earthquake has been developed. Numerical examples are demonstrated.

scholarly journals Thermal dependence of large-scale freckle defect formation

2019 ◽  
Vol 377 (2143) ◽  
pp. 20180206 ◽  
Author(s):  
A. Kao ◽  
N. Shevchenko ◽  
M. Alexandrakis ◽  
I. Krastins ◽  
S. Eckert ◽  
...  
Keyword(s):  
Large Scale ◽  
Defect Formation ◽  
Solute Concentration ◽  
Convective Transport ◽  
Three Dimensions ◽  
Thermal Dependence ◽  
Bulk Fluid ◽  
Freckle Formation ◽  
Region Flow ◽  
Boltzmann Method

The fundamental mechanisms governing macroscopic freckle defect formation during directional solidification are studied experimentally in a Hele–Shaw cell for a low-melting point Ga-25 wt.% In alloy and modelled numerically in three dimensions using a microscopic parallelized Cellular Automata Lattice Boltzmann Method. The size and distribution of freckles (long solute channels, or chimneys) are shown to be strongly dependent on the thermal profile of the casting, with flat, concave and convex isotherms being considered. For the flat isotherm case, no large-scale freckles form, while for concave or convex isotherms, large freckles appear but in different locations. The freckle formation mechanism is as expected buoyancy-driven, but the chimney stability, its long-term endurance and its location are shown to depend critically on the detailed convective transport through the inter-dendritic region. Flow is generated by curved isopleths of solute concentration. As solute density is different from that of the bulk fluid, gravity causes ‘uphill’ or ‘downhill’ lateral flow from the sample centre to the edges through the mush, feeding the freckle. An excellent agreement is obtained between the numerical model and real-time X-ray observations of a solidifying sample under strictly controlled temperature conditions. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

A Simple and Efficient Numerical Method for Dynamic Interaction Analysis of a High-Speed Train and Railway Structure During an Earthquake

2008 ◽  
Vol 3 (4) ◽  
Author(s):  
M. Tanabe ◽  
N. Matsumoto ◽  
H. Wakui ◽  
M. Sogabe ◽  
H. Okuda ◽  
...  
Keyword(s):  
Numerical Method ◽  
High Speed ◽  
Large Scale ◽  
Interaction Analysis ◽  
Plastic Material ◽  
Equations Of Motion ◽  
Material Model ◽  
Dynamic Interaction ◽  
Contact Dynamics ◽  
High Speed Train

In this paper, a simple and efficient numerical method to solve for the dynamic interaction of a high-speed train and railway structure during an earthquake is given. The motion of the train is modeled in multibody dynamics with nonlinear springs and dampers used to connect components. An efficient mechanical model for contact dynamics between the wheel and rail during an earthquake is presented. The railway structure is modeled with various finite elements. A nonlinear spring element based on a trilinear elastic-plastic material model is given for the concrete railway structure during an earthquake. A substructure model where a train runs repeatedly has been devised to obtain an approximated combined motion of the long train with many cars connected and the railway structure during an earthquake. A modal method has been developed to solve large-scale nonlinear equations of motion of the train and railway structure effectively. Based on the present method, a computer program DIASTARS for the dynamic interaction analysis of a Shinkansen train (high-speed train in Japan) and the railway structure during an earthquake has been developed. Numerical examples are demonstrated.

New Models of Content Creation and Scholarship at the Intersection of Library Spaces, Technologies, and Expertise

2018 ◽  
Author(s):  
Mike Nutt ◽  
Gregory Raschke
Keyword(s):  
Large Scale ◽  
Interactive Media ◽  
Scholarly Communication ◽  
Three Dimensions ◽  
Organizational Capabilities ◽  
High Definition ◽  
Content Creation ◽  
Full Life Cycle ◽  
Digital Scholarship ◽  
Digital Objects

Library spaces that blend collaboration areas, advanced technologies, and librarian expertise are creating new modes of scholarly communication. These spaces enable scholarship created within high-definition, large-scale visual collaborative environments. This emergent model of scholarly communication can be experienced within those specific contexts or through digital surrogates on the networked Web. From experiencing in three dimensions the sermons of John Donne in 1622 to interactive media interpretations of American wars, scholars are partnering with libraries to create immersive digital scholarship. Viewing the library as a research platform for these emergent forms of digital scholarship presents several opportunities and challenges. Opportunities include re-engaging faculty in the use of library space, integrating the full life-cycle of the research enterprise, and engaging broad communities in the changing nature of digitally-driven scholarship. Issues such as identifying and filtering collaborations, strategically managing staff resources, creating surrogates of immersive digital scholarship, and preserving this content for the future present an array of challenges for libraries that require coordination across organizations. From engaging and using high-technology spaces to documenting the data and digital objects created, this developing scholarly communication medium brings to bear the multifaceted skills and organizational capabilities of libraries.

