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Hybrid approach to 3d porous microstructure reconstruction via Gaussian random field

Hybrid approach to 3d porous microstructure reconstruction v...

ASME 2012 International Design engineering Technical Conferences and Computers and Information in engineering Conference, IDETC/CIE 2012

作者： Jiang, Zhen Chen, Wei Burkhart, Craig Dept. of Mechanical Engineering Northwestern University Evanston IL 60208 United States Global Materials Science Division Goodyear Tire and Rubber Company Akron OH 44305 United States

ISBN: (纸本)9780791845011

Obtaining an accurate three-dimensional (3D) structure of a porous microstructure is important for assessing the material properties based on finite element analysis. While directly obtaining 3D images of the microstructure is impractical under many circumstances, two sets of methods have been developed in the literature to generate (reconstruct) 3D microstructure from its 2D images: one characterizes the microstructure based on certain statistical descriptors, typically two-point correlation function and cluster correlation function, and then performs an optimization process to build a 3D structure that matches those statistical descriptors;the other method models the microstructure using stochastic models like a Gaussian random field (GRF) and generates a 3D structure directly from the function. The former obtains a relatively accurate 3D microstructure, but the optimization process can be very computationally intensive, especially for problems with a large image size;the latter generates a 3D microstructure quickly but sacrifices the accuracy. A hybrid optimization approach of modeling the 3D porous microstructure of random isotropic two-phase materials is proposed in this paper, which combines the two sets of methods and hence maintains the accuracy of the correlation-based method with improved efficiency. The proposed technique is verified for 3D reconstructions based on silica polymer composite images with different volume fractions. A comparison of the reconstructed microstructures and the optimization histories for both the original correlation-based method and our hybrid approach demonstrates the improved efficiency of the approach. Copyright © 2012 by ASME.

关键词： Microstructure

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Swarm formations under nonholonomic and numerosity constraints

ASME 2012 5th Annual Dynamic Systems and Control Conference ...

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ASME 2012 5th Annual Dynamic Systems and Control Conference Joint with the JSME 2012 11th Motion and Vibration Conference, DSCC 2012-MOVIC 2012 2012年 1卷 475-481页

作者： Fricke, Gregory K. Lieberman, Kevin M. Garg, Devendra P. Dept. of Mechanical Engineering and Materials Science Duke University Durham NC 27708 United States

ISBN: (纸本)9780791845295

In this paper, we propose a fully distributed, scalable method of controlling agents with nonholonomic constraints using a Morse potential function. This method successfully controls a swarm of differential-drive (unicycle-type) agents to stable and predictable formations whose structures are not defined a priori. The system achieves a stable, minimal energy state. We consider the effect of numerosity constraints, as observed in birds and fish in their shoaling and flocking behavior as a mechanism of reducing complexity, in the interest of achieving fully distributed control over a swarm of any size. The application of numerosity constraints to a swarm system allows the swarm to grow without bound and with no increase in required processing capability of the individual agents. We explore this parameter as a method of minimizing processing and storage requirements while still achieving the qualitative swarm performance. Results from simulations are given for swarms ranging in size over N=f6,. . . ,100g acting under our proposed controller as applied to differential-drive (unicycle-type) robots. Copyright © 2012 by ASME.

关键词： Morse potential

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Analysis of the notch effect in fatigue

Analysis of the notch effect in fatigue

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38th National Symposium on Fatigue and Fracture Mechanics

作者： Yanase, K. Endo, M. Dept. of Mechanical Engineering Fukuoka Univ. Institute of Materials Science and Technology Fukuoka Univ. 8-19-1 Nanakuma Jonan-ku Fukuoka City Fukuoka 814-0180 Japan

ISBN: (纸本)9780803175327

The fatigue-crack propagation at stress concentrations is a topic of significant importance in a number of engineering applications. Further, it is recognized that the fatigue limit of notched components is dictated by the critical condition for either initiation or propagation of a small crack at the root of a notch. Moreover, because most fatigue cracks spend the vast majority of their lives as short cracks, the behavior of such a flaw is of significant importance. In the literature, McEvily and co-workers [McEvily, A. J., Eifler, D., and Macherauch, E., "An analysis of the Fatigue Growth of Short Fatigue Cracks," Eng. Fract. Mech., Vol. 40, No. 3, 1991, pp. 571-584] developed a modified linear elastic fracture mechanics (LEFM) approach to tackle a number of fatigue problems, including the growth and threshold behavior of small fatigue cracks. In this study, a further extension is presented to deal with notch effects in fatigue. In this method, the elastic-plastic behavior and the crack closure are taken into account, as the major factors responsible for the peculiar behavior of small fatigue cracks emanating from notches. In the present paper, the notch effect in fatigue is systematically investigated by making use of a mechanism-based computational framework. A series of parametric studies demonstrate the predictive capability of the proposed framework. Based on the thorough investigation for notch-fatigue problem, the novelty of present study is illustrated. Copyright © 2012 by ASTM International.

