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New algorithms for virtual reconstruction of heterogeneous microstructures

COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2018年 338卷 275-298页

作者： Yang, Ming Nagarajan, Anand Liang, Bowen Soghrati, Soheil Ohio State Univ Dept Mech & Aerosp Engn Columbus OH 43210 USA Ohio State Univ Dept Mat Sci & Engn 116 W 19Th Ave Columbus OH 43210 USA

A new set of algorithms is introduced for the virtual reconstruction of heterogeneous material microstructures, in which morphologies of embedded particles/fibers are explicitly represented. As a pre-processing phase, a shape library containing morphologies of heterogeneities, parameterized in terms of Non-Uniform Rational B-Splines (NURBS), is extracted from digital data such as micro-computed tomography images. Two packing algorithms are then introduced to reconstruct an initial (raw) periodic microstructure: In the first approach, a set of hierarchical bounding boxes approximating particle shapes are employed to check for overlap. The second approach, which is specialized for fibrous microstructures, uses the NURBS representation of fiber centerlines during the packing process. An optimization phase is applied to build the final microstructural model, relying either on the Genetic algorithm to selectively eliminate some of the inclusions or their sequential relocation within the raw microstructure. The objective functions of this optimization phase are designed to replicate the target statistical microstructural descriptors such as the volume fraction, size distribution, and spatial arrangement of inclusions. Several example problems are presented to show the application of these algorithms for synthesizing various heterogeneous microstructures, as well as their finite element modeling and simulation. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Microstructure reconstruction NURBS Heterogeneous material packing algorithm Mesh generation CISAMR

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A novel geometric embedding algorithm for efficiently generating dense polymer structures

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JOURNAL OF CHEMICAL PHYSICS 2001年第22期114卷 9764-9771页

作者： Müller, M Nievergelt, J Santos, S Suter, UW Swiss Fed Inst Technol Inst Theoret Comp Sci Dept Comp Sci Zurich Switzerland Swiss Fed Inst Technol Inst Polymers Dept Mat Zurich Switzerland

A new algorithm for generating starting polymer structures for molecular simulations (e.g., MD) in dense phase is presented. The algorithm yields structures that fulfill to a large extent rotational isomeric state (RIS) probabilities and avoid atomic overlap. The heuristic search bases on the new parallel-rotation (ParRot) technique. We tested the performance of the algorithm on two polymeric systems: Atomistic polyethylene and polystyrene. The algorithm permits to tackle the problem of packing chains into large boxes of size up to 50 Angstrom in a couple of hours on common workstations. Moreover, our packing algorithm is applicable for general polymer systems. The algorithm requires CPU effort scaling with a power 2.8 in the chain length, and with a power 1.5 in the number of chains. (C) 2001 American Institute of Physics.

关键词： .Technische Hochschule polyethylene macromolecules generating dense rotational isomeric state RIS probabilities ParRot polystyrene packing algorithm polymer systems number of chains

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A Software Framework for Simulating Stationkeeping of a Vessel in Discontinuous Ice

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MODELING IDENTIFICATION AND CONTROL 2014年第4期35卷 211-248页

作者： Metrikin, Ivan NTNU Dept Civil & Transport Engn N-7491 Trondheim Norway Statoil ASA Artic Design & Operat N-7053 Trondheim Norway

This paper describes a numerical package for simulating stationkeeping operations of an offshore vessel in floating sea ice. The software has found broad usage in both academic and industrial projects related to design and operations of floating structures in the Arctic. Interactions with both intact and broken ice conditions can be simulated by the numerical tool, but the main emphasis is placed on modelling managed ice environments relevant for prospective petroleum industry operations in the Arctic. The paper gives a thorough description of the numerical tool from both theoretical and software implementation perspectives. Structural meshing, ice field generation, multibody modelling and ice breaking aspects of the model are presented and discussed. Finally, the main assumptions and limitations of the computational techniques are elucidated and further work directions are suggested.

关键词： global ice loads numerical simulation physics engine computational geometry packing algorithm

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Modified algorithm for generating high volume fraction sphere packings

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COMPUTATIONAL PARTICLE MECHANICS 2015年第2期2卷 161-172页

作者： Rosello Valera, Roberto Perez Morales, Irvin Vanmaercke, Simon Recarey Morfa, Carlos Arguelles Cortes, Lucia Diaz-Guzman Casanas, Harold Univ Cent Marta Abreu Las Villas UCLV UCLV CIMNE Classroom Ctr Res Computat & Numer Methods Engn CIMCNI Carretera Camajuani Km 5 1-2 Santa Clara 54830 Villa Clara Cuba Katholieke Univ Leuven Div Mechatron Biostat & Sensors MeBioS B-3001 Leuven Belgium Univ Cent Marta Abreu Las Villas UCLV Fac Math Phys & Comp Sci Santa Clara 54830 Villa Clara Cuba