scholarly journals Higher order Hamiltonian Monte Carlo sampling for cosmological large-scale structure analysis

2021 ◽  
Vol 502 (3) ◽  
pp. 3976-3992
Author(s):  
Mónica Hernández-Sánchez ◽  
Francisco-Shu Kitaura ◽  
Metin Ata ◽  
Claudio Dalla Vecchia
Keyword(s):  
Fourth Order ◽  
Large Scale ◽  
Equations Of Motion ◽  
Large Scale Structure ◽  
Real Space ◽  
Higher Order ◽  
Second Order ◽  
Scale Structure ◽  
Integration Schemes ◽  
Reconstruction Methods

ABSTRACT We investigate higher order symplectic integration strategies within Bayesian cosmic density field reconstruction methods. In particular, we study the fourth-order discretization of Hamiltonian equations of motion (EoM). This is achieved by recursively applying the basic second-order leap-frog scheme (considering the single evaluation of the EoM) in a combination of even numbers of forward time integration steps with a single intermediate backward step. This largely reduces the number of evaluations and random gradient computations, as required in the usual second-order case for high-dimensional cases. We restrict this study to the lognormal-Poisson model, applied to a full volume halo catalogue in real space on a cubical mesh of 1250 h−1 Mpc side and 2563 cells. Hence, we neglect selection effects, redshift space distortions, and displacements. We note that those observational and cosmic evolution effects can be accounted for in subsequent Gibbs-sampling steps within the COSMIC BIRTH algorithm. We find that going from the usual second to fourth order in the leap-frog scheme shortens the burn-in phase by a factor of at least ∼30. This implies that 75–90 independent samples are obtained while the fastest second-order method converges. After convergence, the correlation lengths indicate an improvement factor of about 3.0 fewer gradient computations for meshes of 2563 cells. In the considered cosmological scenario, the traditional leap-frog scheme turns out to outperform higher order integration schemes only when considering lower dimensional problems, e.g. meshes with 643 cells. This gain in computational efficiency can help to go towards a full Bayesian analysis of the cosmological large-scale structure for upcoming galaxy surveys.

Challenges Associated with the Characterisation of Nanocrystalline Materials Using Atom Probe Tomography

2010 ◽  
Vol 654-656 ◽  
pp. 2366-2369 ◽  
Author(s):  
Feng Zai Tang ◽  
Talukder Alam ◽  
Michael P. Moody ◽  
Baptiste Gault ◽  
Julie M. Cairney
Keyword(s):  
Quantitative Analysis ◽  
Atom Probe Tomography ◽  
Nanocrystalline Materials ◽  
Atom Probe ◽  
Atomic Scale ◽  
Three Dimensions ◽  
Specimen Preparation ◽  
Compositional Information

Atom probe tomography provides compositional information in three dimensions at the atomic scale, and is therefore extremely suited to the study of nanocrystalline materials. In this paper we present atom probe results from the investigation of nanocomposite TiSi¬Nx coatings and nanocrystalline Al. We address some of the major challenges associated with the study of nanocrystalline materials, including specimen preparation, visualisation, common artefacts in the data and approaches to quantitative analysis. We also discuss the potential for the technique to relate crystallographic information to the compositional maps.

Synthetic reflection seismograms in three dimensions by a locked‐mode approximation

Geophysics ◽  
1989 ◽  
Vol 54 (3) ◽  
pp. 350-358 ◽  
Author(s):  
G. Nolet ◽  
R. Sleeman ◽  
V. Nijhof ◽  
B. L. N. Kennett
Keyword(s):  
Finite Difference ◽  
Born Approximation ◽  
Large Scale ◽  
Layered Medium ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Realistic Model ◽  
Three Dimensions ◽  
Acoustic Response ◽  
Many Sources

We present a simple algorithm for computing the acoustic response of a layered structure containing three‐dimensional (3-D) irregularities, using a locked‐mode approach and the Born approximation. The effects of anelasticity are incorporated by use of Rayleigh’s principle. The method is particularly attractive at somewhat larger offsets, but computations for near‐source offsets are stable as well, due to the introduction of anelastic damping. Calculations can be done on small minicomputers. The algorithm developed in this paper can be used to calculate the response of complicated models in three dimensions. It is more efficient than any other method whenever many sources are involved. The results are useful for modeling, as well as for generating test signals for data processing with realistic, model‐induced “noise.” Also, this approach provides an alternative to 2-D finite‐difference calculations that is efficient enough for application to large‐scale inverse problems. The method is illustrated by application to a simple 3-D structure in a layered medium.