关键词： Crack closure

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Computation of shock waves in inert binary diatomic gas mixtures in non-equilibrium using the generalized Boltzmann equation

Computation of shock waves in inert binary diatomic gas mixt...

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43rd AIAA Thermophysics Conference 2012

作者： Qian, Geng Agarwal, Ramesh K. Wilson, Christopher D. Beijing Institute of Technology School of Aerospace Engineering Beijing 100081 China Washington University Dept. of Mechanical engineering and Materials Science St. Louis MO 63130 United States Boeing Company St. Louis MO 63166 United States

ISBN: (纸本)9781624101861

For numerical solution of the Generalized Boltzmann Equation (GBE) for simulating rarefied hypersonic flows in a gas mixture of multiple species, the GBE is formulated in the impulse space. The gas mixtures may consist of both monatomic and diatomic gases with arbitrary constituents, concentrations, and mass ratios. The conservative discrete ordinates method of Tcheremissine is applied to validate the solutions against the existing simulations for shock waves in an inert binary mixture of monoatomic gases. The method is then exercised for various concentration ratios, mass ratios, and density ratios to evaluate its ability to simulate a wide range of binary gas mixtures of monoatomic and diatomic gases. In particular, the method is applied to simulate two of the three primary constituents of air (N2, O2, Ar) in a binary mixture at 1:1 density ratio and air concentration ratio with gases in translational, rotational and vibrational non-equilibrium. The solutions presented in the paper can serve as validation test cases for other methods as well as an important building block in developing complex 3D simulations for shock waves in a mixture of multiple gases. © 2012 by G. Qian, R.K. Agarwal and C. D. Wilson.

关键词： Boltzmann equation

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Ab initio model of intrinsic defects in Sc2O3 for thermionic cathode systems

Ab initio model of intrinsic defects in Sc2O3 for thermionic...

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International Vacuum Electron Sources Conference, IVESC

作者： Ryan M. Jacobs Dane Morgan John H. Booske Materials Science Program University of Wisconsin-Madison Madison WI USA Materials Science Program University of Wisconsin-Madison Madison WI USA Materials Science and Engineering Electrical and Computer Engineering Dept.

A defect model for Sc 2 O 3 was developed using quantum mechanical modeling and evaluated under cathode operating conditions to determine the electronic properties of Sc 2 O 3 used in cathode experiments. We find that Sc 2 O 3 can conduct well enough with a sub-ppm impurity concentration such that the limiting step of emission is not conduction through bulk Sc 2 O 3 .

关键词： Cathodes Temperature Lattices Computational modeling Thermionic emission Current density Approximation methods

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PVP addition during hydroxyapatite synthesis: Effect on albumin adsorption

PVP addition during hydroxyapatite synthesis: Effect on albu...

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23rd Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2011

作者： Fernandes, T.J. Mavropoulos, E. Campos, J.B. Gobbo, L.A. Prado Da Silva, M.H. Military Institute of Engineering - IME Dept of Mechanical and Materials Science Eng. Rio de Janeiro Brazil Brazilian Centre for Research in Physics CBPF Dept. of Applied Physics Rio de Janeiro Brazil Panalytical Sao Paulo Brazil

ISBN: (纸本)9783037852552

Hydroxyapatite nanoparticles were synthesized by preparing an aqueous solution comprising 0.5M Ca(OH)2, 0.3M H3PO4 and 1M CH3CHCO2HOH (lactic acid) at pH of 3.7. KOH was added to the solution until pH=12 was reached, to precipitate hydroxyapatite. The incubation time ranged from 24 to 88 hours and the precipitates were then filtered on filter paper with the aid of a vacuum pump. The powders were synthesized with and without PVP addition. The powders were then sintered at 1100°C. Sintered and non sintered powders were characterized by scanning electron microscopy with field emission gun (FEG-SEM) and transmission electron microscopy (TEM) in order to assess particles morphology. Structural characterization was performed by X-ray diffractometry with Rietveld refinement. Albumin adsorption experiments were carried out on the powders with the aid of UV-VIS spectrometry. The results showed that the samples produced in the presence of PVP showed smaller particles when compared to non-dispersed samples. Albumin adsorption was more effective on the powders synthesized with dispersant. © (2012) Trans Tech Publications.