Advancing front packing algorithms have proven to be very efficient in 2D for obtaining high density sets of particles, especially disks. However, the extension of these algorithms to 3D is not a trivial task. In the present paper, an advancing front algorithm for obtaining highly dense sphere packings is presented. It is simpler than other advancing front packing methods in 3D and can also be used with other types of particles. Comparison with respect to other packing methods have been carried out and a significant improvement in the volume fraction (VF) has been observed. Moreover, the quality of packings was evaluated with indicators other than VF. As additional advantage, the number of generated particles with the algorithm is linear with respect to time.

关键词： packing algorithm Volume fraction Discrete Element Method packing quality analysis

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Empirical quantitative characterization of holographic phase images of normal and abnormal cervical cells by fractal descriptors

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COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING-IMAGING AND VISUALIZATION 2018年第4期6卷 386-395页

作者： Mihailescu, Mona Scarlat, Eugen I. Paun, Irina Alexandra Grigorescu, Irina Radu, Roxana Nedelcu, Oana Tatiana Univ Politehn Bucuresti Appl Sci Phys Dept Bucharest Romania Univ Politehn Bucuresti Comp Sci & Informat Technol Dept Bucharest Romania LOTUS Hosp SRL Ploiesti Romania Natl Inst Res & Dev Microtechnol Bucharest Romania

The paper proposes a way to examine whether cervical cells qualify as normal or abnormal on the basis of phase profiles,and to subsequently perform local fractal descriptions of their three dimensional holographic images. The method is an alternative tool to discriminate among normal and abnormal cervical cells by exploiting the whole image of the cell not only limited zones like random cross sections. The empirical findings indicate correlation between cross sectional phase profile and fractal characterisation. The results are useful for developing cell counting algorithms based on Bayesian programming.

关键词： Digital holographic microscopy fractal descriptors cell discrimination packing algorithm cervical cells quantitative phase imaging

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Validation of Pore-Scale Simulations of Hydrodynamic Dispersion in Random Sphere packings

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Communications in Computational Physics 2013年第3期13卷 801-822页

作者： Siarhei Khirevich Alexandra Holtzel Ulrich Tallarek Department of Chemistry Philipps-Universitat MarburgHans-Meerwein-Strasse35032 MarburgGermany

We employ the lattice Boltzmann method and random walk particle tracking to simulate the time evolution of hydrodynamic dispersion in bulk,random,monodisperse,hard-sphere packings with bed porosities(interparticle void volume fractions)between the random-close and the random-loose packing *** JodreyTory and Monte Carlo-based algorithms and a systematic variation of the packing protocols we generate a portfolio of packings,whose microstructures differ in their degree of heterogeneity(DoH).Because the DoH quantifies the heterogeneity of the void space distribution in a packing,the asymptotic longitudinal dispersion coefficient calculated for the packings increases with the packings’*** investigate the influence of packing length(up to 150 d_(p),where d_(p) is the sphere diameter)and grid resolution(up to 90 nodes per d_(p))on the simulated hydrodynamic dispersion coefficient,and demonstrate that the chosen packing dimensions of 10 d_(p)×10 d_(p)×70 d_(p) and the employed grid resolution of 60 nodes per d_(p) are sufficient to observe asymptotic behavior of the dispersion coefficient and to minimize finite size *** values of the dispersion coefficients calculated for the generated packings are compared with simulated as well as experimental data from the literature and yield good to excellent agreement.

关键词： packing microstructure degree of heterogeneity packing algorithm hydrodynamic dispersion random sphere packings

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Partitioned Scheduling of Multi-Modal Mixed-Criticality Real-Time Systems on Multiprocessor Platforms 20

Partitioned Scheduling of Multi-Modal Mixed-Criticality Real...