scholarly journals Analysis of Radiation Damage in Light Water Reactors: Comparison of Cluster Analysis Methods for the Analysis of Atom Probe Data

2017 ◽  
Vol 23 (2) ◽  
pp. 366-375 ◽  
Author(s):  
Jonathan M. Hyde ◽  
Gérald DaCosta ◽  
Constantinos Hatzoglou ◽  
Hannah Weekes ◽  
Bertrand Radiguet ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Radiation Damage ◽  
Defect Formation ◽  
Chemical Species ◽  
Atom Probe ◽  
Three Dimensions ◽  
Multiple Sources ◽  
Damage Models ◽  
Combining Data ◽  
Water Reactors

AbstractIrradiation of reactor pressure vessel (RPV) steels causes the formation of nanoscale microstructural features (termed radiation damage), which affect the mechanical properties of the vessel. A key tool for characterizing these nanoscale features is atom probe tomography (APT), due to its high spatial resolution and the ability to identify different chemical species in three dimensions. Microstructural observations using APT can underpin development of a mechanistic understanding of defect formation. However, with atom probe analyses there are currently multiple methods for analyzing the data. This can result in inconsistencies between results obtained from different researchers and unnecessary scatter when combining data from multiple sources. This makes interpretation of results more complex and calibration of radiation damage models challenging. In this work simulations of a range of different microstructures are used to directly compare different cluster analysis algorithms and identify their strengths and weaknesses.

A Rubber Bag for Liquid Cargo to Improve Ship Collision Safety

2016 ◽  
Author(s):  
Jan M. Kubiczek ◽  
Boyuan Liang ◽  
Lars Molter ◽  
Sören Ehlers
Keyword(s):  
Structural Design ◽  
Large Scale ◽  
Material Model ◽  
Tensile Tests ◽  
Additional Increase ◽  
Safety Level ◽  
Oil Leakage ◽  
Collision Safety ◽  
Reaction Forces ◽  
Ship Collision

Collisions and grounding accidents of ships, but also the failure of the hull-integrity, can lead to oil leakage. Examples are the Rena in 2011, the Hebei Spirit in 2007 and the much known accident of the Prestige in 2002. Consequently research regarding the enhancement of the structural design to increase the safety-level of ships in case of accidents is important. In this paper the use of a rubber bag as a second barrier is presented as an alternative concept to prevent oil leakage in case of accidents. The influence of the rubber bag is investigated using the example of a ship collision. A simplified tanker side structure as well as a box shaped rubber bag are analyzed with the finite element method. The material model for the rubber bag is calibrated with tensile tests to obtain the required material parameters. The reaction forces and the associated penetration depth are analyzed. The comparison is done between the structure with and without the rubber bag. For the latter, the general behavior is compared with large-scale experimental results. Furthermore an additional increase of the survivability of the ship due to the rubber bag without changing the common structural design is discussed.

scholarly journals Site-Specific Electrodeposition Enables Self-Terminating Growth of Atomically Dispersed Metal Catalysts

2020 ◽  
Author(s):  
Yi Shi ◽  
Wenmao Huang ◽  
Jian Li ◽  
Yue Zhou ◽  
Zhongqiu Li ◽  
...  
Keyword(s):  
Large Scale ◽  
Transition Metal Dichalcogenides ◽  
Metal Catalysts ◽  
Atomic Scale ◽  
Single Atom ◽  
Scale Production ◽  
Heterogenous Catalysis ◽  
Site Specific ◽  
Metal Support ◽  
Metal Dichalcogenides

<p>The growth of atomically dispersed metal catalysts (ADMCs) remains a great challenge owing to the thermodynamically driven atom aggregation. Here we report a surface-limited electrodeposition technique that uses site-specific substrates for the rapid and room-temperature synthesis of ADMCs. We obtained ADMCs by the underpotential deposition (UPD) of a single-atom nonnoble metal onto the chalcogen atoms of chemically exfoliated transition metal dichalcogenides and subsequent galvanic displacement with a more-noble single-atom metal. The site-specific electrodeposition (SSED) enables the formation of energetically favorable metal–support bonds, and then automatically terminates the sequential formation of metallic bonding. The self-terminating effect restricts the metal deposition to the atomic scale. The modulated ADMCs exhibit remarkable activity and stability in the hydrogen evolution reaction compared to state-of-the-art single-atom electrocatalysts. We demonstrate that this SSED methodology could be extended to the synthesis of a variety of ADMCs (for example, Pt, Pd, Rh, Cu, Pb, Bi, and Sn single atoms), showing its general scope for the large-scale production of functional ADMCs in heterogenous catalysis. </p>

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