关键词： Hydroxyapatite

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X-RAY EVALUATION OF DEFORMATION BEHAVIOR OF SPUTTEREDCuTHIN FILMS UNDER TENSILE LOADING

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International Journal of Modern Physics: Conference Series 2012年第6期ijmpcs卷 497-502页

作者： YOSHIAKI AKINIWA Dept. of Mechanical Engineering and Materials Science Yokohama National University 79-1 Tokiwadai Hodogaya-ku Yokohama 240-8501 Japan

Tensile tests were carried out for sputtered copper thin films. Thin films were fabricated by RF magnetron sputtering. The target power of the sputtering equipment was set from 10 to 150 W to control the grain size. The grain size increased with increasing target power. The effect of grain size on the deformation behavior under tensile loading was investigated by X-ray method. The changes in the internal stress and the full width at half maximum were measured under tensile loading. The 0.2% proof stress decreased with grain size. For the full width at half maximum, the value was almost constant in the elastic region. When the plastic deformation occurred, the value increased rapidly with applied strain. For the specimen with fine grains, the value returned to the initial value in spite of after large plastic deformation. After tensile loading, many intergranular cracks could be observed on the specimen surface.

关键词： X-ray Copper thin film Plastic deformation Grain size Line broadening

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Modeling shear instability and fracture in dynamically deformed Al/W granular composites

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AIP Conference Proceedings 2012年第1期1426卷 729-732页

作者： Karl Olney David Benson Vitali F. Nesterenko Dept. of Mechanical and Aerospace Engineering University of California San Diego CA 92027 USA Dept. of Structural Engineering University of California San Diego CA 92027 USA Materials Science and Eng. Program University of California San Diego CA 92093 USA

Aluminum/Tungsten granular composites are materials which combine high density and strength with bulk distributed fracture of Al matrix into small particles under impact or shock loading. They are processed using cold and hot isostatic pressing of W particles/rods in the matrix of Al powder. Numerical models were used to elucidate the dynamic behavior of these materials under dynamic conditions simulating low velocity high energy impact in drop weight test (10 m/s). It was demonstrated that arrangement of W components and bonding between Al particles dramatically affect the samples shear localization and mode of fracture of the Al matrix in agreement with experiments.

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The effect of Cytochalasin D on F-actin behavior of single-cell electroendocytosis using multi-chamber micro cell chip

The effect of Cytochalasin D on F-actin behavior of single-c...

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7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2012

作者： Lin, Ran Chang, Donald. C. Lee, Yi-Kuen Bioengineering Graduate Program HKUST Kowloon Hong Kong Dept. of Mechanical Engineering HKUST Kowloon Hong Kong Division of Life Science HKUST Kowloon Hong Kong Joint KAUST-HKUST Micro/Nanofluidics Laboratory HKUST Clear Water Bay Kowloon Hong Kong

ISBN: (纸本)9781467311243

Electroendocytosis (EED) is a pulsed-electric-field (PEF) induced endocytosis, facilitating cells uptake molecules through nanometer-sized EED vesicles. We herein investigate the effect of a chemical inhibitor, Cytochalasin D (CD) on the actin-filaments (F-Actin) behavior of single-cell EED. The CD concentration (CCD) can control the depolymerization of F-actin. A multi-chamber micro cell chip was fabricated to study the EED under different conditions. Large-scale single-cell data demonstrated EED highly depends on both electric field and CCD. © 2012 IEEE.

关键词： Electric fields

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Flexible tactile sensors based on nanoimprinted sub-20 NM piezoelectric copolymer nanograss films

Flexible tactile sensors based on nanoimprinted sub-20 NM pi...

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IEEE SENSORS

作者： Alan Chen Kai-Lun Lin Chien-Chong Hong Tong-Miin Liou Jiann Shieh Szu-Hung Chen Dept. of Power Mechanical Engineering National Tsing Hua University Hsinchu Taiwan Dept. of Materials Science and Engineering National United University Miaoli Taiwan National Nano Device Laboratories Hsinchu Taiwan

ISBN: (纸本)9781457717666

This paper presents flexible tactile sensors based on nanoimprinted sub-20 nm piezoelectric copolymer nanograss films. The performance of the sensors is significantly affected by surface morphology of sensing materials. In this abstract, we develop non-electrical poling for the developed PVDF-TrFE nanograss, which greatly improve the piezoelectric response, and apply the developed PVDF-TrFE nanograss films as flexible tactile sensors.

关键词： Films Tactile sensors Silicon Electrodes Surface morphology Nanoscale devices

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