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20th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS) as part of the Cyber-Physical Systems Week

作者： de Niz, Dionisio Phan, Linh T. X. Carnegie Mellon Univ SEI Pittsburgh PA 15213 USA Univ Penn Philadelphia PA 19104 USA

ISBN: (纸本)9781479948291

Real-time systems are becoming increasingly complex. A modern car, for example, requires a multitude of control tasks, such as braking, active suspension, and collision avoidance. These tasks not only exhibit different degrees of safety criticality but also change their criticalities as the driving mode changes. For instance, the suspension task is a critical part of the stability of the car at high speed, but it is only a comfort feature at low speed. Therefore, it is crucial to ensure timing guarantees for the system with respect to the tasks' criticalities, not only within each mode but also during mode changes. This paper presents a partitioned multi-processor scheduling scheme for multi-modal mixed-criticality real-time systems. Our scheme consists of a packing algorithm and a scheduling algorithm for each processor that take into account both mode changes and criticalities. The packing algorithm maximizes the schedulable utilization across modes using the sustained criticality of each task, which captures the overall criticality of the task across modes. The scheduling algorithm combines Rate-Monotonic scheduling with a mode transition enforcement mechanism that relies on the transitional zero-slack instants of tasks to control low-criticality tasks during mode changes, so as to preserve the schedulability of high-criticality tasks. We also present an implementation of our scheduler in the Linux operating system, as well as an experimental evaluation to illustrate its practicality. Our evaluation shows that our scheme can provide close to twice as much tolerance to overloads (ductility) compared to a mode-agnostic scheme.

关键词： Linux multiprocessing systems processor scheduling real-time systems safety-critical software Linux operating system mixed-criticality real-time systems mode transition enforcement mechanism multiprocessor platforms packing algorithm partitioned scheduling rate-monotonic scheduling safety criticality scheduling algorithm transitional zero-slack instant Interference Processor scheduling Real-time systems Road transportation Schedules Scheduling Timing real-time systems Linux scheduling of multiprocessor Multiprocessing systems safety-critical software Road transport Scheduling algorithms Religious Missions

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Traffic Reduction in Computer Networks by Agent Technology

Traffic Reduction in Computer Networks by Agent Technology

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2nd Conference on Human System Interactions

作者： Bartczak, T. Paszczynski, S. Korniak, J. Univ Informat Technol & Management Dept Distributed Syst Rzeszow Poland Univ Informat Technol & Management Rzeszow Autonomous Dept Elect & Telecommun Rzeszow Poland

ISBN: (纸本)9781424439591

The rapid growth of band requirements for data transmission in computer networks is commonly known. The growth of the network infrastructure in many countries is much slower than expected. Therefore this paper presents some introductory research towards effective and inexpensive algorithmic ways for improving the efficiency of data transmission in all network layers. In this research human behavior is also taken into account.

关键词： transmission efficiency packing algorithm data compression agent technology

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A Resource-Efficient FFT/IFFT Architecture for PRIME PLC Systems 13

A Resource-Efficient FFT/IFFT Architecture for PRIME PLC Sys...

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13th IEEE International Conference on Design and Technology of Integrated Systems In Nanoscale Era (DTIS)

作者： Yang, Jing Tan, Nianxiong Tzou, Ching-Kae Harris Zhejiang Univ Coll Informat Sci & Elect Engn Hangzhou Peoples R China Hangzhou Vango Commun Inc Hangzhou Peoples R China

ISBN: (纸本)9781538652916

This paper presents a resource-efficient real-valued fast Fourier transform (RFFT) and Hermitian symmetric inverse fast Fourier transform (HSIFFT) architecture for narrowband power line communication (N-PLC) systems. The proposed architecture has high flexibility and low complexity in control, and can be easily extended to different radices and points. Based on the structure, a novel FFT/IFFT processor is designed for PRIME (PoweRline Intelligent Metering Evolution) N-PLC systems.

关键词： fast Fourier transform (FFT) real-valued signals memory-based architecture narrowband power line communication (N-PLC) packing algorithm

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Optimal Filler Sizes for Thermal Interface Materials 18

Optimal Filler Sizes for Thermal Interface Materials

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18th IEEE InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

作者： Chowdhury, Piyas Sikka, Kamal Grill, Alfred Parekh, Dishit P. IBM Res 257 Fuller Rd Albany NY 12203 USA

ISBN: (纸本)9781728124612

The principal challenge in developing a new thermal interface material (TIM) is to co-design its micro-attributes (e.g. filler type, packing fraction, size distribution) that simultaneously ensure high effective theinial conductivity (k(eff)), low elastic modulus (E-eff) and low viscosity (eta(eff)). Today there exists little physical insight into size distributions of fillers that would optimize desired properties. These thermo-mechanical metrics follow contradicting trends if filler content is only monotonically increased. In this paper, we elucidate microstructure-property correlations vital for optimizing effective properties. First, we systematically vary filler size distributions and generate different particulate structures with a previously developed packing algorithm [1]. Then, we employ mechanistic models, based upon physics of micro scale heat/force transport, to predict k(eff), E-eff and eta(eff) of the particulate structure, thereby identifying filler size domains that optimize the desired properties.

关键词： packing algorithm Thermal Conductivity Elastic Modulus Viscosity Filler Size Distributions

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